Formation Of Anodic Oxide Films Research Articles

Formation of Porous Anodic Oxide Film on Titanium in Phosphoric Acid Electrolyte

A sequential breakdown anodizing conditions on cp-Ti in phosphoric acid has been investigated in the present study. Anodic oxide films were formed at 100, 150, and 200 V, examined by scanning electron microscopy, Raman spectroscopy, glow discharge optical emission spectrometry, and electrochemical impedance spectroscopy. A porous oxide texture was formed at each voltage. The thickness of anodic porous oxide increased with the increase of anodic voltage. Nano-particulates were formed around and within the pores, and the size of pores increased with increased voltage due to the expansion of particulates. The amorphous-to-crystalline transition was initiated during the film growth. The degree of crystallinity in the anodic oxide film fabricated at 200 V is more abundant than 150 and 100 V. Increased content of the phosphorus species was incorporated into the porous film with the increase of anodic voltage, stabilizing for the nanocrystals developed within the oxide.

Characterization of anodic oxide growth on commercially pure titanium in NaTESi electrolyte

The present study examines the formation of anodic oxide films on commercially pure titanium in NaTESi electrolyte at a constant current density of 20mAcm−2. The barrier-type titanium oxide films of ~30, 37 and 67nm thick are formed when anodized to 5, 10 and 20V. However, a porous film of approximately 80.0nm thick is developed after anodizing to 40V. Significant sodium species were found throughout the oxides and the concentration increases with the increase of anodic voltage. The growth efficiency is reduced by increasing the anodic voltage, due to formation of crystalline phase in the oxide, which induces oxygen generation. The degree of crystallinity of the anodic oxide film formed on titanium is increased associated with the increase of the anodic voltage. The dielectric permittivity of the anodic oxide film is estimated as 2.35 based on the oxide thickness measured when anodized to 10V.

Anodic Oxide Film Formed on Ti-6Al-4V at a Low Current Density in Monocalciumphosphate Monohydrate (MCPM) Electrolyte and its Biocompatibility

Anodic oxide film on titanium alloy (Ti-6Al-4V) substrate was prepared by anodization. The reaction was done by applying low current densities from 0.25 to 2 mA/cm2 for 30 minutes using monocalciumphosphate monohydrate (MCPM) solution as an electrolyte. Essential parameters which affected to the formation of anodic oxide film were studied. The properties of the anodic oxide film would be optimized when the parameters were appropriately controlled. Increasing of the current density and the concentration of MCPM electrolyte could promote hydrophilicity and surface roughness of the film. After anodization, the anodic oxide film formed at 2 mA/cm2 in 1M MCPM showed the best hydrophilicity (lowest water contact angle) and the film formed at 0.25 mA/cm2 in 0.5M MCPM showed the lowest hydrophilicity (highest water contact angle). XPS analyses confirmed that the chemical species of as-anodized film formed at 2 mA/cm2 in 1M MCPM changed. Ti2p spectra scarcely changed while the O1s spectra significantly changed due to the presence of chemisorbed water and Ti-OH formed during anodization. The SEM micrographs also revealed the biocompatibility from the growth of the cementoblast cell on anodized surface. It was indicated that anodization using MCPM as an electrolyte at 2 mA/cm2 in 1M MCPM could modify the surface roughness and chemical species and that both are likely to be crucial key factors for enhancing of hydrophilicity of as-anodized film which would enhance the biocompatibility of Ti-6Al-4V as a result.

被覆した白金線対極を用いる溶液フロー型微小液滴セルによる線状多孔質型アルミニウム陽極酸化皮膜の形成

被覆した白金線対極を用いる溶液フロー型微小液滴セルによる線状多孔質型アルミニウム陽極酸化皮膜の形成

Electro-Dielectric Effect in the Formation of Anodic Aluminum Oxide Films

We investigated the variation of the capacity of metal–oxide–metal systems (MOM systems) of the aluminum – anodic aluminum oxide film (A–AAOF) type during their thermodepolarization. The temperature dependence of the capacity was nonmonotonic and correlated with the temperature dependence of the thermostimulated depolarization (TSD) current during the first thermostimulation. The effect relates to the corresponding change of the dielectric susceptibility of the oxide due to the destruction of the electret state of the A–AAOF system. Experimental estimates of the electric moment related to the Н–О bond in γ-АlООН oxyhydroxide molecules are presented.

