Fabrication Ideally Ordered Filter Membranes Based on Electrochemical Selfordering Process

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The filter membranes with highly ordered hole configuration were prepared based on the self-organizing process of anodic porous alumina. The obtained results are stmmarized as follows :[1] In order to apply the anodic porous alumina for filter membranes, conditions for naturally occurring self-ordering in anodic porous alumna were investigated. The conditions for the long-range ordering of the hole configuration of anodic porous alumina were dependent on anodization period and anodizing voltage. During the long-range ordering of the hole configurations of the anodic porous alumina, self-ordering proceeds through the rearrangement of the hole configuration.[2] To improve the ordering of the hole configuration, a novel process which can control the growth of the hole array in the anodic porous alumina, was introduced. In this process, an array of shallow concaves was formed on Al by indentation using a mold, which served as initiation sites for ideally arranged hole configuration in the initial stage of anodization. The hole interval could be controlled from 60 nm to 500 nm by changing the interval of the pretextured pattern and the applied voltage.[3] A two-step replication process using ordered anodic porous alumina as a starting structure was applied to prepare the metal hole arrays to improve the chemical stability of the filter membranes. In this process, the fabrication of negative-type anodic porous alumina and the subsequent formation of the positive type generates hole arrays of metals (Ni, Ag, Au) with a geomtrical structure identical to that of the starting anodic porous alumina.[4] The microfiltration properties of the obtained filter membranes were investigated. The flow rates of the highly ordered membranes were examined using high pressure feed systems. Through these experiment, high flow rates and the high entrapment efficiencies of the membranes for small particles could be confirmed.