Institute of High-temperature Electrochemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

S. V. Vakarin, Senior Researcher, e-mail: s.vakarin@ihte.uran.ru

O. L. Semerikova, Researcher

S. A. Surat, Engineer

A. A. Pankratov, Researcher

Yu. P. Zaykov, Director

The aim of this study is determination of conditions of obtaining of nanocrystalline coating of oxide tungsten bronzes with hexagonal structure on tungsten substrates. The following object of the study was selected: K_xLi_yWO₃ bronze, obtained by electrolysis of 0.30K₂WO₄ – 0.25Li₂WO₄ – 0.45WO₃ % (mol.) melt at the temperature of 700 and 750 ^oC. Electrolysis was carried out by pulse potentiostatic method in a three-electrode cell. Platinum wire was used as anode. There was taken a platinum foil (1 cm²), half-immersed in the melt as a reference electrode. Tungsten foil was used as a cathode. The obtained deposits were examined by electron microscopy, X-ray and chemical analysis. There was established, that electrochemical method allows to get nanocrystalline coatings on a tungsten substrate. Each micro-crystal of deposit is characterized as oriented nano-needle structure. Additionally, dependence of “overvoltage – pulse duration” parameters is linear. There was found that nanocrystalline bronze contains less alkali metal than coarse-grained structure. There was made a conclusion that bronze with such composition is formed with participation of more polymerized anionic forms. The areas of conditions (“overvoltage – pulse duration”) are determined for the case when (0001) planes of micro-crystals differ in their morphology. Nanocrystalline bronze is formed with more polymerized anionic forms. The conclusions are devoted to formation of mechanism for micro-crystal of oxide tungsten bronze with hexagonal structure during the electrochemical synthesis from molten salts. Nanocrystalline bronze can find application in medicine, electrotechnics, radio, food and chemical industry for manufacturing of ion-selective elements for analysis of micro-media, electrochromic devices, cold cathodes and catalysts for chemical reactions.

The authors express their gratitude to S. V. Plaksin, N. G. Molchanova and A. A. Melyaeva for the help in carrying out of experiments and analysis of the deposits.

The work is supported by the project: “Nanocrystalline oxide tungsten bronzes, obtained by electrolysis of melts in catalytic processes of oxidative desulfurization and upgrading petroleum fractions”, within the programs of Ural Branch of Russian Academy of Sciences (project No. 12-I-3-2058 (12-И-3-2058)).

