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Switching the properties of the Ag contact groups of an electromagnetic relay with the electrodeposited Ni-W and Co-W alloy coatings was studied. It is shown that these coatings are able to stabilize the spread of contact resistance within the entire test interval and to increase the service life of Ag contact groups from 2.3 × 106 to 4.5 × 106 commutation cycles. According to our research, the service life of coated contact groups is mainly determined by a change in the surface morphology caused by the electrical erosive transfer of the contact materials and to a lesser extent by the formation of poorly conductive adsorbed hydrocarbon films.

We have developed a solid electrolyte ion source (SEIS) with CsAg4Br2.68I2.32 film deposited on a silver tip. In the paper, Ag+ ion emission was significantly enhanced and the ion current of 1.6 μA was obtained at 168 °C temperature and 20 kV accelerating voltage. I-T and I-U characteristics were well described by the field evaporation (FEV) model, and the surface potential barrier was estimated to be 0.19 eV. Experimental investigations of the Ag+ ion emission mechanisms revealed that the solid electrolyte film plays an important role of ion-transport system, and the emitted Ag+ ions were compensated by the ions diffusing from the silver reservoir (Ag-tip). The developed SEIS was exploited for the synthesis of Ag nanoparticles on Si surface. The average size of these nanoparticles was estimated 15.5 ± 0.3 nm, and the projected range Rp of the low-energy high-dose Ag+ ions implanted Si sample was found to be less than 5 nm using TOF-SIMS depth profiling. The future application of SEISs in ion propulsion systems of miniature spacecraft with limited on-board payloads was discussed, and the thrust was estimated within μN range.

Currently, the main material for the production of solar cells is still silicon. More than 70% of the global production of solar cells are silicon based. For solar-grade silicon production the technologies based on the reduction of silicon from organosilicon compounds are mainly used. These technologies are energy-consuming, highly explosive and unsustainable. The present paper studies the technology of purification of metallurgical-grade silicon by vacuum-thermal and plasma-chemical treatment of silicon melt under electromagnetic stirring using numerical simulation and compares this technology with the existing ones (silane technologies and Elkem Solar silicon (ESS) production process) in terms of energy consumption, environmental safety and the process scalability. It is shown that the proposed technology is environmentally safe, scalable and has low power consumption. The final product of this technology is multicrystalline silicon, ready for silicon wafer production.

As a result of studies of a new gas-discharge current switch in a nanosecond voltage pulse generator, the megawatt power managed to achieve the following operating parameters. The pressure range when the device operated in the break current mode was 30 Pa - 45 Pa; the rise time range of the leading edge of the voltage pulse varied from 30 ns to 100 ns; the minimum recorded value of this parameter was 30 ns. The limit of the generator output voltage with the new device was 70 kV; the limit value of the switched current was 600A.

The paper presents the research results of 3D model of internal macrostructure of a multicrystalline silicon ingot obtained by directional crystallization method using high performance multicrystalline silicon technology. The 3D model is based on digital processing of signal images of photoluminescence intensity from the surface of wafers obtained from the investigated ingot. The purpose of the paper is the experimental study of the heightwise distribution of defect cluster areas in the silicon ingot. The study of the internal multicrystalline structure and the defect distribution in the course of the ingot crystallization using classical methods requires much time and destruction of the sample along the growth direction. This is unsuitable for the manufacturing process. In this paper, the results of the analysis of the defect distribution in the direction of silicon crystal growth are presented. The 3D model construction is performed using the MATLAB software environment.

The paper substantiates the composition and choice of a microgrid for settlements in the Central European part of Russia that are not connected to centralized public electricity networks. An economic analysis of microgrid costs in comparison with traditional methods of power supply (diesel, power lines) has been carried out. The economic advantages of using microgrid are shown both from the point of view of customers and the state in providing the availability of electricity for the population.

Funding Information: This work was supported by the Ministry of Education and Science of the Russian Federation in the frame of the state assignment FSSN-2020-0003. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. The performance characteristics (microhardness, porosity, roughness, and transient resistance) of Au–Ru coatings with and without the Co–W alloy barrier sublayer electrodeposited on the surface of contact blades of commercially produced reed switches were investigated. It was found that the barrier sublayer reduces the average roughness of the coatings without significant change in their porosity. The Au–Ru coatings without sublayer exhibited a greater variation in the transient resistance during an increase in the pressing force. The service time of reed switches with the barrier sublayer increased in both testing modes: in low-power (50 mV, 5 µA, 50 Hz) by more than 4 × 106 switching cycles, and in mean-power (12 V, 0.25 A, 50 Hz) by more than 1.8 × 106 switching cycles. publishersversion published

In this paper, we present the research results of plasma-chemical purification of metallurgical-grade silicon from boron and carbon under the conditions of electromagnetic stirring of silicon melt. The research is carried out by mathematical modeling using COMSOL Multiphysics software. The regularities between the process parameters and the efficiency of silicon purification from boron and carbon are established. The obtained data show that silicon plasma-chemical purification using electromagnetic stirring allows achievement of a purity level corresponding to the solar-grade silicon requirements.

