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Porous Materials (porous + material)
Selected AbstractsModeling of a Constrained Porous Material with an InclusionPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Pasquale Giovine Prof. Dr. A recently developed theory allows to describe a porous solid with very large lacunae partially, or totally, filled by a uid inclusion like an atypical immiscible mixture which consists of a solid with an ellipsoidal microstructure and of a classical fluid. Here we investigate the condition of saturation when the fluid inclusion is incompressible. [source] Dr Olivier Coussy, Scientist and Engineer of the Mechanics and Physics of Porous Materials (1953,2010)INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2010Franz-Josef Ulm No abstract is available for this article. [source] High-Pressure Device for Fluid Extraction from Porous Materials: Application to Cement-Based MaterialsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Martin Cyr A high-pressure device, reaching an axial pressure of 1000 MPa, intended to the extraction of the pore solution of rigid and slightly porous materials, has been developed to improve the efficiency of extraction. This paper gives an application of fluid extraction from mortars made with Portland cement. It includes an experimental study of the performance of the apparatus, and an analysis of the results in terms of efficiency of extraction, repeatability of measurement, and effect of the squeezing pressure on the pore solution composition. Results shows that: (1) the squeezing efficiency using our apparatus is higher than those found in the literature; (2) the measurement uncertainty ranges between 1.5% and 14%; (3) no significant effect of pressure (up to 1000 MPa) is observed for concentrations of Ca, Na, K, and Si. This paper suggests conducting extraction at 1000 MPa, especially on old concrete or concrete made with low W/C ratios. [source] Structure Characterization of HSQ Films for Low Dielectrics Uses D4 as Sacrificial Porous MaterialsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2007Guiqin Yin Hydrogensilsesquioxane (HSQ) (low- k) films were prepared by spin-on deposition using D4 (octamethyl cyclotetrasiloxane) as a sacrificial porous material. The dielectric constant of silica films significantly changed from 3.0 to 2.2. Fourier transform infrared spectroscopy was used to identify the network structure and cage structure of the Si,O,Si bond and other bonds that may appear. We studied the structural and electrical properties of the spin-coated films prepared by mixing HSQ and D4 films after oxygen plasma exposure for 5 min, and studied the structural recovery of the damage by annealing at 350°C for 1.5 h in a nitrogen (N2) ambient. This structure results in significant lowering of the dielectric constant (k) on annealing at 350°C for 1.5 h in an N2 ambient and improvement in the leakage current density. [source] 3rd Workshop on Semiconductor Nanodevices and Nanostructured Materials (NanoSemiMat-3)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2004E. F. da Silva Jr. The 3rd Workshop on Semiconductor Nanodevices and Nanostructured Materials (NanoSemiMat-3) took place in Salvador, Bahia, Brazil, 24,27 March 2004. The NanoSemiMat network is part of the Brazilian Initiative on Nanoscience and Nanotechnology (N&N). The papers include the following topics: Photodetectors, Lasers and LEDs, Porous Materials, New Materials, New Technologies, Molecular Technology and Interfaces, Nanostructured Materials and Nanobiotechnology. The presentations reflect theoretical and experimental research on nanostructured semiconductor materials such as III,V and II,VI, Si and SiC based nanodevices, wide gap materials, ceramics, polymers, porous materials, optical and transport properties of low-dimensional structures, magnetic nanostructures and structures under the influence of high fields, spintronics and sensor applications. This issue is devoted to Prof. J. R. Leite, Sao Paulo, former Regional Editor of physica status solidi and Guest Editor in memoriam of the present Proceedings. [source] Preface: phys. stat. sol. (c) 1/S2PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2004E. F. da Silva Jr. The papers in this special issue of physica status solidi (c) are selected manuscripts including diverse research lines presently in development in the ambit of the NanoSemiMat network in Brazil. The 3rd Workshop on Semiconductor Nanodevices and Nanostructured Materials (NanoSemiMat-3) took place in Salvador, Bahia, Brazil, at the Catussaba Resort Hotel, during the period of 24,27 March 2004. The NanoSemiMat network is part of the Brazilian Initiative on Nanoscience and Nanotechnology (N&N), with strategic cooperative research support in this area. The initiative started in 2001, through the formation of four research networks nationwide in different scientific fields associated to NanoScience and Nanotechnology (N&N). The 3rd Workshop on Nanodevices and