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Substitutional metal doping is a powerful strategy for manipulating the emission spectra and excited state dynamics of semiconductor nanomaterials. Here, we demonstrate the synthesis of colloidal manganese (Mn

This article presents a study of special material properties of the single crystalline material Ca3TaGa3Si2O14 (CTGS = Catangasite). The comparatively highly ordered crystal structure and acceptable piezoelectric strength make it a candidate for microacoustic applications under extreme conditions. Obviously, low-loss dynamic behavior is typical for this crystal which consequently enables high-temperature use. As a particular challenge, the behavior at gigahertz frequencies is investigated here. For that, High overtone Bulk Acoustic wave Resonator (HBAR) type measurements in the range of 1–6 GHz are performed. The selection of five distinctive propagation directions for exclusively pure or quasi-longitudinal modes enables to derive the dynamic viscosities from the quality factors of HBAR results. The observed frequency dependences exhibit Akhiezer behavior as the predominant loss mechanism in the cases examined.

The results of laboratory investigation of the tribological characteristics of a new grease based on Solidol, a polyurea thickener providing an increase in the dropping point to 118 °C, and a complex of additives are presented. It has been established that the proposed lubricant is efficient in a wider temperature range, provides higher antiwear properties for tribocoupling parts and considerably reduces friction losses during boundary lubrication in comparison with the original grease Solidol. The developed composition of the lubricant grease is supposed to be used when operating road construction machines in the tropical conditions of Vietnam.

Aluminum-matrix composite materials based on commercial-purity AD0 aluminum are studied. An SiC powder and Al2O3 whiskers and nanofibers are selected as fillers. These fillers slightly are found to weakly increase the density and exert a modifying effect on the microstructure. The grain refinement is maximal (by 35.3%) in the composite modified with Al2O3 nanofibers. This composite exhibits a quasi-brittle character of fracture and the maximum fracture energy.

The effect of carbon (3 wt %) on the electrical resistivity of alloys based on aluminum nickelides Ni–Al and Ni–Al–C synthesized by electrothermal explosion in the temperature range of 300–1300 K in a vacuum of 2 × 10–3 Pa has been studied. At an electrothermal explosion in a powder reaction medium, a Ni–Al-based melt is formed in which carbon dissolves. It is shown that, during the crystallization of the final product, due to its low solubility in Ni–Al, carbon is located at the boundaries of intermetallic grains of Ni–Al in the form of multilayer graphite nanofilms 50–80 nm thick, filling the intergranular space. It is shown that the synthesized alloys have a metallic character of conductivity, and the electrical resistivity in the measured temperature range of 300–1300 K increases monotonically for Ni–Al from 16 to 40 μΩ cm and for the carbon-bearing alloy Ni–Al–C from 22 to 60 μΩ cm. In this case, an increase in the temperature coefficient of resistance (TCR) is also observed from 1.45 × 10–3 K–1 for Ni–Al to 1.77 × 10–3 K–1 for Ni–Al–C. The slope of the curves of the dependence of electrical resistance on temperature in the studied temperature range of 300–1300 K remains constant and is well described by a linear function.

This study describes the mathematical modeling of an electrothermal explosion (ETE) of a gasless system placed in the annular layer of a conductive product. The influence of a change in the thermoelectric characteristics of a sample on the implementation, thermal conditions, and heat patterns of an ETE are considered. Based on the results obtained, the previously established experimental result about the anomalous effect of the electric heating power on the parameters of an ETE of a mixture of titanium and soot powders is explained.

Fundamental photophysical behavior in CsPbBr3 nanocrystals (NCs), especially at low temperatures, is under active investigation. While many studies have reported temperature-dependent photoluminescence, comparatively few have focused on understanding the temperature-dependent absorption spectrum. Here, we report the temperature-dependent (35-300 K) absorption and photoluminescence spectra of zwitterionic ligand-capped CsPbBr3 NCs with four different edge lengths (d = 4.9, 7.2, 8.1, and 13.2 nm). The two lowest-energy excitonic transitions are quantitatively modeled over the full temperature range within the effective mass approximation considering the quasi-cubic NC shape and nonparabolicity of the electronic bands. Significantly, we find that the effective dielectric constant determined from the best fit model parameters is independent of temperature. Moreover, we observe a temperature-dependent Stokes shift that saturates at a finite value of Δ ≈ 10 meV at low temperatures for d = 7.2 nm NCs, which is absent in bulk CsPbBr3 films. Overall, these observations highlight differences between the temperature-dependent dielectric behavior of NC and bulk perovskites and point to the need for a more unified theoretical understanding of absorption and emission in halide perovskites.

