UDC 544.344.012:539.89
V. Z. Turkevich, A. G. Garan, N. N. Belyavina (Kiev)
Al-Ni-C and Si-Ni-C Systems at High Pressures: Methods for Constructing Phase Diagrams and Diamond Synthesis
Phase equilibria in the ternary systems Al-Ni-C and Si-Ni-C at a pressure of 5.8-7.4 GPa were studied using metallographic, X-ray, and micro-X-ray spectral analyses on samples obtained by quenching. The experimental results were used to find unknown parameters in phenomenological models of phases competing at high pressures. Thermodynamic calculations were performed and phase diagrams of the Al-Ni-C and Si-Ni-C systems were constructed at a pressure of 6 GPa. The diagram data were compared with the results of experiments on diamond synthesis in the studied systems. A method for constructing phase diagrams at high pressures is described, combining an experimental study of phase equilibria (including equilibria with diamond) and thermodynamic calculation.
UDC 666.792.34:539.89
A. A. Shulzhenko, D. A. Stratiychuk, G. S. Oleynik, V. M. Vereshchaka (Kiev)
Structural transformations during the formation of a superhard composite in the B—C—Si system
Based on the results of electron microscopic studies, the processes and mechanisms of structural-phase transformations in the contact zone of a diamond particle—the B4C—Si matrix during sintering of a composite of the initial composition B4C + diamond + Si are considered. It is shown that the formation of the zone microstructure with increasing sintering temperature in the range of 1300-2000 °C is due to the following sequence of processes: formation of nanodispersed secondary boron carbide on the surface of diamond particles › thickening of such a layer due to the growth of its grains, realized as a result of boron diffusion from the matrix component to the surface of diamond particles › transformation of the resulting layer of anisometric grains with the formation of a fine-grained sublayer in contact with diamond at the first stage, and then its complete reconstruction with the formation of a fine-grained boron carbide—silicon carbide composition. A generalized scheme of the formation of the microstructure of the transition layer arising in the contact zone at different stages of sintering is presented. It is concluded that the microstrength properties of the composite are determined by the microstructure of the diamond particle—B4C—Si matrix transition layer. The maximum of these properties, determined by the highest degree of diamond particle retention by the matrix, is characteristic of the case of formation of a layer of anisometric (elongated) boron carbide grains on the surface of diamond particles.
UDC 669.017.11:669.784.25.74
V. M. Perevertaylo, O. B. Loginova, O. G. Kulik (Kyiv)
Formation of the contact interaction zone of nickel alloys with a carbon surface
The features of the formation of the structure of the contact zone in graphite-nickel melts systems with additives of carbide-forming metals Fe, Mn, Cr, V, Ti, Mo, W are considered depending on the structure of the state diagram, thermodynamic and capillary characteristics of the contact system. It is shown that the processes of interaction at the interface are largely determined by the structure of the phase diagram, with each phase region characterized by its own concentration dependence and rate of change of the wetting angle. A scheme for the formation of a contact interaction zone in metal-carbon systems is proposed, and recommendations are made for the selection of growth media compositions for obtaining diamond crystals.
UDC 666.233
V. Yu. Dolmatov (St. Petersburg, Russia)
Modern industrial technology for producing detonation nanodiamonds and the main areas of their use. Message 3
The amazing ability of detonation synthesis nanodiamonds to have a positive effect on all objects where these nanodiamonds are included is shown. The complex of positive properties of various polymer-diamond compositions, compacts-sinters is enhanced, the possibility of creating new generations of various drugs, new laser-sensitive composite initiating explosives, means of protection against biodestruction of buildings, structures, cultural monuments appears.
UDC 621.762 -539.89-548.73
V. M. Volkogon, S. K. Avramchuk, A. S. Osipov, A. V. Kravchuk, T. R. Balan (Kyiv)
Kinetics of compaction and phase transformations during sintering under high pressures of wurtzite boron nitride powders deformed by rolling
The article presents the results of an experimental study of the compaction features and accompanying phase transformations of compacts formed during sintering under high static pressures (p = 7.7 GPa) and temperatures (T = 1200-1800 °C) of wurtzite boron nitride powders subjected to preliminary compaction by rolling with different values of deformation stresses (p = 0.2-1.5 GPa). The regularities of phase transformations and density changes at various stages of sintering were studied using quantitative X-ray phase analysis and hydrostatic weighing of samples. It was found that rolling of BNв powders promotes intensification of the compaction process of compacts during sintering, as well as reducing the amount of graphite-like boron nitride formed as a result of thermal action. The magnitude of the deformation stress during rolling determines the level of manifestation of these effects.
UDC 539.893.621.317.4
G. P. Bogatyreva, V. M. Maevsky, G. D. Il’nitskaya, G. F. Nevstruev, V. N. Tkach, I. N. Zaitseva (Kyiv)
Impurities and inclusions in powders of synthetic diamonds of the AC4 and AC6 grades
The elemental composition of impurities and inclusions in powders of synthetic diamonds of low-strength grades AC4 and AC6, separated in a magnetic field into magnetic and non-magnetic fractions, was studied by the method of X-ray fluorescence integral analysis using a scanning electron microscope. The performed studies of the elemental composition of impurities and inclusions in powders of diamond grades AC4 and AC6 have shown that the content of elements of the alloy-solvent in inclusions is 81.0-83.5 ‰ of the total number of inclusions in powders of diamond of the non-magnetic fraction, and in the magnetic fraction – 94.0-95.0 ‰. The method of electron paramagnetic resonance was used to study the defect structure of samples of diamond grades AC4 and AC6 and it was shown that ferromagnetic impurities and inclusions are located mainly near the surface of grains, and their concentration significantly exceeds the concentration of nitrogen. The obtained data allow us to assume that the main reason for the variation in the strength of the studied samples is the uneven distribution of impurities over the diamond crystal, especially in the near-surface region. UDC 622.24
I. A. Sveshnikov, V. N. Kolodnitsky (Kyiv)
Optimization of the placement of carbide cutters in the body of a drill bit
The optimal distance between carbide cutters of a drill bit for a solid pattern of bottomhole damage for new and heavily worn cutters was determined. A pattern of change in this distance depending on the distance of the cutter to the axis of the bit was established.
21.762.5:661.657.5
N. P. Bezhenar, A. A. Shulzhenko, L. K. Shvedov, S. A. Bozhko, N. N. Belyavina (Kyiv)
Phase transition cBN –›hBN in nanopowder under high quasi-hydrostatic pressure without thermal activation
UDC 661.8.611.849
A. B. Lyashchenko, V. N. Paderno, V. B. Filippov, D. F. Borschevsky (Kiev)
Production and some properties of rhenium diboride single crystals