Preparation of Aluminum Nitride Powders and Whiskers Using Aluminum(III) Salts as a Precursor

Abstract

Aluminum nitride (AlN) powders were synthesized by using a mixture of an aluminum nitrate or sulfate salt and carbon (mole ratio of Al 3+ to carbon=1 : 30). The AlN was obtained by calcining the mixture under a flow of nitrogen in the temperature range 1100-1600℃ and then burning out the residual carbon. The process of conversion of the salt to AlN was monitored by XRD and 27 Al magic-angle spinning (MAS) NMR spectroscopy. The salt decomposed to ?-alumina and then converted to AlN without phase transition from ?- to α-alumina. 27 Al MAS NMR spectroscopy shows that the formation of AlN commenced at 1100℃ AlN powders obtained from the sulfate salt were superior to those from the nitrate salt in terms of homogeneity and crystallinity. A very small amount of AlN whiskers was obtained by calcining a mixture of an aluminum sulfate salt and carbon at 1150℃for 40 h, and the growth of the whiskers is well explained by the particle-to-particle self-assembly mechanism.