• Journal of Magnetics
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• v.19 no.2
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• pp.126-129
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• 2014

We report the crystallographic and magnetic properties of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a M$\ddot{o}$ssbauer spectroscopy. In particular, $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was studied by M$\ddot{o}$ssbauer analysis for evidence of spin reorientation. The chalcogenide material $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was fabricated by a direct reaction method. XRD analysis confirmed that $Ni_{0.3}Fe_{0.7}Ga_2S_4$ has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The M$\ddot{o}$ssbauer spectra of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, $E_Q$ has anomalous two-points of temperature dependence of $E_Q$ curve as freezing temperature, $T_f=11K$, and N$\acute{e}$el temperature, $T_N=26K$. This suggests that there appears to be a slowly-fluctuating "spin gel" state between $T_f$ and $T_N$, caused by non-paramagnetic spin state below $T_N$. This comes from charge re-distribution due to spin-orientation above $T_f$, and $T_N$, due to the changing $E_Q$ at various temperatures. Isomer shift value ($0.7mm/s{\leq}{\delta}{\leq}0.9mm/s$) shows that the charge states are ferrous ($Fe^{2+}$), for all temperature range. The Debye temperature for the octahedral site was found to be ${\Theta}_D=260K$.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1197-1202
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• 2005

The Ln(III) complexes with picrate ligand, $[Sm(Pic)_2(H_2O)_6]Pic{\cdot}6H_2O$, 1, and $[Ho(Pic)(H_2O)_7](Pic)_2{\cdot}3H_2O$, 2, have been synthesized and their crystal structures are analyzed by X-ray diffraction methods. Complex 1, crystallizes in the monoclinic $P2_1/n$ space group and complex 2 in the triclinic P-1 space group. In complex 1, two picrate ligands coordinate to the Sm(III) ion, one of them in the bidentate fashion. There are one picrate anion and six water molecules in the crystal lattice. The nine-coordinated Sm(III) ion forms a slightly distorted tricapped trigonal prism. In complex 2, only one picrate ligand coordinates to the metal ion as a monodentate. There are two picrate anions and three water molecules in the crystal lattice. The eight-coordinated Ho(III) ion forms a distorted bicapped trigonal prism. Based on the results of the TG-DTG and DSC thermal analysis, it was analyzed that the lanthanide picrate complexes 1 and 2 are thermally decomposed in three distinctive stages, the dehydration, the picrate decomposition, and the formation of the metal oxide.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.1985-1992
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• 2007

Ordered mesoporous silica (MCM-41) materials with different textural properties were prepared using alkyl (dodecyl, cetyl, eicosane) trimethyl ammonium bromide (DTAB, CTAB, ETAB, respectively) as structure directing surfactants, functionalized with amine groups and used as adsorbent for the toxic metal ions, Cr (VI), As (V), Pb (II) and Hg (II). Amino functionalization of mesoporous MCM-41 was achieved by cocondensation of N-[3-(trimethoxysilyl)-propyl] aniline with tetraethyl orthosilicate. Adsorption isotherm and adsorption capacity of the amine functionalized materials for Cr (VI), As (V), Pb (II) and Hg (II) ions were followed by inductively coupled plasma mass spectrometry (ICP-MS). Results demonstrate that amine functionalized MCM-41 prepared with ETAB showed higher adsorption capacity for Cr (VI), As (V), Pb (II) and Hg (II) ions in comparison to MCM-41 prepared with CTAB and DTAB. The higher adsorption capacity for MCM-41(ETAB) was correlated with amine content in the material (determined by CHN analysis) and relative decrease in pore volume and pore diameter. X-ray diffraction (XRD) analysis, nitrogen adsorptiondesorption measurements and Fourier Transform infrared spectrometry (FTIR) were used to follow the changes in the textural parameters and surface properties of the mesoporous materials as a result of amine functionalization to correlate with the adsorption characteristics. The adsorption process was found to depend on the pH of the medium.

• Journal of Physiology & Pathology in Korean Medicine
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• v.26 no.1
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• pp.81-87
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• 2012

The structural and biomechanical characteristics of pelvic and foot are important factors of back pain, but it is still complicated to clearly explain the relationship among them. The purpose of this study was to find out the characteristic of pelvic parameters and biomechanics of foot in patients with low back pain. Thirty-three female subjects with chronic low back pain were enrolled and ODI and VAS score were measured for back pain index. All subjects were taken the X-ray examination for major pelvic parameters and foot scan analysis for foot pressure, gait angle, fore-foot/rear-foot peak pressure ratio and asymmetric index. Statistical analysis were performed to examine the inter-relation between the measurement. As a result, it was shown the positive interrelation between back pain and F/R ratio, but others were not shown the relationship related to low back pain. And there were correlations between the lumbo-pelvic structure and biomechanics of foot in some aspects, but the causal relationship between them are still indefinable. In order to get more information about structures and biomechanics related to low back pain, subsequent researches are needed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.2
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• pp.49-55
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• 2001

ZnO films were fabricated on p-type Si(100) wafer ITO glass and quartz glass by the sol-gel process using zinc acetate dihydrate as starting material. A homogeneous and stable solution was prepared by dissolving the zinc acetate dihydrate in a solution of 2-methoxyethanol and monoethanolamine (MEA). ZnO films were deposited by spin-coating at 2800 rpm for 25 s and were dried on a hot plate at $250^{\circ}C$ for 10 min. Crystallization of the films was carried out at $400^{\circ}C$~$800^{\circ}C$ for 1 h in air. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), UV-vis transmittance spectroscopy, FTIR transmittance spectroscopy and Photoluminescence (PL) spectroscopy measurements have been used to study the structural and optical properties of the films. ZnO films highly oriented along the (002)plane were obtained. In all cases the films were found to be transparent (above 70%) in visible range with a sharp absorption edge at wavelengths of about 380nm, which is very close to the intrinsic band-gap of ZnO(3.2 eV). The low temperature band-edge photoluminescence revealed a complicated multi-line structure in terms of bound exciton complexes and the phonon replicas.

