Tailored microwave absorption performance through interface evolution by in-situ reduced Fe nanoparticles on the surface of FeSiAl microflake

Abstract

Poor impedance matching and low-frequency magnetic resonance are great challenge for Fe-based micron-scale materials as microwave absorber in GHz range. Here, we propose in situ interface engineer strategy for tailoring the interface through in situ reduced Fe nanoparticles and introduce planar anisotropy for flattening particles with high aspect ratio during high-energy vertical ball milling process, which can synchronously enhance impedance matching and exceed Snoke’s limit. With increasing milling time, the interface experiences the following in situ evolution: the nano oxide layer-micro particles interface, the partial interface between nano oxide layer and Fe nanoparticles, the integrity Fe nanoparticles-oxide layer interface, the nano oxide layer-microflake interface. Meanwhile, the aspect ratio is up to 74.93. The evolution of interface and high aspect ratio can effectively tailor permittivity and permeability. Due to the novel microstructure that FeSiAl flake are covered by ∼ 30 nm oxide layer containing ∼ 10 nm Fe nanoparticles, natural resonance induced by planar anisotropy, eddy current loss of metallic microflake, relaxation loss induced by interface polarization, conductive loss from electric resistivity together led to good microwave absorption performance (effective absorbing bandwidth of 3.12 GHz at 3.2 mm and minimal reflection loss of −44.47 dB at 7.44 GHz and 3.3 mm). The present finding might highlight for developing the composite absorbers with multi loss type coupling across nano-micro scales.