纳米尺度下金属的塑性成形：纳米晶须的相互扩散诱导弯曲
Plastic forming of metals at the nanoscale: interdiffusion-induced bending of bimetallic nanowhiskers
摘要：
通过施加机械载荷来控制纳米级金属物体的塑性成形是一个挑战，因为无缺陷的纳米晶体通常在接近理论剪切强度下屈服，随后是不受控制的灾难性失效。在这里，而不是机械负载，我们利用化学应力不平衡相互扩散来操纵纳米晶须的形状。采用分子束外延技术制备了具有超高抗弯强度的金铁双金属纳米晶须。无缺陷的单晶Au纳米晶须上的单面Fe涂层表现出单晶和多晶区域。在高温下退火的纳米晶须的曲率和不可逆的弯曲，这是由于晶界Kirkendall效应的Au沿晶界在Fe层中的扩散过程中的逐渐变化。本研究的结果表明，在超强金属纳米结构的受控塑性成形中，化学相互扩散具有很高的潜力。
英文摘要：
Controlled plastic forming of nanoscale metallic objects by applying mechanical load is a challenge, since defect-free nanocrystals usually yield at near theoretical shear strength, followed by an uncontrolled catastrophic failure. Herein, instead of mechanical load, we utilize chemical stress from imbalanced interdiffusion to manipulate the shape of nanowhiskers. Bimetallic Au-Fe nanowhiskers with an ultra-high bending strength were synthesized employing the molecular beam epitaxy technique. The one-sided Fe coating on the defect-free, single-crystalline Au nanowhisker exhibited both single- and poly-crystalline regions. Annealing the bimetallic nanowhiskers at elevated temperatures led to gradual change of curvature and irreversible bending, which is attributed to the grain boundary Kirkendall effect during the diffusion of Au along the grain boundaries in the Fe layer. The results of this study demonstrate a high potential of chemical interdiffusion in the controlled plastic forming of ultra-strong metal nanostructures.
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