Role of Catalyst Nanoparticle Size On the Growth of Single-Walled Carbon Nanotubes

This study investigates the effect of metal catalyst size on the growth of single-walled carbon nanotubes (SWNT). The synthesis process of SWNTs is a target of many studies. An understanding of how they grow will open more possibilities for controlling the structure and properties of SWCTs. During the synthesis of SWNTs, numerous variables such as temperature, flow rate of the precursor gas, and diffusion of carbon inside and outside the surface play a vital role in the growth of SWNTs. Reactive Molecular Dynamics simulations are performed in order to determine which catalyst sizes are favorable for growth and which are not. The use of MD simulations allows for observation at initial stages of the synthesis process which provides the work of adhesion between the metal nanoparticle catalyst and graphite structure. Our results illustrate the diameter of the fullerene corresponds to the size of the nanoparticle, hence, its curvature energy. When a catalyst size is favored for growth, the SWNT is characterized by a cap lift-off; otherwise, a graphitic encapsulation occurs. Therefore, the work of adhesion must be weak enough to obtain curvature energy similar to a cap lift-off.