Nanostructured Materials (NanoSemiMat-3) is an evolution of the two previous meetings which were held in Recife, PE, Brazil and Natal, RN, Brazil in 2002 and 2003, respectively. The meeting comprised 16 invited plenary talks, each 30 minutes long, given by eminent researchers from Brazil, Canada, France, Germany and the United States of America. These invited talks extend through different topics of N&N associated to Nanodevices and Nanostructured Materials: Photodetectors, Lasers and LEDs, Porous Materials, New Materials, and New Technologies, among others. There were short talks presented by representatives of the other N&N networks in Brazil dealing with Molecular Technology and Interfaces, Nanostructured Materials and Nanobiotechnology. Also a poster session, with about 60 presentations, highlighted the main research activities presently being developed by the network members at the different sites which constitute the NanoSemiMat network. The presentations reflected theoretical and experimental research lines which lead to the development of basic and applied research in nanostructured semiconductor materials such as III,V and II,VI, Si and SiC based nanodevices, wide gap materials, ceramics, polymers, porous materials, optical and transport properties of low dimensional structures, magnetic nanostructures and structures under the influence of high fields, spintronics and sensor applications. The participants of the workshop came from 20 research institutions within Brazil and from 7 research laboratories and universities in Europe and North America. In total about 120 researchers, members of the network, invited researchers, representatives of supporting and funding agencies in Brazil, undergraduate and graduate students, technical staff and supporting personal as well as researchers from complementary fields were present. The realization of the NanoSemiMat-3 was possible due to the financial support of the Brazilian Ministry of Science and Technology (MCT) and the Brazilian National Research Council (CNPq) and the logistic support of Federal University of Bahia. All activities during the NanoSemiMat-3 were open to the general public with interest in nanoscience and nanotechnology. In this third workshop of the series, we highlight the expansion of its format, with plenary and invited talks, poster sessions, as well as the presence of seven invited speakers from abroad. We expect that the continuation of the NanoSemiMat series will be a forum for discussions of state-of-the-art research developed in Brazil on N&N and the multidisciplinary field of semiconductor nanodevices and nanostructured materials as well as its superposition to other branches of science. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cinchona Alkaloid,Metal Complexes: Noncovalent Porous Materials with Unique Gas Separation Properties,ANGEWANDTE CHEMIE, Issue 39 2010Prof. Smarte Poren: Zweikernige Aluminium-Cinchonin-Komplexe dienen als Bausteine zur Selbstorganisation chiraler Architekturen mit nichtkovalenten Wechselwirkungen (siehe Bild). Das flexible desolvatisierte Material mit Ultramikroporen ist ein selektives Adsorptionsmittel mit einzigartigen Eigenschaften, z.,B. hohen Affinitäten für H2, CO2 und CH4 und einer temperaturgeregelten Adsorption von N2. [source] ChemInform Abstract: Postsynthetic Modification Switches an Achiral Framework to Catalytically Active Homochiral Metal,Organic Porous Materials.CHEMINFORM, Issue 45 2009Mainak Banerjee Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Development of Porous Materials for Heterogeneous Catalysis: Kinetic Resolution of Epoxides.CHEMINFORM, Issue 15 2005Leilani L. Welbes Abstract For Abstract see ChemInform Abstract in Full Text. [source] Pectin-Derived Porous MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Robin Abstract Porous forms of pectin, a major industrial waste biomass polysaccharide, have been prepared by aqueous phase expansion routes (SBET>200,m2,g,1; Vpore>0.80,cm3,g,1). It was demonstrated that the aqueous phase acidity crucially influenced the properties of the porous pectin form. Preparation route selection allows direction of material textural and morphological properties, thought to be the result of polysaccharide configuration, and methyl ester group hydrolysis, believed to alter the lowest energy accessible metastable polysaccharide state during gel recrystallisation. The resulting low density amorphous powders or mouldable monoliths (,powder ,0.20,g,cm,3/,monolith ,0.07,g,cm,3) can be directly transformed by thermal carbonisation into low density mesoporous carbonaceous materials (e.g. , ,0.27,g,cm,3 (Tp=550,°C)), which possess textural and nanoscale material morphology reflective of the porous pectin precursor employed. Acidic gelation promotes methyl ester groups hydrolysis of the polysaccharide structure, generating carbons with unusual interdigitated rod-like nanoscale morphology. Importantly, the materials presented herein are produced directly from the