Study of the performance of Ti-Zr based hydrogen storage alloys

The P-C-I and charging-discharging properties of three Ti-Zr based alloys have been studied. Ni substitution for Mn and Cr in the alloy was found to increase the plateau pressure of the P-C-I curve. In addition, the partial substitution of Cr by V greatly improved the discharge capacity. However, the six-element alloy, Ti0.5Zr0.5V0.2Mn0.7Cr0.5Ni0.6, degraded rapidly in the gas-solid reaction. Hydrogen contents in the alloy under low pressure were increased during hydrogen absorption-desorption cycling. Annealing at 1050 degrees C for 4 h before the P-C-I experiment helped in releasing the retained hydrogen under low pressure. Only a slightly flattened P-C-I slope was obtained for the annealed alloy. Microstructures of the as-cast and annealed alloys were examined and related to the above results. Alloy powder was poisoned after 2-month storage in air, which resulted in the deterioration of discharge capacity. Surface pretreatment on alloy powders by HCl-HF solution decreased the activation time of charge-discharge reaction. (C) 1999 Elsevier Science S.A. All rights reserved.