Activities of FeO in CaO-Al2O3-SiO2-FeO and CaO-Al2O3-CaF2-FeO slags

Activity coefficients of FeO in molten CaO-Al2O3-SiO2-FeO (<5%) slags were determined at 1673 and 1873 K by equilibrating the slags with copper-iron alloys in a controlled oxygen partial pressure (P-O2=5.71 x 10(-12) atm at 1673 K, 1.90x10(-10) atm at 1873 K). Activity coefficients of iron in copper-iron (<4%) alloys at 1673 K were preliminarily determined by controlling the activity of iron using FeO.Cr2O3 saturated with Cr2O3 in a various oxygen partial pressures (P-O2=3.66x10(-12)-9.14x10(-11) atm). It was found that the activity coefficients of FeO obey Henry's law, and have the maximum value when the ratio of N-CaO/N-SiO2 is about 2 at a constant Al2O3 content. The activity coefficients of iron in copper-iron alloy referred to pure liquid were determined as In gamma(Fe)=2.76-11.3N(Fe). The effect of a CaF2 addition to the CaO-Al2O3-FeO system on the activity coefficient of FeO was also investigated at 1723 K.