Study of physicochemical properties and active oxygen in structures of layered mixed La4BaCu5-xMxO13+lambda (M = Mn, Co)

Two series of layered mixed oxides La4BaCu5-xMxO13+lambda(M = Mn, Co, x = 0 similar to 5) were prepared and characterized by means of XRD, XPS, O-2-TPD and chemical analysis. The results show that their structures are 5-layered ABO(3) perovskite, and the XPS and O-2-TPD investigation confirms that there exists synergistic effect between Cu ion and M when M ion is doped into the lattice of La4BaCu5O13+lambda,, and the synergistic effect between Mn and Cu is stronger than that of Cu-Co.

Low temperature preparation and fuel cell properties of rare earth doped barium cerate solid electrolytes

The solid electrolytes, BaCe(0.8)Ln(0.2)O(2.9) (Ln: Gd, Sm, Eu), were prepared by the sol-gel method. XRD indicated that a pure orthorhombic phase was formed at 900 degrees C. The synthesis temperature by the sol-gel method was about 600 degrees C: lower than the high temperature solid phase reaction method. The electrical conductivity and impedance spectra were measured and the conduction mechanism was studied. The grain-boundary resistance of the solid electrolyte could be reduced or eliminated by the sol-gel method. The conductivity of BaCe0.8Gd0.2O2.9 is 7.87 x 10(-2) S.cm(-1) at 800 degrees C. The open-circuit voltage of hydrogen-oxygen fuel cell using BaCe0.8Gd0.2O2.9 as electrolyte was near to 1 V and its maximum power density was 30 mW.cm(-2).

Study on the synthesis of mixed oxide La2CuO4 and the effect on the catalytic activity to catalytic removal of NO

The mixed oxide La2CuO4 was synthesized by four different methods and characterized with XRD, BET, TEM and low angle XRD. The effect of the synthetic method on the crystal structure, crystal size, surface area and catalytic activity to NO - CO reaction were studied. The results showed that the samples derived from different methods exhibited different activity to NO-CO reaction, the reason may be that the concentration and type of oxygen defect were different when the synthetic methods were different.

Sol-gel synthesis and electrical properties of ceria-based solid electrolytes

A series of solid electrolytes (Ce0.8RE0.2)(1-x)MxO2-delta(RE: Rare earth, M: Alkali earth) were prepared by sol-gel methods. XRD indicated that a pure fluorite phase was formed at 800 degrees C. The synthesis temperature by the sol-gel methods was about 700 degrees C lower than by the traditional ceramic method. The electrical conductivity and impedance spectra were measured. XPS showed that the oxygen vacancy increased obviously by doping MO, thus, resulting in the increase of the oxygen ionic transport number and conductivity. The performance of ceria-based solid electrolyte was improved. The effects of RE2O3 and MO on the electrical properties were discussed. The conductivity and the oxygen ionic transport number of (Ce0.8Sm0.2)(1-0.05)Ca0.05O2-delta is 0.126 S.cm(-1) and 0.99 at 800 degrees C, respectively.

Catalytic combustion of CH4 and CO on La1-xMxMnO3 perovskites

The activities of perovskites depend on compositions and preparation methods. Various perovskites, La1-xMxMnO3 (M=Ag, Sr, Ce, La), have been prepared by two different methods (co-precipitation and spray decomposition). The new preparation method, spray decomposition, produced perovskites of a high surface area of over 10 m(2)/g. The catalytic activities for CH4 and CO oxidation have been studied on a series of catalysts, La1-xMxMnO3. The perovskite-type oxide, La0.7Ag0.3MnO3, shows the highest catalytic activity: the complete conversion of CO and CH4 at 370 and 825 K, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.

