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Mixed Oxides (mixed + oxide)
Selected AbstractsDirect Electrochemical Preparation of NbSi Alloys from Mixed Oxide Preform Precursors,ADVANCED ENGINEERING MATERIALS, Issue 3 2009Fanke Meng A new method of preparation of NbSi alloys has been provided in this article. Electro-deoxidizing mixed Nb2O5 and SiO2 small cylindrical pellets in molten CaF2 at high temperature (1500,°C) could produce homogenous NbSi alloys. And then, the cyclic voltammogram (CV) method was used to analyze the electroreduction mechanism. This effective method could shorten procedures of production of NbSi alloys and will be promising for industrial utilization. [source] ChemInform Abstract: A Tin,Tungsten Mixed Oxide as an Efficient Heterogeneous Catalyst for C,C Bond-Forming Reactions.CHEMINFORM, Issue 35 2009Yoshiyuki Ogasawara Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Solidus and Liquidus of Plutonium and Uranium Mixed Oxide.CHEMINFORM, Issue 20 2008Masato Kato Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Study of the Influence of Composition on the Microstructural Properties of ZnO/Al2O3 Mixed Oxides,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2009Shaojun Miao Abstract A series of ZnO/Al2O3 mixed oxide samples with varyingZn/Al ratio is prepared by coprecipitation, ageing, drying, and calcination. Samples are investigated in the state after drying and calcination. The applied methods include X-ray diffraction, solid-state 27Al magic-angle spinning nuclear magnetic resonance spectroscopy, transmission electron microscopy and thermogravimetric experiments coupled with evolved gas analysis. Phases present in the dried precursor samples include hydrozincite, zaccagnaite, and an unknown phase. After calcination zinc oxide and spinel can be found. All results indicate the substitution of Al ions for Zn ions in zinc oxide of zinc-rich samples. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Sintering Behavior and Dielectric Properties of Bi3NbO7 Ceramics Prepared by Mixed Oxides and High-Energy Ball-Milling MethodsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2007Di Zhou The sintering behavior and dielectric properties of Bi3NbO7 ceramics prepared by the high-energy ball milling (HEM) method and conventional mixed oxides method with V2O5 addition were investigated. All the samples were sintered between 840° and 960°C. For the ceramics prepared by the mixed oxides method, the pure tetragonal Bi3NbO7 phase formed without any cubic phase. With changing sintering temperature, the dielectric constant ,r lies between 79 and 92, while the Q×f values are between 300 and 640 GHz. The samples sintered at 870°C have the best microwave dielectric properties with ,r=79, Q×f=640 GHz, and the temperature coefficients of resonant frequency ,f between 0 and ,20 ppm/°C. For the ceramics prepared by the HEM, a pure cubic phase was obtained. The ,r changes between 78 and 80 and Q×f were between 200 and 290 GHz. [source] ChemInform Abstract: Titanium-Based Mixed Oxides from a Series of Titanium(IV) Citrate Complexes.CHEMINFORM, Issue 21 2008Yuan-Fu Deng Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Self-Assembling of Er2O3,TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal RouteCHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Beatriz Julián-López Dr. Abstract An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3,TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O3,TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313,m2,g,1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol,gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers. [source] The Role of Functionalisation, Asymmetry and Shape of a New Macrocyclic Compartmental Ligand in the Formation of Mononuclear, Homo- and Heterodinuclear Lanthanide(III) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009Sergio Tamburini Abstract The compartmental [1+1] macrocycle H3L, obtained by self-condensation of the formyl precursor 3,3,-(3,6-dioxaoctane-1,8-diyldioxy)bis(2-hydroxybenzaldehyde) with the amine precursor N,N -bis(2-aminoethyl)-2-hydroxybenzylamine, contains one inner ON3O2 Schiff base and one outer O2O4 crown-like chamber. According to the experimental conditions it forms, by a template process, the stable mononuclear complexes Ln(H3L)(Cl)2(CH3COO)·nS·mHCl or [Ln(L)]·nS (Ln = La, Lu, Y, Yb, Er, Dy, Tb, Gd, Eu, Ce) with the lanthanide(III) ion encapsulated in the crown-ether-like and in the Schiff base site. The mononuclear complexes Ln(H3L)(Cl)2(CH3COO)·nS·mHCl, by further complexation with a different lanthanide(III) ion, give rise to the related heterodinuclear complexes [LnLn,(L)(Cl)2(CH3COO)]·nS while the homodinuclear and the heterodinuclear complexes [Ln2(L)](Cl)3·nH2O and [LnLn,(L)](Cl)3·nS could be prepared by a template reaction using the appropriate molar ratio of reactants. Their properties have been studied by using SEM-EDS microscopy, IR and NMR spectroscopy and their compositions confirmed by thermal and ESI-Mass spectrometric analyses. In the heterodinuclear complexes, the site occupancy of the different lanthanide(III) ions was determined by 1H and 13C NMR spectroscopy in CD3OD or (CD3)2SO , it was found that heterodinuclear complexation occurs in methanol with the smaller lanthanide(III) ion mainly coordinating to the Schiff base site and the larger lanthanide(III) ion to the crown site whereas, in dimethyl sulfoxide, demetalation of the weaker coordinated lanthanide(III) ion into the crown ether chamber occurs with the subsequent formation of mononuclear species in solution. The thermal decomposition of the heterodinuclear complexes forms the related mixed oxides, the stoichiometries and properties of which were determined by SEM-EDS microscopy and X-ray powder diffraction studies (XRD). