• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.377-387
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• 2023

Ni-W/Al₂O₃ nano-composites were electrodeposited on mild steel substrate for mechanical and corrosion resistance applications. This study focused on the preparation of Ni-W/Al₂O₃ nano-composite coating with various quantity of Al₂O₃ incorporations. The addition of Al₂O₃ in the electrolytes were varied from 1-10 g/L in electrolytes and the Al₂O₃ incorporation in Ni-W/Al₂O₃ nano-composite coatings were obtained from 1.82 to 13.86 wt.%. The incorporation of Al₂O₃ in Ni-W alloy matrix influenced the grain size, surface morphology and structural properties were observed. The distributions of Al₂O₃ particle in alloy matrix were confirmed using electron microscopy (FESEM and TEM) and EDAX mapping analysis. The crystal structure informations were studied using X-ray diffraction method and it confirms that the deposits having cubic crystal structure. The better corrosion rate (0.87 mpy) and microhardness (965 HV) properties were obtained for the Ni-W/Al₂O₃ nano-composite coating with 13.86 wt.% of Al₂O₃ incorporations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.68-73
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• 2024

In this study, the praseodymium-doped yttrium phosphate (YPO₄:Pr³⁺) powder, which is well known for its high luminescent efficiency, and long life in the UV range, was synthesized with various content ratios of Pr₆O₁₁ and calcination temperature. Crystal structure and luminescent properties of various phosphor powders based on different concentrations and calcination conditions were characterized by XRD (X-Ray Diffraction) and PL (photoluminescence) spectrometers. From the XRD analysis, the structure of YPO₄:Pr³⁺ which is calcinated at 1,200℃ was stable tetragonal phase and crystal size was calculated about 25 nm by Scherrer equation. PL emission of YPO₄:Pr³⁺ with a different content ratio of Pr₆O₁₁ by excitation λ_exc=250 nm shows that 0.75 mol% phosphor powder has maximum PL intensity and PL decreases with the increase of the ratio of Pr₆O₁₁ up to 1.25 mol% which is caused by changes of crystallinity of phosphor powders. With increasing dopant ratio, photo-luminescence Emission decreases due to Concentration quenching, which is commonly observed in phosphors. Currently, 0.75 mol% is considered the optimal doping concentration. A hybrid ultraviolet-emitting device incorporating YPO₄:Pr³⁺ fluorescent material with plasma discharge was fabricated to enhance UV germicidal effects while minimizing ozone generation. UV emission from the plasma discharge device was shown at about 200 nm and 350 nm which caused additional emission of the regions of 250 nm, 315 nm, and 370 nm from the YPO₄:Pr³⁺ phosphor.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.105-114
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• 1973

The crystal structure of morpholinothiosemicarbazide has been determined by single crystal X-ray analysis. The lattice constants are a = 4.19(2), b = 6.56(2) and c = 26.67(4)${\AA}$. The unit cell contains 4 molecules and the space group is$P2_12_12_1$. The atomic parameters have been refined by least-squares method to a final R value of 0.07, based on the 651 observed reflexions. The amino nitrogen atom forms hydrogen bonds to the sulfur atoms of the other molecules related by the two-fold screw axis parallel to the a-axis, the distances of the hydrogen bonds being 3.48 and 3.49${\AA}$. On the other hand, the imino nitrogen atom forms a hydrogen bond to the amino nitrogen atom of the other molecule related by the two-fold screw axis parallel to the a-axis, the distance of the hydrogen bond being 3.04${\AA}$. These three hydrogen bonds arrange the molecules around the two-fold screw axis. Apart from the hydrogen bonding system the structure is held together by van der Waals forces.

• Journal of the Korean earth science society
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• v.27 no.3
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• pp.313-327
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• 2006

This study investigated the geochernical characteristics of Mn scale formed in groundwater wells at the Damyang area. The composition of Mn scale consists mainly of MnO and $SiO_2$. The content of Mn ranges from56.61wt.% to 68.69wt.%, and $SiO_2$ content ranges from 1.56wt.% to 10.45wt.%. The contents of Mo and Ba in Mn scale increased with increased depth; whereas, the content of Zn and Pb decreased with increased depth. Birnessite, quartz and feldspars were identified in Mn scales using x-ray powder diffraction studies. The IR absorption bands for Mn scales show major absorption band due to OH stretching, adsorbed molecular water, and birnessite stretching, respectively. In the SEM and EDS analysis, the Mn scale consists of botryoidal, spherical, spherulite, and empty straw structure. Those structure may be precipitated simply due to oversaturation with concentrated Mn content or may be formed through biogenic precipitation by Lepthothrix discophora. Under microanalysis using EDS on those structure surface of Mn scales, the Mn atomic percent range from 28 to 44, and such elements revealed the presence of Si, K, Na, Ca, Cl, Cu, Zn, and Ba.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.13-23
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• 2008

