- 學位論文
磁流體於陽極氧化鋁表面之磁濕潤探討
Investigation of the magnetowetting characteristics of magnetic fluids on AAO surfaces
摘要
隨著智慧型流體的蓬勃發展，為達到有效的控制磁流體靜態及動態特性，探討其界面性質有其重要性。本論文完成磁流體於陽極氧化鋁表面之磁濕潤分析。主要目的在探討於外部磁場作用下，陽極氧化鋁奈米結構對磁流體靜態及動態磁濕潤之影響。首先，透過正向應力平衡修正Young–Laplace方程式，數值求解並理論探討流體材料性質及磁場梯度對靜態磁流體座滴輪廓及接觸角之影響。接著，分別以化學共沉法及溶膠凝膠法合成水基磁流體與陽極氧化處理製備陽極氧化鋁表面。在靜態實驗分析部分，以光學測試系統量測陽極氧化鋁奈米管徑及磁場梯度對靜態磁流體座滴接觸角之影響。在動態實驗分析部分，以動態擷取系統實驗獲得陽極氧化鋁表面型態及磁場梯度對動態磁流體液滴濕潤直徑之影響。 結果發現，針對理論分析，磁流體座滴輪廓隨著外部向下或向上磁場梯度提升而逐漸外擴或內縮，且導致接觸角逐漸下降及上升。而此磁濕潤效應可藉由降低磁流體表面張力或增加粒子體積分率來達到進一步的增強。針對實驗分析，在磁流體之靜態座滴磁濕潤分析部分，隨著陽極氧化鋁平均管徑的擴大(32.36~97.62 nm)，其表面非濕潤性可增強29.48%。而隨著外部磁場梯度作用逐漸提升，小管徑之陽極氧化鋁表面具有較明顯的靜態磁濕潤性。在磁流體之動態液滴磁濕潤分析部分，在無外部磁場梯度作用下，透過陽極氧化處理之鋁試片於液體及固體間具有較大之黏著性。而在外部磁場梯度作用下，氧化鋁表面型態可提升其49.91%之動態磁濕潤性。預期研究成果將有助於磁控流體領域的元件發展與應用。
並列摘要
With the vigorous development of smart nanomaterials, to achieve effective control of magnetic fluids static and dynamic characteristics, the investigation on the interfacial properties play an important role. This thesis conducts an analysis of the magnetowetting of magnetic fluids on anodic aluminum oxide (AAO) surfaces. The main purpose is to investigation the influence of AAO structures on the magnetic fluids static and dynamic magnetowetting. The Young–Laplace equation is first revised on the basis of the normal stress balance principle. The numerical results and discussion are presented for the influence of fluid properties and magnetic field gradients on magnetic fluid sessile droplet profile and contact angle. Then, water-based magnetic fluids are prepared by combining the chemical co-precipitation with the sol-gel technique, and AAO surfaces are fabricated by the anodizing process. For static experimental analysis, an optical test system is used to investigate the influence of tube diameter and magnetic field gradient on the sessile droplet contact angle of magnetic fluids on AAO surfaces. For dynamic experimental analysis, a dynamic capture system is used to record the influence of AAO surface topography and magnetic field gradient on the wetted diameter during magnetic fluids impact on AAO surfaces. For magnetic fluid sessile droplet profile analysis, the theoretical results showed that a downward/upward magnetic field gradient could be used to cause a profile to be expanded/ contracted (contact angle to be reduced/enhanced). This magnetowetting effect could be further enhanced by reducing the surface tension or increasing the particle concentration of magnetic fluid. For static magnetowetting analysis, the experimental results showed that the surface non-wettability behavior enhance with the increase of the average tube size of AAO (32.36~97.62 nm). The percentage increase in non-wettability behavior is 29.48%. The static magnetowetting has a more significant phenomenon at smaller AAO tube size. For dynamic magnetowetting analysis, without a magnetic field gradient, the experimental results showed that the processed surface displayed a slightly higher adhesion between the liquid and solid. The influence of AAO surface topography could be further enhanced under the action of a magnetic field gradient. The percentage increase in dynamic magnetowetting is 49.91%. This study may benefit the development and application of fluidic devices in the research areas of the magnetically controllable fluids.