| In this paper,a boehmite-coated transparent superhydrophobic material was prepared on a glass substrate by hydrothermal method.The effects of hydrothermal time,temperature,and the different ratio of aluminum source(aluminum nitrate and aluminum isopropoxide)and precipitant(ammonium oxalate and sodium acetate)on the phase and morphology of the obtained product were studied.Different coupling agents(KH550 and PTES)regulate the morphology of the film and improve the adhesion of the film to the substrate.The obtained samples were characterized and systematically studied the properties of film transmittance,thermal stability,mechanical durability,corrosion resistance and wettability.The main research contents and results are as follows:1.In the aluminum nitrate system,the content of aluminum nitrate affects the morphology of boehmite,but the type of precipitant has less effect on the morphology.When the reaction conditions were controlled at 190?/10 h,the content of ammonium oxalate or sodium acetate was 1mmol and the content of aluminum nitrate was in the range of 2mmol-16 mmol,as the content of aluminum nitrate increased,the more grains,the larger the grain size.Both 2mmol and 4mmol aluminum nitrate will form a 1?m-2?m shuttle shape,and 8mmol aluminum nitrate will form a flower shape of about 2?m.Only when the aluminum nitrate is 16 mmol,different precipitants will produce different morphologies.As a precipitant,ammonium oxalate forms a bundle of 2?m-2.5?m,and sodium acetate forms a flower-like structure of 3?m-5?m.The hydrothermal reaction time only affects the integrity of this crystal structure.The hydrothermal reaction time only affects the crystallinity.When the reaction is performed at 190? for 4h-10 h,The boehmite produced by the reaction of 4mmol of aluminum nitrate and 1mmol of different precipitants will cause the crystal to form a more complete spindle-like structure with the extension of the hydrothermal reaction time.Temperature change is significant for morphology.The reaction between 4mmol of aluminum nitrate and 1mmol of different precipitants first formed a needle-like structure at 150?/10 h,then a small number of shuttle-like structures were appeared at 170?/10 h,until the needle-like structure was completely transformed into a spindle-like structure at 190?/10 h.2.The morphology and size of the boehmite prepared by the aluminum isopropoxide system were little affected by the hydrothermal time,temperature,and the concentration of aluminum isopropoxide.At 190?/10 h,the boehmite formed by aluminum isopropoxide at different concentrations(molar ratio of aluminum isopropoxide to pure water is 1: 200,1: 100,and 1:50)are hexagonal flakes,but as the content of aluminum isopropoxide increases,the crystal structure is more complete and the grain size is larger,70 nm grain size at 1:50 molar ratio.When the molar ratio of aluminum propoxide to pure water is 1:50,adjusting the reaction temperature or time will not change the morphology,but the grain size will increase with the increase of the reaction temperature or time.The smallest hexagonal flaky grains at 150?/10 h,only 20 nm.The small grain size of boehmite prepared by aluminum isopropoxide makes the film highly transparent and has good bonding force.3.Different coupling agents(KH550 and PTES)are added to the aluminum nitrate system to increase the adhesion of the film to the substrate.Among them,the addition of KH550 makes the morphology change,disperses the grains,refines the grains,and improves the adhesion between the coating and the substrate.When the reaction conditions were 190?/10 h,and the content of aluminum nitrate and precipitant were 4 mmol and 1 mmol,respectively,as the amount of KH550 added increased,the grains of the coating became finer and more uniformly dispersed.With sodium acetate as the precipitant,when 0.2g KH550 was added,the 1?m-2?m shuttle morphology without KH550 was transformed into a fibrous shape of 650 nm.As the KH550 content increased to 0.8g,it gradually changed into a 500 nm sheet structure.When the fixed KH550 content is 0.8g,the grains become finer with increasing temperature and time in the range of 150?-190? and 4h-10 h.When the precipitating agent is ammonium oxalate,although the morphology similar to that of sodium acetate is formed,the refining effect is poor(the grain size is about 1?m).In addition,KH550 can not only refine the grains to obtain a high transparent coating,but also make the boehmite film tightly connected to the glass substrate.Adding PTES under the same conditions formed no effect of dispersing and refining the grains,and the more obvious the phenomenon of agglomeration with the increase of the content of PTES,the obtained boehmite film had a large grain size,a thick coating and easy to fall off.4.The effect of fluorosilane concentration(0.5wt%-2wt%)and modification time(5min-120min)on the contact angle of the film was studied by using perfluorodecyltriethoxysilane to modify the boehmite film.With the increase of fluorosilane concentration and grafting time,the contact angle of the glass substrate increased first and then stabilized.The maximum contact angle was obtained by grafting 1wt% perfluorodecyltriethoxysilane in ethanol solution for 30 minutes.As the modification time is extended,the contact angle of the surface of the material gradually increases,until the modification time is basically 30 minutes.The grafted boehmite film not only has a contact angle of 166°±2° and 1.8°±0.2° sliding angle and average transmittance in the visible light range of 400nm-800 nm is about 80%.And the wettability,adhesion,mechanical durability,corrosion resistance,heat resistance and transmittance of the obtained film were tested.Experimental results show that in addition to excellent transparent and hydrophobic properties,boehmite films also have good mechanical durability,corrosion resistance and heat resistance.It remains superhydrophobic even after wear 100 cm under 8kPa pressure,strong acid and alkali erosion for 1h and heat treatment at 400? for 2h. |
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