• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.16-16
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• 2002

The presently commercialized lithium-ion batteries use layer structured LiCoO₂ cathodes. Because of the high cost and toxicity of cobalt, an intensive search for new cathode materials has been underway in recent years. Recently, a concept of a one-to-one solid state mixture of LiNO₂ and LiMnO₂, i.e., Li[Ni/sub 0.5/Mn/sub 0.5/]O₂, was adopted by Ohzuku and Makimura to overcome the disadvantage of LiNiO₂ and LiMnO₂. Li[Ni/sub 0.5/Mn/sub 0.5/]O₂ has the -NaFeO₂ structure, which is characteristic of the layered LiCoO₂ and LiNiO₂ structures and shows excellent cycleability with no indication of spinel formation during electrochemical cycling. Layered Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials with high homogeneity and crystallinity were synthesized using a mechanical alloying method. The Li[Ni/sub 0.475/Co/sub 0.05/Mn/sub 0.475/]O₂ electrode delivers a high discharge capacity of 187 mAh/g between 2.8 and 4.6 V at a high current density of 0.3 mA/㎠(30 mA/g) with excellent cycleability. The charge/discharge and differential capacity vs. voltage studies of the Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂ (x = 0.5 and 0.475) materials showed only one redox peak up to 50 cycles, which indicates that structural phase transitions are not occurred during electrochemical cycling. The magnitude of the diffusion coefficients of lithium ions for Li[Ni/sub x/Co/sub 1-2x/Mn/sub x/]O₂(x = 0.5 and 0.475) are around 10/sup -9/ ㎠/s measured by the galvanostatic intermittent titration technique (GITT).

• Corrosion Science and Technology
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• v.3 no.4
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• pp.131-139
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• 2004

Effects of PbO on the repassivation kinetics and characteristics of passive film of Alloy 690 were examined to elucidate the influences of PbO on the SCC resistance of that alloy. The repassivation kinetics of the alloy was analyzed in terms of the current density flowing from the scratch, i(t), as a function of the charge density that has flowed from the scratch, q(t). Repassivation on the scratched surface of the alloy occurred in two kinetically different processes; passive film initially nucleated and grew according to the place exchange model in which log i(t) is linearly proportional to q(t), and then grew according to the high field ion conduction model in which log i(t) is linearly proportional to 1/q(t) with a slope of cBV. The cBV is found to be a parameter representing repassivation rate and hence SCC susceptibility of the alloy. The lower the value of cBV, the faster the repassivation rate and the higher the SCC resistance of an alloy. Addition of PbO to pH 4 and 10 solutions increased the value of cBV of alloy 690, reflecting slower repassivation rate than without PbO. The change in the value of cBV was grater in pH 10 than in pH 4. The increase in SCC susceptibility of alloy 690 with the addition of PbO to solution was presumably due to the Cr-depletion in the outer parts of passive film of the alloy with an incorporation of Pb compounds in the film, which was revealed by Mott-Schottky, AES and XPS analyses.

• Korean Journal of Materials Research
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• v.27 no.4
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• pp.192-198
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• 2017

Carbon nanofiber (CNF) is used as an electrode material for electrical double layer capacitors (EDLCs), and is being consistently researched to improve its electrochemical performance. However, CNF still faces important challenges due to the low mesopore volume, leading to a poor high-rate performance. In the present study, we prepared the unique architecture of the activated mesoporous CNF with a high specific surface area and high mesopore volume, which were successfully synthesized using PMMA as a pore-forming agent and the KOH activation. The activated mesoporous CNF was found to exhibit the high specific surface area of $703m^2g^{-1}$, total pore volume of $0.51cm^3g^{-1}$, average pore diameter of 2.9 nm, and high mesopore volume of 35.2 %. The activated mesoporous CNF also indicated the high specific capacitance of $143F\;g^{-1}$, high-rate performance, high energy density of $17.9-13.0W\;h\;kg^{-1}$, and excellent cycling stability. Therefore, this unique architecture with a high specific surface area and high mesopore volume provides profitable synergistic effects in terms of the increased electrical double-layer area and favorable ion diffusion at a high current density. Consequently, the activated mesoporous CNF is a promising candidate as an electrode material for high-performance EDLCs.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.658-658
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• 2013

