Features of combustion in the Mo-Si-B system: Part 2. Effect of mechanical activation

Abstract

This study is devoted to investigating the effect of mechanical activation (MA) on the kinetics and combustion mechanism of a reaction mixture in the Mo-Si-B ternary system, as well as ceramic material production by the self-propagating high-temperature synthesis (SHS) method. Elemental molybdenum, silicon, and boron powders are used as the initial components. The MA was carried out in a planetary mill. The MA modes with maximum heat release amount and rate were determined. MA results in an increase in the heat release rate and reactivity of the mixture because of the reagent size reduction, reduction of coherent-scattering regions, and increase in the density of structural defects and dislocations. In contrast with nonactivated mixtures, initial temperature dependences of the combustion temperature and rate are linear for MA mixtures. The MA contribution to the effective activation energy (Eeff) of the combustion process is evaluated quantitatively.