The purpose of the work was to develop technological and operational measures for the creation and implementation of wear-resistant protective coatings to harden tool surfaces and improve performance. 

Materials and methods of research. The steels used by 5KHNM, 9KHS, SHX15, used for the production of injection molding molds, as well as the following powder materials were selected as objects of research: PN85Y15, PCM, tungsten carbide. To study the hardening process of injection molding molds by diffusion metallization and laser radiation, samples with a size of 50×10 mm were prepared. During diffusion metallization, coatings with the above powders were applied to the surface of the samples with a plasma torch using the following technology: degreasing the surface with uyat spirit; shot blasting of the surface (to improve the quality of adhesion of the coating to the substrate); plasma spraying of the coating. After diffusion metallization, the mold samples were subjected to diffusion annealing in the atmosphere of a chamber furnace of the OKB-laboratory type and in a protective hydrogen atmosphere. After annealing, the samples were cooled in air. 

Results and discussion. It is established that the degree of hardening of steel under laser heating conditions is greatly influenced by the content of carbon and carbide-forming elements in it. It is shown that the maximum hardening is observed in steel SHX15, since it has an increased carbon content. It is revealed that during diffusion metallization, which includes as an initial operation plasma spraying of chromium coating and subsequent annealing in a protective atmosphere of hydrogen at a temperature of 1200 ℃ for five hours, a diffusion layer with a depth of 20...60 microns is formed on the surface of steel samples of injection molds, providing an improvement in the performance characteristics of the material.

Conclusion. The results obtained can be used to establish patterns of behavior of various types of ingot, powder and composite materials with high dispersion in phase and structural components in various conditions and states.

The purpose. To study the effect of electrodeposition conditions on the submicrostructure of deposits obtained from sulfate-chloride electrolyte.

Methods. For research, an electrolyte containing 200 kg/m³ of ferrous sulfate and 50–200 kg/m³ of ferric chloride was adopted. The submicrostructure was evaluated radiographically on a Shimadzu XRD-6000 diffractometer. The sizes of the regions of coherent scattering and microdistortions were determined by the method of harmonic analysis of the line shape. The dislocation density was estimated using the P.B. Hirsch

Results. The research results have shown that with an increase in the cathode current density from 5 to 25 A/dm², the size of the mosaic blocks decreases, while the magnitude of relative microdistortions and the density of dislocations increase. An increase in the electrolyte temperature from 293 to 343 K leads to an increase in the size of the mosaic blocks and to a decrease in the dislocation density and the magnitude of microdistortions of electrolytic iron deposits. As the solution pH increases, the coherent scattering regions grow up to a certain acidity value (pH), while microdistortions and dislocation density decrease. Then, with a further increase in pH, the coherent scattering regions decrease, while microdistortions and the dislocation density increase; the values of the coherent scattering regions, microdistortions and dislocation density, depending on the pH of the electrolyte, pass through extreme values, which are obtained approximately at pH equal to 1.5.

Conclusion. The study of the effect of electrodeposition conditions on the submicrostructure of the resulting deposits makes it possible to recommend the parameters of the cathode current density, electrolyte temperature, as well as the acidity index of the solution for specific tasks related to improving the reliability and wear resistance of restored machine parts.

Purpose. Conducting an experiment aimed at the study of new tungsten-free carbide electroerosive materials (phase composition) obtained on the basis of waste alloy grade KNT16 in an oxygen-containing working fluid.

Methods. To obtain new experimental tungsten-free carbide electroerosive materials (charges), an electroerosive dispersion unit was used. As a material for processing, the waste of a tungsten–free hard alloy of the KNT16 brand in the form of spent turning and milling plates was selected, distilled water was used as a working fluid. After receiving the electroerosive material, its phase composition was studied by X-ray diffraction using the Rigaku Ultima IV X-ray diffractometer.

