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Nat Mater. 2018 Jun;17(6):514-518. doi: 10.1038/s41563-018-0078-5. Epub 2018 May 7.

Atomic origins of water-vapour-promoted alloy oxidation.

Author information

1
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA.
2
Computational Mathematics Group, Pacific Northwest National Laboratory, Richland, Washington, USA.
3
CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China.
4
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
5
Department of Mechanical Engineering & Multidisciplinary Program in Materials Science and Engineering, State University of New York, Binghamton, NY, USA.
6
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA.
7
Computational Mathematics Group, Pacific Northwest National Laboratory, Richland, Washington, USA. Zhijie.Xu@pnnl.gov.
8
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA. chongmin.wang@pnl.gov.

Abstract

The presence of water vapour, intentional or unavoidable, is crucial to many materials applications, such as in steam generators, turbine engines, fuel cells, catalysts and corrosion1-4. Phenomenologically, water vapour has been noted to accelerate oxidation of metals and alloys5,6. However, the atomistic mechanisms behind such oxidation remain elusive. Through direct in situ atomic-scale transmission electron microscopy observations and density functional theory calculations, we reveal that water-vapour-enhanced oxidation of a nickel-chromium alloy is associated with proton-dissolution-promoted formation, migration, and clustering of both cation and anion vacancies. Protons derived from water dissociation can occupy interstitial positions in the oxide lattice, consequently lowering vacancy formation energy and decreasing the diffusion barrier of both cations and anions, which leads to enhanced oxidation in moist environments at elevated temperatures. This work provides insights into water-vapour-enhanced alloy oxidation and has significant implications in other material and chemical processes involving water vapour, such as corrosion, heterogeneous catalysis and ionic conduction.

PMID:
29736001
DOI:
10.1038/s41563-018-0078-5

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