Technology Research Association for Single Wall Carbon Nanotubes, Tsukuba 305-8565, Japan.
ACS Nano. 2012 Jul 24;6(7):5837-44. doi: 10.1021/nn300142j. Epub 2012 Jun 22.
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.
由于其极高的纵横比和一维特性，对齐表示碳纳米管 (CNT) 的一个重要结构参数。在本文中，我们通过在催化剂形成阶段调整活性催化剂的密度，展示了一种控制少壁 CNT 森林从几乎随机到几乎理想对齐的通用方法，这可以通过控制 CNT 森林的质量密度来在实验上实现。实验上，我们发现由于相邻 CNT 的拥挤效应，催化剂密度和对齐程度是不可分割的，即随着密度的增加 CNT 的限制越来越多。因此，CNT 密度决定了对齐程度，该程度随着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，我们开发了一个基于 CNT 弯曲模量的简单一阶模型，该模型可以定量描述任何类型 CNT 的对齐程度（HOF）与碳纳米管间距（拥挤效应）之间的关系。
