Science.gov

Sample records for model porous materials

  1. Designing and modeling doubly porous polymeric materials

    NASA Astrophysics Data System (ADS)

    Ly, H.-B.; Le Droumaguet, B.; Monchiet, V.; Grande, D.

    2015-07-01

    Doubly porous organic materials based on poly(2-hydroxyethyl methacrylate) are synthetized through the use of two distinct types of porogen templates, namely a macroporogen and a nanoporogen. Two complementary strategies are implemented by using either sodium chloride particles or fused poly(methyl methacrylate) beads as macroporogens, in conjunction with ethanol as a porogenic solvent. The porogen removal respectively allows for the generation of either non-interconnected or interconnected macropores with an average diameter of about 100-200 μm and nanopores with sizes lying within the 100 nm order of magnitude, as evidenced by mercury intrusion porosimetry and scanning electron microscopy. Nitrogen sorption measurements evidence the formation of materials with rather high specific surface areas, i.e. higher than 140 m2.g-1. This paper also addresses the development of numerical tools for computing the permeability of such doubly porous materials. Due to the coexistence of well separated scales between nanopores and macropores, a consecutive double homogenization approach is proposed. A nanoscopic scale and a mesoscopic scale are introduced, and the flow is evaluated by means of the Finite Element Method to determine the macroscopic permeability. At the nanoscopic scale, the flow is described by the Stokes equations with an adherence condition at the solid surface. At the mesoscopic scale, the flow obeys the Stokes equations in the macropores and the Darcy equation in the permeable polymer in order to account for the presence of the nanopores.

  2. Simplified modeling of transition to detonation in porous energetic materials

    NASA Astrophysics Data System (ADS)

    Stewart, D. Scott; Asay, Blaine W.; Prasad, Kuldeep

    1994-07-01

    A simplified model that can predict the transitions from compaction to detonation and shock to detonation is given with the aim of describing experiments in beds of porous HMX. In the case of compaction to detonation, the energy of early impact generates a slowly moving, convective-reactive deflagration that expands near the piston face and evolves in a manner that is characteristic of confined deflagration to detonation transition. A single-phase state variable theory is adopted in contrast to a two-phase axiomatic mixture theory. The ability of the porous material to compact is treated as an endothermic process. Reaction is treated as an exothermic process. The algebraic (Rankine-Hugoniot) steady wave analysis is given for inert compaction waves and steady detonation waves in a piston supported configuration, typical of the experiments carried out in porous HMX. A structure analysis of the steady compaction wave is given. Numerical simulations of deflagration to detonation are carried out for parameters that describe an HMX-like material and compared with the experiments. The simple model predicts the high density plug that is observed in the experiments and suggests that the leading front of the plug is a secondary compaction wave. A shock to detonation transition is also numerically simulated.

  3. Simplified modeling of transition to detonation in porous energetic materials

    SciTech Connect

    Stewart, D.S. ); Asay, B.W. ); Prasad, K. )

    1994-07-01

    A simplified model that can predict the transitions from compaction to detonation and shock to detonation is given with the aim of describing experiments in beds of porous HMX. In the case of compaction to detonation, the energy of early impact generates a slowly moving, convective-reactive deflagration that expands near the piston face and evolves in a manner that is characteristic of confined deflagration to detonation transition. A single-phase state variable theory is adopted in contrast to a two-phase axiomatic mixture theory. The ability of the porous material to compact is treated as an endothermic process. Reaction is treated as an exothermic process. The algebraic (Rankine--Hugoniot) steady wave analysis is given for inert compaction waves and steady detonation waves in a piston supported configuration, typical of the experiments carried out in porous HMX. A structure analysis of the steady compaction wave is given. Numerical simulations of deflagration to detonation are carried out for parameters that describe an HMX-like material and compared with the experiments. The simple model predicts the high density plug that is observed in the experiments and suggests that the leading front of the plug is a secondary compaction wave. A shock to detonation transition is also numerically simulated.

  4. System level permeability modeling of porous hydrogen storage materials.

    SciTech Connect

    Kanouff, Michael P.; Dedrick, Daniel E.; Voskuilen, Tyler

    2010-01-01

    A permeability model for hydrogen transport in a porous material is successfully applied to both laboratory-scale and vehicle-scale sodium alanate hydrogen storage systems. The use of a Knudsen number dependent relationship for permeability of the material in conjunction with a constant area fraction channeling model is shown to accurately predict hydrogen flow through the reactors. Generally applicable model parameters were obtained by numerically fitting experimental measurements from reactors of different sizes and aspect ratios. The degree of channeling was experimentally determined from the measurements and found to be 2.08% of total cross-sectional area. Use of this constant area channeling model and the Knudsen dependent Young & Todd permeability model allows for accurate prediction of the hydrogen uptake performance of full-scale sodium alanate and similar metal hydride systems.

  5. Modelling dynamic compaction of porous materials with the overstress approach

    NASA Astrophysics Data System (ADS)

    Partom, Y.

    2014-05-01

    To model compaction of a porous material we need 1) an equation of state of the porous material in terms of the equation of state of its matrix, and 2) a compaction law. For an equation of state it is common to use Herrmann's suggestion, as in his Pα model. For a compaction law it is common to use a quasi-static compaction relation obtained from 1) a meso-scale model (as in Carroll and Holt's spherical shell model), or from 2) quasi-static tests. Here we are interested in dynamic compaction, like in a planar impact test. In dynamic compaction the state may change too fast for the state point to follow the quasi-static compaction curve. We therefore get an overstress situation. The state point moves out of the quasi-static compaction boundary, and only with time collapses back towards it at a certain rate. In this way the dynamic compaction event becomes rate dependent. In the paper we first write down the rate equations for dynamic compaction according to the overstress approach. We then implement these equations in a hydro-code and run some examples. We show how the overstress rate parameter can be calibrated from tests.

  6. Advances in design and modeling of porous materials

    NASA Astrophysics Data System (ADS)

    Ayral, André; Calas-Etienne, Sylvie; Coasne, Benoit; Deratani, André; Evstratov, Alexis; Galarneau, Anne; Grande, Daniel; Hureau, Matthieu; Jobic, Hervé; Morlay, Catherine; Parmentier, Julien; Prelot, Bénédicte; Rossignol, Sylvie; Simon-Masseron, Angélique; Thibault-Starzyk, Frédéric

    2015-07-01

    This special issue of the European Physical Journal Special Topics is dedicated to selected papers from the symposium "High surface area porous and granular materials" organized in the frame of the conference "Matériaux 2014", held on November 24-28, 2014 in Montpellier, France. Porous materials and granular materials gather a wide variety of heterogeneous, isotropic or anisotropic media made of inorganic, organic or hybrid solid skeletons, with open or closed porosity, and pore sizes ranging from the centimeter scale to the sub-nanometer scale. Their technological and industrial applications cover numerous areas from building and civil engineering to microelectronics, including also metallurgy, chemistry, health, waste water and gas effluent treatment. Many emerging processes related to environmental protection and sustainable development also rely on this class of materials. Their functional properties are related to specific transfer mechanisms (matter, heat, radiation, electrical charge), to pore surface chemistry (exchange, adsorption, heterogeneous catalysis) and to retention inside confined volumes (storage, separation, exchange, controlled release). The development of innovative synthesis, shaping, characterization and modeling approaches enables the design of advanced materials with enhanced functional performance. The papers collected in this special issue offer a good overview of the state-of-the-art and science of these complex media. We would like to thank all the speakers and participants for their contribution to the success of the symposium. We also express our gratitude to the organization committee of "Matériaux 2014". We finally thank the reviewers and the staff of the European Physical Journal Special Topics who made the publication of this special issue possible.

  7. Modeling Dynamic Compaction of Porous Materials with the Overstress Approach

    NASA Astrophysics Data System (ADS)

    Partom, Yehuda

    2013-06-01

    To model compaction of a porous material (PM) we need 1) an equation of state (EOS) of the PM in terms of the EOS of its matrix, and 2) a compaction law. For the EOS it is common to use Herrmann's suggestion, as in his P α model. For a compaction law it is common to use a quasi-static compaction relation obtained from 1) a mezzo-scale model (as in Carroll and Holt's spherical shell model), or from 2) quasi-static tests. Here we are interested in dynamic compaction, like in a planar impact test. In dynamic compaction, the state may change too fast for the state point to follow the quasi-static compaction curve. We therefore get an overstress situation. The state point moves out of the quasi-static compaction boundary, and only with time collapses back towards it at a certain rate. In this way the dynamic compaction event becomes rate dependent. In the paper we first write down the rate equations for dynamic compaction according to this overstress approach. We then implement these equations in a hydro-code, and run some examples. We show how the overstress rate parameter can be calibrated from tests.

  8. Tailored Porous Materials

    SciTech Connect

    BARTON,THOMAS J.; BULL,LUCY M.; KLEMPERER,WALTER G.; LOY,DOUGLAS A.; MCENANEY,BRIAN; MISONO,MAKOTO; MONSON,PETER A.; PEZ,GUIDO; SCHERER,GEORGE W.; VARTULI,JAMES C.; YAGHI,OMAR M.

    1999-11-09

    Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol-gel derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

  9. DDT modeling and shock compression experiments of porous or damaged energetic materials

    SciTech Connect

    Baer, M.R.; Anderson, M.U.; Graham, R.A.

    1994-05-01

    In this presentation, we present modeling of DDT in porous energetic materials and experimental studies of a time-resolved, shock compression of highly porous inert and reactive materials. This combined theoretical and experimental studies explore the nature of the microscale processes of consolidation, deformation and reaction which are key features of the shock response of porous or damaged energetic materials. The theoretical modeling is based on the theory of mixtures in which multiphase mixtures are treated in complete nonequilibrium allowing for internal boundary effects associated mass/momentum and energy exchange between phases, relative flow, rate-dependent compaction behavior, multistage chemistry and interphase boundary effects. Numerous studies of low-velocity impacts using a high resolution adaptive finite element method are presented which replicate experimental observations. The incorporation of this model into multi-material hydrocode analysis will be discussed to address the effects of confinement and its influence on accelerated combustion behavior. The experimental studies will focus on the use of PVDF piezoelectric polymer stress-rate gauge to precisely measure the input and propagating shock stress response of porous materials. In addition to single constituent porous materials, such as granular HMX, we have resolved shock waves in porous composite intermetallic powders that confirm a dispersive wave nature which is highly morphologically and material dependent. This document consists of viewgraphs from the poster session.

  10. Preparation of asymmetric porous materials

    DOEpatents

    Coker, Eric N.

    2012-08-07

    A method for preparing an asymmetric porous material by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.

  11. Porous material neutron detector

    DOEpatents

    Diawara, Yacouba; Kocsis, Menyhert

    2012-04-10

    A neutron detector employs a porous material layer including pores between nanoparticles. The composition of the nanoparticles is selected to cause emission of electrons upon detection of a neutron. The nanoparticles have a maximum dimension that is in the range from 0.1 micron to 1 millimeter, and can be sintered with pores thereamongst. A passing radiation generates electrons at one or more nanoparticles, some of which are scattered into a pore and directed toward a direction opposite to the applied electrical field. These electrons travel through the pore and collide with additional nanoparticles, which generate more electrons. The electrons are amplified in a cascade reaction that occurs along the pores behind the initial detection point. An electron amplification device may be placed behind the porous material layer to further amplify the electrons exiting the porous material layer.

  12. A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory.

    PubMed

    Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

    2015-12-15

    Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber. PMID:26291782

  13. Supersonic flow around a cylinder with front gas-permeable insert which modeled by skeleton of porous material

    NASA Astrophysics Data System (ADS)

    Poplavskaya, T. V.; Kirilovskiy, S. V.; Mironov, S. G.

    2016-10-01

    Experimental data and results of numerical simulation of a supersonic flow around a streamwise aligned cylinder with a frontal gas-permeable insert made of a high-porosity cellular material are presented. The porous material structure is modeled by a system of staggered rings of different diameters (discrete model of a porous medium). The model skeleton of the material corresponds to the pore size (diameter 1mm) and porosity (0.95) of a real cellular porous material. The computed results are compared with the data of wind tunnel experiments performed in a T-327B supersonic continuous-flow wind tunnel at the flow Mach number M∞ = 4.85.

  14. Strong, Lightweight, Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Meador, Mary Ann B.; Johnston, James C.; Fabrizio, Eve F.; Ilhan, Ulvi

    2007-01-01

    A new class of strong, lightweight, porous materials has been invented as an outgrowth of an effort to develop reinforced silica aerogels. The new material, called X-Aerogel is less hygroscopic, but no less porous and of similar density to the corresponding unmodified aerogels. However, the property that sets X-Aerogels apart is their mechanical strength, which can be as much as two and a half orders of magnitude stronger that the unmodified aerogels. X-Aerogels are envisioned to be useful for making extremely lightweight, thermally insulating, structural components, but they may also have applications as electrical insulators, components of laminates, catalyst supports, templates for electrode materials, fuel-cell components, and filter membranes.

  15. Model for the interpretation of nuclear magnetic resonance relaxometry of hydrated porous silicate materials.

    PubMed

    Faux, D A; Cachia, S-H P; McDonald, P J; Bhatt, J S; Howlett, N C; Churakov, S V

    2015-03-01

    Nuclear magnetic resonance (NMR) relaxation experimentation is an effective technique for probing the dynamics of proton spins in porous media, but interpretation requires the application of appropriate spin-diffusion models. Molecular dynamics (MD) simulations of porous silicate-based systems containing a quasi-two-dimensional water-filled pore are presented. The MD simulations suggest that the residency time of the water on the pore surface is in the range 0.03-12 ns, typically 2-5 orders of magnitude less than values determined from fits to experimental NMR measurements using the established surface-layer (SL) diffusion models of Korb and co-workers [Phys. Rev. E 56, 1934 (1997)]. Instead, MD identifies four distinct water layers in a tobermorite-based pore containing surface Ca2+ ions. Three highly structured water layers exist within 1 nm of the surface and the central region of the pore contains a homogeneous region of bulklike water. These regions are referred to as layer 1 and 2 (L1, L2), transition layer (TL), and bulk (B), respectively. Guided by the MD simulations, a two-layer (2L) spin-diffusion NMR relaxation model is proposed comprising two two-dimensional layers of slow- and fast-moving water associated with L2 and layers TL+B, respectively. The 2L model provides an improved fit to NMR relaxation times obtained from cementitious material compared to the SL model, yields diffusion correlation times in the range 18-75 ns and 28-40 ps in good agreement with MD, and resolves the surface residency time discrepancy. The 2L model, coupled with NMR relaxation experimentation, provides a simple yet powerful method of characterizing the dynamical properties of proton-bearing porous silicate-based systems such as porous glasses, cementitious materials, and oil-bearing rocks. PMID:25871114

  16. Porous bioactive materials

    NASA Astrophysics Data System (ADS)

    Zhang, Kai

    Bioactive materials chemically bond to tissues through the development of biologically active apatite. Porous structures in biomaterials are designed to enhance bioactivity, grow artificial tissues and achieve better integration with host tissues in the body. The goal of this research is to design, fabricate and characterize novel porous bioactive materials. 3D ordered macroporous bioactive glasses (3DOM-BGs, pore size: 200--1000 nm) were prepared using a sol-gel process and colloidal crystal templates. 3DOM-BGs are more bioactive and degradable than mesoporous (pore size <50 nm) sol-gel BGs in simulated body fluid (SBF). Apatite formation and 3DOM-BG degradation rates increased with the decrease of soaking ratio. Apatite induction time in SBF increased with 3DOM-BG calcination temperature (600--800°C). Apatite formation and 3DOMBG degradation were slightly enhanced for a phosphate containing composition. Large 3DOM-BG particles formed less apatite and degraded less completely as compared with small particles. An increase in macropore size slowed down 3DOM-BG degradation and apatite formation processes. After heating the converted apatite at a temperature higher than 700°C, highly crystalline hydroxyapatite and a minor tri-calcium phosphate phase formed. 3DOM-BGs have potential applications as bone/periodontal fillers, and drugs and biological factors delivery agents. Anchoring artificial soft tissues (e.g., cartilage) to native bone presents a challenge. Porous polymer/bioactive glass composites are candidate materials for engineering artificial soft tissue/bone interfaces. Porous composites consisting of polymer matrices (e.g., polysulfone, polylactide, and polyurethane) and bioactive glass particles were prepared by polymer phase separation techniques adapted to include ceramic particles. Composites (thickness: 200--500 mum) have asymmetric structures with dense top layers and porous structures beneath. Porous structures consist of large pores (>100 mum) in a

  17. Analytical Fractal Model for Calculating Effective Thermal Conductivity of the Fibrous Porous Materials.

    PubMed

    Kan, An-Kang; Cao, Dan; Zhang, Xue-Lai

    2015-04-01

    Accurately predicting the effective thermal conductivity of the fibrous materials is highly desirable but remains to be a challenging work. In this paper, the microstructure of the porous fiber materials is analyzed, approximated and modeled on basis of the statistical self-similarity of fractal theory. A fractal model is presented to accurately calculate the effective thermal conductivity of fibrous porous materials. Taking the two-phase heat transfer effect into account, the existing statistical microscopic geometrical characteristics are analyzed and the Hertzian Contact solution is introduced to calculate the thermal resistance of contact points. Using the fractal method, the impacts of various factors, including the porosity, fiber orientation, fractal diameter and dimension, rarified air pressure, bulk thermal conductivity coefficient, thickness and environment condition, on the effective thermal conductivity, are analyzed. The calculation results show that the fiber orientation angle caused the material effective thermal conductivity to be anisotropic, and normal distribution is introduced into the mathematic function. The effective thermal conductivity of fibrous material increases with the fiber fractal diameter, fractal dimension and rarefied air pressure within the materials, but decreases with the increase of vacancy porosity.

  18. Constitutive model for geological and other porous materials under dynamic loading

    SciTech Connect

    Dey, T.N.

    1991-01-01

    An effective stress model is described for use in numerical calculations on porous materials which are partially or fully saturated with water. The flow rule chosen for the shear failure portion of the model is examined and shown to have significant influence on wave propagation results. A flow rule which produces dilatancy results in less attenuation than a rule producing shear-enhanced void collapse. The dilatancy producing rule is less prone to producing liquefaction and results in significantly higher stress levels behind the wave front. 8 refs., 6 figs.

  19. Transfer matrix modeling and experimental validation of cellular porous material with resonant inclusions.

    PubMed

    Doutres, Olivier; Atalla, Noureddine; Osman, Haisam

    2015-06-01

    Porous materials are widely used for improving sound absorption and sound transmission loss of vibrating structures. However, their efficiency is limited to medium and high frequencies of sound. A solution for improving their low frequency behavior while keeping an acceptable thickness is to embed resonant structures such as Helmholtz resonators (HRs). This work investigates the absorption and transmission acoustic performances of a cellular porous material with a two-dimensional periodic arrangement of HR inclusions. A low frequency model of a resonant periodic unit cell based on the parallel transfer matrix method is presented. The model is validated by comparison with impedance tube measurements and simulations based on both the finite element method and a homogenization based model. At the HR resonance frequency (i) the transmission loss is greatly improved and (ii) the sound absorption of the foam can be either decreased or improved depending on the HR tuning frequency and on the thickness and properties of the host foam. Finally, the diffuse field sound absorption and diffuse field sound transmission loss performance of a 2.6 m(2) resonant cellular material are measured. It is shown that the improvements observed at the Helmholtz resonant frequency on a single cell are confirmed at a larger scale. PMID:26093437

  20. Transfer matrix modeling and experimental validation of cellular porous material with resonant inclusions.

    PubMed

    Doutres, Olivier; Atalla, Noureddine; Osman, Haisam

    2015-06-01

    Porous materials are widely used for improving sound absorption and sound transmission loss of vibrating structures. However, their efficiency is limited to medium and high frequencies of sound. A solution for improving their low frequency behavior while keeping an acceptable thickness is to embed resonant structures such as Helmholtz resonators (HRs). This work investigates the absorption and transmission acoustic performances of a cellular porous material with a two-dimensional periodic arrangement of HR inclusions. A low frequency model of a resonant periodic unit cell based on the parallel transfer matrix method is presented. The model is validated by comparison with impedance tube measurements and simulations based on both the finite element method and a homogenization based model. At the HR resonance frequency (i) the transmission loss is greatly improved and (ii) the sound absorption of the foam can be either decreased or improved depending on the HR tuning frequency and on the thickness and properties of the host foam. Finally, the diffuse field sound absorption and diffuse field sound transmission loss performance of a 2.6 m(2) resonant cellular material are measured. It is shown that the improvements observed at the Helmholtz resonant frequency on a single cell are confirmed at a larger scale.

  1. Porous materials. Function-led design of new porous materials.

    PubMed

    Slater, Anna G; Cooper, Andrew I

    2015-05-29

    Porous solids are important as membranes, adsorbents, catalysts, and in other chemical applications. But for these materials to find greater use at an industrial scale, it is necessary to optimize multiple functions in addition to pore structure and surface area, such as stability, sorption kinetics, processability, mechanical properties, and thermal properties. Several different classes of porous solids exist, and there is no one-size-fits-all solution; it can therefore be challenging to choose the right type of porous material for a given job. Computational prediction of structure and properties has growing potential to complement experiment to identify the best porous materials for specific applications.

  2. Highly porous thermal protection materials: Modelling and prediction of the methodical experimental errors

    NASA Astrophysics Data System (ADS)

    Cherepanov, Valery V.; Alifanov, Oleg M.; Morzhukhina, Alena V.; Budnik, Sergey A.

    2016-11-01

    The formation mechanisms and the main factors affecting the systematic error of thermocouples were investigated. According to the results of experimental studies and mathematical modelling it was established that in highly porous heat resistant materials for aerospace application the thermocouple errors are determined by two competing mechanisms provided correlation between the errors and the difference between radiation and conduction heat fluxes. The comparative analysis was carried out and some features of the methodical error formation related to the distances from the heated surface were established.

  3. Limit analysis and conic programming: `porous Drucker Prager' material and Gurson's model

    NASA Astrophysics Data System (ADS)

    Trillat, Malorie; Pastor, Joseph; Thoré, Philippe

    2006-10-01

    Extending a previous work on the Gurson model for a 'porous von Mises' material, the present study first focuses on the yield criterion of a 'porous Drucker-Prager' material with spherical cavities. On the basis of the Gurson micro-macro model and a second order conic programming ( SOCP) formulation, calculated inner and outer approaches to the criterion are very close, providing a reliable estimate of the yield criterion. Comparison with an analytical criterion recently proposed by Barthélémy and Dormieux—from a nonlinear homogenization method—shows both excellent agreement when considering tensile average boundary conditions and substantial improvement under compressive conditions. Then the results of an analogous study in the case of cylindrical cavities in plane strain are presented. It is worth noting that obtaining these results was made possible by using MOSEK, a recent commercial SOCP code, whose impressive efficiency was already seen in our previous works. To cite this article: M. Trillat et al., C. R. Mecanique 334 (2006).

  4. Lattice Boltzmann modeling of permeability in porous materials with partially percolating voxels.

    PubMed

    Li, Ruru; Yang, Y Sam; Pan, Jinxiao; Pereira, Gerald G; Taylor, John A; Clennell, Ben; Zou, Caineng

    2014-09-01

    A partial-bounce-back lattice Boltzmann model has been used to simulate flow on a lattice consisting of cubic voxels with a locally varying effective percolating fraction. The effective percolating fraction of a voxel is the total response to the partial-bounce-back techniques for porous media flow due to subvoxel fine structures. The model has been verified against known analytic solutions on two- and three-dimensional regular geometries, and has been applied to simulate flow and permeabilities of two real-world rock samples. This enables quantitative determination of permeability for problems where voxels cannot be adequately segmented as discrete compositions. The voxel compositions are represented as volume fractions of various material phases and void. The numerical results have shown that, for the tight-sandstone sample, the bulk permeability is sensitive to the effective percolating fraction of calcite. That is, the subvoxel flow paths in the calcite phase are important for bulk permeability. On the other hand, flow in the calcite phase in the sandstone sample makes an insignificant contribution to the bulk permeability. The calculated permeability value for the sandstone sample is up to two orders of magnitude greater than the tight sandstone. This model is generic and could be applied to other oil and gas reservoir media or to material samples.

  5. Acoustic Absorption in Porous Materials

    NASA Technical Reports Server (NTRS)

    Kuczmarski, Maria A.; Johnston, James C.

    2011-01-01

    An understanding of both the areas of materials science and acoustics is necessary to successfully develop materials for acoustic absorption applications. This paper presents the basic knowledge and approaches for determining the acoustic performance of porous materials in a manner that will help materials researchers new to this area gain the understanding and skills necessary to make meaningful contributions to this field of study. Beginning with the basics and making as few assumptions as possible, this paper reviews relevant topics in the acoustic performance of porous materials, which are often used to make acoustic bulk absorbers, moving from the physics of sound wave interactions with porous materials to measurement techniques for flow resistivity, characteristic impedance, and wavenumber.

  6. Finite element modelling approaches for well-ordered porous metallic materials for orthopaedic applications: cost effectiveness and geometrical considerations.

    PubMed

    Quevedo González, Fernando José; Nuño, Natalia

    2016-01-01

    The mechanical properties of well-ordered porous materials are related to their geometrical parameters at the mesoscale. Finite element (FE) analysis is a powerful tool to design well-ordered porous materials by analysing the mechanical behaviour. However, FE models are often computationally expensive. This article aims to develop a cost-effective FE model to simulate well-ordered porous metallic materials for orthopaedic applications. Solid and beam FE modelling approaches are compared, using finite size and infinite media models considering cubic unit cell geometry. The model is then applied to compare two unit cell geometries: cubic and diamond. Models having finite size provide similar results than the infinite media model approach for large sample sizes. In addition, these finite size models also capture the influence of the boundary conditions on the mechanical response for small sample sizes. The beam FE modelling approach showed little computational cost and similar results to the solid FE modelling approach. Diamond unit cell geometry appeared to be more suitable for orthopaedic applications than the cubic unit cell geometry.

  7. Metal recovery from porous materials

    DOEpatents

    Sturcken, Edward F.

    1992-01-01

    A method for recovering plutonium and other metals from materials by leaching comprising the steps of incinerating the materials to form a porous matrix as the residue of incineration, immersing the matrix into acid in a microwave-transparent pressure vessel, sealing the pressure vessel, and applying microwaves so that the temperature and the pressure in the pressure vessel increase. The acid for recovering plutonium can be a mixture of HBF.sub.4 and HNO.sub.3 and preferably the pressure is increased to at least 100 PSI and the temperature to at least 200.degree. C. The porous material can be pulverized before immersion to further increase the leach rate.

  8. Porous media modeling and micro-structurally motivated material moduli determination via the micro-dilatation theory

    NASA Astrophysics Data System (ADS)

    Jeong, J.; Ramézani, H.; Sardini, P.; Kondo, D.; Ponson, L.; Siitari-Kauppi, M.

    2015-07-01

    In the present contribution, the porous material modeling and micro-structural material parameters determination are scrutinized via the micro-dilatation theory. The main goal is to take advantage of the micro-dilatation theory which belongs to the generalized continuum media. In the first stage, the thermodynamic laws are entirely revised to reach the energy balance relation using three variables, deformation, porosity change and its gradient underlying the porous media as described in the micro-dilatation theory or so-called void elasticity. Two experiments over cement mortar specimens are performed in order to highlight the material parameters related to the pore structure. The shrinkage due to CO2 carbonation, porosity and its gradient are calculated. The extracted values are verified via 14C-PMMA radiographic image method. The modeling of swelling phenomenon of Delayed Ettringite Formation (DEF) is studied later on. This issue is performed via the crystallization pressure application using the micro-dilatation theory.

  9. EQUATION OF STATE AND HUGONIOT LOCUS FOR POROUS MATERIALS: P-ALPHA MODEL REVISITED

    SciTech Connect

    R. MENIKOFF; ET AL

    1999-08-01

    Foams, porous solids and granular materials have a characteristic Hugoniot locus that for weak shocks is concave in the (particle velocity, shock velocity)-plane. An equation of state (EOS) that has this property can be constructed implicitly from a Helmholtz free energy of the form {Psi}{sub s}(V,T,{phi}) = {Psi}{sub s}(V,T)+B({phi}) where the equilibrium volume fraction {phi}{sub eq} is determined by minimizing {Psi}, i.e., the condition {partial_derivative}{sub {psi}} {Psi} = 0. For many cases, a Hayes EOS for the pure solid {Psi}{sub s}(V,T) is adequate. This provides a thermodynamically consistent framework for the P-{alpha} model. For this form of EOS the volume fraction has a similar effect to an endothermic reaction in that the partial Hugoniot loci with fixed {psi} are shifted to the left in the (V,P)-plane with increasing f. The equilibrium volume fraction can then be chosen to match the concavity of the principal Hugoniot locus. An example is presented for the polymer estane. A small porosity of only 1.4 percent is required to match the experimental concavity in the Hugoniot data. This type of EOS can also be used to obtain the so-called ''universal'' Hugoniot for liquids.

  10. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1991-01-01

    The present invention relates to recovery of metals. More specifically, the present invention relates to the recovery of plutonium and other metals from porous materials using microwaves. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the US Department of Energy and Westinghouse Savannah River Company.

  11. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1992-10-13

    A method is described for recovering plutonium and other metals from materials by leaching comprising the steps of incinerating the materials to form a porous matrix as the residue of incineration, immersing the matrix into acid in a microwave-transparent pressure vessel, sealing the pressure vessel, and applying microwaves so that the temperature and the pressure in the pressure vessel increase. The acid for recovering plutonium can be a mixture of HBF[sub 4] and HNO[sub 3] and preferably the pressure is increased to at least 100 PSI and the temperature to at least 200 C. The porous material can be pulverized before immersion to further increase the leach rate.

  12. Thermal conductivity and electrical resistivity of porous materials

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Fortini, A.

    1972-01-01

    Process for determining thermal conductivity and electrical resistivity of porous materials is described. Characteristics of materials are identified and used in development of mathematical models. Limitations of method are examined.

  13. Micromechanics-based modelling of post-yield behavior of porous materials and its effect on hardness properties from conical indentation

    NASA Astrophysics Data System (ADS)

    Traxl, Roland; Lackner, Roman

    2013-08-01

    Based on a multi-scale approach comprising a multi-scale material model, on the one hand, and a respective finite-element (FE) model, on the other hand, the indentation response of porous materials is examined. The considered material is assumed to consist of a homogeneous Drucker-Prager-type matrix-phase containing spherical pores, where the macroscopic strength criterion is obtained from nonlinear homogenization as proposed by Barthélémy and Dormieux. As regards modeling of the material behavior after onset of yielding, two types of behavior originating from different post-yield characteristics of the matrix material (ductile and quasi-brittle) are considered. The material model is implemented in a FE program within the framework of elastoplasticity and applied to the analysis of indentation experiments. The so-obtained relations provide first insight into the influence of the post-yield behavior of the matrix material on the hardness of porous materials.

  14. Contaminant tailing in highly heterogeneous porous formations: Sensitivity on model selection and material properties

    NASA Astrophysics Data System (ADS)

    Maghrebi, Mahdi; Jankovic, Igor; Weissmann, Gary S.; Matott, L. Shawn; Allen-King, Richelle M.; Rabideau, Alan J.

    2015-12-01

    Coupled impacts of slow advection, diffusion and sorption were investigated using two heterogeneity models that differ in structure and in the mathematical framework that was used to simulate flow and transport and to quantify contaminant tailing. Both models were built using data from a highly heterogeneous exposure of the Borden Aquifer at a site located 2 km north-west of the Stanford-Waterloo experimental site at Canadian Forces Base Borden, Ontario, Canada. The inclusions-based model used a simplified representation of the different materials found at the site, while the second model was based on transitional probability geostatistics of the formation. These two models were used to investigate sensitivity of contaminant tailing on model selection and on geometric and material properties. While simulations were based on data collected at Borden, models were exercised beyond the geometric and material properties that characterize the site. Various realizations have identified very low conductive silty clay, found at volume fraction of 23.4%, as the material with dominant influence on tailing, and vertical diffusion in and out of low conductive units, affected by sorption, as the dominant transport mechanism causing tailing. The two models yielded almost identical transport results when vertical correlation lengths of silty clay were matched. Several practical implications relevant for characterization of low conductive units were identified and briefly discussed.

  15. A domain decomposition method for modelling Stokes flow in porous materials

    NASA Astrophysics Data System (ADS)

    Liu, Guangli; Thompson, Karsten E.

    2002-04-01

    An algorithm is presented for solving the Stokes equation in large disordered two-dimensional porous domains. In this work, it is applied to random packings of discs, but the geometry can be essentially arbitrary. The approach includes the subdivision of the domain and a subsequent application of boundary integral equations to the subdomains. This gives a block diagonal matrix with sparse off-block components that arise from shared variables on internal subdomain boundaries. The global problem is solved using a biconjugate gradient routine with preconditioning. Results show that the effectiveness of the preconditioner is strongly affected by the subdomain structure, from which a methodology is proposed for the domain decomposition step. A minimum is observed in the solution time versus subdomain size, which is governed by the time required for preconditioning, the time for vector multiplications in the biconjugate gradient routine, the iterative convergence rate and issues related to memory allocation. The method is demonstrated on various domains including a random 1000-particle domain. The solution can be used for efficient recovery of point velocities, which is discussed in the context of stochastic modelling of solute transport. Copyright

  16. SPUTTERING FROM A POROUS MATERIAL BY PENETRATING IONS

    SciTech Connect

    Rodriguez-Nieva, J. F.; Bringa, E. M.; Cassidy, T. A.; Caro, A.; Loeffler, M. J.; Farkas, D.

    2011-12-10

    Porous materials are ubiquitous in the universe and weathering of porous surfaces plays an important role in the evolution of planetary and interstellar materials. Sputtering of porous solids in particular can influence atmosphere formation, surface reflectivity, and the production of the ambient gas around materials in space. Several previous studies and models have shown a large reduction in the sputtering of a porous solid compared to the sputtering of the non-porous solid. Using molecular dynamics simulations we study the sputtering of a nanoporous solid with 55% of the solid density. We calculate the electronic sputtering induced by a fast, penetrating ion, using a thermal spike representation of the deposited energy. We find that sputtering for this porous solid is, surprisingly, the same as that for a full-density solid, even though the sticking coefficient is high.

  17. Sputtering from a Porous Material by Penetrating Ions

    NASA Astrophysics Data System (ADS)

    Rodriguez-Nieva, J. F.; Bringa, E. M.; Cassidy, T. A.; Johnson, R. E.; Caro, A.; Fama, M.; Loeffler, M. J.; Baragiola, R. A.; Farkas, D.

    2011-12-01

    Porous materials are ubiquitous in the universe and weathering of porous surfaces plays an important role in the evolution of planetary and interstellar materials. Sputtering of porous solids in particular can influence atmosphere formation, surface reflectivity, and the production of the ambient gas around materials in space. Several previous studies and models have shown a large reduction in the sputtering of a porous solid compared to the sputtering of the non-porous solid. Using molecular dynamics simulations we study the sputtering of a nanoporous solid with 55% of the solid density. We calculate the electronic sputtering induced by a fast, penetrating ion, using a thermal spike representation of the deposited energy. We find that sputtering for this porous solid is, surprisingly, the same as that for a full-density solid, even though the sticking coefficient is high.

  18. Sputtering from a Porous Material by Penetrating Ions

    NASA Technical Reports Server (NTRS)

    Rodriguez-Nieva, J. F.; Bringa, E. M.; Cassidy, T. A.; Johnson, R. E.; Caro, A.; Fama, M.; Loeffler, M.; Baragiola, R. A.; Farkas, D.

    2012-01-01

    Porous materials are ubiquitous in the universe and weathering of porous surfaces plays an important role in the evolution of planetary and interstellar materials. Sputtering of porous solids in particular can influence atmosphere formation, surface reflectivity, and the production of the ambient gas around materials in space, Several previous studies and models have shown a large reduction in the sputtering of a porous solid compared to the sputtering of the non-porous solid. Using molecular dynamics simulations we study the sputtering of a nanoporous solid with 55% of the solid density. We calculate the electronic sputtering induced by a fast, penetrating ion, using a thermal spike representation of the deposited energy. We find that sputtering for this porous solid is, surprisingly, the same as that for a full-density solid, even though the sticking coefficient is high.

  19. Advances in modeling sorption and diffusion of moisture in porous reactive materials.

    PubMed

    Harley, Stephen J; Glascoe, Elizabeth A; Lewicki, James P; Maxwell, Robert S

    2014-06-23

    Water-vapor-uptake experiments were performed on a silica-filled poly(dimethylsiloxane) (PDMS) network and modeled by using two different approaches. The data was modeled by using established methods and the model parameters were used to predict moisture uptake in a sample. The predictions are reasonably good, but not outstanding; many of the shortcomings of the modeling are discussed. A high-fidelity modeling approach is derived and used to improve the modeling of moisture uptake and diffusion. Our modeling approach captures the physics and kinetics of diffusion and adsorption/desorption, simultaneously. It predicts uptake better than the established method; more importantly, it is also able to predict outgassing. The material used for these studies is a filled-PDMS network; physical interpretations concerning the sorption and diffusion of moisture in this network are discussed.

  20. Microwave impregnation of porous materials with thermal energy storage materials

    DOEpatents

    Benson, David K.; Burrows, Richard W.

    1993-01-01

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  1. Microwave impregnation of porous materials with thermal energy storage materials

    DOEpatents

    Benson, D.K.; Burrows, R.W.

    1993-04-13

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  2. Microwave impregnation of porous materials with thermal energy storage materials

    SciTech Connect

    Benson, D.K.; Burrows, R.W.

    1991-03-13

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent tc the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  3. Microwave impregnation of porous materials with thermal energy storage materials

    SciTech Connect

    Benson, D.K.; Burrows, R.W.

    1992-12-31

    A method for impregnating a porous, non-metallic construction material with a solid phase-change material is described. The phase-change material in finely divided form is spread onto the surface of the porous material, after which the porous material is exposed to microwave energy for a time sufficient to melt the phase-change material. The melted material is spontaneously absorbed into the pores of the porous material. A sealing chemical may also be included with the phase-change material (or applied subsequent to the phase-change material) to seal the surface of the porous material. Fire retardant chemicals may also be included with the phase-change materials. The treated construction materials are better able to absorb thermal energy and exhibit increased heat storage capacity.

  4. Porous Materials Reinforced by Statistically Oriented Fibres

    NASA Astrophysics Data System (ADS)

    Federico, Salvatore; Grillo, Alfio

    2010-09-01

    Hydrated soft biological tissues, such as articular cartilage, are well represented by a porous matrix saturated by a fluid and reinforced by a network of statistically oriented, impermeable collagen fibres. A previously developed homogenisation method for porous fibre-reinforced materials with an isotropic matrix, under small deformations, was capable of correctly predicting some specific aspects of the anisotropy and inhomogeneity of the permeability in the tissue. The aim of this work is to generalise this model to the case of large deformations. This is achieved by means of a rescaled pull-back of the structure tensor describing fibre orientation, and directional averaging methods allowing to account for the statistical distribution of the orientation. The resulting permeability tensor contains an integral term that must be implemented numerically, because of the explicit presence of the deformation in the integrand function.

  5. Thermal evolution and sintering of chondritic planetesimals. III. Modelling the heat conductivity of porous chondrite material

    NASA Astrophysics Data System (ADS)

    Henke, Stephan; Gail, Hans-Peter; Trieloff, Mario

    2016-05-01

    Context. The construction of models for the internal constitution and temporal evolution of large planetesimals, which are the parent bodies of chondrites, requires as accurate as possible information on the heat conductivity of the complex mixture of minerals and iron metal found in chondrites. The few empirical data points on the heat conductivity of chondritic material are severely disturbed by impact-induced microcracks modifying the thermal conductivity. Aims: We attempt to evaluate the heat conductivity of chondritic material with theoretical methods. Methods: We derived the average heat conductivity of a multi-component mineral mixture and granular medium from the heat conductivities of its mixture components. We numerically generated random mixtures of solids with chondritic composition and packings of spheres. We solved the heat conduction equation in high spatial resolution for a test cube filled with such matter. We derived the heat conductivity of the mixture from the calculated heat flux through the cube. Results: For H and L chondrites, our results are in accord with empirical thermal conductivity at zero porosity. However, the porosity dependence of heat conductivity of granular material built from chondrules and matrix is at odds with measurements for chondrites, while our calculations are consistent with data for compacted sandstone. The discrepancy is traced back to subsequent shock modification of the currently available meteoritic material resulting from impacts on the parent body over the last 4.5 Ga. This causes a structure of void space made of fractures/cracks, which lowers the thermal conductivity of the medium and acts as a barrier to heat transfer. This structure is different from the structure that probably exists in the pristine material where voids are represented by pores rather than fractures. The results obtained for the heat conductivity of the pristine material are used for calculating models for the evolution of the H chondrite

  6. Interface shear strength and fracture behaviour of porous glass-fibre-reinforced composite implant and bone model material.

    PubMed

    Nganga, Sara; Ylä-Soininmäki, Anne; Lassila, Lippo V J; Vallittu, Pekka K

    2011-11-01

    Glass-fibre-reinforced composites (FRCs) are under current investigation to serve as durable bone substitute materials in load-bearing orthopaedic implants and bone implants in the head and neck area. The present form of biocompatible FRCs consist of non-woven E-glass-fibre tissues impregnated with varying amounts of a non-resorbable photopolymerisable bifunctional polymer resin with equal portions of both bis-phenyl-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). FRCs with a total porosity of 10-70 vol% were prepared, more than 90 vol% of which being functional (open pores), and the rest closed. The pore sizes were greater than 100 μm. In the present study, the push-out test was chosen to analyse the shear strength of the interface between mechanically interlocked gypsum and a porous FRC implant structure. Gypsum was used as a substitute material for natural bone. The simulative in vitro experiments revealed a significant rise of push-out forces to the twofold level of 1147 ± 271 N for an increase in total FRC porosity of 43%. Pins, intended to model the initial mechanical implant fixation, did not affect the measured shear strength of the gypsum-FRC interface, but led to slightly more cohesive fracture modes. Fractures always occurred inside the gypsum, it having lower compressive strength than the porous FRC structures. Therefore, the largest loads were restricted by the brittleness of the gypsum. Increases of the FRC implant porosity tended to lead to more cohesive fracture modes and higher interfacial fracture toughness. Statistical differences were confirmed using the Kruskal-Wallis test. The differences between the modelled configuration showing gypsum penetration into all open pores and the real clinical situation with gradual bone ingrowth has to be considered. PMID:22098879

  7. Interface shear strength and fracture behaviour of porous glass-fibre-reinforced composite implant and bone model material.

    PubMed

    Nganga, Sara; Ylä-Soininmäki, Anne; Lassila, Lippo V J; Vallittu, Pekka K

    2011-11-01

    Glass-fibre-reinforced composites (FRCs) are under current investigation to serve as durable bone substitute materials in load-bearing orthopaedic implants and bone implants in the head and neck area. The present form of biocompatible FRCs consist of non-woven E-glass-fibre tissues impregnated with varying amounts of a non-resorbable photopolymerisable bifunctional polymer resin with equal portions of both bis-phenyl-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). FRCs with a total porosity of 10-70 vol% were prepared, more than 90 vol% of which being functional (open pores), and the rest closed. The pore sizes were greater than 100 μm. In the present study, the push-out test was chosen to analyse the shear strength of the interface between mechanically interlocked gypsum and a porous FRC implant structure. Gypsum was used as a substitute material for natural bone. The simulative in vitro experiments revealed a significant rise of push-out forces to the twofold level of 1147 ± 271 N for an increase in total FRC porosity of 43%. Pins, intended to model the initial mechanical implant fixation, did not affect the measured shear strength of the gypsum-FRC interface, but led to slightly more cohesive fracture modes. Fractures always occurred inside the gypsum, it having lower compressive strength than the porous FRC structures. Therefore, the largest loads were restricted by the brittleness of the gypsum. Increases of the FRC implant porosity tended to lead to more cohesive fracture modes and higher interfacial fracture toughness. Statistical differences were confirmed using the Kruskal-Wallis test. The differences between the modelled configuration showing gypsum penetration into all open pores and the real clinical situation with gradual bone ingrowth has to be considered.

  8. Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework

    PubMed Central

    Fletcher, Rachel E.; Wells, Stephen A.; Leung, Ka Ming; Edwards, Peter P.; Sartbaeva, Asel

    2015-01-01

    Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves – as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si—O—Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the ‘rigid unit mode’ (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the ‘flexibility window’ phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework. PMID:26634720

  9. Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework.

    PubMed

    Fletcher, Rachel E; Wells, Stephen A; Leung, Ka Ming; Edwards, Peter P; Sartbaeva, Asel

    2015-12-01

    Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves - as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si-O-Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the `rigid unit mode' (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the `flexibility window' phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework.

  10. Ordered porous materials for emerging applications.

    PubMed

    Davis, Mark E

    2002-06-20

    "Space--the final frontier." This preamble to a well-known television series captures the challenge encountered not only in space travel adventures, but also in the field of porous materials, which aims to control the size, shape and uniformity of the porous space and the atoms and molecules that define it. The past decade has seen significant advances in the ability to fabricate new porous solids with ordered structures from a wide range of different materials. This has resulted in materials with unusual properties and broadened their application range beyond the traditional use as catalysts and adsorbents. In fact, porous materials now seem set to contribute to developments in areas ranging from microelectronics to medical diagnosis.

  11. Methane storage in advanced porous materials.

    PubMed

    Makal, Trevor A; Li, Jian-Rong; Lu, Weigang; Zhou, Hong-Cai

    2012-12-01

    The need for alternative fuels is greater now than ever before. With considerable sources available and low pollution factor, methane is a natural choice as petroleum replacement in cars and other mobile applications. However, efficient storage methods are still lacking to implement the application of methane in the automotive industry. Advanced porous materials, metal-organic frameworks and porous organic polymers, have received considerable attention in sorptive storage applications owing to their exceptionally high surface areas and chemically-tunable structures. In this critical review we provide an overview of the current status of the application of these two types of advanced porous materials in the storage of methane. Examples of materials exhibiting high methane storage capacities are analyzed and methods for increasing the applicability of these advanced porous materials in methane storage technologies described.

  12. A modal-based reduction method for sound absorbing porous materials in poro-acoustic finite element models.

    PubMed

    Rumpler, Romain; Deü, Jean-François; Göransson, Peter

    2012-11-01

    Structural-acoustic finite element models including three-dimensional (3D) modeling of porous media are generally computationally costly. While being the most commonly used predictive tool in the context of noise reduction applications, efficient solution strategies are required. In this work, an original modal reduction technique, involving real-valued modes computed from a classical eigenvalue solver is proposed to reduce the size of the problem associated with the porous media. In the form presented in this contribution, the method is suited for homogeneous porous layers. It is validated on a 1D poro-acoustic academic problem and tested for its performance on a 3D application, using a subdomain decomposition strategy. The performance of the proposed method is estimated in terms of degrees of freedom downsizing, computational time enhancement, as well as matrix sparsity of the reduced system.

  13. Large Deformations of a Soft Porous Material

    NASA Astrophysics Data System (ADS)

    MacMinn, Christopher W.; Dufresne, Eric R.; Wettlaufer, John S.

    2016-04-01

    Compressing a porous material will decrease the volume of the pore space, driving fluid out. Similarly, injecting fluid into a porous material can expand the pore space, distorting the solid skeleton. This poromechanical coupling has applications ranging from cell and tissue mechanics to geomechanics and hydrogeology. The classical theory of linear poroelasticity captures this coupling by combining Darcy's law with Terzaghi's effective stress and linear elasticity in a linearized kinematic framework. Linear poroelasticity is a good model for very small deformations, but it becomes increasingly inappropriate for moderate to large deformations, which are common in the context of phenomena such as swelling and damage, and for soft materials such as gels and tissues. The well-known theory of large-deformation poroelasticity combines Darcy's law with Terzaghi's effective stress and nonlinear elasticity in a rigorous kinematic framework. This theory has been used extensively in biomechanics to model large elastic deformations in soft tissues and in geomechanics to model large elastoplastic deformations in soils. Here, we first provide an overview and discussion of this theory with an emphasis on the physics of poromechanical coupling. We present the large-deformation theory in an Eulerian framework to minimize the mathematical complexity, and we show how this nonlinear theory simplifies to linear poroelasticity under the assumption of small strain. We then compare the predictions of linear poroelasticity with those of large-deformation poroelasticity in the context of two uniaxial model problems: fluid outflow driven by an applied mechanical load (the consolidation problem) and compression driven by a steady fluid throughflow. We explore the steady and dynamical errors associated with the linear model in both situations, as well as the impact of introducing a deformation-dependent permeability. We show that the error in linear poroelasticity is due primarily to kinematic

  14. Magnetic and porous molecule-based materials.

    PubMed

    Roques, Nans; Mugnaini, Veronica; Veciana, Jaume

    2010-01-01

    In this chapter, we give an overview of the recent state-of-the-art research of porous and magnetic molecule-based materials. The subject is introduced by a section devoted to the fundamentals of magnetism in molecular magnets, with special attention to the design strategies to prepare molecular magnetic materials. We will then focus on the two main families of materials combining porosity and magnetism: the purely organic and the metal-organic porous magnetic materials. For both families, a selection of the most representative examples has been made. A complete section is devoted to magnetic and porous materials with flexible frameworks, an area of emerging importance in this field, because of their wide range of applications. Finally, we conclude with a brief overview on the most recent approaches for the future development of these materials.

  15. Porous polymeric materials for hydrogen storage

    DOEpatents

    Yu, Luping; Liu, Di-Jia; Yuan, Shengwen; Yang, Junbing

    2013-04-02

    A porous polymer, poly-9,9'-spirobifluorene and its derivatives for storage of H.sub.2 are prepared through a chemical synthesis method. The porous polymers have high specific surface area and narrow pore size distribution. Hydrogen uptake measurements conducted for these polymers determined a higher hydrogen storage capacity at the ambient temperature over that of the benchmark materials. The method of preparing such polymers, includes oxidatively activating solids by CO.sub.2/steam oxidation and supercritical water treatment.

  16. Determination of connectivity in porous materials.

    PubMed

    Caccianotti, L; Lucchelli, E; Ramello, S; Spanò, G

    2012-12-01

    A method of practical use was set up to determine the connectivity in a porous material, modelling the physical system as a lattice, whose coordination number is assumed to be an index of connectivity itself. This task was approached through the theory of percolation and input data were provided by two different experimental techniques, that is, adsorption/desorption of nitrogen and mercury porosimetry. The overall procedure is based on the calculation of probability f(P) of occupation of the porous channels and of probability F(P) of percolation. In the framework of the above--mentioned lattice model, the average coordination number Z is calculated through the best fitting of a universal curve to the values found for F(P) and f(P), adopting as fitting parameter the ratio L between the characteristic linear dimension of the whole lattice and the characteristic linear dimension of each of its cells. The procedure described was implemented through a numerical code and applied to three commercial alumina. A simple empirical relationship was found between Z and the percolation threshold, showing an excellent coefficient of statistical correlation. The three products proved different in connectivity, allowing subtle distinctions from each other, despite their hysteresis cycles in the adsorption/desorption process appeared quite similar from a qualitative standpoint. PMID:23447967

  17. Modelling parallel assemblies of porous materials using the equivalent circuit method.

    PubMed

    Pieren, Reto; Heutschi, Kurt

    2015-02-01

    Recently, the accuracy of the parallel transfer matrix method (P-TMM) and the admittance sum method (ASM) in the prediction of the absorption properties of parallel assemblies of materials was investigated [Verdière, Panneton, Elkoun, Dupont, and Leclaire, J. Acoust. Soc. Am. 136, EL90-EL95 (2014)]. It was demonstrated that P-TMM is more versatile than ASM, as a larger variety of different backing configurations can be handled. Here it will be shown that the same universality is offered by the equivalent circuit method.

  18. Experimental validation of a combined electromagnetic and thermal model for a microwave drying of capillary porous materials inside a rectangular wave guide (effects of irradiation time, particle sizes and initial moisture content).

    PubMed

    Ratanadecho, P; Aoki, K; Akahori, M

    2002-01-01

    In this paper, the experimental validation of a combined electromagnetic and thermal model for a microwave drying of capillary porous materials inside a rectangular wave guide is presented. The effects of the irradiation time, particle sizes and the variation of initial moisture content on the microwave drying kinetics are clarified in detail, considering the interference between incident and reflected waves in the capillary porous materials. The established model has allowed us to determine the space-time evolution of electric field, temperature and moisture content within capillary porous materials during microwave drying process.

  19. Macroscopic strain potentials in nonlinear porous materials

    NASA Astrophysics Data System (ADS)

    Yi, Liu; Zhuping, Huang

    2003-02-01

    By taking a hollow sphere as a representative volume element (RVE), the macroscopic strain potentials of porous materials with power-law incompressible matrix are studied in this paper. According to the principles of the minimum potential energy in nonlinear elasticity and the variational procedure, static admissible stress fields and kinematic admissible displacement fields are constructed, and hence the upper and the lower bounds of the macroscopic strain potential are obtained. The bounds given in the present paper differ so slightly that they both provide perfect approximations of the exact strain potential of the studied porous materials. It is also found that the upper bound proposed by previous authors is much higher than the present one, and the lower bounds given by Cocks is much lower. Moreover, the present calculation is also compared with the variational lower bound of Ponte Castañeda for statistically isotropic porous materials. Finally, the validity of the hollow spherical RVE for the studied nonlinear porous material is discussed by the difference between the present numerical results and the Cocks bound.

  20. Porous polymeric materials for hydrogen storage

    DOEpatents

    Yu, Luping; Liu, Di-Jia; Yuan, Shengwen; Yang, Junbing

    2011-12-13

    Porous polymers, tribenzohexazatriphenylene, poly-9,9'-spirobifluorene, poly-tetraphenyl methane and their derivatives for storage of H.sub.2 prepared through a chemical synthesis method. The porous polymers have high specific surface area and narrow pore size distribution. Hydrogen uptake measurements conducted for these polymers determined a higher hydrogen storage capacity at the ambient temperature over that of the benchmark materials. The method of preparing such polymers, includes oxidatively activating solids by CO.sub.2/steam oxidation and supercritical water treatment.

  1. An adaptable peptide-based porous material.

    PubMed

    Rabone, J; Yue, Y-F; Chong, S Y; Stylianou, K C; Bacsa, J; Bradshaw, D; Darling, G R; Berry, N G; Khimyak, Y Z; Ganin, A Y; Wiper, P; Claridge, J B; Rosseinsky, M J

    2010-08-27

    Porous materials find widespread application in storage, separation, and catalytic technologies. We report a crystalline porous solid with adaptable porosity, in which a simple dipeptide linker is arranged in a regular array by coordination to metal centers. Experiments reinforced by molecular dynamics simulations showed that low-energy torsions and displacements of the peptides enabled the available pore volume to evolve smoothly from zero as the guest loading increased. The observed cooperative feedback in sorption isotherms resembled the response of proteins undergoing conformational selection, suggesting an energy landscape similar to that required for protein folding. The flexible peptide linker was shown to play the pivotal role in changing the pore conformation.

  2. Porous graphene materials for water remediation.

    PubMed

    Niu, Zhiqiang; Liu, Lili; Zhang, Li; Chen, Xiaodong

    2014-09-10

    Water remediation has been a critical issue over the past decades due to the expansion of wastewater discharge to the environment. Currently, a variety of functional materials have been successfully prepared for water remediation applications. Among them, graphene is an attractive candidate due to its high specific surface area, tunable surface behavior, and high strength. This Concept paper summarizes the design strategy of porous graphene materials and their applications in water remediation, such as the cleanup of oil, removal of heavy metal ions, and elimination of water soluble organic contaminants. The progress made so far will guide further development in structure design strategy of porous materials based on graphene and exploration of such materials in environmental remediation.

  3. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2003-12-23

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  4. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2002-01-01

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  5. Filter casting nanoscale porous materials

    DOEpatents

    Hayes, Joel Ryan; Nyce, Gregory Walker; Kuntz, Joshua David

    2012-07-24

    A method of producing nanoporous material includes the steps of providing a liquid, providing nanoparticles, producing a slurry of the liquid and the nanoparticles, removing the liquid from the slurry, and producing a monolith.

  6. Filter casting nanoscale porous materials

    DOEpatents

    Hayes, Joel Ryan; Nyce, Gregory Walker; Kuntz, Jushua David

    2013-12-10

    A method of producing nanoporous material includes the steps of providing a liquid, providing nanoparticles, producing a slurry of the liquid and the nanoparticles, removing the liquid from the slurry, and producing monolith.

  7. Activation of porous MOF materials

    SciTech Connect

    Hupp, Joseph T; Farha, Omar K

    2013-04-23

    A method for the treatment of solvent-containing MOF material to increase its internal surface area involves introducing a liquid into the MOF in which liquid the solvent is miscible, subjecting the MOF to supercritical conditions for a time to form supercritical fluid, and releasing the supercritical conditions to remove the supercritical fluid from the MOF. Prior to introducing the liquid into the MOF, occluded reaction solvent, such as DEF or DMF, in the MOF can be exchanged for the miscible solvent.

  8. Activation of porous MOF materials

    SciTech Connect

    Hupp, Joseph T; Farha, Omar K

    2014-04-01

    A method for the treatment of solvent-containing MOF material to increase its internal surface area involves introducing a liquid into the MOF in which liquid the solvent is miscible, subjecting the MOF to supercritical conditions for a time to form supercritical fluid, and releasing the supercritical conditions to remove the supercritcal fluid from the MOF. Prior to introducing the liquid into the MOF, occluded reaction solvent, such as DEF or DMF, in the MOF can be exchanged for the miscible solvent.

  9. Dynamic magnetic compaction of porous materials

    SciTech Connect

    1998-10-29

    IAP Research began development of the Dynamic Magnetic Compaction (DMC) process three years before the CRADA was established. IAP Research had experimentally demonstrated the feasibility of the process, and conducted a basic market survey. IAP identified and opened discussions with industrial partners and established the basic commercial cost structure. The purpose of this CRADA project was to predict and verify optimum pressure vs. time history for the compaction of porous copper and tungsten. LLNL modeled the rapid compaction of powdered material from an initial density of about 30% theoretical maximum to more than 90% theoretical maximum. The compaction simulations were benchmarked against existing data and new data was acquired by IAP Research. The modeling was used to perform parameter studies on the pressure loading time history, initial porosity and temperature. LLNL ran simulations using codes CALE or NITO and compared the simulations with published compaction data and equation of state (EOS) data. This project did not involve the development or modification of software code. CALE and NITO were existing software programs at LLNL. No modification of these programs occurred within the scope of the CRADA effort.

  10. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1991-01-01

    An empirical extension of the two-fluid model is used to characterize He II flow through porous materials. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about +/- 20 percent.

  11. Porous material for protection from electromagnetic radiation

    SciTech Connect

    Kazmina, Olga E-mail: bdushkina89@mail.ru; Dushkina, Maria E-mail: bdushkina89@mail.ru; Suslyaev, Valentin; Semukhin, Boris

    2014-11-14

    It is shown that the porous glass crystalline material obtained by a low temperature technology can be used not only for thermal insulation, but also for lining of rooms as protective screens decreasing harmful effect of electromagnetic radiation as well as to establish acoustic chambers and rooms with a low level of electromagnetic background. The material interacts with electromagnetic radiation by the most effective way in a high frequency field (above 100 GHz). At the frequency of 260 GHz the value of the transmission coefficient decreases approximately in a factor times in comparison with foam glass.

  12. Characterization of porous media and refractory materials

    NASA Astrophysics Data System (ADS)

    Chen, Xin

    Because of its unique advantages on energy savings and casting complex shapes, Lost Foam Casting (LFC) has been widely used as a replacement to the conventional techniques (sand and investment castings). In order to continuously improve the quality of the Lost Foam Casting process for reducing scrap rate and increasing energy savings, the US Department of Energy sponsored the present study to develop new characterization techniques for enhancing the understanding of the fundamental properties of the refractory materials used in the Lost Foam Casting process. In this study, new techniques are proposed to characterize the refractory materials' properties such as particle size, particle shape, rheological behavior, transport properties, microstructure, thickness, as well as packing properties. The microstructure information obtained from the proposed technique is found to be well correlated with the transport properties of the porous coating materials. A procedure using a three-dimensional computational fluid dynamics code is developed to simulate experimental gas flow data for solving complex boundary value problems. In this study, the effects of dilution and dispersion on the coating properties such as transport properties and microstructures are also investigated. Results show that the dilution and dispersion have opposing influences on the pore size and transport properties. In addition, this study also includes another part of the permeability system, the un-bonded granular materials used in the Lost Foam Casting process. A three-dimensional (3-D) computer program is developed to simulate the packing behavior of granular materials at a loose state using a "drop and roll" method. This study provides a systematic characterization of the LFC refractory coating slurries, dried refractory coating, and the granular media. This study also demonstrates the application of proposed characterization techniques for coating quality control using statistical process control

  13. Analysis of acoustic damping in duct terminated by porous absorption materials based on analytical models and finite element simulations

    NASA Astrophysics Data System (ADS)

    Guan Qiming

    Acoustic absorption materials are widely used today to dampen and attenuate the noises which exist almost everywhere and have adverse impact upon daily life of human beings. In order to evaluate the absorption performance of such materials, it is necessary to experimentally determine acoustic properties of absorption materials. Two experimental methods, one is Standing Wave Ratio Method and the other is Transfer-Function Method, which also totally called as Impedance Tube Method, are based on two analytical models people have used to evaluate and validate the data obtained from acoustic impedance analyzers. This thesis first reviews the existing analytical models of previous two experimental methods in the literature by looking at their analytical models, respectively. Then a new analytical model is developed is developed based on One-Microphone Method and Three-Microphone Method, which are two novel experimental approaches. Comparisons are made among these analytical models, and their advantages and disadvantages are discussed.

  14. Mechanical properties of a porous mullite material

    NASA Technical Reports Server (NTRS)

    Viens, Michael J.

    1991-01-01

    Modulus of rupture specimens were used to determine crack growth parameters of a porous mullite material. Strength testing was performed in ambient and moist environments. The power law crack growth rate parameters n and 1n B in 50 percent relative humidity were found to be 44.98 and 0.94, respectively. The inert strength, fracture toughness, and elastic modulus were also determined and found to be 19 MPa, 055 MPa(m) exp 1/2, and 11.6 GPa, respectively.

  15. Acoustical properties of highly porous fibrous materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1979-01-01

    Highly porous, fibrous bulk sound absorbing materials are studied with a view toward understanding their acoustical properties and performance in a wide variety of applications including liners of flow ducts. The basis and criteria for decoupling of acoustic waves in the pores of the frame and compressional waves in the frame structure are established. The equations of motion are recast in a form that elucidates the coupling mechanisms. The normal incidence surface impedance and absorption coefficient of two types of Kevlar 29 and an open celled foam material are studied. Experimental values and theoretical results are brought into agreement when the structure factor is selected to provide a fit to the experimental data. A parametric procedure for achieving that fit is established. Both a bulk material quality factor and a high frequency impedance level are required to characterize the real and imaginary part of the surface impedance and absorption coefficient. A derivation of the concepts of equivalent density and dynamic resistance is presented.

  16. Wire Cloth as Porous Material for Transpiration-cooled Walls

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Kinsler, Martin R; Cochran, Reeves B

    1951-01-01

    The permeability characteristics and tensile strength of a porous material developed from stainless-steel corduroy wire cloth for use in transpiration-cooled walls where the primary stresses are in one direction were investigated. The results of this investigation are presented and compared with similar results obtained with porous sintered metal compacts. A much wider range of permeabilities is obtainable with the wire cloth than with the porous metal compacts considered and the ultimate tensile strength in the direction of the primary stresses for porous materials produced from three mesh sizes of wire cloth are from two to three times the ultimate tensile strengths of the porous metal compacts.

  17. Molecular Rotors Built in Porous Materials.

    PubMed

    Comotti, Angiolina; Bracco, Silvia; Sozzani, Piero

    2016-09-20

    Molecules and materials can show dynamic structures in which the dominant mechanism is rotary motion. The single mobile elements are defined as "molecular rotors" and exhibit special properties (compared with their static counterparts), being able in perspective to greatly modulate the dielectric response and form the basis for molecular motors that are designed with the idea of making molecules perform a useful mechanical function. The construction of ordered rotary elements into a solid is a necessary feature for such design, because it enables the alignment of rotors and the fine-tuning of their steric and dipolar interactions. Crystal surfaces or bulk crystals are the most suitable to adapt rotors in 2D or 3D arrangements and engineer juxtaposition of the rotors in an ordered way. Nevertheless, it is only in recent times that materials showing porosity and remarkably low density have undergone tremendous development. The characteristics of large free volume combine well with the virtually unhindered motion of the molecular rotors built into their structure. Indeed, the molecular rotors are used as struts in porous covalent and supramolecular architectures, spanning both hybrid and fully organic materials. The modularity of the approach renders possible a variety of rotor geometrical arrangements in both robust frameworks stable up to 850 K and self-assembled molecular materials. A nanosecond (fast dynamics) motional regime can be achieved at temperatures lower than 240 K, enabling rotor arrays operating in the solid state even at low temperatures. Furthermore, in nanoporous materials, molecular rotors can interact with the diffusing chemical species, be they liquids, vapors, or gases. Through this chemical intervention, rotor speed can be modulated at will, enabling a new generation of rotor-containing materials sensitive to guests. In principle, an applied electric field can be the stimulus for chemical release from porous materials. The effort needed to

  18. Molecular Rotors Built in Porous Materials.

    PubMed

    Comotti, Angiolina; Bracco, Silvia; Sozzani, Piero

    2016-09-20

    Molecules and materials can show dynamic structures in which the dominant mechanism is rotary motion. The single mobile elements are defined as "molecular rotors" and exhibit special properties (compared with their static counterparts), being able in perspective to greatly modulate the dielectric response and form the basis for molecular motors that are designed with the idea of making molecules perform a useful mechanical function. The construction of ordered rotary elements into a solid is a necessary feature for such design, because it enables the alignment of rotors and the fine-tuning of their steric and dipolar interactions. Crystal surfaces or bulk crystals are the most suitable to adapt rotors in 2D or 3D arrangements and engineer juxtaposition of the rotors in an ordered way. Nevertheless, it is only in recent times that materials showing porosity and remarkably low density have undergone tremendous development. The characteristics of large free volume combine well with the virtually unhindered motion of the molecular rotors built into their structure. Indeed, the molecular rotors are used as struts in porous covalent and supramolecular architectures, spanning both hybrid and fully organic materials. The modularity of the approach renders possible a variety of rotor geometrical arrangements in both robust frameworks stable up to 850 K and self-assembled molecular materials. A nanosecond (fast dynamics) motional regime can be achieved at temperatures lower than 240 K, enabling rotor arrays operating in the solid state even at low temperatures. Furthermore, in nanoporous materials, molecular rotors can interact with the diffusing chemical species, be they liquids, vapors, or gases. Through this chemical intervention, rotor speed can be modulated at will, enabling a new generation of rotor-containing materials sensitive to guests. In principle, an applied electric field can be the stimulus for chemical release from porous materials. The effort needed to

  19. [Porous tarflen as a possible membrane material for membrane blood oxygenators. III. O2 and CO2 transport in the system modeling an artificial lung].

