Search

Spin defects in semiconductors are attracting interest as a material basis for quantum information and computing technologies. In this work, the spin properties of negatively charged nitrogen-vacancy (NV−) centers in a 6H-SiC silicon carbide crystal enriched with the 28 Si isotope were studied by high-frequency (94 GHz) electron paramagnetic resonance (EPR) methods. Due to an optical excitation channel at the NV− centers, it was possible to initialize the electron spin of the defect using a laser source, which led to a significant increase in the intensity of the recorded EPR signal. The dependences of the observed spin polarization were analyzed at different optical excitation wavelengths (λ = 640 – 1064 nm), output power (0 – 500 mW), and temperature (50 – 300 K) of the crystal. The results obtained reveal the optimal experimental conditions for maximizing the efficiency of optical quantum energy transfer to the spin system. This opens up new possibilities for using NV− centers in 6H-SiC to create multi-qubit spin-photon interfaces operating in the infrared region.

Objectives. To calculate the effect of leakage of volatile synthesis products on silicon carbide yield in an electrothermal fluidized bed reactor, as well as to develop a general model of the synthesis of finely divided silicon carbide. This will be achieved by particularizing a mathematical model of leakage of volatile products of chemical reactions from the reaction volume of the reactor with the fluidizing inert gas.Methods. As a method to produce silicon carbide, synthesis in an electrothermal fluidized bed was studied. The model of leakage of volatile products was validated by comparing the calculation results with existing experimental data on the SiC synthesis in a hightemperature fluidized bed reactor. The comparison parameters were: mass yield of silicon carbide, and the total synthesis time in a reactor with batch loading of silicon dioxide into the reaction volume.Results. The value of the parameter p in the general model of SiC synthesis in a fluidized bed was established. The parameter p is equal to the ratio of the number of carbon-containing particles involved in the formation of SiO, to the total number of silicon dioxide particles. It also characterizes the composition of stable complexes of particles of the charge at various operating temperatures of the fluidized bed. The discrepancy between the calculated and experimental values of the masses of the synthesized silicon carbide was shown not to exceed 15.5% at a high temperature of the fluidized bed (T = 1800°C) and decreases with a decrease in the operating temperature to 4.7% at T = 1450°C.Conclusions. The general computational model for silicon carbide synthesis with a built-in procedure for calculating the leakage of volatile products of chemical reactions enables the variants of SiC production in electrothermal fluidized bed reactors to be analyzed. In this case, it is important to establish an energy-efficient working cycle without preliminary expensive experimental studies.

The article discusses the possibility of using silicon carbide as the main component for preliminary deoxidation of a carbonaceous intermediate product when the latter is discharged from the converter into a ladle in order to adjust the costs of tradition‑ ally used deoxidizing materials. It has been established that the use of silicon carbide as a deoxidizer is economically feasible in the smelting of low‑carbon low‑alloy steels of converter production.The method of adding the material is described and the results of the work performed are presented.

Relevance. The search for a useful application of carbonaceous residues of rice husks thermal processing. These residues due to high silicon content in the inorganic part can potentially be used to produce silicon carbide – an important functional material for various fields of science and technology. Useful utilization of this waste will allow not only solving the environmental problem associated with their inefficient application and formal disposal, but also obtaining value-added products in the form of SiC-based ceramics. Aim. To obtain SiC-based bulk products from carbonaceous residues of rice husk thermal processing by spark plasma sintering with a minimum number of additional stages of feedstock processing. Objects. SiC-based bulk products obtained using carbonaceous residues of rice husk thermal processing. The samples were obtained by spark plasma sintering at 1800 °C, pressure of 60 MPa and holding time of 10 minutes. Methods. Spark plasma sintering; X-ray diffractometry (X-ray phase analysis); scanning electron microscopy; vacuumless arc discharge synthesis method. Results. The authors have carried out the experimental studies to assess the possibility of applying carbonaceous residue of rice husk thermal processing as a precursor for the synthesis of silicon carbide in bulk (ceramics) and dispersed (powder) forms. A series of experiments on spark plasma sintering of carbonaceous residue from rice husk thermal processing in the initial and milled form, with SiO2 silica sand additives, as well as with the use of silicon carbide powders synthesized from carbonaceous residue by vacuumless arc discharge method were implemented. The latter is performed within a one-stage fast-flowing process in an air environment and does not require the use of a vacuum system. Preliminary results demonstrated the possibility of obtaining bulk products and dispersed powders based on silicon carbide with a content of at least 50 and 60 wt %, respectively, and indicate the prospects of further increasing phase purity by optimizing spark plasma sintering and vacuumless arc discharge synthesis.

