Outstanding Elastic Limit of a Thin Film Composed of Nickel Nanosprings.
Outstanding Elastic Limit of a Thin Film Composed of Nickel Nanosprings.
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由镍纳米弹簧组成的薄膜的杰出弹性极限。
DOI：
10.1166/jnn.2017.12384
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发表时间：
2017
影响因子：
--
通讯作者：
T. Kitamura
中科院分区：
文献类型：
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作者：
Shaoguang Chen;Kazuya Iwata;T. Sumigawa;T. Kitamura
本文介绍了使用原子力显微镜 (AFM) 在由掠射角沉积 (GLAD) 技术形成的镍螺旋纳米元件（纳米弹簧）组成的薄膜上进行垂直加载的实验结果。由于螺旋元件通常具有较大的可逆变形极限，因此预计薄膜的屈服会出现特征行为。从载荷与位移曲线中，我们发现镍纳米弹簧薄膜具有突出的弹性极限。表观屈服应变计算为ε′ Y = 5.2～6.2 × 10−2，约为块状镍（ε Y = 0.29～0.44 × 10−3）的200倍。然而，比较螺旋弹簧和固体薄膜中的最大剪切应力，由于应力条件（扭转）的差异，形状效应（螺旋形状）仅约为10～20倍。差异的根源在于纳米弹簧的尺寸效应，因为由于底层结构形态的差异，纳米级金属比块体金属具有更高的屈服应变。形状效应和尺寸效应的结合给薄膜带来了巨大的弹性极限。
This paper presents experimental results of vertical loading using an atomic force microscope (AFM) performed on a thin film consisting of nickel helical nanoelements (nanosprings) formed by glancing angle deposition (GLAD) technique. As a helical element has large reversible deformation limit in general, a characteristic behavior is expected on the yielding of the film. From the load versus displacement curves, we find the outstanding elastic limit of nickel nanosprings film. The apparent yield strain is evaluated as ε′ Y = 5.2˜6.2 × 10−2, which is around 200 times of that in bulk nickel (ε Y = 0.29˜0.44 × 10−3). However, comparing the maximum shear stress in the helical spring and the solid film, the shape effect (helical shape) is only around 10˜20 times stemmed from the difference in the stress condition (torsion). The origin of difference is attributed to the size effect of nanosprings, as nano-scale metals have higher yield strain than that of bulk counterpart because of the difference in the understructure morphology. The combination of shape effect and size effect brings about the giant elastic limit on the film.