Effect on SiO2 gel for optical fiber preform by hydrochloric acid and formamide in sol-gel method

To prepare SiO₂ gel for optical fiber perform which has higher transparency and better crack control, adopting sol-gel method, tetraethoxysilane(TEOS) as raw material, ethanol alcohol and water as solvents. To study on the main effects on SiO₂ gel by hydrochloric acid(HCl) and formamide, XRD, SEM and electron spectrometer were adopted to test and analyze gel microstructure, chemical bond, phase structure and purity. To develop transparency and crack control as, choose and test gel from many experiment projects is chose and tested, and the result indicates that the microstructure is amorphous of which main element are Si and O. The experiment shows that there is delamination at 90°C, if hydrochloric acid is added less. However, delamination disappear and time of making gel reduces with more hydrochloric acid. There is yellow substance appears with a fixed quantify of hydrochloric acid. Tested by electron spectrometer,The less hydrochloric acid, the higher gel purity is obtained. AsTEOS: alcohol: water: HCl = 1: 4: 8: a, gel purity which is 98.6% is the highest.From SEM, with more formamide gel surface levels off, crack control reduce obviously, while the gel purity decreases. Therefore, TEOS: ethanol: water: HCl: CH₃NO = 1: 4: 8: a :b is taken as best project.