Low temperature synthesis of ALN nanopowders by the microwave assisted combustion method

Aluminum nitride (AlN) powder was calcined at low temperature through the carbothermal reduction nitridation (CRN) assisted by microwave heating. Their phase formation and microstructure were investigated with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The starting materials such as aluminum nitrate nonahydrate (Al(NO₃)₃ · 9H₂O), urea (NH₂CONH₂) and glucose anhydrous (C₆H₁₂O₆) were dissolved by stirring with a magnetic bar at 100°C for 25 min and then the precursor solution was dried at oven. The mixing molar ratio of urea to aluminum nitrate = 1.6 and that of glucose to aluminum nitrate = 1.0 were selected, respectively. The dried precursor mixtures were calcined at 1200 ~ 1500°C for 60 min. in N₂ atmosphere by a microwave heating furnace and then carburized at 700°C for 2 hrs in air. The homogeneous AlN powders, free of alumina, were obtained by calcining at temperatures above 1300°C. The particle size of AlN powder increases monotonically with increasing the calcination temperature. From TEM micrographs, the AlN powders calcined at 1300°C and 1500°C were found to be around 30 nm and 90 nm, respectively.