Preparation Of SiO₂ Superhydrophilic Coating By Sol-Gel Method

With the increasing antifogging requirement of transparent materials,research of material surfaces with a special infiltration ability has recently been receiving extensive scientific attention.To date,there are two mainapproaches to prepare super-hydrophilic coatings:one is photo-induced super-hydrophilic;the other is to construct a special configuration with certain roughness laying on the surface of high surface energy materials.Since photo-induced super-hydrophilic hydrophilicity will gradually weaken under the no light cricumstance,this drawback is extremely prone to making a negative effect of fabrication,application,sustainable life.Hence,it has attracted thousands of scholars and researchers who are studying the scratchy special configuration construction for the preparation of super-hydrophilic coatings.In addition,during the preparation of super-hydrophilic coatings,lots of expensive equipments and instruments are involved,high-temperature heat treatment process and complicated craft process makes it difficult to realize the large scale production of coatings,which hinder the commercial application of super-hydrophilic coatings.In order to promote the progress of production and application of super-hydrophilic coatings,this paper combines the principle of particle grading fabricates SiO₂super-hydrophilic coating lby a simple sol-gel method at room temperature.In this paper,the stable SiO₂ sols with different particle sizes were prepared by sol-gel method under acid catalysis and base catalysis,investigating the influence of the changes of particle size and distribution of SiO₂ sol in different reaction conditions.The results show that under the acid catalysis condition,the sol particle size decreases with the increase of ethanol dosage.With the increase of water dosage,reaction temperature and reaction time,the sol particle size increases gradually.s the pH increases,the sol particle size increases first,and then decreases,reaching a maximum value when pH equals 4.Under the condition of alkali catalysis,with the increase of the amount of ethanol,pH value,reaction temperature and the prolongation of reaction time,the particle size of sol gradually decreased.With the increase of water dosage,the particle size of sol Increase first,and then decreases,reaching a maximum when the water-ester ratio is 11.In addition,the resulting sol has good monodispersity regardless of the catalytic conditions.Combined with the principle of particle grading,the SiO₂ coating was prepared by dip coating at room temperature,and the microstructure,wetting property and anti-fog performance of the coating were analyzed.The results show that when a hydrophilic coating is prepared by using a single particle size SiO₂ sol,the water contact angle of the coating decreases with the decrease of the sol particle size,and increases with the decrease of the sol concentration.When the concentration is 2 vol%at 9.26 nm,the contact angle of the coating is reduced to 11.8°,which has a good anti-fog effect.When the hydrophilic coating is prepared by using a multi-stage particle size SiO₂ sol,according to the hexagonal closest packing model in the secondary particle grading,the SiO₂ sol having a particle diameter of 60.29 nm and 9.26 nm is selected at a concentration ratio of 10:3.The resulting coating had a contact angle of 6.6°.ccording to the hexagonal closest packing model in the three-stage particle grading,the contact angle of the obtained coating was 2.3°when the concentration ratio of SiO₂ sol of particle size 60.29nm,9.26nm and 3.68nm was 7.5:2:0.5.It achieves super-hydrophilic properties and has excellent anti-fog effect.