Interface thermodynamics of nano-sized crystalline, amorphous and liquid metallic systems

Abstract

Abstract Expressions for the Gibbs energies of interfaces occurring in particular for solid and/or liquid/amorphous metals or alloys in contact with each other have been developed. To consider its energetics, an amorphous alloy has been modelled as a mixture of the undercooled liquid metal components near to the glass transition temperature making use of the enthalpy of melting, the entropy of melting and the temperature-dependent contribution of the heat capacity of the undercooled melt. Gibbs surface and interface energies have been obtained on the basis of the “macroscopic atom” Miedema model, where the entropy contributions of alloys have been derived applying a recently developed formalism. The Gibbs energy of a crystalline interface phase has been formulated. The molar fractions of the components of the alloy at the surfaces have been determined by minimising the surface energy. These results provide a thermodynamic basis for unusual phenomena observed in nano-sized systems. The formalism has been applied to calculate the thermodynamic stability of interface phases in a nano-sized, multi-layered system of iron and zirconium and to explain the aluminium-induced crystallisation of amorphous silicon and the layer exchange occurring in bi-layers of crystalline aluminium and amorphous silicon.