| Nowadays,human beings use electronic devices more and more frequently.When using these electronic devices,their internal integrated circuit systems will form electromagnetic wave radiation.These electromagnetic waves will not only endanger human health,but also cause other electronic devices and their own signal disorder.Electromagnetic wave absorbing materials can well absorb these electromagnetic wave radiation and interference,thereby reducing the harm caused by electromagnetic waves,and have indispensable value in electronic communication,integrated circuits and aircraft stealth technology.CNTs can be used as a good carbon source and as a precursor of carbon-based composite aerogels;chitosan is a polymer material obtained from chitin by deacetylation,and is widely used in medical,in biology,food and agriculture.In this paper,based on the layered structure of chitosan,carbon nanotubes with excellent dielectric properties were composited with chitosan to form a CNTs/chitosan composite aerogel.The CNTs/chitosan composite aerogel has both good impedance matching performance and electromagnetic loss ability,and can achieve excellent microwave absorption performance.And by changing its artificial microstructure design,different structures can be designed to enhance microwave absorption and electromagnetic shielding performance.The details are as follows:(1)The oxidized CNTs were composited with chitosan by calcination and annealing to form a CNTs/chitosan composite aerogel.The microstructure of the CNTs/chitosan composite aerogel was observed by SEM,and it was found that its multi-layer structure can be the realization of multiple losses of electromagnetic waves inside the material is beneficial to microwave absorption.The electromagnetic parameters are measured by a vector network analyzer,and the reflection loss RL is calculated.The final result is that when the mass fraction is 25% and the thickness is3.5mm,the effective bandwidth coverage is 4.72GHz(10.72～15.28GHz),and the strongest absorption intensity is-45 d B at 8.3GHz.(2)Using electromagnetic parameters of CNTs/chitosan composite aerogel as data,the microwave absorption structure was designed by electromagnetic simulation software.Firstly,the plate structure is simulated,and the microwave absorption performance of the plate structure is obtained,and the absorption performance is compared with that of the stepped structure.Finally,the effective absorption bandwidth of CNTs/chitosan aerogel was widened from 2GHz(4.5～6.5GHz)to 9.9GHz(8.1～18GHz),and the absorption effect was significantly improved.The absorption mechanism of the stepped structure was analyzed.(3)The electromagnetic shielding structure is designed by using electromagnetic simulation software,and its structural parameters are optimized and compared with the plate structure.The back-shaped structure widens the effective shielding bandwidth(SE>30d B)from 0GHz without obvious shielding performance to 5.3GHz(12.6～17.9GHz),and the shielding effect is greatly improved.The shielding mechanism of shielding performance is analyzed,and its shielding performance is dominated by absorption performance,which will not cause secondary pollution due to reflection. |
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