V. T. Burtsev.

ABSTRACT

Deoxidizing of heat-resistant nickel-based alloys during vacuum melting is carried out in the presence of aluminum strong deoxidizers boron and hafnium, which requires additional knowledge about the activity of dissolved oxygen. For this purpose, we studied a_[O] in model melts Ni–O–B/Hf (0.001–0.1% wt. % of each) and Ni–O–Al (5%) – B/Hf (0.001–0.1% of mass) at 1560^оС and P_Ar = 0.1 MPa by the method of instantaneous recording of the EDS using certified sensors. It was shown that for the melts Ni–O–(B/Hf), the dependences a_[O] = f [B/Hf] are described by logarithmic functions and at 0.05% of the deoxidizer a_[O] with the introduction of B is 1.1 times less than Hf, and for the melts Ni–O–Al (5%) –B/Hf (0.05% of each) a_[O] with the introduction of B decreased by 1.5 times compared to Hf, what determines the order of introduction of deoxidizers and its number, preferring B as the final deoxidizer.

KEYWORDS:

melts nickel-oxygen, boron, hafnium, EMF method, deoxidation.

DOI: 10.31857/S0235010620040039

V. B. Malkov, I. V. Nikolaenko, G. P. Shveykin, V. G. Pushin, A. V. Malkov,

B. V. Shulgin, O. V. Malkov, P. N. Chernenkiy. 

ABSTRACT

Electron-microscopic study of the nanothin spatial dissipative structures of hexagonal selenium formed in amorphous films, whose lattice undergoes elastic rotational curvature, mirror and inversion symmetries of systems of bending extinction contours present on electron-microscopic images of nanothin spatial dissipative structures are found. It has been established that the mirror and inversion symmetries of the systems of bending extinction contours present on the electron microscopic images of nanothin spatial dissipative structures are due to the mirror and inversion symmetry of the straight lattice of nanothin spatial dissipative structures of hexagonal selenium, which is experiencing an elastic rotational curvature.

KEYWORDS:

symmetry, selenium, spatial, dissipative, structure, crystal.

DOI: 10.31857/S0235010620040076

Kh. B. Kushkhov, M. N. Ligidova, J. Z. Ali, A. A. Khotov, M. R. Tlenkopachev, R. Kh. Karatsukova. 

ABSTRACT

The regularities of the electrochemical behavior of melts of a mixture of alkali metal carbonates K₂CO₃–Na₂CO₃ and K₂CO₃–Na₂CO₃–Li₂CO₃ on platinum and gold electrodes in an atmosphere of air and carbon dioxide under an overpressure of up to 10∙10⁵ Pa were established. The peculiarities of the current-voltage dependences of alkali metal carbonate melts are explained taking into account acid-base equilibria with the participation of the carbonate ion CO₃^2- CO₂ + O^2-. It was shown that in the eutectic melt K₂CO₃–Na₂CO₃, the carbonate ion is stable, i.e. Na⁺ and K⁺ cations possess weakly pronounced oxoacidic properties and do not exhibit electrochemical activity up to the discharge potentials of alkali metal cations. Under these conditions, the electroreduction of CO₃^2– occurs together with Na⁺ and K⁺ cations, or a secondary reduction of the carbonate ion by the liberated alkali metal takes place. The addition of lithium carbonate containing a cation with a higher polarizing force (greater oxoacidity) to the K₂CO₃–Na₂CO₃ melt shifts the acid – base equilibrium toward the formation of CO₂ and affects the electrochemical behavior of carbonate melts, leading to the appearance of a cathodic wave of CO₂ reduction to elemental carbon. The creation of excess pressure of carbon dioxide over the melt of the K₂CO₃–Na₂CO₃ and K₂CO₃–Na₂CO₃–Li₂CO₃ mixture to 10 ∙ 10⁵ Pa leads to saturation of the melts with carbon dioxide, and the polarization of the platinum and gold electrodes in these systems leads to the reduction of CO₂ to elemental carbon. It was shown that the product of galvanostatic electrolysis in a wide range of current densities of 0.25–2.0 A/cm² of the equimolar mixture Na₂CO₃–Li₂CO₃ and the eutectic mixture K₂CO₃–Na₂CO₃–Li₂CO₃ at a temperature of 873 K consists of graphite phases, C₆₀ and C₇₀ fullerenes, and carbon nanotubes.

