Controllable modification of helical carbon nanotubes for high-performance microwave absorption

Helical carbon nanotubes (HCNTs) are a kind of potential microwave absorption (MA) material due to their chiral and dielectric properties. However, the inert surface property makes HCNTs with poor polarization loss ability and impedance matching characteristic, which impedes its ability in attenuating microwaves. Herein, the HCNTs were modified with defects and functional groups on the surface to optimize their electromagnetic response characteristics and achieve an enhanced MA performance. The experimental results show that the modified HCNTs (F-HCNTs) exhibit a significant enhancement in MA performance when compared with HCNTs. The minimum reflection (RLmin) loss of F-HCNTs reaches −45.4 dB at 17.5 GHz at a thickness of 2.4 mm and the bandwidth of RL < −10 dB is 3.6 GHz (from 14.4 to 18.0 GHz). Further analysis demonstrates that proper modification of HCNTs leads to enhanced dielectric loss ability and optimized impedance matching characteristics, both of which are beneficial to the MA performance of HCNTs.