UDC 546.26-162:548.735
B. Tian*, B. Xu, Y. Xu
School of Materials Science & Engineering, Shandong Jianzhu University, Jinan, China
*btin198@163.com
Analysis of direct transformation from graphite to diamond crystal (p. 3–10)
The lattice parameters of cubic diamond and rhombohedral graphite under the probable direct transformation synthesis conditions have been obtained by means of linear expansion coefficient and elastic constant. Based on the empirical electron theory in solids and molecules, the valence electron structures (VESs) of graphite and diamond, the covalent electron densities (CEDs), and the relative electron density differences (REDDs) of the diamond growth interfaces have been calculated. It has been found that the REEDs of graphite/diamond interfaces were awfully large and the CEDs were discontinuous at the first order approximation. Not any meaningful atomic state of graphite structure, which satisfied the bond length difference formula, existed on the detonation synthetic conditions. Accordingly, it was considered that the direct transformation from graphite to diamond could not come true from the perspective of VES. In addition, the mechanism of synthesis diamond by explosive detonation was discussed based on the VESs of graphite and diamond.
Keywords: graphite, diamond, direct transformation, HPHT, VES.
UDC 620.22-621.921.34
M. V. Novikov1, V. A. Mechnyk1, *, M. O. Bondarenko1, Yu. V. Nesterenko2, B. A. Lyashenko3, M. O. Kuzin4
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2National Technical University of Ukraine
“Kyiv Polytechnic Institute”, Kyiv, Ukraine
3V. G. S. Pisarenko NAS of Ukraine, Kyiv, Ukraine
4Lviv Branch of Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lviv, Ukraine
*vlad.me4nik@ukr.net
Composite materials of the diamond–(Co–Cu–Sn) system with improved mechanical characteristics. Communication 2. Effect of CrB2 additive on the structure and properties of the diamond-(Co–Cu–Sn) composite (pp. 11–27)
Changes in the structure of the diamond–metal bond transition zone and the metal bond in the diamond-(78.4Co–11.76Cu–7.84Sn–2CrB2) composite after its sintering in a mold in a hydrogen environment at a temperature of 800 °C for 1 h depending on the parameters of hot pressing were studied, and their effect on the physicomechanical and tribological properties of the composites was investigated. It is shown that the addition of CrB2 to the composition of the initial diamond-(80Сo–12Cu–8Sn) composite in an amount of 2% (by weight) provides an increase in the ultimate strength during compression from 816 to 1720 MPa, bending from 790 to 1250 MPa, and wear resistance by 2.4 times. The improvement of the properties of the composite and its increase in wear resistance is ensured by the formation of Cr3C2 nanocarbide in the transition zone and a metallic bond with Co, CrB2 phases and CoSn inclusions evenly distributed throughout its volume.
Keywords: diamond, cobalt, copper, tin, chromium diboride, transition zone, phase, composite, decarburization, pressure, temperature, structure, tribological properties.
UDC 541.1+541.128
E. V. Ishchenko*, S. V. Gaidai, T. M. Zakharova, A. IN. Yatsymirskyi, Ya. WITH. Shevchuk
Kyiv National University named after Taras Shevchenko, Kyiv, Ukraine
*isch@voliacable.com
Study of kinetic regularities of CO oxidation on Cu–Co–Fe oxide catalysts, massive and supported on carbon nanotubes (pp. 28–36)
The influence of catalysts for the synthesis of carbon nanotubes, as well as the technology of applying the active oxide Cu–Co–Fe mass, on the kinetic regularities of the CO oxidation reaction was studied. It is shown that, both for massive oxide Cu–Co–Fe catalysts and for those supported on carbon nanotubes, the experimental data are consistent with the Ili-Rydil kinetic scheme. On the basis of the proposed mechanism, the effective rate constants of the reaction were calculated using different methods, and the prospect of using oxide Cu–Co–Fe catalysts applied to carbon nanotubes was shown.
Keywords: catalyst, carbon monoxide, kinetics, carbon nanotubes, oxide Cu–Co–Fe system.
UDC 691.327:666.973.6
M. AND. Tsar
Institute of Superhard Materials named after IN. N. Bakulya National Academy of Sciences of Ukraine, Kyiv, Ukraine
ts_maxim@ukr.net
Investigation of surface anisotropy of a polycrystalline gallium nitride coating using a tunneling microscope equipped with a boron-doped diamond tip (pp. 37–47)
The structural features of the polycrystalline gallium nitride coating formed on a silicon oxide substrate are considered. It was experimentally shown that as the crystals grow, not only the surface morphology changes, but also the crystal structure, as well as electrophysical parameters. It is shown that the topography of the crystal surface at the initial stage of coating deposition is formed due to diffusional mass transfer.
Key words: polycrystalline coating of gallium nitride, wurtzite, sphalerite, diffusion mass transfer, scanning tunneling microscope, semiconductor tip made of diamond, doped about boron.
