2–13 nm gold films were obtained by the method of ion-beam sputtering on silicon and quartz substrates. It is shown that the use of an additional operation of deposition followed by the sputtering of a gold layer of 2–3 nm thickness makes it possible to reduce the electrical resistance and surface roughness of the metal films, in comparison with similar films obtained without its use. The results of measuring the temperature coefficient of resistance of nanosized gold films on silicon substrates allowed us to conclude that the films deposited become continuous at a thickness of 6-8 nm. The results of optical measurements of 10 nm gold films, obtained on quartz substrates, showed that the reflection coefficient of electromagnetic radiation at a wavelength of 850 nm is 2.8 % higher than the corresponding coefficient for the same films obtained without using this operation, and is 83 %. An important role in the formation of nanoscale gold layers is played by the processes of self-irradiation of the growing layer of the high-energy component of the gold atoms flux. When using an additional operation of deposition/sputtering, high-energy gold atoms are implanted into the substrate to a depth of about 2 nm. On the one hand, these atoms are point defects in the surface damaged layer of the substrate; on the other hand, they serve as additional centers of cluster formation. This ensures strong adhesion of the metal layer to the substrate and, therefore, the gold films become continuous and more homogeneous in microstructure. The method of ion-beam deposition can be successfully applied to obtain high-quality conductive optically transparent nanosized gold films.

v

The possibilities and methods of creating a stable defective structure, including dislocation structure near the zones of p–n-transitions of silicon diodes of noise generators on plates with crystallographic orientations (111) and (001) have been investigated. The effective distribution control of uncontrolled impurities in monocrystalline silicon is achieved by forming a stable dislocation structure in its volume. In order to obtain the reproducible characteristics of noise generator diodes, it is necessary that the dislocation density be homogeneous throughout the plate area. Since the density of dislocations is slightly lower at the edge of the dislocation trail than in the middle, this means that the dislocation traces formed by the adjacent melting zones with the help of a laser beam should overlap. On the basis of experimental studies, it has been established that the necessary degree of uniformity of the density of defects generated is achieved by compliance with the condition of a = (1.5–5.0)d, where a is a step, d is a width of the laser spot on the wafer. The melting process was carried out in a nitrogen environment using a laser hettering unit. The real width of the melting zone turns out to be slightly larger than the diameter of the laser spot due to the thermal conductivity of the silicon and is about 10 μm. Increased dislocation generation on the Si3N4 inclusions, as opposed to dislocations on the Si–SiO2 border, leads to an additional expansion of the dislocation track at the work surface of the plate of noise diodes. The presence of the stable dislocation structure, as well as the presence of impurities and secondary metal atoms in the noise diodes ND 103L structure are confirmed by the secondary ion mass spectroscopy (SIMS) method. The results of the study have been tested at Corporation “INTEGRAL” (Belarus) and can be used in the manufacture of silicon noise diodes.

Tribotechnical tests and microstructural studies were carried out. Wear mechanism of nanostructured metalpolymer self-lubricating composite materials has been established. This mechanism involves in the formation of separating polymer layers on the friction surface, which reduces the coefficient of friction and running-in period of parts of friction units. Carbon nanoparticles move along the friction surface, hinder the development of seizure processes during the interaction of microroughnesses of the contacting surfaces of the material and the counterbody during the destruction of the separating polymer layers. It was found that the polymer filler is displaced from the friction zone, carbon nanoparticles are pressed into the open areas of the surface of the copper matrix of the composite when the pressure in the tribocontact is higher than 1.5 MPa. The temperature in the tribocontact increases, the polymer filler degrades, the carbon nanoparticles are removed from the friction zone, the strength properties of the composite decrease, the friction coefficient and the wear rate increase at a sliding speed above 1.5 m/s. The obtained research results can be used in mechanical engineering, transportation industry and power engineering.

