• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.47-50
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• 2007

[ $ZnCr_2O_4$ ] shows geometrically frustrated magnet. Recently, $CoCr_2O_4$ has been investigated for multiferroic property and dielectric anomalies by spin-current model. Polycrystalline $CoCr_2O_4$ and $CoCrFeO_4$ compounds was prepared by wet-chemical process. Crystallographic and magnetic properties of $CoCr_2O_4$ and $CoCrFeO_4$ were investigate by using the x-ray diffractometer(XRD), vibrating sample magnetometer(VSM), superconducting quantum interference device magnetometer(SQUID), and $M\"{o}ssbauer$ spectroscopy. The crystal structure was found to be single-phase cubic spinel with space group of Fd3m. The lattice constants of $CoCr_2O_4$ and $CoCrFeO_4$ $a_0$ were determined to be 8.340 and 8.377 ${\AA}$, respectively. The ferrimagnetic transition temperature for the both samples were observed at 97 K and 320 K. The $M\"{o}ssbauer$ absorption spectra at 4.2 K show that the well developed two sextets are superposed with small difference of hyperfine field($H_{hf1}=507\;and\;H_{hf2}=492\;kOe$). Isomer shift values($\delta$) of the two sextets are found to be 0.33 and 0.34 mm/s relative to the Fe metal, respectively, which are consistent with the high spin $Fe^{3+}$ charge state.

• Journal of the Korean Chemical Society
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• v.23 no.3
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• pp.141-151
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• 1979

The selective absorption of metal ions by chelating agent-loaded resins was studied in aqueous media. The resins were prepared by loading the conventional anion exchange resin, Dowex 1-X8 (50 to 100 mesh) with chelating agents containing sulfonic group, such as 8-hydroxy-quinoline-5-sulfonic acid (HQS) and 7-nitroso-8-hydroxyquinoline-5-sulfonic acid (NHQS). The stability of the resin was markedly influenced by the following factors; (1) the affinity and concentration of anions in the external solution, (2) the pH of the media. The optimum conditions for the absorption of metal ions were determined with respect to the pH, shaking time, and the effect of anion concentration in the medium. Under the optimum condition the order of the absorption of metal ions such as Fe(Ⅲ), Cu(Ⅱ), Pb(Ⅱ), and Zn(Ⅱ) was in accord with that of the stability constants of the chelates. The total capacities of the resins were found in the range of 0.6∼1.6 mmole metal per gram.

• Journal of Life Science
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• v.8 no.5
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• pp.598-603
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• 1998

A marine microbe, Vibrio anguillarum was isolated from fish and studied for its concerning pathogenic substance of hemolysin. Purification of hemolysin was achieved by the procedure of ammonium sulfate precipitation from cul-ture filtrate, DEAE-cellulose chromatography, and G-200 gel filtration with 36 fold of purification and 2.3% yield. The molecular weight of the purified hemolysin was 38,000 dalton by SDS-PAGE. The purified hemolysin was stable at pH 6-9, below 45$^{\circ}C$, and up to 1% of NaCl, respectively. $Ca^{2+}, Cu^{2+}, Zn^{2+}, Fe^{2+}$ inhibited the hemolytic activity whereas EDTA and $Mg^{2+}$ did not.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.34-37
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• 2007

The crystallographic and magnetic properties of $Fe_{0.9}Zn_{0.1}Cr_2S_4$ have been studied by X-ray diffractometer(XRD), vibrating sample magnetometer(VSM) and $M\"{o}ssbauer$ spectroscopy measurement. The crystal structure was determined by the normal cubic spinel of space group Fd3m and the lattice constant was $a_0=9.9967\;{\AA}$. The specific phenomenon which looks like cusp pattern at 77 K was observed in magnetization corves(ZFC : Zero Field Cooling) under 100 Oe applied field. $N\acute{e}el$ temperature($T_N$) was determined to be 153 K by VSM and $M\"{o}ssbauer$ spectra. The asymmetric 8-line profile has been observed at 4.2 K, which was attributed by the colossal electric quadupole interaction(${\Delta}E_Q$), ${\Delta}E_Q$ has 2.22 mm/s at 4.2 K. The ${\Delta}E_Q$ abruptly decreases around 77 K and then it disappears above 77 K with diminishing of 8-line pattern. The isomer shift $\delta$ at room temperature is 0.48 mm/s relative to Fe metal, which means that the charge state of Fe ions is ferrous in character.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.747-751
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• 2010

