• Journal of Powder Materials
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• v.9 no.5
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• pp.329-335
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• 2002

Recently, the fabrication process of the W-Cu nanocomposite powders has been studied to improve the sinterability through the mechanical alloying and reduction of W and Cu oxide mixtures. In this study. the W-Cu composites were produced by mechanochemical process (MCP) using $WO_3-CuO$ mixtures with two different milling types of low and high energy, respectively. These ball-milled mixtures were reduced in $H_2$ atmosphere. The ball-milled and reduced powders were analyzed through XRD, SEM and TEM. The fine W-Cu powder could be obtained by the high energy ball-milling (HM) compared with the large Cu-cored structure powder by the low energy ball-milling (LM). After the HM for 20h, the W grain size of the reduced W-Cu powder was about 20-30 nm.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.103-104
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• 2007

$CuInO_2$ 단일상은 합성조건이 매우 까다롭기 때문에 일반적인 고상법으로 얻기 힘든 것으로 알려저 있다. 투명전도성 $CuInO_2$ 박막을 증착하기 위하여 일반적인 고상법으로 Cu와 In의 비율이 1:1인 $Cu_2O-In_2O_3$ composite target 및 In 대신 Ca, Mg, Ti가 각각 1mol% 도핑된 target을 제작하였다. 제작된 각각의 composite target을 이용하여 pulsed laser deposition(PLD) 공정으로 투명전도성 $CuInO_2$ 박막을 증착하였다. Cu와 In이 1:1 인 $Cu_2O-In_2O_3$ composite target을 사용한 경우, 증착된 박막이 Cu와 In의 비율이 1:1인 c-axis 배향된 단일상의 $CuInO_2$ 박막임을 확인하였다.

• Journal of the Korean Magnetics Society
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• v.9 no.4
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• pp.217-222
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• 1999

The pick up impurity was studied for preparing the NiCuZn ferrite powder by a ball milling method that usually uses in the industrial ceramic process. The raw materials of NiO, CuO, ZnO, and $Fe_2O_3$ powder were weighted according to various spinel composition and mixed for 18 hrs by a wet ball milling method after that the slurry was followed by spray dried and calcined at $700^{\circ}C$ 3 hrs. The calcined NCZF powder was finally ball milled during 65 hrs as same method. The stainless steel ball and jar are used as mixing and milling equipment and the solid concentration of the slurry was 25 vol%. The impurities, stainless steel pickup, were effected by the composition of raw materials especially iron oxide, nickel oxide in the mixing process and by the rate of calcine of NiCuZn ferrite in final milling process. The empirical equation of stainless steel pickup was driven in the wet ball milling system. Finally, the composition of NiCuZn ferrite could be controlled by the empirical equation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.382.2-382.2
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• 2014

We explain a method to fabricate multi-layered transparent conductive films (TCF) using graphene oxide (GO), copper powder and polyurethane (PU) solution. The flexible graphene nanosheets (GNSs) serve as nanoscale connection between conductive copper nanoparticles (CuNps) and PU nanofibers, resulting in a highly flexible TCF. To fabricate conductive films with high transmittance, polyurethane (PU) nanofibers were used for a conductive network consisting of CuNps and GNSs (CuNps-GNSs). In this experiment, copper powder and graphene oxides were mixed in deionized water with the ultrasonication for 2 h. NaBH4 solution is used as a reduction agents of CuNps and GNSs (CuNps-GNSs) under a nitrogen atmosphere in the oil bath at 100% for 24 h to mixed. The purified and dispersed CuNp-GNS were obtained in deionized water, and diluted to a 10wt.% based on the contents of GNSs. Polyurethane (PU) nanofibers on a PET substrate were formed by electrospinning method. PET slides coated with the PU nanofibers were immersed into CuNp-GNS solution for several second, rinsed briefly in deionized water, and dried to obtain self-assembled CuNp-GNS/PU films. The morphology of the multi-layered films were characterized with a field emission scanning electron microscope (FE-SEM, Hitachi S-4700) and atomic force microscope (AFM, PSIA XE-100). The electrical property was analysed by the I-V measurement system and the optical property was measured by the UV/VIS spectroscopy.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.722-726
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• 2013

