L. Matzui

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.

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.

Peculiarities of Charge Transfer in Graphite Intercalation Compounds with Bromine and Iodine Chloride

The results of studies of resistivity, thermopower, and the Hall phenomenon based on fine crystalline pyrolytic anisotropic graphite intercalated compounds (GICs) with bromine and iodine chloride in the temperature range of phase transformation in intercalate layers are presented. It is shown that the anomalous temperature dependences of resistivity, thermopower, and the Hall coefficient for intercalated compounds with bromine in the phase transformation temperature region are connected with a change in this temperature interval of charge that is transmitted from intercalate molecules to graphite layers. Based on obtained experimental data in terms of a simple two-dimensional electron structure model of GICs, the accommodation coefficient, charge carrier concentration, and Fermi energy for GICs with bromine and iodine chloride are estimated.

Semiconducting and Optical Properties of Compact Graphene-Like Nanoparticles of Molybdenum Disulfide

The research in the influence of graphene-like 2H-MoS2 nanoparticle structure on the behavior electroresistivity and optical properties has shown that the conductivity of semiconductor type (n-type) in the compact samples correlates with the particle sizes, in particular the size of 17–53 nm, along the basal plane [100] at a constant number of S–Mo–S nanolayers (n = 6–8) in graphene-like 2H-MoS2 nanoparticles. The mechanism of conductivity is supposed to be hopping conduction with variable hopping length for 2D case. The results of Raman studies indicate a significant impact of anisotropy sizes of 2H-MoS2 nanoparticles in direction [110] under constant number of nanolayers of S–Mo(W)–S on the formation of the structure-sensitive optical properties and, accordingly, the characteristics of the semiconductor as a whole.

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).

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.

Interaction of vertically oriented carbon nanotubes in solid monolith with millimeter waves

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