Deepak Mankotia al. International Journal of Recent Research Aspects ISSN: 2349-7688, Vol. 1, Issue 2, September 2014, pp. 171-176 © 2014 IJRRA All Rights Reserved page - 171- Review of Highly Ordered Anodic Porous Alumina Membrane Development Deepak Mankotia 1 , Dr. Y.C. Sharma 2 , Dr. S.K.Sharma 3 1 Research Scholar, Vivekananda Global University Jaipur 2 Professor, Dept. of Physics, VIT, Jaipur 3 Professor, Dept. of Physics, Maharishi Ved Vyas College, Jagadhari Abstract— Anodic alumilminium oxide (AAO) formation is an electrochemical process. Using this process hexagonal cylindrical shape nano pore can be produced i.e. nanoporous membrane. Hexagonal nano pore can be obtained in anodic alumina film by repeated anodization. This review paper is an overview of AAO membrane by two step anodization, effect of anodization parameter. A new method for characterization of pore structures of AAO membranes has also been suggested by flow porometry and bubble point method. Keywords— AAO, nanoporous membrane, Two step anodization, flow porometry bubble point . I. INTRODUCTION Anodization is an electrochemical oxidation process. Two type of anodic aluminum oxide (AAO) are formed depending on the electrolyte: one is nonporous barrier type oxide from neutral oxide and other is a porous type oxide from acid electrolyte. The porous type Aluminum anodization received growing attention because AAO widely used for fabrication of various nanostructure materials. A number of studies have been performed in which nanporous structure is used as template in the production of nanowires or nanotubes from various materials, used as a filter for purification of DNA or whole cell from blood. Various structures and devices based on AAO such as carbon nanotubes (CNTs), metal nanowires, nanodotes, nanoholes and other nanodevices and In many applications AAO membranes act as barriers to particles or organisms. (1-5) The porous anodic alumina may be represented as honeycomb structure of fine channels characterized by a closed packed array of hexagonal cells, each containing cylindrical pore, as shown in fig1.Pore diameter ranging from 30 to 400 nm, oxide thickness from 0.3 to 200μm and pore densities in the range 10 9 to 10 11 cm -2 can be obtained. The size and interval can be easily controlled by changing the processing condition. Figure 1: A schematic drawing of porous alumina In an anodizing process, an aluminum plate is connected to the anode of DC source. A week acid solution used as electrolyte. The cathode can be made from chemically inert conductive material. When apply tension, hydrogen ions are reducing in order to form hydrogen gas at cathode and aluminium is oxidized into Al 3+ cations. Some of these cations are dissolved in the electrolyte, and some part form oxide layer on the metal surface, For further reaction,oxygen containing anions are supplied by electrolyte (6). Type of anodic oxide Film: The anodizing of aluminium can result in two different type of oxide film a barrier type anodic film and porous oxide film. The adherent, non-porous and non conducting barrier type of anodic film can be formed by anodizing aluminium in neutral solution (PH = 5-7) in which anodic oxide layer stays practical in soluble. These film are thin and dielectrically compact .The group of electrolyte used for this film formation include boric acid, ammonium borate, ammonium tartrate and aqueous phosphate solution, as well as tetraborate in ethylene glycol, and some organic electrolyte such as citric, malic, succinic and glycolic acid. Porous oxide film are made using strong electrolyte solution such as sulfuric acid, oxalic, phosphoric acid and chromic acid solution ,where the resulting oxide film can be only sparingly soluble. For anodic porous alumina. The film growth is associated with localized dissolution of the oxide, as a result of which pores are formed in oxide film (6, 7). Electrochemistry of porous alumina: Electrolyte Pore Diameter (nm) Interpore distance (nm) Voltage(V) Sulphuric Acid 30-35 60-70 25-27 Oxalic acid 40-100 80-200 30-80 Phosphoric Acid 130-250 250-500 100-195 Table: 1 Comparison of pore diameter and inter pore distance with different electrolyte.