Preparation and microwave absorption properties of Ni–Fe3O4 hollow spheres

Nickel–magnetite hollow spheres with the diameter about 150 nm were prepared by an autocatalytic reduction method. The effect of Fe3O4 content in hollow spheres on microwave absorption properties has been investigated. With an increase of magnetite content, permittivity of sphere–wax composite decreased, while permeability increased. For composite layers, a minimum reflection loss (RL, −38.4 dB) was predicted at 10.8 GHz with a thickness of 2.5 mm. In addition, the increasing content of magnetite resulted in the peak of RL moves to higher frequency and the minimal reflection loss increases obviously.