The Experts below are selected from a list of 15528 Experts worldwide ranked by ideXlab platform
Zhaohui Chen - One of the best experts on this subject based on the ideXlab platform.
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Fabrication and characterization of porous silicon oxycarbide ceramics from silicone resin pyrolysis
Rare Metals, 2011Co-Authors: Zhaohui ChenAbstract:Porous silicon oxycarbide ceramics were fabricated by pyrolysis of silicone resin filled with cured polysiloxane powders. Silicone resin content has great effects on Pore structure and flexural strength of porous ceramics. Higher silicone resin content leads to higher linear shrinkage, fracture strength and Average Pore Size and lower open porosity. Heating rate during pyrolysis has indiscernible effects on open porosity and fracture strength. However, Average Pore Size is affected, to a great extent, by heating rate. When a fast pyrolysis rate was employed, large Pores are obtained. The fracture surfaces of porous ceramics were observed.
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fabrication and characterization of nanoporous sio2 ceramics via pyrolysis of silicone resin filled with nanometer sio2 powders
Ceramics International, 2010Co-Authors: Zhaohui ChenAbstract:Abstract Mesoporous SiO 2 ceramics are fabricated by pyrolysis of silicone resin filled with nanometer SiO 2 powders in air at 1273 K. With the increase of shaping pressure, open porosity and Average Pore Size decrease, while bulk density and fracture strength are improved. The fracture surface of porous SiO 2 ceramics was observed.
Gongming Yang - One of the best experts on this subject based on the ideXlab platform.
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A sol–gel-derived α-Al2O3 crystal interlayer modified 316L porous stainless steel to support TiO2, SiO2, and TiO2–SiO2 hybrid membranes
Journal of Materials Science, 2011Co-Authors: Zupei Yang, Nongxue Qiu, Gongming YangAbstract:A homogeneous α-Al2O3 crystal membrane was fabricated by the sol–gel technique on 316L porous stainless steel (PSS) substrate with an Average Pore Size of 1.0 μm. The preparation process was optimized by carefully choosing the binder, the concentrations of the casting solutions and the sintering temperatures of the membranes. Compared to methylcellulose and polyethylene glycol 20000, polyvinyl alcohol 1750 was found to be the most effective binder to fabricate a homogeneously structured Al2O3 membrane without defects. The concentration to prepare an uniform coverage membrane with a thickness of ~10 μm was 0.032 mol/L. When sintered at 1000 °C, γ-Al2O3 membrane with ~3 μm grains was obtained. When sintered at 1200 °C, γ-Al2O3 completely transformed into α-Al2O3 and the grains grew to ~5 μm. Accordingly, the process was applied to a bigger Pore-Sized PSS with an Average Pore Size of 1.5 μm to fabricate an α-Al2O3 intermediate layer to initially modify its surface. A single α-Al2O3 crystal layer with a thickness of ~5 μm and an Average Pore Size of 0.7 μm was achieved. Subsequently, TiO2, SiO2, and TiO2–SiO2 hybrid membranes were tried on the modified PSS. Defect-free microfiltration membranes with Average Pore Sizes of ~0.3 μm were readily fabricated. The results indicate that the sol–gel method is promising to initially modify the PSS substrates and the sol–gel-derived α-Al2O3 crystal layer is an appropriate intermediate layer to modify the PSS and to support smaller grain-Sized top membranes.
Carlo G. Pantano - One of the best experts on this subject based on the ideXlab platform.
