Abstract Anodic Oxide Films Research Articles

In vitro Biocompatibility Evaluation of Anodic Alumina Substrates with Electrochemically Embedded Silver

Anodic aluminum oxide films modified by silver incorporation (Al-O-Ag) under specific electrodeposition conditions were produced and their biocompatibility was analyzed by in vitro assays using mammalian cell lines. The results obtained demonstrate that Al-O-Ag substrates are well tolerated by human dermal fibroblasts. The alumina pads doped with silver for short time-period (30 seconds) showed the highest biocompatibility among all modified metal substrates and in comparison with three dental alloys.

Role of anodic oxide films in the corrosion of aluminum and its alloys

Abstract Anodic oxide films on aluminum are classified into two groups: porous-type anodic oxide films (PAOF) and barrier-type anodic oxide films (BAOF). The present paper is a review of the corrosion of pure aluminum (Al) and Al alloys covered with PAOF and BAOF, focusing on the role of anodic oxide films in the process of corrosion. Several topics are discussed in detail, including (a) changes in the dissolution mode of PAOF in acidic media by pore sealing, (b) hydration and dissolution of BAOF in pure water and neutral solutions containing organic and inorganic electrolytes, (c) pitting corrosion during the cathodic polarization of Al covered with PAOF and BAOF, (d) corrosion of PAOF-covered Al/Bi/Sn alloys in alcohols at 142°C, and (e) synergistic effects of Cl− and Cu2+ ions in the corrosion of PAOF-covered Al alloys in aqueous solutions.

EIS characterization of sealed anodic oxide films on titanium alloy Ti-10V-2Fe-3Al

Anodic oxide films grown on titanium alloy Ti-10V-2Fe-3Al in the solution of sodium tartrate, then sealed in boiling deionised water and calcium acetate solution were observed by using field emission scanning electron microscopy (FE-SEM), and were chemically analysed by using energy dispersive spectroscopy (EDS). Corrosion behaviour was investigated in a 3.5% sodium chloride solution, using electrochemical impedance spectroscopy (EIS). The morphology of the anodic oxide films was dependent on the sealing processes. The surface sealed in calcium acetate solution presented a more homogeneous and smooth structure compared with that sealed in boiling deionised water. The corrosion resistance of the oxide films sealed in calcium acetate solution was better than that sealed in boiling deionised water.

Unique AAO films with adjustable hierarchical microstructures

Anodic aluminium oxide (AAO) films with novel nano-/submicron-/micron-porous hierarchical structures have been fabricated by using a simple anodization method.

The Structure and Frictional Properties of Aluminum Alloy Anodic Oxide Film

Anodic oxide films were prepared firstly on the surface of a 2024 aluminum alloy. Then the effect of different heat-treatment temperatures on the structure and properties of the films was studied. The results indicate that the construction units of Al2O3 oxide film were composed of tubules less than 100nm in external diameter, and the film became more compact and uniform as a result of the increased temperature after the heat treatments of 100, 150, 200, 250, 300, 350, and 400°C under the protection of a H2 atmosphere. The hardness of the films increased linearly with the increase of heat treatment temperature; whereas the wear loss tended to decrease first and then increase. After being treated at the temperature of 250°C, the hardness reaches 606HV, the wear loss is a minimum of 11mg. The structure of the film heat-treated at 250°C has a compact structure, higher hardness, and the best wear resistance.

Effect of electrolyte concentration on morphology, microstructure and electrochemical impedance of anodic oxide film on titanium alloy Ti-10V–2Fe–3Al

Anodic oxide films were fabricated on titanium alloy Ti-10V–2Fe–3Al in ammonium tartrate solutions at the concentrations: 1, 3, 5, 10 and 15 g L−1. The morphological characteristics and microstructures of the films of the alloy were studied by optical microscopy (OM) and Raman spectroscopy (Raman), respectively. The electrochemical impedances of the films in 0.5 mol L−1 H2SO4 solution were investigated by electrochemical impedance spectroscopy (EIS). It was showed that different electrolyte concentrations led to different change rates of anodizing forming voltage. The change rate significantly affected the morphology, microstructure and electrochemical impedance of anodic oxide film. When electrolyte concentration was 5 g L−1, anodic oxide film was the most uniform, exhibited by the least and smallest breakpoints on the film. In addition, the amount of crystal phase of the film was the largest at 5 g L−1, showed by the highest intensity of Raman peaks. Furthermore, the electrochemical impedance of the film of the alloy was the greatest at 5 g L−1, demonstrated by the highest values of polarization resistances and lowest values of capacitances. These phenomenon were associated with the minimum value of the change rate of anodizing forming voltage at 5 g L−1.

