• Title/Summary/Keyword: Oxygen-free copper

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Fabricatiion and Characterization of ${Bi_2}{Sr_2}{CaCu_2}{O_8}$ Superconductor Thick Films on Cu Substrates using Cu-free Precursors (Cu-free 전구체를 이용하여 구리 기판 위에 ${Bi_2}{Sr_2}{CaCu_2}{O_8}$ 초전도 후막의 제조 및 특성)

  • 한상철;김상준;한영희;성태현;한병성
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.4
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    • pp.349-358
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    • 2000
  • Fabrication and Characterization of Bi$_{2}$/Sr$_{2}$/CaCu$_{2}$/O$_{8}$(Bi2212) superconductor thick films were fabricated successfully on C tapes by liquid reaction between Cu-free precursors of Bi$_{x}$/SrCaO/$_{y}$(x=1.2-2) and Cu tapes. Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-87$0^{\circ}C$ for several minutes in air oxygen nitrogen and low oxygen pressure. In order to obtain the optimum heat-treatment condition we studied the effect of the precursor composition the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism. Microstructures and phases of thick films were analyzed by films and the reaction mechanism. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superonducting films were examined by the four probe method. At heat-treatment temperature the thick films were in a partially molten state by liquid reaction between CuO of the oxidized copper tape and the precursors which were printed on Cu tapes. During the heat-treatment procedure Bi2212 superconducting particle nucleate and grow in preferred orientations.ons.s.

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Change in Microstructure and Mechanical Properties of Deoxidized Low-Phosphorous Copper Processed by Accumulative Roll-Bonding with Annealing (ARB가공된 인탈산동의 어닐링에 따른 미세조직 및 기계적 특성 변화)

  • Lee, Seong-Hee;Kim, Chun-Su;Kim, Sang-Shik;Han, Seung-Zeon;Lim, Cha-Yong
    • Korean Journal of Materials Research
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    • v.17 no.7
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    • pp.361-365
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    • 2007
  • A deoxidized low-phosphorous copper processed by eight cycles of accumulative roll-bonding (ARB) was annealed at various temperatures ranging from 100 to $400^{\circ}C$. The annealed copper was characterized by transmission electron microscopy (TEM) and tensile & hardness test. TEM observation revealed that the ultrafine grains developed by the ARB still remained up to $350^{\circ}C$, however above $400^{\circ}C$ they were replaced by equiaxed and coarse grains due to an occurrence of the static recrystallization. The hardness of the copper decreased slightly with the annealing temperature up to $350^{\circ}C$, however they dropped largely above $400^{\circ}C$. Annealing characteristics of the copper were compared with those of an oxygen free copper processed by ARB and subsequently annealed.

The Fabrication of Low Cost High Temperature Superconducting Tape (저비용 고온초전도 선재 제조 연구)

  • 한상철;성태현;한영희;이준성;이영우;정년호;김상준
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2000.02a
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    • pp.85-88
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    • 2000
  • Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-$870^{\circ}C$ for several minutes in air, oxygen, nitrogen and low oxygen pressure. Cu-free precursors were composed of Bi_{x}$SrCaO_{y}$ (x=1.2-2). In order to obtain the optimum heat-treatment condition, we studied on an effect of the precursor composition, the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism of their rapid formation. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superconducting films were examined by the four probe method. At heat-treatment temperature, the thick films were in a partially molten state by liquid reaction between CuO in the oxidized copper tape and the precursors which were printed on Cu tapes.

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Characterization of Low-cycle Fatigue of Copper and Isothermal Aging of 2.25Cr Ferritic Steel by Ultrasonic Nonlinearity Parameter (초음파 비선형파라미터를 이용한 무산소동 저주기피로와 2.25Cr 페라이트강의 등온열화 평가)

