The Russian scientific journal «Melts» is devoted to the problems of the high temperature physical chemistry and electrochemistry of metal, oxide and salt melts. It is intended for publication of results related to the theoretical and experimental research regarding structure, physicochemical properties, thermodynamics of melts, composition of melts boundaries with solid, liquid and gaseous phases, and processes which take place on these boundaries at production of ferrous, non-ferrous and rare metals; physical modeling and computer simulation of structure and properties of liquid and amorphous materials. Established in 1987, the Russian scientific journal «Rasplavy/Melts» is issued six times a year. It is on the list of the leading peer-reviewed Russian scientific journals, issued by the Russian Higher Attestation Commission, which is proposed for publishing achievements of the doctoral and PhD thesis works. The journal editorial board selects articles to be translated in English in order to publish them in the second and eighth issues of the Russian scientific journal «Russian Metallurgy (Metally)».

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No 3 (2023)

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Stepanov V.P.

The results of the study of the interface properties for immiscible mixtures LiF + KBr, LiF + CsCl, LiF + RbBr, LiF + KI, LiF + CsBr, LiF + RbI, LiF + CsI, LiCl + AgBr, LiCl + AgI и NaCl+AgI are summarized. It is established that the thickness of the interface increases when the temperature grows, tending to infinity near the critical mixing temperature. At equal temperature and the ratio of ion sizes, the layer thickness for melts containing silver halides turned out to be less than in mixtures of alkali metal halides. The surface energy for mixtures of alkali metal halides decreases as the temperature increases, obeying a power equation with a critical exponent equal to 1.5 in the vicinity of the critical mixing temperature. The critical exponent for the galvanic potential for mixtures containing silver halide turned out to be 18% less than the critical exponent for interfacial tension, which is due to the peculiarities of the chemical bond of silver halides. It is shown that at the same temperature, an increase in the size difference of the mixed ions leads to an increase in the energy and a decrease in the diffusivity of the transition layer due to a decrease in the mutual solubility of the components in this direction.

Rasplavy. 2023;(3):223-240
pages 223-240 views
Vorontsov B.S., Moskvin V.V., Babina I.A.

It shows a significant change in structurally sensitive properties in the experiment of modifying a melt (or glass) of the B2O3–Na2O system with lanthanum oxide La2O3 with the destruction of superstructural units when lanthanum atoms hit, since small additions of rare earth metal oxides lead to a significant change in the properties of alkali borate melts. Molecular models of some of the superstructural units, the structure and properties of which were calculated by semi-empirical quantum chemical methods with MNDO and PM7 parameters: as a result of the optimization procedure, both methods lead to models that are qualitatively close, but differ in bond lengths, and practically the same value of heat of formation. The superstructural unit of the considered type is preserved, while its characteristics change: the volume occupied by it increases, the newly formed bond is less strong and its ionic degree is greater.

Rasplavy. 2023;(3):241-249
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Pavlyuk E.V., Alexandrov D.V., Kropotin N.V., Toropova L.V., Starodumov I.O.

The research is focused on the development of mathematical models and software based on them to simulate complex processes of structural-phase transformations for new-generation materials, such as materials with phase transitions (PCM), biomedical materials, materials for additive manufacturing, and materials for the space industry. The mathematical description of the enthalpy-porosity model is performed in this work. The equations of viscous fluid hydrodynamics are used to describe fluid motion in time and space. The analysis of necessary restrictions and assumptions in the model related to consideration of laminar flows and Newtonian fluid model is performed. The computational problem is formulated in terms of the finite volume method and the computational domain and hydrodynamic equations are discretized. The OpenFOAM software, an open integrated platform for numerical simulation of continuum mechanics problems, was used for the computations. The computational algorithm OpenFOAM was developed to analyze the physical state of the system taking into account the initial and boundary conditions in the case of conductive and convective heat transfer. The simulations of gallium melting are performed and the model is verified for the conductive and convective cases. It is shown that in the conductive case the material melting occurs uniformly along the heat sources, while different velocities of convection flows have a significant influence on the formation of the melting boundary. The mathematical models developed in the study, as well as the analytical dependences and the computer simulations are applied to describe real experimental data on crystal growth in supersaturated solutions and supercooled melts.

Rasplavy. 2023;(3):250-266
pages 250-266 views
Ivenko V.M., Shishkin V.Y.

