Diffraction of electrons by oxide films on molten metals

Darbyshire, J. A.; Cooper, E. R.

doi:10.1039/tf9343001038

Cited by 14 publications

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“…The structure of the oxide film on aluminum has been studied in some detail by Steinheil (18), Yamaguti (24), Preston and Bircumshaw (17), Darbyshire and Cooper (2), Hass (10), and more recently by de Brouckére (1), using the electron-diffraction technique. The following results are found: The film found on molten aluminum is usually crystalline and corresponds to 7-AI2O3.…”

Section: Literature Surveymentioning

confidence: 99%

Thin Oxide Films on Aluminum.

Gulbransen¹,

Wysong²

1947

J. Phys. Chem.

118

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Section: Literature Surveymentioning

confidence: 99%

Thin Oxide Films on Aluminum.

Gulbransen¹,

Wysong²

1947

J. Phys. Chem.

118

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“…If the metal has a tendency to ignite in air, it is covered with a zinc chloride flux. This procedure has been used by Bragg and Darbyshire (24) and also by Cooper (111). They have also used a method suggested by Ponte (15), namely, collecting the oxide vapors from the ignited metal on some sort of support.…”

Section: Scattering Of Electrons By Crystalline and Semi-crystalline ...mentioning

confidence: 99%

A résumé of electron diffraction

Clark¹,

Wolthuis²

1938

J. Chem. Educ.

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“…Compared to the literature on solid aluminium oxidation, there is a much smaller body of work on the structure of oxides formed on (pure) molten aluminium (e.g. [27,[67][68][69][70][71][72]). From this relatively limited amount of available literature, there appear to be some similarities with behaviour observed in the solid-state.…”

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confidence: 99%

“…From this relatively limited amount of available literature, there appear to be some similarities with behaviour observed in the solid-state. Darbyshire [67], for example, examined oxide films formed on several molten 14 metals, including aluminium. Oxide specimens were sampled from the melt surface using a loop of wire.…”

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confidence: 99%

A microstructural and kinetic study of molten aluminium oxidation in relation to dross formation

Bonner¹

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Oxidation and dross formation on molten aluminium is estimated to directly cause losses of tens of millions of dollars per annum to the Australian smelting industry. Although there has been significant study of molten aluminium oxidation over the past few decades, the formation mechanisms are still not fully understood. There is also lack of reliable and useful kinetic data that can be applied to computational simulations of industrial melt handling processes involving the oxidation of either quiescent pools or turbulent transfers of molten aluminium. There is additional uncertainty in the literature relating to the physical processes underlying molten aluminium oxidation, and the microstructural evolution of the growing oxide film. Past oxidation studies have been confounded by the detrimental effect of the pre-existing oxide ubiquitously present on aluminium specimens. Recent studies conducted at The University of Queensland have indicated a way forward in this respect, with the development of an experimental technique that enables the melt surface to be skimmed free of pre-existing oxide prior to each oxidation experiment. This project is based on previous outcomes and expands on them to create new insights into the oxidative behaviour of molten aluminium in response to various key parameters, such as melt temperature and isothermal holding time. It also aims to resolve some ambiguities in the literature.Melts of commercial purity aluminium were isothermally held at various temperatures ranging from 750°C to 900°C, and exposed to ambient air for times ranging up to ~20 h. The oxide grown on each melt was removed and treated to separate the oxide itself from the underlying aluminium metal, using a molten salt flux. The mass of oxide was then determined as a function of melt temperature and exposure time. These gravimetric experiments were complemented by morphological and microstructural characterization of grown oxide films, using scanning electron microscopy, transmission electron microscopy, and electron diffraction. These two approaches were combined to develop a simple kinetic model based on the parabolic rate law.The amount of oxide formed was found to be significantly lower than what has previously been reported, and was attributed to the removal of the pre-existing oxide. The amount of oxide that formed increased with increasing temperature, and the oxidation rate continuously decreased with increasing exposure time. These observations are consistent with diffusion-limited growth.Microstructural characterisation showed two stages of oxidation. In the early stage, nano-sized, planar, polyhedral crystallites of γ-alumina nucleate at the metal/oxide interface. In the later stage, flake-like γ-alumina crystallites were observed to grow outwards from the oxide/air interface. The time at which the second stage of growth became active decreased with increasing temperature, and the flake-like crystallites continued to increase in size with increasing exposure time.iii Crystallographic texture was obser...

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Diffraction of electrons by oxide films on molten metals

Cited by 14 publications

References 0 publications

Thin Oxide Films on Aluminum.

Thin Oxide Films on Aluminum.

A résumé of electron diffraction

A microstructural and kinetic study of molten aluminium oxidation in relation to dross formation

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