• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.379-384
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• 2012

It is investigated that that the physical properties of Glutathione layer formed on gold surfaces may make an effect on the distribution of either gold particle adsorbed to the $TiO_2$ surface or vice versa with the adjustment of the electrostatic interactions. For the investigation, the atomic force microscope (AFM) was used to measure the surface forces between the surfaces as a function of the salt concentration and pH value. With the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the forces were quantitatively analyzed to acquire the surface potential and charge density of the surfaces for each salt concentration and each pH value. The surface potential and charge density dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface. The salt concentration dependence of the surface properties, found from the measurement at pH 8 and 11, was consistent with the prediction from the law. It was found that the Glutathione layer had higher values for the surface charge densities and potentials than the titanium dioxide surfaces at pH 8 and 11, which may be attributed to the ionized-functional-groups of the Glutathione layer.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.93-99
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• 2011

We investigated how the surface roughness of electrode affects the charge injection at the pentacene/Au interface. After depositing Au film on the Si substrate by sputtering, we annealed the sample to control the Au surface roughness. Pentacene and Au top electrode were subsequently deposited to complete the sample. The nucleation density of pentacene was slightly higher on the rougher Au electrode, but surface morphologies of thick pentacene films were similar on both the as-prepared and the roughened Au electrodes. The current-voltage curves obtained from the Au/pentacene/Au structure measured as a function of temperature indicated that the interface barrier was higher for the rougher Au bottom-electrode. We propose that the higher barrier was caused by the lower work function of rougher electrode surface and the higher trap density at the interface.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.710-718
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• 2021

Recently, due to high theoretical capacitance and excellent ion diffusion rate caused by the 2D layered crystal structure, transition metal hydroxides (TMHs) have generated considerable attention as active materials in supercapacitors (or electrochemical capacitors). However, TMHs should be designed using morphological or structural modification if they are to be used as active materials in supercapacitors, because they have insulation properties that induce low charge transfer rate. This study aims to modify the morphological structure for high cycling stability and fast charge storage kinetics of TMHs through the use of nickel cobalt hydroxide [NiCo(OH)₂] decorated on nickel foam. Among the samples used, needle-like NiCo(OH)₂ decorated on nickel foam offers a high specific capacitance (1110.9 F/g at current density of 0.5 A/g) with good rate capability (1110.9 - 746.7 F/g at current densities of 0.5 - 10.0 A/g). Moreover, at a high current density (10.0 A/g), a remarkable capacitance (713.8 F/g) and capacitance retention of 95.6% after 5000 cycles are noted. These results are attributed to high charge storage sites of needle-like NiCo(OH)₂ and uniformly grown NiCo(OH)₂ on nickel foam surface.

• Journal of the Korean Ceramic Society
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• v.53 no.3
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• pp.312-316
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• 2016

The energetics of defects in the presence of domain walls in $LiNbO_3$ are characterized using density-functional theory calculations. Domain walls show stronger interactions with antisite defects than with interstitial defects or vacancies. As a result, antisite defects act as a strong pinning center for the domain wall in $LiNbO_3$. Analysis of migration behavior of the antisite defects across the domain wall shows that the migration barrier of the antisite defects is significantly high, such that the migration of antisite defects across the domain wall is energetically not preferable. However, further study on excess electrons shows that the migration barrier of antisite defects can be lowered by changing the charge states of the antisite defects. So, excess electrons can enhance the migration of antisite defects and thus facilitate domain wall movement by weakening the pinning effect.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.388-395
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• 2016

Electric vehicles (EV) and hybrid EVs (HEV) are designed and manufactured by GM, Toyota, Honda, and Hyundai motors. The propulsion system design process for EV requires integrating subsystem designs into an overall system model to maximize the performance of a given propulsion architecture. Therefore, high-power density and high-torque density are important attributes required for EV applications. To improve torque and power density, propulsion motors are designed for saturation during high-torque operation. The nonlinearity associated with core saturation is modeled by incorporating the cross-coupling inductances, which also behave nonlinearly. Furthermore, in EV environments, the battery is directly connected to the DC link, and the battery changes depending on the state of charge. It will be onerous if as many optimal current commands as different $V_{dc}$ were made. This paper presents the optimal current commands in the various operating condition and the current control technique in EV environments.

• Journal of the Korean Society of Safety
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• v.6 no.2
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• pp.15-20
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• 1991

In this paper, we have investigated the effect of organic additives and prestressed D C. voltage on the impulse tree initiation in low density polyethylene. The five klnds of organic compounds was selected for the purpose of inhibiting tree initiation and 10 wt % of each additive was mixed in low density polyethylene. The positive or negative impulse voltage was applied after prestressed D.C. voltage was applied in order to investigate the effect of the space charge influenced on tree initiation. The lengths of tree initiation in case of belng same polarity between prestressed D.C. voltage and impulse voltage were longer than those in case of being different polarity between prestressed D.C. voltage and impulse voltage. When the polarity prestressed D.C. voltage was the different plarity of impulse voltage, the length of tree initiation increased with increasing the prestressed D.C. voltage and decreasing the rest time Among the organic additives used in this paper, the m-cresol can be shown to be the most effective inhibiter to tree initiation.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.181-182
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• 2017

In the battery system, an isolated converter is used for the stability of the system when controlling the charge and discharge of the battery. A fixed frequency LLC converter which is a type of isolated converter, has the advantage of high efficiency and power density with zero voltage switching at high frequency. Therefore, in this paper, the operation analysis, design and experimental verification of the LLC resonant converter with high efficiency and high power density for the ESS system were conducted.

• Journal of the Korean Applied Science and Technology
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• v.21 no.2
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• pp.164-173
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• 2004

The capacity and long life of gel electrolyte batteries is connected with gas recombination producting $PbO_2$ and Pb electrode. We prepared with sulfuric acid gel electrolyte to know gel characteristics per density to assemble valve regulated lead-acid (VRLA) batteries. We studied on actions of sulphuric acid gel electrolyte by measuring electrolyte dispersion using Brewster-angle microscope (BAM), charge-discharge cycle, and electrode structure using scanning election microscope (SEM). Sulphuric acid density 1.210 showed excellent gel dispersion in sol condition, electrode condition after fifty cycles in this study.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.8
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• pp.927-933
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• 2006

The structural and electrical characteristics of PLZT thin films fabricated onto $Pt/IrO_2/Ir/Ti/SiO_2/Si$ substrates by a pulsed laser deposition were investigated to develop the high dielectric thin films for capacitor layer of semiconductor memory devices The slim region 14/50/50 PLZT thin films were fabricated by PLD and estimated the characteristics for memory application 14/50/50 PLZT thin films have crystallize into perovskite structure at the $600^{\circ}C$ deposition temperature, 200 mTorr of oxygen pressure, and 2 $J/cm^2$ of laser energy density. In this condition PLZT thin films had the dielectric constant as high as 985, storage charge density 8.17 ${\mu}C/cm^2$ and charging time 0.20 ns. Leakage current density was less than $10^{-10}A/cm^2$ up to 5 V bias voltage.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.296-308
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• 2003

The capacity and long life of gel electrolyte batteries is connected with gas recombination producting $PbO_2$ and Pb electrode. We were prepared with phosphoric acid gel electrolyte to know gel characteristics per density to assemble VRLA batteries. We studied by measuring electrolyte dispersion using Brewster-angle microscope(BAM), charge-discharge cycle and electrode structure using scanning election microscope(SEM) per electrolyte density. As a results, phosphoric acid density 1.210 was excellent gel dispersion in sol condition, electrode condition after fifty cycles in this study.