Electrical stiffness modulation—confirming the impact of surface excess elasticity on the mechanics of nanomaterials
Electrical stiffness modulation—confirming the impact of surface excess elasticity on the mechanics of nanomaterials
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DOI：
10.1016/j.actamat.2014.04.067
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发表时间：
2014-09
期刊：
影响因子：
9.4
通讯作者：
N. Mameka;J. Markmann;H. Jin;J. Weissmüller
中科院分区：
文献类型：
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作者：
N. Mameka;J. Markmann;H. Jin;J. Weissmüller
表面刚度的局部变化可能会影响纳米结构的弹性响应，但实验对表面过剩弹性常数的大小甚至符号存在分歧。本研究报告了当在电化学环境中的电位控制下调节表面状态时，纳米多孔金块状样品的有效宏观刚度的变化。使用动态机械分析仪中的原位实验来测量储能模量和损耗模量，我们表明，吸附⩽ 1个原子单层的氧物质以及表面上电容控制的过量电子使材料变硬，而氧解吸/电子耗尽则增强了顺应性。有效刚度的相对变化高达 8%，意味着表面过剩弹性常数的变化约为 60 N m−1，远大于从先前清洁表面的原子模拟研究推导出来的该常数的绝对值。由于电极电位仅影响表面，因此我们的观察结果为表面局部刚度变化对纳米结构有效弹性响应的影响提供了确凿的证据。
Local variations in the stiffness at surfaces may affect the elastic response of nanostructures, yet experiments disagree on the magnitude and even sign of the surface excess elastic constants. The present study reports the variation in the effective macroscopic stiffness of bulk samples of nanoporous gold when the surface state is modulated under potential control in an electrochemical environment. Using in situ experiments in a dynamic mechanical analyzer to measure the storage and loss moduli, we show that adsorption of⩽ 1 atomic monolayer of oxygen species as well as a capacitively controlled excess of electrons at the surface stiffen the material, while oxygen desorption/electron depletion enhance the compliance. Relative changes in the effective stiffness of up to 8% imply the variation of a surface excess elastic constant of the order of 60 N m− 1, much larger than the absolute value of that constant deduced from previous atomistic simulation studies of clean surfaces. Since the electrode potential affects exclusively the surface, our observations provide conclusive evidence for the impact of local stiffness variation at surfaces on the effective elastic response of nanostructures.