Low-temperature oxidation behavior of MoSi2 powders

The oxidation behavior of molybdenum disilicide (MoSi2) powders at 400, 500, and 600°C for 12 h in air were investigated by using X-ray diffraction (XRD) and transmission electron microscopic (TEM) techniques. Significant changes were observed in volume, mass, and color. Especially at 500°C, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with SiO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600°C compared with those at 500°C, probably due to the less reaction rate at 400°C and the formation of silica glass scale at 600°C, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of MoSi2 powder appeared at 500°C and the volume expansion was the sign of accelerated oxidation.