The influence of layered graphene (2–12 layers) on the structure and properties of polycrystalline composite materials with a hybrid diamond base obtained under NRNT conditions was investigated. It was established that during the formation of the composite, the pores located between the diamond grains are filled with graphene, due to which a sufficiently high pressure is provided inside the pores to prevent diamond graphitization. As a result of the interaction of graphene with the liquid phase of the activating additive during sintering, carbide is formed, which improves the chemical or diffusion bonding of diamond grains. In general, the addition of layered graphene particles to the sintered mixture contributes to the production of a composite with a dense and homogeneous structure and an increase in the strength of the material by at least 30%, and the effectiveness of such a positive influence increases with a decrease in the number of layers in graphene (Ak. NAS of Ukraine V.Z. Turkevich, O.M. Sokolov, V.G. Gargin). room temperature. Such grinding powders can serve as a starting material for obtaining diamond polycrystals at high pressure and high temperature.
Nitrogen-containing glasses were synthesized by the sol-gel method using carbamic acid melts. The catalytic effect of small concentrations of tungsten compounds (0.01÷0.1 wt.%) on the efficiency of nitrogen incorporation into the glass was revealed. IR and Raman spectroscopy methods established that the molar concentration of –Si–N– bonds in the synthesized materials is 1.5–5.6% relative to –Si–O– and –B–O– bonds. The DTA method established that the decrease in the softening temperature of glasses is 32±3 oC per 1 mol. % of implemented nitrogen. The obtained low-melting glasses were used as binders for the manufacture of abrasive tools made of diamond and cubic boron nitride with increased dimensional stability when grinding ultrafine-grained hard alloys (E.O. Pashchenko, D.O. Savchenko, S.A. Kukharenko, O.M. Kaidash, S.V. Skorokhod, O.M. Koshkin, S.V. Ryabchenko).
The structural features of three varieties of hexagonal graphitic boron nitride hBN, which serves as the starting component for obtaining BL composites, have been determined. It has been established that pyrolytic hBN has an unlimited axial texture, in which the B-N hexagon grids in the crystallites are oriented parallel to the deposition plane, and improvement of the material structure is possible after a short-term recrystallization annealing at a pressure of 2 GPa and a temperature of 2625-2700 ° C. The metastable rBN obtained by pyrolysis contains about 28% of turbostratic type defects, which completely disappear after annealing at a pressure of 2 GPa and a temperature of 3000 °C, and the metastable rBN is transformed into a single-phase, structurally perfect hBN. It was determined that dispersed carbothermic hBN has a degree of three-dimensional ordering of the crystal structure of 87% and contains 2% of oxygen impurities adsorbed on the surface of the lamellar habit particles, and during barothermic annealing at 7 GPa and a radial temperature gradient, it is sequentially transformed, through an intermediate cubic cBN phase, into stable, so-called, inverse hBN (Ak. of the National Academy of Sciences of Ukraine V.Z. Turkevich, Doctor of Technical Sciences I.A. Petrusha).
Methods for growing single crystals of diamond of types Ib, IIa and IIb in the area of thermodynamic stability have been developed, which ensure the controlled introduction of nitrogen and boron impurities into the crystal structure and make it possible to vary the electrophysical properties for use as active and passive elements of electronic devices. The composition of solvents for the growth process has been studied and optimized, algorithms and growth process cycle diagrams have been developed for obtaining single crystals up to 20 mm in size, and experimental samples of single crystals of various types with high structural perfection have been obtained. The conditions for the formation of single-sector growth zones 100, 111 and 113 have been established, as well as the kinetic and morphological features of the growth of single crystals of various compositions (Corresponding Member of the National Academy of Sciences of Ukraine S.O. Ivakhnenko, V.V. Lysakovsky).
A study of the effect of surface modification of diamond nanopowder particles with C–W bonds on the degree of densification during high-pressure sintering of samples of composites based on statically synthesized diamond nanopowder, as well as polycrystal sintered from statically synthesized nanopowder without modification and degassing of diamond nanoparticles, showed that the degree of densification of diamond nanopowder increases by 8% due to surface modification with carbon–tungsten bonds in combination with degassing before sintering and the reactive interaction of diamond with tungsten. In such a composite, sintered at a pressure of 8 GPa, a temperature of 1650 °C and a sintering time of more than 20 s, a high degree of densification of the diamond framework is combined with a one hundred percent filling of the space between the diamond particles with tungsten carbide (O.O. Bochechka, O.I. Chernienko, O.V. Kushch, V.S. Gavrilova, L. O. Romanko, D. V. Sokolyuk, V. O. Venikov).
