Molecular dynamics calculation of self-diffusion coefficients in molten LiF-RbBr and LiF-CsBr mixtures

M. A. Kobelev, K. I. Oleinik, A. S. Tatarinov

ABSTRACT

The self-diffusion coefficients of the ions constituting the reciprocal molten LiF-RbBr and LiF-CsBr mixtures, which are located at a temperature of 1420 K throughout the concentration range within the framework of the classical molecular dynamics method, are calculated. It is shown that the character of the microscopic motion of the fluoride ion changes qualitatively depending on the nature of the cation forming the nearest environment. Thus, in the reciprocal molten LiF-RbBr mixture at low concentrations of rubidium bromide, the nearest environment of the fluoride ion contributes to an increase in its self-diffusion coefficient, in spite of the fact that the density of the system increases.

KEY WORDS

molten alkali halides, MD simulations, self-diffusion coefficients, rigid ion model.

Electrochemical kinetics of diffusion problems with a moving phase boundary

A. V. Guntsov, N. V. Khlynova

ABSTRACT

The processes of growth and dissolution of nucleus and a film of a deposition on a solid electrode are considered. The results of solving diffusion problems on the growth and dissolution of hemispherical nuclei and a thin film of precipitate are presented. The equations of volt-ampere curves, chronoamperograms for reversible, irreversible and quasi-reversible electrode processes, ratios for the peak current, the quantity of deposition at the electrode, the peak current potential and the half-peak width of the current-voltage curve from the parameters of pre-electrolysis are given. The processes of the formation of a new phase at the solid-liquid interface, the mass-exchange processes at the electrode–low-soluble film interface, and the low-soluble film–solution boundary are discussed. The results of an experimental study of anode films are considered. There is linear dependency of the quantity of the forming compound on the electrode surface from the concentration of the ions and from the time of the pre-electrolysis in case of growing a nuclei or a thick anodic film.

KEY WORDS

electrodeposition, electrodissolution, nucleus, film, deposition, peak current, solid electrode.

Electrical conductivity and raman spectra of the α-Al2O3 – molten Li2CO3-Na2CO3-K2CO3-NaCl disperse systems

D. Zakiryanova, Е. V. Nikolaeva, А. L. Bove, B. D. Antonov.

ABSTRACT

Information on the specific electric conductivity of the dispersed system a-Al2O3-molten carbonate-chloride mixture of Li2CO3-Na2CO3-K2CO3-NaCl in the temperature range of 455–550 °C is obtained. Using the method of Raman spectroscopy, it was shown that in the investigated temperature range a-Al2O3 does not enter into a chemical interaction with the carbonate-chloride melt. Data on the strength and energy characteristics of the CO32– anion in these systems are obtained.

KEY WORDS

Conductivity, Raman spectra, disperse system, melts.

The high-volage penonena in aluminum Molten chloride electrolytes

L. A. Kazieva, S. I. Suleymanov.

ABSTRACT

The electrical conductivity of the molten chloroaluminates NaAlCl4 and KAlCl4 increases with increasing of electrical field strength and reach the limiting values (the Wien effect) which surpass their usual low-voltage conductivity up to 200 and 700 percent respectively. These results have been obtained on the base of analysis of the microsecond high-voltage discharges in the melts (the Wien effect). After the high-voltage pulses discharges having been completed in the melts, their conductivity and electrolyze current have been found to rise up to 50% and their decomposition potentials has found to decrease more than 20% (the “memory effect”). The relaxation time of a non-equilibrium state reaches 5 minutes and more.
KEY WORDS

activation, melts, chloroaluminates, Wine effect, relaxation, structure, aluminum, conductivity.

Determination of synthesis modes of powder intermetallic compound of composition Co2Er in halogenide melt.

D. A. Kondratyev, I. V. Tolstobrov, A. N. Bushuev, O. V. El’kin, O. S. Bervickaya, O. V. Chernova.

ABSTRACT

The present study examines the synthesis capacity of powdered Co2Er intermetallic compound in molten eutectic Lithium- Potassium Chlorides mix at constant temperature of 850K when using no-current diffusion saturation technique.

Based on the obtained results, the synthesis modes for the specified composition of powdered Co2Er intermetallic compound were derived. The components’ composition ratio of the reaction mix for the metal phase was established, at which point the synthesis of the specified powdered compound could still be possible. In this case, the powdered compound did not contain admixtures of both the other-phase intermetallic compounds and the unreacted metal substrate powder (Co).
The credibility of the obtained findings was confirmed through X-ray fluorescence and X-ray diffraction analyses using the EDX‑720 energy dispersion X-ray fluorescence spectrometer along with the XDR‑7000S X-ray powder diffractometer.

KEY WORDS

powder alloy, intermetallic compound, cobalt, erbium, permanent magnet, diffusion saturation, non-current transfer, expanded salt mixture, phase, Co2Er.

