• Title/Summary/Keyword: Hydrogenation Properties

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The Changes of the Hydrogenation Properties of Zr0.9Ti0.1Cr0.7Fe1.3 Alloy Upon the Pressure Induced Hydriding-Dehydriding Cycling (수소흡수-방출 사이클에 의한 Zr0.9Ti0.1Cr0.7Fe1.3 합금의 수소화 반응 특성의 변화)

  • Lee, Jon-Ha;Lee, Jai-Young
    • Transactions of the Korean hydrogen and new energy society
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    • v.2 no.1
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    • pp.29-37
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    • 1990
  • The effect of pressure cycling of $Zr_{0.9}Ti_{0.1}Cr_{0.7}Fe_{1.3}$ on the hydrogenation properties was investigated using the P-C-Isotherm curves and hydrogen absorption rate curves in the isotherm condition. The reversible hydrogen absorption capacity was decreased about 45 % after 3300 cycles. In the case of activated sample, the rate controlling steps of hydriding reaction changed from the surface reaction to the hydrogen diffusion process through hydride phase sequentially as reaction proceeded. After 3300 cycles, the sequential change of rate controlling step was same as activated one. However, the hydrogen absorption rate significantly decreased. It is suggested that the degradation of $Zr_{0.9}Ti_{0.1}Cr_{0.7}Fe_{1.3}$ can be interpreted with the formation of $ZrFe_3$ phase at the particle surface.

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Mass Production of Mg based Hydrogen Absorbing Alloys and Evalution of Hydrogenation and Degradation Properties by Hydriding/Dehydriding Cyclic Test (교반관법에 의한 Mg 기지 수소저항합금의 대량제조와 반복적 수소화 반응에 따른 수소화 특성 및 열화특성 평가)

  • Ha, Won;Lee, Sung-Gon;Hong, Tae-Whan;Kim, Young-Jig
    • Transactions of the Korean hydrogen and new energy society
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    • v.13 no.1
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    • pp.13-23
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    • 2002
  • Hydrogenation properties of Mg-Ni and Mg-Ti-Ni alloys were investigated by Pressure-Composition Isotherm (PCI) test. Those alloys were fabricated by a new alloying method, Rotation-Cylinder Method (RCM). The as-cast microstructure of Mg-10 mass% Ni alloy consists of an island-like hydride forming $\alpha$-Mg phase and the eutectic structure. After 350 cyclic tests, Mg-lO mass % Ni alloy was pulverized into fine particles of 100 nm. The fine particles, which have a large specific surface area, are highly reactive with hydrogen. However, extreme pulvehzation can separate Mg from $Mg_2Ni$ in the eutectic structure, so $Mg_2Ni$ of the eutectic structure cannot behave as a dissociated hydrogen supplier.

Improvement of the Magnetic Properties of (Nd, Dy)-Fe-B Sintered Magnets by Modification of HD and Annealing Processes (HD 처리 및 열처리공정 개선에 의한 (Nd, Dy)-Fe-B 소결자석의 자기특성 향상)

  • NamKung, S.;Lee, Y.H.;Kim, M.K.;Jang, T.S.
    • Journal of Powder Materials
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    • v.17 no.5
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    • pp.359-364
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    • 2010
  • In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at $400^{\circ}C$ increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive $2^{nd}$ and $3^{rd}$ step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

The Fabrication of Mg9Ti1-(10, 20 wt%)Ni Hydrogen Absorbing Alloys by Hydrogen Induced Mechanical Alloying and Evaluation of Hydrogenation Properties (Part I : Preparations and Characterizations of Alloys) (수소 가압형 기계적 합금화법을 이용한 Mg9Ti1-(10, 20 wt%)Ni 수소저장합금의 제조와 수소화 특성 (제 1보 : 합금제조와 특성평가))

