Self-propagating exothermic reactions between silicon and transition metals of groups IVA-VIA induced by mechanical alloying

Chemical reactions between Si and transition metals of groups IVA-VIA induced by mechanical alloying have been investigated. Depending on the exothermicity, reactions could proceed via the solid-state diffusion mechanism or the mechanically induced self-propagating reaction (MSR) mechanism, which is analogous to that of the combustion synthesis. For reactant systems with high adiabatic temperatures (T-ad), such as silicides of Zr and Nb, Ti5Si3, TiSi, and MoSi2, spontaneous reactions proceeded via the MSR mechanism. There existed a threshold T-ad of 1850 K, below which silicon-metal systems reacted via the gradual solid-state diffusion mechanism during mechanical alloying. Since morphological observations of the MSR product indicated the occurrence of self-propagating reactions in the presence of a liquid phase, the effect of reactant melting temperatures on the threshold T-ad was elucidated with additional experiments involving carbon-metal reactant systems. (C) 2001 American Institute of Physics.