• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Synthesis of titania-based nanostructured materials using a sol-gel process in supercritical carbon dioxide.
【24h】

Synthesis of titania-based nanostructured materials using a sol-gel process in supercritical carbon dioxide.

机译：在超临界二氧化碳中使用溶胶-凝胶法合成基于二氧化钛的纳米结构材料。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

One-dimensional nanostructures (e.g. nanotubes, nanowires, nanobelts) of titania (TiO2) are receiving considerable attention due to their unique physical properties, high activity, strong photooxidation capability, chemical stability and numerous potential applications in solar energy systems. These nanostructured materials bear tremendous promise in the effective utilization of solar energy based on photovoltaic and water-splitting devices. However, the available preparation techniques have limitations. In this respect, a sol-gel process using supercritical carbon dioxide (scCO 2) as solvent offers a viable alternative to obtain these nanostructured materials, due to the unique enabling properties of scCO2.;This research has focused on the synthesis and modification of TiO 2 nanomaterials via an acid modified sol-gel process in scCO2. In this regard, the doping agents used were Fe, Zr, and N. Because of its zero surface tension, scCO2 helps to form and maintain nanostructures and high surface areas of the synthesized nanomaterials. The low dielectric constant results in lower solubility with LA-LB interactions helping to stabilize the hydrolysis products, resulting in new and desirable morphologies. The synthesis was carried out in a batch reactor, i.e. in a view cell equipped with sapphire windows, for observation of the phase changes. The synthesis process was also studied using in situ FTIR spectrometry with the resulting nanomaterials being characterized using electron microscopy, N2 physisorption, FTIR, XRD, XPS, thermal analysis, TPD and UV-Vis analysis. A kinetic model for the phase changes involved during heat treatment of the synthesized nanomaterials was developed, and the performance of the synthesized nanomaterials was evaluated as a photocatalyst to degrade methylene blue in aqueous solution under UV light.;The results showed that the type of dopant significantly altered the morphology as well as the surface properties of the hybrid nanomaterials. For instance, while being synthesized under similar experimental conditions in scCO2 pure TiO2 formed nanofibers of 20-50 nm dia, Zr doped TiO2 samples formed sheets with 100-300 nm width and nanotubes with a diameter of 50-140 nm, depending on the initial concentration of precursor(s). However, Fe doped samples showed a flake type flat structure while zirconia modified N doped TiO2 samples showed a sheet type structure. Crystalline structures were obtained when the prepared materials were calcined at 500°C. Anatase TiO2 nanocrystallites with a size range ca. 6-14 nm were obtained depending on the amount and type of doping. The resulting materials exhibited a mesoporous structure and a higher surface area compared to pure TiO2 nanomaterials.;This work revealed that the direct sol-gel process in scCO2 is a promising technique for synthesizing and modifying TiO2 nanomaterials. The formed modified TiO2 nanostructured materials had a higher surface area, smaller crystallite size, and greater thermal stability, which are all desirable features for catalysts, support materials, semiconductors, and electrodes in dye-sensitized solar cells (DSSC). The simple synthesis procedure, which is scalable, used mild reaction conditions with a green solvent, providing a high yield and high quality nanomaterials, making this route potentially attractive for commercial employment.;Key words. nanomaterials, TiO2, ZrO 2 doped TiO2, N doped TiO2, Fe doped TiO 2, aerogel, modified sol-gel process, green solvent, scCO2, photocatalyst, solar energy, solid state reaction kinetics, activation energy.
机译：二氧化钛（TiO2）的一维纳米结构（例如纳米管，纳米线，纳米带）由于其独特的物理特性，高活性，强大的光氧化能力，化学稳定性以及在太阳能系统中的众多潜在应用而受到广泛关注。这些纳米结构材料在基于光伏和水分解装置的太阳能的有效利用方面具有广阔的前景。但是，可用的制备技术有局限性。在这方面，由于scCO2具有独特的促成特性，使用超临界二氧化碳（scCO 2）作为溶剂的溶胶-凝胶工艺为获得这些纳米结构材料提供了可行的替代方法;该研究的重点是TiO的合成和改性通过在scCO2中进行酸改性的溶胶-凝胶工艺制备2种纳米材料。在这方面，所使用的掺杂剂是Fe，Zr和N。由于其零表面张力，scCO2有助于形成和维持合成的纳米材料的纳米结构和高表面积。低介电常数导致与LA-LB相互作用的溶解度降低，从而有助于稳定水解产物，从而产生新的理想形态。合成在间歇反应器中进行，即在配备有蓝宝石窗口的观察室中进行，以观察相变。还使用原位FTIR光谱研究了合成过程，并使用电子显微镜，N2物理吸附，FTIR，XRD，XPS，热分析，TPD和UV-Vis分析对所得纳米材料进行了表征。建立了纳米材料热处理过程中所涉及的相变动力学模型，并评价了该纳米材料作为光催化剂在紫外光下降解水溶液中亚甲基蓝的性能。显着改变了杂化纳米材料的形态和表面性能。例如，当在类似的实验条件下用scCO2合成纯TiO2形成直径为20-50 nm的纳米纤维时，掺Zr的TiO2样品可形成宽度为100-300 nm的薄片和直径为50-140 nm的纳米管，具体取决于初始前体的浓度。然而，Fe掺杂的样品显示为片状扁平结构，而氧化锆改性的N掺杂的TiO2样品显示为片状结构。当将制备的材料在500℃下煅烧时，获得晶体结构。锐钛矿型TiO2纳米晶体的尺寸范围约为。根据掺杂的数量和类型获得6-14nm。所得材料与纯TiO2纳米材料相比具有中孔结构和更高的表面积。这项工作表明，在scCO2中直接进行溶胶-凝胶工艺是合成和改性TiO2纳米材料的有前途的技术。所形成的改性的TiO2纳米结构材料具有较大的表面积，较小的微晶尺寸和较高的热稳定性，这些都是染料敏化太阳能电池（DSSC）中的催化剂，载体材料，半导体和电极的理想特征。这种简单的合成方法具有可扩展性，在温和的反应条件下使用绿色溶剂，可提供高收率和高质量的纳米材料，这条路线对于商业用途具有潜在的吸引力。纳米材料，TiO2，ZrO 2掺杂的TiO2，N掺杂的TiO2，Fe掺杂的TiO 2，气凝胶，改进的溶胶-凝胶工艺，绿色溶剂，scCO2，光催化剂，太阳能，固态反应动力学，活化能。

著录项

  • 作者

    Lucky, Rahima A.;

  • 作者单位

    The University of Western Ontario (Canada).;

  • 授予单位 The University of Western Ontario (Canada).;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 241 p.
  • 总页数 241
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化工过程（物理过程及物理化学过程）;
  • 关键词

  • 入库时间 2022-08-17 11:38:24

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号