Nanocrystalline Fe-(Co,Ni)-Si-B: The mechanical crystallization of amorphous alloys and the effects on electrocatalytic reactions

Abstract

We have studied the process of mechanical crystallization on amorphous Fe-(Co,Ni)-Si-B metallic powders. Under high-energy mechanical deformations, these alloys crystallize into a nanocrystalline structure. The presence of Co accelerates the crystallization kinetics, while Ni slows it down. The dynamical equilibrium between crystal growth and fracture of the crystallites by the mechanical deformations gives rise to a distribution of crystal sizes whose average value is localized between 8 and 10 nm. The electrocatalytic activity of these nanocrystalline materials for the hydrogen evolution reaction in alkaline solutions is related to the presence of extremely small \ensuremath{\alpha}-iron crystallites. The mechanical crystallization process can be used effectively for producing highly electroactive metastable materials.