The results of experimental studies aimed at studying the structure and properties of electroerosive nichrome powders obtained in distilled water are presented. The high efficiency of the application of the electrodispersion technology, which provides, at low energy costs, the production of new nichrome powder materials suitable for industrial use, is shown.

This work is devoted to the description of a new design solution for the gas distribution mechanism of a reciprocating compressor. The study of the factors that have a significant effect on the vibration and noise performance of hermetic refrigerant compressors allows the authors to conclude that the world leaders in the cost and sales of compressors are manufacturers whose products have a sound power level in the range of 32-36 dBA. The authors propose a new design solution for a unified valve plate for use in a parametric range of hermetic piston refrigerant compressors of the SKO series. The proposed valve train contains a 1.015 mm thick composite valve plate containing five 0.203-mm Sandvik 20-C valve steel plates that are bonded with anaerobic adhesives. Laboratory studies revealed the advantages of S-KO compressors in terms of the average sound power level at 4.8-5.54 dBA; supply coefficient (refrigeration coefficient) decreased by 27.4 ÷ 14.4%. Such results were achieved due to the use of anaerobic adhesives, which made it possible, instead of a machined valve plate, to use a composite 1.015 mm thick and provide a stronger contact between the surfaces of the plates.

The possibility of introduction of antifriction and wear-resistant modifying agents into the matrix of a composite nickel-phosphorus coating to obtain effective composite coatings, is considered. The analysis of the possible influence of modifying additives in the form of ultrafine powders on the tribological properties of the developed coatings, is carried out.

The effect of 100-hour aging at 1350°C on the matrix–fiber interfacial bond, matrix structure, bond type, and high-temperature strength of Nb composite reinforced with α-Al2O3 single crystal fibers has been studied. It has been found that, in the samples after pressing, as well as after 100-hour aging, no chemical interaction is detected at the matrix–fiber interface, i.e., there is no “chemical” bond, and a “mechanical” bond is realized in Bauman’s notation. At the same time, the process of mutual diffusion of matrix and fiber elements after 100-hour aging has been studied and an increase in the strength of the composite has been found. This indicates an increase in the frictional bond and/or formation of another type of bond, which at this stage does not cause fiber degradation. It was not possible to determine numerical values of the contribution of the “new type” of bonds to the increase in the strength of the composition.

The absorption spectra of a water molecule perturbed by argon pressure were measured in the 6700–7650 cm−1 region. The spectra were recorded at an IFS 125HR Fourier spectrometer with a high signal-to-noise ratio at a room temperature with a spectral resolution of 0.01 cm−1. The argon pressure was varied from 0 to 0.9 atm. Using three line profile models (the traditional Voigt profile; the quadratic Voigt profile, which depends on the speed of an absorbing molecule; and the Hartmann–Tran profile), the parameters of the absorption lines of the water molecule were calculated. A better agreement with the experimental data is provided by the Hartmann–Tran profile. It is suggested to use a relatively simple Voigt profile for mass measurements at pressures above 300 mbar.

Yb:CaWO4 and Yb, Nb:CaWO4 single crystals have been grown by the Czochralski method in air and in protective atmospheres and subjected to additional annealing in air, in CO/CO2 atmosphere, and in forevacuum. The optical absorption spectra in the range from 250 to 1500 nm and the luminescence spectra of these crystals in the visible and near-IR spectral regions upon UV excitation have been investigated. It is shown that additional introduction of Nb5+ ions into Yb:CaWO4 crystal increases by an order of magnitude (almost to unity) the Yb3+ distribution coefficient between CaWO4 crystal and melt. It is found that optical excitation of the crystals in the range of 260–355 nm induces down-conversion luminescence of Yb3+ ions from the 2F5/2 level in the vicinity of 1 µm. An increase in the oxidative potential of synthesis atmosphere, as well as the introduction of niobium into the crystal composition, weakens this luminescence. A consistent pattern explaining the nature of the donor centers involved in down-conversion population of excited state 2F5/2 of Yb3+ in the crystals is proposed. Within this pattern, Yb2+ ions play the role of these donor centers. Another (much less efficient) mechanism of population of the 2F5/2 level is intracenter relaxation from the higher-lying charge transfer excited state within Yb3+ ions. At the same time, it is confirmed that color centers based on oxygen vacancies and partially reduced tungsten ions, as well as self-trapped excitons on tungstate complexes, are not involved in population of the excited state 2F5/2 of Yb3+ ions, and the optical centers formed in Yb:CaWO4 crystals as a result of vacuum annealing suppress ytterbium luminescence.

