Papers by Keyword: Anodic Aluminum Oxide (AAO)

Abstract: Anodic aluminum oxide (AAO) is well known for its nanoscopic structures and its applications in microfluidics, sensors and nanoelectronics. The pore density, the pore diameter, and the interpore distance of an AAO substrate can be controlled by varying anodization process conditions. In this research, the self-organized two-step anodization is carried out with a low-grade (Al6061) aluminium substrate using a 40V voltage at the temperature of 2 to 5 °C. Three experiments are done with the anodization time of 24 hours, 48 hours and 72 hours. The structural features of AAO are characterized by a field emission electron microscope (FE-SEM). The data from FE-SEM show that the average pore diameter increases with the anodization time, and that the Al6061 aluminium substrate can be used to fabricate a nanoporous AAO film with an average pore diameter smaller than 17 nanometers.

Abstract: Highly ordered copper nanowire arrays were prepared by electrolytic deposition using porous anodic aluminum oxide (AAO) as template. The technique of removing the barrier layer of the AAO template by the pore widening procedure was investigated. The quality of the Au conducting layers sputtered at the bottom side of the AAO template was also studied. The direct current (DC) electrodeposition of copper nanowire arrays was performed efficiently above the Au layer inside the pores. The morphology of the copper nanowires was characterized by scanning electronic microscopy (SEM) and the composition of Cu nanowires was confirmed by energy dispersive X-Ray spectroscopy (EDS). The results showed that the best condition was found to be in phosphoric acid (6%wt) for 10 min to remove the barrier layer completely. Au layer was uniform and dense after sputtering for four times. Copper nanowire arrays were successfully prepared by three-electrode and two-electrode cell electro-deposition, but the nanowire arrays were more ordered by using three-electrode cell and the length of nanowires was more uniform. The diameter of a single Cu nanowire is less than 100 nm with the length up to around 10 μm, and the nanowires are well arranged in arrays.

Abstract: A new and facile method for improving the procedure of anodic aluminum oxide (AAO) film preparation was presented, which was based on an electrochemical detachment procedure. The detachment and pore-opening were performed just through one step in a solution of HClO₄ and C₂H₅OH at a voltage of 40V. The as-obtained AAO film was characterized by scanning electron microscopy (SEM) and scanning probing microscopy (SPM). The process of detachment and pore-opening was also discussed.

Abstract: Carbon membranes have high adsorption capacitiy with respect to its incredible properties such as unique structural, electronic, optoelectronic, semiconductor, mechanical, chemical and physical. Carbon nanotube (CNT) membranes because of its high permeance have been recently developed.Great attention has been currently paid to the field of fabrication methods capable of producing uniform, well-aligned and monodispersed CNT array. Current research concerns with fabrication of vertically aligned CNT membrane in order to remove heavy metal ion presents in waste water. For this purpose, CNTs are vertically grown up through the holes of anodic aluminium oxide (AAO); as a template, by chemical vapor deposition (CVD) of acetylene gas.In this work a few heavy metals such as Pb (II), Cu (II) and Cd (II) has been examined for checking the perfomance of membrane in aqueous solution. The morphological properties of the aligned CNT membrane were investigated with scanning electron microscopy (SEM). The method has simple technology, low cost, and easy reproduction.

Abstract: It is important to generate aluminum oxide layer on the surface of aluminum in order to enhance the adhesion of the dye molecules in coloring aluminum industry. One of the major advantages of aluminum is the formation of a resistant oxide layer naturally, but the thickness of this layer is not high enough and it should be damaged due to lack of mechanical strength. However, the thickness of oxide layer can be increased through anodizing; this process improves its abrasion and corrosion resistance as well as its mechanical properties. In the present study, specimens of pure aluminum were anodized under galvanostatic condition in sulfuric acid electrolyte and porous nanostructured aluminum oxide layer was formed. Porosity of the anodized layer was controlled by optimizing the working conditions such as electrolyte concentration, anodizing time and current density. Finally, the specimens were electrolytically colored by applying alternating current to copper (Cu) solutions. Colored coatings were created at constant voltage and different coloring duration. The results indicated that the shade of different metal ions can be optimized by controlling the coloring parameters, the longer time of coloring results in the darker colors. The samples were examined by X-Ray Diffraction (XRD) spectroscopy and Scanning Electron Microscopy (SEM) and electrochemical test.

