Table 2: Typical properties of silica aerogels.

PropertyValue

Apparent density0.03–0.35 g/cm3
Internal surface area600–1000 m2/g
% solids0.13–15%
Mean pore diameter~20 nm
Primary particle diameter2–5 nm
Refractive index1.0–1.08
Coefficient of thermal expansion 2 . 0 - 4 . 0 × 1 0 6
Dielectric constant~1.1
Sound velocity100 m/s