• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.469-476
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• 2015

The purpose of this work is to investigate main factors to design a solid-state hydrogen stroage system with magnesium hydride with 10 wt% graphite using numerical simulation tools. The heat transfer characteristic of this material was measured in order to perform the highly reliable simulation for this system. Based on the measured effective thermal conductivity, a transient heat and mass transfer simulation revealed that the total performance of hydrogen storage system is prone to depend on heat and mass transfer behaviors of hydrogen storage medium instead of its inherent kinetic rate for hydrogen adsorption. Furthermore, we demonstrate that the thermodynamic aspect between equlibrium presssure and temperature is one of key factor to design the hydrogen storage system with high performance using magnesium hydride.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1123-1129
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• 2010

In order to apply the Sievert's type automatic apparatus to thermal analysis of hydrogen absorbing materials, the dehydrogenation of the Mg-H system was investigated. As the initial wt% of hydrogen was increased to 4.4, the peak temperature of evolution rate shifted to higher temperature. However, with the initial wt% of hydrogen higher than 4.4, peak temperature of evolution rate did not change. The peak temperatures of evolution rate obtained by automatic apparatus were almost the same as those measured by a manual apparatus. As the heating rate was increased, the peak temperatures increased; the peak temperatures for heating rates 1, 2 and 3 K/min were 664, 687 and 702 K, respectively. The activation energy for the decomposition of Mg hydride was 101 kJ/mol. The Sievert's type automatic apparatus can be successively applied to the thermal analysis of metal hydride.

• Korean Journal of Metals and Materials
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• v.50 no.5
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• pp.375-381
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• 2012

Magnesium prepared by mechanical grinding under $H_2$ (reactive mechanical grinding) with transition elements or oxides showed relatively high hydriding and dehydriding rates when the content of additives was about 20 wt%. Ni was chosen as a transition element to be added. $Fe_2O_3$ was selected as an oxide to be added. Ti was also selected since it was considered to increase the hydriding and dehydriding rates by forming Ti hydride. A sample $Mg-14Ni-3Fe_2O_3-3Ti$ was prepared by reactive mechanical grinding, and its hydrogen storage properties were examined. This sample absorbs 4.02 wt% H for 5 min, and 4.15 wt% H for 10 min, and 4.42 wt% H for 60 min at n = 2. It desorbs 2.46 wt% H for 10 min, 3.98 wt% H for 30 min, and 4.20 wt% H for 60 min at n = 2. The effects of the Ni, $3Fe_2O_3$, and Ti addition, and hydriding-dehydriding cycling were discussed.

• Korean Journal of Metals and Materials
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• v.56 no.11
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• pp.829-834
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• 2018

Although magnesium-based alloys are attractive materials for hydrogen storage applications, their activation properties, hydrogenation/dehydrogenation kinetics, thermodynamic equilibrium parameters, and degradation characteristics must be improved for practical applications. Further, magnesium poses several risks, including explosion hazard, environmental pollution, insufficient formability, and industrial damage. To overcome these problems, CaO-added Mg alloys, also called Eco-Mg (environment-conscious Mg) alloys, have been developed. In this study, $Eco-MgH_x$ composites were fabricated from Mg-CaO chips by hydrogen-induced mechanical alloying in a high-pressure atmosphere. The balls-to-chips mass ratio (BCR) was varied between a low and high value. The particles obtained were characterized by X-ray diffraction (XRD), and the absorbed hydrogen was quantified by thermogravimetric analysis. The XRD results revealed that the $MgH_2$ peaks broadened for the high BCR. Further, PSA results revealed particles size were decreased from $52{\mu}m$ to $15{\mu}m$.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.3
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• pp.220-226
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• 2019

Magnesium hydride has a high hydrogen storage capacity (7.6 wt.%), and is cheap and lightweight, thus advantageous as a hydrogen storage alloy. However, Mg-based hydrides undergo hydrogenation/dehydrogenation at high temperature and pressure due to their thermodynamic stability and high oxidation reactivity. MWCNTs exhibit prominent catalytic effect on the hydrogen storage properties of $MgH_2$, weakening the interaction between Mg and H atoms and reducing the activation energy for nucleation of the metal phase by co-milling Mg with carbon nanotubes. Therefore, it is suggested that combining transition metals with carbon nanotubes as mixed dopants has a significant catalytic effect on the hydrogen storage properties of $MgH_2$. In this study, Material life cycle evaluation was performed to analyze the environmental impact characteristics of Mg-CaO-10 wt.% MWCNTs composites manufacturing process. The software of material life cycle assessment (MLCA) was Gabi 6. Through this, environmental impact assessment was performed for each process.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.553-557
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• 2020

