The plasma dynamic synthesis of aluminum nitride in system with gaseous and solid precursors

Aluminum nitride is widely-used material for semiconductor devices and ceramics production. Despite the large number of known ways to obtain AlN powder, the problem of synthesizing high-purity and nanosized product is still urgent. This paper shows results on plasma dynamic synthesis of aluminum nitride using system based coaxial magneto plasma accelerator. The influence of using gaseous or solid precursors on such characteristics of the final product as phase content and particle size distribution was investigated. According to X-Ray diffractometry AlN phase content is increased in the case of use of solid nitrogen-containing precursor (melamine) in comparison with the use of gaseous nitrogen. The particle sizes distribution histograms are built in accordance with the data of bright-field TEM-images and shown in this paper. The most of particles are less than 100 nm in both experiment but there are some differences, depended on the precursor type, that are also described

Influence of non-vacuum electric arc synthesis energy on the product of tungsten ore concentrate processing

Relevance. Caused by the problem of developing methods for obtaining tungsten carbide, especially from tungsten-containing waste. As a solution, a non-vacuum electric arc method is proposed. It is easy to operate and cheap compared to a direct analogue (arc discharge method in inert gas atmosphere). The resulting product can be used as a catalyst carrier in hydrogen production reactions. Aim. To determine the current and the energy entered in the system, necessary to obtain a product with a largest proportion of the hexagonal phase of tungsten carbide WC from tungsten ore concentrate by a non-vacuum electric arc method and investigate a sample with the largest proportion of tungsten carbide phase. Object. Electric arc synthesis in open air from tungsten ore concentrate. Methods. Grinding in a SAMPLE SPEX 8000M ball mill, magnetic separation, non-vacuum electric arc method of synthesis, X-ray phase analysis on a Shimadzu XRD 7000s X-ray diffractometer (λ=1.54060 Å), scanning electron microscopy combined with X-ray fluorescence energy-dispersive analysis based on a TESCAN VEGA 3 microscope SBU with OXFORD X-Max prefix, transmission electron microscopy combined with energy dispersive spectroscopy and selected area electron diffraction based on the JEM-2100F microscope, scanning electron-ion microscopy based on the QUANTA 200 3D microscope. Results. The authors have built the dependence of the phase composition of the product of non-vacuum electric arc synthesis at current strengths from 50 to 220 A. Mass fraction of each of the identified phases in the synthesis product was determined using the reference intensity ratio. The current and the energy entered in the system, which provide the largest proportion of tungsten carbide WC in the synthesis product, are determined. The authors studied the product containing the largest proportion of tungsten carbide WC using scanning and transmission electron microscopy methods

Plasma dynamic synthesis of ultradispersed copper oxides

Copper oxide is necessary material for production of superconductors. The issue of obtaining high purity and nanosides CuO is actual. This article shows the results on the obtaining of nanodispersed copper oxide by plasma dynamic method in system based on coaxial magneto plasma accelerator with copper electrodes. Such analyses of ultradispersed synthesized products as X-Ray diffractometry, IR-spectroscopy and thermal analysis were carried out. According to XRD such phases as copper Cu, copper oxide (I) Cu[2]O, copper oxide (II) CuO, and copper hydroxide hydrate Cu(OH)[2]xH[2]O were identified in the product. It was found that with the gradual heating of the initial product up to 800°С the phase content changed dramatically in terms of enhancing copper oxide phase (up to 97%)

Studying the influence of supply pulse duration on the phase composition of iron oxides obtained by the plasma-dynamic method

