A new method for synthetizing nanocrystalline aluminium nitride via a solid–gas direct reaction

• Simple method for obtaining powders with controlled amounts of nanocrystalline Al/AlN
• Al milling in NH3 flow allows the incorporation of N into the Al crystal lattice.
• Heat treatment of milled powders allowed the formation of substantial amounts of AlN.
• Powders, milled for 25 h, lead to an amount of nanocrystalline AlN, higher than 97 wt%.

Herein, we describe a new method for preparing AlN powder by milling aluminium powder at room temperature under a flowing NH3 gas atmosphere. The initial aluminium powder has a mean particle size of 80.5 μm. During mechanical alloying, NH3 decomposed at room temperature and N was incorporated into the aluminium crystal lattice. A subsequent heat treatment of the milled powders under vacuum for 1 h resulted in the formation of substantial amounts of AlN. Two different heat treatment temperatures have been tested (650 and 1000 °C).Different milling runs were carried out to evaluate the influence of the milling duration on the amount of AlN formed. Quantification by XRD indicated that the AlN amount that was formed was strongly influenced by the milling time. The heat-treated powders, which were milled for 25 h, led to a significant amount of nanocrystalline AlN (i.e., higher than 97 wt.%).

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