Graphene is an attractive material for various device applications due to great electrical properties and chemical properties. However, lack of band gap is significant hurdle of graphene for future electrical device applications. In the past few years, several methods have been attempted to open and tune a band gap of graphene. For example, researchers try to fabricate graphene nanoribbon (GNR) using various templates or unzip the carbon nanotubes itself. However, these methods generate small driving currents or transconductances because of the large amount of scattering source at edge of GNRs. At 2009, Bai et al. introduced graphene nanomesh (GNM) structures which can open the band gap of large area graphene at room temperature with high current. However, this method is complex and only small area is possible. For practical applications, it needs more simple and large scale process. Herein, we introduce a photosensitive graphene device fabrication using CdSe QD coated nano-porous graphene (NPG). In our experiment, NPG was fabricated by thin film anodic aluminum oxide (AAO) film as an etching mask. First of all, we transfer the AAO on the graphene. And then, we etch the graphene using O2 reactive ion etching (RIE). Finally, we fabricate graphene device thorough photolithography process. We can control the length of NPG neckwidth from AAO pore widening time and RIE etching time. And we can increase size of NPG as large as 2 $cm^2$. Thin CdSe QD layer was deposited by spin coatingprocess. We carried out NPG structure by using field emission scanning electron microscopy (FE-SEM). And device measurements were done by Keithley 4200 SCS with 532 nm laser beam (5 mW) irradiation.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.3
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• pp.237-244
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• 1999

Magnesium ion is known to selectively block the N-methyl-D-aspartate (NMDA)-induced responses and to have anticonvulsive action, neuroprotective effect and antinociceptive action in the behavioral test. In this study, we investigated the effect of $Mg^{2+}$ on the responses of dorsal horn neurons to cutaneous thermal stimulation and graded electrical stimulation of afferent nerves as well as to excitatory amino acids and also elucidated whether the actions of $Ca^{2+}$ and $Mg^{2+}$ are additive or antagonistic. $Mg^{2+}$ suppressed the thermal and C-fiber responses of wide dynamic range (WDR) cell without any effect on the A-fiber responses. When $Mg^{2+}$ was directly applied onto the spinal cord, its inhibitory effect was dependent on the concentration of $Mg^{2+}$ and duration of application. The NMDA- and kainate-induced responses of WDR cell were suppressed by $Mg^{2+}$, the NMDA-induced responses being inhibited more strongly. $Ca^{2+}$ also inhibited the NMDA-induced responses current-dependently. Both inhibitory actions of $Mg^{2+}$ and $Ca^{2+}$ were additive, while $Mg^{2+}$ suppressed the EGTA-induced augmentation of WDR cell responses to NMDA and C-fiber stimulation. Magnesium had dual effects on the spontaneous activities of WDR cell. These experimental findings suggest that $Mg^{2+}$ is implicated in the modulation of pain in the rat spinal cord by inhibiting the responses of WDR cell to noxious stimuli more strongly than innocuous stimuli.

• Journal of Surface Science and Engineering
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• v.47 no.2
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• pp.68-74
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• 2014

The seed step-coverage enhancement process (SSEP) using Pd/Cu/PVP colloids was investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd/Cu nano-particles were well dispersed in aqueous solution with the average diameter of 6.18 nm. This Pd/Cu nano-particles were uniformly deposited on the substrate of Si/$SiO_2$/Ti wafer using electrophoresis with the high frequency Alternating Current (AC). After electroless Cu deposition on the substrate treated with Pd/Cu/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. The Cu deposit obtained by SSEP with Pd/Cu/PVP colloids showed superior adhesion property to that on Pd ion catalyst-treated substrate. Finally, by implementing the SSEP using Pd/Cu/PVP colloids, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free filling in high aspect ratio TSV.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.129-134
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• 2005

