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首页> 外文学位 >Control of Wettability of Carbon Nanotube Array by Reversible Dry Oxidation for Superhydrophobic Coating and Supercapacitor Applications.
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Control of Wettability of Carbon Nanotube Array by Reversible Dry Oxidation for Superhydrophobic Coating and Supercapacitor Applications.

机译：通过可逆干式氧化控制碳纳米管阵列的润湿性，以用于超疏水涂层和超级电容器应用。

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摘要

In this thesis, dry chemical modification methods involving UV/ozone, oxygen plasma, and vacuum annealing treatments are explored to precisely control the wettability of CNT arrays.;The effect of oxidation using UV/ozone and oxygen plasma treatments is highly reversible as long as the O/C ratio of the CNT arrays is kept below 18%. At O/C ratios higher than 18%, the effect of oxidation is no longer reversible. This irreversible oxidation is caused by irreversible changes to the CNT atomic structure during the oxidation process. During the oxidation process, CNT arrays undergo three different processes. For CNT arrays with O/C ratios lower than 40%, the oxidation process results in the functionalization of CNT outer walls by oxygenated groups. Although this functionalization process introduces defects, vacancies and micropores opening, the graphitic structure of the CNT is still largely intact. For CNT arrays with O/C ratios between 40% and 45%, the oxidation process results in the etching of CNT outer walls. This etching process introduces large scale defects and holes that can be obviously seen under TEM at high magnification. Most of these holes are found to be several layers deep and, in some cases, a large portion of the CNT side walls are cut open. For CNT arrays with O/C ratios higher than 45%, the oxidation process results in the exfoliation of the CNT walls and amorphization of the remaining CNT structure. This amorphization process can be implied from the disappearance of C-C sp2 peak in the XPS spectra associated with the π-bond network.;The impact behavior of water droplet impinging on superhydrophobic CNT arrays in a low viscosity regime is investigated for the first time. Here, the experimental data are presented in the form of several important impact behavior characteristics including critical Weber number, volume ratio, restitution coefficient, and maximum spreading diameter. As observed experimentally, three different impact regimes are identified while another impact regime is proposed. These regimes are partitioned by three critical Weber numbers, two of which are experimentally observed. The volume ratio between the primary and the secondary droplets is found to decrease with the increase of Weber number in all impact regimes other than the first one. In the first impact regime, this is found to be independent of Weber number since the droplet remains intact during and subsequent to the impingement. Experimental data show that the coefficient of restitution decreases with the increase of Weber number in all impact regimes. The rate of decrease of the coefficient of restitution in the high Weber number regime is found to be higher than that in the low and moderate Weber number. Experimental data also show that the maximum spreading factor increases with the increase of Weber number in all impact regimes. The rate of increase of the maximum spreading factor in the high Weber number regime is found to be higher than that in the low and moderate Weber number. Phenomenological approximations and interpretations of the experimental data, as well as brief comparisons to the previously proposed scaling laws, are shown here.;Dry oxidation methods are used for the first time to characterize the influence of oxidation on the capacitive behavior of CNT array EDLCs. The capacitive behavior of CNT array EDLCs can be tailored by varying their oxygen content, represented by their O/C ratio. The specific capacitance of these CNT arrays increases with the increase of their oxygen content in both KOH and Et4NBF4/PC electrolytes. As a result, their gravimetric energy density increases with the increase of their oxygen content. However, their gravimetric power density decreases with the increase of their oxygen content. The optimally oxidized CNT arrays are able to withstand more than 35,000 charge/discharge cycles in Et4NBF4/PC at a current density of 5 A/g while only losing 10% of their original capacitance. (Abstract shortened by UMI.).
机译：本文研究了采用紫外/臭氧，氧等离子体和真空退火处理的干法化学修饰方法，以精确控制CNT阵列的润湿性。只要紫外线/臭氧和氧等离子体处理的氧化作用可高度逆转， CNT阵列的O / C比保持在18％以下。在O / C比率高于18％时，氧化作用不再可逆。这种不可逆的氧化是由氧化过程中CNT原子结构的不可逆变化引起的。在氧化过程中，CNT阵列会经历三种不同的过程。对于O / C比率低于40％的CNT阵列，氧化过程导致CNT外壁被氧化基团官能化。尽管此功能化过程引入了缺陷，空位和微孔开口，但CNT的石墨结构仍基本完好无损。对于O / C比率在40％和45％之间的CNT阵列，氧化过程会导致CNT外壁的蚀刻。这种蚀刻工艺引入了大规模缺陷和孔，这些缺陷和孔在高放大倍数下的TEM下可见。这些孔中的大多数被发现有几层深，在某些情况下，CNT侧壁的大部分被切开了。对于O / C比率高于45％的CNT阵列，氧化过程会导致CNT壁剥落和剩余CNT结构的非晶化。从与π键网络相关的XPS光谱中C-C sp2峰的消失可以暗示这种无定形过程。首次研究了水滴在低粘度条件下撞击超疏水性CNT阵列的行为。在这里，实验数据以几种重要的冲击行为特征的形式呈现，包括临界韦伯数，体积比，恢复系数和最大铺展直径。如实验观察到的，确定了三种不同的冲击方式，同时提出了另一种冲击方式。这些制度被三个关键的韦伯数划分，其中两个是实验观察到的。发现在除第一冲击力之外的所有冲击方式中，第一和第二液滴之间的体积比随着韦伯数的增加而减小。在第一冲击方式中，发现这与韦伯数无关，因为液滴在撞击期间和撞击之后保持完整。实验数据表明，在所有冲击状态下，恢复系数都随着韦伯数的增加而减小。发现高韦伯数态的恢复系数的降低率高于低和中等韦伯数的恢复系数的降低率。实验数据还表明，在所有冲击方式下，最大扩散因子均随韦伯数的增加而增加。发现高韦伯数态中最大扩展因子的增加率高于中低韦伯数系中最大扩散因子的增加率。此处显示了实验数据的现象学近似和解释，以及与先前提出的比例定律的简要比较。首次使用干式氧化方法来表征氧化对CNT阵列EDLC电容行为的影响。 CNT阵列EDLC的电容特性可以通过改变其氧含量（以O / C比表示）来调整。这些CNT阵列的比电容随KOH和Et4NBF4 / PC电解质中氧含量的增加而增加。结果，它们的重量能密度随其氧含量的增加而增加。然而，它们的重量功率密度随其氧含量的增加而降低。经过最佳氧化的CNT阵列能够以5 A / g的电流密度在Et4NBF4 / PC中承受超过35,000个充电/放电循环，而仅损失其原始电容的10％。 （摘要由UMI缩短。）。

著录项

  • 作者

    Aria, Adrianus Indrat.;

  • 作者单位

    California Institute of Technology.;

  • 授予单位 California Institute of Technology.;
  • 学科 Nanoscience.;Nanotechnology.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 258 p.
  • 总页数 258
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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