Preparation of highly transparent and wear-resistant SiO2 coating by alkali/acid dual catalyzed sol-gel method

In this paper, a sol-gel method was adopted, using tetraethyl orthosilicate (TEOS) as a precursor, to prepare hollow silica spheres through alkali-catalyzed sol, and further to form a long-chain structure through acid catalysis. The alkali-aluminosilicate glass is coated with hollow silica spheres by a dip coating method, and the anti-reflection (AR) nanostructured silica coatings with different thicknesses and porosities are obtained. The prepared hollow silica spheres have an inner diameter of 20 nm and a wall thickness of 6-20 nm. The average transmittance of the coating at normal incidence within the wavelength range of 300-900 nm is between 94 and 96.9%, a great improvement compared with 91.8% of the substrate. Hollow spherical and long-chain structure of silica is conducive to film formation on the glass surface and endows the film with a high mechanical strength. After 60 friction cycles, the average transmittance is only decreased by 0.6%.