High-temperature oxidation of silicon carbide and silicon nitride

Oxidation behavior of silicon-based ceramics such as SiC and Si3N4 at high temperatures is important for their practical applications to structural or electronic materials. In the present paper two kinds of oxidation (passive and active) and active-to-passive transition of silicon-based ceramics were discussed thermodynamically, and the rate constants of passive/active oxidation and active-to-passive transition oxygen potentials for SiC and Si3N4 were reviewed. Passive and active oxidation behavior depended on the microstructure of oxide films and SiO gas pressure on silicon-based ceramics, respectively. Wagner model, volatility diagram and solgasmix-based calculation were used to estimate the active-to-passive transition.