Surface modification and oxidation kinetics of hot pressed AlN-SiC-MoSi2 electroconductive ceramic composite

The effects of oxidation on the microstructural modification and on the electrical resistivity and mechanical strength of a hot-pressed AlN-SiC-MoSi2 electroconductive ceramic composite were studied. The kinetic of the oxidation was also evaluated. After the oxidation at temperatures below 1000°C samples do not gain weight, due to simultaneous formation of SiO2 and evaporation of MoO3 formed by the oxidation of MoSi2. However, the AlN/SiC matrix disables the “pesting” phenomena and strength degradation, despite the fact that at these temperatures MoSi2 oxidizes rapidly. . At temperatures above 1000°C the composite gains weight due to protective mullite layer formation on the surface, that provides a good oxidation resistance for use at higher temperatures. The kinetics of the oxidation follows the parabolic law. The possible rate-controlling mechanism is the diffusion of oxygen through the mullite-rich surface oxide scale.