With the development of minimally invasive treatment technology, coronary stents made of corrosion-resistant steel are in demand for restoring the patency of blood vessels. The effectiveness of coronary stenting depends on various factors, but the quality of the surface of the stents is a major factor. The higher the quality of the surface of the stent is, the less negative the effect on the circulatory system, arterial walls, and the higher the biocompatibility of the stent is. The complex shape, small cross-section, size, and low rigidity of coronary stents are the main reasons for the inability to ensure high surface quality using mechanical finishing methods. Therefore, electrochemical methods are used to polish stents. For electrochemical polishing (ECP) of stents, an electric mode based on direct current is traditionally used. The disadvantages of direct current ECP are excessive metal removal and the need to use electrolytes of complex compositions, often containing toxic components. As an alternative to the traditional ECP with the use of direct current, we have proposed a method of pulsed ECP using pulses of microsecond duration for polishing stents. The use of pulsed current allows one to achieve a significant increase in the efficiency of the SEC process, when, due to the localization of the anodic dissolution, the smoothing speed of the microroughness of the treated surface, referred to the total metal removal, increases significantly. The paper presents a comparative analysis of ECP modes using direct and pulse current to change the surface roughness, removal, radius of curvature of the edges, and corrosion resistance on the example of stents made of the 316LVM stainless steel. Based on the results of the studies, technological regimes of pulsed ECP were established that provide the highest quality polishing of the stent surface with a small metal removal with a slight rounding of the edges.

The article examines the physicomechanical and barrier properties of non-pigmented epoxy coatings formed from various film-forming systems based on epoxy resins and amine hardeners. The barrier properties of the coatings were evaluated by the nature of the frequency dependencies of the capacitance and resistance of the painted metal plates in contact with a 3 % aqueous solution of sodium chloride, and also by the magnitude of the displacement of the open circuit potential of the painted electrode compared to unpainted. It was experimentally established that a higher content of gel fraction is observed for coatings formed from low-viscosity film-forming compositions. It is shown that the physicomechanical and protective properties of epoxy coatings depend on the content of the functional groups in the epoxy resin and the nature of the amine hardener. It was found that to obtain coatings with better properties, it is preferable to use amine hardeners characterized by a low content of amine groups and a reduced proportion of secondary amino groups. A relationship was found between the protective properties of coatings and their water absorption. It is proposed to use the characteristics of water absorption of coatings as a simple method for assessing their barrier properties. The technological aspects of the use of the studied film-forming systems in the production of anticorrosive paints are considered. The advantages of using low viscosity epoxy film-forming systems without inert solvents are shown. 

The aim of the work is to assess the influence of the method for preparing on the porosity of sintered polytetrafluoroethylene blanks as well as PTFE mixtures with carbon fiber and additives of powdered graphite. The article provides a comparative analysis of the method for preparing influence on the microporosity of sintered blanks made of filled and unfilled polytetrafluoroethylene. Microporosity has been determined through the comparison of the actual and theoretical (for a non-porous material) density of blanks, calculated by the methods of structural mechanics of composites. The studies made it possible to establish that the porosity of the unfilled polytetrafluoroethylene blanks pressed at a pressure of 70…80 MPa stands at 1.3 to 5.9 %. An exception was a specimen obtained by sintering in a jig, which has reached apparent density 2200 kg/m3 equal to theoretical density. It has been established, that the porosity of blanks obtained from polytetrafluoroethylene filled with shredded carbon fiber and powdered graphite stood at 0.4 to 3.9 %. An exception was a specimen with a high mass content of filler (40 %), in which the porosity was 16 %. It has been ascertained that sintering in a constrained state helps to reduce the residual microporosity for both the filled and unfilled polytetrafluoroethylene. This shows the technical efficiency of sintering in a constrained state, despite the increased labor intensity of the manufacturing process and the sophistication of technical equipment.

The mathematical analysis of plastic flow processes under uniform plane, axisymmetric and volumetric deformation is carried out. The analysis is based on the external shape change of the body, which determines the movement of material points. It is shown that the plastic flow of an isotropic rigid-plastic body under plane deformation obeys the hyperbolic law, and for axisymmetric and volumetric deformations – the inverse square law. Spatial-geometric expressions of these laws made it possible to reveal and explain in a new way the physical essence of plastic shear. It is proved that the stressed state of a body under uniform tension-compression deformation is complex and cannot be defined as “linear”. The normal stress, which coincides with the direction of the resulting deformation force, is not the main one, since in the areas perpendicular to this direction, the shear stresses are not equal to zero. Examples of solving technological problems are given: extrusion of cylindrical billets and wire drawing, rolling of a wide strip of rectangular profile. It is shown that the problems of determining the stress-strain state of isotropic rigid-plastic bodies along the known trajectories of movement of material points are statically definable.

