Preparation of β-SiAlON from coal-mine schists

Different SiAlONs (X, O′, AlN polytypoïd, β) are prepared by carboreduction under nitrogen of coal-mine schists, varying three synthesis parameters (carbon percentage, reaction time, reaction temperature) and using a new heating procedure. Iron oxides, present in the starting product, react with silicon to give iron suicides. β-SiAlONs begin to crystallize at 1300 °C. The optimum conditions for getting a pure phase are 30 mass % of carbon, 1400 °C, and 2 hours. Two morphologies are observed in the final product: fibers and spheres.