KINETICS OF CARBOTHERMAL REDUCTION AND NITRIDATION OF SILICON DIOXIDECARBON MIXTURE

The carbothermal reduction and nitridation kinetics of silicon dioxide /carbon pellet were studied under conditions of various reaction param eters including gas now rate, pellet size, pellet-forming pressure, C/ SiO2 molar ratio, grain sizes of both carbon and silicon dioxide, and reaction temperature by using a thermal gravimetric analysis (TGA) tec hnique. The rate equation and kinetic model expressions of the nitrida tion process in the chemical reaction-controlled region were presented . The activation energy investigated in the temperature range between 1623 and 1748 K was 448 +/- 10 kJ/mol. The reaction-mechanism includin g the formation of a gaseous SiO intermediate was also discussed. The SiO formed from SiO2 being a rate-determining step was confirmed by ex perimental results. These theoretical developments correlated sufficie ntly with observed experimental results.