Behavior Analysis of CaF2 in Magnesia Carbothermic Reduction Process in Vacuum

Magnesium production by carbothermic reduction of magnesia with CaF₂ in vacuum was investigated experimentally by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermodynamic analysis. Thermodynamic calculations indicate that magnesium was generated by a carbothermic reduction among MgO-C system, which should be above 1500 K (1227 °C) (50 Pa). According to the carbothermic reduction analysis, the CaF₂ does not participate in the carbothermic process. The experimental results demonstrated that the mass loss increased along with increasing CaF₂. The percentage was up to 92 pct with 5 pct CaF₂.The reduction degree increased with CaF₂ more than it without CaF₂ obviously. Considering the reduction degree and economic benefit, 5 pct CaF₂ was the optimal choice. The purity of metal magnesium reached 95.59 wt pct, which has perfect crystallization and lamellar structure. CaF₂ did not participate in magnesia carbothermic reduction in vacuum; instead, it played a catalytic role during the process.