Microwave absorbing properties of NiFe₂O₄ nanosheets synthesized via a simple surfactant-assisted solution route

Abstract

NiFe₂O₄ nanosheets have been synthesized via a simple surfactant-assisted solution route, which are confirmed by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. The NiFe₂O₄ sample exhibits the sheet-like structure, with width varying from 200 to 800 nm and thickness ranging from 20 to 60 nm. The electromagnetic properties of NiFe₂O₄ nanosheets-paraffin composites have been deeply investigated. The multiple dielectric relaxation loss in NiFe2O4 nanosheets is attributed to the size distribution and morphology of the NiFe₂O₄ nanosheets. The magnetic loss in the present system is caused mainly by the natural resonance. An absorber with a thickness of 4.3 mm exhibits an optimal reflection loss (RL) value of-47.1 dB at 7.67 GHz. RL values exceeding-20 dB in the 2.68-17.96 GHz range are obtained by choosing an appropriate absorption-layer thickness between 1.9 and 10 mm. Not only the RL peak frequency but also the number of the peaks can be well explained by the quarter-wavelength cancellation model.