Browsing by Author "Shtapenko, Eduard P."
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Item Application of Pulse Current for Producing a Strengthening Composite Nickel Coating(Eugen G. Leuze Verlag, 2019) Tytarenko, Valentyna V.; Zabludovsky, Vladimir A.; Shtapenko, Eduard P.; Tytarenko, Igor V.EN: Carbon-containing nickel coatings deposited with use of pulse current from aqueous electrolyte solution comprising ultradispersed diamond particles were studied. Effect of pulse current on concentration and distribution of co-deposited nanodiamond particles through a metal substrate matrix, structure, mechanical and resistance properties of composite electrolytic coatings was analyzed. It was demonstrated that application of new generation additives, more specifically nanocarbon ones, provides opportunity for improving physicochemical properties of coatings. During pulse mode of deposition fine-grained coatings are formed with microlayer growth structure in cross section that enhance their microhardness, wear strength and corrosion resistance.Item Determination of Activation Energy of Surface Diffusion Based on Thermal Oscillations of Atoms(Прикарпатський національний університет імені Василя Стефаника, 2021) Syrovatko, Yu. V.; Shtapenko, Eduard P.EN: This paper covers calculations of the activation energy of surface diffusion of ad-atoms on the substrate surface from the point of view of thermal oscillations of substrate atoms and ad-atoms. The main characteristic of oscillations of atoms and geometric mean frequency was calculated based on statistical approximation of the Debye model using the reference values of entropy and heat capacity of metals. The basic principle of the model of activation energy calculation presented in the paper is the formation of potential wells and barriers during oscillations of atoms localized in the sites of the lattice. Oscillations of atoms were considered in the framework of quasiclassical quantum approximation as the oscillations of harmonic oscillators in the potential parabolic wells. Dimensions of the negative part of values of the potential well energy were determined by the amplitude of thermal oscillations of atoms. Positive values constituted a significant part of the potential well energy values. Barriers were formed owing to interaction of positive values of the energy of parabolic wells of adjacent atoms. Therefore, in order to make the ad-atom jump, it is necessary to get out of the potential well having the negative values, and to overcome the potential barrier. The energy required for the ad-atom jump on the substrate surface was the activation energy of surface diffusion. The results obtained in this paper agree satisfactorily with the results of another method, which is based on determining the energy of ad-atom binding with the substrate atoms.Item Heat Capacity of Thin Films at High Temperatures(Інститут металофізики ім. Г. В. Курдюмова НАН України, Київ, 2023) Shtapenko, Eduard P.; Syrovatko, Yu. V.ENG: The purpose of this paper is to develop a model, which allows determining the heat capacity of thin films at the temperatures comparable to and exceeding the Debye temperature. The model presented in the paper takes into consideration the anisotropy of vibrations of the corresponding bending waves and wave vibrations in the plane occurring with the decrease in the film thickness. Furthermore, the model is based on the quadratic dispersion law for bending wave vibrations in the normal direction of a thin film and the linear dispersion law for the wave vibrations in the film plane. In order to expand the existing model representations for the heat capacity of thin films at low temperatures, we used the Debye’s method in the integral expression for the free energy. We considered this approach earlier in the model representations of the heat capacity of anisotropic quasi-crystals. Our findings show that the thin-film heat-capacity dependence on the temperature has a maximum and exceeds the heat capacity of a bulk sample. This circumstance confirms the experimental data obtained earlier by other authors. Besides, according to the experimental data collected from the literature, heat capacity of the thin films rises, compared to values of the bulk sample, when the film thickness decreases. This factor is also reflected in the model under consideration, and the calculated dependence of the increase in thin films on the number of atomic layers correlates well with the experimental data. Therefore, the proposed model allows determining the heat capacity of thin films at the temperatures exceeding the Debye temperature with sufficient accuracy without experimental