Surface treatment and hydrolysis kinetics of organic films coated AlN powder

The resistance to hydrolysis of aluminium nitride (AlN) powder was improved by coating the surface of the AlN particles with oleic (OA) and 8-hydroxyquinoline (HQ). The treated powders did not react with water at 40°C when soaked for up to 70 h at constant pH, whereas under the same conditions uncoated AlN reacted with water after 2–10 h soaking. However, with an increase in temperature (65–80°C), hydrolysis of the coated powder took place rapidly. The hydrolysis kinetics of AlN powder with OA and HQ films were found to occur in two stages, a diffusion controlled stage and a surface reaction controlled stage, both of which were first order reactions with activation energies of 125 and 114 kJ mol^-1, respectively. The increased resistance to hydrolysis was the result of the organic films forming a diffusion barrier between the water and the AlN surface. Hydrolysis of the coated AlN powder at high temperature was attributed to the ready breakdown of the film by erosion by the hot water. This explanation was supported by TG–DTA, XRD, and IR examination.