Aluminium oxide

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An analysis of the elastic properties of a porous aluminium oxide film by means of indentation techniques

An analysis of the elastic properties of a porous aluminium oxide film by means of indentation techniques

a b s t r a c t The elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performed at a nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11 GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73 GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represent the elastic modulus variation.
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Impact of the type of anodic film formed and deposition time on the characteristics of porous anodic aluminium oxide films containing Ni metal

Impact of the type of anodic film formed and deposition time on the characteristics of porous anodic aluminium oxide films containing Ni metal

Keywords: aluminium, porous anodic film, metal AC electro-deposition Introduction The pioneering works on the electro-deposition of metals in porous anodic aluminium oxide films were reported in Italy in 1936 (Wernick et al., 1987). But its widespread use started in Japan after World War 2 for colouring purposes (Wernick et al., 1987). Then, new applications emerged for the first time in different fields such as magnetism (Kawai & Ueda, 1975), thermo-optics and dyeing (Anderson et al., 1980), catalysis (McBren & Moskovits, 1987), elec- tronics (Preston & Moskovits, 1993), corrosion protec- tion (Fukuda & Fukushima, 1982), and for antibacte- rial activity (Chi et al., 2002). Recently, the electro- deposition of metals in anodic films has acquired re- newed interest due to the possibility of preparing nan- odevices using porous templates based on anodic alu- minium oxide films. The two main applications are in the preparation of metal nanorods from Au (For- rer et al., 2000; Wang et al., 2002), Ni (Nielsch et al., 2000; Yin et al., 2001; Jagminas et al., 2003), Bi (Yin et al., 2001), Cu, Co, Sn (Jagminas et al., 2003), Ag
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Aluminium tri-iso-propoxide: Shelf life, transport properties, and decomposition kinetics for the low temperature processing
of aluminium oxide-based coatings

Aluminium tri-iso-propoxide: Shelf life, transport properties, and decomposition kinetics for the low temperature processing of aluminium oxide-based coatings

3. Conclusions Despite its instability and trend to ageing, ATI can be used for depositing aluminium oxide provided that it is stored in a glove box, and renewed in the bubbler after a few hours of use. Interestingly enough, water vapour assisted MOCVD of alu- minium oxide from ATI yields amorphous pure alumina at temperature as low as 300–350 °C and above. This temperature is one of the lowest reported in the literature for the processing of pure alumina films and is about 80 °C lower than through thermal decomposition of ATI. Despite the low temperature, it is the ATI concentration in the input gas that controls film growth rate. Potential applications for the use of amorphous alumina as oxidation barrier applied on thermally sensitive materials are currently investigated.
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Electrical conductivity of carbon nanotubes grown inside a mesoporous anodic aluminium oxide membrane

Electrical conductivity of carbon nanotubes grown inside a mesoporous anodic aluminium oxide membrane

Well-aligned, open-ended carbon nanotubes (CNTs), free of catalyst and other carbon prod- ucts, were synthesized inside the pores of an anodic aluminium oxide (AO) template with- out using any metallic catalyst. The CNTs and the CNT/AO composites were characterized by scanning and transmission electron microscopy, thermogravimetric analysis, Raman spectroscopy and X-ray diffraction. Particular care was devoted to the reactor design, syn- thesis conditions, the catalytic role of the templating alumina surface and the preservation of the alumina structure. The transport properties (sorption, diffusion and permeability) to water vapor were evaluated for both the alumina template and the CNT/AO composite membrane. The measured effective electrical volume conductivity of the CNT/AO compos- ite was found ranging from a few up to 10 kS/m, in line with the recent literature. The esti- mated averaged values of the CNTs-wall conductivity was around 50 kS/m.
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Chemical analysis of a single basic cell of porous anodic
aluminium oxide templates

Chemical analysis of a single basic cell of porous anodic aluminium oxide templates

A B S T R A C T We prepared anodic aluminium oxide (AAO) templates with “honeycomb” geometry, i.e. hexagonally ordered circular pores. The structures were extensively studied and characterized by EPMA coupled with FEG-SEM and FEG-TEM coupled with EDX at meso and nanoscopic scales, in other words, at the scale of a single basic cell making up the highly ordered porous anodic film. The analyses allowed the identification of the chemical compounds present and the evaluation of their levels in the different parts of each cell. Of note was the absence of phosphates inside the “skeleton” and their high content in the “internal part”. Various models of porous anodic film growth are discussed on the basis of the results, contributing to a better understanding of AAO template preparation and self- nanostructuring phenomena.
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Effect of electric field polarization and temperature on the effective permittivity and conductivity of porous anodic aluminium oxide membranes

