Design,Preparation And Optimization Of Infrared Optical Properties Of Core-Shell-Type Thermotropic Emissivity Materials

In order to overcome the intelligent thermal control problem of small spacecraft in orbit and meet its adaptive temperature control requirements under the influence of solar irradiation and internal heat flux,a thermal temperature control coating was designed based on the thermally induced emissivity of VO₂ at 68?;Combined with computer simulation and experimental testing methods,the effects of coating structure parameters and material preparation methods on its infrared optical properties were systematically studied.The preparation and performance optimization of thermal temperature control coating samples were preliminarily completed,which is expected to provide a new idea for the development of high performance thermal control coating.Specific research work includes:Firstly,in order to achieve the purpose of low emissivity at low temperature and high emissivity at high temperature,a composite coating system with high reflective substrate was designed.The coating is mainly composed of functional particles with thermal transformation characteristics of VO₂ material with core-shell structure and infrared transparent resin.The effects of the size of core particles,the solid content of coating filler,the thickness of coating and the thickness of VO₂shell on the infrared emissivity of coating were systematically studied by using finite element simulation method.ulation results show that when Ca F₂particle size is3?m,filler solid content is 10%,coating thickness is 15?m,and VO₂ shell thickness is 20 nm,the reflectivity has the maximum variation range at about 0.7 under high and low temperature.Secondly,in order to prepare CaF₂ core microspheres with uniform surface and sui Tab.le particle size,hydrothermal method was used to study the influence of the preparation process parameters,such as morphology agent type,morphology agent concentration,reaction p H value and hydrothermal time,on the particle size and morphology of core particle.The results show that Ca F₂microspheres with smooth surface and particle size of about 3?m can be obtained by using EDTA as morphology agent,controlling the concentration ratio of EDTA to Ca²⁺to 2:1and hydrothermal treatment at 190?for 1 hour.Finally,in order to prepare the coating with variable reflectivity,the preparation process of packing particle VO₂(M)@Ca F₂ microspheres was studied,and the effects of shell thickness of VO₂,solid content of packing and coating thickness on the reflectivity were discussed.VO₂(D)@Ca F₂precursor microspheres coated by VO₂ were successfully prepared by solvothermal method in the presence of 0.03 g of cohesive morphology agent dopamine.Then VO₂(D)@Ca F₂ precursor microspheres were transformed into VO₂(M)@Ca F₂ powders with strong s Tab.ility by high temperature annealing.Finally,a variable reflectivity coating with a reflectivity difference of about 0.38 was obtained by spin coating method,and the coating thickness and solid content of the filler were optimized.