12.09.2023
Controlled radio-frequency components are imperative for various modern microwave devices and communication systems, especially wideband and multistandard ones. Key parts of such components are active switching elements based on some materials sensitive to external factors. Our group collaborates with the faculty of chemistry to search and study smart materials capable of elecrtodynamic properties alteration under different factors such as electric and magnetic fields, power microwave pulses, temperature etc. Particularly, among the studied materials are spin–crossovers. They show temperature–dependent spin transition which means switching between two electron configurations in a material and, properly, two appreciably different physical properties.
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Vanadium dioxide composite as one of materials manifesting phase transition is also studied due to the technologically attractive temperature 341K of “metal-insulator” hysteresis transition. This transition from low–temperature monoclinic to high–temperature rutile crystal form fundamentally changes the electrodynamic properties of the composite, mainly its microwave permittivity, and the formative polymer matrix provides the proper mechanical processability.
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Research and development of multifunctional electroconductive nanocomposite materials for electromagnetic protection.
Interaction of microwave radiation with composites with segregate structures is conjointly investigated with the faculty of physics. Segregated structures are formed by the conductive filler nanoparticles localization primarily on the polymer granules. Electroconductive properties of a segregated composite are characterized by low percolation threshold which is attained by much lower filler concentrations compared with the case of simple composite. It allows achieving anomalously high microwave absorption in a composite at much lower conductive admixture concentration. Protective elements against the microwave radiation are among practical applications of such composites.
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The correlation dependence of the real and imaginary parts of the microwave complex permittivity of the segregated composite on the carbon nanotubes content is evidence of several factors which take part in the microwave polarization forming. The latter occurs by the interphase and dipole polarization of the filler clusters. Those factors can be controlled by variation of filler concentration and morphology, and multifunctional electroconductive nanocomposite materials with enhanced electromagnetic protection properties can be obtained.
Contacts:
Viktor Oliynyk, PhD, Oliynyk@univ.kiev.ua
Zagorodnii Volodymir, zvv@univ.kiev.ua
Select publications:
Lozitsky, O.V., Vovchenko, L.L., Matzui, L.Y., Oliynyk, V.V., Zagorodnii, V.V. Complex permittivity of epoxy composites with carbon nanotubes and TiO2 in microwave range. Molecular Crystals and Liquid Crystals, 2021, 717(1), стр. 121–127.
https://doi.org/10.1080/15421406.2020.1860537.
Matzui, L.Y., Syvolozhskyi, O.A., Vovchenko, L.L., Yakovenko, O.S., Oliynyk, V.V., Zagorodnii, V.V. Lazarenko A.A., Len T.A. Electrical and electromagnetic interference shielding properties of GNP-NiFe hybrid composite with segregate structure of conductive networks, Journal of Applied Physics, 2022, 131(5), 055110. https://doi.org/10.1063/5.0071157
O.I. Kucheriv, V.V. Oliynyk, V.V. Zagorodnii, V.L. Launets, I.O. Fritsky, I.A. Gural’skiy. Hybrid organic-inorganic perovskites as microwave radiation switches, Materials Advances, 2022, DOI:10.1039/D2MA00633B.
O.I. Kucheriv, V.V. Oliynyk, V.V. Zagorodnii, V.L. Launets, A. Rotaru, , I.A. Gural’skiy. A Vanadium Dioxide-PMMA Composite For Microwave Radiation Switching, ChemPlusChem, 2022, Volume 87, Issue 6, https://doi.org/10.1002/cplu.202200107