• Title/Summary/Keyword: Cu Powder

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Comparative Study on the Fabrication of Single Grain YBCO Bulk Superconductors using Liquid Infiltration and Conventional Melt Growth Processes (단결정 YBCO 벌크 초전도체 제조에 대한 액상침투법과 고전적 용융공정의 비교연구)

  • Mahmood, Asif;Jun, Byung-Hyuk;Kim, Chan-Joong
    • Progress in Superconductivity
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    • v.11 no.1
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    • pp.42-46
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    • 2009
  • With an aim of comparison, single grain Y-Ba-Cu-O (YBCO) bulk superconductors were fabricated using a liquid infiltration growth (LIG) process and a conventional melt growth (MTG) process with top seeding. The MTG process uses an $YBa_2Cu_3O_{7-x}$(Y123) powder as a precursor, while the LIG process uses $Y_2BaCuO_5(Y211)/Ba_3Cu_5O_8(Y035)$ pre-forms. The growth of a single Y123 domain on the top seed was successful in the both processes. Different feature between the two processes is the interior microstructure regarding the critical current density ($J_c$). The LIG-processed YBCO sample showed a lower porosity, more uniform distribution of Y211 particles and the enhanced Y211 refinement compared to the conventional MTG process. The $J_c$ improvement in the LIG process is attributed to the dispersion of finer Y211 particles as well as lower porosity within the Y123 superconducting matrix.

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Removal of Cd(II) and Cu(II) from Aqueous Solution by Agro Biomass: Equilibrium, Kinetic and Thermodynamic Studies

  • Reddy, Desireddy Harikishore Kumar;Lee, Seung-Mok;Seshaiah, Kalluru
    • Environmental Engineering Research
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    • v.17 no.3
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    • pp.125-132
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    • 2012
  • The removal of Cd(II) and Cu(II) from aqueous solution by an agricultural solid waste biomass prepared from Moringa oleifera bark (MOB) was investigated. The biosorbent was characterized by Fourier transform infrared spectroscopy and elemental analysis. Furthermore, the effect of initial pH, contact time, biosorbent dosage, initial metal ion concentration and temperature on the biosorption of Cd(II) and Cu(II) were studied using the batch sorption technique. Kinetic studies indicated that the biosorption process of the metal ions followed the pseudo-second order model. The biosorption data was analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. Based on the Langmuir isotherm, the maximum biosorption capacities for Cd(II) and Cu(II) onto MOB were 39.41 and 36.59 mg/g at 323 K, respectively. The thermodynamic parameters, Gibbs free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$), and entropy (${\Delta}S^o$) changes, were also calculated, and the values indicated that the biosorption process was endothermic, spontaneous and feasible in the temperature range of 303-323 K. It was concluded that MOB powder can be used as an effective, low cost, and environmentally friendly biosorbent for the removal of Cd(II) and Cu(II) ions from aqueous solution.

Preparation of Graphene Based PdOx and CuOx/MnOx Nanocomposites and Their Catalytic Applications in C-C Coupling and CH3SH Decomposition Reactions

  • Lee, Gyeong-Hun;Park, Jun-Beom
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.175.2-175.2
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    • 2014
  • Graphene (G) has been modified with palladium, copper, and manganese oxide nanoparticles (NPs), and their catalytic applications have been studied in C-C coupling reactions and methylmercaptan (CH3SH) decomposition reactions. In this research, graphite oxide (GO) sheets were exfoliated and oxidized from graphite powder and impregnated with metal precursors including Pd2+, Cu2+, and Mn2+. The thermal treatments of the metal impregnated GO in preferred gas environments produced Pd NPs on graphene (Pd/G), PdO NPs on GO (PdO/GO), and CuOx and MnOx NPs on graphene (CuOx/MnOx/G). In case of Pd/G and PdO/GO, the TEM images show that, although the mean size of the Pd NPs changed significantly before and after the C-C coupling reaction, that of the PdO NPs didn't, implying that the PdO/GO was superior to Pd/G in terms of the recyclability. Also, we demonstrate that the CuOx/MnOx/G exerts the excellent catalytic efficiency in CH3SH decomposition reaction comparing with conventional catalysts. The chemical and electronic structural changes were investigated using XRD and XPS.

