Preparation of single phase nano-sized AlN powder by carbothermal reduction and nitridation of hydrothermal synthesized carbon coated γ-Al2O3 from glucose via fast heating

By twice pre-milling γ-Al2O3 in absolute ethyl alcohol plus in glucose aqueous solution, γ-Al2O3 was first coated by carbon via hydrothermal treatment technique. Then, at a fast heating speed of 50 °C/min, nano-sized pure AlN powders were synthesized through carbothermal reduction and nitridation (CRN) at 1550–1600 °C for 60–120 min in N2. The pre-milling in absolute ethyl alcohol effectively broke the initial aggregation of γ-Al2O3, and the subsequent milling in glucose aqueous solution led to well contact between γ-Al2O3 and glucose, which contributed to the formation of intact carbon coating on the surface of γ-Al2O3 during hydrothermal treatment. The coated carbon served as one reactant and inhibitor of particle aggregation for CRN, which also led to retention of γ-Al2O3 and its morphology during heating with the help of high heating speed. As a result, fine AlN of ∼100 nm was directly formed by nitridation of γ-Al2O3. The synthesis mechanism of nano-sized AlN powder by the carbon coated Al2O3/C precursor was discussed.