Analysis of the Reactive Element Effect on the Oxidation of Ceria Doped Nickel
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The effects of external doping with CeO2 on the oxidation of nickel have been evaluated. The materials studied were pure Ni and Ni with the surface doped with CeO2 by pulsed laser deposition. The oxidation kinetics were measured using thermogravimetric analysis. The oxidation microstructures were observed by scanning electron microscopy and cross-sectional transmission electron microscopy. Compositional analysis was performed with energy dispersive X-ray analysis and sputtering neutrals mass spectrometry. Phase identification was performed using X-ray diffraction. Doping with CeO2 resulted in a significant decrease in the NiO growth rate at intermediate temperatures, e.g. 800 °C. The scales on doped Ni grew primarily inward whereas those on the undoped Ni grew primarily outward. Deposition of the CeO2 dopant onto Ni with a thin, preformed NiO layer produced a similar reduction in the subsequent NiO growth rate. The CeO2 dopant did not reduce the growth rate at high temperature (1,300 °C). The results indicate that the CeO2 dopant influences grain boundary transport in the NiO. Mechanisms are presented to attempt to describe the above observations.
KeywordsNickel oxide Reactive element effect Oxidation kinetics
Financial support of this study by the Office of Naval Research through Grant No. N00014-09-1-0564 is gratefully acknowledged.
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