    PubMed

    Krajewska, B; Leszko, M

    1986-01-01

    Diffusional examinations of tarflen porous barriers of home make and porous teflon membranes of American make as well as selected nonporous membranes were performed in a system: O2--barrier--water + CO2, in order to evaluate the influence of aqueous phase on O2 and CO2 transport rate through barriers listed above. It was found that the effectiveness of O2 and CO2 exchange through the porous barriers in the examined system is controlled by O2 transport through the boundary water layer in contradistinction to the nonporous membranes. The effect of reduction of O2 and CO2 transport through the porous barriers, caused by the aqueous phase was noted. The higher the water pressure on a barrier the larger the effect is. Considerable water permeability of porous barriers as compared to that of nonporous membranes was stated. The results of the performed examinations indicate the usefulness of porous tarflen materials as a membrane material in membrane oxygenators of blood.

  20. Acoustics of porous materials with partially opened porosity.

    PubMed

    Leclaire, P; Dupont, T; Panneton, R

    2013-12-01

    A theoretical and experimental study of the acoustic properties of porous materials containing dead-end (or partially opened) porosity was recently proposed by Dupont, Leclaire, Sicot, Gong, and Panneton [J. Appl. Phys. 110, 094903 (2011)]. The present article provides a description of partially opened porosity systems and their numerous potential applications in the general context of the study of porous materials, the classical models describing them, and the characterization techniques. It is shown that the dead-end pore effect can be treated independently and that the description of this effect can be associated with any acoustic model of porous media. Different theoretical developments describing the dead-end porosity effect are proposed. In particular, a model involving the average effective length of the dead-end pores is presented. It is also shown that if the dead-end effect can be treated separately, the transfer matrix method is particularly well suited for the description of single or multilayer systems with dead-end porosity.

  1. Siloxane treatment by adsorption into porous materials.

    PubMed

    Ricaurte Ortega, D; Subrenat, A

    2009-09-01

    Siloxanes are widely used in different applications: health care, dry cleaning, household products, paints and coatings, paper, personal care, for example. This explains their prevalence in the environment. Because of their volatile nature, most of the time they are dispersed in the atmosphere, but they can also be present in the slurry from landfills. During anaerobic digestion, when the temperature goes up to 60 degrees C, siloxanes are volatilized, forming part of the biogas. Operational problems using biogas to produce energy, heat and hydrogen have been identified. At high temperatures the siloxanes are transformed into silicate dioxide (commonly called sand transmission). These white deposits may adhere to metal or catalytic substrate surfaces, seriously reducing equipment efficiency, and this can be a reason for changing equipment warranties. Consequently, elimination of siloxanes has become very important. Unfortunately, relatively little information can be found on this subject. Nevertheless some authors have described different analytical methods for siloxane quantification, and recent studies have looked at the presence of siloxanes in landfills and the restriction on the energy recovery equipment using the biogas produced. The growing consumption of siloxanes and silicones in industrial processes consequently increase their prevalence in the environment, hampering the use of biogas as a source of 'green energy'. Therefore, the principal focus of this study is the treatment of siloxanes. Their elimination was carried out using an adsorption process with four different porous materials: activated carbon cloths (ACC), granular activated carbon (GAC), zeolite and silica gel. Two representative siloxane compounds were used in this study, hexamethyldisiloxane (L2) and octamethylcyclotetrasiloxane (D4). Adsorption kinetics and isotherms in batch reactors were performed. It was observed that the mass transfer into the porous material was more rapid for the

  2. Fabricating porous materials using interpenetrating inorganic-organic composite gels

    DOEpatents

    Seo, Dong-Kyun; Volosin, Alex

    2016-06-14

    Porous materials are fabricated using interpenetrating inorganic-organic composite gels. A mixture or precursor solution including an inorganic gel precursor, an organic polymer gel precursor, and a solvent is treated to form an inorganic wet gel including the organic polymer gel precursor and the solvent. The inorganic wet gel is then treated to form a composite wet gel including an organic polymer network in the body of the inorganic wet gel, producing an interpenetrating inorganic-organic composite gel. The composite wet gel is dried to form a composite material including the organic polymer network and an inorganic network component. The composite material can be treated further to form a porous composite material, a porous polymer or polymer composite, a porous metal oxide, and other porous materials.

  3. Dissolution of a surfactant-containing active porous material.

    PubMed

    Brielles, Nelly; Chantraine, Florence; Viana, Marylène; Chulia, Dominique; Branlard, Paul; Rubinstenn, Gilles; Lequeux, François; Mondain-Monval, Olivier

    2008-12-15

    We have studied the imbibition and dissolution of a porous material in two separate scenarios: (1) when the porous material contains a surfactant powder and (2) when the porous material is dissolved in a surfactant solution. We show that the dissolution kinetics in both scenarios is significantly affected by the presence of the surfactant and results in an increase in the characteristic imbibition time of the porous material, which can be well understood in the framework of the classical law of capillarity. Slowing of the imbibition kinetics was found to be affected by a modification of the liquid wetting properties, but is also affected by a variation in the solubility of the porous material in the presence of the surfactant. Furthermore, there is a depletion effect of the surfactant inside the rising liquid, which is in good agreement with previous work and theoretical predictions.

  4. An improvement of Gurson-type models of porous materials by using Eshelby-like trial velocity fields

    NASA Astrophysics Data System (ADS)

    Monchiet, Vincent; Charkaluk, Eric; Kondo, Djimedo

    2007-01-01

    New expressions of the macroscopic criteria of perfectly plastic rigid matrix containing prolate and oblate cavities are presented. The proposed approach, derived in the framework of limit analysis, consists in the consideration of Eshelby-like trial velocity fields for the determination of the macroscopic dissipation. It is shown that the obtained results significantly improve existing criteria for ductile porous media. Moreover, for low stress triaxialities, these new results also agree perfectly with the (nonlinear) Hashin-Shtrikhman bound established by Ponte-Castañeda and Suquet. To cite this article: V. Monchiet et al., C. R. Mecanique 335 (2007).

  5. Porous silicon as a substrate material for potentiometric biosensors

    NASA Astrophysics Data System (ADS)

    Thust, Marion; Schöning, M. J.; Frohnhoff, S.; Arens-Fischer, R.; Kordos, P.; Lüth, H.

    1996-01-01

    For the first time porous silicon has been investigated for the purpose of application as a substrate material for potentiometric biosensors operating in aqueous solutions. Porous silicon was prepared from differently doped silicon substrates by a standard anodic etching process. After oxidation, penicillinase, an enzyme sensitive to penicillin, was bound to the porous structure by physical adsorption. To characterize the electrochemical properties of the so build up penicillin biosensor, capacitance - voltage (C - V) measurements were performed on these field-effect structures.

  6. Studies of acoustical properties of bulk porous flexible materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1984-01-01

    Acoustic prediction and measurement of bulk porous materials with flexible frames is investigated. The acoustic properties of Kevlar 29 are examined. Various acoustic tests are employed to determine impedance, sound wave propagation, and wave pressure equations for the highly porous fiber composites. The derivation of design equations and future research goals are included.

  7. METHOD OF IMPREGNATING A POROUS MATERIAL

    DOEpatents

    Steele, G.N.

    1960-06-01

    A method of impregnating a porous body with an inorganic uranium- containing salt is outlined and comprises dissolving a water-soluble uranium- containing salt in water; saturating the intercommunicating pores of the porous body with the salt solution; infusing ammonia gas into the intercommunicating pores of the body, the ammonia gas in water chemically reacting with the water- soluble uranium-containing salt in the water solvent to form a nonwater-soluble uranium-containing precipitant; and evaporating the volatile unprecipitated products from the intercommunicating pores whereby the uranium-containing precipitate is uniformly distributed in the intercommunicating peres of the porous body.

  8. Characterizing He 2 flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Vansciver, Steven W.; Maddocks, J. R.

    1991-01-01

    Proposed space applications, such as the cooling of infrared and x ray telescopes, have generated substantial interest in the behavior of He(2) flowing in porous materials. For design purposes, classical porous media correlations and room temperature data are often used to obtain order of magnitude estimates of expected pressure drops, while the attendant temperature differences are either ignored or estimated using smooth tube correlations. A more accurate alternative to this procedure is suggested by an empirical extension of the two fluid models. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He(2) flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about + or - 20 percent.

  9. Characterizing He II flow through porous materials using counterflow data

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R., Jr.; Vansciver, Steven W.

    1990-01-01

    Proposed space applications, such as the cooling of infrared and x ray telescopes, have generated substantial interest in the behavior of He II flowing in porous materials. For design purposes, classical porous media correlations and room temperature data are often used to obtain order of magnitude estimates of expected pressure drops, while the attendant temperature differences are either ignored or estimated using smooth tube correlations. A more accurate alternative to this procedure is suggested by an empirical extension of the two fluid model. It is shown that four empirical parameters are necessary to describe the pressure and temperature differences induced by He II flow through a porous sample. The three parameters required to determine pressure differences are measured in counterflow and found to compare favorably with those for isothermal flow. The fourth parameter, the Gorter-Mellink constant, differs substantially from smooth tube values. It is concluded that parameter values determined from counterflow can be used to predict pressure and temperature differences in a variety of flows to an accuracy of about + or - 20 pct.

  10. Dynamic mean field theory for lattice gas models of fluids confined in porous materials: Higher order theory based on the Bethe-Peierls and path probability method approximations

    SciTech Connect

    Edison, John R.; Monson, Peter A.

    2014-07-14

    Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved.

  11. Stochastic modeling of filtrate alkalinity in water filtration devices: Transport through micro/nano porous clay based ceramic materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clay and plant materials such as wood are the raw materials used in manufacture of ceramic water filtration devices around the world. A step by step manufacturing procedure which includes initial mixing, molding and sintering is used. The manufactured ceramic filters have numerous pores which help i...

  12. Processing and Modeling of Porous Copper Using Sintering Dissolution Process

    NASA Astrophysics Data System (ADS)

    Salih, Mustafa Abualgasim Abdalhakam

    The growth of porous metal has produced materials with improved properties as compared to non-metals and solid metals. Porous metal can be classified as either open cell or closed cell. Open cell allows a fluid media to pass through it. Closed cell is made up of adjacent sealed pores with shared cell walls. Metal foams offer higher strength to weight ratios, increased impact energy absorption, and a greater tolerance to high temperatures and adverse environmental conditions when compared to bulk materials. Copper and its alloys are examples of these, well known for high strength and good mechanical, thermal and electrical properties. In the present study, the porous Cu was made by a powder metallurgy process, using three different space holders, sodium chloride, sodium carbonate and potassium carbonate. Several different samples have been produced, using different ratios of volume fraction. The densities of the porous metals have been measured and compared to the theoretical density calculated using an equation developed for these foams. The porous structure was determined with the removal of spacer materials through sintering process. The sintering process of each spacer material depends on the melting point of the spacer material. Processing, characterization, and mechanical properties were completed. These tests include density measurements, compression tests, computed tomography (CT) and scanning electron microscopy (SEM). The captured morphological images are utilized to generate the object-oriented finite element (OOF) analysis for the porous copper. Porous copper was formed with porosities in the range of 40-66% with density ranges from 3 to 5.2 g/cm3. A study of two different methods to measure porosity was completed. OOF (Object Oriented Finite Elements) is a desktop software application for studying the relationship between the microstructure of a material and its overall mechanical, dielectric, or thermal properties using finite element models based on

  13. Modeling Dynamic Ductility: An Equation of State for Porous Metals

    SciTech Connect

    Colvin, J

    2007-07-27

    Enhanced heating from shock compression of a porous material can potentially suppress or delay cracking of the material on subsequent expansion. In this paper we quantify the expected enhanced heating in an experiment in which a sector of a thin cylindrical shell is driven from the inside surface by SEMTEX high explosive ({approx}1 {micro}s FWHM pressure pulse with peak pressure {approx}21.5 GPa). We first derive an analytical equation of state (EOS) for porous metals, then discuss the coupling of this EOS with material elastic-plastic response in a 2D hydrocode, and then discuss the modeling of the HE experiment with both fully dense and 10% porous Ta and a Bi/Ta composite. Finally, we compare our modeling with some recent experimental data.

  14. Adsorption and Separation Modeling of Porous Networks

    NASA Astrophysics Data System (ADS)

    Malanoski, Anthony; van Swol, Frank

    2001-03-01

    With the advent of self-assembly techniques has come the potential to tailor materials for adsorption and separation applications. For example, using surfactants as templating agents it is now feasible to finely control both the three-dimensional (3D) porosity as well as the surface chemistry. With an eye on assisting the emerging materials design we have embarked on a program that focuses on modeling adsorption/desorption, reactions and permeation phenomena in such structures. What makes the modeling particularly challenging is the coupling of length scales. The role of the atomic length scale features such as surface reactions and surface structure must be captured as well as the role of the network connectivity and other larger length scales. The latter include the pore shape and length, and the presence of external surfaces. This paper reports on how we employ refineable lattice models to tackle the modeling problems. We use both equilibrium and non-equilibrium Monte Carlo (MC) and 3D density functional theory (DFT) techniques to study the equilibrium and transport behavior in nanostructured porous materials. We will present 1) results of both adsorption/desorption hysteresis in large regular and random networks and 2) the results of using reactive sites in separation membranes, and compare these with experiments.

  15. Predicting Pressure Drop In Porous Materials

    NASA Technical Reports Server (NTRS)

    Lawing, Pierce L.

    1990-01-01

    Theory developed to predict drop in pressure based on drag of individual fibers. Simple correlation method for data also developed. Helps in predicting flow characteristics of many strain-isolation pad (SIP) glow geometries in Shuttle Orbiter tile system. Also helps in predicting venting characteristics of tile assemblies during ascent and leakage of hot gas under tiles during descent. Useful in study of mechanics of flows through fibrous and porous media, and procedures applicable to purged fiberglass insulation, dialysis filters, and other fibrous and porous media.

  16. Molecular simulation of adsorption and transport in hierarchical porous materials.

    PubMed

    Coasne, Benoit; Galarneau, Anne; Gerardin, Corine; Fajula, François; Villemot, François

    2013-06-25

    Adsorption and transport in hierarchical porous solids with micro- (~1 nm) and mesoporosities (>2 nm) are investigated by molecular simulation. Two models of hierarchical solids are considered: microporous materials in which mesopores are carved out (model A) and mesoporous materials in which microporous nanoparticles are inserted (model B). Adsorption isotherms for model A can be described as a linear combination of the adsorption isotherms for pure mesoporous and microporous solids. In contrast, adsorption in model B departs from adsorption in pure microporous and mesoporous solids; the inserted microporous particles act as defects, which help nucleate the liquid phase within the mesopore and shift capillary condensation toward lower pressures. As far as transport under a pressure gradient is concerned, the flux in hierarchical materials consisting of microporous solids in which mesopores are carved out obeys the Navier-Stokes equation so that Darcy's law is verified within the mesopore. Moreover, the flow in such materials is larger than in a single mesopore, due to the transfer between micropores and mesopores. This nonzero velocity at the mesopore surface implies that transport in such hierarchical materials involves slippage at the mesopore surface, although the adsorbate has a strong affinity for the surface. In contrast to model A, flux in model B is smaller than in a single mesopore, as the nanoparticles act as constrictions that hinder transport. By a subtle effect arising from fast transport in the mesopores, the presence of mesopores increases the number of molecules in the microporosity in hierarchical materials and, hence, decreases the flow in the micropores (due to mass conservation). As a result, we do not observe faster diffusion in the micropores of hierarchical materials upon flow but slower diffusion, which increases the contact time between the adsorbate and the surface of the microporosity.

  17. TESTING ANTIMICROBIAL EFFICACY ON POROUS MATERIALS

    EPA Science Inventory

    The efficacy of antimicrobial treatments to eliminate or control biological growth in the indoor environment can easily be tested on nonporous surfaces. However, the testing of antimicrobial efficacy on porous surfaces, such as those found in the indoor environment [i.e., gypsum ...

  18. Attenuation of shock waves propagating through nano-structured porous materials

    NASA Astrophysics Data System (ADS)

    Al-Qananwah, Ahmad K.; Koplik, Joel; Andreopoulos, Yiannis

    2013-07-01

    Porous materials have long been known to be effective in energy absorption and shock wave attenuation. These properties make them attractive in blast mitigation strategies. Nano-structured materials have an even greater potential for blast mitigation because of their high surface-to-volume ratio, a geometric parameter which substantially attenuates shock wave propagation. A molecular dynamics approach was used to explore the effects of this remarkable property on the behavior of traveling shocks impacting on solid materials. The computational setup included a moving piston, a gas region and a target solid wall with and without a porous structure. The gas and porous solid were modeled by Lennard-Jones-like and effective atom potentials, respectively. The shock wave is resolved in space and time and its reflection from a solid wall is gradual, due to the wave's finite thickness, and entails a self-interaction as the reflected wave travels through the incoming incident wave. Cases investigated include a free standing porous structure, a porous structure attached to a wall and porous structures with graded porosity. The effects of pore shape and orientation have been also documented. The results indicate that placing a nano-porous material layer in front of the target wall reduced the stress magnitude and the energy deposited inside the solid by about 30 percent, while at the same time substantially decreasing the loading rate.

  19. Porous materials produced from incineration ash using thermal plasma technology.

    PubMed

    Yang, Sheng-Fu; Chiu, Wen-Tung; Wang, To-Mai; Chen, Ching-Ting; Tzeng, Chin-Ching

    2014-06-01

    This study presents a novel thermal plasma melting technique for neutralizing and recycling municipal solid waste incinerator (MSWI) ash residues. MSWI ash residues were converted into water-quenched vitrified slag using plasma vitrification, which is environmentally benign. Slag is adopted as a raw material in producing porous materials for architectural and decorative applications, eliminating the problem of its disposal. Porous materials are produced using water-quenched vitrified slag with Portland cement and foaming agent. The true density, bulk density, porosity and water absorption ratio of the foamed specimens are studied here by varying the size of the slag particles, the water-to-solid ratio, and the ratio of the weights of the core materials, including the water-quenched vitrified slag and cement. The thermal conductivity and flexural strength of porous panels are also determined. The experimental results show the bulk density and the porosity of the porous materials are 0.9-1.2 g cm(-3) and 50-60%, respectively, and the pore structure has a closed form. The thermal conductivity of the porous material is 0.1946 W m(-1) K(-1). Therefore, the slag composite materials are lightweight and thermal insulators having considerable potential for building applications.

  20. An analytical model for porous single crystals with ellipsoidal voids

    NASA Astrophysics Data System (ADS)

    Mbiakop, A.; Constantinescu, A.; Danas, K.

    2015-11-01

    A rate-(in)dependent constitutive model for porous single crystals with arbitrary crystal anisotropy (e.g., FCC, BCC, HCP, etc.) containing general ellipsoidal voids is developed. The proposed model, denoted as modified variational model (MVAR), is based on the nonlinear variational homogenization method, which makes use of a linear comparison porous material to estimate the response of the nonlinear porous single crystal. Periodic multi-void finite element simulations are used in order to validate the MVAR for a large number of parameters including cubic (FCC, BCC) and hexagonal (HCP) crystal anisotropy, various creep exponents (i.e., nonlinearity), several stress triaxiality ratios, general void shapes and orientations and various porosity levels. The MVAR model, which involves a priori no calibration parameters, is found to be in good agreement with the finite element results for all cases considered in the rate-dependent context. The model is then used in a predictive manner to investigate the complex response of porous single crystals in several cases with strong coupling between the anisotropy of the crystal and the (morphological) anisotropy induced by the shape and orientation of the voids. Finally, a simple way of calibrating the MVAR with just two adjustable parameters is depicted in the rate-independent context so that an excellent agreement with the FE simulation results is obtained. In this last case, this proposed model can be thought as a generalization of the Gurson model in the context of porous single crystals and general ellipsoidal void shapes and orientations.

  1. Migration Mechanism for Atomic Hydrogen in Porous Carbon Materials

    SciTech Connect

    Narayanan, B.; Zhao, Y. F.; Ciobanu, C. V.

    2012-05-14

    To explain the fast kinetics of H in porous carbon, we propose that the migration relies on H hopping from a carbon nanotube (CNT) to another. Using density functional theory, we have found that the barrier for H hopping becomes smaller than that for diffusion along a tube for certain CNT separations, decreasting to less than 0.5 eV for separations of -3.1 {angstrom}. Such significant reduction occurs irrespective of radius, chirality, registry, and orientation of the two CNTs: the diffusion is thus facilitated by the porous nature of the material itself. The mechanism proposed is applicable for any porous carbon-based nanomaterials.

  2. Thermal conductivity and electrical resistivity of porous material

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Fortini, A.

    1971-01-01

    Thermal conductivity and electrical resistivity of porous materials, including 304L stainless steel Rigimesh, 304L stainless steel sintered spherical powders, and OFHC sintered spherical powders at different porosities and temperatures are reported and correlated. It was found that the thermal conductivity and electrical resistivity can be related to the solid material properties and the porosity of the porous matrix regardless of the matrix structure. It was also found that the Wiedermann-Franz-Lorenz relationship is valid for the porous materials under consideration. For high conductivity materials, the Lorenz constant and the lattice component of conductivity depend on the material and are independent of the porosity. For low conductivity, the lattice component depends on the porosity as well.

  3. Constitutive modeling of rate dependence and microinertia effects in porous-plastic materials with multi-sized voids (MSVs)

    NASA Astrophysics Data System (ADS)

    Liu, J. X.; El Sayed, T.

    2013-01-01

    Micro-voids of varying sizes exist in most metals and alloys. Both experiments and numerical studies have demonstrated the critical influence of initial void sizes on void growth. The classical Gurson-Tvergaard-Needleman model summarizes the influence of voids with a single parameter, namely the void-volume fraction, excluding any possible effects of the void-size distribution. We extend our newly proposed model including the multi-sized void (MSV) effect and the void-interaction effect for the capability of working for both moderate and high loading rate cases, where either rate dependence or microinertia becomes considerable or even dominant. Parametric studies show that the MSV-related competitive mechanism among void growth leads to the dependence of the void growth rate on void size, which directly influences the void's contribution to the total energy composition. We finally show that the stress-strain constitutive behavior is also affected by this MSV-related competitive mechanism. The stabilizing effect due to rate sensitivity and microinertia is emphasized.

  4. Filling Porous Microspheres With Magnetic Material

    NASA Technical Reports Server (NTRS)

    Chang, Manchium; Colvin, Michael S.

    1990-01-01

    New process produces magnetic microspheres with controllable sizes, compositions, and properties for use in medical diagnostic tests, biological research, and chemical processes. Paramagnetic microspheres also made with process. Porous plastic microspheres prepared by polymerization of monomer in diluent by cross-linking agent. When diluent removed, it leaves tiny pores throughout polymerized spheres. Size and distribution of pores determined by amount and type of diluent and cross-linking agent.

  5. Advances in monoliths and related porous materials for microfluidics.

    PubMed

    Knob, Radim; Sahore, Vishal; Sonker, Mukul; Woolley, Adam T

    2016-05-01

    In recent years, the use of monolithic porous polymers has seen significant growth. These materials present a highly useful support for various analytical and biochemical applications. Since their introduction, various approaches have been introduced to produce monoliths in a broad range of materials. Simple preparation has enabled their easy implementation in microchannels, extending the range of applications where microfluidics can be successfully utilized. This review summarizes progress regarding monoliths and related porous materials in the field of microfluidics between 2010 and 2015. Recent developments in monolith preparation, solid-phase extraction, separations, and catalysis are critically discussed. Finally, a brief overview of the use of these porous materials for analysis of subcellular and larger structures is given. PMID:27190564

  6. Tissue engineering scaffold material of porous nanohydroxyapatite/polyamide 66.

    PubMed

    Xu, Qian; Lu, Hongyan; Zhang, Jingchao; Lu, Guoyu; Deng, Zhennan; Mo, Anchun

    2010-05-13

    The aim of the study was to investigate a porous nanohydroxyapatite/polyamide 66 (n-HA/PA66) scaffold material that was implanted into muscle and tibiae of 16 New Zealand white rabbits to evaluate the biocompatibility and osteogenesis and osteoinductivity of the materials in vivo. The samples were harvested at 2, 4, 12 and 26 weeks respectively, and subjected to histological analysis. At 2 weeks, the experiment showed that osteogenesis was detected in porous n-HA/PA66 composite and the density of new bone formation was similar to the surrounding host bone at 12 weeks. The study indicated that three-dimensional pore structures could facilitate cell adhesion, differentiation and proliferation, and help with fibrovascular and nerve colonization. In conclusion, porous n-HA/PA66 scaffold material could be a good candidate as a bone substitute material used in clinics due to its excellent histocompatibility, osteoconductivity and osteoinductivity.

  7. Approach to failure in porous granular materials under compression

    NASA Astrophysics Data System (ADS)

    Kun, Ferenc; Varga, Imre; Lennartz-Sassinek, Sabine; Main, Ian G.

    2013-12-01

    We investigate the approach to catastrophic failure in a model porous granular material undergoing uniaxial compression. A discrete element computational model is used to simulate both the microstructure of the material and the complex dynamics and feedbacks involved in local fracturing and the production of crackling noise. Under strain-controlled loading, microcracks initially nucleate in an uncorrelated way all over the sample. As loading proceeds the damage localizes into a narrow damage band inclined at 30∘-45∘ to the load direction. Inside the damage band the material is crushed into a poorly sorted mixture of mainly fine powder hosting some larger fragments. The mass probability density distribution of particles in the damage zone is a power law of exponent 2.1, similar to a value of 1.87 inferred from observations of the length distribution of wear products (gouge) in natural and laboratory faults. Dynamic bursts of radiated energy, analogous to acoustic emissions observed in laboratory experiments on porous sedimentary rocks, are identified as correlated trails or cascades of local ruptures that emerge from the stress redistribution process. As the system approaches macroscopic failure consecutive bursts become progressively more correlated. Their size distribution is also a power law, with an equivalent Gutenberg-Richter b value of 1.22 averaged over the whole test, ranging from 3 to 0.5 at the time of failure, all similar to those observed in laboratory tests on granular sandstone samples. The formation of the damage band itself is marked by a decrease in the average distance between consecutive bursts and an emergent power-law correlation integral of event locations with a correlation dimension of 2.55, also similar to those observed in the laboratory (between 2.75 and 2.25).

  8. Approach to failure in porous granular materials under compression.

    PubMed

    Kun, Ferenc; Varga, Imre; Lennartz-Sassinek, Sabine; Main, Ian G

    2013-12-01

    We investigate the approach to catastrophic failure in a model porous granular material undergoing uniaxial compression. A discrete element computational model is used to simulate both the microstructure of the material and the complex dynamics and feedbacks involved in local fracturing and the production of crackling noise. Under strain-controlled loading, microcracks initially nucleate in an uncorrelated way all over the sample. As loading proceeds the damage localizes into a narrow damage band inclined at 30°-45° to the load direction. Inside the damage band the material is crushed into a poorly sorted mixture of mainly fine powder hosting some larger fragments. The mass probability density distribution of particles in the damage zone is a power law of exponent 2.1, similar to a value of 1.87 inferred from observations of the length distribution of wear products (gouge) in natural and laboratory faults. Dynamic bursts of radiated energy, analogous to acoustic emissions observed in laboratory experiments on porous sedimentary rocks, are identified as correlated trails or cascades of local ruptures that emerge from the stress redistribution process. As the system approaches macroscopic failure consecutive bursts become progressively more correlated. Their size distribution is also a power law, with an equivalent Gutenberg-Richter b value of 1.22 averaged over the whole test, ranging from 3 to 0.5 at the time of failure, all similar to those observed in laboratory tests on granular sandstone samples. The formation of the damage band itself is marked by a decrease in the average distance between consecutive bursts and an emergent power-law correlation integral of event locations with a correlation dimension of 2.55, also similar to those observed in the laboratory (between 2.75 and 2.25). PMID:24483436

  9. Approach to failure in porous granular materials under compression.

    PubMed

    Kun, Ferenc; Varga, Imre; Lennartz-Sassinek, Sabine; Main, Ian G

    2013-12-01

    We investigate the approach to catastrophic failure in a model porous granular material undergoing uniaxial compression. A discrete element computational model is used to simulate both the microstructure of the material and the complex dynamics and feedbacks involved in local fracturing and the production of crackling noise. Under strain-controlled loading, microcracks initially nucleate in an uncorrelated way all over the sample. As loading proceeds the damage localizes into a narrow damage band inclined at 30°-45° to the load direction. Inside the damage band the material is crushed into a poorly sorted mixture of mainly fine powder hosting some larger fragments. The mass probability density distribution of particles in the damage zone is a power law of exponent 2.1, similar to a value of 1.87 inferred from observations of the length distribution of wear products (gouge) in natural and laboratory faults. Dynamic bursts of radiated energy, analogous to acoustic emissions observed in laboratory experiments on porous sedimentary rocks, are identified as correlated trails or cascades of local ruptures that emerge from the stress redistribution process. As the system approaches macroscopic failure consecutive bursts become progressively more correlated. Their size distribution is also a power law, with an equivalent Gutenberg-Richter b value of 1.22 averaged over the whole test, ranging from 3 to 0.5 at the time of failure, all similar to those observed in laboratory tests on granular sandstone samples. The formation of the damage band itself is marked by a decrease in the average distance between consecutive bursts and an emergent power-law correlation integral of event locations with a correlation dimension of 2.55, also similar to those observed in the laboratory (between 2.75 and 2.25).

  10. Application of porous materials for laminar flow control

    NASA Technical Reports Server (NTRS)

    Pearce, W. E.

    1978-01-01

    Fairly smooth porous materials were elected for study Doweave; Fibermetal; Dynapore; and perforated titanium sheet. Factors examined include: surface smoothness; suction characteristics; porosity; surface impact resistance; and strain compatibility. A laminar flow control suction glove arrangement was identified with material combinations compatible with thermal expansion and structural strain.

  11. Application of a model of plastic porous materials including void shape effects to the prediction of ductile failure under shear-dominated loadings

    NASA Astrophysics Data System (ADS)

    Morin, Léo; Leblond, Jean-Baptiste; Tvergaard, Viggo

    2016-09-01

    An extension of Gurson's famous model (Gurson, 1977) of porous plastic solids, incorporating void shape effects, has recently been proposed by Madou and Leblond (Madou and Leblond, 2012a, 2012b, 2013; Madou et al., 2013). In this extension the voids are no longer modelled as spherical but ellipsoidal with three different axes, and changes of the magnitude and orientation of these axes are accounted for. The aim of this paper is to show that the new model is able to predict softening due essentially to such changes, in the absence of significant void growth. This is done in two steps. First, a numerical implementation of the model is proposed and incorporated into the SYSTUS® and ABAQUS® finite element programmes (through some freely available UMAT (Leblond, 2015) in the second case). Second, the implementation in SYSTUS® is used to simulate previous "numerical experiments" of Tvergaard and coworkers (Tvergaard, 2008, 2009, 2012, 2015a; Dahl et al., 2012; Nielsen et al., 2012) involving the shear loading of elementary porous cells, where softening due to changes of the void shape and orientation was very apparent. It is found that with a simple, heuristic modelling of the phenomenon of mesoscopic strain localization, the model is indeed able to reproduce the results of these numerical experiments, in contrast to Gurson's model disregarding void shape effects.

  12. Study on Solidification of Phase Change Material in Fractal Porous Metal Foam

    NASA Astrophysics Data System (ADS)

    Zhang, Chengbin; Wu, Liangyu; Chen, Yongping

    2015-02-01

    The Sierpinski fractal is introduced to construct the porous metal foam. Based on this fractal description, an unsteady heat transfer model accompanied with solidification phase change in fractal porous metal foam embedded with phase change material (PCM) is developed and numerically analyzed. The heat transfer processes associated with solidification of PCM embedded in fractal structure is investigated and compared with that in single-pore structure. The results indicate that, for the solidification of phase change material in fractal porous metal foam, the PCM is dispersedly distributed in metal foam and the existence of porous metal matrix provides a fast heat flow channel both horizontally and vertically, which induces the enhancement of interstitial heat transfer between the solid matrix and PCM. The solidification performance of the PCM, which is represented by liquid fraction and solidification time, in fractal structure is superior to that in single-pore structure.

  13. Methods for removing contaminant matter from a porous material

    DOEpatents

    Fox, Robert V [Idaho Falls, ID; Avci, Recep [Bozeman, MT; Groenewold, Gary S [Idaho Falls, ID

    2010-11-16

    Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

  14. Dynamic Compaction Modeling Comparison for Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John; Schwalbe, Larry; Chapman, D. J.; Lloyd, Andrew; Ward, Aaron

    2005-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized porous material models, P-lambda and P-alpha, in conjunction with a linear Us-up Hugoniot. Two hydrocodes were used to simulate the compaction event: CTH and KO. CTH is a three-dimensional Eulerian hydrocode developed at Sandia National Laboratory and KO is a one-dimensional Lagrangian hydrocode developed at Lawrence Livermore National Laboratory. A comparison of the advantages and disadvantages, along with a discussion of the salient features, of the two models are presented.

  15. Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

    NASA Astrophysics Data System (ADS)

    Marynowicz, Andrzej

    2016-06-01

    The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

  16. Gas sensing using porous materials for automotive applications.

    PubMed

    Wales, Dominic J; Grand, Julien; Ting, Valeska P; Burke, Richard D; Edler, Karen J; Bowen, Chris R; Mintova, Svetlana; Burrows, Andrew D

    2015-07-01

    Improvements in the efficiency of combustion within a vehicle can lead to reductions in the emission of harmful pollutants and increased fuel efficiency. Gas sensors have a role to play in this process, since they can provide real time feedback to vehicular fuel and emissions management systems as well as reducing the discrepancy between emissions observed in factory tests and 'real world' scenarios. In this review we survey the current state-of-the-art in using porous materials for sensing the gases relevant to automotive emissions. Two broad classes of porous material - zeolites and metal-organic frameworks (MOFs) - are introduced, and their potential for gas sensing is discussed. The adsorptive, spectroscopic and electronic techniques for sensing gases using porous materials are summarised. Examples of the use of zeolites and MOFs in the sensing of water vapour, oxygen, NOx, carbon monoxide and carbon dioxide, hydrocarbons and volatile organic compounds, ammonia, hydrogen sulfide, sulfur dioxide and hydrogen are then detailed. Both types of porous material (zeolites and MOFs) reveal great promise for the fabrication of sensors for exhaust gases and vapours due to high selectivity and sensitivity. The size and shape selectivity of the zeolite and MOF materials are controlled by variation of pore dimensions, chemical composition (hydrophilicity/hydrophobicity), crystal size and orientation, thus enabling detection and differentiation between different gases and vapours. PMID:25982991

  17. Gas sensing using porous materials for automotive applications.

    PubMed

    Wales, Dominic J; Grand, Julien; Ting, Valeska P; Burke, Richard D; Edler, Karen J; Bowen, Chris R; Mintova, Svetlana; Burrows, Andrew D

    2015-07-01

    Improvements in the efficiency of combustion within a vehicle can lead to reductions in the emission of harmful pollutants and increased fuel efficiency. Gas sensors have a role to play in this process, since they can provide real time feedback to vehicular fuel and emissions management systems as well as reducing the discrepancy between emissions observed in factory tests and 'real world' scenarios. In this review we survey the current state-of-the-art in using porous materials for sensing the gases relevant to automotive emissions. Two broad classes of porous material - zeolites and metal-organic frameworks (MOFs) - are introduced, and their potential for gas sensing is discussed. The adsorptive, spectroscopic and electronic techniques for sensing gases using porous materials are summarised. Examples of the use of zeolites and MOFs in the sensing of water vapour, oxygen, NOx, carbon monoxide and carbon dioxide, hydrocarbons and volatile organic compounds, ammonia, hydrogen sulfide, sulfur dioxide and hydrogen are then detailed. Both types of porous material (zeolites and MOFs) reveal great promise for the fabrication of sensors for exhaust gases and vapours due to high selectivity and sensitivity. The size and shape selectivity of the zeolite and MOF materials are controlled by variation of pore dimensions, chemical composition (hydrophilicity/hydrophobicity), crystal size and orientation, thus enabling detection and differentiation between different gases and vapours.

  18. Computer simulation of chemical reactions in porous materials

    NASA Astrophysics Data System (ADS)

    Turner, Christoffer Heath

    Understanding reactions in nanoporous materials from a purely experimental perspective is a difficult task. Measuring the chemical composition of a reacting system within a catalytic material is usually only accomplished through indirect methods, and it is usually impossible to distinguish between true chemical equilibrium and metastable states. In addition, measuring molecular orientation or distribution profiles within porous systems is not easily accomplished. However, molecular simulation techniques are well-suited to these challenges. With appropriate simulation techniques and realistic molecular models, it is possible to validate the dominant physical and chemical forces controlling nanoscale reactivity. Novel nanostructured catalysts and supports can be designed, optimized, and tested using high-performance computing and advanced modeling techniques in order to guide the search for next-generation catalysts---setting new targets for the materials synthesis community. We have simulated the conversion of several different equilibrium-limited reactions within microporous carbons and we find that the pore size, pore geometry, and surface chemistry are important factors for determining the reaction yield. The equilibrium-limited reactions that we have modeled include nitric oxide dimerization, ammonia synthesis, and the esterification of acetic acid, all of which show yield enhancements within microporous carbons. In conjunction with a yield enhancement of the esterification reaction, selective adsorption of ethyl acetate within carbon micropores demonstrates an efficient method for product recovery. Additionally, a new method has been developed for simulating reaction kinetics within porous materials and other heterogeneous environments. The validity of this technique is first demonstrated by reproducing the kinetics of hydrogen iodide decomposition in the gas phase, and then predictions are made within slit-shaped carbon pores and carbon nanotubes. The rate

  19. Dynamic Compaction Modeling of Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John P.; Schwalbe, Larry; Cogar, John; Chapman, D. J.; Tsembelis, K.; Ward, Aaron; Lloyd, Andrew

    2006-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements.

  20. The Uniaxial Tensile Response of Porous and Microcracked Ceramic Materials

    SciTech Connect

    Pandey, Amit; Shyam, Amit; Watkins, Thomas R; Lara-Curzio, Edgar; Lara-Curzio, Edgar; Stafford, Randall; Hemker, Kevin J

    2014-01-01

    The uniaxial tensile stress-strain behavior of three porous ceramic materials was determined at ambient conditions. Test specimens in the form of thin beams were obtained from the walls of diesel particulate filter honeycombs and tested using a microtesting system. A digital image correlation technique was used to obtain full-field 2D in-plane surface displacement maps during tensile loading, and in turn, the 2D strains obtained from displacement fields were used to determine the Secant modulus, Young s modulus and initial Poisson s ratio of the three porous ceramic materials. Successive unloading-reloading experiments were performed at different levels of stress to decouple the linear elastic, anelastic and inelastic response in these materials. It was found that the stress-strain response of these materials was non-linear and that the degree of nonlinearity is related to the initial microcrack density and evolution of damage in the material.

  1. Methyl alcohol used as penetrant inspection medium for porous materials

    NASA Technical Reports Server (NTRS)

    Hendron, J. A.

    1971-01-01

    Porous material thoroughly wetted with alcohol shows persistent wet line or area at locations of cracks or porosity. Inspection is qualitative and repeatable, but is used quantitatively with select samples to grade density variations in graphite blocks. Photography is employed to achieve permanent record of results.

  2. Structure and Stability of Deflagrations in Porous Energetic Materials

    SciTech Connect

    stephen B. Margolis; Forman A. Williams

    1999-03-01

    Theoretical two-phase-flow analyses have recently been developed to describe the structure and stability of multi-phase deflagrations in porous energetic materials, in both confined and unconfined geometries. The results of these studies are reviewed, with an emphasis on the fundamental differences that emerge with respect to the two types of geometries. In particular, pressure gradients are usually negligible in unconfined systems, whereas the confined problem is generally characterized by a significant gas-phase pressure difference, or overpressure, between the burned and unburned regions. The latter leads to a strong convective influence on the burning rate arising from the pressure-driven permeation of hot gases into the solid/gas region and the consequent preheating of the unburned material. It is also shown how asymptotic models that are suitable for analyzing stability may be derived based on the largeness of an overall activation-energy parameter. From an analysis of such models, it is shown that the effects of porosity and two-phase flow are generally destabilizing, suggesting that degraded propellants, which exhibit greater porosity than their pristine counterparts, may be more readily subject to combustion instability and nonsteady deflagration.

  3. Porous graphene materials for advanced electrochemical energy storage and conversion devices.

    PubMed

    Han, Sheng; Wu, Dongqing; Li, Shuang; Zhang, Fan; Feng, Xinliang

    2014-02-12

    Combining the advantages from both porous materials and graphene, porous graphene materials have attracted vast interests due to their large surface areas, unique porous structures, diversified compositions and excellent electronic conductivity. These unordinary features enable porous graphene materials to serve as key components in high-performance electrochemical energy storage and conversion devices such as lithium ion batteries, supercapacitors, and fuel cells. This progress report summarizes the typical fabrication methods for porous graphene materials with micro-, meso-, and macro-porous structures. The structure-property relationships of these materials and their application in advanced electrochemical devices are also discussed.

  4. SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

    SciTech Connect

    E. W. Coryell; L. J. Siefken; S. Paik

    1998-09-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. A design is also described for implementing a model of heat transfer by radiation from debris to the interstitial fluid. A design is described for implementation of models for flow losses and interphase drag in porous debris. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  5. Wormhole growth in soluble porous materials

    SciTech Connect

    Nilson, R.H.; Griffiths, S.K. )

    1990-09-24

    Analytical solutions are derived for the quasisteady shape and speed of a single wormhole resulting from the coupled processes of Darcian fluid motion and chemical dissolution in a soluble permeable material. For an initially unsaturated medium, two-dimensional solutions are obtained by addressing an inverted free-boundary problem in which the spatial coordinates are treated as dependent variables on the plane of a complex potential. For initially saturated materials, solutions are obtained by analogy to Ivantsov's problem of dendrite growth.

  6. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  7. SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris

    SciTech Connect

    Siefken, Larry James; Coryell, Eric Wesley; Paik, Seungho; Kuo, Han Hsiung

    1999-07-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  8. Modeling Methane Adsorption in Interpenetrating Porous Polymer Networks

    SciTech Connect

    Martin, RL; Shahrak, MN; Swisher, JA; Simon, CM; Sculley, JP; Zhou, HC; Smit, B; Haranczyk, M

    2013-10-03

    Porous polymer networks (PPNs) are a class of porous materials of particular interest in a variety of energy-related applications because of their stability, high surface areas, and gas uptake capacities. Computationally derived structures for five recently synthesized PPN frameworks, PPN-2, -3, -4, -5, and -6, were generated for various topologies, optimized using semiempirical electronic structure methods, and evaluated using classical grand canonical Monte Carlo simulations. We show that a key factor in modeling the methane uptake performance of these materials is whether, and how, these material frameworks interpenetrate and demonstrate a computational approach for predicting the presence, degree, and nature of interpenetration in PPNs that enables the reproduction of experimental adsorption data.

  9. Novel polymeric nanocomposites and porous materials prepared using organogels

    NASA Astrophysics Data System (ADS)

    Lai, Wei-Chi; Tseng, Shen-Chen

    2009-11-01

    We propose a new method for preparing polymeric nanocomposites and porous materials using self-assembled templates formed by 1,3:2,4-dibenzylidene sorbitol (DBS) organogels. DBS is capable of self-assembling into a 3D nanofibrillar network at relatively low concentrations in some organic solvents to produce organogels. In this study, we induced the formation of such physical cross-linked networks in styrene. Subsequently, we polymerized the styrene in the presence of chemical cross-linkers, divinyl benzene (DVB), with different amounts of DBS using thermal-initiated polymerization. The resulting materials were transparent, homogeneous polystyrene (PS) nanocomposites with both physical and chemical cross-links. The porous polymeric materials were obtained by solvent extraction of the DBS nanofibrils from the PS. Brunauer-Emmett-Teller (BET) measurements show that the amounts of DBS and DVB influenced the specific surface area after the removal of the DBS fibrils.

  10. Urothermal Synthesis of Crystalline Porous Materials

    PubMed Central

    Zhang, Jian; Bu, Julia T.; Chen, Shumei; Wu, Tao; Zheng, Shoutian; Chen, Yigang; Nieto, Ruben A.; Feng, Pingyun

    2015-01-01

    Pores from Urea Urea derivatives are shown here to be a highly verstaile solvent system for the synthesis of crystalline solids. In particular, reversible binding of urea derivatives to framework metal sites has been utilized to create a variety of materials integrating both porosity and open-metal sites. PMID:20954225

  11. Porous silicon based anode material formed using metal reduction

    SciTech Connect

    Anguchamy, Yogesh Kumar; Masarapu, Charan; Deng, Haixia; Han, Yongbong; Venkatachalam, Subramanian; Kumar, Sujeet; Lopez, Herman A.

    2015-09-22

    A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m.sup.2/g to about 200 m.sup.2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800 mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm.sup.2 to about 3.5 mg/cm.sup.2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

  12. Roughening of porous SiCOH materials in fluorocarbon plasmas

    NASA Astrophysics Data System (ADS)

    Bailly, F.; David, T.; Chevolleau, T.; Darnon, M.; Posseme, N.; Bouyssou, R.; Ducote, J.; Joubert, O.; Cardinaud, C.

    2010-07-01

    Porous SiCOH materials integration for integrated circuits faces serious challenges such as roughening during the etch process. In this study, atomic force microscopy is used to investigate the kinetics of SiCOH materials roughening when they are etched in fluorocarbon plasmas. We show that the root mean square roughness and the correlation length linearly increase with the etched depth, after an initiation period. We propose that: (1) during the first few seconds of the etch process, the surface of porous SiCOH materials gets denser. (2) Cracks are formed, leading to the formation of deep and narrow pits. (3) Plasma radicals diffuse through those pits and the pore network and modify the porous material at the bottom of the pits. (4) The difference in material density and composition between the surface and the bottom of the pits leads to a difference in etch rate and an amplification of the roughness. In addition to this intrinsic roughening mechanism, the presence of a metallic mask (titanium nitride) can lead to an extrinsic roughening mechanism, such as micromasking caused by metallic particles originating form the titanium nitride mask.

  13. Unified water isotherms for clayey porous materials

    NASA Astrophysics Data System (ADS)

    Revil, A.; Lu, N.

    2013-09-01

    We provide a unified model for the soil-water retention function, including the effect of bound and capillary waters for all types of soils, including clayey media. The model combines a CEC-normalized isotherm describing the sorption of the bound water (and the filling of the trapped porosity) and the van Genuchten model to describe the capillary water sorption retention but ignore capillary condensation. For the CEC-normalized isotherm, we tested both the BET and Freundlich isotherms, and we found that the Freundlich is more suitable than the BET isotherm in fitting the data. It is also easier to combine the Freundlich isotherm with the van Genuchten model. The new model accounts for (1) the different types of clay minerals, (2) the different types of ions sorbed in the Stern layer and on the basal planes of 2:1 clays, and (3) the pore size distribution. The model is validated with different data sets, including mixtures of kaolinite and bentonite. The model parameters include two exponents (the pore size exponent of the van Genuchten model and the exponent of the Freundlich isotherm), the capillary entry pressure, and two critical water contents. The first critical water content is the water content at saturation (porosity), and the second is the maximum water content associated with adsorption forces, including the trapped nonbound water.

  14. Bacteria transport through porous material: Final technical report

    SciTech Connect

    Yen, T.F.

    1989-02-13

    The injection and penetration of bacteria into a reservoir is the most problematic and crucial of the steps in microbial enhanced recovery (MEOR). In the last phase of our work valuable information on bacterial transport in porous media was obtained. A great deal of progress was made to determine chemical bonding characteristics between adsorbed bacteria and the rock surfaces. In order to further enhance our knowledge of the effects of surface tensions on bacteria transport through porous media, a new approach was taken to illustrate the effect of liquid surface tension on bacterial transport through a sandpack column. Work in surface charge characterization of reservoir rock as a composite oxide system was also accomplished. In the last section of this report a mathematical model to simulate the simultaneous diffusion and growth of bacteria cells in a nutrient-enriched porous media is proposed.

  15. Combustion Synthesis of Advanced Porous Materials in Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Johnson, D. P.

    1999-01-01

    Combustion synthesis, otherwise known as self-propagating high temperature synthesis (SHS), can be used to produce engineered advanced porous material implants which offer the possibility for bone ingrowth as well as a permanent structure framework for the long-term replacement of bone defects. The primary advantage of SHS is based on its rapid kinetics and favorable energetics. The structure and properties of materials produced by SHS are strongly dependent on the combustion reaction conditions. Combustion reaction conditions such as reaction stoichiometry, particle size, green density, the presence and use of diluents or inert reactants, and pre-heating of the reactants, will affect the exothermicity of the reaction. A number of conditions must be satisfied in order to obtain high porosity materials: an optimal amount of liquid, gas and solid phases must be present in the combustion front. Therefore, a balance among these phases at the combustion front must be created by the SHS reaction to successfully engineer a bone replacement material system. Microgravity testing has extended the ability to form porous products. The convective heat transfer mechanisms which operate in normal gravity, 1 g, constrain the combustion synthesis reactions. Gravity also acts to limit the porosity which may be formed as the force of gravity serves to restrict the gas expansion and the liquid movement during reaction. Infiltration of the porous product with other phases can modify both the extent of porosity and the mechanical properties.

  16. Characterisation of porous materials for bioseparation.

    PubMed

    Barrande, M; Beurroies, I; Denoyel, R; Tatárová, I; Gramblicka, M; Polakovic, M; Joehnck, M; Schulte, M

    2009-10-01

    A set of chromatographic materials for bioseparation were characterised by various methods. Both commercial materials and new supports presenting various levels of rigidity were analysed. The methods included size-exclusion and capillary phenomena based techniques. Both batch exclusion and inverse size-exclusion chromatography were used. Gas adsorption, mercury porosimetry and thermoporometry were applied as well as a new method based on water desorption starting from the saturated state. When the rigidity of adsorbents is high enough, the agreement is reasonable between the values of the structural parameters that were determined (surface area, porosity, and pore size) by various methods. Nevertheless, a part of macroporosity may not be evidenced by inverse size-exclusion chromatography whereas it is visible by batch exclusion and the other methods. When the rigidity decreases, for example with soft swelling gels, where standard nitrogen adsorption or mercury porosimetry are no more reliable, two main situations are encountered: either the methods based on capillary phenomena (thermoporometry or water desorption) overestimate the pore size with an amplitude that depends on the method, or in some cases it is possible to distinguish water involved in the swelling of pore walls from that involved in pore filling by capillary condensation. PMID:19740472

  17. Characterisation of porous materials for bioseparation.

    PubMed

    Barrande, M; Beurroies, I; Denoyel, R; Tatárová, I; Gramblicka, M; Polakovic, M; Joehnck, M; Schulte, M

    2009-10-01

    A set of chromatographic materials for bioseparation were characterised by various methods. Both commercial materials and new supports presenting various levels of rigidity were analysed. The methods included size-exclusion and capillary phenomena based techniques. Both batch exclusion and inverse size-exclusion chromatography were used. Gas adsorption, mercury porosimetry and thermoporometry were applied as well as a new method based on water desorption starting from the saturated state. When the rigidity of adsorbents is high enough, the agreement is reasonable between the values of the structural parameters that were determined (surface area, porosity, and pore size) by various methods. Nevertheless, a part of macroporosity may not be evidenced by inverse size-exclusion chromatography whereas it is visible by batch exclusion and the other methods. When the rigidity decreases, for example with soft swelling gels, where standard nitrogen adsorption or mercury porosimetry are no more reliable, two main situations are encountered: either the methods based on capillary phenomena (thermoporometry or water desorption) overestimate the pore size with an amplitude that depends on the method, or in some cases it is possible to distinguish water involved in the swelling of pore walls from that involved in pore filling by capillary condensation.

  18. Drying of porous materials in a medium with variable potentials

    SciTech Connect

    Liu, J.Y. )

    1991-08-01

    This paper presents an application of the Luikov system of heat and mass transfer equations in dimensionless form to predict the temperature and moisture distributions in a slab of capillary-porous material during drying. The heat and mass potentials of the external medium in the boundary conditions are assumed to vary linearly with time. The method of solution is illustrated by considering the drying of a slab of lumber. Numerical results based on the estimated thermophysical properties of spruce are presented.

  19. Sound Transmission Through Multi-Panel Structures Lined with Elastic Porous Materials

    NASA Astrophysics Data System (ADS)

    Bolton, J. S.; Shiau, N.-M.; Kang, Y. J.

    1996-04-01

    Theory and measurements related to sound transmission through double panels lined with elastic porous media are presented. The information has application to the design of noise control barriers and to the optimization of aircraft fuselage transmission loss, for example. The major difference between the work described here and earlier research in this field relates to the treatment of the porous material that is used to line the cavity between the two panels of the double panel structure. Here we have used the porous material theory proposed by Biot since it takes explicit account of all the wave types known to propagate in elastic porous materials. As a result, it is possible to use the theory presented here to calculate the transmission loss of lined double panels at arbitrary angles of incidence; results calculated over a range of incidence angles may then be combined to yield the random incidence transmission loss. In this paper, the equations governing wave propagation in an elastic porous material are first considered briefly and then the general forms for the stresses and displacements within the porous material are given. Those solutions are expressed in terms of a number of constants that can be determined by application of appropriate boundary conditions. The boundary conditions required to model double panels having linings that are either directly attached to the facing panels or separated?!from them by air gaps are presented and discussed. Measurements of the random incidence transmission loss of aluminium double-panel structures lined with polyurethane foam are presented and have been found to be in good agreement with theoretical predictions. Both the theoretical predictions and the measured results have shown that the method by which an elastic porous lining material is attached to the facing panels can have a profound influence on the transmission loss of the panel system. It has been found, for example, that treatments in which the lining material

  20. Gravitational Effects on Combustion Synthesis of Advanced Porous Materials

    NASA Technical Reports Server (NTRS)

    Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Thorne, K.

    2000-01-01

    Combustion Synthesis (self-Propagating high-temperature synthesis-(SHS)) of porous Ti-TiB(x), composite materials has been studied with respect to the sensitivity to the SHS reaction parameters of stoichiometry, green density, gasifying agents, ambient pressure, diluents and gravity. The main objective of this research program is to engineer the required porosity and mechanical properties into the composite materials to meet the requirements of a consumer, such as for the application of bone replacement materials. Gravity serves to restrict the gas expansion and the liquid movement during SHS reaction. As a result, gravitational forces affect the microstructure and properties of the SHS products. Reacting these SHS systems in low gravity in the KC-135 aircraft has extended the ability to form porous products. This paper will emphasize the effects of gravity (low g, 1g and 2g) on the SHS reaction process, and the microstructure and properties of the porous composite. Some of biomedical results are also discussed.

  1. Network models of soil porous structure

    NASA Astrophysics Data System (ADS)

    Samec, M.; Santiago, A.; Cardenas, J. P.; Benito, R. M.; Tarquis, A. M.; Mooney, S. J.; Korošak, D.

    2010-05-01

    Soils sustain life on Earth. In times of increasing anthropogenic demands on soils [1] there is growing need to seek for novel approaches to understand the relationships between the soil porous structure and specific soil functions. Recently [2-4], soil pore structure was described as a complex network of pores using spatially embedded varying fitness network model [2] or heterogeneous preferential attachment scheme [3-4], both approaches revealing the apparent scale-free topology of soils. Here, we show, using a large set of soil images of structures obtained by X-ray computed tomography that both methods predict topological similar networks of soil pore structures. Furthermore, by analyzing the node-node link correlation properties of the obtained networks we suggest an approach to quantify the complexity of soil pore structure. [1] R. Lal, Soil science and the carbon civilization, Soil Sci. Soc. Am. J., 71: 1425-1437, 2007. [2] S. J. Mooney, D. Korošak, Using Complex Networks to Model Two- and Three-Dimensional Soil Porous Architecture, Soil Sci. Soc. Am. J., 73: 1094-1100, 2009. [3] A. Santiago, J. P. Cardenas, J. C. Losada, R. M. Benito, A. M. Tarquis, F. Borondo, Multiscaling of porous soils as heterogeneous complex networks, Nonlin. Proc. Geophys., 15: 893-902, 2008. [4] A. Santiago, R. M. Benito, An extended formalism for preferential attachment in heterogeneous complex networks, Eur. Phys. Lett., 82: 58004, 2008.

  2. Elastic properties of model 3-D porous ceramics and foams

    NASA Astrophysics Data System (ADS)

    Roberts, Anthony; Garboczi, Edward

    2000-03-01

    The novel properties of many new porous materials are related to their interesting internal microstructure. Apart from simple cases, there exist no theoretical means of predicting the bulk properties of these materials. This limits our ability to guide microstructure optimization for a particular purpose. We use a large scale finite element method to demonstrate the complex relationship between microstructure and the effective properties of realistic three-dimensional model porous ceramics and foams. We find that pore-shape and interconnectivity strongly influence the properties of sintered ceramics. For porous foams we have studied the role of coordination number, random disorder, and strut shape on the Young's modulus and Poisson's ratio. We find that that Voronoi tesselations, commonly used to model solid foams, show unphysical behavior, in particular they are incompressible (rubber-like) at low densities. Deletion of just 10% of the bonds in the model reduces the bulk modulus by 75%, more in line with experimental evidence. The FEM results are generally in good agreement with experimental data for ceramics and foams, and can be used as both a predictive and interpretative tool by experimentalists.

  3. A Compaction Model for Highly Porous Silica Powder.

    NASA Astrophysics Data System (ADS)

    Church, P. D.; Tsembelis, K.

    2005-07-01

    This paper describes research to develop an equation of state to describe the behaviour of a highly porous silica powder. It shows that whilst molecular modelling techniques can be readily applied to develop a description of a compact material the description of the compaction process is more problematic. An empirical model, based upon the Lennard-Jones potential, has been shown to be capable of describing the compaction process observed in simple experiments. This development and application of the model in the Eulerian hydrocode GRIM to reproduce experimental plate impact data over a wide range of impact velocities is described and the results compared with experimental data.

  4. Coupled hydromechanical and electromagnetic disturbances in unsaturated porous materials.

    PubMed

    Revil, A; Mahardika, H

    2013-02-01

    A theory of cross-coupled flow equations in unsaturated soils is necessary to predict (1) electroosmotic flow with application to electroremediation and agriculture, (2) the electroseismic and the seismoelectric effects to develop new geophysical methods to characterize the vadose zone, and (3) the streaming current, which can be used to investigate remotely ground water flow in unsaturated conditions in the capillary water regime. To develop such a theory, the cross-coupled generalized Darcy and Ohm constitutive equations of transport are extended to unsaturated conditions. This model accounts for inertial effects and for the polarization of porous materials. Rather than using the zeta potential, like in conventional theories for the saturated case, the key parameter used here is the quasi-static volumetric charge density of the pore space, which can be directly computed from the quasi-static permeability. The apparent permeability entering Darcy's law is also frequency dependent with a critical relaxation time that is, in turn, dependent on saturation. A decrease of saturation increases the associated relaxation frequency. The final form of the equations couples the Maxwell equations and a simplified form of two-fluid phases Biot theory accounting for water saturation. A generalized expression of the Richard equation is derived, accounting for the effect of the vibration of the skeleton during the passage of seismic waves and the electrical field. A new expression is obtained for the effective stress tensor. The model is tested against experimental data regarding the saturation and frequency dependence of the streaming potential coupling coefficient. The model is also adapted for two-phase flow conditions and a numerical application is shown for water flooding of a nonaqueous phase liquid (NAPL, oil) contaminated aquifer. Seismoelectric conversions are mostly taking place at the NAPL (oil)/water encroachment front and can be therefore used to remotely track the

  5. Coupled hydromechanical and electromagnetic disturbances in unsaturated porous materials

    PubMed Central

    Revil, A; Mahardika, H

    2013-01-01

    A theory of cross-coupled flow equations in unsaturated soils is necessary to predict (1) electroosmotic flow with application to electroremediation and agriculture, (2) the electroseismic and the seismoelectric effects to develop new geophysical methods to characterize the vadose zone, and (3) the streaming current, which can be used to investigate remotely ground water flow in unsaturated conditions in the capillary water regime. To develop such a theory, the cross-coupled generalized Darcy and Ohm constitutive equations of transport are extended to unsaturated conditions. This model accounts for inertial effects and for the polarization of porous materials. Rather than using the zeta potential, like in conventional theories for the saturated case, the key parameter used here is the quasi-static volumetric charge density of the pore space, which can be directly computed from the quasi-static permeability. The apparent permeability entering Darcy's law is also frequency dependent with a critical relaxation time that is, in turn, dependent on saturation. A decrease of saturation increases the associated relaxation frequency. The final form of the equations couples the Maxwell equations and a simplified form of two-fluid phases Biot theory accounting for water saturation. A generalized expression of the Richard equation is derived, accounting for the effect of the vibration of the skeleton during the passage of seismic waves and the electrical field. A new expression is obtained for the effective stress tensor. The model is tested against experimental data regarding the saturation and frequency dependence of the streaming potential coupling coefficient. The model is also adapted for two-phase flow conditions and a numerical application is shown for water flooding of a nonaqueous phase liquid (NAPL, oil) contaminated aquifer. Seismoelectric conversions are mostly taking place at the NAPL (oil)/water encroachment front and can be therefore used to remotely track the

  6. Fundamental problems in porous materials: Experiments & computer simulation

    NASA Astrophysics Data System (ADS)

    Xu, Zhanping

    Porous materials have attracted massive scientific and technological interest because of their extremely high surface-to-volume ratio, molecular tunability in construction, and surface-based applications. Through my PhD work, porous materials were engineered to meet the design in selective binding, self-healing, and energy damping. For example, crystalline MOFs with pore size spanning from a few angstroms to a couple of nanometers were chemically engineered to show 120 times more efficiency in binding of large molecules. In addition, we found building blocks released from those crystals can be further patched back through a healing process at ambient and low temperatures down to -56 °C. When building blocks are replaced with graphenes, ultra-flyweight aerogels with pore size larger than 100 nm were made to delay shock waves. More stable rigid porous metal with larger pores (~um) was also fabricated, and its performance and survivability are under investigation. Aside from experimental studies, we also successfully applied numerical simulations to study the mutual interaction between the nonplanar liquid-solid interface and colloidal particles during the freezing of the colloidal suspensions. Colloidal particles can be either rejected or engulfed by the evolving interface depending on the freezing speed and strength of interface-particle interaction. Our interactive simulation was achieved by programming both simulation module and visualization module on high performance GPU devices.

  7. Propagation of Terahertz Radiation in Porous Polymer and Ceramic Materials

    NASA Astrophysics Data System (ADS)

    Dodson, Caroline; Spicer, James; Fitch, Michael; Schuster, Paul; Osiander, Robert

    2005-04-01

    In this work we investigate the propagation of terahertz radiation through polyurethane foam and porous alumina ceramics to understand the effects of structure on the optical properties of these materials at terahertz frequencies. A terahertz time domain system with a GaAs photoconductive emitter and a ZnTe electro-optic crystal was used to generate and detect the transmitted terahertz signal. Using the amplitude and phase characteristics of these signals, the thickness, index of refraction, and other physical and optical properties of the materials were determined.

  8. Method of preparing thin porous sheets of ceramic material

    DOEpatents

    Swarr, Thomas E.; Nickols, Richard C.; Krasij, Myron

    1987-03-24

    A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.

  9. Method of preparing thin porous sheets of ceramic material

    DOEpatents

    Swarr, T.E.; Nickols, R.C.; Krasij, M.

    1984-05-23

    A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.

  10. Ceramic porous material and method of making same

    SciTech Connect

    Liu, Jun; Kim, Anthony Y.; Virden, Jud W.

    1997-01-01

    The invention is a mesoporous ceramic membrane having substantially uniform pore size. Additionally, the invention includes aqueous and non-aqueous processing routes to making the mesoporous ceramic membranes. According to one aspect of the present invention, inserting a substrate into a reaction chamber at pressure results in reaction products collecting on the substrate and forming a membrane thereon. According to another aspect of the present invention, a second aqueous solution that is sufficiently immiscible in the aqueous solution provides an interface between the two solutions whereon the mesoporous membrane is formed. According to a further aspect of the present invention, a porous substrate is placed at the interface between the two solutions permitting formation of a membrane on the surface or within the pores of the porous substrate. According to yet another aspect of the present invention, mesoporous ceramic materials are formed using a non-aqueous solvent and water-sensitive precursors.

  11. Ceramic porous material and method of making same

    DOEpatents

    Liu, J.; Kim, A.Y.; Virden, J.W.

    1997-07-08

    The invention is a mesoporous ceramic membrane having substantially uniform pore size. Additionally, the invention includes aqueous and non-aqueous processing routes to making the mesoporous ceramic membranes. According to one aspect of the present invention, inserting a substrate into a reaction chamber at pressure results in reaction products collecting on the substrate and forming a membrane thereon. According to another aspect of the present invention, a second aqueous solution that is sufficiently immiscible in the aqueous solution provides an interface between the two solutions whereon the mesoporous membrane is formed. According to a further aspect of the present invention, a porous substrate is placed at the interface between the two solutions permitting formation of a membrane on the surface or within the pores of the porous substrate. According to yet another aspect of the present invention, mesoporous ceramic materials are formed using a non-aqueous solvent and water-sensitive precursors. 21 figs.

  12. Supported metal nanoparticles on porous materials. Methods and applications.

    PubMed

    White, Robin J; Luque, Rafael; Budarin, Vitaliy L; Clark, James H; Macquarrie, Duncan J

    2009-02-01

    Nanoparticles are regarded as a major step forward to achieving the miniaturisation and nanoscaling effects and properties that have been utilised by nature for millions of years. The chemist is no longer observing and describing the behaviour of matter but is now able to manipulate and produce new types of materials with specific desired physicochemical characteristics. Such materials are receiving extensive attention across a broad range of research disciplines. The fusion between nanoparticle and nanoporous materials technology represents one of the most interesting of these rapidly expanding areas. The harnessing of nanoscale activity and selectivity, potentially provides extremely efficient catalytic materials for the production of commodity chemicals, and energy needed for a future sustainable society. In this tutorial review, we present an introduction to the field of supported metal nanoparticles (SMNPs) on porous materials, focusing on their preparation and applications in different areas. PMID:19169462

  13. Porous materials for thermal management under extreme conditions.

    PubMed

    Clyne, T W; Golosnoy, I O; Tan, J C; Markaki, A E

    2006-01-15

    A brief analysis is presented of how heat transfer takes place in porous materials of various types. The emphasis is on materials able to withstand extremes of temperature, gas pressure, irradiation, etc. i.e. metals and ceramics, rather than polymers. A primary aim is commonly to maximize either the thermal resistance (i.e. provide insulation) or the rate of thermal equilibration between the material and a fluid passing through it (i.e. to facilitate heat exchange). The main structural characteristics concern porosity (void content), anisotropy, pore connectivity and scale. The effect of scale is complex, since the permeability decreases as the structure is refined, but the interfacial area for fluid-solid heat exchange is, thereby, raised. The durability of the pore structure may also be an issue, with a possible disadvantage of finer scale structures being poor microstructural stability under service conditions. Finally, good mechanical properties may be required, since the development of thermal gradients, high fluid fluxes, etc. can generate substantial levels of stress. There are, thus, some complex interplays between service conditions, pore architecture/scale, fluid permeation characteristics, convective heat flow, thermal conduction and radiative heat transfer. Such interplays are illustrated with reference to three examples: (i) a thermal barrier coating in a gas turbine engine; (ii) a Space Shuttle tile; and (iii) a Stirling engine heat exchanger. Highly porous, permeable materials are often made by bonding fibres together into a network structure and much of the analysis presented here is oriented towards such materials. PMID:18272456

  14. Porous materials for thermal management under extreme conditions.

    PubMed

    Clyne, T W; Golosnoy, I O; Tan, J C; Markaki, A E

    2006-01-15

    A brief analysis is presented of how heat transfer takes place in porous materials of various types. The emphasis is on materials able to withstand extremes of temperature, gas pressure, irradiation, etc. i.e. metals and ceramics, rather than polymers. A primary aim is commonly to maximize either the thermal resistance (i.e. provide insulation) or the rate of thermal equilibration between the material and a fluid passing through it (i.e. to facilitate heat exchange). The main structural characteristics concern porosity (void content), anisotropy, pore connectivity and scale. The effect of scale is complex, since the permeability decreases as the structure is refined, but the interfacial area for fluid-solid heat exchange is, thereby, raised. The durability of the pore structure may also be an issue, with a possible disadvantage of finer scale structures being poor microstructural stability under service conditions. Finally, good mechanical properties may be required, since the development of thermal gradients, high fluid fluxes, etc. can generate substantial levels of stress. There are, thus, some complex interplays between service conditions, pore architecture/scale, fluid permeation characteristics, convective heat flow, thermal conduction and radiative heat transfer. Such interplays are illustrated with reference to three examples: (i) a thermal barrier coating in a gas turbine engine; (ii) a Space Shuttle tile; and (iii) a Stirling engine heat exchanger. Highly porous, permeable materials are often made by bonding fibres together into a network structure and much of the analysis presented here is oriented towards such materials.

