• 한국수소및신에너지학회논문집
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• 제7권2호
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• pp.157-164
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• 1996

The AB5-type metal hydride electrodes using $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$(LM : Lanthaniumrich Mischmetal) alloy powders(${\leq}200$mesh) which were coated with 25wt% copper in an acidic bath were prepared with or without addition of 10wt% PTFE as a binder. Prior to electrochemical measurements, the electrodes were sintered at $40^{\circ}C$ for 1 and 2hrs in vacuum with Mm(mischmetal) and sponge type Ti getters. The properties such as maximum capacity, cycle life and mechanical strength of the negative electrode have been investigated. The surface analysis of the electrode was also obtained before and after charge-discharge cycling using scanning electron microscope(SEM). From the observations of electrochemical behavior, it was found that the sintered electrode shows a lower maximum discharge capacity compared with non-sintered electrode but it shows a better cycle life. For the both electrodes with or without addition of PTFE binder, the values of mechanical strength were obtained, and their values increased with increasing sintering time. However, there is little difference of discharge capacity for both electrodes.

• 한국초전도ㆍ저온공학회논문지
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• 제19권2호
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• pp.25-28
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• 2017

In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses that could affect its electromechanical transport property. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with the delamination problem of multi-layered REBCO CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal and mechanical cycling. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in the multi-layered REBCO CC tapes becomes a critical issue. Various trials to increase the delamination strength by improving interface characteristics at interlayers have been performed. In this study, in order to investigate the influences of laser cleaning and Ag annealing treated at the substrate side surface, transverse tensile tests were conducted under different sample configurations using $4.5mm{\times}8mm$ upper anvil. The mechanical delamination strength of differently processed CC samples was examined at room temperature (RT). As a result, the Sample 1 with the additional laser cleaning and Ag annealing processes and the Sample 2 with additional Ag annealing process only showed higher mechanical delamination strength as compared to the Sample 3 without such additional treatments. Sample 3 showed quite different behavior when the loading direction is to the substrate side where the delamination strength much lower as compared to other cases.

• 대한화학회지
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• 제50권3호
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• pp.243-246
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• 2006

박막은 Pt/Ti/SiO2/Si 기판 위에 구연산 졸을 이용하여 spin coating에 의해 제작하였다. 기판위에 코팅된 구연산 졸을 380oC에서 15분간 건조시킨 후 750oC에서 10분간 열처리하여 박막을 얻었다. 얻어진 박막은 X-선 회절분석 결과 R3m의 결정구조를 가짐을 알수 있었고, 전기화학적 특성의 측정결과 1차 방전용량은 0.35Ah/cm2-m로 측정되었다.

• 한국세라믹학회지
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• 제34권1호
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• pp.88-94
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• 1997

플라즈마 용사법(plasma spray method)으로 제작된 상용 가스 터빈 연소기의 finned segment의 열차폐용 코팅계, ZrO2-8wt%Y2O3 top coat/Ni-26Cr-5Al-0.5Y bond coat/Hastelloy X superalloy 기판에서 NiCrAlY bond coat의 산화 거동과 열피로 파괴에 대하여 조사하였다. 생성된 bond coat의 주산화물은 NiO, CrO2, Al2O3였다. ZrO2/bond coat계면에서 생성된 산화물의 분포는 고온에서의 사용 전에 이 계면 아래에 얇은 층의 Al2O3가없는 곳에서는 NiO 산화층 및에 Cr2O3와 Al2O3가 혼합된 형태를 나타내었다. 열피로에 의해 박리된 시편의 파면을 관찰한 결과, 파괴는 주로 ZrO2/산화층 계면보다 세라믹층내로 약간 치우쳐서 일어나지만, 산화층 내에서도 약간 일어남을 알 수 있었다.

• 세라미스트
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• 제21권2호
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• pp.4-18
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• 2018

Lastly, neuromorphic computing chip has been extensively studied as the technology that directly mimics efficient calculation algorithm of human brain, enabling a next-generation intelligent hardware system with high speed and low power consumption. Three-terminal based synaptic transistor has relatively low integration density compared to the two-terminal type memristor, while its power consumption can be realized as being so low and its spike plasticity from synapse can be reliably implemented. Also, the strong electrical interaction between two or more synaptic spikes offers the advantage of more precise control of synaptic weights. In this review paper, the results of synaptic transistor mimicking synaptic behavior of the brain are classified according to the channel material, in order of silicon, organic semiconductor, oxide semiconductor, 1D CNT(carbon nanotube) and 2D van der Waals atomic layer present. At the same time, key technologies related to dielectrics and electrolytes introduced to express hysteresis and plasticity are discussed. In addition, we compared the essential electrical characteristics (EPSC, IPSC, PPF, STM, LTM, and STDP) required to implement synaptic transistors in common and the power consumption required for unit synapse operation. Generally, synaptic devices should be integrated with other peripheral circuits such as neurons. Demonstration of this neuromorphic system level needs the linearity of synapse resistance change, the symmetry between potentiation and depression, and multi-level resistance states. Finally, in order to be used as a practical neuromorphic applications, the long-term stability and reliability of the synapse device have to be essentially secured through the retention and the endurance cycling test related to the long-term memory characteristics.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.161-164
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• 2008

