• Applied Biological Chemistry
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• v.48 no.3
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• pp.189-200
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• 2005

Biological nitrogen fixation is an important process for academic and industrial aspects. This review will briefly compare industrial and biological nitrogen fixation and cover the characteristics of biological nitrogen fixation studied in Azotobacter vinelandii. Various organisms can carry out biological nitrogen fixation and recently the researches on the reaction mechanism were concentrated on the free-living microorganism, A. vinelandii. Nitrogen fixation, which transforms atmospheric $N_2$ into ammonia, is chemically a reduction reaction requiring electron donation. Nitrogenase, the biological nitrgen fixer, accepts electrons from biological electron donors, and transfers them to the active site, FeMo-cofactor, through $Fe_4S_4$ cluster in Fe protein and P-cluster in MoFe protein. The electron transport and the proton transport are very important processes in the nitrogenase catalysis to understand its reaction mechanism, and the interactions between FeMo-cofactor and nitrogen molecule are at the center of biological nitrogen fixation mechanism. Spectroscopic studies including protein X-ray crystallography, EPR and $M{\ddot{o}}ssbauer$, biochemical approaches including substrate and inhibitor interactions as well as site-directed mutation study, and chemical approach to synthesize the FeMo-cofactor model compounds were used for biological nitrogen fixation study. Recent research results from these area were presented, and finally, a new nitrogenase reaction mechanism will be proposed based on the various research results.

• Korean Journal of Crystallography
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• v.4 no.1
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• pp.18-24
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• 1993

The phase diagram of the Pt-Sb system was reinvestigated, using the conventional sealedcapsule technique. The identification of phases present in the reaction products was made by reflected light microscopy, X-ray diffraction and electron microprobe analysis. The existence of compounds, Pt5Sb, Pt3Sb, Pt3Sb2, PtSb and PtSb5 was confirmed. A new phase, Pt5Sb with a composition of 83at% Pt and tetragonal structure of the lattice parameters a=3.948(3), c=16.85(1)A, was found. The X-ray powder data of Ptsb may be indexable on a tetragonal cell with a=3.9455(7), c=16.959(5)A. PtSb is stoichiometric up to 800t and becomes Pt-deficient as much as lat% at 1000t. Solid solubility limits of Sb in Pt were determined to be 7.5,10.0 and 6.1at% at 1000˚,800˚ and 600˚ , respectively. The earlier reported Pts Sbf was not found in this study. The liquidus curve between the Ptsb2 and Sb phases was revised.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3635-3640
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• 2013

We prepared Ni and Pd-modified $TiO_2@SiO_2$ core-shell nanostructures and then analyzed them by scanning electron microscopy, optical microscopy, X-ray diffraction crystallography, FT-IR and UV-Visible absorption spectroscopy. In addition, their CO oxidation performance was tested by temperature-programmed mass spectrometry. The CO oxidation activity showed an order of Ni-$TiO_2@SiO_2$ ($900^{\circ}C$) < Ni-$TiO_2@SiO_2$ ($90^{\circ}C$) < Ni-$TiO_2@SiO_2$ ($450^{\circ}C$) in the first CO oxidation run, and greatly improved activity in the same order in the second run. The $T_{10%}$ (the temperature at 10% CO conversion) corresponds to the CO oxidation rate of $2.8{\times}10^{-5}$ molCO $g{_{cat}}^{-1}s^{-1}$. For Ni-$TiO_2@SiO_2$ ($450^{\circ}C$), the $T_{10%}$ was observed at $365^{\circ}C$ in the first run and at $335^{\circ}C$ in the second run. For the Pd-$TiO_2@SiO_2$ ($450^{\circ}C$), the $T_{10%}$ was observed at a much lower temperature of $263^{\circ}C$ in the first CO oxidation run, and at $247^{\circ}C$ in the second run. The CO oxidation activities of transition metal modified $TiO_2@SiO_2$ core-shell nanostructures presented herein provide new insights that will be useful in developing catalysts for various environments.

