Kinetics of the reaction between quartz and silicon carbide in different gas atmospheres

Abstract

This thesis examined the influence of different gas species in the kinetics of SiO2+SiC reaction. The quartz and silicon carbide were crushed to < 38µm, uniformly mixed together with weight ratio of 3:1 and pelletized into pellets. The reaction was studied in isothermal experiments at 1700°C in a high temperature furnace in argon, hydrogen, Ar-CO gas mixtures and Ar-H2 gas mixtures. The concentration of CO in the off gas was measured by a gas analyzer. The samples before and after experiments were characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy and electron microprobe micro-analyzer. The activation energy was determined to be 15.9 to 195kJ/mole by isoconversional method. The SiO2+SiC reaction was accelerated by the increasing concentration of H¬2 in Ar-H2 gas mixtures, which was attributed to the faster diffusion of SiO gas or CO gas in H¬2. CO gas, as one of the products, suppressed this reaction. It is found that the unimolecular decay model described the reaction between SiO2+SiC best and the mathematical expressions of the reaction rate in different gas species were proposed. The SEM results indicated that the quartz became softened at 1700°C.

Key words: SiO2+SiC reaction, isothermal experiment, CO gas, H2 gas, Si production