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Sample records for model porous materials

  1. On the sensitivity analysis of porous material models

    NASA Astrophysics Data System (ADS)

    Ouisse, Morvan; Ichchou, Mohamed; Chedly, Slaheddine; Collet, Manuel

    2012-11-01

    Porous materials are used in many vibroacoustic applications. Different available models describe their behaviors according to materials' intrinsic characteristics. For instance, in the case of porous material with rigid frame, and according to the Champoux-Allard model, five parameters are employed. In this paper, an investigation about this model sensitivity to parameters according to frequency is conducted. Sobol and FAST algorithms are used for sensitivity analysis. A strong parametric frequency dependent hierarchy is shown. Sensitivity investigations confirm that resistivity is the most influent parameter when acoustic absorption and surface impedance of porous materials with rigid frame are considered. The analysis is first performed on a wide category of porous materials, and then restricted to a polyurethane foam analysis in order to illustrate the impact of the reduction of the design space. In a second part, a sensitivity analysis is performed using the Biot-Allard model with nine parameters including mechanical effects of the frame and conclusions are drawn through numerical simulations.

  2. 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.

  3. Modeling heat transfer within porous multiconstituent materials

    NASA Astrophysics Data System (ADS)

    Niezgoda, Mathieu; Rochais, Denis; Enguehard, Franck; Rousseau, Benoit; Echegut, Patrick

    2012-06-01

    The purpose of our work has been to determine the effective thermal properties of materials considered heterogeneous at the microscale but which are regarded as homogenous in the macroscale environment in which they are used. We have developed a calculation code that renders it possible to simulate thermal experiments over complex multiconstituent materials from their numerical microstructural morphology obtained by volume segmentation through tomography. This modeling relies on the transient solving of the coupled conductive and radiative heat transfer in these voxelized structures.

  4. 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.

  5. 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.

  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 adsorption of liquid mixtures on porous materials.

    PubMed

    Monsalvo, Matias A; Shapiro, Alexander A

    2009-05-01

    The multicomponent potential theory of adsorption (MPTA), which was previously applied to adsorption from gases, is extended onto adsorption of liquid mixtures on porous materials. In the MPTA, the adsorbed fluid is considered as an inhomogeneous liquid with thermodynamic properties that depend on the distance from the solid surface (or position in the porous space). The theory describes the two kinds of interactions present in the adsorbed fluid, i.e. the fluid-fluid and fluid-solid interactions, by means of an equation of state and interaction potentials, respectively. The proposed extension of the MPTA onto liquids has been tested on experimental binary and ternary adsorption data. We show that, for the set of experimental data considered in this work, the MPTA model is capable of correlating binary adsorption equilibria. Based on binary adsorption data, the theory can then predict ternary adsorption equilibria. Good agreement with the theoretical predictions is achieved in most of the cases. Some limitations of the model are also discussed. PMID:19243781

  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. SCDAP/RELAP5 Modeling of Movement of Melted Material Through Porous Debris in Lower Head

    SciTech Connect

    Siefken, Larry James; Harvego, Edwin Allan

    2000-04-01

    A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material may permeate to near the bottom of a 1m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material was calculated to cause a 12% increase in the heat flux on the external surface of the lower head.

  10. SCDAP/RELAP5 modeling of movement of melted material through porous debris in lower head

    SciTech Connect

    L. J. Siefken; E. A. Harvego

    2000-04-02

    A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material may permeate to near the bottom of a 1m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material was calculated to cause a 12% increase in the heat flux on the external surface of the lower head.

  11. Porous Organic Molecular Materials

    SciTech Connect

    Tian, Jian; Thallapally, Praveen K.; McGrail, B. Peter

    2012-01-01

    Most nanoporous materials with molecular-scale pores are extended frameworks composed of directional covalent or coordination bonding, such as porous metal-organic frameworks and organic network polymers. By contrast, nanoporous materials comprised of discrete organic molecules, between which there are only weak non-covalent interactions, are seldom encountered. Indeed, most organic molecules pack efficiently in the solid state to minimize the void volume, leading to non-porous materials. In recent years, a significant number of nanoporous organic molecular materials, which may be either crystalline or amorphous, have been confirmed by the studies of gas adsorption and they are surveyed in this Highlight. In addition, the possible advantages of porous organic molecular materials over porous networks are discussed.

  12. 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.

  13. 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.

  14. 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

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    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), 10.1103/PhysRevE.56.1934]. 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.

  17. 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

  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. SCDAP/RELAP5 Modeling of Movement of Melted Material through Porous Debris in Lower Head (Rev. 2)

    SciTech Connect

    Siefken, Larry James

    1999-10-01

    A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material my permeate in about 120 s to the bottom of a 1 m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material at the bottom of the debris bed decreases the thermal resistance of the interface between the debris bed and the lower head. This report is a revision of the report with the identifier of INEEL/EXT-98-01178 REV 1, entitled "SCDAP/RELAP5 Modeling of Movement of Melted Material Through Porous Debris in Lower Head."

  1. Macro-meso two-scale model for predicting the VOC diffusion coefficients and emission characteristics of porous building materials

    NASA Astrophysics Data System (ADS)

    Xiong, Jianyin; Zhang, Yinping; Wang, Xinke; Chang, Dongwu

    Through the observation of the pore structure and mercury intruding porosimetry (MIP) experiments of some typical porous building materials, we found that the diffusion coefficient of the material can be expressed by that of a representative elementary volume (REV) in which the pore structure can be simplified as a connection in series of macro and meso pores. Based upon that, a macro-meso two-scale model for predicting the diffusion coefficient of porous building materials is proposed. In contrast to the traditional porous mass transfer model for determining the diffusion coefficient described in the literature [Blondeau, P., Tiffonnet, A.L., Damian, A., Amiri, O., Molina, J.L., 2003. Assessment of contaminant diffusivities in building materials from porosimetry tests. Indoor Air 13, 302-310; Seo, J., Kato, S., Ataka, Y., Zhu, Q., 2005. Evaluation of effective diffusion coefficient in various building materials and absorbents by mercury intrusion porosimetry. In Proceedings of the Indoor Air, Beijing, China, pp. 1854-1859], the proposed model relates the volatile organic compound (VOC) diffusion coefficient of building material not only to the porosity of the building material, but also to the pore size distribution and pore connection modes. To verify the model, a series of experiments of VOC emissions of three types of medium-density board were conducted. The comparison of the model and experimental results shows that the proposed model agrees much better with the experimental results than the traditional models in the literature. More validation for other building materials is needed. The proposed model is useful for predicting the VOC diffusion coefficient of porous building materials and for developing low VOC emission building materials.

  2. 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. PMID:25314558

  3. 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.

  4. 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

    2016-06-01

    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. PMID:26260268

  5. 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.

  6. 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.

  7. Equation of State and Hugoniot locus for porous materials: P--α model revisited

    NASA Astrophysics Data System (ADS)

    Menikoff, Ralph; Kober, Edward

    1999-06-01

    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 F(V,T,φ) = F_s(V,T) + B(φ) where the equilibrium volume fraction φ_eq is determined by minimizing F, phi.e., the condition partial_φ F = 0. For many cases, a Hayes EOS for the pure solid F_s(V,T) is adequate. This provides a thermodynamically consistent framework for the P--α model. For this form of EOS, we show that the volume fraction has a similar effect to an endothermic reaction in that the partial Hugoniot loci with fixed φ are shifted to the left in the (V,P)-plane with increasing φ. 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 per cent 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.

  8. 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.

  9. Ultrasonic Nondestructive Characterization of Porous Materials

    NASA Astrophysics Data System (ADS)

    Yang, Ningli

    2011-12-01

    Wave propagation in porous media is studied in a wide range of technological applications. In the manufacturing industry, determining porosity of materials in the manufacturing process is required for strict quality control. In the oil industry, acoustic signals and seismic surveys are used broadly to determine the physical properties of the reservoir rock which is a porous media filled with oil or gas. In porous noise control materials, a precise prediction of sound absorption with frequency and evaluation of tortuosity are necessary. Ultrasonic nondestructive methods are a very important tool for characterization of porous materials. The dissertation deals with two types of porous media: materials with relatively low and closed porosity and materials with comparatively high and open porosity. Numerical modeling, Finite Element simulations and experimental characterization are all discussed in this dissertation. First, ultrasonic scattering is used to determine the porosity in porous media with closed pores. In order get a relationship between the porosity in porous materials and ultrasonic scattering independently and to increase the sensitivity to obtain scattering information, ultrasonic imaging methods are applied and acoustic waves are focused by an acoustic lens. To verify the technique, engineered porous acrylic plates with varying porosity are measured by ultrasonic scanning and ultrasonic array sensors. Secondly, a laser based ultrasonic technique is explored for predicting the mechanical integrity and durability of cementitious materials. The technique used involves the measurement of the phase velocity of fast and slow longitudinal waves in water saturated cement paste. The slow wave velocity is related to the specimen's tortuosity. The fast wave speed is dependent on the elastic properties of porous solid. Experimental results detailing the generation and detection of fast and slow wave waves in freshly prepared and aged water-saturated cement samples

  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. Porous heat-insulation material

    SciTech Connect

    Chentemirov, M.G.; Dyachkovsky, F.S.; Enikolopov, N.S.; Gavrilov, J.A.; Gorbachev, J.G.; Kudinova, O.I.; Lukienko, E.P.; Maklakova, T.A.; Novokshonova, L.A.; Parsamian, L.O.; Poluyanov, A.F.

    1980-12-23

    A porous heat-insulation material comprising blocks molded from granules of a porous mineral filler with a polyolefin coating is described. The coating thickness is 1/1000 to 1/25 of the average granule diameter; in contact regions, said granules are spaced from each other at a distance of from 0.5 to 2.0 of the coating thickness, and the mass ratio between said porous mineral filler and said polyolefin is 80-98:20-2, respectively. The material of this invention has a volume mass of from 60 to 250 kg/m/sup 3/. The material features a high plasticity (its flexural strength is as high as 3-4 kgf/cm/sup 2/). The compression strength of the material is 9-1 kgf/cm/sup 2/. The material also has a low thermal conductivity; its thermal conductivity coefficient is 0.03-0.04 kcal/M/h//sup 0/C. The material is substantially non-combustible.

