Facile fabrication of Fe/Fe5C2@N-doped porous carbon as an efficient microwave absorbent with strong and broadband absorption properties at an ultralow filler loading

The challenge of realizing low filler loading and high-performance microwave absorbing (MA) materials is still an urgent issue to be solved. Herein, porous N-doped carbon wrapped Fe/Fe5C2 (Fe/Fe5C2@NC) nanocomposite is successfully synthesized by a facile one-step calcination of carbon nitride and ferrocene precursors. The magnetic Fe/Fe5C2 nanoparticles are tightly and uniformly anchored on the wrinkled carbon nanosheets. Abundant of voids exist between the three-dimensional conductive carbon network, which can result in a low density and a strong interfacial polarization relaxation with effect. Based on the double attenuation mechanisms of dielectric loss and magnetic loss, the optimized Fe/Fe5C2@NC-800 possesses a minimum reflection loss value reaching −63.1 dB and an effective absorption bandwidth (EAB) as broad as 7.3 GHz with an extremely low filler loading of 4 wt%. The Fe/Fe5C2@NC-800 can even achieve a broad EAB within 4.5–18.0 GHz by tuning the absorber thickness in the range of 2.5–5.0 mm, covering nearly 85% of the whole measured frequency band. This work provides new insights for the development of advanced lightweight MA materials, which has wide effective absorption frequency range and strong absorption intensity at low filling levels.