Microwave properties of double layer absorber reinforced with carbon fibre powders

Abstract

Epoxy resin based double layer absorbing coatings were prepared, employing carbonyl iron and carbon black as original absorbents in the matching layer and absorbing layer respectively. Carbon fibre powders (CFPs) were introduced as additional absorbent in the two layers. The absorbers were tested to investigate their absorbing performances, including SEM, electromagnetic parameters and reflection loss. The advantage of adding CFP to the absorbing layer in improving the microwave performance was more obvious than that to matching layer. Results showed that an optimal content of CFP/carbon black/epoxy resin in the absorbing layer was 0·25∶0·25∶1 with a bandwidth (reflection loss <−10 dB) of 4·5 GHz. The absorption peak shifted to lower frequency when the content of CFP increased, as explained by Maxwell–Garnett equation and quarter wavelength resonance equation. The extra addition of CFP to the coatings was verified to be effective in controlling the wave absorbing properties.