• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.169-175
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• 2012

Purpose: In this study, brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature were investigated. Materials and methods: The sample size of the $ZrO_2$ was $3mm{\times}3mm{\times}3mm$ (thickness), and Ti-6Al-4V was $10mm(diameter){\times}5mm(thickness)$. The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under $5{\times}10^{-6}$ torr atmosphere, while the brazing temperature was changed from 700 to $800^{\circ}C$ for 30 min. Results: The experimental results shows that brazed joint of $ZrO_2$ and Ti-6Al-4V occurred at $700-800^{\circ}C$. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of $ZrO_2$ and Ti-6Al-4V bonded interfaces decreased with brazing temperature. Conclusion: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between $ZrO_2$ and Ti did not occur enough.

• Journal of Integrative Natural Science
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• v.10 no.4
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• pp.245-248
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• 2017

The Cu and CuSn/PVP nanofibers were fabricated by electrospinning method by controlling various parameters. The precursor solution was prepared with copper(II) acetate monohydrate ($Cu(CH_3COO)_2$) and tin chloride dihydrate ($SnCl_2{\cdot}2H_2O$), and polyvinylpyrrolidone (PVP) for adjusting viscosity. The fabricated nanofibers were calcined at 873 K in Ar atmospheric environment for 5 hours to remove the solvent and polymer. The morphology and diameter of nanofibers were measured by optical microscopy (OM) with Motic image plus 2.0 program. The components and chemical environment were investigated with X-ray photoelectron spectroscopy (XPS). From the XPS survey spectra, we confirmed that CuSn/PVP nanofibers were successfully fabricated. The XPS peaks of C 1s and N 1s were remarkably decreased after calcination of the nanofibers at 873 K. It implies that the PVP was completely decomposed after calcination at 873 K.

• ETRI Journal
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• v.13 no.2
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• pp.42-53
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• 1991

고유전율 적충세라믹 커패시터 소재인 $BaTiO_3$ 자기물은 일반적으로 큐리오도인 약 $120^{\circ}C$부근에서 유전율이 최고 약 10,000정도로 증가한 다음 급격히 감소하므로 적절한 이동체를 첨가하여 큐리온도를 상온으로 이동시켜 상온에서 최대 유전율을 이용하여야 한다. 그리고$BaTiO_3$ 자기물은 $1300^{\circ}C$이상의 고온소결시 고가인 Pd전극이 요구된다. 그러나 자기물의 소결온도를 저온화화면 저가의 Ag합금으로 전극재료를 대체할 수 있다. 본 연구에서는 이동제로서 $CaSnO_3$ 를 이용하여 큐리온도를 상온으로 이동시켰다. 또한 소결온도를 저온화하기 위하여 $BaTiO_3$ 세라믹에 여러가지 산화물을 첨가하여 소결현상을 살펴보았다. 실험결과 첨가제를 넣지 않은 경우 소결온도는 $1350^{\circ}C$의 고온이 필요한 반면, $CuO,B_2O_3$는 $1050^{\circ}C$의 낮은 온도에서도 치밀화와 입도성장이 잘 일어났다. 특히 $B_2$$O_3$ 를 첨가한 경우는 $1250^{\circ}C$이상에서 소결할 때 절연저항이 낮아 유전손실이 큰 문제점을 보였지만, 최대 유전율이 11,000 정도로 높고, 양호한 유전율의 온도변화 특성을 나타내어 우수한 고유전율 소재의 첨가제로 응용될 가능성을 보였다

• Progress in Superconductivity and Cryogenics
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• v.19 no.3
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• pp.18-22
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• 2017

Addition of $BaSnO_3$ (BSO) to $GdBa_2Cu_3O_{7-{\delta}}$ (GdBCO) is reported to enhance the flux pinning property of GdBCO thick films. To investigate the effect of growth condition on the pinning properties, 700 nm-thick BSO-added GdBCO films deposited with varying temperatures and growth rates were prepared by using a pulsed laser deposition method. As the deposition temperature increases, the critical current density and the pinning force density show an improved field dependence up to $750^{\circ}C$ due to the increase in the formation of the a-axis growth and the BSO nanostructures. The films deposited at higher temperatures show degraded surfaces and as a result, degraded pinning behaviors. For the change in growth rate, the critical current density and the pinning force increase as the repetition rate increase at low magnetic fields, but this behavior is reversed in high magnetic fields. These results indicate that the film growth conditions significantly affect the formation of BSO nanostructures and the pinning properties of BSO-added GdBCO films.

• Journal of the Korean Ceramic Society
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• v.37 no.9
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• pp.900-908
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• 2000

일반적인 유리용융과 열처리법을 이용하여 많은 양의 금속구리 미립자가 분산된 Zinc Phosphate 유리를 제조하였다. 금속산화물로는 Cu$_2$O를, 환원제로는 SnO를 사용하였다. XRD와 전자회절로부터 열처리에 의해 금속구리의 결정상이 석출됨을 알 수 있었고, TEM에 의해 석출상의 크기는 수~20nm 정도임을 알 수 있었다. 또한 570nm에서의 광흡수 피크로부터도 금속구리의 석출을 확인할 수 있었다. 석출입자의 크기와 흡광은 석출을 위한 열처리 온도와 시간이 증가함에 따라 증가하였다. XPS 스펙트럼으로는 구리의 산화상태 중 Cu$^{2+}$ 이온의 상태만을 분명히 할 수 있었다. 매질유리의 BO/NBO의 비는 열처리 전후 크게 변화가 없었으며, 열처리 후 Cu$^{2+}$ 이온이 다소 감소되는 경향을 보였다.