Freeze drying of a porous Cu-Sn alloy with unidirectionally aligned pore channels was accomplished by using a composite powder of CuO-$SnO_2$ and camphene. Camphene slurries with CuO-$SnO_2$ content of 3, 5 and 10 vol% were prepared by mixing with a small amount of dispersant at $50^{\circ}C$. Freezing of a slurry was done at $-25^{\circ}C$ while the growth direction of the camphene was unidirectionally controlled. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green bodies were hydrogen-reduced at $650^{\circ}C$ and then were sintered at $650^{\circ}C$ and $750^{\circ}C$ for 1 h. XRD analysis revealed that the CuO-$SnO_2$ powder was completely converted to Cu-Sn alloy without any reaction phases. The sintered samples showed large pores with an average size of above $100{\mu}m$ which were aligned parallel to the camphene growth direction. Also, the internal walls of the large pores had relatively small pores. The size of the large pores decreased with increasing CuO-$SnO_2$ content due to the change of the degree of powder rearrangement in the slurry. The size of the small pores decreased with increase of the sintering temperature from $650^{\circ}C$ to $750^{\circ}C$, while that of the large pores was unchanged. These results suggest that a porous alloy body with aligned large pores can be fabricated by a freeze-drying and hydrogen reduction process using oxide powders.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.79-87
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• 1998

Melt spun YbBa2Cu3Agx(x=0, 5, 12, 16 and 53) precursor alloy ribbons were oxidized at 263-330$^{\circ}C$ and treated at 820$^{\circ}C$, 855$^{\circ}C$ and 885$^{\circ}C$ under 1.0 atm oxygen pressure. In the ribbons treated at 820$^{\circ}C$, 855$^{\circ}C$and 885$^{\circ}C$ 1-2-4 phase (YbBa2Cu4O8) and 1-2-3 phase (YbBa2Cu3O{{{{ OMICRON _7-$\delta$ }})were formed respectively. The shape of 1-2-4 phase was distorted or ellipsoid. The 2-4-7 and 1-2-3 phases tooked the shape of bar. All the ribbons showed zero critical current density Jc at 77K in zero magnetic field. By considering the shape and the highest critical temperature (among the three phases) of the 1-2-3 phase we tried to increase the critical current density of the ribbons treated at 885$^{\circ}C$ by press deformation. About tenribbons were stacked and coupled by press deformation and then treated at 885$^{\circ}C$ These 1-2-3 phase did not show any texture in any of the ribbons. However they exhibited weak texture in the multilayered specimens. Among the multilayered specimens YbBa2Cu3Ag16 exhibited a Jc of 180 A/cm2 Among the above ribbons YbBa2Cu3Ag16 ribbon has the optimum composition to produce textured superconducting oxide with improved Jc by press deformation. Onset critical temperatures Ton of the multilayered YbBa2Cu3Agx(x=5, 12, 16 and 53) were measured as 88-90 K.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.15-31
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• 2024