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Manufacturing of Cu-26.7Zn-4.05Al(wt.%) Shape Memory Alloy Using Spark Plasma Sintering (Spark Plasma Sintering을 이용한 Cu-26.7Zn-4.05Al(wt.%) 형상기억합금의 제조)

  • Park, No-Jin;Lee, In-Sung;Cho, Kyeong-Sik;Kim, Sung-Jin
    • Korean Journal of Materials Research
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    • v.13 no.6
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    • pp.352-359
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    • 2003
  • In order to control the grain size, the spark plasma sintering technique is applied for the manufacturing of Cu-26.7Al-4.05AI(wt.%) shape memory alloy with pure Cu, Zn, and Al element powders. The sintering processes were carried out under different atmospheres. The sintered bodies were denser under Ar or Ar+4%$H_2$gas atmosphere than under vacuum. With use of small-sized powders, a very small average grain size of 2∼3 $\mu\textrm{m}$ was obtained, but the single phase was not formed. With the large-sized powders the single austenitic phase was observed with the average grain size of $70∼72\mu\textrm{m}$. When the different size of raw powders was mixed, it is confirmed that the average grain size of the manufactured alloys was 15 $\mu\textrm{m}$ with single austenitic phase, but the distribution of grain size was not uniform.

Cu2ZnSnSe4 Thin Films Preparation by Pulsed Laser Deposition Using Powder Compacted Target

  • Kim, Kyoo-Ho;Wibowo, Rachmat Adhi;Alfaruqi, M.Hilmy;Ahn, Jong-Heon
    • Journal of Surface Science and Engineering
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    • v.44 no.5
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    • pp.185-189
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    • 2011
  • $Cu_2ZnSnSe_4$ thin films for solar absorber application were prepared by pulsed laser deposition of a synthesized $Cu_2ZnSnSe_4$ compound target. The film's composition revealed that the deposited films possess an identical composition with the target material. Further film compositional control toward a stoichiometric composition was performed by optimizing substrate temperature, deposition time and target rotational speed. At the optimum condition, X-ray diffraction patterns of films showed that the films demonstrated polycrystalline stannite single phase with a high degree of (112) preferred orientation. The absorption coefficient of $Cu_2ZnSnSe_4$ thin films were above 104 cm.1 with a band gap of 1.45 eV. At an optimum condition, films were identified as a p type semiconductor characteristic with a resistivity as low as $10^{-1}{\Omega}cm$ and a carrier concentration in the order of $10^{17}cm^{-3}$.

Preparation of Yba2Cu3Ox Superconductor Prepared with Additives of PbO and Ag2O

  • Chu, Soon-Nam;Park, Jung-Cheul;Jeon, Yong-Woo
    • Transactions on Electrical and Electronic Materials
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    • v.10 no.1
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    • pp.31-34
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    • 2009
  • The improvement of preparation process of ${YBa_2}{Cu_3}{O_x}$ superconductor and its conducting properties is important for practical applications. In this study, the additives such as $Ag_{2}O$ and PbO were used to improve the preparation conditions of ${YBa_2}{Cu_3}{O_x}$ superconducting bulk samples and the properties of ${YBa_2}{Cu_3}{O_x}$ superconductors prepared with powders using sol-gel method and solid state reaction method were studied. The effects of the different powders and the additives to the density, grain alignment, and porosity of samples, that affect the critical current density of superconductor, also have been investigated. It is found that the properties of ${YBa_2}{Cu_3}{O_x}$ prepared with sol-gel synthesized powder and the additives showed better superconductivities than those of conventionally prepared superconductors.

A Nanoindentation Based Study of Mechanical Properties of Al-Si-Cu-Mg Alloy Foam Cell Wall (나노인덴테이션에 의한 Al-Si-Cu-Mg 합금 폼 셀 벽의 기계적 물성 연구)

  • Ha, San;Kim, Am-Kee;Lee, Chang-Hun;Lee, Hak-Joo;Ko, Soon-Gyu;Cho, Seong-Seock
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.382-387
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    • 2004
  • Nanoindentation technique has been used to measure the mechanical properties of aluminium alloy foam cell walls. Al-Si-Cu-Mg alloy foams of different compositions and different cell morphologies were produced using powder metallurgical method. Cell morphology of the foam was controlled during production by varying foaming time and temperature. Mechanical properties such as hardness and Young's modulus were calculated using two different methods: a continuous stiffness measurement (CSM) and an unloading stiffness measurement (USM) method. Experimental results showed that hardness and Young's modulus of Al-5%(wt.)Si-4%Cu-4%Mg (544 alloy) precursor and foam walls are higher than those of Al-3%Si-2%Cu-2%Mg (322 alloy) precursor and foam walls. It was noticed that mechanical properties of cell wall are different from those of precursor materials.

