The Preparation Technology Control And Performances Of Anti-reflective Films On Evacuated Solar Collector Tubes

The use of solar energy can avoid environmental crisis from the fossil fuel, and meet the growing demand for energy. Solar photothermal and photoelectric technologies can provide thermal and electric energy.Evacuated solar collector tubes are the key components in solar thermal power generation, and their performances determine the heat collecting efficiency of the whole system. Anti-reflective (AR) films need to be covered on glass of evacuated solar collector tubes in order to improve efficiency of solar light. Moreover, in outdoor application of evacuated solar collector tubes, dust and pollutants attached on glass can reduce the transmittance of the glass, which require the AR films with self-cleaning function.Silicon dioxide (SiO2) film has attracted attention due to its low reflective index and low surface scattering, which could enhance the light transmittance. Therefore, SiO2is considered to be the preferred material of AR film preparation. In this thesis, SiO2films have been designed and prepared by different methods to meet the needs of high transmittance and self-cleaning properties. The contents of this thesis include the following:1. The SiO2film was prepared by electron beam evaporation. The effect of film thickness on the optical property of the film was discussed, and the optimized technology was selected in order to obtain better optical property. The result shows that the light transmittance of glass coated with SiO2film is over95%.2. The single-layer, double-layer and composite SiO2film systems were prepared by sol-gel method. Some literatures have been involved in SiO2film. In those reports, Tetraethylorthosilicate (Si(OEt)4, TEOS) was always used as precursor of SiO2sol and absolute ethanol was used as solvent. This technology was not low-cost in preparing large-area films and limited the use of such films. In the thesis, SiO2colloid solution and industrial alcohol were used to substitute TEOS and absolute ethanol, respectively, and used acid or base as catalyst. The mechanisms of different catalysts were studied theoretically. The obtained SiO2films enhance the transmittance of glass from92%to96%, and some of them have been used in solar thermal power industry.3. In order to obtain the AR film with self-cleaning property, SiO2/TiO2double-layer films were prepared using vacuum deposition. SiO2and TiO2film were prepared by electron beam evaporation and megnetron sputtering, respectively. By controlling the thickness of films and process of calcination, the bi-layer films enhance the transmittance of glass from92%to95%, and the double-layer films have superhydrophilicity and photocatalysis simultaneously.4. SiO2/TiO2double-layer films and SiO2/TiO2composite thin film were prepared via sol-gel route. The optical characters, surface morphology, component analysis and self-cleaning properties were investigated detailedly, and the optimum technology conditions were confirmed. The films can meet the practical needs.