The influence of thermal treatment on the microstructure and thermal insulation performance of silica aerogels
The influence of thermal treatment on the microstructure and thermal insulation performance of silica aerogels
复制标题
热处理对二氧化硅气凝胶微观结构和隔热性能的影响
DOI：
10.1016/j.jnoncrysol.2017.05.020
复制
发表时间：
2017-08-15
影响因子：
3.5
通讯作者：
Cao, Bin
中科院分区：
文献类型：
--
作者：
Lei, Yaofei;Chen, Xiaohong;Cao, Bin
本研究通过对制备的二氧化硅气凝胶进行热处理，减少气凝胶中的大孔，从而提高气凝胶的隔热性能。实验结果表明，经800 ℃热处理后，SiO2气凝胶的孔径略有减小，大孔体积分数从63.05%急剧下降到24.82%。热导率不随密度的增加而增加，但从未经热处理的样品的0.0090 W/（mK）降低到400 ℃处理的气凝胶的0.0080 W/（mK）。其原因是气凝胶中大孔的减少导致对气体传热的限制程度增强，通过两个模型的理论计算证明了这一点。然而，导热系数急剧攀升至0.030 W/（mK）后，800 ℃，由于孔结构被破坏，固体传热得到显着增强，这是由理论计算证实。研究表明，对所制备的气凝胶进行适当的高温处理，可以提高二氧化硅气凝胶的隔热性能和室温使用性能。
In this work, thermal treatment to the as-prepared silica aerogels was explored as a strategy to reduce the macropores in aerogels, thus to improve the thermal insulation performance. The experimental results show that the pore size exhibits a slight shift to the value lower than the pore size of no-heat-treated silica aerogels and the macropore volume fraction experiences sharp decline from 63.05 to 24.82% after thermal treatment at 800 degrees C. The thermal conductivity doesn't increase with the enhancement of density but decreases from 0.0090 W/(mK) for the no-heat-treated sample to 0.0080 W/(mK) for the 400 degrees C-treated aerogels. The reason is that the reduction of macropores results in the restriction degree of gaseous thermal transfer being enhanced in aerogels, which is proved through theoretical calculation by two models. However, the thermal conductivity dramatically climbs to 0.030 W/(mK) after 800 degrees C owing to the pore structures being damaged and solid heat transfer gets significantly enhanced, which is confirmed by the theoretical calculation. This study suggests that appropriate high-temperature treatment to the as-prepared aerogels could improve the thermal insulation performance and the usability of silica aerogels at room temperature.