In the paper, the effects of type, dose and temperature of irradiation with stable elementary particles (0.9 MeV electrons and 15 MeV protons) on the properties of the high-voltage 4H-SiC Junction Barrier Schottky diodes at room temperature (23°С) and the limiting operating one (175°С) have been compared. The electron irradiation of the objects with equal doses at 23°С и 175°С was found to cause a significant increase in its base differential resistance in the former case and the absence of this effect in the latter. However, in the latter, DLTS spectra exhibited a noticeable increase in the concentration of deep levels in the upper half of the band gap. The proton irradiation resulted in a noticeable rise in the mentioned resistance even at 175°С. The results obtained make it possible to evaluate the radiation resistance of the studied devices to proton and electron irradiation within the framework of any given requirements.

Compositions of ultrafine Si and C particles are promising anode materials for lithium-ion power sources with improved energy characteristics. In the work, samples of lithium-ion power sources with an anode made of ultrafine SiC fibers, as well as mixtures of SiC fibers with graphite (C/SiC) and electrolytically deposited submicron silicon fibers (C/Si/SiC) were fabricated and studied for energy characteristics. The working ability of the mixtures obtained during lithiation/delithiation was shown, and the main energy characteristics of the investigated anode half-cells were determined. After 100 cycles, the SiC anode reached a discharge capacity of 180 and 138 mA⋅h/g at a charge current of C/20 and C, respectively. Anodes made of mixtures (wt%) 29.5C-70.5SiC and 50Si-14.5C-35.5SiC show discharge capacities of 328 and 400 mA⋅h/g at a charge current of C/2. The Coulomb efficiency of all samples was above 99%.

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 technique of obtaining and the first results of studying thin crystalline silicon carbide films by deposition from a gas phase in a reactor with cold walls is presented in the article. Trimethylchlorosilane was used as the precursor material, nitrogen was used as the carrier gas for the formation of the vapor-gas mixture. The films were produced on the Easytube 3000 chemical synthesis unit from the manufacturer Firstnano. X-ray patterns of synthesized samples were obtained and investigated.

The article presents the results of comparative tests on the wear resistance of composite materials (CM) sintered at high pressures and temperatures based on impact diamond (diamond-lonsdaleite abrasive — DLA) when processing silicon carbide (SiC). To assess the CM performance based on impact diamonds, a method has been developed for determining the wear resistance, based on the determination of the CM specific productivity. It is shown that for CMs based on impact diamond, it is expedient to use SiC as a binder. For CMs based on impact diamond with an additive of 40 vol.% SiC, specific productivity when machining a silicon carbide wheel is 25–30 % higher than for compositions containing dense BN phases — wBN and cBN. The decrease in the specific productivity of CM “impact diamond — cBN” relative to CM “impact diamond — SiC” is determined by the higher dispersion of crystals of dense BN phases in comparison with SiC, which generally impairs the abrasive ability of the material. In this case, the addition of a coarse fraction of impact diamond 100/63 μm to the charge composition does not lead to an increase in the specific productivity of the abrasive element as compared to CM based on DLA with a particle size of less than 40 μm. Preliminary mechanical activation of the initial charge also reduces the CM abrasive ability due to the formation of a highly dispersed structure of the material.

Copyright of News of Kazakhstan Science / Novosti nauki Kazahstana is the property of NCSTE (JSC National Center for State Scientific and Technical Evaluations) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A study of a mixture of copper and silicon carbide powders after one-sided cold forming in a closed mold was carried out by the next methods: scanning electron microscopy, hydrostatic weighing and analysis of pressing diagrams. The main stages of molding, their boundaries and characteristic processes occurring at each of them are identified. It was found that at least three areas can be distinguished in the molding diagram. It is shown that their boundaries (in terms of pressure) are determined by the mechanical properties of the materials of the used powders and the processes of redistribution / packing of structural elements and their elastic / inelastic deformation.

The article studies the structure, phase composition and physicomechanical characteristics of the nanocomposite based on impact diamonds. It is shown that the additions of a binder based on SiC and Si lead to reduction of the defectiveness of the nanocomposite and increase in the uniformity of its structure compared to the material without additives. Moreover, increase in the binder content also leads to the inversion of the structure type of the nanocomposite from polycrystalline to matrix. It is established that the addition of amorphous carbon black and boron affects the refinement of the nanocomposite matrix structure due to the formation of secondary finedispersed nanostructured SiC and boron carbide. Preliminary mechanical activation of the reaction mixture leads to structural changes in the synthesized material in comparison with the material obtained without the use of mechanical activation. In this case, the hardness of the samples obtained under comparable synthesis modes increases, which is associated both with the formation of a fine-grained structure of the material and with the phase transformation of lonsdaleite to diamond. An analysis of the microhardness and heat resistance of the obtained samples makes it possible to conclude that the achieved level of physicomechanical parameters of the diamond nanocomposite allows it to be used in a stone-processing tool for treating medium hard rocks.

