• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.139-145
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• 2001

Various compositions of iron oxide based materials as a cathode of lithium secondary battery have been fabricated and tested with electrochemical method. A layered form of $LiFeO_2$ was synthesized by mixing and heating the initial materials of $FeCl_3\;6H_2O,\;LiOH$ and NaOH at low temperature. The effect of changing the precursors composition was investigated. As a result, when increasing the additive amount of NaOH, the capacity of the electrode is decreased but the performance and declining rate of capacity became smaller. $LiFeO_2$ synthesized with the weight ratio of $NaOH/FeCl_3/LiOH,\;2/1/7$ showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles. Charge-discharge tests of lithium cells with $LiFeO_2$ cathode having the layer structure were performed. This cell showed the reversibility in the range of 1.5-4.5V of cell voltage. By using CPR method, chemical diffusion coefficients were measured in 1M $LiPF_6/EC/DEC$ solution. The value of chemical diffusion coefficient decreased with increasing the lithium content x, In 0.5$10^{-11}^cm^2/s$.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.130-131
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• 2003

The magnetic and thermal properties of NiFe/IrMn/CoFe with Mn additions have been studied. As grown CoFe pinned-layers with IrMn-Mn have dominantly larger exchange biasing field( $H_{ex}$) and blocking temperature( $T_{b}$) than when pure I $r_{22}$M $n_{78}$ is used. The magnetic properties improve, $H_{ex}$ and $T_{b}$ improve with 77-78 vol% Mn, but drop considerably with more Mn additions, losing magnetic properties of theb NiFe/IrMn/CoFe with addition 0.6 vol % Mn. The average x-ray diffraction peak ratios fcc (111)CoFe of (111)IrM $n_3$ textures for the Mn inserted total vol of 75, 77, and 79 vol% were about 1.4, 0.8, and 0.6, respectively. For the sample without Mn inserted layer, the $H_{ex}$ between I $r_{22}$M $n_{78}$ and CoFe layers is almost nothing. For two multilayer as-grown samples with ultra-thin Mn layers of 77 vol % and 79 vol %, the $H_{ex}$s are 250 Oe and 150 Oe, respectively. In case of IrMn with 77.5 vol% Mn, the $H_{ex}$ was 444 Oe up to 30$0^{\circ}C$ endured of 363 Oe at 40$0^{\circ}C$, respectively. Mn additions improve the magnetic properties and thermal stabilities of NiFe/IrMn/CoFe. Those increase the $H_{ex}$ and $T_{b}$. In applications where higher $H_{ex}$ and $T_{b}$ are accept, proper concentrations of Mn can be used.n can be used.be used.

• Journal of the Mineralogical Society of Korea
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• v.17 no.1
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• pp.75-83
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• 2004

Blackening on stone monuments is serious problem, because it is not only aesthetically unattractive, but also an important process in stone deterioration. Black surface layers contain often a large amounts of iron compound. Therefore it is assumed that besides another elements the iron have influence on blackening of surface. After the samples of black surface layers were collected from the stone monuments (Museumsinsel) in Berlin, Germany, especially in this study has been used Mossbauer spectroscopy in order to determine the valence and chemical composition of iron. Mineralogical and chemical analyses were carried out X-ray diffractormetry and X-ray fluorescence method on the black surface layer's samples and original stone samples. The origin of Iron compound in the black surface provides the important clue for the conservation work of stone monuments, like removing of black surface. To find it, black surface layer on white sandstone -it contains very small amount of iron compound- was compared with that on the red sandstone (Fe contains very small amount of iron compound- was compared with that on the red sandstone (Fe abundant). As a results, it is assumed that the iron in black layer on white sandstone is originated mainly from a surrounding environmental material and for the iron in black layer on the red sandstone is responsible the original stone. Even if black surface layer was removed from the red sandstone, some other conservation method should be studied beyond removing of black surface layer, because the iron can move continuously from the inner zone of original stone to surface area.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.142-145
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• 2003

The nonreciprocal phase shift characteristics of infinite slab optical waveguides with magneto-optic materials in the cladding layer was calculated at 1.55 ${\mu}{\textrm}{m}$ for optical isolators. The infinite slab waveguide structures considered in this paper were as follows. rho magneto-optic materials used as a cladding layer were Ce:YIG and LNB(LuNdBi)$_3$(FeAl)$_{5}$)$_{12}$,). Their specific Faraday rotations Θ$_{F}$ are 4500$^{\circ}$/cm, 500$^{\circ}$/cm at wavelength 1.55 ${\mu}{\textrm}{m}$ respectively. The guiding layer with multi-quantum well structure was used, and it consists of 1.3Q and InGaAs. In order to investigate the effect of evanescent field penetrating the cadding, layer, guiding mode characteristics were calculated for the cases when the substrate is InP and air. We calculated the minimum lengths of 90$^{\circ}$ nonreciprocal phase shifters and their optimum guiding layer thicknesses in various optical waveguide structures.res.s.

• Progress in Superconductivity
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• v.12 no.2
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• pp.110-113
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• 2011

We have grown a Nb/Gd bilayer on a$SiO_2$/Si substrate by using a DC magnetron sputtering system, which was fabricated in situ with silicon stencil masks. In order to investigate proximity effect of the Nb/Gd bilayer, we used a planar tunnel junction with an AlOx tunnel barrier by oxidizing the Al ground electrode at the bottom. A $Co_{60}Fe_{40}$ backing of Al was deposited so as to reduce the superconductivity of the Al, ensuring a normal counterelectrode. With a 50-nm-thick Nb layer, we have measured dI/dV (dynamic conductance) by varying the thickness of Gd, which can reveal the density of states (DOS) of the Nb/Gd bilayer as a function of the Gd thickness resulting from the proximity effect of a superconductor/ferromagnet bilayer (S/F). The SF proximity effect in Nb/Gd will be discussed in comparison to our previous results of the CoFe/Nb, Ni/Nb and CuNi/Nb proximity effect; Gd is expected to show different effects since Gd has f-electrons, while CoFe, Ni, and CuNi have only d-electrons. Our studies will focus on the triplet correlation in a superconducting pair.