Results. During the study, it was experimentally established that the dispersion by electroerosion of the waste of the KNT16 alloy in distilled water leads to the formation of a charge with the following phase composition: TiC, MoNi₃, Ni, Mo, as well as Ni₂O₃, which is formed as a result of the interaction of nickel with oxygen contained in the working fluid. This study confirms the influence of the chemical composition of the working fluid on the phase composition and properties of the resulting erosion material.

Conclusion. The results obtained allow us to conclude that the dispersion by electroerosion of the KNT16 alloy in an oxygen–containing working fluid - distilled water leads to the formation of a charge with a phase composition that allows it to be used as a starting material for the production of new tungsten-free hard alloys.

The purpose of this study is to study the influence of the parameters of an experimental installation for electroerosive dispersion, namely, the voltage at the ends of the electrodes, the frequency of electrical pulses and the capacity of discharge capacitors on the productivity of the process of obtaining the charge of the SSu3 alloy of the acid battery plate

Methods. To carry out the study, a number of experiments were performed on an experimental installation for electroerosive dispersion (. The dispersion process was carried out at the following installation parameters: voltage 100– 200 V, 25.5.–65.5 UF, 25–75 Hz, constant parameters in this study were: the distance between the electrodes  100 mm, dispersion time 300 min. On this equipment, a charge of lead-antimony alloy was obtained in the form of powder. Then the resulting charge was weighed on a laboratory scale "MASSA K", model VK-1500. 

Results. During the study, it was found that the productivity of the charge in the form of lead-antimony alloy powder is higher when the indicator of the variable parameter is higher. When changing the pulse repetition frequency, the maximum powder output was obtained at the highest frequency parameter – 75 Hz. Also in the course of the study, the dependence of the powder yield during the electrodispersion of the lead-antimony alloy SSu-3 with such an installation parameter as the voltage on the electrodes was established, with the same values of frequency and capacitance, it is noted that the higher the voltage index, the higher the productivity of the process, and, accordingly, the production of lead-antimony powder. A study of the performance of lead-antimony powder when changing the capacitance parameter of discharge capacitors showed a direct relationship, the largest powder yield is achieved at the maximum allowable capacity of discharge capacitors at this installation – 65.5 UF.

Conclusion. The obtained results can be used for further study and improvement of the composition and structure of the alloy, as well as for the selection of optimal operating modes of the installation in further studies.

Purpose of research. Study of the composition, structure and properties of composite electrochemical coatings based on electroerosive lead bronze.

Methods. To obtain the charge, an installation for grinding metal waste was used, scrap lead bronze of the BrS30 brand was used as metal waste, distilled water GOST 6709-72 acted as the working medium for dispersion. In accordance with the experimental technology, samples were obtained at the L1 DIGIT installation by adding a universal copper sulphate electrolyte to a suspension of the obtained electroerosive particles, having previously prepared the samples.

Metallographic studies (microstructure, porosity) were carried out using the OLYMPUS GX51 optical inverted microscope equipped with the SIMAGIS Photolab automated image analysis system.

The wear resistance of sintered samples and coatings was determined on a high-temperature tribometer manufactured by CSM Instruments.

The hardness tests of the samples on the surface and the transverse section were carried out using the DM-8 automatic microhardness analysis system using the micro-Vickers method.

Results. In the course of studies of the properties of the coatings obtained, it was found that the addition of a suspension of lead bronze particles to a copper sulphate electrolyte at a concentration of 0.05 g / l leads to an increase in the hardness of the coatings by 12%. The study of the microstructure of the transverse section of the samples showed that coatings were obtained without visible defects at the "coating/substrate" boundary. It is established that there is an increase in the wear resistance of the composite electrolytic coating. The presence of lead inclusions acting as a lubricant helps to reduce the coefficient of friction by 10%.

Conclusion. Based on the presented research results, it can be concluded that due to the hardening of metal vapors in the working fluid during dispersion, electroerosive particles of lead bronze contribute to an increase in the wear resistance of coatings, the presence of lead inclusions leads to a decrease in the coefficient of friction, which allows us to recommend the developed technology for the restoration and hardening of sliding bearings operating under boundary friction conditions.

