疏水性SiO2气凝胶常压干燥制备与表征

以正硅酸乙酯(TEOS)为硅源,以NH4F为催化剂,实现了纳米多孔SiO2气凝胶材料的常压干燥制备,采用三甲基氯硅烷(TMCS)进行疏水改性,以减少样品在使用过程中的收缩和塌陷.结果表明:TMCS疏水改性的SiO2气凝胶样品的表观密度为0.191 g/cm3,导热系数为0.031 W/(m· K),比表面积为667 m2/g.SEM和TEM的测试结果表明,所得样品为纳米介孔材料.接触角的测定分析表明,TMCS疏水改性的SiO2气凝胶样品与水的接触角为147°,表现出良好的疏水性.400 ℃热处理后,气凝胶因失去大量的甲基基团,由疏水性变为亲水性.

Preparation and Characterization of Hydrophobic SiO2 Aerogel via Ambient Pressure Drying

Nano-porous hydrophobic SiO2aerogels were prepared via ambient pressure drying method with tetraethoxysilane(TEOS)as precursor and ammonium fluoride(NH4F)as catalyst.TMCS was used as hydrophobic modifiers,so as to reduce shrinkage and collapsing of the sample during of the application. The results show that the bulk density,thermal conductivity and specific surface area of TMCS modified SiO2aerogels are 0.191 g/cm3, 0.031 W/(m· K)and 667 m2/g, respectively.The experimental results of SEM and TEM show that SiO2aerogels have amorphous nano-mesoporous structure.The results of contact angle test prove that the contact angle of TMCS modified SiO2aerogels could reach 147°,so it shows good hydrophobicity.After heat treatment at 400℃,the aerogel becomes hydrophilic because it is lost most of its hydrophobic groups(-CH3).