С О N T E N T S

A. V. Kaibichev, I. A. Kaibichev. 

ABSTRACT

The electric field, acting on the surface of the melt, promoted the formation of ions of different atomicity. The atomicity of ions was determined from the change in the weight of the Fe-Al melt in the experiment with negative and positive polarity. The influence of temperature, amount of electricity passed, polarity and interelectrode voltage is taken into account. The atomicity of the ions of the transported element is calculated by the mass of the monoatomic one. It is determined by the amount of electricity required for its transfer and the corresponding proportion of ions. The required amount of electricity represented a fraction of the past. It is calculated as the ratio of the product of the fraction of ions in electricity and the atomic weight of an element to the sum of their values ​​of all participants in the transfer. The sum of the products of the masses of monatomic ions by the determined number of atoms in polyatomic ions corresponded to the mass transfer in the experiment. The obtained linear equations made it possible to determine the number of atoms and the mass of ions. Their change was traced during the periods of the experiment at different polarities of the melt. With negative polarity, the elements were removed from the melt, with positive polarity, from the surface of the molybdenum electrode. The atomicity and mass of ions decreased with the removal of elements from the melt during the period of the experiment. At the beginning, ions Al₇⁺, Fe₃⁺, FeAl⁺ were removed, at the end Al⁺, Fe⁺. The transfer of elements into the melt is associated with the formation of MoAl₃ and the lack of stability in the composition of the surface layer of the molybdenum electrode. At the beginning, the ions Al₃⁺, Fe₅⁺, FeAl⁺ and MoAl₃⁺ were transferred. The rest of the time, ions were transferred without MoAl₃ with a smaller difference in atomicity. The stability of the composition of the surface layer increased. The discrepancy between the calculated masses of ions of the transferred elements in helium at negative and positive polarity and those obtained in the experiment was less than a percent.

 KEYWORDS

amount of electricity, voltage, speed, electron, ion, atomicity, mass.

DOI: 10.31857/S0235010622020037

N. I. Sidorov, S. Kh. Estemirova, E. D. Kurbanova, V. A. Polukhin. 

ABSTRACT

The analysis of kinetic characteristics – diffusion (D) and permeability (Ф) of hydrogen in membrane alloys based on binary alloys Fe-Ni, Nb-Ni, V-Ni. Various structural modifications of membrane alloys were studied – amorphous, nanocrystalline and duplex, and the efficiency of selectivity processes in each of these modifications was determined. The influence of thermodynamic parameters – temperature and pressure – on the permeability, diffusion of hydrogen and its flux (J_H ~ D · Ф) in the indicated alloys is revealed. The analysis of the results of calculations and experimental measurements for hydrogenated and titanium-doped membrane alloys based on binary compositions Nb₈₅Ni₁₅ and V₈₅Ni₁₅ as alternatives to those known based on Pd_1-xAg_x is carried out. It has been found that the intense formation of hydrides in these alternative membrane alloys is as undesirable as for traditional Pd-based alloys. Titanium-doped crystalline alloys Nb-Ti-Ni and V-Ti-Ni – are a combination of solid solutions: a primary phase with a bcc structure [Nb (V), Ti] and a eutectic phase {bcc – [Nb (V), Ti) + B2 – TiNi}. In this case, the eutectic phase, as a part of the duplex matrix structure, prevents the hydrogen embrittlement of the Nb-Ti-Ni and V-Ti-Ni alloys.

KEYWORDS

membrane alloys, amorphous structure, interatomic bonds, clusters, hydrogenation, glass transition, sorption, diffusion, permeability, intermetallics, hydrides, hydrogen energy, molecular dynamics.

DOI: 10.31857/S0235010622020086

E. A. Karfidov, B. A. Rusanov, V. E. Sidorov, E. V. Nikitina, D. Janickovic, P. Svec Sr. 

ABSTRACT

Amorphous and nano-crystalline aluminum-based alloys especially compositions with transition and rare-earth metals have improved mechanical characteristics and high chemical resistance. The influence of transition metals ratio on corrosion-electrochemical behavior of aluminum-nickel-cobalt-neodymium amorphous compositions was studied in present work. It was found that Al₈₆Ni₄Co₄Nd₆ amorphous alloy demonstrates greater corrosion resistance than Al₈₆Ni₆Co₂Nd₆ composition according to the data of gravimetric and chemical analysis (corrosion rates 0.635 and 2.1 mg/m²·h, respectively). Corrosion potential shifts to the electronegative region with increase in concentration of nickel in composition of the initial alloy. The investigated amorphous compositions have a wide passivation area due to the formation of stable layer of aluminum oxide on surface, which determines their resistance under the conditions under study. Al-Ni-Co-Nd amorphous alloys can be considered as promising compositions for the manufacture of aluminum-based protective coatings.

