Search

The most popular modern programs for quantum chemical and molecular dynamics (classical, ab initio, and QM/MM) calculations, which are relevant for the investigation of nature and various properties of different molecules and periodic chemical systems such as nanotubes, surfaces and films, polymers, and crystalline solids, are highlighted and briefly discussed.

The article considers the change in the physical and mechanical characteristics of cement stone made of the CEM I 42,5 N Portland cement in the process of bacterial and fungal corrosion for 6 months in the air and moisture conditions. It is established that the density of concrete during microbiological corrosion increases under constant moistening of the sample. However, after drying, a decrease in the density of concrete is recorded by 10 % under the influence of Bacillus subtilis bacteria and by 14 % under the influence of black mold. The degree of influence of microorganisms on the amount of water absorption of cement stone is established experimentally. Bacteria increases water absorption by 7 %, black mold increases water absorption by 10 %. Within 6 months, water absorption increased from 21 to 24,5 % for bacterial corrosion in indoor conditions, and from 24 to 29 % for fungal corrosion. When exposed to capillary moisture for 6 months, the water absorption of concrete increased to 30,4 % under the influence of Bacillus subtilis bacteria and to 37,3% under the influence of Aspergillus niger van Tieghem fungi. An increase in the water absorption of concrete is associated with an increase in porosity due to biodegradation. Under room conditions of exposure to bacteria, the porosity increases from 14,1 to 15,3 %, and from 14,3 to 17,9 % after exposure to black mold. With constant moistening, the porosity of cement concrete increases to 19,1 and 25,6 % with bacterial and fungal corrosion, respectively. The loss of compressive strength of cement stone is 13 % under the influence of bacteria and 15 % under the influence of fungi in the air for 6 months. In case of microbiological corrosion of concrete under conditions of constant wetting, the strength decreases by about 35 % in 6 months

Charge transport in amorphous silicon nitride (Si3N4) is studied experimentally in a wide range of electric fields and temperatures. The experimental data are compared with the results of numerical calculations. To describe the ionization of deep centers (traps) in Si3N4, the Frenkel effect is used with the account for thermally assisted tunneling and the multiphonon mechanism. It is shown that the Frenkel effect with allowance for thermally assisted tunneling formally describes the experiment. However, an anomalously small frequency factor (109 s–1) and a large effective tunneling mass (3m0) must be used in calculations in this case. A satisfactory agreement between the results of experiments and calculations was attained using the theory of multiphonon ionization of traps with the following parameters: $$W_{T}^{{e,h}}$$ = 1.6 eV, $$W_{{{\text{opt}}}}^{{e,h}}$$ = 3.2 eV, $$W_{{{\text{ph}}}}^{{e,h}}$$ = 0.064 eV, $$m_{{e,h}}^{*}$$ = 0.6m0, and Ne,h = 6 × 1018 cm–3, which correspond to the thermal energy, optical energy, phonon energy, tunneling effective mass, and concentrations of electron and hole traps, respectively.

The Sr1-xSmxTiO3 (х = 0.025, 0.05, 0.075, 0.1, 0.2) strontium titanate solid solutions were prepared from oxides and carbonates using a conventional ceramic technology based on the mechanochemical activation. The electrical conductivity and Seebeck coefficient of the synthesized compounds were measured in the temperature range from 300 to 800 K. We found that the properties of the samples significantly depend on the preliminary mechanochemical activation. The thermoelectric power factor attains maximum value in the hydrogen reduced samples with concentration of х = 0.05 and 0.075 obtained from nanoparticles: 5.5 μW/(cm · K2) for Sr0.95Sm0.05TiO3 (580 K) and 4.10 μW/(cm · K2) for Sr0.925Sm0.075TiO3 (650 K). An increase in the annealing temperature of mechanically activated samples leads to an even greater increase in electrical conductivity and power factor: 9.2 μW/(cm · K2) for Sr0.925Sm0.075TiO3 (650 K).

Short supramolecular Br···Br and I···I contacts in chalcogenides Ti4Se9I6, V4S9Br4, Ta4S9Br8, and Ta4Se9I8 with a square {M4Q9} core are theoretically studied by quantum chemical calculations within the density functional theory (ωB97XD/DZP-DKH) and the QTAIM topological analysis of the electron density distribution.