  15. Numerical modelling of moisture transfer in saturated and non-saturated porous media

    NASA Astrophysics Data System (ADS)

    Krejci, T.; Koudelka, T.; Broucek, M.

    2013-10-01

    The paper presents a numerical model of coupled hydro-mechanical behaviour of soils. The micro-mechanics model is based on the effective stress concept which covers the theory of deformation of soils (soil skeleton) and other porous materials. The final set of equations is simplified and derived for the water flow in porous media, and the spatial discretization is performed by the finite element method. The model was implemented into the SIFEL software package and some numerical examples are presented.

  16. Avalanches in compressed porous SiO(2)-based materials.

    PubMed

    Nataf, Guillaume F; Castillo-Villa, Pedro O; Baró, Jordi; Illa, Xavier; Vives, Eduard; Planes, Antoni; Salje, Ekhard K H

    2014-08-01

    The failure dynamics in SiO(2)-based porous materials under compression, namely the synthetic glass Gelsil and three natural sandstones, has been studied for slowly increasing compressive uniaxial stress with rates between 0.2 and 2.8 kPa/s. The measured collapsed dynamics is similar to Vycor, which is another synthetic porous SiO(2) glass similar to Gelsil but with a different porous mesostructure. Compression occurs by jerks of strain release and a major collapse at the failure point. The acoustic emission and shrinking of the samples during jerks are measured and analyzed. The energy of acoustic emission events, its duration, and waiting times between events show that the failure process follows avalanche criticality with power law statistics over ca. 4 decades with a power law exponent ɛ≃ 1.4 for the energy distribution. This exponent is consistent with the mean-field value for the collapse of granular media. Besides the absence of length, energy, and time scales, we demonstrate the existence of aftershock correlations during the failure process.

  17. Symbolic regression modeling of noise generation at porous airfoils

    NASA Astrophysics Data System (ADS)

    Sarradj, Ennes; Geyer, Thomas

    2014-07-01

    Based on data sets from previous experimental studies, the tool of symbolic regression is applied to find empirical models that describe the noise generation at porous airfoils. Both the self noise from the interaction of a turbulent boundary layer with the trailing edge of an porous airfoil and the noise generated at the leading edge due to turbulent inflow are considered. Following a dimensional analysis, models are built for trailing edge noise and leading edge noise in terms of four and six dimensionless quantities, respectively. Models of different accuracy and complexity are proposed and discussed. For the trailing edge noise case, a general dependency of the sound power on the fifth power of the flow velocity was found and the frequency spectrum is controlled by the flow resistivity of the porous material. Leading edge noise power is proportional to the square of the turbulence intensity and shows a dependency on the fifth to sixth power of the flow velocity, while the spectrum is governed by the flow resistivity and the integral length scale of the incoming turbulence.

  18. Biodegradable elastic patch plasty ameliorates left ventricular adverse remodeling after ischemia–reperfusion injury: A preclinical study of a porous polyurethane material in a porcine model

    PubMed Central

    Hashizume, Ryotaro; Fujimoto, Kazuro L.; Hong, Yi; Guan, Jianjun; Toma, Catalin; Tobita, Kimimasa; Wagner, William R.

    2013-01-01

    Objective Myocardial infarction (MI) can lead to irreversible adverse left ventricular remodeling resulting in subsequent severe dysfunction. The objective of this study was to investigate the potential for biodegradable, elastomeric patch implantation to positively alter the remodeling process after MI in a porcine model. Methods Yorkshire pigs underwent a 60-minute catheter balloon occlusion of the left circumflex artery. Two weeks after MI animals underwent epicardial placement of a biodegradable, porous polyurethane (poly(ester urethane)urea; PEUU) patch (MI+PEUU, n = 7) or sham surgery (MI+sham, n = 8). Echocardiography before surgery and at 4 and 8 weeks after surgery measured the end-diastolic area (EDA) and fractional area change (% FAC). All animals were humanely killed 8 weeks after surgery and hearts were histologically assessed. Results At 8 weeks, echocardiography revealed greater EDA values in the MI+sham group (23.6 ± 6.6 cm2 , mean ± standard deviaation) than in the MI+PEUU group (15.9 ± 2.5 cm2) (P < .05) and a lower %FAC in the MI+sham group (24.8 ± 7.6) than in the MI+PEUU group (35.9 ± 7.8) (P < .05). The infarcted ventricular wall was thicker in the MI+PEUU group (1.56 ± 0.5 cm) than in the MI+sham group (0.91 ± 0.24 cm) (P < .01). Conclusions Biodegradable elastomeric PEUU patch implantation onto the porcine heart 2 weeks post-MI attenuated left ventricular adverse remodeling and functional deterioration and was accompanied by increased neovascularization. These findings, although limited to a 2-month follow-up, may suggest an attractive clinical option to moderate post-MI cardiac failure. PMID:23219497

  19. The Interaction of Sound and Shock Waves with Flexible Porous Materials

    NASA Astrophysics Data System (ADS)

    Abbott, James Fuller

    Several topics are studied which illustrate the role of flexibility in determining the acoustical properties of flexible porous materials. A power balance relation is obtained for the flexible porous material which explicitly identifies two loss mechanisms for sound absorption: the losses due to the irreversible deformation of the structure, and those attributed to the viscous drag between the fluid and the structure. The finite flexible porous layer backed by a rigid wall is then considered. Irreversible deformation of the structure is shown to be the dominant loss mechanism for closed layers. Three departures from the basic model-- a porous layer with anisotropic flow resistance and structure factor, periodic structures consisting of porous layers separated by air gaps, and the porous medium in bulk with mean fluid flow--are considered. The reflection of shock waves is also studied, and a quasi-linear theory is developed which reproduces the principal features of experimental results obtained previously by Ingard. The theory assumes that the propagating pulses in the air and structure are linear and the gross, zeroth order motion of the porous layer is modeled by including its energy and momentum in the conservation equations; these equations compare the system just before and just after the reflection of the incident shock from the front surface of the layer. The substantial motion of the layer and its dragging against a constraining boundary (in this case the walls of the shock tube) are found to introduce a dependence of the front reflection coefficient and maximal layer deformation on the peak pressure of the incident shock. Lastly, we address the question of measurement of the complex compressibility K, a key parameter used to describe the dynamics of a given flexible porous material. The standard long-wavelength assumption used to determine K from experimental measurements of the frequency dependent velocity transfer function across a sample is shown to

  20. Water-based technique to produce porous PZT materials

    NASA Astrophysics Data System (ADS)

    Galassi, C.; Capiani, C.; Craciun, F.; Roncari, E.

    2005-09-01

    Water based colloidal processing of PZT materials was investigated in order to reduce costs and employ more environmental friendly manufacturing. The technique addressed was the production of porous thick samples by the so called “starch consolidation”. PZT “soft” compositions were used. The “starch consolidation” process allows to obtain the green body by raising the temperature of a suspension of PZT powder, soluble starch and water, cast into a metal mould. The influence of the processing parameters and composition on the morphology, pore volumes, pore size distributions and piezoelectric properties are investigated. Zeta potential determination and titration with different deflocculants were essential tools to adjust the slurry formulation.

  1. Synergistic Carbon Dioxide Capture and Conversion in Porous Materials.

    PubMed

    Zhang, Yugen; Lim, Diane S W

    2015-08-24

    Global climate change and excessive CO2 emissions have caused widespread public concern in recent years. Tremendous efforts have been made towards CO2 capture and conversion. This has led to the development of numerous porous materials as CO2 capture sorbents. Concurrently, the conversion of CO2 into value-added products by chemical methods has also been well-documented recently. However, realizing the attractive prospect of direct, in situ chemical conversion of captured CO2 into other chemicals remains a challenge.

  2. Acoustic structure and propagation in highly porous, layered, fibrous materials

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.; Tesar, J. S.

    1984-01-01

    The acoustic structure and propagation of sound in highly porous, layered, fine fiber materials is examined. Of particular interest is the utilization of the Kozeny number for determining the static flow resistance and the static structure factor based on flow permeability measurements. In this formulation the Kozeny number is a numerical constant independent of volume porosity at high porosities. The other essential parameters are then evaluated employing techniques developed earlier for open cell foams. The attenuation and progressive phase characteristics in bulk samples are measured and compared with predicted values. The agreements on the whole are very satisfactory.

  3. Advanced Porous Coating for Low-Density Ceramic Insulation Materials

    NASA Technical Reports Server (NTRS)

    Leiser, Daniel B.; Churchward, Rex; Katvala, Victor; Stewart, David; Balter, Aliza

    1988-01-01

    The need for improved coatings on low-density reusable surface insulation (RSI) materials used on the space shuttle has stimulated research into developing tougher coatings. The processing of a new porous composite "coating" for RST called toughened unipiece fibrous insulation Is discussed. Characteristics including performance in a simulated high-speed atmospheric entry, morphological structure before and after this exposure, resistance to Impact, and thermal response to a typical heat pulse are described. It is shown that this coating has improved impact resistance while maintaining optical and thermal properties comparable to the previously available reaction-cured glass coating.

  4. The usable capacity of porous materials for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Schlichtenmayer, Maurice; Hirscher, Michael

    2016-04-01

    A large number of different porous materials has been investigated for their hydrogen uptake over a wide pressure range and at different temperature. From the absolute adsorption isotherms, the enthalpy of adsorption is evaluated for a wide range of surface coverage. The usable capacity, defined as the amount of hydrogen released between a maximum tank pressure and a minimum back pressure for a fuel cell, is analyzed for isothermal operation. The usable capacity as a function of temperature shows a maximum which defines the optimum operating temperature. This optimum operating temperature is higher for materials possessing a higher enthalpy of adsorption. However, the fraction of the hydrogen stored overall that can be released at the optimum operating temperature is higher for materials with a lower enthalpy of adsorption than for the ones with higher enthalpy.

  5. Basalt fiber reinforced porous aggregates-geopolymer based cellular material

    NASA Astrophysics Data System (ADS)

    Luo, Xin; Xu, Jin-Yu; Li, Weimin

    2015-09-01

    Basalt fiber reinforced porous aggregates-geopolymer based cellular material (BFRPGCM) was prepared. The stress-strain curve has been worked out. The ideal energy-absorbing efficiency has been analyzed and the application prospect has been explored. The results show the following: fiber reinforced cellular material has successively sized pore structures; the stress-strain curve has two stages: elastic stage and yielding plateau stage; the greatest value of the ideal energy-absorbing efficiency of BFRPGCM is 89.11%, which suggests BFRPGCM has excellent energy-absorbing property. Thus, it can be seen that BFRPGCM is easy and simple to make, has high plasticity, low density and excellent energy-absorbing features. So, BFRPGCM is a promising energy-absorbing material used especially in civil defense engineering.

  6. High Velocity Impact Interaction of Metal Particles with Porous Heterogeneous Materials with an Inorganic Matrix

    NASA Astrophysics Data System (ADS)

    Glazunov, A. A.; Ishchenko, A. N.; Afanasyeva, S. A.; Belov, N. N.; Burkin, V. V.; Rogaev, K. S.; Tabachenko, A. N.; Khabibulin, M. V.; Yugov, N. T.

    2016-03-01

    A computational-experimental investigation of stress-strain state and fracture of a porous heterogeneous material with an inorganic matrix, used as a thermal barrier coating of flying vehicles, under conditions of a high-velocity impact by a spherical steel projectile imitating a meteorite particle is discussed. Ballistic tests are performed at the velocities about 2.5 km/s. Numerical modeling of the high-velocity impact is described within the framework of a porous elastoplastic model including fracture and different phase states of the materials. The calculations are performed using the Euler and Lagrange numerical techniques for the velocities up to 10 km/s in a complete-space problem statement.

  7. Porous Media Approach for Modeling Closed Cell Foam

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Sullivan, Roy M.

    2006-01-01

    In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is

  8. Freeze fracturing of elastic porous media: a mathematical model

    PubMed Central

    Vlahou, I.; Worster, M. G.

    2015-01-01

    We present a mathematical model of the fracturing of water-saturated rocks and other porous materials in cold climates. Ice growing inside porous rocks causes large pressures to develop that can significantly damage the rock. We study the growth of ice inside a penny-shaped cavity in a water-saturated porous rock and the consequent fracturing of the medium. Premelting of the ice against the rock, which results in thin films of unfrozen water forming between the ice and the rock, is one of the dominant processes of rock fracturing. We find that the fracture toughness of the rock, the size of pre-existing faults and the undercooling of the environment are the main parameters determining the susceptibility of a medium to fracturing. We also explore the dependence of the growth rates on the permeability and elasticity of the medium. Thin and fast-fracturing cracks are found for many types of rocks. We consider how the growth rate can be limited by the existence of pore ice, which decreases the permeability of a medium, and propose an expression for the effective ‘frozen’ permeability. PMID:25792954

  9. Moisture storage parameters of porous building materials as time-dependent properties

    NASA Astrophysics Data System (ADS)

    Záleská, Martina; Pavlíková, Milena; Pavlík, Zbyšek

    2016-06-01

    Three different types of bricks and two different types of sandstones are studied in terms of measurement moisture storage parameters for over-hygroscopic moisture area using pressure plate device. For researched materials, basic physical properties as bulk density, matrix density and total open porosity are determined. From the obtained data of moisture storage measurement, the water retention curves and curves of degree of saturation in dependence on suction pressure are constructed. Water retention curve (also called suction curve, capillary potential curve, capillary-pressure function and capillary-moisture relationship) is the basic material property used in models for simulation of moisture storage in porous building materials.

  10. Characterization of porous carbon fibers and related materials

    SciTech Connect

    Fuller, E.L. Jr.

    1996-07-15

    This program was geared to support the Fossil Energy Material Sciences Program with respect to several areas of interest in efficient production and utilization of energy. Carbon molecular sieves have great potential for economically purifying gases; i.e. removal of carbon dioxide from natural gas without having to resort to cryogenic techniques. Microporous carbons can be tailored to serve as adsorbents for natural gas in on-board storage in automotive applications, avoiding high pressures and heavy storage tanks. This program is a laboratory study to evaluate production methodologies and activation processes to produce porous carbons for specific applications. The Carbon Materials Technology Group of Oak Ridge National Laboratory (ORNL) is engaged in developmental programs to produce activated carbon fibers (ACF) for applications in fixed beds and/or flowing reactors engineering applications.

  11. Getting Out Of A Tight Spot: Physics Of Flow Through Porous Materials

    NASA Astrophysics Data System (ADS)

    Datta, Sujit Sankar

    We study the physics of flow through porous materials in two different ways: by directly visualizing flow through a model three-dimensional (3D) porous medium, and by investigating the deformability of fluid-filled microcapsules having porous shells. In the first part of this thesis, we develop an experimental approach to directly visualize fluid flow through a 3D porous medium. We use this to investigate drainage, the displacement of a wetting fluid from a porous medium by a non-wetting fluid, as well as secondary imbibition, the subsequent displacement of the non-wetting fluid by the wetting fluid. We characterize the intricate morphologies of the non-wetting fluid ganglia left trapped within the pore space, and show how the ganglia configurations vary with the wetting fluid flow rate. We then visualize the spatial fluctuations in the fluid flow, both for single- and multi-phase flow. We use our measurements to quantify the strong variability in the flow velocities, as well as the pore-scale correlations in the flow. Finally, we use our experimental approach to study the simultaneous flow of both a wetting and a non-wetting fluid through a porous medium, and elucidate the flow instabilities that arise for sufficiently large flow rates. In the second part of this thesis, we study the mechanical properties of porous spherical microcapsules. We first introduce emulsions, and describe how their rheology depends on the microscopic interactions between the drops comprising them. We then study the formation and buckling of one class of microcapsule -- nanoparticle-coated emulsion drops. We also use double emulsions, drops within drops, as templates to form another class of microcapsule -- drops coated with thin, porous, polymer shells. We investigate how, under sufficient osmotic pressure, these microcapsules buckle, and show how the inhomogeneity in the shell structure can guide the folding pathway taken by a microcapsule as it buckles. Finally, we study the expansion

  12. Quantitative properties of complex porous materials calculated from x-ray μCT images

    NASA Astrophysics Data System (ADS)

    Sheppard, Adrian P.; Arns, Christoph H.; Sakellariou, Arthur; Senden, Tim J.; Sok, Rob M.; Averdunk, Holger; Saadatfar, Mohammad; Limaye, Ajay; Knackstedt, Mark A.

    2006-08-01

    A microcomputed tomography (μCT) facility and computational infrastructure developed at the Department of Applied Mathematics at the Australian National University is described. The current experimental facility is capable of acquiring 3D images made up of 2000 3 voxels on porous specimens up to 60 mm diameter with resolutions down to 2 μm. This allows the three-dimensional (3D) pore-space of porous specimens to be imaged over several orders of magnitude. The computational infrastructure includes the establishment of optimised and distributed memory parallel algorithms for image reconstruction, novel phase identification, 3D visualisation, structural characterisation and prediction of mechanical and transport properties directly from digitised tomographic images. To date over 300 porous specimens exhibiting a wide variety of microstructure have been imaged and analysed. In this paper, analysis of a small set of porous rock specimens with structure ranging from unconsolidated sands to complex carbonates are illustrated. Computations made directly on the digitised tomographic images have been compared to laboratory measurements. The results are in excellent agreement. Additionally, local flow, diffusive and mechanical properties can be numerically derived from solutions of the relevant physical equations on the complex geometries; an experimentally intractable problem. Structural analysis of data sets includes grain and pore partitioning of the images. Local granular partitioning yields over 70,000 grains from a single image. Conventional grain size, shape and connectivity parameters are derived. The 3D organisation of grains can help in correlating grain size, shape and orientation to resultant physical properties. Pore network models generated from 3D images yield over 100000 pores and 200000 throats; comparing the pore structure for the different specimens illustrates the varied topology and geometry observed in porous rocks. This development foreshadows a new

  13. Estimation of moisture transport coefficients in porous materials using experimental drying kinetics

    NASA Astrophysics Data System (ADS)

    Zaknoune, A.; Glouannec, P.; Salagnac, P.

    2012-02-01

    From experimental drying kinetics, an inverse technique is used to evaluate the moisture transport coefficients in building hygroscopic porous materials. Based on the macroscopic approach developed by Whitaker, a one-dimensional mathematical model is developed to predict heat and mass transfers in porous material. The parameters identification is made by the minimisation of the square deviation between numerical and experimental values of the surface temperature and the average moisture content. Two parameters of an exponential function describing the liquid phase transfer and one parameter relative to the diffusion of the vapour phase are identified. To ensure the feasibility of the estimation method, it is initially validated with cellular concrete and applied to lime paste.

  14. Conductive porous scaffolds as potential neural interface materials.

    SciTech Connect

    Hedberg-Dirk, Elizabeth L.; Cicotte, Kirsten N.; Buerger, Stephen P.; Reece, Gregory; Dirk, Shawn M.; Lin, Patrick P.

    2011-11-01

    Our overall intent is to develop improved prosthetic devices with the use of nerve interfaces through which transected nerves may grow, such that small groups of nerve fibers come into close contact with electrode sites, each of which is connected to electronics external to the interface. These interfaces must be physically structured to allow nerve fibers to grow through them, either by being porous or by including specific channels for the axons. They must be mechanically compatible with nerves such that they promote growth and do not harm the nervous system, and biocompatible to promote nerve fiber growth and to allow close integration with biological tissue. They must exhibit selective and structured conductivity to allow the connection of electrode sites with external circuitry, and electrical properties must be tuned to enable the transmission of neural signals. Finally, the interfaces must be capable of being physically connected to external circuitry, e.g. through attached wires. We have utilized electrospinning as a tool to create conductive, porous networks of non-woven biocompatible fibers in order to meet the materials requirements for the neural interface. The biocompatible fibers were based on the known biocompatible material poly(dimethyl siloxane) (PDMS) as well as a newer biomaterial developed in our laboratories, poly(butylene fumarate) (PBF). Both of the polymers cannot be electrospun using conventional electrospinning techniques due to their low glass transition temperatures, so in situ crosslinking methodologies were developed to facilitate micro- and nano-fiber formation during electrospinning. The conductivity of the electrospun fiber mats was controlled by controlling the loading with multi-walled carbon nanotubes (MWNTs). Fabrication, electrical and materials characterization will be discussed along with initial in vivo experimental results.

  15. Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures.

    PubMed

    Jiang, Lili; Fan, Zhuangjun

    2014-02-21

    In order to make full utilization of the high intrinsic surface area of graphene, recently, porous graphene materials including graphene nanomesh, crumpled graphene and graphene foam, have attracted tremendous attention and research interest, owing to their exceptional porous structure (high surface area, and high pore volume) in combination with the inherent properties of graphene, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Interestingly, porous graphene materials and their derivatives have been explored in a wide range of applications in the fields of electronic and photonic devices, energy storage, gas separation/storage, oil absorption and sensors. This article reviews recent progress in the synthesis, characterization, properties, and applications of porous graphene materials. We aim to highlight the importance of designing different porous structures of graphene to meet future challenges, and the trend on future design of porous graphene materials is analyzed.

  16. Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures

    NASA Astrophysics Data System (ADS)

    Jiang, Lili; Fan, Zhuangjun

    2014-01-01

    In order to make full utilization of the high intrinsic surface area of graphene, recently, porous graphene materials including graphene nanomesh, crumpled graphene and graphene foam, have attracted tremendous attention and research interest, owing to their exceptional porous structure (high surface area, and high pore volume) in combination with the inherent properties of graphene, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Interestingly, porous graphene materials and their derivatives have been explored in a wide range of applications in the fields of electronic and photonic devices, energy storage, gas separation/storage, oil absorption and sensors. This article reviews recent progress in the synthesis, characterization, properties, and applications of porous graphene materials. We aim to highlight the importance of designing different porous structures of graphene to meet future challenges, and the trend on future design of porous graphene materials is analyzed.

  17. Theoretical and experimental investigation of acoustic streaming in a porous material.

    PubMed

    Poesio, Pietro; Ooms, Gijs; Schraven, Arthur; van der Bas, Fred

    2002-07-01

    An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. A high external pressure was applied in order to avoid cavitation. A microphone was used to measure the damping of the waves in the porous material and also temperature and pressure measurements in the flowing liquid inside the cores were carried out. To model the acoustic streaming effect Darcy's law was extended with a source term representing the momentum transfer from the acoustic waves to the liquid. The model predictions for the pressure distribution inside the core under acoustic streaming conditions are in reasonable agreement with the experimental data.

  18. A bipotential-based limit analysis and homogenization of ductile porous materials with non-associated Drucker-Prager matrix

    NASA Astrophysics Data System (ADS)

    Cheng, Long; Jia, Yun; Oueslati, Abdelbacet; de Saxcé, Géry; Kondo, Djimedo

    2015-04-01

    In Gurson's footsteps, different authors have proposed macroscopic plastic models for porous solid with pressure-sensitive dilatant matrix obeying the normality law (associated materials). The main objective of the present paper is to extend this class of models to porous materials in the context of non-associated plasticity. This is the case of Drucker-Prager matrix for which the dilatancy angle is different from the friction one, and classical limit analysis theory cannot be applied. For such materials, the second last author has proposed a relevant modeling approach based on the concept of bipotential, a function of both dual variables, the plastic strain rate and stress tensors. On this ground, after recalling the basic elements of the Drucker-Prager model, we present the corresponding variational principles and the extended limit analysis theorems. Then, we formulate a new variational approach for the homogenization of porous materials with a non-associated matrix. This is implemented by considering the hollow sphere model with a non-associated Drucker-Prager matrix. The proposed procedure delivers a closed-form expression of the macroscopic bifunctional from which the criterion and a non-associated flow rule are readily obtained for the porous material. It is shown that these general results recover several available models as particular cases. Finally, the established results are assessed and validated by comparing their predictions to those obtained from finite element computations carried out on a cell representing the considered class of materials.

  19. On mesoscale methods to enhance full-stress continuum modeling of porous compaction

    NASA Astrophysics Data System (ADS)

    Herbold, Eric B.; Swift, Damian C.; Kraus, Richard G.; Homel, Michael; Lorenzana, Hector E.

    2015-06-01

    The dynamic compaction of initially porous material is typically treated in continuum dynamics simulations via adjustments to the scalar equation of state (EOS) of the bulk, porous material relative to that of the solid. However, the behavior during compaction is governed by inelastic processes, as the solid material deforms, largely by shearing, to fill the voids. The resulting response depends on the strain path, e.g. isotropic versus uniaxial loading. Adjustments to the EOS are therefore fundamentally unsuited to describing porous compaction, and it is desirable to consider porous effects through the stress and strain tensors. We have investigated porous modifications to continuum strength models, designed to reproduce elastic wave speeds in porous materials and the crush response observed experimentally during compaction. We have performed mesoscale simulations, resolving the microstructure explicitly, to guide the construction of continuum models. These simulations allow us to study the interplay between strength and EOS in the solid, the extent of dissipative flow versus non-dissipative displacement, and the evolution of porosity and micro-morphological features can be captured. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  20. A homogenization-based constitutive model for two-dimensional viscoplastic porous media

    NASA Astrophysics Data System (ADS)

    Danas, Kostas; Idiart, Martin I.; Ponte Castañeda, Pedro

    2008-01-01

    An approximate model based on the so-called 'second-order' nonlinear homogenization method is proposed to estimate the effective behavior of viscoplastic porous materials exhibiting transversely isotropic symmetry. The model is constructed in such a way that it reproduces exactly the behavior of a 'composite-cylinder assemblage' in the limit of in-plane hydrostatic loading, and therefore coincides with the hydrostatic limit of Gurson's criterion for plastic porous materials. As a consequence, the new model improves on earlier 'second-order' homogenization estimates, which have been found to be overly stiff at sufficiently high triaxialities and nonlinearities. The proposed model is compared with exact results obtained for a special class of porous materials with sequentially laminated microstructures. The agreement is found to be excellent for the entire range of stress triaxialities, and all values of the porosity and nonlinearity considered. To cite this article: K. Danas et al., C. R. Mecanique 336 (2008).

  1. The pressure drop in a porous material layer during combustion

    SciTech Connect

    Kondrikov, B.N.

    1995-07-01

    During the combustion of a porous material layer, a manometer, which is attached to the cold end of the charge, records at the bottom of the layer a pressure reduction, which was discovered more than 20 years ago but which remains essentially unexplained up to the present. It is experimentally shown that this effect is similar to the pressure change in the cavities when a light gas (helium, hydrogen) diffuses from (or to) them under isothermal conditions and that it increases during the combustion mainly due to the accompanying Stefan type flow, and probably also as a result of the thermal diffusion. A pressure drop in the cavities is evidently made possible also by the pressure reduction in the flame which follows from the Hugoniot adiabatic theory.

  2. Salt transport and crystallization in porous building materials.

    PubMed

    Pel, L; Huinink, H; Kopinga, K

    2003-01-01

    Salt weathering is a major cause of deterioration of porous building materials. To obtain information about the mechanisms underlying these damage processes we have studied the moisture and ion transport. We measured the time evolution of NaCl saturated samples of fired-clay brick during one-sided drying using Nuclear Magnetic Resonance. The moisture content and amount of dissolved Na ions could be measured quantitatively as a function of position. The NaCl concentration profiles obtained from these data reflect the competition between advection to the surface and redistribution by diffusion. By representing the measured moisture and NaCl profiles in an efflorescence pathway diagram (EPD) also the crystallization can be taken into account.

  3. Porous multi-component material for the capture and separation of species of interest

    DOEpatents

    Addleman, Raymond S.; Chouyyok, Wilaiwan; Li, Xiaohong S.; Cinson, Anthony D.; Gerasimenko, Aleksandr A

    2016-06-21

    A method and porous multi-component material for the capture, separation or chemical reaction of a species of interest is disclosed. The porous multi-component material includes a substrate and a composite thin film. The composite thin film is formed by combining a porous polymer with a nanostructured material. The nanostructured material may include a surface chemistry for the capture of chemicals or particles. The composite thin film is coupled to the support or device surface. The method and material provides a simple, fast, and chemically and physically benign way to integrate nanostructured materials into devices while preserving their chemical activity.

  4. Electrochemical differential photoacoustic cell to study in situ the growing process of porous materials.

    PubMed

    Gutiérrez, Adriana; Giraldo, Jairo; Velázquez-Hernández, Rubén; Mendoza-López, Maria Luisa; Espinosa-Arbeláez, Diego G; del Real, Alicia; Rodríguez-García, Mario E

    2010-01-01

    In order to study in situ the growing process of porous materials, a new electrochemical differential photoacoustic cell (DPC) was developed. This system allows to obtain the thermal signals coming from the growing process of the pores without the external noise component. The DPC is a good system to growth porous silicon and study their growing process with reproducibility. The porous silicon samples were obtained by using electrochemical etching of (100) n-type silicon wafers with different nominal resistivity values in the range of 1-25 Omega cm. The samples were formed in a solution of hydrofluoric acid and ethanol having a composition ratio of 1:1 in volume with etching voltage of 10 V and an etching time of 2 min using back illumination provided by a laser beam with a wavelength of 808 nm. The porous samples were characterized by means of Raman microscopy, x-ray diffraction, and scanning electron microscopy. The crystallite sizes of the samples were obtained through the analysis of the micro-Raman spectra using a phonon confinement model, and the analysis of the x-ray diffractograms.

  5. Metal-organic frameworks as functional, porous materials

    NASA Astrophysics Data System (ADS)

    Rood, Jeffrey A.

    The research presented in this thesis investigates the use of metal carboxylates as permanently porous materials called metal-organic frameworks (MOFs). The project has focused on three broad areas of study, each which strives to develop a further understanding of this class of materials. The first topic is concerned with the synthesis and structural characterization of MOFs. Our group and others have found that the reaction of metal salts with carboxylic acids in polar solvents at elevated temperatures often leads the formation of crystalline MOF materials that can be examined by single crystal X-ray diffraction. Specifically, Chapter 2 reports on some of the first examples of magnesium MOFs, constructed from formate or aryldicarboxylate ligands. The magnesium formate MOF, [Mg3(O2CH) 6] was found to be a permanently porous 3-D material capable of selective uptake and exchange of small molecules. Once the synthesis and structures of some of these materials was known, their physical properties were studied. The magnesium formate MOF, [Mg 3(O2CH)6], was found to be permanently porous and able to reversibly adsorb both N2 and H2 gas. Furthermore, the material was also capable of taking up a variety of organic molecules to form new inclusion compounds that were characterized by XRD studies. Size exclusion was shown for cyclohexane and larger molecules. Chapters 3, 5, and 6 attempt to build off of the synthetic findings reported in Chapter 2. Specifically, the ability of these materials to take up guest molecules is expanded by the attempted synthesis of porous, homochiral MOFs using enantiopure carboxylic acids in the synthesis. It was found that under the appropriate synthetic conditions, both L-tartaric acid and (+)-camphoric acid were robust linkers for the formation of homochiral MOFs. Of the compounds synthesized, the most interesting were the set of compounds, [Zn2(Cam) 2(bipy)⊃3DMF] and [Zn2(Cam)2(apyr)⊃2DMF]. These compounds formed isoreticular cubic

  6. SCDAP/RELAP5 modeling of heat transfer and flow losses in lower head porous debris. Revision 1

    SciTech Connect

    Siefken, L.J.; Coryell, E.W.; Paik, S.; Kuo, H.

    1999-05-01

    Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate ma nner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region.

  7. Electronically and ionically conductive porous material and method for manufacture of resin wafers therefrom

    DOEpatents

    Lin, YuPo J.; Henry, Michael P.; Snyder, Seth W.

    2011-07-12

    An electrically and ionically conductive porous material including a thermoplastic binder and one or more of anion exchange moieties or cation exchange moieties or mixtures thereof and/or one or more of a protein capture resin and an electrically conductive material. The thermoplastic binder immobilizes the moieties with respect to each other but does not substantially coat the moieties and forms the electrically conductive porous material. A wafer of the material and a method of making the material and wafer are disclosed.

  8. Electronically and ionically conductive porous material and method for manufacture of resin wafers therefrom

    DOEpatents

    Lin, YuPo J.; Henry, Michael P.; Snyder, Seth W.

    2008-11-18

    An electrically and ionically conductive porous material including a thermoplastic binder and one or more of anion exchange moieties or cation exchange moieties or mixtures thereof and/or one or more of a protein capture resin and an electrically conductive material. The thermoplastic binder immobilizes the moieties with respect to each other but does not substantially coat the moieties and forms the electrically conductive porous material. A wafer of the material and a method of making the material and wafer are disclosed.

  9. Limit analysis and homogenization of porous materials with Mohr–Coulomb matrix. Part I: Theoretical formulation

    NASA Astrophysics Data System (ADS)

    Anoukou, K.; Pastor, F.; Dufrenoy, P.; Kondo, D.

    2016-06-01

    The present two-part study aims at investigating the specific effects of Mohr-Coulomb matrix on the strength of ductile porous materials by using a kinematic limit analysis approach. While in the Part II, static and kinematic bounds are numerically derived and used for validation purpose, the present Part I focuses on the theoretical formulation of a macroscopic strength criterion for porous Mohr-Coulomb materials. To this end, we consider a hollow sphere model with a rigid perfectly plastic Mohr-Coulomb matrix, subjected to axisymmetric uniform strain rate boundary conditions. Taking advantage of an appropriate family of three-parameter trial velocity fields accounting for the specific plastic deformation mechanisms of the Mohr-Coulomb matrix, we then provide a solution of the constrained minimization problem required for the determination of the macroscopic dissipation function. The macroscopic strength criterion is then obtained by means of the Lagrangian method combined with Karush-Kuhn-Tucker conditions. After a careful analysis and discussion of the plastic admissibility condition associated to the Mohr-Coulomb criterion, the above procedure leads to a parametric closed-form expression of the macroscopic strength criterion. The latter explicitly shows a dependence on the three stress invariants. In the special case of a friction angle equal to zero, the established criterion reduced to recently available results for porous Tresca materials. Finally, both effects of matrix friction angle and porosity are briefly illustrated and, for completeness, the macroscopic plastic flow rule and the voids evolution law are fully furnished.

  10. Limit analysis and homogenization of porous materials with Mohr-Coulomb matrix. Part I: Theoretical formulation

    NASA Astrophysics Data System (ADS)

    Anoukou, K.; Pastor, F.; Dufrenoy, P.; Kondo, D.

    2016-06-01

    The present two-part study aims at investigating the specific effects of Mohr-Coulomb matrix on the strength of ductile porous materials by using a kinematic limit analysis approach. While in the Part II, static and kinematic bounds are numerically derived and used for validation purpose, the present Part I focuses on the theoretical formulation of a macroscopic strength criterion for porous Mohr-Coulomb materials. To this end, we consider a hollow sphere model with a rigid perfectly plastic Mohr-Coulomb matrix, subjected to axisymmetric uniform strain rate boundary conditions. Taking advantage of an appropriate family of three-parameter trial velocity fields accounting for the specific plastic deformation mechanisms of the Mohr-Coulomb matrix, we then provide a solution of the constrained minimization problem required for the determination of the macroscopic dissipation function. The macroscopic strength criterion is then obtained by means of the Lagrangian method combined with Karush-Kuhn-Tucker conditions. After a careful analysis and discussion of the plastic admissibility condition associated to the Mohr-Coulomb criterion, the above procedure leads to a parametric closed-form expression of the macroscopic strength criterion. The latter explicitly shows a dependence on the three stress invariants. In the special case of a friction angle equal to zero, the established criterion reduced to recently available results for porous Tresca materials. Finally, both effects of matrix friction angle and porosity are briefly illustrated and, for completeness, the macroscopic plastic flow rule and the voids evolution law are fully furnished.

  11. Modeling failure in brittle porous ceramics

    NASA Astrophysics Data System (ADS)

    Keles, Ozgur

    Brittle porous materials (BPMs) are used for battery, fuel cell, catalyst, membrane, filter, bone graft, and pharmacy applications due to the multi-functionality of their underlying porosity. However, in spite of its technological benefits the effects of porosity on BPM fracture strength and Weibull statistics are not fully understood--limiting a wider use. In this context, classical fracture mechanics was combined with two-dimensional finite element simulations not only to account for pore-pore stress interactions, but also to numerically quantify the relationship between the local pore volume fraction and fracture statistics. Simulations show that even the microstructures with the same porosity level and size of pores differ substantially in fracture strength. The maximum reliability of BPMs was shown to be limited by the underlying pore--pore interactions. Fracture strength of BMPs decreases at a faster rate under biaxial loading than under uniaxial loading. Three different types of deviation from classic Weibull behavior are identified: P-type corresponding to a positive lower tail deviation, N-type corresponding to a negative lower tail deviation, and S-type corresponding to both positive upper and lower tail deviations. Pore-pore interactions result in either P-type or N-type deviation in the limit of low porosity, whereas S-type behavior occurs when clusters of low and high fracture strengths coexist in a fracture data.

  12. Use of a porous material description of forests in infrasonic propagation algorithms.

    PubMed

    Swearingen, Michelle E; White, Michael J; Ketcham, Stephen A; McKenna, Mihan H

    2013-10-01

    Infrasound can propagate very long distances and remain at measurable levels. As a result infrasound sensing is used for remote monitoring in many applications. At local ranges, on the order of 10 km, the influence of the presence or absence of forests on the propagation of infrasonic signals is considered. Because the wavelengths of interest are much larger than the scale of individual components, the forest is modeled as a porous material. This approximation is developed starting with the relaxation model of porous materials. This representation is then incorporated into a Crank-Nicholson method parabolic equation solver to determine the relative impacts of the physical parameters of a forest (trunk size and basal area), the presence of gaps/trees in otherwise continuous forest/open terrain, and the effects of meteorology coupled with the porous layer. Finally, the simulations are compared to experimental data from a 10.9 kg blast propagated 14.5 km. Comparison to the experimental data shows that appropriate inclusion of a forest layer along the propagation path provides a closer fit to the data than solely changing the ground type across the frequency range from 1 to 30 Hz. PMID:24116403

  13. Use of a porous material description of forests in infrasonic propagation algorithms.

    PubMed

    Swearingen, Michelle E; White, Michael J; Ketcham, Stephen A; McKenna, Mihan H

    2013-10-01

    Infrasound can propagate very long distances and remain at measurable levels. As a result infrasound sensing is used for remote monitoring in many applications. At local ranges, on the order of 10 km, the influence of the presence or absence of forests on the propagation of infrasonic signals is considered. Because the wavelengths of interest are much larger than the scale of individual components, the forest is modeled as a porous material. This approximation is developed starting with the relaxation model of porous materials. This representation is then incorporated into a Crank-Nicholson method parabolic equation solver to determine the relative impacts of the physical parameters of a forest (trunk size and basal area), the presence of gaps/trees in otherwise continuous forest/open terrain, and the effects of meteorology coupled with the porous layer. Finally, the simulations are compared to experimental data from a 10.9 kg blast propagated 14.5 km. Comparison to the experimental data shows that appropriate inclusion of a forest layer along the propagation path provides a closer fit to the data than solely changing the ground type across the frequency range from 1 to 30 Hz.

  14. Dynamic behavior of particulate/porous energetic materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, Vitali

    2011-06-01

    Dynamic behavior of particulate/porous energetic materials in a broad range of impact conditions and types of deformation (shock, shear) will be discussed. Samples of these materials were fabricated using Cold Isostatic Pressing, sintering and Hot Isostatic Pressing with and without vacuum encapsulation. The current interest in these materials is due to the combination of their high strength with energy efficiency under critical conditions of mechanical deformation. They may exhibit high compressive and tensile strength with the ability to bulk distributed fracture resulting in a small size reactive fragments and possible reaction on later stages. The results of dynamic deformation and fragmentation of these materials in conditions of low velocity (10 m/s), high energy impact, under localized deformation in single and multiple shear bands generated using explosively driven Thick Walled Cylinder method will be discussed. The mechanical properties of these materials are highly sensitive to mesostructure. For example, a dynamic strength of Al-W composites with fine W particles is significantly larger than the strength of composite with the coarse W particles at the same porosity. Morphology of W inclusions had a strong effect on dynamic strength. Samples with W wires arranged in axial direction with the same volume content of components had a highest dynamic strength. Porosity in these materials can provide a strain hardening mechanism effect due to in situ densification which was observed experimentally for cold isostatically pressed Al and Al-coarse W powders. Experimental results will be compared with available numerical data. The support for this project provided by ONR MURI N00014-07-1-0740 (Program Officer Dr. Clifford Bedford).

  15. Enhancement of a dynamic porous model considering compression-release hysteresis behavior: application to graphite

    NASA Astrophysics Data System (ADS)

    Jodar, B.; Seisson, G.; Hébert, D.; Bertron, I.; Boustie, M.; Berthe, L.

    2016-08-01

    Because of their shock wave attenuation properties, porous materials and foams are increasingly used for various applications such as graphite in the aerospace industry and polyurethane (PU) foams in biomedical engineering. For these two materials, the absence of residual compaction after compression and release cycles limits the efficiency of the usual numerical dynamic porous models such as P-α and POREQST. In this paper, we suggest a simple enhancement of the latter in order to take into account the compression-release hysteresis behavior experimentally observed for the considered materials. The new model, named H-POREQST, was implemented into a Lagrangian hydrocode and tested for simulating plate impact experiments at moderate pressure onto a commercial grade of porous graphite (EDM3). It proved to be in far better agreement with experimental data than the original model which encourages us to pursue numerical tests and developments.

  16. Asymmetric Wicking and Reduced Evaporation Time of Droplets Penetrating a Thin Double-Layered Porous Material

    NASA Astrophysics Data System (ADS)

    Vahdani, Aria; Gat, Amir; Nowakowski, Albert; Navaz, Homayun; Gharib, Morteza

    2013-11-01

    We study numerically and experimentally the penetration and evaporation dynamics of droplets wicking into a thin double-layered porous material with order-of-magnitude difference in the physical properties (such as capillary pressure drop, porosity or permeability) between the layers. We show that such double-layered porous materials can be used to create highly asymmetrical wicking properties, preventing liquid droplets wicking from one surface to the other, while allowing for wicking in the reverse direction. In addition, these double-layered porous materials are shown to reduce the evaporation time of droplets penetrating into the porous surface, compared with a single-layered material of equal thickness and physical properties similar to either of the layers. The asymmetric wicking and reduced evaporation time demonstrated in such double-layered porous materials may be of interest to applications such as medical bandages and wearable fabrics.

  17. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials.

    PubMed

    Félix, V; Jannot, Y; Degiovanni, A

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10(-1) to 10(5) Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent. PMID:22667640

  18. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    NASA Astrophysics Data System (ADS)

    Félix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10-1 to 105 Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  19. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    SciTech Connect

    Felix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-15

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10{sup -1} to 10{sup 5} Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  20. Model for high rate gas flows in deformable and reactive porous beds

    SciTech Connect

    Weston, A M

    1985-01-08

    This report presents the development of a one dimensional planar Lagrange hydrodynamic computer model which describes the processes preceding detonation. The model treats gas flow, deflagration, and compaction in a porous bed of reactive material. The early part of deflagration to detonation experiment with porous HMX is simulated. Sensitivity of the simulation calculation to ignition and burn rate parameters is illustrated and discussed. The effects of changing the mean particle size of the porous material are investigated. There is widespread interest in runaway reaction hazards that may be associated with porosity in propellant and explosive materials. Experimentally, such reactions are initiated and observed in long, thick walled hollow tubes, filled with a granular porous bed of reactive material. We will present comparisons with an experiment on porous HMX to illustrate details of the model and to point out what we believe are important features of the observed phenomenon. A geometric finite element cell is devised that allows gas to flow through a compacting matrix. The experimental simulation considers the DDT process from initial squib burn through the onset of general matrix deflagration (convective burning), to the development of a fully dense compaction wave. While this simulation did not calculate turnover to detonation, it did illustrate that the transition occurred as soon as the compaction wave became fully dense. It is shown that deflagration and gas permeation lags compaction at the time of transition. This suggests that the actual transition involves an additional compaction dependent process. 18 references, 20 figures, 3 tables.

  1. Detection of water deposits and movement in porous materials by infrared imaging

    NASA Astrophysics Data System (ADS)

    Avdelidis, N. P.; Moropoulou, A.; Theoulakis, P.

    2003-06-01

    Since a large amount of damage in porous materials arises as a direct or indirect consequence of moisture (static and dynamic phenomena), detection and monitoring of moisture in porous materials is important, in an attempt to determine the actual damage, as well as the deterioration rate. The most common methodology to assess the moisture content in porous materials is to collect representative samples from the sites investigated and then weigh them before and after drying. In this research, infrared thermography, an indirect moisture assessment technique, was used in the investigation of various porous stones in the laboratory during capillary rise tests. Supplementary investigation of the stones in terms of their microstructure (mercury intrusion porosimetry) and isothermic behaviour (water sorption) was also performed. Finally, an in field diagnostic survey on historic structures was carried out. The results of this study indicate that infrared imaging provides significant information in the study of moisture in porous materials.

  2. Phase field modeling of grain growth in porous polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Ahmed, Karim E.

    The concurrent evolution of grain size and porosity in porous polycrystalline solids is a technically important problem. All the physical properties of such materials depend strongly on pore fraction and pore and grain sizes and distributions. Theoretical models for the pore-grain boundary interactions during grain growth usually employ restrictive, unrealistic assumptions on the pore and grain shapes and motions to render the problem tractable. However, these assumptions limit the models to be only of qualitative nature and hence cannot be used for predictions. This has motivated us to develop a novel phase field model to investigate the process of grain growth in porous polycrystalline solids. Based on a dynamical system of coupled Cahn-Hilliard and All en-Cahn equations, the model couples the curvature-driven grain boundary motion and the migration of pores via surface diffusion. As such, the model accounts for all possible interactions between the pore and grain boundary, which highly influence the grain growth kinetics. Through a formal asymptotic analysis, the current work demonstrates that the phase field model recovers the corresponding sharp-interface dynamics of the co-evolution of grain boundaries and pores; this analysis also fixes the model kinetic parameters in terms of real materials properties. The model was used to investigate the effect of porosity on the kinetics of grain growth in UO2 and CeO2 in 2D and 3D. It is shown that the model captures the phenomenon of pore breakaway often observed in experiments. Pores on three- and four- grain junctions were found to transform to edge pores (pores on two-grain junction) before complete separation. The simulations demonstrated that inhomogeneous distribution of pores and pore breakaway lead to abnormal grain growth. The simulations also showed that grain growth kinetics in these materials changes from boundary-controlled to pore-controlled as the amount of porosity increases. The kinetic growth

  3. Attenuation of intense sinusoidal waves in air-saturated, bulk porous materials

    NASA Technical Reports Server (NTRS)

    Kuntz, Herbert L.; Blackstock, David T.

    1987-01-01

    As intense, initially sinusoidal waves propagate in fluids, shocks form and excess attenuation of the wave occurs. Data are presented indicating that shock formation is not necessary for the occurrence of excess attenuation in nonlinear, lossy media, i.e., air-saturated, porous materials. An empirical equation is used to describe the excess attenuation of intense sinusoids in porous materials. The acoustic nonlinearity of and the excess attenuation in porous materials may be predicted directly from dc flow resistivity data. An empirical relationship is used to relate an acoustic nonlinearity parameter to the fundamental frequency and relative dc nonlinearity of two structurally different materials.

  4. High-intensity sound in air saturated fibrous bulk porous materials

    NASA Technical Reports Server (NTRS)

    Kuntz, H. L., II

    1982-01-01

    The interaction high-intensity sound with bulk porous materials in porous materials including Kevlar 29 is reported. The nonlinear behavior of the materials was described by dc flow resistivity tests. Then acoustic propagation and reflection were measured and small signal broadband measurements of phase speed and attenuation were carried out. High-intensity tests were made with 1, 2, and 3 kHz tone bursts to measure harmonic generation and extra attenuation of the fundamental. Small signal standing wave tests measured impedence between 0.1 and 3.5 kHz. High level tests with single cycle tone bursts at 1 to 4 kHz show that impedance increases with intensity. A theoretical analysis is presented for high-porosity, rigid-frame, isothermal materials. One dimensional equations of motion are derived and solved by perturbation. The experiments show that there is excess attenuation of the fundamental component and in some cases a close approach to saturation. A separate theoretical model, developed to explain the excess attenuation, yields predictions that are in good agreement with the measurements. Impedance and attenuation at high intensities are modeled.

  5. Calibration of thermocouple psychrometers and moisture measurements in porous materials

    NASA Astrophysics Data System (ADS)

    Guz, Łukasz; Sobczuk, Henryk; Połednik, Bernard; Guz, Ewa

    2016-07-01

    The paper presents in situ method of peltier psychrometric sensors calibration which allow to determine water potential. Water potential can be easily recalculated into moisture content of the porous material. In order to obtain correct results of water potential, each probe should be calibrated. NaCl salt solutions with molar concentration of 0.4M, 0.7M, 1.0M and 1.4M, were used for calibration which enabled to obtain osmotic potential in range: -1791 kPa to -6487 kPa. Traditionally, the value of voltage generated on thermocouples during wet-bulb temperature depression is calculated in order to determine the calibration function for psychrometric in situ sensors. In the new method of calibration, the field under psychrometric curve along with peltier cooling current and duration was taken into consideration. During calibration, different cooling currents were applied for each salt solution, i.e. 3, 5, 8 mA respectively, as well as different cooling duration for each current (from 2 to 100 sec with 2 sec step). Afterwards, the shape of each psychrometric curve was thoroughly examined and a value of field under psychrometric curve was computed. Results of experiment indicate that there is a robust correlation between field under psychrometric curve and water potential. Calibrations formulas were designated on the basis of these features.

  6. A simple model of gas flow in a porous powder compact.

    SciTech Connect

    Shugard, Andrew D.; Robinson, David B.

    2014-04-01

    This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media.

  7. Small-angle and surface scattering from porous and fractal materials.

    SciTech Connect

    Sinha, S. K.

    1998-09-18

    We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.

  8. Analysis of ignition of a porous energetic material

    SciTech Connect

    Telengator, A.M.; Williams, F.A.; Margolis, S.B.

    1998-04-01

    A theory of ignition is presented to analyze the effect of porosity on the time to ignition of a semi-infinite porous energetic solid subjected to a constant energy flux. An asymptotic perturbation analysis, based on the smallness of the gas-to-solid density ratio and the largeness of the activation energy, is utilized to describe the inert and transition stages leading to thermal runaway. As in the classical study of a nonporous solid, the transition stage consists of three spatial regions in the limit of large activation energy: a thin reactive-diffusive layer adjacent to the exposed surface of the material where chemical effects are first felt, a somewhat thicker transient-diffusive zone, and finally an inert region where the temperature field is still governed solely by conductive heat transfer. Solutions in each region are constructed at each order with respect to the density-ratio parameter and matched to one another using asymptotic matching principles. It is found that the effects of porosity provide a leading-order reduction in the time to ignition relative to that for the nonporous problem, arising from the reduced amount of solid material that must be heated and the difference in thermal conductivities of the solid and gaseous phases. A positive correction to the leading-order ignition-delay time, however, is provided by the convective flow of gas out of the solid, which stems from the effects of thermal expansion and removes energy from the system. The latter phenomenon is absent from the corresponding calculation for the nonporous problem and produces a number of modifications at the next order in the analysis arising from the relative transport effects associated with the gas flow.

  9. On wave propagation characteristics in fluid saturated porous materials by a nonlocal Biot theory

    NASA Astrophysics Data System (ADS)

    Tong, Lihong; Yu, Yang; Hu, Wentao; Shi, Yufeng; Xu, Changjie

    2016-09-01

    A nonlocal Biot theory is developed by combing Biot theory and nonlocal elasticity theory for fluid saturated porous material. The nonlocal parameter is introduced as an independent variable for describing wave propagation characteristics in poroelastic material. A physical insight on nonlocal term demonstrates that the nonlocal term is a superposition of two effects, one is inertia force effect generated by fluctuation of porosity and the other is pore size effect inherited from nonlocal constitutive relation. Models for situations of excluding fluid nonlocal effect and including fluid nonlocal effect are proposed. Comparison with experiment confirms that model without fluid nonlocal effect is more reasonable for predicting wave characteristics in saturated porous materials. The negative dispersion is observed theoretically which agrees well with the published experimental data. Both wave velocities and quality factors as functions of frequency and nonlocal parameter are examined in practical cases. A few new physical phenomena such as backward propagation and disappearance of slow wave when exceeding critical frequency and disappearing shear wave in high frequency range, which were not predicted by Biot theory, are demonstrated.

  10. Comparison of porous and nonporous materials for methane storage

    SciTech Connect

    Thallapally, Praveen K.; Kirby, Karen A.; Atwood, Jerry L.

    2007-05-10

    Sublimed, low-density p-tert-buytlcalix(4)arene absorbs methane more readily at room temperature and 1 atm pressure than do either single wall carbon nanotubes (SWNT) or a comparaitive porous metal-organic framework (MOF-1).

  11. Stability of quasi-steady deflagrations in confined porous energetic materials

    SciTech Connect

    Alexander M. Telengator; Stephen B. Margolis; Forman A. Williams

    2000-03-01

    Previous analyses have shown that unconfined deflagrations propagating through both porous and nonporous energetic materials can exhibit a thermal/diffusive instability that corresponds to the onset of various oscillatory modes of combustion. For porous materials, two-phase-flow effects, associated with the motion of the gas products relative to the condensed material, play a significant role that can shift stability boundaries with respect to those associated with the nonporous problem. In the present work, additional significant effects are shown to be associated with confinement, which produces an overpressure in the burned-gas region that leads to reversal of the gas flow and hence partial permeation of the hot gases into the unburned porous material. This results in a superadiabatic effect that increases the combustion temperature and, consequently, the burning rate. Under the assumption of gas-phase quasi-steadiness, an asymptotic model is presented that facilitates a perturbation analysis of both the basic solution, corresponding to a steadily propagating planar combustion wave, and its stability. The neutral stability boundaries collapse to the previous results in the absence of confinement, but different trends arising from the presence of the gas-permeation layer are predicted for the confined problem. Whereas two-phase-flow effects are generally destabilizing in the unconfined geometry, the effects of increasing overpressure and hence combustion temperature associated with confinement are shown to be generally stabilizing with respect to thermal/diffusive instability, analogous to the effects of decreasing heat losses on combustion temperature and stability in single-phase deflagrations.

  12. Mechanisms of CCl4 Retention and Slow Release in Model Porous Solids and Sediments

    SciTech Connect

    Riley, Robert; Amonette, James

    2005-06-01

    Provide a better description of the processes by which non-polar compounds are retained by sediments and subsequently released. The objective will be reached through a combination of theory and experimentation with model porous materials and natural sediments. Focus is on the behavior of carbon tetrachloride in aquifer sediments.

  13. Examining porous bio-active glass as a potential osteo-odonto-keratoprosthetic skirt material.

    PubMed

    Huhtinen, Reeta; Sandeman, Susan; Rose, Susanna; Fok, Elsie; Howell, Carol; Fröberg, Linda; Moritz, Niko; Hupa, Leena; Lloyd, Andrew

    2013-05-01

    Bio-active glass has been developed for use as a bone substitute with strong osteo-inductive capacity and the ability to form strong bonds with soft and hard tissue. The ability of this material to enhance tissue in-growth suggests its potential use as a substitute for the dental laminate of an osteo-odonto-keratoprosthesis. A preliminary in vitro investigation of porous bio-active glass as an OOKP skirt material was carried out. Porous glass structures were manufactured from bio-active glasses 1-98 and 28-04 containing varying oxide formulation (1-98, 28-04) and particle size range (250-315 μm for 1-98 and 28-04a, 315-500 μm for 28-04b). Dissolution of the porous glass structure and its effect on pH was measured. Structural 2D and 3D analysis of porous structures were performed. Cell culture experiments were carried out to study keratocyte adhesion and the inflammatory response induced by the porous glass materials. The dissolution results suggested that the porous structure made out of 1-98 dissolves faster than the structures made from glass 28-04. pH experiments showed that the dissolution of the porous glass increased the pH of the surrounding solution. The cell culture results showed that keratocytes adhered onto the surface of each of the porous glass structures, but cell adhesion and spreading was greatest for the 98a bio-glass. Cytokine production by all porous glass samples was similar to that of the negative control indicating that the glasses do not induce a cytokine driven inflammatory response. Cell culture results support the potential use of synthetic porous bio-glass as an OOKP skirt material in terms of limited inflammatory potential and capacity to induce and support tissue ingrowth.

  14. Hierarchical simulator of biofilm growth and dynamics in granular porous materials

    NASA Astrophysics Data System (ADS)

    Kapellos, George E.; Alexiou, Terpsichori S.; Payatakes, Alkiviades C.

    2007-06-01

    A new simulator is developed for the prediction of the rate and pattern of growth of biofilms in granular porous media. The biofilm is considered as a heterogeneous porous material that exhibits a hierarchy of length scales. An effective-medium model is used to calculate the local hydraulic permeability and diffusion coefficient in the biofilm, as functions of the local geometric and physicochemical properties. The Navier-Stokes equations and the Brinkman equation are solved numerically to determine the velocity and pressure fields within the pore space and the biofilm, respectively. Biofilm fragments become detached if they are exposed to shear stress higher than a critical value. The detached fragments re-enter into the fluid stream and move within the pore space until they exit from the system or become reattached to downstream grain or biofilm surfaces. A Lagrangian-type simulation is used to determine the trajectories of detached fragments. The spatiotemporal distributions of a carbon source, an electron acceptor and a cell-to-cell signaling molecule are determined from the numerical solution of the governing convection-diffusion-reaction equations. The simulator incorporates growth and apoptosis kinetics for the bacterial cells and production and lysis kinetics for the EPS. The specific growth rate of active bacterial cells depends on the local concentrations of nutrients, mechanical stresses, and a quorum sensing mechanism. Growth-induced deformation of the biofilms is implemented with a cellular automaton approach. In this work, the spatiotemporal evolution of biofilms in the pore space of a 2D granular medium is simulated under high flow rate and nutrient-rich conditions. Transient changes in the pore geometry caused by biofilm growth lead to the formation of preferential flowpaths within the granular porous medium. The decrease of permeability caused by clogging of the porous medium is calculated and is found to be in qualitative agreement with published

  15. Supercritical adsorption testing of porous silicon, activated carbon, and zeolite materials

    NASA Astrophysics Data System (ADS)

    Harvey, Brendan

    The supercritical adsorption of methane gas on porous silicon, activated carbon, and zeolite materials was studied. An apparatus that utilizes the volumetric adsorption measurement technique was designed and constructed to conduct the experiments. Activated carbon materials consisted of Norit RX3 Extra, Zorflex FM30K woven activated carbon cloth, and Zorflex FM10 knitted activated carbon cloth. Zeolite materials consisted of 3A, 4A, 5A, and 13X zeolites. Porous silicon materials consisted of stain etched and electrochemically etched porous films, and stain etched porous powder. All adsorption tests were conducted at room temperature (approximately 298 K) and pressures up to approximately 5 MPa. Overall, the Norit RX3 Extra granulated activated carbon produced the highest excess adsorption and effective storage capacities. Effective storage and delivery capacities of 109 and 90 stpmlml were obtained at a pressure of 3.5 MPa and a temperature of approximately 298 K.

  16. Sound transmission through double cylindrical shells lined with porous material under turbulent boundary layer excitation

    NASA Astrophysics Data System (ADS)

    Zhou, Jie; Bhaskar, Atul; Zhang, Xin

    2015-11-01

    This paper investigates sound transmission through double-walled cylindrical shell lined with poroelastic material in the core, excited by pressure fluctuations due to the exterior turbulent boundary layer (TBL). Biot's model is used to describe the sound wave propagating in the porous material. Three types of constructions, bonded-bonded, bonded-unbonded and unbonded-unbonded, are considered in this study. The power spectral density (PSD) of the inner shell kinetic energy is predicted for two turbulent boundary layer models, different air gap depths and three types of polyimide foams, respectively. The peaks of the inner shell kinetic energy due to shell resonance, hydrodynamic coincidence and acoustic coincidence are discussed. The results show that if the frequency band over the ring frequency is of interest, an air gap, even if very thin, should exist between the two elastic shells for better sound insulation. And if small density foam has a high flow resistance, a superior sound insulation can still be maintained.

  17. Modeling 1-D deflagration to detonation transition (DDT) in porous explosive

    SciTech Connect

    Weston, A.M.; Lee, E.L.

    1985-04-04

    A one-dimensional Lagrange hydrodynamic computer model is presented that describes gas flow, compaction, ignition, and deflagration processes in deformable porous beds. The model makes use of a consumable finite element cell that allows gas to flow through a compacting matrix. The model can be regarded as structural in the sense that the initial cell dimension is directly related to mean particle size. Experimental investigation of the DDT phenomenon are typically carried out using long thick-walled tubes filled with a granular porous bed of reactive material. In this configuration, much of the process can be described by flow in one dimension. We present calculations that simulate both squib initiated and piston initiated experiments on porous HMX to point out various observed features. Our purpose is to establish a basis for setting bounds on the physical parameters that describe such transient reaction processes. 16 refs., 17 figs., 1 tab.

  18. A fully coupled porous flow and geomechanics model for fluid driven cracks: a peridynamics approach

    NASA Astrophysics Data System (ADS)

    Ouchi, Hisanao; Katiyar, Amit; York, Jason; Foster, John T.; Sharma, Mukul M.

    2015-03-01

    A state-based non-local peridynamic formulation is presented for simulating fluid driven fractures in an arbitrary heterogeneous poroelastic medium. A recently developed peridynamic formulation of porous flow has been coupled with the existing peridynamic formulation of solid and fracture mechanics resulting in a peridynamic model that for the first time simulates poroelasticity and fluid-driven fracture propagation. This coupling is achieved by modeling the role of pore pressure on the deformation of porous media and vice versa through porosity variation with medium deformation, pore pressure and total mean stress. The poroelastic model is verified by simulating the one-dimensional consolidation of fluid saturated rock. An additional porous flow equation with material permeability dependent on fracture width is solved to simulate fluid flow in the fractured region. Finally, single fluid-driven fracture propagation with a two-dimensional plane strain assumption is simulated and verified against the corresponding classical analytical solution.

  19. Idealized radiation efficiency model for a porous radiant burner

    SciTech Connect

    Fu, X.; Viskanta, R.; Gore, J.P.

    1999-07-01

    A simple, highly idealized radiation efficiency model has been developed for a porous radiant burner with or without a screen to assess the thermal performance of an ideal porous burner that yields the highest radiation efficiency and against which test results and/or more realistic model predictions could be benchmarked. The model is based on thermodynamics principles (first law of thermodynamics) with idealizations made for some of the physical processes. Empirical information, where necessary, is then used to close the model equations. The maximum radiation efficiency at a given firing rate is predicted. The effects of input parameters such as the firing rate, the equivalence ratio, and the effective emittance of the burner on the radiation efficiency of the porous radiant burner are reported.

  20. An investigation of the influence of acoustic waves on the liquid flow through a porous material.

    PubMed

    Poesio, Pietro; Ooms, Gijs; Barake, Sander; van der Bas, Fred

    2002-05-01

    An experimental and theoretical investigation has been made of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material. The experiments have been performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. Also, a temperature measurement of the flowing liquid inside the core was made. A high external pressure was applied in order to avoid cavitation. The acoustic waves were found to produce a significant effect on the pressure gradient at constant liquid flow rate through the core samples. During the application of acoustic waves the pressure gradient inside the core decreases. This effect turned out to be due to the decrease of the liquid viscosity caused by an increase in liquid temperature as a result of the acoustic energy dissipation inside the porous material. Also, a theoretical model has been developed to calculate the dissipation effect on the viscosity and on the pressure gradient. The model predictions are in reasonable agreement with the experimental data.

  1. Iterated linear comparison bounds for viscoplastic porous materials with “ellipsoidal” microstructures

    NASA Astrophysics Data System (ADS)

    Agoras, M.; Ponte Castañeda, P.

    2013-03-01

    Analytical estimates are obtained for the effective constitutive response of porous viscoplastic materials consisting of aligned ellipsoidal voids that are distributed randomly with "ellipsoidal" symmetry in the matrix material. These estimates are obtained by means of a novel iterative homogenization strategy recently proposed by Ponte Castañeda (2012), and can be shown to be bounds for certain classes of multi-scale microstructures. By design, the resulting constitutive model agrees exactly with the earlier "variational linear comparison" model at the first iteration (N=1), and provides estimates that get progressively more accurate as the number of iterations increases (N→∞), especially for high-triaxiality loading conditions, and low porosity and strain-rate sensitivity. However, in practice, a small number of iterations (N≈10) is sufficient to get very accurate results. It is important to emphasize that, unlike other models that have been proposed in the literature, the new model requires no fitting parameters, solely depending on the properties of the matrix phase and microstructural information, such as the porosity, the average void shape and orientation, as well as the generally different shape and orientation of their distribution. Results are given for the yield and gauge surfaces of ideally plastic and power-law viscoplastic porous materials for the special cases of aligned spheroidal and ellipsoidal voids, and the results are compared with available numerical results and with the results of other models. Compared to available numerical results, the new estimates are found to be quite accurate, while they also provide more flexibility than competing models in terms of the characterization of the microstructure. In particular, it was found that the effect of different shapes for the average pore shape and distribution on the yield surfaces of the porous materials can be significant at high triaxialities, even for very small porosities. In addition

  2. Modeling microbial processes in porous media

    NASA Astrophysics Data System (ADS)

    Murphy, Ellyn M.; Ginn, Timothy R.

    The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation: (1) transport of bacteria as inert colloids in porous media, and (2) the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater-contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate availability, metabolic activity, growth, and attachment/detachment rates. This linkage requires both a detailed understanding of the biological processes and robust quantitative representations of these processes that can be tested experimentally. This paper presents an overview of current approaches used to represent physicochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases. Résumé L'introduction des processus microbiologiques dans des modèles de transport réactif a généralement suivi deux voies différentes de recherches: (1) le transport de bactéries sous forme de colloïdes inertes en milieu poreux, et (2) la biodégradation de polluants dissous par une phase stationnaire de bactéries. Les recherches conduites au cours des dix dernières années indiquent que ces processus sont intimement liés. Cette liaison peut intervenir lorsqu

  3. Modeling microbial processes in porous media

    NASA Astrophysics Data System (ADS)

    Murphy, Ellyn M.; Ginn, Timothy R.

