Reduction of Platelet Fe₂O₃ Single Crystal Reacted with Na₂O,K₂O,CaO and Silicate Slag at the Surface of Fe₂O₃ c Plane

　The effect of K₂O, Na₂O and CaO on the reduction behavior of Fe₂O₃ was investigated. Platelets of Fe₂O₃ single crystals were prepared by the flux method. The size of the crystals was approx. 3mm in width and 0.3mm in thickness. For the reaction of Fe₂O₃ with K₂O, Na₂O, and CaO, small amounts of each carbonate powder were placed on the flat plane (0001) of Fe₂O₃ and heated at 1100〜1300℃ in the air. It was confirmed by EPMA that the reaction products with those substances were formed on some parts of the Fe₂O₃ crystal. The crystals were reduced at 750℃ in CO and H₂ streams, and the surface structures were observed by SEM.
　The results obtained were as follows. When alkaline metals (as Na₂O, K₂O) were present in Fe₂O₃, the abnormal swelling took place during the reduction. It was considered that the swelling was caused by (1) the cracking of the crystal at the early stage of the reduction, (2) the fibrous iron formation and (3) the carbon deposition on the reduced iron. The fibrous iron formation was also observed in the grain boundary of calcium ferrite. The reduction with a glassy slag (SiO₂-Al₂O₃-CaO) was also investigated and no swelling phenomenon was shown.