Controllable Synthesis And Investigation Of Nano-carbon-Based Composites As Electromagnetic Wave Absorbers

With the development of wireless communication technology and electronic equipment,the problem of electromagnetic wave interference and pollution is becoming more and more serious.The electromagnetic wave absorbing material(MAM)can absorb and convert electromagnetic wave energy through magnetic loss,resistive loss,or dielectric loss.In recent years,scientists have conducted extensive research on absorbing materials,hoping to develop high-performance absorbing materials with thin effective thickness,lightweight,low reflection loss(RL),and effective absorption bandwidth(EAB).Carbon-based materials have attracted much attention due to their lightweight,high-temperature resistance,good thermal stability,strong oxidation resistance,and excellent dielectric properties.However,its absorption is low and the bandwidth is narrow.In this paper,by introducing nano-magnetic particles to improve the wave-absorbing properties of materials,by constructing a certain microstructure,different loss-type materials can be effectively composited,so as to achieve the purpose of synergistic loss of electromagnetic waves.A series of composite materials with excellent electromagnetic wave absorption properties were prepared,and their absorption mechanism was studied.The specific research results are as follows:1)Multi-walled carbon nanotubes(MWCNTs)have multi-dimensional structures,high chemical stability,low density,and significant electrical conductivity loss,making them an attractive electromagnetic wave absorbing material with promising practical application prospects.In this work,cobalt ferrite/multi-walled carbon nanotubes(CoFe2O4/MWCNTs)composites were synthesized by a simple and controllable solvothermal technique.The composition,morphological structure,and electromagnetic parameters of the prepared composites were characterized and tested.The results show that the cobalt ferrite microspheres and multi-walled carbon nanotubes in the composite form a complex network structure.The minimum reflection loss(RLmin)of the as-synthesized cobalt ferrite/multi-walled carbon nanotube composite is-50.80 dB at a thickness of 4.2 mm and an effective absorption bandwidth(EAB)of 3.36 GHz at a thickness of 1.6 mm.Compared with the reported magnetic composite-derived absorbers,the prepared composites exhibited better RLmin.In this study,multi-walled carbon nanotube-based composites with unique structures were precisely designed and fabricated as efficient and lightweight electromagnetic wave-absorbing materials.2)The lightweight,interface-rich nanoporous structure can incorporate electromagnetic waves into the pores,absorb and attenuate the electromagnetic waves through the multi-level absorption and scattering of the pore walls,and has the ability to match impedance,thus having the potential to become a high-performance absorbing material.Using a solvothermal technique,iron arsenide/graphene oxide composites with porous topology were prepared.By changing the weight of graphene oxide,the electromagnetic properties of iron arsenide/graphene oxide composites can be well-tuned.Due to its porous structure and suitable electromagnetic parameters,the impedance matching ability and attenuation ability are directly improved.Due to its tuneable composition,porous structure,and strong synergistic effect between iron arsenide and graphene oxide,the iron arsenide/graphene oxide composite exhibits excellent microwave absorption performance with a thickness of 1.6 mm near 5.2 GHz.Ultrawide effective absorption bandwidth,covering 75%of the research frequency range.At the same thickness,the reflection loss reaches-43.7 dB.This work enables the tuning of electromagnetic parameters and expands the use of high-performance microwave-absorbing materials.3)Graphite is a promising electromagnetic(EM)absorber due to its good conductivity loss,low density,and high chemical stability.In the field of microwave absorption,the inherent electromagnetic properties and nano-composition of functional materials have an important impact on their electromagnetic wave energy conversion.Cobalt ferrite/graphite flakes(CoFe2O4/Grs)composites with different graphite flake compositions were synthesized by a facile solvothermal method,and the electromagnetic parameters,morphology,structure,and composition of the prepared composites were characterized and studied.The minimum reflection loss(RLmin)of the cobalt ferrite/graphite flake composite with 10%graphite flakes is-31.98 dB at 1.2 mm,and the effective absorption bandwidth is 5.6 GHz at 1.3 mm,which is due to the cobalt ferrite carbonization It was converted into electromagnetic absorbing material,and the energy conversion of the electromagnetic wave was tuned.In this paper,a series of new nano-carbon-based composite materials are designed and developed by chemical method,which can be used as high-efficiency and lightweight electromagnetic wave absorber materials,and have broad application prospects in the fields of electronic communication and national defense security.