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Effects of synthetic conditions and heat-treatment on the structure of partially ion-exchanged titanate nanotubes

机译:合成条件和热处理对部分离子交换钛酸酯纳米管结构的影响

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TiO2-derived nanotubes prepared by hydrothermal treatment in NaOH (aq.) have been widely studied with regard to their composition and their formation mechanism. There exist some contradictions among previous reports, e.g. proposed crystal structure and thermal stability. Some difference of processing conditions and remnant sodium in nanotubes in previous works lead to the confusions on nanotubes' structure, thermal stability, and so on. In this paper, microstructural change during the hydrothermal and post-heat-treatments was studied for well-defined sodium contained (i.e. partially ion-exchanged) nanotubes, with nominal composition of similar to H1.5Na0.5Ti3O7. Under the hydrothermal treatment at 120 degrees C, the nanotubes grew longer until 12 h, and became almost constant length for more than 12 h. By the post-heat-treatment above 350 degrees C, some of the nanotubes began to break into particles of anatase phase, and the others remained as nanotubes where a lot of Na existed, indicating the remnant Na stabilized nanotube structure. At higher heat-treatment temperatures, the particles changed into rutile phase, and the nanotubes converted into Na2Ti6O13 nanorods. In situ high-temperature SEM study also clarified their structural change during heating. (c) 2004 Elsevier B.V. All rights reserved.
机译:在NaOH(水溶液)中通过水热处理制备的TiO 2衍生的纳米管已经对其组成和形成机理进行了广泛的研究。以前的报告之间存在一些矛盾,例如建议的晶体结构和热稳定性。以往的工艺条件和纳米管中残留的钠存在一些差异,导致纳米管的结构,热稳定性等方面的混乱。在本文中,研究了水热处理和后热处理过程中微观结构的变化,其中定义明确的钠包含(即部分离子交换)的钠纳米管,其名义组成类似于H1.5Na0.5Ti3O7。在120摄氏度的水热处理下,纳米管的生长时间延长到12小时,并在12小时以上的时间内几乎保持恒定的长度。通过在350摄氏度以上的后热处理,一些纳米管开始分解为锐钛矿相颗粒,而其他纳米管则保留为存在大量Na的纳米管,表明残留的Na稳定了纳米管结构。在较高的热处理温度下,颗粒变成金红石相,纳米管转变为Na2Ti6O13纳米棒。原位高温SEM研究也阐明了它们在加热过程中的结构变化。 (c)2004 Elsevier B.V.保留所有权利。

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