• Title/Summary/Keyword: Ni variation

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THE CONTROL OF PERMITTIVITY IN THE Ni-Zn FERRITE ABSORBER

  • Cho, S.B.;Oh, J.H.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.730-734
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    • 1995
  • The variation of magnetic permeability and dielectric constant and their relationship with microwave absorbing properties are investigated in sintered Ni-Zn ferrite. Toroid specimens of ${(Ni_{0.5}Zn_{0.5}O)}_{1-y}{(Fe_{2}O_{3})}_{1+y}$ ferrites are prepared by conventional ceramic processing technique. The large change in magnetic permeability is observed by the variation of excess $Fe_{2}O_{3}$ in the Ni-Zn ferrites. The more the iron-excess from y=0.04 to y=0.12, the lower value of both $\mu_{r}'$ and $\mu_{r}"$ is observed. However dielectric permittivity increases with the increase of the increase of the excess $Fe_{2}O_{3}$. The control of permittivity is realized by nitrogen sintering atmosphere and excess $Fe_{2}O_{3}$ respectively.

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The study of magnetoresistance and magnetic properties in [(CoO/NiO)/NiFe/Cu/NiFe] spin-valve thin films ([(CoO/NiO)/NiFe/Cu/NiFe] spin-valve 박막에서의 자기저항효과와 자기적 특성에 대한 연구)

  • 현준원
    • Electrical & Electronic Materials
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    • v.9 no.10
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    • pp.1060-1065
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    • 1996
  • We have studied the magnetoresistance phenomena on spin valve thin films of antiferromagnetic NiO/CoO. Interlayer coupling oscillates between the antiferrocoupling and ferrocoupling with the variation of Cu thickness. The exchange coupling strength between NiO (antiferromagnetic) and NiFe(ferromagnetic) as a function of NiO texture and interface roughness is investigated by CoO insertion. CoO has significantly higher anisotropy in the (111) plane and interface roughness. It seems that the MR-ratio is increased by CoO inserted films. From the AFM and XRD data, the increase of MR-ratio and exchange field is influenced by the roughness of CoO.

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Local Structure Study of Ni in Ni-Zn Alloy Coating on Steel by X-ray Absorption Spectroscopy (X선 흡수 분광법을 이용한 Ni-Zn 도금 강판에서의 Ni의 국부 구조에 관한 연구)

  • Lee, Do-Hyung
    • Analytical Science and Technology
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    • v.11 no.3
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    • pp.202-205
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    • 1998
  • X-ray absorption fine structure spectroscopic studies at the Ni K-edge have been performed for the Ni-Zn alloy coating layer on steel. The Ni-Zn interatomic distances and Debye-Waller factors were determined by fitting the experimental data with the theoretical spectra in the temperature range of 80 to 300K. The average Ni-Zn interatomic distance was found to be $2.557{\AA}$ and the variation of the Ni-Zn interatomic distance with temperature in this range was insignificant. From the comparison of the Ni-Zn interatomic distance with the nearest neighbor distance of pure Zn lattice it has been suggested that there is an apparent contraction around Ni atom.

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The Variation of Fracture Strength and Modes in $ZrO_2/NiTi$ Bond by Changing Reaction Layer ($ZrO_2/NiTi$ 접합부 반응조직에 따른 꺽임강도 및 파괴거동 변화)

  • 김영정
    • Journal of the Korean Ceramic Society
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    • v.31 no.10
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    • pp.1197-1201
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    • 1994
  • The fracture strength and fracture modes were studied in 3Y-TZP/NiNi bonding which change their interfacial structure with bonding condition. Average 4-point bending strength of 200 MPa to 400 MPa were achieved. The formation of Ti-oxide phase at the interface critically influenced the bonding strength and fracture mode. The fracture surface of Ti-oxide free interface contained multiphase in some case including ZrO2. From the result it was confirmed that in order to maximize the bonding strength crack deflection from interface to ceramic was required.

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Fabrication and Interface Properties of TiNi/6061Al Composite (TiNi 형상기억합금을 이용한 복합재료의 제조 및 계면 특성)

  • Kim, Sun-Guk;Lee, Jun-Hui
    • Korean Journal of Materials Research
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    • v.9 no.4
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    • pp.419-427
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    • 1999
  • TiNi shape memory alloy was shape memory heat-treated and investigated its mechanical properties with the variation of prestrain. Also 6061 Al matrix composites with TiNi shape memory alloy fiber as reinforcement have been fabricated by Permanent Mold Casting to investigate the microstructures and interface properties. Yield stress of TiNi wire was the most high in the case of before heat-treatment and then decreased as increasing heat-treatment time. In each heat-treatment condition, the yield stress of TiNi wire was not changed with increasing the amount of prestrain. The interface bonding of TiNi/6061Al composite was fine. There was a 2$\mu\textrm{m}$ thickness of diffusion reaction layer at the interface. We could find out that this diffusion reaction layer was made by the mutual diffusion. The diffusion rate from Al base to TiNi wire was faster than that of reverse diffusion and the amount of the diffusion was also a little more than that of reverse.

