Effect of cyclic mechanical treatment on the final properties of Nb + 2Si powder mixtures prepared for SHS

Abstract

The mechanical pretreatment of a powder mixture of niobium and silicon was studied experimentally and theoretically using the new macrokinetic theory of mechanochemical synthesis. The method of organizing the operation mode of the ball mill affects the degree of grinding and activation of the powder composition, as well as the rate of formation of intermediate phases. The effect of cycling on the temperature inside the mill drum, particle size of the powder mixture, formation of mechanically synthesized niobium silicides, and structure of the initial components has been studied. Varying the cycling can lead to safe and emergency operation of the mill. The final mixtures' characteristics may vary significantly depending on the number of cycles of discontinuous mechanical treatment, even if the total operating time of the ball mill remains the same. The safe conditions for cyclic operation of the mill were determined. The effects of different mechanical treatment modes on the grinding, activation, and phase formation of a powder mixture were investigated. Various parameters were analyzed, including thermophysical, physico-chemical, and kinetic characteristics of the cyclic operation of the AGO-3 ball mill, the kinetics of grinding and activation of Nb and Si particles, and the rate of mechanochemical reaction in the mechanically activated mixture of Nb + 2Si.