Preparation of black-colored thin films from silica sol containing dissolved metal nitrates by the sol-gel method

• Published in: Journal of materials science Vol. 36; no. 18; pp. 4503 - 4510
• Main Authors: AKAMATSU, Y, TAKAMATSU, A, MAKITA, K, INABA, H, MINAMI, T
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 15.09.2001; Springer Nature B.V
• Subjects: Abrasion; Abrasives; Chromium; Composition; Copper; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Film thickness; Haze; Heat treatment; Light transmittance; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Manganese; Materials science; Metal nitrates; Methods of deposition of films and coatings; film growth and epitaxy; Nitrates; Optimization; Organic chemistry; Physics; Product design; Scratching; Silicon dioxide; Sol-gel processes; Spinel; Thin films; Additives; Inorganic compounds; Colored glass; Transition element compounds; Oxides; Cobalt oxides; XRD; Experimental study; Thin films; Thickness; Inorganic dye; Precipitation; Optical transmission; Silicon oxides; Chromium oxides; SEM; Iron oxides; Copper oxides; Sol-gel process
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/A:1017990921511

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°C. 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 36SiO2·64CuMnCrO4. The durabilities of the glasses with black-colored coatings against scratching, abrasion and chemicals are good enough for the practical applications.