Predictive kinetics-based model for shock-activated reaction synthesis of Ti_3SiC_2

摘要

A kinetics model based on mass and heat transport has been developed for Ti_3SiC_2 formation via shock-activated reaction synthesis of powder precursors. The model allows prediction of heat treatment conditions under which an otherwise steady-state reaction is taken over by a "run-away" combustion-type reaction during post-shock reaction synthesis of Ti_3SiC_2. Shock compression of Ti, SiC, and graphite precursors generates a densely packed highly activated state of reactants, which lowers the activation energy and results in an increased rate of formation of Ti_3SiC_2 at a lower temperature and in shorter times. The predictive model correlated with experimental results of fraction reacted as a function of time at heat-treatment temperatures of 1400 and 1600 deg C illustrates an increased rate of reaction due to lowering activation energy, which also results in the reaction at 1600 deg C being taken over by a "run-away" combustion-type reaction, as the rate of heat release due to reaction exceeds the rate of heat dissipation through the compact. Correlation of the model with experimental results illustrates that the predictive model can be used to optimize reaction synthesis conditions in shock-densified compacts of Ti_3SiC_2-forming powder precursors, to better understand the processes leading to a steady-state reaction being taken over by the combustion mode.