UDC 539.2 + 541.183
AND. IN. Romanyuk (Vyshhorod) N. IN. Novikov (Kyiv) Yu. I. Horlov, E. I. Moshkovsky (Vyshhorod)
Electronic structure and reactivity of diamond surface structures
The electronic and spatial structure of the surface layer of a diamond crystal modeled by clusters with a (111) facet structure was considered using the molecular orbital method in the PM3 valence approximation. Within the framework of the deformation model of activation barriers of chemical reactions on the surface of a solid body, an explanation of the chemical inertness of diamond is given, and attention is focused on the antibattery correlation of hardness and reactivity of the surface structures of a number of superhard materials.
UDC 541.1:546.273.171
IN. WITH. Turkevich, O. G. Kulyk, P. P. Itsenko, A. N. Sokolov, A. N. Lutsenko, A. N. Vashchenko (Kyiv)
State diagram of the Mg-B system at high pressures
Phase equilibria in the dual system Mg—B at pressures of 4.5—5.5 GPa were studied using methods of high-pressure quenching, metallographic, X-ray, and micro-X-ray spectral analysis. The obtained experimental results are used to find unknown parameters in phenomenological models of phases competing at high pressures. A thermodynamic calculation was performed and a state diagram of the Mg—B system was constructed at a pressure of 4.5 GPa. The system is characterized by the presence of three eutectic and one peritectic equilibria, with MgB2 and MgB7 borides melting congruently, and MgB4 boride melting incongruently.
UDC 666.233
N. AND. Kolchemanov, A. IN. Nozhkina, A. I. Laptev, D. N. Kolchemanov (Moscow)
The influence of the conditions of production of carbonado diamond polycrystals on their magnetic properties
Magnetic properties of polycrystalline carbonado diamonds ASPK-2 and ASPK-9, synthesized at a pressure of 7.0—10.0 GPa using catalysts based on nickel and X20N80 alloy, were studied. It was established that the magnetic characteristics of polycrystals synthesized using the X20N80 alloy depend significantly on the pressure and time of their formation. The magnetic properties of polycrystals synthesized using nickel as a catalyst are weakly dependent on the conditions of their synthesis.
UDC 548.33:621
IN. M. Volkogon, G. WITH. Oleynyk (Kyiv)
Effect of preliminary processing of BN powder by rolling on phase transformation wurtzite -> sphalerite during sintering of hexanite-P
An explanation of the nature of the increase in the degree of phase transition wurtzite -> sphalerite during sintering (р = 7.7 GPa, T = 1000—1800 °С) of BNv powder deformed by rolling compared to powders in the initial state and after processing by compression at high static pressure is proposed. The results of a comparative study of the structural phase transformations during sintering in the particles of the indicated types of powders allowed us to conclude that this is due to an increase in the driving force component of the deformational phase transformation of the metastable wurtzite phase into a stable sphalerite phase caused by shear stresses in the (0001) plane of the particles. The increase is determined by a combination of factors contributing to the development of shifts in the base layers of particles: the chaotic arrangement of developed surfaces (0001) of particle-plates in relation to axial compression in the high-pressure chamber; distinctive features of the structural state of the particles after rolling — a smaller size in the developed surface, the presence of basic packing defects, plastic deformation and reorientation of the developed surface.
UDC 621.762.5: 546.261 (088.8)
G. L. Zhunkovsky, T. M. Evtushok, P. IN. Mazur, V. AND. Kotenko (Kyiv)
Interaction in the Ti—B4C system. Message 1. Features of the formation of the structure of the resulting composite
It is shown that in the Ti—B4C system, the interaction of powdered boron carbide and titanium occurs by the mechanism of self-propagating high-temperature synthesis with the formation of a composite based on titanium carbide, mono- and diboride. The volume ratio of phases in the structure of the composite, its porosity is determined by the content of boron carbide and titanium in the initial mixture. Formation of the structure is carried out through the liquid phase.
UDC 539.89
WITH. AND. Vynogradov (Kyiv)
On the development of similarity criteria for modeling the process of compression of a thin disk between flat Bridgman anvils
A generalized analysis of the experimental results obtained during the compression of thin disks on Bridgman’s anvils is proposed, with the introduction of similarity criteria, which leads to conclusions consistent with the experimental results. The experimental dependences between the similarity criteria can be used to investigate the properties of new materials on Bridgman’s anvils.
