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1

Properties of interfaces between metals and binary oxides.  

NASA Astrophysics Data System (ADS)

Metallic gate contacts are fundamental components of MOSFET architectures, and understanding their physical properties at a fundamental level is of great importance for the engineering of advanced electronic devices. In this poster we will present preliminary results of a comprehensive ab initio study of the structural and electronic properties of interfaces between metals and high-k dielectrics, mostly crystalline binary oxides. Our primary interest is in the characterization of the influence of lattice matching and chemical composition at the interface on the Schottky barrier formation and properties. In particular we will frame our results in a broad perspective that embraces, at its ends, the Bardeen and Schottky views of the band alignment problem.

Nunez, Matias; Nardelli, Marco

2004-11-01

2

Properties of interfaces between metals and binary oxides.  

NASA Astrophysics Data System (ADS)

Metallic gate contacts are fundamental components of MOSFET architectures, and understanding their physical properties at a fundamental level is of great importance for the engineering of advanced electronic devices. In this poster we will present preliminary results of a comprehensive ab initio study of the structural and electronic properties of interfaces between metals and high-k dielectrics, mostly crystalline binary oxides. Our primary interest is in the characterization of the influence of lattice matching and chemical composition at the interface on the Schottky barrier formation and properties. In particular we will frame our results in a broad perspective that embraces, at its ends, the Bardeen and Schottky views of the band alignment problem.

Nunez, Matias

2005-03-01

3

Nonpolar resistance switching of metal\\/binary-transition-metal oxides\\/metal sandwiches: Homogeneous\\/inhomogeneous transition of current distribution  

Microsoft Academic Search

Exotic features of a metal\\/oxide\\/metal sandwich, which will be the basis for a drastically innovative nonvolatile memory device, is brought to light from a physical point of view. Here the insulator is one of the ubiquitous and classic binary-transition-metal oxides (TMO), such as Fe2O3 , NiO , and CoO . The sandwich exhibits a resistance that reversibly switches between two

I. H. Inoue; S. Yasuda; H. Akinaga; H. Takagi

2008-01-01

4

Hydrolysis of CF 4 over alumina-based binary metal oxide catalysts  

Microsoft Academic Search

Carbon tetrafluoride (CF4), which is the most stable compound in perfluorocarbons (PFCs), was catalytically decomposed by the hydrolysis reaction at mild condition as 850–950K on alumina-based binary metal oxide catalysts. The catalytic activities for the hydrolysis reaction of CF4 with water on the selected metal-Al oxide catalysts were optimized in terms of H2O\\/CF4 ratio, loading amount of metal oxide to

Z. M. El-Bahy; Ryuichiro Ohnishi; Masaru Ichikawa

2003-01-01

5

Electrodeposition of metallic tungsten coating from binary oxide molten salt on low activation steel substrate  

NASA Astrophysics Data System (ADS)

Tungsten is considered a promising plasma facing armor material for future fusion devices. An electrodeposited metallic tungsten coating from Na2WO4-WO3 binary oxide molten salt on low activation steel (LAS) substrate was investigated in this paper. Tungsten coatings were deposited under various pulsed currents conditions at 1173 K in atmosphere. Cathodic current density and pulsed duty cycle were investigated for pulsed current electrolysis. The crystal structure and microstructure of tungsten coatings were characterized by X-ray diffractometry, scanning electron microscopy, and energy X-ray dispersive analysis techniques. The results indicated that pulsed current density and duty cycle significantly influence tungsten nucleation and electro-crystallization phenomena. The average grain size of the coating becomes much larger with increasing cathodic current density, which demonstrates that appropriate high cathodic current density can accelerate the growth of grains on the surface of the substrate. The micro-hardness of tungsten coatings increases with the increasing thickness of coatings; the maximum micro-hardness is 482 HV. The prepared tungsten coatings have a smooth surface, a porosity of less than 1%, and an oxygen content of 0.024 wt%.

Liu, Y. H.; Zhang, Y. C.; Jiang, F.; Fu, B. J.; Sun, N. B.

2013-11-01

6

Slag Metal Reactions in Binary CaF2-Metal Oxide Welding Fluxes  

E-print Network

submerged arc welds on carbon steel plate. Supplementary argon shielding was used to prevent atmospheric fluxes may decompose into suboxides in the presence of welding arcs, thereby providing higher levels of 0 chemically, may decompose into suboxides in the presence of the welding arc plasma. Such oxides produce

Eagar, Thomas W.

7

Excellent uniformity and reproducible resistance switching characteristics of doped binary metal oxides for non-volatile resistance memory applications  

Microsoft Academic Search

We have investigated various doped metal oxides such as copper doped molybdenum oxide, copper doped Al2O3, copper doped ZrO2, aluminium doped ZnO, and CuxO for novel resistance memory applications. Compared with non-stoichiometric oxides (Nb2O5-x, ZrOx, SrTiOx), doped metal oxides show higher device yield. Moreover, Cu:MoOx have demonstrated excellent memory characteristics such as reliability under programming cycles, potential multi-bit operation, good

Dongsoo Lee; Dong-jun Seong; Hye jung Choi; Inhwa Jo; R. Dong; W. Xiang; Seokjoon Oh; Myeongbum Pyun; Sun-ok Seo; Seongho Heo; Minseok Jo; Dae-Kyu Hwang; H. K. Park; M. Chang; M. Hasan; Hyunsang Hwang

2006-01-01

8

Resistance Switching and Formation of a Conductive Bridge in Metal\\/Binary Oxide\\/Metal Structure for Memory Devices  

Microsoft Academic Search

The resistance switching mechanism of a metal\\/CuO\\/metal sandwich with a planar device structure has been studied. We report the direct observation of a conducting bridge within the CuO channel of the device, which is formed upon the initial voltage application (forming process). It is found that the resistance switching phenomenon only occurs when just a single bridge is formed during

Kohei Fujiwara; Takumi Nemoto; Marcelo J. Rozenberg; Yoshinobu Nakamura; Hidenori Takagi

2008-01-01

9

Modeling selective intergranular oxidation of binary alloys  

NASA Astrophysics Data System (ADS)

Intergranular attack of alloys under hydrothermal conditions is a complex problem that depends on metal and oxygen transport kinetics via solid-state and channel-like pathways to an advancing oxidation front. Experiments reveal very different rates of intergranular attack and minor element depletion distances ahead of the oxidation front for nickel-based binary alloys depending on the minor element. For example, a significant Cr depletion up to 9 ?m ahead of grain boundary crack tips was documented for Ni-5Cr binary alloy, in contrast to relatively moderate Al depletion for Ni-5Al (˜100 s of nm). We present a mathematical kinetics model that adapts Wagner's model for thick film growth to intergranular attack of binary alloys. The transport coefficients of elements O, Ni, Cr, and Al in bulk alloys and along grain boundaries were estimated from the literature. For planar surface oxidation, a critical concentration of the minor element can be determined from the model where the oxide of minor element becomes dominant over the major element. This generic model for simple grain boundary oxidation can predict oxidation penetration velocities and minor element depletion distances ahead of the advancing front that are comparable to experimental data. The significant distance of depletion of Cr in Ni-5Cr in contrast to the localized Al depletion in Ni-5Al can be explained by the model due to the combination of the relatively faster diffusion of Cr along the grain boundary and slower diffusion in bulk grains, relative to Al.

Xu, Zhijie; Li, Dongsheng; Schreiber, Daniel K.; Rosso, Kevin M.; Bruemmer, Stephen M.

2015-01-01

10

Metal oxide films on metal  

DOEpatents

A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

Wu, Xin D. (Los Alamos, NM); Tiwari, Prabhat (Los Alamos, NM)

1995-01-01

11

An Acidity Scale for Binary Oxides.  

ERIC Educational Resources Information Center

Discusses the classification of binary oxides as acidic, basic, or amphoteric. Demonstrates how a numerical scale for acidity/basicity of binary oxides can be constructed using thermochemical data for oxoacid salts. Presents the calculations derived from the data that provide the numeric scale values. (TW)

Smith, Derek W.

1987-01-01

12

Metal oxide-polymer composites  

NASA Technical Reports Server (NTRS)

A method of making metal oxide clusters in a single stage by reacting a metal oxide with a substoichiometric amount of an acid in the presence of an oxide particle growth terminator and solubilizer. A method of making a ceramer is also disclosed in which the metal oxide clusters are reacted with a functionalized polymer. The resultant metal oxide clusters and ceramers are also disclosed.

Wellinghoff, Stephen T. (Inventor)

1994-01-01

13

Metal oxide-polymer composites  

NASA Technical Reports Server (NTRS)

A method of making metal oxide clusters in a single stage by reacting a metal oxide with a substoichiometric amount of an acid in the presence of an oxide particle growth terminator and solubilizer. A method of making a ceramer is also disclosed in which the metal oxide clusters are reacted with a functionalized polymer. The resultant metal oxide clusters and ceramers are also disclosed.

Wellinghoff, Stephen T. (Inventor)

1997-01-01

14

Extracting metals directly from metal oxides  

DOEpatents

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of {beta}-diketones, halogenated {beta}-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process. 4 figs.

Wai, C.M.; Smart, N.G.; Phelps, C.

1997-02-25

15

Extracting metals directly from metal oxides  

DOEpatents

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of .beta.-diketones, halogenated .beta.-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process.

Wai, Chien M. (Moscow, ID); Smart, Neil G. (Moscow, ID); Phelps, Cindy (Moscow, ID)

1997-01-01

16

Thermodynamic stability of binary oxides in contact With silicon  

Microsoft Academic Search

Using tabulated thermodynamic data, a comprehensive investigation of the thermodynamic stability of binary oxides in contact with silicon at 1000 K was conducted. Reactions between silicon and each binary oxide at 1000 K, including those involving ternary phases, were considered. Sufficient data exists to conclude that all binary oxides except the following are thermodynamically unstable in contact with silicon at

K. J. Hubbard; D. G. Schlom

1996-01-01

17

Stochastic learning in oxide binary synaptic device for neuromorphic computing  

PubMed Central

Hardware implementation of neuromorphic computing is attractive as a computing paradigm beyond the conventional digital computing. In this work, we show that the SET (off-to-on) transition of metal oxide resistive switching memory becomes probabilistic under a weak programming condition. The switching variability of the binary synaptic device implements a stochastic learning rule. Such stochastic SET transition was statistically measured and modeled for a simulation of a winner-take-all network for competitive learning. The simulation illustrates that with such stochastic learning, the orientation classification function of input patterns can be effectively realized. The system performance metrics were compared between the conventional approach using the analog synapse and the approach in this work that employs the binary synapse utilizing the stochastic learning. The feasibility of using binary synapse in the neurormorphic computing may relax the constraints to engineer continuous multilevel intermediate states and widens the material choice for the synaptic device design. PMID:24198752

Yu, Shimeng; Gao, Bin; Fang, Zheng; Yu, Hongyu; Kang, Jinfeng; Wong, H.-S. Philip

2013-01-01

18

Oxidation Behavior of Binary Niobium Alloys  

NASA Technical Reports Server (NTRS)

This investigation concludes a study to determine the effects of up to 25 atomic percent of 55 alloying additions on the oxidation characteristics of niobium. The alloys were evaluated by oxidizing in an air atmosphere for 4 hours at 1000 C and 2 hours at 1200 C. Titanium and chromium improved oxidation resistance at both evaluation conditions. Vanadium and aluminum improved oxidation resistance at 1000 C, even though the V scale tended to liquefy and the Al specimens became brittle and the scale powdery. Copper, cobalt, iron, and iridium improved oxidation resistance at 1200 C. Other investigations report tungsten and molybdenum are protective up to about 1000 C, and tantalum at 1100 C. The most important factor influencing the rate of oxidation was the ion size of the alloy additions. Ions slightly smaller than the Nb(5+) ion are soluble in the oxide lattice and tend to lower the compressive stresses in the bulk scale that lead to cracking. The solubility of the alloying addition also depends on the valence to some extent. All of the elements mentioned that improve the oxidation resistance of Nb fit this size criterion with the possible exception of Al, whose extremely small size in large concentrations would probably lead to the formation of a powdery scale. Maintenance of a crack-free bulk scale for as long as possible may contribute to the formation of a dark subscale that ultimately is rate- controlling in the oxidation process. The platinum-group metals, especially Ir, appear to protect by entrapment of the finely dispersed alloying element by the incoming Nb2O5 metal-oxide interface. This inert metallic Ir when alloyed in a sufficient amount with Yb appears to give a ductile phase dispersed in the brittle oxide. This scale would then flow more easily to relieve the large compressive stresses to delay cracking. Complex oxide formation (which both Ti and Zr tend to initiate) and valence effects, which probably change the vacancy concentration in the scale, are masked by the overriding tendency for a porous scale.

Barrett, Charles A.; Corey, James L.

1960-01-01

19

Polymorphism Control in Nanostructured Metal Oxides  

NASA Astrophysics Data System (ADS)

Polymorphic phase transformations are common to all nanocrystalline binary metal oxides. The polymorphic nature of such metal oxides makes available a large number of phases with differing crystal structures, each stable under certain conditions of temperature, pressure, and/or particle size. These different crystal structures translate to unique physical and chemical properties for each structural class of polymorphs. Thus predicting when polymorphic phase transitions are likely to occur becomes important to the synthesis of stable functional materials with desired properties. Theoretical calculations using a heuristic approach have resulted in an accurate estimation of the critical particle size predicting metastable to stable phase transitions. This formula is applied to different case studies: for anatase to rutile titania; gamma-Alumina to alpha-Alumina; and tetragonal to monoclinic zirconia. The theoretical values calculated have been seen to be very close to the experimental results from the literature. Manifestation of the effect of phase transitions in nanostructured metal oxides was provided in the study of metastable to stable phase transitions in WO3. Nanowires of tungsten trioxide have been synthesized in-situ inside an electron microscope. Such structure of tungsten trioxide result due to a metastable to stable phase transformation, from the cubic to the monoclinic phase. The transformation is massive and complete. The structures formed are unique one-dimensional nanowires. Such a method can be scaled inside any equipment equipped with an electron gun, for example lithography systems either using STEM or E-beam lithography. Another study on nanowire formation in binary metal oxides involved the synthesis of stable orthorhombic MoO3 by means of blend electrospinning. Both a traditional single jet electrospinning set up and a novel high-throughput process to get high aspect ratio nanowires. The latter is a jet-controlled and flow controlled electrospinning. The mechanism of the formation of nanowires of both tungsten trioxide and molybdenum trioxide are discussed in relation to the polymorphic nature of the oxides.

Sood, Shantanu

20

Thin film hydrous metal oxide catalysts  

DOEpatents

Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

Dosch, Robert G. (Albuquerque, NM); Stephens, Howard P. (Albuquerque, NM)

1995-01-01

21

Homogeneous crystal nucleation in binary metallic melts  

NASA Technical Reports Server (NTRS)

A method for calculating the homogeneous crystal nucleation frequency in binary metallic melts is developed. The free energy of crystallization is derived from regular solution models for the liquid and solid and is used, together with model-based estimates of the interfacial tension, to calculate the nucleation frequency from the classical theory. The method can account for the composition dependence of the maximum undercooling observed in a number of experiments on small droplet dispersions. It can also be used to calculate the driving force for crystal growth and to obtain more precise estimates of the homogeneous crystal nucleation frequency in glass-forming alloys. This method, although approximate, is simple to apply, and requires only knowledge of the phase diagram and a few readily available thermodynamic quantities as input data.

Thompson, C. V.; Spaepen, F.

1983-01-01

22

Water oxidation catalysis: electrocatalytic response to metal stoichiometry in amorphous metal oxide films containing iron, cobalt, and nickel.  

PubMed

Photochemical metal-organic deposition (PMOD) was used to prepare amorphous metal oxide films containing specific concentrations of iron, cobalt, and nickel to study how metal composition affects heterogeneous electrocatalytic water oxidation. Characterization of the films by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed excellent stoichiometric control of each of the 21 complex metal oxide films investigated. In studying the electrochemical oxidation of water catalyzed by the respective films, it was found that small concentrations of iron produced a significant improvement in Tafel slopes and that cobalt or nickel were critical in lowering the voltage at which catalysis commences. The best catalytic parameters of the series were obtained for the film of composition a-Fe20Ni80. An extrapolation of the electrochemical and XPS data indicates the optimal behavior of this binary film to be a manifestation of iron stabilizing nickel in a higher oxidation level. This work represents the first mechanistic study of amorphous phases of binary and ternary metal oxides for use as water oxidation catalysts, and provides the foundation for the broad exploration of other mixed-metal oxide combinations. PMID:23883103

Smith, Rodney D L; Prévot, Mathieu S; Fagan, Randal D; Trudel, Simon; Berlinguette, Curtis P

2013-08-01

23

Spectroscopic studies of metal growth on oxides  

E-print Network

Metal/oxide chemistry and metal cluster growth on oxides are fundamental to our understanding of the catalytic activity and selectivity of metal catalysts, thus considerable research recently has addressed the physical and chemical properties...

Luo, Kai

2000-01-01

24

METAL OXIDE NANOPARTICLES  

SciTech Connect

This chapter covers the fundamental science, synthesis, characterization, physicochemical properties and applications of oxide nanomaterials. Explains fundamental aspects that determine the growth and behavior of these systems, briefly examines synthetic procedures using bottom-up and top-down fabrication technologies, discusses the sophisticated experimental techniques and state of the art theory results used to characterize the physico-chemical properties of oxide solids and describe the current knowledge concerning key oxide materials with important technological applications.

FERNANDEZ-GARCIA,M.; RODGRIGUEZ, J.A.

2007-10-01

25

Process for fabrication of metal oxide films  

SciTech Connect

This invention is comprised of a method of fabricating metal oxide films from a plurality of reactants by inducing a reaction by plasma deposition among the reactants. The plasma reaction is effective for consolidating the reactants and producing thin films of metal oxides, e.g. electro-optically active transition metal oxides, at a high deposition rate. The presence of hydrogen during the plasma reaction enhances the deposition rate of the metal oxide. Various types of metal oxide films can be produced.

Tracy, C.E.; Benson, D.; Svensson, S.

1990-07-17

26

Diffusion and interdiffusion in binary metallic melts  

NASA Astrophysics Data System (ADS)

We discuss the dependence of self- and interdiffusion coefficients on temperature and composition for two prototypical binary metallic melts, Al-Ni and Zr-Ni, in molecular-dynamics computer simulations and the mode-coupling theory of the glass transition (MCT). Dynamical processes that are mainly entropic in origin slow down mass transport (as expressed through self-diffusion) in the mixture as compared to the ideal-mixing contribution. Interdiffusion of chemical species is a competition of slow kinetic modes with a strong thermodynamic driving force that is caused by nonentropic interactions. The combination of both dynamic and thermodynamic effects causes qualitative differences in the concentration dependence of self-diffusion and interdiffusion coefficients. At high temperatures, the thermodynamic enhancement of interdiffusion prevails, while at low temperatures, kinetic effects dominate the concentration dependence, rationalized within MCT as the approach to its ideal-glass transition temperature Tc. The Darken equation relating self- and interdiffusion qualitatively reproduces the concentration dependence in both Zr-Ni and Al-Ni, but quantitatively, the kinetic contributions to interdiffusion can be slower than the lower bound suggested by the Darken equation. As temperature is decreased, the agreement with Darken's equation improves, due to a strong coupling of all kinetic modes that is a generic feature predicted by MCT.

Kuhn, P.; Horbach, J.; Kargl, F.; Meyer, A.; Voigtmann, Th.

2014-07-01

27

Lithium metal reduction of plutonium oxide to produce plutonium metal  

DOEpatents

A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by sublimation and converted to the chloride salt, and after electrolysis, is removed as lithium metal. Zinc may be used as a solvent metal to improve thermodynamics of the reduction reaction at lower temperatures. Lithium metal reduction enables plutonium oxide reduction without the production of huge quantities of CaO--CaCl.sub.2 residues normally produced in conventional direct oxide reduction processes.

Coops, Melvin S. (Livermore, CA)

1992-01-01

28

Method for plating with metal oxides  

DOEpatents

A method is disclosed of plating hydrous metal oxides on at least one substrate, which method is indifferent to the electrochemical properties of the substrate, and comprises reacting metallic ions in aqueous solution with an appropriate oxidizing agent such as sodium hypochlorite or calcium sulfite with oxygen under suitable conditions of pH and concentration such that oxidation and precipitation of metal oxide are sufficiently slow to allow satisfactory plating of metal oxide on the substrate. 1 fig.

Silver, G.L.; Martin, F.S.

1994-08-23

29

Method for plating with metal oxides  

DOEpatents

A method of plating hydrous metal oxides on at least one substrate, which method is indifferent to the electrochemical properties of the substrate, and comprises reacting metallic ions in aqueous solution with an appropriate oxidizing agent such as sodium hypochlorite or calcium sulfite with oxygen under suitable conditions of pH and concentration such that oxidation and precipitation of metal oxide are sufficiently slow to allow satisfactory plating of metal oxide on the substrate.

Silver, Gary L. (Centerville, OH); Martin, Frank S. (Farmersville, OH)

1994-08-23

30

Metal Oxides in the Environment  

SciTech Connect

Oxides are ubiquitous in much of environmental chemistry. Silica and related glasses are potential vehicles by which radioactive elements may be sequestered and stored. The migration of toxic waste in ground water is largely influenced by interactions at the liquid-solid interface, with several metal oxides making up the bulk of soil. In addition, metal oxides with Bronsted acid or Lewis base functionality are potential replacements for many traditional liquid catalysis that are hazardous to work with and difficult to dispose. In this proposal, we targeted two such areas of oxide chemistry. The long-term behavior of silicate materials slated for use in the entombment of high-level waste (HLW), and the use of solid acid metal oxides as replacements for toxic sulfuric and hydrofluoric acid used in industry (referred to as Green Chemistry). Thus, this project encompassed technology that can be used to both remediate and prevent pollution. These oxide systems were studied using density functional theory (DFT). The comparatively large size and complexity of the systems that will bweree studied made use of high-accuracy electronic structure studies intractable on conventional computers. The 512 node parallel processor housed in the Molecular Science Computing Facility (MSCF) provided the required capability.

Jonsson, Hannes; Corrales, L. Rene; Gabriel, Peggy; Haw, James F.; Henkelman, Graeme A.; Neurock, Matthew; Nicholas, John B.; Park, Byeongwon; Song, Jakyoung; Trout, Bernhardt; Tsemekhman, Kiril L.; Uberuaga, Blas P.; Van Ginhoven, Renee M.

2002-08-30

31

Preparation of uniform nanoparticles of ultra-high purity metal oxides, mixed metal oxides, metals, and metal alloys  

DOEpatents

In preferred embodiments, metal nanoparticles, mixed-metal (alloy) nanoparticles, metal oxide nanoparticles and mixed-metal oxide nanoparticles are provided. According to embodiments, the nanoparticles may possess narrow size distributions and high purities. In certain preferred embodiments, methods of preparing metal nanoparticles, mixed-metal nanoparticles, metal oxide nanoparticles and mixed-metal nanoparticles are provided. These methods may provide tight control of particle size, size distribution, and oxidation state. Other preferred embodiments relate to a precursor material that may be used to form nanoparticles. In addition, products prepared from such nanoparticles are disclosed.

Woodfield, Brian F.; Liu, Shengfeng; Boerio-Goates, Juliana; Liu, Qingyuan; Smith, Stacey Janel

2012-07-03

32

Molecular Level Coating for Metal Oxide Particles  

NASA Technical Reports Server (NTRS)

Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar aprotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper, making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

McDaniel, Patricia R. (Inventor); Saint Clair, Terry L. (Inventor)

2000-01-01

33

A Search for Binary Stars at Low Metallicity  

E-print Network

We present initial results measuring the companion fraction of metal-poor stars ([Fe/H]$<-$2.0). We are employing the Lick Observatory planet-finding system to make high-precision Doppler observations of these objects. The binary fraction of metal-poor stars provides important constraints on star formation in the early Galaxy (Carney et al. 2003). Although it has been shown that a majority of solar metallicity stars are in binaries, it is not clear if this is the case for metal-poor stars. Is there a metallicity floor below which binary systems do not form or become rare? To test this we are determining binary fractions at metallicities below [Fe/H]$=-2.0$. Our measurments are not as precise as the planet finders', but we are still finding errors of only 50 to 300 m/s, depending on the signal-to-noise of a spectrum and stellar atmosphere of the star. At this precision we can be much more complete than previous studies in our search for stellar companions.

David K. Lai; Sara Lucatello; Michael Bolte; Debra A. Fischer; Jennifer A. Johnson

2007-08-30

34

Nanostructured transition metal oxides useful for water oxidation catalysis  

DOEpatents

The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

Frei, Heinz M; Jiao, Feng

2013-12-24

35

Multi-metallic modelling for biosorption of binary systems.  

PubMed

In this paper a specially propagated biomass of Sphaerotilus natans was tested as adsorbent for binary solutions of Cu-Cd, Cu-Pb and Cu--Zn at different equilibrium pH. The experimental results outline the buffering effect of H+ at low pH. which masks the competition among metals. In each binary system the biomass affinity follows the acidic properties of the heavy metals probably due to an ionic exchange mechanism operating among active sites and metals in solution. The experimental results were fitted according to an empirical approach with growing complexity that outlines the inadequacy of the predictive models and the non-ideal interactions among metals. PMID:12405418

Pagnanelli, Francesca; Esposito, Antonio; Vegliò, Francesco

2002-09-01

36

Ammonia release method for depositing metal oxides  

DOEpatents

A method is described for depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates. 1 figure.

Silver, G.L.; Martin, F.S.

1994-12-13

37

Ammonia release method for depositing metal oxides  

DOEpatents

A method of depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates.

Silver, Gary L. (Centerville, OH); Martin, Frank S. (Farmersville, OH)

1994-12-13

38

Method for producing metal oxide nanoparticles  

DOEpatents

Method for producing metal oxide nanoparticles. The method includes generating an aerosol of solid metallic microparticles, generating plasma with a plasma hot zone at a temperature sufficiently high to vaporize the microparticles into metal vapor, and directing the aerosol into the hot zone of the plasma. The microparticles vaporize in the hot zone into metal vapor. The metal vapor is directed away from the hot zone and into the cooler plasma afterglow where it oxidizes, cools and condenses to form solid metal oxide nanoparticles.

Phillips, Jonathan (Santa Fe, NM); Mendoza, Daniel (Santa Fe, NM); Chen, Chun-Ku (Albuquerque, NM)

2008-04-15

39

Reaction experiments for thermochemical water-splitting. [Classes of cycles: metal-metal oxide; metal oxide-metal hydroxide; metal oxide-metal sulfate; metal-metal halide; metal oxide-metal halide  

Microsoft Academic Search

Almost all known pure thermochemical hydrogen production cycles can be grouped into five generic classes, each involving either a metal oxide or a metal halide as an intermediate. In general, those cycles with the highest-temperature endothermic reactions and the least number of reactions are the most efficient. This is expected because thermochemical cycles are special types of heat engines. The

J. Gahimer; J. Pangborn; S. Foh; M. Mazumder; R. Stotz

1976-01-01

40

Glycothermal synthesis of metal oxides  

NASA Astrophysics Data System (ADS)

The author has been exploring the synthesis of inorganic materials in organic solvents at temperatures (200-300 °C) higher than their boiling points (solvothermal reaction), and has developed various reaction methods for the synthesis of ultrafine particles of metal oxides. In this paper, the reactions of aluminium compounds (aluminium hydroxide (Al(OH)3; gibbsite), aluminium alkoxides, and aluminium salts) in various organic solvents (alcohols, glycols, aminoalcohols, and inert organic solvents) are first reviewed, and reaction mechanisms and effects of the starting materials and solvents on the products are discussed. Then, the specificity of the use of glycols, especially 1,4-butanediol (glycothermal reaction), is clarified, and glycothermal synthesis of crystalline mixed oxides such as yttrium aluminium garnet is described. Finally, the use of the solvothermally prepared products as the catalyst materials is described.

Inoue, Masashi

2004-04-01

41

Spectroscopic Metallicity Determinations for W UMa-type Binary Stars  

NASA Astrophysics Data System (ADS)

This study is the first attempt to determine the metallicities of W UMa-type binary stars using spectroscopy. We analyzed about 4500 spectra collected at the David Dunlap Observatory. To circumvent problems caused by the extreme spectral line broadening and blending and by the relatively low quality of the data, all spectra were subject to the same broadening function (BF) processing to determine the combined line strength in the spectral window centered on the Mg I triplet between 5080 Å and 5285 Å. All individual integrated BFs were subsequently orbital-phase averaged to derive a single line-strength indicator for each star. The star sample was limited to 90 W UMa-type (EW) binaries with the strict phase-constancy of colors and without spectral contamination by spectroscopic companions. The best defined results were obtained for an F-type sub-sample (0.32 < (B - V)0 < 0.62) of 52 binaries for which integrated BF strengths could be interpolated in the model atmosphere predictions. The logarithmic relative metallicities, [M/H], for the F-type sub-sample indicate metal abundances roughly similar to the solar metallicity, but with a large scatter which is partly due to combined random and systematic errors. Because of the occurrence of a systematic color trend resulting from inherent limitations in our approach, we were forced to set the absolute scale of metallicities to correspond to that derived from the m 1 index of the Strömgren uvby photometry for 24 binaries of the F-type sub-sample. The trend-adjusted metallicities [M/H]1 are distributed within -0.65 < [M/H]1 < +0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]1 within -0.37 < [M/H]1 < +0.10, a median of -0.04 and a mean of -0.10, with a tail toward low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently obtained proper motion and radial velocity data for 78 binaries of the full sample, shows that the F-type sub-sample binaries (44 stars with both velocities and metallicity determinations) have similar kinematic properties to solar-neighborhood, thin-disk dwarfs with space velocity component dispersions: ?U = 33 km s-1, ?V = 23 km s-1 and ?W = 14 km s-1. FU Dra with a large spatial velocity, V tot = 197 km s-1 and [M/H]1 = -0.6 ± 0.2, appears to be the only thick-disk object in the F-type sub-sample. The kinematic data indicate that the F-type EW binaries are typical, thin-disk population stars with ages about 3-5.5 Gyr. The F-type binaries that appear to be older than the rest tend to have systematically smaller mass ratios than most of the EW binaries of the same period. Based on observations obtained at the David Dunlap Observatory, University of Toronto.

Rucinski, Slavek M.; Pribulla, Theodor; Budaj, Ján

2013-09-01

42

SPECTROSCOPIC METALLICITY DETERMINATIONS FOR W UMa-TYPE BINARY STARS  

SciTech Connect

This study is the first attempt to determine the metallicities of W UMa-type binary stars using spectroscopy. We analyzed about 4500 spectra collected at the David Dunlap Observatory. To circumvent problems caused by the extreme spectral line broadening and blending and by the relatively low quality of the data, all spectra were subject to the same broadening function (BF) processing to determine the combined line strength in the spectral window centered on the Mg I triplet between 5080 A and 5285 A. All individual integrated BFs were subsequently orbital-phase averaged to derive a single line-strength indicator for each star. The star sample was limited to 90 W UMa-type (EW) binaries with the strict phase-constancy of colors and without spectral contamination by spectroscopic companions. The best defined results were obtained for an F-type sub-sample (0.32 < (B - V){sub 0} < 0.62) of 52 binaries for which integrated BF strengths could be interpolated in the model atmosphere predictions. The logarithmic relative metallicities, [M/H], for the F-type sub-sample indicate metal abundances roughly similar to the solar metallicity, but with a large scatter which is partly due to combined random and systematic errors. Because of the occurrence of a systematic color trend resulting from inherent limitations in our approach, we were forced to set the absolute scale of metallicities to correspond to that derived from the m{sub 1} index of the Stroemgren uvby photometry for 24 binaries of the F-type sub-sample. The trend-adjusted metallicities [M/H]{sub 1} are distributed within -0.65 < [M/H]{sub 1} < +0.50, with the spread reflecting genuine metallicity differences between stars. One half of the F-sub-sample binaries have [M/H]{sub 1} within -0.37 < [M/H]{sub 1} < +0.10, a median of -0.04 and a mean of -0.10, with a tail toward low metallicities, and a possible bias against very high metallicities. A parallel study of kinematic data, utilizing the most reliable and recently obtained proper motion and radial velocity data for 78 binaries of the full sample, shows that the F-type sub-sample binaries (44 stars with both velocities and metallicity determinations) have similar kinematic properties to solar-neighborhood, thin-disk dwarfs with space velocity component dispersions: {sigma}U = 33 km s{sup -1}, {sigma}V = 23 km s{sup -1} and {sigma}W = 14 km s{sup -1}. FU Dra with a large spatial velocity, V{sub tot} = 197 km s{sup -1} and [M/H]{sub 1} = -0.6 {+-} 0.2, appears to be the only thick-disk object in the F-type sub-sample. The kinematic data indicate that the F-type EW binaries are typical, thin-disk population stars with ages about 3-5.5 Gyr. The F-type binaries that appear to be older than the rest tend to have systematically smaller mass ratios than most of the EW binaries of the same period.

Rucinski, Slavek M. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4 (Canada); Pribulla, Theodor; Budaj, Jan, E-mail: rucinski@astro.utoronto.ca, E-mail: pribulla@ta3.sk, E-mail: budaj@ta3.sk [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia)

2013-09-15

43

The oxidation of metals and alloys  

NASA Technical Reports Server (NTRS)

This paper reviews the various types of oxidation processes occurring with pure metals and gives explanations for the varying time-temperature-oxidation rate relations that exist for copper, tungsten, zinc, cadmium, and tantalum. The effect of shape and crystal structure on oxidation is discussed. Principles derived are applied to the oxidation of alloys.

Scheil, Erich

1952-01-01

44

Oxidation of dodecane on transition metal oxides  

NASA Astrophysics Data System (ADS)

The catalytic oxidation of dodecane on individual and mixed vanadium and molybdenum oxides is studied. Products of the oxidation of alkane are studied qualitatively and quantitatively. The activities of the samples of the catalysts with various ratios of vanadium and molybdenum oxides are compared. One possible scheme for the activation of reagents on a catalyst is given.

Vishnetskaya, M. V.; Vakhrushin, P. A.

2012-11-01

45

Reduction of Metal Oxide to Metal using Ionic Liquids  

SciTech Connect

A novel pathway for the high efficiency production of metal from metal oxide means of electrolysis in ionic liquids at low temperature was investigated. The main emphasis was to eliminate the use of carbon and high temperature application in the reduction of metal oxides to metals. The emphasis of this research was to produce metals such as Zn, and Pb that are normally produced by the application of very high temperatures. The reduction of zinc oxide to zinc and lead oxide to lead were investigated. This study involved three steps in accomplishing the final goal of reduction of metal oxide to metal using ionic liquids: 1) Dissolution of metal oxide in an ionic liquid, 2) Determination of reduction potential using cyclic voltammetry (CV) and 3) Reduction of the dissolved metal oxide. Ionic liquids provide additional advantage by offering a wide potential range for the deposition. In each and every step of the process, more than one process variable has been examined. Experimental results for electrochemical extraction of Zn from ZnO and Pb from PbO using eutectic mixtures of Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3+Cl-) or (ChCl) in a molar ratio 2:1, varying voltage and temperatures were carried out. Fourier Transform Infra-Red (FTIR) spectroscopy studies of ionic liquids with and without metal oxide additions were conducted. FTIR and induction coupled plasma spectroscopy (ICPS) was used in the characterization of the metal oxide dissolved ionic liquid. Electrochemical experiments were conducted using EG&G potentiostat/galvanostat with three electrode cell systems. Cyclic voltammetry was used in the determination of reduction potentials for the deposition of metals. Chronoamperometric experiments were carried out in the potential range of -0.6V to -1.9V for lead and -1.4V to -1.9V for zinc. The deposits were characterized using XRD and SEM-EDS for phase, morphological and elemental analysis. The results showed that pure metal was deposited on the cathode. Successful extraction of metal from metal oxide dissolved in Urea/ChCl (2:1) was accomplished. The current efficiencies were relatively high in both the metal deposition processes with current efficiency greater than 86% for lead and 95% for zinc. This technology will advance the metal oxide reduction process by increasing the process efficiency and also eliminate the production of CO2 which makes this an environmentally benign technology for metal extraction.

Dr. Ramana Reddy

2012-04-12

46

Shock-Induced Reactions in Metal\\/Metal Oxide = Systems  

Microsoft Academic Search

Start your abstract by replacing this line with your text. A recent study of shock induced reactions in metal\\/metal oxide systems has been completed. The systems studied included oxides of Iron, Copper, Molybdenum mixed in a stoichiometric ratio with aluminum. Also add ed was a small amount of Teflon (5 weight percent) to act as a binder. Other materials studied

Fallen J. Lindfors; Philip J. Miller; Jeff J. Davis

1997-01-01

47

Nanocomposite of graphene and metal oxide materials  

DOEpatents

Nanocomposite materials comprising a metal oxide bonded to at least one graphene material. The nanocomposite materials exhibit a specific capacity of at least twice that of the metal oxide material without the graphene at a charge/discharge rate greater than about 10C.

Liu, Jun; Aksay, Ilhan A.; Choi, Daiwon; Wang, Donghai; Yang, Zhenguo

2012-09-04

48

High temperature, oxidation resistant noble metal-Al alloy thermocouple  

NASA Technical Reports Server (NTRS)

A thermocouple is disclosed. The thermocouple is comprised of an electropositive leg formed of a noble metal-Al alloy and an electronegative leg electrically joined to form a thermocouple junction. The thermocouple provides for accurate and reproducible measurement of high temperatures (600 - 1300 C) in inert, oxidizing or reducing environments, gases, or vacuum. Furthermore, the thermocouple circumvents the need for expensive, strategic precious metals such as rhodium as a constituent component. Selective oxidation of rhodium is also thereby precluded.

Smialek, James L. (inventor); Gedwill, Michael G. (inventor)

1994-01-01

49

Method of producing adherent metal oxide coatings on metallic surfaces  

DOEpatents

Provided is a process of producing an adherent synthetic corrosion product (sludge) coating on metallic surfaces. The method involves a chemical reaction between a dry solid powder mixture of at least one reactive metal oxide with orthophosphoric acid to produce a coating in which the particles are bound together and the matrix is adherent to the metallic surface.

Lane, Michael H. (Clifton Park, NY); Varrin, Jr., Robert D. (McLean, VA)

2001-01-01

50

Methods of producing adsorption media including a metal oxide  

DOEpatents

Methods of producing a metal oxide are disclosed. The method comprises dissolving a metal salt in a reaction solvent to form a metal salt/reaction solvent solution. The metal salt is converted to a metal oxide and a caustic solution is added to the metal oxide/reaction solvent solution to adjust the pH of the metal oxide/reaction solvent solution to less than approximately 7.0. The metal oxide is precipitated and recovered. A method of producing adsorption media including the metal oxide is also disclosed, as is a precursor of an active component including particles of a metal oxide.

Mann, Nicholas R; Tranter, Troy J

2014-03-04

51

Method for making monolithic metal oxide aerogels  

DOEpatents

Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The present invention is especially advantageous for making metal oxides other than silica that are prone to forming opaque, cracked aerogels. 6 figs.

Droege, M.W.; Coronado, P.R.; Hair, L.M.

1995-03-07

52

Method for making monolithic metal oxide aerogels  

DOEpatents

Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The present invention is especially advantageous for making metal oxides other than silica that are prone to forming opaque, cracked aerogels.

Droege, Michael W. (Livermore, CA); Coronado, Paul R. (Livermore, CA); Hair, Lucy M. (Livermore, CA)

1995-01-01

53

Metal ion binding to iron oxides  

Microsoft Academic Search

The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE

M. Ponthieu; F. Juillot; T. Hiemstra; W. H. van Riemsdijk; M. F. Benedetti

2006-01-01

54

Direct electrochemical reduction of metal-oxides  

DOEpatents

A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.

Redey, Laszlo I. (Downers Grove, IL); Gourishankar, Karthick (Downers Grove, IL)

2003-01-01

55

Oscillatory surface intermixing in binary metallic alloys*  

NASA Astrophysics Data System (ADS)

The creation of a surface of a metallic system often leads to an oscillatory charge density distribution propagating into the bulk [1], which may further induce an oscillatory interlayer lattice relaxation [2]. Oscillatory intermixing has also been frequently observed in disordered alloys, with one of the constituents enriched or depleted from layer to layer. Here we investigate the oscillation of the concentration profiles in the first few layers of different alloys using the density functional theory, with the Mo-Re and Mo-Ta systems as specific examples. The Re (Ta) atom has charge excess (deficiency) with respect to the host Mo atom. The Re (Ta) is found to follow the maxima (minima) of the oscillatory charge density distribution of the Mo surface layers, thus elucidating the microscopic origin of the oscillation of the alloy concentration at different layers. [1] N. D. Lang and W. Kohn, Phys. Rev. B 1 4555 (1970). [2] Jun-Hyung Cho, Ismail, Z. Zhang and E. W. Plummer, Phys. Rev. B 59 1677 (1999).

Varga, Kalman; Wang, Ligen; Pennycook, Stephen J.; Pantelides, Sokrates T.; Zhang, Zhenyu

2001-03-01

56

Adsorption of divalent metals to metal oxide nanoparicles: Competitive and temperature effects  

NASA Astrophysics Data System (ADS)

The presence of metals in natural waters is becoming a critical environmental and public health concern. Emerging nanotechnology and the use of metal oxide nanoparticles has been identified as a potential remediation technique in removing metals from water. However, practical applications are still being explored to determine how to apply their unique chemical and physical properties for full scale remediation projects. This thesis investigates the sorption properties of Cd(II), Cu(II), Pb(II) and Zn(II) to hematite (alpha-Fe2O3) and titanium dioxide (TiO2) nanoparticles in single- and binary-adsorbate systems. Competitive sorption was evaluated in 1L batch binary-metal systems with 0.05g/L nano-hematite at pH 8.0 and pH 6.0. Results indicate that the presence of a secondary metal can affect the sorption process depending upon the molar ratios, such as increased or reduced adsorption. Thermodynamic properties were also studied in order to better understand the effects of temperature on equilibrium and kinetic adsorption capabilities. Understanding the thermodynamic properties can also give insight to determine if the sorption process is a physical, chemical or ion exchange reaction. Thermodynamic parameters such as enthalpy (DeltaH), entropy (DeltaS), and Gibbs free energy (DeltaG) were evaluated as a function of temperature, pH, and metal concentration. Results indicate that Pb(II) and Cu(II) adsorption to nano-hematite was an endothermic and physical adsorption process, while Zn(II) and Cd(II) adsorption was dependent upon the adsorbed concentration evaluated. However, metal adsorptions to nano-titanium dioxide were all found to be endothermic and physical adsorption processes; the spontaneity of metal adsorption was temperature dependent for both metal oxide nanoparticles.

Grover, Valerie Ann

57

Catalytic production of metal carbonyls from metal oxides  

DOEpatents

This invention relates to the formation of metal carbonyls from metal oxides and specially the formation of molybdenum carbonyl and iron carbonyl from their respective oxides. Copper is used here in admixed form or used in chemically combined form as copper molybdate. The copper/metal oxide combination or combined copper is utilized with a solvent, such as toluene and subjected to carbon monoxide pressure of 25 atmospheres or greater at about 150.degree.-260.degree. C. The reducing metal copper is employed in catalytic concentrations or combined concentrations as CuMoO.sub.4 and both hydrogen and water present serve as promoters. It has been found that the yields by this process have been salutary and that additionally the catalytic metal may be reused in the process to good effect.

Sapienza, Richard S. (Shoreham, NY); Slegeir, William A. (Hampton Bays, NY); Foran, Michael T. (Rocky Point, NY)

1984-01-01

58

Catalytic production of metal carbonyls from metal oxides  

DOEpatents

This invention relates to the formation of metal carbonyls from metal oxides and specially the formation of molybdenum carbonyl and iron carbonyl from their respective oxides. Copper is used here in admixed form or used in chemically combined form as copper molybdate. The copper/metal oxide combination or combined copper is utilized with a solvent, such as toluene and subjected to carbon monoxide pressure of 25 atmospheres or greater at about 150 to 260/sup 0/C. The reducing metal copper is employed in catalytic concentrations or combined concentrations as CuMoO/sub 4/ and both hydrogen and water present serve as promoters. It has been found that the yields by this process have been salutary and that additionally the catalytic metal may be reused in the process to good effect. 3 tables.

Sapienza, R.S.; Slegeir, W.A.; Foran, M.T.

1984-01-06

59

High surface area, electrically conductive nanocarbon-supported metal oxide  

DOEpatents

A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust.

Worsley, Marcus A; Han, Thomas Yong-Jin; Kuntz, Joshua D; Cervanted, Octavio; Gash, Alexander E; Baumann, Theodore F; Satcher, Jr., Joe H

2014-03-04

60

Biomimetic alkane oxidation involving metal complexes  

Microsoft Academic Search

The state-of-the-art of investigations in the field of catalysis of biological oxidation of saturated hydrocarbons by molecular oxygen and simulation of this process based on metal complexes is reviewed. The bibliography includes 296 references.

Elena I Karasevich; Vera S Kulikova; Aleksandr E Shilov; Al'bert A Shteinman

1998-01-01

61

Lithium metal oxide electrodes for lithium batteries  

DOEpatents

An uncycled electrode for a non-aqueous lithium electrochemical cell including a lithium metal oxide having the formula Li.sub.(2+2x)/(2+x)M'.sub.2x/(2+x)M.sub.(2-2x)/(2+x)O.sub.2-.delta., in which 0.ltoreq.x<1 and .delta. is less than 0.2, and in which M is a non-lithium metal ion with an average trivalent oxidation state selected from two or more of the first row transition metals or lighter metal elements in the periodic table, and M' is one or more ions with an average tetravalent oxidation state selected from the first and second row transition metal elements and Sn. Methods of preconditioning the electrodes are disclosed as are electrochemical cells and batteries containing the electrodes.

Thackeray, Michael M. (Naperville, IL); Kim, Jeom-Soo (Naperville, IL); Johnson, Christopher S. (Naperville, IL)

2008-01-01

62

Process for etching mixed metal oxides  

DOEpatents

An etching process is described using dicarboxylic and tricarboxylic acids as chelating etchants for mixed metal oxide films such as high temperature superconductors and ferroelectric materials. Undesirable differential etching rates between different metal oxides are avoided by selection of the proper acid or combination of acids. Feature sizes below one micron, excellent quality vertical edges, and film thicknesses in the 100 Angstrom range may be achieved by this method. 1 fig.

Ashby, C.I.H.; Ginley, D.S.

1994-10-18

63

Process for etching mixed metal oxides  

DOEpatents

An etching process using dicarboxylic and tricarboxylic acids as chelating etchants for mixed metal oxide films such as high temperature superconductors and ferroelectric materials. Undesirable differential etching rates between different metal oxides are avoided by selection of the proper acid or combination of acids. Feature sizes below one micron, excellent quality vertical edges, and film thicknesses in the 100 Angstom range may be achieved by this method.

Ashby, Carol I. H. (Edgewood, NM); Ginley, David S. (Evergreen, CO)

1994-01-01

64

Versatile Applications of Nanostructured Metal Oxides  

E-print Network

intercalation/extraction processes in the metal oxide/electrolyte interface. Despite the wide usage in various disciplines, the utilization of metal oxides in en- hanced Raman spectroscopy has been rare. In Chapter 7, we discover that the reverse case... ,22] This capability of integrating different components into a single entity is undoubtedly very attractive in many fields, such as multiplexed signalling and recoverable photocatalysis, as was demonstrated in nanoporous titania films doped with rare-earth ions[20...

Li, Li

2014-05-29

65

Multilevel metallization method for fabricating a metal oxide semiconductor device  

NASA Technical Reports Server (NTRS)

An improved method is described of constructing a metal oxide semiconductor device having multiple layers of metal deposited by dc magnetron sputtering at low dc voltages and low substrate temperatures. The method provides multilevel interconnections and cross over between individual circuit elements in integrated circuits without significantly reducing the reliability or seriously affecting the yield.

