纳米孔超级绝热材料气凝胶的制备与热学特性

Preparation and Investigation of Nanoporous Super Thermal Insulation: Silica Aerogels

以正硅酸四乙酯(TEOS)为硅源,通过溶胶凝胶及超临界干燥过程制备了SiO2气凝胶. 同时,采用相对廉价的多聚硅(E40)为硅源,以三甲基氯硅烷(TMCS)为表面修饰剂,硅油为干燥介质, 在常压条件下制备了同样具有纳米多孔结构的SiO2气凝胶. 用透射电镜、扫描电镜及孔径分布仪对其结构进行了表征,并用动态热线法对其热学特性进行了测试. 结果表明: 两种方法制备的气凝胶均是典型的纳米孔超级绝热材料,后者热导率略高但成本低许多,所以更具应用推广潜力.

Nano-porous SiO2 aerogel insulations were prepared via two methods: (1) Using tetraethoxysilane (TEOS) as the precursor and followed by ethanol supercritical drying; (2) Surface modification of alcogels prepared from polyethoxydisiloxanes (E40) and followed by drying at ambient pressure. TEM, SEM and pore size distribution techniques were used to characterize the morphology and pore structure of the silica aerogels. The thermal conductivity of the silica aerogels was determined using the transient hot-wire technique. The results show that the pore size distribution of silica aerogels is from several nanometer to dozens of nanometer, the size of the particles is 5~10 nm and the average pore size (BJH) is about 20 nm and 10 nm respectively for samples derived from the two different methods, while the thermal conductivity of the silica aerogels (100 kg/m3) are 0.0125 and 0.014 W/(m.K) respectively at room temperature and 1.01105 Pa.