AlN ultrafine powder was synthesized in N2 via carbothermal reduction nitridation with different aluminum sources (i.e., Al(OH)3, Al(NO3)3·9H2O, and α-Al2O3) and high-activity nanocarbon black as raw materials. The effects of different aluminum sources, aluminum dosage, and calcination temperature on the phase composition and microstructure of the synthesized AlN powder were studied. Thermodynamic analysis of the reaction process was performed and the reaction mechanism of AlN powder was discussed. Results showed that fully nitrided phase-pure AlN powder was synthesized after incubating the precursor powder samples at 1500 oC for 2 hrs with Al(OH)3 or Al(NO3)3·9H2O as the aluminum source. At a 1 : 5 molar ratio of Al2O3/C, a weak Al2O3 diffraction peak was present in the AlN powder samples that were synthesized at 1550 oC with α-Al2O3 as the aluminum source. The quality of AlN powder samples that were synthesized with Al(NO3)3·9H2O as the aluminum source was optimal relative to those of AlN powder samples that were synthesized with the two other aluminum sources. Flake-like particles (~ 100-300 nm) in the powder samples exhibited reduced agglomeration. Moreover, approximately spherical structures that were 0.5-1.0 μm in size formed between the flake-like particles. During carbothermal reduction nitriding, Al2O3 in the raw material first underwent carbothermal reduction to produce metallic aluminum vapor and aluminum low valence gas oxides (Al2O), and then underwent further nitriding to form AlN.

Keywords: AlN powder, Different aluminium sources, Synthesis, Phase composition, Mechanism