Spectral and Texture Properties of Hydrophobic Aerogel Powders Obtained from Room Temperature Drying

Dimitar Shandurkov; Petar Ignatov; Ivanka Spassova; Stoyan Gutzov

doi:10.3390/molecules26061796

Spectral and Texture Properties of Hydrophobic Aerogel Powders Obtained from Room Temperature Drying

Molecules. 2021 Mar 23;26(6):1796. doi: 10.3390/molecules26061796.

Authors

Dimitar Shandurkov¹, Petar Ignatov¹, Ivanka Spassova², Stoyan Gutzov¹

Affiliations

¹ Faculty of Chemistry and Pharmacy, Department of Physical Chemistry, University of Sofia St. Kliment Ohridski, 1164 Sofia, Bulgaria.
² Bulgarian Academy of Sciences, Institute of General and Inorganic Chemistry, 1113 Sofia, Bulgaria.

Abstract

Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy and texture measurements based on nitrogen adsorption-desorption isotherms are combined to characterize silica aerogel granules with different degrees of hydrophobicity. The aerogels were prepared from tetraethoxysilane via a room temperature hydrolysis-gelation process, solvent exchange, hydrophobization, and drying at subcritical conditions. The dependencies between the texture properties, pore architectures, surface fractal dimensions, and degree of hydrophobicity of the samples are extracted from the ATR-IR spectra and the adsorption-desorption isotherms. The IR absorption in the region of the Si-O-Si and Si-OH vibrations is used for a description of the structural and chemical changes in aerogel powders connected with their surface hydrophobization. The Frenkel-Halsey-Hill (FHH) theory is applied to determine the surface fractal dimension of the powder species.

Keywords: IR; adsorption; aerogel; fractal dimension; sol-gel.