Computer simulation of multicomponent melts of metallurgical slags

E. V. Dyul’dina, B. R. Gelchinski, V. N. Selivanov

ABSTRACT

Based on the experimental data on the density, the molecular dynamics simulation of multicomponent oxide-fluoride metallurgical slagFforming systems: SiO2–CaO–Al2O3–MgO–CaF2–Na2O–K2O–FeO was carried out for the first time in the approximation of the ionic bond model. The results were discussed and compared with literary experimental and calculated data. The obtained model indicates a weak temperature dependence of the structure of the melt. An increased diffusion mobility of fluorine ions as well as ions of alkali metals in comparison with other elements has been revealed.

KEYWORDS

melt, metallurgical slag, computer simulation, structure, properties

Stratification of liquid Pb–Bi alloys of different composition in glass capillaries

N. P. Ouglev, N. S. Boosov

ABSTRACT

The process of stratification of binary melts in the entire concentration range of the lead-bismuth system is studied. The correlation of results of stratification with the type of the state diagram, as well as with other physicochemical properties of melts of the system is shown. The results of the experiment confirm the absence of a stratification mechanism based on the Marangoni–Gibbs effect. The absence of stratification of gallium isotopes in the liquid metal under conditions corresponding to the experiment with lead-bismuth melts is shown experimentally. This clearly confirms not only the absence of a three-dimensional mechanism of stratification associated with the movement of individual atoms, but also indicates the mechanism associated with the formation of structures of atoms of components having different density and different chemical potential in the gravitational field. The comparison with the dynamics of melt stratification of lead-tin indicates the absence of mechanical resistance in this process, which confirms the previously proposed mechanism of transfer of components over the interphase space between the melt and the capillary wall by atoms in the state of two-dimensional super fluidity gas.

KEYWORDS

metal melt, the stratification in the capillary, cluster, barometric distribution, molten Pb–Bi, the correlation of the stratification, the stratification of the isotopes

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.

Production of alloy-coating of nickel-golmium in equimolar melt NaCl–KCl with addition of HoCl3

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

ABSTRACT

In the present work, the reduction of holmium ions at a nickel electrode in a molten equimolar mixture of sodium and potassium chlorides with the addition of holmium chloride in the temperature range 1073–1173 K was studied by the cyclic voltammetry method. The potentials for the formation of nickel–holmium intermetallic compounds were found. A nickel-holmium alloy was synthesized by potentiostatic electrolysis. It is shown that under the selected conditions of electrolysis the resulting coating is single-phase and corresponds to the composition of HoNi2. The diffusion coefficients of holmium in nickel are calculated and the activation energy of the alloy formation process is determined.

KEYWORDS:

ionic melts, holmium, nickel, cyclic voltammetry, diffusion coefficient, activation energy

Corrosion investigation of steel 12Cr18Ni10Ti in the melt LiCl–KCl–nNdCl3

N. A. Kazakovtseva, M. A. Maikov, E. V. Nikitina

ABSTRACT

The high-temperature corrosion of 12Cr18Ni10Тi steel in the melt of lithium and potassium chlorides was investigated, with addition of neodymium trichlorides at an operating temperature of 773 K. The NdCl3 concentration varied from 0.2 to 5 mol %. In this study, neodymium is an analog of plutonium. The composition of the electrolyte was close to the composition of real electrolytes used for processing nitride spent nuclear fuel (SNF). The main method of investigation is gravimetric, with aging of the steel sample in the melt for 1–24 hours. The atomic-adjective and micro-XFray spectral analysis methods were also used.

KEYWORDS:

corrosion, neodymium, gravimetry, melts

High-temperature corrosion of steel 12Cr18Ni10Ti in the melt of lithium and potassium chlorides, with additions of trichlorides of cerium

E. V. Nikitina, N. A. Kazakovtseva

ABSTRACT

The high-temperature corrosion of 12Cr18Ni10Ti steel in the melt of lithium and potassium chlorides was investigated, with addition of cerium trichlorides at an operating temperature of 773 K. The CeCl3 concentration varied from 0.2 to 5 mol%. In this study, cerium is an analog of plutonium. The composition of the electrolyte was close to the composition of real electrolytes used for processing nitride spent nuclear fuel (SNF). The main method of investigation is gravimetric, with aging of the steel sample in the melt for 1–24 hours. The atomic-adjective and micro-X-ray spectral analysis methods were also used.

KEYWORDS:

corrosion, neodymium, cerium, gravimetry.

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.

Thermodynamic analysis of oxidation of radioactive graphite in the melt Na2CO3–K2CO3–Sb2O3 in the carbon dioxide atmosphere

N. М. Barbin, I. A. Sidash, D. I. Terentyev, S. G. Alekseev

ABSTRACT

Currently in the world there are power reactors, reactors for plutonium production and research reactors whose number is more than 100 pieces of Graphite in the above mentioned reactors is used as the reflector, moderator, and also as Fuel cladding. Flameless combustion is a promising method of reducing the amount of solid radioactive waste. Method of flameless combustion is based on the oxidation of TRO in the oxide-carbonate melts and significantly reduces the volume of radioactive graphite. Thermodynamic modeling of oxidation of radioactive graphite in molten Na2CO3–K2CO3–Sb2O3 in an atmosphere of carbon dioxide. To conduct thermodynamic analysis was used the program complex TERRA. Thermodynamic modeling was carried out with initial pressure of one atmosphere, at an initial temperature of 273 K and the final temperature 3273 К. The step change in temperature is 100 K. Based on these data, the analysis of the distribution of elements between the condensed and gas phases. The modelling shows that the carbon disappears at a temperature of 873 K.

The heating of the system up to 1073 K leads to the evaporation of condensed compounds of antimony. The heating system up to 1673 K leads to the evaporation of condensed compounds of potassium, sodium, chlorine, uranium and cesium. The heating system up to 2273 K, leads to evaporation of condensed compounds of nickel. The heating system up to 2573 K leads to the evaporation of condensed calcium compounds, plutonium, beryllium, strontium, americium and europium. At temperatures above 2573 K, there is only a steam and gas phase.

KEYWORDS:

thermodynamic modeling, radioactive graphite, radionuclides, heating, oxidation, melt, carbonates.