In situ experimental mechanics of nanomaterials at the atomic scale

Abstract

Sub-micron and nanostructured materials exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. These properties are important for their applications as building blocks for the fabrication of nano-and micro-devices as well as for their use as components for composite materials, high-strength structural and novel functional materials. These nano-related deformation and mechanical behaviors, which are derived from possible size and dimensional effects and the low density of defects, are considerably different from their conventional bulk counterparts. The atomic-scale understanding of the microstructural evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these 'unusual' phenomena and is important for designing new materials, novel structures and applications. This review presents the recent developments in the methods, techniques, instrumentation and scientific progress for atomic-scale in situ deformation dynamics on nanomaterials, including nanowires, nanotubes, nanocrystals, nanofilms and polycrystalline nanomaterials. The unusual dislocation initiation, partial-full dislocation transition, crystalline-amorphous transitions and fracture phenomena related to the experimental mechanics of the nanomaterials are reviewed. Current limitations and future aspects using in situ high-resolution transmission electron microscopy of nanomaterials are also discussed. A new research field of in situ experimental mechanics at the atomic scale is thus expected. Keywords: atomic scale; dislocation; experimental mechanics; in situ; nanomaterial; twin INTRODUCTION Recent studies on nanostructured materials, including nanowires (NWs), 1,2 nanotubes (NTs), 1,3 nanocrystals (NC), 4 micro/nanopillars (NPs) 5-7 and nanocrystalline, 8,9 have revealed a variety of 'unusual deformation' phenomena compared with their bulk counterparts, such as high strength, nano-piezoelectric effects and unusual plastic deformation behaviors. Nanostructured materials can apparently sustain a larger dynamic range of elastic and plastic strains than conventional materials. The results from these studies indicate that the fundamental dislocation processes that initiate and sustain plastic flow and fracture in nanoscale materials are considerably different than in their conventional bulk counterparts. These 'unusual' phenomena not only allow these materials to possess excellent mechanical properties but also enable the tuning of their band structures and related novel electronic, magnetic, optical, photonic and catalytic properties. Revealing the atomic-scale deformation mechanisms of nanomaterials (NM) and controlling their elastic and plastic properties are useful for realizing the desired mechanical, physical and chemical properties through the application of stress or strain.Although extensive studies have been conducted to investigate the mechanical properties of NM, 10 the majority of the atomic

Dynamic and atomic-scale understanding of the twin thickness effect on dislocation nucleation and propagation activities by in situ bending of Ni nanowires

“…It has been demonstrated that twin-structured metallic NWs exhibit strong HallPetch effects with a decrease in twin thickness (TT) [6,8,[13][14][15], with a nearly ideal strength achieved by decreasing the TT [6,[13][14][15]. These findings indicate that the strength of twin-structured metallic NWs can be significantly affected by the TT [16,17]. However, whether the TT has an effect on dislocation behavior and how twin-structured NWs accommodate plastic deformation remain unclear [6,17,[18][19][20][21][22][23][24][25][26][27][28][29].…”

Shear modulus and Poisson's ratio of single‐walled carbon nanotubes: Numerical evaluation

“…Experimental methods for measuring the elastic modulus of CNTs, based on in situ techniques of atomic force microscopy (AFM) and transmission electron microscopy (TEM) have been established [4][5][6][7]. The common point in the experimental studies is the evidence of unequalled mechanical properties of the individual CNTs.…”

Observation of enhanced carrier transport properties of Si ⟨100⟩-oriented whiskers under uniaxial strains

“…For low-dimensional materials, the effect of strain on tuning physical properties becomes enhanced when compared with their bulk counterparts owing to the broader tunable range resulted from the large elasticity when the dimension of a material is scaled down. [7][8][9][10][11][12] For example, the loadable elastic strain of nanomaterials can be approximately reached to their theoretical values, [13][14][15][16][17][18][19][20] which can be increased by 2-3 orders of magnitude higher than their bulk forms. Thus, such a huge difference for the loadable strain between the nanomaterials and their bulk counterparts may bring remarkable changes in physical properties.…”