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Surface-induced structural transformation in nanowires

机译：纳米线中表面诱导的结构转变

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摘要

One of the unique features of nanomaterials is that they have large surface-to-volume atom ratios compared to bulk materials. The intrinsic compressive stress along the nanowire axis can be as large as tens of GPa, and spontaneous reorientation or phase transformation may occur in order for the nanowires to return to the low-energy state. Upon tensile loading, the nanowires can revert back to the original high-energy orientation or phase without introducing any defects. Two mechanisms are mainly involved in the deformation: (1) twinning/detwinning and (2) stress-induced martensitic phase transformation (MT)/inverse MT. Generally, this surface-induced behavior can only occur at a temperature higher than the critical temperature, T_c, due to the energy barrier for structural transformation. As a result, ordinary nanoscale metals can exhibit pseudo-elasticity and shape memory effects previously only observed from special alloys such as nickel titanium (NiTi). These nanowires have the predicted recoverable strain on the order of 40%-70% which is much larger than that of bulk NiTi (5%-10%), but have extremely low energy dissipation (2% for W nanowires, for example). Surface-induced structural transformation has been observed from fcc, bcc, and hcp single-element metal nanowires, intermetallic alloy nanowires, multiiayered and core-shell composite nanowires, and even oxide and nitride compound semiconductor nanowires. This unique phenomenon enables the design of novel and flexible nanoelectromechanical systems (NEMS) having potential applications in nanomanipulators, energy storage, sensors, switches, and so on. We will review the breakthrough and development in this field in the past ten years, mainly focusing on the physical mechanisms and dominant factors governing this spontaneous structural transition. Future developments will also be discussed.
机译：纳米材料的独特特征之一是，与块状材料相比，它们具有较大的表面积与体积之比。沿着纳米线轴的固有压缩应力可以高达数十GPa，并且可以发生自发的重新取向或相变，以使纳米线返回到低能量状态。在拉伸载荷下，纳米线可以回复到原始的高能取向或相，而不会引入任何缺陷。变形主要涉及两个机制：（1）孪生/孪生和（2）应力诱发的马氏体相变（MT）/逆MT。通常，由于结构转变的能垒，这种表面感应行为只能在高于临界温度T_c的温度下发生。结果，普通的纳米级金属可以表现出伪弹性和形状记忆效应，以前只能从诸如镍钛（NiTi）的特殊合金中观察到。这些纳米线的预测可恢复应变约为40％-70％，远大于块状NiTi的可恢复应变（5％-10％），但能量耗散极低（例如W纳米线为2％）。已从fcc，bcc和hcp单元素金属纳米线，金属间合金纳米线，多层和核壳复合纳米线，甚至氧化物和氮化物化合物半导体纳米线观察到表面诱导的结构转变。这种独特的现象可以设计出新颖而灵活的纳米机电系统（NEMS），在纳米操纵器，能量存储，传感器，开关等方面具有潜在的应用前景。我们将回顾过去十年中该领域的突破和发展，主要集中在控制这种自发结构转变的物理机制和主导因素上。还将讨论未来的发展。

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  • 来源
    《Materials Science & Engineering》 |2013年第6期|173-209|共37页
  • 作者

    Fei Ma; Ke-Wei Xu; Paul K. Chu;

  • 作者单位

    State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, China,Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China;

    State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, China;

    Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Nanowires; Reorientation; Phase transformation; Pseudo-elasticity; Surface effect;

    机译：纳米线;重新定位;相变;伪弹性;表面效果;

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