It is shown that it is very effective to remove corrosion products from various surfaces, including the metal surface of the propeller, using the new technology of reverse-jet cleaning (RJC) developed by the authors. The RJS technology is based on the physical principle that the jet of the working fluid (pulp based on river sand or bentonite clay), upon impact with the surface to be cleaned, turns 180°, which leads to an increase in the jet effect on the surface to be cleaned by 1.5–2 times due to the occurrence of the reactive component. To ensure the marked turn of the jet, an original design of the body was developed, which is distinguished by a patent novelty. One of the main elements in this design is a jet-forming device in the form of a confuser. The presented theoretical studies of the pressure loss of the working fluid in the confuser channel, based on the study of the pressure loss function to the extremum, which made it possible to obtain a dependence for calculating the optimal taper angle in a wide range of Reynolds numbers characterizing the turbulent mode of motion taking into account the influence of the working fluid density and its dynamic viscosity, the average speed of movement of the working fluid, the radius of the confuser, as well as the coefficient of equivalent roughness, i.e. from gradual wear of the confuser channel. The resulting dependence can be recommended for calculation in the design of jet cleaning devices and other installations of jet technology.

An object of investigation is pointed - the metal articles being in water and exposed to pulse laser treating. The purpose of research was the investigation of the processes occurring near the metal target treated by pulse laser radiation with flux density ∼106 W/cm–2. The results of the experimental investigation of the pulse laser treating of a led target being in water are described. The process of steam and gas plume generation on the surface of the irradiated metal was investigated experimentally. The features of steam and gas plume form and dimensions evolution on different stages of the process (even after completion of laser treating of the material) were investigated. It is shown that when using GOR-100M operating in free oscillating regime (pulse duration 1.2 ms, laser radiation flux density ∼106 W/cm–2), the form of a crater developed on the irradiated target surface being in water essentially differs from the topography of the crater developed on the analogical target surrounded by air at normal pressure (105 Pa). It is pointed in the conclusions that the substantial difference of the forms of crater surfaces developed as a result of processing of the identical targets being in water or air by laser pulses with the identical parameters , determines by principally different character of plasma and steam and gas mixture flow in the mentioned cases.

An adaptive phase-locked loop is considered, which makes it possible to improve the stability of synchronous active filters, to achieve compensation for high-quality harmonic components of the current consumed by autonomous objects. Therefore, the use of such an active filter will improve the power quality and the normal trouble-free operation of the equipment in general. A control system with an adaptive phase-locked loop often has the advantages of a reliable and efficient control system. It makes it possible to quickly respond to dynamic changes in the load, which is typical for the operation of functional equipment of autonomous objects. The control system becomes more flexible, reliable, efficient and provides an instantaneous value of the compensation current from the measured values of the load current curve. Calculations can be carried out in real time. LMS, NLMS, RLS algorithms are considered as adjusting the weighted adaptive phase-locked loop in the system for correcting the supply voltage parameters. Based on the simulation of algorithms carried out in the MATLAB environment, a comparative analysis of their effectiveness is made. It is shown that the NLMS algorithm has the highest suppression quality and minimum transient time. The NLMS algorithm works in real time and is recommended for use in the supply voltage correction system.

This paper presents the results of an experimental study of the external heat-exchange with a tube bundle in a bidisperse fluidized bed with marked bimodality of particle size distribution. The dependence of the maximum heat-transfer coefficient on the rate of air filtration was determined. The influence of the mass fraction of large particles on the heat-transfer coefficient in a mixture has been established. An interpolation dependence for calculating the optimal filtration rate of the investigated mixtures has been obtained. It is recommended to use the average surface diameter of the polydisperse particles mixture as the equivalent diameter when calculating the heat-exchange. A method for calculating the maximum heat-transfer coefficient and the optimal filtration rate for a quasi-bidisperse fluidized bed has been developed. The method is based on the use of heat transfer coefficients and optimal filtration rates of individual components of the bidisperse mixture. The equations for calculating the maximum heat-transfer coefficient and the optimal filtration rate in the bidisperse mixture has been obtained.

