酸催化正硅酸乙脂溶胶-凝胶二氧化硅薄膜的制备

Preparation of Silica Films from Tetraethyl Orthosilicate Sol-Gel Process Catalyzed with Acid

针对正硅酸乙脂 (TEOS)溶胶 -凝胶工艺制备的二氧化硅凝胶薄膜在热处理过程中出现的龟裂现象 ,通过控制TEOS水解条件 ,使反应体的最初水解中间体以任意三维方向线状聚合 ,再水解时能形成线状 -粒状结构二氧化硅溶胶 .水解体系中引入的有机添加剂丙三醇与水解中间体结合后 ,改变了二氧化硅的聚集状态 ,而聚乙烯醇使二氧化硅溶胶具有无机 -有机网状结构 .通过该工艺制备的二氧化硅溶胶易于成膜 ;所形成的二氧化硅薄膜结构均匀 ,厚度可控 ,表面致密 ,其折射率为 1 5 43～ 1 5 80 ,热导率为 0 3W / (m·K) .

To refrain from cracking of the silica film prepared by tetraethyl orthosilicate (TEOS) sol gel catalyzed with acid, a new process based on two step hydrolysis procedure of TEOS with organic additives (glycerol and poly vinyl alcohol) is presented. A granular polymeric silica sol is made by the process. The glycerol controls the hydrolytic intermediate and silica aggregating, while the poly (vinyl alcohol) (PVA) makes the colloidal silica sol with co polymeric structure, which is easily filmed. The gel sillical films with a hetero structure restrains the cracking by plastic effect, while the thermal strain induces the silica films compacted. Crack free uniform silica films are fabricated, and the corresponding physical properties of these films are:refractive index 1 543～1 580,thermal conductivity 0 3W/(m·K).