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연순화,장대규,이철경,Yeon, Sun-Hwa,Jang, Dae-Gyu,Lee, Cheol-Gyeong 한국재료학회 2001 한국재료학회지 Vol.11 No.3
The Self-propagating High-temperature Synthesis (SHS) for synthesizing ($Mo_{1-z}$ , $W_{z}$)$Si_2$was conducted experimentally with the mole fraction of Tungsten(W) from z=0.0 to z=0.5. The temperature profile was measured according to the reaction time through the thermocouple that was equipped into the center of these samples. When the reaction front is propagated around the thermocouple, the highest temperature appears and we regard this temperature as the adiabatic temperature. We found out by experimental results that the reaction velocity is in the range of 2.14~1.35mm/sec and the adiabatic temperature is in the range of 1883~1507K for the six samples. The reaction velocity and the adiabatic temperature were inclined to decrease with an increasing of the mole fraction of Tungsten (W). The SHS modeling is presented in order to predict the temperature profiles and these results are compared with the experimental results. It is predicted that in case of increasing the initial temperature of these six samples, the reaction temperature increased and that the sample of z=0.5 needs the preheating up to 800~900K in order to become reaction temperature 1900K. 자전고온합성반응법을 이용하여 이규화 몰리브덴-텅스텐($Mo_{1-z}$ , $W_{z}$)$Si_2$을 합성하였다. 조성 (z)을 변화시켜 성형한 원통형 시편에 합성반응 중 전달되는 온도변화를 예측하기 위하여 시편의 중앙에 열전대를 삽입하였다. 반응 선단면이 열전대를 통과할 때 가장 높은 반응온도를 보이고 이것을 단열반응 온도라 간주하였다. 따라서 본 연구에서는 이러한 온도변화를 예측하기 위하여 자전조온합성반응의 모델링을 계시하고자 하였으며, 실험을 통하여 측정한 반응온도 분포곡선의 거동을 비교하였다. 각각의 시료에 대한 실험결과 측정된 반응속도는 약 2.14~1.35mm/sec, 반응온도는 1883K~1507K의 간을 보였다. 두 항 모두 텅스텐의 함량이 증가함에 따라 감소하는 경향을 나타냈으며, 수치해석을 통하여 거의 유사한 반응온도를 얻었다. 시료의 초기온도를 증가시킬 경우 반응온도는 증가함이 예측되었고, z=0.5인 시료에 대하여 반응온도가 1900k 이상이 되기 위해서는 약 800K-900K의 예열이 필요하였다.
PVDF와 PP 중공사막 접촉기를 이용한 Alkanolemine 수용액의 이산화탄소 흡수 분리 특성
연순화 ( Sun Hwa Yeon ),서봉국 ( Bong Kuk Sea ),이기섭 ( Ki Sub Lee ),박유인 ( You In Park ),이규호 ( Kew Ho Lee ) 한국공업화학회 2002 공업화학 Vol.13 No.8
중공사막 접촉기를 기존의 흡수장치에 흡수기로 도입하여 구축한 hybrid 시스템을 이용하여 이산화탄소의 분리효율과 흡수제에 대한 중공사막의 물리ㆍ화학적 안정성에 관한 연구를 수행하였다. 서로 다른 구조적 특성을 지니는 PVDF 중공사막과 PP 중공사막을 사용하여 흡수제 MEA, TEA, MDEA 수용액의 이산화탄소 분리효율을 측정하였다. 또한 위의 흡수제에 대한 막의 물리적 그리고 화학적 안정성을 막의 젖음성(wettibility)과 IR 분석을 통해 분석한 결과, MEA와 MDEA 수용액의 경우 PVDF 막에서 물리ㆍ화학적 불안정성을 보였다. 각 흡수제에 대한 long-term 실험을 실시한 결과 3급 아민인 TEA 수용액의 경우 가장 오랜 시간 동안 steady-state 상태를 유지하였다. TEA 수용액에 소량의 MEA를 첨가한 혼합 흡수제의 경우 상당한 분리효율의 상승을 기대할 수 있으며, 막의 pore 내에서 안정적 기-액 계면의 형성으로 인하여 장기간 안정적 운전이 가능하므로 중공사막의 적합한 흡수제로 기대된다. A hollow fiber membrane contactor-stripper hybrid process was used to recover CO_2 from the flue gas, and the physical and chemical stability test of hollow fibers against alkanolamine-based absorbents was conducted. The CO_2 removal efficiency of the polyvinylidenefluoride (PVDF) and polypropylene (PP) hollow fiber membrane contactor was tested with aqueous monoethanolamine (MEA), triethanolamine (TEA) and methyl-diethanolamine (MDEA) absorbents. For MEA, the hollow fibers showed a high CO_2 removal efficiency, but poor chemical and physical stability because the MEA absorbent chemically attacked fibers or physically well penetrated into fiber`s pores. For TEA, the hollow fibers showed a low CO_2 removal efficiency, but good chemical and physical stability. In the case of mixed absorbent adding MEA to aqueous TEA solution, CO_2 removal efficiency of the hollow fiber membrane contactor was enlargd, and this mixed absorbent made it possible to operate this system under long term steady-state conditions due to creating stable liquid-gas interface among the fiber`s pores.