  12. 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.

  13. Lower-bound and Upper-bound Rigid-plastic Constitutive Models for Porous Materials:Comparison and Examination

    NASA Astrophysics Data System (ADS)

    Yin, Yajun; Xue, Mingde; Yu, Shouwen

    A lower bound rigid plastic constitutive model for porous materials has been published recently, but its reliability and accuracy is still kept unknown. Therefore, this paper is confined to examine this model by comparing it with other ones such as the upper bound one and experimental-based one. Under three loading states (i.e. uniaxial stress condition, biaxial equal stress condition and uniaxial strain condition), the sintered copper’s ductility, compressibility, strength property, deformation characteristics, stress˜strain curves and damage evolution process predicted by these models are systematically compared. The advantage of the lower bound model in describing the yield property and its limitations in evaluating the ductility, compressibility, strength variation and damage evolution process of porous materials are clarified. Systematical analysis reveals that these limitations may be attributed to the short of void interaction mechanism in the lower bound model. This discovery lays the foundation for further improvement and modification of the lower bound model in the future research.

  14. Theoretical Equations of State for Porous/Granular Materials

    NASA Astrophysics Data System (ADS)

    Boettger, Jonathan

    2013-06-01

    Although the equation of state (EOS) for a porous/granular material is identical to the EOS for the equivalent non-porous material, the requirement that the EOS must provide a realistic model of the material in its porous/granular state adds additional challenges for EOS modelers. These difficulties can be divided into two broad categories. First, dynamic processes often drive porous/granular materials through regions of thermodynamic phase space that are poorly described by standard wide-ranging tabular EOS. Second, for materials that are only available in a granular form, it can be difficult to accurately measure the material properties/parameters that are routinely used to constrain a theoretical EOS. This talk will attempt to describe in some detail the many challenges posed to EOS modelers by porous/granular materials. Work supported by the U.S. Dept. of Energy under contract DE-AC52-06NA25396.

  15. Uniaxial deformation of a soft porous material

    NASA Astrophysics Data System (ADS)

    MacMinn, Chris; Dufresne, Eric; Wettlaufer, John

    2015-11-01

    Compressing a porous material will decrease the volume of pore space, driving fluid out. Similarly, injecting fluid into a porous material will drive mechanical deformation, 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 linear elasticity and then further linearizing in the strain. This is a good model for very small deformations, but it becomes increasingly inappropriate as deformations grow larger, and moderate to large deformations are common in the context of phenomena such as swelling, damage, and extreme softness. Here, we compare the predictions of linear poroelasticity with those of a rigorous large-deformation framework in the context of two uniaxial model problems. We explore the error associated with the linear model in both steady and dynamic situations, as well as the impact of allowing the permeability to vary with the deformation.

  16. Tensile instabilities for porous plasticity models

    SciTech Connect

    BRANNON,REBECCA M.

    2000-02-29

    Several concepts (and assumptions) from the literature for porous metals and ceramics have been synthesized into a consistent model that predicts an admissibility limit on a material's porous yield surface. To ensure positive plastic work, the rate at which a yield surface can collapse as pores grow in tension must be constrained.

  17. Lattice simulation method to model diffusion and NMR spectra in porous materials.

    PubMed

    Merlet, Céline; Forse, Alexander C; Griffin, John M; Frenkel, Daan; Grey, Clare P

    2015-03-01

    A coarse-grained simulation method to predict nuclear magnetic resonance (NMR) spectra of ions diffusing in porous carbons is proposed. The coarse-grained model uses input from molecular dynamics simulations such as the free-energy profile for ionic adsorption, and density-functional theory calculations are used to predict the NMR chemical shift of the diffusing ions. The approach is used to compute NMR spectra of ions in slit pores with pore widths ranging from 2 to 10 nm. As diffusion inside pores is fast, the NMR spectrum of an ion trapped in a single mesopore will be a sharp peak with a pore size dependent chemical shift. To account for the experimentally observed NMR line shapes, our simulations must model the relatively slow exchange between different pores. We show that the computed NMR line shapes depend on both the pore size distribution and the spatial arrangement of the pores. The technique presented in this work provides a tool to extract information about the spatial distribution of pore sizes from NMR spectra. Such information is difficult to obtain from other characterisation techniques. PMID:25747093

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

    2016-04-01

    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

  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. 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

  8. 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. PMID:22990753

  9. 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. PMID:23145601

  10. 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

  11. Light scattering in porous materials: Geometrical optics and stereological approach

    NASA Astrophysics Data System (ADS)

    Malinka, Aleksey V.

    2014-07-01

    Porous material has been considered from the point of view of stereology (geometrical statistics), as a two-phase random mixture of solid material and air. Considered are the materials having the refractive index with the real part that differs notably from unit and the imaginary part much less than unit. Light scattering in such materials has been described using geometrical optics. These two - the geometrical optics laws and the stereological approach - allow one to obtain the inherent optical properties of such a porous material, which are basic in the radiative transfer theory: the photon survival probability, the scattering phase function, and the polarization properties (Mueller matrix). In this work these characteristics are expressed through the refractive index of the material and the random chord length distribution. The obtained results are compared with the traditional approach, modeling the porous material as a pack of particles of different shapes.

  12. 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

  13. 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.

  14. 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. PMID:25698040

  15. Biomass Growth and Clogging in Porous Media: From Microscale and Mesoscale Observations in Silicon Pore Imaging Elements to the Modeling of Aggregates in Network Models Using Material Mechanics

    NASA Astrophysics Data System (ADS)

    Dupin, H. J.; Mccarty, P. L.; Kitanidis, P. K.

    2002-05-01

    An apparatus for non-destructive continuous visualization of biological growth and clogging in porous media has been constructed. Silicon Pore Imaging Elements (micromodels featuring two-dimensional pore networks) were seeded with mixed cultures. A feed solution was then continuously forced through the SPIEs. Subsequently, several forms of biomass developped simultaneously: aggregates, biofilms and filaments ressembling mycellia. Clogging appeared mostly related to the presence of aggregates along preferential flow paths. Due to clogging, mesocale flow paths were modified, and flow was reversed in channels. A novel numerical model was then developped to investigate bioclogging of two-dimensional pore networks by aggregates. Each pore (channel) is seeded with initial biomass that consumes an electron donor and an electron acceptor according to dual Monod kinetics. Biomass is modeled as a continuous uniform isotropic hyperelastic material, whose expansion and deformation are governed by material mechanics stress-strain relations, unlike traditional approaches that use ad hoc empirical schemes. The Stokes flow, the advection-diffusion- reaction mass transport, and the biomass deformation partial differential equations are solved using finite elements. Simple networks are investigated to identify phenomena of interest: four channels of different width operating in parallel to study the effect of local heterogeneity; a periodic network to quantify the effects of distance from the injection point on clogging and substrate utilization; and square lattice 5 x 5 random width networks. Although square-lattice random-width networks are deemed better approximations of porous media, the simpler networks exhibit all the phenomena of interest, with the added advantage of these phenomena being decoupled. Results of numerical simulations for different network types under various boundary conditions show that aggregates have a far greater potential than biofilms to clog a porous

  16. Superhydrophobicity on nanostructured porous hydrophilic material

    NASA Astrophysics Data System (ADS)

    Jiang, Hong-Ren; Chan, Deng-Chi

    2016-04-01

    By applying laser oxidation, ablation, and plasma treatment to modify a surface of polydimethylsiloxane, we show that creating hydrophobic sites on an originally superhydrophilic nanostructured porous surface greatly changes the wetting properties of the surface. The modified surface may even become superhydrophobic while the ratio of added hydrophobic site to the surface is relatively low. The relation between the contact angles and the effect of hydrophobic sites is further tested in blade scraping method and a similar result is also obtained. This method to achieve superhydrophobicity on the hydrophilic nanostructured porous material may open possibilities for achieving superhydrophobicity and enable functional superhydrophobic surfaces with heterogeneous components.

  17. 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.

  18. 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. PMID:24619776

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Adhesion of liquids to porous materials and fibers

    NASA Astrophysics Data System (ADS)

    Trofimov, Artem

    This research is centered on the analysis of adhesion properties of porous materials and fibers of elliptical shapes. Composites are a unique class of materials having properties, which could not be achieved by either of the constituent materials alone. Composites with porous filler are put into service in buildings, roads, bridges, etc. Fiber-reinforced composites are actively involved in flight vehicles, automobiles, boats, and dozens of other products. In the first part of this study we developed a procedure for evaluation of adhesion of liquids to porous solids, where water, hexadecane and asphalt binder and different rocks were studied to illustrate the methodology. An experimental protocol to evaluate the work of adhesion, a characteristic thermodynamic parameter of the liquid/porous solid pair, was discussed and a mathematical model describing the kinetics of liquid penetration into inhomogeneous porous material was developed and used for interpretation of the experiments. The second part is devoted to the analysis of interactions of liquids with circular and elliptical wires. The behavior of menisci embracing the fiber in the capillary rise experiment was investigated. In particular, we study the profiles of the contact line around cylinders, contact angle, and the work of adhesion of a set of different liquids. Compared to the circular wires, elliptical wires produced taller menisci, hence the wetted area increases. It is expected that the kinetics of resin impregnation into a preforms made of elliptical fibers will significantly change.

  4. Activation of porous MOF materials

    DOEpatents

    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.

  5. Activation of porous MOF materials

    DOEpatents

    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.

  6. 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.

  7. (Fracture mechanics of porous materials)

    SciTech Connect

    Gray, L.J.

