Perspectives on the Growth of High Edge Density Carbon Nanostructures: Transitions from Vertically Oriented Graphene Nanosheets to Graphenated Carbon Nanotubes.
Perspectives on the Growth of High Edge Density Carbon Nanostructures: Transitions from Vertically Oriented Graphene Nanosheets to Graphenated Carbon Nanotubes.
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DOI：
10.1021/jp502317u
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发表时间：
2014-07-24
期刊：
影响因子：
--
通讯作者：
Glass JT
中科院分区：
文献类型：
--
作者：
Ubnoske SM;Raut AS;Brown B;Parker CB;Stoner BR;Glass JT
通过等离子体增强化学气相沉积（PECVD）的系统参数研究，深入了解了高边缘密度碳纳米结构的生长。这种结构对电极性能在各种应用中都很重要，如超级电容器、神经刺激和电催化。形貌趋势是温度的函数，石墨化碳纳米管（g-CNTs）在较低温度下作为碳纳米管（CNTs）和由少层石墨烯组成的垂直取向碳纳米片（CNS）之间的中间结构出现。这是首次在同一反应室中通过改变单一参数（温度）合成三种不同形态和维度的碳纳米结构（即1D CNTs、2D CNTs和3D g-CNTs）。采用实验设计（DOE）方法来了解微波PECVD反应器中允许的生长范围，重点是确定工艺空间内石墨化碳纳米管的生长。实验设计中研究的因素包括温度、气体比、催化剂厚度、预处理时间和沉积时间。这一过程有助于预测和模拟在各种生长条件下产生各种纳米级碳形态的高边缘密度碳纳米结构特征。除了受温度影响的形态趋势外，DOE研究还发现了沉积温度与比电容之间的关系。利用透射电子显微镜观察了各种高边缘密度结构的形貌和微观结构。根据这些结果，提出了一种新的石墨烯叶状形成机制，用于在单次沉积过程中合成g-CNTs。
Insights into the growth of high edge density carbon nanostructures were achieved by a systematic parametric study of plasma-enhanced chemical vapor deposition (PECVD). Such structures are important for electrode performance in a variety of applications such as supercapacitors, neural stimulation, and electrocatalysis. A morphological trend was observed as a function of temperature whereby graphenated carbon nanotubes (g-CNTs) emerged as an intermediate structure between carbon nanotubes (CNTs) at lower temperatures and vertically oriented carbon nanosheets (CNS), composed of few-layered graphene, at higher temperatures. This is the first time that three distinct morphologies and dimensionalities of carbon nanostructures (i.e., 1D CNTs, 2D CNSs, and 3D g-CNTs) have been synthesized in the same reaction chamber by varying only a single parameter (temperature). A design of experiments (DOE) approach was utilized to understand the range of growth permitted in a microwave PECVD reactor, with a focus on identifying graphenated carbon nanotube growth within the process space. Factors studied in the experimental design included temperature, gas ratio, catalyst thickness, pretreatment time, and deposition time. This procedure facilitates predicting and modeling high edge density carbon nanostructure characteristics under a complete range of growth conditions that yields various morphologies of nanoscale carbon. Aside from the morphological trends influenced by temperature, a relationship between deposition temperature and specific capacitance emerged from the DOE study. Transmission electron microscopy was also used to understand the morphology and microstructure of the various high edge density structures. From these results, a new graphene foliate formation mechanism is proposed for synthesis of g-CNTs in a single deposition process.
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