Monolithische, anorganisch-organische Hybridmaterialien auf Sol-Gel-Basis für die Anwendung als Wärmedämmung

Abstract

The present work shows the synthesis of porous, monolithical, organic-inorganic hybrid xerogels with low density using a sol-gel process with subsequent subcritical drying. A variety of different educts and routes of synthesis has been investigated. Using a co-gelation of TEOS (tetraethoxysilane) with the synthesized co-precursor AEGM (IUPAC: 15,15-diethoxy-3,3-dimethoxy-2,7,16-trioxa-11-aza-3,15-disilaoctadecan-9-ol) porous materials were obtained that could be dried subcritically, showing high mechanical stiffness (22,1 MPa) and a heat conductivity as low as 27 mW/(m K) at room temperature. These properties were found to be very similar to the properties of analogous hypercritically dried samples.

The characterization, e.g. with nitrogen sorption and thermal methods leads to the hypothesis that the three-dimensional network of the porous solid consists of homogeneous hybrid particles.

Additionally, pure inorganic materials have been formed by thermal decomposition of the organic fraction of the hybrid materials in oxidizing and inert atmospheres, respectively. These materials have also been characterized and show a slightly higher density compared to the hybrid materials, however, exhibiting very remarkable properties originating from the unusual combination of their temperature stability up to 400°C and mechanical stiffness.