Purpose. Investigation of the composition, structure and properties of powder materials obtained by electrodispersion of nickel waste of the PNK-0T1 brand in an oxygen-containing medium – distilled water.

Methods. To determine the composition, structure and properties of powder materials, samples of powders obtained from waste nickel grade PNK-0T1 were studied. The powder material was obtained by electroerosive dispersion in distilled water. Microanalysis of powder particles was carried out using a scanning electron microscope, an analysis of the size distribution of powder particles was obtained using a particle size analyzer, an X-ray spectral microanalysis of powder particles was carried out using an energy-dispersive X-ray analyzer embedded in a scanning electron microscope, an analysis of the phase composition of powder particles was carried out using X-ray diffraction on the diffractometer.

Results. During the study, it was revealed that the shape of the particles obtained from nickel powders is spherical and elliptical, and agglomerates of smaller particles are also noted on the increase. Oxygen and nickel are present in the composition of powder materials. The phases of pure nickel and nickel oxide NiO are marked in the phase composition. From the analysis of the granulometric histogram, it follows that the particle size spread varies in the range of 0.26...18.62 microns, the average volume diameter of the particles was 5.2 microns.

Conclusion. The obtained research results can be used to develop a new heavy pseudo-alloy using metal waste from expensive raw materials by the method of electroerosive dispersion, followed by improvement and optimization of the composition and structure of the alloy.

The purpose of this work is to establish the dependence of the coefficients of planar anisotropy on the intensity of localized deformations in various loading ranges of transverse and longitudinal sections of samples of heat-resistant powder alloy Inconel 718 manufactured using SLM technology. The role of technological anisotropy of samples characteristic of SLM technology and its effect on the hardening of Inconel 718 alloy products is evaluated. 

Methods. To achieve this goal, the deformation diagrams of Inconel 718 powder alloy samples manufactured using SLM technology, measured during their stretching according to GOST 11701-84, were analyzed. Flat samples with a dividing grid applied to their surface were subjected to loading. During the tests, localized deformation of the samples in different sections was determined by measuring the geometry of the images of the dividing grid. A specially developed photo and video recording technology was used to capture these images. 

Results. The statistical analysis of the type and parameters of the deformation diagrams made it possible to determine the nature of changes in the intensity of stresses and deformations of the samples of the studied material. The linear character of its tensile hardening in the region of small values of strain intensity and the power-law character of hardening in the range of strain intensity  from 0.03 to 0.17 were established. 

Conclusion. A significant effect of the technological anisotropy of Inconel 718 heat-resistant powder alloy samples obtained using SLM technology on the intensity of deformations is shown. The necessity of taking this fact into account in the development of technological processes for the production of responsible products from the studied material has been revealed.

Purpose. Obtaining and studying the composition, structure and properties of tungsten carbide powder from VA grade tungsten metal waste in aviation kerosene.

Methods. Tungsten carbide powder from tungsten metal waste of the VA brand was obtained in the following sequence. The reactor was filled with a working medium – aviation kerosene of the TS-1 brand, the waste was loaded into the reactor. Electrodes were mounted from the same waste tungsten of the VA brand. The mounted electrodes were connected to a pulse generator. The necessary electrical parameters of the installation were set: the capacitance of the condensers is 42.0–43.5 UF; the voltage on the electrodes is from 115–120 V; the pulse repetition rate is 50–55 Hz. The resulting tungsten powder was studied using: a scanning electron microscope QUANTA 600 FEG; a particle size analyzer Analysette 22 NanoTec; an energy-dispersed X-ray analyzer from the company EDAX; X-ray diffraction on a diffractometer Rigaku Ultima IV.

Results. Based on the conducted experimental studies, a new method for producing tungsten carbide powder has been developed, characterized in that the powder is obtained by electroerosive dispersion of tungsten metal waste of the VA brand in aviation kerosene at a capacitor capacity of 42.0–43.5 UF, an electrode voltage of 115–120 V and a pulse repetition frequency of 50–55 Hz. It has been experimentally established that spherical and elliptical particles of tungsten carbide powder W2C have sizes from 2.26 microns to 90.72 microns with an average volumetric diameter of 20.2 microns and contain carbon on the surface.

