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  • 1
    Electronic Resource
    Electronic Resource
    Bingley : Emerald
    Aircraft engineering and aerospace technology 75 (2003), S. 372-379 
    ISSN: 0002-2667
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper reviews the role of alloying elements in aluminium and alloy fabrication on performance during surface treatment and surface finishing. Such elements may be present in solid solution as fine segregates, strengthening phase and equilibrium phases. For surface treatment and finishes, which generally proceed in the presence of alumina film, knowledge of the processes proceeding at the alloy/film and film/electrolyte interfaces, and those within anodic alumina films, gives rise to the possibility of controlling features of nanoscale dimensions, for improved performance, arises. Its influence on nanotextures at treated surfaces and compositionally and morphologically modified films is explained briefly.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bingley : Emerald
    Aircraft engineering and aerospace technology 71 (1999), S. 228-238 
    ISSN: 0002-2667
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Anodizing is used widely in the surface treatment of aluminium alloys for aerospace applications. Considers recent advances in understanding of the influences of alloying elements in anodizing of aluminium alloys and, in particular, their applicability to second phase particles during anodizing of commercial alloys. Through more precise knowledge of the response of second phase materials to anodic polarization, improved anodizing and related surface treatment processes may be developed in order to enhance the performance of aluminium alloys.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Thin Solid Films 123 (1985), S. 127-133 
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Thin Solid Films 148 (1987), S. 333-341 
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 4909-4916 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Barrier-type film growth on the high strength aluminium alloy FVS0812 has been studied by a combination of transmission electron microscopy and Rutherford backscattering spectroscopy. The film is composed mainly of amorphous anodic alumina, but is contaminated with iron species incorporated into the film from the alloy. The film may also be contaminated with silicon and vanadium species at levels below the detection limit of the present experiments. The contaminant species are primarily incorporated locally into the film during oxidation of Al13(Fe, V)3Si dispersoids and the resulting film material is of reduced resistivity compared with anodic alumina of high purity. As a consequence of the presence of regions of film material of differing resistivities, the film is of irregular thickness. The average thickness corresponds to a nm/V ratio of about 1.3. Iron species incorporated into the film migrate outwards at roughly 2.1 times the rate of Al3+ ions. The iron species are not ejected in significant amounts to the electrolyte on reaching the film/electrolyte interface and hence, a thin layer of film material highly enriched in iron species develops at the film surface. The layer may also be enriched in vanadium species, if these are incorporated into the film and migrate more rapidly than Al3+ ions. Enrichment of iron, and possibly other alloying element atoms, is found in a thin layer of alloy immediately beneath the anodic film, paralleling enrichments of alloying element atoms found following anodic oxidation of other aluminium alloys. The enrichments at both the alloy/film and film/electrolyte interfaces do not appear to be continuous across the macroscopic surface of the specimens, probably due to the non-uniformity of film growth on the two-phase substrate. The maximum voltage for the selected conditions of anodizing was limited to 68 V as a result of oxygen generation at flaws which are present extensively in the anodic film.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 497-502 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An investigation has been carried out into the possibility of in situ formation of MoS2 within porous anodic films on aluminium, to improve subsequent tribological behaviour, by re-anodizing in thiomolybdate electrolyte. Acidification of thiomolybdate was employed to simulate the conditions for formation of the sulphide at the anodic film/electrolyte interface, followed by appropriate vacuum heat treatments to study possible temperature effects on the sulphide due to either friction or Joule heating during anodizing. The products of both acidification and heat treatment, characterized by X-ray powder diffraction and scanning electron microscopy, were compared with those formed by direct thermal decomposition of ammonium tetrathiomolybdate crystals. The precipitate formed by acidification was mainly amorphous molybdenum trisulphide (MoS3), which on heat treatment at 450 and 850°C yielded 3R-MoS2. 3R-MoS2 also formed by the thermal decomposition of thiomolybdate crystals. Thermogravimetric and differential thermal analyses showed that the decomposition of MoS3 to MoS2 occurred in the range 220–370°C and revealed the sequence of reaction steps. The findings suggest that mainly amorphous MoS3 is formed as a consequence of changes in the pH of the film/electrolyte interface during re-anodizing but the product is relatively easily transformed to crystalline MoS2 on moderate heating which may occur during wear processes.