    The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation: (1) transport of bacteria as inert colloids in porous media, and (2) the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater-contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate availability, metabolic activity, growth, and attachment/detachment rates. This linkage requires both a detailed understanding of the biological processes and robust quantitative representations of these processes that can be tested experimentally. This paper presents an overview of current approaches used to represent physicochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases. Résumé L'introduction des processus microbiologiques dans des modèles de transport réactif a généralement suivi deux voies différentes de recherches: (1) le transport de bactéries sous forme de colloïdes inertes en milieu poreux, et (2) la biodégradation de polluants dissous par une phase stationnaire de bactéries. Les recherches conduites au cours des dix dernières années indiquent que ces processus sont intimement liés. Cette liaison peut intervenir lorsqu

  4. a Fractal Network Model for Fractured Porous Media

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Li, Cuihong; Qiu, Shuxia; Sasmito, Agus Pulung

    2016-04-01

    The transport properties and mechanisms of fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of fractured porous media, where a fractal tree-like network model is used to characterize the fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of fracture system and fractured porous media, tortuosity, fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for fracture length and aperture have significant effect on the equivalent hydraulic properties of fractured porous media. The effective permeability of fracture system can be increased with the increase of fractal dimensions for fracture length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the fracture density and fractal dimension for fracture length has been found, where the scaling exponent depends on the fracture number. The present fractal dual-porosity model may shed light on the transport physics of fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.

  5. Limit analysis and homogenization of porous materials with Mohr-Coulomb matrix. Part II: Numerical bounds and assessment of the theoretical model

    NASA Astrophysics Data System (ADS)

    Pastor, F.; Anoukou, K.; Pastor, J.; Kondo, D.

    2016-06-01

    This second part of the two-part study is devoted to the numerical Limit Analysis of a hollow sphere model with a Mohr-Coulomb matrix and its use for the assessment of theoretical results. Brief background and fundamental of the static and kinematic approaches in the context of numerical limit analysis are first recalled. We then present the hollow sphere model, together with its axisymmetric FEM discretization and its mechanical position. A conic programming adaptation of a previous iterative static approach, based on a piecewise linearization (PWL) of the plasticity criterion, was first realized. Unfortunately, the resulting code, no more than the PWL one, did not allow sufficiently refined meshes for loss of convergence of the conic optimizer. This problem was solved by using the projection algorithm of Ben Tal and Nemriovski (BTN) and the (interior point) linear programming code XA. For the kinematic approach, a first conic adaptation appeared also inefficient. Then, an original mixed (but fully kinematic) approach dedicated to the general Mohr-Coulomb axisymmetric problem was elaborated. The final conic mixed code appears much more robust than the classic one when using the conic code MOSEK, allowing us to take into account refined numerical meshes. After a fine validation in the case of spherical cavities and isotropic loadings (for which the exact solution is known) and comparison to previous (partial) results, numerical lower and upper bounds (a posteriori verified) of the macroscopic strength are provided. These bounds are used to assess and validate the theoretical results of the companion (part I) paper. Effects of the friction angle as well as that of the porosity are illustrated.

  6. A transfer-matrix approach for estimating the characteristic impedance and wave numbers of limp and rigid porous materials

    PubMed

    Song; Bolton

    2000-03-01

    A method for evaluating the acoustical properties of homogeneous and isotropic porous materials that may be modeled as fluids having complex properties is described here. To implement the procedure, a conventional, two-microphone standing wave tube was modified to include: a new sample holder; a section downstream of the sample holder that accommodated a second pair of microphone holders and an approximately anechoic termination. Sound-pressure measurements at two upstream and two downstream locations were then used to estimate the two-by-two transfer matrix of porous material samples. The experimental transfer matrix method has been most widely used in the past to measure the acoustical properties of silencer system components. That procedure was made more efficient here by taking advantage of the reciprocal nature of sound transmission through homogeneous and isotropic porous layers. The transfer matrix of a homogeneous and isotropic, rigid or limp porous layer can easily be used to identify the material's characteristic impedance and wave number, from which other acoustical quantities of interest can be calculated. The procedure has been used to estimate the acoustical properties of a glass fiber material: good agreement was found between the estimated acoustical properties and those predicted by using the formulas of Delany and Bazley.

  7. Method for the preparation of ferrous low carbon porous material

    DOEpatents

    Miller, Curtis Jack

    2014-05-27

    A method for preparing a porous metal article using a powder metallurgy forming process is provided which eliminates the conventional steps associated with removing residual carbon. The method uses a feedstock that includes a ferrous metal powder and a polycarbonate binder. The polycarbonate binder can be removed by thermal decomposition after the metal article is formed without leaving a carbon residue.

  8. Investigations on deflagration to detonation transition in porous energetic materials. Final report

    SciTech Connect

    Stewart, D.S.

    1999-07-01

    The research carried out by this contract was part of a larger effort funded by LANL in the areas of deflagration to detonation in porous energetic materials (DDT) and detonation shock dynamics in high explosives (DSD). In the first three years of the contract the major focus was on DDT. However, some researchers were carried out on DSD theory and numerical implementation. In the last two years the principal focus of the contract was on DSD theory and numerical implementation. However, during the second period some work was also carried out on DDT. The paper discusses DDT modeling and DSD modeling. Abstracts are included on the following topics: modeling deflagration to detonation; DSD theory; DSD wave front tracking; and DSD program burn implementation.

  9. Investigation into the optimal hydrologic design of porous concrete sites using mathematical modeling

    NASA Astrophysics Data System (ADS)

    Syrrakou, C.; Fitch, J.; Eliassen, T.; Ahearn, W.; Pinder, G. F.

    2011-12-01

    Increase in the amount of paved areas as a result of urbanization in modern societies has lead to the need of stormwater best management practices (BMPs). In that direction, porous pavement has been used successfully in regions of warm climate and application in regions of colder climate is an object of ongoing research with encouraging results to date. The significant cost and effort that accompanies the maintenance of porous pavement facilities calls for a design tool that can be used prior construction to facilitate the design process and also post production to evaluate the site's overall performance. Such a tool is a mathematical model which takes into account the different physical processes that can occur in a porous concrete system including recharge from rainfall, runoff from surrounding conventionally paved areas, vertical flow, storage and finally infiltration into the subsurface. In this research a three-dimensional saturated-unsaturated flow and transport model is modified to account for flow through the porous concrete slab and also evaporation. Runoff is accounted by means of a two-dimensional surface flow model which calculates the infiltration into the perimeter porous concrete area. The mathematical model is used to simulate a porous concrete site which operates as a public parking lot facility in Randolph, Vermont. The subgrade soil in the area of interest consists mainly of dense till deposits typically found in New England. Such deposits can result in small infiltration rates. The specific site is unique not only in terms of the underlying geology but also the heavy instrumentation not usually observed in similar sites. The instrumentation includes a number of groundwater wells which are being monitored continuously through a pressure transducer system, temperature probes installed inside the porous concrete and a detailed underdrain system located in the porous concrete's sub-base accumulating infiltrated water. Laboratory research is also

  10. A comparison of measured and modeled velocity fields for a laminar flow in a porous medium

    NASA Astrophysics Data System (ADS)

    Wood, B. D.; Apte, S. V.; Liburdy, J. A.; Ziazi, R. M.; He, X.; Finn, J. R.; Patil, V. A.

    2015-11-01

    Obtaining highly-resolved velocity data from experimental measurements in porous media is a significant challenge. The goal of this work is to compare the velocity fields measured in a randomly-packed porous medium obtained from particle image velocimetry (PIV) with corresponding fields predicted from direct numerical simulation (DNS). Experimentally, the porous medium was comprised of 15 mm diameter spherical beads made of optical glass placed in a glass flow cell to create the packed bed. A solution of ammonium thiocyanate was refractive-index matched to the glass creating a medium that could be illuminated with a laser sheet without distortion. The bead center locations were quantified using the imaging system so that the geometry of the porous medium was known very accurately. Two-dimensional PIV data were collected and processed to provide high-resolution velocity fields at a single plane within the porous medium. A Cartesian-grid-based fictitious domain approach was adopted for the direct numerical simulation of flow through the same geometry as the experimental measurements and without any adjustable parameters. The uncertainties associated with characterization of the pore geometry, PIV measurements, and DNS predictions were all systematically quantified. Although uncertainties in bead position measurements led to minor discrepancies in the comparison of the velocity fields, the axial and normal velocity deviations exhibited normalized root mean squared deviations (NRMSD) of only 11.32% and 4.74%, respectively. The high fidelity of both the experimental and numerical methods have significant implications for understanding and even for engineering the micro-macro relationship in porous materials. The ability to measure and model sub-pore-scale flow features also has relevance to the development of upscaled models for flow in porous media, where physically reasonable closure models must be developed at the sub-pore scale. These results provide valuable data

  11. A volume-balance model for flow on porous media

    NASA Astrophysics Data System (ADS)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2015-11-01

    Volume-balance models are used by petroleum engineers for simulating multiphase and multicomponent flow phenomena in porous media and the extraction process in oil reservoirs. In these models, mass conservation equations and Darcy's law are supplemented by a balance condition for the pore and fluid volumes. This provides a pressure equation suitable for simulating a compressible flow within a compressible solid matrix. Here we present an alternative interpretation of the volume-balance condition that includes the advective transport within a consolidated porous media. We obtain a modified equation for the time evolution of the pressure field. Numerical tests for phase separation under gravity are presented for multiphase three dimensional flow in heterogeneous porous media. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER grant number 42536 (DGAJ-SPI-34-170412-217).

  12. Fluid-Structure interaction modeling in deformable porous arteries

    NASA Astrophysics Data System (ADS)

    Zakerzadeh, Rana; Zunino, Paolo

    2015-11-01

    A computational framework is developed to study the coupling of blood flow in arteries interacting with a poroelastic arterial wall featuring possibly large deformations. Blood is modeled as an incompressible, viscous, Newtonian fluid using the Navier-Stokes equations and the arterial wall consists of a thick material which is modeled as a Biot system that describes the mechanical behavior of a homogeneous and isotropic elastic skeleton, and connecting pores filled with fluid. Discretization via finite element method leads to the system of nonlinear equations and a Newton-Raphson scheme is adopted to solve the resulting nonlinear system through consistent linearization. Moreover, interface conditions are imposed on the discrete level via mortar finite elements or Nitsche's coupling. The discrete linearized coupled FSI system is solved by means of a splitting strategy, which allows solving the Navier-Stokes and Biot equations separately. The numerical results investigate the effects of proroelastic parameters on the pressure wave propagation in arteries, filtration of incompressible fluids through the porous media, and the structure displacement. The fellowship support from the Computational Modeling & Simulation PhD program at University of Pittsburgh for Rana Zakerzadeh is gratefully acknowledged.

  13. Is Macroporosity Absolutely Required for Preliminary in Vitro Bone Biomaterial Study? A Comparison between Porous Materials and Flat Materials

    PubMed Central

    Lee, Juliana T.Y.; Chow, King L.; Wang, Kefeng; Tsang, Wai Hung

    2011-01-01

    Porous materials are highly preferred for bone tissue engineering due to space for blood vessel ingrowth, but this may introduce extra experimental variations because of the difficulty in precise control of porosity. In order to decide whether it is absolutely necessary to use porous materials in in vitro comparative osteogenesis study of materials with different chemistries, we carried out osteoinductivity study using C3H/10T1/2 cells, pluripotent mesenchymal stem cells (MSCs), on seven material types: hydroxyapatite (HA), α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP) in both porous and dense forms and tissue culture plastic. For all materials under test, dense materials give higher alkaline phosphatase gene (Alp) expression compared with porous materials. In addition, the cell density effects on the 10T1/2 cells were assessed through alkaline phosphatase protein (ALP) enzymatic assay. The ALP expression was higher for higher initial cell plating density and this explains the greater osteoinductivity of dense materials compared with porous materials for in vitro study as porous materials would have higher surface area. On the other hand, the same trend of Alp mRNA level (HA > β-TCP > α-TCP) was observed for both porous and dense materials, validating the use of dense flat materials for comparative study of materials with different chemistries for more reliable comparison when well-defined porous materials are not available. The avoidance of porosity variation would probably facilitate more reproducible results. This study does not suggest porosity is not required for experiments related to bone regeneration application, but emphasizes that there is often a tradeoff between higher clinical relevance, and less variation in a less complex set up, which facilitates a statistically significant conclusion. Technically, we also show that the base of normalization for ALP activity may influence the conclusion and there may be ALP activity from

  14. Synthesis, structure and properties of hierarchical nanostructured porous materials studied by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Chae, Kisung

    For applications of porous materials in many fields of technological importance, such as catalysis, filtration, separation, energy storage and conversion, the efficiency is often limited by chemical kinetics, and/or diffusion of reactants and products to and from the active sites. Hierarchical nanostructured porous materials (HNPMs) that possess both mesopores (2 nm < pore size < 50 nm) and micropores (pore size < 2 nm) have shown great potential for these applications as their bimodal porous structure can provide highly efficient mass transport through mesopores and high electrochemically accessible surface area from micropores. Despite extensive experimental studies, it remains a great challenge to quantify the synthesis-structure-properties relations in HNPMs due to the limitations of existing characterization tools and the difficulty in separating the sum of many effects in experiments. In this thesis work, we carried out a detailed study on the synthesis-structure-property relations in hierarchical nanostructured porous carbons (HNPCs) by using classical molecular dynamics (MD) simulations. We first developed a unique computational nanocasting approach in MD to mimic the synthesis of HNPCs with both mesopores from the templating and micropores from the direct quench of carbon source in MD. Mesoporous structure such as the pore size and the pore wall roughness as well as the microporous structure such as the density and the graphitic pore walls can be independently controlled by synthesis parameters, such as the size of the template, the interaction strength between the template and carbon source, the initial carbon density and the quench rate, respectively. These atomic models allowed us to quantify the structure-mechanical properties relation in aligned carbon nanotubes/amorphous porous carbon nanocomposites. Our study shows that there is an optimum balance between the crystallinity of CNTs and the number bridging bonds between CNTs and the microporous matrix

  15. Modeling isothermal and non-isothermal flows in porous media

    NASA Astrophysics Data System (ADS)

    Mohseni Languri, Ehsan

    2011-12-01

    A complete understanding of the physics of flow and heat transfer phenomena in porous media is vital for accurate simulation of flow processes in industrial applications. In one such application pertaining to liquid composite molding (LCM) for manufacturing polymer composites, the fiber preforms used in LCM as reinforcements are limited not only to the single-scale porous media in the form of random fiber-mats, but also include dual-scale porous media in the form of woven or stitched fiber-mats. The conventional flow physics is not able to model the resin filling process in LCM involving the dual-scale porous media. In this study, the flow in dual-scale porous media is studied in order to predict the permeability of these fiber mats. The effect of aspect ratio of the fiber preform on the accuracy and flow during permeability estimation in single- and dual-scale porous media is analyzed experimentally and numerically. Flow of liquid in a free channel bounded on one side by porous medium is studied next, and two well-known boundary conditions of stress continuity and stress jump at the interface of the two regions are evaluated numerically. A point-wise solution for Stokes flow through periodic and non periodic porous media (made of cylindrical particles) adjacent to the free channel is presented using the Imite element based CFD software COMSOL. The efficacy of the two interfacial conditions is evaluated after volume averaging the point-wise velocity using a long averaging volume, also called the representative elementary volume or REV, and then comparing such a volume-averaged velocity profile with the available analytical solution. The investigation is carried out for five different porosities at three different Reynolds numbers to cover a wide range of applications. The presence of randomly-placed cylinders during the creation of non-periodic porous media damps out spatial fluctuations in the averaged velocity observed in periodic porous media. The analytical

  16. An alternative Biot's displacement formulation for porous materials.

    PubMed

    Dazel, Olivier; Brouard, Bruno; Depollier, Claude; Griffiths, Stéphane

    2007-06-01

    This paper proposes an alternative displacement formulation of Biot's linear model for poroelastic materials. Its advantage is a simplification of the formalism without making any additional assumptions. The main difference between the method proposed in this paper and the original one is the choice of the generalized coordinates. In the present approach, the generalized coordinates are chosen in order to simplify the expression of the strain energy, which is expressed as the sum of two decoupled terms. Hence, new equations of motion are obtained whose elastic forces are decoupled. The simplification of the formalism is extended to Biot and Willis thought experiments, and simpler expressions of the parameters of the three Biot waves are also provided. A rigorous derivation of equivalent and limp models is then proposed. It is finally shown that, for the particular case of sound-absorbing materials, additional simplifications of the formalism can be obtained.

  17. Hydrogen-Bonded Organic Frameworks (HOFs): A New Class of Porous Crystalline Proton-Conducting Materials.

    PubMed

    Karmakar, Avishek; Illathvalappil, Rajith; Anothumakkool, Bihag; Sen, Arunabha; Samanta, Partha; Desai, Aamod V; Kurungot, Sreekumar; Ghosh, Sujit K

    2016-08-26

    Two porous hydrogen-bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra-high proton conduction values (σ) 0.75× 10(-2)  S cm(-1) and 1.8×10(-2)  S cm(-1) under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic-based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen-bonded porous organic frameworks as solid-state proton conducting materials. PMID:27464784

  18. An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

    PubMed Central

    Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

    2010-01-01

    Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts. PMID:20559508

  19. An overview of recent development in composite catalysts from porous materials for various reactions and processes.

    PubMed

    Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

    2010-01-01

    Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts. PMID:20559508

  20. A novel multiple batch extraction test to assess contaminant mobilization from porous waste materials

    NASA Astrophysics Data System (ADS)

    Iden, S. C.; Durner, W.; Delay, M.; Frimmel, F. H.

    2009-04-01

    Contaminated porous materials, like soils, dredged sediments or waste materials must be tested before they can be used as filling materials in order to minimize the risk of groundwater pollution. We applied a multiple batch extraction test at varying liquid-to-solid (L/S) ratios to a demolition waste material and a municipal waste incineration product and investigated the release of chloride, sulphate, sodium, copper, chromium and dissolved organic carbon from both waste materials. The liquid phase test concentrations were used to estimate parameters of a relatively simple mass balance model accounting for equilibrium partitioning. The model parameters were estimated within a Bayesian framework by applying an efficient MCMC sampler and the uncertainties of the model parameters and model predictions were quantified. We tested isotherms of the linear, Freundlich and Langmuir type and selected the optimal isotherm model by use of the Deviance Information Criterion (DIC). Both the excellent fit to the experimental data and a comparison between the model-predicted and independently measured concentrations at the L/S ratios of 0.25 and 0.5 L/kg demonstrate the applicability of the model for almost all studied substances and both waste materials. We conclude that batch extraction tests at varying L/S ratios provide, at moderate experimental cost, a powerful complement to established test designs like column leaching or single batch extraction tests. The method constitutes an important tool in risk assessments, because concentrations at soil water contents representative for the field situation can be predicted from easier-to-obtain test concentrations at larger L/S ratios. This helps to circumvent the experimental difficulties of the soil saturation extract and eliminates the need to apply statistical approaches to predict such representative concentrations which have been shown to suffer dramatically from poor correlations.

  1. Sound propagation in and low frequency noise absorption by helium-filled porous material.

    PubMed

    Choy, Y S; Huang, Lixi; Wang, Chunqi

    2009-12-01

    Low-frequency noise is difficult to deal with by traditional porous material due to its inherent high acoustic impedance. This study seeks to extend the effective range of sound absorption to lower frequencies by filling a low density gas, such as helium, in the porous material. Compared with conventional air-filled absorption material, the helium-filled porous material has a much reduced characteristic impedance; hence, a good impedance matching with pure air becomes more feasible at low frequencies. The acoustic properties of a series of helium-filled porous materials are investigated with a specially designed test rig. The characteristic of the sound propagation in a helium-filled porous material is established and validated experimentally. Based on the measured acoustic properties, the sound absorption performance of a helium-filled absorber (HA) of finite thickness is studied numerically as well as experimentally. For a random incidence field, the HA is found to perform much better than the air-filled absorber at low frequencies. The main advantage of HA lies in the middle range of oblique incidence angles where wave refraction in the absorber enhances sound absorption. The advantage of HA as duct lining is demonstrated both numerically and experimentally.

  2. Fabrication of porous materials (metal, metal oxide and semiconductor) through an aerosol-assisted route

    NASA Astrophysics Data System (ADS)

    Sohn, Hiesang

    Porous materials have gained attraction owing to their vast applications in catalysts, sensors, energy storage devices, bio-devices and other areas. To date, various porous materials were synthesized through soft and hard templating approaches. However, a general synthesis method for porous non-oxide materials, metal alloys and semiconductors with tunable structure, composition and morphology has not been developed yet. To address this challenge, this thesis presents an aerosol method towards the synthesis of such materials and their applications for catalysis, hydrogen storage, Li-batteries and photo-catalysis. The first part of this thesis presents the synthesis of porous metals, metal oxides, and semiconductors with controlled pore structure, crystalline structure and morphology. In these synthesis processes, metal salts and organic ligands were employed as precursors to create porous metal-carbon frameworks. During the aerosol process, primary metal clusters and nanoparticles were formed, which were coagulated/ aggregated forming the porous particles. Various porous particles, such as those of metals (e.g., Ni, Pt, Co, Fe, and Ni xPt(1-x)), metal oxides (e.g., Fe3O4 and SnO2) and semiconductors (e.g., CdS, CuInS2, CuInS 2x-ZnS(1-x), and CuInS2x-TiO2(1-x)) were synthesized. The morphology, porous structure and crystalline structure of the particles were regulated through both templating and non-templating methods. The second part of this thesis explores the applications of these materials, including propylene hydrogenation and H2 uptake capacity of porous Ni, NiPt alloys and Ni-Pt composites, Li-storage of Fe3O4 and SnO2, photodegradation of CuInS2-based semiconductors. The effects of morphology, compositions, and porous structure on the device performance were systematically investigated. Overall, this dissertation work unveiled a simple synthesis approach for porous particles of metals, metal alloys, metal oxides, and semiconductors with controlled

  3. Highly Porous Wood Based Carbon Materials for Supercapacitors

    NASA Astrophysics Data System (ADS)

    Volperts, A.; Dobele, G.; Zhurinsh, A.; Vervikishko, D.; Shkolnikov, E.; Ozolinsh, J.; Mironova-Ulmane, N.; Sildos, I.

    2015-03-01

    Wood based activated carbons synthesized by two-stage thermocatalytical synthesis with NaOH activator were studied and used as supercapacitor electrodes (sulphuric acid electrolyte). Porous structure and electrochemical properties of carbons vs synthesis conditions were assessed. It was found that there are correlations between carbons synthesis variables, their porosity and supercapacitors functional characteristics. At the temperature 600°C and activator/precursor ratio 1.25 porosity decreased, however energy capacitance of supercapacitor increased calculating on elementary cell mass.

  4. Modeling of two-phase porous flow with damage

    NASA Astrophysics Data System (ADS)

    Cai, Z.; Bercovici, D.

    2009-12-01

    Two-phase dynamics has been broadly studied in Earth Science in a convective system. We investigate the basic physics of compaction with damage theory and present preliminary results of both steady state and time-dependent transport when melt migrates through porous medium. In our simple 1-D model, damage would play an important role when we consider the ascent of melt-rich mixture at constant velocity. Melt segregation becomes more difficult so that porosity is larger than that in simple compaction in the steady-state compaction profile. Scaling analysis for compaction equation is performed to predict the behavior of melt segregation with damage. The time-dependent of the compacting system is investigated by looking at solitary wave solutions to the two-phase model. We assume that the additional melt is injected to the fracture material through a single pulse with determined shape and velocity. The existence of damage allows the pulse to keep moving further than that in simple compaction. Therefore more melt could be injected to the two-phase mixture and future application such as carbon dioxide injection is proposed.

  5. Pore network model of electrokinetic transport through charged porous media

    NASA Astrophysics Data System (ADS)

    Obliger, Amaël; Jardat, Marie; Coelho, Daniel; Bekri, Samir; Rotenberg, Benjamin

    2014-04-01

    We introduce a method for the numerical determination of the steady-state response of complex charged porous media to pressure, salt concentration, and electric potential gradients. The macroscopic fluxes of solvent, salt, and charge are computed within the framework of the Pore Network Model (PNM), which describes the pore structure of the samples as networks of pores connected to each other by channels. The PNM approach is used to capture the couplings between solvent and ionic flows which arise from the charge of the solid surfaces. For the microscopic transport coefficients on the channel scale, we take a simple analytical form obtained previously by solving the Poisson-Nernst-Planck and Stokes equations in a cylindrical channel. These transport coefficients are upscaled for a given network by imposing conservation laws for each pores, in the presence of macroscopic gradients across the sample. The complex pore structure of the material is captured by the distribution of channel diameters. We investigate the combined effects of this complex geometry, the surface charge, and the salt concentration on the macroscopic transport coefficients. The upscaled numerical model preserves the Onsager relations between the latter, as expected. The calculated macroscopic coefficients behave qualitatively as their microscopic counterparts, except for the permeability and the electro-osmotic coupling coefficient when the electrokinetic effects are strong. Quantitatively, the electrokinetic couplings increase the difference between the macroscopic coefficients and the corresponding ones for a single channel of average diameter.

  6. Averaged model for momentum and dispersion in hierarchical porous media

    NASA Astrophysics Data System (ADS)

    Chabanon, Morgan; David, Bertrand; Goyeau, Benoît.

    2015-08-01

    Hierarchical porous media are multiscale systems, where different characteristic pore sizes and structures are encountered at each scale. Focusing the analysis to three pore scales, an upscaling procedure based on the volume-averaging method is applied twice, in order to obtain a macroscopic model for momentum and diffusion-dispersion. The effective transport properties at the macroscopic scale (permeability and dispersion tensors) are found to be explicitly dependent on the mesoscopic ones. Closure problems associated to these averaged properties are numerically solved at the different scales for two types of bidisperse porous media. Results show a strong influence of the lower-scale porous structures and flow intensity on the macroscopic effective transport properties.

  7. Examining Asphaltene Solubility on Deposition in Model Porous Media.

    PubMed

    Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Fatt, Yap Yit; Chai, John C; Goharzadeh, Afshin; Vargas, Francisco M; Biswal, Sibani Lisa

    2016-08-30

    Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Péclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection-diffusion effects on deposition. PMID:27532331

  8. Ductile damage of porous materials with two populations of voids

    NASA Astrophysics Data System (ADS)

    Vincent, Pierre-Guy; Monerie, Yann; Suquet, Pierre

    2008-01-01

    This study is devoted to the modelling of ductile damage in uranium dioxide. This polycrystalline material contains two populations of voids of well separated size. The problem addressed here is the prediction of the effective flow surface of a Gurson material containing randomly oriented oblate voids. The case of spherical voids is considered first and the variational approach of Gurson is generalized by adding a compressible component to his original velocity field. The case of aligned oblate voids is then considered and a suitable generalization of a velocity field due to Gologanu et al. (ASME J. Engrg. Mater. Technol. 116 (1994) 290-297) is proposed. The extension to randomly oriented voids is achieved by averaging over all orientations. In each case, rigorous upper bounds and approximate estimates are derived and compared (in the case of spherical voids) with Finite Element simulations. To cite this article: P.-G. Vincent et al., C. R. Mecanique 336 (2008).

  9. Modelling of nickel-cadmium batteries using porous electrode theory

    NASA Technical Reports Server (NTRS)

    Timmerman, Paul J.; Di Stefano, Salvador; Glueck, Peter R.; Perrone, David E.

    1991-01-01

    A porous electrode modeling technique is discussed which is considered a viable means for quantitatively predicting Ni-Cd cell performance. The authors describe the integration of the cell model into a battery model useful in the design and operation of aerospace applications. Test data from a sealed boilerplate cell are presented for constant current charge and discharge conditions. Performance predictions for similar cases have been performed, and a comparison to the boilerplate data is made. Areas for further development are also noted.

  10. Synthesis and gas adsorption study of porous metal-organic framework materials

    NASA Astrophysics Data System (ADS)

    Mu, Bin

    Metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) have become the focus of intense study over the past decade due to their potential for advancing a variety of applications including air purification, gas storage, adsorption separations, catalysis, gas sensing, drug delivery, and so on. These materials have some distinct advantages over traditional porous materials such as the well-defined structures, uniform pore sizes, chemically functionalized sorption sites, and potential for postsynthetic modification, etc. Thus, synthesis and adsorption studies of porous MOFs have increased substantially in recent years. Among various prospective applications, air purification is one of the most immediate concerns, which has urgent requirements to improve current nuclear, biological, and chemical (NBC) filters involving commercial and military purposes. Thus, the major goal of this funded project is to search, synthesize, and test these novel hybrid porous materials for adsorptive removal of toxic industrial chemicals (TICs) and chemical warfare agents (CWAs), and to install the benchmark for new-generation NBC filters. The objective of this study is three-fold: (i) Advance our understanding of coordination chemistry by synthesizing novel MOFs and characterizing these porous coordination polymers; (ii) Evaluate porous MOF materials for gasadsorption applications including CO2 capture, CH4 storage, other light gas adsorption and separations, and examine the chemical and physical properties of these solid adsorbents including thermal stability and heat capacity of MOFs; (iii) Evaluate porous MOF materials for next-generation NBC filter media by adsorption breakthrough measurements of TICs on MOFs, and advance our understanding about structureproperty relationships of these novel adsorbents.

  11. Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling

    NASA Astrophysics Data System (ADS)