Effect of electric field polarization and temperature on the effective permittivity and conductivity of porous anodic aluminium oxide membranes

Complex permittivity measurement a b s t r a c t Porous insulators offer new opportunities for the controlled guest–host synthesis of nanowires for future integrated circuits characterized by low propagation delay, crosstalk and power consumption. We pro- pose a method to estimate the effect of the electric field polarization and temperature on the electrical properties of different types of synthesized porous anodic aluminium oxide membranes. It results that the effective permittivity along the pore axis is generally 20% higher than the one in the orthogonal direc- tion. The type of solution and the voltage level applied during anodization are the main parameters affecting the AAO templates characteristics, i.e. their porosity and chemical content. The values of permit- tivity of the final material, are typically in the range 2.6–3.2 for large pore diameter membranes including phosphorus element and having a low water content, and in the range 3.5–4 for the ones with smaller pores, and showing sulphur element incorporation. Moreover, the dc conductivity of the different mem- branes appears to be correlated to the pore density.
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Electrical conductivity of carbon nanotubes grown inside a mesoporous anodic aluminium oxide membrane

Electrical conductivity of carbon nanotubes grown inside a mesoporous anodic aluminium oxide membrane

Well-aligned, open-ended carbon nanotubes (CNTs), free of catalyst and other carbon prod- ucts, were synthesized inside the pores of an anodic aluminium oxide (AO) template with- out using any metallic catalyst. The CNTs and the CNT/AO composites were characterized by scanning and transmission electron microscopy, thermogravimetric analysis, Raman spectroscopy and X-ray diffraction. Particular care was devoted to the reactor design, syn- thesis conditions, the catalytic role of the templating alumina surface and the preservation of the alumina structure. The transport properties (sorption, diffusion and permeability) to water vapor were evaluated for both the alumina template and the CNT/AO composite membrane. The measured effective electrical volume conductivity of the CNT/AO compos- ite was found ranging from a few up to 10 kS/m, in line with the recent literature. The esti- mated averaged values of the CNTs-wall conductivity was around 50 kS/m.
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Human health risk assessment for aluminium, aluminium oxide, and aluminium hydroxide.

Human health risk assessment for aluminium, aluminium oxide, and aluminium hydroxide.

Although it has been suggested that AlF 3 may play a role in aluminium toxicity, the fraction of intracellular aluminium as AlF 3 is < 1%, making this unlikely. Intracellular aluminium is more likely associated with phosphate, ATP and phosphorylated proteins. Concurrent gavage administration of aluminium, as 200 mg Al/kg, and folic acid in some rats, as 20 mg/kg, 5 days weekly for 8 weeks, resulted in significantly less aluminium in femur, brain and kidney, but not serum, in the rats that received the folic acid (Bayder et al., 2005). It is not clear if folic acid reduced aluminium absorption or enhanced its elimination. Although the stability constant of the aluminium-folate complex is quite high, (log K = 15.15 (Nayan & Dey, 1970)), the low molar ratio of folate to aluminium of 0.006:1 suggests the results are not due to formation of an aluminium folate complex. Dietary supplementation with vitamin E (5, 15 or 29 mg/g chow) with i.p. injections of aluminium in the rat reduced plasma and brain aluminium compared to the absence of vitamin E supplements, although the effect was most pronounced with the lowest vitamin E concentration (Abubakar et al., 2004). The authors speculated that the vitamin E effect could be due to preservation of cell membrane ion transport and membrane fluidity. However, an effect on aluminium excretion cannot be ruled out.
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Electrical behaviour, characteristics and properties of anodic
aluminium oxide films coloured by nickel electrodeposition

Electrical behaviour, characteristics and properties of anodic aluminium oxide films coloured by nickel electrodeposition

Introduction Although the principle of metal electrodeposition in porous anodic films on aluminium alloys was reported in 1936 in Italy [ 1 , 2 ] and 1940 in Norway [ 1 , 2 ], the industrial advent of the process really occurred in Japan in the 1960s with Asada’s works [ 1 ] on the preparation of coloured coatings. In this case, the electrodeposition process is known as electrocolouring: the two main fields of application are coloured coatings for architecture and selective surfaces for solar energy storage and conversion.

