Interrelation between Hydrogen Desorption Kinetics and Structure of (Mg2Ni)Hx and Hydrogenated Eutectic(Mg/Mg2Ni)Hy

Mg-rich alloys of the binary system Mg-Ni are prospective hydrogen-storage materials. In the present study, desorption characteristics of hydrided Mg2Ni intermetalic and hydrided Mg/Mg2Ni eutectic mixture were investigated. Structure of experimental materials during the hydrogenation was observed by SEM. Three modifications of (Mg2Ni)Hx (x ~ 4) were prepared differing in the ratio of two low-temperature phases f = LT2/LT1: with (i) f >1, (ii) f ~ 1 and with (iii) f <1. Evolution of the ratio f during hydrogen desorption was checked by XRD. It was found that the micro-twinned phase LT2 is not desirable in hydrogen-storage materials containing Mg2Ni intermetallic. Diffusion coefficient of hydrogen in LT2 is about 20 times lower than in LT1.

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Crystallitic Structure and Thermodynamics of Magnesium-Based Hydrogen Storage Materials from Reactive Milling under Hydrogen Atmosphere

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.724-725.1021 ◽

2013 ◽

Vol 724-725 ◽

pp. 1021-1024

Author(s):

Shi Xue Zhou ◽

Qian Qian Zhang ◽

Nai Fei Wang ◽

Zong Ying Han ◽

Wei Xian Ran ◽

...

Keyword(s):

Hydrogen Storage ◽

Xrd Analysis ◽

Hydrogen Desorption ◽

Hydrogen Atmosphere ◽

Hydrogen Storage Materials ◽

Storage Materials ◽

Reactive Milling ◽

Anthracite Coal ◽

Enthalpy And Entropy Changes ◽

Hoff Equation

Magnesium-based hydrogen storage materials were prepared by reactive milling of magnesium under hydrogen atmosphere with crystallitic carbon, prepared from anthracite coal, as milling aid. The XRD analysis shows that in the presence of 30 wt.% of crystallitic carbon, the Mg easily hydrided into β-MgH2of crystal grain size 29.7 nm and a small amount of γ-MgH2after 3 h of milling under 1 MPa H2. The enthalpy and entropy changes of the hydrogen desorption reaction are 42.7 kJ/mol and 80.7 J/mol K, respectively, calculated by the vant Hoff equation from thep-C-Tdata in 300-380°C.

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Syntheses and Hydrogen Desorption Properties of Metal-Borohydrides M(BH4)n (M=Mg, Sc, Zr, Ti, and Zn; n=2–4) as Advanced Hydrogen Storage Materials

MATERIALS TRANSACTIONS ◽

10.2320/matertrans.47.1898 ◽

2006 ◽

Vol 47 (8) ◽

pp. 1898-1901 ◽

Cited By ~ 75

Author(s):

Yuko Nakamori ◽

Haiwen Li ◽

Kazutoshi Miwa ◽

Shin-ichi Towata ◽

Shin-ichi Orimo

Keyword(s):

Hydrogen Storage ◽

Hydrogen Desorption ◽

Hydrogen Storage Materials ◽

Storage Materials

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Ternary MgTiX-Alloys: A Promising Route towards Low-Temperature, High-Capacity, Hydrogen-Storage Materials

Chemistry - A European Journal ◽

10.1002/chem.200700747 ◽

2007 ◽

Vol 13 (35) ◽

pp. 9892-9898 ◽

Cited By ~ 29

Author(s):

Paul Vermeulen ◽

Emile F. M. J. van Thiel ◽

Peter H. L. Notten

Keyword(s):

Low Temperature ◽

Hydrogen Storage ◽

High Capacity ◽

Hydrogen Storage Materials ◽

Storage Materials

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Improvement of the hydrogen-storage performances of Li–Mg–N–H system

Journal of Materials Research ◽

10.1557/jmr.2007.0165 ◽

2007 ◽

Vol 22 (5) ◽

pp. 1339-1345 ◽

Cited By ~ 35

Author(s):

Yongfeng Liu ◽

Jianjiang Hu ◽

Zhitao Xiong ◽

Guotao Wu ◽

Ping Chen

Keyword(s):

Activation Energy ◽

Low Temperature ◽

Hydrogen Storage ◽

Hydrogen Absorption ◽

Hydrogen Desorption ◽

Partial Substitution ◽

Desorption Kinetics ◽

High Activation ◽

Molar Ratios ◽

Desorption Isotherms

Li2MgN2H2 can reversibly store more than 5.5 wt% hydrogen. However, the high activation energy of hydrogen desorption poses a kinetic barrier for low-temperature operation. In this work, the composition of the Li–Mg–N–H system has been modified by the partial substitution of Mg or Li by Na. The changes in structure and hydrogen absorption/desorption kinetics have been investigated. It was found that the peak temperature for hydrogen desorption was decreased by ∼10 °C, and that the hydrogen absorption/desorption isotherms were also significantly changed. Furthermore, the activation energy calculated by the Kissinger’s approach was reduced after the substitution of Mg or Li by Na. In addition, the different dehydrogenation structures were detected at different molar ratios of Mg, Li, and Na.

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