Acquirement of Strong Microwave Absorption of ZnFe2O4@SiO2@Reduced Graphene Oxide/PVDF Composite Membranes by Regulating Crystallization Behavior

Currently, the microwave absorption materials with high absorbing efficiency are in urgent need to reduce electromagnetic pollution. Herein, the ZnFe2O4@SiO2 core–shell microspheres were synthesized and combined with reduced graphene oxide (RGO) to form the ingenious hierarchical composites (ZnFe2O4@SiO2@RGO), which were used as wave absorbing functional nanofillers of semicrystalline polyvinylidene fluoride (PVDF) matrix. The microstructure and crystallization behavior of ZnFe2O4@SiO2@RGO/PVDF composite membranes were systematically analyzed. The addition of ZnFe2O4@SiO2@RGO nanofillers facilitated the formation of β-phase crystal of PVDF, and the transition from β-phase to α-phase of PVDF occurred when the processing temperature increased. The effects of the crystallization behavior of the PVDF matrix on the microwave absorption performance were investigated in detail. The wave absorbing properties of the resulting composites can be effectively regulated by changing the processing temperature, sample thickness, and nanofiller content. The heterogeneous interfaces (ZnFe2O4–SiO2, SiO2–RGO, and RGO–PVDF) also contributed to the wave absorption performance. The optimal reflection loss (RL) of ZnFe2O4@SiO2@RGO/PVDF composite membranes with a thickness of only 1.6 mm can reach −49.8 dB with 10 wt % nanofiller content when the processing temperature is 60 °C. The strong wave absorption function of the composite system can be attributed to the synergy of good impedance matching, interfacial polarization, dipole polarization, eddy current loss, and ferromagnetic resonance loss under the optimal process conditions.