On the electrodeposition of titanium in ionic liquids.
ABSTRACT The ability to electrodeposit titanium at low temperatures would be an important breakthrough for making corrosion resistant layers on a variety of technically important materials. Ionic liquids have often been considered as suitable solvents for the electrodeposition of titanium. In the present paper we have extensively investigated whether titanium can be electrodeposited from its halides (TiCl(4), TiF(4), TiI(4)) in different ionic liquids, namely1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf(2)N), 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl-sulfonyl)amide ([BMP]Tf(2)N), and trihexyltetradecyl-phosphonium bis(trifluoromethylsulfonyl)amide ([P(14,6,6,6)]Tf(2)N). Cyclic voltammetry and EQCM measurements show that, instead of elemental Ti, only non-stoichiometric halides are formed, for example with average stoichiometries of TiCl(0.2), TiCl(0.5) and TiCl(1.1). In situ STM measurements show that-in the best case-an ultrathin layer of Ti or TiCl(x) with thickness below 1 nm can be obtained. In addition, results from both electrochemical and chemical reduction experiments of TiCl(4) in a number of these ionic liquids support the formation of insoluble titanium cation-chloride complex species often involving the solvent. Solubility studies suggest that TiCl(3) and, particularly, TiCl(2) have very limited solubility in these Tf(2)N based ionic liquids. Therefore it does not appear possible to reduce Ti(4+) completely to the metal in the presence of chloride. Successful deposition processing for titanium in ionic liquids will require different maybe tailor-made titanium precursors that avoid these problems.
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ABSTRACT: The electrochemical behavior of Ti(IV) and the electrodeposition of Zn-Ti alloys were investigated in a ZnCl2-urea (1:3 molar ratio) deep eutectic solvent containing 0.27 mol L−1 TiCl4. The electrochemical reduction of Ti(IV) to Ti was complicated by the formation of intermediate oxidation states of Ti(III) and Ti(II), as well as the precipitation of TiCl3. It was possible to prepare Zn-Ti alloys containing 5.8–16.7 at.% Ti. The composition and surface morphology of Zn-Ti alloys depended on deposition potential and temperature. The deposits could be indexed to a disordered hexagonal close-packed structure similar to pure Zn and were completely chloride-free. The current efficiency for the deposition of Zn-Ti alloys varied from 38.4 to 67.9 %.Journal of Solid State Electrochemistry 08/2014; 18(8):2149-2155. DOI:10.1007/s10008-014-2468-1 · 2.23 Impact Factor
Russian Chemical Reviews 01/2015; 84(2):159-193. DOI:10.1070/RCR4438 · 2.58 Impact Factor
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ABSTRACT: Electrochemical methods are attractive for thin film deposition due to their simplicity, conformal and high rate deposition, the ability to easily make multilayers of different composition, ease of scale-up to large surface areas, and applicability to wide variety of different shapes and surface geometries. However, many elements from periodic table of commercial importance are too active to be electrodeposited from aqueous solution. Recent advances are briefly reviewed for room temperature methods for electrochemical deposition, including electrodeposition from ionic liquids, electrodeposition from organic solvents, combined electrodeposition and precipitation on liquid metal cathodes, and galvanic deposition. Recent studies of electrodeposition from ionic liquids include deposition of thick (40 μm) Al coatings on high-strength steel screws in a manufacturing environment; deposition of continuous Si, Ta and Nb coatings; and numerous interesting mechanistic studies. Recent studies of electrodeposition from organic solvents include Al coatings from the AlCl3–dimethylsulfone electrolyte, which demonstrate that additives can be employed to suppress impurity incorporation and to improve the deposit quality, and thick (5–7 μm) and continuous Si coatings from SiCl4 in acetonitrile. Galvanic deposition of Ti, Mo and Si coatings onto Al alloys has recently been reported, which is potentially much simpler and less expensive than electrodeposition from ionic liquids and organic solvents, but has complications associated with substrate consumption and coating adhesion.Current Opinion in Solid State and Materials Science 12/2014; 19(2). DOI:10.1016/j.cossms.2014.11.006 · 7.17 Impact Factor