Ordered macroporous silica by ice templating
Ordered macroporous silica by ice templating
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DOI：
10.1021/cm048725f
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发表时间：
2005-02-08
影响因子：
8.6
通讯作者：
Tamon, H
中科院分区：
文献类型：
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作者：
Nishihara, H;Mukai, SR;Tamon, H
有序大孔二氧化硅是一种硅胶微蜂窝（SMH），是通过使用微米级冰晶作为模板的方法制备的。模板冰晶，具有连续的棒状形状。在前驱体二氧化硅水凝胶内部，在它们继续伪稳态生长的条件下，生长出多边形横截面和有序直径。除了有序的大孔之外，微孔/中孔还通过浸泡在叔丁醇中的 SMH 的冷冻干燥在蜂窝壁内部形成。 SMH 具有直的和多边形的大孔空隙，这些空隙是通过冰晶的形成和去除而产生和保留的。通过扫描电子显微镜观察、氮气吸附-脱附测量和热重分析，详细研究了SMHs的微观形貌，包括大孔尺寸和壁厚、蜂窝壁内的微孔/中孔率以及热稳定性。研究发现，可以通过改变冷浴的浸入速率和冷冻温度来控制SMHs的大孔尺寸，而不改变其蜂窝壁的微孔/中孔率。还发现蜂窝壁的厚度受SiO2浓度和大孔尺寸的影响。另一方面，通过在碱性水溶液中对所制备的 SMH 进行水热处理，可以将蜂窝壁的孔隙率控制为微孔和介孔。此外，还发现具有发达介孔的SMH表现出更高的热处理稳定性。
Ordered macroporous silica, a silica gel microhoneycomb (SMH), has been prepared through a method which uses micrometer-sized ice crystals as a template. Template ice crystals, which have a continuous rod shape. a polygonal cross section, and ordered diameters, were grown inside precursor silica hydrogels Under a condition where the pseudo-steady-state growth of them continues. Besides their ordered macroporosity, micro-/mesopores develop inside the honeycomb walls through the freeze-drying of SMHs soaked in tert-butyl alcohol. SMHs have straight and polygonal macroporous voids, which are created and retained through the formation and removal of the ice crystals. Micromorphology including macropore size and wall thickness, micro-/mesoporosity inside the honeycomb walls, and thermal stability of SMHs were investigated in detail through scanning electron microscopy observation, nitrogen adsorption-desorption measurements, and thermogravimetric analysis. It was found that the macropore size of the SMHs can be controlled by changing the immersion rate into a cold bath and the freezing temperature without changing the micro-/mesoporosity of their honeycomb walls. It was also found that the thickness of the honeycomb walls was affected by the SiO2 concentration and the macropore size. On the other hand, the porosity of the honeycomb walls could be controlled to be microporous as well as mesoporous by hydrothermal treatment of as-prepared SMHs in basic aqueous Solutions. Moreover, it was found that SMHs with developed mesopores showed a higher stability against heat treatment.