• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.276-277
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• 2005

본 연구에서는 MCP법을 이용하여 Bi2212 초전도 튜브를 제작하고 공정 변수에 따른 초전도 튜브의 전기적 특성을 평가하였다. 초전도 분말은 $1100^{\circ}C$에서 용융하여 $300\sim500^{\circ}C$로 예열된 몰드 내에 주입하였으며 몰드는 1000 RPM으로 회전시켰다 제작된 초전도 튜브는 $840^{\circ}C$ 의 $O_2$ 분위기에서 72시간 열처리 하였다. SEM과 XRD 분석결과 튜브는 약 $40{\mu}m$의 크기를 갖는 Bi2212 초전도 상이 일정한 방향성을 갖으며 XRD 분석 결과 튜브 바깥부문에 Bi2201상이 존재하였다. 전기적 특성은 몰드 회전 속도가 증가할수록, 튜브의 두께가 증가할수록, 길이가 감소할수록 높은 $I_c$ 값을 나타내었으며, 이때 50 mm$\times$70 mm$\times$2.5 mm, 1000 RPM의 튜브에서 전기적 특성은 $I_c$=890 A, $T_c$= 80 K의 값을 나타내었다.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.182.2-182
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• 2003

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.846-849
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• 2003

Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2＋}$, $Pb^{2＋}$,$ Ca^{2＋}$ , $Bi^{3＋}$ , $La^{3＋}$ , $Ti^{4＋}$ , $Mo^{6＋}$ , and $W^{6＋}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2＋}$ , $Ba^{2＋}$ , $La^{3＋}$ doping, but the transition temperature increased with $Ca^{2＋}$ , $Bi^{3＋}$ , $Ti^{4＋}$, $Mo^{6＋}$ , or$ W^{6＋}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

• Journal of Magnetics
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• v.14 no.3
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• pp.120-123
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• 2009

In this study, BiFe$O_3$-BaTi$O_3$ ceramics have been fabricated by a solid-state reaction method. The effects of BaTi$O_3$ content in the (1-x)BiFe$O_3$-xBaTi$O_3$ (x = 0.1, 0.2, 0.25, 0.3, 0.4, 0.5) system on crystal structure and magnetic, dielectric, and ferroelectric properties were investigated. Perovskite BiFe$O_3$ was stabilized through the formation of a solid solution with BaTi$O_3$. Rhombohedrally distorted structure (1-x)BiFe$O_3$-xBaTi$O_3$ ceramics showed strong ferromagnetism at x = 0.5. Dielectric and ferroelectric properties of the BiFe$O_3$-BaTi$O_3$ system also changed significantly upon addition of BaTi$O_3$. It was found that the maximum dielectric and ferroelectric properties were exhibited in the (1-x)BiFe$O_3$-xBaTi$O_3$ system at x = 0.25. This suggested the morphotropic phase boundary (MPB) with the coexistence of both rhombohedral and cubic phases of the (1-x)BiFe$O_3$-xBaTi$O_3$ system at x = 0.25.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.1-7
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• 2004

Tin plating on component finishes may grow whiskers under certain conditions, which may cause failures in electronics equipment. To protect the environment, 'lead-free' among component finishes is being promoted worldwide. This paper presents the evaluation results of whiskers on two kinds of lead-free plating materials at the plating temperature and under the reliability test. The rising plating temperature caused increasing the size of plating grain and shorting the growth of whisker. The whisker was grown under the temperature cycling the bent type in matt Sn plating and striated type in malt Sn-Bi. The whisker growth in Sn-Bi plating was shorter than that in Sn plating. In FeNi42 leadframe, the $7.0{\~}10.0{\mu}m$ diameter and the $25.0{\~}45.0{\mu}m$ long whisker was grown under 300 cycles. In the 300 cycles of Cu leadframe, only the nodule(nuclear state) grew on the surface, and in the 600 cycles, a $3.0{\~}4.0{\mu}m$ short whisker grew. After 600 cycles, the ${\~}0.34{\mu}m$ thin $Ni_3Sn_4$ formed on the Sn-plated FeNi42. However, we observed the amount of $0.76{\~}1.14{\mu}m$ thick $Cu_6Sn_5$ and ${\~}0.27{\mu}m$ thin $Cu_3Sn$ intermetallics were observed between the Sn and Cu interfaces. Therefore, the main growth factor of a whisker is the intermetallic compound in the Cu leadframe, and the coefficient of thermal expansion mismatch in FeNi42.

