Abstract
Mechanical properties of nanomaterials, such as nanowires and nanotubes, are an important feature for the design of novel electromechanical nano-architectures. Since grain boundary structures and surface modifications can be used as a route to modify nanostructured materials, it is of interest to understand how they affect material strength and plasticity. We report large-scale atomistic simulations to determine the mechanical response of nickel nanowires and nanotubes subject to uniaxial compression. Our results suggest that the incorporation of nanocrystalline structure allows completely flexible deformation, in sharp contrast with single crystals. While crystalline structures at high compression are dominated by dislocation pinning and the multiplication of highly localized shear regions, in nanocrystalline systems the dislocation distribution is significantly more homogeneous. Therefore, for large compressions (large strains) coiling instead of bulging is the dominant deformation mode. Additionally, it is observed that nanotubes with only 70% of the nanowire mass but of the same diameter, exhibit similar mechanical behavior up to 0.3 strain. Our results are useful for the design of new flexible and light-weight metamaterials, when highly deformable struts are required.
Highlights
Mechanical properties of nanomaterials, such as nanowires and nanotubes, are an important feature for the design of novel electromechanical nano-architectures
The relevance of the aspect ratio in the ductile to brittle fracture of nanocrystalline nanowires was discussed by Wu et al.[24]; we adopted the aspect ratio of 4.8 to reduce possible finite size effects due to the characteristic length scale of the plastic deformation sources, such as dislocations, and fracture or shear localization z ones[25]
Uniaxial compression is applied to both crystalline and nanocrystalline NTs and NWs until a strain of 0.3 is reached
Summary
Mechanical properties of nanomaterials, such as nanowires and nanotubes, are an important feature for the design of novel electromechanical nano-architectures. The development of lightweight hierarchical metallic nanostructures constitutes an alternative to create materials with novel and unexpected mechanical properties, a subject that recently has attracted much attention and has been extensively studied[1,2] These structures correspond to a collection of mostly nanocrystalline (nc) nanotubes (NTs) or nanowires (NWs), self-assembled as building blocks and suitably arranged to ensure, for a given deformation, a cooperative response of all constituents[3,4,5,6]. The large specific surface areas of NTs allows a richer behavior of grain boundary and dislocation motion Both factors could lead to materials with unexpected mechanical properties. The way these systems recover from different deformation scenarios is discussed
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