Achieving ultra-low frequency microwave absorbing properties based on anti-corrosive silica-pinned flake FeSiAl hybrid with full L band absorption

The inevitable corrosion of magnetic microwave absorber (MA) remains a great challenge to adapt oxygen-containing environment. Herein we developed a plasma-induced approach for protecting the magnetic MA by anchoring robust SiO2 layers on their surface. Keeping the original flaky shape of FeSiAl (FSA) led to breaking the Snoek limit, which brought excellent ultra-low-frequency absorption. In detail, the ultrathin amorphous silica layer (5 nm) grew on FSA surface by the facile Stober method at low cost firstly. Plasma technology was introduced to make these SiO2 layers dense and attain the integrated P-FSA@SiO2. SiO2 layer protected FSA from the corrosive medium, which increased polarization resistance to 186.9 k Omega.cm(2) of PFSA@SiO2 (from 97.46 k Omega.cm(2) of pure FSA) and decreased the corrosion current to 18.45 mu A/cm(2) (from 63.35 mu A/cm(2)). The corrosion of the samples in acid solution also verified the electrochemical characterizations. Meanwhile, rich interface and sheet ordered structure enable P-FSA@SiO2 exhibit enhanced microwave absorption in ultra-low-frequency through multiple reflections, magnetic loss and the interface polarization between core and shell. The minimum reflection loss of P-FSA@SiO2 reduced from -8.0 dB (FSA) to -12.4 dB and the efficient absorption band (<-5 dB) increased from 0.18 GHz (FSA) to 1.44 GHz. The densification SiO2 layer coating technology opens up a fantastic avenue for devising anti-corrosion absorber. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Utilizing a plasma-induced method to anchor SiO2 layers on the surface of magnetic microwave absorbers successfully protected them against corrosion in oxygen-containing environments, increasing polarization resistance and reducing corrosion current. The SiO2 layer enhanced ultra-low-frequency microwave absorption performance through multiple reflections, magnetic loss, and interface polarization, leading to improved absorption efficiency.