Fabrication and electrochemical performance of nickel- and gadolinium-doped ceria-infiltrated La_0·2Sr_0·8TiO₃ anodes for solid oxide fuel cells

Lee, Min-Jin,Shin, Jae-Hwa,Ji, Mi-Jung,Hwang, Hae-Jin Elsevier 2018 Journal of Power Sources Vol.374 No.-

<P><B>Abstract</B></P> <P>In this work, nickel and gadolinium-doped ceria (GDC)-infiltrated lanthanum strontium titanate (LST) anodes are fabricated, and their electrode performances under a hydrogen atmosphere is investigated in terms of the Ni:GDC ratios and cell operating temperature. The Ni/GDC-infiltrated LST anode exhibits excellent electrode performance in comparison with the Ni- or GDC-infiltrated anodes, which is attributed to the synergistic effect of an extended triple-phase boundary length by GDC and good catalytic activity for hydrogen oxidation because of the Ni particles. The polarization resistances (R<SUB>p</SUB>) of Ni/GDC-infiltrated LST are 0.07, 0.08, and 0.12 Ω cm<SUP>2</SUP> at 800, 750, and 700 °C, respectively, which are approximately three orders of magnitude lower than that of the LST anode (68.5 Ω cm<SUP>2</SUP> at 700 °C). The effect of Ni and GDC on the electrochemical performance of LST was also investigated by using electrochemical impedance spectroscopy (EIS). The anode polarization resistance (R<SUB>p</SUB>) is confirmed to be dependent on the content and dispersion state (microstructure) of the Ni and GDC nanoparticles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lanthanum doped Strontium Titanate is used in an oxide-based anode backbone. </LI> <LI> An oxide-based anode with Ni and GDC nano particles was fabricated by infiltration. </LI> <LI> Ni and GDC-infiltrated anodes exhibited remarkably reduced polarization resistance. </LI> <LI> We investigated the role of Ni and GDC on the performance of infiltrated anodes. </LI> </UL> </P>

세계 4번째 글로벌 데이터 센터와 KASI GDC의 상시 운영 시스템

이대규,조중현,박종욱 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-

한국천문연구원(KASI)은 국제 GNSS 관측망(IGS)의 글로벌 데이터 센터(GDC)를 설립하였다. KASI GDC는 공식적으로 IGS GDC이고 세계 4번째로 설립되었으며, 아시아 및 오세아니아 지역에서는 최초이다. KASI GDC는 IGS GNSS 데이터를 기록하고, IGS GPS 데이터와 IGS 산출물을 인터넷을 통해 제공한다. GDC에서 다루는 데이터의 양은 매우 빠르게 증가한다. GDC 데이터의 대용량을 처리하기 위해서 는 시스템의 높은 효율성과 신뢰성이 요구된다. 그래서 KASI GDC는 높은 신뢰성과 대용량 저장 장치를 필요로 하는 저장 시스템을 구성하기 위해 RAID와 LVM을 적용했다. KASI GDC의 공식 출범 이후 데이터 이용 현황을 확인하고, 항상 시스템이 Active 상태로 유지하기 위한 무정전 시스템 구성에 대해 기술한다.

‘세계디아스포라연맹’ 창설의 제안: 필요성과 방향

윤황 전남대학교 글로벌디아스포라연구소 2016 디아스포라 연구 Vol.10 No.2

This article is designed to study the necessity of the establishment of 'Global Diaspora's Coalition'(GDC) and to present the desirable direction of its founding. The followings are the main points of this proposal. Firstly, the numbers of dispora and international NGOs have been increasing. Many countries have founded governmental institutions dealing with diapora and the state of network type are being appeared. Secondly, the GDC would be founded on the cooperation of organizations, groups, and collectivities of the different countries. The objectives of GDC is to guarantee the rights and interests of diaspora and to resolve problems concerning diaspora. This article proposes the strategy of three steps to take concrete shape of GDC. The first step is to found international non-governmental organization which is the stage of networking based on Association of Global Diaspra Studies, The second one is to organize the GDC as a coalition body of international non-governmental institutions. The third step is that this GDC would be recognized as one of the UN specialized agencies with the integration of UNHCR. In conclusion, the founding of GDC is quite necessary in this period of global diasporas and it is very timely to have a such kind of international institution. 이 연구의 목적은 ‘세계디아스포라연맹’의 창설에 관한 필요성을 규명하고, ‘세계디아스포라연맹’의 창설을 위한 바람직한 방향을 제시하는 데에 있다. 이에 따른 본 연구의 분석결과는 다음과 같다. 첫째, ‘세계디아스포라연맹’의 창설 필요성은 1) 세계디아스포라의 수 증대, 2) 국제비정부기구의 수 급증, 3) 디아스포라 관련 정부기구 및 전담기구를 설립하는 국가 증가, 4) 네트워크 형태의 국가가 만들어지고 있다는점이다. 둘째, ‘세계디아스포라연맹’의 창설방향은 각국의 기관, 단체, 집단등을 중심으로 추진주체가 만들어져야 하고, 세계디아스포라의 권익보장과행복추구를 확보하는 목표와 디아스포라의 보호, 디아스포라문제의 해결과관련된 제반업무 수행의 설립목적이 명확하게 설정되어야 한다. 명칭문제의정립과 관련해서는 ‘세계디아스포라연맹’의 영문 명칭을 ‘Global Diaspora's Coalition’(GDC), 한자어 명칭을 ‘世界離散同胞聯盟’이라고 표기해야 한다. 단계별 전략은 ‘3단계 추진전략’으로써, 제1단계 국제비정부기구조직화, 세계디아스포라학회 중심 네트워크화 → 제2단계 국제비정부기구 간 연대연합 활동화 → 제3단계 UN 전문기구화, 유엔난민기구(UNHCR)와통합화 발전단계 방향으로 이루어져야 하고, 기구의 제도화 준비에도나서야 할 것이다.

