8th International Materials Science Conference HighMatTech-2023
October 2-6, 2023 Kyiv, Ukraine
Low-dimensional and Nanomaterials
Head:
Dr.Sc., Professor Andrey Ragulya
Deputy Director of Frantsevich Institute for Problems of Materials Science of National Academy of Science of Ukraine
President of Frantsevich Ukrainian Materials Research Society
Full member of the National Academy of Sciences of Ukraine, full member of the International Institute for the Science of Sintering. Dr. A. Ragulya graduated from Moscow Institute of Fine Chemical Technology in 1983. He received his M.S. degree in Powder Metallurgy and Materials Science from the Baikov Institute of Metallurgy and Materials Science in 1985 (Moscow, Russia). He received his Ph.D. (1993) and D.Sc. (2001) degrees from the Frantsevich Institute for Problems of Materials Science of National Academy of Science of Ukraine. Since 1985 he has been working at Frantsevich Institute for Problems of Materials Science (IPMS) of National Academy of Science of Ukraine. Since 1985 he has been working at IPMS in the field of sintering technology.
At the beginning of 90th Andrey Ragulya proposed the theoretical basis for Rate Controlled Sintering Process (RCSP), which previously had been experimentally considered by Prof. H.Palmour III. For the first time RCSP has been applied in the area of nanograined materials. Andrey Ragulya put forward a new ideology of so-called rate-controlled thermally activated processes, which has been confirmed experimentally for numerous technological processes, in particular, synthesis of nanosized particles of ceramic and metallic materials. His recent research activity focuses on the obtaining and characterization of nanosized particles, nanostructured ceramics & ceramic nanocomposites. In 2015 he was awarded with the State Prize of Ukraine for these efforts. Since 2002 he has been in the position of Deputyirector at IPMS and the research team leader in the development of nanomaterials at IPMS. He is an author of 6 books and 1 textbook in the area of nanomaterials, more than 270 papers and 16 patents.
Speakers:
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Oral Session |
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H3-OO1107 |
Reduced graphene oxide in metal oxide thermoelectrics Olena Okhay1, Oleksandr Tkach2 1TEMA- Center for Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, Portugal Today the energy demands are exponentially rising, and the worldwide research is focused on the clean and sustainable energy sources during the last years. As one of the possible ways to enable the transformation from a fossil fuel based to a low-carbon socio-economical epoch is the harvesting of unused heat in automotive exhaustion, industrial processes and home heating, etc.
Thermoelectric (TE) generators can convert the heat to electrical energy thanks to Seebeck effect when electricity appears between cold and hot ends of usually semiconductor materials. To be interesting for potential commercial use in TE generators the materials need to be of high figure of merit (ZT), possessing high electrical conductivity and Seebeck coefficient together with low thermal conductivity. Driven by a need to improve TE performance of n-type oxides, ceramics and composites based on donor-doped SrTiO3 are considered as a promising material.
Addition of reduced graphene oxide (rGO) in combination with introduction of Sr vacancies provides a synergistic effect of fastening charge transport in Nb-doped SrTiO3 and thereby increasing electrical conductivity and suppressing thermal conductivity.
The increasing electrical conductivity and suppressing the thermal conductivity, together with a moderate Seebeck coefficient, result in a high power factor PF ∼1.98 mW/(K2m) and ZT up to 0.29. Such findings offer further prospects for seeking high performance SrTiO3-based TEs by modification with rGO. Deep comparison with other thermoelectric composites with rGO is done.
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Olena Okhay |
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H3-MD1847 |
The structure and characteristics of all-dielectric opal-based nanocrystalline composites Mykhailo Derhachov1, Vasyl Moiseienko1, Bilal Abu Sal2 1Oles Honchar Dnipro National University, Ukraine Fabrication of opal-based composites with regularly spaced nanocrystals of active dielectrics is of a significant interest. Having a permittivity period close to light wavelength, these structures could be applied in light manipulating systems. Crystallization under specific conditions could result in changing initial substance parameters and forming the other phases. Herein, we examinate properties of nanocomposites fabricated by melt infiltration process with exploiting dielectrics, prospective for applying in optoelectronics (NaBi(MoO4)2, Pb3(P0.5V0.5O4)2, Bi12(Si)GeO20, Bi2TeO5, Li2B4O7).
