Editor’s column

D.V. Belov^1,2, S.N. Belyaev^1,2, P.A. Yunin², A.A. Nazarov^2
1 Federal Research Center A.V. GaponovGrekhov Institute of Applied Physics of the RAS
² The Institute for Physics of Microstructures – branch of the IAP RAS

Abstract: In this work, biocorrosion of D16T and AMg6 aluminum alloys under the influence of microscopic fungi was studied. It has been shown that micromycetes produce reactive oxygen species – superoxide anion-radical, hydrogen peroxide, which initiate biocorrosion of metals. The composition products of biocorrosion of D16T and AMg6 after exposure of the alloys on the lawn of a consortium of micromycetes was determined by energy-dispersive X-ray spectroscopy. An X-ray phase study of alloy biocorrosion products was carried out. Scanning electron microscopy and X-ray diffraction analysis show the formation of nanosized and submicron copper clusters. A physicochemical mechanism of biocorrosion of aluminum alloys by microscopic fungi is proposed. An assumption is made about the mechanism of operation of the «zerovalent metal – hydrogen peroxide» systems, which can trigger a cascade of reactions leading to the destructive oxidation of metals. The paper attempts to explain the role of microfungal community biofilms as the main factor in the mycological corrosion of metals.
Keywords: biocorrosion, microbiological corrosion, aluminum alloys D16T, AMg6, zerovalent aluminum, zerovalent copper, microscopic fungi, reactive oxygen species, superoxide anion radical, hydrogen peroxide, copper clusters

Z.V. Shomakhov¹, S.S. Nalimova², A.A. Rybina², S.S. Buzovkin², Z.Kh. Kalazhokov¹, V.A. Moshnikov^2
1 KabardinoBalkarian State University named after H.M. Berbekov
² Saint Petersburg Electrotechnical University «LETI»

Abstract: Currently, adsorption gas sensors are of great interest for environmental monitoring. The approaches to improving their properties include synthesis of nanostructured materials of various shapes and modification of the metal oxide chemical composition. The aim of this work is to develop ways to improve the sensor properties of zinc oxide nanowires by changing the surface structure during processing in solutions of tin and iron compounds, as well as adding special precursors during their synthesis. The layers consisting of zinc oxide nanowires were produced by hydrothermal method. Ternary Zn-Sn-O and Zn-Fe-O nanosystems were synthesized as a result of processing of zinc oxide nanowires in solutions containing potassium stannate and iron sulfate, respectively. ZnO nanowires were also synthesized in a solution containing sodium bromide in addition to the general precursors. The surface chemical composition was analyzed using X-ray photoelectron spectroscopy. Sensor properties were investigated by detecting acetone, isopropanol and methanol vapors. It was shown that the sensor response of the produced samples exceeds the response of the initial zinc oxide nanowires. The samples of Zn-Sn-O ternary oxide system have the best response. The improvement of the sensor response may be associated with an increase in the content of adsorbed oxygen ions on the surface of the samples, the presence of metal cations with different properties as well as the formation of heterostructures.
Keywords: gas sensors, metal oxides, nanomaterials, zinc oxide, X-ray photoelectron spectroscopy, adsorption centers

D.D. Tumarkina¹, O.Ya. Butkovskii¹, A.V. Bolachkov¹, A.A. Burtsev^2
1 Vladimir State University named after Alexander and Nikolay Stoletovs
² Institute on Laser and Information Technologies of Russian Academy of Sciences – Branch of Federal Scientific Research Center «Crystallography and Photonics» of Russian Academy of Sciences

Abstract: The paper presents experiments on crystallization from a melt with an analysis of the morphology of the emerging crystal structures, showing examples of the formation of dendritic crystals. Using energy dispersive X-ray analysis, studies of the microelement analysis of the areas of effect of two pulsed laser beams on the surface of stainless steel have been carried out for irradiation parameters corresponding to the appearance of dendritic structures in the area of effect. It is shown that in the dendritic regions concentrations of all the components of AISI 304 stainless steel are equalized. Estimation of the entropy of mixing from experimental data showed that in the area of surface dendrites or their accumulations, the surface entropy of mixing corresponded to its value for a high-entropy alloy. Based on the maximum entropy production principle, the phase transition temperature was calculated. Although dendritic crystallization should reduce the entropy of the system, experiments show that the entropy of the alloy increases. Preliminarily it can be concluded that this process is associated with a high oxygen content in the region of dendritic crystal formation after laser irradiation. The results presented in this work allow us to conclude that the formation of structures with complex morphology occurs after thermal oxidative ablation.
Keywords: two-pulse laser ablation, dendritic crystals, high-entropy alloys, entropy of mixing, entropy conductivity

