金属性单壁碳纳米管的宏量可控制备及其透明导电特性研究

It is highly important and challenging to selectively grow metallic single-wall carbon nanotubes (m-SWCNTs), because SWCNTs synthesized by conventional methods are usually a mixture of 67% semiconducting (s-) SWCNTs and 33% m-SWCNTs, which greatly limits their applications as transparent conductive materials in flexible electronics field. Based on the principle that small-diameter SWCNTs are more chemically active than big ones and would be preferentially removed under appropriate conditions, we propose to synthesize large-diameter m-SWCNTs in large scale by using a “diameter control/in situ-etching” floating catalyst chemical vapor deposition (CVD) technique. By optimizing catalyst structure and growth thermodynamic and kinetic conditions, we will first try to obtain SWCNT samples containing large-diameter m-SWCNTs and small-diameter s-SWCNTs. Then gas phase etchants, like hydrogen and moisture, will be introduced in situ to selectively remove the more active s-SWCNTs due to their samll diameter. By optimizing the type and concentration of the etchant and the thermodynamics and kinetics of etching reactions, high purity m-SWCNTs with large diameter will be directly synthesized. The competition between the diameter-selective etching and electrical type-selective etching will be studied. The “diameter-control/in situ-etching” floating catalyst CVD method will be established and optimized for the bulk synthesis of m-SWCNTs. Furthermore, large-area transparent conductive films will be fabricated by using the m-SWCNTs obtained. The influence of the structure and configuration of the m-SWCNTs on the performance of the transparent conductive films will be investigated. We are to make high-performance transparent conductive thin films based on m-SWCNTs and then pave the way for future applications of m-SWCNTs in flexible electronics devices.

针对通常制备的单壁碳纳米管（简称碳管）中金属性和半导体性碳管共存这一制约其作为透明导电材料在柔性电子学等领域实际应用的瓶颈问题，本项目将采用浮动Fe基催化剂CVD法，利用大直径碳管稳定性高的特点，提出通过“直径调控-原位刻蚀”这一策略制备大直径金属性碳管。首先通过优化Fe基催化剂结构、碳管生长的热力学和动力学条件，实现较大直径金属性碳管和较小直径半导体性碳管的控制生长；继而原位通入水蒸气或氢气等刻蚀剂选择性去除小直径半导体性碳管，从而获得大直径金属性碳管。研究大直径金属性碳管和小直径半导体性碳管的成核、生长机制，阐明碳管选择性刻蚀的直径和导电属性的依赖关系，建立宏量制备金属性碳管的“直径调控-原位刻蚀”方法。进而利用制备的金属性碳管构建大面积柔性透明导电膜，研究金属性碳管的结构及搭接方式对其透明导电特性的影响规律，为金属性碳管高性能透明导电膜在柔性电子器件中的应用提供科学依据和材料基础。

金属性单壁碳纳米管的可控制备是当前碳纳米管研究的难点之一。本项目提出了三种金属性单壁碳纳米管的可控制备方法，探讨了非金属催化剂、双金属催化剂、载气、碳源等化学气相沉积生长条件对不同导电属性单壁碳纳米管直径的影响机制，研究了影响单壁碳纳米管透明导电性能的关键因素，设计、制备了高性能单壁碳纳米管透明导电薄膜，并构建了高性能纳电子器件。项目执行期间，主要取得的研究进展和成果有：1）通过调控非金属SiOx催化剂的颗粒尺寸及Si/O比，选择性制备出高纯度金属性单壁碳纳米管，研究表明，SiOx的颗粒尺寸和氧含量对于选择生长金属性单壁碳纳米管起到了重要作用；2）以尺寸均一、单分散、密排六方结构、高熔点的双金属固溶体CoRe4纳米颗粒为催化剂，结合生长动力学条件控制，实现了窄直径分布、高纯度金属性单壁碳纳米管的可控生长；3）以二茂铁、六羰基钨作为催化剂前驱体、正己烷为碳源、噻吩为生长促进剂、氢气和氦气为载气，用直接注射浮动催化剂化学气相沉积法制备了金属性富集的单壁碳纳米管；4）采用浮动催化剂化学气相沉积法制备出具有“碳焊”结构、单根分散的单壁碳纳米管透明导电薄膜，所得单壁碳纳米管薄膜在90%透光率下的方块电阻仅为41Ω □-1；建立了米级单壁碳纳米管薄膜的宏量连续制备方法，利用这种高性能单壁碳纳米管透明导电薄膜构建了柔性有机发光二极管原型器件，其电流效率达到已报道单壁碳纳米管柔性有机发光二极管器件最高值的7.5倍，并具有优异的柔性和稳定性。.项目组成员发表高质量学术论文7篇，申请/授权发明专利4项，相关研究工作在学术会议上作邀请/口头报告/会议展板5次。