| The lunar dust is considered as the main obstacle to the progress of the lunar exploration project.Once deposited on the surface of the rover’s flexible photovoltaic modules,the lunar dust particles will reduce light transmission,resulting in reduced power output of the solar cells,and have a huge impact on energy supply.Passive method can inhibit the adhesion of lunar dust by constructing dust removal coating on the surface of solar cell.The dusting mechanism of hydrophobic coating,which uses water droplets to roll away dust,is not suitable for the anhydrous lunar environment.Developing a dust mitigation scheme suitable for the lunar environment is vital to ensure the success of lunar exploration missions.Polyimide as the substrate and cover film material of the flexible photovoltaic modules on the lunar rover has low surface energy and poor adhesion with the coating.Thus,how to prepare dust removal coating on polyimide surface suitable for lunar environment is an urgent problem to be solved.Aiming at the dust removal coating requirements of polyimide based photovoltaic modules for lunar rover,the dust removal coating with rough structure was prepared by using silica（SiO2）and silicic acid（Si（OH）4）.The influence of SiO2 content,SiO2 and Si（OH）4 molar ratio on the coating’s performance,such as light transmittance and dust removal percentage,were discussed.The bending resistance,thermal stability and high-low temperature resistance of the coating were investigated.In order to further improve the adhesion of the coating,γ-aminopropyltrethoxysilane（KH550）was used as SiO2 coupling agent.The influence of p H,SiO2 and KH550 mass ratio on the surface morphology,optical properties and dust removal properties of the coating were discussed.The bending resistance,thermal stability and high-low temperature resistance of the coating were investigated.The results were as follows:SiO2/Si（OH）4 coating has the rough structure.The molar ratio of SiO2 to Si（OH）4 has significant influence on the roughness of coating,and the content of SiO2 mainly affected the density and pore diameter of coating.When the content of SiO2 was 1.5%and the molar ratio of SiO2 to Si（OH）4 was 1:0.25,the SiO2/Si（OH）4 coating has 73.8%transmittance and 92.3%dust removal percentage.The SiO2/Si（OH）4 coating showed good bending resistance in bending experiments.After PI substrate was treated by plasma,hydrophilic groups were generated,which was conducive to improving the adhesion of the coating,and the adhesive force of the coating was increased from5 level to 4 level.The thermal stability experiment showed that the plasma treatment can prevent the cracking of the coating at high temperature,and the SiO2/Si（OH）4 coating has good high-low temperature resistance.In order to further improve the adhesion between the coating and PI film,SiO2/KH550 coating was prepared by using KH550 as SiO2 coupling agent.SiO2/KH550 coating solution prepared with p H=3 has the highest stability,sol particle size is 326.2 nm,PDI is 0.295,and sol dispersion is uniform.SiO2/KH550 coating formed a nanoporous rough structure,and the highest transmittance was 86.4%.With the decrease of the mass ratio of SiO2 to KH550,the roughness of SiO2/KH550coating increased,the transmittance decreased,the surface contact angle increased from 9.0±0.4°to 34.7±1.5°,and the dust removal percentage decreased.When the p H was 3,the mass ratio of SiO2 to KH550 was 1:1.5,the adhesive force of the coating reached 0 level,and the dust removal percentage was 85.5%.After 500 cycles with a bending radius of 2 cm,the transmittance of the SiO2/KH550 coating was 84.3%,maintaining high transparency.The light transmittance of the coating after bending for3000 times was basically unchanged,and it has excellent bending resistance.The maximum thermal decomposition temperature of SiO2/KH550 coating was 344.4℃.The surface structure of SiO2/KH550 coating was not damaged by high-low temperature impact from-196℃to 160℃.After five cycles,the dust removal percentage of the coating is 84.0%,with excellent high-low temperature resistance. |
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