Thermal stability and electrode properties of melt-spun Mg 65Cu 25Nd 10 amorphous alloy

Abstract

Amorphous Mg-based alloy Mg 65Cu 25Nd 10 was prepared by melt-spinning. Thermal stability and phase transition in the as-quenched alloy were studied by TEM, DSC, X-ray and electron diffraction. It was found that the crystallization process of melt-spun Mg 65Cu 25Nd 10 ribbons consists of three steps. The first crystallization reaction at about 180 °C is connected with the formation of Mg 2Cu nanocrystalline phase, followed by formation of a coarser grained α-Mg crystalline phase (210–225 °C) corresponding to a second crystallization reaction. At higher temperatures a third exothermic effect (at about 320 °C) can be detected and the stable Mg 2Cu, α-Mg and Cu 5Nd phases are present. The electrode properties of the as-quenched and the annealed samples (partially and fully crystallized) were measured and compared as well. The amorphous Mg 65Cu 25Nd 10 alloy shows the highest discharge capacity (430.4 mAh/g) and the best life cycle properties in comparison with those of partially crystalline (421.8 mAh/g) and almost completely crystallized microstructural states (304.3 mAh/g). It was conformed that the discharge capacity is significantly dependent on the composition and microstructure of the electrode materials.