Enhanced thermal insulation performance of silica aerogel composites through infrared opacifier integration for high-temperature applications

The inclusion of different fillers in silica aerogels reinforced by a reticulated polyurethane skeleton, allows for the development of a strategy to obtain composites with superior characteristics. Different fillers (TiO₂, GO, SiC) and contents (0.2, 0.5 and 1.0 wt.%) were explored, analyzing their effects on the porous structures, mechanical stiffness and thermal conductivity of the composites. These exhibited low densities, reduced shrinkage, and high specific surface areas of approximately 550 m²/g. The incorporated fillers were homogeneously dispersed, leading to a general decrease in the mean pore size. Despite observing a slight reduction in the elastic modulus with respect to the non-doped composite, the benefits of this strategy are twofold; the composites can withstand strains above 80 % without breaking, significantly improving the mechanical stability when compared to non-reinforced silica aerogels, and while achieving high resilience. Additionally, enhanced thermal insulating performance was found for some materials. After analyzing the heat transfer contributions, the optimum particle contents for an improved thermal insulation were identified (1.0 wt.% TiO₂ and 0.2 wt.% SiC), leading to an effective reduction of the radiation term and reaching overall reductions of 10 and 6.5 % at 100 °C. Therefore, the silica aerogel-based composites herein produced represent a step forward in their usability and versatility for cutting-edge applications.