    1989-09-15

    The primary subject of this trip was the development of a boundary element/finite element analysis system for computational fracture mechanics. The procedures for merging the ORNL/Cornell University boundary element fracture code with the finite element program SESAM were agreed upon, and are currently being implemented. The adopted algorithm relies on the superelement capabilities of the SESAM code. Discussions were held with scientists at the Bergen Scientific Centre on the modeling of fractured rock. A project to develop realistic computer models of naturally occurring fracture patterns is being carried out by a geologist and a physicist; it is expected that these models can be employed in future environmental modeling work. 6 refs.

  8. Deformation Timescales of Porous Volcanic Materials

    NASA Astrophysics Data System (ADS)

    Quane, S.; Friedlander, B.; Robert, G.; Lynn, H.

    2007-12-01

    We describe results from 20 high-temperature, constant strain rate and constant load deformation experiments on natural pyroclastic materials. Experiments were run unconfined and under variable H2O confining pressures at temperatures between 650 and 900 C. Starting materials comprised 4.3 cm diameter, 6 cm length cores of sintered Rattlesnake Tuff rhyolite ash with starting porosities of 70 percent. Experimental displacement was controlled to achieve total strain values between 10 and 90 percent. In thin section, the deformed experimental end products exhibit striking similarities to all facies of natural welded pyroclastic rocks including variably flattened pumice fiamme and systematically deformed bubble wall shards. To quantify the amount of strain accumulation, we placed three manually rounded 1 cm diameter pumice lapilli at different heights in each experimental product. Axial ratios (x-axis dimension/y-axis dimension) of the deformed lapilli (fiamme) show a systematic increase with increased deformation. To further quantify strain, we measured flattening ratios of originally spherical bubble wall shards. These analyses are compared to similar measurements on natural samples to evaluate current methods of quantifying deformation in welded pyroclastic facies. Stress-strain and strain-time experimental results indicate that the glassy, porous aggregates have a strain- dependent rheology; the effective viscosity of the mixture increases non-linearly with decreasing porosity. Temperature, rather than stress is the dominant factor controlling the rheology of these materials. Results also indicate that the presence of moderate H2O pressure allows for viscous deformation (e.g., welding) to occur at significantly lower temperatures than in anhydrous conditions. Results from these experiments are used to develop a constitutive relationship in which the effective viscosity of the experimental cores is predicted using melt viscosity, sample porosity and an empirically

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Structure and Thermal Properties of Porous Geological Materials

    NASA Astrophysics Data System (ADS)

    Kirk, Simon; Williamson, David

    2011-06-01

    Understanding the behaviour of porous geological materials is important for developing models of the explosive loading of rock in mining applications. To this end it is essential to first characterise its complex internal structure. Knowing the structure shows how the properties of the component materials relate to the overall properties of rock. The structure and mineralogy of Gosford sandstone was investigated and this information was used to predict its thermal properties. The thermal properties of the material were measured experimentally and compared against these predictions.

  15. Shock compaction of a porous pyrotechnic material

    SciTech Connect

    Lee, L. M.; Schwarz, A. C.

    1980-01-01

    The results of an experimental program to generate Hugoniot data for an unreacted pyrotechnic material are discussed and the data presented. The program included both sample fabrication and experimental determination of stress-particle velocity Hugoniot data for the pyrotechnic, titanium hydride-potassium perchlorate (TiH/sub 2/-KClO/sub 4/), at two densities. The TiH/sub 2/-KClO/sub 4/, which was supplied as a powder mixture, was pressed to the desired bulk sample density and size using a ram and die technique. Samples were produced with nominal 2.02 or 2.27 g/cm/sup 3/ densities. Hugoniot data were generated on the porous pyrotechnic samples using standard flat plate impact techniques. The experimental program provided information defining the shock compaction behavior of porous TiH/sub 2/-KClO/sub 4/ up to 70 kbar. The Hugoniot data for both sample densities indicated full compaction was achieved in the 15 to 20 kbar stress range.

  16. Layer like porous materials with hierarchical structure.

    PubMed

    Roth, Wieslaw J; Gil, Barbara; Makowski, Wacław; Marszalek, Bartosz; Eliášová, Pavla

    2016-06-13

    Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks. PMID:26489452

  17. Porous materials with high negative Poisson’s ratios—a mechanism based material design

    NASA Astrophysics Data System (ADS)

    Kim, Kwangwon; Ju, Jaehyung; Kim, Doo-Man

    2013-08-01

    In an effort to tailor functional materials with customized anisotropic properties—stiffness and yield strain, we propose porous materials consisting of flexible mesostructures designed from the deformation of a re-entrant auxetic honeycomb and compliant mechanisms. Using an analogy between compliant mechanisms and a cellular material’s deformation, we can tailor the in-plane properties of mesostructures; low stiffness and high strain in one direction and high stiffness and low strain in the other direction. An analytical model is developed to obtain the effective moduli and yield strains of the porous materials by combining the kinematics of a rigid link mechanism and deformation of flexure hinges. A numerical technique is implemented with the analytical model for the nonlinear constitutive relations of the mesostructures and their strain-dependent Poisson’s ratios. A finite element analysis (FEA) is used to validate the analytical and numerical models. The designed moduli and yield strain of porous materials with an aluminum alloy are 2 GPa and 0.28% in one direction and 0.2 MPa and 28% in the other direction. These porous materials with mesostructures have high negative Poisson’s ratios, {\

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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...

  6. 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.

  7. 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.

  8. 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.

  9. Design of energy absorbing materials and composite structures based on porous shape memory alloys (SE)

    NASA Astrophysics Data System (ADS)

    Zhao, Ying

    Recently, attention has been paid to porous shape memory alloys. This is because the alloys show large and recoverable deformation, i.e. superelasticity and shape memory effect. Due to their light weight and potential large deformations, porous shape memory alloys have been considered as excellent candidates for energy absorption materials. In the present study, porous NiTi alloy with several different porosities are processed by spark plasma sintering (SPS). The compression behavior of the porous NiTi is examined with an aim of using it for a possible high energy absorbing material. Two models for the macroscopic compression behavior of porous shape memory alloy (SMA) are presented in this work, where Eshelby's inhomogeneous inclusion method is used to predict the effective elastic and superelastic behavior of a porous SMA based on the assumption of stress-strain curve. The analytical results are compared with experimental data for porous NiTi with 13% porosity, resulting in a reasonably good agreement. Based on the study upon porous NiTi, an energy absorbing composite structure made of a concentric NiTi spring and a porous NiTi rod is presented in this PhD dissertation. Both NiTi spring and porous NiTi rod are of superelastic grade. Ductile porous NiTi cylindrical specimens are fabricated by spark plasma sintering. The composite structure exhibits not only high reversible force-displacement behavior for small to intermediate loading but also high energy absorbing property when subjected to large compressive loads. A model for the compressive force-displacement curve of the composite structure is presented. The predicted curve is compared to the experimental data, resulting in a reasonably good agreement.

  10. 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 ...

  11. 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. PMID:23718554

  12. Structural and dynamic properties of confined water in nanometric model porous materials (8 Å⩽∅⩽40 Å)

    NASA Astrophysics Data System (ADS)

    Floquet, N.; Coulomb, J. P.; Dufau, N.; Andre, G.; Kahn, R.

    2004-07-01

    Structural and dynamic properties of confined water have been investigated by ‘‘in situ’’ neutron-scattering experiments. In the medium confinement regime (for MCM-41 host materials: 20 Å⩽∅⩽40 Å) confined water has rather similar properties to bulk (3d) water. The major difference concerns the solidification phase transition. Strong triple-point depression Δ T3t is observed and Δ T3t increases when decreasing the pore diameter ∅ (213 K⩽Δ T3t⩽233 K). Such a confined water behaves as a supercooled liquid phase. The ultra-confinement (AlPO 4-N zeolites: 8 Å⩽∅⩽12 Å), is seen to induce the structuration of the confined water and its stability at room temperature T=300 K due to commensurability effect with the AlPO 4-5 inner surface. No wetting phenomena are observed for both host materials, the silicic MCM-41 samples and the AlPO 4-N zeolite family.

  13. 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.

  14. Chemically modified and nanostructured porous silicon as a drug delivery material and device

    NASA Astrophysics Data System (ADS)

    Anglin, Emily Jessica

    This thesis describes the fabrication, chemical modification, drug release, and toxicity studies of nanostructured porous silicon for the purposes of developing a smart drug delivery device. The first chapter is an introductory chapter, presenting the chemical and physical properties of porous silicon, the concepts and issues of current drug delivery devices and materials, and how porous silicon can address the issues regarding localized and controlled drug therapies. The second chapter discusses chemical modifications of nanostructured porous Si for stabilizing the material in biologically relevant media while providing an extended release of a therapeutic in vitro. This chapter also demonstrates the utility of the porous silicon optical signatures for effectively monitoring drug release from the system and its applications for development of a self-reporting drug delivery device. In chapter three, the concept of providing a triggered release of a therapeutic from porous silicon microparticles through initiation by an external stimulus is demonstrated. The microparticles are chemically modified, and the release is enhanced by a short application of ultrasound to the particulate system. The effect of ultrasound on the drug release and particle size is discussed. Chapter four presents a new method for sustaining the release of a monoclonal antibody from the porous matrix of porous SiO2. The therapeutic is incorporated into the films through electrostatic adsorption and a slow release is observed in vitro. A new method of quantifying the extent of drug loading is monitored with interferometry. The last chapter of the thesis provides a basic in vivo toxicity study of various porous Si microparticles for intraocular applications. Three types of porous Si particles are fabricated and studied in a rabbit eye model. The toxicity studies were conducted by collaborators at the Shiley Eye Center, La Jolla, CA. This work, demonstrates the feasibility of developing a self

  15. 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.

  16. 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

  17. 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).