UDC 62-987: 621. 785. 6: 669. 187. 56
P. AND. Balabanov, A. I. Borymskyi, V. G. Delevy, L. I. Alexandrova, T. Yu. Chipenko (Kyiv)
The influence of quenching regimes on the microstructure and mechanical properties of AWD matrices made of P6M5 steel obtained by the method of electroslag remelting
The influence of the duration of heating at different temperatures on the microstructure and mechanical properties of the matrices of high-altitude devices was studied pressures of the “anvil with depressions” type, made from ingots of P6M5 steel, obtained by the method of electroslag remelting in a crystallizer. The expediency of increasing the tempering temperature of matrices up to 1240 °С, at which an optimal combination of their mechanical properties is ensured.
UDC 538.945:539.893
Y.M. Savchuk, T.O. Prikhna, V.E. Moshchil, N.V. Sergienko, P.A. Nagornyi, V.S. Melnikov, S. M. Dub (Kyiv) V. Havalek, O. B. Surzhenko, M. Wendt, K. Schmidt (Jena, Germany)
Synthesis of a superconducting material based on MgB2 under high pressure
As a result of studying the process of synthesis of MgB2 from magnesium and boron elements under conditions of quasi-hydrostatic pressure of 2 GPa at temperatures of 750-1000 °C, the relationship between the conditions of preparation, structure, superconducting and mechanical properties of the material was established. The high level of superconducting characteristics of samples manufactured under optimal conditions (2 GPa, 800 °C, 1 h) and rather large dimensions (d 27 mm, height 18 mm) make it possible and promising to use the synthesized material in cryogenics. The results of the study of microhardness, nanohardness and Young’s modulus showed that MgB2 can be attributed to the class of superhard materials.
UDC 621.923
P. G. Matyukha, A. A. Hrynev (Donetsk)
The cutting ability of a diamond wheel when grinding P6M5F3 steel with a large contact area
The effect of grinding time on the reduction of the cutting ability of a diamond wheel when processed according to the elastic scheme of high-speed steel P6M5F3 with a large contact area of the wheel with the part is considered. It was established that the reason for the sharp deterioration of the cutting ability is a decrease in the actual effort on a single grain as a result of an increase in the number of simultaneously contacting grains, as well as a salting of the microrelief on the grains.
UDC 621.762:679.8.05
E. V. Zvonarev, A. A. Baran, A. V. Belyaev (Minsk)
Copper-tin bundle modified with SVS-powders for diamond stone-working tools
The expediency of strengthening copper-based ligaments for stone-working tools by alloying them with carbides of chromium and titanium, obtained by self-propagating high-temperature synthesis together with binder metals, in particular, nickel, is substantiated. The influence of mass fractions of tin and carbides on the basic physical and mechanical characteristics of the bonding system of Cu—Sn—Ni—carbide was studied. Based on the results of the optimization of the composition of this system, a bundle was selected for the tool used in cutting solid rocks.
UDC 621.928.4:621.921.1:621.922.34.
G. A. Petasiuk (Kyiv)
Stochastic mathematical model of the procedure of sieve analysis of abrasive powders of synthetic diamonds
A new experimental and analytical method of indirect (without the use of sieves) identification of grain size and grain composition of synthetic diamond grinding powders based on the number of grains by fractions and by their mass is presented. The method is based on a stochastic approach and geometric analogs of a grain and a sieve cell in the form of a triaxial ellipsoid and a square, respectively. The probabilistic-geometric mathematical model of the standard DSTU 3292-95 procedure for sieve classification of abrasive powders was obtained. Microscopic analysis data — length and width of grain projections — are used as input information. The main advantage of the proposed method is its universality. The results of testing the method on standard abrasive powders are given.
UDC 661.657.5
V. L. Solozhenko, E. G. Solozhenko (Kyiv) Zh. P. Petite (Paris)
About cubic boron nitride crystals grown in the BN—N—H system
UDC 669.018.25.
A. F. Lysovsky, S. A. Ivanov, V. P. Pereyaslov (Kyiv)
On the formation of mesostructures in sintered hard alloys.