粉末和颗粒状二氧化硅气凝胶绝热材料的热导率测量

Thermal Conductivity Measurements on Granular and Powdered Silica Aerogel Insulation Materials

采用瞬态热带法在不同温度和不同压力下对粉末状及颗粒状SiO_2气凝胶的热导率进行了测量。采用低温氮气吸附法测量了样品的比表面积和介孔孔径分布。结果表明,两种被测样品的热导率随压力的变化规律相似,当压力约为1000 Pa时,热导率变化曲线会出现转折,当p>1000 Pa时,热导率随压力的降低而减少缓慢,当p<1000 Pa时,热导率下降很快。样品的热导率随环境温度的增加而显著增加,温度一定时,随平均孔尺寸的增大而增大。误差分析表明采用瞬态热带法测量时室温下的误差在3%以内。

The transient hot-strip method was used to measure the thermal conductivity of granular and powdered silica aerogel materials at different temperatures and pressures. The low-temperature nitrogen adsorption method was used to measure the specific surface area and mesoporous pore size distribution of the samples. The results show that The measured samples demonstrated similar patterns in thermal conductivity as gas pressure decreased. A turning point exists at approximately 1000 Pa with the thermal conductivity first declining slowly when p 〉 1000 Pa, than with an accelerated decline once p 〈 1000 Pa. The thermal conductivity of the measured granular and powdered silica aerogels distinctly increased with increasing temperature. Silica aerogel samples with larger macropores achieved greater thermal conductivity at elevated temperatures. The uncertainty analysis shows that the measurement error of THW method is within 3% at room temperature.