The results of diagnostics of thermal conditions of an electric thermal explosion (ETE) of a mixture of titanium and soot powders under quasistatic compression are presented. The effect of quasistatic compression pressure on the thermal and electrical parameters of an ETE is studied. It is shown that nonuniform heating occurs at low pressure, while uniform heating occurs at high pressure. A criterion is proposed for determining the thermal regime of the ETE of a heterogeneous mixture, based on the ratio of the exothermic interaction times and the electric current variation during a thermal explosion. It is established that the dependence of the electric current variation rate on time has one peak when the sample is heated nonuniformly and two peaks when it is heated uniformly. An abnormally low effective flash point of the heterogeneous titanium-soot mixture is explained.

In this work the physical properties of the piezoelectric aluminum-scandium nitride (ASN) solid solution as a function of scandium concentration were studied using the density functional theory and experimental methods. The phase transition from the wurtzite phase to the rock salt phase at a Sc concentration of 43% was shown. The barriers of transformation from the wurtzite phase to the rock salt phase for various Sc concentrations were obtained. The behavior of the ASN piezoelectric constant d33 calculated by the piezoelectric constants e33, e31, and e15 shows a sharp increase with increasing Sc concentration compared to aluminum nitride AlN. The relationship between the increase in the piezoelectric response of ASN and the softening of the lattice, accompanied by a decrease in the main elastic constants C11, C33, C44 and C66, as well as a decrease in the c/a ratio with increasing Sc concentration, is shown. ASN films with a predominance of the crystal orientation (00·2) were obtained experimentally by magnetron sputtering. The structural properties of the films were studied by X-ray diffraction analysis. A comparison of the experimentally obtained dependence of the c/a ratio on the Sc concentration with the theoretical values showed a good correspondence. Studies of the physical properties of ASN thin films were performed using microwave multi-overtone composite resonators on diamond substrates with a longitudinal bulk acoustic wave (BAW) as the operating mode in the range of 0.5 – 20 GHz. The frequency dependences of the Q-factor of BAW-resonators with different ASN films were obtained, and the frequency dependences of the square of the modulus of the form factor as |m|2 were calculated. The dependences of the elastic constant С33 and the piezoelectric constant e33 for the ASN films with different Sc concentrations were calculated. The calculated and measured values of these constants are agreed within the experimental error.

The procedure for determining the activation energy of conductivity Еκ is analyzed depending on the temperature step ΔT. It is shown that with increasing ΔT, the error in the calculation of Eκ decreases, but the calculated value of Eκ decreases. In order not to lose the temperature dependence of the activation energy, it is necessary to choose the optimal value of Δt. In our opinion, this value should not exceed 5 – 10 °C. Taking into account the decrease in concentration with increasing temperature due to a decrease in density has virtually no effect on the accuracy of determining Eκ, provided that ΔT is 5 – 10 °C. It has been shown that in the temperature range 20 – 80 °C, the activation energy of conductivity decreases with increasing temperature. This decrease is due to the rupture of intermolecular hydrogen bonds of the solvent with increasing temperature. It was suggested that the movement of ions in an aqueous solution may be accompanied by the breaking of hydrogen bond of the solvent.

There are offered dependences for the definition of parameters formed for surface layer quality when finishing and finish-strengthening with surface-plastic deformation, for the definition of processing modes, tool geometrical parameters taking into account initial parameters of surface layer quality. Criteria for the choice of the processing method ensuring quality parameters required for a surface layer and surface operation properties are offered.

Accumulation of microcracks in response to point impact damage in MgAl2O4 ceramics doped with Cr3+ ions has been studied using acoustic emission measurements. The results demonstrate that the maximum crack length at a higher chromium concentration in the ceramics is smaller than that at lower doping levels. By contrast, doping with LiF (in addition to Cr3+) reduces the decrease in microcrack length caused by chromium oxide.

