(650d) Silicon Carbide Sintered Supports and Silicon Carbide Membranes for Gas Separation Applications

Efficient separation of H₂ under high temperatures and pressures is fundamental to the development of clean energy industry, and has driven the research on inorganic membranes for two decades. Although several types of nanoporous membranes have been prepared, the fabrication of high-temperature and steam-stable inorganic membranes with high fluxes and large separation factors still remains a challenge. Of all the potential membrane materials, silicon carbide (SiC) is particularly promising due to its high temperature/corrosion resistance, high thermal conductivity, and excellent chemical/mechanical stability. In this work, we prepared highly permeable, mechanically strong porous SiC tubular supports for fabrication of nanoporous SiC membranes. We systematically investigated the effects of sintering temperature, the amount of sintering aids, the composition of the starting particles, and surface modifications on the transport characteristics of sintered SiC supports. The best SiC supports exhibit a He permeance of 5.82×10^-5 mol•m^-2•Pa^-1•s^-1, which is two orders of magnitude larger than the permeance of supports we previously prepared, and also 3~10 times larger than those of similar supports reported by other groups. These substrates are also mechanically strong, as manifested by their Vickers hardness tests. We have fabricated nanoporous SiC membranes on such supports by two different techniques: (i) the pyrolysis of thin pre-ceramic polymer films coated using slip-casting and dip-coating techniques, combined with a sacrificial polystyrene inter-layer method; (ii) the pyrolysis of pre-ceramic polymer films formed by the initiated chemical vapor deposition (iCVD) technique. These SiC membranes show good improvement on both permeance and selectivity compared to our previous membranes.