利用表面活性剂量改变孔洞率制备的纳米多孔SiO_2膜(英文)

Preparation of nanoporous silica films with varying porosity by manipulating the amount of surfactant

采用表面活性剂十六烷基三甲基溴化氨(CTAB)为模板剂,在酸性条件下产生多孔结构,再经热处理去除CTAB。实验中使用溶胶?凝胶技术,正硅酸乙酯(TEOS)为硅源,以及二次去离子水,盐酸为催化剂等原料,利用表面活性剂与硅源水解后形成的聚集体相互作用,在溶液中形成分子自组装体,制备前驱体溶胶。通过简单提拉迅速蒸发溶剂制备纳米多孔或纳米介孔SiO2薄膜,分析和研究了表面活性剂浓度对纳米多孔SiO2薄膜的结构和孔洞率的影响,通过操纵表面活性剂的含量,能控制薄膜的纳米结构、孔洞率、孔大小和孔的形态以及膜的形貌。小角度射线衍射、场发射透射电子显微镜、原子力显微镜显示可以制得具有六方、立方和由三维六方和简单立方组成的新相结构以及比介孔大的纳米多孔结构的薄膜。椭偏仪测量得到所制备薄膜的孔洞率为51.8%-65.6%,借助此孔洞率能计算薄膜的折射率和介电常数。

A surfactant Cetyltrimethyl ammonium bromide （CTAB） is used as an organic template as the structure directing agent, under acidic conditions to generate the porous structure upon removal by heat treatment. A precursor sol containing tetraethoxysilane （TEOS）, surfactant and hydrochloric acid catalyst was prepared by sol - gel process. Depositing the precursor sol on a substrate wherein evaporation of solvent and water causes the formation of nanoporous or mesoporous silica films on the substrate surface. The interaction between polymer after hydrolysis of tetraethoxysilane and surfactant was used to form molecules self- assembly in the solution by rapid solvent evaporation during dip coating. Influence of surfactant concentration on the structures and porosity of the nanoporous silica films was examined and analysed. By manipulating the amount of surfactant, nanostructure and porosity, pore size and pore shape as well as the morphology of the films could be controlled. Small angle X - ray diffraction, Field emission scanning electron microscope（TEM）, Atomic force microscopy （AFM） exhibite hexagonal, cubic and new phase composed of primitive cubic and 3 -d hexagonal （3 - dH） as well as nano - porous larger than mesoporous organizations of the films. The porosities of 51.8% -65.6% were obtained via spectroscopic el- lipsometry, which measures the refractive index of the film and the dielectric constant is calculated via porosity.