Conclusion. The production of tungsten carbide suitable for industrial use at low energy costs from metal waste has shown high efficiency of the technology of electroerosion dispersion.

Purpose. Study of the dependence of the thermal modulus of elasticity of a two-component magnetic fluid on the magnitude of the magnetic field strength, the frequency of external disturbance and the volumetric concentration of magnetic particles.

Method. The research method is based on the kinetic theory of liquid systems. Based on previously constructed kinetic equations for one-particle and two-particle distribution functions and a microscopic expression for the heat flux vector, an explicit dynamic expression for the thermal modulus of elasticity of magnetic fluids is obtained. In fast processes  in liquids, heat transfer occurs in waves and their propagation is similar to the propagation of second sound in helium II. The thermal modulus of elasticity in liquids appears at high frequencies and ensures the propagation of second sound. The expression for the thermal modulus of elasticity consists of potential and kinetic parts, taking into account structural and translational relaxation processes, respectively. To study the thermoelastic properties of magnetic fluids, appropriate expressions of potential interaction energies were selected for each subsystem, allowing for numerical calculations.

Results. Numerical calculations of the frequency and concentration dependence of the dynamic thermal modulus of elasticity in the presence of an external magnetic field in a kerosene-based magnetic fluid were carried out. The calculation results show that an increase in the influence of external disturbances leads to a nonlinear increase in the thermal modulus of elasticity in the magnetic fluid. An increase in the volume concentration of magnetic particles and an increase in the magnetic field strength also led to a nonlinear increase in the thermal modulus of elasticity in the magnetic fluid.

Conclusion. It has been established that, due to taking into account translational and structural relaxation processes, the region of frequency dispersion of the thermal elastic modulus is wide. Numerical calculations carried out at different values of the external magnetic field and the volume concentration of magnetic particles showed that although an increase in the magnetic field and concentration of magnetic particles leads to an increase in the thermal modulus of elasticity, their increase does not affect the change in the frequency dispersion region.

Purpose. Obtaining information on the influence of the location of the inhomogeneous magnetic field source relative to the heated section of a vertical hydrodynamic loop filled with magnetic fluid on the intensity of convective heat transfer along the loop.

Methods. Experiments were carried out using a hydrodynamic loop made of a thin tube of circular cross-section and placed in a vertical plane. Heat source was carried out by a heater on a short vertical section of the loop, and heat removal was implement out by blowing the entire surface of the tube with thermostated air. The source of the magnetic field was the flat pole tips of the ferrite magnetic core, in the gap between which the heater was located. The position of the pole tips relative to the heater varied vertically in the experiments. In the control experiments, the source of the magnetic field was deleted. The circuit was filled with medium concentrated magnetic liquid of the type "magnetite - kerosene - oleic acid". The intensity of steady-state convective heat flow along the tube was calculated from the results of measuring the tube surface temperature by copper-constantane thermocouples. The measurement results were presented in dimensionless form - the relationship between the Nusselt number and Rayleigh number.

Results. The unfluctuating mixed, thermomagnetic and gravitational, convection of the magnetic fluid in the loop was observed at any location of the pole tips of the magnetic core relative to the heater. At location of pole tips above the heater, competition of gravitational and thermomagnetic convection was observed, and the heat flux was weak. When the pole tips were placed below the heater, the Nusselt number was 2 - 4 times higher than in the control tests (only gravitational convection) with equal Rayleigh numbers. The highest Nusselt numbers were obtained when the field source was placed in center of the heater.

Conclusion. Information on the influence of the relative location of the magnetic field source and the heater on convective heat transfer by magnetic fluid in a hydrodynamic loop is obtained experimentally. The optimal concerning of heat transfer intensity position of the field source was found.

Purpose. Characterization of the chemical structure of boron nitride nanoparticles by IR spectroscopy during the evaporation of their colloidal system and their sizes by small-angle X-ray scattering.