parent porous pectin material, without the need for additive catalyst (or template) to yield highly mesoporous products (e.g. Vmeso,0.45,cm3,g,1; polydispersity (PD)>10,nm), with accessible tuneable functionally rich surfaces. Due to the high mesoporosity (>85,%), materials have potential application in chromatography, heterogeneous catalysis and large molecule adsorption strategies. [source] Novel TRIP-Steel/Mg-PSZ Composite,Open Cell Foam Structures for Energy AbsorptionADVANCED ENGINEERING MATERIALS, Issue 3 2010Christos G. Aneziris Porous materials have received extensive attention for energy absorption in the last years. In terms of this study austenitic TRIP-steel/Mg-PSZ composite,open cell foam structures are formed based on replicas using open-celled polyurethane foam as a skeleton with and without a supporting dense face (jacket) coating. Their compression strength as well as their specific energy absorption SEA has been registered as a function of the compressive strain. The zirconia addition has reinforced the composite material with the face coating up to a compressive strain of 50%. The stress-induced martensitic transformation of partially stabilized zirconia phases has been investigated as a function of the compressive strain by EBSD. The zirconia phase transformation is triggered already at low compressive strains below 2%. [source] Surface morphology engineering of metal-oxide films by chemical spray pyrolysisPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007J. Rodriguez Abstract The Chemical Spray Pyrolysis technique and a combination of sol-gel and spray pyrolysis techniques have been used in order to monitor the morphology of metal-oxide-based thin films to be used as functional materials. We can obtain surfaces from specular to rough-porous according to the physico-chemical conditions of the precursor/spraying solution. We have produced coatings of ZnO-based and NiOx -based coatings from alcoholic and aqueous solutions. A single glass, ITO-precoated glass or alumina was used as the substrate. Porous materials of WO3, WO3 -SnO2 and SnO2 have been produced by spraying either inorganic or metal alkoxide gels over a hot substrate. The morphologies of coatings were evaluated by either SEM or optical measurements. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Self-Assembly of p -Sulfonatocalix[4]arene and a Ag,hmt Coordination Polymer into a Porous StructureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2008Guo-li Zheng Abstract A novel porous material constructed from p -sulfonatocalix[4]arene molecules and a AgI coordination polymer has been structurally characterized. The porous supramolecular complex features a bilayer arrangement of p -sulfonatocalix[4]arene molecules linked by a AgI,hmt (hmt: hexamethylenetetramine) coordination polymer through metal,ligand bonding, hydrogen bonding and host,guest interactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Organosilica Materials with Bridging Phenyl Derivatives Incorporated into the Surfaces of Mesoporous Solids,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2008Andreas Kuschel Abstract An interesting class of materials is mesoporous organosilica materials containing a bridging, organic group along the pore-surface. Such materials are prepared from silsesquioxane precursors of the type (R,O)3Si-R-Si(OR,)3 where R is the bridging organic group of interest, in combination with a lyotropic phase as a template for the generation of the pores. A new silsesquioxane precursor, 1,3-bis-(trialkoxysilyl)-5-bromobenzene, and the related mesoporous organosilica material containing bromobenzene groups located at the pore walls are presented in the current publication. The latter precursor allows access to the derivatization reactions known for halogenated aromatic compounds. Materials containing phenyl derivatives can be obtained either by chemical modifications starting from the mentioned precursor on the molecular scale, or the modifications can be performed directly at the surfaces of the porous material. Materials with surfaces containing benzoic acid, styrene, and phenylphosphonic acid are described. [source] The influences of thermophysical properties of porous media on superadiabatic combustion with reciprocating flowHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2006Liming Du Abstract The influences of thermophysical properties of porous media on superadiabatic combustion with reciprocating flow is numerically studied in order to improve the understanding of the complex heat transfer and optimum design of the combustor. The heat transfer performance of a porous media combustor strongly depends on the thermophysical properties of the porous material. In order to explore how the material properties influence reciprocating superadiabatic combustion of premixed gases in porous media (short for RSCP), a two-dimensional mathematical model of a simplified RSCP combustor is developed based on the hypothesis of local thermal non-equilibrium