以正硅酸乙酯(TEOS)及异丙醇(IPA)为原料, 以六甲基二硅胺烷(HMDZ)、三甲基氯硅烷(TMCS)为改性剂, 采用溶胶-凝胶法、衍生法及超临界干燥工艺, 制备了疏水SiO2气凝胶;采用SEM、IR、XRD及TG等对其进行了表征。结果表明: 两种表面改性剂改性前后获得的SiO2疏水气凝胶均含有非晶态SiO2相, 均由Si-O-Si所组成的纳米多孔连续三维网络骨架结构构成, 骨架平均直径为3 nm;改性后的SiO2气凝胶在450 ℃前几乎没有质量损失, 450～600 ℃内, TMCS和HMDZ改性的SiO2气凝胶质量损失分别约为17%和9.21%;TMCS改性后的SiO2气凝胶密度由改性前的0.192 g·cm-3减至0.149 g·cm-3, 比孔体积由改性前的4.70 cm3·g-1增至6.19 cm3·g-1, 接触角达到了157°, 吸水率仅为1.5%;HMDZ改性后的密度为0.181 g·cm-3, 比孔体积为5.01 cm3·g-1, 接触角为120°, 吸水率达2.5%, 疏水改性效果比TMCS差。

Hydrophobic silica aerogels were prepared by tetraethoxysilane(TEOS) and isopropanol (IPA) as raw materials, hexamethyldisilazane (HMDZ) and trimethylchlorosilane(TMCS) as modifier through sol-gel method, derivatization and followed by supercritical drying process, and they were characterized by means of SEM, IR, XRD, TG and so on. The results indicate that the hydrophobic silica aerogels before and after modification both had amorphous silica phase, which consisted of nano-porous continuous three-dimensional network skeleton by Si-O-Si, and the average diameter of skeleton was 3 nm. The silica aerogels after modification virtually had no mass loss before 450 ℃. However, when temperature was increased from 450 ℃ to 600 ℃, the mass loss of the silica arogels modified by TMCS and HMDZ reached 17% and 9.21% respectively. After TMCS modification, the density of silica aerogel reduced from 0.192 g·cm-3 to 0.149 g·cm-3, porous volume increased from 4.70 cm3·g-1 to 6.19 cm3·g-1, contact angle reached 157°, and water absorption was only 1.5%. The density of silica aerogel modified by HMDZ was 0.181 g·cm-3, porous volume was 5.01 cm3·g-1, contact angle was 120°, water absorption was 2.5%, and its hydrophobic effect was lower than modified by TMCS.