Hollis, B. R., Jr.; Feltner, W. R.; Bouldin, D. L.; Routh, D. E. (inventors)

1978-01-01

66

Development of techniques for processing metal-metal oxide systems  

NASA Technical Reports Server (NTRS)

Techniques for producing model metal-metal oxide systems for the purpose of evaluating the results of processing such systems in the low-gravity environment afforded by a drop tower facility are described. Because of the lack of success in producing suitable materials samples and techniques for processing in the 3.5 seconds available, the program was discontinued.

Johnson, P. C.

1976-01-01

67

Aerosol-spray diverse mesoporous metal oxides from metal nitrates.  

PubMed

Transition metal oxides are widely used in solar cells, batteries, transistors, memories, transparent conductive electrodes, photocatalysts, gas sensors, supercapacitors, and smart windows. In many of these applications, large surface areas and pore volumes can enhance molecular adsorption, facilitate ion transfer, and increase interfacial areas; the formation of complex oxides (mixed, doped, multimetallic oxides and oxide-based hybrids) can alter electronic band structures, modify/enhance charge carrier concentrations/separation, and introduce desired functionalities. A general synthetic approach to diverse mesoporous metal oxides is therefore very attractive. Here we describe a powerful aerosol-spray method for synthesizing various mesoporous metal oxides from low-cost nitrate salts. During spray, thermal heating of precursor droplets drives solvent evaporation and induces surfactant-directed formation of mesostructures, nitrate decomposition and oxide cross-linking. Thirteen types of monometallic oxides and four groups of complex ones are successfully produced, with mesoporous iron oxide microspheres demonstrated for photocatalytic oxygen evolution and gas sensing with superior performances. PMID:25897988

Kuai, Long; Wang, Junxin; Ming, Tian; Fang, Caihong; Sun, Zhenhua; Geng, Baoyou; Wang, Jianfang

2015-01-01

68

Cyclic Catalytic Upgrading of Chemical Species Using Metal Oxide Materials  

NASA Technical Reports Server (NTRS)

Processes are disclosure which comprise alternately contacting an oxygen-carrying catalyst with a reducing substance, or a lower partial pressure of an oxidizing gas, and then with the oxidizing gas or a higher partial pressure of the oxidizing gas, whereby the catalyst is alternately reduced and then regenerated to an oxygenated state. In certain embodiments, the oxygen-carrying catalyst comprises at least one metal oxide-containing material containing a composition having the following formulas: (a) Ce(sub x)B(sub y)B'(sub z)B''O(sub gamma; wherein B=Ba, Sr, Ca, or Zr; B'=Mn, Co, and/or Fe; B''=Cu; 0.01binary metal oxides.

White, James H. (Inventor); Schutte, Erick J. (Inventor); Rolfe, Sara L. (Inventor)

2013-01-01

69

Cyclic catalytic upgrading of chemical species using metal oxide materials  

DOEpatents

Processes are disclosure which comprise alternately contacting an oxygen-carrying catalyst with a reducing substance, or a lower partial pressure of an oxidizing gas, and then with the oxidizing gas or a higher partial pressure of the oxidizing gas, whereby the catalyst is alternately reduced and then regenerated to an oxygenated state. In certain embodiments, the oxygen-carrying catalyst comprises at least one metal oxide-containing material containing a composition having the following formulas: (a) Ce.sub.xB.sub.yB'.sub.zB''O.sub..delta., wherein B=Ba, Sr, Ca, or Zr; B'=Mn, Co, and/or Fe; B''=Cu; 0.01binary metal oxides.

White, James H; Schutte, Erick J; Rolfe, Sara L

2013-05-07

70

Metal oxide thin film based supercapacitors  

Microsoft Academic Search

Supercapacitors have been known for over fifty years and are considered as one of the potential energy storage systems. Research into supercapacitors is presently based primarily on their mode of energy storage, namely: (i) the redox electrochemical capacitors and (ii) the electrochemical double layer capacitor. The commonly investigated classes of materials are transition metal oxides (notably, ruthenium oxide) and conducting

C. D. Lokhande; D. P. Dubal; Oh-Shim Joo

2011-01-01

71

Method for making monolithic metal oxide aerogels  

DOEpatents

Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The containment vessel is enclosed within an aqueous atmosphere that is above the supercritical temperature and pressure of the solvent of the metal alkoxide solution.

Coronado, Paul R. (Livermore, CA)

1999-01-01

72

PLUTONIUM METAL: OXIDATION CONSIDERATIONS AND APPROACH  

SciTech Connect

Plutonium is arguably the most unique of all metals when considered in the combined context of metallurgical, chemical, and nuclear behavior. Much of the research in understanding behavior and characteristics of plutonium materials has its genesis in work associated with nuclear weapons systems. However, with the advent of applications in fuel materials, the focus in plutonium science has been more towards nuclear fuel applications, as well as long term storage and disposition. The focus of discussion included herein is related to preparing plutonium materials to meet goals consistent with non-proliferation. More specifically, the emphasis is on the treatment of legacy plutonium, in primarily metallic form, and safe handling, packaging, and transport to meet non-proliferation goals of safe/secure storage. Elevated temperature oxidation of plutonium metal is the treatment of choice, due to extensive experiential data related to the method, as the oxide form of plutonium is one of only a few compounds that is relatively simple to produce, and stable over a large temperature range. Despite the simplicity of the steps required to oxidize plutonium metal, it is important to understand the behavior of plutonium to ensure that oxidation is conducted in a safe and effective manner. It is important to understand the effect of changes in environmental variables on the oxidation characteristics of plutonium. The primary purpose of this report is to present a brief summary of information related to plutonium metal attributes, behavior, methods for conversion to oxide, and the ancillary considerations related to processing and facility safety. The information provided is based on data available in the public domain and from experience in oxidation of such materials at various facilities in the United States. The report is provided as a general reference for implementation of a simple and safe plutonium metal oxidation technique.

Estochen, E.

2013-03-20

73

Metal oxide solubility behavior in high temperature aqueous solutions  

Microsoft Academic Search

The solubility behavior of metal oxides in sub- and super-critical aqueous solutions is quantified using thermodynamic concepts. Three physicochemical phenomena are discussed: (1) metal oxide solid phase stability, (2) metal oxide dissolution reaction equilibria and (3) metal ion hydrocomplex formation. Thermochemical properties of metal oxides\\/ions representative of the most common constituents of construction metal alloys, i.e., elements having atomic numbers

Ziemniak

1991-01-01

74

Metal oxide solubility behavior in high temperature aqueous solutions  

Microsoft Academic Search

The solubility behavior of metal oxides in sub- and super-critical aqueous solutions is quantified using thermodynamic concepts. Three physicochemical phenomena are discussed: (1) metal oxide solid phase stability; (2) metal oxide dissolution reaction equilibria; and (3) metal ion hydroxocomplex formation. Thermochemical properties of metal oxides\\/ions representative of the most common constituents of construction metal alloys, i.e., elements having atomic numbers

S. E. Ziemniak

1992-01-01

75

Ternary spinel cadmium stannate, cadmium indate, and zinc stannate and binary tin oxide and indium oxide transparent conducting oxides as front contact materials for cadmium sulfide\\/cadmium tellurium photovoltaic devices  

Microsoft Academic Search

Transparent conducting oxides (TCO's) of Cd2SnO 4 (cadmium stannate), CdIn2O4 (cadmium indate), and Zn2SnO4 (zinc stannate) thin films were investigated from a materials and applications point of view through. All films were deposited by co-sputtering using either binary oxide or metallic (reactive sputtering) targets. The film properties were investigated as a function of film composition and stoichiometry. The effect of

Robert Mamazza Jr.

2003-01-01

76

Vapor-phase mechanism of the laser oxidation of metals  

Microsoft Academic Search

Based on an analysis of experimental results obtained for D16 Duralumin specimens, a model is proposed for the oxidation of metals irradiated by short laser pulses. The oxidation process involves metal evaporation, its oxidation in the vapor phase, onset of a backflow of oxide molecules, and their condensation and additional oxidation on the specimen surface. This oxidation mechanism, which has

A. G. Akimov; A. M. Bonch-Bruevich; A. P. Gagarin; I. A. Dorofeev; V. G. Dorofeev

1987-01-01

77

Resistance switching in amorphous and crystalline binary oxides grown by electron beam evaporation and atomic layer deposition  

Microsoft Academic Search

Resistance switching random access non-volatile memories (ReRAM) could represent the leading alternative to floating gate technology for post 32nm technology nodes. Among the currently investigated materials for ReRAM, transition metal binary oxides, such as NiO, CuxO, ZrOx, TiO2, MgO, and Nb2O5 are receiving increasing interest as they offer high potential scalability, low-energy switching, thermal stability, and easy integration in CMOS

S. Spiga; A. Lamperti; C. Wiemer; M. Perego; E. Cianci; G. Tallarida; H. L. Lu; M. Alia; F. G. Volpe; M. Fanciulli

2008-01-01

78

Lithium metal oxide electrodes for lithium batteries  

DOEpatents

An uncycled preconditioned electrode for a non-aqueous lithium electrochemical cell including a lithium metal oxide having the formula xLi2-yHyO.xM'O2.(1-x)Li1-zHzMO2 in which 0metal ion with an average trivalent oxidation state selected from two or more of the first row transition metals or lighter metal elements in the periodic table, and M' is one or more ions with an average tetravalent oxidation state selected from the first and second row transition metal elements and Sn. The xLi2-yHy.xM'O2.(1-x)Li1-zHzMO2 material is prepared by preconditioning a precursor lithium metal oxide (i.e., xLi2M'O3.(1-x)LiMO2) with a proton-containing medium with a pH<7.0 containing an inorganic acid. Methods of preparing the electrodes are disclosed, as are electrochemical cells and batteries containing the electrodes.

Thackeray, Michael M.; Johnson, Christopher S.; Amine, Khalil; Kang, Sun-Ho

2010-06-08

79

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths.  

PubMed

Binary oxide systems (CuCr2O4, CuCo2O4), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O2, NOx, H2O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3?NO2>H2O>NO>O2>CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem. PMID:25662252

Soloviev, Sergiy O; Kapran, Andriy Y; Kurylets, Yaroslava P

2015-02-01

80

Oxidation of metals at the chromium oxide interface  

NASA Astrophysics Data System (ADS)

Metal thin-film deposition, over the Cr2O3 surface of CrO2 thin-film substrates, exhibits a redox reaction at the interface. The transition metal forms an oxide in combination with the reduction of the near-surface chromium oxide to Cr2O3. The insulating barrier layer Cr2O3 increases with the formation of Pb3O4 in Pb/Cr2O3/CrO2 and CoO in Co/Cr2O3/CrO2 junctions, respectively.

Cheng, Ruihua; Borca, C. N.; Pilet, N.; Xu, Bo; Yuan, L.; Doudin, B.; Liou, S. H.; Dowben, P. A.

2002-09-01

81

Metal ion binding to iron oxides  

NASA Astrophysics Data System (ADS)

The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to show that it is possible to model the adsorption of protons and TE on a crystallized oxide (i.e., goethite) and on an amorphous oxide (HFO) in an identical way. Here, we use the CD-MUSIC approach in combination with valuable and reliable surface spectroscopy information about the nature of surface complexes of the TE. The other objective of this work is to obtain generic parameters to describe the binding of the following elements (Cd, Co, Cu, Ni, Pb, and Zn) onto both iron oxides for the CD-MUSIC approach. The results show that a consistent description of proton and metal ion binding is possible for goethite and HFO with the same set of model parameters. In general a good prediction of almost all the collected experimental data sets corresponding to metal ion binding to HFO is obtained. Moreover, dominant surface species are in agreement with the recently published surface complexes derived from X-ray absorption spectroscopy (XAS) data. Until more detailed information on the structure of the two iron oxides is available, the present option seems a reasonable approximation and can be used to describe complex geochemical systems. To improve our understanding and modeling of multi-component systems we need more data obtained at much lower metal ion to iron oxide ratios in order to be able to account eventually for sites that are not always characterized in spectroscopic studies.

Ponthieu, M.; Juillot, F.; Hiemstra, T.; van Riemsdijk, W. H.; Benedetti, M. F.

2006-06-01

82

Role of metal oxides in chemical evolution  

NASA Astrophysics Data System (ADS)

Steps of chemical evolution have been designated as formation of biomonomers followed by their polymerization and then to modify in an organized structure leading to the formation of first living cell. Formation of small molecules like amino acids, organic bases, sugar etc. could have occurred in the reducing atmosphere of the primitive Earth. Polymerization of these small molecules could have required some catalyst. In addition to clay, role of metal ions and metal complexes as prebiotic catalyst in the synthesis and polymerization of biomonomers cannot be ruled out. Metal oxides are important constituents of Earth crust and that of other planets. These oxides might have adsorbed organic molecules and catalyzed the condensation processes, which may have led to the formation of first living cell. Different studies were performed in order to investigate the role of metal oxides (especially oxides of iron and manganese) in chemical evolution. Iron oxides (goethite, akaganeite and hematite) as well as manganese oxides (MnO, Mn2O3, Mn3O4 and MnO2) were synthesized and their characterization was done using IR, powder XRD, FE-SEM and TEM. Role of above oxides was studied in the adsorption of ribose nucleotides, formation of nucleobases from formamide and oligomerization of amino acids. Above oxides of iron and manganese were found to have good adsorption affinity towards ribose nucleotides, high catalytic activity in the formation of several nucleobases from formamide and oligomerization of glycine and alanine. Characterization of products was performed using UV, IR, HPLC and ESI-MS techniques. Presence of hematite-water system on Mars has been suggested to be a positive indicator in the chemical evolution on Mars.

Kamaluddin

2013-06-01

83

Reduction of metal oxides through mechanochemical processing  

DOEpatents

The low temperature reduction of a metal oxide using mechanochemical processing techniques. The reduction reactions are induced mechanically by milling the reactants. In one embodiment of the invention, titanium oxide TiO.sub.2 is milled with CaH.sub.2 to produce TiH.sub.2. Low temperature heat treating, in the range of 400.degree. C. to 700.degree. C., can be used to remove the hydrogen in the titanium hydride.

Froes, Francis H. (Moscow, ID); Eranezhuth, Baburaj G. (Moscow, ID); Senkov, Oleg N. (Moscow, ID)

2000-01-01

84

Orbital Physics in Transition-Metal Oxides  

Microsoft Academic Search

An electron in a solid, that is, bound to or nearly localized on the specific atomic site, has three attributes: charge, spin, and orbital. The orbital represents the shape of the electron cloud in solid. In transition-metal oxides with anisotropic-shaped d-orbital electrons, the Coulomb interaction between the electrons (strong electron correlation effect) is of importance for understanding their metal-insulator transitions

Y. Tokura; N. Nagaosa

2000-01-01

85

Uranium Metal to Oxide Conversion by Air Oxidation ?Process Development  

SciTech Connect

Published technical information for the process of metal-to-oxide conversion of uranium components has been reviewed and summarized for the purpose of supporting critical decisions for new processes and facilities for the Y-12 National Security Complex. The science of uranium oxidation under low, intermediate, and high temperature conditions is reviewed. A process and system concept is outlined and process parameters identified for uranium oxide production rates. Recommendations for additional investigations to support a conceptual design of a new facility are outlined.

Duncan, A

2001-12-31

86

Atomic diffusion mechanisms in a binary metallic melt  

NASA Astrophysics Data System (ADS)

The relation between static structure and dynamics as measured through the diffusion coefficients in viscous multicomponent metallic melts is elucidated by the example of the binary alloy Zr64Ni36, by a combination of neutron-scattering experiments and mode-coupling theory of the glass transition. Comparison with a hard-sphere mixture shows that the relation between the different self diffusion coefficients strongly depends on chemical short-range ordering. For the Zr-Ni example, the theory predicts both diffusivities to be practically identical. The kinetics of concentration fluctuations is dramatically slower than that of self-diffusion, but the overall interdiffusion coefficient is equally large or larger due to a purely thermodynamic prefactor. This result is a general feature for non-demixing dense melts, irrespective of chemical short-range order.

Voigtmann, Th.; Meyer, A.; Holland-Moritz, D.; Stüber, S.; Hansen, T.; Unruh, T.

2008-06-01

87

Metal oxide solubility behavior in high temperature aqueous solutions  

SciTech Connect

The solubility behavior of metal oxides in sub- and super-critical aqueous solutions is quantified using thermodynamic concepts. Three physicochemical phenomena are discussed: (1) metal oxide solid phase stability, (2) metal oxide dissolution reaction equilibria and (3) metal ion hydrocomplex formation. Thermochemical properties of metal oxides/ions representative of the most common constituents of construction metal alloys, i.e., elements having atomic numbers between 22 (Ti) and 30 (Zn), are summarized on the basis of metal oxide solubility studies. 41 refs., 4 tabs., 3 figs.

Ziemniak, S.E.

1991-05-01

88

Task specific ionic liquid for direct electrochemistry of metal oxides  

Microsoft Academic Search

We present the first report on task specific ionic liquid (TSIL) for direct electrochemical detection of heavy metal oxides including cadmium oxide, copper oxide and lead oxide at room temperature. This TSIL based electrochemical sensor demonstrated a high sensitivity and selectivity towards the online monitoring of these trace metal oxide particulates, along with short detection time, low cost and high

Donglai Lu; Nasim Shomali; Amy Shen

2010-01-01

89

Metal sulfide initiators for metal oxide sorbent regeneration  

DOEpatents

A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing gas. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream.

Turk, Brian S. (Durham, NC); Gupta, Raghubir P. (Durham, NC)

2001-01-01

90

Metal sulfide initiators for metal oxide sorbent regeneration  

DOEpatents

A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing gas. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream. 1 fig.

Turk, B.S.; Gupta, R.P.

1999-06-22

91

Metal sulfide initiators for metal oxide sorbent regeneration  

DOEpatents

A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream.

Turk, Brian S. (Durham, NC); Gupta, Raghubir P. (Durham, NC)

1999-01-01

92

Pressure-Induced Electronic Phase Transitions Transition Metal Oxides and Rare Earth Metals  

E-print Network

Pressure-Induced Electronic Phase Transitions in Transition Metal Oxides and Rare Earth Metals Metal Oxides and Rare Earth Metals by Brian Ross Maddox Electron correlation can affect profound changes transition in a transition metal monoxide. iv #12;The lanthanides (the 4f metals also known as rare-earths

Islam, M. Saif

93

Oxide Electronics Utilizing Ultrafast Metal-Insulator  

E-print Network

-insulator transition near room temperature at ultrafast timescales. The article begins with an introduction to metal in correlated oxides such as, but not limited to, high-temperature superconductivity in cuprates (20 sequioxide (Ti2O3), increases by several orders of magnitude when the temperature decreases from high to low

Yang, Zheng

94

Morphology engineering of high performance binary oxide electrodes.  

PubMed

Advances in materials have preceded almost every major technological leap since the beginning of civilization. On the nanoscale and microscale, mastery over the morphology, size, and structure of a material enables control of its properties and enhancement of its usefulness for a given application, such as energy storage. In this review paper, our aim is to present a review of morphology engineering of high performance oxide electrode materials for electrochemical energy storage. We begin with the chemical bonding theory of single crystal growth to direct the growth of morphology-controllable materials. We then focus on the growth of various morphologies of binary oxides and their electrochemical performances for lithium ion batteries and supercapacitors. The morphology-performance relationships are elaborated by selecting examples in which there is already reasonable understanding for this relationship. Based on these comprehensive analyses, we proposed colloidal supercapacitor systems beyond morphology control on the basis of system- and ion-level design. We conclude this article with personal perspectives on the directions toward which future research in this field might take. PMID:25406718

Chen, Kunfeng; Sun, Congting; Xue, Dongfeng

2015-01-14

95

Spinel-structured metal oxide on a substrate and method of making same by molecular beam epitaxy  

DOEpatents

A method of making a spinel-structured metal oxide on a substrate by molecular beam epitaxy, comprising the step of supplying activated oxygen, a first metal atom flux, and at least one other metal atom flux to the surface of the substrate, wherein the metal atom fluxes are individually controlled at the substrate so as to grow the spinel-structured metal oxide on the substrate and the metal oxide is substantially in a thermodynamically stable state during the growth of the metal oxide. A particular embodiment of the present invention encompasses a method of making a spinel-structured binary ferrite, including Co ferrite, without the need of a post-growth anneal to obtain the desired equilibrium state.

Chambers, Scott A.

2006-02-21

96

Reactor process using metal oxide ceramic membranes  

DOEpatents

A reaction vessel for use in photoelectrochemical reactions includes as its reactive surface a metal oxide porous ceramic membrane of a catalytic metal such as titanium. The reaction vessel includes a light source and a counter electrode. A provision for applying an electrical bias between the membrane and the counter electrode permits the Fermi levels of potential reaction to be favored so that certain reactions may be favored in the vessel. The electrical biasing is also useful for the cleaning of the catalytic membrane. Also disclosed is a method regenerating a porous metal oxide ceramic membrane used in a photoelectrochemical catalytic process by periodically removing the reactants and regenerating the membrane using a variety of chemical, thermal, and electrical techniques.

Anderson, Marc A. (Madison, WI)

1994-01-01

97

Reactor process using metal oxide ceramic membranes  

DOEpatents

A reaction vessel for use in photoelectrochemical reactions includes as its reactive surface a metal oxide porous ceramic membrane of a catalytic metal such as titanium. The reaction vessel includes a light source and a counter electrode. A provision for applying an electrical bias between the membrane and the counter electrode permits the Fermi levels of potential reaction to be favored so that certain reactions may be favored in the vessel. The electrical biasing is also useful for the cleaning of the catalytic membrane. Also disclosed is a method regenerating a porous metal oxide ceramic membrane used in a photoelectrochemical catalytic process by periodically removing the reactants and regenerating the membrane using a variety of chemical, thermal, and electrical techniques. 2 figures.

Anderson, M.A.

1994-05-03

98

Molecular Rectification in Metal-SAM-Metal Oxide-Metal Christian A. Nijhuis, William F. Reus, and George M. Whitesides*  

E-print Network

Molecular Rectification in Metal-SAM-Metal Oxide-Metal Junctions Christian A. Nijhuis, William F ) voltage (V)). That is, 68% of the distribution of R lies within the range from 33 to 3.0 × 102 , in metal-insulator-metal oxide-metal junctions. R ) |J(-V)|/|J(V)| (1) The junctions comprised self-assembled monolayers (SAMs

Prentiss, Mara

99

Method for producing nanostructured metal-oxides  

DOEpatents

A synthetic route for producing nanostructure metal-oxide-based materials using sol-gel processing. This procedure employs the use of stable and inexpensive hydrated-metal inorganic salts and environmentally friendly solvents such as water and ethanol. The synthesis involves the dissolution of the metal salt in a solvent followed by the addition of a proton scavenger, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively. Using this method synthesis of metal-oxide nanostructured materials have been carried out using inorganic salts, such as of Fe3+, Cr3+, Al3+, Ga3+, In3+, Hf4+, Sn4+, Zr4+, Nb5+, W6+, Pr3+, Er3+, Nd3+, Ce3+, U3+ and Y3+. The process is general and nanostructured metal-oxides from the following elements of the periodic table can be made: Groups 2 through 13, part of Group 14 (germanium, tin, lead), part of Group 15 (antimony, bismuth), part of Group 16 (polonium), and the lanthanides and actinides. The sol-gel processing allows for the addition of insoluble materials (e.g., metals or polymers) to the viscous sol, just before gelation, to produce a uniformly distributed nanocomposites upon gelation. As an example, energetic nanocomposites of FexOy gel with distributed Al metal are readily made. The compositions are stable, safe, and can be readily ignited to thermitic reaction.

Tillotson, Thomas M.; Simpson, Randall L.; Hrubesh, Lawrence W.; Gash, Alexander

2006-01-17

100

A Numerical Model Describing Multiphase Binary Diffusion in Liquid Metal/Solid Metal Couples  

NASA Astrophysics Data System (ADS)

A numerical model for multiphase binary diffusion in liquid metal/solid metal infinite couples is developed by introducing a bisection method which determines a location of the Matano interface. The model makes use of phase diagram sources and kinetic data without any adjustable parameters. The model gives displacements of the interphase interfaces including the liquid/solid interface relative to the x = 0 plane, a change in the mass of a solid metal and a distance-composition profile at diffusion time given. The calculated rates of phase layer growth agreed reasonably well with the measured rates by other researchers in liquid Sn saturated with Cu/solid Cu couples and liquid Zn/solid Fe couples in the diffusion-controlled stage.

Tsuji, Shinji

2014-11-01

101

40 CFR 721.10006 - Mixed metal oxide (generic).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Mixed metal oxide (generic). 721.10006 Section...Chemical Substances § 721.10006 Mixed metal oxide (generic). (a) Chemical substance...substance identified generically as mixed metal oxide (PMN P-99-511) is...

2014-07-01

102

40 CFR 721.10006 - Mixed metal oxide (generic).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Mixed metal oxide (generic). 721.10006 Section...Chemical Substances § 721.10006 Mixed metal oxide (generic). (a) Chemical substance...substance identified generically as mixed metal oxide (PMN P-99-511) is...

2012-07-01

103

40 CFR 721.5549 - Lithiated metal oxide.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Lithiated metal oxide. 721.5549 Section 721.5549...Chemical Substances § 721.5549 Lithiated metal oxide. (a) Chemical substance and...substance identified generically as lithiated metal oxide (LiNiO2 ) (PMN...

2012-07-01

104

Binary Metal Sorption by Pine Bark: Study of Equilibria and Mechanisms  

Microsoft Academic Search

Pine bark was able to sorb cadmium, copper, and nickel ions from aqueous solutions. Binary equilibrium data from the combination of these metals were collected in this work using this sorbent. These data were modeled using three types of binary component equilibrium isotherms, all of which resulted in good fitting of the experimental data, with the Langmuir—Freundlich model resulting in

Sameer Al-Asheh; Z. Duvnjak

1998-01-01

105

Reactor vessel using metal oxide ceramic membranes  

DOEpatents

A reaction vessel for use in photoelectrochemical reactions includes as its reactive surface a metal oxide porous ceramic membrane of a catalytic metal such as titanium. The reaction vessel includes a light source and a counter electrode. A provision for applying an electrical bias between the membrane and the counter electrode permits the Fermi levels of potential reaction to be favored so that certain reactions may be favored in the vessel. The electrical biasing is also useful for the cleaning of the catalytic membrane.

Anderson, Marc A. (Madison, WI); Zeltner, Walter A. (Oregon, WI)

1992-08-11

106

High temperature zirconia oxygen sensor with sealed metal\\/metal oxide internal reference  

Microsoft Academic Search

Potentiometric internal reference oxygen sensors are created by embedding a metal\\/metal oxide mixture within a yttria-stabilized zirconia oxygen-conducting ceramic superstructure. Three metal\\/metal oxide systems based on Pd, Ni, and Ru are examined. A static internal reference oxygen pressure is produced inside the reference chamber of the sensor at the target application temperature. The metal\\/metal oxide-containing reference chamber is sealed within

John V. Spirig; Ramasamy Ramamoorthy; Sheikh A. Akbar; Jules L. Routbort; Dileep Singh; Prabir K. Dutta

2007-01-01

107

Hydrous metal oxide catalysts for oxidation of hydrocarbons  

SciTech Connect

This report describes work performed at Sandia under a CRADA with Shell Development of Houston, Texas aimed at developing hydrous metal oxide (HMO) catalysts for oxidation of hydrocarbons. Autoxidation as well as selective oxidation of 1-octene was studied in the presence of HMO catalysts based on known oxidation catalysts. The desired reactions were the conversion of olefin to epoxides, alcohols, and ketones, HMOs seem to inhibit autoxidation reactions, perhaps by reacting with peroxides or radicals. Attempts to use HMOs and metal loaded HMOs as epoxidation catalysts were unsuccessful, although their utility for this reaction was not entirely ruled out. Likewise, alcohol formation from olefins in the presence of HMO catalysts was not achieved. However, this work led to the discovery that acidified HMOs can lead to carbocation reactions of hydrocarbons such as cracking. An HMO catalyst containing Rh and Cu that promotes the reaction of {alpha}-olefins with oxygen to form methyl ketones was identified. Although the activity of the catalyst is relatively low and isomerization reactions of the olefin simultaneously occur, results indicate that these problems may be addressed by eliminating mass transfer limitations. Other suggestions for improving the catalyst are also made. 57 refs.

Miller, J.E.; Dosch, R.G.; McLaughlin, L.I. [Sandia National Labs., Albuquerque, NM (United States). Process Research Dept.

1993-07-01

108

Reactivity of aluminum nanopowders with metal oxides  

Microsoft Academic Search

During the past few years, significant progress has been made in research of the formation of nanopowders and their application in both civilian and military sectors. One example of such an application is the development of nanoscale energetic materials. This paper presents the recent experimental studies of ultra-fast reactions between nanosized aluminum and various metal oxides, including WO3, MoO3, CuO,

S. Valliappan; J. Swiatkiewicz; J. A. Puszynski

2005-01-01

109

Removal of metallic iron on oxide slags  

SciTech Connect

It is possible, in some cases, for ground coal particles to react with gasifier gas during combustion, allowing the ash material in the coal to form phases besides the expected slag phase. One of these phases is metallic iron, because some gasifiers are designed to operate under a reducing atmosphere (pO{sub 2}) of approximately 10{sup -4} atm). Metallic iron can become entrained in the gas stream and deposit on, and foul, downstream equipment. To improve the understanding of the reaction between different metallic iron particles and gas, which eventually oxidizes them, and the slag that the resulting oxide dissolves in, the kinetics of iron reaction on slag were predicted using gas-phase mass-transfer limitations for the reaction and were compared with diffusion in the slag; the reaction itself was observed under confocal scanning laser microscopy. The expected rates for iron droplet removal are provided based on the size and effective partial pressure of oxygen, and it is found that decarburization occurs before iron reaction, leading to an extra 30- to 100-second delay for carbon-saturated particles vs pure iron particles. A pure metallic iron particle of 0.5 mg should be removed in about 220 seconds at 1400{sup o}C and in 160 seconds at 1600{sup o}C.

Shannon, G.N.; Fruehan, R.J.; Sridhar, S. [Carnegie Mellon University, Pittsburgh, PA (United States). Dept. of Material Science & Engineering

2009-10-15

110

Method for producing metal oxide aerogels  

DOEpatents

A two-step hydrolysis-condensation method was developed to form metal oxide aerogels of any density, including densities of less than 0.003g/cm{sup 3} and greater than 0.27g/cm{sup 3}. High purity metal alkoxide is reacted with water, alcohol solvent, and an additive to form a partially condensed metal intermediate. All solvent and reaction-generated alcohol is removed, and the intermediate is diluted with a nonalcoholic solvent. The intermediate can be stored for future use to make aerogels of any density. The aerogels are formed by reacting the intermediate with water, nonalcoholic solvent, and a catalyst, and extracting the nonalcoholic solvent directly. The resulting monolithic aerogels are hydrophobic and stable under atmospheric conditions, and exhibit good optical transparency, high clarity, and homogeneity. The aerogels have high thermal insulation capacity, high porosity, mechanical strength and stability, and require shorter gelation times than aerogels formed by conventional methods. 8 figs.

Tillotson, T.M.; Poco, J.F.; Hrubesh, L.W.; Thomas, I.M.

1995-04-25

111

Method for producing metal oxide aerogels  

DOEpatents

A two-step hydrolysis-condensation method was developed to form metal oxide aerogels of any density, including densities of less than 0.003g/cm.sup.3 and greater than 0.27g/cm.sup.3. High purity metal alkoxide is reacted with water, alcohol solvent, and an additive to form a partially condensed metal intermediate. All solvent and reaction-generated alcohol is removed, and the intermediate is diluted with a nonalcoholic solvent. The intermediate can be stored for future use to make aerogels of any density. The aerogels are formed by reacting the intermediate with water, nonalcoholic solvent, and a catalyst, and extracting the nonalcoholic solvent directly. The resulting monolithic aerogels are hydrophobic and stable under atmospheric conditions, and exhibit good optical transparency, high clarity, and homogeneity. The aerogels have high thermal insulation capacity, high porosity, mechanical strength and stability, and require shorter gelation times than aerogels formed by conventional methods.

Tillotson, Thomas M. (Tracy, CA); Poco, John F. (Livermore, CA); Hrubesh, Lawrence W. (Pleasanton, CA); Thomas, Ian M. (Livermore, CA)

1995-01-01

112

Infrared reflection spectroscopy for precise tracking of corrosion behavior in 3d-transition metals doped binary lead silicate glass  

NASA Astrophysics Data System (ADS)

Fourier transform infrared reflection (FTIRR) spectroscopy was used to monitor and confirm the proposed corrosion mechanisms and structural differences in the surface regions of some prepared undoped binary lead silicate PbO-SiO 2 glass (LSG) together with samples doped with one of the first 3d-transition metal oxides (TMOs) (TiO 2?CuO) exposed to aqueous solutions of different pHs for a fixed time (1 h). The traditional proposed mechanism for silicate glass corrosion through ion exchange is analyzed to confirm and testify the applicability to such studied lead silicate glasses. The effects of 3d-transition metal oxides on the corrosion behavior of lead silicate glasses are followed and interpreted.

El-Batal, F. H.; Khalil, E. M. A.; Hamdy, Y. M.; Zidan, H. M.; Aziz, M. S.; Abdelghany, A. M.

2010-06-01

113

Method for inhibiting oxidation of metal sulfide-containing material  

DOEpatents

The present invention provides means for inhibiting the oxidation of a metal sulfide-containing material, such as ore mine waste rock or metal sulfide taiulings, by coating the metal sulfide-containing material with an oxidation-inhibiting two-tail lipid coating (12) thereon, thereby inhibiting oxidation of the metal sulfide-containing material in acid mine drainage conditions. The lipids may be selected from phospholipids, sphingolipids, glycolipids and combinations thereof.

Elsetinow, Alicia; Borda, Michael J.; Schoonen, Martin A.; Strongin, Daniel R.

2006-12-26

114

The competing oxide and sub-oxide formation in metal-oxide molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

The hetero-epitaxial growth of the n-type semiconducting oxides ?-Ga2O3, In2O3, and SnO2 on c- and r-plane sapphire was performed by plasma-assisted molecular beam epitaxy. The growth-rate and desorbing flux from the substrate were measured in-situ under various oxygen to metal ratios by laser reflectometry and quadrupole mass spectrometry, respectively. These measurements clarified the role of volatile sub-oxide formation (Ga2O, In2O, and SnO) during growth, the sub-oxide stoichiometry, and the efficiency of oxide formation for the three oxides. As a result, the formation of the sub-oxides decreased the growth-rate under metal-rich growth conditions and resulted in etching of the oxide film by supplying only metal flux. The flux ratio for the exclusive formation of the sub-oxide (e.g., the p-type semiconductor SnO) was determined, and the efficiency of oxide formation was found to be the highest for SnO2, somewhat lower for In2O3, and the lowest for Ga2O3. Our findings can be generalized to further oxides that possess related sub-oxides.

Vogt, Patrick; Bierwagen, Oliver

2015-02-01

115

Activity and diffusion of metals in binary aluminum alloys  

SciTech Connect

To determine the activity of zinc in Zn-Al alloys, the electromotive force (emf) of the cell: Zn/ZnCl/sub 2/-KC1 (eut)/Zn,Al was measured at temperatures between 569.5 K (296.5C) and 649.5 K (376.5C). The applicability of a two-suffix Margules equation was demonstrated, in good agreement with theoretical expectations. The diffusion coefficient of Zn in Al determined from a planar diffusion model for the experimental data was about 3 x 10/sup -10/ cm/sup 2//sec to 2 x 10/sup -9/ cm/sup 2//sec in the range of temperature studied. This is higher than that found in the literature. The most plausible reason appears to be the high alumina concentration in the working electrode because of partial oxidation. Oxidation of the alloying metals was the primary cause of poor alloying between calcium/or zinc and aluminum, thereby frustrating similar measurements at a Ca-Al/or Zn-Al alloy. The literature on the activity of calcium and zinc is aluminum is reviewed.

Jao, C. S.

1980-12-01

116

Frequency-selective surface coupled metal-oxide-metal diodes  

NASA Astrophysics Data System (ADS)

Metal-Oxide-Metal diodes offer the possibility of directly rectifying infrared radiation. To be effective for sensing or energy harvesting they must be coupled to an antenna which produces intense fields at the diode. While antennas significantly increase the effective capture area of the MOM diode, it is still limited and maximizing the captured energy is still a challenging goal. In this work we investigate integrating MOM diodes with a slot antenna Frequency Selective Surface (FSS). This maximizes the electromagnetic capture area while minimizing the transmission line length which helps reduce losses because metal losses are much lower at DC than at infrared frequencies. Our design takes advantage of a single self-aligned patterning step using shadow evaporation. The structure is optimized at 10.6 µm to have less than 2% reflection (polarization sensitive) and simulations predict that 70% of the incident energy is dissipated into the oxide layer. Initial experimental results fabricated with e-beam lithography are presented and the diode coupled FSS is shown to produce a polarization sensitive unbiased DC short circuit current. This work is promising for both infrared sensing and imaging as well as direct conversion of thermal energy.

Kinzel, Edward C.; Brown, Robert L.; Ginn, James C.; Lail, Brian A.; Slovick, Brian A.; Boreman, Glenn D.

2013-06-01

117

Metal oxide semiconductors for solar energy harvesting  

NASA Astrophysics Data System (ADS)

The correlation between energy consumption and human development illustrates the importance of this societal resource. We will consume more energy in the future. In light of issues with the status quo, such as climate change, long-term supply and security, solar energy is an attractive source. It is plentiful, virtually inexhaustible, and can provide more than enough energy to power society. However, the issue with producing electricity and fuels from solar energy is that it is expensive, primarily from the materials (silicon) used in building the cells. Metal oxide semiconductors are an attractive class of materials that are extremely low cost and can be produced at the scale needed to meet widespread demand. An industrially attractive thin film synthesis process based on aerosol deposition was developed that relies on self-assembly to afford rational control over critical materials parameters such as film morphology and nanostructure. The film morphology and nanostructure were found to have dramatic effects on the performance of TiO2-based photovoltaic dye-sensitized solar cells. Taking a cue from nature, to overcome the spatial and temporal mismatch between the supply of sunlight and demand for energy consumption, it is desirable to produce solar fuels such as hydrogen from photoelectrochemical water splitting. The source of water is important---seawater is attractive. The fundamental reaction mechanism for TiO2-based cells is discussed in the context of seawater splitting. There are two primary issues with producing hydrogen by photoelectrochemical water splitting using metal-oxide semiconductors: visible light activity and spontaneous activity. To address the light absorption issue, a combined theory-experiment approach was taken to understand the fundamental role of chemical composition in determining the visible light absorption properties of mixed metal-oxide semiconductors. To address the spontaneous activity issue, self-biasing all oxide p/n bulk-heterojunctions were synthesized and the nanostructure was systematically varied to understand the fundamental role of various characteristic length scales in the nanostructured region of the device on performance. The conclusion of this work is that solar energy harvesting by metal oxide semiconductors is highly promising. All of the scientific concepts have been proven, and steady gains in efficiency are being achieved as researchers continue to tackle the problem.

Thimsen, Elijah James

118

Process for producing metal compounds from graphite oxide  

NASA Technical Reports Server (NTRS)

A process for providing elemental metals or metal oxides distributed on a carbon substrate or self-supported utilizing graphite oxide as a precursor. The graphite oxide is exposed to one or more metal chlorides to form an intermediary product comprising carbon, metal, chloride, and oxygen This intermediary product can be flier processed by direct exposure to carbonate solutions to form a second intermediary product comprising carbon, metal carbonate, and oxygen. Either intermediary product may be further processed: a) in air to produce metal oxide; b) in an inert environment to produce metal oxide on carbon substrate; c) in a reducing environment to produce elemental metal distributed on carbon substrate. The product generally takes the shape of the carbon precursor.

Hung, Ching-Cheh (Inventor)

2000-01-01

119

Process for Producing Metal Compounds from Graphite Oxide  

NASA Technical Reports Server (NTRS)

A process for providing elemental metals or metal oxides distributed on a carbon substrate or self-supported utilizing graphite oxide as a precursor. The graphite oxide is exposed to one or more metal chlorides to form an intermediary product comprising carbon. metal. chloride. and oxygen This intermediary product can be flier processed by direct exposure to carbonate solutions to form a second intermediary product comprising carbon. metal carbonate. and oxygen. Either intermediary product may be further processed: a) in air to produce metal oxide: b) in an inert environment to produce metal oxide on carbon substrate: c) in a reducing environment. to produce elemental metal distributed on carbon substrate. The product generally takes the shape of the carbon precursor.

Hung, Ching-Cheh (Inventor)

2000-01-01

120

MATERIALS THEORY From transition metal oxides to cosmic strings  

E-print Network

in the universe? Very long time ago Today Temperature Time Low High Ã? Complex Oxides #12;MATERIALS THEORY We can use transition metal oxides to study the GUT Very long time ago Today Temperature Time Low HighMATERIALS THEORY From transition metal oxides to cosmic strings (and how electronic structure

121

Graphene oxide-based flexible metal-insulator-metal capacitors  

NASA Astrophysics Data System (ADS)

This work explores the fabrication of graphene oxide (GO)-based metal-insulator-metal (MIM) capacitors on flexible polyethylene terephthalate (PET) substrates. Electrical properties are studied in detail. A high capacitance density of ˜4 fF µm-2 measured at 1 MHz and permittivity of ˜6 have been obtained. A low voltage coefficient of capacitance, VCC-?, and a low dielectric loss tangent indicate the potential of GO-based MIM capacitors for RF applications. The constant voltage stressing study has shown a high reliability against degradation up to a projected period of 10 years. Degradation in capacitance of the devices on flexible substrates has been studied by bending radius down to 1 cm even up to 6000 times of repeated bending.

Bag, A.; Hota, M. K.; Mallik, S.; Maiti, C. K.

2013-05-01

122

The Effect of Metal Oxide on Nanoparticles from Thermite Reactions  

ERIC Educational Resources Information Center

The purpose of this research was to determine how metal oxide used in a thermite reaction can impact the production of nanoparticles. The results showed the presence of nanoparticles (less than 1 micron in diameter) of at least one type produced by each metal oxide. The typical particles were metallic spheres, which ranged from 300 nanometers in…

Moore, Lewis Ryan

2006-01-01

123

Polymer-assisted aqueous deposition of metal oxide films  

DOEpatents

An organic solvent-free process for deposition of metal oxide thin films is presented. The process includes aqueous solutions of necessary metal precursors and an aqueous solution of a water-soluble polymer. After a coating operation, the resultant coating is fired at high temperatures to yield optical quality metal oxide thin films.

Li, DeQuan (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM)

2003-07-08

124

Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces  

NASA Astrophysics Data System (ADS)

Utilizing a combination of ab initio density-functional theory and thermodynamics formalism, we have established the microscopic mechanisms for oxidation of the binary and ternary alloy surfaces and provided a clear explanation for the experimental results of the oxidation. We construct three-dimensional surface phase diagrams (SPDs) for oxygen adsorption on three different Nb-X(110) (X = Ti, Al or Si) binary alloy surfaces. On the basis of the obtained SPDs, we conclude a general microscopic mechanism for the thermodynamic oxidation, that is, under O-rich conditions, a uniform single-phase SPD (type I) and a nonuniform double-phase SPD (type II) correspond to the sustained complete selective oxidation and the non-sustained partial selective oxidation by adding the X element, respectively. Furthermore, by revealing the framework of thermodynamics for the oxidation mechanism of ternary alloys through the comparison of the surface energies of two separated binary alloys, we provide an understanding for the selective oxidation behavior of the Nb ternary alloy surfaces. Using these general microscopic mechanisms, one could predict the oxidation behavior of any binary and multi-component alloy surfaces based on thermodynamics considerations.

Liu, Shi-Yu; Liu, Shiyang; Li, De-Jun; Wang, Sanwu; Guo, Jing; Shen, Yaogen

2015-02-01

125

Metallic oxide switches using thick film technology  

NASA Technical Reports Server (NTRS)

Metallic oxide thick film switches were processed on alumina substrates using thick film technology. Vanadium pentoxide in powder form was mixed with other oxides e.g., barium, strontium copper and glass frit, ground to a fine powder. Pastes and screen printable inks were made using commercial conductive vehicles and appropriate thinners. Some switching devices were processed by conventional screen printing and firing of the inks and commercial cermet conductor terminals on 96% alumina substrates while others were made by applying small beads or dots of the pastes between platinum wires. Static, and dynamic volt-ampere, and pulse tests indicate that the switching and self-oscillatory characteristics of these devices could make them useful in memory element, oscillator, and automatic control applications.

Patel, D. N.; Williams, L., Jr.

1974-01-01

126

Orbital physics in transition-metal oxides  

PubMed

An electron in a solid, that is, bound to or nearly localized on the specific atomic site, has three attributes: charge, spin, and orbital. The orbital represents the shape of the electron cloud in solid. In transition-metal oxides with anisotropic-shaped d-orbital electrons, the Coulomb interaction between the electrons (strong electron correlation effect) is of importance for understanding their metal-insulator transitions and properties such as high-temperature superconductivity and colossal magnetoresistance. The orbital degree of freedom occasionally plays an important role in these phenomena, and its correlation and/or order-disorder transition causes a variety of phenomena through strong coupling with charge, spin, and lattice dynamics. An overview is given here on this "orbital physics," which will be a key concept for the science and technology of correlated electrons. PMID:10775098

Tokura; Nagaosa

2000-04-21

127

Orbital Physics in Transition-Metal Oxides  

NASA Astrophysics Data System (ADS)

An electron in a solid, that is, bound to or nearly localized on the specific atomic site, has three attributes: charge, spin, and orbital. The orbital represents the shape of the electron cloud in solid. In transition-metal oxides with anisotropic-shaped d-orbital electrons, the Coulomb interaction between the electrons (strong electron correlation effect) is of importance for understanding their metal-insulator transitions and properties such as high-temperature superconductivity and colossal magnetoresistance. The orbital degree of freedom occasionally plays an important role in these phenomena, and its correlation and/or order-disorder transition causes a variety of phenomena through strong coupling with charge, spin, and lattice dynamics. An overview is given here on this ``orbital physics,'' which will be a key concept for the science and technology of correlated electrons.

Tokura, Y.; Nagaosa, N.

2000-04-01

128

Metal oxide membranes for gas separation  

DOEpatents

A method for formation of a microporous ceramic membrane onto a porous support includes placing a colloidal suspension of metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane having mean pore sizes less than 30 Angstroms and useful for ultrafiltration, reverse osmosis, or gas separation. 4 figs.

Anderson, M.A.; Webster, E.T.; Xu, Q.

1994-08-30

129

Metal oxide membranes for gas separation  

DOEpatents

A method for permformation of a microporous ceramic membrane onto a porous support includes placing a colloidal suspension of metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane having mean pore sizes less than 30 Angstroms and useful for ultrafiltration, reverse osmosis, or gas separation.

Anderson, Marc A. (Madison, WI); Webster, Elizabeth T. (Madison, WI); Xu, Qunyin (Plainsboro, NJ)

1994-01-01

130

The interactions between transition metal nanoparticles and their metal-oxide supports are often critical for heterogeneous metal nanoparticle  

E-print Network

Reports The interactions between transition metal nanoparticles and their metal- oxide supports are often critical for heterogeneous metal nanoparticle catalysts (1). However, the roles of the species at the metal-support interface is widely regarded as the key step in room-temperature CO oxidation (13

Napp, Nils

131

FUNCTIONALIZED METAL OXIDE NANOPARTICLES: ENVIRONMENTAL TRANSFORMATIONS AND ECOTOXICITY  

EPA Science Inventory

This study will provide fundamental information on alterations in the surface chemistry of commercially important functionalized metal oxide NPs under environmentally relevant oxidative and reductive conditions, as well as needed data on the inherent and photo-enhanced toxicit...

132

High performance oxide fibers for metal and ceramic composites  

Microsoft Academic Search

A family of oxide fibers, Nextel™ 610 Ceramic Oxide Fiber, Nextel™ 720 Ceramic Oxide Fiber and a new fiber, Nextel™ 650 Ceramic Oxide Fiber, has been developed specifically for the reinforcement of metal and ceramic matrix composites. This paper summarizes room and high temperature properties for these fibers. The strength of both single filaments and multi-filament rovings of Nextel 610,

D. M Wilson; L. R Visser

2001-01-01

133

Adsorption behavior and mechanism of arsenate at Fe-Mn binary oxide/water interface.  