Initial opals were porous matrices formed by the 250 nm SiO2 particles. The composite fabrication technique was based on capillary forced infiltration of initial opals with wetting melt of the input component. Characterisation was made with SEM, XRD, impedance and Raman spectroscopy techniques.
XRD patterns and Raman spectra indicate the nano-crystalline state of the embedded substance. Formation of nanocrystals is caused by mesoporous structure of SiO2 particles served as multi-crystallization centres. An average linear size of nanocrystals, derived from the XRD paterrn, does not exceed 30 nm for all composites, and it is well correlated with that defined from the impedance data in opal-NaBi(MoO4)2 composite. The change of lattice parameters is detected. With embedding Bi12Si(Ge)O20 and Bi2TeO5, the Bi4Si3O12 and α-cristobalite phases are additionally formed. The α-quartz phase is formed in opals soaked with the Li2B4O7 melt. Meanwhile, no stoichiometry deviations and new phases are detected in opal-NaBi(MoO4)2 and opal-Pb3(P0.5V0.5O4)2 composites. The observed changes are explained by interaction of the broken Si–O bonds on the SiO2 particle surface with Bi and Li ions, considering their charge state and concentration. Thus, the most stable components for melt infiltration process and ways to vary the composition have been found.
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Mykhailo Derhachov |
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Poster session Important.session is online-only and include 5 min presentation in the common conference room and 1 hour of discussion in individual rooms (Zoom) |
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H3-MB1006 |
Synthesis of multi-walled carbon nanotubes by the method of chemical deposition from methane air conversion products Alexander Khovavko1, Denis Filonenko1, Alexey Svyatenko1, Andriy Nebesnyi1, Anastasiya Kolesnichenko2, Yeva Boboshko2,3, Maksym Barabash1,2,3 1The Gas Institute, N.A.S of Ukraine The method of carbon nanotubes (CNTs) synthesis by chemical vapor deposition (CVD) is currently modern and widely used in industry [1,2]. Important factors affecting the synthesis of CNTs by the CVD method are: the choice of precursor gas, temperature and pressure in the reaction chamber, gas flow rate, nature and size of the catalyst grain [3]. The CNTs synthesis process was carried out using the products of air conversion of natural gas as raw material. The classical spectrum of carbon nanotubes with two characteristic peaks at 1298 and 1586 cm-1 corresponding to D and G modes, respectively. At the same time, on the first, second, and fourth spectra, classical spectra for nanotubes with characteristic D- and G-modes are clearly observed. However, it was found that in all three samples the D mode has a higher intensity than the second mode, which is not characteristic for single-walled intact nanotubes. That is, it can be concluded that the nanotubes obtained in our experiment by CVD method are multi-walled and most likely have a curved structure. In all three samples, a shoulder in the G mode is clearly visible (which may be an overtone of the D mode) and indicates the high defectiveness of the obtained samples. Raman spectra confirmed the presence of carbon nanotubes with two characteristic peaks at 1310 and 1578 cm-1 corresponding to D and G modes, respectively. Based on the ratio of the two modes, the ratio of the planes under the G and D bands was calculated and a significant number of carbon nanotubes defects was determined. According to the peak half-width parameter D, it can be clearly determined that the samples have the smallest peak half-width, which indicates their highest crystallinity. All nanotubes, according to the calculated ratios, have a high number of defects and bends, however, sample number 2 has the most perfect (smallest number of defects) compared to the others.
