Thermal and Acoustic Properties of Aerogels: Preliminary Investigation of the Influence of Granule Size

The influence of granules size in silica aerogels is experimentally investigated in terms of thermal and acoustic performance characteristics. The transmission loss (TL) is measured at normal incidence in a traditional impedance tube, whereas the thermal conductivity (λ) is evaluated using a Hot Plate apparatus, setting up an appropriate methodology, due to the nature of the sample. The results reveal that the small granules (granules size in the 0.01-1.2 mm range), which have the highest density, have the best performance both in terms of thermal and acoustic properties. Depending on the granules size, λ varies in 19-22 mW/mK range at 10 °C, whereas a TL equal to 13 dB at about 6400 Hz for 20 mm thickness is obtained for small granules.