Novel route for combustion synthesis of zirconia–mullite/TiB2 composites

Abstract

Abstract One serious drawback limits the scope of combustion synthesis technique is its inability to handle endothermic reactions. This is because the reactions carried out by this method should not only be exothermic but also generate immense amounts of energy in a very short time. In this work the possibility of conducting endothermic formation reaction of zirconia–mullite in a self-sustaining manner is investigated. This is accomplished by loading this endothermic reaction onto the exothermic reaction of TiO 2 –B 2 O 3 –Al mixture. Zirconia–mullite/TiB 2 composites having different amounts of alumina have been successfully prepared in a self-sustaining manner with the advantages of energy saving and very short time of reaction. Despite the dilution effect due to zircon addition (46–51.5 wt%) and the endothermic nature of zirconia–mullite formation, thermodynamic calculations show that the overall reaction between the reactants is still highly exothermic. Ignition of this blend is successfully conducted at 300 °C. Zircon stoichiometry and preheating temperature were found to have magnificent influence on the mullitization reaction completion. Adiabatic combustion temperature and mullite molten fraction are calculated as a function of preheating temperature.