Studies of intrawall porosity in the hexagonally ordered mesostructures of SBA-15 by small angle X-ray scattering and nitrogen adsorption
Studies of intrawall porosity in the hexagonally ordered mesostructures of SBA-15 by small angle X-ray scattering and nitrogen adsorption
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DOI：
10.1016/j.apsusc.2009.12.068
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发表时间：
2010-06-15
影响因子：
6.7
通讯作者：
Kozak, Maciej
中科院分区：
文献类型：
--
作者：
Pikus, Stanislaw;Celer, Ewa B.;Kozak, Maciej
有序介孔二氧化硅（OMSs）如SBA-15（p6 mm对称群）在含有聚（环氧乙烷）嵌段的嵌段共聚物存在下合成，在有序介孔的壁中具有不规则的互补孔。由这种互补孔隙度引起的X射线散射有助于SAXS图案的背景。这项工作表明，使用小角X射线散射数据的内壁通道的相互连接有序的圆柱体在SBA-15的研究的可能性。通过使用在不同水热处理温度（从60到180摄氏度）下获得的一系列SBA-15样品来测试所提出的SAXS分析。一系列SBA-15样品的SAXS模式记录的结构建模进行了使用连续密度函数（CDF）技术结合导数差最小化（DDM）方法的全轮廓细化。该方法适用于从小角X射线散射谱图中提取背景曲线。通过用于评价非均质分布的SAXS理论中的众所周知的方法来分析所得到的平滑背景曲线，在这种情况下，其表征壁内互补孔隙度。一个相对较好的协议已被观察到的SAXS和氮吸附分析所获得的数据之间。SAXS分析对于SBA-15材料中的非均质微孔性的检查是足够灵敏的。在60 ℃下获得的SBA-15样品的壁内孔的平均直径仅为约1.4nm。然而，该直径随着水热处理温度的增加而增加;即，对于在80、100、120、140、160和180 ℃下水热处理的SBA-15样品，其分别为1.5、1.8、2.6、2.6、3.5和5.2 nm。(C)2009 Elsevier B. V.保留所有权利。
Ordered mesoporous silicas (OMSs) such as SBA-15 (p6mm symmetry group) synthesized in the presence of block copolymers containing poly(ethylene oxide) blocks possess irregular complementary pores in the walls of ordered mesopores. The X-ray scattering caused by this complementary porosity contributes to the background of the SAXS patterns. This work shows the possibility of using the SAXS data for the study of intrawall channels interconnecting ordered cylinders in SBA-15. The proposed SAXS analysis was tested by using a series of SBA-15 samples obtained at different temperatures of hydrothermal treatment (from 60 to 180 degrees C). The structural modelling of the SAXS patterns recorded for a series of SBA-15 samples was performed by using the continuous density function (CDF) technique in combination with the derivative difference minimization (DDM) method of full-profile refinement. This method is well suited for extraction of the background curves from the SAXS patterns. The resulting smooth background curves were analyzed by the well-known method in the SAXS theory used for evaluation of heterogeneity distributions, which in this case characterize the intrawall complementary porosity. A relatively good agreement has been observed between the data obtained by SAXS and nitrogen adsorption analysis. The SAXS analysis is sufficiently sensitive for examination of heterogeneous microporosity in SBA-15 materials. The average diameter of intrawall pores for the SBA-15 sample obtained at 60 degrees C was only about 1.4 nm. However, this diameter increased with the increasing temperature of hydrothermal treatment; namely, it was 1.5, 1.8, 2.6, 2.6, 3.5 and 5.2 nm for the SBA-15 samples hydrothermally treated at 80, 100, 120, 140, 160 and 180 degrees C, respectively. (C) 2009 Elsevier B.V. All rights reserved.