1. Banks E., Wold A. Oxide Bronzes in Preparative Inorganic Reactions. 1968. No. 4. pp. 237–268.
2. Hagenmuller P. Tungsten bronzes, vanadium bronzes and related compounds. Pergamon texts in inorganic chemistry. 1973. Vol. 1. pp. 541–605.
3. Uedsli A. D. Neorganicheskie nestekhiometricheskie soedineniya (Inorganic nonstoichiometric compounds). Nestekhiometricheskie soedineniya (Non-stoichiometric compounds). Moscow : Khimiya, 1971. pp. 102–200.
4. Nikitina E. A., Kokurina A. S. Zhurnal obshchey khimii — Russian Journal of General Chemistry. 1950. Vol. 20, Iss. 8. pp. 1380–1383.
5. Zivkovic O., Yan C, Wagner M. J. Tetragonal alkali metal tungsten bronze and hexagonal tungstate nanorods synthesized by alkalide reduction. Journal of Materials Chemistry. 2009. Vol. 19, No. 33. pp. 6029–6033.
6. Gu Z., Ying M., Zhai T., Gao B., Yang W., Yao J. A simple hydrothermal method for the large-scale synthesis of single-crystal potassium tungsten bronze nanowires. Chemistry — A European Journal. 2006. Vol. 12, No. 29. pp. 7717–7723.
7. Rattanakam R., Supothina S. Hydrothermal synthesis and electrochromic properties of potassium tungsten oxide nanorods. Journal of Nanoscience and Nanotechnology. 2011. Vol. 11, No. 10. pp. 8974–8978.
8. Supothina S., Rattanakam R. Effect of stirring and temperature on synthesis yield and crystallization of hydrothermally synthesized K₂W₄O₁₃ nanorods. Materials Chemistry and Physics. 2011. Vol. 129, No. 1–2. pp. 439–445.
9. Yang X.-G., Li C., Mo M.-S., Zhan J.-H., Yu W.-C., Yan Y., Qian Y.-T. Growth of K_0,4WO₃ whiskers via a pressure-reliefassisted hydrothermal process. Journal of Crystal Growth. 2003. Vol. 249, No. 3–4. pp. 594–599.
10. Spitsin V. I., Drobasheva T. I., Kazanskiy L. P. O shchelochnykh bronzakh volframa, poluchennykh elektrolizom rasplavlennykh izopolivolframatov (About alkaline bronzes of tungsten, obtained by electrolysis of melt isopolytungstates). Khimiya soedineniy Mo i W (Chemistry of Mo and W compounds). Novosibirsk : Nauka, 1979. pp. 3–23.
11. Kaliev K. A., Baraboshkin A. N. Elektrokristallizatsiya oksidnykh bronz perekhodnykh metallov iz rasplavlennykh soley (Electrocrystallization of oxide bronzes of transition metals from molten salts). Oksidnye bronzy : sbornik nauchnykh trudov (Oxide bronzes : collection of scientific proceedings). Moscow : Nauka, 1982. pp. 137–175.
12. Vakarin S. V. Orientirovannyy rost volframovykh bronz pri elektrolize rasplavov (Oriented growth of tungsten bronzes during the electrolysis of melts). Ekaterinburg : Ural Branch of Russian Academy of Sciences, 2005. 108 p.
13. Baraboshkin A. N. Elektrokristallizatsiya metallov iz rasplavlennykh soley (Electrocrystallization of metals from molten salts). Moscow : Nauka, 1976. 279 p.
14. Kolmakov A. G., Alymov M. I. Perspektivnye materialy — Journal of Advanced Materials. 2006. No. 5. pp. 5–13.
15. Miao X. Use of natural topaz as transporting agent in the vapor growth of potassium tungsten oxide bronze fibres. Journal of Crystal Growth. 1999. Vol. 197, No. 4. pp. 1008–1011.
16. Zheng Z., Yan B., Zhang J., You Y., Lim C.T., Shen Z., Yu T. Potassium tungsten bronze nanowires: polarized micro-raman scattering of individual nanowires and electron field emission from nanowire films. Advanced Materials. 2008. Vol. 20, No. 2. pp. 352–356.
17. Vakarin S. V. Sposob polucheniya igolchatykh oksidnykh volframovykh bronz (Method of obtaining of needle-shaped oxide tungsten bronzes). Patent RF, No. 2354753. Published: May 10, 2009.
18. Vakarin S. V., Melyaeva A. A., Pankratov A. A., Kochedykov V. A., Akashev L. A., Plaksin S. V., Zaykov Yu. P. Sposob polucheniya nanokristallicheskikh pokrytiy oksidnykh volframovykh bronz (Method of obtaining of nanocrystalline coverings of oxide tungsten bronzes). Patent RF, No. 2426822. Published: June 20, 2011.
19. Vakarin S. V., Melyaeva A. A., Semerikova O. L., Kondratyuk V. S., Pankratov A. A., Plaksin S. V., Porotnikova N. M., Zaykov Yu. P., Petrov L. A., Mikushina Yu. V., Shishmakov A. B., Chupakhin O. N. Sposob polucheniya nanoigolchatykh katalizatorov okislitelnovosstanovitelnykh protsessov na osnove oksidnykh volframovykh bronz (Method of obtaining of nano needle-shaped catalysts of oxidation reduction processes on the basis of oxide tungsten bronzes). Patent RF, No. 2456079. Published: May 10, 2012.
20. Vakarin S. V., Melyaeva A. A., Semerikova O. L., Kondratyuk V. S., Pankratov A. A., Plaksin S. V., Porotnikova N. M., Zaykov Yu. P., Petrov L. A., Mikushina Yu. V., Shishmakov A. B., Chupakhin O. N. Izvestiya Akademii Nauk. Seriya khimicheskaya — Russian Chemical Bulletin. 2011. No. 10. pp. 1951–1954.
21. N. G. Molchanova, V. N. Strekalovskiy, I. V. Kaluzhnikova. Sposob rastvoreniya kislorodsoderzhashchikh volframovykh bronz (Method of dissolution of oxygen-containing tungsten bronzes). Certificate of Authority USSR, No. 038145, MKI⁴ G 01 N 31/00. Applied: August 25, 1980. Published: June 23, 1982. Bulletin No. 23.
22. A. Müller, S Roy. Uspekhi khimii — Russian Chemical Reviews. 2002. Vol. 71. pp. 1107–1119.
23. Talismanov S. S., Eremenko I. L. Uspekhi khimii — Russian Chemical Reviews. 2003. Vol. 72. pp. 627–642.
24. Krause H. B., Vincent R., Steeds J. W. Microstructures in non — stoichiometric potassium tungsten bronzes K_хWO₃. Solid State Communications. 1988. Vol. 68, No. 10. pp. 937–942.
25. Geguzin Ya. E. Fizika spekaniya — Sintering Physics. Moscow : Nauka, 1984. 311 p.
26. Vakarin S. V., Baraboshkin A. N., Kaliev K. A., Zyrianov V. G. Crystal growth of tungsten bronzes with hexagonal structure. Journal of Crystal Growth. 1995. Vol. 151. pp. 121–126.