• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.856-862
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• 1998

Vanadium oxide catalyst supported on ZrO2-WO3 was prepared by adding the Zr(OH)4 powder into a mixed aqueous solution of ammonium metavanadate and ammonium metatungstate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using solid-state 51V NMR and FTIR. In the case of calcination temperature at 773 K, for the samples containing low loading V2O5 below 18 wt % vanadium oxide was in a highly dispersed state, while for samples containing high loading V2O5 equal to or above 18 wt % vanadium oxide was well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of ZrO2-WO3. The ZrV2O7 compound was formed through the reaction Of V2O5 and ZrO2 at 873 K and the compound decomposed into V2O5 and ZrO2 at 1073 K, which were confirmed by FTIR and 51V NMR.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.218-221
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• 2004

The electronic state of ZnO doped with Al, Ga and In, which belong to III family elements in periodic table, was calculated using the density functional theory. In this study, the program used for the calculation on theoretical structures of ZnO and doped ZnO was Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The detail of electronic structure was obtained by the describe variational $X{\alpha}(DV-X{\alpha})$(DV-Xa) method, which is a sort of molecular orbital full potential method. The optimized crystal structures obtained by calculations were compared to the measured structure. The density of state and energy levels of dopant elements was shown and discussed in association with properties.

• Bulletin of the Korean Chemical Society
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• 제33권10호
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• pp.3213-3217
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• 2012

Reactive adsorption desulfurization (RADS) experiments were conducted over a series of commercial metal oxide supports ($Al_2O_{3-}$, $SiO_{2-}$, $TiO_{2-}$ and $ZrO_{2-}$) supported Ni/ZnO adsorbents. The adsorbents were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), and Fourier transform infrared spectroscopy (FTIR) in order to find out the influence of specific types of surface chemistry and structural characteristics on the sulfur adsorptive capacity. The desulfurization performance of all the studied adsorbents decreased in the following order: Ni/ZnO-$TiO_2$ > Ni/ZnO-$ZrO_2$ > Ni/ZnO-$SiO_2$ > Ni/ZnO-$Al_2O_3$. Ni/ZnO-$TiO_2$ shows the best performance and the three hour sulfur capacity can achieve 12.34 mg S/g adsorbent with a WHSV of $4h^{-1}$. Various characterization techniques suggest that weak interaction between active component and support component, high dispersion of NiO and ZnO, high reducibility and large total Lewis acidity of the adsorbents are important factors in achieving better RADS performance.

• 한국세라믹학회지
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• 제27권3호
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• pp.423-429
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• 1990

YBa2Cu3Ox ceramics superconductors fabricated using solid state reaction usually contain second phases, such as BaCuO2 and CuO. These second phases are located long the grain boundaries and enhance the abnormal growth of YBa2Cu3Ox grains and, consequently, generate the microcracks. These second phaases were reduced by adding Y2BaCuO5 into solid state reacted YBa2Cu3Ox ceramics. Y2BaCuO5 reacts with grain boundary second phases and reduces the grian size of the ceramics. It was observed the critical current density was improved by adding Y2BaCuO5 into solid state reacted YBa2Cu3Ox ceramic superconductor.

• 한국인터넷방송통신학회논문지
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• 제9권3호
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• pp.173-178
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• 2009

금속산화물 박막 소자를 제작하여 전기적 특성을 조사하였다. 소자는 Electrode를 TOP-TOP구조로 제작하였으며 스위칭 특성을 연구하기 위해 전극간의 산화금속박막의 전도특성이 측정되었다. 소자의 저항변화는 전압을 선형적으로 인가하여 측정하였다. 제작된 소자는 MIM구조로써 외부에서 인가하는 전기적 신호에 의하여 전기전도도가 큰 On-state와 전기전도도가 낮은 Off-state로 바뀌는 특성을 나타내었다. $Si/SiO_2/MgO$ 소자는 Forming에 의해 저항이 큰 상태에서 저항이 작은 상태로 전기적 특성이 변화하면서 스위칭 특성을 보였다. 본 연구를 통하여 산화금속은 차세대 비휘발성 메모리로는 물론 다른 전기적 응용이 기대되는 물질임을 확인하게 되었다.

