Research On Radiation Characteristics Of Microstructure Thermal Control Coating Based On Thermally Induced Phase Change Materialphase Change Materials

Space is a special environment with a very high vacuum.When a spacecraft is operating in space,it will pass through the sun’s direct irradiation area and the earth’s shadow area,and it will be directly and non-irradiated by the sun.The temperature range can reach hundreds of degrees Celsius.To ensure the normal operation of the spacecraft,all the loads and equipment on the spacecraft must be kept within a relatively constant temperature range.Therefore,we need to control the thermal emissivity,and the conventional control of thermal radiation is usually based on micro-nano structures.However,the traditional static micro-nano structure cannot flexibly control the thermal emissivity,and needs to dynamically control the thermal emissivity.Thermal control coating is a functional material specially used to adjust the heat radiation properties of the solid surface to achieve the purpose of thermal control.The intelligent thermal control coating has a low emissivity under low temperature conditions to avoid losing too much heat;under high temperature conditions,it achieves radiant heat dissipation and cooling through its own high emissivity.The intelligent thermal control coating realizes dynamic adjustment of emissivity by combining with thermally induced phase change materials.Therefore,this paper introduces thermo-induced phase change materials,and uses the finite difference time domain method to explore the radiation characteristics of intelligent thermal control coatings with different structures composed of thermo-induced phase change materials.The specific conclusions are as follows:(1)First of all,for the thin film structure thermal control coating,the influence of size parameters and materials on the radiation characteristics of the two-layer(AI-VO2)and three-layer(AI-HfO2-VO2)thin film structure coatings is explored,and the coating’s the average emissi’vity,the adjustable range of emissivity,etc.,deeply analyze the radiation performance.Studies have shown that the emissivity and radiant cooling power of the two coatings increase sharply before and after the phase change;By changing the material and structure of the coating,the spectral emissivity of the coating can achieve the desired effect.(2)Continue to improve the coating structure on the basis of the above-mentioned thin film structure thermal control coating,introduce periodic grating structure,and simulate the emission spectra of one-dimensional periodic grating structure coating and two-dimensional periodic grating structure coating,and explore the radiation characteristics of the coating.Studies have shown that when the outside temperature is lower than the phase transition temperature,the emissivity of the coating is lower,and when the temperature rises,the emissivity of the coating is higher.The grating structure coating is improved compared to the thin film structure coating;the average emissivity of the grating structure coating can be adjusted to about 0.5;the radiation cooling power of the one-dimensional grating structure coating before and after the phase change is increased by 363.39W/m2,The increase of the two-dimensional grating structure coating is 404.76W/m2.(3)There is still a lot of room for improvement due to the adjustable range of emissivity and radiant cooling power of the intelligent thermal control coating,and there is a lack of methods suitable for large-area non-planar surfaces.Therefore,this paper proposes an intelligent thermal control coating with spherical particle structure,simulates the emission spectrum,and explores the radiation characteristics of the coating.Studies have shown that the average emissivity of the coating can be adjusted to a maximum range of 0.52;before and after the phase change temperature,the increase of the radiant cooling power of the coating before and after the phase change is 477.02W/m2.The simulation obtains the electromagnetic field cloud picture at the peak of the coating.The study shows that the difference of electromagnetic field distribution in different areas of the coating leads to the difference in the emission spectrum of the coating at high and low temperatures.