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Composition, preferred orientation and magnetic properties of Ni-Fe-Co alloy electrodeposits (Ni-Fe-Co 박막도금층의 조성, 우선배향 및 자기적 성질)

  • 예길촌;김선윤;문근호;김용웅
    • Journal of the Korean institute of surface engineering
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    • v.28 no.6
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    • pp.352-360
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    • 1995
  • The effect of electrolysis conditions on the composition, the magnetic properties and the preferred orientation of Ni-Fe-Co alloy deposits was investigated using the sulfate-chloride bath paddle agitated. Cathode current efficiency increases with the current density, showing the different tendency of the variation from that of the Ni-Fe electrodeposits. The Co content of the deposits decreases with increasing current density, while the content of Ni and Fe is shown to be minimum or maximum at 3A/$dm^2$ respectively. The Ni/Fe ratio of the alloy deposits is lower than that of Ni-Fe deposits. The coercive force($H_c$) of the deposits increases with the Co content in deposit, showing the relatively low value in the range of 1.8~5.0Wt.% Co. The anisotropy field ($H_k$) of the deposits is higher than that of Ni-Fe alloy deposits, The preferred orientation of the deposits is generally (200), but the orientation factor(R) changes with both the increase of current density and the magnetic field applied during deposition.

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A Study on the Thermal Stability of Unidirectionally Solidified Eutectic Composites of Ni-Base Superalloys (일방향 응고한 Ni기 초내열 공정복합재료의 열적 안정성에 관한 연구)

  • 이현규;공창덕
    • Journal of the Korean Society of Propulsion Engineers
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    • v.2 no.1
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    • pp.67-77
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    • 1998
  • Homogeneous liquids of Ni-21.5Nb-2.5Al and Ni-23.3Nb eutectic superalloys were solidified into Ni/$Ni_3$Al-$Ni_3$Nb(${\gamma}$/${\gamma}$'-${\delta}$)and Ni-Ni/$Ni_3$Nb(${\gamma}$-${\delta}$) phase by directional solidification and the effect of interlamellar spacing on microsturctural stability at high temperatures, hardness variation with growth rate was studied. The interlamellar spacing(${\lambda}$) in the eutectics was varied with the growth rate(R), corresponding to "${\lambda}^2$R =Constant" relationship. Isothermal heat treatments of the eutectics used in this study, provided the microstructural stability improvement at hight temperature as the interlamellar spacing increases. It was also seen that the hardness improvement is made with the growth raterowth rate

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A Study on the Microscopic Damage Behavior and the Damage Position Evaluation of TiNi/Al6061 Share Memory Alloy Composite (TiNi/A16061 형상기억복합재료의 미시적 손상거동과 손상위치측정에 관한 연구)

  • Lee, Jin-Gyeong;Park, Yeong-Cheol;Gu, Hu-Taek;Lee, Gyu-Chang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.9
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    • pp.1787-1794
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    • 2002
  • TiNi alloy fiber was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber improves the tensile strength of composite by occurring compressive residual stress in the matrix using shape memory effect. In order to generate compressive residual stress in TiNi/Al6061 shape memory alloy(SMA) composite, 1, 3 and 5% pre-strains were applied to the composite in advance. It was also evaluated the effect of compressive residual stress corresponding to the pre-strain variation and the volume fraction of TiNi alloy. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain in TiNi/Al6061 SMA composite. The results of the microscopic damage evaluation of TiNi/Al6061 SMA composite under various pre-strain using AE technique can be divided into three stage corresponding to the AE signals. AE counts and events were useful parameters to evaluate the fracture mechanism according to the variation of pre-strain. In addition, two dimensional AE source location technique was applied for monitoring the crack initiation and propagation in composite.

Physical Oceanographic Characteristics between Hawaii and Chuuk Observed in Summer of 2006 and 2007 (2006년과 2007년 여름에 관측한 Hawaii-Chuuk 사이의 물리특성)

  • Shin, Chang-Woong;Kim, Dong-Guk;Jeon, Dong-Chull;Kim, Eung
    • Ocean and Polar Research
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    • v.33 no.spc3
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    • pp.371-383
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    • 2011
  • To investigate the physical characteristics and variations of oceanic parameters in the tropical central North Pacific, oceanographic surveys were carried out in summer of 2006 and 2007. The survey periods were classified by Oceanic Ni$\tilde{n}$o Index as a weak El Ni$\tilde{n}$o in 2006 and a medium La Ni$\tilde{n}$a in 2007. The survey instruments were used to acquire data on CTD (Conductivity Temperature and Depth), XBT (Expendable Bathythermograph), and TSG (Thermosalinograph). The dominant temporal variation of surface temperature was diurnal. The diurnal variation in 2007, when the La Ni$\tilde{n}$a weather pattern was in place, was stronger than that in 2006. Surface salinity in 2006 was affected by a northwestward branch of North Equatorial Current, which implies that the El Ni$\tilde{n}$o affects surface properties in the North Equatorial Current region. Two salinity minimum layers existed at stations east of Chuuk in both year's observations. The climatological vertical salinity section along $180^{\circ}E$ shows that the two salinity minimum layers exist in $2^{\circ}N{\sim}12^{\circ}N$ region, consistent with our observations. Analysis of isopycnal lines over the salinity section implies that the upper salinity minimum layer is from intrusion of the upper part of North Pacific Intermediate Water into the lower part of South Pacific Subtropical Surface Water and the lower salinity minimum layer is from Antarctic Intermediate Water.