Effect of an Aqueous Ammonia Solution Concentration on the Porous Structure and Properties of a Xerogel Obtained by Sol-Gel Synthesis of Silicon Dioxide

To produce a xerogel a two-stage sol-gel synthesis of silicon dioxide was carried out including acid hydrolysis of thetreathoxysilane in the presence of ethanol, followed by polycondensation of hydrolysis products. An aqueous solution of ammonia of various mass concentrations was used as a catalyst for the polycondensation reaction: 0.8, 1, 2, 3, 5%. The properties of the obtained xerogels, such as bulk density, specific surface area, particle size distribution, and porosity, have been studied. A decrease in the concentration of an aqueous ammonia solution leads to the formation of a microporous xerogel and the rise of the medium (100- 500 microns) and fine (