• Transactions of the Korean hydrogen and new energy society
• /
• v.11 no.1
• /
• pp.11-18
• /
• 2000

In order to investigate the dehydriding properties of the $Mg_2NiH_x$ formed by hydrogen induced mechanical alloying, we performed isothermal thermogravimetry analysis at 453, 463, 473, 483, 493, 503 and 513K for 1 hours. Dehydrogenation kinetics were dependant strongly on the MA conditions which determine the In other words, kinds of synthesized hydrides phases and the crystal microstructures. The MA condition, 66:1 BCR(balls to chips mass ratio), especially 96h milling time, revealed the hydride phases of nano-/ amorphous state and the dehydriding activation energy of $43.4{\pm}3.6kJ/mole$.

• Korean Journal of Metals and Materials
• /
• v.49 no.12
• /
• pp.989-994
• /
• 2011

Samples with compositions of 80 wt% Mg-14 wt% Ni-6 wt% $Fe_2O_3$ (named $Mg-Ni-Fe_2O_3$), and 78 wt% Mg-14 wt% Ni-6 wt% $Fe_2O_3-2$ wt% CNT (named $Mg-Ni-Fe_2O_3-CNT$ ) were prepared by reactive mechanical grinding. Hydriding and dehydriding properties and effects of CNT addition on the hydriding and dehydriding rates of $Mg-Ni-Fe_2O_3$ were then investigated. Activation of the $Mg-14Ni-6Fe_2O_3$ sample was completed after three hydriding (under 12 bar $H_2$)-dehydriding (under 1.0 bar $H_2$) cycles at 573 K. The addition of CNT to the $Mg-14Ni-6Fe_2O_3$ sample made the activation process unnecessary, with a small decrease in the hydrogen-storage capacity.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.6
• /
• pp.787-793
• /
• 2011

A 76.5wt%Mg - 23.5wt%Ni (Mg-23.5Ni) sample was prepared by reactive mechanical grinding (RMG) and its hydriding and dehydriding properties were then investigated. Activation of the Mg-23.5Ni sample was completed only after two hydriding (under 12 bar $H_2$) - dehydriding (under 1.0 bar $H_2$) cycles at 593K. The reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation and shorten diffusion distances of hydrogen atoms. After hydriding - dehydriding cycling, the Mg-23.5Ni sample contained Mg2Ni phase.

• Transactions of the Korean hydrogen and new energy society
• /
• v.7 no.2
• /
• pp.181-191
• /
• 1996

Samples with the compositions of Mg-10wt.%Ni and Mg-25wt.%Ni were prepared by mechanical alloying in a planetary mill. $Mg_2Ni$ phase was formed in the mixture with hydriding dehydriding cycling. The activation of Mg-10wt.%Ni and Mg-25wt.%Ni was completed after n=7 and n=6 around, respectively, at 583K, $0{\sim}8barH_2$. Mg-10wt.% Ni and Mg-25wt. %Ni are considered as excellent hydrogen-storage materials with very high hydriding rates, high dehydriding rates and relatively large hydrogen-storage capacity. The effets of mechanical alloying and hydriding dehydriding cycling are considered the augmentation in the density of active nucleation sites and the diminution in the particle size.

• Transactions of the Korean hydrogen and new energy society
• /
• v.9 no.4
• /
• pp.151-160
• /
• 1998

The variation of the hydrogen-storage properties of Mg contained in the mechanically-allyed mixture with the weight percentage of nickel in the sample is investigated. The weight percentage of nickel transformed into the Mg2Ni phase, on the basis of the nickel weight, is highest in the Mg-10 wt.%Ni sample. For the first hydriding cycle, the effect of mechanical alloying on the hydriding rate of Mg is highest in the Mg-25 wt.%Ni sample. After activation, the effects of mechanical alloying and hydriding-dehydriding cycling on the hydriding rate of Mg are highest in the Mg-10 wt.%Ni sample. After sufficient hydriding-dehydriding cycling, the effects on the hydrogen-storage capacity of Mg are highest in the Mg-10 wt.%Ni sample. The effects on the hydriding and dehydriding rates of Mg are highest in the Mg-25wt.%Ni sample. Mg-25wt.%Ni, followed by Mg-10 wt.%Ni, is the optimum composition which has the best effects on the hydrogen-storage properties of Mg contained in the sample. The mechanical alloying and the hydriding-dehydriding cycling produce many defects, which can act as active nucleation sites, and increase the specific surface area, shortening the diffusion distance of hydrogen.