UDC 621.762.242: 669.27
I. V. Andreev
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
aigor@i.ua
The Effect of Cooling Rate of Tungsten Heavy Alloys of the W–Ni–Fe Type from the Sintering Temperature on the Formation of Their Physico-Mechanical Properties (pp. 48–53)
The effect of cooling conditions after liquid-phase sintering of tungsten heavy alloys was studied. It was found that to ensure high plasticity of tungsten heavy alloy, the cooling rate from the sintering temperature should ensure the removal of the main part of hydrogen dissolved in the volume of the heavy alloy in the temperature range of the existence of the liquid phase.
Keywords: tungsten heavy alloy, sintering, physico-mechanical properties, cooling.
UDC 669.018.25:621.793.6:669.38’781
S. M. Chernega1, , I. A. Polyakov1, *, M. A. Krasovsky2
1National Technical University of Ukraine “Kyiv Polytechnic Institute”, Kyiv, Ukraine
2Institute of Problems of Materials Science named after I. M. Frantsevich NAS of Ukraine, Kyiv, Ukraine
*smchernega@ukr.net
**polykov_igor@ukr.net
Improving the Wear Resistance of T15K6 Hard Alloy by Boriding and Borocoppering (pp. 54–62)
The results of the study on the formation of complex diffusion boride layers by the powder method on T15K6 hard alloy are presented. The phase and chemical composition, thickness and microhardness of the obtained layers on T15K6 hard alloy are determined. It was found that the diffusion layers obtained in the boronizing medium with the addition of copper-containing compounds serving as a source of copper consist of TiB, CoB, WC and Cu phases. Boriding allows the formation of boride phases in the surface zone of the hard alloy with a microhardness of up to 33 GPa, and borocopperization – up to 25 GPa compared to the base material (13.5 GPa) and, thus, increase the wear resistance of the T15K6 hard alloy by 2.0–2.2 times.
Keywords: boron carbide, boronizing, boride layer, hard alloy, copper, structure, diffusion, friction, microstructure, microhardness, wear resistance.
UDC 621.623
A. Yu. Filatov*, V. I. Sidorko, S. V. Kovalev, Yu. D. Filatov, A. G. Wind
Institute of Superhard Materials named after IN. N. Bakulya National Academy of Sciences of Ukraine, Kyiv, Ukraine
*filatov@ism.kiev.ua
Roughness of polished surfaces of opto-electronic elements from single crystal materials (pp. 63–76)
As a result of studies of the regularities of the formation of single crystal planes with different crystallographic orientation, it was established that when polishing sapphire, the roughness parameters Ra, Rq, Rmax decrease in the order c > r > m > a with a decrease in the dielectric permittivity, thermal conductivity coefficient of the processed material, the height of the sludge particles, and the Lifshitz constant, which characterizes the energy of interaction of the polishing powder grains with the processed surface. The minimum permissible values of the roughness parameters of atomically smooth surfaces, which depend linearly on the interplane distances and decrease in the series r > a > c > m, are determined.
Keywords: polishing, slime particle, roughness parameters.
UDC 621.922.34
M. N. Sheiko
Institute of Superhard Materials named after IN. N. Bakulya National Academy of Sciences of Ukraine, Kyiv, Ukraine
max-kiev@i.ua
The shape of the grains as a factor determining the parameters of the diamond-galvanic coating of the straightening tool. Message 3. The simplest spatial model of a diamond grain – “barrel of parabolic and circular rivets” (pp. 77–88)
The simplest spatial model of a diamond grain in a diamond-galvanic coating of a straightening tool is given – “barrel of a parabolic and circular rivet”. It is shown that the accepted ideas about the shape of the grain allow, on the one hand, to adequately describe, including at the quantitative level, the experimentally known ratios of parameters of the diamond-galvanic coating, on the other hand, to obtain more detailed information for their application with given characteristics.
Key words: diamond-galvanic coating, diamond powder, straightening tool, spatial model of diamond grain.
UDC 546.273-31:536.42:539.89
V. Z. Turkevich1, *, D. V. Turkevich1, V. L. Solozhenko2, **
1Institute for Superhard Materials, National Academy of Sciences of Ukraine, Kiev, Ukraine
2LSPM–CNRS, Université Paris Nord, Villetaneuse, France
*vturk@ism.kiev.ua
** vladimir.solozhenko@univ-paris13.fr
Phase diagram of the B–B2O3 system at pressures to 24 Gpa (pages 89–91)
The evolution of topology of the B–B2O3 phase diagram has been studied at pressures up to 24 GPa using models of phenomenological thermodynamics with interaction parameters derived from experimental data on phase equilibria at high pressures and high temperatures.
Keywords: B–B2O3 system, high pressure, high temperature, phase diagram.