Silicon oxycarbide amorphous ceramics have carbon atoms in glass networks and have a higher level of elastic modulus, hardness, and high temperature viscosity than silicon dioxide. In this study, silicon oxycarbide ceramics were prepared by heat treatment of polymethyl and polymethylphenyl silsesquioxane polymer precursors at 1000-1500 οC in an argon atmosphere. The silicon oxycarbide ceramics prepared were found to have amorphous structures and compositions of SiOxCy where x = 1.40-1.46, y = 0.57-0.70 or x = 1.44-1.53, y = 2.60-2.68 depending on the type of precursor. Silicon oxycarbide amorphous ceramics made from polymethylphenyl silsequioxane were unstable at high temperatures, showing a weight loss of 24% in air and 4% in argon during thermogravimetric analysis. Silicon oxycarbide amorphous ceramics made from polymethyl silsesquioxane precursor were stable in argon at 1500 οC without loss of weight or crystallization. However, they showed weight losses of 1.7 and 2.8% in air at 1500 and 1650 οC, respectively.

Keywords: Silicon oxycarbide glass, Polymer-derived ceramics, High temperature stability, Oxidation resist