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Metal Oxides (metal + oxide)
Kinds of Metal Oxides Terms modified by Metal Oxides Selected AbstractsLow-Temperature-Grown Transition Metal Oxide Based Storage Materials and Oxide Transistors for High-Density Non-volatile MemoryADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Myoung-Jae Lee Abstract An effective stacked memory concept utilizing all-oxide-based device components for future high-density nonvolatile stacked structure data storage is developed. GaInZnO (GIZO) thin-film transistors, grown at room temperature, are integrated with one-diode (CuO/InZnO),one-resistor (NiO) (1D,1R) structure oxide storage node elements, fabricated at room temperature. The low growth temperatures and fabrication methods introduced in this paper allow the demonstration of a stackable memory array as well as integrated device characteristics. Benefits provided by low-temperature processes are demonstrated by fabrication of working devices over glass substrates. Here, the device characteristics of each individual component as well as the characteristics of a combined select transistor with a 1D,1R cell are reported. X-ray photoelectron spectroscopy analysis of a NiO resistance layer deposited by sputter and atomic layer deposition confirms the importance of metallic Ni content in NiO for bi-stable resistance switching. The GIZO transistor shows a field-effect mobility of 30,cm2,V,1,s,1, a Vth of +1.2,V, and a drain current on/off ratio of up to 108, while the CuO/InZnO heterojunction oxide diode has forward current densities of 2,×,104,A,cm,2. Both of these materials show the performance of state-of-the-art oxide devices. [source] The Role of Transition Metal Oxides in Charge-Generation Layers for Stacked Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Sami Hamwi Abstract The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs2CO3 -doped 4,7-diphenyl-1,10-phenanthroline layer and a WO3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance,current density,voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5,nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO3 layer and its neighboring hole-transport material, 4,4',4"-tris(N -carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED. [source] Efficient Polymer Light-Emitting Diode Using Air-Stable Metal Oxides as Electrodes,ADVANCED MATERIALS, Issue 1 2009Henk J. Bolink Poly(phenylenevinylene)-based organic light-emitting diodes (OLEDs) are fabricated using air-stable metal oxides as electrodes, producing very efficient and bright electroluminescent devices. Efficiencies of 8,cd,A,1 and luminances above 20000,cd,m,2 are obtained, comparable to the values reported for classic OLED structures using reactive metals as cathodes. [source] Synthesis of Nanophased Metal Oxides in Supercritical Water: Catalysts for Biomass ConversionINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2006Caroline Levy Nanoparticles of zinc oxide-based materials (ZnO, ZnAl2O4) with various morphologies were synthesized in supercritical water (SCW) with a flow-type apparatus and in sub- and supercritical water with a batch reactor. In the flow-type apparatus, smaller particles were obtained. Depending on the precursors, the morphology of crystallites is rod, hexagonal, or rectangular shaped. ZnAl2O4 was synthesized with a high specific surface area (SBET) reaching 210 m2/g and nanocrystallite sizes ,10 nm. The KOH concentration played a major role in the formation of ZnO and ZnAl2O4 phases. Then, the synthesized materials were used as catalysts for the biomass conversion by the oxidation process to produce hydrogen. [source] Improvement of Mechanical Properties of Self Setting Calcium Phosphate Bone Cements Mixed With Different Metal OxidesMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 12 2003U. Gbureck Calciumphosphat Zemente; Metalloxide; Mechanische Eigenschaften Abstract Calcium phosphate cements (CPC), based on multicomponent powder mixtures of calcium orthophosphates with medium particle sizes in the region of 1 - 20 ,m, set isothermally in an aqueous environment to form hydroxyapatite (HA). HA cement reactants include tetracalcium phosphate (TTCP), tricalcium phosphate (TCP), dicalcium phosphate anhydrate (DCPA), dicalcium phosphate dihydrate (DCPD), monocalcium phosphate (MCPA) or octacalcium phosphate (OCP). The aim of this study was to improve the mechanical performance of TTCP / DCPA cement by adding several metal oxides to tetracalcium phosphate during the fabrication process. Cements based on tetracalcium phosphate mixed with silica or titanium oxide showed significant increases in compressive strength, approximately 80 - 100 MPa, whilst no change in the mechanical behavior of CPC was observed if zirconia was added. X-ray diffraction measurement confirmed the setting