Crystal structure and hydrogen absorption-desorption properties of Zr1-xTixNi (0.05 ≤ x ≤ 0.5) alloys

Ti-substituted ZrNi alloys, Zr1-xTixNi (0.05 ≤ x ≤ 0.5), were prepared by arc-melting, and their hydrogen absorption/desorption properties were investigated. Each alloy consists of the primary phase with B33-type orthorhombic structure, which is characteristic of ZrNi, and the Zr9Ni11 secondary phase for x ≤ 0.3 or the Ti0.6Zr0.4Ni secondary phase for x = 0.5. The lattice parameter and unit cell volume for the primary phase and the Zr9Ni11 secondary phase decrease with increasing Ti content. The hydrogen storage capacity decreases with increasing Ti content because of the decrease in the unit cell volume of the primary phase and segregation of the secondary phase. The hydrogen storage capacity for the alloy with x = 0.4 was the highest in this study, but it was lower than that of the pristine ZrNi alloy. The temperature at which the plateau pressure for the hydrogen absorption of monohydride to trihydride was 0.1 MPa decreased with increasing Ti content. The enthalpy change for hydride formation (|ΔH|) decreases linearly with decreasing unit cell volume or increasing Ti content.