Electroplating copper is the important role in formation of 3D stacking interconnection in SiP (System in Package). The I-V characteristics curves are investigated at different electrolyte conditions. Inhibitor and accelerator are used simultaneously to investigate the effects of additives. Three different sizes of via are tested. All via were prepared with RIE (reactive ion etching) method. Via's diameter are 50, 75, $100{\mu}m$ and the height is $100{\mu}m$. Inside via, Ta was deposited for diffusion barrier and Cu was deposited fer seed layer using magnetron sputtering method. DC, pulse and pulse revere current are used in this study. With DC, via cannot be filled without defects. Pulse plating can improve the filling patterns however it cannot completely filled copper without defects. Via was filled completely without defects using pulse-reverse electroplating method.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.5
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• pp.46-54
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• 1984

A silicon-gate n-well CMOS process with 3 $\mu$m gate length was developed and its possibility for the applications was discussed,. Threshold voltage was easily controlled by ion implantation and 3-$\mu$m gate length with 650 $\AA$ oxide shows ignorable short channel effect. Large value of Al-n+ contact resistance is one of the problems in fabrications of VLSI circuits. Transfer characteristics of CMOS inverter is fairly good and the propagation delay time per stage in ring oscillator with layout of (W/L) PMOS /(W/L) NMOS =(10/5)/(5/5) is about 3.4 nsec. catch-up occurs on substrate current of 3-5 mA in this process and critically dependent on the well doping density and nt-source to n-well space. Therefore, research, more on latch-up characteristics as a function of n-well profile and design rule, especially n+-source to n-well space, is required.

• Journal of the Korean Chemical Society
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• v.9 no.2
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• pp.67-70
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• 1965

Polarographic studies of reduction of Ni(Ⅱ)-CN complex on Hg-electrode have indicated that $Ni(CN)_4^{2-}$ is reduced by two paths, via one electron process Ni(CN)42- + e [1]↔[2] Ni(CN)43- =(eq) Ni(CN)2- + 2CN- and via two electron process Ni(CN)42- + 2e [3]→ 1/2[Ni(CN)33-]2 + CN- of which reduction [1] must be faster than reduction [3]. At very dilute cyanide concentration (0.004 to 0.01 M) cathodic wave is practically responsible for reaction [1] and two cyanide ions appear to contribute to the reaction. As increasing cyanide ion concentration the rate of oxidation reaction [2] catalysed by Hg increases and reaction [1] and [2] approach to equilibrium. Therefore, reaction [3] represents the cathodic wave at high concentration of cyanide (above 0.2 M). This mechanism can also explain the fact that limiting current at $[CN^-]$ = 8 M is approximately twice of that at 0.004 M CN.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2923-2928
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• 2010

This study examined the synthesis of the crystal structure of bis(2,2'-bipyridine)nitrato zinc (II) nitrate, $[Zn(bipy)_2(NO_3)]^+NO_3^-$ using a microwave treatment at 300 W and 60 Hz for the application to dye-sensitized solar cells. The simulated complex structure of the complex was optimized with the density functional theory calculations for the UV-vis spectrum of the ground state using Gaussian 03 at the B3LYP/LANL2DZ level. The structure of the acquired complex was expected a penta-coordination with four nitrogen atoms of bipyridine and the oxygen bond of the $NO_3^-$ ion. The reflectance UV-vis absorption spectra exhibited two absorptions (L-L transfers) that were assigned to the transfers from the ligand ($\sigma$, $\pi$) of $NO_3$ to the ligand ($\sigma^*$, $\pi^*$) of pyridine at around 200 - 350 nm, and from the non-bonding orbital (n) of O in $NO_3$ to the p-orbital of pyridine at around 450 - 550 nm, respectively. The photoelectric efficiency was approximately 0.397% in the dye-sensitized solar cells with the nanometer-sized $TiO_2$ at an open-circuit voltage (Voc) of 0.39 V, a short-circuit current density (Jsc) of $1.79\;mA/cm^2$, and an incident light intensity of $100\;mW/cm^2$.