Synthesis of complex plutonium oxides with alkaline-earth metals

International Nuclear Information System (INIS)

Suzuki, Yasufumi; Nakajima, Kunihisa; Iwai, Takashi; Ohmichi, Toshihiko; Yamawaki, Michio.

1995-03-01

Complex plutonium(IV) oxides with strontium and barium, SuPuO 3 and BaPuO 3 , were synthesized and their crystal structure was analyzed. Compacted mixture of plutonium dioxide powder and the carbonate of strontium or barium was heated in a stream of argon gas using a cell with a small orifice. The products obtained were found to be composed of a nearly single phase showing the structure of orthorhombic slightly distorted from cubic. (author)

Diffusionless phase transitions and related structures in oxides

International Nuclear Information System (INIS)

Boulesteix, C.

1992-01-01

The relative importance of oxides in the field of materials science has been spectacularly increasing during the last twenty years. First the study of ferroelectrics kept the attention of scientists. Nevertheless this domain is far from being worked out and a lot of new results and of new fields of interest were recently discovered. Other ferroic oxides, especially ferroelastics, have also been the subject of a very great number of new results. In these cases the properties of oxides are at room temperature very tightly related to the phase transition that is generally occurring a few hundred of degrees above this room temperature. In many other cases also properties of oxides can be related to the existence of a phase transition or to a rather similar phenomenon. This book has been specially devoted to the study of the properties of oxides which are in some way related to the existence of a phase transition. The first chapters are focussed on general considerations: the first one is devoted to a general study of phase transitions, the second one to the twinning phenomenon which is of special interest for many oxides. Chapters 3 and 4 are focussed on ferroelectric and ferroelastic materials. These four chapters consitute the first part of the book. Chapters 5 to 8 are devoted to the study of oxides of special interest which have some of their properties related to a phase transition or to a rather similar phenomenon: rare earth oxides, oxides with a diffuse phase transition, zirconia and alumina systems, tungsten oxides and their relatives. These four chapters constitute the second part of the book. (orig.)

Origin of Fe-Ti Oxide Mineralization in the Middle Paleoproterozoic Elet'ozero Syenite-Gabbro Intrusive Complex (Northern Karelia, Russia)

Science.gov (United States)

Sharkov, E. V.; Chistyakov, A. V.; Shchiptsov, V. V.; Bogina, M. M.; Frolov, P. V.

2018-03-01

Magmatic oxide mineralization widely developed in syenite-gabbro intrusive complexes is an important Fe and Ti resource. However, its origin is hotly debatable. Some researchers believe that the oxide ores were formed through precipitation of dense Ti-magnetite in an initial ferrogabbroic magma (Bai et al., 2012), whereas others consider them as a product of immiscible splitting of Fe-rich liquid during crystallization of Fe-Ti basaltic magma (Zhou et al., 2013). We consider this problem with a study of the Middle Paleoproterozoic (2086 ± 30 Ma) Elet'ozero Ti-bearing layered intrusive complex in northern Karelia (Baltic Shield). The first ore-bearing phase of the complex is mainly made up of diverse ferrogabbros, with subordinate clinopyroxenites and peridotites. Fe-Ti oxides (magnetite, Ti-magnetite, and ilmenite) usually account for 10-15 vol %, reaching 30-70% in ore varieties. The second intrusive phase is formed by alkaline and nepheline syenites. Petrographical, mineralogical, and geochemical data indicate that the first phase of the intrusion was derived from a moderately alkaline Fe-Ti basaltic melt, while the parental melt of the second phase was close in composition to alkaline trachyte. The orebodies comprise disseminated and massive ores. The disseminated Fe-Ti oxide ores make up lenses and layers conformable to general layering. Massive ores occur in subordinate amounts as layers and lenses, as well as cross-cutting veins. Elevated Nb and Ta contents in Fe-Ti oxides makes it possible to consider them complex ores. It is shown that the Fe-Ti oxide mineralization is related to the formation of a residual (Fe,Ti)-rich liquid, which lasted for the entire solidification history of the first intrusive phase. The liquid originated through multiple enrichment of Fe and Ti in the crystallization zone of the intrusion owing to the following processes: (1) precipitation of silicate minerals in the crystallization zone with a corresponding increase in the Fe and

In between matters, interfaces in complex oxides

NARCIS (Netherlands)

van Zalk, M.

2009-01-01

Complex oxides are emerging as a versatile class of materials, exhibiting a wide variety of properties. In recent years, it has become increasingly clear that the properties of complex-oxide interfaces can differ considerably from those of the bulk. This opens up the possibility of tuning and

In Between Matters : Interfaces in Complex Oxides

NARCIS (Netherlands)

van Zalk, M.

2009-01-01

Complex oxides are emerging as a versatile class of materials, exhibiting a wide variety of properties. In recent years, it has become increasingly clear that the properties of complex-oxide interfaces can differ considerably from those of the bulk. This opens up the possibility of tuning and

Structural phase transitions in niobium oxide nanocrystals

Science.gov (United States)

Yuvakkumar, R.; Hong, Sun Ig

2015-09-01

Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

Integration of functional complex oxide nanomaterials on silicon

Directory of Open Access Journals (Sweden)

Jose Manuel eVila-Fungueiriño

2015-06-01

Full Text Available The combination of standard wafer-scale semiconductor processing with the properties of functional oxides opens up to innovative and more efficient devices with high value applications that can be produced at large scale. This review uncovers the main strategies that are successfully used to monolithically integrate functional complex oxide thin films and nanostructures on silicon: the chemical solution deposition approach (CSD and the advanced physical vapor deposition techniques such as oxide molecular beam epitaxy (MBE. Special emphasis will be placed on complex oxide nanostructures epitaxially grown on silicon using the combination of CSD and MBE. Several examples will be exposed, with a particular stress on the control of interfaces and crystallization mechanisms on epitaxial perovskite oxide thin films, nanostructured quartz thin films, and octahedral molecular sieve nanowires. This review enlightens on the potential of complex oxide nanostructures and the combination of both chemical and physical elaboration techniques for novel oxide-based integrated devices.

Methods for forming complex oxidation reaction products including superconducting articles

International Nuclear Information System (INIS)

Rapp, R.A.; Urquhart, A.W.; Nagelberg, A.S.; Newkirk, M.S.

1992-01-01

This patent describes a method for producing a superconducting complex oxidation reaction product of two or more metals in an oxidized state. It comprises positioning at least one parent metal source comprising one of the metals adjacent to a permeable mass comprising at least one metal-containing compound capable of reaction to form the complex oxidation reaction product in step below, the metal component of the at least one metal-containing compound comprising at least a second of the two or more metals, and orienting the parent metal source and the permeable mass relative to each other so that formation of the complex oxidation reaction product will occur in a direction towards and into the permeable mass; and heating the parent metal source in the presence of an oxidant to a temperature region above its melting point to form a body of molten parent metal to permit infiltration and reaction of the molten parent metal into the permeable mass and with the oxidant and the at least one metal-containing compound to form the complex oxidation reaction product, and progressively drawing the molten parent metal source through the complex oxidation reaction product towards the oxidant and towards and into the adjacent permeable mass so that fresh complex oxidation reaction product continues to form within the permeable mass; and recovering the resulting complex oxidation reaction product

Engineering complex oxide interfaces for oxide electronics

NARCIS (Netherlands)

Roy, Saurabh

2015-01-01

A complex interplay of physics and chemistry in transition metal oxides determines their electronic, magnetic, and ferroic properties enabling a wide range of applications of these materials. BiFeO_3, a canonical multiferroic system exhibits the interesting feature of enhanced conductivity on

Synthesis, characterization and oxidative behaviour of dioxoruthenium(VI) complexes

International Nuclear Information System (INIS)

Agarwal, D.D.; Rastogi, Rachana

1995-01-01

Dioxoruthenium(VI) complexes are found to give low yield of epoxide but good yield of cyclohexanone. The complexes are electro active giving metal centered Ru VI /Ru V couple. Cis-stilbene gives trans epoxide and benzaldehyde. Norbornene gives exo epoxy norbornene. The selectivity for allylic oxidation is high. In the present note the synthesis of dioxoruthenium(VI) complexes and their oxidation behaviour is reported. The dioxoruthenium(VI) complexes have been stoichiometrically found to be good oxidants. (author). 21 refs., 1 tab

Non-equilibrium phase transitions in complex plasma

International Nuclear Information System (INIS)

Suetterlin, K R; Raeth, C; Ivlev, A V; Thomas, H M; Khrapak, S; Zhdanov, S; Rubin-Zuzic, M; Morfill, G E; Wysocki, A; Loewen, H; Goedheer, W J; Fortov, V E; Lipaev, A M; Molotkov, V I; Petrov, O F

2010-01-01

Complex plasma being the 'plasma state of soft matter' is especially suitable for investigations of non-equilibrium phase transitions. Non-equilibrium phase transitions can manifest in dissipative structures or self-organization. Two specific examples are lane formation and phase separation. Using the permanent microgravity laboratory PK-3 Plus, operating onboard the International Space Station, we performed unique experiments with binary mixtures of complex plasmas that showed both lane formation and phase separation. These observations have been augmented by comprehensive numerical and theoretical studies. In this paper we present an overview of our most important results. In addition we put our results in context with research of complex plasmas, binary systems and non-equilibrium phase transitions. Necessary and promising future complex plasma experiments on phase separation and lane formation are briefly discussed.

Poly(N-4-vinylbenzyl-1,4,7-triazacyclononane Copper Complex Grafted Solid Catalyst for Oxidative Polymerization of 2,6-Dimethylphenol

Directory of Open Access Journals (Sweden)

Kei Saito

2016-01-01

Full Text Available A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane copper(I complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl-1,4,7-triaza-cyclononane onto polystyrene particles using a radical mediated polymerization method and next by creating the polymer-metal complex of copper-triazacyclononane with these modified particles. Poly(2,6-dimethyl-1,4-phenylene oxide was successfully obtained from the polymerization of 2,6-dimethylphenol using this new metal-organic solid phase catalyst.

Synthesis of complex oxides with garnet structure by spray drying of an aqueous salt solution

Science.gov (United States)

Makeenko, A. V.; Larionova, T. V.; Klimova-Korsmik, O. G.; Starykh, R. V.; Galkin, V. V.; Tolochko, O. V.

2017-04-01

The use of spray drying to obtain powders of complex oxides with a garnet structure has demonstrated. The processes occurring during heating of the synthesized oxide-salt product, leading to the formation of a material with a garnet structure, have been investigated using DTA, TGA, XPS, and XRD. It has been shown that a single-phase garnet structure of system (Y x Gd(3- x))3Al5O12 can be synthesized over the entire range of compositions.

Phthalocyanines with eight oligo(ethylene oxide) alkoxy units: thermotropic phase behavior, aggregate formation and ion complexation with redox-active ions

NARCIS (Netherlands)

Piet, D.P.; Verheij, H.J.; Zuilhof, H.

2003-01-01

The thermotropic phase behavior of phthalocyanines (Pc's) with eight oligo(ethylene oxide) alkoxy side chains has been investigated. An increase in the number of ethylene oxide units results in a decrease in the solid-to-mesophase and isotropization temperatures. The investigated compounds display a

Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films

Science.gov (United States)

Zhang, H.; Gauquelin, N.; McMahon, C.; Hawthorn, D. G.; Botton, G. A.; Wei, J. Y. T.

2018-03-01

It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7 -δ grown by pulsed laser deposition are annealed at up to 700 atm O2 and 900 ∘C , in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15 -δ and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9 -δ and YBa2Cu6O10 -δ phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7 -δ powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.

Whey Peptide-Iron Complexes Increase the Oxidative Stability of Oil-in-Water Emulsions in Comparison to Iron Salts.

Science.gov (United States)

Caetano-Silva, Maria Elisa; Barros Mariutti, Lilian Regina; Bragagnolo, Neura; Bertoldo-Pacheco, Maria Teresa; Netto, Flavia Maria

2018-02-28

Food fortification with iron may favor lipid oxidation in both food matrices and the human body. This study aimed at evaluating the effect of peptide-iron complexation on lipid oxidation catalyzed by iron, using oil-in-water (O/W) emulsions as a model system. The extent of lipid oxidation of emulsions containing iron salts (FeSO 4 or FeCl 2 ) or iron complexes (peptide-iron complexes or ferrous bisglycinate) was evaluated during 7 days, measured as primary (peroxide value) and secondary products (TBARS and volatile compounds). Both salts catalyzed lipid oxidation, leading to peroxide values 2.6- to 4.6-fold higher than the values found for the peptide-iron complexes. The addition of the peptide-iron complexes resulted in the formation of lower amounts of secondary volatiles of lipid oxidation (up to 78-fold) than those of iron salts, possibly due to the antioxidant activity of the peptides and their capacity to keep iron apart from the lipid phase, since the iron atom is coordinated and takes part in a stable structure. The peptide-iron complexes showed potential to reduce the undesirable sensory changes in food products and to decrease the side effects related to free iron and the lipid damage of cell membranes in the organism, due to the lower reactivity of iron in the complexed form.

Phase-field modeling of corrosion kinetics under dual-oxidants

Science.gov (United States)

Wen, You-Hai; Chen, Long-Qing; Hawk, Jeffrey A.

2012-04-01

A phase-field model is proposed to simulate corrosion kinetics under a dual-oxidant atmosphere. It will be demonstrated that the model can be applied to simulate corrosion kinetics under oxidation, sulfidation and simultaneous oxidation/sulfidation processes. Phase-dependent diffusivities are incorporated in a natural manner and allow more realistic modeling as the diffusivities usually differ by many orders of magnitude in different phases. Simple free energy models are then used for testing the model while calibrated free energy models can be implemented for quantitative modeling.

