工程科学学报，第41卷，第6期：788-796,2019年6月 Chinese Journal of Engineering,Vol.41,No.6:788-796,June 2019 DOI:10.13374/j.issn2095-9389.2019.06.011:http://journals.ustb.edu.cn 纳米隔热材料的孔隙结构特征与气体热传输特性 杨海龙四，胡子君，孙陈诚，胡胜泊，杨景兴 航天材料及工艺研究所先进功能复合材料技术重点实验室，北京100076 ☒通信作者，E-mail:hl20032003@126.com 摘要为研究纳米隔热材料孔隙结构内部的气体热传输特性，采用溶胶一凝胶工艺结合超临界干燥技术，制备了一系列具 有不同孔隙结构特征的样品，通过热导率、氮气吸一脱附和真密度测试，全面、准确获取了其孔隙结构信息，并专门、系统研究 了孔隙结构特征与气体热传输特性之间的关系.研究结果表明：与气相贡献热导率相对应，材料具有双尺度孔隙结构特征，并 且当大孔隙尺度不及小孔隙的10倍时，可进一步等效为单尺度孔隙.考虑气固耦合传热的本征气相贡献热导率随孔隙尺度 的增大而升高，与气相热导率变化类似且成一定的比例关系，孔隙尺度小于200m和大于500nm时的比例系数分别为2.0和 1.5,200~500nm时则为2.0-1.5.当大、小孔隙尺度的比值不超过10时，或者这一比值为100-1000且大孔隙含量低于 10%时，气相贡献热导率随环境气压的降低依次呈现快速下降、缓慢下降和无变化三个阶段：当这一比值超过3000时，即使大 孔隙含量很低（不超过10%），气相贡献热导率也会依次呈现快速下降、缓慢下降、快速下降和无变化四个阶段. 关键词纳米隔热材料；气相贡献热导率：气相热导率：孔隙结构：等效孔径 分类号TB34 Pore structure of nano-porous thermal insulating materials and thermal transport via gas phase in their pores YANG Hai-ong,HU Zijun,SUN Chen-cheng,HU Sheng-bo,YANG Jing-xing Science and Technology on Advanced Functional Composites Laboratory,Aerospace Research Institute of Materials Processing Technology,Beijing 100076,China Corresponding author,E-mail:yhl20032003@126.com ABSTRACT The thermal insulation properties of nano-porous thermal insulating materials largely depend on thermal transport via gas phase within their pores,and this process relies on their pore structures.Therefore,investigating pore structures and thermal transport via gas phase is important to understand the heat transfer mechanism.Current research mainly focuses on the theoretical calculation and analysis from the perspective of heat transfer,and special and systematic studies based on actual materials have not been reported yet. In addition,accurate analysis of pore structures using usual techniques is difficult due to the complex pore network and the poor me- chanical properties of their solid skeleton.In this study,nano-porous thermal insulating materials with different pore structures were synthesized via a sol-gel process followed by supereritical drying.The materials were then characterized by thermal conductivity tester, nitrogen adsorption-desorption,and helium pyenometer.The pore structures of the resulting materials were obtained,and the relation- ship between pore structures and thermal transport via gas phase was studied.Results show that the bimodal distribution of pores in the resulting materials,corresponding to gas-contributed thermal conductivity.All pores within the resulting materials can be equivalent to pores with a single diameter when the equivalent size of large pores is 10 times less than that of small pores.Similar to the pure gaseous thermal conductivity,the intrinsic gas-contributed thermal conductivity including gas-solid coupling effects rises with increasing pore diameter of the materials.The ratio of intrinsic gas-contributed thermal conductivity to pure gaseous thermal conductivity is 2.0,1.5, 收稿日期：2018-06-11 基金项目：国家“973”计划资助项目(2015CB655200)工程科学学报，第 41 卷，第 6 期: 788--796，2019 年 6 月 Chinese Journal of Engineering，Vol． 