Reduction kinetics, magnetic behavior and morphological changes during reduction of magnetite single crystal

Abstract

The true fundamental trends of the different phase transformation steps (Fe 2O 3–Fe 3O 4–FeO–Fe) during iron oxide reduction process are necessary requested. Both of the macroscopic and microscopic changes during these steps have a direct bearing on the overall reduction kinetics. Magnetite single crystals were isothermally reduced in pure hydrogen at 900–1100 °C. The oxygen weight loss during reduction process was recorded as a function of time. The magnetite samples and its reduction products were characterized by X-ray diffraction analysis, reflected light microscope, scanning electron microscope and vibrating sample magnetometer to reveal the effect of hydrogen reduction at different temperatures on reduction behavior, composition, microstructure and magnetic properties of the produced samples. The reduction rate increases with reaction temperature. The reduction at 900 and 950 °C was stopped at 83 and 89% extent, respectively. Depending on the kinetics obtained data from reduction process, the reduction rate was found to be controlled by the solid-state diffusion mechanism. The magnetic characterizations of the reduced magnetite at 900–1100 °C were measured whereas the magnetization value increased from 114.1 to 132.1 emu/g with increasing temperature. Magnetite single crystal was partially reduced at 20, 40, 60, and 80%, its magnetic properties was found to be dependent on the morphology, core–shell like structure is formed at 40% reduction extent.