Structural Transformations of High-Purity Xerogel SiO2 in the Temperature Range of 300–1200°C

Based on synchronous thermal analysis (TGA–DSC), the structural transformations of high-purity synthetic xerogel SiO2 is studied during heat treatment in various media (argon, air, and oxygen) in the temperature range of 300–1200°C. Chromatography–mass spectrometry and controlled combustion of the sample in a stream of oxygen show that the removal of organic components occurs predominantly in the temperature range of 400–600°C, but continues up to 1050°C. Analysis of porosity, specific surface area, apparent density, and Raman spectra show that in the range of 1000–1200°C, pores are closed and the structural network of the SiO2 xerogel is compacted with transition to a glassy state.