• 한국레이저가공학회지
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• 제3권2호
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• pp.13-24
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• 2000

The weldability of dissimilar materials between sintered materials which are consisted of Co, Co＋Ni and carbon steel has been investigated using CO$_2$ laser. Autogeneous CO$_2$ laser welding were run along the butt between two alloys using sets of parameters variation-power and travel speed. In order to study weldability, mechanical tests (bending strength test, microhardness test) and metallurgical analyses (microstructure, phase transformation, fracture mode) were carried out. From the results obtained, it was found that the porosity which exists in a weld metal greatly affects the soundness of the weld. The optimum energy input to have a proper strength over than the requirement by a specification, found to be around 0.3-0.35kJ/m. There are two kinds of fracture mode in the weld metal, depending upon alloy combination, brittle fracture in the case of Co-carbon steel and a ductile fracture in the case of Co＋Ni-carbon steel. In general, Co＋Ni sintered material showed a better weld properties as compared to the Co sintered material.

• 한국결정성장학회지
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• 제10권1호
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• pp.17-22
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• 2000

수직보자력이 크고 CoCrPt에 비하여 noise 저감 효과가 큰 것으로 알려진 CoCrPtTa계 합금박막의 수직이방성을 더욱 개선하기 위해 Ti를 우선 증착하였다. 본 연구에서는 Ti 두께 변화에 따른 비교적 높은 수직보자력치를 보였던 $CoCr_{16.2}Pt_{10.8}Ta_4$Ti/glass 시편에서 자기적 특성과 자구형상의 변화를 살펴보았다. 또한 VSM(Vibrating Sample Magnetometer)을 이용하여 M-H loop를 측정하였으며 자구형상은 MFM(Magnetic Force Microscopy)로 관찰하였다. 육방정 Ti가 하지층으로서 우선증착되면 bare glass 직접 증착되는 경우보다 CoCrPtTa 자성층의 수직이방성에 현저한 향상을 가져왔으며 Ti의 두께가 두꺼울수록 c-축 배향성도 개선되었다. MFM 결과에 의하면 Ti두레가 20 nm에서 90 nm로 증가함에 따라 자구형상이 연속적인 stripe type에서 mass type으로 분절된 형태로 변하였다. 이는 Ti의 증착이 비자성 Cr 편석 거동에 영향을 미쳐 자화반전시 인접 columnar grain의 자화벡터들간의 상호교환작용을 억제하는 자기적 분리 효과에 기여했음을 의미한다. 아울러 이와 같은 거동은 Ti가 CoCr계 자성층의 수직이방성을 개선하는데 있어서 형상자기이방성적인 측면에서의 기여가 현저함을 의미하기도 한다.

• 한국주조공학회지
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• 제25권1호
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• pp.30-35
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• 2005

The structures and mechanical property of the unidirectionally solidified Al-Co eutectic alloy were investigated. Al-Co eutectic alloy was unidirectionally solidified with growth rates(R) between I cm/hr and 10 cm/hr in the induction furnace maintaining the thermal gradient (G) at solid-liquid interface, $32^{\circ}C$/cm. The eutectic microstructure was varied with the growth condition(G/R ratio). When the G/R ratio was larger than $8.5{\times}10^{3}^{\circ}C/cm^{2}/sec$, a lamellar structure was formed, But the G/R ratio was smaller than $8.5{\times}10^{3}^{\circ}C/cm^{2}/sec$, a colony structure was formed. It was found that the interlamellar spacing(${\lambda}$) was dependent on the growth rate(R) with the relationship, ${\lambda}^{2}{\cdot}R=constant$. The microhardness of this eutectic alloy increased with increase in the growth rate.

• Tribology and Lubricants
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• 제25권4호
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• pp.231-235
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• 2009

In this study, the influence of contact pressure on the variation in coefficients of friction between porcine knee joint cartilage and Co-Cr alloy in a repeat pass sliding motion was investigated. Flat-ended cartilage pin specimens(9 mm diameter, 8 mm long) were prepared from porcine(6 months old) knee joints by a drill-type punch. Friction tests were conducted by using a pin-on-disk type friction tester for an hour in PBS lubricated condition under the contact pressures of 0.5, 1 and 2 MPa with 50 mm distance per a cycle at ambient condition. As a result, coefficients of friction increased as the test duration increased for all contact pressures. The maximum coefficients of friction were 0.082, 0.06 and 0.098 for 0.5, 1, and 2 MPa, respectively. It showed that coefficients of friction of porcine knee joint cartilage against Co-Cr alloy depended on the level of contact pressure and related to squeeze film lubrication mechanism.

• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.242-248
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• 2002

SnCo alloy powder prepared by high energy ball milling is examined as an anode material for lithium-ion batteries. As the ball-milling time increased, the crystallinity of SnCo decreased. XRD and TEM SADP showed that nanocrystalline and amorphous phase coexisted after 16 h ball-milling. As the crystallinity decreased, the cycleability increased. At first cycle, there are 4 plateau potentials. The observation of voltage plateau at about 0.68 V confirms the formation of Sn-Li alloy and Co metal. It is considered that The plateau potentials below 0.68 V were reaction between Li and Sn. The change of chemical diffusion coefficient showed that the structure of SnCo alloy abruptly changed at first cycle, and maintained after 2nd cycle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1485-1487
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• 1997

