• Journal of Powder Materials
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• v.15 no.1
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• pp.6-12
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• 2008

[ $YBa_2Cu_3O_{7-y}$ ](123) powders were synthesized by the solid state reaction method using two different purity $BaCO_3$ powders (99.75% and 99.7% purity) and $Y_2O_3$ (99.9%) and CuO (99.9%) powders. The effect of $BaCO_3$ purity on the formation of a 123 phase and the superconducting properties were investigated. The mixtures of raw powders were calcined at temperature ranges of $800^{\circ}C-880^{\circ}C$ in air and finally made into a single grain samples by a melt processing with top seeding. It was found that a 123 phase was well formed at temperature above $870^{\circ}C$, but the purity effect on the 123 formation was negligible. The single-grain 123 samples prepared from the different $BaCO_3$ powders showed the same $T_c$ value of 90.5 K and similar $J_c$ values about $10^4\;A/cm^2$ at 0 T and 77 K, and $10^3\;A/cm^2$ at 2 T and 77 K. This result indicates that the low purity, cheap price $BaCO_3$ powder can be used as a raw material for the fabrication of single-grain, high-$J_c$ superconducting levitator.

• Journal of Powder Materials
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• v.23 no.1
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• pp.21-25
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• 2016

The microstructural properties and electrical characteristics of sputtering films deposited with a Cu-Ga target are analyzed. The Cu-Ga target is prepared using the cold spray process and shows generally uniform composition distributions, as suggested by secondary ion mass spectrometer (SIMS) data. Characteristics of the sputtered Cu-Ga films are investigated at three positions (top, center and bottom) of the Cu-Ga target by X-ray diffraction (XRD), SIMS, 4-point probe and transmission electron microscopy (TEM) analysis methods. The results show that the Cu-Ga films are composed of hexagonal and unknown phases, and they have similar distributions of composition and resistivity at the top, center, and bottom regions of the Cu-Ga target. It demonstrates that these films have uniform properties regardless of the position on the Cu-Ga target. In conclusion, the cold spray process is expected to be a useful method for preparing sputter targets.

• Journal of Powder Materials
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• v.5 no.4
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• pp.273-278
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• 1998

$De-NO_x$ transition metals(Cu, Co)/ZSM-5 catalyst was made by mechanical alloying method, and their microstructures and repeated usage-properties were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The conversions ability of NO in the catalyst was measured. A part of ZSM-5 in CO/ZSM-5 composite powders was amorphous and the amorphous phase became less stable with increasing Co content. Conversion ability of NO in 10Cu/ZSM-5 powders decreased from 89% to 12% and that in 10Co/ZSM-5 decreased from 22% to 17% by 7 times conversion tests.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.383-384
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• 2006

Fe-4Ni-0.5Mo-1Cu powder was selected as raw material, pressed and sinter-hardened at $1135\;^{\circ}C$ for 30 min with rapid cooling. The density varies in the range of $7.24-7.29\;g/cm^3$. Its fatigue properties have been tested in axial loading of alternating tensile/compressive stress at R=-1 with a servo-pulse pump. The fatigue endurance limit was measured to be 260 MPa. The microstructure showed more homogeneous bainite and martensite. Fractography displayed the fatigue cracks initiated from the pore areas near the surface. A non-typical ductile fatigue striation was found. More dimples occurred on fracture surface due to the plastic deformation, which can prohibit cracking propagation and improve its fatigue properties.

• Journal of Powder Materials
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• v.11 no.2
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• pp.143-148
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• 2004

In the present study, $TiO_2$ imbedded composite powders have been successfully prepared from the (Cu. Zn)/$TiO_2$ composite salt solution. The composite (Cu, Zn)/$TiO_2$ powders were formed by drying the solution at 200~$600^{\circ}C$ in the hydrogen atmosphere. Photocatalytic characteristics was evaluated by detecting the decomposition ratio of aniline blue with UV-visible spectrophotometer(Shimazu Co., UV-1601). Phase analysis of (Cu, Zn)/$TiO_2$ composite powders was carried out by XRD and DSC, and powder size was measured with TEM. The mean particle size of composite powders was about 100mm. As the reduction temperature increases, a few zinc sulfide and oxide phases was formed and copper oxide phase was reduced. The decomposition ratio of aniline blue was about 80％ under the UV irradiation by the TiO$_2$ phase in the composite (Cu, Zn)/$TiO_2$ powders and similar decomposition ratio of 80％ was obtained at the UV lightless condition by virtue of Cu and Zn compounds.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.61-64
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• 2007

Ni/YSZ ($Y_{2}O_{3}-stabilized$ $ZrO_{2}$), Cu/YSZ and CuO/YSZ composite powder for a cathode material in high temperature electrolysis (HTE) was synthesized by a mechanical alloying method with Ni (or Cu, CuO, Co) and YSZ powder. Microstructure of the composite for HTE reaction has been analyzed with various techniques of XRD, SEM to investigate effects of fabrication conditions. And conductivity of electrode was measured, Cu/YSZ cermet showed the higher electrical conductivity value than Ni/YSZ.