The antimalarial drug hydroxychloroquine sulphate (HCQ) has taken much attention during the first COVID-19 pandemic phase for the treatment of severe acute respiratory infection (SARI) patients. Hence it is interest to study the electrochemical properties and photocatalytic degradation of the HCQ drug. Copper oxide (CuO) nanoparticles, graphene oxide (GO) and CuO/GO NC (nanocomposite) modified carbon paste electrodes (MCPE) are used for the detection of HCQ in an aqueous medium. Electrochemical behaviour of HCQ (20 μM) was observed using CuO/MCPE, GO/MCPE and CuO/GO NC/MCPE in 0.1 M phosphate buffer at pH 7 with a scan rate of 20 to 120 mV s^-1 by cyclic voltammetry (CV). Differential pulse voltammetry (DPV) of HCQ was performed for 0.6 to 16 μM HCQ. The CuO/GO NC/MCPE showed a reasonably good sensitivity of 0.33 to 0.44 μA μM cm^-2 with LOD of 69 to 92 nM for HCQ. Furthermore, the CuO/GO NC was used as a catalyst for the photodegradation of HCQ by monitoring its UV-Vis absorption spectra. About 98% was degraded in about 34 min under visible light and after 4 cycles it was 87%. The improved photocatalytic activity may be attributed to decrease in bandgap energy and enhanced ability for the electrons to migrate. Thus, CuO/GO NC showed good results for both sensing and degradation applications as well as reproducibility.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.1985-1988
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• 2014

$Cu_2ZnSnSe_4$ (CZTSe) thin films were synthesized on transparent conducting oxide glass substrates via a simple, non-toxic, and low-cost process using a precursor solution paste. A three-step heating process (oxidation, sulfurization, and selenization) was employed to synthesize a CZTSe thin film as an absorber layer for use in thin-film solar cells. In particular, we focused on the effects of sulfurization conditions on CZTSe film formation. We found that sulfurization at $400^{\circ}C$ involves the formation of secondary phases such as $CuSe_2$ and $Cu_2SnSe_3$, but they gradually disappeared when the temperature was increased. The formed CZTSe thin films showed homogenous and good crystallinity with grain sizes of approximately 600 nm. A solar cell device was tentatively fabricated and showed a power conversion efficiency of 2.2% on an active area of 0.44 $cm^2$ with an open circuit voltage of 365 mV, a short current density of 20.6 $mA/cm^2$, and a fill factor of 28.7%.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.246-256
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• 2021

Mo,Cu-doped CeO₂ (CMCuO) nanopowders were synthesized by the nitrate-fuel combustion method aiming to improve the electrical and electrochemical properties of its Mo-doped CeO₂ (CMO) parent by the addition of copper. An electrical conductivity of ca. 1.22·10^-2 S cm^-1 was measured in air at 800℃ for CMCuO, which is nearly 10 times higher than that reported for CMO. This increase was associated with the inclusion of copper into the crystal lattice of ceria and the presence of Cu and Cu₂O as secondary phases in the CMCuO structure, which also could explain the increase in the charge transfer activities of the CMCuO based anode for the hydrogen and carbon monoxide electro-oxidation processes compared to the CMO based anode. A maximum power density of ca. 120 mW cm^-2 was measured using a CMCuO based anode in a solid oxide fuel cell (SOFC) with YSZ electrolyte and LSM-YSZ cathode operating at 800℃ with humidified syngas as fuel, which is comparable to the power output reported for other SOFCs with anodes containing copper. An increase in the area specific resistance of the SOFC was observed after ca. 10 hours of operation under cycling open circuit voltage and polarization conditions, which was attributed to the anode delamination caused by the reduction of the Cu₂O secondary phase contained in its microstructure. Therefore, the addition of a more electroactive phase for hydrogen oxidation is suggested to confer long-term stability to the CMCuO based anode.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.77-82
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• 2015

To increase the performance of solid oxide fuel cell operating at intermediate temperature ($600^{\circ}C{\sim}800^{\circ}C$), $Sm_{0.2}Ce_{0.8}O_2$ (SDC) thin layer was applied to the $La_{0.8}Sr_{0.2}Mn_{0.8}Cu_{0.2}O_3$ (LSMCu) cathode by sol-gel coating method. The SDC was employed as a diffusion barrier layer on the yttria-stabilized zirconia(YSZ) to prevent the interlayer by-product formation of $SrZrO_3$ or $La_2Zr_2O_7$. The by-products were hardly formed at the electrolyte-cathode interlayer resulting to reduce the cathode polarization resistance. Moreover, SDC thin film was coated on the cathode pore wall surface to extend the triple phase boundary (TPB) area.