Synthesis of Mg-α SiAlON powders from talc and halloysite clay minerals

Carbothermal reduction and nitridation (CRN) of SiO2 is an attractive method to manufacture Si3N4 powders with controlled grain morphology. Some inexpensive raw materials were previously used to synthesize β-sialon powder, resulting in cheaper products to be useful for some engineering applications. In this work, Mg-α sialon (MgxSi12−m−nAlm+nOnN16−n) powders were achieved by CRN of mixtures of talc (Mg3(Si2O5)2(OH)2) and NZ halloysite clay (Al2Si2O5(OH)4) minerals. The final products consisted mainly of α-sialon and β-sialon phases. Small amounts of 15R AlN-polytypoid and SiC were also identified in the synthesized powder. By adding a small amount of α-Si3N4 powder as seeds to the starting composition, the conversion rate of α-sialon phase was significantly enhanced and powders with up to 90 wt% of α-sialon were produced.