Ultrafine AlN synthesis by alumina carbothermal reduction under vacuum: Mechanism and experimental study

Abstract

Ultrafine AlN powders were synthesized by carbothermal reduction nitridation method under vacuum (VCRN) in a double temperature zones vacuum furnace with alumina and carbon black as raw materials. The mechanism of the process was investigated. The results show that when the soaking time was 1.5 h at 1650 °C, 300 Pa N2 pressure, the purity ultrafine AlN powders were obtained. By analyzing the results of density function theory (DFT) calculation and XRD, the mechanism of VCRN can be identified as Al2O3 → Al2OC/Al4C3 → Al6C3N2/AlN → AlN. The results of theoretical study further proved that the compound of Al6C3N2 can be nitrogenized quickly through the reaction of Al6C3N2 + 2 N2(g) → 6AlN + 3C.