Hydrogen absorption-desorption characteristics of Ti _{(0.22 + X)}Cr_{(0.28 + 1.5X)}V_{(0.5 - 2.5X)} (0 ≤ X ≤ 0.12) alloys

The hydrogen absorption-desorption characteristics of Ti _{(0.22 + X)}Cr_{(0.28 + 1.5X)}V_{(0.5 - 2.5X)} (X = 0, 0.04, 0.08, 0.10, 0.12) bcc alloys have been investigated at 303 K. The compositions of alloys were chosen for alloys to have equal lattice parameters of about 3.03 Å by a linear combination of each element. The alloys of about 20 g each were arc-melted into button shaped ingots under argon atmosphere and re-melted five times to improve their homogeneities. The XRD analysis showed that all of the samples prepared had bcc single phases and their lattice parameters were nearly the same regardless of their chemical compositions. The PC isotherms of the alloys revealed that the hydrogen storage capacities of the alloys exceeded 3 mass% owing to the control of the lattice parameters and only the second plateau was reversible at room temperature. A reversible structural transition from fcc to bcc occurred with dehydrogenation of the second plateau. Some hydrogen remained unreleased even at a considerable low pressure corresponds to the bcc hydride and needed thermal activation energy for desorption. The hydrogen absorption rate of the Ti_0.32Cr _0.43V_0.25 alloy was considerably fast and more than 95% of the hydrogen was absorbed within the first 10 min.