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

Precrystallization Changes in Structural Dynamic Characteristics of Amorphous Metallic Melts under Deep Cooling, Glassforming and Hydrogenation

V. A. Polukhin, N. I. Sidorov, N. A. Vatolin

ABSTRACT

The processes of amorphization and crystallization of binary and multicomponent melts based on transition metals are considered. A comparative analysis of pre-crystallization structural changes and atomic dynamics in conditions of forced quenching and deep supercooling of metallic melts and other liquid substances, depending on their composition, the size of the atoms, the nature of the interatomic bonds, the presence of eutectics and saddles on the phase diagrams of states is carried out. Hydrogenation of the melts introduces additional specificity on the flow of pre-crystallization processes, affecting the atomic configuration, the modulation of the frequency spectrum and the fluctuations of the band (electronic) structure that determines the specificity of vitrification.

KEYWORDS

multicomponent melts, transition metals, atomic dynamics, configuration, interatomic bonds, molecular dynamics, hydrogenation, vitrification, phonons, band structure, precursors, viscosity, diffusion, levitation, crossovers, frequency

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.

Solvation of In(III) ion in (InCl3)n clusters from quantum chemistry calculations

V. Ju. Buz’ko, G. Ju. Chujko, H. B. Kushhov

ABSTRACT

The results of quantum chemistry modeling of In(III) ion solvation in clusters with compositions (InCl3)n (n = 1–30) performed. Interatomic interaction potential functions were described in semiempirical MNDO/PM3 quantum chemistry approximation. The mean of In-Cl distance in the most energetically stable (InCl3)30 cluster was calculated and was equal to 2.64 ± 0.15 Å. The microstructural characteristics of In(III) ion in model (InCl3)30 cluster at 850 and 870 К were studied by means molecular dynamic simulation in NVT-approximation with MNDO/PM3 interatomic interaction potential.
The results shows that InCl3 melts has net-shaped structure with dominated complex anion-type [InCl6]3– species of disported octahedral polyhedron. The results of molecular dynamic simulation are evidence that in conditions of (InCl3)30 melting the decreasing of In(III) ion coordination number from 5.98 to 5.92 was observed because formation of tightly packaged complex anion [InCl5]2– species.

KEY WORDS

indium trichloride, solvation, coordination number, quantum chemistry modeling, molecular dynamic simulation.

Influence of non-stationary electric current on system oxide melt – gas phase

S. A. Krasikov, B. T. Utelbayev, E. N. Suleimenov

ABSTRACT

Results of studying of impact of non-stationary electric current on oxide melt are presented. It is revealed that non-stationary power inf luence can cause changing of a microstructure of liquid systems and promote improbable chemical reactions between the oxide melt and gas components. Thus division of components of a gas phase into gases – oxidizers and gases – reducers becomes very conditional. It is established that stable giving of electric current can bring system into a quasi-equilibrium state which will slow down further development of chemical reaction and directly chemical reaction can generate electric current on the course of process.

KEY WORDS

oxide melt, gas phase, non-stationary electric current, chemical reactions, microstructure

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.