Porous silicon carbide (SiC)‐based ceramics are widely used in numerous applications of technical importance owing to their exceptional structural (e.g., excellent chemical, mechanical, and thermal stability) and functional (e.g., controlled electrical resistivity) properties. Porous SiC with controlled electrical resistivity is required for various advanced applications, for example, power electronic devices, semiconductor processing parts, fusion reactors, thermoelectric energy conversion, electromagnetic shielding, and environmental applications such as heatable filters. The electrical properties of sintered porous SiC are significantly affected by its chemical composition, processing conditions, and microstructure. This article reviews the influence of certain critical factors, such as the polytype, doping conditions, porosity (%), additive composition (oxide additives, element additives, metal nitride/carbide additives, etc.), and processing conditions on the electrical resistivity of porous SiC. Novel applications of porous SiC with controlled electrical resistivity are also discussed in this review.
19 June 2023 in Journal of the Korean Ceramic Society
We introduced a modified sol-gel method using polyvinyl alcohol (PVA) as an additive to improve the permeability of γ-Al2O3 membranes by minimizing the thickness of the selective layer and maximizing the porosity. First, the analysis revealed that the thickness of γ-Al2O3 decreased as the concentration of PVA increased in the boehmite sol. Second, the properties of the γ-Al2O3 mesoporous membranes were greatly influenced by the modified route (method B) compared to the conventional route (method A). The results showed that the porosity and surface area of the γ-Al2O3 membrane increased, and the tortuosity decreased considerably using method B. This effect was attributed to the adsorption of PVA molecules on the surface of the boehmite particles, which depended on the synthesis route. The experimentally determined pure water permeability trend and the Hagen–Poiseuille mathematical model confirmed that the modified method improved the performance of the γ-Al2O3 membrane. Finally, the γ-Al2O3 membrane fabricated via a modified sol-gel method with a pore size of 2.7 nm (MWCO = 5300 Da) exhibited a pure water permeability of over 18 LMH/bar, which is three times higher than that of the γ-Al2O3 membrane prepared using the conventional method.
Membrane technology has become a highly efficient separation technology for industrial applications over the past few decades. The key requirements for porous ceramic membranes are mechanical stability, controlled pore morphology, and high permeability. However, only a few studies have been conducted to optimise commercial membrane filters. In this study, a multichannel cylindrical-tube-type support with a microfiltration (MF) coating was prepared. To design a reliable porous structure and avoid shrinkage defects, the support layer was extruded using a combination of different-sized Al2O3 particles. The alumina microfiltration coating was developed using multiple dip-coatings to control the membrane thickness. An inorganic surface modification was conducted for the first time on an extruded membrane using a SiO2 sol-gel technique to enhance the antifouling properties. Furthermore, the membrane properties were investigated with scanning electron microscopy, mercury porosimetry, and a dead-end microfiltration system.
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Korea Institute of Materials Science, Changwon, Gyeongnam, 51508, Republic of Korea
Korea Institute of Materials Science, Changwon, Gyeongnam, 51508, Republic of Korea