Y-Ba-Cu-O mixed oxides for production of diphenols in liquid-solid phase

Superconductor mixed oxides were often used as catalysts at higher temperature in gas phase oxidations, and considered not suitable for lower temperature reactions in the liquid-solid phase; here the catalysis of YBa2Cu3O7+/-x and Y2BaCuO5+/-x in the phenol hydroxylation at lower temperature with H2O2 as oxygen donor was studied, and found that the superconductor YBa2Cu3O7+/-x, has no catalytic activity for phenol hydroxylation, but Y2BaCuO5+/-x does, even has better catalytic activity and stability than most previously reported ones. With the studies of catalysis of other simple metal oxides and perovskite-like mixed oxides, a radical substitution mechanism is proposed and the experimental facts are explained clearly, and draw a conclusion that the perovskite-like mixed oxides with (AO)(ABO(3)) and (AO)2(ABO(3)) structure have better catalytic activity than the simple perovskite oxides with (ABO(3))(3) structure alone, and (AO) structure unit is the key for the mixed oxides to have the phenol hydroxylation activity. No pollution of this process is very important for its further industrial application.

LaSrNiO4-lambda with K2NiF4 structure - A highly active catalyst for direct decomposition of nitrogen monoxide

A series of perovskite-like mixed oxides La(2-x)Sr(x)MO(4+lambda) (M=Cu, Co,Ni; x=0,1) was prepared and characterized using X-ray powder diffraction. The catalytic properties of these catalysts in NO decomposition were tested. The results showed that LaSrNiO4-lambda with K2NiF4 structure is very active and stable for the decomposition of NO.

SYNTHESIS, CHARACTERIZATION AND CATALYTIC BEHAVIOR OF LA2-XSRXCOO4+/-LAMBDA (X=0-2) IN COMPLETE OXIDATION

A series of mixed oxides La2-xSrxCoO4+/-lambda (x=0-2) with varying x values was synthesized. The crystal structure of this series of mixed oxides was studied by using XRD. The result showed that when x=0.25-1.5 the mixed oxides possessing K2NiF4 structure are formed. The valences of the transition metal Co and the relation between +/-lambda content and x value by using chemical analysis method have been measured, too. The redox property of this series of mixed oxides and different kinds of oxygen species were studied by IR, TPD, TPR, XPS and SEM methods. The catalytic activity in the complete oxidation of CO and CH4 was investigated and the relationships between the activity, composition and structure of the mixed oxides have been elucidated.

X-Ray Photoelectron Spectroscopy Study of LaMn1-xFexO3 (x=0-1) Oxides

The redox potential, surface composition and oxygen species of a series of complex oxides LaMn1-xFexO3 (x=0-1) having perovskite structure (ABO(3)) have been investigated by means of XI'S. The variation of binding energies referring to Mn2p and Fe 2p under different treatment offerred an obvious evidence of redox between Mn and Fe, which could be expressed as Mn4+ + Fe(3-delta)+ Mn(4-delta)+ Fe3+ Feat Through computer fit three kinds of adsorbed oxygen species (O-I, O-II, O-III) have been evaluated based on the XPS spectra of O1s. From the variation of contents of different oxygen species, it could be concluded that. the redox occuring in the surface might be related with the adsorbed oxygen species O-I and O-II, furthermore the possibility of transfer of electron between adsorption site and oxygen was also discussed.

CRYSTAL-STRUCTURES AND MOSSBAUER-SPECTRA OF LAFE1-XMNXO3 AND LAFE1-XCOXO3 (X=0 TO 0.9)

The crystal structures and Mossbauer spectra of various mixed oxides LaFe1-xMnxO3 and LaFe1-xCoxO3 (x = 0 to 0.9) are determined and measured at room temperature. The results indicate that the crystal structure of both the La-Fe-Mn-O and the La-Fe-Co-O sy

XPS Study of the Oxygen State in LaMnyCo1-yO3 Catalysts

A series of LaMnyCo1-yO3 compounds were prepared by the complexation method with citric acid. XPS was used to investigate the oxygen state in perovskite-type (ABO(3)) Complex oxide LaMnyCo1-yO3 catalysts. The result showed that three oxygen species (alpha