The formation of a copper coating on a nickel substrate upon the electrical explosion of a conductor in the presence of an external magnetic field is studied. The effect of a magnetic field on the morphological and structural characteristics of the coating is established. The dependences of the shape and size of the coating islands on the magnitude of the magnetic field are determined.

The electrophysical (donor-acceptor) properties of the of glass carbon (GC) surface before and after its electrochemical modification in conditions of chemisorption of fluorine-containing nanogroups were studied using the methods of scanning probe microscopy. The values of the coefficients characterizing local (for atomic-scale) electrophysical properties of the surface are calculated on the basis of obtained local spectral dependences of the tunneling current on the tunnelling voltage. Fluorination of the GC surface resulted in change of the ratio of its donor-acceptor atomic characteristics, acceleration of electrode processes, and increase of the overall tunneling activity of local places.

Electrodeposition in pulse current mode of nickel-molybdenum alloy on a nickel substrate was studied. The range of current density variation from 2 to 9 A/dm2 was investigated. The range of pulse and pause step lengths is from tens to hundreds of milliseconds. SEM-images of applied coatings surfaces are obtained. The method of energy dispersive spectroscopy determined that the molybdenum content in the coating is 21-24 wt%. It was found that under transient pulse mode of electrolysis, with the pulse step corresponding to hundreds of milliseconds, the most rigid and smooth coatings of the electrolytic nickel-molybdenum alloy are obtained from ammonium-citrate electrolyte. It is shown that the percentage of nickel in the alloy does not depend on the electrolysis mode.

The paper presents the results of experimental research of a gas discharge current interrupter with a slotted configuration of holes and improved discharge parameters in a high-voltage pulse generator with inductive energy storage. The obtained results showed that in this device, in comparison with the analog, it was possible to reduce the average value of the turn-off time by 2.5 times, the range varied from 40 to 200 ns; the minimum turn-off time decreased by 4 times and was equal to 37 ns. The maximum amplitude of the pulse voltage was fixed at 85 kV, which exceeded the previously obtained value for a device with a slotted configuration by 20%. The increase of the peak pulse power to 24 MW, i.e by 70%, was achieved. The influence of the grid node temperature on the critical charge is shown.

The work presents the data of numerical modeling of silicon vacuum refining at different temperatures under electromagnetic stirring for purification of large volumes of silicon (≈500 kg). Time dependencies of the concentration decrease of impurities (P, Al, Ca, Zn, Na and Cu) at different rates of electromagnetic stirring and silicon melt temperatures are obtained. The influence of the silicon melt temperature on the purification efficiency rate is established. The numerical studies are performed by COMSOL Multiphysics.

Using mass-resolved ion scattering spectrometry, spectra of Ne+ ions scattered at an angle of 120° from the surface of GaP in the energy range of 0.4–1.96 keV have been studied in detail. In the spectra, in addition to the peaks of elastic binary Ne+/P and Ne+/Ga collisions, the peak of sputtered neon ions has been found, as well as the wide peak (a “hump”), the energy of which slightly depends on the energy of primary ions and the intensity considerably increases with an increase in this energy. In our opinion, the main contribution to this peak is made by neon ions that undergo multiple collisions with gallium and phosphorus atoms on the surface and deeper layers of the sample and keep their charge due to reionization processes.

The paper presents the research results of formation features of nanoporous titanium oxide structure under electrochemical anodizing by AC-DC current. It is shown that addition of current AC-component (at the frequency of 100 Hz – 10 kHz) leads to increase of the coating formation rate and to structure quality changes of nanoporous TiO2 coatings: open intertubular space appears, intertubular bridges are formed and the nanotubes section form becomes round.

Ar2900 clusters with energy in the range of 10.4–69 keV were used to bombard the surface of pressed Si nanopowder targets. High nonmonotonic sputtering yield is observed within the energy range of 10.4–34.5 keV, which is considered as enhanced by the finite size effect of the target particles. The cluster bombardment results in the sputtering of Si nanoparticles with a mean size of ca. 12 nm. The number of the sputtered nanoparticles is correlated with the sputtering yield within the energy range of 10.4–34.5 keV. Hence, their formation is associated with the finite size effect. Scanning electron microscopy revealed the formation of debris on the target surface starting at the cluster energy of 15.3 keV, which results in reducing the finite size effect and consequently the sputtering yield. Individual impacts of the argon clusters are observed as craters of 3–6 nm in diameter on the Si particles surface. The crater formation is considered to be responsible for the sputtering at the cluster energy in the range of 15.3–69 keV.

