Hydrolysis control of alumina and AlN mixture for aqueous colloidal processing of aluminum oxynitride

AlN powder, surface modified by phosphoric acid treatment was employed for the aqueous colloidal processing of Aluminum Oxynitride (AlON). The hydrolysis of AlN leads to the formation of Al(OH)3 and NH3. On mixing of alumina to the phosphoric acid treated AlN in aqueous medium this reaction reoccurred. The phosphoric acid shield around AlN particles is ruptured by alumina addition thus exposing AlN surface to hydrolysis reactions. Hence hydrolysis can be effectively controlled by providing a phosphoric acid treatment to the alumina, prior to its addition to AlN. AlON precursor mixture thus obtained can be successfully shaped by an aqueous slip casting process and sintered to phase pure AlON at 1925 °C for 2 h. Viscosity, pH, SEM, FTIR, and XRD measurements are employed to elucidate the effect of Al2O3 addition on surface modified AlN for colloidal processing of AlON.