Thermomechanical Insight into the Stability of Nanoporous Graphene Membranes

TL;DR

This study uses atomistic simulations to analyze the mechanical and thermal stability of nanoporous graphene membranes, revealing their high thermal stability, fracture behavior, and dependence of strength on pore size.

Contribution

It provides a comprehensive atomistic analysis of the elastic, fracture, and thermal properties of nanoporous graphene membranes with varying pore sizes.

Findings

Thermally stable up to 4660K, below graphene melting point.

Fracture strains range from 15% to 34%, increasing with pore size.

Critical tensile strength depends on pore size, not temperature.

Abstract

Porous graphene (PG) is a graphene derivative endowed of nanoporous architectures. This material possesses a particular structure with interconnected networks of high pore volume, producing membranes with a large surface area. Experiments revealed that PG combines remarkable properties such as high mechanical strength and good thermal stability. In this work, we have carried out fully-atomistic reactive (ReaxFF) molecular dynamics simulations to perform a comprehensive study on the elastic properties, fracture mechanism, and thermal stability of 2D porous n-Benzo-CMPs (CMP and n refer, respectively, to pi-conjugated microporous polymers and the pore diameter) membranes with distinct nanoporous architectures. For comparison purposes, the results were also contrasted with the ones for graphene sheets of similar dimensions. We adopted three different nanoporous diameters: small (3.45 A), medium (8.07 A), and large (11.93 A). Results showed that PG is thermally stable up to 4660K, about 1000K smaller than the graphene melting point (5643K). During the PG heating, linear atomic chains are formed combining carbon and hydrogen atoms. The fracture strains range between 15%-34% by applying a uniaxial loading in both plane directions for temperatures up to 1200K. The fracture strain increases proportionally with the nanoporous size. Remarkably, the critical tensile strength for the PG complete fracture is temperature independent. Instead, it depends only on the nanoporous diameter. All the PG membranes go abruptly from elastic to completely fractured regimes after a critical strain threshold.