The main features of high-voltage electric pulse consolidation (HVC) of refractory powder materials and the resulting unique capabilities of the method are considered. The electro-thermal processes of HVC at the contacts between powder particles and at the macroscale of the entire consolidated sample are analyzed. The results of experimental studies of the parameters of high-voltage electrical impulse action in the processes of consolidation of high-temperature powder compositions, high-voltage welding of dissimilar materials, as well as high-voltage discharges in liquid are presented. The results of measuring the intensity of thermal radiation of the investigated materials under high-voltage electrical impulse action, recorded by the method of pulse photometry using photodiode sensors, which, together with the Rogowski coil, are components of the measuring complex developed by the authors, are presented.

A number of methods for testing bending of thin discs on an annular support designed to determine the tensile strength of brittle materials, are considered. The methods differ in the type of a loading indenter (with flat, spherical, or toroidal tips), support devices, and calculation equations for determination of the breaking stress. The results of testing samples on an annular support made of two model materials which differ in the degree of brittleness, i.e., cast iron and graphite, are presented. It is shown that the calculated strength of the tested materials depends on the character of the sample destruction and on the type of bending diagram. Cast iron samples were destructed under a significant plastic deformation (characteristic bending diagram passed through the maximum), and the tensile strength of the samples corresponded to the compressive strength of the material being several times higher than the tensile strength of the material. Graphite samples underwent brittle fracture (within the linear section of the bending diagram), and the calculated strength value was comparable to the tensile strength of the material. A conclusion is made that the use of the test method of thin disk samples on an annular support for determination of the tensile strength of the material is substantiated only in the case of absolutely brittle fracture of samples with a bending diagram similar to the fracture diagram of graphite samples. Disk samples made of aluminum oxide obtained by electro-pulse sintering were tested using two methods (with flat and spherical tips). In both cases, the bending diagram of aluminum oxide samples was similar to that of graphite samples, i.e., their destruction occurred at the initial linear section of the diagram and was absolutely brittle. The results of comparative testing of the samples made of aluminum oxide, taking into account the results of testing samples made of model materials (cast iron and graphite), showed that tests on the annular support of disks using a flat-tipped indenter are the most grounded. The samples should be made of brittle materials having a linear bending diagram up to the sample destruction.

Abstract. Breast cancer is one of the most commonly diagnosed cancers worldwide. According to the World Health Organization, the incidence of breast cancer was 2.26 million in 2020, overtaking the incidence of lung cancer. In Russian Federation, the increase in new cases of breast cancer over the ten years from 2005 to 2015 was 31.76 %. Microscopic calcium deposits within breast tissue, microcalcifications, can be early signs of breast cancer. Being a significant diagnostic finding, microcalcifications allow the assessment of the extent of the disease. A detailed understanding of the morphogenesis of microcalcifications can improve knowledge about early stages of breast cancer, but there is no studies that would combine the results of the latest basic scientific research and current knowledge about their clinical significance.The aim of the study was to analyze and summarize the available data on the prognostic value of microcalcifications in patients with breast cancer.Material and Methods. A search was carried out for available literary sources published in the Medline, Elibrary, etc. databases for the period since 2015. A total of 250 sources devoted to the analysis of the morphogenesis of microcalcifications and their diagnostic value were found. Of them, 37 were included in this review.

The electrical conductivity of powder media depends on the composition, impurities, oxide films, morphology and the nature of the contact surface. We present the results of studying the electrical resistance of powder materials and their compounds under continuous loading by the four-contact method. The electrical resistance is determined using a special experimental cell. Industrial powders Al (ASD-1), Ti (PTK), Hf (GFM-1), soot and their mixtures, as well as TaC and HfC powders obtained by self-propagating high-temperature synthesis were studied. It is shown that an increase in the mechanical pressure up to 80 MPa leads to a decrease in the electrical resistance of the materials under study. The morphology of the particles (spherical or fragmentary shape), their dispersion affects the quality of the contact surface and, accordingly, the magnitude of the electrical resistance. Moreover, the electrical resistance of the material depends on the degree of cleaning of the particle surface from oxide films. The proposed method in combination with other analytical methods used for studying powder media allows us to reveal the regularities of this relationship, characteristic of all morphological features, composition and electrophysical properties of powders of various compositions under loading conditions. The results obtained can be used to select the optimal characteristics of consolidation by electric current depending on the initial pressure, as well as in case of high-voltage electric pulse consolidation of powder materials by spark plasma sintering and electrothermal explosion methods.

