A side-by-side comparison of the solidification dynamics of quasicrystalline and approximant phases in the Al-Co-Ni system
A side-by-side comparison of the solidification dynamics of quasicrystalline and approximant phases in the Al-Co-Ni system
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DOI：
10.1107/s2053273318017114
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发表时间：
2019-03-01
影响因子：
1.8
通讯作者：
Shahani, Ashwin J.
中科院分区：
文献类型：
--
作者：
Han, Insung;Xiao, Xianghui;Shahani, Ashwin J.
准晶及其类似物由于其复杂的晶体结构和可能的特殊性质而引起了人们的广泛兴趣。类似物的结构模体与相应准晶的结构模体相似，但它们的结晶路径在多大程度上是相同的？不幸的是，很少有现场实验调查来回答这个问题。在这里，利用硬X射线的高穿透能力，进行了基于同步加速器的X射线层析成像，以捕捉十方准晶及其相关准晶的形核和生长过程。将数据驱动的计算分析与新的热力学数据库相结合，可以高精度地表征结晶的成分和动力学驱动力。实验结果表明，这两种晶体的生长均为一级动力学过程。然而，有些令人惊讶的是，它们的成核和生长速度存在显著差异。根据当代的金属间化合物结晶理论讨论了这种不同行为的原因。
Quasicrystals and their approximants have triggered widespread interest due to the challenge of solving their complex crystal structures as well as their possibly exceptional properties. The structural motifs of approximants are similar to those of the corresponding quasicrystals, but to what extent are their crystallization pathways the same? Unfortunately, there have been very few in situ experimental investigations to answer this question. Here, by leveraging the high penetrating power of hard X-rays, synchrotron-based X-ray tomography was conducted in order to capture the nucleation and growth of a decagonal quasicrystal and its related approximant. The combination of data-driven computational analysis with new thermodynamic databases allowed the characterization, with high precision, of the constitutional and kinetic driving forces for crystallization. The experimental results prove that the growth of both crystals from a liquid is dominated by first-order kinetics. Nevertheless, and somewhat surprisingly, significant differences were observed in their rates of nucleation and growth. The reasons for such divergent behaviours are discussed in light of contemporary theories of intermetallic crystallization.