10×10 ㎠ 단전지를 이용한 고체산화물 연료전지 스택개발

이종호(Jong-Ho Lee),정화영(Hwa Young Jung),손지원(Ji Won Son),김주선(Joosun Kim),이해원(Hae-Weon Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

In this research, 10x10 ㎠ unit cells were fabricated via liquid condensation process and uni-axial pressing followed by the screen printing of electrolyte and cathode layer. The SOFC stack was assembled with unit cells, gasket-type sealant and metal interconnect. The stack was designed to have a single column with internal-manifold and cross-flow type gas-channels. Stack was evaluated in terms of cell performance, electrical contacting, sealing, thermal stability and degradation. In addition, key issues in fabricating components and unit cell are addressed with respect to the performance optimization and microstructure development.

고정우선순위 선점가능 스케쥴링 환경에서의 캐쉬에 의한 선점지연시간 분석 (pp.243-256)

이창건(Chang-Gun Lee),한주선(Joosun Hahn),서양민(Yang-Min Seo),민상렬(Sang Lyul Min),하란(Rhan Ha),홍성수(Seongsoo Hong),박창윤(Chang Yun Park),이민석(Minsuk Lee),김종상(Chong Sang Kim) 한국정보과학회 1998 정보과학회논문지 : 시스템 및 이론 Vol.25 No.3

프로세서와 메모리사이의 속도차가 증가함에 따라, 범용 컴퓨터 시스템에서 뿐만 아니라 실시간 컴퓨터 시스템에서도 캐쉬 메모리의 필요성이 증대되었다. 캐쉬 메모리의 사용은 태스크의 평균 수행시간을 감소시키는 긍정적인 측면을 가지고 있는 반면, 태스크간의 선점이 허용되는 멀티태스킹 환경에서는 태스크의 수행시간에 예측하기 힘든 추가비용(캐쉬에 의한 선점지연시간)을 초래한다는 부정적 측면도 가지고 있다. 이러한 부정적 측면은 주어진 시간안에 태스크의 수행 완료를 보장해야 하는 실시간 컴퓨터 시스템이 캐쉬 메모리를 사용하는 것을 어렵게 만드는 요소로 작용한다. 본 논문에서는 고정우선순위 선점가능 스케쥴링 환경에서 보다 정확하게 케쉬에 의한 선점지연시간을 예측하기 위한 분석기법을 제안한다. 캐쉬에 의한 선점지연시간을 예측하기 위한 현재까지의 연구는 “선점하는 태스크는 현재 캐쉬에 올라와 있는 선점되는 태스크의 메모리블럭을 캐쉬로부터 모두 쫓아내며, 이렇게 쫓겨난 메모리블럭들은 선점된 태스크가 이후에 수행을 재개했을 때 모두 다시 캐쉬로 올라와야 한다”는 비관적인 가정을 바탕으로한다. 그러나 본 논문에서 제안하는 기법은 각 태스크가 선점시 지불해야하는 캐쉬에 의한 선점비용으로 유용한 - 이후에 다시 사용되는 - 캐쉬블럭만을 고려하므로써 보다 정확하게 캐쉬에 의한 선점지연시간을 예측할 수 있다. 제안되는 기법은 두 단계로 이루어진다. 첫번째 단계에서는 각각의 태스크를 독립적으로 분석하여, 주어진 태스크의 각 수행지점에서의 유용한 캐쉬블럭의 수를 계산하고 이를 이용하여 해당 수행 지점에서의 캐쉬에 의한 선점비용을 구한다. 이렇게 구해진 선점비용들은 각 태스크가 특정 횟수만큼 선점될 때 부가적으로 지불하게 되는 캐쉬에 의한 최악 선점비용을 나타내도록 표의 형태로 정리된다. 두번째 단계에서는 첫번째 단계의 결과를 본 논문에서 정의한 선형계획법의 입력으로 이용하여 주어진 시간동안 발생할 수 있는 캐쉬에 의한 최악 선점지연시간을 계산하고, 이를 최악 반응시간식에 적용하여 각 태스크의 최악 반응시간을 구한다. 이렇게 구해진 최악 반응시간은 기존의 기법에 의해 구해진 값에 비해 보다 정확한 최악 반응시간 예측값이며, 따라서 이를 이용하면 보다 정확하게, 주어진 태스크가 마감시간 이내에 수행을 완료할 수 있는가 여부( 스케쥴 가능성 - schedulability)를 판단할 수 있다. 본 논문에서 행한 실험에 따르면, 제안된 기법은 기존의 기법에 비해 최고 60%까지 더 정확하게 캐쉬에 의한 선점지연시간을 예측해낸다. Cache memory is increasingly being used in real-time computer systems as well as general purpose computer systems due to the ever increasing speed gap between processors and main memory. However, the use of cache memory in real-time systems introduces variation to task execution time when preemptions are allowed among tasks. This paper proposes a technique for analyzing the cache-related preemption delays of tasks that cause such unpredictable variation in task execution time in the context of fixed-priority preemptive scheduling. Unlike previous approaches that make a pessimistic assumption that each memory block of a preempting task replaces from cache memory a memory block needed by a lower priority task, the proposed technique considers the usefulness of cache blocks in computing cache-related preemption delay to improve prediction accuracy. The proposed technique consists of two steps The first step performs a per-task analysis to estimate cache-related preemption cost for each execution paint in a given task from the number of useful cache blocks at the execution point. The results of this first step are given in a table that specifies the (worst case) preemption cost for a given number of preemptions. The second step computes the worst case response time of each task using a response time equation and a linear programming technique which takes as its input the preemption cost information of tasks obtained in the first step. Our experimental results show that the proposed technique gives a prediction of the worst case cache-related preemption delay that is up to 60% tighter than that obtained from previous approaches.

