Textural characteristics of silica aerogels from SAXS experiments

Small angle X-ray scattering measurements on silica aerogels give systematically low values for the solid phase density. In order to explain these results, a hierarchical structure is proposed. Textural parameters such as specific surface area, size and density of clusters, and pore size are a function of the number of levels in the structure. Experimental values are consistent with values calculated for a hierarchy of two to four levels, depending on the initial sol concentration. The model can explain the fractal features for lower density aerogels.