Preparation and Electromagnetic Properties of Ni-Co Coated W-type Barium Ferrite Hollow Microspheres

The Ni-Co coated W-type barium ferrite (BaZn0.6Co1.4Fe16O27) hollow microspheres (W-BFHMs) have been prepared by the self-reaction quenching technology and heat treatment at 1250 ℃. The W-BFHMs is a type of light microwave absorbing material in GHz frequencies and its average particle size is 60 μm. A conductive and magnetic Ni-Co layer was coated on the surface of W-BFHMs by electroless plating. Effects of plating time on the particle size, morphology, phase structure and microwave absorption properties of Ni-Co coated W-BFHMs are investigated through SEM, XRD, particle size analyzer and vector network analyzer. The results show that the Ni-Co deposits in the sag and the trench firstly and grows as the branch after filling the sag and the trench. With the increase of the plating time from 5 min to 25 min, the magnetic loss increase from 0.15 to 0.35, while the dielectric loss is not significantly change due to the incompletely covered. The effective absorbing bandwidth increase from 1 GHz to 2.7 GHz, while the absorption peak decrease from -12 dB to -32dB when the plating time is 25 min.