Aluminum Ion Diffusion in Aluminum Oxide

Paladino, Anna; Kingery, W. D.

doi:10.1063/1.1733252

Cited by 366 publications

(71 citation statements)

References 7 publications

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“…15,16) In this case, the appropriate tracer 26 Al has a very low specific activity and an extremely long half-life of 7:2 Â 10 5 years, making it very difficult to perform radiotracer diffusion experiments. Nychka et al, 10) then, deduced the aluminum grain boundary flux through an Al 2 O 3 scale during oxidation of alumina forming alloys by measuring the scale thickness, which consisted of double layers, such as equiaxial grains produced by outward diffusion of aluminum and underlying columnar grains developed by inward diffusion of oxygen.…”

Section: Introductionmentioning

confidence: 99%

Mass-Transfer Mechanism of Alumina Ceramics under Oxygen Potential Gradients at High Temperatures

2009

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The oxygen permeability of an undoped polycrystalline -Al 2 O 3 wafer that was exposed to oxygen potential gradients was evaluated at temperatures up to 1973 K. Oxygen preferentially permeated through the grain boundaries of -Al 2 O 3 . The main diffusion species, which were attributed to oxygen permeation, depended on oxygen partial pressures (P O2 ), forming oxygen potential gradients. Under oxygen potential gradients generated by P O2 below about 1 Pa, oxygen permeation occurred by oxygen diffusing from regions of higher P O2 to regions of lower P O2 . By contrast, under oxygen potential gradients generated by P O2 above about 1 Pa, oxygen permeation proceeded by aluminum diffusing from regions of lower P O2 to regions of higher P O2 . In other words, O 2 molecules were adsorbed onto a surface at higher P O2 and subsequently dissociated into oxygen ions (forming Al 2 O 3 ), while oxygen ions on the opposite surface at lower P O2 were desorbed by association into O 2 molecules (decomposition of Al 2 O 3 ). The grain-boundary diffusion coefficients of oxygen and aluminum as a function of P O2 were determined from the oxygen permeation constants.

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Section: Introductionmentioning

confidence: 99%

Mass-Transfer Mechanism of Alumina Ceramics under Oxygen Potential Gradients at High Temperatures

2009

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“…One data set is from Kingery and co-workers. 21,22 While the validity of the calculated lattice diffusion data from this work has been questioned, 23 the grain-boundary diffusion data have not and appear to be consistent with other data sets. 20 Using the Kingery relationships for grain-boundary diffusion to extrapolate to 1200°C, values for k g were calculated using Eqs.…”

Section: ͔ ͑2͒mentioning

confidence: 62%

“…A reasonable agreement was found between the calculated rate, assuming growth by oxygen diffusion via grain boundaries and values measured for RE-doped alumina formers in 1-atm O 2 at 1200°C. 24,25 Surprisingly, using an extrapolated value for aluminum diffusion in polycrystalline alumina 22 produced a rate similar to those measured for undoped alumina scales ͑Table I͒. However, undoped scales have been found to grow by a combination of Al and O boundary transport.…”

Section: ͔ ͑2͒mentioning

confidence: 62%