V. V. Oliynyk

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

A comparative study of epoxy resin filled with thermoexfoliated graphite (TEG) of various dispersities has been carried out to investigate the effect of filler particles 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.

Nanocarbon-Epoxy Composites as Electromagnetic Shielding Materials

We present the results of studies of the electromagnetic radiation (EMR) shielding by epoxy-nanocarbon composites (CMs). The EMR frequency range was 25.5–37.5 GHz. Thermoexfoliated graphite and multiwalled carbon nanotubes (CNT) have been used as fillers in CM (the content of a filler was 0.5–2 wt.%). We examined the effect of carbon fillers type in CM on characteristics of the electromagnetic shielding. It is shown that, even for low contents (∼ 1–2 wt.%) of a nanocarbon filler in CMs, the coefficient of EMR transmission is − (25-27) dB (for h = 1 mm).The real ϵ′ and imaginary ϵ″ parts of dielectric permittivity of the composites under investigation have been determined.

MODIFIED EXFOLIATED GRAPHITE AS A MATERIAL FOR SHIELDING AGAINST ELECTROMAGNETIC RADIATION

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.

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

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.

Modeling of gradient composite structures for shielding of microwaves

ABSTRACT The simulation of shielding properties of gradient composite structures (g-CMs) nanocarbon-polymer in the frequency range of electromagnetic radiation (EMR) (25.5 – 55.5 GHz) has been implemented in C++ code. The simulation has shown a significant decrease of EMR reflection index (R) and sufficient increase of EMR absorption (A) and shielding efficiency in gradient composite structures with filler concentration growth in the direction of EMR propagation as compared with composite with uniform distribution of nanocarbon filler. The simulated results coincide with the experimental data for the set of the epoxy composites with gradient distribution of 5 wt.% of graphite nanoplatelets.

Electrophysical properties of epoxy-based composites with graphite nanoplatelets and magnetically aligned magnetite

ABSTRACT Novel graphite nanoplatelets/magnetite (GNP/Fe3O4)/epoxy composites with aligned under external magnetic field fillers and random fillers distribution have been developed. The influence of loading content of GNP nanoparticles and viscosity of composite medium on the alignment degree of fillers and electrical conductivity, shielding properties of GNP/Fe3O4/epoxy composites were considered. The results showed that Fe3O4 addition to the composite is reflected in increase in electrical conductivity by 3–5 orders of magnitude for the investigated composites with binary filler with random fillers distribution in comparison with composites with monofiller (GNP). Shielding properties of GNP/Fe3O4/epoxy composites were significantly improved due to increase in absorption.

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

ABSTRACT 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.

Dielectric properties of composite materials containing aligned carbon nanotubes

This paper presents a study of the electrodynamic properties of polymer-matrix composite materials containing a filler in the form of multiwalled carbon nanotubes. We have examined the effect of filler alignment in the composites on their interaction with electromagnetic radiation. The composite materials have an anisotropic electrical conductivity, dielectric permittivity, and electromagnetic radiation attenuation coefficient because an applied electric field produces a preferential filler alignment direction.

Near-field microwave microscope for investigation of dielectrics

Elaboration results for a near-field microwave microscope are presented. The main parameters of the microscope are given. The possibility of its application for investigation of heterogeneous dielectrics and nondestructive quality inspection in the microwave range is assessed. An open-ended coaxial waveguide is used as a probe.