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Novel Multi-functional Mixed-oxide Catalysts for Effective NOx Capture, Decomposition, and Reduction,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2007J. Yu Abstract In this paper, novel multi-functional mixed-oxide catalysts have been rationally designed and developed for the effective abatement of NOx. CaxCo3,,,xAl hydrotalcite-like compounds (where x,=,0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) are first synthesized by co-precipitation and calcined at 800,°C for 4,h in air to derive the mixed oxides. The resultant mixed oxides are generally of spinel phase, where the CaO phase is segregated when x,,,2.5. It has subsequently been found that the derived oxides are catalytically multi-functional for NOx decomposition, capture, and reduction. For example, the mixed Ca2Co1Al1 -oxide can decompose 55,% NO at 300,°C in 8,% oxygen, completely trap NO for 750,s, and capture 12.88,and 18.06,mg,g,1 NO within 30,and 60,min, respectively. The catalytic activities of the Ca2Co1Al1 -oxide catalyst have been further improved by incorporating La to form a quaternary catalyst Ca2Co1La0.1Al0.9 -oxide. This catalyst significantly enhances the NO decomposition to 75,%, extends the complete trapping time to 1100,s, and captures more NO at 300,°C in 8,% O2 (19.02,mg,g,1 NO within 60,min). The in-situ IR spectra of the catalysts with adsorbed NO indicates that the major nitrogen species formed on the catalysts are various kinds of nitrites and nitrates, which can be readily reduced by H2 within 6,min at 350,°C. Therefore, the excellent catalytic activity of layered double hydroxide (LDH)-based mixed oxides for NO decomposition, storage, and reduction can be achieved by the elegant combination of normal transition metals. [source] Mechanical Activation-Assisted Synthesis of Pb(Fe2/3W1/3)O3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2000Seok Khim Ang Perovskite Pb(Fe2/3W1/3)O3 (PFW) was prepared via a mechanical activation-assisted synthesis route from mixed oxides of PbO, Fe2O3, and WO3. The mechanically activated oxide mixture, which exhibited a specific area of >10 m2/g, underwent phase conversion from nanocrystalline lead tungstate (PbWO4) and pyrochlore (Pb2FeWO6.5) phases on sintering to yield perovskite PFW, although the formation of perovskite phase was not triggered by mechanical activation. When heated to 700°C, >98% perovskite phase was formed in the mechanically activated oxide mixture. The perovskite phase was sintered to a density of ,99% of theoretical density at 870°C for 2 h. The sintered PFW exhibited a dielectric constant of 9800 at 10 kHz, which was ,30% higher than that of the PFW derived from the oxide mixture that was not subjected to mechanical activation. [source] Kinetic measurements from in situ TEM observationsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2009Renu Sharma Abstract Environmental transmission or scanning transmission electron microscope is ideally suited to observe gas solid interactions at nanoscale. It is shown that the time and temperature resolved data, obtained from in situ observations, can be used to obtain reaction rates and understand the kinetics of the processes. Low or high magnification images provide the change in length, area or volume with time at constant temperature and pressure conditions during nitridation of Cu,Cr thin films, deposition of Au particles, growth of Si nanowire and carbon nanotubes. Effect of electron beam is estimated by making observations with and without constant electron beam exposure. Quantitative electron energy loss spectroscopy is employed to measure the reduction rate of Ce+4 in pure ceria, mixed oxides (ceria-zirconia) and catalyst (Rh-ceria-zirconia) powders. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. [source] Synthetic hydrotalcites from different routes and their application as catalysts and gas adsorbents: a reviewAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2009M. R. Othman Abstract In this paper, widely accepted methods of hydrotalcite preparation such as co-precipitation, urea hydrolysis, hydrothermal, sol,gel, microwave irradiation, steam activation and solvothermal have been selected and reviewed. Our review indicates that the nature of the divalent cations, the synthesis method, the calcination temperature and the nature of the interlayer species are determinant factors in shaping the surface properties of the layered double hydoxides. The basic strength of the surface base site and structural changes produced in the mixed oxides can be adjusted conveniently by varying the Al content during the synthesis. The combination of sol,gel with microwave irradiation during the gelling and crystallization steps has also been found to increase the surface area of the hydrotalcite-like compound. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ordered Mesoporous Thin Films of Rutile TiO2 Nanocrystals Mixed with Amorphous Ta2O5CHEMPHYSCHEM, Issue 5 2008Jin-Ming Wu Dr. Abstract Ordered mesoporous thin films of composites of rutile TiO2 nanocrystals with amorphous Ta2O5 are fabricated by evaporation-induced self-assembly followed by subsequent heat treatment beyond 780,°C. Incorporation of selected amounts of Ta2O5 (20 mol,%) in the mesoporous TiO2 film, together with the unique mesoporous structure itself, increased the onset of crystallization temperature which is high enough to ensure the crystallization of amorphous titania to rutile. The ordered mesoporous structure benefits from a block-copolymer template, which stabilizes the mesostructure of the amorphous mixed oxides before crystallization. The surface and in-depth composition analysis by X-ray photoelectron spectroscopy suggests a homogeneous intermixing of the two oxides in the thin film. A detailed X-ray absorption fine structure measurement on the composite film containing 20 mol,% Ta2O5 and heated to 800,°C confirms the amorphous nature of the Ta2O5 phase. Photocatalytic activity evaluation suggests that the rutile nanocrystals in the synthesized ordered mesoporous thin film possess good ability to assist the photodegradation of rhodamine B in water under illumination by UV light. [source] | |||||||||||||