In the study, the characteristics of the etched Zinc oxide (ZnO) thin films surface, the etch rate of ZnO thin film in $Cl_2/BCl_3/Ar$ plasma was investigated. The maximum ZnO etch rate of 53 nm/min was obtained for $Cl_2/BCl_3/Ar$=3:16:4 sccm gas mixture. According to the x-ray diffraction (XRD) and atomic force microscopy (AFM), the etched ZnO thin film was investigated to the chemical reaction of the ZnO surface in $Cl_2/BCl_3/Ar$ plasma. The field emission auger electron spectroscopy (FE-AES) analysis showed an elemental analysis from the etched surfaces. According to the etching time, the ZnO thin film of etched was obtained to The AES depth-profile analysis. We used to atomic force microscopy to determine the roughness of the surface. So, the root mean square of ZnO thin film was 17.02 in $Cl_2/BCl_3/Ar$ plasma. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the plasmas.

• Korean Journal of Plant Tissue Culture
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• v.27 no.1
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• pp.31-37
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• 2000

Proton extrusion by hairy roots of Panax ginseng C.A. Meyer was enhanced by iron-deficiency or single salt solutions of nitrate or ammonium salts. The enhancement effect of iron-deficiency was confined to the apical zones, whereas that of nitrate and ammonium was confined to the basal root zones. tinder iron-deficiency medium, the proton extrusion of ginseng hairy roots was higher at two times than that grown in the medium of iron-sufficiency. According to pH in the medium, uptake of inorganic elements showed various patterns for the kind of inorganic elements. $Ca^{2＋}$, $Mg^{2＋}$ and Fe$^{2＋}$ were highest uptake at the pH 4.8 and Mn$^{2＋}$, Zn$^{2＋}$ and Cu$^{2＋}$ were highest uptake at the pH 3.8. Free sugars and ginsenosides were analyzed by HPLC. Five kinds of free sugars were indentified in ginseng hairy roots. Glucose, fructose and sucrose were a major sugar in ginseng hairy roots and contents of free sugars were highest at pH 6.8 and pH 4.8, respectively. The contents of ginsenosides and phenolic compounds were highest at pH 5.8. This physiological responses in ginseng hairy root indicated that it may well be a good model system for the study of mechanism of mobilization and uptake of inorganic elements related with the red-colored phenomenon in ginseng roots.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.712-720
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• 2008

Sediment and interstitial water samples from ten lagoons in the Northeastern coastal part of South Korea were analyzed to obtain the concentrations of metals and inorganic ligand. These data, coupled with pH and ionic strength, were used to compute the aqueous speciation of the metals in the interstitial water using the MINTEQA2 equilibrium program. The K and Na were almost entirely present as the free aqua ions, but Co, Cd, Ni, Pb and Zn were existed as various metal-ligand complexes. Metals such as Al, As, and Cr formed 3$\sim$4 metal-ligand complexes. In the interstitial water with high chloride concentrations, almost all of the metals were dominated by free aqua ions. Metals of Cd, Co, Ni, Pb and Zn were bound as chloride-metal complexes of the type M$^{x+}$ + xCl$^-$, and Fe, Mn and Mg were dominated by sulfate equilibria(M$^{2+}$ + SO$_4{^{2-}}$). Hg(II) was speciated as HgCl$_2$(aq), HgCl$_3{^-}$ and HgCl$_4{^-}$. However, in the interstitial water with low chloride concentrations, Hg(II) and Cd(II) were existed as chloride-metal complexes, metals of Cu, Mg, Mn, Ni, Pb and Zn were dominated by sulfate equilibria, and the speciation of Fe(II) was bound as Fe(OH)$_2{^+}$, Fe(OH)$_3$(aq). However, Al, As and Cr were dominated by hydroxy-metal and oxide-metal species in nearly all of the lagoons.

