Independently regulating the electric and magnetic properties of flaky FeSiAl powder based composites for high-performance microwave absorber

Abstract

Flaky structures can effectively enhance the microwave absorbing properties of metallic magnetic particles, but the interaction between the electromagnetic waves and particles in different directions is not well understood. Here, the oriented FeSiAl/paraffin composites were prepared under a rotational magnetic field and made into co-axial rings for electromagnetic measurements. The FeSiAl flakes in the rings are oriented along different angles with respect to the electric and magnetic fields of the microwave. The effects of the angles on the electric and magnetic properties as well as the microwave absorbing properties of the composite are investigated. It is found that the electric and magnetic properties can be modified independently by adjusting the angles between the flakes and the electric field and between the flakes and the magnetic field, respectively. The underlying mechanisms can be understood using electromagnetic and micromagnetic simulations. The anisotropic permittivity originates from the induced electric field of the flaky particles, while the anisotropic permeability results from the effect of the demagnetization field. An optimal orientation structure can reduce the permittivity by suppressing the induced electric field while maintaining high permeability by reducing the demagnetization energy in the magnetization process, which is beneficial to the impedance matching of the composite. Thus, the orientation structure is extremely efficient in regulating the microwave absorption performance of the flaky particles. This work proposed a general strategy for microwave absorbers to modulate microwave absorption performances between high-frequency and low-frequency by simply operating the orientation structures of the flaky particles.