SOFC용 유리-세라믹섬유 복합기밀재의 고온 기체누설 거동

이재춘,권혁천,권영필,박성,장진식,이종호,김주선,이해원,Lee, Jae-Chun,Kwon, Hyuk-Chon,Kwon, Young-Pil,Park, Sung,Jang, Jin-Sik,Lee, Jongho,Kim, Joosun,Lee, Hae-Won 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.12

Glass composites containing ceramic fiber have been developed for Solid Oxide Fuel Cell (SOFC) seals. Effect of glass type, loading pressure and thermal cycle the leak rates of composite seals was investigated. Seal performance of two commercial glasses was compared with that of $SiO_2BaO-B_2O_3$ glass synthesized in this work. The leak rate for seals made of pyrex(R) increases from $\~0.0005\;to\;\~0.004sccm/cm$ as the gas pressure increases from 10 to 50 kPa. The soda lime silicate glass seal shows the leak rate two times higher than the one made of pyrex(R) or $SiO_2BaO-B_2O_3$ glass. The viscosity of glass at the seal test temperature is presumed to affect the leak rate of the glass seal. As the applied loading pressure increases from 0.4 to 0.8 MPa at $750^{\circ}C$, the leak rate decreases from 0.038 to 0.024 sccm/cm for composite seals. It has been found that during 50 thermal cycles between $450^{\circ}C\;to\;700^{\circ}C$ leak rates remained almost constant, ranging from 0.025 to 0.03sccm/cm. The results showed an excellent thermal cycle stability as well as sealability of the glass matrix ceramic fiber composite seals.

음극지지형 단전지를 사용한 소형 SOFC 스택의 제조 및 출력특성

정화영,김우식,최선희,김주선,이해원,고행진,이기춘,이종호,Jung, Hwa-Young,Kim, Woo-Sik,Choi, Sun-Hee,Kim, Joosun,Lee, Hae-Weon,Ko, Haengjin,Lee, Ki-Chun,Lee, Jong-Ho 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.10

