Negative permittivity adjusted by SiO2-coated metallic particles in percolative composites

Negative permittivity has taken off as a research topic recent years in percolative composites. However, how to effectively tune the negative permittivity is still a challenge remained unsolved. Herein, the percolative composites with SiO2-coated metallic particles homogeneously dispersed in epoxy resin were prepared using blending and hot-molding procedure. The negative permittivity was realized with the form of three-dimensional metallic network, and the value and frequency range of negative permittivity were precisely adjusted by the distribution of coated particles. The analysis of Drude model indicated that negative permittivity was attributed to low frequency plasmonic state from the dilution of electron concentration. Moreover, coated particle can also change conductive path of electrons in composite, leading to an unusual linear relationship between conductivity and filler content, which is further certified by the equivalent circuit analysis. Our reported work would facilitate applications of negative permittivity materials especially in electromagnetic shielding, absorbing, attenuation and so on. (C) 2017 Elsevier B.V. All rights reserved.