Studies on the formation of MoSi 2[sbnd]SiC by reaction of Si 3N 4 with molybdenum and carbon

Abstract

Si 3N 4 powder was reacted with Mo powder and carbon black at 1200–1600°C in an argon atmosphere. The effects of carbon content and pressure on the formation of molybdenum silicides were studied. MoSi 2 and SiC formed at all temperatures. With a low initial carbon content or on conducting the reaction under a positive pressure of argon, the formation of Mo 5Si 3 and Mo 3Si can be suppressed. However, at higher temperatures (1500 and 1600°C), the formation of large quantities of SiC, Mo 5Si 3, and Mo 3Si was observed. Vapor—liquid—solid whisker type morphology was observed at lower temperatures. At higher temperatures various types (hexagonal, trigonal, polyhedral) of SiC particulate formed. The tendency of the reaction product to agglomerate was found to increase with a decrease in the carbon content.