Surface morphology of silica films derived by the sol-gel method and its application to a water repellent glass

Silica films with various surface morphologies, such as flatness, mesoporosity, uneveness, convexity, were prepared by hydrolysis and polymerization of tetraethoxysilane, Si(OC2H5)(4)(TEOS) and methyltrietoxysilane, CH3Si(OC2H5)(3)(MTES) under acid-catalyzed conditions, The morphology of coatings could be changed by changing the molar ratio (denoted as f,f=MTES/TEOS) in TEOS-MTES mixture, as well as the conditions of drying process and heat treatment temperature, Especially, in the case of 5<f less than or equal to 7.5, the surface of coatings was uneven, when films were prepared at humidities higher than 45 RH%. Water repellent glasses obtained by coating hydrolyzed heptadecafluorodecyltrimethoxysilane, CF3(CF2)(7)CH2CH2Si(OCH3)(3) on to this uneven surface showed an excellent abrasion resistance and W-light stability for windows of automobiles and buildings.