reaction of doped cements was similar to that of pure CPC. Low crystalline HA was found to be the main constituant of set cement; additional phases, such as calcium titanate or calcium zirconate, were not involved in the reaction. A mechanical reinforcement effect was thought to result from changes in the thermodynamic or kinetic solubilities of doped tetracalcium phosphates, this would lead to slower HA crystal formation and a more cross-linked cement structure. Verbesserung der mechanischen Eigenschaften von Calciumphosphat-Zementen durch Modifikation mit verschiedenen Metalloxiden Calciumphosphat-Zemente, CPC, bestehen aus Pulvermischungen verschiedener Calcium orthophophate, beispielsweise Tetracalciumphosphat (TTCP), Tricalciumphosphat (TCP), Dicalciumphosphatanhydrid (DCPA), Dicalciumphosphatdihydrat (DCPD), Monocalcium phosphatanhydrid (MCPA) oder Octacalciumphosphat (OCP) mit durchschnittlichen Partikelgrößen im Bereich von 1 , 20 ,m. Die Zemente binden in wässriger Umgebung isotherm zu Hydroxylapatit ab. Das Ziel dieser Arbeit war die Verbesserung materialspezifischer Eigenschaften , wie die mechanische Festigkeit - eines TTCP / DCPA-Zementes durch die Verwendung von Metalloxiden im Syntheseprozess von Tetracalciumphosphat. Zemente, die aus mit Silicium- oder Titandioxid versetzten Tetracalciumphosphaten hergestellt wurden, zeigten eine deutliche Steigerung der Druckfestigkeit auf Werte von 80 , 100 MPa, während im Falle von Zirkoniumdioxid keine Änderung der mechanischen Stabilität erreicht werden konnte. Röntgendiffraktometrische Untersuchungen ergaben, dass die Abbindereaktion dieser Zemente ähnlich der eines reinen TTCP / DCPA-Zements verläuft. Jeweiliges Hauptprodukt war niedrigkristalliner Hydroxylapatit, die im Herstellungsprozess von Tetracalciumphosphat entstandenen Nebenprodukte Calciumtitanat bzw. ,zirkonat waren nicht an der Abbindereaktion beteiligt. Ein Grund für die Steigerung der mechanischen Stabilität ist offensichtlich die Veränderung der kinetischen und thermodynamischen Löslichkeit der synthetisierten Tetracalciumphosphate, die zu einer langsameren Abbindereaktion und somit einer besseren Vernetzung in der Hydroxylapatitstruktur führt. [source] Selective Reduction of C=O in ,,,-Unsaturated Carbonyls Through Catalytic Hydrogen Transfer Reaction over Mixed Metal Oxides.CHEMINFORM, Issue 20 2004Sachin U. Sonavane Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Aqueous Crystallization of Manganese(II) Group 6 Metal Oxides.CHEMINFORM, Issue 25 2001Meehae Jang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Porous Metal Oxides as Gas SensorsCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2007Michael Tiemann Dr. Abstract Semiconducting metal oxides are frequently used as gas-sensing materials. Apart from large surface-to-volume ratios, well-defined and uniform pore structures are particularly desired for improved sensing performance. This article addresses the role of some key structural aspects in porous gas sensors, such as grain size and agglomeration, pore size or crack-free film morphology. New synthesis concepts, for example, the utilisation of rigid matrices for structure replication, allow to control these parameters independently, providing the opportunity to create self-diagnostic sensors with enhanced sensitivity and reproducible selectivity. [source] Influences of passivating elements on the corrosion and biocompatibility of super stainless steelsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Young-Ran Yoo Abstract Biometals need high corrosion resistance since metallic implants in the body should be biocompatible and metal ion release should be minimized. In this work, we designed three kinds of super stainless steel and adjusted the alloying elements to obtain different microstructures. Super stainless steels contain larger amounts of Cr, Mo, W, and N than commercial alloys. These elements play a very important role in localized corrosion and, thus, their effects can be represented by the "pitting resistance equivalent number (PREN)." This work focused on the behavior which can arise when the bare surface of an implant in the body is exposed during walking, heavy exercise, and so on. Among the experimental alloys examined herein, Alloy Al and 316L stainless steels were mildly cytotoxic, whereas the other super austenitic, duplex, and ferritic stainless steels were noncytotoxic. This behavior is primarily related to the passive current and pitting resistance of the alloys. When the PREN value was increased, the passivation behavior in simulated body solution was totally different from that in acidic chloride solution and, thus, the Cr2O3/Cr(OH)3 and [Metal oxide]/[Metal + Metal oxide] ratios of the passive film in the simulated body solution were larger than those in acidic chloride solution. Also, the critical current density in simulated body solution increased and, thus, active dissolution may induce metal ion release into the body when the PREN value and Ni content are increased. This behavior was closely related to the presence of EDTA in the simulated body solution. