Phase diagrams of refractory bimetallic nanoalloys

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 Mo-based 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. Graphical abstract