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.

Fabrication of Multifunctional Silylated GO/FeSiAl Epoxy Composites: A Heat Conducting Microwave Absorber for 5G Base Station Packaging

“…However, epoxy compounds with pure magnetic particles or a low GO amount show fairly narrow effective bandwidths, and strong absorption peaks only fall in a very low frequency band. As shown in Figure 7c for the GF-3 sample with 1% of GO, the maximum reflection loss increases to −48.29 dB at 1.6 GHz and the effective bandwidth increases to 3.8 GHz, which exhibits a wider bandwidth (3.8 GHz vs. 3.12 GHz [42] and 3.52 GHz [43]) and a higher refection loss (−48.29 dB vs. −47 dB [44], −44.47 dB [42] and −48.08 dB [39]) in the most recent relevant literature, using FeSiAl as a microwave absorber. This provides a perfect match for 5G station application, as the effective bandwidth just falls in the range of the 5G antennas' operating frequency band in the 2.575-2.645 GHz range [45], as shown in Figure 8.…”