新型纳米多孔SiO_2气凝胶微球材料的制备

Synthesis of Nanoporous SiO_2 Areogel Microsphere Materials

气凝胶是由胶体粒子或高聚物分子相互聚结构成纳米多孔网络结构．并在孔隙中充满气态分散介质的一种高分散轻质固体材料。它具有密度低、孔隙率和比表面积高、孔分布均匀等特点。此外其折射率．声阻抗和热传导率都很低．吸附性能极其优良。这使得气凝胶在声阻抗耦合材料、高效高能电极、隔热保温材料、催化剂及其载体等领域有着非常广阔的应用前景。迄今为止．已经研制出了多种气凝胶如SiO2、Al2O3、TiO2、TiO2，SiO2气凝胶以及有机气凝胶和碳气凝胶等．然而目前所报道的气凝胶多为不规则的块状固体材料．在实际应用中不可避免地存在着填充不均匀或回收困难等问题．严重制约了气凝胶的使用效率和及其应用范围。气凝胶如能制成外形规则且粒径可控的微球．将极大地扩展这一功能材料在高效液相色谱填充柱（特别是应用于生物大分子的分离上）等领域的应用。

A new type of nanoporous SiO2 aerogel microsphere materials were synthesized by using SiO2 sols as raw materials in the W/O emulsion formed by the emulsification of Tween-85 and Span-80. The obtained wet gel microspheres were aged by a successive solvent exchanging of alcohol, tetraethylorthosilicate （TEOS）/ethanol solution and ethanol at 60℃, and then were dried at ambient pressure to produce SiO2 aerogel microspheres. The resultant SiO2 aerogel microspheres were characterized by SEM, TEM and nitrogen adsorption-desorption. The results show that the prepared SiO2 aerogel microspheres are nanoporous materials with coherent network nanoporous structure consisting of SiO2 nanoparticles with an average diameter of about 10 nm. The apparent density of a typical sample is 0.4 g·cm^-3, while the specific surface area is 386 m^2·g^-1, and the average pore size is 18 nm with the porosity of 84%. Various SiO2 aerogel microspheres with the apparent particle sizes of 10-200 μm can be synthesized by controlling the stirring speed at 600-2 000 r·min^-1, the volume ratio of water/oil from 0.10 to 0.30, and the weight ratio of Tween-85/Span-80 less than 0.40.