Kinetics of heterogenous nucleation and growth

利用成核的随机性，实验确定了成核动力学参数，特别是成核势垒高度和成核速率。因此，在不应用特定的成核模型的情况下，进行测量，允许对有关成核率的实验数据进行统计分析。这些数据应在较大的过冷间隔下获得，对应于成核速率的几个数量级变化。为此，应采用常规量热法和微芯片量热法。随着最近建立的使用中断熔融过程的重复凝固循环组合，可以研究定义和已知的核相的非均相成核，其中核相由与二元合金相同的元素组成。此外，该方法还可以研究成核相的形状和形态或其丰度对成核和生长的影响。因此，本构非均相结构、体积分数及其与熔体界面形态的系统变化将用于将实验获得的数据与合作项目中进行的原子场和相场模拟进行比较。

Utilizing the stochastic nature of nucleation, nucleation kinetics parameters, specifically the nucleation barrier heights and the nucleation rates are determined experimentally. Thus, measurements are conducted that allow statistically analyzing the experimental data concerning the nucleation rate without applying a specific nucleation model. These data shall be obtained for large undercooling intervals corresponding to several orders of magnitude variations in the nucleation rates. For this reason, conventional and micro-chip calorimetry shall be employed. With a recently established combination of repeated solidification cycling using an interrupted melting procedure, heterogeneous nucleation can be studied for defined and known nucleant phases where the nucleant phase consists of the same elements as the binary alloy. Additionally, this method allows investigating the impact of the shape and the morphology of the nucleant phases or of their abundance on nucleation and growth. Thus, systematic variations of the structure of the intrinsic heterogeneous phase, of its volume fraction and of the morphology of its interface with the melt will be used for comparing the experimentally obtained data with atomistic – and phase field simulations performed in collaborative projects.