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우병철,김병국,이종호,박현민,김병호,Woo, Byong-Chul,Kim, Byung-Kook,Lee, Jong-Ho,Park, Hyun-Min,Kim, Byong-Ho 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.9
$Pb(Fe_{1/2}Ta_{1/2})O_3$의 $Ta^{5+}$을 $Ta^{5+}$과 이온반경이 같고 원자량이 약 1/2배인 $Nb^{5+}$으로 치환한 $Pb{{Fe_{1/2}(Ta_(1-x)Nb_x)_{1/2}}O_3$ (x=0.0∼1.0) 고용체를 단일상으로 합성하여 그 유전특성 및 B자리 양이온 질서배열구조를 조사하였다. $Pb(Fe_{1/2}Ta_{1/2})O_3$는 유전완화현상 및 완만한 상전이가 뚜렷하게 관찰되는 전형적인 완화형 강유전특성을 보였지만, $Ta^{5+}$이 $Nb^{5+}$으로 치환됨에 따라 유전완화현상은 감소하고 상전이는 급격해져 결국 $Pb(Fe_{1/2}Nb_{1/2})O_3$는 유전완화현상이 전혀 관찰되지 않는 정상 강유전특성을 보였다. Raman 분광법에 의해 $Pb(Fe_{1/2}Ta_{1/2})O_3$의 $Fe^{3+}$과 $Ta^{5+}$은 XRD는 물론 TEM의 제한시야회절패턴으로도 검출하기 어려울 정도의 단거리영역에서 화학양론적으로 1:1 질서배열하고 있으며, $Ta^{5+}$이 $Nb^{5+}$으로 치환됨에 따라 $Fe^{3+}$과 ($Ta^{5+}-Nb^{5+}$) 간의 질서배열은 약화되어 결국 $Pb(Fe_{1/2}Nb_{1/2})O_3$의 $Fe^{3+}$과 $Nb^{5+}$은 완전 무질서배열하고 있음이 밝혀졌다. $Pb(Fe_{1/2}Ta_{1/2})O_3$의 완화형 강유전특성은 B자리 양이온들이 XRD는 물론 TEM의 제한시야회절패턴으로도 검출하기 어려울 정도의 단거리영역에서 화학양론적 1:1 질서배열을 하고 있는 것과, 또 $Pb(Fe_{1/2}Ta_{1/2})O_3$의 $Ta^{5+}$이 $Nb^{5+}$으로 치환됨에 따라 완화형 강유전특성이 감소되는 것은 이 질서배열이 약화되는 것과 그리고 $Pb(Fe_{1/2}Nb_{1/2})O_3$의 정상 강유전특성은 B자리 양이온들이 완전 무질서배열을 하고 있는 것과 연관지을 수 있었다. The Single phase $Pb(Fe_{1/2}Ta_{1/2})O_3$ (x=0.0∼1.0) solid solutions were successfully synthesized and their ordering structures as well as dielectric properties were investigated ${{r(Nb^{5+})=r(Ta^{5+})=0.78 {\AA},\;AW(Nb^{5+})=92.91,\;AW(Ta^{5+})=180.95}}$. While $Pb(Fe_{1/2}Ta_{1/2})O_3$ showed typical relaxor ferroelectric characteristics such as dielectric relaxation and diffuse phase transition, the sharpeness of the phase transition increased as $Ta^{5+}$ was replaced by $Nb^{5+}$ and finally $Pb(Fe_{1/2}Nb_{1/2})O_3$ showed normal ferroelectric characteristics with no dielectric relaxation. By using Raman spectroscopy, it was revealed that the $Fe^{3+}\;and\;Ta^{5+}\;of\;Pb(Fe_{1/2}Ta_{1/2})O_3$ were stoichiometrically 1:1 ordered within the short range which can be hardly probed even by TEM. Also, The degree of ordering in $Pb(Fe_{1/2}Ta_{1/2})O_3$ decreased as $Ta^{5+}$ was replaced by $Nb^{5+}$ and finally $Fe^{3+}\;and\;Nb^{5+}\;of\;Pb(Fe_{1/2}Nb_{1/2})O_3$ were completely disordered. The relaxor ferroelectric characteristics of $Pb(Fe_{1/2}Ta_{1/2})O_3$ could be correlated with the stoichiometric 1:1 ordering of B-site cations within the short range which can be hardly probed even by TEM. Also, the decrease of the relaxor ferroelectric characteristics with the replacement of $Ta^{5+}\;by\;Nb^{5+}$ could be correlated with the weakening of the ordering and the normal ferroelectric characteristics of $Pb(Fe_{1/2}Nb_{1/2})O_3$ could be correlated with the complete disordering of B-site cations.
