Purpose. Investigation of the relationships between the composition, structure and properties of the initial Cobalt metal waste and the powder obtained by crushing these wastes by electric erosion in liquid dielectrics.

   Methods. Finely dispersed powder from Cobalt metal waste of the K1Au brand was obtained on an original patented installation in a liquid dielectric medium - distilled water by electric erosion. The pieces of the metal tube were loaded into a reactor filled with a working fluid, and a pulse voltage from a pulse generator was applied through electrodes made of the same metal tube. When the energy was reached to penetrate the liquid dielectric, electrical discharges occurred between the pieces of metal waste to form powder microparticles, which were further investigated by various methods to determine their granulometric, chemical, and phase compositions using modern research equipment.

   Results. It was found that the resulting electroerosive Cobalt powder has dimensions ranging from 0.45 microns to 38.72 microns and contains oxygen on the surface. The phase analysis showed the presence of only one phase in the particles of electroerosive cobalt powder – the Cobalt phase. From the analysis of the particle shape and morphology, it was found that the obtained parts mostly have the shape of a sphere with an average size of 8.6 microns and lumps of agglomerates consisting of finely dispersed particles.

   Conclusion. The obtained research results can be used to develop a new hard alloy using waste materials of expensive cobalt raw materials by the method of electroerosion dispersion with subsequent improvement and optimization of the composition and structure of the alloy.

   Purpose. Determination of the optimal unit operating parameters and molybdenum content in the coating. To achieve optimal performance and proper physico-mechanical properties, it was necessary to conduct a full factorial experiment.

   Methods. The chosen factors were: asymmetry coefficient, cathode current density within the range of 20–60 A/dm², and Molybdenum disulfide concentration within the range of 0.2–3.4 kg/m³. The resulting function chosen was microhardness. Since preliminary research indicated that the response functions should be nonlinear, the factors had three variation levels. An orthogonal central composite second-order design was used to find the polynomial coefficients. The significance of the regression coefficients was checked using Student's t-test, and the adequacy of the obtained equations was verified using Fisher's F-test.

   Results. As a result of the conducted experiments and statistical data processing, a regression equation in coded form was obtained, linking the coating's microhardness with the studied parameters. Analysis of the coefficient significance showed that the MoS₂ concentration has the greatest influence on microhardness. The interaction effects of the factors were also statistically significant. The calculated value of Fisher's criterion was F = 3.87, which is lower than the tabulated value (Ftab = 19.4) at a 95 % significance level. Consequently, the obtained regression equation adequately describes the electrodeposition process within the studied region.

   Conclusion. The method of mathematical experiment planning was successfully applied to optimize the process of electrodeposition of coatings alloyed with Molybdenum disulfide. An adequate second-order regression equation was obtained, linking the coating's microhardness with the asymmetry coefficient, cathode current density, and MoS₂ concentration. The results of the work allow for recommending optimal coating application regimes for their use in conditions of increased wear and corrosion.

   Purpose. Investigation of the mechanical properties of Titanium alloy samples subjected to complex treatment, including thermocyclic treatment, low-temperature ion nitriding and electric spark alloying.

   Methods. A rod made of Titanium deformable alloy of VT20 grade was used as an object of hardening. The thermocyclic processing of the rod was carried out at the IMASH 20-78 installation. Ionic low-temperature nitriding was performed at the ION installation. Electric spark doping of the sample surface was performed on the UR-121 electric spark doping unit. The microhardness of the samples was studied using an Instron instrument. The wear resistance of the samples was studied using a Tribometer friction machine.

   Results. It can be seen from the data obtained that the microhardness of the hardened samples of titanium deformable alloy grade VT20 increased 1.1 times after thermal cycling, 1.24 times after thermal cycling and nitriding, and 2.33 times after thermal cycling, nitriding and alloying. This result was facilitated by the coagulation of VT20 alloy grains and the appearance of Titanium nitride TiN phase in its structure. It can be seen from the obtained data that the average value of the coefficient of friction of hardened samples of Titanium deformable alloy grade VT20 decreases by 1.25 times after thermal cycling, by 1.45 times after thermal cycling and nitriding, and by 2 times after thermal cycling, nitriding and alloying. This result was facilitated by the grinding of alloy grains and the coagulation of α-grains.

   Conclusion. In general, the evolution of the mechanical properties of the studied samples was facilitated by the evolution of their structural and phase state, namely, the finer-grained and highly rigid surface structure of the hardened material. The application of the proposed technology will make it possible to obtain titanium alloys, which should surpass their domestic and foreign counterparts in terms of their combined properties.