KEYWORDS

crystallization, corrosion, aluminum alloys, amorphous alloys

DOI: 10.31857/S0235010622010054

I. Zh. Sattybaev, V. G. Postovalov, V. P. Kondratiev. 

ABSTRACT

Systematic experimental data on the density and volume properties of binary melts are extremely scarce, although they are necessary for accurate measurement of the thermophysical properties of melts and optimization of production processes in metallurgy. The paper presents the original procedure for calculating the density and volume properties of binary melts. In the case of the aluminum-copper system, it is used to derive empirical equations that make it possible to enough accurately calculate the density, molar and excess volumes of melts containing from 0 to 100% copper in the temperature range from liquidus to 1730-1900 K. Adequacy of density and volume properties calculation results are shown by comparing them with experimental data. In addition, they are in good agreement with the data on the excess Gibbs energy and the phase diagram of the aluminum-copper system.

KEYWORDS

aluminium-copper melts, density, molar volume, excess volume.

DOI: 10.31857/S0235010622020074

A. S. Vusikhis, E. N. Selivanov, L. I. Leont’ev.

ABSTRACT

To describe the processes of joint reduction of iron and copper from an oxide melt (1273–1773 K) of the B₂O₃-CaO-FeO-CuO system with carbon monoxide and hydrogen, we used the thermodynamic modeling technique in the approximation to open systems, with fractional introduction of CO (H₂) and periodic removal of metal phases and gases from the composition of the working fluid.

The calculations were carried out taking into account the disproportionation of FeO into Fe and Fe₃O₄. For the considered compositions of the melt, having a FeO/CuO ratio equal to 10, disproportionation of the lower iron oxide and its interaction with CuO allows, at low temperatures, to transfer copper to the metallic state by 20–80%.

The relationships between the contents of iron and copper oxides in the oxide melt, the degrees of their reduction and the composition of the resulting alloy on the temperature and the amount of the introduced reducing agent are revealed. It is shown that the required amount of hydrogen for the reduction of metals to a fixed degree of copper metallization is significantly lower than that of carbon monoxide. The information obtained is useful for predicting thermoextraction processes occurring during the extraction of useful components from nonferrous metallurgy slags.

KEYWORDS

thermodynamic modeling; oxide melt; recovery; gas; hydrogen; carbon monoxide, metal, iron, copper

DOI: 10.31857/S0235010622020104

V. A. Polukhin, N. I. Sidorov, E. D. Kurbanova, R. M. Belyakova. 

ABSTRACT

The analysis of alloys and methods of their synthesis for membrane technologies for producing ultrapure hydrogen has been carried out. Both traditional Pd-based alloys and alloys based on cheaper metals of V and VIII groups are considered by the example of binary Nb-Ni, V-Ni, Ta-Nb doped with Ti, Zr, Mo, Hf and W. Achievements of kinetic, strength characteristics, thermal stability, wear resistance and stable functionality of membrane amorphous and nanocrystalline alloys with alternative compositions based on Group V elements are considered. The problems of intermetallic hydrogen embrittlement during long-term processes of hydrogen selectivity are considered. A solution to these problems has been proposed by developing new alloys based on Group V and VIII metals alloyed with Ti, Mo, Hf, W; limiting the temperature range from 473 to 673 K; limiting the maximum permissible concentration of hydrogen H/M– less than 0.22. Membrane alloys of solid solutions of Nb (V, Ta)-Ti-Ni compositions with a duplex matrix structure – eutectic phases and primary phases, respectively {BCC- (Nb, Ti) + TiNi} + {Nb (V, Ta), Ti} and NiTi and NiTi₂ compounds, which stabilize and protect the matrix structure from brittle fracture. The considered alternative alloys actually make it possible to obtain high-purity gaseous hydrogen using new compositions instead of expensive membranes based on Pd-Au/Ag/Cu alloys. 

KEYWORDS

amorphous and nanocrystalline alloys, nickel, titanium, zirconium, niobium, structuring, membrane gas separation, hydrogen purification, solubility, hydrogen permeability, accumulation, thermal stability, fragility, crystallization, modeling, diffusion, nanophases, Me-H hydrides, embrittlement, duplex matrix microstructure.

DOI: 10.31857/S0235010622020050

Yu. G. Mikhalev, N. Yu. Zharinova. 