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Maksym Barabash |
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H3-OL1221 |
Nanostructured photocatalytically active TiO2-based nanocomposite systems Olena Lavrynenko, Maksim Zahornyi, Olesja Pavlenko, Serhiy Korichev I. Frantsevych Institute for Problems of Materials Science of NAS of Ukraine Titanium dioxide is widely used for remediation of organic dyes in wastewater, but its application requires exposure to UV radiation due to the wide band gap (Eg~3.2 eV). Various elements are injected into the structure to extend the activity of TiO2-based catalysts to the visible light region. The aim of the work is the synthesis of TiO2-based nanocomposite systems and the verification of their photocatalytic activity for the discoloration of the malachite green (MG) water solution. The synthesis of the nanocomposites was performed via the co-precipitation of TTIP with the Ag, Au, and Ce-containing species (0.2-4.0 wt.%). The precipitates were washed, filtered, lyophilized at 120 °C and calcined at 600 °C in 2 h. Composite particles were studied by XRD-analysis, SEM, and an energy-dispersive spectroscopy. The photocatalytic activity of the systems was tested using a MG water solution (20 mg/dm3) at pH 7. Dispersion was stirred in the dark and then stirred under UV (254 nm). XRD data showed the formation of anatase for all studied systems. Lattice parameters are the following: a – 0.3740÷0.3778 nm, c – 0.9428÷0.9645 nm, V – 0.133÷0.136 nm3. CSR of pure TiO2 is 12.7 nm, and CSR of the nanocomposites is 8.3-10.6 nm. Right shift of the (101) plane is typical for the all samples. The tetragonality degree of TiO2&Au and TiO2&Ag samples is 2.51, but it increases to 2.57 for TiO2&CeO2 composites. Decolorization of the MG solution under UV irradiation in 5 min increases in the row TiO2&Au < Pure TiO2 < TiO2&CeO2 < TiO2&Ag < TiO2&CeO2&Ag. However, the clusters of Ag on the anatase surface are oxidized under UV in contact with the MG in 45 min. Also, TiO2-based nanostructures exhibited sorption activity in the dark. The degree of MG decolorization was more than 95% even after 5 min of contact. Thus, the obtained nanostructures are promising materials for creating photoactive catalysts for MG destruction.
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Olena Lavrynenko |
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H3-AD2223 |
Modeling of photovoltaic characteristics of a TiO2/porous-Si/Si-based heterojunction solar cell Alena Dyadenchuk Dmytro Motornyi Tavria State Agrotechnological University, Ukraine Recently, the issues of increasing the conversion coefficient of solar energy into electrical energy, identifying ways to increase efficiency, and reducing the electricity cost have been predominant in microelectronics. Тhere is a need to replace monocrystalline silicon with other promising materials. The purpose of the paper is to conduct simulation and optimization of the functional characteristics of the photoconverter based on heterostructures TiO2/PS/Si.
Simulation is proposed to conduct in a freely distributed program PC1D. During the simulation, the thickness of the layers was varied from 100 nm to 1.0 μm for the PS and TiO2 layers, respectively, the concentration of the main charge Nd carriers from 10^13 to 10^20 cm-3. The values of the main physical parameters used in the modeling of solar cells are obtained from scientific sources.
Simulation has shown that changing the thickness of the porous layer does not significantly affect the short circuit current at the selected values (Isc=33.5 mA). At a thickness of 0.2 μm, the efficiency of the solar cell is on a maximum value, but with an increase in the thickness of the porous layer, a decrease in efficiency from 21.3 % to 21.0 % is observed. In this case, there is also a decrease in Voc values from 0.799 to 0.798 V. The analysis of the data shows that increasing the doping level of the PS layer from 10^13 to 10^19 cm-3 leads to an increase in the short circuit current Isc. The efficiency increases from 18.0 % to 22.3 %. It can be seen that the dependence of the open circuit voltage Voc on the level of the layer doping is weak and decreases by 16.8 mV. The optimal thickness of the TiO2 layer is d=100 nm. The analysis shows that increasing the TiO2 layer doping level from 10^13 to 10^20 cm-3 has no particular effect on the short circuit current value, but at Nd=1∙10^20 cm-3 this value decreases by 0.4 mA. Changing the doping level Nd has little effect on the no-load voltage.
