Preparation Of Super-wetting SiO₂ Nano-pillar Arrays With Templates

Nano materials with super-wettability play an important role in production and life.It is an effective way to prepare super-wetting surface by controlling micro/nano hierarchical structure and chemical composition of the surface.In this work,we report a novel and facile method to fabricate SiO2 nano-pillar arrays on glass surface by using acidic SiO2 sol as coating material and anodized nanoporous aluminum oxide(AAO)as template.Surface roughness of SiO2 nano-pillar arrays can be adjusted by changing pore size of AAO templates.The nano-pillar array with suitable aspect ratio exhibits super-hydrophilicity.Meanwhile,transparent super-hydrophobic glass can be obtained when the super-hydrophilic nano-pillar array is modified by fluoroalkylsilane.The main results are shown as follows:1.A transparent SiO2 sol was prepared by acid hydrolysis of tetraethyl orthosilicate and adding a coupling agent(KH560)as a binder.The coating processes were studied to prepare appropriate coating layer for template imprinting.The spin coating method was adopted,and by comparing surface state,initial gel time,film thickness,visible light transmittance,adhesion,wear resistance of the coating layer obtained,the spin coating process factors of 500 rpm,10 s were determined.Results show that different heat treatment temperatures also have a certain effect on the properties of the coating layer.With the increase of temperature,the wear resistance and adhesion of the film increase.However,when the temperature is too high,the coating layer will peel off due to the large stress difference between the layer and the glass substrate.The surface state and comprehensive performances of the coating layer at a treatment temperature of 180? is the best.Meanwhile,the infrared characterization of the coating layer shows that the three-dimensional network structure of SiO2 is formed.2.The UVO treatment of the coating layer can improve its hydrophilicity.The hydrophilic surface of the coating layer becomes hydrophobic surface when modified by fluorosilane.The longer the UVO treatment time,the smaller the rolling angle of the hydrophobic surface.The infrared characterization results show that the binder KH560 in the sol is oxidized to hydrophilic carbonyl group,which combines with the fluorosilane and the rolling angle decreases3.By imprinting the coating layer with the templates with same hole spacing,same pore size but different hole depths,the obtained nano-pillars tend to aggregate and the visible light transmittance of the film sharply decreases,when the aspect ratio of the nano-pillar is greater than 10.Imprinting with the templates with same hole spacing,same hole depths but different pore size under the condition of the aspect ratio less than 10,a series of regularly arranged nano-pillar arrays were obtained.With the pore size of the template increases,the diameter of the nano-pillar increases,the surface roughness decreases,and the contact angle decreases.The prepared SiO2 nano-pillar array by using a template with the hole spacing of 125 nm,the pore diameter of 40 nm and the hole depth of 150 nm shows super-hydrophilic property.4.After being modified by fluorosilane,the hydrophilic SiO2 nano-pillar arrays turn to be hydrophobic.With the proportion of surface solid increases,the hydrophobicity gradually decreases.Comparing the gravity and capillary force of the nano-pillars,results show that these nano-pillar arrays are in the Cassie state.The apparent contact angles calculated according the equation of Cassie are basically consistent with the experimental values.The super-hydrophobic glass with a contact angle of 150.720 and a rolling angle of 9° was successfully prepared by fluorosilane modification of super-hydrophilic nano-pillar arrays.