• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.148-154
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• 2020

Highly ordered mesoporous manganese oxide films were electrodeposited onto indium tin oxide coated (ITO) glass using sodium dodecyl sulfate (SDS) and ethylene glycol (EG) which were used as a templating agent and stabilizer for the formation of micelle, respectively. The manganese oxide films synthesized with surfactant templating exhibited a highly mesoporous structure with a long-range order, which was confirmed by SAXRD and TEM analysis. The unique porous structure offers a more favorable diffusion pathway for electrolyte transportation and excellent ionic conductivity. Among the synthesized samples, Mn₂O₃-SDS+EG exhibited the best electrochemical performance for a supercapacitor in the wide range of scan rate, which was attributed to the well-developed mesoporous structure. The Mn₂O₃ prepared with SDS and EG displayed an outstanding capacitance of 72.04 F g^-1, which outperform non-porous Mn₂O₃ (32.13 F g^-1) at a scan rate of 10 mV s^-1.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2249-2252
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• 2011

Two new carborane complexes containing closo- or nido-carborane diphosphine ligands with the formula: complex $[Hg(7,8-(PPh_2)_2-7,8-C_2B_9H_{10})_2]$ $CH_2Cl_2$ (1) and $[Ag_2({\mu}-Cl)_2(1,2-(P^iPr_2)_2-1,2-C_2B_{10}H_{10})_2]$ (2) have been synthesized and characterized by elemental analysis, 1H and 13C NMR spectroscopy and X-ray structure determination. The X-ray structure analyses revealed that the carborane diphosphine ligand was degraded from closo-1,2-$(PPh_2)_2-1,2-C_2B_{10}H_{10}$ to nido-[$7,8-(PPh_2)_2-7,8-C_2B_9H_{10}]^-$ in complex 1, while the closo nature of the starting ligand $1,2-(P^iPr_2)_2-1,2-C_2B_{10}H_{10}$ was retained in complex 2. In either of the two complexes, the carborane diphosphine ligand was coordinated bidentately to the Hg(II) or Ag(I) center through its two phosphorus atoms, therefore forming a five-member cheating ring between the carborane ligand and the metal center. The coordination geometry of the metal atom is distorted tetrahedron formed by $P_4$ unit in complex 1 and $P_2Cl_2$ unit in complex 2, respectively.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.117-126
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• 2005

The chemical property analysis on the deposited clay using scanning electron microscope and energy dispersive x-ray spectrometer were performed. Also, the triaxial compression tests and consolidation tests using NaCl aqueous solution and leachate as substitute pore (or saturated) water in samples were carried out to find out the behaviour characteristics of strength and deformation of contaminated deposited clay. from the chemical composition analysis results of clay samples, the magnitudes of composition ratio were revealed in the order of O, C, Si, Al, and Fe. Of these, why the ratio of carbon appeared to be large is estimated as due to the increase of the phyto-planktons after the construction of tide embankment. In the triaxial compression test and consolidation test results, the shear strength and compression properties have increased with the increase in concentration of contaminant (NaCl). This phenomenon is considered as to be caused by the changes of soil structure to flocculent structure owing to the decrease in the thickness of diffuse double layer in proportion to increase in the concentration of electrolyte.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1845-1850
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• 2012

Layered metal hydroxides (LMHs) containing calcium were synthesized by coprecipitation in solution having two different trivalent metal ions, iron and aluminum. Two mixed metal solutions ($Ca^{2+}/Al^{3+}$ and $Ca^{2+}/Fe^{3+}$ = 2/1) were added to sodium hydroxide solution and the final pH was adjusted to ~11.5 and ~13 for CaAl-and CaFe-LMHs. Powder X-ray diffraction (XRD) for the two LMH samples showed well developed ($00l$) diffractions indicating 2-dimensional crystal structure of the synthesized LMHs. Rietveld refinement of the X-ray diffraction pattern, the local structure analysis through X-ray absorption spectroscopy, and thermal analysis also confirmed that the synthesized precipitates show typical structure of LMHs. The chemical formulae, $Ca_{2.04}Al_1(OH)_6(NO_3){\cdot}5.25H_2O$ and $Ca_{2.01}Fe_1(OH)_6(NO_3){\cdot}4.75H_2O$ were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Particle morphology and thermal behavior for the synthesized LMHs were examined by field emission scanning electron microscopy and thermogravimetricdifferential scanning calorimetry.

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.501-507
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• 1995

The electronic structure of cis-$[Cr(cyclam)Cl_2]Cl$ has been investigated by the emission and excitation spectroscopy at 77K, and infrared and visible spectroscopy at room temperature. The ten electronic transitions due to spin-allowed and spin-forbidden are assigned. The zero-phonon line in the excitation spectrum splits into two components by $139\;cm^{-1}$, and it can be reproduced by modern ligand field theory. According to the results of ligand field analysis, we can confirm that nitrogen atoms of the cyclam ligand have a strong ${\sigma}$-donor character, but chloride ligand has weak ${\sigma}-$ and ${\pi}-$donor properties toward chromium(III) ion.

• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.91-102
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• 2017

Recently, a new type of LNG membrane Tank called the "KC-1 membrane LNG Tank" was developed by KOGAS (Korean Gas Corporation). It is necessary to estimate the temperature distribution of the hull structure and insulation system for this new LNG tank, as well as the BOR (Boil-Off Rate) when exposed to outside temperature conditions to ensure the integrity of the tank structure and limit LNG evaporation, from a safety evaluation point of view. In this study, temperature distribution calculations for the hull structure and insulation system of the KC1 membrane tank were compared by employing four numerical approaches under the IGC condition. Approaches 1-3 studied 2D simulations and approach 4 used a 3D numerical simulation. Approach 1 was calculated by in-house Excel VBA codes and the three other approaches utilized ANSYS Fluent. The BOR of approach 4, the 3D simulation case, for the IGC condition was 0.0986%/day.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.374-378
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• 2013

Two novel binuclear metal-organic coordination complexes [$Cd_2(Hdpa)_4(bpy)_2$] (1), [$Dy_2(dpa)_2(bpy)_2(NO_3)_2-(H_2O)_2$](bpy) (2) (where $H_2dpa$ = biphenyl-2,2'-dicarboxylic acid, bpy = 2,2'-bipyridine) have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, spectral method (IR), elemental analysis (EA), powder X-ray diffraction (XRD), electronic spectra (UV-vis), fluorescent in the solid state and thermogravimetric analysis (TGA). Complexes 1-2 crystallizes isomorphously in the Triclinic space group P-1. The ${\pi}-{\pi}$ stacking interactions and hydrogen-bonds play a vital role in determining the crystal packing and construction of the extended 3-D supramolecular network.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1875-1880
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• 2010

A dicycle pyrazoline derivative, 1-phenyl-5-(p-fluorophenyl)-3,4-($\alpha$-p-fluoro-tolylenecyclohexano) pyrazoline, was synthesized and characterized by elemental analysis, IR, UV-vis, fluorescence spectra and X-ray single crystal diffraction. Density function theory (DFT) calculations were performed by using B3LYP method with 6-$311G^{**}$ basis set. The optimized geometry can well simulate the molecular structure. Vibrational frequencies were predicted, assigned and compared with the experimental values, which suggest that B3LYP/6-$311G^{**}$ method can well predict the IR spectra. Both the experimental electronic absorption spectra and the predicted ones by B3LYP/6-$311G^{**}$ method reveal three electron-transition bands, with the theoretical ones having some red shifts compared with the experimental data. Natural bond orbital analyses indicate that the absorption bands are mainly derived from the contribution of n $\rightarrow\pi^*$ and $\pi\rightarrow\pi^*$ transitions. Fluorescence spectra determination shows that the title compound can emit blue-light at about 478 nm. On the basis of vibrational analysis, the thermodynamic properties of title compound at different temperature have been calculated, revealing the correlations between $C^0_{p,m}$, $S^0_m$, $H^0_m$ and temperature.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1951-1959
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• 2008

Pentamer cluster of azodicarbonamide (ADA) based on the crystalline structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties at various levels of the density functional theory. Stretching force constants of N${\cdot}{\cdot}{\cdot}$H or O${\cdot}{\cdot}{\cdot}$H, and angle-bending force constants of N-H${\cdot}{\cdot}{\cdot}$N or N-H${\cdot}{\cdot}{\cdot}$O for intermolecular hydrogen bonds in the pentamer cluster were obtained in 0.2-0.5 mdyn/$\AA$ and 1.6-2.0 mdyn$\AA$, respectively. The geometry of central ADA molecule fully hydrogen bonded with other four molecules shows good coincidence to the crystalline structure except the bond distances of N-H. Calculated Raman and infrared spectra of central ADA molecule in cluster represent well the experimental spectra of ADA obtained in the solid state compared to a single molecule. Detailed structural and vibrational properties of central ADA molecule in the pentamer cluster are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.1-7
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• 2015

This paper predicts the spring-in effect of curved laminated composite structure for various stacking sequence using finite element analysis(ABAQUS). In composite manufacturing process, large temperature difference, different coefficient of thermal expansion and chemical shrinkage effect cause distortion of composite parts such as spring-in and warpage. Distortion of composite structure is important issue on quality of product, and it should be considered in manufacturing process. In finite element analysis, a CHILE(Cure Hardening Instantaneously Linear Elastic) model and chemical shrinkage effects are considered developing user subroutine in ABAQUS and some cases are simulated.