利用不同陽極處理製備之奈米氧化鋁薄膜及其微觀結構與機械性質之研究

Study on the Microstructure and Mechanical Properties of Nano-Aluminum Oxide Films Prepared via Different Anodizing Processes

本研究利用高純度鋁片進行兩次陽極氧化處理，製得規則分布且均一奈米孔洞之陽極氧化鋁（AAO）薄膜，當調整電解液類型（如：硫酸與磷酸）之條件，可獲得平均孔徑（20nm~270nm）以及孔隙率（18%~41%），進而使用奈米壓痕機分析，施加之荷重分別為1000μN、5500μN、10000μN，並且探討其機械性質與摩擦學行為。從硫酸系統實驗數據得知，AAO孔徑越大，得到之硬度值相對較小，表示其孔徑越大，整體結構相對鬆散；而施加荷重越大，硬度值也會越大，表示多孔性結構受到正向力時，孔壁會崩塌且層層堆疊使材料密度局部增大；而在使用磷酸作為電解液時的實驗數據中也可得出隨著孔徑越大，薄膜之硬度值越低的相同趨勢。而在奈米刮痕方面，施加荷重為10000μN，AAO孔徑越大，摩擦係數越大，表示探針阻力隨孔徑增大而增加，這些特性可以代表多孔性結構之獨特機械性質。

In this study, we use the high-purity aluminum foil to do anodization to obtain anodic aluminum oxide (AAO) films with high porosity, and regular pore size distribution. In order to study mechanical properties and tribological behavior of AAO, it was manufactured in different electrolytes such as sulfuric acid and phosphoric acid, providing adjustable pore size (20nm ~ 270nm) and porosity (18% ~ 41%). The hardness and friction coefficient of AAO templates were investigated by using nanoindentation with normal forces 1000μN, 5500μN, and 10000μN. According to the experimental data of the sulfuric acid system, the larger the AAO pore size, the smaller the hardness value because the larger pore size causes the structure loosely. The results show that hardness increases with the applied loads. Because porous structure of the film pressed down by the normal force, which leads the straight pore wall to collapse and makes the structure density increase partly. Furthermore, it has the same tendency when we use the phosphoric acid as our electrolyte. In terms of scratch test, the larger the pore size, the higher the coefficient of friction. The result indicated that the probe would be obstructed more easily in large pores. The mechanical properties of AAO found in our study show the unique features for porous structures.