Preparation And Electromagnetic Wave Absorbing Performance Of Zinc Ferrite Nanocomposites

The composition of ferrites and carbon materials can improve the impedance matching and enhance the wave absorption performance.It is well known that polymer materials have good processability,chemical stability,and flexibility.The combination of polymers and wave absorbing nanomaterials can help broaden the practical application of nanomaterials and also it is a useful way to improve the comprehensive property.In this paper,we chose the ZnFe2O4,carbon nanotubes(CNTs),reduced graphene oxide(RGO),and the matrix material of polyvinylidene fluoride(PVDF).In this study,the ZnFe2O4 nanoparticles were combined with carbon material(CNTs?RGO)and then processed into composite membranes using the PVDF matrix.The effects of the crystallization behavior of PVDF on wave absorbing properties were studied in detail by changing the functional nanofiller content and processing temperature of composite membranes.The electromagnetic wave absorption performance and mechanisms of the composite materials in X-band were discussed.The main research results are as follows:(1)The magnetic ZnFe2O4 nanoparticles were synthesized through the solvothermal method and ZnFe2O4@CNT nanofillers with a special tangled structure were prepared by means of ultrasonic treatment.The mass ratio of ZnFe2O4 to CNTs in optimized ZnFe2O4@CNT functional nanofillers was about 8:1.A series of ZnFe2O4@CNT/PVDF composite membranes were fabricated by adding ZnFe2O4@CNT nanofillers to PVDF.The incorporation of ZnFe2O4@CNT nanofillers affected the crystallization behavior of the PVDF matrix,which in turn influenced the wave absorption performance of the resulting composites.The addition of ZnFe2O4@CNT nanofillers promoted the formation of the ?-phase crystal of PVDF.The transition from ?-phase to ?-phase of PVDF occurred when the processing temperature increased.Through an appropriate collocation of dielectric loss and magnetic loss,the composite membranes exhibited remarkable wave absorption performance.The optimal reflection loss(RL)of PVDF composite membranes containing 7 wt%ZnFe2O4@CNT nanofillers reached-54.5 dB at 10.00 GHz with a sample thickness of 2.4 mm under a processing temperature of 60?.When the processing temperature rose to 150?,the RL reached-35.2 dB,admirably achieving an effective wave absorption of the whole X-band.(2)The ZnFe2O4@SiO2@RGO ternary nanofillers were prepared by a stepwise method.The core-shell ZnFe2O4@SiO2 was wrapped by RGO successfully.The mass ratio of ZnFe2O4@SiO2 to RGO was about 1:1.Then the ZnFe2O4@SiO2@RGO/PVDF flexible composite membranes were fabricated.The ZnFe2O4@SiO2@RGO/PVDF membranes containing 10 wt%nanofillers displayed an optimal RL of-49.8 dB at 8.4 GHz with a sample thickness of only 1.6 mm when the processing temperature was 60?,and the effective bandwidth(RL<-10 dB)was from 8.2 GHz to 9.5 GHz.The effective absorption bandwidth can be widened as the processing temperature increased.