二氧化硅复合气凝胶红外隐身材料的制备及表征

以正硅酸乙酯(TEOS)为硅源,采用酸碱两步催化法经过溶胶-凝胶和冷冻干燥制备出SiO2气凝胶基材,并在凝胶老化过程中通过加入不同含量β-氯乙基二甲胺盐酸盐(β-DCH)制备出兼具中远红外吸收特性的硅基复合气凝胶。利用X射线衍射、扫描电子显微镜、氮吸附-脱附和傅里叶红外吸收光谱对气凝胶的结构和性能进行表征。结果表明:基材和复合气凝胶的表观密度分别为0.25g/cm3和0.36～0.54 g/cm3;基材和大部分复合气凝胶均为非晶型,只有当复合气凝胶中N:Si摩尔比为1时才有微弱的β-DCH结晶峰出现;所添加的胺盐以球形颗粒或无规则块状附着于硅气凝胶网络结构中;基材属于介孔材料,比表面积、最大孔容和平均孔径分别为:524.5m2/g、1.209 cm3/g和9.216 nm,添加胺盐后复合气凝胶不断向非多孔、大孔材料过渡,比表面积、最大孔容和平均孔径分别为:1.688～103.5 m2/g、0.0079～0.2695 cm3/g和10.42～18.68 nm。复合气凝胶在中远红外窗口具有宽频吸收的特性,且随着β-DCH量的增加,中红外相对吸收强度成比例增强。

Preparation and Characterization of Silica Composite Aerogels for Infrared Stealth

The silicon aerogel substrate was prepared by a two-step base/acid catalyzed sol-gel process using tetraethoxysilane (TEOS) as silicon source and by freeze drying. By adding different content of β-Dimethylaminoethyl chloride hydrochloride (β-DCH) to the substrate during the aging process, Composite aerogels with broadband absorption in mid- and far-infrared windows was prepared. The structure and property of composite aerogels were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), N2 physisorption at 77 K and fourier-transform infrared spectroscopy (FT-IR). Results showed that: The apparent density of silicon aerogel substrate and composite aerogels are 0.25 g/cm3 and 0.36～0.54 g/cm3 respectively. Both the silicon substrate and most composite aerogels are amorphous. Only when the N:Si mol ratio reaches as high as 1, does the comosity aerogel have the weak crystallization peak of β-DCH. The β-DCH agglomerated into spherical particles or irregular blocks adhering to the whole three-dimensional network of silicon aerogel. The silicon aerogel is mesoporous material, which has the specific surface area about 524.5 m2/g, total pore volume about 1.209 cm3/g and average pore diameter about 9.216 nm. The composite aerogels transform to non-porous and macropore materials gradually with the increase of β-DCH, which has the specific surface area about 1.688～103.5 m2/g, total pore volume about 0.0079～0.2695 cm3/g and average pore diameter about 10.42～18.68 nm. Composite aerogels have broadband absorption characteristic in mid- and far-infrared. The relative absorption intensity in mid-infrared increased in proportion with the increased content of β-DCH.