Solvothermal synthesis of hollow glass microspheres/Fe₃O₄ composites as a lightweight microwave absorber

Hollow glass microspheres/Fe₃O₄ (HGMs/Fe₃O₄) composites with low density were successfully synthesized by solvothermal method at 160 °C. The morphology, composition, and microstructure of the samples were characterized by scanning electron microscopy and X-ray diffraction, respectively. The results show that the HGMs/Fe₃O₄ composites exhibit compact and continuous Fe₃O₄ particles coating on the surface of HGMs. The complex permeability and permittivity of HGMs/Fe₃O₄ composites obtained at 160 °C for different reaction times were measured in the frequency range of 1–18 GHz by vector network analysis. The microwave absorption properties were well-elucidated by the traditional coaxial line method. The as-prepared HGMs/Fe₃O₄ composites show excellent microwave absorption properties. When the thicknesses of these HGMs/Fe₃O₄ composites are more than 1.5 mm, they all exhibit strong absorption peaks (lower than −10 dB). A possible mechanism of the improved microwave absorption properties was discussed.