K.V. Suliz¹, N.Yu.. Sdobnyakov², A.V. Pervikov^1
1 Institute of Strength Physics and Materials Science of Siberian Branch of RAS
² Tver State University

Abstract: Using method of the joint electric explosion of wires of various metals/alloys, for the first time nanoparticles were obtained of a multicomponent alloy with high activity in the ammonia decomposition reaction. It is shown that the obtained samples are represented by spherical particles with an average size of about 40 nm. The crystal structure of nanoparticles contains fcc, bcc phases, as well as a phase corresponding to an intermetallic compound. Energy dispersive analysis data show that in the obtained samples two types of copper segregation in the of particles are observed: enrichment in the central region of the particles and segregation on the surface with formation of a structure characteristic of «Janus» particles. The data obtained indicate the need to involve atomistic modeling methods in the search for optimal quantitative compositions of nanoparticles of multicomponent alloys to provide the necessary desirable structure and functional properties. The prospects for applying atomistic simulation to high-entropy alloys are noted.
Keywords: nanoparticles, high-entropy alloys, exploding wires, catalysis, powder

K.V. Suliz, A.V. Pervikov
Institute of Strength Physics and Materials Science of Siberian Branch of RAS

Abstract: In this work, for the first time, samples of nanoparticles of the multicomponent AlCuNiCoCrFe alloy were obtained by the method of joint electric explosion of wires of Al, Cu, Ni metals and N06003, NiCo29-18 alloys in an argon atmosphere. As the basic mode of wire explosion, a mode close to the matched one was chosen, which made it possible to minimize the influence of the energy of the arc stage of the discharge on the structural-phase state of the forming nanoparticles. It is shown that the obtained samples are represented by spherical particles with sizes ranging from 15 to 500 nm. The number-average size of nanoparticles of the obtained samples varies from 40 to 58 nm. The particle size distribution is described by a normal-logarithmic law, the crystal structure of the particles corresponds to substitutional solid solutions with a bcc and/or fcc lattice. An increase in the Al content in the explosion products leads to an increase in the content of the phase with a bcc lattice in the samples, while an increase in the Cu content leads to an increase in the phase with a fcc lattice. The resulting samples can be used in electrocatalysis.
Keywords: nanoparticles, high-entropy alloys, structural-phase state, electric explosion, current, voltage, powder

V.V. Stolyarov
Mechanical Engineering Research Institute of the RAS

Abstract: The article is devoted to the review of structural factors influencing the tribological behavior of nanostructure metals and alloys without lubrication. The scientific significance of this topic is related to the understanding of wear mechanisms and the possibility of its prediction during long-term operation. Particular attention is focused on the effect of the grain size in the range of 0,01-10 µm, as one of the most important structural parameters. Emphasis is placed on materials with ultrafine grains obtained by severe plastic deformation, and nanocrystalline materials obtained by non-deformation methods of sputtering and deposition. It is shown that nanocrystalline films on the contact surface are more preferable for increasing wear resistance, since they are more resistant to structural-phase transformations during friction. Among pure metals, as objects without phase transformations, copper, nickel, aluminum and titanium are considered. As an example of more complex objects, alloys based on titanium (an intermetallic compound with shape memory TiNi and two phases Ti-Al-V alloy) are presented. In addition to the classical scheme of friction during macrodisplacement of the indenter on the contact surface, the fretting friction during microdisplacement is considered.
Keywords: slip, wear, friction coefficient, nanostructure, fretting, roughness