Methods. The solvent evaporation process from the colloidal system was studied using a Nicolet iS 50 FT-IR spectrometer in the mid-IR range (400 – 4000 cm^-1), with an attenuated total reflectance accessory with a diamond crystal (incident angle of 45°) and a liquid cell (200 μL). The sizes of the colloidal particles were determined using an smallangle X-ray scattering diffractometer in linear collimation mode (resolution 0.03 nm^-1, copper anode X-ray tube 2.2 kW, λ = 0.154 nm, exposure time 30 s).

Results. The IR spectrum of boron nitride nanoparticles powder was measured, containing lines characteristic of cubic (952 cm^-1) ) – c-BN and hexagonal crystalline phases (758, 1301, and 1372 cm^-1)  – h-BN. The average size of boron nitride nanoparticles in the colloidal system, according to small-angle X-ray scattering data, was 46 and 84 nm. The size of stearic acid, which acts as a stabilizing shell, was 0.8, 1.3, and 2.5 nm. Analysis of the IR spectra showed complete evaporation of the solvents (hexane and chloroform) from a drop of colloidal solution 1.2 mm thick within 30 minutes.

Conclusion. In this work, the average sizes of boron nitride nanoparticles stabilized with stearic acid in a colloidal system were determined and the process of its evaporation was studied.

Purpose of research. To obtain analytical expressions that allow calculating the strength and velocity of a moderately large, highly viscous droplet, taking into account the direct contribution of the evaporation coefficient, linear corrections by the Knudsen number and the reactive effect of a plane wave moving in the field of mono-chromatic radiation

Methods. Methods of perturbation theory, gas kinetic methods, mathematical methods for solving linear partial differential equations with variable coefficients (the system of Stokes equations, Laplace and Poisson equations) were used.

Results. In a quasi-stationary approximation, a theoretical description of the photophoretic motion of a moderately large evaporating highly viscous spherical droplet (there is no circulation of matter inside the droplet and interfacial surface tension forces) in a viscous binary gas mixture is carried out. A velocity-linearized system of Navi-Stokes equations and heat and mass transfer was solved. Expressions are obtained for the fields of mass velocity, pressure, temperature and the relative numerical concentration of the first component. The strength and speed of photophoresis of a highly viscous droplet was determined by integrating a stress tensor over the surface of the particle. Under boundary conditions on the surface of a highly viscous droplet, linear corrections in terms of the Knudsen number (isothermal, thermal and diffusion slips, temperature and concentration jumps, as well as sliding due to temperature inhomogeneity along the curved surface of the particle), the reactive effect and the contribution of the direct influence of the evaporation coefficient were taken into account. The contributions to the obtained formulas for the photophoresis of a moderately large highly viscous droplet are analyzed and the preliminary transitions to the results known in the literature (moderately large and large solid particles of spherical shape) are considered 

Conclusion. The obtained formulas based on the hydrodynamic method allow us to evaluate the effect of the direct contribution of the evaporation coefficient and linear corrections by the Knudsen number on the strength and speed of photophoresis of a moderately large evaporating highly viscous droplet in a binary gas mixture.

Purpose. Experimental study of the density, thermal expansion and dynamic viscosity of halogenated arenes at temperatures from 293.15 to 343.15 K and atmospheric pressure 97.992 kPa.

Methods. Density was determined by the pycnometric method, viscosity by the capillary method. A quartz pycnometer type PZh2 with a nominal capacity of 10 ml and a glass capillary viscometer type VPZh-2 with a nominal capillary diameter of 0.34 mm were used. The mass of liquids was measured using an electronic scale VSL-200/0.1A with a division value of 0.0001 g. Numerical methods were used to process the experimental results.

