Schöpe Hans Joachim, Wette Patrick
Institut für Physik, Johannes Gutenberg-Universität Mainz, Mainz, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 1):051405. doi: 10.1103/PhysRevE.83.051405. Epub 2011 May 27.
Understanding the process that drives an undercooled fluid to the crystal state is still a challenging issue for condensed matter physics and plays a key role in designing new materials. The crystallization kinetics and the resulting polycrystalline morphology are given by a complex interplay of crystal nucleation, growth, and ripening. A great deal of progress has been made in recent years using colloidal suspensions as model systems in the study of crystallization. Close analogies to atomic systems are observed which can be exploited to address questions not accessible in atomic solidification. Here we present systematic measurements of the crystallization kinetics of a charged colloidal model system adding small amounts of seeds using time resolved scattering techniques. Large seeds show strong sedimentation under gravity even on the time scale of the crystallization process. To avoid this problem we performed our measurements under microgravity during parabolic flights. We report how the seed size and structure affect crystal nucleation and growth as functions of metastability giving the possibility to modify the crystallization process and the resulting microstructure of the polycrystal.
对于凝聚态物理而言，理解驱动过冷流体转变为晶体状态的过程仍是一个具有挑战性的问题，并且在新型材料设计中起着关键作用。结晶动力学以及由此产生的多晶形态是由晶体成核、生长和熟化的复杂相互作用所决定的。近年来，在利用胶体悬浮液作为模型系统研究结晶方面取得了很大进展。人们观察到与原子系统有密切的相似之处，可利用这些相似之处来解决原子凝固中无法解决的问题。在此，我们使用时间分辨散射技术，对添加少量晶种的带电胶体模型系统的结晶动力学进行了系统测量。即使在结晶过程的时间尺度上，大晶种在重力作用下也会出现强烈沉降。为避免这个问题，我们在抛物线飞行的微重力条件下进行了测量。我们报告了晶种尺寸和结构如何作为亚稳性的函数影响晶体成核和生长，从而有可能改变结晶过程以及多晶的最终微观结构。
