| Spacecraft operating in low Earth orbit(LEO)will be subjected to high vacuum,electromagnetic radiation,space debris impact and atomic oxygen(AO)bombardment and oxidation.Especially,the existence of AO causes serious erosion of polymer materials,leading to performance degradation and even failure.In this paper,the preparation of AO protective coating and interface adhesion between the coating and polymer matrix are discussed.New design concepts of coatings were used,such as St?ber microspheres combined with silica(SiO2)sol,in-situ growth of polyhedral oligomeric silsesquioxane(POSS),and magnetron sputtering POSS transition layers.Through the construction of coating and the study of interface adhesion mechanism,the possibility that induce coating failure can be reduced to the greatest extent.Explore AO protection technologies for polymer surfaces that can be used for engineering.The main research contents are as follows:(1)High content SiO2 coating was prepared by St?ber microspheres and sol-gel methods:The SiO2 nanospheres prepared by St?ber method were dispersed in a silica sol system,and the SiO2 content coatings were prepared on the surfaces of modified polycarbonate(PC)and polyimide(PI,Kapton)substrates,respectively.The results show that after irradiation with 3.09×1020 atoms/cm2,the AO erosion rate decreased from3.74×10-24 cm3/atom to 0.56×10-24 cm3/atom for PC samples.In the coated Kapton sample,the AO erosion rate decreased from 3.17×10-24 cm 3/atom to 0.22×10-24 cm3/atom,which was only 6.9% of original Kapton.This method is simple and practical.The coating with high SiO2 content is helpful to improve the anti-oxidation ability of polymers.(2)SiO2/POSS coating was constructed on Kapton surface by in-situ growth:The modified Kapton was placed in a reaction solution of POSS to grow a transition layer in situ,and then SiO2 coating was prepared on the POSS layer by sol-gel method.The results indicated that after irradiation with 3.30×1020atoms/cm2,the AO erosion rate was decreased from 3.74×10-24 cm3/atom to 0.56×10-24 cm3/atom for SiO2/amine-POSS/Kapton sample.The POSS layer was constructed between SiO2 coating and Kapton substrate,which strengthened the interface adhesion between the coating and substrate.After AO irradiation,the coating did not crack or fall off.(3)SiO2/POSS protective coating was prepared on Kapton surface by magnetron sputtering:In order to solve damages caused by small molecule residues in POSS/PI composites to spacecraft devices in high-vacuum environment,magnetron sputtering method is adopted to deposit SiO2/POSS coating on Kapton surface with self-made POSS target.The composite coating has excellent AO protection performance,and the AO erosion rate is only 1.58%of original Kapton.In addition,the coating keeps the optical performance of sample unaffected,which has certain research significance for the application of space thermal control coatings and solar cell array substrates. |
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