Phase Transformation of Hot Dipped Aluminium during High Temperature Oxidation

International Nuclear Information System (INIS)

Zaifol Samsu; Muhammad Daud; Hishamuddin Husain; Mohd Saari Ripin; Rusni Rejab; Zaiton Selamat; Mohd Shariff Sattar

2014-01-01

Low alloy carbon steel was coated by hot-dipping into a molten aluminum bath. Isothermal oxidations were carried out at 750 degree Celsius in static air to study the oxidation behaviour of the hot-dipped aluminide steel. The phase transformation in the aluminide layer during diffusion at 750 degree Celsius in static air was analyzed by SEM-EDX and XRD. After hot-dip treatment, the coating layers consisted of three phases, where Al, thinner layer of FeAl 3 , and thicker layer of Fe 2 Al 5 were detected from external topcoat to the aluminide/ steel substrate. After oxidation, the Fe 2 Al 5 formed during the immersion process completely transformed to Fe 2 Al 5 , FeAl 2 , FeAl and Al-Fe(Al) phases because of the composition gradient and the chemical diffusion by oxidation. After oxidation, there are some voids were found at the coating/ substrate interface due to the rapid inter-diffusion of iron and aluminium during oxidation. The FeAl phase kept growing with increasing exposure time at 750 degree Celsius, while the Fe 2 Al 5 was consumed during oxidation. After 168 hrs oxidation, the Fe 2 Al 5 phase was going disappeared as the aluminum layer was consumed. (author)

Heterogeneity in magnetic complex oxides

Science.gov (United States)

Arenholz, Elke

Heterogeneity of quantum materials on the nanoscale can result from the spontaneous formation of regions with distinct atomic, electronic and/or magnetic order, and indicates coexistence of competing quantum phases. In complex oxides, the subtle interplay of lattice, charge, orbital, and spin degrees of freedom gives rise to especially rich phase diagrams. For example, coexisting conducting and insulating phases can occur near metal-insulator transitions, colossal magnetoresistance can emerge where ferromagnetic and antiferromagnetic domains compete, and charge-ordered and superconducting regions are present simultaneously in materials exhibiting high-temperature superconductivity. Additionally, externally applied fields (electric, magnetic, or strain) or other external excitations (light or heat) can tip the energy balance towards one phase, or support heterogeneity and phase coexistence and provide the means to perturb and tailor quantum heterogeneity at the nanoscale. Engineering nanomaterials, with structural, electronic and magnetic characteristics beyond what is found in bulk materials, is possible today through the technique of thin film epitaxy, effectively a method of `spray painting' atoms on single crystalline substrates to create precisely customized layered structures with atomic arrangements defined by the underlying substrate. Charge transfer and spin polarization across interfaces as well as imprinting nanoscale heterogeneity between adjacent layers lead to intriguing and important new phenomena testing our understanding of basic physics and creating new functionalities. Moreover, the abrupt change of orientation of an order parameter between nanoscale domains can lead to unique phases that are localized at domain walls, including conducting domain walls in insulating ferroelectrics, and ferromagnetic domain walls in antiferromagnets. Here we present our recent results on tailoring the electronic anisotropy of multiferroic heterostructures by

Liquid phase oxidation chemistry in continuous-flow microreactors.

Science.gov (United States)

Gemoets, Hannes P L; Su, Yuanhai; Shang, Minjing; Hessel, Volker; Luque, Rafael; Noël, Timothy

2016-01-07

Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described.

From Two-Phase to Three-Phase: The New Electrochemical Interface by Oxide Electrocatalysts

Science.gov (United States)

Xu, Zhichuan J.

2018-03-01

Electrochemical reactions typically occur at the interface between a solid electrode and a liquid electrolyte. The charge exchange behaviour between these two phases determines the kinetics of electrochemical reactions. In the past few years, significant advances have been made in the development of metal oxide electrocatalysts for fuel cell and electrolyser reactions. However, considerable gaps remain in the fundamental understanding of the charge transfer pathways and the interaction between the metal oxides and the conducting substrate on which they are located. In particular, the electrochemical interfaces of metal oxides are significantly different from the traditional (metal) ones, where only a conductive solid electrode and a liquid electrolyte are considered. Oxides are insulating and have to be combined with carbon as a conductive mediator. This electrode configuration results in a three-phase electrochemical interface, consisting of the insulating oxide, the conductive carbon, and the liquid electrolyte. To date, the mechanistic insights into this kind of non-traditional electrochemical interface remain unclear. Consequently conventional electrochemistry concepts, established on classical electrode materials and their two-phase interfaces, are facing challenges when employed for explaining these new electrode materials. [Figure not available: see fulltext.

The relation between intensity and complexity of coronary artery lesion and oxidative stress in patients with acute coronary syndrome.

Science.gov (United States)

Turan, Turhan; Menteşe, Ümit; Ağaç, Mustafa Tarık; Akyüz, Ali Rıza; Kul, Selim; Aykan, Ahmet Çağrı; Bektaş, Hüseyin; Korkmaz, Levent; Öztaş Menteşe, Seda; Dursun, İhsan; Çelik, Şükrü

2015-10-01

Oxidative stress plays a major role in the development of atherosclerosis. However, the relationship between oxidative stress and complexity and intensity of coronary artery disease is less clear. The aim of this study is to assess the relationship between oxidative stress markers and the complexity and intensity of coronary artery disease in patients with acute coronary syndrome (ACS). Sixty-seven consecutive patients with an early phase of ACS (=22). Likewise patients were divided into two CAD severity groups according to the median Gensini score of 64: less intensive CAD with Gensini score (=64. Blood samples were taken in 1 hour within administration in order to measure total oxidative status (TOS) and total antioxidant capacity (TAC) levels determined by Erel method. Oxidative stress index (OSI) was calculated by TOS /TAC. There was no significant difference between the two SYNTAX groups for oxidative stress markers. Median TOS and OSI values were significantly high in the intensive CAD group (p=0.005, p=0.04, respectively). The Gensini score was positively correlated with TOS and OSI (p=0.003, p=0.02, respectively). Oxidative stress markers may be considered supportive laboratory parameters related to CAD intensity but not complexity in ACS patients.

Zirconium metal-water oxidation kinetics. III. Oxygen diffusion in oxide and alpha Zircaloy phases

International Nuclear Information System (INIS)

Pawel, R.E.

1976-10-01

The reaction of Zircaloy in steam at elevated temperature involves the growth of discrete layers of oxide and oxygen-rich alpha Zircaloy from the parent beta phase. The multiphase, moving boundary diffusion problem involved is encountered in a number of important reaction schemes in addition to that of Zircaloy-oxygen and can be completely (albeitly ideally) characterized through an appropriate model in terms of oxygen diffusion coefficients and equilibrium concentrations for the various phases. Conversely, kinetic data for phase growth and total oxygen consumption rates can be used to compute diffusion coefficients. Equations are developed that express the oxygen diffusion coefficients in the oxide and alpha phases in terms of the reaction rate constants and equilibrium solubility values. These equations were applied to recent experimental kinetic data on the steam oxidation of Zircaloy-4 to determine the effective oxygen diffusion coefficients in these phases over the temperature range 1000--1500 0 C

Dissolution of Fe(III) (hydr) oxides by metal-EDTA complexes

Science.gov (United States)

Ngwack, Bernd; Sigg, Laura

1997-03-01

The dissolution of Fe(III)(hydr)oxides (goethite and hydrous ferric oxide) by metal-EDTA complexes occurs by ligand-promoted dissolution. The process is initiated by the adsorption of metal-EDTA complexes to the surface and is followed by the dissociation of the complex at the surface and the release of Fe(III)EDTA into solution. The dissolution rate is decreased to a great extent if EDTA is complexed by metals in comparison to the uncomplexed EDTA. The rate decreases in the order EDTA CaEDTA ≫ PbEDTA > ZnEDTA > CuEDTA > Co(II)EDTA > NiEDTA. Two different rate-limiting steps determine the dissolution process: (1) detachment of Fe(III) from the oxide-structure and (2) dissociation of the metal-EDTA complexes. In the case of goethite, step 1 is slower than step 2 and the dissolution rates by various metals are similar. In the case of hydrous ferric oxide, step 2 is rate-limiting and the effect of the complexed metal is very pronounced.

Phases and structural characteristics of high Tc superconducting oxide in (Bi, Pb)-Sr-Ca-Cu-O system

International Nuclear Information System (INIS)

Chen, Zuyano; Li, Zhengrong; Qian, Yitai; Zhou, Quien; Cheng, Tingzhu

1989-01-01

The various phases, which are responsible for variant maximum d-value including 18.5 angstrom, 15.4 angstrom, 12.2 angstrom, 6.2 angstrom, 3.2 angstrom and possible 9.1 angstrom respectively, observed in high Tc superconducting complex oxide of (Bi,Pb)-Sr-Ca-Cu-O system are reported in this paper according to the result of X-ray diffraction on platelike crystals or crystallites synthesized under different preparation conditions. The phase of tetragonal system with c=3.21 angstrom, a=3.86 angstrom is possible parent structural unit and it is of great significance to the structure constitution of various phases with large lattice parameter c and structural characteristics of superconducting oxide. In view of the above a model of two-dimension stack-up which causes a stack in variant styles along c-axis and constitute various phases with different lattice parameter c is proposed and discussed

A new liquid-phase-separation glaze containing neodymium oxide

International Nuclear Information System (INIS)

Jing, S.; Xianque, C.; Luxing, K.; Pentecost, J.L.

1986-01-01

A color-changeable opaque glaze containing neodymium oxide was investigated. Results show that the glaze is a new example of the liquid-phase-separation type. The discrete phase droplets are from 50 to 500 nm in size. They are rich in Nd, Zn, Ca, and Mg and the continuous phase is rich in Si, Al, and K. The concentration of the discrete phase is approx. =45%. The large number of discrete droplets and the zinc oxide in the glaze increase its opacity to cover the selective light absorption and scattering of the neodymium ion and reduce the opalescence effect

Complexation of amidocarbamoyl phosphine oxides with Ln+3 (Ln = La, Nd, Pm, Sm and Eu) cation series: structural and thermodynamical features

International Nuclear Information System (INIS)

Hosseinnejad, Tayebeh; Kazemi, Tayebeh

2016-01-01

In the present study, we have mainly investigated the nature of interactions in Ln 3+ (Ln = La, Nd, Pm, Sm, Eu) complexes with amidocarbamoyl methyl phosphine oxide (CMPO) and amidocarbamoyl propyl phosphine oxide (CPPO) ligands based on density functional theory (DFT) approaches. In the first step, thermodynamical properties for complexation of CMPO and CPPO ligands with Ln 3+ cation series have been determined in the gas phase and with the presence of three solvents: n-hexane, chloroform and toluene, via polarized continuum model (PCM) computations. The trend of metal-ligand interaction strength has been analyzed and compared with the trend of ionic hardness within the series of lanthanide cations and different size of alkyl chain of amidocarbamoyl phosphine oxide ligand. The calculated thermochemical results in the gas and solution phases reveals that there is a consistency between increasing trend in the hardness of Ln 3+ cation series and also electron-donating property of alkyl chain with increasing in thermodynamical stability of [Ln-CMPO] 3+ and [Ln-CPPO] 3+ complex series. We have also demonstrated that in the complexation reaction of all complex series, using n-hexane as solvent is more favorable thermodynamically than chloroform and toluene. It should be stated that this issue has been observed in many experiments. Finally, analysis of calculated deformation energies and also the variation in bond order of some selected key bonds in CMPO and CPPO ligands and their corresponded Ln 3+ complexes series show a similar trend with increasing in the hardness of Ln 3+ cation series and electron-donating of alkyl chain of amidocarbamoyl phosphine oxide ligand.

Long-term oxidization and phase transition of InN nanotextures

Directory of Open Access Journals (Sweden)

Dražic Goran

2011-01-01

Full Text Available Abstract The long-term (6 months oxidization of hcp-InN (wurtzite, InN-w nanostructures (crystalline/amorphous synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-O x -N y (indium oxynitride phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-O x -N y oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-O x -N y phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

Some organoperoxo complexes of antimony, niobium and tantalum and their oxidation properties

International Nuclear Information System (INIS)

Tarafder, M.T.H.

1999-05-01

Several novel organoperoxo complexes of Nb(V), Ta(V) and Sb(V) have been synthesized and characterized. The complexes have the compositions [M(O 2 ) 2 L Cl] and [M(O 2 ) 2 L'] [L = monodentate and bidentate, neutral ligand; L' = bidentate, uninegative ligand]. These complexes are very reactive to both organic and inorganic substrates. Niobium and tantalum complexes were found to oxidize phosphines and arsines to their oxides. These also oxidize olefins to epoxides under stoichiometric conditions while under catalytic conditions, ring opening of the epoxides occur producing α-hydroxyketone when the substrate is trans-stilbene. The antimony complexes are decidedly inert towards oxidation. (author)

Kinetics, Mechanism, and Secondary Organic Aerosol Yield of Aqueous Phase Photo-oxidation of α-Pinene Oxidation Products.

Science.gov (United States)

Aljawhary, Dana; Zhao, Ran; Lee, Alex K Y; Wang, Chen; Abbatt, Jonathan P D

2016-03-10

Formation of secondary organic aerosol (SOA) involves atmospheric oxidation of volatile organic compounds (VOCs), the majority of which are emitted from biogenic sources. Oxidation can occur not only in the gas-phase but also in atmospheric aqueous phases such as cloudwater and aerosol liquid water. This study explores for the first time the aqueous-phase OH oxidation chemistry of oxidation products of α-pinene, a major biogenic VOC species emitted to the atmosphere. The kinetics, reaction mechanisms, and formation of SOA compounds in the aqueous phase of two model compounds, cis-pinonic acid (PIN) and tricarballylic acid (TCA), were investigated in the laboratory; TCA was used as a surrogate for 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA), a known α-pinene oxidation product. Aerosol time-of-flight chemical ionization mass spectrometry (Aerosol-ToF-CIMS) was used to follow the kinetics and reaction mechanisms at the molecular level. Room-temperature second-order rate constants of PIN and TCA were determined to be 3.3 (± 0.5) × 10(9) and 3.1 (± 0.2) × 10(8) M(-1) s(-1), respectively, from which were estimated their condensed-phase atmospheric lifetimes. Aerosol-ToF-CIMS detected a large number of products leading to detailed reaction mechanisms for PIN and MBTCA. By monitoring the particle size distribution after drying, the amount of SOA material remaining in the particle phase was determined. An aqueous SOA yield of 40 to 60% was determined for PIN OH oxidation. Although recent laboratory studies have focused primarily on aqueous-phase processing of isoprene-related compounds, we demonstrate that aqueous formation of SOA materials also occurs from monoterpene oxidation products, thus representing an additional source of biogenically driven aerosol formation.