CHARGE COMPENSATION AND VALENCY STABILITY OF EU(II)-DOPED KMGF3 CRYSTAL

The spectrochemistry of Eu2+-doped perovskite KMgF3 was examined and discussed. Eu2+ can replace some of the K+ in the KMgF3 crystal, and simultaneously the corresponding cation hole can be compensated with the F- or O2- in the matrix. The emission intensity of Eu2+ due to the f --> f transition increased when Na+, Rb+ or F- was doped in KMgF3:Eu2+. Two mechanisms of charge compensation were proposed. No obvious valence change of Eu2+ occurred in KMgF3:Eu2+ after calcinating at high temperature, e.g. 900-degrees-C. It was found that the valence stability of Eu2+ improved after incorporation into the matrix.

COORDINATION CHEMISTRY AND SUPERCONDUCTIVITY

Analysing the coordination state of copper ions in cuprate superconductors, it is found that the larger the energy splitting between d(x2-y2) and d(z2) orbitals of Cu or the higher the energy of the d(x2-y2) orbital, the higher the Tc. Thus, appropriate coordination structures and strong-field ligands must be chosen for expanding the energy splitting and increasing the energy of the d(x2-y2) orbital when searching for new high-Tc superconductors. Summarizing the experimental results of ESR and XPS, it is considered that the [Cu2+ - O open-square-box 2- - Cu3+] resonance exists in cuprate superconductors and the electron field breathing mode is present. Analysing the mechanism and the relationship between the coordination state of Cu and Tc, we consider that the two dimensional Cu-O planes are responsible for the superconductivity of YBa2Cu3O7-y.