• Korean Journal of Crystallography
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• v.11 no.4
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• pp.212-223
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• 2000

A stochiometric mix of CuInTe₂ polycrystal was prepared in a honizonatal furnace. To obtain the single crystal thin films, CuInTe₂ mixed crystal was deposited on throughly etched GaAs(100) by the HWE system. The source and substrate temperatures were 610℃ and 450℃ respectively, and the thickness of the deposited single crystal thin film was 2.4㎛. CuInTe₂ single crystal thin film was proved to be the optimal growth condition when the excition emission spectrum was the strongest at 1085.3 nm(1.1424 eV) of photoluminescence spectrum at 10 K, and also FWHM of Double Crystal X-ray Rocking Curve (DCRC) was the smallest, 129 arcsec. The Hall effect on this sample was measured by the method of Van der Pauw, and the carrier density and mobility dependent on temperature were 9.57x10/sup 22/ electron/㎥, 1.31x10/sup -2/㎡/V·s at 293 K, respectively. The ΔCr(Crystal field splitting) and the ΔSo (spin orbit coupling splitting( measured at f10K from the photocurrent peaks in the short wavelength of the CuInTe₂ single crystal thin film were about 0.1200 eV, 0.2833 eV respectively. From the PL spectra of CuInTe₂ single crystal thin film at 10 K, the free exciton (E/sub x/) was determined to be 1064.5 nm(1.1647 eV) and the donor-bound exciton(D/sup 0/, X) and acceptor-bound exciton (A/sup 0/, X) were determined to be 1085.3 nm(1.1424 eV) and 1096.8 nm(1.1304 eV0 respectively. And also, the donor-acciptor pair (DAP)P/sub 0/, DAP-replica P₁, DAP-replica P₂ and self-activated (SA) were determined to be 1131 nm (1.0962 eV), 1164 nm(1.0651 eV), 1191.1 nm(1.0340 eV) and 1618.1 nm (0.7662 eV), respectively.

• Korean Journal of Crystallography
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• v.15 no.1
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• pp.18-23
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• 2004

In order to find the optical properties of CdSe thin film and CdSe nanostructure, the following experiments were performed: the CdSe wurtzite nanostructure was made by using 99.99% CdSe (Aldrich) powder with the $SiO_x$ substrates and the $AlO_x$ membranes in $7{\times}10^{-6}$ torr vacuum. (The average vacuum coating speed being 1 ${\AA}$/sec). The calculations obtained were about 200 nm diameter of nanotubes on the $AlO_x$ membranes and a crystallite size of about 2 nm on the $SiO_x$ substrates. These results were verified through the Scanning Electron Microscopy (SEM) analysis, thin film X-ray diffraction analysis and emission spectroscopy.

• Korean Journal of Crystallography
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• v.1 no.2
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• pp.66-75
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• 1990

The Pd-Te system has been investigated by differential thermal analysis, X-ray diffration, electron probe microanalysis and reflected light microscopy. New phase relations in 0-50at% Te portion of the binary system are proposed. Eight binary phases exist in the system:Pd17Te4, Pd20Te7.PdsTe3, P477e3, P497e4, P637e2, PeTe and PaTe2. Of these, P677e3 is a newly reported phase. P4177e4 is cubic, space group Fd3c, with a=12.678(5)A. The X-ray powder data of PdsTe3, indexed on an orthorhombic cell, give a= 12.843(3), b=15.126(3), c: 11.304(2)A and those of PdTTe.1, indexed on a monoclinic cell, give a=7.444(1), b= 13.918(2) , c=8.873(2)A. p =92.46(2). Some physical and optical properties of synthetic phases in the system are also reported.

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.482-487
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• 2022

In this study, the activity test and characterization were performed to evaluate the hydrogen sulfide removal characteristics using a V/TiO₂ catalyst at room temperature. The optimal vanadium loading was 10 wt%, and the durability was greater than 60 minutes at 60~80% relative humidity. The Brunauer-Emmett-Teller (BET) surface area and raman spectroscopy results confirmed that the structure of the vanadium site exposed to the surface was a dominant factor in catalyst activity. From Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray crystallography (XRD) analyses, it was found that sulfur can be accumulated on the catalyst surface, which results in a decrease in durability under catalytic activity tests. Therefore, it is judged that a combined process of catalytic oxidation and regeneration is needed.

