Changes in Morphology and Microstructure of Magnesia-carbon Pellets

The morphology of magnesia-carbon pellets heated in a nitrogen atmosphere between 600 - 1400 C was examined via a number of analytical techniques. Three main activity regions were identified: recalcination (removal of hydroxides and carbonates) up to 800 C; sintering of the MgO between 700 - 1100 C; and commencement of the carbothermal reduction of magnesia above 1200 C. Electron microprobe analysis highlighted the formation of calcium silicate phases from SiO2and CaO impurities in the magnesia. X-ray diffraction analysis showed that densification and grain growth occurred in the magnesia. The findings are useful for the development of the carbothermal process for magnesium production.