The interest in high-entropy materials has increased rapidly in recent decades due to their applications in various fields such as environmental barrier coatings, superhard and wear resistant coatings, nuclear energy, batteries, catalysts, thermoelectrics, supercapacitors, biocompatible structures, and microelectronics. In the present work, comprehensive theoretical and experimental studies are carried out to discover a new way to prepare highentropy ceramic nanopowders of carbides and carbonitrides of IV-V transition metals. The possibility of (TiZrNbHfTa)CxNy formation is investigated using both ab initio and machine learning approaches. The chosen single-stage plasma dynamic technique allowed us to synthesize high-entropy carbide TiZrNbHfTaC5 and the corresponding carbonitrides (N up to 8 wt%) in the form of single-crystalline nanoparticles. By varying the experimental system conditions, we demonstrate not only the production of pure powders, but also the ability to apply different precursors, including pure metals and their oxides. The presented technique provides a simple and universal way to produce high-entropy nanomaterials and opens the door to the synthesis of many functional ceramic powders composed of other carbonitrides with selective nitrogen content.

Aluminium matrix composites are popular due to the excellent ductility, corrosion resistance, reusability and formability of aluminium, as well as the high rigidity, strength, hardness and wear resistance of the ceramic component. However, achieving the predicted high physical and mechanical properties still remains an urgent task, since the common ex-situ approaches for obtaining mixed compositions results in decreasing the final parameters of the bulk samples. In this paper, a unified strategy for obtaining bulk aluminium matrix composites with improved mechanical properties has been demonstrated. Reinforcing particles in the form of tungsten, silicon and boron carbides are introduced into the metal matrix during pulsed process of high-speed pulsed thermal plasma spraying. The proposed approach results in obtaining composite materials with a variable content of the carbide phase (from 5.85 to 16.38 %) depending on the initial process conditions. High-speed pulsed co-spraying of MMC components provides a uniform distribution and polymodal particles size range from 10 nm to 20 mu m. When producing bulk samples, the unique structure of as-prepared powder materials is a key factor in achieving a high degree of densification (up to 99 %) and improved physical and mechanical properties (103-215 HV) compared to samples from commercially available MMC components (47-62 HV). The proposed method of in-situ combining the metal matrix material (aluminium) and the reinforcing ceramic component (superhard carbide) prevents bulk samples from a high porosity and particles recrystallization that sufficiently improve the final properties of metal matrix composites.

Relevance. The search for suitable materials for creating a new generation of anodes in lithium-ion batteries that have not only high capacity, but also high electrical conductivity. For this purpose, the attempts have been made to use silicon Si, which has a high specific capacitance, instead of graphite C, but this material does not have high electrical conductivity. Copper silicides, in addition to high specific capacity, have high electrical conductivity values, since they do not react with lithium during operation, and therefore can be used to solve problems in the development of the above-mentioned lithium-ion anodes. Aim. To obtain dispersed materials in a high-speed jet of electric discharge plasma in the Cu-Si-C system. Objects. Dispersed materials obtained in the Cu-Si-C system. Methods. Plasma dynamic synthesis, X-ray diffractometry (X-ray phase analysis), scanning electron microscopy, transmission electron microscopy. Results. The authors have carried out the experimental studies to obtain dispersed materials of the Cu-Si-C system in a high-speed electric-discharge plasma jet and studied the microstructure and composition of the synthesized materials. It was revealed that the product consists of nanodispersed particles, which is confirmed by the results of scanning and electron microscopy. According to the results of X-ray diffractometry, crystalline phases of copper of the cubic system and copper silicides Cu3Si and Cu7Si of the hexagonal system are identified in the composition of the synthesized material.

