Solidification of a colloidal hard sphere like model system approaching and crossing the glass transition.
Solidification of a colloidal hard sphere like model system approaching and crossing the glass transition.
复制标题
接近并跨越玻璃化转变的胶体硬球状模型系统的凝固。
作者：
M. Franke;Sebastian Golde;H. Schöpe
我们研究了胶体硬球模型体系中的玻璃化和结晶过程。用时间分辨静态光散射法测量了凝固过程的动力学，用时间分辨动态光散射法测定了动态性质的时间演化。通过进一步的分析，我们证实了硬球胶体的固化是由前驱体介导的。对动力学性质的分析表明，亚稳熔体的长时间动力学以及剪切刚度与形核的固体团簇(前驱体)数密度密切相关。在结晶过程中，这些物体转变成高度有序的晶体，而在玻璃化的情况下，这种转变被阻止，系统(暂时)锁定在亚稳定的前体状态。从凝固的早期阶段，人们不能清楚地断定熔体是否会结晶或玻璃化。此外，我们的数据表明，胶体硬球玻璃可以通过均匀成核来析晶。
We investigated the process of vitrification and crystallization in a model system of colloidal hard spheres. The kinetics of the solidification process was measured using time resolved static light scattering, while the time evolution of the dynamic properties was determined using time resolved dynamic light scattering. By performing further analysis we confirm that solidification of hard sphere colloids is mediated by precursors. Analyzing the dynamic properties we can show that the long time dynamics and thus the shear rigidity of the metastable melt is highly correlated with the number density of solid clusters (precursors) nucleated. In crystallization these objects convert into highly ordered crystals whereas in the case of vitrification this conversion is blocked and the system is (temporarily) locked in the metastable precursor state. From the early stages of solidification one cannot clearly conclude whether the melt will crystallize or vitrify. Furthermore our data suggests that colloidal hard sphere glasses can crystallize via homogeneous nucleation.