| Void Formation Induced by the Divergence of the Diffusive Ionic Fluxes in Metal Oxides Under Chemical Potential Gradients |
| Toshio Maruyama, Mitsutoshi Ueda |
| Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology |
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| ABSTRACT |
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When metal oxides are exposed to chemical potential gradients, ions are driven to diffusive mass transport. During this transport process, the divergence of ionic fluxes offers the formation/annihilation of oxides. Therefore, the divergence of ionic flux may play an important role in the void formation in oxides. Kinetic equations were derived for describing chemical potential distribution, ionic fluxes and their divergence in oxides. The divergence was found to be the measure of void formation. Defect chemistry in scales is directly related to the sign of divergence and gives an indication of the void formation behavior. The quantitative estimation on the void formation was successfully applied to a growing magnetite scale in high temperature oxidation of iron at 823 K. |
| Key words:
Chemical potential distribution, Divergence of ionic fluxes, Void formation, Magnetite, Volume fraction of voids in oxide scales |
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