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Light Scattering in a Critical Binary Mixture under a Flow

流动下临界二元混合物中的光散射

基本信息

批准号：
07454089
负责人：
HAMANO Kenzi
金额：
$ 4.8万
依托单位：
Gunma University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

In this work we have investigated shear-induced effects arising from a coupling between the phase separation in a binary mixture and shear in presence of a macroscopic flow. Besides, for the purpose to get informations associated with the time-dependent correlation function in a sheared system we have measured dynamic light scattering for a dilute solution of Brownian particles with shear. We summarize here our main results :(1) It has been observed using a technique of phase-contrast optical microscopy that the phase separation of a critical mixture under shear results in the formation of a stationary domain structure, sometimes referred to a string phase, in which the highly anisotropic concentration-domains in the form of long tubes oriented parallel to the flow are present. The long tube-like string phase were broken up to small spherical domains when the shear was turned off.(2) We have measured the effective viscosity in a critical mixture involving phase-separating concentration … More -domains, which are imposed to shearing by a Couette flow in a gap between two concentric cylinders. The effective viscosity thus obtained are almost compatible with the rheological equation predicted very recently by Onuki, derived from the biccontinuous condition that the shear stresses should balance at the interface when the emerging two phases have different viscosities.(3) The time-dependent correlation function has been investigated for a sheared solution of a polystirene latex, which depends on the scattering geometry, especially the scattered wave vector component associated with the direction of the flow. The factors affecting the time-dependent correlation function include the rate of shear, the scattering volume observed, and the orientation of the scattering angle with respect to the velocity and shear in the solution. Despite these problems there may be ways to measure the critical fluctuations of a binary mixture under the flow for a given scattering geometry.The present results would provide a key to understanding the shearing process in a fluid mixture in terms of critical-point universality. Less

在这项工作中，我们已经调查了剪切诱导的影响所产生的耦合之间的相分离的二元混合物和剪切存在的宏观流。此外，为了得到与剪切系统中的含时关联函数有关的信息，我们还测量了布朗粒子稀溶液在剪切作用下的动态光散射。本文总结了我们的主要结果：（1）用相差光学显微镜技术观察到临界混合物在剪切作用下的相分离导致了稳定畴结构的形成，有时称为弦相，其中存在平行于流动方向的长管形式的高度各向异性的浓度畴。当剪切停止时，长管状的弦状相被破碎成小的球形畴。(2)本文测量了含有分相浓度的临界混合物的有效粘度 ...更多信息 - 域，这是强加给两个同心圆柱体之间的间隙中的库埃特流剪切。由此获得的有效粘度几乎是相容的流变方程预测最近Onuki，来自双连续条件，即剪切应力应平衡时，新兴的两相界面具有不同的粘度。(3)本文研究了聚苯乙烯胶乳剪切溶液的时间相关函数，它依赖于散射几何形状，特别是与流动方向有关的散射波矢量分量。影响时间相关函数的因素包括剪切速率、观察到的散射体积以及散射角相对于溶液中的速度和剪切的取向。尽管存在这些问题，但对于给定的散射几何形状，仍有可能测量二元混合物在流动下的临界波动，本研究结果将为理解流体混合物中剪切过程的临界点普适性提供一把钥匙。少