• Journal of the Korean Ceramic Society
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• v.48 no.3
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• pp.222-227
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• 2011

The hexavalent chromium ions in wastewater are highly toxic chemicals even at low concentrations. It causes serious diseases, such as cancer, skin disease, digestive trouble et. al. In this study, $Cr^{6+}$ ions were removed by using borosilicate glasses. Various glasses system with different compositions were prepared and then reacted in a solution contaning $Cr^{6+}$ ions. After the reaction, the concentration of the $Cr^{6+}$ ions remained in the solution was measured by ICP-OES. The reacted surface of the glasses was also analyzed by using a XRD, SEM, and EDS. When $Na_2O-RO-SiO_2-B_2O_3$ (RO=MgO, CaO, SrO, BaO) glasses were reacted with a solution containing $Cr^{6+}$ ions, the optimum removal efficiency of $Cr^{6+}$ ions was observed in the BaO glass. $Ba^{2+}$ ions leached out of these glasses combine with $Cr^{6+}$ ions in a solution to form $BaCrO_4$ crystals on the glass surface. In this manner, the $Cr^{6+}$ ions can be removed from the solution. It is conceivable that $Ba^{2+}$ ions are reacted with $Cr^{6+}$ ions in a solution immedeately after leaching out of the glasses. The pH of the solution for optimum removal of $Cr^{6+}$ ions were 3.0~5.0.

• Journal of Magnetics
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• v.17 no.1
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• pp.6-8
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• 2012

M$\ddot{o}$ssbauer spectra of hexagonal $BaFe_{12}O_{19}$ single crystals were studied at various temperatures (4-300 K). It was found that the spin states in Fe atoms were parallel to the ${\gamma}$-ray's direction into a single crystal along the caxis. The location of the Fe ion in the 2b site is unusual in an oxide structure and has strong anisotropic lattice vibrations. Moreover, at room temperature, the zero absorption lines of the Fe ions at the 2b site were observed due to fast diffusion motion in a double well atomic potential. The two Fe ions of the single crystal mainly enter into the sites in the mirror plane of the trigonalbipyramidal structure.

• Journal of Magnetics
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• v.21 no.1
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• pp.61-64
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• 2016

In this study, we report the as-prepared MgO-doped $BaFe_{12}O_{19}$, which was prepared by calcination technique and high-energy ball milling process, as an electromagnetic wave absorber. The phase analysis of $BaFe_{12}O_{19}$ and the as-prepared MgO-doped $BaFe_{12}O_{19}$ was detected utilizing X-ray Diffractometer (XRD). The microstructure was characterized using Scanning Electron Microscope (SEM). By means of the transmission/reflection coaxial line method, the electromagnetic properties and microwave absorbing properties of the as-prepared electromagnetic wave absorber were studied. It is found that the electromagnetic wave absorber has a minimum reflection loss value of -41 dB at 4.27 GHz with a matching thickness of 2.6 mm. The experiment results revealed that the as-prepared electromagnetic wave absorber could find potential applications in many military as well as commercial industries.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.16-23
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• 1992

High $T_c$, superconductor $(Y_{1-x}Eu_x)Ba_2Cu_3O_{7-{\delta}}$ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared and the physical properties were observed. XRD analysis showed that the structures of all the specimen were orthorhombic and the lattice parameters a, b and c increased with the increasing x value. Electrical resistivity and magnetization measurements revealed that pure high $T_c$, superconducting phases were formed at above 90 K. The critical temperatures increased with increasing the amount of Eu. From the measurement of magnetization and the size of the grains using SEM micrographs, volume diamagnetic susceptibilities for each specimen were calculated. These values decreased with the increasing x value. The composition of Ba in the lattice site decreased as the concentration of Eu increased, and this was confirmed by EPMA. It was found out that the volume diamagnetic susceptibility of each specimen was directly influenced by the composition of Ba in the lattice site.

• Journal of the Korean Society of Groundwater Environment
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• v.3 no.1
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• pp.37-49
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• 1996

The objectives of this study are to investigate the groundwater and surface water contamination, to interpret the attenuation mechanism of contaminant transport, and to find the appropriate contamination indicator. at the two big landfill sites : Nanjido Landfill and Hwasung Landfill. Leachate from the Nanjido, th, Hwasung and the Kimpo waste disposal sites is characterized by high temperature (31.7-40.1$^{\circ}C$), high electric conductivity (14,650-32,800 ${\mu}$S/cm), somewhat higher pH(7.58-8.45) and low Eh (-119.4-20.4 mV), and is enriched in both major (Na$^{＋}$, K$^{＋}$, Ca$^{2＋}$, Mg$^{2＋}$, HC $O_3$$^{－}$, Cl$^{－}$) and minor (Mn, Sr$^{2＋}$, Ba$^{2＋}$, Li$^{＋}$, F$^{－}$, Br$^{－}$) ions. Municipal solid waste leachate and industrial waste leachate are effectively discriminated by the content of S $O_4$$^{2－}$, Fe, and heavy metals. The attenuation mechanism of each component was assessed using the chemical analysis. Cl-normalizing process, WATEQ4F simulation, and preceding flownet analysis. Based on the calculation of Contamination Factor, K, Na, Ca, Mg, B, Zn, HC $O_3$, Cl, F, Br and TOC are effective contamination indicators in the Nanjido landfill site, and K, Na, Ca, Mg, B, S $O_4$, HC $O_3$, Cl, F, Br and TOC in the Habsburg landfill site Particularly, TOC is the best contamination indicator in landfill sites influenced by sea water.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.385-390
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• 1996

