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The possibility of electrodeposition of W and Co from carbamide melts at 408 K has been examined. When studying the electrochemical behaviour of cobalt and tungsten oxides and their compounds (WO3, Li2WO4, Na2WO4, K2WO4) in molten carbamide, it can be concluded that maximum limiting currents are typical of the system (NH2)2CO -Li2WO4. Cyclic voltammograms showed the potentials of deposition of tungsten and cobalt. Layered W-Co coatings on nickel cathodes have been obtained by the electrolysis of the molten system (NH2)2CO-CoO- Li2WO4.

The great demand for advanced batteries in applications such as mobile devices, the transportation sector, and stationary storage has spurred intensive research and development on rechargeable lithium batteries. The corrosion behavior of Al-foil, as material for theirs current collectors, has long been a concern due to uniform or localized pitting corrosion occurs in contact with an organic electrolyte. Pitting corrosion is attributed to inhomogeneous current flow through the aluminum / electrode interface and results in local breakdown of the passive film on Al-foil. Particular attention among different protective coatings of Al-foil excites Ti-B coatings as conductive and electrochemically inactive protective layers. The main objectives of the present work are investigation of regimes for electrodeposition of Ti-B protective coatings onto Al-foil and examination of the corrosion behavior of Al-foil with such electrodeposited Ti-B protective coatings in contact with an organic electrolyte under various electrodes charging conditions. Low melting point of aluminium (tm = 6600C) made impossible electrodeposition of Ti-B coatings from chloride-fluoride melts (tel = 7000C). But it is possible from ion-organic melts at 70−2000C. In this work was investigated electrodeposition of Ti-B coatings from carbamide melt contains titanium and boron oxides. Cyclic voltammetry has shown the limit current density and potential of electrochemical synthesis. Ultra fine Ti-B coatings were electrodeposited onto Al-foil at 1300C. Figure shows the surface morphologies of an obtained Ti-B coating. Such cost-effective method of obtaining Ti-B protective coatings on Al-foils gives excellent results under theirs using as current collectors in rechargeable lithium batteries. Figure 1

Lanthanum silicides (La5Si4, La5Si3, La4Si, LaSi and LaSi2) are metal-like compounds with semiconductor properties. If this were true, it could become technologically important as an infrared detector material [1]. The possibility of electrochemical synthesis of lanthanum silicides from molten salts were investigated in this work. It can be concluded from thermodynamic calculation that silicon discharge from molten salts more positive than La (~ 0.8 V), in this case electrochemical synthesis possible only in two step, first deposited of Si, next step deposition of La onto Si with formation of lanthanum disilicide: I. 2Si + La(III) +3 e = LaSi2 ΔE0 10233 K = ΔG0 1023 K/ (nF) ≈ 0.500 V,where ΔE0 – is potential (V), ΔG0 - is the Gibbs energy of the reaction I. (J), n – is the number of electrons involved in the reaction (in our case, n = 3), F – is Faraday constant. The electrochemical behaviour of the molten salts system NaCl-NaF-LaF3-K2SiF6 was studied by cyclic voltammetry. A glassy carbon crucible served as a vessel for the melt and as an auxiliary electrode; a W wire was used as the working electrode; the measurements were made with respect to glassy carbon reference electrode 1023 K in argon atmosphere. Typical cyclic voltammogram for molten salts system NaCl-NaF-LaF3-K2SiF6 show two step process of electrochemical synthesis of LaSi2at 1023 K in Ar on W working electrode (Fig. 1 .). On the base of thermodynamic calculation and voltammetric investigation, it has been show that lanthanum disilicide can by electrochemical synthesized from a NaCl-NaF- LaF3-K2SiF6 melt at 1023 K in two step. References R.G. Long, M.C. Bost, J.E. Mahan., Appl. Phys. Lett. 5 3, 1272 (1988). Fig. 1. Voltammogram of a NaCl-NaF-LaF3- K2SiF6 melts on a W working electrode, v= 0.1 V/s. Figure 1

