UDC 620.22:669.018.25А. F. Lysovsky (Kyiv)
The PMR phenomenon: scientific basis and practical application
The results of theoretical and experimental studies of the process of absorption of metal melts by nonporous sintered composite materials are presented, as well as the main provisions of the phenomenological theory of liquid phase migration in dispersed structured solid-liquid systems, the areas of practical use of the PMR phenomenon are described, in particular, for the creation of gradient structures at the nano- and microlevels, the formation of mesostructures in composite materials.
UDC 519.711.3:621.762.5
IN. AND. Dutka, V. P. Pereyaslov (Kyiv)
On the selection of parameters of structural elements of the technological unit and the heating mode of the process of high-speed electrosintering of diamond-containing composites
The results of numerical studies of the influence of various factors on the temperature distribution in billets made of composite diamond-containing materials (CBM) during their high-speed electrosintering under pressure are presented. It was established that, compared to the heating stage, at the stage of cooling under pressure (after the end of heating) when the optimum temperature level for compaction of CBM is reached in the billet, the maximum temperature difference in it decreases insufficiently to ensure its permissible value. Therefore, even at the heating stage, the permissible temperature difference in the billets should not be exceeded. A number of numerical experiments were performed and, based on the analysis of their results, specific variants of structural elements of the technological unit and heating modes of the process of high-speed electrosintering of CBM were proposed.
UDC 536.42:661.657.5
P. Bezhenar, S. A. Bozhko, N. M. Bilyavina, V. Ya. Markiv (Kyiv)
X-ray structural study of KNB powders after high-pressure treatment at room temperature
The real crystal structure of BNsf in powders with grain sizes from 1/0 to –40 after their treatment at room temperature at pressures of 2.5, 4.2 and 7.7 GPa was studied by the method of X-ray structural analysis using a hardware and software complex for obtaining and analyzing X-ray diffraction spectra.
UDC 666.3:539.5
G.S. Oleinyk, M.A. Kuzenkova, N.V. Danilenko, I.P. Fesenko, I.A. Petrusha (Kyiv)
The influence of the dispersion of the initial powder on the formation of the grain structure of AlN polycrystals obtained by thermobaric sintering
The structural transformations (sintering in the same p, T conditions) of AlN powders of plasma chemical (0.01—0.05 microns) and furnace (5—7 microns) syntheses were investigated using the methods of transmission electron microscopy (thin foils and replicas). It was established that in the case of a dispersed powder, as the duration of sintering at constant p and T increases, as well as with an increase in T at constant t and p, only grain coarsening takes place, i.e. collective recrystallization. Centers of collective growth are formed on the basis of aggregates of initial particles, which become monocrystalline as a result of coalescence. During sintering under the same conditions, larger AlN particles always undergo primary recrystallization. Nuclei of recrystallization are formed on the basis of subgrains formed at the stage of dynamic return.
UDC 546.26-162:541.183
I. I. Kulakova, A. P. Rudenko (Moscow)
Chemical state of the diamond surface: influence on properties and role in processing
Modern ideas about the chemical nature of the diamond substance and an overview of the results of the authors’ work on the study of the chemical state of the diamond surface depending on the conditions of its preliminary chemical treatment are presented. It is shown that this or that functional coating of the diamond surface is formed as a result of synthesis, oxidation or hydrogenolysis of the diamond substance itself, or when the crystal surface is modified. It has been established that the chemical state of the diamond surface determines many of its properties (adsorption and adhesion capacity; wettability; resistance to oxidation, up to complete inhibition; catalytic activity in the ortho-para-conversion of hydrogen; compressibility and sinterability of diamond powders, as well as mechanical and physical properties of compacts and diamond ceramics made from them). The possibility of using the chemistry of the diamond surface in the creation of various chemical-catalytic methods of non-abrasive diamond processing is shown.
UDC 621.315.592:537.311.33
L. AND. Romanko, A. G. Gontar, S. I. Khandozhko, A. M. Kutsai, V. Yu. Horokhov (Kyiv)
Peculiarities of the transport of charge carriers in a-C:H films
The influence of deposition parameters on the electrophysical properties of amorphous hydrogenated carbon films is investigated. For films deposited at the minimum power of the RF discharge, the dielectric properties do not depend on the concentration of methane in the working gas mixture. The main electrophysical properties of such films are determined by their polymer structure.
With an increase in the discharge power, the magnitude of the dielectric permittivity and the tangent of the dielectric loss angle increase, which is due to the presence of a significant number of charged structural units from the 5-memberedx and 7-membered rings. At the same time, the transfer of charge in the material is limited by the formation of strongly localized states — polarons of a small radius, and has a jumping character.
UDC 541.183:621.921.34-488
L. Yu. Ostrovskaya, V. M. Overturned, O. B. Loginova (Kyiv), V. G. Ralchenko, A. P. Dementyev (Moscow)
Wetting of diamond films: influence of hydrogenation and surface oxidation
The wettability of polycrystalline diamond films with liquids of different physico-chemical nature (water, glycerin, molten tin) was studied, depending on the chemical state of the surface of the films, which changes under the influence of various types of processing (hydrogenation, oxidation).
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It is shown that the hydrogenation of diamond films under the influence of microwave plasma in a hydrogen environment leads to a significant increase in their hydrophobic properties. This is caused by a decrease in the free surface energy of the film due to adsorption-induced hydrogen surface reconstruction of the film and saturation of free bonds of surface carbon atoms.
UDC 548.0
Yu. I. Sozin, M. I. Katsai (Kyiv)
Kinetics of structural and phase transformed C60 fullerite at high pressures and temperatures with the formation of amorphous diamond
The processes occurring in C60 fullerite under the influence of high pressures and temperatures at different exposure times were studied using the methods of traditional X-ray photography and diffraction of coordination spheres.
The stages of the occurring changes are established: the compression of the fcc lattice of fullerite, accompanied by a decrease in its perfection, the appearance of graphite, the destruction of fullerite, and the formation of amorphous diamond, detected by the appearance of a spectrum from the coordination spheres of diamond in the absence of its diffraction spectrum from crystallographic planes.
UDC 621.919
Yu. AND. Tsekhanov (Voronezh), O. AND. Rosenberg, Yu. Kh. Kuzhba, S. THERE ARE. Sheykin (Kyiv)
Analysis of the stress-strain state of a multilayer cylinder during deforming stretching
The stress-strain state of one-, two-, and three-layer pipe blanks was analyzed by the experimental-calculation method of visioplasticity. The distribution of axial and circumferential stresses and strains on the outer surface was obtained. The used plasticity resource of the studied products is calculated.
UDC 621.9.01
WITH. IN. Shvets (Sumy)
Calculation of cutting modes
In order to ensure the given stability of the tool by automating the process of assigning cutting modes, a method of their analytical calculation based on the hypothesis of the attractor of the cutting system is proposed. The reliability of the proposed method is confirmed by comparing the calculated values of the cutting modes with those recommended by Sandvik Coromant for turning steel with multi-faceted cutters.