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

Abstract

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.

Synthesis of ZnFe2O4@Mg‐Al‐SDBS LDH composites for regulating heat and fire safety properties of polyurea

“…In Figure 2A, it can be concluded that six relatively strong diffraction peaks appear at 2 θ = 29.9°, 35.2°, 42.8°, 53.1°, 56.6°, and 62.2°, which are assigned to (220), (311), (400), (422), (511), and (440) crystal planes of ZnFe 2 O 4 nanospheres (JCPDS No. 22‐1012) 29 . There are no characteristic peaks of impurities observed, indicating that the prepared ZnFe 2 O 4 nanospheres have high purity and crystallinity 30 .…”

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

“…3, it can be observed that apparent diffraction peaks of ZnFe 2 O 4 , which are well consistent with the ZnFe 2 O 4 (JCPDS card no. 22-1012), 22 the results indicate that ZnFe 2 O 4 with good crystallinity has been successfully prepared. Compared with ZnFe 2 O 4 , the position of ZnFe 2 O 4 @C of the diffraction peak does not change except only the peak intensity decreases after recombination with the C shell.…”

Reduced graphene oxide-wrapped Fe–Fe3O4@mSiO2 hollow core–shell composites with enhanced electromagnetic wave absorption properties

“…It is well known that the contribution of pure RGO to EMA performance is mainly due to its dielectric loss, which can lead to impedance mismatch. 44–46 The excellent EMA performance of FFmSR in the current research is mainly due to the conductivity loss caused by the introduction of RGO. The high density free charge movement in RGO generates micro-currents that interact with the electromagnetic wave and thereafter cause conductivity loss and dissipate the electromagnetic wave into heat energy, improving the EMA performance of the composites.…”