UDC 666.3:539.5, 621.315.592.4
L. O. Romanko*, O. O. Bochechka, O. I. Cherniyenko, O. V. Kushch
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*ludmila.romanko@gmail.com
Dielectric properties of synthetic diamond polycrystals (pp. 3-18)
The change in dielectric properties, electrical conductivity, and complex impedance of polycrystalline samples sintered from synthetic diamond powder at a pressure of 8 GPa and different temperatures as a function of temperature and frequency was investigated. The sample obtained at a higher temperature has a higher electrical conductivity, which is formed due to conductivity along the intergranular boundaries, and a higher dielectric constant and a stronger dispersion due to distributed capacitance, which occurs during the formation of carrier-depleted layers at the interface of media with different conductivity. Analysis of complex impedance using the equivalent circuit method showed that for these polycrystalline samples, the dominant influence at room temperature is exerted by the intergranular boundaries.
Keywords: synthetic diamond polycrystals, electrical conductivity, impedance spectroscopy.
UDC 548.5:546.26-162:62-987
L. M. Devin1,*, P. M. Lytvyn2, S. O. Ivakhnenko1, O. O. Zanevsky1
1 V. M. Institute of Superhard Materials Bakulya NAS of Ukraine, Kyiv, Ukraine
2V. E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, Kyiv, Ukraine
*ldevin350@gmail.com
Improved Methodology for Studying the Fracture of NTNR Diamond Single Crystals Due to Crack Propagation During Impact Loads (pp. 19-28)
The results of the study of the fracture of NTNR diamond single crystals of type IIa during impact loads using Hopkinson–Kolsky measuring rods are presented. Due to the controlled dosing of the amplitude and duration of the load pulses, an imprint of the entire history of crack propagation was obtained from its nucleation in the zone of maximum stresses with rapid propagation and formation of a smooth surface, with subsequent stable development and formation of a dense array of small ribs up to the deceleration and jump-like propagation of the crack with the formation of a stepped structure in the process of completing the formation of the chip. Topographic features of the fracture surface with dimensions from 3 to 600 nm are shown by atomic force microscopy. Three-dimensional distribution of equivalent von Mises stresses in compression in the whole crystal and corresponding crystal fragments after brittle fracture is simulated.
Keywords: NTNR-single crystals of diamond type IIa, crack propagation, fractographic features of fracture, dynamic loading, crack propagation history.
UDC 548.74:681.723
V. I. Grushko1, *, R. Yu. Chaplynsky2, **, Yu. S. Yamnenko3, 4, O. O. Leshchuk1, E. I. Mitskevich1, S. O. Ivakhnenko1, V. V. Lysakovsky1, O. O. Zanevsky1, E. Ye. Petrosyan2, T. V. Mykytyuk2
1V. M. Bakul Institute of Superhard Materials, National Academy of Sciences of Ukraine, Kyiv, Ukraine
2Institute of Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine
3National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine
4Institute for Advanced Study, Technical University of Munich, Germany
*dumerion@gmail.com
**chaplinskiyryu@gmail.com
Anisotropic charge transport in diamonds grown at high pressures and temperatures (pp. 29-39)
The anisotropy of the transport properties of the main charge carriers in HPHT diamonds with electronic conductivity type was determined by the photovoltaic method. A comparative analysis of the mobility and lifetime of the main charge carriers in the cubic {001} and octahedral {111} growth sectors of diamond single crystals grown in the Fe–Ni–C system was performed. The mobility of the main carriers was estimated from the experimentally measured dependence of the resistivity of the diamond sample on the voltage applied to its contacts. In the case of a change in the electric field strength in the range from –1 to 1 V×μm–1, the resistivity of the samples from the cubic and octahedral growth sectors of diamond changed on average within the limits of 0.15×1013–2.5×1013 and 0.1×1013–0.8×1013 Ohm·cm, respectively. The estimation of the main carrier lifetime was performed from measurements of the spectral current sensitivity in the case of irradiation of diamond with UV light with a wavelength of 225 nm. It was found that the best mobility and lifetime values are obtained from diamond samples cut from the cubic sector of crystal growth. In such samples, the lifetime and mobility of the main carriers are 3.5–4.5 and 1.7–2.5 times higher, respectively, than in samples obtained from the octahedral sector. The results of the studies showed the suitability of the photovoltaic method for a fast and effective comparative analysis of the transport properties of charge carriers, which can be used in the technology of selecting diamond substrates in the production of electronic devices based on diamond.