PubMed

Preliminary study revealed that a prepared Fe-Mn binary oxide adsorbent with a Fe:Mn molar ratio of 3:1 was more effective for As(V) removal than pure amorphous FeOOH, which was unanticipated. In this paper, the As(V) adsorption capacities of Fe-Mn binary oxide and amorphous FeOOH were compared in detail. Furthermore, the adsorption behaviors as well as adsorption mechanism of As(V) at the Fe-Mn binary oxide/water interface were investigated. The higher uptake of As(V) by the Fe-Mn binary oxide may be due to its higher surface area (265 m(2)/g) and pore volume (0.47 cm(3)/g) than those of amorphous FeOOH. The As(V) adsorption process on the Fe-Mn binary oxide is endothermic and the increase of temperature is favoring its adsorption. A slight increase in the As(V) adsorption was observed with increasing ionic strength of the solution, which indicated that As(V) anions might form inner-sphere surface complexes at the oxide/water interface. The Zeta potential along with FTIR analysis confirmed further the formation of inner-sphere surface complexes between As(V) anions and the surface of Fe-Mn binary oxide. In addition, the influences of coexisting ions such as phosphate, bicarbonate, silicate, sulfate, chloride, calcium and magnesium which are generally present in groundwater on As(V) adsorption were examined. Among the tested anions, chloride and sulfate had no significant effect on As(V) removal, silicate decreased obviously the As(V) removal, while phosphate caused the greatest percentage decrease in As(V) adsorption. On the contrary, the presence of cations of Ca(2+) and Mg(2+) enhanced the adsorption of As(V). PMID:19342165

Zhang, Gaosheng; Liu, Huijuan; Liu, Ruiping; Qu, Jiuhui

2009-09-15

134

Fluidized reduction of oxides on fine metal powders without sintering  

NASA Technical Reports Server (NTRS)

In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts.

Hayashi, T.

1985-01-01

135

Nanotoxicity: oxidative stress mediated toxicity of metal and metal oxide nanoparticles.  

PubMed

Metal and metal oxide nanoparticles are often used as industrial catalysts or to improve product's functional properties. Recent advanced nanotechnology have been expected to be used in various fields, ranging from sensors, environmental remediation to biomedicine, medical biology and imaging, etc. However, the growing use of nanoparticles has led to their release into environment and increased levels of these particles at nearby sites or the surroundings of their manufacturing factories become obvious. The toxicity of metal and metal oxide nanoparticles on humans, animals, and certainly to the environment has become a major concern to our community. However, controversies still remain with respect to the toxic effects and the mechanisms of these nanoparticles. The scientific community now feels that an understanding of the toxic effects is necessary to handle these nanoparticles and their use. A new discipline, named nanotoxicology, has therefore been developed that basically refers to the study of the interactions of nanoparticles with biological systems and also measures the toxicity level related to human health. Nanoparticles usually generate reactive oxygen species to a greater extent than micro-sized particles resulting in increased pro-inflammatory reactions and oxidative stress via intracellular signaling pathways. In this review, we mainly focus on the routes of exposure of some metal and metal oxide nanoparticles and how these nanoparticles affect us or broadly the cells of our organs. We would also like to discuss the responsible mechanism(s) of the nanoparticle-induced reactive oxygen species mediated organ pathophysiology. A brief introduction of the characterization and application of these nanoparticles has also been included in the article. PMID:24730293

Sarkar, Abhijit; Ghosh, Manoranjan; Sil, Parames Chandra

2014-01-01

136

Method of producing solution-derived metal oxide thin films  

DOEpatents

A method of preparing metal oxide thin films by a solution method. A .beta.-metal .beta.-diketonate or carboxylate compound, where the metal is selected from groups 8, 9, 10, 11, and 12 of the Periodic Table, is solubilized in a strong Lewis base to form a homogeneous solution. This precursor solution forms within minutes and can be deposited on a substrate in a single layer or a multiple layers to form a metal oxide thin film. The substrate with the deposited thin film is heated to change the film from an amorphous phase to a ceramic metal oxide and cooled.

Boyle, Timothy J. (Albuquerque, NM); Ingersoll, David (Albuquerque, NM)

2000-01-01

137

The role of metal/transition metal oxide/organic interface  

NASA Astrophysics Data System (ADS)

In this paper, we report a study with UPS and XPS data of metal/transition-metal-oxide/organic interfaces. Transition metal oxides are widely used in organic light- emitting (OLEDs) in recently years, such as Wo3, ReO3, MoO3, and V2O5. These metal oxides have been proven to be good hole injection layers in OLEDs, interlayers in tandem OLEDs, and nanocomposite electrodes. Although a large number of studies have been made, little is known about the mechanism of metal/transition-metal-oxide/organic interfaces. UPS and XPS data performed by synchrotron radiation research show that these oxides would catch electrons from organic and results in p-type doping in organic material. In addition, there is a significant structure transition from insulating metal oxide to metallic metal oxide. As a result of high work function metallic metal oxides in anode structures and p-type doping organic hole transport layers (HTLs), holes can easily be injected from anode to HTLs. Current-voltage characteristics (I-V) and quantum-efficiency (?-J) measurements also show the improvement of device performance with insertion of thin transition metal oxides between anodes HTLs.

Lin, Chang-Ting; Lee, Guan-Ru; Wu, Chih-I.; Pi, Tun-Wen

2008-03-01

138

The Close Binary Frequency of Wolf-Rayet Stars as a Function of Metallicity in M31 and M33  

NASA Astrophysics Data System (ADS)

Here we investigate whether the inability of the Geneva evolutionary models to predict a large enough WC/WN ratio at high metallicities (while succeeding at lower metallicities) is due to their single star nature. We hypothesize that Roche-lobe overflow in close binary systems may produce a greater number of WC stars at higher metallicities. But, this would suggest that the frequency of close massive binaries is metallicity dependent. We now present our results based on observations of ~100 Wolf-Rayet binaries in the varying metallicity environments of M31 and M33.

Neugent, Kathryn F.; Massey, Philip

2015-01-01

139

Task-specific ionic liquid for solubilizing metal oxides.  

PubMed

Protonated betaine bis(trifluoromethylsulfonyl)imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium(II) oxide, mercury(II) oxide, nickel(II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese(II) oxide, and silver(I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis(trifluoromethylsulfonyl)imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C (temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis(trifluoromethylsulfonyl)imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations. PMID:17048916

Nockemann, Peter; Thijs, Ben; Pittois, Stijn; Thoen, Jan; Glorieux, Christ; Van Hecke, Kristof; Van Meervelt, Luc; Kirchner, Barbara; Binnemans, Koen

2006-10-26

140

Synthesis of Metallic Iridium Oxide Nanowires via Metal Organic Chemical Vapor Deposition Fengyan ZHANG  

E-print Network

Synthesis of Metallic Iridium Oxide Nanowires via Metal Organic Chemical Vapor Deposition Fengyan, U.S.A. (Received December 9, 2004; accepted February 3, 2005; published March 4, 2005) Iridium oxide) iridium (I) as the precursor on Si or SiO2 substrate with and without metal nanoparticles as catalysts

Wang, Deli

141

Experimental determination of systems suitable for study as monotectic binary metallic alloy solidification models  

NASA Technical Reports Server (NTRS)

Transparent binary metallic alloy solidification models are important in attempts to understand the processes causing liquid-liquid and solid-liquid phase transformations in metallic alloy systems. These models permit visual observation of the phase transformation and the processes proceding solidification. The number of these transparent monotectic binary models needs to be expanded to distinguish between the unique and general phenomena observed. The expansion of the number of accurately determined monotectic phase diagrams of model systems, and contribution to a data base for eventual use with UNIFAC group contribution methods is examined.

Smith, J. E., Jr.

1985-01-01

142

Synthesis of nanostructured manganese oxides from a dipolar binary liquid (water\\/benzene) system and hydrogen storage ability research  

Microsoft Academic Search

A new dipolar binary liquid strategy has been developed to manganese oxide nanostructure’s synthesis, in which different manganese oxide nanostructures have been easily obtained without using any templates or catalysts. It has been found that the reaction temperatures, alkali precipitators’ concentrations and Mn2+ concentrations play a significant role in our dipolar binary liquid technique. This novel approach can be potentially

Hai Men; Peng Gao; Yuzeng Sun; Yujin Chen; Xiaona Wang; Longqiang Wang

2010-01-01

143

Solder for oxide layer-building metals and alloys  

Microsoft Academic Search

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel is disclosed. The composition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal

Kronberg

1992-01-01

144

Solder for oxide layer-building metals and alloys  

Microsoft Academic Search

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel. The comosition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the

Kronberg; James W

1992-01-01

145

Porous silicon with embedded metal oxides for gas sensing applications  

Microsoft Academic Search

This paper presents an analysis of the sol deposition process on porous silicon in order to produce highly sensitive gas detectors. Sol solutions were deposited within the dendrite structural pore regions of n-type silicon. The parameters for the structures, built of metal oxides (Fe, Ni, Sn), were analyzed. A morphological study of porous silicon, with embedded metal oxide nanocomposites, was

Vyatcheslav A. Moshnikov; Irina Gracheva; Aleksandr S. Lenshin; Yulia M. Spivak; Maxim G. Anchkov; Vladimir V. Kuznetsov; Jan M. Olchowik

146

Metal Oxide Semiconductor Gas Sensors and Neural Networks  

E-print Network

Olfaction Metal Oxide Semiconductor Gas Sensors and Neural Networks M. W. Siegel Carnegie Mellon four classes of chemicals in water solution on our tongues, and smell or olfaction, our ability to motivate autonomous activity. #12;2 First, I describe the characteristics of metal oxide semiconductor (MOS

Siegel, Mel

147

Detection of chemical warfare agents using nanostructured metal oxide sensors  

Microsoft Academic Search

The feasibility of thick-film chemical sensors based on various semiconductor metal oxides to reliably detect chemical warfare agents has been studied. Nanocrystalline semiconductor metal oxide (SMO) powders were used as initial materials for the sensors’ fabrication. The thick films were prepared using a simple drop-coating technique accompanied with in situ annealing of the deposited films by a heater that is

Alexey A. Tomchenko; Gregory P. Harmer; Brent T. Marquis

2005-01-01

148

Role of excipients on N-oxide raloxifene generation from raloxifene-excipients binary mixtures.  

PubMed

Raloxifene HCl (RHCl) is known to be susceptible to oxidation and forms the corresponding N-oxide derivative as the primary degradation product. The purpose of this study was to evaluate the role of excipients on the generation of the N-oxide derivative from the corresponding RHCl-excipient binary mixtures. Binary mixtures of RHCl with crospovidone, povidone, magnesium stearate, Tween 80 and anhydrous lactose in drug: excipients ratio of 1:1 (crospovidone and povidone); 10:1 (Tween 80 and magnesium stearate) and 1:5 (anhydrous lactose) were prepared by both dry blending (trituration) and wet blending (to improve contact between drug and excipients). The prepared binary mixtures were then stored at 25, 40, 75 and 125 degrees C and generation of the N-oxide derivative was monitored over six months using a validated HPLC method. Pure drug and excipients stored similarly acted as controls. Further, all the individual excipients (used as control) were monitored for peroxide impurity generation using an in-house colorimetric method. The results showed that N-oxide generation was observed from all binary mixtures and the amount of N-oxide derivative formed were always higher from the mixtures prepared by wet blending and the amount of N-oxide derivative formed was dependent on storage temperature. This study thus shows that the presence of peroxide in the excipient and its role in oxidative degradation of drug substance calls for monitoring of the peroxide impurity present in the excipients used for formulating of drug sensitive to oxidation as used herein. PMID:19801885

Yarkala, Sanjeeva; Amaravadi, Sivakumar; Rao, Vinay U; Vijaykumar, V; Navalgund, Sameer G; Jagdish, Balasubramaniam

2009-10-01

149

Conductive metal oxide film and method of making  

DOEpatents

The present invention is a method for reducing a dopant in a film of a metal oxide wherein the dopant is reduced and the first metal oxide is substantially not reduced. The method of the present invention relies upon exposing the film to reducing conditions for a predetermined time and reducing a valence of the metal from a positive valence to a zero valence and maintaining atoms with a zero valence in an atomic configuration within the lattice structure of the metal oxide. According to the present invention, exposure to reducing conditions may be achieved electrochemically or achieved in an elevated temperature gas phase.

Windisch, Jr., Charles F. (Kennewick, WA); Exarhos, Gregory J. (Richland, WA)

1999-01-01

150

Solder for oxide layer-building metals and alloys  

SciTech Connect

A low-temperature solder and method for soldering an oxide layer-building metal such as Al, Ti, Ta or stainless steel. The composition comprises Sn and Zn; Ge as a wetting agent; preferably small amounts of Cu and Sb; and a grit, such as SiC. The grit abrades any oxide layer formed on the surface of the metal as the Ge penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The Ge comprises less than 10 wt.% of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above 300 C. The method comprises the steps rubbing the solder against the metal surface so that the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

Kronberg, J.W.

1991-04-08

151

Solder for oxide layer-building metals and alloys  

DOEpatents

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel is disclosed. The composition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than approximately 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300 C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

Kronberg, J.W.

1992-09-15

152

Solder for oxide layer-building metals and alloys  

DOEpatents

A low temperature solder and method for soldering an oxide layer-building metal such as aluminum, titanium, tantalum or stainless steel. The comosition comprises tin and zinc; germanium as a wetting agent; preferably small amounts of copper and antimony; and a grit, such as silicon carbide. The grit abrades any oxide layer formed on the surface of the metal as the germanium penetrates beneath and loosens the oxide layer to provide good metal-to-metal contact. The germanium comprises less than aproximatley 10% by weight of the solder composition so that it provides sufficient wetting action but does not result in a melting temperature above approximately 300.degree. C. The method comprises the steps rubbing the solder against the metal surface so the grit in the solder abrades the surface while heating the surface until the solder begins to melt and the germanium penetrates the oxide layer, then brushing aside any oxide layer loosened by the solder.

Kronberg, James W. (108 Independent Blvd., Aiken, SC 29801)

1992-01-01

153

Immobilization of selenite in soil and groundwater using stabilized Fe-Mn binary oxide nanoparticles.  

PubMed

Stabilized Fe-Mn binary oxide nanoparticles were synthesized and tested for removal and in-situ immobilization of Se(IV) in groundwater and soil. A water-soluble starch or food-grade carboxymethyl cellulose (CMC) was used as a stabilizer to facilitate in-situ delivery of the particles into contaminated soil. While bare and stabilized nanoparticles showed rapid sorption kinetics, starch-stabilized Fe-Mn offered the greatest capacity for Se(IV). The Langmuir maximum capacity was determined to be 109 and 95 mg-Se/g-Fe for starch- and CMC-stabilized nanoparticles, respectively, and the high Se(IV) uptake was observed over the typical groundwater pH range of 5-8. Column breakthrough tests indicated that the stabilized nanoparticles were deliverable in a model sandy soil while non-stabilized particles were not. When a Se(IV)-spiked soil was treated in situ with the nanoparticles, >90% water leachable Se(IV) was transferred to the nanoparticle phase, and thereby immobilized as the particles were retained in the downstream soil matrix. The nanoparticle amendment reduced the TCLP (toxicity characteristic leaching procedure) leachability and the California WET (waste extraction test) leachability of Se(IV) by 76% and 71%, respectively. The technology holds the potential to fill a major technology gap in remediation of metals-contaminated soil and groundwater. PMID:25577492

Xie, Wenbo; Liang, Qiqi; Qian, Tianwei; Zhao, Dongye

2015-03-01

154

Oxidized film structure and method of making epitaxial metal oxide structure  

DOEpatents

A stable oxidized structure and an improved method of making such a structure, including an improved method of making an interfacial template for growing a crystalline metal oxide structure, are disclosed. The improved method comprises the steps of providing a substrate with a clean surface and depositing a metal on the surface at a high temperature under a vacuum to form a metal-substrate compound layer on the surface with a thickness of less than one monolayer. The compound layer is then oxidized by exposing the compound layer to essentially oxygen at a low partial pressure and low temperature. The method may further comprise the step of annealing the surface while under a vacuum to further stabilize the oxidized film structure. A crystalline metal oxide structure may be subsequently epitaxially grown by using the oxidized film structure as an interfacial template and depositing on the interfacial template at least one layer of a crystalline metal oxide.

Gan, Shupan [Richland, WA; Liang, Yong [Richland, WA

2003-02-25

155

The MSFC complementary metal oxide semiconductor (including multilevel interconnect metallization) process handbook  

NASA Technical Reports Server (NTRS)

The fabrication techniques for creation of complementary metal oxide semiconductor integrated circuits at George C. Marshall Space Flight Center are described. Examples of C-MOS integrated circuits manufactured at MSFC are presented with functional descriptions of each. Typical electrical characteristics of both p-channel metal oxide semiconductor and n-channel metal oxide semiconductor discrete devices under given conditions are provided. Procedures design, mask making, packaging, and testing are included.

Bouldin, D. L.; Eastes, R. W.; Feltner, W. R.; Hollis, B. R.; Routh, D. E.

1979-01-01

156

40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Nickel, cobalt mixed metal oxide (generic). 721...Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). ...substance identified generically as nickel, cobalt mixed metal oxide. (PMN...

2010-07-01

157

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2013-07-01

158

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2012-07-01

159

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2011-07-01

160

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2010-07-01

161

Oxidation energies of transition metal oxides within the GGA+U framework Lei Wang, Thomas Maxisch, and Gerbrand Ceder*  

E-print Network

Oxidation energies of transition metal oxides within the GGA+U framework Lei Wang, Thomas Maxisch; published 4 May 2006 The energy of a large number of oxidation reactions of 3d transition metal oxides error makes it possible to address the correlation effects in 3d transition metal oxides with the GGA

Ceder, Gerbrand

162

The chemical and catalytic properties of nanocrystalline metal oxides prepared through modified sol-gel synthesis  

NASA Astrophysics Data System (ADS)

The goal of this research was to synthesize, characterize and study the chemical properties of nanocrystalline metal oxides. Nanocrystalline (NC) ZnO, CuO, NiO, Al2O3, and the binary Al2O 3/MgO and ZnO/CuO were prepared through modified sol gel methods. These NC metal oxides were studied in comparison to the commercial (CM) metal oxides. The samples were characterized by XRD, TGA, FTIR, BET, and TEM. The NC samples were all accompanied by a significant increase in surface area and decrease in crystallite size. Several chemical reactions were studied to compare the NC samples to the CM samples. One of the reactions involved a high temperature reaction between carbon tetrachloride and the oxide to form carbon dioxide and the corresponding metal chloride. A similar high temperature reaction was conducted between the metal oxide and hydrogen sulfide to form water and the corresponding metal sulfide. A room temperature gas phase adsorption was studied where SO2 was adsorbed onto the oxide. A liquid phase adsorption conducted at room temperature was the destructive adsorption of paraoxon (a toxic insecticide). In all reactions the NC samples exhibited greater activity, destroying or adsorbing a larger amount of the toxins compared to the CM samples. To better study surface area effects catalytic reactions were also studied. The catalysis of methanol was studied over the nanocrystalline ZnO, CuO, NiO, and ZnO/CuO samples in comparison to their commercial counterparts. In most cases the NC samples proved to be more active catalysts, having higher percent conversions and turnover numbers. A second catalytic reaction was also studied, this reaction was investigated to look at the support effects. The catalysis of cyclopropane to propane was studied over Pt and Co catalysts. These catalysts were supported onto NC and CM alumina by impregnation. By observing differences in the catalytic behavior, support effects have become apparent.

Carnes, Corrie Leigh

163

Metal oxide/organic interface investigations for photovoltaic devices  

E-print Network

the performance and stability of interfacial charge extraction layers for organic solar cells. Two novel ternary metal oxides, zinc-strontrium- oxide (ZnSrO) and zinc-barium-oxide (ZnBaO), were fabricated and their use as electron extraction layers in inverted...

Pachoumi, Olympia

2014-10-07

164

THEORY OF MOTTTRANSITION : APPLICATION S TO TRANSITION METAL OXIDES  

E-print Network

125 THEORY OF MOTTTRANSITION : APPLICATION S TO TRANSITION METAL OXIDES M. CYROT Institut Laue discutons l'application de la théorie aux oxydes de métaux de transition. Abstract. 2014 We study the metal of the metal insulator transition is band splitting. For large values of the ratio U/W, the material remains

Paris-Sud XI, Université de

165

Reduction of spalling in mixed metal oxide desulfurization sorbents by addition of a large promoter metal oxide  

DOEpatents

Mixed metal oxide pellets for removing hydrogen sulfide from fuel gas mixes derived from coal are stabilized for operation over repeated cycles of desulfurization and regeneration reactions by addition of a large promoter metal oxide such as lanthanum trioxide. The pellets, which may be principally made up of a mixed metal oxide such as zinc titanate, exhibit physical stability and lack of spalling or decrepitation over repeated cycles without loss of reactivity. The lanthanum oxide is mixed with pellet-forming components in an amount of 1 to 10 weight percent.

Poston, J.A.

1997-12-02

166

Reduction of spalling in mixed metal oxide desulfurization sorbents by addition of a large promoter metal oxide  

DOEpatents

Mixed metal oxide pellets for removing hydrogen sulfide from fuel gas mixes derived from coal are stabilized for operation over repeated cycles of desulfurization and regeneration reactions by addition of a large promoter metal oxide such as lanthanum trioxide. The pellets, which may be principally made up of a mixed metal oxide such as zinc titanate, exhibit physical stability and lack of spalling or decrepitation over repeated cycles without loss of reactivity. The lanthanum oxide is mixed with pellet-forming components in an amount of 1 to 10 weight percent.

Poston, James A. (Star City, WV)

1997-01-01

167

Ba and Ni speciation in a nodule of binary Mn oxide phase composition from Lake Baikal  

E-print Network

Ba and Ni speciation in a nodule of binary Mn oxide phase composition from Lake Baikal Alain in a ferromanganese nodule from Lake Baikal were charac- terized by X-ray microfluorescence, microdiffraction layer sites in the interlayer. Ã? 2007 Elsevier Ltd. All rights reserved. 1. INTRODUCTION Lake Baikal

168

Heterometallic M/Mn (M=Cu, Co, Zn) acetate complexes as precursors for binary oxides  

SciTech Connect

A facile one-pot procedure, or so-called 'direct synthesis,' was used to prepare the novel heterometallic complexes [M{sub 2}Mn(OAc){sub 6}(bpy){sub 2}], where M=Cu (1), Co (2), Zn (3), bpy=2,2'-bipyridyl, with high yields via oxidative dissolution of pure metals in a liquid phase. The complexes were characterized by an elemental analysis, single crystal X-ray diffraction method and FTIR. These complexes are proposed as precursors, whose thermal degradation may lead to the formation of solids possessing nano- to microsize levels of dispersity. The thermal behavior of the complexes obtained was studied by thermal analysis (TG/DTA/DTG) in both air and N{sub 2} and also by TPD mass-spectrometry in vacuo. The FTIR, X-ray powder diffraction (PXRD) and thermoanalytical data were used for the identification of the solid products of thermal degradation. The morphology and microstructure of the solid residues were analyzed, using scanning electron microscopy with energy dispersive X-ray microanalysis (SEM/EDX) at mkm and sub-micro levels. -- Graphical abstract: The novel heterometallic complexes [M{sub 2}Mn(OAc){sub 6}(bpy){sub 2}] (M=Cu, Co, Zn, bpy=2,2'-bipyridyl) were isolated and used as precursors for low-temperature synthesis of binary oxides. Single crystal X-ray diffraction, FTIR, TG/DTA/DTG, TPD-MS, PXRD, SEM/EDX analysis was performed on complexes and powders. Display Omitted

Makhankova, Valeriya G., E-mail: leram@univ.kiev.u [Department of Inorganic Chemistry, Kyiv National Taras Shevchenko University, Volodymyrska street 64, Kyiv 01601 (Ukraine); Khavryuchenko, Oleksiy V.; Lisnyak, Vladyslav V.; Kokozay, Vladimir N. [Department of Inorganic Chemistry, Kyiv National Taras Shevchenko University, Volodymyrska street 64, Kyiv 01601 (Ukraine); Dyakonenko, Viktoriya V. [STC 'Institute for Single Crystals' National Academy of Sciences of Ukraine, 60 Lenina Avenue Kharkiv 61001 (Ukraine); Shishkin, Oleg V. [STC 'Institute for Single Crystals' National Academy of Sciences of Ukraine, 60 Lenina Avenue Kharkiv 61001 (Ukraine); Department of Inorganic Chemistry, V.N. Karazin Kharkiv National University, 4 Svobody sq., Kharkiv 61077 (Ukraine); Skelton, Brian W. [Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 6009 (Australia); Jezierska, Julia [Faculty of Chemistry, University of Wroclaw, 14 F. Joliot-Curie, 50-383 Wroclaw (Poland)

2010-11-15

169

Magnetic enhancement and magnetic reduction in binary clusters of transition metal atoms  

Microsoft Academic Search

Electronic and magnetic properties of small binary clusters containing one or two transition metal atoms are investigated using ab initio calculations with a view to explain the experimentally observed magnetic enhancement\\/reduction in these systems. As the present investigations do not rely on spin-orbit effects, our results reveal the enhancement or reduction in the magnetic moment to depend on two main

Antonis N. Andriotis; Giannis Mpourmpakis; George E. Froudakis; Madhu Menon

2004-01-01

170

Biomimetic metal oxides for the extraction of nanoparticles from water  

NASA Astrophysics Data System (ADS)

Contamination of nanomaterials in the environment will pose significant health risks in the future. A viable purification method is necessary to address this problem. Here we report the synthesis and application of a series of metal oxides prepared using a biological template for the removal of nanoparticles from the aqueous environment. A simple synthesis of metal oxides such as ZnO, NiO, CuO, Co3O4 and CeO2 employing eggshell membrane (ESM) as a biotemplate is reported. The morphology of the metal oxide powders was characterized using electron microscopes and the lattice structure was established using X-ray diffraction methods. Extraction of nanoparticles from water was carried out to compare the efficiency of metal oxides. NiO showed good extraction efficiency in removing gold and silver nanoparticles from spiked water samples within an hour. Easy access and enhanced stability of metal oxides makes them interesting candidates for applications in industrial effluent treatments and water purifications.Contamination of nanomaterials in the environment will pose significant health risks in the future. A viable purification method is necessary to address this problem. Here we report the synthesis and application of a series of metal oxides prepared using a biological template for the removal of nanoparticles from the aqueous environment. A simple synthesis of metal oxides such as ZnO, NiO, CuO, Co3O4 and CeO2 employing eggshell membrane (ESM) as a biotemplate is reported. The morphology of the metal oxide powders was characterized using electron microscopes and the lattice structure was established using X-ray diffraction methods. Extraction of nanoparticles from water was carried out to compare the efficiency of metal oxides. NiO showed good extraction efficiency in removing gold and silver nanoparticles from spiked water samples within an hour. Easy access and enhanced stability of metal oxides makes them interesting candidates for applications in industrial effluent treatments and water purifications. Electronic supplementary information (ESI) available: XRD and EDS analysis of the prepared metal oxides, EDS analysis of nanoparticles adsorbed on the surface of metal oxides and SEM micrographs of metal oxides are included. See DOI: 10.1039/c3nr34221b

Mallampati, Ramakrishna; Valiyaveettil, Suresh

2013-03-01

171

Structure, adhesion, and stability of metal/oxide and oxide/oxide interfaces  

SciTech Connect

During the past six months, we have begun our studies of the fundamental properties of metal/oxide and oxide/oxide heterogeneous interfaces which are being prepared by epitaxial growth of ultra-thin-films on single crystal TiO{sub 2} and NiO surfaces. A new ultra-high vacuum film growth chamber was assembled and coupled to an existing surface analysis chamber; a sample transfer system, metal deposition sources, and a RHEED systems with microchannel plate detection were constructed and implemented. Atomic Force Microscopy was used to characterize and refine the preparation procedures for the single crystal surfaces. The electronic structure of stoichiometric, oxygen-deficient, and potassium-covered TiO{sub 2} (110) surfaces was investigated. Preliminary results on the Al/TiO{sub 2} (110) system have been obtained. Two graduate students have begun thesis research on the project. 6 figs.

Lad, R.J.

1991-01-01

172

High-Pressure Thermodynamic Properties of f-electron Metals, Transition Metal Oxides, and Half-Metallic Magnets  

SciTech Connect

This project involves research into the thermodynamic properties of f-electron metals, transition metal oxides, and half-metallic magnets at high pressure. These materials are ones in which the changing importance of electron-electron interactions as the distance between atoms is varied can tune the system through phase transitions from localized to delocalized electrons, from screened to unscreened magnetic moments, and from normal metal to one in which only a single spin specie can conduct. Three main thrusts are being pursued: (1) Mott transitions in transition metal oxides, (2) magnetism in half-metallic compounds, and (3) large volume-collapse transitions in f-band metals.

Scalettar, Richard T.; Pickett, Warren E.

2004-07-01

173

Noble Metal Nanoparticle-loaded Mesoporous Oxide Microspheres for Catalysis  

NASA Astrophysics Data System (ADS)

Noble metal nanoparticles/nanocrystals have attracted much attention as catalysts due to their unique characteristics, including high surface areas and well-controlled facets, which are not often possessed by their bulk counterparts. To avoid the loss of their catalytic activities brought about by their size and shape changes during catalytic reactions, noble metal nanoparticles/nanocrystals are usually dispersed and supported finely on solid oxide supports to prevent agglomeration, nanoparticle growth, and therefore the decrease in the total surface area. Moreover, metal oxide supports can also play important roles in catalytic reactions through the synergistic interactions with loaded metal nanoparticles/nanocrystals. In this thesis, I use ultrasonic aerosol spray to produce hybrid microspheres that are composed of noble metal nanoparticles/nanocrystals embedded in mesoporous metal oxide matrices. The mesoporous metal oxide structure allows for the fast diffusion of reactants and products as well as confining and supporting noble metal nanoparticles. I will first describe my studies on noble metal-loaded mesoporous oxide microspheres as catalysts. Three types of noble metals (Au, Pt, Pd) and three types of metal oxide substrates (TiO2, ZrO2, Al 2O3) were selected, because they are widely used for practical catalytic applications involved in environmental cleaning, pollution control, petrochemical, and pharmaceutical syntheses. By considering every possible combination of the noble metals and oxide substrates, nine types of catalyst samples were produced. I characterized the structures of these catalysts, including their sizes, morphologies, crystallinity, and porosities, and their catalytic performances by using a representative reduction reaction from nitrobenzene to aminobenzene. Comparison of the catalytic results reveals the effects of the different noble metals, their incorporation amounts, and oxide substrates on the catalytic abilities. For this particular reaction, I found that Pd nanoparticles supported on mesoporous TiO2 exhibit the best catalytic performance. The demonstrated low-cost and high-productivity preparation method can be extended to other catalysts, which can contain various metals and oxide substrates and will have high potential for industrial applications. Our preparation method also provides a platform for the studies of the synergetic catalytic effects between different oxide substrates and metals. I further fabricated hollow mesoporous microspheres containing differently shaped noble metal nanocrystals. Hollow structures are strongly desired in many applications because of their high pore volumes, surface areas, and possible light-trapping effect. In my study, the hollow structures were obtained by simply dispersing polystyrene (PS) nanospheres into the precursor solution for aerosol spray. The PS spheres were removed by thermal calcination to produce hollow mesoporous microspheres. In my first study, the noble metal salts were dissolved in the precursor solutions, and the noble metal nanoparticles were obtained through thermal calcination. In this way, the size and shape of the metal nanoparticles cannot be well controlled. In my second study, I first grew noble metal nanocrystals and then incorporated them into the oxide supports. This preparation route allowed me to incorporate metal nanocrystals with controlled sizes, shapes, and compositions into the oxide matrices. The metal nanocrystals I used in this experiment included Pd nanocubes, Au nanorods, and Au core--Pd shell nanorods. These nanocrystals were functionalized with thiol-terminated methoxypoly(ethylene glycol) . The surface functionalization allowed them to adsorb on the PS spheres. After thermal calcination, the noble metal nanocrystals were left inside and adsorbed on the inner surface of the hollow mesoporous metal oxide microspheres. I investigated the catalytic activities of the Pd nanocube-embedded hollow mesoporous TiO2 and ZrO2 microspheres for the reduction of 4-nitrophenol to 4-aminophenol. I also examined the recycla

Jin, Zhao

174

Method for converting uranium oxides to uranium metal  

DOEpatents

A process is described for converting scrap and waste uranium oxide to uranium metal. The uranium oxide is sequentially reduced with a suitable reducing agent to a mixture of uranium metal and oxide products. The uranium metal is then converted to uranium hydride and the uranium hydride-containing mixture is then cooled to a temperature less than -100.degree. C. in an inert liquid which renders the uranium hydride ferromagnetic. The uranium hydride is then magnetically separated from the cooled mixture. The separated uranium hydride is readily converted to uranium metal by heating in an inert atmosphere. This process is environmentally acceptable and eliminates the use of hydrogen fluoride as well as the explosive conditions encountered in the previously employed bomb-reduction processes utilized for converting uranium oxides to uranium metal.

Duerksen, Walter K. (Norris, TN)

1988-01-01

175

Process for making a noble metal on tin oxide catalyst  

NASA Technical Reports Server (NTRS)

A quantity of reagent grade tin metal or compound, chloride-free, and high-surface-area silica spheres are placed in deionized water, followed by deaerating the mixture by boiling and adding an oxidizing agent, such as nitric acid. The nitric acid oxidizes the tin to metastannic acid which coats the spheres because the acid is absorbed on the substrate. The metastannic acid becomes tin oxide upon drying and calcining. The tin-oxide coated silica spheres are then placed in water and boiled. A chloride-free precious metal compound in aqueous solution is then added to the mixture containing the spheres, and the precious metal compound is reduced to a precious metal by use of a suitable reducing agent such as formic acid. Very beneficial results were obtained using the precious metal compound tetraammine platinum(II) hydroxide.

Upchurch, Billy T. (inventor); Davis, Patricia (inventor); Miller, Irvin M. (inventor)

1989-01-01

176

Catalysis using hydrous metal oxide ion exchangers  

DOEpatents

In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

Dosch, R.G.; Stephens, H.P.; Stohl, F.V.

1983-07-21

177

Nanoscale Metal Oxide Semiconductors for Gas Sensing  

NASA Technical Reports Server (NTRS)

A report describes the fabrication and testing of nanoscale metal oxide semiconductors (MOSs) for gas and chemical sensing. This document examines the relationship between processing approaches and resulting sensor behavior. This is a core question related to a range of applications of nanotechnology and a number of different synthesis methods are discussed: thermal evaporation- condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed, providing a processing overview to developers of nanotechnology- based systems. The results of a significant amount of testing and comparison are also described. A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. The TECsynthesized single-crystal nanowires offer uniform crystal surfaces, resistance to sintering, and their synthesis may be done apart from the substrate. The TECproduced nanowire response is very low, even at the operating temperature of 200 C. In contrast, the electrospun polycrystalline nanofiber response is high, suggesting that junction potentials are superior to a continuous surface depletion layer as a transduction mechanism for chemisorption. Using a catalyst deposited upon the surface in the form of nanoparticles yields dramatic gains in sensitivity for both nanostructured, one-dimensional forms. For the nanowire materials, the response magnitude and response rate uniformly increase with increasing operating temperature. Such changes are interpreted in terms of accelerated surface diffusional processes, yielding greater access to chemisorbed oxygen species and faster dissociative chemisorption, respectively. Regardless of operating temperature, sensitivity of the nanofibers is a factor of 10 to 100 greater than that of nanowires with the same catalyst for the same test condition. In summary, nanostructure appears critical to governing the reactivity, as measured by electrical resistance of these SnO2 nanomaterials towards reducing gases. With regard to the sensitivity of the different nascent nanostructures, the electrospun nanofibers appear preferable

Hunter, Gary W.; Evans, Laura; Xu, Jennifer C.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Michael J.

2011-01-01

178

Improving Metal-Oxide-Metal (MOM) Diode Performance Via the Optimization of the Oxide Layer  

NASA Astrophysics Data System (ADS)

Small area metal-oxide-metal (MOM) diodes are being investigated in many research groups for the detection of THz frequency radiation. In order to create a high-speed rectifying device, the central oxide layer of the MOM structure must be thin and have known physical characteristics. The thickness, structure and uniformity of the oxide can be controlled during the fabrication process. In the work presented here, the effects of both oxygen plasma concentration and annealing temperature during fabrication of {{Ti}/{TiO}x/{Pt}} MOM diodes have been explored. It has been found that, by reducing the oxygen gas concentration from previous work, the {{TiO}x} layer can be more repeatable and uniform. Furthermore, for an anneal temperature up to a threshold temperature in the {200°{C}} to {250°{C}} range, the performance of the diodes is excellent, with a value of zero-bias curvature coefficient (CCZB) that can be up to {4.6 {V}^{-1}} . For higher temperature treatments, the value of CCZB decreases to a maximum of {2.0 {V}^{-1}} . Similar trends in AC tests can be seen for voltage and current responsivity values.

Dodd, Linzi E.; Shenton, Samantha A.; Gallant, Andrew J.; Wood, David

2015-01-01

179

X-ray Absorption Study of Graphene Oxide and Transition Metal Oxide Nanocomposites.  

PubMed

The surface properties of the electrode materials play a crucial role in determining the performance and efficiency of energy storage devices. Graphene oxide and nanostructures of 3d transition metal oxides were synthesized for construction of electrodes in supercapacitors, and the electronic structure and oxidation states were probed using near-edge X-ray absorption fine structure. Understanding the chemistry of graphene oxide would provide valuable insight into its reactivity and properties as the graphene oxide transformation to reduced-graphene oxide is a key step in the synthesis of the electrode materials. Polarized behavior of the synchrotron X-rays and the angular dependency of the near-edge X-ray absorption fine structures (NEXAFS) have been utilized to study the orientation of the ? and ? bonds of the graphene oxide and graphene oxide-metal oxide nanocomposites. The core-level transitions of individual metal oxides and that of the graphene oxide nanocomposite showed that the interaction of graphene oxide with the metal oxide nanostructures has not altered the electronic structure of either of them. As the restoration of the ? network is important for good electrical conductivity, the C K edge NEXAFS spectra of reduced graphene oxide nanocomposites confirms the same through increased intensity of the sp(2)-derived unoccupied states ?* band. A pronounced angular dependency of the reduced sample and the formation of excitonic peaks confirmed the formation of extended conjugated network. PMID:25152800

Gandhiraman, Ram P; Nordlund, Dennis; Javier, Cristina; Koehne, Jessica E; Chen, Bin; Meyyappan, M

2014-08-14

180

Stimulated oxidation of metals (laser, electric field, etc.): Comparative studies  

NASA Astrophysics Data System (ADS)

In this report we demonstrate the importance of metal oxides, e.g. thin films and nanostructures, in modern science and technology. The basic laws of oxide thickness on base of diffusion of specimens versus time in different circumstances (Cabrera-Mott and Wagner laws) under the influence of external fields, e.g. electromagnetic field, static electric and magnetic field, are demonstrated. We give experimental results for various metal oxide layers over a wide range of different metals. Theoretical explanations are provided as well for the most reliable circumstances.

Nánai, László; Füle, Miklós

2014-11-01

181

Metal Oxide Gas Sensors: Sensitivity and Influencing Factors  

PubMed Central

Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. PMID:22294916

Wang, Chengxiang; Yin, Longwei; Zhang, Luyuan; Xiang, Dong; Gao, Rui

2010-01-01

182

Binary metal sorption by pine bark: Study of equilibria and mechanisms  

SciTech Connect

Pine bark was able to sorb cadmium, copper, and nickel ions from aqueous solutions. Binary equilibrium data from the combination of these metals were collected in this work using the sorbent. These data were modeled using three types of binary component equilibrium isotherms, all of which resulted in good fitting of the experimental data, with the Langmuir-Freundlich model resulting in their best representation. In general, the capacity of bark for each metal in the binary system was lower than in the single metal systems. The study also examined the mechanisms of metal biosorption by bark. Scanning electron microscopy (SEM) and energy-dispersive c-ray (EDX) microanalyses revealed that metal ions were sorbed mainly at the cell wall of the bark and only a small amount of ions diffused into the cytoplasm. Both the EDX analysis and the atomic absorption spectrophotometry (AAS) measurements showed that ion exchange was an important mechanism in this sorption process. Electron spin resonance (ESR) tests demonstrated that free radicals from the sorbent also have a significant role in the sorption processes.

Al-Asheh, S.; Duvnjak, Z. [Univ. of Ottawa, Ontario (Canada). Dept. of Chemical Engineering

1998-06-01

183

Oxidation of tunnel barrier metals in magnetic tunnel junctions  

SciTech Connect

The oxidation of an ultrathin metal layer (<1 nm) to form an oxide tunnel barrier is of critical importance for the fabrication of magnetic tunnel junctions (MTJs) with low product of resistance and area (RxA). Nonuniform and excessive or insufficient oxidation will occur by using conventional plasma, air, or O{sub 2} and noble gas mixtures as oxidation methods. An oxidation method was investigated to oxidize only an ultrathin layer of metal (such as Y) without oxidizing adjacent ferromagnetic thin film layers. We have now demonstrated that a gas mixture of H{sub 2}O/H{sub 2} with a fixed chemical potential of oxygen determined by the relative amounts of the two gases can oxidize Y and Ta thin layers while simultaneously keeping a Co ferromagnetic layer completely unoxidized. This universal method can be used to preferentially oxidize a host of other metals with high tendency to form oxides, such as Zr, Hf, Nb, rare earth metals, etc. and may allow us to access the feasible lower limit of barrier thickness in MTJs.

Yang, J. Joshua; Ladwig, Peter F.; Yang Ying; Ji Chengxiang; Chang, Y. Austin; Liu, Feng X.; Pant, Bharat B.; Schultz, Allan E. [Department of Materials Science and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Recording Head Operations, Seagate Technology, Bloomington, Minnesota 55431 (United States)

2005-05-15

184

First principles theory of metal/oxide and metal/ferroelectric interfaces: Towards an integrated design  

NASA Astrophysics Data System (ADS)

The current limits of semiconductor electronics and the challenges for future developments involve the continuous shrinking of the physical dimensions of the devices and the attainment of higher speeds. The drive to produce smaller devices has forced the current research towards the rethinking of electronic phenomena in terms of the individual microscopic component that dominate the quantum effects at the nanoscale. Therefore, it becomes fundamental to be able to obtain a detailed atomistic description of the physical properties of the systems in order to understand fully and manipulate their electronic and response properties. Using calculations from first principles, I will discussthe interplay between structure and functionality at metal-insulator interfaces, where the effects of nanoscale dimensions and scaling are extremely important for the design of efficient and performing electronic devices. Using the paradigmatic example of the junctions between various metals (Ag, Pd, Pt, Ni, Cu, Al) and binary alkaline earth crystalline oxides (BaO, CaO and SrO) and ferroelectric thin films (BaTiO3) I will demonstrate that it is possible to tune the electronic properties of the systems by manipulating the nanoscale structure of the interface. I will start by demonstrating that it is possible to tune the Schottky barrier height between a metal and an insulator such as BaO in a very broad range of values by manipulating the metal at the interface, and elucidate the role of the relative overlap in the density of states of the different components in determining the band alignment. This will allow meto state a modified Schottky-Mott rule for this class of metal-insulator heterojunctions. I have elucidated the nanoscale organization and local polarization in ferroelectric thin films sandwiched between metallic contacts. The profile of the local polarization for different film thicknesses unveils a peculiar spatial pattern of atomic layers with uncompensated dipoles in what was originally thought to be a ferroelectric domain. This effectively ferrielectric behavior is induced by the dominant roles of the interfaces at such reduced dimensionality and can be interpreted using a simple classical model where the latter are explicitly taken into account. I will describe how the interface structure in a metal-ferroelectric junction can be controlled by the introduction of metallic intralayers and how this effect can be used to tune the polarization of the ferroelectric film. Using a Pt/BaTiO3/Pt as a prototypical system, I will show how the polarization of the oxide can be tuned and how this effect varies with the thickness of the ferroelectric film. These results can be easily interpreted in terms of the local electronic structure of the interface and provide a phenomenological criterion for choosing the metal intralayer in order to obtain the desired polarization. Finally, I will discuss some preliminary results on the effect of polarization tuning on the quantum transport properties of the electronic tunnel junction.

Nunez, Matias

185

Dielectric response of sputtered transition metal oxides  

NASA Astrophysics Data System (ADS)

We have investigated the dielectric properties of thin layers of five oxides of transition metals (Ta2O5, HfO2, ZrO2, (ZrO2)0.91(Y2O3)0.09, and Sn0.2Zr0.2Ti0.6O2) sputtered from ceramic targets at different pressures. We find that layers deposited at low pressure behave as expected from literature, whereas layers deposited at high pressure all exhibit an anomalous dielectric response similar to that reported for the so-called "colossal" dielectric constant materials. The characterization of the thickness, frequency, and temperature dependence of the capacitance, as well as the comparison of film properties before and after annealing show that the anomalous dielectric response is due to quenched-in vacancies that act as dopants and cause the insulating layers to behave as semiconductors. An increase in quenched-in vacancies concentration with sputtering pressure results in a transition from normal to anomalous dielectric response and gradual increase in layer conductivity. In contrast, the refractive index does not depend on sputtering pressure. This observation indicates the possible application of these materials as transparent coatings with a tunable electrical conductivity.

Iosad, N. N.; Ruis, G. J.; Morks, E. V.; Morpurgo, A. F.; van der Pers, N. M.; Alkemade, P. F. A.; Sivel, V. G. M.

2004-06-01

186

Epitaxial Electrodeposition of Chiral Metal Oxide Films  

NASA Astrophysics Data System (ADS)

Chirality is ubiquitous in Nature. One enantiomer of a molecule is often physiologically active, while the other enantiomer may be either inactive or toxic. Chiral surfaces offer the possibility of developing heterogeneous enantiospecific catalysts that can more readily be separated from the products and reused. Chiral surfaces might also serve as electrochemical sensors for chiral molecules- perhaps even implantable chiral sensors that could be used to monitor drug levels in the body. Our trick to produce chiral surfaces is to electrodeposit low symmetry metal oxide films with chiral orientations on achiral substrates (see, Nature 425, 490, 2003). The relationship between three-dimensional and two-dimensional chirality will be discussed. Chiral surfaces lack mirror or glide plane symmetry. It is possible to produce chiral surfaces of materials which do not crystallize in chiral space groups. We have deposited chiral orientations of achiral CuO onto single-crystal Au and Cu using both tartaric acid and the amino acids alanine and valine to control the handedness of the electrodeposited films. We will present results on the chiral recognition of molecules such as tartaric or malic acid and L-dopa on the chiral electrodeposited CuO. Initial work on the electrochemical biomineralization of chiral nanostructures of calcite will also be discussed.

Switzer, Jay

2006-03-01

187

Arsenate uptake and arsenite simultaneous sorption and oxidation by Fe-Mn binary oxides: influence of Mn/Fe ratio, pH, Ca2+, and humic acid.  

