• 전기화학회지
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• 제16권2호
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• pp.91-97
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• 2013

이온성 액체 전해질염 1-ethyl-3-methylimidazolium tetrafluoroborate ($EMIBF_4$)과 용매 acrylonitrile (ACN) 및 propylene carbonate (PC)와 각각 혼합한 용액에 poly(ethylene glycol)diacrylate (PEGDA)를 45-60 wt.% 첨가하고 자외선 조사를 통해 경화시켜 고체 고분자 전해질 필름을 제조하였다. 이 고체 고분자 전해질 필름을 분리막으로 채택하고 활성탄 전극을 사용하는 수퍼커패시터를 제조하여 그 전기화학적 특성을 사이클릭 볼타메트리와 임피던스 방법으로 조사하였다. 결과적으로 PEGDA를 45 wt.% 첨가하여 제조한 고체 고분자 전해질 필름을 채택한 경우가 스캔속도 $20mVs^{-1}$에서 $46Fg^{-1}$의 가장 우수한 축전용량을 나타내는데, 이것은 PEGDA의 저함량 때문에 상대적으로 자외선 경화가 약하게 진행되어 고분자 전해질 필름의 유연성이 충분히 확보되므로 필름 내 이온전도가 가장 활발히 진행될 수 있었기 때문이다.

• 한국세라믹학회지
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• 제43권12호
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• pp.812-822
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• 2006

This study amis to investigate the functional analysis of anode and cathode materials in Anode supported Solid Oxide Fuel Cell. The concentration polarization of single cell was investigated with CFD (Computational Fluid Dynamics) method for the case of the different morphology by using four types of unit cell and discussed to reduce the concentration polarization. The concentration polarization at anode side effected the voltage loss in Anode supported Solid Oxide Fuel Cell and increased contact areas between fuel gas and anode side could reduce the concentration polarization. For intermediate temperature operation, Anode-supported single cells with thin electrolyte layer of YSZ (Yttria-Stabilized Zirconia) were fabricated and short stacks were built and evaluated. We also developed diesel and methane autothermal reforming (ATR) reactors in order to provide fuels to SOFC stacks. Influences of the $H_2O/C$ (steam to carbon ratio), $O_2/C$ (oxygen to carbon ratio) and GHSV (Gas Hourly Space Velocity) on performances of stacks have been investigated. Performance of the stack operated with a diesel reformer was lower than with using hydrogen as a fuel due to lower Nernst voltage and carbon formation at anode side. The stack operated with a natural gas reformer showed similar performances as with using hydrogen. Effects of various reformer parameters such as $H_2O/C$ and $O_2/C$ were carefully investigated. It is found that $O_2/C$ is a sensitive parameter to control stack performance.

• 한국미생물·생명공학회지
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• 제27권4호
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• pp.311-319
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• 1999

Leaves of Aloe vera Linne and bloods of domestic animal were composted in a soild state fermentation reactor (SSFR) by using microbial additive including a bulking and moisture controlling agent. From solid-culture of microbial additive, 10 species of bacteria and 10 species of fungi were isolated and, their enzyme activities including amylase, carboxy methyl cellulase CMCase, lipase and protease were detected. Optimum fermentation conditions of Aloe leaves and domestic animal bloods in SSFR were obtained from the studies of response surface analysis employing microbial additive content, initial moisture content, and fermentation temperature as the independent variables. The optimum conditions for SSFR using Aloe leaves were obtained at 9.45$\pm$73%(w/w) of microbial additives, 62.73$\pm$4.54%(w/w) of initial moisture content and 55.32$\pm$3.14$^{\circ}C$ of fermentation temperature while those for SSFR using domestic animal bloods were obtained at 10.25$\pm$2.04%, 58.68$\pm$4.97% and 57.85$\pm$5.$65^{\circ}C$, respectively. Composting process in SSFR was initially proceeded through fermentation and solid materials were decomposed within 24 hours by maintaining higher moisture level, and maturing and drying steps are followed later. After the fermentation step, the concentrations of solid phase inorganic components were increased while that of organic components were decreased. Also, concentrations of total organic carbon(TOC), peptides, amino acids, polysaccharides, and low fatty acids in water extracts were increased. As fermentation in composting process depends on initial C/N ratios in water extracts of two samples were increased because of increased water-soluble TOC. From these results, it was revealed that solid state fermentation reactor using microbial additives can be used in composting process of organic wastes with broad C/N ratio.

