• Title/Summary/Keyword: lattice oxygen

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A Study on the Oxygen Behavior Characterization of V2O5/TiO2 Catalysts by Ball Milling (V2O5/TiO2 촉매의 Ball Milling에 따른 산소 거동 특성 연구)

  • Kwon, Dong Wook;Park, Kwang Hee;Lee, Sang Moon;Jang, Du Hun;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.22 no.6
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    • pp.605-609
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    • 2011
  • We study on the oxygen behavior of $V_2O_5/TiO_2$ catalysts in the $NH_3$-selective catalytic reduction (SCR) prepared by the ball milling processing. There are not any changes in crystal structure and surface area of the $TiO_2$ catalyst by ball milling, but the maximal reduction temperature decreased in $H_2$-temperature programmed reduction (TPR) analysis. Experimental observations with various concentrations of oxygen indicate that all catalysts showed a very low NOx conversion rate in the absence of oxygen and the reactivity of ball milled catalyst higher depending on the oxygen. It is occurred because the degree of participation of atmospheric oxygen and lattice oxygen is great than that of the not-milled catalyst.

Atomic Structure Analysis of BaO Layers on the Si(100) Surface by Impact-Collision ion Scattering Spectroscopy

  • Hwang, Yeon
    • Korean Journal of Crystallography
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    • v.17 no.2
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    • pp.51-54
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    • 2006
  • BaO layers were formed on the Si(100) surface by thermal evaporation of barium metal with simultaneous oxidation. The atomic structure of BaO layers at the initial stage of the deposition was investigated by the scattering intensity variation of $He^+$ions on time-of-flight (TOF) impact-collision ion scattering (ICISS). The results show that several number of BaO layers are formed on the Si(100) surface with the lattice parameter of bulk phase, and the occupation of oxygen atoms of the BaO layers is on-top site of silicon atoms.

Effects of Additives and Atmospheres on the Grain Growth of TiO2 Ceramics (분위기와 첨가제가 TiO2 세라믹스의 입자성장에 미치는 영향)

  • 박정현;최헌진;박한수
    • Journal of the Korean Ceramic Society
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    • v.25 no.4
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    • pp.390-398
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    • 1988
  • Effects of atmospheres and adidtives on the grain growth of TiO2 ceramics were investigated. In the range of 1300~140$0^{\circ}C$, grain growth was increased in CO2 as compared with O2 atmosphere and the grain boundary migration activation energy was lower than the diffusion activation energy of oxygen ion in TiO2. Also, in the case of addition of oxides, the grain growth was increased by oxides acting as a acceptor andinhibited by oxides acting as a donor. From the above results, when the oxygen vacancy concentration was increased, the intrinsic grain boundary mobility was increased and the pore drag force was decreased due to the rapid densification. Also it seems that the pore was migrated by the surface diffusion rather than lattice diffusion.

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Synthesis of AlN Powder from $Al_2(SO_4)_3.18H_2O$: II. Deoxidation Effect ($Al_2(SO_4)_3.18H_2O$로부터 AlN 분말의 합성: II. 탈산화 효과)

  • 송태호;이홍림
    • Journal of the Korean Ceramic Society
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    • v.29 no.6
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    • pp.471-479
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    • 1992
  • AlN powder was synthesized by carbothermal reduction and nitridation using Al2(SO4)3.18H2O as the starting material. The synthesized AlN powder was fine but contained oxygen. Therefore carbonaceous material (carbon black or phenol novolac) was added teogether with the sintering aids (CaO, CaF2, CaCl2, Y2O3 and YF3). It was found that pressureless sintering at 1700~180$0^{\circ}C$ after deoxidation at 150$0^{\circ}C$ suppressed the formation of second phase (27R) and reduced the contents of lattice oxygen within AlN ceramics.

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The crystal structure transition in YBCO superconductor by Rietveld analysis Method (Rietveld 해석법에의한 YBCO 초전도체의 결정 구조 전이 연구)

  • 채기병;전용우;소대화
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.05a
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    • pp.239-243
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    • 1996
  • In this paper, we have tried to focus on the optimum conditions of crystal structure parameters on YBCO high Tc oxide-superconductor as an excel lent electronic parts. When we verify the characteristic improvement of superconductance and accurate reproduction and so forth, we have made use of RIETAN. We have varied the lattice constant with oxygen content from 6.0 to 7.0 as for transition of orthogonal structure and tetragonal structure for the superconductor. As the result of above, we have preyed that transition from orthogonal structure to tetragonal structure is made at the point of 6.6(oxygen content) by using the simulation.

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The Structure and Ab Initio Studies of Thiourea Dioxide

  • 송진수;김은희;강성권;윤석성;서일환;최성산;이삼근;William P. Jensen
    • Bulletin of the Korean Chemical Society
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    • v.17 no.2
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    • pp.201-205
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    • 1996
  • The crystal and molecular structure of thiourea dioxide, (NH2)2CSO2, was determined by x-ray single crystal diffraction techniques. Lattice constants are a=10.669(2), b=10.119(2), and c=3.9151(5) Å with the space group Pnma and Z=4. The thiourea portion of the molecule has a planar conformation. When the two oxygen atoms are included, the sulfur atom is at the apex of a trigonal pyramid formed with the two oxygen atoms and the carbon atom as the base. The crystal structure is stabilized by strong intermolecular hydrogen bonds. Ab initio calculations were performed to investigate the bonding features and reactivity of thiourea dioxide. The calculated bond order of S-C is only 0.481. The hydrogen bond energy was computed to be 22.3 kcal/mol for dimer. MEP analysis reveals that the sites on nucleophilic reactions are S and C atoms.