  • Kim, Chungseok
    • Journal of the Korean Society for Heat Treatment
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    • v.35 no.5
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    • pp.239-245
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    • 2022
  • The purpose of this study is to evaluate the degree of microstructural change of materials using ultrasonic nonlinear parameters. For microstructure change, isothermal heat-treated ferritic 2.25Cr steel and low-cycle fatigue-damage copper alloy were prepared. The variation in ultrasonic nonlinearity was analyzed and evaluated through changes in hardness, ductile-brittle transition temperature, electron microscopy, and X-ray diffraction tests. Ultrasonic nonlinearity of 2.25Cr steel increased rapidly during the first 1,000 hours of deterioration and then gradually increased thereafter. The variation in non-linear parameters was shown to be coarsening of carbides and an increase in the volume fraction of stable M6C carbides during heat treatment. Due to the low-cycle fatigue deformation of oxygen-free copper, the dislocation that causes lattice deformation developed in the material, distorting the propagating ultrasonic waves, and causing an increase in the ultrasonic nonlinear parameters.

Predictions of Fatigue Life of Copper Alloy for Regenerative Cooling Channel of Thrust Chamber (연소기 재생냉각 채널용 구리합금의 피로수명예측)

  • Lee, Keumoh;Ryu, Chulsung;Heo, Seongchan;Choi, Hwanseok
    • Journal of the Korean Society of Propulsion Engineers
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    • v.21 no.6
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    • pp.73-82
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    • 2017
  • Low-cycle thermal fatigue problem resulting from multiple use of a liquid rocket engine has to be considered for the development of a reusable launch vehicle. In this study, life prediction equations suggested by previous researchers were compared as applied to various copper alloy cases to predict fatigue lives from tensile test data. The present study has revealed that among the presently considered life prediction methods, universal slopes method provides the best life prediction result for the copper alloys, and the modified Mitchell's method provides the best life prediction result for oxygen free high conductivity (OFHC) copper.

Effects of the Atmosphere on the Comparative Solderability of Lead-Tin and Lead-Free Solders

  • Bin, Jeong-Uk;S.M.Adams;P.F.Stratton
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • 2001.04a
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    • pp.45-47
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    • 2001
  • Due to pressure from threatened legislation in Europe, consumer and governmental pressure in Japan, and glob머 market considerations in the US, there is a rapidly growing interest in lead-free solderinger, Although the move to lead free soldering seems inevitable, many problems will arise in production assembly. It is generally acknowledged that the lead-free solders available offer a much s smaller process window than lead/tin, related mainly to the higher soldering temperatures which naturally result from increases of liquidus temperatures of at least 300 C. However, raising reflow temperatures from the current 220-2300 C to 250 2600 C will lead to problems with the boards and components as well as i increasing oxidation effects. There is a need to keep reflow temperatures low without reducing solderablity. Some results on benefits of inert atmospheres are discussed in this paper. For example, testing in a nitrogen atmosphere, with 300 ppm oxygen, by the N National Physical Laboratory (NPU has revealed clear benefits for ine$\pi$mg lead-free alloys, by restoring the solderability to lead/tin levels, by enabling lower soldering temperatures. However, there has been little testing over a range of oxygen levels in nitrogen and this is an important issue in determining n nitrogen supply and oven costs. Some results are reported here from work by NPL conducted for BOC in w which solderability was evaluated for tin기ead and tin/silver/copper eutectic a alloys in a wetting balance over a range of oxygen levels form 10 ppm to 21% ( (air). The studies confirm that acceptable wetting times occur in inert atmospheres a at soldering temperatures 20 to 300 C lower than are possible in air.

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Role of Added Metal Oxide in the Adherence Mechanism of Low Melting Glass to Several Metal Seals (저융점유리와 각종금속과의 봉착기구에 있어서 금속산화물의 역할)

  • 정창주
    • Journal of the Korean Ceramic Society
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    • v.11 no.1
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    • pp.3-9
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    • 1974
  • The role of added metal oxide in the adherence mechanism of low melting glass to several metal plates such as oxygen free high conducting copper, low carbon steel, chrominum galvanized on copper, and stainless steel was investigated. The metal oxide which added to glass were cupric oxide, ferric oxide, chromic oxide, and stainless steel oxide. The glass to that various metla oxide were added, sealed with several metal plates in the electric furnace at $650^{\circ}C$ for 5 minutes. The results as follows; 1) The interfacial reaction was promoted and strong chemical bonding with glass and metals by which the surface energy was decreased showed excellent sealing by addition of metal oxide. 2) When the interfacial reaction of glass and metals was promoted by addition of metal oxide found out that various adhernece mechanism were related to the sealing. 3) When the amount of metal oxide addition was 3-5% the excellent sealing was achieved.

