Thermodynamic models for metal-salt-oxide liquid solutions

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The objective of the proposed research program is to develop a strong and systematic approach for the modeling of mixed metallic and ionic molten phases in order to obtain reliable predictions of the liquid phase thermodynamic properties and its equilibria with solid and gas phases in multicomponent systems of industrial and scientific interests. Primary metals production tions, diffusion of species under different conditions. The CALPHAD Method has very strongly established itself as a mandatory tool in the calculation of phase equilibria and thermodynamic properties of metallurgical and chemical inorganic systems. It consists in developing Gibbs energy functions, calibrated on experimental data and First-Principles calculations, for every given phase in a chemical system. Chemical and phase equilibria can be computed by the use of minimization techniques applied to find the combination and composition of phases that give a minimum in the energy. This approach is now applied worldwide for multicomponent chemical systems. Unfortunately, the proper modeling of the miscibility and immiscibility between liquid metals and molten oxides/salts is not well established, especially relative to the known chemical species that are affecting their electrical conductivity. Molten metal-salt equilibria show cases of full liquid miscibility (Fe-FeS, Cs-CsCl), partial miscibility (Cu-Cu2O), strong immiscibility (Cu-Cu2S, Li-LiF), or virtually complete immiscibility (Mg-MgCl2). The scientific approach in this project consist in systematic tests and implementation of a liquid thermodynamic model which will use ion species derived from the electrical conductivity measurements to cover, with a single Gibbs energy function, the complete composition range between the liquid metal and the ionic composition range. This model will be tested for alkali metal-alkali halide salts, for Mg-Cd-Bi-chlorides and for metal alloys that exhibits a partial ionic character, such as the alkali-heavy metals, and finally for the Cu-Fe-S-O-Si system used for Cu-smelting and converting. For the first time, the proposed research permit to evaluate correctly both the metal dissolution in ionic melts and non-metal dissolution in alloys. Benefits for Canada will be in the field of metal production (Cu smelting, specialty metals and alloys) and in the energy efficiency by increasing current efficiency in electrolysis.