Gravimetric determination of free carbon and silicon carbide in silica fume

Silica fume is formed as a by-product in the manufacture of silicon from quartzite. This paper describes an analytical method for the determination of free carbon and silicon carbide in silica fume. The silicon carbide was determined after removal of free carbon, amorphous silica, crystalline silica, graphite and silicon from the fume. The free carbon content was found to vary from 2 to 8% while the silicon carbide content ranged from 1 to 5%. X-ray diffraction, thermal analysis, scanning electron microscopy and Fourier Transform infrared spectroscopy were used to validate the steps used in the analytical procedure. The purpose of determining the free carbon and silicon carbide content of the fume is to help understand the efficiency of the reduction process and mechanism of the reaction.