Purpose of research. To determine the dependence of the pre-sintering parameters on the formation of the structure and properties of high-density dispersed-hardened alloy alloys for further efficient use of heat treatment in order to improve their mechanical and operational properties.

Technological features in the formation of high-quality interparticle fusion of dispersed-hardened materials are considered. Qualitative splicing is primarily determined by the mechanical properties of the alloys, which show the degree of its completeness during sintering. Depending on the density of the materials, the sintering temperature and the percentage of carbon that is introduced into the alloy charge.

To achieve this goal, it was necessary to establish the regularities of the formation of properties and the creation of qualitative bonds between the particles of dispersed-hardened alloys when carbon was introduced into the charge. Methods. This paper provides a detailed description of the heat treatment of alloys and examines the change in structural features compared to compact materials. The test was carried out in a medium of dissociated ammonia at various temperatures. The obtained samples were subjected to mechanical tests.

Results. The following has been experimentally established – The strength and plastic characteristics of sintered alloys are determined from the density of the samples, as well as from the carbon introduced into the charge. According to the data of this work, it follows that sintering for 30 minutes for pure iron alloys is the minimum time at which carbon homogenization occurs in the metal matrix. The sintering temperature of 1100°C for such materials is absolutely reasonable and an increase in the sintering temperature will not matter to accelerate the sintering process.

Conclusions. The paper shows the strength properties of the alloys under consideration, depending on the percentage of carbon content in the initial charge. For the PL-N4D2M alloy, the optimal sintering temperature is 1200°C, which is 100°C higher than the sintering temperature for iron alloys.

Purpose. Standing waves arising in a magnetic fluid layer in the presence of a vertically oscillating magnetic field were investigated experimentally. This paper is a continuation of our previous work aimed to study the free surface deformation of a magnetic fluid layer lying on a liquid substrate in a vertically oscillating spatially uniform magnetic field.  Metods. The research method was based on a standard experimental setup consisting of Helmholtz coils powered by alternating current. It was used to study the stability of a two-layer system of liquids in an alternating vertical field. To effectively process the results of the experiments, the optical part of the experimental setup was modernized, for which the surface of the liquid under study was illuminated by an LED circular light source. To process the profiles of the surface of the magnetic fluid obtained during the experiment, based on GNU Octave, an author's algorithm was developed that allows determining the length of the generated waves. 

Results. The results of an experiment with different thicknesses of magnetic fluid layers in cuvettes of different diameters are presented, processed, and generalized. It is shown that the length of the emerging standing wave decreases with increasing frequency of the alternating magnetic field, increases with increasing cell diameter, and does not depend on the thickness of the MF layer. The wave number of standing waves increases monotonically with the growth of the dimensionless frequency of magnetic field oscillations. All the parameters and dependences considered in the problem are valid for the case of deep water. 

Conclusion. As a conclusion, we note that the results obtained in the course of the experiment expand the understanding of the behavior of multiphase systems with a ferrofluid in a magnetic field.

Purpose. Carry out numerical simulation of electrohydrodynamic heat exchange processes for dielectric liquids in various electrode systems. Obtain a mathematical model for numerical calculations of electrohydrodynamic flows and heat transfer properties of electrohydrodynamic systems using the finite element method; develop a program in the C++ programming language that implements the resulting model; carry out numerical simulation of electrohydrodynamic flows for dielectric liquids in various electrode systems.

Methods. Numerical modeling of EHD processes was carried out using the finite element method using the FreeFem++ library for the C++ programming language, which implements the main algorithms of this numerical method for solving partial differential equations. The three-ion model was chosen as a theoretical model describing EHD processes. As a model of computational fluid dynamics, the k-ε turbulence model was used.

