Heterogeneity in aqueous solutions: electron microscopy of citric acid solutions
Heterogeneity in aqueous solutions: electron microscopy of citric acid solutions
复制标题
水溶液中的异质性：柠檬酸溶液的电子显微镜
DOI：
10.1016/0009-2509(92)80300-2
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发表时间：
1992
影响因子：
4.7
通讯作者：
M. Ueda
中科院分区：
文献类型：
--
作者：
K. Ohgaki;N. Hirokawa;M. Ueda
通过扫描电子显微镜（SEM）直接检查不同浓度的柠檬酸水溶液（包括过饱和溶液）的结构。通过以非常高的淬火速度在制冷剂中固化一滴溶液来制备电子显微镜样品，然后用电子束喷枪的铂和碳复制它。无论溶质浓度如何，在所有样品中都观察到溶质簇及其聚集体。该溶液在扫描电子显微照片中显示出双区结构，由光滑区域和许多溶质簇的隔室组成。随着溶质浓度的增加，室的数量密度增加，而体积减小。因此，电子显微镜强烈表明所检查的溶液是异质的，即所谓的胶体混合物。 X射线衍射分析揭示了一个非常重要的事实，即一水柠檬酸晶体中含有细小颗粒，这些颗粒似乎是溶液中溶质簇的残余物。在晶体和细颗粒溶液之间的边界区域中观察到的结果支持了这一点，这些细颗粒像弹性一样拉伸以形成网络结构。
The structures of aqueous citric acid solutions of various concentrations, including supersaturated solutions, were examined directly by scanning electron microscopy (SEM). Electron microscopic samples were prepared by solidifying a droplet of solution in a refrigerant at very high quenching speed, then replicating it with electron-beam-gunned platinum and carbon. Solute clusters and their aggregates were observed in all the samples irrespective of the solute concentration. The solutions showed a double-zone structure in scanning electron microphotographs, consisting of a smooth zone and a compartment of many solute clusters. With the increase in solute concentration, the number density of compartments increased, while their volume decreased. Electron microscopy thus strongly suggested that the solutions examined were heterogeneous, namely, the so-called colloidal mixtures. X-ray diffraction analysis revealed the very important fact that the crystal of citric acid monohydrate contains fine particles which seem to be the remnants of solute clusters in solution. This is supported by the observation in the boundary region between the crystal and solution of fine particles which stretch like elastic to form a network structure.