Suppressed conductive loss of flower-like NiCo2O4-wrapped flaky FeSiAl for excellent low-frequency microwave absorption

Abstract

Abstract Flaky FeSiAl is a high potential absorbent for low-frequency microwave applications. However, impedance mismatching due to its excessively high complex permittivity presents a challenge. Herein, inspired by the surface modification strategy, flaky FeSiAl wrapped with flower-like NiCo2O4 (NiCo2O4@flaky FeSiAl) was developed via a hydrothermal method. The introduction of a surface NiCo2O4 insulating layer was expected to reduce the complex permittivity and increase the high complex permeability in the NiCo2O4@flaky FeSiAl composite. Subsequently, an excellent low-frequency microwave absorption performance was achieved. The designed NiCo2O4@flaky FeSiAl displayed a robust minimum refection loss (RL min) of −33.41 dB at 6.32 GHz and increased the effective absorption bandwidth (EAB, RL < −10 dB) to 4.08 GHz when the matching thickness was 1.6 mm. The enhanced low-frequency microwave absorption performance was mainly attributed to the improvement in impedance matching, which originated from the collaborative regulation of electromagnetic parameters. This study provides a promising approach for designing flaky FeSiAl-based composites and high-performance low-frequency microwave absorbents.