Keywords: anisotropy of electrophysical properties, HPHT diamonds, diamond growth sectors, photovoltaic method.
UDC 621.762
O. A. Yurkova, A. V. Minitsky*, S. O. Nakonechny, E. S. Shaposhnikova, I. I. Bilyk
National Technical University of Ukraine “Kyiv Polytechnic Institute them. Igor Sikorsky”, Kyiv, Ukraine
*aminitsky@gmail.com
Study of the influence of high-speed sintering modes on the structure and properties of a hard alloy composite based on WC with high-entropy bonding (pp. 40-49)
The influence of high-speed sintering modes by electron beam (EBS) and spark plasma (SPS) methods on the formation of the microstructure and properties of the 90WC + 10FeCrNiWMo composite (in % (by mass)) was established. The influence of technological parameters of sintering on the formation of the structure and phase composition of a metal-ceramic composite with high-entropy bonding was established. The change in the stoichiometric composition of tungsten carbide after sintering the composite by the SPS method was established. The mechanical properties (strength, hardness, crack resistance, compressive strength) were compared for samples sintered by the EBS and SPS methods. It was established that optimal modes electron-beam sintering method of metal-ceramic composite with high-entropy bond is more promising, compared to spark-plasma method. The results of the research can be used in tool production and in the military industry for the manufacture of armor-piercing cores of small arms.
Keywords: high-entropy alloy, tungsten carbide, electron-beam sintering, spark-plasma sintering.
UDC 667.64:678.026
A. V. Buketov1, *, Yu. M. Shulga1, I. P. Fesenko2, **, O. M. Bezbakh1, O. A. Pastukh3, ***1Kherson State Maritime Academy, Kherson, Ukraine
2V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
3Ternopil National Technical University named after Ivan Pulyuy, Ternopil, Ukraine
*buketov@tntu.edu.ua
**igorfesenko@ukr.net
***oleg.pastuh@gmail.com
Increased service life of water transport vehicles due to the use of multifunctional composites with a polymer matrix, ultradispersed diamond and discrete fibrous filler (pp. 50-68)
Polymer composites with improved mechanical and thermophysical properties based on epoxy resin were developed. Ultradispersed diamond and multifunctional discrete fibrous filler (polyester-viscose-elastane) were introduced into the epoxy oligomer to improve the characteristics of the materials. The properties of the composites were investigated: hardness, residual stresses, thermal coefficient of linear expansion. It was established that the optimal content of a multifunctional discrete fibrous filler, which is in the range of q = 0.02–0.03% (by mass) per 100% (by mass) of epoxy matrix and 0.05% (by mass) of ultradispersed diamond. Models of the formation of the structure of composites during their crosslinking are proposed. They include the presence of the polymer itself in the composites, an additional filler in the form of fibers, as well as a third structure – external surface layers that are formed around the fibers during the polymerization process. The models illustrate the formation of the structure of composites at the micro-, meso- and macro-levels.
Keywords: polymer composite material, ultrasound-modified epoxy matrix, ultradispersed diamond, discrete fibers, mechanical and thermophysical properties, structure formation model.
UDC 621.923.7
Yu. D. Filatov1, *, V. I. Sidorko2, S. V. Kovalev1, A. Yu. Boyaryntsev3, V. A. Kovalev4, O. Ya. Yurchyshyn4
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2State Enterprise “Engineering and Production Center ALKON” NTAK (ALKON) NAS of Ukraine, Kyiv, Ukraine
3Institute of Scintillation Materials, NAS of Ukraine, Kharkiv, Ukraine
4National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine
*filatov2045@gmail.com
Formation and localization of a coating of nanoparticles of wear of polishing powder on the treated surface during polishing of polymeric optical materials (pp. 69-80)
As a result of the study of the regularities of the formation and localization of a coating of nanoparticles of wear of polishing powder on the treated surface during polishing of polymeric materials using dispersed systems of micro- and nanopowders, it was found that the total scattering cross section of nanoparticles of wear of polishing powder on nanoparticles of sludge increases nonlinearly with increasing average velocity of their movement, is extremely dependent on the product of spectral separation by the separation by dielectric permittivity between the treated material, polishing powder and dispersed system and increases exponentially with increasing resonator detuning. It is shown that the formation of plaque on the treated surface is most likely during the polishing of polystyrene using cerium dioxide micropowder in the event of reaching the largest value of the total scattering cross section of the wear nanoparticles of the polishing powder on the sludge nanoparticles of 49.7 Mb. It is experimentally confirmed that the localization of plaque from the wear nanoparticles of the polishing powder on the treated surface occurs in accordance with the distribution function of the total scattering cross section of the wear nanoparticles of the polishing powder ku on sludge nanoparticles in circular zones, which is in good agreement with the experimental results for a deviation of 12.5%. The average thickness of plaque fragments from nanoparticles of wear of polishing powder, which form a complete or partial coating of the surface of the part, was experimentally determined, which is 1.1–1.5 μm.