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. New approach for porous materials obtaining using centrifugal casting

    NASA Astrophysics Data System (ADS)

    Bălţătescu, O.; Axinte, M.; Barbu, G.; Manole, V.

    2015-11-01

    It has been presented different methods for obtaining porous materials, (mainly used for metallic foams) and highlighting a new technology developed in the Faculty of Materials science and engineering, of Iasi. Our technology for obtaining porous materials is called centrifugal casting for porous materials. This technology is included in the method number 8: co-pressing of a metal powder with a leachable powder being in the same time a newer approach in the porous materials field. This technology is currently in the developmental phase. Since now we made experiments on the metallic materials, aluminum alloys. The technology is briefly described in this paper. The obtained parts were used for making samples in order to characterize the properties of the materials. The cellular structure of metallic foams requires special precautions that must be taken in characterization and testing. In this paper we have characterized the samples structurally by its cell topology (open cells, closed cells), relative density, cell size and cell shape and anisotropy. Also it was used scanning electron microscopy (SEM) which is straightforward; the only necessary precaution is that relating to surface preparation.

  3. 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.

  4. 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.

  5. 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.

  6. Strain rate effects in porous materials

    SciTech Connect

    Lankford, J. Jr.; Dannemann, K.A.

    1998-12-31

    The behavior of metal foams under rapid loading conditions is assessed. Dynamic loading experiments were conducted in their laboratory using a split Hopkinson pressure bar apparatus and a drop weight tester; Strain rates ranged from 45 s{sup {minus}1} to 1200 s{sup {minus}1}. The implications of these experiments on open-cell, porous metals, and closed- and open-cell polymer foams are described. It is shown that there are two possible strain-rate dependent contributors to the impact resistance of cellular metals: (i) elastic-plastic resistance of the cellular metal skeleton, and (ii) the gas pressure generated by gas flow within distorted open cells. A theoretical basis for these implications is presented.

  7. In-situ probing of Low Density Porous Materials

    NASA Astrophysics Data System (ADS)

    Hawreliak, James

    2013-06-01

    The shock response of porous materials is of interest in High Energy Density Physics because the PdV heating from void closure allows off principle Hugoniot states for modeling many astrophysical processes. While continuum models exists of shockwave propagation in foams the relevant physical phenomena spans three different length scales: the micro-length scale defined by the pore size and length between solid structures in the foam (10 to 1000 nm), the shock front thickness which determines material and energy flow (0.1 to 100 nm), and the hydrodynamic length scale associated with the expanding spherical wave (>10 μm), all of which impact the shock response of the low density foam. With the advent of new HED experimental facilities for generating shockwaves at x-ray light sources this gives new tools for performing pump probe experiments to understand the microstructural response of low density materials. Currently, we have used x-ray radiograph to make Hugoniot EOS measurements the of shock compressed low density SiO2 and Carbon based foams. We will show recent result of measurements of experiments conducted on the Omega laser facility and discuss imaging shockwaves in low density foams on the soon to be commissioned DCS end station at APS and the MEC end station at LCLS. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. 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.

  9. 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

  10. A Two-Phase Model for Shocked Porous Explosive

    NASA Astrophysics Data System (ADS)

    Lambourn, Brian; Handley, Caroline

    2015-06-01

    Mesoscale calculations of hotspots created by a shock wave in a porous explosive show that the hotspots do not cool in times of order at least a microsecond. This suggests that single phase models of porosity like the snowplough model, which assume that a shocked porous explosive jumps to a point on the Hugoniot that is instantaneously in thermodynamic equilibrium, are not correct. A two-phased model of shocked porous explosive has been developed in which a small fraction of the material, representing the hotspots, has a high temperature but the bulk of the material is cooler than the temperature calculated by, for example, the snowplough model. In terms of the mean state of the material, it is shown that the two-phase model only minimally affects the pressure - volume and shock velocity - particle velocity plot of the Hugoniot, but that the mean state lies slightly off the equation of state surface. The results of the model will be compared with two dimensional mesoscale calculations.

  11. 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.

  12. Molecules with polymerizable ligands as precursors to porous doped materials

    SciTech Connect

    Hubert-Pfalzgraf, L.G.; Pajot, N.; Papiernik, R.; Parraud, S.

    1996-12-31

    Titanium and aluminum alkoxide derivatives with polymerizable ligands such as 2-(methacryloyloxy)ethylacetoacetate (HAAEMA), oleic acid and geraniol (HOGE) have been obtained. The various compounds have been characterized by FT-IR and NMR {sup 1}H. Copolymerization with styrene and divinylbenzene affords porous doped organic materials which have been characterized by scanning electron microscopy (SEM), elemental analysis, density measurements.

  13. 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.

  14. 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.

  15. 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.

  16. Development of materials and fabrication of porous and pebble bed beryllium multipliers

    NASA Astrophysics Data System (ADS)

    Davydov, D. A.; Solonin, M. I.; Markushkin, Yu. E.; Gorokhov, V. A.; Gorlevsky, V. V.; Nikolaev, G. N.

    2000-12-01

    Beryllium is considered to be a neutron multiplier material for the reference ITER breeding blanket. The main requirements for the porous beryllium multiplier for the breeding blanket are: (1) inherently open porosity within 20 ± 2% for easy removal of radioactive gases; (2) high thermal conductivity; (3) close contact with a stainless steel (SS) shell to provide high heat transfer. A beryllium multiplier can be fabricated by two different techniques: by manufacturing porous or pebble bed beryllium. The method designed (patent 2106931 RU) in SSC RF-VNIINM (Russia) provides for the production of porous beryllium conforming to the requirements mentioned above. For comparative fission tests and the optimization of breeding zone functional capabilities, porous (21.9%) and binary pebble bed (density=78%) beryllium multipliers were fabricated. DEMO breeding blanket models and a mock-up of fission (IVV-2M reactor) tests have been manufactured at SSC RF-VNIINM.

  17. The Tribological Efficiency and the Mechanism of Action of Nano-Porous Composition Base Brake Lining Materials

    NASA Astrophysics Data System (ADS)

    Kutelia, E. R.; Gventsadze, D. I.; Eristavil, B. G.; Maisuradze, N. I.; Tsurtsumia, O. O.; Gventsadze, L. D.; Olofsson, U.; Wahlström, J.; Olander, L.

    2011-12-01

    Based on the comparative analysis of the experimental values determined for the tribological parameters for the three novel nano-porous composition base and two conventional brake lining materials while friction with the grey cast iron disc, it was shown the considerable high tribological efficiency of the novel nano-porous composition base lining materials in comparison with the conventional (from EU and USA market) brake lining materials. The explanation is given to the action mechanism of nano-porous composition base brake lining material and its tribological efficiency basing on the "triple phase" tribo-pair model.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. A variational constitutive model for porous metal plasticity

    NASA Astrophysics Data System (ADS)

    Weinberg, K.; Mota, A.; Ortiz, M.

    2006-01-01

    This paper presents a variational formulation of viscoplastic constitutive updates for porous elastoplastic materials. The material model combines von Mises plasticity with volumetric plastic expansion as induced, e.g., by the growth of voids and defects in metals. The finite deformation theory is based on the multiplicative decomposition of the deformation gradient and an internal variable formulation of continuum thermodynamics. By the use of logarithmic and exponential mappings the stress update algorithms are extended from small strains to finite deformations. Thus the time-discretized version of the porous-viscoplastic constitutive updates is described in a fully variational manner. The range of behavior predicted by the model and the performance of the variational update are demonstrated by its application to the forced expansion and fragmentation of U-6%Nb rings.

  3. 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

  4. Nanocomposite Materials - Ferroelectric Nanoparticles Incorporated into Porous Matrix

    NASA Astrophysics Data System (ADS)

    Rysiakiewicz-Pasek, E.; Poprawski, R.; Ciżman, A.; Sieradzki, A.

    The aim of this work is to develop a technique of introducing selected ferroelectric materials (TGS, NaNO2, NaNO3, KNO3, ADP and KDP) into porous glasses with various average pore dimensions. The major efforts have been focused on the investigations of the influence of the pore size on physical properties and phase transition of nanocrystals embedded into porous matrix with different methods. The ferroelectrics have been introduced into porous glasses from the melt and a water solution. The results of electrical (dielectric, pyroelectric) and thermal (dilatometric and calorimetric) measurements have shown that the observed sequences of phase transitions in ferroelectric materials embedded into the porous glasses are similar to that in bulk crystals. The relationship between phase transition and melt temperatures versus average values of pore dimensions has been determined. The experimentally observed shift of phase transition temperatures is the superposition of the size effect and pressure effect created by the difference of thermal expansion coefficients of ferroelectrics nanoparticles and glass matrix.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Recent Advances on Fractal Modeling of Permeability for Fibrous Porous Media

    NASA Astrophysics Data System (ADS)

    Cai, Jianchao; Luo, Liang; Ye, Ran; Zeng, Xiangfeng; Hu, Xiangyun

    2015-03-01

    Permeability is an important hydraulic parameter for characterizing heat and mass transfer properties of fibrous porous media. However, it is difficult to be quantitatively predicted due to the complex and irregular pore structure of fibrous porous media. Fractal geometry has been verified to be an effective method for determining the permeability of fibrous porous media. In this study, recent works on the permeability of fibrous porous media by means of fractal geometry are reviewed, the advances for each presented fractal model are analyzed and summarized, parameter equations used in available fractal permeability models are also briefly compared and reviewed. Future work for more generalized permeability model of fibrous porous media need to conducted by considering the special characters of fibrous materials, uniform pore structure parameter model and the influence factor of capillary pressure, electrokinetic phenomena, etc.

  15. 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

  16. 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

  17. Supercritical nitrogen processing for the purification of reactive porous materials.

    PubMed

    Stadie, Nicholas P; Callini, Elsa; Mauron, Philippe; Borgschulte, Andreas; Züttel, Andreas

    2015-01-01

    Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml(-1), modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 Å. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride. PMID:26066492

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Solvent extraction of polychlorinated organic compounds from porous materials

    SciTech Connect

    Knowles, V.M.