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Synthesis, characterization and dielectric properties of EuBa2SbO6 nanocrystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2010V. T. Kavitha Abstract Nanoparticles of EuBa2SbO6, a complex perovskite metal oxide were synthesized by a self-sustained combustion method employing citric acid as the complexing agent. The powders were characterized by X-ray diffraction, IR and Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. Nanocrystals of EuBa2SbO6 were sintered to 97 % of theoretical density at 1450 °C for 4 h without any sintering aid. The dielectric properties (dielectric constant, ,r and loss factor, tan,) of the ceramics have been measured in the frequency range 50 Hz to 5 MHz at room temperature. The chemical non-reactivity of EuBa2SbO6 with YBa2Cu3O7-, makes it an ideal substrate for YBa2Cu3O7-, superconductors. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanical activation of precursors for nanocrystalline materialsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2003H. Heegn Abstract Nanostructured materials win big scientific interest and increasingly economic meaning through their specific exceptional properties. Precursors that were compacted by pressing and sintering are normally used preparation of materials. In present work, the influence of mechanical activation by grinding on the structure as well as on compacting and sintering behavior of oxides from magnesium, aluminium and silicon has been investigated. Starting materials for each metal oxide differ in microstructure, dispersity, and porosity. The influence of mechanical activation on the destruction of crystalline structure to nanocrystalline, as well as to the amorphous stage and the compaction of powders with nano-particles, as well as structures with nanoscale pores have been compared. The possibilities of the consolidation of nanostructured materials were investigated. The mechanical activation took place in a disc vibration mill. The mechanical activated materials as well as their pressing and their sintering products were characterized by density, particle-sizedistribution, specific surface, pore-structure, microstructure, and crystallite size by X-ray powder diffraction (XRD). The mechanical activation of the model-substances led, in most cases, to an improvement of the compaction properties; thus, this improvement can be achieved with subsequent sintering densities up to 98% of the theoretical density. From these experiments, generalizations transferable to other materials can be made. [source] Advances in sol-gel based columns for capillary electrochromatography: Sol-gel open-tubular columnsELECTROPHORESIS, Issue 22-23 2002Abdul Malik Abstract The development of sol-gel open-tubular column technology in capillary electrochromatography (CEC) is reviewed. Sol-gel column technology offers a versatile means of creating organic-inorganic hybrid stationary phases. Sol-gel column technology provides a general approach to column fabrication for microseparation techniques including CEC, and is amenable to both open-tubular and monolithic columns. Direct chemical bonding of the stationary phase to the capillary inner walls provides enhanced thermal and solvent stability to sol-gel columns. Sol-gel stationary phases inherently possess higher surface area, and thus provide an effective one-step alternative to conventional open-tubular column technology. Sol-gel column technology is applicable to both silica-based and transition metal oxide-based hybrid stationary phases, and thus, provides a great opportunity to utilize advanced material properties of a wide range of nontraditional stationary phases to achieve enhanced selectivity in analytical microseparations. A wide variety of stationary phase ligands can be chemically immobilized on the capillary inner surface using a single-step sol-gel procedure. Sol-gel chemistry can be applied to design stationary phases with desired chromatographic characteristics, including the possibility of creating columns with either a positive or a negative charge on the stationary phase surface. This provides a new tool to control electroosmotic flow (EOF) in the column. Column efficiencies on the order of half a million theoretical plates per meter have been reported for sol-gel open-tubular CEC columns. The selectivity of sol-gel stationary phases can be easily fine-tuned by adjusting the composition of the coating sol solution. Open-tubular columns have significant advantages over their packed counterparts because of the simplicity in column making