Low-density Silica Aerogel Research Articles

Thermal loss coefficients of low-density silica aerogel tiles

The thermal losses of a monolithic low-density SiO 2 aerogel tile (thickness d = 9 mm, density ϱ = 80 kg/m 3) have been determined in our evacuable guarded hot plate system LOLA II. The measurements were performed for two values of boundary emissivities (ϵ ≈ 0.05 and 0.9) under variation of temperature and of gas pressure for several types of gases. From our results we conclude that low-density silica aerogel tiles about 10 mm thickness provide excellent thermal insulation with overall loss coefficients k ≲ 0.7 W/(m 2 · K) at ambient temperatures (10°C or 283 K) and pressures ≲ 10 mbar. Their use in window systems and covers for passive use of solar energy thus is extremely promising. From the change of thermal losses with gas pressure, a mean free path within the (evacuated) skeleton of about 120 nm can be derived.