Nitridation of δ-Alumina to aluminum nitride under a flow of ammonia and its mechanism

Abstract

Nanosized δ-alumina (δ-Al2O3) powders were calcined at various temperatures under a flow of ammonia (NH3) passing over a carbon black-containing crucible. The nitridation process of δ-Al2O3 to aluminum nitride (AlN) was monitored by powder X-ray diffraction, infrared (IR) spectroscopy, and 27Al magic-angle spinning nuclear magnetic resonance spectroscopy. δ-Al 2O3 began to be converted to AlN at 1150°C without δ-α alumina transformation and the conversion was completed at 1300°C for 5 h. The IR spectra of the gases evolved during the nitridation revealed the inclusion of NH3, CH4, HCN, and CO gases. Results on the calcination of δ-Al2O3 under a flow of acetonitrile diluted in argon indicated that HCN is involved in the nitridation reaction of δ-Al2O3. © 2011 The Ceramic Society of Japan.