Computational Studies of Graphene Growth and Carbonaceous Polyethylene Nanocomposites
Licentiate thesis, 2012
Graphene, the youngest allotrope of carbon, has attracted a lot of attention in different fields of science due to its unique electrical, mechanical, and optical properties. Controlling the growth of graphene is a very topical subject and critical for producing material with desired properties since the properties of graphene are highly dependent on its atomic structure and it is often desirable that the material contains very few or (if possible) no defects. Another allotrope of carbon which has become of great interest in the field of polymeric nanocomposites (PNCs) is carbon nanotubes (CNTs); this is due to the unique mechanical, electrical and thermal properties as well as the light weight of CNTs which make them suitable as reinforcement additives in PNCs. This includes composites of polyethylene (PE), which is widely used in different commercial applications.
In this study, Monte Carlo simulations based on a tight binding model is used to study the growth of graphene in the absence of a catalyst, and compare this with the growth mechanism on a Ni(111) surface. This is the first simulation of the growth of defect-free structures at the atomic level and also allows for the study of the mechanisms of defect formation and healing.
A valid force field is selected to study the effect of SWCNTs on the polymer morphology in large PE composite systems. The results show that the PE wrapped around the SWCNT thereby increasing the radius of gyration of the PE. Interfacial shear strength, interfacial bonding energy and Young’s modulus is measured and results show that short SWCNTs as reinforcement do not increase the Young’s modulus for the systems studied here, whereas longer, aligned SWCNTs increased the Young’s modulus in the SWCNT axial direction.