Study On The Preparation And Properties Of Transparent Protective And Electromagnetic Shielding Coating For Canopy

The canopy is the “eye” of the aircraft,which is the most important passage for pilots to observe the situation and judge the flight conditions outside.Modern aircraft canopy is made of the optical plastic which can be molded integrally,these kind of materials generally have a light proportion,high light transmission and so on.But the defects of optical plastic is also obvious that is its poor surface hardnesss and wear resistance.Therefore,in order to ensure security of the canopy during service process,its surface must be effectively hardened.Besides the basic requirements of flight safety,the fighter also requires the capabilities of electromagnetic shielding and radar stealth.Engineers prepare a layer of transparent conductive film on the surface of the canopy,so that it can effectively shield harmful electronic radiation,ultraviolet light and far infrared rays and realize the stealth function.Mordern aircraft canopy requires the capabilities of transparent conductive and wear resistance.In this paper,we used sol-gel method to prepare transparent conductive and hard wear-resistant coatings,in order to meet these two requirements.Firstly,We used In Cl3 and acetylacetone as raw materials,SnCl4·5H2O as dopant,ethanolamine as film accelerator,to prepare the ITO soliquid by Sol-gel process,and plate ITO film on quartz substrate by spin coating.X-ray photoelectron spectroscopy?XRD?,X-ray photoelectron spectroscopy?XPS?,ultraviolet-visible spectrophotometer and Hall voltage were used to characterize the crystal structure,surface morphology,chemical composition,Light rate and resistivity of the ITO film.We also studied the effects of different doping concentrations,coating layers and heat treatment temperature on the structure and properties of ITO films.Experimental results:?1?With the increase of tin content,the transmittance of ITO film decreases gradually,the resistance decreases first and then increases,the optimum concentration of tin is 5%;?2?With the increase of coating layer number,the transmittance of ITO film decreases gradually,the resistance increases first and then slowly increases,the optimum coating number is 3 layers;?3?With the increase of annealing temperature,crystallization characteristics of ITO film is more and more obvious,the crystal structure is also more complete,the transmittance of the films increases gradually,the resistance decreases first and then increases gradually,the optimum annealing temperature is 600?;?4?When the tin doping concentration is5%,the coating layer is 3,the heat treatment temperature is 600?,the conductive properties of ITO films is best,whose resistivity is 0.1435 ?·cm,carrier concentration is 1.75×1020·cm-3,and carrier mobility is 1.773 cm2V-1s-1.Then,using methyl trimethoxysilane?MTMS?as film-forming material,adding tetraethylorthosilicate?TEOS?hydrolysis product of silica sol as inorganic reinforcing material,We preparared abrasion resistant coatings by Sol-gel method and plate Si O₂ coating on PMMA substrate by spin coating method.Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,thermogravimetric analysis?TG?,UV-Vis spectrophotometer and nanoindentation,wear-resistant test equipment were used to characterize the functional groups,thermal stability,visible light transmittance and mechanical properties.The effects of MTMS/TEOS ratio,the amount of catalyst and curing agent,heat treatment temperature and the number of coating layers on the structure,optical and mechanical properties of SiO₂ wear-resistant coating were studied.Experimental results:?1?The cross-linked structure of Si—O—Si is formed in the coating.after the wear-resistant coating is cured.?2?The nano-SiO₂ prepared by sol-gel method is amorphous amorphous structure.?3?When the MTMS/TEOS ratio is 3:2,the amount of catalyst is 500 ?l,the curing agent is 20 mg,the solvent is 20 ml,the coating layer is 3 layers,the wear resistance of the wear-resistant coating is the best,the loss quality is 15 mg,scratch critical load is 17 g,550 nm visible light transmittance is over93%.