and hassle-free fritless operation. Open-tubular CEC columns possess low sample capacity and low detection sensitivity. Full utilization of the analytical potential of sol-gel open-tubular columns will require a concomitant development in the area of high-sensitivity detection technology. [source] Time,Temperature,Transformation (TTT) Diagrams for Crystallization of Metal Oxide Thin FilmsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Jennifer L. M. Rupp Abstract Time,temperature,transformation (TTT) diagrams are proposed for the crystallization of amorphous metal oxide thin films and their specific characteristics are discussed in comparison to glass-based materials, such as glass-ceramics and metallic glasses. The films crystallize from amorphous to full crystallinity in the solid state. As an example the crystallization kinetics for a single-phase metal oxide, ceria, and its gadolinia solid solutions are reported made by the precipitation thin-film method spray pyrolysis. The crystallization of an amorphous metal oxide thin film generally follows the Lijschitz,Sletow,Wagner (LSW) Ostwald ripening theory: Below the percolation threshold of 20 vol% single grains crystallize in the amorphous phase and low crystallization rates are measured. In this state no impact of solute on crystallization is measurable. Once the grains form primary clusters above the threshold the solute slows down crystallization (and grain growth) thus shifting the TTT curves of the doped ceria films to longer times and higher temperatures in comparison to undoped ceria. Current views on crystallization of metal oxide thin films, the impact of solute dragging, and primary TTT diagrams are discussed. Finally, examples on how to use these TTT diagrams for better thermokinetic engineering of metal oxide thin films for MEMS are given, for example, for micro-Solid Oxide Fuel Cells and resistive sensors. In these examples the electrical properties depend on the degree of crystallinity and, thereby, on the TTT conditions. [source] The Role of Transition Metal Oxides in Charge-Generation Layers for Stacked Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Sami Hamwi Abstract The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs2CO3 -doped 4,7-diphenyl-1,10-phenanthroline layer and a WO3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance,current density,voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5,nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO3 layer and its neighboring hole-transport material, 4,4',4"-tris(N -carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED. [source] Optically-Pumped Lasing in Hybrid Organic,Inorganic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Myoung Hoon Song Abstract Here, the use of metal oxide layers both for charge transport and injection into an emissive semiconducting polymer and also for the control of the in-plane waveguided optical modes in light-emitting diodes (LEDs) is reported. The high refractive index of zinc oxide is used to confine these modes away from the absorbing electrodes, and include a nano-imprinted grating in the polymer layer to introduce distributed feedback and enhance optical out-coupling. These structures show a large increase in the luminescence efficiency over conventional devices, with photoluminescence efficiency increased by up to 45%. Furthermore, optically-pumped lasing in hybrid oxide polymer LEDs is demonstrated. A tuneable lasing emission is also obtained in a single device structure by employing a graduated thickness of a zinc oxide inter-layer. This demonstrates the scope for using such architectures to improve the external efficiency of organic semiconductor LEDs, and opens new possibilities for the realization of polymer injection lasers. [source] Inorganic Macroporous Films from Preformed Nanoparticles and Membrane Templates: Synthesis and Investigation of Photocatalytic and Photoelectrochemical Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2003D.G. Shchukin Abstract Colloidal dispersions of titania, zirconia, tin oxide, indium oxide, and ceria have been successfully used to impregnate membrane templates and form the respective metal oxide (MO) porous films. The use of alumina and iron oxide sols in the same procedure, however, resulted in compact structures. By mixing different nanoparticle solutions before impregnation, final inorganic films containing two metal oxides, of variable metal oxide ratios, were obtained. The porous inorganic materials were analyzed in terms of surface area, pore size, film thickness, and crystallinity. The mechanism of nanoparticle infiltration and particle adsorption to the template walls is proposed based on the stability of the inorganic film and a study of the influence of either the sol concentration or washing times on the amount of inorganic