Search results for "anodizing"

Surface structure promoted high-yield growth and magnetotransport properties of Bi2Se3 nanoribbons

2019

AbstractIn the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20–100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed. It is shown that the yield and average length of the nanoribbons can base tuned by adjustment of the synthesis parameters. Analysis of magnetotransport measurements for the individual Bi2Se3…

Influence of initial treatments of aluminium on the morphological features of electrochemically formed alumina membranes

2003

Abstract The fabrication of alumina membranes by electrochemical oxidation of annealed aluminium was investigated. Porous layers were grown in 0.4 M H3PO4 at −1 and 5 °C at different anodising times. The morphology of the outer surface was found to be dependent on temperature and charge density, with both determining the extent of chemical dissolution of the anodic oxide. The inner-surface morphology was found to depend on the applied voltage only. The chemical dissolution rate of anodic oxide grown on annealed aluminium was found to be lower than that formed on unannealed aluminium under otherwise identical conditions. Such a difference in behaviour is explained in terms of a higher finish…

The Effect of Electronic Properties of Anodized and Hard Anodized Ti and Ti6Al4V on Their Reactivity in Simulated Body Fluid

2022

The electronic properties of barrier and porous layers on Ti and Ti6Al4V were studied. Barrier anodic oxides grown to 40 V on Ti and on Ti6Al4V are both n-type semiconductors with a band gap of 3.3 eV and 3.4 eV respectively, in agreement with the formation of amorphous TiO2. Anodizing to 200 V at 20 mA cm−2 in calcium acetate and β-glycerol phosphate disodium pentahydrate leads to the formation of Ca and P containing porous films with a photoelectrochemical behaviour dependent on the metallic substrate. A band gap of 3.2 eV and the flat band potential of −0.5 V vs Ag/AgCl were measured for the porous oxide on Ti, while optical transitions at 2.15 eV and a significantly more positive flat b…

Photoelectrochemical characterization of anatase-rutile mixed TiO2 nanosponges

2016

This work studies the influence of using hydrodynamic conditions during anodization on the morphology and electrochemical properties of anatase/rutile mixed TiO2 nanotubes (Reynolds number, Re = 0) and nanosponges (Re > 0). To this purpose different techniques were used, such as: microscopy techniques (Field-Emission Scanning Electron Microscope, FE-SEM, and Confocal Laser-Raman Spectroscopy), Electrochemical Impedance Spectroscopy (EIS), Mott Schottky (MS) analysis and photoelectrochemical water splitting tests. This investigation demonstrates that the morphology of TiO2 nanostructures may be greatly affected due to the hydrodynamic conditions and it can be adjusted in order to increase th…

Effect of Reynolds number on TiO2 nanosponges doped with Li+ cations

2018

[EN] Anatase TiO2 nanosponges have been synthesized by anodization of Ti, and Li+ cations have been inserted in these nanostructures. The influence of hydrodynamic conditions (Reynolds number, Re = 0 to Re = 600) during anodization has been studied. Li-Doped TiO2 nanosponges were characterized by field emission scanning electron microscopy (FE-SEM), Raman confocal microscopy, electrochemical impedance spectroscopy (EIS) and Mott¿Schottky analysis (M¿S). The photoelectrochemical performance and resistance to photocorrosion were also measured. Li¿TiO2 nanosponges proved to be better photocatalysts for water splitting than Li¿TiO2 nanotubes. Moreover, the photoelectrochemical behavior of the L…

Original Approach to Synthesize TiO2/ZnO Hybrid Nanosponges Used as Photoanodes for Photoelectrochemical Applications

2021

[EN] In the present work, TiO2/ZnO hybrid nanosponges have been synthesized for the first time. First, TiO2 nanosponges were obtained by anodization under hydrodynamic conditions in a glycerol/water/NH4F electrolyte. Next, in order to achieve the anatase phase of TiO2 and improve its photocatalytic behaviour, the samples were annealed at 450 degrees C for 1 h. Once the TiO2 nanosponges were synthesized, TiO2/ZnO hybrid nanosponges were obtained by electrodeposition of ZnO on TiO2 nanosponges using different temperatures, times, and concentrations of zinc nitrate (Zn(NO3)(2)). TiO2/ZnO hybrid nanosponges were used as photoanodes in photoelectrochemical water splitting tests. The results indi…

Anodizing Science and Technology: achievements and perspectives. A personal view

2008

Photoelectrochemical evidence of nitrogen incorporation during anodizing sputtering--deposited Al-Ta alloys.

2015

Anodic films were grown to 20 V on sputtering-deposited Al–Ta alloys in ammonium biborate and borate buffer solutions. According to glow discharge optical emission spectroscopy, anodizing in ammonium containing solution leads to the formation of N containing anodic layers. Impedance measurements did not evidence significant differences between the dielectric properties of the anodic films as a function of the anodizing electrolyte. Photoelectrochemical investigation allowed evidencing that N incorporation induces a red-shift in the light absorption threshold of the films due to the formation of allowed localized states inside their mobility gap. The estimated Fowler threshold for the intern…

Kinetics of coloration of anodic electrochromic films of WO3·H2O

1980

Polycrystalline layers of WO3·H2O are obtained by anodization of tungsten in 1 N H2SO4 at 70° C. The cathodic reduction of these layers in acid solutions causes the formation of blue WO3−x·H2O (0<x⩽:0.12) oxides. The kinetics of coloration are investigated by galvanostatic and potentiostatic techniques. The experimental results are compared with the theoretical data obtained by solving the diffusion equation for a constant flow of oxygen vacancies and for a time-dependent surface vacancy concentration. Except in the initial stage of coloration, the process controlling rate can be ascribed to the diffusion of oxygen vacancies from the oxide-electrolyte interface into the bulk of the layers. …

Microporous alumina membranes electrochemically grown

2003

Abstract The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid and oxalic acid solutions, in the temperature interval from −1 to 16 °C, was investigated in order to study the influence of different parameters (initial treatment of aluminium surface, nature and composition of electrolyte, temperature) on the final characteristics of the membranes. Porous layers were grown using a linear potential scan at 0.2 V s −1 up to 160 V in H 3 PO 4 solution and 70 V in oxalic acid solution. The efficiency of porous layer formation was calculated by using Faraday's law and weight measurements. Pore size distribution and porosity of membranes prepared in 0.4 M…