Surface Engineering and Applied Electrochemistry最新文献

In this work, a harmonic oscillator with elastic elements is adopted as a model of a mechanical system sensitive to various force disturbances. The developed physical and mathematical models for the interaction of the oscillator with the tribosystem model formed the basis for the creation of a method and a set of experimental tools for assessing the tribological state of the contact and the behavior of the sliding tribosystem under dynamic operating conditions. For this purpose, an original installation was designed and built with a specially prepared test chamber using a harmonic oscillator as a sensitive unit. The installation was equipped with a specially developed measuring system for monitoring the state of the tribomodel and the oscillator, implemented using experimental data collection tools (products of National Instruments). According to the methodology, specialized software has been developed using LabVIEW, which allows the collection, processing, and storage of experimental data in large volumes and with high productivity. The experimental tools together with the developed software expand the range of test conditions for sliding tribosystems and make it possible to evaluate their behavior in various dynamic operating modes, including frictional self-oscillations.

Electrical erosion has been experimentally determined for Zn, Al, Zr, Ti, V, Fe, Ni, Co, Cr, Nb, Mo, Cu, and W. A mixture of granules made of the above metals, taken in equal molar ratios, has been used for the first time as a nonlocalized electrode for electric spark deposition of steel 35. A mathematical model for calculating the volume of molten metals under electric discharge conditions during electric spark deposition is proposed based on solving the problem of the thermal field on electrodes using their thermophysical constants. It is shown that the active heat source upon a discharge is an order of magnitude narrower than the erosion zone and three orders of magnitude more powerful than it has been assumed previously. The melt volumes on metals per discharge are calculated and the corresponding series of the electrical erosion resistance of the metals under study is constructed. It is shown that the developed theoretical series of the electrical erosion resistance of metals is in better agreement with the experimental data as compared to the data in the liter-ature.

The paper presents experimental study results of self-oscillations of the current of the recombination wave (RW) type in silicon doped with impurity selenium atoms. Doping of silicon with impurity selenium atoms was carried out using a newly developed technology, which allows for the formation of nanoclusters of impurity selenium atoms in the silicon lattice consisting of Se₂ and Se₄ molecules, without erosion of the surface of the samples. Self-oscillations in the ({text{Si}}leftlangle {{text{Se}}} rightrangle ) samples were detected at room temperature and at sufficiently low electric fields. The dependences of the RW parameters (amplitude and frequency) in the Si(leftlangle {{text{Se}}} rightrangle ) samples on the resistivity and concentration of the formed nanoclusters of selenium atoms, as well as on the influence of a magnetic field, which makes it possible to control the amplitude in the range of J = 10^–5–5 × 10^–3 A and the frequency of self-oscillations of f = 10⁴–(5 × 10⁶) Hz. The mechanism of the observed RWs is explained by the formation of nanoclusters consisting of two (Se₂) or four (Se₄) selenium atoms in silicon, which leads to the formation of fluctuations (clusters) of the main charge carriers and their reaching contact when determining the magnitude of the applied constant electric field. A possibility of practical use of self-oscillations of current observed in silicon diffusion doped with selenium impurity atoms to create solid-state generators is shown.

In this study, the corrosion behavior and microstructural transformations of 1000 series aluminum and copper tubes after an explosive welding process were investigated. Welding was performed with a fixed stand-off distance and various explosion thicknesses. Explosive welding was carried out using a consistent stand-off distance of 2 mm while varying the thickness of the explosive material of 60 mm (sample 1) and 80 mm (sample 2). The explosion velocity employed during the process was measured at 2504 m/s. Optical and electron microscopy images revealed that the thickness of the melting layer at the interface increases proportionally with the thickness of the explosive charge. Specifically, as the explosive thickness increased from 60 to 80 mm, the thickness of the melting layer increased as well. Also, the resuls of the potentiodynamic polarization test indicated a decrease in the corrosion potential from –670 mV (sample 1) to –665 mV (sample 2) as the explosive material thicknesses increased. At the same time, the corrosion current density rose from 52.34 µA/cm² (sample 1) to 78.32 μA/cm² (sample 2). An analysis of the Nyquist diagram for explosive welding samples revealed that the curve radius of sample 2 exceeded that of sample 1, suggesting a higher corrosion resistance in sample 1 compared to that in sample 2.