The triaxial compression tests and consolidation tests using NaCl solution and leachates as substitute pore (or saturated) water in samples were carried out to find out the behavior characteristics of strength, deformation and permeability coefficient of contaminated clay. Also, the chemical property analysis on the clay samples using scanning electron microscope and energy dispersive x-ray spectrometer were involved. The magnitudes of composition ratio were shown in the order of O, C, Si, Al, and Fe as a result of chemical composition analysis for clay samples. Besides, as the results of triaxial compression tests and consolidation tests, the shear strength, compression and permeability properties were increased with increasing in the concentration of contaminant (NaCl). It may be considered that these circumstances be caused by the changes of soil structure to flocculent structure due to the decrease in the thickness of diffuse double layer with increasing in the concentration of electrolyte. MT3D model was also using to grasp the procedures that the groundwater may be contaminated by the leachates permeated through the clay liner. The results of contaminant transport analysis showed a tendency that the predicted concentration of groundwater was higher with increasing in the initial concentration of $Cl^-$ ion and increased as a nonlinear curves with time. The transportation distance calculated by the use of regression equation between the distance from contaminant source and the concentration of $Cl^-$ ion was increased with increasing the initial concentration.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.606-610
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• 2010

Films consisting of a silicon quantum dot superlattice were fabricated by alternating deposition of silicon rich silicon nitride and $Si_3N_4$ layers using an rf magnetron co-sputtering system. In order to use the silicon quantum dot super lattice structure for third generation multi junction solar cell applications, it is important to control the dot size. Moreover, silicon quantum dots have to be in a regularly spaced array in the dielectric matrix material for in order to allow for effective carrier transport. In this study, therefore, we fabricated silicon quantum dot superlattice films under various conditions and investigated crystallization behavior of the silicon quantum dot super lattice structure. Fourier transform infrared spectroscopy (FTIR) spectra showed an increased intensity of the $840\;cm^{-1}$ peak with increasing annealing temperature due to the increase in the number of Si-N bonds. A more conspicuous characteristic of this process is the increased intensity of the $1100\;cm^{-1}$ peak. This peak was attributed to annealing induced reordering in the films that led to increased Si-$N_4$ bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that peak position was shifted to higher bonding energy as silicon 2p bonding energy changed. This transition is related to the formation of silicon quantum dots. Transmission electron microscopy (TEM) and electron spin resonance (ESR) analysis also confirmed the formation of silicon quantum dots. This study revealed that post annealing at $1100^{\circ}C$ for at least one hour is necessary to precipitate the silicon quantum dots in the $SiN_x$ matrix.

• Journal of Life Science
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• v.14 no.5
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• pp.752-760
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• 2004

The function of the [4Fe-4S] cluster containing iron (Fe-) protein in nitrogenase catalysis is to serve as the nucleotide-dependent electron donor to the MoFe protein which contains the sites for substrate binding and reduction. The ability of the Fe protein to function in this manner is dependent on its ability to adopt the appropriate conformation for productive interaction with the MoFe protein and on its ability to change redox potentials to provide the driving force required for electron transfer. The MgADP-bound (or off) conformational state of the nitrogenase Fe protein structure described reveals mechanisms for long-range communication from the nucleotide-binding sites to control affinity of association with the MoFe protein component. Two pathways, termed switches I and II, appear to be integral to this nucleotide signal transduction mechanism. In addition, the structure of the MgADP bound Fe protein provides the basis for the changes in the biophysical properties of the [4Fe-4S] observed when Fe protein binds nucleotides. The structures of the nitrogenase Fe protein with defined amino acid substitutions in the nucleotide dependent signal transduction pathways of the Switch I and Switch II have been determined by X-ray diffraction methods. These two pathways have been also implicated by site directed mutagenesis studies, structural analysis and analogies to other proteins that utilize similar nucleotide dependent signal transduction pathways. We have examined the validity of the assignment of these pathways in linking the signals generated by MgATP binding and hydrolysis to macromolecular complex formation and intermolecular electron transfer. The results provide a structural basis for the observed biophysical and biochemical properties of the Fe protein variants and interactions within the nitrogenase Fe protein-MoFe protein complex.

• Imaging Science in Dentistry
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• v.35 no.3
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• pp.167-173
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• 2005

Purpose : To investigate the relationship between three-dimensional (3D) bone imaging parameters and trabecular strength in the mandible. Materials and Methods : Bone specimens were obtained from the mandibles of five male pigs weighing around 110 kg each. Of those, 43 samples were selected for 3D analysis and measured by micro-computed tomography. The five morphometric parameters were trabecular thickness (Tb.Th), bone specific surface (BS/BV), percent bone volume (BV/TV), structure model index (SMI) and degree of anisotropy (DA). Through destructive mechanical testing, strength parameters were obtained. Results : BV/TV, SMI, BS/BV, and Tb.Th showed significant correlations with strength parameters. DA did not show any correlation with the other parameters. In multiple linear regression analysis, BV/TV alone explained $43\%$ of the variance in Young's modulus. By stepwise inclusion of SMI, the variance in the Young's modulus was better explained up to $52\%$. Conclusions : Predicting trabecular strength in the mandible through architectural analysis would be possible. Further study is needed to establish the tendency and variety of trabecular architecture and strength according to the locations within the mandible.

• 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.