Synthesis of β-sialon/Ti(C, N) powders from mineral waste residue via carbothermal reduction nitridation

Abstract

β-sialon/Ti(C, N) composite powders were synthesized via carbothermal reduction nitridation method with low-grade bauxite and ilmenite as starting materials and coke as the reducing agent. The influences of the synthesis temperature, the low-grade bauxite–ilmenite mass ratio, and the amount of coke additive on the phase transformation and morphology of β-sialon/Ti(C, N) composite powders were investigated with X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The results showed that the optimal experimental conditions for the CRN synthesis of β-sialon/Ti(C, N) composite powders were as follows: 4 h treatment, nitrogen atmosphere, and the theoretical coke quantity. When the ratio of ilmenite in raw materials increased from 10% to 50%, the synthesis temperature declined from 1400 °C to 1350 °C. The morphology of well-developed β-sialon crystals was columnar. After the carbothermal reduction nitridation process of ilmenite, the resultant Ti(C, N) particles were distributed dispersedly among the composite powders, and either Fe or Fe₃Si existed in the products, depending on the reaction temperature.