Tunable shape transformation of freezing liquid water marbles.
Tunable shape transformation of freezing liquid water marbles.
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DOI：
10.1039/c3sm51885j
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发表时间：
2014-02
期刊：
影响因子：
3.4
通讯作者：
D. Zang;Kejun Lin;Wen-Kuan Wang;Yaxi Gu;Yongjia Zhang;Xingguo Geng;B. Binks
中科院分区：
文献类型：
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作者：
D. Zang;Kejun Lin;Wen-Kuan Wang;Yaxi Gu;Yongjia Zhang;Xingguo Geng;B. Binks
涂有气相二氧化硅纳米颗粒的液态水弹珠在冷冻时表现出各种形状转变，这取决于纳米颗粒的疏水性。形状可以在重熔过程中恢复。对于涂覆有最疏水颗粒的大理石，在冷冻时形成顶部具有尖状突起的垂直延长形态。对于涂覆有疏水性较低的颗粒的大理石，形成横向扩展的飞碟状形态。由于颗粒在气-水界面上的位置不同，异相成核位置不同，从而导致对冻结的不同响应。如果颗粒更多地浸入水中，则冰胚倾向于在颗粒之间的凹腔中形成。由冻结和连续成核引起的水的体积膨胀导致覆盖液滴表面的颗粒网络的连续横向拉伸，并最终导致大理石的水平膨胀形状。如果颗粒更多地暴露于空气，则成核发生在颗粒的凸面上，类似于疏水性基底上的裸水滴。
Liquid water marbles coated with fumed silica nanoparticles exhibit various shape transformations upon freezing which are dependent on the hydrophobicity of the nanoparticles. The shape can be recovered during re-melting. For marbles coated with the most hydrophobic particles, a vertically prolonged morphology with a pointed protrusion on the top is formed on freezing. For marbles coated with less hydrophobic particles, a lateral expanded flying saucer-shaped morphology is formed. The different responses to freezing result from the different heterogeneous nucleation sites owing to the different positions of the particles at the air-water interface. If the particles are more immersed in water, ice embryos tend to form in the concave cavities between the particles. The volume expansion of water caused by freezing and continuous nucleation lead to continuous lateral stretching of the particle network coating the droplet surface and ultimately to the horizontally inflated shape of the marble. If the particles are more exposed to air, nucleation occurs on the convex surface of the particles, similar to that of a bare water droplet on a hydrophobic substrate.