Results. Experimental data were obtained on the density, coefficient of volumetric thermal expansion and dynamic viscosity of liquid o-xylene, ethylbenzene, fluorobenzene, chlorobenzene, bromobenzene, toluene, o-fluorotoluene, mfluorotoluene, p-fluorotoluene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, 2,4-dichlorotoluene, 2,6-dichlorotoluene. Density and dynamic viscosity data are approximated by a third-degree polynomial. Data on the coefficient of volumetric thermal expansion are obtained from approximated measured density data. The maximum estimate of the measurement error for density was 0.13 %, for dynamic viscosity – 3.5 %. The maximum calculation error for the coefficient of thermal expansion is estimated at 3 %.

Conclusion. Mathematical processing of the obtained experimental data on density and dynamic viscosity made it possible to obtain analytical relations in the form of power polynomials that allow calculating the values of these quantities at any temperature from the studied temperature range and atmospheric pressure with an error not exceeding the error of experimental determination. The calculated values are in good agreement with the data provided in the reference and scientific literature. The experimental data obtained complement the information on the properties of some of the liquids under consideration, for which the dependences of density and viscosity on temperature are poorly understood. The substances under study are used in various sectors of the economy and are therefore technically important liquids. The measurement results can be used in condensed matter physics, for the analysis of liquid hydrocarbons, and can be useful in the chemical industry.

Purpose. Identification of the behavior of a magnetic polymersome placed in an inhomogeneous field of a point dipole using coarse-grained molecular dynamics simulations.

Methods. The system under the study is represented as a set of interacting particles of two types: polymeric particles simulating a double layer of an amphiphilic membrane, and magnetic nanoparticles located in the membrane layer. Polymeric particles interact through elastic potentials designed to maintain an equilibrium spherical vesicular geometry. Magnetic nanoparticles interact with each other and external fields as point dipoles. The excluded volume and steric interaction of magnetic particles with polymeric walls are modeled in the form of soft repulsion. The entire system is under isothermal conditions, and the model parameters are chosen according to typical interaction energies relative to thermal fluctuations. A model polymersome with a diameter of about 100 nm in an aqueous solution at 25°C is considered. An inhomogeneous magnetic field is created by a dipole of constant direction located at a fixed distance. The dynamics of the system is monitored by numerical solution of the equations of particles motion with introduced interactions and imposed conditions.

Results. In numerical experiments, the response of the polymersome to a magnetic field was obtained for three values of the parameter describing the inhomogeneity of the field. The problem with a gradual increase in the strength (and its gradient) of the magnetic field near the polymersome is considered. Changes in the magnetization of the system are shown, and the redistribution of the concentration of nanoparticles is analyzed. A simulation of the situation when the center of the polymersome at the initial moment was placed at a point with a fixed value of the magnetic field for three cases of inhomogeneity of the field was carried out. A significant restructuring of the magnetic layer of the vesicle combined with movement of the entire capsule was detected. Estimates are made about the average velocity based on the displacement of the object.

Conclusion. The model allows to evaluate the features of the combined magnetic, structural and mechanical response of the polymersome to an inhomogeneous field in the context of potential applications for controlled delivery of contents into cells.

Purpose of the work. Development and testing of a theoretical model of an acousto-optic quasi-collinear tunable filter on crystalline quartz, operating in the spectral range of 0.25-0.4 microns with a spectral resolution of 0.2 nm.

Methods. The paper analyzes the basic properties of acousto-optic tunable filters based on crystals of various classes. Based on literature analysis and calculations, an experimental AOTF model was proposed and practically implemented. The study of the physical properties of light filtration on an α-SiO2 crystal was carried out using an experimental method.

Practical studies of the spectral tuning of the device at experimental optical frequencies were carried out in the proposed ultrasonic standing wave system in accordance with the tuning characteristic. Based on known experimental data, a theoretical model for describing the passband taking into account piezoelectric effects is proposed.

Results. The influence of crystal anisotropy on their acoustoelectric properties is shown. The optimal crystallographic parameters for the operation of filters on a silicon oxide crystal have been determined. A computer model of AOTF has been developed, implemented on the basis of numerical calculations in the Wolfram Mathematica environment. It was experimentally revealed that in the red part of the spectrum under study, the maximum intensity of the frequencies of diffracted light is observed, which corresponds to those closest to the natural frequencies of the piezoelectric transducer, while at the same time, in the blue and violet spectra, the lowest transmission was observed. Practical studies have confirmed that the broadening of the filter passbands occurs due to an increase in the divergence of light.

