Tunable and enhanced microwave absorption properties by adjusting the distribution of Co/CoFe embedded into the carbon nanohorns and graphene microspheres

Designing unique structures of magnetic particle/carbon composites with multiple heterogeneous interfaces is an effective strategy for improving the properties of microwave absorption. Herein, hierarchical spacing arrangements for Co@carbon nanohorns and Co@graphene microspheres (Co@CNHs/G) with N enrichment were synthesized by a simple self-assembly method. As a result, Co@CNHs/G exhibited excellent electromagnetic wave absorption performance, and its reflection loss (RL) values of − 44.72 dB and − 41.39 dB at the C band had thicknesses of 2.9 mm and 2.5 mm, respectively. Additionally, the maximum effective absorption bandwidth (RL ≤ −10 dB) was 5.7 GHz at 1.4 mm. More importantly, the distribution of metal nanoparticles into CNHs and graphene microspheres were adjusted by forming the CoFe alloy embedded into CNHs and graphene microspheres during arc discharge process. Consequently, the frequency of RL ≤ −40.00 dB was from the C band to the X band by changing the multiple scattering paths, and the corresponding thickness for the minimum RL (−40.00 dB) was 1.8 mm. The outstanding electromagnetic absorbing performance was mainly attributed to the enhanced dielectric loss involving interfacial polarization derived from multiple heterogeneous interfaces, dipolar polarization induced by N-doping, and defects in the CNHs and graphene. In addition, multiple complex scattering paths can further improve the attenuation of electromagnetic waves.