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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >In-Situ GISAXS Investigation of Pore Orientation Effects on the Thermal Transformation Mechanism in Mesoporous Titania Thin Films
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In-Situ GISAXS Investigation of Pore Orientation Effects on the Thermal Transformation Mechanism in Mesoporous Titania Thin Films

机译：介孔二氧化钛薄膜中孔取向对热转变机理影响的原位GISAXS研究

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摘要

This study addresses the effects of mesopore orientation on mesostructural stability and crystallization of titania thin films during calcination based on measurements with in-situ grazing incidence small angle X-ray scattering (GISAXS). Complementary supporting information is provided by ex-situ electron microscopy. Pluronic surfactant P123 (with average structure (EO)_(20)(PO)_(70)(EO)_(20) where EO is an ethylene oxide unit and PO is a propylene oxide unit) serves as the template to synthesize titania thin films on P123- modified glass slides with 2D he.xagonally close-packed cylindrical mesopores. The orientation of the pores at the top surface is controlled by sandwiching another P123- modified glass .slide on top of the titania thin film to completely orient the pores orthogonal to the films in some samples. This provides the opportunity to directly observe how pore orientation affects the evolution of pore order and crystallinity during calcination. The results show that when the pores are oriented parallel to the substrate at the top surface (for unsandwiched films), the pore structure is stable upon calcination at 400 °C but that the structure is quickly lost due to crystallization throughout the film during calcination at 500 °C. Films with pores oriented orthogonal to the substrate at the top surface (sandwiched films) retain their long-range pore order even after calcination at 500 °C. The reasons for this difference are ascribed to greater resistance to anisotropic stress during heating of the orthogonally oriented pores and titania crystallization nucleation at the top surface of the films with orthogonally oriented pores.
机译：这项研究基于原位掠入射小角度X射线散射（GISAXS）的测量结果，探讨了介孔取向对二氧化钛薄膜介观结构稳定性和结晶的影响。辅助支持信息通过异位电子显微镜提供。多元醇表面活性剂P123（平均结构为（EO）_（20）（PO）_（70）（EO）_（20），其中EO为环氧乙烷单元，PO为环氧丙烷单元）用作合成二氧化钛的模板P123修饰的玻璃载玻片上的薄膜具有2D六角形紧密堆积的圆柱形中孔。通过将另一块P123改性的玻璃片夹在二氧化钛薄膜的顶部，以完全定向正交于某些样品中膜的孔的方向来控制孔在顶部表面的方向。这提供了直接观察孔取向如何影响煅烧过程中孔序和结晶度演变的机会。结果表明，当孔在顶表面平行于基材取向时（对于非夹心膜而言），孔结构在400°C下煅烧时是稳定的，但由于在200°C下煅烧过程中整个膜的结晶，该结构很快消失了。 500℃。即使在500°C煅烧后，具有在顶表面上与基材正交的孔的膜（夹层膜）仍保持其长距离的孔顺序。这种差异的原因归因于在正交取向的孔的加热过程中对各向异性应力的更大抵抗力以及在具有正交取向的孔的膜的顶表面处的二氧化钛结晶成核。

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