A complete set of particular theoretical problems that must be solved for predictive description of radical reactions in aqueous solutions under external mechanical impact is substantiated and formulated. Some of the problems stated are found to be conceptually similar to certain problems of the physics of magnetism and laser physics. Schemes of experiments for estimating the biochemical activity and background content of substances in highly purified water are proposed by an example of hydrogen peroxide.

The paper studies the effect of mechanical activation (MA) modes when stirring a stoichiometric mixture of titanium and soot powders in a ball mill on the properties of mixtures, combustion parameters, relative density, and the microstructure of consolidated titanium carbide samples obtained by SHS. MA conditions for Ti + C reaction mixtures in a ball mill were determined. An increase in the mass of grinding bodies activates the MA mechanism. It was shown that the greatest effect from MA was obtained with a two-stage preparation of mixtures: firstly, the titanium powder was activated separately, then the components were mixed together, and this process included not only their mixing, but also soot powder activation. It was found that combustion behavior is affected by the activation of not only titanium, but also soot. After MA of both components, an anomalous increase in the burning rate (more than 100 cm/s) was found on pressed samples. At the bulk density, there was no effect of MA on the mixture combustion process, since in this case the burning rate of all mixtures was in the range of 1.5–2.5 cm/s. It was revealed that MA of reagents for pressed samples leads to an increase in the combustion temperature, an increase in the relative density of the consolidated refractory product to 93–95 %, and a decrease in the average size of TiC grains. A decrease in the residual porosity of consolidated TiC is due to an increase in the hot pressing temperature and plasticity of the product synthesized during the reaction mixture combustion after MA. The main reason is an increase in the exothermic interaction rate. It was shown that MA when mixing reagents makes it possible to control combustion parameters, the microstructure of consolidated products and opens up new opportunities for obtaining refractory materials featuring a unique structure and properties by SHS pressing.

Electrical and dielectric properties of polycrystalline yttrium–iron garnet samples grown by the technology of radiation-thermal sintering in the fast electron beam are considered. In the frequency range from 25 Hz to 1 MHz, the normal complex permittivity, dielectric loss tangent, and ac conductivity spectra are measured. For comparison, in addition to frequency measurements, dc resistivity is measured. The temperature dependences of the above parameters are also measured at frequencies of 1 and 100 kHz in the temperature range of 25–300°C. The activation energies of the ac and dc conduction processes on the Arrhenius coordinates are determined by the temperature dependences of the conductivity. It is shown that as the sintering temperature increases from 1300 to 1450°C, the electrical parameters reach values characteristic of samples grown by conventional ceramic technology.

This paper studies the influence of mixing modes for titanium and boron powder mixtures with the 81.5% Ti + 18.5% B composition in a ball mill on the process characteristics of mixtures, combustion parameters, and microstructure of SHS composites. It is shown that the dependence of the electrical resistivity on the density of charge compacts for the composition under study can be used as a criterion for mixing quality and mixture uniformity. It is noted that an increase in the grinding media mass includes the mechanism of mechanical activation (MA) of mixtures. Dependences of the burning speed and temperature on density were obtained for all mixtures under study. Burning speeds for mixtures subjected to mechanical activation (Мch/Мball = 1 : 7; 1 : 12) and without it (Мch/Мball = 1 : 4) differ significantly. Mechanically activated mixtures feature differences in burning speeds depending on the charge compact thickness. Thin compacts burn at a higher speed. The burning speed of mixtures without MA (in the case of smaller grinding media masses) does not depend on the compact thickness. Maximum burning temperatures of all the mixtures studied have insignificant differences depending on the density, mixing time, and grinding media mass. There was also no effect of the compact thickness on the burning temperature observed. The structure of SHS composites depends on mixing modes. The finely dispersed structure of composites with titanium diboride grains (less than 1 μm) and a titanium-based binder phase can be obtained only from MA mixtures. Alloys with a structure consisting mainly of elongated titanium monoboride grains (up to 40 μm) and a binder phase of a solid solution of boron in titanium were synthesized of the mixtures for which mechanical activation processes are not essential.

