The Reduction of Iron Oxide Single Crystal

Abstract

The change of crystal structure during the reduction of iron oxide and the growth mechanism of fibrous iron were investigated. In order to elucidate the crystallographic transition of Fe₂O₃ during the reduction, platelets of Fe₂O₃ single crystal with flat (0001) plane (approx. 5 mm in width and 0.5 mm in thickness) were used as samples. Each of Fe₃O₄, FeO, and Fe was prepared by the reduction of the Fe₂O₃ sample at 750°C in the CO-CO₂ mixture with an appropriate composition for each. The structures of the products were analyzed by X-ray diffraction including the Lane methods and scanning electron microscopy (SEM).
The X-ray diffraction revealed that (0001) plane of Fe₂0₃ changed to (111) plane of Fe3O4 and (111) plane of FeO by epitaxial reactions. SEM revealed that as the reduction proceeded, steps parallel to (0001) plane of Fe₂O₃ appeared remarkably, and fibrous iron grew from some nuclei on the steps. The fibrous iron was never seen on (0001) plane of Fe₂O₃, and the direction of most active growth was [2110] of Fe₂O₃.