Effects of Combustion Conditions on the Characteristics of Al_2O_3/AlB_(12) Composite Powders Produced by Self-Propagation High-Temperature Synthesis

Al2O3/AlB12 composite powders were produced by self-propagation high-temperature synthesis (SHS) employing Al and B2O3 as initial reactants. The effects of combustion conditions on the characteristics of the powders were discussed. The results show that, Al2O3 has an average particle size of 3~4μm, while the size of AlB12 is in the submicron range. The composite powders have an average specific surface of ~1 m2/g. Impurities of B2O3 and 9Al2O3.2B2O3 can be observed at the surface of the products because of the evaporization and condensation of B2O3. By decrease the argon pressure in the reactor, Al2O3/AlB12 powders of high purity can be obtained. The adiabatic temperature of the reaction 13Al+6B2O3=6Al2O3+AlB12 obtained from thermodynamic calculations is significantly higher than the measured combustion temperature.