A composite material based on the Ni–Al–C system is synthesized by the method of an electrothermal explosion at a pressure of 96 MPa. During the electrothermal explosion in a reactive powder medium (Ni + Al + C), a Ni- and Al-based melt is formed, in which carbon dissolves. In the process of crystallization of the final product, carbon, due to its low solubility in NiAl, is located on the surface of intermetallic grains of NiAl in the form of multilayer graphite nanofilms 50–80 nm thick and fills the intergranular space. The microhardness of the synthesized material is 3084 MPa.

In the present study, an easily accessible method for obtaining copper-containing tribological nanomaterials by thermolysis of copper(II) laurate at 300 °C was developed. The obtained nanoparticles were studied using X-ray diffraction, atomic force microscopy, and sedimentation analysis. The composition of nanoparticles and the size of crystallites are shown to depend on the thermolysis time. The tribological characteristics of copper-containing nanomaterials derived from copper(II) laurate were analyzed as additives to liquid paraffin using a pin-on-disc tribometer (additive concentration 0.025–0.2%, normal loads 49 and 96 N, rotation speed 200 rpm). The optimal concentration of nanomaterials at which the coefficient of friction is the lowest is determined. An increase in load to 98 N leads to a decrease in the coefficient of friction. The mechanism of friction in the presence of the studied nanolubricants is discussed.

Shape and polarity of thermo-emf signals arising during combustion of Ti–хB mixtures (x = 0.75–5.5) in conditions of quasi-static compression were found to depend on boron content x: emf signal was positive for x ≤ 1, negative for 1.5 ≤ x ≤ 3.0, and short negative for x ≥ 3.5. Generation of positive emf signals was associated with the n-type conductivity of Ti while negative ones, with the p-type conductivity of boron.

Ultra-refractory Hf4ZrC5–(Hf,Zr)B2 composites were prepared by electrothermal explosion (ETE) under pressure in a one-stage process, with special emphasis on the influence of high-energy ball milling (HEBM) of starting Hf–Zr–C–B powder mixtures. Synthesized Hf4ZrC5–(Hf,Zr)B2 composites had a grain size of 0.5–1.0 μm and a porosity of 10–12%.

The article describes the development, fabrication, and test results of a double pancake сoil made using second-generation high-temperature superconductors (HTSC-2G). The HTSC-2G coil is the key element of the cryomagnetic system intended for use as part of an experimental research setup for remotely controlling the expression of neurons by means of constant and low-frequency (up to 100 Hz) magnetic field. This project is a continuation of works [1] carried out on the integrated topic “Electronic Components and Neuromorphic Ccontrol Systems”, which includes, as a constituent part, the development and fabrication of an HTSC-2G cryomagnetic system for studying neuron activity under the effect of external magnetic field. A distinctive feature of the project is the use of a cryomagnetic system with a low energy consumption achieved owing to the use of modern HTSC materials. This will open the possibility to continuously observe the object under study from the start of its exposure to magnetic field to the occurrence of reaction signs. The technology for winding a double pancake HTSC-2G coil is developed and described. For making the coil, an HTSC-2G wire in polyamide varnish insulation was used. The technology of making inner junctions in double pancake HTSC-2G coils with a transition resistance of less than 120 nΩ at 77 K has been developed and successfully tried out. The results from preliminary tests of the HTSC-2G coil in liquid nitrogen are presented.

The article presents data on heat resistance high-temperature tests of powder materials based on copper-nickel have been carried out. The oxidation features of materials samples with various alloying elements have been studied. Compaction of copper-nickel alloys samples was done by spark plasma sintering (SPS). The dependence of the growth rate of the oxide film on the temperature of high-temperature oxidation was established, and the effect of alloying elements in the composition of the samples on their heat resistance was considered. Based on the study’s results the dependence of the oxide film growth rate on high-temperature oxidation and the influence of alloying elements in the composition of sintered copper-nickel alloys on their heat resistance are considered. It was determined that for all the considered samples compositions of copper-nickel alloys synthesized by spark plasma sintering, the temperature 1000 °C of 20-hour heating heat resistance test is not the limiting one, since the samples retain their integrity. It is shown that simultaneous alloying of copper-nickel alloys with aluminum and chromium provides the highest heat resistance. The scale growth rate for composition Cu – Ni – Cr – Al 1.49·10–3 g/cm3 is lower than the oxidation rate of pure nickel 3.78·10–3 g/cm3 at 1000 °C. These two samples demonstrate the lowest weight gain after testing at 1000 °С, for compositions Cu – Ni – Al, Cu – Ni – Cr – Si and 50 wt. % Cu – 50 wt. % Ni the oxidation rate increases by two orders of magnitude, for compositions Cu – Ni – Si and Ni — by three orders of magnitude.