Mercury Oxidation via Catalytic Barrier Filters Phase II

Energy Technology Data Exchange (ETDEWEB)

Wayne Seames; Michael Mann; Darrin Muggli; Jason Hrdlicka; Carol Horabik

2007-09-30

In 2004, the Department of Energy National Energy Technology Laboratory awarded the University of North Dakota a Phase II University Coal Research grant to explore the feasibility of using barrier filters coated with a catalyst to oxidize elemental mercury in coal combustion flue gas streams. Oxidized mercury is substantially easier to remove than elemental mercury. If successful, this technique has the potential to substantially reduce mercury control costs for those installations that already utilize baghouse barrier filters for particulate removal. Completed in 2004, Phase I of this project successfully met its objectives of screening and assessing the possible feasibility of using catalyst coated barrier filters for the oxidation of vapor phase elemental mercury in coal combustion generated flue gas streams. Completed in September 2007, Phase II of this project successfully met its three objectives. First, an effective coating method for a catalytic barrier filter was found. Second, the effects of a simulated flue gas on the catalysts in a bench-scale reactor were determined. Finally, the performance of the best catalyst was assessed using real flue gas generated by a 19 kW research combustor firing each of three separate coal types.

Aliasing in the Complex Cepstrum of Linear-Phase Signals

DEFF Research Database (Denmark)

Bysted, Tommy Kristensen

1997-01-01

Assuming linear-phase of the associated time signal, this paper presents an approximated analytical description of the unavoidable aliasing in practical use of complex cepstrums. The linear-phase assumption covers two major applications of complex cepstrums which are linear- to minimum-phase FIR......-filter transformation and minimum-phase estimation from amplitude specifications. The description is made in the cepstrum domain, the Fourier transform of the complex cepstrum and in the frequency domain. Two examples are given, one for verification of the derived equations and one using the description to reduce...... aliasing in minimum-phase estimation...

Heterogeneous Oxidation of Atmospheric Organic Aerosol: Kinetics of Changes to the Amount and Oxidation State of Particle-Phase Organic Carbon.

Science.gov (United States)

Kroll, Jesse H; Lim, Christopher Y; Kessler, Sean H; Wilson, Kevin R

2015-11-05

Atmospheric oxidation reactions are known to affect the chemical composition of organic aerosol (OA) particles over timescales of several days, but the details of such oxidative aging reactions are poorly understood. In this study we examine the rates and products of a key class of aging reaction, the heterogeneous oxidation of particle-phase organic species by the gas-phase hydroxyl radical (OH). We compile and reanalyze a number of previous studies from our laboratories involving the oxidation of single-component organic particles. All kinetic and product data are described on a common basis, enabling a straightforward comparison among different chemical systems and experimental conditions. Oxidation chemistry is described in terms of changes to key ensemble properties of the OA, rather than to its detailed molecular composition, focusing on two quantities in particular, the amount and the oxidation state of the particle-phase carbon. Heterogeneous oxidation increases the oxidation state of particulate carbon, with the rate of increase determined by the detailed chemical mechanism. At the same time, the amount of particle-phase carbon decreases with oxidation, due to fragmentation (C-C scission) reactions that form small, volatile products that escape to the gas phase. In contrast to the oxidation state increase, the rate of carbon loss is nearly uniform among most systems studied. Extrapolation of these results to atmospheric conditions indicates that heterogeneous oxidation can have a substantial effect on the amount and composition of atmospheric OA over timescales of several days, a prediction that is broadly in line with available measurements of OA evolution over such long timescales. In particular, 3-13% of particle-phase carbon is lost to the gas phase after one week of heterogeneous oxidation. Our results indicate that oxidative aging represents an important sink for particulate organic carbon, and more generally that fragmentation reactions play a major

Catalytic wet-air oxidation of lignin in a three-phase reactor with aromatic aldehyde production

Directory of Open Access Journals (Sweden)

Sales F.G.

2004-01-01

Full Text Available In the present work a process of catalytic wet air oxidation of lignin obtained from sugar-cane bagasse is developed with the objective of producing vanillin, syringaldehyde and p-hydroxybenzaldehyde in a continuous regime. Palladium supported on g-alumina was used as the catalyst. The reactions in the lignin degradation and aldehyde production were described by a kinetic model as a system of complex parallel and series reactions, in which pseudo-first-order steps are found. For the purpose of producing aromatic aldehydes in continuous regime, a three-phase fluidized reactor was built, and it was operated using atmospheric air as the oxidizer. The best yield in aromatic aldehydes was of 12%. The experimental results were compatible with those values obtained by the pseudo-heterogeneous axial dispersion model (PHADM applied to the liquid phase.

Patterning of high mobility electron gases at complex oxide interfaces

DEFF Research Database (Denmark)

Trier, Felix; Prawiroatmodjo, G. E. D. K.; von Soosten, Merlin

2015-01-01

Oxide interfaces provide an opportunity for electronics. However, patterning of electron gases at complex oxide interfaces is challenging. In particular, patterning of complex oxides while preserving a high electron mobility remains underexplored and inhibits the study of quantum mechanical effects...... of amorphous-LSM (a-LSM) thin films, which acts as a hard mask during subsequent depositions. Strikingly, the patterned modulation-doped interface shows electron mobilities up to ∼8 700 cm2/V s at 2 K, which is among the highest reported values for patterned conducting complex oxide interfaces that usually...... where extended electron mean free paths are paramount. This letter presents an effective patterning strategy of both the amorphous-LaAlO3/SrTiO3 (a-LAO/STO) and modulation-doped amorphous-LaAlO3/La7/8Sr1/8MnO3/SrTiO3 (a-LAO/LSM/STO) oxide interfaces. Our patterning is based on selective wet etching...

TiO2 Photocatalyzed Oxidation of Free and Complex Metallic Cyanides.

Energy Technology Data Exchange (ETDEWEB)

Valladares, J. E.; Esteghamatdarsthad, B.; Renteria, J.

2006-07-01

The TiO2 photo catalyzed oxidation of free cyanide and transition metal cyanide complexes often found in industrial mining wastes were studied. The photoreactor system used was a UV illuminated and stirred tank with suspended particles of TiO2. After to determine the optimization parameters such as light intensity, concentration of complex and free cyanides, in ideal conditions, the effect of the presence of different type of anions was also studied. The model substances chosen were potassium cyanide and cyanides complexes of Iron, Cobalt and Copper in a strong alkaline solution (pH = 11.0 - 12.0). The experimental results indicate that in the case of the hexaferricyanide complex Fe(CN)6 3, the reaction occur in two steps. The first step is the breakdown of the metal-cyanide bond (photo-dissociation) forming free cyanide (CN-) and Fe3+ ions. The second step is the photo-oxidation of the free cyanides formed before. The ions Fe3+ and OH- present in the alkaline solution, precipitate as iron hydroxide Fe(OH)3. During the photo-dissociation step of the iron complex, free CN- ions produced reaches a maximum concentration before it is eliminated by photo-oxidation. The free cyanide produced from the hexaferricyanide complex disappears rapidly at a velocity of 64.6 + - 5.0 ?M/min. This rate of photo-oxidation is comparable with the experiments using just alkaline solutions of potassium cyanide ('free cyanides'). In contrast, in alkaline solutions of cyanide complexes of Cu and Co the rate of photo-oxidation was substantially reduced (6.17+ - 0.80 ?M/min and 0.04 + - 0.010 ?M/min, respectively) and do not show any initial increase of free cyanides in the suspension. The slower rate of photo-oxidation suggests the formation of very stable hydroxyl-cyanide polymeric metallic complexes in the reaction mix. The photo-oxidation pathway of the nitrogen oxide products was also investigated and found that the final product consists mainly of nitrate ions. (Author)

Heteroaggregation of graphene oxide with minerals in aqueous phase.

Science.gov (United States)

Zhao, Jian; Liu, Feifei; Wang, Zhenyu; Cao, Xuesong; Xing, Baoshan

2015-03-03

Upon release into waters, sediments, and soils, graphene oxide (GO) may interact with fine mineral particles. We investigated the heteroaggregation of GO with different minerals, including montmorillonite, kaolinite, and goethite, in aqueous phase. GO significantly enhanced the dispersion of positively charged goethite (>50%) via heteroaggregation, while there was no interaction between GO and negatively charged montmorillonite or kaolinite. Electrostatic attraction was the dominant force in the GO-goethite heteroaggregation (pH 4.0-8.5), and the dissolved Fe ions (formation of multilayered GO-goethite complex with high configurational stability. These findings are useful for understanding the interaction of GO with mineral surfaces, and potential fate and toxicity of GO under natural conditions in aquatic environments, as well as in soils and sediments.

Complexation of amidocarbamoyl phosphine oxides with Ln{sup +3} (Ln = La, Nd, Pm, Sm and Eu) cation series: structural and thermodynamical features

Energy Technology Data Exchange (ETDEWEB)

Hosseinnejad, Tayebeh; Kazemi, Tayebeh [Alzahra Univ., Tehran (Iran, Islamic Republic of). Dept. of Chemistry

2016-05-01

In the present study, we have mainly investigated the nature of interactions in Ln{sup 3+} (Ln = La, Nd, Pm, Sm, Eu) complexes with amidocarbamoyl methyl phosphine oxide (CMPO) and amidocarbamoyl propyl phosphine oxide (CPPO) ligands based on density functional theory (DFT) approaches. In the first step, thermodynamical properties for complexation of CMPO and CPPO ligands with Ln{sup 3+} cation series have been determined in the gas phase and with the presence of three solvents: n-hexane, chloroform and toluene, via polarized continuum model (PCM) computations. The trend of metal-ligand interaction strength has been analyzed and compared with the trend of ionic hardness within the series of lanthanide cations and different size of alkyl chain of amidocarbamoyl phosphine oxide ligand. The calculated thermochemical results in the gas and solution phases reveals that there is a consistency between increasing trend in the hardness of Ln{sup 3+} cation series and also electron-donating property of alkyl chain with increasing in thermodynamical stability of [Ln-CMPO]{sup 3+} and [Ln-CPPO]{sup 3+} complex series. We have also demonstrated that in the complexation reaction of all complex series, using n-hexane as solvent is more favorable thermodynamically than chloroform and toluene. It should be stated that this issue has been observed in many experiments. Finally, analysis of calculated deformation energies and also the variation in bond order of some selected key bonds in CMPO and CPPO ligands and their corresponded Ln{sup 3+} complexes series show a similar trend with increasing in the hardness of Ln{sup 3+} cation series and electron-donating of alkyl chain of amidocarbamoyl phosphine oxide ligand.

Comprehensive Analysis of the Gas- and Particle-Phase Products of VOC Oxidation

Science.gov (United States)

Bakker-Arkema, J.; Ziemann, P. J.

2017-12-01

Controlled environmental chamber studies are important for determining atmospheric reaction mechanisms and gas and aerosol products formed in the oxidation of volatile organic compounds (VOCs). Such information is necessary for developing detailed chemical models for use in predicting the atmospheric fate of VOCs and also secondary organic aerosol (SOA) formation. However, complete characterization of atmospheric oxidation reactions, including gas- and particle-phase product yields, and reaction branching ratios, are difficult to achieve. In this work, we investigated the reactions of terminal and internal alkenes with OH radicals in the presence of NOx in an attempt to fully characterize the chemistry of these systems while minimizing and accounting for the inherent uncertainties associated with environmental chamber experiments. Gas-phase products (aldehydes formed by alkoxy radical decomposition) and particle-phase products (alkyl nitrates, β-hydroxynitrates, dihydroxynitrates, 1,4-hydroxynitrates, 1,4-hydroxycarbonyls, and dihydroxycarbonyls) formed through pathways involving addition of OH to the C=C double bond as well as H-atom abstraction were identified and quantified using a suite of analytical techniques. Particle-phase products were analyzed in real time with a thermal desorption particle beam mass spectrometer; and off-line by collection onto filters, extraction, and subsequent analysis of functional groups by derivatization-spectrophotometric methods developed in our lab. Derivatized products were also separated by liquid chromatography for molecular quantitation by UV absorbance and identification using chemical ionization-ion trap mass spectrometry. Gas phase aldehydes were analyzed off-line by collection onto Tenax and a 5-channel denuder with subsequent analysis by gas chromatography, or by collection onto DNPH-coated cartridges and subsequent analysis by liquid chromatography. The full product identification and quantitation, with careful

Bimetallic oxamato complexes synthesized into mesoporous matrix as precursor to tunable nanosized oxide

Energy Technology Data Exchange (ETDEWEB)

Kalinke, Lucas H.G. [Instituto de Química, Universidade Federal de Goiás—UFG, Goiânia, GO 74001-970 (Brazil); Instituto Federal de Goiás—IFG, Anápolis, GO (Brazil); Stumpf, Humberto O. [Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG (Brazil); Mazali, Italo O. [Instituto de Química, Universidade Estadual de Campinas—UNICAMP, Campinas, SP (Brazil); Cangussu, Danielle, E-mail: danielle_cangussu@ufg.br [Instituto de Química, Universidade Federal de Goiás—UFG, Goiânia, GO 74001-970 (Brazil)

2015-10-15

Highlights: • The bimetallic oxamato complexes as single-source precursor. • We prepared into a porous silica glass tunable nanosized oxide powders. • X-ray diffraction shows the formation of CeO{sub 2}/CuO and spinel cobaltite. • The different number of IDC allows control of the nanoparticle size. - Abstract: The bimetallic complexes were employed to prepare into a porous silica glass tunable nanosized oxide powders through the single source precursor (SSP) method. These materials were prepared by first anchoring of [Cu(opba)]{sup 2−} [opba = ortho-phenylenebis(oxamato)], second by reaction in situ with second metal [Co(II) or Ce(III)] and followed by a thermal treatment. The different number of impregnation–decomposition cycles (IDC) allows control of the nanoparticle size. X-ray diffraction shows the formation of mixture CeO{sub 2}–CuO and spinel copper cobaltite. Raman spectroscopy confirmed the formation of such phases. Transmission electron microscopy images revealed that spinel cobaltite particles (8 IDC) present a mean size of about 9 nm, whereas for the CeO{sub 2}–CuO phase the particle diameters are 4 nm (2 IDC) and 8 nm (6 IDC). For CeO{sub 2}–CuO the diffuse reflectance spectroscopy indicates a consistent red shift in band gap from 3.41 to 2.87 eV with increasing of particle size due to quantum confinement effect.

