Physicochemical properties of ambient pressure dried surface modified silica aerogels: effect of pH variation

This work demonstrates the synthesis of hydrophobic silica aerogels from silicic acid with pH variations by using a cost-effective and safe ambient pressure drying process. The work aims to evaluate the effect of pH variation on physicochemical properties of silica aerogels by standard techniques. In the present investigation, we have selected hexane as the solvent and trimethylchlorosilane/hexane was used to perform the surface modification of wet gel in order to elude the contraction and disintegration of gel association subsequent to a drying process. The effect pH on gelation in the form hydrolysis and condensation as well as on amorphous structure, physical properties such as density, thermal stability, surface area, pore-volume, pore radius, optical transmittance were investigated. FTIR spectroscopy was used to confirm the silylation (surface modification) of the prepared silica aerogel samples. Water contact angles were measured to verify the hydrphobic behaviour of all the samples. Among the prepared pH varied samples, the sample having pH similar to 5 shows better results such as high optical transmittance, thermal stability, hydrophobicity and high surface area.