PubMed

Arsenate retention, arsenite sorption and oxidation on the surfaces of Fe-Mn binary oxides may play an important role in the mobilization and transformation of arsenic, due to the common occurrence of these oxides in the environment. However, no sufficient information on the sorption behaviors of arsenic on Fe-Mn binary oxides is available. This study investigated the influences of Mn/Fe molar ratio, solution pH, coexisting calcium ions, and humic acids have on arsenic sorption by Fe-Mn binary oxides. To create Fe-Mn binary oxides, simultaneous oxidation and co-precipitation methods were employed. The Fe-Mn binary oxides exhibited a porous crystalline structure similar to 2-line ferrihydrite at Mn/Fe ratios 1:3 and below, whereas exhibited similar structures to ?-MnO(2) at higher ratios. The As(V) sorption maximum was observed at a Mn/Fe ratio of 1:6, but As(III) uptake maximum was at Mn/Fe ratio 1:3. However, As(III) adsorption capacity was much higher than that of As(V) at each Mn/Fe ratio. As(V) sorption was found to decrease with increasing pH, while As(III) sorption edge was different, depending on the content of MnO(2) in the binary oxides. The presence of Ca(2+) enhanced the As(V) uptake under alkaline pH, but did not significantly influence the As(III) sorption by 1:9 Fe-Mn binary oxide; whereas the presence of humic acid slightly reduced both As(V) and As(III) uptake. These results indicate that As(III) is more easily immobilized than As(V) in the environment, where Fe-Mn binary oxides are available as sorbents and they represent attractive adsorbents for both As(V) and As(III) removal from water and groundwater. PMID:22014399

Zhang, Gaosheng; Liu, Huijuan; Qu, Jiuhui; Jefferson, William

2012-01-15

188

Micro- and Nanostructured Metal Oxide Chemical Sensors for Volatile Organic Compounds  

NASA Technical Reports Server (NTRS)

Aeronautic and space applications warrant the development of chemical sensors which operate in a variety of environments. This technical memorandum incorporates various kinds of chemical sensors and ways to improve their performance. The results of exploratory investigation of the binary composite polycrystalline thick-films such as SnO2-WO3, SnO2-In2O3, SnO2-ZnO for the detection of volatile organic compound (isopropanol) are reported. A short review of the present status of the new types of nanostructured sensors such as nanobelts, nanorods, nanotube, etc. based on metal oxides is presented.

Alim, M. A.; Penn, B. G.; Currie, J. R., Jr.; Batra, A. K.; Aggarwal, M. D.

2008-01-01

189

Systematic study of metal-insulator-metal diodes with a native oxide  

NASA Astrophysics Data System (ADS)

In this paper, a systematic analysis of native oxides within a Metal-Insulator-Metal (MIM) diode is carried out, with the goal of determining their practicality for incorporation into a nanoscale Rectenna (Rectifying Antenna). The requirement of having a sub-10nm oxide scale is met by using the native oxide, which forms on most metals exposed to an oxygen containing environment. This, therefore, provides a simplified MIM fabrication process as the complex, controlled oxide deposition step is omitted. We shall present the results of an investigation into the current-voltage characteristics of various MIM combinations that incorporate a native oxide, in order to establish whether the native oxide is of sufficient quality for good diode operation. The thin native oxide layers are formed by room temperature oxidation of the first metal layer, deposited by magnetron sputtering. This is done in-situ, within the deposition chamber before depositing the second metal electrode. Using these structures, we study the established trend where the bigger the difference in metal workfunctions, the better the rectification properties of MIM structures, and hence the selection of the second metal is key to controlling the device's rectifying properties. We show how leakage current paths through the non-optimised native oxide control the net current-voltage response of the MIM devices. Furthermore, we will present the so-called diode figures of merit (asymmetry, non-linearity and responsivity) for each of the best performing structures.

Donchev, E.; Gammon, P. M.; Pang, J. S.; Petrov, P. K.; Alford, N. McN.

2014-10-01

190

Aerosol chemical vapor deposition of metal oxide films  

DOEpatents

A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said FIELD OF THE INVENTION The present invention relates to the field of film coating deposition techniques, and more particularly to the deposition of multicomponent metal oxide films by aerosol chemical vapor deposition. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

Ott, Kevin C. (4745 Trinity Dr., Los Alamos, NM 87544); Kodas, Toivo T. (5200 Noreen Dr. NE., Albuquerque, NM 87111)

1994-01-01

191

The oxidative transformation of methane over the nickel-based catalysts modified by alkali metal oxide and rare earth metal oxide  

Microsoft Academic Search

Two completely different behaviors of the oxidative transformation of methane were performed over the nickel-based catalysts because of the different modifications by alkali metal oxide and rare earth metal oxide and the different interactions between nickel and supports, and two types of catalysts, namely the LiNiLaOx catalyst with a good Oxidative Coupling of Methane (OCM) performance and the LiNiLaOx\\/Al2O3 supported

Qing Miao; Guoxing Xiong; Shishan Sheng; Wei Cui; Xiexian Guo

1996-01-01

192

Method of physical vapor deposition of metal oxides on semiconductors  

DOEpatents

A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

Norton, David P. (Knoxville, TN)

2001-01-01

193

Liquid-metal binary cycles for stationary power  

NASA Technical Reports Server (NTRS)

The use of topping cycles to increase electric power plant efficiency is discussed, with particular attention to mercury and alkali metal Rankine cycle systems that could be considered for topping cycle applications. An overview of this technology, possible system applications, the required development, and possible problem areas is presented.

Gutstein, M.; Furman, E. R.; Kaplan, G. M.

1975-01-01

194

Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection  

PubMed Central

A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.

2009-01-01

195

Charge, orbital and magnetic ordering in transition metal oxides   

E-print Network

Neutron and x-ray diffraction has been used to study charge, orbital and magnetic ordering in some transition metal oxides. The long standing controversy regarding the nature of the ground state (Verwey structure) of the ...

Senn, Mark Stephen

2013-06-29

196

Electrolytic separation of crystals of transition-metal oxides  

NASA Technical Reports Server (NTRS)

Versatile flux system grows large, well-formed, stoichiometric single crystals of mixed oxides of the transition-metal elements. These crystals have important uses in the microwave field, and applications as lasers and masers in communications.

Arnott, R. J.; Feretti, A.; Kunnamann, W.

1969-01-01

197

Growth and Characterization of Metal Oxides Layers on CVD Graphene  

NASA Astrophysics Data System (ADS)

Thin metal oxide layers deposited on graphene can be utilized as dielectric barriers between ferromagnetic metals and graphene to help overcome conductivity mismatch between the metal and graphene. Furthermore, these layers have been shown to increase the spin relaxation time measured utilizing non local detection and spin precession measurements. However, simply depositing metal oxide layers such as aluminum oxide on graphene results in non uniform film lowering the quality of the interface barrier. This presentation will show our work growing uniform aluminum oxide layers on graphene under ultra high vacuum conditions utilizing a Ti seed layer. The surface roughness of the films was measured with atomic force microscopy with and without titanium seed layers. The results show titanium seed layers reduced the surface roughness by a factor of 4 indicating a more uniform film. In addition, X-ray photoelectron spectroscopy results will be presented to confirm the stoichiometry of the films.

Matsubayashi, A.; Abel, J.; Sinha, D. P.; Lee, J. U.; Labella, V. P.

2012-02-01

198

Surface Stabilization Mechanisms in Metal Oxides  

NASA Astrophysics Data System (ADS)

Metal oxide surfaces play a central role in modern applications, ranging from heterogeneous catalysis to electronic devices, yet little is known about the processes determining their structural stabilization. Several such stabilization mechanisms are explored via a combination of theoretical and experimental methods. The processes of periodic reconstruction, adsorption and segregation are studied through case studies of model material systems. The evaluation of structural models of periodic SrTiO3(001) reconstructions via bonding analysis and simulated scanning tunneling microscopy images supports the family of "DL" models terminating in two consecutive layers of TiO2 composition, and discards alternative proposals such as the models based on periodic Sr adatoms. Experimental and simulated scanning tunneling microscopy images and complementary spectroscopic data are used to determine the structure of linear Ti-rich SrTiO 3(001) nanostructures. The structural solution exemplifies the recurrence of locally stable motifs across numerous surfaces. In particular, the arrangement of edge-sharing TiO5 surface polyhedra is a trait is shared by (001) nanostructures and DL reconstructions. This is a flexible framework which allows for optimal bonding in surface atoms. Modeling of water adsorption on reconstructed SrTiO3(001) surfaces reveals that water plays two major roles in the stabilization of oxide surfaces: it may mediate the formation of certain ordered structures, or it may be part of the ultimately stable structures themselves. This can be understood in terms of the inevitable presence of chemisorbed water on defective surfaces. Since the surface mobility of cationic species is relatively low, the kinetics associated to water diffusion and desorption dominate the surface ordering process. High-temperature annealing of SrLaAlO4 single crystals leads to the segregation of SrO to the surfaces, in the form of islands. This process is in fact a bulk stabilization mechanism, due initially to the increasing number of bulk Sr-O vacancy pairs. This material enables a second accommodation mechanism for further surface segregation and increasing bulk non-stoichiometry, consisting of the formation of low-energy stacking faults. In spite of previous speculation of a similar fault-based compensation process taking place in SrTiO3, this is found to be decidedly unviable in perovskite systems.

Becerra Toledo, Andres Enrique

2011-07-01

199

Thermochemical analyses of the oxidative vaporization of metals and oxides by oxygen molecules and atoms  

NASA Technical Reports Server (NTRS)

Equilibrium thermochemical analyses are employed to describe the vaporization processes of metals and metal oxides upon exposure to molecular and atomic oxygen. Specific analytic results for the chromium-, platinum-, aluminum-, and silicon-oxygen systems are presented. Maximum rates of oxidative vaporization predicted from the thermochemical considerations are compared with experimental results for chromium and platinum. The oxidative vaporization rates of chromium and platinum are considerably enhanced by oxygen atoms.

Kohl, F. J.; Leisz, D. M.; Fryburg, G. C.; Stearns, C. A.

1977-01-01

200

Dynamics of stellar black holes in young star clusters with different metallicities - II. Black hole-black hole binaries  

E-print Network

In this paper, we study the formation and dynamical evolution of black hole-black hole (BH-BH) binaries in young star clusters (YSCs), by means of N-body simulations. The simulations include metallicity-dependent recipes for stellar evolution and stellar winds, and have been run for three different metallicities (Z = 0.01, 0.1 and 1 Zsun). Following recent theoretical models of wind mass-loss and core-collapse supernovae, we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars. We find that BH-BH binaries form efficiently because of dynamical exchanges: in our simulations, we find about 10 times more BH-BH binaries than double neutron star binaries. The simulated BH-BH binaries form earlier in metal-poor YSCs, which host more massive black holes (BHs) than in metal-rich YSCs. The simulated BH-BH binaries have very large chirp masses (up to 80 Msun), because the BH mass is assumed to depend on metallicity, and because BHs can grow in mass due to the merger with stars. The simulated BH-BH binaries span a wide range of orbital periods (10^-3-10^7 yr), and only a small fraction of them (0.3 per cent) is expected to merge within a Hubble time. We discuss the estimated merger rate from our simulations and the implications for Advanced VIRGO and LIGO.

Brunetto Marco Ziosi; Michela Mapelli; Marica Branchesi; Giuseppe Tormen

2014-05-20

201

Metal oxide nano-crystals for gas sensing  

Microsoft Academic Search

This review article is focused on the description of metal oxide single crystalline nanostructures used for gas sensing. Metal oxide nano-wires are crystalline structures with precise chemical composition, surface terminations, and dislocation-defect free. Their nanosized dimension generate properties that can be significantly different from their coarse-grained polycrystalline counterpart. Surface effects appear because of the magnification in the specific surface of

Elisabetta Comini

2006-01-01

202

Bacterial adhesion to glass and metal-oxide surfaces  

Microsoft Academic Search

Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength

Baikun Li; Bruce E. Logan

2004-01-01

203

Mechanism for bipolar resistive switching in transition metal oxides  

Microsoft Academic Search

Resistive andom access memories (RRAM) composed of a transtition metal oxide dielectric in a capacitor-like structure is a candidate technology for next generation non-volatile memory devices. We introduce a model that accounts for the bipolar resistive switching phenomenom observed in many perovskite transition metal oxides. It qualitatively describes the electric field-enhanced migration of oxygen vacancies at the nano-scale. The numerical

Marcelo Rozenberg; Maria Jose Sanchez; Ruben Weht; Carlos Acha; Fernando Gomez-Marlasca; Pablo Levy

2010-01-01

204

Low-alloy powdered steels obtained by metal oxide technology  

Microsoft Academic Search

We have studied and described the mechanism and kinetics of thermodiffusional alloying of iron powder by Cr, Ni, Mo oxides and carbon in halogen-containing media. Oxides of Cr, Ni, and Mo are easily reduced to the metal in the presence of metallic iron, ammonium chloride, and combination media (H2+C, H2+CO). We have studied the chemical compositions and physicotechnological properties of

S. G. Agbalyan; S. A. Assila; N. N. Manukyan; B. F. Badeyan; A. S. Arutyunyan; L. G. Filosyan

1995-01-01

205

Water oxidation by an electropolymerized catalyst on derivatized mesoporous metal oxide electrodes.  

PubMed

A general electropolymerization/electro-oligomerization strategy is described for preparing spatially controlled, multicomponent films and surface assemblies having both light harvesting chromophores and water oxidation catalysts on metal oxide electrodes for applications in dye-sensitized photoelectrosynthesis cells (DSPECs). The chromophore/catalyst ratio is controlled by the number of reductive electrochemical cycles. Catalytic rate constants for water oxidation by the polymer films are similar to those for the phosphonated molecular catalyst on metal oxide electrodes, indicating that the physical properties of the catalysts are not significantly altered in the polymer films. Controlled potential electrolysis shows sustained water oxidation over multiple hours with no decrease in the catalytic current. PMID:24735242

Ashford, Dennis L; Lapides, Alexander M; Vannucci, Aaron K; Hanson, Kenneth; Torelli, Daniel A; Harrison, Daniel P; Templeton, Joseph L; Meyer, Thomas J

2014-05-01

206

Physical properties of magnetic macromolecule-metal and macromolecule-metal oxide nanoparticle complexes  

Microsoft Academic Search

Magnetic nanoparticles are of considerable interest owing to their potential applications in biotechnology and the magnetic recording industry. Iron oxides have received much attention owing to their oxidative stability and biocompatibility; however, other transition metals and their alloys are also under investigation. Cobalt has one of the largest magnetic susceptibilities of these materials, but it readily oxidizes upon exposure to

Michael Andrew Zalich

2005-01-01

207

Inert electrode containing metal oxides, copper and noble metal  

DOEpatents

A cermet composite material is made by treating at an elevated temperature a mixture comprising a compound of iron and a compound of at least one other metal, together with an alloy or mixture of copper and a noble metal. The alloy or mixture preferably comprises particles having an interior portion containing more copper than noble metal and an exterior portion containing more noble metal than copper. The noble metal is preferably silver. The cermet composite material preferably includes alloy phase portions and a ceramic phase portion. At least part of the ceramic phase portion preferably has a spinel structure.

Ray, Siba P. (Murrysville, PA); Woods, Robert W. (New Kensington, PA); Dawless, Robert K. (Monroeville, PA); Hosler, Robert B. (Sarver, PA)

2001-01-01

208

Inert electrode containing metal oxides, copper and noble metal  

DOEpatents

A cermet composite material is made by treating at an elevated temperature a mixture comprising a compound of iron and a compound of at least one other metal, together with an alloy or mixture of copper and a noble metal. The alloy or mixture preferably comprises particles having an interior portion containing more copper than noble metal and an exterior portion containing more noble metal than copper. The noble metal is preferably silver. The cermet composite material preferably includes alloy phase portions and a ceramic phase portion. At least part of the ceramic phase portion preferably has a spinel structure.

Ray, Siba P. (Murrysville, PA); Woods, Robert W. (New Kensington, PA); Dawless, Robert K. (Monroeville, PA); Hosler, Robert B. (Sarver, PA)

2000-01-01

209

Process for Making a Noble Metal on Tin Oxide Catalyst  

NASA Technical Reports Server (NTRS)

To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

Davis, Patricia; Miller, Irvin; Upchurch, Billy

2010-01-01

210

Route to transition metal carbide nanoparticles through cyanamide and metal oxides  

Microsoft Academic Search

We have designed an efficient route to the synthesis of transition metal carbide nanoparticles starting from an organic reagent cyanamide and transition metal oxides. Four technologically important metal carbide nanoparticles such as tungsten carbide, niobium carbide, tantalum carbide and vanadium carbide were synthesized successfully at moderate temperatures. It is found that cyanamide is an efficient carburization reagent and that the

P. G. Li; M. Lei; W. H. Tang

2008-01-01

211

Effects of NOM on Oxidative Reactivity of Manganese Dioxide in Binary Oxide Mixtures with Goethite or Hematite.  

PubMed

MnO2 typically coexists with iron oxides as either discrete particles or coatings in soils and sediments. This work examines the effect of Aldrich humic acid (AHA), alginate, and pyromellitic acid (PA) as representative natural organic matter (NOM) analogues on the oxidative reactivity of MnO2, as quantified by pseudo-first-order rate constants of triclosan oxidation, in mixtures with goethite or hematite. Adsorption studies showed that there was low adsorption of the NOMs by MnO2, but high (AHA and alginate) to low (PA) adsorption by the iron oxides. Based on the ATR-FTIR spectra obtained for the adsorbed PA on goethite or goethite + MnO2, the adsorption of PA occurred mainly through formation of outer-sphere complexes. The Fe oxides by themselves inhibited MnO2 reactivity through intensive heteroaggregation between the positively charged Fe oxides and the negatively charged MnO2; the low solubility of the iron oxides limited surface complexation of soluble Fe(3+) with MnO2. In ternary mixtures of MnO2, Fe oxides, and NOM analogues, the reactivity of MnO2 varied from inhibited to promoted as compared with that in the respective MnO2 + NOM binary mixtures. The dominant interaction mechanisms include an enhanced extent of homoaggregation within the Fe oxides due to formation of oppositely charged patches within the Fe oxides but an inhibited extent of heteroaggregation between the Fe oxide and MnO2 at [AHA] < 2-4 mg-C/L or [alginate/PA] < 5-10 mg/L, and an inhibited extent of heteroaggregation due to the largely negatively charged surfaces for all oxides at [AHA] > 4 mg-C/L or [alginate/PA] > 10 mg/L. PMID:25652230

Zhang, Huichun; Taujale, Saru; Huang, Jianzhi; Lee, Gang-Juan

2015-03-10

212

Custom-designed nanomaterial libraries for testing metal oxide toxicity.  

PubMed

Advances in aerosol technology over the past 10 years have enabled the generation and design of ultrafine nanoscale materials for many applications. A key new method is flame spray pyrolysis (FSP), which produces particles by pyrolyzing a precursor solution in the gas phase. FSP is a highly versatile technique for fast, single-step, scalable synthesis of nanoscale materials. New innovations in particle synthesis using FSP technology, including variations in precursor chemistry, have enabled flexible, dry synthesis of loosely agglomerated, highly crystalline ultrafine powders (porosity ? 90%) of binary, ternary, and mixed-binary-and-ternary oxides. FSP can fulfill much of the increasing demand, especially in biological applications, for particles with specific material composition, high purity, and high crystallinity. In this Account, we describe a strategy for creating nanoparticle libraries (pure or Fedoped ZnO or TiO?) utilizing FSP and using these libraries to test hypotheses related to the particles' toxicity. Our innovation lies in the overall integration of the knowledge we have developed in the last 5 years in (1) synthesizing nanomaterials to address specific hypotheses, (2) demonstrating the electronic properties that cause the material toxicity, (3) understanding the reaction mechanisms causing the toxicity, and (4) extracting from in vitro testing and in vivo testing in terrestrial and marine organisms the essential properties of safe nanomaterials. On the basis of this acquired knowledge, we further describe how the dissolved metal ion from these materials (Zn²? in this Account) can effectively bind with different cell constituents, causing toxicity. We use Fe-S protein clusters as an example of the complex chemical reactions taking place after free metal ions migrate into the cells. As a second example, TiO? is an active material in the UV range that exhibits photocatalytic behavior. The induction of electron-hole (e?/h?) pairs followed by free radical production is a key mechanism for biological injury. We show that decreasing the bandgap energy increases the phototoxicity in the presence of near-visible light. We present in detail the mechanism of electron transfer in biotic and abiotic systems during light exposure. Through this example we show that FSP is a versatile technique for efficiently designing a homologous library, meaning a library based on a parent oxide doped with different amounts of dopant, and investigating the properties of the resulting compounds. Finally, we describe the future outlook and state-of-the-art of an innovative two-flame system. A double-flame reactor enables independent control over each flame, the nozzle distances and the flame angles for efficient mixing of the particle streams. In addition, it allows for different flame compositions, flame sizes, and multicomponent mixing (a grain-grain heterojunction) during the reaction process. PMID:23194152

Pokhrel, Suman; Nel, André E; Mädler, Lutz

2013-03-19

213

A rapid microwave-assisted solvothermal approach to lower-valent transition metal oxides.  

PubMed

A green, rapid microwave-assisted solvothermal process using tetraethylene glycol (TEG) as a reducing agent has been explored as a soft-chemistry route for the preparation of various lower-valent transition metal oxides. To demonstrate the feasibility of the approach, lower-valent binary oxides such as V4O9, Mn3O4 or MnO, CoO, and Cu2O have been obtained within a short reaction time of 30 min by reducing, respectively, V2O5, MnO2, Co3O4, and CuO with TEG at <300 °C. Moreover, the approach has been used to extract oxygen from ternary oxides such as LaFeO3, SrMnO3, LaCoO3, LaNiO3, and La4Ni3O10. The oxidation state of the transition metal ions and the oxygen content in these ternary oxides could be tuned by precisely controlling the reaction temperatures from 160 to 300 °C. The products have been characterized by X-ray powder diffraction and iodometric titration. The versatility of this novel technique is demonstrated by the facile synthesis of V4O9, which has only been produced recently in single-phase form. PMID:24191765

Moorhead-Rosenberg, Zachary; Harrison, Katharine L; Turner, Travis; Manthiram, Arumugam

2013-11-18

214

Graphene oxide for metal-insulator-semiconductor tunneling diodes  

Microsoft Academic Search

In this study, we have inserted the graphene oxide (GO) in the metal\\/insulator\\/semiconductor tunneling diodes. The graphene oxide devices reveal the better stability as compared with the control devices. At a small positive bias, different control devices have different magnitude of photocurrents, while photocurrents of GO devices have close magnitude. At 2 V, the photocurrent density of the GO device

Chu-Hsuan Lin; Wei-Ting Yeh; Chun-Hui Chan; Chun-Chieh Lin

2011-01-01

215

Enhanced Half-Metallicity in Edge-Oxidized Zigzag Graphene  

E-print Network

Enhanced Half-Metallicity in Edge-Oxidized Zigzag Graphene Nanoribbons Oded Hod,* Vero´nica Barone theoretical study of the electronic properties and relative stabilities of edge-oxidized zigzag graphene with nanometer scale dimen- sions. Recently, a new type of graphene-based material was experimentally realized.12

Hod, Oded

216

Thermomechanical and oxidation behaviour of high temperature advanced metallic alloys  

Microsoft Academic Search

The main focus of this paper is on materials for radiant burners application. Two advanced metallic alloys, a Ni and Fe-based alloy are studied and compared to a reference ferritic stainless steel. Oxidation kinetics of such alloys at different temperatures are reported. Oxide formation mechanisms are discussed. Furthermore, thermo-mechanical resistance and eventual strengthening mechanism in temperature are studied. Finally, technical

Ildiko Peter; Alessandro Zago; Marco Actis Grande; Daniele Ugues

2009-01-01

217

Field-induced resistive switching in metal-oxide interfaces  

Microsoft Academic Search

We investigate the polarity-dependent field-induced resistive switching phenomenon driven by electric pulses in perovskite oxides. Our data show that the switching is a common occurrence restricted to an interfacial layer between a deposited metal electrode and the oxide. We determine through impedance spectroscopy that the interfacial layer is no thicker than 10 nm and that the switch is accompanied by

S. Tsui; A. Baikalov; J. Cmaidalka; B. Lorenz; Y. Q. Wang; C. W. Chu; A. J. Jacobson

2004-01-01

218

Integrated photo-responsive metal oxide semiconductor circuit  

NASA Technical Reports Server (NTRS)

An infrared photoresponsive element (RD) is monolithically integrated into a source follower circuit of a metal oxide semiconductor device by depositing a layer of a lead chalcogenide as a photoresistive element forming an ohmic bridge between two metallization strips serving as electrodes of the circuit. Voltage from the circuit varies in response to illumination of the layer by infrared radiation.

Jhabvala, Murzban D. (inventor); Dargo, David R. (inventor); Lyons, John C. (inventor)

1987-01-01

219

Oxidative mechanisms in the toxicity of metal ions  

Microsoft Academic Search

The role of reactive oxygen species, with the subsequent oxidative deterioration of biological macromolecules in the toxicities associated with transition metal ions, is reviewed. Recent studies have shown that metals, including iron, copper, chromium, and vanadium undergo redox cycling, while cadmium, mercury, and nickel, as well as lead, deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of reactive

S. J. Stohs; D. Bagchi

1995-01-01

220

Surface Precipitation of Hydrolyzable Metal Ions on Oxide Surfaces  

E-print Network

Surface Precipitation of Hydrolyzable Metal Ions on Oxide Surfaces S. E. Fendorf Heavy metalO2 and TiO2 near and beyond monolayer coverage. Surface precipitation of Al(III) and La(III) was observed on MnO2, but was not apparent on TiO2 nor in bulk solution. Al(III) formed a surface precipitate

Sparks, Donald L.

221

DEVELOPMENTAL PHYTOTOXICITY OF METAL OXIDE NANOPARTICLES TO ARABIDOPSIS THALIANA  

E-print Network

, root growth inhibition by 2,000 mg/L nano-aluminum oxide (nAl2O3) was reported for five plant species on the effects of four metal oxide nanoparticles, aluminum oxide (nAl2O3), silicon dioxide (nSiO2), magnetite (n concentration of dissolved zinc salt (ZnCl2), indicating that zinc dissolution could not solely account

Alvarez, Pedro J.

222

Development of multimetal binding model and application to binary metal biosorption onto peat biomass  

Microsoft Academic Search

Biosorption of Cr3+, Cu2+ and Cd2+ from binary metal solutions onto peat in the batch systems was investigated at pH 4. The order of maximum uptake was Cr?Cu>Cd and maximum uptake levels of ca. 0.4mmol\\/g were observed for chromium and copper while cadmium was taken up to a maximum of ca. 0.2mmol\\/g. Co-ion competition resulted in up to 70 percent

Wei Ma; J. M. Tobin

2003-01-01

223

Metal biosorption by algae Gelidium derived materials from binary solutions in a continuous stirred adsorber  

Microsoft Academic Search

Continuous metal biosorption from Pb(II)\\/Cu(II) and Pb(II)\\/Cd(II) solutions onto algae Gelidium and granulated algal waste was performed in a continuous stirred tank adsorber (CSTA). Biosorption was simulated by a mass transfer model including intraparticle and film resistances and equilibrium described by the Langmuir binary equation. The breakthrough curves present an initial “knee” suggesting a film resistance to mass transfer. Biosorption

Vítor J. P. Vilar; Cidália M. S. Botelho; Rui A. R. Boaventura

2008-01-01

224

Interactions of Hydrogen Isotopes and Oxides with Metal Tubes  

SciTech Connect

Understanding and accounting for interaction of hydrogen isotopes and their oxides with metal surfaces is important for persons working with tritium systems. Reported data from several investigators have shown that the processes of oxidation, adsorption, absorption, and permeation are all coupled and interactive. A computer model has been developed for predicting the interaction of hydrogen isotopes and their corresponding oxides in a flowing carrier gas stream with the walls of a metallic tube, particularly at low hydrogen concentrations. An experiment has been constructed to validate the predictive model. Predictions from modeling lead to unexpected experiment results.

Glen R. Longhurst

2008-08-01

225

Adsorptive removal of arsenic from water by an iron-zirconium binary oxide adsorbent.  

PubMed

Arsenate and arsenite may exist simultaneously in groundwater and have led to a greater risk to human health. In this study, an iron-zirconium (Fe-Zr) binary oxide adsorbent for both arsenate and arsenite removal was prepared by a coprecipitation method. The adsorbent was amorphous with a specific surface area of 339 m(2)/g. It was effective for both As(V) and As(III) removal; the maximum adsorption capacities were 46.1 and 120.0 mg/g at pH 7.0, respectively, much higher than for many reported adsorbents. Both As(V) and As(III) adsorption occurred rapidly and achieved equilibrium within 25 h, which were well fitted by the pseudo-second-order equation. Competitive anions hindered the sorption according to the sequence PO(4)(3-)>SiO(3)(2-)>CO(3)(2-)>SO(4)(2-). The ionic strength effect experiment, measurement of zeta potential, and FTIR study indicate that As(V) forms inner-sphere surface complexes, while As(III) forms both inner- and outer-sphere surface complexes at the water/Fe-Zr binary oxide interface. The high uptake capability and good stability of the Fe-Zr binary oxide make it a potentially attractive adsorbent for the removal of both As(V) and As(III) from water. PMID:21440898

Ren, Zongming; Zhang, Gaosheng; Chen, J Paul

2011-06-01

226

Metal-oxide-metal point contact junction detectors. [detection mechanism and mechanical stability  

NASA Technical Reports Server (NTRS)

The detection mechanism(s) and design of a mechanically stable metal-oxide-metal point contact junction detector are considered. A prototype for a mechanically stable device has been constructed and tested. A technique has been developed which accurately predicts microwave video detector and heterodyne mixer SIM (semiconductor-insulator-metal) diode performance from low dc frequency volt-ampere curves. The difference in contact potential between the two metals and geometrically induced rectification constitute the detection mechanisms.

Baird, J.; Havemann, R. H.; Fults, R. D.

1973-01-01

227

Aerosol chemical vapor deposition of metal oxide films  

DOEpatents

A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said substrate.

Ott, K.C.; Kodas, T.T.

1994-01-11

228

Emerging applications of liquid metals featuring surface oxides.  

PubMed

Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide "skin" enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects. PMID:25283244

Dickey, Michael D

2014-11-12

229

Emerging Applications of Liquid Metals Featuring Surface Oxides  

PubMed Central

Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide “skin” enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects. PMID:25283244

2014-01-01

230

X-ray Photoelectron Spectroscopic Studies of Interactions in Multicomponent Metal and Metal Oxide Thin Films.  

PubMed

Changes in chemical oxidation states in alloys and at solid-solid interfaces were monitored by using x-ray photoelectron spectroscopy. For an oxidized Nichrome surface, the chromium component was selectively converted to chromic oxide while nickel remained in the metallic state. When this surface was overlaid with a 20-angstrom-thick aluminum film, the chromic oxide was reduced to chromium and the aluminum was oxidized to aluminum oxide in a reaction zone consisting of no more than 10 angstroms of the interface. This scheme appeared general for solid-solid contacts and was predicted, to a first approximation, by bulk thermodynamic free energies. PMID:17755031

Winograd, N; Baitinger, W E; Amy, J W; Munarin, J A

1974-05-01

231

Metal Oxide Growth and Characterization on CVD Graphene  

NASA Astrophysics Data System (ADS)

Thin metal oxide layers deposited on graphene can be utilized as dielectric barriers between metals and graphene to help isolate a metal contact from the graphene channel. This is important for graphene based spintronic devices as dielectric layers between the ferromagnetic electrode and graphene have been shown to increase the spin relaxation time measured utilizing non-local detection and spin precession measurements. However, simply depositing metal oxide layers such as aluminum oxide on graphene results in non-uniform film lowering the quality of the interface barrier. We will present a systematic study of aluminum oxide layers grown on CVD (chemical vapor deposition) graphene under ultra-high vacuum conditions with and without titanium seed layers. The aluminum oxide layers with the titanium seed layers showed reduced surface roughness. The chemical and structural composition determined by XPS (X-ray photoelectron spectroscopy) will be also presented that shows full oxidation of the aluminum and partial oxidation of the titanium. Our previous work which demonstrated that introducing HfO2 barrier layer in the epitaxial graphene devices on SiC wafer improves the measured lifetime and spin injection efficiency will be briefly presented as well.

Matsubayashi, Akitomo; Abel, Joseph; Prasad Sinha, Dhiraj; Lee, Ji Ung; Labella, Vincent

2013-03-01

232

Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review  

PubMed Central

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called “small size effect”, yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given. PMID:22736968

Sun, Yu-Feng; Liu, Shao-Bo; Meng, Fan-Li; Liu, Jin-Yun; Jin, Zhen; Kong, Ling-Tao; Liu, Jin-Huai

2012-01-01

233

Partial oxidation of methane to syngas over nickel-based catalysts modified by alkali metal oxide and rare earth metal oxide  

Microsoft Academic Search

The NiO\\/Al2O3 catalyst was modified by alkali metal oxide (Li, Na, K) and rare-earth metal oxide (La, Ce, Y, Sm) in order to improve the thermal stability and the carbon-deposition resistance during the partial oxidation of methane to syngas (POM) reaction at high temperature. The reaction performance, thermal stability, structure, dispersity of nickel and carbon-deposition of the modified NiO\\/Al2O3 catalyst

Qing Miao; Guoxing Xiong; Shishan Sheng; Wei Cui; Ling Xu; Xiexian Guo

1997-01-01

234

Ultrathin amorphous zinc-tin-oxide buffer layer for enhancing heterojunction interface quality in metal-oxide solar cells  

E-print Network

We demonstrate a tunable electron-blocking layer to enhance the performance of an Earth-abundant metal-oxide solar-cell material. A 5 nm thick amorphous ternary metal-oxide buffer layer reduces interface recombination, ...

Heo, Jaeyeong

235

Oxidation of magnesium in the systems NaClO 4 -Mg-Metal oxide (peroxide)  

Microsoft Academic Search

Oxidation of magnesium in mixtures NaClO4 + Mg + metal oxide or peroxide has been investigated using differential thermal analysis (DTA). In the systems with peroxides\\u000a Na2O2, Li2O2, BaO2, CaO2 or ZnO, magnesium oxidizes simultaneously with decomposition of NaClO4 in the region 380–520C, which is 100–200C below the oxidation temperature of magnesium in air. In the ternary systems with\\u000a transition-metal

V. D. Sasnovskaya; A. P. Razumova

2006-01-01

236

Ethanol oxidation on metal oxide-supported platinum catalysts  

SciTech Connect

Ethanol is a renewable fuel that can be used as an additive to gasoline (or its substitute) with the advantage of octane enhancement and reduced carbon monoxide exhaust emissions. However, on Ethanol is a renewable fuel that can be used as an additive to gasoline (or its substitute) with the advantage of octane enhancement and reduced carbon monoxide exhaust emissions. However, on the standard three-way catalysts, the conversion of unburned ethanol is low because both ethanol and some of its partially oxidized derivatives are highly resistant to oxidation. A combination of first-principles density-functional theory (DFT) based calculations and in-situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis was applied to uncover some of the fundamental phenomena associated with ethanol oxidation on Pt containing catalysts. In particular, the objective was to analyze the role of the oxide (i.e., ?-Al2O3 or SiO2) substrate on the ethanol oxidation activity. The results showed that Pt nanoparticles trap and accumulate oxygen at their surface and perimeter sites and play the role of “stoves” that burn ethanol molecules and their partially oxidized derivatives to the “final” products. The ?-Al2O3 surfaces provided higher mobility of the fragments of ethanol molecules than the SiO2 surface and hence increased the supply rate of these objects to the Pt particles. This will in turn produce a higher conversion rate of unburned ethanol.and some of its partially oxidized derivatives are highly resistant to oxidation. A combination of first-principles density-functional theory (DFT) based calculations and in-situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis was applied to uncover some of the fundamental phenomena associated with ethanol oxidation on Pt containing catalysts. In particular, the objective was to analyze the role of the oxide (i.e., ?-Al2O3 or SiO2) substrate on the ethanol oxidation activity. The results showed that Pt nanoparticles trap and accumulate oxygen at their surface and perimeter sites and play the role of “stoves” that burn ethanol molecules and their partially oxidized derivatives to the “final” products. The ?-Al2O3 surfaces provided higher mobility of the fragments of ethanol molecules than the SiO2 surface and hence increased the supply rate of these objects to the Pt particles. This will in turn produce a higher conversion rate of unburned ethanol.

L. M. Petkovic 090468; Sergey N. Rashkeev; D. M. Ginosar

2009-09-01

237

Electron spectroscopic studies of perfect and defect metal oxide surfaces  

NASA Astrophysics Data System (ADS)

A number of surface sensitive electron spectroscopic techniques have been used during the last few years to study the geometric and electronic structure of well characterized surfaces of metal oxide single crystals. For rocksalt monoxides, the (100) surface has been found to be very nearly a truncation of the bulk lattice; only qualitative low energy electron diffraction (LEED) measurements have been performed on other oxide crystal structures. The electronic structure of nearly perfect oxide surfaces is generally very similar to that of the bulk, although excitonic surface states have been found on some rocksalt oxides. However, the presence of O-vacancy point defects on transition metal oxide surfaces changes their electronic structure drastically, increasing the d-orbital population of the cations adjacent to the defect. These surface defects are generally the active sites for chemisorption, with nearly perfect surfaces being relatively inert with respect to most of the molecules that have been studied.

Henrich, Victor E.

1987-09-01

238

REDUCTION OF NITRIC OXIDE WITH METAL SULFIDES  

EPA Science Inventory

The report gives results of research to determine the technical feasibility of using metal sulfide for the chemical reduction of NOx to N2. Nineteen different metal sulfides were investigated, using a test gas of pure NO. Although most sulfides resulted in some NO reduction, BaS,...

239

Methods of making metal oxide nanostructures and methods of controlling morphology of same  

DOEpatents

The present invention includes a method of producing a crystalline metal oxide nanostructure. The method comprises providing a metal salt solution and providing a basic solution; placing a porous membrane between the metal salt solution and the basic solution, wherein metal cations of the metal salt solution and hydroxide ions of the basic solution react, thereby producing a crystalline metal oxide nanostructure.

Wong, Stanislaus S; Hongjun, Zhou

2012-11-27

240

CO-oxidation catalysts: Low-temperature CO oxidation over Noble-Metal Reducible Oxide (NMRO) catalysts  

NASA Technical Reports Server (NTRS)

Oxidation of CO to CO2 is an important reaction technologically and environmentally and a complex and interesting reaction scientifically. In most cases, the reaction is carried out in order to remove CO as an environmental hazard. A major application of heterogeneous catalysts is catalytic oxidation of CO in the exhaust of combustion devices. The reaction over catalysts in exhaust gas is fast and often mass-transfer-limited since exhaust gases are hot and O2/CO ratios are high. The main challenges to catalyst designers are to control thermal sintering and chemical poisoning of the active materials. The effect of the noble metal on the oxide is discussed, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form unique catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

Herz, Richard K.

1990-01-01

241

High-Resolution Spectroscopy of Extremely Metal-Poor Stars from SDSS/SEGUE. II. Binary Fraction  

NASA Astrophysics Data System (ADS)

The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] \\lt -3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-mass stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey and observed at high spectral resolution in a previous study by Aoki et al. That survey reported 3 double-lined spectroscopic binaries and 11 CEMP stars, which we consider along with a sample of EMP stars from the literature compiled in the SAGA database. We have conducted measurements of the velocity components for stacked absorption features of different spectral lines for each double-lined spectroscopic binary. Our estimate indicates that the fraction of binary stars having orbital periods shorter than 1000 days is at least 10%, and possibly as high as 20% if the majority of CEMP stars are formed in such short-period binaries. This result suggests that the period distribution of EMP binary systems is biased toward short periods, unless the binary fraction of low-mass EMP stars is significantly higher than that of other nearby stars.

Aoki, Wako; Suda, Takuma; Beers, Timothy C.; Honda, Satoshi

2015-02-01

242

Reductive mobilization of oxide-bound metals  

SciTech Connect

This project is concerned with the mobilization of MnO{sub 2}- and FeOOH-bound toxic metals in subsurface environments arising from an influx of natural organic matter or organic-containing wastes. Our work to date emphasizes the importance of characterizing the reductant, complexant, and adsorptive characteristics of constituent organic chemicals. Organic chemicals may interact with pollutant metals directly, or may bring about changes in speciation and solubility indirectly by acting upon MnO{sub 2} and FeOOH host phases. The primary application of this work is the understanding of metal sorption and release processes within subsurface environments undergoing changes in redox status.

Stone, A.T.

1992-01-01

243

Photocatalytic activity of nanostructured ZnO-ZrO2 binary oxide using fluorometric method.  

PubMed

Evaluation of the photocatalytic activity of ZnO-ZrO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, ZnO-ZrO2 mixed oxides coupled with various ZnO dosages (0, 10, 30, 50, 70wt%) were prepared by impregnation method. These nanomaterials were characterized by studying their structural, surface and optical properties. The photocatalytic activity in term of quantitative determination of the active oxidative species (OH) produced on the surface of binary oxide was evaluated using fluorescent probe method. The interaction between ZnO and ZrO2 was affected on the photocatalytic efficiency of mixture. The results show that, the addition of ZnO to ZrO2 decreased the electron-hole recombination and increased the rate of OH radicals formation. 50wt% ZnO-ZrO2 photocatalyst exhibited much higher photocatalytic activity. The profound effect of binary oxide catalyst was generally considered due to the high surface area, small particle size, high monoclinic phase of ZrO2 content, low band gap and the presence of surface OH groups. PMID:25797223

Ibrahim, M M

2015-06-15

244

CATALYTIC OXIDATION OF DIMETHYL SULFIDE WITH OZONE: EFFECT OF PROMOTER AND PHYSICO-CHEMICAL PROPERTIES OF METAL OXIDE CATALYSTS  

EPA Science Inventory

This study reports improved catalytic activities and stabilities for the oxidation of dimethyl sulfide (DMS), a major pollutant of pulp and paper mills. Ozone was used as an oxidant and Cu, Mo, V, Cr and Mn metal oxides, and mixed metal oxides support on y-alumina as catalysts ov...

245

Nanoporous metal oxides with tunable and nanocrystalline frameworks via conversion of metal-organic frameworks.  

PubMed

Nanoporous metal oxide materials are ubiquitous in the material sciences because of their numerous potential applications in various areas, including adsorption, catalysis, energy conversion and storage, optoelectronics, and drug delivery. While synthetic strategies for the preparation of siliceous nanoporous materials are well-established, nonsiliceous metal oxide-based nanoporous materials still present challenges. Herein, we report a novel synthetic strategy that exploits a metal-organic framework (MOF)-driven, self-templated route toward nanoporous metal oxides via thermolysis under inert atmosphere. In this approach, an aliphatic ligand-based MOF is thermally converted to nanoporous metal oxides with highly nanocrystalline frameworks, in which aliphatic ligands act as the self-templates that are afterward evaporated to generate nanopores. We demonstrate this concept with hierarchically nanoporous magnesia (MgO) and ceria (CeO2), which have potential applicability for adsorption, catalysis, and energy storage. The pore size of these nanoporous metal oxides can be readily tuned by simple control of experimental parameters. Significantly, nanoporous MgO exhibits exceptional CO2 adsorption capacity (9.2 wt %) under conditions mimicking flue gas. This MOF-driven strategy can be expanded to other nanoporous monometallic and multimetallic oxides with a multitude of potential applications. PMID:23651169

Kim, Tae Kyung; Lee, Kyung Joo; Cheon, Jae Yeong; Lee, Jae Hwa; Joo, Sang Hoon; Moon, Hoi Ri

2013-06-19

246

Realizing a family of transition-metal-oxide memristors based on volatile resistive switching at a rectifying metal/oxide interface  

NASA Astrophysics Data System (ADS)

There is strong interest in creating new memristors due to their significant impact in many fields including digital information systems, analogue circuits and artificial neural networks as a new class of fundamental electronic elements. Here we report a volatile resistive switching effect at a prototypical Schottky metal/oxide interface and realize a family of transition-metal-oxide memristors showing distinct hysteresis characteristics based on the interface. The results not only provide further understanding on the electrical behaviour of metal/oxide interfaces but also indicate the key role of metal/oxide interfaces as basic building blocks in transition-metal-oxide memristors.

Yang, M.; Qin, N.; Ren, L. Z.; Wang, Y. J.; Yang, K. G.; Yu, F. M.; Zhou, W. Q.; Meng, M.; Wu, S. X.; Bao, D. H.; Li, S. W.

2014-01-01

247

Anaerobic Nitrate-Dependent Metal Bio-Oxidation  

NASA Astrophysics Data System (ADS)

Direct biological oxidation of reduced metals (Fe(II) and U(IV)) coupled to nitrate reduction at circumneutral pH under anaerobic conditions has been recognized in several environments as well as pure culture. Several phylogentically diverse mesophilic bacteria have been described as capable of anaerobic, nitrate-dependent Fe(II) oxidation (NFOx). Our recent identification of a freshwater mesophilic, lithoautotroph, Ferrutens nitratireducens strain 2002, capable of growth through NFOx presents an opportunity to further study metal bio- oxidation. Continuing physiological studies revealed that in addition to Fe(II) oxidation, strain 2002 is capable of oxidizing U(IV) (4 ?M) in washed cell suspensions with nitrate serving as the electron acceptor. Pasteurized cultures exhibited abiotic oxidation of 2 ?M U(IV). Under growth conditions, strain 2002 catalyzed the oxidation of 12 ?M U(IV) within a two week period. Cultures amended with sodium azide, an electron transport inhibitor, demonstrated limited oxidation (7 ?M) similar to pasteurized cultures, supporting the direct role of electron transport in U(IV) bio-oxidation. The oxidation of U(IV) coupled denitrification at circumneutral pH would yield enough energy to support anaerobic microbial growth (?G°'= -460.36 kJ/mole). It is currently unknown whether or not strain 2002 can couple this metabolism to growth. The growth of F. nitratireducens strain 2002 utilizing Fe(II) as the sole electron donor was previously demonstrated. The amount of U(IV) (~12 ?M) that strain 2002 oxidized under similar autotrophic growth conditions yields 0.0019 kJ, enough energy for the generation of ATP (5.3 x 10-20 kJ ATP-1), but not enough energy for cell replication as calculated for nitrate-dependent Fe(II) oxidizing conditions (0.096 kJ) assuming a similar metabolism. In addition to F. nitratireducens strain 2002, a nitrate-dependent Fe(II) oxidizing bacterium isolated from U contaminated groundwater, Diaphorobacter sp. strain TPSY, was also capable of nitrate- dependent U(IV) oxidation (8 ?M over 24 hours, pseudo first order rate constant of 0.12 ± 0.02 hr-1) in washed cell suspensions. Further biochemical investigation of nitrate-dependent U(IV) oxidation in strain TPSY revealed the expression of several putative high molecular weight proteins specific to this metabolism. Together with the previously described metabolic ability of Geobacter metallireducens (Finneran et al. 2002) and Thiobacillus denitrificans (Beller 2005), these data indicate that anaerobic, metal oxidation may be a ubiquitous microbial metabolism.

Weber, K.; Knox, T.; Achenbach, L. A.; Coates, J. D.

2007-12-01

248

The mechanism of electroforming of metal oxide memristive switches.  

PubMed

Metal and semiconductor oxides are ubiquitous electronic materials. Normally insulating, oxides can change behavior under high electric fields--through 'electroforming' or 'breakdown'--critically affecting CMOS (complementary metal-oxide-semiconductor) logic, DRAM (dynamic random access memory) and flash memory, and tunnel barrier oxides. An initial irreversible electroforming process has been invariably required for obtaining metal oxide resistance switches, which may open urgently needed new avenues for advanced computer memory and logic circuits including ultra-dense non-volatile random access memory (NVRAM) and adaptive neuromorphic logic circuits. This electrical switching arises from the coupled motion of electrons and ions within the oxide material, as one of the first recognized examples of a memristor (memory-resistor) device, the fourth fundamental passive circuit element originally predicted in 1971 by Chua. A lack of device repeatability has limited technological implementation of oxide switches, however. Here we explain the nature of the oxide electroforming as an electro-reduction and vacancy creation process caused by high electric fields and enhanced by electrical Joule heating with direct experimental evidence. Oxygen vacancies are created and drift towards the cathode, forming localized conducting channels in the oxide. Simultaneously, O(2-) ions drift towards the anode where they evolve O(2) gas, causing physical deformation of the junction. The problematic gas eruption and physical deformation are mitigated by shrinking to the nanoscale and controlling the electroforming voltage polarity. Better yet, electroforming problems can be largely eliminated by engineering the device structure to remove 'bulk' oxide effects in favor of interface-controlled electronic switching. PMID:19423925

Joshua Yang, J; Miao, Feng; Pickett, Matthew D; Ohlberg, Douglas A A; Stewart, Duncan R; Lau, Chun Ning; Williams, R Stanley

2009-05-27

249

Plasma electrolytic oxide coatings on valve metals and their activity in CO oxidation  

NASA Astrophysics Data System (ADS)

Two approaches have been examined for obtaining titanium- or aluminum-supported catalysts with transition and noble metals using the plasma electrolytic oxidation (PEO) technique. Elemental compositions, distribution of active elements and catalytic activity in CO oxidation have been compared for composites formed by one-stage PEO technique and those obtained as a result of modification of PEO coatings by impregnation.

