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標題: | 軟球粒子垂直於平面邊界之擴散泳現象探討 Diffusiophoresis of a Soft Particle Normal to a Planar Boundary |
作者: | Chieh-Kai Hsu 許傑凱 |
指導教授: | 李克強(Eric Lee) |
關鍵字: | 擴散泳,化學泳效應,軟球,邊界效應,雙球座標, diffusiophoresis,chemiphoresis,soft particle,boundary effect,bipolar coordinate, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 本研究探討接地平板對高帶電軟球粒子於電解質溶液中擴散泳之影響。為了適當的描述軟球粒子與平面邊界,本研究採用雙球座標系統並以數值方法模擬膠體粒子的泳動行為。我們進行電動力學方程組的多區聯解,並以牛頓-拉福生疊代法求得系統之穩態解。加入平面邊界的條件後,我們將分析化學泳效應、電泳效應與流體拖曳力等作用力對軟球粒子擴散泳的影響。 研究結果發現,電解質溶液的選取會大幅度的改變粒子的運動行為,因陰陽離子擴散速度不同會產生一擴散電場以符合總電流量為零之條件。擴散電場的方向取決於陰陽離子何者擴散較快,擴散電場大小則由陰陽離子擴散速度差來決定,而擴散電場方向可能與化學泳方向相反。透過電雙層厚度控制可以觀察兩種驅動力競爭的過程中發現:在大多數的情況下泳動行為由電泳效應主導。 此外,平面邊界對粒子的影響不單只是增加流體拖曳力,因為平面邊界的存在,導致電雙層受到擠壓變形,加上接地平板使電位分佈改變,進而讓反離子重新分佈並使局部濃度梯度上升、增強了化學泳效應。因此,當粒子逐漸靠近平板時,上述二效應的拉鋸決定泳動度呈現上升或下降的趨勢。 Diffusiophoresis of highly charged soft particles which effected by conducting plane was investigated in the electrolyte solution in this study. In order to properly describe the planar boundary and the soft particles, this study characterized by bipolar coordinate and numerically simulates the act of motion of colloidal particles. The coupled electrokinetic equation are solved linearly with a pseudo-spectral method based on Chebyshev polynomials. The Newton-Raphson iteration scheme are adopted here for solution. After considering the conditions of the plane-boundary, we will analyze the effects of chemiphoresis, electrophoresis and drag force on diffusiophoresis of soft particles. According to results of this study, we found that the choice of electrolyte solution will greatly change the act of motion of particles. Different diffusion speeds of anions and cations will generate a diffusion electric field to meet the condition that the total ion flux is zero, and the direction of this diffusion electric field depends on which anions and cations diffuse faster. The force caused by diffusion electric field is determined by the degree of difference in the diffusion speed of anions and cations. However, the direction of the diffusion electric field may be opposite to the direction of chemiphoresis. By adjustment of the double layer thickness, we can observe the process of the two driving forces competing.We can find that the act of motion is dominated by the electrophoresis in most cases. In addition, the effect of the planar boundary on the particles is not only to increase the drag force. Because of the planar boundary, the double layer is deformed. Then, the potential distribution is changed on the conducting plane. In turn, the counter ion is redistributed and the local concentration gradient is increased, enhancing the chemiphoresis. Therefore, when the particle gradually approach the plane, the tug of two effects determine that the mobility shows an upward or downward trend. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/54061 |
DOI: | 10.6342/NTU202002342 |
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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