Oxidation of SiC powders in SiC/alumina/zirconia compacts

Oxidation of SiC powder in compacts of SiC/alumina/zirconia was studied between 1000 and 1200°C in air for up to 10 h. The thermogravimetric analysis showed that the weight gain due to passive SiC powder oxidation became significant at temperatures ⩾937°C. After oxidation, the particle usually consisted of a SiC core surrounded by a layer of amorphous silica. However, the amorphous layer would crystallize into cristobalite if the powders were oxidized at 1200°C for a longer time (⩾8 h). The oxidation rate decreased if cristobalite formed. The square of weight gain fraction after oxidation was linearly proportional to the oxidation time when the weight gain fraction was less than 0.34. The activation energy of the oxidation of SiC powders was estimated to be 213.1 kJ/mol.