Technological features of the growth of single crystal silicon carbide inevitably create condi-tions for the formation of crystal structure defects in them. A method is proposed for recognizing and analyzing a dislocation structure of single crystal silicon carbide based on the use of optical microscopy and a direct distribution neural network. The method was tested on homoepitaxial lay-ers of 4H-polytype silicon carbide. Software has been developed that allows building maps of the dislocation structure distribution over the surface of single crystal silicon carbide. The software was tested on digital images of the surface of silicon carbide epitaxial layers. The accuracy of recognition of dislocation structure was 95%. The dislocation mapping is used in the development of process technologies for reducing their density during the growth of single crystals.

This article presents the results of a study of the microstructure and density of powder materials of the Al – SiC and Cu – SiC systems. They are obtained by cold forming a mixture of powders of copper, aluminum and silicon carbide. A model for molding powder systems consisting of plastic (metal) and brittle (SiC) materials is proposed.

The results of modeling of electron transfer processes in a three-dimensional semiconductor structure containing a single layer of graphene using the Monte-Carlo method are presented. The use of graphene, which has a high mobility of charge carriers, high thermal conductivity and a number of other positive properties, is promising for the creation of new semiconductor devices with good output characteristics . As a result of modeling, the dependences of the velocity, average energy, mobility, diffusion coefficient on the structure length and electric field intensity in a semiconductor structure containing a graphene layer and a region of a 4H-SiC silicon carbide material are obtained.

The results of the simulation of electron transfer processes in the three-dimensional structure of 4H-SiC silicon carbide are presented using the Monte Carlo method. The dependence of the average drift velocity, average energy and electron mobility of electrons and the diffusion coefficient from the electric field are obtained.

The article presents the research results of semiconductor silicon carbide (porous) structures with the implanted carbon-14. The results of experimental measurements collected data on parameters of photovoltaic energy conversion of light quanta into a photo-EMF to confirm the efficiency of p-n junction, an evaluation of the effectiveness of the introduction of carbon-14 in the molecule silicon carbide electrophysical measurements. In the process used the technology of solid-phase transformation of the surface of the monocrystalline silicon substrate in the phase of monocrystalline silicon carbide by chemical transport of carbon in the environment of hydrogen.

The interest in silicon carbide (SiC-based) ceramics and composites as matrix material for nuclear waste immobilization is grown up. Long-term chemical durability and radiation resistance of SiC are important factors for radionuclides immobilization. Advantages of SiC-based ceramics as structural materials in nuclear applications are the high-temperature properties, high density and reduced neutron activation. The use of radiation resistant materials is a strong requirement for safe and environmentally beneficial energy system. The SiC ceramics stability under irradiation for temperatures up to 1273 K is also very important for nuclear power applications. The SiC matrices doped by additives of Cr, Si were fabricated using High Speed Hot Pressing Method. Additives content was in the range from 0.5 to 3 wt %. Microstructural characteristics of silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and infra-red spectroscopy (IR) methods. The results of microcracking under indentation conditions were revealed the lack of cracks in the SiC ceramics with Cr additives before and after irradiation process. In addition, it was demonstrated that samples of SiC with alloying additives Cr and Si possess high mechanical parameters under γ-irradiation process. The strength of ceramics increases with the uniform and fine-grained structure formation. The modification of phase composition and mechanical properties of the SiC ceramics with Cr and Si additives under γ-irradiation were analyzed for further development of radiation resistant and matrix materials for radioactive wastes immobilization.

Cu − SiC composites were studied by scanning electron microscopy after processes of molding and a heat treatment. After pressing, plastic deformation of copper particles and traces of destruction of silicon carbide (cracks and debris) are observed. After the solid-phase sintering, formation of a porous structure in the matrix material is noted without significant changes in the filler particles. Data on the distribution of chemical elements near the SiC − Cu interface indicate an insignificant effect of diffusion processes.

Copyright of Problems of Friction & Wear is the property of National Aviation University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of News of Kazakhstan Science / Novosti nauki Kazahstana is the property of NCSTE (JSC National Center for State Scientific and Technical Evaluations) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The problems of stability semiconductor device structures to open space conditions influence are studied. It is shown that complex investigation of electrophysical properties of semiconductor layers during the time of cosmic flight is necessary. Samples of device structures for investigation of open space conditions influence on semiconductor layer resistivity, metal-semiconductor and insulator-semiconductor interfaces properties are proposed. Methods of measuring resistivity, Hall factor, current-voltage characteristics and volt capacitive characteristics of device structures samples are considered. Measurement circuits adapted for operation with automatic measurement systems are proposed.