It has been shown that massive and film MAX materials of the Ti-Al-C system, subjected to prolonged heating at 600 °C in air for 1000 h, retain a fairly high resistance to oxidation (Dm/S=0.07-0.13 g/cm2), but change their electrical conductivity in different ways: the massive MAX material becomes semiconductive conductor (s=1.73·10-2 Sm/m) due to the formation of a thin surface layer of aluminum and titanium oxides, while the film MAX material remains electrically conductive (s=1.3·106 Sm/m) due to the formation of an electrically conductive solid solution Ti2Al(C1-xNx), electrically conductive phases Ti3AlC with an antiperovskite structure, and aluminides TiAl and TiAl3. Also, after heating in air due to nitriding, the nanohardness of the film materials increases by 1.7 times, and their Young’s modulus increases by 1.4 times. Thus, due to their high physical and mechanical characteristics, thin titanium plates with a Ti-Al-C coating applied by the vacuum-arc method can be considered as lightweight substitutes for Crofer steel joints operating at intermediate temperatures (600 ℃) (Acad. of the National Academy of Sciences of Ukraine T.O. Prikhna, V. B. Sverdun, T.B. Serbeniuk, V.E. Moshchil, O.P. Ostash, O.S. Kuprin, V.K. Podgurska, O.Hryb).
A technology for the physicochemical assembly of combined oxide-, silicate- and carbide-containing coatings on grinding powders of superhard materials (diamond, cBN, composite powders) has been developed, which involves the preparation of a suspension of the grinding powder together with soluble and insoluble components in distilled water with subsequent drying of the solid residue. Based on soluble compounds B2O3, Na2SiO3, K2SiO3 and insoluble Al2O3, SiO2, B4C, SiC, TiC, 2- and 3-component protective coatings were obtained, which contribute to increasing the heat resistance of grinding powders of superhard materials by an average of 1.7 times (V.I. Lavrinenko, O.O. Pasichny, O.O. Bochechka, V.G. Poltoratsky, G.A. Petasyuk).
By magnetron sputtering and gas transport metal movement in a gaseous environment of halides, titanium coatings were obtained on particles of diamond grinding powders with a grain size of 100/80, 400/315. It was established that in addition to carbon and titanium, the coating contains oxygen atoms, the number of which in magnetron sputtering is 6 times, and in the case of gas transport application – 2 times, exceeds the number of titanium atoms. high pressure and high temperature (O.O. Bochechka, D.V. Sokolyuk, A.G. Filipovich, O.I. Chernienko, S.O. Lysovenko, V.M. Tkach, S.P. Staryk, V.V. Belorusets).
A new non-porous, highly viscous (K1C>8.0MPa·m0.5) wear-resistant (HV15 = 17.8 GPa), heterophase metal-ceramic material with a gradient eutectic structure based on Al2O3 – 32% ZrO2 has been developed by using exothermic mixtures of ZrO2(TiO2) – Al, C in the process of high-performance free sintering in contact with the eutectic powder mixture of Al2O3 – 32%ZrO2 and a nitrogen-containing gas environment. The specified material can be used for the manufacture of parts of the “hot zone” of gas turbine engines, cutting inserts for stable high-speed cutting of nickel-based alloys, high-precision hexagonal elements with spherical end surfaces for mounting dense mosaic armor plates for the 5th and 6th levels of personnel protection (M.M. Prokopiv).
The possibility of intensification of cutting modes without destruction with a PcBN tool during the processing of difficult-to-machine materials has been established by strengthening its surface layer with protective coatings based on the TiAlSiYN system, applied by vacuum-plasma spraying, with residual compressive stresses. It has been shown that the presence of compressive residual stresses in the protective coatings, having a value of –1.0 GPa, contributes to the reduction of equivalent stresses at dangerous points on the front surface of the tool during the initial cutting period; The most significant reduction in equivalent stresses at dangerous points on the front surface of the tool is observed in the presence of shock loads – in this case, equivalent stresses decrease from 1.9 to 0.5 GPa; to reduce equivalent stresses on the back surface side of tools with significant wear (∼ 0.3 mm), coatings with residual compressive stresses of 3 GPa are optimal (Corresponding Member of the National Academy of Sciences of Ukraine S. A. Klymenko, A. S. Manokhin, S. A. Klymenko, M. Yu. Kopeikina).
A technology for precision machining of ceramic balls for hybrid bearings has been developed. The conditions and modes of diamond machining have been experimentally determined, which allow the production of ceramic balls from B4C and Si3N4, the size, accuracy and surface quality of which meet the requirements of the State Enterprise “Zaporizhzhya Machine-Building Design Bureau “Progress” named after Academician O. G. Ivchenko”. According to ISO 3290-2:2014, the accuracy and roughness of the polished surface of experimental batches of ceramic balls with a diameter of Æ12.7 mm made of B4C and Si3N4 by hot pressing under high pressures were determined, which were transferred to the State Enterprise “Ivchenko-Progress” for testing operation in hybrid bearings of gas turbine engines (S.V. Sokhan, Corresponding Member of the National Academy of Sciences of Ukraine A.L. Maistrenko).
