Preparation of nanosized aluminum nitride powders by the cyanonitridation method

Abstract

Nanosized aluminum nitride (AlN) powders were prepared by calcining ¤-alumina (¤-Al 2 O 3 ) nanopowders under a flow of acetonitrile (CH 3 CN) diluted in argon. The nitridation process of ¤-Al 2 O 3 to AlN was monitored by powder X-ray diffraction patterns and 27 Al magic-angle spinning nuclear magnetic resonance spectroscopy. ¤-Al 2 O 3 began to be converted to AlN at 1050°C without ¤-¡ alumina transformation and the conversion was completed at 1300°C. The cyanide radical, which was produced by thermal decomposition of CH 3 CN, reacted with Al 2 O 3 to form AlN. The cyanonitridation method can considerably mitigate the two main drawbacks of the carbothermal reduction and nitridation method: high reaction temperature and intimate mixing of Al 2 O 3 with carbon. Cathodoluminescence spectra of the nanosized AlN powders obtained in this study showed an intense ultraviolet emission band at 376 nm.

Conversion of Alumina to Aluminum Nitride Using Polymeric Carbon Nitride as a Nitridation Reagent

“…indicated that δ‐Al 2 O 3 converted to AlN without δ‐α alumina transformation. The change in XRD patterns with calcination temperatures was similar to that when using CH 3 CN or melamine except that the sample at 1000°C showed intense AlN peaks.…”

“…This temperature was similar to those for the nitridation of γ‐Al 2 O 3 in a mixture of NH 3 ‐C 3 H 8 and ammonolysis of δ‐Al 2 O 3 and was ca. 100°C higher than that for the cyanonitridation by CH 3 CN . The comparison between XRD patterns and NMR spectra demonstrated that the complete nitridation of Al 2 O 3 to AlN should be confirmed by both 27 Al MAS NMR spectroscopy and powder XRD.…”

“…(b)] of the sample obtained at 1000°C showed a distinct peak assigned to AlN, together with peaks assigned to δ‐Al 2 O 3 . The broad and intense shoulder peak on the higher field side of AlN peak was ascribed to reaction intermediates (AlN x O 4‐ x units where x = 1–3) . As shown in Fig.…”

“…The HCN formed by the reaction of a mixed N 2 ‐H 2 gas with carbon was also used for the nitridation of Al 2 O 3 . Recently, organic compounds such as CH 3 CN and melamine, which yield HCN by the thermal decomposition, were employed as nitridation reagents in the conversion of Al 2 O 3 to AlN …”