低密度二氧化硅气凝胶微观结构与隔热性能表征

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11kg/m³的低密度二氧化硅气凝胶块体材料，并与密度为25kg/m³和38kg/m³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，11kg/m³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40kg/m³的范围内，呈现出密度越小，导热系数越大的规律。

Micro-structure and thermal insulation performance characterization of low density SiO2 aerogel

SiO₂ aerogel with the density of 11kg/m³ was prepared by sol-gel method and supercritical drying technique from tetraethoxysilane (TEOS). To compare the properties of the low-density SiO₂ aerogel of 11kg/m³, SiO₂ aerogels of 25kg/m³ and 38kg/m³ were prepared at the same time, respectively. Scanning electron microscopy (SEM)、transmission electron microscope (TEM) and multipoint 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 11kg/m³ possessed thinner skeleton structure and bigger holes. Therefore, it got the higher thermal conductivity. Within the density of less than 40kg/m³, it shows the tendency that the thermal conductivity increases as the aerogel density decreases.