The characterization and preparation of core–shell structure particles of carbon-sphere@NiFe₂O₄@PPy as microwave absorbing materials in X band

An excellent PPy/NiFe₂O₄/CS microwave absorbing materials with a three-layer core–shell structure, was synthesized successfully by two reaction steps of solvothermal reaction and in situ polymerization. The surface morphology, phase structure and chemical components of the composite have been characterized by a scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscope. The results suggest that the surface of CS is covered by NiFe₂O₄ completely and PPy wraps the obtained NiFe₂O₄/CS successfully. The conductivity and the saturation magnetization (Ms) of the resulting PPy/NiFe₂O₄/CS composites are 0.38 S/cm and 46 emu/g, respectively. The vector network analysis shows the composite performs better microwave absorbing ability than that of CS and NiFe₂O₄/CS. The maximum reflection loss of the composite with 1.97 mm coating thickness is −53 dB at 10.5 GHz and the bandwidth of reflection loss less than −10 dB is 3.4 GHz (8.9–12.3 GHz). This ternary composite with light weight, thin thickness and strong absorbing capacity can be an attractive candidate in the field of microwave absorption.