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 TiYZrFeNiMn, via the vacuum induction melting technique. Subsequently, the TiYZrFeNiMn 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 ZrMn 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) and entropy (Δ) 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.