between the solid and the gas phases by solving separate energy equations for these two phases. The porous media is assumed to emit, absorb, and isotropically scatter radiation. The finite-volume method is used for computing radiation heat transfer processes. The flow and temperature fields are calculated by solving the mass, moment, gas and solid energy, and species conservation equations with a finite difference/control volume approach. Since the mass fraction conservation equations are stiff, an operator splitting method is used to solve them. The results show that the volumetric convective heat transfer coefficient and extinction coefficient of the porous media obviously affect the temperature distributions of the combustion chamber and burning speed of the gases, but thermal conductivity does not have an obvious effect. It indicates that convective heat transfer and heat radiation are the dominating ways of heat transfer, while heat conduction is a little less important. The specific heat of the porous media also has a remarkable impact on temperature distribution of gases and heat release rate. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(5): 336,350, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20120 [source] An operator-split ALE model for large deformation analysis of geomaterialsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2007Y. Di Abstract Analysis of large deformation of geomaterials subjected to time-varying load poses a very difficult problem for the geotechnical profession. Conventional finite element schemes using the updated Lagrangian formulation may suffer from serious numerical difficulties when the deformation of geomaterials is significantly large such that the discretized elements are severely distorted. In this paper, an operator-split arbitrary Lagrangian,Eulerian (ALE) finite element model is proposed for large deformation analysis of a soil mass subjected to either static or dynamic loading, where the soil is modelled as a saturated porous material with solid,fluid coupling and strong material non-linearity. Each time step of the operator-split ALE algorithm consists of a Lagrangian step and an Eulerian step. In the Lagrangian step, the equilibrium equation and continuity equation of the saturated soil are solved by the updated Lagrangian method. In the Eulerian step, mesh smoothing is performed for the deformed body and the state variables obtained in the updated Lagrangian step are then transferred to the new mesh system. The accuracy and efficiency of the proposed ALE method are verified by comparison of its results with the results produced by an analytical solution for one-dimensional finite elastic consolidation of a soil column and with the results from the small strain finite element analysis and the updated Lagrangian analysis. Its performance is further illustrated by simulation of a complex problem involving the transient response of an embankment subjected to earthquake loading. Copyright © 2007 John Wiley & Sons, Ltd. [source] A viscoelastic model for the dynamic response of soils to periodical surface water disturbanceINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2006P. C. Hsieh Abstract In many instances soils can be assumed to behave like viscoelastic materials during loading/unloading cycles, and this study is aimed at setting up a viscoelastic model to investigate the dynamic response of a porous soil layer of finite thickness under the effect of periodically linear water waves. The waves and homogeneous water are described by potential theory and the porous material is described by a viscoelastic model, which is modified from Biot's poroelastic theory (1956). The distributions of pore water pressures and effective stresses of various soils such as silt, sand, and gravel are demonstrated by employing the proposed viscoelastic model. The discrepancies of the dynamic response between the simulations of viscoelastic model and elastic model are found to be strongly dependent on the wave frequency. Copyright © 2006 John Wiley & Sons, Ltd. [source] Solid,liquid,air coupling in multiphase porous mediaINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2003Lyesse Laloui Abstract This paper addresses various issues concerning the modelling of solid,liquid,air coupling in multiphase porous media with an application to unsaturated soils. General considerations based on thermodynamics permit the derivation and discussion of the general form of field equations; two cases are considered: a three phase porous material with solid, liquid and gas, and a two phase porous material with solid, liquid and empty space. Emphasis is placed on the presentation of differences in the formulation and on the role of the gas phase. The finite element method is used for the discrete approximation of the partial differential equations governing the problem. The two formulations are then analysed with respect to a documented drainage experiment carried out by the authors. The merits