Факультет електроніки та інформаційних технологій (ЕлІТ)
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Item Advanced “Green” Prebiotic Composite of Bacterial Cellulose/Pullulan Based on Synthetic Biology-Powered Microbial Coculture Strategy(MDPI, 2022) Zhantlessova, S.; Savitskaya, I.; Kistaubayeva, A.; Ignatova, L.; Talipova, A.; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Digel, I.Bacterial cellulose (BC) is a biopolymer produced by different microorganisms, but in biotechnological practice, Komagataeibacter xylinus is used. The micro- and nanofibrillar structure of BC, which forms many different-sized pores, creates prerequisites for the introduction of other polymers into it, including those synthesized by other microorganisms. The study aims to develop a cocultivation system of BC and prebiotic producers to obtain BC-based composite material with prebiotic activity. In this study, pullulan (PUL) was found to stimulate the growth of the probiotic strain Lactobacillus rhamnosus GG better than the other microbial polysaccharides gellan and xanthan. BC/PUL biocomposite with prebiotic properties was obtained by cocultivation of Komagataeibacter xylinus and Aureobasidium pullulans, BC and PUL producers respectively, on molasses medium. The inclusion of PUL in BC is proved gravimetrically by scanning electron microscopy and by Fourier transformed infrared spectroscopy. Cocultivation demonstrated a composite effect on the aggregation and binding of BC fibers, which led to a significant improvement in mechanical properties. The developed approach for “grafting” of prebiotic activity on BC allows preparation of environmentally friendly composites of better quality.Item Microstructure, Mechanical and Tribological Properties of Advanced Layered WN/MeN (Me = Zr, Cr, Mo, Nb) Nanocomposite Coatings(MDPI, 2022) Смирнова, Катерина Василівна; Смирнова, Екатерина Васильевна; Smyrnova, Kateryna Vasylivna; Sahul, M.; Harsani, M.; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Ivashchenko, V.; Beresnev, V.; Stolbovoy, V.; Caplovic, L.; Caplovicova, M.; Vanco, L.; Kusy, M.; Kassymbaev, A.; Satrapinskyy, L.; Flock, D.Due to the increased demands for drilling and cutting tools working at extreme machining conditions, protective coatings are extensively utilized to prolong the tool life and eliminate the need for lubricants. The present work reports on the effect of a second MeN (Me = Zr, Cr, Mo, Nb) layer in WN-based nanocomposite multilayers on microstructure, phase composition, and mechanical and tribological properties. The WN/MoN multilayers have not been studied yet, and cathodic-arc physical vapor deposition (CA-PVD) has been used to fabricate studied coating systems for the first time. Moreover, first-principles calculations were performed to gain more insight into the properties of deposited multilayers. Two types of coating microstructure with different kinds of lattices were observed: (i) face-centered cubic (fcc) on fcc-W2N (WN/CrN and WN/ZrN) and (ii) a combination of hexagonal and fcc on fcc-W2N (WN/MoN and WN/NbN). Among the four studied systems, the WN/NbN had superior properties: the lowest specific wear rate (1.7 × 10−6 mm3/Nm) and high hardness (36 GPa) and plasticity index H/E (0.93). Low surface roughness, high elastic strain to failure, Nb2O5 and WO3 tribofilms forming during sliding, ductile behavior of NbN, and nanocomposite structure contributed to high tribological performance. The results indicated the suitability of WN/NbN as a protective coating operating in challenging conditions.Item DC and AC Tests of Moisture Electrical Pressboard Impregnated with Mineral Oil or Synthetic Ester—Determination of Water Status in Power Transformer Insulation(MDPI, 2022) Zukowski, P.; Rogalski, P.; Kołtunowicz, T.N.; Kierczynski, K.; Zenker, M.; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Kucera, M.In this study, the conductivity and permittivity of electrical pressboard—insulating liquid—water composites were investigated, and the electrical properties of the composites and water were analysed comparatively. Mineral oil and synthetic ester were used as insulating liquids. It was found that the presence of water caused an increase in the permeability of the composite in the frequency range below 100 Hz. The value of static permittivity determined by water in the content of 5 wt. % was approximately 15. To obtain this value caused by liquid water, its volume should be approximately five (oil) and four times (ester) higher than its actual content, respectively. The determined values of the activation energy of the DC conductivity of the composites were several times higher than the values of the activation energy of the conductivity of the liquid water. The experimental values of the dielectric relaxation times were many orders of magnitude higher than the dielectric relaxation times of water. This means that the experimental results obtained for the dielectric permittivity, the activation energy of conductivity and the dielectric relaxation times for moisture electrical pressboard impregnated by mineral oil or synthetic ester exclude the possibility of the presence of liquid water in the composites. It was found that the conductivity of the composites increased exponentially with increasing water content. Such dependencies are