Influences of melt spinning on electrochemical hydrogen storage performance of nanocrystalline and amorphous Mg2Ni-type alloys

Abstract

In order to improve the electrochemical hydrogen storage performance of the Mg 2 Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg 2 Ni-type Mg 20−x La x Ni 10 (x=0, 2) alloys were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage properties of the experimental alloys were tested. The results show that no amorphous phase is detected in the as-spun Mg 20 Ni 10 alloy, but the as-spun Mg 18 La 2 Ni 10 alloy holds a major amorphous phase. As La content increases from 0 to 2, the maximum discharge capacity of the as-spun (20 m/s) alloys rises from 96.5 to 387.1 mA·h/g, and the capacity retaining rate (S 20 ) at the 20th cycle grows from 31.3% to 71.7%. Melt-spinning engenders an impactful effect on the electrochemical hydrogen storage performances of the alloys. With the increase in the spinning rate from 0 to 30 m/s, the maximum discharge capacity increases from 30.3 to 135.5 mA·h/g for the Mg 20 Ni 10 alloy, and from 197.2 to 406.5 mA·h/g for the Mg 18 La 2 Ni 10 alloy. The capacity retaining rate (S 20 ) of the Mg 20 Ni 10 alloy at the 20th cycle slightly falls from 36.7% to 27.1%, but it markedly mounts up from 37.3% to 78.3% for the Mg 18 La 2 Ni 10 alloy.

The Current Status of Hydrogen Storage Alloy Development for Electrochemical Applications

“…Nanocrystalline/amorphous structure was shown to improve hydriding/dehydriding kinetics [189]; such structure can be achieved by mechanical alloying and melt-spin fabrication techniques or elemental substitution. Although the exact effect of melt-spin cooling rates depends on the type of elemental substitution, a higher cooling rate was frequently found to be beneficial in enhancing electrochemical properties and cycle stability [190,191,192,193,194,195,196,197]. Furthermore, the length of milling time plays an important role in varying the performances of mechanically alloyed materials [198,199].…”