• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.302-303
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• 2010

Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

• Korean Chemical Engineering Research
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• 제51권2호
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• pp.263-266
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• 2013

본 연구에서는 친수화 처리된 격리막을 이용한 니켈수소전지의 전기화학적 특성을 연구하였다. 수계 전해액을 사용하는 니켈수소전지로의 적용을 위해 폴리올레핀계 분리막을 친수화 처리하였다. 친수화 미처리품은 방전성능, 용량보존성, 내구성 등의 전기화학적 성능에서 KS 규격기준에 미달되었지만 친수화 처리품은 KS 규격기준을 모두 만족시켰다. 친수화 처리품을 적용한 모든 시료는 유사한 전지성능을 보여주었다. 그 중 술폰화 처리 시료의 경우 용량 보존율(>88%) 측면에서 가장 우수한 특성을 보였으며, 불소화 처리시료는 내구성 측면에서 가장 우수한 성능을 보였는데, 이는 KS 규격기준(500회)과 비교할 때 약 3배 정도(1480회)의 우수한 성능을 유지함을 확인하였다.

• 공업화학
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• 제29권5호
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• pp.549-555
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• 2018

본 연구에서는 울트라 배터리의 전기화학적 성능을 향상시키기 위해서 Nano-Pb/Activated Carbon (Nano-Pb/AC) 복합소재와 전해액 첨가제의 특성이 조사되었다. 제조된 복합 소재의 물리적 특성은 FE-SEM, TEM, XPS, BET를 이용하여 분석하였고, 울트라 배터리의 전기화학적 성능은 사이클, 율속, 임피던스 테스트를 통해 조사되었다. 납 산 배터리에 비하여 나노 납 함량이 9 wt%인 복합소재로 코팅된 울트라 배터리는 사이클 성능이 150%로 개선되었으며, 1-5 C 율속 테스트에서 방전 용량이 119-122%로 증가되었다. 또한 임피던스 테스트 결과 나노 납 함량이 증가할수록 내부 저항의 크기가 작아지는 것을 확인하였다. 전해액 첨가제가 0.45 vol% 포함된 배터리의 장기 사이클 성능은 140%로 향상되었다.

• Asian-Australasian Journal of Animal Sciences
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• 제12권6호
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• pp.923-931
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• 1999

An experiment was conducted to determine the effect of lysine on performance and carcass composition of broilers under heat stress during the grower period (3-6 weeks). A factorial arrangement of three levels of dietary protein (18, 20, and 22%), three levels of dietary lysine (1.26, 1.39, and 1.52%), and two rearing temperature regimens were used in this study. Birds were kept under either moderate temperature ($24{\pm}1^{\circ}C/24h$) or hot cycling temperature ($26-34^{\circ}C/6h$, $34{\pm}1^{\circ}C/12h$, and $34-26^{\circ}C/6h$). Body weight (BW), weight gain (WG), feed intake (FI), feed conversion (FE), carcass weight (CW), carcass yield (CY), and percentages of breast meat (BM), abdominal fat (AF), drumsticks (DS), and thighs (TH) were determined at the end of experiment. Exposure to high ambient temperature significantly (p<0.05) decreased BW, WG, FI, FE, CW, BM, AF, and increased CY, DS, and TH. High dietary protein significantly (p<0.05) decreased AF and TH, and improved CW only under moderate temperature, resulting in significant (p<0.05) protein by temperature interaction. High dietary lysine significantly (p<0.05) decreased BW, WG, FI, CW, CY and AF, while BM was reduced only when high dietary protein was fed, resulting in significant (p<0.05) protein by lysine interaction. It is concluded that increasing dietary lysine adversely affected broilers' performance and carcass composition irrespective of rearing temperature.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제13권6호
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• pp.371-377
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• 2007

본 논문에서는 컨테이너의 위치 정보를 실시간으로 제공해 주는 RTLS(Real Time Location System)를 활용하여 컨테이너터미널 장치장의 효율적인 운영방안 제안을 통해 항만 운영시스템의 성능을 개선하는 것을 목적으로 한다. 이를 위해, 본 논문에서는 컨테이너 및 YT(Yard Tractor)의 위치 정보를 적용한 '개선된 듀얼 사이클링 방식'을 제안하였다. 컨테이너터미널 장치장에 RTLS를 적용하여 컨테이너 위치 정보를 운영시스템에 실시간적으로 전송하게 하였으며, 또한 YT의 위치정보를 GPS 수신기를 통해 수신하여 CDMA 모듈을 통해 운영시스템에 실시간적으로 제공하도록 설계하였다. 제안된 본 방식의 성능 분석 및 평가 결과, 작업시간, 작업시간 분산 및 비용평가는 기존의 방식보다 최대 24% 정도 향상됨을 알 수 있었다. 따라서 RTLS와 GPS 수신기가 항만운영 효율화를 위해 중요한 요소임을 증명하였다.

