Effects of Drying-control Chemical Additives on the Structure and Characteristics of Sodium Silicate-based Silica Aerogels

• Main Authors: TSAI,LI-KAI, 蔡立凱
• Other Authors: HSIEH,TAR-HWA
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/a3ucc6

碩士 === 國立高雄科技大學 === 化學工程與材料工程系 === 107 === In this study, silica aerogels (SAs) were fabricated by sol-gel process at ambient pressure drying, where sodium silicate, deionized water, ammonia hydroxide, dimethylformamide (DMF), ethanol and n-hexane as well as hexamethyldisilazane (HMDS) acted as the precursor of SA, the hydrolysis solution, the base catalyst, the drying-control chemical additives, the exchange solvent and the silylating agent, respectively. The structure and characteristics of SA was investigated by Fourier-transform infrared spectroscopy, scanning electron microscope, thermogravimetric analyzer, Brunauer-Emmett-Teller, respectively. The process parameters of hydrolysis ratio, aging temperature and DMF/Si molar ratio of SA were further discussed. Result showed that at an appropriate deionized water/sodium silicate volume ratio, the density of SA is significantly decreased. At higher aging temperature, lower density and higher porosity of SA can be prepared, which is attributed to more complete hydrogel condensation. As the DMF/Si molar ratio is 0.12, the highest surface area (884 m2/g), the lowest density (0.3432 g/cm3), the highest porosity (84.4%) and the lowest heat transfer coefficient (0.061 W/m K) can be obtained.