| Abstract |
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: KxLiyWO3 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)). |
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