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In magnesium alloys castings, the casting defects such as shrinkage porosity are often occur. Such defects can be suppressed by repair welding or surfacing using a special filler rod. Unfortunately, in Russia, the low amount of filler rod is consumed. Therefore, native enterprises do not manufacture it, limiting themselves to imports or homemade low-quality substitutes. Nevertheless, there is a need for filler rod, and recently it has become unprofitable to replace them with imported materials due to a significantly increased price. Therefore, there is a need to study the technology of its production to replace imported filler rod with native material. Magnesium alloys based on the Mg–Zn–Zr (La, Nd) system: SV1, SV122, and ML12 (ZK51) that used as a filler rod for repair welding of ZK51 alloy castings were studied in this work. The samples were obtained by permanent mold casting into aluminum molds followed by hot extrusion into a filler rod with a diameter of 4 mm. It was shown that all the investigated alloys could be obtained in the form of a rod with a diameter of 4 mm. Therefore, the investigated rod samples from the SV122 alloy were used as filler material for repair welding of ZK51 magnesium alloy castings. The weld seam in the T1 condition has an ultimate tensile strength (UTS) about 80 % of the UTS of the casting material.

The properties of coatings formed on the MA8 magnesium alloy by the plasma electrolytic oxidation in electrolytes containing mechanical mixture of zirconia and silica nanoparticles in concentrations of 2, 4 and 6 g/l have been investigated. It has been established by SEM, EDS, and XPS that ZrO2/SiO2 nanoparticles successfully were incorporated into the coatings. Micro-Raman spectroscopy showed the presence of ZrO2 in tetragonal and monoclinic forms in the PEO-coating composition as well as Mg2SiO4 in tetrahedral configuration uniformly distributed in the outer part of coatings. Obtained coatings significantly reduce corrosion current density in comparison with bare Mg alloy and base PEO-layer (from 2.4 × 10–7 A/cm2 for base PEO layer to 0.7 × 10–7 A/cm2 for coatings with nanoparticles). It has been found that the presence of solid nanoparticles in the composition of coating has a positive effect on their hardness (this parameter was increased from 2.1 ± 0.3 GPa to 3.1 ± 0.4 GPa) and wearproof (the wear was reduced from (4.3 ± 0.4)×10–5 mm3/(N × m) to (3.5 ± 0.2)×10–5 mm3/(N × m)).

In this paper, we calculate the Andreev bound state spectrum in a half-infinite superconducting wire with an arbitrary number of bands crossing the chemical potential. Electrons in the wire are affected by the asymmetric (Rashba) spin–orbit coupling due to the presence of a substrate. The normal state of the wire is assumed to have an antiunitary symmetry (time reversal or its combination with a point group operation), which may be broken by the superconducting order parameter and/or the boundary. The bound state spectrum is calculated without relying on any particular microscopic model, using the semiclassical approach with the boundary conditions described by a phenomenological scattering matrix.

The monthly marriage and birth rate of the population of the Tambov province in 1915—1916 is considered in the article. The methodological basis of the work was the theory of modernization, which is considered by the author in the context of the history of Russia in the 19th — first half of the 20th centuries in the classical interpretation of the transition from traditional society to modern. The novelty of the article lies in the introduction into the scientific circulation of data on the seasonal dynamics of marriage and fertility of the Tambovites during the First World War. A comparative analysis of the corresponding numerical indicators among the townspeople and villagers in 1915—1916 with the pre-war period is carried out. The author comes to the conclusion that the seasonal dynamics of marriage and fertility can be used as a quantitative substantiation of such directions of spiritual modernization as the level of secularization and the propensity to innovate. The analysis shows that the general model of the demographic behavior of Tambov residents is generally correlated with the previous periods. The author comes to the conclusion that the revealed differences between the townspeople and villagers of the Tambov province in the studied plan indicate a greater inclination of the former to innovations and their higher level of secularization, and this confirms the position that the Tambov society was only at the initial stage of spiritual modernization.

The article discusses the issue of determining the specifics of game sports with morphofunctional indicators, identifying the characteristic features of the physical development of players of all roles.

Aluminum oxynitride ALON powders obtained by plasma-chemical synthesis are studied using the Rietveld X-ray method and Auger spectroscopy. In addition to the spinel phase, these powders contain aluminum nitride and a long-period polytypoid based on it; the total content of these admixtures is ~50 vol %. The presence of aluminum particles that have not fully reacted with oxygen and ammonia in the quenching chamber is recorded. The results of refinement of the spinel phase structure correspond to the model in which the localization of vacancies is associated with the positions occupied by aluminum atom, while the increase in nitrogen concentration and replacement of oxygen with nitrogen lead to population of the vacancies by aluminum.

