Optical and mechanical properties of sol-gel silica-titania hard optical coatings derived from methyltrimethoxysilane and tetrapropylorthotitanate as precursors

摘要

Silica-titania hard optical coatings based on titania/organically modified silane composite materials were prepared by the sol-gel spin coating technique. Acid catalyzed solutions of methyltrimethoxysilane mixed with tetrapropylorthotitanate were used as precursors for the silica-titania coatings. Atomic force microscopy, thermal gravimetric analysis, UV-visible spectroscopy, and Fourier transform infrared spectroscopy have been used to investigate the optical and structural properties of the coatings. The results indicated that purely inorganic and crack-free silica-titania coatings could be obtained after heating at a temperature of 500℃ or higher. The hardness and Young's modulus of the coatings were characterized by a nanoindenter and they showed a dependence on the heat-treatment temperature and titanium content. Hardness as high as about 7.0 GPa was observed in a high titanium content coating heat-treated at 800℃.