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Sample records for materials porous

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1992-10-13

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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  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. 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.

  18. Sputtering from a Porous Material by Penetrating Ions

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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 ...

  8. 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.

  9. 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

  10. Application of porous materials for laminar flow control

    NASA Technical Reports Server (NTRS)

    Pearce, W. E.

    1978-01-01

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

  11. 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.

  12. 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.

  13. Methods for removing contaminant matter from a porous material

    DOEpatents

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

    2010-11-16

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

  14. 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.

  15. 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.

  16. Gas sensing using porous materials for automotive applications.

    PubMed

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

    2015-07-01

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  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. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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, {\

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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).

  17. 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.

  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. 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.

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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).

  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. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  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. 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

  5. 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).

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Mu, Bin

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

  8. Porous hollow carbon spheres for electrode material of supercapacitors and support material of dendritic Pt electrocatalyst

    NASA Astrophysics Data System (ADS)

    Fan, Yang; Liu, Pei-Fang; Huang, Zhong-Yuan; Jiang, Tong-Wu; Yao, Kai-Li; Han, Ran

    2015-04-01

    Porous 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 material 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.

  9. 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.

  10. 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.

  11. 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.

  12. Template-assisted formation of porous vanadium oxide as high performance cathode materials for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Su, Yanhui; Pan, Anqiang; Wang, Yaping; Huang, Jiwu; Nie, Zhiwei; An, Xinxin; Liang, Shuquan

    2015-11-01

    Similar to carbonaceous materials, porous 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 porous vanadium pentoxide (V2O5) as high performance cathode material for lithium ion batteries. Ketjen black (KB), a porous carbon material, has been employed as hard templates to host precursor species in their porous structures. The porous V2O5 electrode material is prepared after removing the KB carbon framework by calcinating the composites in air. As cathode materials for lithium ion batteries, the porous 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.

  13. Tailoring of the porous structure of soft emulsion-templated polymer materials.

    PubMed

    Kovalenko, Artem; Zimny, Kévin; Mascaro, Benoit; Brunet, Thomas; Mondain-Monval, Olivier

    2016-06-21

    This paper discusses the formation of soft porous materials 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 porous structure and properties of the final material. 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 materials with either interconnected or isolated pores. These two systems present completely different behavior upon drying, which results in macroporous air-filled materials in the interconnected case and in a collapsed material 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 materials 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 materials with a collapsed porous structure are similar to those of non-porous silicone, which makes them acoustically inactive. PMID:27195990

  14. Systems and strippable coatings for decontaminating structures that include porous material

    DOEpatents

    Fox, Robert V.; Avci, Recep; Groenewold, Gary S.

    2011-12-06

    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.

  15. 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

  16. Laser-induced growth of nanocrystals embedded in porous materials

    NASA Astrophysics Data System (ADS)

    Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed

    2013-06-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  17. Laser-induced growth of nanocrystals embedded in porous materials

    PubMed Central

    2013-01-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  18. Graded porous inorganic materials derived from self-assembled block copolymer templates

    NASA Astrophysics Data System (ADS)

    Gu, Yibei; Werner, Jörg G.; Dorin, Rachel M.; Robbins, Spencer W.; Wiesner, Ulrich

    2015-03-01

    Graded porous inorganic materials directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional porous inorganic materials. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded porous carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge-like support structure. Substructure walls between macropores are themselves mesoporous, constituting a structural hierarchy in addition to the pore gradation. Final graded structures can be tailored by tuning casting conditions of self-assembled templates as well as the backfilling processes. We expect that these graded porous inorganic materials may find use in applications including separation, catalysis, biomedical implants, and energy conversion and storage.Graded porous inorganic materials directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional porous inorganic materials. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded porous carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge

  19. Freeze-drying of “pearl milk tea”: A general strategy for controllable synthesis of porous materials

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  20. Effect of crystallization time on the physico-chemical and catalytic properties of the hierarchical porous materials

    SciTech Connect

    Xu, Ling; Ma, Yuanyuan; Ding, Wenli; Guan, Jingqi; Wu, Shujie; Kan, Qiubin

    2010-09-15

    A series of hierarchical porous materials were prepared by a dual template method. The effect of different crystallization time on the channel architecture, morphology, acid performance of the hierarchical porous materials was investigated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption and {sup 27}Al nuclear magnetic resonance were performed to obtain information on the physico-chemical properties of the materials. It was shown that the change in crystallization time could influence the structure/texture and surface acid properties of the hierarchical porous materials. In addition, alkylation of phenol with tert-butanol reaction was carried out to investigate the catalytic performance of the hierarchical porous materials. The results showed that the catalytic activity of the hierarchical porous materials and the selectivity to the bulkly product 2,4-di-tert-butyl-phenol decreased with processing time.

  1. Freeze-drying of “pearl milk tea”: A general strategy for controllable synthesis of porous materials

    PubMed Central

    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

  2. Process of making porous ceramic materials with controlled porosity

    DOEpatents

    Anderson, Marc A.; Ku, Qunyin

    1993-01-01

    A method of making metal oxide ceramic material is disclosed by which the porosity of the resulting material can be selectively controlled by manipulating the sol used to make the material. The method can be used to make a variety of metal oxide ceramic bodies, including membranes, but also pellets, plugs or other bodies. It has also been found that viscous sol materials can readily be shaped by extrusion into shapes typical of catalytic or adsorbent bodies used in industry, to facilitate the application of such materials for catalytic and adsorbent applications.

  3. Dimpled elastic sheets: a new class of non-porous negative Poisson’s ratio materials

    PubMed Central

    Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia

    2015-01-01

    In this study, we report a novel periodic material with negative Poisson’s ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications. PMID:26671169

  4. Dimpled elastic sheets: a new class of non-porous negative Poisson's ratio materials.

    PubMed

    Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C; Shanian, Ali; Weaver, James C; Bertoldi, Katia

    2015-01-01

    In this study, we report a novel periodic material with negative Poisson's ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications. PMID:26671169

  5. Dimpled elastic sheets: a new class of non-porous negative Poisson’s ratio materials

    NASA Astrophysics Data System (ADS)

    Javid, Farhad; Smith-Roberge, Evelyne; Innes, Matthew C.; Shanian, Ali; Weaver, James C.; Bertoldi, Katia

    2015-12-01

    In this study, we report a novel periodic material with negative Poisson’s ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications.

  6. Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

    NASA Technical Reports Server (NTRS)

    Park, Junhong; Palumbo, Daniel L.

    2004-01-01

    For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

  7. Porous structured vanadium oxide electrode material for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Reddy, Ravinder N.; Reddy, Ramana G.

    A nano porous vanadium oxide (V 2O 5) was prepared by sol-gel method. The preparation involved elutriation of aqueous sodium meta vanadate over a cation exchange resin. The product was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, surface area analysis and thermogravimetric analysis. Electrochemical characterization was done using cyclic voltammetry in a three electrode system consisting of a saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and V 2O 5 mounted on Ti mesh as the working electrode. Two molars of aqueous KCl, NaCl and LiCl were used as electrolytes. A maximum capacitance of 214 F g -1 was obtained at a scan rate of 5 mV s -1 in 2 M KCl. The effect of different electrolytes and the effect of concentration of KCl on the specific capacitance of V 2O 5 were studied. Specific capacitance faded rapidly over 100 cycles in 2 M KCl at a 5 mV s -1 scan rate.

  8. Hierarchical Porous Carbon Materials Derived from Sheep Manure for High-Capacity Supercapacitors.

    PubMed

    Zhang, Caiyun; Zhu, Xiaohong; Cao, Min; Li, Menglin; Li, Na; Lai, Liuqin; Zhu, Jiliang; Wei, Dacheng

    2016-05-10

    3 D capacitance: Hierarchical porous carbon-based electrode materials with a composite structure are prepared from a biomass waste by a facile carbonization and activation process without using any additional templates. Benefiting from the composite structure, the ions experience a variety of environments, which contribute significantly to the excellent electrochemical properties of supercapacitors. PMID:27059168

  9. 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

  10. Generalization of experimental data on heat transfer in permeable shells made of porous reticular materials

    NASA Astrophysics Data System (ADS)

    Polyakov, A. F.; Strat'ev, V. K.; Tret'yakov, A. F.; Shekhter, Yu. L.

    2010-06-01

    Heat transfer from six samples of porous reticular material to cooling gas (air) at small Reynolds numbers is experimentally studied. The specific features pertinent to heat transfer essentially affected by longitudinal heat conductivity along gas flow are analyzed. The experimental results are generalized in the form of dimensionless empirical relations.

  11. Controlled High-Rate-Strain Shear Bands in Inert and Reactant Porous Materials

    NASA Astrophysics Data System (ADS)

    Nesterenko, Vitali

    1997-07-01

    Shear localization was considered as one of the main reasons for initiation of chemical reaction in energetic materials under dynamic loading (Dremin and Breusov 1968, Winter and Field 1975, Frey 1981, Kipp 1985, Iyer, Bennet et al., 1994) and for particles bonding during shock compaction (Nesterenko 1985). However despite of wide spread recognition of the importance of rapid shear flow the shear bands in 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 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 107 s-1. Experimental results will be presented for inert materials (granular, fractured ceramics) and for reactant porous mixtures (Nb-Si, Ti-Si, Ti-C). Mechanisms of material deformation and shear induced chemical reactions inside shear localization zone as well as conditions for the initiation of the chemical reaction in the bulk of energetic material by array of shear bands will be considered.

  12. Mechanically Strong, Lightweight Porous Materials Developed (X-Aerogels)

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2005-01-01

    Aerogels are attractive materials for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other materials. Potential NASA applications for these materials include lightweight insulation for spacecraft, habitats, and extravehicular activity (EVA) suits; catalyst supports for fuel cell and in situ resource utilization; and sensors for air- and water-quality monitoring for vehicles, habitats, and EVA suits. Conventional aerogels are extremely fragile and require processing via supercritical fluid extraction, which adds cost to the production of an aerogel and limits the sizes and geometries of samples that can be produced from these materials. These issues have severely hampered the application of aerogels in NASA missions.

  13. Characterization of Porous Materials as Radon Source and its Radiological Implications

    SciTech Connect

    Lopez-Coto, I.; Bolivar, J. P.; Mas, J. L.; Garcia-Tenorio, R.

    2008-08-07

    In this work, a magnitude is proposed in order to compare the potential radiological risk due to radon exposition generated by different materials, and a method based in the {sup 222}Rn accumulation technique is presented for its determination. The obtained results indicate that the proposed magnitude and their corresponding measurement methodology are useful in order to take decisions about the management of different kinds of porous materials.

  14. Potential of hybrid functionalized meso-porous materials for the separation and immobilization of radionuclides

    SciTech Connect

    Luca, V.

    2013-07-01

    Functionalized meso-porous materials are a class of hybrid organic-inorganic material in which a meso-porous metal oxide framework is functionalized with multifunctional organic molecules. These molecules may contain one or more anchor groups that form strong bonds to the pore surfaces of the metal oxide framework and free functional groups that can impart and or modify the functionality of the material such as for binding metal ions in solution. Such materials have been extensively studied over the past decade and are of particular interest in absorption applications because of the tremendous versatility in choosing the composition and architecture of the metal oxide framework and the nature of the functional organic molecule as well as the efficient mass transfer that can occur through a well-designed hierarchically porous network. A sorbent for nuclear applications would have to be highly selective for particular radio nuclides, it would need to be hydrolytically and radiolytically stable, and it would have to possess reasonable capacity and fast kinetics. The sorbent would also have to be available in a form suitable for use in a column. Finally, it would also be desirable if once saturated with radio nuclides, the sorbent could be recycled or converted directly into a ceramic or glass waste form suitable for direct repository disposal or even converted directly into a material that could be used as a transmutation target. Such a cradle-to- grave strategy could have many benefits in so far as process efficiency and the generation of secondary wastes are concerned.This paper will provide an overview of work done on all of the above mentioned aspects of the development of functionalized meso-porous adsorbent materials for the selective separation of lanthanides and actinides and discuss the prospects for future implementation of a cradle-to-grave strategy with such materials. (author)

  15. 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.

  16. Low-Temperature Synthesis of Porous Materials from Mortar Sands

    NASA Astrophysics Data System (ADS)

    Kazmina, O. V.; Volland, S. N.; Dushkina, M. A.

    2015-08-01

    It is established that the eliminations of construction sand with the content of SiO2 about 70 wt.% and particle size less than 60 μm are suitable for the production of a foam-glass-crystal material on the basis of the low-temperature frit, which was synthesized at the temperature of 900°C. The obtained foam-glass-crystal material exceeds foam-glass (by 3.0 times) and clayite (by 1.5 times) by strength and is characterized by the low value of water absorption (0.1%).

  17. Computing the Seismic Attenuation in Complex Porous Materials

    NASA Astrophysics Data System (ADS)

    Masson, Yder Jean

    The present work analyzes seismic attenuation due to wave-induced flow in complex poroelastic materials containing an arbitrary amount of heterogeneity and fully or partially saturated with a mixture of fluids. In the first part, two distinct finite-difference (FDTD) numerical schemes for solving Biot's poroelastic set of equations are introduced. The first algorithm is designed to be used in the seismic band of frequencies; i.e., when the permeability of the medium doesn't depend on frequency. The second algorithm accounts for viscous boundary layers that appear in the pores at high frequencies (in this case, the permeability depends on frequency) and can be used across the entire band of frequencies. An innovative numerical method is presented in the second part allowing computation of seismic attenuation due to wave-induced flow for any poroelastic material. This method is applied to study the attenuation associated with different classes of materials saturated with a single fluid (water). For a material having a self-affine (fractal) distribution of elastic properties, it is demonstrated that frequency dependence in the attenuation is controlled by a single parameter that is directly related to the fractal dimension of the material. For anisotropic materials, a relation is established between the attenuation levels associated with waves propagating in different directions and the geometrical aspect ratio of the heterogeneities present within the material. The third part concerns the study of attenuation associated with materials having a homogeneous solid skeleton saturated with a mixture of immiscible fluids. The special case where the distribution of fluids is the result of an invasion-percolation process is treated in detail. Finally, the last part presents a novel experimental setup designed to measure fluctuations of the elastic properties in real rock samples. This device performs automated micro-indentation tests at the surface of rock samples and

  18. Recent advances in porous polyoxometalate-based metal-organic framework materials.

    PubMed

    Du, Dong-Ying; Qin, Jun-Sheng; Li, Shun-Li; Su, Zhong-Min; Lan, Ya-Qian

    2014-07-01

    Polyoxometalate (POM)-based metal-organic framework (MOF) materials contain POM units and generally generate MOF materials with open networks. POM-based MOF materials, which utilize the advantages of both POMs and MOFs, have received increasing attention, and much effort has been devoted to their preparation and relevant applications over the past few decades. They have good prospects in catalysis owing to the electronic and physical properties of POMs that are tunable by varying constituent elements. In this review, we present recent developments in porous POM-based MOF materials, including their classification, synthesis strategies, and applications, especially in the field of catalysis. PMID:24676127

  19. Electrode including porous particles with embedded active material for use in a secondary electrochemical cell

    DOEpatents

    Vissers, Donald R.; Nelson, Paul A.; Kaun, Thomas D.; Tomczuk, Zygmunt

    1978-04-25

    Particles of carbonaceous matrices containing embedded electrode active material are prepared for vibratory loading within a porous electrically conductive substrate. In preparing the particles, active materials such as metal chalcogenides, solid alloys of alkali or alkaline earth metals along with other metals and their oxides in powdered or particulate form are blended with a thermosetting resin and particles of a volatile to form a paste mixture. The paste is heated to a temperature at which the volatile transforms into vapor to impart porosity at about the same time as the resin begins to cure into a rigid, solid structure. The solid structure is then comminuted into porous, carbonaceous particles with the embedded active material.

  20. Dark-field X-ray imaging of unsaturated water transport in porous materials

    SciTech Connect

    Yang, F. E-mail: michele.griffa@empa.ch; Di Bella, C.; Lura, P.; Prade, F.; Herzen, J.; Sarapata, A.; Pfeiffer, F.; Griffa, M. E-mail: michele.griffa@empa.ch; Jerjen, I.

    2014-10-13

    We introduce in this Letter an approach to X-ray imaging of unsaturated water transport in porous materials based upon the intrinsic X-ray scattering produced by the material microstructural heterogeneity at a length scale below the imaging system spatial resolution. The basic principle for image contrast creation consists in a reduction of such scattering by permeation of the porosity by water. The implementation of the approach is based upon X-ray dark-field imaging via Talbot-Lau interferometry. The proof-of-concept is provided by performing laboratory-scale dark-field X-ray radiography of mortar samples during a water capillary uptake experiment. The results suggest that the proposed approach to visualizing unsaturated water transport in porous materials is complementary to neutron and magnetic resonance imaging and alternative to standard X-ray imaging, the latter requiring the use of contrast agents because based upon X-ray attenuation only.

  1. Computational study of porous materials for gas separations

    NASA Astrophysics Data System (ADS)

    Lin, Li-Chiang

    Nanoporous materials such as zeolites, zeolitic imidazolate frameworks (ZIFs), and metal-organic frameworks (MOFs) are used as sorbents or membranes for gas separations such as carbon dioxide capture, methane capture, paraffin/olefin separations, etc. The total number of nanoporous materials is large; by changing the chemical composition and/or the structural topologies we can envision an infinite number of possible materials. In practice one can synthesize and fully characterize only a small subset of these materials. Hence, computational study can play an important role by utilizing various techniques in molecular simulations as well as quantum chemical calculations to accelerate the search for optimal materials for various energy-related separations. Accordingly, several large-scale computational screenings of over one hundred thousand materials have been performed to find the best materials for carbon capture, methane capture, and ethane/ethene separation. These large-scale screenings identified a number of promising materials for different applications. Moreover, the analysis of these screening studies yielded insights into those molecular characteristics of a material that contribute to an optimal performance for a given application. These insights provided useful guidelines for future structural design and synthesis. For instance, one of the screening studies indicated that some zeolite structures can potentially reduce the energy penalty imposed on a coal-fired power plant by as much as 35% compared to the near-term MEA technology for carbon capture application. These optimal structures have topologies with a maximized density of pockets and they capture and release CO2 molecules with an optimal energy. These screening studies also pointed to some systems, for which conventional force fields were unable to make sufficiently reliable predictions of the adsorption isotherms of different gasses, e.g., CO2 in MOFs with open-metal sites. For these systems, we

  2. Preparation of steel slag porous sound-absorbing material using coal powder as pore former.

    PubMed

    Sun, Peng; Guo, Zhancheng

    2015-10-01

    The aim of the study was to prepare a porous sound-absorbing material using steel slag and fly ash as the main raw material, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the porous sound-absorbing material was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the porous sound-absorbing material were a proportion of fly ash of 50% (wt.%), percentage of coal powder of 30% (wt.%), sintering temperature of 1130°C, and sintering time of 6.0hr, which were determined by analyzing the properties of the sound-absorbing material. PMID:26456608

  3. Water Adsorption in Porous Metal-Organic Frameworks and Related Materials

    SciTech Connect

    Furukawa, H; Gandara, F; Zhang, YB; Jiang, JC; Queen, WL; Hudson, MR; Yaghi, OM

    2014-03-19

    Water adsorption in porous materials is important for many applications such as dehumidification, thermal batteries, and delivery of drinking water in remote areas. In this study, we have identified three criteria for achieving high performing porous materials for water adsorption. These criteria deal with condensation pressure of water in the pores, uptake capacity, and recyclability and water stability of the material. In search of an excellently performing porous material, we have studied and compared the water adsorption properties of 23 materials, 20 of which are metal organic frameworks (MOFs). Among the MOFs are 10 zirconium(IV) MOFs with a subset of these, MOF-801-SC (single crystal form), -802, -805, -806, -808, -812, and -841 reported for the first time. MOF-801-P (microcrystalline powder form) was reported earlier and studied here for its water adsorption properties. MOF-812 was only made and structurally characterized but not examined for water adsorption because it is a byproduct of MOF-841 synthesis. All the new zirconium MOFs are made from the Zr6O4(OH)(4)(-CO2)(n) secondary building units (n = 6, 8, 10, or 12) and variously shaped carboxyl organic linkers to make extended porous frameworks. The permanent porosity of all 23 materials was confirmed and their water adsorption measured to reveal that MOF-801-P and MOF-841 are the highest performers based on the three criteria stated above; they are water stable, do not lose capacity after five adsorption/desorption cycles, and are easily regenerated at room temperature. An X-ray single-crystal study and a powder neutron diffraction study reveal the position of the water adsorption sites in MOF-801 and highlight the importance of the intermolecular interaction between adsorbed water molecules within the pores.

  4. Hydrothermal Synthesis of Meso-porous Materials using Diatomaceous Earth

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Kato, S.; Maeda, H.; Ishida, E. H.

    2007-03-01

    In order to sustain the inherent properties of diatomaceous earth (DE), a low-temperature synthesis of mesoporous material from DE was carried out using a hydrothermal processing technique under saturated steam pressure at 200 °C for 12 h. The experimental results showed that the most important strength-producing constituent in the solidified specimens was tobermorite formed by hydrothermal processing, and the addition of slaked lime was favorable to tobermorite formation. At Ca/Si ratio around 0.83 in the starting material, tobermorite appeared to form readily. A high autoclave curing temperature (200 °C), or a longer curing time (12 h) seemed to accelerate the tobermorite formation, thus leading to a higher strength development.

  5. Characterization of Porous Carbon Fibers and Related Materials

    SciTech Connect

    Fuller, E.L., Jr.

    1993-01-01

    A one-year subcontract sponsored by the Carbon Materials Technology Group of the Oak Ridge National Laboratory (ORNL) with the Department of Geological Sciences, University Of Tennessee, has been completed. A volumetric sorption system has been upgraded, in cooperation with commercial vendor, to allow the acquisition of data relevant to the program for the production of activated carbon molecular fiber sieves (ACFMS). The equipment and experimental techniques have been developed to determine the pore structure and porosity of reference materials and materials produced at ORNL as part of the development of methods for the activation of carbon fibers by various etching agents. Commercial activated coconut shell charcoal (ACSC) has been studied to verify instrument performance and to develop methodology for deducing cause and effects in the activation processes and to better understand the industrial processes (gas separation, natural gas storage, etc.). Operating personnel have been trained, standard operating procedures have been established, and quality assurance procedures have been developed and put in place. Carbon dioxide and methane sorption have been measured over a temperature range 0 to 200 C for both ACFMS and ACSC and similarities and differences related to the respective structures and mechanisms of interaction with the sorbed components. Nitrogen sorption (at 77 K) has been used to evaluate ''surface area'' and ''porosity'' for comparison with the large data base that exists for other activated carbons and related materials. The preliminary data base reveals that techniques and theories currently used to evaluate activated carbons may be somewhat erroneous and misleading. Alternate thermochemical and structural analyses have been developed that show promise in providing useful information related both to the activation process and to industrial applications of interest in the efficient and economical utilization of fossil fuels in a manner that is

  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

    numerical laboratory approach to the study of complex porous materials.

  7. Porous carbon material containing CaO for acidic gas capture: preparation and properties.

    PubMed

    Przepiórski, Jacek; Czyżewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W

    2013-12-15

    A one-step process for the preparation of CaO-containing porous carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric material and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw materials used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing porous carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid materials was confirmed as a suitable method to obtain highly porous carbon materials. PMID:23743266

  8. 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

  9. Enhancing activated-peroxide formulations for porous materials :

    SciTech Connect

    Krauter, Paula; Tucker, Mark D.; Tezak, Matthew S.; Boucher, Raymond

    2012-12-01

    During an urban wide-area incident involving the release of a biological warfare agent, the recovery/restoration effort will require extensive resources and will tax the current capabilities of the government and private contractors. In fact, resources may be so limited that decontamination by facility owners/occupants may become necessary and a simple decontamination process and material should be available for this use. One potential process for use by facility owners/occupants would be a liquid sporicidal decontaminant, such as pHamended bleach or activated-peroxide, and simple application devices. While pH-amended bleach is currently the recommended low-tech decontamination solution, a less corrosive and toxic decontaminant is desirable. The objective of this project is to provide an operational assessment of an alternative to chlorine bleach for low-tech decontamination applications activated hydrogen peroxide. This report provides the methods and results for activatedperoxide evaluation experiments. The results suggest that the efficacy of an activated-peroxide decontaminant is similar to pH-amended bleach on many common materials.

  10. Fly Ash Porous Material using Geopolymerization Process for High Temperature Exposure

    PubMed Central

    Abdullah, Mohd Mustafa Al Bakri; Jamaludin, Liyana; Hussin, Kamarudin; Bnhussain, Mohamed; Ghazali, Che Mohd Ruzaidi; Ahmad, Mohd Izzat

    2012-01-01

    This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic materials (fly ash). In this paper, we report on our investigation of the performance of porous geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic materials (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the porous geopolymers exhibited strength increases after temperature exposure. PMID:22605984

  11. 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.

  12. Ordered porous mesostructured materials from nanoparticle-block copolymer self-assembly

    SciTech Connect

    Warren, Scott; Wiesner, Ulrich; DiSalvo, Jr., Francis J

    2013-10-29

    The invention provides mesostructured materials and methods of preparing mesostructured materials including metal-rich mesostructured nanoparticle-block copolymer hybrids, porous metal-nonmetal nanocomposite mesostructures, and ordered metal mesostructures with uniform pores. The nanoparticles can be metal, metal alloy, metal mixture, intermetallic, metal-carbon, metal-ceramic, semiconductor-carbon, semiconductor-ceramic, insulator-carbon or insulator-ceramic nanoparticles, or combinations thereof. A block copolymer/ligand-stabilized nanoparticle solution is cast, resulting in the formation of a metal-rich (or semiconductor-rich or insulator-rich) mesostructured nanoparticle-block copolymer hybrid. The hybrid is heated to an elevated temperature, resulting in the formation of an ordered porous nanocomposite mesostructure. A nonmetal component (e.g., carbon or ceramic) is then removed to produce an ordered mesostructure with ordered and large uniform pores.

  13. Explicit accounting of electronic effects on the Hugoniot of porous materials

    NASA Astrophysics Data System (ADS)

    Nayak, Bishnupriya; Menon, S. V. G.

    2016-03-01

    A generalized enthalpy based equation of state, which includes thermal electron excitations explicitly, is formulated from simple considerations. Its application to obtain Hugoniot of materials needs simultaneous evaluation of pressure-volume curve and temperature, the latter requiring solution of a differential equation. The errors involved in two recent papers [Huayun et al., J. Appl. Phys. 92, 5917 (2002); 92, 5924 (2002)], which employed this approach, are brought out and discussed. In addition to developing the correct set of equations, the present work also provides a numerical method to implement this approach. Constant pressure specific heat of ions and electrons and ionic enthalpy parameter, needed for applications, are calculated using a three component equation of state. The method is applied to porous Cu with different initial porosities. Comparison of results with experimental data shows good agreement. It is found that temperatures along the Hugoniot of porous materials are significantly modified due to electronic effects.

  14. Synthetic Methodology for the Fabrication of Porous Porphyrin Materials with Metal-Organic-Polymer Aerogels.

    PubMed

    Zhao, Xin; Yuan, Lin; Zhang, Zeng-Qi; Wang, Yong-Song; Yu, Qiong; Li, Jun

    2016-06-01

    A promising fabrication strategy used for designing porous porphyrin materials and a group of rigid carboxyl porphyrins based metal-organic-polymer aerogels (MOPAs) has been proposed recently. These newly synthesized MOPAs were exemplarily characterized by FT-IR, UV-vis-DRS, EDS, PXRD, TGA, SEM, TEM, and gas sorption measurements. A gelation study has shown that solvents, molar ratio, temperature, and peripheral carboxyl number in porphyrins all affect gel generation. The MOPA series exhibit eminent thermal stability, high removal efficiency in dye adsorption, versatile morphologies, and permanent tunable porosity; also the BET surface areas fall within the range 249-779 m(2) g(-1). All of the mentioned properties are significantly superior to some other porous materials, which enable these compounds to be potential candidates for dye uptake, gas storage, and separation. PMID:27159626

  15. 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

  16. Fly ash porous material using geopolymerization process for high temperature exposure.

    PubMed

    Abdullah, Mohd Mustafa Al Bakri; Jamaludin, Liyana; Hussin, Kamarudin; Bnhussain, Mohamed; Ghazali, Che Mohd Ruzaidi; Ahmad, Mohd Izzat

    2012-01-01

    This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic materials (fly ash). In this paper, we report on our investigation of the performance of porous geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic materials (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the porous geopolymers exhibited strength increases after temperature exposure. PMID:22605984

  17. 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.

  18. 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.

  19. Preparation and application of highly porous aerogel-based bioactive materials in dentistry

    NASA Astrophysics Data System (ADS)

    Kuttor, Andrea; Szalóki, Melinda; Rente, Tünde; Kerényi, Farkas; Bakó, József; Fábián, István; Lázár, István; Jenei, Attila; Hegedüs, Csaba

    2014-03-01

    In this study, the possibility of preparation and application of highly porous silica aerogel-based bioactive materials are presented. The aerogel was combined with hydroxyapatite and β-tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in the mesoporous region with a maximum pore diameter of 7.4 and 12.7 nm for the composite materials. The newly developed bioactive materials were characterized by scanning electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.

  20. Maintaining the structure of templated porous materials for reactive and high-temperature applications.

    PubMed

    Rudisill, Stephen G; Wang, Zhiyong; Stein, Andreas

    2012-05-15

    Nanoporous and nanostructured materials are becoming increasingly important for advanced applications involving, for example, bioactive materials, catalytic materials, energy storage and conversion materials, photonic crystals, membranes, and more. As such, they are exposed to a variety of harsh environments and often experience detrimental morphological changes as a result. This article highlights material limitations and recent advances in porous materials--three-dimensionally ordered macroporous (3DOM) materials in particular--under reactive or high-temperature conditions. Examples include systems where morphological changes are desired and systems that require an increased retention of structure, surface area, and overall material integrity during synthesis and processing. Structural modifications, changes in composition, and alternate synthesis routes are explored and discussed. Improvements in thermal or structural stability have been achieved by the isolation of nanoparticles in porous structures through spatial separation, by confinement in a more thermally stable host, by the application of a protective surface or an adhesive interlayer, by alloy or solid solution formation, and by doping to induce solute drag. PMID:22409622

  1. Porous manganese-based magnetocaloric material for magnetic refrigeration at room temperature

    NASA Astrophysics Data System (ADS)

    Lozano, J. A.; Kostow, M. P.; Brück, E.; de Lima, J. C.; Prata, A. T.; Wendhausen, P. A. P.

    The powder metallurgy technique has been exploited as a means to prepare porous magnetocaloric materials. The alloy Mn 1.1Fe 0.9P 0.46As 0.54 was previously synthesized by mechanical alloying followed by a solid-state reaction for crystallization and homogenization. Subsequently, the alloy was comminuted and sintered at 1298 K. The obtained sintered product is aimed to be tested in a magnetic regenerator of a prototype machine.

  2. Preparation of porous nickel-titania cermets and their application to anode materials

    SciTech Connect

    Taimatsu, H.; Kudo, K.; Kaneko, H.; Matsukaze, N.; Iwata, T.

    1995-12-31

    Porous nickel-titania cermets have been prepared as new-type anode materials for solid oxide fuel cells using the solid-state displacement reaction method. The microstructures of the cermets were interwoven aggregate-type, differently from those of conventional nickel-YSZ cermets: nickel and titania phases three-dimensionally entangled each other. These cermets revealed good properties in compatibility of thermal expansion with YSZ, strength, gas permeation and electrical conduction.

  3. A homochiral metal-organic porous material for enantioselective separation and catalysis

    NASA Astrophysics Data System (ADS)

    Seo, Jung Soo; Whang, Dongmok; Lee, Hyoyoung; Jun, Sung Im; Oh, Jinho; Jeon, Young Jin; Kim, Kimoon

    2000-04-01

    Inorganic zeolites are used for many practical applications that exploit the microporosity intrinsic to their crystal structures. Organic analogues, which are assembled from modular organic building blocks linked through non-covalent interactions, are of interest for similar applications. These range from catalysis, separation and sensor technology to optoelectronics, with enantioselective separation and catalysis being especially important for the chemical and pharmaceutical industries. The modular construction of these analogues allows flexible and rational design, as both the architecture and chemical functionality of the micropores can, in principle, be precisely controlled. Porous organic solids with large voids and high framework stability have been produced, and investigations into the range of accessible pore functionalities have been initiated. For example, catalytically active organic zeolite analogues are known, as are chiral metal-organic open-framework materials. However, the latter are only available as racemic mixtures, or lack the degree of framework stability or void space that is required for practical applications. Here we report the synthesis of a homochiral metal-organic porous material that allows the enantioselective inclusion of metal complexes in its pores and catalyses a transesterification reaction in an enantioselective manner. Our synthesis strategy, which uses enantiopure metal-organic clusters as secondary building blocks, should be readily applicable to chemically modified cluster components and thus provide access to a wide range of porous organic materials suitable for enantioselective separation and catalysis.

  4. 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.

  5. Fabrication of interpenetrating polymer network chitosan/gelatin porous materials and study on dye adsorption properties.

    PubMed

    Cui, Li; Xiong, Zihao; Guo, Yi; Liu, Yun; Zhao, Jinchao; Zhang, Chuanjie; Zhu, Ping

    2015-11-01

    One kind of adsorbent based on chitosan and gelatin with interpenetrating polymer networks (IPN) and porous dual structures was prepared using genipin as the cross-linker. These dual structures were demonstrated by means of Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Adsorptions of acid orange II dye from aqueous solution were carried out at different genipin contents, adsorption times and pH values. The results showed that this material was put up the largest adsorption capacity when the genipin content is 0.25 mmol/L, meanwhile, the lower the solution pH value the greater the adsorption capacity. The chitosan/gelatin interpenetrating polymer networks porous material displayed pH-sensitive and rapidly response in adsorption and desorption to pH altered. It is indicated that the cross-linked chitosan/gelatin interpenetrating polymer networks porous material could be used as a recyclable adsorbent in removal or separation of anionic dyes as environmental pH condition changed. PMID:26256356

  6. Porous coordination polymers as novel sorption materials for heat transformation processes.

    PubMed

    Janiak, Christoph; Henninger, Stefan K

    2013-01-01

    Porous coordination polymers (PCPs)/metal-organic frameworks (MOFs) are inorganic-organic hybrid materials with a permanent three-dimensional porous metal-ligand network. PCPs or MOFs are inorganic-organic analogs of zeolites in terms of porosity and reversible guest exchange properties. Microporous water-stable PCPs with high water uptake capacity are gaining attention for low temperature heat transformation applications in thermally driven adsorption chillers (TDCs) or adsorption heat pumps (AHPs). TDCs or AHPs are an alternative to traditional air conditioners or heat pumps operating on electricity or fossil fuels. By using solar or waste heat as the operating energy TDCs or AHPs can significantly help to minimize primary energy consumption and greenhouse gas emissions generated by industrial or domestic heating and cooling processes. TDCs and AHPs are based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. The process is driven and controlled by the microporosity and hydrophilicity of the employed sorption material. Here we summarize the current investigations, developments and possibilities of PCPs/MOFs for use in low-temperature heat transformation applications as alternative materials for the traditional inorganic porous substances like silica gel, aluminophosphates or zeolites. PMID:23945102

  7. 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

  8. Hierarchical meso-macro structure porous carbon black as electrode materials in Li-air battery

    NASA Astrophysics Data System (ADS)

    Kang, Jun; Li, Oi Lun; Saito, Nagahiro

    2014-09-01

    A new class of hierarchical structure porous carbon black, carbon nanoballs (CNBs), was generated by solution plasma process (SPP) with benzene. The structural characterization revealed that CNBs have excellent meso-macro hierarchical pore structure, with an averaged diameter size of 14.5 nm and a total pore volume of 1.13 cm3 g-1. The CNBs are aggregated forming inter-connected pore channels in different directions on both the meso- and macrometer length scales. The discharge capacity of CNBs reached 3600 mAh g-1, which exceeded the capacity of Ketjen Black EC-600JD (a commercial carbon black with highest cell performance) by 30-40%. The excellent discharge capacity was contributed by the co-existence of high pore volume and meso-macro hierarchical porous structure. This new class carbon material exhibited higher discharge capacity compared to commercial porous carbon materials, and is possible to apply as the next generation of electrode materials in lithium-air (Li-air) battery. The structural and electrochemical properties accompanied with the synthesis mechanism of CNBs were discussed in details.

  9. Determination of water retention in stratified porous materials

    USGS Publications Warehouse

    Constantz, J.

    1995-01-01

    Predicted and measured water-retention values, ??(??), were compared for repacked, stratified core samples consisting of either a sand with a stone-bearing layer or a sand with a clay loam layer in various spatial orientations. Stratified core samples were packed in submersible pressure outflow cells, then water-retention measurements were performed between matric potentials, ??, of 0 to -100 kPa. Predictions of ??(??) were based on a simple volume-averaging model using estimates of the relative fraction and ??(??) values of each textural component within a stratified sample. In general, predicted ??(??) curves resembled measured curves well, except at higher saturations in a sample consisting of a clay loam layer over a sand layer. In this case, the model averaged the air-entry of both materials, while the air-entry of the sample was controlled by the clay loam in contact with the cell's air-pressure inlet. In situ, avenues for air-entry generally exist around clay layers, so that the model should adequately predict air-entry for stratified formations regardless of spatial orientation of fine versus coarse layers. Agreement between measured and predicted volumetric water contents, ??, was variable though encouraging, with mean differences between measured and predicted ?? values in the range of 10%. Differences in ?? of this magnitude are expected due to variability in pore structure between samples, and do not indicate inherent problems with the volume averaging model. This suggets that explicit modeling of stratified formations through detailed characterization of the stratigraphy has the potential of yielding accurate ??(??) values. However, hydraulic-equilibration times were distinctly different for each variation in spatial orientation of textural layering, indicating that transient behavior during drainage in stratified formations is highly sensitive to the stratigraphic sequence of textural components, as well as the volume fraction of each textural

  10. Method and apparatus for measuring surface changes, in porous materials, using multiple differently-configured acoustic sensors

    DOEpatents

    Hietala, Susan Leslie; Hietala, Vincent Mark; Tigges, Chris Phillip

    2001-01-01

    A method and apparatus for measuring surface changes, such as mass uptake at various pressures, in a thin-film material, in particular porous membranes, using multiple differently-configured acoustic sensors.

  11. Small angle scattering methods to study porous materials under high uniaxial strain.

    PubMed

    Le Floch, Sylvie; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso

    2015-02-01

    We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly porous materials. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of porous materials by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar porous systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells. PMID:25725857

  12. Small angle scattering methods to study porous materials under high uniaxial strain

    NASA Astrophysics Data System (ADS)

    Le Floch, Sylvie; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso

    2015-02-01

    We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly porous materials. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of porous materials by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar porous systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.

  13. Small angle scattering methods to study porous materials under high uniaxial strain

    SciTech Connect

    Le Floch, Sylvie Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso

    2015-02-15

    We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly porous materials. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of porous materials by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar porous systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.

  14. 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

  15. Hierarchical porous nickel oxide-carbon nanotubes as advanced pseudocapacitor materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Su, Aldwin D.; Zhang, Xiang; Rinaldi, Ali; Nguyen, Son T.; Liu, Huihui; Lei, Zhibin; Lu, Li; Duong, Hai M.