Grain growth in the textureless material characterized by bimodal grain size distribution has been investigated. Grain growth in a pure material can eliminate the second maximum in the distribution, despite the presence of abnormally coarse crystallites in the initial structure. This is true when the number of coarse crystallites in the initial state is small and can be explained by normal grain growth in the fine-grained matrix. The size effect of matrix grains on the second maximum in the distribution under these conditions has been analyzed. The second maximum has been shown to remain and even increase due to the inhibition of boun-dary migration.

The influence of the processing of scanning electron microscope (SEM) images on its calibration using test objects with a trapezoidal profile and large inclination angles of the side walls is considered. The influence of different methods of the linearization of SEM signals on the calibration accuracy is shown. Two methods of SEM calibration are presented and the best method is selected. The advantage of correlation analysis for SEM calibration is demonstrated. It is shown that only the use of a virtual scanning electron microscope (VSEM) guarantees correct calibration of the SEM.

The article considers the change in the structural and phase composition of cement stone made of Portland cement of the CEM I 42.5 N brand in the process of bacterial and fungal corrosion during 6 months when humidified. The X-ray images of cement stone show peaks that characterize the non-hydrated components of Portland cement alite, belite, tricalcium aluminate, four-calcium aluminoferrite and gypsum. By the method of X-ray phase analysis, it is found that during microbiological corrosion, the content of all phases of cement stone decreases. The aspergillus niger van Tieghem fungi have a stronger effect on the structural and phase composition of cement stone. Fungal microorganisms destroy the crystalline phases and absorb amorphous phases – calcium hydrosilicates C-S-H (I) and C-S-H (II) and tobermorite. When bacteria Bacillus subtilis affects the cement stone, the content of the calcite phase increases, which is a product of corrosion, while the action of black mold reduces the intensity of CaCO3 peaks. A decrease in the content of low-base calcium hydrosilicates and ettringite, as well as other crystalline phases, leads to a decrease in the compressive strength of the cement stone. During 6 months of microbiological corrosion of cement concrete under conditions of constant wetting, the compressive strength decreases by about 35 %.

The article is devoted to research in the development of composite materials based on polyvinyl chloride and industrial waste from the metallurgical, energy and mining industries. The properties of dispersed waste have been studied, which make it possible to speak of the possibility of their use as fillers for polymer compositions. A comparative analysis of the tested physical and mechanical properties is carried out, depending on the characteristics of the particle size of the fillers. It was revealed that from the point of view of construction materials, all the wastes under study can be used as fillers. The development will make it possible to dispose of industrial waste to obtain useful products and save natural non-metallic materials used in the creation of composites.

The results of experimental studies of the porosity of the psevdosplav sintered from electroerosive powders obtained in distilled water are presented. It is shown that the use of the spark plasma sintering method for the production of products from the powder obtained by electrodispersion of the pseudoalloy VNJ 95 will ensure the porosity of the sintered samples of the order of 0.43% with an average micro-porosity of the samples of 349 HV

A polycrystalline sample of the Sn20.5□3.5As22I8 clathrate was synthesised by a standard ampoule method from elements. Temperature dependencies of the heat capacity Cp(T) and unit cell parameter a(...

This paper provides a comparative assessment of the results of modeling the processes of deformation and destruction of objects under uniaxial tension in the MSC.Marc and DEFORM software packages and in a full-scale experiment, as well as a study of the influence of the form factor of these objects and the form of unit cells on the fracture parameters in modeling and experiment.

A model of the magnitude of the stresses of the tip of the cutting blades of a thread-forming tool based on the theory of a homogeneous body is proposed. A model of second-order materials is considered. A description of the stress state is given using two stress tensors independent of each other.

The accident at the Fukushima NPP (Japan) showed the particular danger of a steam-zirconium reaction arising when the temperature of the fuel-rod cladding rises after loss of coolant. Work on the development of accident-tolerant fuel (ATF) has intensified in almost all countries with developed nuclear energy. When considering cladding options for such fuel, at first, for many manufacturers the application of a chromium-based protective coating to the surface of a fuel rod made of zirconium alloy appeared to be most promising. VNIINM has developed a technology for depositing a protective heat-resistant chromium-based coating on the cladding of fuel rods – fast, ion-plasma, magnetron sputtering. It has been shown experimentally that a single-layer chromium coating is optimal for making the zirconium cladding of fuel rods more heat-resistant.

