The oxidation behavior of porous high-purity SiC was studied at 1600 and 1700K for 15h in Ar-O2 (PO2: 0.02-97kPa) by measuring the oxidation rate. In oxidation at 1600K, only the weight gain of the SiC was ob served after the oxidation, and the amount of cristobalite on the oxidized surface increased with increasing PO2. In oxidation at 1700K, the weight loss was observed at the oxygen partial pressure of 0.02kPa while the weight gains were observed at an oxygen partial pressures of 2 and

more »

... The oxidation rate was deter mined by measuring the evolved gases throughout the oxidation reaction using a mass spectrometer. The oxi dation kinetics obeyed the parabolic law under 0.02-97kPa at 1600K and under 2-97kPa at 1700K, indicat ing that. the passive oxidation occurred. The transition oxygen partial pressure below which the oxidation mechanism changes from passive to the active one, is presumed to be approximately 0.1kPa in the case of the oxidation at 1700K.