• Journal of Welding and Joining
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• 제20권1호
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• pp.47-54
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• 2002

Powder type Ag system insert metals were manufactured by ball milling process. The variables of milling process such as milling media, revolution speed and powder/ball weight ratio were constant except the milling time. The milling times were selected for 24, 48 and 72 hours. The insert metals made by milling process were evaluated by performing scanning electron microscope, x-ray and DSC(differential scanning calorimetry) analysis, and further in terms of wettability test. The selected insert metals that have the good characteristics compared to commercial insert metals were applied to make the brazed joints of the steel/steel and the steel/WC superhard particles. The characterizations of those brazed joints were also conducted by microstructural observations, shear tensile tests and microhardness measurements. The results indicated that milling time of 48 hours for making powder type insert metals was the best condition showing the small amount of oxides residue, low wetting angle and stable microstructure. The brazed joints that applied the 48 hours milled insert metal were very sound condition indicating the shear tensile value of $2.29{\times}102$ MPa and the microhardness of 138VHN. Further, the amount of the porosity was appeared to be lower than that of the commercial insert metals.

• 한국세라믹학회지
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• 제39권11호
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• pp.1074-1082
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• 2002

소결온도가 $1200{\circ}C$인 PMN-PT-BT에 소량의 $AgNO_3$와 MgO 졸을 첨가하여 $950{\circ}C$ 소결로 PMN-PT-BT/Ag/MgO 나노복합체를 제조하였다. Modified mixed oxide 방법으로 제조된 저온 소결용 PMN-PT-BT/Ag 분말을 $600{\circ}C$/1h 하소한 다음 MgO 졸을 0-1.0wt% 첨가하여, 산소 분위기에서 $850-950{\circ}C$에서 4시간 소결하여 MgO 졸의 첨가량과 소결온도에 따른 미세구조의 발달과 유전특성을 조사하였다. MgO 졸이 0.5wt% 첨가되고, $950{\circ}C$에서 소결하여 얻은 PMN-PT-BT/Ag/MgO(0.5wt%) 소결체는 $1-3{\mu}m$의 입의 크기에 $0.1-0.3{\mu}m$의 MgO가 2차상을 입경, 삼중접, 입내에 분포되어 있음을 SEM으로 볼 수 있었으며, Ag는 SIMS로 << $1{\mu}m$로 분포되어 있음을 정성적으로 확인하였다. 상대소결밀도 99%, 실온유전율 17200, 유전손실 2.1%, 비저항 $5.46{\times}10^{12}{\Omega}{\cdot}cm$의 특성을 나타내었다. 그러나 MgO 졸이 첨가되지 않은 PMN-PT-BT/Ag/MgO(0 wt%)의 $950{\circ}C$ 소결체는 상대 소결밀도 99.5%, 상온유전율 19500, 유전손실 2.1%, 비저항 $7.30{\times}10^{12}{\Omega}{\cdot}cm$의 좀더 높은 특성을 나타내었다.

• 한국분말재료학회지
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• 제19권6호
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• pp.393-397
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• 2012

$AgNO_3$ has the characteristic is controlling the inhibition or promotion of particle growth by adsorbing onto specific facets of platinum nanoparticles. Therefore, in this study, $AgNO_3$ was added to control the shape of platinum nanoparticles during the liquid phase reduction process. Consequently, platinum cubes were synthesized when $AgNO_3$ of 1.1 mol% (with respect to the Pt concentration) was added into the solution. Platinum octahedrons were synthesized when 32 mol% (with respect to the Pt concentration) was added into the solution. These results demonstrate that the metal salt $AgNO_3$, effectively controlled the relative growth rates of each facet of Pt nano particles.

• 한국재료학회지
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• 제18권1호
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• pp.12-17
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• 2008

Carbon nanotube (CNT) cathodes were fabricated using nano-sized silver (Ag) powders as a bonding material between the CNTs and cathode electrodes. The effects of the powder size on the sintering behavior, the current density and emission image for CNT cathodes were investigated. As the diameter of the Ag powders decreases to 10 nm, the sintering temperature of the CNT cathode was lowered primarily due to the higher specific surface area of the Ag powders. In this study, it was demonstrated that nano-sized Ag powders can be feasibly used as a bonding material for a screen-printed CNT cathode, yielding a high current density and a uniform emission image.

