The Preparation And Electromagnetic Performance Of Graphene-based Lightweight And High Efficiency Microwave Absorbing Materials

To prepare light and efficient electromagnetic wave absorption material,need to meet two basic conditions:first,the absorber has a significant ability to dissipate electromagnetic waves.Second,absorber has a low density.It is expected to achieve low absorption of the absorber(filler).The research considers the two aspects of electromagnetic wave dissipation mechanism and impedance matching.The structure and dispersion performance of the graphene-based lightweight and efficient absorbing materials were prepared and optimized to provide experimental and theoretical basis for the preparation of light and high efficiency absorbing materials.The research contents are as follows:1.In the alcohol system,the reduction of nickel ions(Ni2+)and grapheme oxide(GO)were achieved by chemical reduction method,and different proportions of Ni/RGO(reduced grapheme oxide)composites S1,S2 and S3(the mass ratio of Ni:GO is 1:1,2:1 and 5:1,respectively).By means of in-situ synthesis,Ni nanoparticles and RGO are separated from each other.The Ni nanoparticles and RGO are uniformly dispersed and the interface between them is combined to give the material more dissipation mechanism.The results show that the Ni/RGO composites decrease with the increase of the RGO ratio when the content of the composites is 10 wt.%.The minimum RL of S3 reaches-21.67 dB at 8.08 GHz.And the effective bandwidth ranges is 8.4 GHz.When the ratio of RGO in composites is increased,the dielectric loss of the material increases,the impedance matching becomes worse.The electromagnetic wave is reflected on the surface of the absorbing material.In order to further verify the above conclusions,the effects of different absorber contents on the absorbing property of S1(2 wt.%,3 wt.%,5.7 wt.%And 10 wt.%)were studied.The results show that the dielectric loss of the material increases with the increase of absorber content.And when the content of absorber is 3 wt.%,the RL reach-18.75 dB and the effective band width of RL<-10 dB is 10.96 GHz.2.The above study showed that the material absorption properties is dielectric loss and magnetic loss is negligible when the absorber content is low.So when the dielectric loss of RGO is high enough and the dispersibility in the matrix is good,it is expected to reflect the better absorbing performance under the condition of lower absorber content.It provides the ideas for the study of light and high efficiency electromagnetic wave absorbing materials.In this study,RGO aerogels with different pore structures were prepared by hydrothermal method.The results show that the larger the structure of RGO aerogels,the better the dispersibility of RGO flakes under the same absorber content(1.7 wt.%).The results show that the RL of the RGO aerogels with the largest pore structure is-15.44 dB.and the effective bandwidth ranges from 6 to 14.44 GHz.The RL reach-20.94 dB at 11.84 GHz.The effective band width is 12.88 GHz.when the absorber content is 2 wt.%.3.The electromagnetic wave dissipation of RGO is limited.It is very important to improve its electromagnetic wave dissipation capability and meet the impedance matching to improve the absorbing performance of graphene-based materials.In this study,the Fe3O4/RGO composite was obtained by hydrothermal method.It was beneficial to realize the synergistic effect of dielectric loss and magnetic loss of composites,which gave the material more dissipation ability.It is conducive to achieve impedance matching to achieve efficient microwave material preparation.The results show that the RL of the Fe3O4/RGO composite is-48.76 dB.and the effective bandwidth ranges from 5.6 to 18 GHz.when the content of absorber is 5 wt.%.Combined with electromagnetic properties we found that the magnetic loss is difficult to reflect when the absorber content is low.We based on the electromagnetic wave dissipation mechanism and impedance matching mechanism to solve this contradiction.Wave-transparent material SiO2 was added in the Fe3O4/RGO to achieve further control of electromagnetic properties.In this study,Fe3O4/RGO/SiO2 ternary composites with different Si02 were prepared by hydrothermal reaction using ethyl orthosilicate(TEOS)as precursors.The results showed that the absorbing material exhibits magnetic loss and a low dielectric loss at the high frequency when 0.5 mL of ethyl orthosilicate was added and it exhibits better impedance matching and absorbing performance.The RL of the composites reaches-33.51dB at 12 GHz.The effective band width is 12.8 GHz(5.2 to 18 GHz)when the absorber content is 20 wt.%.In this study,RGO is the research object.we take into account the electromagnetic wave dissipation capacity and impedance matching performance.The optimization of electromagnetic properties is achieved by means of the composition and structural to achieve a series of RGO-based lightweight high efficiency electromagnetic wave absorber.The research not only provides experimental and theoretical basis for the application of RGO in the field of electromagnetic wave absorption,but also provides a new design idea for the design and preparation of lightweight and high efficiency absorbing materials.