Colloidal crystal growth monitored by Bragg diffraction interference fringes.
Colloidal crystal growth monitored by Bragg diffraction interference fringes.
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DOI：
10.1016/j.jcis.2010.04.072
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发表时间：
2010-10-15
影响因子：
9.9
通讯作者：
Asher, Sanford A.
中科院分区：
文献类型：
--
作者：
Bohn, Justin J.;Tikhonov, Alexander;Asher, Sanford A.
我们监测的剪切熔融结晶胶体阵列（CCA）的结晶的晶体生长动力学。fcc CCA在流动池壁表面处非均匀地成核。我们研究了（111）布拉格衍射峰的演化，并首次通过测量布拉格衍射干涉条纹的时间演化来定量监测生长。模拟的条纹图案的演变暴露的晶体厚度的增加的时间依赖性。最初的扩散驱动的线性增长，其次是成熟驱动的增长。在80 ~ 90 μM NaCl浓度范围内，面心立方晶体首先以1.9 ~ 4.2 μm/sec的速率线性生长，直到它们接触到本体中均匀成核的晶体。在较低的盐浓度下，干涉条纹是不可见的，因为颗粒之间的强静电相互作用导致高活化势垒，防止缺陷退火并导致较低的晶体质量。fcc晶体在>90 μM NaCl浓度下熔化成液相。增加NaCl浓度减缓了fcc CCA的生长速率，这与经典的Wilson-Frenkel生长理论的预期一致。壁形核CCA的最终厚度由异质形核CCA和同质形核CCA之间的竞争决定，并且随着NaCl浓度的增加而增加。
We monitor the crystal growth kinetics of crystallization of a shear melted crystalline colloidal array (CCA). The fcc CCA heterogeneously nucleates at the flow cell wall surface. We examined the evolution of the (111) Bragg diffraction peak, and, for the first time, quantitatively monitored growth by measuring the temporal evolution of the Bragg diffraction interference fringes. Modeling of the evolution of the fringe patterns exposes the time dependence of the increasing crystal thickness. The initial diffusion driven linear growth is followed by ripening-driven growth. Between 80 to 90 μM NaCl concentrations the fcc crystals first linearly grow at rates between 1.9 and 4.2 μm/sec until they contact homogeneously nucleated crystals in the bulk. At lower salt concentrations interference fringes are not visible because the strong electrostatic interactions between particles result in high activation barriers, preventing defect annealing and leading to a lower crystal quality. The fcc crystals melt to a liquid phase at >90 μM NaCl concentrations. Increasing NaCl concentrations slows the fcc CCA growth rate consistent with the expectation of the classical Wilson-Frenkel growth theory. The final thickness of wall nucleated CCA is determined by the competition between growth of heterogeneously and homogenously nucleated CCA and increases with higher NaCl concentrations.
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