Effects of synthesis temperature and raw materials composition on preparation of β-Sialon based composites from fly ash

beta-Sialon based composites were successfully prepared from fly ash and carbon black under nitrogen atmosphere by carbothermal reduction-nitridation process. Effects of heating temperature and raw materials composition on synthesis process were investigated, and the formation process of the composites was also discussed. The phase composition and microstructure of the composites were characterized by X-ray diffraction and scanning electronic microscopy. The results show that increasing heating temperature or mass ratio of carbon black to fly ash can promote the formation of beta-Sialon. The beta-Sialon based composites can be synthesized at 1723 K for 6 h while heating the sample with mass ratio of carbon black to fly ash of 0.56. The as-received beta-Sialon in the composites exists as granular with an average particle size of 2-3 mu m. The preparation process of beta-Sialon based composites includes the formation of O'-Sialon, X-Sialon and beta-Sialon as well as the conversion processes of O'-Sialon and X-Sialon to beta-Sialon.