High-temperature mass spectrometric study of the vaporization processes of V2O3 and vanadium-containing slags

A Knudsen effusion mass spectrometric method was used to study the vaporization processes and thermodynamic properties of pure V(2)O(3) and 14 samples of vanadium-containing slags in the CaO-MgO-Al(2)O(3)-SiO(2) system in the temperature range 1875-2625 K. The system was calibrated using gold in the liquid state as the standard. Vaporization was carried out from double tungsten effusion cells. First it was shown that, in vapor over V(2)O(3) and the vanadium-containing slags in the temperature range 1875-2100 K, the following vapor species were present: VO(2), VO, O, WO(3) and WO(2), with the latter two species being formed as a result of interaction with the tungsten crucibles. The temperature dependencies of the partial pressures of these vapor species were obtained over V(2)O(3) and the slags. The ion current comparison method was used for the determination of the V(2)O(3) activities in slags as a function of temperature with solid V(2)O(3) as a reference state. The V(2)O(3) activity coefficients in the slags under investigation indicated positive deviations from ideality at 1900 K and a tendency to ideal behavior at 2100 K. It was shown that the V(2)O(3) activity as a function of the slag basicity decreased at 1900 K and 2000 K and was practically constant in the slag melts at 2100 K. The results are expected to be valuable in the optimization of slag composition in high-alloy steelmaking processes as well as for their environmental implications.