Atomic-scale dynamic observation reveals temperature-dependent multistep nucleation pathways in crystallization
Atomic-scale dynamic observation reveals temperature-dependent multistep nucleation pathways in crystallization
复制标题
DOI：
10.1039/c9nh00308h
复制
发表时间：
2019-11-01
影响因子：
9.7
通讯作者：
Deepak, Francis Leonard
中科院分区：
文献类型：
--
作者：
Li, Junjie;Li, Yunping;Deepak, Francis Leonard
在原子尺度上揭示非经典多步成核的动力学途径对于理解非均匀成核和结晶的复杂微观机制至关重要。然而，由于在实验上解决这些具有挑战性的课题的复杂性，中间态的结构和温度依赖的影响，在原子尺度上的多步成核仍然没有完全理解。在这里，我们进行直接原位原子尺度的观察界面多步成核途径的动力学过程中使用像差校正的TEM。我们提供了直接的证据，温度依赖的多步成核途径在支持铋系统在原子尺度：在接近块体铋熔点的高温下的液滴-晶体两步成核途径，在临界温度T-c1和铋纳米颗粒的最低尺寸相关熔化温度之间的中温下的液滴-局部有序结构-晶体三步成核途径，以及在低于最低熔点（T-1）的温度下的团簇-晶体两步成核途径。根据T-c1纳米颗粒的尺寸相关熔化相图，确定了三种途径中相关的临界温度Tc 1和最低熔点。统计分析表明，成核途径对成核和结晶动力学起重要作用，晶体成核的临界尺寸受温度控制。了解成核过程中的多个中间步骤以及温度对成核途径的影响对团簇、非晶态和晶态材料的合成和生长具有重要意义，这些发现可能进一步丰富成核理论。
Uncovering kinetic pathways of non-classical multistep nucleation at the atomic-scale is critical for understanding the complex microscopic mechanism of heterogeneous nucleation and crystallization. However, due to the intricacies in tackling such challenging topics experimentally, the structure of intermediate states and the temperature dependent effect on multistep nucleation at the atomic-scale are still not fully understood. Here, we conduct direct in situ atomic-scale observations of kinetic processes of interfacial multistep nucleation pathways using an aberration-corrected TEM. We provide direct evidence for temperature-dependent multistep nucleation pathways in a supported bismuth system at the atomic-scale: a droplet-crystal two-step nucleation pathway at high temperature close to the melting point of bulk bismuth, a droplet-local ordered structure-crystal three-step nucleation pathway at medium temperature between a critical temperature T-c1 and the lowest size-dependent melting temperature of bismuth nanoparticles, and a cluster-crystal two-step nucleation pathway at a temperature lower than the lowest melting point (T-l). The related critical temperature Tc1 and the lowest melting point in the three pathways are confirmed based on the size-dependent melting phase diagram of T-c1 nanoparticles. Statistical analyses imply that the nucleation pathway plays an important role in deciding the nucleation and crystallinity kinetics, and the critical size of crystal nucleation is controlled by temperature. The understanding of multiple intermediate steps in nucleation and the temperature effect on nucleation pathways has important implications for the synthesis and growth of clusters, amorphous and crystalline materials, and these findings may further enrich the nucleation theory.