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

摘要

This work demonstrates the synthesis of hydrophobic silica aerogels from silicic acid with pH variations by using a costeffectiveand safe ambient pressure drying process. The work aims to evaluate the effect of pH variation on physicochemicalproperties of silica aerogels by standard techniques. In the present investigation, we have selected hexane as thesolvent and trimethylchlorosilane/hexane was used to perform the surface modification of wet gel in order to elude thecontraction and disintegration of gel association subsequent to a drying process. The effect pH on gelation in the formhydrolysis 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 confirmthe silylation (surface modification) of the prepared silica aerogel samples. Water contact angles were measured to verifythe hydrphobic behaviour of all the samples. Among the prepared pH varied samples, the sample having pH ～ 5 showsbetter results such as high optical transmittance, thermal stability, hydrophobicity and high surface area.