Flaky FeSi particles with tunable size, morphology and microstructure developing for high-efficiency and broadband absorbing materials

Abstract

Abstract Compared with spherical ferromagnetic particles, flaky particles due to the higher permeability present great potentials as high-efficiency electromagnetic absorbing materials, especially in S band (2–4\xa0GHz). FeSi flakes with different diameters were synthesized by ball-milling and subsequent screened processes, and hydrogen annealing and SiO2 coating were then utilized to further optimize the electromagnetic parameters for high-efficiency absorption. FeSi flakes with high diameter possess higher permittivity for the larger specific areas and higher permeability for the increased shape anisotropy. The decreased defects after annealing induce the reducing permittivity. The eddy current effect can be effectively suppressed after the SiO2 is coated on the surface of FeSi flakes. As for the coating containing 70\xa0wt% FeSi@SiO2 flakes, the maximum reflection loss (RLmax) of –73\xa0dB can be observed at 2.5\xa0GHz with the coating thickness of 3\xa0mm. Effective absorption band (ERL5, RL