Bubble formation in water with addition of a hydrophobic solute
Bubble formation in water with addition of a hydrophobic solute
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DOI：
10.1140/epje/i2015-15072-9
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发表时间：
2015-07-07
影响因子：
1.8
通讯作者：
Onuki, Akira
中科院分区：
文献类型：
--
作者：
Okamoto, Ryuichi;Onuki, Akira
我们发现，在单组分液体的共存曲线（CX）外，加入少量溶质可以发生相分离。溶质浓度随液气溶剂化化学势差的增大而减小。作为一种典型的气泡形成溶质，我们考虑O-2在环境液态水中的存在，它具有温和的疏水性，临界温度低于水的临界温度。当周围液体压力高于饱和蒸汽压p（cx）时，这种溶质可以从液体中排出形成气畴。这种溶质诱导的气泡形成是在部分干燥壁面上的一级转变，而气体膜在完全干燥壁面上连续生长。我们建立了气泡自由能G对于体积分数很小的体泡和表面泡。在拉普拉斯压力平衡下，它变成了泡半径R的函数。然后，对于大于阈值的足够大的溶质密度，δ G在临界半径处显示局部最大值，在平衡半径处显示最小值。我们还研究了发生在CX外的溶质诱导成核，在那里气泡比临界半径大，直到达到平衡。
We show that phase separation can occur in a one-component liquid outside its coexistence curve (CX) with addition of a small amount of a solute. The solute concentration at the transition decreases with increasing the difference of the solvation chemical potential between liquid and gas. As a typical bubble-forming solute, we consider O-2 in ambient liquid water, which exhibits mild hydrophobicity and its critical temperature is lower than that of water. Such a solute can be expelled from the liquid to form gaseous domains while the surrounding liquid pressure is higher than the saturated vapor pressure p(cx). This solute-induced bubble formation is a first-order transition in bulk and on a partially dried wall, while a gas film grows continuously on a completely dried wall. We set up a bubble free energy Delta G for bulk and surface bubbles with a small volume fraction phi. It becomes a function of the bubble radius R under the Laplace pressure balance. Then, for sufficiently large solute densities above a threshold, Delta G exhibits a local maximum at a critical radius and a minimum at an equilibrium radius. We also examine solute-induced nucleation taking place outside CX, where bubbles larger than the critical radius grow until attainment of equilibrium.