Coalescence and Phase Separation During Spinodal Decomposition of Solvent Mixtures Far From the Critical Point

abstractcts - 9978781 r。在这项工作的前几个阶段，我们研究了部分可混相液体的混合物在其混相曲线[2][4]上深度淬火时发生的相变。这项研究的动机是由以前的nsf资助的调查，其中溶剂b[3]。这项工作的主要结果之一是发现，在相变之后，即使乳化剂和表面活性化合物溶解在混合物中，聚并和相分离也非常迅速。与大多数输运过程一样，相分离是由两种基本输运过程驱动的：要么使用高粘度体系（如聚合物熔体和合金），要么将液体混合物淬火至低于其混相曲线[6]-[9]的几毫米。在这些情况下，当体系的温度刚刚超过混相曲线的温度时，混合相分离形成了定义明确的斑块，其典型尺寸随时间增长为t1/3[6]-[10]。另一方面，由于吸引力的影响，低粘度、深度淬火的液体混合物通过对流分离，使界面面积趋于最小。在我们最近关于spinodal分解的研究中，我们发现对流导致了快速聚并的雨滴信息，其典型的大小随时间线性增长。此外，我们的研究结果表明，表面张力驱动的吸引力远远大于排斥的静电力，从而解释了为什么低粘度液体混合物的相分离发生得很快，而不管乳化剂的存在。虽然我们的研究产生了新颖和意想不到的结果，但要实现我们的最终目标并模拟在存在表面活性化合物的相变过程中液体混合物的流动，还需要做很多工作。下面的建议旨在解决其中的一些问题。我们特别希望集中在以下四个领域的研究。部分可混相液体混合物相分离和独立分解过程中形成乳剂和阻碍聚结的化合物和杂质的作用。正如我们所看到的，在萃取过程中使用部分混溶溶剂的主要优点之一是相分离不受乳化剂存在的影响。在这项研究中，我们打算更好地理解这一现象，强调在这种现象停止发生的限制下。粘度在相分离中的作用。由于我们知道低粘度液体混合物（Peclet数大于10,000）的相分离与高粘度液体混合物（Peclet数小于10）的相分离有很大的不同，我们建议研究中等粘度液体混合物的宏观静态相分离动力学，即Peclet数在10到10,000.3之间。剪切对独立分解的作用。这项研究的动机是，在实际的提取过程中，快速冷却需要混合，这反过来可能导致乳化。这一过程可以在库埃特装置中模拟，其中流体混合物经历恒定的剪切。扩展我们的理论模型来模拟前三点所研究的效应。

ABSTRACTCTS-9978781R. MauriCUNY City CollegeIn the previous stages of this work we have studied the phase transition occurring when a mixture of partially miscible liquids is deeply quenched across its miscibility curve [2][4]. This study was motivated by a previous NSF-funded investigation, where solvents [1][3]. One of the main results of this work was the discovery that, following phase transition, coalescence and phase segregation are very rapid, even when emulsifiers and surface-active compounds are dissolved within the mixture.Like most transport processes, phase separation is driven by two basic demising process is retarded by either using high-viscosity systems, such as polymer melts and alloys, or by quenching the liquid mixtures only by few millikelvins below their miscibility curve [6]-[9]. In these cases, right after the temperature of the system has crossed that of the miscibility curve, the mixture phase separates by forming well-defined patches, whose typical size grows wit time as t1/3 [6]-[10]. On the other hand, low-viscosity, deeply quenched liquid mixtures separates by convection, due to the influence of an attractive force, which tends to minimize the interfacial area. In our recent studies on spinodal decomposition, we showed that convection leads to the information of rapidly coalescing drops, whose typical size grows linearly in time. In addition, our results have shown that surface tension-driven attractive forces are far larger that repulsive electrostatic forces, thus explaining why the phase separation of low-viscosity liquid mixtures occurs rapidly, irrespectively of the presence of emulsifiers.While our investigation has produced novel and unexpected results, much work is required to achieve our ultimate goal and model the flow of liquid mixtures during phase transition in the presence of surface-active compounds. The following proposal is intended to address some of these problems. In particular, we want to focus on the following four areas of research.1. The role of emulsion-forming and coalescence-hindering compounds and impurities during phase segregation and spinodal decomposition of partially miscible liquid mixtures. As we saw, one of the main advantages of using partially miscible solvents in extraction processes is that phase segregation is unaffected by the presence of emulsifiers. In this research we intend to better understand this phenomenon, stressing the limitations under which is ceases to occur.2. The role of viscosity during phase separation. Since we know that phase separation in low-viscosity fluid mixtures (with Peclet numbers larger than 10,000) is very different than in high-viscosity's (with Peclet numbers smaller than 10), we propose to study the dynamics of macroscopically quiescent phase separating liquid mixtures with intermediate viscosity, i.e. with Peclet numbers ranging from 10 to 10,000.3. The role of shear on spinodal decomposition. This investigation is motivated by the fact that in practical extraction processes a rapid cooling requires mixing, which in turn may cause emulsification. This process can be modeled in a Couette apparatus, where the fluid mixture undergoes constant shear.4. Extension of our theoretical model to simulate the effects studied in the previous 3 points.