Affiliation:
1. Department of Chemistry, Islamic Azad University, Tehran Science and Research Branch, Tehran, Iran
2. Iranian Space Research Center, Space Transportation Research Institute, Tehran, Iran
Abstract
In this work, response surface methodology (RSM) in combination with central composite design was employed to study the effect of independent variables on the nanoporous characteristics of silica aerogels prepared via ambient pressure drying. Different techniques such as attenuated total reflection–Fourier transform infrared, field-emission scanning electron microscopy, Brunauer–Emmett–Teller, and thermogravimetric differential thermal analyses were used to characterize the aerogel samples. The independent variables in this study were water:Na2SiO3 and trimethylchlorosilane (TMCS):Na2SiO3 volume ratio. The results showed that contemporaneous change of these factors affects the porous structure of silica aerogels considerably. Actually, when water:Na2SiO3 and TMCS:Na2SiO3 volume ratio were 6–7 and 0.8–1.4, respectively, specific surface area was maximum (∼660 m2 g−1). In addition, in this range, mean pore diameter was minimum, approximately 18 nm. Generally, the increasing water:Na2SiO3 volume ratio (to about 8), and the simultaneous increase of TMCS:Na2SiO3 volume ratio (to about 1.6), led to the decrease of mean pore diameter, while the density of the aerogels increased slightly. The combination of using low-cost precursors and ambient pressure drying method followed by applying RSM for producing silica aerogels with optimized properties is a key step toward commercializing these materials. Such a porous structure is ideal for thermal insulation applications.
Subject
Condensed Matter Physics,Ceramics and Composites
Cited by
4 articles.
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