• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.15-22
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• 1991

When $YBa_2Cu_3Ox$ is liquid-phase sintered at $925^{\circ}C$ in $O_2$ for 16h, liquid pockets are entrapped within the grains. The liquid pockets show a thin parallelepiped shape with short edge lengths in the c axis, even after reannealing $925^{\circ}C$ in $O_2$ for 16h. All grains in contact with the liquid matrix show the same shape. However, when liquid-phase sintered at 925^{circ}C in $N_2$ for 16h, the grains dispersed in the liquid matrix show a thicker parallelepiped shape than in $O_2$, and their shape remains intact even after reannealing at $925^{\circ}C$ in $N_2$ for 16h. The effect of atmosphere on the grain shape is expected to be due to the variation of oxygen vacancy concentraion in $CuO_2$ plane of tetragonal unit cell.

• Proceedings of the Korean Magnestics Society Conference
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• 1993.11a
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• pp.52-53
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• 1993

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.941-948
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• 1997

CuCl nanocrystallites dispersed nonlinear optical silica and borosilicate glasses were fabricated by sol-gel process. CuCl powder was dissolved in TEOS(Si(OC2H5)4) and TMB((CH3O)3B), precursors of silica and borosilicate glasses, with ethanol, water and HCl, and precipitated through the heat treatment in the matrix glass. The optical properties of CuCl doped glasses were measured using the spectrophotometer at room temperature and low temperature(77K); Z1, 2 and Z3 exciton peaks from the absorption spectra, were observed at about 370 nm and 380 nm, respectively. The average radius of nanocrystallites, calculated from the blue shift of Z3 excitons, was measured according to annealing temperature and time. The precipitation temperature of CuCl nanocrystallites was decreased when boron was added to silica glass. Increase of annealing temperature and time made average radius of nanocrystallites saturated about 2 nm.

• BMB Reports
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• v.28 no.4
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• pp.311-315
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• 1995

Exogenous $Cu^{2+}$ or $Zn^{2+}$ at micromolar concentration had a strong inhibitory effect on detergent-solubilized cytochrome c oxidase. A similar effect was observed when $Cu^{2+}$ was added to vesicular cytochrome c oxidase, although the extent of inhibition was significantly larger for the uncoupled state than for the coupled state. Interestingly, the inhibition by $Zn^{2+}$ was almost negligible for both the coupled and uncoupled states. These results suggest that the binding sites for $Cu^{2+}$ ions are exposed to the extravesicular side. whereas those for $Zn^{2+}$ are exposed to the matrix side. The EPR spectra of bound $Cu^{2+}$ ions at 77 K indicate that each of the first two $Cu^{2+}$ ions is ligated by three or four histidine residues, as evidenced by distinct $^{14}N$ superhyperfine splitting. These $Cu^{2+}$ ions can not be removed readily by EDTA and inhibit the enzyme activity by as much as 80%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.141-144
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• 2005

[ $(Y_{0.5}Sm_{0.25}Nd_{0.25})Ba_2Cu_3O_y$ ] [(YSN)-123] high $T_c$ composite superconductors with $CeO_2$ addition were systematically investigated by top seeded melt growth (TSMG) process in air atmosphere. A melt textured $NdBa_2Cu_3O_y$ (Nd-123) single crystal was used as a seed for achieving the c-axis alignment large grains perpendicular to the surface of (YSN)-123 composite oxides. The size of $(Y_{0.5}Sm_{0.25}Nd_{0.25})_2BaCuO_5$ [(YSN)211] nonsuperconducting inclusions of the melt textured (YSN)-123 samples with $CeO_2$ addition were remarkably reduced and uniformly distributed within the (YSN)123 superconducting matrix except in the region very close to the Nd-123 seed crystal. The sample showed a sharp superconducting transition of 91 K.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.950-951
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• 2006

[ $Mg_{55}Y_{15}Cu_{30}$ ] metallic glass powders were prepared by the mechanical alloying of pure Mg, Y, and Cu after 10 h of milling. The thermal stability of these $Mg_{55}Y_{15}Cu_{30}$ amorphous powders was investigated using the differential scanning calorimeter (DSC). $T_g$, $T_x$, and ${\Delta}T_x$ are 442 K, 478 K, and 36 K, respectively. The as-milled $Mg_{55}Y_{15}Cu_{30}$ powders were then consolidated by vacuum hot pressing into disk compacts with a diameter and thickness of 10 mm and 1 mm, respectively. This yielded bulk $Mg_{55}Y_{15}Cu_{30}$ metallic glass with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix. The pressure applied during consolidation can enhance thermal stability and prolong the existence of amorphous phase within $Mg_{55}Y_{15}Cu_{30}$ powders.