    GÜLdemeister, Nicole; WÜNnemann, Kai; Durr, Nathanael; Hiermaier, Stefan

    2013-01-01

    Abstract-Generation and propagation of shock waves by meteorite impact is significantly affected by <span class="hlt">material</span> properties such as porosity, water content, and strength. The objective of this work was to quantify processes related to the shock-induced compaction of pore space by numerical <span class="hlt">modeling</span>, and compare the results with data obtained in the framework of the Multidisciplinary Experimental and <span class="hlt">Modeling</span> Impact Research Network (MEMIN) impact experiments. We use mesoscale <span class="hlt">models</span> resolving the collapse of individual pores to validate macroscopic (homogenized) approaches describing the bulk behavior of <span class="hlt">porous</span> and water-saturated <span class="hlt">materials</span> in large-scale <span class="hlt">models</span> of crater formation, and to quantify localized shock amplification as a result of pore space crushing. We carried out a suite of numerical <span class="hlt">models</span> of planar shock wave propagation through a well-defined area (the "sample") of <span class="hlt">porous</span> and/or water-saturated <span class="hlt">material</span>. The <span class="hlt">porous</span> sample is either represented by a homogeneous unit where porosity is treated as a state variable (macroscale <span class="hlt">model</span>) and water content by an equation of state for mixed <span class="hlt">material</span> (ANEOS) or by a defined number of individually resolved pores (mesoscale <span class="hlt">model</span>). We varied porosity and water content and measured thermodynamic parameters such as shock wave velocity and particle velocity on meso- and macroscales in separate simulations. The mesoscale <span class="hlt">models</span> provide additional data on the heterogeneous distribution of peak shock pressures as a consequence of the complex superposition of reflecting rarefaction waves and shock waves originating from the crushing of pores. We quantify the bulk effect of porosity, the reduction in shock pressure, in terms of Hugoniot data as a function of porosity, water content, and strength of a quartzite matrix. We find a good agreement between meso-, macroscale <span class="hlt">models</span> and Hugoniot data from shock experiments. We also propose a combination of a porosity compaction <span class="hlt">model</span> (ɛ-α <span class="hlt">model</span>) that was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhDT.......375H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhDT.......375H"><span id="translatedtitle">Strengthening of <span class="hlt">porous</span> matrix <span class="hlt">materials</span> with evaporation/condensation sintering for composite <span class="hlt">materials</span> applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haslam, Jeffery John</p> <p>1998-12-01</p> <p>The need for improved fuel economy and reduced environmental emissions from power turbines has prompted the development of high temperature fiber composite <span class="hlt">materials</span>. One use of these <span class="hlt">materials</span> is for liners of the hot combustion regions of jet engines and land based power turbines. Stability of the composite <span class="hlt">materials</span> against oxidative damage during long term use at high temperatures has motivated recent research into fiber composite <span class="hlt">materials</span> composed entirely of oxide ceramics. All-oxide fiber reinforced composites containing <span class="hlt">porous</span>, strongly bonded matrices have become of interest. The porosity provides for crack deflection along the fibers to prevent catastrophic failure of the fiber reinforcements. A new application of a processing method that produces evaporation/condensation sintering was employed to prevent shrinkage of the matrix. This processing method and the properties of the matrix, fibers, and composite were evaluated in this work. Producing a matrix without shrinkage is important to prevent undesirable crack-like voids from forming in the matrix. These voids are caused by constraint against shrinkage by the fiber reinforcements. Dry hydrogen chloride gas produced a reactive gas atmosphere that was used to sinter the zirconia particles with minimal shrinkage because the gas promotes evaporation/condensation sintering with zirconia. Sintering of samples that did not contain fiber reinforcements was studied to evaluate the properties of the matrix <span class="hlt">material</span>. The sintering of monoclinic, tetragonal, and cubic zirconias in the reactive gas atmosphere was compared. Additions of mullite (which did not sinter significantly at processing temperatures) further reduced the shrinkage. The effects of the processing conditions on the sintering shrinkage, microstructure development, and mechanical properties were studied. Cubic and monoclinic zirconia coarsened significantly in the HCl gas sintering atmosphere. The coarsening of the particles during the sintering</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPS...280...30F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPS...280...30F"><span id="translatedtitle"><span class="hlt">Porous</span> hollow carbon spheres for electrode <span class="hlt">material</span> of supercapacitors and support <span class="hlt">material</span> of dendritic Pt electrocatalyst</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Yang; Liu, Pei-Fang; Huang, Zhong-Yuan; Jiang, Tong-Wu; Yao, Kai-Li; Han, Ran</p> <p>2015-04-01</p> <p><span class="hlt">Porous</span> hollow carbon spheres (PHCSs) are prepared through hydrothermal carbonization of alginic acid and subsequent chemical activation by KOH. The porosity of the alginic acid derived PHCSs can be finely modulated by varying activation temperature in the range of 600-900 °C. The PHCSs activated at 900 °C possess the largest specific surface area (2421 m2 g-1), well-balanced micro- and mesoporosity, as well as high content of oxygen-containing functional groups. As the electrode <span class="hlt">material</span> for supercapacitors, the PHCSs exhibit superior capacitive performance with specific capacitance of 314 F g-1 at current density of 1 A g-1. Pt nanodendrites supported on the PHCSs are synthesized by polyol reduction method which exhibit high electrocatalytic activity towards methanol oxidation reaction (MOR). Moreover, CO-poisoning tolerance of the Pt nanodendrites is greatly enhanced owing to the surface chemical property of the PHCSs support.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JAP...107c4912B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JAP...107c4912B"><span id="translatedtitle">Velocity measurements of inert <span class="hlt">porous</span> <span class="hlt">materials</span> driven by infrared-laser-ablated thin-film titanium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bedeaux, Brett C.; Trott, Wayne M.; Castañeda, Jaime N.</p> <p>2010-02-01</p> <p>This article presents and interprets a series of experiments performed to measure the velocity of four inert low-density <span class="hlt">porous</span> <span class="hlt">materials</span> that were accelerated by an ablated thin-film titanium metal, created by vaporizing a 250-nm-thick layer of titanium with a high-energy, Q-switched, pulsed, and 1.054 μm neodymium-glass laser. Inert powder <span class="hlt">materials</span> were chosen to match, among other characteristics, the morphology of energetic <span class="hlt">materials</span> under consideration for use in detonator applications. The observed behavior occurs near the thin-film titanium ablation layer, through complex physical mechanisms, including laser absorption in the metal layer, ablation and formation of confined plasma that is a blackbody absorber of the remaining photon energy, and vaporization of the remaining titanium metal. One-dimensional hydrodynamic <span class="hlt">modeling</span> provided a basis of comparison with the measured velocities. We found, as predicted in wave-propagation-code <span class="hlt">modeling</span>, that an Asay foil can indicate total momentum of the driven <span class="hlt">material</span> that is mechanically softer (lower in shock impedance) than the foil. The key conclusion is that the specific impulse delivered by the laser transfers a corresponding momentum to soft, organic power columns that are readily compacted. Impulse from the laser is less efficient in transferring momentum to hard inorganic particles that are less readily compacted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPS...295..254S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPS...295..254S"><span id="translatedtitle">Template-assisted formation of <span class="hlt">porous</span> vanadium oxide as high performance cathode <span class="hlt">materials</span> for lithium ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, Yanhui; Pan, Anqiang; Wang, Yaping; Huang, Jiwu; Nie, Zhiwei; An, Xinxin; Liang, Shuquan</p> <p>2015-11-01</p> <p>Similar to carbonaceous <span class="hlt">materials</span>, <span class="hlt">porous</span> metal oxides have attracted wide attention in energy storage and conversion systems because of their structural advantages, including high activity and electrolyte accessibility. In this work, we report the novel preparation of <span class="hlt">porous</span> vanadium pentoxide (V2O5) as high performance cathode <span class="hlt">material</span> for lithium ion batteries. Ketjen black (KB), a <span class="hlt">porous</span> carbon <span class="hlt">material</span>, has been employed as hard templates to host precursor species in their <span class="hlt">porous</span> structures. The <span class="hlt">porous</span> V2O5 electrode <span class="hlt">material</span> is prepared after removing the KB carbon framework by calcinating the composites in air. As cathode <span class="hlt">materials</span> for lithium ion batteries, the <span class="hlt">porous</span> V2O5 electrodes exhibit high capacity, good cycling stability and rate capability. An initial discharge capacity of 141.1 mA h g-1 is delivered at a current density of 100 mAg-1, very close to the theoretical capacity of 147 mA h g-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1050750','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1050750"><span id="translatedtitle">Characterization of <span class="hlt">porous</span> <span class="hlt">materials</span> using combined small-angle X-ray and neutron scattering techniques</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hu, Naiping; Borkar, Neha; Kohls, Doug; Schaefer, Dale W.</p> <p>2014-09-24</p> <p>A combination of ultra small angle X-ray scattering (USAXS) and ultra small angle neutron scattering (USANS) is used to characterize <span class="hlt">porous</span> <span class="hlt">materials</span>. The analysis methods yield quantitative information, including the mean skeletal chord length, mean pore chord length, skeletal density, and composition. A mixed cellulose ester (MCE) membrane with a manufacturer-labeled pore size of 0.1 {mu}m was used as a <span class="hlt">model</span> to elucidate the specifics of the method. Four approaches describing four specific scenarios (different known parameters and form of the scattering data) are compared. Pore chords determined using all four approaches are in good agreement with the scanning electron microscopy estimates but are larger than the manufacturer's nominal pore size. Our approach also gives the average chord of the skeletal solid (struts) of the membrane, which is also consistent for all four approaches. Combined data from USAXS and USANS gives the skeletal density and the strut composition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27195990','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27195990"><span id="translatedtitle">Tailoring of the <span class="hlt">porous</span> structure of soft emulsion-templated polymer <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kovalenko, Artem; Zimny, Kévin; Mascaro, Benoit; Brunet, Thomas; Mondain-Monval, Olivier</p> <p>2016-06-21</p> <p>This paper discusses the formation of soft <span class="hlt">porous</span> <span class="hlt">materials</span> obtained by the polymerization of inverse water-in-silicone (polydimethylsiloxane, PDMS) emulsions. We show that the initial state of the emulsion has a strong impact on the <span class="hlt">porous</span> structure and properties of the final <span class="hlt">material</span>. We show that using a surfactant with different solubilities in the emulsion continuous phase (PDMS), it is possible to tune the interaction between emulsion droplets, which leads to <span class="hlt">materials</span> with either interconnected or isolated pores. These two systems present completely different behavior upon drying, which results in macroporous air-filled <span class="hlt">materials</span> in the interconnected case and in a collapsed <span class="hlt">material</span> with low porosity in the second case. Finally, we compare the mechanical and acoustical properties of these two types of bulk polymer monoliths. We also describe the formation of micrometric polymer particles (beads) in these two cases. We show that <span class="hlt">materials</span> with an interconnected macroporous structure have low mechanical moduli and low sound speed, and are suitable for acoustic applications. The mechanical and acoustical properties of the <span class="hlt">materials</span> with a collapsed <span class="hlt">porous</span> structure are similar to those of non-<span class="hlt">porous</span> silicone, which makes them acoustically inactive. PMID:27195990</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1034349','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1034349"><span id="translatedtitle">Systems and strippable coatings for decontaminating structures that include <span class="hlt">porous</span> <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Fox, Robert V.; Avci, Recep; Groenewold, Gary S.</p> <p>2011-12-06</p> <p>Methods of removing contaminant matter from <span class="hlt">porous</span> <span class="hlt">materials</span> include applying a polymer <span class="hlt">material</span> to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer <span class="hlt">material</span> from the surface. Systems for decontaminating a contaminated structure comprising <span class="hlt">porous</span> <span class="hlt">material</span> include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture <span class="hlt">material</span> onto the surface of the structure. Polymer <span class="hlt">materials</span> that can be used in such methods and systems include polyphosphazine-based polymer <span class="hlt">materials</span> having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1163140','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1163140"><span id="translatedtitle">New Carbon-Based <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Increased Heats of Adsorption for Hydrogen Storage</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Snurr, Randall Q.; Hupp, Joseph T.; Kanatzidis, Mercouri G.; Nguyen, SonBinh T.</p> <p>2014-11-03</p> <p>Hydrogen fuel cell vehicles are a promising alternative to internal combustion engines that burn gasoline. A significant challenge in developing fuel cell vehicles is to store enough hydrogen on-board to allow the same driving range as current vehicles. One option for storing hydrogen on vehicles is to use tanks filled with <span class="hlt">porous</span> <span class="hlt">materials</span> that act as “sponges” to take up large quantities of hydrogen without the need for extremely high pressures. The <span class="hlt">materials</span> must meet many requirements to make this possible. This project aimed to develop two related classes of <span class="hlt">porous</span> <span class="hlt">materials</span> to meet these requirements. All <span class="hlt">materials</span> were synthesized from molecular constituents in a building-block approach, which allows for the creation of an incredibly wide variety of <span class="hlt">materials</span> in a tailorable fashion. The <span class="hlt">materials</span> have extremely high surface areas, to provide many locations for hydrogen to adsorb. In addition, they were designed to contain cations that create large electric fields to bind hydrogen strongly but not too strongly. Molecular <span class="hlt">modeling</span> played a key role as a guide to experiment throughout the project. A major accomplishment of the project was the development of a <span class="hlt">material</span> with record hydrogen uptake at cryogenic temperatures. Although the ultimate goal was <span class="hlt">materials</span> that adsorb large quantities of hydrogen at room temperature, this achievement at cryogenic temperatures is an important step in the right direction. In addition, there is significant interest in applications at these temperatures. The hydrogen uptake, measured independently at NREL was 8.0 wt %. This is, to the best of our knowledge, the highest validated excess hydrogen uptake reported to date at 77 K. This <span class="hlt">material</span> was originally sketched on paper based on a hypothesis that extended framework struts would yield <span class="hlt">materials</span> with excellent hydrogen storage properties. However, before starting the synthesis, we used molecular <span class="hlt">modeling</span> to assess the performance of the <span class="hlt">material</span> for hydrogen uptake</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1038224','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1038224"><span id="translatedtitle"><span class="hlt">Modeling</span> reactive transport in deformable <span class="hlt">porous</span> media using the theory of interacting continua.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Turner, Daniel Zack</p> <p>2012-01-01</p> <p>This report gives an overview of the work done as part of an Early Career LDRD aimed at <span class="hlt">modeling</span> flow induced damage of <span class="hlt">materials</span> involving chemical reactions, deformation of the <span class="hlt">porous</span> matrix, and complex flow phenomena. The numerical formulation is motivated by a mixture theory or theory of interacting continua type approach to coupling the behavior of the fluid and the <span class="hlt">porous</span> matrix. Results for the proposed method are presented for several engineering problems of interest including carbon dioxide sequestration, hydraulic fracturing, and energetic <span class="hlt">materials</span> applications. This work is intended to create a general framework for flow induced damage that can be further developed in each of the particular areas addressed below. The results show both convincing proof of the methodologies potential and the need for further validation of the <span class="hlt">models</span> developed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008CRMec.336..176L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008CRMec.336..176L"><span id="translatedtitle">A theoretical approach of strain localization within thin planar bands in <span class="hlt">porous</span> ductile <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leblond, Jean-Baptiste; Mottet, Gérard</p> <p>2008-01-01</p> <p>Propagation of cracks in ductile <span class="hlt">materials</span> is well known to occur through two possible mechanisms: coalescence of cavities and formation of shear bands ('void sheet mechanism'). The classical Gurson-Tvergaard-Needleman (GTN) homogenized <span class="hlt">model</span> for such <span class="hlt">materials</span> incorporates some phenomenological <span class="hlt">modelling</span> of coalescence, but not of formation of shear bands assisted by the presence of microvoids, and this generates a number of shortcomings. In order to solve these difficulties, this paper presents a unified <span class="hlt">model</span> of both coalescence and formation of shear bands in <span class="hlt">porous</span> plastic solids, including the possible couplings between the two. Both phenomena are viewed as expressions of the same basic effect, namely strain localization within thin planar bands, the only difference being the mode of deformation. The <span class="hlt">model</span> is first developed assuming a periodic distribution of cavities, then critically assessed through comparison with some micromechanical numerical simulations based on the same assumption, and finally extended to the case of a random distribution of voids. To cite this article: J.-B. Leblond, G. Mottet, C. R. Mecanique 336 (2008).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.738a2090E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.738a2090E"><span id="translatedtitle">Potential of Lattice Boltzmann Method to Determine the Ohmic Resistance in <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Espinoza-Andaluz, Mayken; Andersson, Martin; Sundén, Bengt</p> <p>2016-08-01</p> <p>The lattice Boltzmann method (LBM) is a suitable tool for solving transport phenomena that occur in gas- and liquid phases at different length scales, especially when complex geometries such as <span class="hlt">porous</span> media are involved. However, investigations about applications of LBM in the solid electrical conducting <span class="hlt">material</span> have not been carried out yet. Since in fuel cells (FCs) the multifunctional layers play an important role during the energy conversion process, and such layers consist of <span class="hlt">porous</span> <span class="hlt">material</span>, the ohmic resistance of <span class="hlt">porous</span> <span class="hlt">materials</span> represents a crucial characteristic to be studied to predict the internal ohmic losses. The purpose of this paper is to show the feasibility of LBM to determine the ohmic resistance of electrical conducting <span class="hlt">materials</span> whose dimensions are modified considering the crosssectional area and length. Characteristics, limitations and recommendations of LBM applied to solid electrical conducting <span class="hlt">materials</span> calculating the ohmic resistance are presented considering the coupling of the methodology with the Ohm's Law. Additionally, the behavior of the ohmic resistance for a given <span class="hlt">porous</span> <span class="hlt">material</span> is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12366250','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12366250"><span id="translatedtitle">Lattice Boltzmann <span class="hlt">model</span> for incompressible flows through <span class="hlt">porous</span> media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guo, Zhaoli; Zhao, T S</p> <p>2002-09-01</p> <p>In this paper a lattice Boltzmann <span class="hlt">model</span> is proposed for isothermal incompressible flow in <span class="hlt">porous</span> media. The key point is to include the porosity into the equilibrium distribution, and add a force term to the evolution equation to account for the linear and nonlinear drag forces of the medium (the Darcy's term and the Forcheimer's term). Through the Chapman-Enskog procedure, the generalized Navier-Stokes equations for incompressible flow in <span class="hlt">porous</span> media are derived from the present lattice Boltzmann <span class="hlt">model</span>. The generalized two-dimensional Poiseuille flow, Couette flow, and lid-driven cavity flow are simulated using the present <span class="hlt">model</span>. It is found the numerical results agree well with the analytical and/or the finite-difference solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RMRE...48..223X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RMRE...48..223X"><span id="translatedtitle">An Experimental Study and Constitutive <span class="hlt">Modeling</span> of Saturated <span class="hlt">Porous</span> Rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, S. Y.; Shao, J. F.</p> <p>2015-01-01</p> <p>This paper is devoted to the experimental characterization and constitutive <span class="hlt">modeling</span> of saturated <span class="hlt">porous</span> rocks. A typical <span class="hlt">porous</span> chalk is investigated. Drained hydrostatic and triaxial compression tests are first performed to characterize the basic mechanical behavior of chalk. Drained triaxial tests with constant interstitial pressure are then carried out to study the effects of interstitial pressure on the plastic deformation and failure criterion. Finally, undrained triaxial compression tests are performed to investigate poromechanical coupling in saturated conditions. Based on the experimental data and some relevant micromechanical considerations, a micromechanics-based plastic <span class="hlt">model</span> is proposed and extended to poroplastic coupling using the effective stress concept. The proposed <span class="hlt">model</span> is verified through comparisons between the numerical results and experimental data for both drained and undrained tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMagR.269....1K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMagR.269....1K"><span id="translatedtitle">Diffusion-mediated nuclear spin phase decoherence in cylindrically <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knight, Michael J.; Kauppinen, Risto A.</p> <p>2016-08-01</p> <p>In NMR or MRI of complex <span class="hlt">materials</span>, including biological tissues and <span class="hlt">porous</span> <span class="hlt">materials</span>, magnetic susceptibility differences within the <span class="hlt">material</span> result in local magnetic field inhomogeneities, even if the applied magnetic field is homogeneous. Mobile nuclear spins move though the inhomogeneous field, by translational diffusion and other mechanisms, resulting in decoherence of nuclear spin phase more rapidly than transverse relaxation alone. The objective of this paper is to simulate this diffusion-mediated decoherence and demonstrate that it may substantially reduce coherence lifetimes of nuclear spin phase, in an anisotropic fashion. We do so using a <span class="hlt">model</span> of cylindrical pores within an otherwise homogeneous <span class="hlt">material</span>, and calculate the resulting magnetic field inhomogeneities. Our simulations show that diffusion-mediated decoherence in a system of parallel cylindrical pores is anisotropic, with coherence lifetime minimised when the array of cylindrical pores is perpendicular to B0. We also show that this anisotropy of coherence lifetime is reduced if the orientations of cylindrical pores are disordered within the system. In addition we characterise the dependence on B0, the magnetic susceptibility of the cylindrical pores relative to the surroundings, the diffusion coefficient and cylinder wall thickness. Our findings may aid in the interpretation of NMR and MRI relaxation data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/485961','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/485961"><span id="translatedtitle">In situ bioremediation: A network <span class="hlt">model</span> of diffusion and flow in granular <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Griffiths, S.K.; Nilson, R.H.; Bradshaw, R.W.</p> <p>1997-04-01</p> <p>In situ bioremediation is a potentially expedient, permanent and cost- effective means of waste site decontamination. However, permeability reductions due to the transport and deposition of native fines or due to excessive microorganism populations may severely inhibit the injection of supplemental oxygen in the contamination zone. To help understand this phenomenon, we have developed a micro-mechanical network <span class="hlt">model</span> of flow, diffusion and particle transport in granular <span class="hlt">porous</span> <span class="hlt">materials</span>. The <span class="hlt">model</span> differs from most similar <span class="hlt">models</span> in that the network is defined by particle positions in a numerically-generated particle array. The <span class="hlt">model</span> is thus widely applicable to computing effective transport properties for both ordered and realistic random <span class="hlt">porous</span> media. A laboratory-scale apparatus to measure permeability reductions has also been designed, built and tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980001239','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980001239"><span id="translatedtitle"><span class="hlt">Porous</span> and Microporous Honeycomb Composites as Potential Boundary-Layer Bleed <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, D. O.; Willis, B. P.; Schoenenberger, M.</p> <p>1997-01-01</p> <p>Results of an experimental investigation are presented in which the use of <span class="hlt">porous</span> and microporous honeycomb composite <span class="hlt">materials</span> is evaluated as an alternate to perforated solid plates for boundary-layer bleed in supersonic aircraft inlets. The terms "<span class="hlt">porous</span>" and "microporous," respectively, refer to bleed orifice diameters roughly equal to and much less than the displacement thickness of the approach boundary-layer. A Baseline <span class="hlt">porous</span> solid plate, two <span class="hlt">porous</span> honeycomb, and three microporous honeycomb configurations are evaluated. The performance of the plates is characterized by the flow coefficient and relative change in boundary-layer profile parameters across the bleed region. The tests were conducted at Mach numbers of 1.27 and 1.98. The results show the <span class="hlt">porous</span> honeycomb is not as efficient at removing mass compared to the baseline. The microporous plates were about equal to the baseline with one plate demonstrating a significantly higher efficiency. The microporous plates produced significantly fuller boundary-layer profiles downstream of the bleed region for a given mass flow removal rate than either the baseline or the <span class="hlt">porous</span> honeycomb plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3751908','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3751908"><span id="translatedtitle">Laser-induced growth of nanocrystals embedded in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated <span class="hlt">porous</span> xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in <span class="hlt">porous</span> silica xerogels, which allows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NRL.....8..266C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NRL.....8..266C"><span id="translatedtitle">Laser-induced growth of nanocrystals embedded in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed</p> <p>2013-06-01</p> <p>Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated <span class="hlt">porous</span> xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in <span class="hlt">porous</span> silica xerogels, which allows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatMa..15..371C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatMa..15..371C"><span id="translatedtitle"><span class="hlt">Materials</span> <span class="hlt">modelling</span> in London</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ciudad, David</p> <p>2016-04-01</p> <p>Angelos Michaelides, Professor in Theoretical Chemistry at University College London (UCL) and co-director of the Thomas Young Centre (TYC), explains to Nature <span class="hlt">Materials</span> the challenges in <span class="hlt">materials</span> <span class="hlt">modelling</span> and the objectives of the TYC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890007948','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890007948"><span id="translatedtitle">Mechanics of <span class="hlt">materials</span> <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Meister, Jeffrey P.</p> <p>1987-01-01</p> <p>The Mechanics of <span class="hlt">Materials</span> <span class="hlt">Model</span> (MOMM) is a three-dimensional inelastic structural analysis code for use as an early design stage tool for hot section components. MOMM is a stiffness method finite element code that uses a network of beams to characterize component behavior. The MOMM contains three <span class="hlt">material</span> <span class="hlt">models</span> to account for inelastic <span class="hlt">material</span> behavior. These include the simplified <span class="hlt">material</span> <span class="hlt">model</span>, which assumes a bilinear stress-strain response; the state-of-the-art <span class="hlt">model</span>, which utilizes the classical elastic-plastic-creep strain decomposition; and Walker's viscoplastic <span class="hlt">model</span>, which accounts for the interaction between creep and plasticity that occurs under cyclic loading conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27255561','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27255561"><span id="translatedtitle">Applications of hierarchically structured <span class="hlt">porous</span> <span class="hlt">materials</span> from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Ming-Hui; Huang, Shao-Zhuan; Chen, Li-Hua; Li, Yu; Yang, Xiao-Yu; Yuan, Zhong-Yong; Su, Bao-Lian</p> <p>2016-06-13</p> <p>Over the last decade, significant effort has been devoted to the applications of hierarchically structured <span class="hlt">porous</span> <span class="hlt">materials</span> owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these <span class="hlt">materials</span> is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into <span class="hlt">materials</span> has led to a significant improvement in the performance of <span class="hlt">materials</span>. Herein, recent progress in the applications of hierarchically structured <span class="hlt">porous</span> <span class="hlt">materials</span> from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically <span class="hlt">porous</span> structures and properties, with examples of each type of hierarchically structured <span class="hlt">porous</span> <span class="hlt">material</span> according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span> and to have a good idea about selecting and designing suitable hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span> for a specific application. In addition to focusing on the applications of hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span>, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically <span class="hlt">porous</span> solids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H14A..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H14A..01L"><span id="translatedtitle"><span class="hlt">Modelling</span> the Complex Conductivity of Charged <span class="hlt">Porous</span> Media using The Grain Polarization <span class="hlt">Model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leroy, P.; Revil, A.; Jougnot, D.; Li, S.</p> <p>2015-12-01</p> <p>The low-frequency complex conductivity response of charged <span class="hlt">porous</span> media reflects a combination of three polarization processes occuring at different frequency ranges. One polarization process corresponds to the membrane polarization phenomenon, which is the polarization mechanism associated with the back-diffusion of salt ions through different pore spaces of the <span class="hlt">porous</span> <span class="hlt">material</span> (ions-selective zones and zones with no selectivity). This polarization process generally occurs at the lowest frequency range, typically in the frequency range [mHz Hz] because it involves polarization mechanism occurring over different pore spaces (the relaxation frequency is inversely proportional to the length of the polarization process). Another polarization process corresponds to the electrochemical polarization of the electrical double layer coating the surface of the grains. In the grain polarization <span class="hlt">model</span>, the diffuse layer is assumed to not polarize because it is assumed to form a continuum in the <span class="hlt">porous</span> medium. The compact Stern layer is assumed to polarize because the Stern layer is assumed to be discontinuous over multiple grains. The electrochemical polarization of the Stern layer typically occurs in the frequency range [Hz kHz]. The last polarization process corresponds to the Maxwell-Wagner polarization mechanism, which is caused by the formation of field-induced free charge distributions near the interface between the phases of the medium. In this presentation, the grain polarization <span class="hlt">model</span> based on the O'Konski, Schwarz, Schurr and Sen theories and developed later by Revil and co-workers is showed. This spectral induced polarization <span class="hlt">model</span> was successfully applied to describe the complex conductivity responses of glass beads, sands, clays, clay-sand mixtures and other minerals. The limits of this <span class="hlt">model</span> and future developments will also be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019031','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019031"><span id="translatedtitle">Determination of water retention in stratified <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Constantz, J.</p> <p>1995-01-01</p> <p>Predicted and measured water-retention values, ??(??), were compared for repacked, stratified core samples consisting of either a sand with a stone-bearing layer or a sand with a clay loam layer in various spatial orientations. Stratified core samples were packed in submersible pressure outflow cells, then water-retention measurements were performed between matric potentials, ??, of 0 to -100 kPa. Predictions of ??(??) were based on a simple volume-averaging <span class="hlt">model</span> using estimates of the relative fraction and ??(??) values of each textural component within a stratified sample. In general, predicted ??(??) curves resembled measured curves well, except at higher saturations in a sample consisting of a clay loam layer over a sand layer. In this case, the <span class="hlt">model</span> averaged the air-entry of both <span class="hlt">materials</span>, while the air-entry of the sample was controlled by the clay loam in contact with the cell's air-pressure inlet. In situ, avenues for air-entry generally exist around clay layers, so that the <span class="hlt">model</span> should adequately predict air-entry for stratified formations regardless of spatial orientation of fine versus coarse layers. Agreement between measured and predicted volumetric water contents, ??, was variable though encouraging, with mean differences between measured and predicted ?? values in the range of 10%. Differences in ?? of this magnitude are expected due to variability in pore structure between samples, and do not indicate inherent problems with the volume averaging <span class="hlt">model</span>. This suggets that explicit <span class="hlt">modeling</span> of stratified formations through detailed characterization of the stratigraphy has the potential of yielding accurate ??(??) values. However, hydraulic-equilibration times were distinctly different for each variation in spatial orientation of textural layering, indicating that transient behavior during drainage in stratified formations is highly sensitive to the stratigraphic sequence of textural components, as well as the volume fraction of each textural</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Nanos...7.5826G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Nanos...7.5826G"><span id="translatedtitle">Graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> derived from self-assembled block copolymer templates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, Yibei; Werner, Jörg G.; Dorin, Rachel M.; Robbins, Spencer W.; Wiesner, Ulrich</p> <p>2015-03-01</p> <p>Graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional <span class="hlt">porous</span> inorganic <span class="hlt">materials</span>. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded <span class="hlt">porous</span> carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge-like support structure. Substructure walls between macropores are themselves mesoporous, constituting a structural hierarchy in addition to the pore gradation. Final graded structures can be tailored by tuning casting conditions of self-assembled templates as well as the backfilling processes. We expect that these graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> may find use in applications including separation, catalysis, biomedical implants, and energy conversion and storage.Graded <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional <span class="hlt">porous</span> inorganic <span class="hlt">materials</span>. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded <span class="hlt">porous</span> carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872234','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4872234"><span id="translatedtitle">Freeze-drying of “pearl milk tea”: A general strategy for controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Yingke; Tian, Xiaohui; Wang, Pengcheng; Hu, Min; Du, Guodong</p> <p>2016-01-01</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> have been widely used in many fields, but the large-scale synthesis of <span class="hlt">materials</span> with controlled pore sizes, pore volumes, and wall thicknesses remains a considerable challenge. Thus, the controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span> is of key general importance. Herein, we demonstrate the “pearl milk tea” freeze-drying method to form <span class="hlt">porous</span> <span class="hlt">materials</span> with controllable pore characteristics, which is realized by rapidly freezing the uniformly distributed template-containing precursor solution, followed by freeze-drying and suitable calcination. This general and convenient method has been successfully applied to synthesize various <span class="hlt">porous</span> phosphate and oxide <span class="hlt">materials</span> using different templates. The method is promising for the development of tunable <span class="hlt">porous</span> <span class="hlt">materials</span> for numerous applications of energy, environment, and catalysis, etc. PMID:27193866</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...626438Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...626438Z"><span id="translatedtitle">Freeze-drying of “pearl milk tea”: A general strategy for controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Yingke; Tian, Xiaohui; Wang, Pengcheng; Hu, Min; Du, Guodong</p> <p>2016-05-01</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> have been widely used in many fields, but the large-scale synthesis of <span class="hlt">materials</span> with controlled pore sizes, pore volumes, and wall thicknesses remains a considerable challenge. Thus, the controllable synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span> is of key general importance. Herein, we demonstrate the “pearl milk tea” freeze-drying method to form <span class="hlt">porous</span> <span class="hlt">materials</span> with controllable pore characteristics, which is realized by rapidly freezing the uniformly distributed template-containing precursor solution, followed by freeze-drying and suitable calcination. This general and convenient method has been successfully applied to synthesize various <span class="hlt">porous</span> phosphate and oxide <span class="hlt">materials</span> using different templates. The method is promising for the development of tunable <span class="hlt">porous</span> <span class="hlt">materials</span> for numerous applications of energy, environment, and catalysis, etc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1683b0020B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1683b0020B"><span id="translatedtitle">A mesomechanical analysis of the deformation and fracture in polycrystalline <span class="hlt">materials</span> with ceramic <span class="hlt">porous</span> coatings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balokhonov, R. R.; Zinoviev, A. V.; Romanova, V. A.; Batukhtina, E. E.</p> <p>2015-10-01</p> <p>The special features inherent in the mesoscale mechanical behavior of a <span class="hlt">porous</span> ceramic coating-steel substrate composite are investigated. Microstructure of the coated <span class="hlt">material</span> is accounted for explicitly as initial conditions of a plane strain dynamic boundary-value problem solved by the finite difference method. Using a mechanical analogy method, a procedure for generating a uniform curvilinear finite difference computational mesh is developed to provide a more accurate description of the complex grain boundary geometry. A modified algorithm for generation of polycrystalline microstructure of the substrate is designed on the basis of the cellular automata method. The constitutive equations for a steel matrix incorporate an elastic-plastic <span class="hlt">model</span> for a <span class="hlt">material</span> subjected to isotropic hardening. The Hall-Petch relation is used to account for the effect of the grain size on the yield stress and strain hardening history. A brittle fracture <span class="hlt">model</span> for a ceramic coating relying on the Huber criterion is employed. The <span class="hlt">model</span> allows for crack nucleation in the regions of triaxial tension. The complex inhomogeneous stress and plastic strain patterns are shown to be due to the presence of interfaces of three types: coating-substrate interface, grain boundaries, and pore surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.......264M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......264M"><span id="translatedtitle"><span class="hlt">Modeling</span> imbibition of liquids into rigid and swelling <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masoodi, Reza</p> <p></p> <p>In <span class="hlt">porous</span> media studies, imbibition is the spontaneous movement of a liquid into a <span class="hlt">porous</span> medium under the influence of capillary forces. It is also known by the name wicking, and can sometimes be aided by an external pressure, as in the case of forced infiltration of liquid polymers into a bed of fibermats. In this study, the imbibition of liquids into <span class="hlt">porous</span> media in important engineering applications is studied. A relatively new approach of using the single-phase flow behind a clearly-defined liquid front in a <span class="hlt">porous</span> medium has been adopted in this work to <span class="hlt">model</span> imbibition or wicking. Such an approach employs Darcy's law in conjunction with the continuity equation to <span class="hlt">model</span> the liquid flow behind the front. First the <span class="hlt">modeling</span> of liquid flow in polymer wicks is undertaken. A new formula to predict the capillary suction-pressure at the liquid fronts in commercial wicks made of sintering the polymer beads was proposed. Later, a more general formula was derived and verified for estimating the capillary suction pressure in any kind of <span class="hlt">porous</span> substance. We compared the performance of the proposed Darcy's-law based approach with that of the Lucas-Washburn equation; some new methods were suggested to improve the accuracy of these two dominant methods for <span class="hlt">modeling</span> the liquid transport in aforementioned wicks. Our Darcy's law based <span class="hlt">modeling</span> approach is superior to the previous Washburn Equation based approaches as the former can be easily extended to 2-D and 3-D unlike the latter. The 3-D liquid flow in the wicks was studied numerically using PORE-FLOW(c), an in-house computer program to <span class="hlt">model</span> <span class="hlt">porous</span>-media flows. For the first time, the finite element/control volume (FE/CV) algorithm is employed to solve the moving- boundary problem encountered in wicking. A good validation is achieved against the 1-D wicking-flow analytical solution as well as a 3-D wicking experiment involving a wick with two different cross-sections. A special case of wicking, in which both the external</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1083394','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1083394"><span id="translatedtitle">Dissipative particle dynamics <span class="hlt">model</span> for colloid transport in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pan, W.; Tartakovsky, A. M.</p> <p>2013-08-01</p> <p>We present that the transport of colloidal particles in <span class="hlt">porous</span> media can be effectively <span class="hlt">modeled</span> with a new formulation of dissipative particle dynamics, which augments standard DPD with non-central dissipative shear forces between particles while preserving angular momentum. Our previous studies have demonstrated that the new formulation is able to capture accurately the drag forces as well as the drag torques on colloidal particles that result from the hydrodynamic retardation effect. In the present work, we use the new formulation to study the contact efficiency in colloid filtration in saturated <span class="hlt">porous</span> media. Note that the present <span class="hlt">model</span> include all transport mechanisms simultaneously, including gravitational sedimentation, interception and Brownian diffusion. Our results of contact efficiency show a good agreement with the predictions of the correlation equation proposed by Tufenkji and EliMelech, which also incorporate all transport mechanisms simultaneously without the additivity assumption.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.H53A1235C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004AGUFM.H53A1235C&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Modeling</span> Multi-process Transport of Pathogens in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, L.; Brusseau, M. L.</p> <p>2004-12-01</p> <p>The transport behavior of microorganisms in <span class="hlt">porous</span> media is of interest with regard to the fate of pathogens associated with wastewater recharge, riverbank filtration, and land application of biosolids. This interest has fomented research on the transport of pathogens in the subsurface environment. The factors influencing pathogen transport within the subsurface environment include advection, dispersion, filtration, and inactivation. The filtration process, which mediates the magnitude and rate of pathogen retention, comprises several mechanisms such as attachment to <span class="hlt">porous</span>-medium surfaces, straining, and sedimentation. We present a mathematical <span class="hlt">model</span> wherein individual filtration mechanisms are explicitly incorporated along with advection, dispersion, and inactivation. The performance of the <span class="hlt">model</span> is evaluated by applying it to several data sets obtained from miscible-displacement experiments conducted using various pathogens. Input parameters are obtained to the extent possible from independent means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H53H..01R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H53H..01R"><span id="translatedtitle">Pore Topology Method: A General and Fast Pore-Scale <span class="hlt">Modeling</span> Approach to Simulate Fluid Flow in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riasi, M. S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.</p> <p>2014-12-01</p> <p>Micro-scale <span class="hlt">modeling</span> of multiphase flow in <span class="hlt">porous</span> media is critical to characterize <span class="hlt">porous</span> <span class="hlt">materials</span>. Several <span class="hlt">modeling</span> techniques have been implemented to date, but none can be used as a general strategy for all <span class="hlt">porous</span> media applications due to challenges presented by non-smooth high-curvature and deformable solid surfaces, and by a wide range of pore sizes and porosities. Finite approaches like the finite volume method require a high quality, problem-dependent mesh, while particle-based approaches like the lattice Boltzmann require too many particles to achieve a stable meaningful solution. Both come at a large computational cost. Other methods such as pore network <span class="hlt">modeling</span> (PNM) have been developed to accelerate the solution process by simplifying the solution domain, but so far a unique and straightforward methodology to implement PNM is lacking. Pore topology method (PTM) is a new topologically consistent approach developed to simulate multiphase flow in <span class="hlt">porous</span> media. The core of PTM is to reduce the complexity of the 3-D void space geometry by working with its medial surface as the solution domain. Medial surface is capable of capturing all the corners and surface curvatures in a <span class="hlt">porous</span> structure, and therefore provides a topologically consistent representative geometry for <span class="hlt">porous</span> structure. Despite the simplicity and low computational cost, PTM provides a fast and straightforward approach for micro-scale <span class="hlt">modeling</span> of fluid flow in all types of <span class="hlt">porous</span> media irrespective of their porosity and pore size distribution. In our previous work, we developed a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space of <span class="hlt">porous</span> media as well as a set of simple rules to determine the capillary pressure-saturation curves for a <span class="hlt">porous</span> system assuming quasi-static two-phase flow with a planar w-nw interface. Our simulation results for a highly <span class="hlt">porous</span> fibrous <span class="hlt">material</span> and polygonal capillary tubes were in excellent agreement</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999DPS....31.5928P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999DPS....31.5928P"><span id="translatedtitle">Monte Carlo <span class="hlt">Modeling</span> of the Thermal Conductivity of <span class="hlt">Porous</span> Ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prialnik, D.; Shoshany, Y.; Podolak, M.</p> <p>1999-12-01</p> <p>The thermal conductivity of low temperature ice has been derived both experimentally and by theoretical considerations. The formulae provided by Klinger (1980, 1981) have gained widespread use. But cometary <span class="hlt">material</span> is highly <span class="hlt">porous</span> and, although it is certain that porosity lowers the thermal conductivity, it is unclear to what extent, and how does the correction depend on porosity and on the pore size distribution. So far, answers to these questions have been either vague or widely discrepant. Early estimates of the effect of porosity (p) on the thermal conductivity (K) of cometary ice were based on purely geometrical considerations, yielding correction factors of order unity. Later work included the 'Hertz factor', the reduced area of contact between grains, which resulted in a much (orders of magnitude) lower correction factor. Attempts to determine the 'Hertz factor' by fitting laboratory data yielded a rather wide range of values, between 0.1 and 0.001. All these corrections are temperature independent. However, the correction due to porosity should also depend on temperature (T), since heat may be transferred through the pores by radiation. In order to obtain the desired relation K(T,p), we adopt a 3-D Monte Carlo procedure. This procedure has the advantage that, given the bulk conductivities of the constituents, the conductivity of the medium can be <span class="hlt">modeled</span> as a function of both porosity and temperature. The basic structure assumed is fractal, with the pore size distribution spanning several orders of magnitude. Obviously, in order to <span class="hlt">model</span> such a structure a very fine 3-D grid would be required, so as to accommodate the smallest and largest voids. Such an approach is impractical (impossible, in fact, in view of computational constraints!). In order to circumvent this difficulty, we adopt a hierarchical procedure. We find that the thermal conductivity is lowered by several orders of magnitude at high porosities; in addition it is strongly dependent on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1013030','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1013030"><span id="translatedtitle">Variably <span class="hlt">porous</span> structures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Braun, Paul V.; Yu, Xindi</p> <p>2011-01-18</p> <p>A method of making a monolithic <span class="hlt">porous</span> structure, comprises electrodepositing a <span class="hlt">material</span> on a template; removing the template from the <span class="hlt">material</span> to form a monolithic <span class="hlt">porous</span> structure comprising the <span class="hlt">material</span>; and electropolishing the monolithic <span class="hlt">porous</span> structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1738U0047K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1738U0047K"><span id="translatedtitle">Numerical <span class="hlt">modeling</span> of fresh concrete flow through <span class="hlt">porous</span> medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kolařík, F.; Patzák, B.; Zeman, J.</p> <p>2016-06-01</p> <p>The paper focuses on a numerical <span class="hlt">modeling</span> of a non-Newtonian fluid flow in a <span class="hlt">porous</span> domain. It presents combination of a homogenization approach to obtain permeability from the underlying micro-structure with coupling of a Stokes and Darcy flow through the interface on the macro level. As a numerical method we employed the Finite Element method. The results obtained from the homogenization approach are validated against fully resolved solution computed by direct numerical simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/868855','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/868855"><span id="translatedtitle">Process of making <span class="hlt">porous</span> ceramic <span class="hlt">materials</span> with controlled porosity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Anderson, Marc A.; Ku, Qunyin</p> <p>1993-01-01</p> <p>A method of making metal oxide ceramic <span class="hlt">material</span> is disclosed by which the porosity of the resulting <span class="hlt">material</span> can be selectively controlled by manipulating the sol used to make the <span class="hlt">material</span>. The method can be used to make a variety of metal oxide ceramic bodies, including membranes, but also pellets, plugs or other bodies. It has also been found that viscous sol <span class="hlt">materials</span> can readily be shaped by extrusion into shapes typical of catalytic or adsorbent bodies used in industry, to facilitate the application of such <span class="hlt">materials</span> for catalytic and adsorbent applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040084809','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040084809"><span id="translatedtitle">Measurements of Acoustic Properties of <span class="hlt">Porous</span> and Granular <span class="hlt">Materials</span> and Application to Vibration Control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Park, Junhong; Palumbo, Daniel L.</p> <p>2004-01-01</p> <p>For application of <span class="hlt">porous</span> and granular <span class="hlt">materials</span> to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic <span class="hlt">materials</span>. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic <span class="hlt">materials</span> - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing <span class="hlt">porous</span> and granular <span class="hlt">materials</span> as damping treatment was measured also. The data were used to extract the damping <span class="hlt">materials</span> characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4680965','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4680965"><span id="translatedtitle">Dimpled elastic sheets: a new class of non-<span class="hlt">porous</span> negative Poisson’s ratio <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia</p> <p>2015-01-01</p> <p>In this study, we report a novel periodic <span class="hlt">material</span> with negative Poisson’s ratio (also called auxetic <span class="hlt">materials</span>) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic <span class="hlt">materials</span> are either <span class="hlt">porous</span> or comprise at least two phases, the <span class="hlt">material</span> proposed here is non-<span class="hlt">porous</span> and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic <span class="hlt">materials</span> that significantly expand their design space and possible applications. PMID:26671169</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...518373J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...518373J"><span id="translatedtitle">Dimpled elastic sheets: a new class of non-<span class="hlt">porous</span> negative Poisson’s ratio <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia</p> <p>2015-12-01</p> <p>In this study, we report a novel periodic <span class="hlt">material</span> with negative Poisson’s ratio (also called auxetic <span class="hlt">materials</span>) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic <span class="hlt">materials</span> are either <span class="hlt">porous</span> or comprise at least two phases, the <span class="hlt">material</span> proposed here is non-<span class="hlt">porous</span> and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic <span class="hlt">materials</span> that significantly expand their design space and possible applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26353534','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26353534"><span id="translatedtitle">Influence of Environmental Factors on the Adsorption Capacity and Thermal Conductivity of Silica Nano-<span class="hlt">Porous</span> <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Hu; Gu, Wei; Li, Ming-Jia; Fang, Wen-Zhen; Li, Zeng-Yao; Tao, Wen-Quan</p> <p>2015-04-01</p> <p>In this work, the influence of temperature and humidity environment on the water vapor adsorption capacity and effective thermal conductivity of silica nano-<span class="hlt">porous</span> <span class="hlt">material</span> is conducted within a relative humidity range from 15% to 90% at 25 °C, 40 °C and 55 °C, respectively. The experiment results show that both the temperature and relative humidity have significant influence on the adsorption capacity and effective thermal conductivity of silica nano-<span class="hlt">porous</span> <span class="hlt">materials</span>. The adsorption capacity and effective thermal conductivity increase with humidity because of the increases of water vapor concentration. The effective thermal conductivity increases linearly with adsorption saturation capacity at constant temperature. Because adsorption process is exothermic reaction, the increasing temperature is not conducive to the adsorption. But the effective thermal conductivity increases with the increment of temperature at the same water uptake because of the increment of water thermal conductivity with temperature Geometric <span class="hlt">models</span> and unit cell structure are adopted to predict the effective thermal conductivity and comparisons with the experimental result are made, and for the case of moist silica nano-<span class="hlt">porous</span> <span class="hlt">materials</span> with high porosity no quantitative agreement is found. It is believed that the adsorbed water will fill in the nano-pores and gap and form lots of short cuts, leading to a significant reduction of the thermal resistance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26677099','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26677099"><span id="translatedtitle">Highly <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Unique Mechanical Properties from Smart Capillary Suspensions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dittmann, Jens; Maurath, Johannes; Bitsch, Boris; Willenbacher, Norbert</p> <p>2016-02-24</p> <p>Smart capillary suspensions are used to fabricate macroporous solids with unique features regarding porosity and mechanical strength from a wide range of <span class="hlt">materials</span>, including carbon layers and polyethylene membranes, even if sintering or high-temperature treatment is not feasible. High-strength <span class="hlt">porous</span> ceramics are obtained, tailoring neck and pore shape via controlled deposition of fine particles at the sintering necks. PMID:26677099</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/86395','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/86395"><span id="translatedtitle">Elastic constants of Transversely Isotropically <span class="hlt">Porous</span> (TIP) <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tuchinskii, L.I.; Kalimova, N.L.</p> <p>1994-11-01</p> <p>The authors derive formulas describing the dependence of the elastic characteristics of multicapillary <span class="hlt">materials</span> on the capillary porosity. The investigated <span class="hlt">materials</span> are classified as transversely isotropic, and the anisotropy in their properties is the result of the directionality of the capillary pores. Analysis of the dependences obtained has shown that the elasticity moduli of these <span class="hlt">materials</span> may be calculated using formulas suggested for reinforced <span class="hlt">materials</span>, in which the elastic constants of the fibers are assumed to be equal to zero. The authors derive a relation between the Poisson`s ratios and the capillary porosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24031095','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24031095"><span id="translatedtitle">A <span class="hlt">Porous</span> Media <span class="hlt">Model</span> for Blood Flow within Reticulated Foam.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ortega, J M</p> <p>2013-08-01</p> <p>A <span class="hlt">porous</span> media <span class="hlt">model</span> is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10(-8) to 10. This empirical <span class="hlt">model</span> effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the <span class="hlt">model</span> adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. PMID:24031095</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3767460','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3767460"><span id="translatedtitle">A <span class="hlt">Porous</span> Media <span class="hlt">Model</span> for Blood Flow within Reticulated Foam</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ortega, J.M.</p> <p>2013-01-01</p> <p>A <span class="hlt">porous</span> media <span class="hlt">model</span> is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10−8 to 10. This empirical <span class="hlt">model</span> effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the <span class="hlt">model</span> adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. PMID:24031095</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/15020420','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/15020420"><span id="translatedtitle"><span class="hlt">Modeling</span> of Biomass Plug Development and Propagation in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stewart, Terri L.; Kim, Dong-Shik</p> <p>2004-02-01</p> <p>Biomass accumulation and evolution in <span class="hlt">porous</span> media were simulated using a combination of biofilm evolution <span class="hlt">model</span> and a biofilm removal <span class="hlt">model</span>. Theses <span class="hlt">models</span> describe biomass plug development, removal, and propagation in biological applications such as microbial enhanced oil recovery, in situ bioremediation, and bio-barrier techniques. The biofilm evolution <span class="hlt">model</span> includes the cell growth rate and exopolymer production kinetics. The biofilm removal <span class="hlt">model</span> was used for describing the biomass plug propagation and channel breakthrough using Bingham yield stress of biofilm, which represents the stability of biofilm against shear stress. Network <span class="hlt">model</span> was used to describe a <span class="hlt">porous</span> medium. The network <span class="hlt">model</span> consists of pore body and pore bond of which the sizes were determined based on the pore size distribution of ceramic cores. The pressure drop across the network is assumed to be generated from pore bonds only, and the cell growth and biomass accumulation took place in pore bonds. The simulation results showed that the biofilm <span class="hlt">models</span> based on Bingham yield stress predicted the biomass accumulation and channel breakthrough well. The pressure oscillation (or, permeability oscillation) was also demonstrated well indicating the process of biomass accumulation and breakthrough channel formation. In addition, the effects of cell and biofilm sucrose concentration were significant on the biomass plug development and permeability reduction rates. The <span class="hlt">modeling</span> elucidated some deficiencies in our knowledge of the biomass yield stress that enables us to predict the stability of biomass plug against shear stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24350641','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24350641"><span id="translatedtitle"><span class="hlt">Porous</span> organic <span class="hlt">material</span> from discotic tricarboxyamide: side chain-core interactions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jana, Poulami; Paikar, Arpita; Bera, Santu; Maity, Suman Kumar; Haldar, Debasish</p> <p>2014-01-01</p> <p>The benzene-1,3,5-tricarboxyamide containing three l-methionine (1) self-assemble through 3-fold amide-amide hydrogen bonds and π-π stacking to fabricate one-dimensional nanorod like structure. However, the tyrosine analogue (2) carrying multiple H-bonding side chains lost the C3 symmetry and 3-fold amide-amide hydrogen bonds and developed a <span class="hlt">porous</span> structure. The <span class="hlt">porous</span> <span class="hlt">material</span> exhibits ten times more N2 sorption (155 cc/g) than the columnar one, indicating that side chain-core interactions have a drastic effect on structure and function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997APS..SHK..M201N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997APS..SHK..M201N&link_type=ABSTRACT"><span id="translatedtitle">Controlled High-Rate-Strain Shear Bands in Inert and Reactant <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nesterenko, Vitali</p> <p>1997-07-01</p> <p>Shear localization was considered as one of the main reasons for initiation of chemical reaction in energetic <span class="hlt">materials</span> under dynamic loading (Dremin and Breusov 1968, Winter and Field 1975, Frey 1981, Kipp 1985, Iyer, Bennet et al., 1994) and for particles bonding during shock compaction (Nesterenko 1985). However despite of wide spread recognition of the importance of rapid shear flow the shear bands in <span class="hlt">porous</span> heterogeneous <span class="hlt">materials</span> did not become an object of research. The primary reason for this was a lack of appropriate experimental method. The "Thick-Walled Cylinder" method, which allows to reproduce shear bands in controlled conditions, was initially proposed by Nesterenko et al., 1989 for solid inert <span class="hlt">materials</span> and then modified by Nesterenko, Meyers et al., 1994 to fit <span class="hlt">porous</span> inert and energetic <span class="hlt">materials</span>. The method allows to reproduce the array of shear bands with shear strains 10 - 100 and strain rate 107 s-1. Experimental results will be presented for inert <span class="hlt">materials</span> (granular, fractured ceramics) and for reactant <span class="hlt">porous</span> mixtures (Nb-Si, Ti-Si, Ti-C). Mechanisms of <span class="hlt">material</span> deformation and shear induced chemical reactions inside shear localization zone as well as conditions for the initiation of the chemical reaction in the bulk of energetic <span class="hlt">material</span> by array of shear bands will be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008NIMPB.266..155C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008NIMPB.266..155C"><span id="translatedtitle">High-speed neutron radiography for monitoring the water absorption by capillarity in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cnudde, Veerle; Dierick, Manuel; Vlassenbroeck, Jelle; Masschaele, Bert; Lehmann, Eberhard; Jacobs, Patric; Van Hoorebeke, Luc</p> <p>2008-01-01</p> <p>Fluid flow through <span class="hlt">porous</span> natural building stones is of great importance when studying their weathering processes. Many traditional experiments based on mass changes are available for studying liquid transport in <span class="hlt">porous</span> stones, such as the determination of the water absorption coefficient by capillarity. Because thermal neutrons experience a strong attenuation by hydrogen, neutron radiography is a suitable technique for the study of water absorption by capillarity in <span class="hlt">porous</span> stones. However, image contrast can be impaired because hydrogen mainly scatters neutrons rather than absorbing them, resulting in a blurred image. Capillarity results obtained by neutron radiography and by the European Standard 1925 for the determination of the water absorption coefficient by capillarity for natural building stones with a variable porosity were compared. It is illustrated that high-speed neutron radiography can be a useful research tool for the visualization of internal fluid flow inside inorganic building <span class="hlt">materials</span> such as limestones and sandstones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26235127','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26235127"><span id="translatedtitle">Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span> by Fluorescence Correlation Spectroscopy Super-resolution Optical Fluctuation Imaging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kisley, Lydia; Brunetti, Rachel; Tauzin, Lawrence J; Shuang, Bo; Yi, Xiyu; Kirkeminde, Alec W; Higgins, Daniel A; Weiss, Shimon; Landes, Christy F</p> <p>2015-09-22</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> such as cellular cytosol, hydrogels, and block copolymers have nanoscale features that determine macroscale properties. Characterizing the structure of nanopores is difficult with current techniques due to imaging, sample preparation, and computational challenges. We produce a super-resolution optical image that simultaneously characterizes the nanometer dimensions of and diffusion dynamics within <span class="hlt">porous</span> structures by correlating stochastic fluctuations from diffusing fluorescent probes in the pores of the sample, dubbed here as "fluorescence correlation spectroscopy super-resolution optical fluctuation imaging" or "fcsSOFI". Simulations demonstrate that structural features and diffusion properties can be accurately obtained at sub-diffraction-limited resolution. We apply our technique to image agarose hydrogels and aqueous lyotropic liquid crystal gels. The heterogeneous pore resolution is improved by up to a factor of 2, and diffusion coefficients are accurately obtained through our method compared to diffraction-limited fluorescence imaging and single-particle tracking. Moreover, fcsSOFI allows for rapid and high-throughput characterization of <span class="hlt">porous</span> <span class="hlt">materials</span>. fcsSOFI could be applied to soft <span class="hlt">porous</span> environments such hydrogels, polymers, and membranes in addition to hard <span class="hlt">materials</span> such as zeolites and mesoporous silica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050217168','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050217168"><span id="translatedtitle">Mechanically Strong, Lightweight <span class="hlt">Porous</span> <span class="hlt">Materials</span> Developed (X-Aerogels)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leventis, Nicholas</p> <p>2005-01-01</p> <p>Aerogels are attractive <span class="hlt">materials</span> for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other <span class="hlt">materials</span>. Potential NASA applications for these <span class="hlt">materials</span> include lightweight insulation for spacecraft, habitats, and extravehicular activity (EVA) suits; catalyst supports for fuel cell and in situ resource utilization; and sensors for air- and water-quality monitoring for vehicles, habitats, and EVA suits. Conventional aerogels are extremely fragile and require processing via supercritical fluid extraction, which adds cost to the production of an aerogel and limits the sizes and geometries of samples that can be produced from these <span class="hlt">materials</span>. These issues have severely hampered the application of aerogels in NASA missions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMPSo..94..230S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMPSo..94..230S"><span id="translatedtitle">Phase field <span class="hlt">modeling</span> of partially saturated deformable <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sciarra, Giulio</p> <p>2016-09-01</p> <p>A poromechanical <span class="hlt">model</span> of partially saturated deformable <span class="hlt">porous</span> media is proposed based on a phase field approach at <span class="hlt">modeling</span> the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the <span class="hlt">porous</span> skeleton, depending on the <span class="hlt">porous</span> texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field <span class="hlt">model</span> based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field <span class="hlt">model</span>. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged <span class="hlt">model</span> with that one endowed with the concept of average interfacial area. The considered poromechanical <span class="hlt">model</span> is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492612','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492612"><span id="translatedtitle">Mathematical <span class="hlt">modeling</span> of deformation of a <span class="hlt">porous</span> medium, considering its strengthening due to pore collapse</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sadovskii, V. M. Sadovskaya, O. V.</p> <p>2015-10-28</p> <p>Based on the generalized rheological method, the mathematical <span class="hlt">model</span> describing small deformations of a single-phase <span class="hlt">porous</span> medium without regard to the effects of a fluid or gas in pores is constructed. The change in resistance of a <span class="hlt">material</span> to the external mechanical impacts at the moment of pore collapse is taken into account by means of the von Mises–Schleicher strength condition. In order to consider irreversible deformations, alongside with the classical yield conditions by von Mises and Tresca– Saint-Venant, the special condition <span class="hlt">modeling</span> the plastic loss of stability of a <span class="hlt">porous</span> skeleton is used. The random nature of the pore size distribution is taken into account. It is shown that the proposed mathematical <span class="hlt">model</span> satisfies the principles of thermodynamics of irreversible processes. Phenomenological parameters of the <span class="hlt">model</span> are determined on the basis of the approximate calculation of the problem on quasi-static loading of a cubic periodicity cell with spherical voids. In the framework of the obtained <span class="hlt">model</span>, the process of propagation of plane longitudinal waves of the compression in a homogenous <span class="hlt">porous</span> medium, accompanied by the plastic deformation of a skeleton and the collapse of pores, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1684g0006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1684g0006S"><span id="translatedtitle">Mathematical <span class="hlt">modeling</span> of deformation of a <span class="hlt">porous</span> medium, considering its strengthening due to pore collapse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadovskii, V. M.; Sadovskaya, O. V.</p> <p>2015-10-01</p> <p>Based on the generalized rheological method, the mathematical <span class="hlt">model</span> describing small deformations of a single-phase <span class="hlt">porous</span> medium without regard to the effects of a fluid or gas in pores is constructed. The change in resistance of a <span class="hlt">material</span> to the external mechanical impacts at the moment of pore collapse is taken into account by means of the von Mises-Schleicher strength condition. In order to consider irreversible deformations, alongside with the classical yield conditions by von Mises and Tresca- Saint-Venant, the special condition <span class="hlt">modeling</span> the plastic loss of stability of a <span class="hlt">porous</span> skeleton is used. The random nature of the pore size distribution is taken into account. It is shown that the proposed mathematical <span class="hlt">model</span> satisfies the principles of thermodynamics of irreversible processes. Phenomenological parameters of the <span class="hlt">model</span> are determined on the basis of the approximate calculation of the problem on quasi-static loading of a cubic periodicity cell with spherical voids. In the framework of the obtained <span class="hlt">model</span>, the process of propagation of plane longitudinal waves of the compression in a homogenous <span class="hlt">porous</span> medium, accompanied by the plastic deformation of a skeleton and the collapse of pores, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1616405K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1616405K"><span id="translatedtitle">P-adic <span class="hlt">model</span> of transport in <span class="hlt">porous</span> disordered media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khrennikov, Adrei Yu.; Oleschko, Klaudia</p> <p>2014-05-01</p> <p>The soil porosity and permeability are the most important quantitative indicators of soil dynamics under the land-use change. The main problema in the <span class="hlt">modeling</span> of this dynamic is still poor correlation between the real measuring data and the mathematical and computer simulation <span class="hlt">models</span>. In order to overpassed this deep divorce we have designed a new technique, able to compare the data arised from the multiscale image analices and time series of the basic physical properties dynamics in <span class="hlt">porous</span> media studied in time and space. We present a <span class="hlt">model</span> of the diffusion reaction type describing transport in disordered <span class="hlt">porous</span> media, e.g., water or oil flow in a complex network of pores. Our <span class="hlt">model</span> is based on p-adic representation of such networks. This is a kind of fractal representation. We explore advantages of p- adic representation, namely, the possibility to endow p-adic trees with an algebraic structure and ultrametric topology and, hence, to apply analysis which have (at least some) similarities with ordinary real analysis on the straight line. We present the system of two diffusion reaction equations describing propagation of particles in networks of pores in disordered media. As an application, one can consider water transport through the soil pore Networks, or oil flow through capillaries nets. Under some restrictions on potentials and rate coefficients we found the stationary regime corresponding to water content or concentration of oil in a cluster of capillaries. Usage of p-adic analysis (in particular, p-adic wavelets) gives a possibility to find the stationary solution in the analytic form which makes possible to present a clear pedological or geological picture of the process. The mathematical <span class="hlt">model</span> elaborated in this paper (Khrennikov, 2013) can be applied to variety of problems from water concentration in aquifers to the problem of formation of oil reservoirs in disordered media with <span class="hlt">porous</span> structures. Another possible application may have real practical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22257906','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22257906"><span id="translatedtitle">Potential of hybrid functionalized meso-<span class="hlt">porous</span> <span class="hlt">materials</span> for the separation and immobilization of radionuclides</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Luca, V.</p> <p>2013-07-01</p> <p>Functionalized meso-<span class="hlt">porous</span> <span class="hlt">materials</span> are a class of hybrid organic-inorganic <span class="hlt">material</span> in which a meso-<span class="hlt">porous</span> metal oxide framework is functionalized with multifunctional organic molecules. These molecules may contain one or more anchor groups that form strong bonds to the pore surfaces of the metal oxide framework and free functional groups that can impart and or modify the functionality of the <span class="hlt">material</span> such as for binding metal ions in solution. Such <span class="hlt">materials</span> have been extensively studied over the past decade and are of particular interest in absorption applications because of the tremendous versatility in choosing the composition and architecture of the metal oxide framework and the nature of the functional organic molecule as well as the efficient mass transfer that can occur through a well-designed hierarchically <span class="hlt">porous</span> network. A sorbent for nuclear applications would have to be highly selective for particular radio nuclides, it would need to be hydrolytically and radiolytically stable, and it would have to possess reasonable capacity and fast kinetics. The sorbent would also have to be available in a form suitable for use in a column. Finally, it would also be desirable if once saturated with radio nuclides, the sorbent could be recycled or converted directly into a ceramic or glass waste form suitable for direct repository disposal or even converted directly into a <span class="hlt">material</span> that could be used as a transmutation target. Such a cradle-to- grave strategy could have many benefits in so far as process efficiency and the generation of secondary wastes are concerned.This paper will provide an overview of work done on all of the above mentioned aspects of the development of functionalized meso-<span class="hlt">porous</span> adsorbent <span class="hlt">materials</span> for the selective separation of lanthanides and actinides and discuss the prospects for future implementation of a cradle-to-grave strategy with such <span class="hlt">materials</span>. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..MARZ10004A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..MARZ10004A"><span id="translatedtitle">Optical second-harmonic generation measurements of <span class="hlt">porous</span> low-k dielectric <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Atkin, Joanna; Shaw, Thomas; Laibowitz, Robert; Heinz, Tony</p> <p>2009-03-01</p> <p>Low-k dielectric <span class="hlt">materials</span> based on <span class="hlt">porous</span> carbon-doped oxides, with relative dielectric constants as low as 2.1, are widely used as thin insulating films in the microelectronics industry. Knowledge of these <span class="hlt">materials</span>' basic electronic properties, such as energy gaps, barrier heights, and trap states, is essential for <span class="hlt">modeling</span> their electrical leakage and stability characteristics. We use femtosecond laser pulses to probe the dynamics of charge-carrier transfer processes across Si/LKD interfacial barriers by optical second harmonic generation (SHG). Larger electric fields from multiphoton injection can be developed in Si/LKD systems compared to Si/SiO2, indicating a significantly higher density of traps in the LKD. This is consistent with previously reported measurements of trap density by photoinjection techniques^*. We will also discuss results on the dynamics of discharging and on the dependence of charging phenomena on layer thickness. ^*J. M. Atkin, D. Song, T. M. Shaw, E. Cartier, R. B. Laibowitz, and T. F. Heinz, J. Appl. Phys. 103, 094104 (2008).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25920830','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25920830"><span id="translatedtitle">Acoustical properties of air-saturated <span class="hlt">porous</span> <span class="hlt">material</span> with periodically distributed dead-end pores.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leclaire, P; Umnova, O; Dupont, T; Panneton, R</p> <p>2015-04-01</p> <p>A theoretical and numerical study of the sound propagation in air-saturated <span class="hlt">porous</span> media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at "nodes" periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical properties of the <span class="hlt">material</span> and can increase significantly the absorption at low frequencies (a few hundred hertz). These depend strongly on the geometry (diameter and length) of the dead-ends, on their number per node, and on the periodicity along the propagation axis. These effects are primarily due to low sound speed in the main pores and to thermal losses in the dead-end pores. The <span class="hlt">model</span> predictions are compared with experimental results. Possible designs of <span class="hlt">materials</span> of a few cm thicknesses displaying enhanced low frequency absorption at a few hundred hertz are proposed. PMID:25920830</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25920830','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25920830"><span id="translatedtitle">Acoustical properties of air-saturated <span class="hlt">porous</span> <span class="hlt">material</span> with periodically distributed dead-end pores.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leclaire, P; Umnova, O; Dupont, T; Panneton, R</p> <p>2015-04-01</p> <p>A theoretical and numerical study of the sound propagation in air-saturated <span class="hlt">porous</span> media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at "nodes" periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical properties of the <span class="hlt">material</span> and can increase significantly the absorption at low frequencies (a few hundred hertz). These depend strongly on the geometry (diameter and length) of the dead-ends, on their number per node, and on the periodicity along the propagation axis. These effects are primarily due to low sound speed in the main pores and to thermal losses in the dead-end pores. The <span class="hlt">model</span> predictions are compared with experimental results. Possible designs of <span class="hlt">materials</span> of a few cm thicknesses displaying enhanced low frequency absorption at a few hundred hertz are proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.......420M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......420M"><span id="translatedtitle">Computing the Seismic Attenuation in Complex <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masson, Yder Jean</p> <p></p> <p>The present work analyzes seismic attenuation due to wave-induced flow in complex poroelastic <span class="hlt">materials</span> containing an arbitrary amount of heterogeneity and fully or partially saturated with a mixture of fluids. In the first part, two distinct finite-difference (FDTD) numerical schemes for solving Biot's poroelastic set of equations are introduced. The first algorithm is designed to be used in the seismic band of frequencies; i.e., when the permeability of the medium doesn't depend on frequency. The second algorithm accounts for viscous boundary layers that appear in the pores at high frequencies (in this case, the permeability depends on frequency) and can be used across the entire band of frequencies. An innovative numerical method is presented in the second part allowing computation of seismic attenuation due to wave-induced flow for any poroelastic <span class="hlt">material</span>. This method is applied to study the attenuation associated with different classes of <span class="hlt">materials</span> saturated with a single fluid (water). For a <span class="hlt">material</span> having a self-affine (fractal) distribution of elastic properties, it is demonstrated that frequency dependence in the attenuation is controlled by a single parameter that is directly related to the fractal dimension of the <span class="hlt">material</span>. For anisotropic <span class="hlt">materials</span>, a relation is established between the attenuation levels associated with waves propagating in different directions and the geometrical aspect ratio of the heterogeneities present within the <span class="hlt">material</span>. The third part concerns the study of attenuation associated with <span class="hlt">materials</span> having a homogeneous solid skeleton saturated with a mixture of immiscible fluids. The special case where the distribution of fluids is the result of an invasion-percolation process is treated in detail. Finally, the last part presents a novel experimental setup designed to measure fluctuations of the elastic properties in real rock samples. This device performs automated micro-indentation tests at the surface of rock samples and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.H32B..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.H32B..02S"><span id="translatedtitle">Experiments versus <span class="hlt">modeling</span> of buoyant drying of <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salin, D.; Yiotis, A.; Tajer, E.; Yortsos, Y. C.</p> <p>2012-12-01</p> <p>Experiments versus <span class="hlt">modeling</span> of buoyant drying of <span class="hlt">porous</span> media D. Salin and A.G. Yiotis, Laboratoire FAST, Univ Pierre & Marie Curie, Univ. Paris-Sud, CNRS, Orsay 91405, France and E.S. Tajer and Y.C. Yortsos, Mork Family Department of Chemical Engineering and <span class="hlt">Materials</span> Science, University of Southern California, Los Angeles, CA 90089-1450 A series of isothermal drying experiments in packed glass beads saturated with volatile hydrocarbons (hexane or pentane) are conducted. The transparent glass cells containing the packing allow for the visual monitoring of the phase distribution patterns below the surface, including the formation of liquid films, as the gaseous phase invades the pore space, and for the control of the thickness of the diffusive mass boundary layer over the packing. We demonstrate the existence of an early Constant Rate Period, CRP, that lasts as long as the films saturate the surface of the packing, and of a subsequent Falling Rate Period, FRP, that begins practically after the detachment of the film tips from the external surface. During the CRP, the process is controlled by diffusion within the stagnant gaseous phase in the upper part of the cells, yielding a Stefan tube problem solution. During the FRP, the process is controlled by diffusion within the packing, with a drying rate inversely proportional to the observed position of the film tips in the cell. The critical residual liquid saturation that marks the transition between these two regimes is found to be a function of the average bead size in our packs and the incline of the cells with respect to the flat vertical, with larger beads and angles closer to the vertical position leading to earlier film detachment times and higher critical saturations. We developed a <span class="hlt">model</span> for the drying of <span class="hlt">porous</span> media in the presence of gravity. It incorporated effects of corner film flow, internal and external mass transfer and the effect of gravity. Analytical results were derived when gravity opposes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24676127','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24676127"><span id="translatedtitle">Recent advances in <span class="hlt">porous</span> polyoxometalate-based metal-organic framework <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Du, Dong-Ying; Qin, Jun-Sheng; Li, Shun-Li; Su, Zhong-Min; Lan, Ya-Qian</p> <p>2014-07-01</p> <p>Polyoxometalate (POM)-based metal-organic framework (MOF) <span class="hlt">materials</span> contain POM units and generally generate MOF <span class="hlt">materials</span> with open networks. POM-based MOF <span class="hlt">materials</span>, which utilize the advantages of both POMs and MOFs, have received increasing attention, and much effort has been devoted to their preparation and relevant applications over the past few decades. They have good prospects in catalysis owing to the electronic and physical properties of POMs that are tunable by varying constituent elements. In this review, we present recent developments in <span class="hlt">porous</span> POM-based MOF <span class="hlt">materials</span>, including their classification, synthesis strategies, and applications, especially in the field of catalysis. PMID:24676127</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27160665','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27160665"><span id="translatedtitle">Dynamics of H2 adsorbed in <span class="hlt">porous</span> <span class="hlt">materials</span> as revealed by computational analysis of inelastic neutron scattering spectra.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pham, Tony; Forrest, Katherine A; Space, Brian; Eckert, Juergen</p> <p>2016-06-29</p> <p>The inelastic scattering of neutrons from adsorbed H2 is an effective and highly sensitive method for obtaining molecular level information on the type and nature of H2 binding sites in <span class="hlt">porous</span> <span class="hlt">materials</span>. While these inelastic neutron scattering (INS) spectra of the hindered rotational and translational excitations on the adsorbed H2 contain a significant amount of information, much of this can only be reliably extracted by means of a detailed analysis of the spectra through the utilization of <span class="hlt">models</span> and theoretical calculations. For instance, the rotational tunneling transitions observed in the INS spectra can be related to a value for the barrier to rotation for the adsorbed H2 with the use of a simple phenomenological <span class="hlt">model</span>. Since such an analysis is dependent on the <span class="hlt">model</span>, it is far more desirable to use theoretical methods to compute a potential energy surface (PES), from which the rotational barriers for H2 adsorbed at a particular site can be determined. Rotational energy levels and transitions for the hindered rotor can be obtained by quantum dynamics calculations and compared directly with experiment with an accuracy subject only to the quality of the theoretical PES. In this paper, we review some of the quantum and classical mechanical calculations that have been performed on H2 adsorbed in various <span class="hlt">porous</span> <span class="hlt">materials</span>, such as clathrate hydrates, zeolites, and metal-organic frameworks (MOFs). The principal aims of these calculations have been the interpretation of the INS spectra for adsorbed H2 along with the extraction of atomic level details of its interaction with the host. We describe calculations of the PES used for two-dimensional quantum rotation as well as rigorous five-dimensional quantum coupled translation-rotation dynamics, and demonstrate that the combination of INS measurements and computational <span class="hlt">modeling</span> can provide important and detailed insights into the molecular mechanism of H2 adsorption in <span class="hlt">porous</span> <span class="hlt">materials</span>. PMID:27160665</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27160665','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27160665"><span id="translatedtitle">Dynamics of H2 adsorbed in <span class="hlt">porous</span> <span class="hlt">materials</span> as revealed by computational analysis of inelastic neutron scattering spectra.