This paper presents the results of an experimental study of shock compression of titanium hydride (TiH2) and the deuterides of zirconium (ZrD2), tantalum (TaD0.8), and titanium (TiD2, TiD1.6, and TiD1.1) in the pressure range 30–220 GPa. The synthesis of titanium and zirconium deuterides from titanium and zirconium powders and tantalum deuterides from tantalum rods is described. Experiments to determine the Hugoniots of deuterides and hydrides were performed using the well-known reflection method. Shock-wave generators with explosive charges of different power were used for compression of samples. A description of the obtained experimental data using simple equations of state is proposed.

An apparatus for the rapid thermal extraction of Re radioisotopes from an irradiated tungsten target has been developed. Its operation was tested using a tungsten target pre-irradiated with deuterons on the U-150 cyclotron of the Kurchatov Institute. A description of the design of the apparatus and the principle of its operation are given. It has been shown that in one two-stage calcination–sublimation cycle, at least 89% of the Re activity from the W target can be collected on the receiving area of the collector. The apparatus can be used to isolate the 186Re isotope formed from 186W upon irradiation with protons or deuterons of cyclotron targets.

The influence of electron-proton irradiation on the process of changing the surface structure of K‑208 glass, caused by the formation of gas-filled bubbles and their destruction, is studied by atomic-force microscopy (AFM). These phenomena are associated with the formation of hydrogen atoms H in the process of the recombination of protons with electrons injected into the glass and those that appeared in it during ionization. The migration of hydrogen atoms and their aggregation into H-clusters in the vicinity of glass structure defects leads to the formation of molecular hydrogen (H2) bubbles. The glass is exposed to electrons and protons with energies of 40 and 20 keV, respectively. Irradiation is carried out in a vacuum chamber with a residual pressure of 10–4 Pa. At a fixed value of the proton flux density φр = 5.5 × 1010 cm–2 s–1, the electron flux density φe varies in the range (0–16.8) × 1010 cm–2 s–1. It is shown that the size of the bubbles depends on the ratio of the parameters φe and φр. Analysis of the experimental data suggests that the destruction of a bubble occurs with a local decrease in the thickness of its cap to 10–20 nm, as a result of heating and growth in the direction normal to the surface under the pressure of the accumulating gas. It is also found that electrostatic discharges developing along the irradiated glass surface stimulate the destruction of bubbles.

It has been shown that pulsed magnetic fields (the first mode: pulse duration of 2 ms, frequency repetitions of 6.25 Hz, the pulse was bell-shaped; and the second mode: pulse duration of 1 ms, repetition frequency of 100 Hz, the pulse was bell-shaped) affected the intensity of luminol-dependent chemiluminescence of neutrophils in a wide range of pulsed magnetic fields (0.0004–10 mT). For the detection of the effects of pulsed magnetic fields by this method, it was necessary to add forbol-12-meristat-13-acetate, an activator of the production of reactive oxygen species, to the suspension of neutrophils. However, this mechanism of action of pulsed magnetic fields on the production of reactive oxygen species in neutrophils was not the only one, since lucigenin-dependent chemiluminescence also reacted to their action in a system without activators.

Magnetic and magnetoelastic methods of stress control are based on changes in the magnetic parameters of steel upon deformation. However, the magnetic properties of different steel grades, and even of the same grade in different heats may differ noticeably. The inhomogeneity of the magnetic and magnetoelastic properties of steel attributed to variations in the chemical composition, as well as in the modes of rolling and heating during manufacture affects the accuracy of stress control being a common disadvantage of magnetoelastic methods used for monitoring the stress-strain state of steel structures. The goal of the study is to consider the possibility of monitoring uniaxial mechanical stresses in steel structures in the «magnetoelastic memory» mode, based on H(σ) dependence of the strength of magnetic field of scattering local remanent magnetization of steel on the uniaxial stresses. The exponential function is shown to provide a satisfactory description of the experimental dependence of the strength of the magnetic field of scattering of the permanently magnetized 17G1S and 15KhSND steels on the stresses induced in steels by tension, compression, and impact. To improve the accuracy of the control, we propose to introduce the magnetoelastic sensitivity of steel (MSS) into the accepted form of the exponential dependence H(σ). A way to MSS determination not only on laboratory samples under ideal conditions, but directly on the construction under control (which reduces the errors of the control attributed to variations in the magnetic and magnetoelastic properties of steels) is considered. To implement the proposed procedure, prototypes of the devices for static and dynamic local loading of metal structure elements have been developed and manufactured. The devices have undergone a pilot test when monitoring the stress-strain state of the load-bearing beams of an automobile overpass. Using the developed devices, a local dosed loading with a hemispherical indenter was carried out through shock or static loading of a pre-magnetized region of the structure resulted in a decrease in the intensity of the magnetic field of scattering. A procedure for monitoring uniaxial stresses in steel structure elements by the method of magnetoelastic «memory» is proposed taking into account the measured magnetoelastic sensitivity of their material.

