Hydrogen storage properties of TiMn2-based alloys for metal hydride heat pump

Several TiMn2-based C14 Laves phase alloys were prepared and their hydrogen storage properties were studied in order to develop a suitable material for metal hydride heat pump applications. The metal hydride should have a suitable plateau pressure under 10 atm and low sloping. The plateau pressure was effectively decreased by the partial substitutions of Zr for Ti, while the slope was increased. It was found that the decrease of stoichiometry and the substitution of V, Cu were very effective in improving the sloping properties and the improvement of sloping properties was mainly attributed to the strain energy effect. After careful balancing of the substitution effects of the alloying elements, it was found that (Ti0.8Zr0.2)1.05Mn0.8Cr1.05V0.05Cu0.1 alloy showed good plateau characteristics with considerably small hysteresis and sloping.