• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.564-567
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• 1990

A lithiated compound $Li_{0.1}Pr^{3+}Ba_2Cu_3O_y$ has been successfully prepared by electrochemical method, which is achieved with a two electrode cell of the type: Metal(Li)/($Li^+\;,\;ClO_4^-$) + propylene carbonate/$PrBa_2Cu_3O_y$. All Pr ions in the lithiated compound are stabilized with a trivalent state as the other rare earths (Ⅲ) substituted in the 90K superconductor lattice ($Y_{1-x}Ln_x^-Ba_2Cu_3O_{7-{\delta}}$). Powder X-ray diffraction analysis shows that both compounds, $PrBa_2Cu_3O_y$ and $Li_{0.1}PrBa_2Cu_3O_y$ are isostructural with the 90 K superconductor, ($YBa_2Cu_3O_{7-{\delta}}$), nevertheless both of them are non-metallic and also non-superconducting down to 10 K. Magnetic susceptibility ${\chi}$ vs. temperature data indicate that Curie contribution from the magnetic ions (Pr and Cu) is weakened on the one hand, but on the other hand temperature-independent part of susceptibility ${\chi}_o$ increases depending upon the rate of lithium intercalation in $PrBa_2Cu_3O_y$ lattice.

• Journal of the Korean Magnetics Society
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• v.23 no.5
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• pp.149-153
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• 2013

The electronic structures of $TCr_2O_4$ (T = Fe, Co, Ni) spinel oxides have been investigated by employing synchrotron radiation-based soft X ray absorption spectroscopy (XAS). The measured 2p XAS spectra of transition-metal ions reveal that Cr ions are trivalent ($Cr^{3+}$), and all the T (T = Fe, Co, Ni) ions are divalent ($Fe^{2+}$, $Co^{2+}$, $Ni^{2+}$). It is also found that most of T (T = Fe, Co, Ni) ions occupy the A sites under the tetrahedral symmetry, while Cr ions occupy mainly the B sites under the octahedral symmetry. These findings show that the structures of $TCr_2O_4$ (T = Fe, Co, Ni) are very close to the normal spinel structures. Based on these findings, it is expected that Jahn-Teller (JT) effects are important in $FeCr_2O_4$ and $NiCr_2O_4$. In contrast, $CoCr_2O_4$ maintains the cubic structure without having the JT distortion since both $Cr^{3+}$ and $Co^{2+}$ ions are non-JT ions. This work suggests that the antiferromagnetic interaction between $Cr^{3+}$ and $T^{2+}$ ions plays an important role in determining the magnetic properties of $TCr_2O_4$ (T = Fe, Co, Ni).

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.156-161
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• 1998

We have measured changes of the non-stoichiometry, $\Delta\delta$, in Fe-doped nicked oxide , by thermogravimetry for four iron fractions, x=0.01, 0.031, 0.057 and 0.10, and three temperatures, T=1273, 1373 and 1473 K. The obtained data can be modelled by a defect structure in which substitutional trivalent iron ions, FeNi, are compensated by cation vacancies, $V_{Ni}$", and (4:1)-clusters. These clusters consist of tetravalent interstitial iron, $Fe_i\;^4$

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.4
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• pp.263-267
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• 2003

Magnetic nanoparticles prepared from an alkaline solution of divalent and trivalent iron ions could covalently bind protein via the activation of Nethyl-N-(3-dimethylaminopropyl) carbodiimide (EDC). Trypsin and avidin were taken as the model proteins for the formation of protein-nanoparticle conjugates. The immobilized yield of protein increased with molar ratio of EDC/nanoparticie. Higher concentrations of added protein could yield higher immobilized protein densities on the particles. In contrast to EDC, the yields of protein immobilization via the a ctivation of cyanamide were relatively lower. Nanoparticles bound with avidin could attach a single-stranded DNA through the avidin-biotin interaction and hybridize with a DNA probe. The DNA hybridization was confirmed by fluorescence microscopy observations. Immobilized DNA on nanoparticles by this technique may have widespread applicability to the detection of specific nucleic acid sequence and targeting of DNA to particular cells.

• Transactions on Electrical and Electronic Materials
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• v.2 no.2
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• pp.5-15
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• 2001

The experiment established optimal conditions for over-carbonization. With the use of the electron microscopy and X-ray phase analysis the regularities of carbon deposit formation in process of methane and propane pyrolysis on the zeolites, Kazakhstan natural clays, chrome and bauxite sludge containing metal oxides of iron subgroup, have been studied. In process of over-carbonization the trivalent iron was reduced to metal form. In addition, the carbon tubes of divers morphology had been impregnated with ultra-dispersed metal particles. The kinetic parameters of carbon formation in process of methane decomposition on the zeolite - CoO mixture surface were investigated by method of thermo-gravimetric analysis. The morphology and structure of formed carbon fibrils, with the metal particles fixed at their ends, have been investigated, the formation of branched carbon fibrils pattern, so called octopus, being found. Also, the walnut shells and grape kernel carbonization, their immobilization by the cells of selective absorption of heavy metal and sulfur dioxide ions have been studied. The example of metal-carbon composites used as adsorbents for wastewater purification, C$_3$- C$_4$ hydrocarbon cracking catalysts and refractory materials with improved properties have been considered.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.79-83
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• 1999

