• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2423-2426
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• 2012

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.755-762
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• 2005

A series of catalysts, NiO/$CeO_2-ZrO_2/WO_3$, for ethylene dimerization was prepared by the precipitation and impregnation methods. For NiO/$CeO_2-ZrO_2/WO_3$ sample, no diffraction line of nickel oxide was observed up to 40 wt%, indicating good dispersion of nickel oxide on the surface of catalyst. The hexagonal and monoclinic phases of $WO_3$ up to the calcination temperature of 500 ${^{\circ}C}$ were observed, whereas the hexagonal phase of WO3 completely was transformed into monoclinic phase of $WO_3$ at 600 ${^{\circ}C}$ and above. The role of $CeO_2$ in the catalysts was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity. The catalytic activities for ethylene dimerization were correlated with the acidity of catalysts measured by the ammonia chemisorption method. 25-NiO/5-$CeO_2-ZrO_2/15-WO_3$ containing 25 wt% NiO, 15 wt% $WO_3$ and 5 mol% $CeO_2$, and calcined at 400 ${^{\circ}C}$ exhibited a maximum catalytic activity due to the effects of $WO_3$ modifying and $CeO_2$ doping.

• Korean Journal of Crystallography
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• v.18 no.1_2
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• pp.1-6
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• 2007

An Organometallic compound, $C_{16}H_{35}B_{10}IrS_2Si$, was synthesized from o-carborane, $Cp^*Ir(S_2C_2B{10}H_{10})$, and $Me_3SiCHN_2$. The molecular structure of this complex has been determined by X-ray diffraction. Crystallographic data : monoclinic, space group $P2_1/n$, $a=10.1986(12)\;{\AA}$, $b=14.834(5)\;{\AA}$, $c=17.139\;{\AA}$, ${\beta}=92.24(2)^{\circ}$, Z=4, $V=2591.0(14)\;{\AA}^3$. The structure was solved by direct methods and refined by full-matrix leat-squares methods to give a model with a reliability factor R=0.053 for 5080 reflections.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.247-256
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• 2000

Precursor gels with the composition of $xZrO_2{\cdot}(100-x)SiO_2$ systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence on tetragonal to monoclinic transformation of $ZrO_2$ was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal $ZrO_2$ occurred through 3-dimensional diffusion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about $310{\sim}325{\pm}10kJ/mol$. The growth of $t-ZrO_2$, in proportion to the cube of radius, increased with increasing heating temperature and heat-treatment time. It was suggested that the diffusion of Zr4+ions by Ostwald ripening was rate-limiting process for the growth of $t-ZrO_2$ crystallite size. The fracture toughness of $xZrO_2{\cdot}(100-x)SiO_2$ systems glass ceramics increased with increasing crystallite size of $t-ZrO_2$. The fracture toughness of $30ZrO_2{\cdot}70SiO_2$ system glass ceramics heated at $1,100^{\circ}C$ for 5 h was $4.84Mpam^{1/2}$ at a critical crystaliite size of 40 nm.

• Molecules and Cells
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• v.19 no.2
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• pp.219-222
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• 2005

The a-subunit of Escherichia coli tryptophan synthase (${\alpha}TS$), a component of the tryptophan synthase ${\alpha}_2{\beta}_2$ complex, is a monomeric 268-residues protein (Mr = 28,600). ${\alpha}TS$ by itself catalyzes the cleavage of indole-3-glycerol phosphate to glyceraldehyde-3-phosphate and indole, which is converted to tryptophan in tryptophan biosynthesis. Wild-type and P28L/Y173F double mutant ${\alpha}$-subunits were overexpressed in E. coli and crystallized at 298 K by the hanging-drop vapor-diffusion method. X-ray diffraction data were collected to $2.5{\AA}$ resolution from the wild-type crystals and to $1.8{\AA}$ from the crystals of the double mutant, since the latter produced better quality diffraction data. The wild-type crystals belonged to the monoclinic space group C2 ($a=155.64{\AA}$, $b=44.54{\AA}$, $c=71.53{\AA}$ and ${\beta}=96.39^{\circ}$) and the P28L/Y173F crystals to the monoclinic space group $P2_1$ ($a=71.09{\AA}$, b=52.70, $c=71.52{\AA}$ and ${\beta}=91.49^{\circ}$). The asymmetric unit of both structures contained two molecules of ${\alpha}TS$. Crystal volume per protein mass ($V_m$) and solvent content were $2.15{\AA}^3\;Da^{-1}$ and 42.95% for the wild-type and $2.34{\AA}^3\;Da^{-1}$ and 47.52% for the double mutant.

• Korean Journal of Materials Research
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• v.4 no.6
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• pp.704-709
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• 1994

The $(LaS)_xCrS_2(x \approx 1.20$) of the incommensurate misfit layer was systhesized from reactant mixture of$La_S_3$,Cr and S at 1273K. Powder X-ray diffration of $(LaS)_xCrS_2(x \approx 1.20$) was indexed as a complex structure consisted with a monoclinic LaS-sublattice, a triclinic $CrS_{2}$-sublattice and their superlattice. The temperature dependence of sublattice dimension was investigated by the X-ray diffraction analysis at low temperature. The magnetic susceptibility of $(LaS)_xCrS_2(x \approx 1.20$) was measured between 77K and room temperature using a Faraday balance method. $(LaS)_xCrS_2(x \approx 1.20$) was paramagnetic on a $\sigma$-H plot at room temperature. The observed effective magnetic moment( p dr) was in fair agreement with the value calculated by spin-only contribution for $Cr^{3+}$ and spin and orbital contribution for $La^{3+}$.