Effects of Co-doping on Densification of Gd-doped CeO₂ Ceramics and Adhesion Characteristics on a Yttrium Stabilized Zirconia Substrate

Lee, Ho-Young,Kang, Bo-Kyung,Lee, Ho-Chang,Heo, Young-Woo,Kim, Jeong-Joo,Lee, Joon-Hyung The Korean Ceramic Society 2018 한국세라믹학회지 Vol.55 No.6

In this study, a small amount of CoO was added to commercial Gd-doped $CeO_2$ (GDC) powder. The CoO addition greatly enhanced sinterability at low temperatures, i.e., more than 98% of relative density was achieved at $1,000^{\circ}C$. When GDC/8YSZ (8 mol% yttrium stabilized zirconia) bilayers were sintered, Co-doped GDC showed excellent adhesion to the YSZ electrolyte. Transmission electron microscope (TEM) analysis showed that there were no traces of liquid films at the grain boundaries of GDC, whereas liquid films were observed in the Co-doped GDC sample. Because liquid films facilitate particle rearrangement and migration during sintering, mechanical stresses at the interface of a bilayer, which are developed based on different densification rates between the layers, might be reduced. In spite of $Co^{2+}$ doping in GDC, the electrical conductivity was not significantly changed, relative to GDC.

소결 조제층을 적용하여 제작한 GDC Interlayer 의 부반응 억제 분석

이호재(H. J. Lee),박정흠(J. H. Park),임용현(Y. H. Lim),김선민(S, M. Kim),김영범(Y. B. Kim) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

차세대 재생에너지 장치로 각광받고 있는 고체산화물 연료전지는 고효율과 연료유연성 등의 특징을 가지고 있다. 또한, 다른 연료전지보다 높은 온도에서 동작하기 때문에 값비싼 귀금속 대신에 세라믹 소재를 전극으로 사용할 수 있는 장점이 있다. 세라믹 전극 재료 중 페로브스카이트 기반의 LSCF와 LSC 등이 널리 사용되는데 YSZ 전해질을 함께 소결하면 부반응에 의해 절연체인 SrZr₃ 가 생성된다는 문제점을 가지고 있다. 이러한 문제점을 극복하기 위해 전극과 전해질 사이에 세리아계 물질의 기능층을 도입하는 방법이 활발히 연구되고 있다. 이 기능층은 2 차상의 형성을 억제하기 위해 조밀한 층을 형성해야 하지만, 기존의 전지 제조 공정에서는 구속 소결 조건에서 조밀한 기능층을 제조하기 어려웠다. 본 연구에서는 GDC 층 위에 Bismuth Oxide Sintering Aid Layer 를 적용하여 제한된 소결 조건에서도 조밀한 GDC 기능 층을 제작하였다. 소결이 진행됨에 따라 Bismuth Oxide Sintering Aid Layer 는 Liquid Phase 로 GDC를 소결 시킨 뒤, 최종 소결 온도에서는 Sublimation 되어 제거되었다. 제작된 GDC Interlayer 위에 LSCF 전극을 증착 후 소결하여 부반응이 억제되는 양상을 확인하였으며, SOFC Full Cell 에 제작된 조밀한 GDC 기능층을 적용하여 구조적 및 성능 향상을 확인하였다.

전자상거래 국제물류센터(GDC)의 운용모델

허은숙 한국무역연구원 2020 무역연구 Vol.16 No.6

The purpose of this study is to derive a conceptual framework of how GDC should be operated in order to be successful. Design/Methodology/Approach In order to analyze the GDC operating model, we adopt the AHP(Analytic Hierarchy Process) technique consisting of three mainfactors, namely, the logistics factor, economic factor and administration factor. A total of 17 data observations were collected through a questionnaire survey for experts, and the weights of each evaluation item were derived through the AHP method with 12 data observations that had completed reliability verification. Findings As a result of the analysis, it was found that the logistics factor, economic factor and should be considered as these are important in constructing the GDC operation model. In addition, can be expected to have more positive effects in attracting global sellers, job creation, and consumer welfare than the current transshipment center type. Research Implications In this study, based on the analysis results, The GDC’s operation model should have the function of synthesizing an import bonded warehouse type that adds domestic imports and an e-commerce export distribution center from the current transshipment center type.

