• 제목/요약/키워드: Electrochemical parameters

검색결과 339건 처리시간 0.03초

황토로부터 합성한 제올라이트에 의한 Cd(II) 및 Cu(II) 흡착특성 (Adsorption Characteristics of Cd(II) and Cu(II) by Zeolites Synthesized from Hwangto)

  • 감상규;홍정연;허철구;이민규
    • 한국환경과학회지
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    • 제12권7호
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    • pp.817-824
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    • 2003
  • Various kinds of zeolites, such as analcime (ANA), cancrinite (CAN), Na-Pl and sodalite octahydrate (SOD) could be synthesized from Hwangto by hydrothermal reaction in a high-pressure vessel. The adsorption characteristics of Cu(II) and Cd(II) by Hwangto and its synthetic zeolites were investigated using the chemical and electrochemical surface parameters of these adsorbents. The heavy metal adsorptivity among the adsorbents decreased in the following sequences: Na-Pl > SOD > ANA > CAN > Hwangto. This sequence was the same with the values of surface site density (Ns) of these adsorbents and was correlated inversely with the values of pHpzc (pH of the point of zero charge) and the va]ues of K$\_$a2/(int) (intrinsic surface deprotonation constant) of the adsorbents for synthetic zeolites, i.e., the adsorbents with higher values of Ns and with lower values of pHpzc and K$\_$a2/(int) for synthetic zeolites showed higher heavy metal adsorptivity. With increasing pH, the heavy metal adsorptivity increased greatly between pHpzc and pH 6 or 7 because of the steep increase of negatively charged sites for synthetic zeolites, but for Hwangto, it increased broadly because of slow increase of negatively charged sites based on its lower surface sites.

Efficient Simulation Method for Dielectric Barrier Discharge Load

  • Oleg, Kudryavtsev;Ahmed, Tarek;Nakaoka, Mutsuo
    • Journal of Power Electronics
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    • 제4권3호
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    • pp.188-196
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    • 2004
  • The dielectric barrier discharge is recognized as one of the efficient methods of ultraviolet light generation and ozone production. As well, it is widely utilized for gaseous wastes neutralization and other technological processes in industry. This electrochemical reaction is electrically equivalent to a nonlinear capacitive load that represents some difficulties for designing the power supply. Therefore, a conventional power supply is designed for a drastically simplified model of the load and generally is not optimal. This paper presents a fast simulation approach for the nonlinear capacitive model representation of the dielectric barrier discharge load lamp. The main idea of the proposed method is to use analytical solutions of the differential state equations for the load and find the unknown initial conditions for the steady state by an optimization method. The derived expressions for the analytical solutions are rather complicated, however they greatly reduce the calculation time, which make sense when a deeper analysis is performed. This paper introduces the proposed simulation method and gives some examples of its application such as estimation of the load equivalent parameters and load matching conditions.

Numerical study of effect of membrane properties on long-cycle performance of vanadium redox flow batteries

  • Wei, Zi;Siddique, N.A.;Liu, Dong;Sakri, Shambhavi;Liu, Fuqiang
    • Advances in Energy Research
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    • 제4권4호
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    • pp.285-297
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    • 2016
  • Fundamental understanding of vanadium ion transport and the detrimental effects of cross-contamination on vanadium redox flow battery (VRFB) performance is critical for developing low-cost, robust, and highly selective proton-conducting membranes for VRFBs. The objective of this work is to examine the effect of conductivity and diffusivity, two key membrane parameters, on long-cycle performance of a VRFB at different operating conditions using a transient 2D multi-component model. This single-channel model combines the transport of vanadium ions, chemical reactions between permeated ions, and electrochemical reactions. It has been discovered that membrane selecting criterion for long cycles depends critically on current density and operating voltage range of the cell. The conducted simulation work is also designed to study the synergistic effects of the membrane properties on dynamics of VRFBs as well as to provide general guidelines for future membrane material development.