Various silicon carbide nanostructures are attracting close attention due to their excellent performance and great potential, including utilization in a variety of catalytic applications. Approaches, utilizing different industrial wastes as a starting material for the synthesis of SiC nanoparticles, are especially distinguished due to their environmental friendliness. This paper demonstrates a new two-stage technique of the preparation of dispersed SiC/C nanocomposite. A highly mineralized carbonaceous residue obtained by thermal processing of agricultural waste was used as a precursor for the synthesis in a pulsed arc discharge plasma. Rice husks, oat husks and oat straw were chosen as agricultural wastes with a high content of silicon in the mineral component. Carbonaceous residues (biochars) were obtained from the selected wastes by oxidative carbonization in a reactor with a fluidized bed of a deep oxidation catalyst at 460 C-degrees. High-energy (up to 20 kJ) treatment of the obtained biochars in a pulsed (up to 1 ms) arc discharge plasma jet resulted in synthesizing a nanodispersed material (particle size <50 nm) containing hexagonal silicon carbide alpha-SiC. The principal possibility of using the synthesized SiC-based composite as a catalyst and cocatalyst of platinum in the hydrogen evolution reaction (HER) of water splitting is shown. The most impressive results (eta(10) = 18-28 mV, eta(100) = 84-98 mV, b = 32-64 mV) comparable with standard commercial Pt/C samples were obtained by modifying the synthesized SiC-based composite with 5 % platinum. Thus, the developed approach allows us to convert the agricultural waste into useful high-tech products in the form of an electrocatalytically active material.

Relevance. Currently, there is an active search for photocatalytic materials suitable for water decomposition and hydrogen production that exhibit activity when exposed to visible light, and are also accessible, chemically stable and safe. In this regard, a number of materials with the general formula TinO2n-1 (n=2–10) are distinguished, they are called Magnéli phases. Despite the fact that Magnéli phases exhibit significantly higher photocatalytic activity compared to traditional titanium oxides (rutile, anatase, brookite), their practical application is currently extremely difficult due to the complexity of their synthesis. Promising approaches are those that provide well-controlled conditions with the possibility of rapid stabilization of the system, among which plasma synthesis methods stand out. Aim. To develop a method for synthesizing a product containing Magnéli phases in a high-speed jet of electric discharge plasma. Objects. Dispersed materials obtained in the Ti-O system. Methods. Plasma dynamic synthesis, X-ray diffractometry (X-ray phase analysis), scanning electron microscopy, transmission electron microscopy. Results. Using a high-speed jet of electric discharge plasma generated by a coaxial magnetoplasma accelerator, experimental studies were performed on the synthesis of non-stoichiometric titanium oxides in a carbon dioxide environment. The composition and microstructure of the obtained dispersed products were studied. It was revealed that the materials contain Magnéli phases TinO2n−1, as well as traditional stoichiometric rutile and anatase. From the point of view of the efficiency of obtaining Magnéli phases, the single-pulse mode of operation is more attractive (content over 50%), while the efficiency of CO2 conversion is higher in the multi-pulse mode (up to 10% of CO2 is converted into CO). A distinctive feature of the synthesized materials at both the micro- and nanolevels is the tendency to form particles with a high degree of sphericity. The nanofraction of the products mainly consists of rounded particles with sizes up to hundreds of nanometers, of which the Magnéli phases primarily include nanoparticles with a characteristic highly defective crystalline structure with dislocation shifts.

Relevance. The fact that composites with a metal matrix and structural products based on them are in great demand in various industries, including the automotive industry, aerospace industry, and shipbuilding. Aluminum matrix composites are the most popular since they combine the excellent ductility, low density, good corrosion resistance of aluminum and the high strength, hardness and wear resistance of a ceramic reinforcing component. Aim. To obtain bulk Al-WC metal matrix composites with different contents of the reinforcing phase and with increased physical and mechanical characteristics using spark plasma sintering. Objects. Sintered bulk products made of pure aluminum and obtained at 400, 450, 500, 550, 600°C and bulk metal matrix composites Al-1%WC, Al-5%WC, Al-10%WC, Al-15%WC obtained at 600°C. Methods. Spark plasma sintering; X-ray diffractometry (XRD phase analysis); scanning electron microscopy; indentation (microhardness measurement). Results. The authors have obtained bulk composite metal matrix products with an aluminum matrix and tungsten carbide as a reinforcing component. Compacting mixtures of nanosized initial powders of aluminum and tungsten carbide using spark plasma sintering made it possible to obtain products with a WC content of 1 to 15 wt %. Taking into account the results of a preliminary series of experiments, when pure aluminum samples were sintered to determine the optimal sintering temperature, bulk composite materials were obtained. A distinctive feature of the obtained samples is their high degree of compaction, which is due to the simultaneous application of a heating current and external pressure, coupled with the relative preservation of the fine-grained structure of the material due to the short process time. The analysis of various sintering modes revealed the need to carry out sintering of composites at 600°C. The research has shown that, although adding a reinforcing phase to a metal matrix significantly reduces the degree of compaction of the material from 97.45% in the absence of an additive to 62.32% with the addition of 15%WC, an increase in the microhardness of products is observed when the concentration of the reinforcing component increases from 3.95 to 5.75 HV. This proves the possibility of reinforcing a metal material using ceramic WC particles. The results can be used in a variety of structural applications, including automotive and aerospace.

