Nassyrbayev, A. R.

Pogorelova, S. O.

Shanenkov, Ivan Igorevich

Electronic archive of Tomsk Polytechnic University

XIX Международная научно-практическая конференция имени профессора Л.П. Кулёва496PLASMODYNAMIC SYNTHESIS OF NANOSCALE SILICON CARBIDE: WAYS OF OPTIMIZATIONA.R. Nassyrbayev, S.O. Pogorelova, I.I. ShanenkovScientific adviser – PhD in Engineering sciences, Prof. of TPU A.A. SivkovNational Research Tomsk Polytechnic University 634050, Russia, Tomsk, 30 Lenin Avenue, arn1@tpu.ruSilicon carbide has been used in many fields of human activity: power electronics, the produc-tion of abrasive materials and ceramic products for working in corrosive environments. SiC is used due to its properties: high hardness, comparable with diamond, and wear resistance, wide band gap, re-fractory [1]. The characteristics of the materials can be improved by using nanoparticles in their produc-tion [2].Silicon carbide synthesis techniques are not effective enough, because they have unsatisfactory dispersity, high duration etc. The synthesis of na-no-sized SiC was carried out on a coaxial magneto-plasma accelerator (CMPA) [3]. This work is aimed at studying ways to optimize the plasmodynamic synthesis of nanoscale silicon carbide. Two series of experiments were carried out: changing the ratio of precursors and the influence of pressure in the reactor-chamber.The identification of the best ratio of precursors is necessary to improve the purity of the product, to reduce the mass content of unreacted phases: silicon and carbon. Experiments with various precursors ratio (Si : C = 1.5 : 1, 2.3 : 1, 3 : 1, 9 : 1) were carried out. The intensity peaks on the X-ray diffractograms correspond to cubic silicon carbide. When the sil-icon content in the mixture is increased, the mass content of carbon in the synthesis product decreas-es.Optimal phase composition (over 90 % silicon carbide) is achieved with a relative atomic ratio Si : C = 0.56 : 0.44 which corresponds to the mass ratio Si : C = 3 : 1. The stoichiometric equilibrium occurs when there is a lack of the carbon in the mix-ture, because carbon is partially produced by elec-troerosion from the graphite accelerating channel.The synthesis and growth of silicon carbide crystals occurs in the head shock of plasma jet compaction. The reactor-chamber’s atmosphere is located in the path of plasma propagation, thereby affecting the synthesis product.A series with different pressures (low – 0.1 and 0.5 atm., normal – 1.0 and 1.5 atm., high – 3.0 and 5.0 atm.) was carried out to study the effect of the reactor-chamber’s atmosphere pressure on the phase composition of the synthesized product.The following dependence was revealed. The high pressure of atmosphere inhibits the propa-gation of plasma, thereby slowing the rate of the plasma flow. This means that the energy pT-param-eters in the head shock of plasma jet compression decrease. Reducing energy parameters leads to de-creasing formation of silicon carbide particles and increasing the content of unreacted silicon and car-bon particles. At a low pressure, the lifetime of the quasistationary mode decreases significantly, that leads to a decrease in the content of cubic silicon carbide in the synthesized powder.The result of this work is the optimization of the plasmadynamic synthesis of nanoscale cubic silicon carbide. The synthesis products were inves-tigated by X-ray diffractometry (XRD) and trans-mission electron microscopy (TEM). Based on the results of X-ray diffraction analysis, it was found that the optimal phase composition (over 97 % in the synthesized product) is achieved when the rec-tor-chamber’s atmosphere pressure reaches p = 1.5 atm. and the precursors ratio reaches Si : C = 3 : 1. Transmission electron microscopy provides visual proofs of synthesis nanosized product (average par-ticle size 70 nm).Fig. 1.  TEM-image of synthesized product Секция 7.  Химия и химическая технология на иностранном языке497References1. Andrievski R.A. Nano-sized silicon carbide: synthesis, structure and properties // Russian Chemical	Reviews,	2009.–	V.78.–	№9.–	P.821.2. Klabunde K.J. Introduction to nanotechnology // Nanoscale Materials in Chemistry, 2001.– P.1–13.3. Sivkov A.A., Pak A.Y. Coaxial magnetoplasma accelerator	//	RF	Patent,	2011.–	№	2431947.DEPENDENCE OF THE PRODUCT'S PHASE COMPOSITION ON THE RATIO OF PRECURSORS IN PLASMODYNAMIC SYNTHESIS OF TITANIUM DIBORIDES.O. Pogorelova, A.R. Nassyrbayev, I.I. ShanenkovScientific adviser – PhD in Engineering sciences, Prof. of ISE TPU A.A. SivkovNational Research Tomsk Polytechnic University 634050, Russia, Tomsk, 30 Lenin Avenue, sop2@tpu.ruIn present time materials with high physic-me-chanical properties are in demand. Materials based on nanostructured powder show higher properties than coarse-grained analogs. Titanium diboride (TiB2) is an excellent powder for functional ceram-ics, which needs in a lot of application in industry, for example, metallurgy, mechanical engineering [1]. It can be used as surface coatings on iron, steels, refractory metals, because TiB2 has high hardness, good wear and corrosion resistance [2].In this paper presents one of a possible way of obtaining TiB2 – plasmodynamic synthesis us-ing coaxial magnetoplasma accelerator (CMPA). The aim of this work was to find the optimal ra-tio of precursors to synthesize the phase of titani-um diboride hexagonal syngony with spatial group P6/mmm. The possibility of synthesis nanopowders was shown in the work [3].According to the aim series of experiments with different mass ratio of Ti:B precursors were implemented (26.7 : 73.3; 45.5 : 54.5; 61.1 : 38.9; 86.4 : 13.6). Synthesized powder products without any pretreatment were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM). Quantitative X-ray analysis was performed using the PowderCell program. The highest yield of the ti-tanium diboride phase (96.2 %) was achieved in the experiment with a Ti : B ratio of 45.5 : 54.5, bur the average size of particles is 67.8 nm. The experiment with a boron percentage of 73 % was implemented, which from the Ti-B state diagram is the region for the production of titanium diboride. The yield of TiB2 is 93.2 % and the particle size is the smallest in comparison with the other experiments – 56.1 nm.The analysis of the crystal forms of the product was carried out on the basis of a set of light-field TEM and HRTEM images. There is typical bright-field image of transmission electron microscopy in figure 1. It can be seen that the product basically includes at least two types of particles. The first type is prismatic crystals of a hexagonal and dihexagonal forms, which looks like a circle in a plan. This form corresponds to the spatial group P6/mmm of the hexagonal system. The habit of a crystal can exist in several simple forms: hexagonal and dihexago-nal prisms and pyramids. In other areas they can be related to the second type – crystals in the form of a cube that corresponds to the spatial group Fm3m for the corresponding phase of titanium diboride TiB cubic syngony. This product consists only of particles of two fractions: cubes and hexagons with a narrow width distribution up to 100 nm in size.Thus, plasmodynamic synthesis of nanocrys-talline particles of titanium diboride with hexagonal syngony with the spatial group P6/mmm was car-Fig. 1.		Typical	bright-field	image	of	transmission electron microscopy

Plasmodynamic synthesis of nanoscale silicon carbide: ways of optimization

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Plasmodynamic synthesis of nanoscale silicon carbide: ways of optimization

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