• 전기화학회지
• /
• 제3권2호
• /
• pp.121-126
• /
• 2000

[ $AB_5$ ] 수소저장합금인 $LaNi_5$, 합금분말에 Ni 및 Cu 무전해 도금의 영향을 전기 화학적 실험을 통하여 고찰하였다. 전기 화학적 실험은 정전류 충$\cdot$방전 실험, 순환전류전위 실험, 교류 임피던스 실험 등을 실시하여 도금하지 않은 $LaNi_5$ 전극과 Ni 및 Cu 무전해 도금한 전극간의 특성을 비교 연구하였다. 현상학적인 분석으로는 SEM을 이용하여 분말상의 미세조직을 관찰하였으며 X-선 회절시험을 실시하였다 무전해 도금을 실시하여 Ni 및 Cu박막이 피복된 수소저장 합금은 활성화 특성파 싸이클 수명 등의 특성이 개선되었으며 도금하지 않은 전극에 비하여 반응속도가 증가하였다. 또한 충$\cdot$방전이 반복됨에 따라 전극과 전해질 계면에서의 전하이동저항이 현저하게 감소하였다. 따라서 본 연구에서 실시한 $LaNi_5$, 활물질에 Ni및 Cu 무전해 도금을 실시하면 초기 활성화반응을 촉진시키며 $LaNi_5$활물질이 전해질과의 직접 접촉을 피하게 되어 전극의 수명을 증가시키는 것을 알 수 있었다.

• Korean Chemical Engineering Research
• /
• 제57권5호
• /
• pp.672-678
• /
• 2019

리튬이차전지용 음극재로서 피치로 코팅된 천연흑연의 전기화학적 특성이 조사되었다. 천연흑연과 피치의 혼합물을 $1000^{\circ}C$에서 소성하여 음극재를 제조하였다. 다양한 연화점의 피치가 탄소전구체로 사용되었다. 제조된 음극재의 물리적 특성은 TGA, SEM, PSA 및 BET로 분석하였다. 피치의 연화점이 증가할수록 코팅 층의 두께가 증가하였고, 비표면적이 감소하였다. 초기 충 방전 효율, 사이클, 순환전압전류, 속도 특성 및 임피던스 테스트를 통해 전기화학적 성능을 조사하였다. 연화점 $250^{\circ}C$의 피치로 탄소 코팅된 천연흑연은 초기 방전용량 361 mAh/g과 쿨롱 효율 92.6%을 보였다. 또한 출력 특성(5 C/0.2 C)은 코팅되지 않은 천연흑연에 비해 1.6배 향상되었으며, 0.5 C로 진행된 사이클 테스트에서 50 사이클 후 90%의 용량 유지율을 나타내었다.

• E2M - 전기 전자와 첨단 소재
• /
• 제7권4호
• /
• pp.317-324
• /
• 1994

In this study, new preparation method of LiCoO$_{2}$ was applied to develop cathode active material for Li rechargeable cell, and followed by X-ray diffraction analysis, electrochemical properties and initial charge/discharge characteristics as function of current density. HC8A72- and CC9A24-LiCoO$_{2}$ were prepared by heating treatment of the mixture of LiOH H$_{2}$O/CoCO$_{3}$(1:1 mole ratio) and the mixture of Li$_{2}$CO$_{3}$/CoCO$_{3}$(1:2 mole ratio) at 850 and 900.deg. C, respectively. Two prepared LiCoO$_{2}$s were identified as same structure by X-ray diffraction analysis. a and c lattice constant were 2.816.angs. and 14.046.angs., respectively. The electrochemical potential of CFM-LiCoO$_{2}$(Cyprus Foote Mineral Co.'s product), HC8A72-LiCoO$_{2}$ and CC9A24 LiCoO$_{2}$ electrode were approximately between 3.32V and 3.42V vs. Li/Li reference electrode. Stable cycling behavior was obtained during the cyclic voltammetry of LiCoO$_{2}$ electrode. According as scan rate increases, cathodic capacity decreases, but redox coulombic efficiency was about 100% at potential range between 3.6V and 4.2V vs. Li/Li reference electrode. Cathodic capacity of HC8A72-LiCoO$_{2}$ was 32% higher than that of CFM-LiCoO$_{2}$ and that of CC9A24-LiCoO$_{2}$ was 47% lower than that of CFM-LiCoO$_{2}$ at 130th cycle in the condition of lmV/sec scan rate. Constant cur-rent charge/discharge characteristics of LiCoO$_{2}$/Li cell showed increasing Ah efficiency with initial charge/discharge cycle. Specific discharge capacities of CFM and HC8A72-LiCoO$_{2}$ cathode active materials were about 93mAh/g correspondent to 34% of theretical value, 110mAh/g correspondent to 40% of theretical value, respectively. In the view of reversibility, HC8A72-LiCoO$_{2}$ was also more excellent than CFM- and CC9A24-LiCoO$_{2}$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제48권6호
• /
• pp.469-474
• /
• 1999

Methods and systems to remove static electricity are requested in the field of industry because the static electricity causes a flammable gas explosion or fire and a reduction of production rate in manufacturing semiconductor devices and so on. This paper is a basic study about a new structure of electrode system to control the quantities of generated ions and to solve the problem of dust attachment to needle electrode. In addition, a new type field controlled electrostatic charge neutralizer was proposed, and it could control the electric field in the end of the needle electrode by controlling the voltage of the third electrode around the tip of the needle electrode. As aresult, it was possible to control the quantities of generated ion by controlling the electric field in the needle electrode with the third electrode, which shows the possibilities to solve the nonequilibrium of generated ions in ac power source and the problem of the dust in the needle electrode.