    1988-07-19

    A method of reducing the level of hexachlorinated organic compounds selected from hexachloroethane, hexachlorobutadiene, hexachlorobenzene, or mixtures thereof to a non-hazardous level in a solid, porous DERAKANE vinyl ester resin, which has been previously used as the material of construction of a cell to produce chlorine, which vinyl ester resin was in contact with chlorine during chlorine manufacture is descried which comprises: (a) contacting the hexachlorinated compound-containing porous vinyl ester resin with an extraction solvent wherein the extraction solvent is selected from chloroform, carbon tetrachloride, trichlorethane, methyl chloroform, tetrachloroethane, perchloroethylene, benzene, toluene, xylene, acetone, methyl ethyl ketone, or mixtures thereof, at a temperature and for a time sufficient to remove the absorbed hexachlorinated organic compound; and (b) separating the hexachlorianated organic compound-containing extraction solvent and vinyl ester resin.

  3. Ceramic porous material and method of making same

    DOEpatents

    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.

  4. 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

  5. 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

  6. Measuring static thermal permeability and inertial factor of rigid porous materials (L).

    PubMed

    Sadouki, M; Fellah, M; Fellah, Z E A; Ogam, E; Sebaa, N; Mitri, F G; Depollier, C

    2011-11-01

    An acoustic method based on sound transmission is proposed for deducing the static thermal permeability and the inertial factor of porous materials having a rigid frame at low frequencies. The static thermal permeability of porous material is a geometrical parameter equal to the inverse trapping constant of the solid frame [Lafarge et al., J. Acoust. Soc. Am. 102, 1995 (1997)] and is an important characteristic of the porous material. The inertial factor [Norris., J. Wave Mat. Interact. 1, 365 (1986)] describes the fluid structure interactions in the low frequency range (1-3 kHz). The proposed method is based on a temporal model of the direct and inverse scattering problems for the propagation of transient audible frequency waves in a homogeneous isotropic slab of porous material having a rigid frame. The static thermal permeability and the inertial factor are determined from the solution of the inverse problem. The minimization between experiment and theory is made in the time domain. Tests are performed using industrial plastic foams. Experimental and theoretical data are in good agreement. Furthermore, the prospects are discussed. This method has the advantage of being simple, rapid, and efficient. PMID:22087887

  7. 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. PMID:25215740

  8. Modeling transport phenomena in porous media

    SciTech Connect

    Bear, J.

    1996-12-31

    The paper reviews the continuum approach to modelling the transport of mass, momentum and energy, of phases and of their components in a porous medium domain. The review begins with the definition of a porous medium, making use of the concept of a Representative Elementary Volume (REV) as a tool for overcoming the effect of the microscopic heterogeneity resulting from the presence of a solid matrix and a void space. The microscopic and macroscopic levels of description are defined. By averaging the description of a transport phenomenon at the microscopic level over an REV, using certain {open_quote}averaging rules{close_quote}, the macroscopic or continuum description of the same phenomenon is obtained. This methodology is first introduced in general terms for any extensive quantity, and then demonstrated for the transport of mass, momentum and energy. In the process of deriving the macroscopic models, expressions are presented also for the advective, dispersive and diffusive fluxes of extensive quantities that appear in them, in terms of averaged, measurable values of state variables.

  9. 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

  10. 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.

  11. MAS PFG NMR Studies of Mixtures in Porous Materials

    NASA Astrophysics Data System (ADS)

    Gratz, Marcel; Hertel, Stefan; Wehring, Markus; Schlayer, Stefan; Stallmach, Frank; Galvosas, Petrik

    2011-03-01

    Pulsed field gradient (PFG) and magic angle spinning (MAS) NMR techniques have been successfully combined for the study of mixture diffusion in porous materials. Using a modular setup of commercially available components, gradient pulses of up to ±2.6 T/m can be applied coinciding with fast sample rotation at the magic angle. Methods for the proper alignment of all components are presented along with protocols for MAS PFG NMR experiments. Finally, first diffusion measurements of n-hexane and benzene being adsorbed together in the metal-organic framework MOF-5 are presented.

  12. 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. PMID:26216701

  13. (De)compaction of porous viscoelastoplastic media: Model formulation

    NASA Astrophysics Data System (ADS)

    Yarushina, Viktoriya M.; Podladchikov, Yuri Y.

    2015-06-01

    A nonlinear viscoelastoplastic theory is developed for porous rate-dependent materials filled with a fluid in the presence of gravity. The theory is based on a rigorous thermodynamic formalism suitable for path-dependent and irreversible processes. Incremental evolution equations for porosity, Darcy's flux, and volumetric deformation of the matrix represent the simplest generalization of Biot's equations. Expressions for pore compressibility and effective bulk viscosity are given for idealized cylindrical and spherical pore geometries in an elastic-viscoplastic material with low pore concentration. We show that plastic yielding around pores leads to decompaction weakening and an exponential creep law. Viscous and plastic end-members of our model are consistent with experimentally verified models. In the poroelastic limit, our constitutive equations reproduce the exact Gassmann's relations, Biot's theory, and Terzaghi's effective stress law. The nature of the discrepancy between Biot's model and the True Porous Media theory is clarified. Our model provides a unified and consistent formulation for the elastic, viscous, and plastic cases that have previously been described by separate "end-member" models.

  14. 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.

  15. 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.

  16. Anomalous reactive transport in porous media: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Edery, Yaniv; Dror, Ishai; Scher, Harvey; Berkowitz, Brian

    2015-05-01

    We analyze dynamic behavior of chemically reactive species in a porous medium, subject to anomalous transport. In this context, we present transport experiments in a refraction-index-matched, three-dimensional, water-saturated porous medium. A pH indicator (Congo red) was used as either a conservative or a reactive tracer, depending on the tracer solution pH relative to that of the background solution. The porous medium consisted of an acrylic polymer material formed as spherical beads that have pH-buffering capacity. The magnitude of reaction during transport through the porous medium was related to the color change of the Congo red, via image analysis. Here, we focused on point injection of the tracer into a macroscopically uniform flow field containing water at a pH different from that of the injected tracer. The setup yielded measurements of the temporally evolving spatial (local-in-space) concentration field. Parallel experiments with the same tracer, but without reactions (no changes in pH), enabled identification of the transport itself to be anomalous (non-Fickian); this was quantified by a continuous time random walk (CTRW) formulation. A CTRW particle tracking model was then used to quantify the spatial and temporal migration of both the conservative and reactive tracer plumes. Model parameters related to the anomalous transport were determined from the conservative tracer experiments. An additional term accounting for chemical reaction was established solely from analysis of the reactant concentrations, and significantly, no other fitting parameters were required. The measurements and analysis emphasized the localized nature of reaction, caused by small-scale concentration fluctuations and preferential pathways. In addition, a threshold radius for pH-controlled reactive transport processes was defined under buffering conditions, which delineated the region in which reactions occurred rapidly.

  17. 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.

  18. 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

  19. Effects of grafting on porous metal ingrowth. A canine model.

    PubMed

    Lewis, C G; Jones, L C; Hungerford, D S

    1997-06-01

    Twenty-five mongrel dogs were studied using implantation of autograft, fresh-frozen allograft, and beta-tricalcium phosphate around a porous-coated chrome-cobalt plug in the distal femoral metaphysis; interference-fit and overreamed control specimens were also studied. Over the course of this 4-month study, bone ingrowth through the grouting materials into the center plug was noted for autologous, allograft, and ceramic specimens. Quantitatively, in terms of push-out strength and histology, there were no significant differences between grafted groups; significantly higher push-out strengths were attained in each grafted subgroup compared with nongrafted, overreamed control subjects. In the setting of uncemented revision total hip arthroplasty, bone-grafting is frequently required. Because of the limited availability of autogenous bone and the potential liabilities of allograft material, attention has been given to bone substitutes. On the basis of this preliminary study, bone ingrowth into a porous metal substrate has been documented to occur through autograft, allograft, or ceramic grouting agents. Within the limits of this nonloaded experimental model, it appears that these materials are comparable in terms of their osteoconductive capability. Even in the optimal laboratory situation, bone ingrowth does not appear to occur in a canine model across a nongrafted 2-mm gap with regularity over a 16-week period. PMID:9195322

  20. 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

  1. Gas-phase diffusion in porous media: Comparison of models

    SciTech Connect

    Webb, S.W.

    1998-09-01

    Two models are commonly used to analyze gas-phase diffusion in porous media in the presence of advection, the Advective-Dispersive Model (ADM) and the Dusty-gas Model (DGM). The ADM, which is used in TOUGH2, is based on a simple linear addition of advection calculated by Darcy`s law and ordinary diffusion using Fick`s law with a porosity-tortuosity-gas saturation multiplier to account for the porous medium. Another approach for gas-phase transport in porous media is the Dusty-Gas Model. This model applies the kinetic theory of gases to the gaseous components and the porous media (or dust) to combine transport due to diffusion and advection that includes porous medium effects. The two approaches are compared in this paper.

  2. Effective permeabilities for model heterogeneous porous media

    SciTech Connect

    Otevo, C.; Rusinek, I. ); Saez, A.E. )

    1990-01-01

    This paper presents a technique to evaluate effective absolute permeabilities for heterogeneous porous media. The technique is based on a perturbation analysis of the equations of motion of a slightly compressible fluid in a homogeneous porous medium at low Reynolds numbers. The effective permeabilities can be calculated once the local geometry of the heterogeneous medium is specified. The technique is used to evaluate two- and three-dimensional effective vertical permeabilities in porous media with shale intercalations, including the case in which the porous matrix is anisotropic.

  3. 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.

  4. 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.

