Dual Resonance Behavior and Enhanced Microwave Absorption Performance of FeO@C@MoS Composites with Shape Magnetic Anisotropy.

Ternary hierarchical FeO@C@MoS composites and binary hierarchical FeO@C composites were successfully fabricated by a modified mixed solvothermal method, a self-oxidation polymerization method, and a hydrothermal process. Their magnetic properties and microwave absorption performance were investigated. Dual resonance behavior was observed in the FeO@C@MoS composites. One of the resonances was attributed to natural resonance with a resonance frequency of 2.58 GHz, which was much higher than that for FeO bulk (1.5 GHz). The other originated from the superparamagnetic/ferromagnetic relaxation with a resonance frequency of 12.45 GHz. The minimum reflection loss (RL) reached -64.30 dB with a matched thickness of 2.24 mm at 11.64 GHz, and the maximum effective absorption bandwidth (EAB) covered 6.39 GHz with a matched thickness of 1.89 mm. In addition, the maximum Radar cross section (RCS) reduction value reached 31.90 dB m at a scattering angle of 0°. Electron holography analysis confirmed a dense magnetic absorption network in the FeO@C@MoS composites. The boost in microwave absorption performance was caused by the synergistic effects of magnetic and dielectric properties owing to the ternary hierarchical structure, shape magnetic anisotropy, and incorporation of 1T/2H MoS. Besides, the binary hierarchical FeO@C composites also exhibited good absorbing performance caused by natural resonance, with an RL of -52.90 dB at 5.80 mm, an EAB of 5.98 GHz at 3.38 mm, and a relatively high RCS reduction value of 13.04 dB m at θ = 20°. This work paves the way for designing multicomponent hierarchical absorbers with broadband and intensive microwave absorption.