Synthesis Ca-α-SiAlON powder by carbothermal reduction nitridation of colloidal sol-gel derived powder precursor

Ca-alpha-SiAlON powder was prepared by carbothermal reduction nitridation process at nitrogen atmosphere without using high pressure and long holding time. The precursor was prepared by a novel colloidal sol-gel process consisting of silica, alumina, calcium oxide and carbon. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The XRD and SEM analysis results revealed that by heating at 1200 degrees C for 2 h, spherical particles consisting of amorphous calcium aluminosilicate liquid phase were formed. With increasing temperature to 1360 degrees C and held for 2 h, the spherical particles with the dominant phase of O-SiAlON were observed. Finally, as the temperature climbed to 1500 degrees C and held for 2 h, spherical particles disappeared and Ca-alpha-SiAlON was formed. The XRD analysis of the products showed that with increasing temperature from 1360 degrees C to 1500 degrees C, O-SiAlON, beta-SiAOlN and Ca-alpha-SiAlON were formed, respectively, and colloidal sol-gel method, due to the high homogeneity of the reactants, had a significant role in increasing the purity of Ca-alpha-SiAlON.