Antireflective and Self-Cleaning Properties of SiO 2 -MgF 2 /TiO 2 Double-Layer Films Prepared by Sol-Gel Method at Low
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Antireflective and Self-Cleaning Properties of SiO2-MgF2/TiO2 Double-Layer Films Prepared by Sol-Gel Method at Low Calcination Temperature Hung-Chou Liao1; Sheng-Min Yu 1; Wen-Ching Sun1; Wan-Ying Chou1; Shou-Yi Ho1; Tzu-Yu Wang 2; Wei-Jen Lu2; Li-Fang Lu2 1 Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Rd., Chutung, Hsinchu, Taiwan 310, R.O.C. 2 JM Material Technology Inc, O. 5F.-3, No.40-2, Sec.1, Minsheng N.Rd.,Guishan Township, Taoyuan County, Taiwan 333, R.O.C. ABSTRACT SiO2-MgF2/TiO2 double-layer films with antireflective, self-cleaning and adherent properties were prepared by spin-coating SiO2-MgF2 and TiO2 sol on glass substrate successively and subsequently being calcined at 250°C. The optical and structural properties of films have been investigated by visible spectrophotometer and field emission scanning electron microscope, respectively. At the same time, self-cleaning property generated from superhydrophilicity and photocatalysis was obtained. The results indicated that the as-prepared SiO2-MgF2/TiO2 double-layer films show a maximum increase in transmittance near 520 nm wavelength of 2.8% and photocatalytic property with the R value of 4.7(JIS R 1703–2).It has been demonstrated that high transmittance, self-cleaning and adherent composite has been obtained by a simple sol–gel route presenting good potential to be applied on photovoltaics systems. INTRODUCTION Glass coatings have been studied and currently employed since the second half of the 20th century. Coatings can modify the surface properties of glass, such as transmittance (antireflective coatings) and glass maintenance (self-cleaning coatings). During the last years the development of novel anti-reflection sol–gel coatings has recently attracted great interest, mainly due to their relatively low cost and to their potential application on a variety of commercial purposes [1-4]. In order to shift the reflectance to a minimum value, a fine control of the coating thickness and refractive index is required [5]. The most common approach is using a nanoporous coating to produce graded refractive index coatings [6]. In order to prevent scattering, homogenous pore distribution, pore size noticeably smaller than the wavelength of light (i.e., mesoporosity: 2–50 nm), and nanometric particle sizes are required. Sol–gel processes [7, 8] or use of removable templates [9] have shown to be suitable synthetic routes to prepare antireflective (AR) coatings that satisfy the later requirements. Due to the increasing demand of more competitive technologies a coating with only anti-reflection capacity will present a limited use. The incorporation of additional properties, such as self-cleaning (SC), energy-saving, anti-adhesion or UV-cutting, would greatly facilitate the application of these multifunctional coatings in the areas of architectural glass, glazing materials for solar collectors and so on. In fact, some recent research works consolidate the interest and feasibility of the elaboration of multifunctional coatings. Multifunctional coati
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