• Title/Summary/Keyword: Ag Powder

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Synthesis of Core/shell Structured Ag/C Nano Particles and Properties on Annealing Conditions (전기선폭발법을 이용한 core/shell 구조 Ag/C 나노 입자의 제조 및 열처리조건에 따른 특성)

  • Jun, S.H.;Uhm, Y.R.;Rhee, C.K.
    • Journal of Powder Materials
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    • v.17 no.4
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    • pp.295-301
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    • 2010

  • Multi shell graphite coated Ag nano particles with core/shell structure were successfully synthesized by pulsed wire evaporation (PWE) method. Ar and $CH_4$ (10 vol.%) gases were mixed in chamber, which played a role of carrier gas and reaction gas, respectively. Graphite layers on the surface of silver nano particles were coated indiscretely. However, the graphite layers are detached, when the particles are heated up to $250^{\circ}C$ in the air atmosphere. In contrast, the graphite coated layer was stable under Ar and $N_2$ atmosphere, though the core/shell structured particles were heated up to $800^{\circ}C$. The presence of graphite coated layer prevent agglomeration of nanoparticles during heat treatment. The dispersion stability of the carbon coated Ag nanoparticles was higher than those of pure Ag nanoparticles.

  • https://doi.org/10.4150/KPMI.2010.17.4.295 인용 PDF KSCI

Properties of Bi-2223/Ag HTS tapes using different content of precursors (조성이 다른 전구체 분말에 따른 Bi-2223/Ag 초전도 테이프의 특성 변화)

  • Ha, Dong-Woo;Yang, Joo-Saeng;Ha, Hong-Soo;Oh, Sang-Soo;Hwang, Sun-Yuk;Lee, Dong-Hoon;Choi, Jung-Kyu;Lee, En-Yong;Kwon, Young-Kil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05a
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    • pp.69-72
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    • 2003

  • Bi-2223 superconducting wires were fabricated by stacking, drawing process with different precursor powders and different heat-treatment histories. The precursor powders were 2 kinds of Pb content. And a part of the tapes were experienced pre-annealing process which caused tetragonal structure of Bi-2212 phase to orthorhombic structure of it was during drawing process. We confirmed the transformation of Bi-2212 phase from tetragonal structure to orthorhombic structure and reduction of second phases. XRD and DC magnetization analysis were performed in order to investigate the fraction of Bi-2223 phase in Bi-2223/Ag HTS tape. We could achieve best Ic of 70 A class at the Bi-2223/Ag tape using low Pb content of precursor powder and experienced pre-annealing process. DC magnetization analysis was useful to investigate the fraction of Bi-2223 phase in the Bi-2223/Ag tape.

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Pretreatment Condition of Cu by Ammonium-Based Mixed Solvent and Its Effects on the Fabrication of Ag-Coated Cu Particles (Ag 도금 Cu 입자의 제조에서 암모늄 기반 혼합 용매를 사용한 Cu 입자의 전처리 조건과 이의 영향)

  • Lee, Hee Bum;Lee, Jong-Hyun
    • Korean Journal of Materials Research
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    • v.26 no.3
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    • pp.109-116
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    • 2016

  • To achieve the fabrication of high-quality Ag-coated Cu particles through a wet chemical process, we reported herein pretreatment conditions using an ammonium-based mixed solvent for the removal of a $Cu_2O$ layer on Cu particles that were oxidized in air for 1 hr at $200^{\circ}C$ or for 3 days at room temperature. Furthermore, we discussed the results of post-Ag plating with respect to removal level of the oxide layer. X-ray diffraction results revealed that the removal rate of the oxide layer is directly proportional to the concentration of the pretreatment solvent. With the results of Auger electron spectroscopy using oxidized Cu plates, the concentrations required to completely remove 50-nm-thick and 2-nm-thick oxides within 5 min were determined to be X2.5 and X0.13. However, the optimal concentrations in an actual Ag plating process using Cu powder increased to X0.4 and X0.5, respectively, because the oxidation in powder may be accelerated and the complete removal of oxide should be tuned to the thickest oxide layer among all the particles. Back-scattered electron images showed the formation of pure fine Ag particles instead of a uniform and smooth Ag coating in the Ag plating performed after incomplete removal of the oxide layer, indicating that the remaining oxide layer obstructs heterogeneous nucleation and plating by reduced Ag atoms.

  • https://doi.org/10.3740/MRSK.2016.26.3.109 인용 PDF KSCI