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Porous Silicon Oxycarbide Glasses
Journal of the American Ceramic Society, 2005Co-Authors: Anant K. Singh, Carlo G. PantanoAbstract:High-surface-area silicon oxycarbide gels and glasses were syntheSized from mixtures of methyldimethoxysilane (MDMS) and tetraethoxysilane (TEOS) through acidic hydrolysis and condensation. A surface area of ∼275 m2/g and an Average Pore Size of ∼30 A was obtained for a 50% MDMS-50% TEOS glass at 800°C under a flowing argon atmosphere. The Average Pore Size was increased by aging the precursor gels in ammonium hydroxide. The increased Average Pore Size and the higher strength of the mesoporous gel network enhanced the surface-area stability of the glasses; in this case, surface areas >200 m2/g were retained at 1200°C under an argon atmosphere. 29Si MAS NMR spectra revealed that an oxycarbide structure was established in the mesoporous glasses obtained after pyrolysis of the aged gels. The role of carbon was demonstrated by comparing the surface-area stability of the oxycarbide glasses with that of pure silica and that of oxycarbide glasses where all the carbon groups were removed through low-temperature plasma-oxidation treatments. In the absence of carbon, the thermal stability of the surface area decreased dramatically.
Y.s. Lin - One of the best experts on this subject based on the ideXlab platform.
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Evolution of Pore Size distribution and Average Pore Size of porous ceramic membranes during modification by counter-diffusion chemical vapor deposition
Journal of Membrane Science, 1997Co-Authors: George Xomeritakis, Jonghee Han, Y.s. LinAbstract:Abstract The modification of porous ceramic membranes by counter-diffusion chemical vapor deposition (CVD) is studied theoretically and experimentally. Numerical simulations of the evolution of the membrane permeance, Average Pore Size and Pore Size distribution as a function of extent of modification are presented and compared with experimetal data. It is found that the change of the Average Pore Size of the membranes after modification strongly depends on the initial Pore Size distribution of the membrane, CVD reaction kinetics and characterization method. Experimental data suggest that CVD of zirconia (and yttria) inside porous ceramic membranes by reaction of zirconium (and yttrium) chlorides with steam/air at elevated temperatures proceeds by quasi-zero reaction kinetics with respect to the oxidant, typical of non-stoichiometric supply of the reactants from opposite sides of the membrane. Under such conditions, CVD modification may result in a modest increase of the Average Pore Size of coarse-Pore ceramic membranes as suggested by numerical calculations and experimental data.
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A theoretical analysis on Pore Size change of porous ceramic membranes after modification
Journal of Membrane Science, 1993Co-Authors: Y.s. LinAbstract:Abstract The evolution of the Pore Size distribution and the Average Pore Size of porous ceramic membranes during a modification process of deposition of solids in the membrane Pores are analyzed using a method based on the population balance theory. The theoretical analysis suggests that the results of modification on the Pore Size change of ceramic membrane are strongly determined by the initial Pore Size distribution of the membrane and the Pore narrowing kinetics of the modification process. For a ceramic membrane having a Pore Size distribution with a large amount of smaller Pores and a modification process with a Pore Size independent Pore narrowing rate, the modification could result in an increase in the Average Pore Size, unless the porosity (or permeability) of the membrane is substantially reduced. The Average Pore Size of ceramic membranes can be reduced if the membranes have rather uniform initial Pore Size distribution, or if the modification process has a Pore narrowing kinetics which gives a Pore narrowing rate being proportional to the Pore Size.
Zhihong Zhao - One of the best experts on this subject based on the ideXlab platform.
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Time domain-NMR studies of Average Pore Size of wood cell walls during drying and moisture adsorption
Wood Science and Technology, 2020Co-Authors: Zhihong ZhaoAbstract:The change in the Pore Size of cell walls affects many physical properties of wood. In this paper, the dynamic changes in the Pore Size of wood cell walls during drying and moisture adsorption were studied at four relative humidities. The results showed that the Average Pore Size of cell walls of Qingpi poplar (Populus- platyphylla var. glauca) was larger than that of pine wood (Pinus sylvestris var. mongolica Litv.) under the same experimental conditions, and the changes in Pore Size of Qingpi poplar cell walls were more sensitive to ambient humidity no matter whether during drying or moisture adsorption. Moreover, the Average Pore Size of cell walls at saturated-water state is about 2.5 times of the Average Pore Size of cell walls when woods reached the moisture absorption equilibrium from the oven-dry state. This article is useful for the wood manufacture industry and for wood modification. It is not only important for wood processing and utilization but also for the research on other porous materials.