The electrodepositions of tungsten and its alloys has been of considerable interest because of usual properties of the metal and alloys. The electrodepositions of W and Co from water solutions and Na2WO4-WO3-CoO at 1023 K were investigated in more works. The possibility of electrodeposition of W-Co alloys from carbamide melts at 408 K has been examined. When studying the electrochemical behaviour of cobalt and tungsten oxides and its compounds (WO3, Li2WO4, Na2WO4, K2WO4) in molten carbamide, it can be concluded that maximum limiting currents are typical of the system (NH2)2CO-Li2WO4. Cyclic voltammograms showed the potentials of deposition of tungsten and cobalt. Layered Co-W coatings on nickel cathodes have been obtained by the electrolysis of the molten system (NH2)2CO-CoO- Li2WO4 at current densities of 5-10 mA/cm2. The cathodic products were analyzed by XRD and JEM-2100F SEM. Fig. SEM of the surface morphology of W-Co coating deposited by electrolysis from (NH2)2CO-CoO- Li2WO4 melt. Figure 1

Nickel silicides are used as Schottky barrier and as ohmic contacts owing to the combination of properties typical of metal (high electrical conductivity) and nonmetal (low heat conductivity) [1]. Nickel silicides are usually produced by the thermal vacuum spraying of nickel on single-crystalline silicon plates [2]. The objective of this work was to examine the possibility of obtaining nickel silicides by electrolysis of molten salts, containing silicon ions, on a Ni cathode. It can be concluded from thermodynamic calculation that silicon discharge depolarization through NiSi2 formation is 0.110 V at 993K: I. Ni + 2Si = NiSi2 The electrochemical behaviour of the system NaCl-NaF-K2SiF6 was studied by cyclic voltammetry. A glassy carbon crucible served as a vessel for the melt and as an auxiliary electrode; a Ni wire was used as the working electrode; the measurements were made with respect to glassy carbon reference electrode 7200С in argon atmosphere. Current-potential curves exhibited, at potentials more positive (~100 mV) than silicon discharge potential, a new irreversible electrochemical process followed by a chemical reaction. Up to 25 mm thick dense NiSi2 layers have been obtained by the electrolysis of a NaCl-NaF-K2SiF6 melt on a Ni plate at 7200С in argon atmosphere at current density of 50 mA/cm2 (Fig. 1.), which was confirmed by X-ray phase analysis. The chemical composition map of metallographic section shows the silicon distributions. On the base of thermodynamic calculation, voltammetric investigation and electrolysis experiments, it has been show that nickel disilicides can by electrochemical synthesized in a NaCl-NaF-K2SiF6 melt at 7200С on a nickel cathode in argon atmosphere. References M. Lawrence, A. Dass, David B. Fraser, Chih-shihWei, Appl. Phys. Lett. 58, 1308 (1991). Y. He, J.Y. Feng, W.Z. Li, Journal of Crystal Growth, 254, 70-74 (2003). Fig. 1. SEM micrograph: cross-section of a Ni cathode after the electrolysis of a NaCl-NaF-K2SiF6 melts at 7200С in Ar atmosphere.

In this work, the interaction of Si, SiC and TiC with a Na2CO3-K2CO3 melt at 7500С on Ar atmosphere and in air was investigated. The optimal process for the fabrication of carbon fibers or nanotubes is interaction between silicon carbide and carbonate melts. It has been show that the modification of carbon materials depends on SiC powder fineness.

The electrochemical behaviour of vanadium oxides in a carbamide- KCl melt at 1200C was studied by cyclic voltammetry. In the (NH2)2CO-KCl melt with additions of trivalent vanadium, an electrochemical process of oxidation of trivalent vanadium to pentavalent one was observed in the anodic region. V2O5 is irreversibly discharged in the (NH2)2CO-KCl melt with reactant adsorbed strongly.

