N-doped CNTs/CoNi nanochains-carbon hollow microspheres multi-level multi-scale heterogeneous interface structures and microwave absorption properties

Constructing multi-level multi-scale heterogeneous interfaces in magnetic carbon-based composites remains a formidable challenge, requiring rational material combinations to effectively balance dielectric and magnetic losses for achieving high strength and wide frequency wave absorption. Electromagnetic wave (EMW) absorbing materials consisted of cobalt-nickel (CoNi) magnetic nanochain, nitrogen-doped carbon nanotubes (NCNTs) and hollow carbon microspheres were prepared by hydrothermal method without external magnetic field. These composites possessed a unique multi-level multi-scale heterogeneous interface structure that is highly advantageous for efficient absorption of EMWs. The CoNi nanoparticles were self-assembled into uniformly distributed and randomly oriented magnetic nanochains, which were further reassembled with NCNTs and hollow carbon microspheres to form heterogeneous interface structures resembling a rose, chrysanthemum, hedgehog ball, and bauhinia tree. Due to the high-density interface enhancing the loss ability of interface polarization, as well as the higher saturation magnetization, coercivity, and wave absorption ability of the magnetic nanochains compared to the magnetic nanoparticles themselves, the minimum reflection loss achieved is −66.86 dB, and the effective absorption bandwidth achieved is 5.01 GHz, at a content as low as 11 wt%. This study provides a new idea for generating nanochains without magnetic fields and constructing multi-level and multi-scale heterogeneous interface structures to achieve strong absorption and wide effective absorption bandwidth (EAB).