Is Solid Phase Microextraction (SPME) an appropriate method for extraction of volatile oxidation products from complex food systems

DEFF Research Database (Denmark)

Jacobsen, Charlotte; Horn, Anna Frisenfeldt; Lu, Henna Fung Sieng

Volatile secondary lipid oxidation products can be identified and quantified by GC-FID or GC-MS. An extraction step is, however, needed before GC analysis. A range of different extraction methods are available such as static headspace, dynamic headspace and SPME. Each of these methods has its...... advantages and drawbacks. Among the advantages of the SPME method are its high sensitivity compared to static headspace and that it is less laborious than the dynamic headspace method. For these reasons, the use of SPME has increased in both academia and industry during the last decade. The extraction...... for analysis of lipid oxidation during storage of complex food matrices. Examples on how uncontrollable factors have affected results obtained with the SPME method in the authors’ lab will be given and the appropriateness of the SPME method for the analysis of volatile oxidation products in selected food...

Solid phase microextraction (SPME) for extraction of volatile oxidation products from complex food systems – Pros and cons

DEFF Research Database (Denmark)

Jacobsen, Charlotte; Horn, Anna Frisenfeldt; Lu, Henna Fung Sieng

Volatile secondary lipid oxidation products can be identified and quantified by GC-FID or GC-MS. An extraction step is, however, needed before GC analysis. A range of different extraction methods are available such as static headspace, dynamic headspace and SPME. Each of these methods has its...... advantages and drawbacks. Among the advantages of the SPME method are its high sensitivity compared to static headspace and that it is less laborious than the dynamic headspace method. For these reasons, the use of SPME has increased in both academia and industry during the last decade. The extraction...... for analysis of lipid oxidation during storage of complex food matrices. Examples on how uncontrollable factors have affected results obtained with the SPME method in the authors’ lab will be given and the appropriateness of the SPME method for the analysis of volatile oxidation products in selected food...

Reaction pathways for catalytic gas-phase oxidation of glycerol over mixed metal oxides

Energy Technology Data Exchange (ETDEWEB)

Suprun, W.; Glaeser, R.; Papp, H. [Leipzig Univ. (Germany). Inst. of Chemical Technology

2011-07-01

Glycerol as a main by-product from bio-diesel manufacture is a cheap raw material with large potential for chemical or biochemical transformations to value-added C3-chemicals. One possible way of glycerol utilization involves its catalytic oxidation to acrylic acid as an alternative to petrochemical routes. However, this catalytic conversion exhibits various problems such as harsh reaction conditions, severe catalyst coking and large amounts of undesired by-products. In this study, the reaction pathways for gas-phase conversion of glycerol over transition metal oxides (Mo, V und W) supported on TiO{sub 2} and SiO{sub 2} were investigated by two methods: (i) steady state experiments of glycerol oxidation and possible reactions intermediates, i.e., acrolein, 3-hydroxy propionaldehyde and acetaldehyde, and (ii) temperature-programmed surface reaction (TPSR) studies of glycerol conversion in the presence and in the absence of gas-phase oxygen. It is shown that the supported W-, V and Mo-oxides possess an ability to catalyze the oxidation of glycerol to acrylic acid. These investigations allowed us to gain a deeper insight into the reaction mechanism. Thus, based on the obtained results, three possible reactions pathways for the selective oxidation of glycerol to acrylic acid on the transition metal-containing catalysts are proposed. The major pathways in presence of molecular oxygen are a fast successive destructive oxidation of glycerol to CO{sub x} and the dehydration of glycerol to acrolein which is a rate-limiting step. (orig.)

Formation of tungsten blue oxide and its phase constitution

International Nuclear Information System (INIS)

Zou, Z.; Wu, E.; Tan, A.; Qian, C.

1984-01-01

By means of X-ray diffraction structure analysis, SEM observation, chemical analysis and particle specific surface analysis etc., an investigation was made in order to determine the regularity of tungsten blue oxide formation during reductional calcine process of APT. It was found that the oxygen index (OI) decreased continuously with increasing calcine temperature. The decrease rate of OI variated as the calcine atmosphere being changed, the stronger the reductivity of the atmosphere is, the more OI decreases. The deammonia-dewater process and the phase constitution variation during calcine was studied, some idea for description of phase transformation path was suggested. It was found that the most important parameter affecting phase constitution and transformation is calcine temperature. At the temperature lower than 450 0 C, the main formed phase was ATB, while at higher temperature, the different phase like W/sub 20/O/sub 58/, WO/sub 3/ etc., could be formed by different ways depending on the atmosphere reductivity. The composition and the OI of ATB are changeable. An experiment for some blue oxides reduction at low temperature was carried out. It was found that OI and the constitution of blue oxide strongly affected the particle size of the formed W-powder

Nematic phase formation in suspensions of graphene oxide

Science.gov (United States)

Fresneau, Nathalie; Campidelli, Stéphane

The last decade has seen the rise of graphene. Graphene is a single layer of graphite; it can be obtained by direct liquid phase exfoliation of the latter through harsh sonication. This technique presents the disadvantage to produce small graphene flakes (typically in the 0.05 to 0.4 μm2 range for the monolayers) and multilayer graphene with uncontrolled thickness distributions. In order to improve the exfoliation process, one has to counter the strong van der Waals interactions between the carbon planes of graphite. This implies to increase the distance between two planes and it can be done, for example, by oxidizing graphite to introduce oxygen species in the graphenic planes. The fabrication of graphite oxide is known for almost 150 years, and it became popular again these last ten years. Generally, the oxidation of graphite is performed following a method described by Hummers in the 1950's and the material produced by this technique exfoliates quasi-spontaneously into monolayer species called graphene oxide (GO). The highly anisotropic shape of GO (several μm in length and width for a thickness of ca. 1 nm) combined with the presence of oxygenated functions on the sp2 carbon structure of graphene lead to the formation of a lyotropic liquid crystalline phase in water. Above a certain concentration of graphene flakes the gain in translational entropy for a long-range ordered phase outweighs the loss in rotational entropy, and the liquid crystal phase then forms. The value of the threshold is affected by the aspect ratio of the graphene flakes but other factors such as the interactions also play a strong role.

Partial thermodynamic functions of hydrogen in complex hydrated vanadium(5) and tungsten(6) oxides

International Nuclear Information System (INIS)

Volkov, V.L.; Zakharova, G.S.

2003-01-01

The partial thermodynamic characteristics of hydrogen in the complex hydrated vanadium(5) and tungsten(6) oxides, obtained through the sol-gel method, of the general formula H 2 V 12-y W y O 31+δ ·nH 2 O (0 ≤ x ≤ 0.33) are determined through the emf method. The changes in these values (ΔG-bar(H 2 ), ΔH-bar(H 2 ) and ΔS-bar(H 2 )) in dependence on the compound composition are discussed. It is established that ΔG-bar(H 2 ) phases, amorphous to X-rays are determined by the ΔS-bar(H 2 ) value and crystalline ones by ΔH-bar(H 2 ). The scheme of the phase relationships of the H 2 O-H-WO 3 -V 2 O 5 system, whereto the given phases are related are presented [ru

Controlling the oxidation of bis-tridentate cobalt(ii) complexes having bis(2-pyridylalkyl)amines: ligand vs. metal oxidation.

Science.gov (United States)

Anjana, S; Donring, S; Sanjib, P; Varghese, B; Murthy, Narasimha N

2017-08-22

Two bis-tridentate chelated cobalt(ii) complexes, which differ in the ligand structure by a methylene group, activate molecular oxygen (O 2 ), and give different oxidation products. The O 2 reaction of [Co II (pepma) 2 ] 2+ (1) with unsymmetrical 2-(2-pyridyl)-N-(2-pyridylmethyl)ethanamine (pepma) results in ligand oxidation, to the corresponding Co(ii) imine complex [Co II (pepmi) 2 ] 2+ (2). Contrastingly, the Co(ii) complex [Co II (bpma) 2 ] 2+ (3) of similar symmetrical bis(2-pyridylmethyl)amine (bpma), undergoes metal oxidation, yielding a cobalt(iii) complex, [Co III (bpma) 2 ] 2+ (4). The reversibility of the amine to imine conversion and the stability of the Co(ii) imine complex (2) are investigated. Furthermore, the solution dynamics of Co(ii) complexes are highlighted with the help of paramagnetic 1 H-NMR spectroscopy.

Laser-induced partial oxidation of cyclohexane in liquid phase

International Nuclear Information System (INIS)

Oshima, Y.; Wu, X.W.; Koda, S.

1995-01-01

A laser-induced partial oxidation of cyclohexane was studied in the liquid phase. With KrF excimer laser (248 nm) irradiation to neat liquid cyclohexane in which O 2 was dissolved, cyclohexanol and cyclohexanone were obtained with very high selectivities, together with cyclohexane as a minor product. Radical recombination reactions to produce dicyclohexyl ether and bicyclohexyl also took place, while these products were not observed in the gas phase reaction. These experimental results were considered to be due not only to higher concentration of cyclohexane but to the cage effect in the liquid phase oxidation. To clarify the reaction progress including the photoabsorption process, the effects of laser intensity and O 2 pressure on product distribution were studied. (author)

Flow assurance : complex phase behavior and complex work requires confidence and vigilance

Energy Technology Data Exchange (ETDEWEB)

Brown, L.D. [ConocoPhillips, Major Projects, Advanced Integrated Simulation, Houston, TX (United States)

2008-07-01

Petroleum exploration and development projects and operations increasingly rely on flow assurance definition. Flow assurance is an integrating discipline as it follows the fluid from the reservoir to the market. Flow assurance works across complex technical and non-technical interfaces, including the reservoir, well completions, operation processes, project management, physical/organic chemistry, fluid mechanics, chemical engineering, mechanical engineering and corrosion. The phase behaviour in real fluids also has complex interfaces. The understanding and management of flow assurance of complex phase behaviour must be well communicated in order to enable proper selection, execution, and operation of development concepts designed to manage successful production within the fluid's phase behaviour. Simulation tools facilitate the translation of science into engineering. Academic, industrial, and field research is the core of these tools. The author cautioned that vigilance is required to assist and identify the right time to move innovation into the core tools.

Complex phase dynamics in coupled bursters

DEFF Research Database (Denmark)

Postnov, D E; Sosnovtseva, Olga; Malova, S Y

2003-01-01

The phenomenon of phase multistability in the synchronization of two coupled oscillatory systems typically arises when the systems individually display complex wave forms associated, for instance, with the presence of subharmonic components. Alternatively, phase multistability can be caused...... the number of spikes per train and the proximity of a neighboring equilibrium point can influence the formation of coexisting regimes....

Complex network analysis in inclined oil–water two-phase flow

International Nuclear Information System (INIS)

Zhong-Ke, Gao; Ning-De, Jin

2009-01-01

Complex networks have established themselves in recent years as being particularly suitable and flexible for representing and modelling many complex natural and artificial systems. Oil–water two-phase flow is one of the most complex systems. In this paper, we use complex networks to study the inclined oil–water two-phase flow. Two different complex network construction methods are proposed to build two types of networks, i.e. the flow pattern complex network (FPCN) and fluid dynamic complex network (FDCN). Through detecting the community structure of FPCN by the community-detection algorithm based on K-means clustering, useful and interesting results are found which can be used for identifying three inclined oil–water flow patterns. To investigate the dynamic characteristics of the inclined oil–water two-phase flow, we construct 48 FDCNs under different flow conditions, and find that the power-law exponent and the network information entropy, which are sensitive to the flow pattern transition, can both characterize the nonlinear dynamics of the inclined oil–water two-phase flow. In this paper, from a new perspective, we not only introduce a complex network theory into the study of the oil–water two-phase flow but also indicate that the complex network may be a powerful tool for exploring nonlinear time series in practice. (general)

Vertical blind phase search for low-complexity carrier phase recovery of offset-QAM Nyquist WDM transmission

Science.gov (United States)

Lu, Jianing; Fu, Songnian; Tang, Haoyuan; Xiang, Meng; Tang, Ming; Liu, Deming

2017-01-01

Low complexity carrier phase recovery (CPR) scheme based on vertical blind phase search (V-BPS) for M-ary offset quadrature amplitude modulation (OQAM) is proposed and numerically verified. After investigating the constellations of both even and odd samples with respect to the phase noise, we identify that the CPR can be realized by measuring the verticality of constellation with respect to different test phase angles. Then measurement without multiplication in the complex plane is found with low complexity. Furthermore, a two-stage configuration is put forward to further reduce the computational complexity (CC). Compared with our recently proposed modified blind phase search (M-BPS) algorithm, the proposed algorithm shows comparable tolerance of phase noise, but reduces the CC by a factor of 3.81 (or 3.05) in the form of multipliers (or adders), taking the CPR of 16-OQAM into account.

The analysis of magnesium oxide hydration in three-phase reaction system

Energy Technology Data Exchange (ETDEWEB)

Tang, Xiaojia; Guo, Lin; Chen, Chen; Liu, Quan; Li, Tie; Zhu, Yimin, E-mail: ntp@dlmu.edu.cn

2014-05-01

In order to investigate the magnesium oxide hydration process in gas–liquid–solid (three-phase) reaction system, magnesium hydroxide was prepared by magnesium oxide hydration in liquid–solid (two-phase) and three-phase reaction systems. A semi-empirical model and the classical shrinking core model were used to fit the experimental data. The fitting result shows that both models describe well the hydration process of three-phase system, while only the semi-empirical model right for the hydration process of two-phase system. The characterization of the hydration product using X-Ray diffraction (XRD) and scanning electron microscope (SEM) was performed. The XRD and SEM show hydration process in the two-phase system follows common dissolution/precipitation mechanism. While in the three-phase system, the hydration process undergo MgO dissolution, Mg(OH){sub 2} precipitation, Mg(OH){sub 2} peeling off from MgO particle and leaving behind fresh MgO surface. - Graphical abstract: There was existence of a peeling-off process in the gas–liquid–solid (three-phase) MgO hydration system. - Highlights: • Magnesium oxide hydration in gas–liquid–solid system was investigated. • The experimental data in three-phase system could be fitted well by two models. • The morphology analysis suggested that there was existence of a peel-off process.