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The native oxide film on a model aluminium-copper alloy studied by XPS and ToF-SIMS

The native oxide film on a model aluminium-copper alloy studied by XPS and ToF-SIMS

3.3.2 Oxide layer thickness and model of the native oxide The ToF-SIMS and XPS analyses showed that the Al-Cu alloy surface is covered by an aluminium oxide/hydroxide layer. Some copper oxide is also present at the surface of the IMPs which are protruding into the oxide. The oxide present above the IMPs is therefore thinner than on the matrix. The first step to evaluate the oxide thickness is to determine the coverage (γ) of IMPs on the surface. The data obtained by ToF-SIMS and SEM allow us to calculate a particle coverage from images by measuring the areas where metallic copper signal is intense. The coverage γ is evaluated at 3.2% of the surface analysed by ToF-SIMS 2D images and 3.4% by SEM images. These results are very close, and in good agreement with the literature which indicates that intermetallic particles typically represent between 2 and 4% of aluminium-copper alloys[2,6,53].
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Direct electrodeposition of aluminium nano-rods

Direct electrodeposition of aluminium nano-rods

3.2.2. Free standing aluminium nano-rods We show that aluminium was successfully electrodeposited as nano-rods within ordered alumina templates under pulsed-poten- tial conditions. Applying during 1 h, potential pulses of 0.4 V for 50 ms and 0.1 V for 200 ms, and afterwards dissolving the tem- plate led to an array of free standing aluminium columns, as shown in Fig. 5 . The height of the aluminium columns is depending on the charge passed during the electrodeposition step, provided that the alumina membrane was well-impregnated with the ionic liquid prior to the electrodeposition. The morphology of the obtained pil- lars is entirely dependent on the alumina template used. The alu- minium once deposited is completely filling the aluminium oxide pores. However, the template used has not a perfect ordering and displays defects. So once the template is removed, all the defects observed in the template are also visible among the aluminium pil- lars. This was particularly obvious when commercial membranes were used, as is shown in Fig. 5 .
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Imperfection-sensitive ductility of aluminium thin films

Imperfection-sensitive ductility of aluminium thin films

The tests were performed using a novel internal stress- driven lab-on-chip mechanical testing technique de- scribed in detail elsewhere [15] . The fabrication process in- volves the deposition of three layers on top of a silicon wafer. The first layer is a 1 lm thick silicon dioxide film deposited by plasma-enhanced chemical vapour deposi- tion. This film acts as a sacrificial layer. The second layer is a 250 nm thick silicon nitride film deposited at 800 °C by low-pressure chemical vapour deposition, which provides approximately 1 GPa of internal stress. The high level of stress essentially comes from the thermal expansion mis- match between the silicon wafer and the silicon nitride. The third layer is made of a 200 or 375 nm thick film of pure Al deposited by e-beam evaporation; the grain size was measured on cross-sections by transmission electron microscopy (TEM) and was equal to 150 and 200 nm, respectively. The silicon nitride and aluminium layers are patterned by photolithography (see Fig. 1 a and Ref. [15] ). Dissolution of the underlying sacrificial layer is per- formed with 73% concentrated fluorohydric acid (HF), in order to release the two other layers from the substrate. The high tensile internal stress present in the second film, called the actuator, can now relax and, owing to its con-
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Comportement électrochimique d’alliages modèles binaires aluminium-cuivre

Comportement électrochimique d’alliages modèles binaires aluminium-cuivre

Les résultats obtenus dans le cadre de cette thèse ont montré que, lorsque l’on suivait la variation du potentiel au cours du temps, pendant le processus d’anodisation, deux types de com[r]

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Galvanic corrosion of aluminium–copper model alloys

Galvanic corrosion of aluminium–copper model alloys

Fig. 11. Variation of galvanic coupling current with time for couples of Al–Cu alloys with high copper content. ode. The pits cannot propagate in depth more than 400 nm since they are stopped when they reach the substrate due to passiva- tion of pure aluminium in sulphate solutions. They cannot also propagate laterally because of the columnar structure of grains ( Fig. 1 ). In these conditions, the anodic current generated by pit- ting is very low and has negligible influence on the net measured current.

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Alternative black coatings prepared on aluminium alloy 1050

Alternative black coatings prepared on aluminium alloy 1050

Introduction A large number of black inorganic colouring processes have been or are now being developed, depending on the part design and the material used (e.g. metal alloy or carbon fibre reinforced polymer). For metals, black paints [ 1 , 2 ], electroless coatings [ 3–5 ], cathodic deposits [ 6 ], coloured anodic films [ 7 ] or micro-arc coatings [ 8–11 ] have thus been tested on copper [ 12 ], stainless steel [ 13 ], magnesium alloys [ 14 , 15 ], titanium alloys [ 16 ] and aluminium alloys (AAs). In particular, aluminium alloys are widely used due to their low density and high strength/weight ratio [ 17 ]. Black anodic films are usually prepared on alu- minium alloys [ 18 ] by anodising the aluminium surface, followed by inorganic colouring based on the precipitation of CoS pigments. Goueffon et al. [ 19–23 ] extensively studied this black inorganic col- ouring process and highlighted in particular the punc- tual location of the black pigments, i.e. mainly at the top of the pores of the anodic films. This punctual location has a critical influence during thermal aging as for example when simulating a space environment, and explains the crazing and flaking phenomena, i.e. respectively crack formation and particle removal from the black coating.
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Développement d'assemblages de dispositif de retenue pour les ponts à platelage en aluminium

