Application of chromium additives to Ti2Ni-based hydrogen carrier material

The effect of chromium alloying (0–1.5 at.%) on the structural features and crystal lattice of monolithic Ti₂Ni intermetallic compounds was studied to optimize their hydrogen storage properties. A comprehensive analysis using optical and scanning electron microscopy, as well as X-ray diffraction, revealed that the introduction of chromium in the studied concentration range does not lead to the formation of new phases. However, alloying did cause a statistically significant increase in the lattice parameter of the main Ti₂Ni phase. The maximum lattice parameter (11.3400 Å) was recorded for the alloy containing 1.5 at.% Cr.

A parallel evolution of the morphology was observed: with increasing chromium concentration, a transition occurred from a branched dendritic structure to an ordered lamellar structure. This transformation is explained by the segregation of chromium atoms along the interphase boundaries during crystallization, which alters the surface energy and growth kinetics.

Lattice expansion directly contributes to an increase in the volume of octahedral interstitial sites, which are key sites for hydrogen occlusion in the Ti₂Ni structure. Thus, the study's results confirm the potential of chromium alloying as a strategy for targeted capacity enhancement and improved thermodynamic stability of monolithic Ti₂Ni-based intermetallic materials intended for use in hydrogen storage systems.

This research was financially supported by the Russian Science Foundation (grant No. 25-79-10232).