Direct observation of oscillatory-shear-induced order in colloidal suspensions
Direct observation of oscillatory-shear-induced order in colloidal suspensions
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DOI：
10.1103/physreve.57.6859
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发表时间：
1998-06-01
影响因子：
2.4
通讯作者：
Pusey, PN
中科院分区：
文献类型：
--
作者：
Haw, MD;Poon, WCK;Pusey, PN
我们使用光学显微镜直接研究模型硬球进行振荡剪切在一个平行的浓缩胶体悬浮液中的顺序。接骨板几何形状。在高应变振幅的颗粒顺序迅速进入剪切平面中的六边形平面，定向，使得密堆积的方向是平行于速度轴，对应于以前的散射观测在其他几何形状。在低应变下，多晶结构形成，由六边形有序区域组成，现在具有不同取向的分布，在紧密堆积方向垂直于速度轴的取向周围达到峰值。这种多晶性解释了先前在散射图案中注意到的无序的证据。有序区域生长，直到“颗粒”填充样品。在剪切有序结构中观察到局部无序的各种例子，包括空位、位错和堆垛层错。在循环中观察到的平面运动是复杂的，但有一些证据表明，在高应变下，平面的“Z字形”运动，正如以前的研究所提出的那样。
We use optical microscopy to directly study ordering in concentrated colloidal suspensions of model hard spheres subjected to oscillatory shear in a parallel. plate geometry. At high strain amplitude the particles order quickly into hexagonal planes in the plane of shear, oriented so that a close-packed direction is parallel to the velocity axis, corresponding to previous scattering observations in other geometries. At low strain a polycrystalline structure forms, consisting of hexagonally ordered regions now with a distribution of different orientations, peaked around an orientation where a close-packed direction is now perpendicular to the velocity axis. Such polycrystallinity explains the evidence of disorder previously noted in scattering patterns. The ordered regions grow until "grains" fill the sample. Various examples of local disorder are observed,in the shear-ordered structures, including vacancies, dislocations, and stacking faults. The observed.motion of the planes during the cycle is complicated, but there is some evidence of a "zigzag" motion of planes at high strain, as has been proposed in previous studies.