PhC-2022

D.A. Zernitsa
Mozyr State Pedagogical University named after I.P.Shamyakin

Abstract: The results of studies of the structures of rapidly solidified foils of alloys of the Sn – Zn system with a low content of alloying elements (up to ~1,5 wt.%), alloys of near-eutectic compositions, as well as alloys with an alloying element content of 20 – 95 wt.% are presented. In rapidly solidified alloys containing 1,5 wt. % Sn and 1,2 wt. % Zn, supersaturated solid solutions are formed, which decompose according to the mechanism of formation and growth of nuclei of a new phase at room temperature. Alloys (4,4 – 15 wt.% Zn) after rapidly solidification are supercooled and supersaturated with both components, and experience spinodal decomposition followed by the formation of supersaturated solid solutions based on Sn and Zn, which decompose at room temperature. In all other alloys, a two-phase structure is formed from solid solutions based on Sn and Zn. It was found that as the crystallization front moves from the surface of the contacting foil layer with the surface of the mold, the Sn particles coarsen and the specific surface of the interface
decreases. It has been established that rapidly solidified foils have a microcrystalline grain structure, with an increase in the concentration of alloying elements, a tendency to a decrease in grain size is observed.
Keywords: rapidly solidified alloys, zinc, tin, grain, spinodal decomposition, supersaturated solution, eutectic, structure

A.D. Zigert, E.M. Semenova, N.B. Kuz`min, N.Yu. Sdobnyakov
Tver State University

Abstract: The results of fractal analysis of images of the surface of a permanent magnet KS37 obtained by the method of the polar Kerr effect using an indicator bismuth-containing ferrite-garnet film after magnetization reversal by a pulsed field of 0,1 – 1,5 T are presented. The obtained dependences of the remanent magnetization on the magnitude of the external pulsed field are compared with the fractal dimension of the magneto-optical images of the magnet surface after exposure to the pulsed field. It is hypothesized that the field dependences of the fractal dimension of the profile of magneto-optical images of the magnet surface coincide in shape with the graphs of the first derivative dMr(H)/dH of the magnetization with respect to the field, i.e. there is a relationship between the nature of the magnetization change in a pulsed field and the type of the magneto-optical image analyzed by using the fractal geometry methods.
Keywords: permanent magnet, effect, ferrite-garnet films, domain structure, fractal dimension, derivative of magnetization with respect to magnetic field

D.V. Ivanov¹, A.S. Antonov^1,2, E.M. Semenova¹, A.I. Ivanova¹, N.B. Kuz`min¹, N.Yu. Sdobnyakov^1
1 Tver State University
² Tver State Agricultural Academy

Abstract: The patterns of formation of the fractal relief of nanosized iron films on the mica surface are considered using the atomic force microscopy. In order to prevent the formation of an oxide layer, iron films were studied immediately after their production employing at a magnetron sputtering unit. It has been established that magnetron sputtering makes it possible to obtain island films of iron, the structural element of which are truncated nanocubes – nanopyramids. The fractal dimension of the resulting agglomerates was determined at various scales: on a scale of 5 µm Dc = 2,462±0,113; on a scale of 3 µm Dc = 2,373±0,122; on a scale of 1 µm Dc = 2,298±0,139. The distribution of the probability of detecting agglomerates on the films under study with a certain fractal dimension of the surface of iron films is estimated. The subsequent elemental analysis of the iron films showed the presence of oxygen and, consequently, the formation of ordered oxide films of the core-shell type.
Keywords: atomic force microscopy, magnetron sputtering, fractal dimension, iron films, nanopyramids

A.I. Ivanova, P.A. Svesnikov, K.A. Marinicheva, K.A. Gugutsidze, A.D. Vasilev, S.A. Tretiakov, A.Yu. Karpenkov
Tver State University

