TEM OBSERVATION MGO-BEARING OR CAO-BEARIN G WUSTITE SOLID-SOLUTION REDUCED TO IRON BY HYDROGEN

Wustite pellets containing MgO or CaO was reduced and the morphologies and microstructure of reduced iron phase were observed. The reduction rate of wustite pellets increased with increasing CaO or MgO, and the rate accelerating effect of CaO was larger than that of MgO. The oxid e particles were uniformly dispersed in the reduced iron. The average particle size of MgO and CaO were 90-120 nm and 10-20 nm, respectively . The particle size distribution of CaO was more narrow than that of M gO. The iron phase reduced from pure wustite was well sintered, wherea s sintering was prevented by MgO or CaO particles. Especially the poro us iron was formed from wustite containing CaO. During the reduction, the concentration of magnesium ion or calcium ion in wustite increased at the reaction interface. The ratio of the vacancy diffusivity to th e chemical reaction rate was calculated from the distance between oxid e particles in reduced iron.