Abstract
The influence of the F/Cl atomic ratio on the morphology of titanium metal, deposited by electrorefining in various alkali halide solvent mixtures and K2TiF6 solute, was investigated. A continuous transition from powdery deposits in chloride mixtures (F/Cl = 0), through dendritic deposits in chloride-fluoride mixtures (0 < C/Cl < ∞), to coherent and adherent deposits in fluoride mixtures (F/Cl = ∞), was evidenced. This dependence was explained in terms of the increase of the thermodynamic stability of TiF6 3− anion (and the consequent decrease of the activity of Ti3+, i.e. electrocrystallization centres available in the melt), with increase of the parameter F/Cl. This is supported by the observed increase in the decomposition potential, E d, and the shift of the Ti3+ discharge potential, E p, toward more negative values, in the same sequence. The influence of the F/Cl atomic ratio on current efficiency, η, on the grain size distribution and on the chemical purity of electrodeposited titanium metallic powder, was also discussed.
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Abbreviations
- cd:
-
current density
- E d :
-
decomposition potential
- E p :
-
discharge potential
- (E 1/2)c :
-
half wave potential of the complex
- (E 1/2)f :
-
half wave potential of the free ion
- η:
-
current efficiency
- d m :
-
average diameter
- P m :
-
molar polarizing strength
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Ene, N., Zuca, S. Role of free F− anions in the electrorefining of titanium in molten alkali halide mixtures. J Appl Electrochem 25, 671–676 (1995). https://doi.org/10.1007/BF00241929
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DOI: https://doi.org/10.1007/BF00241929