Lukiyanchuk, I. V.; Rudnev, V. S.; Tyrina, L. M.; Chernykh, I. V.

2014-10-01

250

Metal nanoparticle catalysts decorated with metal oxide clusters.  

PubMed

Au nanoparticles decorated with mononuclear Ti-oxo units dispersed in silica clusters were formed by activating Au nanoparticles (~2 nm) stabilized with Ti- and amine-functionalized siloxane oligomers. These Au nanoparticles were active catalysts for selective oxidation of propane to acetone, and the activity increased with increasing Ti density. PMID:22945251

Mashayekhi, Neema A; Wu, Yi Y; Kung, Mayfair C; Kung, Harold H

2012-10-18

251

Low frequency noise in GaN metal semiconductor and metal oxide semiconductor field effect transistors  

E-print Network

by the growth of a Si-doped GaN channel. The thickness and doping level of the channel extracted fromLow frequency noise in GaN metal semiconductor and metal oxide semiconductor field effect for publication 27 March 2001 The low frequency noise in GaN field effect transistors has been studied as function

Pala, Nezih

252

Utilization of Metal Oxides and Chalcogenides Stabilized in Organic Solvents  

NASA Astrophysics Data System (ADS)

Metal oxides and metal chalcogenides are important materials for a variety of applications including photocatalysis for decomposition of water, conductive and optical coatings, catalysts, photovoltaics, pryoelectrics, self-cleaning surfaces, pigments, and high efficiency Li-insertion materials in batteries among many other applications. Fundamental discoveries of surprising solubility of insoluble materials such as single and multi-walled carbon nanotubes and graphene has lead us to discover that certain metal oxides and metal chalcogenides such as TiO2 are soluble in certain solvents. Due to the industrial importance of TiO2, discovering stable pure solvent systems demonstrates a possibility to avoid surface modification of TiO2 nanoparticles by use materials such as of (3-methacryloxypropyl)-trimethoxysilane and various other methods of artificial stabilization. We have created thin films of TiO2, transparent ultraviolet (UV) --absorptive polymers, and Li-ion battery anodes with graphene-TiO2 hybrid materials.

Lampert, Lester; Flaig, Robby; Camacho, Jorge; Hamilton, James

2011-03-01

253

Universal medium-range order of amorphous metal oxides.  

PubMed

We propose that the structure of amorphous metal oxides can be regarded as a dual-dense-random-packing structure, which is a superposition of the dense random packing of metal atoms and that of oxygen atoms. Our ab initio molecular dynamics simulations show that the medium-range order of amorphous HfO2, ZrO2, TiO2, In2O3, Ga2O3, Al2O3, and Cu2O is characterized by the pentagonal-bipyramid arrangement of metal atoms and that of oxygen atoms, and prove the validity of our dual-random-sphere-packing model. In other words, we find that the pentagonal medium-range order is universal independent of type of metal oxide. PMID:24160612

Nishio, Kengo; Miyazaki, Takehide; Nakamura, Hisao

2013-10-11

254

Universal Medium-Range Order of Amorphous Metal Oxides  

NASA Astrophysics Data System (ADS)

We propose that the structure of amorphous metal oxides can be regarded as a dual-dense-random-packing structure, which is a superposition of the dense random packing of metal atoms and that of oxygen atoms. Our ab initio molecular dynamics simulations show that the medium-range order of amorphous HfO2, ZrO2, TiO2, In2O3, Ga2O3, Al2O3,, and Cu2O is characterized by the pentagonal-bipyramid arrangement of metal atoms and that of oxygen atoms, and prove the validity of our dual-random-sphere-packing model. In other words, we find that the pentagonal medium-range order is universal independent of type of metal oxide.

Nishio, Kengo; Miyazaki, Takehide; Nakamura, Hisao

2013-10-01

255

Progress in base-metal water oxidation catalysis.  

PubMed

This minireview provides a brief overview of the progress that has been made in developing homogeneous water oxidation catalysts based on base metals (manganese, iron, cobalt, nickel, and copper) from the 1990s to mid-2014. The impact of each contribution is analyzed, and opportunities for further improvement are noted. In addition, the relative stabilities of the base-metal catalysts that have been reported are compared to illustrate the importance of developing more robust catalytic systems by using these metals. This manuscript is intended to provide a firm foundation for researchers entering the field of water oxidation based on base metals and a useful reference for those currently involved in the field. PMID:25066264

Parent, Alexander Rene; Sakai, Ken

2014-08-01

256

Heavy metal biosorption in binary systems: simulation in single- and two-stage UF\\/MF membrane reactors  

Microsoft Academic Search

In this paper, the continuous biosorption of binary metal systems onto Sphaerotilus natans cells confined in a membrane reactor was studied. The simulation of the dynamic response of the system to step perturbations was performed developing a model based on the metal mass balances and the Langmuir competitive isotherm. Simulation profiles predict the effect of the different affinity of the

F. Vegliò; A. Di Biase; F. Beolchini; F. Pagnanelli

2002-01-01

257

Exposure characterization of metal oxide nanoparticles in the workplace.  

PubMed

This study presents exposure data for various metal oxides in facilities that produce or use nanoscale metal oxides. Exposure assessment surveys were conducted at seven facilities encompassing small, medium, and large manufacturers and end users of nanoscale (particles <0.1 ?m diameter) metal oxides, including the oxides of titanium, magnesium, yttrium, aluminum, calcium, and iron. Half- and full-shift sampling consisting of various direct-reading and mass-based area and personal aerosol sampling was employed to measure exposure for various tasks. Workers in large facilities performing handling tasks had the highest mass concentrations for all analytes. However, higher mass concentrations occurred in medium facilities and during production for all analytes in area samples. Medium-sized facilities had higher particle number concentrations in the air, followed by small facilities for all particle sizes measured. Production processes generally had the highest particle number concentrations, particularly for the smaller particles. Similar to particle number, the medium-sized facilities and production process had the highest particle surface area concentration. TEM analysis confirmed the presence of the specific metal oxides particles of interest, and the majority of the particles were agglomerated, with the predominant particle size being between 0.1 and 1 ?m. The greatest potential for exposure to workers occurred during the handling process. However, the exposure is occurring at levels that are well below established and proposed limits. PMID:21936697

Curwin, Brian; Bertke, Steve

2011-10-01

258

Large Lateral Photovoltaic Effect in Metal-(Oxide-) Semiconductor Structures  

PubMed Central

The lateral photovoltaic effect (LPE) can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures. PMID:22163463

Yu, Chongqi; Wang, Hui

2010-01-01

259

Carbon monoxide oxidation over three different states of copper: Development of a model metal oxide catalyst  

SciTech Connect

Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu{sub 2}O), and copper (II) oxide (CuO) as a test case for developing a model metal oxide catalyst amenable to study by the methods of modern surface science and catalysis. Copper was deposited and oxidized on oxidized supports of aluminum, silicon, molybdenum, tantalum, stainless steel, and iron as well as on graphite. The catalytic activity was found to decrease with increasing oxidation state (Cu > Cu{sub 2}O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/mol < Cu{sub 2}O, 14 kcal/mol < CuO, 17 kcal/mol). Reaction mechanisms were determined for the different oxidation states. Lastly, NO reduction by CO was studied. A Cu and CuO catalyst were exposed to an equal mixture of CO and NO at 300--350 C to observe the production of N{sub 2} and CO{sub 2}. At the end of each reaction, the catalyst was found to be Cu{sub 2}O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.

Jernigan, G G [California Univ., Berkeley, CA (United States). Dept. of Chemistry

1994-10-01

260

Isopropanol oxidation by pure metal oxide catalysts: number of active surface sites and turnover frequencies  

Microsoft Academic Search

The objective of the present study was to determine the number of active surface sites and their nature, redox or acidic, for bulk metal oxide catalysts using isopropanol as a chemical probe molecule. Isopropanol oxidation activity on the following metal oxides was investigated: MgO, CaO, SrO, BaO, Y2O3, La2O3, CeO2, TiO2, ZrO2, HfO2, V2O5, Nb2O5, Ta2O5, Cr2O3, MoO3, WO3, Mn2O3,

Deepak Kulkarni; Israel E. Wachs

2002-01-01

261

Metal current collect protected by oxide film  

DOEpatents

Provided are low-cost, mechanically strong, highly electronically conductive current collects and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical devices having as current interconnects a ferritic steel felt or screen coated with a protective oxide film.

Jacobson, Craig P. (Lafayette, CA); Visco, Steven J. (Berkeley, CA); DeJonghe, Lutgard C. (Lafayette, CA)

2004-05-25

262

Amorphous semiconducting and conducting transparent metal oxide thin films and production thereof  

SciTech Connect

Metal oxide thin films and production thereof are disclosed. An exemplary method of producing a metal oxide thin film may comprise introducing at least two metallic elements and oxygen into a process chamber to form a metal oxide. The method may also comprise depositing the metal oxide on a substrate in the process chamber. The method may also comprise simultaneously controlling a ratio of the at least two metallic elements and a stoichiometry of the oxygen during deposition. Exemplary amorphous metal oxide thin films produced according to the methods herein may exhibit highly transparent properties, highly conductive properties, and/or other opto-electronic properties.

Perkins, John (Boulder, CO); Van Hest, Marinus Franciscus Antonius Maria (Lakewood, CO); Ginley, David (Evergreen, CO); Taylor, Matthew (Golden, CO); Neuman, George A. (Holland, MI); Luten, Henry A. (Holland, MI); Forgette, Jeffrey A. (Hudsonville, MI); Anderson, John S. (Holland, MI)

2010-07-13

263

Laboratory SIP signatures associated with oxidation of disseminated metal sulfides  

NASA Astrophysics Data System (ADS)

Oxidation of metal sulfide minerals is responsible for the generation of acidic waters rich in sulfate and metals. When associated with the oxidation of sulfide ore mine waste deposits the resulting pore water is called acid mine drainage (AMD); AMD is a known environmental problem that affects surface and ground waters. Characterization of oxidation processes in-situ is challenging, particularly at the field scale. Geophysical techniques, spectral induced polarization (SIP) in particular, may provide a means of such investigation. We performed laboratory experiments to assess the sensitivity of the SIP method to the oxidation mechanisms of common sulfide minerals found in mine waste deposits, i.e., pyrite and pyrrhotite, when the primary oxidant agent is dissolved oxygen. We found that SIP parameters, e.g., phase shift, the imaginary component of electrical conductivity and total chargeability, decrease as the time of exposure to oxidation and oxidation degree increase. This observation suggests that dissolution-depletion of the mineral surface reduces the capacitive properties and polarizability of the sulfide minerals. However, small increases in the phase shift and imaginary conductivity do occur during oxidation. These transient increases appear to correlate with increases of soluble oxidizing products, e.g., Fe2 + and Fe3 + in solution; precipitation of secondary minerals and the formation of a passivating layer to oxidation coating the mineral surface may also contribute to these increases. In contrast, the real component of electrical conductivity associated with electrolytic, electronic and interfacial conductance is sensitive to changes in the pore fluid chemistry as a result of the soluble oxidation products released (Fe2 + and Fe3 +), particularly for the case of pyrrhotite minerals.

Placencia-Gómez, Edmundo; Slater, Lee; Ntarlagiannis, Dimitrios; Binley, Andrew

2013-05-01

264

The Close Binary Frequency of Wolf-Rayet Stars as a Function of Metallicity in M31 and M33  

NASA Astrophysics Data System (ADS)

Massive star evolutionary models generally predict the correct ratio of WC-type and WN-type Wolf-Rayet stars at low metallicities, but underestimate the ratio at higher (solar and above) metallicities. One possible explanation for this failure is perhaps single-star models are not sufficient and Roche-lobe overflow in close binaries is necessary to produce the "extra" WC stars at higher metallicities. However, this would require the frequency of close massive binaries to be metallicity dependent. Here we test this hypothesis by searching for close Wolf-Rayet binaries in the high metallicity environments of M31 and the center of M33 as well as in the lower metallicity environments of the middle and outer regions of M33. After identifying ~100 Wolf-Rayet binaries based on radial velocity variations, we conclude that the close binary frequency of Wolf-Rayets is not metallicity dependent and thus other factors must be responsible for the overabundance of WC stars at high metallicities. However, our initial identifications and observations of these close binaries have already been put to good use as we are currently observing additional epochs for eventual orbit and mass determinations. The spectroscopic observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. MMT telescope time was granted by NOAO, through the Telescope System Instrumentation Program (TSIP). TSIP is funded by the National Science Foundation. This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory.

Neugent, Kathryn F.; Massey, Philip

2014-07-01

265

Thermochemistry of rare-earth-metal-alkaline-earth-metal-copper oxide superconductors  

Microsoft Academic Search

Enthalpies of formation of the perovskite-related oxides LaâCuOâ, La\\/sub 1.85\\/Sr\\/sub 0.15\\/CuOâ, and YBaâCuâO\\/sub y\\/(y = 6.25, 6.47, 6.69, and 6.93) have been determined at 298.15 K by solution calorimetry. Room-temperature stabilities of these compounds have been assessed in terms of the parent binary oxides and of the oxygen content. High-temperature (to 900\\/degree\\/C) thermal behavior of YBaâCuâO\\/sub y\\/ has been used

Lester R. Morss; David C. Sonnenberger; R. J. Thorn

1988-01-01

266

Lithium metal oxide electrodes for lithium cells and batteries  

DOEpatents

A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2M'O.sub.3 in which 0oxidation state and with at least one ion being Ni, and where M' is one or more ions with an average tetravalent oxidation state. Complete cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

Thackeray, Michael M.; Johnson, Christopher S.; Amine, Khalil; Kim, Jaekook

2006-11-14

267

A Green Strategy to Prepare Metal Oxide Superstructure from Metal-Organic Frameworks  

PubMed Central

Metal or metal oxides with diverse superstructures have become one of the most promising functional materials in sensor, catalysis, energy conversion, etc. In this work, a novel metal-organic frameworks (MOFs)-directed method to prepare metal or metal oxide superstructure was proposed. In this strategy, nodes (metal ions) in MOFs as precursors to form ordered building blocks which are spatially separated by organic linkers were transformed into metal oxide micro/nanostructure by a green method. Two kinds of Cu-MOFs which could reciprocally transform by changing solvent were prepared as a model to test the method. Two kinds of novel CuO with three-dimensional (3D) urchin-like and 3D rods-like superstructures composed of nanoparticles, nanowires and nanosheets were both obtained by immersing the corresponding Cu-MOFs into a NaOH solution. Based on the as-formed CuO superstructures, a novel and sensitive nonenzymatic glucose sensor was developed. The small size, hierarchical superstructures and large surface area of the resulted CuO superstructures eventually contribute to good electrocatalytic activity of the prepared sensor towards the oxidation of glucose. The proposed method of hierarchical superstructures preparation is simple, efficient, cheap and easy to mass production, which is obviously superior to pyrolysis. It might open up a new way for hierarchical superstructures preparation. PMID:25669731

Song, Yonghai; Li, Xia; Wei, Changting; Fu, Jinying; Xu, Fugang; Tan, Hongliang; Tang, Juan; Wang, Li

2015-01-01

268

A novel microstructured metal-supported solid oxide fuel cell  

NASA Astrophysics Data System (ADS)

An innovative design, alternative to the conventional metal supported fuel cells (MSC) is proposed. This new design of Solid Oxide Fuel Cell (SOFC), comprises a 200 ?m layer of a honeycomb-metallic framework with hexagonal cells which supports a 250 ?m layer of electrolyte. Each hexagonal cell is further functionalized with a thin 5-10 ?m of Ni-YSZ anode. This new design allows a reduction of ?65% of the metallic supporting material, rendering performances over 300 mW cm-2 under pure hydrogen at 850 °C, with an OCV of ?1.1 V.

Fernández-González, R.; Hernández, E.; Savvin, S.; Núñez, P.; Makradi, A.; Sabaté, N.; Esquivel, J. P.; Ruiz-Morales, J. C.

2014-12-01

269

All-alkoxide synthesis of strontium-containing metal oxides  

DOEpatents

A method for making strontium-containing metal-oxide ceramic thin films from a precursor liquid by mixing a strontium neo-pentoxide dissolved in an amine solvent and at least one metal alkoxide dissolved in a solvent, said at least one metal alkoxide selected from the group consisting of alkoxides of calcium, barium, bismuth, cadmium, lead, titanium, tantalum, hafnium, tungsten, niobium, zirconium, yttrium, lanthanum, antimony, chromium and thallium, depositing a thin film of the precursor liquid on a substrate, and heating the thin film in the presence of oxygen at between 550 and 700.degree. C.

Boyle, Timothy J. (Albuquerque, NM)

2001-01-01

270

Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. I. Detailed analysis of 15 binary stars with known orbital periods  

NASA Astrophysics Data System (ADS)

AGB stars are responsible for producing a variety of elements, including carbon, nitrogen, and the heavy elements produced in the slow neutron-capture process (s-elements). There are many uncertainties involved in modelling the evolution and nucleosynthesis of AGB stars, and this is especially the case at low metallicity, where most of the stars with high enough masses to enter the AGB have evolved to become white dwarfs and can no longer be observed. The stellar population in the Galactic halo is of low mass (?0.85 M?) and only a few observed stars have evolved beyond the first giant branch. However, we have evidence that low-metallicity AGB stars in binary systems have interacted with their low-mass secondary companions in the past. The aim of this work is to investigate AGB nucleosynthesis at low metallicity by studying the surface abundances of chemically peculiar very metal-poor stars of the halo observed in binary systems. To this end we select a sample of 15 carbon- and s-element-enhanced metal-poor (CEMP-s) halo stars that are found in binary systems with measured orbital periods. With our model of binary evolution and AGB nucleosynthesis, we determine the binary configuration that best reproduces, at the same time, the observed orbital period and surface abundances of each star of the sample. The observed periods provide tight constraints on our model of wind mass transfer in binary stars, while the comparison with the observed abundances tests our model of AGB nucleosynthesis. For most of the stars in our sample, we find that an episode of efficient wind mass transfer, combined with strong angular momentum loss, has occurred in the past. In some cases we find discrepancies between the observed and modelled abundances even if we adopt a fine-tuned set of parameters in our binary evolution model. These discrepancies are probably caused by missing physical ingredients in our models of AGB nucleosynthesis and they provide indications of how to improve our knowledge of the process of nucleosynthesis in AGB stars. Appendices are available in electronic form at http://www.aanda.org

Abate, C.; Pols, O. R.; Karakas, A. I.; Izzard, R. G.

2015-04-01

271

Metal-accelerated oxidation in plant cell death  

SciTech Connect

Cadmium and mercury toxicity is further enhanced by external oxidizing conditions O[sub 3] or inherent plant processes. Lepidium sativum L, Lycopersicon esculentum Mill., or Phaseolus vulgaris L, were grown inpeat-lite to maturity under continuous cadmium exposure followed by one oxidant (O[sub 3]-6 hr. 30 pphm) exposure, with or without foliar calcium pretreatments. In comparison, Daucus carota, L and other species grown in a 71-V suspension, with or without 2,4-D were exposed continuously to low levels of methylmercury during exponential growth and analyzed in aggregates of distinct populations. Proteins were extracted and analyzed. Mechanisms of toxicity and eventual cell death are Ca-mediated and involve chloroplast, stomatal-water relations and changes in oxidant-anti-oxidant components in cells. Whether the metal-accelerated oxidative damage proceeds to cell death, depends on the species and its differential biotransformation system and cell association component.

Czuba, M. (National Research Council, Ottawa, Ontario (Canada))

1993-05-01

272

Metal Permeation into Multi-layered Graphene Oxide  

PubMed Central

Understanding the chemical and physical properties of metal/graphene oxide (M/GO) interfaces is important when GO is used in electronic and electrochemical devices because the metal layer must be firmly attached to GO. Here, permeation of metal from the surface into GO paper bulk at the M/GO interface was observed at room temperature for metals such as Cu, Ag, Ni, Au, and Pt. Cu, Ag, and Ni quickly permeated GO as ions into the bulk under humid conditions. At first, these metals changed to hydrated ions as a result of redox reactions (with reduction of GO) at the surface, and then permeated the interlayers. Au and Pt were observed to permeate GO as atoms into the GO bulk at room temperature, although the permeation rates were low. These surprising results are considered to be due to the presence of many defects and/or edges with oxygenated groups in the GO paper. PMID:24413270

Ogata, Chikako; Koinuma, Michio; Hatakeyama, Kazuto; Tateishi, Hikaru; Asrori, Mohamad Zainul; Taniguchi, Takaaki; Funatsu, Asami; Matsumoto, Yasumichi

2014-01-01

273

Metal Permeation into Multi-layered Graphene Oxide  

NASA Astrophysics Data System (ADS)

Understanding the chemical and physical properties of metal/graphene oxide (M/GO) interfaces is important when GO is used in electronic and electrochemical devices because the metal layer must be firmly attached to GO. Here, permeation of metal from the surface into GO paper bulk at the M/GO interface was observed at room temperature for metals such as Cu, Ag, Ni, Au, and Pt. Cu, Ag, and Ni quickly permeated GO as ions into the bulk under humid conditions. At first, these metals changed to hydrated ions as a result of redox reactions (with reduction of GO) at the surface, and then permeated the interlayers. Au and Pt were observed to permeate GO as atoms into the GO bulk at room temperature, although the permeation rates were low. These surprising results are considered to be due to the presence of many defects and/or edges with oxygenated groups in the GO paper.

Ogata, Chikako; Koinuma, Michio; Hatakeyama, Kazuto; Tateishi, Hikaru; Asrori, Mohamad Zainul; Taniguchi, Takaaki; Funatsu, Asami; Matsumoto, Yasumichi

2014-01-01

274

High-temperature Complementary Metal Oxide Semiconductors (CMOS)  

NASA Technical Reports Server (NTRS)

The results of an investigation into the possibility of using complementary metal oxide semiconductor (CMOS) technology for high temperature electronics are presented. A CMOS test chip was specifically developed as the test bed. This test chip incorporates CMOS transistors that have no gate protection diodes; these diodes are the major cause of leakage in commercial devices.

Mcbrayer, J. D.

1981-01-01

275

Oxidation resistant filler metals for direct brazing of structural ceramics  

DOEpatents

A method of joining ceramics and metals to themselves and to one another is described using essentially pure trinickel aluminide and trinickel aluminide containing small amounts of carbon. This method produces strong joints that can withstand high service temperatures and oxidizing environments.

Moorhead, Arthur J. (Knoxville, TN)

1986-01-01

276

Towards Carbon-free Metals Production by Molten Oxide Electrolysis  

E-print Network

Towards Carbon-free Metals Production by Molten Oxide Electrolysis Deepak Khetpal, Andrew Ducret by-products problems with electrolytic technologies: Al electrolysis makes CO2 (½ kg C / kg Al) Mg electrolysis makes Cl2 C & F react to make CF4 & C2F6 C & Cl in presence of O dioxins? furans? #12;Sadoway, MIT

Sadoway, Donald Robert

277

Facile self-assembly and stabilization of metal oxide nanoparticles.  

PubMed

This paper describes a facile method of self-assembling different metal oxide nanoparticles into nanostructured materials via di-carboxylate linkers (oxalic acid) using TiO2 as an example. In this method, the di-carboxylate linkers react with surface hydroxyls on metal oxide nanoparticles forming covalent, ester-like bonds, which enable the binding of two metal oxide particles, one at either end of the linker and facilitates efficient self-assembly of one group of metal oxide nanoparticles homogeneously distributed onto the surface of another group. The oxalate linkers can then be removed by thermal decomposition. This approach is shown to be effective using differently-sized TiO2 nanoparticles, namely in-house synthesized 3-5nm anatase nanocrystals and Degussa P25 titania particles (mean 21nm particle size). Our data show that the application of a high temperature heat treatment (450°C for 30min), conventionally applied to achieve a stable porous structure by thermal decomposition of the linker molecules and by inducing inter-particle necking, damages the surface area of the nanostructured material. However, here we show that sintering at 300°C for 30min or by flash near infrared radiation sintering for 12s efficiently decomposes the oxalate linkers and stabilizes the nanostructure of the material whilst maintaining its high surface area. PMID:25525978

Charbonneau, Cecile; Holliman, Peter J; Davies, Matthew L; Watson, Trystan M; Worsley, David A

2015-03-15

278

Metal complexes of substituted Gable porphyrins as oxidation catalysts  

DOEpatents

Transition metal complexes of Gable porphyrins are disclosed having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

Lyons, J.E.; Ellis, P.E. Jr.; Wagner, R.W.

1996-01-02

279

Metal complexes of substituted Gable porphyrins as oxidation catalysts  

DOEpatents

Transition metal complexes of Gable porphyrins having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

Lyons, James E. (Wallingford, PA); Ellis, Jr., Paul E. (Downingtown, PA); Wagner, Richard W. (Murrysville, PA)

1996-01-01

280

Molten-Metal Electrodes for Solid Oxide Fuel Cells  

SciTech Connect

Molten In, Pb, and Sb were examined as anodes in solid oxide fuel cells (SOFC) that operate between 973 and 1173 K. The results for these metals were compared with those reported previously for molten Sn electrodes. Cells were operated under “battery” conditions, with dry He or N2 flow in the anode compartment, to characterize the electrochemical oxidation of the metals at the yttria-stabilized zirconia (YSZ)-electrolyte interface. In most cases, the open-circuit voltages (OCVs) were close to that based on equilibrium between the metals and their oxides. With Sn and In, the cell impedances increased dramatically at all temperatures after drawing current due to formation of insulating, oxide barriers at the electrolyte interface. Similar results were observed for Pb at 973 and 1073 K, but the impedance remained low even after PbO formation at 1173 K because this is above the melting temperature of PbO. Similarly, the impedances of molten Sb electrodes at 973 K were low and unaffected by current flow because of the low melting temperature of Sb{sub 2}O{sub 3}. The potential of using molten-metal electrodes for direct-carbon fuel cells and for energy-storage systems is discussed.

Jayakumar, A.; Vohs, J. M.; Gorte, R. J.

2010-01-01

281

The Protonation Behavior of Metal Oxide Surfaces to Hydrothermal Conditions  

SciTech Connect

Metal oxide surface protonation under hydrothermal conditions is summarized. Important concepts and definitions are introduced first, followed by a brief overview of experimental methods and presentation of representative results. Finally, the modeling methods that are most useful in predicting surface protonation behavior between 0 and 300oC are presented and compared.

Machesky, Michael L. [Illinois State Water Survey, Champaign, IL; Wesolowski, David J [ORNL; Ridley, Mora K. [Texas Tech University, Lubbock; Palmer, Donald [ORNL; Rosenqvist, Jorgen K [ORNL; Lvov, Serguei N. [Pennsylvania State University; Predota, M. [University of South Bohemia, Czech Republic; Vlcek, L. [Vanderbilt University

2008-01-01

282

ELECTRICAL CHARACTERIZATION OF METAL - ZINC OXIDE - SILICON DIOXIDE - SILICON STRUCTURES  

Microsoft Academic Search

Two of the basic problems associated with monolithic Metal - Zinc Oxide - Silicon Dioxide - Silicon (MZOS) surface acoustic wave devices involve (1) drifting of device characteristics due to charge injection and trapping associated with the ZnO and (2) radiation damage in the Si-SiO(,2) subsystem. Both of these problems are addressed in this thesis.^ A quantitative comparison of radiation

RICHARD DANA CHERNE

1983-01-01

283

Disorder driven quantum phase transitions in transition metal oxides  

Microsoft Academic Search

We investigate the effect of disorder on a class of transition metal oxides described by a single orbital Hubbard model at half filling and away from half filling. The phases are characterized by the nature of the electronic and spin excitations. We calculate the local density of states, frequency and temperature-dependent conductivity and spin susceptibility as functions of disorder and

Kohjiro Kobayashi; Nandini Trivedi

2007-01-01

284

Faraday Discussion # 114 The Surface Science of Metal Oxides  

E-print Network

-1- Faraday Discussion # 114 The Surface Science of Metal Oxides Ultrathin Alumina Film Al ____________________________________________________________________________ First principles density-functional slab calculations have produced the following results: 1) For 5 Ã? (two O-layer) alumina films on Al(111) and Ru(0001), with larger unit cells than in recent work

Jennison, Dwight R.

285

Selection of Metal Oxide Charge Transport Layers for Colloidal Quantum  

E-print Network

02139 L ight emitting devices (LEDs) that uti- lize colloidal quantum dots (QDs) as luminescent centersSelection of Metal Oxide Charge Transport Layers for Colloidal Quantum Dot LEDs V. Wood,* M. J. To date, QD-LED demonstrations used semi- conducting polymers, molecular organics, and ceramics as charge

286

METALLICITY EFFECT ON LOW-MASS X-RAY BINARY FORMATION IN GLOBULAR CLUSTERS  

SciTech Connect

We present comprehensive observational results of the metallicity effect on the fraction of globular clusters (GCs) that contain low-mass X-ray binaries (LMXB), by utilizing all available data obtained with Chandra for LMXBs and Hubble Space Telescope Advanced Camera for Surveys (ACS) for GCs. Our primary sample consists of old elliptical galaxies selected from the ACS Virgo and Fornax surveys. To improve statistics at both the lowest and highest X-ray luminosity, we also use previously reported results from other galaxies. It is well known that the fraction of GCs hosting LMXBs is considerably higher in red, metal-rich, GCs than in blue, metal-poor GCs. In this paper, we test whether this metallicity effect is X-ray luminosity-dependent and find that the effect holds uniformly in a wide luminosity range. This result is statistically significant (at {>=}3{sigma}) in LMXBs with luminosities in the range L {sub X} = 2 Multiplication-Sign 10{sup 37} to 5 Multiplication-Sign 10{sup 38} erg s{sup -1}, where the ratio of GC-LMXB fractions in metal-rich to metal-poor GCs is R = 3.4 {+-} 0.5. A similar ratio is also found at lower (down to 10{sup 36} erg s{sup -1}) and higher luminosities (up to the ULX regime), but with less significance ({approx}2{sigma} confidence). Because different types of LMXBs dominate in different luminosities, our finding requires a new explanation for the metallicity effect in dynamically-formed LMXBs. We confirm that the metallicity effect is not affected by other factors such as stellar age, GC mass, stellar encounter rate, and galacto-centric distance.

Kim, D.-W.; Fabbiano, G.; Fragos, T. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Ivanova, N.; Sivakoff, G. R. [Department of Physics, University of Alberta, Edmonton, AB (Canada)] [Department of Physics, University of Alberta, Edmonton, AB (Canada); Jordan, A. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Santiago (Chile)] [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Santiago (Chile); Voss, R. [Department of Astrophysics/IMAPP, Radboud University, Nijmegen (Netherlands)] [Department of Astrophysics/IMAPP, Radboud University, Nijmegen (Netherlands)

2013-02-10

287

Platinum redispersion on metal oxides in low temperature fuel cells.  

PubMed

We have analyzed the aptitude of several metal oxide supports (TiO(2), SnO(2), NbO(2), ZrO(2), SiO(2), Ta(2)O(5) and Nb(2)O(5)) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtO(x) (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO(2) might be a good support for platinum redispersion at PEMFC cathodes. PMID:23358311

Tripkovi?, Vladimir; Cerri, Isotta; Nagami, Tetsuo; Bligaard, Thomas; Rossmeisl, Jan

2013-03-01

288

The growth of one-dimensional oxide nanostructures by thermal oxidation of metals  

NASA Astrophysics Data System (ADS)

Fundamental understanding of metals and alloys oxidation and reduction is important for the next generation technology. A detailed study on the oxide nanostructures growth from the oxidation of model metal systems, Cu, Fe, Zn and brass has been investigated to bridge the information gap between the oxidation mechanisms of buck metals and alloys to metal oxide nanostructures. It is observed that CuO nanowires have a bicrystal structure and form directly on top of underlying CuO grains. The driving force for the oxide nanowire growth is attributed to the compressive stresses generated during the oxidation. To verify this growth mechanism, Cu foils are bent or sandblasted to create stresses. We show that the oxide nanowire formation can be effectively promoted by surface bending tensile stresses or surface roughening via sandblasting. The formation of alpha-Fe2O3 nanowires by oxidation of Fe also follows the same stress driven mechanism as Cu. It is also found that decreasing the oxygen pressure or modifying the surface roughness by sandblasting can be employed to tune the hematite nanostructures from nanowires to nanobelts or nanoblades. The growth of ZnO nanowires by direct oxidation of pure Zn follows different mechanisms depending on the temperatures: the oxidation below the melting point of Zn is dominated by a solid-solid transformation process, a liquid-solid process between the melting and boiling points of Zn, and a vapor-solid process above the boiling point of Zn. ZnO nanowires can also be synthesized by thermal oxidation of brass (Cu0.7Zn0.3). With increasing the oxidation temperature or exerting sandblasting onto brass, the formation of ZnO nanowires can be effectively suppressed. The thermally induced reduction of CuO nanowires are studied by in situ transmission electron microscopy. Reduction of CuO nanowires results in the formation of a unique hierarchical hybrid nanostructure, in which the lower oxide (Cu2O) nanoparticles partially embedded into the parent oxide phase (CuO). For the CuO nanowires sheathed by a carbon shell, we show that confined nanoscale geometry leads to changes in the oxide reduction mechanism from a surface dominated process to the bulk dominated process.

Yuan, Lu

289

Nanoscale limitations in metal oxide electrocatalysts for oxygen evolution.  

PubMed

Metal oxides are attractive candidates for low cost, earth-abundant electrocatalysts. However, owing to their insulating nature, their widespread application has been limited. Nanostructuring allows the use of insulating materials by enabling tunneling as a possible charge transport mechanism. We demonstrate this using TiO2 as a model system identifying a critical thickness, based on theoretical analysis, of about ?4 nm for tunneling at a current density of ?1 mA/cm(2). This is corroborated by electrochemical measurements on conformal thin films synthesized using atomic layer deposition (ALD) identifying a similar critical thickness. We generalize the theoretical analysis deriving a relation between the critical thickness and the location of valence band maximum relative to the limiting potential of the electrochemical surface process. The critical thickness sets the optimum size of the nanoparticle oxide electrocatalyst and this provides an important nanostructuring requirement for metal oxide electrocatalyst design. PMID:25216362

Viswanathan, Venkatasubramanian; Pickrahn, Katie L; Luntz, Alan C; Bent, Stacey F; Nørskov, Jens K

2014-10-01

290

A metallic room-temperature oxide ion conductor.  

PubMed

Nanoparticles of Bi3 Ir, obtained from a microwave-assisted polyol process, activate molecular oxygen from air at room temperature and reversibly intercalate it as oxide ions. The closely related structures of Bi3 Ir and Bi3 IrOx (x?2) were investigated by X-ray diffraction, electron microscopy, and quantum-chemical modeling. In the topochemically formed metallic suboxide, the intermetallic building units are fully preserved. Time- and temperature-dependent monitoring of the oxygen uptake in an oxygen-filled chamber shows that the activation energy for oxide diffusion (84?meV) is one order of magnitude smaller than that in any known material. Bi3 IrOx is the first metallic oxide ion conductor and also the first that operates at room temperature. PMID:24866268

Heise, Martin; Rasche, Bertold; Isaeva, Anna; Baranov, Alexey I; Ruck, Michael; Schäfer, Konrad; Pöttgen, Rainer; Eufinger, Jens-Peter; Janek, Jürgen

2014-07-01

291

Evolution of massive stars at very low metallicity including rotation and binary interactions  

E-print Network

We discuss recent models on the evolution of massive stars at very low metallicity including the effects of rotation, magnetic fields and binarity. Very metal poor stars lose very little mass and angular momentum during the main sequence evolution, and rotation plays a dominant role in their evolution. In rapidly rotating massive stars, the rotationally induced mixing time scale can be even shorter than the nuclear time scale throughout the main sequence. The consequent quasi-chemically homogeneous evolution greatly differs from the standard massive star evolution that leads to formation of red giants with strong chemical stratification. Interesting outcomes of such a new mode of evolution include the formation of rapidly rotating massive Wolf-Rayet stars that emit large amounts of ionizing photons, the formation of a long gamma-ray bursts and a hypernovae, and the production of large amounts of primary nitrogen. We show that binary interactions can further enhance the effects of rotation, as mass accretion i...

Yoon, S -C; Langer, N

2008-01-01

292

Electrical excitation of colloidally synthesized quantum dots in metal oxide structures  

E-print Network

This thesis develops methods for integrating colloidally synthesized quantum dots (QDs) and metal oxides in optoelectronic devices, presents three distinct light emitting devices (LEDs) with metal oxides surrounding a QD ...

Wood, Vanessa Claire

2010-01-01

293

Volatile organometallic complexes suitable for use in chemical vapor depositions on metal oxide films  

DOEpatents

Novel ligated compounds of tin, titanium, and zinc are useful as metal oxide CVD precursor compounds without the detriments of extreme reactivity yet maintaining the ability to produce high quality metal oxide coating by contact with heated substrates.

Giolando, Dean M.

2003-09-30

294

Dissolution of metal and metal oxide nanoparticles in aqueous media.  

PubMed

The dissolution of Ag (citrate, gelatin, polyvinylpyrrolidone and chitosan coated), ZnO, CuO and carbon coated Cu nanoparticles (with two nominal sizes each) has been studied in artificial aqueous media, similar in chemistry to environmental waters, for up to 19 days. The dissolved fraction was determined using DGT (Diffusion Gradients in Thin films), dialysis membrane (DM) and ultrafiltration (UF). Relatively small fractions of Ag nanoparticles dissolved, whereas ZnO dissolved nearly completely within few hours. Cu and CuO dissolved as a function of pH. Using DGT, less dissolved Ag was measured compared to UF and DM, likely due to differences in diffusion of organic complexes. Similar dissolved metal concentrations of ZnO, Cu and CuO nanoparticles were determined using DGT and UF, but lower using DM. The results indicate that there is a need to apply complementary techniques to precisely determine dissolution of nanoparticles in aqueous media. PMID:24832924

Odzak, Niksa; Kistler, David; Behra, Renata; Sigg, Laura

2014-08-01

295

Fluorine in carbon-enhanced metal-poor stars: a binary scenario  

E-print Network

A super-solar fluorine abundance was observed in the carbon-enhanced metal-poor (CEMP) star HE 1305+0132 ([F/Fe] = +2.90, [Fe/H] = -2.5). We propose that this observation can be explained using a binary model that involve mass transfer from an asymptotic giant branch (AGB) star companion and, based on this model, we predict F abundances in CEMP stars in general. We discuss wether F can be used to discriminate between the formation histories of most CEMP stars: via binary mass transfer or from the ejecta of fast-rotating massive stars. We compute AGB yields using different stellar evolution and nucleosynthesis codes to evaluate stellar model uncertainties. We use a simple dilution model to determine the factor by which the AGB yields should be diluted to match the abundances observed in HE 1305+0132. We further employ a binary population synthesis tool to estimate the probability of F-rich CEMP stars. The abundances observed in HE 1305+0132 can be explained if this star accreted 3-11% of the mass lost by its former AGB companion. The primary AGB star should have dredged-up at least 0.2 Msun of material from its He-rich region into the convective envelope via third dredge-up, which corresponds to AGB models of Z ~ 0.0001 and mass ~ 2 Msun. Many AGB model uncertainties, such as the treatment of convective borders and mass loss, require further investigation. We find that in the binary scenario most CEMP stars should also be FEMP stars, that is, have [F/Fe] > +1, while fast-rotating massive stars do not appear to produce fluorine. We conclude that fluorine is a signature of low-mass AGB pollution in CEMP stars, together with elements associated with the slow neutron-capture process.

M. Lugaro; S. E. de Mink; R. G. Izzard; S. W. Campbell; A. I. Karakas; S. Cristallo; O. R. Pols; J. C. Lattanzio; O. Straniero; R. Gallino; T. C. Beers

2008-05-08

296

Mechanistic aspects of photooxidation of polyhydroxylated molecules on metal oxides  

PubMed Central

Polyhydroxylated molecules, including natural carbohydrates, are known to undergo photooxidation on wide-gap transition metal oxides irradiated by ultraviolet light. In this study, we examine mechanistic aspects of this photoreaction on aqueous TiO2, ?-FeOOH, and ?-Fe2O3 particles using electron paramagnetic resonance (EPR) spectroscopy and site-selective deuteration. We demonstrate that the carbohydrates are oxidized at sites involved in the formation of oxo-bridges between the chemisorbed carbohydrate molecule and metal ions at the oxide surface. This bridging inhibits the loss of water (which is the typical reaction of the analogous free radicals in bulk solvent) promoting instead a rearrangement that leads to elimination of the formyl radical. For natural carbohydrates, the latter reaction mainly involves carbon-1, whereas the main radical products of the oxidation are radical arising from H atom loss centered on carbon-1, -2, and -3 sites. Photoexcited TiO2 oxidizes all of the carbohydrates and polyols, whereas ?-FeOOH oxidizes some of the carbohydrates, and ?-Fe2O3 is unreactive. These results serve as a stepping stone for understanding the photochemistry on mineral surfaces of more complex biomolecules such as nucleic acids. PMID:21532934

Shkrob, Ilya A.; Marin, Timothy M.; Chemerisov, Sergey D.; Sevilla, Michael D.

2011-01-01

297

Mechanistic aspects of photooxidation of polyhydroxylated molecules on metal oxides.  

SciTech Connect

Polyhydroxylated molecules, including natural carbohydrates, are known to undergo photooxidation on wide-gap transition-metal oxides irradiated by ultraviolet light. In this study, we examine mechanistic aspects of this photoreaction on aqueous TiO{sub 2}, {alpha}-FeOOH, and {alpha}-Fe{sub 2}O{sub 3} particles using electron paramagnetic resonance (EPR) spectroscopy and site-selective deuteration. We demonstrate that the carbohydrates are oxidized at sites involved in the formation of oxo bridges between the chemisorbed carbohydrate molecule and metal ions at the oxide surface. This bridging inhibits the loss of water (which is the typical reaction of the analogous free radicals in bulk solvent) promoting instead a rearrangement that leads to elimination of the formyl radical. For natural carbohydrates, the latter reaction mainly involves carbon-1, whereas the main radical products of the oxidation are radical arising from H atom loss centered on carbon-1, -2, and -3 sites. Photoexcited TiO{sub 2} oxidizes all of the carbohydrates and polyols, whereas {alpha}-FeOOH oxidizes some of the carbohydrates, and {alpha}-Fe{sub 2}O{sub 3} is unreactive. These results serve as a stepping stone for understanding the photochemistry on mineral surfaces of more complex biomolecules such as nucleic acids.

Shkrob, I. A.; Marin, T. M.; Sevilla, M. D.; Chemerisov, S. (Chemical Sciences and Engineering Division); (Benedictine Univ.); (Oakland Univ.)

2011-03-24

298

Solubility Behavior and Phase Stability of Transition Metal Oxides in Alkaline Hydrothermal Environments  

SciTech Connect

The solubility behavior of transition metal oxides in high temperature water is interpreted by recognizing three types of chemical reaction equilibria: metal oxide hydration/dehydration, metal oxide dissolution and metal ion hydroxocomplex formation. The equilibria are quantified using thermodynamic concepts and the thermochemical properties of the metal oxides/ions representative of the most common constituents of construction metal alloys, i.e., element shaving atomic numbers between Z = 22 (Ti) and Z = 30 (Zn), are summarized on the basis of metal oxide solubility studies conducted in the laboratory. Particular attention is devoted to the uncharged metal ion hydrocomplex, M{sup Z}(OH){sub Z}(aq), since its thermochemical properties define minimum solubilities of the metal oxide at a given temperature. Experimentally-extracted values of standard partial molal entropy (S{sup 0}) for the transition metal ion neutral hydroxocomplex are shown to be influenced by ligand field stabilization energies and complex symmetry.

S.E. Ziemniak

2000-05-18

299

Evolution of massive stars at very low metallicity including rotation and binary interactions  

E-print Network

We discuss recent models on the evolution of massive stars at very low metallicity including the effects of rotation, magnetic fields and binarity. Very metal poor stars lose very little mass and angular momentum during the main sequence evolution, and rotation plays a dominant role in their evolution. In rapidly rotating massive stars, the rotationally induced mixing time scale can be even shorter than the nuclear time scale throughout the main sequence. The consequent quasi-chemically homogeneous evolution greatly differs from the standard massive star evolution that leads to formation of red giants with strong chemical stratification. Interesting outcomes of such a new mode of evolution include the formation of rapidly rotating massive Wolf-Rayet stars that emit large amounts of ionizing photons, the formation of a long gamma-ray bursts and a hypernovae, and the production of large amounts of primary nitrogen. We show that binary interactions can further enhance the effects of rotation, as mass accretion in a close binary spins up the secondary.

S. -C. Yoon; M. Cantiello; N. Langer

2008-01-28

300

Oxidation kinetics of Ni metallic films: Formation of NiO-based resistive switching structures  

Microsoft Academic Search

Resistive switching controlled by external voltage has been reported in many Metal\\/Resistive oxide\\/Metal (MRM) structures in which the resistive oxide was simple transition metal oxide thin films such as NiO or TiO2 deposited by reactive sputtering. In this paper, we have explored the possibility to form NiO-based MRM structures from the partial oxidation of a blanket Ni metallic film using

L. Courtade; Ch. Turquat; Ch. Muller; J. G. Lisoni; L. Goux; D. J. Wouters; D. Goguenheim; P. Roussel; L. Ortega

2008-01-01

301

Spectroscopic investigations of complex transition metal oxides  

NASA Astrophysics Data System (ADS)

In this dissertation, I present spectroscopic studies of several model electronic and magnetic materials. Compounds of interest include VO x nanoscrolls, VOHPO4·1/2H2O, and (La0:4Pr0:6)1:2Sr1:8Mn 2O7. These materials are attractive systems for the investigation of optical gap tuning, lattice and charge dynamics, spin-lattice-charge coupling, and hydrogen bonding effects. I measured the optical properties of VO x nanoscrolls and the ion-exchanged derivatives to investigate the lattice and charge degrees of freedom. Selected V-O-V stretching modes sharpen and redshift with increasing amine size, which are microscopic manifestations of strain. We observed bound carrier localization in the metal exchanged nanoscrolls, indicating they are weakly metallic in their bulk form. I also investigated the variable temperature vibrational properties of single crystals of the S = 1/2 Heisenberg antiferromagnet VOHPO4·1/2H 2O. In order to explain the activation and polarization dependence of the singlet-to-triplet gap in the far-infrared response, we invoke a dynamic Dzyaloshinskii-Moriya mechanism and we identify the low-energy phonons that likely facilitate this coupling. Vibrational mode splitting of VOHPO 4·1/2H2O also points toward a weak local symmetry breaking near 180 K, and the low-temperature redshift of V-O and H-O related modes demonstrates enhanced low-temperature hydrogen bonding. Finally, I measured the magneto-optical response of (La0:4Pr0:6)1:2 Sr1:8Mn2O7 to investigate the microscopic aspects of the magnetic field driven spin-glass insulator to ferromagnetic metal transition. Application of a magnetic field recovers the ferromagnetic state with an overall redshift of the electronic structure, growth of the bound carrier localization associated with ferromagnetic domains, development of a pseudogap, and softening of the Mn-O stretching and bending modes that indicate a structural change. By exploiting the electronic mechanisms, we can induce large high energy magnetodielectric contrast in (La0:4Pr 0:6)1:2Sr1:8Mn2O7. The dielectric contrast is over 100% near 0.8 eV at 4.2 K. Remnants of the transition also drive the high energy magnetodielectric effect at room temperature.

Cao, Jinbo

302

A molecular catalyst for water oxidation that binds to metal oxide surfaces.  

