New Perspectives in Science Education
Silica Aerogels: Synthesis and Experiments of a Fascinating Material for Upper Secondary School Level
Janina Dege, Department of Chemistry Education, Georg-August-University Göttingen (Germany)
Timm Wilke, Georg-August-University Göttingen, Department of Chemistry Education (Germany)
Adrian Pflugmacher, Department of Chemistry Education, Georg-August-University Göttingen (Germany)
Thomas Waitz, Department of Chemistry Didactics, Georg-August-University Göttingen (Germany)
Abstract
During the last years, material scientists have developed plenty of new materials with fascinating properties. Although a lot of these innovations do not find their way into everyday life, they hold an enormous didactic potential for chemistry education by, for example, allowing a clear insight into current research in material sciences.
Examples for these materials are silica-based aerogels, a nanoscale, mesoporous, light material. Although this material is not that new - the first successful synthesis was in 1931[1] - it is rapidly gaining in importance especially in technical applications. Reasons for this are its fascinating, exceptional physical properties such as its large surface area (500 – 1500 m2/g), high porosity (80 - 99 %), low bulk density (∼0.03 g/cm3) and extremely low thermal conductivities (0.005 W/mk).[2] Due to these properties, an aerogel has been recognized by Guiness World Records as the world lightest solid with the lowest density. In addition, it was part of NASA’s Stardust spacecraft acting as a particle-collecting substance.[3] Other applications are, for example, the use of aerogels as isolators or filters and new uses will follow.
The objective of this article is to show how silica-based aerogels can be synthesized in a school setting. Furthermore, experiments are presented which illustrate the special properties of aerogels such as their low density and their unique structure caused by the small size of nanoparticles. These experiments can also be used to learn and to discuss important contents from the curricula such as material characteristics (e.g. density and surface activity) or reaction mechanisms such as hydrolysis and condensation.
References
[1] S.S. Kistler: Coherent expanded aerogels and jellies. In: Nature, Ed. 127, 1931. [2] A. Hilonga, J.-K. Kim, P.B. Sarawade, H.T. Kim: Low-density TEOS-based silica aerogels prepared at ambient pressure using isopropanol as the preparative solvent. In: J. Alloys Compd., Ed. 487, 2009. [3] California Institute of Technology: Jet Propulsion Laboratory. http://stardust.jpl.nasa.gov/news/ news93.html [21.11.2014].