Results. A program has been obtained that implements the three-ion model of EHD processes in numerical calculations of electrohydrodynamic flows by the finite element method for the two-dimensional case, numerical simulation of electrohydrodynamic flows has been carried out, as well as the calculation of the density of the injection and impurity charge, for dielectric liquids in systems of electrodes of the type " two parallel wires", "needle over plane" and "plate capacitor".

Conclusion. The obtained software implementation of the application of the three-ion model for numerical calculations of EHD processes makes it possible to simulate EHD flows in various electrode systems, which can be useful for a theoretical analysis of the prospects for using one or another electrode geometry for practical purposes.

Purpose of the study. The purpose of this work is to conduct a model experiment to study the possibility of external adsorption capacity of carbon nanotubes containing impurity boron atoms in relation to fluorine and chlorine using modern quantum chemical calculation methods, namely density functional theory.

Methods. In order to clarify the mechanisms of adsorption of gas atoms onto the surface of borocarbon nanotubes and the dependence of these processes on the concentration of impurity boron atoms, the results of model experiments conducted using the density functional theory (DFT) were used.

Results. With an increase in the concentration of impurity boron atoms, positive effects are observed due to the greater electrical inhomogeneity of the structure under consideration. That is, a heterostructure based on the equilibrium concentration of boron and carbon is a very likely chlorine adsorbent. As in the case of atomic chlorine, the most probable adsorption centers upon addition of atomic fluorine are either the boron atom itself or the bonding center between boron and carbon.

Conclusion. Model experiments have allowed us to conclude that the introduction of impurity boron atoms into carbon nanotubes makes them a promising material for solving one of the key problems of modern society – protecting the environment and human health from harmful gases.

Purpose of research. The study of the features of the formation of quasicrystalline films and the conditions for the formation of quantum dots in their structure as electromagnetic traps for electrons or protons.

Methods. A method of modeling the structure of clusters in the approximation of absolutely hard spheres on the principles of close packing of particles and the rule of the "golden section" is applied.

Results. It is shown that in the structure of quasicrystalline films, the formation of quantum dots is possible, which are potential wells of various shapes with quantized motion of an electron or proton. In the case of an electron in a potential well, such a well becomes a source of electromagnetic radiation in the ultraviolet region of the spectrum; in the case of a proton in a potential well, the radiation of a quantum dot is in the infrared region of the spectrum.

Conclusion. When a crystal surface is irradiated with proton-ion fluxes with a certain ratio of the diameters of the atoms of the irradiated metal and the ions of the irradiating flux, a quasicrystalline film with a densest packing of atoms can form on the crystal surface. In the structure of the quasicrystalline film, atom-free regions of the order of 1 Å in size are formed, which are traps for protons from the irradiating flux, so a quantum dot appears.

The atomic packing of a quasicrystalline film is a packing of equilateral Penrose rhombuses at the vertices of which are the centers of mass of atoms.

A mathematical relation is obtained that allows one to predict the radii of the ions of the irradiating flow for the formation of a quasicrystalline film and to choose the atomic composition of the resulting film with predetermined properties.

Purpose of research. To construct a method for the analysis of temperature measurement results in an experimental investigation of thermomagnetic convection in a closed hydrodynamic circuit.

Methods. The experiment was carried out using a long closed hydrodynamic loop made of a thin tube of circular cross section. A short vertical segment of the loop, located in a gradient magnetic field with an intensity amplitude of 24 kA/m, was heated. The heat was removed from the entire surface of the loop tubes by blowing them with thermostatic air. The experiments were carried out with colloidal solution of magnetite in paraffin stabilized with oleic acid. Control measurements in zero magnetic field were carried out using pure illuminating paraffin. An exponential temperature distribution was established in the steady-state flow regime along the circuit. The exponent was measured. The results of the temperature measurements were analysed using approximate solution of the convective heat transfer equation in the cooled section of the circuit. The solution used a parabolic approximation of the velocity profile and the smallness of the molecular axial heat flux compared with the convective axial heat flux.

