Predicting the effective thermal conductivity of silica/clay mineral nanocomposite aerogels

The crucial effect of the morphology of nanocomposite aerogel on its effective thermal conductivity caused the presence of comprehensive theoretical investigation. Classic unit cell model provided an analytical relationship between microstructure and thermal conductivity of pristine silica aerogels, but the predicted results showed more than 250% deviation from the experimental results. In this work, the classic unit cell model was modified for nanocomposite aerogel by considering the effect of phonon scattering, secondary porosity, and clay mineral presence. The modified classic unit cell model (MCUM) acted as a powerful tool in the analysis of thermal conductivity mechanism of silica/clay mineral nanocomposite aerogels. Clay mineral was utilized to improve thermal radiation insulation properties of nanocomposite aerogels. Experimental results revealed that addition of 7 wt% clay mineral to silica aerogel led to a 55% reduction in thermal radiation heat transport at 700 °C. MCUM showed good agreement with experimental results with a less than 10% deviation for neat and nanocomposite aerogel.