低密度纳米孔二氧化硅气凝胶的制备工艺

Fabrication of nanoporous silica aerogels with low density

以廉价水玻璃为硅源,综合运用离子交换法和溶胶凝胶法,在常压下制备出低密度的二氧化硅气凝胶;试验研究了凝胶体系pH值、干燥温度、溶剂交换和表面修饰对凝胶时间、二氧化硅气凝胶密度、孔隙率和微观结构的影响。结果表明：当凝胶体系pH值为6时,干燥工艺为50℃干燥84 h,60℃干燥72 h;采用三甲基氯硅烷（TMCS）与正己烷（n-hexane）、异丙醇（IPA）的混合溶液进行表面修饰时,所得气凝胶的密度可低至0.2 g/cm^3,孔隙率可高达90.1%,孔径为20-40 nm。

The SiO2 aerogels of low density was fabricated by ion exchange and sol-gel method on the basis of sodium silicate.The effect of pH value,annealed temperature and solvent exchange process on the gel time,aerogel density,porosity and the micro-structure was studied.The results show that when the pH value is 6,the gel system is annealed at 50 ℃ for 84 h,60 ℃ for 72 h,and a mixed trimethyl chlorosilane,n-hexane and isopropyl alcohol solution is used for surface modification,the best quality of silica aerogels with low density（0.2 g/cm^3）,higher porosity（90.1%） and pore size of 20-40 nm can be obtained.4 tabs,5 figs,8 refs.