A cationic demand(CD) is a very useful indication for determining the optimum dosage rate of retention aids to the papermaking stock at the wet end. Polyelectrolyte titration has been most often used to determine a CD. Highly accurate results can be obtained by this method when the ionic strength of sample is low. But this is accompanied by the serious errors when the ionic strength is higher than that corresponding to 20 milli molar(mM) monovalent, 2 mM divalent or 0.2 mM trivalent ions because of no occurrence of the end point of titration. Therefore, it is very difficult or almost impossible for the conventional method to be applied to the industrial suspensions such as papermaking stock and industrial waste water. Then a novel method using chromophoric labeled cationic polymer which can be applicable to the sample with high ionic strength has been developed.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.72-78
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• 1993

The application of time-resolved laser induced fluorescence spectroscopy (TRLIF) to the complexation studies of Eu(III) and Cm(III) with humic substances is described. Using this method, three different spectroscopic characteristics(excitation spectra, emission spectra, and lifetimes) of these aquo ions and their complexes can be directly measured. By observing shifts in the wavelength and changes in the lifetime and intensities of the fluorescence emission, the information on the complexation behavior of humic substances with these trivalent metal cations in an aqueous solution, as well as energy transfer mechanisms, can be obtained. In addition, this method allows precise spectroscopic quantification of the complexation processes at very low concentrations of both components.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.161-166
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• 1999

Transfer of lanthanide ions across the liquid/liquid interface facilitated by ionopore ETH4120 has been studied by using cyclic voltammetry (CV) and chronopotentiometry with cyclic linear current-scanning (CPCLCS) under the condition where the concentration of ETH4120 in nitrobenzene was much smaller than the concentration of lanthanide ions in aqueous solution. One cathodic current peak (transfer from aqueous to nitrobenzene phase) and two anodic current waves (transfer from nitrobenzene to aqueous phase) were observed. The cathodic wave was due to the formation of 1:1 (metal:ligand) complex and two anodic waves showed successive formation of 1:2 and 1:3 complexes in nitrobenzene solution. But there was no cathodic wave corresponding to two anodic waves. The ion transfer mechanism has also been discussed.

• Korean Journal of Materials Research
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• v.23 no.9
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• pp.537-542
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• 2013

Two types of Tb- and Na-substituted green phosphors $Ca_{(1-1.5x)}WO_4:Tb_x^{3+}$: and $Ca_{(1-2x)}WO_4:Tb_x^{3+},Na_x^+$ were synthesized with various x values, using a solid-state reaction. The former phosphors contained both substitutional and vacancy point defects, while the later had only substitutional defects. X-ray diffraction results showed that the main diffraction peak, (112), was centered at $2{\theta}=28.72^{\circ}$ and indicated that there was no basic structural deformation caused by substitutions or vacancies. The photoluminescence emission and photoluminescence excitation spectra revealed the optical properties of trivalent terbium ions, $Tb^{3+}$. Typical transitions, $^5D_3{\rightarrow}^7F_6,\;^7F_5,\;^7F_4$ and $^5D_4{\rightarrow}^7F_6,\;^7F_5,\;^7F_4,\;^7F_3$, and cross relaxations were observed. Subtle differences in the photoluminescence of green phosphors were observed as a result of the point defects. The FT-IR spectra indicated that some of the ungerade vibrational modes had shifted positions and changed shapes, spreading out over a wide range of frequencies. This change can be attributed to the different masses of $Tb^{3+}$ and $Na^+$ ions and $V_{Ca}$" vacancies compared to $Ca^{2+}$ ions. The gerade normal modes of the Raman spectra exhibited subtle differences resulting from point defects in $Ca_{(1-1.5x)}Tb_xWO_4$ and $Ca_{(1-2x)}Tb_xNa_xWO_4$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.210-213
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• 2002

The blue phosphor, $BaMgAl_{10}O_{17}$:$Eu^{2+}$, showing a blue emission band at about 450 nm were prepared by solid state reaction of BaC $O_3$, A $l_2$ $O_3$, MgO and E $u_2$ $O_3$ with Al $F_3$ as a flux. The thermal quenching of BaMgAl $O_{17}$:E $u^{2+}$ phosphor significantly reduces the intensity of the blue emission. It is reduced by an amount of 50% after heating at around 800$^{\circ}C$ for 1 hr. The red emission in the 580∼720 nm region of $^{5}$ $D_{0}$\longrightarro $w^{7}$ $F_1$ and $^{5}$ $D_{0}$\longrightarro $w^{7}$ $F_2$ transition of $Eu^{3+}$ is produced from the phosphor heated above 1,100$^{\circ}C$. The EPR spectrum also reveals that some part of E $u^{2+}$ ions are oxidized to trivalent ions above 1,100$^{\circ}C$ at around 90 and 140mT. This oxidation evidence is also detected from XANES absorption spectra for $L_{III}$ shell of Eu ions: an absorption peak is at 6,977eV of E $u^{2+}$ and 6,984eV of $Eu^{3+}$. The combined X-ray and neutron data suggests that the new phase of EuMgA $l_{11}$ $O_{19}$ magnetoplumbite structure may be formed by heat treatment.eat treatment.tment.eat treatment.tment.t.