Abstract: In this paper, we present the results of microhardness tests performed by Vickers indentation of germanium and silicon single crystals. It’s shown that in the investigated samples there is a dependence of microhardness on the crystallographic directions and the nature of the alloying impurity. Microhardness anisotropy coefficients are calculated: for germanium K_II=1,2 and for silicon K_II=1,3. The analysis of high-temperature annealing influence on microhardness value of germanium and silicon crystals is carried out. It has been established, that the microhardness of Ge(111) crystals grows on 12% after annealing at 550°С, the further thermal processing of germanium crystals at T=650°С considerably changes the structure and surface relief which contribute to a decrease in microhardness values. It is shown that the microhardness of silicon crystals increases by 10% after annealing at 750°C, further annealing to T=850°C leads to a decrease in microhardness. The surfaces of single crystals after high-temperature annealing have been studied; it has been established that thermal treatment at T≈0.6 Tm (Tm – the melting temperature of the single crystal) leads to the appearance of defects and a tenfold increase in the maximum height of the surface profile (from 10-12 nm to 100-200 nm).
Keywords: germanium and silicon single crystals, microhardness, Vickers method, microhardness anisotropy coefficient, interatomic bonds, dopants, high-temperature annealing, surface nanorelief, defects

A.I. Ivanova¹, I.I. Musabirov², E.M. Semenova¹, A.D. Vasilev¹, K.A. Gugutsidze¹, A.Yu. Karpenkov^1
1 Tver State University
² Institute for Metals Superplasticity Problems of the Russian Academy of Sciences

Abstract: This paper presents the results of studies of the effects of deformation obtained by the method of multiple isothermal forging on the microstructure and magnetic properties of the NiMnGa alloy system. It is shown that the microstructure of the initial alloy during deformation undergoes changes, grain size decreases and a two-component structure is formed. The magnetic domain structure of the original and deformed alloys was visualized by magnetic force microscopy. It is shown that the distortion of the domain shape is associated with the presence of a martensitic relief and grain boundaries, 180-degree magnetic domains are continuous within the crystallites, while they cross the flat parallel boundaries of the martensite plates. The study of temperature and field magnetization dependences of the initial and isothermal forging samples demonstrates an insignificant magnetization decrease and a shift of the phase transition temperature toward low temperatures. It’s concluded that deformation by the isothermal forging method can be considered as a way to correct the phase transition temperature in NiMnGa alloys with preservation of magnetization.
Keywords: Heusler alloys, martensitic relief, multiple isothermal forging, micro and nanostructure, magnetic domain structure, magnetostructural transition

V.G. Kul’kov, V.V. Kul’kova
Branch of the National Research University «Moscow Power Engineering Institute» in Volzhsky

Abstract: The model of internal friction at the migrating intercrystalline boundary is considered. Under the action of an alternating external stress oriented normally to the boundary, compression and stretching of the mating crystallites occurs. Due to their anisotropy and mutual reversal, Young’s modules in the direction of the stress action are different. The volume density of elastic energy in crystallites is different. This leads to the emergence of an effective driving force for boundary migration. As a model, a square segment of the boundary is selected, fixed along the perimeter by triple grain joints. The Laplace stress from the side of the curved boundary is counteracting. The differential equation of the connection of the boundary displacement with the total voltage is solved by the Fourier method. Based on this solution, the internal friction is calculated. The relaxation time spectrum consists of a series of lines. Each of them corresponds to the peak of Debye. The main peak has a significant value, smaller peaks are superimposed on it. The resulting maximum of internal friction widens in comparison with the Debye peak.
Keywords: driving force, migration of the intercrystalline boundary, peak of internal friction, relaxation time

V.A. Lapin^1,2, I.V. Kasyanov^1,2
1 Federal Research Center Southern Scientific Center of the Russian Academy of Sciences
² North-Caucasus Federal University

Abstract: InAlN films on Si (111) were obtained by the ion-beam deposition with various technological growth parameters. The results of the study of grown films by the scanning electron microscopy were used to identify the conditions for obtaining InAlN continuous films. Due to the mismatch of the lattice parameters of the film and substrate, the growth has an island character, a solid film was obtained only with the following technological parameters: the energy level of the beam U = 600 eV at the ion current of the beam ji = 32 mA, with the neutralization current of the beam jn = 32 mA, the substrate temperature of 400°C. With an increase of the nitrogen concentration to 80-90% in the gas mixture, a transition from an island to an epitaxial growth mechanism took place. The ratio of the elements In, Al and N in the film showed that the active plasma of the ion beam breaks down weakly bound ions and leaves only normally embedded nitrogen atoms N^-3, but excessively strong exposure leads to metallization of the films.
Keywords: heteroepitaxy, InAlN, ion-beam deposition, elemental analysis, scanning electron microscopy, heterostructures

