Hydrogen storage properties of TiFe-based composite with Ni addition

Abstract

This paper presents the preparation of the parental experimental alloy, featuring a standard composition of Ti 1.08 Y 0.02 Zr 0.1 Fe 0.7 Ni 0.3 Mn 0.2 , via the vacuum induction melting technique. Subsequently, the Ti 1.08 Y 0.02 Zr 0.1 Fe 0.7 Ni 0.3 Mn 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 ZrMn 2 phase segregated on the surface of the primary TiFe phase, as well as Ni phase. The alloy, which underwent ball-milling for 15 minutes, displayed excellent activation characteristics, featuring a 12-second 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 H ) and entropy (Δ S ) changes exhibited a decreasing trend followed by an increase as the ball milling time extended from 5 minutes to 180 minutes 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 minutes, at 19.1 kJ/mol and 22.3 kJ/mol, respectively.

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