The results of the first studies of the ecosystem state of the underwater part of the channel, artificially created in the middle of the 20th century on the western shore of the Balaklava Bay (Sevastopol) as a naval base of the Black Sea Fleet for the submarines repair, are presented. Channel's ecosystem is determined by uniqueness of anthropogenic formation and considered as analogue of natural Black Sea cave. Hydrospelological survey of the channel and biological studies allowed assessing its current state, the nature of biofouling of its walls and anthropogenic and technical pollution of the bottom. Macrofauna of the channel wall biofouling is represented by the Mytilaster lineatus community, which has a high level of species abundance (about 80 species have been registered) and quantitative development. Both in taxonomic diversity and in quantitative terms, this community is comparable to the rocky substrate community near open Crimean coasts, but with a smaller share of crustacean group development. Due to weakened hydrodynamics, well developed fauna of bryozoans forming plurannual crusty structures and single sponges is observed on the channel's walls. In contrast to the channel walls biofouling, its bottom macrofauna has relatively lower quantitative and qualitative composition. Meiobenthos in the channel’s wall biofouling is represented by 18 higher taxa (type, class, order) of Protozoa and Metazoa with predominance of harpacticoids by abundance. Meiobenthos of the soft bottom of underground channel is represented by 15 higher taxa with predominance of free-living nematodes and harpacticoids by abundance. Average density of meiobenthos in the channel’s bottom sediments is comparable with similar parameters of its development in open water areas and Sevastopol bays.

The heterophase interaction of exogenous ZrO2 and Y2O3 nanoparticles with a surfactant (tin) in the Fe–Cr model system is studied with allowance for the use of oxide nanoparticles in the production of oxide dispersion strengthened steels. The study of the influence of the size factor demonstrates that the extreme values of the degree of tin removal are 15.4 rel. % for the Fe–Cr–Sn–ZrO2 system and 7.1 rel. % for the Fe–Cr–Sn–Y2O3 system. The sessile drop method is used to investigate the capillary properties of a metal with nanoparticles. The introduction of nanoparticles into the Fe–Cr–Sn melt is found to cause the inversion of coefficient ∂σ/∂T and the decompression of the melt.

Spheroidization of Fe and steel powders in a plasma stream of an DC arc plasma torch is investigated. The possibility of obtaining a product with a spherical particle content of up to 100% is established. The fluidity of the best samples of obtained powder is 13–20 s with a fluidity of the feedstock of 39 s. The bulk density of the initial powder (3.05 g/cm3) during the plasma treatment increases to 4.1–4.4 g/cm3. The nanofraction content in spheroidized powders varied from 0 to 75 wt % and it depends mainly on the enthalpy of the plasma stream, consumption of raw materials, and the organization of the flow of the plasma-forming gas in the discharge channel of the plasma torch. It is established that Fe powders spheroidized in plasma can be used in selective laser melting technology to obtain compact samples whose density reaches 7.86 g/cm3.

Processes of converting CO2 to methanol and dimethyl ether (DME) in a flow-circulation mode where the converted gas is partially returned to the reactor are studied to address the issue of utilizing carbon dioxide emissions. Experimental data are presented on methanol synthesis (industrial catalyst MegaMax 507) and the direct synthesis of DME (MegaMax 507/industrial zeolite TsVM in a mass ratio of 1 : 1). In methanol synthesis from synthesis gas (composition, vol %: Н2 76.6, СО2 19.8, and N2 3.6), high СО2 conversion of 84–99.6% is achieved at 240–260°С and a pressure of 5.3 MPa with low selectivity in regard to the side reaction (

The effect of processing multicomponent nanopowders of the W–C system, obtained by plasma-chemical synthesis, in microwave fields with a frequency of 2.45 and 24 GHz generated using a magnetron and gyrotron, respectively, is studied experimentally. It is established that microwave processing results in the formation of nanosized particles of tungsten carbide WC. The influence of processing time on the phase, disperse, and chemical compositions of nanopowders is investigated.

