Effect of firing temperature on the properties of sol-gel films of the CuO-TiO2 system

Abstract

The viscosity, surface tension, and refractive index of 2-day-old film-forming solutions of the CuO -TiO 2 system of different composition were compared with the structure and properties of coatings on float glass made from them. Regardless of the composition and firing conditions, the film thickness remained constant. The refractive index and mirror reflection coefficient of the coatings are correlated by a directly proportional dependence. Increasing the firing temperature does not change or increases the values of the refractive index and mirror-reflection coefficient of the films. The chemical resistance of the coatings to water or hydrochloric acid solution is not a function of or improves with an increase in the firing temperature.The properties of glass are related to the equilibrium diagram of the corresponding system to a significant degree and are a function of the thermal history [1], determined by the temperature-time conditions of melting, firing, and finishing of the glass. In [2], it is assumed that the nature of thin-layer sol-gel coatings is close to glass. This forms grounds for hypothesizing that their properties will definitely be a function of the conditions of thermal treatment (firing temperature and firing time) of the films.We investigated the correlation between the thermal history and properties of films of different molar composition made from 2-day-old film-forming solutions (FFS).We studied five compositions in the two-component CuO -TiO 2 system which differed in the ratio of the filmforming oxides or raw materials used for fabricating the FFS. Copper oxide was added to a solution with copper chloride or nitrate, TiO 2 was added with alkoxides: tetraethoxytitanium Ti(OC 2 H 5 ) 4 (TET) or tetrabutoxytitanium Ti(OC 4 H 9 ) 4 (TBT). Hydrochloric or nitric acid (if the copper oxide was added with chloride or nitrate, respectively) was the catalyst of hydrolysis of the alkoxides and ethyl alcohol was the solvent. The total mass content of film-forming oxides in all solutions (concentration of FFS) was the same and equal to 5%. The sol ripening time was 2 days. The viscosity of the FFS was measured by the capillary method (VPZh-1 viscometer) and the surface tension was measured by the sessile drop method.Samples of thermally polished sheet glass measuring 70´70´5 mm were immersed in the solution and removed at the constant rate of 1 mm/sec, then held for 2 -3 h in air at room temperature to complete hydrolysis and polycondensation processes, and fired in a furnace with Silit heaters at 350, 450, or 550°C for 30 min. All measurements were performed on the side of the glass in contact with the protective gas atmosphere of the furnace during processing.The structural changes in the films were investigated with micrographs made with magnification of 100 times (MIM-8M light microscope). The refractive index n, thickness h (LEF-ZM-1 ellipsometer), and mirror-reflection coefficient R (Pulsar spectrocolorimeter) were measured. The chemical stability T was estimated by the decrease in the thickne...

Effect of technological parameters on the properties of Cuo-TiO2 sol-gel films

“…The factors which relate the viscosity with the form of the raw material used and the characteristics of the variation of the microstructure of the coatings are examined in [2]. After 42 days of storage precipitates formed in all FCS except for composition No.…”

“…The coatings heat-treated at a fixed temperature can be arranged in the following order according to the change in the confidence intervals of the distribution of the values of n, R, h, T H O 2 and T HCl (the numbers represent the number of a composition): Table 1). The numbers on the curves correspond to the composition numbers.…”