Engineered Nanosystems

Centre of Excellence in Computational Complex Systems Research

 

Mechanical Properties of Carbon Nanotubes

Researchers: Maria Sammalkorpi, Kaisa Kautto, Antti Kuronenand Kimmo Kaski

Carbon nanotubes are cylindrical all-carbon molecules composed of concentric graphitic shells with extremely strong covalent bonding of atoms within the shells but very weak van der Waals type interaction between them. Due to the unique atomic structure nanotubes have exceptional electronic and mechanical properties which imply a broad range of possible applications as constituents of nanometer-scale devices and novel composite materials.

In this work we are using computational methods to study the atomistic structure of twist grain boundaries of different rotation angles. We are interested in knowing if the interface of all grain boundaries is comprised of a thin amorphous layer, or if there are certain angles for which the interface is crystalline. We are also interested in the grain boundary energy, since it can be compared to experimental results.

The properties of a carbon nanotube depend on the local atomic configuration and defects. For composite and device development it is essential to understand how structural changes affect the properties and our work strives after shedding some more light on the occurring phenomena. Current projects concentrate on evaluating irradiation and irradiation induced defects as a means to improve carbon nanotube strength, load transfer and inter-shell friction. The tools employed are both classical molecular dynamics and dynamical tight binding methods. Fig. 1 shows an example of a defect typical to irradiation and how such defects can link tubes which efficiently prevents tube-tube slippage.

Figure 1

Figure 1. A defect typical to irradiation, a vacancy.

Figure 2

Figure 2.Example of a nanotube bundle in which the nanotubes are linked together by the presence of vacancies.