Phase diagrams of refractory bimetallic nanoalloys
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RESEARCH PAPER
Phase diagrams of refractory bimetallic nanoalloys Rafael Mendoza-Pérez
&
Stephen Muhl
Received: 20 July 2020 / Accepted: 24 September 2020 # Springer Nature B.V. 2020
Abstract Nanostructured materials exhibit remarkable properties significantly different from their bulk counterparts. Metal alloys at the nanoscale show an impressive potential to produce new systems having well-designed functionalities. By using a nanothermodynamic approach, here, we present the effects of the size and shape of the nanoparticles (NPs) on the phase diagrams (PDs) of the Mo-M (M = Nb, Ta, and W) alloys. A well-known group of morphologies at 50, 20, and 10 nm in diameter was considered, which are as follows: tetrahedron, cube, octahedron, decahedron, dodecahedron, cuboctahedron, rhombic dodecahedron, sphere, icosahedron, and truncated octahedron. From an examination of the liquidus and solidus curves, we calculated the expansion or contraction of the coexistence solid-liquid region of the PDs and how these changes are related to the size and shape of the NPs. Through a detailed Gibbs free energy (GFE) analysis, we also determined the thermal stability of the three Mobased nanoalloys as a function of the size (10–50 nm) of the mentioned polyhedra, by fixing the temperature and the chemical composition. Finally, the surface segregated element was predicted in each bimetallic system.
Keywords Refractory alloys . Nanothermodynamics . Phase diagrams at the nanoscale . Theory and modeling R. Mendoza-Pérez (*) : S. Muhl Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n, Ciudad Universitaria, 04510 Coyoacán, CDMX, Mexico e-mail: [email protected]
Abbreviations NP Nanoparticle PD Phase diagram GFE Gibbs free energy MD Molecular dynamics
Introduction Among nanomaterials, nanoalloys supply a vast number of possibilities to generate new systems with properties or functionalities unpremeditated beforehand (Ferrando et al. 2008). This is due to the employment of theoretical and experimental research focused on better understand and control of properties, such as size (Alloyeau et al. 2009), miscibility (Andrews and O’Brien 1992; Christensen et al. 1995), geometric shape (Shishulin et al. 2019; Velázquez-Salazar et al. 2019), and synergistic (Wu et al. 2019) effects. In addition to the rich diversity of alloying elements (Wang et al. 2013), it is possible to vary the composition (Jellinek 2008) and chemical ordering (Rahm and Erhart 2018; Nelli and Ferrando 2019). As a comprehensive result, the physical and chemical properties of nanoalloys can be tuned to achieve ambitious scientific and technological applications (Lim et al. 2009; McNamara and Tofail 2015; Wu et al. 2017). Refractory metals (Nb, Mo, Ta, and W) and their alloys are widely used in electrical and electronic devices, nuclear reactors, superconductors, and superalloys (Mints and Rakhmanov 1981; Simnad 2001;
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Franke and Neuschütz 2006; Turnlund and Friberg 2007; Snead et al. 2019) due to their high melting temperatures an
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