Structural, out-gassing and nanomechanical properties of super-hydrophobic transparent silica aerogels developed by ambient pressure drying for space application

Abstract

Transparent super-hydrophobic monolithic silica aerogels are prepared by the cost-effective ambient pressure drying. The drying of aerogel is performed at various temperatures ranging from 25 to 200°C. Oxidation states of different silica aerogels are investigated by XPS which shows the presence of both SiO and SiO2 phases. Thermal stability of hydrophobic aerogel is found as ~320°C investigated by TGA and DSC. The chemical bonds (i.e., –CH3) responsible for the hydrophobic (WCA > 170°) nature of synthesized silica aerogels are identified by FTIR. Further, out-gassing properties of the silica aerogels have been investigated and they are found in limit for the space application. The highest hardness and Young’s modulus are measured by the nanoindentation technique for the aerogel dried at 120°C which has higher density, while density decreases for the aerogel dried at 200°C and the corresponding nanomechanical properties are found to be lowest as expected.