• Title/Summary/Keyword: Oxygen-free copper

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Effects of Grain Morphology on Plastic Flow of Ultrafine Grained OFHC Cu (초미세립 Cu의 소성변형거동에 미치는 결정립 형상의 영향)

  • Park, L.J.;Kim, H.W.;Lee, C.S.;Park, K.T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.263-265
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    • 2009
  • In this study, ultrafine grained (UFG) oxygen free high conductivity copper (OFHC Cu) having two different grain morphologies, one the severely elongated and the other the equiaxed, was prepared by equal channel angular pressing (ECAP) with routes A and $B_c$, respectively. The results of quasi-static tensile tests at $10^{-1}\;s^{-1}$ and $1\;s^{-1}$ and dynamic compression tests at $10^3\;s^{-1}$ order revealed that the equiaxed UFG Cu exhibited higher strength and less ductility compared to the elongated one. The difference of the plastic flow characteristics between the two were rationalized by considering their dislocation mean free length based on the orientation relationship between the possible slip planes and the loading direction.

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Fabrication of YBCO films in MOD processing using F-free Y & Cu precursor solution (F-free Y & Cu 전구용액을 이용한 YBCO 박막 제조)

  • Kim, Young-Kuk;Yoo, Jai-Moo;Ko, Jae-Woong;Chung, Kook-Chae;Kim, Young-Jun;Han, Bong-Soo;Wang, X.L.;Dou, S.X.
    • Progress in Superconductivity and Cryogenics
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    • v.8 no.1
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    • pp.15-18
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    • 2006
  • A new precursor solution wilt low fluorine content was synthesized for MOD processing of coated conductors. In this study, the precursor solution for MOD processing was synthesized using F-free yttrium and copper precursor. It was shown that crack-free and uniform precursor films were formed after calcination in humidified oxygen atmosphere. Less than 2 hours were required to finish the calcination process. The relatively gradual weight loss during the calcination process is attributed to the feasibility of fast calcination profile. The calcined precursor film was converted to a YBCO film without any secondary phases after annealing in wet $Ar/O_2$ atmosphere. Fully converted film shows uniform microstructure and high critical current density. $(Jc=2.7MA/cm^2) $.

The Fabrication of the Single Crystal Wire from Cu Single Crystal Grown by the Czochralski Method and its Physical Properties (Czochralski법을 이용한 금속 단결정의 성장과 구조적, 전기적 성질에 관한 연구)

  • Park, Jeung-Hun;Cha, Su-Young;Park, Sang-Eon;Kim, Sung-Kyu;Cho, Chae-Ryong;Park, Hyuk-K.;Kim, Hyung-Chan;Jeong, Myung-Hwa;Jeong, Se-Young
    • Korean Journal of Crystallography
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    • v.16 no.2
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    • pp.141-148
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    • 2005
  • It is well known that the general metals have a lot of grain boundaries. The grain boundaries play a negative role to increase the resistivity and to decrease the conductivity. The small resistivity and the large conductivity have been a goal of the material scientists, and no signal noise, perfect signal transfer, and the realization of the real sound are the dream of electronic engineers and audio manias. Generally, oxygen free copper (OFC) and Ohno continuous casting (OCC) copper cables have been used for the purpose of the precise signal transfer and low noise. However they still include a lot of grain boundaries. In our study, we have grown the single crystal by the Czochralski method and succeeded to produce single crystal wires from the crystal in the dimension of $0.5{\times}0.5{\times}2500mm$. The produced wire still possesses very good single crystal properties. We observed the structure of the wire, and measured the resistance and impedance. Glow Discharge Spectrometer (GDS) was used for analyzing the compositions of copper single crystals and commercial copper. Current-Voltage curve, resistance, total harmonic distortion and speaker frequency response were measured for comparing electrical and acoustic properties of two samples.

Laser Welding Characteristics of Aluminum and Copper Sheets for Lithium-ion Batteries (자동차 이차전지 제조를 위한 알루미늄과 무산소동의 레이저 용접특성)

  • Kang, Minjung;Park, Taesoon;Kim, Cheolhee;Kim, Jeonghan
    • Journal of Welding and Joining
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    • v.31 no.6
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    • pp.58-64
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    • 2013
  • Several joining methods involving resistance welding, laser welding, ultrasonic welding and mechanical joining are currently applied in manufacturing lithium-ion batteries. Cu and Al alloys are used for tab and bus bar materials, and laser welding characteristics for these alloys were investigated with similar and dissimilar material combinations in this study. The base materials used were Al 1050 and oxygen-free Cu 1020P alloys, and a disk laser was used with a continuous wave mode. In bead-on-plate welding of both alloys, the joint strength was higher than the strength of O tempered base material. In overlap welding, the effect of welding parameters on the tensile shear strength and bead shape was evaluated. Tensile shear strength of overlap welded joint was affected by interfacial bead width and weld defect formation. The tensile-shear specimen was fractured at the heat affected zone by selecting proper laser welding parameters.

