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首页> 外文期刊>Nanotechnology >Multistep structural transition of hydrogen trititanate nanotubes into TiO_2-B nanotubes: a comparison study between nanostructured and bulk materials
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Multistep structural transition of hydrogen trititanate nanotubes into TiO_2-B nanotubes: a comparison study between nanostructured and bulk materials

机译：钛酸氢纳米管向TiO_2-B纳米管的多步结构转变：纳米结构材料与块状材料的比较研究

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摘要

H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO_2 followed by proton exchange were compared to their bulk H_2Ti_3O_7 counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H_2Ti_3O_7 nanotubes showed the same sequence of structural transformations as then-bulk counterpart obtained by conventional solid state reaction. Nanostructured H_2Ti_3O_7 converts into TiO_2(B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 deg C through topotactic mechanisms with the intermediate formation of nanostructured H_2Ti_6O_(13) and H_2Ti_(12)O_(25), which are more condensed layered titanates eventually rearranging to TiO_2(B). Our results suggest that the intermediate tunnel structure H_2Ti_(12)O_(25) is the final layered intermediate phase, on which TiO_2(B) nucleates and grows. The conversion of nanostructured TiO_2(B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology.
机译：通过对TiO_2进行碱水热处理，然后进行质子交换，获得的H-三钛酸酯纳米管与它们的整体H_2Ti_3O_7对应物的热诱导结构转变路径进行了比较。通过XRD，TEM / SAED，DSC和光谱技术对合成后和热处理后的样品进行了表征，表明H_2Ti_3O_7纳米管的结构转化顺序与常规固态反应获得的大批量对应物相同。纳米结构的H_2Ti_3O_7通过多步转化转变为TiO_2（B），而不会失去其纳米管形态。转变通过定势机理在120到400摄氏度之间发生，中间形成了纳米结构的H_2Ti_6O_（13）和H_2Ti_（12）O_（25），它们是更稠密的层状钛酸盐，最终重排为TiO_2（B）。我们的结果表明，中间隧道结构H_2Ti_（12）O_（25）是最终的层状中间相，TiO_2（B）在其上成核并生长。纳米结构的TiO_2（B）向锐钛矿的转化要比其本体的TiO2（B）转化温度低得多，并且伴随着纳米管形态的丧失。

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