Scientific and methodological principles of synthesis of heterophase filler with nanoparticles of SiC, α-Al2O3, Si, Fe are developed on the basis of oxides micropowder and carbide-forming elements. The processed filler, introduced into aluminum melts, provides reinforcement of the aluminum-matrix composites. It is found that the effect of this process is refinement of alloy matrix structure 2–3 times, which leads to increase in the microhardness of the alloy structural phases. It is shown that introduction of 3 wt.% α-phase increases microhardness by 100 MPa and 100–105 MPa at the eutectic point. The samples of the composite material on the base of silumin AK12M2MgN, containing 1–2 wt.% of the composite modifier, have the increased wear resistance 2–4 times higher than the initial alloy samples.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Method of magnetron sputtering targets polycrystalline SiC-AlN on substrates SiC and Al2O3 thin films received solid solutions (SiC)1-x(AlN)x. The methods of Xray and electron microscopy studies the structure and composition of films. There are factors that determine the composition and structure of films, as well as conditions for the formation of monocrystalline films of (SiC)1-x(AlN)x to the substrate SiC. The basic technological parameters of process magnetron sedimentation of films (SiC)1-x(AlN)x are calculated.

Experimental results of research of switching characteristics of high-voltage carbide-silicon switchboards on the basis of drift diodes with sharp restoration (DDSR) and the generator of nanosecond voltage impulses developed on their basis with a megawatt pulse power are presented. Possibility of a consecutive compression of energy is for the first time shown by the DDSR cascades which are switched on parallel to silicon and carbide-silicon.

The paper analyzes the available literature data on the properties of different materials currently used in the means of individual armor protection and the methods for improving their bulletproof and other service properties are evaluated. It is shown that at the present time to create the means of individual armor protection, a variety of materials are used: fabric aramid or polyethylene fibers, metal plates based on steels, titanium, aluminum and their alloys, as well as ceramics based on boron and silicon carbides, etc. The main advantages and disadvantages of these armored materials are shown. On the basis of literary data, it was established that for the 3-5 class of protection, the armored plates of structural alloyed steels were widely used. To minimize the disadvantages inherent in steel armored plates, it is necessary to use bimetallic compositions with alternating hard and soft layers, produced, among others, by welding or surfacing methods. 20 Ref., 4 Tab., 3 Fig. [ABSTRACT FROM AUTHOR]

In the proposed work conventional methods of SiC layers formation and polytypes of this compound have been reviewed. A new methodology of silicon carbide obtaining has been proposed. It is based on magnetron sputtering of compound targets. The optimal geometrical characteristics of the compound targets made of silicon and graphite have been calculated. The condensates structure and composition were studied with help of transmission electron microscopy (TEM), electron diffraction along with the energy dispersive X-ray elemental analysis. On the basis of the investigations the geometrical characteristics of the compound target and the optimal technological parameters required for the formation of silicon carbide in the form of 3C-SiC polytype with element composition close to stoichiometric have been determined. [ABSTRACT FROM AUTHOR]

The present paper demonstrates the results of an EPR study of n-type hexagonal 6H- and cubic 3CSiC crystals irradiated with fast neutrons in a dose range of 2·1018-5·1019 cm-2. We reveal that the negatively charged silicon monovacancy V-Si is a dominant paramagnetic defect. We also observe some changes of intensity and line shape for its EPR spectrum in the dose range and uncover that the introduction rate of this defect is about 1,3 cm-1. Crucially, we identify a novel EPR spectrum of a defect labeled Ky5 in the cubic SiC crystals irradiated with 1·1019 cm-2 neutrons, except for the intense signal from V-Si. The spin-Hamiltonian parameters identity for Ky5 and divacancies in the 6H-SiC and 4H-SiC crystals makes it possible to attribute the Ky5 center to the divacancy [VSiVC]0 in the cubic SiC. [ABSTRACT FROM AUTHOR]

In this paper, we studied the influence of the microplasma structure, operating voltage and temperature on the ultraviolet component of the spectrum distribution of quantum output of SiC-6H and SiC-15R based light emitting diodes, working in the electrical breakdown regime. Moreover, revealed was the well-formed connection of samples parameters with the initial crystallites properties and microplasma structure of the breakdown. The obtained results proved the probability of the range extension of the devices' stable work in the ultraviolet region to 250nm. [ABSTRACT FROM AUTHOR]

Theoretical bases of technology of formation of ohmic contacts metal-support, which represents thin films on the basis of refractory metals applied to silicon and silicon carbide, have been developed. For these supports the Physical processes occurring at deposition of refractory metal vapour on ideal surface and on stepped chip of crystal, have been analyzed. [ABSTRACT FROM AUTHOR]