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In Situ Oxidation Studies of High-Entropy Alloy Nanoparticles
Boao Song1, Yong Yang2,3, Muztoba Rabbani4
1Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
ACS Nano
|October 20, 2020
Summary
High-entropy alloy nanoparticles oxidize slower than expected, governed by Kirkendall effects and logarithmic rates, offering insights for designing stable alloys for extreme environments.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- High-entropy alloys (HEAs) show promise for demanding applications but their behavior in complex environments is poorly understood.
- High-temperature oxidation is a critical factor limiting the service life of materials in many applications.
- Understanding nanoparticle oxidation mechanisms is crucial for developing advanced materials.
Purpose of the Study:
- To investigate the high-temperature oxidation behavior of a specific high-entropy alloy (HEA) nanoparticle composition.
- To elucidate the oxidation mechanisms and kinetics of HEA nanoparticles under atmospheric pressure dry air.
- To compare the oxidation resistance of HEA nanoparticles with monometallic nanoparticles.
Main Methods:
- In situ gas-cell transmission electron microscopy (TEM) for real-time observation of oxidation.
- Analytical energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) for material characterization.
- Hybrid Monte Carlo and molecular dynamics simulations based on first-principles calculations.
Main Results:
- HEA nanoparticles exhibit logarithmic oxidation rates, deviating from Wagner's theory, and are governed by Kirkendall effects.
- Oxidation rates of HEA nanoparticles are significantly slower compared to monometallic nanoparticles.
- Outward diffusion of transition metals, formation of a disordered oxide layer with embedded crystallites (Fe2O3, CoO, NiO, CuO), and core-shell segregation (Pt core) were observed.
Conclusions:
- The study reveals unique oxidation mechanisms and enhanced stability of HEA nanoparticles at high temperatures.
- Kirkendall effects and logarithmic oxidation kinetics contribute to the superior oxidation resistance of these HEA nanoparticles.
- Findings provide critical insights for designing robust HEA materials for high-temperature and corrosive applications.
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