Influence of CaO or CeO_2 coatings on oxidation of nickel polycrystals

摘要

The present study is concerned with the influence of CaO, or CeO_2, sputter coatings onrnthe oxidation behavior of specpure Ni polycrystals. The experiments were performedrnbetween 800° and 1200℃. The CeO_2-coated specimens show a more pronouncedrndecrease of the oxidation kinetics than those coated with CaO. The beneficial influence ofrnthese coatings is first explained by the presence of CaO, or CeO_2 precipitates near thernposition of the initial metal surface. For the CeO_2-coated specimens, the lower oxidationrnrates are also due to the decrease of the vacancy diffusion coefficient, while for the CaOrncoatings, it results of the decrease of the driving force of diffusion, due to the shift of thernNi/NiO phase boundary to higher P_(O2).