41，No． 6: 788--796，June 2019 DOI: 10． 13374 /j． issn2095--9389． 2019． 06． 011; http: / /journals． ustb． edu． cn 纳米隔热材料的孔隙结构特征与气体热传输特性 杨海龙，胡子君，孙陈诚，胡胜泊，杨景兴 航天材料及工艺研究所先进功能复合材料技术重点实验室，北京 100076 通信作者，E-mail: yhl20032003@ 126． com 摘 要 为研究纳米隔热材料孔隙结构内部的气体热传输特性，采用溶胶—凝胶工艺结合超临界干燥技术，制备了一系列具 有不同孔隙结构特征的样品，通过热导率、氮气吸--脱附和真密度测试，全面、准确获取了其孔隙结构信息，并专门、系统研究 了孔隙结构特征与气体热传输特性之间的关系． 研究结果表明: 与气相贡献热导率相对应，材料具有双尺度孔隙结构特征，并 且当大孔隙尺度不及小孔隙的 10 倍时，可进一步等效为单尺度孔隙． 考虑气固耦合传热的本征气相贡献热导率随孔隙尺度 的增大而升高，与气相热导率变化类似且成一定的比例关系，孔隙尺度小于 200 nm 和大于 500 nm 时的比例系数分别为 2. 0 和 1. 5，200 ～ 500 nm 时则为 2. 0 ～ 1. 5． 当大、小孔隙尺度的比值不超过 10 时，或者这一比值为 100 ～ 1000 且大孔隙含量低于 10% 时，气相贡献热导率随环境气压的降低依次呈现快速下降、缓慢下降和无变化三个阶段; 当这一比值超过 3000 时，即使大 孔隙含量很低( 不超过 10% ) ，气相贡献热导率也会依次呈现快速下降、缓慢下降、快速下降和无变化四个阶段． 关键词 纳米隔热材料; 气相贡献热导率; 气相热导率; 孔隙结构; 等效孔径 分类号 TB34 收稿日期: 2018--06--11 基金项目: 国家“973”计划资助项目( 2015CB655200) Pore structure of nano-porous thermal insulating materials and thermal transport via gas phase in their pores YANG Hai-long ，HU Zi-jun，SUN Chen-cheng，HU Sheng-bo，YANG Jing-xing Science and Technology on Advanced Functional Composites Laboratory，Aerospace Ｒesearch Institute of Materials ＆ Processing Technology，Beijing 100076，China Corresponding author，E-mail: yhl20032003@ 126． com ABSTＲACT The thermal insulation properties of nano-porous thermal insulating materials largely depend on thermal transport via gas phase within their pores，and this process relies on their pore structures． Therefore，investigating pore structures and thermal transport via gas phase is important to understand the heat transfer mechanism． Current research mainly focuses on the theoretical calculation and analysis from the perspective of heat transfer，and special and systematic studies based on actual materials have not been reported yet． In addition，accurate analysis of pore structures using usual techniques is difficult due to the complex pore network and the poor me￾chanical properties of their solid skeleton． In this study，nano-porous thermal insulating materials with different pore structures were synthesized via a sol--gel process followed by supercritical drying． The materials were then characterized by thermal conductivity tester， nitrogen adsorption--desorption，and helium pycnometer． The pore structures of the resulting materials were obtained，and the relation￾ship between pore structures and thermal transport via gas phase was studied． Ｒesults show that the bimodal distribution of pores in the resulting materials，corresponding to gas-contributed thermal conductivity． All pores within the resulting materials can be equivalent to pores with a single diameter when the equivalent size of large pores is 10 times less than that of small pores． Similar to the pure gaseous thermal conductivity，the intrinsic gas-contributed thermal conductivity including gas--solid coupling effects rises with increasing pore diameter of the materials． The ratio of intrinsic gas-contributed thermal conductivity to pure gaseous thermal conductivity is 2. 0，1. 5