In this paper, the authors present the design, operating principle, and results from the study of two-phase heat conductors intended for thermal regulation of heat-loaded equipment: ring thermosyphons with a horizontally located evaporator and condenser and a porous coating in the evaporator. Two modifications of thermosyphons—with a cylindrical evaporator and liquid cooling of the condenser and with a flat evaporator and air cooling of the condenser—were tested. The porous wick promotes uniform distribution of liquid and heat flow in the longitudinal and cross sections of the evaporator and equalization of the temperature field over the surface of the evaporator and, consequently, the cooled object. Thermosyphons are made of copper, and the operating fluids are water and freon R245fa.

This work is devoted to the development of a diffusion technology for creating gallium antimonide (GaSb)-type complexes in the silicon crystal lattice, as well as to the study the electrical characteristics of the resulting layers. Based on the X-ray spectral analysis of the microcrystals formed on a silicon sample surface that was simultaneously doped with gallium and antimony atoms, it was demonstrated that the sample surface layer contains microcrystals containing silicon, gallium, and antimony atoms. This allowed to speculate about a possibility of the oriented growth of crystals of the composition (GaSb)_0.8Si_0.2 on the silicon surface. A substantial impact of the processes of the complex formation that occured at high concentrations of ions of diffusing impurities on the distribution profile of charge carriers is demonstrated. Materials containing GaSb-type complexes in the bulk of the silicon lattice can be produced using ion doping, simultaneous diffusion, or epitaxy processes.

The paper proposes to use the method of dividing massive conductors into elementary cells to determine the distribution of the characteristics of the primary electric field at the boundaries of a liquid metal object processed by passing an electric current. Simulation modeling of the characteristics of the electric field in the melt during its treatment with a direct current by one current source or simultaneously by two using two-electrode and four-electrode systems, respectively, was carried out. It is shown that the distribution of potentials and currents at the boundaries of the container with the melt, depending on the type of the electrode system, has qualitative and quantitative differences, which determines their multivariance and makes it possible to find favorable conditions for the thermal force load of the processing object.

The results from the studies into electrical modes of the high-frequency, high-voltage plasma electrolytic oxidation (PEO) on the properties of the formed protective coatings on the B95 T1 and D16ch T aluminum alloys are presented. The control of the PEO process was carried out by changing the amplitude values of anode and cathode voltage pulses. The local mechanical characteristics and the structure of the PEO coatings were studied using instrumented indentation and scanning electron microscopy. As a result of the studies, optimal modes of the PEO process were determined: potentiodynamic modes with a smooth decrease in the amplitude of anode voltage pulses at a speed of 5 V/min and a smooth increase in the amplitude of cathode voltage pulses at a speed of 1 V/min. The coatings formed in the optimal modes of the PEO were characterized by a reduced number of defects (microcracks, craters, pores) and high values of hardness of 27.5–27.8 GPa and elastic modulus of 286–309 GPa averaged over their thickness. These characteristics turned out to be higher by 33–45 and 15–30%, respectively, compared with a hardness and elastic modulus of the coatings formed in other studied PEO modes.

Based on the results of the mathematical modeling and experimental studies of the hydrodynamic characteristics of a high-voltage electrochemical explosion with a controlled input of electrical energy into the discharge channel, а possibility of the targeted and operational control of the force effect on the treatment object during a controlled high-voltage electrochemical explosion is substantiated. By varying the mass of the exothermic composition placed in the inter-electrode gap and the modes of introducing electrical energy into the channel of a high-voltage electrochemical explosion, it is possible to control its hydrodynamic characteristics, forming pressure waves in the medium with a rational spatiotemporal distribution, providing an effective force effect on the treatment object.

The article presents a method for processing whey with low protein content during electroactivation carried out in different electrolyzers with different ratios of the volume of whey processed to the surface of the electrode (cathode), as well as different geometric shapes and different distances between the electrodes and the membrane, which affects the specific energy consumption per unit volume. The recovery of whey proteins depending on the main parameters characterizing electroactivation to optimize the technical characteristics of electrolyzers is analyzed.