Thickness Of Anodic Oxide Research Articles

Hard anodizing of AA2099-T8 aluminum‑lithium‑copper alloy: Influence of electric cycle, electrolytic bath composition and temperature

AA2099-T8 samples have been hard anodized in a traditional sulphuric bath with the aim of studying the influence of i) electrolyte temperature, ii) Al3+ concentration and iii) different electric cycles in direct current, multi-step direct current and pulsed current (both completely anodic cycles and with cathodic “off” pulses). Anodic oxide thickness, volumetric expansion ratio (Vox/VAl), mean hardness (HV0.05), faradic efficiency and defective state have been analyzed. As temperature decreases, the oxide hardness increases but defectiveness steeply worsens; similarly a middle compromise of Al3+ concentration ensures the best performances. Regimes of high current, from one side, and of low current and current transient, from the other side, strongly affect oxide defective state introducing different types of flaws; an appropriate balance is crucial for a performing non-defected oxide. High current induces the occurrence of parasitic reactions which produce rough and defected Al/ox interface. Low current and current transient induce diffused cracking and detachments of coating fragments which decrease corrosion resistance as shown by potentiodynamic polarization tests. Li-based intermetallics play a crucial role in the last mentioned flaw-creation phenomena since they produce inhomogeneities in electric field distribution and contribute to create unstable oxide structures.

Pulsed current hard anodizing of heat treated aluminum alloys: Frequency and current amplitude influence

Abstract Pulsed current hard anodizing procedures have been applied to the widely used heat treated aluminum alloys AA2024-T3, AA6082-T6 and AA7075-T6. The influence of frequency and of current amplitude on anodic oxide thickness, hardness, defectiveness, volumetric expansion ratio and on process faradic efficiency has been studied. Higher frequencies generate a decrease in coating electric resistance and in general they are less effective in order to overcome typical critical issues arising in alloys difficult to be anodized. In AA2024-T3 and AA6082-T6 higher frequencies led to slight increase in thickness, decrease in compactness and faradic efficiency while hardness remained almost constant or a bit higher. With higher frequencies in AA2024-T3 defective state significantly got worse, in AA6082-T6 it improved. In AA7075-T6 an almost frequency independent behavior occurred. The highest wave amplitude with a slightly cathodic “off” current (reverse pulse) allowed to obtain greater thickness, hardness and compactness while other current amplitudes did not show significant influence on properties analyzed; a very low, but still anodic, “off” current however induced slight hardness decreases.

Preparation and Characterization of Microporous Layers on Titanium by Anodization in Sulfuric Acid with and without Hydrogen Charging

The formation of microporous oxide layers on titanium (Ti) by anodization in sulfuric acid (H2SO4) solution and the influence of prior hydrogen charging on their properties are examined using electrochemical techniques, scanning electron microscopy, grazing incident X-ray diffraction, and X-ray photoelectron spectroscopy. When Ti is anodized in 1 M aqueous H2SO4 solution at a high direct current (DC) potential (>150 V) for 1 min, a porous surface layer develops, and the process takes place with spark-discharge. Under these conditions, oxygen evolution at the Ti electrode proceeds vigorously and concurrently with the formation of anodic oxide. The oxygen gas layer adjacent to the Ti surface acts as an insulator and triggers spark-discharge; the latter stimulates the development of pores. In the absence of spark-discharge, the oxide layer has extended surface roughness but low porosity. A porous oxide layer can be prepared by applying a lower DC voltage (130 V) and without spark-discharge, but Ti requires prior hydrogen charging by cathodic polarization in 1 M aqueous H2SO4 solution. Mott-Schottky measurements indicate that the oxide layers are n-type semiconductors and that the charge carrier density in the anodic oxide layer on the hydrogen-charged Ti is lower than in the case of untreated Ti. The hydrogen charging also affects the flat band potential of the anodic oxide layers on Ti by increasing its value. The reduced charge carrier density brought about by hydrogen charging decreases the oxide layer conductivity and creates favorable conditions for its electrical breakdown that stimulates the development of pores. The porous layer on the hydrogen-charged Ti consists of anatase and rutile phases of TiO2; it has the same chemical composition as the porous layer obtained on untreated Ti. X-ray photoelectron spectroscopy measurements show that prior hydrogen charging does not affect the thickness of anodic oxides on Ti. The porous oxide layer on Ti enables the growth of hydroxyapatite, thus revealing good bioactivity in simulated body fluids.

