Deciphering atomistic mechanisms of the gas-solid interfacial reaction during alloy oxidation.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32494632.
- Also identified by DOI 10.1126/sciadv.aay8491 and PMC identifier 7182408.
- Licence recorded as CC BY-NC.
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Abstract
Gas-solid interfacial reaction is critical to many technological applications from heterogeneous catalysis to stress corrosion cracking. A prominent question that remains unclear is how gas and solid interact beyond chemisorption to form a stable interphase for bridging subsequent gas-solid reactions. Here, we report real-time atomic-scale observations of Ni-Al alloy oxidation reaction from initial surface adsorption to interfacial reaction into the bulk. We found distinct atomistic mechanisms for oxide growth in O<sub>2</sub> and H<sub>2</sub>O vapor, featuring a "step-edge" mechanism with severe interfacial strain in O<sub>2</sub>, and a "subsurface" one in H<sub>2</sub>O. Ab initio density functional theory simulations rationalize the H<sub>2</sub>O dissociation to favor the formation of a disordered oxide, which promotes ion diffusion to the oxide-metal interface and leads to an eased interfacial strain, therefore enhancing inward oxidation. Our findings depict a complete pathway for the Ni-Al surface oxidation reaction and delineate the delicate coupling of chemomechanical effect on gas-solid interactions.