substance incorporated in the hybrid material. The photocatalytic decomposition of an organic pollutant, 2-chlorophenol, was demonstrated for the porous titania material along with the structures containing mixtures of titania with zirconia, indium oxide, and tin oxide. A ratio of 9:1 TiO2/MO gave the highest photocatalytic activity, which was higher than the activity of Degussa P25 for the TiO2/In2O3 and TiO2/SnO2 systems under the same conditions. The titania films have also been attached to substrates,glass or indium tin oxide (ITO) surfaces,and the photoelectrochemical properties of the porous film attained. A comparison with a spin-coated titania film (prepared from the same colloidal dispersion) showed that the structured porous inorganic film has two times the photoelectrochemical efficiency as the spin-coated film. [source] Nanoscale Organic Hybrid ElectrolytesADVANCED MATERIALS, Issue 33 2010Jennifer L. Nugent Nanoscale organic hybrid electrolytes are composed of organic-inorganic hybrid nanostructures, each with a metal oxide or metallic nanoparticle core densely grafted with an ion-conducting polyethylene glycol corona - doped with lithium salt. These materials form novel solvent-free hybrid electrolytes that are particle-rich, soft glasses at room temperature ; yet manifest high ionic conductivity and good electrochemical stability above 5V. [source] Synthesis of Porous Bi2WO6 Thin Films as Efficient Visible-Light-Active PhotocatalystsADVANCED MATERIALS, Issue 12 2009Li-Wu Zhang Bi2WO6 ordered porous film with open pores, an example of a photocatalytically active ternary metal oxide under visible-light irradiation, is prepared using a simple and reproducible route. The ordered porous Bi2WO6 films exhibited much higher photocatalytic activity and photocurrent coversion efficiency than nonporous Bi2WO6 films under visible-light irradiation (,,>,420,nm). [source] Mineralization improvement of phenol aqueous solutions through heterogeneous catalytic ozonationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2003Fernando J Beltrán Abstract To assess the mineralization level achieved, aqueous solutions of phenol have been treated with ozone in the presence of different solid catalysts. Activated carbon was the principal catalyst investigated, although some additional experiments were carried out by utilizing metal oxide-based catalysts (ie Ti, Co and Fe) supported onto alumina. Usage of Co/Al2O3 led to the highest values of phenol byproduct mineralization, nevertheless some metal leaching was experienced in the process. The operating variables studied when using activated carbon as the catalyst were ozone gas concentration, amount of catalyst added and temperature. Regardless of the catalyst type used, two different ozonation kinetic regimes were observed: (I) an initial period, corresponding to the presence of phenol in solution, characterized by small amounts of dissolved ozone and no improvement of the mineralization degree if comparing catalytic and non-catalytic runs; (II) a second period, free of phenol, in which dissolved ozone accumulated in water and the beneficial effects of catalysts on mineralization were noticed. Experimental data also demonstrated the improvement in oxalic acid elimination in the presence of heterogeneous catalysts. Finally, consumption of ozone per mass of carbon removed, reaction factors and Hatta numbers were also calculated. Copyright © 2003 Society of Chemical Industry [source] Chemical-looping combustion process: Kinetics and mathematical modelingAICHE JOURNAL, Issue 4 2010Ion Iliuta Abstract Chemical Looping Combustion technology involves circulating a metal oxide between a fuel zone where methane reacts under anaerobic conditions to produce a concentrated stream of CO2 and water and an oxygen rich environment where the metal is reoxidized. Although the needs for electrical power generation drive the process to high temperatures, lower temperatures (600,800°C) are sufficient for industrial processes such as refineries. In this paper, we investigate the transient kinetics of NiO carriers in the temperature range of 600 to 900°C in both a fixed bed microreactor (WHSV = 2-4 g CH4/h/g oxygen carrier) and a fluid bed reactor (WHSV = 0.014-0.14 g CH4/h per g oxygen carrier). Complete methane conversion is achieved in the fluid bed for several minutes. In the microreactor, the methane conversion reaches a maximum after an initial induction period of less than 10 s. Both CO2 and H2O yields are highest during this induction period. As the oxygen is consumed, methane conversion drops and both CO and H2 yields increase, whereas the CO2 and H2O concentrations decrease. The kinetics parameter of the gas,solids reactions (reduction of NiO with CH4, H2, and CO) together with catalytic reactions (methane reforming, methanation, shift, and gasification) were estimated using experimental data obtained on the fixed bed microreactor. Then, the kinetic expressions were combined with a detailed hydrodynamic model to successfully simulate the comportment of the fluidized bed reactor. