Fabrication of magnetic tubular fiber with multi-layer heterostructure and its microwave absorbing properties

A new type of microwave absorbing material (TCF@Fe₃O₄@NCLs) with multi-layer heterostructure is designed and fabricated via a one-step pyrolysis process of the precursor (PF@Fe₃O₄@PDA). PF@Fe₃O₄@PDA is prepared by the technology of confined self-polycondensation, solvothermal method coupled with polymerization of dopamine (DA). The as-obtained material has the structure of tubular carbon nanofibers (TCF) embedded with Fe₃O₄ nanoparticles, dispersed Fe₃O₄ nanoparticles, and nitrogen-doped carbon layers (NCLs) from inside to outside. Notably, tubular carbon nanofibers provide the major dielectric loss. Fe₃O₄ nanoparticles significantly improve the microwave absorption ability at low frequencies and provide appropriate magnetic loss. NCLs improve the conductivity and facilitate the generation of multiple polarization effects, resulting in enhanced dielectric loss. The absorption mechanism is further elucidated. Based on the synergistic effect of double dielectric/magnetic loss composite materials, the interface introduced by multi-layer heterostructure, and conductive networks, TCF@Fe₃O₄@NCLs exhibits excellent reflection loss (RL) of −43.6 dB and effective absorption bandwidth (EBA) of 4.6 GHz (8.2–12.8 GHz) with a loading of 10%. The results demonstrate potentially promising prospects of TCF@Fe₃O₄@NCLs as new material candidate for microwave absorption.