Anodized aluminium

Composites of aluminium alloy with a thin cladding on one or both surfaces of a more anodic aluminium alloy or pure aluminium, enable sheet, plate and tube to be produced with special combinations of strength and corrosion resistance appropriate to service conditions. Although originally applied to high strength aircraft alloys, this principle of cladding is now utilised in several important industrial applications. 

Furneaux, R. C. and M. C. Thornton. 1988. Porous "ceramic membranes produced from anodizing aluminium. Brit. Cer. Proc., Advanced Ceramics in Chemical Process Engineering Eds. B. C. H. Steele and D. P. Thompson, vol. 43, pp. 93-101. 

A TurboVap Workstation is used to dry beakers in an anodized aluminium heated block with a nitrogen purge at 104°C or 108°C. 

Oliveira GB, Eilho JLL, Chaves MEC, Azevedo WM, Carvalho LB (2008) Enzyme immobilization on anodic aluminium oxide/polyethyleneimine or polyaniline composites. React Fund Polym 68(l) 27-32... 

In addition to the dyeing and printing of natural and acrylic fibers, triarylmethane dyes are suitable for the coloration of other substrates such as paper, ceramics, leather, fur, anodized aluminium, waxes, polishes, soaps, plastics, drugs, and cosmetics. Several triarylmethane dyes are used as food colorants and aie manufactured under stringent processing controls. 

As previously stated, for zirconium-based adhesion promoters, suitable functional groups on the substrate and the overcoat would be oxygenated species. Typically suitable oxygenated functional groups can be found on corona discharge-treated plastics, anodized aluminium, etc. [4]. 

Lithographic printing plates. Zirconium fluorides, such as potassium zirconium hexafluoride, are used to surface-treat anodized aluminium lithographic printing plates to give improved corrosion resistance of the subsequently treated plate [7],... 

Mordant wool, leather, and anodized aluminium applied in conjunction with Cr salts azo and anthraquinone... 

Thick compact exterior grade laminates are self-supporting and suitable for applications such as infill panels or the decorative cladding of exterior walls. They are available with surfaces of anodized aluminium and coloured lacquer-coated foil as well as normal melamine. 

Apart from simple corrosive attack on a metal surface, Gabel reported a more specific situation leading to corrosion. This occurred when a dry-film-lubricated metal surface was in contact with an unlubricated anodized aluminium surface. Laboratory investigation at 95% relative humidity and 49°C (120°F) confirmed that in this situation the corrosion resistance of the anodized aluminium was reduced from 1100 hours to fewer than 200 hours. It was not clear whether dissimilar metals were involved, but the occurrence suggested that corrosion might be due to the development of an external potential in the presence of an electrolyte. 

Skeldon, P., Wang, H.W. and Thompson, G.E., Formation and Characterization of Self-Lubricating MoS, Precursor Films on Anodized Aluminium, Wear, 206, 187, (1997). 

Mesoporous alumina membranes ( anodic aluminium oxide , or AAO) are prepared by anodic oxidation of aluminium metal [1,2]. The cylindrical pores, perpendicular to the membrane surface, form hexagonal arrays of straight non-intersecting channels with pore densities up to lO Vcm. Their diameters are controllable within the range 5 - 100 nm as a linear function of anodisation voltage. These membranes are used as molecular sieves, and have also found application as templates for metallic nanowires [3,4,5,6], metal elusters and colloids [7,8], and carbon nanotubes [9,10]. 

Abbreviations AAO anodic aluminium oxides ANSA 5-aminonaphthalene-2-sulfonic acid APS—Ammonium persulphate ASA — Anthracene Sulfonic acids CB — conduction band CPs — conducting polymers CSA... 

SEM was used for morphological studies of anodic aluminium oxide films, formed at various formation current densities up to a formation voltage of 60 V. The total thickness of the films was determined by cross-section SEM micrographs as shown in Figure 23.1, but it should be emphasised that one can not clearly identify barrier and porous layers of the oxide film by using this technique. 

Figure 23.1 High-resolution cross-sectional SEM micrograph of an anodic aluminium oxide film of 66 nm formed at 0.3 mA/cm and a formation voltage of 60 V (Al thickness remaining 633 nm).

To interpret the impedance data, a model of the anodic aluminium oxide film must be established. The anodic aluminium oxide film is a sandwich film consisting of two layers, a barrier layer and a porous layer (Figure 23.4A [2]). 

Figure 23.3 Bode plots of natural and anodic aluminium oxide films. The aluminium oxide film was formed at 2.5 mA/cm and a formation voltage of 60 V, experimental (points) and fitting (lines).

Figure 23.4 Two-layer model of the anodic aluminium oxide film (A) and associated equivalent circuit (B)...

The average capacitance and specific resistivity of the barrier aluminium oxide films are determined to be 430. .. 470nF/cm and 1.3. .. 2.4 10 " Qcm, respectively. By using the anodisation factor of 1.2 nm/V for the films formed at low formation voltage, dielectric constants of 5.8. .. 6.4 are calculated from the measured capacitance values. The comparatively low dielectric constant is in agreement with the formation of an amorphous anodic aluminium oxide film as discussed above rather than a crystalline structure for which a higher dielec-... 

Expts. Transition metal anode Aluminium anodic loss [mg] Anodic circulated charge in C Al Trans, metal Polymerization time [h] Converted ethylene [%1 Polymer yield [%I... 

Aluminium is a hard, white metal. Thermod5mami-cally, it should react with air and water but it is resistant owing to the formation of an oxide layer, 10 to 10 " mm thick. A thicker layer of AI2O3 can be obtained by making A1 the anode in the electrolysis of H2SO4 the result is anodized aluminium which will take up dyes and pigments... 

Fig. 14. Growth (in direction G) followed by dissolution (direction D) of anodic aluminium oxide film. The "loop is an ellipsometric signature of a spontaneous substrate roughening-self-smoothing cycle.

Anodic aluminium oxide Successfully depleted surface [31]... 

The new nanostructure porous material based on anodic A12O3 and WO3 has been fabricated. The pore sizes can be tuned both by anodic forming regimes and W atom content in initial Al-W alloy films. The composite nanostructures based on anodic aluminium and tungsten oxides opens new opportunities for nanotechnology in electronics and photonics. 

In a template synthesis, CP is polymerized within the pores or channels of a nanoporous template to obtain the controlled structure and morphology upon removal of the template. Templates can be either a masking of a confined area that CP can grow in or a structured surface that CP is deposited upon. Masking type templates, namely nanoporous anodic aluminium oxide (AAO also commonly known as AI2O3, alumina, or anodise ) [113-118], hydrogels [119,120] and latex particles [121-130], have been used to prepare nanoscale fibrils, particles, and tubules of CPs. 

Using porous anodic aluminium oxide films, Routkevitchand associates electrodeposited very thin CdS nanowires [49]. The alumina membranes were typically 1 - 3-pm thick with pore sizes ranging from 9 to 35 nm. The CdS was electrodeposited, using ac electrodeposition, from a DMSO solution containing CdCl2 and elemental S. The porous alumina, as anodized, was separated from the A1 by a dense oxide... 

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