Oxidation Transitions for SiC Part I. Active‐to‐Passive Transitions

Oxidation of SiC can occur in a passive mode where a protective film is generated or in an active mode where a volatile suboxide is generated and can lead to rapid material consumption. The transition between these two modes of oxidation is a critical issue. Evidence indicates that this transition occurs via a different mechanism for the active‐to‐passive transition as compared with that of the passive‐to‐active transition. In Part I of this article, the former (active‐to‐passive mode) is explored. Three different types of SiC are examined: Si ‐rich SiC , stoichiometric SiC , and C ‐rich SiC . Evidence suggests that the SiO 2 / SiC equilibrium requirements as well as formation of SiO (g) at the SiC surface and subsequent oxidation to SiO 2 (s) are critical issues in the active‐to‐passive transition.