UDC 62-987:621.921.34
AND. I. Prykhna (Kyiv)
High-pressure devices in the production of synthetic diamonds (review)
Brief information on the creation of high-pressure devices since the thirties of the last century is given. Devices developed by employees of the Institute of Superhard Materials named after V.N. Bakulya of the National Academy of Sciences of Ukraine in the second half of the 20th century.
Key words: apparatus, pressure, anvil, tension, synthesis, punch.
UDC 541.1:661.657
IN. WITH. Turkevich, I. AND. Petrusha, D. IN. Turkevich, S. N. Dub, N. N. Belyavina (Kyiv) N. Frage, N. Frumina (Beer Sheva, Israel)
Formation of phases in the B—BN—B2O3 system at high pressures and temperatures, their wettability by copper-based melts
In a high-pressure device of the “toroid” type, from the initial β-rhombohedral or amorphous boron, hexagonal graphite-like boron nitride hBN, and amorphous boron oxide B2O3 at a pressure of 8 GPa and temperatures of 2100—2900 K, multiphase materials were obtained, including boron subnitride B6N, boron suboxide B6O, and cubic boron nitride cBN; their hardness was measured. The formation of ternary phases in the B—BN—B2O3 system was not observed. The wettability of the obtained materials with copper-based melts was studied. It was established that the introduction of 10 ‰ (mol.) Ti into the copper melt reduces the contact angle to less than 20 degrees.
Key words: boron suboxide, boron subnitride, high pressures and temperatures, synthesis, wetting.
UDC 621.762.4.045:621.921.34
AND. AND. Shulzhenko, A. N. Sokolov, M. G. Loshak, L. I. Aleksandrova, N.I. Zayka (Kiev)
Physico-mechanical properties and structure of diamond polycrystalline composite materials obtained from powders of different dispersion
Using nanotechnology powder materials, a nanostructured diamond composite material with an average grain size of 0.08 μm and a hardness corresponding to the hardness of diamond composite materials with a grain size of 30 μm was obtained. A comparative study of the temperature dependence of the hardness of diamond nanostructured composites of different dispersions was carried out. It is shown that the thermal stability of the diamond composite depends not only on the composition of the activating additive, but also on the size of the diamond powders. The research results indicate the prospect of using the obtained material for finishing non-ferrous metals and alloys instead of natural diamonds.
Key words: diamond, high pressure, nanocomposite, thermal stability.
UDC 621.762.5:539.26
M. P. Bezhenar, S. A. Bozhko, N. M. Bilyavina, O. V. Krishtova, G. S. Oleinyk (Kyiv)
Structure formation during reaction sintering of submicron and nanometer powders of cubic boron nitride with aluminum at the stage of impregnation under high pressure
The porosity characteristics, phase composition and structure of samples obtained from submicron and nanometric cBN powders after their impregnation with aluminum under a pressure of 2.5 GPa at a temperature of 1300 K were studied. It was shown that a feature of the consolidation of nanopowders at such p,T parameters is the formation of local volumes of different densities, which causes the complexity of impregnation and leads to an increase in closed porosity, stress gradients over the volume and, as a result, to the development deformation phase transformation of cBN–› hBN, as well as crack formation in samples with decreasing temperature and pressure. It is shown that for obtaining a homogeneous impregnation structure, starting cBN powders with a small content of nanorange fractions can be promising, when nanoparticles do not form aggregates of different densities, but are distributed over the surface of larger ones.
Keywords: cubic boron nitride, nanopowder, pressure impregnation, sintering, aluminum, structure
UDK 544.3:621.762
A. F. Lisovsky (Kyiv)
Thermodynamics of nanoparticle consolidation in a two-phase solid-mobile phase system
Thermodynamic functions describing the process of nanoparticle consolidation in a two-phase dispersed solid-mobile phase system and the processes of deconsolidation of a polycrystalline body and spontaneous formation of a nanodispersed system are derived. An expression for shrinkage pressure was obtained, which allows to calculate the stresses arising in the volume of heterophase composite materials during the period of consolidation of nanoparticles.
Key words: thermodynamics, nanoparticles, consolidation, two-phase system.
UDC 621.623
Yu. D. Filatov (Kyiv)
Polishing of precision surfaces of parts made of non-metallic materials with a tool with associated polishing powder
On the basis of cluster and physical-statistical models of the formation of sludge particles of the processed material, the regularities of the microrelief formation of the polished surface are described. It is shown that the productivity of polishing non-metallic materials decreases exponentially with an increase in their binding energy, and the roughness of the polished surface depends on the ratio of the frequencies of natural oscillations of molecular fragments on the surface of the tool and the processed part.
Key words: polishing, sludge particles, polishing performance, microrelief, etc surface roughness.
UDC 519.711.3:621.762.5
V. A. Dutka (Kyiv)
On determining the operating parameters of the electric sintering of a diamond-containing layer on a metal tool body based on the assessment of diffusion processes
It is proposed to determine the operating parameters (intensity and duration of heating) in the process of electric sintering under pressure of a diamond-containing layer on a body based on the assessment of the thickness of diffusion layers formed during the diffusion process in the zones of contact with the metal tool body of particles of powder compositions. In this case, a previously developed numerical model of electric heating of a technological unit (macromodel) and a model of the diffusion process (micromodel) were used, which took into account the temperature dependence of the diffusion coefficient. An example of choosing the optimal heating modes for the process of sintering under pressure is given. The obtained results can be used to optimize the modes of the technological process of sintering products from powder compositions.
Key words: computer modeling, diffusion process, electrosintering under pressure, diamond-containing materials, diffusion layer.
UDC 621.928.4; 621.921.1:621.922.34
Yu. I. Nikitin, G. AND. Petasiuk (Kyiv)
Methods, devices and results of determining the specific surface area of diamond powders
An overview of methods for determining the specific surface area of various dispersed materials is given. The fundamental differences between the used devices and procedures for conducting analyzes of the external and total specific surface are reflected, including those applied to powders of superhard materials and refractory compounds. For practical use, data on the specific surface area of polished, micro- and sub-micro powders of synthetic diamond are presented.
Key words: specific surface, physical methods, methods of geometric measurements, adsorption, desorption, BET, chromatography, mathematical modeling.
UDC 621.921.34; 666.233.004.14
IN. AND. Mukhanov, A. AND. Kurakevych, V. L. Solozhenko (Paris)
Regarding the hardness of boron (III) oxide
Keywords: boron (III) oxide, α-B2O3, β-B2O3, g-B2O3, hardness, structure.