Experimental studies of aluminium boride synthesis as a result of interaction of disperse aluminum with diborane B2H6 and disperse boron in a flow of thermal plasma of different composition generated in electric arc plasma torch have been carried out. Experimental work on the synthesis of aluminium boride nanoparticles from elements (a mixture of disperse aluminum and boron) has shown the possibility of obtaining in thermal plasma arc discharge of such phases of the boride as AlB12 and AlB31. The specific surface of the powders obtained is from 3 to 27 m2/g. According to X-ray phase analysis, the powders obtained, except for aluminum boride phases, also contain boron, aluminum, aluminum nitride and boric acid phases. The greatest yield of aluminum boride phases is provided by using the nitrogen plasma with hydrogen and enthalpy 4.5 kWt∙h/m3 in the reactor with increased high-temperature zone. The use of gaseous diborane made it possible to eliminate restrictions on the evaporation of boron particles but did not provide an opportunity to obtain aluminum borides in the plasma-chemical process. It was concluded that it is necessary to perform quenching of high-temperature gas flow containing boron and aluminum vapor to form aluminum borides from the gas phase in plasma-chemical synthesis. Such an approach should ensure that the temperature is reduced to the values at which aluminum borides are stable and that the formation of aluminum boride nanoparticles will occur as a result of condensation from the gas phase under these conditions.

The possibility of obtaining composite micropowders of the W-C-Co system with a spherical particle shape having a submicron/nanoscale internal structure was experimentally confirmed. In the course of work carried out, W-C-Co system nanopowders with the average particle size of approximately 50 nm were produced by plasma-chemical synthesis. This method resulted in the uniform distribution of W, Co and C among the nanoparticles of the powder in the nanometer scale range. Dense microgranules with an average size of 40 microns were obtained from the nanopowders by spray drying. The spherical micropowders with an average particle size of 20 microns were received as a result of plasma treatment of 25.36 microns microgranule fraction. The spherical particles obtained in the experiments had a predominantly dense microstructure and had no internal cavities. The influence of plasma treatment process parameters on dispersity, phase, and chemical composition of spherical micropowders and powder particles microstructure has been established.

A comparative study of the results of Spark-Plasma Sintering (SPS) of two-types of aluminum oxide nanopowders, obtained by the method of conductor explosion and plasma synthesis. When the parameters of both powders are similar (spherical form of the particles, size, phase composition) as well as SPS modes the properties of the resulting compacts are significantly different both in mechanical properties and microstructure. The reason of differences in the properties of the obtained compacts is in technological impurities in powders, obtained by different methods. Artificial addition of impurities, contained in the nanopowder, obtained by electro explosion of conductor, into the powder, made by synthesis in plasma and not containing these impurities, allowed to reveal their effect on the formation of the microstructure and properties of the sintered by SPS method sample.

The motion of the outer boundary of a quasi-spherical tungsten wire array at currents of 2−4 MA was studied experimentally. It is shown that the outer boundary shifts later than it is predicted by simulations by the heterogeneous array model. The instabilities developing at the boundary of the quasi-spherical array are similar to those occurring in a cylindrical array made of the same material. It is found that, in spite of the different time behaviors of the inductances during implosions of quasi-spherical and cylindrical arrays, the energies required to compress these arrays to ~0.4 of the initial radius differ insignificantly.

Introduction:mining has recently aroused substantial interest inRussia due to the rise in crypto-currency rates. Therefore, new coins are harder to obtain, and mining equipment turns more expensive. Computation capacities are provided by mining farms, and the number of their computation modules reaches 20 units, if operated by natural persons, and 300 – 5,000 units, if operated by major computation centres. One of the factors restraining the development of industrialscale mining, consists in high power consumption rates demonstrated by major computation centres. Therefore, the problem of high-quality power supply to mining farms gains relevance both in terms of the efficient use of electric power sources and in terms of the protection of expensive machines.Methods:the co-authors have analyzed power saving problems that accompany the incorporation of industrial mining farms, substantiated the need to design and develop the unique equipment, connectable to mining farms because the circulation of the reactive component of electric power between the source of alternate current and the accumulator causes losses of energy in the wires of the electric circuit. The overloading of the circuit by the reactive current causes the need to improve the capacity of the energy source, reduces the circuit voltage and makes it fluctuate. The co-authors have performed an overview of air and liquid-based cooling systems applied to mining farms. They also describe the principle of the cooling system involving submersion, which has a strong potential as a constituent component of major mining farms.Findings and discussion:the co-authors have formulated their idea aimed at the improvement of the performance of mining farms. They present a power saving system centered around the reactive capacity compensation, filtration of upper harmonics and compensation of voltage tilts.Conclusion:the co-authors have formulated the objectives of research in the area of power efficiency and capacity improvement at mining farms.

