Influence of Heating Temperature, Keeping Time and Raw Materials Grain Size on Al₄O₄C Synthesis in Carbothermal Reduction Process and Oxidation of Al₄O₄C

Abstract

Several factors, influencing synthesis of Al₄O₄C in carbothermal reduction process from Al₂O₃ and C starting raw materials in argon atmosphere, and oxidation characteristics of Al₄O₄C were investigated. The formed Al₄O₄C in heated specimens was increased and Al₂O₃ and C were decreased with increase of heating temperature and extension of keeping time. Grain size of Al₂O₃ had obvious influence on synthesis of Al₄O₄C and fine Al₂O₃ was more advantageous. The activation energy of the reduction reaction from Al₂O₃ and graphite to form Al₄O₄C was calculated as 358.0 kJ/mol basing on experimental data. Al₄O₄C was observed to be oxidized from about 820°C in air. Al₄O₄C, buried in graphite powder and heated in air, was converted into Al₂O₃ and C.