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Caractérisation photoélectrochimique des oxydes formés sur alliages base nickel en milieu primaire des réacteurs à eau pressurisée

Abstract : In this thesis, we are interested in semiconducting properties of oxides formed on nickel base alloys. The aim is to demonstrate the effects of hydrogen partial pressure, the nature of the alloy and the surface conditions on the semi-conduction type and the band gap energies. Photoelectrochemical technique was used to characterize the semiconducting properties. Other complementary techniques were also used such as FEG-SEM, X-ray diffraction, Raman spectroscopy and XPS. Corrosion tests were performed in simulated primary medium (titanium autoclave, temperature 325°C, duration 500 hours). Samples of alloys 600 and 690 of 1 µm diamond polishing were oxidized at P(H2) < 0,01 ; 0,3 et 6,5 bar. The surface conditions concerned only the alloy 600 oxidized at P(H2) = 0,3 bar. We used a new method for fitting energy spectra to obtain the band gap energies. The obtained results show that only the hydrogen pressure affects the semiconducting type of oxides presented by the high energies, it shift from n-type (P(H2) < 0,01 bar) to insulating type (P(H2) = 0,3 and 6,5 bar). An n-type behavior was recorded at low energy whatever the study parameters. Band gaps energies of NiO, Cr2O3 and NiFe2O4 were revealed.
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Abdelhalim Loucif. Caractérisation photoélectrochimique des oxydes formés sur alliages base nickel en milieu primaire des réacteurs à eau pressurisée. Autre. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENI033⟩. ⟨tel-00842998⟩

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