Oxygen Contents in Molten Ni in Equilibrium with Slag of CaO–SiO<sub>2</sub>–MgO–NiO System

Abstract

A study has been carried out to measure the oxygen contents in molten Ni in equilibrium with NiO in the top slag, contained in a magnesia crucible, in the temperature range higher than 1500°C. The slag was composed of CaO–SiO2–MgO satd.-NiO system with (mass% CaO)/(mass% SiO2) = 1 and 8 mass% NiO. Firstly, it was found that oxygen content rapidly increased after adding the slag of CaO–SiO2–MgO–NiO system into molten Ni and that it took 30 minutes to attain equilibrium. The measured oxygen contents were lower than those in equilibrium with pure solid NiO and increased with an increase in temperature. Thermodynamic analysis was made on the basis of the above results. It was found that activity of NiO in the present slag of CaO–SiO2–MgO satd.-NiO system was positively deviated from ideal solution. In addition, Henry constant of NiO in this oxide system was obtained as the following relation under the assumption that Henry’s law is available: