利用動力蒙地卡羅模擬膠體粒子於電沉積系統的分佈

Distribution of Colloidal Particles In Electrophoretic Deposition Using Kinetic Monte Carlo Simulation

拉瑪

指導教授 ： 廖朝光

元智大學/工程學院/化學工程與材料科學學系/碩士(2012年)

摘要

本論文採用動力蒙地卡羅(KMC)演算法進行模擬，利用電泳沉積系統中，自我組裝的二氧化矽膠理粒子堆疊程序，探討的變因有粒子表面電位(η)數值、外加電壓強度以及開關式(on-off)的電位處理，最終成功使底層的空缺密度降低，使底層粒子呈現規則排列。此系統中的粒子沉降過程中會受到彼此的作用力影響，分別是吸引力-凡德瓦爾力以、排斥力-表面靜電斥力與外加電場的驅動力。藉由模擬結果得知，當控制調整表面電位(η)較小時，會因凡德瓦爾吸引力而使粒子聚集在一起，相反地控制調整表面電位較大時，會因表面靜電斥力而使粒子分散至系統邊緣。當對系統施加電壓，利用電泳沉積法( EDP )驅動膠體粒子時，發現在較低的表面電位下，則會使底層空缺密度( LVD % )降低。當對系統施以開關式電位處理，可觀察到粒子並不會因開關電位處理而改善底層的空缺密度。

關鍵字

電泳沉積法 ； 動力蒙地卡羅法 ； 膠體粒子 ； 表面電位

並列摘要

Electrophoretic deposition (EPD) patterns of colloidal SiO2 particles (400 nm) in solution were analyzed and demonstrated using the kinetic Monte Carlo (KMC) simulation method. The behavior of the colloidal particles which formed electrical double layers in solution was described by the DLVO theory. The dynamic particle migrations of the EPD process were estimated by the KMC simulation to statistically determine the probable particle distribution based on thermodynamic theories. Results show that the particle distribution and deposition in solution were significantly influenced by the presence of the zeta potential value (η) in the solution, and applied voltage in the EPD system. The particles aggregated together in the solution with a small η value due to the strong Van der Waals attractive forces among the particles. If a large η value was adopted, all the particles moved away from central and scattered around the edge the system space because of strong electrostatic (repulsive) forces among them. The external voltage applied to the EPD system in different η values can affect the formation of particle deposition pattern. The EPD pattern with little vacancy site can be fabricated using a small η value with a constant voltage operating condition. However, the vacancy sites of the EPD pattern became large by the on-off voltage operating scheme. The quality of the EPD films cannot be improved using this strategy.

並列關鍵字

Electrophoretic deposition (EPD) ； Kinetic Monte Carlo (KMC) ； Colloidal particle ； Zeta potential (η) value

參考文獻

Arthur F Voter. Introduction to the Kinetic Monte Carlo Method. Publisher: Springer 235 (2005) Pages: 1–23.

Bergstrom, L., Hamaker constants of inorganic materials, Adv. Colloid Interface Sci., 70 (1997) 125–169.

B. Raissi , E. Marzbanrad, A.R. Gardeshzadeh. Particle Size Separation by Alternating Electrophoretic Deposition. Journal of the European Ceramic Society 29 (2009) 3289–3291.

B.W. Ninham. On progress in forces since the DLVO Theory. Advances in Colloid and Interface Science 83 (1999) 1-17.

Byung Kee Lee, Young Hwa Jung, Do Kyung Kim. Synthesis of Monodisperse Sphirical SiO2 and Self Assembly for Photonic Crystals. Journal Korean Ceramic Society Vol 46. No 5. (2009) pp. 472-477.