Synthesis of Complex-Alloyed Nickel Aluminides from Oxide Compounds by Aluminothermic Method

Directory of Open Access Journals (Sweden)

Victor Gostishchev

2018-06-01

Full Text Available This paper deals with the investigation of complex-alloyed nickel aluminides obtained from oxide compounds by aluminothermic reduction. The aim of the work was to study and develop the physicochemical basis for obtaining complex-alloyed nickel aluminides and their application for enhancing the properties of coatings made by electrospark deposition (ESD on steel castings, as well as their use as grain refiners for tin bronze. The peculiarities of microstructure formation of master alloys based on the Al–TM (transition metal system were studied using optical, electronic scanning microscopy and X-ray spectral microanalysis. There were regularities found in the formation of structural components of aluminum alloys (Ni–Al, Ni-Al-Cr, Ni-Al-Mo, Ni-Al-W, Ni-Al-Ti, Ni-Cr-Mo-W, Ni-Al-Cr-Mo-W-Ti, Ni-Al-Cr-V, Ni-Al-Cr-V-Mo and changes in their microhardness, depending on the composition of the charge, which consisted of oxide compounds, and on the amount of reducing agent (aluminum powder. It is shown that all the alloys obtained are formed on the basis of the β phase (solid solution of alloying elements in nickel aluminide and quasi-eutectic, consisting of the β′ phase and intermetallics of the alloying elements. The most effective alloys, in terms of increasing microhardness, were Al-Ni-Cr-Mo-W (7007 MPa and Al-Ni-Cr-V-Mo (7914 MPa. The perspective is shown for applying the synthesized intermetallic master alloys as anode materials for producing coatings by electrospark deposition on steel of C1030 grade. The obtained coatings increase the heat resistance of steel samples by 7.5 times, while the coating from NiAl-Cr-Mo-W alloy remains practically nonoxidized under the selected test conditions. The use of NiAl intermetallics as a modifying additive (0.15 wt. % in tin bronze allows increasing the microhardness of the α-solid solution by 1.9 times and the microhardness of the eutectic (α + β phase by 2.7 times.

Laser beam complex amplitude measurement by phase diversity.

Science.gov (United States)

Védrenne, Nicolas; Mugnier, Laurent M; Michau, Vincent; Velluet, Marie-Thérèse; Bierent, Rudolph

2014-02-24

The control of the optical quality of a laser beam requires a complex amplitude measurement able to deal with strong modulus variations and potentially highly perturbed wavefronts. The method proposed here consists in an extension of phase diversity to complex amplitude measurements that is effective for highly perturbed beams. Named camelot for Complex Amplitude MEasurement by a Likelihood Optimization Tool, it relies on the acquisition and processing of few images of the beam section taken along the optical path. The complex amplitude of the beam is retrieved from the images by the minimization of a Maximum a Posteriori error metric between the images and a model of the beam propagation. The analytical formalism of the method and its experimental validation are presented. The modulus of the beam is compared to a measurement of the beam profile, the phase of the beam is compared to a conventional phase diversity estimate. The precision of the experimental measurements is investigated by numerical simulations.

Investigations in physical mechanism of the oxidative desulfurization process assisted simultaneously by phase transfer agent and ultrasound.

Science.gov (United States)

Bhasarkar, Jaykumar B; Chakma, Sankar; Moholkar, Vijayanand S

2015-05-01

This paper attempts to discern the physical mechanism of the oxidative desulfurization process simultaneously assisted by ultrasound and phase transfer agent (PTA). With different experimental protocols, an attempt is made to deduce individual beneficial effects of PTA and ultrasound on the oxidative desulfurization system, and also the synergy between the effects of PTA and ultrasound. Effect of PTA is more marked for mechanically stirred system due to mass transfer limitations, while intense emulsification due to ultrasound helps overcome the mass transfer limitations and reduces the extent of enhancement of oxidation by PTA. Despite application of PTA and ultrasound, the intrinsic factors and properties of the reactants such as polarity (and hence partition coefficient) and diffusivity have a crucial effect on the extent of oxidation. The intrinsic reactivity of the oxidant also plays a vital role, as seen from the extent of oxidation achieved with performic acid and peracetic acid. The interfacial transport of oxidant in the form of oxidant-PTA complex reduces the undesired consumption of oxidant by the reducing species formed during transient cavitation in organic medium, which helps effective utilization of oxidant towards desulfurization. Copyright © 2014 Elsevier B.V. All rights reserved.

Gel phase formation in dilute triblock copolyelectrolyte complexes

Science.gov (United States)

Srivastava, Samanvaya; Andreev, Marat; Levi, Adam E.; Goldfeld, David J.; Mao, Jun; Heller, William T.; Prabhu, Vivek M.; de Pablo, Juan J.; Tirrell, Matthew V.

2017-02-01

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

[DNA complexes, formed on aqueous phase surfaces: new planar polymeric and composite nanostructures].

Science.gov (United States)

Antipina, M N; Gaĭnutdinov, R V; Rakhnianskaia, A A; Sergeev-Cherenkov, A N; Tolstikhina, A L; Iurova, T V; Kislov, V V; Khomutov, G B

2003-01-01

The formation of DNA complexes with Langmuir monolayers of the cationic lipid octadecylamine (ODA) and the new amphiphilic polycation poly-4-vinylpyridine with 16% of cetylpyridinium groups (PVP-16) on the surface of an aqueous solution of native DNA of low ionic strength was studied. Topographic images of Langmuir-Blodgett films of DNA/ODA and DNA/PVP-16 complexes applied to micaceous substrates were investigated by the method of atomic force microscopy. It was found that films of the amphiphilic polycation have an ordered planar polycrystalline structure. The morphology of planar DNA complexes with the amphiphilic cation substantially depended on the incubation time and the phase state of the monolayer on the surface of the aqueous DNA solution. Complex structures and individual DNA molecules were observed on the surface of the amphiphilic monolayer. Along with quasi-linear individual bound DNA molecules, characteristic extended net-like structures and quasi-circular toroidal condensed conformations of planar DNA complexes were detected. Mono- and multilayer films of DNA/PVP-16 complexes were used as templates and nanoreactors for the synthesis of inorganic nanostructures via the binding of metal cations from the solution and subsequent generation of the inorganic phase. As a result, ultrathin polymeric composite films with integrated DNA building blocks and quasi-linear arrays of inorganic semiconductor (CdS) and iron oxide nanoparticles and nanowires were obtained. The nanostructures obtained were characterized by scanning probe microscopy and transmission electron microscopy techniques. The methods developed are promising for investigating the mechanisms of structural organization and transformation in DNA and polyelectrolyte complexes at the gas-liquid interface and for the design of new extremely thin highly ordered planar polymeric and composite materials, films, and coatings with controlled ultrastructure for applications in nanoelectronics and

Thermal neutron detectors based on complex oxide crystals

CERN Document Server

Ryzhikov, V; Volkov, V; Chernikov, V; Zelenskaya, O

2002-01-01

The ways of improvement of spectrometric quality of CWO and GSO crystals have been investigated with the aim of their application in thermal neutron detectors based on radiation capture reactions. The efficiency of the neutron detection by these crystals was measured, and the obtained data were compared with the results for sup 6 LiI(Tl) crystals. It is shown that the use of complex oxide crystals and neutron-absorption filters for spectrometry of thermal and resonance neutrons could be a promising method in combination with computer data processing. Numerical calculations are reported for spectra of gamma-quanta due to radiation capture of the neutrons. To compensate for the gamma-background lines, we used a crystal pair of heavy complex oxides with different sensitivity to neutrons.

Oxidation kinetics of zircaloy-4 in the temperature range correspondent to alpha phase

International Nuclear Information System (INIS)

Medeiros, L.F.

1975-12-01

Oxidation kinetics of Zry-4 in the alpha phase is isothermally studied in the temperature range from 600 0 C to 800 0 C, by continuous and discontinuous gravimetric methods. The total mass gain during the oxidation takes place by two distinct ways: oxide formation and solid solution formation. The first one has been studied by microscopy: the latter by microhardness. The oxygen diffusion coefficients in the zirconium are experimentally determined by microhardness measurements and are compared with those obtained by the oxide layer thickness and by oxygen mass in the oxide. The oxygen diffusion coefficients in the oxide are obtained too by oxide layer thickness and by oxygen diffusivities in the alpha phase and compared with literature. (author)

Study of complex formation of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel

International Nuclear Information System (INIS)

Ismailova, M.M.; Egorova, L.A.; Khamidov, B.O.

1993-01-01

Present article is devoted to study of complex formation of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel. The condition of cobalt in various rate of oxidation in acrylamide aqueous solutions was studied. The concentration conditions of stability of system Co(II)-Co(III) were defined. The composition of coordination compounds of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel was determined.

Complementation of biotransformations with chemical C-H oxidation: copper-catalyzed oxidation of tertiary amines in complex pharmaceuticals.

Science.gov (United States)

Genovino, Julien; Lütz, Stephan; Sames, Dalibor; Touré, B Barry

2013-08-21

The isolation, quantitation, and characterization of drug metabolites in biological fluids remain challenging. Rapid access to oxidized drugs could facilitate metabolite identification and enable early pharmacology and toxicity studies. Herein, we compared biotransformations to classical and new chemical C-H oxidation methods using oxcarbazepine, naproxen, and an early compound hit (phthalazine 1). These studies illustrated the low preparative efficacy of biotransformations and the inability of chemical methods to oxidize complex pharmaceuticals. We also disclose an aerobic catalytic protocole (CuI/air) to oxidize tertiary amines and benzylic CH's in drugs. The reaction tolerates a broad range of functionalities and displays a high level of chemoselectivity, which is not generally explained by the strength of the C-H bonds but by the individual structural chemotype. This study represents a first step toward establishing a chemical toolkit (chemotransformations) that can selectively oxidize C-H bonds in complex pharmaceuticals and rapidly deliver drug metabolites.

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.

Science.gov (United States)

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati; Yang, Young Nam; Aro, Eva-Mari; Carpentier, Robert; Eaton-Rye, Julian J; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

2012-10-01

The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 Å resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster.

Surface reaction of SnII on goethite (α-FeOOH): surface complexation, redox reaction, reductive dissolution, and phase transformation.

Science.gov (United States)

Dulnee, Siriwan; Scheinost, Andreas C

2014-08-19

To elucidate the potential risk of (126)Sn migration from nuclear waste repositories, we investigated the surface reactions of Sn(II) on goethite as a function of pH and Sn(II) loading under anoxic condition with O2 level redox state and surface structure were investigated by Sn K edge X-ray absorption spectroscopy (XAS), goethite phase transformations were investigated by high-resolution transmission electron microscopy and selected area electron diffraction. The results demonstrate the rapid and complete oxidation of Sn(II) by goethite and formation of Sn(IV) (1)E and (2)C surface complexes. The contribution of (2)C complexes increases with Sn loading. The Sn(II) oxidation leads to a quantitative release of Fe(II) from goethite at low pH, and to the precipitation of magnetite at higher pH. To predict Sn sorption, we applied surface complexation modeling using the charge distribution multisite complexation approach and the XAS-derived surface complexes. Log K values of 15.5 ± 1.4 for the (1)E complex and 19.2 ± 0.6 for the (2)C complex consistently predict Sn sorption across pH 2-12 and for two different Sn loadings and confirm the strong retention of Sn(II) even under anoxic conditions.

Crystalline oxides on semiconductors: A structural transition of the interface phase

Science.gov (United States)

Walker, F. J.; Buongiorno-Nardelli, Marco; Billman, C. A.; McKee, R. A.

2004-03-01

The growth of crystalline oxides on silicon is facilitated by the preparation of a surface phase of alkaline earth silicide. We describe how the surface phase serves as a precursor of the final interface phase using reflection high energy electron diffraction (RHEED) and density functional theory (DFT). RHEED intensity oscillations of the growth of BaSrO show layer-by-layer build up of the oxide on the interface. The 2x1 symmetry of the surface precursor persists up to 3 ML BaSrO coverage at which point a 1x1 pattern characteristic of the rock-salt structure of BaSrO is observed. Prior to 3 ML growth of alkaline earth oxide, DFT calculations and RHEED show that the surface precursor persists as the interface phase and induces large displacements in the growing oxide layer away from the rock-salt structure and having a 2x1 symmetry. These distortions of the rock-salt structure are energetically unfavorable and become more unfavorable as the oxide thickness increases. At 3 ML, the stability of the rock-salt structure drives a structural transformation of the film and the interface phase to a structure that is distinct from the surface precursor. Research sponsored jointly by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory under contract DE-AC05-00OR22725 with UT-Battelle, LLC and at the University of Tennessee under contract DE-FG02-01ER45937. Calculations have been performed on CCS supercomputers at Oak Ridge National Laboratory.

Process for forming a homogeneous oxide solid phase of catalytically active material

Science.gov (United States)

Perry, Dale L.; Russo, Richard E.; Mao, Xianglei

1995-01-01

A process is disclosed for forming a homogeneous oxide solid phase reaction product of catalytically active material comprising one or more alkali metals, one or more alkaline earth metals, and one or more Group VIII transition metals. The process comprises reacting together one or more alkali metal oxides and/or salts, one or more alkaline earth metal oxides and/or salts, one or more Group VIII transition metal oxides and/or salts, capable of forming a catalytically active reaction product, in the optional presence of an additional source of oxygen, using a laser beam to ablate from a target such metal compound reactants in the form of a vapor in a deposition chamber, resulting in the deposition, on a heated substrate in the chamber, of the desired oxide phase reaction product. The resulting product may be formed in variable, but reproducible, stoichiometric ratios. The homogeneous oxide solid phase product is useful as a catalyst, and can be produced in many physical forms, including thin films, particulate forms, coatings on catalyst support structures, and coatings on structures used in reaction apparatus in which the reaction product of the invention will serve as a catalyst.

Structural phase transitions and superconductivity in lanthanum copper oxides

International Nuclear Information System (INIS)

Crawford, M.K.; Harlow, R.L.; McCarron, E.M.

