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Pore Walls (pore + wall)

Distribution by Scientific Domains

Polymers and Materials Science	53%
Chemistry	33%

Selected Abstracts

ChemInform Abstract: Facile Method to Synthesize Mesoporous Multimetal Oxides (ATiO3, A: Sr, Ba) with Large Specific Surface Areas and Crystalline Pore Walls.

CHEMINFORM, Issue 32 2010
Xiaoxing Fan
Abstract Mesoporous SrTiO3 and BaTiO3 are prepared based on the evaporation-induced self-assembly approach using in-situ inorganic pore-makers (carbonate). [source]

Arrays of Inorganic Nanodots and Nanowires Using Nanotemplates Based on Switchable Block Copolymer Supramolecular Assemblies

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
Bhanu Nandan
Abstract Here, a novel and simple route to fabricate highly dense arrays of palladium nanodots and nanowires with sub-30,nm periodicity using nanoporous templates fabricated from supramolecular assemblies of a block copolymer, polystyrene- block -poly(4-vinylpyridine) (PS- b -P4VP) and a low molecular weight additive, 2-(4,-hydroxybenzeneazo) benzoic acid (HABA) is demonstrated. The palladium nanoparticles, which are directly deposited in the nanoporous templates from an aqueous solution, selectively migrate in the pores mainly due to their preferential attraction to the P4VP block covering the pore wall. The polymer template is then removed by oxygen plasma etching or pyrolysis in air resulting in palladium nanostructures whose large scale morphology mirrors that of the original template. The method adopted in this work is general and versatile so that it could easily be extended for patterning a variety of metallic materials into dot and wire arrays. [source]

Growth of osteoblast-like cells on biomimetic apatite-coated chitosan scaffolds

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008
I. Manjubala
Abstract Porous scaffold materials that can provide a framework for the cells to adhere, proliferate, and create extracellular matrix are considered to be suitable materials for bone regeneration. Interconnected porous chitosan scaffolds were prepared by freeze-drying method, and were mineralized by calcium and phosphate solution by double-diffusion method to form nanoapatite in chitosan matrix. The mineralized chitosan scaffold contains hydroxyapatite nanocrystals on the surface and also within the pore channels of the scaffold. To assess the effect of apatite and porosity of the scaffolds on cells, human osteoblast (SaOS-2) cells were cultured on unmineralized and mineralized chitosan scaffolds. The cell growth on the mineralized scaffolds and on the pure chitosan scaffold shows a similar growth trend. The total protein content and alkaline phosphatase enzyme activity of the cells grown on scaffolds were quantified, and were found to increase over time in mineralized scaffold after 1 and 3 weeks of culture. The electron microscopy of the cell-seeded scaffolds showed that most of the outer macropores became sealed off by a continuous layer of cells. The cells spanned around the pore wall and formed extra cellular matrix, consisting mainly of collagen in mineralized scaffolds. The hydroxyproline content also confirmed the formation of the collagen matrix by cells in mineralized scaffolds. This study demonstrated that the presence of apatite nanocrystals in chitosan scaffolds does not significantly influence the growth of cells, but does induce the formation of extracellular matrix and therefore has the potential to serve for bone tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source]

Copper-filled macroporous Si and cavity underneath for microchannel heat sink technology

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008
F. Zacharatos
Abstract Thermal management in ICs becomes essential as integration density and total power consumption increase. The use of microchannels in high power density electronics cooling is a well-known technique for heat transfer. In this work we developed Cu-filled macroporous Si channels with a Cu-filled cavity underneath, which may be used as heat sinks in high power density electronics cooling. Macroporous Si is formed by electrochemical dissolution of bulk Si, while pore filling with copper is achieved by electro-deposition. Using appropriate design, the resulting composite material may be fabricated on selected areas on the silicon substrate for use as heat sink on Si. The surface area is defined by patterning. The macroporous Si structure is composed of either randomly distributed pores or pores arranged in two-dimensional (2-D) arrays, fabricated by pre-patterning the Si surface before anodization so as to form pore initiation pits. The pore size in this work was 5,m, while the porous layer and the cavity underneath had both a thickness of 40 ,m. Copper deposition proceeds first by filling the micro-cavity underneath the porous layer. This is achieved by linearly increasing the applied potential during electro-deposition. After full Cu-filling of the cavity, pore filling starts from the bottom of each pore and proceeds laterally, while no nucleation takes place on pore wall. In this way, homogeneous copper wires within pores may be fabricated. The Cu/Si composite material is appropriate for forming channels with improved heat transfer within the Si wafer. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Combined Analytical and Phonon-Tracking Approaches to Model Thermal Conductivity of Etched and Annealed Nanoporous Silicon

