Synthesis and Hydrogen Storage Behaviour of Pure Mg<SUB>2</SUB>FeH<SUB>6</SUB> at Nanoscale

Abstract

Pure Mg 2 FeH 6 compounds with two different morphologies have been successfully synthesized directly by mechanical milling (MM) and sintering of a mixture of 2Mg+Fe nanoparticles under an H 2 atmosphere, respectively. The successful preparation of pure Mg 2 FeH 6 can be attributed to the small particle sizes of Mg and Fe nanoparticles prepared by hydrogen plasma-metal reaction (HPMR), which provides shorter diffusion distance for hydrogen and the metals. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that the Mg 2 FeH 6 synthesized by mechanical milling has larger particle size but smaller crystallite size compared with the Mg 2 FeH 6 synthesized by sintering. The Mg 2 FeH 6 synthesized by mechanical milling can desorb more than 4.5 mass% hydrogen in 10 min under an initial hydrogen pressure of 0.001 bar at 573 K. Compared with the Mg 2 FeH 6 synthesized by sintering under the same conditions as the Mg 2 FeH 6 synthesized by mechanical milling, it is suggested that decrease of crystallite size is beneficial for enhancing desorption property of Mg 2 FeH 6 .

Effect of Complex Metal Hydrides on the Elimination of Hydrochloric Acid Exhaust Products from High‐Performance Composite Solid Propellants: A Theoretical Analysis

“…In the present paper, magnesium iron hexahydride (Mg2FeH6) has the highest value density (Table 1). This latter complex transition-metal hydride, recently synthesized in its pure state [44], has attracted great attention due to its high stability compared with MgH2 and its highest volumetric hydrogen density (150 kg/m 3 ), in addition to the large abundance and low cost of iron and magnesium [55][56][57][58][59]. Table 4 displays the calculated 𝐼 𝑠𝑝,𝑣 delivered by three AP/HTPB propellants at optimal compositions.…”

Metallurgical Synthesis of Mg2FexSi1–x Hydride: Destabilization of Mg2FeH6 Nanostructured in Templated Mg2Si

“…On the other hand, for x = 1, the Mg 2 FeH 6 phase with a = 6.4424 Å is observed, but a small amount of the α-Fe phase still remains even after heat treatment at 673 K under 5 MPa of H 2 . The yield of the Mg 2 FeH 6 phase is affected by the conditions of ball milling and heat treatment ,,− because Mg and Fe cannot form a stable alloy phase without H. For the Fe-rich compositions of x = 0.50, 0.75, and 0.90, the diffraction patterns indicate that the Mg 2 FeH 6 and Mg 2 Si phases are formed, resulting in double reflections of the same cubic structure (Figure b). The diffraction peaks of the Mg 2 FeH 6 phase are broadened with decreasing x , suggesting heavy lattice distortion.…”

The kinetics of lightweight solid-state hydrogen storage materials: A review

“…The Mg 2 FeH 6 compounds desorb hydrogen very quickly due to a shorter diffusion distance between hydrogen and the metals that is not usually observed [151]. More than 4.5 wt% H 2 can be desorbed in 10 min at 573 K, and 5.0 wt% H 2 can be desorbed in 1 h, which is close to the theoretical value of 5.47 wt% H 2 [151]. In conclusion, a novel method for preparing ultrafine nanoparticles using the HPMR method was developed.…”

“…Mg UFPs are one of the possible materials for hydrogen storage applications in the future, but further studies and research on these materials are needed. Pure Mg 2 FeH 6 is difficult to obtain with normal Mg and Fe elements, but by using the HPMR method, pure Mg 2 FeH 6 is successfully prepared from the small particle sizes of Mg and Fe nanoparticles [151]. The Mg 2 FeH 6 compounds desorb hydrogen very quickly due to a shorter diffusion distance between hydrogen and the metals that is not usually observed [151].…”

“…Pure Mg 2 FeH 6 is difficult to obtain with normal Mg and Fe elements, but by using the HPMR method, pure Mg 2 FeH 6 is successfully prepared from the small particle sizes of Mg and Fe nanoparticles [151]. The Mg 2 FeH 6 compounds desorb hydrogen very quickly due to a shorter diffusion distance between hydrogen and the metals that is not usually observed [151]. More than 4.5 wt% H 2 can be desorbed in 10 min at 573 K, and 5.0 wt% H 2 can be desorbed in 1 h, which is close to the theoretical value of 5.47 wt% H 2 [151].…”