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Synthesis and stability of iron nanoparticles for lunar environment studiesMETEORITICS & PLANETARY SCIENCE, Issue 6 2010Ching-Cheh HUNG However, unlike the true lunar dust, today's simulants do not contain nanophase iron. Two different processes have been developed to fabricate nanophase iron to be used as part of a lunar dust simulant. (1) The first is to sequentially treat a mixture of ferric chloride, fluorinated carbon, and soda lime glass beads at about 300 °C in nitrogen, at room temperature in air, and then at 1050 °C in nitrogen. The product includes glass beads that are gray in color, can be attracted by a magnet, and contains ,-iron nanoparticles (which seem to slowly lose their lattice structure in ambient air during a period of 12 months). This product may have some similarity to the lunar glassy agglutinate, which contains FeO. (2) The second is to heat a mixture of carbon black and a lunar simulant (a mixed metal oxide that includes iron oxide) at 1050 °C in nitrogen. This process simulates lunar dust reactions with the carbon in a micrometeorite at the time of impact. The product contains a chemically modified simulant that can be attracted by a magnet and has a surface layer whose iron concentration increased during the reaction. The iron was found to be ,-iron and Fe3O4 nanoparticles, which appear to grow after the fabrication process. This growth became undetectable after 6 months of ambient air storage, but may last for several years or longer. [source] Retarded surface photovoltage response from dye molecules adsorbed on metal oxide surfacesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2004Th. DittrichArticle first published online: 11 AUG 200 Abstract A retarded surface photovoltage response has been observed on metal oxide layers (SnO2:F, TiO2) covered with adsorbed dye molecules while only the dye molecules were excited by short laser pulses. The retardation ranged between 30 and 570 ns depending on the nature of the metal oxide and on surface treatment. Therefore, charge separation in space of electrons injected from dye molecules into metal oxides is strikingly different from ultrafast electron injection measured by time-resolved optical techniques. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Specific response of ultra-thin metal oxide films to gasPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009etkus Abstract Tin and indium oxide ultra-thin film (UTF) based structures are investigated in the present study. Current-voltage characteristics (IVC) are measured in the samples by a contact current mode of scanning probe microscopy (SPM). It is proved that the IVC splits into two paths corresponding to increase and decrease of applied voltage, respectively. Detailed investigations of the electrical properties of the ultra-thin metal oxide (MOX) films revealed a dependence of the IVC on the structure of the films, on initial conductivity and on the surrounding gases. It was proved that the IVC is typically split only if the maximum dc-voltage exceeds some critical magnitude that is not the same in indium and tin oxide based films. The properties of the ultra-thin MOX structures are explained in terms of distribution of stoichiometry in MOX based nanometer systems. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Preparation of Core,Shell-Structured Nanoparticles (with a Noble-Metal or Metal Oxide Core and a Chromia Shell) and Their Application in Water Splitting by Means of Visible LightCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010Kazuhiko Maeda Dr. Abstract Core,shell-structured nanoparticles, consisting of a noble metal or metal oxide core and a chromia (Cr2O3) shell, were studied as promoters for photocatalytic water splitting under visible light. Core nanoparticles were loaded by impregnation, adsorption or photodeposition onto a solid solution of gallium nitride and zinc oxide (abbreviated GaN:ZnO), which is a particulate semiconductor photocatalyst with a band gap of approximately 2.7,eV, and a Cr2O3 shell was formed by photodeposition using a K2CrO4 precursor. Photodeposition of Cr2O3 on GaN:ZnO modified with a noble metal (Rh, Pd and Pt) or metal oxide (NiOx, RuO2 and Rh2O3) co-catalyst resulted in enhanced photocatalytic activity for overall water splitting under visible light (,>400,nm). This enhancement in activity was primarily due to the suppression of undesirable reverse reactions (H2,O2 recombination and/or O2 photoreduction) and/or protection of the core component from chemical corrosion, depending on the core type. Among