Continuous Transformations of the Nucleation Mechanism in the Undercooled State
Continuous Transformations of the Nucleation Mechanism in the Undercooled State
复制标题
过冷态成核机制的持续转变
DOI：
10.1021/acs.cgd.7b01759
复制
发表时间：
2017
影响因子：
3.8
通讯作者：
Wilde G.
中科院分区：
文献类型：
--
作者：
Zhang Y;Simon C;Volkmann T;Kolbe M;Wilde G.
几十年来，成核研究一直依赖于经典成核理论。在这张图中，热波动控制着新发展相的临界尺寸、均匀核的形成。同时，结构不均匀性或杂质或外在基质（例如表面或容器壁）可能有利于临界尺寸核的形成，导致所谓的异质成核。具体来说，根据这个理论框架，预计在临界冷却速率下会发生异质和均质之间的动力学成核转变。自经典成核理论发展以来，这种成核的基本图景就一直被应用，但这种转变很少在简单金属系统的实验中观察到。现在，随着快速扫描芯片量热法的发展和模型合金的仔细选择，我们已经能够通过实验绘制这两种基本成核模式之间的动力学转变。
Studies on nucleation have relied for many decades on the classical nucleation theory. Within that picture, thermal fluctuations govern the formation of critically sized, homogeneous nuclei of the newly developing phase. At the same time, structural inhomogeneities or impurities or extrinsic substrates such as surfaces or container walls can favor the formation of a critical-sized nucleus, leading to so-called heterogeneous nucleation. Specifically, according to this theoretical framework, a kinetic nucleation transition between heterogeneous and homogeneous is predicted to happen at a critical cooling rate. This underlying picture of nucleation has been applied since the development of classical nucleation theory, but this transition has rarely been observed experimentally for simple metallic systems. Now, with the development of fast scanning chip calorimetry and careful selection of a model alloy, we have been able to experimentally map the kinetic transition between these two fundamental modes of nucleation.