Unconventional Alloys Confined in Nanoparticles: Building Blocks for New Matter

doi:10.1016/j.matt.2020.07.027

Matter

Volume 3, Issue 5, 4 November 2020, Pages 1646-1663

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Highlights

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Unprecedented alloys (e.g., HEAs) are formed via vapor-crystal transformation
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Brief oscillatory sparks mix vapors that are quenched to create 55 distinct alloys
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Miscibility limits for mixing bulk-immiscible systems are broken at the nanoscale
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Mixing abilities diversify materials for additive manufacturing and catalysis

Progress and Potential

Emerging technologies, such as artificial intelligence, quantum computing, three-dimensional printing, and wearable devices, have great promise for improving the lives of individuals worldwide. Materials science holds the key to realizing the emerging technologies via system-level integration and packaging solutions. High-entropy alloys represent a paradigm shift in materials science, and their exceptional properties were thought to be related to entropy maximization. In reality, this entropy, used as the only driving force for mixing, is often insufficient for alloying via traditional liquid-solid transformations. In contrast, this work breaks the miscibility limits by directly quenching well-mixed vapors to form alloys stabilized through a nanosize effect. This discovery contradicts observations that "smaller is less stable" and that mixing multiple elements in a nanoparticle is difficult. Our work is a breakthrough and enables unprecedented additive manufacturing, catalysis, and metallurgy.

Summary

Manufacturing unconventional alloys remains challenging owing to the seamless interplay between kinetics and thermodynamics. High-entropy alloys (HEAs), for example, enable paradigm shifts in materials science but these shifts are hindered by traditional liquid-solid transformations. In contrast, vapor–crystal transformations offer the most kinetically efficient pathways to form alloys. Here, a well-mixed vapor is quenched to create 55 distinct alloys confined in nanoparticles (NPs), including unprecedented ones. This confinement is found to stabilize their alloyed states. Unlike precursor feeding, a microseconds-long oscillatory spark mixes the vapors and determines the composition of the alloy NPs. To epitomize practicalities, we apply the NPs as integral building blocks for high-performance catalysts and to nanoscale additive manufacturing. The resulting HEA nanostructures cannot be fabricated by other additive manufacturing techniques. The present work breaks the miscibility limits, thereby providing a powerful roadmap to uncharted territories in metallurgy, catalysis, and additive manufacturing.

Graphical Abstract

Material Advancement Progression

MAP1: Discovery

Keywords

high-entropy alloys

vapor–crystal transformation

catalysts

alloy nanoparticles for nanoscale additive manufacturing

spark ablation

vapor mixing

breaking miscibility limits

metal alloying

kinetic trapping

Miedema approach

Cited by (0)

⁴: These authors contributed equally

⁵: Lead Contact