The issues of decarbonization, which have recently received increased attention from the world community mainly in connection with global warming, require the search for new solutions related to the utilization of carbon dioxide. The main problem of carbon dioxide conversion is the need to overcome the high stability of its molecules, which requires the supply of a substantial amount of energy. This study describes experimental results on the high energy plasma dynamic synthesis of metal oxides in a carbon dioxide medium using the Ti–O and Fe–O systems as an example. Nano- and micropowders of iron and titanium oxides are obtained by utilizing CO2 in a sectioned capacitive energy storage device with a coaxial magnetoplasma accelerator with titanium and steel electrodes, which are the main components of the plasma dynamic synthesis system. The powders are synthesized using plasma chemical reactions that occur during high-speed sputtering of a carbon electric discharge plasma into the atmosphere of a reactor chamber filled with carbon dioxide. The possibility of controlling the volume of CO2 utilized in the synthesis process by changing the type of electrodes and the number of successive power supply pulses is shown. It is established that up to 15 vol

Link for citation: Tsimmerman A.I., Shanenkov I.I., Nassyrbayev A.R., Nikitin D.S., Sivkov A.A. Influence of configuration of the electrode system of a coaxial magneto plasma accelerator on arc discharge formation and development. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 39-50. In Rus. The relevance of the research is explained by a wide range of practical areas, where various plasma generators can be used, including analytical devices, technological installations, tokamaks, ion and plasma engines, satellites, laser technology, as well as by the possibility of applying them for both producing coatings on various surfaces and synthesizing fine and nanopowders. The main aim of the research is to determine the best way to initiate an arc discharge in the acceleration channel of the coaxial magnetoplasma accelerator, to estimate the effect of the plasma formation zone configuration on the electrodynamic loads of the accelerator, and to calculate the efficiency of conversion of stored energy to supplied one. Objects: coaxial magnetoplasma accelerator, arc discharge initiation, central electrode, electrode-barrel, plasma formation zone. Methods: experiment, plasma dynamic synthesis, measurement and registration of pulsed currents and voltages, electrical erosion measurement by means of weighing the eroding electrode-bore, high-speed photoregistration of the plasma jet. Results. Two methods of arc discharge initiation using metal wires and graphitization were considered. It is established that they do not affect the energy parameters of the plasma dynamic synthesis, but the graphitization looks preferable due to the greater processability of the procedure that provides easy accelerator preparation and reliability of its operation. The possibility of reducing the arc discharge current amplitude by 29 % with increasing the plasma formation zone length from 5,5 to 11,5 mm was established that results in reducing electrodynamic loads on all system nodes. The optimal plasma formation zone length of 9,5 mm was determined to provide obtaining a high efficiency of conversion of stored energy into supplied energy and reliability of the system operation.