The paper presents the results of modeling and development of a thyratron type grid node with improved discharge parameters of gas-discharge current interrupter for a high-voltage pulse generator with inductive energy storage. With the help of modeling, it is shown that the change in geometry of the holes in the grid assembly does not lead to the dropping of electrical strength index. Advantages of gas-discharge current interrupter with such a grid node in a high-voltage generator are described. 3D model of the fabricated grid assembly is shown. Comparative description of the developed grid node and existing analogs is given.

Silicon is the main material for solar cells production. The silicon growing technology improvement, its cost reduction is the important task for the development of photovoltaics. The paper presents the research results of electromagnetic stirring of silicon melt by mathematic modeling using COMSOL Multiphysics software. The effect of electromagnetic stirring under conditions of various configurations of an alternating magnetic field is investigated. The efficiencies of various configurations of stirring field are compared with the qualitative and quantitative characteristics of mass transfer within silicon melt. The interconnection between the parameters of electromagnetic stirring and the characteristics of the silicon flows induced by the field, as well as the rate of surface mass transfer of silicon melt is established. The research was carried out by mathematical modeling.

The paper presents the results of mathematical modeling of vacuum refining of silicon melt under the conditions of electromagnetic stirring. The results of calculations of the dynamics of silicon purification from impurities (e.g., P, Zn, Na) with high saturated vapour pressure at the temperature above the silicon melting temperature are presented. The effect of the electromagnetic stirring rate on the silicon purification rate is determined. Basic regularities and factors limiting the purification rate are shown. The research is carried out by mathematical modeling using COMSOL Multiphysics software.

Currently the improvement of stand-alone PV power systems characteristics, including increase of their service life is the actual direction of ground solar power development. The analysis of stand-alone PV power systems efficiency with the use of ultra capacitors is carried out by the means of mathematical modeling. The obtained data shows that the use of ultra capacitors as additional short-term energy storage devices in stand-alone PV power systems contributes to considerable increase of storage batteries lifetime and the total system operating time.

The paper presents an approach to the development of microgrid on the basis of renewable energy sources for settlements in the Central European part of Russia not connected to centralized electrical network providing comfortable level of the population living. The paper determines the annual power consumption and energy as well as firm capacity which are to be provided by microgrid. The optimum relationship of PV and wind power stations is determined; the structure of microgrid providing continuous power supply of a customer is determined.

The paper presents the research results of interaction of inert gas (argon) plasma jet containing chemically active impurity vapors with the surface of silicon melt under the conditions of its high turbulence to determine the optimal conditions for purification of silicon for solar cells. The interconnection between the plasma parameters (current, power) and the rate of surface mass transfer of the silicon melt is established. It has been found that under the conditions of the melt high turbulence the most efficient removal of impurities from silicon melt surface takes place. The research is carried out by mathematical modeling using COMSOL Multiphysics and Matlab software.

One of the major lines of solar energy development is the creation of environmentally friendly, wasteless, and cheap solar-grade silicon production technologies. Currently the main silicon production technologies are based on a reduction of silicon hydrogen chloride compounds: trichlorosilane, tetrachlorosilane, and monosilane. These technologies use environmentally dangerous and nonfireproof compounds in quantity. Such production levels can be profitable only in large volumes (more than 1000 tons per year). This chapter examines the research results of methods of silicon purification by extraction from a solid phase and plasma-chemical purification of metallurgical-grade silicon from impurities to the solar-grade level.

One of the major lines of solar energy development is the creation of environmentally friendly, wasteless and cheap solar-grade silicon production technology. Currently the main silicon production technologies are based on reduction of silicon hydrogen chloride compounds: trichlorosilane, tetrachlorosilane, monosilane. These technologies use harmful and potentially dangerous compounds in quantity. These productions can be profitable only at big volumes (more than 1000 tons per year). The paper presents the research results of mathematical modeling and experimental research of metallurgical-grade silicon purification by the method of plasma chemical treatment of silicon melt up to solar-grade level with further direct crystallization in one reactor.

The main features of electrochemical deposition of coatings based on Ni&ndash, W binary alloy in the pulse current mode using pyrophosphate electrolytes were studied. Two electrolytes with a pH of 8.7 and 9.5 were used. The deposition was carried out with the current density varying in the range of 0.01&ndash, 0.1 A&middot, cm&minus, 2, and the duty cycle (the relative pulse duration) was changed within the range 20&ndash, 100%. The surface morphology and elemental and phase composition of the coatings were studied by scanning electron microscopy, energy-dispersive X-ray microanalysis and X-ray diffractometry. The experimental conditions allowing us to achieve the maximum Faradaic efficiency and W content in the coatings were determined. It was found that the pulse current mode enabled the fabrication of crack-free coatings with a thickness greater than 6 &mu, m.

