Development And Application Of A Group Of Novel And Effective Microwave Absorbing Marerials With "Light Weight,Thin Thickness,Wide Bandwidth,and Strong Absorption"

Electromagnetic wave absorbing materials are a kind of functional material which can absorb or attenuate the incident electromagnetic wave.These materials are widely used in the fields of military shielding,stealth technology and electronic devices.With the development of communication technology,electronic devices tend to be miniaturized and integrated.The massive connection of various devices and the increase of diversified electromagnetic wave emission sources make the electromagnetic environment around increasingly complex,which will generate more serious EMI problems.The traditional absorbing materials are difficult to meet the requirements of“ultra-thin,ultra-light,wide bandwidth and strong absorption”for effective absorbing materials.The metamaterial absorbers,as an artificially designed subwavelength structure,easily reach strong absorption with thin thickness.Their characteristics of flexible design and diverse absorption mechanisms can greatly improve many defects of traditional materials.Considering the metamaterial design principles,we designed and prepared three metamaterial absorbers by using chiral spiral as metamaterial structure unit,reasonable periodic arrangement,coaxially nesting unit cells and recombining with magnetic absorbers.We have carried out the research as follows:?1?Based on the characteristics of metal helical structure and chiral metamaterials,helical metamaterial absorbers?HMMAs?,which consisting of a periodic array of coaxially nested magnetic helices were designed and prepared.The generated absorber exhibits ultrawide BW,polarization insensitivity,and wide-angle absorption.Their absorption BW,peak position,and peak intensity are facily controlled by changing the array period,helix diameter,and nesting type.The effective bandwidth with reflection loss below-10 dB?90%attenuation?is up to27.68 GHz at 8–40 GHz.The HMMAs also show polarization insensitivity in the incident range of 0°–315°and angle insensitivity at all incident angles in the range of35°–70°.Current distributions and coupling property are provided,and results reveal that the synergistic effect of the LC resonance and dipole responses of the patterned structure is responsible for the broadband absorption mechanism.?2?An ultrathin,ultralight,ultra-wideband tunable metamaterial absorber have been designed and prepared based on planar spiral structures,which EG/Fe/Fe₃O₄composites were filled in a periodic array of hollowed out chiral mosquito-incense units.The absorbing bandwidth was controlled by changing the periodic array of spiral unit and the mass fraction ratio of absorbents.It is verified by experiment that the absorptions of the hybrid absorber remain over 90%at the frequency range of21.4–36.3 GHz,corresponding to an ultrathin thickness?0.5 mm?,ultralight weight?0.83 kg/m²?,polarization insensitivity?0–90°?,and wide-angle absorption?15–60°?.The superior mmWave absorption properties mainly stem from the synergistic effect of?/4 resonances,multiple resonances,LC-resonances and dipole responses of the patterned structure.?3?A double semi-helical metamaterial absorber is designed and fabricated by3D printing technology.Using flexible substrate,the absorber exhibits good flexibility,which can perfectly adapt to the irregular surface of objects.The double semi-helical metamaterial absorbers were insensitive to the polarization of incident electromagnetic wave owing to double rotating symmetry structure.The optimized thickness of the metamaterial absorbers is 0.5 mm,the absorption remains over 90%at the frequency range of 25.70 to 37.38 GHz and the bandwidth is 11.68 GHz.The CST was used to simulate the metamaterial structure and the mechanism of ultra-wideband absorption and absorption adjustment were explored based on the distribution of surface current and equivalent circuit model.