    2013-03-01

    Hierarchical porous carbon anode and metal oxide cathode are promising for supercapacitor with both high energy density and high power density. This Letter uses NiO and commercial carbon nanotubes (CNTs) as electrode materials for electrochemical capacitors with high energy storage capacities. Experimental results show that the specific capacitance of the electrode materials for 10%, 30% and 50% CNTs are 279, 242 and 112 F/g, respectively in an aqueous 1 M KOH electrolyte at a charge rate of 0.56 A/g. The maximum specific capacitance is 328 F/g at a charge rate of 0.33 A/g.

  16. Superior supercapacitor electrode material from hydrazine hydrate modified porous polyacrylonitrile fiber

    NASA Astrophysics Data System (ADS)

    Li, Ying; Lu, Chunxiang; Wang, Junzhong; Yan, Hua; Zhang, Shouchun

    2016-03-01

    A hierarchical porous carbon fiber with high nitrogen doping was fabricated for high-performance supercapacitor. For the purpose of high nitrogen retention, the porous polyacrylonitrile fiber was treated by hydrazine hydrate, and then underwent pre-oxidation, carbonization, and activation in sequence. The resulted material exhibited high nitrogen content of 7.82 at.%, large specific surface area of 1963.3m2 g‑1, total pore volume of 1.523cm3 g‑1, and the pores with size range of 1-4nm were account for 49.1%. Due to these features, the high reversible capacitance of 415F g‑1 and the good performance in heavy load discharge were obtained. In addition, the amazing cyclability was observed after 10,000 circles without capacitance fading.

  17. Sponge-Like Behaviour in Isoreticular Cu(Gly-His-X) Peptide-Based Porous Materials.

    PubMed

    Martí-Gastaldo, Carlos; Warren, John E; Briggs, Michael E; Armstrong, Jayne A; Thomas, K Mark; Rosseinsky, Matthew J

    2015-11-01

    We report two isoreticular 3D peptide-based porous frameworks formed by coordination of the tripeptides Gly-L-His-Gly and Gly-L-His-L-Lys to Cu(II) which display sponge-like behaviour. These porous materials undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2 O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal-organic frameworks built from more rigid "classical" linkers. PMID:26406996

  18. Sponge-Like Behaviour in Isoreticular Cu(Gly-His-X) Peptide-Based Porous Materials

    PubMed Central

    Martí-Gastaldo, Carlos; Warren, John E; Briggs, Michael E; Armstrong, Jayne A; Thomas, K Mark; Rosseinsky, Matthew J

    2015-01-01

    We report two isoreticular 3D peptide-based porous frameworks formed by coordination of the tripeptides Gly-l-His-Gly and Gly-l-His-l-Lys to CuII which display sponge-like behaviour. These porous materials undergo structural collapse upon evacuation that can be reversed by exposure to water vapour, which permits recovery of the original open channel structure. This is further confirmed by sorption studies that reveal that both solids exhibit selective sorption of H2O while CO2 adsorption does not result in recovery of the original structures. We also show how the pendant aliphatic amine chains, present in the framework from the introduction of the lysine amino acid in the peptidic backbone, can be post-synthetically modified to produce urea-functionalised networks by following methodologies typically used for metal–organic frameworks built from more rigid “classical” linkers. PMID:26406996

  19. 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.

  20. From spent Mg/Al layered double hydroxide to porous carbon materials.

    PubMed

    Laipan, Minwang; Zhu, Runliang; Chen, Qingze; Zhu, Jianxi; Xi, Yunfei; Ayoko, Godwin A; He, Hongping

    2015-12-30

    Adsorption has been considered as an efficient method for the treatment of dye effluents, but proper disposal of the spent adsorbents is still a challenge. This work attempts to provide a facile method to reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II (OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washed with acid to obtain porous carbon materials. Thermogravimetric analysis results suggested that the carbonization could be well achieved above 600°C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000°C, respectively. Scanning electron microscope showed that the obtained carbon materials possessed a crooked flaky morphology. Nitrogen adsorption-desorption results showed that the carbon materials had large BET surface area and pore volume, e.g., 1426 m(2)/g and 1.67 cm(3)/g for the sample carbonized at 800°C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon materials had high efficiency in toluene removal. This work provided a facile approach for synthesizing porous carbon materials using spent Mg/Al-LDH. PMID:26257095

  1. Hierarchical ZnO-Ag-C composite porous microspheres with superior electrochemical properties as anode materials for lithium ion batteries.

    PubMed

    Xie, Qingshui; Ma, Yating; Zeng, Deqian; Zhang, Xiaoqiang; Wang, Laisen; Yue, Guanghui; Peng, Dong-Liang

    2014-11-26

    Hierarchical ZnO-Ag-C composite porous microspheres are successfully synthesized by calcination of the preproduced zinc-silver citrate porous microspheres in argon. The carbon derives from the in situ carbonization of carboxylic acid groups in zinc-silver citrate during annealing treatment. The average particle size of ZnO-Ag-C composite porous microspheres is approximate 1.5 μm. When adopted as the electrode materials in lithium ion batteries, the obtained composite porous microspheres display high specific capacity, excellent cyclability, and good rate capability. A discharge capacity as high as 729 mA h g(-1) can be retained after 200 cycles at 100 mA g(-1). The excellent electrochemical properties of ZnO-Ag-C are ascribed to its unique hierarchical porous configuration as well as the modification of silver and carbon. PMID:25350718

  2. 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

  3. Ignition analysis of a porous energetic material. 2. Ignition at a closed heated end

    SciTech Connect

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

    1998-11-01

    A continuation of an ignition analysis for porous energetic materials subjected to a constant energy flux is presented. In the first part, the analysis was developed for the case of an open-end, semi-infinite material such that gas flow, generated by thermal expansion, flowed out of the porous solid, thereby removing energy from the system. In the present study, the case of a closed end is considered, and thus the thermally-induced gas flow is now directed into the solid. In these studies, an asymptotic perturbation analysis, based on the smallness of the gas-to-solid density ratio and the largeness of the activation energy, is utilized to describe the inert and transition stages leading to thermal runaway. In both cases it is found that the effects of porosity provide a leading-order reduction in the time to ignition relative to that for the nonporous problem, arising from the reduced amount of solid material that must be heated and the difference in thermal conductivities of the solid and gaseous phases. A correction to the leading-order ignition-delay time, however, is provided by the convective flow of gas through the solid, and the sign of this correction is shown to depend on the direction of the gas flow. Thus, gas flowing out of an open-end solid was previously shown to give a positive correction to the leading-order time to ignition. Here, however, it is demonstrated that when the flow of gas is directed into the porous solid, the relative transport effects associated with the gas flow serve to preheat the material, resulting in a negative correction and hence a decrease in the ignition-delay time.

  4. Bioinspired large-scale aligned porous materials assembled with dual temperature gradients

    PubMed Central

    Bai, Hao; Chen, Yuan; Delattre, Benjamin; Tomsia, Antoni P.; Ritchie, Robert O.

    2015-01-01

    Natural materials, such as bone, teeth, shells, and wood, exhibit outstanding properties despite being porous and made of weak constituents. Frequently, they represent a source of inspiration to design strong, tough, and lightweight materials. Although many techniques have been introduced to create such structures, a long-range order of the porosity as well as a precise control of the final architecture remain difficult to achieve. These limitations severely hinder the scale-up fabrication of layered structures aimed for larger applications. We report on a bidirectional freezing technique to successfully assemble ceramic particles into scaffolds with large-scale aligned, lamellar, porous, nacre-like structure and long-range order at the centimeter scale. This is achieved by modifying the cold finger with a polydimethylsiloxane (PDMS) wedge to control the nucleation and growth of ice crystals under dual temperature gradients. Our approach could provide an effective way of manufacturing novel bioinspired structural materials, in particular advanced materials such as composites, where a higher level of control over the structure is required. PMID:26824062

  5. Porous TiO₂ materials through Pickering high-internal phase emulsion templating.

    PubMed

    Li, Xiaodong; Sun, Guanqing; Li, Yecheng; Yu, Jimmy C; Wu, Jie; Ma, Guang-Hui; Ngai, To

    2014-03-18

    We report a facile method for preparing porous structured TiO2 materials by templating from Pickering high-internal phase emulsions (HIPEs). A Pickering HIPE with an internal phase of up to 80 vol %, stabilized by poly(N-isopropylacrylamide)-based microgels and TiO2 solid nanoparticles, was first formulated and employed as a template to prepare the porous TiO2 materials with an interconnected structure. The resultant materials were characterized by scanning electron microscopy, X-ray diffraction, and mercury intrusion. Our results showed that the parent emulsion droplets promoted the formation of macropores and interconnecting throats with sizes of ~50 and ~10 μm, respectively, while the interfacially adsorbed microgel stabilizers drove the formation of smaller pores (~100 nm) throughout the macroporous walls after drying and sintering. The interconnected structured network with the bimodal pores could be well preserved after calcinations at 800 °C. In addition, the photocatalytic activity of the fabricated TiO2 was evaluated by measuring the photodegradation of Rhodamine B in water. Our results revealed that the fabricated TiO2 materials are good photocatalysts, showing enhanced activity and stability in photodegrading organic molecules. PMID:24601731

  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. A novel nano-porous alumina biomaterial with potential for loading with bioactive materials.

    PubMed

    Walpole, Andrew R; Xia, Zhidao; Wilson, Crispian W; Triffitt, James T; Wilshaw, Peter R

    2009-07-01

    Nano-porous alumina, with the potential for being loaded with bioactive materials, has been proposed as a novel material for coating implants. In this study, the shear strength of the interface between such nano-porous anodic aluminium oxide (AAO) coatings and titanium substrates, their biocompatibility, and their potential for pore loading have been investigated. An interface shear strength in excess of 29 MPa was obtained which is comparable with that of conventional plasma sprayed hydroxyapatite implant coatings. The viability and differentiation of MG63 osteoblastic cells co-cultured on the coating was found to be broadly comparable to that of similar cells co-cultured on conventional bioinert implant materials such as titanium and fully dense alumina. Extensive pore loading with silica nano-particles of different sizes and in different combinations was demonstrated throughout the thickness of AAO layers 1 microm and 60 microm thick. This work has demonstrated, that with suitable choice of pore filling materials, this novel coating might simultaneously combat infection, encourage bone regeneration, and secure fixation of the implant to bone. PMID:18481790

  10. 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.

  11. 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)

  12. Infiltrating sulfur into a highly porous carbon sphere as cathode material for lithium–sulfur batteries

    SciTech Connect

    Zhao, Xiaohui; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Cho, Kwon-Koo; Ahn, Jou-Hyeon

    2014-10-15

    Highlights: • A highly porous carbon (HPC) with regular spherical morphology was synthesized. • Sulfur/HPC composites were prepared by melt–diffusion method. • Sulfur/HPC composites showed improved cyclablity and long-term cycle life. - Abstract: Sulfur composite material with a highly porous carbon sphere as the conducting container was prepared. The highly porous carbon sphere was easily synthesized with resorcinol–formaldehyde precursor as the carbon source. The morphology of the carbon was observed with field emission scanning electron microscope and transmission electron microscope, which showed a well-defined spherical shape. Brunauer–Emmett–Teller analysis indicated that it possesses a high specific surface area of 1563 m{sup 2} g{sup −1} and a total pore volume of 2.66 cm{sup 3} g{sup −1} with a bimodal pore size distribution, which allow high sulfur loading and easy transportation of lithium ions. Sulfur carbon composites with varied sulfur contents were prepared by melt–diffusion method and lithium sulfur cells with the sulfur composites showed improved cyclablity and long-term cycle life.

  13. Porous Materials with Tunable Structure and Mechanical Properties via Templated Layer-by-Layer Assembly.

    PubMed

    Ziminska, Monika; Dunne, Nicholas; Hamilton, Andrew R

    2016-08-31

    The deposition of stiff and strong coatings onto porous templates offers a novel strategy for fabricating macroscale materials with controlled architectures at the micro- and nanoscale. Here, layer-by-layer assembly is utilized to fabricate nanocomposite-coated foams with highly customizable properties by depositing polymer-nanoclay coatings onto open-cell foam templates. The compressive mechanical behavior of these materials evolves in a predictable manner that is qualitatively captured by scaling laws for the mechanical properties of cellular materials. The observed and predicted properties span a remarkable range of density-stiffness space, extending from regions of very soft elastomer foams to very stiff, lightweight honeycomb and lattice materials. PMID:27513218

  14. 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."

  15. 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

  16. Strengthening of polymer ordered porous materials based on a layered nanocomposite internal structure

    NASA Astrophysics Data System (ADS)

    Heng, Liping; Guo, Xieyou; Guo, Tianqi; Wang, Bin; Jiang, Lei

    2016-07-01

    Ordered porous polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered porous polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on.Ordered porous polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered porous polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on. Electronic supplementary information (ESI) available: SEM image of hexagonal silicon pillar templates, AFM images of clay platelets on a silicon substrate, photographs of free-standing gels, X-ray diffraction profiles for dried materials, FTIR and TGA of the samples, and

  17. Regular Heat Regime of Heating of Moist Capillary-Porous Materials in the Process of Their Drying

    NASA Astrophysics Data System (ADS)

    Ol'shanskii, A. I.

    2014-11-01

    Results of investigation of the drying of plane samples of different capillary-porous materials by the method of regular heat regime are presented. Experimental empirical dependences defining the kinetics of drying of these materials have been obtained. The dependences of the rate of heating of a moist capillary-porous material and the rate of decrease in the moisture content in it on different factors determining the drying process were investigated. The influence of these factors on the rate of heating of such a material and the rate of removal of moisture from it were determined.

  18. The use of acoustic methods to determine the parameters of porous materials

    NASA Astrophysics Data System (ADS)

    Malecki, Ignacy; Ranachowski, Jerzy

    Porous media are a subject of research in a variety of scientific disciplines, including physics, mechanics, electrical engineering, materials science, and acoustics. The subject of this article is a comparison of the methods used in theoretical mechanics with standard acoustic methods. The authors start by examining the method of static averaging of the mechanical properties of porous media. This method makes it possible to determine substitute static moduli of elasticity, which, however, does not meet the needs of acoustics. More suitable methods include the dynamic methods developed in the works of J. Lewandowski, among others. These methods are based on a motion equation in which the tensor of elasticity is assigned a complex value which accounts for the medium's dynamic properties and losses. The transition from a complex tensor of elasticity to the velocity and damping of an acoustic wave poses no particular problems. On the backdrop of the theory of porous materials used in mechanics, the authors present their own theory for the acoustic properties of these materials. They call it the theory of 'compound obstacles', which initially examines the interference offered by a solitary inclusion in a homogeneous medium to the propagation of an acoustic wave. This is followed by the calculation of the interference caused by a group of inclusions using the concept of the density of obstacles. In turn, this leads to general formulas for acoustic wave velocity and damping as functions of obstacle density. The authors consider examples of a spherical inclusion in a liquid and a hollow spheroidal inclusion in a solid. The article also contains the results of experiments conducted to verify the 'compound obstacles' theory. The authors measured the velocity of an ultrasound wave in electrical engineering porcelain with varying degrees of porosity and in glycerine in which glass balls were suspended.

  19. 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.

  20. Solvability of a quasi-steady rolling problem for porous materials

    NASA Astrophysics Data System (ADS)

    Angelov, T. A.

    2014-04-01

    A quasi-steady rolling problem with nonlocal friction, for porous rigid-plastic, strain-rate-sensitive and strain hardening materials, is considered. A variational formulation is derived, consisting of a variational inequality and two evolution equations, coupling the velocity, strain hardening and relative density variables. The convergence of a variable stiffness parameters method is proved, and existence and uniqueness results are obtained. An algorithm, combining this method with the finite element method, is proposed and used for solving an illustrative rolling problem.

  1. Solvability of a quasi-steady rolling problem for porous materials

    NASA Astrophysics Data System (ADS)

    Angelov, T. A.

    2013-05-01

    A quasi-steady rolling problem with nonlocal friction, for porous rigid-plastic, strain-rate-sensitive and strain hardening materials, is considered. A variational formulation is derived, consisting of a variational inequality and two evolution equations, coupling the velocity, strain hardening and relative density variables. The convergence of a variable stiffness parameters method is proved, and existence and uniqueness results are obtained. An algorithm, combining this method with the finite element method, is proposed and used for solving an illustrative rolling problem.

  2. Cost-effective synthesis of amine-tethered porous materials for carbon capture.

    PubMed

    Lu, Weigang; Bosch, Mathieu; Yuan, Daqiang; Zhou, Hong-Cai

    2015-02-01

    A truly cost-effective strategy for the synthesis of amine-tethered porous polymer networks (PPNs) has been developed. A network containing diethylenetriamine (PPN-125-DETA) exhibits a high working capacity comparable to current state-of-art technology (30 % monoethanolamine solutions), yet it requires only one third as much energy for regeneration. It has also been demonstrated to retain over 90 % capacity after 50 adsorption-desorption cycles of CO2 in a temperature-swing adsorption process. The results suggest that PPN-125-DETA is a very promising new material for carbon capture from flue gas streams. PMID:25314657

  3. 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

  4. High-throughput Characterization of Porous Materials Using Graphics Processing Units

    SciTech Connect

    Kim, Jihan; Martin, Richard L.; Ruebel, Oliver; Haranczyk, Maciej; Smit, Berend

    2012-03-19

    We have developed a high-throughput graphics processing units (GPU) code that can characterize a large database of crystalline porous materials. In our algorithm, the GPU is utilized to accelerate energy grid calculations where the grid values represent interactions (i.e., Lennard-Jones + Coulomb potentials) between gas molecules (i.e., CH$_{4}$ and CO$_{2}$) and material's framework atoms. Using a parallel flood fill CPU algorithm, inaccessible regions inside the framework structures are identified and blocked based on their energy profiles. Finally, we compute the Henry coefficients and heats of adsorption through statistical Widom insertion Monte Carlo moves in the domain restricted to the accessible space. The code offers significant speedup over a single core CPU code and allows us to characterize a set of porous materials at least an order of magnitude larger than ones considered in earlier studies. For structures selected from such a prescreening algorithm, full adsorption isotherms can be calculated by conducting multiple grand canonical Monte Carlo simulations concurrently within the GPU.

  5. 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.

  6. 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

  7. Optimization and Use of 3D sintered porous material in medical field for mixing fibrin glue.

    NASA Astrophysics Data System (ADS)

    Delmotte, Y.; Laroumanie, H.; Brossard, G.

    2012-04-01

    In medical field, Mixing of two or more chemical components (liquids and/or gases) is extremely important as improper mixing can affect the physico-chemical properties of the final product. At Baxter Healthcare Corporation, we are using a sintered porous material (PM) as a micro-mixer in medical device for mixing Fibrinogen and Thrombin in order to obtain a homogeneous polymerized Fibrin glue clot used in surgery. First trials were carried out with an interconnected PM from Porvair® (made of PE - porosity: 40% - permeability: 18Darcy). The injection rate is very low, usually about 10mL/min (Re number about 50) which keeps fluids in a laminar flow. Such a low flow rate does not favour mixing of fluids having gradient of viscosity if a mixer is not used. Promising results that were obtained lead the team to understand this ability to mix fluids which will be presented in the poster. Topology of porous media (PM) which associates a solid phase with interconnected (or not) porous structure is known and used in many commodity products. Researches on PM usually focus on flows inside this structure. By opposition to transport and filtration capacity, as well as mechanic and thermic properties, mixing is rarely associated with PM. However over the past few years, we shown that some type of PM have a real capacity to mix certain fluids. Poster will also describe the problematic of mixing complex biological fluids as fibrinogen and Thrombin. They indeed present a large viscosity difference (ratio about 120) limiting the diffusion and the interaction between the two solutions. As those products are expensive, we used Water (1cPo) and Glycerol 87% (120cPo) which are matching the viscosities of Thrombin and Fibrinogen. A parametric investigation of the "porous micro-mixer" as well as a scale up investigation was carried out to examine the influence of both diffusion and advection to successful mix fluids of different viscosity. Experiments were implemented with Planar Laser

  8. Methods of using structures including catalytic materials disposed within porous zeolite materials to synthesize hydrocarbons

    DOEpatents

    Rollins, Harry W.; Petkovic, Lucia M.; Ginosar, Daniel M.

    2011-02-01

    Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

  9. 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

  10. Multi-contrast 3D X-ray imaging of porous and composite materials

    SciTech Connect

    Sarapata, Adrian; Herzen, Julia; Ruiz-Yaniz, Maite; Zanette, Irene; Rack, Alexander; Pfeiffer, Franz

    2015-04-13

    Grating-based X-ray computed tomography allows for simultaneous and nondestructive determination of the full X-ray complex index of refraction and the scattering coefficient distribution inside an object in three dimensions. Its multi-contrast capabilities combined with a high resolution of a few micrometers make it a suitable tool for assessing multiple phases inside porous and composite materials such as concrete. Here, we present quantitative results of a proof-of-principle experiment performed on a concrete sample. Thanks to the complementarity of the contrast channels, more concrete phases could be distinguished than in conventional attenuation-based imaging. The phase-contrast reconstruction shows high contrast between the hardened cement paste and the aggregates and thus allows easy 3D segmentation. Thanks to the dark-field image, micro-cracks inside the coarse aggregates are visible. We believe that these results are extremely interesting in the field of porous and composite materials studies because of unique information provided by grating interferometry in a non-destructive way.

  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. Porous materials with pre-designed single-molecule traps for CO2 selective adsorption

    SciTech Connect

    Li, JR; Yu, JM; Lu, WG; Sun, LB; Sculley, J; Balbuena, PB; Zhou, HC

    2013-02-26

    Despite tremendous efforts, precise control in the synthesis of porous materials with pre-designed pore properties for desired applications remains challenging. Newly emerged porous metal-organic materials, such as metal-organic polyhedra and metal-organic frameworks, are amenable to design and property tuning, enabling precise control of functionality by accurate design of structures at the molecular level. Here we propose and validate, both experimentally and computationally, a precisely designed cavity, termed a 'single-molecule trap', with the desired size and properties suitable for trapping target CO2 molecules. Such a single-molecule trap can strengthen CO2-host interactions without evoking chemical bonding, thus showing potential for CO2 capture. Molecular single-molecule traps in the form of metal-organic polyhedra are designed, synthesised and tested for selective adsorption of CO2 over N-2 and CH4, demonstrating the trapping effect. Building these pre-designed single-molecule traps into extended frameworks yields metal-organic frameworks with efficient mass transfer, whereas the CO2 selective adsorption nature of single-molecule traps is preserved.

  13. 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

  14. One-dimensional scanning of moisture in heated porous building materials with NMR

    NASA Astrophysics Data System (ADS)

    van der Heijden, G. H. A.; Huinink, H. P.; Pel, L.; Kopinga, K.

    2011-02-01

    In this paper we present a new dedicated NMR setup which is capable of measuring one-dimensional moisture profiles in heated porous materials. The setup, which is placed in the bore of a 1.5 T whole-body scanner, is capable of reaching temperatures up to 500 °C. Moisture and temperature profiles can be measured quasi simultaneously with a typical time resolution of 2-5 min. A methodology is introduced for correcting temperature effects on NMR measurements at these elevated temperatures. The corrections are based on the Curie law for paramagnetism and the observed temperature dependence of the relaxation mechanisms occurring in porous materials. Both these corrections are used to obtain a moisture content profile from the raw NMR signal profile. To illustrate the methodology, a one-sided heating experiment of concrete with a moisture content in equilibrium with 97% RH is presented. This kind of heating experiment is of particular interest in the research on fire spalling of concrete, since it directly reveals the moisture and heat transport occurring inside the concrete. The obtained moisture profiles reveal a moisture peak building up behind the boiling front, resulting in a saturated layer. To our knowledge the direct proof of the formation of a moisture peak and subsequent moisture clogging has not been reported before.

  15. Open flow hot isostatic pressing assisted synthesis of highly porous materials and catalysts

    NASA Astrophysics Data System (ADS)

    Siadati, Mohammad Hossein

    Open-flow hot isostatic pressing (OFHIP) technique is applied for synthesizing molecular sieves and highly porous catalytic materials. First, the isostatic pressure is applied to the starting material/catalyst precursor, and then heat is applied. Under this condition, as the organic components gradually decompose and leave the material, the voids left behind are immediately filled/replaced by the gas (pressure medium) in flow. This substitution warrants the preservation as well as the uniformity of the voids/pores. The result is a very porous material with very uniform pore size distribution. Another advantage is the production of the catalyst directly from the precursor, in the absence of solvent (neat), rendering the process simpler and less costly than previous processes. The entire process takes place under flow of the gas that is used as medium to develop the isostatic pressure. Consequently, the entire process, as well as the final product produced, is devoid of any undesirable residues. This endeavor also introduces a viable technique for mass-producing porous materials/catalysts. The resulting materials are termed "amorphous sulfide sieves" to reflect their unique properties that include high surface area, narrow pore size distribution and high activity. The catalysts are potentially licensable to all petroleum and petroleum chemical companies for a wide variety of environmental and product improvement purposes. The results obtained on unpromoted samples synthesized at 300°C indicate that as the synthesis pressure is increased, both surface area and catalytic activity of the materials produced increase. The increase in activity k value from 3 to 6 x 10-7 mol/g.s corresponds to increase in pressure from 100 to 800 psi, respectively. The N2 gas used as pressure medium results in highly porous materials but low activity. H 2 seems to be the ideal gas for both pressure medium and reducing agent. Co-promoted catalysts synthesized at 1400 psi and 300°C show

  16. The Effect of Plasma Surface Treatment on a Porous Green Ceramic Film with Polymeric Binder Materials

    NASA Astrophysics Data System (ADS)

    Jeong, Woo Yun

    2013-06-01

    To reduce time and energy during thermal binder removal in the ceramic process, plasma surface treatment was applied before the lamination process. The adhesion strength in the lamination films was enhanced by oxidative plasma treatment of the porous green ceramic film with polymeric binding materials. The oxygen plasma characteristics were investigated through experimental parameters and weight loss analysis. The experimental results revealed the need for parameter analysis, including gas material, process time, flow rate, and discharge power, and supported a mechanism consisting of competing ablation and deposition processes. The weight loss analysis was conducted for cyclic plasma treatment rather than continuous plasma treatment for the purpose of improving the film's permeability by suppressing deposition of the ablated species. The cyclic plasma treatment improved the permeability compared to the continuous plasma treatment.

  17. Production of nanotubes in delignified porous cellulosic materials after hydrolysis with cellulase.

    PubMed

    Koutinas, Αthanasios Α; Papafotopoulou-Patrinou, Evgenia; Gialleli, Angelika-Ioanna; Petsi, Theano; Bekatorou, Argyro; Kanellaki, Maria

    2016-08-01

    In this study, tubular cellulose (TC), a porous cellulosic material produced by delignification of sawdust, was treated with a Trichoderma reesei cellulase in order to increase the proportion of nano-tubes. The effect of enzyme concentration and treatment duration on surface characteristics was studied and the samples were analyzed with BET, SEM and XRD. Also, a composite material of gelatinized starch and TC underwent enzymatic treatment in combination with amylase (320U) and cellulase (320U) enzymes. For TC, the optimum enzyme concentration (640U) led to significant increase of TC specific surface area and pore volume along with the reduction of pore diameter. It was also shown that the enzymatic treatment did not result to a significant change of cellulose crystallinity index. The produced nano-tubular cellulose shows potential for application to drug and chemical preservative delivery systems. PMID:26996258

  18. Superstructured Carbon Nanotube/Porous Silicon Hybrid Materials for Lithium-Ion Battery Anodes

    NASA Astrophysics Data System (ADS)

    Lee, Jun-Ki; Kang, Shin-Hyun; Choi, Sung-Min

    2015-03-01

    High energy Li-ion batteries (LIBs) are in great demand for electronics, electric-vehicles, and grid-scale energy storage. To further increase the energy and power densities of LIBs, Si anodes have been intensively explored due to their high capacity, and high abundance compared with traditional carbon anodes. However, the poor cycle-life caused by large volume expansion during charge/discharge process has been an impediment to its applications. Recently, superstructured Si materials were received attentions to solve above mentioned problem in excellent mechanical properties, large surface area, and fast Li and electron transportation aspects, but applying superstructures to anode is in early stage yet. Here, we synthesized superstructured carbon nanotubes (CNTs)/porous Si hybrid materials and its particular electrochemical properties will be presented. Department of Nuclear and Quantum Engineering

  19. Liners of natural porous materials to minimize pollutant migration. Final report, Oct. 1975 - Sep. 1977

    SciTech Connect

    Fuller, W.H.

    1981-07-01

    The use of natural low-cost materials as barriers for minimizing pollution migration out of landfills by retaining contaminants from liquids was investigated. The relative effectiveness of natural low-cost liners of crushed limestone, clayey soil, hydrous oxides of iron, and crushed pecan hulls for minimizing the migration of Be, Cd, Cr, Fe, Ni, Zn, and total organic carbon constituents of municipal solid waste landfill leachates was evaluated. Several leachate variables such as aqueous dilution, aeration, pH, and flux were also studied for their effect on movement of metals through 11 representative U.S. soils. Laboratory investigations using soil columns as a first step in screening for potential liners and manipulation practices are described. Limestone and hydrous iron oxide were found to be potentially useful as porous liners for retention of metallic leachate constituents. The amounts of these materials in natural soil were also found to be useful predictors of contaminant removal.

  20. 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.

  1. Short time proton dynamics in bulk ice and in porous anode solid oxide fuel cell materials

    SciTech Connect

    Basoli, Francesco; Senesi, Roberto; Kolesnikov, Alexander I; Licoccia, Silvia

    2014-01-01

    Oxygen reduction and incorporation into solid electrolytes and the reverse reaction of oxygen evolution play a cru-cial role in Solid Oxide Fuel Cell (SOFC) applications. However a detailed un derstanding of the kinetics of the cor-responding reactions, i.e. on reaction mechanisms, rate limiting steps, reaction paths, electrocatalytic role of materials, is still missing. These include a thorough characterization of the binding potentials experienced by protons in the lattice. We report results of Inelastic Neutron Scattering (INS) measurements of the vibrational state of the protons in Ni- YSZ highly porous composites (75% to 90% ), a ceramic-metal material showing a high electrical conductivity and ther mal stability, which is known to be most effectively used as anodes for solid ox ide fuel cells. The results are compared with INS and Deep Inelastic Neutron Scattering (DINS) experiments on the proton binding states in bulk ice.

  2. Development of a Chitosan-Based Biofoam: Application to the Processing of a Porous Ceramic Material

    PubMed Central

    Mathias, Jean-Denis; Tessier-Doyen, Nicolas; Michaud, Philippe

    2011-01-01

    Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the material. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m−1·K−1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic material with open porosity from a slurry prepared with an organic solvent infiltrating the porous network of the foam. PMID:21541051

  3. Rapid Generation of Superheated Steam Using a Water-containing Porous Material

    NASA Astrophysics Data System (ADS)

    Mori, Shoji; Okuyama, Kunito

    Heat treatment by superheated steam has been utilized in several industrial fields including sterilization, desiccation, and cooking. In particular, cooking by superheated steam is receiving increased attention because it has advantages of reducing the salt and fat contents in foods as well as suppressing the oxidation of vitamin C and fat. In this application, quick startup and cut-off responses are required. Most electrically energized steam generators require a relatively long time to generate superheated steam due to the large heat capacities of the water in container and of the heater. Zhao and Liao (2002) introduced a novel process for rapid vaporization of subcooled liquid, in which a low-thermal-conductivity porous wick containing water is heated by a downward-facing grooved heating block in contact with the upper surface of the wick structure. They showed that saturated steam is generated within approximately 30 seconds from room-temperature water at a heat flux 41.2 kW⁄m2. In order to quickly generate superheated steam of approximately 300°C, which is required for cooking, the heat capacity of the heater should be as small as possible and the imposed heat flux should be so high enough that the porous wick is able to dry out in the vicinity of the contact with the heater and that the resulting heater temperature becomes much higher than the saturation temperature. The present paper proposes a simple structured generator to quickly produce superheated steam. Only a fine wire heater is contacted spirally on the inside wall in a hollow porous material. The start-up, cut-off responses and the rate of energy conversion for input power are investigated experimentally. Superheated steam of 300°C is produced in approximately 19 seconds from room-temperature water for an input power of 300 W. The maximum rate of energy conversion in the steady state is approximately 0.9.

  4. Excellent cycling stability and superior rate capability of a graphene-amorphous FePO4 porous nanowire hybrid as a cathode material for sodium ion batteries.

    PubMed

    Yang, Gaoliang; Ding, Bing; Wang, Jie; Nie, Ping; Dou, Hui; Zhang, Xiaogang

    2016-04-28

    A porous nanowire material consisting of graphene-amorphous FePO4 was investigated as an advanced cathode material for sodium ion batteries for large-scale applications. This hybrid cathode material showed excellent cycling performance and superior rate capability, which were attributed to the porous nanowire structure and the existence of graphene. PMID:27064740

  5. Atmospheric methane removal by methane-oxidizing bacteria immobilized on porous building materials.

    PubMed

    Ganendra, Giovanni; De Muynck, Willem; Ho, Adrian; Hoefman, Sven; De Vos, Paul; Boeckx, Pascal; Boon, Nico

    2014-04-01

    Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six porous carrier materials have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building materials at high (~20 % (v/v)) and low (~100 ppmv) methane mixing ratios. Methylocystis parvus in autoclaved aerated concrete (AAC) exhibited the highest methane removal rate at high (28.5 ± 3.8 μg CH₄ g⁻¹ building material h⁻¹) and low (1.7 ± 0.4 μg CH₄ g⁻¹ building material h⁻¹) methane mixing ratio. Due to the higher volume of pores with diameter >5 μm compared to other materials tested, AAC was able to adsorb more bacteria which might explain for the higher methane removal observed. The total methane and carbon dioxide-carbon in the headspace was decreased for 65.2 ± 10.9 % when M. parvus in Ytong was incubated for 100 h. This study showed that immobilized MOB on building materials could be used to remove methane from the air and also act as carbon sink. PMID:24337222

  6. Monodisperse Porous Silicon Spheres as Anode Materials for Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S.

    2015-03-01

    Highly monodisperse porous silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g-1. In particular, reversible Li storage capacities above 1500 mAh g-1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing porous Si-based LIB anode materials by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures.

  7. Monodisperse porous silicon spheres as anode materials for lithium ion batteries.

    PubMed

    Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S

    2015-01-01

    Highly monodisperse porous silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g(-1). In particular, reversible Li storage capacities above 1500 mAh g(-1) were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing porous Si-based LIB anode materials by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures. PMID:25740298

  8. Monodisperse Porous Silicon Spheres as Anode Materials for Lithium Ion Batteries

    PubMed Central

    Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S.

    2015-01-01

    Highly monodisperse porous silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g−1. In particular, reversible Li storage capacities above 1500 mAh g−1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing porous Si-based LIB anode materials by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures. PMID:25740298

  9. Test Method To Quantify The Wicking Properties Of Porous Insulation Materials Designed To Prevent Interstitial Condensation

    NASA Astrophysics Data System (ADS)

    Binder, Andrea; Zirkelbach, Daniel; Künzel, Hartwig

    2010-05-01

    Applying an interior insulation often is the only option for a thermal retrofit, especially when heritage buildings are concerned. In doing so, the original construction becomes colder in winter and interstitial condensation may occur. The common way to avoid harmful condensation beneath the interior insulation of the external wall is the installation of a vapor barrier. Since such a barrier works both ways, it may adversely affect the drying potential of the wall during the warmer seasons. One way to avoid the problems described is the installation of an interior insulation system without a vapor barrier to the inside. Here, the effect of capillary transport in porous hydrophilic media is used to conduct condensing moisture away from the wall/insulation interface back to the surface in contact with the indoor air. Following an increasing demand, several water wicking insulation materials (e.g. Calcium-silicate, Autoclave Aerated Concrete based mineral foam, hydrophilic Glass fiber, Cellulose fiber) have appeared on the market. In the past, different methods have been developed to measure and describe the liquid transport properties of hydrophilic porous media. However, the evaluation of the moisture transport mechanisms and their efficiency in this special field of implementation is very complex because of the interacting vapor- and liquid moisture transfer processes. Therefore, there is no consensus yet on its determination and quantification.

  10. 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

  11. Porous-structured Cu2O/TiO2 nanojunction material toward efficient CO2 photoreduction

    NASA Astrophysics Data System (ADS)

    Xu, Hua; Ouyang, Shuxin; Liu, Lequan; Wang, Defa; Kako, Tetsuya; Ye, Jinhua

    2014-04-01

    Porous-structured Cu2O/TiO2 nanojunction material is successfully fabricated by a facile method via loading Cu2O nanoparticles on the network of a porous TiO2 substrate. The developed Cu2O/TiO2 nanojunction material has a size of several nanometers, in which the p-type Cu2O and n-type TiO2 nanoparticles are closely contacted with each other. The well designed nanojunction structure is beneficial for the charge separation in the photocatalytic reaction. Meanwhile, the porous structure of the Cu2O/TiO2 nanojunction can facilitate the CO2 adsorption and offer more reaction active sites. Most importantly, the gas-phase CO2 photoreduction tests reveal that our developed porous-structured Cu2O/TiO2 nanojunction material exhibits marked photocatalytic activity in the CH4 evolution, about 12, 9, and 7.5 times higher than the pure TiO2, Pt-TiO2, and commercial Degussa P25 TiO2 powders, respectively. The greatly enhanced activity can be attributed to the well designed nanojunction structure combined with the porous structure, which can simultaneously enhance the charge separation efficiency and facilitate the CO2 adsorption.

  12. Porous carbon materials synthesized using IRMOF-3 and furfuryl alcohol as precursor

    NASA Astrophysics Data System (ADS)

    Deka, Pemta Tia; Ediati, Ratna

    2016-03-01

    IRMOF-3 crystals have been synthesized using solvothermal method by adding zinc nitrate hexahydrate with 2-amino-1,4-benzenedicarboxylic acid in N'N-dimethylformamide (DMF) at 100°C for 24 (note as IR-24) and 72 h (note as IR-72). The obtained crystals were characterized using X-ray Diffraction (XRD), SEM (Scanning Electron Microscopy) and Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), FTIR and Isothermal adsorption-desorption N2. The diffractogram solids synthesized show characteristic peak at 2θ 6.8, 9.6 and 13.7°. SEM micrograph show cubic shape of IRMOF-3 crystal. Based on FTIR characterization, IRMOF-3 appear at wavelength (1691,46; 1425,3; 1238,21; 1319,22 dan 3504,42)cm-1. The Isotherm of crystal IRMOF-3 at heating time 24 h and 72 h are type IV. The surface area of IR-24 and IR-72 are respectively 24,758 m2/g and 29,139 m2/g with its dominant mesopores. Carbonaceous materials has been successfully synthesized using IR-24, IR-72 and furfuryl alcohol (FA) as second carbon precursor with variation of carbonation temperature 550, 700 and 850°C. The XRD result from both carbonaceous materials show formation of amorphous carbon and caharacteristic peak of ZnO oxide. Micrograph SEM show that carbonaceous materials have cubic shape as IRMOF-3 and SEM-EDX result indicate Zn and nitrogen content of these materials has decrease until temperature 850°C. Porous carbon using IR-24 and FA (notes as C-24) has increased surface area with higher carbonation temperature. The highest surface area is 1495,023 m2/g. Total pore volume and pore size of C-24 from low to high temperature respectively as (0,338; 0,539 and 1,598) cc/g; (0,107; 0,152 and 0,610) cc/g. Porous carbon using IR-72 and FA (notes as C-72) has smaller surface area than C-24 but its also increased during higher carbonation heating. The highest surface area is 1029,668 m2/g.The total pore volume and pore size of these carbon materials from low to high temperature respectively as (0,390; 0

  13. Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene.

    PubMed

    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

    2016-07-01

    The trade-off between physical adsorption capacity and selectivity of porous materials 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 modeling 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

  14. 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.