마우스 태생간 조혈세포이식시 이식거부 반응을 극복하기 위한 조혈세포 용량 및 흉선세포의 역할에 관한 연구
김승택(Seung Taik Kim),박선양(Seon Yang Park),김병국(Byong Kook Kim),이홍복(Hong Bock Lee),김은실(Eun Shik Kim),계경채(Kyung Chae Kye),서정선(Jeong Sun Seo),강위생(Wee Saing Kang),이현순(Hyun Soon Lee),궁성수(Sung Soo Koong),이재훈(J 대한내과학회 1990 대한내과학회지 Vol.39 No.5
N/A To observe whether an increase in cell doses can overcome graft rejection, whether sustained chimerism is present, and whether fetal thymic cell transplantation has any effect on the survival and the cell dose needed, fetal liver transplantation was done from 17-18-day old DDY fetus to an ICR mouse (syngeneic transplantationl) previously irradiated. The results revealed that better survival was obtained, regardless of syngeneic of allogeneic fetal liver cell transplantion, through an increase of the cell dose. A 90F long- term survial was noticed with a cell dose of 15×108/kg in syngeneic transplantation. In the case of allogeneic transplantation, however, only a 50% long - term survival rate was observed with the same dose. The concurrent thymic cell transplantation had a good effect on the long - term survival and the reduction of cell dose required, The cell dose needed for the achievement of a 90% long - term survival in syngeneic and allogeneic transplantation was 5x108/kg and 15x108/kg, respectively The sustained chimerism was evident and the graft-versus-host disease was mininal in fetal liver cell transplantation. It was evident that fetal liver cell transplantation could be one of substitution in solving the problems of bone marrow transplantation The cell dose required to prevent graft failure decreased with fetal thymic cell transplantation The mechanism of the salutary effect of concurrent thymic cell transplantation is not yet to be elucidated.
반응성 스퍼터링에 의해 제조된 Fe - Hf - N 박막의 연자기 특성에 미치는 열처리 영향
김경일(Kyong-Il Kim),김병호(Byong-Ho Kim),김병국(Byung-Kook Kim),제해준(Hae-June Je) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.4
The purpose of this study is to investigate the effect of annealing conditions on physical and magnetic properties of Fe-Hf-N thin films. When the thin films were annealed in N₂ gas, a surface oxide layer, comprised of Fe₂O₃ and Fe₃O₄, was formed at the surface of the thin films and a Fe-Hf-O-N layer was also formed under this surface oxide layer. It was found that the thicknesses of the surface oxide layer and the Fe-Hf-O-N layer increased, as the annealing temperature increased. It was also found that if the thickness of the surface oxide layer was excluded in the property calculation, the soft magnetic properties of the annealed thin films were not much different from those of the as-deposited thin films. Therefore, it was suggested that the Fe-Hf-O-N layer formed under the surface oxide layer did not lose significantly the soft magnetic properties of the Fe-Hf-N films and the Fe-Hf-N films annealed in N₂ gas showed the soft magnetic properties of the Fe-Hf-N and Fe-Hf-O-N multi-layers.
초미립 $\textrm{La}^{3+}$-doped $\textrm{BaTiO}_3$세라믹스의 미세구조 및 유전특성
조지만,김병호,김긍호,제해준,이해원,김병국,Cho, Ji-Man,Kim, Byong-Ho,Kim, Gyeung-Ho,Je, Hae-June,Lee, Hae-Won,Kim, Byung-Kook 한국재료학회 1999 한국재료학회지 Vol.9 No.10
초미립 $BaTiO_3$분말을 출발물질로 하고 $\textrm{La}_{3+}$을 0~2 mol% 첨가하여 $1200~1400^{\circ}C$에서 소결하였을 때 $\textrm{La}_{3+}$을 첨가하지 않고 $1350^{\circ}C$ 이상에서 소결한 경우를 제외하고는 모두 110~240 nm의 평균입경을 갖는 초미립의 $\textrm{La}_{3+}$-doped $BaTiO_3$소결체를 얻을 수 있었다. 이 때, 평균입경이 240 nm에서 110 nm로 감소함에 따라 정방정비 (c/a), $90^{\circ}$ 분역의 부피분율, 상온 비유전율, 상전이온도($\textrm{T}_{c}$)에서의 최대 비유전율, $\textrm{T}_{c}$ 에서의 상전이 완만화도 등은 모두 감소하였다. 이와 같은 유전특성의 입경 의존성은 평균입경 감소에 따른 $90^{\circ}$ 분역 생성의 억제 및 그에 따른 내부응력의 영향으로 해석하였다. When the 0-2 mol% of $\textrm{La}_{3+}$ were added to the nanocrystalline $BaTiO_3$ powders and sintered at $1200~1400^{\circ}C$, the nanocrystailine $BaTiO_3$ ceramics having the average grain size of 110-240 nm were obtained except for when no $\textrm{La}_{3+}$ was added and sintered at > $1350^{\circ}C$. As the average grain size decreased from 240 nm to 110 nm, the tetragonality (c/a) and volume fraction of the $90^{\circ}$ domain decreased, and all the properties such as relative dielectric constant at room temperature, maximum relative dielectric constant at the temperature of phase transformation $\textrm{T}_{c}$ and diffuseness of phase transformation at $\textrm{T}_{c}$ also decreased. The results were attributed to the internal stress induced by inhibition of the $90^{\circ}$ domain formation in the case of finer grain size.
Current Status of SOFC Materials and Processing Core Technology
이종호(Lee, Jong-Ho),손지원(Son, Jiwon),김혜령(Kim, Heryong),김병국(Kim, Byong-Kook),이해원(Lee, Hae-Weon) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06
The solid oxide fuel cell (SOFC) has attracted great deal of attention due to its high electrical efficiency, high waste-heat utilization, fuel flexibility, and application versatility. However, SOFC technology is still not matured enough to fulfill the practical requirements for commercialization. Therefore, all the research and development activities are mainly focused on a development of practically viable SOFCs with higher performance and better reliability. We were successful in fabricating high-performance anode-supported unit cells by employing hierarchically controlled multi-layered electrodes for both structural reliability and high performance. In addition, a novel composite sealing gasket made it possible to achieve excellent sealing integrity even with considerable surface irregularities in a multi-cell planar arrayed stack.