Porous microstructures

Chul, M Phillips, R McCarthy, M, Measurement of the Porous Microstructure of Hydrogels by Nuclear Magnetic Resonance, Journal of Colloid and Interface Science 174, 336, 1995. Cohen, Y Ramon, O Kopeknan, IJ Mizrahi, S, Characterization of Inhomogeneous Polyacrylamide Hydrogels, Journal of Polymer Science Part B Polymer Physics 30, 1055, 1992. Cohen Addad, JP, NMR and Statistical Structures of Gels. In The Physical Properties of Polymeric Gels Cohen Addad, JP, ed. Wiley Chichester, UK, 1996 39. 

The use of chemically assembled multiclusters as precursors to solids with metastable porous microstructures constitutes a new approach to the preparation of heterogeneous hydrogenation... 

Corbin SF, Lee J, and Qiao X. Influence of green formulation and pyrolyzable particulates on the porous microstructure and sintering characteristics of tape cast ceramics. J. Am. Cer. Soc. 2001 84 41 17. 

Sponge Porous microstructure with walls that are generally anisotropic but with pores and walls that vary in size... 

Faraday s constant (96,487 C/mol) overpotential total current current density exchange current density ratio of ohmic constriction to inter-facial resistance surface exchange coefficient volume-specific interfacial resistance in a composite thickness utilization length characteristic length of a porous microstructure... 

By far the most studied PolyHIPE system is the styrene/divinylbenzene (DVB) material. This was the main subject of Barby and Haq s patent to Unilever in 1982 [128], HIPEs of an aqueous phase in a mixture of styrene, DVB and nonionic surfactant were prepared. Both water-soluble (e.g. potassium persulphate) and oil-soluble (2,2 -azo-bis-isobutyronitrile, AIBN) initiators were employed, and polymerisation was carried out by heating the emulsion in a sealed plastic container, typically for 24 hours at 50°C. This yielded a solid, crosslinked, monolithic polymer material, with the aqueous dispersed phase retained inside the porous microstructure. On exhaustive extraction of the material in a Soxhlet with a lower alcohol, followed by drying in vacuo, a low-density polystyrene foam was produced, with a permanent, macroporous, open-cellular structure of very high porosity (Fig. 11). 

PolyHIPE has found a successful application in the field of solid phase peptide synthesis (SPPS), where the highly porous microstructure acts as a support material for a polyamide gel [134]. The polystyrene matrix is functionalised to give vinyl groups on its internal surfaces, and is then impregnated with a DMF solution of N, JV -dimethylacrylamide, acryloylsarcosine methyl ester, crosslinker and initiator. Polymerisation grafts the soft gel onto the rigid support, giving a novel composite material (Fig. 16). 

Polytetrafluoroethylene suture is composed of expanded polytetrafluoroethylene (ePTFE), resulting in a porous microstructure having longitudinally oriented nodes and fibrils. The suture is sold by W. L. Gore Associates, Inc. under the trade name Gore-Tex Suture. 

Detailed description of a porous microstructure is an essential prerequisite for unveiling the influence of pore morphology on the underlying two-phase behavior. This can be achieved either by 3-D volume imaging or by constructing a digital microstructure based on stochastic reconstruction models. Non-invasive techniques, such as X-ray micro-tomography, are the popular methods for 3-D... 

Pad Porosity/Density Type I, II, and III pads all have pores although their microstructures are different. Type IV pads (noncell, nonporous, solid) do not have native porous microstructure except those generated by the conditioning process. Typical physical properties of ICIOOO pad (type III, porous) and IC2000 pad (type IV, noncell, nonporous, solid) are listed in Table 5.2. 

MPa) do not differ substantially from each other. In spite of the fact that the gel films (especially the homopolymers) show a porous microstructure, the H values are much larger ( 50%) than those obtained for conventionally crystallized samples... 

Ribbonlike parallel-ordered anisotropic domains that can also occur as folded structures Lenticular anisotropic domains of various sizes that are not aligned parallel to the particle surface Ribbon and lenticular anisotropic domains of various sizes in curved and irregular layered arrangements Porous microstructure with walls that are generally anisotropic but with pores and walls that vary in size Ribbon and lenticular anisotropic domains arranged in concentric patterns to form shothke coke Isotropic carbon form closely associated with parent hquor. Higher in volatile matter than incipient mesophase... 

Traditional ceramics are characterized by mostly silicate-based porous microstructures that are quite coarse, nonuniform, and multiphase. They are typically formed by mixing clays and feldspars, followed by forming either by slip casting or on a potter s wheel, firing in a flame kiln to sinter them, and finally glazing. 

Kuhs, W.F., Genov, G.Y., Goreshnik, E., Zeller, A., Techmer, K., and Bohrmann, G. 2004. The impact of porous microstructures of gas hydrates on their macroscopic properties. International Journal of Offshore and Polar Engineering, 14 305-309. 

Another reason is the scattering of light by surface and volume imperfections [211-215]. Such imperfections include surface roughness, rough internal boundaries, and density fluctuations which stem from crystallinity, porous microstructure, pinholes, cracks, splashes, microdust, etc. 

Three of the SEM micrographs for the titania foams are shown in Fig. 4.5. The magnifications are shown in each figure. As can be observed, the Ti02 foam exhibits a very porous microstructure with pore diameters ranging from 1.5 to 3.0)dm (mean values). Furthermore, the observed morphological features are quite different from those verified for a titania sample prepared by using a similar experimental approach previously reported [9]. 

Jung, Y.S., Cavanagh, A.S., Gedvilas, L., Widjonarko, N.E., Scott, I.D., Lee, S.H., Kim, G.H., George, S.M., Dillon, A.C., 2012. Improved functionality of lithium-ion batteries enabled by atomic layer deposition on the porous microstructure of polymer separators and coating electrodes. Adv. Energy Mater. 2, 1022-1027. 

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