   Purpose. Study the morphology and granulometric distribution of new powder materials obtained on the basis of tungsten-free hard alloys by electroerosive dispersion in a carbon-containing medium.

   Methods. To obtain new materials from tungsten-free hard alloy waste, an experimental laboratory setup for electroerosive dispersion was used. Morphological and particle size distribution studies were carried out using a QUANTA 600 FEG scanning electron microscope and an Analysette 22 NanoTec laser particle size analyzer.

   Results. The results of studying the morphology and granulometric distribution of new electroerosive powder materials based on tungsten-free hard alloys obtained in a carbon-containing medium showed that the powder particles have a regular spherical and elliptical shapes, and the particle size ranges from 0,320 μm to 67 μm.

   Conclusion. Based on experimental studies of the experimental tungsten-free hard alloy powder obtained by electroerosive dispersion in kerosene for lighting, it was found that the particles have a regular spherical and elliptical shape due to the process of rapid crystallization of the molten material in the liquid working medium of kerosene for lighting. In turn, the spherical and elliptical particles shapes have a beneficial effect on the compaction of the powder material for its further sintering into a new tungsten-free hard alloy with an obviously low porosity index. The presented results of studying the granulometric distribution allow us to conclude that the production of new powder materials from tungsten-free hard alloys waste by electroerosive dispersion in a carbon-containing medium leads to the formation of the product with an optimal particle size for obtaining a new alloy with specified properties.

   Purpose. Study of electrocatalytic activity of porous composite nanofilms CNPs/CuO, causing degradation of molecular gases.

   Methods. The research methods included the use of a specially designed experimental setup consisting of a glass chamber with a closed-loop air flow system, a blower to generate a constant air flow, and an air filter with composite electrocatalytic nanofilms. During the experiment, isopropyl alcohol and butyl acetate were added dropwise to the chamber. The vapors of these substances, evaporating under the influence of the air flow, passed through the composite filter. The degradation efficiency of volatile organic compounds was recorded in real time using a gas sensor, and in certain series of experiments, Fourier transform infrared (FTIR) spectral analysis was additionally performed to study the processes occurring in the system in more detail.

   The study results demonstrate the high efficiency of the electrocatalytic decomposition of volatile organic compounds on CNPs/CuO composite coatings. Applied electrical voltage initiates the formation of electron-hole pairs, which, by interacting with water and oxygen molecules, generate reactive oxygen species (OH, O₂^-), ensuring the complete mineralization of isopropyl alcohol and butyl acetate to CO₂ and H₂O. Fourier transform IR spectroscopy revealed the absence of characteristic absorption bands of the starting compounds and the appearance of signals from the reaction
products.

   Conclusion. According to the results of FTIR spectroscopy, the passage of high-molecular gases such as isopropyl alcohol and butyl acetate through an air filter with CNPs/CuO composite films with applied electric voltage (9V, 17V) leads to their complete decomposition into CO₂ and H₂O due to electrocatalytic processes occurring on the surface of the synthesized films.

   Purpose of research. Investigation of the functional relationship between integral heat flux and both thermal and magnetic Rayleigh numbers in combined (gravitational and thermomagnetic) convection of ferrofluid within a closed hydrodynamic loop, with assessment of the thermomagnetic convection mechanisms contribution.

   Methods: Experimental data were obtained from a vertical hydrodynamic loop filled with a magnetite-kerosene-oleic acid ferrofluid, subjected to localized heating and magnetic fields up to 29 kA/m. Four ferrofluid samples with identical particle size distributions but varying magnetic phase concentrations were investigated. The dimensionless integral heat flux, expressed as the Nusselt number (Nu), was determined from steady-state temperature profiles along the circuit. Both gravitational (RaT) and magnetic (Ram) Rayleigh numbers were calculated using the channel diameter and temperature difference across the heated section. The ferrofluid's pyromagnetic coefficient was evaluated via a bidisperse model.

   Results: The experimental results demonstrate that the integral heat flux data, including the zero-field case, follow a universal scaling relation Nu = f(Rae).

   Conclusion: To characterize the experimental results, we employed dimensionless parameters—the Nusselt number (Nu) and the effective Rayleigh number (Rae)—which incorporate the system geometry, the ferrofluid's thermophysical and magnetic properties, and the applied magnetic field conditions. Our analysis demonstrates that a universal scaling relation Nu = f(Rae) can be established by defining the effective Rayleigh number as a linear combination of the thermal (RaT) and magnetic (Ram) Rayleigh numbers: Rae = RaT + ζ⋅Ram. This unified representation successfully describes convective heat transfer across all tested conditions, including ferrofluids of varying concentrations subjected to magnetic fields up to 29 kA/m. The empirical coefficient ζ was determined to be 0.29 in our experimental configuration, though we note this parameter may generally depend on system geometry.

