Microwave carbothermic reduction from Fe₂O₃ to Fe₃O₄ powders

A microwave carbothermal reduction process of weakly magnetic Fe₂O₃ powders to ferromagnetic Fe₃O₄ powders was experimentally studied with argon gas as a protective gas and activated carbon as a reduetant. The influences of roasting temperature, holding time and SiO₂ addition on the ingredients of reduced resultants and the magnetization effect of Fe₂O₃ powders were discussed. Under quantificational carbon, roasting temperature is a key factor of the microwave carbothermal reduction. The content of Fe₃O₄ in reduced resultants regularly changed with the roasting temperature increasing. Pure Fe₃O₄ powders were made at a roasting temperature of 650℃ for a holding time of 5 min, and their magnetisability and percent reduction reach the theoretical values of 2.33 and 11.11%, respectively. Above the roasting temperature of 750℃, a plenty of FeSiO₄ and FeO formed in reduced resultants after the microwave carbothermal reduction of Fe₂O₃ powders containing SiO₂, making Fe₃O₄ in reaction resultants decrease and the magnetization effect worsen. It is concluded that the best boasting temperature of Fe₂O₃ powders is from 570℃ to 650℃.