The effects of the conditions of a raw material introduction as well as mixing of it with a high-temperature gas flow under the plasma chemical synthesis of superdispersed powder of W–C have been studied. In the case of incomplete raw material evaporation and its fast quenching, preferred cubic tungsten carbide β-WC formation is found to occur, as well as nano- and microparticles with a complicated phase composition. In the case of complete raw material evaporation, the products of reducing synthesis are nanopowder of tungsten or semicarbide W2C depending on the amount of hydrocarbon introduced. There is a second stage of the process of low-temperature synthesis which leads to a single-phase of tungsten carbide α-WC formation. Complete evaporation of raw material must be ensured in the plasma chemical process for obtaining of α-WC powder with a maximum specific surface area.

The interaction of exogenous refractory compound ZrO2 nanoparticles with model multicomponent nickel alloys, which contain harmful tin surfactant impurities, is studied. The removal of the surfactant from the metal after the introduction of ZrO2 nanoparticles is shown to depend on the time of isothermal holding in an induction furnace. The degree of tin removal is 15–28 rel %.

The processes of interaction of exogenous nanoparticles Al 2 O 3 and MgAl 2 O 4 with iron melts containing surfactant-copper have been studied. Thermodynamic calculations confirmed the choice of these nanoparticles. The dependence of the degree of copper removal during heterophase interaction on size factors was studied: the time of isothermal holding after nanoparticle introduction, the type of nanoparticles, and the concentration of copper in the metal. It was shown that the introduction of Al 2 O 3 nanoparticles led to a decrease in the copper content from 9 to 20 rel. %, and MgAl 2 O 4 - from 10 to 24 rel. %. After the introduction of Al 2 O 3 into stainless steel, the degree of copper removal was from 6 to 23 rel. %, depending on the holding time of nanoparticles in the melt and their concentration.

Spheroidization of micropowders of a heat-resistant alloy based on nickel aluminide with a particle size of 20 to 45 μm was studied. The alloy was produced by calcium hydride reduction (CHR) and elemental synthesis (SHS). The spheroidization was carried out in a flow of argon–hydrogen thermal plasma generated by a direct-current (DC) plasma torch. The degree of spheroidization of the micropowders reached 98.5%, and the flowability was 20 s/50 g.

The surface tension and density of Fe–C-containing melts with SiC and TiC0.8N0.16O0.04 nanosized phases have been investigated and show that the presence of SiC leads to a slight increase in the surface tension and the introduction of TiC0.8N0.16O0.04 leads to its decrease. It is shown that coefficients ∂σ/∂Τ of these melts without and with nanophases are positive. It is found that, with the introduction of nanophases into the metal, the density of the melts decreases and loosening increases. The composition of heterogeneous nonmetallic inclusions depends on nanophases: the introduction of SiC reduces the oxygen content in them, TiC0.8N0.16 O0.04 increases it, and the composition of homogeneous inclusions depends on the interaction of nanophases with sulfur and leads to a decrease in the element in them.

Per the literature, the thermodynamic stability criterion of the dispersed system of nanosized phases in metal melts is reproduced, with the latter considered the specific change in free energy (referred to the unit of change in the contact surface of the phases) of the disperse system aggregation. For iron–carbon melts with [C] > 2 wt %, according to the published scientific results, the selection of two refractory phases SiC and TiC0.8N0.16O0.04 for introduction into the Fe–C–Si–Mn–P–S–O melt is justified. The preparation of nanophases, the preparation of briquettes of a composite material, and the method used to study the interfacial interaction of nanophases with sulfur and oxygen of the melt is described. It is shown that a decrease in the surfactant content of the nanophase content upon 5–10 min of exposure indicates the interaction of the surfactant with nanoparticles, and the concentration dependences are characterized by extreme minimum values.

