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.