Platinum-Cobalt alloy thin films were deposited on $Al_2O_3$ substrates by co sputtering for RTD temperature sensors. We made Pt-Co alloy resistance patterns on $Al_2O_3$ substrate by lift-off method and investigated the physical and electrical characteristics of these films under sputtering conditions (; the input power, working vacuum), annealing conditions (; temperature, time) and also after annealing these films. After the annealing treatment at $800^{\circ}C$ for 60min, the resistivity and sheet resistivity of Pt-Co thin films was $0.0302{\mu}{\Omega}{\cdot}cm$ and $0.1{\Omega}/{\square}$, respectively, and the TCR value of Pt-Co RTD was $3600ppm/^{\circ}C$ in the temperature range of $25{\sim}400^{\circ}C$. These results indicate that Pt-Co thin films have potential for the excellent RTD temperature sensors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.128.2-128.2
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• 2013

Crucially, effective catalysts must be capable of efficiently catalyzing the protonation of adsorbed CO to adsorbed CHO or COH. One of the strategies is alloying with metals with higher oxygen affinity and Au-Zn alloy is one of the best candidates. At first, we made Au-Zn alloy using vacuum evaporating method. Zn was deposited on the Au(211) surface and the amount was estimated by X-ray photoelectron spectroscopy (XPS) using the relative sensitivity of Au 4f and Zn 3d. We investigated CO adsorption on a clean Au(211) and Au-Zn alloy using temperature-programmed desorption (TPD) and XPS. From the TPD results, we can conclude that the presence of the particular step sites at the Au(211) surface imparts stronger CO bonding and Zn atoms are sitting on the step sites at the Au(211) when Zn is deposited. The XPS results show the oxygen atoms of CO bond Zn atoms on Au-Zn surface. It should be an evidence that alloying Zn atoms that has high oxygen affinity into an electrocatalyst may allow CHO* to bind to the surface through both the carbon and oxygen atoms.

• 한국재료학회지
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• 제28권10호
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• pp.583-589
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• 2018

This study investigates the effect of fatigue stress on the damping capacity in a damaged Fe-22Mn-12Cr-3Ni-2Si-4Co damping alloy under fatigue stress. ${\alpha}^{\prime}$ and ${\varepsilon}-martensite$ forms by fatigue stress in the damaged Fe-22Mn-12Cr-3Ni-2Si4-Co damping alloy under fatigue stress. The ${\alpha}^{\prime}$ and ${\varepsilon}-martensite$ forms with the specific direction and surface relief, or they cross each other. With an increasing fatigue stress, the volume fraction of ${\alpha}^{\prime}-martensite$ and ${\varepsilon}-martensite$ increases. With an increasing fatigue stress, the damping capacity increases with an increase in the volume fraction of ${\varepsilon}-martensite$. The increase in the damping capacity in the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co alloy under fatigue stress strongly affects the increase of ${\varepsilon}-martensite$ formed by fatigue stress, but the damping capacity of the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co damping alloy under fatigue stress is strongly controlled by a large amount of ${\alpha}^{\prime}-martensite$.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2000년도 추계 기술심포지움 논문집
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• pp.57-57
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• 2000

본 논문에서는 MCM 및 패키지의 Lid로 사용되는 합금인 Kovar (Fe-Ni-Co alloy) 와 LTCC (Low Temperature Co-fired Ceramics) 간의 Brazing 특성을 연구하였다. 기존에 사용되고 있는 알루미나 패키지의 경우, 주로 80$0^{\circ}C$ 이상의 온도에서 Brazing을 실시하고 있으며, 조성은 Ag-Cu 계열을 사용하고 있다. 하지만, LTCC 의 경우, 소결온도가 85$0^{\circ}C$ 내외로서 기존의 방법을 그대로 적용하기는 어려움이 있다. 또한 Brazing 특성에 따른 접착 강도는 Brazing Alloy 의 영향뿐만 아니라 LTCC 와 전도체 전극사이의 Metallization 에 크게 영향을 받는다. 따라서, 본 논문에서는 Brazing Alloy의 종류 (Ag-Cu, Au-Sn) 및 Brazing 조건에 따른 Brazing 특성뿐만 아니라, 전도체 전극내 유리질 함량에 따른 Brazing 특성을 평가하여 LTCC/Kovar 간의 최적의 Brazing 조건을 구현하고자 하였다.

• 한국진공학회지
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• 제2권4호
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• pp.439-454
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• 1993

The phase sequence of codeposited Co-Si alloy and Co/si multilayer thin film was investigated by differential scanning calormetry(DSC) and X-ray diffraction (XRD) analysis, The phase sequence in codeposition and codeposited amorphous Co-Si alloy thin film were CoSilongrightarrow Co2Si and those in Co/Si multilayer thin film were CoSilongrightarrowCo2Silongrightarrow and CoSilongrightarrowCo2Si longrightarrowCoSilongrightarrowCoSi2 with the atomic concentration ration of Co to Si layer being 2:1 and 1:2 respectively. The observed phase sequence was analyzed by the effectvie heat of formatin . The phase determining factor (PDF) considering structural facotr in addition to the effectvie heat of formation was used to explain the difference in the first crystalline phase between codeposition, codeposited amorphous Co-Si alloy thin film and Co/Si multilayer thin film. The crystallinity of Co-silicide deposited by multitarget bias cosputter deposition (MBCD) wasinvestigated as a funcion of deposition temperature and substrate bias voltage by transmission electron microscopy (TEM) and epitaxial CoSi2 layer was grown at $200^{\circ}C$ . Parameters, Ear, $\alpha$(As), were calculate dto quantitatively explain the low temperature epitaxial grpwth of CoSi2 layer. The phase sequence and crystallinity had a stronger dependence on the substrate bias voltage than on the deposition temperature due to the collisional daxcade mixing, in-situ cleannin g, and increase in the number of nucleation sites by ion bombardment of growing surface.