• 한국재료학회지
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• 제27권4호
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• pp.192-198
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• 2017

Carbon nanofiber (CNF) is used as an electrode material for electrical double layer capacitors (EDLCs), and is being consistently researched to improve its electrochemical performance. However, CNF still faces important challenges due to the low mesopore volume, leading to a poor high-rate performance. In the present study, we prepared the unique architecture of the activated mesoporous CNF with a high specific surface area and high mesopore volume, which were successfully synthesized using PMMA as a pore-forming agent and the KOH activation. The activated mesoporous CNF was found to exhibit the high specific surface area of $703m^2g^{-1}$, total pore volume of $0.51cm^3g^{-1}$, average pore diameter of 2.9 nm, and high mesopore volume of 35.2 %. The activated mesoporous CNF also indicated the high specific capacitance of $143F\;g^{-1}$, high-rate performance, high energy density of $17.9-13.0W\;h\;kg^{-1}$, and excellent cycling stability. Therefore, this unique architecture with a high specific surface area and high mesopore volume provides profitable synergistic effects in terms of the increased electrical double-layer area and favorable ion diffusion at a high current density. Consequently, the activated mesoporous CNF is a promising candidate as an electrode material for high-performance EDLCs.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.533-544
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• 2016

This paper provides a reference to determine the seal performance of metallic O-rings for a reactor pressure vessel (RPV). A nonlinear elastic-plastic model of an O-ring was constructed by the finite element method to analyze its intrinsic properties. It is also validated by experiments on scaled samples. The effects of the compression ratio, the geometrical parameters of the O-ring, and the structure parameters of the groove on the flange are discussed in detail. The results showed that the numerical analysis of the O-ring agrees well with the experimental data, the compression ratio has an important role in the distribution and magnitude of contact stress, and a suitable gap between the sidewall and groove can improve the sealing capability of the O-ring. After the optimization of the sealing structure, some key parameters of the O-ring (i.e., compression ratio, cross-section diameter, wall thickness, sidewall gap) have been recommended for application in megakilowatt class nuclear power plants. Furthermore, air tightness and thermal cycling tests were performed to verify the rationality of the finite element method and to reliably evaluate the sealing performance of a RPV.

• Electronic Materials Letters
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• 제14권6호
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• pp.755-765
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• 2018

In situ nitrogen doped hard carbon nanotubes (NHCNT) were fabricated by pyrolyzing tubular nitrogen doped conjugated microporous polymer. KOH activated NHCNT (K-NHCNT) were also prepared to improve their porous structure. XRD, SEM, TEM, EDS, XPS, Raman spectra, $N_2$ adsorption-desorption, galvanostatic charging-discharge, cyclic voltammetry and EIS were used to characterize the structure and performance of NHCNT and K-NHCNT. XRD and Raman spectra reveal K-NHCNT own a more disorder carbon. SEM indicate that the diameters of K-NHCNT are smaller than that of NHCNT. TEM and EDS further indicate that K-NHCNT are hollow carbon nanotubes with nitrogen uniformly distributed. $N_2$ adsorption-desorption analysis reveals that K-NHCNT have an ultra high specific surface area of $1787.37m^2g^{-1}$, which is much larger than that of NHCNT ($531.98m^2g^{-1}$). K-NHCNT delivers a high reversible capacity of $918mAh\;g^{-1}$ at $0.6A\;g^{-1}$. Even after 350 times cycling, the capacity of K-NHCNT cycled after 350 cycles at $0.6A\;g^{-1}$ is still as high as $591.6mAh\;g^{-1}$. Such outstanding electrochemical performance of the K-NHCNT are clearly attributed by its superior characters, which have great advantages over those commercial available carbon nanotubes ($200-450mAh\;g^{-1}$) not only for its desired electrochemical performance but also for its easily and scaling-up preparation.

• Korean Chemical Engineering Research
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• 제59권3호
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• pp.393-398
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• 2021

리튬이온전지의 성능을 최적화하기 위해서는 여러 열화 요소들을 고려한 성능 예측 모델링 기술이 필요하다. 본 연구에서는 리튬이온전지의 사이클 노화로 인한 방전 거동 및 사이클 수명 변화를 수학적으로 모델링하였다. 모델링의 신뢰성을 검증하기 위해 0.25C로 사이클 시험을 진행했으며, 30 사이클 간격으로 진행한 RPT (Reference performance test)를 통해 전기적 거동을 파악하였다. 기존의 리튬이온전지의 사이클 수명 예측 모델에 BOL (Beginning of life)에서 일어나는 현상 중 하나인 Break-in 메커니즘을 반영하여 수명예측 정확도를 개선시켰다. 모델에 근거하여 예측된 사이클 수명 변화는 실제 시험 결과와 잘 일치하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2021-2025
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• 2007

Performance of single cell at solid oxide fuel cell (SOFC) system is largely affected by electrocatalytic and thermal properties of cathode. Samarium-based perovskite oxide material is recently recognized as promising cathode material for intermediate temperature-operating SOFC due to its high electrocatalytic property. Perovskite structured $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ and its composite material, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}/Sm_{0.2}Ce_{0.8}O_{1.9}$ were investigated in terms of area specific resistance (ASR), thermal expansion coefficient (TEC), thermal cycling and long term performance. $Sm_{0.2}Ce_{0.8}O_{1.9}$ was used as electrolyte material. Electrochemical ac impedance spectroscopy (EIS) and dilatometer were used to measure the cathodic properties. Composite cathode ($Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$: $Sm_{0.2}Ce_{0.8}O_{1.9}$ = 6:4) showed a good ASR of 0.13${\Omega}$ $cm^2$ at 650$^{\circ}C$ and its TEC value was 12.3${\times}$10-6/K at 600$^{\circ}C$ which is similar to the value of ceria-based electrolyte of 11.9${\times}$10-6/K. Performance of composite cathode was maintained with no degradation even after 13 times thermal cycle test.