Preparation of hard optical coatings based on an organic/inorganic composite by sol-gel method

Hard optical coating films based on SiO2/TiO2/organically modified silane ( ORMOSIL) were obtained by the sol-gel technique. Tetraethoxysilane [TEOS, S i(OC2H5)(4)], gamma-Glycidoxypropyltrimethoxysilane [GLYMO, (CH2OCH)CH2O-(C H2)(3)Si(OCH3)(3)], and tetrapropylorthotitanate [TIP, Ti(O-i-C3H7)(4)] wer e used as precursors for the SiO2/TiO2/ORMOSIL coatings. The hardness and Y oung's modulus of the coatings were characterized and found to depend on th e heat-treatment temperature. Hardness as high as 10 GPa was achieved at a heat-treatment temperature of 1000 degrees C for 20 min. Thermal gravimetri c analysis (TGA), scanning electron microscopy (SEM), and Raman spectroscop y were also used to investigate the structural properties of the coating. I t is proposed that the high hardness of the coating film is related to the carbon and titanium content in the film. (C) 2000 Elsevier Science B.V. All rights reserved.