Pseudo Hall–Petch Strength Reduction in Polycrystalline Graphene

Abstract

The fracture of polycrystalline graphene is explored by performing molecular dynamics simulations with realistic finite-grain-size models, emphasizing the role of grain boundary ends and junctions. The simulations reveal a ~50% or more strength reduction due to the presence of the network of boundaries between polygonal grains, with cracks preferentially starting at the junctions. With a larger grain size, a surprising systematic decrease of tensile strength and failure strain is observed, while the elastic modulus rises. The observed crack localization and strength behavior are well-explained by a dislocation-pileup model, reminiscent of the Hall-Petch effect but coming from different underlying physics.

Polycrystalline graphene and other two-dimensional materials

“…Propagation of cracks both along GBs and within single-crystalline grains was observed (Fig. 5f) 134,135 . Importantly, the failure of graphene can be considered as brittle, since dislocations are completely immobile at normal conditions 135,136 .…”

“…5f) 134,135 . Importantly, the failure of graphene can be considered as brittle, since dislocations are completely immobile at normal conditions 135,136 . In addition to mechanical properties, it is also interesting to consider whether and how GBs may affect or even be used to engineer phonon (thermal) transport 137,138 .…”

Charge and Spin Transport in Disordered Graphene-Based Materials

“…[179] More restricted models containing several connected hexagonal graphene grains have recently confirmed these findings. [180] Although much progress has been made in understanding the mechanical strength of polycrystalline graphene, questions still remain. For example, the breaking loads for early measurements [14,174] differ significantly from those measured more recently.…”

“…4.23d) shows a summary of the values of ρ GB derived from measurements compared to the simulation results. [17,180,26,120,23,216] The solid symbols are from the electrical measurements described earlier In this section, and the open symbols are the numerical simulations. Here, most measurements give ρ GB in the range of 1 to 10 kΩ.µm, except for one that gives values one to two orders of magnitude smaller.…”

Status and Prospect of Application about the New Materials Graphene

“…Graphene is a nano material, that it has the thinnest, maximum strength and strongest conductive thermal conductivity [1], also known as the "wonder material", "black gold", "king of the new materials". Since the discovery of graphene materials, technical personnel in various countries to make full use of their excellent performance, expected to be applied in many industrial areas [2], but so far there is still not a large-scale industrial production and application.…”