• 한국재료학회지
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• 제24권2호
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• pp.116-122
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• 2014

$Bi_2Sr_2CaCu_2O_x$(Bi-2212) and $Bi_2Sr_2Ca_2Cu_3O_y$(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.

• Journal of Magnetics
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• 제20권4호
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• pp.336-341
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• 2015

MnBi alloys were fabricated by arc melting and annealing at 573 K. The heat treatment enhanced the content of the low-temperature phase (LTP) of MnBi up to 83 wt%. The Bi-excess assisted LTP MnBi alloys were used in the hybridization with the Nd-Fe-B commercial Magnequench ribbons to form the hybrid magnets (100-x)NdFeB/xMnBi, x = 20, 30, 40, 50, and 80 wt%. The as-milled powder mixtures of Nd-Fe-B and MnBi were aligned in a magnetic field of 18 kOe and warm-compacted to anisotropic and dense bulk magnets at 573 K by 2,000 psi for 10 min. The magnetic ordering of two hard phase components strengthened by the exchange coupling enhanced the Curie temperature ($T_c$) of the magnet in comparison to that of the powder mixture sample. The prepared hybrid magnets were highly anisotropic with the ratio $M_r/M_s$ > 0.8. The exchange coupling was high, and the coercivity $_iH_c$ of the magnets was ~11-13 kOe. The maximum value of the energy product $(BH)_{max}$ was 8.4 MGOe for the magnet with x = 30%. The preparation of MnBi alloys and hybrid magnets are discussed in details.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.571-574
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• 2003

The thin films fabricated by using the layer-by-layer sputtering was compared with the thin film fabricated by using the evaporation method. Re-evaporation in the form of Bi atoms or $Bi_2O_3$ molecules easily bring out the deficiency of Bi atoms in thin film due to the long sputtering time of the layer-by-layer deposition. On the other hand, the respective atom numbers corresponding to BiSrCaCuO phase is concurrently supplied on the film surface in the evaporation deposition process and leads to BiSrCaCuO phase formation. Also, it is cofirmed that by optimizing the deposition condition, each single phase of the Bi2201 phase and the Bi2212 phase can be fabricated, the sticking coefficient of Bi element is clearly related to the changing of substrate temperature and the formation of the Bi2212 phase.

• 대한한의학방제학회지
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• 제22권1호
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• pp.47-64
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• 2014

Objectives : Bi-jeung is a traditional oriental medical name. Bi-jeung is similar to rheumatoid arthritis(RA). This study was investigated to get the practical use of Bi-jeung prescriptions in Byunjeungrok. Methods: Original records related Bi-jeung in Byunjeungrok are interpreted and contemplated. Results: Bi-jeung prescriptions in Byunjeungrok are put stress on Byunjeung in conformity with entrails good energy enforcing as well as evil energy eliminating removing damp-evil among wind-evil cold-evil and damp-evil showing concrete prognosis. Conclusions: This study indicates that Bi-jeung prescriptions in Byunjeungrok have an influences for RA. It may also suggest that Bi-jeung prescriptions may expand therapy field for treatment of RA. and its complications.

• 공업화학
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• 제3권1호
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• pp.53-63
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• 1992

프로필렌을 선택산화시켜 아크로레인을 제조하는 반응을 Bi-molybdate 촉매상에서 고정층 반응기를 사용하여 연구하였다. ${\alpha}-Bi_2Mo_3O_{12}$위에 $MoO_3$를 담지시킨 M/BM-series 촉매는 함침법으로 제조되었고, 역으로 BM/M-series 촉매는 $MoO_3$위에 ${\alpha}-Bi_2Mo_3O_{12}$을 침전시켜 제조하였다. 또한 촉매의 특성분석을 위하여 질소흡착과 XRD, SEM을 이용하였다. M/BM-series 촉매에서는 $MoO_3$가 작은 입자로 분산되고 ${\alpha}-Bi_2Mo_3O_{12}$의 결정구조는 $MoO_3$상이 추가되어도 그 형상이 변하지 않는 채로 유지되었으나, BM/M-series 촉매의 표면형상 및 전체 구조는 촉매제조 중에 생기는 침전물인 $Bi(OH)_3$가 소성 도중 $MoO_3$와 반응하여 ${\alpha}-Bi_2Mo_3O_{12}$을 형성하는 관계로 그 조성에 따라 매우 불규칙적으로 변화하였다. 반응실험 결과, 두 종류의 촉매 모두에서 excess $MoO_3$가 포함되었을 때 활성이 크게 증가하였는데, 이는 선별산화반응이 주로 ${\alpha}-Bi_2Mo_3O_{12}$에서 일어나고 $MoO_3$는 ${\alpha}-Bi_2Mo_3O_{12}$에 산소 공급을 원활히 하여 활성을 증가시키기 때문으로 판명되었다. 또한 이러한 활성 증가는 ${\alpha}-Bi_2Mo_3O_{12}$와 기계적 혼합물 (mechanical mixture)에서도 관찰되었다.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.163-169
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• 2019