• Journal of the Korea Safety Management & Science
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• v.9 no.6
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• pp.197-204
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• 2007

Ceramic pigments were developed by using 4 kinds of Brass scraps. Each Brass scraps were mixed with same weight-ratio of Husk ash, and fine-ground by Rotate ring mill(RRG-120, Armstech industrial. co. Ltd, Korea) after firing at $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. As a result, analysis of particle size of synthetic pigments by particle size analyser, they are $3{\mu}m$ as average. The resulting pigments were characterized by using XRD, FT-IR, SEM Structure of the crystals are Zn2SiO4,, and ZnO, Cu2O, CuO, and cristobalite are existed and particles' shape are plate or needle. As a result of analysis of chemical composition by XRF, synthetic pigments have high SiO2 and CuO content and have SnO2, ZnO and NiO, too. 1wt%, 3wt% and 5wt% pigments were added in each lime glaze, lime-barium glaze and lime-magnesia glaze, and fired at oxidation and reducing atmosphere to figure hue in glazes out. As a result of analysis of color, chroma and brightness by UV, colors of glazes fired at oxidation atmosphere turned into green from sky blue, and colors of glazes fired at reducing atmosphere turned into pink and red.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.5
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• pp.563-571
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• 2012

In 3D integration package using TSV technology, bonding is the core technology for stacking and interconnecting the chips or wafers. During bonding process, however, warpage and high stress are introduced, and will lead to the misalignment problem between two chips being bonded and failure of the chips. In this paper, a finite element approach is used to predict the warpages and stresses during the bonding process. In particular, in-plane deformation which directly affects the bonding misalignment is closely analyzed. Three types of bonding technology, which are Sn-Ag solder bonding, Cu-Cu direct bonding and SiO2 direct bonding, are compared. Numerical analysis indicates that warpage and stress are accumulated and become larger for each bonding step. In-plane deformation is much larger than out-of-plane deformation during bonding process. Cu-Cu bonding shows the largest warpage, while SiO2 direct bonding shows the smallest warpage. For stress, Sn-Ag solder bonding shows the largest stress, while Cu-Cu bonding shows the smallest. The stress is mainly concentrated at the interface between the via hole and silicon chip or via hole and bonding area. Misalignment induced during Cu-Cu and Sn-Ag solder bonding is equal to or larger than the size of via diameter, therefore should be reduced by lowering bonding temperature and proper selection of package materials.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.199-206
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• 2013

The Daehyun gold-silver deposit consists of two hydrothermal quartz veins that fill NE-trending fractures in the Cambro-Ordovician calcitic marble. I have sampled wallrock, hydrothermaly-altered rock and gold-silver ore vein to study the element dispersion and element gain/loss during wallrock alteration. The hydrothermal alteration doesn't remarkably recognized at this deposit and consists of mainly calcite, dolomite, quartz and minor epidote. The ore minerals composed of arsenopyrite, pyrrhotite, pyrite, sphalerite, stannite, chalcopyrite, galena, electrum, native bismuth and silver-bearing mineral. Based on analyzed data, the chemical composition of wallrock consists of mainly $SiO_2$, CaO, $CO_2$ with amounts of $Al_2O_3$, $Fe_2O_3(T)$ and MgO. The contents of $SiO_2$, $Fe_2O_3(T)$, MgO, CaO and $CO_2$ vary significantly with distance from ore vein. The element dispersion doesn't remarkably recognized during wallrock alteration and only occurs near the ore vein margin because of physical and chemical properties of wallrock. Remarkable gain elements during wallrock alteration are $Fe_2O_3(T)$, total S, Ag, As, Bi, Cd, Cu, Ni, Pb, Sb, Sn, W and Zn. Remarkable loss elements are $SiO_2$, MnO, MgO, CaO. $CO_2$ and Sr. Therefore, Our result may be used when geochemical exploration carry out at deposits hosted calcitic marble in the Hwanggangri metallogenic district.

• Resources Recycling
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• v.7 no.5
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• pp.46-51
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• 1998

A study has been on the recovery of nitric acid and valuable metals such as Fe, Cu, Sn, Pb, from spent nitric etching solutions. The effects of extractant of extractant type, concentrations, phase raios and selectivity from Fe, Cu, Sn, Pb on nitric acid extraction were studied. The results showed that TBP as an extractant for recovering of nitric acid was more effective than Alamine336, and the optimal concentration of TBP was found to be 60~70% of organic phase. Also, the nitric acid were only extracted by TBP from the spent etching solutions and the heavy metals such as Fe, Cu, Sn, Pb were not extracted above 0.1N nitric acid in spent etching solutions, From the analysis of McCabe-Thiele diagram, the extraction of 95% nitric acid is attained at a ratio of O/A=3 with five stages by 60% TBP and the stripping of 98% nitric acid from 80 g/l nitric acid in organic phase is attained at a ratio of O/A=1 with four stages by distilled water.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.7-8
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• 1993