**1. Introduction**

Hydrogen can be a promising energy carrier for future energy economy [1,2], which, of course, involves changes in the transport infrastructure [3,4] and the adaptation of the entire energy system to the properties of hydrogen. One of the most important challenges is hydrogen storage [5]. In this context, the solid-state alloys that allow for reversible hydrogen storage [6] belong to the class of materials that can be suitable for application.

The titanium-zirconium-based alloys are the second largest class of solids, for which quasicrystallinity was found, e.g., TiZrNi [7] or TiZrFe [8–10]. The Ti-Zr compounds are promising candidates for many applications such as biomedical [11–13], filler metal [14], medium entropy alloys [15], bulk metallic glasses [16], dental implant [17], shape memory alloys [18], and high-entropy alloys [19]. The TiZrNi quasicrystal seems to be especially suitable for hydrogen storage due to its large hydrogen uptake capacity [20,21]. In this case, the hydrogen atoms are situated preferentially near Ti and Zr atoms in the quasicrystal lattice.

**Citation:** Zywczak, A.; Gondek, Ł.; ˙ Czub, J.; Janusz, P.; Selvaraj, N.B.; Takasaki, A. Physical Properties of Ti45Zr38Fe17 Alloy and Its Amorphous Hydride. *Energies* **2022**, *15*, 4236. https://doi.org/10.3390/ en15124236

Academic Editor: Giovanni Esposito

Received: 29 March 2022 Accepted: 30 May 2022 Published: 9 June 2022

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The chemical-physical properties of the Ti45Zr38Ni17 compositions can be changed by substituting other elements such as Ag [22], Pd [23–25], V [26], Co [27], Cu [28], Li [29], Ce [30], Mg [31], and Fe [32] in order to increase hydrogen sorption.

Since the discovery of quasicrystals, magnetic properties have not been studied much due to the lack of translational symmetry required for establishing long-range magnetic order. However, some quasicrystals exhibited spin-glass-like behavior [33]. Recently, the quasicrystals showing both ferromagnetic and antiferromagnetic behavior have been studied [34–38]. The magnetism in the TiZrNi quasicrystals was highly demanded [39]. The ferromagnetic signal for the Ti45Zr38Ni17 originated from nickel nano-cluster precipitations in the quasicrystalline alloy [40].

The present work aims at tracking the transformation of the Ti45Zr38Fe17 from the amorphous to the quasicrystalline/crystalline phases by the in-situ neutron diffraction technique and monitoring the magnetic properties. Additionally, our goal is to obtain the amorphous Ti45Zr38Fe17 alloy with the highest hydrogen capacity.
