Hierarchically Porous Carbon/α-Fe@Fe3C Absorbers Derived from Luffa Sponge with Efficient Microwave Absorption

Biomass-based carbon materials have attracted much attention in the field of microwave absorption because of their light weight, environmental friendliness, low cost and high efficiency. In this work, carbon matrix of porous microtubule structure with different magnetic particles was synthesized from natural luffa sponge by a simple calcination process. The carbon matrix possesses hierarchical porous structures including micrometer-scale tubular channels, nanometer-scale macrospores, mesopores and micropores, of which microspores are the most. The Fe3O4, FeO/alpha-Fe, alpha-Fe/gamma-Fe and alpha-Fe/Fe3C particles were formed in the temperature range of 700-1000 degrees C. The porous carbon/alpha-Fe@Fe3C composites obtained at 1000 degrees C exhibit excellent microwave absorption (MA) performance, its minimum reflection loss can reach -48.9 dB with only a thickness of 1.5 mm, and the effective absorption bandwidth (RL <=-10 dB) is 3.86 GHz. The porous structure, synergies between dielectric loss and magnetic loss, high attenuation constant are the key factors for good MA performance.