• Journal of Powder Materials
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• v.20 no.3
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• pp.197-202
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• 2013

A novel route to prepare Nd-Fe-B magnetic particles by utilizing both spray drying and reduction/diffusion processes was investigated in this study. Precursors were prepared by spray drying method using the aqueous solutions containing Nd salt, Fe salt and boric acid with stoichiometric ratios. Precursor particles could be obtained with various sizes from 2 to $10{\mu}m$ by controlling concentrations of the solutions and the average size of $2{\mu}m$ of precursors were selected for further steps. After heat treatment of precursors in air, Nd and Fe oxides were formed through desalting procedure, followed by reduction processes in Hydrogen ($H_2$) atmosphere and with Calcium (Ca) granules in Argon (Ar) successively. Moreover, diffusion between Nd and Fe occurred during Ca reduction and $Nd_2Fe_{14}B$ particles were formed. With Ca amount added to particles after $H_2$ reduction, intrinsic coercivity was changed from 1 to 10 kOe. In order to remove and leach CaO and residual Ca, de-ionized water and dilute acid were used. Acidic solutions were more effective to eliminate impurities, but Fe and Nd were dissolved out from the particles. Finally, $Nd_2Fe_{14}B$ magnetic particles were synthesized after washing in de-ionized water with a mean size of $2{\mu}m$ and their maximum energy product showed 9.23 MGOe.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.298-305
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• 2016

The development of non-precious metal based electrocatalysts is highly desired for the oxygen reduction reaction (ORR) as alternates to noble metal based ORR electrocatalysts. Herein, we report mononulcear copper(II) complex $[CuLbpy]ClO_4$ (L=4-[(2-hydroxyphenylimino)methyl]benzoic acid) containing poly(allylamine.HCl) polymer (PAlACuLbpy) as an electrocatalyst for oxygen reduction reaction (ORR). PAlACuLbpy was mixed with poly(acrylic acid) and tetraethylortho silicate to prepare a composite and then deposited on the screen printed electrode surface. The modified electrode (PAlACuLbpy/PCE) is highly stable and showed a quasi-reversible redox behavior with $E_{1/2}=-0.2V$ vs. Ag/AgCl(3 M KCl) in 0.1 M phosphate buffer at pH 7 under argon atmosphere. PAlACuLbpy/PCE exhibited a remarkable ORR activity with an onset potential of -0.1 V vs Ag/AgCl in 0.1 M PB (pH 7) in the presence of oxygen. The kinetics for ORR was studied by rotating disk voltammetry in neutral aqueous medium and the results indicated that the number of electrons involving in the ORR is four and the conversion products are water and hydrogen peroxide.

• Journal of Radiation Protection and Research
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• v.30 no.1
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• pp.45-54
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• 2005

A dynamic compartment model was developed to appraise the level of the contamination of agricultural plants by accidentally released tritium from nuclear facility. The model consists of a set of inter-connected compartments representing atmosphere, soil and plant. In the model three categories of plant are considered: leafy vegetables, grain plants and tuber plants, of which each is modeled separately to account for the different transport pathways of tritium. The predictive accuracy of the model was tested through the analysis of the tritium exposure experiments for rice-plants. The predicted TFWT(tissue free water tritium) concentration of the rice ear at harvest was greatly affected by the absolute humidity of air, the ratio of root uptake, and the rate of rainfall, while its OBT(organically bound tritium) concentration the stowing period of the ear, the absolute humidity of air and the content of hydrogen in the organic phase. There was a good agreement between the model prediction and the experimental results lot the OBT concentration of the ear.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.941-950
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• 2013

The Korean Nuclear-Hydrogen Technology Development (NHTD) Plan will be performing irradiation testing of coated particle fuel at HANARO to support the development of VHTR in Korea. This testing will be carried out to demonstrate and qualify TRISO-coated particle fuel for use in VHTR. The testing will be irradiated in an inert gas atmosphere without on-line temperature monitoring and control combined with on-line fission product monitoring of the sweep gas. The irradiation device contains two test rods, one has nine fuel compacts and the other five compacts and eight graphite specimens. Each compact contains about 260 TRISO-coated particles. The irradiation device is being loaded and irradiated into the OR5 hole of the in HANARO core from August 2013. The device will be operated for about 150 effective full-power days at a peak temperature of about $1030^{\circ}C$ in BOC (Beginning of Cycle) during irradiation testing. After a peak burn-up of about 4 atomic percentage and a peak fast neutron fluence of about $1.7{\times}10^{21}\;n/cm^2$, PIE (Post-Irradiation Examination) of the irradiated coated particle fuel will be performed at IMEF (Irradiated Material Examination Facility). This paper reviews the design of test rod and irradiation device for coated particle fuel, and discusses the technical results for irradiation testing at HANARO.