characteristic of hopping conductivity, caused by the quantum phenomenon of electron tunnelling between nanometre-sized potential wells. As the increase in conductivity is determined by the presence of water in the composites, therefore, the nanometre potential wells were single-water molecules or nanodrops.Item Investigation of AC Electrical Properties of MXene-PCL Nanocomposites for Application in Small and Medium Power Generation(Centre of Sociological Research in co-operation with University of Szczecin (Poland); Széchenyi István University (Hungary); Mykolas Romeris University (Lithuania); Dubcek University of Trencín, Faculty of Social and Economic Relations (Slovak Republic), 2021) Kołtunowicz, T.N.; Gałaszkiewicz, P.; Kierczyński, K.; Rogalsk, P.; Okal, P.; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Буранич, Володимир Володимирович; Буранич, Владимир Владимирович; Buranych, Volodymyr Volodymyrovych; Погорєлов, Максим Володимирович; Погорелов, Максим Владимирович; Pohorielov, Maksym Volodymyrovych; Дєдкова, Катерина Андріївна; Дедкова, Екатерина Андреевна; Diedkova, Kateryna Andriivna; Zahorodna, V.; Balitskyi, V.; Serhiienko, V.; Baginskyi, I.; Gogotsi, O.The paper examined Ti3C2Tx MXene (T—OH, Cl or F), which is prepared by etching a layered ternary carbide Ti3AlC2 (312 MAX-phase) precursor and deposited on a polycaprolactone (PCL) electrospun membrane (MXene-PCL nanocomposite). X-ray Diffraction analysis (XRD) and Scanning Electron Microscopy (SEM) indicates that the obtained material is pure Ti3C2 MXene. SEM of the PCL-MXene composite demonstrate random Ti3C2 distribution over the nanoporous membrane. Results of capacitance, inductance, and phase shift angle studies of the MXene-PCL nanocomposite are presented. It was found that the frequency dependence of the capacitance exhibited a clear sharp minima in the frequency range of 50 Hz to over 104 Hz. The frequency dependence of the inductance shows sharp maxima, the position of which exactly coincides with the position of the minima for the capacitance, which indicates the occurrence of parallel resonances. Current conduction occurs by electron tunneling between nanoparticles. In the frequency range from about 104 Hz to about 105 Hz, there is a broad minimum on the inductance relationship. The position of this minimum coincides exactly with the position of the maximum of the phase shift angle—its amplitude is close to 90°. The real value of the inductance of the nanocomposite layer was determined to be about 1 H. It was found that the average value of the distance over which the electron tunnels was determined with some approximation to be about 5.7 nm and the expected value of the relaxation time to be τM ≈ 3 × 10−5 s.Item Multilayer and high-entropy alloy-based protective coatings for solving the issue of critical raw materials in the aerospace industry(IOP Publishing, 2021) Постольний, Богдан Олександрович; Постольный, Богдан Александрович; Postolnyi, Bohdan Oleksandrovych; Буранич, Володимир Володимирович; Буранич, Владимир Владимирович; Buranych, Volodymyr Volodymyrovych; Смирнова, Катерина Василівна; Смирнова, Екатерина Васильевна; Smyrnova, Kateryna Vasylivna; Araujo, J.P.; Rebouta, L.; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Рогоз, Владислав Миколайович; Рогоз, Владислав Николаевич; Rohoz, Vladyslav MykolaiovychAerospace is an actively developing industry that continuously requires the implementation of modern technologies. The rapid growth in new vehicle production demands much support. Hence, the problem of resources with complicated supply and distribution is always of current interest. These critical raw materials (CRMs) are involved in almost all areas of aerospace manufacturing and service. An efficient and profitable solution to the problem of critical materials can be found in protective coatings, especially in such advanced concepts as multilayer and high-entropy alloy (HEA)-based coatings. In this paper, we study both ways of manufacturing effective coatings. We have shown that multilayer CrN/MoN coatings with exceptional toughness and hardness could find promising applications in the aerospace industry. The developed strategy for the novel materials screening based on the prediction of their properties has been demonstrated on the example of the refractory HEA-based coatings. A brief state of the art of the EU critical raw materials and their place in the aerospace/defence industry has been given.Item Mechanical and tribological characterization of nanostructured HfB2 flms deposited from compound target(Springer Nature, 2020) Буранич, Володимир Володимирович; Буранич, Владимир Владимирович; Buranych, Volodymyr Volodymyrovych; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Budzynski, P.; Шелест, Ігор Владиславович; Шелест, Игорь Владиславович; Shelest, Ihor Vladyslavovych; Prószyński, A.; Chocyk, D.; Гончаренко, Олексій Сергійович; Гончаренко, Алексей Сергеевич; Honcharenko, Oleksii Serhiiovych; Юнда, Андрій Миколайович; Юнда, Андрей Николаевич; Yunda, Andrii MykolaiovychFabrication and development of HfB2-based nanostructured coatings was investigated. All flms were deposited on stainless-steel substrates by RF magnetron sputtering from stochiometric HfB2 target in argon atmosphere. The aim of this work is to evaluate the efects of the bias potential on