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標題: | 膠體粒子在不含鹽類的介質中之靜電交互作用 Electrostatic Interactions between Colloidal Particles in a Salt-free Medium |
作者: | Hsiu-Yu Yu 游琇伃 |
指導教授: | 徐治平(Jyh-Ping Hsu) |
關鍵字: | 膠體,不含鹽類的介質,靜電交互作用,電位分布,臨界凝聚濃度, colloid,salt-free,electrostatic interaction,potential,critical coagulation concentration,Schulze-Hardy,Poisson-Boltzmann, |
出版年 : | 2006 |
學位: | 碩士 |
摘要: | 本論文中推導出了在不含鹽類的介質中,平面、圓柱、與圓球狀單顆膠體表面的空間電位分布近似解析解;根據單一面的結果,兩膠體表面間的空間電位分布也由類比的方式而導出。結果顯示曲率效應在粒徑超過100倍的粒子電雙層厚度時可以忽略,而當需要考慮曲率效應時,曲面系統的電位分布結果可由平面系統的結果乘上一曲率校正函數而來。由已推導出的粒子間電位分布可進一步求得粒子間每單位面積之靜電作用力,也就是滲透壓;而在同樣的參數之下,滲透壓的大小依序為平面系統>圓柱系統>圓球系統。最後,吾人求出了球型膠體分散系統在不含鹽類的介質中之臨界凝聚濃度。其中,傳統的 Schulze-Hardy 通則於此分散相中與反離子之臨界凝聚濃度偏差大小可由一校正因子來修正,而此校正因子同時為系統中反離子價數、粒子表面電位、以及凝聚發生時粒子間中點電位的函數。吾人發現此校正因子大致上會隨著表面電位與反離子濃度的增加而變大,但是當表面電位夠高時,校正因子會趨近於定值—0.8390。 Approximate analytical expressions for the electrical potential of planar, cylindrical, and spherical surfaces are derived for the case when the dispersion medium contains counterions only. Based on the results for single surfaces, those for two identical surfaces can be derived. The curvature effect of a surface on the electrical potential distribution can be neglected when the order of its radius exceeds about 102 of the thickness of the corresponding double layer. If this effect needs be considered, it can be taken into account by multiplying a correction function to the electrical potential of a planar surface. The electrical potential at the center between two surfaces derived is readily applicable to the evaluation of the electrostatic force per unit area between two surfaces, or the osmotic pressure. For the same set of parameters, the magnitude of the osmotic pressure for various types of surfaces follows the order planar surface>cylindrical surfaces>spherical surfaces. Furthermore, the planar results obtained are used to evaluate the critical coagulation concentration of a spherical dispersion. A correction factor, which is a function of the valence of counterions, the surface potential of a particle, and the potential on the mid-plane between two particles at the onset of coagulation, is derived to modify the classic Schulze-Hardy rule for the dependence of the critical coagulation concentration on the valence of counterions. The correction factor is found to increase with the increase in the valence of counterions and/or with the increase in the surface potential. However, it approaches a constant value of 0.8390 if the surface potential is sufficiently high. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/33631 |
全文授權: | 有償授權 |
顯示於系所單位: | 化學工程學系 |
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