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Molten oxide electrolysis (MOE) is an electrometallurgical technique that enables the direct production of metal in the liquid state from oxide feedstock (1,2), and compared with traditional methods of extractive [...]

Mixed-metal oxides play a very important role in many areas of chemistry, physics, materials science, and geochemistry. Recently, there has been a strong interest in understanding phenomena associated with the deposition of oxide nanoparticles on the surface of a second (host) oxide. Here, scanning tunneling microscopy, photoemission, and density-functional calculations are used to study the behavior of ceria nanoparticles deposited on a Ti[O.sub.2](110) surface. The titania substrate imposes nontypical coordination modes on the ceria nanoparticles. In the Ce[O.sub.x]/Ti[O.sub.2](110) systems, the Ce cations adopt an structural geometry and an oxidation state (+3) that are quite different from those seen in bulk ceria or for ceria nanoparticles deposited on metal substrates. The increase in the stability of the [Ce.sup.3+] oxidation state leads to an enhancement in the chemical and catalytic activity of the ceria nanoparticles. The codeposition of ceria and gold nanoparticles on a Ti[O.sub.2](110) substrate generates catalysts with an extremely high activity for the production of hydrogen through the water-gas shift reaction ([H.sub.2]O + CO [right arrow] [H.sub.2] + C[O.sub.2]) or for the oxidation of carbon monoxide (2CO + [O.sub.2] [right arrow] 2C[O.sub.2]). The enhanced stability of the [Ce.sup.3+] state is an example of structural promotion in catalysis described here on the atomic level. The exploration of mixed-metal oxides at the nanometer level may open avenues for optimizing catalysts through stabilization of unconventional surface structures with special chemical activity. heterogeneous catalysis | imaging | structural properties | surface reactivity

The unique catalytic, electrochemical, and oxygen storage properties of ceria and mixed ceria/titania hybrid composites were used to fabricate a new type of electrochemical enzyme biosensor. These materials provided increased analytical performance and possibilities for operation in oxygen-free conditions of an oxidase enzyme biosensor using tyrosinase as a model example. The investigation of the enzymatic reaction in the presence and absence of oxygen was first carried out using cyclic voltammetry. The results were used to identify the role of each metal oxide in the immobilization matrix and fabricate a simple amperometric tyrosinase biosensor for the detection of phenol and dopamine. The biosensor was optimized and characterized with respect to response time, detection limit, linear concentration range, sensitivity, and kinetic parameters. The detection limit for phenol was in the nanomolar range, with a detection limit of 9.0 x [10.sup.-9] M and a sensitivity of 86 mA [M.sup.-1] in the presence of oxygen and of 5.6 x [10.sup.-9] M and a sensitivity of 65 mA [M.sup.-1] in the absence of oxygen. The optimized biosensor also showed selective determination of the neurotransmitter dopamine with a detection limit of 3.4 x [10.sup.-8] M and a sensitivity of 14.9 mA [M.sup.-1] in the presence of oxygen and of 4.2 x [10.sup.-8] M and 14.8 mA [M.sup.-1] in the absence of oxygen. This strategy shows promise for increasing the sensitivity of oxidase enzyme sensors and provides opportunities for operation in oxygen limited conditions. It can also be extended for the development of other enzyme biosensors.

In a large capacity tangentially fired boiler, the final reheater tubing sustained abnormal oxidation and localized excessive metal wastage in a short time of the unit operation. The root causes of the problem are identified by test data analysis. The test data indicated that the reheater tubing metal temperatures in the affected areas exceeded the recommended limit of the metal oxidation temperature due to higher than expected local gas temperatures and velocities. A soot-blower facing the overheated portion of the reheater leading tubes accelerated the process of metal wastage by periodically removing the oxide layer. The configuration of the boiler internals upstream of the reheater section is found to be the main cause of the localized overheating. Side-to-side gas flow/temperature stratification due to tangential firing contributed to a lesser degree to the problem. The results and conclusions presented in this paper should be a beneficial guide to the designer of large capacity boilers. [DOI: 10.1115/1.2795769]

