• Journal of the Korean Magnetics Society
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• 제22권4호
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• pp.125-129
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• 2012

By employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD), the electronic structures of molecule-based nano bioparticles, such as Helicobacter pylori ferritin (H. pylori ferritin), Heme, $NaM[Fe(CN)_6]{\cdot}H_2O$-type Prussian Blue (M=Co, Ni) analogue, have been investigated. The measured Fe 2p XAS spectra reveal that Fe ions are trivalent ($Fe^{3+}$) in H. pylori ferritins, while they are in the $Fe^{2+}-Fe^{3+}$ mixed-valent states in $NaM[Fe(CN)_6]{\cdot}H_2O$ Prussian Blue analogues (M=Co, Ni). According to the Fe 2p XMCD spectrum of high-state H. pylori ferritin, all the $Fe^{3+}$ ions have the same local symmetry and their magnetic moments are aligned in the same direction. It is also found that the Fe 3d orbitals in $NaM[Fe(CN)_6]{\cdot}H_2O$ have a strong covalent bonding to $(CN)^-$ ligands, but with a very weak bonding to the 2p orbitals of O ligands.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.307-307
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• 2010

최근 유한연료의 고갈로 인해 세계 유가가 불안정 됨으로서 대체 에너지에 대한 연구가 많이 진행 되고 있다. 특히 압전 소자를 이용한 에너지 하베스팅은 압전 역효과를 이용한 것으로서 주변에서 무의미하게 버려지는 진동이나 바람, 열 에너지를 실 생활에 사용할 수 있는 전기 에너지로 변환할 수 있는 유망한 기술 중 하나이다. 이러한 에너지 하베스팅 기술은 일본과 같은 선진국에서 이미 지하철 및 일반 다리와 같이 진동이 극히 많은 곳에서 응용되고 있다. 이러한 에너지 하베스팅 기술을 응용 하려면 전압출력 계수($g_{33}$)가 높아야 한다. 이것은 압전 d 상수와 유전상수에 영향을 많이 받는 것으로 알려져 있다. 현재가지 응용되는 압전 하베스팅 조성은 Pb(Zr,Ti)$O_3$ (PZT)를 기초로한 세라믹이 응용되고 있다. Pb(Zr,Ti)$O_3$ (PZT) 세라믹은 Morpohotropic phase boundary(MPB)에서 전기기계 결합계수 (kp) 와 기계적 품질계수 (Qm) 이 각각 0.5와 500으로 우수한 특성을 나타낸다. 또한 큐리온도 (Tc) 도 $400^{\circ}C$로 온도 안정성 또한 높다. 하지만 $1000^{\circ}C$ 이상에서 소결하는 PbO는 소결 중 급격한 휘발로 환경적 오염 뿐 아니라 특성의 저하를 야기시킨다. 그래서 몇몇 나라에서는 그 사용을 제한하고 점차적으로 사용을 줄여 나가고 있는 동시에 PbO가 첨가되어 있지 않은 Lead-Free 세라믹의 연구가 많이 진행되고 있다. Lead-Free 세라믹 중 alkaline niobate를 기초로 한 페로브스카이트 구조의 ($Na_{0.5}K_{0.5})NbO_3$ (NKN) 은 PbO를 기초로 한 세라믹을 대체할 유망한 후보자 중 하나이다. 하지만 NKN세라믹의 K 성분의 조해성 및 고온에서의 휘발로 인해 일반 적인 소결 방법으로는 고밀도의 세라믹을 얻기 매우 어렵다. 그래서 Hot pressing, Hot forging, RTGG(Reactive Template Grain Growth), SPS(Spark plasma Sintering)와 같은 특별한 소결 법을 이용하거나 $K_8CuNb_4O_{23}$(KCN) 이나 $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$(KCT) 등을 첨가하여 그 소결성을 향상 시키는 방법도 있다. 또한 압전 d상수를 향상 시키기 위해 $Nb_2O_5$나, $La_2CO_3$, $CeO_2$, $Li_2CO_3$ 등을 치환함으로써 압전 d상수를 향상 시켜 전압출력 계수를 높이는 연구 또한 많은 보고가 되어 있다. 특히 $Li_2CO_3$의 첨가는 일반 적인 소결 방법으로도 밀도의 조밀함을 향상 시켜 그에 따른 높은 유전율과 전기기계 결합계수, 압전 d상수를 가져 많은 연구가 되어지고 있다. 그래서 본 연구에서는 일반적인 ($K_{0.5}N_{0.5})_{1-x}Li_x(Nb_{0.96}Sb_{0.04})O_3$ + 0.2mol%$La_2O_3$ + 1.2mol%$K_8CuNb_4O_{23}$ 세라믹에 x(=Li) 치환에 따른 유전 및 압전특성을 조사하였다.

