ISSN:
1662-9752
Quelle:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Thema:
Maschinenbau
Notizen:
The present study is concerned with the influence of sputter-coatings CaO on theoxidation behavior of Ni polycrystals. The experiments were performed in air, in the temperaturerange 800°-1200°C. Below 1200°C, CaO coatings reduce the oxidation rate, while this beneficialeffect disappears at 1200 °C. The oxidized specimens were examined by SEM and X-Raydiffraction, but also by EPMA depth profiling to evaluate the scale composition. Furthermore,electrical conductivity measurements and kinetic demixing studies were carried out on Ca-dopedNiO single crystals, to get a better insight regarding the transport processes involved duringoxidation. These last results show that the key features allowing to explain the effect of CaOcoatingson the oxidation rate of Ni are the influence of calcium on the increase of the dissociationpressure of NiO, which delays the oxidation of nickel, the kinetic demixing of the cations, whichcontrols the distribution of CaO precipitates in the scale responsible for blocking effects, and theincrease of the diffusion coefficient of both the cations and the cationic vacancies, which play adecisive role at high temperature, when the scale growth is dominated by lattice diffusion
Materialart:
Digitale Medien
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/20/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.595-598.1075.pdf
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