Fe3C/helical carbon nanotube hybrid: Facile synthesis and spin-induced enhancement in microwave-absorbing properties

Exploring effective microwave absorption materials is always a challenge especially in the relatively low frequency range of 2-8 GHz and broad absorption band. Here we developed a Fe3C/helical carbon nanotube (HCNT) hybrid structures synthesized via catalytic chemical vapor deposition (CCVD) using Fe3O4 nanoparticles as catalyst. The microwave-absorbing characteristics of such hybrid nanomaterials were investigated based on the transmission line theory through the evaluation of the experimental data including complex permittivity and permeability. Considering the reaction temperature range of 400-750 °C, the as-prepared hybrid synthesized at 700 °C can be adjusted to have effective performance of RL value less than −10 dB in the relatively lower frequency ranged from 2.9 GHz to 9.9 GHz at the thickness range of 2-5 mm. Furthermore, the hybrid in case of 750 °C bears bandwidths with RL lower than −10 dB from 7.3 GHz to 18 GHz and the minimum RL is about −21 dB. The observed advantageous reflection loss was attributed to the pronounced impedance match owing to the reasonable synergistic effect between magnetic nanoparticles and HCNTs.