Abstract: The use of nanostructured thin films to improve physical and mechanical properties of cutting tools have been recently achieved wonderful progress in industrial and research centres. In this present work, anodic aluminium oxide (AAO) film is formed on the cutting tool by anodizing a thin film of aluminium foil. Aluminium coating is performed using an innovative electroplating method. Then the nanometric pores which are formed by the anodizing are filled with the resistant AlTiN using physical vapour deposition (PVD) method. This procedure results in a nanostructure with an aluminium oxide resistant texture which attains a high hardness and Young modulus. In this project we succeeded in designing aluminium oxide nanostructured as scaffolds for aluminium titanium nitride. Along with nanostructured alloy AlTiN, a unique hardness and wear resistance is obtained. This coating texture improvements the efficiency and tool life much better than other coating methods done, and as a result, a greater efficiency in production and reduction in costs is achieved.

Abstract: Carbon nanotube (CNT) is one of the most attractive nanomaterials which may be used in many potential applications of nanotechnology due to its excellent mechanical, electrical and thermal properties. We demonstrated the fabrication of carbon nanotube at the surface of anodic aluminum oxide (AAO) membrane by chemical vapor deposition (CVD) method. Acetylene was used as a hydrocarbon source and Fe as catalyst. CNT was synthesized at different temperature. The iron catalyst was confined in the holes of the AAO membrane. A variety of carbon structures such as nanotubes, helices, spiral, and hook-like curved shapes in the range of micrometer were synthesized. High graphitic multiwall carbon nanotube (MWCNT) was found at 700-750°C temperature.

Abstract: In this article we address the process perspective of anodization for fabrication of nickel coating materials. In this work, we also report the mechanical properties and morphology of coating materials with various parameters. We investigated the effect of temperature and plating time with 0.3 (A/cm³) of current density. Light microscopes, Scanning Electron Microscopy and Hardness tester were used to confirm morphology and hardness of target object, respectively. In general it was observed that anodization process also affected on properties of target object. The hardness of target object with anodization process will be increased in first period and slightly decreased with high temperature and longer plating time. The chemical etching treatment had an impact on the morphological features of the AAO templates lead to morphological features of nickel coating materials.

Abstract: Anodic aluminium oxide fabricated at ambient temperature and low potential in phosphoric acid electrolyte was used as the working electrode for the electrochemical measurement of phosphate buffer saline under different pH conditions using the cyclic voltammetry tool. We investigate the reversibility of the electrochemical reaction as a redox reaction from the cyclic graphs that were obtained. We observed that the ratio of the peak current passed at both the reduction and oxidation when measured was very close to unity in all the pH but except one which produced a none reversible reaction with a non cyclic graph. The peak potential for both reduction and oxidation reactions using phosphate buffer saline as the analyte under different pH of 3, 5, 7, and 9 was also obtained.

Abstract: Antidot arrays of various diameters were patterned in permalloy thin films to explore their magnetic behavior. Porous anodic alumina had been used as a template to fabricate magnetic films with antidot array. Permalloy had been fabricated by depositing Ni₈₀Fe₂₀ onto anodic alumina membrane templates. The film thickness was 30 and 40 nm and the diameters of antidot varied from 200 to 350 nm. The coercivity of the antidot arrays is greater than that of unpatterned films and shows weak dependence on antidot diameter. The increase of the pore diameter was suggested to enhance domain wall pinning. The coercivity reaches a maximum value for the antidot array with the smallest pore diameter and reduces to an almost constant value for the antidot arrays with larger pore diameters.