Combustion Synthesis Involving Thermite Reactions

Abstract

The self-propagating high-temperature synthesis (SHS) process involving thermite reactions was introduced as a promising alternative to prepare various Al2O3-reinforced materials, including borides, carbides, and aluminides. The influence of different thermite mixtures on the SHS process is explored in terms of the combustion sustainability, propagation rate of the reaction front, combustion temperature, and phase composition of the synthesized products. On formation of the TiB2-Al2O3 composite, the thermite mixture of Al-TiO2-B2O3 was found to improve the phase conversion when compared with that of Al and TiO2. The addition of the Al-TiO2 thermite mixture to the Ti-Si-C reaction system was demonstrated to produce in situ Ti3SiC2-Al2O3 composites. The thermite reaction of Al and TiO2 can also be applied to prepare the TiAl-Al2O3 composite through combustion synthesis. Two niobium aluminides Nb3Al and Nb2Al were obtained in almost pure form from a thermite-based SHS process with the powder compacts of Al:Nb2O5 = 12:3 and 13:3, respectively. As the thermite reagent of Al-Nb2O5 or Al-Nb2O5-B2O3 was added to the Nb-B combustion system, products were the composites of niobium borides and Al2O3.