Vusikhis A.S., Selivanov E.N., Ryabov V.V., Chentsov V.P. 

ABSTRACT

          Boron oxide systems have been used for refining metals in pyrometallurgical aggregates, as well as for the modeling of various metallurgical processes. Aim of this work is to determine viscosity and electrical conductivity of B₂O₃−CaO−FeO system melts depending on compositions and temperature. The work presents viscosity and electrical conductivity of B₂O₃−CaO systems measuring results at B₂O₃/CaO ratios: 3.0, 1.86 and 1.22, respectively. The melts contained FeO additives (up to 20%). The measurements have been carried out in wide temperature range of the glass formation region. Vibration viscometry technique has been used to measure viscosity. Electric conductivity has been measured by contact method using AC bridge. Temperature dependences of viscosity and electrical conductivity in the 1100−1750 K range have been established. Temperature increase leads to viscosity (η) decrease of B₂O₃−CaO−FeO system melts and electric conductivity (æ) increase. In the temperature ranges (Т_max−Т₁) and (Т₁−Т₂) corresponding to the high and low temperature zones of homogeneous melt, the viscosity and electric conductivity in the coordinates lnη − 1/Т and lnæ − 1/T have linear dependence. The activation energies of viscous flow (E_η) and electric conductivity (E_ϰ) are determined. In the high-temperature region, the activation energies of melts viscous flow vary from 13 to 103 kJ/mol. Temperature decrease leads to it changes from 59.7 to 185 kJ/mol. Comparison of the values of Е_η and Е_ϰ showed that its ratio is not constant. This indicates difference of the groupings responsible for viscous flow and electrical conductivity. In the temperature range (T₂−T_min), the presence of nonlinear dependence section is shown, where glass transition occurs in the entire range of changes (B₂O₃/CaO is 3.0). Glass transition takes place up to temperatures close to 1150 K (B₂O₃/CaO is 1.86) with subsequent formation of crystallites. Partial crystallization of melt in the measurement temperature range (B₂O₃/CaO is equal to 1.22) also take place. The results obtained have been used to describe borate melts structure. In addition, the obtained information is useful for recommendation of melts compositions for refining metals in pyrometallurgical aggregates.

KEY WORDS:

oxide melt, borate glasses, viscosity, electrical conductivity, structure.

DOI: 10.31857/S0235010621020109

N.P. Ouglev, N.S. Boosov, S.N. Uglev. 

ABSTRACT

The main goal of this work is to clarify the mechanism of diffusion in melts and its relationship with the mechanism of separation of metals in capillaries. When a binary melt is stratified in a capillary at a given temperature, a stable equilibrium distribution of the concentration of components along its height is established in 1–2 hours, which does not change further. A number of works have shown that this distribution is associated with the barometric distribution of clusters of components of a certain size in the planet’s gravitational field, which strongly depends on temperature. As the temperature rises, the delamination depth decreases. Obviously, in the presence of concentration gradients inside the capillary, there are also diffusion fluxes of both components directed against the separation process; therefore, the achieved equilibrium state is probably stationary. This assumption was verified in an experiment involving the creation of special conditions in a capillary with a melt, under which the separation process is excluded, but the conditions for diffusion remain unchanged. For this, capillaries with a Sn + 40 wt. % Pb after reaching equilibrium was heated to a higher temperature. In the experiment, the dynamics of the transition of the concentration curve along the height of the capillary to a new state of equilibrium was investigated. The experimental results confirmed that in the state of stationary equilibrium, both processes occur simultaneously: diffusion concentration equalization and stratification directed in opposite directions. The results of processing experimental data based on a mathematical model of the separation process based on the concept of the motion of components in the form of a monoatomic film suggest that the diffusion process also proceeds according to the mechanism of flow of components in the form of a film between melt clusters. This indicates a common carrier of these processes. The method of conducting the experiment and processing the experimental data additionally made it possible to determine the diffusion coefficient of lead in tin, corresponding to the literature data, and therefore this method can be recommended for practical use.

KEY WORDS:

stratification of metals, stratification in capillaries, barometric distribution of clusters, Landau equation, reverse stratification of metals, diffusion coefficient, surface stratification mechanism, single carrier.

DOI: 10.31857/S0235010621020080

A.A. Redkin, S.I. Kumkov. 

ABSTRACT

Analysis of literature data on heat of fusion and melting temperature of coordination compounds of rare earth elements halides was carried out. The interval approach was applied to describing the empirical dependencies. The approach is based on methods of the Interval Analysis and allows one to perform processing the experimental data that have measuring error of significant values under completely unknown their probabilistic properties and under very short sample of measurements. Only the maximal (on modulus) value of the errors can be given in advance. Under such conditions, the standard approaches of the mathematical statistics can be used formally. For description of the process under investigation, the empiric linear dependence of the fusion heat on the fusion temperature is used. The interval processing results (building the information set of parameters and the tube of compatible dependences was performed by the partial information sets method) are compared with estimations of these parameters calculated by the formal application of the standard least squares method (LSQM). Comparison of these results shows that these estimates are sufficiently close, but the interval approach gives better accuracy. For the linear dependency on temperature, its parameters for the rare earth metal halide compounds are sufficiently close to ones for the alkali metal halides. Since the melting temperatures of almost all coordination compounds of the rare-earth metal halides are known, the found estimations and dependences make it possible to estimate the fusion heat of these halides in the case when the experimental data are unavailable.

