title: Mechanism of strength reduction along the graphenization pathway.
abstract: Even though polycrystalline graphene has shown a surprisingly high tensile strength, the influence of inherent grain boundaries on such property remains unclear. We study the fracture properties of a series of polycrystalline graphene models of increasing thermodynamic stability, as obtained from a long molecular dynamics simulation at an elevated temperature. All of the models show the typical and well-documented brittle fracture behavior of polycrystalline graphene; however, a clear decrease in all fracture properties is observed with increasing annealing time. The remarkably high fracture properties obtained for the most disordered (less annealed) structures arise from the formation of many nonpropagating prefracture cracks, significantly retarding failure. The stability of these reversible cracks is due to the nonlocal character of load transfer after a bond rupture in very disordered systems. It results in an insufficient strain level on neighboring bonds to promote fracture propagation. Although polycrystallinity seems to be an unavoidable feature of chemically synthesized graphenes, these results suggest that targeting highly disordered states might be a convenient way to obtain improved mechanical properties.
authors.affiliation: Laboratoire des Composites ThermoStructuraux, Université de Bordeaux, CNRS, Commissariat à l'énergie atomique et aux énergies alternatives, Herakles, Pessac 33600, France. ; Institut des Sciences Moléculaires, Université de Bordeaux, CNRS, Talence 33400, France. ; Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mor 62209, Mexico.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gamboa
authors.affiliation: Laboratoire des Composites ThermoStructuraux, Université de Bordeaux, CNRS, Commissariat à l'énergie atomique et aux énergies alternatives, Herakles, Pessac 33600, France.
authors.forename: Baptiste
authors.identifier: 0000-0001-5797-0946
authors.initials: B
authors.lastname: Farbos
authors.affiliation: Institut des Sciences Moléculaires, Université de Bordeaux, CNRS, Talence 33400, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Aurel
authors.affiliation: Laboratoire des Composites ThermoStructuraux, Université de Bordeaux, CNRS, Commissariat à l'énergie atomique et aux énergies alternatives, Herakles, Pessac 33600, France.
authors.forename: Gérard L
authors.identifier: 0000-0003-1606-6867
authors.initials: GL
authors.lastname: Vignoles
authors.affiliation: Laboratoire des Composites ThermoStructuraux, Université de Bordeaux, CNRS, Commissariat à l'énergie atomique et aux énergies alternatives, Herakles, Pessac 33600, France. ; MultiScale Material Science for Energy and Environment, Massachusetts Institute of Technology-CNRS, Cambridge, MA 02139, USA.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Leyssale
keywords: fracture; grain boundaries; molecular dynamics; polycrystalline graphene; strength; thermal annealing