Measurement And Simulation Of Far Infrared Reflectance Characteristics Of Simulated Abalone Shell Microstructure

Infrared stealth technology is widely used in the field of national defense,but there are many disadvantages in infrared stealth materials as the main means.The structure color widely exists in nature.The high reflectivity in a specific wavelength range can be achieved by using optical phenomena such as interference diffraction.According to Kirchhoff law,infrared stealth can be realized.The simulation of biological structure by bionic technology provides a new way for infrared stealth.In this paper,the mathematical model of pearl layer of abalone shell is constructed.The incident wave is introduced and boundary conditions are built by finite element analysis.The reflection characteristics of the structure in the mid far infrared band are simulated.The simulation of the local structure of pearl layer of abalone shell was completed by using the wave optics module of COMSOL,which is consistent with the optical characterization peak of abalone shell.In the process of further study on the influence of structural parameters,the concepts of layer number,spacing,layer thickness,period,refractive index are introduced.The number of layers and refractive index of layer a contribute to the improvement of reflectivity and peak width.The difference between layers and refractive index of layer B is opposite.The influence of layer thickness and period is more complex,but the overall rule is in line with the expectation.Finally,the optimal structure model is determined to be 42 layers,the refractive index of layer A is 2,the refractive index of layer B is 1,and the thickness and period are controlled within 0.5μm-1.5μm and 5.5μm respectively.In this range,the layer thickness and period are further refined.After many times of simulation and calculation,it is determined that the structure is a 40 layer brick mud structure,in which the thickness of layer a is 1.17μm,the refractive index is 2,the thickness of layer B is 2μm,and the refractive index of filled air is 1.According to the parameters of the model,the structure of the model is established by the freeze-drying technology to verify the infrared stealth effect of the mathematical model.In the process of determining different materials,by comparing the relationship between microstructure and the parameters of the model,the polyvinyl alcohol solution with a mass fraction of 10% was determined.After 5 repeated freezing thawing processes,the hydrogel was formed,and a layered structure similar to the mathematical model was formed during the subsequent freeze drying process.In the mid and far infrared reflectance test,the reflectance peak value is 4-6μm,which verifies the feasibility of infrared stealth.