The electromechanical model for analyzing a homopolar electric motor with a magnetic system made using second-generation high-temperature superconductors (HTSC 2G) is described. Homopolar electric motors made with a disk-shaped rotor have the simplest design of their magnetic system and heavy-current contact. Owing to the use of HTSC 2G conductors for producing constant magnetic field in the rotor area, it becomes possible to achieve a higher current density in the windings, thereby increasing the motor power capacity. Due to the HTSC ability to operate at the liquid nitrogen temperature (77 K), it becomes possible to have a simpler cryostat design in comparison with magnetic systems based on low-temperature superconductors. For large-capacity homopolar motors, the use of liquid metal contacts for supplying current to the rotating rotor seems to be the most promising design solution. The advantage of motors of this type is that their torque depends linearly on the rotor current. The homopolar motor operation governed by a proportional-integral-differentiating (PID) controller was simulated using the SciLab Xcos software. The application of the analysis model for selecting the optimal PID-controller coefficients is demonstrated. The electric motor dynamic operation modes are analyzed. The numerical simulation results are compared with the previously obtained experimental data.

The paper reviews the results of development of a new class of high-temperature composites based on niobium and various types of reinforcers continuous monocrystalline fibers (MCF) α-Al2O3, with TiN, Mo, W barrier coatings, and with controlled (Si, Ti) and uncontrolled (O, C) impurities. The analysis of Nb–Si, Nb–C, Nb–O binary diagrams and Nb–Si–Ti, Nb–Fe–Ti ternary diagrams was performed, on the basis of which the matrix compositions were selected. The basis for the preparation of composites was the powder method of mechanical alloying of the mixture preparing, followed by its pressing together with α-Al2O3 MCF by spark plasma sintering (SPS) and further preparation of experimental samples. An analysis of the interaction of fibers with a matrix was carried out, where the matrix was Nb or system on the basis of the above mentioned binary or ternary diagrams.

Aluminum-matrix composite materials based on commercial aluminum AD0 have been investigated. SiC powder, whiskers and Al2O3 nanofibers were chosen as fillers. It was found out that the selected fillers slightly increase density and have the modifying effect on the microstructure. The maximum grain refinement (by 35.3%) was achieved in the composite modified with Al2O3 nanofibers. This composite exhibits a quasi-brittle fracture pattern and the greatest fracture work.

In this paper we consider the problems arising in the numerical estimation of the ultimate load of welded joints of high-strength steels with slight hardening. The stress concentrator in the transition node from the deposited to the base metal is modeled based on the example of welding a roller wire on a plate made of high-strength steel. The use of welding wire with a yield point lower than that of the base metal allowed to simulate areas of the welded joint with heterogeneous mechanical properties. The geometry of three areas of the welded joint is studied, i.e. weld metal, heat-affected zone (HAZ) and the base metal. Mechanical properties of all three areas are determined by calculation and experimentally. For this purpose, it is proposed to consider the material in all sections as ideally elastic-plastic, and the yield strength is uniquely associated with the hardness in the indentation zone (a Rockwell diamond cone is used). Calculations of the inelastic indentation process by the finite element method (FEM) in axis-symmetric formulation allowed obtaining a linear relationship between the hardness and the yield strength with a coefficient of 0.418. Tests at a quasi-static three-point bend (with stretching in the surfacing area) were carried out on sample beams cut perpendicular to the direction of welding. The “force-deflection” diagrams are obtained and compared with the calculated curves (FEM in a three-dimensional formulation with an explicit consideration of the complex configuration of all sections and different yield stress in the areas determined by local hardness values). There is a good agreement between the calculated and experimental ultimate loads. The proposed method of the three-stage study (determination of local hardness, yield strength in the areas and the ultimate load) can be effectively used to assess the ultimate loads of the welded joints due to the low parametricity of the proposed models of materials inelastic deformation in areas for which it is impossible to manufacture standard samples for the study of mechanical properties. The experimental study of the strengthening effect of the seam with a stress concentrator in the form of an angle of 90 degrees on the value of the ultimate bending load showed that the removal of the deposited metal does not lead to an increase in the ultimate load of the welded joint when using the welding wire of low-carbon high-plastic steel.