• Journal of Conservation Science
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• v.32 no.2
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• pp.109-121
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• 2016

Mother-of-pearl turtle shell lacquerware refers to a decoration made of a mother-of-pearl, a turtle shell and metal wires. This lacquerware features bright color tone as it is produced by sprinkling metal powder over its entire surface. This study aimed to find out its material properties and characteristics by using an optical microscopy and conducting a SEM-EDS analysis on the cross section of lacquer coating. As a result, it was found that charcoal powder and soil powder were mixed for undercoating. Then a mixture of cinnabar lacquer and monoclinic arsenic sulfide mineral ($As_2S_3$) was coated on the undercoating and brass powder was sprinkled on top of it. Especially, a little amount of pigment was found on the lacquer layer, which is distinguished from the colors used for conventional lacquer patterns. In addition, it was also found that the cinnabar lacquer and monoclinic arsenic sulfide mineral were mixed together.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.241.1-241.1
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• 2011

Numerous possible applications for $ZrO_2$ nanotubes exist such as for catalyst support structures, for sensing or for applications as a solid state electrolyte. Especially, because of a large specific surface area, high efficiency for solid oxide fuel cell (SOFC) application at low temperature can be expected for nanotublar structures in even small size. A zirconium precursor, Tetrakis (ethylmethylamino) zirconium, TEMAZr and $H_2O$ oxidant were used to deposit$ZrO_2$ thin films on an anodized aluminum oxide (AAO) templates having sub-100nm cylindrical pores by atomic layer deposition (ALD) in the temperature range of 150~250$^{\circ}C$. The crystalline structures of as-prepared and post-annealed $ZrO_2$ nanotubes were characterized by x-ray diffraction and high-resolution transmission electron microscopy. The as-prepared samples at $150^{\circ}C$ and $200^{\circ}C$ were showed amorphous, whereas a mixed phase of tetragonal, monoclinic and amorphous polymorph was observed at $250^{\circ}C$. In the bulk, zirconia remains monoclinic phase up to $1,175^{\circ}C$, however, $ZrO_2$ nanotubes were showed tetragonal phase upon post thermal treatments merely at $400^{\circ}C$. This trend may be indicative of high-curvature surfaces of nanotubes and thereby the presence of intrinsic compressive strain. The amount of amorphous structures in the mixed phase as well as as-grown $ZrO_2$ nanotubes were also gradually decreased by subsequent heat treatment.

• Journal of the Korean Chemical Society
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• v.62 no.1
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• pp.14-18
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• 2018

The complexes $[Zn(L)(H_2O)_2]{\cdot}2NO_2$ (1) and $[Zn(L)(NO_3)_2]$ (2) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo $[14,4,0^{1.18},0^{7.12}]$docosane) have been synthesized and structurally characterized. The compound 1 crystallizes in the monoclinic system $P2_1/c$ with a = 8.74650(10), b = 18.6880(3), c = $7.96680(10){\AA}$, ${\beta}=109.1920(10)^{\circ}$, $V=1229.84(3){\AA}^3$, Z = 2. The compound 2 crystallizes in the monoclinic system P1 with a = 8.1292(5), b = 8.9244(5), c = $9.1398(5){\AA}$, ${\alpha}=68.035(2)$, ${\beta}=70.109(2)$, ${\gamma}=75.649(3)^{\circ}$, $V=572.70(6){\AA}^3$, Z = 1. The crystal structures of the compounds 1 and 2 show a distorted octahedral coordination geometry around the zinc(II) ion, with four secondary amines and two oxygen atoms of the two water and two nitrate ligands at the axial position. The TGA behaviors of the complexes are significantly affected by the nature of the tetraaza macrocycle and the axial ligands.

• Korean Journal of Crystallography
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• v.15 no.1
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• pp.24-28
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• 2004

The structure of $C_{12}H_{15}N_3O_3$ has been determined by X-ray diffraction methods. The crystal system is monoclinic, space group $P2_1/c$, unit cell constants, a = 12.9955(9) ${\AA}$, b = 7.7137(5) ${\AA}$, c = 13.4699(11) ${\AA}$, ${\beta}$ = 107.86(1)$^{\circ}$, V = 1285.2(1) ${\AA}^3$, T = 296 K, Z = 4, $D_c$ = 1.350 $Mgm^{-3}$. The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with graphite monochromated Mo $K{\alpha}$ radiation (${\lambda}$ = 1.71073 ${\AA}$). The molecular structure was solved by direct methods and refined by full-matrix least squares to a final R = 4.19% for 1644 unique observed $F_0\;>\;4{\sigma}(F_0)$ reflections 193 parameters.