Magnetic microwave heating of magnetite–carbon black mixtures

The kinetics of the carbothermal reduction of magnetite to iron using carbon black was investigated in situ using the time-resolved X-ray powder diffraction synchrotron radiation technique for the case of magnetic microwave heating in an H-field maximum and conventional heating, respectively. The phase transformation sequence and the reaction kinetics were studied with respect to the case of heating in a microwave E-field maximum investigated earlier. The reduction to iron proceeds an order of magnitude faster when using microwaves. It proceeds at comparable rates in the E- and the H-field microwave heating, yet the reaction temperature is lowered to 770 °C in magnetic H-field microwave heating, compared to nearly 1200 °C for the E-field case.

► First in situ synchrotron study of reduction of Fe3O4 to Fe during H-field microwave heating.
► Faster kinetics of the carbothermal reaction when microwaves are used.
► The carbothermal reaction occurs at much lower temperature in microwave H-field than in E-field.