ABSTRACT

This work is a continuation of studies of nonstationary dependences (inclusion curves) during cathodic polarization of liquid electrodes made of lead, bismuth, cadmium, aluminum in chloride melts, when structures in the form of vortices – circulation cells (CC), due to the Marangoni microeffect. In this case, the time dependences of the overvoltage η and the current density i with a stepwise setting of the current under galvanostatic conditions or the potential under potentiostatic conditions (inclusion curves) have extrema of the current or overvoltage, decreasing in magnitude until a steady state is established. The values ​​of η and i at the first extremum η_extr and i_extr always have the largest amplitude. The time of τ_extr achievement η_extr and i_extr and the values ​​of η_extr and i_extr  themselves characterize the process of forming the CC. The τ_extr value is the most convenient for analysis, since it does not depend on the concentration of electrochemically active particles. It is assumed that the formation of circulation cells is the slower, and the value of τ_extr is the greater, the greater the intensity of mass transfer processes at the electrode-electrolyte interface, which is determined by the polarization conditions.

It is shown in the work that with increasing temperature τ_extr increases, which means that the formation of the CC proceeds more slowly. When an external magnetic field is applied, which helps to slow down mass transfer, τ_extr decreases and when the electrode is immersed in a quartz holder τ_extr also decreases. On the whole, these results indicate the correctness of the assumption about the rate of CC formation.

When the current pulses are successively applied to the already polarized electrode, the overvoltage extremum is clearly visible on the turn-on curves, the value of which decreases in the sequence of pulses. τ_extr values ​​are also reduced. The existence of overvoltage extrema can be associated with energy difficulties in the integration of newly formed CC into the structure of existing ones.

KEYWORDS

molten salts, liquid metal electrodes, circulation cells, formation time of circulation cells, current density, overvoltage, turn-on curves.

DOI: 10.31857/S0235010622020049

R. M. Belyakova, E. D. Kurbanova, N. I. Sidorov, V. A. Polukhin. 

ABSTRACT

Membrane evolution of ultrapure hydrogen is now considered one of the most effective technologies largely due to the alternative replacement of expensive Pd-Ag membrane alloys with cheaper ones based on bcc metals of the VB group (V, Nb, Ta, etc.) with an amorphous, nanocrystalline structure with a permeability exceeding that of palladium alloys with an fcc structure. However, hydrogen-selective membrane alloys of bcc metals Co, V, Cr, Ta, Nb, although they demonstrate very high hydrogen permeability, are subject to brittle destruction due to excessive absorption of hydrogen. A comparative analysis of the kinetics of hydrogen in titanium-doped membrane binary alloys Nb-Ni and V-Ni, according to such criteria as strength characteristics, thermal stability and resistance to hydrogen embrittlement. The dissolution of Ni and Ti in the niobium and vanadium phases increases the critical temperature of β-hydride formation from 200 to 400°C. In addition, Ni-Ti and NiTi₂ compounds stabilize the matrix structure of membrane alloys and prevent hydride formation.

KEYWORDS

membrane alloys, alloying, niobium-titanium-nickel, vanadium-titanium-nickel, matrix microstructure, hydrogenation, absorption, diffusion, hydrogen permeability, phase formation, Me-H hydrides, embrittlement, duplex structure

DOI: 10.31857/S0235010622020025

A. A. Polyakov. 

ABSTRACT

The 3D Penrose tiling (3DPT) is a quasiperiodic lattice with icosahedral symmetry, it is used in the crystallography of quasicrystals. The work aims to formulate the principles of selecting fractals for repeating 3DPT. The building elements of the fractals are the great (I) and the small (D) stellated dodecahedrons. An absolute inflationary approach to fractal construction is used. Each point of both 3DPT and the fractals is described by a 6-index. These six indices are vector components on a non-orthogonal basis, with 6 unit vectors directed from the centre to the vertices of the regular icosahedron. The fractal points can be classified into four types according to two criteria: integer or half-integer 6-indices, an even or odd sum of six indices. Multiplying the vectors of fractal points by the golden ratio leads to a cyclical change in these types. The rules for modification of these types when summing vectors are formulated. These rules made it possible to determine the types of points of each prefractal. For 3DPT repetition, prefractals with integer indices having an even and odd sum are chosen. It was proposed a method for determining the minimum 3D star of the fractal. Based on these principles, the points of the fractal 2I3I4I… are analysed. When choosing this fractal, no extra points that are not part of the 3DPT were found. This approach allowes 85% of the 3DPT points to be repeated.

KEYWORDS

fractals, three-dimensional Penrose tiling, quasiperiodic lattice, great stellated dodecahedron, small stellated dodecahedron

DOI:10.31857/S0235010622020062