地幔副矿物和硫化物的热（PVT）状态方程研究

矿物PVT状态方程是研究矿物在一定温压条件下的晶胞体积与温度、压力之间的关系，依据这个基本关系，可以了解矿物在高温高压下的密度、弹性、热膨胀等性质。矿物PVT状态方程的研究可以了解矿物在地球深部存在的结构状态，为进一步的理论计算提供基础的数据，其结果也可以与天然和人工地震的地震波反演的结果对比，对地球深部的地质作用过程、物质结构状态和组成进行限制。然而，目前矿物PVT状态方程的研究主要集中在氧化物矿物和上地幔主要矿物（橄榄石和辉石）及其高压相（瓦兹利石、林伍德石、方镁铁矿、Majorite、Mg-Perovskite、Ca-Perovskite）的研究上，对石榴石、尖晶石等地幔常见副矿物和硫化物矿物的PVT状态方程的研究很少。 作者在参与搭建并完善金刚石压腔外加温系统的基础上，利用北京同步辐射X射线衍射实验技术结合金刚石压腔外加温技术对天然铁铝榴石、锰铝榴石、铬尖晶石进行了PVT状态方程的研究，同时对闪锌矿、辰砂、方铅矿、辉钼矿、辉锑矿等硫化物矿物进行了相变及状态方程的研究。结合前人研究成果，讨论了类质同象置换对镁铝－铁铝系列石榴石、锰铝－铁铝系列石榴石、尖晶石和硫化物矿物相变及状态方程的影响。获得了以下研究结果： 1）镁铝－铁铝系列石榴石和锰铝－铁铝系列石榴石的体弹模量都随着铁铝榴石组分的增加而增大。其主要原因是在二价阳离子位置上Fe2+取代了Mg2+、Mn2+。在镁铝－铁铝榴石系列中Mg2+的共价键半径（1.36Å）要大于Fe2+的共价键半径（1.17Å），而Mg2+－O键长（2.270Å）与铁铝榴石中的Fe2+－O（2.299Å）键长基本相当。在锰铝－铁铝榴石系列中， 尽管Mn2+的共价键半径（1.17Å）与铁铝榴石中的Fe2+共价键半径（1.17Å）相等，但是Mn2+－O键长（2.326Å）大于Fe2+－O键长（2.299Å）。较小的键长和共价键半径将会增强离子间的结合力，从而具有较强的抗压缩能力，因此随铁铝榴石组分的增加，镁铝－铁铝榴石系列和锰铝－铁铝榴石系列具有较大的体弹模量。 2）首次获得了铬尖晶石（(Mg0.6766Fe0.2808Na0.0073Ti0.0014)0.9661(Cr1.4874Al0.5367)2.0241O4）的体弹模量的温度导数。结合前人关于其他组分尖晶石的实验结果发现，尖晶石中在四面体位置上发生Fe2+－Mg2+置换对体弹模量的影响要大于在八面体位置上发生Cr3+－Al3+置换对体弹模量的影响。而造成铬尖晶石的体弹模量值比其他组分尖晶石的体弹模量值大的主要原因也是四面体位置上的Fe2+－Mg2+的类质置换。 3）依据获得的尖晶石和石榴石的状态方程计算了不同地幔岩模型（橄榄岩和榴辉岩模型）的密度值在上地幔温压条件下的变化情况。结果表明，在尖晶石二辉橄榄岩模型中尖晶石含量的改变（2％－10％）会引起较大的密度变化（2.2％）；在石榴石二辉橄榄岩（石榴石含量14％－20％）和榴辉岩（石榴石含量37％－45％）模型中石榴石含量的变化几乎未引起其密度值的变化，但石榴石是这两种地幔岩模型中的重要组成矿物。 4）首次获得了辰砂的Cinnabar相、方铅矿的B33相、辉钼矿、辉锑矿体弹模量的温度导数和热膨胀系数。讨论了闪锌矿、辰砂、方铅矿的相变情况。 5）总结了锌的、汞的、铅的硫族化合物发生结构相变的规律。认为造成锌的、汞的、铅的硫族化合物的相变压力随阴离子原子序数的增加（S→Se→Te）而逐渐减小的原因是：元素周期表中相对较大原子序数的原子具有更多的核内电子，引起价电子及导带电子的有效位能相对变弱，引起电离能降低，因此在相对较低的压力下就容易发生结构相变。 6）分析了ZnS中Fe2+替代Zn2+、Sb2S3－Bi2S3、MoS2－WS2以及同族相同结构不同组分的简单硫化物矿物的阴、阳离子对体弹模量值的影响。认为简单硫化物矿物的体弹模量值取决于阴、阳离子的离子半径、电负性以及键长。

Partial oxidation of ethane to syngas in an oxygen-permeable membrane reactor

A perovskite-type oxide of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCFO) with mixed electronic and oxygen ionic conductivity at high temperatures was used as an oxygen-permeable membrane. A tubular membrane of BSCFO made by extrusion method has been used in the membrane reactor to exclusively transport oxygen for the partial oxidation of ethane (POE) to syngas with catalyst of LiLaNiO/gamma-Al2O3 at temperatures of 800-900 degreesC. After only 30 min POE reaction in the membrane reactor, the oxygen permeation flux reached at 8.2 ml cm(-2) min(-1). After that, the oxygen permeation flux increased slowly and it took 12 h to reach at 11.0 ml cm(-2) min(-1). SEM and EDS analysis showed that Sr and Ba segregations occurred on the used membrane surface exposed to air while Co slightly enriched on the membrane surface exposed to ethane. The oxygen permeation flux increased with increasing of concentration of C2H6, which was attributed to increasing of the driving force resulting from the more reducing conditions produced with an increase of concentration of C2H6 in the feed gas. The tubular membrane reactor was successfully operated for POE reaction at 875 degreesC for more than 100 h without failure, with ethane conversion of similar to 100%, CO selectivity of >91% and oxygen permeation fluxes of 10-11 ml cm(-2) min(-1). (C) 2002 Elsevier Science B.V. All rights reserved.