화학공학소재연구정보센터
Journal of Materials Science, Vol.36, No.18, 4503-4510, 2001
Preparation of black-colored thin films from silica sol containing dissolved metal nitrates by the sol-gel method
Black-colored SiO2-based films, containing colorant inorganic spinel crystals such as Cu2MnO4, CuMn2O4, CuMnCrO4, CuMnFeO4 or CuMnCoO4, were prepared from a silica sol containing dissolved metal nitrates using the dipping-withdrawing technique. The inorganic colorants were formed in the SiO2 matrix of the films by heat-treatment at temperatures from 600 to 660 degreesC. The black-colored coating films were uniform and transparent with a low haze value (less than 1.0%) and with a thickness of 100-800 nm in the SiO2-(Cu-Mn-Cr-O) system, for which the colorant was the spinel crystal of CuMnCrO4. The visible light transmittance of the colored films was controlled in a relatively wide range of 15-65% by changing the film thickness or the colorant concentration in the coating solution. Optimization of the composition of the coating solution and the preparation conditions gave black-colored films with excellent durability and visible light transmittance of about 25%, which is similar to that of deeply black-colored glasses commonly produced by the melting method. For example, a black-colored film with a visible light transmittance of 24.6% and a film thickness of 160 nm was obtained from a coating solution with a nominal composition of 36SiO(2). 64CuMnCrO(4). The durabilities of the glasses with black-colored coatings against scratching, abrasion and chemicals are good enough for the practical applications.