The fundamental aspects of the process of high-voltage consolidation of powder materials, as well as its advantages and limits, are discussed in this study. In this respect, the electrothermal processes at the contacts between powder particles (mesoscale), and also at the macroscale of the total volume of the consolidated sample, are investigated. Moreover, the dynamics of interparticle pore closure (collapse) in the consolidated material are calculated. The results of HVC experiments of difficult-to-sinter tungsten-based alloys are presented. The macro- and microstructure examinations of consolidated specimens, as well as stress-strain tests, are also evaluated. Compression tests show that all tested alloys can withstand compressive stress without failure at room temperature. In particular, a criterion for determining the range of technological variables for the fabrication of high-density samples is described. Finally, a promising future research area for this approach is proposed.

The article presents a new approach to the organization of the temperature control system in the room. It is proposed to use optical wireless data transmission technology via led lighting, in order to controller actuator. The emergence of new directions based on the optical range in the field of communication was explained by existing problems in the organization of modern wireless infrastructure. Nowadays, the radio frequency band widely used for data transmission is overloaded and cannot meet the rapidly growing traffic and demand for wireless data services. Additional implementation of wireless systems based on the use of the optical range can help in solving existing problems. In this article, we consider an experimental model of an automated temperature control system. We proposed a block diagram of the indoor temperature control system using with data transmission via visible light. For the organization of traffic developed transmitting and receiving devices. A digital temperature sensor is connected to the transmitter. The transmitting device has a 3W white lighte-mitting diode, which performs the function of lighting and additionally transmits temperature data. A photodetector is used to receive the signal. The control and data processing is carried out by ATmega 328 microcontrollers, which are located in both devices. The actuator is a 30W heating element. Experimental results of the control system operation, which show stable data transmission and the maintenance of the specified temperature regimes in working condition for a long period of time, are presented. The level and quality of lighting during the operation of the control system remain in the normalized range.

A comparative study of the results of Spark-Plasma Sintering (SPS) of two-types of aluminum oxide nanopowders, obtained by the method of conductor explosion and plasma synthesis. When the parameters of both powders are similar (spherical form of the particles, size, phase composition) as well as SPS modes the properties of the resulting compacts are significantly different both in mechanical properties and microstructure. The reason of differences in the properties of the obtained compacts is in technological impurities in powders, obtained by different methods. Artificial addition of impurities, contained in the nanopowder, obtained by electro explosion of conductor, into the powder, made by synthesis in plasma and not containing these impurities, allowed to reveal their effect on the formation of the microstructure and properties of the sintered by SPS method sample.

The article provides an analytical overview of ways to contact the capacitor welding. Using rigid modes effects on the bonding region in most cases causes the formation of a contact during the crystallization in the liquid phase, which is highly undesirable when connecting non-ferrous metals and their alloys. Forming permanent joints in the liquid phase facilitate processes atomic hetero diffusion or reactive diffusion, which intensifies the nucleation of intermetallic phases.

The main features of high-voltage electropulse consolidation (H-VEC) of powder materials and the unique possibilities of the method caused by them are considered. The electrothermal processes in the H-VEC at the contacts between the powder particles and in the macroscale of the whole consolidated sample are analyzed. The results of calculations of the dynamics of closure (collapse) of interparticle pores in the consolidated material are presented.