Dimerization of tert-Butylmercaptan over the Surface of Aerosil? Impregnated with Copper and Manganese

  • Park, Dong Geon;Park, Seon Hui;Lee, Su Jin
    • Bulletin of the Korean Chemical Society
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    • v.21 no.7
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    • pp.715-719
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    • 2000
  • A ceramic powder of destructive adsorbent was synthesized by impregnating copper and manganese on the surface of silica aerosil@. In-site FTIR measurements on pulses of malodorant tert-butylmercaptan injected over the powder showed that rert-butylmercaptan dimerized into di-tert-hutyldisulfide on the surface of the adsorbent in an ambient condition. GC/MS measurement on the gas over the adsorbent showed no tert-butylmercaptan remaining, and showed only the dimerization product of di-tert-butyldisulfide. Most of the dimerization product, di-tert-butyldisulfide,remained on the surface of the adsorbent as physisorbed condense, and apparently Iowered the destruction efficiency by blocking the surface from the access by tert-butylmercaptan. Upon being heated above $100^{\circ}C$ it was observed that the physisorbed di-tert-butyldisulfide dissociated back into tert-butylmercaptan. tert-butylmercaptan physisorbed on the activated carbon, thereby no dimerization was occurring on the surface of the activated carbon. In an argn environment, the dimerization reaction was practically not occurring even on the surface of the adsorbent, indicating the free oxygen in air was also participating in the dimerization reaction. Water was identified as a by-product of the dimerization reaction. Possible reactions on the surface of the adsorbent were proposed.

Design & Animal Experiment of Artificial Oxygenator (인공폐(산화기) 제작과 실험)

  • 김형묵
    • Journal of Chest Surgery
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    • v.15 no.2
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    • pp.259-265
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    • 1982
  • We have designed a new type of bubble oxygenator (KOREA-KIM VENOTHERM OXYGENATOR) made of PVC sheet and deforming mesh incorporated in the heat exchanger, and evaluated in experimental animal for the analysis of it`s efficiency. The Oxygenator has low priming volume with high flow rate up to 6 L/rain, and efficiency of heat exchanger was excellent as 1-$1.5^{\circ}C.$ using total cardiopulmonary bypass method under moderate to deep hypothermia. Average priming volume of 1317 ml with 30% hemodilution method was perfused with an average of 1.1-3.0 L/min.$M^2$of arterial blood and pure oxygen at a rate of 2-3.4 L/min for 49.6 minutes continuously in average. During total cardiopulmonary bypass, average $PaO_2$ was $159.8{\pm}60$mmHg, $PaCO_2$ $41.0{\pm}3$mmHg respectively under $SaO_2$ over 96% with systolic arterial pressure of 70 mmHg and CVP of 5-10 cm$H_2O$. Plasma free Hemoglobin was $7.0{\pm}4$ mg/dl with 25% drop of hemoglobin and hematocrit at the end of cardiopulmonary bypass. This KKV Oxygenator was observed to have excellent capabillty of oxygen and carbon dioxide gas transfer with small amount of blood trauma, and the efficiency of heat exchanger was satisfactory during cooling and rewarming of the bubbled blood. Disadvantages have included the somewhat poor deforming effect due to loose PVC fiber mesh, the extracompact character of Teflon filters, and the rough inner surface of the heat exchanger copper pipes.

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New technology Trends on Friction Stir Welding Based on Milling Process in terms of Tools, Machine and Applied Parts (밀링기반 마찰교반접합 신기술동향: 공구, 장비 및 응용부품)

  • Noh, Joong-Suk;Kim, Ju-Ho;Go, Gun-Ho;Kang, Myung-Chang
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.12 no.6
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    • pp.37-44
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    • 2013
  • Friction stir welding (FSW) is a solid state joining technique that has expanded rapidly since its development in 1991 and has numerous applications in a wide variety of industries. This paper introduces the basic principles of friction stir welding (FSW) and presents a survey of the latest technologies and applications in the field. The basic principles that are discussed include the terminology, tool/workpiece processes, FSW merits and process variants. In particular, the process variants including the rotation speed and traveling speed are discussed, which include the defect-free zone in an oxygen free copper and Al alloy, respectively. Multiple aspects of the FSW machine are developed, including a horizontal 2D FSW machine and a hybrid complex FSW machine. The latest applications are introduced, with an emphasis on the recent advances in the aerospace, automotive, and IT display industries. Finally, the direction for future research and potential applications are examined.