To minimize interfacial power losses, thin (5-80 nm) layers of NiO, a p-type oxide semiconductor, are inserted between the active organic layer, poly(3-hexylthiophene) (P3HT) + [6,6]-phenyI-[C.sub.61] butyric acid methyl ester (PCBM), and the ITO (tin-doped indium oxide) anode of bulk-heterojunction ITO/P3HT:PCBM/LiF/AI solar cells. The interfacial NiO layer is deposited by pulsed laser deposition directly onto cleaned ITO, and the active layer is subsequently deposited by spin-coating. Insertion of the NiO layer affords cell power conversion efficiencies as high as 5.2% and enhances the fill factor to 69% and the open-circuit voltage ([V.sub.oc]) to 638 mV versus an ITO/P3HT:PCBM/LiF/AI control device. The value of such hole-transporting/electron-blocking interfacial layers is clearly demonstrated and should be applicable to other organic photovoltaics. interface | photovoltaic | solar energy

Three classification of the bonded interactions of a material in terms of the bond critical point and the local density properties displayed by an electron density distribution are examined for a relatively large number of non-transition-metal oxygen M-O bonded interactions in terms of their experimental and theoretical bond lengths. It is found that of the three classifications, the use of the sign and magnitude of H([r.sub.c]) appears to be adequate and seems to provide a more consistent measure of the way the character of the interactions changes with the coordination number and the net charges of the bonded atoms.

The effects of the interfacial bonding are examined by experiments with submonolayer atomic-layer deposition (ALD) metal oxides and atomistic simulation. It is concluded that for Al2O3 (aluminum oxide) gate dielectrics, the pinning takes place just above the Si (silicon) valence band and is not as strong as for HfO2 (hafnium dioxide).

Knowing the thermodynamic stability of transition metal oxide nanoparticles is important for understanding and controlling their role in a variety of industrial and environmental systems. Using calorimetric data on surface energies for cobalt, iron, manganese, and nickel oxide systems, we show that surface energy strongly influences their redox equilibria and phase stability. Spinels ([M.sub.3][O.sub.4]) commonly have tower surface energies than metals (M), rocksalt oxides (MO), and trivalent oxides ([M.sub.2][O.sub.3]) of the same metal; thus, the contraction of the stability field of the divalent oxide and expansion of the spinel field appear to be general phenomena. Using tabulated thermodynamic data for bulk phases to calculate redox phase equilibria at the nanoscale can lead to errors of several orders of magnitude in oxygen fugacity and of 100 to 200 kelvin in temperature. 10.1126/science.1195875

Byline: Sardar K. Bahador Due to energy crises and vital necessities for finding some truly clean and durable energy sources as well as providing the means required for efficient conversion, storage, and utilisation of such energies, intensive systematic work have been carried out since 1979 which deals primarily with the materials, processes and devices of interest excluding absolutely the nuclear energy. Effective exploitation of the eternally available, environmentally clean and embargo-proof solar power is the most promising one where utilisation of its radiant energy at least, will enable us to cope with the world's future energy needs. In this respect, various organic and inorganic semiconducting materials and corresponding energy systems are investigated. The nature and fates of parameters involved in the preparative processes and characterization methodologies of the thermal and anodic oxides, CVD and rf sputtered thin films, and the chemicallv synthesised powders are taken into account. Ample evidences showing the effects of such parameters on the system efficiencies have been furnished via stepwise tests on structural, surface, electrical, optical, magnetic, photovoltaic, PV, and photoelectrochemical, PEC, behaviours using XRD, XRF, SEM, AES, ESCA, EXAFS, EPMA, IR. Raman, ESR, NMR, spectrography, atomic absorption, magnetic susceptibility techniques. Beside the application of primarily oxides in lithium batteries, sensors, pigment technologies, microelectronics, PV and PEC devices, by taking into account the PEC cell functions, even though buffered electrolytes are usually employed, a three dimensional graphic correlation of the electrode potential, E.SUB.H, with PH and percent oxidation (or reduction) of the redox species present in the non-buffered electrolyte is drawn. The roles of sensitising dyes such as RhB, Th, and MB together with the results of PEC measurements on sintered and rf sputtered thin film electrodes, and the energetic diagram of a PEC cell operating under power generating conditions are presented. The diverse impacts of many of the electrode materials' processing and PEC cell parameters on (photo-)electrodics are explored elsewhere.