It is possible that hydrogen could replace coal and petroleum as the predominant energy source in the near future, but several challenges including cost, efficiency, and stability. Mg and Mg alloys are attractive hydrogen storage materials because of their lightweight and high absorption capacity. Their range of applications could be further extended if their hydrogenation properties could be improved. The main emphasis of this study was to investigate their hydrogenation properties for Synthesis of 10wt.% CaF2 in Mg2NiHx systems. The effect of BCR (66:1) and MA time (96 hours) on the hydrogenation properties of the composite was investigated. also, Mg2NiHx-10wt% CaF2 composites prepared by Mechanical Alloying are used in this work to illustrate the effect of catalysts on activation energy and kinetics of Magnesium hydride.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.2
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• pp.148-157
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• 2022

Research on hydrogen storage is active to properly deal with hydrogen, which is considered a next-generation energy medium. In particular, research on metal hydride with excellent safety and energy efficiency has attracted attention, and among them, magnesium-based hydrogen storage alloys have been studied for a long time due to their high storage density, low cost, and abundance. However, Mg-based alloys require high temperature conditions due to strong binding enthalpy, and have many difficulties due to slow hydrogenation kinetics and reduction in hydrogen storage capacity due to oxidation, and various strategies have been proposed for this. This research manufactured Mg₂Ni to improve hydrogenation kinetics and synthesize about 5, 10, 20 wt% of CaF₂ as a catalyst for controlling oxidation. Mg₂NiHx-CaF₂ produced by hydrogen induced mechanical alloying analyzed hydrogenation kinetics through an automatic PCT measurement system under conditions of 423 K, 523 K, and 623 K. In addition, material life cycle assessment was conducted through Gabi software and CML 2001 and Eco-Indicator 99' methodology, and the environmental impact characteristics of the manufacturing process of the composites were analyzed. In conclusion, it was found that the effects of resource depletion (ARD) and fossil fuels had a higher burden than other impact categories.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.935-940
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• 2002

Magnesium-3, 6wt% Nickel alloys were fabricated by Rotation-Cylinder Method(RCM) in ambient atmosphere. The alloys were divided into two different heat-treating conditions, as-cast and thixotropic treated. Thixotropic heat treatment enhances the separation of primary hydride former of Mg and the catalytic phase of $Mg_2$Ni. Hydrogenation properties of the each alloy were evaluated and compared by PCI(Pressure-Composition Isotherm) measurement. The maximum hydrogen capacity and the reversible capacity of as -cast Mg-6wt% Ni alloy were 5.2wt% and 3.8wt% at 623k, respectively.

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.266-270
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• 2013

The hydrogen storage properties of pure $MgH_2$ were studied and compared with those of pure Mg. At the first cycle, pure $MgH_2$ absorbed hydrogen very slowly at 573 K under 12 bar $H_2$. The activation of pure $MgH_2$ was completed after three hydriding-dehydriding cycles. At the $4^{th}$ cycle, the pure $MgH_2$ absorbed 1.55 wt% H for 5 min, 2.04 wt% H for 10 min, and 3.59 wt% H for 60 min, showing that the activated $MgH_2$ had a much higher initial hydriding rate and much larger $H_a$ (60 min), quantity of hydrogen absorbed for 60 min, than did activated pure Mg. The activated pure Mg, whose activation was completed after four hydriding-dehydriding cycles, absorbed 0.80 wt% H for 5 min, 1.25 wt% H for 10 min, and 2.34 wt% H for 60 min. The particle sizes of the $MgH_2$ were much smaller than those of the pure Mg before and after hydriding-dehydriding cycling. The pure Mg had larger hydrogen quantities absorbed at 573K under 12 bar $H_2$ for 60 min, $H_a$ (60 min), than did the pure $MgH_2$ from the number of cycles n = 1 to n = 3; however, the pure $MgH_2$ had larger $H_a$ (60 min) than did the pure Mg from n = 4 to n = 6.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.429-436
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• 2012

Mg and Mg-based alloys are regarded as strong candidate hydrogen storage materials since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogenation properties of Mg-based hydrogen storage composites. The effect of transition metal oxides, such as $Nb_2O_5$ on the kinetics of the Magnesium hydrogen absorption kinetics was investigated. $MgH_x$-5wt.% $Nb_2O_5$ composites have been synthesized by hydrogen induced mechanical alloying. The powder fabricated was characterized by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (Fe-SEM), Energy Dispersive X-ray (EDX), BET and simultaneous Thermo Gravimetric Analysis / Differential Scanning Calorimetry (TG/DSC) analysis. The Absorption / desorption kinetics of $MgH_x$-5wt.% $Nb_2O_5$ (type I and II) are determined at 423, 473, 523, 573 and 623 K.