Comparison of Microstructure and Hardness of Pure Copper Fabricated by Multi-Axial Forging and Multi-Axial Diagonal Forging (다축단조와 다축대각단조로 제조된 순동의 미세조직 및 경도 비교)

  • Lee, J.K.;Kwon, S.C.;Kim, S.T.;Jeong, H.T.;Kim, Y.G.;Park, S.H.
    • Transactions of Materials Processing
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    • v.28 no.5
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    • pp.257-265
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    • 2019
  • Multi-axial forging (MAF), a severe plastic deformation technique, is known to be difficult to obtain materials with homogeneous microstructures. Recently, multi-axial diagonal forging (MADF) process has been developed to solve this problem. In this study, in order to compare the microstructural and mechanical homogeneities of the MAFed and MADFed samples, oxygen-free copper (OFC) cubes measuring 25 mm in length were deformed through MAF and MADF processes and the average grain size and hardness were measured at the edge, face, and center regions of the samples. In the MAFed samples, ultrafine grains were formed at the center region, but a considerable amount of coarse grains remain at the face region. Therefore, the MAFed samples showed a high inhomogeneity in regards to grain size and hardness. On the contrary, in the case of the MADFed sample, the grain sizes at the edge, face, and center regions were similar and the hardness in all the regions are almost similar. This indicates that the MADFed sample has a homogeneous microstructure and uniform mechanical properties, which can be attributed to the homogeneous distribution of the effective strain throughout the material. The results of this study suggests that the MADF is a suitable process in the fabrication of high-strength copper materials with a homogeneous and ultrafine grain structure.

Mechanical Properties of OFC Copper Fabricated by Multi-Axial Diagonal Forging (MADF) (다축대각단조(MADF) 가공한 구리의 기계적 성질)

  • Kwon, S.C.;Kim, S.T.;Kim, D.V.;Lee, J.K.;Seo, S.J.;Yoon, T.S.;Jeong, H.T.
    • Transactions of Materials Processing
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    • v.27 no.4
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    • pp.250-256
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    • 2018
  • Oxygen-free copper (OFC) was prepared as a 90 mm cube and then processed with Multi-Axial Diagonal Forging - Initialization of Prior manufacturing History (MADF). The MADF process has been newly developed as a severe plastic deformation method. The MADF process consists of upset forging with a thickness reduction of 30% and diagonal forging with a diagonal angle of $135^{\circ}$. 1 cycle process consists of a 12 passes forging process. In order to analyze the characteristic changes according to the number of iterations, 1, 2, and 3 cycles of the MADF process were performed. The OFC specimens were MADF processed without surface cracks up to 3 cycles. The microstructure, hardness and tensile test of processed materials were analyzed to study the change of material properties according to the amount of MADF process. The results showed that the MADF process effectively refined the microstructure and increased the strength of OFC. In the case of specimens processed for more than 2 cycles, the grains of all measurement regions were refined to be less than $7{\mu}m$ of grain size. The 1 cycle MADF processed OFC showed the highest mechanical properties with the hardness of 132 HV and tensile strength of 395 MPa. Hardness and strength seemed to be saturated when processed over 2 cycles.

Dynamic Deformation Behavior of Ultra-Fine-Grained Pure Coppers Fabricated by Equal Channel Angular Pressing (ECAP으로 제조된 초미세립 순동의 동적 변형거동)

  • Kim, Yang Gon;Hwang, Byoungchul;Lee, Sunghak;Lee, Chul Won;Shin, Dong Hyuk
    • Korean Journal of Metals and Materials
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    • v.46 no.9
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    • pp.545-553
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    • 2008
  • Dynamic deformation behavior of ultra-fine-grained pure coppers fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four copper specimens using a torsional Kolsky bar, and then the test data were analyzed by their microstructures and tensile properties. The 1-pass ECAP'ed specimen consisted of fine dislocation cell structures elongated along the ECAP direction, which were changed to very fine, equiaxed subgrains of 300~400 nm in size as the pass number increased. The dynamic torsional test results indicated that maximum shear stress increased with increasing ECAP pass number. Adiabatic shear bands were not found at the gage center of the dynamically deformed torsional specimen of the 1- or 4-pass ECAP'ed specimen, while some weak bands were observed in the 8-pass ECAP'ed specimen. These findings suggested that the grain refinement according to the ECAP was very effective in strengthening of pure coppers, and that ECAP'ed coppers could be used without serious reduction in fracture resistance under dynamic torsional loading as adiabatic shear bands were hardly formed.