the core materials examined, Rh species exhibited relatively high performance for this application. The activity for visible-light water splitting on GaN:ZnO modified with an Rh/Cr2O3 core,shell configuration was dependent on both the dispersion of Rh nanoparticles and the valence state. In addition, the morphology of the Cr2O3 photodeposits was significantly affected by the valence state of Rh and the pH at which the photoreduction of K2CrO4 was conducted. When a sufficient amount of K2CrO4 was used as the precursor and the solution pH ranged from 3 to 7.5, Cr2O3 was successfully formed with a constant shell thickness (,2,nm) on metallic Rh nanoparticles, which resulted in an effective promoter for overall water splitting. [source] Spontaneous Organization of Uniform CeO2 Nanoflowers by 3D Oriented Attachment in Hot Surfactant Solutions Monitored with an In Situ Electrical Conductance TechniqueCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2008Huan-Ping Zhou Abstract Uniform CeO2 nanoflowers were synthesized by rapid thermolysis of (NH4)2Ce(NO3)6 in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO2 nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10,40,nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO2 nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO3,) via hydrolysis of (NH4)2Ce(NO3)6 at temperatures in the range 140,220,°C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220,°C in a strong redox reaction. After calcination at 400,°C for 4,h the 33.8,nm CeO2 nanoflowers have a specific surface area as large as 156,m2,g,1 with high porosity, and they are highly active for conversion of CO to CO2 in the low temperature range of 200,400,°C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuOx) nanoflowers. [source] Development of an oxide semiconductor thick film gas sensor for the detection of total volatile organic compoundsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2010Masahiro Kadosaki Abstract Since the amendment of the Building Standards Law in 2003, the installation of ventilators is compulsory in newly built houses, because many persons suffer from indoor air pollution caused by volatile organic compounds (VOCs). The goal of this research is to develop a gas sensor that can monitor the total VOC (TVOC) gases indoors and then to control the ventilator efficiently using the sensor. In order to develop a sensor that detects TVOC, the responses of four oxide semiconductor materials to 37 different VOC gases were studied. These materials showed small responses to halogenated and aliphatic hydrocarbon gases. As a result of improving the response to these gases, among four metal oxides examined, SnO2 and WO3 showed high sensitivities by the addition of Pd and Pt. The sensing properties of SnO2 for halogenated hydrocarbon gases were greatly improved by the addition of 0.5 wt% Pd. The sensing properties of SnO2 for aliphatic hydrocarbon gases were improved by the addition of 0.7 wt% Pt. In addition, a sensor element with the addition of both platinum and palladium, that is, Pt (0.5 wt%)-Pd (0.5 wt%)-SnO2, showed a large response to many of the VOC gases examined. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(10): 34,41, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10190 [source] Factors influencing the sorption of oxytetracycline to soilsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005Aaryn D. Jones Abstract Veterinary antibiotics such as oxytetracycline (OTC) increasingly are found in the environment and often come into direct contact with soils via the release of animal wastes. Oxytetracycline is known to sorb strongly to soils by interaction with soil organic matter, clay minerals, and metal oxides. However, current knowledge of the influence of soil properties on OTC sorption is limited, as is our ability to predict OTC sorption to soils. This work was aimed at identifying properties that most influence the extent of OTC sorption in a suite of soils from the eastern United States representing a wide range in soil properties. Thirty soils were well characterized, an OTC soil-water distribution coefficient (Kd) was determined for each soil, and statistical analyses were employed to determine appropriate soil descriptors of OTC sorption. Soil texture, cation exchange capacity, and iron oxide content seemed to most influence the extent of OTC sorption in soils with organic carbon (OC) content between 0 and 4%. Thus, the knowledge of these three soil properties would be key to anticipating the extent of OTC sorption and gaining insight into OTC fate within a given soil system. Notably, OC content appeared to influence OTC sorption only in a soil with 9% OC. [source] Synthesis and Characterisation of a New Cu(O2CNAllyl2)2 Carbamato Complex and an Unusual Polymeric CuI Complex [CuI4Cl4(NHAllyl2)4]n: New Insights