Porous Fe Hollow Structures with Optimized Impedance Matching as Highly Efficient, Ultrathin, and Lightweight Electromagnetic Wave Absorbers

Porous Fe hollow nanospheres (HNs) were fabricated successfully through hydrogen thermal reduction on solvothermal synthesized Fe3O4 HNs. The electromagnetic wave (EMW) absorption performances of the porous Fe3O4 and Fe HNs were investigated in 2.0-18.0 GHz. Owing to an optimized matching from the modulated permittivity and increased permeability, the porous Fe HNs exhibited remarkably enhanced EMW absorption than porous Fe3O4 HNs as well as previously reported Fe-based absorbers. The minimum reflection loss (RL) for porous Fe HNs reached -47.1 dB at 15.2 GHz, and the matching thickness was as thin as 1.69 mm. The effective bandwidth (RL < -10 dB) from 13.2 to 18.0 GHz at 1.69 mm almost covered the whole K-u band. Our results provided a highly efficient and ultrathin EMW absorber with easy preparation, strong absorption, broad bandwidth, and lightweight.