Thin and ultra-broadband electromagnetic absorption carbonyl iron-based metamaterial via multiscale synergic dielectric-magnetic design

Thin and ultra-broadband electromagnetic wave (EMW) absorption material is essential in the fields of electromagnetic compatibility and radiation protection. Unfortunately, conventional materials are difficult to achieve low frequency EMW absorption such as 2–4 GHz at a limited thickness. Herein, a multiscale design strategy is presented to overcome this shortcoming. Carbonyl iron particle was used as the starting material. Firstly, microstructure modification from spherical morphology (SCIP) to flake one (FCIP) via a ball milling process was used to improve CIP's electromagnetic properties. Afterthat, macroscopic electromagnetic metastructure with the FCIP/polyurethane (PU) composite units was designed and its geometrical configuration was optimized. Through the multiscale design, an effective absorption in 2∼40 GHz was achieved at a thickness of merely 5 mm, surpassing most of the reported metamaterials. The broadband absorption mechanism was deciphered by CST simulation, which includes the synergic low-frequency absorption contributed by the FCIP/PU composite with delicate dielectric/magnetic synergistic property and the optimized impedance matching in broadband frequency caused by the well-designed metastructure. Our study provides valuable insights for the development of thin and ultra-broadband-absorbing material.