연순화(Yeon, Sun-Hwa),설지웅(Seol, Ji-Woong),이흔(Lee, Huen) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.06
We report here that under strong attacksof external CH₄ guest molecules the sII and sH methane hydrates are structurally transformed to the crystalline me framework of sI, leading to favorable change of the lattice dimension of the host-guest networks. The High Power Decoupling <sup>13</sup>C NMR and Raman spectroscopies were used to identify structure transitions of the mixed CH₄+C₂H<sub>6</sub> hydrates (sIIl) and hydrocarbons (methylcyclohexane, isopentane) + CH₄ hydrates (sH). The resulting spectra indicate that most of the synthesized sII and sH hydrates were transformed to methane hydrate of sl under 110 bar and particularly the coexistence of sl with sII or sH appear according to the surrounding methane-rich gas conditions. The present findings might be expected to Provide rational evidences regarding the preponderant occurrence of naturally-occurring sI methane hydrates in marine sediments.
이차전지 성능향상을 위한 결정성 MAX 상으로부터 유도된 카본의 전극 응용 연구
연순화(Sun-Hwa Yeon),진창수(Chang-Soo Jin),신경희(Kyoung-Hee Shin),황승혜(Seunghae Hwang) 한국전지학회 2022 한국전지학회지 Vol.2 No.1
본 논문에서는 에너지저장 디바이스 성능을 발현시키는데 필수적인 결정성 및 기공도 제어가 가능한 카바이드에서 유도된 카본의 제어된 형태에 따른 응용성, 전극재료 활물질로서의 가능성을 살펴보고, 특히 이차 전지의 음극전극에서 독특한 충방전 특성의 결과를 보이는 MAX 유도 카본 (MAX-Derived Carbon, MDC)의 특성을 파악하고 차세대 고용량 리튬이온전지의 활용 가능성을 제시하고자 한다. In this paper, carbide-derived carbons demonstrate a potential candidate of electrode application for energy storage system because of graphitic porous characteristics. The MAX-derived carbon, using the precursor of MAX phase among carbides, exhibited a peculiar discharge capacity pattern during long-term cycling, in which the discharge capacity decreased from 620 mA h g<SUP>-1</SUP> (1st cycle) to 500 mA h g<SUP>-1</SUP> (20th cycle) and then increased in proportion to the cycle number, reaching a value of ~680 mA h g<SUP>-1</SUP> (300th cycle) at 0.1C-rate.
리튬공기전지의 집전체 특성이 사이클 성능에 미치는 영향
홍대선(Dae-Seon Hong),최연지(Yeon-Ji Choi),진창수(Chang-Su Jin),신경희(Kyoung-Hee Shin),송우진(Woo-Jin Song),연순화(Sun-Hwa Yeon) 한국전지학회 2023 한국전지학회지 Vol.3 No.2
리튬공기전의 일반적인 집전체로 사용되는 Ni foam과 GDL(Gas Diffusion Layer)의 성능을 비교하기 위하여 케첸 블랙(Ketjen black)를 활물질로 사용하여 Cells을 제작하였다. 전기화학적 평가 방법으로는 EIS, 방전/충전 사이클 및 충전-방전 전압 차이를 통하여 성능을 조사하였다. 그리고 물리적 특성을 알아보기 위하여 30 사이클 이후 전극 표면을 SEM 분석하였다. 전기화학적 평가 결과 GDL이 Ni foam보다 안정적인 사이클 특성을 나타내었다. 사이클이 안정적인 이유는 표면 분석을 통하여 확인하였다. To compare the performance of Ni foam and GDL(Gas Diffusion Layer) commonly used in Li-Air batteries for current collector, cells were fabricated using Ketjen black as the active material. As part of the electrochemical evaluation, investigations were conducted using techniques such as EIS, discharge/charge cycles, and assessment of Terminal Voltage gap performance. Furthermore, to examine the physical characteristics, the electrode surfaces were subjected to SEM analysis after 30 cycles. The analysis results revealed that the GDL(Gas Diffusion Layer) exhibited more stable cycling characteristics compared to Ni foam. The reason for the stable cycling was confirmed through surface analysis.
Liquid State with Multi-electron Active Molecule for High Energy Density Redox Flow Battery
Sang-Soon Jang(장상순),Se-Kook Park(박세국),Sun-Hwa Yeon(연순화),Kyoung-Hee Shin(신경희),Han-Su Kim(김한수),Chang-Soo Jin(진창수) 한국신재생에너지학회 2021 한국신재생에너지학회 학술대회논문집 Vol.2021 No.7
With the shift of energy resources to renewable energy, energy storage systems (ESS) have been in charge of a critical role in the efficient energy management of renewable energy resources. Vanadium utilizing aqueous redox flow batteries (VRFBs) with their scalability (up to MW and MWh), long lifetime, and safety features are promising options for large-scale ESS. Although VRFB has been commercialized by numerous companies, it suffers from several challenges that limit its widespread application, particularly due to low energy density (〈 20-35 Wh L<sup>-1</sup>). Therefore, organic redox-active molecules featured with potentially low cost and molecular engineering have been targeted as alternatives. For the high energy density of the RFB, the solubility of the active molecule should be as high as possible, as well as the number of electrons transferred in the reaction should be many. If the active molecule itself is liquid so that utilized as a solo electrolyte or dissolves the salt, high energy density can be achieved. Therefore, the liquid state with multi-electron organic redox-active species would be one of the best strategies for high energy density RFB. In this study, the liquid state with multi-electron organic redox-active molecule was synthesized by applying the mechanism of room temperature ionic liquids to viologen structure. Through the ongoing optimization work of critical cell materials, significant increases in the performance of high energy density RFB can be expected.