Effects of additives on the synthesis of spherical aluminum nitride granules by carbothermal reduction-nitridation process

In this work, the effects of various additives on the AlN conversion fraction, weight loss, phase compositions and surface morphology during the carbothermal synthesis of spherical AlN granules were investigated in detail. The results inferred that additives played an important role in the improvement of nitridation rate, the formation of spherical morphology and the growth of particle size. The simultaneous addition of CaF2 and YF3 resulted in the highest nitridation rate in all samples, while excessive CaF2 appeared to retard the nitridation process at a particular temperature. However, Ca-aluminates forming in the synthesis process tended to be reduced and further volatilized at high temperature. Furthermore, by analyzing the weight loss during the carbothermal reduction-nitridation process, the reaction mechanisms in the systems using different additives were also attentively disclosed.