Low Voltage Specific Charge ( CV / g ) Loss in Tantalum Capacitors

The systematic decrease in charge per unit weight in electrolytic tantalum capacitors as a function of decreasing anodization voltage is explored from both experimental and theoretical viewpoints for a range of tantalum particle sizes. Analysis by transmission electron microscopy shows that a native thermal oxide about 3.3 nm in thickness is present on the tantalum surface before anodization and that the thickness is independent of tantalum particle size. Studies in which the initial oxide thickness is altered via a preanodization heat-treatment show that the anodic oxide thickness becomes independent of the initial thermal oxide thickness once its thickness is exceeded. A theoretical model based on a cylindrical geometry explains the loss in the with decreasing anodization voltage and attributes the behavior to the 3.3 nm oxide thickness corresponding to zero anodization voltage.

Effect of an Interfacial Oxide Layer on the Electroluminescence Efficiency of Metal–Quantum-Confined Semiconductor Heterostructures

The effect of different surface treatments of GaAs/In(Ga)As/GaAs quantum-confined heterostructures on the electroluminescence efficiency of Schottky diodes based on these structures is investigated. It is ascertained that the largest increase in electroluminescence intensity is observed when the surface is treated in CCl4 at 580°C with subsequent anodic oxidation. It is shown that the interfacial tunnel-thin anodic oxide plays an important role in the injection of minority carriers from the metal into gallium arsenide. The electroluminescence efficiency depends strongly on the anodic-oxide thickness.

Electronic properties of surfaces, subsurface layers and interfaces for semiconductor and semimetal solid solutions

The electronic and physical-chemical properties of restorded (dDX≤0.5−1.0 nm) surfaces at the depth of the space-charge region and of semiconductor(semimetal)-native anodic oxide (dDX=1.0−100 nm) interfaces have been investigated by the combined field effect in electrolytes (CFEE) method at T = 273−305 K and in metal-oxide-semiconductor (MOS) systems at T = 77−305 K for monocrystalline solid solutions CdxHg1−xTe (0≤x≤0.4) and MnxHg1−xTe (0≤x≤0.24). The interpretation of experimental capacitance-potential and current-potential characteristics has been effectuated allowing for the degeneracy of the electron-hole gas and conduction band non-parabolicity (considered in the Kane approximation). The electronic properties of the surface and subsurface regions have been determined: the forbidden zone (Eg), the thermodynamic equilibrium (ni) and non-equilibrium (nix) carrier concentrations for intrinsic material or the doping level (NA,D) for extrinsic material, the density-of- states effective masses (mcx, mhx), the equilibrium semiconductor(semimetal) surface potential (Vs0) and total electric charge captured at the interface defects (Qtot0), the fast surface states (FSS) density (NSS). The FSS density and the total electric charge at the interface (Qtotox) increase drastically (0.5–2 orders) as a function of the anodic oxide thickness at dOX < 8−12 nm.

A Simple Impedance Spectra Method to Measure the Thickness of Nonporous Anodic Oxides on Aluminum

A simple ac impedance method is described for measuring the thickness of anodic oxide coatings on aluminum. The measurements are made using a Schlumberger Sl 1260 instrument and only two electrodes. The counterelectrode should be the same alloy as the anodized working‐electrode in order to avoid galvanic corrosion. Results are shown for aluminum anodized in borate solution with differing thicknesses of oxide.