The article presents the results of monitoring the rotor vibration occurring in gas-pumping units. An assessment of the effect of vibration loads on seal leakage has been carried out. The maximum amplitudes and frequencies of vibration of rotors of gas-pumping units under operating conditions have been determined. A dynamic model of a "dry" seal is proposed, in which axial, angular and bending vibrations of the seal rings are realized. The theoretical definition of the rotor vibration parameters admissible for the operation of "dry" compaction is carried out.

We suggest a new strategy for creating stimuli-responsive bio-integrated optical nanostructures based on Mie-resonant silicon nanoparticles covered by an ensemble of similarity negatively charged polyelectrolytes (heparin and sodium polystyrene sulfonate). The dynamic tuning of the nanostructures' optical response is due to light-induced heating of the nanoparticles and swelling of the polyelectrolyte shell. The resulting hydrophilic/hydrophobic transitions significantly change the shell thickness and reversible shift of the scattering spectra for individual nanoparticles up to 60 nm. Our findings bring novel opportunities for the application of smart nanomaterials in nanomedicine and bio-integrated nanophotonics.

The thermoelectric properties of thin Cr0.33Si0.67 films in amorphous and crystalline states, as well as at different annealing stages in the temperature range 100–900 K have been studied. The crystallization of amorphous films at a temperature of ~550 K is accompanied by an increase in the resistivity and thermoelectric power. Amorphous films crystallize with the formation of CrSi2 nanocrystals with an average grain size of 10–20 nm. The increase in resistivity is due to the appearance of a crystalline phase and the formation of interphase boundaries between the crystalline and amorphous phases. The scattering of charge carriers at interphase boundaries is selective, which leads to the appearance of an additional contribution to the thermopower.

We study the thermoelectric and galvanomagnetic properties of cobalt monosilicide (CoSi) and its solid solutions with FeSi and NiSi. Recent CoSi band structure calculations, confirmed by ARPES measurements, revealed several differences of the electronic structure from the previous standard two-band model for semi-metallic compounds. The discovered features of the CoSi band structure require modifications of previously used models for description of material transport properties. We investigate the temperature dependences of the Seebeck coefficient, electrical resistivity, and Hall coefficient in the temperature range from 100 to 800 K for CoSi and for its solid solutions with FeSi and NiSi. The ab initio calculation of the band structure and transport coefficient were carried out using the Quantum Espresso software package. The results of the study showed that the main features of the thermoelectric and galvanomagnetic properties of CoSi and its solid solutions with FeSi and NiSi at high temperatures can be adequately described using the ab initio calculated band structure, taking into account the energy dependence of the relaxation time.

The paper presents the results of studying the process of electrodeposition of metals on a rotating electrode. The numerical experiment was used to calculate the dynamics of nucleus growth according to the model developed by Isaev A.V. and Baraboshkin N. A. under different conditions of galvanostatic electrolysis. The dependences of changes in the nucleus radius, overvoltage, and equilibrium concentration of adatoms under different electrolysis conditions are established. Studies were conducted in three different electrolytes. Kinetic parameters of metal reduction and specific electrical conductivity were determined in these solutions. The equilibrium concentration of adatoms is calculated from the inclusion curves. Galvanostatic electrolysis was performed when three current values were set. The initial data obtained during the experiment were used to calculate the growth dynamics of a single nucleus on an inert substrate.

