High-Entropy Alloys: Assessing Atomic-Scale Mixing and Surface Passivation with Time-of-Flight Secondary Ion Mass...

Area of Science:

• Materials Science
• Surface Science
• Analytical Chemistry

Background:

• High-entropy alloys (HEAs) are advanced materials with five or more principal elements in near-equiatomic proportions.
• HEAs exhibit unique properties due to high mixing entropy, making them promising for catalysis.
• Analyzing the complex surface chemistry of HEAs is challenging but crucial for understanding their performance.

Purpose of the Study:

• To demonstrate the utility of time-of-flight secondary ion mass spectrometry (ToF-SIMS) for analyzing HEAs.
• To develop a robust data processing framework for ToF-SIMS analysis of HEAs.
• To quantify atomic-level mixing and surface oxidation in HEAs.

Main Methods:

• Utilized time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze porous HEAs (Ru-Pt-Pd-Ir-Rh-based) and simpler alloys.
• Developed an automated quantification process for large ToF-SIMS datasets.
• Introduced cluster ratio (CR) and oxide ratio (OR) metrics to quantify atomic mixing and oxidation.

Main Results:

• Established a data processing framework enabling accurate interpretation of ToF-SIMS spectra from HEAs.
• Demonstrated that increasing elemental complexity in alloys enhances atomic mixing.
• Found that HEAs with greater atomic mixing exhibit increased resistance to surface oxidation.

Conclusions:

• ToF-SIMS, coupled with the developed metrics (CR and OR), is a powerful tool for characterizing HEA surface properties.
• Elemental complexity is a key factor in achieving enhanced atomic mixing in HEAs.
• Improved atomic mixing in HEAs correlates with superior oxidation resistance, beneficial for catalytic applications.