Nanocarbon/Co₃O₄/epoxy composites for microwave shielding and absorption

The epoxy composites with random distribution of nanosized Co3O4 and carbon nanoparticles (graphite nanoplatelets GNP and carbon nanotubes CNT) were fabricated. Complex permittivity, permeability and shielding properties of composite materials with 30 wt.% of Co3O4 and (2‐5) wt.% of nanocarbon were 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 were 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 were used for modeling the reflection loss RL for studied composites. It was shown the most preferable for microwave absorption are the composites containing 2wt.% of nanocarbon filler for a sample thickness of 0.5‐0.7 mm. The highest reflection loss |RLmin|=30 dB with an absorption bandwidth of 15 GHz was found for epoxy composite filled with 2wt.% of GNP and 30wt.% of Co3O4 for a sample thickness of 0.5 mm.This article is protected by copyright. All rights reserved.