• The Korean Journal of Ceramics
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• 제1권4호
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• pp.209-213
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• 1995

The electrical conductivity was investigated in two series of alkali aluminosilicate glass melts, $25R_2O(R: Na and K)-xAl2O3-(75-x)SiO_2$ at temperatures ranging from 1000 to 140$0^{\circ}C$. The dependences of conductivity or activation energy on $Al_2O_3/R_2O$ of both series in the molten state showed a same behavior. These results in the molten state were compared with previous studies for sodium alkali aluminosilicate glasses in the molten and solid state, and explained in terms of the binding state: $[-O]-R^+\; and\; [AlO_4]-R^+$.

• Economic and Environmental Geology
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• 제43권3호
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• pp.269-278
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• 2010

We investigated characteristics of the coloring material of Dancheong pigments and hope that this study contributes the revival of traditional Dancheong pigments color. For this purpose, we collected Dancheong fragment samples that fell off naturally from old wooden buildings in Gwangju and Jeonnam and analyzed the natural coloring material by XRD and EDS-SEM analysis method. In white pigments of Dancheong fragments, it is confirmed that gypsum$(CaSO_{4}{\cdot}2H_{2}O)$, quartz$(SiO_{2})$, white lead$(PbCO_{3})$ and calcite$(CaCO_{3})$ which have been used for white pigments since ancient times and $TiO_{2}$ which is common used in modern times. In red pigments of Dancheong fragments, it is confirmed that hematite$(Fe_{2}O_{3})$ and red lead$(Pb_{3}O_{4})$, which have been used for red pigments since ancient times and C.I. pigment orange $13(C_{32}H_{24}C_{12}N_{8}O_{2})$ but there is no cinnabar(HgS) which has been used since B.C. 3000 in China. In yellow pigments of Dancheong fragments, it is confirmed that crocoite$(PbCrO_{4})$ and massicot(PbO). In blue pigments of Dancheong fragments, it is confirmed that sodalite$(Na_{4}BeAlSi_{4}O_{12}Cl)$ and nosean $(Na_{8}Al_{6}Si_{6}O_{24}SO_{4})$ as coloring material of blue pigment and C.I. pigments blue $29(Na_{7}Al_{6}Si_{6}O_{24}S_{3})$ which is used in modern times. In green pigments of Dancheong fragments, it is confirmed that calumetite$(Cu(OHCI)_{2}{\cdot}2H_{2}O)$, escolaite(Cr2O3), dichromium trioxide$(Cr_{2}O_{3})$, emerald green$(C_{2}H_{3}As_{3}Cu_{2}O_{8})$, and C.I. pigments green$(C_{32}H_{16}-XCl_{x}Cu_{8})$ which is used in modern time. In black pigments of Dancheong fragments, Chiness ink(carbon black) is confirmed.

• Journal of the Korean Electrochemical Society
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• 제16권2호
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• pp.59-64
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• 2013

Using $Na_2CO_3$ and $MeSO_4$ (Me = Ni, Co and Mn) as starting materials, the precursor of $[Ni_{0.6}Co_{0.2}Mn_{0.2}]CO_3$ has been synthesized by carbonate co-precipitation. The precursor was mixed with $Li_2CO_3$, and calcined at 750, 850, and$950^{\circ}C$ in air. Effect of calcinations temperature on characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ cathode materials was investigated. The structure and characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ were determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrochemical measurements. The X-ray diffraction (XRD) results show that the intensity ratio of $I_{(003)}/I_{(104)}$ increased and the R-factor ratio decreased with the increase of calcinations temperature. And Scanning electron microscopy (SEM) result show that the primary particle size increased. Especially, the $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ calcined at $950^{\circ}C$ for 24 H shows excellent electrochemical performances with reversible specific capacity of $165.3mAhg^{-1}$ [cut-off voltage 2.5~4.3 V, 0.1 C($17mAhg^{-1}$)] and good capacity retention of 95.4% after 50th charge/discharge cycles[cut-off voltage 2.5~4.3 V, 1 C($170mAhg^{-1}$)].

