• Journal of the Korean Ceramic Society
• /
• v.51 no.4
• /
• pp.278-282
• /
• 2014

Due to high ionic conductivity and favorable oxygen electrocatalysis, doped $Bi_2O_3$ systems are promising candidates as solid oxide fuel cell cathode materials. Recently, several researchers reported reasonably low cathode polarization resistance by adding electronically conducting materials such as (La,Sr)$MnO_3$ (LSM) or Ag to doped $Bi_2O_3$ compositions. Despite extensive research efforts toward maximizing cathode performance, however, the inherent catalytic activity and electrochemical reaction pathways of these promising materials remain largely unknown. Here, we prepare a symmetrical structure with identically sized $Y_{0.5}Bi_{1.5}O_3$/LSM composite electrodes on both sides of a YSZ electrolyte substrate. AC impedance spectroscopy (ACIS) measurements of electrochemical cells with varied cathode compositions reveal the important role of bismuth oxide phase for oxygen electrocatalysis. These observations aid in directing future research into the reaction pathways and the site-specific electrocatalytic activity as well as giving improved guidance for optimizing SOFC cathode structures with doped $Bi_2O_3$ compositions.

• Journal of the Korean institute of surface engineering
• /
• v.46 no.5
• /
• pp.181-186
• /
• 2013

We performed plasma spraying for 2001 (Bi:Cu = 2:1), 0212 (Sr:Ca:Cu = 2:1:2) oxide powders. $Bi_2Sr_2CaCu_2Ox$ (2212) superconductor has been prepared by PMP-AT (partial melting process-annealing treatment). The 2212 phase is synthesized between Sr-Ca-Cu oxide coating layer (0212) and Bi-Cu oxide coating layer (2001) by movement of partial melted Bi on 2001 layer and the diffusion reaction (Cu, Sr, Ca) after PMP-AT. There are two different coating layers on joining process. The one is ABAB coating layers and the other is BAAB coating layers by arrangement of 2001 (A), 0212 (B) layers. We performed heat treatment these two different coating layers processes under same PMP-AT conditions. We obtained Bi-2212 superconducting layers at each experimental condition, and the result of MPMS, the critical temperature was showed about 78 K. But the microstructure images and result of EDS as each experimental variable were showed about the qualitatively different Bi-2212 superconducting phases. We also deduced the generation mechanism of Bi-2212 superconducting layer as a result of these experimental data, microstruc ture images, EDS data and phase diagram.

• Journal of the Korean Ceramic Society
• /
• v.42 no.12 s.283
• /
• pp.808-815
• /
• 2005

[ $Bi_xCe_{l-x}O_{2-x/2}$ ](BD C : Bismuth Doped Ceria) powders with x = 0.1, 0.2, and 0.3 were synthesized using the Glycine Nitrate Process (GNP). They were then calcined at $500^{\circ}C$ for 2 hand sintered in a pellet or rod form at 900, 1000 or $1100^{\circ}C$ for 4 h for characterization as the alternative electrolyte material for intermediate temperature solid oxide fuel cells. The BDC powder consisted of a single phase of $CeO_2-Bi_2O_3$ solid solution in the as-synthesized state as well as in the as-calcined state with a mean powder size of 4.5nm in the former state and 6.5 - 10.1nm in the latter. On the contrary, the second phase of $\alpha-Bi_2O_3$ was observed to have been formed in the sinter with its amount increasing roughly with increasing temperature or $Bi_2O_3$ content. The BOC powder was superior in sinterability to other alternative electrolyte materials such as GDC, ScSZ, and LSGM with the minimum sintering temperature for a relative density of $95\%$ or larger as low as $1100^{\circ}C$. The ionic conductivity of BOC increased with $Bi_2O_3$ content and the maximum value of 0.119 S/cm was obtained at $800^{\circ}C$ for $Bi_{0.3}Ce_{0.7}O_{1.85}$.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2018.11a
• /
• pp.103-103
• /
• 2018

The liquid cathode processing is necessary to separate cadmium from the actinide elements in the pyroprocessing since the actinide deposits are dissolved or precipitated in a liquid cathode. Distillation process was employed for the cathode processing owing to the compactness. It is very important to avoid a splattering of cadmium during evaporation due to the high vapor pressure. Several methods have been proposed to lower the splattering of cadmium during distillation. A multi-layer porous round cover was proposed to avoid a cadmium splattering in our previous study. In this study, distillation behavior of $Cd-ZrO_2$ and Cd - Bi systems were investigated to examine a multi-layer porous round cover for the development of the cadmium splatter shield of distillation crucible. It was designed that the cadmium vapor can be released through the holes of the shield, whereas liquid drops can be collected in the multiple hemisphere. The cover was made with three stainless steel round plates with a diameter of 33.50 mm. The distance between the hemispheres and the diameter of the holes are 10 and 1 mm, respectively. Bismuth or zirconium oxide powder was used as a surrogate for the actinide elements. About 40 grams of Cd was distilled at a reduced pressure for two hours at various temperatures. The mixture of the cadmium and the surrogate was distilled at 470, 570 and $620^{\circ}C$ in the crucible with the cover. Most of the bismuth or zirconia remained in the crucible after distillation at 470 and $570^{\circ}C$ for two hours. It was considered that the crucible cover hindered the splattering of the liquid cadmium from the distillation crucible. A considerable amount of the surrogate material reduced after distillation at $620^{\circ}C$ due to the splattering of the liquid cadmium. The low temperature is favorable to avoid a liquid cadmium splattering during distillation. However, the optimum temperature for the cadmium distillation should be decided further, since the evaporation rate decreases with a decreasing temperature.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1734-1741
• /
• 2023