For a number of years, the Institute of High-Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences has been determining the solubility of silver depending on temperature both in individual potassium and cesium, and with additions to these alkali metals of their halides. At the beginning of the study, they were assumed to be corrosive due to the prevailing opinion in the literature about the low solubility of silver in potassium and even less in cesium. In this work, it is shown that the solubility of silver in cesium is greater than in potassium. Here are measurements of the solubility of silver in liquid cesium at temperatures from 500 to 900°C. The average value of solubility for each temperature varied from 0.94 to 11.1 mol % Ag, respectively. Experimental data on the solubility of silver in cesium are approximated by a polynomial of the second degree. NAg = 6.066 · 10–5T2 – 5.966 · 10–2T + 15.58, where NAg is silver solubility in mol %, Т is temperature in °C. In this article, using data on the solubility of silver in cesium and the ideal Schroeder solubility equation, the values of the activity coefficients of silver and the partial enthalpy of mixing of silver and its partial excess entropy in these solutions were obtained. They are respectively equal: = 38 154.8 J/mol and = 14.215 J/(mol · K). The Schroeder equation was used under the assumption that the enthalpy of silver melting is independent of temperature. The values of the logarithm of the silver activity coefficient versus temperature are approximated by the equation: ln(yAg) = 4589 · 1/T – 1.7097. Approximation error R2 = 0.9818.

Rasplavy. 2023;(3):267-273
pages 267-273 views
Olimov N.S., Ganiev I.N., Shirinov M.C.

When melting cast aluminum alloys, their waste is observed, or more precisely, oxidation by the gas phase of the furnace. To select the optimal regime for melting alloys, it is necessary to know the physicochemical laws of this process, which are little studied. To study the kinetics of oxidation of metal melts, the method of continuous sample weighing is used, which is usually used in the study of high-temperature corrosion of solid metals. The mechanism of interaction of liquid metals with oxygen is similar in nature to high-temperature gas corrosion of solid metals. In both cases, adsorption of gas molecules on the metal surface, nucleation, and then growth of an oxide film take place. The kinetics of oxidation of strontium-modified AL2, AL4, and AL9 melts with atmospheric oxygen was studied by thermogravimetry. It is shown that the addition of strontium up to 0.1 wt % increases the oxidizability of melts. An increase in temperature promotes an increase in the rate of oxidation of these melts. The process of oxidation of the investigated melts obeys the parabolic law. The true rate of oxidation is on the order of 10–4 kg/m2 · s. The apparent activation energy of oxidation, depending on the amount of modifiers in the alloys, is: for AL2 alloy – 56.52–43.75, for AL4 alloy 59.74–37.09, for AL9 alloy 61.40–39.90 kJ/mol. The mechanism of influence of strontium on the kinetics of oxidation of melts AL-2, AL4 and AL9 has been established. Aluminum oxide Al2O3 plays a dominant role in the formation of a protective oxide film.

Rasplavy. 2023;(3):274-286
pages 274-286 views
Bobrova K.O., Dokytovich V.N.

The paper presents experimental data on the thermal conductivity of molten salt mixtures СeCl3–MCl, where M = Li, Na, K, Cs. The concentration of cerium trichloride varies from 0.25 to 0.75 mole percent in 0.25 increments. The initial salts of alkali metal chlorides were certified by DSC. The obtained values of melting temperatures are in good agreement with the literature data. Anhydrous cerium trichloride was obtained from cerium(IV) oxide in 2 stages: preparation of cerium crystalline hydrate and removal of water of crystallization. The measurements were carried out by the stationary method of coaxial cylinders in a nickel device in the temperature range individually selected for each composition. The relative measurement error does not exceed 5%. In this work, the convective and radiative contributions to heat transfer were estimated. The value of the product of Prandtl and Grashof numbers is less than 1000, which confirms the absence of convection. The calculated radiative contribution to heat transfer does not exceed 2.4%. The thermal conductivity of all investigated melts increases with increasing temperature. The concentration dependences of molten mixtures of cerium and alkali metal chlorides were obtained. The thermal conductivity decreases upon passing from Li to Cs, which is due to an increase in the radius of the alkali metal cation and, as a consequence, an increase in the interionic distance.

Rasplavy. 2023;(3):287-297
pages 287-297 views
Rusanov B.A., Sidorov V.E., Son L.D., Sabirzyanov A.A.

