Modelling of hollow-fiber doping in silica aerogel composites for radiative and conductive insulation under high temperatures

Doping opacifier and fiber has been developed to improve the thermal insulation performance of silica aerogels at high tempearture. However, this will inevitably increase the density and enhance heat conduction in practical applications. In the present work, to explore a way of not only avoiding the thermal insulation compromise but also reducing the density, hollow fibers as dopants are investigated. Their radiative properties and the overall thermal insulation performance of hollow fiber-doped silica aerogel composites are numerically evaluated. In addition, the dependence of the optimal hollow ratio on the fiber diameter at different temperatures is analyzed, and the temperature-dependent optimal diameter of fibers for different hollow ratios is obtained. It is shown that the hollow-fiber-doped aerogel composite with a hollow ratio of 0.6 can present not only a low effective thermal conductivity (compared with the conventional solid fiber doped ones), but also a decrease in density by up to 11.45%, between 300 and 1300 K. The present work can illustrate the potential of hollow fiber doping towards an optimal trade-off between the density and thermal insulations of silica aerogels for high temperature circumstances and can inspire more explorations of hollow structures in silica aerogels.