Anodization of Aluminium using a fast two-step process (original) (raw)
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Materials Chemistry and Physics, 1993
The pore-filling method is a known process for measuring the porosity of porous anodic oxide layers on aluminium. This method has been used to study the relationship between the anodizing conditions and the porosity of the porous anodic film. In a series of experiments, the influence of the anodization voltage and temperature on the porosity of an anodization layer formed in 15 wt.% sulphuric acid was investigated. From these results a mathematical equation was deduced that gives the porosity as a function of the anodization voltage and temperature. In the second part of the study the height of the voltage jump, on which the thickness of the barrier layer at the start of the re-anodization process depends, was investigated as a function of the anodization voltage. A linear relationship was found between the voltage jump and the anodization voltage.
Porous and mesh alumina formed by anodization of high purity aluminum films at low anodizing voltage
Thin Solid Films, 2014
Electrochemical oxidation of high-purity aluminum (Al) films under low anodizing voltages (1-10) V has been conducted to obtain anodic aluminum oxide (AAO) with ultra-small pore size and inter-pore distance. Different structures of AAO have been obtained e.g. nanoporous and mesh structures. Highly regular pore arrays with small pore size and inter-pore distance have been formed in oxalic or sulfuric acids at different temperatures (22-50°C). It is found that the pore diameter, inter-pore distance and the barrier layer thickness are independent of the anodizing parameters, which is very different from the rules of general AAO fabrication. The brand formation mechanism has been revealed by the scanning electron microscope study. Regular nanopores are formed under 10 V at the beginning of the anodization and then serve as a template layer dominating the formation of ultra-small nanopores. Anodization that is performed at voltages less than 5 V leads to mesh structured alumina. In addition, we have introduced a simple one-pot synthesis method to develop thin walls of oxide containing lithium (Li) ions that could be used for battery application based on anodization of Al films in a supersaturated mixture of lithium phosphate and phosphoric acid as matrix for Li-composite electrolyte.
Room Temperature Anodization of Aluminum at Low Voltage
2013
Membranes with nanometer-scale features have many applications, such as in optics, electronics, catalysis, selective molecule separation, filtration and purification, biosensing, and single-molecule detection. Anodiztion process was conducted using 15, 20, 30 and 35% by volume phosphoric acid. Results showed that Porous Anodized Aluminum (PAA) with ideal nanopore arrays can be fabricated at room temperature by one-step anodization on high purity aluminum foil at 5V. Morphology of the PAA was characterized by scanning electron microscopy (SEM). The electrochemical behavior of anodized aluminum was studied in 0.1M Na2SO4 solutions using electrochemical impedance spectroscopy (EIS). The highest resistance of the porous layer (Rp) was detected for the samples anodized in 20% phosphoric acid.
Effect of Formation Voltage on the Pore Size of Porous Anodic Aluminum Oxide
IOP Conference Series: Materials Science and Engineering
This work is aimed to clarify the effect of formation voltage on the pore size of porous anodic aluminum oxide (PAAO) layer formed on commercially pure aluminum. The PAAO layers were obtained by anodization process in 0.3 M sulfuric acid solution at constant voltages of 10, 15, 20, and 25 V at 10°C. The structure and morphology of PAAO layers were characterized by using FE-SEM. The pore diameters which were estimated by using ImageJ software were 19.61 + 15.35 nm, 20.03 + 13.59 nm, 20.31 + 12.36 nm, 25.06 + 12.10 nm, and the wall thicknesses were 33 nm, 49.99 nm, 74.97 nm, 83.33 nm for the PAAO formed at 10, 15, 20 and 25V, respectively. The structure of the porous oxide layer became more uniform and organized, and the diameter of the pores increased linearly with applied voltage. High anodization voltage is known to cause Joule heating because of the fast movement of electrons and ions. It is believed that the Joule heat was transferred to the bulk electrolyte which results in larger pore diameter and interpore distance. The optimum condition to obtain high order PAAO is at 25 V.