Oxygen Interstitial Defects and Ion Hopping Conduction of $X ThO_2 + (1-X) Gd_2O_3 $Solid Solutions: $O.O8{\le}X{\le}0.12$

  • Park, Sung-Ho;Kim, Yoo-Young;Kim, Keu-Hong
    • Bulletin of the Korean Chemical Society
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    • v.11 no.4
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    • pp.339-342
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    • 1990
  • $Gd_2O_3-ThO_2$ solid solutions containing 8,10 and 12 mol % $ThO_2$ were synthesized with spectroscopically pure $Gd_2O_3,$ and $ThO_2$ polycrystalline powders. X-ray diffraction revealed that all synthesized specimens have the modified fluorite structure, and the lattice parameter of $Gd_2O_3$ is nearly unchanged with increasing $ThO_2$ mol %. Both ac and dc conductivities were measured in the temperature range $500-1100^{\circ}C$ under $Po_2's$ from $10^{-6}$ to $10^{-1}$ atm. The dc conductivities are nearly independent of $Po_2,$ and agree with the ac values. This implies that the solid solutions are ionic conductors. The conductivity increases with increasing $ThO_2$ mol % with an average activation energy of 1.23 eV. An oxygen interstitial defect and ionic hopping conduction are suggested.

Thermal Behaviors of (Cu0.5Mn0.5)Fe2O4 for H2 production by thermochemical cycles (열화학싸이클 수소를 제조를 위한 (Cu0.5Mn0.5)Fe2O4의 열적 거동)

  • Kim, J.W.;Choi, S.C.;Joo, O.S.;Jung, K.D.
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.1
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    • pp.32-38
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    • 2004
  • Thermal behaviors of $(Cu_{0.5}Mn_{0.5})Fe_2O_4$, prepared by a solid method, were investigated for $H_2$ production by a thermochemical cycle. The thermal reduction of $(Cu_{0.5}Mn_{0.5})Fe_2O_4$ started from $300^\circ{C}$ and the weight loss was 1.3 wt% up to 1200. XRD shows the prepared ferrite has the spinel structure with a lattice constant of $8.414{\AA}$ and changed to the oxygen deficient structure by thermal reduction. Oxygen and hydrogen can be separately produced by the cycles of thermal reduction and water oxidation of the oxygen deficient ferrite.

An XRD Study on the Structures of Ferrites : Hematite, Ba-ferrite and Zn2Y(Ba2Zn2Fe12O22) (분말 X-선 회절법에 의한 페라이트의 구조 연구 : 헤마타이트, 바륨페라이트, Zn2Y(Ba2Zn2Fe12O22))

  • 신형섭;권순주
    • Journal of the Korean Ceramic Society
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    • v.30 no.6
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    • pp.499-509
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    • 1993
  • Structures of hematite(${\alpha}$-Fe2O3), Ba-ferrite(BaFe12O19) and Zn2Y(Ba2Zn2Fe12O22) were studied by powder X-ray diffraction(XRD) method. Powder XRD patterns of the ferrites were analyzed with the Rietveld method, and the final refined R-factors were RWP<0.01 and RI<0.03. The lattice parameters refined with hexagonal crystal system were a=5.0342${\AA}$, c=13.746${\AA}$ for hematite, a=5.8928${\AA}$, c=23.201${\AA}$ for Ba-ferrite, and a=5.8763${\AA}$, c=43.567${\AA}$ for Zn2Y. In the hematite, the oxygen parameter is 0.3072 and the Fe-O distances in FeO6octahedron are 1.941${\AA}$ and 2.118${\AA}$, close to the single crystal data of Blake et al.. In the Ba-ferrite, the Fe atom in oxygen trigonal bipyramid is displaced 0.155${\AA}$ away from the BaO3 mirror plane into 4e position. In the Zn2Y, 75% of Zn is located at the oxygen terahedral site in S-block.

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The Role of Metal Catalyst on Water Permeation and Stability of BaCe0.8Y0.2O3-δ

  • Al, S.;Zhang, G.
    • Journal of Electrochemical Science and Technology
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    • v.9 no.3
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    • pp.212-219
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    • 2018
  • Perovskite type ceramic membranes which exhibit dual ion conduction (proton and oxygen ion conduction) can permeate water and can aid solving operational problems such as temperature gradient and carbon deposition associated with a working solid oxide fuel cell. From this point of view, it is crucial to reveal water transport mechanism and especially the nature of the surface sites that is necessary for water incorporation and evolution. $BaCe_{0.8}Y_{0.2}O_{3-{\alpha}}$ (BCY20) was used as a model proton and oxygen ion conducting membrane in this work. Four different catalytically modified membrane configurations were used for the investigations and water flux was measured as a function of temperature. In addition, CO was introduced to the permeate side in order to test the stability of membrane against water and $CO/CO_2$ and post operation analysis of used membranes were carried out. The results revealed that water incorporation occurs on any exposed electrolyte surface. However, the magnitude of water permeation changes depending on which membrane surface is catalytically modified. The platinum increases the water flux on the feed side whilst it decreases the flux on the permeate side. Water flux measurements suggest that platinum can block water permeation on the permeate side by reducing the access to the lattice oxygen in the surface layer.