   Purpose of research. Testing of the spectral selection method using narrow-band interference filters for the analysis of spatial inhomogeneities in light-scattering and luminescent media using the example of astrophysical objects of various nature.

   Methods. The studies were carried out using a specialized optical complex based on a cooled color CCD camera QHY 533c and selective interference filter Svbony SV220 (Hα and OIII lines). Two optical schemes were used: a wide-field configuration with a 200 mm f/4 telephoto lens for studying large-scale structure, and a high-resolution configuration with an Askar FRA 500 astrograph (500 mm f/5.6) for detailed morphology analysis. Specialized software with implemented algorithms for photometric calibration and mosaic composition was used for data processing.

   Results. For the luminescent medium (IC 1805), a spatial resolution of ~0.04 pc/pixel was obtained, which made it possible to identify structures tens of thousands of AU long and estimate the dynamic pressure of the stellar wind (~10^-11 Pa). For the light-scattering medium (LBN 667), a resolution of ~600 AU/pixel was achieved, which ensured the identification of fibrous structures of substellar scale (< 0.1 pc). The method's capability for selective mapping of various environment components with contrast > 90 % has been demonstrated.

   Conclusion. The spectral selection method demonstrates high efficiency for diagnosing spatial inhomogeneities and can be adapted for solving materials science problems, including the analysis of luminescent coatings, defect control in transparent media, and non-destructive testing of multilayer structures. The development of specialized interference filters for specific technological applications is a promising direction.

   Purpose. Metal-semiconductor contacts form the basis of modern solid-state electronics.

   In the presented work the aim is to study the electrical properties of Ni-GaAs contact structures obtained by electrochemical method.

   The main task was to study the influence of impurity type and doping degree of semiconductor crystals on the current-voltage characteristics of metal-semiconductor contacts.

   Methods. The object of the study is nickel contacts to crystalline gallium arsenide obtained by the drop electrochemical method.

   For the practical production of metal-semiconductor contact structures, a Watts solution was used in the low-current density mode. The surface topography of the formed films was studied using scanning tunnel microscopy. The electrical parameters of the semiconductors were determined by Van der Pauw contact methods. The resistance of current spreading in the contact region was taken into account by means of an analytical solution of the Laplace equation with Neumann boundary conditions on the boundaries.

   Results. Experimental current-voltage characteristics of the investigated Ni-GaAs contacts are obtained and analyzed. Using a mathematical model of potential distribution in the sample area and experimental data, the resistances of nickel-gallium arsenide contacts are calculated and their volt-ampere characteristics are constructed. Energy models of metal-semiconductor contacts in the case of non-degenerate and degenerate GaAs are presented, explaining the electrical properties of the obtained structures.

   Conclusion. It is shown that the obtained Ni-p-GaAs contact structures based on non-degenerate semiconductors exhibit ohmic properties, and the volt-ampere characteristics of the Ni-n-GaAs contacts have a nonlinear region, characteristic of Schottky diodes. The obtained electrochemical contact structures of Ni-GaAs with semiconductors of different types of impurities at a carrier concentration above 10²⁵ m^-3 have only linear volt-ampere characteristics, i. e. ohmic properties are manifested.

   Purpose. Comprehensive study of the effect of the activation process on the morphological, structural, and elemental characteristics of technical Carbon in order to create functional carbon-containing materials with specified properties.

   Methods. Surface morphology and dispersity were investigated by scanning electron microscopy (JEOL 6610LV, secondary electron detector, 20 kV, magnification up to ×100,000). Local elemental composition was determined by energy-dispersive X-ray analysis (Oxford Instruments) with element mapping. Confocal laser microscopy (OmegaScope AIST-NT, resolution up to 300 nm) was used to analyze particle shape, size, and aggregation. Crystallochemical analysis was carried out by the method of rethgenophase analysis of X-ray diffraction (EMMA, CuKα, λ = 1.5406 Å, 2θ range = 10 – 80°). Structural defects and functional groups were identified by the method of Raman scattering spectroscopy (laser λ = 532 nm, spectral resolution 3 cm^-1).

   Results. It has been established that the activation process leads to a significant transformation of the technical Carbon structure. There is a decrease in the average particle size from ~3 μm for pyrolytic Carbon to ~2 μm for the activated form, accompanied by a decrease in the polydispersity coefficient from 1.2 to 0.3, which indicates a narrowing of the particle size distribution. The activation process ensures the uniform incorporation of silicon into the Carbon matrix, reaching a concentration of up to 3.2 at. %, resulting in the formation of a homogeneous Carbon-silica nanocomposite
structure. At the same time, the Carbon component is structurally ordered, reaching the parameters characteristic of graphite with d₀₀₂ = 0.3354 nm.