into Metal Carbamato ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009Alberto Albinati Abstract Transition-metal N,N -dialkylcarbamato complexes represent an interesting class of compounds that can be conveniently used as precursors for the controlled formation of inorganic compounds, typically oxides. They can also be used as convenient precursors for chemical grafting of metal oxides on oxide surfaces as well as for the synthesis of inorganic,organic hybrid materials. In this last case, the presence of double bonds on the complex would enable its covalent embedding into a polymer matrix through reaction with suitable monomers. To this aim, we addressed the synthesis of an allyl-functionalised copper carbamato complex. During the synthesis of the N,N -diallylcarbamato complex Cu(O2CNAllyl2)2 (Cu1), the formation of the crystalline and unusual polymeric CuI complex [CuI4Cl4(NHAllyl2)4]n (Cu2) was observed. The new compound was characterised by X-ray single crystal diffraction and FTIR, 1H and 13C NMR spectroscopic analysis. In an attempt to investigate the redox mechanism and the equilibria leading to the formation of the observed unusual CuI polymeric complex, gas chromatography coupled with mass spectrometry (GC,MS) experiments were carried out, which allowed us to identify 3,4-dimethylpyrrole as the oxidation product of the reaction, leading to the reduction of CuII to CuI.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Calcite-specific coupling protein in barnacle underwater cementFEBS JOURNAL, Issue 24 2007Youichi Mori The barnacle relies for its attachment to underwater foreign substrata on the formation of a multiprotein complex called cement. The 20 kDa cement protein is a component of Megabalanus rosa cement, although its specific function in underwater attachment has not, until now, been known. The recombinant form of the protein expressed in bacteria was purified in soluble form under physiological conditions, and confirmed to retain almost the same structure as that of the native protein. Both the protein from the adhesive layer of the barnacle and the recombinant protein were characterized. This revealed that abundant Cys residues, which accounted for 17% of the total residues, were in the intramolecular disulfide form, and were essential for the proper folding of the monomeric protein structure. The recombinant protein was adsorbed to calcite and metal oxides in seawater, but not to glass and synthetic polymers. The adsorption isotherm for adsorption to calcite fitted the Langmuir model well, indicating that the protein is a calcite-specific adsorbent. An evaluation of the distribution of the molecular size in solution by analytical ultracentrifugation indicated that the recombinant protein exists as a monomer in 100 mm to 1 m NaCl solution; thus, the protein acts as a monomer when interacting with the calcite surface. cDNA encoding a homologous protein was isolated from Balanus albicostatus, and its derived amino acid sequence was compared with that from M. rosa. Calcite is the major constituent in both the shell of barnacle base and the periphery, which is also a possible target for the cement, due to the gregarious nature of the organisms. The specificity of the protein for calcite may be related to the fact that calcite is the most frequent material attached by the cement. [source] Crystallization and Grain Growth Kinetics for Precipitation-Based Ceramics: A Case Study on Amorphous Ceria Thin Films from Spray PyrolysisADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Jennifer L. M. Rupp Abstract The introductory part reviews the impact of thin film fabrication, precipitation versus vacuum-based methods, on the initial defect state of the material and microstructure evolution to amorphous, biphasic amorphous-nanocrystalline, and fully nanocrystalline metal oxides. In this study, general rules for the kinetics of nucleation, crystallization, and grain growth of a pure single-phase metal oxide thin film made by a precipitation-based technique from a precursor with one single organic solvent are discussed. For this a complete case study on the isothermal and non-isothermal microstructure evolution of dense amorphous ceria thin films fabricated by spray pyrolysis is conducted. A general model is established and comparison of these thin film microstructure evolution to kinetics of classical glass-ceramics or metallic glasses is presented. Knowledge on thermal microstructure evolution of originally amorphous precipitation-based metal oxide thin films allows for their introduction and distinctive microstructure engineering in devices-based on microelectromechanical (MEMS) technology such as solar cells, capacitors, sensors, micro-solid oxide fuel cells, or oxygen separation membranes on Si-chips. [source] | ||||||||||||||||||||||||||||||||||||||||