Tuning the properties of silica aerogels through pH controlled sol-gel processes

In this study, silica aerogels were produced by two-step sol-gel method to investigate the effect of pH on the physical, chemical and textural structure of aerogels. Tetraethyl orthosilicate (TEOS) used as a silica source. (3-aminopropyl) triethoxysilane (APTES) acted as a silica co-precursor. The quantity of sol precursors kept constant through the experiments and the pH of hydrolysis and condensation reactions were varied. As a result of the experimental studies, the optimum pH values to achieve monolithic aerogel were obtained when the pH of hydrolysis is 3 and the pH of condensation is 10. Physical, chemical and morphological characteristics of the samples were examined by performing FTIR and SEM and density analyses. Results showed that the sample SG-pH3/7 had also well-defined porous structure with homogenous pore distribution, a stable lightweight and monolithic form.