Abstract
The following basic physico-chemical and electrochemical factors, along with the considerations of electrochemical engineering science, are all important in the optimum design of electrolytic cells for the winning, refining, plating and forming of refractory metals: (a) anionic composition of the molten salt solvent; (b) cationic composition of the molten salt solvent; (c) concentration of the solute; (d) temperature of operation of the cell; (e) cathode potential; (f) cathode current density; and (g) acid-base, redox and complexation reactions that can be carried out in the electrolytic bath. In addition, practical limitations arise from such factors as the corrosion of cell and electrode materials, the hydrolysis of many of the hygroscopic salts employed as solutes and solvents and the reactions that occur at the counterelectrodes. More fundamental limitations which have been particularly recognized and characterized recently, arise from highly volatile, high-valency state compounds, insoluble cluster-type compounds and disproportionation reactions that involve intermediate valency state compounds. Examples of the above factors and limitations that have been applied or encountered in recent studies of the electrodeposition of titanium, molybdenum and tantalum are given and discussed. Ways to avoid these limitations are suggested and, in addition, scale-up and cell design are considered within the constraints of total energy and conventional economic process costing.
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Inman, D., White, S.H. The production of refractory metals by the electrolysis of molten salts; design factors and limitations. J Appl Electrochem 8, 375–390 (1978). https://doi.org/10.1007/BF00615833
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DOI: https://doi.org/10.1007/BF00615833