구조물은 사용연한 경과에 따른 노후화 및 용도 변경 등에 의한 보수.보강시 널리 행해지는 부착공법 중 탄소섬유, 아라미드섬유, 유리섬유 등을 이용한 섬유보강 폴리머(Fiber-reinforced polymer,FRP) 보강공법은 섬유 자체의 내화학성, 내구성과 우수한 시공성 등의 장점을 지니고 있다. 현재 FRP 부착공법을 이용한 보강설계 및 보강구조물의 내력 계산시, 콘크리트 부재와의 부착력을 완전부착으로 가정하고 있으나 콘크리트 구조물이 내부적 요인 및 외부 환경요인에 의해 열화될 경우 내력저하 및 1차적인 표면부 열화로 인한 FRP 부착면적의 손실발생이 우려된다. 하게 된다. 따라서 노후화에 따라 내력저하를 보이는 철근콘크리트 구조물에 FRP 보강시 열화에 따른 FRP 보강부재와 콘크리트 모재 간의 부착력 손실에 관한 연구가 필요하며, 본 연구에서는 환경적 요인에 의해 열화되는 철근콘크리트 부재의 파괴양상 및 구조성능과 FRP 보강부재와 콘크리트 모재와의 부착성능 저하현상을 분석하기 위하여 동결융해에 따른 CFRP 쉬트의 보강성능을 실험적으로 규명하고자 한다.

• 한국세라믹학회지
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• 제50권6호
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• pp.480-484
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• 2013

Since SiOC was introduced as an anode material for lithium ion batteries, it has been studied with different chemical compositions and microstructures using various silicon based inorganic polymers. Poly(phenyl carbosilane) is a SiOC precursor with a high carbon supply in the form of the phenyl unit, and it has been investigated for film applications. Unlike any other siloxane-based polymers, oxygen atoms must be utilized in an oxidation process, and the amount of oxygen is controllable. In this study, SiOC anodes were prepared using poly(phenyl carbosilane) with different heat treatment conditions, and their electrochemical properties as an anode material for lithium ion batteries were studied. In detail, cyclic voltammetry and charge-discharge cycling behavior were evaluated using a half-cell. A SiOC anode which was prepared under a heat treatment condition at $1200^{\circ}C$ after an oxidation step showed stable cyclic performance with a reversible capacity of 360 mAh/g.

• 한국수소및신에너지학회논문집
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• 제10권2호
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• pp.131-139
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• 1999

The objective of this works was to synthesize the$Mg_2Ni$ hydrogen storage materials economically and to eliminate the intial activation process. $Mg_2NiH_x$ was mechanically alloyed under purified hydrogen gas atmosphere using pure Mg and Ni chips. M.A(Mechanical Alloying) was carried out using planetary ball mill for times varying from 12h to 96h under 20bars of hydrogen gas pressure. $Mg_2NiH_x$ started to form after 48h and the homogeneous $Mg_2NiH_x$ composites was synthesized after 96h. From TG analysis, the dehydriding reaction of $Mg_2NiH_x$ started at around $200^{\circ}C$. The result of P-C-T at $300^{\circ}C$ revealed the hydrogen storage capacity of $Mg_2NiH_c$ reached 3.68 wt% and the effective hydrogen storage was 2.38 wt%. The enthalpy difference of absorption-desorption cycling for the hydride formation and the hysteresis were reduced and the plateau flatness and the sloping were improved according to M.A time.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.384-388
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• 2013

Fluorine-doping on the $Li_{1+x}Mn_{1.9-x}Al_{0.1}O_4$ spinel cathode materials is found to alter crystal shape, and enhance initial interfacial reactivity and solid electrolyte interphase (SEI) formation, leading to improved initial coulombic efficiency in the voltage region of 3.3-4.3 V vs. Li/$Li^+$ in the room temperature electrolyte of 1 M $LiPF_6$/EC:EMC. SEM imaging reveals that the facetting on higher surface energy plane of (101) is additionally developed at the edges of an octahedron that is predominantly grown with the most thermodynamically stable (111) plane, which enhances interfacial reactivity. Fluorine-doping also increases the amount of interfacially reactive $Mn^{3+}$ on both bulk and surface for charge neutrality. Enhanced interfacial reactivity by fluorine-doping attributes instant formation of a stable SEI layer and improved initial cyclic efficiency. The data contribute to a basic understanding of the impacts of composition on material properties and cycling behavior of spinel-based cathode materials for lithium-ion batteries.

• 한국재료학회지
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• 제29권3호
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• pp.167-174
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• 2019

To improve the performance of carbon nanofibers as electrode material in electrical double-layer capacitors (EDLCs), we prepare three types of samples with different pore control by electrospinning. The speciments display different surface structures, melting behavior, and electrochemical performance according to the process. Carbon nanofibers with two complex treatment processes show improved performance over the other samples. The mesoporous carbon nanofibers (sample C), which have the optimal conditions, have a high sepecific surface area of $696m^2g^{-1}$, a high average pore diameter of 6.28 nm, and a high mesopore volume ratio of 87.1%. In addition, the electrochemical properties have a high specific capacitance of $110.1F\;g^{-1}$ at a current density of $0.1A\;g^{-1}$ and an excellent cycling stability of 84.8% after 3,000 cycles at a current density of $0.1A\;g^{-1}$. Thus, we explain the improved electrochemical performance by the higher reaction area due to an increased surface area and a faster diffusion path due to the increased volume fraction of the mesopores. Consequently, the mesoporous carbon nanofibers are demonstrated to be a very promising material for use as electrode materials of high-performance EDLCs.