Vacancy-oxygen complexes VnOm (n, m ≥ 1) in crystalline silicon are nucleation centers for oxygen precipitates, which are widely used as internal getters in modern technologies of production of silicon-based electronic devices and integrated circuits. For the controllable formation of oxygen precipitates in Si crystals in the technology processes the methods of determination of concentrations of the V_nO_m complexes are required. The aim of the present work was to find values of the calibration coefficients for determination of concentrations of the V_nO_m defects in Si from intensities of infrared (IR) absorption bands associated with the local vibrational modes (LVM) of these complexes. A combined electrical (Hall effect) and optical (IR absorption) study of vacancy-oxygen defects in identical silicon crystals irradiated with 6 MeV electrons was carried out. Based on the analysis of the data obtained, the values of the calibration coefficient for the determination of concentration of the vacancy-oxygen (VO) complex in silicon by the infrared absorption method were established: for measurements at room temperature (RT) – NVO = 8.5 · 10¹⁶ · αVO-RT ^cm–3, in the case of low-temperature (LT, Т ≡ 10 K) measurements – N_VO = 3.5 · 10¹⁶ · αVO-LT ^cm–3, where αVO-RT(LT) are absorption coefficients in maxima of the LVM bands due to the VO complex in the spectra measured at corresponding temperatures. Calibration coefficients for the determination of concentrations of other V_nOm (VO₂, VO₃, VO₄, V₂O and V₃O) complexes and the oxygen dimer (O₂) from an analysis of infrared absorption spectra measured at room temperature have been also determined.

The characteristics dependence on the ambient temperature for three types of silicon photoelectronic multipliers have been studied in this research. The prototypes of Si-photoelectronic multipliers with a p⁺–p–n⁺ structure produced by JSC Integral (Republic of Belarus), serially produced silicon photoelectronic multipliers KETEK РМ3325 and ON Semi FC 30035 have been used as objects of research. We present the setup diagram and research technique. Measurements of the photocurrent magnitude versus the illumination intensity, calculations of the critical and threshold intensities, and the dynamic range have been performed. We also present the photocurrent dependences on the illumination intensity at different ambient temperatures. As it was found, these dependences have a linear section, the length of which characterizes the critical intensity value, and the inclination angle of the linear section to the intensity axis characterizes the photodetector sensitivity to optical radiation. It has been determined that the temperature increase leads to an increase in the critical intensity value and to a decrease in the sensitivity value. We present the dependences of the threshold intensity on the overvoltage at different ambient temperatures. The dependence of the threshold intensity on overvoltage is most strongly pronounced when the supply voltage is below the breakdown voltage. It was found that the threshold intensity is increased with the temperature increase and the threshold intensity dependence on the temperature is the same for all investigated photodetectors. It was found that the dynamic range value is decreased with the temperature increase, which is caused by a more significant change in the threshold intensity as compared to the critical one. The results given in this article can be applied when developing and designing the tools and devices for recording optical radiation based on silicon photoelectronic multipliers.

An approach to solving the problem of improving the accuracy of an automatic control system for unmanned aerial vehicles (UAVs) in conditions of non-stationary interference is considered. Such interference is caused by random changes in the noise of the measuring sensors, which are installed in the UAV, when changing the yaw, roll and flight altitude of the UAV due to restructuring or transformation of the operating mode of the propulsion system of the UAV. Non-stationary noises do not allow obtaining the maximum effect of applying the theory of optimal filtration based on the classical Kalman filter. The authors proposed a method of stabilizing sensor noise by using a noise automatic gain control circuit installed in front of the Kalman filter. For its quantitative assessment, a team of authors developed a computer model and carried out dynamic modeling based on test signals, which showed the applicability of the classical Kalman filter in non-stationary conditions and a decrease in the filtering errors of the automatic control system.

The relevance of the work is due to the lack of a physical interpretation of the process of extinguishing jet burning systems with fire extinguishing powders, which is important for ensuring effective fire extinguishing at gas and oil complexes and hazardous chemical industries. A mathematical model of the reaction kinetics of heterogeneous inhibition of active flame centers of a jet burning system by fire extinguishing powder particles in an unsteady mode is considered in the approximation of a purely molecular transfer of matter in the reaction zone. The regularities of the mechanism of heterogeneous inhibition of the active flame centers by the particles of the extinguishing powder under conditions when the active particles of the combustion products participate not only in diffuse, but also in convective transport are established. It is shown, that the convective motion of the active flame centers increases the reaction rate of heterogeneous inhibition of their particles of the extinguishing agent. The results obtained allow us to optimize the conditions for the supply of fire extinguishing powder to the jet burning medium for effective flame suppression.