Link for citation: Nikitin D.S., Shanenkov I.I., Nassyrbayev A., Vympina Yu. N., Orlova E.G., Ivashutenko A.S., Sivkov A.A. Obtaining bulk products from Cu-SiC metal-matrix composite for energy-efficient heat-conducting systems. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 93-101. In Rus. The relevance of the research is associated with the rapid development of modern high-performance computing systems, superneurocomputers and artificial intelligence devices. Today such development is held back largely due to the lack of an effective cooling system for high-power elements of their structures. Composite materials Cu-SiC with improved physical, mechanical and thermophysical characteristics can be used to solve problems of heat removal intensification. The main aim of the research is to obtain bulk products from metal-matrix composite Cu-10% SiC with improved physical, mechanical and thermal characteristics by spark plasma sintering. Objects of the research are bulk products from metal-matrix composite Cu-10%SiC. The samples were obtained by spark plasma sintering at temperatures of 700, 750, 800, 850 °C and a pressure of 60 MPa. Methods: spark plasma sintering, X-ray diffractometry (X-ray phase analysis), scanning electron microscopy, indentation, laser flash method. Results. Experimental studies have been carried out to obtain bulk metal-matrix composites with a copper matrix and the addition of reinforcing superhard particles of silicon carbide Cu-10%SiC. The compaction of dispersed composite materials was carried out by spark plasma sintering at various temperatures of 700, 750, 800, and 850 °C. The microstructure and composition of initial dispersed materials and final bulk products have been studied. It is shown that the spark plasma sintering method has advantages for obtaining relatively dense materials with high physical, mechanical and thermal properties. Analysis of the obtained samples showed the formation of a dense (up to ~88 %) homogeneous fine-grained composite structure. The greatest densification of the material is achieved at the highest sintering temperature of 850 °C, which causes this sample to demonstrate the maximum hardness (H=3,63 GPa) and Young's modulus (E=159,63 GPa), as well as the thermal conductivity at room temperature (λ=223 W/m K). The obtained composite materials can be used as structural and functional materials for energy-efficient heat-conducting systems.

The issues of decarbonization, which have recently received increased attention from the world community, mainly due to global warming, require the search for new solutions related to the utilization of carbon dioxide. The main problem of carbon dioxide conversion is the need to overcome the high stability of its molecules that requires the supply of a significant amount of energy. This paper presents the experimental results on the high-energy plasma dynamic synthesis of metal oxides in a carbon dioxide medium using the Ti – O and Fe – O systems as an example. By applying a sectioned capacitive energy storage device and a coaxial magnetoplasma accelerator with titanium and steel electrodes, which are the main elements of the plasma dynamic synthesis system, nano- and micropowders of iron and titanium oxides were obtained by utilizing CO2. Synthesis of powders was carried out as a result of plasma-chemical reactions occurring during high-speed sputtering of carbon electric discharge plasma into the atmosphere of a reactor chamber filled with carbon dioxide. The possibility of controlling the volume of CO2 utilized in the synthesis process by changing the type of electrodes and the number of successive power supply pulses is shown. It has been established that when using titanium electrodes and a multi-pulse operating mode in the considered system, it is possible to utilize up to 15 vol. % of CO2 to obtain up to ~ 9 g of dispersed products. It should be noted that when titanium electric discharge plasma is sputtered in a CO2 medium, the formation of “classical” rutile and anatase phases, as well as Magneli phases and titanium carbide without traces of pure metal is observed. This indicates that when implementing the plasma dynamic synthesis, it is possible not only to utilize carbon dioxide, but also to obtain useful powder products, which can later be used as feedstock for various applications.

An experimental study is performed of the plasma dynamic synthesis of ultra-dispersed titanium dioxide powders upon a change in the energy supplied to the accelerator. It is shown that the energy of synthesis affects the anatase/rutile mass percentage ratio in the composition of the final product. The maximum content of anatase at a level of 80.0% is obtained at a supplied energy of ~33 kJ.

Comprehensive theoretical and experimental studies are performed to discover a new way of synthesis of HfTaC coatings. Here, an evolutionary search for stable crystal structures in the ternary HfTaC system with subsequent selective large‐scale experimental synthesis of coatings using a unique plasma dynamic experimental setup is performed. Optimization of the experimental process allows us to perform selective synthesis of coatings made of hafnium–tantalum carbides with predefined stoichiometry, crystal structure, and properties. Along with more than 70 compounds, the HfTaC system belongs to ternary and quaternary carbides of group IV and V transition metals, and this study opens the door to synthesis of a large number of functional coatings composed of other carbides including high‐entropy carbides.

