Production of transparent metal oxide (eg silica) aerogels by a two-stage process with the gel stage accelerated by the introduction of carbon dioxide

摘要

The 2-stage production of a metal oxide aerogel using a first stage as per WO9203378 is accelerated by using super-critical CO2 during the gelling process. Production of a metal oxide aereogel comprises (a) catalysing a metal alkoxide in presence of a sub-stoichiometric amount of water and sufficient solvent to give a a liquid phase; (b) adding water up to the stoichiometric amount and a solvent so as to give the desired density; (c) treating the mixture in the pressure vessel with CO2; (d) reacting at 20-150 deg C and at the CO2-imposed pressure to give a metal oxide gel; and (e) ageing the mixture for /-1 (especially 8-12) hours at the reaction temperature without moving the pressure vessel.