Influence of the microstructure on the high temperature behaviour of gel-derived SiOC glasses

Hybrid gels, made from HSi(OEt)3 and CH3SiH(OEt)2, were used to produce SiOC glasses and to study their stability at high temperature. The variation of the hydrolysis ratio allowed the formation of either dense or highly porous xerogels. This difference in microstructure was maintained at 1000°C in the glassy state and influenced the stability of these materials at higher temperature. Indeed, it plays a major role on their carbothermal degradation by promoting or hindering the removal of the gaseous products in the case of porous or dense materials respectively. In the latter case, SiOC glass appears to be a suitable candidate for thermostructural applications.