• 한국재료학회지
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• 제11권4호
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• pp.294-299
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• 2001

기계적 합금화 방법을 이용하여 제작한 Ni-MH 전지용 $Mg_2$Ni전극의 표면 불화처리에 대한 전기화학적 충.방전 특성이 조사되었다. 20시간 밀링을 통해 제조된 $Mg_2$Ni합금은 나노결정을 가졌으며 그 $Mg_2$Ni전극의 KOH전해질내에서 충.방전 실험 결과, 초기 방전 용량이 280mAh/g이상으로 증가하였으나 10cyc1e이내에 급격히 퇴화되었다. 전극표면에서 지속적이고 안정한 불화층 형성을 목적으로 KOH용액에 잉여의 불소이온이 첨가된 $Mg_2$Ni전극의 내구성은 크게 향상되었으며 특히 2N KF를 첨가했을 경우 전극의 내구성이 가장 크게 향상되었다. 고율 방전실험의 경우도 그 성능이 90-100mAh/g으로 유지되었다 이러한 내구성 향상의 이유는 표면에 얕고 다공성인 $Mg_2$Ni층의 형성으로 인해 퇴화의 주요인인 Mg(OH)$_2$의 생성이 억제되었기 때문이었다. Effects of the surface fluorination on the electrochemical charge-discharge properties of $Mg_2$Ni electrode in Ni-MH batteries fabricated by mechanical alloying were investigated. After 20h ball milling, Mg and Ni powder formed nanocrystalline $Mg_2$Ni. Discharge capacity of this alloy increased greatly at first one cycle, but due to the formation of Mg(OH)$_2$ passive layer, it showed a rapid degradation in alkaline solution within 10cyc1es. In case of 6N KOH +xN KF electrolyte (x = 0.5, 1, 2), a continuous and stable fluorinated layer formed by adding excess F$^{-}$ ion, increased durability of $Mg_2$Ni electrode greatly and high rate discharge capability(90-100mAh/g). 2N KF addition led to the highest durability of all tested here. The reason of the improvement is due to thin MgF$_2$, which can prevent the $Mg_2$Ni electrode from forming Mg(OH)$_2$layer that is the main cause of degradation.

• 조명전기설비학회논문지
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• 제20권6호
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• pp.69-74
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• 2006

[ $Mg_2Ni$ ] 합금 및 $Mg_2Ni$와 카본 혼합물 입자의 수소저장 특성에 대한 기계적 분쇄(MG, Mechanical Grinding) 처리 효과를 고온 가스상의 PCT 측정 및 전기화학적인 마이크로 전극 측정법 등에 의해 검토되었다. PCT 측정은 약 $300[^{\circ}C]$의 고온에서 실시되었으며 전기화학적인 실험은 카본-섬유로 구성된 마이크로 전극을 1M KOH 수용액 속에서 조정자를 사용하여 MG 처리한 합금 단일입자에 접촉시켰다. 그 결과 $Mg_2Ni$ 합금과 카본 혼합물 입자의 경우 가스상에서 수소 해리압이 감소하고 상온에서 전기화학적인 수소화 특성이 크게 개선되었다. 이것은 기계적 분쇄(MG) 작용에 의한 합금의 미세화 및 나노화에 기인한다고 판단된다. 즉 고온 가스상의 PCT 측정 결과 수소 해리압이 MG 처리에 의해 0.55[MPa]에서 0.42[MPa]로 감소하였으며 동일 샘플 입자에 대해 마이크로 전극에 의한 평가에서도 수소화 피크가 보다 분명하게 관찰되었다.

• 대한금속재료학회지
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• 제50권12호
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• pp.949-953
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• 2012

$MgH_2$ was employed as a starting material instead of Mg in this work. A sample with a composition of 94 wt% $MgH_2-6$ wt% Ni (called $MgH_2-6Ni$) was prepared by reactive mechanical grinding. The hydriding and dehydriding properties were then examined. An $MgH_2-Ni$ hydrogen storage alloy that does not require an activation process was developed. The alloy was prepared in a planetary ball mill by grinding for 4 h at a ball disc revolution speed of 250 rpm under a hydrogen pressure of about 12 bar. The sample absorbed 3.74 wt% H for 5 min, 4.07 wt% H for 10 min, and 4.41 wt% H for 60 min at 573 K under 12 bar $H_2$, and desorbed 0.93 wt% H for 10 min, 1.99 wt% H for 30 min, and 3.16 wt% H for 60 min at 573 K under 1.0 bar $H_2$. $MgH_2-6Ni$ after reactive mechanical grinding contained ${\beta}-MgH_2$ (a room temperature form of $MgH_2$), Ni, ${\gamma}-MgH_2$ (a high pressure form of $MgH_2$), and a very small amount of MgO. Reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation, and to reduce the particle size of Mg. $Mg_2Ni$ formed during reactive mechanical grinding also increases the hydriding and dehydriding rates of the sample.