Electric exploding of a tungsten carbide – cobalt material near-by high-speed steel surface forms on it a hardening coating. The essential structure properties of the formed coatings are determined by specifications of contact exploding electrode and the pulse current amplitude and duration. The investigations of coating structures were done by optical and electronic metallography. They have shown that the contact electric exploding caused the transfer of tungsten carbide and cobalt on the surface of high-speed steel. The breakdown of tungsten carbide – cobalt material took place during electrical exploding. The hardening layers of tungsten carbide and pure nanocrystalline tungsten have been formed upon the surface of high-speed steel as a result of electric exploding. Crystalline grains of tungsten have an almost spherical form and their characteristic size less than 400 nm. Micro hardness of the coating layers and high-speed steel structures was measured.

Abstract Advanced technologies for the production of new materials and, in particular, nanostructured materials, using powder technologies require fundamentally new approaches for the formation and preservation of a given structural-phase state. Precision control of the state of materials in the process of consolidating powders of nanomaterials can be carried out using pulsed electromagnetic fields. The aim of the project is to study the effect of high-voltage and low-voltage pulsed electromagnetic fields in the technologies of powder consolidation. The experimental devices of spark-plasma sintering, flash-sintering, high-voltage consolidation and magnetic-pulse compaction are used in our laboratory for the production of advanced materials from metal powders, ceramic and composite powders. We can produce boron carbide, silicon carbide, uranium nitride, tungsten carbide - cobalt - diamond composites, tungsten heavy alloys, and others by electromagnetic methods of powder consolidation. Experimental results to consolidation metal powders, ceramic and composites powders by electromagnetic methods presage fruitful results.

Investigated were the spark plasma sintering (SPS) of β-sialon ceramics according two different schemes: the simple sintering of pure β-Si5AlON7 powder and the reactive sintering of mixture of α-Si3N4 and β-Si2Al4O4N4 powders. The high-density homogenous structure of simple sintered β-Si5AlON7 ceramics was achieved at maximum temperature of isothermal holding Tmax = 1550 °C by using submicron raw powder. While ceramics from coarse raw powder had porous structure and was subjected to thermal decomposition at Tmax ≥ 1750 °C. Three specific temperature intervals were revealed for the reactive sintering. At Tmax ≤ 1650 °C, the shrinkage rate attained the values sufficient for densification near to a theoretical density, without any changes in the size/morphology of starting particles and without transformation of starting α-Si3N4 into β-sialon. At Tmax = 1700–1750 °C, starting α-Si3N4 was found to undergo transformation into β-sialon but without marked changes in the size/morphology of starting particles. At Tmax ≥ 1750 °C, the sintered ceramics exhibited a marked growth in the size and change in the shape of sintered particles.

Current-assisted sintering of combustion-synthesized β-Si5AlON7, h-BN, and TiN powders was explored in comparison with conventional sintering. High relative density of product (above 92%) was achieved by using high-voltage electric discharge consolidation (HVEDC) and spark plasma sintering (SPS). Better results were obtained in case of SPS processing.

The article presents the results of a research of the operation of a new electronic circuit for transmitting sound signals using light emitting diodes (LED) lighting devices. It also analyzes the available data transmission schemes using Visible Light Communication (VLC) technology, which allows a light source, in addition to lighting, to transmit information using the same light signal. The advantages and disadvantages of the available schemes are shown. There is an experiment to study the quality of sound transmission. As a result, optimization of electronic circuits was carried out and recommendations were made on the use of VLC technology in LED lighting systems in administrative and residential buildings.The article describes a new scheme for the transmission of audio signals. The frequency characteristics of the developed circuit are shown. Experiments on the transmission of audio signals, which showed that when using conventional LED lighting devices, can be transmitted in the daytime with exposure to sunlight no more than 20%. Such systems are convenient in rooms without natural light (basements, tunnels, mines, etc.).This direction is relevant in connection with the prospect of its development and the transition to new technologies for organizing a data network.