PubMed

Molecular catalysts are known for their high activity and tunability, but their solubility and limited stability often restrict their use in practical applications. Here we describe how a molecular iridium catalyst for water oxidation directly and robustly binds to oxide surfaces without the need for any external stimulus or additional linking groups. On conductive electrode surfaces, this heterogenized molecular catalyst oxidizes water with low overpotential, high turnover frequency and minimal degradation. Spectroscopic and electrochemical studies show that it does not decompose into iridium oxide, thus preserving its molecular identity, and that it is capable of sustaining high activity towards water oxidation with stability comparable to state-of-the-art bulk metal oxide catalysts. PMID:25757425

Sheehan, Stafford W; Thomsen, Julianne M; Hintermair, Ulrich; Crabtree, Robert H; Brudvig, Gary W; Schmuttenmaer, Charles A

2015-01-01

303

A molecular catalyst for water oxidation that binds to metal oxide surfaces  

PubMed Central

Molecular catalysts are known for their high activity and tunability, but their solubility and limited stability often restrict their use in practical applications. Here we describe how a molecular iridium catalyst for water oxidation directly and robustly binds to oxide surfaces without the need for any external stimulus or additional linking groups. On conductive electrode surfaces, this heterogenized molecular catalyst oxidizes water with low overpotential, high turnover frequency and minimal degradation. Spectroscopic and electrochemical studies show that it does not decompose into iridium oxide, thus preserving its molecular identity, and that it is capable of sustaining high activity towards water oxidation with stability comparable to state-of-the-art bulk metal oxide catalysts. PMID:25757425

Sheehan, Stafford W.; Thomsen, Julianne M.; Hintermair, Ulrich; Crabtree, Robert H.; Brudvig, Gary W.; Schmuttenmaer, Charles A.

2015-01-01

304

Technetium Dichloride: A New Binary Halide Containing Metal-Metal Multiple Bonds  

SciTech Connect

Technetium dichloride has been discovered. It was synthesized from the elements and characterized by several physical techniques, including single crystal X-ray diffraction. In the solid state, technetium dichloride exhibits a new structure type consisting of infinite chains of face sharing [Tc{sub 2}Cl{sub 8}] rectangular prisms that are packed in a commensurate supercell. The metal-metal separation in the prisms is 2.127(2) {angstrom}, a distance consistent with the presence of a Tc {triple_bond} Tc triple bond that is also supported by electronic structure calculations.

Poineau, Frederic; Malliakas, Christos D.; Weck, Philippe F.; Scott, Brian L.; Johnstone, Erik V.; Forster, Paul M.; Kim, Eunja; Kanatzidis, Mercouri G.; Czerwinski, Kenneth R.; Sattelberge, Alfred P. (UNLV); (NWU); (LANL)

2011-10-19

305

Technetium dichloride : a new binary halide containing metal-metal multiple bonds.  

SciTech Connect

Technetium dichloride has been discovered. It was synthesized from the elements and characterized by several physical techniques, including single crystal X-ray diffraction. In the solid state, technetium dichloride exhibits a new structure type consisting of infinite chains of face sharing [Tc{sub 2}Cl{sub 8}] rectangular prisms that are packed in a commensurate supercell. The metal-metal separation in the prisms is 2.127(2) {angstrom}, a distance consistent with the presence of a Tc {triple_bond} Tc triple bond that is also supported by electronic structure calculations.

Poineau, F.; Malliakas, C. D.; Weck, P. F.; Scott, B. L.; Johnstone, E. V.; Forster, P. M.; Kim, E.; Kanatzidis, M. G.; Czerwinski, K. R.; Sattelberger, A. P. (Materials Science Division); ( OTD-EESA); (Univ. of Nevada at Las Vegas); (LANL); (Northwestern Univ.)

2011-06-15

306

Direct electroplated metallization on indium tin oxide plastic substrate.  

PubMed

Looking foward to the future where the device becomes flexible and rollable, indium tin oxide (ITO) fabricated on the plastic substrate becomes indispensable. Metallization on the ITO plastic substrate is an essential and required process. Electroplating is a cost-effective and high-throughput metallization process; however, the poor surface coverage and interfacial adhesion between electroplated metal and ITO plastic substrate limits its applications. This paper develops a new method to directly electroplate metals having strong adhesion and uniform deposition on an ITO plastic substrate by using a combination of 3-mercaptopropyl-trimethoxysilane (MPS) self-assembled monolayers (SAMs) and a sweeping potential technique. An impedance capacitive analysis supports the proposed bridging link model for MPS SAMs at the interface between the ITO and the electrolyte. PMID:24380434

Hau, Nga Yu; Chang, Ya-Huei; Huang, Yu-Ting; Wei, Tzu-Chien; Feng, Shien-Ping

2014-01-14

307

Synthesis and structural, magnetic, thermal, and transport properties of several transition metal oxides and aresnides  

SciTech Connect

Oxide compounds containing the transition metal vanadium (V) have attracted a lot of attention in the field of condensed matter physics owing to their exhibition of interesting properties including metal-insulator transitons, structural transitions, ferromagnetic and antiferromagnetic orderings, and heavy fermion behavior. Binary vanadium oxides V{sub n}O{sub 2n-1} where 2 {le} n {le} 9 have triclinic structures and exhibit metal-insulator and antiferromagnetic transitions. The only exception is V{sub 7}O{sub 13} which remains metallic down to 4 K. The ternary vanadium oxide LiV{sub 2}O{sub 4} has the normal spinel structure, is metallic, does not undergo magnetic ordering and exhibits heavy fermion behavior below 10 K. CaV{sub 2}O{sub 4} has an orthorhombic structure with the vanadium spins forming zigzag chains and has been suggested to be a model system to study the gapless chiral phase. These provide great motivation for further investigation of some known vanadium compounds as well as to explore new vanadium compounds in search of new physics. This thesis consists, in part, of experimental studies involving sample preparation and magnetic, transport, thermal, and x-ray measurements on some strongly correlated eletron systems containing the transition metal vanadium. The compounds studied are LiV{sub 2}O{sub 4}, YV{sub 4}O{sub 8}, and YbV{sub 4}O{sub 8}. The recent discovery of superconductivity in RFeAsO{sub 1-x}F{sub x} (R = La, Ce, Pr, Gd, Tb, Dy, Sm, and Nd), and AFe{sub 2}As{sub 2} (A = Ba, Sr, Ca, and Eu) doped with K, Na, or Cs at the A site with relatively high T{sub c} has sparked tremendous activities in the condensed matter physics community and a renewed interest in the area of superconductivity as occurred following the discovery of the layered cuprate high T{sub c} superconductors in 1986. To discover more superconductors with hopefully higher T{sub c}'s, it is extremely important to investigate compounds having crystal structures related to the compounds showing high T{sub c} superconductivity. Along with the vanadium oxide compounds described before, this thesis describes our investigations of magnetic, structural, thermal and transport properties of EuPd{sub 2}Sb{sub 2} single crystals which have a crystal structure closely related to the AFe{sub 2}As{sub 2} compounds and also a study of the reaction kinetics of the formation of LaFeAsO{sub 1-x}F{sub x}.

Das, Supriyo

2010-05-16

308

Chemically synthesized metal-oxide-metal segmented nanowires with high ferroelectric response.  

PubMed

A chemical synthesis method is presented for the fabrication of high-definition segmented metal-oxide-metal (MOM) nanowires in two different ferroelectric oxide systems: Au-BaTiO(3)-Au and Au-PbTiO(3)-Au. This method entails electrodeposition of segmented nanowires of Au-TiO(2)-Au inside anodic aluminum oxide (AAO) templates, followed by topotactic hydrothermal conversion of the TiO(2) segments into BaTiO(3) or PbTiO(3) segments. Two-terminal devices from individual MOM nanowires are fabricated, and their ferroelectric properties are measured directly, without the aid of scanning probe microscopy (SPM) methods. The MOM nanowire architecture provides high-quality end-on electrical contacts to the oxide segments, and allows direct measurement of properties of nanoscale volume, strain-free oxide segments. Unusually high ferroelectric responses, for chemically synthesized oxides, in these MOM nanowires are reported, and are attributed to the lack of residual strain in the oxides. The ability to measure directly the active properties of nanoscale volume, strain-free oxides afforded by the MOM nanowire architecture has important implications for fundamental studies of not only ferroelectric nanostructures but also nanostructures in the emerging field of multiferroics. PMID:20657040

Herderick, Edward D; Polomoff, Nicholas A; Huey, Bryan D; Padture, Nitin P

2010-08-20

309

Chemically synthesized metal-oxide-metal segmented nanowires with high ferroelectric response  

NASA Astrophysics Data System (ADS)

A chemical synthesis method is presented for the fabrication of high-definition segmented metal-oxide-metal (MOM) nanowires in two different ferroelectric oxide systems: Au-BaTiO3-Au and Au-PbTiO3-Au. This method entails electrodeposition of segmented nanowires of Au-TiO2-Au inside anodic aluminum oxide (AAO) templates, followed by topotactic hydrothermal conversion of the TiO2 segments into BaTiO3 or PbTiO3 segments. Two-terminal devices from individual MOM nanowires are fabricated, and their ferroelectric properties are measured directly, without the aid of scanning probe microscopy (SPM) methods. The MOM nanowire architecture provides high-quality end-on electrical contacts to the oxide segments, and allows direct measurement of properties of nanoscale volume, strain-free oxide segments. Unusually high ferroelectric responses, for chemically synthesized oxides, in these MOM nanowires are reported, and are attributed to the lack of residual strain in the oxides. The ability to measure directly the active properties of nanoscale volume, strain-free oxides afforded by the MOM nanowire architecture has important implications for fundamental studies of not only ferroelectric nanostructures but also nanostructures in the emerging field of multiferroics.

Herderick, Edward D.; Polomoff, Nicholas A.; Huey, Bryan D.; Padture, Nitin P.

2010-08-01

310

The Close Binary Properties of Massive Stars in the Milky Way and Low-metallicity Magellanic Clouds  

NASA Astrophysics Data System (ADS)

In order to understand the rates and properties of Type Ia and Type Ib/c supernovae, X-ray binaries, gravitational wave sources, and gamma-ray bursts as a function of galactic environment and cosmic age, it is imperative that we measure how the close binary properties of O- and B-type stars vary with metallicity. We have studied eclipsing binaries with early B main-sequence primaries in three galaxies with different metallicities: the Large and Small Magellanic Clouds (LMC and SMC, respectively) and the Milky Way (MW). The observed fractions of early B stars that exhibit deep eclipses 0.25 < ?m (mag) < 0.65 and orbital periods 2 < P (days) < 20 in the MW, LMC, and SMC span a narrow range of (0.7-1.0)%, which is a model-independent result. After correcting for geometrical selection effects and incompleteness toward low-mass companions, we find for early B stars in all three environments (1) a close binary fraction of (22 ± 5)% across orbital periods 2 < P (days) < 20 and mass ratios q = M 2/M 1 > 0.1, (2) an intrinsic orbital period distribution slightly skewed toward shorter periods relative to a distribution that is uniform in log P, (3) a mass-ratio distribution weighted toward low-mass companions, and (4) a small, nearly negligible excess fraction of twins with q > 0.9. Our fitted parameters derived for the MW eclipsing binaries match the properties inferred from nearby, early-type spectroscopic binaries, which further validates our results. There are no statistically significant trends with metallicity, demonstrating that the close binary properties of massive stars do not vary across metallicities -0.7 < log(Z/Z ?) < 0.0 beyond the measured uncertainties.

Moe, Maxwell; Di Stefano, Rosanne

2013-12-01

311

The nature of transition-metal-oxide surfaces  

NASA Astrophysics Data System (ADS)

The surfaces of the 3d-transition-metal oxides form a rich and important system in which to study the effects of atomic geometry, ligand coordination and d-orbital population on surface electronic structure and chemisorption. This article considers the properties of those surfaces in terms of the types of surface structures that can exist, including steps and point defects, and their relation to the experimental data that is available for well characterized, single-crystal surfaces. The electronic structure of nearly perfect surfaces is very similar to that of the bulk for many of the oxides that have been studied; atoms at step sites also appear to have properties similar to those of atoms on terraces. Point defects are often associated with surfaces 0 vacancies and attendant transfer of electrons to adjacent metal cations. Those cations are poorly screened from each other, and the excess charge is presumably shared between two or more cations having reduced ligand coordination. Point defects are generally more active for chemisorption than are perfect surfaces, however for Ti 2O 3 and V 2O 3, whose cations have 3d 1 and 3d 2 electronic configurations respectively, the cleaved (047) surface is more active than are surfaces having a high density of defects. The chemisorption behavior of both nearly perfect and defect surfaces of 3d-transition-metal oxides varies widely from one material to another, and it is suggestive to correlate this with cation d-orbital population. However, too few oxides have yet been studied to draw any firm conclusions. Additional theoretical work on perfect surfaces, defects and chemisorption is also necessary in order to gain a more complete understanding of transition-metal-oxide surfaces.

Henrich, V. E.

312

Sol-flame synthesis: a general strategy to decorate nanowires with metal oxide/noble metal nanoparticles.  

PubMed

The hybrid structure of nanoparticle-decorated nanowires (NP@NW) combines the merits of large specific surface areas for NPs and anisotropic properties for NWs and is a desirable structure for applications including batteries, dye-sensitized solar cells, photoelectrochemical water splitting, and catalysis. Here, we report a novel sol-flame method to synthesize the NP@NW hybrid structure with two unique characteristics: (1) large loading of NPs per NW with the morphology of NP chains fanning radially from the NW core and (2) intimate contact between NPs and NWs. Both features are advantageous for the above applications that involve both surface reactions and charge transport processes. Moreover, the sol-flame method is simple and general, with which we have successfully decorated various NWs with binary/ternary metal oxide and even noble metal NPs. The unique aspects of the sol-flame method arise from the ultrafast heating rate and the high temperature of flame, which enables rapid solvent evaporation and combustion, and the combustion gaseous products blow out NPs as they nucleate, forming the NP chains around NWs. PMID:22494023

Feng, Yunzhe; Cho, In Sun; Rao, Pratap M; Cai, Lili; Zheng, Xiaolin

2013-03-13

313

Three-dimensional Metal Nano Pattern Transfer on PET using Metal Oxide Layer  

NASA Astrophysics Data System (ADS)

There is a strong need for a fine three-dimensional metal patterning technique for fabricating next-generation devices such as patterned media and plasmon photonic and nano-scale electrodes. In addition, flexible and transparent electronic devices on plastic substrates are desired for wearable devices and flexible thin-film displays. Therefore, a technique for patterning metals onto plastic substrates is required. Nanotransfer printing (nTP) has received much attention recently because of its high throughput and high resolution compared to inkjet printing. However, it is difficult to create sub-100 nm metal patterns using nTP because the PDMS stamp is deformed by transfer pressure. Therefore, we have developed a technique for transferring three-dimensional metal patterns onto a polyethylene terephthalate (PET) substrate by nanoimprint lithography using a metal oxide release layer. The three-dimensional nanoimprint mold was fabricated by control of acceleration voltage electron beam lithography (CAV-EBL) with spin-on-glass (SOG). As a result, three-dimensional metal nano patterns were obtained using a metal oxide release layer. Moreover, the metal moth-eye structure, which has a very high aspect ratio, was transferred onto a PET substrate by applying our process to the moth-eye structure on glassy carbon.

Unno, Noriyuki; Taniguchi, Jun

314

Transition Metal Exchanged Zeolite Layers for Selectivity Enhancement of Metal-Oxide Semiconductor Gas Sensors  

Microsoft Academic Search

A novel method of improving the selectivity of metal oxide gas sensors has been developed by using catalytically active molecular sieve materials. They have been successfully introduced into a proprietary sensor array. The cracking patterns of linear alkanes over transition metal exchanged zeolite Y have been measured using a zeolite bed\\/GC\\/MS experimental set-up within a temperature range of 300degC to

Dominic P. Mann; Keith F. E. Pratt; Themis Paraskeva; Ivan P. Parkin; David E. Williams

2007-01-01

315

Band engineering of metal oxide heterostructures for catalysis applications  

NASA Astrophysics Data System (ADS)

Supported metal oxides are used as catalysts for a wide variety of industrially and environmentally important reactions such as the selective oxidation of hydrocarbons and alcohols and the selective catalytic reduction of nitrogen oxides. The support often plays an important role in the activity and selectivity of such catalysts, beyond just the provision of mechanical support and large surface area. V2O5 supported on TiO2 is an example of a catalyst that is widely used, where the synergy between the support and the overlayer is taken advantage of. The support effect has often been ascribed to the electronegativity of the support cation which affects the electron density on the metal--oxygen bond in the overlayer. However, this effect may not hold for thicker overlayers and for doped supports. In the current work, a model is proposed in which the supported catalyst is considered as a heterostructure. Most metal oxides are (wide band-gap) semiconductors and hence a semiconductor heterojunction is formed when one oxide is deposited on another. This conception of supported oxide catalysts allows for the use of heterojunction physics to predict the electron richness at the surface of the catalyst. Moreover, effect of overlayer thickness and support doping can be easily determined using such a model. Thus quantitative estimates of surface electron richness were obtained for the system of V 2O5/TiO2. It is shown that modification of overlayer thickness and the carrier concentration in the support can lead to modification of the surface electron richness (represented by the surface Fermi level) of the catalyst. A semi-empirical model was also developed to relate the Fermi level of oxide catalysts to their activity. Using these models, the quantitative variation of catalytic activity with the heterostructure parameters (overlayer thickness, support carrier concentration) was determined, for the test reaction of partial oxidation of methanol to formaldehyde. Results from experiments using thin films of polycrystalline oxides (V 2O5 supported on TiO2) and methanol oxidation as the test reaction, matched qualitatively with the model predictions. The quantitative enhancement (> 10x) in rate obtained by reducing the overlayer thickness was better than the model predictions. Surface potential measurements combined with kinetic data proved the validity of the model relating Fermi level and catalytic activity, and showed directions for further development of the heterojunction model to predict the surface electron richness.

Nandakumar, Navaneetha Krishnan

316

Characterization and catalysis studies of small metal particles on planar model oxide supports  

Microsoft Academic Search

Planar model oxide-supported metal catalysts have been prepared by evaporating metals of catalytic interest onto various oxide thin films supported on refractory metal single crystals, followed by annealing to promote the formation of small metal clusters. The employment of these relatively simple supported catalysts prepared in ultrahigh vacuum (UHV) represent a promising method of simulating heterogeneous catalytic processes over high

Darrell R. Rainer; Chen Xu; D. Wayne Goodman

1997-01-01

317

Factors that affect Li mobility in layered lithium transition metal oxides Kisuk Kang and Gerbrand Ceder*  

E-print Network

Factors that affect Li mobility in layered lithium transition metal oxides Kisuk Kang and Gerbrand in layered lithium transition metal oxides are systematically studied in this paper by means of first, and the nature of the metal ion in the transition metal layer have all been proposed to influence the Li mobility

Ceder, Gerbrand

318

Electronic entanglement in late transition metal oxides  

E-print Network

Here we present a study of the entanglement in the electronic structure of the late transition metal monoxides - MnO, FeO, CoO, and NiO - obtained by means of density-functional theory in the local density approximation combined with dynamical mean-field theory (LDA+DMFT). The impurity problem is solved through Exact Diagonalization (ED), which grants full access to the thermally mixed many-body ground state density operator. The quality of the electronic structure is affirmed through a direct comparison between the calculated electronic excitation spectrum and photoemission experiments. Our treatment allows for a quantitative investigation of the entanglement in the electronic structure. Two main sources of entanglement are explicitly resolved through the use of a fidelity based geometrical entanglement measure, and additional information is gained from a complementary entropic entanglement measure. We show that the interplay of crystal field effects and Coulomb interaction causes the entanglement in CoO to take a particularly intricate form.

Patrik Thunström; Igor Di Marco; Olle Eriksson

2013-01-28

319

Influence of uranium hydride oxidation on uranium metal behaviour  

SciTech Connect

This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

Patel, N.; Hambley, D. [National Nuclear Laboratory (United Kingdom); Clarke, S.A. [Sellafield Ltd (United Kingdom); Simpson, K.

2013-07-01

320

Preparation and evaluation of novel hydrous metal oxide (HMO)-supported noble metal catalysts  

SciTech Connect

Hydrous Metal Oxides (HMOs) are chemically synthesized materials that, because of their high cation exchange capacity, possess a unique ability to allow the preparation of highly dispersed supported-metal catalyst precursors with high metal loadings. This study evaluates high weight loading Rh/HMO catalysts with a wide range of HMO support compositions, including hydrous titanium oxide (HTO), silica-doped hydrous titanium oxide (HTO:Si), hydrous zirconium oxide (HZO), and silica-doped hydrous zirconium oxide (HZO:Si), against conventional oxide-supported Rh catalysts with similar weight loadings and support chemistries. Catalyst activity measurements for a structure-sensitive model reaction (n-butane hydrogenolysis) as a function of catalyst activation conditions show superior activity and stability for the ZrO{sub 2}, HZO, and HZO:Si supports, although all of the Rh/HMO catalysts have high ethane selectivity indicative of high Rh dispersion. For the TiO{sub 2}-, HTO-, and HTO:Si supported Rh catalysts, a significant loss of both catalyst activity and Rh dispersion is observed at more aggressive activation conditions, consistent with TiO{sub x} migration associated with SMSI phenomena. Of all the Rh/HMO catalysts, the Rh/HZO:Si catalysts appear to offer the best tradeoff in terms of high Rh dispersion, high activity, and high selectivity.

Gardner, T.J.; McLaughlin, L.I.; Evans, L.R. [Sandia National Labs., Albuquerque, NM (United States). Catalysis and Chemical Technologies Dept.; Datye, A.K. [Univ. of New Mexico, Albuquerque, NM (United States)

1998-04-01

321

Binaries, Rotation, and Velocity Jitter in Metal-Poor Field Red Giants  

NASA Astrophysics Data System (ADS)

We have monitored the radial velocities of 93 metal-poor field red giants for intervals of up to 16 years. Fourteen stars have been found to be spectroscopic binaries. Velocity jitter is detected among half the giants with MV <=\\ -1.5. The two best-observed cases, HD 3008 and BD+22 2411, show apparent periodicities of 172 and 186 days, too long to be due to pulsation. Photometric variability seen in HD 3008 and two other stars showing velocity jitter suggests that starspots are the cause. The implied rotational velocities for HD 3008 and BD+22 2411, both with R ? 50 Rsun, exceed 10 km/s. Eight of the sixteen red giants with MV <= -1.5 have vrot sin i values of this size or larger. In some cases, BD+30 2034, CD-37 14010, and HD 218732, this probably arises from tidal locking between the axial rotation and the orbital motion with close stellar companions. But this cannot explain the other five stars, comprising roughly one-third of the luminous red giants in our sample. There appear to be too few stellar binary systems with short enough periods among field metal-poor main sequence stars to explain such a large frequency of high rotational velocities among field metal-poor luminous red giants. Capture of a planetary-mass companion as a red giant expands in radius could explain the high rotational velocities, and perhaps the high rotational velocities seen in field and cluster blue horizontal branch stars. We also find that four of the red horiozontal branch stars in our program show comparable rotational velocities. Transport of internal angular momentum to the surface appears unlikely since the high rotation does not appear at luminosities when the stellar convection zone is at its deepest. We thank the National Science Foundation for support at UNC and BGSU.

Stefanik, R. P.; Carney, B. W.; Latham, D. W.; Morse, J. A.; Laird, J. B.

2001-12-01

322

Microelectronic components and metallic oxide studies and applications  

NASA Technical Reports Server (NTRS)

The project involved work in two basic areas: (1) Evaluation of commercial screen printable thick film conductors, resistors, thermistors and dielectrics as well as alumina substrates used in hybird microelectronics industries. Results of tests made on materials produced by seven companies are presented. (2) Experimental studies on metallic oxides of copper and vanadium, in an effort to determine their electrochemical properties in crystalline, powder mixtures and as screen printable thick films constituted the second phase of the research effort. Oxide investigations were aimed at finding possible applications of these materials as switching devices memory elements and sensors.

Williams, L., Jr.

1976-01-01

323

Field-induced resistive switching in metal-oxide interfaces  

SciTech Connect

We investigate the polarity-dependent field-induced resistive switching phenomenon driven by electric pulses in perovskite oxides. Our data show that the switching is a common occurrence restricted to an interfacial layer between a deposited metal electrode and the oxide. We determine through impedance spectroscopy that the interfacial layer is no thicker than 10 nm and that the switch is accompanied by a small capacitance increase associated with charge accumulation. Based on interfacial I-V characterization and measurement of the temperature dependence of the resistance, we propose that a field-created crystalline defect mechanism, which is controllable for devices, drives the switch.

Tsui, S.; Baikalov, A.; Cmaidalka, J.; Sun, Y.Y.; Wang, Y.Q.; Xue, Y.Y.; Chu, C.W.; Chen, L.; Jacobson, A.J. [Department of Physics and Texas Center for Superconductivity and Advanced Materials, University of Houston, 202 Houston Science Center, Houston, Texas 77204-5002 (United States); Department of Physics and Texas Center for Superconductivity and Advanced Materials, University of Houston, 202 Houston Science Center, Houston, Texas 77204-5002, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Hong Kong University of Science and Technology, Hong Kong (China); Department of Chemistry, University of Houston, 136 Fleming Building, Houston, Texas 77204-5003 (United States)

2004-07-12

324

Catalytic oxidation of dimethyl sulfide with ozone: Effects of promoter and physico-chemical properties of metal oxide catalysts  

Microsoft Academic Search

This study reports improved catalytic activities and stabilities for the oxidation of dimethyl sulfide (DMS), a major pollutant of pulp and paper mills. Ozone was used as an oxidant and activities of Cu, Mo, Cr and Mn oxides, and mixed metal oxides supported on ?-alumina, were tested over the temperature ranging from 100 to 200°C. The best catalytic activity was

Venu Gopal Devulapelli; Endalkachew Sahle-Demessie

2008-01-01

325

CATALYTIC OXIDATION OF DIMETHYL SULFIDE WITH OZONE: EFFECTS OF PROMOTER AND PHYSICO-CHEMICAL PROPERTIES OF METAL OXIDE CATALYSTS  

EPA Science Inventory

This study reports improved catalytic activities and stabilities for the oxidation of dimethyl sulfide (DMS), a major pollutant of pulp and paper mills. Ozone was used as an oxidant and activities of Cu, Mo, Cr and Mn oxides, and mixed metal oxides supported on -alumina, were tes...

326

Single-crystal-like nanoporous spinel oxides: a strategy for synthesis of nanoporous metal oxides utilizing metal-cyanide hybrid coordination polymers.  

PubMed

Development of a new method to synthesize nanoporous metal oxides with highly crystallized frameworks is of great interest because of their wide use in practical applications. Here we demonstrate a thermal decomposition of metal-cyanide hybrid coordination polymers (CPs) to prepare nanoporous metal oxides. During the thermal treatment, the organic units (carbon and nitrogen) are completely removed, and only metal contents are retained to prepare nanoporous metal oxides. The original nanocube shapes are well-retained even after the thermal treatment. When both Fe and Co atoms are contained in the precursors, nanoporous Fe-Co oxide with a highly oriented crystalline framework is obtained. On the other hand, when nanoporous Co oxide and Fe oxide are obtained from Co- and Fe-contacting precursors, their frameworks are amorphous and/or poorly crystallized. Single-crystal-like nanoporous Fe-Co oxide shows a stable magnetic property at room temperature compared to poly-crystalline metal oxides. We further extend this concept to prepare nanoporous metal oxides with hollow interiors. Core-shell heterostructures consisting of different metal-cyanide hybrid CPs are prepared first. Then the cores are dissolved by chemical etching using a hydrochloric acid solution (i.e., the cores are used as sacrificial templates), leading to the formation of hollow interiors in the nanocubes. These hollow nanocubes are also successfully converted to nanoporous metal oxides with hollow interiors by thermal treatment. The present approach is entirely different from the surfactant-templating approaches that traditionally have been utilized for the preparation of mesoporous metal oxides. We believe the present work proves a new way to synthesize nanoporous metal oxides with controlled crystalline frameworks and architectures. PMID:25359496

Zakaria, Mohamed B; Hu, Ming; Imura, Masataka; Salunkhe, Rahul R; Umezawa, Naoto; Hamoudi, Hicham; Belik, Alexei A; Yamauchi, Yusuke

2014-12-22

327

Multichannel Multiphoton Imaging of Metal Oxides Nanoparticles in Biological System  

SciTech Connect

Near-IR ultrafast pulse laser and confocal microscope are combined to create a multiphoton multichannel non-linear imaging technique, which allows in situ 3-D characterization of nonfluorescent nanoparticles in biological systems. We observed intense CARS signals generated from various metal oxides due to their high third-order nonlinear susceptibilities (x(3)), which do not depend on the vibrational resonance but on the electronic resonance. We show that fine and ultrafine particles of metal oxides in alveolar macrophage cells may be imaged in vitro using CARS and multiphoton fluorescence microscopy with highest optical resolution for extended periods without photobleaching effects. The advantage of the epidetection over the forward detection for imaging sub-micron particles has been investigated.

Zheng, Yuangang; Holtom, Gary R.; Colson, Steve D.; Periasamy, A. and So, S.T.C.

2004-09-15

328

Metal Oxide Decomposition In Hydrothermal Alkaline Sodium Phosphate Solutions  

SciTech Connect

Alkaline hydrothermal solutions of sodium orthophosphate (2.15 < Na/P < 2.75) are shown to decompose transition metal oxides into two families of sodium-metal ion-(hydroxy)phosphate compounds. Equilibria for these reactions are quantified by determining phosphate concentration-temperature thresholds for decomposition of five oxides in the series: Ti(IV), Cr(III), Fe(III, II), Ni(II) and Zn(II). By application of a computational chemistry method General Utility Lattice Program (GULP), it is demonstrated that the unique non-whole-number Na/P molar ratio of sodium ferric hydroxyphosphate is a consequence of its open-cage structure in which the H{sup +} and excess Na{sup +} ions are located.

S.E. Ziemniak

2003-09-24

329

Analysis of lipids: metal oxide laser ionization mass spectrometry.  

PubMed

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been used for lipid analysis; however, one of the drawbacks of this technique is matrix interference peaks at low masses. Metal oxide surfaces are described here for direct, matrix-free analysis of small (MW < 1000 Da) lipid compounds, without interferences in the resulting spectra from traditional matrix background peaks. Spectra from lipid standards produced protonated and sodiated molecular ions. More complex mixtures including vegetable oil shortening and lipid extracts from bacterial and algal sources provided similar results. Mechanistic insight into the mode of ionization from surface spectroscopy, negative ion mass spectrometry, and stable isotope studies is also presented. The metal oxide system is compared to other reported matrix-free systems. PMID:22873784

McAlpin, Casey R; Voorhees, Kent J; Corpuz, April R; Richards, Ryan M

2012-09-18

330

Understanding Organic Film Behavior on Alloy and Metal Oxides  

PubMed Central

Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides namely, nickel, chromium, molybdenum, manganese, iron and titanium were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid and octadecylsulfonic acid on these substrates was examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy and matrix assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation. PMID:20039608

Raman, Aparna; Quiñones, Rosalynn; Barriger, Lisa; Eastman, Rachel; Parsi, Arash

2010-01-01

331

Spin-Orbit Interaction Rediscovered in Transition Metal Oxides  

NASA Astrophysics Data System (ADS)

The 5d-transition metal oxides are a class of novel materials that exhibit nearly every collective state known for solids. It is commonly expected that iridium oxides should be more metallic and less magnetic than their 3d and 4f counterparts due to the extended nature of the 5d orbitals. In marked contrast, many iridates are magnetic insulators that exhibit a large array of phenomena seldom or never seen in other materials. We review the anomalous physical properties of several iridates and address potential underlying mechanisms, which include strong orbital magnetism, the Jeff = .5ex1 -.1em/ -.15em.25ex2 insulating state, and spin-orbit coupling; the latter strongly competes with other interactions to create an unusual balance between relevant degrees of freedom in this class of materials.

Cao, Gang

2011-03-01

332

Nanostructured iron(III)-copper(II) binary oxide: a novel adsorbent for enhanced arsenic removal from aqueous solutions.  

PubMed

To obtain a highly efficient and low-cost adsorbent for arsenic removal from water, a novel nanostructured Fe-Cu binary oxide was synthesized via a facile co-precipitation method. Various techniques including BET surface area measurement, powder XRD, SEM, and XPS were used to characterize the synthetic Fe-Cu binary oxide. It showed that the oxide was poorly crystalline, 2-line ferrihydrite-like and was aggregated with many nanosized particles. Laboratory experiments were performed to investigate adsorption kinetics, adsorption isotherms, pH adsorption edge and regeneration of spent adsorbent. The results indicated that the Fe-Cu binary oxide with a Cu: Fe molar ratio of 1:2 had excellent performance in removing both As(V) and As(III) from water, and the maximal adsorption capacities for As(V) and As(III) were 82.7 and 122.3 mg/g at pH 7.0, respectively. The values are favorable, compared to those reported in the literature using other adsorbents. The coexisting sulfate and carbonate had no significant effect on arsenic removal. However, the presence of phosphate obviously inhibited the arsenic removal, especially at high concentrations. Moreover, the Fe-Cu binary oxide could be readily regenerated using NaOH solution and be repeatedly used. The Fe-Cu binary oxide could be a promising adsorbent for both As(V) and As(III) removal because of its excellent performance, facile and low-cost synthesis process, and easy regeneration. PMID:23571113

Zhang, Gaosheng; Ren, Zongming; Zhang, Xiwang; Chen, Jing

2013-08-01

333

Synthesis, characterization, and property measurement of novel metal-oxide-metal heterojunction nanowires with ferroelectric functionality  

NASA Astrophysics Data System (ADS)

A new "bottom-up" paradigm of electronics offers the possibility of assembling virtually any electronic device using nanoscale building blocks to provide functionality. Essential to this vision is the synthesis of such building blocks with customized composition, morphology, and properties in a reproducible, controlled manner. In the case of functional oxides, extensive studies have been carried out synthesizing all-oxide nanowires that are assembled across metal contact-pad electrodes to create devices. However, there are drawbacks to this approach including: high ohmic losses; the active oxide region is determined by spacing of the electrodes; the contacts made to the functional segment are on the side-wall of the nanowire; and making reproducible contacts over a range of devices is difficult. In this context, metal-oxide-metal (MOM) heterojunction nanowires, where two Au nanowires are separated by a nanoscale segment of a functional oxide, offer several advantages over all-oxide nanowires. The MOM nanowire structure precisely defines the active oxide region within the building block itself and the metal interconnects are integrated within the building block making them more suitable for device assembly. In addition, the small interfacial area of the metal interconnects to the oxide offer the possibility of measuring coupled electronic properties of nanoscale volumes of oxides without substrate effects. In this work, a novel method is developed to synthesize Au-TiO2 -Au, Au-BaTiO3-Au and Au-PbTiO3-Au MOM heterojunction nanowires. This is the first report of successful synthesis of MOM nanowires with ternary oxides. Results from the synthesis and characterization of these nanowires are presented. In order to measure properties of these nanowires, single-nanowire-based devices are fabricated using the focused ion beam (FIB) direct write method to make connections to macroscale electrode pads. The charge transport properties are measured and show a non-linear, non-rectifying response. This response is shown to be due to a transition between ohmic and space-charge-limited-conduction (SCLC) and is investigated using Au-NiO-Au nanowires as a model system. In the Au-BaTiO3-Au and Au-PbTiO3-Au nanowire system, ferroelectric polarization measurements are performed using both electrical measurements and a scanning probe microscope approach.

Herderick, Edward D.

2009-12-01

334

Synthesis of metal-metal oxide catalysts and electrocatalysts using a metal cation adsorption/reduction and adatom replacement by more noble ones  

DOEpatents

The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen. The invention also relates to methods of making the metal-metal oxide composites.

Adzic, Radoslav; Vukmirovic, Miomir; Sasaki, Kotaro

2010-04-27

335

Titanium oxide aerogels prepared from titanium metal and hydrogen peroxide  

Microsoft Academic Search

The reaction of hydrogen peroxide with excess titanium metal produces rigid titanium oxide aquagels. Subsequent solvent exchanges with ethanol and carbon dioxide, and supercritical drying produces the corresponding aerogels. The aerogels are translucent yellow in appearance, are amorphous to X-rays, and have a BET surface area of 350 m2\\/g. The empirical formula of the material, as prepared, is TiO3H2.7C0.35. Infrared

M. R Ayers; A. J Hunt

1998-01-01

336

Metal-insulator phase transition in vanadium oxides films  

Microsoft Academic Search

Vanadium oxide films (VO2) are of a typical phase transition ranging between metal phase to a semi-conducting phase. The theoretical metamorphose temperature of VO2 is around 340K (67°C). This transition temperature is mostly governed by the deposition method in which the film was made, and the film's composition. Optical and electrical properties of VO2 films are dramatically changed during this

G. Golan; A. Axelevitch; B. Sigalov; B. Gorenstein

2003-01-01

337

Ignition in alkane oxidation on noble-metal catalysts  

Microsoft Academic Search

The ignition behavior in the oxidation of four simple alkanes (methane, ethane, propane and isobutane) with air on a platinum-foil catalyst, as well as that of ethane\\/air mixtures on four noble-metal foil catalysts (Pt, Pd, Rh, and Ir) was studied at atmospheric pressure over the entire range of fuel-to-air ratios. While, Pd showed the widest range of surface flammability, ignition

Götz Veser; Murtaza Ziauddin; Lanny D. Schmidt

1999-01-01

338

Dynamics of stellar black holes in young star clusters with different metallicities - I. Implications for X-ray binaries  

NASA Astrophysics Data System (ADS)

We present N-body simulations of intermediate-mass (3000-4000 M?) young star clusters (SCs) with three different metallicities (Z = 0.01, 0.1 and 1 Z?), including metal-dependent stellar evolution recipes and binary evolution. Following recent theoretical models of wind mass-loss and core-collapse supernovae, we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars. In particular, massive metal-poor stars (Z ? 0.3 Z?) are enabled to form massive stellar black holes (MSBHs, with mass ?25 M?) through direct collapse. We find that three-body encounters, and especially dynamical exchanges, dominate the evolution of the MSBHs formed in our simulations. In SCs with Z = 0.01 and 0.1 Z?, about 75 per cent of simulated MSBHs form from single stars and become members of binaries through dynamical exchanges in the first 100 Myr of the SC life. This is a factor of ?3 more efficient than in the case of low-mass (<25 M?) stellar black holes. A small but non-negligible fraction of MSBHs power wind-accreting (10-20 per cent) and Roche lobe overflow (RLO, 5-10 per cent) binary systems. The vast majority of MSBH binaries that undergo wind accretion and/or RLO were born from dynamical exchange. This result indicates that MSBHs can power X-ray binaries in low-metallicity young SCs, and is very promising to explain the association of many ultraluminous X-ray sources with low-metallicity and actively star-forming environments.

Mapelli, M.; Zampieri, L.; Ripamonti, E.; Bressan, A.

2013-03-01

339

For cermet inert anode containing oxide and metal phases useful for the electrolytic production of metals  

DOEpatents

A cermet inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode comprises a ceramic phase including an oxide of Ni, Fe and M, where M is at least one metal selected from Zn, Co, Al, Li, Cu, Ti, V, Cr, Zr, Nb, Ta, W, Mo, Hf and rare earths, preferably Zn and/or Co. Preferred ceramic compositions comprise Fe.sub.2 O.sub.3, NiO and ZnO or CoO. The cermet inert anode also comprises a metal phase such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. A preferred metal phase comprises Cu and Ag. The cermet inert anodes may be used in electrolytic reduction cells for the production of commercial purity aluminum as well as other metals.

Ray, Siba P. (Murrysville, PA); Liu, Xinghua (Monroeville, PA); Weirauch, Douglas A. (Murrysville, PA)

2002-01-01

340

Predictions of binary sorption isotherms for the sorption of heavy metals by pine bark using single isotherm data  

Microsoft Academic Search

The adsorption of three heavy metal ions by pine bark was studied. The study was divided into two parts; single component adsorption of the metals Cu2+, Cd2+ and Ni2+ and bisolute adsorption of the three binary systems Cu2+?Cd2+, Cu2+?Ni2+ and Cd2+?Ni2+. Extended Langmuir model, extended Freundlich model, Sips model and ideal adsorption solution theory (IAST) models were used to predict

S Al-Asheh; F Banat; R Al-Omari; Z Duvnjak

2000-01-01

341

Efficient removal of trace arsenite through oxidation and adsorption by magnetic nanoparticles modified with Fe-Mn binary oxide.  

PubMed

Magnetic nanoparticles (MNPs) modified simultaneously with amorphous Fe and Mn oxides (Mag-Fe-Mn) were synthesized to remove arsenite [As(III)] from water. Mag-Fe-Mn particles were fabricated through heterogeneous nucleation technique by employing the maghemite as the magnetic core and Fe-Mn binary oxide (FMBO) as the coating materials. Powder X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy were utilized to characterize the hybrid material. With a saturation magnetization of 23.2 emu/g, Mag-Fe-Mn particles with size of 20-50 nm could be easily separated from solutions with a simple magnetic process in short time (within 5 min). At pH 7.0, 200 ?g/L of As(III) could be easily decreased to below 10 ?g/L by Mag-Fe-Mn particles (0.1 g/L) within 20 min. As(III) could be effectively removed by Mag-Fe-Mn particles at initial pH range from 4 to 8 and the residual As was completely oxidized to less toxic arsenate [As(V)]. The co-occurring redox reactions between Mn oxide and As(III) was confirmed by XPS analysis. Chloride, sulfate, bicarbonate, and nitrate at common concentration range had negligible influence on As(III) removal, whereas, silicate and phosphate reduced the As(III) removal by competing with arsenic species for adsorption sites. As(III) removal was not obviously affected by natural organic matter (up to 8 mg/L as TOC). Mag-Fe-Mn could be regenerated with ternary solution of NaOH, NaCl, and NaClO. Throughout five consecutive cycles, the adsorption and desorption efficiencies maintained above 98% and 87%, respectively. Mag-Fe-Mn had a larger adsorption capacity for As(III) (47.76 mg/g) and could remove trace As(III) more thoroughly than MNPs modified solely with either Fe or Mn oxide due to the synergistic effect of the coating Fe and Mn oxides. This research extended the potential applicability of FMBO to a great extent and provided a convenient approach to efficiently remove trace As(III) from water. PMID:23587265

Shan, Chao; Tong, Meiping

2013-06-15

342

Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles  

NASA Astrophysics Data System (ADS)

A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al2O3 and Fe3O4, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An

2014-06-01

343

Optical properties of transition metal oxide quantum wells  

NASA Astrophysics Data System (ADS)

Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/SrTiO3/SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered.

Lin, Chungwei; Posadas, Agham; Choi, Miri; Demkov, Alexander A.

2015-01-01

344

Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring  

PubMed Central

Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. PMID:22219672

Fine, George F.; Cavanagh, Leon M.; Afonja, Ayo; Binions, Russell

2010-01-01

345

Fabrication of porous materials (metal, metal oxide and semiconductor) through an aerosol-assisted route  

NASA Astrophysics Data System (ADS)

Porous materials have gained attraction owing to their vast applications in catalysts, sensors, energy storage devices, bio-devices and other areas. To date, various porous materials were synthesized through soft and hard templating approaches. However, a general synthesis method for porous non-oxide materials, metal alloys and semiconductors with tunable structure, composition and morphology has not been developed yet. To address this challenge, this thesis presents an aerosol method towards the synthesis of such materials and their applications for catalysis, hydrogen storage, Li-batteries and photo-catalysis. The first part of this thesis presents the synthesis of porous metals, metal oxides, and semiconductors with controlled pore structure, crystalline structure and morphology. In these synthesis processes, metal salts and organic ligands were employed as precursors to create porous metal-carbon frameworks. During the aerosol process, primary metal clusters and nanoparticles were formed, which were coagulated/ aggregated forming the porous particles. Various porous particles, such as those of metals (e.g., Ni, Pt, Co, Fe, and Ni xPt(1-x)), metal oxides (e.g., Fe3O4 and SnO2) and semiconductors (e.g., CdS, CuInS2, CuInS 2x-ZnS(1-x), and CuInS2x-TiO2(1-x)) were synthesized. The morphology, porous structure and crystalline structure of the particles were regulated through both templating and non-templating methods. The second part of this thesis explores the applications of these materials, including propylene hydrogenation and H2 uptake capacity of porous Ni, NiPt alloys and Ni-Pt composites, Li-storage of Fe3O4 and SnO2, photodegradation of CuInS2-based semiconductors. The effects of morphology, compositions, and porous structure on the device performance were systematically investigated. Overall, this dissertation work unveiled a simple synthesis approach for porous particles of metals, metal alloys, metal oxides, and semiconductors with controlled compositions and structures for broad spectrum of applications.

Sohn, Hiesang

346

Strengthening of metallic alloys with nanometer-size oxide dispersions  

DOEpatents

Austenitic stainless steels and nickel-base alloys containing, by wt. %, 0.1 to 3.0% V, 0.01 to 0.08% C, 0.01 to 0.5% N, 0.05% max. each of Al and Ti, and 0.005 to 0.10% O, are strengthened and ductility retained by atomization of a metal melt under cover of an inert gas with added oxygen to form approximately 8 nanometer-size hollow oxides within the alloy grains and, when the alloy is aged, strengthened by precipitation of carbides and nitrides nucleated by the hollow oxides. Added strengthening is achieved by nitrogen solid solution strengthening and by the effect of solid oxides precipitated along and pinning grain boundaries to provide temperature-stabilization and refinement of the alloy grains. 20 figs.

Flinn, J.E.; Kelly, T.F.

1999-06-01

347

Strengthening of metallic alloys with nanometer-size oxide dispersions  

DOEpatents

Austenitic stainless steels and nickel-base alloys containing, by wt. %, 0.1 to 3.0% V, 0.01 to 0.08% C, 0.01 to 0.5% N, 0.05% max. each of Al and Ti, and 0.005 to 0.10% O, are strengthened and ductility retained by atomization of a metal melt under cover of an inert gas with added oxygen to form approximately 8 nanometer-size hollow oxides within the alloy grains and, when the alloy is aged, strengthened by precipitation of carbides and nitrides nucleated by the hollow oxides. Added strengthening is achieved by nitrogen solid solution strengthening and by the effect of solid oxides precipitated along and pinning grain boundaries to provide temperature-stabilization and refinement of the alloy grains.

Flinn, John E. (Idaho Falls, ID); Kelly, Thomas F. (Madison, WI)

1999-01-01

348

The Development of Metal Oxide Chemical Sensing Nanostructures  

NASA Technical Reports Server (NTRS)

This paper discusses sensor development based on metal oxide nanostructures and microsystems technology. While nanostructures such as nanowires show significant potential as enabling materials for chemical sensors, a number of significant technical challenges remain. This paper discusses development to address each of these technical barriers: 1) Improved contact and integration of the nanostructured materials with microsystems in a sensor structure; 2) Control of nanostructure crystallinity to allow control of the detection mechanism; and 3) Widening the range of gases that can be detected by fabricating multiple nanostructured materials. A sensor structure composed of three nanostructured oxides aligned on a single microsensor has been fabricated and tested. Results of this testing are discussed and future development approaches are suggested. It is concluded that while this work lays the foundation for further development, these are the beginning steps towards realization of repeatable, controlled sensor systems using oxide based nanostructures.

Hunter, G. W.; VanderWal,R. L.; Xu, J. C.; Evans, L. J.; Berger, G. M.; Kulis, M. J.

2008-01-01

349

Dual-environment effects on the oxidation of metallic interconnects  

SciTech Connect

Metallic interconnects in solid oxide fuel cells are exposed to a dual environment: fuel on one side (i.e., H2 gas) and oxidizer on the other side (i.e., air). It has been observed that the oxidation behavior of thin stainless steel sheet in air is changed by the presence of H2 on the other side of the sheet. The resulting dual-environment scales are flaky and more friable than the single-environment scales. The H2 disrupts the scale on the air side. A model to explain some of the effects of a dual environment is presented where hydrogen diffusing through the stainless steel sheet reacts with oxygen diffusing through the scale to form water vapor, which has sufficient vapor pressure to mechanically disrupt the scale. Experiments on preoxidized 316L stainless steel tubing exposed to air-air, H2-air, and H2-Ar environments are reported in support of the model.

Holcomb, G.R.; Ziomek-Moroz, M.; Covino, B.S., Jr.; Bullard, S.J.

