| Microwave that frequency range within 2-18 GHz is widely used in communication,radar detection,and other fields due to it could be transmitted long-distance in atmospheric environment.Although this provides convenience for human activity,but brings a lot of problems to be solved urgently.On the one hand,the popularization of 5G communication technology has brought higher microwave transmission efficiency to mankind,however,serious electromagnetic wave pollution and interference occur due to the limited anti-jamming ability of electronic devices;on the other hand,microwave radar has been widely used in many countries and thus become a universal anti-stealth technology,how to achieve microwave stealth of weapon to avoid radar detection has become an important issue of national security.Therefore,researchers around the world bend themselves to develop new microwave absorption materials,in order to solve above problems by effective microwave absorption.However,the application of microwave absorbing material requires it to reduce the thickness as much as possible under the premise of broadband absorption,such as microwave absorbing paster,stealth coating,et al.But the thickness of material will be much less than the working wavelength after it is reduced overly,i.e.reached deep subwavelength thickness.In this case,microwave absorbing material is difficult to achieve broadband absorption because of it is limited by the Plank-Rozanov limit,thus how to improve the absorbing performance under the deep subwavelength thickness has become the key factor for the material.Moreover,the application environment requires the material realize functional integration,such as multi-band and multi-function adaptability,which restricts the application of microwave absorbing materials.In this context,present dissertation utilized the new strategy according to bionic by combining microwave absorbing material with biological model,take advantage of the nature model that has been perfected derived from billions of years evolution,extract biological models that have electromagnetic wave absorption property in nature,the microwave absorption materials are prepared into bionic units and ordered arrangement,and the bionic units are designed as a sub-wavelength scale,i.e.the characteristic size of the units are equal to or smaller than the working wavelength,this scale relation has been proved a good anti-reflection effect on electromagnetic waves,so it is suitable for microwave absorbing materials.In present dissertation,above design is adopted to break through the performance limitation of traditional microwave absorption materials,which make the materials realize broadband absorption under deep-subwavelength thickness,also reveal the mechanism of bionic material to realize broadband absorption,and the materials have multi-band and multi-function adaptability.Present dissertation mainly obtained following research results:Firstly,inspired by the grating structure of butterfly wing,the Fe-Si alloy strip is arranged as grating mode in the carbonyl iron/polyurethane matrix,the tuning of resonance frequency and enhanced absorption could be achieved by adjusting strip orientation and spacing.The tunable effective absorption bandwidth covers 10.2-18 GHz frequency range(reflection loss,RL?10 dB),the value of absorption peak enhanced from-38.43 dB to-66.90 dB,which material thickness of 1.25 mm,and the coupling effect among strip and matrix is verified by simulation model.However,above mentioned grid material has not obvious effect of improving absorption bandwidth,in order to realize broadband absorption under deep subwavelength thickness,the biomimetic ordered structure is prepared that encouraged by the microstructure of moth-eye.It improves the effective absorption bandwidth(RL?-10 dB)from 0 to 8.04-17.88 GHz in the circumstance of 1 mm thickness,thus break through the Plank-Rozanov limit of traditional microwave absorption materials;according to the Poincare-Brouwer theorem in algebraic topology,demonstrate the absorption performance of bionic units can be improved by the existence of current zero,and proved by simulation results.After the broadband absorption property of biomimetic ordered material has been demonstrated,in order to further improve the microwave absorbing performance of the ordered materials,according to the rotational polarization principle of the jewelled beetle's chiral structure,the absorption and bandwidth are improved by constructing the gyrotropic arrangement of units.By designing the non-eigen chiral ordered structure as right-hand helix eigen chiral(twisted 15°),the absorption peak within high frequency range enhanced from-26.36 dB to-48.83 dB,the effective absorption bandwidth(RL?-10 dB)expands from 13.14-15.96 GHz to 12.96-18 GHz,and in the case of light(surface density 1.45 kg/m2),the bandwidth of more than 80%absorption(RL?-7 dB)covers entire 4-18 GHz frequency range.The mechanism is verified by phase delay and simulation model,and the functional units are prepared by Fe-based alloy,which increased the degree of freedom of ordered material design.Finally,in order to achieve effective absorption of full 2-18 GHz frequency range,to extract the holes structure model of the Pachliopta aristolochiae wing surface,the bionic hole-ordered microwave absorption material is designed and prepared.Compared with ordinary microwave absorbing materials that not bionics,the bandwidth with absorption more than 90%is widened from 0 to the full band absorption of 2-18 GHz,and the absorption peak enhanced from-8.90 dB to-58.49 dB.The mechanism is analyzed by phase delay and electromagnetic simulation.The bionics research paradigm is introduced into the design of microwave absorbing materials in present dissertation,the broadband absorption is realized under deep subwavelength thickness,which provides the foundation for perfecting the theory of ordered microwave absorbing materials.Furthermore,the biomimetic ordered materials mentioned above are constructed by the arrangement of units as well as the selecting of matrix matter,which realized such functions as flexibility,impact resistance,corrosion resistance,and multi-band adaptability,and exhibite the application advantage of this order structure. |
PDF Full Text Request