Measurements of electromagnetic wave absorption properties of carbon nanotube–epoxy composites at microwave frequencies around 8.43 GHz

Microwave (8.43 GHz) absorption properties have been measured for multiwalled carbon nanotube (MWCNT)–epoxy composites. A microwave resonant cavity technique was utilized as a probe. Six groups of MWCNT–epoxy composite samples with different MWCNT outside diameters were fabricated and tested. The weight percentages of MWCNTs in each sample group were in the range of 1%–10%. The amplitudes of the absorption profiles, the linewidths at half-power maxima, and the shifts in resonant frequencies under load for the six groups of MWCNT–epoxy composite samples were compared. Similar to our previous results measured at 9.968 GHz [Z. Ye et al., J. Appl. Phys. 108, 054315 (2010)], the microwave absorption properties of our samples strongly rely on two parameters: the number of nanotubes and the density of nanotube bundles. It was found that the measured microwave absorption properties of the samples around 8.43 GHz showed a more sensitive response to the magnetic component of the microwave field rather than the electric component.