Phase diagram of the LiCl– MnCl2 binary system

I. V. Korzun, V. N. Dokutovich, E. V. Stepanova, N. K. Tkachev.

ABSTRACT:

Phase diagram of the LiCl–MnCl2 binary system was studied by the method of synchronous thermal analysis. It is established that this system is characterized by the presence of a congruently melting compound Li2MnCl4 (Tm = 855 K) and two eutectics with coordinates Te1 = 829 K; x(MnCl2) = 0.525 and Te2 = 851 K; x(MnCl2) = 0.255. It was found that in the solid state the Li2MnCl4 compound undergoes a secondEorder phase transition at T = 733 K with a jump in the heat capacity Δcp = 117 J/(mol К).

KEYWORDS:

lithium chloride-manganese dichloride, phase diagram, DSC, lithium tetra-chloromanganite

DOI: 10.7868/S0235010618050067

Electroconductivity of GdCl3–KCl–Gd2O3 system

E. V. Nikolaeva, I. D. Zakir’yanova, A. L. Bovet, T. V. Sosnovtseva.

ABSTRACT:

The temperature dependence of the electrical conductivity of the molten eutectic GdCl3(0.515)–KCl (0.485), containing up to 3.3 mol. % of gadolinium oxide have been investigated. The temperature dependences of the specific electrical conductivity of the molten GdCl3–KCl–Gd2O3 system were approximated by the second order polynomials. The formation of gadolinium oxychloride was confirmed by spectral studies of frozen melt.

KEYWORDS:

conductivity, gadolinium oxide, impedance

DOI: 10.1134/S0235010618060051

Simulation of redox reactions in liquid media with nonconstant force field molecular dynamics

A. A. Raskovalov, A. A. Latypov.

ABSTRACT:

In the paper application of non-constant force field molecular dynamics is shown for studying of redox reactions in liquid (molten) media. The method was applied to a system of ions. Interaction between these ions consisted of short-range Lennard-Jones and Coulombic pair potentials. Electron transfer between donor-acceptor pairs is implemented via special algorithms. Simulation results showed that concentrations of interacting ions changed during the simulations and reached some stationary values. Comparison between thermodynamics and the simulated results has revealed that difference in own energies of ions must include not only EMF value but additional terms too. It was shown that stationary concentrations depended on temperature, starting ion concentrations and a value of a solvent ionic radius. It was shown that the method can separate electronic transfer between different kinds of donor-acceptor pairs. In some simulations a system demonstrated behavior similar to Marcus “inverted region”.

KEYWORDS:

non-constant force field molecular dynamics, redox reactions, electron transfer, melt, Marcus theory

DOI: 10.1134/S0235010618060063

Selective anode dissolution of gold alloys in a molten eutectic mixture of cesium, potassium, sodium chlorides

L. V. Sitnikov, N. P. Kulik, N. K. Tkachev, A. A. Pankratov, V. B. Malkov, V. M. Ivenko, N. G. Molchanova, N. I. Moskalenko, B. D. Antonov

ABSTRACT

The features of selective anodic dissolution of Al11Au6 intermetallide and Au–Cu–Ag solid solution in the melt of CsCl–KCl–NaCl eutectic at 520оС were studied. Microporous structures containing up to 95 mol % of gold were fabricated in the potentiostatic regime. It is shown that the pore size and distribution depend essentially on the nature of the alloy, and the mechanical strength of the sample during and after the dealloing is strongly influenced by the magnitude of the applied potential.

KEYWORDS:

selective dissolution, gold alloys, anodic polarization, molten salts, porous structure

The preparation of intermetallic yttrium compounds on surface of copper samples in the molten NaCl–KCl

I. V. Tolstobrov, O. V. El’kin, A. N. Bushuev, D. A. Kondrat’ev, V. A. Kozvonin

ABSTRACT

Electrochemical behaviors of Y(III) on copper electrode in molten NaCl–KCl + 5 wt % YCl3 was studied in this work. The potentials for the formation of copper-yttrium compounds were determined from CV method at 1023 K. The different Cu–Y alloys, such as Cu6Y, Cu4Y, Cu2Y, CuY were formed by potentiostatic electrolysis at different potentials and characterized by XFray diffraction (XRD) and scanning electron microscopy (SEM). Also two intermetallic compounds, Cu6Y and Cu4Y were synthesized by current-free diffusion saturation at 973 K and 1023 K. It was established that the samples obtained by current-free diffusion saturation have a thickness greater than those obtained by electrolysis. We can obtain copper-yttrium compounds of a given composition by potentiostatic electrolysis.

