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1. Plasmonic high-entropy carbides

   https://doi.org/10.1038/s41467-022-33497-1  

   Calzolari, Arrigo; Oses, Corey; Toher, Cormac; Esters, Marco; Campilongo, Xiomara; Stepanoff, Sergei P.; Wolfe, Douglas E.; Curtarolo, Stefano (December 2022, Nature Communications)

   Abstract Discovering multifunctional materials with tunable plasmonic properties, capable of surviving harsh environments is critical for advanced optical and telecommunication applications. We chose high-entropy transition-metal carbides because of their exceptional thermal, chemical stability, and mechanical properties. By integrating computational thermodynamic disorder modeling and time-dependent density functional theory characterization, we discovered a crossover energy in the infrared and visible range, corresponding to a metal-to-dielectric transition, exploitable for plasmonics. It was also found that the optical response of high-entropy carbides can be largely tuned from the near-IR to visible when changing the transition metal components and their concentration. By monitoring the electronic structures, we suggest rules for optimizing optical properties and designing tailored high-entropy ceramics. Experiments performed on the archetype carbide HfTa 4 C 5 yielded plasmonic properties from room temperature to 1500K. Here we propose plasmonic transition-metal high-entropy carbides as a class of multifunctional materials. Their combination of plasmonic activity, high-hardness, and extraordinary thermal stability will result in yet unexplored applications. 

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2. High-entropy fluorite oxides

   https://doi.org/10.1016/j.jeurceramsoc.2018.04.010  

   Gild, Joshua; Samiee, Mojtaba; Braun, Jeffrey L.; Harrington, Tyler; Vega, Heidy; Hopkins, Patrick E.; Vecchio, Kenneth; Luo, Jian (August 2018, Journal of the European Ceramic Society)
3. Sustainable high-entropy materials?

   https://doi.org/10.1126/sciadv.ads3926  

   Han, Liuliu; Mu, Wangzhong; Wei, Shaolou; Liaw, Peter K; Raabe, Dierk (December 2024, Science Advances)

   High-entropy materials (HEMs) show inspiring structural and functional properties due to their multi-elemental compositions. However, most HEMs are burdened by cost-, energy-, and carbon-intensive extraction, synthesis, and manufacturing protocols. Recycling and reusing HEMs are challenging because their design relies on high fractions of expensive and limited-supply elements in massive solid solutions. Therefore, we review the basic sustainability aspects of HEMs. Solutions include using feedstock with lower carbon and energy footprints, sustainable primary synthesis routes from minerals, attenuation of the equimolar alloying rule, and a preference for scrap and dumped waste for secondary and tertiary synthesis. The high solubility, compositional flexibility, and chemical robustness of HEMs offer pathways for using higher fractions of mixed and contaminated scrap and waste feedstocks, which are not admissible for synthesizing conventional materials. We also discuss thermodynamic and kinetic design strategies to reconcile good material properties with high impurity tolerance and variable compositions. 

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4. Disordered enthalpy–entropy descriptor for high-entropy ceramics discovery

   https://doi.org/10.1038/s41586-023-06786-y  

   Divilov, Simon; Eckert, Hagen; Hicks, David; Oses, Corey; Toher, Cormac; Friedrich, Rico; Esters, Marco; Mehl, Michael J; Zettel, Adam C; Lederer, Yoav; et al (January 2024, Nature)

   Abstract The need for improved functionalities in extreme environments is fuelling interest in high-entropy ceramics^1–3. Except for the computational discovery of high-entropy carbides, performed with the entropy-forming-ability descriptor⁴, most innovation has been slowly driven by experimental means^1–3. Hence, advancement in the field needs more theoretical contributions. Here we introduce disordered enthalpy–entropy descriptor (DEED), a descriptor that captures the balance between entropy gains and enthalpy costs, allowing the correct classification of functional synthesizability of multicomponent ceramics, regardless of chemistry and structure. To make our calculations possible, we have developed a convolutional algorithm that drastically reduces computational resources. Moreover, DEED guides the experimental discovery of new single-phase high-entropy carbonitrides and borides. This work, integrated into the AFLOW computational ecosystem, provides an array of potential new candidates, ripe for experimental discoveries. 

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5. Nanoprecipitate‐Strengthened High‐Entropy Alloys

   https://doi.org/10.1002/advs.202100870  

   Liu, Liyuan; Zhang, Yang; Han, Jihong; Wang, Xiyu; Jiang, Wenqing; Liu, Chain‐Tsuan; Zhang, Zhongwu; Liaw, Peter_K (October 2021, Advanced Science)

   Abstract Multicomponent high‐entropy alloys (HEAs) can be tuned to a simple phase with some unique alloy characteristics. HEAs with body‐centered‐cubic (BCC) or hexagonal‐close‐packed (HCP) structures are proven to possess high strength and hardness but low ductility. The faced‐centered‐cubic (FCC) HEAs present considerable ductility, excellent corrosion and radiation resistance. However, their strengths are relatively low. Therefore, the strategy of strengthening the ductile FCC matrix phase is usually adopted to design HEAs with excellent performance. Among various strengthening methods, precipitation strengthening plays a dazzling role since the characteristics of multiple principal elements and slow diffusion effect of elements in HEAs provide a chance to form fine and stable nanoscale precipitates, pushing the strengths of the alloys to new high levels. This paper summarizes and review the recent progress in nanoprecipitate‐strengthened HEAs and their strengthening mechanisms. The alloy‐design strategies and control of the nanoscale precipitates in HEAs are highlighted. The future works on the related aspects are outlined. 

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