Thermodynamic and kinetic analyses of vacuum synthesis of AlN by the alumina carbothermal reduction nitridation method
Li Liu, Bingyang He, Xiumin Chen, Zhongqian Zhao, Qi Yin, Peilin Xu, Bin Yang, Baoqiang Xu, Dachun Liu
Abstract
Abstract Ultrafine single‐phase aluminium nitride (AlN) particles were successfully synthesized by the vacuum carbothermal reduction nitridation (VCRN) method at shorter times and lower temperatures. The mechanism of the process was investigated. By analyzing the X‐ray diffraction (XRD) patterns and thermodynamic calculations, the main reaction path was determined to be Al 2 O 3 →Al 2 CO→Al 4 C 3 →Al 5 C 3 N→AlN. By investigating the kinetics mechanism, the process was a gas–solid reaction model, which was controlled by the crystalline chemical reaction from 0.5 to 1.5 h, combination control from 1.5 to 2 h, and gas diffusion control from 2 to 2.5 h. Moreover, the apparent activation energy ( E a ) was calculated from the nitridation ratio, the value obtained, 237.71 kJ mol –1 , is 31% of the energy reported for the conventional synthesis method. These results show that ultrafine AlN could be effectively synthesized at 1823–1873 K and 300 Pa N 2 pressure for 2.5 h.