Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles
Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles
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DOI：
10.1016/j.colsurfa.2015.06.044
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
Erik de Malmazet;Frédéric Risso;O. Masbernat;V. Pauchard
中科院分区：
文献类型：
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作者：
Erik de Malmazet;Frédéric Risso;O. Masbernat;V. Pauchard
研究了微粒和界面老化对毫米级水滴与油/水界面聚结的影响。该系统是不纯的，界面污染随着时间的推移而增长，导致界面张力随着时间的推移缓慢但连续的下降（从35到10 mN/m），这是使用原始技术原位测量的。在没有添加微粒的情况下，聚结时间是随机分布的，并且与液滴直径或界面张力无关。在油/水界面处存在10 μm尺寸的中空玻璃颗粒时，聚结时间变得更具重现性，并且显示出对液滴直径和界面老化的明显依赖性。结果是一致的经典的排水模型假设，在该临界厚度处，间隙膜破裂尺度的微粒直径，结果往往验证桥接的情况。有趣的是，在聚结过程中的膜收缩速度并不遵循平面几何形状中的理论预测。对回缩膜的高速成像显示，回缩时孔缘向上弯曲，导致回缩速度大幅减慢。这是由于新形成的油/液滴界面和老化的油/水界面之间的界面张力差异造成的。
The effect of micro-particles and interface aging on coalescence of millimetre-sized water drops with an oil/water interface is studied over long times. The system is not pure and interface contamination grows with time, resulting in a slow but continuous decrease of interfacial tension over time (from 35 to 10 mN/m), which is measured in situ using an original technique. Without added micro-particles, coalescence times are randomly distributed and uncorrelated to drop diameter or interfacial tension. In presence of 10 μm size hollow glass particles at the oil/water interface, coalescence times become more reproducible and show a clear dependence upon drop diameter and interface aging. Results are consistent with a classical drainage model assuming that the critical thickness at which interstitial film ruptures scales as the micro-particle diameter, a result that tends to validate the bridging scenario. Interestingly, the film retraction speed during the coalescence process does not follow theoretical predictions in a planar geometry. High-speed imaging of the retracting film reveals that the hole rim is bending upward while retracting, resulting in a strong slowdown of retraction speed. This is caused by the difference of interfacial tension between oil/drop freshly formed interfaces and the aged oil/water interface.