Protection of AlN powder against hydrolysis using aluminum dihydrogen phosphate

The hydrolysis of AlN powder in a dilute aqueous suspension was studied by following the pH vs. time in different media. The results show that phosphoric acid is effective in protecting AlN powder at room temperature, whereas at elevated temperatures hydrolysis takes place. When silicic acid or aluminum dihydrogen phosphate were present in the slurry no hydrolysis was observed even at 70°C. Further experiments indicate that by soaking in aluminum dihydrogen phosphate, water-resistant AlN powder can be prepared which will not react with water even after drying and/or redispersion. The protected AlN powder is hydrophilic, which facilitates aqueous powder processing.