In this research, $5\times5cm^2$ unit cells were fabricated via liquid condensation process and uniaxial pressing followed by the screen printing of electrolyte and cathode layer. The SOFC stack was assembled with unit cells, gasket-type sealant and metal interconnect. The stack was designed to have a single column with internal-manifold and cross-flow type gas-channels. The SOFC stack produced 15 W, which is $50\%$ of the maximum power being expected from the maximum power density of the unit cell. Controlling factors for the proper operation of the SOFC stack and other designing factors of stack manifold and gas channels were discussed. 액상응결 공정법과 일축가압성형법으로 제조된 기판위에 전해질과 양극층을 스크린 인쇄법으로 구성한 후 열처리함으로써 최종크기가 $5\times5cm^2$인 SOFC 단전지를 제조하였다. 본 연구에서는 이들 단전지와 인코넬 합금으로 제조된 접속자 그리고 가스켓형의 밀봉재를 이용하여 스택을 구성하였다. 본 연구에 사용된 스택은 연료가스와 산화가스가 교차되는 형태의 가스채널을 가지며 가스매니폴드가 내부에 구성되어 있는 형태로 설계되었다. 제작된 3단 스택의 성능을 평가해 본격과 15W 정도의 최고출력을 나타내었는데 이는 단전지 출력성능으로부터 예측된 최고출력치의 $50\%$ 정도에 해당되는 출력이었다. 본 연구에서는 이러한 스택성능에 영향을 주는 조정인자들과 스택디자인 인자들에 대한 분석을 수행하였다.

Direct methane solid oxide fuel cells based on catalytic partial oxidation enabling complete coking tolerance of Ni-based anodes

Lee, Daehee,Myung, Jaeha,Tan, Jeiwan,Hyun, Sang-Hoon,Irvine, John T.S.,Kim, Joosun,Moon, Jooho Elsevier Sequoia 2017 Journal of Power Sources Vol. No.

<P><B>Abstract</B></P> <P>Solid oxide fuel cells (SOFCs) can oxidize diverse fuels by harnessing oxygen ions. Benefited by this feature, direct utilization of hydrocarbon fuels without external reformers allows for cost-effective realization of SOFC systems. Superior hydrocarbon reforming catalysts such as nickel are required for this application. However, carbon coking on nickel-based anodes and the low efficiency associated with hydrocarbon fueling relegate these systems to immature technologies. Herein, we present methane-fueled SOFCs operated under conditions of catalytic partial oxidation (CPOX). Utilizing CPOX eliminates carbon coking on Ni and facilitates the oxidation of methane. Ni-gadolinium-doped ceria (GDC) anode-based cells exhibit exceptional power densities of 1.35 W cm<SUP>−2</SUP> at 650 °C and 0.74 W cm<SUP>−2</SUP> at 550 °C, with stable operation over 500 h, while the similarly prepared Ni-yttria stabilized zirconia anode-based cells exhibit a power density of 0.27 W cm<SUP>−2</SUP> at 650 °C, showing gradual degradation. Chemical analyses suggest that combining GDC with the Ni anode prevents the oxidation of Ni due to the oxygen exchange ability of GDC. In addition, CPOX operation allows the usage of stainless steel current collectors. Our results demonstrate that high-performance SOFCs utilizing methane CPOX can be realized without deterioration of Ni-based anodes using cost-effective current collectors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Direct CH<SUB>4</SUB> fueled SOFCs operated via catalytic partial oxidation are demonstrated. </LI> <LI> A high performance of 0.74 W cm<SUP>−2</SUP> at 550 °C is achieved. </LI> <LI> Enhanced CH<SUB>4</SUB> conversion suggests a promising internal reforming by CPOX. </LI> <LI> Adsorption dynamics on Ni catalysts is elucidated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Salami-like Electrospun Si Nanoparticle-ITO Composite Nanofibers with Internal Conductive Pathways for use as Anodes for Li-Ion Batteries

Lee, Daehee,Kim, Bokyung,Kim, Joosun,Jeong, Sunho,Cao, Guozhong,Moon, Jooho American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.49

<P>We report novel salami-like core–sheath composites consisting of Si nanoparticle assemblies coated with indium tin oxide (ITO) sheath layers that are synthesized via coelectrospinning. Core–sheath structured Si nanoparticles (NPs) in static ITO allow robust microstructures to accommodate for mechanical stress induced by the repeated cyclical volume changes of Si NPs. Conductive ITO sheaths can provide bulk conduction paths for electrons. Distinct Si NP-based core structures, in which the ITO phase coexists uniformly with electrochemically active Si NPs, are capable of facilitating rapid charge transfer as well. These engineered composites enabled the production of high-performance anodes with an excellent capacity retention of 95.5% (677 and 1523 mAh g<SUP>–1,</SUP> which are based on the total weight of Si-ITO fibers and Si NPs only, respectively), and an outstanding rate capability with a retention of 75.3% from 1 to 12 C. The cycling performance and rate capability of core–sheath-structured Si NP-ITO are characterized in terms of charge-transfer kinetics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-49/acsami.5b08401/production/images/medium/am-2015-08401v_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b08401'>ACS Electronic Supporting Info</A></P>

