Du Guixiang, Feng Shouai, Zhao Jianghong, Song Chang, Bai Shuli, Zhu Zhenping
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, People's Republic of China.
J Am Chem Soc. 2006 Dec 6;128(48):15405-14. doi: 10.1021/ja064151z.
The synthesis of carbon nanotubes (CNTs) has been proved to be greatly promoted by vapor metal catalysts, but the fast reaction feature and the required high-temperature environment involved in CNT evolution usually make it difficult for an insight into the evolution mechanism. Here, we successfully freeze the synthetic reaction at intermediary stages and observe the detailed morphologies and structures of the obtained intermediates and various objects related to carbon nanotubes. It is unveiled that there is a kindred evolution linkage among carbon nanoparticles, nanowires, and nanotubes in the vapor catalyst-involved synthetic processes: tiny carbon nanoparticles first form from a condensation of gaseous carbon species and then self-assemble into nanowires driven by an anisotropic interaction, and the nanowires finally develop into nanotubes, as a consequence of particle coalescence and structural crystallization. The function of metals is to promote the anisotropic interactions between the nanoparticles and the structural crystallization. An annealing transformation of carbon nanoparticles into nanotubes is also achieved, which gives further evidence for the evolution mechanism.
碳纳米管（CNT）的合成已被证明在气相金属催化剂的作用下能得到极大促进，然而，碳纳米管生长过程中快速的反应特性以及所需的高温环境，通常使得深入了解其生长机制变得困难。在此，我们成功地将合成反应冻结在中间阶段，并观察到所获得的中间体以及与碳纳米管相关的各种物体的详细形态和结构。结果表明，在涉及气相催化剂的合成过程中，碳纳米颗粒、纳米线和纳米管之间存在一种类似的生长联系：微小的碳纳米颗粒首先由气态碳物种凝聚形成，然后在各向异性相互作用的驱动下自组装成纳米线，最终由于颗粒聚结和结构结晶，纳米线发展成纳米管。金属的作用是促进纳米颗粒之间的各向异性相互作用以及结构结晶。我们还实现了碳纳米颗粒向纳米管的退火转变，这进一步证明了该生长机制。
