• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1472-1474
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• 1997

In this study, the $Nb_3Sn$ wire was tried to fabricate by internal tin process to investigate the relationship between the processing parameters in a cold working and the microstructure. The critical current densities of $Nb_3Sn$ wires were evaluated in magnetic fields at 4.2 K. $Nb_3Sn$ compound layer was found to be formed between Nb core and Cu-Sn. The Cu part in the wire transformed to Cu-Sn by the reaction with Sn and the Sn in the Cu-Sn part reacted with Nb.

• Korean Journal of Materials Research
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• v.7 no.7
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• pp.623-631
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• 1997

본 연구에서는 주조 2상 스테인리스강의열시효에 대한 시효온도, 시효시간 및 Nb함유량의 영향을 관찰하기 위해 기계적 성질 및 조직을 조사하였으며 Nb을 함유한 주조 2상 스테인리스강의 파괴기구를 규명하기 위해 SEM에 의한 파단면 관찰과 WDS성분분석을 통해 파괴기구의 특성을 고찰하였다. 시효온도와 시효시간이 증가함에 따라 페라니트으 미소경도가 증가하였으며 항복강도의 경우 시효온도와 시효시간에는 영향을 받지 않았으나 Nb을 함유한 재료들이 Nb을 함유치 않은 재료들에 비해 다소 낮은 항복강도 값을 보였다. 충격흡수에너지 값은 시효시간 및 시효온도의 증가에 따라 시험된 모든 재료에서 저하되었는데 0.4% Nb을 함유하는 경우 Nb을 약간 함유하거나 함유치 않은 재료들에 비해 시효시간에 따라 급격한 감소 경향을 보였다. 파단면 관찰결과 페라이트 기지 또는 페라이트/오스테나이트 상경계에서 석출된 VbC를 비롯한 탄화물들이 취성저항성을 낮추는데 크게 기여했음을 알 수 있었다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.333-336
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• 2005

The reduction behavior of $Nb_2O_5$ in aluminum containing self-reducing briquettes(SRNB) was investigated. The time required for slag/metal equilibrium was estimated as about 20 minutes from the addition of SRNB on to the surface of molten steel. The maximum yield of Nb was expected with the slag composition of $60\%CaO-40\%Al_2O_3$. When $CaCO_3$ was used as a flux, the oxidation loss of Al by $CO_2$ should be compensated, and the chemical equivalent ratio of Al to $Nb_2O_5$ of about 1.43 was required to maximize the yield of Nb.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.256-259
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• 1996

$(Sr_{1-x}{\cdot}Ca_x)TiO_3+yNb_2O_5$($0.05{\leq}x{\leq}0.2$, 0.004$1350[^{\circ}C]$ in a reducing atmosphere($N_2$ gas). Dielectric propertries were investigated with contents of $Nb_2O_5$. The grain size and dielectric constant increase with increase $Nb_2O_5$, but decrease in $Nb_2O_5$ exceed($Nb_2O_5=0.6[mol%]$). Also, the temperature characteristics of the dielectric loss factor exhibited a stable value within 0.5[%]. The capacitance characteristics appeals a stab]e value in ${\pm}10[%]$.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.1
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• pp.1-7
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• 2001

A method to simultaneously synthesize and consolidate the silicide $NiSi_2$ and the composite $NiSi_2$-20vol.%Nb from powders of Ni, Si, and Nb was investigated. Combustion synthesis was carried out under the combined effect of an electric field and mechanical pressure. The final density of the products increased nearly linearly with the applied pressure. Highly dense $NiSi_2$ and $NiSi_2$-20vol.%Nb with relative densities of up to 97% were produced under the simultaneous application of a 60MPa pressure and a 3000A current on the reactant powders. The respective Vickers microhardness values for these materials were 6.0 and 5.8 GPa. From indentation crack measurements, the fracture toughness values for $NiSi_2$ and $NiSi_2$-20vol.%Nb were calculated to be 3.3 and 4.7 $MPa{\cdot}m^{1/2}$, respectively.

