基于疏水改性常压干燥法制备介孔块状SiO2气凝胶

Synthesis of mesoporous bulk SiO2 aerogel based on hydrophobic modification and ambient pressure drying

块状气凝胶是胶体粒子聚结、整体成型且均匀分布的多孔网络结构,可规避颗粒气凝胶掉粉掉渣、包裹成板或调成浆料再应用的缺陷.通常常压干燥获得的SiO2气凝胶多为颗粒状,因其表面含大量亲水性Si⁃OH,易与空气中水蒸气结合,导致表面张力过大而颗粒化.为解决此难题,采用三甲基氯硅烷(TMCS)疏水改性,使-Si(CH3)3取代Si⁃OH中H原子,再经常压干燥获得块状SiO2气凝胶.测得接触角为152.31°,属于超疏水材料.N2吸脱附实验测得比表面积为786 m2/g,且介孔分布变窄.热重分析其耐热温度达226℃,是良好的疏水耐温材料.

The bulk aerogel is a uniformly distributed porous network structure which is coalesced by colloidal particles and formed integrally and relatively.It can avoid the defects of the particle aerogel such as the falling off the powder and slag,wrapped board,or adjusted into a slurry.However,the SiO2 aerogel obtained by normal pressure drying is usually in the form of particle due to the combination between its hydrophilic Si⁃OH and the water molecule in the air,leading to the excessive surface tension.In order to solve above problem,trimethylchlorosilane(TMCS)was used to hydrophobic modification with the-Si(CH3)3 groups replacing the H atoms in Si⁃OH,and bulk SiO2 aerogel was obtained directly by atmospheric drying.The characterizations demonstrate that the contact angle is 152.31°,which implies that the aerogel should belong to the super⁃hydrophobic material,and the BET surface area is 786 m^2/g accompaning with narrower mesoporous distribution.Meanwhile,the thermogravimetric analysis shows that its heat resistance temperature is 226℃,further indicating that the obtained bulk aerogel is a good hydrophobic and temperature resistant material.