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Alena Dyadenchuk |
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H3-YY0561 |
Impact of mechanical treatment duration on the structure of nanopowder composite SiO2/TiO2 Yurii Yavorskyi1,2, Myroslav Karpets1,2, Andrii Hrubiak3, Oleksandr Dudka1,2, Tiancheng An1,2, Yulong Guo1,2 1Y.O.Paton ER IMW, Ukraine The properties of nanosized materials depend on their structural and morphological features, electronic structure, development and surface defects, and others. Different methods of synthesis and processing are used to increase the surface activity of materials. One of the methods that allows to achieve this is machining, and in this case mechanical treatment on the microbreaker (MBT) [1,2]. In this work, we conducted a study of the effect of different duration of such treatment on the structural and morphological features of the mixture 0.8SiO2+0.2TiO2. Preparation of the initial mixture was performed by conventional stirring for 5 minutes, followed by stirring in a 50 Hz mechanical microbreaker Ardenne with stainless steel sphere (25 mm in diameter) and ball (10 mm in diameter). Mechanical processing was carried out under the same conditions, but for 3, 5, 10, 15 and 20 minutes. The morphology of the nanoparticles before and after MBT was studied using scanning electron microscopy (SEM) PEM-106. The crystalline structure of the powder blends were studied using the Ultima IV diffractometer (XRD). From the results of SEM studies, it was established that a uniform distribution of oxide agglomerates occurs in the mixture after 3 min of MBT; 5 minutes of processing leads to fragmentation of these agglomerates and the formation of new ones from nanoparticles of both oxides; Processing for 10-20 minutes leads to an increase in the density of the nanocomposite. From the results of XRD, it was found that anocomposite consist of amorphous SiO2 and two phases of TiO2 (rutile, anatase). As a result of MBT for 3 and 5 min, the coherent region scattering (CRS) of rutile decreases and anatase increase. Subsequent MBT for 10-20 min is accompanied by its rapid increase of CRS of rutile and normalize anatase. It should be noted that the changes in lattice parameters and phase composition were within the error limits of the experiment.
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Yurii Yavorskyi |
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H3-NK2053 |
Electrochemical properties of 2D MoS₂/Mo nanocomposites Leonid Kulikov, Nataliia Konih-Ettel, Victor Talash, Yuliia Rudenko, Mykolai Shevchuk Frantsevich Institute for Problems of Materials Science, NAS of Ukraine Recently, the development of 2D transition metal chalcogenides (TMDs) nanomaterials with a variety of physicochemical properties has shown their potential as eminent non-noble metal-based nanoscale (photo)electrocatalysts for hydrogen evolution (HER).
Electrochemical properties of 2D MoS₂/Mo nanocomposites were studied in 0.5M H₂SO₄ electrolyte by using potentiodynamic polarization curves method. It was used Platinum as the counter electrode and Ag/AgCl as the references.
Sufficient chemical stability of the MoS₂ nanocoating on Mo was established, as well as the possibility of the formation of intercalated H⁺ₓ(H₂O)ᵧMoS₂₋ₓ/Mo nanophases at the removing process of cathodic polarization curves.
The pre-treatment annealing of the MoS₂/Mo nanocomposite in the air (400 K, 1 h) was performed to study the surfaces oxidation effect on the cathode polarization curves (as to the synthesis of MoO₃₋ₓ/MoO₃ layer on their surface and the formation of complex MoO₃₋ₓ/MoO₃/MoS₂/Mo nanocomposite).
The iodine pre-treatment (halogenation) of MoS₂/Mo nanocomposites was carried out as to the possible formation of intercalated IₓMoS₂/Mo compounds, and their effect on polarization curves and increasing of the electrical conductivity.
The obtained results clearly indicate to the positive role of the pre-treatment annealing and halogenation of the initial MoS₂/Mo nanocomposites, what leads to a significant increase in the electrical conductivity (an increasing of current density by almost order of magnitude at -1.5 V).
2D MoS₂/Mo nanocomposite has the potential as electrocatalysts for HER, suggesting the development of new type of catalyst with efficient activity in HER as well as other renewable energy fields.
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Nataliia Konih-Ettel |
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H3-TV1732 |
Phase formation in layered Pd/Ag/Fe films and their magnetic properties during annealing in hydrogen Oleksandr Sliesarenko1, Leonid Levchuk1, Maryna Natalenko1, Katerina Graivoronska2, Ruslan Shkarban1, Tetyana Verbytska1, Iurii Makogon1, Sergiy Sidorenko1 1Y.О. Paton Educational and Research Institute of Materials Science and Welding National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” Nanoscale films based on FePd with an ordered structure are promising for use as ultrahigh-density magnetic recording media, future spintronic memory and logic devices.
