Structural and In Situ X-ray Diffraction Study of Hydrogenation of CaxMg1−xNi2 (0 ≤ x ≤ 1)

Zia Ur Rehman,Mayeen Uddin Khandaker,Abubakr M Idris,Hameed Ullah,Pervaiz Ahmad,Sirajul Haq,Mohsan Nawaz,Abdelmoneim Sulieman

doi:10.3390/cryst12010047

Abstract

In the quasi-binary system CaNi2-MgNi2 solid-solutions CaxMg1−xNi2 (0 ≤ x ≤ 1) were prepared from the elements. They crystallize in the hexagonal Laves phase type (MgNi2, C36) for x ≤ 0.33 (P63/mmc, a = 482.51(7) pm, c = 1582.1(3) pm for x = 0, a = 482.59(3), c = 1583.1(1) for x = 0.33) and in the cubic Laves phase type (MgCu2, C15) for 0.33 < x (Fd3¯m, a = 697.12(3) pm for x = 0.5, a = 705.11(2) pm for x = 0.67, a = 724.80(2) pm for x = 1). After hydrogenation in an autoclave the X-ray diffraction patterns changed completely. Reflections assigned to CaNiH3, and Ni and Rietveld refinement confirmed this. The hydrogenation properties of CaxMg1−xNi2 (0 ≤ x ≤ 1) compounds were also studied in situ by X-ray powder diffraction. In situ X-ray powder diffraction of CaxMg1−xNi2 (0 ≤ x ≤ 1) compounds under 0.3 MPa hydrogen gas flow (15 sccm), data collected on a Rigaku SmartLab diffractometer in an Anton Paar XRK 900 Reactor Chamber using Cu-Kα1 radiation. Scanning electron microscopy and EDX spectroscopy confirmed the entitled materials and elemental composition, respectively. From the Transmission electron microscopy and Selected area electron diffraction concluded that the CaxMg1−xNi2 (0 ≤ x ≤ 1) compounds were crystalline.

Highlights

IntroductionCompounds were studied in situ by X-ray powder diffraction
Wlodzimierz Bogdanowicz and Department of Physics, University of Azad Jammu and Kashmir, Muzaffarabad 13100, Pakistan; Centre for Applied Physics and Radiation Technologies, School of Engineering and Technology, Department of Chemistry, College of Science, King Khalid University, Abha 61421, Saudi Arabia; Research Center for Advanced Materials Science (RCAMS), King Khalid University, Abha 61421, Saudi Arabia
The problem is that the high thermodynamics stability and slow kinetics of its absorption and desorption reactions complicate its uses

Summary

Introduction

Compounds were studied in situ by X-ray powder diffraction. In term of hydrogen storage, magnesium hydride is the mostly studied materials because of reversible absorption and desorption, high gravimetric density and relatively low cost [10]. The problem is that the high thermodynamics stability and slow kinetics of its absorption and desorption reactions complicate its uses. There are a number of publications regarding the possibility of improving these properties, mainly by doping with transition group elements published maps and institutional affiliations. There are a number of publications regarding the possibility of improving these properties, mainly by doping with transition group elements or other chemical compounds and the and formation of ternary metal hydrides [11,12,13,14].[11,12,13,14]

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Conclusion