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pham, Tony; Forrest, Katherine A; Space, Brian; Eckert, Juergen</p> <p>2016-06-29</p> <p>The inelastic scattering of neutrons from adsorbed H2 is an effective and highly sensitive method for obtaining molecular level information on the type and nature of H2 binding sites in <span class="hlt">porous</span> <span class="hlt">materials</span>. While these inelastic neutron scattering (INS) spectra of the hindered rotational and translational excitations on the adsorbed H2 contain a significant amount of information, much of this can only be reliably extracted by means of a detailed analysis of the spectra through the utilization of <span class="hlt">models</span> and theoretical calculations. For instance, the rotational tunneling transitions observed in the INS spectra can be related to a value for the barrier to rotation for the adsorbed H2 with the use of a simple phenomenological <span class="hlt">model</span>. Since such an analysis is dependent on the <span class="hlt">model</span>, it is far more desirable to use theoretical methods to compute a potential energy surface (PES), from which the rotational barriers for H2 adsorbed at a particular site can be determined. Rotational energy levels and transitions for the hindered rotor can be obtained by quantum dynamics calculations and compared directly with experiment with an accuracy subject only to the quality of the theoretical PES. In this paper, we review some of the quantum and classical mechanical calculations that have been performed on H2 adsorbed in various <span class="hlt">porous</span> <span class="hlt">materials</span>, such as clathrate hydrates, zeolites, and metal-organic frameworks (MOFs). The principal aims of these calculations have been the interpretation of the INS spectra for adsorbed H2 along with the extraction of atomic level details of its interaction with the host. We describe calculations of the PES used for two-dimensional quantum rotation as well as rigorous five-dimensional quantum coupled translation-rotation dynamics, and demonstrate that the combination of INS measurements and computational <span class="hlt">modeling</span> can provide important and detailed insights into the molecular mechanism of H2 adsorption in <span class="hlt">porous</span> <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/863064','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/863064"><span id="translatedtitle">Electrode including <span class="hlt">porous</span> particles with embedded active <span class="hlt">material</span> for use in a secondary electrochemical cell</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Vissers, Donald R.; Nelson, Paul A.; Kaun, Thomas D.; Tomczuk, Zygmunt</p> <p>1978-04-25</p> <p>Particles of carbonaceous matrices containing embedded electrode active <span class="hlt">material</span> are prepared for vibratory loading within a <span class="hlt">porous</span> electrically conductive substrate. In preparing the particles, active <span class="hlt">materials</span> such as metal chalcogenides, solid alloys of alkali or alkaline earth metals along with other metals and their oxides in powdered or particulate form are blended with a thermosetting resin and particles of a volatile to form a paste mixture. The paste is heated to a temperature at which the volatile transforms into vapor to impart porosity at about the same time as the resin begins to cure into a rigid, solid structure. The solid structure is then comminuted into <span class="hlt">porous</span>, carbonaceous particles with the embedded active <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862922','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862922"><span id="translatedtitle">Method of preparing <span class="hlt">porous</span>, active <span class="hlt">material</span> for use in electrodes of secondary electrochemical cells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Vissers, Donald R.; Nelson, Paul A.; Kaun, Thomas D.; Tomczuk, Zygmunt</p> <p>1977-01-01</p> <p>Particles of carbonaceous matrices containing embedded electrode active <span class="hlt">material</span> are prepared for vibratory loading within a <span class="hlt">porous</span> electrically conductive substrate. In preparing the particles, active <span class="hlt">materials</span> such as metal chalcogenides, solid alloys of alkali or alkaline earth metals along with other metals and their oxides in powdered or particulate form are blended with a thermosetting resin and particles of a volatile to form a paste mixture. The paste is heated to a temperature at which the volatile transforms into vapor to impart porosity at about the same time as the resin begins to cure into a rigid, solid structure.The solid structure is then comminuted into <span class="hlt">porous</span>, carbonaceous particles with the embedded active <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22350935','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22350935"><span id="translatedtitle">Dark-field X-ray imaging of unsaturated water transport in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang, F. E-mail: michele.griffa@empa.ch; Di Bella, C.; Lura, P.; Prade, F.; Herzen, J.; Sarapata, A.; Pfeiffer, F.; Griffa, M. E-mail: michele.griffa@empa.ch; Jerjen, I.</p> <p>2014-10-13</p> <p>We introduce in this Letter an approach to X-ray imaging of unsaturated water transport in <span class="hlt">porous</span> <span class="hlt">materials</span> based upon the intrinsic X-ray scattering produced by the <span class="hlt">material</span> microstructural heterogeneity at a length scale below the imaging system spatial resolution. The basic principle for image contrast creation consists in a reduction of such scattering by permeation of the porosity by water. The implementation of the approach is based upon X-ray dark-field imaging via Talbot-Lau interferometry. The proof-of-concept is provided by performing laboratory-scale dark-field X-ray radiography of mortar samples during a water capillary uptake experiment. The results suggest that the proposed approach to visualizing unsaturated water transport in <span class="hlt">porous</span> <span class="hlt">materials</span> is complementary to neutron and magnetic resonance imaging and alternative to standard X-ray imaging, the latter requiring the use of contrast agents because based upon X-ray attenuation only.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......168L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......168L"><span id="translatedtitle">Computational study of <span class="hlt">porous</span> <span class="hlt">materials</span> for gas separations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Li-Chiang</p> <p></p> <p>Nanoporous <span class="hlt">materials</span> such as zeolites, zeolitic imidazolate frameworks (ZIFs), and metal-organic frameworks (MOFs) are used as sorbents or membranes for gas separations such as carbon dioxide capture, methane capture, paraffin/olefin separations, etc. The total number of nanoporous <span class="hlt">materials</span> is large; by changing the chemical composition and/or the structural topologies we can envision an infinite number of possible <span class="hlt">materials</span>. In practice one can synthesize and fully characterize only a small subset of these <span class="hlt">materials</span>. Hence, computational study can play an important role by utilizing various techniques in molecular simulations as well as quantum chemical calculations to accelerate the search for optimal <span class="hlt">materials</span> for various energy-related separations. Accordingly, several large-scale computational screenings of over one hundred thousand <span class="hlt">materials</span> have been performed to find the best <span class="hlt">materials</span> for carbon capture, methane capture, and ethane/ethene separation. These large-scale screenings identified a number of promising <span class="hlt">materials</span> for different applications. Moreover, the analysis of these screening studies yielded insights into those molecular characteristics of a <span class="hlt">material</span> that contribute to an optimal performance for a given application. These insights provided useful guidelines for future structural design and synthesis. For instance, one of the screening studies indicated that some zeolite structures can potentially reduce the energy penalty imposed on a coal-fired power plant by as much as 35% compared to the near-term MEA technology for carbon capture application. These optimal structures have topologies with a maximized density of pockets and they capture and release CO2 molecules with an optimal energy. These screening studies also pointed to some systems, for which conventional force fields were unable to make sufficiently reliable predictions of the adsorption isotherms of different gasses, e.g., CO2 in MOFs with open-metal sites. For these systems, we</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21067433','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21067433"><span id="translatedtitle">The Limits of <span class="hlt">Porous</span> <span class="hlt">Materials</span> in the Topology Optimization of Stokes Flows</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Evgrafov, Anton</p> <p>2005-10-15</p> <p>We consider a problem concerning the distribution of a solid <span class="hlt">material</span> in a given bounded control volume with the goal to minimize the potential power of the Stokes flow with given velocities at the boundary through the <span class="hlt">material</span>-free part of the domain.We also study the relaxed problem of the optimal distribution of the <span class="hlt">porous</span> <span class="hlt">material</span> with a spatially varying Darcy permeability tensor, where the governing equations are known as the Darcy-Stokes, or Brinkman, equations. We show that the introduction of the requirement of zero power dissipation due to the flow through the <span class="hlt">porous</span> <span class="hlt">material</span> into the relaxed problem results in it becoming a well-posed mathematical problem, which admits optimal solutions that have extreme permeability properties (i.e., assume only zero or infinite permeability); thus, they are also optimal in the original (non-relaxed) problem. Two numerical techniques are presented for the solution of the constrained problem. One is based on a sequence of optimal Brinkman flows with increasing viscosities, from the mathematical point of view nothing but the exterior penalty approach applied to the problem. Another technique is more special, and is based on the 'sizing' approximation of the problem using a mix of two different <span class="hlt">porous</span> <span class="hlt">materials</span> with high and low permeabilities, respectively. This paper thus complements the study of Borrvall and Petersson (Internat. J. Numer. Methods Fluids, vol. 41, no. 1, pp. 77-107, 2003), where only sizing optimization problems are treated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26456608','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26456608"><span id="translatedtitle">Preparation of steel slag <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> using coal powder as pore former.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Peng; Guo, Zhancheng</p> <p>2015-10-01</p> <p>The aim of the study was to prepare a <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> using steel slag and fly ash as the main raw <span class="hlt">material</span>, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> were a proportion of fly ash of 50% (wt.%), percentage of coal powder of 30% (wt.%), sintering temperature of 1130°C, and sintering time of 6.0hr, which were determined by analyzing the properties of the sound-absorbing <span class="hlt">material</span>. PMID:26456608</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26456608','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26456608"><span id="translatedtitle">Preparation of steel slag <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> using coal powder as pore former.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Peng; Guo, Zhancheng</p> <p>2015-10-01</p> <p>The aim of the study was to prepare a <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> using steel slag and fly ash as the main raw <span class="hlt">material</span>, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the <span class="hlt">porous</span> sound-absorbing <span class="hlt">material</span> were a proportion of fly ash of 50% (wt.%), percentage of coal powder of 30% (wt.%), sintering temperature of 1130°C, and sintering time of 6.0hr, which were determined by analyzing the properties of the sound-absorbing <span class="hlt">material</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1211169','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1211169"><span id="translatedtitle">Water Adsorption in <span class="hlt">Porous</span> Metal-Organic Frameworks and Related <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Furukawa, H; Gandara, F; Zhang, YB; Jiang, JC; Queen, WL; Hudson, MR; Yaghi, OM</p> <p>2014-03-19</p> <p>Water adsorption in <span class="hlt">porous</span> <span class="hlt">materials</span> is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing <span class="hlt">porous</span> <span class="hlt">materials</span> for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the <span class="hlt">material</span>. In search of an excellently performing <span class="hlt">porous</span> <span class="hlt">material</span>, we have studied and compared the water adsorption properties of 23 <span class="hlt">materials</span>, 20 of which are metal organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)(4)(-CO2)(n) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended <span class="hlt">porous</span> frameworks. The permanent porosity of all 23 <span class="hlt">materials</span> was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temperature. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermolecular interaction between adsorbed water molecules within the pores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/814269','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/814269"><span id="translatedtitle">Characterization of <span class="hlt">Porous</span> Carbon Fibers and Related <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fuller, E.L., Jr.</p> <p>1993-01-01</p> <p>A one-year subcontract sponsored by the Carbon <span class="hlt">Materials</span> Technology Group of the Oak Ridge National Laboratory (ORNL) with the Department of Geological Sciences, University Of Tennessee, has been completed. A volumetric sorption system has been upgraded, in cooperation with commercial vendor, to allow the acquisition of data relevant to the program for the production of activated carbon molecular fiber sieves (ACFMS). The equipment and experimental techniques have been developed to determine the pore structure and porosity of reference <span class="hlt">materials</span> and <span class="hlt">materials</span> produced at ORNL as part of the development of methods for the activation of carbon fibers by various etching agents. Commercial activated coconut shell charcoal (ACSC) has been studied to verify instrument performance and to develop methodology for deducing cause and effects in the activation processes and to better understand the industrial processes (gas separation, natural gas storage, etc.). Operating personnel have been trained, standard operating procedures have been established, and quality assurance procedures have been developed and put in place. Carbon dioxide and methane sorption have been measured over a temperature range 0 to 200 C for both ACFMS and ACSC and similarities and differences related to the respective structures and mechanisms of interaction with the sorbed components. Nitrogen sorption (at 77 K) has been used to evaluate ''surface area'' and ''porosity'' for comparison with the large data base that exists for other activated carbons and related <span class="hlt">materials</span>. The preliminary data base reveals that techniques and theories currently used to evaluate activated carbons may be somewhat erroneous and misleading. Alternate thermochemical and structural analyses have been developed that show promise in providing useful information related both to the activation process and to industrial applications of interest in the efficient and economical utilization of fossil fuels in a manner that is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19830032286&hterms=porous+material&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dporous%2Bmaterial','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19830032286&hterms=porous+material&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dporous%2Bmaterial"><span id="translatedtitle">Preliminary results on the abradability of <span class="hlt">porous</span>, sintered seal <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wolak, J.; Emery, A. F.; Etemad, S.; Choi, S. R.</p> <p>1982-01-01</p> <p>Preliminary results are presented for the case of titanium blade specimens, with bare tips (or covered with wear resistant, plasma sprayed <span class="hlt">materials</span>) rubbing at 100 m/s against specimens of abradable nickel-chromium seal <span class="hlt">material</span> moving toward the rotating blades at 0.0125 mm/s or at 0.025 mm/s. Using a two component dynamometer, the normal force of the rub interaction was measured and the shear component estimated. The elastoplastic properties of the seal <span class="hlt">material</span> have been determined and those parameters as well as the rigidity of the rub tester system are considered in conjunction with those affecting the accuracy of the measurement of the forces arising at the blade-seal interface. The average and the 'local instantaneous' temperatures of the seal specimen and the temperature of the blade tip surface during rubbing are presented as functions of time. A seal densification factor is defined and its functional relationships with contact force components, temperature, wear ratio and blade tip abrading capability are indicated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H21A1320H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H21A1320H"><span id="translatedtitle">Pore-scale <span class="hlt">Modelling</span> of Capillarity in Swelling Granular <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hassanizadeh, S. M.; Sweijen, T.; Nikooee, E.; Chareyre, B.</p> <p>2015-12-01</p> <p>Capillarity in granular <span class="hlt">porous</span> media is a common and important phenomenon in earth <span class="hlt">materials</span> and industrial products, and therefore has been studied extensively. To <span class="hlt">model</span> capillarity in granular <span class="hlt">porous</span> media, one needs to go beyond current <span class="hlt">models</span> which simulate either two-phase flow in <span class="hlt">porous</span> media or mechanical behaviour in granular media. Current pore-scale <span class="hlt">models</span> for two-phase flow such as pore-network <span class="hlt">models</span> are tailored for rigid pore-skeletons, even though in many applications, namely hydro-mechanical coupling in soils, printing, and hygienic products, the <span class="hlt">porous</span> structure does change during two-phase flow. On the other hand, <span class="hlt">models</span> such as Discrete Element Method (DEM), which simulate the deformable <span class="hlt">porous</span> media, have mostly been employed for dry or saturated granular media. Here, the effects of porosity change and swelling on the retention properties was studied, for swelling granular <span class="hlt">materials</span>. A pore-unit <span class="hlt">model</span> that was capable to construct the capillary pressure - saturation curve was coupled to DEM. Such that the capillary pressure - saturation curve could be constructed for varying porosities and amounts of absorbed water. The study <span class="hlt">material</span> was super absorbent polymer particles, which are capable to absorb water 10's to 200 times their initial weight. We have simulated quasi-static primary imbibition for different porosities and amounts of absorbed water. The results reveal a 3 dimensional surface between capillary pressure, saturation, and porosity, which can be normalized by means of the entry pressure and the effective water saturation to a unique curve.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008A%26A...484..859P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008A%26A...484..859P"><span id="translatedtitle">Numerical determination of the <span class="hlt">material</span> properties of <span class="hlt">porous</span> dust cakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paszun, D.; Dominik, C.</p> <p>2008-06-01</p> <p>The formation of planetesimals requires the growth of dust particles through collisions. Micron-sized particles must grow by many orders of magnitude in mass. To understand and <span class="hlt">model</span> the processes during this growth, both the mechanical properties and the interaction cross sections of aggregates with surrounding gas must be well understood. Recent advances in experimental (laboratory) studies now provide the background for pushing numerical aggregate <span class="hlt">models</span> to a new level. We present the calibration of a previously tested <span class="hlt">model</span> of aggregate dynamics. We use plastic deformation of surface asperities as the physical <span class="hlt">model</span> to match the velocities needed for sticking with experimental results. The modified code is then used to compute both the compression strength and the velocity of sound in the aggregate at different densities. We compare these predictions with experimental results and conclude that the new code is capable of studying the properties of small aggregates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/956632','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/956632"><span id="translatedtitle">Ensemble phase averaging equations for multiphase flows in <span class="hlt">porous</span> media, part I: the bundle-of-tubes <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang, Dali; Zhang, Duan; Currier, Robert</p> <p>2008-01-01</p> <p>A bundle-of-tubes construct is used as a <span class="hlt">model</span> system to study ensemble averaged equations for multiphase flow in a <span class="hlt">porous</span> <span class="hlt">material</span>. Momentum equations for the fluid phases obtained from the method are similar to Darcy's law, but with additional terms. We study properties of the additional terms, and the conditions under which the averaged equations can be approximated by the diffusion <span class="hlt">model</span> or the extended Darcy's law as often used in <span class="hlt">models</span> for multiphase flows in <span class="hlt">porous</span> media. Although the bundle-of-tubes <span class="hlt">model</span> is perhaps the simplest <span class="hlt">model</span> for a <span class="hlt">porous</span> <span class="hlt">material</span>, the ensemble averaged equation technique developed in this paper assumes the very same form in more general treatments described in Part 2 of the present work (Zhang 2009). Any <span class="hlt">model</span> equation system intended for the more general cases must be understood and tested first using simple <span class="hlt">models</span>. The concept of ensemble phase averaging is dissected here in physical terms, without involved mathematics through its application to the idealized bundle-of-tubes <span class="hlt">model</span> for multiphase flow in <span class="hlt">porous</span> media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23743266','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23743266"><span id="translatedtitle"><span class="hlt">Porous</span> carbon <span class="hlt">material</span> containing CaO for acidic gas capture: preparation and properties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Przepiórski, Jacek; Czyżewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W</p> <p>2013-12-15</p> <p>A one-step process for the preparation of CaO-containing <span class="hlt">porous</span> carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric <span class="hlt">material</span> and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw <span class="hlt">materials</span> used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing <span class="hlt">porous</span> carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid <span class="hlt">materials</span> was confirmed as a suitable method to obtain highly <span class="hlt">porous</span> carbon <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H23R..06G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H23R..06G"><span id="translatedtitle">Colloid Transport in <span class="hlt">Porous</span> Media: A Continuing Survey of Conceptual <span class="hlt">Model</span> Developmen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ginn, T. R.; Nelson, K.; Kamai, T.; Massoudieh, A.; Nguyen, T. H.; Le Borgne, T.; Meheust, Y.; Turuban, R.; Benjamin, A.; Palomino, A.</p> <p>2014-12-01</p> <p>The grand challenge problem of understanding colloid transport and filtration processes in <span class="hlt">porous</span> media continues to defy fundamental solution, limiting progress of engineering science in in fields ranging from human health to water quality to <span class="hlt">materials</span> engineering to energy production to microbiology. Focused experimental and <span class="hlt">modeling</span> studies continue to chip away at our ignorance, in particular as regards colloid interactions with surfaces and colloid motion. In this continuing survey we give an updated overview of some of the currently active research areas with a focus on the exciting new conceptual <span class="hlt">model</span> development and testing, with reference to pore-to-continuum scale experiments and simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1177074','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1177074"><span id="translatedtitle">Enhancing activated-peroxide formulations for <span class="hlt">porous</span> <span class="hlt">materials</span> :</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krauter, Paula; Tucker, Mark D.; Tezak, Matthew S.; Boucher, Raymond</p> <p>2012-12-01</p> <p>During an urban wide-area incident involving the release of a biological warfare agent, the recovery/restoration effort will require extensive resources and will tax the current capabilities of the government and private contractors. In fact, resources may be so limited that decontamination by facility owners/occupants may become necessary and a simple decontamination process and <span class="hlt">material</span> should be available for this use. One potential process for use by facility owners/occupants would be a liquid sporicidal decontaminant, such as pHamended bleach or activated-peroxide, and simple application devices. While pH-amended bleach is currently the recommended <U+2018>low-tech<U+2019> decontamination solution, a less corrosive and toxic decontaminant is desirable. The objective of this project is to provide an operational assessment of an alternative to chlorine bleach for <U+2018>low-tech<U+2019> decontamination applications <U+2013> activated hydrogen peroxide. This report provides the methods and results for activatedperoxide evaluation experiments. The results suggest that the efficacy of an activated-peroxide decontaminant is similar to pH-amended bleach on many common <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003WRR....39.1072D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003WRR....39.1072D"><span id="translatedtitle"><span class="hlt">Modeling</span> of contaminants mobility in underground domains with multiple free/<span class="hlt">porous</span> interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, D. B.; Nassehi, V.</p> <p>2003-03-01</p> <p>Existing simulation techniques for subsurface water quality management remain inadequate despite the phenomenal progress made in the computing capabilities in the past 2 decades. One major lacunas found in mathematical <span class="hlt">models</span> for groundwater hydrodynamics in combined free flow zones (zones that are devoid of <span class="hlt">porous</span> <span class="hlt">materials</span>) and <span class="hlt">porous</span> domains (e.g., soil water regions) in the subsurface is that these <span class="hlt">models</span> impose continuity of all flow/transport parameters to describe the flow behavior at the intermediate surfaces between the two zones. Prescription of such interfacial conditions cannot always be physically justified and, in general, result in ill-posed mathematical formulations. The present paper aims to remove the above limitations of the mathematical <span class="hlt">models</span> by imposing well-posed mathematical formulations of mass and momentum transfer across the boundaries between free and <span class="hlt">porous</span> zones underground for simulating subsurface flow. The possibility of the existence of a multiple number of pervious boundaries in the domain across which water may flow is considered in this work, as it represents the most realistic scenario for the subsurface transport processes. The hydrodynamics of coupled fluid flow and behavior of contaminants transport are described. Combined effects of Darcy and Reynolds numbers on the subsurface transport of contaminants are discussed. Sensitivity of the flow variables to a coefficient of the permeability and porosity of interfacial boundary, which is determined by its structural properties, is also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012WRR....48.9545R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012WRR....48.9545R"><span id="translatedtitle">A new <span class="hlt">model</span> for the spectral induced polarization signature of bacterial growth in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Revil, A.; Atekwana, E.; Zhang, C.; Jardani, A.; Smith, S.</p> <p>2012-09-01</p> <p>The complex conductivity of <span class="hlt">porous</span> <span class="hlt">materials</span> and colloidal suspensions comprises two components: an in-phase conductivity associated with electromigration of the charge carriers and a quadrature conductivity associated with the reversible storage of the charges at some polarization length scales. We developed a quantitative <span class="hlt">model</span> to investigate the frequency domain induced polarization response of suspensions of bacteria and bacteria growth in <span class="hlt">porous</span> media. Induced polarization of bacteria (α polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and α polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to their cation exchange capacity. The mobility of the counterions in this Stern layer is found to be very small (4.7 × 10-10 m2 s-1 V-1 at 25°C). This implies a very low relaxation frequency for the αpolarization of the bacteria cells (typically around 0.1-5 Hz), in agreement with experimental observations. This new <span class="hlt">model</span> can be coupled to reactive transport <span class="hlt">modeling</span> codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a <span class="hlt">porous</span> sand can be inferred nonintrusively from time-lapse frequency domain induced polarization data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DFD.AH009D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DFD.AH009D"><span id="translatedtitle">Droplet impact on a <span class="hlt">porous</span> substrate: a capillary tube <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, Hang; Theofanous, Theo</p> <p>2009-11-01</p> <p>The dynamics of impacting (spreading, penetrating) a droplet on a <span class="hlt">porous</span> substrate, <span class="hlt">modeled</span> by an array of capillary tubes, is studied numerically using diffuse interface methods. The absorption rate depends on the diameter ratio of the capillary tube to the droplet, wettability, and liquid properties. The flow dynamics is resolved by solving the Navier-Stokes equations and interface capturing is governed by the Cahn-Hilliard equation. Contact-angle hysteresis is included (Ding&Spelt 2008) and the stress singularity at moving contact lines is relieved using a diffuse interface <span class="hlt">model</span> (Seppecher 1996; Jaqcmin 2000). The <span class="hlt">model</span> is validated by studying the evolution of a droplet initially resting on a <span class="hlt">porous</span> substrate and by comparison to drop-impact experiments involving just one capillary tube (Kogan et al 2008). Comparisons with analytical solutions and results available in the literature (e.g. Hilpert & Ben-David 2009) are presented. Through parametric simulations over relevant ranges of Reynolds and Ohnesorge numbers and contact angles, impact regime maps are derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNG33A1857G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNG33A1857G"><span id="translatedtitle">Thermal conductivity <span class="hlt">modeling</span> in variably saturated <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghanbarian, B.; Daigle, H.</p> <p>2015-12-01</p> <p><span class="hlt">Modeling</span> effective thermal conductivity under variably saturated conditions is essential to study heat transfer in natural sediments, soils, and rocks. The effective thermal conductivity in completely dry and fully saturated <span class="hlt">porous</span> media is an integrated quantity representing the complex behavior of two conducting phases, i.e., pore fluid (either air or water) and solid matrix. Under partially saturated conditions, however, the effective thermal conductivity becomes even more complicated since three phases (air, water, and solid matrix) conduct heat simultaneously. In this study, we invoke an upscaling treatment called percolation-based effective-medium approximation to <span class="hlt">model</span> the effective thermal conductivity in fully and partially saturated <span class="hlt">porous</span> media. Our theoretical porosity- and saturation-dependent <span class="hlt">models</span> contain endmember properties, such as air, solid matrix, and saturating fluid thermal conductivities, a percolation exponent t, and a percolation threshold. Comparing our theory with 216 porosity-dependent thermal conductivity measurements and 25 saturation-dependent thermal conductivity datasets indicate excellent match between theory and experiments. Our results show that the effective thermal conductivity under fully and partially saturated conditions follows nonuniversal behavior. This means the value of t changes from medium to medium and depends not only on topological and geometrical properties of the medium but also characteristics of the saturating fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014FrMS....8...46K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014FrMS....8...46K"><span id="translatedtitle">Preparation and application of highly <span class="hlt">porous</span> aerogel-based bioactive <span class="hlt">materials</span> in dentistry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuttor, Andrea; Szalóki, Melinda; Rente, Tünde; Kerényi, Farkas; Bakó, József; Fábián, István; Lázár, István; Jenei, Attila; Hegedüs, Csaba</p> <p>2014-03-01</p> <p>In this study, the possibility of preparation and application of highly <span class="hlt">porous</span> silica aerogel-based bioactive <span class="hlt">materials</span> are presented. The aerogel was combined with hydroxyapatite and β-tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in the mesoporous region with a maximum pore diameter of 7.4 and 12.7 nm for the composite <span class="hlt">materials</span>. The newly developed bioactive <span class="hlt">materials</span> were characterized by scanning electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22605984','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22605984"><span id="translatedtitle">Fly ash <span class="hlt">porous</span> <span class="hlt">material</span> using geopolymerization process for high temperature exposure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Abdullah, Mohd Mustafa Al Bakri; Jamaludin, Liyana; Hussin, Kamarudin; Bnhussain, Mohamed; Ghazali, Che Mohd Ruzaidi; Ahmad, Mohd Izzat</p> <p>2012-01-01</p> <p>This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic <span class="hlt">materials</span> (fly ash). In this paper, we report on our investigation of the performance of <span class="hlt">porous</span> geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic <span class="hlt">materials</span> (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the <span class="hlt">porous</span> geopolymers exhibited strength increases after temperature exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3344220','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3344220"><span id="translatedtitle">Fly Ash <span class="hlt">Porous</span> <span class="hlt">Material</span> using Geopolymerization Process for High Temperature Exposure</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Abdullah, Mohd Mustafa Al Bakri; Jamaludin, Liyana; Hussin, Kamarudin; Bnhussain, Mohamed; Ghazali, Che Mohd Ruzaidi; Ahmad, Mohd Izzat</p> <p>2012-01-01</p> <p>This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic <span class="hlt">materials</span> (fly ash). In this paper, we report on our investigation of the performance of <span class="hlt">porous</span> geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic <span class="hlt">materials</span> (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the <span class="hlt">porous</span> geopolymers exhibited strength increases after temperature exposure. PMID:22605984</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25797850','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25797850"><span id="translatedtitle">An electrochemical-sensor system for real-time flow measurements in <span class="hlt">porous</span> <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bathany, Cédric; Han, Ja-Ryoung; Abi-Samra, Kameel; Takayama, Shuichi; Cho, Yoon-Kyoung</p> <p>2015-08-15</p> <p>Flow monitoring in <span class="hlt">porous</span> <span class="hlt">materials</span> is critical for the engineering of paper-based microfluidic bioassays. Here, we present an electrochemical-sensor system that monitors the liquid flow in <span class="hlt">porous</span> <span class="hlt">materials</span> without affecting the real flow in paper-strip samples. The developed microfluidic sensor records an amperometric signal created by the solution movement mediated by paper wicking. This approach allows the in situ monitoring of the different hydrodynamic conditions of a specific paper geometry or composition. In addition, the method proposed in this work was employed to characterise the fluid flow of different nitrocellulose paper strips after oxygen-plasma treatment or dextran coating. The dextran fluid-flow modifiers were further used on the paper strip-based assays as means of signal enhancement. The proposed electrochemical-sensing method offers a valuable alternative to existing optical-based monitoring techniques for flow measurement in paper-based microfluidic systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1107637','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1107637"><span id="translatedtitle">Ordered <span class="hlt">porous</span> mesostructured <span class="hlt">materials</span> from nanoparticle-block copolymer self-assembly</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Warren, Scott; Wiesner, Ulrich; DiSalvo, Jr., Francis J</p> <p>2013-10-29</p> <p>The invention provides mesostructured <span class="hlt">materials</span> and methods of preparing mesostructured <span class="hlt">materials</span> including metal-rich mesostructured nanoparticle-block copolymer hybrids, <span class="hlt">porous</span> metal-nonmetal nanocomposite mesostructures, and ordered metal mesostructures with uniform pores. The nanoparticles can be metal, metal alloy, metal mixture, intermetallic, metal-carbon, metal-ceramic, semiconductor-carbon, semiconductor-ceramic, insulator-carbon or insulator-ceramic nanoparticles, or combinations thereof. A block copolymer/ligand-stabilized nanoparticle solution is cast, resulting in the formation of a metal-rich (or semiconductor-rich or insulator-rich) mesostructured nanoparticle-block copolymer hybrid. The hybrid is heated to an elevated temperature, resulting in the formation of an ordered <span class="hlt">porous</span> nanocomposite mesostructure. A nonmetal component (e.g., carbon or ceramic) is then removed to produce an ordered mesostructure with ordered and large uniform pores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......116T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......116T"><span id="translatedtitle">Bio-inspired Supramolecular Assemblies and <span class="hlt">Porous</span> <span class="hlt">Materials</span> for the Degradation of Organophosphate Nerve Agents</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Totten, Ryan K.</p> <p></p> <p>This thesis reports the synthesis of bio-inspired supramolecular assemblies and <span class="hlt">porous</span> <span class="hlt">materials</span> that are catalytically active in the degradation of organophosphate nerve agents. The first catalysts described are a series of cofacial metalloporphyrin dimers <span class="hlt">modeled</span> after the active site of phosphotriesterase that were modularly prepared from a single porphyrin building block and shown to catalyze the methanolysis of p-nitrophenyl diphenyl phosphate (PNPDPP), a simulant for nerve agents. Notably, tuning the active sites inside the cavities of these dimers, from ZnII metal centers to Al-OMe moieties, affords an enhanced nucleophilic environment where a high concentration of methoxy ligands becomes available for reaction with encapsulated phosphate triesters. Up to a 1300-fold rate acceleration over the uncatalyzed reaction can be achieved via a combination of cavity-localized Lewis-acid activation and methoxide-induced methanolysis. Based on the design principles learned from the aforementioned solution-phase Al(porphyrin) dimers, a heterogeneous <span class="hlt">porous</span> organic polymer (POP) catalyst was synthesized by incorporating an Al(porphyrin) functionalized with a large axial ligand into a POP using a cobalt-catalyzed acetylene trimerization strategy. Removal of the axial ligand afforded a microporous <span class="hlt">material</span> that is capable of encapsulating and solvolytically degrading PNPDPP. Supercritical CO 2 processing of the Al(porphyrin)-based POP dramatically increased the pore size and volume, allowing for significantly higher catalytic activities. The syntheses of porphyrin-based POPs with tunable pore diameters and volumes have also been attempted. SnIV(porphyrins) functionalized with bulky trans-diaxial ligands can be incorporated into POPs. Post-synthesis removal of the ligands reveal POPs with a tunable range of micro- and mesopores as well as tunable pore volumes. Expanding upon the idea that active sites that can both bind substrates and deliver nucleophiles should be active</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...5E7910M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...5E7910M"><span id="translatedtitle">Hierarchically <span class="hlt">porous</span> silicon-carbon-nitrogen hybrid <span class="hlt">materials</span> towards highly efficient and selective adsorption of organic dyes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie</p> <p>2015-01-01</p> <p>The hierarchically macro/micro-<span class="hlt">porous</span> silicon-carbon-nitrogen (Si-C-N) hybrid <span class="hlt">material</span> was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid <span class="hlt">material</span> was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir <span class="hlt">model</span>, the adsorption capacity is 1327.7 mg.g-1 and 1084.5 mg.g-1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid <span class="hlt">materials</span> do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically <span class="hlt">porous</span> Si-C-N hybrid <span class="hlt">material</span> from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4300473','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4300473"><span id="translatedtitle">Hierarchically <span class="hlt">porous</span> silicon–carbon–nitrogen hybrid <span class="hlt">materials</span> towards highly efficient and selective adsorption of organic dyes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie</p> <p>2015-01-01</p> <p>The hierarchically macro/micro-<span class="hlt">porous</span> silicon–carbon–nitrogen (Si–C–N) hybrid <span class="hlt">material</span> was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid <span class="hlt">material</span> was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp2-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir <span class="hlt">model</span>, the adsorption capacity is 1327.7 mg·g−1 and 1084.5 mg·g−1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid <span class="hlt">materials</span> do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically <span class="hlt">porous</span> Si–C–N hybrid <span class="hlt">material</span> from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants. PMID:25604334</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25604334','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25604334"><span id="translatedtitle">Hierarchically <span class="hlt">porous</span> silicon-carbon-nitrogen hybrid <span class="hlt">materials</span> towards highly efficient and selective adsorption of organic dyes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie</p> <p>2015-01-01</p> <p>The hierarchically macro/micro-<span class="hlt">porous</span> silicon-carbon-nitrogen (Si-C-N) hybrid <span class="hlt">material</span> was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid <span class="hlt">material</span> was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir <span class="hlt">model</span>, the adsorption capacity is 1327.7 mg·g(-1) and 1084.5 mg·g(-1) for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid <span class="hlt">materials</span> do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically <span class="hlt">porous</span> Si-C-N hybrid <span class="hlt">material</span> from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants. PMID:25604334</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRG..119.1418J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRG..119.1418J"><span id="translatedtitle">Mechanistic <span class="hlt">models</span> of biofilm growth in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, Priyank; Al-Hadrami, Fathiya; Atekwana, Estella A.; Atekwana, Eliot A.</p> <p>2014-07-01</p> <p>Nondestructive acoustics methods can be used to monitor in situ biofilm growth in <span class="hlt">porous</span> media. In practice, however, acoustic methods remain underutilized due to the lack of <span class="hlt">models</span> that can translate acoustic data into rock properties in the context of biofilm. In this paper we present mechanistic <span class="hlt">models</span> of biofilm growth in <span class="hlt">porous</span> media. The <span class="hlt">models</span> are used to quantitatively interpret arrival times and amplitudes recorded in the 29 day long Davis et al. (2010) physical scale biostimulation experiment in terms of biofilm morphologies and saturation. The <span class="hlt">model</span> pivots on addressing the sediment elastic behavior using the lower Hashin-Shtrikman bounds for grain mixing and Gassmann substitution for fluid saturation. The time-lapse P wave velocity (VP; a function of arrival times) is explained by a combination of two rock <span class="hlt">models</span> (morphologies); "load bearing" which assumes the biofilm as an additional mineral in the rock matrix and "pore filling" which assumes the biofilm as an additional fluid phase in the pores. The time-lapse attenuation (QP-1; a function of amplitudes), on the other hand, can be explained adequately in two ways; first, through squirt flow where energy is lost from relative motion between rock matrix and pore fluid, and second, through an empirical function of porosity (φ), permeability (κ), and grain size. The squirt flow <span class="hlt">model</span>-fitting results in higher internal φ (7% versus 5%) and more oblate pores (0.33 versus 0.67 aspect ratio) for the load-bearing morphology versus the pore-filling morphology. The empirical <span class="hlt">model</span>-fitting results in up to 10% increase in κ at the initial stages of the load-bearing morphology. The two morphologies which exhibit distinct mechanical and hydraulic behavior could be a function of pore throat size. The biofilm mechanistic <span class="hlt">models</span> developed in this study can be used for the interpretation of seismic data critical for the evaluation of biobarriers in bioremediation, microbial enhanced oil recovery, and CO2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015ApSS..354..115C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015ApSS..354..115C&link_type=ABSTRACT"><span id="translatedtitle">Atomic layer deposition HfO2 capping layer effect on <span class="hlt">porous</span> low dielectric constant <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, Yi-Lung; Kao, Kai-Chieh; Huang, Chi-Jia; Chen, Giin-Shan; Fang, Jau-Shiung</p> <p>2015-11-01</p> <p>Low dielectric constant (low-k) <span class="hlt">materials</span> are used as inter-level insulators between copper (Cu) conductors to improve the characteristics of integrated circuits. This work proposes a new method for improving the characteristics of <span class="hlt">porous</span> low-k dielectric film by capping it with an HfO2 film by atomic layer deposition (ALD). Experimental results revealed that capping a <span class="hlt">porous</span> low-k dielectric film with a ∼1.0 nm-thick HfO2 film increases its dielectric constant from 2.56 to 2.65 because the pores in the surface of the film are sealed by Hf precursors. The leakage current density and reliability of the <span class="hlt">porous</span> low-k dielectrics are greatly improved. The HfO2 capping film also increased resistances against Cu diffusion and damage by oxygen plasma. Therefore, this ALD-deposited HfO2 capping film can be used as a pore-sealing layer and a Cu barrier layer for the <span class="hlt">porous</span> low-k dielectric film in the future advanced technologies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11350000','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11350000"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">material</span> characterization--ultrasonic method for estimation of tortuosity and characteristic length using a barometric chamber.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moussatov, A; Ayrault, C; Castagnède, B</p> <p>2001-04-01</p> <p>An ultrasonic method of acoustic parameter evaluation for <span class="hlt">porous</span> <span class="hlt">materials</span> saturated by air (or any other gas) is discussed. The method is based on the evolution of speed of sound and the attenuation inside the <span class="hlt">material</span> when the static pressure of the gas saturating the <span class="hlt">material</span> is changed. Asymptotic development of the equivalent fluid <span class="hlt">model</span> of Johnson-Allard is used for analytical description. The method allows an estimation of three essential parameters of the <span class="hlt">model</span>: the tortuosity, and the viscous and thermal characteristic lengths. Both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed with industrial plastic foams and granular substances (glass beads, sea sand) over a gas pressure range from 0.2 to 6 bars at the frequencies 30-600 kHz. The present technique has a number of distinct advantages over the conventional ultrasonic approach: operation at a single frequency, improved signal-to-noise ratio, possibility of saturation the <span class="hlt">porous</span> media by different gases. In the case when scattering phenomena occur, the present method permits a separate analysis of scattering losses and viscothermal losses. An analytical description of the method is followed by a presentation of the set-up and the measurement procedure. Experimental results and perspectives are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11350000','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11350000"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">material</span> characterization--ultrasonic method for estimation of tortuosity and characteristic length using a barometric chamber.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moussatov, A; Ayrault, C; Castagnède, B</p> <p>2001-04-01</p> <p>An ultrasonic method of acoustic parameter evaluation for <span class="hlt">porous</span> <span class="hlt">materials</span> saturated by air (or any other gas) is discussed. The method is based on the evolution of speed of sound and the attenuation inside the <span class="hlt">material</span> when the static pressure of the gas saturating the <span class="hlt">material</span> is changed. Asymptotic development of the equivalent fluid <span class="hlt">model</span> of Johnson-Allard is used for analytical description. The method allows an estimation of three essential parameters of the <span class="hlt">model</span>: the tortuosity, and the viscous and thermal characteristic lengths. Both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed with industrial plastic foams and granular substances (glass beads, sea sand) over a gas pressure range from 0.2 to 6 bars at the frequencies 30-600 kHz. The present technique has a number of distinct advantages over the conventional ultrasonic approach: operation at a single frequency, improved signal-to-noise ratio, possibility of saturation the <span class="hlt">porous</span> media by different gases. In the case when scattering phenomena occur, the present method permits a separate analysis of scattering losses and viscothermal losses. An analytical description of the method is followed by a presentation of the set-up and the measurement procedure. Experimental results and perspectives are discussed. PMID:11350000</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1230814-sandia-material-model-driver','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1230814-sandia-material-model-driver"><span id="translatedtitle">Sandia <span class="hlt">Material</span> <span class="hlt">Model</span> Driver</span></a></p> <p><a target="_blank" href=""></a></p> <p></p> <p>2005-09-28</p> <p>The Sandia <span class="hlt">Material</span> <span class="hlt">Model</span> Driver (MMD) software package allows users to run <span class="hlt">material</span> <span class="hlt">models</span> from a variety of different Finite Element <span class="hlt">Model</span> (FEM) codes in a standalone fashion, independent of the host codes. The MMD software is designed to be run on a variety of different operating system platforms as a console application. Initial development efforts have resulted in a package that has been shown to be fast, convenient, and easy to use, with substantialmore » growth potential.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/242525','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/242525"><span id="translatedtitle">Preparation of <span class="hlt">porous</span> nickel-titania cermets and their application to anode <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Taimatsu, H.; Kudo, K.; Kaneko, H.; Matsukaze, N.; Iwata, T.</p> <p>1995-12-31</p> <p><span class="hlt">Porous</span> nickel-titania cermets have been prepared as new-type anode <span class="hlt">materials</span> for solid oxide fuel cells using the solid-state displacement reaction method. The microstructures of the cermets were interwoven aggregate-type, differently from those of conventional nickel-YSZ cermets: nickel and titania phases three-dimensionally entangled each other. These cermets revealed good properties in compatibility of thermal expansion with YSZ, strength, gas permeation and electrical conduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000Natur.404..982S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000Natur.404..982S"><span id="translatedtitle">A homochiral metal-organic <span class="hlt">porous</span> <span class="hlt">material</span> for enantioselective separation and catalysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seo, Jung Soo; Whang, Dongmok; Lee, Hyoyoung; Jun, Sung Im; Oh, Jinho; Jeon, Young Jin; Kim, Kimoon</p> <p>2000-04-01</p> <p>Inorganic zeolites are used for many practical applications that exploit the microporosity intrinsic to their crystal structures. Organic analogues, which are assembled from modular organic building blocks linked through non-covalent interactions, are of interest for similar applications. These range from catalysis, separation and sensor technology to optoelectronics, with enantioselective separation and catalysis being especially important for the chemical and pharmaceutical industries. The modular construction of these analogues allows flexible and rational design, as both the architecture and chemical functionality of the micropores can, in principle, be precisely controlled. <span class="hlt">Porous</span> organic solids with large voids and high framework stability have been produced, and investigations into the range of accessible pore functionalities have been initiated. For example, catalytically active organic zeolite analogues are known, as are chiral metal-organic open-framework <span class="hlt">materials</span>. However, the latter are only available as racemic mixtures, or lack the degree of framework stability or void space that is required for practical applications. Here we report the synthesis of a homochiral metal-organic <span class="hlt">porous</span> <span class="hlt">material</span> that allows the enantioselective inclusion of metal complexes in its pores and catalyses a transesterification reaction in an enantioselective manner. Our synthesis strategy, which uses enantiopure metal-organic clusters as secondary building blocks, should be readily applicable to chemically modified cluster components and thus provide access to a wide range of <span class="hlt">porous</span> organic <span class="hlt">materials</span> suitable for enantioselective separation and catalysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26256356','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26256356"><span id="translatedtitle">Fabrication of interpenetrating polymer network chitosan/gelatin <span class="hlt">porous</span> <span class="hlt">materials</span> and study on dye adsorption properties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Li; Xiong, Zihao; Guo, Yi; Liu, Yun; Zhao, Jinchao; Zhang, Chuanjie; Zhu, Ping</p> <p>2015-11-01</p> <p>One kind of adsorbent based on chitosan and gelatin with interpenetrating polymer networks (IPN) and <span class="hlt">porous</span> dual structures was prepared using genipin as the cross-linker. These dual structures were demonstrated by means of Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Adsorptions of acid orange II dye from aqueous solution were carried out at different genipin contents, adsorption times and pH values. The results showed that this <span class="hlt">material</span> was put up the largest adsorption capacity when the genipin content is 0.25 mmol/L, meanwhile, the lower the solution pH value the greater the adsorption capacity. The chitosan/gelatin interpenetrating polymer networks <span class="hlt">porous</span> <span class="hlt">material</span> displayed pH-sensitive and rapidly response in adsorption and desorption to pH altered. It is indicated that the cross-linked chitosan/gelatin interpenetrating polymer networks <span class="hlt">porous</span> <span class="hlt">material</span> could be used as a recyclable adsorbent in removal or separation of anionic dyes as environmental pH condition changed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23945102','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23945102"><span id="translatedtitle"><span class="hlt">Porous</span> coordination polymers as novel sorption <span class="hlt">materials</span> for heat transformation processes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Janiak, Christoph; Henninger, Stefan K</p> <p>2013-01-01</p> <p><span class="hlt">Porous</span> coordination polymers (PCPs)/metal-organic frameworks (MOFs) are inorganic-organic hybrid <span class="hlt">materials</span> with a permanent three-dimensional <span class="hlt">porous</span> metal-ligand network. PCPs or MOFs are inorganic-organic analogs of zeolites in terms of porosity and reversible guest exchange properties. Microporous water-stable PCPs with high water uptake capacity are gaining attention for low temperature heat transformation applications in thermally driven adsorption chillers (TDCs) or adsorption heat pumps (AHPs). TDCs or AHPs are an alternative to traditional air conditioners or heat pumps operating on electricity or fossil fuels. By using solar or waste heat as the operating energy TDCs or AHPs can significantly help to minimize primary energy consumption and greenhouse gas emissions generated by industrial or domestic heating and cooling processes. TDCs and AHPs are based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. The process is driven and controlled by the microporosity and hydrophilicity of the employed sorption <span class="hlt">material</span>. Here we summarize the current investigations, developments and possibilities of PCPs/MOFs for use in low-temperature heat transformation applications as alternative <span class="hlt">materials</span> for the traditional inorganic <span class="hlt">porous</span> substances like silica gel, aluminophosphates or zeolites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23945102','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23945102"><span id="translatedtitle"><span class="hlt">Porous</span> coordination polymers as novel sorption <span class="hlt">materials</span> for heat transformation processes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Janiak, Christoph; Henninger, Stefan K</p> <p>2013-01-01</p> <p><span class="hlt">Porous</span> coordination polymers (PCPs)/metal-organic frameworks (MOFs) are inorganic-organic hybrid <span class="hlt">materials</span> with a permanent three-dimensional <span class="hlt">porous</span> metal-ligand network. PCPs or MOFs are inorganic-organic analogs of zeolites in terms of porosity and reversible guest exchange properties. Microporous water-stable PCPs with high water uptake capacity are gaining attention for low temperature heat transformation applications in thermally driven adsorption chillers (TDCs) or adsorption heat pumps (AHPs). TDCs or AHPs are an alternative to traditional air conditioners or heat pumps operating on electricity or fossil fuels. By using solar or waste heat as the operating energy TDCs or AHPs can significantly help to minimize primary energy consumption and greenhouse gas emissions generated by industrial or domestic heating and cooling processes. TDCs and AHPs are based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. The process is driven and controlled by the microporosity and hydrophilicity of the employed sorption <span class="hlt">material</span>. Here we summarize the current investigations, developments and possibilities of PCPs/MOFs for use in low-temperature heat transformation applications as alternative <span class="hlt">materials</span> for the traditional inorganic <span class="hlt">porous</span> substances like silica gel, aluminophosphates or zeolites. PMID:23945102</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25929065','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25929065"><span id="translatedtitle">[Purification of the wastewater of quartz processing by mineral-based <span class="hlt">porous</span> granulation <span class="hlt">material</span>].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, En-Wen; Lei, Shao-Min; Zhang, Shi-Chun; Huang, Teng</p> <p>2015-03-01</p> <p>A mineral-based <span class="hlt">porous</span> granulation <span class="hlt">material</span> (MPGM) was prepared for absorbing the heavy metal ions from quartz processing wastewater. Analytic results of the MPGM were illustrated by the techniques of BET, SEM and FT-IR, which revealed the excellent properties of multi-aperture distribution, large specific surface area, low loss ratio and so on; the N2 adsorption-desorption isotherm was type-III with H4 hysteresis loop; the functional groups were dominated by groups of layer silicate mineral. A batch adsorption study was carried out with varied adsorbent dosage, initial pH and reaction time. The results showed that the residual ion concentrations of Fe, Zn, Mn and As were decreased from 77.760, 3.700, 2.789 and 0.963 mg x L(-1) to 3.421, 0.574, 0.126 and 0.034 mg x L(-1), respectively. MPGM might be re-utilized after desorption by 1.0 mol x L(-1) NaCl for 12 hours, and the ideal adsorption performance was maintained after 5 recyclings. The adsorption equilibrium and kinetics followed Langmuir and typical pseudo-first-order/pseudo-second-order adsorption <span class="hlt">models</span>. Thermodynamic parameters of ΔG(θ) < 0, ΔHθ > 0, ΔSθ > 0 showed that the adsorptions were spontaneous and endothermic processes in the temperature range of 15-45 degrees C. PMID:25929065</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21752539','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21752539"><span id="translatedtitle">Adsorption characteristics of haloacetonitriles on functionalized silica-based <span class="hlt">porous</span> <span class="hlt">materials</span> in aqueous solution.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prarat, Panida; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha; Punyapalakul, Patiparn</p> <p>2011-09-15</p> <p>The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based <span class="hlt">porous</span> <span class="hlt">materials</span> was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm <span class="hlt">models</span> were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS. PMID:21752539</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25929065','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25929065"><span id="translatedtitle">[Purification of the wastewater of quartz processing by mineral-based <span class="hlt">porous</span> granulation <span class="hlt">material</span>].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, En-Wen; Lei, Shao-Min; Zhang, Shi-Chun; Huang, Teng</p> <p>2015-03-01</p> <p>A mineral-based <span class="hlt">porous</span> granulation <span class="hlt">material</span> (MPGM) was prepared for absorbing the heavy metal ions from quartz processing wastewater. Analytic results of the MPGM were illustrated by the techniques of BET, SEM and FT-IR, which revealed the excellent properties of multi-aperture distribution, large specific surface area, low loss ratio and so on; the N2 adsorption-desorption isotherm was type-III with H4 hysteresis loop; the functional groups were dominated by groups of layer silicate mineral. A batch adsorption study was carried out with varied adsorbent dosage, initial pH and reaction time. The results showed that the residual ion concentrations of Fe, Zn, Mn and As were decreased from 77.760, 3.700, 2.789 and 0.963 mg x L(-1) to 3.421, 0.574, 0.126 and 0.034 mg x L(-1), respectively. MPGM might be re-utilized after desorption by 1.0 mol x L(-1) NaCl for 12 hours, and the ideal adsorption performance was maintained after 5 recyclings. The adsorption equilibrium and kinetics followed Langmuir and typical pseudo-first-order/pseudo-second-order adsorption <span class="hlt">models</span>. Thermodynamic parameters of ΔG(θ) < 0, ΔHθ > 0, ΔSθ > 0 showed that the adsorptions were spontaneous and endothermic processes in the temperature range of 15-45 degrees C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26617098','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26617098"><span id="translatedtitle">Automatic Structure Analysis in High-Throughput Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Haranczyk, Maciej; Sethian, James A</p> <p>2010-11-01</p> <p>Inspection of the structure and the void space of a <span class="hlt">porous</span> <span class="hlt">material</span> is a critical step in most computational studies involving guest molecules. Some sections of the void space, like inaccessible pockets, have to be identified and blocked in molecular simulations. These pockets are typically detected by visual analysis of the geometry, potential or free energy landscapes, or a histogram of an initial molecular simulation. Such visual analysis is time-consuming and inhibits characterization of large sets of <span class="hlt">materials</span> required in studies focused on identification of the best <span class="hlt">materials</span> for a given application. We present an automatic approach that bypasses manual visual analysis of this kind, thereby enabling execution of molecular simulations in an unsupervised, high-throughput manner. In our approach, we used a partial differential equations-based front propagation technique to segment out channels and inaccessible pockets of a periodic unit cell of a <span class="hlt">material</span>. We cast the problem as a path planning problem in 3D space representing a periodic fragment of <span class="hlt">porous</span> <span class="hlt">material</span>, and solve the resulting Eikonal equation by using Fast Marching Methods. One attractive feature of this approach is that the to-be-analyzed data can be of varying types, including, for example, a 3D grid representing the distance to the <span class="hlt">material</span>'s surface, the potential or free energy of a molecule inside the <span class="hlt">material</span>, or even a histogram (a set of snapshots) from a molecular simulation showing areas which were visited by the molecule during the simulation. PMID:26617098</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H14C..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H14C..01G"><span id="translatedtitle">A novel approach to <span class="hlt">model</span> hydraulic and electrical conductivity in fractal <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghanbarian, B.; Daigle, H.; Sahimi, M.</p> <p>2014-12-01</p> <p>Accurate prediction of conductivity in partially-saturated <span class="hlt">porous</span> media has broad applications in various phenomena in <span class="hlt">porous</span> media, and has been studied intensively since the 1940s by petroleum, chemical and civil engineers, and hydrologists. Many of the <span class="hlt">models</span> developed in the past are based on the bundle of capillary tubes. In addition, pore network <span class="hlt">models</span> have also been developed for simulating multiphase fluid flow in <span class="hlt">porous</span> media and computing the conductivity in unsaturated <span class="hlt">porous</span> media. In this study, we propose a novel approach using concepts from the effective-medium approximation (EMA) and percolation theory to <span class="hlt">model</span> hydraulic and electrical conductivity in fractal <span class="hlt">porous</span> media whose pore-size distributions exhibit power-law scaling. In our approach, the EMA, originally developed for predicting electrical conductivity of composite <span class="hlt">materials</span>, is used to predict the effective conductivity, from complete saturation to some intermediate water content that represents a crossover point. Below the crossover water content, but still above a critical saturation (percolation threshold), a universal scaling predicted by percolation theory, a power law that expresses the dependence of the conductivity on the water content (less a critical water saturation) with an exponent of 2, is invoked to describe the effective conductivity. In order to evaluate the accuracy of the approach, experimental data were used from the literature. The predicted hydraulic conductivities for most cases are in excellent agreement with the data. In a few cases the theory underestimates the hydraulic conductivities, which correspond to <span class="hlt">porous</span> media with very broad pore-size distribution in which the largest pore radius is more than 7 orders of magnitude greater than the smallest one. The approach is also used to predict the saturation dependence of the electrical conductivity for experiments in which capillary pressure data are available. The results indicate that the universal scaling of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/873832','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/873832"><span id="translatedtitle">Method and apparatus for measuring surface changes, in <span class="hlt">porous</span> <span class="hlt">materials</span>, using multiple differently-configured acoustic sensors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hietala, Susan Leslie; Hietala, Vincent Mark; Tigges, Chris Phillip</p> <p>2001-01-01</p> <p>A method and apparatus for measuring surface changes, such as mass uptake at various pressures, in a thin-film <span class="hlt">material</span>, in particular <span class="hlt">porous</span> membranes, using multiple differently-configured acoustic sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JAP...103i4913G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JAP...103i4913G"><span id="translatedtitle"><span class="hlt">Models</span> of water imbibition in untreated and treated <span class="hlt">porous</span> media validated by quantitative magnetic resonance imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gombia, M.; Bortolotti, V.; Brown, R. J. S.; Camaiti, M.; Fantazzini, P.</p> <p>2008-05-01</p> <p>Fluid imbibition affects almost every activity that directly or indirectly involves <span class="hlt">porous</span> media, including oil reservoir rocks, soils, building <span class="hlt">materials</span>, and countless others, including biological <span class="hlt">materials</span>. In this paper, magnetic resonance imaging (MRI) has been applied to study water imbibition in a <span class="hlt">porous</span> medium, in which capillary properties are artificially changed. As a <span class="hlt">model</span> system, samples of Lecce stone, a <span class="hlt">material</span> of cultural heritage interest, were analyzed before and after treatment with a protective polymer (Silirain-50 or Paraloid PB72). By using MRI, we can visualize the presence of water inside each sample and measure the height z(t ) reached by the wetting front as a function of time during experiments of capillary absorption before and after treatment. The sorptivity S, defined as the initial slope of z versus t1/2, has been determined before treatment and through both treated and untreated faces after treatment. Very good fits to the data were obtained with theoretical and empirical <span class="hlt">models</span> of absorption kinetics, starting from the Washburn <span class="hlt">model</span> for capillary rise, adapted by others to homogeneous <span class="hlt">porous</span> media, and modified by us for application to a sample having a thin low-permeability layer on either surface as a result of a treatment process. This gives us parameters to quantify the effects on imbibition of the changes in the capillary properties. It is known that the Paraloid treatment preferentially affects the larger pore channels and the Silirain the smaller, and our results show this and illustrate the roles played by the different classes of pore sizes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1510181L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1510181L"><span id="translatedtitle">Electrokinetic induced solute dispersion in <span class="hlt">porous</span> media; pore network <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Shuai; Schotting, Ruud; Raoof, Amir</p> <p>2013-04-01</p> <p>Electrokinetic flow plays an important role in remediation process, separation technique, and chromatography. The solute dispersion is a key parameter to determine transport efficiency. In this study, we present the electrokinetic effects on solute dispersion in <span class="hlt">porous</span> media at the pore scale, using a pore network <span class="hlt">model</span>. The analytical solution of the electrokinetic coupling coefficient was obtained to quantity the fluid flow velocity in a cylinder capillary. The effect of electrical double layer on the electrokinetic coupling coefficient was investigated by applying different ionic concentration. By averaging the velocity over cross section within a single pore, the average flux was obtained. Applying such single pore relationships, in the thin electrical double layer limit, to each and every pore within the pore network, potential distribution and the induced fluid flow was calculated for the whole domain. The resulting pore velocities were used to simulate solute transport within the pore network. By averaging the results, we obtained the breakthrough curve (BTC) of the average concentration at the outlet of the pore network. Optimizing the solution of continuum scale advection-dispersion equation to such a BTC, solute dispersion coefficient was estimated. We have compared the dispersion caused by electrokinetic flow and pure pressure driven flow under different Peclet number values. In addition, the effect of microstructure and topological properties of <span class="hlt">porous</span> media on fluid flow and solute dispersion is presented, mainly based on different pore coordination numbers.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080022430','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080022430"><span id="translatedtitle"><span class="hlt">Modeling</span> of Fixed-Exit <span class="hlt">Porous</span> Bleed Systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slater, John W.; Saunders, John D.</p> <p>2008-01-01</p> <p>A <span class="hlt">model</span> has been developed to simulate a fixed-exit <span class="hlt">porous</span> bleed system for supersonic inlets. The fixed-exit <span class="hlt">model</span> allows the amount of bleed flow to vary according to local flow conditions and fixed-exit characteristics of the bleed system. This variation is important for the control of shock-wave/boundary-layer interactions within the inlet. The <span class="hlt">model</span> computes the bleed plenum static pressure rather than requiring its specification. The <span class="hlt">model</span> was implemented in the Wind-US computational fluid dynamics code. The <span class="hlt">model</span> was then verified and validated against experimental data for bleed on a flat plate with and without an impinging oblique shock and for bleed in a Mach 3.0 axisymmetric, mixed-compression inlet. The <span class="hlt">model</span> was able to accurately correlate the plenum pressures with bleed rates and simulate the effect of the bleed on the downstream boundary layer. Further, the <span class="hlt">model</span> provided a realistic simulation of the initiation of inlet unstart. The results provide the most in-depth examination to date of bleed <span class="hlt">models</span> for use in the simulation of supersonic inlets. The results also highlight the limitations of the <span class="hlt">models</span> and aspects that require further research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009CRMec.337...68A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009CRMec.337...68A"><span id="translatedtitle">A mixed damage <span class="hlt">model</span> for unsaturated <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arson, Chloé; Gatmiri, Behrouz</p> <p>2009-02-01</p> <p>The aim of this study is to present a framework for the <span class="hlt">modeling</span> of damage in continuous unsaturated <span class="hlt">porous</span> geomaterials. The damage variable is a second-order tensor. The <span class="hlt">model</span> is formulated in net stress and suction independent state variables. Correspondingly, the strain tensor is split into two independent thermodynamic strain components. The proposed framework mixes micro-mechanical and phenomenological approaches. On the one hand, the effective stress concept of Continuum Damage Mechanics is used in order to compute the damaged rigidities. On the other hand, the concept of equivalent mechanical state is introduced in order to get a simple phenomenological formulation of the behavior laws. Cracking effects are also taken into account in the fluid transfer laws. To cite this article: C. Arson, B. Gatmiri, C. R. Mecanique 337 (2009).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AdWR...51...52H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AdWR...51...52H"><span id="translatedtitle"><span class="hlt">Model</span> coupling for multiphase flow in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Helmig, Rainer; Flemisch, Bernd; Wolff, Markus; Ebigbo, Anozie; Class, Holger</p> <p>2013-01-01</p> <p>Numerical <span class="hlt">models</span> for flow and transport in <span class="hlt">porous</span> media are valid for a particular set of processes, scales, levels of simplification and abstraction, grids etc. The coupling of two or more specialised <span class="hlt">models</span> is a method of increasing the overall range of validity while keeping the computational costs relatively low. Several coupling concepts are reviewed in this article with a focus on the authors’ work in this field. The concepts are divided into temporal and spatial coupling concepts, of which the latter is subdivided into multi-process, multi-scale, multi-dimensional, and multi-compartment coupling strategies. Examples of applications for which these concepts can be relevant include groundwater protection and remediation, carbon dioxide storage, nuclear-waste disposal, soil dry-out and evaporation processes as well as fuel cells and technical filters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22392371','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22392371"><span id="translatedtitle">Small angle scattering methods to study <span class="hlt">porous</span> <span class="hlt">materials</span> under high uniaxial strain</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Le Floch, Sylvie Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso</p> <p>2015-02-15</p> <p>We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly <span class="hlt">porous</span> <span class="hlt">materials</span>. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of <span class="hlt">porous</span> <span class="hlt">materials</span> by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar <span class="hlt">porous</span> systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25725857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25725857"><span id="translatedtitle">Small angle scattering methods to study <span class="hlt">porous</span> <span class="hlt">materials</span> under high uniaxial strain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Le Floch, Sylvie; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso</p> <p>2015-02-01</p> <p>We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly <span class="hlt">porous</span> <span class="hlt">materials</span>. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of <span class="hlt">porous</span> <span class="hlt">materials</span> by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar <span class="hlt">porous</span> systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5043355','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5043355"><span id="translatedtitle">Europium (III) Organic Complexes in <span class="hlt">Porous</span> Boron Nitride Microfibers: Efficient Hybrid Luminescent <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lin, Jing; Feng, Congcong; He, Xin; Wang, Weijia; Fang, Yi; Liu, Zhenya; Li, Jie; Tang, Chengchun; Huang, Yang</p> <p>2016-01-01</p> <p>We report the design and synthesis of a novel kind of organic-inorganic hybrid <span class="hlt">material</span> via the incorporation of europium (III) β-diketonate complexes (Eu(TTA)3, TTA = 2-thenoyltrifluoroacetone) into one-dimensional (1D) <span class="hlt">porous</span> boron nitride (BN) microfibers. The developed Eu(TTA)3@BN hybrid composites with typical 1D fibrous morphology exhibit bright visible red-light emission on UV illumination. The confinement of Eu(TTA)3 within pores of BN microfibers not only decreases the aggregation-caused quenching in solid Eu(TTA)3, but also improves their thermal stabilities. Moreover, The strong interactions between Eu(TTA)3 and <span class="hlt">porous</span> BN matrix result in an interesting energy transfer process from BN host to TTA ligand and TTA ligand to Eu3+ ions, leading to the remarkable increase of red emission. The synthetic approach should be a very promising strategy which can be easily expanded to other hybrid luminescent <span class="hlt">materials</span> based on <span class="hlt">porous</span> BN. PMID:27687246</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..93c3006P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..93c3006P"><span id="translatedtitle">Record-breaking events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G.</p> <p>2016-03-01</p> <p>An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of <span class="hlt">materials</span> and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element <span class="hlt">model</span> of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k*, which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27078440','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27078440"><span id="translatedtitle">Record-breaking events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G</p> <p>2016-03-01</p> <p>An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of <span class="hlt">materials</span> and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element <span class="hlt">model</span> of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k(*), which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23606606','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23606606"><span id="translatedtitle">Hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span> from layer-by-layer photopolymerization of high internal phase emulsions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sušec, Maja; Ligon, Samuel Clark; Stampfl, Jürgen; Liska, Robert; Krajnc, Peter</p> <p>2013-06-13</p> <p>A combination of high internal phase emulsion (HIPE) templating and additive manufacturing technology (AMT) is applied for creating hierarchical porosity within an acrylate and acrylate/thiol-based polymer network. The photopolymerizable formulation is optimized to produce emulsions with a volume fraction of droplet phase greater than 80 vol%. Kinetic stability of the emulsions is sufficient enough to withstand in-mold curing or computer-controlled layer-by-layer stereolithography without phase separation. By including macroscale cellular cavities within the build file, a level of controlled porosity is created simultaneous to the formation of the <span class="hlt">porous</span> microstructure of the polyHIPE. The hybrid HIPE-AMT technique thus provides hierarchically <span class="hlt">porous</span> <span class="hlt">materials</span> with mechanical properties tailored by the addition of thiol chain transfer agent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26406996','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26406996"><span id="translatedtitle">Sponge-Like Behaviour in Isoreticular Cu(Gly-His-X) Peptide-Based <span class="hlt">Porous</span> <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martí-Gastaldo, Carlos; Warren, John E; Briggs, Michael E; Armstrong, Jayne A; Thomas, K Mark; Rosseinsky, Matthew J</p> <p>2015-11-01</p> <p>We report two isoreticular 3D peptide-based <span class="hlt">porous</span> frameworks formed by coordination of the tripeptides Gly-L-His-Gly and Gly-L-His-L-Lys to Cu(II) which display sponge-like behaviour. These <span class="hlt">porous</span> <span class="hlt">materials</span> undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2 O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal-organic frameworks built from more rigid "classical" linkers. PMID:26406996</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4676333','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4676333"><span id="translatedtitle">Sponge-Like Behaviour in Isoreticular Cu(Gly-His-X) Peptide-Based <span class="hlt">Porous</span> <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Martí-Gastaldo, Carlos; Warren, John E; Briggs, Michael E; Armstrong, Jayne A; Thomas, K Mark; Rosseinsky, Matthew J</p> <p>2015-01-01</p> <p>We report two isoreticular 3D peptide-based <span class="hlt">porous</span> frameworks formed by coordination of the tripeptides Gly-l-His-Gly and Gly-l-His-l-Lys to CuII which display sponge-like behaviour. These <span class="hlt">porous</span> <span class="hlt">materials</span> undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal–organic frameworks built from more rigid “classical” linkers. PMID:26406996</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016FML.....950032L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016FML.....950032L"><span id="translatedtitle">Superior supercapacitor electrode <span class="hlt">material</span> from hydrazine hydrate modified <span class="hlt">porous</span> polyacrylonitrile fiber</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Ying; Lu, Chunxiang; Wang, Junzhong; Yan, Hua; Zhang, Shouchun</p> <p>2016-03-01</p> <p>A hierarchical <span class="hlt">porous</span> carbon fiber with high nitrogen doping was fabricated for high-performance supercapacitor. For the purpose of high nitrogen retention, the <span class="hlt">porous</span> polyacrylonitrile fiber was treated by hydrazine hydrate, and then underwent pre-oxidation, carbonization, and activation in sequence. The resulted <span class="hlt">material</span> exhibited high nitrogen content of 7.82 at.%, large specific surface area of 1963.3m2 g‑1, total pore volume of 1.523cm3 g‑1, and the pores with size range of 1-4nm were account for 49.1%. Due to these features, the high reversible capacitance of 415F g‑1 and the good performance in heavy load discharge were obtained. In addition, the amazing cyclability was observed after 10,000 circles without capacitance fading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MPLB...23..501L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MPLB...23..501L"><span id="translatedtitle">Numerical Simulation for Effects of Microcapsuled Phase Change <span class="hlt">Material</span> (mpcm) Distribution on Heat and Moisture Transfer in <span class="hlt">Porous</span> Textiles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Fengzhi</p> <p></p> <p>In recent years, the use of phase change <span class="hlt">materials</span> (PCM) to improve heat and moisture transfer properties of clothing has gained considerable attention. The PCM distribution in the clothing impacts heat and moisture transfer properties of the clothing significantly. For describing the mechanisms of heat and moisture transfer in clothing with PCM and investigating the effect of the PCM distribution, a new dynamic <span class="hlt">model</span> of coupled heat and moisture transfer in <span class="hlt">porous</span> textiles with PCM was developed. The effect of water content on physical parameters of textiles and heat transfer with phase change in the PCM microcapsules were considered in the <span class="hlt">model</span>. Meanwhile, the numerical predictions were compared with experimental data, and good agreement was observed between the two, indicating that the <span class="hlt">model</span> was satisfactory. Also the effects of the PCM distribution on heat transfer in the textiles-PCM microcapsule composites were investigated by using the <span class="hlt">model</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24611543','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24611543"><span id="translatedtitle">In silico design of <span class="hlt">porous</span> polymer networks: high-throughput screening for methane storage <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martin, Richard L; Simon, Cory M; Smit, Berend; Haranczyk, Maciej</p> <p>2014-04-01</p> <p><span class="hlt">Porous</span> polymer networks (PPNs) are a class of advanced <span class="hlt">porous</span> <span class="hlt">materials</span> that combine the advantages of cheap and stable polymers with the high surface areas and tunable chemistry of metal-organic frameworks. They are of particular interest for gas separation or storage applications, for instance, as methane adsorbents for a vehicular natural gas tank or other portable applications. PPNs are self-assembled from distinct building units; here, we utilize commercially available chemical fragments and two experimentally known synthetic routes to design in silico a large database of synthetically realistic PPN <span class="hlt">materials</span>. All structures from our database of 18,000 <span class="hlt">materials</span> have been relaxed with semiempirical electronic structure methods and characterized with Grand-canonical Monte Carlo simulations for methane uptake and deliverable (working) capacity. A number of novel structure-property relationships that govern methane storage performance were identified. The relationships are translated into experimental guidelines to realize the ideal PPN structure. We found that cooperative methane-methane attractions were present in all of the best-performing <span class="hlt">materials</span>, highlighting the importance of guest interaction in the design of optimal <span class="hlt">materials</span> for methane storage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26257095','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26257095"><span id="translatedtitle">From spent Mg/Al layered double hydroxide to <span class="hlt">porous</span> carbon <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Laipan, Minwang; Zhu, Runliang; Chen, Qingze; Zhu, Jianxi; Xi, Yunfei; Ayoko, Godwin A; He, Hongping</p> <p>2015-12-30</p> <p>Adsorption has been considered as an efficient method for the treatment of dye effluents, but proper disposal of the spent adsorbents is still a challenge. This work attempts to provide a facile method to reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II (OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washed with acid to obtain <span class="hlt">porous</span> carbon <span class="hlt">materials</span>. Thermogravimetric analysis results suggested that the carbonization could be well achieved above 600°C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000°C, respectively. Scanning electron microscope showed that the obtained carbon <span class="hlt">materials</span> possessed a crooked flaky morphology. Nitrogen adsorption-desorption results showed that the carbon <span class="hlt">materials</span> had large BET surface area and pore volume, e.g., 1426 m(2)/g and 1.67 cm(3)/g for the sample carbonized at 800°C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon <span class="hlt">materials</span> had high efficiency in toluene removal. This work provided a facile approach for synthesizing <span class="hlt">porous</span> carbon <span class="hlt">materials</span> using spent Mg/Al-LDH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26257095','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26257095"><span id="translatedtitle">From spent Mg/Al layered double hydroxide to <span class="hlt">porous</span> carbon <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Laipan, Minwang; Zhu, Runliang; Chen, Qingze; Zhu, Jianxi; Xi, Yunfei; Ayoko, Godwin A; He, Hongping</p> <p>2015-12-30</p> <p>Adsorption has been considered as an efficient method for the treatment of dye effluents, but proper disposal of the spent adsorbents is still a challenge. This work attempts to provide a facile method to reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II (OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washed with acid to obtain <span class="hlt">porous</span> carbon <span class="hlt">materials</span>. Thermogravimetric analysis results suggested that the carbonization could be well achieved above 600°C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000°C, respectively. Scanning electron microscope showed that the obtained carbon <span class="hlt">materials</span> possessed a crooked flaky morphology. Nitrogen adsorption-desorption results showed that the carbon <span class="hlt">materials</span> had large BET surface area and pore volume, e.g., 1426 m(2)/g and 1.67 cm(3)/g for the sample carbonized at 800°C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon <span class="hlt">materials</span> had high efficiency in toluene removal. This work provided a facile approach for synthesizing <span class="hlt">porous</span> carbon <span class="hlt">materials</span> using spent Mg/Al-LDH. PMID:26257095</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25350718','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25350718"><span id="translatedtitle">Hierarchical ZnO-Ag-C composite <span class="hlt">porous</span> microspheres with superior electrochemical properties as anode <span class="hlt">materials</span> for lithium ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xie, Qingshui; Ma, Yating; Zeng, Deqian; Zhang, Xiaoqiang; Wang, Laisen; Yue, Guanghui; Peng, Dong-Liang</p> <p>2014-11-26</p> <p>Hierarchical ZnO-Ag-C composite <span class="hlt">porous</span> microspheres are successfully synthesized by calcination of the preproduced zinc-silver citrate <span class="hlt">porous</span> microspheres in argon. The carbon derives from the in situ carbonization of carboxylic acid groups in zinc-silver citrate during annealing treatment. The average particle size of ZnO-Ag-C composite <span class="hlt">porous</span> microspheres is approximate 1.5 μm. When adopted as the electrode <span class="hlt">materials</span> in lithium ion batteries, the obtained composite <span class="hlt">porous</span> microspheres display high specific capacity, excellent cyclability, and good rate capability. A discharge capacity as high as 729 mA h g(-1) can be retained after 200 cycles at 100 mA g(-1). The excellent electrochemical properties of ZnO-Ag-C are ascribed to its unique hierarchical <span class="hlt">porous</span> configuration as well as the modification of silver and carbon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27381910','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27381910"><span id="translatedtitle">A Simplified <span class="hlt">Model</span> of Moisture Transport in Hydrophilic <span class="hlt">Porous</span> Media With Applications to Pharmaceutical Tablets.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Klinzing, Gerard R; Zavaliangos, Antonios</p> <p>2016-08-01</p> <p>This work establishes a predictive <span class="hlt">model</span> that explicitly recognizes microstructural parameters in the description of the overall mass uptake and local gradients of moisture into tablets. <span class="hlt">Model</span> equations were formulated based on local tablet geometry to describe the transient uptake of moisture. An analytical solution to a simplified set of <span class="hlt">model</span> equations was solved to predict the overall mass uptake and moisture gradients with the tablets. The analytical solution takes into account individual diffusion mechanisms in different scales of porosity and diffusion into the solid phase. The time constant of mass uptake was found to be a function of several key <span class="hlt">material</span> properties, such as tablet relative density, pore tortuosity, and equilibrium moisture content of the <span class="hlt">material</span>. The predictions of the <span class="hlt">model</span> are in excellent agreement with experimental results for microcrystalline cellulose tablets without the need for parameter fitting. The <span class="hlt">model</span> presented provides a new method to analyze the transient uptake of moisture into hydrophilic <span class="hlt">materials</span> with the knowledge of only a few fundamental <span class="hlt">material</span> and microstructural parameters. In addition, the <span class="hlt">model</span> allows for quick and insightful predictions of moisture diffusion for a variety of practical applications including pharmaceutical tablets, <span class="hlt">porous</span> polymer systems, or cementitious <span class="hlt">materials</span>. PMID:27381910</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDD24005S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDD24005S"><span id="translatedtitle">Tear film dynamics: <span class="hlt">modeling</span> the glycocalyx as a <span class="hlt">porous</span> medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siddique, Javed; Mastroberardinob, , Antonio; Braun, Richard; Anderson, Daniel</p> <p>2015-11-01</p> <p>The human tear film is a complex fluid structure composed of multiple layers: an aqueous layer that comprises most of the film and an outermost thinner lipid layer coat a forest of large transmembrane mucins at the epithelial surface. The glycocalyx helps provide stability to the ocular surface by assisting the tear film to wet it. It is also permeable to water, but less so to ions. We formulate a thin film <span class="hlt">model</span> based on lubrication theory in order to understand the dynamics between the aqueous layer and the glycocalyx, which we treat as a rigid <span class="hlt">porous</span> medium. We present numerical solutions for the evolution of the tear film and discuss the roles played by the key parameters of the system. This work was supported by the Simons Foundation Grant No. 281839.