Effect of Phase Stability on the Microstructure Development of α-SiAlON Ceramics

Kim, Joosun,Lee, Hae-Weon,Chen, I-Wei The Korean Powder Metallurgy Institute 2003 한국분말재료학회지 (KPMI) Vol.10 No.2

Alpha-SiAlON ceramics having various compositions and modifying cations were investigated with respect to their phase stability, transformation kinetics. and resulting microstructures. Each composition was heat treated at 150$0^{\circ}C$ for 1h and measured the $\alpha$-SiAlON transformation. The phase-boundary composition in the single-phase $\alpha$-SiAlON region showed sluggish transformation from $\alpha$-$Si_3N_4$ to $\alpha$-SiAlON compared to the phase-center composition in the diagram. Using the different rare earth modifying cations, dependence of transformation kinetics on the phase stability in a fixed composition was also explained. By changing size of the stable u-phase region with exchanging cations, systematic change in transformation was observed. Transformation rate of $\alpha$-SiAlON at low temperature has an important role on controlling the final microstructure. Less transformation gives more chances to develop elongated grain in the microstructure.

Efficient composition tuning via cation exchange and improved reproducibility of photovoltaic performance in FA_<i>x</i>MA_1-<i>x</i>PbI₃ planar heterojunction solar cells fabricated by a two-step dynamic spin-coating pr

Jung, Kyungeun,Lee, Jae-Ho,Oh, Kwonwoo,Im, Chan,Do, Junghwan,Kim, Joosun,Chae, Weon-Sik,Lee, Man-Jong Elsevier 2018 Nano energy Vol.54 No.-

<P><B>Abstract</B></P> <P>We synthesized uniform FA<SUB> <I>x</I> </SUB>MA<SUB>1-<I>x</I> </SUB>PbI<SUB>3</SUB> perovskite films with a single α phase by a two-step process combined with a dynamically dispensed spin-coating technique. It uses the continuous dropping of precursor solutions with a constant CH<SUB>3</SUB>NH<SUB>3</SUB>I (MAI)/HC(NH<SUB>2</SUB>)<SUB>2</SUB>I (FAI) concentration enabling the kinetically controlled grain growth. Dynamic coating cycles are also changed to facilitate a cation-exchange process, control the degree of the mutual inter-mixing between formamidinium lead triiodide (FAPbI<SUB>3</SUB>) and methylammonium lead triiodide (MAPbI<SUB>3</SUB>) and examine the formation process and properties of the mixed perovskite films formed under the excess MA/FA cation environment, which has not been clarified so far. Notably, without additional solvent washing steps, FA<SUB> <I>x</I> </SUB>MA<SUB>1-<I>x</I> </SUB>PbI<SUB>3</SUB> films are adjustable in composition, pinhole-free, and have various grain sizes depending on the coating cycles. Perovskite solar cells (PSCs) synthesized from FA<SUB> <I>x</I> </SUB>MA<SUB>1-<I>x</I> </SUB>PbI<SUB>3</SUB> films with two cycles of the dynamic spin coating have achieved a maximum power conversion efficiency (PCE) of 18.50% with an average PCE of 17.06 ± 0.42%, which shows much-improved performance as well as reproducibility compared with 14.79 ± 1.82% obtained from the conventional static spin-coating method. In addition, we first found mixed FA<SUB> <I>x</I> </SUB>MA<SUB>1-<I>x</I> </SUB>PbI<SUB>3</SUB> perovskites synthesized under an excess cation environment containing local stoichiometric inhomogeneities as well as excess residual cations (C˭N and NH<SUB>3</SUB> <SUP>+</SUP>) acting as recombination traps, which is supported by the calculation of trap densities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Design a new two-step process combining dynamically dispensed spin-coating technique. </LI> <LI> Single α phase FA<SUB> <I>x</I> </SUB>MA<SUB>1-<I>x</I> </SUB>PbI<SUB>3</SUB> are achieved without any solvent washing steps. </LI> <LI> Depending on dynamic coating cycles, <I>x</I> can be adjusted by an active cation exchange. </LI> <LI> Maximum 18.50% with an average of 17.06 ± 0.42% shows an excellent reproducibility </LI> <LI> Perovskites formed under excess cations resulted in the adsorption of excess residual cations acting as traps, which were probed by 2D FTIR imaging. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrospun Ni-Added SnO₂–Carbon Nanofiber Composite Anode for High-Performance Lithium-Ion Batteries

