液体介质处理对纳米隔热材料细观结构的影响

为研究液体介质处理对纳米隔热材料细观结构的影响,并掌握材料结构对毛细管力的承受性,将纳米隔热材料分别在无水乙醇和去离子水中进行了浸泡和常温常压干燥处理。采用热导率测试结合SEM、N2吸附-脱附、光学显微镜等对材料处理前后的细观结构进行了表征,并以Kaganer双孔模型对气相热导率随环境气压的变化进行了描述。研究结果表明,材料固体骨架颗粒尺度和孔隙结构均不受无水乙醇处理的影响;去离子水处理后的材料固体骨架颗粒尺度虽未改变,但颗粒之间的接触面积有所增大,并且孔隙结构发生了两极分化,一部分变大,另一部分变小;处理前以及无水乙醇处理后,材料的孔隙结构均可以等效为70nm和300nm两种尺度的典型孔隙,占比分别约为81%和19%,而去离子水处理后的材料孔隙结构需要等效为30nm和60μm两种尺度的典型孔隙,占比分别约为58%和42%。

Effect of liquid-wetting on microstructure of nano-porous thermal insulating materials

To investigate the effect of liquid-wetting on their microstructure and determine their structural stability to capillary tension, nano-porous thermal insulating materials were directly immersed in absolute alcohol or deionized water, and then they were dried under room temperature and atmospheric pressure. The microstructure of the materials was characterized by nitrogen adsorption-desorption, SEM and optical microscope, and the gas pressure dependence of their gaseous thermal conductivity was described by Kaganer model with two different pore sizes. The results indicate that the skeleton particle diameter and the pore size are not affected by wetting with alcohol. However, the interfacial area between adjacent skeleton particles increases and the pore size either increases or decreases via water wetting. For the alcohol-wetted material, two different equivalent pore sizes derived from its gaseous thermal conductivity are 70 nm and 300 nm and their contributions to the total porosity are about 82% and 18%, respectively. In case of the water-wetted material, two different equivalent pore sizes deduced from its gaseous thermal conductivity are 30 nm and 60 μm and their contributions to the total porosity are about 58% and 42%, respectively.