  15. Separation of C2 Hydrocarbons by Porous Materials: Metal Organic Frameworks as Platform

    SciTech Connect

    Banerjee, Debasis; Liu, Jun; Thallapally, Praveen K.

    2014-12-22

    The effective separation of small hydrocarbon molecules (C1 – C4) is an important process for petroleum industry, determining the end price of many essential commodities in our daily lives. Current technologies for separation of these molecules rely on energy intensive fractional distillation processes at cryogenic temperature, which is particularly difficult because of their similar volatility. In retrospect, adsorptive separation using solid state adsorbents might be a cost effective alternative. Several types of solid state adsorbents (e.g. zeolite molecular sieves) were tested for separation of small hydrocarbon molecules as a function of pressure, temperature or vacuum. Among different types of plausible adsorbents, metal organic frameworks (MOFs), a class of porous, crystalline, inorganic-organic hybrid materials, is particularly promising. In this brief comment article, we discuss the separation properties of different types of solid state adsorbents, with a particular emphasis on MOF based adsorbents for separation of C2 hydrocarbon molecules.

  16. Sound transmission through double panel constructions lined with elastic porous materials

    NASA Astrophysics Data System (ADS)

    Bolton, J. S.; Green, E. R.

    1986-07-01

    Attention is given to a theory governing one-dimensional wave motion in elastic porous materials which is capable of reproducing experimental transmission measurements for unfaced polyurethane foam layers. Calculations of the transmission loss of fuselage-like foam-lined double panels are presented and it is shown that the foam/panel boundary conditions have a large effect on the panel performance; a hybrid arrangement whereby the foam is bonded directly to one panel and separated from the other by a thin air gap appears to be the most advantageous under practical circumstances. With this configuratiom, the mass-air-mass resonance is minimized and increased low-frequency performance is offered.

  17. Electrochemical synthesis of ZnO nanoflowers and nanosheets on porous Si as photoelectric materials

    NASA Astrophysics Data System (ADS)

    Kou, Huanhuan; Zhang, Xin; Du, Yongling; Ye, Weichun; Lin, Shaoxiong; Wang, Chunming

    2011-03-01

    Well-aligned ZnO nanoflowers and nanosheets were synthesized on porous Si (PS) at different applied potentials by electrodeposition approach. The deposits were grown using the optimized program and were characterized by means of cyclic voltammetry (CV), amperometry I-t (I-t), open-circuit potentiometry. X-ray diffraction (XRD) analysis proved a strong preferential orientation (1 0 0) on PS. Scanning electronic microscopy (SEM) observation showed the deposits consist of nanoflowers with uniform grain size of about 100 nm in diameter and nanosheets, which may have potential applications in nanodevices and nanotechnologies. Thus, ZnO grown on PS can be used as photoelectric materials due to its larger photoelectric effect compared to Si wafer according to open-circuit potential (OCP) study. Optical band gap measurements were made on samples using UV-visible spectrophotometer thus giving a band gap of 3.35 eV.

  18. Diffusion-mediated nuclear spin phase decoherence in cylindrically porous materials

    NASA Astrophysics Data System (ADS)

    Knight, Michael J.; Kauppinen, Risto A.

    2016-08-01

    In NMR or MRI of complex materials, including biological tissues and porous materials, magnetic susceptibility differences within the material 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 model of cylindrical pores within an otherwise homogeneous material, 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.

  19. Diffusion-mediated nuclear spin phase decoherence in cylindrically porous materials.

    PubMed

    Knight, Michael J; Kauppinen, Risto A

    2016-08-01

    In NMR or MRI of complex materials, including biological tissues and porous materials, magnetic susceptibility differences within the material 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 model of cylindrical pores within an otherwise homogeneous material, 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

  20. Measuring sound absorption properties of porous materials using a calibrated volume velocity source

    NASA Astrophysics Data System (ADS)

    Arenas, Jorge P.; Darmendrail, Luis

    2013-10-01

    Measurement of acoustic properties of sound-absorbing materials has been the source of much investigation that has produced practical measuring methods. In particular, the measurement of the normal incidence sound absorption coefficient is commonly done using a well-known configuration of a tube carrying a plane wave. The sound-absorbing coefficient is calculated from the surface impedance measured on a sample of material. Therefore, a direct measurement of the impedance requires knowing the ratio between the sound pressure and the volume velocity. However, the measurement of volume velocity is not straightforward in practice and many methods have been proposed including complex transducers, laser vibrometry, accelerometers and calibrated volume velocity sources. In this paper, a device to directly measure the acoustic impedance of a sample of sound-absorbing material is presented. The device uses an internal microphone in a small cavity sealed by a loudspeaker and a second microphone mounted in front of this source. The calibration process of the device and the limitations of the method are also discussed and measurement examples are presented. The accuracy of the device was assessed by direct comparison with the standardized method. The proposed measurement method was tested successfully with various types of commercial acoustic porous materials.

  1. Ionic Liquids as Versatile Precursors for Functionalized Porous Carbon and Carbon-Oxide Composite Materials by Confined Carbonization

    SciTech Connect

    Dai, Sheng; Wang, Xiqing

    2010-01-01

    Thermolysis of an ionic liquid (IL) gives no char residue, whereas heating the same IL trapped within an oxide framework affords high carbonization yields (see picture). This confinement method allows incorporation of heteroatoms from the parent IL in the final products, for the development of functionalized porous carbon and carbon-oxide composite materials.

  2. Porous graphene-based material as an efficient metal free catalyst for the oxidative dehydrogenation of ethylbenzene to styrene.

    PubMed

    Diao, Jiangyong; Liu, Hongyang; Wang, Jia; Feng, Zhenbao; Chen, Tong; Miao, Changxi; Yang, Weimin; Su, Dang Sheng

    2015-02-25

    Reduced porous graphene oxide as a metal free catalyst was selected for the oxidative dehydrogenation of ethylbenzene to styrene. It showed the best catalytic performance compared with other carbon materials (routinely reduced graphene oxide, graphite powder and oxidized carbon nanotubes) and commercial iron oxide. PMID:25625943

  3. Novel hierarchically porous carbon materials obtained from natural biopolymer as host matrixes for lithium-sulfur battery applications.

    PubMed

    Zhang, Bin; Xiao, Min; Wang, Shuanjin; Han, Dongmei; Song, Shuqin; Chen, Guohua; Meng, Yuezhong

    2014-08-13

    Novel hierarchically porous carbon materials with very high surface areas, large pore volumes and high electron conductivities were prepared from silk cocoon by carbonization with KOH activation. The prepared novel porous carbon-encapsulated sulfur composites were fabricated by a simple melting process and used as cathodes for lithium sulfur batteries. Because of the large surface area and hierarchically porous structure of the carbon material, soluble polysulfide intermediates can be trapped within the cathode and the volume expansion can be alleviated effectively. Moreover, the electron transport properties of the carbon materials can provide an electron conductive network and promote the utilization rate of sulfur in cathode. The prepared carbon-sulfur composite exhibited a high specific capacity and excellent cycle stability. The results show a high initial discharge capacity of 1443 mAh g(-1) and retain 804 mAh g(-1) after 80 discharge/charge cycles at a rate of 0.5 C. A Coulombic efficiency retained up to 92% after 80 cycles. The prepared hierarchically porous carbon materials were proven to be an effective host matrix for sulfur encapsulation to improve the sulfur utilization rate and restrain the dissolution of polysulfides into lithium-sulfur battery electrolytes. PMID:25025228

  4. Gold Nanoparticle Synthesis by 3D Integrated Micro-solution Plasma in a 3D Printed Artificial Porous Dielectric Material

    NASA Astrophysics Data System (ADS)

    Sotoda, Naoya; Tanaka, Kenji; Shirafuji, Tatsuru

    2015-09-01

    Plasma in contact with HAuCl4 aqueous solution can promote the synthesis of gold nanoparticles. To scale up this process, we have developed 3D integrated micro-solution plasma (3D IMSP). It can generate a large number of argon microplasmas in contact with the aqueous solution flowing in a porous dielectric material. The porous dielectric material in our prototype 3D IMSP reactor, however, consists of non-regularly arranged random-sized pores. These pore parameters may be the parameters for controlling the size and dispersion of synthesized gold nanoparticles. We have hence fabricated a 3D IMSP reactor with an artificial porous dielectric material that has regularly arranged same-sized pores by using a 3D printer. We have applied the reactor to the gold- nanoparticle synthesis. We have confirmed the synthesis of gold nanoparticles through the observation of a plasmon resonance absorption peak at 550 nm in the HAuCl4 aqueous solution treated with 3D IMSP. The size and distribution of the synthesized gold nanoparticles are under investigation. We expect that these characteristics of the gold nanoparticles can be manipulated by changing pore size and their distribution in the porous dielectric material.

  5. 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.

  6. Nitrogen-doped porous graphitic carbon as an excellent electrode material for advanced supercapacitors.

    PubMed

    Sun, Li; Tian, Chungui; Fu, Yu; Yang, Ying; Yin, Jie; Wang, Lei; Fu, Honggang

    2014-01-01

    An advanced supercapacitor material based on nitrogen-doped porous graphitic carbon (NPGC) with high a surface area was synthesized by means of a simple coordination-pyrolysis combination process, in which tetraethyl orthosilicate (TEOS), nickel nitrate, and glucose were adopted as porogent, graphitic catalyst precursor, and carbon source, respectively. In addition, melamine was selected as a nitrogen source owing to its nitrogen-enriched structure and the strong interaction between the amine groups and the glucose unit. A low-temperature treatment resulted in the formation of a NPGC precursor by combination of the catalytic precursor, hydrolyzed TEOS, and the melamine-glucose unit. Following pyrolysis and removal of the catalyst and porogent, the NPGC material showed excellent electrical conductivity owing to its high crystallinity, a large Brunauer-Emmett-Teller surface area (SBET =1027 m(2)  g(-1) ), and a high nitrogen level (7.72 wt %). The unusual microstructure of NPGC materials could provide electrochemical energy storage. The NPGC material, without the need for any conductive additives, showed excellent capacitive behavior (293 F g(-1) at 1 A g(-1) ), long-term cycling stability, and high coulombic efficiency (>99.9 % over 5000 cycles) in KOH when used as an electrode. Notably, in a two-electrode symmetric supercapacitor, NPGC energy densities as high as 8.1 and 47.5 Wh kg(-1) , at a high power density (10.5 kW kg(-1) ), were achieved in 6 M KOH and 1 M Et4 NBF4 -PC electrolytes, respectively. Thus, the synthesized NPGC material could be a highly promising electrode material for advanced supercapacitors and other conversion devices. PMID:24307432

  7. Porous ovalbumin scaffolds with tunable properties: a resource-efficient biodegradable material for tissue engineering applications.

    PubMed

    Luo, Baiwen; Choong, Cleo

    2015-01-01

    Natural materials are promising alternatives to synthetic materials used in tissue engineering applications as they have superior biocompatibility and promote better cell attachment and proliferation. Ovalbumin, a natural polymer found in avian egg white, is an example of a nature-derived material. Despite the availability and reported biocompatibility of ovalbumin, limited research has been carried out to investigate the efficacy of ovalbumin-based scaffolds for adipose tissue engineering applications. Hence, the current study was carried out to investigate the effect of different crosslinkers on ovalbumin scaffold properties as first step towards the development of ovalbumin-based scaffolds for adipose tissue engineering applications. In this study, highly porous three-dimensional scaffolds were fabricated by using three different crosslinkers: glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 1,4-butanediol diglycidyl ether. Results showed that the overall scaffold properties such as morphology, pore size and mechanical properties could be modulated based on the type and concentration of crosslinkers used during the fabrication process. Subsequently, the efficacy of the different scaffolds for supporting cell proliferation was investigated. In vitro degradation was also carried on for the best scaffold based on the mechanical and cellular results. Overall, this study is a demonstration of the viability of ovalbumin-based scaffolds as cell carriers for soft tissue engineering applications. PMID:25158688

  8. Giant Negative Area Compressibility Tunable in a Soft Porous Framework Material.

    PubMed

    Cai, Weizhao; Gładysiak, Andrzej; Anioła, Michalina; Smith, Vincent J; Barbour, Leonard J; Katrusiak, Andrzej

    2015-07-29

    A soft porous material [Zn(L)2(OH)2]n·Guest (where L is 4-(1H-naphtho[2,3-d]imidazol-1-yl)benzoate, and Guest is water or methanol) exhibits the strongest ever observed negative area compressibility (NAC), an extremely rare property, as at hydrostatic pressure most materials shrink in all directions and few expand in one direction. This is the first NAC reported in metal-organic frameworks (MOFs), and its magnitude, clearly visible and by far the highest of all known materials, can be reversibly tuned by exchanging guests adsorbed from hydrostatic fluids. This counterintuitive strong NAC of [Zn(L)2(OH)2]n·Guest arises from the interplay of flexible [-Zn-O(H)-]n helices with layers of [-Zn-L-]4 quadrangular puckered rings comprising large channel voids. The compression of helices and flattening of puckered rings combine to give a giant piezo-mechanical response, applicable in ultrasensitive sensors and actuators. The extrinsic NAC response to different hydrostatic fluids is due to varied host-guest interactions affecting the mechanical strain within the range permitted by exceptionally high flexibility of the framework. PMID:25945394

  9. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants.

    PubMed

    Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

    2016-11-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. PMID:27524006

  10. Facile synthesis of reduced graphene oxide-porous silicon composite as superior anode material for lithium-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Jiao, Lian-Sheng; Liu, Jin-Yu; Li, Hong-Yan; Wu, Tong-Shun; Li, Fenghua; Wang, Hao-Yu; Niu, Li

    2016-05-01

    We report a new method for synthesizing reduced graphene oxide (rGO)-porous silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw material source for the synthesis of porous Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the porous structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g-1 can be retained even at a rate of 16 A g-1. A discharge capacity of 830 mA h g-1 at a current density of 1 A g-1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.

  11. Facile synthesis of reduced graphene oxide-porous silicon composite as superior anode material for lithium-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Jiao, Lian-Sheng; Liu, Jin-Yu; Li, Hong-Yan; Wu, Tong-Shun; Li, Fenghua; Wang, Hao-Yu; Niu, Li

    2016-05-01

    We report a new method for synthesizing reduced graphene oxide (rGO)-porous silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw material source for the synthesis of porous Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the porous structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g-1 can be retained even at a rate of 16 A g-1. A discharge capacity of 830 mA h g-1 at a current density of 1 A g-1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.

  12. 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

  13. A mesomechanical analysis of the deformation and fracture in polycrystalline materials with ceramic porous coatings

    NASA Astrophysics Data System (ADS)

    Balokhonov, R. R.; Zinoviev, A. V.; Romanova, V. A.; Batukhtina, E. E.

    2015-10-01

    The special features inherent in the mesoscale mechanical behavior of a porous ceramic coating-steel substrate composite are investigated. Microstructure of the coated material is accounted for explicitly as initial conditions of a plane strain dynamic boundary-value problem solved by the finite difference method. Using a mechanical analogy method, a procedure for generating a uniform curvilinear finite difference computational mesh is developed to provide a more accurate description of the complex grain boundary geometry. A modified algorithm for generation of polycrystalline microstructure of the substrate is designed on the basis of the cellular automata method. The constitutive equations for a steel matrix incorporate an elastic-plastic model for a material subjected to isotropic hardening. The Hall-Petch relation is used to account for the effect of the grain size on the yield stress and strain hardening history. A brittle fracture model for a ceramic coating relying on the Huber criterion is employed. The model allows for crack nucleation in the regions of triaxial tension. The complex inhomogeneous stress and plastic strain patterns are shown to be due to the presence of interfaces of three types: coating-substrate interface, grain boundaries, and pore surfaces.

  14. A Versatile and Scalable Approach toward Robust Superhydrophobic Porous Materials with Excellent Absorbency and Flame Retardancy.

    PubMed

    Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui

    2016-01-01

    The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for materials that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic porous materials, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications. PMID:27501762

  15. A Versatile and Scalable Approach toward Robust Superhydrophobic Porous Materials with Excellent Absorbency and Flame Retardancy

    PubMed Central

    Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui

    2016-01-01

    The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for materials that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic porous materials, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications. PMID:27501762

  16. Porous material based on spongy titanium granules: structure, mechanical properties, and osseointegration.

    PubMed

    Rubshtein, A P; Trakhtenberg, I Sh; Makarova, E B; Triphonova, E B; Bliznets, D G; Yakovenkova, L I; Vladimirov, A B

    2014-02-01

    A porous material has been produced by pressing spongy titanium granules with subsequent vacuum sintering. The material with porosity of more than 30% has an open system of interconnecting pores. The Young's modulus and 0.2% proof strength have been measured for the samples having 20-55% porosity. If the porosity is between 30 and 45%, the mechanical properties are determined by irregular shape of pores, which is due to spongy titanium granules. The experiment in vivo was performed on adult rabbits. Before surgery the implants were saturated with adherent autologous bone marrow cells. The implants were introduced into the defects formed in the condyles of tibias and femurs. Investigations of osseointegration of implants having 40% porosity showed that the whole system of pores was filled with mature bone tissue in 16 weeks after surgery. Neogenic bone tissue has an uneven surface formed by lacunas and craters indicative of active resorption and subsequent rearrangement (SEM examination). The bone tissue is pierced by neoformed vessels. Irregular-shaped pores with tortuous walls and numerous lateral channels going through the granules provide necessary conditions for the formation of functional bone tissue in the implant volume and the periimplant region. PMID:24411389

  17. Acoustical properties of air-saturated porous material with periodically distributed dead-end pores.

    PubMed

    Leclaire, P; Umnova, O; Dupont, T; Panneton, R

    2015-04-01

    A theoretical and numerical study of the sound propagation in air-saturated porous media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at "nodes" periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical properties of the material and can increase significantly the absorption at low frequencies (a few hundred hertz). These depend strongly on the geometry (diameter and length) of the dead-ends, on their number per node, and on the periodicity along the propagation axis. These effects are primarily due to low sound speed in the main pores and to thermal losses in the dead-end pores. The model predictions are compared with experimental results. Possible designs of materials of a few cm thicknesses displaying enhanced low frequency absorption at a few hundred hertz are proposed. PMID:25920830

  18. A Versatile and Scalable Approach toward Robust Superhydrophobic Porous Materials with Excellent Absorbency and Flame Retardancy

    NASA Astrophysics Data System (ADS)

    Ruan, Changping; Shen, Mengxia; Ren, Xiaoyan; Ai, Kelong; Lu, Lehui

    2016-08-01

    The frequent oil spillages and the industrial discharge of organic contaminants have not only created severe environmental and ecological crises, but also cause a risk of fire and explosion. These environmental and safety issues emphasize the urgent need for materials that possess superior sorption capability and less flammability and thus can effectively and safely clean up the floating oils and water-insoluble organic compounds. Here we present the successful hydrophobic modification of the flame retardant melamine sponge with a commercial fluorosilicone, by using a facile one-step solvent-free approach and demonstrate that the resultant superhydrophobic sponge not only exhibits extraordinary absorption efficiency (including high capacity, superior selectivity, good recyclability, and simple recycling routes), but also retains excellent flame retardancy and robust stability. In comparison to conventional methods, which usually utilize massive organic solvents, the present approach does not involve any complicated process or sophisticated equipment nor generates any waste liquids, and thus is a more labor-saving, environment-friendly, energy-efficient and cost-effective strategy for the hydrophobic modification. Taking into account the critical role of hydrophobic porous materials, especially in the field of environmental remediation, the approach presented herein would be highly valuable for environmental remediation and industrial applications.

  19. Probabilistic Prediction of Homogenized Property and Update of Prediction for Spherical Porous Material Considering Microstructural Uncertainties

    NASA Astrophysics Data System (ADS)

    Wen, Pin; Yokota, Kenichiro; Takano, Naoki

    2015-02-01

    The purpose of this work is to simulate uncertainties existing in microscopic field of spherical porous material so that the homogenized property of interest can be predicted with high reliability. Moreover, the final goal is to build a bridge of feedback between microstructure design and fabrication to predict microstructure morphology by limited measurement data of macroscopic property. The uncertainties are identified as parametric variables in constituent material property and nonparametric variables in morphological fluctuation such as disordering and clustering in microstructure. First-order perturbation, based stochastic homogenization (FPSH) method together with mixture distribution technique is employed for probabilistic prediction. Furthermore, the update of prediction is accomplished in the case of an assumed virtual experimental trial. Two numerical examples show that the probabilistic prediction has given a better decision in microstructure design than deterministic prediction. The main conclusion coming from the new method derived by gap between measured data and prediction showed that, when the update is used for morphology prediction of microstructure, it is almost perfect agreement with parameters’ setup of virtual experiment. After it is applied for update of probabilistic homogenized property, it could make the updated homogenized property closer to measurement data so that it becomes more realistic.

  20. Optical second-harmonic generation measurements of porous low-k dielectric materials

    NASA Astrophysics Data System (ADS)

    Atkin, Joanna; Shaw, Thomas; Laibowitz, Robert; Heinz, Tony

    2009-03-01

    Low-k dielectric materials based on porous carbon-doped oxides, with relative dielectric constants as low as 2.1, are widely used as thin insulating films in the microelectronics industry. Knowledge of these materials' basic electronic properties, such as energy gaps, barrier heights, and trap states, is essential for modeling their electrical leakage and stability characteristics. We use femtosecond laser pulses to probe the dynamics of charge-carrier transfer processes across Si/LKD interfacial barriers by optical second harmonic generation (SHG). Larger electric fields from multiphoton injection can be developed in Si/LKD systems compared to Si/SiO2, indicating a significantly higher density of traps in the LKD. This is consistent with previously reported measurements of trap density by photoinjection techniques^*. We will also discuss results on the dynamics of discharging and on the dependence of charging phenomena on layer thickness. ^*J. M. Atkin, D. Song, T. M. Shaw, E. Cartier, R. B. Laibowitz, and T. F. Heinz, J. Appl. Phys. 103, 094104 (2008).

  1. Investigation of Sintering Temperature on Attrition Resistance of Highly Porous Diatomite Based Material

    SciTech Connect

    Garderen, Noemie van; Clemens, Frank J.; Scharf, Dagobert; Graule, Thomas

    2010-05-30

    Highly porous diatomite based granulates with a diameter of 500 mum have been produced by an extrusion method. In order to investigate the relation between microstructure, phase composition and attrition resistance of the final product, the granulates were sintered between 800 and 1300 deg. C. Mean pore size of the granulates was evaluated by Hg-porosimetry. An increase of the pore size is observed in the range of 3.6 nm to 40 mum with increasing sintering temperature. Higher mean pore radii of 1.6 mum and 5.7 mum obtained by sintering at 800 and 1300 deg. C respectively. X-ray diffraction shows that mullite phase appears at 1100 deg. C due to the presence of clay. At 1100 deg. C diatomite (amorphous silicate) started to transform into alpha-cristobalite. Attrition resistance was determined by evaluating the amount of ground material passed through a sieve with a predefined mesh size. It was observed that a material sintered at high temperature leads to an increase of attrition resistance due to the decrease of total porosities and phase transformation. Due to the reason that attrition resistance significantly increased by sintering the granulates at higher temperature, a so called attrition resistance index was determined in order to compare all the different attrition resistance values. This attrition resistance index was determined by using the exponential component of the equation obtained from attrition resistance curves. It permits comparison of the attrition behaviour without a time influence.

  2. A Porous TiAl6V4 Implant Material for Medical Application

    PubMed Central

    Ebel, Thomas; Willumeit, Regine

    2014-01-01

    Increased durability of permanent TiAl6V4 implants still remains a requirement for the patient's well-being. One way to achieve a better bone-material connection is to enable bone “ingrowth” into the implant. Therefore, a new porous TiAl6V4 material was produced via metal injection moulding (MIM). Specimens with four different porosities were produced using gas-atomised spherical TiAl6V4 with different powder particle diameters, namely, “Small” (<45 μm), “Medium” (45–63 μm), “Mix” (90% 125–180 μm + 10% <45 μm), and “Large” (125–180 μm). Tensile tests, compression tests, and resonant ultrasound spectroscopy (RUS) were used to analyse mechanical properties. These tests revealed an increasing Young's modulus with decreasing porosity; that is, “Large” and “Mix” exhibit mechanical properties closer to bone than to bulk material. By applying X-ray tomography (3D volume) and optical metallographic methods (2D volume and dimensions) the pores were dissected. The pore analysis of the “Mix” and “Large” samples showed pore volumes between 29% and 34%, respectively, with pore diameters ranging up to 175 μm and even above 200 μm for “Large.” Material cytotoxicity on bone cell lines (SaOs-2 and MG-63) and primary cells (human bone-derived cells, HBDC) was studied by MTT assays and highlighted an increasing viability with higher porosity. PMID:25386191

  3. Porous Chromatographic Materials as Substrates for Preparing Synthetic Nuclear Explosion Debris Particles

    SciTech Connect

    Harvey, Scott D.; Liezers, Martin; Antolick, Kathryn C.; Garcia, Ben J.; Sweet, Lucas E.; Carman, April J.; Eiden, Gregory C.

    2013-06-13

    In this study, we investigated several porous chromatographic materials as synthetic substrates for preparing surrogate nuclear explosion debris particles. The resulting synthetic debris materials are of interest for use in developing analytical methods. Eighteen metals, including some of forensic interest, were loaded onto materials by immersing them in metal solutions (556 mg/L of each metal) to fill the pores, applying gentle heat (110°C) to drive off water, and then treating them at high temperatures (up to 800°C) in air to form less soluble metal species. High-boiling-point metals were uniformly loaded on spherical controlled-pore glass to emulate early fallout, whereas low-boiling-point metals were loaded on core-shell silica to represent coated particles formed later in the nuclear fallout-formation process. Analytical studies were applied to characterize solubility, material balance, and formation of recalcitrant species. Dissolution experiments indicated loading was 1.5 to 3 times higher than expected from the pore volume alone, a result attributed to surface coating. Analysis of load solutions before and after filling the material pores revealed that most metals were passively loaded; that is, solutions filled the pores without active metal discrimination. However, niobium and tin concentrations were lower in solutions after pore filling, and were found in elevated concentrations in the final products, indicating some metals were selectively loaded. High-temperature treatments caused reduced solubility of several metal species, and loss of some metals (rhenium and tellurium) because volatile species were formed. Sample preparation reproducibility was high (the inter-batch relative standard deviation was 7.8%, and the intra-batch relative standard deviation was 0.84%) indicating that this material is suitable for use as a working standard for analytical methods development. We anticipate future standardized radionuclide-loaded materials will find use in

  4. Influence of elastic strains on the adsorption process in porous materials. Thermodynamics and experiment

    NASA Astrophysics Data System (ADS)

    Grosman, A.; Ortega, C.

    2010-06-01

    If we disregard the shape of the boundary hysteresis loop, H1 for SBA-15, MCM-41 and KIT-6, H2 for p +-type porous silicon and porous glass, the hysteretic features inside the loop are qualitatively the same for all these systems and show that none of them are composed of independent pores whether the pores are interconnected or not. We hence believe that the physical parameter which couples the pores is not the interconnectivity but the elastic deformation of the porous matrix. The thermodynamic approach we develop includes the elastic energy of the solid. We show that the variation of the surface free energy, which is proportional to the deformation of the porous matrix, is an important component of the total free energy. With porous silicon, we experimentally show that a stress external to the porous matrix exerted by the substrate on which it is supported significantly increases the total free energy and the adsorbed amount and decreases the condensation pressure compared to that of the same porous matrix detached from its substrate which is the relaxed state of the supported layer. This stress can be partly relaxed by making thicker porous layers due to the breaking of Si-Si bonds. This results in the shift of the isotherms towards that of the membrane. We propose a new interaction mechanism occurring through the pore wall elastic deformation in which the external mechanical stress is imposed on a given pore by its neighbours.

  5. 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.

  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. Design, synthesis, and characterization of materials for controlled line deposition, environmental remediation, and doping of porous manganese oxide material

    NASA Astrophysics Data System (ADS)

    Calvert, Craig A.

    This thesis covers three topics: (1) coatings formed from sol-gel phases, (2) environmental remediation, and (3) doping of a porous manganese oxide. Synthesis, characterization, and application were investigated for each topic. Line-formations were formed spontaneously by self-assembly from vanadium sol-gels and other metal containing solutions on glass substrates. The solutions were prepared by the dissolution of metal oxide or salt in water. A more straightforward method is proposed than used in previous work. Analyses using optical microscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy showed discreet lines whose deposition could be controlled by varying the concentration. A mechanism was developed from the observed results. Microwave heating, the addition of graphite rods, and oxidants, can enhance HCB remediation from soil. To achieve remediation, a TeflonRTM vessel open to the atmosphere along with an oxidant, potassium persulfate (PerS) or potassium hydroxide, along with uncoated or aluminum oxide coated, graphite rods were heated in a research grade microwave oven. Microwave heating was used to decrease the heating time, and graphite rods were used to increase the absorption of the microwave energy by providing thermal centers. The results showed that the percent HCB removed was increased by adding graphite rods and oxidants. Tungsten, silver, and sulfur were investigated as doping agents for K--OMS-2. The synthesis of these materials was carried out with a reflux method. The doping of K--OMS-2 led to changes in the properties of a tungsten doped K--OMS-2 had an increased resistivity, the silver doped material showed improved epoxidation of trans-stilbene, and the addition of sulfur produced a paper-like material. Rietveld refinement of the tungsten doped K--OMS-2 showed that the tungsten was doped into the framework.

  8. Poly L-lysine (PLL)-mediated porous hematite clusters as anode materials for improved Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Kim, Kun-Woo; Lee, Sang-Wha

    2015-09-01

    Porous hematite clusters were prepared as anode materials for improved Li-ion batteries. First, poly-L-lysine (PLL)-linked Fe3O4 was facilely prepared via cross-linking between the positive amine groups of PLL and carboxylate-bound Fe3O4. The subsequent calcination transformed the PLL-linked Fe3O4 into porous hematite clusters (Fe2O3@PLL) consisting of spherical α-Fe2O3 particles. Compared with standard Fe2O3, Fe3O4@PLL exhibited improved electrochemical performance as anode materials. The discharge capacity of Fe2O3@PLL was retained at 814.7 mAh g-1 after 30 cycles, which is equivalent to 80.4% of the second discharge capacity, whereas standard Fe2O3 exhibited a retention capacity of 352.3 mAh g-1. The improved electrochemical performance of Fe2O3@PLL was mainly attributed to the porous hematite clusters with mesoporosity (20-40 nm), which was beneficial for facilitating ion transport, suggesting a useful guideline for the design of porous architectures with higher retention capacity. [Figure not available: see fulltext.

  9. Porous carbon nanotubes decorated with nanosized cobalt ferrite as anode materials for high-performance lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Lingyan; Zhuo, Linhai; Cheng, Haiyang; Zhang, Chao; Zhao, Fengyu

    2015-06-01

    Generally, the fast ion/electron transport and structural stability dominate the superiority in lithium-storage applications. In this work, porous carbon nanotubes decorated with nanosized CoFe2O4 particles (p-CNTs@CFO) have been rationally designed and synthesized by the assistance of supercritical carbon dioxide (scCO2). When tested as anode materials for lithium-ion batteries, the p-CNTs@CFO composite exhibits outstanding electrochemical behavior with high lithium-storage capacity (1077 mAh g-1 after 100 cycles) and rate capability (694 mAh g-1 at 3 A g-1). These outstanding electrochemical performances are attributed to the synergistic effect of porous p-CNTs and nanosized CFO. Compared to pristine CNTs, the p-CNTs with substantial pores in the tubes possess largely increased specific surface area and rich oxygen-containing functional groups. The porous structure can not only accommodate the volume change during lithiation/delithiation processes, but also provide bicontinuous electron/ion pathways and large electrode/electrolyte interface, which facilitate the ion diffusion kinetics, improving the rate performance. Moreover, the CFO particles are bonded strongly to the p-CNTs through metal-oxygen bridges, which facilitate the electron fast capture from p-CNTs to CFO, and thus resulting in a high reversible capacity and excellent rate performance. Overall, the porous p-CNTs provide an efficient way for ion diffusion and continuous electron transport as anode materials.

  10. 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.

  11. The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in porous low-k materials

    SciTech Connect

    Lionti, K.; Volksen, W.; Darnon, M.; Magbitang, T.; Dubois, G.

    2015-03-21

    As of today, plasma damage remains as one of the main challenges to the reliable integration of porous low-k materials into microelectronic devices at the most aggressive node. One promising strategy to limit damage of porous low-k materials during plasma processing is an approach we refer to as post porosity plasma protection (P4). In this approach, the pores of the low-k material are filled with a sacrificial agent prior to any plasma treatment, greatly minimizing the total damage by limiting the physical interactions between plasma species and the low-k material. Interestingly, the contribution of the individual plasma species to the total plasma damage is not fully understood. In this study, we investigated the specific damaging effect of vacuum-ultraviolet (v-UV) photons on a highly porous, k = 2.0 low-k material and we assessed the P4 protective effect against them. It was found that the impact of the v-UV radiation varied depending upon the v-UV emission lines of the plasma. More importantly, we successfully demonstrated that the P4 process provides excellent protection against v-UV damage.

  12. Anti-graffiti nanocomposite materials for surface protection of a very porous stone

    NASA Astrophysics Data System (ADS)

    Licchelli, Maurizio; Malagodi, Marco; Weththimuni, Maduka; Zanchi, Chiara

    2014-09-01

    The preservation of stone substrates from defacement induced by graffiti represents a very challenging task, which can be faced by applying suitable protective agents on the surface. Although different anti-graffiti materials have been developed, it is often found that their effectiveness is unsatisfactory, most of all when applied on very porous stones, e.g. Lecce stone. The aim of this work was to study the anti-graffiti behaviour of new nanocomposite materials obtained by dispersing montmorillonite nanoparticles (layered aluminosilicates with a high-aspect ratio) into a fluorinated polymer matrix (a fluorinated polyurethane based on perfluoropolyether blocks). Polymeric structure was modified by inducing a cross-linking process, in order to produce a durable anti-graffiti coating with enhanced barrier properties. Several composites were prepared using a naturally occurring and an organically modified montmorillonite clay (1, 3, and 5 % w/w concentrations). Materials were applied on Lecce stone specimens, and then their treated surfaces were soiled by a black ink permanent marker or by a black acrylic spray paint. Several repeated staining/cleaning cycles were performed in order to evaluate anti-graffiti effectiveness. Colorimetric measurements were selected to assess the anti-graffiti performance. It was found that the presence of 3 % w/w organically modified montmorillonite in the polymer coating is enough to induce a durable anti-graffiti effect when the stone surface is stained by acrylic paint. Less promising results are obtained when staining by permanent marker is considered as all the investigated treatments afford a reasonable protection from ink only for the first staining/cleaning cycle.

  13. Excellent cycling stability and superior rate capability of a graphene-amorphous FePO4 porous nanowire hybrid as a cathode material for sodium ion batteries

    NASA Astrophysics Data System (ADS)

    Yang, Gaoliang; Ding, Bing; Wang, Jie; Nie, Ping; Dou, Hui; Zhang, Xiaogang

    2016-04-01

    A porous nanowire material consisting of graphene-amorphous FePO4 was investigated as an advanced cathode material for sodium ion batteries for large-scale applications. This hybrid cathode material showed excellent cycling performance and superior rate capability, which were attributed to the porous nanowire structure and the existence of graphene.A porous nanowire material consisting of graphene-amorphous FePO4 was investigated as an advanced cathode material for sodium ion batteries for large-scale applications. This hybrid cathode material showed excellent cycling performance and superior rate capability, which were attributed to the porous nanowire structure and the existence of graphene. Electronic supplementary information (ESI) available: Experimental section; SEM images, BET, XPS spectrum, TG curve and EIS spectra of the samples; the comparison of electrochemical performance with the reported results. See DOI: 10.1039/c6nr00409a

  14. 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

  15. Oxygen-doped porous silicon carbide spheres as electrode materials for supercapacitors.

    PubMed

    Kim, Myeongjin; Ju, Hyun; Kim, Jooheon

    2016-01-28

    Oxygen-containing functional groups were introduced onto the surface of the micro- and meso-porous silicon carbide sphere (MMPSiC) in order to investigate the relationship between the electric double layer properties and pseudo-capacitive properties; the degree of oxidation of MMPSiC was also optimized. Although the oxygenated surface functionalities can lead to a decrease in the surface area of MMPSiC, the oxygen functional groups attached to the external surface can participate in the redox reaction, resulting in the enhancement of the total super-capacitive performance. The MMPSiC electrode oxidized for 24 h exhibits a high charge storage capacity with a specific capacitance of 301.1 F g(-1) at a scan rate of 5 mV s(-1), with 86.8% rate performance from 5 to 500 mV s(-1) in 1 M KCl aqueous electrolyte. This outstanding capacitive performance of the MMPSiC electrode oxidized for 24 h can be attributed to the harmonious synergistic effect between the electric double layer capacitive contribution of MMPSiC and the pseudo-capacitive contribution of the oxygen-containing functional groups. These encouraging results demonstrate that the MMPSiC electrode oxidized for 24 h is a promising candidate for high performance electrode materials for supercapacitors. PMID:26752728

  16. Oil saturation effects in lead metaniobate porous piezoceramic: transient material characteristics.

    PubMed

    Mezheritsky, Alex

    2015-09-01

    Lead metaniobate PbNb2O6 (PN) has a unique combination of high piezoelectric anisotropy; relatively low dielectric permittivity and high Curie temperature; and a low Q-factor, near 20. The very low Q-factor is the most intriguing PN property among the piezoelectric materials, and as shown in this research, this internal high dissipation and damping effect is directly related to the presence of silicon oil in the porous PN structure; consequently, it is dependent on the oil properties. To the contrary, the quality factor of PN not saturated with oil was found to be as high as nearly 400. Full sets of PN electro-mechanical constants, transient resonance and dissipation characteristics, and their temperature dependencies were determined under both conditions: PN conventionally saturated with oil and PN not saturated with oil. As was experimentally shown, at higher temperatures particularly after a 260°C soak for several days, a transition from the "with oil" state to the "no oil" state takes place in the conventional PN properties; this effect is a consequence of the phase transition in the silicon oil from liquid to solid state. PMID:26415132

  17. Sericin-carboxymethyl cellulose porous matrices as cellular wound dressing material.

    PubMed

    Nayak, Sunita; Kundu, S C

    2014-06-01

    In this study, porous three-dimensional (3D) hydrogel matrices are fabricated composed of silk cocoon protein sericin of non-mulberry silkworm Antheraea mylitta and carboxymethyl cellulose. The matrices are prepared via freeze-drying technique followed by dual cross-linking with glutaraldehyde and aluminum chloride. The microstructure of the hydrogel matrices is assessed using scanning electron microscopy and biophysical characterization are carried out using Fourier transform infrared spectroscopy and X-ray diffraction. The transforming growth factor β1 release from the cross-linked matrices as a growth factor is evaluated by immunosorbent assay. Live dead assay and 3-[4,5-dimethylthiazolyl-2]-2,5-diphenyl tetrazolium bromide assay show no cytotoxicity of blended matrices toward human keratinocytes. The matrices support the cell attachment and proliferation of human keratinocytes as observed through scanning electron microscope and confocal images. Gelatin zymography demonstrates the low levels of matrix metalloproteinase 2 (MMP-2) and insignificant amount of MMP-9 in the culture media of cell seeded matrices. Low inflammatory response of the matrices is indicated through tumor necrosis factor alpha release assay. The results indicate that the fabricated matrices constitute 3D cell-interactive environment for tissue engineering applications and its potential use as a future cellular biological wound dressing material. PMID:23853114

  18. Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution.

