• Title/Summary/Keyword: Electrochemical current

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Current Status and Future Research Directions of Separator Membranes for Lithium-Ion Rechargeable Batteries (리튬이차전지용 분리막 이해 및 최신 연구 동향)

  • Kim, Jung-Hwan;Lee, Sang-Young
    • Membrane Journal
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    • v.26 no.5
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    • pp.337-350
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    • 2016
  • Lithium-ion rechargeable batteries (LIBs) have garnered increasing attention with the rapid advancements in portable electronics, electric vehicles, and grid-scale energy storage systems which are expected to drastically change our future lives. This review describes a separator membrane, one of the key components in LIBs, in terms of porous structure and physicochemical properties, and its recent development trends are followed. The separator membrane is a kind of porous membrane that is positioned between a cathode and an anode. Its major functions involve electrical isolation between the electrodes while serving as an ionic transport channel that is filled with liquid electrolyte. The separator membranes are not directly involved in redox reactions of LIBs, however, their aforementioned roles significantly affect performance and safety of LIBs. A variety of research approaches have been recently conducted in separator membranes in order to further reinforce battery safeties and also widen chemical functionalities. This review starts with introduction to commercial polyolefin separators that are currently most widely used in LIBs. Based on this understanding, modified polyolefin separators, nonwoven separators, ceramic composite separators, and chemically active separators will be described, with special attention to their relationship with future research directions of advanced LIBs.

A Study on Rehabilitation Treatment Using Radiofrequency Treatment (고주파 통증치료기를 이용한 재활 치료에 대한 연구)

  • Jo, Jae-Hyun;Lee, Sang-Yong;Lee, Geun-Yong;Yoon, Se-Jin;Cheong, Ha-Young;Lee, Sang-Sik
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.13 no.3
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    • pp.212-218
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    • 2020
  • When Radiofrequency energy is applied to the human body, the vibration width is very short. Therefore, the electrolyte burn generated when using the direct current does not occur. Ion molecules, polarized molecules, etc., vibrate more than 40,000 times per second, converting them into frictional heat to generate deep heat. The blood flow of capillaries increases 4-5 times more than at rest, increasing the supply of oxygen, nutrients, antibodies, and white blood cells. In addition, the electrochemical reaction does not occur because the vibration width and the pulsation period are very short. It is a physical factor treatment method that does not stimulate the sensory nerves and motor nerves. In this study, an isotonic exercise is performed in a young normal adult using a Radiofrequency pain treatment device. The purpose of this study is to integrate rehabilitation therapy by measuring electromyography data during isotonic exercise and confirming the effect on changes in motor neuron response. The EMG data generated when isotonic exercise of the forearm biceps muscle and the EMG data measured after the use of a Radiofrequency pain treatment device after exercise were RMS, respectively, and verified through t-test. It was confirmed that there was a significant difference in both men and women because the t-value was smaller than the significance level p (<.05).

Effects of PtMn composition on carbon supported PtMn catalysts for PEMFC (Mn조성비(組成比)가 PEMFC용(用) Pt/C 전극촉매(電極觸媒) 특성(特性)에 미치는 영향(影響)에 관(關)한 연구(硏究))

  • Yoo, Sung-Yeol;Kang, Suk-Min;Lee, Jin-A;Rhee, Choong-Kyun;Ryu, Ho-Jin
    • Resources Recycling
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    • v.21 no.2
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    • pp.34-40
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    • 2012
  • $Pt_{10}$/C, $Pt_9Mn_1$/C, $Pt_7Mn_3$/C electrocatalysts for Polymer Electrolyte Membrane Fuel Cells(PEMFCs) were synthesized by reduction with HCHO and their activity as a oxygen reduction reaction(ORR) was examined at half cell. The electrochemical oxygen reduction reaction(ORR) was studied by using a glaasy carbon electrode through cyclic voltammetric curves(CV) in a 1 M $H_2SO_4$ solution. The ORR activities of $Pt_9Mn_1$/C were higher than $Pt_{10}$/C, $Pt_7Mn_3$/C. Also potential-current curves of $Pt_9Mn_1$/C at 0.9, 0.8, 0.7, 0.6V for 5minutes respectively were higher than $Pt_{10}$/C, $Pt_7Mn_3$/C. Physical characterization was made by using x-ray diffraction(XRD) and transmission electron microscope(TEM). The TEM images of $Pt_9Mn_1$/C, $Pt_{10}$/C catalysts showed homogenous particle distribution with particle size of about 2.7 nm, 3 nm respectively and then the XRD results showed that the crystalline structure of the synthesized catalysts are seen FCC structure.

