• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.89-94
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• 2013

Layered $Li_{1+x}(Mn_{0.4}Ni_{0.4}Fe_{0.2})_{1-x}O_2$ (0 < x < 0.3) solid solutions were synthesized using solgel method with adipic acid as chelating agent. Structural and electrochemical properties of the prepared powders were examined by means of X-ray diffraction, Scanning electron microscopy and galvanostatic charge/discharge cycling. All powders had a phase-pure layered structure with $R\bar{3}m$ space group. The morphological studies confirmed that the size of the particles increased at higher x content. The charge-discharge profiles of the solid solution against lithium using 1 M $LiPF_6$ in EC/DMC as electrolyte revealed that the discharge capacity increases with increasing lithium content at the 3a sites. Among the cells, $Li_{1.2}(Mn_{0.32}Ni_{0.32}Fe_{0.16})O_2$ (x = 0.2)/$Li^+$ exhibits a good electrochemical property with maximum initial capacity of 160 $mAhg^{-1}$ between 2-4.5 V at 0.1 $mAcm^{-2}$ current density and the capacity retention after 25 cycles was 92%. Whereas, the cell fabricated with x = 0.3 sample showed continuous capacity fading due to the formation of spinel like structure during the subsequent cycling. The preparation of solid solutions based on $LiNiO_2-LiFeO_2-Li_2MnO_3$ has improved the properties of its end members.

• Journal of Magnetics
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• v.18 no.3
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• pp.221-224
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• 2013

Electron paramagnetic resonance (EPR) spectra of $Mn^{2+}$ impurity ion in Stoichiometric $LiNbO_3$ single crystal (SLN) was investigated with an X-band EPR spectrometer in the temperature range of 3 K~296 K. The intensity of EPR spectrum of $Mn^{2+}$ ion was increased to 20 K and decreased again below 20 K as the temperature decreases. The zero-field splitting parameter D decreased as the temperature increases. It was suggested that $Mn^{2+}$ ion substitute for $Nb^{5+}$ ion instead of $Li^+$ ion. No changes for hyperfine interaction of $Mn^{2+}$ ion was obtained in the temperature range of 3 K~296 K.

• Journal of the Korean Magnetics Society
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• v.13 no.5
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• pp.204-210
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• 2003

Electron magnetic resonance (EMR) of paramagnetic Cr$^{3+}$, Mn$^{2+}$, and Fe$^{3+}$ impurity ions in ferroelectric LiNbO$_3$ and LiTaO$_3$ single crystals has been studied. The actual sites location of paramagnetic impurity ions in the crystals was suggested from the experimental results and zero field splitting parameters calculated by superposition model. It turns out that Cr$^{3+}$ ions in LiNbO$_3$ crystal have two resonance centers and enter both the Li$^{+}$ and Nb$^{5+}$ ions. Mn$^{2+}$ and Fe$^{3+}$ impurity ions in LiNbO$_3$ substitute for Nb$^{5+}$ ions. However, both Cr$^{3+}$ and Fe$^{3+}$ ions in LiTaO$_3$ crystal reside at Li$^{+}$ ions.$ +/ ions.+/ ions.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.80-86
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• 2016

High Ni content layered oxide materials for the positive electrode in lithium-ion batteries have high specific capacity. However, their poor electrochemical and thermal stability at elevated temperature restrict the practical use. A small amount of $Al_2O_3$ was added to the mixture of transition metal hydroxide and lithium hydroxide. The $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ was simultaneously doped and coated with $Al_2O_3$ during heat-treatment. Electrochemical characteristics of modified $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ were evaluated by the galvanostatic cycling and the LSTA(linear sweep thermmametry) at the constant voltage conditions. The nano-sized $Al_2O_3$ added materials show better cycle performance at elevated temperature than that of micro-sized $Al_2O_3$. As the added amount of nano-$Al_2O_3$ increased, the thermal stability of electrode also enhanced, but the use of 2.5 mol% Al showed the best high temperature performance.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.14-22
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• 2020

Purpose: The aim of this study is to evaluate the effectiveness of MnO₂-diatom microbubbler (DM) on the surface of prosthetic materials as a mouthwash by comparing the biofilm removal effect with those previously used as a mouthwash in dental clinic. Materials and methods: DM was fabricated by doping manganese dioxide nanosheets to the diatom cylinder surface. Scanning electron microscopy (SEM) was used to observe the morphology of DM and to analyze the composition of doped MnO₂. Stereomicroscope was used to observe the reaction of DM in 3% hydrogen peroxide. Non-precious metal alloys, zirconia and resin specimens were prepared to evaluate the effect of biofilm removal on the surface of prosthetic materials. And then Streptococcus mutans and Porphyromonas gingivalis biofilms were formed on the specimens. When 3% hydrogen peroxide solution and DM were treated on the biofilms, the decontamination effect was compared with chlorhexidine gluconate and 3% hydrogen peroxide solution by crystal violet staining. Results: Manganese dioxide was found on the surface of the diatom cylinder, and it was found to produce bubble of oxygen gas when added to 3% hydrogen peroxide. For all materials used in the experiments, biofilms of the DM-treated groups got effectively removed compared to the groups used with chlorhexidine gluconate or 3% hydrogen peroxide alone. Conclusion: MnO₂-diatom microbubbler can remove bacterial membranes on the surface of prosthetic materials more effectively than conventional mouthwashes.

