Effect of heat exchange with the environment on phase formation during combustion synthesis of a composite

A combustion synthesis model of the composite in the multicomponent powder mixture is proposed. The fraction of reactants and synthesis products changes are described using theory of formal chemical kinetic. The model takes into account the reaction retardation by the synthesized product layer. The influence of heat loss to the environment on phase formation during the combustion synthesis process is analyzed from combustion initiation and to products cooldown. A powder mixture of titanium, aluminum and boron is considered as a model system of the synthesis. The numerical simulation reveals that intensive heat loss to the lower temperature environment leads to a decrease in the fraction of the boride phase and intermetallic phases in the final composite, while the fraction of the initial reagents increases. It was found that synthesis products begin to form in the reaction wave, but the most intense phase formation occurs after the reaction wave reaches the bottom surface of the sample. The calculation results are in agreement with experimental data.