• Journal of Adhesion and Interface
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• v.12 no.4
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• pp.133-137
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• 2011

Exfoliated graphite oxide (EGO) was prepared by graphite oxide in an aqueous solution of TMAOH. The hybrid graphene/Zn-Al LDH material was fabricated by the hydrothermal reduction of the solution of EGO, $Zn(NO_3)_2{\cdot}6H_2O$, $Al(NO_3)_3{\cdot}9H_2O$, urea, and trisodium citrate. That is, metal ions were absorbed on the surface of EGO, and Zn-Al LDH material was randomly dispersed on the surface of graphene along with a reduction process of EGO to graphene by hydrothermal treatment. The composition, morphology, and thermal property of the obtained graphene-based hybrid material were studied by FE-SEM, EDX, TEM, FT-IR, XRD, TGA, and DSC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.253-257
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• 2008

To enhance the luminescence properties, the red phosphor composed of $(Y,\;Zn)_2O_3$:$Eu^{3+}$ as doping concentration of Zn ion is synthesized at $1200^{\circ}C$ for 6 hrs in air atmosphere by conventional solid reaction method. As a result of the red phosphor $(Y,\;Zn)_2O_3$:$Eu^{3+}$ is measured X-ray diffraction (XRD), The main peak is nearly corresponded to the same as JCPDS card (No. 41-1105). When the doping concentration of Zn ion is more than 5 mol%, However, the ZnO peak is showed by XRD analysis. Therefore, when the doping concentration of Zn ion is less than 5 mol%, the Zn ion is well mixed in $Y_2O_3$ structure without the impurity phases. The photoluminescence (PL) properties is shown as this phosphor is excited in 254 nm region and the highest emission spectra of $(Y,\;Zn)_2O_3$:$Eu^{3+}$ has shown in 612 nm region because of a typical energy transition ($^5D_0{\rightarrow}^7F_2$) of $Eu^{3+}$ ion. As the doping concentration of Zn ion is more than 10 mol%, the emission peak is suddenly decreased. when the highest emission peak as doping concentration of Zn ion is shown, the composition of this phosphor is $(Y_{0.95},\;Zn_{0.05})_2O_3$:$Eu^{3+}_{0.075}$ and the particle size analyzed by FE-SEM is confirmed from 0.4 to $3{\mu}m$.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.132-136
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• 2003

폐광된 광산에 방치된 폐광석에 함유되어 있는 황화광물이 분해되어 다른 광물에 흡착되거나, 산화환경에 안정한 형태의 2차 광물로 침전 혹은 공침 되는가에 대한 연구는 광산복 원을 결정하는데 직접적인 지구화학적 자료로 활용될 수 있다. 따라서 이번 연구에서는 청양광산에 방치된 폐광석을 대상으로 XRD, SEM/EDS연구를 이용하여 산화작용으로 인한 황화광물 주변에 침전된 2차 광물에 대한 광물학적 연구를 수행하였다. 광물학적 연구 결과, 산화환경에서 황화광물의 산화작용으로 인하여 용출된 중금속 이온과 철과 망간 이온들은 침전(Fe, Mn, Pb), 공침 (Fe, Mn, As, Pb) 및 흡착(As, Cu, Pb, Zn) 등의 화학반응을 통하여 다시 고정화됨으로서, 현장에서 자연적으로 정화되고 있는 것이 확인되었다.