Preparation of Silica Films from Tetraethyl Orthosilicate Sol-Gel Process Catalyzed with Acid
Yin Mingzhi,Yao Xi,Li Zhenrong ,Zhang Liangying (Electrenic Materials Research Laboratory, Xi′an Jiaotong University, Xi′an 710049, China)
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).