多种模式发生在固化金属合金的表面

“条纹斑马，斑点豹子，……”。孩子们从独特的身体图案中从未成为无聊的精确点。尽管生物在皮肤上产生不同的模式令人着迷，但更神秘的是它们与冷冻液体金属的皮肤相似。

模式形成是科学家在数百年来一直在思考的自然奇观之一的经典例子。1952年左右，著名的数学家艾伦·图灵（Alan Turing）（现代计算机的父亲）提出了一个概念模型，以解释两种实用系统的模式形成过程。此后，此类模式也称为图灵模式。

Pattern formation is also commonly adopted by manmade systems and this is especially true in the field of metallurgy. It even has a sub-field called 'metallography', which specialises in the study of microscale patterns and compositions of metals and alloys.

If you snap a multi-component alloy apart and take a look at its cross sections, there is a good chance that you will see alternating stripes or aligned spots of different metal components, just like a microscopic version of the patterns on the skin of a zebra or leopard.

然而，尽管对液态金属合金的核心及其大量固化模式有古老的知识，但它们的表面模式形成现象一直被忽略到现在为止。

在杂志上发表的作品中自然纳米技术，新南威尔士大学（UNSW）悉尼及其奥克兰大学（MacDiarmid Institute），RMIT和UCLA的合作者的研究人员发现，固体金属合金表面发生了多种类型的模式。

该团队使用了两个组件的金属混合物，例如含有少量二晶木的镀胶合金。这些合金很容易融化，从而使实验性观察和控制方便。

“我们可以在普通的光学显微镜下观察表面固化过程，当我第一次看到液态金属表面上的固化前端产生固体图案时，我感到惊讶，”said Dr. Jianbo Tang, the leading author of the work."You can imagine the scene of a glacier moving across the ocean surface, but everything seen under our microscope is metallic and microscopic."唐博士补充说。

To see the finer details of the metallic glacier, electron microscopy was used, and the researchers observed a kaleidoscope of highly ordered patterns including alternating stripes, curved fibres, dot arrays, and some exotic stripe-dot hybrids.

Surprisingly, the team found that, when these patterns are formed, the abundance of the low-concentration element bismuth at the surface region was much increased. Such surface enrichment found in this study defies conventional metallurgical understandings.

研究人员将这种新观察到的固化现象背后的魔术与液体金属的独特表面结构相关联，他们还使用超级计算机来模拟该过程。在他们的计算机模拟中，观察到在合金表面积聚的小数量中的鞭毛原子，看似在镀至原子的海洋中随机移动。

"This previously ignored surface solidification phenomenon improves our fundamental understanding of liquid metal alloys and their phase transition processes. In addition, this autonomous surface process can be used as a patterning tool for designing metallic structures and creating devices for advanced applications in future electronics and optics."said Prof. Kourosh Kalantar-Zadeh, a corresponding author of the study.

The collaboration between UNSW and the MacDiarmid Institute for Advanced Materials and Nanotechnology was established by Australian Research Council (ARC) Centre of Excellence Future Low-Energy Electronics Technologies (FLEET).

研究

Unique surface patterns emerging during solidification of liquid metal alloys was published in自然纳米技术January 2021 (DOI 10.1038/s41565-020-00835-7)

Source:https://www.fleet.org.au/