• Korean Journal of Materials Research
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• v.2 no.1
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• pp.52-57
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• 1992

The macro defects of $LiNbO_3$ crystals grown by the Czochralski method were strongly influenced by the single crystal growth parameters such as growth rate, thermal gradient and crystal rotation rate. The optimum growth conditions of a $LiNbO_3$ single crystal with 1" in diameter were $70~100^{circ}C/cm$ temperature gradient, 5~10 mm/hr growth rate and 40 rpm crystal rotation rate. In these conditions, we could grow crystals which had no cellular structure with easy diameter control, and any crack was not formed after the crystal was cooled.oled.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.1
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• pp.30-36
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• 1992

In order to measure the characteristics of Surface Acousitc Wave(SA W) with compositions of $LiNbO_3$ single crystal, $128^{\circ}$ Y cut wafer was fabricated from $LiNbO_3$ single crystals with the composition range of 47-50 $Li_2O$mol%. Delay lines were formed on the $128^{\circ}$ Y cut wafer using photolithography technique. Delay time was measured by pulse-echo overlap method. The compositional dependence of SAW characteristics, SAW velocity, electro-mechanical coupling coefficient$(K_s^2)$ and temperature coefficient of delay time(TCD), were investigated.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.371-374
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• 1999

Y2O3 and Nb2O5 co-doped tetragonal zirconia polycrystals((Y, Nb)-TZP) containing 10 to 30 vol% $Al_2O_3$ were prepared and hydrothermal stability of the composites was evaluated after aging for 5 h at the temperature range of $150^{\circ}C$ $250^{\circ}C$ under 4 MPa $H_2O$ vapor pressure in an autoclave. The (Y, Nb)-TZP/Al2O3 composites showed excellent phase stability under the hydrothermal conditions, as compared with the 3Y-TZP/$Al_2O_3$ composites, due to the combined effects of the Y-Nb ordering in the $t-ZrO_2$ lattice, the reduction of oxygen vacancy concentration, and the $Al_2O_3$ addition. The strength and fracture toughness of the (Y, Nb)-TZP/$Al_2O_3$ composite, containing 20 vol% of 2.8 $Al_2O_3$ particles, were 700 MPa and 8.1 MP.$am^{1/2}$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.205-209
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• 2009

In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, (1-x-0.09)$NaNbO_{3-x}BaTiO_3-0,09LiNbO_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $BaTiO_3$ substitution. All the specimens showed orthorhombic phase structure without secondary phase, $BaTiO_3$ substitution enhanced density, dielectric constant(${\epsilon}_r$) and electromechanical coupling factor($k_p$), However, mechanical quality factor was deteriorated. Curie temperature of specimens was observed as about $380^{\circ}C$. At the $BaTiO_3$ substitution of 4 mol%, density, electromechanical coupling factor($k_p$), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.493g/cm^3$, 0.236, 175, 70 pC/N, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.476-479
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• 2001

The microwave dielectric properties of $[(Pb_{1-x}Ba_{x})_{1/2}La_{1/2}](Mg_{1/2}Nb_{1/2})O_{3}$ ceramics were investigated. When $[(Pb_{0.9}Ba_{0.1})_{1/2}La_{1/2}](Mg_{1/2}Nb_{1/2})O_{3}$ ceramics were sintered at $1250^{\circ}C$ and $1350^{\circ}C$ for 2hr, the microwave dielectric properties were obtained $\varepsilon_{r}=64\sim80$, $Q{\times}f=11,800\sim18,000$. As a result, $[(Pb_{0.9}Ba_{0.1})_{1/2}La_{1/2}](Mg_{1/2}Nb_{1/2})O_{3}$ having $\varepsilon_{r}=80$, $Q{\times}f=11,800$ (at 4 GHz) was developed.