KEY WORDS:

thermophysical data, REM halides, coordination compounds, heat of fusion, melting point, dependence, experimental data, processing, estimation of dependence parameters, interval approach.

DOI:10.31857/S0235010621020067

O.V. Volkova, V.V. Zakharov, E.A. Il’ina, A.A. Pankratov. 

ABSTRACT

Discharge characteristics of the heat activated battery with NiCl₂-CoCl₂ mixtures as a cathode material has been investigated. Using of mixtures instead of individual nickel (II) chloride and cobalt (II) chloride allows to decrease of the discharge temperature of electrochemical cell was founded. The minimum temperature for fixing of a stable discharge plateau is 480°C. The maximum capacity of the discharge plateau is 0.33 A×h×g^-1. The optimal composition of the cathode mixture contains 20 wt. % CoCl₂. Composition and morphology of reduction products of the cathode materials have been determined. It was found that during the discharge of electrochemical cell, the initial nickel and cobalt chlorides are reduced to metals. The reduction process is accompanied by diffusion of lithium halides from the separator into the cathode space. Reduced metals (Ni, Co) form a network of branched dendrites covered with a salt film based on lithium chloride.  The density and morphology of the dendritic sediment is determined by the composition of the initial cathode mixture. The salt film consists of solid solutions and peritectics of the system Li, Co, Ni½½Cl, Br, F. It was shown that the reduction process of Me²⁺-ions (where Me – Ni, Co) to the metal Me⁰ proceeds through the melt mechanism in the mode of diffusion kinetics.

KEY WORDS:

thermoactivated chemical current sources; cathode; cobalt chloride; nickel chloride

DOI: 10.31857/S0235010621020092

K.I. Trifonov, A.S. Larionov, V.E. Krotov, A.F. Nikiforov. 

ABSTRACT

The viscosity of 16 compositions of potassium chloraluminate systems containing 3.8–57.2 mol % of ZrCl₄ and 5.4– 30.2 mol % of HfCl₄ was determined in the temperature range of 563–663 К. Their temperature dependences are given. Binary chloraluminate mixtures containing HfCl₄ additions were found to have the highest viscosity, and those containing ZrCl₄ ones had the lowest viscosity. The viscosity of the three-component system has an intermediate value. The obtained results can be used in the technology of separation of zirconium and hafnium tetrachlorides.

KEY WORDS:

melt, viscosity, three-component system, potassium chloraluminate, zirconium tetrachloride, hafnium tetrachloride

DOI: 10.31857/S0235010621010084

C O N T E N T S

S. K. Vil’danov.

ABSTRACT

     Samples of values ​​of temperature of liquid metal in the process of continuous casting of steel are analyzed. The samples are formed from the values ​​of the temperature of the liquid metal in the steel-pouring ladle measured by the thermocouple and the data from five successive measurements of the temperature of the liquid metal in the tundish. Measurements in the steel-pouring ladle were made after the stage of vacuumizing the steel, before feeding the metal for continuous casting. Temperature measurements in the tundish were carried out throughout the entire casting period, including all heats assigned to the series. A hypothesis has been put forward about the normal distribution of the set of metal temperature values ​​both in the steel-pouring ladle and in the tundish. The hypothesis was tested using three goodness-of-fit tests: the chi-square χ² test, the Kolmogorov λ test and the Shapiro-Wilk W test. It is shown that the hypothesis of the normal distribution of temperature values ​​in the steel-pouring ladle does not contradict the experimental data for all three criteria of agreement, and can be accepted. The hypothesis of a normal temperature distribution during measurements in the tundish should be rejected as inconsistent with the experimental data, while all three goodness-of-fit criteria show the need to reject this hypothesis. The main factors leading to a deviation of the temperature distribution from the normal law are: increased metal cooling rate in the tundish, introduction of slag-forming and heat-insulating mixtures onto the metal surface. With an increase in the number of temperature measurements in the tundish, the absolute values ​​of the statistics of the goodness-of-fit tests, although they remain above the critical limit (the Pearson and Kolmogorov criteria of agreement) and below (the Shapiro-Wilk test), the temperature distribution in the tundish tends to a normal distribution.

KEY WORDS:

population, sample, temperature, steel-pouring ladle, tundish, goodness-of-fit criteria, normal distribution, deviation from the normal distribution law.

