Abstract
The effects of oxidation on the microstructural modification and on the electrical resistivity and mechanical strength of a hot-pressed AlN–SiC–MoSi 2 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 SiO 2 and evaporation of MoO 3 formed by the oxidation of MoSi 2. However, the AlN/SiC matrix disables the “pesting” phenomena and strength degradation, despite the fact that at these temperatures MoSi 2 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.
Published Version
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