Results. It is shown that the exponent measured in the experiment is sufficient to obtain information about the intensity of the axial heat flux. The calculation formula for Nusselt number taking into account geometric parameters of the circuit, fluid properties and heat exchange conditions has been proposed. Dependence of Nusselt number on Rayleigh heat number is plotted for all series of measurements. It has been found that the heat transfer along the loop has increased by a factor of 3 to 3.5 due to the thermomagnetic convection mechanism in comparison with the results of the control experiments.

Conclusion. The method of analysis of temperature measurements during experimental investigation of thermomagnetic convection in a closed long hydrodynamic loop has been proposed. The method has been experimentally tested.

Purpose of the study. Study of the influence of an external stationary magnetic field on the process of photocatalytic degradation of methylene blue in the presence of ultrafine particles of zinc oxide and under the influence of ultraviolet radiation.

Methods. Determination of the degree of photochemical degradation of the dye methylene blue by optical spectrometry using a set of spectrophotometric equipment based on SF-2000 and HR-2000 spectrophotometers. Characterization of the size distribution of photocatalytic zinc oxide particles using SmartSPM atomic force microscopy (AIST-NT), elemental composition on a JEOL 6610LV scanning electron microscope with an energy dispersive analysis attachment

(Oxford), structure and phase composition using X-ray phase analysis on an EMMA X-ray powder diffractometer (Australia).

Results. Dispersed zinc oxide particles synthesized by the sol-gel method have a size from 30 to 120 nm with an average quantitative size of 60 nm. The crystallographic structure of the photocatalyst at interplane distances corresponds to the zinc monoxide of the hexagonal syngony.   An analysis of the data on the process of photocatalytic degradation of methylene blue shows that the photoactivity of zinc oxide particles increases significantly under the action of an external stationary magnetic field. Thus, it was established that in a constant magnetic field of 0,56 Tl, the photocatalytic activity of ZnO particles increases by 20%.

Conclusion. Based on the experimental data obtained, it can be concluded that the introduction of a constant magnetic field can significantly increase the rate of photocatalytic decomposition of methylene blue. The presented results can be applied to industrial water purification from pollutants. By changing the magnitude of the magnetic field, it is possible to control the intensity of decomposition of pollutants.

Purpose of the study. Show the possibilities of using ion-selective potentiometry to assess the compliance of the quality certificate of an organic acid, a product of the chemical industry, with the declared range and content of the main substance. On the example of oxalic and benzoic acids, demonstrate the possibility of determining the equivalence point using a glass electrode as an indicator. Develop a methodology for assessing the compliance of the declared range of organic acids with the gross formula in the quality certificate by comparing the experimentally determined molecular weight with the calculated one.

Methods. The technique of potentiometric acid-base titration was applied with the construction of titration curves, determination of the potential jump and the equivalence point. The possibilities of the method are demonstrated on the example of the identification of oxalic and benzoic acids. It has been shown that the method of potentiometric acidbase titration with the construction of titration curves, the determination of the potential jump and the equivalence point can be used to determine the molecular weight of poorly soluble organic acids in water.

Results. On the example of experimental curves of potentiometric titration of oxalic and slightly water-soluble benzoic acid, the possibility of determining the equivalence point from the potential jump is shown. Based on the law of equality of the equivalents of the reactants, formulas were obtained for calculating the molecular weight of an identified organic acid and the content of the main substance. A technique has been developed for assessing the compliance of an organic acid with a quality certificate using acid-base titration with potentiometric indication of the equivalence point by the response of a glass electrode. The technique is applicable to assess the quality of both soluble and poorly soluble organic acids in water.

Conclusion. Ion-selective potentiometry using a glass electrode as an indicator can be used to determine the molecular weight and content of the main substance of weak and water-soluble organic acids, chemical industry products, in order to assess their compliance with the quality certificate.