抄録
The effect of the presence of K2O, Na2O, and CaO in Fe2O3 on its reduction behavior was investigated.Platelets of Fe2O3 single crystals were prepared by the flux method using Na2B1O7, glass as a flux. The size of the crystals was approx. 3 mm in width and 0.3 mm in thickness. In order to make Fe2O3 react with K2O, Na2O, and CaO, small amounts of Na2CO3, K2CO3 and CaCO3 powders were placed on the flat plane (0001) of Fe2O3 and heated at 1100-1300°C in air. It was confirmed by EPMA that reaction products of those substances were formed on some parts of the (0001) plane of Fe2O3. The Fe2O3, crystals were reduced at 750°C in CO and H2 streams, and surface structures were observed by SEM. The results obtained were as follows. When alkaline metals (as Na2O, K2O) were present in Fe2O3, abnormal swelling took place during reduction. It was considered that the swelling was caused by the net effects of (1) cracking of the crystal at early stage of the reduction (2) fibrous iron formation and (3) carbon deposition on the reduced iron. The fibrous iron formation was also observed in the grain boundary of calcium ferrite.
