| Microwave absorbing materials can absorb external electromagnetic waves and convert them into other forms of energy,which can effectively solve the problem of electromagnetic pollution,and also contribute to the development of stealth technology in the military field.The design of frequency selective surfaces and structural absorbers can further enhance the absorption bandwidth of microwave absorbing materials to meet the needs of engineering applications.In this research,reduced graphene oxide(rGO)with excellent dielectric loss performance and ferric oxide(Fe3O4)with excellent magnetic loss performance are used as the absorbing medium.The performance of different frequency selective surfaces and structural absorbers are investigated by combining numerical simulation and experimental testing.The research contents are as follows:(1)Ferrite-modified graphene(Fe3O4@rGO)is obtained by modifying ferric oxide on the reduced graphene oxide layer,characterized by scanning electron microscopy.The microscopic morphology of the Fe3O4@rGO powder confirm the organic combination of Fe3O4 and rGO.Ferrite-modified graphene/epoxy(Fe3O4@rGO/EP)composite is prepared by adding Fe3O4@rGO powder into shape memory epoxy resin.(2)The electromagnetic parameter test and shape memory test are carried out on the Fe3O4@rGO/EP composite sample,and the results show that with the increase of Fe3O4@rGO mass fraction,the dielectric loss tangent and magnetic loss tangent increase,that is,the electromagnetic wave loss ability increases.Description of shape fixation rate above 99%and shape recovery rate above 96%suggest that the Fe3O4@rGO do not influence the properties of shape memory epoxy resin.(3)ANSYS HFSS is used to model and simulate different types of absorbers,and the reflection loss and effective absorption bandwidth in X bands and Ku bands are used as the evaluation indicators of the microwave absorption performance.The research shows that with the increase of the thickness of the plate absorbers,the microwave absorbing performance of the absorbers first increases and then decreases.The absorber with a thickness of 1.5 mm has the best performance.The effective absorption bandwidth reaches 4.43 GHz,and the minimum reflection loss is as low as-24.03 dB.The design of structural absorber can increase the effective absorption bandwidth to 7.03 GHz;The smaller the size of the frequency selection surface is,the more conducive to the absorption of electromagnetic waves.Combine the above optimal parameters,the Fe3O4@rGO/EP composite structural absorber is obtained.The upper layer is a square ring type frequency selective surface with a pure epoxy resin substrate.While the bottom layer is Fe3O4@rGO/EP composite structural absorber.The results show that the effective absorption bandwidth of the composite structural absorber can reach 8 GHz at most.(4)On the basis of Fe3O4@rGO/EP composite structural absorber,the performance research on stealth/anti-icing/frequency conversion microwave absorption/lightning protection is carried out.By building a hydrophobic surface between the grooves of the composite structural absorber and using the heat energy converted by the microwave absorption process,the surface can be effectively prevented from icing.The finite element simulation shows that the surface temperature rise rate of composite structural absorber with doping content of 15 wt%and 30 wt%are 0.77℃/s and 0.86℃/s respectively.The performance is improved by 11.69%.The change of the period of the composite structural absorber can change the absorption capacity at various frequency bands.The excellent shape memory property of Fe3O4@rGO/EP composite can intelligently control the microwave absorption.The outermost frequency selective surface can also act as a conductive grid to prevent damage of the composite structural absorber and important internal components. |
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