Titanium compounds, electrodeposition

Interesting potential applications of molten salts are electroplating and electrorefining of refractory metals and rare earth metals. Electrowinning of titanium has been tested on a pilot scale. Electrodeposition of refractory compounds like TiB2 has also been demonstrated. Due to space limitations these more exotic applications of molten salts will not be treated here. However, short chapters on molten salt batteries and fuel cells are included. 

Mukhopadhyay et al. [98] studied the titanium electrodeposition on a Au(lll) substrate in the l-methyl-3-butyl-imidazolium bis(trifluoromethylsulfone) imide ([BmimJBTA) ionic liquids with 0.24 M TiCl at room temperature. It was found that TiCl is converted to TiCl in a first step, which is subsequently reduced to metallic Ti. Two-dimensional (2D) clusters form preferentially on the terraces in underpotential deposition range. At a potential of -1.8 V, a dense layer of three-dimensional (3D) clusters of titanium of 1-2 nm thickness is formed. The electrochemical reduction of tetravalent titanium species in hydrophobic 1-n-butyl-l-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]TFSI) room-temperature ionic liquid was studied by Kayayana et al. [182]. It was found that the stepwise reduction from Ti(IV) to Ti(III) and probably Ti(II) in [BMP]TFSI containing TiBr without [BMP] Br. The potentiostatic cathodic reduction gave some deposits at 180°C. The reduction of Ti(rV) species at -2.3 V led to the deposition of some Ti compounds containing... 

Recently, The reduction of TiCl has been studied in Lewis acid ionic liquids [BmimjCl/AlClj in our laboratory. It was found that the aluminum-titanium alloy of 14 pm thickness as given in Fig. 5.9 can be deposited on the titanium or aluminum substrate. Thermodynamically, Ti deposition should be possible in thick layers in ionic liquids, but the right ionic liquid and especially the right titanium precursors still have to be found. An idea might be to make TiCTf N) or similar compounds for titaninm electrodeposition. 

Refractory metals give only rise to few intermetallic compounds, due to the very high temperature of the liquidus of their alloy systems, though de Lepinay et al have obtserved the formation of copper-titanium intermetallic compounds during the electrodeposition of titanium [40]. 

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