Synthesis of Porous Inorganic Materials from Sol-Gel Precursors by Cryochemical Sublimation

Abstract

This paper reports on the results of investigations into the synthesis of consolidated porous materials from sol-gel precursors based on gel-forming aqueous solutions of silicates in the R2O · nSiO2 system (where R2O is Na2O · K2O). Cryochemical sublimation is used as a technological tool for preparing a porous structure. The sublimated material is studied using scanning electron microscopy, X-ray spectral microanalysis, and mercury porosimetry. It is demonstrated that the samples synthesized are characterized by a density of approximately equal to 0.5 g/cm3, a developed biporous structure with 1- to 15-µm pores, and a chemically homogeneous network. Comparative differential thermal analysis of the sublimated product and the xerogel prepared by traditional stepwise heat treatment in the temperature range 60–100°C shows that there are substantial differences in the dynamics and character of the physicochemical transformations in the temperature range 20–800°C. The results of X-ray powder diffraction analysis indicate that the sublimated composite has an X-ray amorphous structure.