The physical, mechanical and operational characteristics of synthetic diamonds obtained in the Fe-Co-C growth system were studied. It was determined that the synthesized diamond grinding powders of different grades have magnetic properties due to the high value of the specific magnetic susceptibility of intracrystalline inclusions of alloy solvents. By separating diamond grinding powders by surface defects of diamond grains of grain size 630/500 of the AC125 brand, products were obtained that differ in strength indicators. A diamond precision straightening tool equipped with elite diamond grinding powders of grain size 315/250 of the AC200 brand, obtained after separation of the original grinding powder of the AC125 brand, has increased wear resistance (V.I. Lavrinenko, G.D. Ilnitska, M.M. Sheiko, V.V. Smokvina).
The effect of anomalous increase in the packing density of polymer chains of polyazomethines upon introduction of structural fragments of diaminoferrocene into them was revealed. NMR, Raman spectroscopy, and small-angle X-ray scattering methods have established the formation of a regular superstructure from domains of increased order, which causes an increase in polymer density by 27÷35% compared to systems that do not contain ferrocene fragments. Thus, the degree of degradation of the aforementioned polymers and diamond-containing composites based on them, estimated by the decrease in microhardness, in highly active alkaline technological environments used by modern CNC machining centers, decreases by 2.1-3.7 times compared to unmodified polyazomethines and traditional binders based on phenol-formaldehyde and bismaleimide oligomers (S.V. Skorokhod, E.O. Pashchenko, O.V. Lazhevska, D.O. Savchenko).
The effect of a constant electric current with a density of 0.5÷2.5 A/cm2, which is passed through concentrated suspensions of graphite powders of different grades in epoxy oligomers based on diphenylolpropane, on the electrical conductivity of the corresponding graphite plastics obtained by polymerization of these oligomer systems has been established. After treating graphite suspensions with current with their subsequent polymerization, graphite plastics with a conductivity that is 1.7÷2.1 times higher than the corresponding indicator for materials made by introducing graphite into the oligomer without the influence of current were obtained. The increase in electrical conductivity correlates with an increase in the ordering of the hydrogen bond system in the oligomer, recorded by the Fourier-IR spectroscopy method (E.O. Pashchenko, V.M. Bychikhin, I.V. Leshchuk, S.V. Ryabchenko, N.A. Shchur).
A model of the wear mechanism is proposed and an analysis of the stress-strain state in the contact zone of rolling friction pairs with balls made of B4C and Si3N4 is performed. It is shown that the wear intensity of hybrid pairs is determined by the intensity of the nucleation and propagation of fatigue cracks in the surface layers of the pair, although the difference in the contact area of ceramic balls with the surface of the groove in the steel ring is only 7%. A comparison of the dependences of the wear intensity and kinetic parameters of fatigue crack propagation for ceramic materials based on B4C and Si3N4 indicates the advantage of using silicon nitride Si3N4 in hybrid rolling friction pairs “ceramics – steel ShKh-15” (V.I. Kushch, Corresponding Member of the NAS of Ukraine A.L. Maistrenko).
It was determined that for the encapsulation and long-term storage of nanoparticles without violating their biological properties, mesoporous matrices with a high adsorption capacity for various substances are best suited. In such matrices, the retention of nanoparticles on the inner surfaces of the mesopores is carried out due to capillary forces, which are tens of times higher than all other forces responsible for the adhesion of nanoparticles. According to this principle, new application materials for medical purposes have been created on the basis of an activated carbon fibrous matrix with immobilized silver nanoparticles by the method of adsorption from solutions for the treatment of patients with wound infection (O.B. Loginova, G.D. Ilnytska, L.D. Kisterska).
A technology and tools have been developed for the finishing mechanical processing of parts that are restored by surfacing in repair facilities. Usually, bringing such parts to the dimensions specified in the drawing is difficult, since the instability of the chemical composition and properties of the deposited material, the presence of macro- and micro-irregularities on the deposited surface cause instability of the process of interaction with the tool, negatively affect its performance indicators, processing accuracy characteristics and surface quality. Therefore, for manual mechanical processing of parts deposited with high-hardness alloys, grinding wheels and grinding heads made of ruby-corundum and special heads made of synthetic diamond powders on a galvanic bond, which are characterized by increased wear resistance and resistance to scaling, have been proposed. It has also been determined that the optimal grinding speeds of deposited parts with an abrasive tool should be 20-28×103 rpm, and with a diamond tool, respectively, 10-17.5×103 rpm. Grinding wheels made of chromium corundum, for example, demonstrated high processing efficiency in flat grinding of wear-resistant surfaces of special dies, welded with the CastoDur N 9060 alloy, to a specified roughness of the welded surface of the products Ra 1.32. Testing of the developed tools and technology in the conditions of the Lutsk repair plant “Motor” showed that they allow to obtain the specified surface quality and accuracy of manufacturing parts of aircraft engines, as well as provide an increase in the processing productivity of parts welded with heat-resistant alloys ZhS6 and ZhS32 by 1.5–1.7 times compared to the tools currently used at the enterprise (S.A. Klymenko, S.V. Ryabchenko, M.Yu. Kopeykina).