1991 Volume 77 Issue 6 Pages 783-789
The rate constant of parabolic law of MgCr2O4 spinel formation from MgO and Cr2O3 was measured during 1 573 and 1 873 K. The rate constant decreased according to -3/4 power of oxygen partial pressure less than about 30 Pa, increased according to 3/4 power one more than the oxygen pressure and was constant less than 0.1 Pa. On the other hand, the electric conductivity was constant against the oxygen pressure. The interface of spinel texture grown from MgO and Cr2O3 devided the spinel layer in the ration of 1:3, respectively. Concludingly, the rate of spinel formation is limited by the diffusion of chromium vacancy in the oxygen pressure more than 30 Pa and by that of interstitial chromium ion less than 30 Pa. In the oxygen pressure less than 0.1 Pa, the concentration of interstitial chromium ion is constant because of the solubility of MgO in the spinel. Finally, the dissolution rate of the spinel into molten slag was estimated using the rate constant of spinel formation.