    PubMed

    Prarat, Panida; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha; Punyapalakul, Patiparn

    2011-09-15

    The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS. PMID:21752539

  19. Evaluation of the acid properties of porous zirconium-doped and undoped silica materials

    SciTech Connect

    Fuentes-Perujo, D.; Santamaria-Gonzalez, J.; Merida-Robles, J.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.; Maireles-Torres, P. . E-mail: maireles@uma.es; Moreno-Tost, R.

    2006-07-15

    A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N{sub 2} adsorption at 77 K. Their acid properties have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites. - Graphical abstract: The adsorption of basic probe molecules and the catalytic behaviour have revealed that MSU-type materials are more acidic than the analogous MCM-41 solids, mainly after the incorporation of zirconium into the silica framework.

  20. 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.

  1. Determination of the thermophysical properties of evolutive porous media: application to Civil Engineering materials

    NASA Astrophysics Data System (ADS)

    Poullain, P.; Mounanga, P.; Bastian, G.; Coué, R.

    2006-01-01

    The purpose of this paper is to describe the development and the use of two measurement techniques especially adapted to the rapid determination of the thermophysical properties of evolutive porous media. The first technique exploits the method of the “heated and non-heated wires” and is validated on wet clay by comparison with previous works [Mounanga et al., Eur. Phys. J. Appl. Phys. 26, 65 (2004)]. It is then used to quantify the evolution of both thermal conductivity and volumetric heat capacity of hardening cement pastes maintained at 294 ± 1 K. The second technique is based on the classical method of the “heating film” and a data treatment using forward calculation. This technique is first used to measure the properties of well-known materials (hardened mortars, wet sand [Mounanga et al., Eur. Phys. J. Appl. Phys. 26, 65 (2004); Delacre, Ph.D. thesis, University of Artois, 2000] and glass [Bastian, Rev. Phys. Appl. 22, 431 (1987)] and then applied to media whose properties evolve both over time and through space (drying sand).

  2. 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.

  3. Preparation and characterization of porous carbon material-coated solid-phase microextraction metal fibers.

    PubMed

    Zhu, Fang; Guo, Jiaming; Zeng, Feng; Fu, Ruowen; Wu, Dingcai; Luan, Tiangang; Tong, Yexiang; Lu, Tongbu; Ouyang, Gangfeng

    2010-12-10

    Two kinds of porous carbon materials, including carbon aerogels (CAs), wormhole-like mesoporous carbons (WMCs), were synthesized and used as the coatings of solid-phase microextraction (SPME) fibers. By using stainless steel wire as the supporting core, six types of fibers were prepared with sol-gel method, direct coating method and direct coating plus sol-gel method. Headspace SPME experiments indicated that the extraction efficiencies of the CA fibers are better than those of the WMC fibers, although the surface area of WMCs is much higher than that of CAs. The sol-gel-CA fiber (CA-A) exhibited excellent extraction properties for non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene), while direct-coated CA fiber (CA-B) presented the best performance in extracting polar compounds (phenols). The two CA fibers showed wide linear ranges, low detection limits (0.008-0.047μgL(-1) for BTEX, 0.15-5.7μgL(-1) for phenols) and good repeatabilities (RSDs less than 4.6% for BTEX, and less than 9.5% for phenols) and satisfying reproducibilities between fibers (RSDs less than 5.2% for BTEX, and less than 9.9% for phenols). These fibers were successfully used for the analysis of water samples from the Pearl River, which demonstrated the applicability of the home-made CA fibers. PMID:21074162

  4. Rapid synthesis of monodispersed highly porous spinel nickel cobaltite (NiCo2O4) electrode material for supercapacitors

    NASA Astrophysics Data System (ADS)

    Naveen, A. Nirmalesh; Selladurai, S.

    2015-06-01

    Monodispersed highly porous spinel nickel cobaltite electrode material was successfully synthesized in a short time using combustion technique. Single phase cubic nature of the spinel nickel cobaltite with average crystallite size of 24 nm was determined from X-ray diffraction study. Functional groups present in the compound were determined from FTIR study and it further confirms the spinel formation. FESEM images reveal the porous nature of the prepared material and uniform size distribution of the particles. Electrochemical evaluation was performed using Cyclic Voltammetry (CV) technique, Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS). Results reveal the typical pseudocapacitive behaviour of the material. Maximum capacitance of 754 F/g was calculated at the scan rate of 5 mV/s, high capacitance was due to the unique porous morphology of the electrode. Nyquist plot depicts the low resistance and good electrical conductivity of nickel cobaltite. It has been found that nickel cobaltite prepared by this typical method will be a potential electrode material for supercapcitor application.

  5. Record-breaking events during the compressive failure of porous materials

    NASA Astrophysics Data System (ADS)

    Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G.

    2016-03-01

    An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of materials and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of porous materials. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element model of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k*, which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial

  6. Porous carbon materials for Li-S batteries based on resorcinol-formaldehyde resin with inverse opal structure

    NASA Astrophysics Data System (ADS)

    Agrawal, Mukesh; Choudhury, Soumyadip; Gruber, Katharina; Simon, Frank; Fischer, Dieter; Albrecht, Victoria; Göbel, Michael; Koller, Stefan; Stamm, Manfred; Ionov, Leonid

    2014-09-01

    This study reports on a novel approach to fabrication of carbon-sulfur composite material and demonstrates its application as cathode for Li-S batteries. Firstly, highly porous carbon material has been prepared by exploiting PMMA colloidal crystal arrays as sacrificial template and subsequently mixing with elemental sulfur at 155 °C. The resulting carbon-sulfur composite cathode material possess very high intrinsic surface area, conductivity and has been found to demonstrate as high as 1600 mAh g-1 capacity in 1st discharge cycle and about 300-400 mAh g-1 in 50th discharge cycle.

  7. Magnesiothermically reduced diatomaceous earth as a porous silicon anode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Shen, Lanyao; Guo, Xianwei; Fang, Xiangpeng; Wang, Zhaoxiang; Chen, Liquan

    2012-09-01

    Three-dimensional porous silicon has been prepared by magnesiothermically reducing diatomaceous earth. BET surface area analysis shows that the specific surface area of the obtained porous silicon is about 96 m2 g-1, much higher than that of the diatomaceous earth (6 m2 g-1). The silicon products after HCl immersion have a porous structure similar to that of the diatomaceous earth, with pore sizes around 200 nm. Galvanostatic cycling tests show that the initial charge and discharge capacities of the porous silicon are 1321 mAh g-1 and 1818 mAh g-1, respectively. A reversible capacity of 633 mAh g-1 is retained after 30 cycles.

  8. Scalable preparation of porous micron-SnO2/C composites as high performance anode material for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Shan; Lei, Ming; Wang, Zhi-Qiang; Zhao, Xing; Xu, Jun; Yang, Wei; Huang, Yun; Li, Xing

    2016-03-01

    Nano tin dioxide-carbon (SnO2/C) composites prepared by various carbon materials, such as carbon nanotubes, porous carbon, and graphene, have attracted extensive attention in wide fields. However, undesirable concerns of nanoparticles, including in higher surface area, low tap density, and self-agglomeration, greatly restricted their large-scale practical applications. In this study, novel porous micron-SnO2/C (p-SnO2/C) composites are scalable prepared by a simple hydrothermal approach using glucose as a carbon source and Pluronic F127 as a pore forming agent/soft template. The SnO2 nanoparticles were homogeneously dispersed in micron carbon spheres by assembly with F127/glucose. The continuous three-dimensional porous carbon networks have effectively provided strain relaxation for SnO2 volume expansion/shrinkage during lithium insertion/extraction. In addition, the carbon matrix could largely minimize the direct exposure of SnO2 to the electrolyte, thus ensure formation of stable solid electrolyte interface films. Moreover, the porous structure could also create efficient channels for the fast transport of lithium ions. As a consequence, the p-SnO2/C composites exhibit stable cycle performance, such as a high capacity retention of over 96% for 100 cycles at a current density of 200 mA g-1 and a long cycle life up to 800 times at a higher current density of 1000 mA g-1.

  9. Nitrogen-doped porous carbon nanosheets as low-cost, high-performance anode material for sodium-ion batteries.

    PubMed

    Wang, Heng-guo; Wu, Zhong; Meng, Fan-lu; Ma, De-long; Huang, Xiao-lei; Wang, Li-min; Zhang, Xin-bo

    2013-01-01

    Between the sheets: Sodium-ion batteries are an attractive, low-cost alternative to lithium-ion batteries. Nitrogen-doped porous carbon sheets are prepared by chemical activation of polypyrrole-functionalized graphene sheets. When using the sheets as anode material in sodium-ion batteries, their unique compositional and structural features result in high reversible capacity, good cycling stability, and high rate capability. PMID:23225752

  10. Effect of flow oscillations on axial energy transport in a porous material

    NASA Technical Reports Server (NTRS)

    Siegel, R.

    1987-01-01

    The effects of flow oscillations on axial energy diffusion in a porous medium, in which the flow is continuously disrupted by the irregularities of the porous structure, are analyzed. The formulation employs an internal heat transfer coefficient that couples the fluid and solid temperatures. The final relationship shows that the axial energy transport per unit cross-sectional area and time is directly proportional to the axial temperature gradient and the square of the maximum fluid displacement.

  11. 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

  12. Cluster-Expanded Solids: A Strategy for Assembling Functional Porous Materials

    SciTech Connect

    Long, Jeffrey R.

    2008-10-31

    This grant provided (partial) support for the research efforts of three graduate students and two undergraduate students. The intention of the program was to explore the use of molecular precursors in generating functional porous materials with precisely tailored structures and properties. Prior work in our laboratory had demonstrated the feasibility of employing face-capped octahedral clusters of the type [Re{sub 6}Q{sub 8}(CN){sub 6}]{sup 3-/4-} (Q = S, Se, Te) in the expansion of known metal-cyanide frameworks. For example, the use of [Re{sub 6}Se{sub 8}(CN){sub 6}]{sup 4-} as a reactant in place of [Fe(CN){sub 6}]{sup 4-} resulted in formation of Fe{sub 4}[Re{sub 6}Se{sub 8}(CN){sub 6}]{sub 3}·36H{sub 2}O, featuring an expanded form of the porous three-dimensional framework of Prussian blue (Fe{sub 4}[Fe(CN){sub 6}]{sub 3}·14H{sub 2}O). This compound could be dehydrated without loss of integrity, and the increase in void volume significantly enhances its capacity as a molecular sieve, enabling absorption of larger molecules. For this project, we continued with our efforts to devise new routes to microporous coordination solids that function as molecular sieves, sensors, or catalysts. In particular, our focus was on: (i) the synthesis of new molecular precursors of specific utility for such purposes, and (ii) attempts to incorporate these and existing molecular precursors into new coordination solids. Investigations of the terminal ligand substitution chemistry of the carbon-centered, trigonal prismatic cluster [W{sub 6}CCl{sub 18}]{sup 2-} generated the solvated species [W{sub 6}CCl{sub 12}(DMF){sub 6}]{sup 2+} and [W{sub 6}CCl{sub 12}(py){sub 6}]{sup 2+}, as well as the potential framework building units [W{sub 6}C(CN){sub 18}]{sup 3-}, [W6CCl{sub 12}(pyrazine){sub 6}]{sup 2+}, [W6CCl{sub 12}(4-cyanopyridine){sub 6}]{sup 2+}, and [W{sub 6}CCl{sub 12}(4,4ʹ′-bipyridine){sub 6}]{sup 2+}. Efforts to produce microporous magnets capable of performing magnetic

  13. A review on solar cells from Si-single crystals to porous materials and quantum dots

    PubMed Central

    Badawy, Waheed A.

    2013-01-01

    Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12–16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper–indium–selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-porous materials. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe–TiO2 architecture have been developed. PMID:25750746

  14. A review on solar cells from Si-single crystals to porous materials and quantum dots.

    PubMed

    Badawy, Waheed A

    2015-03-01

    Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12-16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper-indium-selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-porous materials. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe-TiO2 architecture have been developed. PMID:25750746

  15. Side-chain control of porosity closure in single- and multiple-peptide-based porous materials by cooperative folding

    NASA Astrophysics Data System (ADS)

    Martí-Gastaldo, C.; Antypov, D.; Warren, J. E.; Briggs, M. E.; Chater, P. A.; Wiper, P. V.; Miller, G. J.; Khimyak, Y. Z.; Darling, G. R.; Berry, N. G.; Rosseinsky, M. J.

    2014-04-01

    Porous materials are attractive for separation and catalysis—these applications rely on selective interactions between host materials and guests. In metal-organic frameworks (MOFs), these interactions can be controlled through a flexible structural response to the presence of guests. Here we report a MOF that consists of glycyl-serine dipeptides coordinated to metal centres, and has a structure that evolves from a solvated porous state to a desolvated non-porous state as a result of ordered cooperative, displacive and conformational changes of the peptide. This behaviour is driven by hydrogen bonding that involves the side-chain hydroxyl groups of the serine. A similar cooperative closure (reminiscent of the folding of proteins) is also displayed with multipeptide solid solutions. For these, the combination of different sequences of amino acids controls the framework's response to the presence of guests in a nonlinear way. This functional control can be compared to the effect of single-point mutations in proteins, in which exchange of single amino acids can radically alter structure and function.

  16. Record-breaking events during the compressive failure of porous materials.

    PubMed

    Pál, Gergő; Raischel, Frank; Lennartz-Sassinek, Sabine; Kun, Ferenc; Main, Ian G

    2016-03-01

    An accurate understanding of the interplay between random and deterministic processes in generating extreme events is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophic failure of materials and in the Earth. Here we investigate the statistics of record-breaking events in the time series of crackling noise generated by local rupture events during the compressive failure of porous materials. The events are generated by computer simulations of the uniaxial compression of cylindrical samples in a discrete element model of sedimentary rocks that closely resemble those of real experiments. The number of records grows initially as a decelerating power law of the number of events, followed by an acceleration immediately prior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents. We demonstrate the existence of a characteristic record rank k(*), which separates the two regimes of the time evolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking then accelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlations dominate the location and timing of local ruptures. The size distribution of records of different ranks has a universal form independent of the record rank. Subsequences of events that occur between consecutive records are characterized by a power-law size distribution, with an exponent which decreases as failure is approached. High-rank records are preceded by smaller events of increasing size and waiting time between consecutive events and they are followed by a relaxation process. As a reference, surrogate time series are generated by reshuffling the event times. The record statistics of the uncorrelated surrogates agrees very well with the corresponding predictions of independent identically distributed random variables, which confirms that temporal and spatial

  17. Surface characterization and effectiveness evaluation of anti-graffiti coatings on highly porous stone materials

    NASA Astrophysics Data System (ADS)

    Lettieri, Mariateresa; Masieri, Maurizio

    2014-01-01

    In this study, two commercial sacrificial anti-graffiti systems, provided as water emulsion, were applied on a highly porous stone. The behavior of the anti-graffiti treatments was investigated by means of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy in attenuated total reflectance mode (ATR-FTIR), colorimetric tests, and water static contact angle measurements.

  18. Investigation on thermo-mechanical instability of porous low dielectric constant materials

    NASA Astrophysics Data System (ADS)

    Zin, Emil Hyunbae

    This study investigates the structural stability of porous low dielectric constant materials (PLK) under thermal and mechanical load and the influence of contributing factors including porosity as intrinsic factor and plasma damage and moisture absorption as extrinsic factors on thermo-mechanical instability of PLK in advanced Cu/PLK interconnects. For this purpose, a ball indentation creep test technique was developed to examine the thermal and mechanical instability of PLK at relevant load and temperature conditions in the interconnect structure. Our exploration with the ball indentation creep test found that PLK films plastically deforms with time, indicating that viscoplastic deformation does occur under relevant conditions of PLK processing. On the basis of the results that the increase of the indentation depth with time shows more noticeable difference in PLK films with higher porosity, plasma exposure, and moisture absorption, it is our belief that PLK stability is greatly affected by porosity, plasma damage and moisture. Viscous flow was found to be mechanism for the viscoplastic deformation at the temperature and load of real PLK integration processing. This finding was obtained from the facts that the kinetics of the indentation creep fit very well with the viscous flow model and the extracted stress exponent is close to unity. Based on the results of temperature dependence in all PLK films, the activation energy(~1.5eV) of the viscosity back calculated from the experimental value of the kinetics was found to be much small than that of a pure glass (> 4eV). This suggests that the viscous flow of PLK is controlled by chemical reaction happening in PLK matrix. The FT-IR measurement for the examination of chemical bond reconfiguration shows that the intensity of Si-OH bonds increases with the flow while that of Si-O-Si, -CHX and Si-CH 3 bonds decreases, indicating that chemical reactions are involved in the deformation process. From these findings, it is

  19. Hierarchically porous silicon–carbon–nitrogen hybrid materials towards highly efficient and selective adsorption of organic dyes

    PubMed Central

    Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie

    2015-01-01

    The hierarchically macro/micro-porous silicon–carbon–nitrogen (Si–C–N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp2-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg·g−1 and 1084.5 mg·g−1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si–C–N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants. PMID:25604334

  20. Hierarchically porous silicon-carbon-nitrogen hybrid materials towards highly efficient and selective adsorption of organic dyes

    NASA Astrophysics Data System (ADS)

    Meng, Lala; Zhang, Xiaofei; Tang, Yusheng; Su, Kehe; Kong, Jie

    2015-01-01

    The hierarchically macro/micro-porous silicon-carbon-nitrogen (Si-C-N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg.g-1 and 1084.5 mg.g-1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si-C-N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

  1. Avoiding Errors in Electrochemical Measurements: Effect of Frit Material on the Performance of Reference Electrodes with Porous Frit Junctions.

    PubMed

    Mousavi, Maral P S; Saba, Stacey A; Anderson, Evan L; Hillmyer, Marc A; Bühlmann, Philippe

    2016-09-01

    In many commercially available and in-house-prepared reference electrodes, nanoporous glass frits (often of the brand named Vycor) contain the electrolyte solution that forms a salt bridge between the sample and the reference solution. Recently, we showed that in samples with low ionic strength, the half-cell potentials of reference electrodes comprising nanoporous Vycor frits are affected by the sample and can shift in response to the sample composition by more than 50 mV (which can cause up to 900% error in potentiometric measurements). It was confirmed that the large potential variations result from electrostatic screening of ion transfer through the frit due to the negatively charged surfaces of the glass nanopores. Since the commercial production of porous Vycor glass was recently discontinued, new materials have been used lately as porous frits in commercially available reference electrodes, namely frits made of Teflon, polyethylene, or one of two porous glasses sold under the brand names CoralPor and Electro-porous KT. In this work, we studied the effect of the frit characteristics on the performance of reference electrodes, and show that the unwanted changes in the reference potential are not unique to electrodes with Vycor frits. Increasing the pore size in the glass frits from the <10 nm into the 1 μm range or switching to polymeric frits with pores in the 1 to 10 μm range nearly eliminates the potential variations caused by electrostatic screening of ion transport through the frit pores. Unfortunately, bigger frit pores result in larger flow rates of the reference solution through the pores, which can result in the contamination of test solutions. PMID:27464837

  2. Dynamics of H2 adsorbed in porous materials as revealed by computational analysis of inelastic neutron scattering spectra.

    PubMed

    Pham, Tony; Forrest, Katherine A; Space, Brian; Eckert, Juergen

    2016-06-29

    The inelastic scattering of neutrons from adsorbed H2 is an effective and highly sensitive method for obtaining molecular level information on the type and nature of H2 binding sites in porous materials. While these inelastic neutron scattering (INS) spectra of the hindered rotational and translational excitations on the adsorbed H2 contain a significant amount of information, much of this can only be reliably extracted by means of a detailed analysis of the spectra through the utilization of models and theoretical calculations. For instance, the rotational tunneling transitions observed in the INS spectra can be related to a value for the barrier to rotation for the adsorbed H2 with the use of a simple phenomenological model. Since such an analysis is dependent on the model, it is far more desirable to use theoretical methods to compute a potential energy surface (PES), from which the rotational barriers for H2 adsorbed at a particular site can be determined. Rotational energy levels and transitions for the hindered rotor can be obtained by quantum dynamics calculations and compared directly with experiment with an accuracy subject only to the quality of the theoretical PES. In this paper, we review some of the quantum and classical mechanical calculations that have been performed on H2 adsorbed in various porous materials, such as clathrate hydrates, zeolites, and metal-organic frameworks (MOFs). The principal aims of these calculations have been the interpretation of the INS spectra for adsorbed H2 along with the extraction of atomic level details of its interaction with the host. We describe calculations of the PES used for two-dimensional quantum rotation as well as rigorous five-dimensional quantum coupled translation-rotation dynamics, and demonstrate that the combination of INS measurements and computational modeling can provide important and detailed insights into the molecular mechanism of H2 adsorption in porous materials. PMID:27160665

  3. Porous material characterization--ultrasonic method for estimation of tortuosity and characteristic length using a barometric chamber.

    PubMed

    Moussatov, A; Ayrault, C; Castagnède, B

    2001-04-01

    An ultrasonic method of acoustic parameter evaluation for porous materials saturated by air (or any other gas) is discussed. The method is based on the evolution of speed of sound and the attenuation inside the material when the static pressure of the gas saturating the material is changed. Asymptotic development of the equivalent fluid model of Johnson-Allard is used for analytical description. The method allows an estimation of three essential parameters of the model: the tortuosity, and the viscous and thermal characteristic lengths. Both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed with industrial plastic foams and granular substances (glass beads, sea sand) over a gas pressure range from 0.2 to 6 bars at the frequencies 30-600 kHz. The present technique has a number of distinct advantages over the conventional ultrasonic approach: operation at a single frequency, improved signal-to-noise ratio, possibility of saturation the porous media by different gases. In the case when scattering phenomena occur, the present method permits a separate analysis of scattering losses and viscothermal losses. An analytical description of the method is followed by a presentation of the set-up and the measurement procedure. Experimental results and perspectives are discussed. PMID:11350000

  4. Honeycomb porous films as permeable scaffold materials for human embryonic stem cell-derived retinal pigment epithelium.

    PubMed

    Calejo, Maria Teresa; Ilmarinen, Tanja; Jongprasitkul, Hatai; Skottman, Heli; Kellomäki, Minna

    2016-07-01

    Age-related macular degeneration (AMD) is a leading cause of blindness in developed countries, characterised by the degeneration of the retinal pigment epithelium (RPE), a pigmented cell monolayer that closely interacts with the photoreceptors. RPE transplantation is thus considered a very promising therapeutic option to treat this disease. In this work, porous honeycomb-like films are for the first time investigated as scaffold materials for human embryonic stem cell-derived retinal pigment epithelium (hESC-RPE). By changing the conditions during film preparation, it was possible to produce films with homogeneous pore distribution and adequate pore size (∼3-5 µm), that is large enough to ensure high permeability but small enough to enable cell adherence and spreading. A brief dip-coating procedure with collagen type IV enabled the homogeneous adsorption of the protein to the walls and bottom of pores, increasing the hydrophilicity of the surface. hESC-RPE adhered and proliferated on all the collagen-coated materials, regardless of small differences in pore size. The differentiation of hESC-RPE was confirmed by the detection of specific RPE protein markers. These results suggest that the porous honeycomb films can be promising candidates for hESC-RPE tissue engineering, importantly enabling the free flow of ions and molecules across the material. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1646-1656, 2016. PMID:26914698

  5. Chaperone-Assisted Formation of Cucurbit[8]uril-Based Molecular Porous Materials with One-Dimensional Channel Structure.

    PubMed

    Zhu, Wei; Wang, Chen; Lan, Yue; Li, Jian; Wang, Hui; Gao, Ning; Ji, Jingwei; Li, Guangtao

    2016-09-01

    Exploiting "chaperone molecule" to navigate the successful assembly energy landscapes has been extensively used in biological systems, whereas in artifical supramolecular systems the "chaperone-assisted" assembly strategy to be used for the synthesis of materials with novel structures or the structures to be hardly prepared by "conventional" methods are still far from realizing the potential functions. In this work, we present a new example of small organic molecule acting as "chaperone molecule" in the facile formation of organic molecular porous materials. This porous material is composed of pure cucurbit[8]uril (CB[8]) macrocycle and possesses a honeycomb-like structure with an isolated and relatively large one-dimensional (1D) nanochannel. Moreover, it has good chemical and thermal stability, and shows a good adsorption capability for large molecule loading. Importantly, with the assistance of chaperone molecules, pure CB[8] could also be recycled even from a complex aqueous solution, demonstrating a powerful purification method of CB[8] from complex systems. PMID:27539793

  6. Strengthening of polymer ordered porous materials based on a layered nanocomposite internal structure.

    PubMed

    Heng, Liping; Guo, Xieyou; Guo, Tianqi; Wang, Bin; Jiang, Lei

    2016-07-21

    Ordered porous polymeric films attract more and more attention because they have many advantages and broad application prospects in many fields. But because of their large flexibility and poor mechanical properties, some of the scope for application is greatly limited. Inspired by the ordered pore structure of the honeycomb and the layered structure of natural nacre, we prepared an ordered porous polymer film with a layered structure in the pore wall by the solvent-evaporation-restriction assisted hard template method. Compared with other samples, this kind of film with the layered structure showed both excellent mechanical properties and good stability. This kind of film with high mechanical strength, is considered to have wide applications in the areas of separation, biomedicine, precision instruments, aerospace, environmental protection and so on. PMID:27355160

  7. Fibrin-Loaded Porous Poly(Ethylene Glycol) Hydrogels as Scaffold Materials for Vascularized Tissue Formation

    PubMed Central

    Jiang, Bin; Waller, Thomas M.; Larson, Jeffery C.; Appel, Alyssa A.

    2013-01-01

    Vascular network formation within biomaterial scaffolds is essential for the generation of properly functioning engineered tissues. In this study, a method is described for generating composite hydrogels in which porous poly(ethylene glycol) (PEG) hydrogels serve as scaffolds for mechanical and structural support, and fibrin is loaded within the pores to induce vascularized tissue formation. Porous PEG hydrogels were generated by a salt leaching technique with 100–150-μm pore size and thrombin (Tb) preloaded within the scaffold. Fibrinogen (Fg) was loaded into pores with varying concentrations and polymerized into fibrin due to the presence of Tb, with loading efficiencies ranging from 79.9% to 82.4%. Fibrin was distributed throughout the entire porous hydrogels, lasted for greater than 20 days, and increased hydrogel mechanical stiffness. A rodent subcutaneous implant model was used to evaluate the influence of fibrin loading on in vivo response. At weeks 1, 2, and 3, all hydrogels had significant tissue invasion, but no difference in the depth of invasion was found with the Fg concentration. Hydrogels with fibrin loading induced more vascularization, with a significantly higher vascular density at 20 mg/mL (week 1) and 40 mg/mL (weeks 2 and 3) Fg concentration compared to hydrogels without fibrin. In conclusion, we have developed a composite hydrogel that supports rapid vascularized tissue ingrowth, and thus holds great potential for tissue engineering applications. PMID:23003671

  8. Porous Shape Memory Polymers

    PubMed Central

    Hearon, Keith; Singhal, Pooja; Horn, John; Small, Ward; Olsovsky, Cory; Maitland, Kristen C.; Wilson, Thomas S.; Maitland, Duncan J.

    2013-01-01

    Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use. PMID:23646038

  9. Iron-rich nanoparticle encapsulated, nitrogen doped porous carbon materials as efficient cathode electrocatalyst for microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Guolong; Zhu, Youlong; Lu, Lu; Xu, Kongliang; Wang, Heming; Jin, Yinghua; Jason Ren, Zhiyong; Liu, Zhenning; Zhang, Wei

    2016-05-01

    Developing efficient, readily available, and sustainable electrocatalysts for oxygen reduction reaction (ORR) in neutral medium is of great importance to practical applications of microbial fuel cells (MFCs). Herein, a porous nitrogen-doped carbon material with encapsulated Fe-based nanoparticles (Fe-Nx/C) has been developed and utilized as an efficient ORR catalyst in MFCs. The material was obtained through pyrolysis of a highly porous organic polymer containing iron(II) porphyrins. The characterizations of morphology, crystalline structure and elemental composition reveal that Fe-Nx/C consists of well-dispersed Fe-based nanoparticles coated by N-doped graphitic carbon layer. ORR catalytic performance of Fe-Nx/C has been evaluated through cyclic voltammetry and rotating ring-disk electrode measurements, and its application as a cathode electrocatalyst in an air-cathode single-chamber MFC has been investigated. Fe-Nx/C exhibits comparable or better performance in MFCs than 20% Pt/C, displaying higher cell voltage (601 mV vs. 591 mV), maximum power density (1227 mW m-2 vs. 1031 mW m-2) and Coulombic efficiency (50% vs. 31%). These findings indicate that Fe-Nx/C is more tolerant and durable than Pt/C in a system with bacteria metabolism and thus holds great potential for practical MFC applications.

  10. Dynamic mean field theory of condensation and evaporation processes for fluids in porous materials: application to partial drying and drying.

    PubMed

    Edison, J R; Monson, P A

    2010-01-01

    We study the dynamics of evaporation for lattice gas models of fluids in porous materials using a recently developed dynamic mean field theory. The theory yields a description of the dynamics that is consistent with the mean field theory of the thermodynamics at equilibrium. The nucleation processes associated with phase changes in the pore are emergent features of the dynamics. Our focus is on situations where there is partial drying or drying in the system, associated with weakly attractive or repulsive interactions between the fluid and the pore walls. We consider two systems in this work: (i) a two-dimensional slit pore geometry relevant to the study of adsorption/desorption or intrusion/extrusion dynamics for fluids in porous materials and (ii) a three dimensional slit pore modeling a pair of square plates in a bath of liquid as used in recent theoretical studies of dewetting processes between hydrophobic surfaces. We assess the theory by comparison with a higher order approximation to the dynamics that yields the Bethe-Peierls or quasi-chemical approximation at equilibrium. PMID:21043421

  11. Highly Flexible Freestanding Porous Carbon Nanofibers for Electrodes Materials of High-Performance All-Carbon Supercapacitors.

    PubMed

    Liu, Ying; Zhou, Jinyuan; Chen, Lulu; Zhang, Peng; Fu, Wenbin; Zhao, Hao; Ma, Yufang; Pan, Xiaojun; Zhang, Zhenxing; Han, Weihua; Xie, Erqing

    2015-10-28

    Highly flexible porous carbon nanofibers (P-CNFs) were fabricated by electrospining technique combining with metal ion-assistant acid corrosion process. The resultant fibers display high conductivity and outstanding mechanical flexibility, whereas little change in their resistance can be observed under repeatedly bending, even to 180°. Further results indicate that the improved flexibility of P-CNFs can be due to the high graphitization degree caused by Co ions. In view of electrode materials for high-performance supercapacitors, this type of porous nanostructure and high graphitization degree could synergistically facilitate the electrolyte ion diffusion and electron transportation. In the three electrodes testing system, the resultant P-CNFs electrodes can exhibit a specific capacitance of 104.5 F g(-1) (0.2 A g(-1)), high rate capability (remain 56.5% at 10 A g(-1)), and capacitance retention of ∼94% after 2000 cycles. Furthermore, the assembled symmetric supercapacitors showed a high flexibility and can deliver an energy density of 3.22 Wh kg(-1) at power density of 600 W kg(-1). This work might open a way to improve the mechanical properties of carbon fibers and suggests that this type of freestanding P-CNFs be used as effective electrode materials for flexible all-carbon supercapacitors. PMID:26449440

  12. Preparation of a porous Sn@C nanocomposite as a high-performance anode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Yanjun; Jiang, Li; Wang, Chunru

    2015-07-01

    A porous Sn@C nanocomposite was prepared via a facile hydrothermal method combined with a simple post-calcination process, using stannous octoate as the Sn source and glucose as the C source. The as-prepared Sn@C nanocomposite exhibited excellent electrochemical behavior with a high reversible capacity, long cycle life and good rate capability when used as an anode material for lithium ion batteries.A porous Sn@C nanocomposite was prepared via a facile hydrothermal method combined with a simple post-calcination process, using stannous octoate as the Sn source and glucose as the C source. The as-prepared Sn@C nanocomposite exhibited excellent electrochemical behavior with a high reversible capacity, long cycle life and good rate capability when used as an anode material for lithium ion batteries. Electronic supplementary information (ESI) available: Detailed experimental procedure and additional characterization, including a Raman spectrum, TGA curve, N2 adsorption-desorption isotherm, TEM images and SEM images. See DOI: 10.1039/c5nr03093e

  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. Hierarchically porous Fe-N-C derived from covalent-organic materials as a highly efficient electrocatalyst for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Zuo, Quan; Zhao, Pingping; Luo, Wei; Cheng, Gongzhen

    2016-07-01

    Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the best non-precious catalysts ever reported for ORR.Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the

  15. Polymer composites and porous materials prepared by thermally induced phase separation and polymer-metal hybrid methods

    NASA Astrophysics Data System (ADS)

    Yoon, Joonsung

    The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of the mixtures. Anisotropic crystal growth of the diluents was studied in terms of thermodynamics and kinetics using DSC, optical microscopy and SEM. Microstructures of the porous materials were explained in terms of supercooling and dendritic solidification. Dual functionality of the crystallizable diluents for composite materials was evaluated using isotactic polypropylene (iPP) and compatible diluents that crystallize upon cooling. The selected diluents form homogeneous mixtures with iPP at high temperature and lower the viscosity (improved processability), which undergo phase separation upon cooling to form solid particles that function as a toughening agent at room temperature. Tensile properties and morphology of the composites showed that organic crystalline particles have the similar effect as rigid particles to increase toughness; de-wetting between the particle and iPP matrix occurs at the early stage of deformation, followed by unhindered plastic flow that consumes significant amount of fracture energy. The effect of the diluents, however, strongly depends on the identity of the diluents that interact with the iPP during solidification step, which was demonstrated by comparing tetrabromobisphenol-A and

  16. Bioinspired porous octacalcium phosphate/silk fibroin composite coating materials prepared by electrochemical deposition.

    PubMed

    Yang, Ya; Wang, Hui; Yan, Feng-Yi; Qi, Yu; Lai, Yue-Kun; Zeng, Dong-Mei; Chen, Guoqiang; Zhang, Ke-Qin

    2015-03-18

    The biomimetic structure and composition of biomaterials are recognized as critical factors that determine their biological performance. A bioinspired nano-micro structured octacalcium phosphate (OCP)/silk fibroin (SF) composite coating on titanium was achieved through a mild electrochemically induced deposition method. Findings indicate that SF plays a critical role in constructing the unique biomimetic hierarchical structure of OCP/SF composite coating layers. In vitro cell culture tests demonstrate that the presence of OCP/SF composite coatings, with highly ordered and hierarchically porous structure, greatly enhance cellular responses. The coatings developed in this study have considerable potential for various hard tissue engineering and applications. PMID:25734421

  17. Correlation Function Approach for Estimating Thermal Conductivity in Highly Porous Fibrous Materials

    NASA Technical Reports Server (NTRS)

    Martinez-Garcia, Jorge; Braginsky, Leonid; Shklover, Valery; Lawson, John W.

    2011-01-01

    Heat transport in highly porous fiber networks is analyzed via two-point correlation functions. Fibers are assumed to be long and thin to allow a large number of crossing points per fiber. The network is characterized by three parameters: the fiber aspect ratio, the porosity and the anisotropy of the structure. We show that the effective thermal conductivity of the system can be estimated from knowledge of the porosity and the correlation lengths of the correlation functions obtained from a fiber structure image. As an application, the effects of the fiber aspect ratio and the network anisotropy on the thermal conductivity is studied.

  18. Biofuels and biomass-to-liquid fuels in the biorefinery: catalytic conversion of lignocellulosic biomass using porous materials.

    PubMed

    Stöcker, Michael

    2008-01-01

    At a time when the focus is on global warming, CO(2) emission, secure energy supply, and less consumption of fossil-based fuels, the use of renewable energy resources is essential. Various biomass resources are discussed that can deliver fuels, chemicals, and energy products. The focus is on the catalytic conversion of biomass from wood. The challenges involved in the processing of lignocellulose-rich materials will be highlighted, along with the application of porous materials as catalysts for the biomass-to-liquids (BTL) fuels in biorefineries. The mechanistic understanding of the complex reactions that take place, the development of catalysts and processes, and the product spectrum that is envisaged will be discussed, along with a sustainable concept for biorefineries based on lignocellulose. Finally, the current situation with respect to upgrading of the process technology (pilot and commercial units) will be addressed. PMID:18937235

  19. Propagation of electromagnetic waves through a multilayered structure containing diamond-like carbon, porous silicon, and left-handed material

    NASA Astrophysics Data System (ADS)

    Shabat, Mohammed M.; Ubeid, Muin F.; Altanany, Sameh M.

    2016-05-01

    In this work, reflection and transmission of electromagnetic wave through a multilayered structure containing diamond-like carbon, porous silicon, and left-handed material (LHM) are investigated theoretically and numerically. The mentioned materials are described, and their main parameters are given in detail. After the construction of the problem, the reflection and transmission coefficients are derived in a closed form by a transfer matrix method. The reflected and transmitted powers of the structure are calculated using these coefficients. In the numerical results, the mentioned powers are computed and illustrated as a function of frequency, angle of incidence, and slabs thickness, when the damping coefficient of the LHM changes. The results obtained may be useful to the researchers and designer working in the area solar cells.

  20. Porous materials as high performance adsorbents for CO2 capture, gas separation and purification

    NASA Astrophysics Data System (ADS)

    Wang, Jun

    new series of oxygen-doped ACs were synthesized from polyfuran. Different factors that affect the AC formation were investigated, and two kinds of porogens (ZnC12 and KOH) and two active temperatures (600 and 800 °C) were tested. At 298K and 1bar, an excellent selectivity for separating CO2/N2 (41.7) and CO2/CH 4(6.8) gas mixture pairs was obtained on the PF-600 KOH. A breakthrough simulation was also performed to demonstrate the potential of industrial applications. The PF-600 KOH sample showed the best separation result in the simulated adsorption breakthrough as well. In chapter 4, quinone and hydroquinone on the surface of PF-600 ZnC1 2 were integrated. Significantly pore size shrinkage, improved CO 2/N2 and CO2/CH4 IAST selectivity were observed, which is 58.7% and 28.4 % higher than pristine porous carbon at 298K and 1 atm, respectively. In addition, transient breakthrough simulations for CO2/CH4/N2 binary mixtures were conducted in order to demonstrate the good separation performance in fixed bed adsorbers. In chapter 5, a novel nitrogen doped polymer poly(2-phenyl-1,3,6,8tetraazacyclodecane) will be used as the precursor to produce microporous N-doped activated carbons. Three activation temperatures (600, 700, and 800 °C) has been investigated with KOH as the porogen. High nitrogen content has been remained in the resultant carbon materials. Improved CO2 adsorption capacity and selectivites for the separation of CO2/CH4/N2 binary gas mixtures were achieved by the carbon adsorbents due to their N-containing groups, narrow pore size distribution, and large specific surface area. In chapter 6, MOF-derived activated carbons are developed from MIL-100(Al) as hard-template. Direct carbonization of MIL-100, MIL-100(Al)/F-127 composite, and MIL-100(Al)/KOH mixture has been investigated. Pore structure and surface morphology have been demonstrated. CO2/CH4/N2 binary selectivity, adsorption heats, and kinetic selectivity have been calculated. Breakthrough simulation

  1. Porous materials as high performance adsorbents for CO2 capture, gas separation and purification

    NASA Astrophysics Data System (ADS)

    Wang, Jun

    new series of oxygen-doped ACs were synthesized from polyfuran. Different factors that affect the AC formation were investigated, and two kinds of porogens (ZnC12 and KOH) and two active temperatures (600 and 800 °C) were tested. At 298K and 1bar, an excellent selectivity for separating CO2/N2 (41.7) and CO2/CH 4(6.8) gas mixture pairs was obtained on the PF-600 KOH. A breakthrough simulation was also performed to demonstrate the potential of industrial applications. The PF-600 KOH sample showed the best separation result in the simulated adsorption breakthrough as well. In chapter 4, quinone and hydroquinone on the surface of PF-600 ZnC1 2 were integrated. Significantly pore size shrinkage, improved CO 2/N2 and CO2/CH4 IAST selectivity were observed, which is 58.7% and 28.4 % higher than pristine porous carbon at 298K and 1 atm, respectively. In addition, transient breakthrough simulations for CO2/CH4/N2 binary mixtures were conducted in order to demonstrate the good separation performance in fixed bed adsorbers. In chapter 5, a novel nitrogen doped polymer poly(2-phenyl-1,3,6,8tetraazacyclodecane) will be used as the precursor to produce microporous N-doped activated carbons. Three activation temperatures (600, 700, and 800 °C) has been investigated with KOH as the porogen. High nitrogen content has been remained in the resultant carbon materials. Improved CO2 adsorption capacity and selectivites for the separation of CO2/CH4/N2 binary gas mixtures were achieved by the carbon adsorbents due to their N-containing groups, narrow pore size distribution, and large specific surface area. In chapter 6, MOF-derived activated carbons are developed from MIL-100(Al) as hard-template. Direct carbonization of MIL-100, MIL-100(Al)/F-127 composite, and MIL-100(Al)/KOH mixture has been investigated. Pore structure and surface morphology have been demonstrated. CO2/CH4/N2 binary selectivity, adsorption heats, and kinetic selectivity have been calculated. Breakthrough simulation

  2. Ventilation of porous media

    DOEpatents

    Neeper, Donald A.

