THERMAL TRANSPORT IN ORGANIC AND OPACIFIED SILICA MONOLITHIC AEROGELS

The thermal properties of monolithic aerogels were investigated by changing their density, the gas pressure and the temperature. Results show that opacified SiO2-aerogels and organic aerogels at room temperature in air have a total thermal conductivity as low as 0.013 W/m K and 0.012 W/m K, respectively, and show a flat minimum on variation of density. Aerogels have a very low solid thermal conductivity due to their extremely high porosity. Nanosize pores are responsible for partial suppression of gaseous conduction. A low radiative conductivity caused mainly by absorption is observed for organic aerogels. In the case of SiO2-aerogels, the radiative transport can be reduced by integrating an opacifier such as carbon black in the SiO2-skeleton.