Preparation of High Specific Surface Area Micro/Meso-porous SiOC Ceramics by the Low Temperature Phase Separation Method

Micro/meso-porous SiOC ceramics with high surface area and narrow pore size distribution were prepared by the low temperature phase separation method(namely water vapor assisted pyrolysis) followed by etching in hydrofluoric acid(HF) solution. The cross-linked body was made from hydrogen-containing polysiloxane(PHMS), tetramethyl-tetravinylcycletetrasiloxane(Dvi4) and Pt-complex by thermal cross-linking. Phase compositions, chemical bonds, microstructures, and specific surface area of the prepared SiOC ceramic were investigated by XRD, FT-IR, SEM, and BET, etc. Water vapor can promote the precursor to produce Si-O-Si bonds, SiO2-rich clusters, and SiO2 nanocrystals in SiOC ceramics. All of these species act as pore-forming substrate and can be etched away by HF. Water vapor injection and pyrolysis temperature have important effects on phase compositions, microstructures and specific surface area of SiOC porous ceramics, which have a maximum specific surface area of 1845.5 m2/g and pore size distribution of 2.0-10 nm at pyrolysis temperature of 1300℃.