Physicochemical foundations for the synthesis of zinc oxide in molten chlorides

T. A. Rozdjalovskaja.

ABSTRACT

The results of the investigation of chloride ions oxidation during the oxygen bubbling through zinc and alkali metal (Na, K) chloride melts at 600 °C are presented. The amount of gaseous chlorine produced depends on the molar ratio of chlorides in the mixture. It is shown that the amount of released chlorine is directly proportional to the values of the effective polarizing force of the cations. The kinetic characteristics of chlorine formation were determined and calculated: the reaction order, reaction rate constants, and the activation energy values. Particle size, chemical composition, and surface area for some samples of ZnO were determined.

KEY WORDS

zinc and alkali metals chloride melts, zinc oxide production, molten chlorides oxidation.

Synthesis of aluminium-erbium master alloys from chloride-fluoride melts

Ya. I. Kosov, V. Yu. Bazhin.

ABSTRACT:

Aluminum-erbium master alloy is destined to improve the physical and mechanical properties of aluminum alloys. Current energy intensive foreign technologies and absence of domestic technologies of preparation of Al-Er master alloy make it important to create a technology of the aluminothermic reduction of erbium compounds from chloride-fluoride melts. A thermodynamic analysis of the aluminothermic reduction of various erbium compounds has been carried out. Erbium fluoride was chosen as the preferred starting material, taking into account the physicochemical properties of the erbium compounds. The aluminothermic reduction of erbium fluoride in the salt mixture with sodium fluoride and potassium chloride, taking into account the formation of the intermetallic compound Al3Er, has a high thermodynamic probability. The thermodynamic values of the erbium complex compound have been determined by an indirect method, because of limited information. The аluminum-еrbium master alloys has been synthesized via aluminothermic reduction method in the ErF3-NaF-KCl melts with different ratio ErF3 /NaF and content of KCl in the temperature range 750–900 °C. The result of the investigation of microstructure and phase composition of the synthesized master alloys has been given. The investigation of phase composition of the flux used to synthesize the Al-Er master alloy has been carry out

KEY WORDS: master alloy, aluminum-erbium, aluminothermic reduction, flux, thermodynamic, microstructure, intermetallic compound, Al3Er.

Extraction of scandium and zirconia from their oxides electrolysis of oxide fluoride melt

V. Suzdaltsev, A. A. Filatov, A. Yu. Nikolaev, A. A. Pankratov, N. G. Molchanova, Yu. P. Zaykov.

ABSTRACT. The main regularities of extraction of scandium and zirconium from their oxides into aluminum during aluminothermic and electrolytic preparation of Al-Sc and Al-Zr alloys and ligatures in KF-AlF3, NaF-AlF3 and KF-NaF-AlF3 oxide-fluoride melts with Sc2O3 additives and ZrO2. The effect of the melt composition and its temperature, the duration of synthesis, the content of Sc2O3 and ZrO2 oxides in melts, the mechanical mixing of aluminum and the cathode current density on the content of scandium and zirconium in aluminum, and their extraction from oxides are determined. It is shown that, depending on the synthesis parameters, the average values of extraction of scandium and zirconium are 20–75 and 40–100%, respectively. The electrolytic decomposition of oxides in melts KF-AlF3, NaF-AlF3 and KF-NaF-AlF3 leads to a significant increase in extraction of scandium and zirconium into aluminum. Based on the results of the research, the parameters for obtaining alloys and ligatures Al-Sc and Al-Zr with scandium content up to 10 and zirconium up to 15 wt.% in the electrolysis of oxide-fluoride melts.

KEY WORDS: scandium, zirconium, oxide-fluoride melt, aluminothermy, electrolysis, extraction.

Conductivity of melts in mixtures of gadolinium trichloride with sodium and potassium chlorides

K. I. Trifonov, I. F. Zabotin, S. F. Katyshev, A. F. Nikiforov

ABSTRACT:

The values of specific conductivity of melted mixtures of gadolinium trichloride with sodium and potassium chlorides have been determined. The values of molar conductivity for the examined salt mixtures have been calculated, and the isothermal projection of molar conductivity for the triple system GdCl3–NaCl–KCl is presented. Analysis of the results received makes it possible to offer a hypothesis on the nature of the components interaction.

KEY WORDS:

specific and molar conductivity, gadolinium chlorides, sodium and potassium, interaction of components.

Potential activity coefficient, dissolved in moltables of its halogenides

V. M. Ivenko, V. V. Chebykin, L. A. Tsiovkina

ABSTRACT:

The parameters of the equations for the activity coefficient of potassium dissolved in KF–KCl, KF–KBr, KF–KI and KCl–KI melts with molar ratio of salt components of 3 : 1, 1 : 1, 1 : 3, as well as in equimolar melts KCl–KBr and KBr–KI. The concentration of potassium in the melts varied, from about 1 to 10 mol %. A representation of the authors on the complex structure of solutions of an alkali metal in mixtures of its halides is given, which makes it possible to understand the dependence of the thermodynamic properties of potassium dissolved in them.

KEY WORDS:

solutions, melts, alkali metals, halides of alkali metals, activity, activity coefficient.