A new water-resistant coating for AIN powders

A1N powders were coated with a protective layer at temperatures between 1150-1450 degrees C in a vacuum by the reaction with SiO vapor. The waterproof property of the coated A1N powders was studied. The composition of the protective coating varied with the coating temperature. Si-coated A1N powders at 1200 degrees C showed excellent stability against hydrolysis. On the other hand, the coated layer was not observed when the A1N powders were treated at 1450 degrees C. A silica layer was formed on the surface of the Si-coated A1N powders by the oxidation treatment at 1000 degrees C. These powders showed superior stability against hydrolysis compared to that of the commercially available silica-coated A1N produced by the sol-gel method. Compared to other processes used to coat A1N powders, the vaporization process using SiO vapor is simple and effective.