Preparation of Antireflective Silica Coating by the Sol-Gel Method for Heliothermic Power Plants

This work deals with the deposition of a thin layer of porous silica antireflective coating onto glass substrates. The films were deposited with different withdrawal speeds and heat-treated at 425°C for 30 minutes. The effects of heat treatment and film deposition rate on the films reflectance were evaluated. The diffuse reflectance was measured using ultraviolet-visible (UV-Vis) spectroscopy. Scanning electron microscopy (SEM) was used for microstructural evaluation of the films. The water contact angle upon the films surface was evaluated using a tensiometer and was based on the sessile drop technique. The mechanical characteristics of the films were evaluated by tape test and pencil hardness. The obtained sol-gel silica coatings were homogeneous and free of cracks. UV-Vis analysis of the glass substrate revealed a reflectance value of 3.86%, whereas the lowest reflectance value obtained for antireflective coatings was 2.72%. The contact angle measurement showed that, for all films, there was wetting of the film by water, characterizing them as hydrophilic. The adhesion of the films were 4B and the pencil hardness were 3H.

本研究围绕多孔二氧化硅抗反射涂层（porous silica antireflective coating）薄层在玻璃基板（glass substrates）上的沉积工艺展开。实验中采用不同提拉速率制备该涂层薄膜，并于425℃下热处理30分钟。本研究评估了热处理工艺与薄膜沉积速率对涂层薄膜反射率的影响。采用紫外-可见（ultraviolet-visible, UV-Vis）分光光度法测试了薄膜的漫反射率；采用扫描电子显微镜（scanning electron microscopy, SEM）对薄膜的微观结构进行表征分析。采用基于静滴法（sessile drop technique）的张力仪测试了薄膜表面的水接触角；通过胶带试验与铅笔硬度试验评估了薄膜的力学性能。所制备的溶胶-凝胶二氧化硅涂层均匀无裂纹。对纯玻璃基板的紫外-可见光谱分析显示其反射率为3.86%，而本研究制备的抗反射涂层的最低反射率仅为2.72%。接触角测试结果表明，所有薄膜表面均能被水润湿，表现为亲水性（hydrophilic）。薄膜的附着力等级为4B，铅笔硬度为3H。