• 한국세라믹학회지
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• 제34권6호
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• pp.583-590
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• 1997

The effects of Mn2O3 and Y2O3 additives on the microstructure and dielectric properties of Sr(Zr, Ti)O3 have been investigated. Powders with Sr(Zr1-xTix)O3(0$\leq$x$\leq$0.1) composition were prepared by the conventional solid state processing from commercial TiO2 and precipitation-processed ZrO2. The powders containing sintering additives of Mn2O3 and Y2O3 were compacted and then sintered at 1,55$0^{\circ}C$ for 4 h to get>97% relative density. Mn2O3 suppressed the grain growth and Y2O3 enhanced the density of sintered body. The oxidation state of Mn ions were determined by a chemical wet method and EPR spectroscopy. Mn ions were present as Mn2+ and Mn4+ in SrZrO3, while as Mn3+ and Mn4+ in Ti-substituted Sr(Zr, Ti)O3. With the substitution of Ti, the lattice parameters of SrZrO3 decreased and its dielectric constant increased with remarkable decrease in Q value. The dielectric constant of Sr(Zr, Ti)O3 was in the range of 30 to 40, Q values 1,200~5,400 at 6 GHz and temperature coefficient of resonant frequency -67~100 ppm/K.

• Metals and materials international
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• 제24권6호
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• pp.1394-1402
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• 2018

This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.134-134
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• 2010

Ga-In-Zn-O 물질은 비정질상태에서 높은 전하 운동성을 가지고 있으며 차세대 투명전극 thin film transistor 대안 소재로 각광받고 있다. 그런데 이 물질은 ion sputtering에 따라 전기적인 특성에 큰 변화가 관찰되고 있으며, 이는 표면에서의 화학적 상태가 전기적 특성을 좌우할 것이라는 것을 의미한다. 또한 보다 안정적이고 신뢰적인 소자를 구현하기 위해서는 ion sputtering에 의한 표면에서의 화학적 특성 변화를 이해하는 것이 매우 중요하다는 것을 의미한다. 본 연구에서는 $Ga_2O_3:In_2O_3$:ZnO의 비율이 각각 1:1:1, 2:2:1, 3:2:1 그리고 4:2:1인 시료를 $Ne^+$이온을 이용하여 sputtering하면서 표면에 민감한 분광분석 기법인 x-ray photoelectron spectroscopy와 x-ray absorption spectroscopy를 이용하여 분광정보의 변화들을 연구하였다. 실험에 의하면, Ga 3d의 양에 비해서 In 4d, Zn 3d의 양은 sputtering 시간에 따라서 각 각 양이 줄어들었으며, 전체적으로 보다 산화가가 높은 경향을 보였으며, valence band maximum 근처에 subgap state를 형성하는 것을 관찰하였다. 또한 sputtering을 계속하는 경우 In 3d, In 4d, 및 Fermi energy 근처에 metallic state가 형성되는 것을 관찰하였다. 이러한 subgap state와 metallic state의 관측은 각기 sputtering에 따라서, 아직 명확하지는 않지만, surface state의 형성 및/혹은 oxygen interstitial의 형성 그리고 metallic In의 형성 및/혹은 oxygen defect의 형성이 이루어지는 것을 의미한다.

• Bulletin of the Korean Chemical Society
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• 제21권9호
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• pp.913-918
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• 2000

Vanadium oxide catalyst supported on TiO2-ZrO2 has been prepared by adding Ti(OH)4-Zr(OH)4 powder to an aqueous solution of ammonium metavanadate followed by drying and calcining at high temperatures. The char-acterization ofthe prepared catalysts was performed using solid-state 51V NMR and FTIR.In thecase ofcalci-nation temperature at 773 K, vanadium oxide was in a highly dispersed state for the samples containing low loading V2O5 below 25 wt %, but for samplescontaining high loading V2O5 equal to or above 25 wt %, vana-dium oxidewas well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of TiO2-ZrO2.The ZrV2O7 compound was formed through the reactionof V2O5 and ZrO2 at 773-973 K, where-as the V3Ti6O17 compound was formedthrough the reaction of V2O5 and TiO2 at 973-1073 K. The V3Ti6O17 compound decomposed to V2O5 and TiO2 at 1173 K, which were confirmed by FTIR and 51V NMR.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2607-2610
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• 2011

Monodispersed Ag/$TiO_2$ core/shell nanoparticles were synthesized in solution via colloid-seeded deposition process using Ag nanoparticles as colloid seeds and $Ti(SO_4)_2$ as Ti-source respectively. Silver nitrate was reduced to Ag nanoparticles with $N_2H_4{\cdot}H_2O$ in the presence of CTAB as stabilizing agent. The titania sols hydrolyzed by the $Ti(SO_4)_2$ solution deposited on the surface of Ag nanoparticles to form the Ag/$TiO_2$ core/shell nanoparticles. Inductively coupled plasma atomic emission spectrometry (ICP-AES) showed low amount of Ag ion leaching from the Ag/$TiO_2$ core/shell nanoparticles. The Ag/$TiO_2$ core/shell nanoparticles indicated excellent antibacterial effects against Escherichia coli and maintained long-term antibacterial property.