Compatibility of Oxides in Contact with a LiCl-KCl and Copper Solution at High Temperatures

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Student Presentation

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Chad Watson


Electro-refining, a method for refining and reprocessing metals, requires an electrolytic solution to…. Using molten LiCl-KCl salt as the electrolyte, a dendritic mixture of corrosive molten salts and purified metals is produced. Before the metals can be recycled, they must first be separated from the salts. Current electro-refining processes incorporate liquid-vapor separation techniques, where the salts are distilled from the mixture. Containment materials for this process are paramount; the containment crucibles must not only be able to withstand temperatures approaching 1500oC, but also be resistant to corrosive breakdown by molten salt. Thermally and chemically stable oxides (alumina, zirconia, and yttria) were selected as the most viable material systems for prolonged exposure to the corrosive environment. Each oxide was placed in contact with 30 wt% LiCl-KCl/70wt% copper at temperatures approaching 1500oC for up to 40 hours. The oxides were then analyzed for corrosion products, surface reactions, and penetration depth using X-ray diffraction (XRD) and electron dispersive spectroscopy (EDS). Preliminary XRD characterization demonstrated that for short durations, zirconia is immune to chemical attack by molten LiCl-KCl, whereas alumina suffered extensive surface corrosion.

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