• 한국재료학회지
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• 제8권5호
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• pp.394-398
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• 1998

은(Ag)의 첨가가$ YBa_{2}$$Cu_{3}$$O_{7-\delta}$ (YBCO) 고온초전도체의 미세조직, 기계적 및 전기적 성질에 미치는 효과를 연구하였다. 소량의 Af(5, 10, 15 vol.%)는 각각 금속분말상태와 질산염인 $AgNO_{3}$초전도체의 강도와 인성값이 Ag의 함량이 증가할수록 높게 나타났으며, 이는 Ag입자에 의해 야기되는 강화기루에 의한 것으로 생각된다. 또한 Ag를 질산염의 분말상태로 첨가하여 만든 YBCO-Ag 복합재료가 금속분말상태로 첨가하여 만들었을 때보다 강도 및 인성값이 더 우수한 것으로 나타났다. $AgNO_{3}$를 첨가한 복합체가 상대적으로 더 우수한 기계적 성질을 가지는 것은 Ag 입자가 더 미세하고 균일하게 분포되었기 때문으로 판단된다. Ag 첨가로 인해 YBCO 복합초전도체의 전류밀도값은 미세하게 증가하는 것으로 관찰되었다.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.69-73
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• 2001

In this study, we fabricated Bi-2223/Ag high temperature superconducting tapes using PIT(Powder-In-Tube) process to apply the superconducting magnet, cable and etc. It is inevitable to deform the superconducting taps with axial strain for application. Therefore, for the characterization of the strain sensitivity of the superconducting properties, the degradation of Bi-2223/Ag tapes due to axial strain were investigated by measuring the critical current as a function of applied tension strain and external magnetic field. The critical current of Bi-2223/Ag tapes were decreased slightly up to 0.3∼0.4% applied strain but, drastically decreased more than these strains. Superconducting filament cores consisted of brittle ceramic fibers were broken easily by the large strain and current path were decreased simultaneously.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3209-3212
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• 2014

This paper describes a selective synthetic method of fabricating Ag nanowires by using a modified polyol process. To synthesize the Ag nanowire, an ethylene glycolic solution of silver nitrate and an ethylene glycolic solution of polyvinylpyrrolidone solution containing a small amount of organic oxidant, 1,4-benzoquinone, were slowly added to a hot ethylene glycol medium at $160^{\circ}C$ for 8 min using a syringe pump. The reaction mixtures were heated for an additional 45 min and cooled to room temperature. Finally, the silver nanomaterials were isolated from the mixture by centrifugation. The crystal structure of the nanomaterials was investigated by powder X-ray diffraction analyses, and their morphology was investigated by scanning electron microscopy. A small amount of organic oxidant, 1,4-benzoquinone, played a significant role in controlling the morphology during crystal growth. Consequently, Ag nanowires rather than Ag nanoparticles were selectively obtained.

• 한국세라믹학회지
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• 제31권12호
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• pp.1483-1490
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• 1994

YBa2Cu3Ox-Ag(YBCO-Ag) thick films were fabricated on the zirconia substrate by a screen printing method. The starting powder was a mixture of YBCO, prepared by a coprecipitation in oxalic acid, and Ag2O. The influence of heat treatment conditions on properties of thick films was investigated. It was observed that Jc of thick films was directly proportional to the orientation factor of thick films and the optimimum preparation condition was the heat treatment of thick films at 100$0^{\circ}C$ for 3 min in O2. The improvement of Jc by the addition of Ag was considered as a result of the suppression of microcracks in the films.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1489-1491
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• 1996

The effect of Ag alloy sheath have been investigated in terns of critical current density and mechanical property. Nevertheless the continuous improvement of critical current density($J_c$) of Ag sheathed Bi2223 oxide superconducting wire processed with powder in tube(PIT) method, poor mechanical strength is still considered to be demerits for power application. In this study, we prepared two kinds of Ag- x wt% Cu alloy and pure Ag sheathed Bi2223 superconducting tapes. The hardness and tensile strength of prepared tapes has been measured. Their mechanical propertes were improved by Ag alloying.

• 한국세라믹학회지
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• 제43권4호
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• pp.224-229
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• 2006

Ag-Pd alloy nanoparticles were prepared by a chemical reduction method using hydrazine $(N_2H_4)$ as a reductant in $AgNO_3\;and\;Pd(NO_3)_2$ aqueous solutions. Characterization of these particles by X-ray powder diffraction revealed a bimetallic and crystalline silver-palladium alloy. The average size of the particles was influenced not by the reductant $(N_2H_4)$ concentration, but the concentration of the starting materials $(AgNO_3\;and\;Pd(NO_3)_2)$.