KEYWORDS:

copper-yttrium compounds, cyclic voltammetry, potentiostatic electrolysis, non-current diffusion saturation.

Formation of electrode deposit under galvanostatic conditions

V. A. Isaev, O. V. Grishenkova, M. V. Laptev, A. V. Isakov, Yu. P. Zaykov

ABSTRACT

The regularities of the formation of a continuous deposit layer under constant current are considered. The equations for calculation of time dependences of overpotential for instantaneous nucleation with kinetic- or diffusion-controlled growth of a new phase are analyzed. The theoretical dependences are compared with the experimental ones for the electrodeposition of silicon from a fluorideFchloride melt.

KEYWORDS: electrocrystallization, galvanostatic method, nucleation, growth, continuous layer, melt

Potentiostatic current transients under the diffusion controlled growth of a new phase

V. A. Isaev, O. V. Grishenkova, Yu. P. Zaykov

ABSTRACT

The problem concerning the mathematical description of the formation of deposit layer by means of nucleation/growth/overlapping mechanism of newFphase 3D clusters and their diffusion zones was considered. The characteristics of potentiostatic current transients were analyzed. Expressions for calculating the nucleation parameters and the diffusion coefficient of the deposited ions were obtained.

KEYWORDS: electrocrystallization, chronoamperometry, nucleation, growth, overlap, diffusion.

Selection of the optimal composition of the electrolysis bath for the synthesis of holmium intermetallides with metals of the iron triad

H. B. Kushchov, R. A. Kardanova, V. V. Khasanov, I. A. Borukaeva

ABSTRACT

This paper presents the results of high-temperature electrochemical synthesis of powders of holmium intermetallides with metals of the iron triad in chloride melts. The effect of the current density, the composition of the electrolytic bath, the duration of the electrolysis process and the composition of the products obtained are studied. It was found that during electrolysis of a molten mixture of KCl–NaCl containing holmium trichloride (0.5–2.5 mol%) and nickel (cobalt) dichloride (0.1–2.5 mol%), current density 0.5–2.0 A/cm2, temperatures 973–1073 K and the duration of electrolysis to 30–60 min on the tungsten electrode, a cathodic precipitate is formed in the form of a “metal-salt pear”, containing of a mixture of nickel (cobalt) metal phases, HoNi, HoNi5, HoNi3 (HoCo2 intermetallides, HoCo3, HoCo5, Ho2Co17) and metallic holmium. It has been established that at a constant current density (1.2 A/cm2), the content of intermetallic compounds in the cathode deposit increases with an increase in the concentration of the holmium chloride in the melt, as well as the ratio of the concentration of the holmium chloride to the concentration of nickel chloride (cobalt). By regulating the composition of the electrolysis bath and the electrolysis regimes, it is possible to ensure that the cathode sediment consisted only of a mixture of holmium and nickel intermetallides (cobalt).

Electrochemical synthesis of holmium intermetallides with iron was carried out in the galvanostatic regime in a KCl–NaCl–HoCl3 melt. Iron ions were introduced into the melt by anodic dissolution of metallic iron. The results of the phase analysis of the electrolysis products show the principal possibility of obtaining holmium and iron intermetallides. Optimum conditions for the electrosynthesis of holmium intermetallides with metals of the iron triad are determined.

KEYWORDS:

electrochemical synthesis, intermetallic compounds, holmium, nickel, cobalt, iron.

Solubility of silver in K–KI melts at 850 °С

В. М. Ivenko, V. Yu. Shishkin

ABSTRACT

The solubility of silver in melts K–KI at a temperature of 850 °С and a change in the potassium content in the melt from 0 to 100 mol% is investigated. It is shown that it also increases linearly as in the melt of K–KCl with increasing alkali metal concentration, and in molten potassium at this temperature is 6.0 mole% Ag.

KEYWORDS:

melts, solutions, silver, potassium, potassium iodide.

Mechanism and caloric effects of the GdCl3 ‧ 6H2O crystal hydrate thermal dehydration process

I. V. Korzun, I. D. Zakiryanova, E. V. Nikolaeva

ABSTRACT

Synchronous thermal analysis and mass spectrometry were applied for complex investigation of the thermal dehydration of crystal hydrate GdCl3 ∙ 6H2O. The certified samples were used. The mechanism was established and the caloric effects of the occurred chemical reactions were determined. The thermal decomposition of the crystal hydrate GdCl3 ∙ 6H2O was shown to be accompanied by a hydrolysis reaction, resulted in the GdOCl oxychloride formation.

KEYWORDS:

dehydration, crystalline hydrate, gadolinium chloride, synchronous thermal analysis, mass spectrometry.