Electric current assisted sintering of β-Si5AlON7-TiN ceramic composites from raw materials prepared by combustion synthesis was investigated. A high level of relative density (92% and higher) was achieved by using of two types of electric current assisted sintering technique: high voltage electric discharge consolidation, as well as spark plasma sintering. While only spark plasma sintering, it may be considered as promising technique for obtaining ceramic composites and items with high level of strength properties.

In the present work, the properties of Al 2 O 3 nanocomposite prepared via spark-plasma sintering and reinforced with 0.5–2 wt % graphene are studied. Samples with different graphene contents are subjected to measurements of density, microhardness, coefficient of friction of composite–ruby, and frictional wear rate of composite. The fracture and wear track surface are inspected via fractography, and the composite as a whole is examined via X-ray diffraction. The graphene additive is established to increase the microhardness and to decrease the frictional wear rate by two orders of magnitude on account of absence of flaking of grains.

Spark-plasma sintering (SPS) of composite ceramics in the β-Si5AlON7– system (SiC, TiN, BN) was studied. An effective mechanism of intensification of sintering processes was revealed due to the introduction of h-BN, having a scaly structure and playing the role of a solid lubricant, which improves the compressibility of the sintered powder mixtures under load. For composites containing 0–30 wt. % h-BN, 0–40 wt.% β-SiC, and 0–40 wt. % TiN, with different character distribution of components by volume (homogeneous, layered and gradient), the optimal parameters of the PCA were established, ensuring the achievement of a high level of relative density (not less than 95%) and functional characteristics. According to XRD results, the raw powders of β-Si5AlON7, h-BN, and TiN did not contain impurity phases while β-SiC had trace amounts of Si3N4. According to SEM results, all as-synthesized powders appeared largely as agglomerates. Their specific surface was about 1.3 m2/g for β-Si5AlON7 powders, and from 9.8 to 22.8 m2/g for h-BN, β-SiC, and TiN fine powders. After ball milling, the specific surface increased by a factor of 4–6. The addition of h-BN improves the compactibility of sintered powder mixtures. Under a compressive stress of 50 MPa at 600°C, the initial value of ρrel exceeds 80% for the compact containing 30 wt. % BN and 60% for that of pure β-Si5AlON7 (Figure 1). In parallel, an increase in h-BN content suppresses the consolidation processes due to formation of liquid eutectics. At 30 wt. % BN, the temperature dependence of ρrel becomes much more aligned.

The results presented in this article demonstrate that boron carbide ceramics of a perfect microstructure, of a high density (up to 99.8%) and microhardness (36.1 GPa) can be made from the industrial micron fraction powder thanks to s park plasma sintering , that opens prospects for wide SPS application in economical production of high-quality boron carbide ceramic products. Optimal ceramics production mode is based on B4C (technical powder), which makes the best combination of physical and mechanical properties and uniform microstructure. The experimentally set mode of spark-plasma sintering of high-density B4C ceramics allows to lower the sintering temperature by 300 ° C and to shorten the process time by 20 minutes relative to the corresponding values when traditional hot pressing.

The new approach in developed plasma methods consists in that dispersion-hardening additives (TiC, TiB2 in particular) are not mechanically added to powder mixture as additional component, as in conventional methods, but are instead synthesized during high voltage electric discharges (HVED) in disperse system "hydrocarbon liquid - powder"; preservation of ultrafine structure is ensured due to use of spark plasma sintering (SPS) as a consolidation method. HVED in disperse system "hydrocarbon liquid - powder" due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10(-6) to 10(-7) m) and nanosized (from 10(-7) to 10(-9) m) composite powders of hardening phases. SPS is the passage of pulsed current (superposition of direct and alternating current) through powder with the simultaneous mechanical compressing. The formation of plasma is initiated in gaseous phase that fills gaps between particles. SPS allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10 - 20 %), hardness and wear-resistance (by 30 - 60 %) of obtained materials.