Ti Oxide Films Formed by an Anodizing Process for Use in Dental Implants

Anodic oxide films were formed on titanium using an electrolyte solution containing phosphoric acid for dental implants by an electrochemical method. The parameters of the oxidation process were current density and electrolyte concentration. The micro structural morphology, surface roughness, thickness of the oxide layer and the behavior of voltage-time curves were examined. The results show that the surface roughness, porosity size and the thickness of the oxide layer showed similar trends as the process parameters were changed. The surface morphology of the samples was observed for different current densities at a constant electrolyte concentration. The pore size, thickness and roughness of the anodic oxide films are directly proportional to the maximum voltage and the slope of the voltage to time transient (dV/dt) curves during the growth of the galvanostatic anode oxide film on plate type Ti.

Composition and Structure of Anodic Oxide Films on Titanium–Aluminum Alloys by Fast Electron Reflection Diffraction, Rutherford Backscattering, and Secondary Neutral Particle Mass Spectrometry

Anodic oxide films on some Ti–Al alloys are studied using fast-electron reflection diffraction, Rutherford backscattering, and secondary neutral-particle mass spectrometry. The films are amorphous, with a small amount of crystalline phases, and comprise a mixture of TiO2 and Al2O3. The Ti/Al ratio in an anodic film corresponds to that in the alloy matrix. Constants of anodic oxidation of the alloys are determined.

Ellipsometric Study of Anodic Oxide Films on Alloys of the Ti–Al System

Anodic oxide films (AOF) on neat titanium and on alloys of the Ti–Al system (Ti–10 at. % Al, Ti–24 at. % Al, Ti–50 at. % Al, Ti–75 at. % Al) formed in borate buffer solution are studied by ellipsometry. A model is proposed, which adequately describes the shape of the alloy surface with and without AOF. The model takes into account the roughness factor, allowing one to more correctly determine optical parameters of AOF and dependence of its thickness on anodic potential. It is found that the alloy surface roughness is effectively smoothed with increasing applied potential.

A study of native oxides of β–SiC using Auger electron spectroscopy

Thermal and anodic oxide films of beta silicon carbide are analyzed using Auger electron spectroscopy. Auger depth-composition profiles are obtained in order to determine the chemical composition of the oxide films. The position and shape of silicon spectral peaks are used to estimate the chemical bonding of the oxide constituents. It is found that the wet thermal oxide is almost stoichiometric but contains about 14% carbon. Dry oxide, on the other hand, has less than 3% carbon but is highly nonstoichiometric. The carbon content in the anodic oxide is 12%. Anodic oxide films, like dry-oxide films, are nonstoichiometric. A model of the SiC oxidation process is presented.

磁性複合アルミニウム陽極酸化皮膜とその応用

Anodic oxide films of aluminum, containing ferromagnetic particles electrodeposited in their pores (magnetic composite alumina films) have high perpendicular magnetic anisotropy, making these films suitable for use in hard disks and other magnetic recording media. This study was undertaken to obtain these films with magnetically harder characteristics. By controlling the anodizing conditions, pore widening process and electrodeposition of iron particles, it was possible to obtain films having a coersive force He of greater than 2000oe, a magnetic energy product (BH) max of greater than 0.2MG·Oe, and thickness of 20∼100μm. These films were formed on the sides of rotary drums and were given multipolar magnetization making them applicable for high-precision magnetic rotary encoders.

Ellipsometric investigation of quadratic electrooptic and electrostrictive effects with anodic niobium pentoxide films

Anodic oxide films on niobium were studied in situ during formation using a computer-controlled ellipsometer at a wavelength of 6328 A. They were found to be optically homogeneous, isotropic, and nonabsorbing with no field applied but to become anisotropic (optically uniaxial with optic axis normal to the film surface) with field applied. The ordinary and extraordinary indices decreased, and the thickness increased quadratically with applied field. Values are reported for the refractive index of niobium and of the oxide, and these are compared with previous reports. The quadratic electrooptic coefficients for the oxide are reported and are of the same order of magnitude as those for oxygen-octahedra ferroelectrics and somewhat greater than the values for tantalum pentoxide films.

A PROPOSED STRUCTURE FOR ANNEALED ANODIC OXIDE FILMS OF TANTALUM

Anodic oxide films (~1500 Å thick) formed on tantalum in saturated H3BO3, saturated Na2SO4, 86% H3PO4, 1% H2SO4, and 100% H2SO4 have been examined by a simple but sensitive glancing angle X-ray technique. They are amorphous as formed but can be crystallized on annealing at various temperatures between 500 and 1000 °C. The times and temperatures required for crystallization depend on the electrolyte used. The crystallization process is competitive with the dissolution of oxygen in the substrate metal. The observed powder diffraction patterns show considerable variation from sample to sample. Similar variations have been reported in the literature for different samples of Ta2O5. A structural model is proposed for β-Ta2O5 based on the isostructural relationship with U2O5, whose structure is related to that of α-UO3. This proposed structure consists of linear chains of Ta—O—Ta—O— parallel to the c axis with varying disorder in the ab plane. This disorder accounts for the observed variations in the patterns. The proposed structure is a defect one and the ordering of these defects may account for some of the reports of irreversible transformations observed on heating Ta2O5.