Nanocomposites and nanomaterials

Electrodynamic properties of epoxy composites with mixed filler graphite nanoplatelets/TiO2
Lozitsky O.V., Vovchenko L.L., Matzui L.Y., Yakovenko O.S., Oliynyk V.V.
Department of Physics, Taras Shevchenko National University of Kyiv. 
Volodymyrska str., 64/13, Kyiv, 01601, Ukraine
E-mail: Olozitsky@gmail.com
The permittivity of epoxy composites (CMs) filled with graphite nanoplatelets/titanium dioxide (GNP/TiO2) at GNP contents of 1-5 wt.% and 34 wt.% of TiO2 were measured using waveguide spectroscopy in the frequency range of electromagnetic radiation (EMR) 40-60 GHz. It was found that real part of permittivity has a maximum at 4 wt.% GNP, reaching the value of 22 at frequency 50 GHz (Fig. 1 a). This and the fact that imaginary part keeps increasing at same GNP content suggests that percolation threshold is located around 4 wt.% GNP in such CMs. Permittivity values themselves allow this CMs to be used in EMR shielding and filtering of microwaves, best implemented as part of a compound structure, like layered or sandwich structure [1]. 
 
Figure 1. Complex permittivity at 50 GHz (a) and shielding efficiency at shields’ thickness 2.5 mm (b) of GNP/TiO2/epoxy composites 

It was shown (Fig. 1 b) that the increase of GNP content promotes the significant increase of shielding efficiency SET. The increase of SET value with the increase of EMR frequency is the result of the increased shielding due to EMR absorption compared to EMR reflection.

1. 	F. Ye, C. Song, Q. Zhou, X. Yin, M. Han, X. Li , L. Zhang, L. Cheng, Materials, 2018, 11, 1771.