전자제품에서 사용되던 Sn-Pb계 솔더합금은 RoHS, WEEE, REACH 등의 환경규제에 의해 무연솔더합금(Pb free solder alloy)으로 빠르게 대체되고 있다. 그 중에서도 Sn58%Bi(in wt.%) 합금은 융점이 낮고 Sn-Pb계 합금에 비해 기계적특성이 우수하여, 전자제품 솔더합금으로 사용하기 위한 연구가 진행되고 있다. 그러나 Sn58%Bi 솔더합금은 구성 원소인 Bi의 취성으로 인해 기계적인 신뢰성이 저하되는 문제를 개선할 필요가 있다. 따라서 본 연구에서는 다양한 함량의 Sn-MWCNT (multiwalled carbon nanotube) 입자를 첨가한 Sn58%Bi 복합솔더를 제조한 후, OSP처리된 FR-4 기판 및 FR-4 컴포넌트를 리플로우(reflow) 횟수를 1회부터 7회까지 진행하였다. 접합시편의 접합강도 및 파괴에너지는 전단시험(die shear test)을 통해 측정하였고, 주사전자현미경(scanning electron microscope, SEM)으로 미세조직 및 파괴모드를 분석하였다. Sn-MWCNT 첨가에 의해 Sn58%Bi 복합솔더 접합부에서 조직 미세화가 관찰되었고, 함량이 0.1 wt.%일때 접합강도와 파괴에너지는 각각 20.4%, 15.4% 만큼 증가하였다. 또한 파단면에서 연성파괴(ductile failure) 영역이 관찰되었으며, F-x(force-displacement to failure) 그래프를 통해 Sn-MWCNT의 첨가가 복합솔더의 연성(ductility)을 증가시킨 것을 확인할 수 있었다.

• 한국표면공학회지
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• 제35권1호
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• pp.11-16
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• 2002

As environmental concerns increasing, the electronics industry is focusing more attention on lead free solder alternatives. In this research, we have researched wettability of intermediate solder of Sn3Ag9Bi5In, which include In and Bi and has similar melting temperature to Sn37Pb eutectic solder. We investigated the wetting property of Sn3Ag9Bi5In. To estimate wettability of Sn3Ag9Bi5In solder on various substrates, the wettability of Sn3Ag9Bi5In solder on high-pure Cu-coupon was measured. Cu-coupon that plated Sn, Ni and Au/Ni and Si-wafer adsorbed Ni/Cu under bump metallurgy on one side. As a result, the wetting property of Sn3Ag9Bi5In solder is a little better than that of Sn37Pb and Sn3.5Ag.

