UDC 621.921.34
N. V. Novikov (Kyiv)
About the achievements of the V. N. Bakul Institute of Superhard Materials of the National Academy of Sciences of Ukraine in the field of synthesis and sintering of superhard materials over 50 years of activity
The main achievements of the V. N. Bakul Institute of Superhard Materials of the National Academy of Sciences of Ukraine in the field of synthesis and sintering of superhard materials at extremely high p, T-parameters over 50 years of activity are presented.
Keywords: synthesis, superhard materials, diamond, cubic boron nitride, high pressures and temperatures, single crystals, polycrystals, nanocrystals.
UDC 549.2: 539.1
S. N. Dub (Kiev)
A. A. Goncharov (Kramatorsk)
S. S. Ponomarev, V. B. Filippov (Kyiv)
G. N. Tolmacheva (Kharkiv)
A. V. Agulov (Kramatorsk)
Mechanical properties of nanocrystalline thin films of HfB2,7
Comparative tests of a single crystal of HfB2 and a nanocrystalline thin film of HfB2,7 deposited by magnetron sputtering on a steel substrate, carried out by the nanoindentation method, are described. It is shown that superstoichiometry in boron and small grain size lead to a sharp increase in hardness and a decrease in the elastic modulus of the thin film of HfB2,7 compared to a massive single crystal. An abnormally high (87%) elastic recovery of the indentation depth after unloading the indenter in a thin HfB2.7 film for inorganic materials indicates the prospects of its application as a wear-resistant coating.
Keywords: hafnium diboride, nanoindentation, hardness, elastic modulus.
UDC 621.762.5
V. T. Golovchan, V. P. Bondarenko (Kiev)
Macroscopic model of compaction kinetics during non-isothermal sintering of powders
The compaction kinetics of a powder system is described by a relatively simple analytical expression that contains only two dimensionless parameters. The first of them is equal to the ratio of the maximum linear shrinkage rate and the total shrinkage of the sample, multiplied by the time during which compaction occurs; the second is equal to the ratio of the time to achieve the maximum shrinkage rate to the total compaction time. The graph of the compaction rate versus time is presented by a curve with one or two maxima depending on the values of the parameters included in the model. The work is focused on modeling compaction during sintering of hard-alloy mixtures.
Keywords: compaction, compaction rate, hard-alloy powder mixture, mathematical model.
UDC 620.22:621.762
A. F. Lisovsky (Kiev)
Thermodynamics of sintering of composite materials with the participation of a liquid phase
The thermodynamics of liquid-phase sintering of composite materials consisting of refractory particles and a low-melting binder is described. Expressions for the Helmholtz free energy for the processes of particle rearrangement, formation of a refractory skeleton, and coalescence are obtained. The existence of shrinkage pressure in the volume of the sintered briquette is substantiated. An expression for shrinkage pressure is derived.
Keywords: thermodynamics, liquid-phase sintering, composite materials.
UDS 661.888.3:548.736
Jianfu Li (Linyi, P.R. China)
Xiaoli Wang (Changchun, P.R. China)
Kai Liu, Daoyong Li, Li Chen (Linyi, P.R. China)
Crystal structures, mechanical and electronic properties of tantalum monocarbide and mononitride
With density functional theory, structural, electronic and mechanical properties of tantalum monocarbide (TaC) and tantalum mononitride (TaN) of the tungsten carbide (WC), nickel arsenide (NiAs), rock salt (NaCl), cesium chloride (CsCl), and zinc blende structure were investigated, respectively. Our results indicate that TaN of the WC-type structure (TaN–WC), which has a large bulk modulus, Young’s modulus, and a small Poisson’s ratio, is the most stable one among the considered compounds. The theoretical hardness of TaN–WC is 37.1 GPa, which indicates that TaN–WC is a potential candidate structure to be one of the ultraincompressible and hard materials.
Keywords: tantalum monocarbide, tantalum mononitride, elastic properties, crystal structure.
UDC 661.88
A. A. Sivkov, A. Ya. Pak, I. A. Rakhmatullin (Tomsk, Russia)
Thermographic studies of the product of dynamic synthesis in the C–N system
The results of exploratory studies by the methods of electron scanning and transmission microscopy, thermography and IR Fourier spectroscopy of an ultradispersed product synthesized in a hypervelocity jet of carbon electric discharge plasma in a nitrogen environment are presented. The studies were carried out in order to purify the product from impurity carbon phases and to evaluate the thermal stability of covalent carbon nitride.
Keywords: dynamic synthesis, ultradispersed, crystalline, covalent, carbon nitride, thermography.
UDC 621.744:666.798.2
M. A. Tsysar (Kyiv)
Computer modeling of the formation of a three-dimensional image of the surface of pyrolytic graphite in the scanning tunneling microscopy method using a diamond tip doped with boron
Based on the developed physical and mathematical model of the formation of a surface image in the scanning tunneling microscope method and with a semiconductor diamond tip doped with boron, an image of the surface of pyrolytic graphite was obtained.
Keywords: physical and mathematical computer model, scanning tunnel microscope, pyrolytic graphite, semiconductor diamond tip doped with boron.
UDC 621.923
P. G. Matyukha, A. V. Burdin (Donetsk)
Determination of the pressing force of a combined sample to the cutting surface of a wheel, limited by the mechanical strength of diamond grains
A method is proposed for analytical calculation of the pressing force of a combined steel-hard alloy sample, limited by the strength of diamond grains, during flat plunge grinding according to an elastic scheme.
Keywords: combined steel-hard alloy sample, grain size, grain strength, pressing force, plunge grinding.
UDC 021.771.07.001.5
S. S. Samotugin (Mariupol)
V. I. Lavrinenko (Kyiv)
E. V. Kudinova, Yu. S. Samotugina (Mariupol)
The influence of plasma surface modification technology on the structure and phase composition of tool hard alloys
The article presents the studied patterns of formation of the structure and phase composition of hard alloys under the influence of a highly concentrated plasma jet with the implementation of various modes of plasma surface treatment. The possibility of obtaining modified layers with an ultra-dispersed composite structure and an increased level of operational properties is shown.
Keywords: plasma modification, hard alloys, structure, phase composition, properties.
UDC 621.921.343
G. P. Bogatyreva, M. A. Marinich, G. S. Oleynik, G. A. Bazaliy, V. A. Bilochenko, A. N. Panova (Kyiv)
The influence of diamond nanopowder extraction methods on their physicochemical properties
The influence of diamond nanopowder extraction methods (liquid oxidation of non-diamond carbon with a mixture of sulfuric and chromic acids, selective gas oxidation of non-diamond carbon in the presence of a copper salt catalyst, and oxidation of non-diamond carbon with a mixture of concentrated sulfuric and nitric acids) from a diamond-carbon product of detonation synthesis on the physicochemical properties of diamond determined by the structural state of its surface is shown. It is established that for diamond nanopowders extracted using various technologies, a decrease in the volume fraction of aggregates in particles is observed. Nanodiamonds extracted by catalytic gas-phase oxidation in the presence of copper are characterized by the highest adsorption activity, heat resistance and electrical conductivity due to the presence of a carbon-containing coating of complex composition. Recommendations are given for the use of diamond nanopowders extracted by various technologies.
Keywords: detonation synthesis nanodiamonds, characteristics.