Preparation Of Co/Cu Ferrite Modified Nitrogen-doped Graphene Magnetic Composite Aerogels And Their Microwave Absorption Properties

With the advent of the 5G era,high-frequency,hardware component upgrades,and the number of networked devices and antennas have doubled.Electromagnetic interference between devices and within the device itself is everywhere,and electromagnetic interference and electromagnetic radiation give electronic devices.And the harm caused by human health poses a higher challenge to electromagnetic absorption.Therefore,it is of great significance to design electromagnetic absorbing materials with low pollution,low cost and strong absorption.Graphene has a large specific surface area,good electrical conductivity,and a special two-dimensional layered structure,making it a potential absorbing material.However,studies have found that single graphene has higher dielectric loss and lower magnetic loss,so its absorbing performance is not ideal.At present,the research of graphene-based absorbing materials was concentrated on two-dimensional structure composite materials,and there are few reports on the absorbing properties of graphenebased three-dimensional network structure composite aerogels.In this paper,using graphene oxide(GO)as a template and ethylene diamine(EDA)as a nitrogen-doped reagent and reducing agent,three magnetic ferrites and graphene were composited and self-assembled to construct a new type of graphene-based three-dimensional magnetic composite aerogel through hydrothermal reaction.XRD,Raman,XPS,SEM,TEM,VSM,VNA,etc.were used to characterize the phase structure,graphitization degree,element composition,microscopic morphology,Magnetic properties and agnetic propertiesand electromagnetic parameters of the composite aerogel.Explore the effects of material composition,calcination temperature and metal ion doping on the performance of aerogels,in-depth study of the structure and performance relationship between composite aerogels,and reveal its microwave absorption mechanism.The research results of this paper are expected to provide reference value for the structure design and performance control of graphene-based three-dimensional network lightweight absorbing materials.The main research contents are as follows:(1)In the first chapter.Nitrogen-doped graphene/hollow cobalt ferrite(NRGO/Hollow CoFe2O4)composite aerogel were prepared by solvothermalhydrothermal self-assembly.Explore the influence of ferrite type and material composition on its absorbing performance.It was found that the composite aerogel has a lower density(12.1-14.5 mg·cm-3)and a special three-dimensional network structure.In addition,the composite aerogel has a filling ratio of 15 wt.%(the matrix was paraffin wax)and a matching thickness of It shows good microwave absorption performance at 1.8 mm,that is,the minimum reflection loss(SRLmin)was-24.8 dB·mm-1 and the maximum effective absorption bandwidth(EABmax)reached 5.2 GHz(12.6-17.8 GHz),covering 86.7%of the Ku band.The interfacial polarization loss caused by the accumulation of space charges at the heterogeneous interface between NRGO and CoFe2O4,the surface defects of RGO,residual functional groups and nitrogen atom doping cause dipolar polarization loss,and the magnetic hollow ferrite component causes the synergy of magnetic resonance loss,etc.Function to enhance the attenuation loss of composite materials to microwaves.(2)In the second chapter.Nitrogen-doped graphene/hollow copper ferrite(NRGO/Hollow CuFe2O4)composite aerogel was performed after the preparation the high temperature calcination process.The results show that the calcination temperature has a significant effect on the conductivity,electromagnetic parameters and wave absorbing properties of the composite aerogel.When the filling ratio was 15 wt.%and the thickness is 1.6 mm,the SRLmin of the composite aerogel is-27.1 dB·mm-1,and the EABmax is 5.0 GHz(13.0-18.0 GHz).Exploring the possible absorption mechanism of composite aerogels was the synergy of good impedance matching,conduction loss,dipole polarization,interface polarization and natural resonance.(3)In the third chapter,the NRGO/CuxCo1-xFe2O4 composite aerogel was prepared by a two-step hydrothermal method,and the influence of the doping amount of Cu ions on its wave-absorbing performance was explored.The results show that changing the doping amount of Cu ions can effectively control the impedance matching and attenuation loss.The three-dimensional porous structure of NRGO/CuxCo1-xFe2O4 composite aerogel contains quadrilateral CuxCo1-xFe2O4 particles and is uniformly loaded on the corrugated NRGO sheet.When the filling ratio is 25 wt.%and the thickness is 1.8 mm,the SRLmin of the NRGO/Cu0.3Co0.7Fe2O4 composite aerogel is43.2 dB·mm-1,and the EABmax reaches 4.7 GHz.In addition,the microwave absorption mechanism of NRGO/CuxCo1-xFe2O4 composite aerogel is the synergistic effect of interface polarization,dipolar polarization and conduction loss.Figure[45]Table[6]References[135]...