ADVANCED ENGINEERING MATERIALS, Issue 10 2009
Jaona Randrianalisoa
A combination of analytical and phonon-tracking approaches is proposed to predict thermal conductivity of porous nanostructured thick materials. The analytical approach derives the thermal conductivity as function of the intrinsic properties of the material and properties characterizing the phonon interaction with pore walls. [source]

Grain-scale permeabilities of faceted polycrystalline aggregates

GEOFLUIDS (ELECTRONIC), Issue 4 2006
J. D. PRICE
Abstract Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg,clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10,50% faceted. The relationship of their permeability (k) to porosity (,) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78,90% faceting. These materials showed much lower k for a given ,, with an apparent permeability threshold at ,c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low , with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt. [source]

Organosilica Materials with Bridging Phenyl Derivatives Incorporated into the Surfaces of Mesoporous Solids,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2008
Andreas 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]

Ordered Arrays of Mesoporous Microrods from Recyclable Macroporous Silicon Templates,

ADVANCED MATERIALS, Issue 16 2006
X. Chen
Ordered arrays of freestanding mesoporous microrods (see figure) are obtained from macroporous silicon templates with hydrophobized pore walls. The microrods can be removed from the template by simple mechanical lift-off. Since no wet-chemical etching step is involved, condensation of the rods is avoided and the template can be recycled. The hierarchical structures combine features on the nano- and microscale and have a well-controlled geometry. [source]

Cover Picture: Surfactant-Mediated Generation of Iso-Oriented Dense and Mesoporous Crystalline Metal-Oxide Layers (Adv. Mater.

ADVANCED MATERIALS, Issue 14 2006
14/2006)
Abstract For certain metal oxides (e.g., MoO3) ordered mesoporous films can be obtained with the nanocrystals in the pore walls being uniformly oriented with respect to the substrate by applying evaporation-induced self-assembly followed by heating. This surprisingly facile process, described by Smarsly and co-workers on p.,1827, works on different polar substrates (glass, metals, etc.) for oxides with anisotropic unit cells, based on the interaction with surfactants during nucleation ("soft-epitaxy"). [source]

Simulation of the dynamics of depth filtration of non-Brownian particles

AICHE JOURNAL, Issue 4 2001
V. N. Burganos
A new simulator for flow of aqueous suspensions and deposition of non-Brownian particles in granular media can predict the pattern of deposition and concomitant reduction in permeability as functions of depth, time and system parameters. The porous structure of the granular medium represented as a 3-D network of constricted pores considers the converging,diverging character of flow within pores. Using Lagrangian-type simulation the particle deposition rate was calculated. Gravity and drag, as well as hydrodynamic and physicochemical interactions between suspended particles and pore walls, were considered in calculating 3-D particle trajectories. Deposit configurations were computed, and the evolution of the pore structure was simulated at discrete time steps. Changes in the pore geometry and nature of the collector surface affect flow and trajectory computations directly. Clusters of deposited particles were allowed to become reentrained if exposed to shear stress higher than a critical value. Reentrained clusters, which moved through downstream pores, might redeposit downstream at suitable sites and cause clogging of sufficiently narrow pores. Particle clusters clogging pores have a finite permeability, which significantly affects the system's transient behavior. Clogged pores act as collectors of solitary particles and of reentrained clusters, and substantially affect the transient behavior of the filter. The loss of permeability was monitored by calculating pore and network hydraulic conductance at each time step. Numerical results for the loss of permeability, temporal evolution of filter efficiency, and specific deposit profiles are based on suspension flow simulations in a typical granular porous medium. [source]

Drug adsorption in human skin: A streaming potential study

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2003
Johanna Raiman
Abstract The objective of this study was to investigate the drug adsorption process in human skin using in vitro streaming potential measurements. Streaming potential is an electrokinetic phenomenon, which reflects both the charge density and the pore size of a membrane. Thus, the adsorption of charged solutes on the pore walls can be detected as a change of streaming potential, viz., as a change in the slope ,E/,P. In these streaming potential measurements, hydrophilic nadolol and luteinizing hormone-releasing hormone, and lipophilic propranolol and Nafarelin were used as model drugs. As could be expected, the hydrophilic drugs did not change the slope. The more lipophilic propranolol and Nafarelin, instead, changed the slope. Propranolol changed the slope gradually from negative to positive when the concentration was increased from 1 to 10 mM. With Nafarelin, a straight line with a slope of about 0 was obtained at pH 7.3 and an ascending curve at pH 4.2. These results indicate that the negative charges on the pore walls of human skin are blocked by adsorption of the lipophilic cations. The adsorption of lipophilic cations in the skin alters the permselectivity of the skin, which, in turn, may lead to the inhibition of electroosmotic flow across the skin during iontophoresis and to the shut down of transdermal drug permeation of higher molecular weight drugs. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2366,2372, 2003 [source]

