Improvement of the Silica Aerogel Strengthening Process for Scaling-up Monolithic Tile Production

Previously published results have shown that washing and aging treatments (respectively in water/ethanol and water/polyethoxydisiloxane solutions) of silica gels (synthesised from polyethoxydisiloxane precursors through HF catalysis) have permitted to significantly enhance both the wet gels permeability and mechanical properties. Unfortunately, wet gel enlargement induced severe cracks during supercritical drying. This phenomenon has been related to a pore size distribution gradient between the surface and the bulk of the gel appearing after aging of thick gels. Efforts were consequently put on the optimisation of this step. Aging in less concentrated polyethoxydisiloxane solutions has permitted to homogenize pore size distribution and has enabled us to obtain large monolithic and crack-free aerogels, remaining light and transparent. The present research is funded in part by the European Commission within the frameworks of the Non-Nuclear Energy Programme JOULE III and the Energy, Environment and Sustainable Development Programme EESD; within the frame of the respective contracts JOR3-CT97-0187 and ENK6-CT-2002-00648.