Simulation of Gas-Dynamic and Thermal Processes of Reduction of Molybdenum Fluoride and Synthesis of Its Carbide in Indu
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MA CHEMISTRY
Simulation of Gas-Dynamic and Thermal Processes of Reduction of Molybdenum Fluoride and Synthesis of Its Carbide in Inductively Coupled Radiofrequency Plasma L. V. Shabarovaa, *, P. G. Sennikova, R. A. Korneva, A. D. Plekhovicha, and A. M. Kut’ina aInstitute
of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received May 29, 2020; revised May 29, 2020; accepted July 6, 2020
Abstract—A method has been proposed for simulating the gas-dynamic conditions for the synthesis of molybdenum and its carbides in a radiofrequency induction plasma reactor with a vortex gas supply. A homogeneous flow of a mixture in a turbulent mode has been considered, taking into account inductive heating and the influence of the electromagnetic field force on the plasma motion. The composition of the transformation products has been determined in accordance with the results of thermodynamic calculations. The effect of the main synthesis products on the temperature field and flow in the reactor has been taken into account. The possibility of using a thermal, quasi-equilibrium argon–hydrogen plasma for the production of molybdenum and its carbides Mo2C and Mo3C2 from volatile fluoride and, as a reference, tungsten and its carbide WC has been explored. These results have been compared with those obtained earlier for boron, silicon, and their carbides. Keywords: computational experiment, ideal gas, thermodynamics, hydrogen reduction, radiofrequency induction discharge, molybdenum, molybdenum carbide, tungsten, tungsten carbide DOI: 10.1134/S0018143920060132
Among refractory metals, molybdenum and its compounds (along with tungsten) are in the most demand. A large number of papers and books published in the 1960–1980s are devoted to its chemistry and metallurgy [1–4]. One of the most effective ways to obtain molybdenum in the form of dense layers and powders of various dispersions of high purity, as well as Mo2C carbide, is the CVD method, in which the process of reduction of volatile molybdenum compounds with hydrogen is realized in the gas phase [5]. In the case of obtaining metallic molybdenum, the starting materials are molybdenum halides or its carbonyl, and in the case of carbide, molybdenum halides (or carbonyl) and hydrocarbons [3, 5]. Molybdenum hexafluoride is not among the most commonly used precursors for the production of elemental molybdenum or its compounds, mainly because of the formation of reactive byproducts. However, in recent years, MoF6 has become in demand, being enriched in the stable isotopes 98Mo and 100Mo by the centrifugal method. Because of nuclear transformations, these isotopes can be converted into the radioactive isotope 99Mo, which disintegrates to 99mTc, one of the most important modern radiopharmaceuticals [6]. Therefore, the development of a method for the efficient conversion of small amounts of expensive isotopically enriched
MoF6 seems to be very urgent [7]. Molybdenum hexafluoride is a thermodynamically stable c
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