低密度二氧化硅气凝胶微观结构与隔热性能表征

Micro-structure and thermal insulation performance characterization of low density SiO_2 aerogel

以正硅酸乙酯为原料,采用溶胶-凝胶法及超临界流体干燥技术制备了密度为11 kg/m^3的低密度二氧化硅气凝胶块体材料,并与密度为25 kg/m^3和38 kg/m^3的二氧化硅气凝胶块体材料进行性能对比。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、BET等检测方法对样品的微观结构进行表征,对比了不同密度低密度气凝胶的微观结构,并测试了不同温度下的导热系数。结果表明:相比于密度更大的气凝胶材料,11 kg/m^3低密度气凝胶具有更为纤细的骨架结构和更大的孔洞尺寸,以及较小的比表面积,室温条件下具有最大的导热系数;在气凝胶密度小于40 kg/m^3的范围内,呈现出密度越小,导热系数越大的规律。

SiO2 aerogel with the density of 11 kg/m^3 was prepared by sol-gel method and supercritical drying technique from tetraethoxysilane （ TEOS）. To compare the properties of the low-density SiO2 aerogel of 11 kg/m^3 , SiO2 aerogels of 25 kg/m^3 and 38 kg/m^3 were prepared at the same time, respectively. Scanning electron microscopy （SEM） ,transmission electron microscope （TEM） and muhipoint Brunauer-Emett-Teller （BET） method were used to characterize the porous morphology and structure of the three samples and the thermal conductivities were also measured. The results demonstrated that comparing with SiO2 aerogels with higher densities, the sample of 11 kg/m^3 possessed thinner skeleton structure and bigger holes. Therefore, it got the higher thermal conductivity. Within the density of less than 40 kg/m^3 , it shows the tendency that the thermal conductivity increases as the aerogel density decreases.