1996-01-01

Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La 2 CuO 4 . This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper

Experimental study of the oxide film structural phase state in the E635 and E110 alloys

International Nuclear Information System (INIS)

Shevyakov, A. Yu.; Shishov, V. N.; Novikov, V. V.

2013-01-01

The microstructure, phase and element compositions of oxide films of E110 (Zr-1%Nb) and E635 (Zr-1%Nb-0,35%Fe-1,2%Sn) alloys after autoclave tests in pure water had been studied by the method of transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). TEM investigations of oxide film structure were carried on different oxide layers according to their thickness (near interface of “metal-oxide”, in central part of the oxide film and near outer surface) and in cross-section. The results of the tests show that oxide films of the alloys have different microstructure (grain size, fraction of tetragonal phase, content of defects, etc) and the phase compositions. The crystal structure of oxide films is mainly monoclinic, however, at the “metal-oxide” interface there are a significant fraction of the tetragonal phase. Researching of oxides on different stages of oxidation allow us to determine the kinetics of the second phase precipitate structure change: a) in E635 alloy at early oxidation stages of the amorphization process of the Laves phase precipitates begins with decreasing the content of iron and niobium; b) in E110 alloy the amorphization process of β-Nb precipitates begins at a later stage of oxidation. The influence of changes of the crystal structure and the chemical composition of the second phase precipitates on protective properties of the oxides had been determined. Researching of alloying element redistribution in E635 alloy oxide film shows that iron and niobium are concentrated in pores. Increased porosity of the E635 alloy oxide films at a later oxidation stage, in comparison with the E110 alloy, shows the influence of change composition and subsequent dissolution of the Laves phase particles on the pore formation in the oxide. (authors)

Liquid phase oxidation via heterogeneous catalysis organic synthesis and industrial applications

CERN Document Server

Clerici, Mario G

2013-01-01

Sets the stage for environmentally friendly industrial organic syntheses From basic principles to new and emerging industrial applications, this book offers comprehensive coverage of heterogeneous liquid-phase selective oxidation catalysis. It fully examines the synthesis, characterization, and application of catalytic materials for environmentally friendly organic syntheses. Readers will find coverage of all the important classes of catalysts, with an emphasis on their stability and reusability. Liquid Phase Oxidation via Heterogeneous Catalysis features contributions from an internation

Phases quantification in titanium oxides by means of X-ray diffraction

International Nuclear Information System (INIS)

Macias B, L.R.; Garcia C, R.M.; Ita T, A. de; Chavez R, A.

2001-01-01

In this work two phases of titanium oxides are quantified which belong to the same crystalline system and by means of a computer program named Quanto created by the first author, contains the information for calculating the absorption coefficients, it can be quantified phases having one of the pure phases and the problem samples. In order to perform this work different mixtures of different titanium oxides were prepared measuring by means of the X-ray diffraction technique in the Siemens X-ray diffractometer of ININ which were processed with the Peakfit package and also they were evaluated by means of the computer program with the necessary information finding acceptable results. (Author)

Efficient catalytic cycloalkane oxidation employing a "helmet" phthalocyaninato iron(III) complex.

Science.gov (United States)

Brown, Elizabeth S; Robinson, Jerome R; McCoy, Aaron M; McGaff, Robert W

2011-06-14

We have examined the catalytic activity of an iron(III) complex bearing the 14,28-[1,3-diiminoisoindolinato]phthalocyaninato (diiPc) ligand in oxidation reactions with three substrates (cyclohexane, cyclooctane, and indan). This modified metallophthalocyaninato complex serves as an efficient and selective catalyst for the oxidation of cyclohexane and cyclooctane, and to a far lesser extent indan. In the oxidations of cyclohexane and cyclooctane, in which hydrogen peroxide is employed as the oxidant under inert atmosphere, we have observed turnover numbers of 100.9 and 122.2 for cyclohexanol and cyclooctanol, respectively. The catalyst shows strong selectivity for alcohol (vs. ketone) formation, with alcohol to ketone (A/K) ratios of 6.7 and 21.0 for the cyclohexane and cyclooctane oxidations, respectively. Overall yields (alcohol + ketone) were 73% for cyclohexane and 92% for cyclooctane, based upon the total hydrogen peroxide added. In the catalytic oxidation of indan under similar conditions, the TON for 1-indanol was 10.1, with a yield of 12% based upon hydrogen peroxide. No 1-indanone was observed in the product mixture.

Phase transitions in Pareto optimal complex networks.

Science.gov (United States)

Seoane, Luís F; Solé, Ricard

2015-09-01

The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem, finding phase transitions of different kinds. Distinct phases are associated with different arrangements of the connections, but the need of drastic topological changes does not determine the presence or the nature of the phase transitions encountered. Instead, the functions under optimization do play a determinant role. This reinforces the view that phase transitions do not arise from intrinsic properties of a system alone, but from the interplay of that system with its external constraints.

A novel pre-oxidation method for elemental mercury removal utilizing a complex vaporized absorbent

International Nuclear Information System (INIS)

Zhao, Yi; Hao, Runlong; Guo, Qing

2014-01-01

Graphical abstract: - Highlights: • An innovative liquid-phase complex absorbent (LCA) for Hg 0 removal was prepared. • A novel integrative process for Hg 0 removal was proposed. • The simultaneous removal efficiencies of SO 2 , NO and Hg 0 were 100%, 79.5% and 80.4%, respectively. • The reaction mechanism of simultaneous removal of SO 2 , NO and Hg 0 was proposed. - Abstract: A novel semi-dry integrative method for elemental mercury (Hg 0 ) removal has been proposed in this paper, in which Hg 0 was initially pre-oxidized by a vaporized liquid-phase complex absorbent (LCA) composed of a Fenton reagent, peracetic acid (CH 3 COOOH) and sodium chloride (NaCl), after which Hg 2+ was absorbed by the resultant Ca(OH) 2 . The experimental results indicated that CH 3 COOOH and NaCl were the best additives for Hg 0 oxidation. Among the influencing factors, the pH of the LCA and the adding rate of the LCA significantly affected the Hg 0 removal. The coexisting gases, SO 2 and NO, were characterized as either increasing or inhibiting in the removal process, depending on their concentrations. Under optimal reaction conditions, the efficiency for the single removal of Hg 0 was 91%. Under identical conditions, the efficiencies of the simultaneous removal of SO 2 , NO and Hg 0 were 100%, 79.5% and 80.4%, respectively. Finally, the reaction mechanism for the simultaneous removal of SO 2 , NO and Hg 0 was proposed based on the characteristics of the removal products as determined by X-ray diffraction (XRD), atomic fluorescence spectrometry (AFS), the analysis of the electrode potentials, and through data from related research references

Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy

International Nuclear Information System (INIS)

Castro, V. de; Marquis, E.A.; Lozano-Perez, S.; Pareja, R.; Jenkins, M.L.

2011-01-01

Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% Y 2 O 3 alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.

Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy

Energy Technology Data Exchange (ETDEWEB)

Castro, V. de, E-mail: vanessa.decastro@uc3m.es [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Marquis, E.A.; Lozano-Perez, S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganes, Madrid (Spain); Jenkins, M.L. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom)

2011-06-15

Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% Y{sub 2}O{sub 3} alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.

Imprinted magnetic graphene oxide for the mini-solid phase extraction of Eu (III) from coal mine area

Science.gov (United States)

Patra, Santanu; Roy, Ekta; Madhuri, Rashmi; Sharma, Prashant K.

2017-05-01

The present work represents the preparation of imprinted magnetic reduced graphene oxide and applied it for the selective removal of Eu (III) from local coal mines area. A simple solid phase extraction method was used for this purpose. The material shows a very high adsorption as well as removal efficiency towards Eu (III), which suggest that the material have potential to be used in future for their real time applications in removal of Eu (III) from complex matrices.

Mechanism of water oxidation by trivalent ruthenium trisdipyridyl complex

International Nuclear Information System (INIS)

Moravskij, A.P.; Khannanov, N.K.; Khramov, A.V.; Shafirovich, V.Ya.

1983-01-01

Results of kinetic investigation of water oxidation reaction with photogenerated single-electron oxidizer-trisdipyridyl complex of Ru(3) are presented. CoCl 2 x6H 2 O within the concentration range of [Co 2+ ] 0 =5x10 -7 - 5x10 -5 M was used as a reaction catalyst. The method of stopped flow with spectrophotometric recording was used in order to control the reaction kinetics

Hydrogen Bonding in Phosphine Oxide/Phosphate-Phenol Complexes

NARCIS (Netherlands)

Cuypers, R.; Sudhölter, E.J.R.; Zuilhof, H.

2010-01-01

To develop a new solvent-impregnated resin (SIR) system for the removal of phenols and thiophenols from water, complex formation by hydrogen bonding of phosphine oxides and phosphates is studied using isothermal titration calorimetry (ITC) and quantum chemical modeling. Six different computational

Nanoparticles of complex metal oxides synthesized using the ...

Indian Academy of Sciences (India)

ASHOK K GANGULI∗, TOKEER AHMAD, PADAM R ARYA and PIKA JHA ... nanoparticles of several dielectric oxides like BaTiO3, Ba2TiO4, SrTiO3, PbTiO3 .... reasonable stability till 150◦C. All the lead-doped phases (sintered at 900◦C) show.

Low temperature phase transition of the stoichiometric Ln2NiO4 oxides

International Nuclear Information System (INIS)

Fernandez, F.; Saez-Puche, R.; Botto, I.L.; Baran, E.J.

1991-01-01

In this paper we will present a comparative study of the structural phase transition in Ln 2 NiO 4 oxides, by means of neutron diffraction and infrared(IR) spectroscopy. In the Ln 2 NiO 4 oxides (Ln=La, Pr and Nd), there is a low temperature structural phase transition from the orthorhombic symmetry to a tetragonal phase, of first order character. The IR spectra show, at low temperature, a splitting of the bands related with the stretching Ni-O, strongly correlated with the phase transformation. From the neutron data, the phase transition can be visualized as a sudden tilt of the nickel octahedra

Electrocatalytic Azide Oxidation Mediated by a Rh(PNP) Pincer Complex

NARCIS (Netherlands)

Rebreyend, Christophe; Gloaguen, Yann; Lutz, Martin; Van Der Vlugt, Jarl Ivar; Siewert, Inke; Schneider, Sven; Bruin, Bas De

2017-01-01

One-electron oxidation of the rhodium(I) azido complex [Rh(N3)(PNP)] (5), bearing the neutral, pyridine-based PNP ligand 2,6-bis(di-tert-butylphosphinomethyl)pyridine, leads to instantaneous and selective formation of the mononuclear rhodium(I) dinitrogen complex [Rh(N2)(PNP)]+ (9+). Interestingly,

Electrocatalytic Azide Oxidation Mediated by a Rh(PNP) Pincer Complex

NARCIS (Netherlands)

Rebreyend, C.; Gloaguen, Y.; Lutz, M.; van der Vlugt, J.I.; Siewert, I.; Schneider, S.; de Bruin, B.

2017-01-01

One-electron oxidation of the rhodium(I) azido complex [Rh(N3)(PNP)] ( 5 ), bearing the neutral, pyridine-based PNP ligand 2,6-bis(di-tert-butylphosphinomethyl)pyridine, leads to instantaneous and selective formation of the mononuclear rhodium(I) dinitrogen complex [Rh(N2)(PNP)]+ ( 9 +).

The Fourier Transform Microwave (ftmw) Spectra of Cyclohexene Oxide and its Argon Complex

Science.gov (United States)

Frohman, Daniel J.; Novick, Stewart E.; Pringle, Wallace C.

2012-06-01

The microwave spectrum of cyclohexene oxide and its isotopologues have been observed and assigned, improving upon previous rotational studies of this molecule. Additionally, the 17O isotopomer of cyclohexene oxide and the Ar complex of the normal isotopologue of cyclohexene oxide have been fit for the first time. Fits for the 13C-cyclohexene oxide Ar complexes will also be presented. Tatsuya Ikeda, Roger Kewley, and R. F. Curl, Jr. J. Mol. Spectrosc., 4} (1972), 459-469. Raquel Sánchez, Susana Blanco, Juan C. López, and José L. Alonso. J. Mol. Struct., 780-781 (2006), 57-64.

Using lanthanoid complexes to phase large macromolecular assemblies

International Nuclear Information System (INIS)

Talon, Romain; Kahn, Richard; Durá, M. Asunción; Maury, Olivier; Vellieux, Frédéric M. D.; Franzetti, Bruno; Girard, Eric

2011-01-01

A lanthanoid complex, [Eu(DPA) 3 ] 3− , was used to obtain experimental phases at 4.0 Å resolution of PhTET1-12s, a large self-compartmentalized homo-dodecameric protease complex of 444 kDa. Lanthanoid ions exhibit extremely large anomalous X-ray scattering at their L III absorption edge. They are thus well suited for anomalous diffraction experiments. A novel class of lanthanoid complexes has been developed that combines the physical properties of lanthanoid atoms with functional chemical groups that allow non-covalent binding to proteins. Two structures of large multimeric proteins have already been determined by using such complexes. Here the use of the luminescent europium tris-dipicolinate complex [Eu(DPA) 3 ] 3− to solve the low-resolution structure of a 444 kDa homododecameric aminopeptidase, called PhTET1-12s from the archaea Pyrococcus horikoshii, is reported. Surprisingly, considering the low resolution of the data, the experimental electron density map is very well defined. Experimental phases obtained by using the lanthanoid complex lead to maps displaying particular structural features usually observed in higher-resolution maps. Such complexes open a new way for solving the structure of large molecular assemblies, even with low-resolution data

Mapping gas-phase organic reactivity and concomitant secondary organic aerosol formation: chemometric dimension reduction techniques for the deconvolution of complex atmospheric data sets

Science.gov (United States)

Wyche, K. P.; Monks, P. S.; Smallbone, K. L.; Hamilton, J. F.; Alfarra, M. R.; Rickard, A. R.; McFiggans, G. B.; Jenkin, M. E.; Bloss, W. J.; Ryan, A. C.; Hewitt, C. N.; MacKenzie, A. R.

