1999 Volume 48 Issue 3 Pages 128-134
Silicon-based ceramics have an excellent oxidation resistance at high temperatures due to a protective SiO2 layer which prevents further oxidation. At low oxygen partial pressures, on the other hand, the surface of these ceramics would be directly attacked by an oxidant forming SiO vapor, which may significantly degrade their mechanical or protective performance. These two kinds of distinct behavior are termed passive and active oxidation. Another characteristic oxidation feature of the silicon-based ceramics is bubble formation which probably determines the highest temperature for usage. Therefore, it is important to investigate the oxidation behavior of these ceramics in a wide range of oxygen partial pressures and temperatures. In the present paper, the transition mechanism from the active to passive oxidation and several issues on the passive oxidation are reviewed.