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A study on Properties of YbBaCuO Superconductor with various calcination conditions (하소 조건 변화에 따른 YbBaCuO 초전도체 의 특성 연구)

  • 이영매;박정철;소대화
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.11a
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    • pp.68-72
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    • 1997
  • In this paper, to obtain the YbB $a_2$C $u_3$ $O_{x}$ superconductor, the mixed Powders of Y $b_2$ $O_3$, BaC $O_3$, CuO and Y $b_2$BaCu $O_{5}$, BaCu $O_2$ were used and the various calcining conditions were applied for the 123 phase of YbB $a_2$C $u_3$ $O_{x}$. Samples were prepared by the mixed oxide method and calcined with various temperatures of 88$0^{\circ}C$ ~91$0^{\circ}C$ . It was observed that the distribution of YbB $a_2$C $u_3$ $O_{x}$ phase which was calcined at 90$0^{\circ}C$ for 12 hours and 99 hours. But the result of long time calcination(99 hrs), the 123 phase of YbB $a_2$C $u_3$ $O_{x}$ was existed between 89$0^{\circ}C$ and 91$0^{\circ}C$ . And the best case could be obtained at the calcination temp. of 90$0^{\circ}C$ from the mixed Powder of YbB $a_2$C $u_3$ $O_{5}$ and Bacu $O_2$ which were prepared individually.idually.

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Optimization of synthesis conditions and $CO_2$ capture capability of Cu-BTC Metal-Organic Framework (이산화탄소 흡착용 Cu-BTC MOF 합성 최적화)

  • Peng, Mei Mei;Hemalatha, Pushparaj;Ganesh, Mani;Jang, Hyun-Tae
    • Proceedings of the KAIS Fall Conference
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    • 2011.12a
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    • pp.200-203
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    • 2011
  • A copper-based metal organic framework (MOF) named Cu-BTC, also known as HKUST-1, was synthesized by using a solvothermal method at various synthesis temperature, time and pressure. The obtained samples were characterized with Powder X-ray diffraction (XRD) for phase structure, scanning electron microscopy (SEM) for crystal structure, and nitrogen adsorption-desorption for pore textural structure. The Cu-BTC sample was also studied for $CO_2$ adsorption. The analysis results displayed that the sample synthesized at the condition of temperature: $120^{\circ}C$, synthesis time: 12 hours, pressure: 1 bar exhibited a good crystal structure with uniform size of octahedral particles. The BET data revealed a high surface area of 1741.7 $m^2g^{-1}$ and a pore volume of 0.7137 $cm^3g^{-1}$and exhibiteda maximum $CO_2$ adsorption capacity of 170 mg/g of the sorbent at $25^{\circ}C$.

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The Electromagnetic Wave Absorption Characteristics of Cu-Ni-Zn Ferrite by Thermal Decomposition of Organic Acid Salt (유기산염 열분해법에 의한 Cu-Ni-Zn 페라이트의 전자파 흡수 특성)

  • 정재우;이완재
    • Journal of the Korean Magnetics Society
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    • v.5 no.6
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    • pp.947-951
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    • 1995
  • The electromagnetic interference is prevented by the high magnetic loss of the ferrite. The absorbing property of electromagnetic wave could be improved by the ferrite that has a finer and more uniform microstructure. The thermal decomposition of organic acid salt provided the uniform composition and fine powder. The absorbing properties of electromagnetic wave were evaluated by the relative complex permeability, permittivity, and the attenuation which is calculated from the results of network analyzer. The permeability and permittivity were increased with increase of the density and with decrease of the grain size. The matching thickness could be reduced with increasing sintered temperature. The attenuation of the Cu-Ni-Zn ferrite showed over 20dB when the matching thickness and the matching frequency range were 6.75mm and from 160MHz to 640MHz, respectively.

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