Negative Poisson's ratio in graphene-based carbon foams

TL;DR

This study uses molecular dynamics simulations to reveal an intrinsic negative Poisson's ratio in graphene-based 3D carbon foams, driven by buckling and structural features, with potential for tunable and anisotropic auxetic nanomaterials.

Contribution

It uncovers a novel intrinsic negative Poisson's ratio mechanism in graphene-based carbon foams caused by buckling, expanding the family of auxetic nanomaterials.

Findings

Negative Poisson's ratio exists intrinsically in CFs.

Negative Poisson's ratio depends on cell length and buckling.

Negative Poisson's ratio is strongly anisotropic.

Abstract

Using molecular dynamics simulations, we find an in-plane negative Poisson's ratio intrinsically existing in the graphene-based three-dimensional (3D) carbon foams (CFs) when they are compressed uniaxially. Our study shows that the negative Poisson's ratio in the present CFs is attributed to their unique molecular structures and triggered by the buckling of the CF structures. This novel mechanism makes the negative Poisson's ratio of CFs strongly depend on their cell length, which offers us an efficient means to tune the negative Poisson's ratio in nanomaterials. Moreover, as the buckling modes of CFs are topographically different when they are compressed in different directions, their negative Poisson's ratio is found to be strongly anisotropic, which is in contrast to the isotropic positive Poisson's ratio observed in CFs prior to the buckling. The discovery of the intrinsic negative Poisson's ratio in 3D CFs will significantly expand the family of auxetic nanomaterials. Meanwhile, the novel mechanism of nano-auxetics proposed here may open a door to manufacture new auxetic materials at the nanoscale.