Combustion synthesis of MoSi2 and MoSi2–Mo5Si3 composites: Multilayer modeling and control of the microstructure

In this work, we present a multilayer modeling for the formation of molybdenum silicides in the exothermic reaction between Mo and Si under the influence of a temperature pulse. The heating rate can either be a well-controlled ramp or be generated spontaneously by the propagation of a combustion synthesis front. The model addresses the specific situation above the melting point of silicon and describes the solid–liquid reaction taking place in a single representative particle of molybdenum surrounded by the melt of silicon. We obtain a set of kinetic equations for the propagation of the interfaces between the different layers (Mo/Mo5Si3 and Mo5Si3/MoSi2) in the solid particle and the change in composition of the melt. This approach enables one to understand the specific microstructure observed during the formation of molybdenum silicides and to assess the role of parameters of combustion synthesis such as the initial size of the particles, the combustion temperature or the stoichiometric coefficient.