Synthesis of Ca-Alpha SiAlON by Carbothermal Reduction-Nitridation of CaO-Al₂O₃-SiO₂ Glass

Abstract

Ca-α sialon powders were synthesized via carbothermal reduction-nitridation (CRN) of CaO-Al₂O₃-SiO₂ glass powder.Ca-α sialon content of about 80wt%, together with β-sialon and AlN as a minor phase was obtained by firing the product at 1450^oC for 2h in N₂ gas.SEM observation showed that the resultant powder had ball-like morphology of less than 5μm.According to XRD analysis, crystalline SiO₂, mullite and Si₂N₂O as an intermediate phase were identified at the initial stage of the CRN reaction.The glass powder composed of coarse particle gradually changed into the spherical particles at 1100^oC.The nitridation reaction proceeded from the surface of the spherical particles to generate Si₂N₂O.It was confirmed that the Ca-α sialon particles obtained from CaO-Al₂O₃-SiO₂ glass powder were formed through the same process as CaO-Al₂O₃-SiO₂ powder mixture.This result suggests that the Ca-α sialon synthesized by CRN of CaO-Al₂O₃-SiO₂ system were formed through Ca-Al-Si-O glass.