Evidence for the existence of an effective interfacial tension between miscible fluids: isobutyric acid-water and 1-butanol-water in a spinning-drop tensiometer.
Evidence for the existence of an effective interfacial tension between miscible fluids: isobutyric acid-water and 1-butanol-water in a spinning-drop tensiometer.
复制标题
旋滴张力计中的异丁酸-水和 1-丁醇-水之间存在有效界面张力的证据。
作者：
J. Pojman;Colin D. Whitmore;M. L. Turco Liveri;R. Lombardo;J. Marszalek;R. Parker;B. Zoltowski
我们报告明确的证据，两种类型的混溶流体之间的有效界面张力，使用旋转滴张力仪（SDT）。异丁酸（IBA）和水的上临界溶解温度（UCST）为26.3 ℃。我们在UCST以下的富水相中创造了一滴富IBA相，然后在UCST以上提高温度，在流体达到热平衡后很长时间，这种下降仍然存在。通过绘制液滴半径立方的倒数（r（-）（3））与旋转速率平方（ω（2））的关系，我们证实了界面张力的存在并估计了其值。可混溶流体之间的过渡保持尖锐，而不是变得更加扩散，并且液滴体积随时间减小。当旋转速率降低80%时，我们通过UCST上方的Rayleigh-Tomotika不稳定性观察到液滴破裂，再次证明了有效界面张力的存在。当将纯IBA注入UCST以上的水中时，即使主液滴的体积随时间减小，也在主液滴内部形成液滴。我们还研究了1-丁醇在水中的溶解度极限以下。随时间测量的有效界面张力值几乎是恒定的，而两相之间的界面随着液滴体积的下降而保持尖锐。发现有效界面张力对温度的变化不敏感，并且总是大于平衡界面张力。虽然这些结果可能不适用于所有的混相流体，但它们清楚地表明，对于某些体系，有效界面张力可以存在并通过SDT测量。
We report definitive evidence for an effective interfacial tension between two types of miscible fluids using spinning-drop tensiometry (SDT). Isobutyric acid (IBA) and water have an upper critical solution temperature (UCST) of 26.3 degrees C. We created a drop of the IBA-rich phase in the water-rich phase below the UCST and then increased the temperature above it. Long after the fluids have reached thermal equilibrium, the drop persists. By plotting the inverse of the drop radius cubed (r(-)(3)) vs the rotation rate squared (omega(2)), we confirmed that an interfacial tension exists and estimated its value. The transition between the miscible fluids remained sharp instead of becoming more diffuse, and the drop volume decreased with time. We observed droplet breakup via the Rayleigh-Tomotika instability above the UCST when the rotation rate was decreased by 80%, again demonstrating the existence of an effective interfacial tension. When pure IBA was injected into water above the UCST, drops formed inside the main drop even as the main drop decreased in volume with time. We also studied 1-butanol in water below the solubility limit. Effective interfacial tension values measured over time were practically constant, while the interface between the two phases remains sharp as the volume of the drop declines. The effective interfacial tension was found to be insensitive to changes in temperature and always larger than the equilibrium interfacial tension. Although these results may not apply to all miscible fluids, they clearly show that an effective interfacial tension can exist and be measured by SDT for some systems.