Results of the fulfilled calculations have shown that the design with a moving magnetic beam and a fixed magnetic field concentrator provides an increase of the magnetic sensitivity approximately in 2 times in comparison to the design without concentrators, besides inertial resistance of the switch does not change. It allows stating that usage of magnetic concentrators is an effective method of the magnetically operated MEMS-switches operating characteristics increase. It was shown that usage of crank torsion anchors for the ferromagnetic beam mounting is also an effective method of the magnetic sensitivity increase providing possibility to decrease of mechanical stress caused by the commutation.

The paper presents the results of numerical modeling of thermomechanical stresses and thermal fields for conditions of erosion-resistant electrode coatings of magnetically controlled MEMS switches with W-Ti-Cu structure at local temperature and electric current influence in axially symmetrical approximation. It is shown that the introduction of titan interlayer (30-100 nm) in the coating with W-Ti-Cu structure results in considerable (more than two times) decrease of internal thermomechanical stresses between layers that increases coating resistance to delamination. It is established that there is an optimum value of Ti layer thickness at which the minimum thermomechanical stresses are provided.

The paper presents complex research of the structure and electrophysical properties of thin films on the basis of Cr2O3, V2O5 and SiO2 oxides compounds. The paper studies binary compounds films of Cr2O3 -V2O5 and Cr2O3 - V2O5 -SiO2 films. The method of electron-beam evaporation is used for the films deposition; glass is used as the substrate. The films structure is studied by the methods of slow electron diffraction, infrared spectroscopy, and electron paramagnetic resonance. The films composition is determined by the X-ray microanalysis.In the course of studies the following regularities have been established:- dependence of the films structure on their composition;- dependence of electrophysical films properties on the their composition;- dependence of volt-ampere characteristics on the films composition (memory effect);- high film stability to the effect of electron flow and radiation in the discharge plasma.

The paper reports the tests results of ruthenium contacts coatings of magnetically controlled MEMS switches. During the tests the contact resistance was measured and the lifetime of MEMS switches was evaluated. After testing the analysis of the form and contact surface structure using SEM-method was carried out. The experiment results showed that the application of ruthenium nanolayers as the contact coating at slight increase of the contact resistance improves the lifetime of MEMS switches considerably.

The paper reports the tests results of ruthenium contacts coatings of magnetically controlled MEMS switches. During the tests the contact resistance was measured and the lifetime of MEMS switches was evaluated. After testing the analysis of the form and contact surface structure using SEM-method was carried out. The experiment results showed that the application of ruthenium nanolayers as the contact coating at slight increase of the contact resistance improves the lifetime of MEMS switches considerably.Nowadays the increase of the lifetime of all MEMS switch types (RF MEMS relays, magnetically controlled on-off MEMS switches) is the most actual problem. The work resource and operating characteristics, first of all, contact resistance, of any switching unit, the basis of the construction of which is a dry contact, are determined by the contact coating properties. This is true for MEMS switches too.The paper presents the results of the study of the operating characteristics of magnetically controlled MEMS switches with ruthenium and gold contact coatings of up to 100 nm thickness. During tests the following switching mode was used: switching voltage – 3 V, current - 10 μA. Each MEMS switch was subjected to 100 million cycles switching at the frequency of 100 Hz. After testing the contact surface investigation by SEM-method and electrical characteristics measurement was carried out. The paper presents SEM-images of the contacts surface and statistical date of electrical characteristics.After 100 million switching cycles MEMS switches with nanoscale ruthenium coating have shown 100% operating capacity; 16% of switches with gold contacts turned out to be inoperative due to electrical contacts sticking.The results of researches by SEM-method show that the contacts without nanoscale coating have the traces of strong erosion and melting; the contacts with nanoscale ruthenium coating practically did not change the form and flatness.So, the test results indicate that nanoscale ruthenium coatings of the electrical contacts provide excellent resource for the switches operation of hundred millions and more cycles.

The paper studies the theoretical analysis of silicon purification process using the method of extraction from solid phase in fine-dyspersated condition. Axial profile impurity concentration in silicon particles, time dynamics of average impurity concentration at various purification conditions (temperature, particle size, impurity concentration in extractant) are obtained by numerical simulation. The requirements to a particle size and temperature condition when practically important purification efficiency is reached, are determined. The design of an industrial-scale plant is shown schematically.