One-step deposition of ultrafiltration SiC membranes on macroporous SiC supports

We fabricated nearly defect-free SiC membranes for potential ultrafiltration applications by conducting pyrolysis of allylhydrido polycarbosilane in the presence of submicron α-SiC particles. The SiC membranes were developed on commercial macroporous SiC supports by a low-temperature-process in which allylhydrido polycarbosilane acted to bond together crystalline α-SiC particles to form a porous layer. The suspensions of α-SiC powder and allylhydrido polycarbosilane in n-hexane or n-hexane/n-tetradecane were used for membrane fabrication by dip-coating. By using optimized n-hexane suspension with 5% w/w α-SiC powder and mass ratios of allylhydrido polycarbosilane to α-SiC powder of 0.6 and 0.8, we obtained nearly defect-free and uniform mesoporous membranes in a single coating procedure. No defects were found on the surface of these membranes by scanning electron microscopy. Moreover, during filtration tests, these membranes showed a water permeance of 0.05-0.06 L (h m2 bar)-1 and retention higher than 93% for polyethylene glycol (PEG) with a molecular mass of 100 kDa. Retention for PEG with molecular masses of 1 kDa, 8 kDa and 35 kDa was between 25% and 71%.