    1994-01-01

    Methods for distributing gases throughout the interstices of porous materials and removing volatile substances from the interstices of porous materials. Continuous oscillation of pressures and flows results in increased penetration of the interstices by flowing gases and increased transport of gaseous components out of the interstices. The invention is particularly useful in soil vapor extraction.

  3. Ventilation of porous media

    DOEpatents

    Neeper, D.A.

    1994-02-22

    Methods are presented for distributing gases throughout the interstices of porous materials and removing volatile substances from the interstices of porous materials. Continuous oscillation of pressures and flows results in increased penetration of the interstices by flowing gases and increased transport of gaseous components out of the interstices. The invention is particularly useful in soil vapor extraction. 10 figures.

  4. Porous 3D graphene-based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors

    PubMed Central

    Zhang, Long; Zhang, Fan; Yang, Xi; Long, Guankui; Wu, Yingpeng; Zhang, Tengfei; Leng, Kai; Huang, Yi; Ma, Yanfeng; Yu, Ao; Chen, Yongsheng

    2013-01-01

    Until now, few sp2 carbon materials simultaneously exhibit superior performance for specific surface area (SSA) and electrical conductivity at bulk state. Thus, it is extremely important to make such materials at bulk scale with those two outstanding properties combined together. Here, we present a simple and green but very efficient approach using two standard and simple industry steps to make such three-dimensional graphene-based porous materials at the bulk scale, with ultrahigh SSA (3523 m2/g) and excellent bulk conductivity. We conclude that these materials consist of mainly defected/wrinkled single layer graphene sheets in the dimensional size of a few nanometers, with at least some covalent bond between each other. The outstanding properties of these materials are demonstrated by their superior supercapacitor performance in ionic liquid with specific capacitance and energy density of 231 F/g and 98 Wh/kg, respectively, so far the best reported capacitance performance for all bulk carbon materials. PMID:23474952

  5. Radio-tracer techniques for the study of flow in saturated porous materials

    USGS Publications Warehouse

    Skibitzke, H.E.; Chapman, H.T.; Robinson, G.M.; McCullough, Richard A.

    1961-01-01

    An experiment was conducted by the U.S. Geological Survey to determine the feasibility of using a radioactive substance as a tracer in the study of microscopic flow in a saturated porous solid. A radioactive tracer was chosen in preference to dye or other chemical in order to eliminate effects of the tracer itself on the flow system such as those relating to density, viscosity and surface tension. The porous solid was artificial "sandstone" composed of uniform fine grains of sand bonded together with an epoxy adhesive. The sides of the block thus made were sealed with an epoxy coating compound to insure water-tightness. Because of the chemical inertness of the block it was possible to use radioactive phosphorus (P32). Ion-exchange equilibrium was created between the block and nonradioactive phosphoric acid. Then a tracer tagged with P32 was injected into the block in the desired geometric configuration, in this case, a line source. After equilibrium in isotopic exchange was reached between the block and the line source, the block was rinsed, drained and sawn into slices. It was found that a quantitative analysis of the flow system may be made by assaying the dissected block. ?? 1961.

  6. Redox chemistry and metal-insulator transitions intertwined in a nano-porous material

    NASA Astrophysics Data System (ADS)

    Maximoff, Sergey N.; Smit, Berend

    2014-06-01

    Metal-organic frameworks are nano-porous adsorbents of relevance to gas separation and catalysis, and separation of oxygen from air is essential to diverse industrial applications. The ferrous salt of 2,5-dihydroxy-terephthalic acid, a metal-organic framework of the MOF74 family, can selectively adsorb oxygen in a manner that defies the classical picture: adsorption sites either do or do not share electrons over a long range. Here we propose, and then justify phenomenologically and computationally, a mechanism. Charge-transfer-mediated adsorption of electron acceptor oxygen molecules in the metal-organic framework, which is a quasi-one-dimensional electron-donor semiconductor, drives and is driven by quasi-one-dimensional metal-insulator-metal transitions that localize or delocalize the quasi-one-dimensional electrons. This mechanism agrees with the empirical evidence, and predicts a class of nano-porous semiconductors or metals and potential adsorbents and catalysts in which chemistry and metal-insulator-metal transitions intertwine.

  7. Combination of porous silica monolith and gold thin films for electrode material of supercapacitor

    NASA Astrophysics Data System (ADS)

    Pastre, A.; Cristini-Robbe, O.; Boé, A.; Raulin, K.; Branzea, D.; El Hamzaoui, H.; Kinowski, C.; Rolland, N.; Bernard, R.

    2015-12-01

    An all-solid electrical double layer supercapacitor was prepared, starting from a porous silica matrix coated with a gold thin-film. The metallization of the silica xerogel was performed by an original wet chemical process, based on the controlled growth of gold nanoparticles on two opposite faces of the silica monolith as a seed layer, followed by an electroless deposition of a continuous gold thin film. The thickness of the metallic thin film was assessed to be 700 nm. The silica plays two major roles: (1) it is used as a porous matrix for the gold electrode, creating a large specific surface area, and (2) it acts as a separator (non-metallized part of the silica). The silica monolith was soaked in a polyvinyl alcohol and phosphoric acid mixture which is used as polymer electrolyte. Capacitance effect was demonstrated by cyclic voltammetry experiments. The specific capacitance was found to be equal to 0.95 mF cm- 2 (9.5 F g-1). No major degradation occurs within more than 3000 cycles.

  8. Conductive porous sponge-like ionic liquid-graphene assembly decorated with nanosized polyaniline as active electrode material for supercapacitor

    NASA Astrophysics Data System (ADS)

    Halab Shaeli Iessa, K.; Zhang, Yan; Zhang, Guoan; Xiao, Fei; Wang, Shuai

    2016-01-01

    We report the development of three-dimensional (3D) porous sponge-like ionic liquid (IL)-graphene hybrid material by integrating IL molecules and graphene nanosheets via self-assembly process. The as-obtained IL-graphene architecture possesses high surface area, efficient electron transport network and fast charge transfer kinetics owing to its highly porous structure, and unique hydrophilic properties derived from the IL anion on its surface, which endows it with high desire for supercapacitor application. Redox-active polyaniline (PANI) nanorods are further decorated on IL-graphene scaffold by electropolymerization. When utilized as freestanding 3D electrode for supercapacitor, the resultant PANI modified IL-graphene (PANI-IL-graphene) electrode exhibits a specific capacitance up to 662 F g-1 at the current density of 1.0 A g-1, with a high capacitance retention of 73.7% as current densities increase from 1.0 to 20 A g-1, and the capacitance degradation is less than 7.0% after 5000 charge-discharge cycles at 10 A g-1.

  9. Ultra-thin porous glass membranes--an innovative material for the immobilization of active species for optical chemosensors.

    PubMed

    Müller, R; Anders, N; Titus, J; Enke, D

    2013-03-30

    In addition to polymers, porous glasses can be used for the immobilization of indicators, chromoionophores or enzymes. Advantages of these materials include, among others, the photochemical and thermal stability. Porous glass membranes (CPG) based on phase-separated alkali borosilicate glasses with thicknesses of 250-300 μm and dimensions of approximately 9-13 mm² were used in this work. The average pore diameter was found to be between 12 and 112 nm. Initially, the membrane permeability for water was determined. Furthermore, the absorption spectra for the water-soaked membranes were recorded optically. CPG membranes which are pH-sensitive were prepared based on the covalent immobilization of thymol blue and a derivative of styryl acridine. In each case, the absorption spectra of the immobilized indicators are shown. The t90-times vary between 4 and 20 min and were determined for the thermodynamic equilibrium. The influence of the ionic strength on the characteristic curve is discussed and detailed results are given. After the storage time of about 900 days a pH-sensitivity for a CPG membrane styryl acridine derivative sample was still detectable. PMID:23598220

  10. Hierarchically porous Fe-N-C derived from covalent-organic materials as a highly efficient electrocatalyst for oxygen reduction.

    PubMed

    Zuo, Quan; Zhao, Pingping; Luo, Wei; Cheng, Gongzhen

    2016-08-01

    Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the best non-precious catalysts ever reported for ORR. PMID:27405086

  11. Porous Iron Cobaltate Nanoneedles Array on Nickel Foam as Anode Materials for Lithium-Ion Batteries with Enhanced Electrochemical Performance.

    PubMed

    Liu, Li; Zhang, Huijuan; Mu, Yanping; Yang, Jiao; Wang, Yu

    2016-01-20

    A monocrystalline and porous FeCo2O4 nanoneedles array growing directly on a nickel foam substrate was obtained by a hydrothermal technique accompanying with combustion of the one-dimensional precursor. The average length of the FeCo2O4 nanoneedles is approximately 2 μm, while the diameter of the root segment of the nanoneedle can be estimated to be around 100 nm, which gradually reduces to only several nanometers at the top. When the as-prepared porous FeCo2O4 nanoneedles array with a high surface area of 58.49 m(2) g(-1) was applied as binder-free electrode in lithium-ion batteries, it exhibited satisfactory electrochemical performance, such as outstanding reversibility (Coulombic efficiency of approximately 92-95%), high specific capacity (1962 mAh g(-1) at the current density of 100 mA g(-1)), and excellent rate performance (discharge capacity of 875 mAh g(-1) at the current density of 2000 mA g(-1)), due to the various favorable conditions. Undoubtedly, the simple but effective strategy can be expanded to other high-performance binary metal-oxide materials. PMID:26713359

  12. Nitrogen-Doped Porous Carbons As Electrode Materials for High-Performance Supercapacitor and Dye-Sensitized Solar Cell.

    PubMed

    Wang, Lan; Gao, Zhiyong; Chang, Jiuli; Liu, Xiao; Wu, Dapeng; Xu, Fang; Guo, Yuming; Jiang, Kai

    2015-09-16

    Activated N-doped porous carbons (a-NCs) were synthesized by pyrolysis and alkali activation of graphene incorporated melamine formaldehyde resin (MF). The moderate N doping levels, mesopores rich porous texture, and incorporation of graphene enable the applications of a-NCs in surface and conductivity dependent electrode materials for supercapacitor and dye-sensitized solar cell (DSSC). Under optimal activation temperature of 700 °C, the afforded sample, labeled as a-NC700, possesses a specific surface area of 1302 m2 g(-1), a N fraction of 4.5%, and a modest graphitization. When used as a supercapacitor electrode, a-NC700 offers a high specific capacitance of 296 F g(-1) at a current density of 1 A g(-1), an acceptable rate capability, and a high cycling stability in 1 M H2SO4 electrolyte. As a result, a-NC700 supercapacitor delivers energy densities of 5.0-3.5 Wh kg(-1) under power densities of 83-1609 W kg(-1). Moreover, a-NC700 also demonstrates high electrocatalytic activity for I3- reduction. When employed as a counter electrode (CE) of DSSC, a power conversion efficiency (PCE) of 6.9% is achieved, which is comparable to that of the Pt CE based counterpart (7.1%). The excellent capacitive and photovoltaic performances highlight the potential of a-NCs in sustainable energy devices. PMID:26320745

  13. Simulations on the gelling process of particle suspension systems for in-situ preparing porous materials in a capillary

    NASA Astrophysics Data System (ADS)

    Wang, J.; Xu, J. J.; Yang, Y.; Wang, X. J.; Luo, X.; Zhang, L.; Jiang, G.

    2015-10-01

    The gelling process of particle suspension in a capillary which is crucial for in-situ preparing small size foam products has been simulated with an off-lattice diffusion limited cluster aggregation (DLCA) model by the three-dimensional Monte Carlo simulations. The effects of the model parameters, such as the interaction between capillary wall and particles, particle volume fraction, capillary size etc. on the density distribution of the system have been fully explored. And the aggregation kinetics process over a broad range of volume fractions and interactions have also been discussed. The results show that the geometric constraint of capillary can be analogous to a weak repulsive interaction between capillary wall and particles. And we found that as the capillary size or particle volume fraction increase, particle concentration distribution will be more uniform with other parameters constant. Porous network with relatively uniform density distribution can be also obtained through controlling the interaction between capillary wall and particles. In addition, by analyzing the aggregation kinetics process, we found that the attraction of capillary wall dramatically reduces the probability of gelation in the small-scale capillary. The obtained results will be of great importance in controlling the density distribution of porous materials prepared by in-situ methods.

  14. Immobilization of Bacillus subtilis lipase on a Cu-BTC based hierarchically porous metal-organic framework material: a biocatalyst for esterification.

    PubMed

    Cao, Yu; Wu, Zhuofu; Wang, Tao; Xiao, Yu; Huo, Qisheng; Liu, Yunling

    2016-04-28

    Bacillus subtilis lipase (BSL2) has been successfully immobilized into a Cu-BTC based hierarchically porous metal-organic framework material for the first time. The Cu-BTC hierarchically porous MOF material with large mesopore apertures is prepared conveniently by using a template-free strategy under mild conditions. The immobilized BSL2 presents high enzymatic activity and perfect reusability during the esterification reaction. After 10 cycles, the immobilized BSL2 still exhibits 90.7% of its initial enzymatic activity and 99.6% of its initial conversion. PMID:26988724

  15. Porous-structured Cu2O/TiO2 nanojunction material toward efficient CO2 photoreduction.

    PubMed

    Xu, Hua; Ouyang, Shuxin; Liu, Lequan; Wang, Defa; Kako, Tetsuya; Ye, Jinhua

    2014-04-25

    Porous-structured Cu2O/TiO2 nanojunction material is successfully fabricated by a facile method via loading Cu2O nanoparticles on the network of a porous TiO2 substrate. The developed Cu2O/TiO2 nanojunction material has a size of several nanometers, in which the p-type Cu2O and n-type TiO2 nanoparticles are closely contacted with each other. The well designed nanojunction structure is beneficial for the charge separation in the photocatalytic reaction. Meanwhile, the porous structure of the Cu2O/TiO2 nanojunction can facilitate the CO2 adsorption and offer more reaction active sites. Most importantly, the gas-phase CO2 photoreduction tests reveal that our developed porous-structured Cu2O/TiO2 nanojunction material exhibits marked photocatalytic activity in the CH4 evolution, about 12, 9, and 7.5 times higher than the pure TiO2, Pt-TiO2, and commercial Degussa P25 TiO2 powders, respectively. The greatly enhanced activity can be attributed to the well designed nanojunction structure combined with the porous structure, which can simultaneously enhance the charge separation efficiency and facilitate the CO2 adsorption. PMID:24670915

  16. Micro- and Nano- Porous Adsorptive Materials for Removal of Contaminants from Water at Point-of-Use

    NASA Astrophysics Data System (ADS)

    Yakub, Ismaiel

    Water is food, a basic human need and a fundamental human right, yet hundreds of millions of people around the world do not have access to clean drinking water. As a result, about 5000 people die each day from preventable water borne diseases. This dissertation presents the results of experimental and theoretical studies on three different types of porous materials that were developed for the removal of contaminants from water at point of use (household level). First, three compositionally distinct porous ceramic water filters (CWFs) were made from a mixture of redart clay and sieved woodchips and processed into frustum shape. The filters were tested for their flow characteristics and bacteria filtration efficiencies. Since, the CWFs are made from brittle materials, and may fail during processing, transportation and usage, the mechanical and physical properties of the porous clays were characterized, and used in modeling designed to provide new insights for the design of filter geometries. The mechanical/physical properties that were characterized include: compressive strength, flexural strength, facture toughness and resistance curve behavior, keeping in mind the anisotropic nature of the filter structure. The measured flow characteristics and mechanical/physical properties were then related to the underlying porosity and characteristic pore size. In an effort to quantify the adhesive interactions associated with filtration phenomena, atomic force microscopy (AFM) was used to measure the adhesion between bi-material pairs that are relevant to point-of-use ceramic water filters. The force microscopy measurements of pull-off force and adhesion energy were used to rank the adhesive interactions. Similarly, the adsorption of fluoride to hydroxyapatite-doped redart clay was studied using composites of redart clay and hydroxyapatite (C-HA). The removal of fluoride from water was explored by carrying out adsorption experiments on C-HA adsorbents with different ratios of

  17. Introducing porous silicon as a sacrificial material to obtain cavities in substrate of SOI wafers and a getter material for MEMS devices

    NASA Astrophysics Data System (ADS)

    Mohammad, Wajihuddin

    Microelectromechanical system (MEMS) resonators have been a subject of research for more than four decades. The reason is the huge potential they possess for frequency applications. The use of a MEMS resonator as the timing element has an experimental history and huge progress has been made in this direction. Vacuum encapsulated MEMS resonators are required for high precision frequency control. Hence, a device with a high quality factor and durability is needed. In this effort, a new process for producing a cavity in the substrate of Silicon on insulator (SOI) MEMS devices and augmenting it with a getter using porous silicon is developed. The process involves a mask-less, self-aligned cost effective electrochemical etching process. A 10 mum cavity is introduced in the substrate of SOI dies. This helps in increasing the packaging volume of the SOI resonators along with mitigating the viscous damping effects. The stiction problem in MEMS devices is effectively eliminated and millimeter long slender MEMS structures do not get stuck to the substrate. It also helps in reducing the parasitic capacitance between the device side and the substrate. The porous silicon getter is introduced as a getter material for vacuum encapsulated MEMS devices. This getter needs no external mask and is self-aligned. It requires no external heat or additional materials to operate. The highly reactive porous silicon can readily react with the oxygen gas and form an oxide layer that can trap other gas molecules. This helps in maintaining low pressures in the cavity of the bonded MEMS resonators. A tuning fork resonator with a resonant frequency of 245 kHz was used to realize the benefits of the cavity and the getter. It was observed that the unpackaged device with the cavity in the substrate showed two times better quality factor at different pressures, than the device with no cavity. In order to understand the benefits of porous silicon as a getter, the MEMS devices (one with only a cavity

  18. Application of highly porous materials for simazine removal from aqueous solutions.

    PubMed

    Esposito, Serena; Garrone, Edoardo; Marocco, Antonello; Pansini, Michele; Martinelli, Paola; Sannino, Filomena

    2016-10-01

    The removal of simazine from both pure water and solute-bearing well water was studied by adsorption on two solids: zeolite H-Y from the commercial Na form and porous silica tailored by the sol-gel technique. The pH dependence of the amount adsorbed in a closed system at constant total simazine content as well as the apparent isotherms of adsorption was measured in all four cases. The low ion content of natural water suffices to alter the adsorption features in the case of silica, but not with zeolite H-Y. Iteration of the adsorption process onto constant amounts of solid allowed bringing the residual simazine concentration below 0.05 mg/L, the value allowed by Italian laws in wastewaters. PMID:26852791

  19. Porous glasses as a matrix for incorporation of photonic materials. Pore determination by positron annihilation lifetime spectroscopy

    NASA Astrophysics Data System (ADS)

    Reisfeld, Pore determination by positron annihilation lifetime spectroscopy R.; Saraidarov, T.; Jasinska, B.

    2004-07-01

    Porous glasses prepared by the sol-gel technique have a variety of applications when incorporated by photonic materials: tunable lasers, sensors, luminescence solar concentrators, semiconductor quantum dots, biological markers. The known methods of pore size determinations, the nitrogen adsorption and mercury porosimetry allow to determine the sizes of open pores. Positron annihilation lifetime spectroscopy (PALS) allows to determine pore sizes also of closed pores. As an example we have performed measurements of non-doped zirconia-silica-polyurethane (ZSUR) ormocer glasses and the same glasses doped with lead sulfide quantum dots. The pore radii range between 0.25-0.38 nm, total surface area 15.5-23.8 m 2/g.

  20. Numerical Simulation for Effects of Microcapsuled Phase Change Material (mpcm) Distribution on Heat and Moisture Transfer in Porous Textiles

    NASA Astrophysics Data System (ADS)

    Li, Fengzhi

    In recent years, the use of phase change materials (PCM) to improve heat and moisture transfer properties of clothing has gained considerable attention. The PCM distribution in the clothing impacts heat and moisture transfer properties of the clothing significantly. For describing the mechanisms of heat and moisture transfer in clothing with PCM and investigating the effect of the PCM distribution, a new dynamic model of coupled heat and moisture transfer in porous textiles with PCM was developed. The effect of water content on physical parameters of textiles and heat transfer with phase change in the PCM microcapsules were considered in the model. Meanwhile, the numerical predictions were compared with experimental data, and good agreement was observed between the two, indicating that the model was satisfactory. Also the effects of the PCM distribution on heat transfer in the textiles-PCM microcapsule composites were investigated by using the model.

  1. Multi-physics computational grains (MPCGs) for direct numerical simulation (DNS) of piezoelectric composite/porous materials and structures

    NASA Astrophysics Data System (ADS)

    Bishay, Peter L.; Dong, Leiting; Atluri, Satya N.

    2014-11-01

    Conceptually simple and computationally most efficient polygonal computational grains with voids/inclusions are proposed for the direct numerical simulation of the micromechanics of piezoelectric composite/porous materials with non-symmetrical arrangement of voids/inclusions. These are named "Multi-Physics Computational Grains" (MPCGs) because each "mathematical grain" is geometrically similar to the irregular shapes of the physical grains of the material in the micro-scale. So each MPCG element represents a grain of the matrix of the composite and can include a pore or an inclusion. MPCG is based on assuming independent displacements and electric-potentials in each cell. The trial solutions in each MPCG do not need to satisfy the governing differential equations, however, they are still complete, and can efficiently model concentration of electric and mechanical fields. MPCG can be used to model any generally anisotropic material as well as nonlinear problems. The essential idea can also be easily applied to accurately solve other multi-physical problems, such as complex thermal-electro-magnetic-mechanical materials modeling. Several examples are presented to show the capabilities of the proposed MPCGs and their accuracy.

  2. 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

  3. A three-dimensional porous MoP@C hybrid as a high-capacity, long-cycle life anode material for lithium-ion batteries.

    PubMed

    Wang, Xia; Sun, Pingping; Qin, Jinwen; Wang, Jianqiang; Xiao, Ying; Cao, Minhua

    2016-05-21

    Metal phosphides are great promising anode materials for lithium-ion batteries with a high gravimetric capacity. However, significant challenges such as low capacity, fast capacity fading and poor cycle stability must be addressed for their practical applications. Herein, we demonstrate a versatile strategy for the synthesis of a novel three-dimensional porous molybdenum phosphide@carbon hybrid (3D porous MoP@C hybrid) by a template sol-gel method followed by an annealing treatment. The resultant hybrid exhibits a 3D interconnected ordered porous structure with a relatively high surface area. Benefiting from its advantages of microstructure and composition, the 3D porous MoP@C hybrid displays excellent lithium storage performance as an anode material for lithium-ion batteries in terms of specific capacity, cycling stability and long-cycle life. It presents stable cycling performance with a high reversible capacity up to 1028 mA h g(-1) at a current density of 100 mA g(-1) after 100 cycles. By ex situ XRD, HRTEM, SAED and XPS analyses, the 3D porous MoP@C hybrid was found to follow the Li-intercalation reaction mechanism (MoP + xLi(+) + e(-)↔ LixMoP), which was further confirmed by ab initio calculations based on density functional theory. PMID:27136974

  4. 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

  5. Visualization of water drying in porous materials by X-ray phase contrast imaging.

    PubMed

    Yang, F; Griffa, M; Bonnin, A; Mokso, R; DI Bella, C; Münch, B; Kaufmann, R; Lura, P

    2015-01-01

    We present in this study results from X-ray tomographic microscopy with synchrotron radiation performed both in attenuation and phase contrast modes on a limestone sample during two stages of water drying. No contrast agent was used in order to increase the X-ray attenuation by water. We show that only by using the phase contrast mode it is possible to achieve enough water content change resolution to investigate the drying process at the pore-scale. We performed 3D image analysis of the time-differential phase contrast tomogram. We show by the results of such analysis that it is possible to obtain a reliable characterization of the spatial redistribution of water in the resolved pore system in agreement with what expected from the theory of drying in porous media and from measurements performed with other approaches. We thus show the potential of X-ray phase contrast imaging for pore-scale investigations of reactive water transport processes which cannot be imaged by adding a contrast agent for exploiting the standard attenuation contrast imaging mode. PMID:26469285

  6. Evaluation of the acid properties of porous zirconium-doped and undoped silica materials

    NASA Astrophysics Data System (ADS)

    Fuentes-Perujo, D.; Santamaría-González, J.; Mérida-Robles, J.; Rodríguez-Castellón, E.; Jiménez-López, A.; Maireles-Torres, P.; Moreno-Tost, R.; Mariscal, R.

    2006-07-01

    A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption at 77 K. Their acid properties have been evaluated by NH 3-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites.

  7. Assemblage of Presolar Materials and Early Solar System Condensates in Chondritic Porous Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Nakamura-Messenger, K.; Messenger, S.; Keller, L. P.; Kloeck, W.

    2015-01-01

    Anhydrous chondritic porous inter-planetary dust particles (CP IDPs) contain an assortment of highly primitive solar system components, molecular cloud matter, and presolar grains. These IDPs have largely escaped parent body processing that has affected meteorites, advocating cometary origins. Though the stardust abundance in CP IDPs is generally greater than in primitive meteorites, it can vary widely among individual CP IDPs. The average abundance of silicate stardust among isotopically primitive IDPs is approx. 375 ppm while some have extreme abundances up to approx. 1.5%. H and N isotopic anomalies are common in CP IDPs and the carrier of these anomalies has been traced to organic matter that has experienced chemical reactions in cold molecular clouds or the outer protosolar disk. Significant variations in these anomalies may reflect different degrees of nebular processing. Refractory inclusions are commonly observed in carbonaceous chondrites. These inclusions are among the first solar system condensates and display 16O-rich isotopic compositions. Refractory grains have also been observed in the comet 81P/Wild-2 samples re-turned from the Stardust Mission and in CP IDPs, but they occur with much less frequency. Here we conduct coordinated mineralogical and isotopic analyses of CP IDPs that were characterized for their bulk chemistry by to study the distribution of primitive components and the degree of nebular alteration incurred.

  8. Porous Carbon Nanofibers from Electrospun Biomass Tar/Polyacrylonitrile/Silver Hybrids as Antimicrobial Materials.

    PubMed

    Song, Kunlin; Wu, Qinglin; Zhang, Zhen; Ren, Suxia; Lei, Tingzhou; Negulescu, Ioan I; Zhang, Quanguo

    2015-07-15

    A novel route to fabricate low-cost porous carbon nanofibers (CNFs) using biomass tar, polyacrylonitrile (PAN), and silver nanoparticles has been demonstrated through electrospinning and subsequent stabilization and carbonization processes. The continuous electrospun nanofibers had average diameters ranging from 392 to 903 nm. The addition of biomass tar resulted in increased fiber diameters, reduced thermal stabilities, and slowed cyclization reactions of PAN in the as-spun nanofibers. After stabilization and carbonization, the resultant CNFs showed more uniformly sized and reduced average diameters (226-507 nm) compared to as-spun nanofibers. The CNFs exhibited high specific surface area (>400 m(2)/g) and microporosity, attributed to the combined effects of phase separations of the tar and PAN and thermal decompositions of tar components. These pore characteristics increased the exposures and contacts of silver nanoparticles to the bacteria including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, leading to excellent antimicrobial performances of as-spun nanofibers and CNFs. A new strategy is thus provided for utilizing biomass tar as a low-cost precursor to prepare functional CNFs and reduce environmental pollutions associated with direct disposal of tar as an industrial waste. PMID:26110209

  9. Phase behavior of Stockmayer fluids confined to a nonpolar porous material

    NASA Astrophysics Data System (ADS)

    Spöler, C.; Klapp, S. H. L.

    2003-02-01

    The phase behavior of hard core Stockmayer fluids (i.e., dipolar hard spheres with additional Lennard-Jones interactions) adsorbed into a disordered porous hard sphere matrix is studied by means of replica-integral equations in the reference hypernetted chain approximation. The integral equations are solved for the homogeneous isotropic phase and the low-temperature phase behavior is inferred from those thermal fluctuations which strongly increase when the stability limit of the isotropic phase is approached. Analyzing first number density fluctuations and adsorption isotherms we find that the vapor-liquid transition occuring in bulk Stockmayer fluids still takes place in matrices of sufficiently high porosity. The corresponding critical point is shifted towards a lower temperature and density, in agreement with previous results on simpler fluids. At high fluid densities a diverging dielectric constant indicates the presence of an isotropic-to-ferroelectric transition for all systems considered, and the corresponding transition temperatures are found to increase with increasing matrix density. Comparing the fluid-matrix systems with fully equilibrated mixtures we argue that this enhanced tendency for ferroelectric ordering is essentially due to excluded volume effects.

  10. Graphene-based porous materials with tunable surface area and CO2 adsorption properties synthesized by fluorine displacement reaction with various diamines.

    PubMed

    Li, Baoyin; Fan, Kun; Ma, Xin; Liu, Yang; Chen, Teng; Cheng, Zheng; Wang, Xu; Jiang, Jiaxing; Liu, Xiangyang

    2016-09-15

    A mild, operationally simple and controllable protocol for preparing graphene-based porous materials is essential to achieve a good pore-design development. In this paper, graphene-based porous materials with tunable surface area were constructed by the intercalation of fluorinated graphene (FG) based on the reaction of reactive CF bonds attached to graphene sheets with various amine-terminated molecules. In the porous materials, graphene sheets are like building blocks, and the diamines covalently grafted onto graphene framework act as pillars. Various diamines are successfully grafted onto graphene sheets, but the grafting ratio of diamines and reduction degree of FG differ greatly and depend on the chemical reactivity of diamines. Pillared diamine molecules chemically anchor at one end and are capable of undergoing a different reaction on the other end, resulting in three different conformations of graphene derivatives. Nitrogen sorption isotherms revealed that the surface area and pore distribution of the obtained porous materials depend heavily on the size and structure of diamine pillars. CO2 uptake capacity characterization showed that ethylenediamine intercalated FG achieved a high CO2 uptake density of 18.0 CO2 molecules per nm(2) at 0°C and 1.1bars, and high adsorption heat, up to 46.1kJmol(-1) at zero coverage. PMID:27280538

  11. Use of silicon carbide sludge to form porous alkali-activated materials for insulating application

    NASA Astrophysics Data System (ADS)

    Prud'homme, E.; Joussein, E.; Rossignol, S.

    2015-07-01

    One of the objectives in the field of alkali-activated materials is the development of materials having greater thermal performances than conventional construction materials such as aerated concrete. The aim of this paper is to present the possibility to obtain controlled porosity and controlled thermal properties with geopolymer materials including a waste like silicon carbide sludge. The porosity is created by the reaction of free silicon contains in silicon carbide sludge leading to the formation of hydrogen. Two possible ways are investigated to control the porosity: modification of mixture formulation and additives introduction. The first way is the most promising and allowed the formation of materials presenting the same density but various porosities, which shows that the material is adaptable to the application. The insulation properties are logically linked to the porosity and density of materials. A lower value of thermal conductivity of 0.075 W.m-1.K-1 can be reached for a material with a low density of 0.27 g.cm-3. These characteristics are really good for a mineral-based material which always displays non-negligible resistance to manipulation.

  12. Porous composite materials ZrO2(MgO)-MgO for osteoimplantology

    NASA Astrophysics Data System (ADS)

    Buyakov, Ales; Litvinova, Larisa; Shupletsova, Valeria; Kulbakin, Denis; Kulkov, Sergey

    2016-08-01

    The pore structure and phase composition of ceramic composite material ZrO2(Mg)-MgO at different sintering temperatures were studied. The main mechanical characteristics of the material were determined and it was shown that they are close to the characteristics of natural bone tissues. It was shown that material structure has a positive effect on the pre-osteoblast cells proliferation. In-vitro studies of pre-osteoblast cells, cultivation on material surface showed a good cell adhesion, proliferation and differentiation of MMSC by osteogenic type.

  13. Measuring surface-area-to-volume ratios in soft porous materials using laser-polarized xenon interphase exchange nuclear magnetic resonance

    NASA Technical Reports Server (NTRS)

    Butler, J. P.; Mair, R. W.; Hoffmann, D.; Hrovat, M. I.; Rogers, R. A.; Topulos, G. P.; Walsworth, R. L.; Patz, S.

    2002-01-01

    We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129Xe between gas in the pore space and 129Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with destructive stereological measurements of S/V obtained with optical confocal microscopy. Potential applications of laser-polarized xenon interphase exchange NMR include measurements of in vivo lung function in humans and characterization of gas chromatography columns.

  14. In situ growth and activity and modes of penetration of Escherichia coli in unconsolidated porous materials.

    PubMed Central

    Sharma, P K; McInerney, M J; Knapp, R M

    1993-01-01

    Statistically reliable data on the in situ rates of growth, substrate consumption, and product formation are required to test the validity of the mathematical models developed for microbially enhanced oil recovery and in situ bioremediation processes. A simple, replicable porous-core system that could be aseptically divided into sections at various times was developed to follow the kinetics of microbial growth and metabolism in situ. This core system was used to study the kinetics of growth and the mode of penetration of strains of Escherichia coli through anaerobic, nutrient-saturated, fine Ottawa sand (permeability of 7.0 microns2 and porosity of 37%) under static conditions. The in situ rate of growth of a wild-type, motile, chemotactic strain, RW262, was two times slower inside cores than it was in liquid cultures. The mode of metabolism of galactose by strain RW262 was not altered inside cores, as acetate was the only product detected either inside the cores or in liquid cultures. Without applied advective force, strain RW262 grew exponentially and moved through cores at a rate of about 0.1 m/day. The cell population moved through cores in a band-like fashion, as the front of the moving cells consisted of high cell concentrations (greater than 10(5) cells per ml). Until the breakthrough of the cells occurred, galactose consumption and acetate production were observed only in the proximal sections of the core, showing that the cell propagation preceded the complete depletion of the substrate or the accumulation of large amounts of products.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8285677

  15. Interplay of carbon-silica sources on the formation of hierarchical porous composite materials for biological applications such as lipase immobilization.

    PubMed

    Higuita, Mario; Bernal, Claudia; Mesa, Monica

    2014-10-01

    The porous inorganic materials, with hierarchical structures, find application in many processes where the chemical stability and pore connectivity are key points, such as separation, adsorption and catalysis. Here, we synthesized carbon-silica composite materials, which combine hydrolytic stability of the carbon with the surface chemical reactivity of silica in aqueous media. The polycondensation of carbonaceous and siliceous species from sucrose, Triton X-100 surfactant and tetraethylortosilicate during the hydrothermal synthesis led to the formation of hydrochar composite materials. The subsequent carbonization process of these composite hydrochars gave carbon-silica hierarchical porous materials. The study of the micellar reaction system and the characterization of the derivate materials (carbon-silica composite, carbon and silica) were carried out. The results indicate that synthesis conditions allowed the formation of a silica network interpenetrated with a carbon one, which is produced from the incorporated organic matter. The control of the acidity of the reaction medium and hydrothermal conditions modulated the reaction yield and porous characteristics of the materials. The composite nature in conjunction with the hierarchical porosity increases the interest of these materials for future biological applications, such as lipase immobilization. PMID:25175205

  16. Facile synthesis of a 3D-porous LiNbO3 nanocomposite as a novel electrode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Fan, Qi; Lei, Lixu; Sun, Yueming

    2014-06-01

    A facile and efficient synthesis was developed to fabricate a 3D-porous LiNbO3 nanocomposite by microwave-induced auto-combustion. Such a material shows a high reversible capacity, excellent rate performance and stable cycle performance indicating its great potential as a promising anode material for Li-ion batteries.A facile and efficient synthesis was developed to fabricate a 3D-porous LiNbO3 nanocomposite by microwave-induced auto-combustion. Such a material shows a high reversible capacity, excellent rate performance and stable cycle performance indicating its great potential as a promising anode material for Li-ion batteries. Electronic supplementary information (ESI) available: Experimental details and additional supporting figures. See DOI: 10.1039/c4nr00232f

  17. The application of prepared porous carbon materials: Effect of different components on the heavy metal adsorption.

    PubMed

    Song, Min; Wei, Yuexing; Yu, Lei; Tang, Xinhong

    2016-06-01

    In this study, five typical municipal solid waste (MSW) components (tyres, cardboard, polyvinyl chloride (PVC), acrylic textile, toilet paper) were used as raw materials to prepare four kinds of MSW-based carbon materials (paperboard-based carbon materials (AC1); the tyres and paperboard-based carbon materials (AC2); the tyres, paperboard and PVC-based carbon materials (AC3); the tyres, paperboard, toilet paper, PVC and acrylic textile-based carbon materials (AC4)) by the KOH activation method. The characteristic results illustrate that the prepared carbon adsorbents exhibited a large pore volume, high surface area and sufficient oxygen functional groups. Furthermore, the application of AC1, AC2, AC3, AC4 on different heavy metal (Cu(2+), Zn(2+), Pb(2+), Cr(3+)) removals was explored to investigate their adsorption properties. The effects of reaction time, pH, temperature and adsorbent dosage on the adsorption capability of heavy metals were investigated. Comparisons of heavy metal adsorption on carbon of different components were carried out. Among the four samples, AC1 exhibits the highest adsorption capacity for Cu(2+); the highest adsorption capacities of Pb(2+) and Zn(2+) are obtained for AC2; that of Cr(3+) are obtained for AC4. In addition, the carbon materials exhibit better adsorption capability of Cu(2+) and Pb(2+) than the other two kind of metal ions (Zn(2+) and Cr(3+)). PMID:26951338

  18. Facile Synthesis of Mn-Doped ZnO Porous Nanosheets as Anode Materials for Lithium Ion Batteries with a Better Cycle Durability

    NASA Astrophysics Data System (ADS)

    Wang, Linlin; Tang, Kaibin; Zhang, Min; Xu, Jingli

    2015-07-01

    Porous Zn1 - x Mn x O ( x = 0.1, 0.2, 0.44) nanosheets were prepared by a low-cost, large-scale production and simple approach, and the applications of these nanosheets as an anode material for Li-ion batteries (LIBs) were explored. Electrochemical measurements showed that the porous Zn0.8Mn0.2O nanosheets still delivered a stable reversible capacity of 210 mA h g-1 at a current rate of 120 mA g-1 up to 300 cycles. These results suggest that the facile synthetic method of producing porous Zn0.8Mn0.2O nanostructure can realize a better cycle durability with stable reversible capacity.