• Journal of Powder Materials
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• v.3 no.1
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• pp.33-41
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• 1996

Nanostructured Cu-Pb powders were synthesized by mechanical alloying process. The variation of powder characteristics with mechanical alloying time was investigated by x-ray diffraction, differential scanning calorimetry, SEM and TEM. An electrical resistivity of the hot pressed specimens was also measured by using the nanovoltmeter. It was shown that mechanical alloying for 12 hours leads to a homogenization and a grain refinement to the nanometer scale under 20 nm. The mechanically alloyed Cu-Pb alloys represented the enhanced solid solubility of 10wt% Pb in the Cu matrix. The monotectic temperature of nanostructured Cu-Pb alloy decreased from equilibrium state of 955$^{\circ}C$ to 855$^{\circ}C$ due to reduced grain size effect. The analysis of electrical resistivity showed that the hot pressed MA Cu-5wt% Pb compact existed as a solid solution.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.3
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• pp.150-158
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• 2022

The effects of scandium addition on the Al-6Si-2Cu Alloy were investigated. The Al-6Si-2Cu-Sc alloy was prepared by gravity die casting process. In this study, scandium was added at 0.2 wt%, 0.4 wt%, 0.8 wt%, and 1.0 wt%. The microstructure of Al-6Si-2Cu-Sc alloy was investigated using Optical Microscope, Field Emission Scanning Electron Microscope, Electron Back Scatter Diffraction, and Transmission Electron microscope. The microstructure of Al-6Si-2Cu alloy with scandium added changed from dendrite structure to equiaxed crystal structure in specimens of 0.4 wt% Sc or more, and coarse needle-shape eutectic Si and β-Al₅FeSi phases were segmented and refined. The nanosized Al₃Sc intermetallic compound was observed to be uniformly distributed in the modified Al matrix.

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.27-41
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• 1999

The Ag-Pd-Cu alloys containing a small amount of Au is commonly used for dental purposes, because this alloy cheaper than Au-base alloys for clinical use. However, the most important characteristic of this alloy is age-hardenability, which is not exhibited by other Ag-base dental alloys. The specimens used were Ag-30Pd-10Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electric furnace and centrifugal casting machine in Ar atmosphere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at 350-$550^{\circ}C$ Age-hardening characteristic of the small Au-containing Ag-Pd-Cu dental alloys were investigated by means of hardness testing, X-ray diffraction and electron microscope observations, electrical resistance, differential scanning calorimetric, energy dispersed spectra and electron probe microanalysis. Principal results are as follows ; Maximum hardening occured in two co-phases of ${\alpha}_2$ + PdCu In stage II, decomposition of the $\alpha$ solid solution to a PdCu ordered phase($L1_o$ type) and an Ag-rich ${\alpha}_2$ phase occurred and a discontinuous precipitation occurred at the grain boundary. From the electron microscope study, it was concluded that the cause of age-hardening in this alloy is the precipitation of the PdCu redered phase, which has AuCu I type face-centered tetragonal structure. Precipitation procedure was ${\alpha}{\to}{\alpha}_1+PdCu{\to}{\alpha}_2+PdCu$ at Pd/Cu = 3 Pd element of Ag-Pd-Cu alloy is more effective dental alloy on anti-corrosion and is suitable to isothermal ageing at $450^{\circ}C$.

• ETRI Journal
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• v.41 no.6
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• pp.820-828
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• 2019

A highly reliable conductive adhesive obtained by transient liquid-phase sintering (TLPS) technologies is studied for use in high-power device packaging. TLPS involves the low-temperature reaction of a low-melting metal or alloy with a high-melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag-coated Cu, a Sn96.5-Ag3.0-Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 ℃, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.