• 공업화학
• /
• 제4권1호
• /
• pp.153-161
• /
• 1993

$700-900^{\circ}C$의 온도범위와 여러 산소분압 조건에서 고체전해질 연료전지의 양극인 $La_{0.9}Sr_{0.1}MnO_3$에서 산소의 환원반응특성을 조사하였다. AC 임피던스법과 전류중단법에 의해 산소환원반응의 전하전달저항을 측정하였는데 두 방법으로 구한 간이 서로 잘 일치하였다. 전기화학적 산소환원반응의 활성화에너지는 대기압 조건에서 174kJ/mol의 값을 보였고, 산소분압에 따른 전하전달저항의 측정결과로 부터 이 전극에서 전기화학적 산소환원반응의 율속단계는 전하전달과정임을 알 수 있었다.

• 설비공학논문집
• /
• 제23권4호
• /
• pp.273-280
• /
• 2011

In this study, the steady state performance of a $CO_2$ heat pump water heater was measured with a variation of operating conditions such as refrigerant charge amount, compressor frequency, EEV opening, and water mass flow rate. Transient state performance tests were also conducted to investigate major system effects associated with the interaction between the $CO_2$ heat pump water heater and the water tank. Optimum refrigerant charge amount for the system was 1600 g. At compressor frequencies of 50 Hz and 60 Hz, water mass flow rates of 95 kg/h and 105 kg/h, and EEV opening of 8% and 16%, the water heating temperatures were $65^{\circ}C$ and $68^{\circ}C$ and COPs were 3.0 and 2.8, respectively. In the transient condition, the instantaneous COP decreased with an increase in the inlet water temperature.

• 한국산학기술학회논문지
• /
• 제7권1호
• /
• pp.7-11
• /
• 2006

SCM(Scanning Capacitance Method)를 이용하여, SCM 팁의 전계에 의해 형성되는 실리콘내의 공핍영역를 분석할 수 있는 방법론을 구축하였다. 2차원 유한요소법을 이용하여 SCM으로 측정된 결과로부터 불순물의 농도를 도출할 수 있었다. 이 방법은 캐패시턴스, 공핍화된 체적 및 바이어스에 따른 캐패시턴스의 변화율로부터 구해진다. 본 연구에서는 팁의 크기, 산화층 두께 및 가해지는 바이어스에 따른 공핍 전하와 전위에 따른 영향등을 분석하였다.

• 한국세라믹학회지
• /
• 제29권6호
• /
• pp.463-470
• /
• 1992

Corundum single crystals were grown in cryolite flux with the composition of Na3AlF6:Al2O3=80:20 wt%. This mixture was melted at 115$0^{\circ}C$, followed by slow cooling at a rate of 2$^{\circ}C$/hr to 96$0^{\circ}C$. And by adding of La2O3 to the flux, the change of crystal forms were observed. Crystal forms of corundum grown in cryolite flux had the habits of hexagonal plate which consist of well developed {0001} face and small {101} face. As La2O3 was added and its content was increased, {223} and {110} faces were developed, and crystal habits of equidimensional forms changed into hexagonal prism form. In a charge of 8 mole% B2O3, Al2O3:La2O3=15:1, transparent corundum single crystals of equent form were grown. As the content of B2O3 was increased, twineed crystals which have twin law of 2-fold parallel to [0001], and composition plane of (110) were grown.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 A
• /
• pp.547-549
• /
• 2001

Recently, heating using oil and gas has been continuously replaced by that using midnight power in home, due to increase of oil price. Therefore, midnight power apparatus has been more and more spreading. However, cost of midnight power services is increasing because high fuel cost of generation facilities by existing power generation mix are charge of midnight power services. This paper analyzes trends about rapidly increasing midnight power in winter, and evaluate load pattern and supply cost of midnight power. Also, this study proposes rate direction of midnight power according to introduction of competitiveness system with B/C evaluation of midnight power cost.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.197-198
• /
• 2007

In this paper, a 10Gbps Clock and Data Recovery circuit is designed in $0.18{\mu}m$ CMOS Technology. The circuit incorporates a multiphase LC oscillator, a quarter-rate Bang-Bang phase detector, a Charge Pump and a second order loop filter. The simulation results show that the designed circuit has a peak-to-peak clock jitter of 4.1ps and a peak-to-peak recovered data jitter of 8ps while consuming about 44mW from a 1.8V supply.