Influence of annealing treatment on the microstructure and hydrogen storage performance of Ti1.02Cr1.1Mn0.3Fe0.6 alloy for hybrid hydrogen storage application

• Annealing reduces the hydrogen absorption pressure and the desorption enthalpy.
• Prolonging annealing time flattens the hydrogen desorption plateau of the alloy.
• Prolonging annealing time enhances the hydrogen desorption plateau pressure.
• Ti1.02Cr1.1Mn0.3Fe0.6 annealed at 1123 K for 5 h shows the best overall performance.

The as-cast Ti1.02Cr1.1Mn0.3Fe0.6 alloy for hybrid hydrogen storage vessel application was annealed at different temperatures (873 K, 973 K, 1123 K, 1173 K) for 2 h, and annealed at 1123 K for different time (2, 5, 8 h) respectively, and their microstructure and hydrogen storage properties were investigated systematically. The results show that the as-cast alloy has a single C14 Laves phase, and all annealed alloys consist of a C14 Laves main phase and a secondary phase. After annealing at different temperatures for 2 h, the hydrogen absorption pressure at 298 K decreases, however, the maximum hydrogen storage capacity and desorption pressures at 318 K decrease slightly too. As the annealing time extends, the hydrogen absorption plateau pressure at 298 K and hydrogen desorption plateau pressure at 318 K increase, and the hydrogen desorption capacity increases first and then decreases, which reaches the highest desorption capacity of 1.721 wt.% at the annealing time of 5 h. Among the studied alloys, the alloy annealed at 1123 K for 5 h has the best overall properties for hybrid hydrogen storage application, its hydrogen absorption plateau at 298 K is 29.09 MPa, its hydrogen desorption plateau pressure at 318 K is 45.12 MPa, its hydrogen storage capacity is 1.721 wt.% and its dissociation enthalpy (ΔHd) is 17.78 kJ/mol H2.

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