• 한국세라믹학회지
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• 제37권2호
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• pp.186-193
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• 2000

Effects of 1.0 mol% CoO addition on sintering and the electrical properties of ZnO-Bi2O3-Sb2O3(ZBS) varistor system with 3.0 mol% co-addition of Sb2O3 and Bi2O3 at various Sb/Bi ratio (0.5, 1.0, and 2.0) were investigated. Cobalt had little influence on the liquid-phase formation and the pyrochlore decomposition temepratures of ZBS, while densification was mainly dependent on Sb/Bi ratio: when Sb/Bi=0.5, excess Bi2O3 irrelevant to the formation of pyrochore(Zn2Sb3Bi3O14) forms eutectic liquid at ~75$0^{\circ}C$ which promotes densification and grain growth; with Sb/Bi=2.0, the second phase Zn7Sb2O12 formed by excess Sb2O3 irrelevant to the formation of the pyrochlore retards densification up to ~100$0^{\circ}C$. These phases caused the coarsening and uneven distribution of the second phase particles on the grain boundaries of ZnO above the pyrochlore decomposition temperature(~105$0^{\circ}C$), which led to broad size dist-ribution of ZnO; the specimen with Sb/Bi=1.0 showed homogeneous microstructure compared with the others, which enabled improved varistor characteristics. Doping of Co increased the nonlinearity and the potential barrier height of ZBS, which is thought to stem from improved sintering behavior such as homogenized microstructure due to size reduction and even distribution of the second phase and suppressed volatility of Bi2O3, as well as the improvement in the potential barrier structure via increased donor and interface electron trap densities.

• 한국세라믹학회지
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• 제35권11호
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• pp.1130-1140
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• 1998

Thin films of $Bi_4Ti_3O_{12}\;nBaTiO_3(n=1&2)$ were prepared using sols erived Ba-Bi-Ti complex alkoxides. The sols were spin-cast onto $Pt/Ti/SiO_2/Si$ substrates and followed by pyrolysis for 1 hr at $620^{\circ}C,\;700^{\circ}C\;and\;750^{\circ}C$ In the thin films a pyrochlore phase seemed to be formed at a lower temperature and then tran-formed to the layered perovskite phase as the heating temperature increased. In the thin films pyrolyzed at formed to the layered perovskte phase as the heating temperature increased. In the films pyrolyzed at $750^{\circ}C$ the amount of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ reached to 94% while $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ was 77% in composition. This result shows that the formation of the layered pervoskite phase becomes difficult as the amount of complexing $BaTiO_3$ increases. The microstructures and the electrical properties of the thin films were gen-erally improved with the incease of the heating temperature. However the presence of the pyrochlore phase could not be removed effectively. Our study showed that the electrical properties of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ were pronouncedly improved with complexing with BaTiO3 when compared to those of $Bi_4Ti_3O_{12}$ while the presence of the pyrochlore phase was detrimental to the those of $Bi_4Ti_3O_{12}{\cdot}2BaTiO_3$.

• 한국재료학회지
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• 제5권2호
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• pp.251-258
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• 1995

$Bi_{2}Te_{3}$와 PbTe의 혼합물에서 $Bi_{2}Te_{3}-PbBi_{4}Te_{7}$의 공정조직이 형성됨을 이용, 제2상의 미세조직 제어로 열전도도의 감소에 따른 성능지수 향상을 목적하여 여러 조건에서 제조된 n-type(Bi, Pb)-Te계 공정조성 일방향 응고재의 열전특성을 조사하였다. 일방향응고시 공정상 PbBi_{4}Te_{7}$이 $Bi_{2}Te_{3}$의 벽개면(0001)을 따라 lamellar 형태로 성장하였으며, 성장속도가 1.4 \times 10^{-4}$cm/sec에서 $8.3 \times 10^{-4}$cm/sec로 증가됨에 따라 4PbBi_[4]Te_{7}$의 상간격은 10.4 $\mu \textrm{m}$에서 3.2$\mu \textrm{m}$로 감소되었다. Seeback계수는 성장방향 및 성장속도와 온도구배에는 관계없이 약 $\mid$$\alpha$$\mid$=29 $\mu$ V/K일정하였다. 전기전도도는 성장속도에 따라 약간 감소하는 경향을 보였고 성장방향에 평행한 경우가 수직한 경우보다 약 3배 정도 컸다. 성능지수는 성장방향과 성장속도 및 온도구배에 따라 약간씩 변화를 보였다. 수직한 경우가 평행한 경우에 비해 상대적으로 증가하는 경향을 나타내었는데 이는 lamellar 간격이 줄어듦에 따른 열전도도의 감속에서 비롯된 것으로 분석되었다.