High‐Temperature Active Oxidation of Chemically Vapor‐Deposited Silicon Carbide in an Ar─O ₂ Atmosphere

Abstract

Active oxidation behavior of chemically vapor‐deposited silicon carbide in an Ar─O 2 atmosphere at 0.1 MPa was examined in the temperature range between 1840 and 1923 K. The transition from active oxidation (mass loss) to passive oxidation (mass gain) was observed at certain distinct oxygen partial pressures ( P O 2 t ). The values of P O 2 t increased with increasing temperature and with decreasing total gas flow rates. This behavior was well explained by Wagner's model and thermodynamic calculations. Active oxidation rates ( k a ) increased with increasing O 2 partial pressures and total gas flow rates. The rate‐controlling step of the active oxidation was concluded to be O 2 diffusion through the gaseous boundary layer.