Some thermal and optical properties of a new transparent silica xerogel material with low density

Monolithic silica aerogel is a transparent material with very low thermal conductivity. These properties make the material interesting for use as insulation in, for example, windows, solar collectors, and solar walls. To produce silica aerogel it is necessary to circumvent the high capillary forces working when the solvent is being removed from the gel structure during drying. Supercritical drying has successfully achieved this. However, supercritical drying with an alcohol might be a dangerous and expensive way to produce the aerogel material. In this work we have studied a new type of monolithic silica xerogels made without supercritical drying. The xerogels are produced by strengthening the gel structure before drying, and low densities in the range 0.42 - 0.73 g/cm3 have been obtained. Properties of this new type of silica xerogels have been compared to the properties of silica aerogel made by supercritical drying. Density, pore size, surface area, thermal conductivity, and optical transmittance are reported in this work and some application advantages are discussed.