STUDIES ON THE FORMATION OF MOSI2-SIC BY REACTION OF SI3N4 WITH MOLYBDENUM AND CARBON

Si3N4 powder was reacted with Mo powder and carbon black at 1200-1600 degrees C in an argon atmosphere. The effects of carbon content and pr essure on the formation of molybdenum silicides were studied. MoSi2 an d SiC formed at all temperatures. With a low initial carbon content or on conducting the reaction under a positive pressure of argon, the fo rmation of Mo5Si3 and Mo3Si can be suppressed. However, at higher temp eratures (1500 and 1600 degrees C), the formation of large quantities of SiC, Mo5Si3, and Mo3Si was observed. Vapor-liquid-solid whisker typ e morphology was observed at lower temperatures. At higher temperature s various types (hexagonal, trigonal, polyhedral) of SiC particulate f ormed. The tendency of the reaction product to agglomerate was found t o increase with a decrease in the carbon content.