Viktor Oliynyk

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Microwave absorption in epoxy composites filled with MoS2 and carbon nanotubes

Journal of Applied Physics, 2022

Paper published as part of the special topic on Microwave Absorption by Carbon-Based Materials an... more Paper published as part of the special topic on Microwave Absorption by Carbon-Based Materials and Structures ARTICLES YOU MAY BE INTERESTED IN In situ synchrotron x-ray diffraction studies monitoring mechanochemical reactions of hard materials: Challenges and limitations Review of Scientific Instruments 92, 114102 (2021);

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Polyethylene Composites with Segregated Carbon Nanotubes Network: Low Frequency Plasmons and High Electromagnetic Interference Shielding Efficiency

Materials, 2020

Polyethylene (PE) based composites with segregated carbon nanotubes (CNTs) network was successful... more Polyethylene (PE) based composites with segregated carbon nanotubes (CNTs) network was successfully prepared by hot compressing of a mechanical mixture of PE and CNT powders. Through comparison with a composite comprising randomly distributed carbon nanotubes of the same concentration, we prove that namely the segregated CNT network is responsible for the excellent electrical properties, i.e., 10−1 S/m at 0.5–1% and 10 S/m at 6–12% of CNT. The investigation of the complex impedance in the frequency range 1 kHz–2 MHz shows that the sign of real part of the dielectric permittivity ε r ′ changes from positive to negative in electrically percolated composites indicating metal-like behavior of CNT segregated network. The obtained negative permittivity and AC conductivity behavior versus frequency for high CNT content (3–12%) are described by the Drude model. At the same time, in contrast to reflective metals, high electromagnetic shielding efficiency of fabricated PE composites in the fr...

format_quote1.0 wt.% CNT in PLA composites yields high electrical conductivity (35.5 dB SE) for effective EMI shielding in X-band frequency.format_quote

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Electromagnetic shielding properties of epoxy composites with hybrid filler nanocarbon/BaTiO3

Materials Chemistry and Physics, 2019

Electromagnetic shielding properties of epoxy composites with hybrid filler nanocarbon/BaTiO , (2... more

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Influence of conductive nano- and microfiller distribution on electrical conductivity and EMI shielding properties of polymer/carbon composites

Composites Science and Technology, 2018

In this work, DC conductivity and EMI shielding characteristics in the frequency range of 25.5−37... more In this work, DC conductivity and EMI shielding characteristics in the frequency range of 25.5−37.5 GHz (K a-band) of polymer composites based on ultrahigh-molecular-weight polyethylene (PE) and polypropylene (PP) containing different types of nano-and microfillers were studied. Graphene nanoplatelets (Gr), thermally exfoliated graphite (TEG), thermally treated anthracite (A) and dispersed metals such as iron (Fe) and copper (Cu) were used as conductive fillers. Two types of composites were formed: 1-with ordered distribution of the filler particles in the form of conductive 3D network in polymer matrix (segregated structure), 2-with random distribution of the filler particles. It was found that the percolation threshold for Gr and A filler is 100 and 10 times lower in the segregated system was 100 and 10 times lower than that for A filler with its random distribution in polymer matrix. Distinctly increased value of shielding efficiency (SE T) in the segregated system can be explained by multiple internal reflection of electromagnetic wave in the network formed in the segregated structure. It was also found that the value of SE corresponds with the electrical conductivity of composites. However, for the same conductivity, higher values of SE were observed for the formed segregated structure in comparison with the literature data for composites with random filler distribution.

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The effect of graphite functionalization on electrical and shielding properties of epoxy composites

Molecular Crystals and Liquid Crystals, 2016

Composite materials (CMs) based on epoxy resin and functionalized thermoexfoliated graphite (TEG)... more Composite materials (CMs) based on epoxy resin and functionalized thermoexfoliated graphite (TEG) were prepared. The composition of functional groups at the TEG surface was characterized by FTIR spectroscopy. It was found that some of CMs with pristine TEG have high shielding efficiency in the region of electromagnetic radiation frequency from 25.5 to 37.5 GHz. But the main disadvantage of these CMs is their high porosity and heterogeneity that makes impossible to obtain the stable shielding characteristics for thin sample. However, CMs contained functionalized TEG are sufficiently homogeneous and allow purposefully regulate their electrical and shielding properties by changing TEG content.

