DIFFUSIONAL REACTIONS IN THE COMBUSTION SYNTHESIS OF MOSI2

An attempt has been made to understand the nature of the reactions occurring in the combustion wave during the combustion synthesis of MoSi2 from powders of molybdenum and silicon. The study is also extended to determine the effect of heating rate on the product formation by heating the compacts of molybdenum and silicon at various heating rates. In combustion synthesis, MoSi2 is formed in a single step suggesting the occurrence of liquid silicon-solid molybdenum diffusional reactions during the propagation of the combustion wave. In contrast, at low heating rates, Mo5Si3 is formed first, which is then enriched with liquid silicon by the diffusional reaction of liquid silicon through the product layer of Mo5Si3, forming MoSi2. Evidence for these reactions has been obtained by correlating the exothermic effects observed from the differential thermal analysis curves with the X-ray identification of the products of the reaction.