The results are presented from experimental studies to determine the effect the type of inert gas (helium, nitrogen, or argon) used in a mixture with oxygen as the gaseous medium of a reactor chamber has on the product of plasma dynamic synthesis in an iron–oxygen system. X-ray diffractometry and scanning electron microscopy are used to establish that the synthesized materials were ultrafine powders consisting mainly of magnetite Fe3O4 with small inclusions of hematite α-Fe2O3, wustite FeO, and iron Fe. It is found experimentally that the content of magnetite in the product can be as high as 85 wt % during plasma dynamic synthesis in mixtures of N2/O2 and He/O2, resulting in the highest specific saturation magnetization (up to 78.3 emu/g).

Controlling the surface wetting of silicon carbide (SiC) ceramics is an urgent problem as its solution will significantly expand the scope of this material. In this work, the submicron SiC ceramics was obtained from the ultradispersed SiC powder fabricated by the plasma dynamic synthesis method. The bulk SiC samples were produced by spark plasma sintering at 1600 degrees C, 1700 degrees C, and 1800 degrees C. The effect of sintering temperature and promising methods of surface modification on wetting, elemental composition and surface roughness of SiC ceramics was studied. The surface modification methods included polishing, laser texturing, low-temperature annealing, magnetron chromium sputtering, and their combination. To predict the type of a texture formed after nanosecond laser radiation, the graphic-analytical method was developed. The best hydrophilic properties of SiC ceramics (the contact angle decreased to 9.3 degrees) were obtained after polishing with subsequent nanosecond laser texturing. The best hydrophobic properties of SiC ceramics (the contact angle increased to 135.3 degrees) were obtained after a combination of polishing, laser texturing, and magnetron chromium sputtering. Controlling the surface wetting of SiC ceramics from hydrophilic to hydrophobic makes it possible to significantly expand the scope of this material, for example, to use it in drop cooling systems of advanced digital devices that emit ultrahigh heat fluxes up to 1000 W/cm(2).

Цель. Анализ свойств покрытий на основе модифицированной бактериальной целлюлозы и сравнение их структуры, гемостатической активности и физико-химических свойств с покрытиями из немодифицированной бактериальной целлюлозы.

At the moment, the problems of environmental pollution are urgent; therefore, issues related to photocatalysis as a direction for the future development of unconventional power engineering are being solved by many researchers in the world. To achieve these goals, titanium dioxide, known for its many properties, is used as a photocatalyst. However, its application is limited owing to its wide band gap and high rate of electron pair recombination. The paper proposes a method for direct plasma dynamic synthesis of dispersed titanium dioxide. It has been found that the synthesized product consists of two fractions that differ greatly in size: a coarse fraction with a particle size from ~100 to ~10 μm and a fine one with a particle size from ~1 μm to ~10 nm. It has also been revealed that they contain mainly two crystalline modifications of titanium dioxide: anatase and rutile with a tetragonal crystal system.

This paper reports plasma jet synthesis of nanocrystalline cubic tungsten carbide. Using a coaxial magnetoplasma accelerator with graphite electrodes, we have implemented an experimental process that allows one to obtain up to 95% crystalline WC1 – x. We have demonstrated the feasibility of tuning the parameter 1 – x (stoichiometric ratio) in this compound by varying the energetics of the process and the composition of the starting mixture. Varying the released energy from 8 to 23 kJ and the ν(C)/ν(W) atomic ratio of the starting reagents from 0.6 to 2.5 allows the composition of cubic tungsten carbide to be tuned in the range WC0.64 to WC0.78.

Кабак В.А., Бычичко Д.Ю., Белозерская Г.Г., Момот А.П., Пыхтеева М.В., Неведрова О.Е., Лемперт А.Р., Логвинова Ю.С., Сивков А.А., Шаненков И.И., Голубев Е.М., Широкова Т.И., Миронов М.С., Акопян Л.В. Создание новых полимерных соединений, обладающих гемостатическими свойствами. Сердечно-сосудистые заболевания. Бюллетень НЦССХ им. А.Н. Бакулева РАМН. 2021; 22 (3): 373–81. DOI: 10.24022/1810-0694-2021-22-3-373-381 HTML