懸浮液中球形帶電多孔粒子之擴散泳運動

本論文探討球形帶電多孔粒子均勻懸浮於具有濃度梯度的對稱電解質溶液中所進行之擴散泳運動。多孔粒子是由溶劑與離子皆可穿透之帶電凝聚體或高分子電解質所構成，其所帶之固定電荷密度以及對流體之摩擦阻力密度皆為定值，且多孔粒子周圍之電雙層可為任意厚度。本論文使用單元小室模型以考慮粒子之間的交互作用，且允許相鄰多孔粒子周圍的電雙層彼此重疊。主導電解質溶液的電位分布、離子濃度分布以及流場分布之電動力方程式可以藉由假設相對於平衡狀態，系統只受到微小的擾動來線性化，並利用正規微擾法，以多孔粒子的固定電荷密度為微小擾動參數，再配合適當的邊界條件來求得解析解。多孔粒子之擴散泳速度可以利用作用在多孔粒子上之靜電力以及流體拖曳力之合力為零來求得，且可準確到固定電荷密度的第二階。本論文亦利用單元小室模型在不同的邊界條件下來求得多粒子系統之擴散泳速度，並針對此結果進行定量比較。粒子間交互作用效應對擴散泳來說很顯著與複雜，此效應可視為電泳效應以及化學泳效應之線性相加。結果顯示雖然粒子之電泳可動度隨著多孔粒子佔整個懸浮系統體積分率之增加而下降，但是粒子之化學泳可動度卻不是如此單調遞增或遞減之結果。

關鍵字

擴散泳；電泳；流體可穿透之膠體粒子；粒子濃度效應；單元小室模型

並列摘要

An analysis of the diffusiophoretic motion in a suspension of charged porous spheres in an electrolytic solution with a macroscopic concentration gradient is presented. Each porous particle can be a solvent-permeable and ion-penetrable charged floc or polyelectrolyte molecule, in which the densities of the fixed charges and frictional segments are constant, surrounded by an arbitrary electric double layer. The multi-particle interaction effects are considered through the use of a unit cell model, which allows the overlap of adjacent double layers. The differential equations governing the electric potential, ionic concentration, and fluid velocity distributions inside and outside the porous particle in a unit cell are linearized by assuming that the system is only slightly deviated from equilibrium and then solved as power expansions in its dimensionless fixed-charge density. A closed-form expression for the diffusiophoretic velocity of the porous particle correct to the second order of the fixed charge density is obtained from a balance between the electrostatic and hydrodynamic forces acting on it. Detailed comparisons of the results for the multi-particle diffusiophoresis obtained from the cell model with various boundary conditions are made. The effect of particle interactions on the diffusiophoresis, which is a linear combination of electrophoresis and chemiphoresis, can be significant and complicated in typical situations. Although the electrophoretic mobility of the particles decreases with an increase in the particle volume fraction, their chemiphoretic mobility is not necessarily a monotonic function of it.

並列關鍵字

Diffusiophoresis ； Electrophoresis ； Permeable colloidal sphere ； Particle concentration effect ； Unit cell model

參考文獻

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(6) Chiang, T.-Y.; Velegol, D. Multi-Ion Diffusiophoresis. J. Colloid Interface Sci. 2014, 424, 120-123.

國際替代計量

懸浮液中球形帶電多孔粒子之擴散泳運動

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