Keywords: polishing, polymeric materials, scattering of nanoparticles, plaque fragments.
UDC 549.211.002.61:546.26.162
G. A. Petasyuk*, G. D. Ilnytska, G. A. Bazalii, N. O. Oliynyk, Yu. V. Syrota
Institute of Superhard Materials named after V. M. Bakul, NAS of Ukraine, Kyiv, Ukraine
*petasyuk@ukr.net
Flotation separation as a method of improving the homogeneity of synthetic diamond powders in terms of morphometric characteristics, grain shape and grain composition (pp. 81-92)
The application of flotation separation for synthetic diamond powders, given in various publications, was analyzed. It was found that the applied application of this method focuses generally on the enrichment of the diamond synthesis product and on improving the quality of already manufactured conditioned synthetic diamond powders in terms of their individual characteristics, in particular, the static strength of the grains. The results of a comparative quantitative study of the roughness of the grain projection, other morphometric characteristics and technological properties, foam and chamber products of flotation separation of conditioned grinding powder AC20 100/80 are presented. For the first time, it has been established at a quantitative level that foam fraction powders have lower grain projection roughness and specific perimeter compared to the chamber fraction. These morphometric characteristics are indirectly responsible for the development of the grain surface, i.e., for their roughness. It has been shown that the known scientific and methodological means of indirect analytical diagnostics of morphometric characteristics and technological properties of diamond grinding powders allow obtaining reliable information for making decisions regarding the quality of flotation separation and the feasibility of repeated or multi-stage application of flotation separation.
Keywords: diamond grinding powder, flotation, separation, morphometric characteristics, technological properties, homogeneity.
UDC 621.921.343
D. A. Stratiychuk*, L. M. Devin, S. V. Rychev, V. Z. Turkevich
Institute of Superhard Materials named after V. M. Bakulya, NAS of Ukraine, Kyiv, Ukraine
*d_strat@ukr.net
Dynamic tensile strength limit of BL group ceramomatrix composites obtained in cBN–carbide–Al systems (pp. 93-95)
The dynamic tensile strength limit Rmd of BL group superhard ceramic materials obtained by NRNT sintering in cBN–TiC–Al, cBN–TiCN–Al, cBN–TiC–WC–Al, cBN–Ti4WC5–Al, cBN–NbC–Al systems was investigated. It was shown that the Rmd value for these composites is within 271–378 MPa, which is quite sufficient for their use as cutting tools during metalworking.
Keywords: dynamic tensile strength, superhard cBN ceramics, BL-group cerammatrix composites, NRNT sintering.
UDC 621.923:661.65:621.9.047
V. I. Lavrinenko
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
lavrinen52@gmail.com
On the influence of the hydrogen index of the technological fluid on the operational characteristics of diamond abrasive wheels (pp. 96-100)
It is shown that the value of the hydrogen index of the technological fluid, in the environment of which the contact of the tool and the part and the polarization of such a fluid during friction occur, affects the process of diamond abrasive processing of tool materials. It has been established that during the processing of hard alloys with a diamond tool, it is necessary to use liquids with a neutral pH of 7, and during the grinding of oxide ceramics, technological liquids with an increased pH value of up to 8–9 should be used. The use of polarized, namely, activated by hydrate ions, technological liquid during the processing of porous and conductive oxide-carbide ceramics with a diamond tool allows reducing wheel wear and the specific energy intensity of grinding by up to 2 times.
Keywords: technological liquid, hydrogen index, water activated by hydrate ions, specific energy intensity, diamond abrasive processing.