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Microwave Properties and Conductivity Anisotropy of Oriented Multiwalled Carbon Nanotube/Epoxy Composites

METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2016

Epoxy composites with the aligned network of multiwalled carbon nanotubes generated by applying A... more Epoxy composites with the aligned network of multiwalled carbon nanotubes generated by applying AC electric field during the curing process are fabricated. Industrial nanotubes with diameter of 10-30 nm and length of 10-30 m are used. The nanotubes' concentration is varied from 0.2 to 1.0% wt. DC conductivity is measured for two orientations of multiwalled carbon nanotubes' network-parallel and perpendicular to the direction of the instrument current. Similarly, complex microwave permittivity and conductivity are investigated for parallel and perpendicular orientations of multiwalled carbon nanotubes' network to the microwave electric field. Measured DC conductivity of order of 10 7-10 5 S/m contrasts with microwave conductivity of order of 10 2-10 1 S/m. The conductivity anisotropy varies from 18 to 26 for DC measurements and from 1.26 to 2.04 for microwave ones. Such difference in anisotropies can be attributed to the essential inequality of the actual electron transport mechanisms under DC and microwave electric fields.

format_quoteElectric field induces dipole formations in MWCNTs, promoting their alignment and enhancing network formation.format_quote

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Conductive and Shielding Properties of MWCNTs/Polymer Nanocomposites with Aligned Filler Distribution

NATO Science for Peace and Security Series B: Physics and Biophysics, 2016

The effect of filler alignment on conductive and shielding properties has been investigated in mu... more The effect of filler alignment on conductive and shielding properties has been investigated in multiwall carbon nanotubes (MWCNTs)/polymer nanocomposites (NCs) containing 0.05–1 wt. % of the filler. The filler alignment was produced by applying external AC electric field during the whole process of hardening. MWCNTs network formation was detected by optic microscopy.

Optimization of multilayer electromagnetic shields: A genetic algorithm approach

Materialwissenschaft und Werkstofftechnik, 2016

Composites filled with carbon nanoplatelets designed as multi-layer electromagnetic shields are c... more Composites filled with carbon nanoplatelets designed as multi-layer electromagnetic shields are considered because of their interesting electromagnetic characteristics, such as high electrical conductivity and excellent microwave absorption and shielding behaviour. Layers disposal, their composition and electrical parameters, number and thicknesses are optimized through a real-coded genetic algorithm to achieve the minimization of the transmitted waves and minimization of reflection loss of the absorbing composites as coating on metal surface. Numerical design of wide frequency band radar absorbing multi-layer composite structures and highly shielding structures are presented and compared with experimental results.

format_quoteUtilizing Central Force Optimization outperforms traditional methods in multilayer microwave absorbers, showcasing improvements in design efficiency.format_quote

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Anomalous microwave absorption in multi-walled carbon nanotubes filled with iron

Physica E: Low-dimensional Systems and Nanostructures, 2012

ABSTRACT The interaction of millimeter-wave radiation (MWR) with vertically oriented carbon nanot... more ABSTRACT The interaction of millimeter-wave radiation (MWR) with vertically oriented carbon nanotubes filled with iron (Fe-MWCNT) in solid monolith has been investigated. Fe-MWCNT demonstrated high-efficiency towards electromagnetic shielding due to a high conductivity of CNT and iron-containing filling compound. The shielding efficiency and the reflection loss depending on the CNT orientation have been measured in a rectangular waveguide. A resonant absorption of millimeter waves has been revealed with the orthogonal Fe-MWCNT orientation with respect to the MWR electric field in the waveguide.

