The Phase Diagram of a CaO-Al2O3-VOx Slag System under Argon Atmosphere at 1500 °C

Abstract

The thermodynamic properties of the CaO-Al2O3-VOx slag system are of great significance to the direct alloying of vanadium in the smelting process of vanadium steel. In this paper, the phase equilibrium relationship of the CaO-Al2O3-VOx system under argon atmosphere at 1500 °C was studied with a high-temperature phase equilibrium experiment. Combined with SEM-EDS, XRD, and XPS, the types and compositions of each phase of the equilibrium slag samples and the content of different valence states of the vanadium element were determined. The result shows that under argon atmosphere (p(O2) = 10−3 atm) at 1500 °C, the CaO-Al2O3-VOx slag system contains four three-phase regions, seven two-phase regions, and a single-phase region (glass phase). The phase equilibrium results were plotted in a CaO-Al2O3-V2O5-VO2 spatial phase diagram, and the phase equilibrium results were projected on the CaO-Al2O3-V2O5 and CaO-Al2O3-VO2 pseudo-ternary phase diagrams, respectively. In the end, the rationality of projecting the phase equilibrium results to the pseudo-ternary phase diagram was quantitatively evaluated.

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“…Bao et al based their research on the CaO-MoO3-La2O3 ternary phase diagram, using the solid-state reaction method to design and synthesize two new types of microwave dielectric ceramics, laying the foundation for the scientific research and practical application of related ceramic systems [15]. Liu et al established the CaO-Al2O3-Vox ternary phase diagram, conducting in-depth research on the changes in the valence state of vanadium during vanadium steel smelting processes, also achieving good results [16]. However, experimental studies on phase diagrams require a significant amount of time and economic costs, and they are faced with challenges such as experimental difficulty and time consumption.…”