The review covers problems related to development and application of a new type of “smart” medical materials, mainly, for regeneration of bone tissue that are capable of creating additional stimuli influencing the regeneration process. Application of ferroelectric and magnetoelastic materials is discussed, including their use as sensors and actuators. Physical and materials science principles of development, along with examples of using composite magnetoelectric materials of the piezoelectric/magnetoelastic type as magnetically controlled scaffolds creating local electric fields, are analyzed.

The application of monocrystalline carbon to steel surfaces of rubbing bodies significantly increases the anti-friction and anti-wear properties of lubricants. (Research purpose) The research purpose is in choosing the optimal intermediate layer material based on the evaluation and comparison of the physical, mechanical and tribological characteristics of two-layer coatings obtained using titanium nitride and titanium aluminitride, respectively, as a solid intermediate layer, and compare them with each other. (Materials and methods) The cylindrical surfaces of 100Cr6 steel rollers with a diameter of 8 mm were coated with titanium nitride and titanium alumonitride, using the latest technologies, and on top of these coatings by pulsed condensation of carbon plasma with additional bombardment with argon ions - monocrystalline carbon. The micromechanical and microgeometric characteristics of the studied surfaces were evaluated using NanoScan-4D and SNeox devices. Pure base oil PAO-4, oil with the addition of oleic acid as a surface-active additive, and zinc dialkyldithiophosphate as a chemically active additive were used as a lubricant. (Results and discussion) The use of intermediate layers of titanium nitride and titanium aluminitride improves the adhesion of the carbon coating, which has a positive effect on its wear resistance. The main role in the antifriction effect of two-layer coatings is performed by a thin-layer carbon coating. (Conclusions) The article shows that the use of composite coatings from monocrystalline carbon + heat-resistant coating in friction units operating in the boundary lubrication mode serves as a reserve for improving the lubricating properties of oils, without requiring chemically active additives containing elements that negatively affect the environment. As an intermediate coating, the best result was shown by titanium aluminitride, it is more resistant to wear, and also provides lower friction.

The choice of the composition of the components of a composite material that determines its prospects and demand has been substantiated. Liquid-phase combination is used to fabricate billets of an aluminum-matrix composite material of a new composition. The technological problems of introducing discrete Al2O3 nanofibers into an aluminum matrix are solved. A copper powder is used to overcome surface tension forces and to ensure a uniform reinforcing component distribution. When the components of the composite material are prepared, the reinforcing phase consisting of a transport powder and nanofibers is ground and the resulting conglomerate is introduced into a melt to form a composite material. The hardness of the reinforced specimens is higher than the hardness of the matrix, and sufficient uniformity of the hardness distribution over the cross section demonstrates the uniformity of introduced component distribution. An analysis of the fracture of specimens demonstrates a clear predominance of plastic deformation for the initial matrix alloy and an embrittlement effect in the case of reinforcement. Structural studies on a macrolevel show the signs characteristic of brittle fracture, and scanning electron microscopy (Tescan Vega IILMH microscope) studies demonstrate signs of ductile fracture. The fabrication of high-quality specimens and the results of studying the structure and properties confirm the efficiency of the technology developed for the introduction of fillers.

High-gradient magnetic separator made a good showing at enrichment of low-magnetic ores. However, existing industrial facilities have large dimensions, low specific productivity and high energy costs. Laboratory prototype of high-gradient magnetic separator equipped with superconductor magnet system was developed, manufactured and tested at NRC “Kurchatov Institute”. The device is designed for enrichment of low-magnetic mineral resources, mostly oxidized ferruginous quartzites. The goal of development was both creation of next-generation of separators operating with high-power magnetic fields as well as further progress in applied superconductivity for industrial applications. This paper gives a brief description of the problem, as well as of the process of development, manufacturing and testing the superconducting magnet system. Overall design of the prototype is described, as well as design of collector matrices designed specifically for high-power magnetic field. Next is description of testing process with mineral raw materials obtained from a real industrial enrichment facility. Data on total iron percentage before and after the separation process at the prototype presented, as well as its basic performance characteristics. The results obtained in the course of the project fulfilment can be used in mining industry and metallurgy for manufacturing superconducting magnetic separators of new generation. Such separators will have many advantages comparing with regular separators (with resistive windings) as following: lower energy consumption and less weight, higher induction of the magnetic field in the working gap, possibility to use matrices with coefficient of filling by ferromagnetic precipitating elements at the level of 6-8% with large gaps for pulp passing, higher specific indices due to increased current density in the winding up to 50-100 A/mm2.