• Proceedings of the Korean Magnestics Society Conference
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• 2015.11a
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• pp.150-150
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• 2015

• Journal of Surface Science and Engineering
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• v.52 no.6
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• pp.350-356
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• 2019

In this study, the effect of mechanical polishing of carbon steel on the tribological properties of manganese phosphate coating on carbon steel has investigated. The microstructure, surface morphology and chemical composition were analyzed by SEM, EDS, and XRD. The surface roughness test was carried out in order to calculate Rvk value by 3D laser microscopy. Also, the tribology property of manganese phosphate coating was tested by ball-on disk. In the results of EDS analysis, coating layer consists of elements such in Mn, P, Fe, and O. XRD showed that (Mn,Fe)₅H₂(PO₄)₄·4H₂O in manganese phosphate coating layer was formed by the chemical reaction between manganese phosphate and elements in carbon steel. As the mechanical polishing degree increased, the friction coefficient was reduced. The rougher the mechanical polishing degree, the better corrosion resistance was obtained.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4205-4209
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• 2011

The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ silicate was prepared by blending of $Li_2MnSiO_4$ and $Li_2FeSiO_4$ precursors with same molar ratio. The one of the silicates of $Li_2FeSiO_4$ is known as high capacitive up to ~330 mAh/g due to 2 mole electron exchange, and the other of $Li_2FeSiO_4$ has identical structure with $Li_2MnSiO_4$ and shows stable cycle with less capacity of ~170 mAh/g. The major drawback of silicate family is low electronic conductivity (3 orders of magnitude lower than $LiFePO_4$). To overcome this disadvantage, carbon composite of the silicate compound was prepared by sucrose mixing with silicate precursors and heat-treated in reducing atmosphere. The crystal structure and physical morphology of $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ was investigated by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$/C nanocomposite has a maximum discharge capacity of 200 mAh/g, and 63% of its discharge capacity is retained after the tenth cycles. We have realized that more than 1 mole of electrons are exchanged in $Li_2Mn_{0.5}Fe_{0.5}SiO_4$. We have observed that $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ is unstable structure upon first delithiation with structural collapse. High temperature cell performance result shows high capacity of discharge capacity (244 mAh/g) but it had poor capacity retention (50%) due to the accelerated structural degradation and related reaction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.136-141
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• 2005

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics using Li$_2$CO$_3$, Bi$_2$O$_3$, and CuO as sintering aids were manufactured according to the amount of MnO$_2$ addition. Their microstructural, dielectric and piezoelectric properties were investigated. When the sintering aids were added, specimens could be sintered below 95$0^{\circ}C$, but mechanical qualify factor decreased. Therefore, MnO$_2$ was added excessively to the PCW-PMN-PZT ceramics to increase mechanical quality factor. At the sintering temperature of 95$0^{\circ}C$, the density, dielectric constant($\varepsilon$$_{r}$), electromechanical coupling factor(k$_{p}$), mechanical quality factor(Q$_{m}$) and Curie temperature(T$_{c}$) of 0.1 wt% MnO$_2$ added specimen showed the optimal values of 7.75 g/㎤, 1503, 0.57, 1502, and 337, respectively, for multilayer piezoelectric transformer application.ation.n.

• Journal of Magnetics
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• v.10 no.3
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• pp.95-98
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• 2005

We report hole-induced ferromagnetism in diluted magnetic semiconductor $Zn_{0.99}Mn_{0.01}$ films grown on $SiO_2/Si$ substrates by reactive sputtering. The p-type conduction with hole concentration over $10^{18}\;cm^{-3}$ is achieved by P doping followed by rapid thermal annealing at $800^{\circ}C$ in a $N_2$ atmosphere. The p-type $Zn_{0.99}Mn_{0.01}O:P$ is carefully examined by x-ray diffraction and transmission electron microscopy. The magnetic measurements for $p-Zn_{0.99}Mn_{0.01}O:P$ clearly reveal ferromagnetic characteristics with a Curie temperature above room temperature, whereas those for $n-Zn_{0.99}Mn_{0.01}O:P$ show paramagnetic behavior. The anomalous Hall effect at room temperature is observed for the p-type film. This result strongly supports hole-induced room temperature ferromagnetism in $p-Zn_{0.99}Mn_{0.01}O:P$.