In this study, a structural-deformation analysis of the process of crack development is performed, on the basis of which an engineering methodology is developed for assessing the endurance limit and resource of large-sized structures. A simple analytical dependence (correlation аналитическая зависимость) was obtained, which allows one to determine the critical size of macrocracks for ferritic-pearlitic steels without using the well-known Griffith formula. The results of calculating the cracks critical lengths of various steels depending on their yield strength are presented. The analytical dependence of the calculation of the fatigue limit for the most dangerous symmetric loading cycle according to the standard set of mechanical characteristics of ferrite-pearlite steel is presented. The obtained results make it possible to calculate the endurance limit of structural elements of marine equipment and other structures subject to cyclic loads

The cross sections of the reactions 186W(4He, p3n)186Re, 186W(4He, pn)188Re, and 186W(4He, p)189Re were measured by the activation method in the energy range of 4He nuclei 24–63 MeV. For all three reactions the cross sections in the TENDL-2019 nuclear data library differ from experiment by more than a factor of 2 in a wide energy range.

Objectives. Our aim was to study the dielectric properties of the 4-n-pentyloxybenzoic acid– N-(4-n-butyloxybenzylidene)-4’-methylaniline system and reveal how different concentrations of N-(4-n-butyloxybenzylidene)-4’-methylaniline additives affect the dielectric properties of 4-n-pentyloxybenzoic acid.Methods. System properties were investigated using polarization thermomicroscopy and dielcometry.Results. We found that dielectric anisotropy changes its sign from positive to negative at the transition temperature of the high-temperature nematic subphase to the low-temperature one. The anisotropy of the dielectric constant of N-4-n-butoxybenzylidene-4’-methylaniline has a positive value and increases as to the system approaches the crystalline phase. The crystal structure of the 4-n-pentyloxybenzoic acid contains dimers formed by two independent molecules due to a pair of hydrogen bonds. The crystal structure of N-(4-n-butoxybenzylidene)-4’-methylaniline contains associates formed by orientational interactions of two independent molecules. 4-n-Pentyloxybenzoic acid dimers (270 nm) and associates of N-4-n-butoxybenzylidene-4’- methylaniline (250 nm) proved to have approximately the identical length. Considering the close length values of the structural units of both compounds and the dielectric anisotropy sign, we assume that the N-4-n-butoxybenzylidene-4’-methylaniline associates are incorporated into the supramolecular structure of the 4-n-pentyloxybenzoic acid. The specific electrical conductivity of the compounds under study lies between 10−7 and 10−12 S∙cm−1. The relationship between the specific electrical conductivity anisotropy and the system composition in the nematic phase at the identical reduced temperature, obtained between 100 and 1000 Hz is symbatic. However, the electrical conductivity anisotropy values of the system obtained at 1000 Hz are lower compared to those obtained at 100 Hz. At N-(4-n-butoxybenzylidene)-4’-methylaniline concentrations between 30 and 60 mol %, the electrical conductivity anisotropy values are higher than those of the individual component.Conclusions. A change in the sign of the dielectric constant anisotropy of the 4-n-pentyloxybenzoic acid during nematic subphase transitions was established. We showed that the system has the highest dielectric constant anisotropy value when components have an equal number of moles. Highest electrical conductivity anisotropy values are observed when the concentration of the N-4-n-butoxybenzylidene-4᾽-methylaniline system lies between 30 and 60 mol %.

The problem of use of hi-tech macroporous concrete in load-carrying structures of low-rise buildings is designated and the forthcoming research problems of power resistance and deformation of the compressed and bent elements from foam concrete of natural solidification are formulated. Results of pilot researches of intense state of strain of the compressed and bent elements from foam concrete of average density of 1200-1600 kg/m3 of different structural modification in the conditions of short-term and long action of loading are provided. It is established that foam concrete meet for nonrigid indicators regulatory requirements and take the intermediate place between full-strength cellular and light concrete on expanded aggregates that creates premises for their successful application in the bearing concrete and reinforced concrete constructions. Deformation and strength characteristics of foam concrete of different structural modifications taking into account the impact of the long processes caused by solidification of concrete and external power factors, necessary for calculation and structural design are offered. The received results of researches will allow to project rationally bearing and enclosing structures from foam concrete that leads to increase in technological level of monolithic construction.

The influence of the parameters of a scanning electron microscope (SEM) on its calibration using test objects with a trapezoidal profile and large inclination angles of the side walls is studied. The focusing of the SEM probe and the energy of its electrons affect SEM calibration in the modes of collecting secondary slow electrons and backscattered electrons. It is shown that the microscope can be calibrated only in the low-voltage mode of operation with an energy of primary electrons less than 2 keV and in the mode of collecting secondary slow electrons with an energy of primary electrons more than 10 keV. A model of the formation of microscope signals in these energy ranges is presented. The influence of contamination on the lifetime of the test object and on the calibration accuracy of the scanning electron microscope is considered.

