• Title/Summary/Keyword: Zr Alloys

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A Study on the Electrode Characteristics of a New High Capacity Non-Stoichiometry Zr-Based Laves Phase Alloys for Anode Materials of Ni/MH Secondary Battery

  • Lee Sang-Min;Yu Ji-Sang;Lee Ho;Lee Jai-Young
    • Journal of the Korean Electrochemical Society
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    • v.3 no.2
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    • pp.72-75
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    • 2000
  • For the purpose of developing the non-stoichiometric Zr-based Laves phase alloy with higher capacity and better performance for electrochemical application, extensive work has been carried out in KAIST. After careful alloy design of $ZrMn_2-based$ hydrogen storage alloys through varing their stoichiometry while susbstituting or adding some alloying elements, the $Zr-Ti-(Lh-V-Ni)_{2.2},\;Zr-Ti-(Mn-V-Cr-Ni)_{1.8\pm0.1}$ with high capacity and better performance was developed. Consequently the $Zr-Ti-(Mn-V-Ni)_{2.2}$ alloy has a high discharge capacity of 394mAh/g and shows a high rate capability equaling to that of commercialized $AB_5$ type alloys. On the other hand, in order to develop the hydrogen storage alloy with higher discharge capacity, the hypo-stoichiometric $Zr(Mn-V-Ni)_{2-\alpha}$ alloys substituted by Ti are under developing. As the result of competitive roles of Ti and $stocihiometry({\alpha})$, the discharge capacity of $Zr-Ti-(Mn-V-Cr-Ni)_{l.8\pm0.1}$ alloys is about 400mAh/g(410 mAh/g, which shows the highest level of performance in the Zr-based alloy developed. Our sequential endeavor is improving the shortcoming of Zr-based Laves phase alloy for commercialization, i.e., poor activation property and low rate capability, etc. It is therefore believed that the commercialization of Zr-based Laves phase hydrogen storage alloy for Ni-MH rechargeable battery is in near future.

Effects of Fe and Si Additions on the Ageing Behaviors for High Strength Al-Cu-Mn-Ti-Zr-Cd Casting Alloys (Fe과 Si의 첨가가 주조용 고강도 Al-Cu-Mn-Ti-Zr-Cd 합금의 시효경화거동에 미치는 영향)

  • Kim, Chul-Hyo;Lee, Jeong-Moo;Kim, Kyung-Hyun;Kim, In-Bae
    • Journal of Korea Foundry Society
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    • v.24 no.1
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    • pp.45-51
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    • 2004
  • Fe and Si are common impurity elements in the aluminum alloys. In this investigation, the effects of the addition of Fe and Si on the age-hardening behaviors of the Al-Cu-Mn-Ti-Zr-Cd casting alloys were examined through hardness measurements, calorimetric techniques and observation of the transmission electron microscopy. The addition of Fe depresses the formation of GPII and ${\theta}'$, and thus retards the peak aging time and reduces the peak hardness of the Al-Cu-Mn-Ti-Zr-Cd alloys. On the contrary, the addition of Si accelerates the formation of GPII and ${\theta}'$ and thus accelerates age-hardening behaviors of the Al-Cu-Mn-Ti-Zr-Cd alloys.

The Annealing Effect on Magnetocaloric Properties of Fe91-xYxZr9 Alloys

  • Kim, K.S.;Min, S.G.;Zidanic, J.;Yu, S.C.
    • Journal of Magnetics
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    • v.12 no.4
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    • pp.133-136
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    • 2007
  • We have carried out the study of magnetocaloric effect for as-quenched and annealed $Fe_{91-x}Y_xZr_9$ alloys. Samples were prepared by arc melting the high-purity elemental constituents under argon gas atmosphere and by single roller melt spinning. These alloys were annealed one hour at 773 K in vacuum chamber. The magnetization behaviours of the samples were measured by vibrating sample magnetometer. The Curie temperature increases with increasing Y concentration (x=0 to 8). Temperature dependence of the entropy variation ${\Delta}S_M$ was found to appear in the vicinity of the Curie temperature. The results show that annealed $Fe_{86}Y_5Zr_9$ and $Fe_{83}Y_8Zr_9$ alloys a bigger magnetocaloric effect than that those in as-quenched alloys. The value is 1.23 J/kg K for annealed $Fe_{86}Y_5Zr_9$ alloy and 0.89 J/kg K for as-quenched alloy, respectively. In addition, the values of ${\Delta}S_M$ for $Fe_{83}Y_8Zr_9$ alloy is 0.72 J/Kg K for as-quenched and 1.09 J/Kg K for annealed alloy, respectively.

