Hydrogen storage properties of TiFe-based composite with Ni addition

This paper presents the preparation of the parental experimental alloy, featuring a standard composition of Ti_1.08Y_0.02Zr_0.1Fe_0.7Ni_0.3Mn_0.2, via the vacuum induction melting technique. Subsequently, the Ti_1.08Y_0.02Zr_0.1Fe_0.7Ni_0.3Mn_0.2 alloy, with an addition of 2 wt% Ni, underwent mechanical ball milling to yield a TiFe-based composite for experimental purposes. The results of the experimental tests indicate that the composite alloy's phase composition comprises the TiFe primary phase, with a minor quantity of ZrMn₂ phase segregated on the surface of the primary TiFe phase, as well as Ni phase. The alloy, which underwent ball-milling for 15 min, displayed excellent activation characteristics, featuring a 12-s incubation period at 150 °C and a hydrogen pressure of 3 MPa. Furthermore, the hydrogen absorption capacity was 1.72 wt% at 90 °C and 33 min. The decrease in particle size and grain refinement of the ball-milled alloy resulted in an increase in the grain boundary specific surface area, which provided more nucleation sites for the hydrides of the ball-milled alloy and enhanced the hydrogen absorption and desorption kinetic performance of the alloy. The thermodynamic properties test indicated that the absolute values of enthalpy (Δ<i>H</i>) and entropy (Δ<i>S</i>) changes exhibited a decreasing trend followed by an increase as the ball milling time extended from 5 min to 180 min during the hydrogen absorption and desorption process. The grain refinement occurring in short-term ball milling and the agglomeration occurring in long-term ball milling are the primary reasons for the variations in the alloy powder. The smallest absolute values of enthalpy and entropy changes were observed for the alloy ball-milled for 15 min, at 19.1 kJ/mol and 22.3 kJ/mol, respectively.