Production of well dispersible single walled carbon nanotubes via a “floating catalyst”-method
Production of well dispersible single walled carbon nanotubes via a “floating catalyst”-method
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DOI：
10.1016/j.ces.2015.08.002
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发表时间：
2015-12
影响因子：
4.7
通讯作者：
F. Toni;H. Xing;J. Walter;V. Strauss;Thomas J. Nacken;C. Damm;Karl-Ernst Wirth;D. Guldi;W. Peukert
中科院分区：
文献类型：
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作者：
F. Toni;H. Xing;J. Walter;V. Strauss;Thomas J. Nacken;C. Damm;Karl-Ernst Wirth;D. Guldi;W. Peukert
在本文中，我们提出了生产单壁碳纳米管（SWCNT）的独特工艺链，并记录了气相生产工艺参数、SWCNT 在胆酸钠水溶液中的分散性及其性能之间的关系。 SWCNTs是通过“浮动催化剂”方法使用二茂铁的乙醇溶液作为前驱体制备的。通过使用优化的提升管反应器设计，可以实现 5 至 20 毫克/小时的生产率，从而减少催化剂颗粒和单壁碳纳米管的不良粘壁现象。低前体浓度以及反应器中短停留时间获得了铁催化剂含量低于 30 wt% 的产品。产品的透射电子显微镜 (TEM) 和统计拉曼分析表明，SWCNT 的直径分布范围为 0.5 至 2.0 nm。发现加工条件，包括前体浓度、停留时间等，对单壁碳纳米管平均几何直径仅有轻微影响。原子力显微镜 (AFM)、3D 荧光光谱和多波长分析超速离心 (AUC) 证明，在胆酸钠水溶液中对制备的单壁碳纳米管进行基于超声处理的后处理可有效实现单壁碳纳米管的个体化。总体而言，随着二茂铁分压的降低，未纯化的 SWCNT 在 2 wt% 胆酸钠水溶液中的分散性增加，进而气相中催化剂浓度降低。使用 SWCNT 进行的统计拉曼光谱显示，所产生的碳物质中超过 75% 是 SWCNT，并且约 2/3 是半导体碳物质。
In this paper, we present a unique process chain for the production of single-walled carbon nanotubes (SWCNT) and document the relationship between the process parameters in gas phase production, the dispersibility of SWCNTs in aqueous solutions of sodium cholate and their properties. SWCNTs were prepared by a “floating catalyst” method using a solution of ferrocene in ethanol as precursor. Production rates in the range from 5 to 20 mg/h were achieved by using an optimized riser reactor design, which enables reduction of undesired wall-sticking of the catalyst particles and SWCNTs. Products featuring iron catalyst contents less than 30 wt% were obtained for low precursor concentrations in combination with short residence time in the reactor. Transmission electron microscopy (TEM) and statistical Raman analyses of the products reveal that the SWCNTs exhibit a diameter distribution ranging from 0.5 to 2.0 nm. Processing conditions, including precursor concentration, residence time, etc. were found to have only a slight impact on the mean geometric SWCNT diameter. Sonication based post-processing of the as-prepared SWCNTs in aqueous solutions of sodium cholate leads to an effective individualization of SWCNTs as proven by atomic force microscopy (AFM), 3D fluorescence spectroscopy, and by multi-wavelength analytical ultracentrifugation (AUC). Overall, the dispersibility of the non-purified SWCNTs in a 2 wt% aqueous solution of sodium cholate increases as the ferrocene partial pressure is decreased and, in turn, the catalyst concentration is reduced in the gas phase. Statistical Raman spectroscopy performed with the SWCNTs reveals that more than 75% of the produced carbon species are SWCNTs and that about 2/3 are semiconducting.