Oleksandra Lazarenko

Synergistic Enhancement of the Percolation Threshold in Hybrid Polymeric Nanocomposites Based on Carbon Nanotubes and Graphite Nanoplatelets

Synergistic effect causes significant decreasing of the percolation threshold in the ternary polymer composites filled with carbon nanotubes (CNT) and graphite nanoplatelets (GNP) in comparison with binary ones. Enhancement of the percolation threshold strongly depends only on the relative aspect ratios of the filler particles due to the formation of the bridges between puddles of the different filler components. Conditions of both appearance and fading away of the synergistic effect are investigated depending on the relative morphology of CNT or GNP components of the filler. Different lateral sizes, aspect ratios, and volume concentrations of both CNT and GNP in the selected ternary composites were considered. Conditions of the effective substitution of GNP with CNT and vice versa in equal volume concentrations without enlarging of the percolation threshold were established. The results are obtained numerically using the Monte Carlo simulation of the percolation threshold of the different ternary composites.

Electrical Properties of Composite Materials with Electric Field-Assisted Alignment of Nanocarbon Fillers

The article reports about electric field-induced alignment of the carbon nanoparticles embedded in epoxy matrix. Optical microscopy was performed to consider the effect of the electric field magnitude and configuration, filler morphology, and aspect ratio on alignment process. Characteristic time of aligned network formation was compared with modeling predictions. Carbon nanotube and graphite nanoplatelet rotation time was estimated using an analytical model based on effective medium approach. Different depolarization factor was applied according to the geometries of the particle and electric field.Solid nanocomposites were fabricated by using AC electric field. We have investigated concentration dependence of electrical conductivity of graphite nanoplatelets/epoxy composites using two-probe technique. It was established that the electrical properties of composites with random and aligned filler distribution are differ by conductivity value at certain filler content and distinguish by a form of concentration dependence of conductivity for fillers with different morphology. These differences were explained in terms of the dynamic percolation and formation of various conductive networks: chained in case of graphite nanoplatelets and crossed framework in case of carbon nanotubes filler.

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.

Dielectric Properties of Nanocarbon Polymer Composites with Binary Filler

The rapid development of radio-electronic equipment, particulary the development of radiophones, discovery of the Internet, satellite communications etc. during the last hundred years has led to new problems, which previously were never encountered, such as radio noise and polluting electromagnetic radiation. In the absence of electromagnetic protection, electromagnetic radiation can disrupt normal operation of devices, result in damage of equipment and even affect human health (Geetha et al. J Appl Polym Sci 112:2073–2086, 2009). That is why this paper investigated of polymer hybrid nanocomposites with two nanocarbon fillers (carbon nanotubes (MWCNTs) and graphite nanoplatelets (GNPs)), which can solve these problems (Qin and Brosseau, Appl Phys 111:061301, 2012).

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.

Nanocarbon-polymer multilayer structures for electromagnetic shielding

Composite materials based on latex paint with multi-walled carbon nanotubes (MWCNTs) and graphite nanoplatelets (GNPs) were studied. Several types of single-layer and multi-layer structures with various alternations of polymer and composite layers characterized by different values of electrical conductivity and permittivity were fabricated. The investigation of microwave transmission and reflection parameters of the prepared composites in the frequency range of 26-54 GHz is presented. It is found that single-layer composites containing MWCNTs and GNPs exhibit the shielding efficiency enhancement with the increase of filler concentration. The alternation of composite layers with different content of carbon filler makes it possible to adjust the electromagnetic radiation reflection and absorption characteristics of multi-layer coatings. The attenuation of electromagnetic radiation and reflection loss in multilayer coatings depend strongly on the number and thicknesses of layers. The minimal reflection was observed for multilayered coating consisted of MWCNTs-filled composite layers alternating with latex paint layers.