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Electrochemical Synthesis of Chromium Silicides from Molten Salts

Journal of Chemistry and Chemical Engineering 2014年第9期8卷 845-848页

作者： Liliia Molotovska dmytro shakhnin Oleksandr Podyman Viktor Malyshev Nataliya Uskova Viliam Pavlik Vernadsky Institute of General and Inorganic Chemistry of the NAS (National Academy of Science) of Ukraine Kiev 03142Ukraine Institute of lnorganic Chemistry Slovak Academy of Sciences Bratislava 994536 Slovak Republic

Electrochemical synthesis of chromium silicides from NaCl-KCl-K2SiF6-CrF3 system has been investigated by cyclic voltammetry and DC （direct current） electrolysis at 850℃. The process of Cr and Si joint electroreduction in chloride-fluoride melt proceeds in one stage in a kinetic mode. The cathode product was analyzed using XRD （X-ray diffraction） method. XRD data have confirmed that CraSi is the dominant phase. SEM （scanning electron microscopy） results have shown that Cr3Si powder samples consist of 50-150 lain particles and that tungsten silicide was formed at the surface of tungsten cathode after chrome-free system electrolysis.

关键词： Chromium silicide fluoride molten salt electrochemical synthesis.

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Tungsten Resource-Saving： Cobalt Cermets Wastes Recycling and Concentrates Extraction

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Journal of Environmental Science and Engineering(B) 2015年第10期4卷 521-528页

作者： Viktor Malyshev dmytro shakhnin Angelina Gab Nataliya Uskova Oleksandr Gudymenko Volodymyr Glushakov Nina Kushchevska Department of Physical Chemistry of Ionic Liquids EL Vernadsky Institute of General and Inorganic Chemistry National Academy of Sciences of Ukraine Kyiv 03142 Ukraine Faculty of Chemistry & Technology National Technical University of Ukraine "Kyiv Polytechnical Institute" Kyiv 03056 Ukraine Faculty of Engineering & Technology University "Ukraine" Kyiv 03115 Ukraine

Potentials range is determined in which the cobalt-tungsten alloy phase selectively dissolved in solutions of phosphoric acid to form soluble compounds of these metals, while the tungsten carbide phase remains in the precipitate. It shows that tungsten ores and concentrates are decomposed at 1,050℃-1,100℃ in sodium chloride-sodium metasilicate melts to form two immiscible phases, namely, halide-tungstate, containing 96% to 99% of tungsten, and silicate, containing 90% of the rest ore components.

关键词： Tungsten carbide cobalt halide-metasilicate melts phosophric acid electrochemical dissolution recycling extraction.

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Synthesis of VIB Group Metals Silicides Dispersed Powders by Electrolysis of Halide-Oxide Melts

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Journal of Chemistry and Chemical Engineering 2016年第1期10卷 7-12页

作者： Liliia Molotovska dmytro shakhnin Natalia Uskova Ganna Nikulina Vladymyr Cherednik Serge Stukota Viktor Malyshev Department of Physical Chemistry of lonic Liquids V. I. Vernadsky Institute of General and Inorganic Chemistry National Academy of Sciences of Ukraine 32/34 Palladina Ave. Kyiv 03142 Ukraine Faculty of Engineering & Technology University of Ukraine 23 L vivska St. Kyiv 03115 Ukraine

Study of electrochemical behavior of chromium （molybdenum, tungsten） and silicon containing melts allowed defining conditions for synthesis of silicides of chromium, molybdenum and tungsten in the form of fine powders by electrolysis of halide-oxide melts. Sequence of stages of electrosynthesis of silicides of molybdenum and tungsten was found as follows： deposition of more electroposifve metal （molybdenum or tungsten）, deposition of the second component （silicon） on the surface of metal deposited previously, and reaction diffusion of silicon into the deep of the metal-salt ＂pear＂ with the formation of silicide phases of different compositions up to the higher silicides. In contrast, during the electrodeposition of chromium silicides, one of the components （chromium） is deposited not in elemental form, but in oxide form, and the other （silicon） acts as a reducing agent for this oxide to form binary compounds. Duration of the synthesis first stage （deposition of refractory metal or of its oxide） depends on the refractory metal compound content in the system and on the cathode current density. Synthesis of silicides is possible due to retention of powders of molybdenum （tungsten） or chromium oxide at the cathode without scaling. Optimal values of concentrations ratio, current density, temperature, and duration of electrosynthesis were found. Phase composition of products were obtained, as well as their chemical and thermal stability, were studied.

关键词： Chromium molybdenum tungsten silicides synthesis dispersed powders ionic melts.

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