• Membrane Journal
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• v.25 no.4
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• pp.332-342
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• 2015

In this study, to solve the major problem of reverse osmosis (RO) membrane, surface of reverse osmosis membrane was modified by silane-epoxy multi layer. Octyltrimethoxysilane (OcTES) was polymerized to membrane surface via cross-linking by Sol-gel method. n = 8 alkylgroup of OcTES formed the branch structure by self assembly. And for improve fouling resistance of RO membrane, Ether group of ethylene glycol diglycidyl ether (EGDE) was given to improve hydrophilicity of RO membrane surface by ring-opening. To analyze structure of RO membrane surface with FE-TEM and AFM. Membrane surface of the ridge and valley structure and the bridge structure was confirmed due to the multi-layer surface modification of OcTES and EGDE. And through the increase of the roughness, the branch structure was formed well on membrane surface. Through the XPS analysis was identified chemical structure of membrane surface. And confirmed that the hydrophilic surface modification is given to the surface of the film through a Contact angle analysis. In optimization of EGDE surface modification condition, was suitable 0.5 wt% EGDE concentraion and $70^{\circ}C$ ring-opening temperature. In result of fouling resistance test and MFI is SUL-H10, $PA-OcTES_{1.0}$, $PA-OcTES_{1.0}-EGDE_{0.5}$ 68.7, 60.4, 5.4 ($10E-8hr/mL^2$), multi-layer surface modified membrane improved fouling resistance.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.583-595
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• 2014

The chemical properties and composition (pH, CaO, Fe, $HCO{_3}^-$, and $SO{_4}^{2-}$) of groundwater (GW) and surface water (SW) from the northern (non-carbonate bedrock) and southern (carbonate bedrock) sections of the Daedong River, Pyeongyang were analyzed and compared period of the 1930s. In the southern section, the GW and SW has a higher pH and $SO{_4}^{2-}$ concentration, but lower $HCO{_3}^-$ and Fe levels than in the north. This finding reflects a reaction that formed acid by replacing metal ions in inorganic salts by hydrogen, which resulted from the oxidation of organic material in a clay layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.1
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• pp.24-28
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• 2012

In this study, we fabricated an amorphous InGaZnO pseudo-MOS transistor (a-IGZO ${\Psi}$-MOSFET) with a stacked $Si_3N_4/SiO_2$ (NO) gate dielectric and evaluated reliability of the devices with various thicknesses of a $SiO_2$ buffer layer. The roles of a $SiO_2$ buffer layer are improving the interface states and preventing degradation caused by the injection of photo-created holes because of a small valance band offset of amorphous IGZO and $Si_3N_4$. Meanwhile, excellent electrical properties were obtained for a device with 10-nm-thick $SiO_2$ buffer layer of a NO stacked dielectric. The threshold voltage shift of a device, however, was drastically increased because of its thin $SiO_2$ buffer layer which highlighted bias and light-induced hole trapping into the $Si_3N_4$ layer. As a results, the pseudo-MOS transistor with a 20-nm-thick $SiO_2$ buffer layer exhibited improved electrical characteristics and device reliability; field effective mobility(${\mu}_{FE}$) of 12.3 $cm^2/V{\cdot}s$, subthreshold slope (SS) of 148 mV/dec, trap density ($N_t$) of $4.52{\times}1011\;cm^{-2}$, negative bias illumination stress (NBIS) ${\Delta}V_{th}$ of 1.23 V, and negative bias temperature illumination stress (NBTIS) ${\Delta}V_{th}$ of 2.06 V.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.98.2-98.2
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• 2010

$CuInS_2$ thin films were synthesized by sulfurization of Cu/In Stacked elemental layer deposited onto glass Substrates by vacuum furnace annealing at temperature 200[$^{\circ}C$]. And structural and electrical properties were measured in order to certify optimum conditions for growth of the ternary compound semiconductor $CuInS_2$ thin films with non-stoichiometry composition. $CuInS_2$ thin film was well made at the heat treatment 200[$^{\circ}C$] of SLG/Cu/In/S stacked elemental layer which was prepared by thermal evaporator, and chemical composition of the thin film was analyzed nearly as the proportion of 1 : 1 : 2. Physical properties of the thin film were investigated at various fabrication conditions substrate temperature, annealing and temperature, annealing time by XRD, FE-SEM and hall measurement system. At the same time, carrier concentration, hall mobility and resistivity of the thin films was $9.10568{\times}10^{17}$ [$cm^{-3}$], 312.502 [$cm^2/V{\cdot}s$] and $2.36{\times}10^{-2}$ [${\Omega}{\cdot}cm$], respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.399-402
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• 2009

The Clad sheet is made roll-bonding process of the one or more material with the different property. Good formability is an essential property in order to deform a clad metal sheet to a part or component. In this study, the mechanical properties and formability of a Mg-Al-SUS clad sheet are investigated. The clad sheet was deformed at elevated temperatures because of its poor formability at room temperature. Tensile tests of the each material and clad sheet were performed at various temperatures and at various strain rates. The limited draw ration (LDR) was obtained using a deep drawing test to measure the formability of the clad sheet. A finite element (FE) analysis was performed to predict formability of the cup drawing product, one_layer model and three_layer model.