Electrochemical Behavior of Ti(III) Ions in Molten LiF–LiCl: Comparison with the Behavior in Molten KF–KCl

Abstract

Ti(III) ions has been prepared by the addition of 0.50 mol% of Li2TiF6 and 0.33 mol% of Ti sponge to LiF–LiCl melt, and their electrochemical behavior has been investigated using cyclic voltammetry and square wave voltammetry at 923 K. The reduction of Ti(III) ions to metallic Ti is observed around 1.2 V vs Li+/Li, whereas the oxidation to Ti(IV) ions is observed at 2.78 V as a reversible electrochemical process. The diffusion coefficient of Ti(III) ions is determined to be 3.2 × 10−5 cm2 s−1. The electrochemical behavior of Ti(III) ions in LiF–LiCl melt is compared to that in KF–KCl melt. The potentials for Ti(IV)/Ti(III) and Ti(III)/Ti(0) couples based on the F2/F− potential in LiF–LiCl melt are more positive than those in KF–KCl melt by 0.41 V and 0.31 V, respectively. Such differences in potential are explained by the difference in interactions between Li+–F− and K+–F−.

Electrochemistry of uranium in molten LiCl-LiF

“…the conversion was obtained by graphical estimation of the potential at zero current in the linear variation region during the positive scan of voltammograms as shown in Fig. 1 [38] . The working electrode (WE) was 0.5 mm diameter W wire and the counter electrode (CE) was a 1 mm diameter Mo wire.…”

“…Studies devoted to mixed chloro-fluoride salts are scarce, plating iron in CaCl 2 -CaF 2 was reported by Haarberg and al. [37] and, more recently, Ti electrodeposition in both LiCl-LiF and water soluble KCl-KF has been investigated [38] .…”

Optimization of Electrolysis Conditions for Ti Film Electrodeposition from LiF – LiCl Eutectic Molten Salt

“…After blank measurements in molten LiF-LiCl, 0.50-5.0 mol% of Li2TiF6 and 0.33-3.3 mol% of Ti powder (Kojundo Chemical Laboratory Co., Ltd., 99.9%) were added to the melt. Here, the synthetic method of Li2TiF6 was reported in our previous paper (17). The added amounts of Ti powder were approximately twice the amounts necessary to generate Ti(III) ions by comproportionation reaction between Ti(IV) ions and Ti(0) according to Eq.…”

“…Based on these reports, we have focused on the electrodeposition of titanium in fluoride-chloride mixtures consisting of single cations and having enough fluoride concentrations (14)(15)(16)(17). We have already reported the electrochemical behaviors of Ti(III) ions and the electrodeposition of Ti in molten KF-KCl (45:55 mol%, 923 K) (14)(15)(16) and LiF-LiCl (45:55 mol%, 923 K) (17). We found that LiF-LiCl has an advantage for electrodepositing smooth Ti films due to its lower melting point (774 K at the eutectic composition (18)).…”

Recent Studies on Titanium Refining: 2017–2020

“…126,127) The electrochemical Dy-alloying behaviors of Inconel and Hastelloy in molten LiFCaF 2 DyF 3 were studied by Watanabe et al 128) The diffusion of Ti 3+ was investigated in LiFLiCl0.50 mol% Li 2 TiF 6 0.33 mol% Ti at 923 K. The potentials for Ti(III)/Ti(0) and Ti(VI)/Ti(III) in LiFLiCl were reported to be more positive than those in KFKCl. 129) Electrodeposition on the Ni substrate was conducted using K 3 TiF 6 from K 2 TiF 6 and Ti in the water-soluble KFKCl molten salt at 923 K. The deposited film was adherent, compact, and smooth without cracks or voids. 130)…”