and shortcomings of the two approaches are shown. Copyright © 2003 John Wiley & Sons, Ltd. [source] Chemically induced deformation of a porous layer coupled with advective,dispersive transport.INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2001Analytical solutions Abstract In this paper a chemically induced deformation of porous material taking place during advective,dispersive transport of a chemical is considered. Linearized governing equations are derived and analytical solutions of 2 one-dimensional problems for a homogeneous layer with drained boundaries are developed. Numerical results for a particular clayey material and a chemical migrating through the layer showing distributions of concentration of chemical, changes in porosity of the material and pore fluid pressure, and evolution of settlement of the layer as functions of time are discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] A finite element solution of acoustic propagation in rigid porous mediaINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2005A. Bermúdez Abstract This paper deals with the acoustical behaviour of a rigid porous material. A finite element method to compute both the response to an harmonic excitation and the free vibrations of a three-dimensional finite multilayer system consisting of a free fluid and a rigid porous material is considered. The finite element used is the lowest order face element introduced by Raviart and Thomas, that eliminates the spurious or circulation modes with no physical meaning. For the porous medium a Darcy's like model and the Allard,Champoux model are taken into account. The numerical results show that the finite element method allows us to compute the response curve for the coupled system and the complex eigenfrequencies. Some of them have a small imaginary part but there are also overdamped modes. Copyright © 2004 John Wiley & Sons, Ltd. [source] Nanoporous Gold Leaf: "Ancient Technology"/Advanced Material,ADVANCED MATERIALS, Issue 21 2004Y. Ding A free-standing nanoporous gold (NPG) membrane is made by dealloying commercially available white-gold leaf in nitric acid (see Figure). This porous material has an unusual combination of characteristics in that it is metallic with a continuous crystal lattice throughout the porous network, and has a pore size that is adjustable via simple room-temperature post-processing. This ultra-high-surface-area material is potentially very useful for applications such as electrocatalysis and sensing. [source] Limitation in obtainable surface roughness of hardened cement paste: ,virtual' topographic experiment based on focussed ion beam nanotomography datasetsJOURNAL OF MICROSCOPY, Issue 2 2008P. TRTIK Summary Surface roughness affects the results of nanomechanical tests. The surface roughness values to be measured on a surface of a porous material are dependent on the properties of the naturally occurring pore space. In order to assess the surface roughness of hardened cement paste (HCP) without the actual influence of the usual sample preparation for nanomechanical testing (i.e. grinding and polishing), focussed ion beam nanotomography datasets were utilized for reconstruction of 3D (nanoscale resolution) surface profiles of hardened cement pastes. ,Virtual topographic experiments' were performed and root mean square surface roughness was then calculated for a large number of such 3D surface profiles. The resulting root mean square (between 115 and 494 nm) is considerably higher than some roughness values (as low as 10 nm) reported in the literature. We suggest that thus-analysed root mean square values provide an estimate of a ,hard' lower limit that can be achieved by ,artefact-free' sample preparation of realistic samples of hardened cement paste. To the best of our knowledge, this ,hard' lower limit was quantified for a porous material based on hydraulic cement for the first time. We suggest that the values of RMS below such a limit may indicate sample preparation artefacts. Consequently, for reliable nanomechanical testing of disordered porous materials, such as hardened cement paste, the preparation methods may require further improvement. [source] Structure Characterization of HSQ Films for Low Dielectrics Uses D4 as Sacrificial Porous MaterialsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2007Guiqin Yin Hydrogensilsesquioxane (HSQ) (low- k) films were prepared by spin-on deposition using D4 (octamethyl cyclotetrasiloxane) as a sacrificial porous material. The dielectric constant of silica films significantly changed from 3.0 to 2.2. Fourier transform infrared spectroscopy was used to identify the network structure and cage structure of the Si,O,Si bond and other bonds that may appear. We studied the structural and electrical properties of the spin-coated films prepared by mixing HSQ and D4 films after oxygen plasma exposure for 5 min, and studied the structural recovery of the damage by annealing at 350°C for 1.5 h in a nitrogen (N2) ambient. This