• 제목/요약/키워드: Surface electric property

검색결과 108건 처리시간 0.028초

EDLC 전극용 카본에어로젤의 합성조건에 따른 기공구조 및 전기화학적 특성 (Pore Structure and Electrochemical Properties of Carbon Aerogels as an EDLC-Electrode with Different Preparation Conditions)

  • 서혜인;정지철;김명수
    • 한국재료학회지
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    • 제28권1호
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    • pp.50-61
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    • 2018
  • Various carbon aerogels (CAs) were prepared from polymerization of resorcinol and formaldehyde and applied as the electrode materials of an electric double layer capacitor (EDLC) with the aim of controlling the textural and electrochemical properties of CAs by the type of base catalyst and the ratio of resorcinol to catalyst (R/C). The CAs from $NaHCO_3$ and $KHCO_3$ with $H^+$ ions had higher specific surface areas but exhibited lower electrochemical properties than those from $K_2CO_3$ and $Na_2CO_3$, which had more uniform pore size distributions. The electrochemical properties of $Na_2CO_3$ were superior to those of $K_2CO_3$ probably because the polarizing power of $Na^+$ ions was higher than $K^+$ ions. With an increasing R/C ratio, the pore sizes of CA showed a tendency to increase but the uniformity of the pore size distribution got worse. For the four base catalysts, the highest electrochemical property was obtained at the R/C ratio of 500.

Effects of SiC Particle Size and Inorganic Binder on Heat Insulation of Fumed Silica-based Heat Insulation Plates

  • Jo, Hye Youn;Oh, Su Jung;Kim, Mi Na;Lim, Hyung Mi;Lee, Seung-Ho
    • 한국세라믹학회지
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    • 제53권4호
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    • pp.386-392
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    • 2016
  • Heat insulation plates of fumed silica were prepared by mixing fumed silica, SiC powder and chopped glass fiber by a high speed mixer followed by pressing of the mixture powder in a stainless steel mold of $100{\times}100mm$. Composition of the plates, particle size of SiC, and type of inorganic binder were varied for observation of their contribution to heat insulation of the plate. The plate was installed on the upper portion of an electric furnace the inside temperature of which was maintained at $400^{\circ}C$ and $600^{\circ}C$, for investigation of heat transfer through the plate from inside of the electric furnace to outside atmosphere. Surface temperatures were measured in real time using a thermographic camera. The particle size of SiC was varied in the range of $1.3{\sim}17.5{\mu}m$ and the insulation was found to be most excellent when SiC of $2.2{\mu}m$ was incorporated. When the size of SiC was smaller or larger than $2.2{\mu}m$, the heat insulation effect was decreased. Inorganic binders of alkali silicate and phosphate were tested and the phosphate was found to maintain the heat insulation property while increasing mechanical properties.

원통형 다전극식 정전용량-전기전도도 센서를 이용한 연료전지 차량용 냉각수의 유전특성 평가 (Evaluation about Dielectric Property of Heat Transfer Fluids for Fuel Cell Vehicle using Cylindrical Multi-Terminal Capacitive-Conductive Sensor)

  • 김재훈;김주한;김윤형;최강월;한상옥;용기중
    • 전기학회논문지
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    • 제59권6호
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    • pp.1087-1094
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    • 2010
  • We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.

탄소나노섬유의 밀링에 따른 전기화학적 에너지 저장 특성 (Electrochemical Energy Storage of Milled Carbon Nanofiber)

  • 이혜민;전현;최원경;조태환
    • 한국수소및신에너지학회논문집
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    • 제22권4호
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    • pp.527-533
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    • 2011
  • CNFs had been well addressed due to numerous promising applications in science and technology. Besides the same physicochemical properties of ordinary carbon materials such as active carbons and carbon black, they exhibit specific, e.g., tubular or fibrous structures, a large surface area, high electrical conductivity stability, as well as extremely high mechanical strengh and modulus, which make them a superior material for electrochemical capacitors. In this study, CNFs were pretreated by mechanical milling with different time in mortar and pestle. The milled CNFs were used as active material of electrode whose electrochemical property was tested to find physicochemical characterization variation. CNF electrode milled for 5 min has the highest electric capacitance. XPS spectrum were employed to explore changes in functional group induced from mechanical milling. Crystal size was calculated to analyze change of peak from different milling time by XRD. The CNF milled for 5 min has the largest crystal size and the highest electric capacitance.

