非超临界干燥法制备SiO2气凝胶

应用廉价的国产硅溶胶为原料，通过凝胶过程和干燥过程条件的选择，以非超临界干燥技术最终获得了块状SiO2气凝胶.该气凝胶外观状态与应用正硅酸乙酯为原料制得的完全一致，其微观结构也相当良好，其直径和孔分布均匀.溶液的配比和pH对凝胶过程和气凝胶样品的密度有比较明显的影响，同时pH值与SiO2的粒径之间也有一定的关系.依据制备条件的变化，所得SiO2气凝胶的密度约在200～400 kg•m－3，比表面在250～300 m2•g－1之间变化，平均孔径约为11～20 nm，而孔隙率在91％左右.

Preparation of Silica Aerogels by Non-supercritical Drying

Monolithic silica aerogels have been prepared from cheap silica sols using non supercritical drying by controlling the gelation process and drying conditions. The external appearances of the resulting aerogels are quite in accordance with those prepared by conventional supercritical drying. The microstructures of aerogels，which consist of well primary nanoparticles and pore distribution， are excellent. The compositions and pH of the solutions effectually influence the gelation process and the densities of resulting aerogels, and the variation of the particle diameters of aerogels with pH of the solutions in gelation process is obvious. On the basis of the variations of preparation conditions， the densities of aerogels are in the range of 200～400 kg•m－3， and the specific surface areas can vary from 250 m2•g－1 to 300 m2•g－1, while their average pore sizes are 11～20 nm with porosity of about 91％.