Effects of SiO2-forming additive on polysiloxane derived SiOC ceramics

Novel ultrahigh surface area materials are highly desired for demanding applications such as high temperature catalysts, electrodes, and harsh environment sensors. In-situ conversion of tetraethyl orthosilicate (TEOS) into SiO2 and its incorporation into silicon oxycarbide (SiOC) ceramics during polysiloxane ceramization are investigated by crosslinking TEOS within a polysiloxane matrix and introducing water vapor during pyrolysis. The effects of the TEOS-derived SiO2 on the thermophysical properties, phase development, and the resulting porous SiOC are investigated. The SiOC with 10 wt% TEOS within the crosslinked polymer creates the highest specific surface area of similar to 2100 m(2)/g with an average pore size of similar to 2 nm. The specific surface area and pore size distribution are correlated with the theoretical results from Voronoi diagram simulation and an idealized model calculation.