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A Study on the Tribolayer using Focused Ion Beam (FIB) (FIB를 이용한 트라이보층에 대한 연구)

  • Kim, Hong-Jin
    • Tribology and Lubricants
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    • v.26 no.2
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    • pp.122-128
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    • 2010
  • Focused Ion Beam (FIB) has been used for site-specific TEM sample preparation and small scale fabrication. Moreover, analysis on the surface microstructure and phase distribution is possible by ion channeling contrast of FIB with high resolution. This paper describes FIB applications and deformed surface structure induced by sliding. The effect of FIB process on the surface damage was explored as well. The sliding experiments were conducted using high purity aluminum and OFHC(Oxygen-Free High Conductivity) copper. The counterpart material was steel. Pin-on-disk, Rotational Barrel Gas Gun and Explosively Driven Friction Tester were used for the sliding experiments in order to investigate the velocity effect on the microstructural change. From the FIB analysis, it is revealed that ion channeling contrast of FIB has better resolution than SEM and the tribolayer is composed of nanocrystalline structures. And the thickness of tribolayer was constant regardless of sliding velocities.

A Finite Element Analysis for the Characteristics of Temperature and Stress in Micro-machining Considering the Size Effect (크기효과가 고려된 미소절삭시의 온도 및 응력특성에 관한 유한요소해석)

  • 김국원;이우영
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.10
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    • pp.128-139
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    • 1998
  • In this paper, a finite element method for predicting the temperature and stress distributions in micro-machining is presented. The work material is oxygen-free-high-conductivity copper(OFHC copper) and its flow stress is taken as a function of strain, strain rate and temperature in order to reflect realistic behavior in machining process. From the simulation, a lot of information on the micro-machining process can be obtained; cutting force, cutting temperature, chip shape, distributions of temperature and stress, etc. The calculated cutting force was found to agree with the experiment result with the consideration of friction characteristics on chip-tool contact region. Because of considering the tool edge radius, this cutting model using the finite element method can analyze the micro-machining with the very small depth of cut, almost the same size of tool edge radius, and can observe the 'size effect' characteristic. Also the effects of temperature and friction on micro-machining were investigated.

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A Study on the Microstructure and Anisotropic Mechanical Properties of Oxygen-Free Copper Fabricated by Equal Channel Angular Pressing (ECAP공법으로 제조된 무산소동의 미세조직 및 기계적 성질 이방성에 대한 고찰)

  • Lee, Jaekun;Hong, Younggon;Kim, Hyoungseop;Park, Sunghyuk
    • Journal of the Korea Institute of Military Science and Technology
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    • v.22 no.4
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    • pp.492-500
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    • 2019
  • Equal channel angular pressing(ECAP) is a severe plastic deformation technique capable of introducing large shear strain in bulk metal materials. However, if an ECAPed material has an inhomogeneous microstructure and anisotropic mechanical properties, this material is difficult to apply as structural components subjected to multi-axial stress during use. In this study, extruded oxygen-free copper(OFC) rods with a large diameter of 42 mm are extruded through ECAP by route Bc up to 12 passes. The variations in the microstructure, hardness, tensile properties, and microstructural and mechanical homogeneity of the ECAPed samples are systematically analyzed. High-strength OFC rods with a homogeneous and equiaxed-ultrafine grain structure are obtained by the repeated application of ECAP up to 8 and 12 passes. ECAPed samples with 4 and 8 passes exhibit much smaller differences in terms of the average grain sizes on the cross-sectional area and the tensile strengths along the axial and circumferential directions, as compared to the samples with 1 and 2 passes. Therefore, it is considered that the OFC materials, which are fabricated via the ECAP process with pass numbers of a multiple of 4, are suitable to be applied as high-strength structural parts used under multi-axial stress conditions.