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  • 1
    ISSN: 1573-4889
    Keywords: easy diffusion paths ; Al2O3 films ; γ-Al2O3 nucleation sites ; amorphous film
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermal oxide films grown on electropolished aluminum specimens have been investigated by transmission electron microscopy of stripped oxide films and ultramicrotomed sections. Particular attention has been focused on the nucleation sites γ-Al 2 O 3 crystals and the relationship of such sites to surface features on the electropolished aluminum surface. It is evident that “easy paths” for the diffusion of oxygen, or the nucleation sites of γ-Al 2 O 3 crystals, are not distributed randomly over the electropolished aluminum surface, but form preferentially in the amorphous oxide layer grown over preexisting metal ridges. Thus, the diffusion of molecular oxygen through cracks in the amorphous oxide layer represents the most realistic and acceptable basis for explaining the local growth of the γ-Al 2 O 3 crystals in thermal oxide films on aluminum, although the cracks have not yet been observed directly.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4889
    Keywords: aluminium ; amorphous oxide ; γ-Al2O3 ; induction period
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A novel technique has been employed to allow ready detection of fine crystallites, probably of γ-Al2O3, of sizes generally less than 10 nm in thermal oxide films on aluminium. Using this approach, the relationship between the average population density of γ-Al2O3 crystals and oxidation time has been obtained for the first time. Importantly, it has been found that oxidation at temperatures of 515 or 490°C results in fine crystal development almost from the onset of thermal oxidation. Thus, the so-called induction period for the growth of the γ-Al2O3 crystals, determined previously from weight gain data, should now be regarded as the oxidation time required for both the population density and sizes of the crystals to become sufficiently large to cause significant deviation in the weight gain data from the initial inverse logarithmic law describing the growth of the amorphous oxide.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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