  19. Facile Synthesis of Mn-Doped ZnO Porous Nanosheets as Anode Materials for Lithium Ion Batteries with a Better Cycle Durability.

    PubMed

    Wang, Linlin; Tang, Kaibin; Zhang, Min; Xu, Jingli

    2015-12-01

    Porous Zn1 - x Mn x O (x = 0.1, 0.2, 0.44) nanosheets were prepared by a low-cost, large-scale production and simple approach, and the applications of these nanosheets as an anode material for Li-ion batteries (LIBs) were explored. Electrochemical measurements showed that the porous Zn0.8Mn0.2O nanosheets still delivered a stable reversible capacity of 210 mA h g(-1) at a current rate of 120 mA g(-1) up to 300 cycles. These results suggest that the facile synthetic method of producing porous Zn0.8Mn0.2O nanostructure can realize a better cycle durability with stable reversible capacity. PMID:26138451

  20. Sound-absorbing slabs and structures based on granular materials (bound and unbound). [energy absorbing efficiency of porous material

    NASA Technical Reports Server (NTRS)

    Petre-Lazar, S.; Popeea, G.

    1974-01-01

    Sound absorbing slabs and structures made up of bound or unbound granular materials are considered and how to manufacture these elements at the building site. The raw material is a single grain powder (sand, expanded blast furnace slag, etc.) that imparts to the end products an apparent porosity of 25-45% and an energy dissipation within the structure leading to absorption coefficients that can be compared with those of mineral wool and urethane.

  1. Porous nitrogen-doped carbon derived from silk fibroin protein encapsulating sulfur as a superior cathode material for high-performance lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Jiawei; Cai, Yurong; Zhong, Qiwei; Lai, Dongzhi; Yao, Juming

    2015-10-01

    The features of a carbon substrate are crucial for the electrochemical performance of lithium-sulfur (Li-S) batteries. Nitrogen doping of carbon materials is assumed to play an important role in sulfur immobilisation. In this study, natural silk fibroin protein is used as a precursor of nitrogen-rich carbon to fabricate a novel, porous, nitrogen-doped carbon material through facile carbonisation and activation. Porous carbon, with a reversible capacity of 815 mA h g-1 at 0.2 C after 60 cycles, serves as the cathode material in Li-S batteries. Porous carbon retains a reversible capacity of 567 mA h g-1, which corresponds to a capacity retention of 98% at 1 C after 200 cycles. The promising electrochemical performance of porous carbon is attributed to its mesoporous structure, high specific surface area and nitrogen doping into the carbon skeleton. This study provides a general strategy to synthesise nitrogen-doped carbons with a high specific surface area, which is crucial to improve the energy density and electrochemical performance of Li-S batteries.

  2. Porous nitrogen-doped carbon derived from silk fibroin protein encapsulating sulfur as a superior cathode material for high-performance lithium-sulfur batteries.

    PubMed

    Zhang, Jiawei; Cai, Yurong; Zhong, Qiwei; Lai, Dongzhi; Yao, Juming

    2015-11-14

    The features of a carbon substrate are crucial for the electrochemical performance of lithium-sulfur (Li-S) batteries. Nitrogen doping of carbon materials is assumed to play an important role in sulfur immobilisation. In this study, natural silk fibroin protein is used as a precursor of nitrogen-rich carbon to fabricate a novel, porous, nitrogen-doped carbon material through facile carbonisation and activation. Porous carbon, with a reversible capacity of 815 mA h g(-1) at 0.2 C after 60 cycles, serves as the cathode material in Li-S batteries. Porous carbon retains a reversible capacity of 567 mA h g(-1), which corresponds to a capacity retention of 98% at 1 C after 200 cycles. The promising electrochemical performance of porous carbon is attributed to its mesoporous structure, high specific surface area and nitrogen doping into the carbon skeleton. This study provides a general strategy to synthesise nitrogen-doped carbons with a high specific surface area, which is crucial to improve the energy density and electrochemical performance of Li-S batteries. PMID:26456870

  3. Characterization of porous glass-ceramic material as absorber of electromagnetic radiation

    NASA Astrophysics Data System (ADS)

    Kazmina, O.; Suslyaev, V.; Dushkina, M.; Semukhin, B.

    2015-04-01

    Investigations of a foam glass-ceramic material synthesized from raw siliceous earth material by the two-stage method at temperatures below 950°C have demonstrated the improvement of its physic mechanical properties in comparison with foam glass synthesized from glass cullet. This material actively interacts with microwaves and can be used for the development of protective screens reducing the adverse effect of microwaves on biological objects, anechoic chambers, and rooms with low level of electromagnetic background noise. Spectra of the transmission and absorption coefficients and of the complex dielectric permittivity for frequencies in the range 26-260 GHz are presented. The observed effects demonstrate the existence of regions with partial and total reflection arising on the glass-pore boundary and of the microwave interaction with ultradisperse carbon particles that remain after foaming with incomplete frothier transition from the soot to the gas phase.

  4. Porous wall hollow glass microspheres as a medium or substrate for storage and formation of novel materials

    DOEpatents

    Wicks, George G; Serkiz, Steven M.; Zidan, Ragaiy; Heung, Leung K.

    2014-06-24

    Porous wall hollow glass microspheres are provided as a template for formation of nanostructures such as carbon nanotubes, In addition, the carbon nanotubes in combination with the porous wall hollow glass microsphere provides an additional reaction template with respect to carbon nanotubes.

  5. Study on the deflagration-to-detonation transition course of porous energetic material

    NASA Astrophysics Data System (ADS)

    Wei, Lan; Hao, Pengcheng; Dong, Hefei; Hu, Xiaomian; Zhu, Jianshi

    2012-02-01

    The deflagration-to-detonation transition (DDT) course of energetic material with different porosity ratio was studied utilizing a one-dimensional two-phase flow code. The equations were numerically solved by space-time conservation element and solution element (CE/SE) method. The distribution of physical quantities such as pressure and temperature were obtained together with their evolution history. The physical rules before detonation were mainly analyzed and the effect of convection on the chemical reaction of energetic material was emphasized on.

  6. Deformation and Fracture of Porous Brittle Materials Under Different Loading Schemes

    NASA Astrophysics Data System (ADS)

    Savchenko, N. L.; Sablina, T. Yu.; Sevostyanova, I. N.; Buyakova, S. P.; Kulkov, S. N.

    2016-03-01

    The behavior of alumina and zirconia compression- and shear-test specimens with porosity ranging from 10 to 70% is investigated. Analysis of the stress-strain curves for the materials under study has revealed a transition from a characteristically brittle fracture of fairly dense Al2O3 and ZrO2 specimens to pseudo-plastic fracture for a high porosity level. The ultimate compression strength, effective elastic and shear moduli, and Poisson's ratio are found to decrease with increase in the pore space volume of the ceramic specimens, which is shown to correlate with development of strain-induced multiple cracking of the materials.

  7. 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.

  8. 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

  9. 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

  10. Effects of Temperature, Oxygen Partial Pressure, and Materials Selection on Slag Infiltration into Porous Refractories for Entrained-Flow Gasifiers

    NASA Astrophysics Data System (ADS)

    Kaneko, Tetsuya Kenneth

    The penetration rate of molten mineral contents (slag) from spent carbonaceous feedstock into porous ceramic-oxide refractory linings is a critical parameter in determining the lifecycle of integrated gasification combined cycle energy production plants. Refractory linings that withstand longer operation without interruption are desirable because they can mitigate consumable and maintenance costs. Although refractory degradation has been extensively studied for many other high-temperature industrial processes, this work focuses on the mechanisms that are unique to entrained-flow gasification systems. The use of unique feedstock mixtures, temperatures from 1450 °C to 1600 °C, and oxygen partial pressures from 10-7 atm to 10-9 atm pose engineering challenges in designing an optimal refractory material. Experimentation, characterization, and modeling show that gasifier slag infiltration into porous refractory is determined by interactions between the slag and the refractory that either form a physical barrier that impedes fluid flow or induce an increased fluid viscosity that decelerates the velocity of the fluid body. The viscosity of the slag is modified by the thermal profile of the refractory along the penetration direction as well as reactions between the slag and refractory that alter the chemistry, and thereby the thermo-physical properties of the fluid. Infiltration experiments reveal that the temperature gradient inherently present along the refractory lining limits penetration. A refractory in near-isothermal conditions demonstrates deeper slag penetration as compared to one that experiences a steeper thermal profile. The decrease in the local temperatures of the slag as it travels deeper into the refractory increases the viscosity of the fluid, which in turn slows the infiltration velocity of fluid body into the pores of the refractory microstructure. With feedstock mixtures that exhibit high iron-oxide concentrations, a transition-metal-oxide, the oxygen

  11. Reversible and Selective O2 Chemisorption in a Porous Metal-Organic Host Material

    SciTech Connect

    Southon, Peter D; Price, David J; Nielsen, Pia K; McKenzie, Christine J; Kepert, Cameron J

    2011-11-17

    The metal-organic host material [{CoIII2(bpbp)(O2)}2bdc](PF6)4 (1 ∙ 2O2; bpbp- = 2,6-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-4-tert-butylphenolato; bdc2- = 1,4-benzenedicarboxylato) displays reversible chemisorptive desorption and resorption of dioxygen through conversion to the deoxygenated Co(II) form [{CoII2(bpbp)}2bdc](PF6)4 (1). Single crystal X-ray diffraction analysis indicates that the host lattice 1 ∙ 2O2, achieved through desorption of included water guests from the as-synthesized phase 1 ∙ 2O2 ∙ 3H2O, consists of an ionic lattice containing discrete tetranuclear complexes, between which lie void regions that allow the migration of dioxygen and other guests. Powder X-ray diffraction analyses indicate that the host material retains crystallinity through the dioxygen desorption/chemisorption processes. Dioxygen chemisorption measurements on 1 show near-stoichiometric uptake of dioxygen at 5 mbar and 25 °C, and this capacity is largely retained at temperatures above 100 °C. Gas adsorption isotherms of major atmospheric gases on both 1 and 1 ∙ 2O2 indicate the potential suitability of this material for air separation, with a O2/N2 selectivity factor of 38 at 1 atm. Comparison of oxygen binding in solution and in the solid state indicates a dramatic increase in binding affinity to the complex when it is incorporated in a porous solid.

  12. Effective conductivity and permittivity of unsaturated porous materials in the frequency range 1 mHz–1GHz

    PubMed Central

    Revil, A

    2013-01-01

    A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823

  13. Interaction of finite-amplitude sound with air-filled porous materials

    NASA Technical Reports Server (NTRS)

    Nelson, D. A.

    1985-01-01

    The propagation of high intensity sound waves through an air-filled porus material was studied. The material is assumed: (1) to be rigid, incompressible, and homogeneous, and (2) to be adequately described by two properties: resistivity r and porosity. The resulting wave equation is still nonlinear, however, because of the u sgn(u) term in the resistivity. The equation is solved in the frequency domain as an infinite set of coupled inhomogeneous Helmholtz equations, one for each harmonic. An approximate but analytical solution leads to predictions of excess attenuation, saturation, and phase speed reduction for the fundamental component. A more general numerical solution is used to calculate the propagation curves for the higher harmonics. The u sgn(u) nonlinearity produces a cubic distortion pattern; when the input signal is a pure tone, only odd harmonic distortion products are generated.

  14. Random pseudo promptings applied to the thermal characterization of a wet porous material

    NASA Astrophysics Data System (ADS)

    Delacre, E.; Defer, D.; Antczak, E.; Duthoit, B.

    1999-04-01

    The generalized impedances allow to characterize a one-way thermal system whose two faces are accessible. From experimental measurements of the flux densities and variations in temperature in the access faces of a homogeneous material, the two generalized impedances of storage and transfer are calculated in the frequential field. The theory of the thermal quadripole enables to determine a theoretical expression of these impedances. After a sensitivity study which underlines the accessible parameters and the optimal frequency band, an optimization procedure of the setting of the ideal model of one of the two impedances on the corresponding experimental curve allows to identify the effusivity and the thermal diffusivity of material. The method is applied to the study of a sand with three water contents.

  15. Mechanical behavior of concrete and related porous materials under partial saturation: The effective stress and the viscous softening due to movement of nanometer-scale pore fluid

    NASA Astrophysics Data System (ADS)

    Vlahinic, Ivan

    It has been said that porous materials are like music: the gaps are as important as the filled-in bits. In other words, in addition to the solid structure, pore characteristics such as size and morphology play a crucial role in defining the overall physical properties of the porous materials. This work goes a step further and examines the behaviors of some porous media that arise when the pore network is occupied by two fluids, principally air and water, as a result of drying or wetting. Such a state gives rise to fluid capillarity which can generate significant negative fluid pressures. In the first part, a constitutive model for drying of an elastic porous medium is proposed and then extended to derive a novel expression for effective stress in partially saturated media. The model is motivated by the fact that in a system that is saturated by two different fluids, two different pressure inherently act on the surfaces of the pore network. This causes a non-uniform strain field in the solid structure, something that is not explicitly accounted for in the classic formulations of this problem. We use some standard micromechanical homogenization techniques to estimate the extent of the 'non-uniformity' and on this basis, evaluate the validity of the classic Bishop effective stress expression for partially saturated materials. In the second part, we examine a diverse class of porous materials which behave in an unexpected (and even counterintuitive) way under the internal moisture fluctuations. In particular, during wetting and drying alike, the solid viscosity of these materials appears to soften, sometimes by an order of magnitude or more. Under load, this can lead to significantly increased rates of deformations. On account of the recent experimental and theoretical findings on the nature of water flow in nanometer-size hydrophillic spaces, we provide a physical explanation for the viscous softening and propose a constitutive law on this basis. To this end, it also

  16. 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

  17. Wettability measurement apparatus for porous material using the modified Washburn method

    NASA Astrophysics Data System (ADS)

    Thakker, Manish; Karde, Vikram; Shah, Dinesh O.; Shukla, Premal; Ghoroi, Chinmay

    2013-12-01

    In this work a cost-effective instrument for measuring the wettability of powder materials was designed and developed, which works on the modified Washburn method. The instrument measures the mass gain against time due to penetration of the liquid into the powder materials using a microbalance and LabVIEW-based data acquisition system. The wettability characteristic of different powders was determined from the contact angle using the modified Washburn equation. To demonstrate the performance of the developed instrument, the wettability of as-received corn starch and nano-coated corn starch powders was estimated with water as a test liquid. The corn starch powders coated with hydrophilic grade (Aerosil 200P) and hydrophobic grade (Aerosil R972) nanoparticles at different coating levels showed expected changes in their contact angle. Some of the results were also verified against the available standard instrument for wettability measurement and found to be consistent. The present configuration of the instrument costs about 500 US which is 15 to 20 times less than the available advanced models. The developed instrument is thus a cost-effective solution for wettability measurement which can be used for materials in food processing, pharmaceuticals, horticulture, textile manufacturing, civil engineering etc. The developed instrument is expected to help many small scale industries or research labs who cannot afford an expensive instrument for wettability studies.

  18. A closed-form criterion for dislocation emission in nano-porous materials under arbitrary thermomechanical loading

    NASA Astrophysics Data System (ADS)

    Wilkerson, J. W.; Ramesh, K. T.

    2016-01-01

    Our traditional view of void nucleation is associated with interface debonding at second-phase particles. However, under extreme dynamic loading conditions second-phase particles may not necessarily be the dominant source of void nucleation sites. A few key experimental observations of laser spall surfaces support this assertion. Here, we describe an alternative mechanism to the traditional view, namely shock-induced vacancy generation and clustering followed by nanovoid growth mediated by dislocation emission. This mechanism only becomes active at very large stresses. It is therefore desirable to establish a closed-form criterion for the macroscopic stress required to activate dislocation emission in porous materials. Following an approach similar to Lubarda and co-workers, we derive the desired criterion by making use of stability arguments applied to the analytic solutions for the elastic interactions of dislocations and voids. Our analysis significantly extends that of Lubarda and co-workers by accounting for a more general stress state, finite porosity, surface tension, as well as temperature and pressure dependence. The resulting simple stress-based criterion is validated against a number of molecular dynamics simulations with favorable agreement.

  19. Facile synthesis of porous Li2S@C composites as cathode materials for lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Liang, Sheng; Liang, Chu; Xia, Yang; Xu, Haohui; Huang, Hui; Tao, Xinyong; Gan, Yongping; Zhang, Wenkui

    2016-02-01

    Lithium sulfide (Li2S) is regarded as a promising cathode material for lithium-sulfur (Li-S) batteries in terms of its high theoretical specific capacity of 1166 mAh g-1 and good compatibility with lithium metal-free anodes. However, Li2S suffers from poor cycling stability and rate capability resulted from the serious shuttle effect of lithium polysulfides and its low electronic and ionic conductivity. Here, we present a facile ball milling combined with carbon coating method to synthesize porous carbon-coated Li2S (Li2S@C) composites with a high Li2S content by using polystyrene (PS) as a carbon precursor. The Li2S@C composites show a high reversible specific capacity of 676 mAh g-1 (equal to 971 mAh g-1 sulfur) after 3 cycles at the current density of 0.1 A g-1, superior cycling stability with an average decay rate of 0.18% per cycle over 200 cycles, and improved rate capability of 416 mAh g-1 at the current density of 1.0 A g-1. The enhanced electrochemical properties of Li2S can be attributed to the porosity and core-shell structure of the Li2S@C composites, which increased the electronic and ionic conductivity of Li2S and alleviated the shuttle effect of intermediate lithium polysulfides in the discharge/charge process.

  20. Polymer Crosslinked 3-D Assemblies of Nanoparticles: Mechanically Strong Lightweight Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2005-01-01

    In analogy to supramolecular assemblies, which are pursued because of properties above and beyond those of the individual molecules, self-standing monolithic three-dimensional assemblies of nanoparticles also have unique properties attributed to their structure. For example, ultra low-density 3-D assemblies of silica nanoparticles, known as silica aerogels, are characterized by large internal void space, high surface area and very low thermal conductivity. Aerogels, however, are also extremely fragile materials, limiting their application to a few specialized environments, e.g., in nuclear reactors as Cerenkov radiation detectors, in space (refer to NASA's Stardust Program) and aboard certain planetary vehicles (thermal insulators on Mars Rovers in 1997 and 2004). The fragility problem is traced to well-defined weak points in the aerogel skeletal framework, the interparticle necks. Using the surface functionality of the nanoparticle building blocks as a focal point, we have directed attachment of a conformal polymer coating over the entire framework, rendering all necks wider. Thus, although the bulk density may increase only by 3x, the mesoporosity (pores in the range 2-50 nm) remains unchanged, while the strength of the material increases by up to 300... Having addressed the fragility problem, aerogels are now robust materials, and a variety of applications, ranging from thermal/acoustic insulators to catalyst supports, to platform for sensors, and dielectrics are all within reach. Our approach employs molecular science to manipulate nanoscopic matter for achieving useful macroscopic properties, and in our view it resides at the core of what defines nanotechnology. In that spirit, this technology is expandable in three directions. Thus, we have already crosslinked successfully amine-modified silica, and we anticipate that more rich chemistry will be realized by been creative with the nanoparticle surface modifiers. On the other hand, although we do not expect

  1. Development Of A New Redox-Active Porous Material For Groundwater Remediation

    NASA Astrophysics Data System (ADS)

    Zhuang, Y.; White, M.; Fialips, C. I.

    2008-12-01

    Laboratory experiments have shown that reducing iron in smectites promotes the degradation of various redox sensitive organics, including nitroaromatics and chlorinated compounds. Fe-bearing smectites have however never been used in the design of permeable reactive barriers (PRBs) for groundwater remediation. One basic requirement when designing PRBs is to keep their permeability equal to or higher than that of the surrounding aquifer materials to avoid affecting groundwater flow. Smectite clays are very low permeability materials and, when physically mixed with permeable materials, such as sand, clay particles can migrate and clog up pores, resulting in a progressive loss in permeability. In this study, we are developing a novel Fe-bearing clay-material suitable for permeable water treatment systems, including PRBs. Fe-smectite particles are tightly attached to the surface of sand grains using polyvinyl alcohol (PVA). To identify optimum procedures, we are studying the relationships between the size and texture of the sand grains, the clay/PVA and clay/sand ratio, the quality and extent of clay coverage, the stability of the clay-coated sand to changes in pH and redox conditions, and its hydraulic properties before and after iron reduction. The best clay coatings have been obtained using the most angular sands with rough surfaces and medium grain sizes (0.3-0.6mm). An optimum coating of 61.5 mg clay/g sand was obtained using the nontronite Nau- 2. The clay-coated sand is stable when pH is below 7 (no detachment of the clay particles). For pH higher than 7, a maximum of 14% of the clay-coating is detaching when the sample is not disturbed, and 28% if shaken. XRD analyses of the clay-coated sand also show that the coated smectite retains its swelling properties (d-spacing at 17.1Å after ethylene glycol treatment). The clay-coated sand is also stable to changes in redox conditions, with less than 15% detachment after 4h of treatment with sodium dithionite at 25

  2. Improved porous mixture of molybdenum nitride and tantalum oxide as a charge storage material

    SciTech Connect

    Deng, C.Z.; Pynenburg, R.A.J.; Tsai, K.C.

    1998-04-01

    High surface area {gamma}-molybdenum nitride has shown promise as a charge storage material. The addition of amorphous tantalum oxide to the molybdenum nitride system not only improves the film cohesion tremendously, but also widens the voltage stability window from 0.8 to 1.1 V. This occurs without adversely effecting the capacitance. Ultracapacitors, also called supercapacitors or electrochemical capacitors, are high power storage devices which have found application in products as diverse as cardiac pacemakers, cellular phones, electric vehicles, and air bags.

  3. The influence of Lifshitz forces and gas on premelting of ice within porous materials

    NASA Astrophysics Data System (ADS)

    Boström, M.; Malyi, O. I.; Thiyam, P.; Berland, K.; Brevik, I.; Persson, C.; Parsons, D. F.

    2016-07-01

    Premelting of ice within pores in earth materials is shown to depend on the presence of vapor layers. For thick vapor layers between ice and pore surfaces, a nanosized water sheet can be formed due to repulsive Lifshitz forces. In the absence of vapor layers, ice is inhibited from melting near pore surfaces. In between these limits, we find an enhancement of the water film thickness in silica and alumina pores. In the presence of metallic surface patches in the pore, the Lifshitz forces can dramatically widen the water film thickness, with potential complete melting of the ice surface.

  4. 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

  5. A three-dimensional porous MoP@C hybrid as a high-capacity, long-cycle life anode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Xia; Sun, Pingping; Qin, Jinwen; Wang, Jianqiang; Xiao, Ying; Cao, Minhua

    2016-05-01

    Metal phosphides are great promising anode materials for lithium-ion batteries with a high gravimetric capacity. However, significant challenges such as low capacity, fast capacity fading and poor cycle stability must be addressed for their practical applications. Herein, we demonstrate a versatile strategy for the synthesis of a novel three-dimensional porous molybdenum phosphide@carbon hybrid (3D porous MoP@C hybrid) by a template sol-gel method followed by an annealing treatment. The resultant hybrid exhibits a 3D interconnected ordered porous structure with a relatively high surface area. Benefiting from its advantages of microstructure and composition, the 3D porous MoP@C hybrid displays excellent lithium storage performance as an anode material for lithium-ion batteries in terms of specific capacity, cycling stability and long-cycle life. It presents stable cycling performance with a high reversible capacity up to 1028 mA h g-1 at a current density of 100 mA g-1 after 100 cycles. By ex situ XRD, HRTEM, SAED and XPS analyses, the 3D porous MoP@C hybrid was found to follow the Li-intercalation reaction mechanism (MoP + xLi+ + e- <--> LixMoP), which was further confirmed by ab initio calculations based on density functional theory.Metal phosphides are great promising anode materials for lithium-ion batteries with a high gravimetric capacity. However, significant challenges such as low capacity, fast capacity fading and poor cycle stability must be addressed for their practical applications. Herein, we demonstrate a versatile strategy for the synthesis of a novel three-dimensional porous molybdenum phosphide@carbon hybrid (3D porous MoP@C hybrid) by a template sol-gel method followed by an annealing treatment. The resultant hybrid exhibits a 3D interconnected ordered porous structure with a relatively high surface area. Benefiting from its advantages of microstructure and composition, the 3D porous MoP@C hybrid displays excellent lithium storage performance as an

  6. Rapid synthesis of monodispersed highly porous spinel nickel cobaltite (NiCo{sub 2}O{sub 4}) electrode material for supercapacitors

    SciTech Connect

    Naveen, A. Nirmalesh Selladurai, S.

    2015-06-24

    Monodispersed highly porous spinel nickel cobaltite electrode material was successfully synthesized in a short time using combustion technique. Single phase cubic nature of the spinel nickel cobaltite with average crystallite size of 24 nm was determined from X-ray diffraction study. Functional groups present in the compound were determined from FTIR study and it further confirms the spinel formation. FESEM images reveal the porous nature of the prepared material and uniform size distribution of the particles. Electrochemical evaluation was performed using Cyclic Voltammetry (CV) technique, Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS). Results reveal the typical pseudocapacitive behaviour of the material. Maximum capacitance of 754 F/g was calculated at the scan rate of 5 mV/s, high capacitance was due to the unique porous morphology of the electrode. Nyquist plot depicts the low resistance and good electrical conductivity of nickel cobaltite. It has been found that nickel cobaltite prepared by this typical method will be a potential electrode material for supercapcitor application.

  7. Numerical limit analysis and plasticity criterion of a porous Coulomb material with elliptic cylindrical voids

    NASA Astrophysics Data System (ADS)

    Pastor, Franck; Pastor, Joseph; Kondo, Djimedo

    2015-03-01

    The paper is devoted to a numerical Limit Analysis of a hollow cylindrical model with a Coulomb solid matrix (of confocal boundaries) considered in the case of a generalized plane strain. To this end, the static approach of Pastor et al. (2008) [18] for Drucker-Prager materials is first extended to Coulomb problems. A new mixed-but rigorously kinematic-code is elaborated for Coulomb problems in the present case of symmetry, resulting also in a conic programming approach. Owing to the good conditioning of the resulting optimization problems, both methods give very close bounds by allowing highly refined meshes, as verified by comparing to existing exact solutions. In a second part, using the identity of Tresca (as special case of Coulomb) and von Mises materials in plane strain, the codes are used to assess the corresponding results of Mariani and Corigliano (2001) [13] and of Madou and Leblond (2012) [11] for circular and elliptic cylindrical voids in a von Mises matrix. Finally, the Coulomb problem is investigated, also in terms of projections on the coordinate planes of the principal macroscopic stresses.

  8. Ti-doped nano-porous graphene: A material for hydrogen storage and sensor

    NASA Astrophysics Data System (ADS)

    Li, Sa; Zhao, Hong-min; Jena, Puru

    2011-06-01

    Clustering of Ti on carbon nanostructures has proved to be an obstacle in their use as hydrogen storagematerials. Using density functional theory we show that Ti atoms will not cluster at moderate concentrations when doped into nanoporous graphene. Since each Ti atom can bind up to three hydrogen molecules with an average binding energy of 0.54 eV/H2, this material can be ideal for storing hydrogen under ambient thermodynamic conditions. In addition, nanoporous graphene is magnetic with or without Ti doping, but when it is fully saturated with hydrogen, the magnetism disappears. This novel feature suggests that nanoporous graphene cannot only be used for storing hydrogen, but also as a hydrogen sensor.

  9. Porous silver nanosheets: a novel sensing material for nanoscale and microscale airflow sensors

    NASA Astrophysics Data System (ADS)

    Marzbanrad, Ehsan; Zhao, Boxin; Zhou, Norman Y.

    2015-11-01

    Fabrication of nanoscale and microscale machines and devices is one of the goals of nanotechnology. For this purpose, different materials, methods, and devices should be developed. Among them, various types of miniaturized sensors are required to build the nanoscale and microscale systems. In this research, we introduce a new nanoscale sensing material, silver nanosheets, for applications such as nanoscale and microscale gas flow sensors. The silver nanosheets were synthesized through the reduction of silver ions by ascorbic acid in the presence of poly(methacrylic acid) as a capping agent, followed by the growth of silver in the shape of hexagonal and triangular nanoplates, and self-assembly and nanojoining of these structural blocks. At the end of this process, the synthesized nanosheets were floated on the solution. Then, their electrical and thermal stability was demonstrated at 120 °C, and their atmospheric corrosion resistance was clarified at the same temperature range by thermogravimetric analysis. We employed the silver nanosheets in fabricating airflow sensors by scooping out the nanosheets by means of a sensor substrate, drying them at room temperature, and then annealing them at 300 °C for one hour. The fabricated sensors were tested for their ability to measure airflow in the range of 1 to 5 ml min-1, which resulted in a linear response to the airflow with a response and recovery time around 2 s. Moreover, continuous dynamic testing demonstrated that the response of the sensors was stable and hence the sensors can be used for a long time without detectable drift in their response.

  10. Porous silver nanosheets: a novel sensing material for nanoscale and microscale airflow sensors.

    PubMed

    Marzbanrad, Ehsan; Zhao, Boxin; Zhou, Norman Y

    2015-11-01

    Fabrication of nanoscale and microscale machines and devices is one of the goals of nanotechnology. For this purpose, different materials, methods, and devices should be developed. Among them, various types of miniaturized sensors are required to build the nanoscale and microscale systems. In this research, we introduce a new nanoscale sensing material, silver nanosheets, for applications such as nanoscale and microscale gas flow sensors. The silver nanosheets were synthesized through the reduction of silver ions by ascorbic acid in the presence of poly(methacrylic acid) as a capping agent, followed by the growth of silver in the shape of hexagonal and triangular nanoplates, and self-assembly and nanojoining of these structural blocks. At the end of this process, the synthesized nanosheets were floated on the solution. Then, their electrical and thermal stability was demonstrated at 120 °C, and their atmospheric corrosion resistance was clarified at the same temperature range by thermogravimetric analysis. We employed the silver nanosheets in fabricating airflow sensors by scooping out the nanosheets by means of a sensor substrate, drying them at room temperature, and then annealing them at 300 °C for one hour. The fabricated sensors were tested for their ability to measure airflow in the range of 1 to 5 ml min(-1), which resulted in a linear response to the airflow with a response and recovery time around 2 s. Moreover, continuous dynamic testing demonstrated that the response of the sensors was stable and hence the sensors can be used for a long time without detectable drift in their response. PMID:26451714

  11. Metal-organic framework derived Fe2O3@NiCo2O4 porous nanocages as anode materials for Li-ion batteries.

    PubMed

    Huang, Gang; Zhang, Leilei; Zhang, Feifei; Wang, Limin

    2014-05-21

    Metal-organic frameworks (MOFs) with high surface areas and uniform microporous structures have shown potential application in many fields. Here we report a facial strategy to synthesize Fe2O3@NiCo2O4 porous nanocages by annealing core-shell Co3[Fe(CN)6]2@Ni3[Co(CN)6]2 nanocubes in air. The obtained samples have been systematically characterized by XRD, SEM, TEM and N2 adsorption-desorption analysis. The results show that the Fe2O3@NiCo2O4 porous nanocages have an average diameter of 213 nm and a shell thickness of about 30 nm. As anode materials for Li-ion batteries, the Fe2O3@NiCo2O4 porous nanocages exhibit a high initial discharge capacity of 1311.4 mA h g(-1) at a current density of 100 mA g(-1) (about 0.1 C). The capacity is retained at 1079.6 mA h g(-1) after 100 cycles. The synergistic effect of the different components and the porous hollow structure contributes to the outstanding performance of the composite electrode. PMID:24730026

  12. A 3D Porous Architecture of Si/graphene Nanocomposite as High-performance Anode Materials for Li-ion Batteries

    SciTech Connect

    Xin X.; Zhu Y.; Zhou, X.; Wang, F.; Yao, X.; Xu, X.; Liu, Z.

    2012-04-28

    A 3D porous architecture of Si/graphene nanocomposite has been rationally designed and constructed through a series of controlled chemical processes. In contrast to random mixture of Si nanoparticles and graphene nanosheets, the porous nanoarchitectured composite has superior electrochemical stability because the Si nanoparticles are firmly riveted on the graphene nanosheets through a thin SiO{sub x} layer. The 3D graphene network enhances electrical conductivity, and improves rate performance, demonstrating a superior rate capability over the 2D nanostructure. This 3D porous architecture can deliver a reversible capacity of {approx}900 mA h g{sup -1} with very little fading when the charge rates change from 100 mA g{sup -1} to 1 A g{sup -1}. Furthermore, the 3D nanoarchitechture of Si/graphene can be cycled at extremely high Li{sup +} extraction rates, such as 5 A g{sup -1} and 10 A g{sup -1}, for over than 100 times. Both the highly conductive graphene network and porous architecture are considered to contribute to the remarkable rate capability and cycling stability, thereby pointing to a new synthesis route to improving the electrochemical performances of the Si-based anode materials for advanced Li-ion batteries.

  13. Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

    DOEpatents

    Panitz, Janda K.; Reed, Scott T.; Ashley, Carol S.; Neiser, Richard A.; Moffatt, William C.

    1999-01-01

    Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties.

  14. Metal-organic framework derived porous CuO/Cu2O composite hollow octahedrons as high performance anode materials for sodium ion batteries.

    PubMed

    Zhang, Xiaojie; Qin, Wei; Li, Dongsheng; Yan, Dong; Hu, Bingwen; Sun, Zhuo; Pan, Likun

    2015-11-25

    Porous CuO/Cu2O composite hollow octahedrons were synthesized simply by annealing Cu-based metal-organic framework templates. When evaluated as anode materials for sodium ion batteries, they exhibit a high maximum reversible capacity of 415 mA h g(-1) after 50 cycles at 50 mA g(-1) with excellent cycling stability and good rate capability. PMID:26412211

  15. Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

    DOEpatents

    Panitz, J.K.; Reed, S.T.; Ashley, C.S.; Neiser, R.A.; Moffatt, W.C.

    1999-07-20

    Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties. 6 figs.

  16. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution.

    PubMed

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E; Kung, Chung-Wei; So, Monica; Sampson, Matthew D; Peters, Aaron W; Kubiak, Cliff P; Farha, Omar K; Hupp, Joseph T

    2015-01-01

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm(-2). Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst. PMID:26365764

  17. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    SciTech Connect

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; Hupp, Joseph T.

    2015-09-14

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. In conclusion, although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.

  18. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    DOE PAGESBeta

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; et al

    2015-09-14

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. In conclusion, althoughmore » the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.« less

  19. Effect of Temperature Gradient on Industrial Coal Slag Infiltration into Porous Refractory Materials in Slagging Gasifiers

    SciTech Connect

    Kaneko, Tetsuya Kenneth; Bennett, James P.; Dridhar, Seetharaman

    2011-12-01

    Infiltration characteristics of industrial coal slag into alumina (Al{sub 2}O{sub 3}) refractory material with a temperature gradient induced along the slag's penetration direction are compared to those obtained under near-isothermal conditions. Experiments were conducted with a hot-face temperature of 1450°C and a CO/CO{sub 2} ratio of 1.8, which corresponds to an oxygen partial pressure of ~10{sup −8} atm. The refractory under the near-isothermal temperature profile, with higher average temperatures, demonstrated a greater penetration depth than its counterpart that was under the steeper temperature gradient. Slag that did not infiltrate into the refractory due to the induced temperature gradient, pooled and solidified on the top of the sample. Within the pool, a conglomerated mass of troilite (FeS) formed separately from the surrounding slag. Microscopy of the cross-sectioned infiltrated refractories revealed that the slag preferentially corroded the matrix regions closer to the top surface. Furthermore, the formation of a thick layer of hercynite (FeAl{sub 2}O{sub 4}) at the top of refractory/slag interface significantly depleted the slag of its iron-oxide content with respect to its virgin composition. A qualitative description of the penetration process is provided in this article.

  20. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; Hupp, Joseph T.

    2015-09-01

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm-2. Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.

  1. Compaction of functionalized calcium carbonate, a porous and crystalline microparticulate material with a lamellar surface.

    PubMed

    Stirnimann, Tanja; Atria, Susanna; Schoelkopf, Joachim; Gane, Patrick A C; Alles, Rainer; Huwyler, Jörg; Puchkov, Maxim

    2014-05-15

    In the present study, we aimed to characterize the compressibility and compactibility of the novel pharmaceutical excipient, functionalized calcium carbonate (FCC). We studied three FCC modifications and compared the values for compressibility and compactibility with mannitol, microcrystalline cellulose (MCC), and ground calcium carbonate (CC 330) as well as mixtures of paracetamol and MCC or FCC at drug loads of 0%, 25%, 50%, 75%, and 100% (w/w). We used Heckel analysis, modified Heckel analysis, and Leuenberger analysis to characterize the compaction and compression behavior of the mixtures. Compaction analysis of FCC showed this material to markedly differ from ground calcium carbonate, exhibiting properties, i.e. plastic deformability, similar to those of MCC. This effect was attributed to the highly lamellar structure of FCC particles whose thickness is of the order of a single crystal unit cell. According to Leuenberger parameters, we concluded that FCC-based tablet formulations had mechanical properties equal or superior to those formulated with MCC. FCC tablets with high tensile strength were obtained already at low compressive pressures. Owing to these favorable properties (i.e. marked tensile strength and porosity), FCC promises to be suitable for the preparation of solid dosage forms. PMID:24631309

  2. A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

    PubMed Central

    Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; Hupp, Joseph T.

    2015-01-01

    The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst. PMID:26365764

  3. Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Fabrizio, Eve F.; Ilhan, Faysal; Dass, Amala; Zhang, Guo-Hui; Vassilaras, Plousia; Johnston, J. Chris; Leventis, Nicholas

    2005-01-01

    The mesoporous surfaces of TMOS-derived silica aerogels have been modified with amines by co-polymerization of TMOS with APTES. The amine sites have become anchors for crosslinking the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than two orders of magnitude. Processing variables such as amount of APTES used to make the gels, the epoxy type and concentration used for crosslinking, as well as the crosslinking temperature and time were varied according to a multivariable design-of-experiments (DOE) model. It was found that while elastic modulus follows a similar trend with density, maximum strength is attained neither at the maximum density nor at the highest concentration of -NH2 groups, suggesting surface saturation effects. Aerogels crosslinked with the tri-functional epoxide always show improved strength compared with aerogels crosslinked with the other two epoxides under identical conditions. Solid C-13 NMR studies show residual unreacted epoxides, which condense with ne another by heating crosslinked aerogels at 150 C.

  4. Fabrication of porous carbon composite material from leaves waste as lightweight expanded carbon aggregate (LECA)

    NASA Astrophysics Data System (ADS)

    Sulhadi, Rosita, N.; Susanto, Nisa', K.; Wiguna, P. A.; Marwoto, P.; Aji, M. P.

    2016-04-01

    Leaves waste has been used as Lightweight Expanded Carbon Aggregates (LECA) because of its high carbon material. LECA can be used as a water storage media. LECA is low in density so thatits massis very light. Due to its use as a water storage medium, it is important to find out the absorption which occurs in LECA.The LECA's absorption and evaporation rate is affected by the pores. The pores serves to increase water storage ability from LECA. LECA with PEG (pore-forming agent) mass percent variation of 5%, 10%, 15%, 20% and 25% is the focus of this study. LECA fabrication was conducted by mixing the carbon resulting from leaves waste pyrolysis and PEG and PVAc. The characterization of LECA was found out by calculating the porosity, the pore size distribution, absorption rate and evaporation rate. The result of the calculation shows that the higher PEG mass percentage, the higher LECA's porosity, the pore size distribution, absorption rate and evaporation rate. However, the porosity, the pore size distributionand absorption rate will be saturated by 25% PEG mass percent addition.

