Constructing honeycomb conductive rings in graphene foam/epoxy resin metacomposites for adjustable negative permittivity, low dielectric loss tangent and mechanical enhancement

Abstract

The reduced graphene foam (RGF)/epoxy resin (EP) elastomer composites with adjustable negative permittivity were prepared sequentially through hydrothermal reaction, high-temperature reduction and impregnating processing. The negative permittivity can be achieved by graphene foam owing to the existence of three-dimensional conductive honeycomb rings, and the rise of graphite oxide (GO) content brought in enhancement for negative permittivity. The fundamental principles of Lorentz-like and Drude-type negative permittivity were discussed. The negative permittivity increased significantly as filling multi-walled carbon nanotubes (MWCNTs) with a mass ratio of 2:1 based on the more electrons hopping between the MWCNTs. Low dielectric loss tangent (tan δ) (close to 1.0 over 600 MHz-1 GHz) was investigated in RGF/EP composites as a result of reducing conductance loss, interfacial polarization and dipole polarization loss. Besides, compression strength and compression modulus of the RGF/EP composites also were enhanced with increase of GO content. This work provides an understanding guidance on the mechanism of metamaterials with low dielectric loss and high mechanical property.