Synthesis of hollow core-shell ZnFe₂O₄@C nanospheres with excellent microwave absorption properties

The special hollow core-shell structure and excellent dielectric-magnetic loss synergy of composite materials are two crucial factors that have an important influence on the microwave absorption properties. In this study, hollow ZnFe₂O₄ nanospheres were successfully synthesized by a solvothermal precipitation method firstly; based on this, a C shell precursor phenolic resin was coated on the ZnFe₂O₄ hollow nanospheres' surface by an in situ oxidative polymerization method, and then ZnFe₂O₄@C was obtained by high-temperature calcination. Samples were characterized by SEM, TEM, XRD, XPS, BET, VSM, VNA. The results show that the maximum reflection loss (RL_max) reaches -50.97 dB at 8.0 GHz, and the effective bandwidth (EAB) of hollow core-shell structure ZnFe₂O₄@C is 3.2 GHz (6.16-9.36 GHz) with a coating thickness of 3.5 mm. This work provides a useful method for the design of lightweight and high-efficiency microwave absorbers.