Pore structure of mesoporous silica (KIT-6) synthesized at different temperatures using positron as a nondestructive probe
Pore structure of mesoporous silica (KIT-6) synthesized at different temperatures using positron as a nondestructive probe
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使用正电子作为无损探针在不同温度下合成的介孔二氧化硅（KIT-6）的孔结构
DOI：
10.1016/j.apsusc.2018.03.223
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发表时间：
2018
影响因子：
6.7
通讯作者：
陈志权
中科院分区：
文献类型：
--
作者：
B. Zhou;C.Y. Li;N. Qi;M. Jiang;B. Wang;陈志权
摘要以三嵌段共聚物P123为模板剂，正硅酸乙酯（TEOS，C8H20O4Si）为硅源，合成了有序介孔SiO2（KIT-6）。小角X射线散射和高分辨率电子显微镜测量表明，在30 - 120 ° C下合成的KIT-6的孔结构具有3d立方Ia3d对称性。当合成温度增加到180 ° C时，孔的顺序劣化。通过氮气吸附/脱附测量来估计孔径，随着合成温度从30 ° C增加到180 ° C，孔径从3.8nm增加到18.5nm。随着中孔尺寸的增大，孔壁厚度呈不断减小的趋势。测量了合成的KIT-6的正电子湮没寿命谱。寿命谱可以分解为两个短寿命和两个长寿命分量。两个长寿命τ 3和τ 4分别对应于介孔和微孔中的o-Ps寿命。中孔的尺寸估计从o-Ps寿命通过使用Goworeck的圆柱形孔的模型，这表明随着合成温度的连续增加，并且与N2吸附/脱附测量是一致的。随着合成温度的升高，纳米晶的尺寸基本不变。然而，由于壁厚的减小，壁中的微孔的数量显示随后的减少。此外，第二寿命成分τ 2也是孔径的敏感参数，其与寿命成分τ 4随合成温度的变化趋势相同。
Abstract Ordered mesoporous SiO 2 (KIT-6) was synthesized using triblock copolymer P123 as the structure template and tetraethyl orthosilicate (TEOS, C 8 H 20 O 4 Si) as silica source. Small-angle X-ray scattering and high resolution electron microscope measurements indicate the 3d cubic Ia3d symmetry of the pore structure of KIT-6 synthesized at 30–120° C. When the synthesis temperature increases to 180° C, the order of pores was deteriorated. The pore size was estimated by nitrogen adsorption/desorption measurements, which increases from 3.8 nm to 18.5 nm as the synthesis temperature increases from 30° C to 180° C. With the increase of mesopore size, the pore wall thickness shows continuous decrease. Positron annihilation lifetime spectra was measured for the synthesized KIT-6. The lifetime spectra can be resolved to two short and two long lifetime components. The two long lifetimes τ 3 and τ 4 correspond to o-Ps lifetime in micropore and mesopores, respectively. The size of mesopores was estimated from the o-Ps lifetime by using Goworeck’s model for cylindrical pores, which shows continuous increase with synthesis temperature, and is consistent with the N 2 adsorption/desorption measurements. The size of micropore has no change with increasing synthesis temperature. However due to the decrease in wall thickness, the number of micropores in the wall shows subsequent decrease. In addition, the second lifetime component τ 2 is also found to be a sensitive parameter for the pore size, which shows the same trend as lifetime τ 4 with increasing synthesis temperature.