A Study on Biomineralization Behavior of N -Methylene Phosphochitosan Scaffolds

MACROMOLECULAR BIOSCIENCE, Issue 10 2004
Yu Ji Yin
Abstract Summary: Biomimetic growth of calcium phosphate over natural polymer may be an effective approach to constituting an organic/inorganic composite scaffold for bone tissue engineering. In this work, N -methylene phosphochitosan (NMPCS) was prepared via formaldehyde addition and condensation with phosphoric acid in a step that allowed homogeneous modification without obvious deterioration in chitosan (CS) properties. The NMPCS obtained was characterized by using FT-IR and elemental analysis. The macroporous scaffolds were fabricated through a freeze-drying technique. A comparative study on NMPCS and CS scaffold biomimetic mineralization was carried out in different media, i.e, a simulated body fluid (SBF) or alternative CaCl2 and Na2HPO4 solutions respectively. Apatite formation within NMPCS and CS scaffolds was identified with FT-IR, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffractometery (XRD). The results revealed alternate soaking of the scaffolds in CaCl2 and Na2HPO4 solutions was better than soaking in SBF solution alone in relation to apatite deposition on the scaffold pore walls. Biomineralization provides an approach to improve nature derived materials, e.g., chitosan derivative NMPCS properties e.g., compressive modulus, etc. SEM image of a NMPCS/apatite composite scaffold. [source]

Preparation and characterization of pore wall-functionalized three-dimensionally ordered macroporous syndiotactic polystyrene

POLYMER ENGINEERING & SCIENCE, Issue 2 2009
Xu Zhang
A versatile method for the modification of three-dimensionally ordered macroporous (3DOM) highly syndiotactic polystyrene via chloromethylation at the pore walls has been demonstrated. This was followed by reaction with dimethylamine to establish a versatile approach to functionalization of such macroporous polymers. High syndiotacticity of 3DOM sPS is necessary for maintenance of the morphology of the original ordered pore structure after chloromethylation. The relative content of chloromethyl groups was shown to be 1.89 mmol/g3DOM sPS by TG-titration. The functionalized 3DOM sPS was characterized by SEM, FT-IR, and DSC to demonstrate that chloromethylation had occurred at the pore walls and that the dimethylamino moiety had replaced the chlorine atom of the chloromethyl group. DSC examination of the modified polymer indicated that the crystallinity of 3DOM sPS is little affected by functionalization. Thus the excellent properties of sPS are retained by the functionalized material. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers [source]

Evaluation of porous catalytic membranes operated in pore-flow-through mode for hydrogenation of ,-methylstyrene

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010
Daniel Urbanczyk
Abstract A study of the catalytic membrane contactor operated in pore-flow-through (PFT) mode was carried out for hydrogenation of ,-methylstyrene (AMS) to cumene over palladium as a test reaction. By applying a metalorganic chemical vapour deposition method, the catalyst was deposited as nanoparticles on the pore walls of porous alumina capillaries. Experiments were performed with up to six individual Pd-activated capillaries in a laboratory-scale reactor set-up and with capillary bundles in a small pilot plant. The influence of the operating parameters on the reactor performance such as temperature (303,333 K), hydrogen pressure (5,10 bar), transmembrane flux (up to 200 l·m,2·min,1), pore size of the capillaries (0.6,3.0 µm) and concentration of AMS in n-heptane used as solvent was investigated. Moreover, the performance of the PFT-system was compared to that of conventional reactors (e.g. fixed bed, trickle bed, bubble column, stirred tank) and novel reactor designs (catalytic membrane contactor in diffuser mode, monolith reactor) based on published data. It is shown that the PFT principle enables very high activity, comparable with a suspended powder catalyst in a stirred tank reactor and, at the same time, an excellent space time yield. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Preparation of Ni-Based Metal Monolithic Catalysts and a Study of Their Performance in Methane Reforming with CO2

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 6 2008
Kai Wang
Abstract A series of Ni/SBA-15/Al2O3/FeCrAl metal monolithic catalysts with Ni loadings varying between 3,% and 16,% were prepared, and their structure was characterized by various techniques. The catalytic activity of the catalyst for methane reforming with CO2 leading to synthesis gas was evaluated using a fixed-bed reactor. The results indicate good catalytic activity of the Ni/SBA-15/Al2O3/FeCrAl samples under the reaction conditions. The catalyst with a Ni loading of 8.0,% displays excellent activity and stability at 800,°C over 1400,h time on stream. After reaction, the hexagonal mesoporous structure of SBA-15 is still present and the pore walls of SBA-15 prevent the aggregation of nickel. Interactions between NiO, SBA-15, and the Al2O3/FeCrAl support modify the redox properties of the Ni/SBA-15/Al2O3/FeCrAl catalysts. [source]