• Korean Journal of Materials Research
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• v.25 no.1
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• pp.27-31
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• 2015

This paper proposes a novel way of fabricating aligned porous Sn by freeze-drying of camphene slurry with stannic oxide ($SnO_2$) coated Sn powders. The $SnO_2$ coated Sn powders were prepared by surface oxidation of the initial and ball-milled Sn powders, as well as heat treatment of tin chloride coated Cu powders. Camphene slurries with 10 vol% solid powders were prepared by mixing at $50^{\circ}C$ with a small amount of oligomeric polyester dispersant. Freezing the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled at $-25^{\circ}C$. Improved dispersion stability of camphene slurry and the homogeneous frozen body was achieved using the oxidized Sn powder at $670^{\circ}C$ in air after ball milling. The porous Sn specimen, prepared by freeze-drying of the camphene slurry with oxidized Sn powder from the heat-treated Sn/tin chloride mixture and sintering at $1100^{\circ}C$ for 1 h in a hydrogen atmosphere, showed large pores of about $200{\mu}m$, which were aligned parallel to the camphene growth direction, and small pores in their internal walls. However, $100{\mu}m$ spherical particles were observed in the bottom part of the specimen due to the melting of the Sn powder during sintering of the green compact.

• Journal of Soil and Groundwater Environment
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• v.17 no.5
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• pp.10-19
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• 2012

The aim of this study was to examine chemical and isotopic compositions of groundwater and lake water near an area contaminated by petroleum and to evaluate influence of petroleum on them during the period from March to August 2011. In dry season, $Ca^{2+}$ and $SO{_4}^{2-}$ were dominant in the groundwater and lake water and $Ca^{2+}$ and $HCO{_3}^-$ were significant in wet season. ${\delta}^{18}O$ and ${\delta}D$ of the groundwater and lake water were plotted near LMWL (${\delta}D=8.06{\delta}^{18}O+12.5$). ${\delta}^{18}O$ and ${\delta}D$ of the lake water did not show seasonal variation. However, ${\delta}^{18}O$ and ${\delta}D$ of the groundwater were enriched in wet season compared with those in dry season because of influence of small ponds around wells where evaporation losses were slightly experienced. Redox condition of most lake water was oxidation environment in contact with the atmosphere during the study period. However, redox condition of groundwater was transitional environment in dry season and oxidation environment in wet season because of influence of contaminant such as petroleum. In some groundwater, the concentrations of $NO{_3}^-$ in some groundwater were less than 1 mg/L because of denitrification. Also, $NO{_3}^-$ showed positive correlation with $SO{_4}^{2-}$ and weak negative correlation with $HCO{_3}^-$, because of influence of denitrification.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1222-1227
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• 1998

The crystal structure of a benzene sorption complex of fully dehydrated Cd2+-exchanged zeolite X, Cd46Si100Al92O384·43C6H6 (a=24.880(6) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21 ℃. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Cd(NO3)2 for 3 d, followed by dehydration at 400 ℃ and 2 x 10-6 Torr for 2 d, followed by exposure to about 92 Torr of benzene vapor at 22 ℃. The structure was determined in this atmosphere and refined to the final error indices R1=0.054 and Rw=0.066 with 561 reflections for which I > 3σ(I). In this structure, Cd2+ ions are found at four crystallographic sites: eleven Cd2+ ions are at site 1, at the centers of the double six-oxygen rings; six Cd2+ ions lie at site I', in the sodalite cavity opposite to the double six-oxygen rings; and the remaining 29 Cd2+ ions are found at two nonequivalent threefold axes of unit cell, sites Ⅱ' (in the sodalite cavity ) and site Ⅱ (in the supercage) with occupancies of 2 and 27 ions, respectively. Each of these Cd2+ ions coordinates to three framework oxylkens, either at 2.173(13) or 2.224(10) Å, respectively, and extends 0.37 Å into the sodalite unit or 0.60 Å into the supercage from the plane of the three oxygens to which it is bound. The benzene molecules are found at two distinct sites within the supercages. Twenty-seven benzenes lie on threefold axes in the large cavities where they interact facially with the latter 27 site-Ⅱ Cd2+ ions (Cd2+-benzene center=2.72 Å; occupancy=27 molecules/32 sites). The remaining sixteen benzene molecules are found in 12ring planes; occupancy=16 molecules/16 sites. Each hydrogen of these sixteen benzenes is ca. 2.8/3.0 Å from three 12-ring oxygens where each is stabilized by multiple weak electrostatic and van der Waals interactions with framework oxygens.

