Nanoporous surface treatment of aluminium by anodisation in oxalic acid

Purpose: Well-ordered nanoporous anodic surface on aluminium substrate was obtained by anodisation method in 0.3 M of oxalic acid as an electrolyte. The objective of this perusal is to describe a system for the magnifying diameter of pores and resistance of demolition of the oxide layer at various voltages. The effect of voltage and time of anodisation process in which obtaining the required structure in AAO film. Design/methodology/approach: The experiments have been performed on a setup for anodisation considering variables parameters. In this study, AAO Templates were prepared in oxalic acid of 0.3 M concentration under the potential range of anodisation 30-40 V at relatively temperatures range from 20-30°C of an electrolyte. Anodic voltage, current density and temperature of electrolyte were adopted as electrical parameters during anodisation. Before anodisation starts two crucial pre-treatment i.e. annealing and electropolishing are finished. Findings: The diameter of pores and pitch of pores are well-proportional to anodisation voltage and process time. The pore diameters were 85 nm, 138 nm, 184 nm, 248 nm with having 9, 16, 27, 37 porosity % respectively. The thickness of AAO film in all cases has been found to be maximum or constant after one hour in second step anodisation. The anodisation parameters like voltage, the time duration of the anodisation process and temperature are very essential features which influencing the fabrication of an AAO film. Research limitations/implications: The anodisation process is very easy to perform but very complex to understand as there are many parameters which may affect it. Practical implications: After that, the second step anodisation for the next half hour, there will be no change in the thickness of AAO film but after that dissolution rate starts over the formation rate and finally thickness will be decreasing. Originality/value: Therein is numerous macropores in the membrane with the size of pores variation from 163 to 248 nm. The diameter of pores, thickness, and pore density of AAO film was determined through Scanning Electron Microscopy (SEM), which exhibited that homogeneous honeycomb-like structure has appeared on the entire surface where anodisation performed precisely.

Mesoporous Titanium Dioxide Thin Films on Quartz via Electrochemical Anodisation Process

Titanium dioxide (TiO2) thin films were prepared by means of electrochemical anodisation or anodic spark deposition (ASD) from thin and flat metallic titanium (Ti) films pre-deposited on high quality quartz substrates by electron beam evaporation. AFM analysis indicates the formation of uniform mesoporous layers and a definite increase about 50% of the film thickness upon anodisation and about 90% upon annealing. Anodised mesoporous TiO2films have been characterized by Raman spectroscopy, which indicates the presence of well-defined peaks related to anatase structure. Phase transformation from anatase to rutile was observed after annealing at temperatures up to 900°C for 3h.

The Effect of Applied Voltage and Anodisation Time on Anodized Aluminum Oxide Nanostructures

The use of anodized aluminum oxide (AAO) is vastly being explored in recent years. The application includes molecular separation, sensing, energy storage and template synthesis for various nanostructures. The reason AAO is preferred was because of the ability to control the nanopore structure by manipulating some factors during the anodisation process. This study will investigate the exploitation of voltage and anodisation time during the anodisation process and the effect it has on the nanopore structure of the AAO by examining the structure under Field Emission Scanning Electron Microscope (FE-SEM). The experiment was carried out by anodizing aluminum foil in 0.3 M oxalic acid as electrolyte under the constant temperature of 5 °C. The applied voltage was varied from 40, 60 and 100 V with different anodisation time. The outcome of this study demonstrates that applied voltage has a proportional relationship with the developed pore size. Increasing the applied voltage from 40 to 100 V had increased the pore size of the AAO from 38 nm to 186 nm, respectively. Aluminium oxide anodized at 60 V demonstrates pore size in the range of 76 nm. Prolong anodisation time had improved the pore morphology of anodized aluminium oxide in the case of 40 V, however, the pore wall starts to collapse when anodisation time is more than 4 minutes at 100 V.

Preparation of Porous Alumina Template for Nanostructure Fabrication

Porous alumina films are widely used as templates for fabricating one-dimensional (1-D) nanostructures such as nanowires or nanotubes. Using a two-step anodisation process, we have successfully optimized the growth conditions for fabricating highly ordered porous alumina films with pore diameters ranging from 20 to 150 nm, to be used as templates for 1-D nanostructure synthesis. The effects of the anodisation conditions on pore structure and the formation rate of the films were systematically studied. It was found that low electrolyte temperatures and agitations decreased the growth rate of the films but favored the process of pore ordering. Removal of oxide layer formed from first anodisation process and removal of barrier oxide at pore ends had an important bearing on pore morphology. Besides the stand-alone porous alumina films, we have also fabricated porous alumina films on rod-shaped Al substrates.

Fabrication of Nanoporous Aluminum Oxide via a Two-Step Anodisation Process

In this study, we report the fabrication of nanoporous aluminum oxide film from high purity aluminium foil via a two-step anodisation process controlled by a constant direct current potential ranging from 40 60 V from a DC power supply. The anodisation process was conducted at 20˚C in an electrochemical cell with the Al foil acting as anode, Pt as cathode and an acidic bath as electrolyte. Porous aluminium oxide films of pore diameters ranging between 30 90 nm were successfully fabricated. The morphologies and phase compositions of the anodized porous alumina films were investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD) for characterizations.

Synthesis of Self-Aligned Titanium Oxide Nanotube Arrays in Ammonium Fluoride-Ethylene Glycol Electrolytes with Different Water Contents

The aim of this research is to fabricate of TiO2nanotube arrays by potentiostatic anodisation process on titanium sheets. Anodisation is carried out under various applied potentials ranging from 20 to 30 volts for 1-3 hours at room temperature. Anodised were conducted in 1-4 wt% NH4F, water-based electrolyte and ethylene glycol-based electrolyte. The morphology of the anodised surfaces were characterised by scanning electron microscopy. When titanium sheets were anodised in various conditions, surface morphology of anodised titanium change remarkably with the changing of applied voltages, chemical composition of the electrolyte and anodisation time. The results of the present work show that the highly ordered and uniformly distributed TiO2nanotubes on titanium substrate can be fabricated by using mixtures of NH4F, ethylene glycol and water with appropriate conditions. Moreover, the anodisation potential and the water content play significant roles in the formation of TiO2nanotube with different inner tube diameters. The length of TiO2nanotube was controlled by anodisation time.

Microscopy of plasma anodised materials for VLSI

Plasma anodisation is an attractive technique for growing insulating layers of SiO2 at much lower temperatures then those needed for thermal oxide growth. Defects can be generated in silicon when it is subjected to prolonged high temperature oxidation processes, which in turn lead to degradation in both yield and performance of small geometry devices. An additional disadvantage of thermal oxide growth lies in the lateral oxidation behaviour (i.e. oxidation underneath the mask or ‘bird-beaking’ effect) which limits the minimum device separation which can be achieved. Although plasma anodisation has been widely investigated (see and references therein), previous studies have highlighted the severe difficulty of producing effective masks for this process, particularly during the high power anodisation studies which are the subject of this paper. Most of the established masks against thermal oxidation appear to be consumed during the plasma anodisation process. Therefore an important issue with regard to plasma anodisation is to find material systems in which the vertical oxidation rate of the mask is low compared to silicon and the lateral oxidation of both the mask and the silicon substrate under the mask are minimal. For the present study, two materials systems have been investigated; Si3N4/SiO2 strips on Si and Al/SiO2 strips on Si.