A new hexacoordinate Co(II) complex with the general formula [CoL(NCS)2]·DMSO (1) (L = biscondensation product of diacetyl and 2-hydrazinyl-4,6-dimethylpyrimidine, DMSO = dimethylsulfoxide) exhibit...

The results of an investigation of the structural peculiarities of the thin ta-C coatings obtained by the method of impulse arc sputtering of graphite and of their tribological tests in boundary lubrication conditions are presented.

Controlling deep temperature in parts of the human body is necessary for hyperthermia and thermal ablation used in oncology. UHF heating of single hands of patients was chosen as the model for this procedure. For the control, a plastisol cylinder was heated in the same manner: a substance with acoustic and thermophysical properties close to those of soft tissues of the human body. Passive acoustic thermometry was used to measure the deep temperature of the hand, and infrared thermometry was used to measure the surface temperature. After 5 min of UHF heating, the deep temperature of the hand increased by an average of 0.7 ± 0.6°C, and the surface temperature, by 0.8 ± 0.6°C. The same methods, as well as independent measurements, were used to determine the plastisol temperature. After the same procedure, the deep temperature of the plastisol increased by 4.3 ± 0.4°C; the surface temperature, by 3.2 ± 0.2°C; the temperature measured with a thermometer at the center of the object, by 3.3 ± 0.5°C. The smaller heating of the hand compared to the model object is related to effect of blood flow, which should be adequately taken into account in further studies. The noninvasive methods indicated in the study can be used to control temperature in oncology during hyperthermia and thermal ablation under the effect of a high-frequency electromagnetic field.

We obtained a Raman spectrum for a surface layer of porous carbon ceramic (porosity ≈5%) of ≈80 nm thick. The analysis of the spectrum showed that the ceramics contain crystals of silicon carbide 6H‑SiC and silicon. The destruction of ceramics by diamond microcrystals resulted in fractoluminescence (FL). Its spectrum contained two bands at 1.6 and 1.9 eV. The first is emerged at the destruction of silicon crystals, and the second is emerged at 6H-SiC crystals. We obtained the time dependence of the intensity of the fractoluminescence signals with a time resolution of 2 ns. Three types of signals were observed: one is formed when the 6H-SiC crystals are destroyed; the second is formed when silicon crystals are destroyed; the third is formed when these crystals are simultaneously destroyed. The appearance of signals is associated with the formation of cracks arising from the breakthrough of barriers formed at the intersection of slip planes of dislocations in silicon carbide and silicon crystals. The size of cracks in 6H-SiC has been estimated: the smallest is 5.5 nm, and the largest is ≈18 nm.

—The spectrum is obtained and the time dependences of fractoluminescence signals upon fracture of the surface of quartz are studied. The analysis of the obtained data has shown that at fracture, clusters of four cracks having a size of a few nm appear. Crack formation is associated with the destruction of barriers precluding the motion of dislocations along the sliding planes. The distribution of cracks by sizes (surface areas of crack walls) obeys the Gutenberg–Richter law.

The ZrB2–CrB composites with a ceramic bond content of 80 wt.% and a relative density of 0.85 – 0.90 were obtained by the method of electrothermal explosion under pressure. It is shown that the mechanical activation of the source powder mixture decreases its heterogeneity and increases its reactivity.We also obtained a finely divided ceramic composite with homogeneous microstructure containing needle-like ZrB2 grains.

The experimental study of the high-temperature interaction kinetics of a titanium-soot mixture under quasistatic compression in an electrothermal explosion (ETE) is described. Dependences of the heating rate of a sample mixture on temperature are obtained, and the effective values of the energy of ignition activation and thermal explosion are calculated. The formation of the microstructure of intermediate and final interaction products is investigated. It is shown that the formation of a final product occurs according to a shell-core mechanism. The high rate of the solid-phase interaction of titanium and soot is explained by the formation of micropores and microcracks in the intermediate product, which ensure the high rate of surface diffusion of carbon.