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.