Nanocomposites and nanomaterials

Modeling of dielectric permittivity of polymer composites with mixed fillers 

L.L. Vovchenko, O.V. Lozitsky, L.Y. Matzui, O.S. Yakovenko, V.V. Oliynyk, V.V. Zagorodnii
Department of Physics, Taras Shevchenko National University of Kyiv, Volodymyrska str., 64/13, Kyiv, 01601, Ukraine
E-mail: Olozitsky@gmail.com

An effective permittivity of polymer composites (CMs) with randomly distributed electroconductive and dielectric nanoparticles was considered within the Maxwell Garnett (MG) model. The modeling of effective permittivity showed that the content and parameters of conductive filler particles affect the value and frequency dependence of permittivity of CMs. It was found that at equal parameters of electroconductive inclusions in CMs such as aspect ratio (AR), electrical conductivity and content (lower than the percolation threshold) the using of 1D (carbon nanotubes CNT) particles as filler leads to sufficiently higher values of real and imaginary parts of permittivity and shifts the maximum of dielectric loss into lower frequency range of electromagnetic radiation (EMR) compared with 2D (graphite nanoplatelets GNP) filler particles. The using of mixed 1D/2D conductive 
Figure 1. Simulated permittivity of epoxy composites filled with CNT, GNP and mixed filler GNP/CNT (filler content in vol.%).	filler allows extending the frequency range of dielectric loss in CMs varying the aspect ratio and electrical conductivity of fillers (Fig. 1). The addition of spherical highly dielectric disperse particles (for example BaTiO3 at content up to 34wt.%) into CMs with 1D (or 2D) conductive filler slightly increases permittivity, however,  increases the percolation threshold, so the larger number of conductive particles may be inserted into polymer matrix before percolation and higher permittivity may be achieved.