A Study on the Electrical Strength of Insulating Materials for High-Tc Superconducting Devices

  • Bae, Duck Kweon;Kim, Chung-Hyeok;Pak, Min-Sun;Oh, Yong-Cheul;Kim, Jin-Sa;Shin, Cheol-Gee;Lee, Joon-Ung;Song, Min-Jong;Choi, Woon-Shik
    • Transactions on Electrical and Electronic Materials
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    • 제6권6호
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    • pp.294-300
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    • 2005
  • According to the trend for electric power equipment of high capacity and reduction of its size, the needs for the new high performance electric equipments become more and more important. On of the possible solution is high temperature superconducting (HTS) power application. Following the successful development of practical HTS wires, there have been renewed activities in developing superconducting power equipment. HTS equipments have to be operated in a coolant such as liquid nitrogen ($LN_2$) or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of some insulating materials, such as unfilled epoxy, filled epoxy, and polyimide in $LN_2$ was analyzed. Epoxy is a good insulating material but fragile at cryogenic temperature. The filled epoxy composite not only compensates for this fragile property but enhances its dielectric strength.

RF-Sputtering법에 의한 CoSi2/Si 박막 형성에 관한 특성 (The Characteristic of Formation CoSi2/Si Thin Film by the RF-Sputtering Method)

  • 조금배;이강연;최연옥;김남오;정병호
    • 전기학회논문지
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    • 제59권7호
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    • pp.1255-1258
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    • 2010
  • In this paper, the $CoSi_2$ thin films with thicknesses of about $5{\mu}m$ were deposited on n-type silicon (111) substrates by RF magnetron sputtering method using a $CoSi_2$ target (99.99%). The flow rate of argon of 50 sccm, substrate temperature of $100^{\circ}C$, RF power of 60 watts, deposition time of 30 minutes, and the vacuum of $1\times10^{-6}$ Torr. The annealing treatments of the $CoSi_2$ thin film were performed from 500, 700 and $900^{\circ}C$ for 1h in air ambient by an electric furnace. In order to investigate the $CoSi_2$ thin film X-ray diffraction patterns were measured using the X-ray diffractometer (XRD). The structure of the thin films were investigated by using scanning the electron microscope (SEM) were used for review. The surface morphology of the thin films was measured with a atomic force microscopy (AFM). Temperature dependence of sheet resistivity and property of Hall effect was measured in the $CoSi_2$ thin film.

해양온도차 발전소의 입지선정을 위한 해수 온도차의 공간적 분포특성 분석 (A Property Analysis on Spatial Distribution of Sea Water Temperature Difference for Site Selection of Ocean Thermal Energy Conversion Plant)