Corrosion Characteristics of Ti alloy for Removable Partial Denture (국소의치용 티타늄 합금의 부식 특성)

  • Kim, Jeong-Jae;Kim, Won-Gi
    • The Journal of the Korea Contents Association
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    • v.14 no.4
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    • pp.237-242
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    • 2014
  • In this study, surface characteristics and corrosion behaviors have been investigated in addition to Zr elements on the low elastic modulus Ti-30Ta alloy. Low elastic modulus Ti-30Ta-xZr(x : 3, 7 and 15 wt %) alloys were prepared by arc melting and then heat treated at $1000^{\circ}C$ for 24 hrs in an argon atmosphere. Microstructures of the alloys were examined by field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). Electrochemical experiments were performed using a conventional three-electrode configuration with a sample working electrode, a high density carbon counter electrode and a saturated calomel reference electrode. According to the result of polarization behavior in the Ti-30Ta-xZr alloys, the current density of homogenized Ti-30Ta-15Zr in the passive region was lower than the other alloys.

Hydrogen Absorption Properties of Zr-V-M(M=Fe, Ga, Y) Getter Alloys (Zr-V-M(M=Fe, Ga, Y)게터합금의 수소 흡수특성)

  • Park Je-Shin;Suh Chang-Youl;Kim Won-Baek
    • Korean Journal of Materials Research
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    • v.15 no.6
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    • pp.388-392
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    • 2005
  • The $Zr_{57}V_{36}M_7$ getter alloy was prepared by Fe substituting Ga or Y for Fe on $Zr_{57}V_{36}M_7$ getter alloy(St707), and the activation temperatures and the hydrogen a sorption speeds of these alloys were investigated. The activation temperatures of these alloys were estimated from the ultimate pressure-temperature curve and lowered about $100\~200\;K$ compared to $Zr_{57}V_{36}M_7$, fetter alloy(St707). However, final pressures at fully activated temperature were increased with substitution of Fe by Ga and Y on $Zr_{57}V_{36}M_7$ getter alloy. The hydrogen sorption speeds of these alloys measured by an orifice method were decreased about $0.460\~0.586liter/sec$ g compared to $Zr_{57}V_{36}M_7$ getter alloy.

Effects of Zr, B and P Additions the Grain Refinement of CuZn36 Alloys. (CuZn36 합금의 입자 미세화에 미치는 Zr, B, P 첨가의 영향)

  • Kim, Chung-Keun;Lee, Dong-Woo
    • Journal of Korea Foundry Society
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    • v.13 no.2
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    • pp.168-174
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    • 1993
  • It has been known that the grain refinement of Cu base alloys greatly improved mechanical properties, castability, workability and hot shortness resistance etc. In this study CuZr50, CuP7, CuFe7, CuMg10 binary alloys were added as grain refiners in CuZn36 alloy. The alloys melted in vacuum and controlled in mixed gas conditions and casted at $1050^{\circ}C$. Zr-P-X compound has significantly grain refined but oxygen has been found detrimental to grain refinement. In the case of Zr /B ratio below 4, B acted as grain growth element in this alloy.

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Effect of Final Annealing Temperature on Precipitate and Oxidation of Zr- Nb Alloys (Zr-Nb계 합금의 석출물 특성과 산화 특성에 미치는 마지막 열처리 온도의 영향)

  • Yun, Yeong-Gyun;Jeong, Yong-Hwan;Park, Sang-Yun;Wi, Myeong-Yong
    • Korean Journal of Materials Research
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    • v.11 no.8
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    • pp.647-654
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    • 2001
  • Effects of final annealing temperature on the precipitate and oxidation were investigated for the Zr-lNb and Zr-lNb-lSn-0.3Fe alloys. The microstructure and oxidation of both alloys were evaluated for the optimization of final annealing process of these alloys in the annealing temperature regime of 450 to $800^{\circ}C$. The corrosion test was performed under steam at $400^{\circ}C$ for 270 days in a static autoclave. The oxide formed was identified by low angle X-ray diffraction method. The $\beta$-Zr was observed at annealing temperature above $600^{\circ}C$. Above $600^{\circ}C$, the precipitate area volume fraction of Zr-lNb and Zr-1Nb-lSn-0.3Fe alloys appeared to be increased with increasing the final annealing temperature. The corrosion resistance of Zr-lNb was higher than that of Zr- lNb-lSn-0.3Fe alloy. The corrosion rate of both alloys were accelerated due to the formation and growth of $\beta$-Zr with increasing the annealing temperature.

