Broadband and strong microwave absorption of Fe/Fe3C/C core-shell spherical chains enhanced by dual dielectric relaxation and dual magnetic resonances

By utilizing a simple calcination process in the presence of Fe nanofibers (NFs) and benzene under N-2, we synthesized large amounts of Fe@Fe3C@C core-shell spherical chains (CSSCs) comprising soft magnetic (Fe@Fe3C) NFs as cores and disordered C as shells. Varying the benzene volume from 1 mL to 4 mL conveniently modulated the C/Fe atom ratio over the range of 0-0.283. The composition-dependent static magnetic and microwave absorption properties of the Fe@Fe3C@C CSSCs were systemically investigated. The Fe@Fe3C@C CSSCs with a C/Fe atom ratio of 0.166-0.283 exhibited excellent microwave absorption properties, having stronger absorption and broader bandwidth than other absorbers. An optimal reflection loss (R-L) value of -58.0 dB was observed at 8.68 GHz under an absorber thickness of 2.4 mm. The absorption bandwidth (R-L <= -20 dB, 99% absorption) also reached as high as 16 GHz, which corresponded to the absorber thickness of 1.2-8.0 mm. The mechanism underlying the enhancement in microwave absorption was determined to be the synergy of dual dielectric relaxation, dual magnetic resonances, high attenuation, and good impedance matching caused by the 1D structure, core-shell structure, and heterostructure. The high microwave absorption capacity and wide absorption bandwidth demonstrated the promising practical applications of the Fe@Fe3C@C CSSCs. (C) 2018 Elsevier B.V. All rights reserved.