Dynamics and "Phase Behavior" of Foams and Concentrated Emulsions

摘要Eli Ruckenstein CTS-9522710 SUNY布法罗 泡沫和浓缩液-液乳液的稳定性是它们在任何实际应用中使用的必要先决条件。 重力驱动的排水的连续相，主要是通过一个相互连接的网络高原边界通道（相邻的气泡之间形成）起着关键作用，在确定其稳定性，因为有相当大的排水和崩溃之间的相互作用。 因此，对排水系统的系统研究对于理解这些系统的不稳定性非常重要。 提出了一个统一的理论处理排水，其中考虑到连续相和分散相的分离。 这个问题将被处理在两种方式：一个传统的宏观方法，其中制定了大量的微分元素包含大量的气泡和微观的方法，其中分散相液滴表示Voronoi多面体和详细的平衡写在每个高原边界通道的复杂网络中的平衡。 后一种方法将使我们能够清楚地确定分散相的多分散性对排水过程的影响。 尝试将两种方法的结果联系起来，以制定一个校正的宏观模型，这是计算上更容易处理。 对方程的检查表明，可以根据浓乳液的初始状态来确定在排水平衡（对应于高原边界吸力和重力之间的平衡）建立之前相分离。 应该强调的是，这种平衡不是热力学的;然而，液-液浓缩乳液预计会长时间保持这种机械平衡。 将尝试建立一个相图的基础上的初始状态的系统。 通过简单的实验验证了理论预测的正确性。

ABSTRACT Eli Ruckenstein CTS-9522710 SUNY Buffalo The stability of foams and concentrated liquid-liquid emulsions is a necessary prerequisite for their utilization in any practical application. Gravity driven drainage of the continuous phase which takes place primarily through an interconnected network of Plateau border channels (formed between adjacent bubbles) plays a pivotal role in determining their stability since there is considerable interplay between drainage and collapse. A systematic study of drainage is therefore important in understanding the instability in these systems. A unified theoretical treatment of drainage is proposed which takes into account the separation of the continuous and dispersed phases. The problem will be treated in two ways: a conventional macroscopic approach in which balances are formulated over bulk differential elements containing a large number of bubbles and a microscopic approach in which the dispersed phase droplets are represented by Voronoi polyhedral and detailed balances are written over each Plateau border channel in the complex network. The latter approach will enable us to clearly identify the effect of the polydispersivity of the dispersed phase on the drainage process. An attempt will be made to relate the results from the two approaches to formulate a corrected macroscopic model which is computationally more tractable. Inspection of the equations suggests that it is possible to determine based on the initial state of concentrated emulsion which phase separates out before a drainage equilibrium, which corresponds to a balance between the Plateau border suction and gravity, is established. It should be emphasized that this equilibrium is not thermodynamic; liquid-liquid concentrated emulsions are, however, expected to remain in this mechanical equilibrium for a long time. An attempt will be made to establish a phase diagram based on the initial state of the system. Simple experiments are proposed to verify the theoretical predicti ons.