Formation and Crystallization of Anodic Oxide Films on Sputter-Deposited Titanium in Potentiostatic and Potential-Sweep Modes

Sputter-deposited titanium substrates were anodically treated in sulfuric acid solution both in potentiostatic and potential-sweep modes. The morphology, crystallization, chemical compositions and electrochemical properties of anodic titanium oxide films were detected by AFM, SE, Raman spectra, XPS and EIS. The formed anodic films are smooth and homogeneously crystallized, and that the potentiostatically grown film is slightly thicker and less crystalline than the potentiodynamically formed film. Moreover, a comparison of the structure and properties of the anodic oxides films formed on the mechanical-chemical polished bulk titanium and the sputter-deposited titanium substrates is also presented. The titanium substrates can largely influence the properties of the formed anodic films. A more smooth and compact titanium oxide film could grow on the sputter-deposited titanium substrate, which is unfavorable to the ionic migration through the film and delays the film growth and crystallization.

Surface Modification Phenomenon of X-ray Irradiated Pure Mg

Magnesium (Mg) and it alloys are highly corrosive due to their low standard electrode potential (SEP). The conventional methods to improve corrosion resistance of Mg alloys are anodic oxide film formation and chemical conversion treatment. However, these methods are expensive and also make it hard to recycle the Mg products with these treatments. In this study, unique oxide layer formed by radical reaction between pure Mg surface and radical species generated under X-ray irradiation was investigated. Pure Mg surface was modified by X-ray irradiation under atmospheric condition. XPS analysis indicated MgO layer was formed at the surface of X-ray irradiated pure Mg specimen. Cross-sectional observation by TEM showed the MgO layer was dense compared to the natural oxidation coating films. The thickness of surface modification layer by X-ray irradiation was increased with the increase of irradiation time. After salt water immersion test, X-ray irradiated pure Mg for 24 hours showed about four times corrosion resistance of the as-polished original pure Mg. These results suggest that dense MgO layer formed by X-ray irradiation on pure Mg surface were functioning as a protective film.

Formation and Properties of Anodic Oxide Films of Titanium Formed under Discharge Conditions in an Electrolyte

Formation and Properties of Anodic Oxide Films of Titanium Formed under Discharge Conditions in an Electrolyte

Morphological Instability Leading to Formation of Porous Anodic Oxide Films

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The electrochemical transfer reactions and the structure of the iron|oxide layer|electrolyte interface

The thickness, barrier (protecting) and semiconducting properties of the potentiostatically formed oxide films on the pure iron electrode in an aqueous borate buffer solution were investigated by electrochemical quartz crystal nanobalance (EQCN), electrochemical impedance spectroscopy (EIS), and Mott–Schottky (MS) analysis. The thicknesses of the prepassive Fe(II)hydroxide layer (up to monolayer) nucleated on the bare iron surface and the passive Fe(II)/Fe(III) layer (up to 2nm), deposited on the top of the first one, were determined using in situ gravimetry. Electronic properties of iron prepassive and passive films as well as ionic and electronic transfer reactions at the film|solution interface were discussed on the basis of a band structure model of the surface oxide film and the potential distribution at the interface. The anodic oxide film formation and cathodic decomposition are coupled processes and their reversible inter-conversion is mediated by the availability of free charge carriers on the electrode|solution interface.The structure of the reversible double layer at the iron oxide|solution interface was discussed based on the concept of the specific adsorption of the imidazolium cation on the negatively charged electrode surface at pH>pHpzc.

Morphological Instability Leading to the Formation of Self-Ordered Porous Anodic Oxide Films

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Research on Forming Process of Anodic Oxide Film of AZ91D Magnesium Alloy

The matrix of AZ91D Magnesium alloy can be covered with a coat of protective film through anodic oxidation treatment, it’s able to make certain that the optimal surface combination properties are generated especially on corrosion resistance. This thesis is devoted to the research on forming process of anodic oxide film of AZ91D magnesium alloy; the experiment shows the formation of anodic oxide film at constant pressure is accompanied by precipitation of gases and fluctuation of current, XRD indicates that anodic oxide film is composed of MgO、γ-Al2O3 and a small amount of Si.

Morphological instability leading to formation of porous anodic oxide films

Electrochemical oxidation of metals, in solutions where the oxide is somewhat soluble, produces anodic oxides with highly regular arrangements of pores. Although porous aluminium and titanium oxides have found extensive use in functional nanostructures, pore initiation and self-ordering are not yet understood. Here we present an analysis that examines the roles of oxide dissolution and ionic conduction in the morphological stability of anodic films. We show that patterns of pores with a minimum spacing are possible only within a narrow range of the oxide formation efficiency (the fraction of oxidized metal atoms retained in the film), which should exist when the metal ion charge exceeds two. Experimentally measured efficiencies, over diverse anodizing conditions on both aluminium and titanium, lie within the different ranges predicted for each metal. On the basis of these results, the relationship between dissolution chemistry and the conditions for pore initiation can now be understood in quantitative terms.

