Nikitin, Dmitry Sergeevich

Pogorelova, S. O.

Shanenkov, Ivan Igorevich

Electronic archive of Tomsk Polytechnic University

209 PLASMODYNAMIC SYNTHESIS OF NANODISPERSED TI-B PHASES AND OBTAINING TI-B CERAMICS  S.O. Pogorelova1, D.S. Nikitin2, I.I. Shanenkov2 Tomsk Polytechnic University1,2 Institute of Power Engineering Department of Industrial Electric Power Supply, group 5A5D2  Nowadays, titanium boride (TiB) and titanium diboride (TiB2) have a lot of physical and mechanical properties, such as high hardness, high melting point, high thermal and electrical conductivity, good wear resistance. TiB and TiB2 can be used for obtaining functional ceramics, for producing electrodes for melting metals and in mechanical engineering and metallurgy [1]. So the problem of synthesis becomes ur-gent. Different approaches have been directed to synthesize titanium diboride na-nopowders, including mechanical alloying, sol-gel reduction and high energy ball milling [2]. However, there are some problems in synthesis nanopowders of the Ti-B system: high time and energy costs, unsatisfactory phase composition and dispersity of the product [1].  The present work reported a novel way of making nanocrystalline Ti-B phases (titanium boride and titanium diboride) in a hypersonic plasma jet. A hypersonic plasma jet was generated by an original electrical installation called a coaxial magne-toplasma accelerator with titanium electrodes. Principal construction of a coaxial magnetoplasma accelerator is shown in Fig.1. This method has been already success-fully used for synthesis of different nanopowders (including the system with titani-um) [3]. According to the purpose to synthesize nanosized Ti-B phases, three exper-iments with different ways of discharge initiations were implemented: 1) using titani-um conductors; 2) using carbon fibers; 3) using graphite aerosol (graphitization).  Fig.1. The construction of CMPA: 1 – central electrode; 2 – coaxial electrode Argon was used as an atmosphere of a reactor chamber. The chamber pressure was 2 atm., its purity was provided by double pumping. A magnetoplasma accelerator was suplied by a capacitive energy storage with a charging voltage Uch = 3.75 kV and 210 a capacity C = 9.6 mF, the value of input energy was Win = 67.5 kJ. The level of re-leased energy reached about Wr = 35 kJ. Amorphous boron in a form of powder was placed into the plazma formation zone. Titanium was introduced into the system by electroerosion from surface of a titanium accelerating channel. Synthesized powder products were analyzed without any preparation by the method of X-ray diffraction (XRD) using Shimadzu 7000 diffractometer. Figure 2 presents typical X-ray diffrac-tion patterns of the powders. The main results of the experiments were the powder products with mass up to 2.2 g. The main parameters of the experiments and the results of the study are given in Table 1. We can see the phases of TiB and TiB2 predominate in the synthesized product, which depends on the method of discharge initiation. In the experiment with using graphitization the content of TiB2 was 93.2%.   Fig. 2. Diffraction patterns of the synthesized powders Table 1. The main results of the experiments № Ways of dis-charge initia-tions m, g Uch, kV Pmax, kW W, кJ Phase composition, % TiB2 TiB 1 Ti-conductors 2.20 1.40 201 38.3 26.8 66.2 2 Carbon fibers 1.90 1.34 174 36.8 62.1 21.2 3 Graphitization 1.45 1.26 182 33.9 93.2 6.8 Ceramic simples, which were based on the synthesized powders, were obtained by the method of spark plasma sintering (SPS). The advantages of this method are ef-ficiency, speed of the process and suppression grain growth microstructure [3]. The installation of spark plasma sintering SPS-10-4, Thermal Technology was used for obtaining ceramics. The process of obtaining ceramics was characterized by the next parameters: pressure P = 60 MPa, temperature T = 1800˚C and holding time tT = 5 minutes. Density of the resulting ceramics for each of the experiments was: 211 1) using titanium conductors ρ = 3.40 g/cm3;  2) using carbon fibers ρ = 3.88 g/cm3;  3) using graphite aerosol (graphitization) ρ = 4.45 g/cm3.  These samples were processed on a grinding polishing machine for the prepa-ration thin sections Forcipol 1V. The ceramics samples were measured for micro-hardness on a Galileo hardness tester. The values of microhardness were: 1) P = 24.7 GPa; 2) P = 28.3 GPa; 3) P = 30.3 GPa. Thus, the obtained ceramics showed high values of hardness, depending on the phase composition of the initial powder and hence the way of obtaining the powdered product.  Fig. 3. The ceramic sample obtained from a powder (Experiment 3) This work was supported by the Russian Science Foundation (project no. 15-19-00049).  REFERENCES:   Andrievski R. Nanostructured titanium, zirconium and hafnium diborides: 1.the synthesis, properties, size effects and stability // Russian Chemical Re-views. - 2015.- V. 84 (5).- P. 540-554.  M. Masanta, P. Ganesh, R. Kaul, A. Roy Choudhury Microstructure and 2.mechanical properties of TiB2–TiC–Al2O3–SiC composite coatings devel-oped by combined SHS, sol–gel and laser technology // Surface & Coatings Technology. - 2010.- V. 204.- P. 3471-3480.  Evdokimov A.A. Diss. Plasmodynamis synthesize ultradisperced titanium 3.nitride and obtaining TiN-ceramics by Spark Plasma Sintering PhD in En-gineering sciences. Tomsk: NR TPU, 2013.-p.216.  Scientific adviser: A.A. Sivkov, Grand PhD in Engineering sciences, Prof. of the Department of Industrial Electric Power Supply of the Power Engineering Insti-tute of TPU.    

Plasmodynamic synthesis of nanodispersed Ti-B phases and obtaining Ti-B ceramics

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Plasmodynamic synthesis of nanodispersed Ti-B phases and obtaining Ti-B ceramics

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