遮光剂复合氧化硅气凝胶材料的隔热性能优化

Thermal Insulation Performance Optimization of Opacifier Doped Silica Aerogel Composites

氧化硅气凝胶是一种轻质超级隔热材料。但是纯氧化硅气凝胶对3∼8µm的红外波几乎透明,限制其高温(>600 K)隔热应用。遮光剂复合二氧化硅气凝胶可有效抑制高温辐射,但遮光剂的引入在减少辐射传热同时会增加固相导热。本文采用Mie散射理论计算了遮光剂复合气凝胶材料在高温下的隔热性能,分析了不同温度下遮光剂种类、粒径和含量对复合材料辐射特性的影响规律;并基于遗传算法设计了复合材料在不同环境温度下的最优结构。研究表明,温度低于600 K时应优先选择热导率低的遮光剂,温度高于600 K时则应选择遮光性能好的遮光剂;在多变环境下,应考虑采用宽粒径分布的遮光剂组合来优化复合材料的隔热性能。该研究对高温隔热材料的优化设计具有重要的指导意义。

Silica aerogel,which is a lightweight super insulation material,is transparent to the infrared radiation in the range of 3∼8µm,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.