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The formation of MoS2 by thermal decomposition of ammonium tetrathiomolybdate (ATT) solids under an argon atmosphere has been studied by simultaneous thermogravimetric and differential thermal analysis. The sequential products for the decomposition upon heating to 700 °C is ATT (hydrated)→(NH4)2MoS4→(NH4)HMoS4→H2MoS4→MoS3→ Mo2S5→MoS2. MoS2 forms between 230 and 260 °C and remains stable up to about 360 °C when it tends to be oxidized by residual oxygen, if present in the atmosphere. These findings suggest that the synthesis of MoS2 from (NH4)2MoS4 via formation of MoS3 is not a direct process, as previously reported, but rather a complex process involving a number of intermediate products (NH4)HMoS4, H2MoS4 and Mo2S5 which have not been reported before. That these products are only specific to the very narrow temperature regimes as revealed suggests that they are very unstable and short lived, that their presence is transient in nature and thus that ex-situ characterization of them is normally difficult. The presence of these intermediate products, as justified experimentally, is further interpreted in terms of their mutual structural similarities which improve understanding as to why MoS2 can usually be prepared from ATT by thermal decomposition, as in this case, or by other techniques, such as anodizing. Laminar morphology of MoS2 is revealed by transmission electron microscopy and its crystal structure examined by selected-area diffraction. Further ex-situ examination by X-ray photoelectron spectroscopy of this end product supports the feasibility of preparing MoS2 from aqueous solutions by anodizing. © 1998 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1996), S. 494-496 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 33 (1998), S. 4159-4165 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The formation of porous anodic films on FVS0812 aluminium alloy has been examined by transmission electron microscopy in order to elucidate the processes of film growth. A complex morphology of film material is revealed containing relatively tortuous, branched and terminated porosity and relatively large cavities. The morphology is associated with the differing anodic oxidation behaviour of the aluminium matrix and silicide dispersion regions of the alloy and the differing chemical stabilities of the resultant film regions. The anodic oxidation of the silicide proceeds more slowly than that of the aluminium matrix, with the production of film material of much finer morphology. The reduced rate of oxidation of the silicide is attributed to the effects of alloying element species in the anodic film material and pore solution. The rate of oxidation of the silicide is sufficient for most of the particles to be oxidized completely during anodizing. However, the resultant film material subsequently dissolves in the pore solution leaving relatively large cavities in the film. The differing oxidation rates of the alloy components, coupled with locally differing film properties, leads to a relatively rough alloy/film interface.© 1998 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 892-898 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mechanism of oxidation of copper at the alloy/film interface, and the subsequent migration of copper ions in barrier-type films, has been examined for anodizing of an Al - 1.5 wt.% Cu alloy with a prior chemical polishing treatment. Both chemical polishing and anodizing result in formation of a thin layer of alloy at the alloy/film interface, of ∼2 nm thick, that is highly enriched in copper. The layer is present immediately beneath the different types of film formed by chemical polishing and subsequent anodizing, and contains in both cases ∼6 × 1019 Cu atoms m-2. The amount of copper contained within the enriched layer of alloy is not significantly dependent upon the anodizing voltage. During anodic film growth, both aluminium and copper ions are incorporated into the film at the alloy/film interface, on average in their alloy proportions. However, the film is depleted in copper relative to the alloy because copper ions in the film migrate faster than Al3+ ions and, on reaching the film/electrolyte interface, are ejected directly to solution. The mechanism of oxidation of copper is proposed to depend upon the formation, through prior oxidation of aluminium, of copper-rich clusters in the enriched layer of alloy at the alloy/film interface. Individual clusters are oxidized only on achieving a critical size. Consequently, copper is incorporated into the film discontinuously both in time and in position along the alloy/film interface. The films contain a high population density of flaws, which affects the film composition, the uniformity of ionic current, the faradaic efficiency of film growth, and the detailed distributions of copper ions within the films. However, the general features of film growth are compatible with the usual growth mechanism of anodic alumina, with transport numbers of Al3+ and O2-/OH- ions of ∼0.4 and ∼0.6, respectively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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