The Hydrophobic SiO₂ Film Was Prepared By The Sol-gel Method

Superhydrophobic film had been widely used in production and life due to its good self-cleaning and other functions,especially in the field of solar energy.However,the development and application of superhydrophobic film were limited by many factors,such as the cost of raw materials and preparation methods.In addition,there was also a problem that the high transmittance and superhydrophobicity of film cannot be obtained at the same time.In this paper,tetraethoxysilane（TEOS）and trimethylethoxysilane（TMES）were used as precursors,a series of SiO₂ sols were prepared by acid-catalyzed chemical modification method,alkaline-catalyzed chemical modification method and sol mixing method,high-purity quartz glasses were used as the substrates,and a series of SiO₂ films were prepared by dip-coating technology.Finally,the structure and properties of various SiO₂ films were investigated,and the following conclusions were obtained:（1）The effects of TMES addition on the structure and properties of acid-catalyzed SiO₂ films were investigated,it was found that with the increase of TMES addition,the characteristic peak intensity of the hydrophobic group Si-（CH₃）₃ in SiO₂ increased and the characteristic peak intensity of the hydrophilic group Si-OH decreased,the surface roughness of films had no obvious regular change and their roughness values were extremely low,the average contact angle of films gradually increased from 70.62°to101.53°and the growth rate gradually decreased,the average transmittance values of films were almost the same as that of the substrate.（2）The effects of TMES addition on the structure and properties of alkaline-catalyzed SiO₂ films were investigated,it was found that the addition of ammonia and water promoted the growth of SiO₂ particle size,but the increase of reaction temperature inhibited the growth of SiO₂ particle size.With the increase of TMES addition,the microstructure of films had no obvious change,but the particle size of SiO₂ decreased slightly,the surface roughness of films had no obvious regular change and their roughness values were very low,the average contact angle of films increased from 19.08°to 127.37°and the growth rate gradually decreased,the average transmittance of films decreased from 94.86%to 94.14%and then increased to 94.63%in the range of 380-1100 nm.（3）The effects of sol mixing ratio on the structure and properties of SiO₂ films were investigated,it was found that the surface roughness,contact angle and transmittance of films were greatly improved after sol mixing,the properties of the SiO₂film prepared by mixing the sol with the particle size of 25 nm and 50 nm at the volume ratio of 25%:75%was better,the surface roughness Rq of the film reached the maximum value of 11.2 nm,the average contact angle reached the maximum value of129.47°,its average transmittance reached 96.99%in the range of 380-1100 nm.（4）The effects of TMES addition on the structure and properties of SiO₂ films at the sol mixing ratio of 25%:75%were investigated,it was found that with the increase of TMES addition,the porosity and cracks of the SiO₂ film increased,the surface roughness and average contact angle gradually increased,but the average transmittance gradually decreased.Finally,the superhydrophobic SiO₂ film with the average transmittance of 94.84%in the range of 380-1100 nm and the average contact angle of158.47°was obtained.