(706a) Effects of Pore Morphology and Pore Edge Termination on the Mechanical Behavior of Graphene Nanomeshes

Graphene-based nanomaterials hold great promise for numerous technological applications because of their exceptional mechanical, electronic, and thermal properties. Graphene nanomeshes (GNMs) are ordered, defect-engineered graphene nanostructures consisting of periodic arrays of pores in the graphene lattice with neck widths less than 10 nm. The electronic, transport, and mechanical properties of GNMs can be tuned by varying the structural, chemical, and architectural parameters of the nanomeshes, such as their porosity as well as their pore lattice structure, pore morphology, and pore edge termination. Here, we study the mechanical response of GNMs to uniaxial tensile straining and determine their mechanical properties based on molecular-dynamics simulations of dynamic deformation tests according to a reliable bond-order interatomic potential. We establish the dependences of the fracture strain, ultimate tensile strength, and fracture toughness on the nanomesh porosity and derive scaling laws for GNM modulus-density and strength-density relations. We place special emphasis on establishing the dependence of the above properties on pore morphology for GNMs with circular and elliptical pores over a range of aspect ratios. In addition, we demonstrate elastic stiffening and strength reduction caused by pore edge termination with hydrogen atoms; these effects on the GNMs’ mechanical behavior are directly related to the extent of hydrogenation, namely, strength and toughness are further reduced if the hybridization of the hydrogenated carbon atoms at the GNM’s pore edge is changed from sp² to sp³. The underlying mechanisms of crack initiation and propagation, and of nanomesh failure are characterized in detail and the effects of pore morphology and edge passivation on the fracture behavior are demonstrated.