SiO_2气凝胶的制备与表征

PREPARATION AND CHARACTERIZATION OF SILICA AEROGEL

ＳｉＯ２气凝胶是一种低密度的纳米非晶固体材料．以正硅酸乙酯（ＴＥＯＳ）、乙醇（ＥｔＯＨ）和水为原料，以０．０１ｍｏｌ／Ｌ的硝酸为催化剂，摩尔比为ＴＥＯＳ∶ＥｔＯＨ∶Ｈ２Ｏ＝１∶５∶８，采用溶胶－凝胶法和超临界干燥技术制备了ＳｉＯ２气凝胶．首先，ＴＥＯＳ在室温下水解０．５ｈ制得醇凝胶，然后将乙醇注入醇凝胶以置换其中的水．最后将醇凝胶放入压力容器并加入适量乙醇，升温至２７０℃，压力可达１０．６ＭＰａ．采用ＸＲＤ，ＢＥＴ和ＩＲ对所得气凝胶的结构，比表面积和孔隙率进行研究．气凝胶已广泛应用于分离、绝缘和催化等领域．

The silica aerogels,a kind of nano_porous non_crystalline solids of low density, were prepared by using tetraethylorthosilicate (TEOS), ethanol (EtOH), H2O(the molar ratio: TEOS∶EtOH∶H2O=1∶5∶8) as raw materials and 0.01mol/L HNO3 as catalyst through the sol-gel process and the supercritical drying technique. The preparation procedure was as follows: firstly,the alcogels were made through hydrolysis of TEOS at room temperature for half hour,and then the alcogels were immersed in EtOH for about 2 days to replace water in the gel pores. Alcogels were dried in the supercritical condition in an autoclave and pressurized with nitrogen under a pressure of 10.6MPa, heated to 270℃. XRD, BET and IR technology were used to investigate the microstructure, the specific surface and the porosity of silica aerogels. The aerogels can be applied to the fields of separation insulation and catalysis,etc.