Alignment Control of Carbon Nanotube Forest from Random to Nearly Perfectly Aligned by Utilizing the Crowding Effect
Alignment Control of Carbon Nanotube Forest from Random to Nearly Perfectly Aligned by Utilizing the Crowding Effect
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DOI：
10.1021/nn300142j
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发表时间：
2012-07-01
期刊：
影响因子：
17.1
通讯作者：
Hata, Kenji
中科院分区：
文献类型：
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作者：
Xu, Ming;Futaba, Don N.;Hata, Kenji
由于碳纳米管具有极高的宽高比和一维特性，取向是碳纳米管重要的结构参数。在本文中，我们展示了一种通过在催化剂形成阶段调整活性催化剂的密度来控制少壁碳纳米管森林从近乎随机到近乎理想排列的一般方法，这可以通过控制碳纳米管森林的质量密度来实验实现。实验发现，由于邻近CNTs的拥挤效应，催化剂密度和取向度之间存在不可分割的联系，即随着密度的增加，CNTs的约束也在增加。因此，碳纳米管的密度决定了排列度，排列度随密度的增加而单调增加。这种关系反过来又允许通过控制质量密度来精确控制对齐。为了进一步理解这种行为，我们基于碳纳米管的弯曲模量建立了一个简单的一阶模型，该模型可以定量描述任何类型碳纳米管的排列度（HOF）与碳纳米管间距（拥挤效应）之间的关系。
Alignment represents an important structural parameter of carbon nanotubes (CNTs) owing to their exceptionally high aspect ratio, one-dimensional property. In this paper, we demonstrate a general approach to control the alignment of few-walled CNT forests from nearly random to nearly ideally aligned by tailoring the density of active catalysts at the catalyst formation stage, which can be experimentally achieved by controlling the CNT forest mass density. Experimentally, we found that the catalyst density and the degree of alignment were inseparably linked because of a crowding effect from neighboring CNTs, that is, the increasing confinement of CNTs with increased density. Therefore, the CNT density governed the degree of alignment, which increased monotonically with the density. This relationship, in turn, allowed the precise control of the alignment through control of the mass density. To understand this behavior further, we developed a simple, first-order model based on the flexural modulus of the CNTs that could quantitatively describe the relationship between the degree of alignment (HOF) and carbon nanotube spacing (crowding effect) of any type of CNTs.