Silicon carbide formation from methane and silicon monoxide

Trygve Storm Aarnæs,Eli Ringdalen,Merete Tangstad

doi:10.1038/s41598-020-79006-6

Trygve Storm Aarnæs, Eli Ringdalen + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-79006-6

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Abstract

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 °C and 1750 °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 °C which is right after the melting of silica.

Highlights

Silicon carbide (SiC) formation plays an important role during the production of elemental silicon
The primary purpose of the carbon is to react with the silicon monoxide gas (SiO) gas which rises through the furnace, because SiO that makes it past the upper region without reacting will represent a large reduction in the furnace’s energy efficiency
As a result, CH4 could be used to control the temperature in a silicon furnace, which would allow for increased control over SiO gas losses, and much greater energy efficiency

Summary

OPEN 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. One possibility is SiO and graphite from the crucible reacting to form a SiC layer according to reaction (2), which would reduce the weight loss. Temperature had a large effect on the weight loss caused by the reaction between SiO2 and SiC, which produced SiO gas, reaction (1). The effect of hydrogen is attributed to enhanced diffusion rates Another possibility is that hydrogen may dissolve in the molten S iO213, and the dissolved hydrogen produces an additional contribution participating in the formation of gas bubbles at the SiC/SiO2 interface. As a result, CH4 could be used to control the temperature in a silicon furnace, which would allow for increased control over SiO gas losses, and much greater energy efficiency

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Findings

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