Fast-freezing kinetics inside a droplet impacting on a cold surface
Fast-freezing kinetics inside a droplet impacting on a cold surface
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DOI：
10.1073/pnas.1912406117
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发表时间：
2020-02-11
影响因子：
11.1
通讯作者：
Lohse, Detlef
中科院分区：
文献类型：
--
作者：
Kant, Pallav;Koldeweij, Robin B. J.;Lohse, Detlef
撞击液滴的冻结或固化在自然界和技术中无处不在，无论是落在过冷表面上的雨滴;在喷墨打印中，通常使用熔融蜡;在增材制造或金属生产过程中;或者在用于芯片生产的极紫外光刻（EUV）中，其中熔融锡用于产生EUV辐射。对于许多这些工业应用，对固化过程的详细了解是必不可少的。在这里，通过采用一种光学技术的背景下，冻结，即全内反射（TIR），我们阐明了凝固过程中的液滴，而它的影响过冷表面的冻结动力学。我们发现，在足够高的过冷度，一个奇特的冻结形态存在，涉及连续平流冻结前从中心的液滴到其边界。这一现象的研究相结合的经典成核理论的大规模流体力学的液滴尺度上的元素，把两个子字段，传统上已经相当分离。此外，我们报告了一个自剥离现象的冻结飞溅，这是由凝固过程中的瞬态结晶状态的存在驱动。
Freezing or solidification of impacting droplets is omnipresent in nature and technology, be it a rain droplet falling on a supercooled surface; in inkjet printing, where often molten wax is used; in additive manufacturing or metal-production processes; or in extreme ultraviolet lithography (EUV) for the chip production, where molten tin is used to generate the EUV radiation. For many of these industrial applications, a detailed understanding of the solidification process is essential. Here, by adopting an optical technique in the context of freezing-namely, total-internal reflection (TIR)-we elucidate the freezing kinetics during the solidification of a droplet while it impacts on an undercooled surface. We show that at sufficiently high undercooling, a peculiar freezing morphology exists that involves sequential advection of frozen fronts from the center of the droplet to its boundaries. This phenomenon is examined by combining elements of classical nucleation theory to the large-scale hydrodynamics on the droplet scale, bringing together two subfields which traditionally have been quite separated. Furthermore, we report a self-peeling phenomenon of a frozen splat that is driven by the existence of a transient crystalline state during solidification.