Oxidation treatment of pyrolytically deposited β-SiC in an atmosphere of CO-CO2 gas mixtures

Pyrolytically deposited β-SiC was treated in oxidizing atmospheres of various CO-CO2 mixtures between 1000 and 14000C. Electron scanning microscopy and X-ray structure analysis have been used to investigate the surface changes of SiC. Under these conditions SiO2(β-cristobalite) is developed forming a continuous coating on the SiC substrate. The thickness of the β-cristobalite layer is determined from the relation of the X-ray reflex intensities of SiO2 and SiC. The growth rate in this continuous coating is only dependent on the oxygen diffusion rate in β-cristobalite. The oxygen diffusion coefficient is calculated from the growth rates determined from X-ray analysis of the SiO2-layers at various temperatures. (Auth.)