Recycling of coal ash for production of dense β-Sialon/ZrN/ZrON-based ceramics without sintering aids via pressureless sintering

Abstract

β-Sialon(z = 2, Si4Al2O2N6)/ZrN composite powders have been synthesized from coal ash, zircon, and active carbon at 1550°C for 6 hours, and β-Sialon(z = 2)/ZrN/ZrON-based composite ceramics (SZZCCS) have been prepared from as-synthesized β-Sialon/ZrN composite powders via pressureless sintering process. The effects of sintering temperatures (1450, 1500, 1550°C) on the phase compositions, microstructures, linear shrinkage ratio, bulk density, and oxidation characteristics of the SZZCCS were investigated in detail, and the oxidation process was also analyzed. It was found that the dense SZZCCS could be prepared at 1550°C for 1 hour, and they mainly consisted of β-Sialon(z = 2), ZrN, and ZrON. The ZrN and ZrON particles were uniformly distributed on the β-Sialon matrix. The sintering properties of the SZZCCS were greatly improved with increasing the sintering temperature. The SZZCCS sintered at 1550°C for 1 hour possessed excellent oxidation resistance at 900°C for 6 hours due to their dense microstructures.