• Journal of the Korean Magnetic Resonance Society
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• v.17 no.2
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• pp.86-91
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• 2013

Detailed information about the structural nature of three-coordinate borons in ${\beta}-BaB_2O_4$ is obtained through $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR. The three-coordinate $BO_3$ of the two borons B(1) and B(2) in ${\beta}-BaB_2O_4$ were distinguished. The spin-lattice relaxation time in the laboratory frame $T_1$ for B(1) and B(2) slowly decreases with increasing temperature, whereas the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for B(1) and B(2), which differs from $T_1$, is nearly constant. The B(1) and B(2) of the two types were distinguished by $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.169-178
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• 1998

The crystal phases precipitated in various compositions glass of CaO-$SiO_2-P_2O_5$ system, were identified by XRD. E composition (CaO 49.4, $SiO_2\;36.8,\;P_2O_5$ 8.8 wt%) glass in which both apatite(($Ca_{10}(PO_4)_6O$ and $\beta$-wollastonite($CaSiO_3$) crystals would precipitate by heating, was selected as an experimental composition to prepare the glass ceramics with high bending strength and good bioactivity to the living bone. Glass powders of E composition were unidirectionally crystallized at $1050^{\circ}$C in the temperature-gadient furnace and the resultant glass ceramics were characterized. Bending strength of the glass ceramics was also measured. To investigate the bond forming ability between the glass ceramics and living bone tissue, soaking test of glass ceramics in simulated body fluid was carried out. Densed glass ceramics composed of apatite and $\beta$-wollastonite crystal were prepared by unidirectional crystallization under the optimum conditions. (2 0 2) plane of $\beta$-wollastonite crystals tended to grow perpendicularly to the crystallization direction. Average bending strength of this glass ceramics was 186.9 MPa, higher than that of the glass ceramics prepared by isothermal (not directional) crystallization In soaking test, a thin layer of apatite crystallite was formed on surface of the glass ceramics in 3 days. Apatite crystals formed on the glass ceramics could be act a role to make the chemical bond between the glass ceramics and living bone tissue.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.98-99
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• 2005

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.211-220
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• 1998

The stochiometric composition of $AgGaS_2$polycrystal source materials for the single crystal thin films were prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns, it was found that the polycrystal $AgGaS_2$has tetragonal structure of which lattice constant $a_0\;and \;c_0$ were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$single crystal thin film was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5 $mu \textrm{m}$/h. The crystallinity of the grown single crystal thin films was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$single crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by${\Alpha};=;8.695{\times}10^{-4};eV/K,and;{\beta};=;332;K$. from the photocurrent spectra by illumination of polarized light of the $AgGaS_2$single crystal thin film, we have found that crystal field splitting $\Delta$Cr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Journal of Microbiology and Biotechnology
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• v.28 no.4
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• pp.597-605
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• 2018

Acyl-CoA oxidases (ACOXs) play important roles in lipid metabolism, including peroxisomal fatty acid ${\beta}$-oxidation by the conversion of acyl-CoAs to 2-trans-enoyl-CoAs. The yeast Yarrowia lipolytica can utilize fatty acids as a carbon source and thus has extensive biotechnological applications. The crystal structure of ACOX3 from Y. lipolytica (YlACOX3) was determined at a resolution of $2.5{\AA}$. It contained two molecules per asymmetric unit, and the monomeric structure was folded into four domains; $N{\alpha}$, $N{\beta}$, $C{\alpha}1$, and $C{\alpha}2$ domains. The cofactor flavin adenine dinucleotide was bound in the dimer interface. The substrate-binding pocket was located near the cofactor, and formed at the interface between the $N{\alpha}$, $N{\beta}$, and $C{\alpha}1$ domains. Comparisons with other ACOX structures provided structural insights into how YlACOX has a substrate preference for short-chain acyl-CoA. In addition, the structure of YlACOX3 was compared with those of medium- and long-chain ACOXs, and the structural basis for their differences in substrate specificity was discussed.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.921-923
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• 2002

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.18-26
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• 1997

$\beta-SiC $powder with or without the addition of 1 wt% of $\alpha-SiC$ particles (seeds) was pressureless-sintered at $1950^{\circ}C$ for 0.5, 2 and 4 h using $Y_3Al_5O_{12}$ (yttrium aluminum garnet, YAG) as a sintering aid. The introduction of $\alpha-SiC$ seeds into $\beta-SiC$ accelerated :he grain growth of elongated large grains during sintering, resulting in the coarser microstructure. The fracture toughnesses of materials with $\alpha$-SiC seeds and without $\alpha-SiC$ seeds sintered for 4 h were 7.5 and 6.1 $MPa\cdot \textrm m^{1/2}$, respectively. Higher fracture toughness of the material with seeds was due to the enhanced bridging by elongated grains, resulting from coarser microstructure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.386-391
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• 1996

SiC particles (average size is 270 nm) of 0, 10, 20, 30, 40 vol% were dispersed in $Si_{3}N_{4}$, and $Si_{3}N_{4}/SiC$ nanocomposites were fabricated by hot press. After sintering, matrix phase, ${\alpha}-Si_{3}N_{4}$ was transformed to ${\beta}-Si_{3}N_{4}$, and second phase, ${\beta}-SiC$ was not changed. No grain boundary crystalline phase by adding of sintering additives was detected. Grain growth of $Si_{3}N_{4}$ was supressed with increasing of SiC contents, and then fine grain was occurred. The highest fracture strength was obtained at 10 vol% SiC, and fracture toughness was decreased, but hardness was linearly increased with SiC content.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.3
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• pp.149-156
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• 2002

Europium-activated $Ga_2O_3$ phosphor powders were prepared by homogeneous precipitation method. The resulting powders were characterized by means of TG/DTA, XRD, FT-IR and SEM, Two kinds of powders formed were the crystalline GaOOH and the amorphous-like $\gamma$-$Ga_2O_3$ phases. When the urea concentration was below 0,5 M, rod-like micrometer-sized GaOOH powders were formed. They were transformed via $\alpha$-$Ga_2O_3$ to $\beta$-$Ga_2O_3$ phases under heat treatment. On the other hand, the nanometer-sized $\gamma$-$Ga_2O_3$ powders were formed with urea concentrations higher than 1.0 M, and they were directly changed into $\beta$-$Ga_2O_3$.Photoluminescence (PL) spectra were observed at room temperature, and PL intensities of nanometer-sized $Ga_2O_3$ : $Eu^{3+}$ powders around 610 nm were higher than those of micrometer-sized ones.

• Polymer(Korea)
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• v.28 no.5
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• pp.361-366
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• 2004

The poling characteristics of PVDF (poly(vinylidene fluoride)) film was investigated by measuring the electric voltage generated by the external load for the distributed tactile sensor applications. The poling conditions for the PVDF films were controlled by changing temperature and electric field, and the resulting crystal structure of the $\beta$-phase crystal was confirmed by FT-IR, DSC, and XRD experiments. The $\beta$-phase crystal was increased with the poling temperature and poling voltage, and subsequently the permittivity of the Poled PVDF films was increased. Finally, the prototype tactile sensor was tested by a 8 $\times$ 8 may circuit exhibiting high voltage signal for the highly poled PVDF films.