Oxidation behavior of hot-pressed MoSi2-TiC composite

The oxidation behavior of a hot-pressed MoSi2-TiC composite was investigate d in air over the temperature range of 500 degreesC-1400 degreesC. The comp osite exhibits parabolic oxidation kinetics between 500 degreesC-800 degree sC, where the activation energy was calculated to be 32 kJ/mol. However, ab ove 800 degreesC, it shows two-step parabolic oxidation kinetics, where the first stage (step I) was proposed to be dominated by the oxidation of surf ace TiC particles. After all the surface TiC particles are oxidized, the ox idation of the composite turns into the second stage (step II) which was co ntrolled by the oxidation of MoSi2. The activation energy was determined to be 130 kJ/mol and 141 kJ/mol for step I and step II, respectively. A dense cristobalite scale with TiO2 in lath shapes on the top was observed after oxidation at 1400 degreesC. (C) 2001 Kluwer Academic Publishers.