Improving the properties of flexible hybrid-silica aerogels

Abstract

Silica aerogels with their remarkable properties such as low density and thermal conductivity are prime candidates for a wide range of different applications, such as insulation materials in aviation. While pure silica aerogels are very brittle and difficult to handle, adapting the sol-gel process can result in organic-inorganic hybrid-materials with a high mechanical flexibility, a good hydrophobicity while still retaining a sufficient insulating performance. They were first investigated by Hayase et al. [1] and are based on methyltrimethoxysilane (MTMS) and dimethoxydimethylsilane (DMDMS). For further improvement of the material s properties, the synthesis needs to be tuned. Starting with recipes filed for patenting by the German Aerospace Center (DLR) [2], the synthesis route was first investigated towards varying precursors and their ratios, using different solvents and mixtures, as well as testing a wide range of surfactants and catalysts. Mechanical, thermal, chemical and morphological properties of the samples were investigated. After further polymeric crosslinking the metal-oxygen bonds can be partially substituted by the more lightweight carbon-backbone, while retaining the flexibility of the material. Therefore, investigations using a consistent precursor system of MTMS and dimethoxymethylvinylsilane (DMMVS) are carried out. The above-mentioned properties are required in the field of aviation, and the resulting aerogels can possibly outperform the state-of-the-art compressed fiberglass-mats.