Fabrication and microwave properties of hollow nickel spheres prepared by electroless plating and template corrosion method

Using carbonyl iron as template, hollow nickel spheres were prepared by electroless plating on carbonyl iron and template corrosion method. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), transmission electron microscope (TEM), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and vector network analyzer. Results showed that the shell thickness can be controlled by adjusting the loadage of carbonyl iron templates. The hollow nickel spheres exhibited good magnetic properties with a saturation magnetization of 48.56 emu/g and enhanced coercivity (as high as 260 Oe). The real (ɛ′) and imaginary (ɛ″) parts of complex permittivity of hollow nickel spheres first increased and then decreased as the shell thickness increased, and the sample with the thinnest shell showed the lowest complex permittivity. For the complex permeability, the resonance peak shifted to the lower frequency and then moved to higher frequency, as the shell thickness increased. The microwave absorption performances could be tuned by changing the shell thickness. In this study, the minimum reflection loss (RL) value of −27.2 dB was obtained at 13.4 GHz with a matching thickness of 1.4 mm and the effective absorption band (RL <−5 dB) from 11.8 to 18 GHz, covering the whole Ku-band (12.4−18 GHz).