The regularities of the thermal expansion of cladding tubes and rods from the E110opt alloy, as well as the anisotropy of their thermal properties in the case of layer-by-layer texture inhomogeneity are studied. The thermal linear expansion coefficients (TLEC) of rods and cladding tubes were measured in the axial, radial and tangential directions during heating and cooling in the temperature range of 293–1473 K (20–1200°C). It is shown that as a result of α → β → α phase transformations in the samples, a stable texture of phase transformations is formed which is preserved during subsequent heating and cooling cycles. Analytical expressions are obtained that describe the temperature dependence of the thermal expansion coefficient in the first cycle of heating products from the E110opt alloy, taking into account possible α → β phase transformations and the resulting α-Zr crystal lattice deformation along the a and c axes. It was established that the presence of layer-by-layer inhomogeneity in the samples leads to the appearance of stresses between layers with different crystallographic textures and, as a result, affects the orientation dependence of phase transformations that are sensitive to the stress state in the material. The results obtained indicate the need to take into account the internal stresses arising in textured anisotropic materials during heating and cooling, and to separate the contributions of thermal expansion and plastic deformation when analyzing data from dilatometric measurements of sample sizes..

To achieve oxygen blocking structure on surface of carbon/carbon composites, ZrB2-ZrO2-MoSi2-Al coating was prepared by a multi-chamber detonation accelerator. As-sprayed coating consisted of t-MoSi2, h-ZrB2, m-ZrO2, t-ZrO2, and c-Al. A uniform distribution of ceramic c-ZrO2 particles and the formation of h-(α-Al2O3) are observed in the coating at 1400 °C, which increases the stability of the coating. The structure of coating surface exhibited a without pore and cracks after annealing. The results indicated that a ZrB2-ZrO2-MoSi2-Al composite coating could be used as a protective layer on the surface of C/C composites from oxidation at elevated temperatures.

The influence of nanofibrillar cellulose samples on the coating compositions water retention is considered. It was shown that gels of nanofibrillar cellulose and coating compositions based on them are distinguished by a high water-retention capacity during centrifugation (50.8% and 31.0% versus 17.7% with NaCMC). A preliminary assessment of the printing and technical properties of light weight coated paper (LWC) using nanofibrillar cellulose in the coating composition has been carried out. The technical characteristics of nanofibrillar cellulose have been determined, formulations of lightweight paper coatings have been developed for high-speed modern equipment.

149Tb is currently considered to be a promising α-emitting isotope radioimmunotherapy. It is shown that it can be obtained without the use of a carrier by irradiating a target consisting of Eu2O3 with 4He with energy 63 MeV. After irradiation, radiochemical separation of terbium radioisotopes was performed in a time not exceeding the half-life of 149Tb (4.12 h). It was based on reductive co-precipitation of europium and extraction-chromatographic purification. The obtained product, including 149Tb and the associated terbium radioisotopes, were analyzed by means of alpha- and gamma-spectrometry. It was concluded that the combination and sequence of approaches used in this work allow rapid production of short-lived 149Tb and the use of the technological route implemented in this work in practice.

The magnetoelastic demagnetization of a number of steels in the delivery condition under longitudinal elastic tension, transverse compression, and impact has been investigated. The estimation of the magnetoelastic sensitivity of the studied steel grades in the linear approximation is given. The possibility of determining the tensile and compressive stress in the magnetoelastic memory mode with allowance for the magnetoelastic sensitivity of the selected section of steel is considered, and a method for its determination using dosed loading (impact or compression) is proposed. It is shown that the regression equation in the form of a polynomial is in satisfactory agreement with the experimental result.