Morphological Instability Leading to Formation of Porous Anodic Oxide Films

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Area Selective Formation of Porous Type Aluminum Anodic Oxide Film by a Solution Flow-Type Micro Droplet Cell

A novel solution flow-type micro droplet cell with co-axial dual capillary tubes (Sf-MDC) was applied to form porous type aluminum anodic oxide film locally. This technique makes it possible to form porous type anodic oxide film on aluminum locally. When the droplet cell remains stationary, the oxide film was growing both vertically and laterally. The growth rate in the lateral direction can be controlled by moving the droplet cell. By moving the droplet cell, a porous type anodic oxide film line was successfully formed. The thickness of the oxide film increases with decreasing scanning speed of the cell. The oxide film growth rate was greatly affected by specimen temperature.

Formation of nanoporous anodic films on pure aluminum in sulfuric acid

The effect of the duration of electrochemical anodic oxidation on the formation of nanoporous anodic oxide films on high-purity aluminum (99.99%) in a sulfuric acid solution is studied. The resulting oxide film is analyzed using an atomic force microscope. The method of photoelectric polarization (PEP) and X-ray analysis revealed that these films are sesquioxides of aluminum with variable compositions, nonstoichiometry due to a metal deficiency, and p-type conductivity. The mechanism of the formation of a regular nanoporous oxide structure that results from the nonstoichiometry relation and the intrinsic formation of defects in the oxide is proposed.

Formation and dielectric properties of anodic oxide films on Zr–Al alloys

Zr–Al alloys containing up to 26 at.% aluminum, prepared by magnetron sputtering, have been anodized in 0.1 mol dm−3 ammonium pentaborate electrolyte, and the structure and dielectric properties of the resultant anodic oxide films have been examined by grazing incidence X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, and AC impedance spectroscopy. The anodic oxide film formed on zirconium consists of monoclinic and tetragonal ZrO2 with the former being a major phase. Two-layered anodic oxide films, comprising an outer thin amorphous layer and an inner main layer of crystalline tetragonal ZrO2 phase, are formed on the Zr–Al alloys containing 5 to 16 at.% aluminum. Further increase in the aluminum content to 26 at.% results in the formation of amorphous oxide layer throughout the thickness. The anodic oxide films become thin with increasing aluminum content, while the relative permittivity of anodic oxide shows a maximum at the aluminum content of 11 at.%. Due to major contribution of permittivity enhancement, the maximum capacitance of the anodic oxide films is obtained on the Zr–11 at.% Al alloy, being 1.7 times than on zirconium at the formation voltage of 100 V.

ChemInform Abstract: A Photocurrent Spectroscopic Study of the Initial Stages of Anodic Oxide Film Formation on Niobium.

Abstract An extensive electrochemical and photoelectrochemical investigation has been carried out with very thin anodic oxide layers grown on niobium metal in sulphuric acid solutions. From the experiments the presence of an initial suboxide layer on the metal surface was inferred. Upon anodic polarization a strongly non-stoichiometric pentoxide film is formed, which is subsequently oxidized to the normal amorphous pentoxide phase (a-Nb 2 O 5 ). The use of photocurrent spectroscopy (PCS) allowed this oxidation process to be followed at various potentials and polarization times. Moreover, from the experimental results we obtain information both on the composition and the solid-state structure of the different phases grown on the metal surface. It is shown that the strong non-stoichiometry introduces a continuous defect band near to the conduction band edge of the initial film. Evidence for the existence of localized states inside the mobility gap of the films is also reported. The nature of the defects in anodic a-Nb 2 O 5 is briefly discussed.

Area Selective Formation of Porous Type Aluminum Anodic Oxide Film by Sf-MDC

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Formation of porous anodic titanium oxide films in hot phosphate/glycerol electrolyte

Abstract The present study reveals the formation of porous anodic films on titanium at an increased growth rate in hot phosphate/glycerol electrolyte by reducing the water content. A porous titanium oxide film of 12 μm thickness, with a relatively low content of phosphorus species, is developed after anodizing at 5 V for 3.6 ks in 0.6 mol dm −3 K 2 HPO 4 + 0.2 mol dm −3 K 3 PO 4 /glycerol electrolyte containing only 0.04% water at 433 K. The growth efficiency is reduced by increasing the formation voltage to 20 V, due to formation of crystalline oxide, which induces gas generation during anodizing. The film formed at 20 V consists of two layers, with an increased concentration of phosphorus species in the inner layer. The outer layer, comprising approximately 25% of the film thickness, is developed at low formation voltages, of less than 10 V, during the initial anodizing at a constant current density of 250 A m −2 . The pore diameter is not significantly dependent upon the formation voltage, being ∼10 nm.