Structure and Thermal Properties of Opacifiers‐Doped SiO ₂ Aerogels

ABSTRACT SiO ₂ aerogels have become the most widely used thermal insulation material due to their lightweight nature and simple preparation process. However, SiO ₂ aerogels exhibit high infrared transparency, which results in a substantial amount of heat penetrating SiO ₂ aerogels under high‐temperature conditions, thereby reducing the thermal insulation effect. To further improve the high‐temperature insulation performance of SiO ₂ aerogels, this study compared the effects of several opacifiers and investigated their influence on microstructural and thermal properties of SiO ₂ aerogels. The results indicated that the opacifiers‐doped SiO ₂ aerogels still maintained a nano‐network structure and high specific surface area. Moreover, the stable crystal structure of opacifiers contributed to excellent high‐temperature thermal stability. The thermal conductivities of the opacifiers‐doped SiO ₂ aerogels ranged from 0.0142 to 0.0194 W/(m·K). The back temperatures of the opacifiers‐doped SiO ₂ aerogel were much lower than those of SiO ₂ aerogels, and the back temperature of PTW‐doped SiO ₂ aerogel could be reduced by as much as 394°C. Therefore, opacifiers with strong infrared scattering capability significantly improved the high‐temperature insulation performance of the SiO ₂ aerogels.