浮动催化剂化学气相沉积法控制制备单壁和双壁碳纳米管

IMR OpenIR

	浮动催化剂化学气相沉积法控制制备单壁和双壁碳纳米管
	于冰
学位类型	博士
导师	逯高清 ; 成会明 ; 李峰
	2011
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	半导体性单壁碳纳米管氧辅助浮动催化剂化学气相沉积可控制备透明导电薄膜
摘要	"单壁碳纳米管是单层石墨烯按照一定方式卷曲而成的直径为纳米尺度的一维管状结构，因其具有独特的结构和优异性能而具有广泛的应用前景。对其电属性乃至手性的精确控制一直是碳纳米管研究领域的重点和难点，同时，大量制备高质量的碳纳米管也是制约其在透明导电薄膜等器件中应用的关键问题。本文利用浮动催化剂化学气相沉积法控制生长单壁和双壁碳纳米管，重点研究了单壁碳纳米管的直径和导电属性的调控；高结构完整性碳纳米管的生长及其透明导电特性。取得的主要结果如下：采用原位弱氧化和后处理氧化相结合的方法，有效刻蚀了样品中的金属性单壁碳纳米管，制备出富含半导体性的单壁碳纳米管。热重分析发现：经原位氧化单壁碳纳米管中金属性和半导体性单壁碳纳米管的最大抗氧化温度分别为460°C和530°C，经过10小时400 °C的后处理氧化和盐酸浸泡可有效的去除金属性单壁碳纳米管、小直径单壁碳纳米管、无定形炭及金属催化剂。研究表明在浮动催化剂化学气相沉积法生长碳纳米管的过程中，引入的氧可以原位与单壁碳纳米管发生反应，改变其结构稳定性，使得金属性和半导体性单壁碳纳米管的稳定性差异增大；进而可通过后处理氧化的方法去除金属性单壁碳纳米管。在深入理解氧对单壁碳纳米管作用机制的基础上，提出并建立直接选择性生长半导体性单壁碳纳米管的氧辅助浮动催化剂化学气相沉积法，即通过原位引入适量的氧，实现半导体性单壁碳纳米管的宏量直接生长。透射电镜、拉曼光谱和吸收光谱等表征表明：所得半导体性单壁碳纳米管的含量达到约90%，直径主要分布在1.4-1.8 nm。研究发现在浮动催化剂化学气相沉积法制备碳纳米管过程中，增加载气的流量既可提高催化剂前驱体的挥发速率，又可以在反应管内形成湍流，增加催化剂颗粒在反应区内的滞留时间，从而制备出最高抗氧化温度达到770°C高质量单壁碳纳米管；通过调控加入硫生长促进剂的量，实现了单壁和双壁碳纳米管的控制生长。进而探索了单壁和双壁碳纳米管在透明导电薄膜方面的应用，结果表明：采用高质量单壁和双壁碳纳米管制的成透明导电薄膜透明导电薄膜在79%的透光率下，其表面电阻分别为63 Ω/sq和86 Ω/sq。其透明导电性远优于其他方法制备的碳纳米管。"
其他摘要	"Single-walled carbon nanotubes (SWCNTs) can be imagined to be a one-dimensional tubular structure rolled up from a single layer graphene sheet. Their unique structure, excellent mechanical and electrical properties make SWCNTs attractive in a variety of potential applications. The precise control on the electrical property and even chirality of SWCNTs has been a focus in this research area, which is an important precondition for the application of SWCNTs in nanoelectronic devices. On the other hand, to achieve high-quality CNTs by diminishing defects and improving their crystallinity is a key favor for the application of CNTs in transparent conductive film (TCFs) and some other macroscopic devices. In this dissertation, the growth of SWCNTs and double-walled CNTs (DWCNTs) by floating catalyst chemical vapor deposition is studied, where we mainly focus on the control over the diameter and electronic property of SWCNTs, and the transparent conductive property of the SWCNTs and DWCNTs with good structural integrality is also investigated. By using a combined in situ and post-synthesis oxidation method, metallic SWCNTs are effectively removed and high purity semiconducting SWCNTs are obtained. When oxygen is introduced during the growth of SWCNTs by the floating catalyst chemical vapor deposition, the reaction between SWCNTs and oxygen occurs, and the difference between the thermal stabilities of metallic and semiconducting SWCNTs (m- and s-SWCNTs) is enlarged, so that the m-SWCNTs can be removed by further post-synthesis oxidation treatment. Thermogravimetric analysis shows that the anti-oxidation temperatures of the m- and s- SWCNTs are 460 °C and 530 °C, respectively. After a 10 h post-synthesis oxidation at 400 °C and HCl immersion treatment, m-SWCNTs, small diameter SWCNTs, amorphous carbon, and metal catalyst are removed. Combined characterizations from transmission electron microscopy, Raman spectroscopy and adsorption spectroscopy demonstrate that the content of semiconducting SWCNTs in the resulting sample reaches around 90%. Based on the understanding upon the role that oxygen plays during the growth of SWCNTs, we propose an oxygen-assisted chemical vapor deposition for the direct synthesis of s-SWCNTs. Due to the difference of the reactivity of s- and m-SWCNTs, s-SWCNTs can be well retained while the majority of m-SWCNTs are removed when appropriate oxygen is introduced during growth. Under an optimized condition, enriched s-SWCNTs with a purity of ~90% and diameters in the range of 1.4-1.8 nm are directly obtained. By tuning the experimental parameters of the floating catalyst chemical vapor deposition approach, high purity SWCNTs and DWCNTs with good structural stability are obtained. These CNTs with good structural completeness show advantage in fabricating transparent conducting films. It is found that increasing the flow rate of carrier gas can not only accelerate the evaporation of catalyst precursor but also form turbulence in the reactor and hence prolong the stay of catalyst particles in the reaction zone, and as a result, high quality SWCNTs with an high anti-oxidation temperature of 770 °C are obtained. Transparent conducting films were fabricated using the high quality CNTs, and 63 Ω/sq and 86 Ω/sq at a light transmittance of 79% are obtained for the SWCNTs and DWCNTs, respectively, which are superior than those of the CNTs prepared by other techniques."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64275
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	于冰. 浮动催化剂化学气相沉积法控制制备单壁和双壁碳纳米管[D]. 北京. 中国科学院金属研究所,2011.