Conclusions. A mathematical model of an acousto-optic quasi-collinear tunable filter on crystalline quartz was substantiated and developed, on the basis of which the calculation of the AOTF operating in the spectral range of 0.25 - 0.4 μm with a spectral resolution of about 0.2 nm was performed.

Purpose of the article. Identification and analysis of mathematical expressions for the energy spectrum of charge carriers in nano-sized magnetic films of nickel and Ni-Cu (substrate), as well as NiO-Ni-Cu (substrate) structures.

Methods. In this work, based on basic quantum mechanical concepts and taking into account the boundary conditions for coupled quantum wells, expressions for the energy spectrum of electrons are obtained. The ferrimagnetic properties of nickel are taken into account through the effective mass value. The solution of nonlinear equations that determine discrete energy levels was achieved by numerical methods using the Mathcad mathematical package.

Results. Transcendental expressions for the energies of free charge carriers in quantum wells of ferromagnetic nickel films are obtained, and the influence of the position of nickel on the copper substrate is shown. It has been shown that the use of a copper substrate leads to an increase in the density of energy levels in the nickel nanofilm. The influence of the oxide layer on single-electron states in nanofilms of nickel and its oxide is considered within the framework of the Anderson model. Based on the numerical solution of the transcendental equations obtained in the work, the influence of the ratio of the thicknesses of a ferromagnetic metal and its oxide on the energy levels of electrons localized in the oxide layer is shown.

Conclusions. The formulas presented in the work for the energy spectrum take into account the energy relief of a complex quantum well, the dimensions of the film, surface oxide, and the significant effective mass in the region of the ferromagnetic film. It has been shown that an increase in the effective mass in magnetic heterostructures leads to an increase in the electron density of states. It was found that the density of electronic states in the region of surface nickel oxide is practically independent of the thickness of the nickel film. The results and conclusions of the work can be used for theoretical prediction of the physical properties of magnetic nanostructures, in particular spintronic elements.

Purpose of research. Study of morphological and phase changes in the structure of tantalum nitride nanofilms formed by magnetron reactive sputtering on a silicon substrate.

Methods. Magnetron sputtering on a silicon substrate was performed using the MVU TM-Magna T setup with the sputtering time parameter changing from 300 to 900 sec, and also with constant power parameters of 500 W and working gas pressure of Ar 0,5 Pa. The morphological and phase changes in the structure of tantalum nitride nanofilms were studied using atomic force microscopy and X-ray phase analysis. The fractal dimension was determined using the cube counting method. X-ray diffractometric analysis in the in situ measurement mode with discrete heating (in 100 °C increments) in air up to 1000 °C using the PAAR HTK-16 high-temperature attachment.

Results. Using atomic force microscopy methods, it was found that the granulometric distribution of nanoclusters in the studied TaN nanofilms was Gaussian and an increase in the lateral size of particles was observed with an increase in the deposition time. The nanofilm with a deposition time of 300 s had minimal roughness. The statistical fractal dimension was calculated, the value of which corresponded to their three-dimensionality. According to the X-ray phase analysis data, the sizes of the coherence region, texturing, microdeformations and interplanar deformation distortions were determined, and a mixed Stranski-Krastanov mechanism of nanofilm formation was established.

Conclusion. The surface roughness of nitride nanofilms formed at a constant power (500 W) depends significantly on the magnetron sputtering time and N2 concentration. In all studied nanofilm structures, the dominant growth mechanism was the mixed Stranski–Krastanov mechanism.

Purpose of research. The aim of the study is to systematize the latest literature data related to the modulation of the friction coefficient by external fields when using lubricant compositions with liquid crystal mesogens and polymer composites.