Multi-stage deposition of metals from a sulfate solution with a high concentration of iron, aluminum, copper, zinc, and nickel has been studied. The concentrations of the components correspond to the composition of the sub-basement waters of the Gaisky GOK. Granular magnesia-silicate reagent based on serpentinite (Khalilovsk magnesite deposit, the Orenburg region, Russia) has been used as an alkaline agent. The magnesia-silicate reagent's ability to reduce the acidity of solutions is due to the presence of products of destruction of the original serpentine mineral, mainly magnesium oxide. The results of the solutions multi-stage purification from metals simulation have been presented. It has been found that the reagent did not wholly exhaust its activity during a single contact with the solution. Therefore, the possibility of its repeated use for the 2nd and 3rd time has been studied. As the solution is neutralized according to the known pH range of the beginning and complete deposition of metal compounds, first iron, and then aluminum are deposited. For copper and nickel, the effect of co-precipitation is observed until the pH of precipitation of poorly soluble compounds is reached. Iron is the main component of precipitations at the 1st, 2nd, and 3rd stages, which corresponds to pH = 2.4-3.7. At the 4th stage (pH = 4.0), the precipitations consisted mainly of aluminum compounds. The copper and nickel content in precipitations increase due to decreased concentration of major components (aluminum and iron) and a pH increase. The deposition of zinc from the solution occurs not to the precipitations, but on the granules surfaces. Precipitations enriched in aluminum and iron have been obtained. Sorption and co-precipitation processes have been observed for copper, zinc, and nickel, which prevents individual precipitation by these metals. Thermally activated serpentine minerals can be considered a promising alkaline reagent for technogenic solutions neutralization and purification.

In this paper are considered the essence and design-technological features of products made from new types of porous mesh metals (PMM) based on combination of various permeable and impermeable metallic materials interconnected by hot rolling in the vacuum. To create new materials, a combination of different types of metal grids is used. Therefore, these materials have received the name - combined porous mesh metals (CPMM). The technological problem is to create reliable products with predictable strength, filtration and structural characteristics. The technology of manufacturing products from CPMM is complex and includes a large number of technological operations divided into operations for material manufacture and operations for manufacturing from this material a finished product of required application. Material production includes several operations for preparing the initial metal grids (washing, degreasing, marking-out, grid packaging), and complex technological operations for material manufacturing, consisting in joint the grids and embedded materials between themselves (vacuuming, heating to a predetermined temperature, grid package rolling in vacuum and in hot condition, etc.). Each of technological operations for material manufacturing should be carried out in rigid mode ranges, such as temperature mode, package drafting degree mode, etc. A slight deviation from the mode leads to rejected material or significant deviation from the specified parameters. A difficult problem is the interconnection of metallic grids of various types (distinguishing by thickness, wire diameter, etc.), as well as interconnection of solid metallic embedded elements necessary for products formation from the obtained material. As a result of numerous experiments, it has been able to achieve success and develop the technology for CPMM material manufacturing. The developed material and products made from it have been imbedded at the enterprises of those industries, where highly reliable and efficient constructions, made from permeable materials and having specified functional parameters, are required. A new phase separator filter (PSF) for the fuel tank (FT) of a space item has been created and implemented. Currently, sets including 20 typical sizes of PSF of various modifications are delivered. Using of capillary intakes (CIs) with PSF made from CPMM provides reduction of residual rests of fuel liquid components in fuel tanks. CIs with PSF are almost 2 times lighter than CIs, carried out according to traditional frame-grid design.

The influence of waveguide tubes on the signals received by remote pressure sensors measuring pressure histories in pulsed detonation engines (PDEs) and rotating detonation engines (RDEs) is studied computationally. Two types of pressure sensors are considered: low-frequency static pressure sensors and high-frequency sensors of pressure pulsations. Three approaches to solving the problem are used: based on Euler (inviscid flow), Navier–Stokes (laminar flow), and unsteady Reynolds-averaged Navier–Stokes (turbulent flow) equations. The approaches based on the inviscid and laminar flow models are shown to provide the best predictive capability. The laminar flow model is applied to analyzing the readings of pressure sensors installed remotely in the waveguide tubes attached to the hydrogen-fueled PDE, RDE, and detonation ramjet (DR). It is shown that the measurements of static pressure and pressure pulsations by remote pressure sensors do not correspond to the time-averaged mean and local instantaneous values of pressure in the combustors. The pressure time histories can be recovered based on the measurements and computational fluid dynamics calculations of the operation process. The latter is demonstrated by analyzing the results of test fires with a dual-duct DR model.

The influence of the composition of the underlying surface on the results of aerial radiation reconnaissance of contaminated areas is considered. The analysis of the probability of the presence of various compositions of the underlying surfaces in Russia. The values of the exposure dose rate over the contaminated area were calculated depending on the height and type of the underlying surface using a specialized software package for mathematical simulation of gamma radiation transport and registration processes for the design of spectrometric systems for aviation radiation control.

