Thermomechanical insight into the stability of nanoporous graphene membranes
ML Pereira and LA Ribeiro, FLATCHEM, 24, 100196 (2020).
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 angstrom), medium (8.07 angstrom), and large (11.93 angstrom). Results showed that PG is thermally stable up to 4660 K, about 1000 K smaller than the graphene melting point (5643 K). During the PG heating, linear atomic chains are formed combining carbon and hydrogen atoms. The fracture strains range between 15% and 34% by applying a uniaxial loading in both plane directions for temperatures up to 1200 K. The fracture strain increases proportionally with the nanoporous size. All the PG membranes go abruptly from elastic to completely fractured regimes after a critical strain threshold.
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