Low temperature oxidation behavior of a MoSi2-based material

This article contributes to the characterization of low temperature oxidation behavior of a MoSi2 composite for heating elements. The initial silica growth kinetics, its oxygen partial pressure dependence, MoO3 evaporation rate and the microstructural evolution during oxidation have been examined. The oxidation exposure was carried out in the temperature range from 673 to 873 K in flowing oxygen or mixtures of argon and oxygen gases. The major analytical techniques include X-ray powder diffractometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy and BET method. It is shown that silica growth rate at 773 K decreases with time and the square of silica thickness increases with the oxygen partial pressure. Evaporation rate of MoO3 powder increases exponentially with increasing temperature in the range from 823 to 973 K in flowing O2. Accumulation of Mo-rich phase, presumably MoO3, in the thick silica layer was readily seen at 723 K.