Structural, Electrochemical and Hydrogen Sorption Studies of Nanocrystalline Ti-V-Co and Ti-V-Ni-Co Alloys Synthesized by Mechanical Alloying Method

In this paper, Ti-V-Co and Ti-V-Ni-Co alloys are considered as the hydrogen storage systems and the negative electrodes in Ni-MHx secondary batteries. This work shows results of studies that have been made on Ti0.5V1.5-xCox and Ti0.5V1.4-xNi0.1Cox nanocrystalline alloys (x = 0, 0.1 0.2, 0.3) synthesized by the mechanical alloying technique. The goal of this study is to determine an effect of partial replacement of V by Co atoms on hydrogen storage and electrochemical properties of Ti-V and Ti-V-Ni alloys. X-ray diffraction studies have proven that 14 h of the ball milling has resulted in crystallization of body-centered-cubic solid solution. Studies performed on high-resolution transmission electron microscope confirm creation of nanocrystalline materials. Hydrogen sorption/desorption measurements that have been performed at 303 K show that Co accelerates the hydrogen sorption process, diminishes hysteresis and ameliorates the hydrogen storage reversibility. Properties of Ti-V-Co alloys, described in this work, originate mainly from structure of these materials. Electrochemical measurements of Ti-V-Co alloys have shown these materials poorly absorb hydrogen in 6 M KOH solution. Ti0.5V1.4-xNi0.1Cox alloys are characterized by better activation properties and improved cyclability in comparison to Co-free Ti0.5V1.4Ni0.1 alloy.