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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.
Physical Chemistry Chemical Physics 05/2008; 10(16):2189-99. · 3.57 Impact Factor
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ABSTRACT: In this work the effect of the counterion incorporated into conducting polymer membranes during synthesis has been investigated. The fluxes attainable, the asymmetric nature of the membrane and the selectivity are influenced by the counterion incorporated.
Journal of Membrane Science 87:47-56. · 3.85 Impact Factor
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ABSTRACT: The transport of a range of functionalised sulfonated aromatics across conducting polypyrrole membranes has been considered. In the course of these studies several unique aspects of the chemical selectivity of these conducting materials have been identified. Using electrochemical quartz crystal microbalance (EQCM) the ion-exchange behaviour of these membranes was investigated to further elucidate the transport mechanism.
Journal of Membrane Science.
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ABSTRACT: The transport of potassium chloride across conducting polypyrrole membranes has been studied. In particular the use of transient (pulsed) electrochemical waveforms to instigate and control the rate of transport has been investigated, and the mechanism by which this transport occurs has been considered.
Journal of Electroanalytical Chemistry. 334:111-120.
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ABSTRACT: We have developed a new generation of intelligent membrane systems using conducting polymers, utilising their unique electroactive properties. The chemical and physical properties of the film may be manipulated in-situ by application of electrical stimuli. This in turn allows modulation of the transport properties (even switching the transport off/on) and selectivity of the membrane. In addition, the versatility of synthesis of conducting polymers allows a wide range of chemistries and hence selectivities to be obtained to target particular applications, such as mineral recovery, protein separation, and salt rejection. Membranes can be fabricated as free standing films, composites, layer structures, or as thin films on conventional substrates. This paper reviews the development of these systems and highlights recent work on membranes with thin selective layers of conducting polymer.
Synthetic Metals 102:1338-1341. · 1.83 Impact Factor
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ABSTRACT: The parameters which influence electrochemically facilitated transport of electroinactive ions across conducting electroactive polymer membranes have been investigated. The design of membranes and the materials used as well as transport cells and systems have been addressed to improve selectivity and flux. Polypyrrole-para-toluenesulfonate (PPy-pTS) was compared with the copolymer of pyrrole with 3-carboxy-4-methylpyrrole (PPy/PCMP-pTS) and their different chemistries resulted in different membrane selectivities for ions. Platinum mesh was found to be the most suitable auxiliary electrode material and its placement in the cell chamber(s) facilitated ion incorporation/expulsion at the membrane working electrode. This enhanced the flux of ion transport. The flux can also further enhanced by narrowing the distance between the membrane working electrode and the platinum mesh auxiliary electrode(s), and/or by stirring to improve the hydrodynamics. An alternative cell design, namely a dual membrane flow through cell, also proved to be more efficient for ion transport. Good connection geometry to the membrane as well as the application of a square wave pulsed potential waveform to the membrane was found to be essential for achieving high and sustainable flux in ion transport.
Journal of Membrane Science.