• Journal of Powder Materials
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• v.11 no.3
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• pp.193-201
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• 2004

1960년 Au-Si계 합금에서 처음으로 비정질상이 급속 응고법에 의해 보고된 이래/sup 1)/ 지난 40년 간 많은 합금계에서 비정질상이 보고되어졌다. 대표적으로 Fe-, Ni-, Co기 합금 등 많은 합금계에서 비정질상이 보고되었으나, 비정질상의 형성을 위해서는 약 105 K/s이상의 높은 냉각속도를 필요로 하였다. 1980년대 수백 K/s의 낮은 냉각속도 하에서도 비정질상이 형성될 수 있는 다원계 합금(multi-component alloy)이 Mg-Ln-(Ni, Cu, Zn), Ln-Al-TM 합금에서 보고되어 졌으나 많은 관심을 받지 못하다가 1993년 Zr-Ti-Ni-Cu-Be 합금에서 수 ㎝ 크기의 비정질합금 제조가 보고되면서 전 세계적으로 많은 관심을 받게 되었다. Zr-Ti-Ni-Cu-Be계 벌크 비정질 합금이 보고된 후 Zr-(Nb,Pd)-Al-TM, Pd-Cu-Ni-P, Fe-Co-Zr-Mo-W-B, Ti-Zr-Ni-Cu-Sn등 여러 합금계에서 벌크 비정질 합금이 보고되었다. (중략)

• Journal of Powder Materials
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• v.25 no.2
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• pp.158-164
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• 2018

Multi-walled carbon nanotube (MWCNT)-copper (Cu) composites are successfully fabricated by a combination of a binder-free wet mixing and spark plasma sintering (SPS) process. The SPS is performed under various conditions to investigate optimized processing conditions for minimizing the structural defects of CNTs and densifying the MWCNT-Cu composites. The electrical conductivities of MWCNT-Cu composites are slightly increased for compositions containing up to 1 vol.% CNT and remain above the value for sintered Cu up to 2 vol.% CNT. Uniformly dispersed CNTs in the Cu matrix with clean interfaces between the treated MWCNT and Cu leading to effective electrical transfer from the treated MWCNT to the Cu is believed to be the origin of the improved electrical conductivity of the treated MWCNT-Cu composites. The results indicate the possibility of exploiting CNTs as a contributing reinforcement phase for improving the electrical conductivity and mechanical properties in the Cu matrix composites.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1011-1017
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• 1998

$YBa_2Cu_3O_{6+x}(Y123)-Ag$ high-Tc superconducting wires were fabricated by plastic extrusion technique using pyrophoric synthetic and mechanical mixing powder with and without Ag addition(20 wt.%). This method involves powder preparation, plastic paste making, die extrusion, binder burn-out and the sintering process. In order to fabricate a good-quality superconducting body, it is required to use homogeneous and fine-size power as a starting materials. $Y_2O_3-BaCO_3-CuO$ precursor powders with/without Ag addition were prepared both by pyrophoric synthetic(PS) and mechanical mixing(MM) method of raw powders. The formation kinetics of the powder mixtures into Y123 phase was investigated at various temperatures and times in air atmosphere. The powder prepared by PS method was more easily converted into a Y123 phase than the MM powder. The fine size and good chemical homogeneity of the powder prepared by PS method is attributable to the fast formation into a Y123 phase. The critical current density($J_c$) of the Y123-Ag superconducting wires made by plastic extrusion method were in the range of $150A/cm^2{\sim}230A/cm^2$. depending on the charateristics of starting material powders. $J_c$ of the wire prepared by pyrophoric synthetic powder with 20 wt.% Ag addition was $230A/cm^2$.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.60-67
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• 2020

In this study, copper (II) oxide powder for electroplating was prepared by recovering CuCl₂ from NaClO₃ type etching wastes via recovered non-sintering two step chemical reaction. In case of alkali copper carbonate [mCuCo₃·nCu(OH)₂], first reaction product, CuCo₃ is produced more than Cu(OH)₂ when the reaction molar ratio of sodium carbonate is low, since m is larger than n. As the reaction molar ratio of sodium carbonate increased, m is larger than n and Cu(OH)₂ was produced more than CuCO₃. In the case of m has same values as n, the optimum reaction mole ratio was 1.44 at the reaction temperature of 80℃ based on the theoretical copper content of 57.5 wt. %. The optimum amount of sodium hydroxide was 120 g at 80℃ for production of copper (II) oxide prepared by using basic copper carbonate product of first reaction. At this time, the yield of copper (II) oxide was 96.6 wt.%. Also, the chloride ion concentration was 9.7 mg/L. The properties of produced copper (II) oxide such as mean particle size, dissolution time for sulfuric acid, and repose angle were 19.5 mm, 64 second, and 34.8°, respectively. As a result of the hole filling test, it was found that the copper oxide (II) prepared with 120 g of sodium hydroxide, the optimum amount of basic hydroxide for copper carbonate, has a hole filling of 11.0 mm, which satisfies the general hole filling management range of 15 mm or less.