structure results in significant lowering of the dielectric constant (k) on annealing at 350°C for 1.5 h in an N2 ambient and improvement in the leakage current density. [source] Measuring Permeability of Rigid Materials by a Beam-Bending Method: I, TheoryJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2000George W. Scherer When a saturated porous material is deformed, pressure gradients are created in the liquid, and the liquid flows within the pores to equilibrate the pressure. This phenomenon can be exploited to measure permeability: A rod of saturated porous material is instantaneously bent by a fixed amount, and the force required to sustain the deflection is measured as a function of time. The force decreases as the liquid flows through the pore network, and the rate of decrease depends on the permeability. This technique has been applied successfully to determine the permeability of gels, as well as their viscoelastic properties; in this paper the method is extended to ceramic materials, such as porous glass and cement paste. The theory has been modified to take account of the compressibility of the solid and liquid phases (whereas, those factors are negligible for gels). Analyses are presented for constant deflection, constant rate of deflection, and sinusoidal oscillation, where the solid phase is either purely elastic or viscoelastic, and the beam is either cylindrical or square. Experimental tests on Vycor® glass and cement paste will be presented in companion papers. [source] Physicochemical parameters and magnetic speciation of Iron in Nakivubo Channel and Lake Victoria watersLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2009Naziriwo Betty Bbosa Abstract Magnetic speciation technique was used for the determination of iron species in Nakivubo Channel and Lake Victoria waters. The method consisted of a column of supported Dowex 1-X18, 20,50 US mesh (Cl) surrounded by movable permanent magnets. Dowex was supported by a porous material to permit adequate passage of the eluent through the column. In the presence of an external magnetic field, enhanced capacity for adsorption of iron III was observed. The enhanced capacity is primarily due to the magnetic field produced and ion exchange sorption mechanism. The results show that, most of the Iron in Nakivubo Channel waters is in reduced ferrous form while, in the Lake Victoria waters, it exists in the oxidized ferric form. Physicochemical parameters for the field samples are discussed in this study. Turbidity levels in catchments with substantial vegetation were significantly lower than those without. pH values up to 13 was observed for some of the point source. The physicochemical parameters along Nakivubo Channel waters were relatively higher than the Lake Victoria waters indicating slow increasing pollution load along the Nakivubo Channel. [source] Preparation and Properties of Natural Sand Particles Reinforced Epoxy CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2007Gang Sui Abstract An epoxy composite using Cancun natural hydrophobic sand particle as filler material was fabricated in this study. Three point bending tests demonstrated an enhancement of 7.5 and 8.7% in flexural strength and flexural modulus, respectively, of epoxy composite containing 1 wt.-% sand particles without any chemical treatment involved, compared to the pristine epoxy. Scanning electron microscopy (SEM) studies revealed that the fracture toughness of the epoxy matrix was enhanced owing to the presence of sand particles in an epoxy/sand composite. Through dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) methods, it was found that the storage modulus (E,), glass transition temperature (Tg) and dimensional stability of the sand particles/epoxy composites were increased compared to the pristine epoxy. The friction behavior of epoxy/sand system reflected that the microstructure of epoxy composites was steady. These experimental results suggest that Cancun sand, as a freshly found natural micron porous material, may find promising applications in composite materials. [source] Unsaturated incompressible flows in adsorbing porous mediaMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 16 2003A. Fasano We study a free boundary problem modelling the penetration of a liquid through a porous material in the presence of absorbing granules. The geometry is one dimensional. The early stage of penetration is considered, when the flow is unsaturated. Since the hydraulic conductivity depends both on saturation and on porosity and the latter change due to the absorption, the main coefficient in the flow equation depends on the free boundary and on the history of the process. Some results have been obtained in Fasano (Math. Meth. Appl. Sci. 1999; 22:605) for a simplified version of the model. Here existence and uniqueness are proved in a class of weighted Hölder spaces in a more general situation. A basic tool are the estimates on a non-standard linear boundary value problem for