Titanium diboride is a promising protective material for the cathodic bottom of aluminium baths [1]. Solubility of TiB2 in molten aluminium at 1300 K is 6×10 wt.% [2]. Equilibrium between liquid aluminium and solid titanium diboride is reached within 10 hours of their contact in a laboratory cell. The solubility of aluminium in titanium diboride at 1300 K is so low, that it could not be measured. The possibility of electrochemical synthesis of titanium diboride on carbon cathodes in situ from cryolite-alumina melts containing titanium and boron oxides was shown in Ref. [3]. This experiment was made in pure cryolite. Industrial Hall-Heroult technology uses synthetic cryolite, containing 0.8 % silica. In electrolysis experiments with synthetic cryolite containing titanium and boron oxides, cathode surface was passivated with silicon – oxygen compounds. The present paper examines the possibility of electrochemical synthesis of ternary compounds Ti-Si-B from cryolite-alumina melts containing titanium, silicon and boron oxides. Electrochemical behavior of cryolite-alumina melts containing titanium, silicon or boron oxides was studied by cyclic voltammetry. Voltammetric investigations were conducted in a Pt crucible with the working electrode of Pt wire and oxygen-platinum reference electrode in air at 1000C. As the boron oxide interaction with molten cryolite yields gaseous boron trifluoride, the bath was stabilized by inserting boron into the melt in the form Al4B2O9 compound, which forms from boric acid and alumina. The titanium dioxide and silica was added to the cryolite-alumina melts. In the system Na3AlF6-Al2O3-Al4B2O9 was observed a three electron irreversible change transfer with formation of insoluble product

Tantalum silicides: Ta3Si (Tm = 2613 К) , Ta2Si (Tm = 2783 К), Ta5Si3 (Tm = 2833 К) and TaSi2 (Tm = 2313 К) belong to refractory compounds. In the series of refractory compounds, silicides are distinguished by a high chemical stability at high temperatures; therefore, they widely used as protective materials in the chemical industry. Thanks to semiconductor properties and thermal stability, tantalum silicides promise much as a substitute for silicon in microcircuits. Based on thermodynamic calculation and voltammetric studies, it has been concluded that the synthesis of tantalum silicides is the most electropositive process in the NaCl-KCl-K2SiF6-K2TaF7 melts. Only the compound Ta2Si as coatings or powders has been obtained by electrosynthesis of the NaCl-KCl-K2SiF6-K2TaF7 melt at 973 K.

The determination of the oxidation state in which vanadium is in metallurgical slag's is an important factor in choosing the optimal conditions for the production of ferrovanadium by the silicothermal method. On the basis of thermodynamic calculations, electrochemical investigations and UV-Vis spectroscopy it has been shown that in vanadium-contain metallurgical slag's vanadium is in the form of V2O3.

In quite a number of works, the corrosion of SiC with molten carbonates was studied, but the products of this interaction were not investigated [1, 2]. In this work, the interaction of silicon, TiC and SiC (F 14 and F 36) powders with Na2CO3-K2CO3 melt at 7500С in Ar atmosphere and in air was studied. After washing, the interaction products were analyzed on a SEM and by Raman spectroscopy. A thermodynamic evaluation of the reactions proceeding in carbonates showed that the Gibbs energy for reactions given below is negative at 1023 K; if follows that the reactions proceed from left to right: I. 3Si + 2Na2CO3 = 2C + 4Na + 3SiO2 ΔGo 1023 K = -473 kJ II. 3SiC + 2Na2CO3 = 5C + 4Na + 3SiO2 ΔGo 1023 K = -277 kJ III. 3TiC + 2Na2CO3 = 5C + 4Na + 3TiO2 ΔGo 1023 K = -54 kJ Were silicon interacts with carbonate melts, a large amount of graphite and carbon black is formed, which complicates the process of separation of reaction products. Because titanium oxides are slightly soluble in carbonate melts, the surface of carbon fibers was coated with this reaction product. Silicon oxide are readily soluble in carbonate melts, therefore the most promising method for the fabrication of carbon fibers and nanotubes is interaction between SiC and carbonate melts. When SiC interaction with molten carbonates, both carbon fibers and nanotubes are formed (Fig. 1.). Raman spectroscopy corroborated the presence of carbon fibers in the products. References 1. R. E. Dial, G.E. Mangsen, Corrosion, 17, 35t (1961). 2. R.E. Tressler, M.D. Meiser, T. Yonushonis, J. Am. Ceram. Soc., 59, 278 (1976). Fig. 1. SEM micrograph of SiC (F14) powder after 2 hours interaction with carbonate melts at 7500C .

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