Effect of synthesis temperature on the ordered pore structure in mesoporous silica studied by positron annihilation spectroscopy
Effect of synthesis temperature on the ordered pore structure in mesoporous silica studied by positron annihilation spectroscopy
复制标题
正电子湮没光谱研究合成温度对介孔二氧化硅有序孔结构的影响
DOI：
10.1016/j.apsusc.2015.12.055
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发表时间：
2016-02-15
影响因子：
6.7
通讯作者：
Wang, Z.
中科院分区：
文献类型：
--
作者：
Li, C. Y.;Qi, N.;Wang, Z.
以正硅酸乙酯为硅源，P123为模板剂，在不同温度下合成了具有有序孔结构的介孔氧化硅。小角X射线散射（SAXS）和高分辨率透射电子显微镜（HRTEM）测量验证了有序的孔结构的合成二氧化硅。随着合成温度的升高，在130 ℃时孔结构略有破坏，而在150 ℃时孔结构又重新呈现出有序结构。当合成温度升高到180 ℃时，有序的孔结构被严重破坏。通过扫描电子显微镜（SEM）测量进一步证实了孔结构的变化。正电子寿命测量揭示了合成的介孔SiO2中的四个寿命组分，并且两个长寿命τ（3）和τ（4）分别对应于材料的微孔和大孔中的o-Ps的湮灭。随着合成温度的升高，最长寿命的I-4倾向于略微增加。然而，其强度I-4显示出除在150摄氏度外的总体下降。在180 ℃的合成温度下，强度I-4急剧下降至约17.5%。这表明随着合成温度的升高，孔的尺寸和分数发生变化，并且孔结构在180 ℃时被严重破坏。通过与N-2吸附-脱附测量结果的比较，发现Goworek模型更适合于由o-Ps寿命估算圆柱形孔的尺寸，而Dull和Ito模型分别适用于矩形和球形孔。(C)2015 Elsevier B. V.版权所有。
Mesoporous silica with ordered pore structure was synthesized at various temperatures using TEOS as the silica source and P123 as the template. Both small angle X-ray scattering (SAXS) and high resolution transition electron microscopy (HRTEM) measurements verify the ordered pore structure of the synthesized SiO2. With synthesis temperature increasing, the pore structure has slight damage at 130 degrees C, while it shows ordered structure again at 150 degrees C. When the synthesis temperature increases to 180 degrees C, the ordered pore structure is severely destructed. The change of pore structure is further confirmed by scanning electron microscopy (SEM) measurements. Positron lifetime measurements reveal four lifetime components in the synthesized mesoporous SiO2, and the two long lifetimes tau(3) and tau(4) correspond to the annihilation of o-Ps in the micropores and large pores of the material, respectively. The longest lifetime I-4 tends to increase slightly with increasing synthesis temperature. However, its intensity I-4 shows an overall decrease with exception at 150 degrees C. At the synthesis temperature of 180 degrees C, the intensity I-4 decreases drastically to about 17.5%. This indicates variation of the size and fraction of pores with increasing synthesis temperature, and the pore structure is seriously destructed at 180 degrees C. By comparing with the N-2 adsorption-desorption measurements, it was found that the Goworek's model is more suitable for the size estimation of cylindrical pores from the o-Ps lifetime, while Dull's and Ito's model is appropriate for the rectangular and spherical pores, respectively. (C) 2015 Elsevier B.V. All rights reserved.