Structure of a new ternary compound with high magnesium content, so-called Gd13Ni9Mg78

Abstract

International audienceThe magnesium-rich composition Gd13Ni9Mg78 was synthesized from its constituent elements in sealed tantalum tubes in an induction furnace. X-ray diffraction, electron probe microanalysis and dark-field transmission electron microscopy (TEM) images revealed anewcompound with a composition ranging from Gd10-15Ni8-12Mg72-78 and low crystallinity. In order to increase the crystallinity, different experimental conditions were investigated for numerous compounds with the initial composition Gd13Ni9Mg78. In addition, several heat treatments (from 573 to 823 K) and cooling rates (from room temperature quenched down to 2 K h−1) have been tested. The best crystallinity was obtained for the slower cooling rates ranging from 2 to 6 K h−1. From the more crystallized compounds, the structure was partially deduced using TEM and an average cubic structure with lattice parameter a = 4.55 Å could be assumed. A modulation along both a∗ and b∗ axis with vectors of modulation q1 = 0.42a∗ and q2 = 0.42b∗ was observed. This compound, so-called Gd13Ni9Mg78, absorbs around 3 wt.% of hydrogen at 603 K, 30 bars and a reasonable degree of reversibility is possible, because after the first hydrogenation, irreversible decomposition into MgH2, GdH2 and NiMg2H4 has been shown. The pathway of the reaction is described herein. The powder mixture after decomposition shows an interesting kinetics for magnesium without ball milling

Physical properties of the multifunctional Mg 80 Ni 10 Gd 10 alloy

“…The most intense peak at 2θ ≈ 34° corresponds to the (111) Bragg peak. As previously described by Couillaud et al [18] for a similar composition (Mg78Ni9Gd13), a modulated structure is observed when the crystallinity is high. Then, the satellite (extra) peaks can be indexed by considering vectors of modulation.…”

“…In this paper we explore the microstructure, mechanical and transport properties of the Mg80Ni10Gd10 alloy with emphasis on the effect on the cooling rate during solidification. This alloy was selected because it represents an interesting candidate in the search of multifunctionalities: it exhibits a good hydrogenation capability for energy storage [18] and it can be considered as a base for new light structural HEAs, i.e. Mg80(Co,Cu,Fe,Ni)10(Ce, La, Nd,Y)10.…”

“…Whereas Mg crystallizes in an hcp lattice, it has been shown that alloys with composition ranging from Mg72-78Ni8-12Gd10-15 are single-phase crystallizing in a cubic structure [18].…”

Polycrystalline and Single‐Crystalline Edge Layer of Mg–Gd–TM (TM=Ni, Ag) Alloys Prepared by Ion Thinner

“…[11] Couillaud successfully fabricated the magnesium-rich composition Gd 13 Ni 9 Mg 78 with polycrystalline structure synthesized from its constituent elements in sealed tantalum tubes in an induction furnace. [12] Sakaki reported that all Mg 1.0 RE 1.0 Ni 4 and Mg 1.4 RE 0.6 Ni 4 alloys prepared by high-frequency induction melting had a single phase of a C15b structure with space group F-43 m. [3] The ternary crystal structure Mg 2 GdNi 9 with space group R-3 m was found by mixing the MgNi 2 and GdNi 5 . [13] And, the Mg 2 Ni with space group P6 2 22 was formed by the severe plastic deformation technique to mix the Mg and Ni powder (Fast-Forging).…”

Examples of ordered or disordered ternary intermetallics containing rare earth elements and transition metals

“…A disordered structure is observed with a random distribution of Cu atoms on some La and Mg positions. The structure of the second phase, Gd 13 Ni 9 Mg 78 [8], was not fully determined because of a medium crystallinity. The structure was partially deduced using TEM and an average cubic structure with lattice parameter a = 4.55 Å could be assumed.…”