Preparation of Sialon Powder from Mixture of SiO2 and Al2O3⋅2H2O by Thermal Carbon Reduction

Mixtures of SiO2 and Al2O3⋅2H2O with the atomic ratio Si/Al=1 were reduced by the stoichiometric amount of carbon between 1350° and 1500°C in flowing nitrogen to prepare sialon powder. The nitrogen content in the prepared powder, predominantly β-sialon, leveled off after heating for 5-15h at each temperature. However, loss of Si increased with increasing temperature. The decomposition of the sialon powder was observed at 1500°C. The morphology of the sialon particles prepared at 1350°C was similar to that of the starting mixtures of SiO2 and Al2O3⋅2H2O. The sialon particles prepared at 1470°C were finer than those at 1350°C and different in morphology from the starting powder.