Lightweight NiFe₂O₄ with controllable 3D network structure and enhanced microwave absorbing properties

3D network structure NiFe₂O₄ was successfully synthesized by a templated salt precipitation method using PMMA colloid crystal as templates. The morphology, phase composition and microwave absorbing properties of as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vector network analyzer (VNA), and so on. The results revealed that the 3D network structure was configurated with smooth spherical walls composed of NiFe₂O₄ nanocrystals and their pore diameters being in the range of 80-250 nm. The microwave absorption properties of the 3D network structure NiFe₂O₄ were crucially determined by the special structure. The synergy of intrinsic magnetic loss of magnetic NiFe₂O₄ and the interfacial polarization enhanced by 3D network structure and the interaction of multiple mechanisms endowed the sample with the feature of strong absorption, broad bandwidth and lightweight. There is more than one valley in the reflection loss curves and the maximum reflection loss is 27.5 dB with a bandwidth of 4 GHz. Moreover, the 3D network structure NiFe₂O₄ show a greater reflection loss with the same thickness comparing to the ordinary NiFe₂O₄ nanoparticles, which could achieve the feature of lightweight of the microwave absorbing materials.