  5. Porous graphene for high capacity lithium ion battery anode material

    NASA Astrophysics Data System (ADS)

    Wang, Yusheng; Zhang, Qiaoli; Jia, Min; Yang, Dapeng; Wang, Jianjun; Li, Meng; Zhang, Jing; Sun, Qiang; Jia, Yu

    2016-02-01

    Based on density functional theory calculations, we studied the Li dispersed on porous graphene (PG) for its application as Li ion battery anode material. The hybridization of Li atoms and the carbon atoms enhanced the interaction between Li atoms and the PG. With holes of specific size, the PG can provide excellent mobility with moderate barriers of 0.37-0.39 eV. The highest Li storage composite can be LiC0.75H0.38 which corresponds to a specific capacity of 2857.7 mA h/g. Both specific capacity and binding energy are significantly larger than the corresponding value of graphite, this makes PG a promising candidate for the anode material in battery applications. The interactions between the Li atoms and PG can be easily tuned by an applied strain. Under biaxial strain of 16%, the binding energy of Li to PG is increased by 17% compared to its unstrained state.

  6. 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

  7. Pore-network study of the characteristic periods in the drying of porous materials.

    PubMed

    Yiotis, Andreas G; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Yortsos, Yannis C

    2006-05-15

    We study the periods that develop in the drying of capillary porous media, particularly the constant rate (CRP) and the falling rate (FRP) periods. Drying is simulated with a 3-D pore-network model that accounts for the effect of capillarity and buoyancy at the liquid-gas interface and for diffusion through the porous material and through a boundary layer over the external surface of the material. We focus on the stabilizing or destabilizing effects of gravity on the shape of the drying curve and the relative extent of the various drying periods. The extents of CRP and FRP are directly associated with various transition points of the percolation theory, such as the breakthrough point and the main liquid cluster disconnection point. Our study demonstrates that when an external diffusive layer is present, the constant rate period is longer. PMID:16359693

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. 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. PMID:12241483

  12. Impact cratering and ejection of material on porous asteroids

    NASA Astrophysics Data System (ADS)

    Housen, K.; Sweet, W.

    2014-07-01

    increased lithostatic overburden stresses at large scales. When the target material has significant porosity, much of the crater volume forms by permanent compaction of void spaces. This compaction volume depends only on the crushing strength of the material, independent of size scale. The crater volume cannot be less than the volume created by compaction. Therefore, at large size scales, the cratering efficiency for porous materials levels out to a constant value rather than decreasing as in the usual gravity-dominated cratering. The transition to this asymptote represents the onset of compaction-dominated cratering. The presence of a compaction regime of cratering is important because, as our experiments and scaling arguments have shown, the mass of material that is emplaced in a crater's ejecta blanket drops sharply upon transition into the compaction regime. This causes craters to form without ejecting material outside the crater, resulting in an absence of ejecta blankets on porous asteroids, less erosion of existing pre-existing craters, and reduced gardening of the regolith by impacts. Our experiments now allow us to determine the conditions under which this compaction-dominated cratering and suppression of ejecta occur. In the presentation, these experiments will be summarized, we will show how they are consistent with observations of a lack of ejecta around large craters on Mathilde and Hyperion [2--4], and will discuss the mechanics of cratering on porous bodies. by the NASA Planetary Geology and Geophysics program.

  13. 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.

  14. 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.

  15. Freeze-drying of "pearl milk tea": A general strategy for controllable synthesis of porous materials.

    PubMed

    Zhou, Yingke; Tian, Xiaohui; Wang, Pengcheng; Hu, Min; Du, Guodong

    2016-01-01

    Porous materials have been widely used in many fields, but the large-scale synthesis of materials with controlled pore sizes, pore volumes, and wall thicknesses remains a considerable challenge. Thus, the controllable synthesis of porous materials is of key general importance. Herein, we demonstrate the "pearl milk tea" freeze-drying method to form porous materials 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 porous phosphate and oxide materials using different templates. The method is promising for the development of tunable porous materials for numerous applications of energy, environment, and catalysis, etc. PMID:27193866

  16. 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.

  17. Evaluation and Optimization of Porous and Hierarchically Porous Materials for Applications in Energy Storage and Conversion

    NASA Astrophysics Data System (ADS)

    Petkovich, Nicholas Daniel

    Materials with nm- and mum-scale pores are important in the design of efficient, safe, and versatile energy conversion and storage systems. In the research detailed in this thesis, the synthesis and testing of porous materials for lithium-ion battery anodes and for thermochemical fuel production are explored. The preparation, modification, and performance of various carbon and transition metal oxide composite materials for lithium-ion battery electrodes are discussed in the first part of this work. Of particular interest are TiO 2/carbon composites that possess a three-dimensionally ordered macroporous (3DOM) structure, and, in some instances, additional mesoporosity. By changing the chelating agent used to stabilize the precursor for TiO2, crystallites of TiO2 can either be localized on the surface of the 3DOM structure or buried within the carbon matrix. This positioning has important ramifications for the electrochemical properties of the materials. In addition, the content of carbon in the composite materials can be altered. For carbon-rich composites, improved Li+ insertion/extraction capacities are attained by changing the voltage window used for cycling. Carbon can also be removed altogether, allowing for the formation 3DOM TiO¬2 with good electrochemical properties Conversion of the 3DOM TiO2 to sodium titanate is demonstrated via the ambient pressure treatment of the 3DOM material in sodium hydroxide. Subsequent ion-exchange with H+ results in the formation of hydrogen titanate materials with extremely high surface areas. A remnant of the 3DOM structure remains in these materials. Cerium oxide, praseodymium oxide and perovskite oxide-based catalysts for the thermochemical conversion of solar energy and abundant feedstocks (H2O and CO2) into useable fuels (H2 and CO) are investigated in the second part of this work. All of these materials possess a 3DOM structure and have moderate surface areas intended to improve reaction kinetics. Mixed oxides containing

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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).

  3. Modelling the initial stage of porous alumina growth during anodization

    NASA Astrophysics Data System (ADS)

    Aryslanova, E. M.; Alfimov, A. V.; Chivilikhin, S. A.

    2013-05-01

    Artificially on the surface of aluminum there may be build a thick layer of Al2O3, which has a porous structure. In this paper we present a model of growth of porous alumina in the initial stage of anodizing, identifying dependencies anodizing parameters on the rate of growth of the film and the distance between the pores and as a result of the created model equations were found for changes in the disturbance of alumina for the initial stage of anodizing aluminum oxide porous border aluminum-alumina and alumina-electrolyte, with the influence of surface diffusion of aluminum oxide.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. Mechanical properties of sintered meso-porous silicon: a numerical model

    PubMed Central

    2012-01-01

    Because of its optical and electrical properties, large surfaces, and compatibility with standard silicon processes, porous silicon is a very interesting material in photovoltaic and microelectromechanical systems technology. In some applications, porous silicon is annealed at high temperature and, consequently, the cylindrical pores that are generated by anodization or stain etching reorganize into randomly distributed closed sphere-like pores. Although the design of devices which involve this material needs an accurate evaluation of its mechanical properties, only few researchers have studied the mechanical properties of porous silicon, and no data are nowadays available on the mechanical properties of sintered porous silicon. In this work we propose a finite element model to estimate the mechanical properties of sintered meso-porous silicon. The model has been employed to study the dependence of the Young’s modulus and the shear modulus (upper and lower bounds) on the porosity for porosities between 0% to 40%. Interpolation functions for the Young’s modulus and shear modulus have been obtained, and the results show good agreement with the data reported for other porous media. A Monte Carlo simulation has also been employed to study the effect of the actual microstructure on the mechanical properties. PMID:23107474

  10. New Carbon-Based Porous Materials with Increased Heats of Adsorption for Hydrogen Storage

    SciTech Connect

    Snurr, Randall Q.; Hupp, Joseph T.; Kanatzidis, Mercouri G.; Nguyen, SonBinh T.

    2014-11-03

    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 porous materials that act as “sponges” to take up large quantities of hydrogen without the need for extremely high pressures. The materials must meet many requirements to make this possible. This project aimed to develop two related classes of porous materials to meet these requirements. All materials were synthesized from molecular constituents in a building-block approach, which allows for the creation of an incredibly wide variety of materials in a tailorable fashion. The materials 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 modeling played a key role as a guide to experiment throughout the project. A major accomplishment of the project was the development of a material with record hydrogen uptake at cryogenic temperatures. Although the ultimate goal was materials 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 material was originally sketched on paper based on a hypothesis that extended framework struts would yield materials with excellent hydrogen storage properties. However, before starting the synthesis, we used molecular modeling to assess the performance of the material for hydrogen uptake

  11. 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.

  12. Pore-Scale Simulation for Predicting Material Transport Through Porous Media

    SciTech Connect

    Goichi Itoh; Jinya Nakamura; Koji Kono; Tadashi Watanabe; Hirotada Ohashi; Yu Chen; Shinya Nagasaki

    2002-07-01

    Microscopic models of real-coded lattice gas automata (RLG) method with a special boundary condition and lattice Boltzmann method (LBM) are developed for simulating three-dimensional fluid dynamics in complex geometry. Those models enable us to simulate pore-scale fluid dynamics that is an essential part for predicting material transport in porous media precisely. For large-scale simulation of porous media with high resolution, the RLG and LBM programs are designed for parallel computation. Simulation results of porous media flow by the LBM with different pressure gradient conditions show quantitative agreements with macroscopic relations of Darcy's law and Kozeny-Carman equation. As for the efficiency of parallel computing, a standard parallel computation by using MPI (Message Passing Interface) is compared with the hybrid parallel computation of MPI-node parallel technique. The benchmark tests conclude that in case of using large number of computing node, the parallel performance declines due to increase of data communication between nodes and the hybrid parallel computation totally shows better performance in comparison with the standard parallel computation. (authors)

  13. 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.

  14. The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications

    NASA Astrophysics Data System (ADS)

    Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

    2014-04-01

    Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

  15. 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.

  16. 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.

