UDC 539.2.669.0176:669.018
G. S. Oleynik (Kyiv)
Structural transformations during formation of single-phase superhard materials based on dense phases of carbon and boron nitride
at high pressures and temperatures
The article presents the results of a brief generalization of the known data on the mechanisms of structural transformations during formation of bulk single-phase materials based on diamond and cubic boron nitride at high pressures and temperatures. Two groups of materials are distinguished: based on the initial micropowders of diamond and cBN, graphite-like BN (in the form of powder and pyrolytic deposits). The structure formation of the materials of the first group is controlled by the development of plastic deformation of lattice (slip and twinning) and rotational, and in the case of cBN also by the occurrence of primary recrystallization at T> 1900 °C and p = 7.7 GPa. Rotational deformation causes plastic fragmentation of grains in materials. Formation of materials based on initial graphite-like BN is determined by the occurrence of crystal-oriented phase transformations into dense BN phases (wurtzite and sphalerite) and recrystallization of the resulting cBN phase. The mechanisms of primary recrystallization of cBN are considered.
Keywords: diamond, boron nitride, twinning, deformation, recrystallization.
UDC 621.762.5:661.657.5
M. G. Loshak, L. I. Aleksandrova, A. A. Shulzhenko, N. P. Bezhenar, A. N. Sokolov (Kyiv)
Hardness of superhard polycrystalline materials and its temperature dependence
The paper presents data on the hardness and crack resistance of polycrystalline superhard materials based on diamond and cubic boron nitride and the temperature dependence of the hardness of these materials. It was found that the temperature dependence of hardness in polycrystals based on diamond and boron nitride obtained from powders of different dispersion shows a decrease in hardness for all materials, but the materials have different thermal stability.
Keywords: diamond, cubic boron nitride, polycrystal, hardness, temperature dependence of hardness.
UDC 621.762
A. P. Voznyakovsky, A. V. Kalinin, L. V. Agibalova (St. Petersburg)
Modification of detonation synthesis nanodiamonds with a hydrocarbon radical as a method for obtaining their highly dispersed aqueous suspensions
The paper presents the studied problems of preparing and stabilizing suspensions of detonation nanodiamonds from their dry powders (obtaining secondary suspensions). It is suggested that the main reason for stabilizing detonation nanodiamond aggregates are hydrogen bonds. Modification of the surface of detonation nanodiamond aggregates with hydrophobic radicals was used to destabilize large aggregates and form their highly dispersed suspensions in a polar medium. Hydrophobization of the surface of the initial aggregates led to both their destruction and the preservation of the hydrophilicity of their average surface.
Keywords: detonation nanodiamonds, surface hydrophobization, nanodiamond suspensions, dynamic light scattering method.
UDC 548.736
V. V. Lysakovsky, A. P. Chepugov, V. G. Delevy, T. V. Kovalenko, S. A. Ivakhnenko, O. A. Zanevsky (Kiev)
Features of microrelief formation on the surface of diamond single crystals grown in solvents based on iron-cobalt-zirconium alloy
It is reported that when growing diamond single crystals in the region of thermodynamic stability using solvents based on iron-cobalt-zirconium alloys, a microrelief was observed on the crystal surface on almost all faces, which was a set of depressions and protrusions with a depth and height of no more than several micrometers. The origin of the microrelief is associated with the peculiarities of solvent crystallization and phase transformations in it with decreasing temperature. The liquid solvent crystallizes as a mixture of grains of carbide of the composition (Fe, Co)3C of an elongated shape with layers of α-solid solution of eutectic composition between them, which leads to the formation of depressions and protrusions on the crystal surface. Cooling of the solvent also leads to the formation of microscopic diamond single crystals at the diamond-solvent interface and the release of excess graphite from the α-solid solution (Fe, Co)3C. The observed relief on the faces of the grown crystals has only a superficial character.
Keywords: diamond single crystal, crystal morphology, temperature gradient method, phase transformations.
UDC 621.9.014
A. A. Vinogradov (Kyiv)
On chip formation during cutting of metal materials with a tool with a large negative rake angle
It is noted that the mechanism of chip formation during cutting of metals with a blade tool with a large negative rake angle γ has not been sufficiently studied, methods for assessing a number of chip formation characteristics are proposed and examples of their implementation are given when comparing calculated with experimental values for cases of cutting lead with tools with γ from zero to –60°.
Keywords: cutting, chip formation mechanism, blade tool, negative rake anglel.
UDC 621.9:539.89
V. I. Lavrinenko, G. D. Ilnytska, V. V. Smokvyna (Kyiv)
Application of synthetic diamonds obtained in the Fe–Si–C growth system in grinding tools
The results of the study of the properties of diamond powders obtained in the Fe–Si–C system are presented. The synthesis of diamond was carried out using ferrosilicon with a silicon content in the alloy of 5–7% (by weight). The influence of the ferrosilicon content in synthetic diamonds of the AC6 brand on their specific consumption in the process of diamond and diamond electroerosion grinding was established.
Keywords: specific magnetic susceptibility, elemental composition, relative consumption of diamond, diamond grinding, electroerosion grinding, wear resistance.
UDC 622.24.051.64
N. IN. Novikov, G. P. Bogatyreva, R. K. Bohdanov, G. D. Ilnytskaya, A. M. Isonkin, M. AND. Marynych, V. N. Tkach, M. AND. Tsysar, I. N. Zaitseva (Kyiv)
The influence of nanodispersed diamond additives on the physical and mechanical properties of the metal matrix of the drilling tool
Presented are the results of the study of the effect of additives of ASUD99 nanodiamonds on the physical and mechanical properties of the metal matrix of the drilling tool. The optimal content of additives of nanodiamond powders in the composition of the carbide charge was determined. It is shown that the addition of nanodispersed diamonds in the amount of 1–2% (by mass) contributes to the binding of oxygen during the thermal oxidation of diamonds in the process of manufacturing the tool, which allows to reduce the content of pores in the structure of the matrix material by 1.2 times and leads to an increase in its density by 1.7% and hardness by 24.3%.
Key words: nanodispersed diamond powders, metal matrix of a drilling tool, hardness, density, electron-microscopic image of the surface.
UDC 621.921.34–492.544.023.5:539.215
M. N. Safonova (Yakutsk, Republic of Sakha (Yakutia), Russian Federation)
G. AND. Petasiuk (Kyiv, Ukraine)
AND. WITH. Syromyatnikova, A. AND. Fedotov (Yakutsk, Republic of Sakha (Yakutia), Russian Federation)
Study of grain composition and morphometric characteristics of grinding powders of synthetic and natural diamond
The results of a comparative study of grain composition and morphometric characteristics of grinding powders of natural and synthetic diamond are presented. For the first time, the morphometric characteristics of natural diamond grinding powders were fully diagnosed and a quantitative assessment of their homogeneity was carried out using the system-criterion method.
Key words: grinding powders of natural and synthetic diamond, sieve separation, morphometric characteristics, isometric, homogeneity.
UDC 539.89:548.736:546.786
IN.IN. Lesnyak, D.AND. Stratychuk (Kyiv)
Preparation of oxide tungsten bronze nanoparticles under high pressure conditions
Under the conditions of thermobaric treatment, nanorods of oxide tungsten bronze K0.3W0.95O3 were obtained.
Key words: oxide bronzes, high pressure, precursors, nanosized particles.