Cathodically and Anodically Biased Electroluminescence Decays at Aluminum‐Manganese Alloys

The electroluminescence (EL) decay of Al‐Mn alloys is investigated in sulfuric acid solution. The afterglow spectrum and brightness decay are obtained from cathodically and anodically biased experiments. The influence of the anodic oxide thickness, amplitude, and frequency of the square voltage, and temperature are studied. The brightness decay from both types of experiments fits a first‐order law, although the light intensity from the cathodically biased runs is about ten times greater than that resulting from the anodically biased runs. The explanation of these results is given in terms of the following physical mechanism. The activator is excited by an injected charge trapped in a metastable state. The slow afterglow decay observed in the EL spectra results from a recombination of charge carriers. The latter process is practically independent of the direction of the applied electric field but the corresponding intensity depends on the charge carrier concentration available for the recombination process. Hence, the intensity of the cathodically biased EL decay as it involves electron injection and no faradaic process is much greater than the anodically biased EL decay which involves hole injection and a faradaic reaction. The latter acts as a quenching reaction for those charge carriers.

The Influence of Ti-6AI-4V Chromic Acid Anodization Conditions Upon Anodic Oxide Thickness and Topography

Abstract Chromic acid (CA) anodization of Ti-6A1-4V (6% Al, 4% V by weight) produced an anodic oxide on the alloy surface. The influence of specific CA anodization conditions upon anodic oxide thickness was determined. Each CA anodization condition tested was defined by setting five variables: (1) solution composition; (2) anodization time; (3) solution temperature; (4) initial current density; and, (5) anodization potential. The results confirmed observations by previous workers about oxide thickness and structure. Data indicated an inverse relationship between film thickness and temperature, and that film growth rate decreases with time.

Anodic Oxidation and Electrical Carrier Concentration Profiles of Ion‐Implanted InP

A technique is described that combines controlled anodic oxidation with differential Hall data to obtain electrical carrier concentration profiles of ion‐implanted indium phosphide. Reproducible oxide layers are grown using a citric acid, ethylene glycol electrolyte bath and a controlled voltage rise technique. A variation in material consumption with anodic oxide thickness and with anodizing technique is observed. For the purposes of demonstration, silicon and sulfur species implanted at 1 MeV to fluences of are examined. These profiles are measured on <100> implanted semi‐insulating. The technique could be adapted to measure other alloys in the system.

ChemInform Abstract: ANODIC OXIDE THICKNESS ON ALUMINUM

Chemischer InformationsdienstVolume 8, Issue 14 Preparative Inorganic Chemistry ChemInform Abstract: ANODIC OXIDE THICKNESS ON ALUMINUM J. E. NORMAN, J. E. NORMANSearch for more papers by this author J. E. NORMAN, J. E. NORMANSearch for more papers by this author First published: April 5, 1977 https://doi.org/10.1002/chin.197714034AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume8, Issue14April 5, 1977 RelatedInformation

Anodic oxide thickness on aluminum

A procedure for ellipsometric measurement of oxide film thickness on aluminum foil is reported. A method of cleaning the foil surface to give a reproducible natural film of thickness comparable with that on evaporated film and bulk aluminum is described. Using these techniques, an empirical relation between oxide film thickness and anodization voltage is derived.

縦形電解槽内の電流分布および陽極の焼ケ現象

Current distribution was examined by applying direct current in the vertical type electrolytic cell containing sulfuric acid with an anode of a long aluminum sheet. It was carried out by the measurement of thickness of anodic oxide coating and color difference in dyed specimens and by the observation of burnings of anode.Current distribution was more uniform when the concentration of acid was higher, the concentration of aluminum was lower, anodizing temperature was higher, anode current density was lower, and circulation velocity of electrolyte was higher. When the current density was extremely bad in uniformity, current passed through a certain point, at which burnings were produced. Shape and size of burnings would depend upon convection of heat generated on the anode. The two step raise of the current at the early stage of anodizing was effective for preventing the production of burnings. Moreover, studies were also made on the effects of arrangements of the electrodes.

Determination of Barrier Layer Thickness of Anodic Oxide Coatings

A novel method is described for measuring the thickness of a barrier type anodic oxide coating or the barrier layer portion of a porous type anodic oxide coating. This method is used to follow the evolution of the barrier layer during the early stages of the formation of a porous type coating on aluminum and to establish certain dimensions of the fundamental oxide cells which comprise this type of coating.