Growth Rate Enhancement Phenomena By Microcrystals And Their Effects On Crystal Quality

在工业结晶器中，除了过饱和溶液中晶体的成核和生长外，还会发生由晶体颗粒之间的碰撞引起的结块、破裂或磨损等复杂现象。这些现象对产品晶体的纯度、形貌、粒度分布和结晶度等质量都有显著影响。迄今为止，晶体成核与晶体生长之间的相互关系尚不清楚，因此本研究旨在通过实验研究成核对晶体生长的影响。主要结论如下：1。在NaCl和钾明矾水溶液和间氯硝基苯丙酮溶液中观察到微晶对生长的促进作用。成核后立即观察到过饱和度下降。得到了生成核的数量和大小与增强因子之间的关系。以上事实可以得出一个结论，即生成核作为宏观生长单元，导致生长速度的提高。其促进效果最高为正常生长速率的3倍。增强效应随着核的增大而减弱。强化后生长的晶体存在母液夹杂物和缺陷，使其质量下降。目前，格拉斯哥斯特拉斯克莱德大学的舍伍德教授正在利用x射线形貌对这些缺陷进行调查，并将在分析结束后很快发表。

In industrial crystallizers complicated phenomena such as agglomeration and breakage or attrition caused by collisions between the crystalline particles occur in addition to nucleation and growth of crystals from supersaturated solutions. These phenomena have significant influences on the quality of product crystals which include purity, morphology, size distribution and crystallinity. So far interrelations between nucleation and growth of crystals are unknown so that the present study aims to investigate the effects of nucleation on the growth of crystals experimentally. The main conclusions obtained are as follows.1.Growth enhancement by microcrystals was observed for aqueous solutions of NaCl and potash alum and for acetone solutions of m-chloronitrobenzene.2.Supersaturation decrease was observed immediately after the nucleation.3.Relations were obtained between the number and size of nuclei generated and the enhancement factors.4.The above mentioned facts lead to a conclusion that the generated nuclei act as the macro growth units which results in the growth rate enhancement.5.The enhancement effects were 3 times of the normal growth rates at the maximum.6.The enhancement effects weakened as the nuclei grew.7.The crystal grown after the enhancement have inclusions of the mother liquor and defects, thus decreased their qualities.8.The defects are currently under investigation with the corporation of Prof.Sherwood at Strathclyde University, Glasgow by the use of the X-ray topography, and soon will be published after the analysis is over.