Kim, Dongha,Lee, Daehee,Kim, Joosun,Moon, Jooho American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.10

<P>The SnO<SUB>2</SUB> anode is a promising anode for next-generation Li ion batteries because of its high theoretical capacity. However, it exhibits inherent capacity fading because of the large volume change and pulverization that occur during the charge/discharge cycles. The buffer matrix, such as electrospun carbon nanofibers (CNFs), can alleviate this problem to some extent, but SnO<SUB>2</SUB> particles are thermodynamically incompatible with the carbon matrix such that large Sn agglomerates form after carbonization upon melting of the Sn. Herein, we introduce well-dispersed nanosized SnO<SUB>2</SUB> attached to CNFs for high-performance anodes developed by Ni presence. The addition of Ni increases the stability of the SnO<SUB>2</SUB> such that the morphologies of the dispersed SnO<SUB>2</SUB> phase are modified as a function of the Ni composition. The optimal adding composition is determined to be Ni:Sn = 10:90 wt % in terms of the crystallite size and the distribution uniformity. A high capacity retention of 447.6 mA h g<SUP>–1</SUP> after 100 cycles can be obtained for 10 wt % Ni-added SnO<SUB>2</SUB>–CNFs, whereas Ni-free Sn/SnO<SUB>2</SUB>–CNFs have a capacity retention of 304.6 mA h g<SUP>–1</SUP>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-10/am301328u/production/images/medium/am-2012-01328u_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am301328u'>ACS Electronic Supporting Info</A></P>

Solution-processed flexible planar perovskite solar cells: A strategy to enhance efficiency by controlling the ZnO electron transfer layer, PbI₂ phase, and CH₃NH₃PbI₃ morphologies

Jung, Kyungeun,Lee, Jeongwon,Kim, Joosun,Chae, Weon-Sik,Lee, Man-Jong Elsevier 2016 Journal of Power Sources Vol.324 No.-

<P><B>Abstract</B></P> <P>This paper reports a synergistic strategy to enhance the power conversion efficiency (PCE) of flexible planar perovskite solar cells (PSCs) by controlling the thickness of the ZnO electron transport layer (ETL), PbI<SUB>2</SUB> phase, and size/morphology of the perovskite (MAPbI<SUB>3</SUB>) absorber layer. To optimize the size/morphology of MAPbI<SUB>3</SUB> via a two-step spin coating process, various volumes of CH<SUB>3</SUB>NH<SUB>3</SUB>I precursor solutions with a constant concentration were continuously coated, which greatly affected the grain growth condition of the MAPbI<SUB>3</SUB>. In addition, the remnant PbI<SUB>2</SUB> phase in the MAPbI<SUB>3</SUB>, which acted as a recombination barrier, was simultaneously controlled. This strategic method to synergistically combine the major factors affecting the final PCE resulted in the best efficiency of 12.3%, which is the highest efficiency among ZnO-ETL-based flexible planar PSCs to date.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A modified two-step spin coating process for CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> was proposed. </LI> <LI> Efficient CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> layers with variable grain sizes and remnant PbI<SUB>2</SUB> were prepared. </LI> <LI> ZnO-ETL-based flexible planar cells show the best efficiency of 12.34%. </LI> <LI> ZnO-ETL-based flexible planar cells show excellent stability against bending. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>