  • Hong, Tae-Whan;Kim, Gyung-Bum;Kim, Young-Jig
    • Transactions of the Korean hydrogen and new energy society
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    • v.13 no.3
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    • pp.197-203
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    • 2002
  • The main emphasis of this study was to find an new hydrogen absorbing alloy such as Mg-Ti-Ni-H systems, and to investigate their hydrogenation properties. ($Mg_9Ti_x$)-10, 20wt%Ni-Hx systems were prepared by hydrogen induced mechanical alloying(HIMA) using Mg and Ni chips and sponge Ti. The particles synthesized were characterized by X-ray diffraction, and their morphologies were observed by means of scanning electron microscopy(SEM) with energy dispersive spectrometry (EDS). In addition, the crystal structures were analyzed in terms of their bright-/ dark field images and the selected area diffraction pattern(SADP) of transmission electron microscopy(TEM).

Improvement of Microstructural Anisotropy of Nd-Fe-B-Ga-Nb Alloy by the Control of Hydrogen Reaction (수소반응속도 제어에 의한 Nd-Fe-B-Ga-Nb 합금의 미세조직 이방화율 향상에 관한 연구)

  • Lee, S.H.;Kim, D.H.;Yu, J.H.;Lee, D.W.;Kim, B.K.
    • Journal of Powder Materials
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    • v.17 no.1
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    • pp.23-28
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    • 2010
  • HDDR treated anisotropic Nd-Fe-B powders have been widely used for the sheet motors and the sunroof motors of hybrid or electric vehicles, due to their excellent magnetic properties. Microstructural alignment of HDDR treated powders are mostly depending on the hydrogen reaction in disproportionation step, so the specific method to control hydrogenation reaction is required for improving magnetic properties. In disproportionation step, hydrogenation pressure and reaction time were controlled in the range of 0.15~1.0 atm for 15~180 min in order to control the micorstructural alignment of $Nd_2Fe_{14}B$ phase and, at the same time, to improve remanence of HDDR treated magnet powders. In this study, we could obtain a well aligned anisotropic Nd-Fe-B-Ga-Nb alloy powder having high remanence of 12 kG by reducing hydrogen pressure down to 0.3 atm in disproportionation step.

Hydrogenation Properties of MgH2-CaO Composites Synthesized by Hydrogen-Induced Mechanical Alloying

  • Kim, Min Gyeom;Han, Jeong-Heum;Lee, Young-Hwan;Son, Jong-Tae;Hong, Tae Whan
    • 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 $15{\mu}m$.

Study on the Hydrogenation Properties of MmNi4.5Mn0.5Zrx(x=0, 0.025, 0.05, 0.1) Alloys Containing the Zr by Excess (과잉의 Zr을 첨가한 MmNi4.5Mn0.5Zrx(x=0, 0.025, 0.05, 0.1) 합금의 수소화특성에 관한 연구)

  • Kang, Kil-Ku;Park, Sung-Gap;Kang, Sei-Sun;Kwon, Ho-Young
    • Korean Journal of Materials Research
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    • v.12 no.8
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    • pp.617-623
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    • 2002
  • In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, $MmNi_{ 4.5}$$Mn_{0.5}$ $Zr_{x}$ (x=0, 0.025, 0.05, 0.1), are prepared by adding the excess Zr in $MmNi_{4.5}$ $Mn_{0.5}$ / alloy for the strong resistance to intrinsic degradation. The hydrogen storage alloys of rare-earth metal such as $LaNi_{5}$ , and $MmNi_{5}$X and $MmNi_{4.5}$ /$_Mn{0.5}$ alloys which substituted La by misch metal properties were characterized as well. The hydrogen storage alloys were produced by melting each metal mixture in arc melting furnace, and the as-cast alloys were heat-treated at $1100^{\circ}C$ for 10 hr. The major elements of misch metal(Mm) were La, Ce, Pr and Nd with some impurities less than 1wt.% determined by ICP-AES. X-ray diffraction indicated that the structure for these samples was a single phase of hexagonal with $CaCu^{5}$ type. As the Zr contents increases, the activation time and the plateau pressure decrease and sloping of the plateau pressure increase. Amount of the 2nd phases increases with increase in Zr contents in $MmNi_{ 4.5}$$Mn_{0.5}$ $Zr_{0.1}$ alloy, This phenomenon indicated that $ZrNi_3$ in this phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage..

