Electrochemical Behavior of Titanium Ions in Various Molten Alkali Chlorides

Abstract

Cyclic voltammetry and square wave voltammetry were performed for TiCl 3 at 1023 K, in molten LiCl, LiCl-KCl, NaCl-CsCl and CsCl, respectively. The anodic process from Ti(III) to Ti(IV) is a simple reversible process in all the alkali chloride melts. Ti(III) can be reduced directly to Ti in one step, in CsCl, while Ti(II) will appear before Ti in LiCl, LiCl-KCl and NaCl-CsCl. The electrode potentials of redox couples of titanium species decrease with the decrease of the polarization power of solvent alkali ion.

Electrochemical Deposition of Al-Ti Alloys from Equimolar AlCl3 + NaCl Containing Electrochemically Dissolved Titanium

“…The composition of a solvent-fused salt has a dramatic influence on electrodeposition process of titanium [14,15]. The published works on melts used for titanium deposition (inorganic and organic melts and ILs) emphasize problems encountered with the control of electrolytes made by titanium salts dissolution.…”

“…The potentials related to these processes can be read from voltammograms. Their values greatly depend on temperature, the composition of electrolytes and concentrations (amounts) of dissolved titanium ions in the melt [1,3,10,[13][14][15]24]. In the equimolar AlCl 3 -NaCl melt used, the average recorded values of the reversible potential for the pairs Ti 4+ /Ti 3+ , Ti 3+ /Ti 2+ and Ti 2+ /Ti were approximately 0.410, 0.190 and 0.149 V. However, they can be identified also from the potentiodynamic polarization curve of titanium recorded in the used melt at 200 • C ( Figure 2).…”

“…According to some studies in chloride electrolyte systems, metallic titanium is usually in equilibrium with two different titanium species Ti 2+ and Ti 3+ [9,14]. The presence of different oxidation states of titanium ions in molten chloride electrolytes and the tendency for reoxidation or disproportionation reactions mostly cause poor current efficiency and deposited product quality [9,15]. Furthermore, the melt temperature has a significant influence on equilibrium and electrodeposition processes of titanium in aforementioned electrolytes [14,15].…”

“…In comparison to other molten salt electrolytes systems, the electrochemical behaviour of titanium ions in chloride melts is different because of the stability of various oxidation states of titanium ions, which is caused by the influence of electrolyte composition [12][13][14][15] and temperature [14,15].…”

“…The fundamental aspects of chemistry and electrochemistry of titanium ions in molten salt electrolytes have been investigated, but data on the electrochemical behaviour of titanium ions in molten chloride/fluoride salt electrolytes are scarce and contradictory. The main barrier for successful development of an electrochemical route for aluminium-titanium alloy production is associated with the existence of different oxidation states of dissolved titanium species, namely Ti(II), Ti(III) and Ti(IV) [9,[12][13][14][15].…”