• The korean journal of orthodontics
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• v.40 no.4
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• pp.212-226
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• 2010

Objective: The aim of this study was to evaluate the effect of remineralization and inhibition to demineralization after fluoride gel (acidulated phosphate fluoride, APF) or hydroxyapatite (HAp) paste application on interdentally stripped teeth. Methods: After interdental stripping, 1.23% APF or 5%, 10% HAp paste were applied for 7 days for remineralization. Afterwards, teeth were exposed to lactate carbopol buffer solution for demineralization. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to compare change in surface contents and crystal structures after remineralization, and then after demineralization. Results: EDS analysis indicated that calcium (p < 0.001) and phosphate (p < 0.01) contents were increased after 10% HAp paste application on stripped enamel, calcium (p < 0.05) and phosphate (p < 0.01) contents were increased after 5% HAp paste application, and fluoride (p < 0.01) contents were increased after 1.23% APF application. SEM image showed that enamel surfaces became smoother and crystal structures became small and compact after APF or HAp application. After demineralization, calcium (p < 0.05) and phosphate (p < 0.05) contents remained increased on the enamel remineralized with 10% HAp paste, and phosphate (p < 0.05) contents remained increased on the enamel remineralized with 5% HAp paste. After demineralization, surfaces looked less destroyed in the enamel remineralized beforehand than those of the control, and small pores between crystal structures, formed by remineralization were remained. Conclusions: Hydroxyapatite paste and fluoride gel were helpful to remineralize and inhibit deminerlization on stripped enamel.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.288-293
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• 2011

We investigated the effects of piezoelectric field on the electro-absorption characteristics in InGaN/GaN multiple-quantum well (MQW) green light emitting diodes (LED). Double crystal X-ray diffraction measurement was performed to study the crystalline property and indium (In) composition in the MQW active layer. To measure the electro-luminescence and electro-reflectance (ER) spectroscopy, we fabricated the $1{\times}1\;mm^2$ large-area green LED chip. The piezoelectric field inside the LED structure was evaluated from the Vcomp in active layer by the ER spectra. Finally, we analyzed the electro-absorption characteristics of the green LED by using the photo-current spectroscopy.

• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.471-478
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• 2013

PURPOSE. The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS. Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring $4{\times}2{\times}2$ mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. RESULTS. The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness ($48.16{\pm}3.02$ HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness ($27.40{\pm}3.98$ HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 ${\AA}$). CONCLUSION. After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with the materials that are used in clinic for prosthodontics treatments.

• Journal of the Korean Wood Science and Technology
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• v.33 no.6 s.134
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• pp.63-70
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• 2005

The purpose of this study was to investigate how to modify the physical properties of cellulose after thermal treatment. Cellulose was treated between $225^{\circ}C$ and $325^{\circ}C$ for 3 hrs under air flow, and then the thermally treated cellulose was measured to specific surface area, constitute elements, consumption ofacid and base, as well as the adsorption capacity of ethylamine vapor. The higher was the treating temperature from $225^{\circ}C$ to $325^{\circ}C$, the lower was the total yield of cellulose. Elemental analysis revealed that carbon content in thermally treated cellulose was gradually increased in proportion to temperature increment. The amount of acidic functional groups tended to increase up to $300^{\circ}C$, after then to be lowered slightly. In principle, no alkaline functional groups were found in thermally treated cellulose. In case of treatment with $325^{\circ}C$, only a few amount of alkaline functional groups were detectable. Specific surface area of thermally treated cellulose are determined to $1.9m^2/g$, which value can become higher when the treated temperature rises. The thermally treated cellulose at $275^{\circ}C$ shows the highest adsorption capacity of ethylamine at $40^{\circ}C$ for 4 hrs. Solubility of those two celluloses with WPG (Weight Percent Gain) value of 113% and 108%, respectively, was determined to almost 100%. X-ray diffractogram of thermally treated cellulose suggested that the crystalline structure of cellulose began to be destroyed at the temperature of $275^{\circ}C$. As a conclusion, changes of such a physical properties make it possible to weaken inter and/or intra hydrogen bond in crystal region of cellulose macromolecules. When thermally treated cellulose adsorbs ethylamine, it turns to be well soluble to water.

• Korean Journal of Microbiology
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• v.45 no.3
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• pp.275-280
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• 2009

The optimal medium compositions for the production of bacterial cellulose (BC) by a Acetobacter sp. V6, which was isolated from the traditionally fermented vinegar in Korea, were investigated in static cultures. The optimum medium compositions for BC production were 3% glucose, 3% soytone, 0.8% $K_2HPO_4$, and 0.4% ethanol, respectively. Adding $NaH_2PO_4$ or $KH_2PO_4$ had not shown the increase in BC production. Under the optimum medium compositions, the highest BC production was 44.67 g/$m^2$ in 8 days and the thickness of BC pellicle was about 1 cm. Structural properties of BC produced in the optimal medium were studied using Fourier-transform infrared spectroscopy and X-ray diffractometer. BC from the optimal medium was found to be of cellulose type I, the same as typical native cellulose. No difference in the compositions between bacterial and plant celluloses, but BC showed unique micro-network structure and high crystallinity (82%).