Preparation And Electromagnetic Properties Of Graphene/nickel Ferrite Heterostructure

In recent years,with the rapid development of military stealth technique and radar detection technology,the performance of modern microwave absorbing materials put forward higher requirements.Searching for the high efficiency and lightweight microwave absorbing materials is still a great challenge.Graphene has wide applications in the fields of energy storage,nano-electronic device,composite material,and electromagnetic interference shielding and so on,due to their unique micro-structure,physical,chemical properties,excellent conductive and heat-conducting performance.Among them,the study of graphene heterostructures is an important job.Research about graphene heterostructures indicate that heterostructures can improve interface structure of graphene and enhance their dielectrical and microwave absorbing properties.In this paper,we deposited small magnetic nickel ferrite nanoparticles on reduced graphene oxide nanosheets uniformly?NiFe₂O₄/r-GO?with ammonium hydroxide as reducing agent using a facile one-pot hydrothermal method with free of organic chemical reagents.The microstructure,morphology and static magnetic property of NiFe₂O₄/r-GO heterostructures were detailed characterized through X-ray diffractometer?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Raman spectrometer?Raman?and vibrating sample magnetometer?VSM?.Meanwhile,the growth mechanism of NiFe₂O₄/r-GO heterostructures was revealed.Different mass ratios of NiFe₂O₄/r-GO heterostructures mixed in a paraffin wax matrix?20,30,40,50,60 and 70 wt.%?were prepared to investigate the electromagnetic parameters and microwave absorbing properties in the frequency range of 2¹8 GHz.Use vector network analyzer?VNA?to measure the complex permittivity??'and?"?and complex permeability??'and?"?,and calculate the reflection loss were in the frequency range of 2¹8 GHz.Explore the impact of NiFe₂O₄/r-GO heterostructures loading concentration and thickness of the composites on the properties of microwave absorption,respectively.The study showed that the electromagnetic characteristic and microwave absorbing performance of NiFe₂O₄/r-GO heterostructures composite both exhibited some of regularity with the change of composite thickness and loading concentration.When the loading concentration of NiFe₂O₄/r-GO heterostructures is 70 wt.%,the minimum reflection loss?RL?can reach-42 dB with a broad bandwidth?RL?-10 dB?of 5.3 GHzBased on the electromagnetic characteristic and the microwave response of NiFe2O4/r-GO heterostructures composite,preliminary discussed the microwave absorbing mechanism.Introducing small magnetic NiFe2O4 nanoparticles on the surface of r-GO can improve the magnetic loss of heterostructures effectively,the microwave attenuation can be tuned by the synergistic effect of dielectric and magnetic loss,which originates from introducing multiple relaxations and multiple resonances,and enhance the microwave absorption performance.The electromagnetic wave absorption loss of the NiFe2O4/r-GO heterostructures composite mainly results from two aspects,dielectric loss and magnetic loss.Among them,the dielectric loss mainly comes from dipole polarization,interfacial polarization,the synergies of them and conductivity loss existed in the NiFe2O4/r-GO heterostructures composite.Low frequency natural resonance of small magnetic nanoparticles,exchange resonance and eddy-current loss are the main source of the magnetic loss.The synergistic effect of dielectric loss and magnetic loss exsited in the composite is a key factor for excellent microwave absorption materials.Moreover,the favourable electromagnetic matching characteristic and thickness matching are another significant aspect for the properties of high efficiency and multi-band absorbing.It is remained to be improvement for applied research of graphene based heterostructures in the electromagnetic wave attenuation field,and the mechanism of electromagnetic wave energy attenuation remains to be further researched and improved.Contents of this paper have significant guiding significance for the study of electromagnetic wave absorbing materials of graphene/nickel ferrite,and have laid a solid foundation for the subsequent in-depth study,promote development of the study of graphene based heterostructures.