Structure and Thermal Properties of Opacifiers-Doped SiO₂ Aerogels

SiO₂ aerogels have become the most widely used thermal insulation material due to their lightweight nature and simple preparation process. However, SiO₂ aerogels exhibit high infrared transparency, which results in a substantial amount of heat penetrating SiO₂ aerogels under high-temperature conditions, thereby reducing the thermal insulation effect. To further improve the high-temperature insulation performance of SiO₂ aerogels, this study compared the effects of several opacifiers and investigated their influence on microstructural and thermal properties of SiO₂ aerogels. The results indicated that the opacifiers-doped SiO₂ 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 SiO₂ aerogels ranged from 0.0142 to 0.0194 W/(m·K). The back temperatures of the opacifiers-doped SiO₂ aerogel were much lower than those of SiO₂ aerogels, and the back temperature of PTW-doped SiO₂ 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 SiO₂ aerogels.