ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The oxidation process of MoSi2 is very complex, and controversial results have been reported, especially for the early-stage oxidation before the formation of passive SiO2 film. Most oxidation studies have been carried out on bulk consolidated samples, and the early stage of oxidation has not been studied. In this investigation, very fine MoSi2 powder with an average particle size of 1.6 μm was used. Such a fine particle size makes it easier to study the early stages of oxidation since a significant portion of the powder is oxidized before the formation of passive SiO2 film. The oxidation kinetics of commercial MoSi2-SiC and MoSi2-Si3N4 powder mixtures were also studied for comparison. Weight changes were measured at discrete time intervals at 500° to 1100°C in 0.14 atm of oxygen. X-ray diffraction was used to identify the phases formed during oxidation. Our results show the formation of MoO3 phase and an associated weight gain at low temperatures (500° and 600°C). At temperatures higher than 900°C, Mo5Si3 phase formed first and was subsequently oxidized to solid SiO2 and volatile MoO3, resulting in an initial weight gain followed by subsequent weight loss. A model based on the assumption that oxidation kinetics of both MoSi2 and Mo5Si3 are proportional to their fractions in the system describes the experimental data well.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.1999.tb02156.x
