O papel dos defeitos Stone-Wales nas propriedades tribológicas das bicamadas de grafeno

Abstract

Graphene is a material known for its exceptional properties and has many applications in different areas of science. Among these properties, we can mention its low coefficient of friction, which is a positive feature in some applications, but which hinders the use of this material in others. For example, in a material composed of several graphene layers, the low friction causes the layers to slide when an external force is applied, making the composite material less resistant. There are ways around this problem, such as introducing covalent bonds between graphene layers. However, this end-of-course work proposes as an alternative the application of defects in graphene networks, mainly Stone-Wales, to increase their static friction coefficient. So, in this work, we studied the influence of Stone-Wales defects on the mechanical and tribological properties of graphene bilayers. This was done using Molecular Dynamics simulations using the LAMMPS software and the ReaxFF reactive potential. We considered samples with defects randomly introduced into graphene bilayers. To estimate the static friction force, we measured the force needed to separate the two layers. The results showed a significant increase in the coefficient of static friction for the samples with defects, especially those with Stone-Wales defects. Although the introduction of Stone-Wales defects impairs the mechanical properties of an individual graphene sheet, our results indicate that, for structures composed of several graphene sheets, the introduction of defects can improve the mechanical properties of the whole, making it more difficult to separate the monolayers.