In-Situ Growth and Graphitization Synthesis of Porous Fe3O4/Carbon Fiber Composites Derived from Biomass as Lightweight Microwave Absorber

Biomass waste has emerged as a novel sustainable and renewable material for fabricating functional materials because of the lightweight and easy manufacturing. Herein, we synthesize a porous Fe3O4/carbon fiber (Fe3O4/CF) composites derived from bagasse waste by in-situ growth and a graphitization process. The Fe3O4 nanocrystals uniformly embedded in porous CF significantly construct the multiple interfaces and hierarchical microstructure of Fe3O4/CF composites. Fe3O4/CF composites exhibit a maximum reflection loss value of −48.2 dB at 15.6 GHz with a thin thickness of only 1.9 mm. Meanwhile, a broad effective absorption bandwidth of 5.1 GHz covering the frequency range of 12.9–18.0 GHz is achieved. The rough surface, porous structure, and proper component contribute to the improved impedance matching. Meanwhile, the Debye relaxation and interfacial polarization dominantly promote the attenuation ability of the microwave. The enhancement of attenuation ability and impedance matching together account for the superior microwave absorption performance.