Effect of Milling Treatment on the Particle Size in the Preparation of AIN Powder from Aluminum Polynuclear Complexes

Aluminum nitride powder was synthesized from aluminum polynuclear complexes. Basic aluminum chloride (BAC) provided the aluminum polynuclear complexes. The effect of the milling treatment for the precursor made from basic aluminum chloride and glucose on the particle size was investigated. BAC and glucose were dissolved in water and mixed homogeneously. AIN powder was obtained by calcining under a nitrogen gas flow after drying, milling by vibration mill, and precalcining at 800°C. Then excess carbon was removed by firing in air. It was found that the milling treatment affected the particle size of AIN powder and nitridation mechanism. Without the milling treatment, AIN powder was synthesized directly from the γ-alumina of an intermediate product. In using a milled precursor, however, α-alumina was formed during the calcining, and the particle size of the AIN powder obtained was about five times larger than that of AIN powder synthesized from a raw precursor. The formation of α-alumina phase began at the rather low temperature of 800°C. These results suggest that the mechanochemical effects added by the milling promotes the formation of α-alumina during calcining, and the α-alumina phase formed accelerates the particle growth. AIN powders obtained were very uniform. The oxygen content and the surface area of AIN powders synthesized from the raw and milled precursors were 2.9 wt% and 17.5 m2/g, and 1.1 wt% and 3.6 m2/g, respectively.