Thermal Insulation Performance Optimization of Opacifier Doped Silica Aerogel Composites

Silica aerogel, which is a lightweight super insulation material, is transparent to the infrared radiation in the range of 3∼8 μm, making them not suitable for high-temperature thermal insulation applications (> 600 K). Embedding opacifiers into silica aerogel matrix can effectively reduce high-temperature radiation. However, heat conduction of the solid phase increases simultaneously. Here, the Mie scattering theory was used to calculate the thermal insulation performance of the opacifiers doped silica aerogel composites. The effects of the materials, particle diameter and mass fraction of the opacifiers on the thermal radiation were analyzed under different temperatures. Moreover, the genetic optimization considering both thermal radiation and heat conduction were developed to design the geometric structures of aerogel composites with minimized thermal conductivity. The results show that the opacifiers with low thermal conductivity are preferred when the ambient temperature is lower than 600 K. The opacifiers with high extinction coefficients are needed if the ambient temperature is higher than 600 K. The opacifiers with a broad size distribution enable the aerogel composites have an optimal thermal insulation performance in the environment with changing temperature. The work provides a guideline for the geometric design of aerogel composites for high-temperature thermal insulation applications. © 2021, Science Press. All right reserved.