Self-propagating high-temperature synthesis method for synthesis of AlN powder

A new self-propagating high-temperature synthesis (SHS) process has been developed for synthesis of AlN powder under low nitrogen pressures. Al and NH₄X (X = F, Cl, Br, or I) powders were mixed and pressed into a compact, which was placed in a reaction chamber filled with nitrogen. The combustion synthesis reaction was ignited by heating directly the compact, and high product yields (approx. 90%) were obtained under nitrogen pressures of around 0.5 MPa. The product yield was affected by the reactant composition, the nitrogen pressure, and the compact-forming pressure. The powder as synthesized consists mainly of fibers, coarse granules, and agglomerated fine particles, which become mostly smaller than 10 μm after grinding. A reaction process was also proposed that explains the effects of the experimental parameters on the product yield.