2015-07-01

Highly non-linear dynamical systems, such as those found in atmospheric chemistry, necessitate hierarchical approaches to both experiment and modelling in order to ultimately identify and achieve fundamental process-understanding in the full open system. Atmospheric simulation chambers comprise an intermediate in complexity, between a classical laboratory experiment and the full, ambient system. As such, they can generate large volumes of difficult-to-interpret data. Here we describe and implement a chemometric dimension reduction methodology for the deconvolution and interpretation of complex gas- and particle-phase composition spectra. The methodology comprises principal component analysis (PCA), hierarchical cluster analysis (HCA) and positive least-squares discriminant analysis (PLS-DA). These methods are, for the first time, applied to simultaneous gas- and particle-phase composition data obtained from a comprehensive series of environmental simulation chamber experiments focused on biogenic volatile organic compound (BVOC) photooxidation and associated secondary organic aerosol (SOA) formation. We primarily investigated the biogenic SOA precursors isoprene, α-pinene, limonene, myrcene, linalool and β-caryophyllene. The chemometric analysis is used to classify the oxidation systems and resultant SOA according to the controlling chemistry and the products formed. Results show that "model" biogenic oxidative systems can be successfully separated and classified according to their oxidation products. Furthermore, a holistic view of results obtained across both the gas- and particle-phases shows the different SOA formation chemistry, initiating in the gas-phase, proceeding to govern the differences between the various BVOC SOA compositions. The results obtained are used to describe the particle composition in the context of the oxidised gas-phase matrix. An extension of the technique, which incorporates into the statistical models data from anthropogenic (i

Oxidation studies of β-sialon ceramics containing amorphous and / or crystalline intergranular phases

International Nuclear Information System (INIS)

Persson, J.; Kall, P.O.; Jansson, K.; Nygren, M.

1992-01-01

β-sialon ceramics of equal overall compositions but containing amorphous, partly crystalline and almost completely crystalline intergranular phase(s) have been oxidized in oxygen at 1350 deg C for 20 hours. The obtained weight gain curves do not follow the parabolic rate law (ΔW/A 0 ) 2 = k p t + β. To the extent that crystallization occurs in the oxide scale during the oxidation experiment, the amorphous cross section area through which oxygen most easily diffuses will decrease with time. A brief description of this new rate law is given, and the obtained oxidation curves will be discussed within that framework. 4 refs., 2 tabs., 2 figs

Reaction of CO2 with propylene oxide and styrene oxide catalyzed by a chromium(III) amine-bis(phenolate) complex.

Science.gov (United States)

Dean, Rebecca K; Devaine-Pressing, Katalin; Dawe, Louise N; Kozak, Christopher M

2013-07-07

A diamine-bis(phenolate) chromium(III) complex, {CrCl[O2NN'](BuBu)}2 catalyzes the copolymerization of propylene oxide with carbon dioxide. The synthesis of this metal complex is straightforward and it can be obtained in high yields. This catalyst incorporates a tripodal amine-bis(phenolate) ligand, which differs from the salen or salan ligands typically used with Cr and Co complexes that have been employed as catalysts for the synthesis of such polycarbonates. The catalyst reported herein yields low molecular weight polymers with narrow polydispersities when the reaction is performed at room temperature. Performing the reaction at elevated temperatures causes the selective synthesis of propylene carbonate. The copolymerization activity for propylene oxide and carbon dioxide, as well as the coupling of carbon dioxide and styrene oxide to give styrene carbonate are presented.

Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

Energy Technology Data Exchange (ETDEWEB)

Gomez, Celia L. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Depablos-Rivera, Osmary, E-mail: osmarydep@yahoo.com [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Silva-Bermudez, Phaedra [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Instituto Nacional de Rehabilitación, Calz. México Xochimilco No. 289 Col. Arenal de Guadalupe, C.P.14389, Ciudad de México, D.F. (Mexico); Muhl, Stephen [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre [Laboratoire de Physique de la Matière Condensée, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 1 (France); Camps, Enrique [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, kilómetro 36.5. La Marquesa, Municipio de Ocoyoacac, CP 52750, Estado de México (Mexico); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico)

2015-03-02

The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi{sub 2}O{sub 3} thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi{sub 2}O{sub 3} phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi{sub 2}O{sub 3} thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV.

Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

International Nuclear Information System (INIS)

Gomez, Celia L.; Depablos-Rivera, Osmary; Silva-Bermudez, Phaedra; Muhl, Stephen; Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre; Camps, Enrique; Rodil, Sandra E.

2015-01-01

The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi 2 O 3 thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi 2 O 3 phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi 2 O 3 thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV

Quantifying Complexity in Quantum Phase Transitions via Mutual Information Complex Networks.

Science.gov (United States)

Valdez, Marc Andrew; Jaschke, Daniel; Vargas, David L; Carr, Lincoln D

2017-12-01

We quantify the emergent complexity of quantum states near quantum critical points on regular 1D lattices, via complex network measures based on quantum mutual information as the adjacency matrix, in direct analogy to quantifying the complexity of electroencephalogram or functional magnetic resonance imaging measurements of the brain. Using matrix product state methods, we show that network density, clustering, disparity, and Pearson's correlation obtain the critical point for both quantum Ising and Bose-Hubbard models to a high degree of accuracy in finite-size scaling for three classes of quantum phase transitions, Z_{2}, mean field superfluid to Mott insulator, and a Berzinskii-Kosterlitz-Thouless crossover.

Quantifying Complexity in Quantum Phase Transitions via Mutual Information Complex Networks

Science.gov (United States)

Valdez, Marc Andrew; Jaschke, Daniel; Vargas, David L.; Carr, Lincoln D.

2017-12-01

We quantify the emergent complexity of quantum states near quantum critical points on regular 1D lattices, via complex network measures based on quantum mutual information as the adjacency matrix, in direct analogy to quantifying the complexity of electroencephalogram or functional magnetic resonance imaging measurements of the brain. Using matrix product state methods, we show that network density, clustering, disparity, and Pearson's correlation obtain the critical point for both quantum Ising and Bose-Hubbard models to a high degree of accuracy in finite-size scaling for three classes of quantum phase transitions, Z2, mean field superfluid to Mott insulator, and a Berzinskii-Kosterlitz-Thouless crossover.

Phase Behavior and Equations of State of the Actinide Oxides

Science.gov (United States)

Chidester, B.; Pardo, O. S.; Panero, W. R.; Fischer, R. A.; Thompson, E. C.; Heinz, D. L.; Prescher, C.; Prakapenka, V. B.; Campbell, A.

2017-12-01

The distribution of the long-lived heat-producing actinide elements U and Th in the deep Earth has important implications for the dynamics of the mantle and possibly the energy budget of Earth's core. The low shear velocities of the Large Low-Shear Velocity Provinces (LLSVPs) on the core-mantle boundary suggests that these regions are at least partially molten and may contain concentrated amounts of the radioactive elements, as well as other large cations such as the rare Earth elements. As such, by exploring the phase behavior of actinide-bearing minerals at extreme conditions, some insight into the mineralogy, formation, and geochemical and geodynamical effects of these regions can be gained. We have performed in situ high-pressure, high-temperature synchrotron X-ray diffraction experiments and calculations on two actinide oxide materials, UO2 and ThO2, to determine their phase behavior at the extreme conditions of the lower mantle. Experiments on ThO2 reached 60 GPa and 2500 K, and experiments on UO2 reached 95 GPa and 2500 K. We find that ThO2 exists in the fluorite-type structure to 20 GPa at high temperatures, at which point it transforms to the high-pressure cotunnite-type structure and remains thus up to 60 GPa. At room temperature, an anomalous expansion of the fluorite structure is observed prior to the transition, and may signal anion sub-lattice disorder. Similarly, UO2 exists in the fluorite-type structure at ambient conditions and up to 28 GPa at high temperatures. Above these pressures, we have observed a previously unidentified phase of UO2 with a tetragonal structure as the lower-temperature phase and the cotunnite-type phase at higher temperatures. Above 78 GPa, UO2 undergoes another transition or possible dissociation into two separate oxide phases. These phase diagrams suggest that the actinides could exist as oxides in solid solution with other analogous phases (e.g. ZrO2) in the cotunnite-type structure throughout much of Earth's lower mantle.

Solution of a Complex Least Squares Problem with Constrained Phase.

Science.gov (United States)

Bydder, Mark

2010-12-30

The least squares solution of a complex linear equation is in general a complex vector with independent real and imaginary parts. In certain applications in magnetic resonance imaging, a solution is desired such that each element has the same phase. A direct method for obtaining the least squares solution to the phase constrained problem is described.

Electrocatalytic oxidations of pyridine derivatives using Ru(IV) poly pyridine complex

International Nuclear Information System (INIS)

Oliveira, S.M. de.

1989-01-01

The oxidation reactions electro catalysed by bi pyridine oxo tri pyridine ruthenium perchlorate metallic complex from selected organic substrates are studied. The obtained results are compared with forecasting results showing the coherence of suggested mechanism. The substrates 2-, 2- and 4- picolines with its respective 1-oxides and 1,2 -; 1,3 - and 1,4 - dimethyl pyridine chloride salts were analysed. The oxidation of toluene as reference substrate was also studied and the mass spectra of oxidation products were interpreted. (M.C.K.)

Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex.

Science.gov (United States)

Kafentzi, Maria-Chrysanthi; Papadakis, Raffaello; Gennarini, Federica; Kochem, Amélie; Iranzo, Olga; Le Mest, Yves; Le Poul, Nicolas; Tron, Thierry; Faure, Bruno; Simaan, A Jalila; Réglier, Marius

2018-04-06

Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H 2 O as an oxygen source. To date, this strategy has not been reported for copper complexes. Herein, a copper(II) complex, [(RPY2)Cu(OTf) 2 ] (RPY2=N-substituted bis[2-pyridyl(ethylamine)] ligands; R=indane; OTf=triflate), is used. This complex, which contains an oxidizable substrate moiety (indane), is used as a tool to monitor an intramolecular oxygen atom transfer reaction. Electrochemical properties were investigated and, upon electrolysis at 1.30 V versus a normal hydrogen electrode (NHE), both dioxygen production and oxygenation of the indane moiety were observed. The ligand was oxidized in a highly diastereoselective manner, which indicated that the observed reactivity was mediated by metal-centered reactive species. The pH dependence of the reactivity was monitored and correlated with speciation deduced from different techniques, ranging from potentiometric titrations to spectroscopic studies and DFT calculations. Water oxidation for dioxygen production occurs at neutral pH and is probably mediated by the oxidation of a mononuclear copper(II) precursor. It is achieved with a rather low overpotential (280 mV at pH 7), although with limited efficiency. On the other hand, oxygenation is maximum at pH 8-8.5 and is probably mediated by the electrochemical oxidation of an antiferromagnetically coupled dinuclear bis(μ-hydroxo) copper(II) precursor. This constitutes the first example of copper-centered oxidative water activation for a selective oxygenation reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidation behaviour of a Ti2AlN MAX-phase coating

International Nuclear Information System (INIS)

Wang Qimin; Kim, Kwangho; Garkas, W; Renteria, A Flores; Leyens, C; Sun Chao

2011-01-01

In this paper, we reported the oxidation behaviour of Ti 2 AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti 2 AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti 2 AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

Comparative analysis of oxide phase formation and its effects on electrical properties of SiO{sub 2}/InSb metal-oxide-semiconductor structures

Energy Technology Data Exchange (ETDEWEB)

Lee, Jaeyel [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Park, Sehun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Jungsub; Yang, Changjae; Kim, Sujin; Seok, Chulkyun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Park, Jinsub [Department of Electronic Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Yoon, Euijoon, E-mail: eyoon@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)

2012-06-01

We report on the changes in the interfacial phases between SiO{sub 2} and InSb caused by various deposition temperatures and heat treatments. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to evaluate the relative amount of each phase present at the interface. The effect of interfacial phases on the electrical properties of SiO{sub 2}/InSb metal-oxide-semiconductor (MOS) structures was investigated by capacitance-voltage (C-V) measurements. The amount of both In and Sb oxides increased with the deposition temperature. The amount of interfacial In oxide was larger for all samples, regardless of the deposition and annealing temperatures and times. In particular, the annealed samples contained less than half the amount of Sb oxide compared with the as-deposited samples, indicating a strong interfacial reaction between Sb oxide and the InSb substrate during annealing. The interface trap density sharply increased for deposition temperatures above 240 Degree-Sign C. The C-V measurements and Raman spectroscopy indicated that elemental Sb accumulation due to the interfacial reaction of Sb oxide with InSb substrate was responsible for the increased interfacial trap densities in these SiO{sub 2}/InSb MOS structures. - Highlights: Black-Right-Pointing-Pointer We report the quantitative analysis of interfacial oxides at the SiO{sub 2}/InSb interface. Black-Right-Pointing-Pointer Interfacial oxides were measured quantitatively by X-ray Photoelectron Spectroscopy. Black-Right-Pointing-Pointer As-grown and annealed samples showed different compositions of oxide phases. Black-Right-Pointing-Pointer Considerable reduction of antimony oxide phases was observed during annealing. Black-Right-Pointing-Pointer Interface trap densities at the SiO{sub 2}/InSb interface were calculated.

Monoterpene oxidation in an oxidative flow reactor: SOA yields and the relationship between bulk gas-phase properties and organic aerosol growth

Science.gov (United States)

Friedman, B.; Link, M.; Farmer, D.

2016-12-01

We use an oxidative flow reactor (OFR) to determine the secondary organic aerosol (SOA) yields of five monoterpenes (alpha-pinene, beta-pinene, limonene, sabinene, and terpinolene) at a range of OH exposures. These OH exposures correspond to aging timescales of a few hours to seven days. We further determine how SOA yields of beta-pinene and alpha-pinene vary as a function of seed particle type (organic vs. inorganic) and seed particle mass concentration. We hypothesize that the monoterpene structure largely accounts for the observed variance in SOA yields for the different monoterpenes. We also use high-resolution time-of-flight chemical ionization mass spectrometry to calculate the bulk gas-phase properties (O:C and H:C) of the monoterpene oxidation systems as a function of oxidant concentrations. Bulk gas-phase properties can be compared to the SOA yields to assess the capability of the precursor gas-phase species to inform the SOA yields of each monoterpene oxidation system. We find that the extent of oxygenated precursor gas-phase species corresponds to SOA yield.

