• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.169-176
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• 1998

An experimental study on effect of vapor-cooled heat stations in a 5.5 liter cryogenic vessel has been performed. The cryogenic vessel is made of stainless steel of thickness of 1mm and insulated by the combined insulation of vacuum, MLI(multi-layer insulation) and vapor-cooled radiation shield. Vapor-cooled heat stations are also constructed based on the 1-dimensional thermal analysis to reduce the heat inleak through a filling tube. Thermal analysis indicates that the vapor-cooled heat stations can substantially enhance the performance of vessel for cryogenic fluids with high $C_p/h_{fg}$ where $C_p$ the specific heat and $h_{fg}$ the heat of vaporization, such as $LH_2$ and LHe. The experimental results for $LN_2$ shows that the total heat inleak into inner vessel consists of 14% radiation and 86% conduction through the filling tube. Therefore, it is expected that the conduction heat in leak of the vessel for high $C_p/h_{fg}$ cryogenic fluids can be significantly reduced. powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.179-184
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• 2016

The interface between the surface of a cathode material and the electrolyte gives rise to surface reactions such as solid electrolyte interface (SEI) and chemical side reactions. These reactions lead to increased surface resistance and charge transfer resistance. It is consequently necessary to improve the electrochemical characteristics by suppressing these reactions. In order to suppress unnecessary surface reactions, we coated cathode material using polypropylene (PP). The PP coating layer effectively reduced the SEI film that is generated after a 4.3 V initial charging process. By mitigating the formation of the SEI film, the PP-coated Li[(Ni_0.6Co_0.1Mn_0.3)_0.36(Ni_0.80Co_0.15Al0.05)_0.64)]O₂(NCS) electrode provided enhanced transport of Li⁺ ions due to reduced SEI resistance (R_SEI) and charge transfer resistance (R_ct). The initial charge and discharge efficiency of the PP-coated NCS electrode was 96.2 % at a current density of 17 mA/g in a voltage range of 3.0 ~ 4.3 V, whereas the efficiency of the NCS electrode was only 94.7 %. The presence of the protective PP layer on the cathode improved the thermal stability by reducing the generated heat, and this was confirmed via DSC analysis by an increased exothermic peak.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.202-210
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• 2001

Spin dependent tunneling (SDT) junction devices of Ta/NiFe/Ta/NiFe/FeMn/NiFe/AlOx/CoFe/NiFe/Al with in-situ naturally oxidized Al barrier were fabricated using ion beam deposition and dc sputtering in UHV chamber of 10$^{-9}$ Torr. The maximum tunneling magnetoresistance (TMR) and the product resistance by junction (R$_{j}$ A) are 16-17% and 50-60 $\Omega$${\mu}{\textrm}{m}$$^2$, respectively. The values of TMR and (R$_{j}$ A) with field annealing were slightly increased. The TMR and (R$_{j}$ A) dependence versus the junction area size was observed. These results were explained by using sheet resistance effect of bottom electrode and spin channel effects.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.425-431
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• 2023

An asymmetric metal-semiconductor-metal Al_0.24Ga_0.76N ultraviolet (UV) sensor was fabricated, and the effects of local Joule heating were investigated. After dielectric breakdown, the current density under a reverse bias of 2.0 V was 1.1×10^-9 A/cm², significantly lower than 1.2×10^-8 A/cm² before dielectric breakdown; moreover, the Schottky behavior of the Ti/Al/Ni/Au electrode changed to ohmic behavior under forward bias. The UV-to-visible rejection ratio (UVRR) under a reverse bias of 7.0 V before dielectric breakdown was 87; however, this UVRR significantly increased to 578, in addition to providing highly reliable responsivity. Transmission electron microscopy revealed interdiffusion between adjacent layers, with nitrogen vacancies possibly formed owing to local Joule heating at the AlGaN/Ti/Al/Ni/Au interfaces. X-ray photoelectron microscopy results revealed decreases in the peak intensities of the O 1s binding energies associated with the Ga-O bond and OH-, which act as electron-trapping states on the AlGaN surface. The reduction in dark current owing to the proposed local heating method is expected to increase the sensing performance of UV optoelectronic integrated devices, such as active-pixel UV image sensors.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1733-1737
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• 2009

