Ding Feng, Rosén Arne, Campbell Eleanor E B, Falk Lena K L, Bolton Kim
Department of Physics, Göteborg University, SE-412 96 Göteborg, Sweden.
J Phys Chem B. 2006 Apr 20;110(15):7666-70. doi: 10.1021/jp055485y.
A new model is proposed for the encapsulation of catalyst metal particles by graphite layers that are obtained, for example, in low-temperature chemical vapor deposition production of carbon nanotubes (CNTs). In this model graphite layers are primarily formed from the dissolved carbon atoms in the metal-carbide particle when the particle cools. This mechanism is in good agreement with molecular dynamics simulations (which show that precipitated carbon atoms preferentially form graphite sheets instead of CNTs at low temperatures) and experimental results (e.g., encapsulated metal particles are found in low-temperature zones and CNTs in high-temperature regions of production apparatus, very small catalyst particles are generally not encapsulated, and the ratio of the number of graphitic layers to the diameter of the catalyst particle is typically 0.25 nm(-1)).
提出了一种新模型，用于通过例如在碳纳米管（CNT）的低温化学气相沉积生产中获得的石墨层来封装催化剂金属颗粒。在该模型中，当颗粒冷却时，石墨层主要由金属碳化物颗粒中溶解的碳原子形成。该机制与分子动力学模拟（其表明在低温下沉淀的碳原子优先形成石墨片而不是碳纳米管）和实验结果（例如，在生产设备的低温区发现封装的金属颗粒，在高温区发现碳纳米管，非常小的催化剂颗粒通常不被封装，并且石墨层数与催化剂颗粒直径的比值通常为0.25 nm(-1)）高度吻合。
