Preparation and microwave absorbing properties of hollow glass microspheres/Fe₃O₄/Ag composites with core–shell structure

The low-density, conductive and magnetic hollow glass microspheres (HGM)/Fe₃O₄/Ag composites have been successfully synthesized via co-precipitation and chemical plating method. The morphology, composition, microstructure, magnetic and microwave absorbing properties of the composites were investigated based on the analyses of the results using scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, vibrating sample magnetometer and vector network analyzer. The results showed that the HGM/Fe₃O₄ composites were successfully prepared, and the coating layers on the surface of HGM are compact and continuous. Moreover, the final composites were completely covered with Ag nanoparticles. With the addition of Ag nanoparticles, the saturation magnetization of the HGM/Fe₃O₄ composites reduces from 32.08 to 14.77 emu/g, whereas its conductivity increases to 0.48 S/cm. The reflection loss (R) of HGM/Fe₃O₄/Ag composites is lower than −10 dB at 8.2–8.7, 9.6–10.8 and 11.4–11.9 GHz, and the minimum loss value is −19.1 dB at 9.9 GHz.