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，还会发生由于晶体颗粒之间的碰撞而导致的结块、破碎或磨损等复杂现象。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很大影响。到目前为止，成核和晶体生长之间的相互关系尚不清楚，因此本研究的目的是从实验上研究成核对晶体生长的影响。得到的主要结论如下：1.微晶对氯化钠和钾盐明矾水溶液以及间氯硝基苯的丙酮溶液有生长促进作用。2.成核后过饱和度立即降低。3.生成的晶核数目和大小与促进因子之间的关系。4.上述事实得出结论：所生成的晶核作为宏观生长单元，导致生长速率的提高。5.在最大值时，促进作用是正常生长速率的3倍。6.随着晶核的增大，促进作用减弱。增强后生长的晶体有母液包裹体和缺陷，8.这些缺陷目前正在与格拉斯哥斯特拉斯克莱德大学舍伍德教授的公司一起使用X射线地形进行调查，分析结束后不久将公布。

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.