Développement d'assemblages de dispositif de retenue pour les ponts à platelage en aluminium

Résumé des analyses dynamiques L’évaluation complète du comportement du véhicule entrant en collision avec la glissière MTQ 210a a été réalisée. Pour ce faire, deux étapes importantes ont été nécessaires. Un modèle de collision numérique de référence a tout d’abord été construit, reproduisant les conditions de l’essai de collision à grandeur réelle sur la glissière ancrée sur un chasse-roue de béton selon les détails originaux. Les données de ces deux essais ont alors été comparées à l’aide des procédures V&V, où les résultats ont permis de faire la validation du modèle de référence et d’ainsi s’assurer d’un niveau de confiance suffisant dans la méthode de construction des modèles éléments finis. Des vérifications ont ensuite été effectuées sur un deuxième modèle numérique, où le dispositif de retenue était fixé sur le platelage en aluminium à l’aide de l’assemblage développé de façon statique. Les procédures V&V ont une fois de plus été appliquées afin d’évaluer quantitativement l’interaction entre la glissière et le véhicule. La comparaison avec les historiques des accélérations et des vitesses angulaires du modèle de référence a démontré que les comportements étaient similaires. Une analyse des critères de la table de classement de l’importance des phénomènes a également démontré que la collision demeure sécuritaire lorsque le dispositif de retenue est assemblé sur un platelage en aluminium. Pour l’assemblage du California type 115 barrier, une analyse qualitative de la trajectoire du véhicule a permis de juger le comportement du véhicule comme étant sécuritaire.
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Galvanic corrosion of aluminium-copper model alloys

Galvanic corrosion of aluminium-copper model alloys

[9,10] . For such alloys, it is difficult to analyse the effects of the different galvanic couples. Thus, many authors have used micrometer-scale electrochemical techniques, but these tech- niques are often expensive and difficult to use [7,8,11,12] . Moreover, because of the significant variation in the chemical composition of coarse copper-rich intermetallics, a statistical analysis is required; this is difficult to perform with microm- eter scale approaches. A further possibility is to study the galvanic coupling between different model aluminium–copper alloys which allows simplification of the system [13,14] . Hence, this paper is devoted to further understanding of the influence of copper content on the galvanic coupling current measured when two binary Al–Cu alloys, containing 0.2–100 at.% Cu, are connected.
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Caractérisations et performances des assemblages collés époxyde-amine/aluminium

Caractérisations et performances des assemblages collés époxyde-amine/aluminium

Algorithm 6: [pr ], nbRelax ← Psade [ε∞ ], [τ ], [∆ε], [σDC ], minRelax, maxRelax, [e ε′ ], [e ε′′ ], tol, η, ξ Input: [ε∞ ]: interval for the high frequency permittivity, [τ ]: interval[r]

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Étude vibratoire et dynamique d'un châssis d'autocar en aluminium

Étude vibratoire et dynamique d'un châssis d'autocar en aluminium

Les analyses des contraintes et des réponses dynamiques et vibratoires des châssis sont très importantes. Elles apportent une meilleure évaluation de la résistance aux différents types d[r]

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Optimization of alumina slurry for oxide-oxide ceramic composites manufactured by injection molding

Optimization of alumina slurry for oxide-oxide ceramic composites manufactured by injection molding

of particles with PVA which exhibits a Newtonian behavior combined to a low viscosity represents the best potential with respect to the processability of the oxide/oxide ceramic. At low shear rate, the interparticles forces and the Brow- nian motion dominate whereas the hydrodynamic forces predominate and overcome the interparticles interactions at higher shear rates leading to a decrease of the viscosity. For more concentrated suspensions, the separation distance between particles is narrowed and the probability to aggre- gate increases due to apparition of the Van der Waals attrac- tive forces [8]. This explains the shear-thinning behavior observed for the highly charged suspensions (Figure 6). This rheological behavior was observed for similar systems using oxide nanoparticles in aqueous media, the shear thinning being enhanced by particle loading [12].
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