Enhancing the Microwave Absorption Properties of Fe–Cu–Nb–Si–B Nanocomposite Flakes by Coating With Spinel Ferrite NiFe2O4

Fe-Cu-Nb-Si-B nanocomposite flakes have been coated with spinel ferrite NiFe₂O₄ by a low-temperature chemical deposition. Compared with the uncoated alloy flakes, the complex permittivity of coated flakes decreases dramatically, while the permeability decreases to some extent. Such a large decrease of the complex permittivity has been studied by investigating the microstructure of the coated flakes. Furthermore, it is believed that such coating treatments result in a better impedance matching. For coated flakes, the reflection losses (RLs) (less than -10 dB) can be achieved within 0.7-4.8 GHz for a composite with the thicknesses varying between 1.95 and 10 mm. However, for composites containing uncoated flakes, their RLs values almost cannot be less than -10 dB. Moreover, the matching characteristics have been compared for both kinds of flakes. The obvious enhancement in microwave absorption properties of the coated flakes can be attributed to the improvement in impedance matching.