Influence of particle size on the microwave absorption properties of FeSiAl/ZnO-filled resin composite coatings

FeSiAl/ZnO-filled resin composite coatings with different FeSiAl particle sizes were fabricated by adding FeSiAl and ZnO absorbents to epoxy resin matrix. The complex permittivity and complex permeability were measured by vector network analyzer. The results show that the dielectric loss and magnetic loss increase with the increasing FeSiAl particle size, which is consistent with the attenuation coefficient. The dielectric loss mainly comes from the conductance loss and dielectric relaxation loss. Meanwhile, the magnetic loss is derived from the exchange resonance and natural resonance. The composite coating with < 30 μm FeSiAl particle exhibits a wide effective absorption band of 3.1 GHz in 9.3–12.4 GHz and a strong absorption peak of − 15.1 dB at 11.1 GHz, when the thickness is 1.8 mm. The most promising microwave absorption performance can be ascribed to its best impedance matching and appropriate attenuation coefficient. Therefore, the suitable microwave absorption performance of the coatings could be obtained by means of adjusting the absorbent particle size and the coating thickness.