Multi-scale structural nitrogen-doped rGO@CNTs composites with ultra-low loading towards microwave absorption

A composite of nitrogen-doped reduced graphene oxide and carbon nanotubes (N-rGO@CNTs) was prepared. As the mass ratio of CNTs to rGO increasing, the conductive pathways inside the N-rGO@CNTs were gradually formed with strong electronic transmission ability, which contributed to the conversion of electromagnetic energy into thermal energy. Besides, the nest-like “CNTs clusters”, abundant wrinkled layers and through-tubes were favorable for multiple scattering and polarization of electromagnetic waves. More electromagnetic waves were further dissipated in the form of thermal energy. Doping of N atoms introduced a large number of defects and electronic dipoles among the carbon lattice, which could induce the polarization relaxation for higher dielectric loss to attenuate more electromagnetic waves. The experimental results suggested that the multi-scale structure endowed the composite with well-matched impedance, rich loss modes and strong loss, attributed to electronic conduction, defects polarization as well as dipolar polarization, etc. The resulted N-rGO@CNTs 0.3 exhibited the remarkable microwave absorption performance under the ultra-low mass loading of only 2 wt%. Its effective bandwidth was broad and up to 7.1 GHz (10.5–17.6 GHz) with the minimum reflection loss of −49.4 dB.