遮光剂对气凝胶复合材料隔热性能的影响

纯气凝胶对近红外波长几乎透明，遮光剂的加入可以显著抑制气凝胶的高温辐射性能。采用Mie散射理论计算出掺杂不同种类、粒径遮光剂时复合气凝胶的平均消光系数，从而比较它们的遮光效果。采用基于瞬态平面热源法的Hot Disk TPS2500S导热仪测量了不同温度下复合气凝胶的热导率，获得了遮光剂对气凝胶复合材料隔热性能的影响规律，并与理论分析结果进行了对比。理论计算获得的不同温度下复合气凝胶的热导率与实验值符合良好，表明：在研究的范围内，掺杂的最佳遮光剂粒径在3.5 μm左右；SiC的遮光效果比TiO₂、ZrO₂好；存在一个最佳的遮光剂体积含量（3.75%左右）使得复合气凝胶的整体隔热性能最好；所建立的理论模型可用来预测掺杂遮光剂的影响规律。

Influence of opacifiers on thermal insulation properties of composite aerogels

Aerogels are almost transparent to the near-infrared wavelengths, and therefore the opacifiers are widely doped to enhance aerogels insulation performances. Mie scattering theory was employed to calculate the mean extinction coefficient of composite aerogels doped with different kinds of opacifiers with different diameters and their shading effects were compared. A Hot Disk TPS2500S thermal analyzer based on the transient plane source method was used to measure the thermal conductivity of composite aerogels at different temperature and comparison with the theoretical analysis was conducted. The predicted thermal conductivities by theoretical model are in good agreement with the experimental data obtained by the Hot Disk thermal analyzer at different temperature. The results show that the optimal diameter of doped opacifiers is approximately at 3.5 μm, the shading effect of SiC opacifier is better than that of TiO₂ and ZrO₂, and there exists an optimal volume content of opacifiers (~3.75%) making the overall thermal insulation performance best. The developed theoretical model can be adopted to predict the influence of doped opacifiers on the effective thermal conductivity of composite aerogels.