溶液法制备碳纳米管和石墨烯透明导电膜的研究

IMR OpenIR

	溶液法制备碳纳米管和石墨烯透明导电膜的研究
	裴嵩峰
学位类型	博士
导师	成会明
	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	碳纳米管石墨烯透明导电膜电泳沉积还原
摘要	"透明导电膜是现代光电设备和平板显示设备中的关键材料。碳纳米管和石墨烯具有高导电性和纳米尺度的特点，利用它们制作的厚度为数纳米到数十纳米的薄膜可以同时满足低表面电阻和高透光率的要求；同时，碳纳米管和石墨烯具有资源丰富、柔性等特点，因此制作柔性透明导电薄膜是最有希望实现碳纳米管和石墨烯应用的领域之一。先通过适当的分散方法将碳纳米管、石墨烯或氧化石墨烯制成均匀的溶液，然后再利用溶液制备薄膜的方法称为溶液法。相对于其他制膜方法，溶液法在保证较高性能的前提下还具有成本低、扩展性强的优点。而碳纳米管的高效成膜和氧化石墨烯的高效还原分别是溶液法制备碳纳米管和石墨烯透明导电薄膜的关键研究内容；本论文主要在这两个方面开展研究。本文提出了电泳沉积和热压转移相结合的方法来制备柔性碳纳米管透明导电膜。即首先利用电泳沉积在惰性且具有良好导电性的不锈钢基体上沉积碳纳米管薄膜，然后将薄膜通过热压处理转移到柔性透明基片表面从而得到柔性透明导电膜。通过研究十二烷基硫酸钠(SDS)分散碳纳米管溶液在稀释过程中的状态变化，解决了在极稀SDS溶液中高效分散碳纳米管的难题，使碳纳米管分散液具有低的溶液电导(48mS)和高的碳纳米管表面带电量(-78.8mV)；通过对电沉积时间的控制，可以实现对膜厚的控制；热压转移可以将碳纳米管膜从不锈钢基片的表面完整的转移到柔性的聚合物基体表面并与基体之间产生很强的嵌入式结合，从而使透明导电膜具有很好的耐弯折性能。性能最优的薄膜在透光率为81%时，表面电阻为220 Ω/□，已满足触摸屏电极的需求；经过10000次弯折实验，薄膜透明导电性能基本保持不变。电泳沉积是工业上常用的制膜方法，具有高效、可控和高质量的优点；这种制膜方法可以被放大到轴辊式的连续制膜，从而实现碳纳米管透明导电膜的大面积连续制备。利用氧化石墨烯良好的水溶性，先利用氧化石墨烯溶液成膜，再对薄膜进行还原是制备石墨烯透明导电薄膜的有效方法；其中，成膜后的还原处理是决定薄膜性能的关键步骤。本文提出了基于卤化反应的氢碘酸还原氧化石墨烯的方法，所得薄膜在透光率为84%时，表面电阻为1.1kΩ/□，优于其他化学还原方法的结果。氢碘酸还原具有快速、高效的特点，并且还原过程可以使薄膜结构进一步的致密化，从而使还原后的薄膜具有高的导电性和机械强度。对还原过程的研究发现了碘的取代和自发消去行为，这对揭示氧化石墨烯的还原机理具有重要价值。"
其他摘要	"Transparent conductive film (TCF) is a key material for modern photo-electronic devices and flat panel displays. Single wall carbon nanotube (SWCNT) and graohene are nanoscale materials with excellent electric conductivity, which can be used to produce thin films with thickness of several or tens nanometers. Such films can be visually transparent and with low surface resistance, which are the essential requirements of TCFs. Furthermore, these nanoscale carbon materials are rich in resources and have excellent flexibility compared with the traditional oxide based TCFs, as a result, flexible TCFs can be produced, which may be one of available applications of SWCNT and graphene in the next decade. TCFs using SWCNTs or graphene can be fabricated by solution based processes. These processes are superior in low cost and good quality compared to the other fabrication methods. However, key points are good dispersion of SWCNTs and efficient film formation for SWCNT TCFs and efficient reduction of graphene oxide (GO) at low temperature for graphene TCFs. This work has focused on these two fields. Electrophoretic deposition (EPD) is a widely used industrial method to produce films with high uniformity from colloid solutions. We produce flexible SWCNT TCFs by combining EPD and hot-press transferring. SWCNT films can be first electrophoretically deposited on conductive stainless steel substrates and then fully transferred to transparent polymer substrates by simple hot-press transferring. A pre-dispersion-then-dilution treatment is used to uniformly disperse SWCNTs in sodium dodecyl sulfate (SDS) solution. This treatment makes the SWCNT dispersion with low electrical conductivity (48 mS) and high Zeta potential (-78.8 mV), both of which are the prerequisites for EPD. The film thickness can be well controlled by varying EPD time, which further controls the film transparency and electrical conductivity; and the hot-press during transferring makes SWCNT films partly anchored into the substrate surface. This structure enables strong interaction between SWCNT films and polymer substrates, which makes TCFs with excellent flexibility. The TCF with best performance of is 220 Ω/□ at 81% transparency can bear over 10000 repeated bending without loss of transparency and conductivity. Furthermore, this EPD-transferring method can be scalled up to a roll-to-roll process to realize the continuous fabrication of SWCNT TCFs. Producing graphene TCFs using GO as starting material is a valuable way since GO is readily water soluble. The film formation using GO solution is very simple but the key process is how to reduce insulated GO films into highly conductive graphene films. We propose the reduction of GO by hydroiodic acid (HI) based on the halogenation reaction. The GO films can be effectively reduced at a temperature no more than 100 °C; furthermore, the reduction process can further densify the film, which improves the electrical conductivity and mechanical strength of the films. TCF achieved by HI reduction has surface resistance of 1.1 kΩ/□ at 84% transparency, which is better than those reduced by the other chemical methods. The research on the reduction process of GO films reveals the substitution of hydroxyl groups by iodine and the spontaneous elimination of iodine from the reduced graphene films, which is useful for the understanding of the reduction mechanism of GO."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64263
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	裴嵩峰. 溶液法制备碳纳米管和石墨烯透明导电膜的研究[D]. 北京. 中国科学院金属研究所,2011.