Facile synthesis of core–shell structured C/Fe3O4 composite fiber electromagnetic wave absorbing materials with multiple loss mechanisms

The use of heterostructures in electromagnetic wave absorption applications has been limited by the problem of homogeneous dispersion in composites. In this study, three-dimensional (3D) cross-linked electromagnetic wave absorbing composites with the carbon nanofiber/Fe3O4 (CNF/Fe3O4) core–shell structure were synthesized by expanding the interface of the heterogeneous structure with Fe3O4 nanocrystals uniformly modified on the surface of the carbon nanofiber. The 3D cross-linked structure of the composites contributes to the generation of conductive loss and macroscopic eddy current loss. The heterogeneous interface formed by graphite nanocrystals and amorphous carbon in the carbon nanofiber is identified by high-resolution transmission electron microscopy and Raman spectroscopy as having a strong electromagnetic wave absorption capacity for boundary-type defects. The Fe3O4 nanocrystal particles on the surface of the carbon nanofiber not only have the strong magnetic loss capability of magnetic materials but also form a new heterogeneous interface with the carbon nanofiber surface, which further enhances the interfacial polarization of the composite and improves the electromagnetic wave absorption properties. With the synergistic effects of interfacial polarization, macroscopic and microscopic eddy current losses, conductive losses, and magnetic losses, the electromagnetic wave absorption performance of the composites is further enhanced based on the carbon nanofiber. The reflection loss reaches −51.11, −42.99, and −55.98 dB at 9, 12 (X-band), and 17 GHz (Ku-band), respectively, corresponding to the thicknesses of 2.0, 1.5, and 1.0 mm. In addition, the widest effective absorption bandwidth is 3.3 GHz at 14.7–18 GHz (only 1.09 mm).