Preparation And Characterization Of SiO₂-based Binary Films

In this work, SiO₂-CuxO and SiO₂-ZnO binary films were synthesized on Na2O-Ca O-SiO₂ glass substrates using sol-gel combining diping process. The influence of sol composition and preparation conditions on the structure and properties, including transmittance, photocatalysis, adsorption and wettability, were carefully studied. Some preliminary explanations have been given to the results. The results provide a new route to prepare new types of glasses with increased performance.The main contents and conclusions are as follows:1. Under the condition of acid catalysis, SiO₂-CuxO composite film was successfully fabricated through one-step sol-gel by adding the copper acetate directly into the silica sol. The results show that when the film prepared with the addition of 45 ml ethanol, copper to hydrochloric acid molar ratio of 1.2 and the drying time less than 2 h was crack-free. The amount of TEOS has a great influence on the scratch-resistance of the composite film, while the amounts of copper acetate and hydrochloric acid have a little effect. The amount of copper acetate and TEOS has a big effect on transmittance of the films. With the increase copper acetate, the transmittance of the coated glass becomes lower, and the short wave absorption edge shifts to a longer wavelength and the forbidden band gap decreases. An opposite trend is observed in the case of the variation of TEOS. The photocatalytic performance of the SiO₂-CuxO is poor, while the adsorption towards methylene blue performance is good. And the absorption efficiency increases with increasing copper acetate. The heat treatment temperature affects the adsorption capacity of the composite film. When the temperature is increased to 450, 500 degrees, the adsorption efficiency of methylene blue is greatly increased and the adsorption capacity is regenerative. The film also shows antimicrobial performance. When the copper salt dosage is 1 mol/L, the film can kill Escherichia Coli in 90 min.2. SiO₂-CuxO?where x=0,1,2?composite films were prepared under the catalysis of ammonia. The reults show that PVP can prevent the coagulation of the composite sol. With the increase of aging time, the film becomes dense and the shrinkage reduces. With the increase of the concentration of the copper salt, copper nanoparticles appear in the film and the crystalline phases and the particle size increase. In contrast, the Light transmittance and the forbidden band gap decrease. When the copper salt concentration is 1 mol/L, the forbidden band gap of the composite film is 1.5 e V. In the mean time, the adsorption and photocatalytic efficiency toward methylene blue as well as the antibacterial performance of the film is improved. The crystalline phases in the composite film vary witht he heat treatment temperature. The valence variation of the copper ions through reduction and oxidation are discussed. The transmittance of visible light of the film treated at 250 and 300 oC is low, but high for the infrared light. The adsorption and photocatalytic efficiency of the film treated at 500 oC toward methylene blue solution is highest and is regenerable.3. Silica sol was synthesized through the hydrolysis and condensation of MTES. Under the protection of PVP, copper salt was added into the sol to prepare SiO₂-CuxO composite film. The contact angle of water on the surface of the film is close to 90 o. Copper and cuprous oxide phase were found in the SiO₂-CuxO composite film, which can hinder the transimission of visible light below 420 nm, contributing to its brown color. And film also has a certain antibacterial performance. On the base of the film, a SiO₂-CuxO composite film with a water contacting angle up to128 o was prepared by adding TEOS and HMDS.4. SiO₂-ZnO composite film was prepared by the catalysis of ammonia. XRD and SEM results show that the film contains ball- and rod-shaped zinc oxide nanoparticles. The size of particles increases with the sol aging time, instead, its content decreases. Increasing the concentration of zinc acetate prevents the formations of the cracks in the film, increase the transmittance and photocatalytic efficiency of the coated glass.5. SiO₂-ZnO composite films were prepareed by the co-hydrolysis and co-condensation of TEOS and MTES with HMDS as hydrophobic agent. The effects of heat treatment temperature, and MTES, TEOS, HMDS on the cracking, wettability and transmittance of the composite film were studied. The results show the contact angle of water on the film surface is reduced with the increase of the heat treatment temperature. The contact Angle of films treated 200 and 500 oC are 78 o and 0o, respectively. MTES can be used as both the precursor generating the silica film and the water repellent agent providing methy group. The results show that the film crack more when the the dosage of MTES increases and the contact angle first increases and then decrease. When the dosage of MTES is 4.8 ml, the contact angle of water on the film is 105 o. The increase of TEOS can inhibit the film cracking, and the contact angle first increases and then decreases. The amount of HMDS has little effect on the cracking, however, reducing the HMDS dosage can reduce the contact angle. With the increase of heat treatment temperature and the dosage of MTES, TEOS and HMDS, the light transmittance of the composite films decreases.