• Transactions on Electrical and Electronic Materials
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• 제11권3호
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• pp.126-129
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• 2010

(1-X) $(Na_{0.5}K_{0.5})NbO_3-X$ $K_4CuNb_8O_{23}$ (NKN-X KCN) ceramics were produced using the conventional solid state sintering method, and their sinterability and electric properties were investigated. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCN content and the sintering temperature. In particular, the KCN addition to the NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 2.0 mol% sintered at $1,150^{\circ}C$ possesses the optimum properties (${\varepsilon}_r=241$, $d_{33}=78$, $k_p=0.34$ and $Q_m=1,121$). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제29권4호
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• pp.210-214
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• 2016

We investigated the sintering behavior and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics co-doped with excess 0.01 mol ZnO and x mol $MnO_2$, where x was varied from 0 to 0.03. Excess $MnO_2$ addition was found to retard the grain growth and densification during sintering. However, 0.005 mol $MnO_2$ addition improved the piezoelectric properties of 0.01 mol ZnO added $(K_{0.5}Na_{0.5})NbO_3$ ceramics. The planar mode piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric constant $d_{33}$ of 0.01 mol ZnO and 0.005 mol $MnO_2$ added specimen were 0.40, 304, and 214 pC/N, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.172.1-172.1
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• 2011

본 연구에서는 매립지에서 발생하는 주요한 가스인 $CO_2$(47~55%)와 $CH_4$(47~55%)가스를 분리하기 위하여 여러 $CO_2$ capture 방법 중 Zeolite를 사용한 흡착법을 이용하였다. 국내에서 시판되고 있는 powder형 Zeolite 13X에 Inorganic binder와 organic binder를 최적의 비율로 혼합한 후 증류수를 이용하여 Pellet type 흡착제를 제조하였다. 또한 최종적으로 $CO_2$의 흡착능을 높이기 위하여 양이온(1M의 KCl, NaCl, $CaCl_2$, $LiCl_2$)으로 이온교환을 하였다. 매립지 모사가스($CO_2$:40%, $CH_4$:60%)를 이용하여 실시간 분석기(Delta1600S)를 이용 두 가스의 분리와 $CO_2$ 흡착성능(mg-CO2/g-흡착제)을 확인하였다. 개발된 흡착제(AjouEpl 13X)는 ICP, XRD, XRF, BET 분석으로 제올라이트의 구조와 성분을 분석하였다.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.327-330
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• 2010

$LiCoO_2$, a cathode material for lithium rechargeable batteries, was prepared in a nanoscale through a simple sonochemistry. First, $Co_3O_4$ nanoparticles were prepared by reacting NaOH and $CoCl_2$ or $CoSO_4$ with a sonochemical method, operated at 20 kHz and 220 W for 20 min, very powerful multibubble sonoluminescence conditions for chemical reactions. Second, LiOH was coated onto the $Co_3O_4$ nanoparticles by the same method as above. Finally, $LiCoO_2$ nanoparticles of about 10~30 nm size in diameter were obtained by the thermal treatment of the resulting LiOH-coated $Co_3O_4$ nanoparticles at $500^{\circ}C$ for 3 hr. This synthetic process is relatively quite mild and simple compared to the known method for the synthesis of $LiCoO_2$ nanoparticles. The materials synthesized were characterized by infrared spectroscopy, X-ray diffraction, inductively coupled plasma spectrometer, and high resolution-transmission electron microscopy analyses.

• Conservation Science in Museum
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• 제16권
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• pp.138-153
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• 2015

Wooden standing Bodhisattva in the collection of the National Museum of Korea (Bon 8239) was purchased as part of the museum's Central Asian collection during the Museum of Japanese Goverment General of Korea. The wooden statue exhibiting classical characteristics of Song Dynasty Buddhist sculptures is colored on the whone. The result of condition check for exhibition in 2014, it has severely damaged, with discoloring and exfoliation in color pigment and crack of wood observed in various areas. The object was therefore treated for conservation. A series of analysis were performed also at this time to determine the production technique and the materials, including testing of the X-ray penetration depth, X-ray fluorescence analysis and wood species analysis. This revealed that the statue was made by joining several separate pieces of wood. As for color pigments, the white pigment was either chalk (CaCO₃) or gypsum(CaSO₄·2H₂O), and the green pigment was emerald green (Cu(C₂H₃O₂)₂·3Cu(AsO₂)₂). The red pigment appeared to be lead red(Pb₃O₄) and the blue pigment was ultramarine blue (3Na₂O·3Al₂O₃·6SiO₂·2Na₂S). All the pigments were repainted in later eras. The analysis, indicated that the wood was derived from a tree of the genus Populus, family Salicaceae. The wooden standing Bodhisattva was repaired and reinforced with natural materials and was brought to a stable condition necessary for display.