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.6
• /
• pp.541-546
• /
• 2015

Global energy shortage problem is expected to increase driven by strong energy demand growth from developing countries. Nuclear fusion power offers the prospect of an almost infinite source of energy for future generations. Hydrogen isotope storage and delivery system is a important subsystem of a nuclear fusion fuel cycle. Metal hydride is a method of the high-density storage of hydrogen isotope. For the safety storage of hydrogen isotope, depleted uranium (DU) has been widely proposed. But DU needs a safe test because It is a radioactive substance. The authors studied a small-scale DU bed and a medium-scale DU bed for the safety test. And then we made a large-scale DU bed and stored hydrogen isotopes in the bed. Before the hydriding/dehydriding, we tested it's heating and cooling properties and carried out an activation procedure. As a result, Reaction rate of DU-$H_2$ is more rapid than the other metal hydride ZrCo. Through the successful storage result of our large bed, the development possibility of the hydrogen isotope storage technology seems promising.

• Transactions of the Korean hydrogen and new energy society
• /
• v.4 no.1
• /
• pp.41-50
• /
• 1993

The hydrogen absorption and desorption characteristics of microencapsulated (CFM)$Ni_{4.7}Al_{0.2}Fe_{0.1}$ and $MmNi_4Fe$ powder with Ni and/or Cu by means of chemical plating method have been investigated. Initial hydrogen absorption rate and activation property were increased remarkably by encapsulation and subsequent compacting. Pellets abtained by compacting of Cu-encapsulated fine powder have fairly good strength even after 30 cycles of hydriding and dehydriding. Encapsulated alloy powder and their compacts show a good resistance to degradation by $O_2$ or CO in hydrogen.

• Transactions of the Korean hydrogen and new energy society
• /
• v.19 no.6
• /
• pp.482-489
• /
• 2008

Ti-Cr alloys consist of BCC solid solution, C36, C14 and C15 Laves phase at high temperature. Among others, the BCC solid solution phase was reported to have a high hydrogen storage capacity. However, activation, wide range of hysteresis at hydrogenation/dehydrogenation, and degradation of hydrogen capacity due to hydriding/dehydriding cycles must be improved for its application. In this study, to improve such problems, we added a Nb. For attaining target materials, Ti-10Cr-xNb(x=1, 3, 5wt.%) specimens were prepared by arc melting. The arc melting process was carried out under argon atmosphere. As-received specimens were characterized using XRD(X-ray diffraction), SEM(Scanning Electron Microscopy) with EDX(Energy Dispersive X-ray) and TG/DSC(Thermo Gravimetric Analysis/Differential Scanning Calorimetry). In order to examine hydrogenation behavior, the PCI(pressure-Composition-Isotherm) was performed at 293, 323, 373 and 423K.

• Korean Journal of Metals and Materials
• /
• v.47 no.7
• /
• pp.433-439
• /
• 2009

Ti and Ti based hydrogen storage alloys have been thought to be the third generation of alloys with a high hydrogen capacity, which makes it difficult to handle because of high reactivity. In order to solve the problem, the activation of a wide range of hysteresis of hydriding/dehydriding and without degradation of hydrogen capacity due to the hydriding/dehydriding cycle have to be improved in order to be aplied. Ti-Cr alloys have a high capacity about 0.8 wt.% in an ambient atmosphere. When the Ti-Cr alloys are added to Nb and Ta elements, they formed a laves phase in the alloy system. The Nb element was expected to make easy diffuse hydrogen in the Ti-Cr storage alloy, which was a catalytic element. In this study, the Ti-Nb-Cr ternary alloy was prepared by melt spinning. As-received specimens were characterized using XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy) with EDX (Energy Dispersive X-ray) and TG/DSC (Thermo Gravimetric Analysis/Differential Scanning Calorimetry). In order to examine hydrogenation behavior, the PCI (Pressure-Composition-Isotherm) was performed at 293, 323, 373 and 423 K.

• Korean Journal of Metals and Materials
• /
• v.49 no.4
• /
• pp.298-303
• /
• 2011

Mg-23.5 wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment from a Mg-23.5 wt%Ni-5 wt%Cu alloy synthesized by the gravity casting method. They were then ground under $H_2$ to obtain a fine powder. Among these samples the Mg-23.5Ni-2.5Cu sample had the highest hydriding and dehydriding rates after activation. The Mg-23.5Ni-2.5Cu sample absorbed 3.59 and 4.01 wt%H for 10 and 60 min, respectively, at 573K under 12 bar $H_{2}$. The activated 88(87.5Mg-10Ni-2.5Cu)-$5Nb_{2}O_{5}-7NbF_{5}$ sample absorbed 2.93 wt%H for 10 min, and 3.14 wt%H for 60 min at 573K under 12 bar $H_{2}$.