기중방전의 방전원별 특성분석 및 패턴분류 (Properties and Classification of Patterns of Air Discharges)

  • 박영국;이광우;장동욱;강성화;정광호;김완수;이용희;임기조
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권1호
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    • pp.19-23
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    • 2000
  • Partial discharges(PD)in air insulated electric power apparatus often lead to deterioration of solid insulation by electron bombardments and electrochemical reaction. The PD caused to reduce the life time of power apparatus and to increase power losses. Thus understanding and classification of PD patterns in air are very important to discern sources of PD. In this paper, PD in air by using statistical methods was investigated. We classified air discharges, corona, surface discharges and cavity discharges by Kohonen network. For classification of PD patterns, we used statistical operators and parameters such as skewness$(S^+,\; S^-),\; kurtosis(K^+, K^-),\; mean phase(AP^+, AP^-)$, cross-correlation factor(CC) and asymmetry derived from the mean pulse-height phase distribution$(H_{avg}(\phi))$, the max pulse-height phase distribution $(H_{qmax}(\phi))$, the pulse count phase distribution $(H_n(\phi))$ and the pulse height vs. Repetition rate $(H_q(n))$.

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EDLC용 Carbon-PTFE 전극의 전기화학적 특성에 미치는 변수 연구 (Study of Parameters on the Electrochemical Properties of Carbon-PTFE Electrode for Electric Double Layer Capacitor)

  • 김익준;양선혜;전민제;문성인;김현수
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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    • pp.355-356
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    • 2006
  • This work describes the effect of the number of roll pressing and the composition of carbon black on the electric and mechanical properties of carbon-PTFE electrode, in which composition is MSP20 : carbon black: PTFE = 95-X : X : 5 wt.%. It was found that the best electric and mechanical properties were obtained for sheet electrode roll pressed about 15 times and for sheet electrode, in which composition is MSP20 carbon black : PTFE = 80 : 15 : 5 wt%. These behaviors could be explained by the network structure of PTFE fibrils and conducting paths linked with carbon blacks, respectively. On the other hand, cell capacitor using the sheet electrode with 15 wt.% of carbon black attached on aluminum current collector with the electric conductive adhesive, in composition is carbon black : CMC = 70 : 30 wt.%, has exhibited the best rate capability between 0.5 $mA/cm^2$ ~ 100 $mA/cm^2$ current density and the lowest ESR.

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폴리(옥틸티오펜)/풀러렌 벌크 이종접합의 광기전성에 미치는 CIS 입자의 블렌딩 효과 (The Blending Effect of Electro-deposited Copper-indium-diselenide Particles on the Photovoltaic Properties of Poly(3-octylthiophene)/Fullerene Bulk Heterojunction Cells)

  • 조영돈;이선형;김정수
    • 폴리머
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    • 제34권1호
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    • pp.84-87
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    • 2010
  • 구리, 인디움, 셀레늄 이온을 포함한 혼합물을 전기화학적으로 환원하는 1회 반응으로 CIS 입자를 합성하였다. 합성된 입자를 폴리(옥틸티오펜/풀러렌으로 구성된 벌크이종접합에 블렌딩하거나 박막층으로 삽입하여 여러 가지 광기전셀을 제조하였다. CIS의 함량이 증가할수록 개방전압과 단락전류의 급격한 감소가 일어났다. 이러한 광기전성의 감소현상을 블렌드의 구조, 조성, 모폴로지를 분석 해석하였다.

Electrochemical Characteristics of Zn-mesh Cathodic Protection Systems in Concrete in Natural Seawater at Elevated Temperature

  • Kim, Ki-Joon;Jung, Jin-A;Lee, Woo-Cheol;Jang, Tae-Seub
    • Corrosion Science and Technology
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    • 제6권6호
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    • pp.269-274
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    • 2007
  • The corrosion of steel in concrete is significant in marine environment. Salt damage is one of the most detrimental causes to concrete bridges and port structures. Especially, the splash and tidal zones around water line are comparatively important in terms of safety and life-time point of view. During the last several decades, cathodic protection (cp) has been commonly accepted as an effective technique for corrosion control in concrete structures. Zn-mesh sacrificial anode has been recently developed and started to apply to the bridge column cp in marine condition. The detailed parameters regarding Zn-mesh cp technique, however, have not well understood so far. This study is to investigate how much Zn-mesh cp influences along the concrete column at elevated temperature. About 100 cm column specimens with eight of 10 cm segment rebars have been used to measure the variation of cp potential with the distance from Zn-mesh anode at both $10^{\circ}C$ and $40^{\circ}C$ in natural seawater. The cp potential change and current diminishment along the column specimens have been discussed for the optimum design of cp by Zn-mesh sacrificial anode.

