Fabrication of β-sialon powder from kaolin

Abstract β-Sialon powder was fabricated by carbothermal reduction–nitridation of natural Chinese Yixing kaolin at 1300–1550 °C in nitrogen atmosphere, using carbon black as a reducing agent. The effect of reaction temperature, holding time, nitrogen flow rate and the amount of carbon black on the synthesis of β-sialon powder and its solid solution degree ( z value) have been investigated systematically. The phases of the reaction products are identified by XRD. The results indicate that the products of reaction are more sensitive to the reaction temperature than holding time. Nearly all β-sialon is produced at a temperature of 1450 °C for 6 h. Higher temperatures lead to the presence of SiC phase. A slight amount of carbon favors the carbothermal reduction of kaolin and excess carbon results in the conversion of β-sialon to SiC. The z value of β-sialon (Si 6− z Al z O z N 8− z ) rises with the duration of holding time and varies from 2 to 2.8 as the holding time varies from 2 to 6 h at 1450 °C.