Electrolytic reduction of dissolved iron oxide to metal iron in molten salts with an inert anode is an alternative short route for steelmaking without CO2 emissions. A novel and simple integrated yttria-stabilized zirconia (YSZ) cell was constructed from a YSZ tube with a closed end. The YSZ tube played multiple functions, including the container for the molten salts, the solid electrolyte membrane in the O 2-| YSZ | Pt | O2 (air) reference electrode (RE), and the solid electrolyte membrane between the working and counter electrodes (WE and CE). Electrochemical behavior of ferric ions (Fe 3+) that were formed by dissolution of 0.5 wt pct Fe2O3 in the molten CaCl2-NaCl eutectic mixture was investigated on a Pt WE at 1273 K by various electrochemical techniques including cyclic voltammetry, linear scan voltammetry, square wave voltammetry, chronopotentiometry, chronoamperometry, and potentiostatic electrolysis. Analysis of the mechanism of electrode reactions was further assisted by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Some electrochemical parameters were obtained, including the number of exchanged electrons and the diffusion coefficient of ferric ions in the mixed molten salts. The results from various electrochemical techniques are in good agreement with each other, and show that the electrochemical reduction of Fe 3+ to Fe in the molten salt mixture could be a single three-electron transfer step and diffusion controlled reaction that was also possibly reversible. This work may form the foundation for extraction of iron and alloys from molten salts and also provid a stable O 2-| YSZ | Pt | O2 (air) RE with wide applicability for investigation on electrochemical properties of other electroactive metal oxides in molten salts.

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Effects of the basicity and the CaF2 content on viscosity of CaF2–CaO–SiO2 slag with high CaF2 content for electroslag remelting process were investigated by the rotating cylinder method in the temperature ranging from 1773 to 1533 K. The relationship between the structure and the viscosity variation of the slag was also clarified by the Fourier transform infrared (FT-IR) spectroscopy of water-quenched slags. The results show that the viscosity gradually decreases with the increase in the basicity of the slag from 1 to 3 under the present experimental conditions. It is found that the CaO does not depolymerize all silicate complex anions for the slag with the basicity of 1 at 1773 K and there are still some bridging oxygens. With the increase in the basicity to 3, the silicate complex anions are almost completely depolymerized to simple ions. As the CaF2 content increases from 40 to 80 mass%, the viscosity of the slag decreases due to the dilution of CaF2 for the concentration of the silicate complex anions in unit volume of the slag. Moreover, the effect of the temperature on the viscosity is not remarkable. The activation energy of viscous flow exhibits the decrease from 40.4 to 26.7 kJ · mol−1 with the increase in the basicity from 1 to 3, and also the decrease from 66.6 to 31.0 kJ · mol−1 with the increase in the CaF2 content from 40 to 80 mass%.

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/srin.202200778.