7-氨基头孢烷酸结晶过程聚结现象与晶体表面性质

对7-氨基头孢烷酸（7-ACA）两种结晶方法的聚结现象进行研究．通过对结晶过程不同pH值下晶体SEM照片的比较，发现酸法结晶过程在pH值大于1．5时开始出现花朵状聚结，而碱法结晶不发生聚结；通过时两种结晶方法得到样品的SEM照片处理，发现酸法和碱法样品SEM灰度具有自相似性，应用盒子维法分别求得两种结晶过程中不同pH值下的晶体的分维值．测定了7-ACA在不同pH值水溶液中的Zeta电位．通过毛细升高法测定了酸法和碱法样品对水与丙酮的润湿角，结合两种样品的X-粉末衍射和红外衍射图谱，对晶体表面的官能团进行了推测．

Agglomeration Phenomenon of 7-Aminocephalosporanic Acid and Crystallization Surface Characteristic

The agglomeration phenomenon of 7-aminocephalosporanic acid (7-ACA) crystals made from two different crystallization processes is studied. From the SEM photos of the crystals, it can be seen that the agglomeration of crystals takes place when the pH value higher than 1. 5 in the crystallization process of acid method, but no agglomeration appears in the products from the basic method. The scanning electron microscopy (SEM) micrographs of 7-ACA are processed into digital images by a scanner and the image procession software-Photoshop. From these images, it can be seen that the grayscale distributions are extremely similar, which indicates that the morphology of 7-ACA crystallization exhibits self-similarity at different scales. The fractal dimensions of 7-ACA crystals are determined by box-dimension method. Zeta potentials are measured at different pH values. In addition, the capillary rise of liquid in columns packed with 7-ACA powder is measured and the wettabilities of the two 7-ACA samples on different solvents are determined. Combining the results of IR and powder X-ray diffraction, the functional groups on the surfaces of two kinds of crystals are presumed.