KEYWORDS:

alkali metal carbonates melts, electroreduction, electrolysis, acid-base equilibria, CO₂ overpressure, electrodeposition of carbon nanostructures.

DOI: 10.31857/S0235010620040040

R. M. Guseynov, R. A. Radjabov, U. M. Magomedova. 

ABSTRACT

The aim of this study is to study the behavior of a silver electrode reversible over minority carriers in a sulfate solid electrolyte or in the corresponding ionic melt in the galvanodynamerfic mode. In this work, we apply the Laplace transform method of Ohm’s law on the interaction between current, potential and complex resistance (impedance), which is called operational impedance method in electrochemistry and electrical engineering. In addition to the operator impedance method, in this work we use an equivalent electric circuit of a silver electrode that is reversible with respect to oxygen and minority charge carriers (which are considered oxygen ions). The possibility of using equivalent electrical circuits in the study of relaxation processes in solid electrolytes was shown back in 1973 by the American electrochemist Armstrong [9, 10]. An analytical expression is obtained for the time dependence of the potential of the electrode–solid electrolyte interface or the corresponding ionic melt in the galvanodynamic mode of operation of the electrochemical cell. It was established by a graphoanalytical method that the galvanodynamic curve of the interphase potential versus time obeys an exponential function. In the present work, it was also shown that the difference between the silver electrode in sulfate electrolytes and the classical equivalent Ershler-Randles electric circuit is that, at very low concentrations of silver ions, the silver electrodeperforms another function, namely, the oxygen function.

KEYWORDS:

operational impedance, silver electrode, minority current carriers, galvanodynamic mode

DOI: 10.31857/S0235010620040040

A. V. Ivanov, V. V. Ryabov. 

ABSTRACT

Using a vibrational viscometer, the viscosity values (η) of sodium-borate melts containing 1 wt % mechanically activated lanthanide oxides (Sm₂O₃, Eu₂O₃, Er₂O₃, Tm₂O₃) in the temperature range of 950–1650 K. The laws of viscosity changes in temperature and composition are established, the temperatures of the onset of solidification of the studied melts are determined. The dependences of the logarithm of viscosity on the inverse temperature revealed high and low temperature regions with different activation energies of the viscous flow. The patterns of viscosity change are explained in terms of changes in the structure of the melt.

KEYWORDS:

viscosity, melt, boron oxide, rare earth oxides, sodium oxide, mechanical activation, melt structure

DOI: 10.31857/S0235010620040052

S. K. Vildanov. 

ABSTRACT

We obtained the ratio for calculating the viscosity of multicomponent oxide solution based on SiO₂ depending on the ionic fractions of cations that make up the oxide solution. This allows us to predict the concentration change in viscosity and to calculate its value using data on the viscosity of liquid solutions of two-component systems SiO₂–Me_xO_y in the concentration range of silicon dioxide 65–75 weight % for fixed temperatures. The conclusion of the ratio is based on the idea of an oxide solution as a superposition of elementary structures of the arrangement of cations relative to each other. Moreover, cations of the same sort are located around the oxygen anion. The cationic sites are filled in such a way that four cations of the same sort are located around the oxygen anion. The accepted model assumes that all cations have the same dimensions and the same charge, but differ only in grade. The resulting calculation formula is a polynomial. To find unknown coefficients in the equation for viscosity as a function of composition, a probabilistic model is proposed that takes into account the order of extraction of cations from the cationic mixture under the assumption that the nature of the change in viscosity as a function of composition is similar to the probability of extracting a certain set of cations from a cationic mixture. For the activation viscosity model, regression relations are obtained for the dependence of the activation energy of the viscous flow and the preexponential factor on the ionic fraction of the second component of the SiO₂–Me_xO_y systems. Comparative calculations of viscosity values are carried out using the calculation formula with experimental data on the viscosity of multicomponent oxide silicate melts. The results of the comparative analysis showed a satisfactory agreement between the calculated viscosity values and experimental data.

