Synthesis and enhanced microwave absorption properties of Nii2O3 core-shell particles

In this paper, we reported on the enhanced microwave absorbing properties of the Nii2O3 core-shell soft magnetic particles which were synthesized by a simple hydrogen peroxide oxidation method. The chemical state and the morphology of the Nii2O3 particle surface were analyzed by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM), respectively. Complex electromagnetic parameters (permittivity and permeability) of the paraffin mixed composite were measured in the frequency range of 0.1a18 GHz. Compared with the uncoated Ni/paraffin composite, the permittivity of Nii2O3/paraffin composite decreased dramatically. The reflection loss (RL) of the composite exceeding a20 dB in the frequency range of 4.0a12.6 GHz were obtained for the absorber thicknesses of 1.8a4.3 mm, while an optimal RL of a53.5 dB was achieved at 7.9 GHz for the thickness of 2.5 mm. The good microwave absorption properties resulted from a proper impedance match as a consequence of the insulator Ni2O3 shell around Ni particles. Quantitative calculation demonstrated that not only the RL peak position but also the number of the peaks were determined by the quarter-wavelength matching model.