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  • 1
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Compositions and elemental distributions of anodic films formed on aluminium in aqueous borate electrolytes have been investigated by Rutherford backscattering spectroscopy (RBS) and associated nuclear reaction methods, together with controlled crystallization of film sections in the transmission electron microscope (TEM). Films were found to consist principally of Al2O3; the outer regions of the films were contaminated with boron and, for all cases studied, the inner regions were boron-free. In the absence of film dissolution the contaminated region represented approximately 40% of the film thickness, and this proportion did not vary significantly with changes in current density of film formation. The outer region contained about 1.5 wt% boron, probably as B2O3, and the densities of the inner and outer regions were similar to an accuracy of about 10%.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 4 (1982), S. 208-211 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A technique for the preparation of self-supporting windows of anodic barrier films on aluminium, which are essential for the precise interpretation of Rutherford backscattering data, is described. The generation of the window comprises several steps which include: (1) electropolishing of the superpure aluminium specimen in a perchloric acid/ethanol mixture; (2) masking a region of surface of the electropolished specimen with ‘Lacomit’ paint; (3) anodizing to develop a barrier-type anodic film over the exposed aluminium surface; (4) removal of the paint to reveal the non-anodized region on one face of the aluminium specimen which is then removed by electropolishing to leave the film window. Following this procedure, self-supporting windows of anodic films, free from the aluminium substrate, having effective diameters up to about 10 mm, are produced. It is shown that the use of the self-supporting window enables the Rutherford backscattering technique to be used to its full potential for the analysis of the barrier-type anodic films, enabling Al and O profiles through the film to be resolved clearly.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Stopping powers of an anodic film, formed on aluminium in aqueous ammonium pentaborate solution, have been measured experimentally for α particles, over the energy range 0.7-2.3 MeV. Comparison between the measured stopping powers and theoretically calculated values shows that Bragg's Rule may be applied, with reasonable accuracy (∼5%), to predict the stopping powers of anodic alumina. The density of the barrier-type film was determined by Rutherford backscattering spectroscopy to be 3.10±0.15 × 103 kg m-3.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 36-42 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The initial oxidation behaviour of a Co-20%Ni alloy exposed to air and the longer term oxidation of a metalevaporated magnetic recording tape (MET) of the same composition have been studied using XPS and AES.Air exposure of the alloy for 24 h showed the formation of a mixed hydroxide/carbonate layer over a relatively small amount of oxide. The hydroxide-containing layer was composed of both Co(OH)2 and Ni(OH)2, with the outer surface enriched in Co(OH)2. The carbonates are believed to originate from the hydration of carbides present in the alloy. Analysis of MET showed the presence of the oxides Co3O4 and NiO in addition to the hydroxides and carbonates.An Auger depth profile through MET indicated the presence of significant oxygen below the surface oxide, which increased in concentration towards the metal/polymer interface. This is explained by penetration of oxygen/water vapour into both voids and cracks formed during the manufacturing process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 485-494 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The analysis of the bondline in structural aluminium joints is taken as an example to illustrate how electron microscopy can be used to gain a new insight into the pheneomenon of adhesion. Scanning electron microscopy and transmission electron microscopy of ultramicrotomed sections has been used to characterize the adherend surfaces generated by the pretreatment processes prior to bonding. It is shown how a simple extension of these techniques can be used to analyse and characterize the interfacial and interphasial morphologies of the bonded joint both before and after exposure to ‘hot/wet’ environments. Results have shown that the importance of the so-called mechanical interlocking phenomenon is related to the durability resistance of the joint rather than enhancement of the ‘dry-state’ mechanical properties. It is also concluded that the formation of the voluminous hydrated alumina at the interface occurs post-rupture and is not a prima facie cause. From the observed interphasial morphologies a hypothesis is advanced to explain the effect of various pretreatments on joint durability. Other analytical techniques, such as ‘parallel’ sections, AES, XPS and electron energy-loss spectroscopy (EELS), are discussed and it is shown how these methods can be used, not only to confirm the interphasial structures but also to generate new data in their own right.A Greater understanding, therefore, of the effect of adhesive theology, environmental exposure, adherend composition and pretreatment on the interface between adhesive and adherend, can be obtained using these techniques.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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