Magnetic materials and in particular iron oxides are of a great practical interest. The magnetite phase and the unique epsilon phase of iron oxide can be especially pointed out. The main difficulty in the synthesis of the epsilon phase is connected with the fact that it can exist only in a nanoscale state and is extremely difficult to obtain. We used the method of direct plasma dynamic synthesis, which allows obtaining multiphase powders of iron oxides containing both the epsilon phase and magnetite. It was found that by varying the initial parameters of the power system, namely the pulse duration by increasing the capacitance of the capacitive energy storage, it is possible to influence the phase composition of the obtained products and to achieve the preferential output of the epsilon phase. In addition, in the mode with the maximum pulse duration, when the best product is obtained from the point of the epsilon phase output, the system efficiency of converting the stored energy into released energy significantly increases. In general, it has been established that such a regime is most favorable for the system operation for the purpose of the iron oxides synthesis

Influence of anionic surfactant on stability of nanoparticles in aqueous solutions

Dispersion and aggregation of nanoparticles in aqueous solutions are important factors for safe and effective application of nanoparticles, for instance, in the oil industry. As conventional oil reserves are depleted, it is necessary to advance chemical enhanced oil recovery (cEOR) techniques to develop unconventional oil reservoirs. Nanoparticles modified by surfactants can be a promising reagent in cEOR. These nanomaterials can reduce interfacial tension and change the wettability of reservoir rock, which leads to an increase in oil recovery. However, the application of nanoparticles is limited by their substantial aggregation in aqueous solutions. The purpose of this work is to select nanoparticles for obtaining stable sols in water in the presence of an anionic surfactant and to optimize the conditions (pH) for further modifying the nanoparticles with the anionic surfactant. Sodium dodecyl sulfate (SDS) is used as an anionic surfactant. The aggregation of oxide and carbon nanoparticles in water and anionic surfactant solutions was studied by laser diffraction, dynamic and electrophoretic light scattering methods. Most of the studied nanoparticles in water form aggregates with bi-, three- and polymodal particle size distributions. TiO2 nanoparticles obtained by plasma dynamic synthesis form the most stable sols in anionic surfactant solutions. The range of 5–7 pH is defined as optimal for their modification with surfactants. The stability of carbon nanoparticles in aqueous solutions increases significantly in the presence of a surfactant. The obtained results form the basis for further research on the modification of marked nanoparticles in surfactant solutions

Biochar influence on the development of spring wheat (Triticum aestivum L.) and acidity of soddy-podzolic soil in Western Siberia

The paper purpose was to establish the effect of applying biochar obtained from various organic wastes of agriculture (cow manure, straw), woodworking (pine sawdust) and food industry (pine nut shell), which are typical of Western Siberia, on the morphometric characteristics of plants (using spring wheat (Triticum aestivum L.) as the example) and the soddy-podzolic soil properties. The assessment of biochar influence was performed by a series of vegetation experiments using climatic chambers. As a result, it was found that the introduction of all the noted biochar types into the soil layer leads to a significant (p < 0.05) increase in the morphometric characteristics of spring wheat. For example, when applying the straw biochar to the soil, it results in growing the plant height to the node by 19%, while the number of leaves increased by 8% compared to the control variant. The introduction of biochar from manure leads to the increased length of the spring wheat root by 35%. Moreover, straw and manure biochars contribute to the reduction of soil acidity (increase in pH values from 7.1 to 7.4 and 7.8, respectively). The results of the comprehensive analysis indicate that the agronomic advantages of application of biochars obtained from wheat straw and cattle manure are better compared to biochars from pine sawdust and pine nut shells, which is due to higher concentration of nutrients and substances with alkaline reaction (carbonates and oxides) in the former. The results obtained are useful from the point of view of assessing the environmental risks when applying biochar ameliorants in soils typical of the boreal bioclimatic zone. Subsequent experiments, including studies of the joint application of biochars and fertilizers to the soil, will make it possible to develop recommendations for applying the thermal conversion technology for recycling the regional organic waste into ameliorants that improve soil quality and increase its fertility

OBTAINING BULK PRODUCTS FROM CU-SIC METAL-MATRIX COMPOSITE FOR ENERGY-EFFICIENT HEAT-CONDUCTING SYSTEMS

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