Diffusional reactions in the combustion synthesis of MoSi 2

Abstract

An attempt has been made to understand the nature of the reactions occurring in the combustion wave during the combustion synthesis of MoSi 2 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, MoSi 2 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, Mo 5Si 3 is formed first, which is then enriched with liquid silicon by the diffusional reaction of liquid silicon through the product layer of Mo 5Si 3, forming MoSi 2. 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.