https://scholars.lib.ntu.edu.tw/handle/123456789/63943
標題: | 各種晶體在不同溶劑中次成核現象之探討 Secondary Nucleation of Various Types of Crystal in Different Solvents |
作者: | 戴怡德 | 關鍵字: | 介面過飽和度;次成核;鉀明礬;檸檬酸;碳酸鈣 | 公開日期: | 2001 | 出版社: | 臺北市:國立臺灣大學化學工程學系暨研究所 | 摘要: | 本研究乃以鉀明礬、檸檬酸與碳酸鈣為系統探討 不同物系的晶體在水與丙醇溶液中之次成核現象。在 鉀明礬的系統中,過飽和溶液被維持在適當的過冷度 下,利用溶液噴射法產生流體剪力以引發次成核,實 驗發現鉀明礬晶體之次成核數目明顯隨著停止攪拌時 間越長而遞減,此可解釋為介面過飽和度隨停止攪拌 時間越長而越低故使得次成核數目遞減,此實驗結果 亦可證實介面過飽和度在鉀明礬次成核之形成機制中 的重要性。另一方面,實驗發現檸檬酸在丙醇溶液中 之成核晶體呈細小粉末狀,且成長速度相當慢,故目 前正嘗試其他有機溶劑以製備晶形較完整且顆粒較大 之晶種,以利流體噴射次成核實驗之進行。最後,由 添加碳酸鈣晶種之過飽和溶液中發現,晶核的產生方 式與溶液電導度隨時間之變化情形均類似初成核的結 果,即此系統中確有突爆性次成核現象的存在,研究 中進一步以考慮介面濃度之凝聚理論計算成核引發時 間,結果亦顯示介面過飽和度在碳酸鈣次成核形成過程中確實扮演著重要的角色。 In this study, the secondary nucleation of potassium alum, citric acid and calcium carbonate crystals in the aqueous and alcohol solutions was investigated. In the potassium alum system the water jet was used to induce secondary nucleation by fluid shear. The results show that the number of nuclei formed by secondary nucleation decreases by increasing the time interval between stopping the agitation and injecting the solution. The decrease in number of nuclei can be interpreted by the lower interfacial supersaturation at the longer stop-agitated time. On the other hand, the citric acid nuclei prepared in the propanol are very fine as powders and the growth rate of nuclei is also small. Consequently we are attempting to utilize other organic solvents to prepare the seeds for the fluid-sheared experiment. Finally the catastrophic secondary nucleation of calcium carbonate is observed in this study. Further, the induction period of calcium carbonate is calculated by the coagulation theory, in which the cluster concentration near the interface is taken into account. The results indicate that the interfacial supersaturation plays a significant role in the formation of secondary nuclei not only in the potassium alum but also in the calcium carbonate system. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/9255 | 其他識別: | 892214E002042 | Rights: | 國立臺灣大學化學工程學系暨研究所 |
顯示於: | 化學工程學系 |
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892214E002042.pdf | 60.17 kB | Adobe PDF | 檢視/開啟 |
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