Electrochemical Studies on the Ca‑Based Hydrogen Storage Alloy for Different Milling Times

Abstract

International audienceThe ­CaNi 4.8 Mn 0.2 powder was synthesized by mechanical alloying, under an atmosphere of argon at room temperature,<br&gtat different milling times (2, 10, 20, 30, 40, 50 and 60 h) with ball to powder weight ratio of 8:1. The structural and morphological characterizations of the ­CaNi 4.8 Mn 0.2 powder were carried, respectively, by scanning electron microscopy and X-ray diffraction. After 2 h, all the alloys had a biphasic structure, two major phases, Ni and Ca 2 Ni 7 , remained virtually unchanged when a small amount of Mn was added. After more than 40 h of milling, the same peaks of the Ni and ­Ca 2 Ni 7 phases appeared, while the intensity of the peaks decreased, indicating an additional amorphization process. After 50 h of milling, this damping was followed by the crystallization amorphization. The electrochemical properties of ­CaNi 4.8 Mn 0.2 electrodes were studied at different milling times (10, 20, 30, 40, 50 and 60 h) and in KOH electrolyte concentrations (1 M and 6 M) at ambient temperature, as anodes in the Ni–MH battery. Different techniques were used, such as galvanostatic polarization, potentiostatic polarization and potentiodynamic polarization