Atomic mechanism of metal crystal nucleus formation in a single-walled carbon nanotube
Atomic mechanism of metal crystal nucleus formation in a single-walled carbon nanotube
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DOI：
10.1038/s41557-020-0538-9
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发表时间：
2020-08-28
期刊：
影响因子：
21.8
通讯作者：
Kaiser, Ute
中科院分区：
文献类型：
--
作者：
Cao, Kecheng;Biskupek, Johannes;Kaiser, Ute
了解晶体是如何在原子尺度上成核的，对于理解并进而控制各种材料的结构和性能至关重要。然而，由于原子核的规模和高度动态的性质，很难观察到原子核的形成和早期生长。在这里，我们使用了单壁碳纳米管作为试管，并使用了一个结合了像差校正的透射电子显微镜的原子注入器，以便能够在原子尺度上原位成像成核的初始步骤。对于三种不同的金属，我们观察到了非均相成核之前的三个主要过程：直接从原子种子(Fe)形成晶核，从预先存在的非晶纳米团簇(Au)形成晶核，或者通过两个独立的非晶亚纳米团簇(Re)合并形成晶核。我们论证了非晶态前驱体的作用以及在核形成之前存在的能垒。在所有三种情况下，晶核的形成都是通过两步成核机制进行的。
Knowing how crystals nucleate at the atomic scale is crucial for understanding, and in turn controlling, the structure and properties of a wide variety of materials. However, because of the scale and highly dynamic nature of nuclei, the formation and early growth of nuclei are very difficult to observe. Here, we have employed single-walled carbon nanotubes as test tubes, and an 'atomic injector' coupled with aberration-corrected transmission electron microscopy, to enable in situ imaging of the initial steps of nucleation at the atomic scale. With three different metals we observed three main processes prior to heterogeneous nucleation: formation of crystal nuclei directly from an atomic seed (Fe), from a pre-existing amorphous nanocluster (Au) or by coalescence of two separate amorphous sub-nanometre clusters (Re). We demonstrate the roles of the amorphous precursors and the existence of an energy barrier before nuclei formation. In all three cases, crystal nucleus formation occurred through a two-step nucleation mechanism.