Advanced Materials Letters, 2012
Nanoporous alumina was produced by anodic oxidation of aluminum in both acidic and alkaline electrolytes. Previous reports indicate that nanoporous alumina is mainly produced from strongly acidic electrolytes, and with the use of a low freezing temperature controlled bath to control the propagation and growth of the pores. We design an in-house electrochemical cell with an electronic circuit box attached, to control the anodization of aluminum at room temperature. The electrolytes used were phosphoric acid solution and sodium hydroxide solution. The pH of the acidic electrolyte was adjusted to 1, 3 and 5 with an applied potential of 50V and anodization time of 1 and 3 hrs, respectively, while the alkaline electrolyte pH was adjusted to 9, 11 and 13 with an applied potential of 40V and the templates anodized for 5 hrs. The micrographs of the nanoporous alumina formed from these electrolytes confirm that the nucleation and growth of nanoporous alumina films is achievable with the aid of the electronic circuit box connected to the electrochemical cell.
Electrochimica Acta, 2010
A new approach for studying the effect of temperature on anodic oxide growth on aluminium is presented in this paper. Using an in-house developed electrode holder, anodizing is performed under conditions of applied and controlled electrode temperature. The influence of temperature on the process is evaluated by experiments in a broad temperature range for both the electrode and the electrolyte temperature. The electrochemical behaviour of the aluminium electrodes is demonstrated to be more susceptible to variations of the electrode temperature than to variations of the electrolyte temperature. Concerning the morphology of the anodic film it is shown that by cooling the electrode a normal oxide layer could be grown at high electrolyte temperatures, whereas anodizing in a cool electrolyte at high electrode temperature results in a collapsed porous structure at the oxide surface. Furthermore, the electrode temperature affects the formation ratio of the oxide to a larger extent than the electrolyte temperature, indicating its important influence even on the level of the ionic conductivity during anodic oxide growth. All observations indicate that merely considering the electrolyte temperature upon studying the influence of temperature on the process is not sufficient; the electrode temperature is much more determining.
Formation of nanoscale pore arrays during anodization of aluminum
Europhysics Letters (EPL), 2005
A theory of the spontaneous formation of spatially regular hexagonal arrays of nanopores in aluminum oxide film growing during aluminum anodization is presented. Linear stability analysis shows that, in certain ranges of the applied voltage and electrolyte pH, the oxide film is unstable with respect to perturbations with a well-defined wavelength. The instability is caused by a positive feedback between the oxidation-dissolution rates and variations of electric field caused by perturbations of the metal-oxide and oxide-electrolyte interfaces. The competition between this instability and the stabilizing effects of the Laplace pressure and elastic stress provides the wavelength selection mechanism. The hexagonal ordering of pores results from the resonant quadratic nonlinear interaction of unstable modes.
Fabrication of Commercial Nanoporous Alumina by Low Voltage Anodizing
Egyptian Journal of Chemistry, 2018
T HE PRESENT work is considered as an introductory study on the procurement of membranes from nanoporous alumina through one-step anodization. The nonporous alumina was obtained by anodizing the specimens at low voltage 5V for 20 minutes in phosphoric acid. The self-ordered porous arrangements can be acquired by using this process. The variables of space between pores, high pore density on the alumina surface are subjected to comparison with membranes which obtained by other methods. The mixture of phosphoric acid and chromium trioxide is used for removing the formed aluminum oxide after the first anodization. The self-ordered porous configuration is obtained at the second anodization step at the same conditions of the first anodization process. The nonporous alumina membrane was subjected to characterization of its surface morphology by scanning electron microscopy SEM and the electric properties were examined by using the electrochemical impedance test EIS. The formed nanoporous structures can be used for fabrication of sensor elements.
International Journal of Scientific and Engineering Research
Nanoporous anodic alumina (AAO) was fabricated using one-step anodizing at room temperature and low voltage. All specimens were potentiostaticaly anodized at 5 V for 20 minutes in phosphoric acid (H3PO4). Morphology of the AAO layers was characterized by scanning electron microscopy (SEM). By anodizing at 20% (by vol.) phosphoric acid, a uniform porous structure with nearly parallel cylindrical pores, ~200 nanometers wide, were detected. The thickness of the porous layer was higher than the barrier layer. The electrochemical impedance test (EIS), using 0.1 M Na2SO4 electrolyte, confirmed the presence of a multi layers structure of a barrier layer and a porous layer with the highest resistance value (365.1 kΩ). Using AC impedance technique (IS), samples anodized in 20% (by vol.) phosphoric acid, proved to have the highest electrical resistance (26 kΩ), reflecting a po-rous structure formation. The mechanism of pores formation as well as electrical conductivity is to be discussed.