Oxygen and aluminum diffusion in α-Al2O3: How much do we really understand?
✍ Scribed by A.H. Heuer
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 655 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0955-2219
No coin nor oath required. For personal study only.
✦ Synopsis
The major diffusion processes in ␣-Al 2 O 3 have been reviewed, including oxygen and aluminum lattice diffusion, D oxy and D Al , respectively; oxygen grain boundary diffusion, D b-oxy ; and pipe diffusion, D p . Their relevance to creep of Al 2 O 3 and oxidation of Al 2 O 3 scale-forming alloys is briefly considered.
It is concluded that the answer to the question included in the title is "not a great deal". Eight major questions and issues have been identified that would constitute fitting subjects for future research:
(i) What is the nature of the "buffering" that appears to control D oxy ? (ii) What process(es) are occurring during annealing that eliminate non-Fickian behavior when measuring D oxy ? (iii) How should the magnitude of the measured activation energies for D oxy be interpreted? (iv) Have all the defect types involved in oxygen diffusion been identified? (v) Does oxygen diffusion occur by an interstitialcy mechanism? (vi) What is the order of magnitude of D Al /D oxy ? (vii) What is the order of magnitude of D b-Al /D b-oxy ? (viii) It appears that the activation energy for D b-oxy is greater than that for D oxy . How should this be understood?