   Conclusion. Activation of technical carbon allows for the purposeful formation of ordered Carbon-silica nanocomposites with a developed surface and controlled defectiveness, which are promising for use in sorption processes and catalysis.

   The purpose – paper analyzes the phenomenon of radial periodic instability that occurs during the growth of silicon whiskers using model representations of the growth processes that accompany the formation of whiskers during a chemical reaction at the gas-melt interface that leads to its growth.

   Methods. Gas phase deposition in an open SiCl4 + H2system. Mathematical modeling of the silicon separation process during the growth of filamentous crystals, taking into account the metal etching reaction at the gas-melt interface at the crystal tip.

   Results. Within the framework of the model of growth of nanowhiskers controlled by the chemical reaction of silicon separation at the gas-melt interface, the balance of the flows of the heterogeneous reaction of silicon separation and etching of metal from the melt drop at the crystal top is considered. The presence of a chemical metal compound in the gas phase leads to a dependence of the etching flow on the temperature, which has a maximum in the negative region. With the growth of a filamentous crystal on a substrate of limited size, the dependence of the temperature of the crystal-
substrate system on the magnitude of the crystallizing matter and metal fluxes is considered. In the growing section of the curve, the dependence of the metal etching flux on temperature increases, as the temperature increases as a result of heating during crystallization, the influx of metal into the melt drop at the top of the crystal is replaced by etching and a drop in temperature, which leads to the development of an oscillatory process, a periodic change in the radius of the crystal over time.

   Conclusion. A system of kinetic equations has been obtained that explains the occurrence of radial periodic instability in filamentous crystals. A numerical evaluation conducted using the obtained system of kinetic equations confirmed the possibility of developing radial periodic instability in filamentous crystals.

   Purpose. To explore the specifics of microfluidic chip manufacturing technology using soft lithography, including the following stages: channel structure design; mold fabrication using various methods on glass, foil-clad PCB, and silicon substrates; selection of the required polymer, polymerization modes, mold treatment with a release agent, compound filling and subsequent separation, activation, and subsequent bonding of the resulting chip to the prepared glass.

   Methods. Photolithography experiments were conducted using a monochromatic Anycubic Wash and Cure 2.0 light source on foil-clad PCB substrates, glass slides, and silicon wafers. Formwork for the constructs was fabricated using a FlyingBear Ghost 5 FDM printer. Silagerm 2104 and 2106 were used as PDMS. A Diener PICO low-pressure plasma system with an air environment was used for the bonding process.

   Results. Photolithography studies were conducted to determine the exposure time, the method of covering the transfer template, and the substrate material. Experiments were conducted to create constructs and their viability. The effect of gas pressure in a vacuum chamber during plasma activation of the polymer replica surface was studied.

   Conclusion. The experiments identified a silicon substrate as the best master mold material for soft lithography. Parameters for simplified, cost-effective, and safe plasma bonding of PDMS and glass replicas were determined. The results can be applied as protocols for the fabrication of microfluidic devices by small research laboratories.

   The purpose of the research is to experimentally investigation of physical processes in the interelectrode space of the needle-air-liquid-plane system in a strong non-uniform electric field with a positive tip.

   Methods. Video images of the development of a corona discharge and a microplasma structure are analyzed; I-V characteristics are measured, synchronized with the video image.

   Results. An external method for obtaining a stable cold circuit flow in a needle-plate electrode system coated with a layer of weakly conductive liquid is used. Current-voltage characteristics are measured in a corona discharge environment. Visual analysis of the CR and MPS glow allows one to evaluate the ionic composition of the CR and MPS. CVCs are measured at the initial stage of MPS development. The mechanism of MPS formation is studied.

   Conclusion. The study demonstrated that the IVLP system enables a new method for producing stable ion-flux-discharge with a positive tip. The IFD is shown to be consumed only with a positive tip. It was found that IR ignition in this configuration occurs at E* ≈ 3.6 kV/cm and a gradual, smooth increase in current, as the tip-air-flux-discharge system exhibits fluctuations due to unstable ion cloud states. A comparative analysis of the tip field strengths demonstrated that the latest IR ignition parameters are comparable at different polar states, but their ignition mechanisms differ. Visual analysis of the IR and IFD glow spectra allows one to evaluate the ionic composition of the IR and IFD: in the IVLP system, the contribution of OH and O₂⁺ is noticeable, which differs from the IAF system, where N₂ and N₂⁺ emission predominate. The generation of a micro-electron-like particle in the IVZhP system occurs without preliminary ignition of a static CR, as the CR immediately develops into a micro-electron-like particle. The obtained results reveal the potential of this method for the controlled generation of CP and expand our understanding of the principle of ionization with a positive tip.