  17. Quantifying Biofilm in Porous Media Using Rock Physics Models

    NASA Astrophysics Data System (ADS)

    Alhadhrami, F. M.; Jaiswal, P.; Atekwana, E. A.

    2012-12-01

    Biofilm formation and growth in porous rocks can change their material properties such as porosity, permeability which in turn will impact fluid flow. Finding a non-intrusive method to quantify biofilms and their byproducts in rocks is a key to understanding and modeling bioclogging in porous media. Previous geophysical investigations have documented that seismic techniques are sensitive to biofilm growth. These studies pointed to the fact that microbial growth and biofilm formation induces heterogeneity in the seismic properties. Currently there are no rock physics models to explain these observations and to provide quantitative interpretation of the seismic data. Our objectives are to develop a new class of rock physics model that incorporate microbial processes and their effect on seismic properties. Using the assumption that biofilms can grow within pore-spaces or as a layer coating the mineral grains, P-wave velocity (Vp) and S-wave (Vs) velocity models were constructed using travel-time and waveform tomography technique. We used generic rock physics schematics to represent our rock system numerically. We simulated the arrival times as well as waveforms by treating biofilms either as fluid (filling pore spaces) or as part of matrix (coating sand grains). The preliminary results showed that there is a 1% change in Vp and 3% change in Vs when biofilms are represented discrete structures in pore spaces. On the other hand, a 30% change in Vp and 100% change in Vs was observed when biofilm was represented as part of matrix coating sand grains. Therefore, Vp and Vs changes are more rapid when biofilm grows as grain-coating phase. The significant change in Vs associated with biofilms suggests that shear velocity can be used as a diagnostic tool for imaging zones of bioclogging in the subsurface. The results obtained from this study have significant implications for the study of the rheological properties of biofilms in geological media. Other applications include

  18. 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.

  19. An analytical model for permeability of isotropic porous media

    NASA Astrophysics Data System (ADS)

    Yang, Xiaohu; Lu, Tian Jian; Kim, Tongbeum

    2014-06-01

    We demonstrate that permeability of isotropic porous media e.g., open-cell foams can be analytically presented as a function of two morphological parameters: porosity and pore size. Adopting a cubic unit cell model, an existing tortuosity model from the branching algorithm method is incorporated into a generalized permeability model. The present model shows that dimensionless permeability significantly increases as the porosity of isotropic porous media and unifies the previously reported data in a wide range of porosity (ɛ=0.55-0.98) and pore size (Dp=0.254 mm-5.08 mm).

  20. Investigation of using a Porous Media Approximation for Flow and Heat Transfer through the Nuclear Materials Storage Facility Drywell Array

    SciTech Connect

    Bernardin, J.D.; Gregory, W.S.; Owen, A.C.

    1999-04-21

    The Nuclear Materials Storage Facility (NMSF) is being renovated to provide a safe and secure long-term facility at Los Alamos National Laboratory to store nuclear materials. The concept for storage uses vertical tubes that are called drywells that have nuclear bearing canisters inside the tubes. The NMSF facility may use up to 370 of these tubes containing up to 10 canisters producing 15 W each. Analysts at the Laboratory wish to use CFD computer codes to predict the flow and thermal effects of air flow through the facility and the tube array. However, the complexity and large number of storage tubes precludes modeling the facility in enough detail to resolve the boundary layers around each and every tube. Therefore, certain approximations have to be made. A major approximation that has been used in this modeling effort has been to simulate the array of tubes as a porous media, The assumption-in the use of porous media is that the resistance of the drywells can be accounted for in a general way. The purpose of this study is to evaluate the suitability of the porous media approximation for modeling the tube array in the NMSF. In this study we will compare porous media models results with results from models that resolve the boundary layer around tubes. Finally, we offer a compromise modeling approach to address with this problem.

  1. 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. PMID:23386212

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Exploring with simulations the transport properties of multi-scale porous materials

    NASA Astrophysics Data System (ADS)

    Hyväluoma, Jari; Mattila, Keijo; Puurtinen, Tuomas; Timonen, Jussi

    2015-04-01

    The internal structure of many natural porous materials such as soils and carbonate rocks involves multiple length scales. This severely hinders the research relating structure and transport properties: typically laboratory experiments cannot distinguish contributions from individual scales while computer simulations cannot capture multiple scales due to limited computational resources. 3D imaging and image-based fluid flow simulations are increasingly used for studying the pore-scale transport processes. Combining imaging with pore-scale flow simulation techniques, e.g. the lattice Boltzmann method, provides direct means to quantify pore-scale transport processes. However, pore-scale computer simulations have not really been able to capture multiple scales due to the limited size of the simulation system. We show here that the current computational resources and software techniques already allow transport simulations in domains beyond the realms of current imaging techniques, and, more importantly, enable numerical experiments in multi-scale porous materials. We were able to simulate single-phase fluid flow with the lattice Boltzmann method in a synthetic x-ray-tomography image taken from the set of world's largest 3D images of a porous material [1]. The used image has 163843 image voxels and porosity of 0.134 (i.e., 5.9 - 1011 pore voxels) and it represents the microstructure of Fontainebleau sandstone. While the modelled sandstone image is rather homogeneous and therefore does not really represent a multiscale porous material, from a computational point of view it serves the purpose of demonstrating the power of contemporary software and hardware techniques. The simulation was executed at the Edinburgh Parallel Computing Centre on the ARCHER supercomputer ranked number 25 among all supercomputers. ARCHER has 3008 computing nodes each of which has two 12-core Ivy Bridge 2.7 GHz CPUs and 64 GB of memory providing 1.67 Petaflops of theoretical peak performance. The

  7. 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

  8. 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

  9. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. 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. PMID:12051421

  13. 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.

  14. Overlimiting current and water purification in porous materials

    NASA Astrophysics Data System (ADS)

    Deng, Daosheng; Aouad, Wassim; Schlumpberger, Sven; Bazant, Martin Z.

    2012-11-01

    Salt transport in bulk electrolytes occurs by diffusion and convection, but in microfluidic devices and porous media, the presence of charged side walls leads to additional surface transport mechanisms, surface conduction and electro-osmotic flows, which become more important as the bulk salt concentration decreases. As a result, it is possible to exceed the diffusion-limited current to a membrane or electrode. In this work, we present experimental observations of over-limiting current to an ion-exchange membrane through a porous glass frit with submicron pores. Under this operation conditions, we also demonstrate the continuous extraction of depleted solution for water purification, including removing heavy metal ions, filtrating aggregated particles and reducing dye concentration. The porous media pave the way for practical water desalination and purification.

  15. 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

  16. 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).

  17. Non-Darcian forced convection analysis in an annulus partially filled with a porous material

    SciTech Connect

    Chikh, S.; Boumedien, A.; Bouhadef, K.; Lauriat, G.

    1995-12-01

    Numerical solutions are presented for fully developed forced convection in concentric annuli partially filled with a porous medium. The porous medium is attached at the inner cylinder, which is maintained at uniform heat flux or at uniform wall temperature while the outer cylinder is adiabatic. The Brinkman-Forchheimer-extended Darcy model was used to model the flow inside the porous medium. The dependence of the fluid flow and heat transfer on several parameters of the problem is thoroughly documented. The inertia coefficient at which the inertial effects reduce the flow rate by 5% is determined as a function of the Darcy number for various thicknesses of the porous substrate. It is also shown that a critical thickness at which the value of the Nusselt number reaches a minimum does not exist if the effective thermal conductivity of the fluid-saturated porous medium is much higher than the fluid conductivity.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. Estimation of the effects of longitudinal temperature gradients caused by frictional heating on the solute retention using fully porous and superficially porous sub-2μm materials.

    PubMed

    Fekete, Szabolcs; Fekete, Jenő; Guillarme, Davy

    2014-09-12

    In this study, the retention changes induced by frictional heating were evaluated for model small compounds (150-190Da) and a small protein, namely insulin (5.7kDa). For this purpose, the effect of longitudinal temperature gradient caused by frictional heating was experimentally dissociated from the combined effect of pressure and frictional heating, by working either in constant and variable inlet pressure modes. Various columns packed with core-shell and fully porous sub-2μm particles were tested. It appears that frictional heating was less pronounced on the column packed with smallest core-shell particles (1.3μm), compared to the ones packed with core-shell and fully porous particles of 1.7-1.8μm. This observation was attributed to the low permeability of this material and the fact that it can only be employed in a restricted flow rate range, thus limiting the generated heat power. In addition, the thermal conductivity of the solid silica core of superficially porous particles (1.4W/m/K) is known to be much larger than that of fully porous silica. Then, the heat dissipation is improved. However, if systems with higher pressure capability would be available and the mechanical stability of 1.3μm core-shell material was extended to e.g. 2000bar, the retention would be more severely impacted. At 2000bar, ∼4.4W heat power and +30°C increase at column outlet temperature is expected. Last but not least, when analyzing large molecules, the impact of pressure overcomes the frictional heating effects. This was demonstrated in this study with insulin (∼5.7kDa). PMID:25069746

  5. 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

  6. 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

  7. Controlled high-rate-strain shear bands in inert and reactant porous materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, V. F.

    1998-07-01

    Shear localization is considered as one of the main reasons for initiation of chemical reaction in energetic materials under dynamic loading. However despite of widely spread recognition of the importance of rapid shear flow the shear bands in porous heterogeneous materials 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 strain controlled conditions, was initially proposed by Nesterenko et al., 1989 for solid inert materials and then modified by Nesterenko, Meyers et al., 1994 to fit porous inert and energetic materials. The method allows to reproduce the array of shear bands with shear strains 10-100 and strain rate 107s-1. Experimental results are presented for inert materials (granular, fractured ceramics) and for reactant porous mixtures (Nb-Si, Ti-Si, Ti-graphite and Ti-ultrafine diamond).

  8. 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

  9. 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

  10. 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.