The aim was the investigation of thermal treatment environment, intermediate Ag layer thickness and annealing temperature influence on the phase composition, structure and magnetic properties of the films. Layered Pd(6 nm)/Ag(0.2; 0.4 nm)/Fe(4.6 nm) and Pd(7 nm)/Ag(0.2; 0.4 nm)/Fe(5 nm) films to form Fe 49 Pd 51 and Fe 47 Pd 53 compositions after annealing were deposited on a SiO 2 (100 nm)/Si(001) substrate by magnetron sputtering. Thermal treatment was carried out in three modes: annealing in H 2 in the range of 600 °C - 700 °C for 1 hour, Rapid thermal annealing (RTA) in nitrogen for 90 s, and two-stage heat treatment (RTA + annealing in H 2 ) at 600 °C and 650 °C. The films were investigated by X-ray analysis, SQUID and AFM methods.
Іn the as-deposited Pd(6 nm)/Ag(0.2 nm)/Fe(4.6 nm) film a low intensity Pd(111) reflection is observed. Annealing in H 2 at 600 °C is accompanied by mutual diffusion between the layers with the formation of Pd(Ag, Fe) solid solution. An increase in the Ag thickness to 0.4 nm activates these processes leading to the formation of a soft magnetic disordered A1 FePd phase. An increase in the annealing temperature to 650 °C leads to rise in the coercivity. This is explained by a larger amount of Ag along the FePd grain boundaries, which limits their growth and reduces the exchange interaction. Two-stage heat treatment and an increase in the annealing temperature to 650 °C in both films also lead to the A1 phase formation. It was established that in the Pd/Ag/Fe films, regardless of the thickness of the Ag interlayer, annealing in H 2 in the range of 650 – 700 °C is accompanied by the formation of a disordered A1 phase. Variation in the film composition from Fe 49 Pd 51 to Fe 47 Pd 53 leads to changes in the saturation magnetization which is associated with an electronic structure change.
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Tetyana Verbytska |
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H3-RP2357 |
Diffusion-induced local ordering in Pt/Co bilayers Roman Pedan1, Pavlo Makushko1,2, Oleksandr Dubikovskyi1,3, Andrii Bodnaruk1,4, Andrii Burmak1, Denys Makarov2, Igor Vladymyrskyi1 1National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” Magnetic materials based on Co-Pt alloys have great potential as materials for spintronics and data storage applications [1]. Therefore, it is important to study the diffusion and formation of ordered magnetic phases in thin films made of Co and Pt. In current study Pt(14 nm)/Co(13 nm)/Ta(3 nm) stacks were magnetron sputtered on substrate and then annealed in a high vacuum at temperatures ranging from 200 °C to 550 °C with a constant annealing duration of 30 minutes. Several techniques including secondary ion mass spectrometry (SIMS), X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and VSM magnetometry, have been used to analyze the structure, chemical composition, and magnetic properties of the post-annealed stacks. Although the formation of ordered L10-CoPt phase and the achievement of long-range chemical order was not observed, heat treatment increased the coercive field and created local anisotropy in the CoPt film. These results suggest the need for further investigation into diffusion processes and the formation of hard magnetic phases through a diffusion-induced grain boundary migration mechanism in Co-Pt thin films during low-temperature annealing.
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Roman Pedan |
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H3-SG1252 |
Local straine strengthening of the low-carbon steels near inclusions by severe plastic deformation Svetlana Gubenko1,2 1Iron and Steel Institute of Z. I. Nekrasov National Academy of Science of Ukraine The aim of this work was to study the local processes of plastic structure formation occurring in low-carbon steels near non-metallic inclusions during severe plastic deformation by the method of equal-channel angular pressing.
Samples of steels were subjected to plastic deformation by the ECAP method in four passes which corresponded to a true deformation of 3.2. Structural analysis was performed using an Olympus PME 3 optical microscope, as well as JEM 100CX and JXA-50F electron microscopes.
In the steels under study, structure formation during severe plastic deformation is associated with the formation of oriented structural elements that have dimensions of 100…260 nm and are separated by high-angle boundaries, which are characterized by the presence of dispersed curved mesobands of deformation, and in steel 08Kh18N10T also martensitic plates. Near the inclusions, the grain sizes are significantly smaller than far from them and are 75…100 nm. The nanohardness values of the steel matrix near the inclusions were 25…40% higher than the similar values far from the inclusions. Near plastic inclusions of sulfides and silicates, the values of nanohardness are lower than near non-deformable oxides and titanium carbonitrides, which is associated with a certain deformation relaxation of stresses in the plastic inclusion-matrix system. In cases of localization of dynamic cold recrystallization near inclusions, the nanohardness of the steel matrix decreased by about 10%.