• 한국추진공학회지
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• 제21권2호
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• pp.26-31
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• 2017

고체 추진제의 환경적 문제는 고체 로켓에서 중요한 이슈로 부각되고 있다. 예를 들어 고체추진제의 산화제인 ammonium perchlorate (AP)는 염산과 같은 독성 가스와 대기 오염을 발생시켜 환경적 문제를 야기한다. 산화제 중 N-guanylurea dinitramide (GuDN)는 높은 성능과 압력 지수를 가지고 있으며, 가스발생기 추진제에서 연소하는 동안 친환경적인 연기를 배출하는 성질을 가지고 있기 때문에 환경친화적으로 효과적인 후보 물질이다. 본 논문에서는 가스발생기 추진제로서 특성에 대하여 이론적 분석, 추진제 제조공정성, 추진제 경도 특성 및 연소특성에 대하여 연구하였다.

• 한국세라믹학회지
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• 제55권1호
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• pp.50-54
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• 2018

This study investigated the long-term durability of catalyst(Pd or Fe)-infiltrated solid oxide cells for $CO_2$/steam co-electrolysis. Fuel-electrode supported solid oxide cells with dimensions of $5{\times}5cm^2$ were fabricated, and palladium or iron was subsequently introduced via wet infiltration (as a form of PdO or FeO solution). The metallic catalysts were employed in the fuel-electrode to promote $CO_2$ reduction via reverse water gas shift reactions. The metal-precursor particles were well-dispersed on the fuel-electrode substrate, which formed a bimetallic alloy with Ni embedded on the substrate during high-temperature reduction processes. These planar cells were tested using a mixture of $H_2O$ and $CO_2$ to measure the electrochemical and gas-production stabilities during 350 h of co-electrolysis operations. The results confirmed that compared to the Fe-infiltrated cell, the Pd-infiltrated cell had higher stabilities for both electrochemical reactions and gas-production given its resistance to carbon deposition.

• Advances in nano research
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• 제7권2호
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• pp.109-123
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• 2019

In this article, the free vibration analysis of annular sandwich plates with various functionally graded (FG) porous cores and carbon nanotubes reinforced composite (CNTRC) facesheets is investigated based on modified couple stress theory (MCST) and first order shear deformation theories (FSDT). The annular sandwich plate is composed of two face layers and a functionally graded porous core layer which contains different porosity distributions. Various approaches such as extended mixture rule (EMR), Eshelby-Mori-Tanaka (E-M-T), and Halpin-Tsai (H-T) are used to determine the effective material properties of microcomposite circular sandwich plate. The governing equations of motion are extracted by using Hamilton's principle and FSDT. A Ritz method has been utilized to calculate the natural frequency of an annular sandwich plate. The effects of material length scale parameters, boundary conditions, aspect and inner-outer radius ratios, FG porous distributions, pore compressibility and volume fractions of CNTs are considered. The results are obtained by Ritz solutions that can be served as benchmark data to validate their numerical and analytical methods in the future work and also in solid-state physics, materials science, and micro-electro-mechanical devices.

• Applied Microscopy
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• 제45권4호
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• pp.242-248
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• 2015

In this paper, three carbon sources, i.e., solid graphite, gaseous CH4 and liquid ethanol, and one solid silicon source were employed to synthesize SiC/C nanocomposite powders by arc-discharge plasma. The processing conditions such as the component ratios of raw materials, atmospheric gases, etc. were adjusted for controllable synthesis of the nanopowders. It is indicated that both of solid graphite and silicon can be co-evaporated and reacted to form nanophases of cubic ${\beta}$-SiC with ~50 nm in mean size and a little free graphite; the carbon atoms decomposed from gaseous $CH_4$ favor to combine with the evaporated silicon atoms to form the dominant SiC nanophase; liquid carbon source of ethanol can also be used to harvest the main ${\beta}$-SiC and minor 6H-SiC phases in the assembly of nanoparticles. The as-prepared SiC/C nanocomposite powders were further purified by a heat-treatment in air and their photocatalytic performances were then greatly improved.

