Maximize mixing in highly polyelemental solid solution alloy nanoparticles

In this issue of Matter, Yao et al. report on advanced non-equilibrium high-temperature entropy-controlled synthesis polyelemental nanoparticles. They achieve extreme mixing 15 metals, some them previously immiscible, in the form a single phase solid solution. The compositionally tunable properties such atomic scale mixtures within simple crystal structure makes highly interesting for design new materials, e.g., electrocatalysts. Expanding space materials is important as with tailorable are urgently needed to enable or improve applications. Currently, search and substantially enlarged by multinary high-entropy alloys (HEAs), multiple principal element alloys, complex solutions. Some HEAs have already shown paradigm-changing from overcoming strength-ductility limits1George E.P. Raabe D. Ritchie R.O. High-entropy alloys.Nat. Rev. Mater. 2019; 4: 515-534Crossref Scopus (981) Google Scholar electrocatalysis relying surface sites.2Löffler T. Savan A. Meyer H. Meischein M. Strotkötter V. Ludwig Schuhmann W. Design solid-solution electrocatalysts correlating configuration, adsorption energy distribution patterns, activity curves.Angew. Chem. Int. Ed. Engl. 2020; 59: 5844-5850Crossref PubMed (42) comprise typically four six elements equiatomic ratios, however, number principle not limited. al.3Yao Y. Huang Z. Hughes L.A. Gao J. Li Morris Zeltmann S.E. Savitzky B.H. Ophus C. Finfrock al.Extreme Mixing Nanoscale Transition Metal Alloys.Matter. 2021; 2340-2353Abstract Full Text PDF (22) present record value incorporated solution alloy nanoparticle. single-phase solution, constituent atoms mixed scale, thus, its can be tuned adjusting composition over wide ranges while maintaining same all compositions. However, limitation solutions immiscibility elements, which occurs if too different, terms size, structure, electronegativity. overcome methods, force immiscible during high state, favoring elemental mixing, into metastable subsequent quenching, rapid cooling, avoids decomposition subsystems. Examples methods obtain chemically forced plasma where quenching rates achieved condensation species gas solid, sputtering “sparking mash up”4Feng Chen Pikhitsa P.V. Jung Yang Choi Unconventional Alloys Confined Nanoparticles: Building Blocks New Matter.Matter. 3: 1646-1663Abstract (26) Scholar, well chemical using nonequilibrium solvothermal continuous-flow-synthesis5Kusada K. Yamamoto Toriyama Matsumura S. Sato Nagaoka Terada Ikeda Hirai Kitagawa Nonequilibrium Flow-Synthesis Solid-Solution Alloy From Immiscible Binary High-Entropy Alloys.PhysChemComm. 125: 458-463Google carbothermal shock synthesis,6Yao Xie P. Lacey S.D. Jacob R.J. F. Nie Pu Rehwoldt al.Carbothermal high-entropy-alloy nanoparticles.Science. 2018; 359: 1489-1494Crossref (556) precursor metal salt loaded carbon nanomaterials thermally shocked nanoparticles 8 elements. further develop toward (1) fabrication comprising that were mixable before (e.g., Au-W, Au-Ru, Au-Ir) (2) avoiding, large extent, oxidation metals easily oxidize Zr, Hf). use concept entropy-driven alloying, governed product temperature entropy (T??Smix). Carbothermal direct Joule heating nanomaterials, nanofibers, reaches very temperatures (T = 1800 K) 50 ms achieves necessary cooling order 104–105 K/s avoid separation, could occur slower cooling. enough combinations strong immiscibly, Au-Ru synthesized shows separation. This increasing ?Smix elements: system seven (PtPdRuRhIrAuCu), phase, including repelling binary systems Au-Ir observed. By thus entropy, HEA containing up (PtPdRhRuIrAuCuFeCoNiCrMnWMoSn) synthesized, many combinations, even face centered cubic (fcc) structure. Next immiscibility, challenge nanoscale oxophilicity combined area Here well, (high T, Smix) approach beneficial. substrate acts only heater nanoparticles, but at temperatures, it also reduce eventual forming oxides their state. reduction works some, easily-oxidizable quite accordance classical Ellingham diagram: “above C” reduced Co, W, Mo), like Hf Zr “below remain oxidized due stability these oxides. If now added, included an least less-oxidized inside particles. An example PtPdRhRuIrAuCuFeCoNiZrTiHfVNb, partially metallic whereas was completely subsystem ZrTiHfVNb. On other hand, promising similar oxygen-containing atmosphere used prepare denary oxide catalytic performance stability.7Li Liu Zeng Brozena A.H. Pastel G. al.Denary stable catalysts methane combustion.Nature Catalysis. 62-70Crossref (46) entropy-stabilized investigated detail reveal features lattice distortions strain inhomogeneity, making clear they random uniform, compositional structural fluctuations result quenching. Understanding atomic-scale controlling materials. As need leading formation operation conditions needs addressed. show remarkable 600°C (0.5 h), rationalized thermodynamic kinetic considerations. interest lower do favor relevant short diffusion pathways, phases intermetallics, different solutions) relatively low time. evolution efficiently studied atom probe tomography combinatorial processing platforms.8Li Y.J. Kostka Stein H.S. Accelerated exploration materials.Mater. Horiz. 5: 86-92Crossref Phase state relates back seminal work Cantor9Cantor B. Chang I.T.H. Knight Vincent A.J.B. Microstructural development multicomponent alloys.Mater. Sci. Eng. 2004; 375–377: 213-218Crossref (3856) 20 bulk metallurgy separation out mixture lead discovery CrMnFeCoNi subsequently known Cantor alloy. Recently “natural” characteristics identify refractory compositions starting 9-element alloy.10Wei Kim S.J. Kang Zhang Furuhara Park E.S. Tasan C.C. Natural-mixing guided as-cast tensile ductility.Nat. 19: 1175-1181Crossref (67) Summarizing, gives guidelines nanoalloy broadens available possibilities strongly mix. inspiring scientific questions respect challenges, opportunities limits nanomaterials: whether there maximum we mix; how dissimilar still remaining mixture; best explore exploit stabilize both technological aims. Extreme transition alloysYao al.MatterMay 7, 2021In BriefConventionally, mostly region easy i.e., light potentials. Yet limited combination largely hinders possible tunability material discovery. entropic entropy) favors uniform extended alloying previous unmixable regions called mixing. bring forth exotic broad Full-Text Open Access