CO2超临界一次溶剂抽提法制备SiO2气凝胶

文中采用溶胶-凝胶法结合CO₂超临界一次溶剂抽提法制备SiO₂气凝胶。考察了干燥体系的平衡状态与CO₂+C₂H₅OH二元系的关系对溶剂抽提率及SiO₂性能的影响，并采用XRD,TG/DTA和TEM技术对样品进行了表征。结果表明，干燥体系处于CO₂+C₂H₅OH二元系亚临界区域时，溶剂抽提率随温度(40～60 ℃)变化缓慢，干燥后样品中发现有机杂质；而处于CO₂+C₂H₅OH二元系超临界区域时，溶剂抽提率高于亚临界区域，干燥后样品中未发现有机杂质，其样品近似球形，粒径在20～30 nm，具有较好的网络结构。

Experimental investigation of drying of silica aerogels by supercritical carbon dioxide

The sol-gel process and CO₂ supercritical drying technique were used to prepare silica aerogels. The relations of the equilibrium state of the drying system with the solvent extraction efficiency and SiO₂ performance were studied. The samples were characterized by TG/DTA, TEM and XRD techniques. The results show that the solvent extraction efficiency in the drying condition below the critical point of CO₂+C₂H₅OH system increases only slightly with the increase in temperature (40～60℃) and organic impurities are found after drying. While the solvent extraction efficiency in the drying condition above critical point of CO₂+C₂H₅OH system is higher than that below the critical point of CO₂+C₂H₅OH system and no organic impurities are found after drying. The aerogel particles under supercritical conditions are similar to sphericity, and the particle size is 20~30nm with good network.