• Journal of The Korean Astronomical Society
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• v.54 no.5
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• pp.139-155
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• 2021

We present an updated version of the multilayer spectral inversion (MLSI) recently proposed as a technique to infer the physical parameters of plasmas in the solar chromosphere from a strong absorption line. In the original MLSI, the absorption profile was constant over each layer of the chromosphere, whereas the source function was allowed to vary with optical depth. In our updated MLSI, the absorption profile is allowed to vary with optical depth in each layer and kept continuous at the interface of two adjacent layers. We also propose a new set of physical requirements for the parameters useful in the constrained model fitting. We apply this updated MLSI to two sets of Hα and Ca II line spectral data taken by the Fast Imaging Solar Spectrograph (FISS) from a quiet region and an active region, respectively. We find that the new version of the MLSI satisfactorily fits most of the observed line profiles of various features, including a network feature, an internetwork feature, a mottle feature in a quiet region, and a plage feature, a superpenumbral fibril, an umbral feature, and a fast downflow feature in an active region. The MLSI can also yield physically reasonable estimates of hydrogen temperature and nonthermal speed as well as Doppler velocities at different atmospheric levels. We conclude that the MLSI is a very useful tool to analyze the Hα line and the Ca II 8542 line spectral daya, and will promote the investigation of physical processes occurring in the solar photosphere and chromosphere.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.25-31
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• 2011

Solid oxide fuel cells (SOFCs) have many attractive features for widespread applications in generation systems. Recently, stainless steels have attractive materials for metallic bipolar plate because metallic bipolar plates have many benefits compared to others such as graphite and composite bipolar plates. SOFC operates on high temperature of about $800{\sim}1000^{\circ}C$ than other fuel cell systems. Thus, many studies have attempted to reduced the operation temperature of SOFC to about $600{\sim}800^{\circ}C$, which is the intermediate temperature (IT) of SOFC. Low cost and high-temperature corrosion resistance are very important for the practical applications of SOFC in various industries. In this study, two specimens, 304 and 430 stainless steels with and without different pre-surface treatments on the surface were investigated. And, specimens were exposed at high temperature in the box furnace under oxidation atmosphere of $800^{\circ}C$. Oxidation behavior have been investigated with the materials exposed at different times (100 hrs and 400 hrs) by SEM, EDS and XRD. By increasing exposure time, the amount of metal oxide increased in the order like; STS304 < STS430 and As-received < As-polished < Sand-blast specimens.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.260-264
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• 2012

We have investigated the effect of ambient gases on the structural, electrical, and optical characteristics of IZO thin films intended for use as anode contacts in the organic light emitting diodes (OLED) devices. These IZO thin films were deposited on the PES film by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar + O2, and Ar + H2) at room temperature. In order to investigate the influences of the ambient gases, the flow rate of oxygen and hydrogen in argon has been changed from 0.1 sccm to 0.5 sccm, respectively. All the IZO thin film has an (222) preferential orientation regardless of ambient gases. The electrical resistivity of the IZO film increased with increasing O2 flow rate, whereas the electrical resistivity decreased sharply under an Ar + H2 atmosphere and was nearly similar regardless of the H2 flow rate. The change of electrical resistivity with changes in the ambient gas composition was mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO substrates made with the configuration of IZO/α-NPD/DPVB/Alq3/LiF/Al in order to elucidate the performance of the IZO substrate. The current density and the luminance of OLED devices with IZO thin films deposited in 0.5 sccm H2 ambient gas are the highest amongst all other films.