摘要
气凝胶是一种纳米多孔高效隔热材料,但抑制高温辐射能力较差,通常添加遮光剂颗粒以提高材料的高温隔热性能。基于改进的Kramers-Krnig(KK)关系式和Mie散射理论,建立获得遮光剂颗粒复折射系数的求解模型,揭示遮光剂种类、直径对气凝胶-遮光剂复合材料的隔热影响机制。结果表明,遮光剂的添加种类、直径、体积含量对气凝胶-遮光剂复合隔热材料高温辐射特性有较大影响。高温下,SiC的最佳消光粒径为3μm。中低温下炭黑是较为理想的遮光剂;中高温下SiC和TiO2是较为理想的遮光剂。理想的遮光剂在近红外区应具有较大的复折射系数。
Silica aerogels are nanoporous super thermal insulators with a weak ability to suppress the radiation at high temperatures. Thus, mineral powers are added as opacifiers into the aerogels to minimize the radiation and improve the thermal insulating properties. This study presented a model based on Mie theory and the improved KK relation to numerically calculate the complex refractive indices of opacifiers. The results show that the type, diameter, volume fraction of opacifiers have great effects on the thermal insulation. The optimum diameter of SiC to suppress radiations is 3 ~m for higher temperatures. For lower temperatures, carbon black is the optimum opacifier while SiC and TiO2 are optimum opacifiers at higher temperatures. The optimum opacifiers must have large spectral complex refractive indices throughout the infrared region.
出处
《热科学与技术》
CAS
CSCD
北大核心
2012年第4期283-288,共6页
Journal of Thermal Science and Technology
基金
高等学校博士学科点专项科研基金资助项目(20100002110045)
关键词
气凝胶
遮光剂
复折射系数
消光系数
辐射
silica aerogel
opacifier
complex refractive index
extinction coefficient
radiation