the heat equation in an initially degenerate domain (Rend. Mat. Acc. Lincei 2002; 13:23). Copyright © 2003 John Wiley & Sons, Ltd. [source] Shock-melted material in the Krymka LL3.1 chondrite: Behavior of the opaque mineralsMETEORITICS & PLANETARY SCIENCE, Issue 2 2005Vira P. Semenenko The shock pressure, nominally in the range of 75,90 GPa, could only have been 30,35 GPa in a porous material like fine-grained matrix. The melted regions have an igneous texture and their silicates are zoned and unequilibrated. Large metal-troilite intergrowths formed in these regions. The metal has a nickel content corresponding to martensite and the troilite contains up to 4.2 wt% nickel. Melting must have been very short and cooling very fast (>100 °C/h at high temperature). The metal contains up to 0.7 wt% phosphorus. Abundant chromite crystals and sodium-iron phosphate glass globules are found in troilite. The differences in composition between the opaque phases found in the melted regions and those generally observed in unmetamorphosed chondrules are assigned to melting under closed system conditions. Surprisingly high Co concentrations (up to 13 wt%) were found in some metal grains in or at the periphery of melted regions. They likely resulted from sulfurization of metal by sulfur vapor produced during the shock. After solidification, at least one other shock led to mechanical effects in the melted regions. [source] A Poroelastic Mindlin-PlatePROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Anke Busse Dipl.Ing The numerical treatment of noise insulation of solid walls has been an object of scientific research for many years. The main noise source is the bending vibration of the walls usually modeled as plates. Generally, walls consist of porous material, for instance concrete or bricks. Therefore, a poroelastic plate theory is necessary. A theory of dynamic poroelasticity was developed by Biot using the solid displacements and the pore pressure as unknowns. After formulating the poroelastic theory for thick plates, Mindlin's theory, a variational principle for this poroelastic thick plate model is developed. This is the basis of a Finite Element formulation. [source] An Animal Study of a Newly Developed Skin-Penetrating Pad and Covering Material for Catheters to Prevent Exit-Site Infection in Continuous Ambulatory Peritoneal DialysisARTIFICIAL ORGANS, Issue 12 2009Masato Aoyama Abstract Because currently available peritoneal dialysis catheters are not sufficiently biocompatible with the skin and subcutaneous tissue at the site of penetration, exit-site infection due to pericatheter pocket formation caused by epidermal downgrowth over a long period of time has increasingly become a problem. We developed a new, biocompatible, segmented polyurethane porous material and devised a novel skin-penetrating pad, the form and material of which we optimized for application in peritoneal dialysis catheters. For the extent of tissue ingrowth into this porous material to be examined, test materials with different pore diameters were inserted into hollow silicone tubes and implanted in the subcutaneous tissue of a goat. Four weeks later, the tubes were extracted, and, after the extent of granulation tissue ingrowth was measured, histopathological evaluation was made. Our novel skin-penetrating pad has three disklike layers of the segmented polyurethane material with different pore sizes, into the center of which a polyurethane catheter is inserted. These pads were implanted in the skin of a goat and clinically observed over a 2-year period, after which they were extracted and histopathologically analyzed. In accordance with actual clinical procedures, a commercial CAPD catheter equipped with our skin-penetrating pad was left indwelling in a goat for 4 months, and the performance of the pad was evaluated after repeated periodic infusion and drainage of the dialysate in and out of the abdominal cavity. There was no inflammation of the ingrown tissue in the pores of the segmented polyurethane material as well as the surrounding tissue, which indicated favorable tissue biocompatibility. The extent of tissue ingrowth was greater as the pore size of the material was larger, and the tissue tended to be mature, mainly consisting of collagenous fibers. The skin-penetrating pad using the porous material, of which tissue ingrowth was thus optimized, tightly adhered to the goat skin throughout the 2-year experimental period without any special wound care such as cleansing or disinfection. The performance of the skin-penetrating pad was similarly favorable when attached to a commercial continuous ambulatory peritoneal dialysis catheter. The newly developed segmented polyurethane porous material had excellent tissue biocompatibility and tissue ingrowth. The skin-penetrating pad devised by using this porous material did not cause epidermal downgrowth, suggesting that it may be effective for the prevention of exit-site infection. [source] | |||||||||||||||||||||||||