The development of new, more refractory heat-resistant materials for gas-turbine engines is one of most important problems of modern materials science. This is associated with the fact that nickel superalloys currently used for this purpose have a lower melting point of ~1400°C, which limits their own maximal working temperature by a range of 1100–1150°C. The Ni alloys can be replaced by natural composites, in which refractory metals are a matrix, while their silicides are intermetallic hardeners. Only three “refractory metal–silicon” binary systems manifest stability to the Me5Si3 silicide, notably, Nb5Si3, Re5Si3, and W5Si3. From the viewpoint of a combination of a high melting point and a low density, the Nb5Si3 compound is optimal among other silicides. The use of alloys of the Nb–Si system in additive manufacturing machines is of considerable interest. This work presents the results of experimental investigations into the treatment of the Nb–16 at % Si powder fabricated using mechanical alloying of elemental Nb and Si powders in the thermal plasma flux. The Nb–16Si alloy powder is fabricated by the mechanical alloying of powders of pure elements in a Fritsch Pulverisette 4 planetary mill. The powder spheroidization is performed in a plasma installation based on a discharge vortex-stabilized electric-arc thermal plasma generator. Based on the results of experimental investigations, the principal possibility to perform the plasma spheroidization of particles of the Nb–16Si alloy prepared by mechanical alloying is shown. It is shown that the surface of spheroidized particles is rough and reflects the cast material structure. Three phase components Nb5Si3, Nb3Si, and Nbss having different optical contrast are revealed in microslices, which is confirmed by X-ray phase analysis.

We calculate analytically the spectrum of the Andreev bound states in a half-infinite superconducting wire with an arbitrary number of bands crossing the chemical potential. The normal state of the wire is assumed to have an antiunitary symmetry A (time reversal or its combination with a crystallographic point group operation), with A^2=-1 or +1. This symmetry may be broken by the superconducting order parameter and/or the boundary scattering. We present a model-independent proof of the existence of one Majorana mode near the end of the wire with an odd number of bands., Comment: 9 pages, 2 figures

Powders of new CompoNiAl M5-3 heat-resistant alloy were prepared by mechanoactivated SHS from (Ni–Al–Cr–Co–Hf)–NaCl mixtures. Ni dissolution in Al melt was found to be the motive force of combustion. Unlike the binary Ni–Al system, NiAl is formed not in the melt but in the post-combustion zone as a result of diffusion-controlled processes. Conditions for MASHS were optimized toward fabrication of a superalloy with homogeneous composition/structure and low content of gas impurities. As-prepared combustion product was disintegrated into a powder and the latter was subjected to plasma spheroidization, keeping in mind the needs of additive manufacturing. The attained degree of spheroidization was 98%. The structure and phase/chemical compositions of spherical powders did not differ from those of the synthesized powders. After plasma treatment, the content of gas impurities (О2 and N2) decreased.

We study the behavior of the soliton that encounters a barrier with dissipation while moving in a nondissipative medium. We use the Korteweg–de Vries–Burgers equation to model this situation. The modeling includes the case of a finite dissipative layer similar to a wave passing through air–glass–air and also a wave passing from a nondissipative layer into a dissipative layer (similar to light passing from air to water). The dissipation predictably reduces the soliton amplitude/velocity. Other effects also occur in the case of a finite barrier in the soliton path: after the wave leaves the dissipative barrier, it retains the soliton form, but a reflection wave arises as small and quasiharmonic oscillations (a breather). The breather propagates faster than the soliton passing through the barrier.

The influence of nanoparticles introduced into a molten weld pool using a flux-cored wire on the structure and impact toughness of the weld metal is considered. The use of a flux-cored wire with tungsten carbide particles is shown to decrease the scatter of the impact toughnesses of the weld metal. The use of titanium carbide allows one to increase the average impact toughness.

The influence of tungsten carbide and titanium nitride nanoparticles on the structure and properties of the weld metal of welded joints made by automatic twin submerged arc welding is considered. The nanoparticles have been introduced into the weld pool as a part of the “master alloy” based on nickel powder (PNE-1 according to GOST 9722). It has been shown that modifying the weld metal with tungsten carbide nanoparticles holds promise for enhancing the impact strength. In addition, it has been found that titanium nitride is prone to dissociation under the same conditions. However, microalloying with titanium, which is due to the release of titanium from the nitride, leads to an increase in the impact strength of the weld metal.

The way of protective coatings formation on MA8 magnesium alloy by plasma electrolytic oxidation (PEO) in the electrolyte containing composite zirconia-silica nanoparticles has been developed. It is shown that the coatings, which contain nanoparticles, have a significant advantage in comparison with the surface layers obtained without their use.

A comparative analysis of the physicomechanical characteristics and phase composition of Al23O27N5 ceramic obtained by reaction sintering of the mixture of Al2O3 and AlN powders at different temperatures and pressures is carried out. The samples obtained had properties that correlated well with the published data.