2006-08-01

350

Thermodynamic properties of some metal oxide-zirconia systems  

NASA Technical Reports Server (NTRS)

Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor species is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials.

Jacobson, Nathan S.

1989-01-01

351

Lithium Metal Oxide Electrodes For Lithium Cells And Batteries  

DOEpatents

A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2 M'O.sub.3 in which 0oxidation state and with at least one ion being Mn or Ni, and where M' is one or more ion with an average tetravalent oxidation state. Complete cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

Thackeray, Michael M. (Naperville, IL); Johnson, Christopher S. (Naperville, IL); Amine, Khalil (Downers Grove, IL); Kim, Jaekook (Naperville, IL)

2004-01-20

352

Lithium metal oxide electrodes for lithium cells and batteries  

DOEpatents

A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2M'O.sub.3 in which 0oxidation state and with at least one ion being Mn or Ni, and where M' is one or more ion with an average tetravalent oxidation state. Complete cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

Thackeray, Michael M. (Naperville, IL); Johnson, Christopher S. (Naperville, IL); Amine, Khalil (Oakbrook, IL)

2008-12-23

353

Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. I. Detailed analysis of 15 binary stars with known orbital periods  

E-print Network

AGB stars are responsible for producing a variety of elements, including carbon, nitrogen, and the heavy elements produced in the slow neutron-capture process ($s$-elements). There are many uncertainties involved in modelling the evolution and nucleosynthesis of AGB stars, and this is especially the case at low metallicity, where most of the stars with high enough masses to enter the AGB have evolved to become white dwarfs and can no longer be observed. The stellar population in the Galactic halo is of low mass ($\\lesssim 0.85M_{\\odot}$) and only a few observed stars have evolved beyond the first giant branch. However, we have evidence that low-metallicity AGB stars in binary systems have interacted with their low-mass secondary companions in the past. The aim of this work is to investigate AGB nucleosynthesis at low metallicity by studying the surface abundances of chemically peculiar very metal-poor stars of the halo observed in binary systems. To this end we select a sample of 15 carbon- and $s$-element-en...

Abate, C; Karakas, A I; Izzard, R G

2015-01-01

354

Nanostructured transition metal oxides for aqueous hybrid electrochemical supercapacitors  

NASA Astrophysics Data System (ADS)

In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the capacitance of the metal oxides and the cell voltage of the supercapacitor. It is shown that the cell voltage of an electrochemical supercapacitor can be increased significantly with the use of hybrid systems. The most relevant associations are Fe3O4 or activated carbon as the negative electrode and MnO2 as the positive. The cell voltage of the Fe3O4/MnO2 device is 1.8 V and this value was increased to 2.2 V by using activated carbon instead of Fe3O4. These two systems have shown superior behavior compared to a symmetric MnO2/MnO2 device which only works within a 1 V potential window in aqueous K2SO4. Furthermore, the activated carbon/MnO2 hybrid device exhibits a real power density of 605 W/kg (maximum power density =19.0 kW/kg) with an energy density of 17.3 Wh/kg. These values compete well with those of standard electrochemical double layer capacitors working in organic electrolytes.

Cottineau, T.; Toupin, M.; Delahaye, T.; Brousse, T.; Bélanger, D.

2006-03-01

355

Determination of Systems Suitable for Study as Monotectic Binary Metallic Alloy Solidification Models  

NASA Technical Reports Server (NTRS)

Succinonitrile-water and diethylene glycol-ethyl salicylate are two transparent systems which have been studied as monotectic binary metallic alloy solidification models. Being transparent, these systems allow for the direct observations of phase transformations and solidification reactions. The objective was to develop a screening technique to find systems of interest and then experimentally measure those systems. The succinonitrile-water system was used to check the procedures. To simulate the phase diagram of the system, two computer programs which determine solid-liquid and liquid-liquid equilibria were obtained. These programs use the UNIFAC method to determine activity coefficients and together with several other programs were used to predict the phase diagram. An experimental apparatus was developed and the succinonitrile-water phase diagram measured. The diagram was compared to both the simulation and literature data. Substantial differences were found in the comparisons which serve to demonstrate the need for this procedure.

Smith, J. E., Jr.

1983-01-01

356

Nanomechanical switches based on metal-insulator-metal capacitors from a standard complementary-metal-oxide semiconductor technology  

NASA Astrophysics Data System (ADS)

We report experimental demonstrations of contact-mode nano-electromechanical switches obtained using a capacitor module based on metal-insulator-metal configuration of a standard commercial complementary metal oxide semiconductor technology. The developed 2 terminals Titanium Nitride switches operate at low voltages (˜10 V) thanks to its small gap (27 nm), showing an excellent ION/IOFF ratio (104) and abrupt behavior (5 mV/decade, one decade of current change is achieved with a 5 mV voltage variation). A switch configuration is also presented where using two electrodes three different contact mode states can be obtained, adding functionalities to mechanical switches configurations.

Muñoz-Gamarra, J. L.; Uranga, A.; Barniol, N.

2014-06-01

357

Custom-designed nanomaterial libraries for testing metal oxide toxicity  

PubMed Central

Conspectus Advances in aerosol technology over the past 10 years have provided methods that enable the generation and design of ultrafine nanoscale materials for different applications. The particles are produced combusting a precursor solution and its chemical reaction in the in the gas phase. Flame spray pyrolysis (FSP) is a highly versatile technique for single step and scalable synthesis of nanoscale materials. New innovations in particle synthesis using FSP technology and its precursor chemistry have enabled flexible dry synthesis of loosely-agglomerated highly crystalline ultrafine powders (porosity ? 90%) of binary, ternary and mixed binary or ternary oxides. The flame spray pyrolysis lies at the intersection of combustion science, aerosols technology and materials chemistry. The interdisciplinary research is not only inevitable but is becoming increasingly crucial in the design of nanoparticles (NPs) made in the gas phase. The increasing demand especially in the bio-applications for particles with specific material composition, high purity and crystallinity can be often fulfilled with the fast, single step FSP technique. PMID:23194152

Pokhrel, Suman; Nel, André E.; Mädler, Lutz

2014-01-01

358

Metal thin film growth on multimetallic surfaces: From quaternary metallic glass to binary crystal  

SciTech Connect

The work presented in this thesis mainly focuses on the nucleation and growth of metal thin films on multimetallic surfaces. First, we have investigated the Ag film growth on a bulk metallic glass surface. Next, we have examined the coarsening and decay of bilayer Ag islands on NiAl(110) surface. Third, we have investigated the Ag film growth on NiAl(110) surface using low-energy electron diffraction (LEED). At last, we have reported our investigation on the epitaxial growth of Ni on NiAl(110) surface. Some general conclusions can be drawn as follows. First, Ag, a bulk-crystalline material, initially forms a disordered wetting layer up to 4-5 monolayers on Zr-Ni-Cu-Al metallic glass. Above this coverage, crystalline 3D clusters grow, in parallel with the flatter regions. The cluster density increases with decreasing temperature, indicating that the conditions of island nucleation are far-from-equilibrium. Within a simple model where clusters nucleate whenever two mobile Ag adatoms meet, the temperature-dependence of cluster density yields a (reasonable) upper limit for the value of the Ag diffusion barrier on top of the Ag wetting layer of 0.32 eV. Overall, this prototypical study suggests that it is possible to grow films of a bulk-crystalline metal that adopt the amorphous character of a glassy metal substrate, if film thickness is sufficiently low. Next, the first study of coarsening and decay of bilayer islands has been presented. The system was Ag on NiAl(110) in the temperature range from 185 K to 250 K. The coarsening behavior, has some similarities to that seen in the Ag(110) homoepitaxial system studied by Morgenstern and co-workers. At 185 K and 205 K, coarsening of Ag islands follows a Smoluchowski ripening pathway. At 205 K and 250 K, the terrace diffusion limited Ostwald ripening dominants. The experimental observed temperature for the transition from SR to OR is 205 K. The SR exhibits anisotropic island diffusion and the OR exhibits 1D decay of island length while keeping the corresponding island width constant. Third, LEED indicates that, up to about 6 BL (12 ML), the Ag film adopts the (110) structure on lattice matched NiAl(110) surface, supporting the previous assignment based upon island heights measured in STM. Starting at 4.5 to 6 BL, (111) diffraction pattern is detected. This is also in agreement with previous STM study. Careful examinations of the LEED patterns reveal the slight difference in lattice constants between bulk Ag and bulk NiAl. At last, we performed STM studies of Ni deposition on NiAl(110) in the temperature range from 200 K to 400 K. Ni forms 'dense' Ni(100)-like islands on NiAl(110) with a zig-zag shaped stripe feature which is probably due to strain relief. DFT analysis provides insights into the island growth shapes, which are rationalized by the thermodynamics and kinetics of the film growth process. For thick Ni films (coverage exceeding 6 ML), a Ni(111)-like structure developed. Traditional MF theory is applied to analyze island density at 200 K. Deviation from homogeneous nucleation behavior for island size distribution and island density reveals the presence of heterogeneous nucleation mediated by the Ni antisite point defects on NiAl(110) surface.

Jing, Dapeng

2010-12-15

359

Microstructure and mechanical behavior of metal injection molded Ti-Nb binary alloys as biomedical material.  

PubMed

The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti-6Al-4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong ? stabilizing effect in Ti alloys, which makes Ti-Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti-Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti-Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti-Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility. PMID:23994942

Zhao, Dapeng; Chang, Keke; Ebel, Thomas; Qian, Ma; Willumeit, Regine; Yan, Ming; Pyczak, Florian

2013-12-01

360

Hydrocracking and hydroisomerization of long-chain alkanes and polyolefins over metal-promoted anion-modified transition metal oxides  

SciTech Connect

A method is described for cracking a feedstock by contacting the feedstock with a metal-promoted anion-modified metal oxide catalyst in the presence of hydrogen gas. The metal oxide of the catalyst is one or more of ZrO{sub 2}, HfO{sub 2}, TiO{sub 2} and SnO{sub 2}, and the feedstock is principally chains of at least 20 carbon atoms. The metal-promoted anion-modified metal oxide catalyst contains one or more of Pt, Ni, Pd, Rh, Ir, Ru, (Mn and Fe) or mixtures of them present between about 0.2% to about 15% by weight of the catalyst. The metal-promoted anion-modified metal oxide catalyst contains one or more of SO{sub 4}, WO{sub 3}, or mixtures of them present between about 0.5% to about 20% by weight of the catalyst.

Venkatesh, Koppampatti R.; Hu, Jianli; Tierney, John W.; Wender, Irving

1996-12-01

361

Hydrocracking and hydroisomerization of long-chain alkanes and polyolefins over metal-promoted anion-modified transition metal oxides  

DOEpatents

A method of cracking a feedstock by contacting the feedstock with a metal-promoted anion-modified metal oxide catalyst in the presence of hydrogen gas. The metal oxide of the catalyst is one or more of ZrO.sub.2, HfO.sub.2, TiO.sub.2 and SnO.sub.2, and the feedstock is principally chains of at least 20 carbon atoms. The metal-promoted anion-modified metal oxide catalyst contains one or more of Pt, Ni, Pd, Rh, Ir, Ru, (Mn & Fe) or mixtures of them present between about 0.2% to about 15% by weight of the catalyst. The metal-promoted anion-modified metal oxide catalyst contains one or more of SO.sub.4, WO.sub.3, or mixtures of them present between about 0.5% to about 20% by weight of the catalyst.

Venkatesh, Koppampatti R. (Pittsburgh, PA); Hu, Jianli (Cranbury, NJ); Tierney, John W. (Pittsburgh, PA); Wender, Irving (Pittsburgh, PA)

2001-01-01

362

Metal/metal oxide doped oxide catalysts having high deNOx selectivity for lean NOx exhaust aftertreatment systems  

DOEpatents

A lean NOx catalyst and method of preparing the same is disclosed. The lean NOx catalyst includes a ceramic substrate, an oxide support material, preferably .gamma.-alumina, deposited on the substrate and a metal promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium, cerium, vanadium, oxides thereof, and combinations thereof. The .gamma.-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between about 80 to 350 m.sup.2 /g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to 0.2 weight percent. In a preferred embodiment the .gamma.-alumina is prepared by a sol-gel method, with the metal doping of the .gamma.-alumina preferably accomplished using an incipient wetness impregnation technique.

Park, Paul W.

2004-03-16

363

Development of structure-activity relationship for metal oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Nanomaterial structure-activity relationships (nano-SARs) for metal oxide nanoparticles (NPs) toxicity were investigated using metrics based on dose-response analysis and consensus self-organizing map clustering. The NP cellular toxicity dataset included toxicity profiles consisting of seven different assays for human bronchial epithelial (BEAS-2B) and murine myeloid (RAW 264.7) cells, over a concentration range of 0.39-100 mg L-1 and exposure time up to 24 h, for twenty-four different metal oxide NPs. Various nano-SAR building models were evaluated, based on an initial pool of thirty NP descriptors. The conduction band energy and ionic index (often correlated with the hydration enthalpy) were identified as suitable NP descriptors that are consistent with suggested toxicity mechanisms for metal oxide NPs and metal ions. The best performing nano-SAR with the above two descriptors, built with support vector machine (SVM) model and of validated robustness, had a balanced classification accuracy of ~94%. An applicability domain for the present data was established with a reasonable confidence level of 80%. Given the potential role of nano-SARs in decision making, regarding the environmental impact of NPs, the class probabilities provided by the SVM nano-SAR enabled the construction of decision boundaries with respect to toxicity classification under different acceptance levels of false negative relative to false positive predictions.Nanomaterial structure-activity relationships (nano-SARs) for metal oxide nanoparticles (NPs) toxicity were investigated using metrics based on dose-response analysis and consensus self-organizing map clustering. The NP cellular toxicity dataset included toxicity profiles consisting of seven different assays for human bronchial epithelial (BEAS-2B) and murine myeloid (RAW 264.7) cells, over a concentration range of 0.39-100 mg L-1 and exposure time up to 24 h, for twenty-four different metal oxide NPs. Various nano-SAR building models were evaluated, based on an initial pool of thirty NP descriptors. The conduction band energy and ionic index (often correlated with the hydration enthalpy) were identified as suitable NP descriptors that are consistent with suggested toxicity mechanisms for metal oxide NPs and metal ions. The best performing nano-SAR with the above two descriptors, built with support vector machine (SVM) model and of validated robustness, had a balanced classification accuracy of ~94%. An applicability domain for the present data was established with a reasonable confidence level of 80%. Given the potential role of nano-SARs in decision making, regarding the environmental impact of NPs, the class probabilities provided by the SVM nano-SAR enabled the construction of decision boundaries with respect to toxicity classification under different acceptance levels of false negative relative to false positive predictions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01533e

Liu, Rong; Zhang, Hai Yuan; Ji, Zhao Xia; Rallo, Robert; Xia, Tian; Chang, Chong Hyun; Nel, Andre; Cohen, Yoram

2013-05-01

364

Characterization, sorption, and exhaustion of metal oxide nanoparticles as metal adsorbents  

NASA Astrophysics Data System (ADS)

Safe drinking water is paramount to human survival. Current treatments do not adequately remove all metals from solution, are expensive, and use many resources. Metal oxide nanoparticles are ideal sorbents for metals due to their smaller size and increased surface area in comparison to bulk media. With increasing demand for fresh drinking water and recent environmental catastrophes to show how fragile water supplies are, new approaches to water conservation incorporating new technologies like metal oxide nanoparticles should be considered as an alternative method for metal contaminant adsorbents from typical treatment methods. This research evaluated the potential of manufactured iron, anatase, and aluminum nanoparticles (Al2O3, TiO2, Fe2O3) to remove metal contaminants (Pb, Cd, Cu, Ni, Zn) in lab-controlled and natural waters in comparison to their bulk counterparts by focusing on pH, contaminant and adsorbent concentrations, particle size, and exhaustive capabilities. Microscopy techniques (SEM, BET, EDX) were used to characterize the adsorbents. Adsorption experiments were performed using 0.01, 0.1, or 0.5 g/L nanoparticles in pH 8 solution. When results were normalized by mass, nanoparticles adsorbed more than bulk particles but when surface area normalized the opposite was observed. Adsorption was pH-dependent and increased with time and solid concentration. Aluminum oxide was found to be the least acceptable adsorbent for the metals tested, while titanium dioxide anatase (TiO2) and hematite (alpha-Fe2O3) showed great ability to remove individual and multiple metals from pH 8 and natural waters. Intraparticle diffusion was likely part of the complex kinetic process for all metals using Fe2O3 but not TiO 2 nanoparticles within the first hour of adsorption. Adsorption kinetics for all metals tested were described by a modified first order rate equation used to consider the diminishing equilibrium metal concentrations with increasing metal oxides, showing faster adsorption rates for nanoparticles compared to bulk particles. Isotherms were best fit with most correlations of r=0.99 or better using the Langmuir-Freundlich equation which describes a heterogeneous surface with monolayer adsorption. Calculated rate constants and distribution coefficients (Kd) showed TiO2 nanoparticles were very good sorbents and more rapid in removing metals than other nanoparticles studied here and reported in the literature. Desorption studies concluded Pb, Cd, and Zn appear to be irreversibly sorbed to TiO2 surfaces at pH 8. TiO2 and Fe2O3 nanoparticles were capable of multiple metal loadings, with exhaustion for both adsorbents at pH 6. Exhaustion studies at pH 8 showed hematite exhausted after four consecutive cycles while anatase showed no exhaustion after 8 cycles. Their bulk counterparts exhausted in earlier cycles indicating the lack of ability to adsorb much of the multiple metals in solution. The increased surface area of TiO2 and Fe 2O3 nanoparticles, coupled with strong adsorption at the pH of most natural waters and resistance to desorption of some metals, may offer a potential remediation method for removal of metals from water in the future.

Engates, Karen Elizabeth

365

An exploratory study of diesel soot oxidation with NO 2 and O 2 on supported metal oxide catalysts  

Microsoft Academic Search

A number of supported metal oxide catalysts were screened for their catalytic performance for the oxidation of carbon black (CB; a model diesel soot) using NO2 as the main oxidant. It was found that contact between the carbon and catalyst was a key factor in determining the rate of oxidation by NO2. Oxides with low melting points, such as Re2O7,

Shetian Liu; Akira Obuchi; Junko Uchisawa; Tetsuya Nanba; Satoshi Kushiyama

2002-01-01

366

THE RÔLE OF CERTAIN METALLIC IONS AS OXIDATION CATALYSTS  

PubMed Central

1. When iron and copper are allowed to act on hydrogen peroxide and pyrogallol, enough carbon dioxide is produced to be readily measured. 2. The curve of the production of carbon dioxide may be fitted by an empirical equation, by the use of which the initial rate and the total amount of the oxidation may be determined. 3. The effect of the concentration of the reagents is different in each case, the effect varying as a fractional power of the copper and pyrogallol concentrations and as a logarithmic function of the hydrogen peroxide concentration. 4. When gold or silver is used the rate changes suddenly during the course of the reaction due to the precipitation of colloidal metal. 5. Mercury, cadmium, zinc, tin, and some other metals have no effect. 6. A theoretical set of equations is assumed to account for the action of the metals. 7. The metals are assumed to act by means of the formation of intermediate peroxides. 8. Experiments on the action of gold indicate that the metals are active in the ionic and not in the colloidal state. PMID:19872322

Cook, S. F.

1926-01-01

367

Transition metal oxides deposited on rhodium and platinum: Surface chemistry and catalysis  

SciTech Connect

The surface chemistry and catalytic reactivity of transition metal oxides deposited on Rh and Pt substrates has been examined in order to establish the role of oxide-metal interactions in influencing catalytic activity. The oxides investigated included titanium oxide (TiOx), vanadium oxide (VOx), iron oxide (FeOx), zirconium oxide (ZrOx), niobium oxide (NbOx), tantalum oxide (TaOx), and tungsten oxide (WOx). The techniques used to characterize the sample included AES, XPS, LEED, TPD, ISS, and STM. After characterization of the surface in UHV, the sample was enclosed in an atmospheric reaction cell to measure the influence of the oxide deposits on the catalytic activity of the pure metal for CO and CO{sub 2} hydrogenation. The oxide deposits were found to strongly enhance the reactivity of the Rh foil. The rates of methane formation were promoted by up to 15 fold with the maximum in rate enhancement occurring at oxide coverages of approximately 0.5 ML. TiOx TaOx, and NbOx were the most effective promoters and were stable in the highest oxidation states during both reactions (compared to VOx, WOx, and FeOx). The trend in promoter effectiveness was attributed to the direct relationship between oxidation state and Lewis acidity. Bonding at the metal oxide/metal interface between the oxygen end of adsorbed CO and the Lewis acidic oxide was postulated to facilitate C-O bond dissociation and subsequent hydrogenation. 192 refs.

Boffa, A.B. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Materials Sciences Div.

1994-07-01

368

Non-equilibrium oxidation states of zirconium during early stages of metal oxidation  

NASA Astrophysics Data System (ADS)

The chemical state of Zr during the initial, self-limiting stage of oxidation on single crystal zirconium (0001), with oxide thickness on the order of 1 nm, was probed by synchrotron x-ray photoelectron spectroscopy. Quantitative analysis of the Zr 3d spectrum by the spectrum reconstruction method demonstrated the formation of Zr1+, Zr2+, and Zr3+ as non-equilibrium oxidation states, in addition to Zr4+ in the stoichiometric ZrO2. This finding resolves the long-debated question of whether it is possible to form any valence states between Zr0 and Zr4+ at the metal-oxide interface. The presence of local strong electric fields and the minimization of interfacial energy are assessed and demonstrated as mechanisms that can drive the formation of these non-equilibrium valence states of Zr.

Ma, Wen; Herbert, F. William; Senanayake, Sanjaya D.; Yildiz, Bilge

2015-03-01

369

Synthesis of mesoporous metal oxide by the thermal decomposition of oxalate precursor.  

PubMed

A synthesis method was newly developed to prepare mesoporous transition metal oxides by thermal decomposition of transition metal oxalates, and the method was advantageous in its versatility, low cost, and environmental friendliness. Various mesoporous transition metal oxides were successfully synthesized by the newly developed method, such as magnetic ?-Fe2O3, CoFe2O4, and NiFe2O4, MnxOy, Co3O4, and NiO. Morphology, structure, and magnetic property of the synthesized mesoporous transition metal oxides were characterized by XRD, TG-DTA, SEM, TEM, quantum design SQUID, and N2 sorption techniques. From the dependency of the heating rate, calcination time, and calcination temperature on the metal oxide structures, it was revealed that the calcination temperature was the major factor to determine the final mesoporous structure of the metal oxides. The mesoporous structures were well constructed by their corresponding metal oxide nanoparticles resulting from oxalate thermal decomposition. PMID:23480232

Guo, Limin; Arafune, Hiroyuki; Teramae, Norio

2013-04-01

370

Effect of metallicity on the gravitational-wave signal from the cosmological population of compact binary coalescences  

NASA Astrophysics Data System (ADS)

Context. Recent studies on stellar evolution have shown that the properties of compact objects strongly depend on the metallicity of the environment in which they were formed. Aims: Using some very simple assumptions on the metallicity of the stellar populations, we explore how this property affects the unresolved gravitational-wave background from extragalactic compact binaries. Methods: We obtained a suit of models using population synthesis code, estimated the gravitational-wave background they produce, and discuss its detectability with second- (advanced LIGO, advanced Virgo) and third- (Einstein Telescope) generation detectors. Results: Our results show that the background is dominated by binary black holes for all considered models in the frequency range of terrestrial detectors, and that it could be detected in most cases by advanced LIGO/Virgo, and with Einstein Telescope with a very high signal-to-noise ratio. The observed peak in a gravitational-wave spectrum depends on the metallicity of the stellar population.

Kowalska-Leszczynska, I.; Regimbau, T.; Bulik, T.; Dominik, M.; Belczynski, K.

2015-02-01

371

Effects of reduction of metal oxide sorbents on reactivity and physical properties during hot gas desulphurization in IGCC  

Microsoft Academic Search

In this study, the changes of physical properties and reactivity of the metal oxide sorbents were investigated under the reducing conditions of coal gas. Metal oxide sorbents are converted into metal sulphides as a result of reaction with H2S in synthesis gas. This could cause the reduced reactivity of sorbents if the metal oxides were converted into metallic elements due

No-Kuk Park; Dong-Hwal Lee; Jong-Dae Lee; Si-Ok Ryu; Tae-Jin Lee

2005-01-01

372

Magnetic preferential orientation of metal oxide superconducting materials  

DOEpatents

A superconductor comprised of a polycrystalline metal oxide such as YBa[sub 2]Cu[sub 3]O[sub 7[minus]X] (where 0 < X < 0.5) exhibits superconducting properties and is capable of conducting very large current densities. By aligning the two-dimensional Cu-O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the conduction of high current densities. The highly anisotropic diamagnetic susceptibility of the polycrystalline metal oxide material permits the use of an applied magnetic field to orient the individual crystals when in the superconducting state to substantially increase current transport between adjacent grains. In another embodiment, the anisotropic paramagnetic susceptibility of rare-earth ions substituted into the oxide material is made use of as an applied magnetic field orients the particles in a preferential direction. This latter operation can be performed with the material in the normal (non-superconducting) state. 4 figs.

Capone, D.W.; Dunlap, B.D.; Veal, B.W.

1990-07-17

373

(S)TEM analysis of functional transition metal oxides  

NASA Astrophysics Data System (ADS)

Perovskite vanadates (AVO3) form an ideal family to study the structure-property relationships in transition metal oxides because their physical properties can easily be tailored by varying the A-site cations. (S)TEM is an ideal tool for this type of study due to its capacity for simultaneous imaging and chemical analysis. Determination of the oxidation state of vanadium in complex oxides have been carried out by electron energy loss spectroscopy. SrVO3/LaAlO3 is then studied both experimentally and theoretically as a prototype system. Extra electrons have been detected on the interface layer, and further proven to originate mainly from a change in the local bonding configuration of V at the La-O terminated substrate surface. Cr-containing stainless steel deposited with a LaCrO3 thin-film layer is a promising interconnect material of Solid Oxide Fuel Cells (SOFC). Our investigation on its microstructural evolution reveals that the LaCrO 3 thin film plays a role in inhibiting the growth of an oxide layer on the metal surface and thus protects the surface of the stainless steel. Ca-doped LaCoO3 is a promising SOFC cathode material. The domain structures and the oxidation state of Co in Ca-doped LaCoO3, which are directly related to its mechanical properties and electronic conductivity, are investigated by in-situ TEM and EELS. The formation of microcracks is observed during thermal cycles. Ca-doping in LaCoO3 is shown to not only improve the electronic conductivity of the material, but is also likely to strengthen the grain boundaries. The realization of its application in SOFCs depends on depressing the ferroelastisity to reduce strain formation during thermal cycles. The application of the (S)TEM techniques used for studying the perovskite systems are further extended to other compounds containing transition metal elements. The refractory minerals from Comet 81 P/Wild-2 are studied to investigate the formation of the early solar system. A relatively high Ti3+/Ti 4+ ratio in fassaite and the presence of osbornite indicate that the Comet refractory minerals formed in the inner solar nebula and were later transported to the outer solar system where the comet formed. This implies a much more dynamic and perhaps more violent solar nebula than was previously suspected.

Chi, Miaofang

374

Preparation of Binary and Ternary Oxides by Molten Salt Method and its Electrochemical Properties  

NASA Astrophysics Data System (ADS)

We report simple binary oxides namely SnO2, TiO2, CuO, MnO2, Fe2O3, Co3O4 and ternary oxides like MnCo2O4 by molten salt method at a temperature range of 280°C to 950°C in air and discuss the effect of morphology, crystal structure and electrochemical properties of binary and ternary oxides. Materials were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods. XRD patterns showed all MSM prepared materials exhibited characteristic lattice parameter values. BET surface area varies depending on the nature of the material, molten salt and preparation temperature and the obtained values are in the range, 1 to 160 m2/g. Electrochemical properties were studied using cyclic voltammetry (CV) and electrochemical performance studies were carried in the voltage range, 0.005-1.0V for SnO2, 1.0-2.8V for TiO2 and Fe2O3, MCo2O4 (M = Co, Mn), MnO2 and CuO were cycled in the range, 0.005-3.0V. At a current rates of 30-100 mA/g and a scan rate of 0.058 mV/sec was used for galvanostatic cycling and cyclic voltammetry. SnO2 showed that an alloying-de-alloying reaction occurs at ˜0.2 and ˜0.5 V vs. Li. TiO2 main intercalation and de-interaction reactions at ˜1.7 and ˜1.8 V vs. Li. Co3O4, MnCo2O4, and MnO2 main discharge potentials at ˜1.2, 0.9V and 0.4V, resp. and charge potentials peak ˜2.0V and 1.5V vs. Li. CuO prepared at 750°C exhibited main anodic peak at ˜2.45V and cathodic peaks at ˜0.85V and ˜1.25V. We discussed the possible reaction mechanisms and Li-storage performance values in detail.

Reddy, M. V.; Theng, L. Pei; Soh, Hulbert; Beichen, Z.; Jiahuan, F.; Yu, C.; Ling, A. Yen; Andreea, L. Y.; Ng, C. H. Justin; Liang, T. J. L. Galen; Ian, M. F.; An, H. V. T.; Ramanathan, K.; Kevin, C. W. J.; Daryl, T. Y. W.; Hao, T. Yi; Loh, K. P.; Chowdari, B. V. R.

2013-07-01

375

Stress-induced roughness development during oxide scale growth on a metallic alloy for SOFC interconnects  

Microsoft Academic Search

The metallic alloys employed in solid oxide fuel cell (SOFC) interconnects rely on the growth of a protective oxide scale to sustain the aggressive functioning environment at high temperature. The morphology of the oxide\\/metal interface is critical to the mechanical resistance of the material system upon cooling and therefore to the component lifetime. This work investigates the development of a

Audric Saillard; Mohammed Cherkaoui; Haitham El Kadiri

2011-01-01

376

40 CFR 62.14103 - Emission limits for municipal waste combustor metals, acid gases, organics, and nitrogen oxides.  

Code of Federal Regulations, 2010 CFR

...combustor metals, acid gases, organics, and nitrogen oxides. 62.14103 Section 62...metals, acid gases, organics, and nitrogen oxides. (a) The emission limits...affected facility any gases that contain nitrogen oxides in excess of the emission...

2010-07-01

377

40 CFR 62.14103 - Emission limits for municipal waste combustor metals, acid gases, organics, and nitrogen oxides.  

Code of Federal Regulations, 2013 CFR

...combustor metals, acid gases, organics, and nitrogen oxides. 62.14103 Section 62...metals, acid gases, organics, and nitrogen oxides. (a) The emission limits...affected facility any gases that contain nitrogen oxides in excess of the emission...

2013-07-01

378

40 CFR 62.14103 - Emission limits for municipal waste combustor metals, acid gases, organics, and nitrogen oxides.  

Code of Federal Regulations, 2014 CFR

...combustor metals, acid gases, organics, and nitrogen oxides. 62.14103 Section 62...metals, acid gases, organics, and nitrogen oxides. (a) The emission limits...affected facility any gases that contain nitrogen oxides in excess of the emission...

2014-07-01

379

40 CFR 62.14103 - Emission limits for municipal waste combustor metals, acid gases, organics, and nitrogen oxides.  

Code of Federal Regulations, 2011 CFR

...combustor metals, acid gases, organics, and nitrogen oxides. 62.14103 Section 62...metals, acid gases, organics, and nitrogen oxides. (a) The emission limits...affected facility any gases that contain nitrogen oxides in excess of the emission...

2011-07-01

380

40 CFR 62.14103 - Emission limits for municipal waste combustor metals, acid gases, organics, and nitrogen oxides.  

Code of Federal Regulations, 2012 CFR

...combustor metals, acid gases, organics, and nitrogen oxides. 62.14103 Section 62...metals, acid gases, organics, and nitrogen oxides. (a) The emission limits...affected facility any gases that contain nitrogen oxides in excess of the emission...

2012-07-01

381

VO2 films with strong semiconductor to metal phase transition prepared by the precursor oxidation process  

E-print Network

VO2 films with strong semiconductor to metal phase transition prepared by the precursor oxidation, the precursor oxidation process, for making VO2 films with strong semiconductor-to-metal phase transition and sharpness hysteresis width TC of T-dependent semiconductor-to-metal hysteretic phase transition in VO2 were

Luryi, Serge

382

Characterization of the metal-binding site of human prolactin by site-specific metal-catalyzed oxidation  

Microsoft Academic Search

Site-specific metal-catalyzed oxidation (MCO) was applied to characterize the metal-binding site (MBS) of recombinant human prolactin (hPRL), which belongs to the hematopoietic cytokine family. Copper and ascorbate of various concentrations were used to initiate the oxidation of hPRL, and the oxidation-sensitive motifs were characterized and quantitated by mass spectrometry. Based on the results obtained with 10?M Cu2+ and 0.3–2.0mM ascorbate,

Vikram Sadineni; Nadezhda A. Galeva; Christian Schöneich

2006-01-01

383

[Preparation of cobalt oxide mesoporous metallic oxide-clay composites and their catalytic performance in the oxidation of benzene].  

PubMed

Laponite clays composited with alumina, ceria and zirconia etc. were prepared using polyoxocations or simple metal ions as precursors, and then cobalt oxide was loaded onto them to obtain the catalysts. The results showed that compared with laponite clays, the as-prepared laponite had wide range of pore size distribution and increased pore volume. The pore volumes of laponite clays composited with alumina and ceria were more than 0.75 cm3 · g(-1). N2 isotherm type was maintained after Co3O4 loading, however, the N2 adsorption decreased with the increase of Co3 O4 loading, indicating the decrease of pore volume, which was caused by the blockage of metallic oxide/clay composites support. Furthermore, dispersion and catalytic performance of the catalysts were significantly influenced by the composited metallic elements. It was shown that according to the diffraction peak half-width of 311 crystal facet and scherrer equation, when the Co loading was 21.3% at laponite clays composited with Fe, Zr, Ce, Al, the average sizes of Co3O4 were 17.2, 16.0, 16.5 and 18.0 nm, respectively. Alumina composited clay with 21.3% Co loading showed high catalytic activity, the complete conversion temperature of benzene was 350°C. Among metallic oxide/laponite composites, the ZrO composited laponite with 21.3% Co loading exhibited the best catalytic performance, which could completely convert benzene at 310°C. PMID:25693410

Mu, Zhen; Ma, Chun-Yan; Cheng, Jie; Li, Jin-Jun

2014-10-01

384

Measurements of Total Hemispherical Emissivity of Several Stably Oxidized Metals and Some Refractory Oxide Coatings  

NASA Technical Reports Server (NTRS)

A description of the apparatus and methods used for obtaining total hemispherical emissivity is presented, and data for several stably oxidized metals are included. The metals which were tested included type 347 stainless steel, tungsten, and Haynes alloys B, C, X, and 25. No values of emissivity were obtained for tungsten or Haynes alloy B because of the nature of the oxides produced. The refractory oxide coatings tested were flame-sprayed alumina and zirconia. The results of the investigation indicate that strongly adherent, oxidized surfaces of a high stable emissivity can be produced on type 347 stainless steel for which the total hemispherical emissivity varied from 0.87 to 0.91 for temperatures from 600 F to 2,000 F. For this same temperature range, the Haynes alloys tested showed values of total hemispherical emissivity from 0.90 to 0.96 for alloy C, from 0.85 to 0.88 for alloy X, and from 0.85 to 0.89 for alloy 25. Haynes alloy B and tungsten formed nonadherent oxides at elevated temperatures and, therefore, stable emissivities were not obtained. The results obtained for the flame-sprayed ceramics (alumina and zirconia) showed considerably higher values of total emissivity than those measured for coatings applied by other methods. Emissivity values ranging from 0.69 to 0.44 for aluminum oxide and from 0.62 to 0.44 for zirconium oxide were measured for temperatures from 800 F to 2,000 F.

Wade, William R.

1959-01-01

385

? and ? phases in binary rhenium-transition metal systems: a systematic first-principles investigation.  

PubMed

The Frank-Kasper phases, known as topologically close-packed (tcp) phases, are interesting examples of intermetallic compounds able to accommodate large homogeneity ranges by atom mixing on different sites. Among them, the ? and ? phases present two competing complex crystallographic structures, the stability of which is driven by both geometric and electronic factors. Rhenium (Re) is the element forming the largest number of binary ? and ? phases. Its central position among the transition metals in the periodic table plays an important role in the element ordering in tcp phases. Indeed, it has been shown that Re shows an opposite site preference depending on which elements it is alloyed with. In the present work, ?- and ?-phase stability in binary Re-X systems is systematically studied by a first-principles investigation. The heats of formation of the complete set of ordered configurations (16 for ? and 32 for ?) have been calculated in 16 well-chosen systems to identify stability criteria. They include not only the systems in which ?-Re-X (X = Ti, Mn, Zr, Nb, Mo, Hf, Ta, W) or ?-Re-X (X = V, Cr, Mn, Fe, Nb, Mo, Ta, W) exist but also the systems in which both phases are not stable, including systems in which X is a 3d element from Ti to Ni, a 4d element from Zr to Ru, and a 5d element from Hf to Os. Careful analysis is done of the energetic tendencies as a function of recomposition, size effect, and electron concentration. Moreover, the site preference and other crystallographic properties are discussed. Conclusions are drawn concerning the relative stability of the two phases in comparison with the available experimental knowledge on the systems. PMID:23477863

Crivello, Jean-Claude; Breidi, Abedalhasan; Joubert, Jean-Marc

2013-04-01

386

Magnetic behavior of reduced graphene oxide/metal nanocomposites  

NASA Astrophysics Data System (ADS)

The dispersion of metal nanoparticles on reduced graphene oxide (RGO) sheets potentially provides a new way to develop novel catalytic, magnetic, adsorbing, and electrode materials. In this work, we report the structural and magnetic properties of RGO/metal (Bi, Pt, Ni, and Pt-Ni) nanocomposites. Such nanocomposites are successfully synthesized by a facile in situ co-reduction route. The structure, composition, and morphology of the synthesized materials are systematically investigated by X-ray diffraction, inductively coupled plasma-atomic emission spectrometer , and high resolution transmission electronic microscopy. The M-H curve and zero-field-cooled and field-cooled data for RGO, RGO/Ni, and RGO/Pt-Ni nanocomposites exhibit ferromagnetic behaviour. RGO/Pt nanocomposite shows diamagnetic, while RGO/Bi nanocomposite shows lower magnetization compared to that of RGO. Detailed magnetic studies on these nanocomposites and its correlation with microstructural features are presented here.

Sahoo, P. K.; Panigrahy, Bharati; Li, Dan; Bahadur, D.

2013-05-01

387

Metal Oxide Nanowires As Promising Materials For Miniaturised Electronic Noses  

NASA Astrophysics Data System (ADS)

Nanotechnology is in continuous evolution leading to production of quasi-one dimensional (Q1D) structures in a variety of morphologies: nanowires, nanotubes, nanobelts, nanorods, nanorings, hierarchical structures. In particular, metal oxides represent an appealing category of materials with properties from metals to semiconductors and covering practically all aspects of material science and physics in areas including superconductivity and magnetism. MOX nanowires are crystalline structures with well-defined surface terminations, chemical composition and almost dislocation and defect free. Due to their nanosized dimensions, they can exhibit properties significantly different from their coarse-grained polycrystalline counterpart. The increase in the specific surface causes an enhancement of the surface related properties, such as catalytic activity or surface adsorption, key properties for solid-state gas sensors development. The use of MOX nanowires as gas-sensing materials should reduce instabilities, suffered from their polycrystalline counterpart. The gas experiments confirm good sensing properties and the real integration in low power consumption transducers.

Comini, E.; Faglia, G.; Ferroni, M.; Ponzoni, A.; Sberveglieri, G.

2009-05-01

388

Development of microstrain in aged lithium transition metal oxides.  

PubMed

Cathode materials with high energy density for lithium-ion batteries are highly desired in emerging applications in automobiles and stationary energy storage for the grid. Lithium transition metal oxide with concentration gradient of metal elements inside single particles was investigated as a promising high-energy-density cathode material. Electrochemical characterization demonstrated that a full cell with this cathode can be continuously operated for 2500 cycles with a capacity retention of 83.3%. Electron microscopy and high-resolution X-ray diffraction were employed to investigate the structural change of the cathode material after this extensive electrochemical testing. It was found that microstrain developed during the continuous charge/discharge cycling, resulting in cracking of nanoplates. This finding suggests that the performance of the cathode material can be further improved by optimizing the concentration gradient to minimize the microstrain and to reduce the lattice mismatch during cycling. PMID:24960550

Lee, Eung-Ju; Chen, Zonghai; Noh, Hyung-Ju; Nam, Sang Cheol; Kang, Sung; Kim, Do Hyeong; Amine, Khalil; Sun, Yang-Kook

2014-08-13

389

Cyclic catalytic upgrading of chemical species using metal oxide materials  

DOEpatents

Processes are disclosure which comprise alternately contacting an oxygen-carrying catalyst with a reducing substance, or a lower partial pressure of an oxidizing gas, and then with the oxidizing gas or a higher partial pressure of the oxidizing gas, whereby the catalyst is alternately reduced and then regenerated to an oxygenated state. In certain embodiments, the oxygen-carrying catalyst comprises at least one metal oxide-containing material containing a composition having one of the following formulas: (a) Ce.sub.xB.sub.yB'.sub.zB''O.sub..delta., wherein B=Ba, Sr, Ca, or Zr; B'=Mn, Co, or Fe; B''=Cu; 0.01

White, James H. (Boulder, CO); Schutte, Erick J. (Thornton, CO); Rolfe, Sara L. (Loveland, CO)

2010-11-02

390

Cyclic catalytic upgrading of chemical species using metal oxide materials  

NASA Technical Reports Server (NTRS)

Processes are disclosure which comprise alternately contacting an oxygen-carrying catalyst with a reducing substance, or a lower partial pressure of an oxidizing gas, and then with the oxidizing gas or a higher partial pressure of the oxidizing gas, whereby the catalyst is alternately reduced and then regenerated to an oxygenated state. In certain embodiments, the oxygen-carrying catalyst comprises at least one metal oxide-containing material containing a composition having one of the following formulas: (a) Ce.sub.xB.sub.yB'.sub.zB''O.sub..delta., wherein B=Ba, Sr, Ca, or Zr; B'=Mn, Co, or Fe; B''=Cu; 0.01

White, James H. (Inventor); Schutte, Erick J. (Inventor); Rolfe, Sara L. (Inventor)

2010-01-01

391

Lithium metal oxide electrodes for lithium cells and batteries  

DOEpatents

A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2 M'O.sub.3 in which 0

Thackeray, Michael M. (Naperville, IL); Johnson, Christopher S. (Naperville, IL); Amine, Khalil (Downers Grove, IL); Kim, Jaekook (Naperville, IL)

2004-01-13

392

Oxidative dissolution of nickel metal in hydrogenated hydrothermal solutions  

Microsoft Academic Search

A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of metallic nickel in hydrogenated ammonia and sodium hydroxide solutions between 175 and 315°C. The solubility measurements were interpreted by means of an oxidative dissolution reaction followed by a sequence of Ni(II) ion hydrolysis reactions:Ni(s)+2H+(aq)=Ni2+(aq)+H2(g)andNi2+(aq)+nH2O=Ni(OH)n2-n(aq)+nH+(aq)where n=1 and 2. Gibbs energies associated with these reaction equilibria were determined from

S. E. Ziemniak; P. A. Guilmette; R. A. Turcotte; H. M. Tunison

2008-01-01

393

Giant magnetoresistance in oxide-based metallic multilayers  

SciTech Connect

The authors report on the first measurement of low-field giant magnetoresistance in metallic multilayers of perovskite oxides. The authors performed in-plane measurements of the magnetoelectric transport properties in La{sub 0.75}Sr{sub 0.25}MnO{sub 3}/LaNiO{sub 3} trilayers and succeeded in distinguishing the giant magnetoresistance effect from other contributions to the total magnetoresistance. The samples were grown on single-crystalline SrTiO{sub 3} substrates by dc sputtering.

Granada, Mara; Rojas Sanchez, J. Carlos; Steren, Laura B. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica (R8402AGP) San Carlos de Bariloche, Rio Negro (Argentina)

2007-08-13

394

Ionically-mediated electromechanical hysteresis in transition metal oxides  

SciTech Connect

Electromechanical activity, remanent polarization states, and hysteresis loops in paraelectric TiO2 and SrTiO3 are observed. The coupling between the ionic dynamics and incipient ferroelectricity in these materials is analyzed using extended Ginsburg Landau Devonshire (GLD) theory. The possible origins of electromechanical coupling including ionic dynamics, surface-charge induced electrostriction, and ionically-induced ferroelectricity are identified. For the latter, the ionic contribution can change the sign of first order GLD expansion coefficient, rendering material effectively ferroelectric. These studies provide possible explanation for ferroelectric-like behavior in centrosymmetric transition metal oxides.

Kim, Yunseok [ORNL] [ORNL; Kumar, Amit [ORNL] [ORNL; Jesse, Stephen [ORNL] [ORNL; Kalinin, Sergei V [ORNL] [ORNL

2012-01-01

395

Effect of rare earth metal oxide additions to tungsten electrodes  

Microsoft Academic Search

A comparative study has been made on the operating characteristics of gas-tungsten arc (GTA) welding for several types of\\u000a electrodes. The work was carried out with a pure tungsten electrode and tungsten electrodes activated with a small quantity\\u000a of the rare earth metal oxides, La2O3, Y2O3, CeO2, and with ZrO2, ThO2, and MgO. Their behaviors during arcing were analyzed and

Alber A. Sadek; Masao Ushio; Fukuhisa Matsuda

1990-01-01

396

Physicochemical and functional peculiarities of metal oxide whiskers  

Microsoft Academic Search

Practical aspects of preparation and prospects for practical use of a series of the metal oxide whiskers were studied. The\\u000a procedures for the synthesis were proposed, and the phase composition, micromorphology, and electrochemical and sensor characteristics\\u000a of the macroscopic (up to 5–10 mm long) whiskers in the Ba-V-O, Ba-Mn-O, and Sn-O systems were analyzed. The electroconducting\\u000a BaV8O21-? whiskers were prepared

E. A. Goodilin; E. A. Pomerantseva; D. A. Semenenko; P. B. Kocherginskaya; D. M. Itkis; T. L. Kulova; A. M. Skundin; L. S. Leonova; Yu. A. Dobrovol’skii; M. N. Rumyantseva; A. M. Gas’kov; S. B. Balakhonov; B. R. Churagulov; Yu. D. Tretyakova

2008-01-01

397

Metal-oxide-semiconductor characteristics of lanthanum cerium oxide film on Si  

NASA Astrophysics Data System (ADS)

Metal-organic decomposed lanthanum cerium oxide (La x Ce y O z ) film had been spin-coated on n-type Si substrate. Effects of post-deposition annealing temperature and time on the metal-oxide-semiconductor (MOS) properties of the film were studied. As temperature increased from 400 to 1000°C for 15 minutes dwell time, La x Ce y O z demonstrated a decrease in interface trap density ( D it) and total interface trap density ( D total), which were related to the formation of SiO x /silicates interfacial layer (IL). The lowest leakage current density and highest dielectric breakdown voltage ( V B) was obtained in 1000°C-annealed sample. When longer annealing times (30-120 minutes) were studied on the 1000°C-annealed sample, the sample annealed at 1000°C for 120 min showed the best MOS characteristics with V B of 30 V. Reasons contributing to such observation were discussed.

Lim, Way Foong; Lockman, Zainovia; Cheong, Kuan Yew

2012-05-01

398

Bacterial adhesion to glass and metal-oxide surfaces.  