  11. A General 3-D Methodology for Quasi-Static Simulation of Drainage and Imbibition: Application to Highly Porous Fibrous Materials

    NASA Astrophysics Data System (ADS)

    Riasi, S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.

    2013-12-01

    Micro-scale modeling of multiphase flow in porous media is critical to characterize porous materials. Several modeling techniques have been implemented to date, but none can be used as a general strategy for all porous media applications due to challenges presented by non-smooth high-curvature 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 modeling (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. We have developed a general, stable and fast methodology to model multi-phase fluid flow in porous materials, irrespective of their porosity and solid phase topology. We have applied this methodology to highly porous fibrous materials in which void spaces are not distinctly separated, and where simplifying the geometry into a network of pore bodies and throats, as in PNM, does not result in a topology-consistent network. To this end, we have reduced the complexity of the 3-D void space geometry by working with its medial surface. We have used a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space, and then solved the quasi-static drainage and imbibition on the resulting domain. The medial surface accurately represents the topology of the porous structure including corners, irregular cross sections, etc. This methodology is capable of capturing corner menisci and the snap-off mechanism numerically. It also allows for calculation of pore size distribution, permeability and capillary pressure-saturation-specific interfacial area surface of the porous structure. To show the

  12. 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/cgi-bin/nph-data_query?bibcode=2011PhDT.......205M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011PhDT.......205M&link_type=ABSTRACT"><span id="translatedtitle">Synthesis and gas adsorption study of <span class="hlt">porous</span> metal-organic framework <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>Mu, Bin</p> <p></p> <p>Metal-organic frameworks (MOFs) or <span class="hlt">porous</span> 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 <span class="hlt">materials</span> have some distinct advantages over traditional <span class="hlt">porous</span> <span class="hlt">materials</span> 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 <span class="hlt">porous</span> 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 <span class="hlt">porous</span> <span class="hlt">materials</span> 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 <span class="hlt">porous</span> coordination polymers; (ii) Evaluate <span class="hlt">porous</span> MOF <span class="hlt">materials</span> 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 <span class="hlt">porous</span> MOF <span class="hlt">materials</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1145..941G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1145..941G"><span id="translatedtitle">Towards a Dynamical Collision <span class="hlt">Model</span> of Highly <span class="hlt">Porous</span> Dust Aggregates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Güttler, Carsten; Krause, Maya; Geretshauser, Ralf; Speith, Roland; Blum, Jürgen</p> <p>2009-06-01</p> <p>In the recent years we have performed various experiments on the collision dynamics of highly <span class="hlt">porous</span> dust aggregates and although we now have a comprehensive picture of the micromechanics of those aggregates, the macroscopic understanding is still lacking. We are therefore developing a mechanical <span class="hlt">model</span> to describe dust aggregate collisions with macroscopic parameters like tensile strength, compressive strength and shear strength. For one well defined dust sample <span class="hlt">material</span>, the tensile and compressive strength were measured in a static experiment and implemented in a Smoothed Particle Hydrodynamics (SPH) code. A laboratory experiment was designed to compare the laboratory results with the results of the SPH simulation. In this experiment, a mm-sized glass bead is dropped into a cm-sized dust aggregate with the previously measured strength parameters. We determine the deceleration of the glass bead by high-speed imaging and the compression of the dust aggregate by x-ray micro-tomography. The measured penetration depth, stopping time and compaction under the glass bead are utilized to calibrate and test the SPH code. We find that the statically measured compressive strength curve is only applicable if we adjust it to the dynamic situation with a ``softness'' parameter. After determining this parameter, the SPH code is capable of reproducing experimental results, which have not been used for the calibration before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPS...280...30F&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPS...280...30F&link_type=ABSTRACT"><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/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.ncbi.nlm.nih.gov/pubmed/27198674','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27198674"><span id="translatedtitle">Pore chemistry and size control in hybrid <span class="hlt">porous</span> <span class="hlt">materials</span> for acetylene capture from ethylene.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, Xili; Chen, Kaijie; Xing, Huabin; Yang, Qiwei; Krishna, Rajamani; Bao, Zongbi; Wu, Hui; Zhou, Wei; Dong, Xinglong; Han, Yu; Li, Bin; Ren, Qilong; Zaworotko, Michael J; Chen, Banglin</p> <p>2016-07-01</p> <p>The trade-off between physical adsorption capacity and selectivity of <span class="hlt">porous</span> <span class="hlt">materials</span> is a major barrier for efficient gas separation and purification through physisorption. We report control over pore chemistry and size in metal coordination networks with hexafluorosilicate and organic linkers for the purpose of preferential binding and orderly assembly of acetylene molecules through cooperative host-guest and/or guest-guest interactions. The specific binding sites for acetylene are validated by <span class="hlt">modeling</span> and neutron powder diffraction studies. The energies associated with these binding interactions afford high adsorption capacity (2.1 millimoles per gram at 0.025 bar) and selectivity (39.7 to 44.8) for acetylene at ambient conditions. Their efficiency for the separation of acetylene/ethylene mixtures is demonstrated by experimental breakthrough curves (0.73 millimoles per gram from a 1/99 mixture). PMID:27198674</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="http://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://adsabs.harvard.edu/abs/2015GeoRL..42.4833W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.4833W"><span id="translatedtitle">An electrical conductivity <span class="hlt">model</span> for 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>Wei, Wei; Cai, Jianchao; Hu, Xiangyun; Han, Qi</p> <p>2015-06-01</p> <p>Archie's equation is an empirical electrical conductivity-porosity <span class="hlt">model</span> that has been used to predict the formation factor of <span class="hlt">porous</span> rock for more than 70 years. However, the physical interpretation of its parameters, e.g., the cementation exponent m, remains questionable. In this study, a theoretical electrical conductivity equation is derived based on the fractal characteristics of <span class="hlt">porous</span> media. The proposed <span class="hlt">model</span> is expressed in terms of the tortuosity fractal dimension (DT), the pore fractal dimension (Df), the electrical conductivity of the pore liquid, and the porosity. The empirical parameter m is then determined from physically based parameters, such as DT and Df. Furthermore, a distinct interrelationship between DT and Df is obtained. We find a reasonably good match between the predicted formation factor by our <span class="hlt">model</span> and experimental data.</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> </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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</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_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDD31010A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDD31010A"><span id="translatedtitle">Mathematical <span class="hlt">modeling</span> heat and mass transfer processes 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>Akhmed-Zaki, Darkhan</p> <p>2013-11-01</p> <p>On late development stages of oil-fields appears a complex problem of oil-recovery reduction. One of solution approaches is injecting of surfactant together with water in the form of active impurities into the productive layer - for decreasing oil viscosity and capillary forces between ``oil-water'' phases system. In fluids flow the surfactant can be in three states: dissolved in water, dissolved in oil and adsorbed on pore channels' walls. The surfactant's invasion into the reservoir is tracked by its diffusion with reservoir liquid and mass-exchange with two phase (liquid and solid) components of <span class="hlt">porous</span> structure. Additionally, in this case heat exchange between fluids (injected, residual) and framework of <span class="hlt">porous</span> medium has practical importance for evaluating of temperature influences on enhancing oil recovery. Now, the problem of designing an adequate mathematical <span class="hlt">model</span> for describing a simultaneous flowing heat and mass transfer processes in anisotropic heterogeneous <span class="hlt">porous</span> medium -surfactant injection during at various temperature regimes has not been fully researched. In this work is presents a 2D mathematical <span class="hlt">model</span> of surfactant injections into the oil reservoir. Description of heat- and mass transfer processes in a <span class="hlt">porous</span> media is done through differential and kinetic equations. For designing a computational algorithm is used modify version of IMPES method. The sequential and parallel computational algorithms are developed using an adaptive curvilinear meshes which into account heterogeneous <span class="hlt">porous</span> structures. In this case we can evaluate the boundaries of our process flows - fronts (``invasion'', ``heat'' and ``mass'' transfers), according to the pressure, temperature, and concentration gradient changes.</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> <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/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://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://www.ncbi.nlm.nih.gov/pubmed/27208416','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27208416"><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://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</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. PMID:27208416</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://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://ntrs.nasa.gov/search.jsp?R=19760055232&hterms=porous+burner&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dporous%2Bburner','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760055232&hterms=porous+burner&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dporous%2Bburner"><span id="translatedtitle">Composite propellant combustion <span class="hlt">modeling</span> with a <span class="hlt">porous</span> plate burner</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kumar, R. N.; Strand, L. D.; Mcnamara, R. P.</p> <p>1976-01-01</p> <p>A burner is designed to <span class="hlt">model</span> on a large scale (millimeters) the complex vapor phase processes that take place on awkwardly small scales (about a hundred microns) in the combustion of practical AP/ composite propellants at conventional pressures. Binder vapor evolution is <span class="hlt">modeled</span> with gaseous fuel (ethane in the experiments reported) flow through a <span class="hlt">porous</span> plate and oxidizer vapor with the flow of a gaseous oxidizer (air and enriched air in the experiments reported) through discrete holes in the <span class="hlt">porous</span> plate. Measured flame standoff distance and surface temperature variations are consistent with theoretical predictions at atmospheric pressure. Data obtained at several atmospheres are discussed in the light of the current theories of propellant burning that place varying emphasis on the roles of chemical kinetics and fluid dynamic diffusion/mixing in the vapor phase of a burning composite propellant. The potential and proposed future applications of the burner are indicated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950020938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950020938"><span id="translatedtitle">A probabilistic <span class="hlt">model</span> of a <span class="hlt">porous</span> heat exchanger</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Agrawal, O. P.; Lin, X. A.</p> <p>1995-01-01</p> <p>This paper presents a probabilistic one-dimensional finite element <span class="hlt">model</span> for heat transfer processes in <span class="hlt">porous</span> heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional <span class="hlt">model</span> of heat transfer phenomenon in superfluid flow through a <span class="hlt">porous</span> media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</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_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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