The electrical resistivity of the ceramic glaze coated on ceramic substrate plays an important role on the characteristics of the thick and thin film electrical circuits. In this study the effects of the various modifiers on the electrical resistivity were examined in SiO2-Al2O3-B2O3-RO-Na2O (RO=CaO , SrO, BaO, PbO) glass system. In alkali free glasses where divalent cations are responsible for electrical conduction the electrical conductivity of th glasses increased with the ionic size of divalent cations due to the decrease in the bond strength between oxyben and divalent cation. In Na2O containing glasses however where Na+ ion is responsible for electrical conduction the ionic conductivity decreased with the ionic size of divalent cations because the blocking effect of the cations on Na+ ion movement increased with larger divalent cations. Na+ ionic conduction also depended on the glass structure relaxation due to the corrdination number changes of B2O3 and Al2O3 which varied with the NaO2 content in the glass.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.3-5
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• 1998

The interest in the use of borate crystals in ultraviolet(UV) nonlinear optics(NLO) has increased because all solid-stste UV lasers obtained with NLO are in highly demand. Much effort has been spent on developing borates series, such as{{{{ { beta -BaB }_{2 } {O }_{4 }(BBO), {LiB }_{ 3}{O }_{5 }(LBO)}}}} and{{{{{ CsKiB}_{6 }{O }_{10 }(CLBO)}}}} in this decade. Recently another new borate crystals, {{{{{ YCa}_{4 }O({BO }_{3 })_{3}}}}} and{{{{{Gd }_{x }{Y }_{1-x }{Ca }_{4 }O({BO }_{ 3})({Gd }_{x }{Y }_{1-x }COB)}}}} have been developed by the present authors. Here, the growth and NLO properties of YCOB and {{{{ {Gd }_{ x} {Y }_{ 1-x} }}}}CO B crystal are reported and their properties discussed in relation to those of other nonlinear optical crystals, such as LBO.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.1
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• pp.25-33
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• 1998

We have studied the reduction of NO by propane over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution by substitution of metal into A or B site of perovskite oxides. In addition, the reaction conditions, such as temperature, $O_2$ concentration, space velocity have been studed. In the $LaCoO_3$ type catalyst, the partial substitution of Ba, Sr into A site enhanced the catalytic activity in the reduction of NO. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3(x=0 \sim 1.9)$ catalyst, the partial substitution of Fe into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. The surface area and catalytic activity of perovskite catalysts prepared by malic acid method showed higher values than those of solid reaction method. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$ catalyst, the conversion of NO increased with increasing $O_2$ concentration and contact time. The introduction of water into reactant feed decreased the catalytic activity.

• Journal of the Mineralogical Society of Korea
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• v.10 no.2
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• pp.105-113
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• 1997

Mineral description and mineralogical characterization were made for the wellsite, a barrian zeolite, which found as diagenetic alterations in the Miocene pyroclastic rocks in Gampo area. The wellsite occurs together with clinoptilolite, smectite and apatite as euhedral crystallites (0.2~0.4mm) forming interpenetraion twinning in the vesicles of altered pmice fragments. Compared to other reported wellsites, the wellsite is rather silicic (Si/(Al+Fe): 3.12-3.16) and Ca-rich. Unit cell dimensions and chemical formular determined from XRD, EMPA and TGA data are as follows:a=9.883$\AA$, b=14.204$\AA$, c=8.677$\AA$, $\beta$-124.764$^{\circ}$, (Ba0.57K0.36)(Ca1.18Na0.04)Al3.9Si12.1O32.13.9H2O.The cation composition of the Gampo wellsite, which shows an exchange reaction in the form of Ba2++Ca2+=2(K++Na-), is deviated far from the compositional range of a phillipsite-harmotome series. Due to higher abundance of divalent cations (Ca, Ba) and si in the wellsite, cimpared to those of the phillipsite and harmotome reported in other areas, the zeolite seems to be characteristic of higher water content (18.7 wt%) and higher thermal stability. XRD, chemical and thermo-chemical results of the wellsite reflects that wellsite is rather a Ba- and Ca-rich end member of a phillipsite-harmotome-wellsite series than an intermediate phase of phillipsite-harmotome series or a barrian variety of phillipste.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.178-189
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• 1994

Fine $BaTiO_3$ powder was synthesized from the various starting solution with 0.05 M by ultrasonic spray pyrolysis method. The conditions of synthesis were fixed on flow rate was 0.5 cm/sec, low temperature furnace was $300^{\circ}C$, and high temperatures furnace was $700^{\circ}C$. The formation procedure was investigated directly by SEM with the collected particle from the each reaction step. Also, the trace of particle in reaction tube was researched theoretically. Fine $BaTiO_3$ was synthesized only in the case of nitrate aqueous solution. The synthesized $BaTiO_3$ powder was porous and spherical which was consist of primary particle at the size of 19.1 nm. The formation procedure was as follows : the particle size decreased in drying step and then increased in initial thermal decomposition step. Finally, particle size was decreased to $0.42 {mu}m$. The trace of particle in reaction tube was also theoretically simulated and discussed.