  5. Convenient and controllable preparation of a novel uniformly nitrogen doped porous graphene/Pt nanoflower material and its highly-efficient electrochemical biosensing.

    PubMed

    Ren, Shuang; Wang, Huan; Zhang, Yufan; Sun, Yuena; Li, Lanfen; Zhang, Hongyi; Shi, Zhihong; Li, Mingjie; Li, Meng

    2016-04-25

    By employing dopamine as a nitrogen source and reducing agent, the block copolymer P123 as a pore forming agent, and graphene oxide as a carbon precursor, we present, for the first time, a convenient and controllable approach to the preparation of a novel uniformly nitrogen doped porous graphene (N-PGR) material. Using the prepared N-PGR as the supporting material, a novel nitrogen doped porous graphene/Pt nanoflower material (Pt/N-PGR) was obtained by a green and simple method. The characterization results of scanning electron microscopy (SEM), element mapping, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that Pt nanoflowers are uniformly dispersed on nitrogen doped porous graphene. Electrochemical measurements show that Pt/N-PGR-900/GCE exhibits improved electrocatalytic activity towards H2O2 reduction and glucose oxidation. Linear responses are found for H2O2 and glucose in the range of 0.5-40 326 μM and 0.5-133.5 mM with the detection limit (S/N = 3) of 0.2 μM and 0.05 mM, respectively. In addition, Pt/N-PGR-900/GCE exhibits high sensitivity and good anti-interference ability. The superior catalytic activity and selectivity make Pt/N-PGR a promising nanomaterial for application in electrochemical biosensing studies. PMID:27071465

  6. New bio-cleaning strategies on porous building materials affected by biodeterioration event

    NASA Astrophysics Data System (ADS)

    Valentini, Federica; Diamanti, Alessia; Palleschi, Giuseppe

    2010-09-01

    In this paper, a new bio-cleaning procedure based on the glucose oxidase (GOx) has been applied on the travertine and peperino substrata to remove the biological patina (i.e., biofilm). Glucose oxidase, used as a model enzyme system, is able to produce in situ H 2O 2 (the cleaning agent having oxidizing properties) by the enzymatic reaction at room temperature. The travertine and peperino samples came from the Villa Torlonia in Rome (Italy), and an analytical diagnosis on them was performed applying several analytical techniques, such as the differential interference contrast microscopy (DIC), the optical microscope (OM), the Fourier transform infrared spectroscopy (FT-IR) and the X-ray fluorescence (XRF) that evidence the presence of biofilms on the substrata. Better results were obtained on the travertine samples in terms of the cleaning efficiency and the absence of the etching effect on the surface, eventually induced by the peroxide molecule. These results could be explained in terms of the different porosities of the two kinds of stone materials, according to the BET data. A comparative study was also performed to validate the new bio-cleaning procedure, using both traditional approaches based on saturated (NH 4) 2CO 3 solution and EDTA in buffer solution and the enzyme lipase treatments. Among all, the cleaning procedure via GOx shows the best result, probably because the enzyme controls the concentration of the H 2O 2 in situ and also retains the H 2O 2 preferentially on the surface (where the biological patina is present) depending on the porosity of the substrata. A synergistic effect, with other enzymes such as lipase and protease, combined with the biocompatibility of the enzymatic treatments, could represent a new way for a higher cleaning efficiency to apply on different stone substrata.

  7. Water in Metal-Organic Frameworks: A Computational Study of Adsorption in Porous Materials in the Presence of Ambient Humidity

    NASA Astrophysics Data System (ADS)

    Ghosh, Pritha

    Metal-organic frameworks, or MOFs, are a class of porous crystalline materials renowned for their chemically tunable nature. In this work, molecular-level modeling is used to assess MOFs as potential adsorbents for a variety of applications where ambient humidity is present, such as toxic gas capture, nerve agent decomposition, and sensing via changes in proton conductivity. The concept of hydrophobicity in MOFs is explored from a number of angles. Classical simulation methods and quantum chemistry calculations are used to predict adsorption behavior and to shed light on experimentally observed phenomena. Hydrophobic MOFs are attractive candidates for selective gas capture under ambient conditions, and in this work hydrophobic MOFs are examined for two particular applications: ammonia capture and CO2 capture. In the first study, GCMC simulations are used to evaluate a set of three hydrophobic MOFs for ammonia capture at three humidity conditions: 0% relative humdity (RH), 36% RH, and 80% RH. In the second study, GCMC simulations predict the CO2 loading in a hydrophobic fluorinated MOF at 80% RH, which is the humidity of flue gas. In both of these studies, results demonstrate that hydrophobic MOFs are equally capable of capturing the target adsorbate under humid or dry conditions. In related work, water adsorption behavior is investigated for a fairly hydrophilic Zr MOF, and it is revealed that missing linker defects engender hydrophilicity in this framework. An ideal, defect-free version of this Zr MOF demonstrates hydrophobic behavior. Additionally, perfluoroalkane adsorption is predicted in a related material, a faujasite-type zeolite, and the results suggest the presence of co-adsorbed water molecules. MOFs with coordinated solvent molecules can be used as catalysts and novel chemical sensors. In this work, quantum chemistry calculations are used to study the interaction of a nerve agent simulant with a Zr MOF node. Results indicate that it is favorable for a

  8. Investigation of salt distribution in porous stone material using paper pulp poultices under laboratory condititions and on site

    NASA Astrophysics Data System (ADS)

    Egartner, Isabel; Sass, Oliver

    2016-04-01

    The presented investigation is part of a longer-term project which deals with the influence of salt and moisture on weathering of historic stonework. The main investigation object in the field is a part of the 300 hundred year old boundary wall of the Worchester College in Oxford, UK. A range of non-destructive techniques were applied in course of field campaigns, e.g. mapping of weathering phenomena; handheld moisture sensors; and salt sampling by paper pulp poultices. In a second step we investigated the behaviour and distribution of water and salt solution in a porous material, similar to the limestone of the College wall, under laboratory condititions. Limestone cube samples (5x5x5 cm) were soaked first with ultrapure H2O and second with different concentration of saline solutions of NaCl and Na2SO4. During the dehydration process of the stone cubes a multi-method approach including sampling by drilling, paper pulp poultices, handheld moisture sensor, conductivity sensor and Ion Chromatography (IC) were applied to investigate the moisture and salt content and distribution within the samples. The laboratory analyses were carried out at the department of applied geoscience of the Technical University of Graz, Austria. The main aim was to investigate the effectivity of the paper pulp poultices in soaking up salts from the stone samples and to use the results of the laboratory analysis to interpret and calibrate the field work results from the College wall in Oxford. Keywords: Salt weathering, paper pulp poultices, cultural heritage, field work and laboratory investigation

  9. Comparison of focused ion beam versus nano-scale X-ray computed tomography for resolving 3-D microstructures of porous fuel cell materials

    NASA Astrophysics Data System (ADS)

    Wargo, E. A.; Kotaka, T.; Tabuchi, Y.; Kumbur, E. C.

    2013-11-01

    Focused ion beam-scanning electron microscopy (FIB-SEM) and nano-scale X-ray computed tomography (nano-CT) have emerged as two popular nanotomography techniques for quantifying the 3-D microstructure of porous materials. The objective of this study is to assess the unique features and limitations of FIB-SEM and nano-CT in capturing the 3-D microstructure and structure-related transport properties of porous fuel cell materials. As a test case, a sample of a micro-porous layer used in polymer electrolyte fuel cells is analyzed to obtain 3-D microstructure datasets using these two nanotomography techniques. For quantitative comparison purposes, several key transport properties are determined for these two datasets, including the porosity, pore connectivity, tortuosity, structural diffusivity coefficient, and chord length (i.e., void size) distributions. The results obtained for both datasets are evaluated against each other and experimental data when available. Additionally, these two techniques are compared qualitatively in terms of the acquired images, image segmentation, and general systems operation. The particular advantages and disadvantages of both techniques are highlighted, along with suggestions for best practice.

  10. Tin nanoparticles encapsulated in porous multichannel carbon microtubes: preparation by single-nozzle electrospinning and application as anode material for high-performance Li-based batteries.

    PubMed

    Yu, Yan; Gu, Lin; Zhu, Changbao; van Aken, Peter A; Maier, Joachim

    2009-11-11

    Tin nanoparticles encapsulated in porous multichannel carbon microtubes (denoted as SPMCTs) were prepared by carbonization of electrospun PAN-PMMA-tin octoate nanofibers fabricated using a single-nozzle electrospinning technique. This material exhibited excellent characteristics for lithium ion battery anode applications in terms of reversible capacities, cycling performance, and rate capability. Undertaking such a production configuration allows the long-existing problem of obtaining a high packing density of tin particles while retaining sufficient spare space to buffer the volume variation during lithium alloying and dealloying processes to be properly addressed. Furthermore, the porous carbon shell preserves both the mechanical and chemical stability of the function-active Sn metal, which also serves as a highly conductive medium allowing Li(+) to access. PMID:19886691

  11. 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

  12. Synthesis of SiO2/3D porous carbon composite as anode material with enhanced lithium storage performance

    NASA Astrophysics Data System (ADS)

    Yuan, Zhinan; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; He, Chunnian; He, Fang

    2016-05-01

    A SiO2/porous carbon nanocomposite was synthesized by a facile combined heat and acid treatments method. The nanocomposite featured a 3D porous carbon structure with amorphous SiO2 nanoparticles embedded in the wall of the pores. The microstructure improved the electrical conductivity, shortened the diffusion distance of lithium ions, and alleviated the volume expansion of SiO2 during Li intercalation. Accordingly, the SiO2/porous carbon nanocomposite displayed excellent cyclic performance with a high reversible capacity of 434 mAh g-1 after 50 cycles at 0.1 A g-1 and rate capability delivering a capacity of 187.4 mAh g-1 even at 5 A g-1.

  13. Synthesis of porous graphene/activated carbon composite with high packing density and large specific surface area for supercapacitor electrode material

    NASA Astrophysics Data System (ADS)

    Zheng, Chao; Zhou, Xufeng; Cao, Hailiang; Wang, Guohua; Liu, Zhaoping

    2014-07-01

    A simple method has been developed to prepare graphene/activated carbon (AC) nanosheet composite as high-performance electrode material for supercapacitor. Glucose solution containing dispersed graphite oxide (GO) sheets is hydrothermally carbonized to form a brown char-like intermediate product, and finally converts to porous nanosheet composite by two-step chemical activation using KOH. In this composite, a layer of porous AC coats on graphene to from wrinkled nanosheet structure, with length of several micrometers and thickness of tens of nanometer. The composite has a relatively high packing density of ˜0.3 g cm-3 and large specific surface area of 2106 m2 g-1, as well as containing plenty of mesopores. It exhibits specific capacitance up to 210 F g-1 in aqueous electrolyte and 103 F g-1 in organic electrolyte, respectively, and the specific capacitance decreases by only 5.3% after 5000 cycles. These results indicate that the porous graphene/AC nanosheet composite prepared by hydrothermal carbonization and chemical activation can be applied for high performance supercapacitors.

  14. Natural convection in porous media

    SciTech Connect

    Prasad, V.; Hussain, N.A.

    1986-01-01

    This book presents the papers given at a conference on free convection in porous materials. Topics considered at the conference included heat transfer, nonlinear temperature profiles and magnetic fields, boundary conditions, concentrated heat sources in stratified porous media, free convective flow in a cavity, heat flux, laminar mixed convection flow, and the onset of convection in a porous medium with internal heat generation and downward flow.

  15. A carbon coated NASICON structure material embedded in porous carbon enabling superior sodium storage performance: NaTi2(PO4)3 as an example

    NASA Astrophysics Data System (ADS)

    Jiang, Yu; Zeng, Linchao; Wang, Jiaqing; Li, Weihan; Pan, Fusen; Yu, Yan

    2015-08-01

    Sodium super ion conductor (NASICON) type structure materials (e.g. Na3V2(PO4)3, NaTi2(PO4)3) have been considered as promising electrode materials for sodium-ion batteries (NIBs). However, the inherent poor electronic conductivity of the NASICON type structure materials owing to their poor electronic conductivity of phosphates leads to poor cyclability and rate capability. Here, we develop a general strategy to achieve high rate capability and long cycle life by preparing ``double carbon coating'' NASICON NaTi2(PO4)3 using a soft-chemical method. The obtained carbon-coated NaTi2(PO4)3 within the porous carbon matrix (denoted as NTP@C@PC) imparts a reversible capability of 103 mA h g-1 at 5 C after 5000 cycles and a rate capability of 64 mA h g-1 at 50 C for sodium storage. The high capacity, stable cyclability and excellent rate capability of the NTP@C@PC are attributed to the advantages of the special structure: the fast Na+/e- transfer in the nanocomposites, large surface area and mesoporous nature of the 3D porous carbon matrix that facilitate the electrolyte to soak in, an intimate interaction between the particles and the carbon matrix. In addition, the 3D porous carbon matrix could effectively accommodate the volume variation during a repeated sodiation/desodiation process.Sodium super ion conductor (NASICON) type structure materials (e.g. Na3V2(PO4)3, NaTi2(PO4)3) have been considered as promising electrode materials for sodium-ion batteries (NIBs). However, the inherent poor electronic conductivity of the NASICON type structure materials owing to their poor electronic conductivity of phosphates leads to poor cyclability and rate capability. Here, we develop a general strategy to achieve high rate capability and long cycle life by preparing ``double carbon coating'' NASICON NaTi2(PO4)3 using a soft-chemical method. The obtained carbon-coated NaTi2(PO4)3 within the porous carbon matrix (denoted as NTP@C@PC) imparts a reversible capability of 103 mA h g-1 at

  16. Effect of heat treatment and diffusion welding conditions on the structure and properties of porous material workpieces made of titanium fibers

    NASA Astrophysics Data System (ADS)

    Kollerov, M. Yu.; Shlyapin, S. D.; Gusev, D. E.; Senkevich, K. S.; Runova, Yu. E.

    2015-11-01

    The effect of the diffusion welding conditions on the structure and properties of a porous material (PM) made of titanium fibers is studied. It is shown that the use of fibers produced by melt quenching and then joined to form workpieces or articles by diffusion welding can be a promising trend in the production of PMs for medicine applications. A change in the solidification rate of fibers and their contact substantially affects the mechanical properties of PM workpieces. As the diffusion welding temperature of both sheet and cylindrical workpieces increases, the strength of PM increases and the plasticity of PM decreases.

  17. Sulfur-doped porous reduced graphene oxide hollow nanosphere frameworks as metal-free electrocatalysts for oxygen reduction reaction and as supercapacitor electrode materials

    NASA Astrophysics Data System (ADS)

    Chen, Xi'an; Chen, Xiaohua; Xu, Xin; Yang, Zhi; Liu, Zheng; Zhang, Lijie; Xu, Xiangju; Chen, Ying; Huang, Shaoming

    2014-10-01

    Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and much better methanol tolerance and durability, and to be a supercapacitor electrode material with a high specific capacitance of 343 F g-1, good rate capability and excellent cycling stability in aqueous electrolytes. The impressive performance for ORR and supercapacitors is believed to be due to the synergistic effect caused by sulfur-doping enhancing the electrochemical activity and 3D porous hollow nanosphere framework structures facilitating ion diffusion and electronic transfer.Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and

  18. Porous TiO2/C nanocomposite shells as a high-performance anode material for lithium-ion batteries.

    PubMed

    Wang, Wenshou; Sa, Qina; Chen, Jihua; Wang, Yan; Jung, Heejung; Yin, Yadong

    2013-07-24

    Porous TiO2/C nanocomposite shells with high capacity, excellent cycle stability, and rate performance have been prepared. The synthesis involves coating colloidal TiO2 nanoshells with a resorcinol-formaldehyde (RF) layer with controllable thickness through a sol-gel-like process, and calcining the composites at 700 °C in an inert atmosphere to induce crystallization from amorphous TiO2 to anatase and simultaneous carbonization from RF to carbon. The cross-linked RF polymer contributes to the high stability of the shell morphology and the porous nature of the shells. A strong dependence of the capacity on the amount of incorporated carbon has been revealed, allowing the optimization of the electrode structure for high-rate cell performance. PMID:23829667

  19. Three-dimensional Aerographite-GaN hybrid networks: Single step fabrication of porous and mechanically flexible materials for multifunctional applications

    NASA Astrophysics Data System (ADS)

    Schuchardt, Arnim; Braniste, Tudor; Mishra, Yogendra K.; Deng, Mao; Mecklenburg, Matthias; Stevens-Kalceff, Marion A.; Raevschi, Simion; Schulte, Karl; Kienle, Lorenz; Adelung, Rainer; Tiginyanu, Ion

    2015-03-01

    Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes. In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite material as templates by a single step hydride vapor phase epitaxy process. The GaN nano- and microstructures grow on the surface of Aerographite tubes and follow the network architecture of the Aerographite template without agglomeration. The synthesized 3D networks are integrated with the properties from both, i.e., nanoscale GaN structures and Aerographite in the form of flexible and semiconducting composites which could be exploited as next generation materials for electronic, photonic, and sensors applications.

  20. Au-NiCo2O4 supported on three-dimensional hierarchical porous graphene-like material for highly effective oxygen evolution reaction.

    PubMed

    Xia, Wei-Yan; Li, Nan; Li, Qing-Yu; Ye, Kai-Hang; Xu, Chang-Wei

    2016-01-01

    A three-dimensional hierarchical porous graphene-like (3D HPG) material was synthesized by a one-step ion-exchange/activation combination method using a cheap metal ion exchanged resin as carbon precursor. The 3D HPG material as support for Au-NiCo2O4 gives good activity and stability for oxygen evolution reaction (OER). The 3D HPG material is induced into NiCo2O4 as conductive support to increase the specific area and improve the poor conductivity of NiCo2O4. The activity of and stability of NiCo2O4 significantly are enhanced by a small amount of Au for OER. Au is a highly electronegative metal and acts as an electron adsorbate, which is believed to facilitate to generate and stabilize Co(4+) and Ni(3+) cations as the active centres for the OER. PMID:26996816

  1. Au-NiCo2O4 supported on three-dimensional hierarchical porous graphene-like material for highly effective oxygen evolution reaction

    PubMed Central

    Xia, Wei-Yan; Li, Nan; Li, Qing-Yu; Ye, Kai-Hang; Xu, Chang-Wei

    2016-01-01

    A three-dimensional hierarchical porous graphene-like (3D HPG) material was synthesized by a one-step ion-exchange/activation combination method using a cheap metal ion exchanged resin as carbon precursor. The 3D HPG material as support for Au-NiCo2O4 gives good activity and stability for oxygen evolution reaction (OER). The 3D HPG material is induced into NiCo2O4 as conductive support to increase the specific area and improve the poor conductivity of NiCo2O4. The activity of and stability of NiCo2O4 significantly are enhanced by a small amount of Au for OER. Au is a highly electronegative metal and acts as an electron adsorbate, which is believed to facilitate to generate and stabilize Co4+ and Ni3+ cations as the active centres for the OER. PMID:26996816

  2. Au-NiCo2O4 supported on three-dimensional hierarchical porous graphene-like material for highly effective oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Xia, Wei-Yan; Li, Nan; Li, Qing-Yu; Ye, Kai-Hang; Xu, Chang-Wei

    2016-03-01

    A three-dimensional hierarchical porous graphene-like (3D HPG) material was synthesized by a one-step ion-exchange/activation combination method using a cheap metal ion exchanged resin as carbon precursor. The 3D HPG material as support for Au-NiCo2O4 gives good activity and stability for oxygen evolution reaction (OER). The 3D HPG material is induced into NiCo2O4 as conductive support to increase the specific area and improve the poor conductivity of NiCo2O4. The activity of and stability of NiCo2O4 significantly are enhanced by a small amount of Au for OER. Au is a highly electronegative metal and acts as an electron adsorbate, which is believed to facilitate to generate and stabilize Co4+ and Ni3+ cations as the active centres for the OER.

  3. Chemically Layered Porous Solids

    NASA Technical Reports Server (NTRS)

    Koontz, Steve

    1991-01-01

    Aerogels and other porous solids in which surfaces of pores have chemical properties varying with depth below macroscopic surfaces prepared by sequences of chemical treatments. Porous glass or silica bead treated to make two depth zones having different chemical properties. Beads dropped along tube filled with flowing gas containing atomic oxygen, generated in microwave discharge. General class of materials treatable include oxides of aluminum, silicon, zirconium, tin, titanium, and nickel, and mixtures of these oxides. Potential uses of treated materials include chromatographic separations, membrane separations, controlled releases of chemicals, and catalysis.

  4. Development of an extraction method based on new porous organogel materials coupled with liquid chromatography-mass spectrometry for the rapid quantification of bisphenol A in urine.

    PubMed

    ter Halle, Alexandra; Claparols, Catherine; Garrigues, Jean Christophe; Franceschi-Messant, Sophie; Perez, Emile

    2015-10-01

    A new method based on the use of porous organogel materials in combination with liquid chromatography-tandem mass spectrometry (LC-MS-MS) was assessed for the quantification of trace contaminants in complex matrices. As a demonstration of the use of these new materials, the contaminant chosen as a model was bisphenol A (BPA) and its extraction was investigated in urine. Organogel materials consist of an organic solvent immobilized by an organogelator. The composition of the organogel materials was optimized in terms of extraction efficiency and compatibility with LC-MS-MS. Porosity was introduced into the organogel by means of the particulate leaching method using sugar crystals. This new absorbing material is simple to use; the extraction method is reduced to a few steps. The originality of the method lies in the complete dissolution of the material for analysis by LC-MS-MS. The matrix effect of the organogel components was studied and was found to be minimal in atmospheric-pressure chemical ionization (APCI) compared to electrospray ionization (ESI) in negative mode. The influence of matrix components on the extraction was investigated by working with different media (acidified water, synthetic urine, horse urine and human urine). The partition coefficient was not affected within the margin of error (±0.1). After optimization, bisphenol A recoveries from urine samples reached 80%. The actual concentration factor was 10. The relative standard deviation (RSD, n=6) for the extraction and determination of BPA in horse urine spiked at 10ngmL(-1) was 9%. Tests with spiked human urine showed that the extraction performances were the same as with the solutions tested previously. The use of porous organogel allowed a fast, simple, sensitive, robust, green method to be developed for the determination of trace contaminants in complex matrices. PMID:26342874

  5. 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

  6. Disintegration of porous polyethylene prostheses.

    PubMed

    Kerr, A G; Riley, D N

    1999-06-01

    A Plastipore (porous polyethylene) Total Ossicular Replacement Prosthesis gave an excellent initial hearing result which was maintained for 14 years. Hearing then began to deteriorate and revision surgery showed disintegration of the prosthesis and a defect in the stapes footplate. Histological examination confirmed previous findings in porous polyethylene with multinucleated foreign body giant cells and breakdown of the material. PMID:10384839

  7. Catalytic Graphitization for Preparation of Porous Carbon Material Derived from Bamboo Precursor and Performance as Electrode of Electrical Double-Layer Capacitor

    NASA Astrophysics Data System (ADS)

    Tsubota, Toshiki; Maguchi, Yuta; Kamimura, Sunao; Ohno, Teruhisa; Yasuoka, Takehiro; Nishida, Haruo

    2015-12-01

    The combination of addition of Fe (as a catalyst for graphitization) and CO2 activation (a kind of gaseous activation) was applied to prepare a porous carbon material from bamboo powder (a waste product of superheated steam treatment). Regardless of the heat treatment temperature, many macropores were successfully formed after the heating process by removal of Fe compounds. A turbostratic carbon structure was generated in the Fe-added sample heated at 850°C. It was confirmed that the added Fe acted as a template for pore formation. Moreover, it was confirmed that the added Fe acted as a catalyst for graphitization. The resulting electrochemical performance as the electrode of an electrical double-layer capacitor, as demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge testing, could be explained based on the graphitization and activation effects. Addition of Fe could affect the electrical properties of carbon material derived from bamboo.

  8. Porous carbon-coated silica macroparticles as anode materials for lithium ion batteries: Effect of boric acid

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Moon, Jong-Woo; Lee, Jung-Goo; Baek, Youn-Kyung; Hong, Seong-Hyun

    2014-12-01

    We report carbon-coated porous silica macroparticles (SiO2@C) prepared using polymeric templates and subsequent carbonization with sucrose for improved electrochemical energy storage in lithium-ion batteries (LIBs). In addition, boron is introduced to improve the stability of electrochemical cells by pyrolyzing mixtures of sucrose and boric acid (SiO2@C + B) under inert atmosphere. The initially large surface area of porous SiO2 (SBET ∼ 658 m2 g-1) is reduced to 102 m2 g-1 after carbonization and introduction of boric acid. Surface of both SiO2@C and SiO2@C + B are covered with amorphous carbon. In particular, SiO2@C + B particles containing borosilicate (Si-O-B) phase and B-O bondings and Si-C-O bondings are also detected from the X-ray photoelectron spectra. The SiO2@C + B macroparticles shows high reversible charge capacity up to 503 mAh g-1 after 103 cycles of Li intercalation/de-intercalation although initial capacity was 200 mAh g-1. The improved charge capacity of SiO2@C + B is attributed to formation of advantageous microstructures induced from boric acid.

  9. Porous carbon-coated silica macroparticles as anode materials for lithium ion batteries: Effect of boric acid

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Moon, Jong-Woo; Lee, Jung-Goo; Baek, Youn-Kyung; Hong, Seong-Hyun

    2014-12-01

    We report carbon-coated porous silica macroparticles (SiO2@C) prepared using polymeric templates and subsequent carbonization with sucrose for improved electrochemical energy storage in lithium-ion batteries (LIBs). In addition, boron is introduced to improve the stability of electrochemical cells by pyrolyzing mixtures of sucrose and boric acid (SiO2@C + B) under inert atmosphere. The initially large surface area of porous SiO2 (SBET ˜ 658 m2 g-1) is reduced to 102 m2 g-1 after carbonization and introduction of boric acid. Surface of both SiO2@C and SiO2@C + B are covered with amorphous carbon. In particular, SiO2@C + B particles containing borosilicate (Si-O-B) phase and B-O bondings and Si-C-O bondings are also detected from the X-ray photoelectron spectra. The SiO2@C + B macroparticles shows high reversible charge capacity up to 503 mAh g-1 after 103 cycles of Li intercalation/de-intercalation although initial capacity was 200 mAh g-1. The improved charge capacity of SiO2@C + B is attributed to formation of advantageous microstructures induced from boric acid.

  10. Bone formation in vivo induced by Cbfa1-carrying adenoviral vectors released from a biodegradable porous β-tricalcium phosphate (β-TCP) material

    NASA Astrophysics Data System (ADS)

    Uemura, Toshimasa; Kojima, Hiroko

    2011-06-01

    Overexpression of Cbfa1 (a transcription factor indispensable for osteoblastic differentiation) is expected to induce the formation of bone directly and indirectly in vivo by accelerating osteoblastic differentiation. Adenoviral vectors carrying the cDNA of Cbfa1/til-1(Adv-Cbf1) were allowed to be adsorbed onto porous blocks of β-tricalcium phosphate (β-TCP), a biodegradable ceramic, which were then implanted subcutaneously and orthotopically into bone defects. The adenoviral vectors were released sustainingly by biodegradation, providing long-term expression of the genes. Results of the subcutaneous implantation of Adv-Cbfa1-adsorbed β-TCP/osteoprogenitor cells suggest that a larger amount of bone formed in the pores of the implant than in the control material. Regarding orthotopic implantation into bone defects, the released Adv-Cbfa1 accelerated regeneration in the cortical bone, whereas it induced bone resorption in the marrow cavity. A safer gene transfer using a smaller amount of the vector was achieved using biodegradable porous β-TCP as a carrier.

  11. Porous γ-Fe2O3 spheres coated with N-doped carbon from polydopamine as Li-ion battery anode materials.

    PubMed

    Liang, Jin; Xiao, Chunhui; Chen, Xu; Gao, Ruixia; Ding, Shujiang

    2016-05-27

    Nitrogen doping has been demonstrated to play a crucial role in controlling the electronic properties of carbon-based composites. In this paper, nitrogen-doped carbon coated γ-Fe2O3 (NC@γ-Fe2O3) composite was successfully fabricated through a facile and high-yield strategy, including a hydrothermal reaction process for porous γ-Fe2O3 and a subsequent coating of nitrogen-doped carbon by using dopamine as precursor. The resulting composite combines the superior properties of porous Fe2O3 and heteroatom-doped conductive carbon layer derived from polydopamine. When used as the anode material of the lithium-ion battery, the as-prepared NC@γ-Fe2O3 composite exhibits excellent lithium storage properties in terms of high capacity, stable cycling performance (869.6 mAh g(-1) at the current density of 0.5 A g(-1) after 150 cycles) and excellent rate capability. PMID:27095053

  12. Porous γ-Fe2O3 spheres coated with N-doped carbon from polydopamine as Li-ion battery anode materials

    NASA Astrophysics Data System (ADS)

    Liang, Jin; Xiao, Chunhui; Chen, Xu; Gao, Ruixia; Ding, Shujiang

    2016-05-01

    Nitrogen doping has been demonstrated to play a crucial role in controlling the electronic properties of carbon-based composites. In this paper, nitrogen-doped carbon coated γ-Fe2O3 (NC@γ-Fe2O3) composite was successfully fabricated through a facile and high-yield strategy, including a hydrothermal reaction process for porous γ-Fe2O3 and a subsequent coating of nitrogen-doped carbon by using dopamine as precursor. The resulting composite combines the superior properties of porous Fe2O3 and heteroatom-doped conductive carbon layer derived from polydopamine. When used as the anode material of the lithium-ion battery, the as-prepared NC@γ-Fe2O3 composite exhibits excellent lithium storage properties in terms of high capacity, stable cycling performance (869.6 mAh g‑1 at the current density of 0.5 A g‑1 after 150 cycles) and excellent rate capability.

  13. Porous silicon gettering

    SciTech Connect

    Tsuo, Y.S.; Menna, P.; Pitts, J.R.

    1996-05-01

    The authors have studied a novel extrinsic gettering method that uses the large surface areas produced by a porous-silicon etch as gettering sites. The annealing step of the gettering used a high-flux solar furnace. They found that a high density of photons during annealing enhanced the impurity diffusion to the gettering sites. The authors used metallurgical-grade Si (MG-Si) prepared by directional solidification casing as the starting material. They propose to use porous-silicon-gettered MG-Si as a low-cost epitaxial substrate for polycrystalline silicon thin-film growth.

  14. Hierarchically Flower-like N-Doped Porous Carbon Materials Derived from an Explosive 3-Fold Interpenetrating Diamondoid Copper Metal-Organic Framework for a Supercapacitor.

    PubMed

    Li, Zuo-Xi; Zou, Kang-Yu; Zhang, Xue; Han, Tong; Yang, Ying

    2016-07-01

    A peculiar copper metal-organic framework (Cu-MOF) was synthesized by a self-assembly method, which presents a 3-fold interpenetrating diamondoid net based on the square-planar Cu(II) node. Although it exhibits a high degree of interpenetration, the Cu-MOF still exhibits a one-dimensional channel, which provides a template for constructing porous materials through the "precursor" strategy. Furthermore, the explosive ClO4(-) ion, which resided in the channel, could induce the quick decomposition of organic ingredients and release a huge amount of gas, which is beneficial for the porosity of postsynthetic materials. Significantly, we first utilize this explosive MOF to prepare a series of Cu@C composites through the calcination-thermolysis method at different temperatures, which contain copper particles exhibiting various shapes and combinations with the carbon substrate. Considering the hole-forming effect of copper particles, Cu@C composites were etched by HCl to afford a sequence of hierarchically flower-like N-doped porous carbon materials (NPCs), which retain the original morphology of the Cu-MOF. Interestingly, NPC-900, originating from the calcination of the Cu-MOF at 900 °C, exhibits a more regular flower-like morphology, the largest specific surface area, abundant porosities, and multiple nitrogen functionalities. The remarkable specific capacitances are 138 F g(-1) at 5 mV s(-1) and 149 F g(-1) at 0.5 A g(-1) for the NPC-900 electrode in a 6 M potassium hydroxide aqueous solution. Moreover, the retention of capacitance remains 86.8% (125 F g(-1)) at 1 A g(-1) over 2000 cycles, which displays good chemical stability. These findings suggest that NPC-900 can be applied as a suitable electrode for a supercapacitor. PMID:27304095

  15. An in-situ synthesis of Ag/AgCl/TiO2/hierarchical porous magnesian material and its photocatalytic performance

    PubMed Central

    Yang, Lu; Wang, Fazhou; Shu, Chang; Liu, Peng; Zhang, Wenqin; Hu, Shuguang

    2016-01-01

    The absorption ability and photocatalytic activity of photocatalytic materials play important roles in improving the pollutants removal effects. Herein, we reported a new kind of photocatalytic material, which was synthesized by simultaneously designing hierarchical porous magnesian (PM) substrate and TiO2 catalyst modification. Particularly, PM substrate could be facilely prepared by controlling its crystal phase (Phase 5, Mg3Cl(OH)5·4H2O), while Ag/AgCl particles modification of TiO2 could be achieved by in situ ion exchange between Ag+ and above crystal Phase. Physiochemical analysis shows that Ag/AgCl/TiO2/PM material has higher visible and ultraviolet light absorption response, and excellent gas absorption performance compared to other controls. These suggested that Ag/AgCl/TiO2/PM material could produce more efficient photocatalytic effects. Its photocatalytic reaction rate was 5.21 and 30.57 times higher than that of TiO2/PM and TiO2/imporous magnesian substrate, respectively. Thus, this material and its intergration synthesis method could provide a novel strategy for high-efficiency application and modification of TiO2 photocatalyst in engineering filed. PMID:26883972

  16. An in-situ synthesis of Ag/AgCl/TiO2/hierarchical porous magnesian material and its photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Yang, Lu; Wang, Fazhou; Shu, Chang; Liu, Peng; Zhang, Wenqin; Hu, Shuguang

    2016-02-01

    The absorption ability and photocatalytic activity of photocatalytic materials play important roles in improving the pollutants removal effects. Herein, we reported a new kind of photocatalytic material, which was synthesized by simultaneously designing hierarchical porous magnesian (PM) substrate and TiO2 catalyst modification. Particularly, PM substrate could be facilely prepared by controlling its crystal phase (Phase 5, Mg3Cl(OH)5·4H2O), while Ag/AgCl particles modification of TiO2 could be achieved by in situ ion exchange between Ag+ and above crystal Phase. Physiochemical analysis shows that Ag/AgCl/TiO2/PM material has higher visible and ultraviolet light absorption response, and excellent gas absorption performance compared to other controls. These suggested that Ag/AgCl/TiO2/PM material could produce more efficient photocatalytic effects. Its photocatalytic reaction rate was 5.21 and 30.57 times higher than that of TiO2/PM and TiO2/imporous magnesian substrate, respectively. Thus, this material and its intergration synthesis method could provide a novel strategy for high-efficiency application and modification of TiO2 photocatalyst in engineering filed.

  17. Use of tire rubber in asphalt material and evaluation of asphalt rubber binders in porous friction courses

    SciTech Connect

    Anderton, G.L.; Salami, M.R.

    1995-06-01

    The purpose of this research by Waterways Experiment Station (WES) was to evaluate the effectiveness of using asphalt rubber binders in porous friction course`s (PFC`s). This research provides a sound basis for using asphalt rubber binders in order to provide a more durable, cost-effective PFC. The information provided by this research has the potential to increase the volume of PFC`s constructed in the future and to make these future pavements longer lasting. The objectives of this research were: (1) to determine the potential benefits of asphalt rubber binders when used in PFC`s and (2) to recommend the asphalt cement grades and mix design procedure required to achieve optimum field performance. The scope of this study included a review of available literature and existing data, a three-phase laboratory study, and an analysis of all collected data.

  18. pH-responsive and photostable group IV metal oxide functionalized porous silicon platforms and novel applications of spectroscopic imaging methods for functional and hybrid materials analysis

    NASA Astrophysics Data System (ADS)

    Destino, Joel F.

    This dissertation covers two research topics that center on the spectroscopic characterization of functional materials. First, the performance (i.e. pH stability, photostability, shelf life) of novel photoluminescent group IV metal oxide functionalized porous silicon platforms is discussed. Spectroscopic techniques are used to provide insight into the chemistry of these substrates, and investigate pH-dependent PL response. The second section covers various novel applications of spectroscopic imaging methods. Colocalized Raman and atomic force microscopy and fluorescence imaging results for two- and three-component hybrid antifouling xerogel thin films are presented. Analysis investigates the relationship between surface structure, surface charge, surface pH and chemistry as it relates to antifouling performance. Lastly, practical aspects of tip-enhanced Raman spectroscopy are discussed and preliminary results of WS2 on Au are presented.

  19. Facile synthesis of α-Fe2O3 nanoparticles on porous human hair-derived carbon as improved anode materials for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Dong, Hui; Zhang, Huang; Xu, Yunlong; Zhao, Chongjun

    2015-12-01

    A hybridized composite material of α-Fe2O3 nanoparticles/human hair-derived carbon (HHC) is prepared using a facile two-step method combined carbonization of human hair with homogeneous precipitation under microwave irradiation. Results show that the uniform α-Fe2O3 nanoparticles were highly dispersed on the surface of porous human hair-derived carbon. As an anode material for Li-ion batteries, it retains a reversible capacity of 1000 mAh g-1after 200 cycles at 0.2 C. A discharge capacity higher than 750 mAh g-1and 550 mAh g-1 is also recorded at 1 C and 2 C after 200 cycles, respectively. Such superior electrochemical performance of α-Fe2O3/HHC composite could be attributed to the favorable structure of HHC, which can improve the electron and lithium ion transport ability as anode. This study provides a cost-effective, highly efficient means to fabricate materials which combine keratin wastes-derived carbon with active nanoparticles for the development of high-performance lithium-ion battery materials.

  20. Materials based on carbon-filled porous layers of PVC cyclam derivatives cross-linked with the surfaces of asbestos fabric fibers

    NASA Astrophysics Data System (ADS)

    Tzivadze, A. Yu.; Fridman, A. Ya.; Morozova, E. M.; Sokolova, N. P.; Voloshchuk, A. M.; Petukhova, G. A.; Bardishev, I. I.; Gorbunov, A. M.; Novikov, A. K.; Polyakova, I. Ya.; Titova, V. N.; Yavich, A. A.; Petrova, N. V.

    2016-08-01

    The synthesis of bilayer materials with porous upper layers composed of PVC hydroxyethylcyclam derivatives filled with carbon and a layer consisting of hydroxyethylcyclam, cross-linked via Si-O-C groups with the silica chains of a developed surface of asbestos fabric, is described. The aza-crown groups in these materials are bound with aqua complexes of H2SO4 or NaOH. The structure of the materials is examined, their adsorption characteristics are determined, and the rate of motion of H+ or OH- ions in electrochemical bridges is measured, while the formation of H2 and O2 in their cathodic and anodic polarization is determined as a function of voltage. It is shown that the upper layer of these materials is adsorption-active and electronand H+- or OH-- conductive, while the bottom layer is only H+- or OH-- conductive; through it, the upper layer is supplied with the H+ or OH- ions needed for the regeneration of the aqua complexes broken down to H2 and O2 on carbon particles.

  1. Bridged polysilsesquioxane xerogels: A molecular based approach for the preparation of porous hybrid organic-inorganic materials

    SciTech Connect

    Small, J.H.; Shea, K.J.; Loy, D.A.

