Synthesizing AlN powder by mechanochemical reaction between aluminum and melamine

Abstract

A solid state mechanochemical reaction (MCR) method for synthesizing AlN powder with aluminum and melamine powders as the reactants was proposed and put into practice. It was found that the solid state MCR between aluminum and melamine is an instantaneous and exothermic reaction. For a certain charge ratio, a critical ball milling time is needed for the MCR to occur. The higher the charge ratio, the faster the MCR. Cryogenic environments help to accelerate the MCR between Al and melamine. In addition to the direct one-step MCR synthesis approach mentioned above, AlN powder can also be synthesized by pre-ball-milling Al and melamine powders followed by heat treatment. Using this two-step approach, the heat treatment temperature is only about 638 °C, which is much lower than that used in other ways for synthesizing AlN powder. The lower heat treatment temperature can be attributed to the combined effect of both the adoption of melamine and the high reactivity of powders caused by ball milling. Comparatively, the present solid state MCR method for synthesizing AlN powder may be more cost-effective and hence more promising to be used to industrially produce both AlN powder and in situ AlNP reinforced aluminum matrix composites.