ISSN:
1573-4889
Keywords:
iron oxidation
;
surface pretreatment
;
oxide grain size
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The influence of surface pretreatment and metal orientation on the oxidation of coarse-grained polycrystalline Fe has been studied at 240 to 320°C in 5×10−3 Torr O2 using electron diffraction, electron microscopy, and Mössbauer spectroscopy to complement kinetic data. Consistent with previous studies on Fe single crystals, differences in oxidation kinetics for surfaces covered with an electropolish film from those with a similar thickness prior oxide formed by dry oxidation at room temperature are interpreted in terms of differing densities of leakage paths in the oxide layers. The more complex kinetics for electropolished polycrystalline Fe are a result of the leakage path density, the degree of oxide separation, and the extent of α-Fe2O3 formation varying with substrate orientation. Where adherent Fe3O4 layers are formed on polycrystalline and single-crystal Fe surfaces, the parabolic rate constants give an activation energy which is consistent with a previous value of 32 kcal · mole−1, suggesting that at these low temperatures the transport mechanism for magnetite growth is cation diffusion via easy diffusion paths in the oxide.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00603534
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