The influence of non-metallic inclusions on the local refinement of the steel microstructure is an important effect during severe plastic deformation, which makes it possible to obtain additional nanostructural strengthening near the inclusions during the general refinement of grains to a submicrocrystalline state.
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Svetlana Gubenko |
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H3-AK1057 |
Quality factor of metal nanoparticles having the shape of a bicone and a bipyramid Andrii Korotun1,2 1National University Zaporizhzhia Politechnic, Ukraine Currently, there is an intensive search for the forms of metal nanoparticles in order to achieve certain optimal optical characteristics. So, for example, it is assumed that nanoparticles
with sharp edges and vertices are capable of producing a local amplification of fields near the edges and, especially, at the vertices, that is greater than nanoparticles of other shapes.
Therefore, the study of the optical properties of such particles is an urgent task.
The paper investigates the size-frequency dependence of the diagonal components of the quality factor tensor for particles in the form of
bicones and bipyramids located in a dielectric medium with a permittivity $\epsilon_{\text{m}}$. This dependence is determined by the relation $Q^{\bot ( \parallel)} \left(\omega \right)=\frac{\omega}{2\operatorname{Im}\epsilon^{\bot(\parallel)(\omega)}} \left(\frac{d}{d\omega}\operatorname{Re}\epsilon^{\bot(\parallel)}( \omega )\right)$,where $\omega$ is the frequency of the incident light; $\epsilon^{\bot(\parallel)}(\omega)$ are the diagonal components of the dielectric tensor of the nanoparticle material, determined in the Drude model. To determine the size-frequency dependence of the quality factor of bicones and bipyramids, the “equivalent” spheroid approach proposed in [1] is used. Moreover, for bicones and bipyramids with $h>2r$ and $h>2r_{\text{red}}$ (where $r_{red}$ is the “reduced” radius of the base of the bipyramid, determined from the condition of equality of the areas of the bases of the bicone and bipyramid), the equivalent is a prolate spheroid, and in the case of $h<2r$ and $h<2r_{\text{red}}$, an oblate spheroid.
Calculations of the frequency and size dependences (at the frequency of the surface plasmon resonance) of the dependences of the diagonal components of the Q-factor tensor were carried out for nanosized
bicones and bipyramids made of different metals and having different sizes. It has been established that for prolate bicones and bipyramids to $Q^{\bot }\gg Q^{\parallel }$, while in the case of oblate bicones
and bipyramids, vice versa $Q^{\bot }\ll Q^{\parallel }$. In addition, in the visible region of the spectrum, the maximum $Q^{\bot }$ for $Q^{\parallel}$ Au and Ag bicones and bipyramids. The range of aspect
ratios at which the quality factor of plasmonic nanostructures of the studied forms will be maximum has been determined.
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Andrii Korotun |
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H3-AK1125 |
Features of the spectral characteristics of a metallic nanotube of variable thickness Roman Malysh1, Andrii Korotun1,2, Igor Titov3 1National University Zaporizhzhia Politechnic, Ukraine It is known that metallic cylindrical shells have unique optical properties, in particular, good spectral tunability in biological transparency windows. At the same time, the vast majority of research is devoted to cylindrical shells of constant thickness [1], and the optical properties of shells of variable thickness (non-axial cylinders) have not been practically studied, and therefore this problem is relevant. Since the wavelength of the incident light is much larger than the characteristic transverse dimensions of the considered nanostructure, to solve this problem, one can use the quasi-static approximation, in which the study of the boundary value problem of electrostatics makes it possible to obtain the frequency dependence of the polarizability. In turn, the zeros of the numerator and denominator of the expression for polarizability give dimensional dependences for the frequencies of invisibility and surface plasmon resonance (SPR).
Calculations of the size dependences and dependences on the permeability of the inner cylinder of the SPR and invisibility frequencies were carried out for non-coaxial cylindrical two-layer nanostructures in which the inner cylinder is made of dielectrics and the shell is made of noble metals. The presence of four invisibility and SPR frequencies has been established, and for structures $\text{Si}{{\text{O}}_{2}}\text{Au}$ and $\text{Si}{{\text{O}}_{2}}\text{Ag}$ the splitting of the lower and upper frequencies of invisibility and the lower branch of the SPR frequency is very small.
