HIGH-TEMPERATURE OXIDATION OF SINTERED SILICON-CARBIDE UNDER PURE CO2AT LOW-PRESSURE - ACTIVE-PASSIVE TRANSITION

The study of the oxidation of SiC under CO2 at high temperature and lo w pressure is achieved by means of theoretical and experimental determ inations of the transition zone between the passive oxidation with for mation of a protective silica layer and the active oxidation with majo r vaporization of SiO and etching of the SIC material. The theoretical determination is done using both models: a computer model ''Solgasmix '', applied for a closed system at equilibrium and the other, our anal ytical model, which takes into account the mass transfer at the solid/ gas interface. The comparison is done for these two models and then wi th the experimental results. XPS analyses are performed on ''passive'' and ''active'' samples to confirm the position of the transition line . Moreover, SEM micrographs complete the diagnostics. (C) 1998 Elsevie r Science B.V. All rights reserved.