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A Study on the Electrochemical Hydrogenation Reaction Mechanism of the Laves Phase Hydrogen Storage Alloys (Laves phase계 수소저장합금의 전기화학적 수소화 반응 매카니즘에 관한 연구)

  • Lee, Ji-Youl;Kim, Chan-Jung;Kim, Dai-Ryong
    • Transactions of the Korean hydrogen and new energy society
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    • v.8 no.1
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    • pp.31-41
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    • 1997
  • In order to investigate the mechanism of electrochemical hydrogenation reaction on Zr-based Laves phase hydrogen storage alloy electrodes, electrochemical charge/discharge characteristics, potentiostatic/dynamic polarizations and electrocehmical impedance spectroscopy(EIS) of Zr-Ti-Mn-Ni and Zr-Ti-Mn-Ni-M(M=Fe, Co, Al) alloys were examined. Electrochemical discharge capacities of the alloys were quite different with gas charge capacities. Therefore, it was considered that discharge capacities of the alloys depend on electrochemical kinetic factors rather then thermodynamic ones. Discharge efficiencies were increased linearly with exchange current densities. The results of potentiostatic/dynamic polarization measurements showed that electrochemical charge and discharge reaction of Zr-based Laves phase hydrogen storage alloys is controlled by charge transfer process at the electrode surface. The EIS measurements also confirmed this result.

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A Calorimetric Study on the Martensitic Transformation Characteristics with Chemical Composition and Thermal Cycling in Cu-Zr Binary Alloys (Cu-Zr이원계 합금에서 화학조성 및 열싸이클링에 따른 마르텐사이트변태 특성의 열분석학적 연구)

  • Jang, W.Y.;van Humbeeck, J.;Jo, M.S.;Lee, J.H.;Lee, Y.S.;Kang, J.W.;Gwak, S.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.11 no.2
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    • pp.111-120
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    • 1998
  • The effects of chemical composition and thermal cycling on the martensitic transformation characteristics in Cu-rich, equiatomic and Zr-rich CuZr binary alloys have been studied by calorimetry. Only martensite could be indentified in equiatomic $Cu_{49.9}Zr_{50.1}$ alloy, while $Cu_{10}Zr_7$ and $CuZr_2$ intermetallic compounds as well as martensite were formed by rapid cooling from the melts in Cu-rich $Cu_{52.2}Zr_{47.5}$ alloy and Zr-rich $Cu_{48.4}Zr_{51.6}$ alloy, respectively. The $M_s$ temperature of $Cu_{49.9}Zr_{50.1}$ was $156^{\circ}C$ but those of $Cu_{52.5}Zr_{47.5}$ and $Cu_{48.4}Zr_{51.6}$ alloys, being $109^{\circ}C$ and $138^{\circ}C$, were lower than that of equiatomic $Cu_{49.9}Zr_{50.1}$ alloy. In all the alloys, the $M_s$ temperature has fallen but the $A_s$ temperature has risen, resulting in widening of the transformation hysteresis with thermal cycling. The anomalous characteristics in the transformation temperature are due to the presence of the intermetallic compounds i.e. $Cu_{10}Zr_7$ and $CuZr_2$ formed by an eutectoid reaction during thermal cycling in the temperature range between $-100^{\circ}C$ < $T_c$ < $400^{\circ}C$.

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A Study on the Hydriding Reaction of Pre-oxidized Zr Alloys (산화막을 입힌 지르코늄 합금의 수소화 반응에 관한 연구)

  • Kim, Sun-Ki;Bang, Je-Geon;Kim, Dae-Ho;Lim, Ik-Sung;Yang, Yong-Sik;Song, Kun-Woo
    • Journal of the Korean Ceramic Society
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    • v.47 no.2
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    • pp.106-112
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    • 2010
  • This paper presents some experimental results on incubation time for massive hydriding of Zr alloys with oxide thickness. Oxide effects experiments on massive hydriding reaction of commercial Zr alloy claddings and pre-oxidized Zr alloys with hydrogen gas were carried out in the temperature range from 300 to $400^{\circ}C$ with thermo-gravimetric apparatus. Experimental results for oxide effects on massive hydriding kinetics show that incubation time is not proportional to oxide thickness and that the massive hydriding kinetics of pre-filmed Zr alloys follows linear kinetic law and the hydriding rate are similar to that of oxide-free Zr alloys once massive hydriding is initiated. There was a difference in micro-structures between oxide during incubation time and oxide after incubation time. Physical defects such as micro-cracks and pores were observed in only oxide after incubation time. Therefore, the massive hydriding of Zr alloys seems to be ascribed to short circuit path, mechacical or physical defects, such as micro-cracks and pores in the oxide rather than hydrogen diffusion through the oxide resulting from the increase of oxygen vacancies in the hypostoichiometric oxide.