   Purpose. It is calculated to identify patterns related to frequency-dimensional magnetoelastic effects in a magnet, taking into account DG displacements. To describe the frequency-dimensional effects caused by the geometric parameters of the domain boundaries relative to the voltage wavelength. Since domain boundaries have a certain inertia, this leads to some peculiarities when they shift under the influence of force fields.

   Methods. The paper describes an algorithm for calculating the loss components based on a macroscopic approach, and elucidates the reason for their decrease at critical frequencies in the case of low voltages σ. The review is based on the flexible domain boundary model. The proposed methods for the analytical description of magnetically elastic energy dissipation and machine modeling of the corresponding processes will be useful for both scientific and practical purposes, for example, when creating special electro- and radio-technical ferromagnetic materials.

   Results. The analysis showed that magnetically elastic losses arising from elastic vibrations at critical frequencies in a magnet reach a minimum, provided that the wavefront does not coincide with the plane of the domain boundary in its initial position. This is true for domain boundaries fixed by point or linear defects.

   Conclusion. The approximation of the natural oscillation frequencies of the DG to critical values leads to a sharp increase in the resonant component of internal friction. The resulting value, under the influence of this component, changes slightly. The revealed features of magnetically elastic energy dissipation are of interest in laboratory research and are promising for practice in determining crystal orientation and texture description, as well as in creating new promising magnetic materials.

   Purpose of the research. Comprehensive characterization of lead-acid battery positive electrodes with a double-sided corrosion-resistant Titanium magnetron coating.

   Methods. Magnetron sputtering of a high-purity Ti target onto both sides of standard-sized positive electrode current leads of a 2-volt model cell of the lead-acid battery (two negative current leads and one positive electrode between them) was performed at a power of P = 300 W for t = 10 min. Magnetron films were characterized using X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive analysis. The corrosion resistance and electrical characteristics of 2-volt model cells with positive electrode current leads coated with and without Ti were compared.

   Results. X-ray diffraction analysis revealed the formation of a titanium dioxide oxide film in the magnetron titanium coatings. This film did not alter the measured electrical characteristics and acted as additional chemical passivation. The capacities of fully charged 2-volt model cells, determined in tests under 20-hour discharge conditions with a 0.75 A current and a 50 A cold cranking current at temperatures of -18ºC and -30ºC, were comparable to those of commercially available batteries.

   Conclusion. Lead current leads of positive plates with a titanium magnetron coating demonstrated high corrosion resistance compared to commercially available lead-acid batteries after 26 days of heating at 60°C, including charging at a constant voltage of 2.33 V for 13 days without changing their initial electrical characteristics. Following testing of 2-volt model cells, visual comparison of positive electrode current leads with and without a Ti coating revealed no discontinuities in the grid segments and increased surface development, indicating increased corrosion resistance, which is crucial for the production of such batteries.

   Purpose. In the process of processing the copolymer of dimethyl terephthalate and tetrahydrofuran into finished products, the initial elastomer is subjected to two high-temperature treatments, starting from the raw material preparation stage and including the actual process of converting the material into a finished product. Failure to comply with the drying and extrusion processes can result in a deterioration of the finished product's appearance and performance.

   The purpose of this study is to identify and explain these causes.

   Methods: IR-spectroscopy for structure analysis, physical and chemical methods for determining the fluidity and yield point of the melt, Shore hardness, compression testing, and product appearance control.

   Results. The paper evaluates the effect of heat treatment of a thermoplastic elastomer at the stage of raw material preparation, varying the pre-drying time of a copolymer of dimethyl terephthalate and tetrahydrofuran, on the properties and appearance of the finished product, with an analysis of possible chemical processes of hydrolytic degradation that lead to a deterioration in appearance. The negative impact of excessive melt residence time in the extruder on the performance properties of the finished product has been studied, along with the chemical processes and changes in the chemical structure of the material due to thermo-oxidative degradation.

   Conclusion. It has been established that the presence of moisture in the raw material due to non-compliance with storage conditions and the absence of methods for controlling the water content during the drying process leads to hydrolytic decomposition with the destruction of the polymer chain and the production of an unusable product. Failure to comply with the polymer melt exposure time in the extruder during the processing of the material results in its destruction during thermo-oxidative degradation, affecting the melt yield point and non-compliance with technological requirements.