Country School of Physics and Technology, Center for Electron Microscopy, MOE Key Laboratory of Artificial Micro- and Nano-structures, and Institute for Advanced Studies, Wuhan University, Wuhan, 430072, China.
Suzhou Institute of Wuhan University, Suzhou, Jiangsu, 215123, China.
Small. 2023 May;19(21):e2206380. doi: 10.1002/smll.202206380. Epub 2023 Feb 24.
Deformation twinning merits attention because of its intrinsic importance as a mode of energy dissipation in solids. Herein, through the atomistic electron microscopy observations, the size-dependent twinning mechanisms in refractory body-centered cubic molybdenum nanocrystals (NCs) under tensile loading are shown. Two distinct twinning mechanisms involving the nucleation of coherent and inclined twin boundaries (TBs) are uncovered in NCs with smaller (diameter < ≈5 nm) and larger (diameter > ≈5 nm) diameters, respectively. Interestingly, the ultrahigh pseudo-elastic strain of ≈41% in sub-5 nm-sized crystals is achieved through the reversible twinning mechanism. A typical TB cross-transition mechanism is found to accommodate the NC re-orientation during the pseudo-elastic deformation. More importantly, the effects of different types of TBs on the electrical conductivity based on the repeatable experimental measurements and first-principles calculations are quantified. These size-dependent mechanical and electrical properties may prove essential in advancing the design of next-generation flexible nanoelectronics.
变形孪晶值得关注，因为它是固体中能量耗散的固有模式。在此，通过原子电子显微镜观察，展示了拉伸载荷下难熔体心立方钼纳米晶体（NC）中尺寸相关的孪晶机制。在直径较小（直径<≈5nm）和较大（直径>≈5nm）的 NC 中，分别发现了涉及相干和倾斜孪晶界（TB）成核的两种不同的孪晶机制。有趣的是，亚 5nm 尺寸晶体中高达约 41%的超高拟弹性应变是通过可逆孪晶机制实现的。发现了一种典型的 TB 交叉转变机制，以适应伪弹性变形过程中 NC 的重新取向。更重要的是，基于可重复的实验测量和第一性原理计算，量化了不同类型 TB 对电导率的影响。这些尺寸相关的力学和电学性能可能对下一代柔性纳米电子学的设计具有重要意义。
