Synthesis of Nano-Size AlN Powders by Carbothermal Reduction from Plasma-Assisted Ball Milling Precursor

Nano-size aluminum nitride (AlN) powders have been successfully synthesized with a high efficiency method through annealing from milling assisted by discharge plasma (p-milling) alumina (Al₂O₃) precursors. The characterization of the p-milling Al₂O₃ powders and the synthesized AlN are investigated. Compared to conventional ball milling (c-milling), it can be found that the precursors by p-milling have a finer grain size with a higher specific surface area, which lead to a faster reaction efficiency and higher conversion to AlN at lower temperatures. The activation energy of p-milling Al₂O₃ is found to be 371.5 kJ/mol, a value that is much less than the reported value of the unmilled and the conventional milled Al₂O₃. Meanwhile, the synthesized AlN powders have unique features, such as an irregular lamp-like morphology with uniform particle distribution and fine average particle size. The results are attributed to the unique synergistic effect of p-milling, which is the effect of deformation, fracture, and cold welding of Al₂O₃ powders resulting from ball milling, that will be enhanced due to the introduction of discharge plasma.