García-Moreno Francisco, Kamm Paul Hans, Neu Tillmann Robert, Bülk Felix, Mokso Rajmund, Schlepütz Christian Matthias, Stampanoni Marco, Banhart John
Institute of Applied Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
Institute of Materials Science and Technology, Technische Universität Berlin, Hardenbergstr. 36, 10623, Berlin, Germany.
Nat Commun. 2019 Aug 21;10(1):3762. doi: 10.1038/s41467-019-11521-1.
The complex flow of liquid metal in evolving metallic foams is still poorly understood due to difficulties in studying hot and opaque systems. We apply X-ray tomoscopy -the continuous acquisition of tomographic (3D) images- to clarify key dynamic phenomena in liquid aluminium foam such as nucleation and growth, bubble rearrangements, liquid retraction, coalescence and the rupture of films. Each phenomenon takes place on a typical timescale which we cover by obtaining 208 full tomograms per second over a period of up to one minute. An additional data processing algorithm provides information on the 1 ms scale. Here we show that bubble coalescence is not only caused by gravity-induced drainage, as experiments under weightlessness show, and by stresses caused by foam growth, but also by local pressure peaks caused by the blowing agent. Moreover, details of foam expansion and phenomena such as rupture cascades and film thinning before rupture are quantified. These findings allow us to propose a way to obtain foams with smaller and more equally sized bubbles.
由于研究高温且不透明的系统存在困难，目前对于液态金属在不断演变的金属泡沫中的复杂流动仍知之甚少。我们应用X射线断层扫描技术（即断层（3D）图像的连续采集）来阐明液态泡沫铝中的关键动态现象，如形核与生长、气泡重排、液体回缩、聚结以及液膜破裂。每种现象都发生在一个典型的时间尺度上，我们通过在长达一分钟的时间内每秒获取208张完整的断层图像来涵盖该时间尺度。一种额外的数据处理算法可提供1毫秒尺度上的信息。在此我们表明，气泡聚结不仅如失重条件下的实验所示是由重力诱导的排水以及泡沫生长所产生的应力引起的，还由发泡剂导致的局部压力峰值引起。此外，对泡沫膨胀的细节以及诸如破裂级联和破裂前液膜变薄等现象进行了量化。这些发现使我们能够提出一种获得具有更小且尺寸更均匀气泡的泡沫的方法。