THE PURPOSE. In order to control the technical condition of oil-filled electrical equipment, a number of new analytical methods have recently been created to determine the ultra-low concentrations of impurity compounds in transformer oil. An analysis of the literature data showed that at this stage of the analytical procedure significant errors may occur that worsen the quality of control of the technical condition of oil-filled electrical equipment, and in some cases make its results meaningless. The published literature practically does not discuss the problem of sample preparation of transformer oil, which negatively affects the quality of analytical control, that is, the reliability of the results and, accordingly, the diagnosis of oil-filled electrical equipment. METHODS. The paper discusses a sample preparation system for transformer oil, which is based on various methods for extracting target components from it. The adsorption process is used, the preparation of chemical derivatives, various types of extraction, liquid, gas, solid phase and fluid, as well as using low temperatures, extraction in microwave, magnetic, electromagnetic and centrifugal fields. It is shown that liquid extraction with an organic solvent is widely used from all sample preparation methods, with the help of which furan compounds resulting from the destruction of paper insulation are extracted from transformer oil. The disadvantages of sample preparation using liquid-phase extraction and the possibility of using solid-phase extraction on various adsorbents for this purpose are discussed. RESULTS. The results of an experimental study of the sorption properties of various organic solvents with respect to porous materials differing in the structure of their surface are presented. We used zeolite-bearing rocks of the Tatar-Shatrashansky deposit, synthetic zeolites NaX-13A. Using the ascending variant of liquid column chromatography, the absolute retention values of standard extractants were determined and their dependence on the length of the sorption layer of the porous material was found. CONCLUSIONS. It was shown that the highest retention times for all studied adsorbents are observed for organochlorine extractants, chloroform, carbon tetrachloride, dichloroethane, trichlorethylene. For N. Hexane is a relatively small interaction. Histograms are given of the effect of the retention time of standard sorbates (extractants) on their physicochemical nature.

Nanopowders of the binary system of immiscible components Fe and Cu are synthesized by gas condensation of metal vapors. The structure and magnetic properties of nanopowders of various compositions are investigated, and their Mossbauer spectra are analyzed. It is shown that the method allows one to obtain nonequilibrium Fe(Cu) and Cu(Fe) solid solutions, in which the concentration of dissolved elements depends on the synthesis conditions.

The spectral dependence of current sensitivity and kinetics of photoconductivity and the increase and decrease of photoresistances based on a composite of poly(3-hexylthiophene) polymer and silicon nanoparticles have been investigated. It has been found that the introduction of silicon nanoparticles makes it possible to vary both the spectral operating range and current sensitivity of photo-resistances based on the poly(3-hexylthiophene) polymer composite within a wide range. At the same time, the time characteristics of the photoresistance investigated in this work are not inferior to conventional photodetectors based on P3HT/fullerene.

One of the ways to increase the strength and reliability of building structures is the use of steel – fibre reinforced concrete. Steel – fibre reinforced concrete has significant advantages over conventional concrete. A high degree of resistance to cracking contributes to an increase in such physical and mechanical parameters as compressive, tensile and bending strength, water resistance, frost resistance, resistance to water and chemical penetration. In steel – fibre reinforced concrete, steel – fibre is used as a reinforcing material, evenly distributed over the volume of concrete.In the process of steel – fibre production, the fiber is cut with carbide knives. The article deals with the issues of increasing the wear resistance of carbide knives used for cutting steel – fibre, and suggests ways to increase the durability of cutting tools. The influence of the quality of tungsten-cobalt hard alloy on the wear resistance of knives is analyzed, and a knife attachment device is developed.

A model based on depositing charge in the sensitive volume of an integrated circuit is used to estimate the probability of single event upset as a result of the interaction of single proton with the circuit materials. Calculations of the number of electron—hole pairs produced by the primary proton and secondary ions as a result of inelastic collision with the nucleus in the sensitive volume and surround materials make it possible to estimate the ratio of the contributions of these sources to the deposited charge.

The paper presents the results of studies on the possibility of producing long flax fiber in scutching-and-breaking machines from flax straw obtained from modern varieties of oil flax in the form of whole stems of autumn and spring harvesting. The inexpediency of obtaining scutched flax from this type of raw material has been determined.