• 한국주조공학회지
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• 제17권2호
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• pp.158-163
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• 1997

Properties of $Al_{86}Ni_6Ce_4Mg_4$ alloy powder produced by helium gas atomization process were investigated by using DSC, XRD, SEM and TEM. The powders below 32 ${\mu}m$ in diameter were identified as an amorphous phase mixed with a ${\alpha}-Al$ phase. $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy was manufactured by hot extruding the alloy powders at various temperatures, and the estimation of its mechanical properties was carried out subsequently. As a result, the bulk alloy extruded at the temperature below $450^{\circ}C$ exhibited the microstructure in which the near-spherical shape of some powders below 20 ${\mu}m$ were nearly unchanged and fine voids between matrix and powders were formed during extrusion process. On the other hand, the tensile strength and elongation at room temperature for $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy extruded at $450^{\circ}C$ were 750 MPa and 7.5%, respectively.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2005년도 수소연료전지공동심포지움 2005논문집
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• pp.335-340
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• 2005

Amorphous $MgNi_{1-x}Ti_x$ alloys with the composition of x=0.02, 0.03, 0.05 and 0.07 were synthesized by mechanical alloying. The synthesized alloys were investigated by electrochemical test, XRD and SEM. As increasing Ti concentration, the initial discharge capacity was raised more than that of nanocrystalline Mg-Ni 289 mAh/g, but the electrodes were degraded faster. Comparing to other synthesized alloys, $MgNi_{0.95}Ti_{0.05}$ alloy showed the highest initial discharged capacity 474 mAh/g and maintained $54\%$ of the initial capacity after 10 cycles.

• 대한금속재료학회지
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• 제49권4호
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• pp.298-303
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• 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 $H_{2}$.

• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.123-128
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• 2010

Hydriding combustion synthesis (HCS) can produce full hydrides of alloys and in a short time. The conventional process based on ingot metallurgy cannot produce Mg-based alloy easily with the desired composition and the cast product needs a ling activation process for the practical use of hydrogen storage. In this study, the hydriding properties of Mg-xNi (x=5, 13.5, 54.7wt.%) alloys prepared by hydriding combustion synthesis were evaluated. The hydrogen storage capacity and kinetics of HCS Mg-xNi alloys were strongly dependent on the content of Ni. The HCS Mg-13.5wt.%Ni alloy shows the hydriding behavior to reach the maximum capacity within 30 min. and the reversible $H_2$ storage of 5.3wt.% at 623 K.

• 한국표면공학회지
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• 제22권4호
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• pp.179-184
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• 1989

This study seeks to the morphological changes in the oxide skin of the Al-10wt.%si alloy melts. These changes depend on the oxidation time and the temperature of the molten alloy, as well as the effects of adding Mg, Cu and Ni. Thess affects observed by X-ray diffractometer(XRD) and scanning electron microscope(SEM)' Very litte oxide skins on Al-10wtwt.%Si alloy melts can be detected by XRD because it is less than the measuring capabillity of the XRD, or the formation of noncrystalline oxide skins oxide skins canbe deteced by SEM. The addition of 1%Mg and 1%Cu-1%Mg-2.5%Ni to this base alloy crystallized the structure of the oxide skins and increased the oxidation in proportion to the length of time, but adding 3% had hardiy anyaffect at all on the crystal structure of the oxide skins.

• 대한금속재료학회지
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• 제50권2호
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• pp.171-175
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• 2012

By measuring the absorbed hydrogen quantity as a function of the number of cycles, the cycling properties of the Mg-15 wt%Ni-5 wt%$Fe_2O_3$ alloy were investigated. The absorbed hydrogen quantity decreased as the number of cycles increased. The $H_a$ value varied almost linearly with the number of cycles. The maintainability of absorbed hydrogen quantity at n=100 was 89.0% for the hydriding reaction time of 10 min. After the $150^{th}$ hydriding-dehydriding cycle, Mg, $Mg_2Ni$, $Mg(OH)_2$, MgO, and Fe were observed. The phases were analyzed by Rietveld analysis from the XRD patterns of the Mg-15 wt%Ni-5 wt%$Fe_2O_3$ alloy after 150 hydriding-dehydriding cycles. The crystallite size and strain of Mg were then estimated with the Williamson-Hall technique.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 1999년도 제3회 총회 및 추계학술발표회
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• pp.51-51
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• 1999