Silicon carbide formation from methane and silicon monoxide

Silicon carbide (SiC) formation plays an important role during the production of elemental silicon. SiC forms through a high temperature reaction between silicon monoxide gas (SiO) and carbon. Currently, the carbon sources are solids, however finding a way of substituting the solid carbon with methane could have several advantages. SiC formation was studied in argon, hydrogen and methane containing atmospheres at 1650 degrees C and 1750 degrees C. SiO gas was generated from pellets of a 1:2 molar ratio of SiC and silica (SiO2). The reactions were investigated through CO off-gas analysis in conjunction with measuring the weight change. After each experiment, the reaction products were examined in a scanning electron microscope with secondary electrons and through energy-dispersive X-ray spectroscopy. It was confirmed that SiC may form from SiO and methane. Increasing the methane content to 5% caused a significant increase in SiC formation. Furthermore, the SiC structure was also highly sensitive to the methane content that was used. In addition, the SiO producing reaction was affected by hydrogen. The hydrogen lead to an increased rate of SiO formation relative to what was seen in argon. The effect of hydrogen was most pronounced at 1750 degrees C which is right after the melting of silica.