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/751012','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/751012"><span id="translatedtitle">Ignition analysis of a <span class="hlt">porous</span> energetic <span class="hlt">material</span>. 2. Ignition at a closed heated end</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Alexander M. Telegentor; Stephen B. Margolis; Forman A. Williams</p> <p>1998-11-01</p> <p>A continuation of an ignition analysis for <span class="hlt">porous</span> energetic <span class="hlt">materials</span> subjected to a constant energy flux is presented. In the first part, the analysis was developed for the case of an open-end, semi-infinite <span class="hlt">material</span> such that gas flow, generated by thermal expansion, flowed out of the <span class="hlt">porous</span> solid, thereby removing energy from the system. In the present study, the case of a closed end is considered, and thus the thermally-induced gas flow is now directed into the solid. In these studies, an asymptotic perturbation analysis, based on the smallness of the gas-to-solid density ratio and the largeness of the activation energy, is utilized to describe the inert and transition stages leading to thermal runaway. In both cases it is found that the effects of porosity provide a leading-order reduction in the time to ignition relative to that for the nonporous problem, arising from the reduced amount of solid <span class="hlt">material</span> that must be heated and the difference in thermal conductivities of the solid and gaseous phases. A correction to the leading-order ignition-delay time, however, is provided by the convective flow of gas through the solid, and the sign of this correction is shown to depend on the direction of the gas flow. Thus, gas flowing out of an open-end solid was previously shown to give a positive correction to the leading-order time to ignition. Here, however, it is demonstrated that when the flow of gas is directed into the <span class="hlt">porous</span> solid, the relative transport effects associated with the gas flow serve to preheat the <span class="hlt">material</span>, resulting in a negative correction and hence a decrease in the ignition-delay time.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1684g0005S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1684g0005S"><span id="translatedtitle">Numerical implementation of mathematical <span class="hlt">model</span> of the dynamics of a <span class="hlt">porous</span> medium on supercomputers of cluster architecture</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadovskaya, O. V.; Sadovskii, V. M.</p> <p>2015-10-01</p> <p>The parallel computational algorithm for analysis of the processes of elastic-plastic deformation of a <span class="hlt">porous</span> medium under the action of external dynamic loads is developed. This algorithm is based on the mathematical <span class="hlt">model</span> taking into account threshold nature of change in the strength of a <span class="hlt">material</span> under the collapse of pores. The algorithm is implemented in Fortran by means of functions of the MPI library. The parallel program system has been tested on clusters in computations of the propagation of plane longitudinal shock waves of the compression and in computations of the expansion of a cylindrical cavity in an infinite <span class="hlt">porous</span> medium. The comparison of numerical results and exact solutions has shown their good qualitative and quantitative correspondence. Using the obtained algorithm, the process of propagation of elastic-plastic waves of the compression in a homogenous <span class="hlt">porous</span> medium, accompanied by the deformation of a skeleton and the collapse of pores, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.8795D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.8795D"><span id="translatedtitle">New hydrologic <span class="hlt">model</span> of fluid migration in deep <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dmitrievsky, A.; Balanyuk, I.</p> <p>2009-04-01</p> <p>The authors present a new hydrological <span class="hlt">model</span> of mantle processes that effect on formation of oil-and-gas bearing basins, fault tectonics and thermal convection. Any fluid migration is initially induced by lateral stresses in the crust and lithosphere which result from global geodynamic processes related to the mantle convection. The global processes are further transformed into regional movements in weakness zones. <span class="hlt">Model</span> of <span class="hlt">porous</span> media in deep fractured zones and idea of self-oscillation processes in mantle layers and fractured zones of the crust at different depths was used as the basis for developed concept. The content of these notions resides in the fact that there are conditions of dynamic balance in mantle layers originating as a result of combination and alternate actions of compaction and dilatance mechanisms. These mechanisms can be manifested in different combinations and under different conditions as well as can be complemented by other processes influencing on regime of fluid migration. They can act under condition of passive margin, ocean rift and ocean subduction zones as well as in consolidated platform and sheet. Self-oscillation regime, sub vertical direction of fluid flows, anomalously high layer pressure, and high level of anomalies of various geophysical fields are common for them. A certain class of fluid dynamic <span class="hlt">models</span> describing consolidation of sedimentary basins, free oscillation processes slow and quick (at the final stage) fluid dynamic processes of the evolution of a sedimentary basin in subduction zones is considered for the first time. The last <span class="hlt">model</span> of quick fluid dynamic processes reflects the process of formation of hydrocarbon deposits in the zones of collision of lithosphere plates. The results of numerical simulation and diagrams reflecting consecutive stages of the gas-fluid dynamic front propagation are assessed of the Pri-Caspian depression as the example. Calculations with this <span class="hlt">model</span> will simultaneously be carried out for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4730847','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4730847"><span id="translatedtitle">Bioinspired large-scale aligned <span class="hlt">porous</span> <span class="hlt">materials</span> assembled with dual temperature gradients</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bai, Hao; Chen, Yuan; Delattre, Benjamin; Tomsia, Antoni P.; Ritchie, Robert O.</p> <p>2015-01-01</p> <p>Natural <span class="hlt">materials</span>, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being <span class="hlt">porous</span> and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight <span class="hlt">materials</span>. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, <span class="hlt">porous</span>, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural <span class="hlt">materials</span>, in particular advanced <span class="hlt">materials</span> such as composites, where a higher level of control over the structure is required. PMID:26824062</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26824062','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26824062"><span id="translatedtitle">Bioinspired large-scale aligned <span class="hlt">porous</span> <span class="hlt">materials</span> assembled with dual temperature gradients.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bai, Hao; Chen, Yuan; Delattre, Benjamin; Tomsia, Antoni P; Ritchie, Robert O</p> <p>2015-12-01</p> <p>Natural <span class="hlt">materials</span>, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being <span class="hlt">porous</span> and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight <span class="hlt">materials</span>. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, <span class="hlt">porous</span>, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural <span class="hlt">materials</span>, in particular advanced <span class="hlt">materials</span> such as composites, where a higher level of control over the structure is required. PMID:26824062</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18481790','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18481790"><span id="translatedtitle">A novel nano-<span class="hlt">porous</span> alumina biomaterial with potential for loading with bioactive <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Walpole, Andrew R; Xia, Zhidao; Wilson, Crispian W; Triffitt, James T; Wilshaw, Peter R</p> <p>2009-07-01</p> <p>Nano-<span class="hlt">porous</span> alumina, with the potential for being loaded with bioactive <span class="hlt">materials</span>, has been proposed as a novel <span class="hlt">material</span> for coating implants. In this study, the shear strength of the interface between such nano-<span class="hlt">porous</span> anodic aluminium oxide (AAO) coatings and titanium substrates, their biocompatibility, and their potential for pore loading have been investigated. An interface shear strength in excess of 29 MPa was obtained which is comparable with that of conventional plasma sprayed hydroxyapatite implant coatings. The viability and differentiation of MG63 osteoblastic cells co-cultured on the coating was found to be broadly comparable to that of similar cells co-cultured on conventional bioinert implant <span class="hlt">materials</span> such as titanium and fully dense alumina. Extensive pore loading with silica nano-particles of different sizes and in different combinations was demonstrated throughout the thickness of AAO layers 1 microm and 60 microm thick. This work has demonstrated, that with suitable choice of pore filling <span class="hlt">materials</span>, this novel coating might simultaneously combat infection, encourage bone regeneration, and secure fixation of the implant to bone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27513218','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27513218"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">Materials</span> with Tunable Structure and Mechanical Properties via Templated Layer-by-Layer Assembly.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ziminska, Monika; Dunne, Nicholas; Hamilton, Andrew R</p> <p>2016-08-31</p> <p>The deposition of stiff and strong coatings onto <span class="hlt">porous</span> templates offers a novel strategy for fabricating macroscale <span class="hlt">materials</span> with controlled architectures at the micro- and nanoscale. Here, layer-by-layer assembly is utilized to fabricate nanocomposite-coated foams with highly customizable properties by depositing polymer-nanoclay coatings onto open-cell foam templates. The compressive mechanical behavior of these <span class="hlt">materials</span> evolves in a predictable manner that is qualitatively captured by scaling laws for the mechanical properties of cellular <span class="hlt">materials</span>. The observed and predicted properties span a remarkable range of density-stiffness space, extending from regions of very soft elastomer foams to very stiff, lightweight honeycomb and lattice <span class="hlt">materials</span>. PMID:27513218</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22420594','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22420594"><span id="translatedtitle">Infiltrating sulfur into a highly <span class="hlt">porous</span> carbon sphere as cathode <span class="hlt">material</span> for lithium–sulfur batteries</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhao, Xiaohui; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Cho, Kwon-Koo; Ahn, Jou-Hyeon</p> <p>2014-10-15</p> <p>Highlights: • A highly <span class="hlt">porous</span> carbon (HPC) with regular spherical morphology was synthesized. • Sulfur/HPC composites were prepared by melt–diffusion method. • Sulfur/HPC composites showed improved cyclablity and long-term cycle life. - Abstract: Sulfur composite <span class="hlt">material</span> with a highly <span class="hlt">porous</span> carbon sphere as the conducting container was prepared. The highly <span class="hlt">porous</span> carbon sphere was easily synthesized with resorcinol–formaldehyde precursor as the carbon source. The morphology of the carbon was observed with field emission scanning electron microscope and transmission electron microscope, which showed a well-defined spherical shape. Brunauer–Emmett–Teller analysis indicated that it possesses a high specific surface area of 1563 m{sup 2} g{sup −1} and a total pore volume of 2.66 cm{sup 3} g{sup −1} with a bimodal pore size distribution, which allow high sulfur loading and easy transportation of lithium ions. Sulfur carbon composites with varied sulfur contents were prepared by melt–diffusion method and lithium sulfur cells with the sulfur composites showed improved cyclablity and long-term cycle life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19285930','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19285930"><span id="translatedtitle"><span class="hlt">Porous</span> silicon as a potential electrode <span class="hlt">material</span> in a nerve repair setting: Tissue reactions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Johansson, Fredrik; Wallman, Lars; Danielsen, Nils; Schouenborg, Jens; Kanje, Martin</p> <p>2009-07-01</p> <p>We compared <span class="hlt">porous</span> silicon (pSi) with smooth Si as chip-implant surfaces in a nerve regeneration setting. Silicon chips can be used for recording neural activity and are potential nerve interface devices. A silicon chip with one smooth and one <span class="hlt">porous</span> side inserted into a tube was used to bridge a 5 mm defect in rat sciatic nerve. Six or 12 weeks later, new nerve structures surrounded by a perineurium-like capsule had formed on each side of the chip. The number of regenerated nerve fibers did not differ on either side of the chip as shown by immunostaining for neurofilaments. However, the capsule that had formed in contact with the chip was significantly thinner on the <span class="hlt">porous</span> side than on the smooth side. Cellular protrusions had formed on the pSi side and the regenerated nerve tissue was found to attach firmly to this surface, while the tissue was hardly attached to the smooth silicon surface. We conclude that a pSi surface, due to its large surface area, diminished inflammatory response and firm adhesion to the tissue, should be a good <span class="hlt">material</span> for the development of new implantable electronic nerve devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.5473N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.5473N"><span id="translatedtitle">Measurement and <span class="hlt">modeling</span> of engineered nanoparticle transport and aging dynamics in a reactive <span class="hlt">porous</span> medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naftaly, Aviv; Dror, Ishai; Berkowitz, Brian</p> <p>2016-07-01</p> <p>A continuous time random walk particle tracking (CTRW-PT) method was employed to <span class="hlt">model</span> flow cell experiments that measured transport of engineered nanoparticles (ENPs) in a reactive <span class="hlt">porous</span> medium. The experiments involved a water-saturated medium containing negatively charged, polyacrylamide beads, resembling many natural soils and aquifer <span class="hlt">materials</span>, and having the same refraction index as water. Negatively and positively charged ENPs were injected into a uniform flow field in a 3-D horizontal flow cell, and the spatial and temporal concentrations of the evolving ENP plumes were obtained via image analysis. As a benchmark, and to calibrate the <span class="hlt">model</span>, Congo red tracer was employed in 1-D column and 3-D flow cell experiments, containing the same beads. Negatively charged Au and Ag ENPs demonstrated migration patterns resembling those of the tracer but were slightly more dispersive; the transport was well represented by the CTRW-PT <span class="hlt">model</span>. In contrast, positively charged AgNPs displayed an unusual behavior: establishment of an initial plume of essentially immobilized ENPs, followed by development of a secondary, freely migrating plume. The mobile plume was found to contain ENPs that, with aging, exhibited aggregation and charge inversion, becoming negatively charged and mobile. In this case, the CTRW-PT <span class="hlt">model</span> was modified to include a probabilistic law for particle immobilization, to account for the decreasing tendency (over distance and time) of the positively charged AgNPs to attach to the <span class="hlt">porous</span> medium. The agreement between experimental results and <span class="hlt">modeling</span> suggests that the CTRW-PT framework can account for the non-Fickian and surface-charge-dependent transport and aging exhibited by ENPs in <span class="hlt">porous</span> media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JChPh.137d4118B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JChPh.137d4118B"><span id="translatedtitle">Free energy landscapes for the thermodynamic understanding of adsorption-induced deformations and structural transitions in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bousquet, D.; Coudert, F.-X.; Boutin, A.</p> <p>2012-07-01</p> <p>Soft <span class="hlt">porous</span> crystals are flexible metal-organic frameworks that respond to physical stimuli such as temperature, pressure, and gas adsorption by large changes in their structure and unit cell volume. While they have attracted a lot of interest, molecular simulation methods that directly couple adsorption and large structural deformations in an efficient manner are still lacking. We propose here a new Monte Carlo simulation method based on non-Boltzmann sampling in (guest loading, volume) space using the Wang-Landau algorithm, and show that it can be used to fully characterize the adsorption properties and the <span class="hlt">material</span>'s response to adsorption at thermodynamic equilibrium. We showcase this new method on a simple <span class="hlt">model</span> of the MIL-53 family of breathing <span class="hlt">materials</span>, demonstrating its potential and contrasting it with the pitfalls of direct, Boltzmann simulations. We furthermore propose an explanation for the hysteretic nature of adsorption in terms of free energy barriers between the two metastable host phases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Nanos...813507H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanos...813507H"><span id="translatedtitle">Strengthening of polymer ordered <span class="hlt">porous</span> <span class="hlt">materials</span> based on a layered nanocomposite internal structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heng, Liping; Guo, Xieyou; Guo, Tianqi; Wang, Bin; Jiang, Lei</p> <p>2016-07-01</p> <p>Ordered <span class="hlt">porous</span> polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered <span class="hlt">porous</span> polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on.Ordered <span class="hlt">porous</span> polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered <span class="hlt">porous</span> polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on. Electronic supplementary information (ESI) available: SEM image of hexagonal silicon pillar templates, AFM images of clay platelets on a silicon substrate, photographs of free-standing gels, X-ray diffraction profiles for dried <span class="hlt">materials</span>, FTIR and TGA of the samples, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20681430','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20681430"><span id="translatedtitle">Gas dispersion and immobile gas volume in solid and <span class="hlt">porous</span> particle biofilter <span class="hlt">materials</span> at low air flow velocities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sharma, Prabhakar; Poulsen, Tjalfe G</p> <p>2010-07-01</p> <p>Gas-phase dispersion in granular biofilter <span class="hlt">materials</span> with a wide range of particle sizes was investigated using atmospheric air and nitrogen as tracer gases. Two types of <span class="hlt">materials</span> were used: (1) light extended clay aggregates (LECA), consisting of highly <span class="hlt">porous</span> particles, and (2) gravel, consisting of solid particles. LECA is a commercial <span class="hlt">material</span> that is used for insulation, as a soil conditioner, and as a carrier <span class="hlt">material</span> in biofilters for air cleaning. These two <span class="hlt">materials</span> were selected to have approximately the same particle shape. Column gas transport experiments were conducted for both <span class="hlt">materials</span> using different mean particle diameters, different particle size ranges, and different gas flow velocities. Measured breakthrough curves were <span class="hlt">modeled</span> using the advection-dispersion equation modified for mass transfer between mobile and immobile gas phases. The results showed that gas dispersivity increased with increasing mean particle diameter for LECA but was independent of mean particle diameter for gravel. Gas dispersivity also increased with increasing particle size range for both media. Dispersivities in LECA were generally higher than for gravel. The mobile gas content in both <span class="hlt">materials</span> increased with increasing gas flow velocity but it did not show any strong dependency on mean particle diameter or particle size range. The relative fraction of mobile gas compared with total porosity was highest for gravel and lowest for LECA likely because of its high internal porosity. PMID:20681430</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20681430','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20681430"><span id="translatedtitle">Gas dispersion and immobile gas volume in solid and <span class="hlt">porous</span> particle biofilter <span class="hlt">materials</span> at low air flow velocities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sharma, Prabhakar; Poulsen, Tjalfe G</p> <p>2010-07-01</p> <p>Gas-phase dispersion in granular biofilter <span class="hlt">materials</span> with a wide range of particle sizes was investigated using atmospheric air and nitrogen as tracer gases. Two types of <span class="hlt">materials</span> were used: (1) light extended clay aggregates (LECA), consisting of highly <span class="hlt">porous</span> particles, and (2) gravel, consisting of solid particles. LECA is a commercial <span class="hlt">material</span> that is used for insulation, as a soil conditioner, and as a carrier <span class="hlt">material</span> in biofilters for air cleaning. These two <span class="hlt">materials</span> were selected to have approximately the same particle shape. Column gas transport experiments were conducted for both <span class="hlt">materials</span> using different mean particle diameters, different particle size ranges, and different gas flow velocities. Measured breakthrough curves were <span class="hlt">modeled</span> using the advection-dispersion equation modified for mass transfer between mobile and immobile gas phases. The results showed that gas dispersivity increased with increasing mean particle diameter for LECA but was independent of mean particle diameter for gravel. Gas dispersivity also increased with increasing particle size range for both media. Dispersivities in LECA were generally higher than for gravel. The mobile gas content in both <span class="hlt">materials</span> increased with increasing gas flow velocity but it did not show any strong dependency on mean particle diameter or particle size range. The relative fraction of mobile gas compared with total porosity was highest for gravel and lowest for LECA likely because of its high internal porosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMPSo..59.2323S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMPSo..59.2323S"><span id="translatedtitle">Dynamics of inelastic deformation of <span class="hlt">porous</span> rocks and formation of localized compaction zones studied by numerical <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stefanov, Yu P.; Chertov, M. A.; Aidagulov, G. R.; Myasnikov, A. V.</p> <p>2011-11-01</p> <p>The paper presents a numerical analysis of the inelastic deformation process in <span class="hlt">porous</span> rocks during different stages of its development and under non-equiaxial loading. Although numerous experimental studies have already investigated many aspects of plasticity in <span class="hlt">porous</span> rocks, numerical <span class="hlt">modeling</span> gives valuable insight into the dynamics of the process, since experimental methods cannot extract detailed information about the specimen structure during the test and have strong limitations on the number of tests. The numerical simulations have reproduced all different modes of deformation observed in experimental studies: dilatant and compactive shear, compaction without shear, uniform deformation, and deformation with localization. However, the main emphasis is on analysis of the compaction mode of plastic deformation and compaction localization, which is characteristic for many <span class="hlt">porous</span> rocks and can be observed in other <span class="hlt">porous</span> <span class="hlt">materials</span> as well. The study is largely inspired by applications in petroleum industry, i.e. surface subsidence and reservoir compaction caused by extraction of hydrocarbons and decrease of reservoir pressure. Special attention is given to the conditions, evolution, and characteristic patterns of compaction localization, which is often manifested in the form of compaction bands. Results of the study include stress-strain curves, spatial configurations and characteristics of localized zones, analysis of bifurcation of stress paths inside and outside localized zones and analysis of the influence of <span class="hlt">porous</span> rocks properties on compaction behavior. Among other results are examples of the interplay between compaction and shear modes of deformation. To <span class="hlt">model</span> the evolution of plastic deformation in <span class="hlt">porous</span> rocks, a new constitutive <span class="hlt">model</span> is formulated and implemented, with the emphasis on selection of adequate functions defining evolution of yield surface with deformation. The set of control parameters of the <span class="hlt">model</span> is kept as short as possible; the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994uamd.rept.....M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994uamd.rept.....M"><span id="translatedtitle">The use of acoustic methods to determine the parameters of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malecki, Ignacy; Ranachowski, Jerzy</p> <p></p> <p><span class="hlt">Porous</span> media are a subject of research in a variety of scientific disciplines, including physics, mechanics, electrical engineering, <span class="hlt">materials</span> science, and acoustics. The subject of this article is a comparison of the methods used in theoretical mechanics with standard acoustic methods. The authors start by examining the method of static averaging of the mechanical properties of <span class="hlt">porous</span> media. This method makes it possible to determine substitute static moduli of elasticity, which, however, does not meet the needs of acoustics. More suitable methods include the dynamic methods developed in the works of J. Lewandowski, among others. These methods are based on a motion equation in which the tensor of elasticity is assigned a complex value which accounts for the medium's dynamic properties and losses. The transition from a complex tensor of elasticity to the velocity and damping of an acoustic wave poses no particular problems. On the backdrop of the theory of <span class="hlt">porous</span> <span class="hlt">materials</span> used in mechanics, the authors present their own theory for the acoustic properties of these <span class="hlt">materials</span>. They call it the theory of 'compound obstacles', which initially examines the interference offered by a solitary inclusion in a homogeneous medium to the propagation of an acoustic wave. This is followed by the calculation of the interference caused by a group of inclusions using the concept of the density of obstacles. In turn, this leads to general formulas for acoustic wave velocity and damping as functions of obstacle density. The authors consider examples of a spherical inclusion in a liquid and a hollow spheroidal inclusion in a solid. The article also contains the results of experiments conducted to verify the 'compound obstacles' theory. The authors measured the velocity of an ultrasound wave in electrical engineering porcelain with varying degrees of porosity and in glycerine in which glass balls were suspended.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25314657','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25314657"><span id="translatedtitle">Cost-effective synthesis of amine-tethered <span class="hlt">porous</span> <span class="hlt">materials</span> for carbon capture.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lu, Weigang; Bosch, Mathieu; Yuan, Daqiang; Zhou, Hong-Cai</p> <p>2015-02-01</p> <p>A truly cost-effective strategy for the synthesis of amine-tethered <span class="hlt">porous</span> polymer networks (PPNs) has been developed. A network containing diethylenetriamine (PPN-125-DETA) exhibits a high working capacity comparable to current state-of-art technology (30 % monoethanolamine solutions), yet it requires only one third as much energy for regeneration. It has also been demonstrated to retain over 90 % capacity after 50 adsorption-desorption cycles of CO2 in a temperature-swing adsorption process. The results suggest that PPN-125-DETA is a very promising new <span class="hlt">material</span> for carbon capture from flue gas streams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1082201','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1082201"><span id="translatedtitle">High-throughput Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span> Using Graphics Processing Units</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kim, Jihan; Martin, Richard L.; Ruebel, Oliver; Haranczyk, Maciej; Smit, Berend</p> <p>2012-03-19</p> <p>We have developed a high-throughput graphics processing units (GPU) code that can characterize a large database of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span>. In our algorithm, the GPU is utilized to accelerate energy grid calculations where the grid values represent interactions (i.e., Lennard-Jones + Coulomb potentials) between gas molecules (i.e., CH$_{4}$ and CO$_{2}$) and <span class="hlt">material</span>'s framework atoms. Using a parallel flood fill CPU algorithm, inaccessible regions inside the framework structures are identified and blocked based on their energy profiles. Finally, we compute the Henry coefficients and heats of adsorption through statistical Widom insertion Monte Carlo moves in the domain restricted to the accessible space. The code offers significant speedup over a single core CPU code and allows us to characterize a set of <span class="hlt">porous</span> <span class="hlt">materials</span> at least an order of magnitude larger than ones considered in earlier studies. For structures selected from such a prescreening algorithm, full adsorption isotherms can be calculated by conducting multiple grand canonical Monte Carlo simulations concurrently within the GPU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26593662','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26593662"><span id="translatedtitle">High-Throughput Characterization of <span class="hlt">Porous</span> <span class="hlt">Materials</span> Using Graphics Processing Units.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Jihan; Martin, Richard L; Rübel, Oliver; Haranczyk, Maciej; Smit, Berend</p> <p>2012-05-01</p> <p>We have developed a high-throughput graphics processing unit (GPU) code that can characterize a large database of crystalline <span class="hlt">porous</span> <span class="hlt">materials</span>. In our algorithm, the GPU is utilized to accelerate energy grid calculations, where the grid values represent interactions (i.e., Lennard-Jones + Coulomb potentials) between gas molecules (i.e., CH4 and CO2) and <span class="hlt">materials</span>' framework atoms. Using a parallel flood fill central processing unit (CPU) algorithm, inaccessible regions inside the framework structures are identified and blocked, based on their energy profiles. Finally, we compute the Henry coefficients and heats of adsorption through statistical Widom insertion Monte Carlo moves in the domain restricted to the accessible space. The code offers significant speedup over a single core CPU code and allows us to characterize a set of <span class="hlt">porous</span> <span class="hlt">materials</span> at least an order of magnitude larger than those considered in earlier studies. For structures selected from such a prescreening algorithm, full adsorption isotherms can be calculated by conducting multiple Grand Canonical Monte Carlo (GCMC) simulations concurrently within the GPU.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22769051','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22769051"><span id="translatedtitle">Synthesis of nitrogen-doped <span class="hlt">porous</span> carbon nanofibers as an efficient electrode <span class="hlt">material</span> for supercapacitors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Li-Feng; Zhang, Xu-Dong; Liang, Hai-Wei; Kong, Mingguang; Guan, Qing-Fang; Chen, Ping; Wu, Zhen-Yu; Yu, Shu-Hong</p> <p>2012-08-28</p> <p>Supercapacitors (also known as ultracapacitors) are considered to be the most promising approach to meet the pressing requirements of energy storage. Supercapacitive electrode <span class="hlt">materials</span>, which are closely related to the high-efficiency storage of energy, have provoked more interest. Herein, we present a high-capacity supercapacitor <span class="hlt">material</span> based on the nitrogen-doped <span class="hlt">porous</span> carbon nanofibers synthesized by carbonization of macroscopic-scale carbonaceous nanofibers (CNFs) coated with polypyrrole (CNFs@polypyrrole) at an appropriate temperature. The composite nanofibers exhibit a reversible specific capacitance of 202.0 F g(-1) at the current density of 1.0 A g(-1) in 6.0 mol L(-1) aqueous KOH electrolyte, meanwhile maintaining a high-class capacitance retention capability and a maximum power density of 89.57 kW kg(-1). This kind of nitrogen-doped carbon nanofiber represents an alternative promising candidate for an efficient electrode <span class="hlt">material</span> for supercapacitors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1015419','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1015419"><span id="translatedtitle">Methods of using structures including catalytic <span class="hlt">materials</span> disposed within <span class="hlt">porous</span> zeolite <span class="hlt">materials</span> to synthesize hydrocarbons</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rollins, Harry W.; Petkovic, Lucia M.; Ginosar, Daniel M.</p> <p>2011-02-01</p> <p>Catalytic structures include a catalytic <span class="hlt">material</span> disposed within a zeolite <span class="hlt">material</span>. The catalytic <span class="hlt">material</span> may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite <span class="hlt">material</span> may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic <span class="hlt">material</span> may include copper and zinc oxide. The zeolite <span class="hlt">material</span> may include a first plurality of pores substantially defined by a crystal structure of the zeolite <span class="hlt">material</span> and a second plurality of pores dispersed throughout the zeolite <span class="hlt">material</span>. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite <span class="hlt">material</span> at least partially around a template structure, removing the template structure, and introducing a catalytic <span class="hlt">material</span> into the zeolite <span class="hlt">material</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B13A0450J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B13A0450J"><span id="translatedtitle">Rock Physics <span class="hlt">Models</span> of Biofilm Growth in <span class="hlt">Porous</span> Media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, P.; alhadhrami, F. M.; Atekwana, E. A.</p> <p>2013-12-01</p> <p>Recent studies suggest the potential to use acoustic techniques to image biofilm growth in <span class="hlt">porous</span> media. Nonetheless the interpretation of the seismic response to biofilm growth and development remains speculative because of the lack of quantitative petrophysical <span class="hlt">models</span> that can relate changes in biofilm saturation to changes in seismic attributes. Here, we report our efforts in developing quantitative rock physics <span class="hlt">models</span> to biofilm saturation with increasing and decreasing P-wave velocity (VP) and amplitudes recorded in the Davis et al. [2010] physical scale experiment. We adapted rock physics <span class="hlt">models</span> developed for <span class="hlt">modeling</span> gas hydrates in unconsolidated sediments. Two distinct growth <span class="hlt">models</span>, which appear to be a function of pore throat size, are needed to explain the experimental data. First, introduction of biofilm as an additional mineral grain in the sediment matrix (load-bearing mode) is needed to explain the increasing time-lapse VP. Second, introduction of biofilm as part of the pore fluid (pore-filling mode) is required to explain the decreasing time-lapse VP. To explain the time-lapse VP, up to 15% of the pore volume was required to be saturated with biofilm. The recorded seismic amplitudes, which can be expressed as a function of porosity, permeability and grain size, showed a monotonic time-lapse decay except on Day 3 at a few selected locations, where it increased. Since porosity changes are constrained by VP, amplitude increase could be <span class="hlt">modeled</span> by increasing hydraulic conductivity. Time lapse VP at locations with increasing amplitudes suggest that these locations have a load-bearing growth style. We conclude that permeability can increase by up to 10% at low (~2%) biofilm saturation in load-bearing growth style due to the development of channels within the biofilm structure. Developing a rock physics <span class="hlt">model</span> for the biofilm growth in general may help create a field guide for interpreting porosity and permeability changes in bioremediation, MEOR and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CompM..54.1129B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CompM..54.1129B"><span id="translatedtitle">Multi-physics computational grains (MPCGs) for direct numerical simulation (DNS) of piezoelectric composite/<span class="hlt">porous</span> <span class="hlt">materials</span> and structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bishay, Peter L.; Dong, Leiting; Atluri, Satya N.</p> <p>2014-11-01</p> <p>Conceptually simple and computationally most efficient polygonal computational grains with voids/inclusions are proposed for the direct numerical simulation of the micromechanics of piezoelectric composite/<span class="hlt">porous</span> <span class="hlt">materials</span> with non-symmetrical arrangement of voids/inclusions. These are named "Multi-Physics Computational Grains" (MPCGs) because each "mathematical grain" is geometrically similar to the irregular shapes of the physical grains of the <span class="hlt">material</span> in the micro-scale. So each MPCG element represents a grain of the matrix of the composite and can include a pore or an inclusion. MPCG is based on assuming independent displacements and electric-potentials in each cell. The trial solutions in each MPCG do not need to satisfy the governing differential equations, however, they are still complete, and can efficiently <span class="hlt">model</span> concentration of electric and mechanical fields. MPCG can be used to <span class="hlt">model</span> any generally anisotropic <span class="hlt">material</span> as well as nonlinear problems. The essential idea can also be easily applied to accurately solve other multi-physical problems, such as complex thermal-electro-magnetic-mechanical <span class="hlt">materials</span> <span class="hlt">modeling</span>. Several examples are presented to show the capabilities of the proposed MPCGs and their accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012EGUGA..1413856D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012EGUGA..1413856D&link_type=ABSTRACT"><span id="translatedtitle">Optimization and Use of 3D sintered <span class="hlt">porous</span> <span class="hlt">material</span> in medical field for mixing fibrin glue.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delmotte, Y.; Laroumanie, H.; Brossard, G.</p> <p>2012-04-01</p> <p>In medical field, Mixing of two or more chemical components (liquids and/or gases) is extremely important as improper mixing can affect the physico-chemical properties of the final product. At Baxter Healthcare Corporation, we are using a sintered <span class="hlt">porous</span> <span class="hlt">material</span> (PM) as a micro-mixer in medical device for mixing Fibrinogen and Thrombin in order to obtain a homogeneous polymerized Fibrin glue clot used in surgery. First trials were carried out with an interconnected PM from Porvair® (made of PE - porosity: 40% - permeability: 18Darcy). The injection rate is very low, usually about 10mL/min (Re number about 50) which keeps fluids in a laminar flow. Such a low flow rate does not favour mixing of fluids having gradient of viscosity if a mixer is not used. Promising results that were obtained lead the team to understand this ability to mix fluids which will be presented in the poster. Topology of <span class="hlt">porous</span> media (PM) which associates a solid phase with interconnected (or not) <span class="hlt">porous</span> structure is known and used in many commodity products. Researches on PM usually focus on flows inside this structure. By opposition to transport and filtration capacity, as well as mechanic and thermic properties, mixing is rarely associated with PM. However over the past few years, we shown that some type of PM have a real capacity to mix certain fluids. Poster will also describe the problematic of mixing complex biological fluids as fibrinogen and Thrombin. They indeed present a large viscosity difference (ratio about 120) limiting the diffusion and the interaction between the two solutions. As those products are expensive, we used Water (1cPo) and Glycerol 87% (120cPo) which are matching the viscosities of Thrombin and Fibrinogen. A parametric investigation of the "<span class="hlt">porous</span> micro-mixer" as well as a scale up investigation was carried out to examine the influence of both diffusion and advection to successful mix fluids of different viscosity. Experiments were implemented with Planar Laser</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.........3V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.........3V"><span id="translatedtitle">Mechanical behavior of concrete and related <span class="hlt">porous</span> <span class="hlt">materials</span> under partial saturation: The effective stress and the viscous softening due to movement of nanometer-scale pore fluid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vlahinic, Ivan</p> <p></p> <p>It has been said that <span class="hlt">porous</span> <span class="hlt">materials</span> are like music: the gaps are as important as the filled-in bits. In other words, in addition to the solid structure, pore characteristics such as size and morphology play a crucial role in defining the overall physical properties of the <span class="hlt">porous</span> <span class="hlt">materials</span>. This work goes a step further and examines the behaviors of some <span class="hlt">porous</span> media that arise when the pore network is occupied by two fluids, principally air and water, as a result of drying or wetting. Such a state gives rise to fluid capillarity which can generate significant negative fluid pressures. In the first part, a constitutive <span class="hlt">model</span> for drying of an elastic <span class="hlt">porous</span> medium is proposed and then extended to derive a novel expression for effective stress in partially saturated media. The <span class="hlt">model</span> is motivated by the fact that in a system that is saturated by two different fluids, two different pressure inherently act on the surfaces of the pore network. This causes a non-uniform strain field in the solid structure, something that is not explicitly accounted for in the classic formulations of this problem. We use some standard micromechanical homogenization techniques to estimate the extent of the 'non-uniformity' and on this basis, evaluate the validity of the classic Bishop effective stress expression for partially saturated <span class="hlt">materials</span>. In the second part, we examine a diverse class of <span class="hlt">porous</span> <span class="hlt">materials</span> which behave in an unexpected (and even counterintuitive) way under the internal moisture fluctuations. In particular, during wetting and drying alike, the solid viscosity of these <span class="hlt">materials</span> appears to soften, sometimes by an order of magnitude or more. Under load, this can lead to significantly increased rates of deformations. On account of the recent experimental and theoretical findings on the nature of water flow in nanometer-size hydrophillic spaces, we provide a physical explanation for the viscous softening and propose a constitutive law on this basis. To this end, it also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720010302','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720010302"><span id="translatedtitle">Experimental investigation of the flow, oxidation, cooling, and thermal-fatigue characteristics of a laminated <span class="hlt">porous</span> sheet <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hickel, R. O.; Warren, E. L.; Kaufman, A.</p> <p>1972-01-01</p> <p>The basic flow and oxidation characteristics of a laminated <span class="hlt">porous</span> <span class="hlt">material</span> (Lamilloy) are presented. The oxidation characteristics of Lamilloy are compared to a wireform-type <span class="hlt">porous</span> <span class="hlt">material</span> for the case when both <span class="hlt">materials</span> are made from Hastelloy-X alloy. The cooling performance of an air cooled vane made from Lamilloy, as determined from cascade tests made at gas temperatures ranging from 1388 to 1741 C (2350 to 3165 F) is also discussed, as well as of a cascade-type thermal fatigue test of the Lamilloy vane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060041352&hterms=Sodium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DSodium','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060041352&hterms=Sodium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DSodium"><span id="translatedtitle">A Quantitative <span class="hlt">Model</span> for the Exchange Current of <span class="hlt">Porous</span> Molybdenum Electrodes on Sodium Beta-Alumina in Sodium Vapor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Williams, R. M.; Ryan, M. A.; LeDuc, H.; Cortez, R. H.; Saipetch, C.; Shields, V.; Manatt, K.; Homer, M. L.</p> <p>1998-01-01</p> <p>This paper presents a <span class="hlt">model</span> of the exchange current developed for <span class="hlt">porous</span> molybdenum electrodes on sodium beta-alumina ceramics in low pressure sodium vapor, but which has general applicability to gas/<span class="hlt">porous</span> metal electrodes on solid electrolytes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1211220','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1211220"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">materials</span> with pre-designed single-molecule traps for CO2 selective adsorption</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li, JR; Yu, JM; Lu, WG; Sun, LB; Sculley, J; Balbuena, PB; Zhou, HC</p> <p>2013-02-26</p> <p>Despite tremendous efforts, precise control in the synthesis of <span class="hlt">porous</span> <span class="hlt">materials</span> with pre-designed pore properties for desired applications remains challenging. Newly emerged <span class="hlt">porous</span> metal-organic <span class="hlt">materials</span>, such as metal-organic polyhedra and metal-organic frameworks, are amenable to design and property tuning, enabling precise control of functionality by accurate design of structures at the molecular level. Here we propose and validate, both experimentally and computationally, a precisely designed cavity, termed a 'single-molecule trap', with the desired size and properties suitable for trapping target CO2 molecules. Such a single-molecule trap can strengthen CO2-host interactions without evoking chemical bonding, thus showing potential for CO2 capture. Molecular single-molecule traps in the form of metal-organic polyhedra are designed, synthesised and tested for selective adsorption of CO2 over N-2 and CH4, demonstrating the trapping effect. Building these pre-designed single-molecule traps into extended frameworks yields metal-organic frameworks with efficient mass transfer, whereas the CO2 selective adsorption nature of single-molecule traps is preserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPS...329..339Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPS...329..339Y"><span id="translatedtitle">Natural sisal fibers derived hierarchical <span class="hlt">porous</span> activated carbon as capacitive <span class="hlt">material</span> in lithium ion capacitor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Zhewei; Guo, Huajun; Li, Xinhai; Wang, Zhixing; Yan, Zhiliang; Wang, Yansen</p> <p>2016-10-01</p> <p>Lithium-ion capacitor (LIC) is a novel advanced electrochemical energy storage (EES) system bridging gap between lithium ion battery (LIB) and electrochemical capacitor (ECC). In this work, we report that sisal fiber activated carbon (SFAC) was synthesized by hydrothermal treatment followed by KOH activation and served as capacitive <span class="hlt">material</span> in LIC for the first time. Different particle structure, morphology, specific surface area and heteroatoms affected the electrochemical performance of as-prepared <span class="hlt">materials</span> and corresponding LICs. When the mass ratio of KOH to char precursor was 2, hierarchical <span class="hlt">porous</span> structured SFAC-2 was prepared and exhibited moderate specific capacitance (103 F g-1 at 0.1 A g-1), superior rate capability and cyclic stability (88% capacity retention after 5000 cycles at 1 A g-1). The corresponding assembled LIC (LIC-SC2) with optimal comprehensive electrochemical performance, displayed the energy density of 83 Wh kg-1, the power density of 5718 W kg-1 and superior cyclic stability (92% energy density retention after 1000 cycles at 0.5 A g-1). It is worthwhile that the source for activated carbon is a natural and renewable one and the synthesis method is eco-friendly, which facilitate that hierarchical <span class="hlt">porous</span> activated carbon has potential applications in the field of LIC and other energy storage systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22398914','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22398914"><span id="translatedtitle">Multi-contrast 3D X-ray imaging of <span class="hlt">porous</span> and composite <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sarapata, Adrian; Herzen, Julia; Ruiz-Yaniz, Maite; Zanette, Irene; Rack, Alexander; Pfeiffer, Franz</p> <p>2015-04-13</p> <p>Grating-based X-ray computed tomography allows for simultaneous and nondestructive determination of the full X-ray complex index of refraction and the scattering coefficient distribution inside an object in three dimensions. Its multi-contrast capabilities combined with a high resolution of a few micrometers make it a suitable tool for assessing multiple phases inside <span class="hlt">porous</span> and composite <span class="hlt">materials</span> such as concrete. Here, we present quantitative results of a proof-of-principle experiment performed on a concrete sample. Thanks to the complementarity of the contrast channels, more concrete phases could be distinguished than in conventional attenuation-based imaging. The phase-contrast reconstruction shows high contrast between the hardened cement paste and the aggregates and thus allows easy 3D segmentation. Thanks to the dark-field image, micro-cracks inside the coarse aggregates are visible. We believe that these results are extremely interesting in the field of <span class="hlt">porous</span> and composite <span class="hlt">materials</span> studies because of unique information provided by grating interferometry in a non-destructive way.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24016841','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24016841"><span id="translatedtitle"><span class="hlt">Porous</span> graphitic carbon nanosheets as a high-rate anode <span class="hlt">material</span> for lithium-ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Long; Wang, Zhiyuan; He, Chunnian; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; Li, Jiajun</p> <p>2013-10-01</p> <p>Two-dimensional (2D) <span class="hlt">porous</span> graphitic carbon nanosheets (PGC nanosheets) as a high-rate anode <span class="hlt">material</span> for lithium storage were synthesized by an easy, low-cost, green, and scalable strategy that involves the preparation of the PGC nanosheets with Fe and Fe3O4 nanoparticles embedded (indicated with (Fe&Fe3O4)@PGC nanosheets) using glucose as the carbon precursor, iron nitrate as the metal precursor, and a surface of sodium chloride as the template followed by the subsequent elimination of the Fe and Fe3O4 nanoparticles from the (Fe&Fe3O4)@PGC nanosheets by acid dissolution. The unique 2D integrative features and <span class="hlt">porous</span> graphitic characteristic of the carbon nanosheets with high porosity, high electronic conductivity, and outstanding mechanical flexibility and stability are very favorable for the fast and steady transfer of electrons and ions. As a consequence, a very high reversible capacity of up to 722 mAh/g at a current density of 100 mA/g after 100 cycles, a high rate capability (535, 380, 200, and 115 mAh/g at 1, 10, 20, and 30 C, respectively, 1 C = 372 mA/g), and a superior cycling performance at an ultrahigh rate (112 mAh/g at 30 C after 570 charge-discharge cycles) are achieved by using these nanosheets as a lithium-ion-battery anode <span class="hlt">material</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3896057','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3896057"><span id="translatedtitle">Multiscale <span class="hlt">modelling</span> of hydraulic conductivity in vuggy <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Daly, K. R.; Roose, T.</p> <p>2014-01-01</p> <p>Flow in both saturated and non-saturated vuggy <span class="hlt">porous</span> media, i.e. soil, is inherently multiscale. The complex microporous structure of the soil aggregates and the wider vugs provides a multitude of flow pathways and has received significant attention from the X-ray computed tomography (CT) community with a constant drive to image at higher resolution. Using multiscale homogenization, we derive averaged equations to study the effects of the microscale structure on the macroscopic flow. The averaged <span class="hlt">model</span> captures the underlying geometry through a series of cell problems and is verified through direct comparison to numerical simulations of the full structure. These methods offer significant reductions in computation time and allow us to perform three-dimensional calculations with complex geometries on a desktop PC. The results show that the surface roughness of the aggregate has a significantly greater effect on the flow than the microstructure within the aggregate. Hence, this is the region in which the resolution of X-ray CT for image-based <span class="hlt">modelling</span> has the greatest impact. PMID:24511248</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24483554','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24483554"><span id="translatedtitle">Fractal continuum <span class="hlt">model</span> for tracer transport in a <span class="hlt">porous</span> medium.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Herrera-Hernández, E C; Coronado, M; Hernández-Coronado, H</p> <p>2013-12-01</p> <p>A <span class="hlt">model</span> based on the fractal continuum approach is proposed to describe tracer transport in fractal <span class="hlt">porous</span> media. The original approach has been extended to treat tracer transport and to include systems with radial and uniform flow, which are cases of interest in geoscience. The <span class="hlt">models</span> involve advection due to the fluid motion in the fractal continuum and dispersion whose mathematical expression is taken from percolation theory. The resulting advective-dispersive equations are numerically solved for continuous and for pulse tracer injection. The tracer profile and the tracer breakthrough curve are evaluated and analyzed in terms of the fractal parameters. It has been found in this work that anomalous transport frequently appears, and a condition on the fractal parameter values to predict when sub- or superdiffusion might be expected has been obtained. The fingerprints of fractality on the tracer breakthrough curve in the explored parameter window consist of an early tracer breakthrough and long tail curves for the spherical and uniform flow cases, and symmetric short tailed curves for the radial flow case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JNuM..443..579S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JNuM..443..579S"><span id="translatedtitle">Multiphysics <span class="hlt">modeling</span> of <span class="hlt">porous</span> CRUD deposits in nuclear reactors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Short, M. P.; Hussey, D.; Kendrick, B. K.; Besmann, T. M.; Stanek, C. R.; Yip, S.</p> <p>2013-11-01</p> <p>The formation of <span class="hlt">porous</span> CRUD deposits on nuclear reactor fuel rods, a longstanding problem in the operation of pressurized water reactors (PWRs), is a significant challenge to science-based multiscale <span class="hlt">modeling</span> and simulation. While existing, published studies have focused on individual or loosely coupled processes, such as heat transfer, fluid flow, and compound dissolution/precipitation, none have addressed their coupled effects sufficiently to enable a comprehensive, scientific understanding of CRUD. Here we present the formulation and results of a <span class="hlt">model</span>, MAMBA-BDM, which begins to incorporate mechanistic details in describing CRUD in PWRs. CRUD is treated as a chemical deposition process in an environment of variable concentration, an arbitrary level of heating, and a complex fractal-based flow geometry. We present results on spatial distributions of temperature, pressure, velocity, and concentration that give insight into the interplay between these physical properties and geometrical parameters. We show the role of heat convection which has not been discussed previously. Furthermore, we suggest that the assumption of liquid saturation in the CRUD deserves scrutiny, as a result of our attempt to determine an effective CRUD thermal conductivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27078440','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27078440"><span id="translatedtitle">Record-breaking events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G</p> <p>2016-03-01</p> <p>An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of <span class="hlt">materials</span> and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of <span class="hlt">porous</span> <span class="hlt">materials</span>. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element <span class="hlt">model</span> of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k(*), which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........85T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........85T"><span id="translatedtitle">Supported Intrinsically <span class="hlt">Porous</span> Oligomers as Hybrid <span class="hlt">Materials</span> for Separations, Storage, and Sensing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Anthony Boone</p> <p></p> <p>Adsorption-desorption phenomena are often difficult to study at the molecular level because the surfaces on which they occur can be heterogeneous, giving a wide distribution of adsorption sites and associated energies. Considering that these phenomena underlie an incredibly wide variety of industrially important processes, a better understanding could aid in the development of more efficient methods. In this work, we describe an approach to designing <span class="hlt">materials</span> with well-defined adsorption sites by covalently attaching intrinsically <span class="hlt">porous</span> molecules to solid surfaces by a rigid multidentate linker. These cup-shaped molecules are intended to act as adsorption sites on the <span class="hlt">material</span>, whereas the rigid attachment to the solid support serves to prevent movement and conformational changes of the sites, leading to better understanding of adsorption phenomena. As a proof-of-concept application, <span class="hlt">materials</span> were used for adsorption of n-butanol biofuel and related compounds from dilute aqueous solution. The <span class="hlt">materials</span> were thermally and hydrolytically stable, and adsorption phenomena were reversible. Adsorption sites containing more hydrophobic molecular area led to stronger adsorption, suggesting that it is driven by weak van der Waals forces. Likewise, adsorption sites that were strongly polarized performed poorly, possibly reflecting a greater energy penalty of removing water molecules from the cavity. Upon placing a Lewis acidic metal at the bottom of the cavity, an enhancement was seen only with the most acidic metal, which may indicate weak guest coordination. Observing that hydrophobic interactions dominate adsorption on these <span class="hlt">materials</span>, efforts were made to develop hybrid <span class="hlt">materials</span> with large hydrophobic area for adsorption. Glaser coupling of diethynylbenzene was used to grow oligo(phenylene butadiynylene)s from the surface of silica, resulting in <span class="hlt">materials</span> that were more than 25% organic by weight. In addition to their potential use as adsorbents, these <span class="hlt">materials</span> may</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhDT........24N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhDT........24N"><span id="translatedtitle">Interaction of pressure and momentum driven flows with thin <span class="hlt">porous</span> media: Experiments and <span class="hlt">modeling</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naaktgeboren, Christian</p> <p></p> <p>Flow interaction with thin <span class="hlt">porous</span> media arise in a variety of natural and man-made settings. Examples include flow through thin grids in electronics cooling, and NOx emissions reduction by means of ammonia injection grids, pulsatile aquatic propulsion with complex trailing anatomy (e.g., jellyfish with tentacles) and microbursts from thunderstorm activity over dense vegetation, unsteady combustion in or near <span class="hlt">porous</span> <span class="hlt">materials</span>, pulsatile jet-drying of textiles, and pulsed jet agitation of clothing for trace contaminant sampling. Two types of interactions with thin <span class="hlt">porous</span> media are considered: (i) forced convection or pressure-driven flows, where fluid advection is maintained by external forces, and (ii) inertial or momentum-driven flows, in which fluid motion is generated but not maintained by external forces. Forced convection analysis through thin permeable media using a <span class="hlt">porous</span> continuum approach requires the knowledge of <span class="hlt">porous</span> medium permeability and form coefficients, K and C, respectively, which are defined by the Hazen-Dupuit-Darcy (HDD) equation. Their determination, however, requires the measurement of the pressure-drop per unit of <span class="hlt">porous</span> medium length. The pressure-drop caused by fluid entering and exiting the <span class="hlt">porous</span> medium, however, is not related to the <span class="hlt">porous</span> medium length. Hence, for situations in which the inlet and outlet pressure-drops are not negligible, e.g., for short <span class="hlt">porous</span> media, the definition of Kand C via the HDD equation becomes ambiguous. This aspect is investigated analytically and numerically using the flow through a restriction in circular pipe and parallel plates channels as preliminary <span class="hlt">models</span>. Results show that inlet and outlet pressure-drop effects become increasingly important when the inlet and outlet fluid surface fraction φ decreases and the Reynolds number Re increases for both laminar and turbulent flow regimes. A conservative estimate of the minimum <span class="hlt">porous</span> medium length beyond which the core pressure-drop predominates over the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10197006','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10197006"><span id="translatedtitle">Nonequilibrium multiphase mixture <span class="hlt">modeling</span> of energetic <span class="hlt">material</span> response</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baer, M.R.; Hertel, E.; Bell, R.</p> <p>1995-12-31</p> <p>To <span class="hlt">model</span> the shock-induced behavior of <span class="hlt">porous</span> or damaged energetic <span class="hlt">materials</span>, a nonequilibrium mixture theory has been developed and incorporated into the shock physics code, CTH. Foundation for this multiphase <span class="hlt">model</span> is based on a continuum mixture formulation given by Baer and Nunziato. In this nonequilibrium approach, multiple thermodynamic and mechanics fields are resolved including the effects of <span class="hlt">material</span> relative motion, rate-dependent compaction, drag and heat transfer interphase effects and multiple-step combustion. Benchmark calculations are presented which simulate low-velocity piston impact on a propellant <span class="hlt">porous</span> bed and experimentally-measured wave features are well replicated with this <span class="hlt">model</span>. This mixture <span class="hlt">model</span> introduces micromechanical <span class="hlt">models</span> for the initiation and growth of reactive multicomponent flow which are key features to describe shock initiation and self-accelerated deflagration-to-detonation combustion behavior. To complement one-dimensional simulation, two dimensional numerical simulations are presented which indicate wave curvature effects due to the loss of wall confinement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25179786','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25179786"><span id="translatedtitle">Breath Figures of Nanoscale Bricks: A Universal Method for Creating Hierarchic <span class="hlt">Porous</span> <span class="hlt">Materials</span> from Inorganic Nanoparticles Stabilized with Mussel-Inspired Copolymers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saito, Yuta; Shimomura, Masatsugu; Yabu, Hiroshi</p> <p>2014-09-01</p> <p>High-performance catalysts and photovoltaics are required for building an environmentally sustainable society. Because catalytic and photovoltaic reactions occur at the interfaces between reactants and surfaces, the chemical, physical, and structural properties of interfaces have been the focus of much research. To improve the performance of these <span class="hlt">materials</span> further, inorganic <span class="hlt">porous</span> <span class="hlt">materials</span> with hierarchic <span class="hlt">porous</span> architectures have been fabricated. The breath figure technique allows preparing <span class="hlt">porous</span> films by using water droplets as templates. In this study, a valuable preparation method for hierarchic <span class="hlt">porous</span> inorganic <span class="hlt">materials</span> is shown. Hierarchic <span class="hlt">porous</span> <span class="hlt">materials</span> are prepared from surface-coated inorganic nanoparticles with amphiphilic copolymers having catechol moieties followed by sintering. Micron-scale pores are prepared by using water droplets as templates, and nanoscale pores are formed between the nanoparticles. The fabrication method allows the preparation of hierarchic <span class="hlt">porous</span> films from inorganic nanoparticles of various shapes and <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MAR.V1256L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MAR.V1256L"><span id="translatedtitle">Superstructured Carbon Nanotube/<span class="hlt">Porous</span> Silicon Hybrid <span class="hlt">Materials</span> for Lithium-Ion Battery Anodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Jun-Ki; Kang, Shin-Hyun; Choi, Sung-Min</p> <p>2015-03-01</p> <p>High energy Li-ion batteries (LIBs) are in great demand for electronics, electric-vehicles, and grid-scale energy storage. To further increase the energy and power densities of LIBs, Si anodes have been intensively explored due to their high capacity, and high abundance compared with traditional carbon anodes. However, the poor cycle-life caused by large volume expansion during charge/discharge process has been an impediment to its applications. Recently, superstructured Si <span class="hlt">materials</span> were received attentions to solve above mentioned problem in excellent mechanical properties, large surface area, and fast Li and electron transportation aspects, but applying superstructures to anode is in early stage yet. Here, we synthesized superstructured carbon nanotubes (CNTs)/<span class="hlt">porous</span> Si hybrid <span class="hlt">materials</span> and its particular electrochemical properties will be presented. Department of Nuclear and Quantum Engineering</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1128993','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1128993"><span id="translatedtitle">Short time proton dynamics in bulk ice and in <span class="hlt">porous</span> anode solid oxide fuel cell <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Basoli, Francesco; Senesi, Roberto; Kolesnikov, Alexander I; Licoccia, Silvia</p> <p>2014-01-01</p> <p>Oxygen reduction and incorporation into solid electrolytes and the reverse reaction of oxygen evolution play a cru-cial role in Solid Oxide Fuel Cell (SOFC) applications. However a detailed un derstanding of the kinetics of the cor-responding reactions, i.e. on reaction mechanisms, rate limiting steps, reaction paths, electrocatalytic role of <span class="hlt">materials</span>, is still missing. These include a thorough characterization of the binding potentials experienced by protons in the lattice. We report results of Inelastic Neutron Scattering (INS) measurements of the vibrational state of the protons in Ni- YSZ highly <span class="hlt">porous</span> composites (75% to 90% ), a ceramic-metal <span class="hlt">material</span> showing a high electrical conductivity and ther mal stability, which is known to be most effectively used as anodes for solid ox ide fuel cells. The results are compared with INS and Deep Inelastic Neutron Scattering (DINS) experiments on the proton binding states in bulk ice.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24591265','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24591265"><span id="translatedtitle">Pumping through <span class="hlt">porous</span> hydrophobic/oleophilic <span class="hlt">materials</span>: an alternative technology for oil spill remediation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ge, Jin; Ye, Yin-Dong; Yao, Hong-Bin; Zhu, Xi; Wang, Xu; Wu, Liang; Wang, Jin-Long; Ding, Hang; Yong, Ni; He, Ling-Hui; Yu, Shu-Hong</p> <p>2014-04-01</p> <p>Recently, <span class="hlt">porous</span> hydrophobic/oleophilic <span class="hlt">materials</span> (PHOMs) have been shown to be the most promising candidates for cleaning up oil spills; however, due to their limited absorption capacity, a large quantity of PHOMs would be consumed in oil spill remediation, causing serious economic problems. In addition, the complicated and time-consuming process of oil recovery from these sorbents is also an obstacle to their practical application. To solve the above problems, we apply external pumping on PHOMs to realize the continuous collection of oil spills in situ from the water surface with high speed and efficiency. Based on this novel design, oil/water separation and oil collection can be simultaneously achieved in the remediation of oil spills, and the oil sorption capacity is no longer limited to the volume and weight of the sorption <span class="hlt">material</span>. This novel external pumping technique may bring PHOMs a step closer to practical application in oil spill remediation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3083698','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3083698"><span id="translatedtitle">Development of a Chitosan-Based Biofoam: Application to the Processing of a <span class="hlt">Porous</span> Ceramic <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mathias, Jean-Denis; Tessier-Doyen, Nicolas; Michaud, Philippe</p> <p>2011-01-01</p> <p>Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the <span class="hlt">material</span>. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m−1·K−1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic <span class="hlt">material</span> with open porosity from a slurry prepared with an organic solvent infiltrating the <span class="hlt">porous</span> network of the foam. PMID:21541051</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21541051','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21541051"><span id="translatedtitle">Development of a chitosan-based biofoam: application to the processing of a <span class="hlt">porous</span> ceramic <span class="hlt">material</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mathias, Jean-Denis; Tessier-Doyen, Nicolas; Michaud, Philippe</p> <p>2011-02-16</p> <p>Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the <span class="hlt">material</span>. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m(-1)·K(-1)), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic <span class="hlt">material</span> with open porosity from a slurry prepared with an organic solvent infiltrating the <span class="hlt">porous</span> network of the foam.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26996258','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26996258"><span id="translatedtitle">Production of nanotubes in delignified <span class="hlt">porous</span> cellulosic <span class="hlt">materials</span> after hydrolysis with cellulase.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koutinas, Αthanasios Α; Papafotopoulou-Patrinou, Evgenia; Gialleli, Angelika-Ioanna; Petsi, Theano; Bekatorou, Argyro; Kanellaki, Maria</p> <p>2016-08-01</p> <p>In this study, tubular cellulose (TC), a <span class="hlt">porous</span> cellulosic <span class="hlt">material</span> produced by delignification of sawdust, was treated with a Trichoderma reesei cellulase in order to increase the proportion of nano-tubes. The effect of enzyme concentration and treatment duration on surface characteristics was studied and the samples were analyzed with BET, SEM and XRD. Also, a composite <span class="hlt">material</span> of gelatinized starch and TC underwent enzymatic treatment in combination with amylase (320U) and cellulase (320U) enzymes. For TC, the optimum enzyme concentration (640U) led to significant increase of TC specific surface area and pore volume along with the reduction of pore diameter. It was also shown that the enzymatic treatment did not result to a significant change of cellulose crystallinity index. The produced nano-tubular cellulose shows potential for application to drug and chemical preservative delivery systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGE....12..210E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGE....12..210E"><span id="translatedtitle">Seismic attenuation in fractured <span class="hlt">porous</span> media: insights from a hybrid numerical and analytical <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ekanem, A. M.; Li, X. Y.; Chapman, M.; Main, I. G.</p> <p>2015-04-01</p> <p>Seismic attenuation in fluid-saturated <span class="hlt">porous</span> rocks can occur by geometric spreading, wave scattering or the internal dissipation of energy, most likely due to the squirt-flow mechanism. In principle, the pattern of seismic attenuation recorded on an array of sensors contains information about the medium, in terms of <span class="hlt">material</span> heterogeneity and anisotropy, as well as <span class="hlt">material</span> properties such as porosity, crack density, and pore-fluid composition and mobility. In practice, this inverse problem is challenging. Here we provide some insights into the effects of internal dissipation by analysing synthetic data produced by a hybrid numerical and analytical <span class="hlt">model</span> for seismic wave propagation in a fractured medium embedded within a layered geological structure. The <span class="hlt">model</span> is made up of one anisotropic and three isotropic horizontal layers. The anisotropic layer consists of a <span class="hlt">porous</span>, fluid-saturated <span class="hlt">material</span> containing vertically aligned inclusions representing a set of fractures. This combination allows squirt-flow to occur between the pores in the matrix and the <span class="hlt">model</span> fractures. Our results show that the fluid mobility and the associated relaxation time of the fluid-pressure gradient control the frequency range over which attenuation occurs. This induced attenuation increases with incidence angle and azimuth away from the fracture strike-direction. Azimuthal variations in the induced attenuation are elliptical allowing the fracture orientations to be obtained from the axes of the ellipse. These observations hold out the potential of using seismic attenuation as an additional diagnostic in the characterisation of rock formations for a variety of applications including hydrocarbon exploration and production, subsurface storage of CO2, and geothermal energy extraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27064740','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27064740"><span id="translatedtitle">Excellent cycling stability and superior rate capability of a graphene-amorphous FePO4 <span class="hlt">porous</span> nanowire hybrid as a cathode <span class="hlt">material</span> for sodium ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Gaoliang; Ding, Bing; Wang, Jie; Nie, Ping; Dou, Hui; Zhang, Xiaogang</p> <p>2016-04-28</p> <p>A <span class="hlt">porous</span> nanowire <span class="hlt">material</span> consisting of graphene-amorphous FePO4 was investigated as an advanced cathode <span class="hlt">material</span> for sodium ion batteries for large-scale applications. This hybrid cathode <span class="hlt">material</span> showed excellent cycling performance and superior rate capability, which were attributed to the <span class="hlt">porous</span> nanowire structure and the existence of graphene. PMID:27064740</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27064740','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27064740"><span id="translatedtitle">Excellent cycling stability and superior rate capability of a graphene-amorphous FePO4 <span class="hlt">porous</span> nanowire hybrid as a cathode <span class="hlt">material</span> for sodium ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Gaoliang; Ding, Bing; Wang, Jie; Nie, Ping; Dou, Hui; Zhang, Xiaogang</p> <p>2016-04-28</p> <p>A <span class="hlt">porous</span> nanowire <span class="hlt">material</span> consisting of graphene-amorphous FePO4 was investigated as an advanced cathode <span class="hlt">material</span> for sodium ion batteries for large-scale applications. This hybrid cathode <span class="hlt">material</span> showed excellent cycling performance and superior rate capability, which were attributed to the <span class="hlt">porous</span> nanowire structure and the existence of graphene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1048491','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1048491"><span id="translatedtitle">Computational <span class="hlt">modeling</span> of composite <span class="hlt">material</span> fires.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brown, Alexander L.; Erickson, Kenneth L.; Hubbard, Joshua Allen; Dodd, Amanda B.</p> <p>2010-10-01</p> <p>Composite <span class="hlt">materials</span> behave differently from conventional fuel sources and have the potential to smolder and burn for extended time periods. As the amount of composite <span class="hlt">materials</span> on modern aircraft continues to increase, understanding the response of composites in fire environments becomes increasingly important. An effort is ongoing to enhance the capability to simulate composite <span class="hlt">material</span> response in fires including the decomposition of the composite and the interaction with a fire. To adequately <span class="hlt">model</span> composite <span class="hlt">material</span> in a fire, two physical <span class="hlt">model</span> development tasks are necessary; first, the decomposition <span class="hlt">model</span> for the composite <span class="hlt">material</span> and second, the interaction with a fire. A <span class="hlt">porous</span> media approach for the decomposition <span class="hlt">model</span> including a time dependent formulation with the effects of heat, mass, species, and momentum transfer of the <span class="hlt">porous</span> solid and gas phase is being implemented in an engineering code, ARIA. ARIA is a Sandia National Laboratories multiphysics code including a range of capabilities such as incompressible Navier-Stokes equations, energy transport equations, species transport equations, non-Newtonian fluid rheology, linear elastic solid mechanics, and electro-statics. To simulate the fire, FUEGO, also a Sandia National Laboratories code, is coupled to ARIA. FUEGO represents the turbulent, buoyantly driven incompressible flow, heat transfer, mass transfer, and combustion. FUEGO and ARIA are uniquely able to solve this problem because they were designed using a common architecture (SIERRA) that enhances multiphysics coupling and both codes are capable of massively parallel calculations, enhancing performance. The decomposition reaction <span class="hlt">model</span> is developed from small scale experimental data including thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) in both nitrogen and air for a range of heating rates and from available data in the literature. The response of the composite <span class="hlt">material</span> subject to a radiant heat flux boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007TSE....15...39M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007TSE....15...39M"><span id="translatedtitle">Rapid Generation of Superheated Steam Using a Water-containing <span class="hlt">Porous</span> <span class="hlt">Material</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mori, Shoji; Okuyama, Kunito</p> <p></p> <p>Heat treatment by superheated steam has been utilized in several industrial fields including sterilization, desiccation, and cooking. In particular, cooking by superheated steam is receiving increased attention because it has advantages of reducing the salt and fat contents in foods as well as suppressing the oxidation of vitamin C and fat. In this application, quick startup and cut-off responses are required. Most electrically energized steam generators require a relatively long time to generate superheated steam due to the large heat capacities of the water in container and of the heater. Zhao and Liao (2002) introduced a novel process for rapid vaporization of subcooled liquid, in which a low-thermal-conductivity <span class="hlt">porous</span> wick containing water is heated by a downward-facing grooved heating block in contact with the upper surface of the wick structure. They showed that saturated steam is generated within approximately 30 seconds from room-temperature water at a heat flux 41.2 kW⁄m2. In order to quickly generate superheated steam of approximately 300°C, which is required for cooking, the heat capacity of the heater should be as small as possible and the imposed heat flux should be so high enough that the <span class="hlt">porous</span> wick is able to dry out in the vicinity of the contact with the heater and that the resulting heater temperature becomes much higher than the saturation temperature. The present paper proposes a simple structured generator to quickly produce superheated steam. Only a fine wire heater is contacted spirally on the inside wall in a hollow <span class="hlt">porous</span> <span class="hlt">material</span>. The start-up, cut-off responses and the rate of energy conversion for input power are investigated experimentally. Superheated steam of 300°C is produced in approximately 19 seconds from room-temperature water for an input power of 300 W. The maximum rate of energy conversion in the steady state is approximately 0.9.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24337222','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24337222"><span id="translatedtitle">Atmospheric methane removal by methane-oxidizing bacteria immobilized on <span class="hlt">porous</span> building <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ganendra, Giovanni; De Muynck, Willem; Ho, Adrian; Hoefman, Sven; De Vos, Paul; Boeckx, Pascal; Boon, Nico</p> <p>2014-04-01</p> <p>Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six <span class="hlt">porous</span> carrier <span class="hlt">materials</span> have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building <span class="hlt">materials</span> at high (~20 % (v/v)) and low (~100 ppmv) methane mixing ratios. Methylocystis parvus in autoclaved aerated concrete (AAC) exhibited the highest methane removal rate at high (28.5 ± 3.8 μg CH₄ g⁻¹ building <span class="hlt">material</span> h⁻¹) and low (1.7 ± 0.4 μg CH₄ g⁻¹ building <span class="hlt">material</span> h⁻¹) methane mixing ratio. Due to the higher volume of pores with diameter >5 μm compared to other <span class="hlt">materials</span> tested, AAC was able to adsorb more bacteria which might explain for the higher methane removal observed. The total methane and carbon dioxide-carbon in the headspace was decreased for 65.2 ± 10.9 % when M. parvus in Ytong was incubated for 100 h. This study showed that immobilized MOB on building <span class="hlt">materials</span> could be used to remove methane from the air and also act as carbon sink.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994army.rept.....G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994army.rept.....G"><span id="translatedtitle">Governing equations for multiphase heat and mass transfer in hygroscopic <span class="hlt">porous</span> media with applications to clothing <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gibson, Phillip</p> <p>1994-11-01</p> <p>Whitaker's theory of coupled heat and mass transfer through <span class="hlt">porous</span> media was modified to include hygroscopic <span class="hlt">porous</span> <span class="hlt">materials</span> which can absorb liquid into the solid matrix. The system of equations described in this report should make it possible to evaluate the time-dependent transport properties of hygroscopic and non-hygroscopic clothing <span class="hlt">materials</span> by including many important factors which are usually ignored in the analysis of heat and mass transfer through textile <span class="hlt">materials</span>. The set of equations allows for the unsteady capillary wicking of sweat through fabric structure, condensation and evaporation of sweat within various layers of the clothing system, forced gas phase convection through the <span class="hlt">porous</span> structure of a textile layer, and the swelling and shrinkage of fibers and yarns as they absorb/desorb liquid water and water vapor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22318047','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22318047"><span id="translatedtitle"><span class="hlt">Modeling</span> precursor diffusion and reaction of atomic layer deposition in <span class="hlt">porous</span> structures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Keuter, Thomas Menzler, Norbert Heribert; Mauer, Georg; Vondahlen, Frank; Vaßen, Robert; Buchkremer, Hans Peter</p> <p>2015-01-01</p> <p>Atomic layer deposition (ALD) is a technique for depositing thin films of <span class="hlt">materials</span> with a precise thickness control and uniformity using the self-limitation of the underlying reactions. Usually, it is difficult to predict the result of the ALD process for given external parameters, e.g., the precursor exposure time or the size of the precursor molecules. Therefore, a deeper insight into ALD by <span class="hlt">modeling</span> the process is needed to improve process control and to achieve more economical coatings. In this paper, a detailed, microscopic approach based on the <span class="hlt">model</span> developed by Yanguas-Gil and Elam is presented and additionally compared with the experiment. Precursor diffusion and second-order reaction kinetics are combined to identify the influence of the <span class="hlt">porous</span> substrate's microstructural parameters and the influence of precursor properties on the coating. The thickness of the deposited film is calculated for different depths inside the <span class="hlt">porous</span> structure in relation to the precursor exposure time, the precursor vapor pressure, and other parameters. Good agreement with experimental results was obtained for ALD zirconiumdioxide (ZrO{sub 2}) films using the precursors tetrakis(ethylmethylamido)zirconium and O{sub 2}. The derivation can be adjusted to describe other features of ALD processes, e.g., precursor and reactive site losses, different growth modes, pore size reduction, and surface diffusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DFDD29010B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DFDD29010B"><span id="translatedtitle">Oil drainage in <span class="hlt">model</span> <span class="hlt">porous</span> media by viscoelastic fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beaumont, Julien; Bodiguel, Hugues; Colin, Annie</p> <p>2012-11-01</p> <p>Crude oil recovery efficiency has been shown to depend directly on the capillary number (Ca). If the capillary phenomenon is well described for Newtonian fluids, the consequences of non linear rheology and viscoelasticity require more experimental work at the pore scale. In this work we take advantage of microfluidic to revisit this field. We carried out oil drainage experiments through a micromodel made up with photoresist resin. The wetting phase trapped is a <span class="hlt">model</span> oil. The invading phases used are aqueous solutions of high molecular weight hydrolyzed polyacrylamide (HPAM) and surfactant. Qualitatively, we observed a transition between a capillary fingering at low flow rates and a stable front at high flow rates for the drainage experiments with HPAM and surfactant solutions as it happened for drainage with Newtonian fluids. From movies of the filling of the device, we determine the local velocity of all menisci in the <span class="hlt">porous</span> media. Thus, we quantify the capillary fingering. Surprisingly, local velocities are not significantly different from those measured using water, whereas the HPAM solutions are much more viscous. With betaine solutions, we observed an emulsification of the oil clusters trapped during the invasion leading to a very high oil recovery after percolation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1256902-two-dimensional-model-analysis-contaminant-transport-fractured-porous-medium','SCIGOV-ESTSC'); return false;" href="http://www.osti.gov/scitech/biblio/1256902-two-dimensional-model-analysis-contaminant-transport-fractured-porous-medium"><span id="translatedtitle">A Two-Dimensional <span class="hlt">Model</span> for the Analysis of Contaminant Transport in a Fractured <span class="hlt">Porous</span> Medium.</span></a></p> <p><a target="_blank" href=""></a></p> <p></p> <p>1991-03-05</p> <p>CHAINT-MC is a two-dimensional finite element <span class="hlt">model</span> applicable to the transport of a dissolved radionuclide in a fractured <span class="hlt">porous</span> medium along with radioactive chain decay and subsequent transport of the dissolved daughters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChPhB..25i0202Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhB..25i0202Y"><span id="translatedtitle">Statistical second-order two-scale analysis and computation for heat conduction problem with radiation boundary condition in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Zhi-Qiang; Liu, Shi-Wei; Sun, Yi</p> <p>2016-09-01</p> <p>This paper discusses a statistical second-order two-scale (SSOTS) analysis and computation for a heat conduction problem with a radiation boundary condition in random <span class="hlt">porous</span> <span class="hlt">materials</span>. Firstly, the microscopic configuration for the structure with random distribution is briefly characterized. Secondly, the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell. Then, the statistical prediction algorithm based on the proposed two-scale <span class="hlt">model</span> is described in detail. Finally, some numerical experiments are proposed, which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of <span class="hlt">porous</span> <span class="hlt">materials</span> and demonstrating its significant applications in actual engineering computation. Project supported by the China Postdoctoral Science Foundation (Grant Nos. 2015M580256 and 2016T90276).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ChPhB..25i0202Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ChPhB..25i0202Y&link_type=ABSTRACT"><span id="translatedtitle">Statistical second-order two-scale analysis and computation for heat conduction problem with radiation boundary condition in <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Zhi-Qiang; Liu, Shi-Wei; Sun, Yi</p> <p>2016-09-01</p> <p>This paper discusses a statistical second-order two-scale (SSOTS) analysis and computation for a heat conduction problem with a radiation boundary condition in random <span class="hlt">porous</span> <span class="hlt">materials</span>. Firstly, the microscopic configuration for the structure with random distribution is briefly characterized. Secondly, the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell. Then, the statistical prediction algorithm based on the proposed two-scale <span class="hlt">model</span> is described in detail. Finally, some numerical experiments are proposed, which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of <span class="hlt">porous</span> <span class="hlt">materials</span> and demonstrating its significant applications in actual engineering computation. Project supported by the China Postdoctoral Science Foundation (Grant Nos. 2015M580256 and 2016T90276).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25740298','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25740298"><span id="translatedtitle">Monodisperse <span class="hlt">porous</span> silicon spheres as anode <span class="hlt">materials</span> for lithium ion batteries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S</p> <p>2015-03-05</p> <p>Highly monodisperse <span class="hlt">porous</span> silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g(-1). In particular, reversible Li storage capacities above 1500 mAh g(-1) were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing <span class="hlt">porous</span> Si-based LIB anode <span class="hlt">materials</span> by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1254..242B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1254..242B"><span id="translatedtitle">Test Method To Quantify The Wicking Properties Of <span class="hlt">Porous</span> Insulation <span class="hlt">Materials</span> Designed To Prevent Interstitial Condensation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Binder, Andrea; Zirkelbach, Daniel; Künzel, Hartwig</p> <p>2010-05-01</p> <p>Applying an interior insulation often is the only option for a thermal retrofit, especially when heritage buildings are concerned. In doing so, the original construction becomes colder in winter and interstitial condensation may occur. The common way to avoid harmful condensation beneath the interior insulation of the external wall is the installation of a vapor barrier. Since such a barrier works both ways, it may adversely affect the drying potential of the wall during the warmer seasons. One way to avoid the problems described is the installation of an interior insulation system without a vapor barrier to the inside. Here, the effect of capillary transport in <span class="hlt">porous</span> hydrophilic media is used to conduct condensing moisture away from the wall/insulation interface back to the surface in contact with the indoor air. Following an increasing demand, several water wicking insulation <span class="hlt">materials</span> (e.g. Calcium-silicate, Autoclave Aerated Concrete based mineral foam, hydrophilic Glass fiber, Cellulose fiber) have appeared on the market. In the past, different methods have been developed to measure and describe the liquid transport properties of hydrophilic <span class="hlt">porous</span> media. However, the evaluation of the moisture transport mechanisms and their efficiency in this special field of implementation is very complex because of the interacting vapor- and liquid moisture transfer processes. Therefore, there is no consensus yet on its determination and quantification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23534695','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23534695"><span id="translatedtitle">Electrohydrodynamic bubbling: an alternative route to fabricate <span class="hlt">porous</span> structures of silk fibroin based <span class="hlt">materials</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ekemen, Zeynep; Ahmad, Zeeshan; Stride, Eleanor; Kaplan, David; Edirisinghe, Mohan</p> <p>2013-05-13</p> <p>Conventional fabrication techniques and structures employed in the design of silk fibroin (SF) based <span class="hlt">porous</span> <span class="hlt">materials</span> provide only limited control over pore size and require several processing stages. In this study, it is shown that, by utilizing electrohydrodynamic bubbling, not only can new hollow spherical structures of SF be formed in a single step by means of bubbles, but the resulting bubbles can serve as pore generators when dehydrated. The bubble characteristics can be controlled through simple adjustments to the processing parameters. Bubbles with diameters in the range of 240-1000 μm were fabricated in controlled fashion. FT-IR characterization confirmed that the rate of air infused during processing enhanced β-sheet packing in SF at higher flow rates. Dynamic mechanical analysis also demonstrated a correlation between air flow rate and film tensile strength. Results indicate that electrohydrodynamically generated SF and their composite bubbles can be employed as new tools to generate <span class="hlt">porous</span> structures in a controlled manner with a range of potential applications in biocoatings and tissue engineering scaffolds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...5E8781W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...5E8781W"><span id="translatedtitle">Monodisperse <span class="hlt">Porous</span> Silicon Spheres as Anode <span class="hlt">Materials</span> for Lithium Ion Batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S.