常压下低折射率纳米多孔二氧化硅薄膜的制备

以正硅酸乙酯(TEOS)为有机醇盐前驱体,采用溶胶-凝胶技术,通过酸/碱二步法控制实验条件,结合低表面张力溶剂替换以及甲基非活性基团置换修饰、超声振荡等,在常压下成功地制备出折射率在1.11～1.27范围内的二氧化硅纳米多孔光学薄膜。制备过程中充分注意到稀释、老化、有机修饰表面、热处理和提拉条件对薄膜都有很大的影响,利用这些因素可以对该纳米薄膜的孔洞率、折射率进行控制,尤其是能制备低折射率薄膜,从而为该薄膜的应用开发奠定基础。采用椭偏仪测量薄膜的厚度和折射率,薄膜中高的孔洞率、低的折射率归结于最终干燥阶段中的弹性回跳。扫描电镜(SEM)观察发现修饰薄膜的表面形貌具有明显的多孔结构。耐磨实验表明所制备的薄膜有良好的机械性能。

Preparation of Nano-porous Silica Films with Low Refractive Index at Ambient Pressure

Nano-porous silica optical films with refractive indices in the range of 1. 11 - 1. 27 have been prepared at ambient pressure by a sol-gel technique. Silicate sols were prepared from tetraethoxysilane(TEOS) dissolved in ethanol using a two-step acid/base catalyzed synthetic method and the exchange of solvent and modification of -CH3 group etc. The process was optimized by varying the dilution, aging, organic modification,heat treatment and dip-coating conditions to lower refractive index for development application. It is observed that the high porosity, low refractive index in these films is mainly attributable to dilation or 'springback' of the film during the final stage of drying. Ellipsometry was used to determine the refractive index and thickness of the films. The microstructure of nano-porous optical films with low refractive index is tested using SEM. The mechanical intensity is also tested.