MD Simulation Of The Interfacial Adhesion Between Carbon Nanotube And Different Surfaces

In 1991, Iijima discovered the hollow carbon fiber using electron microscope, which is called'carbon nanotubes (CNTs)'. From then on, CNTs have attracted great research interest and brought rapid development in CNTs science and technology due to their unique properties such as thermal, mechanical, electronic and optical properties, etc. In recent years, experimental results have shown remarkable enhancements in elastic modulus and strength of metal matrix with an addition of small amounts of CNTs. In CNTs reinforced metal composites, it is difficult to investigate the interfacial adhension between CNTs and the surfaces in experiments since it is very complicated. However, the properties of the composites are mostly determined by the interfacial adhension. Therefore, the molecular mechanics (MM) and molecular dynamic (MD) simulations are applied to solve this problem in this area. This paper aims to investigate the interfacial adhesion between CNTs and different surfaces, the mechanism, the deformation problem and the influence of chemical modification on the deformation of the CNTs on different surfaces.The dynamic behaviour of intrinsic single-walled carbon nanotube (SWNT) on the aluminum surface and the radius, length influence of SWNTs are investigated using MD simulation based on the COMPASS force-field. It is found that SWNT can fully collapse onto Al surface easily, the cylindrical structure rapidly transforms into a linked double graphitic layers paralleling to the plane like a ribbon on top of the Al surface. The radius influence is similar as previous results, and the length has no influence on its collapse. We can find that the collapsing structure of the SWNT is various from different surface roughness, but tiny roughness hardly influence the collapse of SWNTs. The SWNTs also fully collapse on Fe, Ni, graphite surfaces, but partially collapse on Si surface. This maybe attributes to the metallicity of these surfaces, the stronger the metallicity of surface is, more easily CNTs collapse. And the deformation of SWNTs with different diameters on Si surface is in line with previous investigation. Besides, with increasing oxygen concentration, the collapse degree of SWNTs on Fe, FeO and Fe2O3 surfaces decreases, which demonstrates that the deformation of SWNTs is mainly caused by the interaction between the SWNT and the metal atoms.Furthermore, we report that the structural stability of cylindrical SWNT on the surfaces can be improved through the surface modification method. The dynamic behaviour of modified SWNT with different amount of chemical modification on the aluminum surface is investigated using MD simulation. The stability of SWNTs can be enhanced by certain modification coverage, and then the collapse of SWNT can be well avoided. The results also show that, with equal modification coverage, the longer and larger SWNTs are, the more modification coverage SWNTs require to avoid SWNT's collapse by chemical modification, vice versa. Take -NH2 modified SWNT as an example, it is found that the modification coverage required for avoiding the collapse of the SWNTs is various from different surfaces. The interaction energies between Fe, Ni, graphite, Si surfaces and -NH2 modified SWNTs linearly decrease with increasing functional group coverage. We compare the ability of -NH2,–COOH, -CH3 and–OH avoiding the collapse of CNTs on Ni surface. For four kinds of functional groups, -NH2 and–COOH have similar and better ability to avoid the collapse of the SWNTs, -CH3 has worse ability and–OH's ability is the worst.Our simulation results, which could reduce the research period and the cost, would be of great importance in the fabrication of CNTs reinforced metal composites. The results also demonstrate that the modified SWNTs can be potentially used as nano-containers, maintaining or transporting molecules, hydrogen storage, etc.