Large aspect ratio makes high low-frequency microwave absorption performance via a unique roll grinding method for flake FeSiAl

Increasing aspect ratio for flake magnetic alloy to facilitate microwave absorption capability in low-frequency is highly desired but remains changes by conventional methods. Here we report a unique roll grinding method to fabricate flake FeSiAl alloys with large aspect ratio of 40–100, which is beyond the limit of traditional ball milling method (< 40). As a result, such roll ground flake FeSiAl obtains a 3 times larger low frequency reflection loss (RL= −56.2 dB at 3.47 GHz) than that of ball milled one. Furthermore, the fabricated microwave absorber shows an ultra-wide effective absorption band of 14 GHz (RL < −20 dB, 2.3–16.3 GHz) with the thin coating thickness of 1.6–6.0 mm. Further analysis showed its exceptional properties stem from large aspect ratio induced satisfied impedance matching, enhanced magnetic loss, and intense dielectric loss. Our findings provide an easy industrial preparation method for making flake magnetic alloys that possess unconventional and technologically important electromagnetic properties.