Evaluation of Characteristics of Welding Zones Welded with Inconel 718 Filler Metal to Piston Crown Forged Material (피스톤 크라운용 단강에 인코넬 718 용접재료로 용접된 용접부의 특성 평가)

  • Lee, Sung-Yul;Moon, Kyung-Man;Jeong, Jae-Hyun;Lee, Myeong-Hoon;Baek, Tae-Sil
    • Journal of Ocean Engineering and Technology
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    • v.30 no.4
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    • pp.334-340
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    • 2016
  • The combustion chamber of a diesel engine is often exposed to a more serious wear and corrosion environment than other parts of the engine because its temperature increases as a result of using heavy oil of low quality. Therefore, repair and built-up welding methods must be performed on worn or corroded parts of the piston crown, exhaust valve, etc. from an economical point of view. In this study, Inconel 718 filler metal was used in repair welding on the groove of a forged steel specimen for a piston crown, along with built-up welding on the surface of another forged steel specimen. Then, the corrosion characteristics of the weld metal zone for the repair welding and the deposited metal zone for the built-up welding were investigated using electrochemical methods in a 35% H2SO4 solution. The deposited metal zone indicated better corrosion resistance than the weld metal zone, showing a nobler corrosion potential, higher impedance, and smaller corrosion current density. It is considered that metal elements with good corrosion resistance were generally included in the filler metal, and these elements were also greatly involved in the deposited meta by built-up welding, whereas the weld metal consisted of metal elements mixed with both the filler metal and base metal elements because of the molten pool produced by the repair welding. Finally, it is considered that the hardness of the weld metal was increased by the repair welding, whereas the built-up welding improved the corrosion resistance of the deposited metal.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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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.

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Durability Evaluation of Stationary PEMFC MEA by OCV Holding Method (정치용 PEMFC MEA의 OCV 유지 방법에 의한 내구 평가)

  • Oh, So-Hydong;Lee, Mihwa;Yun, Jeawon;Lee, Hakju;Kim, Wookwon;Na, Il-Chai;Park, Kwonpil
    • Korean Chemical Engineering Research
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    • v.57 no.3
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    • pp.344-350
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    • 2019
  • Durability is very important for the commercialization of membranes and electrode assemblies (MEA) developed for proton exchange membrane fuel cells (PEMFC). Durability evaluation of stationary PEMFC MEA has a problem that the voltage change rate should be measured for a long time over 1000 hours under constant current conditions. In this study, the electrochemical durability evaluation protocol of membranes (OCV holding method) using to vehicle MEAs was applied to the stationary MEA for the purpose of shortening the durability evaluation time. After operation of the stationary and automobile MEA for 168 hours under conditions of OCV, cathode oxygen, $90^{\circ}C$ and relative humidity of 30%, I-V, LSV, CV, impedance and FER were measured and compared. When the hydrogen permeability, OCV change, ionic conductivity, and fluorine flow rate, which represent the durability of the membrane after degradation, were all examined, it was shown that durability of stationary MEA membrane was better than that of vehicles MEA membrane. In addition, the electrode degradation of stationary MEA was smaller than that of vehicles MEA after degradation operation. It was possible to evaluate in a short time using automotive protocol that the durability of stationary MEA was superior that of vehicle MEA in terms of membrane and the electrode.

A Review of Structural Batteries with Carbon Fibers (탄소섬유를 활용한 구조용 배터리 연구 동향)

  • Kwon, Dong-Jun;Nam, Sang Yong
    • Applied Chemistry for Engineering
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    • v.32 no.4
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    • pp.361-370
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    • 2021
  • Carbon fiber reinforced polymer (CFRP) is one of the composite materials, which has a unique property that is lightweight but strong. The CFRPs are widely used in various industries where their unique characteristics are required. In particular, electric and unmanned aerial vehicles critically need lightweight parts and bodies with sufficient mechanical strengths. Vehicles using the battery as a power source should simultaneously meet two requirements that the battery has to be safely protected. The vehicle should be light of increasing the mileage. The CFRP has considered as the one that satisfies the requirements and is widely used as battery housing and other vehicle parts. On the other hand, in the battery area, carbon fibers are intensively tested as battery components such as electrodes and/or current collectors. Furthermore, using carbon fibers as both structure reinforcements and battery components to build a structural battery is intensively investigated in Sweden and the USA. This mini-review encompasses recent research trends that cover the classification of structural batteries in terms of functionality of carbon fibers and issues and efforts in the battery and discusses the prospect of structural batteries.