In addition, for these nanostructures, the invisibility frequencies are practically independent of the distance between the axes of the cylinders, the lower SPR frequencies decrease, and the splitting of
the upper frequencies increases with increasing distance. It is shown that all four frequencies of invisibility and SPR decrease with an increase in the dielectric constant of the inner cylinder, and the
decrease in the lower frequencies is more significant than the upper ones.
It is shown that when the distance between the axes of the cylinders tends to zero, two upper and two lower frequencies of invisibility and SPR merge, as in the case of a metal shell of constant thickness.
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Roman Malysh |
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H3-MM1135 |
Plasmons in a chain of prolate metallic nanospheroids Maksym Maniuk1, Andrii Korotun1,2, Valery Kurbatsky1, Igor Titov3 1National University Zaporizhzhia Politechnic, Ukraine Periodic chains of metal nanoparticles of various shapes attract the attention of researchers, since they are systems in which the plasmon propagation length turns out to be a macroscopic quantity. This makes it possible to use chains of nanoparticles as plasmonic waveguides in telecommunication technologies, which makes the study of the plasmonic properties of such nanosystems an urgent task.
When the distance between the particles in chains is of the order of their dimensions, it is necessary to take into account the finite size of the particles. In this paper, we study the propagation of surface plasmons in a chain of prolate metal spheroids, taking into account their finite size.
Since dimensions of the nanospheroids included in the chain are much smaller than the light wavelength, the potentials (and, consequently, the field strengths) can be sought in the quasi-static approximation. Expressions are obtained for the field strengths of a prolate spheroid and a point dipole in the case of equality of their dipole moments. It has been found that at small distances from spheroids, these fields
differ significantly (the field of a point dipole is greater than the field of a nanospheroid). Consequently, the field acting on the particle from neighboring spheroids will be smaller, which means that when solving the problem, only the influence of nearest neighbors can be taken into account. Therefore, the dispersion law is studied in the indicated approximation, which makes it possible to obtain the
frequency dependence of the plasmon propagation length. An analysis of the calculation results shows that in the case under consideration, the plasmon free propagation length is longer than in a chain of
spherical particles and oblate spheroids, but shorter than one obtained from calculations using the point dipole approximation.
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Maksym Maniuk |
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H3-AK1142 |
Plasmon resonance in a square lattice of metal nanodisks on a dielectric substrate Nazar Pavlyshche1, Andrii Korotun1,2, Valery Kurbatsky1 1National University "Zaporizhzhia Politechnic", Ukraine As is known, the enhancement of absorption at the frequencies of surface plasmon resonance (SPR) in the lattice of metal nanodisks located on a dielectric substrate can be used to increase
significantly the efficiency of solar cells. Therefore, determining the dependence of SPR frequencies in such a structure on the size and
material of metal nanodisks, as well as on the lattice period, is an urgent task. The size dependences for the frequencies of the transverse SPR can be
found from the condition the denominator of the expression for the lattice polarizability to be equal zero.
In turn, the components of the nanodisk polarizability tensor are determined using the representation by an equivalent spheroid, and in this case, an oblate spheroid will be equivalent [1]. Within the framework of this representation, a dimensional parameter, the effective aspect ratio, is introduced, which makes it possible to replace the study of optical properties of the disk with the study of
the properties of the equivalent oblate spheroid.
The calculations were carried out for lattices of nanodisks of different sizes made of different metals. It has been established that with an increase in the effective aspect ratio, the frequency of the
transverse PPR decreases. In this case, the SPR frequencies decrease in the series of metals Ag → Cu → Au, since the frequency of bulk plasmons for these metals decreases in the same order. It should also
be noted that the frequency of the transverse SPR in the case of latticies of disks with the same dimensions does not depend on the lattice period. Thus, the lattice plasmon resonance can be controlled
by changing material and size of the disk.
