Electrical Resistivity of Transformed Carbon Materials in the Silicon Furnace

Optimal current paths through the silicon furnace depend on the electrical properties of the charge materials. It is essential for good tapping conditions that sufficient current is supplied to the arc and lower part of the furnace. As such, the electrical resistivity of the charge mix as it is transformed in the furnace is investigated. Various carbon materials (coal, charcoal, and char) are partially transformed at high temperatures to silicon carbide (SiC) through reactions with silicon monoxide (SiO) gas. The temperature gradient in the crucible creates layers of varying degrees of conversion. These layers are separated and characterized based on SiC, carbon, and Si content. The electrical resistivity of each layer is then measured from 25–1600 °C. When the majority of the material is transformed to SiC, it will raise the resistivity compared to the carbon material, until silicon forms, when it will decrease again. The original structure appears to be more important to the resistivity than the transformation to SiC.