Experimental investigations of density and electrical resistivity of Al86Ni6Co2R6 (R = Sm, Tb) alloys were carried out in a wide temperature range, including crystalline and liquid states. Density was measured by gamma-penetrating method, and electrical resistance – by contactless method in rotating magnetic field. The solidus and liquidus temperatures were determined, the coefficients of volume expansion and the relative changes in density and resistivity during melting were calculated. The molar volumes of the alloys were calculated. It was found that the alloys are characterized by a wide two-phase zone where density and resistivity dependences show nonlinear behavior. At liquidus temperature an abrupt increase in density and a decrease in electrical resistivity were found. It has been established that terbium increases density of the alloys and reduces their resistivity more than samarium. In liquid phase at temperatures below T = 1300–1350 K density hysteresis was detected, and its absence on resistivity curves was shown. This may indicate the processes of large-scale inhomogeneities decay that do not cause changes in the electronic subsystem of the alloys but play a significant role in amorphization. The revealed features of the properties will make it possible to optimize the process of melts preparing before rapid quenching in order to obtain high-quality amorphous and nanocrystalline samples.

Rasplavy. 2023;(3):298-306
pages 298-306 views
Isakov A.V., Khudorozhkova A.O., Apisarov A.P., Chernyshev .A., Laptev M.V., Shmygalev A.S.

The melting of 60CsBr–40KBr–MoBr3 (mol %) melts was investigated by synchronous thermal analysis and analysis of cooling curves. The concentration dependence of the liquidus temperature of CsBr–KBr–MoBr3 melts was recorded. It was found that increase of the MoBr3 concentration from 0 to 16 wt % leads to increase in the liquidus temperature from 841 to 951 K. It was shown that increase of the MoBr3 concentration from 2 to 16 wt % leads to increase in the relative mass loss of CsBr–KBr–MoBr3 from 3 to 13 wt %. It was found, that MoBr3 crystallizes from CsBr–KBr–MoBr3 melt as a separate phase by X-ray phase analysis. Investigation of density of 60СsBr–40KBr–MoBr3 (mol %) melt was performed by hydrostatic weighing method. It was shown, that increase in the concentration of MoBr3 from 2 to 8 wt % in CsBr–KBr–MoBr3 melts result in to increase of density. The density of the 60CsBr–40KBr–MoBr3 (mol %) melt decreases with temperature. It is shown that the density of melts (60 mol % CsBr–40 mol % KBr)–MoBr3 (0–8 wt %) varies within 2.69–3.20 g/cm3 in the temperature range 871–1071 K.

Rasplavy. 2023;(3):307-315
pages 307-315 views
Nikitin D.I., Polovov I.B., Rebrin O.I.

The technology of pyrochemical processing of mixed nitride uranium-plutonium spent fuel, realizable at the experimental and demonstration energy complex of the site of the Siberian Chemical Plant, includes several operations with the ultimate goal of isolating the target fission products. It’s planned to use the electrofining of the products of the previous stage, metallized spent nuclear fuel, аs the penultimate stage of processing. It’s necessary to determine the processes and technological modes of electrolytic refining of alloys modeling the product of this stage of the processing module to implement electrolytic refining. This paper presents the results of electrofining of model alloys (simulating the raw materials of the stage of electrofining processing) on an enlarged laboratory electrolyzer. The initial parameters of uranium refining processes in melts based on 3LiCl–2KCl–UCl3 were determined earlier. The basic parameters of refining were the use of electrolyte 3LiCl–2KCl–UCl3 (10.1 wt % UCl3) and conducting experiments at 550°C. Uranium alloys containing palladium and neodymium were prepared by direct fusion of uranium metal, PdAP-1 grade palladium metal powders and neodymium metal (99.99%) in a medium of high-purity argon (99.998%). The data obtained showed that at a temperature of 550°C, cathode precipitates are typical dendritic forms of alpha-uranium in rhombic syngony with a tendency to needle formation with an increase in cathode current density. An increase in the company time and cathode current density leads to a decrease in the current output due to short-circuiting of the electrodes with cathode sediment needles or metal shedding from the cathode. The modes of the cathode process have been experimentally refined as a result of electrofining. When electrofining alloys U–Pd(1.59 wt %), U–Pd(1.62 wt %), U–Pd(1.54 wt %), U–Pd(1.58 wt %)–Nd(5.64 wt %), U–Pd(1.84 wt %)–Nd(6.49 wt %), U–Pd(1.79 wt %)–Nd(6.54 wt %), uranium cathode precipitates were obtained, which were subjected to chemical analysis, which showed the high purity of the resulting metallic uranium, as well as the absence of metallic palladium and molybdenum in it. The palladium purification coefficient exceeds 5000, the neodymium purification coefficient exceeds 1000, which meets the requirements for purification from fission products at this stage of pyrochemical processing of spent fuel. Palladium accumulates in anode slime, while the bulk of neodymium passes into the molten electrolyte.

Rasplavy. 2023;(3):316-328
pages 316-328 views
pages 329-330 views

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