Experimental study on the transition from periodit precipitation to fractal crystal aggregates

周期性沉淀到分形晶体聚集体转变的实验研究

基本信息

批准号：
07832011
负责人：
TORAMARU Atsushi
金额：
$ 1.47万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

We made a morphological phase diagram as a function of agar concentration and a ratio of iodide ion and lead anion. In order to understand the crystallization process of lead iodide, we carried out in-situ experiments by which the propagation velocity of crystallization is measured. As a result, it was found that the propagation velocities both in the banding structure and the branching structure are the same, suggesting that the diffusivity difference due to concentration difference of agar does not cause the morphological transition. From the observation of formation process of branching structure, it is found that the heterogeneous nucleation on the surface of large crystals is deeply related to the formation of branching structure. From the observation by the scanning electron microscope (SEM), crystal number density in banding structure is different from that in branching structure by three orders of magnitude. In addition, from the SEM observation, agar structure difference depending on the agar concentration is found not to cause the number density difference. From a series of experiments, it is found that the lead iodide nucleation process is not simple, rather complex that not only the monomer concentration of lead iodide but also the excess anion and ion play important roles. As a result of these experiments, it is concluded that the subtle effect of agar concentration on the nucleation process causes the morphological transition between the banding structure and branching structure.

我们将形态学相图作为琼脂浓度和碘化离子和铅阴离子比的函数。为了了解碘化铅的结晶过程，我们进行了原位实验，通过该实验测量了结晶的传播速度。结果，发现带状结构和分支结构中的传播速度都是相同的，这表明由于琼脂浓度差异而引起的扩散率差异不会导致形态跃迁。从分支结构的形成过程的观察中，可以发现大晶体表面上的异质成核与分支结构的形成密切相关。从扫描电子显微镜（SEM）的观察结果来看，带状结构中的晶体数密度与分支结构的晶体数密度不同。此外，从SEM观察结果中，发现琼脂结构差异取决于琼脂浓度不会引起数量密度差。从一系列实验中可以发现，碘化铅成核过程并不简单，不仅复杂，不仅是碘化铅的单体浓度，而且过量的阴离子和离子起着重要作用。这些实验的结果是，得出的结论是，琼脂浓度对成核过程的微妙影响会导致带结构和分支结构之间的形态跃迁。