Characteristics of ambient-pressure-dried aerogels synthesized via different surface modification methods
Characteristics of ambient-pressure-dried aerogels synthesized via different surface modification methods
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DOI：
10.1007/s10971-015-3760-y
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发表时间：
2015-10-01
影响因子：
2.5
通讯作者：
Yang, Hui
中科院分区：
文献类型：
--
作者：
Li, Zhi;Cheng, Xudong;Yang, Hui
为了比较常压干燥气凝胶的各种表面改性方法，本文研究了共前驱体法、衍生化法和两步法三种不同的气凝胶表面改性方法。从反应过程、微观形貌、孔径分布、疏水性和热稳定性等方面讨论了3种表面改性方法对气凝胶性能的影响。在表面改性过程中，有机基团被连接到湿凝胶骨架上，将亲水性转化为疏水性，通过傅里叶变换红外光谱（FTIR）表征。虽然所有方法都能得到介孔结构，但共前驱体法的比表面积、孔容和平均孔径最小，而衍生化法的孔径分布最均匀，最可几孔径为7 nm，平均孔径为12 nm。在这三种方法中，两步法的样品具有最低的强度，为每千个Si-OH基团的a份，这表明具有优异的疏水性，并且使用接触角计确认接触角为162 A度。两步法制备的气凝胶在DSC曲线上出现了两个放热峰，这是由于气凝胶骨架上的有机基团发生了氧化。同时，两个峰的起始温度均高于衍生化法，表明两步法可以提高SiO2气凝胶的热稳定性。由此可见，表面改性方法对气凝胶的性能有明显的影响。[图形]。
In order to compare the various surface modification methods of ambient-pressure-dried aerogels, three different surface modification methods, namely co-precursor method, derivatization method and two-step method, were studied in this paper. The property differences of the aerogels caused by the three surface modification methods were discussed in terms of the reaction processes, micromorphology, pore size distributions, hydrophobicity and thermal stability. During the surface modification process, organic groups were attached to the wet gel skeletons transforming the hydrophilia to the hydrophobicity which were characterized by Fourier transform infrared spectrometry (FTIR). Though mesoporous structure could be obtained by all the methods, the co-precursor method had the smallest special surface area, pore volume and average pore size, while the derivatization method presented the best uniform pore size distribution with the most probable pore diameter of 7 nm and average pore size of 12 nm. Among the three methods, the samples of the two-step method had the lowest intensity of a parts per thousand Si-OH groups which indicated the excellent hydrophobicity, and the contact angle was confirmed as 162A degrees using a contact angle meter. And two exothermic peaks on the DSC curve of the two-step method samples were observed unexpectedly, attributing to the oxidation of organic groups on the aerogel skeletons. Meanwhile, the initial temperatures of the two peaks were both higher than those of the derivatization method which suggested that the thermal stability of the silica aerogels could be improved by the two-step method. From all mentioned above, it can be drawn that surface modification methods had obvious effects on the properties of aerogels.[GRAPHICS].