DOI: 10.31857/S0235010621010096

F. R. Kapsalamova, S. А. Krasikov, V. V. Zhuravlev. 

ABSTRACT

       In the presented work, the process of mechanochemical alloying of a mixture of Fe, Ni, Cr, Cu, Si, B, C powders in an MPP-2-1K planetary mill with a duration of up to 15 min is carried out in order to study the possibility of obtaining a surfacing powder for flame surfacing. To establish the features of the chemical interaction during mechanochemical alloying between the components of the charge, the sequence and nature of the formation of the phase composition of granular compositions, an X-ray phase analysis of the powder material was carried out on a D8 ADVANCE “Bruker Elemental GmbH” diffractometer. The morphology of granules after MCL was carried out on a JEOLJXA-8230 scanning (raster) electron microscope (SEM). To determine the melting point of the obtained composition, thermogravimetric analysis was carried out on a synchronous thermal analyzer TG-DTA/DSC with a quadrupole mass spectrometer: STA 449 F3 Jupiter® “NETZSCH”. The results of the study showed that in the Fe-Ni-Cr-Cu-Si-B-C powder composition during mechanical activation, both stable and metastable phases are formed. It was revealed that already after 1 min of mechanochemical alloying, numerous new phases are formed, and by 15 min a multiphase system is formed, including intermetallic compounds (Fe_0.95Ni_0.05, Cr_1.07Fe_18.93, etc.), carbides (Fe₃C, Cr_15.58Fe_7.42C₆, etc.), borides (Ni₇₅Si₂₄B_0.04, etc.) and silicides (Ni_0.92Si_0.08, Cr₅Si₃). The main reason for the phase formation during mechanochemical alloying is the impact of the impact of grinding bodies (balls), as a result of which plastic deformation of the particles of the initial components, their destruction and welding along the formed juvenile surfaces, accompanied by exothermic effects with the formation of intermediate liquid phases, is carried out. As a result, the contact surface of the reagents sharply increases and composite particles are formed. During the impact, complex and poorly studied processes of chemical interaction, diffusion of components, phase and structure formation occur.

KEY WORDS:

interactions, transformations, mechanochemical alloying, surfacing powder, energy stresses

DOI: 10.31857/S0235010621010060

A. V. Isakov, A. O. Khudorozhkova, E. G. Vovkotrub, A. S. Vorob’ev, A. A. Red’kin, Yu. P. Zaikov. 

ABSTRACT

       The interaction of KI with the KF–KCl–K₂SiF₆ and KF–KCl–K2SiF₆–SiO₂ salt systems was studied. The KF–KCl and KF–KCl–KI systems containing both K₂SiF­₆ and SiO₂ were studied by Raman spectroscopy. It was shown that the addition of KI to the KF–KCl–K₂SiF₆ and KF–KCl–K₂SiF₆–SiO₂ melts leads to the appearance of groups containing Si–I bonds in the solid samples. It was established that a significant part of silicon dioxide from the KF–KCl–K₂SiF₆–SiO2 and KF–KCl–KI–K₂SiF₆–SiO₂ melts crystallizes in the form of silicate structures characteristic of the K₂SiO₃ phase (K₂O · SiO₂). The Raman spectroscopy data are consistent with the data of X–ray phase analysis of KF–KCl and KF–KCl–KI melts containing both K₂SiF₆ and SiO₂. It was found that the crystallization field of K₃SiF₇ is retained when KI is added to the KF–KCl–K₂SiF₆ and KF–KCl–K₂SiF₆–SiO₂ melts. When KI is introduced into the melt, it is characteristic to precipitate it into a separate phase during crystallization. Low–intensity peaks corresponding to the crystallization of the α-SiO₂ phase were recorded for the KF–KCl–K₂SiF₆–SiO₂ and KF–KCl–KI–K₂SiF₆–SiO₂ systems.

    The study of KF–KCl–KI–K₂SiF₆ and KF–KCl–KI–K₂SiF₆–SiO₂ melts by the method of synchronous thermal analysis was carried out. It was found that at temperatures up to 473 K, phase transitions are observed, which are probably associated with the transformation of SiI_xF_y^z– structures into structures containing SiF₆^2–, which is consistent with information on the thermal stability of mixed silicon halide.

KEY WORDS:

potassium fluoride, potassium chloride, potassium iodide, siliceous melts, Raman spectroscopy, X–ray phase analysis, STA analysis.

DOI: 10.31857/S0235010621010047

I. A. Babina, B. S. Vorontsov, V. V. Moskvin, I. N. Grekhov, A. O. Babin. 

ABSTRACT

      Due to the use of sorbents in various fields of science, technology and in everyday life, the development of new materials with sorption properties is of interest. Amorphous silica was chosen to study the properties of modified sorbents. Since there are problems of strict description of the interactions of the silica surface with grafted structures, it was decided to use a model calculation of the protonation energies of the structure with grafted N-(propyl)ethylenediamintriacetic acid.

    It is shown that the model experiment based on semi-empirical quantum chemical calculations indicates that protonation of silica modified by molecules with weakly basic nitrogen is accompanied by the formation of surface complexes of different structure, including the formation of hydrogen bonds.

KEY WORDS:

 silanol groups, molecular models, protonation, model experiment.

DOI: 10.31857/S0235010621010023