Fabrication of Porous Anodic Alumina(PAA)
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Nanoporous anodic alumina (NAA), obtained via aluminum anodization, have been used as template for fabrication of nanostructure materials and photonic devices. In order to promote the formation of regular porous and to control the desired... more
Nanoporous anodic alumina (NAA), obtained via aluminum anodization, have been used as template for fabrication of nanostructure materials and photonic devices. In order to promote the formation of regular porous and to control the desired properties, high-purity aluminum and pretreatment of Al surfaces are mandatory. This procedure consists in electrochemically removing the external irregular layer of the metal promoting a flat, bright and smooth metallic surface. In this study, the effect of electropolishing parameters on commercial aluminum samples (6061 alloy, 97%) was investigated. This procedure was performed at constant potential in a mixture of perchloric acid and ethyl alcohol solution in different experimental conditions. A factorial design was used to investigate the effect of applied potential, electropolishing time and electrolyte temperature on roughness and specularity of Al substrates. These samples were characterized by Atomic Force Microscopy (AFM) and Diffuse Reflectance Spectroscopy (DRS). All variables presented significant effects on roughness of Al substrates, although electropolishing time presented the most important effect on specularity of these samples. After galvano-static anodization in oxalic acid solution, the results showed the influence of Al surface roughness on morphology of NAA films. Since all Al samples were anodized under same conditions, the differences observed in micrographs of NAA films were related to roughness of Al substrates, which was affected by electropolishing parameters, mainly the applied potential and electropolishing time.
In the present work, hard anodization assisted by anode temperature ramp was employed to fabricate self-ordered nanoporous alumina in the wide range of interpore distances (259–405 nm) in pure oxalic acid and mixture of oxalic and... more
In the present work, hard anodization assisted by anode temperature ramp was employed to fabricate self-ordered nanoporous alumina in the wide range of interpore distances (259–405 nm) in pure oxalic acid and mixture of oxalic and phosphoric acid solutions. Anode temperature ramp technique was employed to adjust the anodization current density to optimize the self-ordering of the nano-pore arrays in the interpore range in which no ordered self-assembled hard anodized anodic aluminum oxide has reported. It is found that the certain ratios of oxalic and phosphoric acid solutions in this anodization technique increased self-ordering of the nanopores especially for anodization voltages over the 170 V by increasing alu-mina's viscous flow which could lead to decrease the overall current density of anodization, yet leveled up by anode temperature ramp. However, below 150 V anodization voltage, the ratio of interpore distance to the anodization voltage of the both anodization techniques was the same (*2 nm/V), while above this voltage, it increased to about 2.2 nm/V.
Nanoporous anodic alumina (NAA), produced by aluminum anodization presents interesting optical effects in luminescence property exhibiting waveguides or Fabry–Pérot interference. This phenomenon, which is used as transducer response in... more
Nanoporous anodic alumina (NAA), produced by aluminum anodization presents interesting optical effects in luminescence
property exhibiting waveguides or Fabry–Pérot interference. This phenomenon, which is used as transducer response in optical sensors, depends on morphological characteristics of the NAA films, such as pore diameter, inter-pore distance and film thickness. In this work, the effect of electrolyte temperature on NAA morphology was investigated and, consequently, how this effect shaped the interference property. For this, all anodizing experimental conditions were kept constant while the electrolyte temperature was changed
(5, 10, 15, 20 and 25 °C). Itwas observed an increase in the minimumand stationary current density values during anodization as the electrolyte temperature increased, which were correlated to enlargement of porous oxide layer, since pore diameter, inter-pores distance and porosity remained constant for all studied temperatures. The photoluminescence (PL) spectra showed an increase in the number of fringes and an amplitude decrease with the increase of electrolyte temperature. NAA film thickness was evaluated using optical and morphological parameters and compared to values in the literature. A brief discussion of the results regarding the ratio of film thickness and pore diameter (L/dp) was performed to validate the NAA films with better waveguides property to be used as a platform for optical sensing applications.
property exhibiting waveguides or Fabry–Pérot interference. This phenomenon, which is used as transducer response in optical sensors, depends on morphological characteristics of the NAA films, such as pore diameter, inter-pore distance and film thickness. In this work, the effect of electrolyte temperature on NAA morphology was investigated and, consequently, how this effect shaped the interference property. For this, all anodizing experimental conditions were kept constant while the electrolyte temperature was changed
(5, 10, 15, 20 and 25 °C). Itwas observed an increase in the minimumand stationary current density values during anodization as the electrolyte temperature increased, which were correlated to enlargement of porous oxide layer, since pore diameter, inter-pores distance and porosity remained constant for all studied temperatures. The photoluminescence (PL) spectra showed an increase in the number of fringes and an amplitude decrease with the increase of electrolyte temperature. NAA film thickness was evaluated using optical and morphological parameters and compared to values in the literature. A brief discussion of the results regarding the ratio of film thickness and pore diameter (L/dp) was performed to validate the NAA films with better waveguides property to be used as a platform for optical sensing applications.
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