  • 서영상;장이현;조명희
    • 에너지공학
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    • 제8권4호
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    • pp.567-575
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    • 1999
  • 한국동해 연근해역의 표층수온은 일반적으로 온대해역에서의 표층수온과 같이 계절변화를 하지만, 심층에서는 연중 1 $^{\circ}C$이하의 온도를 유지하는데 동해고유수로 인하여 표층의 온수와 심층의 냉수간의 온도차를 이용한 해양온도차 발전의 충분한 잠재성이 있다. 해양온도차 발전의 제 1 조건인 표층수와 심층수간의 온도차에 관련된 한국 동해의 해양 환경적 특성을 정량화 하고자 온도차에 대한 연평균, 연진폭, 연위상을 구하고 연중 15$^{\circ}C$이상의 온도차가 유지된는 기간을 일일 단위로 표현하였다. 한국동해 연근 해역 중 온도차 발전의 최적합 해역은 포항 동쪽 35km 해역 (36$^{\circ}$05'N, 129$^{\circ}$48'E)에서 55km 해역 (36$^{\circ}$05'N, 130$^{\circ}$00'E)까지로 조사 연구되었다. 이들 최적합 해역에서는 온도차는 8월의 경우 누년 평균 약 24$^{\circ}C$로 나타났으며, 년 중 15$^{\circ}C$이상의 온도차가 유지되는 기간은 최대 215일 (5/5-12/10)로 나타났다. 아울러 이 해역에서 온도차의 연진폭은 6$^{\circ}C$이며 , 연위상은 236$^{\circ}$로 계획성있는 전력생산을 할수 있을것으로 사료된다. 한국 동해 연근해역에서 표층으로부터 수직으로 최단거리에 존재하는 동해고유수(수온 1$^{\circ}C$이하의 해수)의 수심에 대한 계절변화는 평균 300m를 중심으로 하여 50m 미만의 작은 변동폭을 나타내었다. 향후 이러한 안정된 위치를 나타내는 심층 냉수를 에너지로 전환하기 위한 연구가 수행되어야 할 것으로 판단된다.

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Recent Research and Development on Aerosol Cyclones-Review

  • Lee, K.W.;Kim, H.T.
    • Journal of Korean Society for Atmospheric Environment
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    • 제16권E호
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    • pp.59-68
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    • 2000
  • In this paper Various aerosol cyclones that are developed recently form Kwangju Institute of Science and Technology(KJIST) for increasing collection efficiency or for decreasing pressure drop are reviewed. For the first time, new sets of experimental data are reported on the particle collection efficiency of cyclones with modified surface bodies namely, spiral guide body, circumferential groove body, and vertical groove body. Multi-cylinder cyclones by adding one or two additional cylindrical walls into the conventional cyclone are also described. Ad an attempt to increase the collection efficiency of small particles, electrocyclone using an externally applied electric field was designed and operated. In addition, factors affecting the cyclone performance were studied including flowrate, body and outlet sizes, cyclone dust outlet, and gas property.

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집속이온빔을 이용한 탄소나노튜브 팁의 조작 (Manipulation of Carbon Nanotube Tip Using Focused Ion Beam)

  • 윤여환;박준기;한창수
    • 한국정밀공학회지
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    • 제23권12호
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    • pp.122-127
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    • 2006
  • This paper reports on the development of carbon nanotube tip modified with focused ion beam(FIB). We used an electric field which causes dielectrophoresis, to align and deposit CNTs on a metal-coated canning Probe Microscope (SPM) tip. Using the CNT attached SPM tip, we have obtained an enhanced resolution and wear property compared to that from the bare silicon tip through the scanning of the surface of the bio materials. The carbon nanotube tip was aligned toward the source of the ion beam allowing their orientation to be changed at precise angles. By this technique, metal coated carbon nanotube tips that are several micrometer in length are prepared for SPM.

$LiNbO_3/Si_3N_4$ 구조를 이용한 MFIS 구조의 형성 및 특성 (Formations and properties of MFIS structure using $LiNbO_3/Si_3N_4$ structure)

  • 김용성;정상현;정순원;이남열;김진규;김광호;유병곤;이원재;유인규
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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    • pp.221-224
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    • 2000
  • We have successfully demonstrated metal-ferroel-ectric-insulator-semiconductor (MFIS) devices using Al/LiNbO$_{3}$/SiN/Si structure. The SiN thin films were made into metal -insulator- semiconductor (MIS) devices by thermal evaporation of aluminum source in a dot away on the surface. The interface property of MFIS from 1MHz & quasistatic C-V is good and the memory window width is about 1.5V at 0.2V/s signal voltage sweep rate. The gate leakage current density of MFIS capacitors using a aluminum electrode showed the least value of 1x10$^{-8}$ A/$\textrm{cm}^2$ order at the electric field of 300㎸/cm. And the XRD patterns shows the probability of applications of LN for MFIS devices for FeRAMs on amorphous SiN buffer layer.

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