Modified Exfoliated Graphite as a Material for Shielding Against Electromagnetic Radiation

International Journal of Nanoscience, 2008

We report on the structure and morphology of thermoexfoliated graphite (TEG) powders and TEG–meta... more We report on the structure and morphology of thermoexfoliated graphite (TEG) powders and TEG–metal ( Co , Cu , Ni ) powders. Electrodynamic parameters of the compacted TEG and TEG–metal specimens have been studied along the compacting axis (c axis) within the range of electromagnetic radiation frequencies between 25.5 and 37.5 GHz. Metal particles attached to the surface of the TEG particles yield enhanced radiation shielding within the entire frequency range. Moreover, it is observed that the absorption coefficient increases with the increase in conductivity of the metal particles and is enhanced due to a high concentration of TEG–metal boundaries, which promote multiple reflections.

Attenuation of electromagnetic radia‐ tion by graphite‐epoxy composites

physica status solidi c, 2010

This work presents the results of investigations of the electromagnetic shielding efficiency of c... more This work presents the results of investigations of the electromagnetic shielding efficiency of composite materials (CMs) based on epoxy resin and thermoexfoliated graphite (TEG). The measurements were performed in the wide region of electromagnetic radiation (EMR) frequency from 25.5 to 77.5 GHz. It was shown that structure and morphology of the graphite fillers influence the efficiency of electromagnetic shielding. For example, the composites with nanodispersed TEG (0.56-5.9 vol%) are characterized by low value of transmission coefficient α tr in comparison with composites with TEG or TEG2 (TEG subjected to repeated oxidation and thermoexfoliation): α tr is equal to (-29) dB for CM 10wt%TEG2+epoxy (at the specimen's thickness h=0.6 mm). The real part of permittivity ε′ has been determined for the epoxy CMs with nanoTEG as filler. It also was found that electromagnetic shielding efficiency slightly increases at increasing of EMR frequency.

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The Effect of Filler Morphology and Distribution on Electrical and Shielding Properties of Graphite-Epoxy Composites

Molecular Crystals and Liquid Crystals, 2011

ABSTRACT A comparative study of epoxy resin filled with thermoexfoliated graphite (TEG) of variou... more ABSTRACT A comparative study of epoxy resin filled with thermoexfoliated graphite (TEG) of various dispersities has been carried out to investigate the effect of filler particle&#39;s morphology on electromagnetic interference (EMI) shielding properties of composites within the 25.86–37.5 GHz frequency range of electromagnetic radiation. The shielding properties of a multilayered structure (LS) of TEG-epoxy presenting the set of alternating layers of TEG and epoxy have been investigated as well. The total content of TEG in this multilayered structure was 0.8 and 3 wt.%. It is found that the composites containing TEG exhibit enhancements in the electrical conductivity and the electromagnetic shielding efficiency as compared with those of composites with sonicated TEG.

Shielding coatings based on carbon–polymer composites

Surface and Coatings Technology, 2012

The protective coating against electromagnetic radiation (EMR) on the base of polymer composite f... more The protective coating against electromagnetic radiation (EMR) on the base of polymer composite filled with two types of graphite particles (ultra-disperse graphite C1 and graphite nanoplatelets-GNPs) had been prepared and investigated in the frequency range 25.5-37.5 GHz. The paint and epoxy resin were used as polymer matrix. The content of graphite filler in composite was 5-15 wt.% and composite layer was applied as a coating on polyethylene (PE) substrate. The small size of carbon fillers permits to prepare thin films of composites (beginning from 100 μm) on polyethylene substrate. The using of GNPs as filler in composite coating was found to be more promising for EMI shielding than the using of C1 graphite. The observed difference in the EMR shielding efficiency is related with the better electrical characteristics and low percolation threshold in polymer filled with GNPs (C cr ≈ 5.43 wt.%) as compared with polymer containing conventional carbon fillers. The shielding efficiency SE T increases with the content of graphite conductive component in CM coating and is equal to 8-10 dB for the composite layers 10 wt.%GNPs-epoxy (200-300 μm thick) on PE substrate. Good agreement between experimental and calculated within the model of double-layered medium data on SE T for epoxy coatings with GNPs had been observed at the values of tan δ ranging within 0.15-0.28 and ε′within 17-35 for 5 and 10 wt.% of GNPs in CM-layer, respectively.

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