Preparation, microstructure, and electromagnetic properties of Al18B4O33w/CoxFeyBz composite powders

Al18B4O33w/CoxFeyBz composite powders were prepared through electroless plating CoxFeyBz alloy coating onto the surface of Al18B4O33 whiskers. The microstructure evolution of the CoxFeyBz coating and the relevant variations in the properties of Al18B4O33w/CoxFeyBz composite powders were investigated. Amorphous or nano-crystalline CoxFeyBz coatings with Fe content of up to 80 at.% were obtained in a wide range of [Co2 +]/[Fe2 +] ratios. The presence of Fe2 + reduced the reaction efficiency because of flocculation and the resulted coverage effect. The morphology of the CoxFeyBz coatings changed slightly but crystallization occurred quickly after annealing at 400 °C. The electrical resistivity of the CoxFeyBz coatings decreased dramatically after annealing at 400 °C for less than 60 min, but was maintained at 10− 2 Ω·cm despite the further increase of the temperature. The high resistivity likely hindered the interface polarization; consequently, no dielectric relaxation was detected in the microwave band. The saturation magnetization of the CoxFeyBz coatings persistently increased as the heat treatment proceeded or as the temperature elevated, which contributes to the improvement of permeability. The difference in microstructure evolution and the variations in the properties of Al18B4O33w/CoxFeyBz were discussed, and the effects of composition were preliminarily identified.