Optimized electromagnetic absorbing performances of FeSiAl/phosphate flakes

Abstract

How to obtain excellent electromagnetic absorption properties in microscale powder is still a great challenge. Dielectric loss capacity originating from low electric resistance of metal alloy and Snoek's limit in the microscale powder seriously restrict the application of microscale materials in GHz range. In this work, for optimizing electromagnetic parameters, the flake structure is realized by vertical ball milling and high resistivity phosphate layer is obtained by subsequent phosphoric acid passivation treatment, which can ensure the good microwave absorption performances. Due to the large planar anisotropy, the magnetic loss capacity of FeSiAl flake is enhanced. The high resistance phosphate (FePO4, AlPO4 and Fe3(PO4)2) layer can effectively reduce permittivity. For obtaining good microwave absorption performances, the impedance matching, attenuation constant, and electromagnetic loss capability are optimized by the content of phosphoric acid. By adding only 5 wt% phosphoric acid to FeSiAl flake, the resulting composites display the minimal reflection loss of −43.18 dB and an effective bandwidth of 2.56 GHz. This work can highlight the new strategy for achieving good microwave absorption performances in microscale soft magnetic materials.