Surface modification of aluminium nitride powder

stability of the untreated and treated A1N powders against water was evaluated by measuring the variation in pH as a function of time at 80 °C. This experiment was carried out as follows: the A1N powder (0.5 g) was added to 200 ml of distilled water having pH of about 5.4 and a temperature of 80 °C, and then mixed by stirring to prepare an A1N dispersion. The dispersion was warmed up to about 80 °C. The pH change of the suspension at 80 °C with time was determined with special indicator pHtest paper. For the duration of the hydrolysis process, the suspension was continuously stirred with a magnetic agitator. After completion of hydrolysis, the A1N powder was filtered off and washed with absolute ethanol and acetone, followed by drying at 120°C for 5 h. No further weight changes were observed when the dried powder was heated again at the same temperature. The dried powders were stored in a dry-seal desiccator for subsequent analysis. The nitrogen content of the A1N powder before and after hydrolysis was determined by a neutralization-distillation method. The AIN content, calculated by nitrogen content, and its proportion coefficient is A1N/N=2.926. X-ray diffraction (XRD, Rigaku, Dmax/rB) analysis was performed to identify crystalline phases in the untreated and treated A1N powders before and after the hydrolysis test. The time dependence of the pH value for A1N powder immersed in water at 80 °C is depicted in Fig. 1 and Fig. 2. As is clear from the results, the pH value exhibited a steep rise immediately after A1N powder contact with distilled water at 80 °C; after 30 minutes of hydrolysis, the pH value rose above 9.0. An odour characteristic of ammonia was also detected. It was shown that the untreated powder was quite reactive with water. The increased pH indicates an increase in concentration of NH3 in solution, which is produced through hydrolysis of the AIN powder. A1N powder hydrolysis according to the formula