Nanocarbon/Co3O4/Epoxy Composites for Microwave Shielding and Absorption

Abstract

The epoxy composite materials (CMs) with a random distribution of nanosized Co3O4 and carbon nanoparticles (graphite nanoplatelets GNP and carbon nanotubes CNT) are fabricated. Complex permittivity, permeability, and shielding properties of composite materials with 30 wt% of Co3O4 and (2–5) wt% of nanocarbon are measured in the frequency range of 1–67 GHz using the transmission–reflection method. A significant increase of microwave permittivity and presence of several peaks on the dependencies of the imaginary part of permittivity on the frequency are found for three-phase nanocarbon/Co3O4/epoxy CMs. The observed microwave shielding efficiency of three-phase epoxy composites is enhanced compared to two-phase nanocarbon–epoxy composites. Such enhancement of shielding efficiency correlates with the increase of DC conductivity of these three-phase composites. The measured complex permittivity and permeability spectra for nanocarbon/Co3O4/epoxy CMs are used for modeling the reflection loss (Formula presented.) for studied composites. It is shown that the most preferable for microwave absorption is the composites containing 2 wt% of nanocarbon filler for a sample thickness of 0.5–0.7 mm. The highest reflection loss (Formula presented.) = 30 dB with an absorption bandwidth of 15 GHz is found for epoxy composite filled with 2 wt% of GNP and 30 wt% of Co3O4 for a sample thickness of 0.5 mm.