Preparation of Ce_0.8Gd_0.2O_1.9 Powder Using CeO₂ Powder and Gd Precipitation and Effect of CoO doping on Sintering

Sim, Soo-Man The Korean Ceramic Society 2015 한국세라믹학회지 Vol.52 No.6

$Ce_{0.8}Gd_{0.2}O_{1.9}$(GDC20) powder was prepared from a mixture of submicron-sized $CeO_2$ powder and Gd precipitates using ammonium carbonate $((NH_4)_2CO_3)$ as a precipitant. The mixture was calcined at $700^{\circ}C$ for 4 h followed by ball-milling that resulted in the GDC powder with an average particle size of $0.46{\mu}m$. The powder had a very uniform particle size distribution with particle sizes ranging from $0.3{\mu}m$ to $1{\mu}m$. Sintering of undoped GDC samples did not show a relative density of 99.2% until the temperature was increased to $1500^{\circ}C$, whereas GDC samples doped with 5 mol% CoO exhibited a significant densification at lower temperature reaching a relative density of 97.6% at $1100^{\circ}C$ and of 98.8% at $1200^{\circ}C$.

Preparation of Ce0.8Gd0.2O1.9 Powder Using CeO2 Powder and Gd Precipitation and Effect of CoO doping on Sintering

심수만 한국세라믹학회 2015 한국세라믹학회지 Vol.52 No.6

Ce0.8Gd0.2O1.9(GDC20) powder was prepared from a mixture of submicron-sized CeO2 powder and Gd precipitates using ammonium carbonate ((NH4)2CO3) as a precipitant. The mixture was calcined at 700oC for 4 h followed by ball-milling that resulted in the GDC powder with an average particle size of 0.46 μm. The powder had a very uniform particle size distribution with particle sizes ranging from 0.3 μm to 1 μm. Sintering of undoped GDC samples did not show a relative density of 99.2% until the temperature was increased to 1500oC, whereas GDC samples doped with 5 mol% CoO exhibited a significant densification at lower temperature reaching a relative density of 97.6% at 1100oC and of 98.8% at 1200oC.

Ceria의 소결과 전기전도도에 미치는 첨가제의 영향

유경빈,오은주,최경만,Yoo, Kyung-Bin,Oh, Eun-Ju,Choi, Gyeong-Man 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.12

The doped-ceria is a strong candidate material for an intermediate temperature SOFC. However, the mechanical strength and the magnitude of electrical conductivity need to be increased at low sintering temperature. In this study, to improve both properties, $1at\% $ of Mg, Ca, Cr, Fe, Co, Ni, Cu, Ga, and Zr were added to the GDC20 ($20at\%$ Gd-doped Ceria) and sintered at $1350^{\circ}C$ that is $250^{\circ}C$ lower than $1600^{\circ}C$. With addition, the relative density of the sintered sample increased. Fe, Co, Ni, Cu, Ga doped-GDC20 showed high relative density over $92\%$. Among them, Ga doped-GDC20 showed the most improved sinterability. The conductivity of doped­GDC20 increased by $\~10$ times at $300\~700^{\circ}C$.

Mechanical properties of LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ)–GDC (Ce_0.9Gd_0.1O_2−δ) for oxygen transport membranes

Kim, Seyoung,Kim, Soo Hyun,Lee, Kee Sung,Yu, Ji Haeng,Seong, Young-Hoon,Han, In Sub Elsevier 2017 Ceramics international Vol.43 No.2

<P><B>Abstract</B></P> <P>In this study, for application in oxygen transport membranes, an LSCF (La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Co<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3−δ</SUB>)–GDC (Ce<SUB>0.9</SUB>Gd<SUB>0.1</SUB>O<SUB>2−δ</SUB>) composite was manufactured, and its mechanical properties were studied. Generally, it is known that LSCF has a nonlinear modulus due to changes in its microstructure when a critical stress is loaded. To improve the mechanical properties of this material, which has a perovskite structure, a study was conducted to evaluate whether its properties change according to the rule of mixtures when it is formed into a composite with GDC. The results showed that the nonlinearity of the modulus of the composite for each specimen composition was largely reduced and stable under fatigue loading. The fracture toughness was superior to that of the LSCF (1.05MPam<SUP>1/2</SUP>) or GDC (1.28MPam<SUP>1/2</SUP>) monolithic materials when the composites (1.63MPam<SUP>1/2</SUP>) was manufactured. The mechanisms for these were explained by finite element analysis and the observation of crack propagation. It was also confirmed that when these composite materials are used for oxygen transport membranes, they show stable properties.</P>