“…To produce changes in the diameter while the nanopores are being formed, there are many different possibilities, such as using a modified electrolyte, with additives like ethylene glycol to modify its viscosity 212 , combining constant voltage anodization and chemical etchings 213 , or using the HA method with very high applied voltages 214,215 , where fluctuating diameters along the pore length are obtained. In the last years, the two most used have been the change of electrolyte while performing the anodization 203 ( Figure 11.a and 11.b) or, maintaining the same electrolyte, varying the applied voltage.…”
Section: Nanopores With Modulated Diametersmentioning
Review of Porous Anodic Aluminum Oxide (AAO or NAA) membranes: from fabrication, mechanisms, and internal and surface nanostructuration to applications.
“…To produce changes in the diameter while the nanopores are being formed, there are many different possibilities, such as using a modified electrolyte, with additives like ethylene glycol to modify its viscosity 212 , combining constant voltage anodization and chemical etchings 213 , or using the HA method with very high applied voltages 214,215 , where fluctuating diameters along the pore length are obtained. In the last years, the two most used have been the change of electrolyte while performing the anodization 203 ( Figure 11.a and 11.b) or, maintaining the same electrolyte, varying the applied voltage.…”
Section: Nanopores With Modulated Diametersmentioning
Review of Porous Anodic Aluminum Oxide (AAO or NAA) membranes: from fabrication, mechanisms, and internal and surface nanostructuration to applications.
“…The D p rapidly increases as the EG concentration exceeds 20 wt%. This is probably because the effect of heat exchange overshadowed the role of EG that inhibits the chemical dissolution of alumina during anodization; Second, extensive incorporation of soluble and COO − ions into the oxide framework probably favours cleavages and enhances the oxide dissolution rate along the cell boundaries [ 15 ]. Figure 3.…”
Section: Resultsmentioning
confidence: 99%
“…To solve the problems in the process of HA, organic compounds were added to the aqueous electrolyte, which aimed at prompting the ordered arrangement of AAO [ 12 – 15 ]. Zaraska et al.…”
Section: Introductionmentioning
confidence: 99%
“…Vega et al [ 4 ] commented on the preparation of AAO by HA in a renewed electrolyte with different oxalic acid and ethanol concentrations and explained the role of oxalate ions and their limited diffusion through alumina nano-channels from a bulk electrolyte on the basis of a phenomenological model. Furthermore, Norek et al [ 15 ] have also reported a systematic study on the effect of addition of EG to oxalic acid electrolytes for the HA process of Al.…”
The influence of the addition of ethylene glycol (EG) on the pore self-ordering process in anodic aluminium oxide (AAO) membranes prepared by hard anodization (HA) was investigated. It was illustrated that EG has a substantial effect on the pore arrangement of AAO, and it was found that a smaller pore size can be obtained with an EG concentration reaching 20 wt% in aqueous electrolyte. The number of estimated defects of AAO increases significantly with an increase in EG concentration to 50 wt%. Excellent ordering of pores was realized when the samples were anodized in the 30 wt%-EG-containing aqueous electrolyte.
“…The exposed aluminum substrate possessed a nanoscale dimple array configuration, which corresponded to the negative shape of the bottom of the porous alumina. The ordering behavior of the porous alumina was evaluated using fast Fourier transform (FFT) with the Image-J software package (Wayne Rasband, National Institute of Health, USA) [43][44][45]. After oxide dissolution, several nanostructured specimens were anodized again in arsenic acid solutions under the same operating conditions (two-step anodizing).…”
Section: Post-treatment Of Anodized Specimensmentioning
Anodizing of aluminum in an arsenic acid solution is reported for the fabrication of anodic porous alumina. The highest potential difference (voltage) without oxide burning increased as the temperature and the concentration of the arsenic acid solution decreased, and a high anodizing potential difference of 340 V was achieved. An ordered porous alumina with several tens of cells was formed in 0.1-0.5 M arsenic acid solutions at 310-340 V for 20 h. However, the regularity of the porous alumina was not improved via anodizing for 72 h. No pore sealing behavior of the porous alumina was observed upon immersion in boiling distilled water, and it may be due to the formation of an insoluble complex on the oxide surface. The porous alumina consisted of two different layers: a hexagonal alumina layer that contained arsenic from the electrolyte and a pure alumina honeycomb skeleton. The porous alumina exhibited a white photoluminescence emission at approximately 515 nm under UV irradiation at 254 nm.
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