Kinetic Parameter Analysis of Hydrogen Diffusion Reaction for Hydrogen Storage Alloy of Fuel Cell System (연료전지의 수소저장용 합금에 대한 수소확산반응의 속도론적 해석)

  • Kim, Ho-Sung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.2
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    • pp.45-49
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    • 2006
  • Electrochemical hydrogenation/dehydrogenation properties were studied for a single particle of a Mm-based(Mm : minh metal) hydrogen storage alloy($MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3}$) for fuel cell and Ni-MH batteries. A carbon fiber microelectrode was manipulated to make electrical contact with an alloy particle, and the potential-step experiment was carried out to determine the apparent chemical diffusion coefficient of hydrogen atom($D_{app}$) in the alloy. Since the alloy particle we used here was a dense, conductive sphere, the spherical diffusion model was employed for data analysis. $D_{app}$ was found to vary the order between $10^{-9}\;and\;10^{-10}[cm^2/s]$ over the course of hydrogenation and dehydrogenation process. Compared with the conventional composite film electrodes, the single particle measurements using the microelectrode gave more detailed, true information about the hydrogen storage alloy.

Hydrogenation Study of Mg-based Alloys by mechanical Grinding Reaction for Hydrogen Storage of Fuel Cell (연료전지의 수소저장용 마그네슘계 합금의 기계적 분쇄 반응에 의한 수소화 특성 평가)

  • Kim, Ho-Sung;Suh, Hee-Seok;Cha, Jae-Sang
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.6
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    • pp.69-74
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    • 2006
  • The effects of mechanical grinding(MG) treatment on the hydrogen storage of $Mg_2Ni$ alloy and $Mg_2Ni$ composite alloy($Mg_2Ni+graphite$) were investigated by pressure-composition-temperature(PCT) measurement, the micro-electrode technique of electrochemistry and etc, in which PCT was measured at high temperature(around $300[^{\circ}C]$) of gas phase and a carbon-filament micro-electrode for electrochemical evaluation was manipulated to make electrical contact with the particle in 1M KOH aqueous solution. It was found that the hydrogenation properties of $Mg_2Ni$ and graphite composite particle were greatly improved by the mechanical grinding treatment by which the $Mg_2Ni$ and graphite composite alloys could be changed into microstructure and nano-level particles. namely; the hydrogen dissociation pressure of PCT measurement was decreased from 0.55[MPa] to 0.42[MPa] and hydrogenation peaks by micro-electrode were also observed more clearly on the same sample.

A Study on the Hydrogenation Properties of TiNi Alloy Fabricated by Mechanical Alloying Method (기계적합금법에 의해 제조된 TiNi합금의 수소화반응특성에 관한 연구)

  • Ahn, Hyo-Jun;Kim, Bo-Su;Hwang, Jin-Hwan;Ahn, In-Shup;Kim, Ki-Won;Hur, Bo-Young
    • Transactions of the Korean hydrogen and new energy society
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    • v.5 no.2
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    • pp.73-79
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    • 1994
  • The hydrogenation behavior of Ti-Ni powders prepared by mechanical alloying in a high energy ball mill have been investigated by P-C isotherm curves, DSC(differential scanning calorimetry), X-ray diffractometer, SEM(scanning electron microscope). Amorphous TiNi phase was formed after 10 milling hours. The hydrogen storage capacity gradually decreased as a function of mechanical alloying time. There appears the DSC endothermic peak due to hydrogen evolution of amorphous hydride phase.

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