V.M. Skachkov, L.A. Pasechnik, I.S. Medyankina, N.A. Sabirzyanov
The Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: This article presents the results of a study of the properties of three diffusion-hardening solders based on low-melting gallium alloys and copper-tin alloy powder after the introduction of inert metal powders of titanium, zirconium, and hafnium in an amount of 5% each, which is an additive of 15 wt.%. After heat treatment at low temperatures (125°C) in within 24 hours, and after hightemperature treatment (600°C) for 6 hours, the microhardness of the obtained composite diffusionhardening solders was evaluated. Relatively long-term heat treatment at low temperatures does not lead the composition to achieve equilibrium states, possible physico-chemical transformations do not fully occur in them, which shows an increase in the hardness of samples after high-temperature treatment. X-ray phase analysis has determined the phases formed as a result of diffusion hardening, forming micro- and nanoscale intermetallic compounds, and the metal tin released in the form of nanoscale secretions in the intergrain space. Metal filler powders, inert at low temperature to exposure, but well wetted with gallium at high temperatures, interact with it, forming nanoscale intermetallic compounds, additionally strengthening composite solders.
Keywords: composite diffusion-hardening solders, metal powder, titanium, zirconium, hafnium, properties, microhardness, differential thermal analysis

V.M. Skachkov
The Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: The article considers the effect of vanadium metal powder on the properties of diffusionhardening solder  basedon a low-melting gallium-tin alloy and a solid component consisting of a copper-tin alloy powder. After the introduction of vanadium metal powder in the amount of 5, 10 and 15 wt.%, solder samples were subjected to heat treatment at two different temperatures – 125 and 600°C. The microhardness and thermal stability of composite diffusion-hardening solders are evaluated. It is shown that heat treatment at higher temperatures promotes the transition of solder to an equilibrium state, which leads to an increase in hardness due to the formation and distribution of intermetallic compounds, including nanoscale ones. The phases of vanadium intermetallides formed as a result of interaction with gallium were determined by X-ray phase analysis. Metallic vanadium is wetted by gallium, has limited solubility, and increases solder hardness due to precipitation strengthening.
Keywords: composite diffusion-hardening solders, metal powder, properties, microhardness, differential thermal analysis, vanadium

Yu.Ya. Gafner, D.A. Ryzhkova
Katanov Khakass State University

Abstract: Every year modern industry increases the number of technological processes using highrisk chemicals. Therefore, for the uninterrupted work of personnel, it is necessary to minimize the possible consequences of leakage of these substances, but for this, first of all, a clear definition of the maximum permissible concentration of a particular hazardous substance in the air is required. In the last decade, nanomaterials of various types have been used as active elements for gas sensors, and gas sensors based on tin oxide have become the most popular among researchers. In this work, typical reactions of the interaction of the surface of a nanocompacted SnO₂ layer with some detectable gases were studied. It is shown that with an increase in the concentration of the analyzed gas due to its chemical absorption, the electrons previously captured by oxygen are released, which leads to an increase in the number of nanoparticles in the conducting state. This feature makes it possible to use the nanocompacted SnO₂ layer for the determination of nitrogen mono- and nitrogen dioxide in the atmosphere.
Keywords: absorption, semiconductors, nanocompacted material, gas sensors, simulation

N.A. Pan'kin, V.P. Mishkin
National Research N.P. Ogarev Mordovia State University

Abstract: The method of scanning electron microscopy was used to study the surface morphology of steel SCMnCr3 after its electrospark treatment with a tungsten (without additives) anode electrode. The following structural elements have been identified: bulges, spherical and disk-shaped inclusions, cracks, pores and particles of irregular shape. Their appearance is due to high temperatures in the interelectrode gap (higher than the corresponding melting temperatures of the main electrode materials) and the non-equilibrium of the processes occurring in it. During the formation of pores, the main mechanism is the release of gases during cooling of the electrode materials in the liquid phase. Macrostresses arising from an electric spark discharge in the surface layers of the electrodes, which exceed the mechanical properties of the electrode materials, lead to the ejection of irregularly shaped solid particles into the interelectrode gap and the appearance of cracks. The appearance of sagging, round/oval inclusions, and spherical particles is associated with the interaction of the liquid phase from the interelectrode gap with the cathode surface.
Keywords: steel, tungsten, electrospark processing, morphology, electron microscopy