investigation.Item Laser-Enhanced Electrodeposition of Nickel Coatings(Taylor & Francis Group, London, 2017) Zabludovsky, Vladimir A.; Tytarenko, Valentyna V.; Shtapenko, Eduard P.EN: A method for producing the composite nickel coatings with a programmable pulse current with the changing from one layer to the concentration of particles in the metallic matrix of nanodiamonds. It is shown that this program allows layer-coating with the lowest concentration of nanodiamond in the first coating layers and increasing in subsequent layers, which improves adhesive properties, increases wear resistance and lowers the cost of dispersed particles of nanodiamond.Item Quantum Mechanical Approach for Determining the Activation Energy of Surface Diffusion(Физико-технический институт им. А.Ф. Иоффе Российской академии наук, Санкт-Петербург, 2020) Shtapenko, Eduard P.; Tytarenko, Valentyna V.; Zabludovsky, Volodymyr O.; Voronkov, Eugene O.EN: A quantum mechanical approach was proposed to determine the activation energy of surface diffusion for copper, nickel, zinc and iron atoms adsorbed on a copper substrate during electrocrystallization for various overvoltages of the substrate. The activation energy of surface diffusion was calculated from the crystal total energy. An increase in the activation energy of surface diffusion with increasing surface potential is associated with an increase in the binding energy between the ad-atom and the substrate.Item Quantum-Mechanical Modeling of the Interaction between Carbon Nanostructures and Metal Ions(Pleiades Publishing, Ltd, 2021) Tytarenko, Valentyna V.; Shtapenko, Eduard P.; Voronkov, Eugene O.; Zabludovsky, Volodymyr O.; Kolodziejczyk, Wojciech; Kapusta, Karina; Kuznetsov, Vitaliy N.EN: In order to investigate a deposition mechanism, authors have proposed a set of quantum chemical models for formation of fullerene C60 and single-wall carbon nanotubes (SWNTs) C48 metal complexes with Co, Ni, Cu, and Zn. Obtained results proving that adsorption of Co, Ni, Cu, Zn ions on a surface of fullerene C60 and SWNT C48 from the aqueous solution of electrolytes is possible with formation of stable metal-doped carbon nanoparticle complexes. Minimum energy complexes of C60-Co and C60-Cu have corresponded to the structure where ion is located above the center of C6 cell. Meanwhile, C60-Ni complex reach a minimum energy when ion is above the middle of a C-C bond, and for C60-Zn complex the most stable conformation is the one when ion is upon the carbon atom. All the optimized structure for metal complexes with C48 has shown ions been located above the C6 cell’s center.Item Structure and Properties of Composite Nickel Coatings Deposited by Means of Programmable Pulsed Current under Laser Irradiation(Pleiades Publishing, 2019) Tytarenko, Valentyna V.; Zabludovsky, Volodymyr O.; Shtapenko, Eduard P.EN: A method for the formation of composite electrolytic coatings in the process of electrodeposition in an electrolyte with ultradisperse diamond (UDD) particles in the programmable pulsed current regime under simultaneous laser irradiation has been developed. This method provides the layer-by-layer deposition of gradient nickel coatings 15–20 μm in thickness with a variable content of UDD particles along their depth. The amount of UDD particles is minimal (0.10–0.13 at %) in the layers deposited in the initial period of this process, whereas the concentration of UDD particles in the layers formed at the later process stages grows to 0.19–0.26 at %. The concentration gradient of UDD particles along the depth improves the adhesion properties and wear resistance of coatings and provides a 16% decrease in the consumption of UDD particles with a local increase in the concentration of UDD particles in a coating to 0.32 at %.Item Структура и свойства композиционных электролитических никелевых покрытий, полученных импульсным током(Институт металлофизики им. Г. В. Курдюмова НАН Украины, Киев, 2015) Дудкина, Валентина Васильевна; Заблудовский, Владимир Александрович; Штапенко, Эдуард Филиппович; Штапенко, Едуард Пилипович; Shtapenko, Eduard P.RU: Исследованы композиционные электролитические покрытия (КЭП), осажденные импульсным током из сульфатного никелевого электролита, содержащего частицы ультрадисперсных алмазов (УДА). Рассмотрено влияние параметров импульсного тока при электролитическом нанесении никелевых покрытий на структуру и механические свойства КЭП, содержание и распределение соосажденных частиц наноалмаза в металлической матрице. Результаты исследований показывают, что использование соединений частиц УДА с модифицированной поверхностью никеля повышает микротвердость и износостойкость никелевых покрытий