Research On Manipulation Of Electromagnetic Absorption And Thermal Radiation Based On Micro-nano Structures

The key of the electromagnetic absorption and thermal radiation control technology is how to achieve flexible manipulating of the electromagnetic response of materials.The micro-nano structure materials with sub-wavelength size provide a powerful and effective solution to this kind of electromagnetic manipulation.From the rise of research on daytime radiative cooling to the dramatic reduction in the thickness of electromagnetic absorption materials,micro-nano structure materials have made great contributions.The sub-wavelength micro-nano structural materials can regulate the electromagnetic responses of materials at wavelength scale with more lightweight characteristics,which have a non-negligible potential in the field of electromagnetic absorption and thermal radiation.However,there are still many problems to be solved in this kind of research,such as the slow design speed,some defects in the design theory,and the difficulty in further reducing the thickness of electromagnetic absorbing materials.Aim at the above problems,this thesis proceeded the research around the micronano structures with sub-wavelength scale,especially focusing on the rapid design and the approaches of thickness reduction of these materials.The main research works of this thesis include the following points:1.To solve the problem of low design speed of micro-nano structural materials with sub-wavelength scale,a design method of radiative cooling materials with high design speed is proposed in this thesis,which is based on the combination of the transfer matrix method,equivalent medium theory,and the enhanced genetic algorithm.By using a design method that combining the catenary field theory,transmission line theory,and the enhanced genetic algorithm,this thesis has sharply shorted the design speed of microwave absorber from the order of hours to the order of seconds.2.In view of the current design theory of passive radiative cooling materials,it is difficult to improve the cooling performance while reduce the thickness of materials at the same time.This thesis has verified the traditional design theory,by introducing the solar irradiance and the atmospheric transmittance into the design of radiative cooling materials,radiative cooling materials with 2 times cooling power to thickness ratio compare with other works is designed.In addition,considering the cooling demand of construction with many glass windows,the concept of transmission type radiative cooling is novelty proposed and verified with sub-wavelength structures.3.Aiming at the problem that the thickness of electromagnetic absorbing materials is difficult to be further reduced,the design of microwave broadband absorber closed to the thickness limitation is realized by using the design method that combining the catenary filed theory,the transmission line theory,and the thickness limitation theory.The designed absorbers include the single square ring absorber and the double square ring absorber.The relative bandwidth of the single square ring absorber with reflectivity lower than-10 d B is greater than 167%,and its thickness is within 101% of the thickness limitation.The relative bandwidth of the double square ring absorber with reflectivity lower than-15 d B is over 127%,and the thickness does not exceed 104% of the thickness limitation.