Corrosion Behaviors of TiN Coated Dental Casting Alloys (TiN피막 코팅된 치과주조용 합금의 부식거동)

  • Jo, Ho-Hyeong;Park, Geun-Hyeng;Kim, Won-Gi;Choe, Han-Cheol
    • Korean Journal of Metals and Materials
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    • v.47 no.2
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    • pp.129-137
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    • 2009
  • Corrosion behaviors of TiN coated dental casting alloys have been researched by using various electrochemical methods. Three casting alloys (Alloy 1: 63Co-27Cr-5.5Mo, Alloy 2: 63Ni-16Cr-5Mo, Alloy 3: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting(CF), high frequency induction casting(HFI) and vacuum pressure casting(VP). The specimens were coated with TiN film by RF-magnetron sputtering method. The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion morphologies were analyzed using FE-SEM and EDX. Alloy 1 and Alloy 2 showed the ${\alpha}-Co$ and ${\varepsilon}-Co$ phase on the matrix, and it was disappeared in case of TiN coated Alloy 1 and 2. In the Alloy 3, $Ni_2Cr$ second phases were appeared at matrix. Corrosion potentials of TiN coated alloy were higher than that of non-coated alloy, but current density at passive region of TiN coated alloy was lower than that of non-coated alloy. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.

Preparation and Electrochemical Properties of Freestanding Flexible S/CNT/NiO Electrodes for Li-S Batteries (리튬-황 전지용 프리스탠딩 플렉서블 S/CNT/NiO 전극의 제조 및 전기화학적 특성)

  • Shin, Yun Jung;Lee, Won Yeol;Kim, Tae Yun;Moon, Seung-Guen;Jin, En Mei;Jeong, Sang Mun
    • Korean Chemical Engineering Research
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    • v.60 no.2
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    • pp.184-192
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    • 2022
  • Porous NiO synthesized via hydrothermal synthesis was used in the electrodes of lithium-sulfur batteries to inhibit the elution of lithium polysulfide. The electrode of the lithium-sulfur battery was manufactured as a freestanding flexible electrode using an economical and simple vacuum filtration method without a current collector and a binder. The porous NiO-added S/CNT/NiO electrode exhibited a high initial discharge capacity of 877 mA h g-1 (0.2 C), which was 125 mA h g-1 higher than that of S/CNT, and also showed excellent retention of 84% (S/CNT: 66%). This is the result of suppressing the dissolution of lithium polysulfide into the electrolyte by the strong chemical bond between NiO and lithium polysulfide during the charging and discharging process. In addition, for the flexibility test of the S/CNT/NiO electrode, the 1.6 × 4 cm2 pouch cell was prepared and exhibited stable cycle characteristics of 620 mA h g-1 in both the unfolded and folded state.

Multi-Layered Sintered Porous Transport Layers in Alkaline Water Electrolysis (다층 소결메쉬 확산체를 이용한 알칼라인 수전해 셀)

  • YEOM, SANG HO;YUN, YOUNG HWA;CHOI, SEUNGWOOK;KWON, JIHEE;LEE, SECHAN;LEE, JAE HUN;LEE, CHANGSOO;KIM, MINJOONG;KIM, SANG-KYUNG;UM, SUKKEE;KIM, CHANG-HEE;CHO, WON CHUL;CHO, HYUN-SEOK
    • Journal of Hydrogen and New Energy
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    • v.32 no.6
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    • pp.442-454
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    • 2021
  • The porous transport layer (PTL) is essential to effectively remove oxygen and hydrogen gas from the electrode surface at high current density operation conditions. In this study, the effect of PTL with different characteristics such as pore size, pore gradient, interfacial coating was investigated by multi-layered sintered mesh. A water electrolysis single cell of active area of the 34.56 cm2 was constructed, and IV performance and impedance analysis were conducted in the range of 0 to 2.0 A/cm2. It was confirmed that the multi-layered sintered mesh PTL, which have an average pore size of 25 to 57 ㎛ and a larger pore gradient, removed bubbles effectively and thus seemed to improve IV performance. Also, it was confirmed that the catalytic metals such as Ni, NiMo coating on the PTL reduced activation overpotential, but increased mass transport overpotential.