The structure of silica gel

[摘要] A number of different methods for studying the fine structure of silica gel have been reported in the literature. Extensive sorption-desorption studies have been made and from these studies pore size and distribution, surface area, and average particle size have been determined. Sorption-desorption studies and porosity studies have been employed also to determine the effect of heat treatment on the structure of silica gel. Small-angle x-ray scattering data have been used to determine particle sizes in silica gel. However, the assumptions which were made in the method of analysis of the small-angle x-ray scattering data are not completely justified in the case of silica gel. No investigation of the effect of heat treatment on the small-angle x-ray scattering by silica gel has been reported in the literature. The electron microscopic studies of silica gel reported in the literature are at relatively low magnifications and show the morphology of the aggregates only. No systematic electron microscopic study of the fine structure of silica gel has been reported. If the optimum magnification and resolution of modern electron microscopes is utilized, it should be possible, in a well dispersed sample of silica gel, to resolve the very small particles and pores, which sorption-desorption studies and small-angle x-ray scattering studies indicate to be present. In this investigation an electron microscopic study has been made on a series of silica gels, which had been subjected to systematic heat treatments from 30°C to 930°C. There is also included in this investigation the results of electron diffraction and small-angle x-ray scattering studies on the same series of silica gels.

[发布机构] Rice University