Selective atomic sieving across metal/oxide interface for super-oxidation resistance

Area of Science:

• Materials Science
• Surface Science
• Metallurgy

Background:

• Surface passivation is crucial for corrosion and oxidation resistance in alloys.
• Initial oxidation behavior is known to vary with crystal facet, but the mechanism is unclear.

Purpose of the Study:

• To investigate the atomic-level mechanisms of crystal facet-dependent initial oxidation in alloys.
• To understand how different crystal facets influence the early stages of oxidation.

Main Methods:

• In situ environmental transmission electron microscopy (TEM) was used to observe oxidation at the atomic scale.
• Density functional theory (DFT) calculations were employed to model atomic diffusion at interfaces.

Main Results:

• The (001) surface of a Ni-5Cr alloy exhibited higher initial oxidation resistance compared to the (111) surface.
• An interfacial atomic sieving effect, controlling selective atomic species diffusion, was identified as the mechanism.
• DFT calculations confirmed enhanced oxygen diffusion across the Ni(111)/NiO(111) interface versus the Ni(001)/NiO(111) interface.

Conclusions:

• Crystal facet orientation significantly impacts initial oxidation rates in alloys.
• The observed differences are attributed to facet-dependent interfacial atomic diffusion.
• Materials with initially fast oxidation rates on certain facets may transition to slower steady-state oxidation.