the microstructure, mechanical and tribological properties. These parameters strongly depend on the experimental conditions. X-ray difraction analysis indicated the diference in microstructure: from dense hexagonal structure with (0001) preferred orientation of nanocrystallites to quasi-amorphous with blurred HfB2 phase peaks. All coatings were measured using nanoindentation (using Berkovich tip), tribology (ballon-disk) and nano-scratch (friction). Coatings with a thickness of 1–2 µm had a signifcant dependence of properties on the microstructure: hardness drastically increased from 8 to 45 GPa, H/E ratio and elastic recovery changed respectively: 0.04–0.15 and 0.26–0.72.Item The cathodic electrolytic plasma hardening of the 20Cr2Ni4A chromium-nickel steel(Elsevier, 2020) Rakhadilov, B.K.; Буранич, Володимир Володимирович; Буранич, Владимир Владимирович; Buranych, Volodymyr Volodymyrovych; Satbayeva, Z.A.; Sagdoldina, Z.B.; Kozhanova, R.S.; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr DmytrovychIn order to obtain the modified surface structure of the 20Cr2Ni4A steel plasma electrolytic hardening (PEH) method was used. The surface hardening process was conducted in the aqueous electrolyte solution of 20% sodium carbonate and 20% urea. The sample consists of a ferritic-pearlitic structure, i.e. the part retains its viscous core, and the surface layer contains carbide particles. Hardening process induces martensite transformation and creation of carbide particles in the surface layer. The presence of carbide particles in the surface layers has a positive effect on the tribo-mechanical performance. Hardened structure 600 m long was obtained with hardness increase up to 520 HV and 2.5 times higher wear resistance. Tribological test results showed the difference of the coefficient of friction as a function of surface roughness determined by plasma-electrolytic hardening process.Item Effect of the PEN/C surface layer modification on the microstructure, mechanical and tribological properties of the 30CrMnSiA mild-carbon steel(Elsevier, 2020) Zhurerova, L.G.; Rakhadilov, B.K.; Popova, N.A.; Kylyshkanov, M.K.; Буранич, Володимир Володимирович; Буранич, Владимир Владимирович; Buranych, Volodymyr Volodymyrovych; Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr DmytrovychAs a result of plasma-electrolytic nitrocarburizing 30CrMnSiA carbon steel (ferrite-perlite grade), there was a change in the elemental and phase composition, as well as the surface layer microstructure (40 ÷ 45 microns thick from the surface). A formation of Me23(CN)6 carbonitrides, FeN nitrides, Fe3C - (Fe, Cr)3C carbides and an increase in dislocation density within –phase (tempered martensite crystallites), high-temperature lamellar martensite were observed. As a result of PEN / C exposure for 7min. At 750 ◦C there is a reduction of friction coefficient and wear rate, what is connected with finely dispersed secondary phases FeN, (Fe, Cr)3C, Me23(C, N)6 formation. Thus, there is an 2,5 ÷ 3,3 times increase in hardness of 30CrMnSiA carbon steel samples.Item Effect of ionly-plasma impact on the element composition and structural phase state of the system of Cu-Ti(Харківський фізико-технічний інститут, 2018) Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Міхалєв, Олександр Дмитрович; Михалев, Александр Дмитриевич; Mikhalev, Alexander Dmitrievich; Jarullah, Aid Kussey; Malikov, L.V.Представлені результати дослідження елементного складу та структурно-фазового стану системи Cu-Ti після впливу високої дози іонної імплантації та електронного відпалювання імпульсним низькоенергетич- ним високострумовим електронним пучком (НВЕП). Встановлено, що застосування імплантації з високою дозою ((5…8)∙1017 іон/см2) і подальшим впливом НВЕП призводить до зменшення концентрації титану, а застосування малої дози до 1∙1017 іон/см2 до його дифузії в глибину від поверхні. Дослідження структурно- фазового стану показало часткове випаровування прошарків карбіду-титану і формування субструктури.Item Specific Features of the Microstructure and Properties of Multielement Nitride Coatings Based on TiZrNbAlYCr(Pleiades Publishing, Ltd., 2018) Погребняк, Олександр Дмитрович; Погребняк, Александр Дмитриевич; Pohrebniak, Oleksandr Dmytrovych; Бондар, Олександр В`ячеславович; Бондарь, Александр Вячеславович; Bondar, Oleksandr Viacheslavovych; Кравченко, Ярослав Олегович; Кравченко, Ярослав Олегович; Kravchenko, Yaroslav Olehovych; Beresnev, V.M.; Zhollybekov, B; Kupchishin, A.I.Multicomponent nanostructured coatings based on (TiZrNbAlYCr)N with a hardness as high as 47 GPa were obtained by cathodic arc deposition. The effect of partial nitrogen pressure PN (with constant bias potential Ub = –200 V applied to the substrate) on the phase-composition variation, the size of crystallites, and their relation to the microstructure and hardness was investigated. An increase in the nitrogen pressure resulted in the formation of two phases with characteristic BCC (the lattice period is 0.342 nm) and FCC lattices with averaged nanocrystallite sizes of 15 and 2 nm. At a high pressure of 0.5 Pa, crystallites in the FCC phase with a lattice period of 0.437 nm grew in size to ~7 nm. The hardness of deposited coatings with larger (3.5 nm) FCC-phase crystallites and smaller (7 nm) BCC-phase crystallites was enhanced considerably