Heat transfer mechanism of TiO2-doped silica aerogel

The remarkable thermal insulation properties of silica aerogel stem from its distinctive three-dimensional nanonetwork structure, rendering it a promising candidate for diverse applications such as energy-efficient construction and aerospace engineering, among others. Nonetheless, the application of pure silica aerogels at high temperatures is limited due to their nearly transparent nature in the wavelength range of 2-8 mu m. To overcome this limitation, the incorporation of opacifiers into pure silica aerogels can effectively augment the overall extinction coefficient of the material, consequently minimizing radiative heat transfer. In this paper, titanium dioxide is used to improve the high-temperature thermal insulation performance of silica aerogels. In order to fully understand the internal heat transfer properties of silica aerogel-based composites theoretically and to provide guidance for the structural design of high-temperature insulation materials, a theoretical model is established. This model accounts for the actual microstructure of the materials as well as the porous structural properties of the secondary particles in silica aerogel. Furthermore, it considers the intricate nature of heat transfer in multiphase hybrid materials. This paper compares the predictions of the model with experimental data. The results show that the theoretical model can quickly and accurately predict the thermal conductivity of TiO2-doped silica aerogels, and the error is controlled within 8 %, with a minimum error of 1.1 %.