R.Yu. Karmokova¹, A.M. Karmokov¹, O.A. Molokanov¹, A.I. Khasanov², A.A. Kanametov^1
1 Kabardino-Balkarian State University
² Chechen State University named after A.A. Kadyrov

Abstract: Calculation of parameters of a cavitation bubble during irradiation of aluminum melt with acoustic waves is carried out. The dependences of the Mach number on the amplitude at frequencies of 1-20 kHz used in the experiments are obtained. A relationship has been established between the resonant frequency of acoustic waves and the size of cavitation bubbles in liquid aluminum. Allowing the possibility of generalizing the Minnert linear theory to the case of viscous liquids, the dependence of the maximum radius of cavitation bubbles on the frequency of the acoustic field at different temperatures is obtained, taking into account the surface tension, density and viscosity of liquid aluminum. It has been established that with an increase in the frequency of the acoustic field, the radii of the cavitation bubbles decrease. The temperature change inside the cavitation bubble is estimated as a function of the bubble radius at any moment of its compression under adiabatic conditions. It is shown that when the bubble radius decreases to a critical size, the temperature inside it can increase by an order of magnitude.
Keywords: aluminum, acoustic waves, cavitation, cavitation bubble, Mach number

V.V. Malashenko^1,2, T.I. Malashenko^3,4
1 Donetsk Institute for Physics and Engineering named after A.A. Galkin
² Donetsk National University
³ Donetsk National Technical University
⁴ Donetsk National University of Economics and Trade named after Mikhail Tugan-Baranovskiy

Abstract: A theoretical analysis of inelastic processes in aged alloys under intense external influences is carried out. The analysis was carried out within the framework of the theory of dynamic interaction of defects. An analytical expression for the dependence of the dynamic yield strength on the dislocation density has been obtained. The reason for the different influence of nanostructural defects on the dislocation motion under high strain rate deformation and quasi-static deformation is determined. It is shown that under high strain rate deformation, nanosized defects affect the nature of the dependence of the dynamic yield strength on the dislocation density. This dependence becomes nonmonotonic and has a minimum. At the minimum point, there is a transition from the dominance of the drag of the dislocation by Guinier-Preston zones to the dominance of its drag by other dislocations. Numerical estimates of the contribution of the Guinier-Preston zones to the yield strength are made. It is shown that at a high concentration of Guinier-Preston zones, this contribution is very significant. Numerical estimates are made of the dislocation density at which the Taylor relation is violated.
Keywords: high-speed deformation, dislocations, Guinier-Preston zones, point defects, nanomaterials, Taylor ratio

O.V. Malyshkina, G.S. Shishkov, A.I. Ivanova
Tver State University

Abstract: The paper presents the results of a study of the influence of a constant magnetic field on the dispersion of the complex permittivity of a layered composite (connectivity 2-2) based on barium titanate – barium ferrite. It is shown that in the manufacture of a magnetoelectric composite of barium titanate – barium ferrite with a connectivity of 2-2, a strong diffusion of iron appears into the barium titanate ceramic layer at the interface between the two materials. It was found that iron penetrates evenly, with random deviations, and no exponential decline as iron enters into barium titanate is observed. It has been established that a constant magnetic field does not affect the dielectric characteristics in an alternating electric field at frequencies above 1600 Hz. At lower frequencies, annealing in the paraelectric phase increases the resistance of the sample, and subsequent exposure to a constant magnetic field leads to its decrease. It was revealed that changing the type of connectivity of the magnetoelectric composite from 0-3 to 2-2 adds additional, smaller, resonance and
antiresonance peaks in the study of piezoelectric properties by the resonance-antiresonance method. At the same time, the samples have sufficient values of the piezoelectric modulus for practical application (d31 > 40·10^-12 C/N; d33 > 120·10^-12 C/N).
Keywords: multiferroic, barium ferrite, barium titanate, magneto-electric composite, piezoelectric ceramic structure