Strength and Toughness of Nanocrystalline Graphene
A perspective view of polycrystalline graphene sheet, composed of hexagonal rings of carbon atoms, showing its 3D grain structure (upper image). Modeling of the fracture of such graphene indicates that the crack preferentially extends along the grain boundaries; the color scale indicates the stress distribution (lower image).
The first statistical theory of the toughness of nanocrystalline graphene is developed and used to elucidate the nanoscale origins of the grain-size dependence of its strength and toughness in terms of its inherent point and line defects.
Significance and Impact
Most graphene is synthesized by chemical vapor deposition and thus is polycrystalline. Modeling shows that the strength of such nanocrystalline graphene is 5 times lower than pristine mono-crystalline graphene, with a very low toughness of ~4 MPa√m, i.e., only 4 times that of graphite.
- Calculations were performed using large-scale simulations and continuum modeling to show that the statistical variation in the strength and toughness of nanocrystalline graphene can be quantitatively described in terms of "weakest-link" statistics