介孔SiO_2气凝胶的常压干燥制备研究

Synthesis of Mesoporous Silica Aerogels via Ambient Pressure Drying

以廉价的水玻璃为硅源,用乙醇(EtOH)/三甲基氯硅烷(TMCS)/庚烷(Heptane)溶液对湿凝胶进行改性,采用一种新的常压干燥工艺合成了SiO2气凝胶。通过TMCS与乙醇、湿凝胶孔隙水及Si-OH基团之间的反应,使湿凝胶的溶剂交换和表面改性得以在一步完成。所合成的SiO2气凝胶为轻质透明的块状固体,密度为0.128￣0.136g·cm-3,孔隙率93.8%￣94.2%。利用FTIR、SEM、TEM和BET吸附对气凝胶的微观结构、形貌和性质进行了研究。结果表明,气凝胶为海绵状结构,粒子直径和孔径分布均匀,比表面积559￣618m2·g-1,表面带有较多的Si-CH3基团,呈现出明显的疏水性。

Using cheap waterglass as silica source, silica aerogels were synthesized via a novel fast ambient drying by using EtOH/TMCS/Heptane solution for modification of the wet gel. One-step solvent exchange and surface modification of wet gel were accomplished by reaction of trimethylchlorosilane （TMCS） with ethanol, pore water and Si-OH group in the wet gel. The synthesized silica aerogel was a light and crack-free solid, with a density of 0.128～0.136 g·cm^-3 and porosity of 93.8%～94.2%. The microstructure, morphology and properties of the aerogels were studied by FTIR, SEM, TEM and BET measurement. The results indicate that silica aerogels exhibit a sponge structure with narrow particle and pore size distribution. The specific surface area of silica aerogels is in the range of 559～618m^2·g^-1. Strong hydrophobicity is the characteristics of silica aerogel, and there is obvious Si-CH3 group on the surface of silica aerogel.