Chromia Scale Thermally Grown on Pure Chromium Under Controlled p(O2) Atmosphere: I. Spallation Investigation Using Photoelectrochemical Techniques at a Mesoscale
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Chromia scales isothermally grown on pure chromium at 900 °C and a p(O2) of 10−12 atm during 30 min exhibit n- and p-type conduction associated with a duplex morphology with an internal equiaxed subscale for an inward (anionic) growth and an external columnar subscale for an outward (cationic) growth. After oxidation exposure, spalled regions in the oxide scale can be observed and have been studied with photoelectrochemical techniques at a mesoscale (probe diameter in the range of 50 µm). Owing to the semiconducting properties of each subscale (bandgap and conduction type), a scenario of spallation is proposed and clarifies when and where the oxide scale spallation occurs.
KeywordsChromia Photoelectrochemistry TEM characterization Spallation
This work has benefited from the support of the PSEUDO project of the French National Research Agency (ANR) and was performed within the framework of the Centre of Excellence of Multifunctional Architectured Materials “CEMAM” n°AN-10-LABX-44-01 funded by the “Investments for the Future” Program. Special acknowledgments are given to Gilles Renou for his precious help on TEM microscope.
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