Anomalous elasticity and damping in covalently cross-linked graphene aerogels

Abstract

Understanding materials elasticity is critical for their effective use in numerous applications. Herein, the authors show that a graphene aerogel made of covalently cross-linked graphene sheets exhibits anomalous superelastic behaviour and develop a quantitative origami model that captures stress-strain behaviour of these aerogels. Elasticity in materials is a phenomenon that provides a basis for widespread practical applications in engineering, medicine, and electronics. Most of the conventional materials can withstand only small deformations within the elastic limit, typically below 5% of their original size. Here, we report a graphene aerogel made of covalently cross-linked graphene sheets that exhibits anomalous superelastic behavior up to 92% of compressive and 68% tensile strain. We show that the graphene aerogel has a nonlinear stress-strain characteristic with the compressive and tensile yield strength of 4.5 GPa and 0.6 MPa, respectively. By considering the elastic bending of graphene sheets and buckle folding of pore walls, we develop a quantitative origami model that describes the stress-strain behavior of the aerogel. In addition, we analyze the mechanical oscillations of the graphene aerogel, observing superfast vibration damping within a time scale of 50-250 ns. Our study demonstrates the unusual coexistence of superelasticity and superfast damping within a cellular material with atomically thin pore walls, a phenomenon that does not occur in bulk elastic materials described by Hook's law.