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Nazar Pavlyshche |
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H3-YV1623 |
Intrinsic role of Cu⁺ and In³⁺ cations in the nature of ferrielectric ordering in CuInP₂S₆ ferroics Ruslan Yevych, Vitalii Liubachko, Yulian Vysochanskii Institute for Solid State Physics and Chemistry, Uzhhorod National University, Ukraine 2D CuInP₂S₆ ferroics are one of the most representative materials because of their room-temperature ferroelectricity. The spontaneous ordering of electric dipoles below Tc ≈ 312 K creates macroscopic polarization that may be changed by an external electric field. In condensed matter physics, van der Waals layered materials have emerged as a potential study area. Furthermore, their out-of-plane polarization is more suitable for nonvolatile high-speed memory and heterostructure-based nanoelectronics [1].
The QAO model [2] was used to estimate the contribution of copper and indium cations to the origin of ferrielectricity in CuInP₂S₆ crystals. Such a model considers phonon-like bosonic excitations to describe the temperature dependence of the spatial distribution of Cu⁺ and In³⁺ cations. These results were compared with the analysis of the mean-field approach [3] and with calorimetric studies [4], which allowed us to clarify the dipole ordering of the CuInP₂S₆ crystal.
By the QAO model, it was found that In³⁺ cations play a decisive role in the character of polar ordering which is determined by the energy of side wells with respect to the central well of their local potential. At normal and for positive pressures, the first-order transition occurs, which is determined by the higher energy of side wells with respect to the central well of the local potential for In³⁺. At increasing negative compression, the named side wells are stabilized and ferrielectric transition can evolve to the second order.
The peculiarities of polarization switching in different regions of the CuInP₂S₆ temperature-pressure phase diagram are studied and contributions of copper and indium cationic sublattices into polarization hysteresis loops are determined. The multiple polarization states appear as single, double, and triple hysteresis loops. The genesis of the triple P-E loop, as the sum of contributions from Cu⁺ ordering and In³⁺ shifting under electric field E was analyzed in detail.
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Yulian Vysochanskii |
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H3-AP2206 |
Atomic-scale modeling of the formation mechanism of nanocrystalline nucleі of SiC nanofibers from methyltrichlorosilane molecules Peter Sylenko, Alex Pokropivny, Denis Andrushchenko, Yuriy Solonin I M Frantsevich Institute for Problems of Materials Science of NASU, Kyiv, Ukraine For the first time, a model was built using quantum chemistry method (RHF/STO-3G) and the mechanisms of sequential formation of nanocrystalline nuclei of silicon carbide nanofibers were proposed [1-5]. Two types of reaction with methyltrichlorosilane molecules were obtained, namely, when chlorine atoms of one molecule react with a hydrogen atom of another, and when three chlorine atoms of a methyltrichlorosilane molecule react with three hydrogen atoms of a cluster. It was the simulation of such a reaction with the output of three molecules of HCl that makes it possible to simulate a SiC nanocrystalline nucleus of 1 nm in size. The infrared spectra of the clusters were calculated, which confirm the formation of a crystal lattice in the reaction products.
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Alex Pokropivny |
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H3-AP1504 |
Supercritical fluid synthesis of nanocrystalline c-BN and other BN structures from graphite-like boron nitride Alex Pokropivny1, Sergey Maloshtan2, Anatoly Smolyar2, Peter Sylenko1, Yurii Solonin1 1I M Frantsevich Institute for Problems of Materials Science of NASU, Ukraine Cubic boron nitride (c-BN) is known to be the one of the best industrial abrasive and cutting materials, combining wear resistance, high hardness and thermal stability. It is widely used in
electronics due to chemical and mechanical stability, high electrical insulating properties, optical
transparency etc. Supercritical fluid synthesis of c-BN and other dense, intermediate, soft and amorphous BN phases has been studied at pressures 50 — 200 MPa and temperature ~1000 0K from h-BN and t-BN as precursors and H2O and N2 as fluids. According to the results of electron and X-ray diffractions, Fourier-transform infrared spectroscopy and hardness measurements, c-BN phase is proved to be the main synthesized phase with the level of transformation at least 20 %. Two different mechanisms of c-BN nanocrystals formation are proposed. Hardness values of synthesized crystals fill out all scale of
hardness: ultrasoft, soft, normal and hard, characterizing several unconventional phases of boron nitride, including extradiamond E-BN phase.
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Sergey Maloshtan |
Contacts
Conference Secretary: Storozhenko Maryna
E-mail: conference@umrs.org.ua
E-mail: conference@umrs.org.ua