This work presents the synthesis and preparation of a new glass system described by the equation of (70-x) B₂O₃-5TeO₂ -20SrCO₃-5ZnO -xBi₂O₃, x = 0, 1, 5, 10, and 15 mol. %, using the melt quenching technique at a melting temperature of 1100 ℃. The photon-shielding characteristics mainly the linear attenuation coefficient (LAC) of the prepared glass samples were evaluated using Monte Carlo (MC) simulation N-particle transport code (MCNP-5) at gamma-ray energy extended from 59 keV to 1408 keV emitted by the radioisotopes Am-241, Ba-133, Cs-137, Co-60, Na-22, and Eu-152. Furthermore, we observed that the Bi₂O₃ content of the glasses had a significantly stronger impact on the LAC at 59 and 356 keV. The study of the lead equivalent thickness shows that the performance of fabricated glass sample with 15 mol.% of Bi₂O₃ is four times less than the performance of pure lead at low gamma photon energy while it is enhanced and became two times lower the perforce of pure lead at high energy. Therefore, the fabricated glasses special sample with 15 mol.% of Bi₂O₃ has good shielding properties in low, intermediate, and high energy intervals.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1440-1441
• /
• 2011

Apatite-lanthanum silicate has attracted considerable interest in recent years due to its high oxide ion conductivity, In this paper, Bi-doped samples $La_8Bi_2(SiO_4)_6O_3$ were prepared by conventional solid-state method and the influences of Bi-dopant content on calcining temperature were reported. The Samples were characterized by X-ray diffraction (XRD) and scanning electron micrograph (SEM) and impedance analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.11a
• /
• pp.281-285
• /
• 1998

The microstructure and conduction characteristics of ZnO varistor fabricated in the range of 0.0 ~ 4.0mol% $Y_20_3$ were investigated. With increasing$Y_20_3$ content, distribution of spinel phase decreased, whereas Y-rich phase segregated to the nodal point increased, as a result, the average grain size decreased in the range of $20.0 ~ 4.8{\mu}m$. $Y_20_3$ content showing relatively good conduction characteristics was l.Omol%, then nonlinear exponent and leakage current was 55.3, 0.66mA.respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.146-146
• /
• 2017

산화비스무트는 리튬이온과의 반응에서 현재 상용화된 그래파이트보다 높은 이론용량을 가지고 있으나, 리튬이온과의 반응에서 비교적 큰 부피팽창 특성을 가져 리튬이차전지의 음극재로서 상용화가 어려운 단점이 있다. 본 연구에서는, 이러한 문제점을 개선하기 위하여 양극산화법을 통해 충 방전시 부피팽창 변화가 매우 적은 타이타니아 나노튜브를 제조한 후, 그 위에 스프레이 방법으로 산화비스무트를 코팅하여 두 물질의 복함체를 만듦으로써 용량과 구조적 안정성을 향상시키는 방법을 소개한다. 음극재의 구조적 특성은 고분해능 주사전자현미경 (HR-SEM), 고분해능 엑스선 회절분석기(XRD)를 통해 조사하였으며, 전기화학 임피던스 분광법 (EIS), 순환전류법 (CV), 충 방전 싸이클 분석을 통해 리튬이차전지의 작동원리와 보다 향상된 성능을 규명하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.6
• /
• pp.1596-1603
• /
• 1996

A single body type of fiber-optic current and voltae sensor using a rare earth doped YIG and a bismuth silicon oxide single crystsl is proposed, which is used for simultaneous measurement of the AC electric current and AC electric voltage over the trasmission lines. Experimental results showed that the fiber-optic current sensor has the maximum 7.5% error within the current range of 0A to 400A, and the fiber-optic voltage sensor has the maximum 0.87% error within the current range of 0V to 400V. The output waveforms of proposed fiber-optic sensor system has a good agreement with output waveforms of conductor current and voltage. Experimental results proved that the output of fiber-optic current sensor is not affected by the electric voltage applied to the fiber-optic voltage sensor, and also, that the output of fiber-optic voltage sensor is not affected by the electric current applied to the fiber-optic current sensor.

• Corrosion Science and Technology
• /
• v.5 no.3
• /
• pp.94-98
• /
• 2006

The next generation nuclear power reactor will use Pb-Bi as the cooling material. The steel structure materials such as HT-9 used in the reactor suffer from corrosion when they are exposed to high temperature Pb-Bi. Therefore corrosion should be prevented to use Pb-Bi as the coolant material without any safety problem. One method is to control the oxygen content in Pb-Bi. An appropriate amount of oxygen in Pb-Bi can produce a thin oxide layer on steel, and this layer protects the steel from corrosion attack. Since the required oxygen content in Pb-Bi is in the range of $10^{-5}$ to $10^{-7}$ wt%, this small oxygen content can be controlled by flowing a mixture of hydrogen gas and water vapor. The stagnant corrosion test of HT-9 samples was performed by controlling the oxygen content up to 2,000 hours. The corrosion behavior of HT-9 was analyzed at the temperatures of $500^{\circ}C$ and $650^{\circ}C$ with a reduced condition and a oxygen content of $10^{-6}$ wt%.