A research makes use of a physically based channel mobility model to study the effect of temperature on the field-effect mobility of 4H-SiC metal-oxide semiconductor (MOS) transistors with thermally oxidized gate insulators. The results of the analysis show that the increase in the inversion charge and the reduction of the trapped charge with the increasing temperature lead to an increase even in the field-effect mobility of such devices.

The density functional theory computations along with statistical mechanics are performed in detail to obtain the energetics of O2 adsorption on pure and Au-alloy clusters with Ag, Cu, Pd, and Pt and Na atoms as alloy atoms. It was inferred from the energetics of fragmentations that the bare and O2-covered clusters are stable.

Byline: Lionel Vayssieres Divided and ultra-divided systems such as colloidal and nanoparticle dispersions are generally unstable with regard to the size and number of their constituents because the solid-solution interfacial tension, acting as a driving force, leads to a reduction of the surface area to minimise the dispersion free enthalpy. Such phenomenon known as surface energy minimisation induces an increase in average particle size as a result of the decrease of the surface area at constant volume. For such a reason such dispersions are usually considered thermodynamically unstable. However, they can be thermodynamically stabilised if, by adsorption, the interfacial tension of the system becomes very low. This phenomenon, well known for microemulsions, is for the first time quantitatively modelled and demonstrated for transition metal oxide nanoparticles. When the pH of precipitation is sufficiently far from the point of zero charge and the ionic strength sufficiently high, the ripening of nanoparticles is avoided and their size can be monitored over one order of magnitude by tailoring solution pH and ionic strength. A model based on Gibbs adsorption equation leads to an analytical expression of the water-oxide interfacial tension as a function of the pH and the ionic strength of the dispersion/precipitation medium. The stability condition, defined by a 'zero' interfacial tension, corresponds to the chemical and electrostatic saturation of the water-oxide interface. In such a condition, the density of charged surface groups reaches its maximum, the interfacial tension its minimum and further adsorption forces the surface area to expand and consequently, the size of nanoparticles to decrease. An excellent agreement was found between the model prediction and the experimental results obtained from the aqueous precipitation of magnetite (Fe3O4) nanoparticles in basic medium. A general control of the metal oxide nanoparticle size when precipitated far from their point-of-zero-charge is thus expected.

The advantage of interfacial transition-metal oxides, such as IrOx and Rux, between indium tin oxide (ITO) anodes and hole transport layers of 4'-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl (alpha-NPD) on the electrical and optical properties of optical properties of organic light-emitting diodes (OLEDs) is reported. When IrOx or RuOx layers are present between ITO and alpha-NPD, the operation voltage of OLEDs at the current density of 100 mA/cm(super 2) decreased from 17 to 11 V for the IrOx interlayers and from 17 to 14 V for the RuOx layers.

The results of studies on the solonitsyn memory effect in gas-solid heterogeneous systems with respect to photo-stimulated adsorption of molecular hydrogen, oxygen and methane on a dielectric metal oxide surface are mentioned. The experimental data is explained using a simple model.

Grazing incidence x-ray diffraction (GIXD) is a powerful tool to investigate metal/oxide interfaces from their formation. Cobalt and permalloy films on NiO(111) single crystals exhibit similar behavior, though some difference exists.

A general chemical process is developed for nanoscale-to-macroscale duplication of the complex hierarchical morphology of natural cellulosic substances with metal oxide matrices. The new nano-copying methodology provides positive and negative replicas of targeted objects in nanometer precision.

The preparation of chiral, tubular helical fiber materials of transition-metal (Ti, Ta, V) oxides is described by using the sol-gel polymerization of metal alkoxides using the chiral aggregates of organogelators as templates or structure-directing agents. The helices of metal oxide fibers are always left-handed in the sol-gel system of the R,R-enantiomers and right-handed in the case of the S,S-enantiomer.