• Journal of Periodontal and Implant Science
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• v.28 no.2
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• pp.337-350
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• 1998

The purpose of this' study was to compare surface roughness and morphologic changes after use of various plaque control devices to titanium implant surfaces. The study materials were 6 ITI titanium implants($Bonefit^{(R)}$) and 5 plaque control devices. 6 implants were divided into 6 different groups and instrumented by each plaque control devices as follows. 1) Group I : untreated control 2) Group II : Titanium curette(Titanium $curette^{(R)}$, 3i) 80 vertical/horizontal strokes 3) Group III : Plastic curette($Implacare^{(R)}$, Hu-Friedy) 80 vertical/horizontal strokes 4) Group N : Plastic tip-ultrasonic scaler($Amdent^{(R)}$, Amdent) 160 seconds 5) Group V : Rotating interdental brush($Identobrush^{(R)}$, Identoflex) 160 seconds 6) Group VI : Abrasive rubber cup polisher($Zircate^{(R)}$, Prophy paste, Dentsply) 160 sec-onds. All specimens were prepared for evaluation by surface roughness tester, optical stereomicroscopy(OM) and scanning electron microscopy(SEM). The Ra and Rt mean values of the tested specimens were 1) Group I ($Ra=0.170{\pm}0.007{\mu}m$, $Rt=1.297{\pm}0.016{\mu}m$) 2) Group II ($Ra=0.209{\pm}0.006{\mu}m$, $Rt=1.602{\pm}0.110{\mu}m$) 3) Group III ($Ra=0.179{\pm}0.001{\mu}m$, $Rt=1.429{\pm}0.055{\mu}m$) 4) Group IV ($Ra=0.182{\pm}0.005{\mu}m$, $Rt=1.511{\pm}0.085{\mu}m$) 5) Group V ($Ra=0.301{\pm}0.008{\mu}m$, $Rt=1.882{\pm}0.131{\mu}m$) 6) Group VI ($Ra=0.147{\pm}0.010{\mu}m$, $Rt=1.059{\pm}0.021{\mu}m$) In Ra values, experimental group II, V, VI were statistically significant different when compared with control. OM and SEM observation showed that experimental group III, IV were minimal changes when compared with control and group VI was smoothest among other experimental groups. The results suggested that plastic curette and plastic tip-ultrasonic scaler were predictable devices to titanium implant surface.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.9 s.339
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• pp.1-8
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• 2005

A $0.35\mu$m SiGe BiCMOS fabrication process has been timely developed, which is aiming at wireless RF ICs development and fast growing SiGe RF market. With non-selective SiGe epilayer, SiGe HBTs in this process used trapezoidal Ge base profile for the enhanced AC performance via Ge induced bandgap niuoin. The characteristics of hFE 100, $f_{T}\;45GHz,\;F_{max}\;50GHz,\;NF_{min}\;0.8dB$ have been obtained by optimizing not only SiGe base profile but also RTA condition after emitter polysilicon deposition, which enables the SiGe technology competition against the worldwide cutting edge SiGe BiCMOS technology. In addition, the process incorporates the CMOS logic, which is fully compatible with $0.35\mu$m pure logic technology. High Q passive elements are also provided for high precision analog circuit designs, and their quality factors of W(1pF) and inductor(2nH) are 80, 12.5, respectively.

• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.215-221
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• 2005

Thermoelectric bismuth telluride thin films were prepared on $SiO_{2}$/Si substrate with co-sputtering of bismuth and tellurium targets. The effects of deposition temperature on surface morphology, crystallinity and electrical transport properties were investigated. Hexagonal crystallites were clearly visible at the surface of films deposited above $290 ^{\circ}C$. Change of dominant phase from rhombohedral $Bi_2Te_3$ to hexagonal BiTe was confirmed with X-ray diffraction analysis. The deviation from stoichiometric composition at high deposition temperature resulted in the change of structural and electrical characteristics. Seebeck coefficients of all samples have negative value, indicating the prepared $Bi_XTe_Y$ films are n-type thermoelectric. Optimum of Seebeck coefficient and power factor were obtained at the deposition temperature of $225 \^{circ}$C (about -55 $\mu$V/K and $3\times10^{-4}$ W/$k^{2}$m, respectively). Deterioration of thermoelectric properties at higher temperature.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.266.2-266.2
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• 2008

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.549-552
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• 2002

$(SrBi_2Nb_2O_9)_{0.5}-(Bi_3TiNbO_9)_{0.5}$ ceramics were fabricated by the mixed-oxide method, and the structural and electrical properties with variation of ball-milling time were investigated. All SBN-BTN specimens showed the typical polycrystalline X-ray diffraction patterns without the presence of the second phase. The SBN-BTN specimen sintered at $1200^{\circ}C$ and ball-milled for 168h showed the average grain size of $16{\mu}m$. The dielectric constant and dielectric loss of the SBN-BTN specimen sintered at $1150^{\circ}C$ and ball-mill for 72h were 225, 0.4% at 1KHz, respectively.