A special electroless plating method was used to modify the surface of as-prepared nickel hollow spheres, and the cellular Co films were coated on the surface. The coated nickel hollow spheres were identified by FESEM, TEM, and XRD, and the uniform Co films with porous structure were observed. Specific surface area and microwave absorbing properties were investigated with BET method and the coaxial-line method. The results indicated that the unique cellular Co films could largely increase the specific surface area and permittivity constant of the nickel spheres. This lead the coated spheres to increase the dielectric loss in microwave frequencies, and exhibit better absorption performance than the non-coated ones.

Key words: hollow sub-microsphere, cellular Co film, microwave adsorption