核壳结构遮光剂对SiO_2气凝胶辐射传热的影响

Investigation on the Influence of Core/Shell Opacifiers on the Radiative Heat Transfer of Silica Aerogels

纯SiO_2气凝胶在波长小于8μm范围内几乎透明,加入一定量的遮光剂可以有效抑制辐射传热从而提高气凝胶的高温隔热性能。本文根据分层Mie散射理论和扩散近似理论,研究了不同种类核壳结构的遮光剂如SiO_2、SiC、炭黑(Carbon)空心球结构和Carbon/SiO_2和Carbon/SiC双层球结构的遮光特性和遮光剂掺杂气凝胶的辐射热导率,研究表明:空心结构遮光剂在对遮光性能影响不大的情况下,可以极大的降低遮光剂-气凝胶复合材料的密度;Carbon/SiC遮光剂的遮光性能与纯炭黑相当,可应用于高温隔热材料中。本研究对新型遮光剂的设计以及气凝胶复合材料性能的优化具有重要的指导意义。

Pure silica aerogels are nearly transparent to the electromagnetic wave at wavelength below 8 μm. Doping opacifiers into silica aerogels can reduce the infrared radiative transfer and improve the insulation performance at high temperature. In this work, the extinction performance of different kind of core/shell opacifiers, including hollow spheres and core/shell opacifiers with core of carbon black, and the radiaive thermal conductivity of opacifiers-loaded silica aerogels are invsetigated based on the coated Mie-theory and Rossland diffusion approximation. The results show that the hollow opacifiers could greatly reduce the densities of the opacifier-loaded silica aerogels without deteriorating appreciably their insulating capability. The carbon/SiC opacifier exhibits excllent extinction performance as homogeneous solid carbon opacifier, which should be a promising opacifier for silica aerogels at high temperature. The results of this paper present important references for the process design and improvement of comprehensive performance of opacifier-loaded silica aerogels.