KEYWORDS:

viscosity, oxide solution, oxide melt, cationic mixture, metal, heat-insulating slagforming mixture, experiment, probabilistic model, conditional probability, model oxide solution, energy, matrix

DOI: 10.31857/S0235010620040106

A. B. Salyulev, N. I. Moskalenko, V. Yu. Shishkin, Yu. P. Zaikov. 

ABSTRACT

Experimental studies of the distillation of chlorides from their molten mixtures under various conditions were carried out. In all cases, BaCl₂, SrCl₂, NdCl₃ (1–2 mol. %) dilute solutions, as representatives of alkali, alkaline earth and rare earth metal chlorides solutions in the molten eutectic LiCl–KCl mixture, were subjected to evaporation at the reduced (up to ~1 Pa) pressures and temperatures of 753–1033°C. The compositions of sublimates and molten salts before and after distillation were analyzed. Conclusions about the degree of distillation, the selectivity of evaporation of the components of molten mixtures, and the relative volatility of various chlorides are made.

KEYWORDS:

distillation, evaporation, molten mixtures, eutectic LiCl–KCl, BaCl₂, SrCl₂, NdCl₃.

DOI:10.31857/S023501062004009X

A. R. Aliev, I. R. Akhmedov, M. G. Kakagasanov, Z. A. Aliev. 

ABSTRACT

The processes of molecular relaxation in nitrates of alkaline-earth metals: calcium Ca(NO₃)₂, strontium Sr(NO₃)₂, barium Ba(NO₃)₂ have been studied by Raman spectroscopy. It has been established that in the nitrates of calcium, strontium and barium, the phase transition of the first kind “crystal-melt” has a stretched character. The existence of a premelting region in the studied alkaline earth metal nitrates was found. It is shown that the phenomena of premelting are manifested in the temperature dependences of the spectral values.

KEYWORDS:

ionic melts, Raman scattering, molecular spectroscopy, vibrational relaxation, premelting, alkaline earth metal nitrates

DOI:10.31857/S0235010620040027

Yu. G. Mikhalev, N. Yu. Zharinova. 

ABSTRACT

The results of studies of the behavior of liquid metal electrodes–chloride melts depending on the shape, position in the quartz holder and the size of the electrodes are presented. The intensity of mass transfer during the release and dissolution of lead in the modes of circulation cells, when the polarization dependences (PD) have a maximum current density, and laminar flow, when there is no maximum, is determined. It is shown that during the polarization of liquid metal electrodes, the conditions of mass transfer significantly depend on the geometric conditions, which manifests itself in a change in the shape of the polarization dependencies (PD) and the values of current density and mass transfer coefficient (diffusion layer thickness) for a given overvoltage. For electrodes of rectangular horizontal cross section, with a decrease in the ratio of width to length from 1 to 0.13, together with circulation cells that dominate at the same horizontal dimensions, jets arise, rising in places from the interface, and the magnitude of the maximum current density and the intensity of mass transfer increase 2.7 and 2.5 times, respectively. For electrodes with a horizontal cross section in the form of a circle, the polarization dependences and the mass transfer intensity change when the electrodes are immersed in a quartz holder, and the pattern of the change depends on the diameter of the electrode. In the mode of circulation cells, in the case of electrodes of small diameter (up to 5 mm), immersion by ≈3.5 mm leads to an increase in the maximum current density by ≈2 times and the mass transfer rate by ≈1.8 times. It is significant that the electrode potential corresponding to the maximum of the current density at the PD, when immersed, shifts to the negative side by about 100 mV. When immersing electrodes of larger diameter (8.4–16 mm) by an average of 5 mm, the maximum current density at the PD becomes flatter. In this case, the current density at the maximum PD for an electrode with a diameter of 8.4 mm is practically unchanged, and for an electrode with a diameter of 16 mm it decreases by ≈1.3 times. In the laminar flow regime, the current density and, accordingly, the mass transfer velocity also depend on the level of the electrode relative to the edge of the quartz holder. Moreover, in the case of an electrode with a diameter of 4 mm, an increase in the electrode level by approximately 1.8 mm leads to an increase in the current density by an overvoltage of 120 mV by a factor of about 2, while for an electrode with a diameter of 8.4mm, an increase in the electrode level by about 2.6 mm leads to a decrease in current density at an overvoltage of 55 mV also about 2 times. It has been established that for cathodically polarized electrodes of relatively large diameter (up to 83 mm) circulating cells appear, the current density on the PD has a characteristic maximum, and the current density at the maximum exceeds the current density for a solid electrode by about 8 times. 

KEYWORDS:

molten salts, liquid metal electrodes, dissipative structures, circulation cells, laminar electrolyte layer, polarization dependencies, current density, overvoltage, shape of electrode, diameter of electrode

DOI: 10.31857/S0235010620040088

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