Precisely controlled carbothermal synthesis of spherical beta-Si3N4 granules

High purity spherical beta-Si3N4 particles were synthesized via an efficient carbothermal reduction-nitridation strategy by precise regulation. The results showed that nano-sized reactants with an appropriate ratio was significant for acquiring Si3N4 granules with pure beta phase. c/a,b-axis length ratio of the beta-Si3N4 particles could be adjusted by using various additives. Fine spherical beta-Si3N4 particles can only be obtained with the help of CaO additive by L-S mechanism. Moreover, variations of underlying reaction mechanisms when changing the raw materials were comprehensively revealed. Owing to the high purity and fine spherical morphology, as-obtained beta-Si3N4 powders are promising fillers for preparing resin-based composites with high thermal conductivities.