• 한국가스학회지
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• 제27권3호
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• pp.27-34
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• 2023

고체 산화물 연료전지의 연료로 암모니아를 사용하는 것은 고효율, 환경 친화성, 보관 및 운송의 용이성으로 인해 주목받고 있다. 암모니아 활용 SOFC 시스템의 효율을 더욱 높이려면 시스템의 비효율적인 구성 요소를 이해해야 하며 이를 위해 엑서지 분석을 수행하였다.본 연구에서는 단순 연료전지 시스템(FC), 연료극 재순환 시스템(RC-FC) 및 수분 제거 재순환 시스템(RC-WR-FC)의 세 가지 시스템에 대해 엑서지 분석을 수행하였다. FC, RC-FC 및 RC-WR-FC의 엑서지 효율은 각각 48.7%, 51.6% 및 58.4%이었으며, 세 시스템 모두에서 SOFC 스택은 엑서지 파괴의 주요 원인이었다. 또한 버너, 공기 열 교환기 및 냉각기/응축기와 같이 낮은 효율을 가진 부품들을 재구성한다면 효율을 높일 수 있다.

• 한국토양비료학회지
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• 제46권5호
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• pp.391-398
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• 2013

Soil organic carbon (SOC) has the potential to promote the soil quality for sustainability and mitigation of global warming. There is little information on organic carbon composition despite of having resistance of carbon degradation in soil. In this study, to understand the effect of volcanic ash on organic carbon composition and quantity in soil, we investigated characteristics of volcanic soil and compared organic carbon composition of soil and humic extract by using $^{13}C$-CPMAS-NMR spectra under soil profiles of Namweon series in Jeju. SOC contents of inner soil profiles were 134.8, 101.3, and 27.4 g C $kg^{-1}$ at the layer of depth 10-20, 70-80 and 90-100 cm, respectively. These layers were significantly different to soil pH, oxalate Al contents, and soil moisture contents. Alkyl C/O-alkyl C ratio in soil was higher than that of humic extracts, which was decreased below soil depth. Aromaticity of soil and humic extract was ranged from 29-38 and 24-32%, which was highest at the humic extract of 70-80 cm in soil depth. These results indicate that the changes of SOC in volcanic ash soil resulted from alteration of organic composition by pyrolysis and stability of organic carbon by allophane in volcanic ash soil.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.644-650
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• 2021

본 연구는 지구 온난화의 주요 원인인 이산화탄소를 이용하여 메탄의 개질반응 특성을 수행하였다. 이산화탄소와의 메탄 분해 반응을 전이금속 촉매인 주석을 사용하여 수행되었으며, 주석의 분해 반응성은 니켈, 철과 같은 전이 금속보다 낮으며, 대부분의 분해 반응은 고체 상태 촉매하에 수행된다. 반면에 주석의 녹는점은 505.03K로 액상 촉매하에서 분해가 발생된다. 주석을 사용하는 경우 액상으로 반응하며 메탄이 분해되어 생성되는 고체상 탄소가 촉매에 침적되어 비활성화되는 것을 것을 방지하는 장점이 있다. 이산화탄소를 사용하여 메탄을 분해하는 경우 일산화탄소와 수소를 생성한다. 촉매의 활성과 수명을 높이기 위해 Ni를 사용한 경우 촉매 활성이 향상되었다. 본 연구에서는 과잉습식함침법을 이용하여 촉매를 합성하였으며, 반응 온도, 공간 속도에 따른 활성과 촉매 재생 가능성을 타진하였다. 탄소가 침적된 주석의 촉매 재생 온도는 1023 K로 나타났으며, 니켈을 조촉매로 사용하고 물을 공급하므로써 반응성이 향상되는 것으로 나타났다.