PubMed

Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength (1 and 100 mM, respectively) to 11 different surfaces and examined adhesion as a function of charge, hydrophobicity (water contact angle) and surface energy. Inorganic surfaces included three uncoated glass surfaces and eight metal-oxide thin films prepared on the upper (non-tin-exposed) side of float glass by chemical vapor deposition. The Gram-negative bacteria differed in lengths of lipopolysaccharides on their outer surface (three Escherichia coli strains), the amounts of exopolysaccharides (two Pseudomonas aeruginosa strains), and their known relative adhesion to sand grains (two Burkholderia cepacia strains). One Gram positive bacterium was also used that had a lower adhesion to glass than these other bacteria (Bacillus subtilis). For all eight bacteria, there was a consistent increase in adhesion between with the type of inorganic surface in the order: float glass exposed to tin (coded here as Si-Sn), glass microscope slide (Si-m), uncoated air-side float glass surface (Si-a), followed by thin films of (Co(1-y-z)Fe(y)Cr(z))3O4, Ti/Fe/O, TiO2, SnO2, SnO2:F, SnO2:Sb, A1(2)O3, and Fe2O3 (the colon indicates metal doping, a slash indicates that the metal is a major component, while the dash is used to distinguish surfaces). Increasing the ionic strength from 1 to 100 mM increased adhesion by a factor of 2.0 +/- 0.6 (73% of the sample results were within the 95% CI) showing electrostatic charge was important in adhesion. However, adhesion was not significantly correlated with bacterial charge and contact angle. Adhesion (A) of the eight strains was significantly (P < 10(-25)) correlated with total adhesion free energy (U) between the bacteria and surface (A = 2162e(-1.8U)). Although the correlation was significant, agreement between the model and data was poor for the low energy surfaces (R2 = 0.68), indicating that better models or additional methods to characterize bacteria and surfaces are still needed to more accurately describe initial bacterial adhesion to inorganic surfaces. PMID:15261011

Li, Baikun; Logan, Bruce E

2004-07-15

399

The AMOS cell - An improved metal-semiconductor solar cell. [Antireflection coated Metal Oxide Semiconductor  

NASA Technical Reports Server (NTRS)

A new fabrication process is being developed which significantly improves the efficiency of metal-semiconductor solar cells. The resultant effect, a marked increase in the open-circuit voltage, is produced by the addition of an interfacial layer oxide on the semiconductor. Cells using gold on n-type gallium arsenide have been made in small areas (0.17 sq cm) with conversion efficiencies of 15% in terrestrial sunlight.

Stirn, R. J.; Yeh, Y.-C. M.

1975-01-01

400

Fabrication of arrays of metal and metal oxide nanotubes by shadow evaporation.  

PubMed

This paper describes a simple technique for fabricating uniform arrays of metal and metal oxide nanotubes with controlled heights and diameters. The technique involves depositing material onto an anodized aluminum oxide (AAO) membrane template using a collimated electron beam evaporation source. The evaporating material enters the porous openings of the AAO membrane and deposits onto the walls of the pores. The membrane is tilted with respect to the column of evaporating material, so the shadows cast by the openings of the pores onto the inside walls of the pores define the geometry of the tubes. Rotation of the membrane during evaporation ensures uniform deposition inside the pores. After evaporation, dissolution of the AAO in base easily removes the template to yield an array of nanotubes connected by a thin backing of the same metal or metal oxide. The diameter of the pores dictates the diameter of the tubes, and the incident angle of evaporation determines the height of the tubes. Tubes up to approximately 1.5 mum in height and 20-200 nm in diameter were fabricated. This method is adaptable to any material that can be vapor-deposited, including indium-tin oxide (ITO), a conductive, transparent material that is useful for many opto-electronic applications. An array of gold nanotubes produced by this technique served as a substrate for surface-enhanced Raman spectroscopy: the Raman signal (per molecule) from a monolayer of benzenethiolate was a factor of approximately 5 x 10(5) greater than that obtained using bulk liquid benzenethiol. PMID:19206613

Dickey, Michael D; Weiss, Emily A; Smythe, Elizabeth J; Chiechi, Ryan C; Capasso, Federico; Whitesides, George M

2008-04-01

401

Electron magnetic resonance study of transition-metal magnetic nanoclusters embedded in metal oxides  

Microsoft Academic Search

Here, we report on the results of an electron magnetic resonance (EMR) study of a series of Ni\\/ZnO and Ni\\/gamma-Fe2O3 nanocomposites (NCs) to probe the resonance features of ferromagnetic (FM) Ni nanoclusters embedded in metal oxides. Interest in these NCs stems from the fact that they are promising for implementing the nonreciprocal functionality employed in many microwave devices, e.g., circulators.

Vincent Castel; Christian Brosseau

2008-01-01

402

Metal Ions, Not Metal-Catalyzed Oxidative Stress, Cause Clay Leachate Antibacterial Activity  

PubMed Central

Aqueous leachates prepared from natural antibacterial clays, arbitrarily designated CB-L, release metal ions into suspension, have a low pH (3.4–5), generate reactive oxygen species (ROS) and H2O2, and have a high oxidation-reduction potential. To isolate the role of pH in the antibacterial activity of CB clay mixtures, we exposed three different strains of Escherichia coli O157:H7 to 10% clay suspensions. The clay suspension completely killed acid-sensitive and acid-tolerant E. coli O157:H7 strains, whereas incubation in a low-pH buffer resulted in a minimal decrease in viability, demonstrating that low pH alone does not mediate antibacterial activity. The prevailing hypothesis is that metal ions participate in redox cycling and produce ROS, leading to oxidative damage to macromolecules and resulting in cellular death. However, E. coli cells showed no increase in DNA or protein oxidative lesions and a slight increase in lipid peroxidation following exposure to the antibacterial leachate. Further, supplementation with numerous ROS scavengers eliminated lipid peroxidation, but did not rescue the cells from CB-L-mediated killing. In contrast, supplementing CB-L with EDTA, a broad-spectrum metal chelator, reduced killing. Finally, CB-L was equally lethal to cells in an anoxic environment as compared to the aerobic environment. Thus, ROS were not required for lethal activity and did not contribute to toxicity of CB-L. We conclude that clay-mediated killing was not due to oxidative damage, but rather, was due to toxicity associated directly with released metal ions. PMID:25502790

Otto, Caitlin C.; Koehl, Jennifer L.; Solanky, Dipesh; Haydel, Shelley E.

2014-01-01

403

Oxide Wizard: an EELS application to characterize the white lines of transition metal edges.  

PubMed

Physicochemical properties of transition metal oxides are directly determined by the oxidation state of the metallic cations. To address the increasing need to accurately evaluate the oxidation states of transition metal oxide systems at the nanoscale, here we present "Oxide Wizard." This script for Digital Micrograph characterizes the energy-loss near-edge structure and the position of the transition metal edges in the electron energy-loss spectrum. These characteristics of the edges can be linked to the oxidation states of transition metals with high spatial resolution. The power of the script is demonstrated by mapping manganese oxidation states in Fe3O4/Mn3O4 core/shell nanoparticles with sub-nanometer resolution in real space. PMID:24750576

Yedra, Lluís; Xuriguera, Elena; Estrader, Marta; López-Ortega, Alberto; Baró, Maria D; Nogués, Josep; Roldan, Manuel; Varela, Maria; Estradé, Sònia; Peiró, Francesca

2014-06-01

404

Metal-based turn-on fluorescent probes for nitric oxide sensing  

E-print Network

Chapter 1. Metal-Based Turn-On Fluorescent Probes for Sensing Nitric Oxide. Nitric oxide, a reactive free radical, regulates a variety of biological processes. The absence of tools to detect NO directly, rapidly, specifically ...

Lim, Mi Hee

2006-01-01

405

A simple and generic approach for synthesizing colloidal metal and metal oxide nanocrystals  

NASA Astrophysics Data System (ADS)

A simple and generic approach--alternating voltage induced electrochemical synthesis (AVIES)--has been reported for synthesizing highly dispersed colloidal metal (Au, Pt, Sn, and Pt-Pd) and metal oxide (ZnO and TiO2) nanocrystals. The respective nanocrystals are produced when a zero-offset alternating voltage at 60 Hz is applied to a pair of identical metal wires, which are inserted in an electrolyte solution containing capping ligands. In the case of Au, the obtained nanocrystals are highly crystalline nano-icosahedra of 14 +/- 2 nm in diameter, the smallest Au icosahedra synthesized in aqueous solutions via green chemistry. Their catalytic activity has been demonstrated through facilitating the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride. This AVIES approach is an environmentally benign process and can be adopted by any research lab.

Cloud, Jacqueline E.; Yoder, Tara S.; Harvey, Nathan K.; Snow, Kyle; Yang, Yongan

2013-07-01

406

Electrochemical lithiation and delithiation for control of magnetic properties of nanoscale transition metal oxides  

E-print Network

Transition metal oxides comprise a fascinating class of materials displaying a variety of magnetic and electronic properties, ranging from half-metallic ferromagnets like CrO2, ferrimagnetic semiconductors like Fey's, and ...

Sivakumar, Vikram

2008-01-01

407

Bipolar plating of metal contacts onto oxide interconnection for solid oxide electrochemical cell  

DOEpatents

Disclosed is a method of forming an adherent metal deposit on a conducting layer of a tube sealed at one end. The tube is immersed with the sealed end down into an aqueous solution containing ions of the metal to be deposited. An ionically conducting aqueous fluid is placed inside the tube and a direct current is passed from a cathode inside the tube to an anode outside the tube. Also disclosed is a multi-layered solid oxide fuel cell tube which consists of an inner porous ceramic support tube, a porous air electrode covering the support tube, a non-porous electrolyte covering a portion of the air electrode, a non-porous conducting interconnection covering the remaining portion of the electrode, and a metal deposit on the interconnection. 1 fig.

Isenberg, A.O.

1987-03-10

408

ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium  

E-print Network

ORIGINAL PAPER Influence of the Metal Oxide Substrate Structure on Vanadium Oxide Monomer Formation 2013 � Springer Science+Business Media New York 2013 Abstract Vanadium oxide (VOx) molecular species nature of surface VOx species. Keywords Vanadium oxide Á Strontium titanate Á XPS Á Surface structure 1

Marks, Laurence D.

409

Respective role of Fe and Mn oxide contents for arsenic sorption in iron and manganese binary oxide: an X-ray absorption spectroscopy investigation.  

PubMed

In our previous studies, a synthesized Fe-Mn binary oxide was found to be very effective for both As(V) and As(III) removal in aqueous phase, because As(III) could be easily oxidized to As(V). As(III) oxidation and As(V) sorption by the Fe-Mn binary oxide may also play an important role in the natural cycling of As, because of its common occurrence in the environment. In the present study, the respective role of Fe and Mn contents present in the Fe-Mn binary oxide on As(III) removal was investigated via a direct in situ determination of arsenic speciation using X-ray absorption spectroscopy. X-ray absorption near edge structure results indicate that Mn atoms exist in a mixed valence state of +3 and +4 and further confirm that MnOx (1.5 < x < 2) content is mainly responsible for oxidizing As(III) to As(V) through a two-step pathway [reduction of Mn(IV) to Mn(III) and subsequent Mn(III) to Mn(II)] and FeOOH content is dominant for adsorbing the formed As(V). No significant As(III) oxidation by pure FeOOH had been observed during its sorption, when the system was exposed to air. The extended X-ray absorption fine structure results reveal that the As surface complex on both the As(V)- and As(III)-treated sample surfaces is an inner-sphere bidentate binuclear corner-sharing complex with an As-M (M = Fe or Mn) interatomic distance of 3.22-3.24 Å. In addition, the MnOx and FeOOH contents exist only as a mixture, and no solid solution is formed. Because of its high effectiveness, low cost, and environmental friendliness, the Fe-Mn binary oxide would play a beneficial role as both an efficient oxidant of As(III) and a sorbent for As(V) in drinking water treatment and environmental remediation. PMID:25093452

Zhang, Gaosheng; Liu, Fudong; Liu, Huijuan; Qu, Jiuhui; Liu, Ruiping

2014-09-01

410

Adsorption of enterobactin to metal oxides and the role of siderophores in bacterial adhesion to metals.  

PubMed

The potential contribution of chemical bonds formed between bacterial cells and metal surfaces during biofilm initiation has received little attention. Previous work has suggested that bacterial siderophores may play a role in bacterial adhesion to metals. It has now been shown using in situ ATR-IR spectroscopy that enterobactin, a catecholate siderophore secreted by Escherichia coli, forms covalent bonds with particle films of titanium dioxide, boehmite (AlOOH), and chromium oxide-hydroxide which model the surfaces of metals of significance in medical and industrial settings. Adsorption of enterobactin to the metal oxides occurred through the 2,3-dihydroxybenzoyl moieties, with the trilactone macrocycle having little involvement. Vibrational modes of the 2,3-dihydroxybenzoyl moiety of enterobactin, adsorbed to TiO(2), were assigned by comparing the observed IR spectra with those calculated by the density functional method. Comparison of the observed adsorbate IR spectrum with the calculated spectra of catecholate-type [H(2)NCOC(6)H(3)O(2)Ti(OH)(4)](2-) and salicylate-type [H(2)NCOC(6)H(3)O(2)HTi(OH)(4)](2-) surface complexes indicated that the catecholate type is dominant. Analysis of the spectra for enterobactin in solution and that adsorbed to TiO(2) revealed that the amide of the 2,3-dihydroxybenzoylserine group reorientates during coordination to surface Ti(IV) ions. Investigation into the pH dependence of enterobactin adsorption to TiO(2) surfaces showed that all 2,3-dihydroxybenzoyl groups are involved. Infrared absorption bands attributed to adsorbed enterobactin were also strongly evident for E. coli cells attached to TiO(2) particle films. These studies give evidence of enterobactin-metal bond formation and further suggest the generality of siderophore involvement in bacterial biofilm initiation on metal surfaces. PMID:21744856

Upritchard, Hamish G; Yang, Jing; Bremer, Philip J; Lamont, Iain L; McQuillan, A James

2011-09-01

411

Hydrogen Spillover Enhanced Hydroxyl Formation and Catalytic Activity Toward CO Oxidation at the Metal/Oxide Interface.  

PubMed

H2 -promoted catalytic activity of oxide-supported metal catalysts in low-temperature CO oxidation is of great interest but its origin remains unknown. Employing an FeO(111)/Pt(111) inverse model catalyst, we herewith report direct experimental evidence for the spillover of H(a) adatoms on the Pt surface formed by H2 dissociation to the Pt?FeO interface to form hydroxyl groups that facilely oxidize CO(a) on the neighboring Pt surface to produce CO2 . Hydroxyl groups and coadsorbed water play a crucial role in the occurrence of hydrogen spillover. These results unambiguously identify the occurrence of hydrogen spillover from the metal surface to the noble metal/metal oxide interface and the resultant enhanced catalytic activity of the metal/oxide interface in low-temperature CO oxidation, which provides a molecular-level understanding of both H2 -promoted catalytic activity of metal/oxide ensembles in low-temperature CO oxidation and hydrogen spillover. PMID:25650016

Jin, Yuekang; Sun, Guanghui; Xiong, Feng; Ding, Liangbing; Huang, Weixin

2015-03-01

412

Transition-metal-oxide coated titanium electrodes for redox batteries  

NASA Astrophysics Data System (ADS)

The production of porous electrodes with reproducible surface activity for experiments to corroborate predictions of porous electrode theory to ascertain if simple one step outer sphere electron transfer mechanism applies to the ferric-ferrous redox reaction at high reactant/product concentrations in a strong acid chloride medium was investigated. Kinetic rate expressions of this couple under these conditions at the metal oxide surfaces were sought. Coatings of the conductive and active rutile structure form of selected transition metal oxides were desired. Both IrO2 and RuO2 coatings having the rutile structure were prepared by thermal decomposition of their respective hydrated chloride salts. Low over potential exchange current densities of the ferric-ferrous couple were measured in concentrated solution at Pt, RuO2 and IrO2 RDF's. Significant corrections were necessary for ohmic effects, mass transfer effects, and nonuniform current distribution. It is shown that the electrocatalytic activity of RuO2 is comparable to that of Pt while the activity of IrO2 is approximately an order of magnitude less than Pt. The measured free energy of activation was similar for all three substrates and a nonbinding interaction between the couple and the surfaces is suggested. The variation in exchange currents among the different substrates can be attributed to some extent on double layer effects but primarily to crystal structure differences.

Savinell, R. F.

1982-12-01

413

Preferential orientation of metal oxide superconducting materials by mechanical means  

DOEpatents

A superconductor comprised of a polycrystalline metal oxide such as YBa[sub 2]Cu[sub 3]O[sub 7[minus]X] (where 0 < X < 0.5) is capable of accommodating very large current densities. By aligning the two-dimensional Cu-O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the metal oxide material to accommodate high current densities. The orthorhombic crystalline particles have a tendency to lie down on one of the longer sides, i.e., on the a- or b-direction. Aligning the crystals in this orientation is accomplished by mechanical working of the material such as by extrusion, tape casting or slip casting, provided a single crystal powder is used as a starting material, to provide a highly oriented, e.g., approximately 90% of the crystal particles have a common orientation, superconducting matrix capable of supporting large current densities. 3 figs.

Capone, D.W.

1990-11-27

414

Acoustic plane wave preferential orientation of metal oxide superconducting materials  

DOEpatents

A polycrystalline metal oxide such as YBa.sub.2 Cu.sub.3 O.sub.7-X (where 0metal oxide in the form of a ceramic slip which has not yet set, orientation of the crystal basal planes parallel with the direction of desired current flow is accomplished by an applied acoustic plane wave in the acoustic or ultrasonic frequency range (either progressive or standing) in applying a torque to each crystal particle. The ceramic slip is then set and fired by conventional methods to produce a conductor with preferentially oriented grains and substantially enhanced current carrying capacity.

Tolt, Thomas L. (North Olmsted, OH); Poeppel, Roger B. (Glen Ellyn, IL)

1991-01-01

415

Nanostructured transition metal oxides for energy storage and conversion  

NASA Astrophysics Data System (ADS)

Lithium-ion batteries, supercapacitors and photovoltaic devices have been widely considered as the three major promising alternatives of fossil fuels facing upcoming depletion to power the 21th century. The conventional film configuration of electrochemical electrodes hardly fulfills the high energy and efficiency requirements because heavy electroactive material deposition restricts ion diffusion path, and lowers power density and fault tolerance. In this thesis, I demonstrate that novel nanoarchitectured transition metal oxides (TMOs), e.g. MnO2, V2O 5, and ZnO, and their relevant nanocomposites were designed, fabricated and assembled into devices to deliver superior electrochemical performances such as high energy and power densities, and rate capacity. These improvements could be attributed to the significant enhancement of surface area, shortened ion diffusion distances and facile penetration of electrolyte solution into open structures of networks as well as to the pseudocapacitance domination. The utilization of ForcespinningRTM, a newly developed nanofiber processing technology, for large-scale energy storage and conversion applications is emphasized. This process simplifies the tedious multi-step hybridization synthesis and facilitates the contradiction between the micro-batch production and the ease of large-scale manufacturing. Key Words: Transition metal oxides, energy storage and conversion, ForcespinningRTM, pseudocapacitance domination, high rate capacity

Li, Qiang

416

Thermodynamic Study of Transformation of Methane to Synthesis Gas Over Metal Oxides  

NASA Astrophysics Data System (ADS)

A metal oxide reduction-water splitting cycle is a new developing method to produce synthesis gas without using a catalyst. In the reduction stage, metal oxide reduction and methane activation are combined in an efficient and energy-saving process using methane as a reducing agent. In this study, the effect of temperature and reductant (oxidant) amount on the equilibrium composition of products, graphitic carbon formation, yield of synthesis gas (water splitting stage), and produced ratio are thermodynamically investigated. This investigation includes metal oxides of zinc, tin, cobalt, and nickel. The results show that the synthesis gas is produced simultaneously with gaseous zinc, molten tin, solid cobalt, and solid nickel for those metal oxides in the reduction process. In the case of tin oxide, the feasibility of the graphitic carbon formation is less than the other oxides. The maximum yield of synthesis gas occurs in the stoichiometric molar ratio of methanothermal reduction reactions. From the methane consumption point of view, zinc oxide has a much higher synthesis gas yield. Finally, it is proposed that cobalt and nickel oxides can be used only in the reduction stage to produce synthesis gas and reduced metals due to low equilibrium conversion in the water splitting stage. The metal oxide reduction-water splitting cycle can be developed as an environmentally friendly technology for synthesis gas production over metal oxides.

Roohi, P.; Alizadeh, R.; Fatehifar, E.

2015-01-01

417

Fabrication of Porous Metal Oxide Semiconductor Films by a Self-Template Method Using Layered Hydroxide Metal Acetates  

Microsoft Academic Search

Porous metal oxide (Co3O4, NiO, or ZnO) films were fabricated by a self-template method using layered hydroxide metal acetates (LHMA; metal = Co, Ni, or Zn) as templates. LHMAs were initially grown on glass substrates through a chemical bath deposition in methanolic-aqueous solutions of metal acetates at 60°C. The template films had a unique, nest-like morphology consisting of interlaced flake-like

Shinobu Fujihara; Eiji Hosono; Toshio Kimura

2004-01-01

418

A correlation between the structure and some physical properties of binary molybdates (Tungstates) of uni- and bivalent metals  

Microsoft Academic Search

General principles of arrangement are discussed and analyzed for 13 known structural types (families) of binary molybdates\\u000a and tungstates of uni-and bivalent metals, which were classified according to the degree of condensation of M2+On polyhedral and MoO4 tetrahedral constructions. The structural features of some phases correlate with their ferroelectric, ion-conducting, and\\u000a luminescent (laser) properties. We suggest crystallochemical criteria and mechanisms

S. F. Solodovnikov; R. F. Klevtsova; P. V. Klevtsov

1994-01-01

419

Fabrication of hollow metal oxide nanocrystals by etching cuprous oxide with metal(ii) ions: approach to the essential driving force  

NASA Astrophysics Data System (ADS)

Hollow metal oxide nanocrystals were prepared by etching cuprous oxide with metal ions and were applied as photoelectrodes. As a hard template, polyvinylpyrrolidone stabilized cuprous oxide (PVP-Cu2O) and non-stabilized cuprous oxide (nPVP-Cu2O) were synthesized by a precipitation method. Hollow iron oxide and cobalt oxide nanocrystals with a truncated octahedral morphology were fabricated by an etching reaction with transition metal(ii) ions (Fe2+ or Co2+). In the etching reaction process, a cationic exchange reaction occurs between the divalent metal ion and Cu+ due to the higher Lewis acidity. Facet selective etching of cuprous oxide has been observed during the ionic exchange reaction of Cu+ and O2- ions in PVP-Cu2O complexes with transition metal(ii) ions (Fe2+ or Co2+) at the surface of a (110) facet. Amorphous states of hollow metal oxide products were annealed to form ?-Fe2O3 (hematite) and Co3O4 and their crystal structure was examined with X-ray diffraction and HR-TEM. The optical absorption behavior of semiconductor nanocrystals was measured with UV-vis spectroscopy to define band gap energy. The hollow hematite structure has a 2.08 eV band gap and Co3O4 (Co(ii,iii) oxide) has a 1.80 eV indirect band gap. Using these hollow nanocrystals, a metal oxide monolayer film was fabricated with a secondary growth approach and was studied for its photocatalytic properties.Hollow metal oxide nanocrystals were prepared by etching cuprous oxide with metal ions and were applied as photoelectrodes. As a hard template, polyvinylpyrrolidone stabilized cuprous oxide (PVP-Cu2O) and non-stabilized cuprous oxide (nPVP-Cu2O) were synthesized by a precipitation method. Hollow iron oxide and cobalt oxide nanocrystals with a truncated octahedral morphology were fabricated by an etching reaction with transition metal(ii) ions (Fe2+ or Co2+). In the etching reaction process, a cationic exchange reaction occurs between the divalent metal ion and Cu+ due to the higher Lewis acidity. Facet selective etching of cuprous oxide has been observed during the ionic exchange reaction of Cu+ and O2- ions in PVP-Cu2O complexes with transition metal(ii) ions (Fe2+ or Co2+) at the surface of a (110) facet. Amorphous states of hollow metal oxide products were annealed to form ?-Fe2O3 (hematite) and Co3O4 and their crystal structure was examined with X-ray diffraction and HR-TEM. The optical absorption behavior of semiconductor nanocrystals was measured with UV-vis spectroscopy to define band gap energy. The hollow hematite structure has a 2.08 eV band gap and Co3O4 (Co(ii,iii) oxide) has a 1.80 eV indirect band gap. Using these hollow nanocrystals, a metal oxide monolayer film was fabricated with a secondary growth approach and was studied for its photocatalytic properties. Electronic supplementary information (ESI) available: TEM and SEM images of PVP-Cu2O and nPVP-Cu2O, FTIR result of PVP and PVP-Cu2O etc. See DOI: 10.1039/c3nr03626j

Sohn, Jong Hwa; Cha, Hyun Gil; Kim, Chang Woo; Kim, Do Kyoung; Kang, Young Soo

2013-10-01

420

Active metal oxides and polymer hybrids as biomaterials  

NASA Astrophysics Data System (ADS)

Bone anchored prosthetic attachments, like other percutaneous devices, suffer from poor soft tissue integration, seen as chronic inflammation, infection, epithelial downgrowth and regression. We looked at the use of metal oxides as bioactive agents that elicit different bioresponses, ranging from cell attachment, tissue integration and reduction of inflammation to modulation of cell proliferation, morphology and microbe killing. This study presents a novel method for creating titanium oxide and polydimethylsiloxane (PDMS) hybrid coated microplates for high throughput biological, bacterial and photocatalytic screening that overcomes several limitations of using bulk metal samples. Titanium oxide coatings were doped with silver, zinc, vanadium, aluminum, calcium and phosphorous, while PDMS was doped with titanium, vanadium and silver and subjected to hydrothermal heat treatment to determine the influence of chemistry and crystallinity on the viability, proliferation and adhesion of human fibroblasts, keratinocytes and Hela cells. Also explored was the influence of Ag and Zn doping on E. coli proliferation. We determined how titanium concentration in hybrids and silver doping influenced the photocatalytic degradation of methylene blue by coatings. A combined sub/percutaneous, polyurethane device was developed and implanted into the backs of CD hairless rats to investigate how optimized coatings influenced soft tissue integration in vivo. We demonstrate that the bioresponse of cells to coatings is controlled by elemental doping (V & Ag) and that planktonic bacterial growth was greatly reduced or stopped by Ag, but not Zn doping. Hydrothermal heat treatments (65 °C and 121 °C) did not greatly influence cellular bioresponse to coatings. We discovered a range of temperature resistant (up to 400 °C), solid state dispersions with enhanced ability to block full spectrum photon transmission and degrade methylene using medical x-rays, UV, visible and infrared photons. We show that silver doping improved the photoactivity of oxide coatings, but hindered activity of a specific hybrid. Doped titanium oxide and polymer hybrid coatings have potential for improving soft tissue integration of medical implants and wound healing by modulating cell proliferation, attachment, inflammation and providing controlled delivery of bioactive and antimicrobial compounds and photon induced electro-chemical activity.

Jarrell, John D.

421

Alloy Films Deposited by Electroplating as Precursors for Protective Oxide Coatings on Solid Oxide Fuel Cells Metallic Interconnect Materials  

SciTech Connect

The successful development of stainless steel interconnects for intermediate temperature solid oxide fuel cells (SOFC) may be the materials breakthrough that makes SOFC technology truly commercial. Many of the ferritic stainless steels, however, suffer from a relatively high area specific resistance (ASR) after long exposure times at temperature and the Cr in the native oxide can evaporate and contaminate other cell components. Conductive coatings that resist oxide scale growth and chromium evaporation may prevent both of these problems. In the present study electrochemical deposition of binary alloys followed by oxidation of the alloy to form protective and conductive oxide layers is examined. Results are presented for the deposition of Mn/Co and Fe/Ni alloys via electroplating to form a precursor for spinel oxide coating formation. Analysis of the alloy coatings is done by SEM, EDS and XRD.

Johnson, Christopher; Gemmen, R.S.; Cross, Caleb

2006-10-01

422

Comparative responses to metal oxide nanoparticles in marine phytoplankton.  

PubMed

A series of experiments was undertaken on three different marine microalgae to compare the effect of two metal oxide nanoparticles (NPs) on different physiological responses to stress: zinc oxide (ZnO), a known toxic compound for microalgae, and the never before tested yttrium oxide (Y?O3). The effect of these potential pollutants was estimated for different physiological variables and temporal scales: Growth, carbon content, carbon-to-nitrogen (C:N) ratio, and chlorophyll fluorescence were evaluated in long-term assays, and reactive oxygen species (ROS) production was evaluated in a short-term assay. Population growth was the most susceptible variable to the acute toxic effects of both NPs as measured in terms of number of cells and of biomass. Although Phaeodactylum tricornutum and Alexandrium minutum were negatively affected by ZnO NPs, this effect was not detected in Tetraselmis suecica, in which cell growth was significantly decreased by Y?O? NPs. Biomass per cell was negatively affected in the most toxic treatments in T. suecica but was positively affected in A. minutum. ZnO treatments induced a sharper decrease in chlorophyll fluorescence and higher ROS than did Y?O? treatments. The pronounced differences observed in the responses between the species and the physiological variables tested highlight the importance of analyzing diverse groups of microalgae and various physiological levels to determine the potential effects of environmental pollutants. PMID:24908584

Castro-Bugallo, Alexandra; González-Fernández, África; Guisande, Cástor; Barreiro, Aldo

2014-11-01

423

Experimental Study of Resistive Bistability in Metal Oxide Junctions  

SciTech Connect

We have studied resistive bistability (memory) effects in junctions based on metal oxides, with a focus on sample-to-sample reproducibility, which is necessary for the use of such junctions as crosspoint devices of hybrid CMOS/nanoelectronic circuits. Few-nm-thick layers of NbO{sub x}, CuO{sub x} and TiO{sub x} have been formed by thermal and plasma oxidation, at various deposition and oxidation conditions, both with and without rapid thermal post-annealing. The resistive bistability effect has been observed for all these materials, with particularly high endurance (over 10{sup 3} switching cycles) obtained for single-layer TiO{sub 2} junctions, and the best reproducibility reached for multi-layer junctions of the same material. Fabrication optimization has allowed us to improve the OFF/ON resistance ratio to about 10{sup 3}, but the sample-to-sample reproducibility is so far lower than that required for large-scale integration.

Su, D.; Tan, Z.; Patel, V.; Likharev, K.K.; Zhu, Y.

2011-05-01

424

NANOSTRUCTURED METAL OXIDE CATALYSTS VIA BUILDING BLOCK SYNTHESES  

SciTech Connect

A broadly applicable methodology has been developed to prepare new single site catalysts on silica supports. This methodology requires of three critical components: a rigid building block that will be the main structural and compositional component of the support matrix; a family of linking reagents that will be used to insert active metals into the matrix as well as cross link building blocks into a three dimensional matrix; and a clean coupling reaction that will connect building blocks and linking agents together in a controlled fashion. The final piece of conceptual strategy at the center of this methodology involves dosing the building block with known amounts of linking agents so that the targeted connectivity of a linking center to surrounding building blocks is obtained. Achieving targeted connectivities around catalytically active metals in these building block matrices is a critical element of the strategy by which single site catalysts are obtained. This methodology has been demonstrated with a model system involving only silicon and then with two metal-containing systems (titanium and vanadium). The effect that connectivity has on the reactivity of atomically dispersed titanium sites in silica building block matrices has been investigated in the selective oxidation of phenols to benezoquinones. 2-connected titanium sites are found to be five times as active (i.e. initial turnover frequencies) than 4-connected titanium sites (i.e. framework titanium sites).

Craig E. Barnes

2013-03-05

425

Plasmonic nanostructured metal-oxide-semiconductor reflection modulators.  

PubMed

We propose a plasmonic surface that produces an electrically controlled reflectance as a high-speed intensity modulator. The device is conceived as a metal-oxide-semiconductor capacitor on silicon with its metal structured as a thin patch bearing a contiguous nanoscale grating. The metal structure serves multiple functions as a driving electrode and as a grating coupler for perpendicularly incident p-polarized light to surface plasmons supported by the patch. Modulation is produced by charging and discharging the capacitor and exploiting the carrier refraction effect in silicon along with the high sensitivity of strongly confined surface plasmons to index perturbations. The area of the modulator is set by the area of the incident beam, leading to a very compact device for a strongly focused beam (?2.5 ?m in diameter). Theoretically, the modulator can operate over a broad electrical bandwidth (tens of gigahertz) with a modulation depth of 3 to 6%, a loss of 3 to 4 dB, and an optical bandwidth of about 50 nm. About 1000 modulators can be integrated over a 50 mm(2) area producing an aggregate electro-optic modulation rate in excess of 1 Tb/s. We demonstrate experimentally modulators operating at telecommunications wavelengths, fabricated as nanostructured Au/HfO2/p-Si capacitors. The modulators break conceptually from waveguide-based devices and belong to the same class of devices as surface photodetectors and vertical cavity surface-emitting lasers. PMID:25730698

Olivieri, Anthony; Chen, Chengkun; Hassan, Sa'ad; Lisicka-Skrzek, Ewa; Tait, R Niall; Berini, Pierre

2015-04-01

426

Evaluation of the joint-action toxicity of binary mixtures of heavy metals against the mangrove periwinkle Tympanotonus fuscatus var radula (L.)  

Microsoft Academic Search

The joint-action toxicity of binary mixtures of heavy metal compounds prepared in predefined ratios of 4:1, 3:2, 1:1, 2:3, and 1:4 (wt\\/wt) of Zn:Cu, Zn:Cd, and Cd:Cu, respectively, and tested against the mangrove periwinkle Tympanotonus fuscatus were carried out in laboratory bioassays. The interactions between binary mixtures showed significant departures from the action of the individual constituent metals when acting

Adebayo Akeem Otitoloju

2002-01-01

427

Can the packing efficiency of binary hard spheres explain the glass-forming ability of bulk metallic glasses?  

E-print Network

We perform molecular dynamics simulations to compress binary hard spheres into jammed packings as a function of the compression rate $R$, size ratio $\\alpha$, and number fraction $x_S$ of small particles to determine the connection between the glass-forming ability (GFA) and packing efficiency in bulk metallic glasses (BMGs). We define the GFA by measuring the critical compression rate $R_c$, below which jammed hard-sphere packings begin to form "random crystal" structures with defects. We find that for systems with $\\alpha \\gtrsim 0.8$ that do not de-mix, $R_c$ decreases strongly with $\\Delta \\phi_J$, as $R_c \\sim \\exp(-1/\\Delta \\phi_J^2)$, where $\\Delta \\phi_J$ is the difference between the average packing fraction of the amorphous packings and random crystal structures at $R_c$. Systems with $\\alpha \\lesssim 0.8$ partially de-mix, which promotes crystallization, but we still find a strong correlation between $R_c$ and $\\Delta \\phi_J$. We show that known metal-metal BMGs occur in the regions of the $\\alpha$ and $x_S$ parameter space with the lowest values of $R_c$ for binary hard spheres. Our results emphasize that maximizing GFA in binary systems involves two competing effects: minimizing $\\alpha$ to increase packing efficiency, while maximizing $\\alpha$ to prevent de-mixing.

Kai Zhang; W. Wendell Smith; Minglei Wang; Yanhui Liu; Jan Schroers; Mark D. Shattuck; Corey S. O'Hern

2014-04-02

428

Connection between the packing efficiency of binary hard spheres and the glass-forming ability of bulk metallic glasses  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations to compress binary hard spheres into jammed packings as a function of the compression rate R, size ratio ?, and number fraction xS of small particles to determine the connection between the glass-forming ability (GFA) and packing efficiency in bulk metallic glasses (BMGs). We define the GFA by measuring the critical compression rate Rc, below which jammed hard-sphere packings begin to form "random crystal" structures with defects. We find that for systems with ? ?0.8 that do not demix, Rc decreases strongly with ??J, as Rc˜exp(-1/??J2), where ??J is the difference between the average packing fraction of the amorphous packings and random crystal structures at Rc. Systems with ? ?0.8 partially demix, which promotes crystallization, but we still find a strong correlation between Rc and ??J. We show that known metal-metal BMGs occur in the regions of the ? and xS parameter space with the lowest values of Rc for binary hard spheres. Our results emphasize that maximizing GFA in binary systems involves two competing effects: minimizing ? to increase packing efficiency, while maximizing ? to prevent demixing.

Zhang, Kai; Smith, W. Wendell; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

2014-09-01

429

Simple metal and binary alloy phases based on the hcp structure: Electronic origin of distortions and superlattices  

NASA Astrophysics Data System (ADS)

Crystal structures of simple metals and binary alloy phases based on the close-packed hexagonal (hcp) structure are analyzed within the model of Fermi sphere - Brillouin zone interactions to understand distortions and superlattices. Examination of the Brillouin-Jones configuration in relation to the nearly-free electron Fermi sphere for several representative phases reveals significance of the electron energy contribution to the phase stability. This approach may be useful for understanding high pressure structures recently found in compressed simple alkali and alkali-earth metals.

Degtyareva, Valentina F.; Afonikova, Nataliya S.

2014-11-01

430

Molecular orbital studies in oxidation: Sulfate formation and metal-metal oxide adhesion  

NASA Technical Reports Server (NTRS)

The chemical mechanisms for sulfate formation from sodium chloride and sulfur trioxide, which is a product of jet fuel combustion was determined. Molten sodium sulfate leads to hot corrosion of the protective oxide layers on turbine blades. How yttrium dopants in nidkel-aluminum alloys used in turbine blades reduce the spalling rate of protective alumina films and enhance their adhesion was also determined. Two other fulfate mechanisms were deduced and structure of carbon monoxide on a clean chronium and clean platinum-titanium alloys surfaces was determined. All studies were by use of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. Seven studies were completed. Their titles and abstracts are given.

Anderson, A. B.

1985-01-01

431

Comparison Between Crystalline and Amorphous Surfaces of Transition Metal Oxide Water Oxidation Catalysts: a Theoretical Perspective  

NASA Astrophysics Data System (ADS)

Amorphous films of transition-metal oxide water oxidation catalysts (WOCs) often show an enhanced catalytic activity compared to their crystalline counterparts [1-4]. In particular, in the case of cobalt-oxide based WOCs the observed similarity in their electrochemical properties and catalytic activity, under oxidative conditions, has been correlated with the formation of similar amorphous surface morphologies, suggesting the presence of a common, catalytically active amorphous structural motif [3,4]. We present ab initio calculations of cobalt oxide based material surfaces and we compare the electronic properties of crystalline and amorphous surfaces, with the aim of identifying differences related to their different catalytic activity.[4pt] [1] Blakemore, J. D., Schley, N. D., Kushner-Lenhoff, M. N., Winter, A. M., D'Souza, F., Crabtree, R. H., and Brudvig, G. W. Inorg. Chem. 51, 7749 (2012); [2] Tsuji, E., Imanishi, A., Fukui, K.-I. and Nakato, Y. Electrochimica Acta 56, 2009 (2011); [3] Jia, H., Stark, J., Zhou, L. Q., Ling, C., Takeshi, S., and Markin, Z. RSC Advances 2, 10874 (2012); [4] Lee, S. W., Carlton, C., Risch, M., Surendranath, Y., Chen, S., Furutsuki, S., Yamada, A., Nocera, D. G., and Shao-Horn, Y. J. Am. Chem. Soc. 134, 16959 (2012).

Skone, Jonathan H.; Galli, Giulia

2013-03-01

432

ON THE ORIGIN OF THE METALLICITY DEPENDENCE IN DYNAMICALLY FORMED EXTRAGALACTIC LOW-MASS X-RAY BINARIES  

SciTech Connect

Globular clusters (GCs) effectively produce dynamically formed low-mass X-ray binaries (LMXBs). Observers detect {approx}100 times more LMXBs per stellar mass in GCs compared to stars in the fields of galaxies. Observationally, metal-rich GCs are about three times more likely to contain an X-ray source than their metal-poor counterparts. Recent observations have shown that this ratio holds in extragalactic GCs for all bright X-ray sources with L{sub X} between 2 Multiplication-Sign 10{sup 37} and 5 Multiplication-Sign 10{sup 38} erg s{sup -1}. In this Letter, we propose that the observed metallicity dependence of LMXBs in extragalactic GCs can be explained by the differences in the number densities and average masses of red giants in populations of different metallicities. Red giants serve as seeds for the dynamical production of bright LMXBs via two channels-binary exchanges and physical collisions-and the increase of the number densities and masses of red giants boost LMXB production, leading to the observed difference. We also discuss a possible effect of the age difference in stellar populations of different metallicities.

Ivanova, N.; Avendano Nandez, J. L.; Sivakoff, G. R. [Department of Physics, University of Alberta, Edmonton, AB T6G 2E1 (Canada); Fragos, T.; Kim, D.-W.; Fabbiano, G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lombardi, J. C. [Department of Physics, Allegheny College, Meadville, PA 16335 (United States); Voss, R. [Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Jordan, A., E-mail: nata.ivanova@ualberta.ca [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Macul, Santiago (Chile)

2012-12-01

433

X-raying metal-poor starburst galaxies: Evidence of an overabundance of luminous X-ray binaries  

NASA Astrophysics Data System (ADS)

We have studied the high mass X-ray binary (HMXB) populations within two low-metallicity, starburst galaxies, Haro 11 and VV 114. These galaxies are particularly interesting because they are good analogs of high-redshift (z > 2) Lyman break galaxies, and are part of a larger sample of Lyman break analogs (LBAs). Previous studies of the X-ray emission in LBAs have found that the X-ray luminosity per star formation rate (SFR) in these galaxies is elevated, potentially because of their low metallicities. Theoretically, XRBs formed in lower metallicity environments lose less mass from stellar winds over their lifetimes, resulting in more numerous and luminous HMXBs per SFR. In this talk, I will present how metallicity influences the X-ray luminosity distribution of HMXBs in these galaxies. This study has greater implications on understanding the evolution of X-ray emission from galaxies over the history of the Universe.

Basu-Zych, Antara; Lehmer, Bret; Hornschemeier, Ann E.; Ptak, Andrew; Yukita, Mihoko; Zezas, Andreas

2015-01-01

434

Effect of Element Diffusion Through Metallic Networks During Oxidation of Type 321 Stainless Steel  

NASA Astrophysics Data System (ADS)

A detailed study was conducted on localized oxidation on Type 321 stainless steel (321ss) using synchrotron x-ray nanobeam analysis along with Raman microscopy. The results showed the presence of metallic nanonetworks in the oxide scales, which plays an important role in the continued oxidation of the alloy at 750 °C. A mechanism is proposed to explain the rapid oxidation of 321ss in complex gaseous environments at elevated temperature. Neutral metal atoms could diffuse outward, and carbon atoms could diffuse inward through the metallic nanonetworks in oxide layers. Alternately, diffusion tunnels can dramatically affect the phase composition of the oxide scales. Since the diffusion rate of neutral metal and carbon atoms through the metallic nanonetworks can be much faster than the diffusion of cations through Cr2O3, the metallic nanonetwork provides a path through the protective Cr2O3 layer for the rapid outward diffusion of metallic chromium and iron atoms to the nonprotective spinel layer. This diffusion process affects the solid-state reaction near the alloy-oxide boundary, and a dense Cr2O3 protective layer does not form. The classic stable structure of the oxide scales, with a dense Cr2O3 layer at the bottom, is damaged by the rapid diffusion through the tunnel at the reaction front, resulting in locally accelerated oxidation. This process can subsequently lead to "breakaway" oxidation and catastrophic failure of the alloy.

Zeng, Z.; Natesan, K.; Cai, Z.; Gosztola, D.; Cook, R.; Hiller, J.

2014-04-01

435

STEM characterization of metal clusters in/on oxides  

NASA Astrophysics Data System (ADS)

Dispersed metal clusters in or on a support matrix are key phenomenons in many technological fields. Two widely used examples of them which are investigated in this thesis are supported-metal clusters in heterogeneous catalysis and transition metal clusters in diluted magnetic semiconductors (DMS) applied in spintronics. The catalytic activity and selectivity of catalysts often depend sensitively on structure parameters, such as particles size and shape. With the same analogy, the magnetic properties of DMS oxides are sensitively related to the crystal defects of the host material as a consequence of doping the transition metal. Therefore it is essential to develop and understand the correlation between nanostructure and function of these materials. STEM Z-contrast imaging is the best candidate for this type of study because of a high degree of resolution it provides and the unique ability it offers to detect and differentiate between the clusters and oxide matrix due to the large difference between their atomic numbers. Moreover the technique development in the STEM field fosters the conjugation of electron energy Loss Spectroscopy (EELS) and Z-contrast imaging and their widespread use for nearly atomic level chemical analysis at interface, second phases, and isolated defects. The advanced preparation method of supported clusters catalysts which is by carbonyl ligands offers a controlled cluster size and shape. MgO-supported Os clusters and SiO2-supported Ta clusters prepared by this method are adsorbed on oxide to convert into single-sized supported metal aggregates. The last step of preparation method is by removal of the ligands (decarbonylation) which is very important because it determines the final size distribution and shape of such clusters. Reaching carbonylated decaosmium clusters with the size of theoretically 0.295 nm and the tetrahedral-shape geometry are the aim of the preparation method. The size distribution measurements of sub-nanoclusters of osmium on MgO support after decarbonylation by a modified blurring propagation method of data analysis in Z-contrast images showed a reduction in size compared to the carbonylated clusters and therefore partial decarbonylation of such clusters. STEM analysis of silica-supported tantalum catalyst showed a relatively wide range in the size of subnanoclusters. In contrast to the first catalyst system there is no theoretical information about the desired size and structure of the tantalum clusters. Therefore in the next step the numbers of Ta atoms in each cluster was measured in order to reveal the shape of the clusters. This was done by quantifying the contribution of the clusters to the contrast in the Z-contrast images by mean of cross section factors. Based on these results two models of atomic Ta clusters were introduced. In the study of Co-doped TiO2 in the class of DMS oxides the HAADF-STEM images of the thin film Co0.04Ti0.96O 2 grown in vacuum and in 100 mTorr Ar+H2 gas were compared. STEM images of the first system showed no evidence of clustering and EELS analysis showed the identical intensity for Co-L2,3 peaks across the thin film to prove the homogeneity in the microstructure, therefore there is a strong probability for the origin of ferromagnetism in the thin film to be intrinsic by the contribution of the 3d dopant ions of substitutional Co. STEM/EELS analysis on the second system confirmed the presence of embedded Co clusters with the mixed valance state for the Co and therefore the mechanism of FM to be by the mean of carrier-mediated exchange responsible for magnetism. In this thesis ability of the combined STEM techniques, fast characterization and direct interpretation in the analysis of nanoscale materials and nanostructures provided the basis for predictive material design with more desirable physical properties.

Mehraeen, Shareghe

436

Role of metal oxides in the thermal degradation of poly(vinyl chloride)  

SciTech Connect

Thermal degradation of poly(vinyl chloride) has been studied in the presence of metal oxides by a thermogravimetric method. It follows a two-step mechanism. In the first step chlorine free radical is formed as in the case of pure PVC, and in the second step chlorine free radical replaces oxygen from metal oxide to form metal chloride and oxygen free radical. Subsequently, the oxygen free radical abstracts hydrogen from PVC. Formation of metal chloride is the rate-controlling step. The metal chlorides formed during the thermal degradation either volatilize or decompose simultaneously to lower metallic chlorides depending on the boiling point or the volatilization temperature.

Gupta, M.C.; Viswanath, S.G. [Nagpur Univ. (India)] [Nagpur Univ. (India)

1998-07-01

437

Redefining the metal/charge-transfer insulator paradigm in transition metal oxides  

NASA Astrophysics Data System (ADS)

The universality of the phase diagram in the variables of interaction strength and d-occupancy, shown for late transition metal oxides in Ref.[1], is examined for two series of early transition metal oxides: (SrVO3, SrCrO3, SrMnO3) and (LaTiO3, LaVO3, LaCrO3) using density functional theory (DFT), DFT+U and DFT+dynamical mean field theory methods. The interaction required to drive the metal-insulator transition is found to depend sensitively on the d-occupancy Nd, and beyond a threshold value of the d-occupancy an insulating state cannot be achieved for any practical value of the interaction. The critical Nd values are determined and compared to ab initio and experimental estimates where available. Additionally, the minimal model for the transition is determined and the crucial role played by the Hunds coupling is demonstrated. [4pt] [1] Xin Wang, M. J. Han, Luca de' Medici, C. A. Marianetti, and Andrew J. Millis (2011). arXiv:1110.2782

Dang, Hung; Ai, Xinyuan; Marianetti, Chris; Millis, Andrew

2012-02-01

438