A new cathode material based on Li$Ni_{0.8}Co_{0.15}Al_{0.05}O_2$ (LNCA)/polyaniline (Pani) composite was prepared by in situ self-stabilized dispersion polymerization in the presence of LNCA. The materials were characterized by fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Electrochemical properties including galvanostatic charge-discharge ability, cyclic voltammetry (CV), capacity, cycling performance, and AC impedance were measured. The synthesized LNCA/Pani had a similar particle size to LNCA and exhibited good electrochemical properties at a high C rate. Pani (the emeraldine salt form) interacts with metal-oxide particles to generate good connectivity. This material shows good reversibility for Li insertion in discharge cycles when used as the electrode of lithium ion batteries. Therefore, the Pani coating is beneficial for stabilizing the structure and reducing the resistance of the LNCA. In particular, the LNCA/Pani material has advantageous electrochemical properties.

• Transactions of the Korean hydrogen and new energy society
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• v.7 no.2
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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.

• New & Renewable Energy
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• v.1 no.1 s.1
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• pp.64-71
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• 2005

The stability of alumina-coated NiO cathodes was studied in $Li_{0.62}/K_{0.38}$ molten carbonate electrolyte. Alumina was effectively coated on the porous Ni plate using galvanostatic pulse plating method. The deposition mechanism of alumina was governed by the concentration of hydroixde ions near the working electrode, which was controlled by the temperature of bath solution. Alumina-coated NiO cathodes were formed to $A1_2O_3-NiO$ solid solution by the oxidation process and their Ni solubilities were were than that of NiO up to the immersion time of 100h. However, their Ni solubilities increased and were similar to that of the bare NiO cathode after 100h. It was because aluminum into the solid solution was segregated to $\alpha-LiAlO_2$ on the NiO and its Product did not Play a role of the Physical barrier against NiO dissolution.

• Transactions of the Korean hydrogen and new energy society
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• v.4 no.2
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• pp.23-28
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• 1993

The $(LM)Ni_{4.5}Co_{0.1}Mn_{0.2}Al_{0.2}$ hydrogen storage alloy powders were conducted 25wt% electroless copper plating in an acidic bath. For the preparation of a hydride electrodes, the copper coated alloy powder was mixed with Si-sealant(organosilicon) and compacted with $6t/cm^2$ at room temperature. The electrode characteristics were examined through electrochemical measurements in a half cell. As a sealant contents increased, the initial discharge capacity of si-sealant bounded electrode was lower and the activation rate in high current density was slower. For extended cycles, however, the electrodes with the Si-sealant were superior in a high rate discharge and useful range of temperature over the sealant-free electrode. In addition, the cycle life increased with increasing the amount of Si-sealant added. It can be suggested from the results that the Si-sealant as a binder could be applied to the preparation of the metal hydride electrode.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.50-51
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• 2002

최근 실온에서 약 40％ 이상의 높은 자기저항(magnetoresistance, MR)을 나타내는 자기 터널 접합(magnetic tunnel junction, MTJ)이 보고되면서 비휘발성 자기메모리로의 응용을 눈앞에 두고 있다.[1]. 이에 본 실험에서는 Substrate / Ta (base electrode) / NiFe / PtMn (AF pinning layer) / CoFe (pinned) / Ru / CoFe (fixed) / Al-O/ CoFe (free) / NiFe (free) / Ta & Ru (Capping Layer)과 같은 MTJ 증착 구조를 사용하여, MTJ의 보다 향상된 특성을 확보하기 위한 노력으로서 Al-O 두께, 어닐링 조건(Field Intensity ＆ Sequence)변화 등을 시도하였다. (중략)

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.416-423
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• 1996

Electrochemical reduction of thionyl chloride in 1.5 M $LiAlCl_4/SOCl_2$ electrolyte solution containing tetradentate Schiff base Co(II), Ni(II), Cu(II), and Mn(II) complexes has been investigated at the glassy carbon electrode. The catalyst molecules of transition metal(II) complexes were adsorbed on the electrode surface and reduced thionyl chloride resulting in a generation of oxidized catalyst molecules. There was an optimum concentration for each catalyst compound. The current density of $SOCl_2$ reduction was enhanced up to 150% at the catalyst contained electrolyte solution. The reduction currents of thionyl chloride were increased and the reduction potentials were shifted to the negative potential as scan rates became faster. The reduction of thionyl chloride was proceeded to diffusion controlled reaction.