Fibrous Iron Growth during Reduction of Fe₂O₃ and Fe₃O₄ Single Crystal

　The change of crystal structure during reduction of iron oxide and the growth mechanism of fibrous iron were investigated.
　In order to elucidate the crystallographic transition of Fe₂O₃ during reduction, platelets of Fe₂O₃ single crystal with flat (0001) plane were used as the sample. Each of Fe₃O₄, FeO and Fe was prepared by reducing the Fe₂O₃ sample at 750℃ with CO-CO₂ and H₂-H₂O gaseous mixtures of appropriate compositions. Further a reduction test of octahedral Fe₃O₄ single crystal was conducted. The structures of the products were analyzed by X-ray diffraction including the Laue method and scanning electron microscopy.
　The X-ray diffraction revealed that the (0001) plane of Fe₂O₃ changed to the (111) plane of Fe₃O₄ and (111) plane of FeO by the epitaxial reaction. SEM revealed that as the reduction proceeded, steps parallel to the (0001) plane of Fe₂O₃ appeared remarkably, and fibrous iron grew from some nuclei on the steps. The fibrous iron was not seen on the (0001) plane of Fe₂O₃, and the direction of most active growth was [2110] of Fe₂O₃. It became apparent that the growth of fibrous iron proceeds from the base.