Temperature-dependent brittle-ductile transition of α-graphyne nanoscroll and its micromechanism

Abstract

One-dimensional (1D) carbon nanomaterials are usually stiff, strong, and brittle. In this study, the tensile mechanical properties of α-graphyne nanoscroll (α-GNS) at different temperatures were systematically investigated using the reactive molecular dynamics method. It was found that the α-GNS could undergo a brittle-ductile transition as the temperature increased from 100 K to 1000 K. When the temperature was below the critical brittle-ductile transition temperature (BDTT) of ∼375 K, the α-GNS exhibited brittle behavior; however, when the temperature was above the BDTT, it exhibited ductile behavior. Dynamic analyses demonstrated that the superplastic behavior was influenced by two typical microstructures: intralayer carbon triatomic rings and interlayer carbon bonds. NEB (nudged elastic band) calculations further showed that the intralayer triatomic rings can promote plastic deformation, while the interlayer bonds retard plastic deformation by increasing the energy barrier of formation of intralayer triatomic rings. However, α-GNSs can also be made to exhibit good ductile behavior below the BDTT by introducing interlayer bonds using high-temperature annealing technology, which is mainly due to the postponed crack propagation in α-GNSs. This study could be beneficial for the design of novel 1D carbon nanomaterials with controllable brittleness and ductility.