원자력 이용 고체산화물 고온전기분해 수소 및 합성가스 생산시스템의 열역학적 효율 분석 연구 (A Study on Thermodynamic Efficiency for HTSE Hydrogen and Synthesis Gas Production System using Nuclear Plant)

  • 윤덕주;고재화
    • 한국수소및신에너지학회논문집
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    • 제20권5호
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    • pp.416-423
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    • 2009
  • High-temperature steam electrolysis (HTSE) using solid oxide cell is a challenging method for highly efficient large-scale hydrogen production as a reversible process of solid oxide fuel cell (SOFC). The overall efficiency of the HTSE hydrogen and synthesis gas production system was analyzed thermo-electrochemically. A thermo-electrochemical model for the hydrogen and synthesis gas production system with solid oxide electrolysis cell (SOEC) and very high temperature gas-cooled reactor (VHTR) was established. Sensitivity analyses with regard to the system were performed to investigate the quantitative effects of key parameters on the overall efficiency of the production system. The overall efficiency with SOEC and VHTR was expected to reach a maximum of 58% for the hydrogen production system and to 62% for synthesis gas production system by improving electrical efficiency, steam utilization rate, waste heat recovery rate, electrolysis efficiency, and thermal efficiency. Therefore, overall efficiency of the synthesis production system has higher efficiency than that of the hydrogen production system.

Electrolytes - Quality at Point of Use

  • Heider U.;Jungnitz M.;Oesten R.
    • 한국전기화학회:학술대회논문집
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    • 한국전기화학회 1998년도 전지기술 심포지움
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    • pp.153-166
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    • 1998
  • Lithium ion Batteries commercially available since the early nineties in Japan are going to be more and more important for portable electronic devices and even EV applications. Today several companies around the world are working hard to join to market for Lithium secondary batteries. Based on the growing interest for commercial use of batteries also the materials have to be reviewed in order to meet large scale production needs. The requirements especially for electrolytes for lithium batteries are extremely high. The solvents and the lithium salts should be of highest purity. So the supply of these chemicals including packaging, transportation and storage but also the handling in production are critical items in this field. Frolic impurities are very critical for LiPF6 based electrolytes. The influence of water is tremendous. But also the other protic impurities like alcoholes are playing an Important role for the electrolyte quality. The reaction of these species with LiPF6 leads to formation of HF which further reacts with cathode materials (spinel) and anode. To understand the role of the protic impurities more clearly the electrolyte was doped with such compounds and was analyzed for protic impurities and HF. These results which directly show the relation between impurities and quality will be presented and discussed. In addition several investigations on different packaging materials as well as methods to analyze and handle the sensititive material will be addressed. These questions which are only partly discussed in literature so far and never been investigated systematically cover some of the key parameters for understanding of the battery chemicals. This investigation and understanding however is of major importance for scientist and engineers in the field of Lithium ion and Lithium polymer batteries.

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Electrochemical Properties and Estimation on Active Material LiMnO2 Synthesis for Secondary

  • Wee, Sung-Dong;Kim, Jong-Uk;Gu, Hal-Bon
    • Transactions on Electrical and Electronic Materials
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    • 제4권2호
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    • pp.35-39
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    • 2003
  • This paper is contents on the orthorhombic crystalline calcined by the solid phase method with LiMnO$_2$ thin film structured as the result which an average pore diameter of power was 132.3${\AA}$ in porosity analysis. Voltage ranges are able to get the properties of charge and discharge for experimental results of LiMnO$_2$ thin film were 2.2V 4.3V. The current density and scan speed were 0. 1㎃/$\textrm{cm}^2$ and 0.2㎷/sec respectively. Properties of the charge and discharge are obtained by optimum experiment condition parameters. Li dense ratio of the LiMnO$_2$ thin film that discharged capacities were 87㎃h/g have been 96.9[ppm] at 670.784[nm] wavelength. The dense ratio of Mn analyzed to 837[ppm] at 257.610[nm] wavelength. It can be estimated the quality of the LiMnO$_2$ thin film as that the wrong LiMnO$_2$ thin film pulled up from cell of electrolyte and became dry it at 800$^{\circ}C$. The results of SEM and XRD were the same as that of original researchers.