High Microwave Absorption of Multi-Walled Carbon Nanotubes (Outer Diameter 10 – 20 nm)-Epoxy Composites in R–Band

We studied the microwave absorption of multi-walled carbon nanotubes (MWCNTs)-epoxy composites over a continuous frequency range in R-band (26.5 – 40 GHz). The outer diameters (OD) of the MWCNTs were in the 10 – 20 nm range. We measured and analyzed the microstructures, dielectric and the microwave absorption properties of the composite samples. High attenuation factor which correlates significant absorption of microwave was observed in the 32 – 40 GHz frequency band. Microwave absorption was due to high dielectric losses, interfacial charge polarization, and the free electron mobility in the composite material. Our results also show the dependence of microwave absorption on the loading fractions of MWCNTs and on the thickness of the absorbing material. Significant microwave absorption capabilities of the composite samples were achieved at 7 to 10 wt.% of MWCNT loadings for frequencies above 32 GHz.