A novel process for combustion synthesis of AlN powder

A SHS process has been established for synthesis of AlN powder under low nitrogen pressures. Al and NaN₃ powders were used as the metal and nitrogen sources, respectively. The compact of the mixture of the reactants was wrapped up with aluminum foil and then wrapped up with an igniting agent (i.e., Ti + C). The synthesis reaction was triggered by the combustion of the igniting agent. The wrappings were found necessary in achieving high product conversions under low nitrogen pressures (<1 MPa). The product conversion was also affected by the reactant composition and the nitrogen pressure. High conversions were obtained when the mass ratio of Al to NaN₃ was 1/2 or lower and the nitrogen pressure was 0.5 MPa or higher. The AlN powders as synthesized were observed to have two major types of morphology, i.e., granular particles with 0.5–3 μm in diameter and fibers with aspect ratios of 10–800.