</p> <p>2015-03-01</p> <p>Highly monodisperse <span class="hlt">porous</span> silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g-1. In particular, reversible Li storage capacities above 1500 mAh g-1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing <span class="hlt">porous</span> Si-based LIB anode <span class="hlt">materials</span> by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4350083','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4350083"><span id="translatedtitle">Monodisperse <span class="hlt">Porous</span> Silicon Spheres as Anode <span class="hlt">Materials</span> for Lithium Ion Batteries</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S.</p> <p>2015-01-01</p> <p>Highly monodisperse <span class="hlt">porous</span> silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g−1. In particular, reversible Li storage capacities above 1500 mAh g−1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing <span class="hlt">porous</span> Si-based LIB anode <span class="hlt">materials</span> by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures. PMID:25740298</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25528691','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25528691"><span id="translatedtitle">A 3-D constitutive <span class="hlt">model</span> for pressure-dependent phase transformation of <span class="hlt">porous</span> shape memory alloys.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ashrafi, M J; Arghavani, J; Naghdabadi, R; Sohrabpour, S</p> <p>2015-02-01</p> <p><span class="hlt">Porous</span> shape memory alloys (SMAs) exhibit the interesting characteristics of <span class="hlt">porous</span> metals together with shape memory effect and pseudo-elasticity of SMAs that make them appropriate for biomedical applications. In this paper, a 3-D phenomenological constitutive <span class="hlt">model</span> for the pseudo-elastic behavior and shape memory effect of <span class="hlt">porous</span> SMAs is developed within the framework of irreversible thermodynamics. Comparing to micromechanical and computational <span class="hlt">models</span>, the proposed <span class="hlt">model</span> is computationally cost effective and predicts the behavior of <span class="hlt">porous</span> SMAs under proportional and non-proportional multiaxial loadings. Considering the pressure dependency of phase transformation in <span class="hlt">porous</span> SMAs, proper internal variables, free energy and limit functions are introduced. With the aim of numerical implementation, time discretization and solution algorithm for the proposed <span class="hlt">model</span> are also presented. Due to lack of enough experimental data on multiaxial loadings of <span class="hlt">porous</span> SMAs, we employ a computational simulation method (CSM) together with available experimental data to validate the proposed constitutive <span class="hlt">model</span>. The method is based on a 3-D finite element <span class="hlt">model</span> of a representative volume element (RVE) with random pores pattern. Good agreement between the numerical predictions of the <span class="hlt">model</span> and CSM results is observed for elastic and phase transformation behaviors in various thermomechanical loadings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........47Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........47Y"><span id="translatedtitle">Micro- and Nano- <span class="hlt">Porous</span> Adsorptive <span class="hlt">Materials</span> for Removal of Contaminants from Water at Point-of-Use</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yakub, Ismaiel</p> <p></p> <p>Water is food, a basic human need and a fundamental human right, yet hundreds of millions of people around the world do not have access to clean drinking water. As a result, about 5000 people die each day from preventable water borne diseases. This dissertation presents the results of experimental and theoretical studies on three different types of <span class="hlt">porous</span> <span class="hlt">materials</span> that were developed for the removal of contaminants from water at point of use (household level). First, three compositionally distinct <span class="hlt">porous</span> ceramic water filters (CWFs) were made from a mixture of redart clay and sieved woodchips and processed into frustum shape. The filters were tested for their flow characteristics and bacteria filtration efficiencies. Since, the CWFs are made from brittle <span class="hlt">materials</span>, and may fail during processing, transportation and usage, the mechanical and physical properties of the <span class="hlt">porous</span> clays were characterized, and used in <span class="hlt">modeling</span> designed to provide new insights for the design of filter geometries. The mechanical/physical properties that were characterized include: compressive strength, flexural strength, facture toughness and resistance curve behavior, keeping in mind the anisotropic nature of the filter structure. The measured flow characteristics and mechanical/physical properties were then related to the underlying porosity and characteristic pore size. In an effort to quantify the adhesive interactions associated with filtration phenomena, atomic force microscopy (AFM) was used to measure the adhesion between bi-<span class="hlt">material</span> pairs that are relevant to point-of-use ceramic water filters. The force microscopy measurements of pull-off force and adhesion energy were used to rank the adhesive interactions. Similarly, the adsorption of fluoride to hydroxyapatite-doped redart clay was studied using composites of redart clay and hydroxyapatite (C-HA). The removal of fluoride from water was explored by carrying out adsorption experiments on C-HA adsorbents with different ratios of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1213488','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1213488"><span id="translatedtitle"><span class="hlt">Materials</span> Analysis and <span class="hlt">Modeling</span> of Underfill <span class="hlt">Materials</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wyatt, Nicholas B; Chambers, Robert S.</p> <p>2015-08-01</p> <p>The thermal-mechanical properties of three potential underfill candidate <span class="hlt">materials</span> for PBGA applications are characterized and reported. Two of the <span class="hlt">materials</span> are a formulations developed at Sandia for underfill applications while the third is a commercial product that utilizes a snap-cure chemistry to drastically reduce cure time. Viscoelastic <span class="hlt">models</span> were calibrated and fit using the property data collected for one of the Sandia formulated <span class="hlt">materials</span>. Along with the thermal-mechanical analyses performed, a series of simple bi-<span class="hlt">material</span> strip tests were conducted to comparatively analyze the relative effects of cure and thermal shrinkage amongst the <span class="hlt">materials</span> under consideration. Finally, current knowledge gaps as well as questions arising from the present study are identified and a path forward presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27250142','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27250142"><span id="translatedtitle">Asymptotic limits of some <span class="hlt">models</span> for sound propagation in <span class="hlt">porous</span> media and the assignment of the pore characteristic lengths.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Horoshenkov, Kirill V; Groby, Jean-Philippe; Dazel, Olivier</p> <p>2016-05-01</p> <p><span class="hlt">Modeling</span> of sound propagation in <span class="hlt">porous</span> media requires the knowledge of several intrinsic <span class="hlt">material</span> parameters, some of which are difficult or impossible to measure directly, particularly in the case of a <span class="hlt">porous</span> medium which is composed of pores with a wide range of scales and random interconnections. Four particular parameters which are rarely measured non-acoustically, but used extensively in a number of acoustical <span class="hlt">models</span>, are the viscous and thermal characteristic lengths, thermal permeability, and Pride parameter. The main purpose of this work is to show how these parameters relate to the pore size distribution which is a routine characteristic measured non-acoustically. This is achieved through the analysis of the asymptotic behavior of four analytical <span class="hlt">models</span> which have been developed previously to predict the dynamic density and/or compressibility of the equivalent fluid in a <span class="hlt">porous</span> medium. In this work the <span class="hlt">models</span> proposed by Johnson, Koplik, and Dashn [J. Fluid Mech. 176, 379-402 (1987)], Champoux and Allard [J. Appl. Phys. 70(4), 1975-1979 (1991)], Pride, Morgan, and Gangi [Phys. Rev. B 47, 4964-4978 (1993)], and Horoshenkov, Attenborough, and Chandler-Wilde [J. Acoust. Soc. Am. 104, 1198-1209 (1998)] are compared. The findings are then used to compare the behavior of the complex dynamic density and compressibility of the fluid in a <span class="hlt">material</span> pore with uniform and variable cross-sections. PMID:27250142</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26395819','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26395819"><span id="translatedtitle">A colloidoscope of colloid-based <span class="hlt">porous</span> <span class="hlt">materials</span> and their uses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Phillips, Katherine R; England, Grant T; Sunny, Steffi; Shirman, Elijah; Shirman, Tanya; Vogel, Nicolas; Aizenberg, Joanna</p> <p>2016-01-21</p> <p>Nature evolved a variety of hierarchical structures that produce sophisticated functions. Inspired by these natural <span class="hlt">materials</span>, colloidal self-assembly provides a convenient way to produce structures from simple building blocks with a variety of complex functions beyond those found in nature. In particular, colloid-based <span class="hlt">porous</span> <span class="hlt">materials</span> (CBPM) can be made from a wide variety of <span class="hlt">materials</span>. The internal structure of CBPM also has several key attributes, namely porosity on a sub-micrometer length scale, interconnectivity of these pores, and a controllable degree of order. The combination of structure and composition allow CBPM to attain properties important for modern applications such as photonic inks, colorimetric sensors, self-cleaning surfaces, water purification systems, or batteries. This review summarizes recent developments in the field of CBPM, including principles for their design, fabrication, and applications, with a particular focus on structural features and <span class="hlt">materials</span>' properties that enable these applications. We begin with a short introduction to the wide variety of patterns that can be generated by colloidal self-assembly and templating processes. We then discuss different applications of such structures, focusing on optics, wetting, sensing, catalysis, and electrodes. Different fields of applications require different properties, yet the modularity of the assembly process of CBPM provides a high degree of tunability and tailorability in composition and structure. We examine the significance of properties such as structure, composition, and degree of order on the <span class="hlt">materials</span>' functions and use, as well as trends in and future directions for the development of CBPM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26034014','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26034014"><span id="translatedtitle">Accelerated tissue integration into <span class="hlt">porous</span> <span class="hlt">materials</span> by immobilizing basic fibroblast growth factor using a biologically safe three-step reaction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kakinoki, Sachiro; Sakai, Yusuke; Fujisato, Toshia; Yamaoka, Tetsuji</p> <p>2015-12-01</p> <p>Soft tissue integration into a <span class="hlt">porous</span> structure is important to prevent bacterial infection of percutaneous devices and improve tissue regeneration using <span class="hlt">porous</span> scaffolds. Here, basic fibroblast growth factor (bFGF) was immobilized on <span class="hlt">porous</span> polymer <span class="hlt">materials</span> using a mild and biologically safe three-step reaction: (1) modification with a novel surface-modification peptide (penta-lysine-mussel adhesive sequence, which reacts with various matrices), (2) electrostatic binding of heparin with introduced penta-lysine, and (3) biologically specific binding of bFGF to heparin. <span class="hlt">Porous</span> polyethylene specimens (PPSs) (D = 6.0 mm, H = 2.0 mm) with a good size for tissue integration were selected as a base <span class="hlt">material</span>, immobilized with bFGF, and subcutaneously implanted into mice. Half of the unmodified PPSs extruded out of the body on day 112 postimplantation; however, the three-step reaction completely prevented sample rejection. Tissue integration was greatly accelerated by immobilizing bFGF. Direct physical coating of bFGF on PPS resulted in greater immobilization but lesser tissue integration than that after the three-step bFGF immobilization, indicating that heparin binds and enhances bFGF efficacy. This three-step bFGF immobilization reaction will be applicable to various polymeric, metallic, and ceramic <span class="hlt">materials</span> and is a simple strategy to integrate tissue on <span class="hlt">porous</span> medical devices or scaffolds for tissue regeneration. PMID:26034014</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014Nanot..25p5402X&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014Nanot..25p5402X&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Porous</span>-structured Cu2O/TiO2 nanojunction <span class="hlt">material</span> toward efficient CO2 photoreduction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Hua; Ouyang, Shuxin; Liu, Lequan; Wang, Defa; Kako, Tetsuya; Ye, Jinhua</p> <p>2014-04-01</p> <p><span class="hlt">Porous</span>-structured Cu2O/TiO2 nanojunction <span class="hlt">material</span> is successfully fabricated by a facile method via loading Cu2O nanoparticles on the network of a <span class="hlt">porous</span> TiO2 substrate. The developed Cu2O/TiO2 nanojunction <span class="hlt">material</span> has a size of several nanometers, in which the p-type Cu2O and n-type TiO2 nanoparticles are closely contacted with each other. The well designed nanojunction structure is beneficial for the charge separation in the photocatalytic reaction. Meanwhile, the <span class="hlt">porous</span> structure of the Cu2O/TiO2 nanojunction can facilitate the CO2 adsorption and offer more reaction active sites. Most importantly, the gas-phase CO2 photoreduction tests reveal that our developed <span class="hlt">porous</span>-structured Cu2O/TiO2 nanojunction <span class="hlt">material</span> exhibits marked photocatalytic activity in the CH4 evolution, about 12, 9, and 7.5 times higher than the pure TiO2, Pt-TiO2, and commercial Degussa P25 TiO2 powders, respectively. The greatly enhanced activity can be attributed to the well designed nanojunction structure combined with the <span class="hlt">porous</span> structure, which can simultaneously enhance the charge separation efficiency and facilitate the CO2 adsorption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24411347','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24411347"><span id="translatedtitle">Effect of sintering conditions on the microstructural and mechanical characteristics of <span class="hlt">porous</span> magnesium <span class="hlt">materials</span> prepared by powder metallurgy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Čapek, Jaroslav; Vojtěch, Dalibor</p> <p>2014-02-01</p> <p>There has recently been an increased demand for <span class="hlt">porous</span> magnesium <span class="hlt">materials</span> in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such <span class="hlt">materials</span>. Many works have dealt with the preparation of <span class="hlt">porous</span> magnesium; however, the effect of sintering conditions on <span class="hlt">material</span> properties has rarely been investigated. In this work, we investigated <span class="hlt">porous</span> magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of <span class="hlt">porous</span> magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of <span class="hlt">porous</span> magnesium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26034014','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26034014"><span id="translatedtitle">Accelerated tissue integration into <span class="hlt">porous</span> <span class="hlt">materials</span> by immobilizing basic fibroblast growth factor using a biologically safe three-step reaction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kakinoki, Sachiro; Sakai, Yusuke; Fujisato, Toshia; Yamaoka, Tetsuji</p> <p>2015-12-01</p> <p>Soft tissue integration into a <span class="hlt">porous</span> structure is important to prevent bacterial infection of percutaneous devices and improve tissue regeneration using <span class="hlt">porous</span> scaffolds. Here, basic fibroblast growth factor (bFGF) was immobilized on <span class="hlt">porous</span> polymer <span class="hlt">materials</span> using a mild and biologically safe three-step reaction: (1) modification with a novel surface-modification peptide (penta-lysine-mussel adhesive sequence, which reacts with various matrices), (2) electrostatic binding of heparin with introduced penta-lysine, and (3) biologically specific binding of bFGF to heparin. <span class="hlt">Porous</span> polyethylene specimens (PPSs) (D = 6.0 mm, H = 2.0 mm) with a good size for tissue integration were selected as a base <span class="hlt">material</span>, immobilized with bFGF, and subcutaneously implanted into mice. Half of the unmodified PPSs extruded out of the body on day 112 postimplantation; however, the three-step reaction completely prevented sample rejection. Tissue integration was greatly accelerated by immobilizing bFGF. Direct physical coating of bFGF on PPS resulted in greater immobilization but lesser tissue integration than that after the three-step bFGF immobilization, indicating that heparin binds and enhances bFGF efficacy. This three-step bFGF immobilization reaction will be applicable to various polymeric, metallic, and ceramic <span class="hlt">materials</span> and is a simple strategy to integrate tissue on <span class="hlt">porous</span> medical devices or scaffolds for tissue regeneration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........85Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........85Z"><span id="translatedtitle">Investigation on thermo-mechanical instability of <span class="hlt">porous</span> low dielectric constant <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zin, Emil Hyunbae</p> <p></p> <p>This study investigates the structural stability of <span class="hlt">porous</span> low dielectric constant <span class="hlt">materials</span> (PLK) under thermal and mechanical load and the influence of contributing factors including porosity as intrinsic factor and plasma damage and moisture absorption as extrinsic factors on thermo-mechanical instability of PLK in advanced Cu/PLK interconnects. For this purpose, a ball indentation creep test technique was developed to examine the thermal and mechanical instability of PLK at relevant load and temperature conditions in the interconnect structure. Our exploration with the ball indentation creep test found that PLK films plastically deforms with time, indicating that viscoplastic deformation does occur under relevant conditions of PLK processing. On the basis of the results that the increase of the indentation depth with time shows more noticeable difference in PLK films with higher porosity, plasma exposure, and moisture absorption, it is our belief that PLK stability is greatly affected by porosity, plasma damage and moisture. Viscous flow was found to be mechanism for the viscoplastic deformation at the temperature and load of real PLK integration processing. This finding was obtained from the facts that the kinetics of the indentation creep fit very well with the viscous flow <span class="hlt">model</span> and the extracted stress exponent is close to unity. Based on the results of temperature dependence in all PLK films, the activation energy(~1.5eV) of the viscosity back calculated from the experimental value of the kinetics was found to be much small than that of a pure glass (> 4eV). This suggests that the viscous flow of PLK is controlled by chemical reaction happening in PLK matrix. The FT-IR measurement for the examination of chemical bond reconfiguration shows that the intensity of Si-OH bonds increases with the flow while that of Si-O-Si, -CHX and Si-CH 3 bonds decreases, indicating that chemical reactions are involved in the deformation process. From these findings, it is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1718j0002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1718j0002D"><span id="translatedtitle"><span class="hlt">Porous</span> carbon <span class="hlt">materials</span> synthesized using IRMOF-3 and furfuryl alcohol as precursor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deka, Pemta Tia; Ediati, Ratna</p> <p>2016-03-01</p> <p>IRMOF-3 crystals have been synthesized using solvothermal method by adding zinc nitrate hexahydrate with 2-amino-1,4-benzenedicarboxylic acid in N'N-dimethylformamide (DMF) at 100°C for 24 (note as IR-24) and 72 h (note as IR-72). The obtained crystals were characterized using X-ray Diffraction (XRD), SEM (Scanning Electron Microscopy) and Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), FTIR and Isothermal adsorption-desorption N2. The diffractogram solids synthesized show characteristic peak at 2θ 6.8, 9.6 and 13.7°. SEM micrograph show cubic shape of IRMOF-3 crystal. Based on FTIR characterization, IRMOF-3 appear at wavelength (1691,46; 1425,3; 1238,21; 1319,22 dan 3504,42)cm-1. The Isotherm of crystal IRMOF-3 at heating time 24 h and 72 h are type IV. The surface area of IR-24 and IR-72 are respectively 24,758 m2/g and 29,139 m2/g with its dominant mesopores. Carbonaceous <span class="hlt">materials</span> has been successfully synthesized using IR-24, IR-72 and furfuryl alcohol (FA) as second carbon precursor with variation of carbonation temperature 550, 700 and 850°C. The XRD result from both carbonaceous <span class="hlt">materials</span> show formation of amorphous carbon and caharacteristic peak of ZnO oxide. Micrograph SEM show that carbonaceous <span class="hlt">materials</span> have cubic shape as IRMOF-3 and SEM-EDX result indicate Zn and nitrogen content of these <span class="hlt">materials</span> has decrease until temperature 850°C. <span class="hlt">Porous</span> carbon using IR-24 and FA (notes as C-24) has increased surface area with higher carbonation temperature. The highest surface area is 1495,023 m2/g. Total pore volume and pore size of C-24 from low to high temperature respectively as (0,338; 0,539 and 1,598) cc/g; (0,107; 0,152 and 0,610) cc/g. <span class="hlt">Porous</span> carbon using IR-72 and FA (notes as C-72) has smaller surface area than C-24 but its also increased during higher carbonation heating. The highest surface area is 1029,668 m2/g.The total pore volume and pore size of these carbon <span class="hlt">materials</span> from low to high temperature respectively as (0,390; 0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812444J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812444J"><span id="translatedtitle">A visco-poroelastic damage <span class="hlt">model</span> for <span class="hlt">modelling</span> compaction and brittle failure of <span class="hlt">porous</span> rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jacquey, Antoine B.; Cacace, Mauro; Blöcher, Guido; Milsch, Harald; Scheck-Wenderoth, Magdalena</p> <p>2016-04-01</p> <p>Hydraulic stimulation of geothermal wells is often used to increase heat extraction from deep geothermal reservoirs. Initiation and propagation of fractures due to pore pressure build-up increase the effective permeability of the <span class="hlt">porous</span> medium. Understanding the processes controlling the initiation of fractures, the evolution of their geometries and the hydro-mechanical impact on transport properties of the <span class="hlt">porous</span> medium is therefore of great interest for geothermal energy production. In this contribution, we will present a thermodynamically consistent visco-poroelastic damage <span class="hlt">model</span> which can deal with the multi-scale and multi-physics nature of the physical processes occurring during deformation of a <span class="hlt">porous</span> rock. Deformation of a <span class="hlt">porous</span> medium is crucially influenced by the changes in the effective stress. Considering a strain-formulated yield cap and the compaction-dilation transition, three different regimes can be identified: quasi-elastic deformation, cataclastic compaction with microcracking (damage accumulation) and macroscopic brittle failure with dilation. The governing equations for deformation, damage accumulation/healing and fluid flow have been implemented in a fully-coupled finite-element-method based framework (MOOSE). The MOOSE framework provides a powerful and flexible platform to solve multiphysics problems implicitly and in a tightly coupled manner on unstructured meshes which is of interest for such non-linear context. To validate and illustrate the <span class="hlt">model</span>, simulations of the deformation behaviour of cylindrical <span class="hlt">porous</span> Bentheimer sandstone samples under different confining pressures are compared to experiments. The first experiment under low confining pressure leads to shear failure, the second for high confining pressure leads to cataclastic compaction and the third one with intermediate confining pressure correspond to a transitional regime between the two firsts. Finally, we will demonstrate that this approach can also be used at the field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986aiaa.confQ....B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986aiaa.confQ....B"><span id="translatedtitle">Sound transmission through double panel constructions lined with elastic <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bolton, J. S.; Green, E. R.</p> <p>1986-07-01</p> <p>Attention is given to a theory governing one-dimensional wave motion in elastic <span class="hlt">porous</span> <span class="hlt">materials</span> which is capable of reproducing experimental transmission measurements for unfaced polyurethane foam layers. Calculations of the transmission loss of fuselage-like foam-lined double panels are presented and it is shown that the foam/panel boundary conditions have a large effect on the panel performance; a hybrid arrangement whereby the foam is bonded directly to one panel and separated from the other by a thin air gap appears to be the most advantageous under practical circumstances. With this configuratiom, the mass-air-mass resonance is minimized and increased low-frequency performance is offered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/206497','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/206497"><span id="translatedtitle">Combustion of <span class="hlt">porous</span> energetic <span class="hlt">materials</span> in the merged-flame regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Margolis, S.B.; Williams, F.A.; Telengator, A.M.</p> <p>1996-02-01</p> <p>The structure and burning rate of an unconfined deflagration propagating through a <span class="hlt">porous</span> energetic <span class="hlt">material</span> is analyzed in the limit of merged condensed and gas-phase reaction zones. A global two-step reaction mechanism, applicable to certain types of degraded nitramine propellants and consisting of sequential condensed and gaseous steps, is postulated. Taking into account important effects due to multiphase flow and exploiting the limit of large activation energies, a theoretical analysis based on activation energy asymptotics leads to explicit formulas for the deflagration velocity in a specifically identified regime that is consistent with the merged-flame assumption. The results clearly indicate the influences of two-phase flow and the multiphase, multi-step chemistry on the deflagration structure and the burning rate, and define conditions that support the intrusion of the primary gas flame into the two-phase condensed decomposition region at the propellant surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1188868','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1188868"><span id="translatedtitle">Separation of C2 Hydrocarbons by <span class="hlt">Porous</span> <span class="hlt">Materials</span>: Metal Organic Frameworks as Platform</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Banerjee, Debasis; Liu, Jun; Thallapally, Praveen K.</p> <p>2014-12-22</p> <p>The effective separation of small hydrocarbon molecules (C1 – C4) is an important process for petroleum industry, determining the end price of many essential commodities in our daily lives. Current technologies for separation of these molecules rely on energy intensive fractional distillation processes at cryogenic temperature, which is particularly difficult because of their similar volatility. In retrospect, adsorptive separation using solid state adsorbents might be a cost effective alternative. Several types of solid state adsorbents (e.g. zeolite molecular sieves) were tested for separation of small hydrocarbon molecules as a function of pressure, temperature or vacuum. Among different types of plausible adsorbents, metal organic frameworks (MOFs), a class of <span class="hlt">porous</span>, crystalline, inorganic-organic hybrid <span class="hlt">materials</span>, is particularly promising. In this brief comment article, we discuss the separation properties of different types of solid state adsorbents, with a particular emphasis on MOF based adsorbents for separation of C2 hydrocarbon molecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52..315R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52..315R"><span id="translatedtitle">Percolating length scales from topological persistence analysis of micro-CT images of <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robins, Vanessa; Saadatfar, Mohammad; Delgado-Friedrichs, Olaf; Sheppard, Adrian P.</p> <p>2016-01-01</p> <p>Topological persistence is a powerful and general technique for characterizing the geometry and topology of data. Its theoretical foundations are over 15 years old and efficient computational algorithms are now available for the analysis of large digital images. We explain here how quantities derived from topological persistence relate to other measurements on <span class="hlt">porous</span> <span class="hlt">materials</span> such as grain and pore-size distributions, connectivity numbers, and the critical radius of a percolating sphere. The connections between percolation and topological persistence are explored in detail using data obtained from micro-CT images of spherical bead packings, unconsolidated sand packing, a variety of sandstones, and a limestone. We demonstrate how persistence information can be used to estimate the percolating sphere radius and to characterize the connectivity of the percolating cluster.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MeScT..24j5005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MeScT..24j5005A"><span id="translatedtitle">Measuring sound absorption properties of <span class="hlt">porous</span> <span class="hlt">materials</span> using a calibrated volume velocity source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arenas, Jorge P.; Darmendrail, Luis</p> <p>2013-10-01</p> <p>Measurement of acoustic properties of sound-absorbing <span class="hlt">materials</span> has been the source of much investigation that has produced practical measuring methods. In particular, the measurement of the normal incidence sound absorption coefficient is commonly done using a well-known configuration of a tube carrying a plane wave. The sound-absorbing coefficient is calculated from the surface impedance measured on a sample of <span class="hlt">material</span>. Therefore, a direct measurement of the impedance requires knowing the ratio between the sound pressure and the volume velocity. However, the measurement of volume velocity is not straightforward in practice and many methods have been proposed including complex transducers, laser vibrometry, accelerometers and calibrated volume velocity sources. In this paper, a device to directly measure the acoustic impedance of a sample of sound-absorbing <span class="hlt">material</span> is presented. The device uses an internal microphone in a small cavity sealed by a loudspeaker and a second microphone mounted in front of this source. The calibration process of the device and the limitations of the method are also discussed and measurement examples are presented. The accuracy of the device was assessed by direct comparison with the standardized method. The proposed measurement method was tested successfully with various types of commercial acoustic <span class="hlt">porous</span> <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25386191','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25386191"><span id="translatedtitle">A <span class="hlt">Porous</span> TiAl6V4 Implant <span class="hlt">Material</span> for Medical Application.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deing, Axel; Luthringer, Bérengère; Laipple, Daniel; Ebel, Thomas; Willumeit, Regine</p> <p>2014-01-01</p> <p>Increased durability of permanent TiAl6V4 implants still remains a requirement for the patient's well-being. One way to achieve a better bone-<span class="hlt">material</span> connection is to enable bone "ingrowth" into the implant. Therefore, a new <span class="hlt">porous</span> TiAl6V4 <span class="hlt">material</span> was produced via metal injection moulding (MIM). Specimens with four different porosities were produced using gas-atomised spherical TiAl6V4 with different powder particle diameters, namely, "Small" (<45 μm), "Medium" (45-63 μm), "Mix" (90% 125-180 μm + 10% <45 μm), and "Large" (125-180 μm). Tensile tests, compression tests, and resonant ultrasound spectroscopy (RUS) were used to analyse mechanical properties. These tests revealed an increasing Young's modulus with decreasing porosity; that is, "Large" and "Mix" exhibit mechanical properties closer to bone than to bulk <span class="hlt">material</span>. By applying X-ray tomography (3D volume) and optical metallographic methods (2D volume and dimensions) the pores were dissected. The pore analysis of the "Mix" and "Large" samples showed pore volumes between 29% and 34%, respectively, with pore diameters ranging up to 175 μm and even above 200 μm for "Large." <span class="hlt">Material</span> cytotoxicity on bone cell lines (SaOs-2 and MG-63) and primary cells (human bone-derived cells, HBDC) was studied by MTT assays and highlighted an increasing viability with higher porosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006525','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006525"><span id="translatedtitle">Ballistic Performance <span class="hlt">Model</span> of Crater Formation in Monolithic, <span class="hlt">Porous</span> Thermal Protection Systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, J. E.; Christiansen, E. L.; Deighton, K. D.</p> <p>2014-01-01</p> <p><span class="hlt">Porous</span> monolithic ablative systems insulate atmospheric reentry vehicles from reentry plasmas generated by atmospheric braking from orbital and exo-orbital velocities. Due to the necessity that these <span class="hlt">materials</span> create a temperature gradient up to several thousand Kelvin over their thickness, it is important that these <span class="hlt">materials</span> are near their pristine state prior to reentry. These <span class="hlt">materials</span> may also be on exposed surfaces to space environment threats like orbital debris and meteoroids leaving a probability that these exposed surfaces will be below their prescribed values. Owing to the typical small size of impact craters in these <span class="hlt">materials</span>, the local flow fields over these craters and the ablative process afford some margin in thermal protection designs for these locally reduced performance values. In this work, tests to develop ballistic performance <span class="hlt">models</span> for thermal protection <span class="hlt">materials</span> typical of those being used on Orion are discussed. A density profile as a function of depth of a typical monolithic ablator and substructure system is shown in Figure 1a.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5788155','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5788155"><span id="translatedtitle">Percolation <span class="hlt">models</span> for boiling and bubble growth in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yortsos, Y.C.</p> <p>1991-05-01</p> <p>We analyze the liquid-to-vapor phase change in single-component fluids in <span class="hlt">porous</span> media at low superheats. Conditions typical to steam injection in <span class="hlt">porous</span> media are taken. We examine nucleation, phase equilibria and their stability, and the growth of vapor bubbles. Effects of pore structure are emphasized. It is shown that at low supersaturations, bubble growth can be described as a percolation process. In the absence of spatial gradients, macroscopic flow properties are calculated in terms of nucleation parameters. A modification of gradient percolation is also proposed in the case of spatial temperature gradients, when solid conduction predominates. 22 refs., 10 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1084692','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1084692"><span id="translatedtitle"><span class="hlt">Modeling</span> and Diagnostics of Fuel Cell <span class="hlt">Porous</span> Media for Improving Water Transport</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Allen, Jeff; M'edici, Ezequiel</p> <p>2011-07-01</p> <p>When a fuel cell is operating at high current density, water accumulation is a significant cause of performance and component degradation. Investigating the water transport inside the fuel cell is a challenging task due to opacity of the components, the randomness of the <span class="hlt">porous</span> <span class="hlt">materials</span>, and the difficulty in gain access to the interior for measurement due to the small dimensions of components. Numerical simulation can provide a good insight of the evolution of the water transport under different working condition. However, the validation of those simulations is remains an issue due the same experimental obstacles associated with in-situ measurements. The discussion herein will focus on pore-network <span class="hlt">modeling</span> of the water transport on the PTL and the insights gained from simulations as well as in the validation technique. The implications of a recently published criterion to characterize PTL, based on percolation theory, and validate numerical simulation are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23890630','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23890630"><span id="translatedtitle">Detection of anionic energetic <span class="hlt">material</span> residues in enhanced fingermarks on <span class="hlt">porous</span> and non-<span class="hlt">porous</span> surfaces using ion chromatography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Love, Catherine; Gilchrist, Elizabeth; Smith, Norman; Barron, Leon</p> <p>2013-09-10</p> <p>The ability to link criminal activity and identity using validated analytical approaches can be of great value to forensic scientists. Herein, the factors affecting the recovery and detection of inorganic and organic energetic <span class="hlt">material</span> residues within chemically or physically enhanced fingermarks on paper and glass substrates are presented using micro-bore anion exchange chromatography with suppressed conductivity detection. Fingermarks on both surfaces were enhanced using aluminium powder or ninhydrin after spiking with <span class="hlt">model</span> test mixtures or through contact with black-powder substitutes. A quantitative study of the effects of environmental/method interferences, the sweat matrix, the surface and the enhancement technique on the relative anion recovery of forensically relevant species is presented. It is shown that the analytical method could detect target analytes at the nanogram level even within excesses of enhancement reagents and their reaction products when using solid phase extraction and/or microfiltration. To our knowledge, this work demonstrates for the first time that ion chromatography can detect anions in energetic <span class="hlt">materials</span> within fingermarks on two very different surfaces, after operational enhancement techniques commonly used by forensic scientists and police have been applied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=231115','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=231115"><span id="translatedtitle">Fractal and Multifractal <span class="hlt">Models</span> Applied to <span class="hlt">Porous</span> Media - Editorial</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Given the current high level of interest in the use of fractal geometry to characterize natural <span class="hlt">porous</span> media, a special issue of the Vadose Zone Journal was organized in order to expose established fractal analysis techniques and cutting-edge new developments to a wider Earth science audience. The ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25625943','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25625943"><span id="translatedtitle"><span class="hlt">Porous</span> graphene-based <span class="hlt">material</span> as an efficient metal free catalyst for the oxidative dehydrogenation of ethylbenzene to styrene.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diao, Jiangyong; Liu, Hongyang; Wang, Jia; Feng, Zhenbao; Chen, Tong; Miao, Changxi; Yang, Weimin; Su, Dang Sheng</p> <p>2015-02-25</p> <p>Reduced <span class="hlt">porous</span> graphene oxide as a metal free catalyst was selected for the oxidative dehydrogenation of ethylbenzene to styrene. It showed the best catalytic performance compared with other carbon <span class="hlt">materials</span> (routinely reduced graphene oxide, graphite powder and oxidized carbon nanotubes) and commercial iron oxide. PMID:25625943</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24307432','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24307432"><span id="translatedtitle">Nitrogen-doped <span class="hlt">porous</span> graphitic carbon as an excellent electrode <span class="hlt">material</span> for advanced supercapacitors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Li; Tian, Chungui; Fu, Yu; Yang, Ying; Yin, Jie; Wang, Lei; Fu, Honggang</p> <p>2014-01-01</p> <p>An advanced supercapacitor <span class="hlt">material</span> based on nitrogen-doped <span class="hlt">porous</span> graphitic carbon (NPGC) with high a surface area was synthesized by means of a simple coordination-pyrolysis combination process, in which tetraethyl orthosilicate (TEOS), nickel nitrate, and glucose were adopted as porogent, graphitic catalyst precursor, and carbon source, respectively. In addition, melamine was selected as a nitrogen source owing to its nitrogen-enriched structure and the strong interaction between the amine groups and the glucose unit. A low-temperature treatment resulted in the formation of a NPGC precursor by combination of the catalytic precursor, hydrolyzed TEOS, and the melamine-glucose unit. Following pyrolysis and removal of the catalyst and porogent, the NPGC <span class="hlt">material</span> showed excellent electrical conductivity owing to its high crystallinity, a large Brunauer-Emmett-Teller surface area (SBET =1027 m(2)  g(-1) ), and a high nitrogen level (7.72 wt %). The unusual microstructure of NPGC <span class="hlt">materials</span> could provide electrochemical energy storage. The NPGC <span class="hlt">material</span>, without the need for any conductive additives, showed excellent capacitive behavior (293 F g(-1) at 1 A g(-1) ), long-term cycling stability, and high coulombic efficiency (>99.9 % over 5000 cycles) in KOH when used as an electrode. Notably, in a two-electrode symmetric supercapacitor, NPGC energy densities as high as 8.1 and 47.5 Wh kg(-1) , at a high power density (10.5 kW kg(-1) ), were achieved in 6 M KOH and 1 M Et4 NBF4 -PC electrolytes, respectively. Thus, the synthesized NPGC <span class="hlt">material</span> could be a highly promising electrode <span class="hlt">material</span> for advanced supercapacitors and other conversion devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JAP....93.4226K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JAP....93.4226K"><span id="translatedtitle">Unoxidized <span class="hlt">porous</span> Si as an isolation <span class="hlt">material</span> for mixed-signal integrated circuit applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Han-Su; Xie, Ya-Hong; DeVincentis, Marc; Itoh, Tatsuo; Jenkins, Keith A.</p> <p>2003-04-01</p> <p>An isolation technology for radio frequency (rf) applications based on unoxidized <span class="hlt">porous</span> Si (PS) is demonstrated. This study examines all the important issues pertinent to incorporating PS with Si very-large-scale integration (VLSI) technology, where PS is used as a semi-insulating <span class="hlt">material</span>. Specifically, the issues on rf isolation performance of PS as a function of porosity [from coplanar waveguide (CPW) line measurements] and PS thickness (from on-chip inductors) and the stress generated from incorporating PS regions by anodization are discussed in detail. CPW line measurements show that the relative dielectric constant of PS films decreases from 9 to 3 with increasing porosity from 24% to 78%. PS is a very low loss <span class="hlt">material</span> with loss tangent <0.001 at 20 GHz when its porosity is above 51%. rf crosstalk through a Si substrate can be reduced to that through air by inserting a PS trench between noise generating circuit and noise sensing circuit. On-chip spiral inductors fabricated on top of PS regions of through-the-wafer thickness have Qmax of about 29 at 7 GHz and resonant frequency higher than 20 GHz. With the additional advantage of planar topography and mechanical integrity, we show that unoxidized PS is an outstanding <span class="hlt">material</span> for rf isolation in Si VLSI.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25945394','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25945394"><span id="translatedtitle">Giant Negative Area Compressibility Tunable in a Soft <span class="hlt">Porous</span> Framework <span class="hlt">Material</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cai, Weizhao; Gładysiak, Andrzej; Anioła, Michalina; Smith, Vincent J; Barbour, Leonard J; Katrusiak, Andrzej</p> <p>2015-07-29</p> <p>A soft <span class="hlt">porous</span> <span class="hlt">material</span> [Zn(L)2(OH)2]n·Guest (where L is 4-(1H-naphtho[2,3-d]imidazol-1-yl)benzoate, and Guest is water or methanol) exhibits the strongest ever observed negative area compressibility (NAC), an extremely rare property, as at hydrostatic pressure most <span class="hlt">materials</span> shrink in all directions and few expand in one direction. This is the first NAC reported in metal-organic frameworks (MOFs), and its magnitude, clearly visible and by far the highest of all known <span class="hlt">materials</span>, can be reversibly tuned by exchanging guests adsorbed from hydrostatic fluids. This counterintuitive strong NAC of [Zn(L)2(OH)2]n·Guest arises from the interplay of flexible [-Zn-O(H)-]n helices with layers of [-Zn-L-]4 quadrangular puckered rings comprising large channel voids. The compression of helices and flattening of puckered rings combine to give a giant piezo-mechanical response, applicable in ultrasensitive sensors and actuators. The extrinsic NAC response to different hydrostatic fluids is due to varied host-guest interactions affecting the mechanical strain within the range permitted by exceptionally high flexibility of the framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25158688','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25158688"><span id="translatedtitle"><span class="hlt">Porous</span> ovalbumin scaffolds with tunable properties: a resource-efficient biodegradable <span class="hlt">material</span> for tissue engineering applications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Luo, Baiwen; Choong, Cleo</p> <p>2015-01-01</p> <p>Natural <span class="hlt">materials</span> are promising alternatives to synthetic <span class="hlt">materials</span> used in tissue engineering applications as they have superior biocompatibility and promote better cell attachment and proliferation. Ovalbumin, a natural polymer found in avian egg white, is an example of a nature-derived <span class="hlt">material</span>. Despite the availability and reported biocompatibility of ovalbumin, limited research has been carried out to investigate the efficacy of ovalbumin-based scaffolds for adipose tissue engineering applications. Hence, the current study was carried out to investigate the effect of different crosslinkers on ovalbumin scaffold properties as first step towards the development of ovalbumin-based scaffolds for adipose tissue engineering applications. In this study, highly <span class="hlt">porous</span> three-dimensional scaffolds were fabricated by using three different crosslinkers: glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 1,4-butanediol diglycidyl ether. Results showed that the overall scaffold properties such as morphology, pore size and mechanical properties could be modulated based on the type and concentration of crosslinkers used during the fabrication process. Subsequently, the efficacy of the different scaffolds for supporting cell proliferation was investigated. In vitro degradation was also carried on for the best scaffold based on the mechanical and cellular results. Overall, this study is a demonstration of the viability of ovalbumin-based scaffolds as cell carriers for soft tissue engineering applications. PMID:25158688</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25158688','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25158688"><span id="translatedtitle"><span class="hlt">Porous</span> ovalbumin scaffolds with tunable properties: a resource-efficient biodegradable <span class="hlt">material</span> for tissue engineering applications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Luo, Baiwen; Choong, Cleo</p> <p>2015-01-01</p> <p>Natural <span class="hlt">materials</span> are promising alternatives to synthetic <span class="hlt">materials</span> used in tissue engineering applications as they have superior biocompatibility and promote better cell attachment and proliferation. Ovalbumin, a natural polymer found in avian egg white, is an example of a nature-derived <span class="hlt">material</span>. Despite the availability and reported biocompatibility of ovalbumin, limited research has been carried out to investigate the efficacy of ovalbumin-based scaffolds for adipose tissue engineering applications. Hence, the current study was carried out to investigate the effect of different crosslinkers on ovalbumin scaffold properties as first step towards the development of ovalbumin-based scaffolds for adipose tissue engineering applications. In this study, highly <span class="hlt">porous</span> three-dimensional scaffolds were fabricated by using three different crosslinkers: glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 1,4-butanediol diglycidyl ether. Results showed that the overall scaffold properties such as morphology, pore size and mechanical properties could be modulated based on the type and concentration of crosslinkers used during the fabrication process. Subsequently, the efficacy of the different scaffolds for supporting cell proliferation was investigated. In vitro degradation was also carried on for the best scaffold based on the mechanical and cellular results. Overall, this study is a demonstration of the viability of ovalbumin-based scaffolds as cell carriers for soft tissue engineering applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvE..91c3004C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvE..91c3004C"><span id="translatedtitle">Generalized lattice Boltzmann <span class="hlt">model</span> for flow through tight <span class="hlt">porous</span> media with Klinkenberg's effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Li; Fang, Wenzhen; Kang, Qinjun; De'Haven Hyman, Jeffrey; Viswanathan, Hari S.; Tao, Wen-Quan</p> <p>2015-03-01</p> <p>Gas slippage occurs when the mean free path of the gas molecules is in the order of the characteristic pore size of a <span class="hlt">porous</span> medium. This phenomenon leads to Klinkenberg's effect where the measured permeability of a gas (apparent permeability) is higher than that of the liquid (intrinsic permeability). A generalized lattice Boltzmann <span class="hlt">model</span> is proposed for flow through <span class="hlt">porous</span> media that includes Klinkenberg's effect, which is based on the <span class="hlt">model</span> of Guo et al. [Phys. Rev. E 65, 046308 (2002), 10.1103/PhysRevE.65.046308]. The second-order Beskok and Karniadakis-Civan's correlation [A. Beskok and G. Karniadakis, Microscale Thermophys. Eng. 3, 43 (1999), 10.1080/108939599199864 and F. Civan, Transp. <span class="hlt">Porous</span> Med. 82, 375 (2010), 10.1007/s11242-009-9432-z] is adopted to calculate the apparent permeability based on intrinsic permeability and the Knudsen number. Fluid flow between two parallel plates filled with <span class="hlt">porous</span> media is simulated to validate the <span class="hlt">model</span>. Simulations performed in a heterogeneous <span class="hlt">porous</span> medium with components of different porosity and permeability indicate that Klinkenberg's effect plays a significant role on fluid flow in low-permeability <span class="hlt">porous</span> media, and it is more pronounced as the Knudsen number increases. Fluid flow in a shale matrix with and without fractures is also studied, and it is found that the fractures greatly enhance the fluid flow and Klinkenberg's effect leads to higher global permeability of the shale matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27524006','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27524006"><span id="translatedtitle"><span class="hlt">Porous</span> biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective <span class="hlt">materials</span> for bone implants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit</p> <p>2016-11-01</p> <p><span class="hlt">Porous</span> and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are <span class="hlt">materials</span> with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, <span class="hlt">porous</span> and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. PMID:27524006</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27524006','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27524006"><span id="translatedtitle"><span class="hlt">Porous</span> biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective <span class="hlt">materials</span> for bone implants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit</p> <p>2016-11-01</p> <p><span class="hlt">Porous</span> and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are <span class="hlt">materials</span> with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, <span class="hlt">porous</span> and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JMPSo..56.2188G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JMPSo..56.2188G"><span id="translatedtitle">Continuum <span class="hlt">modeling</span> of a <span class="hlt">porous</span> solid with pressure-sensitive dilatant matrix</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, T. F.; Faleskog, J.; Shih, C. F.</p> <p></p> <p>The pressure-sensitive plastic response of a <span class="hlt">material</span> has been studied in terms of the intrinsic sensitivity of its yield stress to pressure and the presence and growth of cavities. This work focuses on the interplay between these two distinctly different mechanisms and the attendant <span class="hlt">material</span> behavior. To this end, a constitutive <span class="hlt">model</span> is proposed taking both mechanisms into account. Using Gurson's homogenization, an upper bound <span class="hlt">model</span> is developed for a voided solid with a plastically dilatant matrix <span class="hlt">material</span>. This <span class="hlt">model</span> is built around a three-parameter axisymmetric velocity field for a unit sphere containing a spherical void. The void is also subjected to internal pressure; this can be relevant for polymeric adhesives permeated by moisture that vaporizes at elevated temperatures. The plastic response of the matrix <span class="hlt">material</span> is described by Drucker-Prager's yield criterion and an associated flow rule. The resulting yield surface and porosity evolution law of the homogenized constitutive <span class="hlt">model</span> are presented in parametric form. Using the solutions to special cases as building blocks, approximate <span class="hlt">models</span> with explicit forms are proposed. The parametric form and an approximate explicit form are compared against full-field solutions obtained from finite element analysis. They are also studied for loading under generalized tension conditions. These computational simulations shed light on the interplay between the two mechanisms and its enhanced effect on yield strength and plastic flow. Among other things, the tensile yield strength of the <span class="hlt">porous</span> solid is greatly reduced by the internal void pressure, particularly when a liquid/vapor phase is the source of the internal pressure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10166650','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10166650"><span id="translatedtitle">Effects of two-phase flow on the deflagration of <span class="hlt">porous</span> energetic <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Margolis, S.B.; Williams, F.A.</p> <p>1994-07-01</p> <p>Theoretical analyses are developed for the multi-phase deflagration of <span class="hlt">porous</span> energetic solids, such as degraded nitramine propellants, that experience significant gas flow in the solid preheat region and are characterized by the presence of exothermic reactions in a bubbling melt layer at their surfaces. Relative motion between the gas and condensed phases is taken into account in both regions, and expressions for the mass burning rate and other quantities of interest, such as temperature and volume-fraction profiles, are derived by activation-energy asymptotics. The <span class="hlt">model</span> extends recent work by allowing for gas flow in the unburned solid, and by incorporating pressure effects through the gas-phase equation of state. As a consequence, it is demonstrated how most aspects of the deflagration wave, including its structure, propagation speed and final temperature, depend on the local pressure in the two-phase regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPS...315....9J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPS...315....9J"><span id="translatedtitle">Facile synthesis of reduced graphene oxide-<span class="hlt">porous</span> silicon composite as superior anode <span class="hlt">material</span> for lithium-ion battery anodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiao, Lian-Sheng; Liu, Jin-Yu; Li, Hong-Yan; Wu, Tong-Shun; Li, Fenghua; Wang, Hao-Yu; Niu, Li</p> <p>2016-05-01</p> <p>We report a new method for synthesizing reduced graphene oxide (rGO)-<span class="hlt">porous</span> silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw <span class="hlt">material</span> source for the synthesis of <span class="hlt">porous</span> Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the <span class="hlt">porous</span> structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g-1 can be retained even at a rate of 16 A g-1. A discharge capacity of 830 mA h g-1 at a current density of 1 A g-1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JMPSo..44.1649D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JMPSo..44.1649D"><span id="translatedtitle">On the validity of the effective stress concept for assessing the strength of saturated <span class="hlt">porous</span> <span class="hlt">materials</span>: A homogenization approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Buhan, P.; Dormieux, L.</p> <p>1996-10-01</p> <p>The much debated question of whether the strength criterion of a fluid saturated <span class="hlt">porous</span> medium, such as most geomaterials, can be expressed in terms of "effective stress," is critically examined in this paper using the yield design homogenization theory as an investigating tool. Adopting a periodic description of the saturated <span class="hlt">porous</span> <span class="hlt">material</span> at the microscopic level, where the fluid phase exerts a pressure on the solid matrix making up the skeleton, a general definition of the strength properties of the <span class="hlt">porous</span> <span class="hlt">material</span> at the macroscopic scale is given. While some situations are identified where the "effective stress principle," as classically formulated, remains appropriate, it is proved that for a frictional solid matrix, such a principle, even in its generalized form, is not relevant. Nevertheless, the dependence on the pore pressure can still be specified in a simple way, so that the complete knowledge of the criterion for any prescribed value of the pore pressure only requires determining the strength properties of the dry <span class="hlt">porous</span> <span class="hlt">material</span>. Moreover, the possibility of adopting sufficiently accurate approximations of the actual criterion by resorting to an effective stress formulation is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21369760','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21369760"><span id="translatedtitle">A novel synthetic <span class="hlt">material</span> for spinal fusion: a prospective clinical trial of <span class="hlt">porous</span> bioactive titanium metal for lumbar interbody fusion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fujibayashi, Shunsuke; Takemoto, Mitsuru; Neo, Masashi; Matsushita, Tomiharu; Kokubo, Tadashi; Doi, Kenji; Ito, Tatsuya; Shimizu, Akira; Nakamura, Takashi</p> <p>2011-09-01</p> <p>The objective of this study was to establish the efficacy and safety of <span class="hlt">porous</span> bioactive titanium metal for use in a spinal fusion device, based on a prospective human clinical trial. A high-strength spinal interbody fusion device was manufactured from <span class="hlt">porous</span> titanium metal. A bioactive surface was produced by simple chemical and thermal treatment. Five patients with unstable lumbar spine disease were treated surgically using this device in a clinical trial approved by our Ethics Review Committee and the University Hospital Medical Information Network. Clinical and radiological results were reported at the minimum follow-up period of 1 year. The optimal mechanical strength and interconnected structure of the <span class="hlt">porous</span> titanium metal were adjusted for the device. The whole surface of <span class="hlt">porous</span> titanium metal was treated uniformly and its bioactive ability was confirmed before clinical use. Successful bony union was achieved in all cases within 6 months without the need for autologous iliac crest bone grafting. Two specific findings including an anchoring effect and gap filling were evident radiologically. All clinical parameters improved significantly after the operation and no adverse effects were encountered during the follow-up period. Although a larger and longer-term follow-up clinical study is mandatory to reach any firm conclusions, the study results show that this <span class="hlt">porous</span> bioactive titanium metal is promising <span class="hlt">material</span> for a spinal fusion device.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhyA..429..215L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhyA..429..215L"><span id="translatedtitle">Multiple-relaxation-time lattice Boltzmann <span class="hlt">modeling</span> of incompressible flows in <span class="hlt">porous</span> media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Qing; He, Ya-Ling</p> <p>2015-07-01</p> <p>In this paper, a two-dimensional eight-velocity multiple-relaxation-time (MRT) lattice Boltzmann (LB) <span class="hlt">model</span> is proposed for incompressible <span class="hlt">porous</span> flows at the representative elementary volume scale based on the Brinkman-Forchheimer-extended Darcy <span class="hlt">model</span>. In the <span class="hlt">model</span>, the porosity is included into the pressure-based equilibrium moments, and the linear and nonlinear drag forces of the <span class="hlt">porous</span> matrix are incorporated into the <span class="hlt">model</span> by adding a forcing term to the MRT-LB equation in the moment space. Through the Chapman-Enskog analysis, the incompressible generalized Navier-Stokes equations can be recovered. Numerical simulations of several typical <span class="hlt">porous</span> flows are carried out to validate the present MRT-LB <span class="hlt">model</span>. It is found that the present numerical results agree well with the analytical solutions and/or other numerical results reported in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6085334','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6085334"><span id="translatedtitle">Analysis of NSWC quasi-static compaction data for <span class="hlt">porous</span> beds of ball powder, melamine, and Teflon, using structural compaction <span class="hlt">model</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Weston, A.M.; Lee, E.L.</p> <p>1983-04-06</p> <p>A structural compaction <span class="hlt">model</span> is used to correlate NSWC quasi-static compaction data on <span class="hlt">porous</span> beds of six (6) different <span class="hlt">materials</span>, i.e., four (4) ball powders, melamine, and Teflon. Initial densities of the <span class="hlt">porous</span> beds ranged from 44 percent solid theoretical maximum density (TMD) to 70 percent TMD. Maximum compacted densities were about 90 percent TMD except for Teflon which was compacted to approximately 98 percent TMD. Pressures calculated by the <span class="hlt">model</span>, plotted as a function of percent TMD, agree well with the NSWC data.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24411389','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24411389"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">material</span> based on spongy titanium granules: structure, mechanical properties, and osseointegration.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rubshtein, A P; Trakhtenberg, I Sh; Makarova, E B; Triphonova, E B; Bliznets, D G; Yakovenkova, L I; Vladimirov, A B</p> <p>2014-02-01</p> <p>A <span class="hlt">porous</span> <span class="hlt">material</span> has been produced by pressing spongy titanium granules with subsequent vacuum sintering. The <span class="hlt">material</span> with porosity of more than 30% has an open system of interconnecting pores. The Young's modulus and 0.2% proof strength have been measured for the samples having 20-55% porosity. If the porosity is between 30 and 45%, the mechanical properties are determined by irregular shape of pores, which is due to spongy titanium granules. The experiment in vivo was performed on adult rabbits. Before surgery the implants were saturated with adherent autologous bone marrow cells. The implants were introduced into the defects formed in the condyles of tibias and femurs. Investigations of osseointegration of implants having 40% porosity showed that the whole system of pores was filled with mature bone tissue in 16 weeks after surgery. Neogenic bone tissue has an uneven surface formed by lacunas and craters indicative of active resorption and subsequent rearrangement (SEM examination). The bone tissue is pierced by neoformed vessels. Irregular-shaped pores with tortuous walls and numerous lateral channels going through the granules provide necessary conditions for the formation of functional bone tissue in the implant volume and the periimplant region. PMID:24411389</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27501762','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27501762"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-08-09</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ASAJ..118.2021J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ASAJ..118.2021J"><span id="translatedtitle">Technique for measurement of characteristic impedance and propagation constant for <span class="hlt">porous</span> <span class="hlt">materials</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jung, Ki Won; Atchley, Anthony A.</p> <p>2005-09-01</p> <p>Knowledge of acoustic properties such as characteristic impedance and complex propagation constant is useful to characterize the acoustic behaviors of <span class="hlt">porous</span> <span class="hlt">materials</span>. Song and Bolton's four-microphone method [J. Acoust. Soc. Am. 107, 1131-1152 (2000)] is one of the most widely employed techniques. In this method two microphones are used to determine the complex pressure amplitudes for each side of a sample. Muehleisen and Beamer [J. Acoust. Soc. Am. 117, 536-544 (2005)] improved upon a four-microphone method by interchanging microphones to reduce errors due to uncertainties in microphone response. In this paper, a multiple microphone technique is investigated to reconstruct the pressure field inside an impedance tube. Measurements of the acoustic properties of a <span class="hlt">material</span> having square cross-section pores is used to check the validity of the technique. The values of characteristic impedance and complex propagation constant extracted from the reconstruction agree well with predicted values. Furthermore, this technique is used in investigating the acoustic properties of reticulated vitreous carbon (RVC) in the range of 250-1100 Hz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27501762','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27501762"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-01-01</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications. PMID:27501762</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4606457','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4606457"><span id="translatedtitle"><span class="hlt">Porous</span> Structures in Stacked, Crumpled and Pillared Graphene-Based 3D <span class="hlt">Materials</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Guo, Fei; Creighton, Megan; Chen, Yantao; Hurt, Robert; Külaots, Indrek</p> <p>2015-01-01</p> <p>Graphene, an atomically thin <span class="hlt">material</span> with the theoretical surface area of 2600 m2g−1, has great potential in the fields of catalysis, separation, and gas storage if properly assembled into functional 3D <span class="hlt">materials</span> at large scale. In ideal non-interacting ensembles of non-<span class="hlt">porous</span> multilayer graphene plates, the surface area can be adequately estimated using the simple geometric law ~ 2600 m2g−1/N, where N is the number of graphene sheets per plate. Some processing operations, however, lead to secondary plate-plate stacking, folding, crumpling or pillaring, which give rise to more complex structures. Here we show that bulk samples of multilayer graphene plates stack in an irregular fashion that preserves the 2600/N surface area and creates regular slot-like pores with sizes that are multiples of the unit plate thickness. In contrast, graphene oxide deposits into films with massive area loss (2600 to 40 m2g−1) due to nearly perfect alignment and stacking during the drying process. Pillaring graphene oxide sheets by co-deposition of colloidal-phase particle-based spacers has the potential to partially restore the large monolayer surface. Surface areas as high as 1000 m2g−1 are demonstrated here through colloidal-phase deposition of graphene oxide with water-dispersible aryl-sulfonated ultrafine carbon black as a pillaring agent. PMID:26478597</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...631233R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...631233R"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-08-01</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21361434','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21361434"><span id="translatedtitle">Measurement of the resistivity of <span class="hlt">porous</span> <span class="hlt">materials</span> with an alternating air-flow method.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dragonetti, Raffaele; Ianniello, Carmine; Romano, Rosario A</p> <p>2011-02-01</p> <p>Air-flow resistivity is a main parameter governing the acoustic behavior of <span class="hlt">porous</span> <span class="hlt">materials</span> for sound absorption. The international standard ISO 9053 specifies two different methods to measure the air-flow resistivity, namely a steady-state air-flow method and an alternating air-flow method. The latter is realized by the measurement of the sound pressure at 2 Hz in a small rigid volume closed partially by the test sample. This cavity is excited with a known volume-velocity sound source implemented often with a motor-driven piston oscillating with prescribed area and displacement magnitude. Measurements at 2 Hz require special instrumentation and care. The authors suggest an alternating air-flow method based on the ratio of sound pressures measured at frequencies higher than 2 Hz inside two cavities coupled through a conventional loudspeaker. The basic method showed that the imaginary part of the sound pressure ratio is useful for the evaluation of the air-flow resistance. Criteria are discussed about the choice of a frequency range suitable to perform simplified calculations with respect to the basic method. These criteria depend on the sample thickness, its nonacoustic parameters, and the measurement apparatus as well. The proposed measurement method was tested successfully with various types of acoustic <span class="hlt">materials</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15348306','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15348306"><span id="translatedtitle">Titanium powder sintering for preparation of a <span class="hlt">porous</span> functionally graded <span class="hlt">material</span> destined for orthopaedic implants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thieme, M; Wieters, K P; Bergner, F; Scharnweber, D; Worch, H; Ndop, J; Kim, T J; Grill, W</p> <p>2001-03-01</p> <p>This work focuses on basic research into a P/M processed, <span class="hlt">porous</span>-surfaced and functionally graded <span class="hlt">material</span> (FGM) destined for a permanent skeletal replacement implant with improved structural compatibility. Based on a perpendicular gradient in porosity the Young's modulus of the <span class="hlt">material</span> is adapted to the elastic properties of bone in order to prevent stress shielding effects and to provide better long-term performance of the implant-bone system. Using coarse Ti particle fractions the sintering process was accelerated by silicon-assisted liquid-phase sintering (LPS) resulting in a substantial improvement of the neck geometry. A novel evaluation for the strength of the sinter contacts was proposed. The Young's modulus of uniform non-graded stacks ranged from 5 to 80 GPa as determined by ultrasound velocity measurements. Thus, the typical range for cortical bone (10-29 GPa) was covered. The magnitude of the Poisson's ratio proved to be distinctly dependent on the porosity. Specimens with porosity gradients were successfully fabricated and characterized using quantitative description of the microstructural geometry and acoustic microscopy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24411389','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24411389"><span id="translatedtitle"><span class="hlt">Porous</span> <span class="hlt">material</span> based on spongy titanium granules: structure, mechanical properties, and osseointegration.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rubshtein, A P; Trakhtenberg, I Sh; Makarova, E B; Triphonova, E B; Bliznets, D G; Yakovenkova, L I; Vladimirov, A B</p> <p>2014-02-01</p> <p>A <span class="hlt">porous</span> <span class="hlt">material</span> has been produced by pressing spongy titanium granules with subsequent vacuum sintering. The <span class="hlt">material</span> with porosity of more than 30% has an open system of interconnecting pores. The Young's modulus and 0.2% proof strength have been measured for the samples having 20-55% porosity. If the porosity is between 30 and 45%, the mechanical properties are determined by irregular shape of pores, which is due to spongy titanium granules. The experiment in vivo was performed on adult rabbits. Before surgery the implants were saturated with adherent autologous bone marrow cells. The implants were introduced into the defects formed in the condyles of tibias and femurs. Investigations of osseointegration of implants having 40% porosity showed that the whole system of pores was filled with mature bone tissue in 16 weeks after surgery. Neogenic bone tissue has an uneven surface formed by lacunas and craters indicative of active resorption and subsequent rearrangement (SEM examination). The bone tissue is pierced by neoformed vessels. Irregular-shaped pores with tortuous walls and numerous lateral channels going through the granules provide necessary conditions for the formation of functional bone tissue in the implant volume and the periimplant region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4977488','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4977488"><span id="translatedtitle">A Versatile and Scalable Approach toward Robust Superhydrophobic <span class="hlt">Porous</span> <span class="hlt">Materials</span> with Excellent Absorbency and Flame Retardancy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui</p> <p>2016-01-01</p> <p>The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for <span class="hlt">materials</span> that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic <span class="hlt">porous</span> <span class="hlt">materials</span>, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications. PMID:27501762</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16530942','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16530942"><span id="translatedtitle">Preparation and sorption properties of <span class="hlt">porous</span> <span class="hlt">materials</span> from refuse paper and plastic fuel (RPF).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kadirova, Z; Kameshima, Y; Nakajima, A; Okada, K</p> <p>2006-09-01</p> <p><span class="hlt">Porous</span> <span class="hlt">materials</span> consisting of activated carbon and amorphous CaO-Al(2)O(3)-SiO(2) (CAS) compound were prepared from refuse paper and plastic fuel (RPF), (a mixture of old paper and plastic) by carbonizing and/or activating treatments. Samples formed by chemical activation using K(2)CO(3) showed a high specific surface area (S(BET)) of 1330 m(2)/g but a lower ash content due to being washed after activation. By contrast, samples prepared by physical activation using steam showed rather lower S(BET) (510 m(2)/g) due to higher ash contents. The physically activated samples showed much higher uptake properties for Ni(2+) (a representative heavy metal) and phosphate ions (a representative of a harmful oxyanion) than the chemically activated samples because of the higher content of amorphous CAS in the former samples. By contrast, the chemically activated samples showed higher uptake for methylene blue (MB, a representative organic <span class="hlt">material</span>) than the physically activated samples because of the higher activated carbon content of higher surface area. Although differences in the sorption properties for Ni(2+), phosphate ion and MB were found between the physically and chemically activated samples, both samples show excellent multiple sorption properties for cation-anion combinations and inorganic-organic sorbents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/975806','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/975806"><span id="translatedtitle">Bolide dynamics and luminosity <span class="hlt">modeling</span> : comparisons between uniform bulk density and <span class="hlt">porous</span> meteoroid <span class="hlt">models</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>ReVelle, D. O.</p> <p>2001-01-01</p> <p>We compare predictions of bolide behavior using basic meteoroid <span class="hlt">models</span>, first assuming a uniform bulk density throughout the body and secondly assuming a uniform chondritic composition throughout, but with varying amounts of porosity (assumed to be filled with either water-ice or open space). The second <span class="hlt">model</span> is based one the uniformity of spectral observations over many years from shower meteors from the extremes of the Geminids to the dustball-like Draconids. The first <span class="hlt">model</span> utilized is due to ReVelle (1979, 1993) and the second is based upon the <span class="hlt">porous</span> meteoroid <span class="hlt">model</span> of ReVelle (1983, 1993). The standard, uniform bulk density <span class="hlt">model</span> assumes that the drag and heat transfer area are equivalent in the positive, shape change factor limit. For <span class="hlt">porous</span> meteoroids however, the heat transfer area can exceed the drag area by increasingly larger amounts as the body's porosity increases. ReVelle (1983) used this approach to show that the bulk density and ablation parameter compositional group identifications of Ceplecha and McCrosky (1976) were essentially correct. When these factors are introduced into the relevant <span class="hlt">model</span> equations, a set of nearly self-consistent predictive relations are developed which readily allows comparisons to be made of the end-height variations and of the normalized luminous output of the two basic meteoroid <span class="hlt">models</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4214099','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4214099"><span id="translatedtitle">A <span class="hlt">Porous</span> TiAl6V4 Implant <span class="hlt">Material</span> for Medical Application</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ebel, Thomas; Willumeit, Regine</p> <p>2014-01-01</p> <p>Increased durability of permanent TiAl6V4 implants still remains a requirement for the patient's well-being. One way to achieve a better bone-<span class="hlt">material</span> connection is to enable bone “ingrowth” into the implant. Therefore, a new <span class="hlt">porous</span> TiAl6V4 <span class="hlt">material</span> was produced via metal injection moulding (MIM). Specimens with four different porosities were produced using gas-atomised spherical TiAl6V4 with different powder particle diameters, namely, “Small” (<45 μm), “Medium” (45–63 μm), “Mix” (90% 125–180 μm + 10% <45 μm), and “Large” (125–180 μm). Tensile tests, compression tests, and resonant ultrasound spectroscopy (RUS) were used to analyse mechanical properties. These tests revealed an increasing Young's modulus with decreasing porosity; that is, “Large” and “Mix” exhibit mechanical properties closer to bone than to bulk <span class="hlt">material</span>. By applying X-ray tomography (3D volume) and optical metallographic methods (2D volume and dimensions) the pores were dissected. The pore analysis of the “Mix” and “Large” samples showed pore volumes between 29% and 34%, respectively, with pore diameters ranging up to 175 μm and even above 200 μm for “Large.” <span class="hlt">Material</span> cytotoxicity on bone cell lines (SaOs-2 and MG-63) and primary cells (human bone-derived cells, HBDC) was studied by MTT assays and highlighted an increasing viability with higher porosity. PMID:25386191</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23576823','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23576823"><span id="translatedtitle">Effective conductivity and permittivity of unsaturated <span class="hlt">porous</span> <span class="hlt">materials</span> in the frequency range 1 mHz-1GHz.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Revil, A</p> <p>2013-01-01</p> <p>A <span class="hlt">model</span> combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp , which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd , the quadrature conductivity is generally well described by a plateau when clay minerals are present in the <span class="hlt">material</span>. Clay-free <span class="hlt">porous</span> <span class="hlt">materials</span> with a narrow grain size distribution are described by a Cole-Cole <span class="hlt">model</span>. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the <span class="hlt">material</span>. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd , the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified <span class="hlt">model</span> is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3618403','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3618403"><span id="translatedtitle">Effective conductivity and permittivity of unsaturated <span class="hlt">porous</span> <span class="hlt">materials</span> in the frequency range 1 mHz–1GHz</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Revil, A</p> <p>2013-01-01</p> <p>A <span class="hlt">model</span> combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the <span class="hlt">material</span>. Clay-free <span class="hlt">porous</span> <span class="hlt">materials</span> with a narrow grain size distribution are described by a Cole-Cole <span class="hlt">model</span>. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the <span class="hlt">material</span>. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified <span class="hlt">model</span> is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1130683','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1130683"><span id="translatedtitle"><span class="hlt">Porous</span> Chromatographic <span class="hlt">Materials</span> as Substrates for Preparing Synthetic Nuclear Explosion Debris Particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harvey, Scott D.; Liezers, Martin; Antolick, Kathryn C.; Garcia, Ben J.; Sweet, Lucas E.; Carman, April J.; Eiden, Gregory C.</p> <p>2013-06-13</p> <p>In this study, we investigated several <span class="hlt">porous</span> chromatographic <span class="hlt">materials</span> as synthetic substrates for preparing surrogate nuclear explosion debris particles. The resulting synthetic debris <span class="hlt">materials</span> are of interest for use in developing analytical methods. Eighteen metals, including some of forensic interest, were loaded onto <span class="hlt">materials</span> by immersing them in metal solutions (556 mg/L of each metal) to fill the pores, applying gentle heat (110°C) to drive off water, and then treating them at high temperatures (up to 800°C) in air to form less soluble metal species. High-boiling-point metals were uniformly loaded on spherical controlled-pore glass to emulate early fallout, whereas low-boiling-point metals were loaded on core-shell silica to represent coated particles formed later in the nuclear fallout-formation process. Analytical studies were applied to characterize solubility, <span class="hlt">material</span> balance, and formation of recalcitrant species. Dissolution experiments indicated loading was 1.5 to 3 times higher than expected from the pore volume alone, a result attributed to surface coating. Analysis of load solutions before and after filling the <span class="hlt">material</span> pores revealed that most metals were passively loaded; that is, solutions filled the pores without active metal discrimination. However, niobium and tin concentrations were lower in solutions after pore filling, and were found in elevated concentrations in the final products, indicating some metals were selectively loaded. High-temperature treatments caused reduced solubility of several metal species, and loss of some metals (rhenium and tellurium) because volatile species were formed. Sample preparation reproducibility was high (the inter-batch relative standard deviation was 7.8%, and the intra-batch relative standard deviation was 0.84%) indicating that this <span class="hlt">material</span> is suitable for use as a working standard for analytical methods development. We anticipate future standardized radionuclide-loaded <span class="hlt">materials</span> will find use in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1512719A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512719A"><span id="translatedtitle">A numerical <span class="hlt">model</span> of controlled bioinduced mineralization in a <span class="hlt">porous</span> medium to prevent corrosion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Afanasyev, Michael; van Paassen, Leon; Heimovaara, Timo</p> <p>2013-04-01</p> <p>This paper presents a numerical <span class="hlt">model</span> of controlled bioinduced mineralization in a <span class="hlt">porous</span> medium as a possible corrosion protection mechanism. Corrosion is a significant economic problem - recent reports evaluate the annual cost of metal corrosion as 3-4% of the gross domestic product (GDP), in both developed and developing countries. Corrosion control methods currently used are costly and unsustainable as they require the use of larger volumes of <span class="hlt">materials</span>, hazardous chemicals and regular inspections. As an alternative corrosion control method, bioinduced deposition of protective mineral layers has been proposed. Bioinduced precipitation of calcite has already been investigated for CO2 geological sequestration and soil improvement. To our knowledge, though, no numerical study of biomineralization for corrosion protection has been described yet. Our <span class="hlt">model</span> includes three phases - solid, biofilm and mobile water. In the latter the reactive elements are dissolved, which are involved in the precipitation and the biofilm growth. The equations that describe the pore water flow, chemical reactions in the mobile water, consumption of substrate and expulsion of metabolic products by the biofilm are briefly presented. Also, the changes in porosity and permeability of the <span class="hlt">porous</span> medium through biofilm growth and solids precipitation are included. Our main assumptions are that the biofilm is uniform, has a constant density and composition, that all chemical reactions except for substrate consumption occur in the mobile water, and that the precipitates are uniformly distributed on the surface of the solids. We validate the <span class="hlt">model</span> with simple analytical solutions and against experimental data. The metabolism of the micro-organisms introduces changes in the physical and chemical characteristics of the environment, such as concentrations of chemicals and pH levels. As an extension to the <span class="hlt">model</span>, we couple these changes to the rates of biofilm growth and precipitation rates. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/771502','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/771502"><span id="translatedtitle">The Consistent Kinetics Porosity (CKP) <span class="hlt">Model</span>: A Theory for the Mechanical Behavior of Moderately <span class="hlt">Porous</span> Solids</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>BRANNON,REBECCA M.</p> <p>2000-11-01</p> <p>A theory is developed for the response of moderately <span class="hlt">porous</span> solids (no more than {approximately}20% void space) to high-strain-rate deformations. The <span class="hlt">model</span> is consistent because each feature is incorporated in a manner that is mathematically compatible with the other features. Unlike simple p-{alpha} <span class="hlt">models</span>, the onset of pore collapse depends on the amount of shear present. The user-specifiable yield function depends on pressure, effective shear stress, and porosity. The elastic part of the strain rate is linearly related to the stress rate, with nonlinear corrections from changes in the elastic moduli due to pore collapse. Plastically incompressible flow of the matrix <span class="hlt">material</span> allows pore collapse and an associated macroscopic plastic volume change. The plastic strain rate due to pore collapse/growth is taken normal to the yield surface. If phase transformation and/or pore nucleation are simultaneously occurring, the inelastic strain rate will be non-normal to the yield surface. To permit hardening, the yield stress of matrix <span class="hlt">material</span> is treated as an internal state variable. Changes in porosity and matrix yield stress naturally cause the yield surface to evolve. The stress, porosity, and all other state variables vary in a consistent manner so that the stress remains on the yield surface throughout any quasistatic interval of plastic deformation. Dynamic loading allows the stress to exceed the yield surface via an overstress ordinary differential equation that is solved in closed form for better numerical accuracy. The part of the stress rate that causes no plastic work (i.e-, the part that has a zero inner product with the stress deviator and the identity tensor) is given by the projection of the elastic stressrate orthogonal to the span of the stress deviator and the identity tensor.The <span class="hlt">model</span>, which has been numerically implemented in MIG format, has been exercised under a wide array of extremal loading and unloading paths. As will be discussed in a companion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PhDT.......228C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008PhDT.......228C&link_type=ABSTRACT"><span id="translatedtitle">Design, synthesis, and characterization of <span class="hlt">materials</span> for controlled line deposition, environmental remediation, and doping of <span class="hlt">porous</span> manganese oxide <span class="hlt">material</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calvert, Craig A.</p> <p></p> <p>This thesis covers three topics: (1) coatings formed from sol-gel phases, (2) environmental remediation, and (3) doping of a <span class="hlt">porous</span> manganese oxide. Synthesis, characterization, and application were investigated for each topic. Line-formations were formed spontaneously by self-assembly from vanadium sol-gels and other metal containing solutions on glass substrates. The solutions were prepared by the dissolution of metal oxide or salt in water. A more straightforward method is proposed than used in previous work. Analyses using optical microscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy showed discreet lines whose deposition could be controlled by varying the concentration. A mechanism was developed from the observed results. Microwave heating, the addition of graphite rods, and oxidants, can enhance HCB remediation from soil. To achieve remediation, a TeflonRTM vessel open to the atmosphere along with an oxidant, potassium persulfate (PerS) or potassium hydroxide, along with uncoated or aluminum oxide coated, graphite rods were heated in a research grade microwave oven. Microwave heating was used to decrease the heating time, and graphite rods were used to increase the absorption of the microwave energy by providing thermal centers. The results showed that the percent HCB removed was increased by adding graphite rods and oxidants. Tungsten, silver, and sulfur were investigated as doping agents for K--OMS-2. The synthesis of these <span class="hlt">materials</span> was carried out with a reflux method. The doping of K--OMS-2 led to changes in the properties of a tungsten doped K--OMS-2 had an increased resistivity, the silver doped <span class="hlt">material</span> showed improved epoxidation of trans-stilbene, and the addition of sulfur produced a paper-like <span class="hlt">material</span>. Rietveld refinement of the tungsten doped K--OMS-2 showed that the tungsten was doped into the framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EML....11..815K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EML....11..815K"><span id="translatedtitle">Poly L-lysine (PLL)-mediated <span class="hlt">porous</span> hematite clusters as anode <span class="hlt">materials</span> for improved Li-ion batteries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Kun-Woo; Lee, Sang-Wha</p> <p>2015-09-01</p> <p><span class="hlt">Porous</span> hematite clusters were prepared as anode <span class="hlt">materials</span> for improved Li-ion batteries. First, poly-L-lysine (PLL)-linked Fe3O4 was facilely prepared via cross-linking between the positive amine groups of PLL and carboxylate-bound Fe3O4. The subsequent calcination transformed the PLL-linked Fe3O4 into <span class="hlt">porous</span> hematite clusters (Fe2O3@PLL) consisting of spherical α-Fe2O3 particles. Compared with standard Fe2O3, Fe3O4@PLL exhibited improved electrochemical performance as anode <span class="hlt">materials</span>. The discharge capacity of Fe2O3@PLL was retained at 814.7 mAh g-1 after 30 cycles, which is equivalent to 80.4% of the second discharge capacity, whereas standard Fe2O3 exhibited a retention capacity of 352.3 mAh g-1. The improved electrochemical performance of Fe2O3@PLL was mainly attributed to the <span class="hlt">porous</span> hematite clusters with mesoporosity (20-40 nm), which was beneficial for facilitating ion transport, suggesting a useful guideline for the design of <span class="hlt">porous</span> architectures with higher retention capacity. [Figure not available: see fulltext.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. Their policies may differ from this site.</small> </div> </center> <div id="footer-wrapper"> <div class="footer-content"> <div id="footerOSTI" class=""> <div class="row"> <div class="col-md-4 text-center col-md-push-4 footer-content-center"><small><a href="http://www.science.gov/disclaimer.html">Privacy and Security</a></small> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center col-md-pull-4 footer-content-left"> <img src="https://www.osti.gov/images/DOE_SC31.png" alt="U.S. Department of Energy" usemap="#doe" height="31" width="177"><map style="display:none;" name="doe" id="doe"><area shape="rect" coords="1,3,107,30" href="http://www.energy.gov" alt="U.S. Deparment of Energy"><area shape="rect" coords="114,3,165,30" href="http://www.science.energy.gov" alt="Office of Science"></map> <a ref="http://www.osti.gov" style="margin-left: 15px;"><img src="https://www.osti.gov/images/footerimages/ostigov53.png" alt="Office of Scientific and Technical Information" height="31" width="53"></a> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center footer-content-right"> <a href="http://www.osti.gov/nle"><img src="https://www.osti.gov/images/footerimages/NLElogo31.png" alt="National Library of Energy" height="31" width="79"></a> <a href="http://www.science.gov"><img src="https://www.osti.gov/images/footerimages/scigov77.png" alt="science.gov" height="31" width="98"></a> <a href="http://worldwidescience.org"><img src="https://www.osti.gov/images/footerimages/wws82.png" alt="WorldWideScience.org" height="31" width="90"></a> </div> </div> </div> </div> </div> <p><br></p> </div><!-- container --> </body> </html>