    1995-06-01

    Bridged polysilsesquioxanes represent an interesting family of hybrid organic-inorganic composite materials. It has been shown that manipulation of the organic bridging component offers the potential for the synthesis of a variety of materials with a range of surface areas and porosities. In addition, incorporation of a heteroatom within the bridging organic component allows for further chemical transformation of the polysilsesquioxane material.

  2. The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

    NASA Technical Reports Server (NTRS)

    Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.

    1994-01-01

    Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

  3. Singlet oxygen sensitizing materials based on porous silicone: photochemical characterization, effect of dye reloading and application to water disinfection with solar reactors.

    PubMed

    Manjón, Francisco; Santana-Magaña, Montserrat; García-Fresnadillo, David; Orellana, Guillermo

    2010-06-01

    Photogeneration of singlet molecular oxygen ((1)O(2)) is applied to organic synthesis (photooxidations), atmosphere/water treatment (disinfection), antibiofouling materials and in photodynamic therapy of cancer. In this paper, (1)O(2) photosensitizing materials containing the dyes tris(4,4'-diphenyl-2,2'-bipyridine)ruthenium(II) (1, RDB(2+)) or tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (2, RDP(2+)), immobilized on porous silicone (abbreviated RDB/pSil and RDP/pSil), have been produced and tested for waterborne Enterococcus faecalis inactivation using a laboratory solar simulator and a compound parabolic collector (CPC)-based solar photoreactor. In order to investigate the feasibility of its reuse, the sunlight-exposed RDP/pSil sensitizing material (RDP/pSil-a) has been reloaded with RDP(2+) (RDP/pSil-r). Surprisingly, results for bacteria inactivation with the reloaded material have demonstrated a 4-fold higher efficiency compared to those of either RDP/pSil-a, unused RDB/pSil and the original RDP/pSil. Surface and bulk photochemical characterization of the new material (RDP/pSil-r) has shown that the bactericidal efficiency enhancement is due to aggregation of the silicone-supported photosensitizer on the surface of the polymer, as evidenced by confocal fluorescence lifetime imaging microscopy (FLIM). Photogenerated (1)O(2) lifetimes in the wet sensitizer-doped silicone have been determined to be ten times longer than in water. These facts, together with the water rheology in the solar reactor and the interfacial production of the biocidal species, account for the more effective disinfection observed with the reloaded photosensitizing material. These results extend and improve the operational lifetime of photocatalytic materials for point-of-use (1)O(2)-mediated solar water disinfection. PMID:20393668

  4. Porous polymer media

    DOEpatents

    Shepodd, Timothy J.

    2002-01-01

    Highly crosslinked monolithic porous polymer materials for chromatographic applications. By using solvent compositions that provide not only for polymerization of acrylate monomers in such a fashion that a porous polymer network is formed prior to phase separation but also for exchanging the polymerization solvent for a running buffer using electroosmotic flow, the need for high pressure purging is eliminated. The polymer materials have been shown to be an effective capillary electrochromatographic separations medium at lower field strengths than conventional polymer media. Further, because of their highly crosslinked nature these polymer materials are structurally stable in a wide range of organic and aqueous solvents and over a pH range of 2-12.

  5. Lactic acid fermentation by cells immobilised on various porous cellulosic materials and their alginate/poly-lactic acid composites.

    PubMed

    Kumar, Mrinal Nishant; Gialleli, Angelika-Ioanna; Masson, Jean Bernard; Kandylis, Panagiotis; Bekatorou, Argyro; Koutinas, Athanasios A; Kanellaki, Maria

    2014-08-01

    Porous delignified cellulose (or tubular cellulose, abbr. TC) from Indian Mango (Mangifera indica) and Sal (Shorea robusta) wood and Rice husk, and TC/Ca-alginate/polylactic acid composites, were used as Lactobacillus bulgaricus immobilisation carriers leading to improvements in lactic acid fermentation of cheese whey and synthetic lactose media, compared to free cells. Specifically, shorter fermentation rates, higher lactic acid yields (g/g sugar utilised) and productivities (g/Ld), and higher amounts of volatile by-products were achieved, while no significant differences were observed on the performance of the different immobilised biocatalysts. The proposed biocatalysts are of food grade purity, cheap and easy to prepare, and they are attractive for bioprocess development based on immobilised cells. Such composite biocatalysts may be used for the co-immobilisation of different microorganisms or enzymes (in separate layers of the biocatalyst), to efficiently conduct different types of fermentations in the same bioreactor, avoiding inhibition problems of chemical or biological (competition) nature. PMID:24690466

  6. Hierarchically porous carbon encapsulating sulfur as a superior cathode material for high performance lithium-sulfur batteries.

    PubMed

    Xu, Guiyin; Ding, Bing; Nie, Ping; Shen, Laifa; Dou, Hui; Zhang, Xiaogang

    2014-01-01

    Lithium-sulfur (Li-S) batteries are deemed to be a promising energy storage device for next-generation high energy power system. However, insulation of S and dissolution of lithium polysulfides in the electrolyte lead to low utilization of sulfur and poor cycling performance, which seriously hamper the rapid development of Li-S batteries. Herein, we reported that encapsulating sulfur into hierarchically porous carbon (HPC) derived from the soluble starch with a template of needle-like nanosized Mg(OH)2. HPC has a relatively high specific surface area of 902.5 m(2) g(-1) and large total pore volume of 2.60 cm(3) g(-1), resulting that a weight percent of sulfur in S/HPC is up to 84 wt %. When evaluated as cathodes for Li-S batteries, the S/HPC composite has a high discharge capacity of 1249 mAh g(-1) in the first cycle and a Coulombic efficiency as high as 94% with stable cycling over prolonged 100 charge/discharge cycles at a high current density of 1675 mA g(-1). The superior electrochemical performance of S/HPC is closely related to its unique structure, exhibiting the graphitic structure with a high developed porosity framework of macropores in combination with mesopores and micropores. Such nanostructure could shorten the transport pathway for both ions and electrons during prolonged cycling. PMID:24344876

  7. Tuning the adsorption behaviors of water, methanol, and ethanol in a porous material by varying the flexibility of substituted groups.

    PubMed

    Sha, Yunfei; Bai, Shizhe; Lou, Jiaying; Wu, Da; Liu, Baizhan; Ling, Yun

    2016-05-01

    Exploring the adsorption and separation of water, methanol, and ethanol is important concerning the use of a sustainable energy source from biofuel. In this paper, the effects of the flexibility of substituted groups have been studied based on three iso-reticular metal-organic frameworks (MOFs), in which the pore surface is decorated with propargyl (-CH2-C[triple bond, length as m-dash]CH), allyl (-CH2-CH[double bond, length as m-dash]CH2), and propyl (-CH2-CH2-CH3) groups respectively. These substituted groups stretch into the channel, acting as gates, and the gate-opening for guests is controlled by the flexibility as well as host-guest interactions. Our study results indicate that (i) the adsorption capacity of water, methanol and ethanol enhances accordingly with the increase of the flexibility of substituted groups; (ii) the adsorptive discrimination of water, methanol, and ethanol on this porous sorbent could be tuned by varying the substituted groups. PMID:27074997

  8. Three-dimensional Aerographite-GaN hybrid networks: Single step fabrication of porous and mechanically flexible materials for multifunctional applications

    PubMed Central

    Schuchardt, Arnim; Braniste, Tudor; Mishra, Yogendra K.; Deng, Mao; Mecklenburg, Matthias; Stevens-Kalceff, Marion A.; Raevschi, Simion; Schulte, Karl; Kienle, Lorenz; Adelung, Rainer; Tiginyanu, Ion

    2015-01-01

    Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes. In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite material as templates by a single step hydride vapor phase epitaxy process. The GaN nano- and microstructures grow on the surface of Aerographite tubes and follow the network architecture of the Aerographite template without agglomeration. The synthesized 3D networks are integrated with the properties from both, i.e., nanoscale GaN structures and Aerographite in the form of flexible and semiconducting composites which could be exploited as next generation materials for electronic, photonic, and sensors applications. PMID:25744694

  9. Three-dimensional Aerographite-GaN hybrid networks: single step fabrication of porous and mechanically flexible materials for multifunctional applications.

    PubMed

    Schuchardt, Arnim; Braniste, Tudor; Mishra, Yogendra K; Deng, Mao; Mecklenburg, Matthias; Stevens-Kalceff, Marion A; Raevschi, Simion; Schulte, Karl; Kienle, Lorenz; Adelung, Rainer; Tiginyanu, Ion

    2015-01-01

    Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes. In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite material as templates by a single step hydride vapor phase epitaxy process. The GaN nano- and microstructures grow on the surface of Aerographite tubes and follow the network architecture of the Aerographite template without agglomeration. The synthesized 3D networks are integrated with the properties from both, i.e., nanoscale GaN structures and Aerographite in the form of flexible and semiconducting composites which could be exploited as next generation materials for electronic, photonic, and sensors applications. PMID:25744694

  10. Hydrostatic testing of porous assemblies

    NASA Technical Reports Server (NTRS)

    Bigelow, W. L.

    1968-01-01

    Pores of the material were plugged with dust particles suspended in water. The plugging material used was a standard test dust prepared as a slurry in distilled water. This technique provides a permanent high-integrity seal for porous material without affecting its physical properties, yet permitting pressure testing to verify structural adequacy.

  11. Application of perfusion culture system improves in vitro and in vivo osteogenesis of bone marrow-derived osteoblastic cells in porous ceramic materials.

    PubMed

    Wang, Yichao; Uemura, Toshimasa; Dong, Jian; Kojima, Hiroko; Tanaka, Junzo; Tateishi, Tetsuya

    2003-12-01

    Composites of bone marrow-derived osteoblasts (BMOs) and porous ceramics have been widely used as a bone graft model for bone tissue engineering. Perfusion culture has potential utility for many cell types in three-dimensional (3D) culture. Our hypothesis was that perfusion of medium would increase the cell viability and biosynthetic activity of BMOs in porous ceramic materials, which would be revealed by increased levels of alkaline phosphate (ALP) activity and osteocalcin (OCN) and enhanced bone formation in vivo. For testing in vitro, BMO/beta-tricalcium phosphate composites were cultured in a perfusion container (Minucells and Minutissue, Bad Abbach, Germany) with fresh medium delivered at a rate of 2 mL/h by a peristaltic pump. The ALP activity and OCN content of composites were measured at the end of 1, 2, 3, and 4 weeks of subculture. For testing in vivo, after subculturing for 2 weeks, the composites were subcutaneously implanted into syngeneic rats. These implants were harvested 4 or 8 weeks later. The samples then underwent a biochemical analysis of ALP activity and OCN content and were observed by light microscopy. The levels of ALP activity and OCN in the composites were significantly higher in the perfusion group than in the control group (p < 0.01), both in vitro and in vivo. Histomorphometric analysis of the hematoxylin- and eosin-stained sections revealed a higher average ratio of bone to pore in BMO/beta-TCP composites of the perfusion group after implantation: 47.64 +/- 6.16 for the perfusion group and 26.22 +/- 4.84 for control at 4 weeks (n = 6, p < 0.01); 67.97 +/- 3.58 for the perfusion group and 47.39 +/- 4.10 for control at 8 weeks (n = 6, p < 0.05). These results show that the application of a perfusion culture system during the subculture of BMOs in a porous ceramic scaffold is beneficial to their osteogenesis. After differentiation culture in vitro with the perfusion culture system, the activity of the osteoblastic cells and the

  12. 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...

  13. Real-Time Gamma Imaging of Technetium Transport through Natural and Engineered Porous Materials for Radioactive Waste Disposal

    PubMed Central

    2013-01-01

    We present a novel methodology for determining the transport of technetium-99m, a γ-emitting metastable isomer of 99Tc, through quartz sand and porous media relevant to the disposal of nuclear waste in a geological disposal facility (GDF). Quartz sand is utilized as a model medium, and the applicability of the methodology to determine radionuclide transport in engineered backfill cement is explored using the UK GDF candidate backfill cement, Nirex Reference Vault Backfill (NRVB), in a model system. Two-dimensional distributions in 99mTc activity were collected at millimeter-resolution using decay-corrected gamma camera images. Pulse-inputs of ∼20 MBq 99mTc were introduced into short (<10 cm) water-saturated columns at a constant flow of 0.33 mL min–1. Changes in calibrated mass distribution of 99mTc at 30 s intervals, over a period of several hours, were quantified by spatial moments analysis. Transport parameters were fitted to the experimental data using a one-dimensional convection–dispersion equation, yielding transport properties for this radionuclide in a model GDF environment. These data demonstrate that 99Tc in the pertechnetate form (Tc(VII)O4–) does not sorb to cement backfill during transport under model conditions, resulting in closely conservative transport behavior. This methodology represents a quantitative development of radiotracer imaging and offers the opportunity to conveniently and rapidly characterize transport of gamma-emitting isotopes in opaque media, relevant to the geological disposal of nuclear waste and potentially to a wide variety of other subsurface environments. PMID:24147650

  14. Electron beam selectively seals porous metal filters

    NASA Technical Reports Server (NTRS)

    Snyder, J. A.; Tulisiak, G.

    1968-01-01

    Electron beam welding selectively seals the outer surfaces of porous metal filters and impedances used in fluid flow systems. The outer surface can be sealed by melting a thin outer layer of the porous material with an electron beam so that the melted material fills all surface pores.

  15. Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material.

    PubMed

    Dirican, Mahmut; Lu, Yao; Ge, Yeqian; Yildiz, Ozkan; Zhang, Xiangwu

    2015-08-26

    Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) composite that not only has high sodium storage capability, but also maintains its structural integrity while ongoing repetitive cycles. Electrochemical results revealed that this SnO2-containing nanofiber composite anode had excellent electrochemical performance including high-capacity (374 mAh g(-1)), good capacity retention (82.7%), and large Coulombic efficiency (98.9% after 100th cycle). PMID:26252051

  16. First Introduction of NiSe2 to Anode Material for Sodium-Ion Batteries: A Hybrid of Graphene-Wrapped NiSe2/C Porous Nanofiber

    PubMed Central

    Cho, Jung Sang; Lee, Seung Yeon; Kang, Yun Chan

    2016-01-01

    The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process. NiSe2-reduced graphene oxide (rGO)-C composite nanofibers are successfully prepared via electrospinning and a subsequent selenization process. The electrospun nanofibers giving rise to these porous-structured composite nanofibers with optimum amount of amorphous C are obtained from the polystyrene to polyacrylonitrile ratio of 1/4. These composite nanofibers also consist of uniformly distributed single-crystalline NiSe2 nanocrystals that have a mean size of 27 nm. In contrast, the densely structured bare NiSe2 nanofibers formed via selenization of the pure NiO nanofibers consist of large crystallites. The initial discharge capacities of the NiSe2-rGO-C composite and bare NiSe2 nanofibers at a current density of 200 mA g−1 are 717 and 755 mA h g−1, respectively. However, the respective 100th-cycle discharge capacities of the former and latter are 468 and 35 mA h g−1. Electrochemical impedance spectroscopy measurements reveal the structural stability of the composite nanofibers during repeated Na-ion insertion and extraction processes. The excellent Na-ion storage properties of these nanofibers are attributed to this structural stability. PMID:26997350

  17. First Introduction of NiSe2 to Anode Material for Sodium-Ion Batteries: A Hybrid of Graphene-Wrapped NiSe2/C Porous Nanofiber

    NASA Astrophysics Data System (ADS)

    Cho, Jung Sang; Lee, Seung Yeon; Kang, Yun Chan

    2016-03-01

    The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process. NiSe2-reduced graphene oxide (rGO)-C composite nanofibers are successfully prepared via electrospinning and a subsequent selenization process. The electrospun nanofibers giving rise to these porous-structured composite nanofibers with optimum amount of amorphous C are obtained from the polystyrene to polyacrylonitrile ratio of 1/4. These composite nanofibers also consist of uniformly distributed single-crystalline NiSe2 nanocrystals that have a mean size of 27 nm. In contrast, the densely structured bare NiSe2 nanofibers formed via selenization of the pure NiO nanofibers consist of large crystallites. The initial discharge capacities of the NiSe2-rGO-C composite and bare NiSe2 nanofibers at a current density of 200 mA g‑1 are 717 and 755 mA h g‑1, respectively. However, the respective 100th-cycle discharge capacities of the former and latter are 468 and 35 mA h g‑1. Electrochemical impedance spectroscopy measurements reveal the structural stability of the composite nanofibers during repeated Na-ion insertion and extraction processes. The excellent Na-ion storage properties of these nanofibers are attributed to this structural stability.

  18. First Introduction of NiSe2 to Anode Material for Sodium-Ion Batteries: A Hybrid of Graphene-Wrapped NiSe2/C Porous Nanofiber.

    PubMed

    Cho, Jung Sang; Lee, Seung Yeon; Kang, Yun Chan

    2016-01-01

    The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process. NiSe2-reduced graphene oxide (rGO)-C composite nanofibers are successfully prepared via electrospinning and a subsequent selenization process. The electrospun nanofibers giving rise to these porous-structured composite nanofibers with optimum amount of amorphous C are obtained from the polystyrene to polyacrylonitrile ratio of 1/4. These composite nanofibers also consist of uniformly distributed single-crystalline NiSe2 nanocrystals that have a mean size of 27 nm. In contrast, the densely structured bare NiSe2 nanofibers formed via selenization of the pure NiO nanofibers consist of large crystallites. The initial discharge capacities of the NiSe2-rGO-C composite and bare NiSe2 nanofibers at a current density of 200 mA g(-1) are 717 and 755 mA h g(-1), respectively. However, the respective 100(th)-cycle discharge capacities of the former and latter are 468 and 35 mA h g(-1). Electrochemical impedance spectroscopy measurements reveal the structural stability of the composite nanofibers during repeated Na-ion insertion and extraction processes. The excellent Na-ion storage properties of these nanofibers are attributed to this structural stability. PMID:26997350

  19. Porous silicon carbide (SIC) semiconductor device

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1996-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  20. 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.

  1. Graphene Oxide Derived Carbons (GODC); High-Surface Area NanoPorous Materials for Hydrogen Storage and Carbon Capture

    NASA Astrophysics Data System (ADS)

    Yildirim, Taner

    2012-02-01

    Even though there has been extensive research on gas adsorption properties of various carbon materials based on activated carbon and nanotubes, there has been little work done on the gas adsorption properties of graphite oxide (GO). In this study [1], we show that one-and-a-half-century-old graphite oxide can be easily turned into a potentially useful gas storage material. In order to create high-surface nanoporous materials from GO, we used two different approaches. In the first approach, we have successfully synthesized graphene-oxide framework materials (GOFs) by interlinking GO layers by diboronic acids. The resulting GOF materials have well defined pore size and BET surface area up to 500 m2/g with twice larger heat of adsorption of H2 and CO2 than those found in other physisorption materials such as MOF5. In the second approach, we synthesized a range of high surface area GO derived carbons (GODC) and studied their applications toward H2, CO2 and CH4 gas storage. The GODCs, with wide range of pore structure, have been prepared by chemical activation with potassium hydroxide (KOH). We obtain largely increased surface areas up to nearly 1900 m^2/g for GODC samples from 10 m^2/g for initial GO. A detailed experimental study of high pressure excess sorption isotherms on GODCs reveal an increase in both CO2 and CH4 storage capacities compared to other high surface area activated carbons. Finally, we compared the gas sorption properties of our GO-based matarials with other systems such as MOFs, ZIFs, and COFs. [4pt] [1] See http://www.ncnr.nist.gov/staff/taner for references and more information.

  2. Construction of hierarchical porous NiCo{sub 2}O{sub 4} films composed of nanowalls as cathode materials for high-performance supercapacitor

    SciTech Connect

    Zheng, Qingyun Zhang, Xiangyang; Shen, Youming

    2015-04-15

    Graphical abstract: Hydrothermal-synthesized NiCo{sub 2}O{sub 4} mesowall films exhibit porous structure and high capacity as well as good cycling life for supercapacitor application. - Highlights: • Hierarchical porous NiCo{sub 2}O{sub 4} nanowall films are prepared by a hydrothermal method. • NiCo{sub 2}O{sub 4} nanowall films show excellent electrochemical performance. • Hierarchical porous film structure is favorable for fast ion/electron transfer. - Abstract: Hierarchical porous NiCo{sub 2}O{sub 4} films composed of nanowalls on nickel foam are synthesized via a facile hydrothermal method. Besides the mesoporous walls, the NiCo{sub 2}O{sub 4} nanowalls are interconnected with each other to form hierarchical porous structure. These unique porous structured films possess a high specific surface area. The supercapacitor performance of the hierarchical porous NiCo{sub 2}O{sub 4} film is fully characterized. A high capacity of 130 mA h g{sup −1} is achieved at 2 A g{sup −1} with 97% capacity maintained after 2,000 cycles. Importantly, 75.6% of capacity is retained when the current density changes from 3 A g{sup −1} to 36 A g{sup −1}. The superior electrochemical performance is mainly due to the unique hierarchical porous structure with large surface area as well as shorter diffusion length for ion and charge transport.

  3. Anomalous EPR intensity distribution of the methyl radical quartet adsorbed on the surface of porous materials. Comparison with solid gas matrix isolation.

    PubMed

    Benetis, Nikolas P; Dmitriev, Yurij

    2013-05-23

    The two inner lines of the EPR quartet of methyl radicals trapped in cryogenic gas matrices are superpositions of the inner transitions of an A-proton-spin quartet and an E-proton-spin doublet. Their intensity relative to the outer lines provides information on the population of the methyl-rotation quantum states. The above intensity ratio for the CH3 in solids is a challenging problem of the quantum dynamics and statistical thermodynamics. The influence of the quantum-mechanical/inertial rotation on the intensity distribution of the hf components of methyl radical on the surface of porous materials, e.g., silica gel, is investigated by EPR line shape simulations and compared with spectra of the radical isolated in the bulk of solid gas samples. The experimental part of this study includes the first in literature EPR observation of methyl radical in the bulk of N2O solid and provides new essential information on CH3 in CO2 and Ar matrices, thus, covering both strongly hindered and almost free rotation of the radical. We verify the observation of nonrotating methyl radicals in a N2O matrix, discovered earlier in cold CO2, give a thorough account of their EPR characteristics, and explore their formation at the inner surface of porous materials. Combination of a classical spin-Hamiltonian with employment of quantum effects due to nuclear spin-rotation coupling and the radical symmetry were used to interpret the experimental spectral observations. The cause of experimentally found unexpected contribution of the excited degenerate E-doublets to the EPR spectrum down to 4.2 K and A/E transition amplitude ratios sometimes as high as ca. 1:8 at liquid-N2 temperature is sought. The validity of Bose-Einstein quantum (BEq-) statistics of the spin rotation states in addition to the classical Maxwell-Boltzmann (Boltzmann) statistics was also assessed against experimental population A/E-ratio data. The BEq-statistics were not previously applied to similar systems. Furthermore

  4. Multi-functional porous mix-valent manganese oxide nano-materials and ruthenium/titanium dioxide for magnetic, electronic, and catalytic applications

    NASA Astrophysics Data System (ADS)

    Shen, Xiongfei

    This thesis contains two parts: (1) development of porous mixed-valent manganese oxide octahedral molecular sieve (OMS) nano-materials with controlled tunnel structures and muilt-functionalities and (2) application of H 2 adsorption for metal particle size evaluation on TiO2 supported Ru Fischer-Tropsch catalysts. Manganese oxide OMS with different nano-scale tunnel sizes may result in various microporosities for different selective catalysis and separation applications. A hydrothermal method was developed to synthesize manganese oxide nano-materials with controlled nano-scale tunnel sizes by hydrothermal treatments of layered structure manganese oxides under different pH conditions. Manganese oxides with increasing tunnel sizes of 2.3 A x 2.3 A (1x1 tunnel structure), 4.6 A x 6.9 A (2x3 tunnel structure), and 4.6 A x 9.2 A (2x4 tunnel structure) were synthesized with increasing pH value from 1.0, 7.0, to 13.0, respectively. Phase transformation mechanism of layered precursors to tunnel structures was obtained by characterization of the materials during synthesis using in situ synchrotron X-ray diffraction. The obtained phase transformation mechanism was used for synthesis of better materials such as new lxl/1x2 tunnel structures and controlled BET surface areas. Most manganese oxide OMS materials show paramagnetism at temperatures from 100 to 350 K. A new method was established to measure the average oxidation state (AOS) of mix-valent manganese in OMS materials by describing their paramagnetic behavior using the Curie-Weiss law. Measurement results show a maximum 7% deviation error compared to the reference titration method for 10 different samples. Magnetism of OMS was further explored by doping Fe into KOMS-2 (a 2x2 tunnel structure manganese oxide) to create high temperature ferromagnetism. The possession of both semiconducting and high temperature ferromagnetism in the Fe-doped KOMS-2 created a highly promising new group of functional materials for

  5. Porous Carbon Nanoparticle Networks with Tunable Absorbability

    PubMed Central

    Dai, Wei; Kim, Seong Jin; Seong, Won-Kyeong; Kim, Sang Hoon; Lee, Kwang-Ryeol; Kim, Ho-Young; Moon, Myoung-Woon

    2013-01-01

    Porous carbon materials with high specific surface areas and superhydrophobicity have attracted much research interest due to their potential application in the areas of water filtration, water/oil separation, and oil-spill cleanup. Most reported superhydrophobic porous carbon materials are fabricated by complex processes involving the use of catalysts and high temperatures but with low throughput. Here, we present a facile single-step method for fabricating porous carbon nanoparticle (CNP) networks with selective absorbability for water and oils via the glow discharge of hydrocarbon plasma without a catalyst at room temperature. Porous CNP networks were grown by the continuous deposition of CNPs at a relatively high deposition pressure. By varying the fluorine content, the porous CNP networks exhibited tunable repellence against liquids with various degrees of surface tension. These porous CNP networks could be applied for the separation of not only water/oil mixtures but also mixtures of liquids with different surface tension levels. PMID:23982181

  6. Enhanced apatite-forming ability and antibacterial activity of porous anodic alumina embedded with CaO-SiO2-Ag2O bioactive materials.

    PubMed

    Ni, Siyu; Li, Xiaohong; Yang, Pengan; Ni, Shirong; Hong, Feng; Webster, Thomas J

    2016-01-01

    In this study, to provide porous anodic alumina (PAA) with bioactivity and anti-bacterial properties, sol-gel derived bioactive CaO-SiO2-Ag2O materials were loaded onto and into PAA nano-pores (termed CaO-SiO2-Ag2O/PAA) by a sol-dipping method and subsequent calcination of the gel-glasses. The in vitro apatite-forming ability of the CaO-SiO2-Ag2O/PAA specimens was evaluated by soaking them in simulated body fluid (SBF). The surface microstructure and chemical property before and after soaking in SBF were characterized. Release of ions into the SBF was also measured. In addition, the antibacterial properties of the samples were tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results showed that CaO-SiO2-Ag2O bioactive materials were successfully decorated onto and into PAA nano-pores. In vitro SBF experiments revealed that the CaO-SiO2-Ag2O/PAA specimens dramatically enhanced the apatite-forming ability of PAA in SBF and Ca, Si and Ag ions were released from the samples in a sustained and slow manner. Importantly, E. coli and S. aureus were both killed on the CaO-SiO2-Ag2O/PAA (by 100%) samples compared to PAA controls after 3 days of culture. In summary, this study demonstrated that the CaO-SiO2-Ag2O/PAA samples possess good apatite-forming ability and high antibacterial activity causing it to be a promising bioactive coating candidate for implant materials for orthopedic applications. PMID:26478362

  7. Influence of the Porous Microstructure on the Elastic Properties of Sintered Ag Paste as Replacement Material for Die Attachment

    NASA Astrophysics Data System (ADS)

    Milhet, X.; Gadaud, P.; Caccuri, V.; Bertheau, D.; Mellier, D.; Gerland, M.

    2015-10-01

    Silver pastes are good candidates as alternative materials to lead solder alloys. However, little is known about the relationship between their microstructure and their mechanical properties. This issue is addressed by developing a specific route to obtain standalone sintered bulk specimens representative of the real sintered joints. The relationship between the density and the pore surface fraction is established, allowing the density of the material to be obtained independently from its size and geometry. The elastic constants of both sintered joints and sintered bulk specimens are investigated using dynamic resonant testing. A strong correlation between the elastic constants and the density is established. In contrast to the sintered bulk specimens, for which the Young's modulus remains constant after annealing, Young's modulus of the sintered joints evolves significantly towards a stabilized value. This is derived from thermal stresses relaxation within the sintered joint.

  8. 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.

  9. Investigation of a porous NiSi2/Si composite anode material used for lithium-ion batteries by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Jia, Haiping; Rana, Jatinkumar; Placke, Tobias; Klöpsch, Richard; Schumacher, Gerhard; Winter, Martin; Banhart, John

    2016-08-01

    Local structural changes in a porous NiSi2/Si composite anode material are investigated by X-ray absorption spectroscopy. It is observed that the NiSi2 phase shows a strong metal-metal bond character and no clear changes can be observed in XANES during lithiation and de-lithiation. The variation of the number of nearest neighbors of the Ni atom for the 1st coordinate Ni-Si shell and σ2 in the 1st cycle, both determined by refinement, demonstrates that NiSi2 can partially react with lithium during discharge and charge. A partially reversible non-stoichiometric compound NiSi2-y is formed during cell operation, the crystal structure of which is the same as that of the NiSi2 phase. It can be concluded that NiSi2 in the composite not only accommodates the pronounced volume changes caused by the lithium uptake into silicon, but also contributes to the reversible capacity of the cell.

  10. In-plane and through-plane local and average Nusselt numbers in fibrous porous materials with different fiber layer temperatures: Gas diffusion layers for fuel cells

    NASA Astrophysics Data System (ADS)

    Sadeghifar, Hamidreza

    2016-09-01

    Convective heat transfer inside fibrous gas diffusion layers (GDLs) noticeably impacts the heat and water management of air-cooled polymer electrolyte membrane fuel cells (PEMFCs). Cutting-edge experiments have recently proved that convective heat transfer inside fibrous GDLs increases their thermal resistances considerably. However, heat transfer coefficients are difficult to measure experimentally or compute numerically for the millions of the tiny pores inside microstructural GDLs. The present study provides robust analytic models for predicting the heat transfer coefficient for both through-plane and in-plane flows inside fibrous media such as GDLs. The model is based on the unit cell approach and the integral method. Closed-form formulas are developed for local and average heat transfer coefficients. The model considers the temperature variations of the fiber layers along the medium thickness while assuming the same temperature for all the fibers in each layer. The model is well verified by COMSOL numerical data for a few pores inside a GDL. The simple, closed-form easy-to-use formulas developed in this study can be readily employed for predicting Nusselt number inside multilayer fibrous porous materials.

  11. Selective adsorption mechanisms of antilipidemic and non-steroidal anti-inflammatory drug residues on functionalized silica-based porous materials in a mixed solute.

    PubMed

    Suriyanon, Nakorn; Permrungruang, Jutima; Kaosaiphun, Jidanan; Wongrueng, Aunnop; Ngamcharussrivichai, Chawalit; Punyapalakul, Patiparn

    2015-10-01

    The selective adsorption mechanisms of naproxen (NAP), acetaminophen (ACT), and clofibric acid (CFA) on silica-based porous materials were examined by single and mixed-batch adsorption. Effects of the types and densities of surface functional groups on adsorption capacities were determined, including the role of hydrophobic and hydrophilic dissolved organic matters (DOMs). Hexagonal mesoporous silica (HMS), superparamagnetic HMS (HMS-SP) and SBA-15 were functionalized and applied as adsorbents. Compared with powdered activated carbon (PAC), amine-functionalized HMS had a better adsorption capacity for CFA, but PAC possessed a higher adsorption capacity for the other pharmaceuticals than HMS and its two derivatives. In contrast to PAC, the adsorption capacity of the mesoporous silicas varied with the solution pH, being highest at pH 5. Electrostatic interactions and hydrogen bonding were found to be the main mechanisms. Increase in grafted amine group density on silica surfaces can enhance the CFA adsorption capacity. Further, hydrophilic DOM can decrease CFA adsorption capacities on amino-grafted adsorbents by adsorption site competition, while hydrophobic DOM can interfere with CFA adsorption by the interaction between hydrophobic DOM and CFA. Finally, in a competitive adsorption study, the adsorption capacity of hydrophilic adsorbents for acidic pharmaceuticals varied with their pKa values. PMID:26025186

  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. Comparative sound velocity measurements between porous rock and fully-dense material under crustal condition: The cases of Darley Dale sandstone and copper block

    NASA Astrophysics Data System (ADS)

    Kung, J.; Chien, Y. V.; Wu, W.; Dong, J.; Chang, Y.; Tsai, C.; Yang, M.; Wang, K.

    2012-12-01

    within 2%. With a wide porosity range, the measured P and S wave velocities of this set specimens presented a linear function of porosity, the velocity varying from 2.40 km/s to 4.00 km/s for P wave and 1.70 km/s to 2.40 km/s for S wave, yielding a tight value of 1.6(1) for Vp/Vs ratio. High pressure velocity and porosity measurements in the selected specimen showed both P and S wave velocities markedly increasing at low pressure regime (< 40 MPa) and reaching plateau above 60 MPa while the pore closure reaching a steady minimum beyond pressure of 60 MPa. From the measurement of copper block at high pressure, we learned that the velocity at lower pressure regime is disturbed by the coupling of the interface between wave guide and sample, and the pressure range within this kind of experiments has no or little effect on the velocity (or the elasticity) of fully-dense material. Combining the results of porosity and velocity from above measurements, we conclude that the change of velocity observed in the porous rocks under crustal condition should be mainly affected by the closure of narrow microcracks at high pressure.

  14. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials.

    PubMed

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong; Mølhave, Kristian; Liu, Yanguo; Zhao, Yanyan; Wang, Xun; Xu, Shengming; Zhu, Jing

    2016-01-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co3O4 hierarchical electrodes delivered high lithium storage properties comparing to the other Co3O4 nanostructures, including a high reversible capacity of 1053.1 mAhg(-1) after 50 cycles at a current density of 0.2 C (1 C = 890 mAg(-1)), good cycling stability and rate capability. PMID:26846434

  15. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials

    PubMed Central

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong; Mølhave, Kristian; Liu, Yanguo; Zhao, Yanyan; Wang, Xun; Xu, Shengming; Zhu, Jing

    2016-01-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co3O4 hierarchical electrodes delivered high lithium storage properties comparing to the other Co3O4 nanostructures, including a high reversible capacity of 1053.1 mAhg−1 after 50 cycles at a current density of 0.2 C (1 C = 890 mAg−1), good cycling stability and rate capability. PMID:26846434

  16. Identification of Explosives from Porous Materials: Applications Using Reverse Phase High Performance Liquid Chromatography and Gas Chromatography

    SciTech Connect

    C.J. Miller; G. Elias; N.C. Schmitt; C. Rae

    2010-06-01

    High performance liquid chromatography and gas chromatography techniques are well documented and widely used for the detection of trace explosives from organic solvents. These techniques were modified to specifically identify and quantify explosives extracted from various materials taken from people who had recently handled explosives. Documented techniques were modified to specifically detect and quantify RDX, TNT, and PETN from denim, colored flannel, vinyl, and canvas extracted in methanol using no sample cleanup prior to analysis. The methanol extracts were injected directly into several different column types and analyzed by HPLC-UV and/or GC-ECD. This paper describes general screening methods that were used to determine the presence of explosives in unknown samples and techniques that have been optimized for quantification of each explosive from the substrate extracts.

  17. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials

    NASA Astrophysics Data System (ADS)

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong; Mølhave, Kristian; Liu, Yanguo; Zhao, Yanyan; Wang, Xun; Xu, Shengming; Zhu, Jing

    2016-02-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co3O4 hierarchical electrodes delivered high lithium storage properties comparing to the other Co3O4 nanostructures, including a high reversible capacity of 1053.1 mAhg-1 after 50 cycles at a current density of 0.2 C (1 C = 890 mAg-1), good cycling stability and rate capability.

  18. Evaluation of a new wide-pore superficially porous material with carbon core and nanodiamond-polymer shell for the separation of proteins.

    PubMed

    Fekete, Szabolcs; Jensen, David S; Zukowski, Janusz; Guillarme, Davy

    2015-10-01

    In this study, reversed phase liquid chromatographic columns packed with superficially porous material made of a carbon core and nanodiamond-polymer shell were evaluated for the analytical characterization of proteins. The emphasis was put on the impact of pore size on the kinetic performance when analyzing large molecules. Three different types of columns possessing an average pore size of 120, 180, and 250Å were thus evaluated. As expected, the peak capacities were improved with the 180 and above all the 250Å pore size, while the kinetic performance achieved with the 120Å were systematically lower. It was also shown that a trifluoroacetic acid (TFA) concentration of 0.3-0.5% was required when analyzing proteins, to achieve suitable peak shapes (limited broadening and tailing) with this material. Elevated temperature (>60°C) is mandatory when analyzing proteins with silica-based stationary phases, but this was not the case with this particular column made with a carbon core and nanodiamond-polymer shell, since the peak capacities were not improved at high temperature. However, there was a need to increase mobile phase temperature in the range 70-90°C when analyzing monoclonal antibodies (mAbs), to limit adsorption that often occur in RPLC with this specific class of biomolecules. Finally, the FLARE(®) wide-pore column was applied to real life samples of native, oxidative stressed and reduced therapeutic proteins as well as reduced, digested mAbs and antibody drug conjugates (ADCs), to highlight the possibilities offered by this column technology. PMID:26456222

  19. CO 2 adsorption on porous NiO as a cathode material for molten carbonate fuel cells

    NASA Astrophysics Data System (ADS)

    Özkan, Göksel; Özçelik, Emre

    Molten carbonate fuel cells (MCFC) are the systems suitable for large-scale energy production. The cathode material used in these cells is NiO. In this study the NiO cathode was synthesized by tape-casting method and the adsorption of CO 2, one of the cathode feeding gases, was investigated on it. The adsorption studies were carried out by the use of packed column and the adsorption analysis were performed using pulse response technique. There were two 1/4 in. diameter and 5 and 10 cm length columns prepared for the experiments and they were packed with 3 mm average particle sized NiO. The experiments were carried out with gas chromatography using He as a carrier gas. The response curves were taken after pulsing the columns with CO 2. The equilibrium constants and heat of adsorption of CO 2 on NiO were determined by the use of the first absolute moment equations corresponding to retention times. It was observed that the adsorption was physical in nature. From the adsorption constants determined at different temperatures and the heat of adsorption, Δ H0, was found as -1299 cal mol -1.

  20. A modified cryostat for photo-electrical characterization of porous materials in controlled atmosphere at very low gas dosage

    NASA Astrophysics Data System (ADS)

    Cultrera, Alessandro; Amato, Giampiero; Boarino, Luca; Lamberti, Carlo

    2014-08-01

    We developed an integrated system for photo-electrical characterization of materials for sensing applications in strictly controlled environment conditions. The peculiar aspect of this setup is the capability of a fine-tuned gas dosage and a fast dynamic chamber pressure control, coupled with current and voltage sensing within a modified cryostat. To illustrate the capabilities of our system we have characterised both p+-type mesoporous silicon (meso-PS) membranes and nano-crystalline mesoporous titanium dioxide (nc-TiO2) films. In particular, as a main topic is presented a well-resolved characterization of mesoporous silicon electrical conductivity changes induced by presence of ethanol. At low pore filling level adsorbate-shunted conduction is avoided, while dielectric screening effects on frozen doping centres are observable. Beside we presented observation of mesoporous titanium dioxide photo-conductivity as a function of different gas pressure reporting opposite effects of relatively low- and high-pressure regimes. High reproducibility provided by the system is discussed as a final remark.