• Korean Journal of Crystallography
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• v.13 no.3_4
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• pp.165-171
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• 2002

Single phase $Pb(Fe_{1/2}Ta_{1/2})O_3$, ceramics were successfully synthesized from the powders prepared by solid state reaction (sintering temperature: $1100^{\circ}C$, density: $9.3g/cm^3$, average grain size: $5.1{\pm}1.2mm$, space group: Pm3m). Their dielectric properties measured at $-150{\sim}50^{\circ}C$ showed the maximum relative dielectric constant of 31000 at $-41^{\circ}C$. 1 kHz, and typical relaxor ferroelectrics characteristics such as diffuse phase transition and dielectric relaxation phenomena. However, the diffuseness of phase transition decreased and the dielectric properties became more normal ferroelectrics as the time of annealing at $1000^{\circ}C$ increased. By using Raman spectroscopy, it was revealed that the $Fe^{3+}$ and $Ta^{5+}$ ions in the as-sintered $Pb(Fe_{1/2}Ta_{1/2})O_3$, are stoichiometrically 1 : 1 ordered within the short-range that can not be probed even by transmission electron microscopy, and this stoichiometric 1 : 1 ordering is enhanced by the annealing. The relaxor ferroelectric characteristics in the as-sintered $Pb(Fe_{1/2}Ta_{1/2})O_3$, could be correlated with the stoichiometric 1 : 1 short-range ordering of B-site cations, and the decrease of relaxor ferroelectric characteristics in the annealed $Pb(Fe_{1/2}Ta_{1/2})O_3$ could be correlated with the enhanced stoichiometric 1 : 1 short-range ordering of B-site cations.

• Economic and Environmental Geology
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• v.51 no.4
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• pp.345-358
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• 2018

In this study, we have performed electron probe micro analyzer (EPMA), X-ray differaction (XRD), inductively coupled plasma spectroscopy (ICP), Fourier transform Raman spectroscopy (FT-Raman), far-infrared (FIR), nuclear magnetic resonance (NMR), and pH-DO Analyses for characterizing medicinal mineralogy aspect of the black tourmaline (Shantung, china), black and pink tourmaline (Minas Geraris, Brazil), black touemaline (Daeyu mine, Korea). In addition, heating effects of the tourmaline sauna as well as the effects of tourmaline powder-added soap on skin troubles have been investigated. It has been revealed that chemical composition of the tourmaline is either high in Fe-, Al-, B-rich types. Ratio of the K-Ca, Na-K, and Fe-B reflects the component change property of solid solution. $CaO/CaO+Na_2O$ and MgO/FeO+MgO ratio show high positive correlation. When tourmaline reacts with distilled water, extended reaction time DO values approximately decrease and it stabilizes at DO = 10. Otherwise, pH values increase until 6 hours and it stabilizes at pH = 8 after 24 hours. Distilled water changes to alkaline when it reacts with tourmaline powder and particles. Tourmaline showed lower absorption spectrum strength and transmittance at short wave, where absorption spectrum wavelength and strength were determined by the content of the composition elements and characteristics of crystallography. Increase of the Fe content has been confirmed to be the cause for the reduction of irradiation. For the chemical composition and spectral property of the tourmaline particle samples, it has been found that Si and Fe contents show positive correlation with Far-Infrared irradiation, while Al and Mg contents show negative correlation. For tourmaline powder, it has been confirmed that $^{17}O-NMR$ FWHM (full width at half maximum) decreases when reacts with distilled water. Tourmaline sauna (approximately $100^{\circ}C$) was found to increase $0.5-1.5^{\circ}C$ of body temperature, average of 12 heartbeat, and 10mg Hg of blood pressure. Tourmaline soap had very good aesthetic effect to skin and was confirmed to have above the average improvements to skin troubles (e.g., allergy or atopy).