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Abstract. The microstructures of oxide scales formed on MoSi 2 at medium-high temperatures in air were observed by TEM. Based on the observation, relationships between oxidation temperature and formation of MoO 3 and crystallization of amorphous SiO 2 scales were investigated. At 1273 K and 1373 K, the oxide scales had a structure consisting of amorphous SiO 2 with small amounts of fine MoO 3 particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous and crystalline SiO 2 . Growth rate of the oxide scale formed at 1773 K appreciably increased due to crystallization of amorphous SiO 2 . It was thought that the increase in the oxidation rate at 1773 K was caused by a change in the diffusion mechanism from O 2 diffusion to lattice diffusion of O 2-through SiO 2 . In addition, the diffusion coefficient of oxygen was estimated from the growth rate of SiO 2 scale.

Abstract. The microstructures of oxide scales formed on MoSi 2 at medium-high temperatures in air were observed by TEM. Based on the observation, relationships between oxidation temperature and formation of MoO 3 and crystallization of amorphous SiO 2 scales were investigated. At 1273 K and 1373 K, the oxide scales had a structure consisting of amorphous SiO 2 with small amounts of fine MoO 3 particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous and crystalline SiO 2 . Growth rate of the oxide scale formed at 1773 K appreciably increased due to crystallization of amorphous SiO 2 . It was thought that the increase in the oxidation rate at 1773 K was caused by a change in the diffusion mechanism from O 2 diffusion to lattice diffusion of O 2-through SiO 2 . In addition, the diffusion coefficient of oxygen was estimated from the growth rate of SiO 2 scale.