Methods. The article considers the methods of tribological tests using various schemes of friction pairs (cylinder-disk, pin-on-disk). Some commonly used methods of applying coatings to the elements of friction pairs are considered: ion beam-assisted deposition, chemical and physical thermal spraying, molecular layer deposition, photopolymerization, etc. Of the discussed methods of characterizing tribosystems, the following are indicated: dielectric spectroscopy, Raman scattering, polarization optical microscopy, nuclear-physical methods (positron annihilation spectroscopy and Xray diffraction).

Results. The article systematizes modern trends in the development of modulated modes of operation of tribological circuits with lubricant compositions containing liquid crystals and polymer composites. The following approaches are used to implement active control of the friction coefficient: 1) modulation of friction by an electric field, 2) modulation of friction by a temperature field, and 3) modulation of friction on optical gratings under light irradiation. These approaches take into account the changed characteristics of the lubricant associated with the use of mesogenic additives, modes of exposure to electromagnetic and thermal fields, electrical characteristics, geometry of the surface of friction pairs, and provide the values of tribological characteristics (friction coefficient and wear) that are achieved as a result of friction modulation.

Conclusion. A positive effect of mesogenic additives of liquid crystals and polymers on tribological characteristics with active control of the friction coefficient has been established: a decrease in the friction coefficient is observed, which helps to reduce material wear.

Purpose. To investigate the change in the mechanical properties of a magnetorheological silicone elastomer consisting of a polymer filled with magnetite nanoparticles under the influence of an inhomogeneous magnetic field of an electromagnet.

Methods. The experiments were carried out on a magnetic response research facility developed and manufactured independently based on known methods. The value of the deflection angle of the magnetically active receiver was determined by the optical method. Two-component silicone rubbers filled with magnetite particles were studied as samples. The manufactured samples differed in geometric dimensions, magnetic phase concentrations of 1%, 5%, 10% and 20%, and polymerization mechanism. The source of the magnetic field was electromagnets of various sizes connected to power sources. The images were captured using a Micmed 5.0 digital USB microscope.

Results. The analysis of the structure of the manufactured magnetorheological silicone elastomers was carried out, as well as studies of the effect of the magnetic field strength and sample parameters on the deflection angle of the magnetically active cantilever. A theoretical interpretation of the obtained results is proposed.

Conclusion. The experimental dependence of the tilt angle of a magnetically active polymer cantilever on the equilibrium position relative to the magnitude of the magnetic field strength of the electromagnet is determined. The obtained research results can be used to develop actuators and magnetoactive sensors.

The purpose of the work was to study the options for volumetric analysis of isocyanate groups in prepolymers and to search for factors affecting the accuracy of the analysis in order to identify differences between the values specified by the manufacturer and those obtained in the laboratory.

Metods. Intermediate polymerization products based on isocyanates from two or more monomeric units used for the production of polyurethanes, the quality of which is determined by the optimal ratio of isocyanate and hydroxyl groups, were selected as the object of research. The NCO index was determined by the volumetric method based on the interaction of isocyanate groups with diethylamine, with confirmation of the results by methods of mathematical statistics.

Results. the work analyzes currently known methods for determining the content of isocyanate groups in prepolymers and identifies differences in the technique of execution. A volumetric method for determining the NCO index based on the interaction of isocyanate groups with diethylamine was used. The solubility of industrial prepolymer samples was evaluated and the dissolution rate was calculated, on the basis of which the optimal volume of the solution and prepolymer samples were determined, providing an accurate determination of the isocyanate number. The adjusted conditions allowed us to reach the required value of the NCO index of the SKU prepolymer, calculated on the basis of static processing of the results and the construction of the Gauss distribution curve. Changes in the methodology make it possible to reach a certified value of the indicator, which allows its use for further calculations in the synthesis of polyurethane.

Conclusion. Recommendations for determining the isocyanate index for the analysis of prepolymer by the volumetric method will help to monitor incoming raw materials for compliance with certificates to perform an accurate calculation of raw materials in the synthesis of polyurethane.Key words: prepolymer, polyurethane, isocyanate index, volumetric analysis, diethylamine, solubility.