Reaction kinetics of oxygen on single-phase alloys, oxidation of nickel and niobium alloys

International Nuclear Information System (INIS)

Lalauze, Rene

1973-01-01

This research thesis first addresses the reaction kinetics of oxygen on alloys. It presents some generalities on heterogeneous reactions (conventional theory, theory of jumps), discusses the core reaction (with the influence of pressure), discusses the influence of metal self-diffusion on metal oxidation kinetics (equilibrium conditions at the interface, hybrid diffusion regime), reports the application of the hybrid diffusion model to the study of selective oxidation of alloys (Wagner model, hybrid diffusion model) and the study of the oxidation kinetics of an alloy forming a solid solution of two oxides. The second part reports the investigation of the oxidation of single phase nickel and niobium alloys (phase α, β and γ)

Syntrophic acetate oxidation in two-phase (acid-methane) anaerobic digesters.

Science.gov (United States)

Shimada, T; Morgenroth, E; Tandukar, M; Pavlostathis, S G; Smith, A; Raskin, L; Kilian, R E

2011-01-01

The microbial processes involved in two-phase anaerobic digestion were investigated by operating a laboratory-scale acid-phase (AP) reactor and analyzing two full-scale, two-phase anaerobic digesters operated under mesophilic (35 °C) conditions. The digesters received a blend of primary sludge and waste activated sludge (WAS). Methane levels of 20% in the laboratory-scale reactor indicated the presence of methanogenic activity in the AP. A phylogenetic analysis of an archaeal 16S rRNA gene clone library of one of the full-scale AP digesters showed that 82% and 5% of the clones were affiliated with the orders Methanobacteriales and Methanosarcinales, respectively. These results indicate that substantial levels of aceticlastic methanogens (order Methanosarcinales) were not maintained at the low solids retention times and acidic conditions (pH 5.2-5.5) of the AP, and that methanogenesis was carried out by hydrogen-utilizing methanogens of the order Methanobacteriales. Approximately 43, 31, and 9% of the archaeal clones from the methanogenic phase (MP) digester were affiliated with the orders Methanosarcinales, Methanomicrobiales, and Methanobacteriales, respectively. A phylogenetic analysis of a bacterial 16S rRNA gene clone library suggested the presence of acetate-oxidizing bacteria (close relatives of Thermacetogenium phaeum, 'Syntrophaceticus schinkii,' and Clostridium ultunense). The high abundance of hydrogen consuming methanogens and the presence of known acetate-oxidizing bacteria suggest that acetate utilization by acetate oxidizing bacteria in syntrophic interaction with hydrogen-utilizing methanogens was an important pathway in the second-stage of the two-phase digestion, which was operated at high ammonium-N concentrations (1.0 and 1.4 g/L). A modified version of the IWA Anaerobic Digestion Model No. 1 (ADM1) with extensions for syntrophic acetate oxidation and weak-acid inhibition adequately described the dynamic profiles of volatile acid production

Phased array ultrasound testing on complex geometry

International Nuclear Information System (INIS)

Tuan Arif Tuan Mat; Khazali Mohd Zin

2009-01-01

Phase array ultrasonic inspection is used to investigate its response to complex welded joints geometry. A 5 MHz probe with 64 linear array elements was employed to scan mild steel T-joint, nozzle and node samples. These samples contain many defects such as cracks, lack of penetration and lack of fusion. Ultrasonic respond is analysed and viewed using the Tomoview software. The results show the actual phase array images on respective types of defect. (author)

A novel pre-oxidation method for elemental mercury removal utilizing a complex vaporized absorbent

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yi, E-mail: zhaoyi9515@163.com; Hao, Runlong; Guo, Qing

2014-09-15

Graphical abstract: - Highlights: • An innovative liquid-phase complex absorbent (LCA) for Hg{sup 0} removal was prepared. • A novel integrative process for Hg{sup 0} removal was proposed. • The simultaneous removal efficiencies of SO{sub 2}, NO and Hg{sup 0} were 100%, 79.5% and 80.4%, respectively. • The reaction mechanism of simultaneous removal of SO{sub 2}, NO and Hg{sup 0} was proposed. - Abstract: A novel semi-dry integrative method for elemental mercury (Hg{sup 0}) removal has been proposed in this paper, in which Hg{sup 0} was initially pre-oxidized by a vaporized liquid-phase complex absorbent (LCA) composed of a Fenton reagent, peracetic acid (CH{sub 3}COOOH) and sodium chloride (NaCl), after which Hg{sup 2+} was absorbed by the resultant Ca(OH){sub 2}. The experimental results indicated that CH{sub 3}COOOH and NaCl were the best additives for Hg{sup 0} oxidation. Among the influencing factors, the pH of the LCA and the adding rate of the LCA significantly affected the Hg{sup 0} removal. The coexisting gases, SO{sub 2} and NO, were characterized as either increasing or inhibiting in the removal process, depending on their concentrations. Under optimal reaction conditions, the efficiency for the single removal of Hg{sup 0} was 91%. Under identical conditions, the efficiencies of the simultaneous removal of SO{sub 2}, NO and Hg{sup 0} were 100%, 79.5% and 80.4%, respectively. Finally, the reaction mechanism for the simultaneous removal of SO{sub 2}, NO and Hg{sup 0} was proposed based on the characteristics of the removal products as determined by X-ray diffraction (XRD), atomic fluorescence spectrometry (AFS), the analysis of the electrode potentials, and through data from related research references.

Water oxidation catalysis with nonheme iron complexes under acidic and basic conditions: homogeneous or heterogeneous?

Science.gov (United States)

Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi

2013-08-19

Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions.

Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

Energy Technology Data Exchange (ETDEWEB)

Platt, P., E-mail: Philip.Platt@manchester.ac.uk [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Frankel, P. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Gass, M.; Howells, R. [AMEC, Walton House, Faraday Street, Birchwood Park, Risley, Warrington WA3 6GA (United Kingdom); Preuss, M. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom)

2014-11-15

Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal–oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.

Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

Science.gov (United States)

Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.

2014-11-01

Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal-oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.

Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

International Nuclear Information System (INIS)

Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.

2014-01-01

Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal–oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations

Effect of boron oxide on the cubic-to-monoclinic phase transition in yttria-stabilized zirconia

International Nuclear Information System (INIS)

Florio, D.Z. de; Muccillo, R.

2004-01-01

Specimens of yttria fully stabilized zirconia with different amounts of boron oxide have been studied by X-ray diffraction at room temperature and at higher temperatures up to 1250 deg. C. A boron oxide-assisted cubic-to-monoclinic phase transformation was determined in the temperature range 800-1250 deg. C. In situ high temperature X-ray diffraction experiments gave evidences of the dependence of the phase transformation on the heating rate. The possibility of tuning the cubic-monoclinic phase ratio by suitable addition of boron oxide before pressing and sintering is proposed

Multistep Oxidation of Diethynyl Oligophenylamine-Bridged Diruthenium and Diiron Complexes.

Science.gov (United States)

Zhang, Jing; Guo, Shen-Zhen; Dong, Yu-Bao; Rao, Li; Yin, Jun; Yu, Guang-Ao; Hartl, František; Liu, Sheng Hua

2017-01-17

Homo-dinuclear nonlinear complexes [{M(dppe)Cp*} 2 {μ-(-C≡C) 2 X}] (dppe = 1,2-bis(diphenylphosphino)ethane; Cp* = η 5 -C 5 Me 5 ; X = triphenylamine (TPA), M = Ru (1a) and Fe (1b); X = N,N,N',N'-tetraphenylphenylene-1,4-diamine (TPPD), M = Ru (2a)) were prepared and characterized by 1 H, 13 C, and 31 P NMR spectroscopy and single-crystal X-ray diffraction (1a, 2a). Attempts to prepare the diiron analogue of 2a were not successful. Experimental data obtained from cyclic voltammetry, square wave voltammetry, UV-vis-NIR (NIR = near-infrared) spectro-electrochemistry, and very informative IR spectro-electrochemistry in the C≡C stretching region, combined with density functional theory calculations, afford to make an emphasizing assessment of the close association between the metal-ethynyl termini and the oligophenylamine bridge core as well as their respective involvement in sequential one-electron oxidations of these complexes. The anodic behavior of the homo-bimetallic complexes depends strongly both on the metal center and the length of the oligophenylamine bridge core. The poorly separated first two oxidations of diiron complex 1b are localized on the electronically nearly independent Fe termini. In contrast, diruthenium complex 1a exhibits a significantly delocalized character and a marked electronic communication between the ruthenium centers through the diethynyl-TPA bridge. The ruthenium-ethynyl halves in 2a, separated by the doubly extended and more flexible TPPD bridge core, show a lower degree of electronic coupling, resulting in close-lying first two anodic waves and the NIR electronic absorption of [2a] + with an indistinctive intervalence charge transfer character. Finally, the third anodic waves in the voltammetric responses of the homo-bimetallic complexes are associated with the concurrent exclusive oxidation of the TPA or TPPD bridge cores.

Method of forming an oxide superconducting thin film having an R1A2C3 crystalline phase over an R2A1C1 crystalline phase

International Nuclear Information System (INIS)

Lelental, M.; Romanofsky, H.J.

1992-01-01

This patent describes a process which comprises forming a mixed rare earth alkaline earth copper oxide layer on a substrate and converting the mixed rare earth alkaline earth copper oxide layer to an electrically conductive layer. It comprises crystalline R 1 A 2 C 3 oxide phase by heating in the presence of oxygen, wherein rare earth and R is in each instance chosen from among yttrium, lanthanum, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium and alkaline earth and A is in each instance chosen from among calcium, strontium and barium, characterized in that a crystalline R 2 A 1 C 1 oxide phase is first formed as a layer on the substrate and the crystalline R 1 A 2 C 3 oxide phase is formed over the crystalline R 2 A 1 C 1 oxide phase by coating a mixed rare earth alkaline earth copper oxide on the crystalline R 2 A 1 C 1 oxide phase and heating the mixed rare earth alkaline earth copper oxide to a temperature of at least 1000 degrees C

Phase Identification and Internal Stress Analysis of Steamside Oxides on Plant Exposed Superheater Tubes

DEFF Research Database (Denmark)

Pantleon, Karen; Montgomery, Melanie

2012-01-01

During long-term, high-temperature exposure of superheater tubes in thermal power plants, various oxides are formed on the inner side (steamside) of the tubes, and oxide spallation is a serious problem for the power plant industry. Most often, oxidation in a steam atmosphere is investigated...... in laboratory experiments just mimicking the actual conditions in the power plant for simplified samples. On real plant-exposed superheater tubes, the steamside oxides are solely investigated microscopically. The feasibility of X-ray diffraction for the characterization of steamside oxidation on real plant......-exposed superheater tubes was proven in the current work; the challenges for depth-resolved phase analysis and phase-specific residual stress analysis at the inner side of the tubes with concave surface curvature are discussed. Essential differences between the steamside oxides formed on two different steels...

Exploring the oxidation and iron binding profile of a cyclodextrin encapsulated quercetin complex unveiled a controlled complex dissociation through a chemical stimulus.

Science.gov (United States)

Diamantis, Dimitrios A; Ramesova, Sarka; Chatzigiannis, Christos M; Degano, Ilaria; Gerogianni, Paraskevi S; Karadima, Constantina; Perikleous, Sonia; Rekkas, Dimitrios; Gerothanassis, Ioannis P; Galaris, Dimitrios; Mavromoustakos, Thomas; Valsami, Georgia; Sokolova, Romana; Tzakos, Andreas G

2018-06-07

Flavonoids possess a rich polypharmacological profile and their biological role is linked to their oxidation state protecting DNA from oxidative stress damage. However, their bioavailability is hampered due to their poor aqueous solubility. This can be surpassed through encapsulation to supramolecular carriers as cyclodextrin (CD). A quercetin- 2HP-β-CD complex has been formerly reported by us. However, once the flavonoid is in its 2HP-β-CD encapsulated state its oxidation potential, its decomplexation mechanism, its potential to protect DNA damage from oxidative stress remained elusive. To unveil this, an array of biophysical techniques was used. The quercetin-2HP-β-CD complex was evaluated through solubility and dissolution experiments, electrochemical and spectroelectrochemical studies (Cyclic Voltammetry) UV-Vis spectroscopy, HPLC-ESI-MS/MS and HPLC-DAD, fluorescence spectroscopy, NMR Spectroscopy, theoretical calculations (density functional theory (DFT)) and biological evaluation of the protection offered against H 2 O 2 -induced DNA damage. Encapsulation of quercetin inside the supramolecule's cavity enhanced its solubility and oxidation profile is retained in its encapsulated state. Although the protective ability of the quercetin-2HP-β-CD complex against H 2 O 2 was diminished, iron serves as a chemical stimulus to dissociate the complex and release quercetin. We found that in a quercetin-2HP-β-CD inclusion complex quercetin retains its oxidation profile similarly to its native state, while iron can operate as a chemical stimulus to release quercetin from its host cavity. The oxidation profile of a natural product once it is encapsulated in a supramolecular cyclodextrin carrier as also it was discovered that decomplexation can be triggered by a chemical stimulus. Copyright © 2018. Published by Elsevier B.V.

Pentachlorophenol dechlorination with zero valent iron: a Raman and GCMS study of the complex role of surficial iron oxides.

Science.gov (United States)

Gunawardana, Buddhika; Swedlund, Peter J; Singhal, Naresh; Nieuwoudt, Michel K

2018-04-20

The dechlorination of chlorinated organic pollutants by zero valent iron (ZVI) is an important water treatment process with a complex dependence on many variables. This complexity means that there are reported inconsistencies in terms of dechlorination with ZVI and the effect of ZVI acid treatment, which are significant and are as yet unexplained. This study aims to decipher some of this complexity by combining Raman spectroscopy with gas chromatography-mass spectrometry (GC-MS) to investigate the influence of the mineralogy of the iron oxide phases on the surface of ZVI on the reductive dechlorination of pentachlorophenol (PCP). Two electrolytic iron samples (ZVI-T and ZVI-H) were found to have quite different PCP dechlorination reactivity in batch reactors under anoxic conditions. Raman analysis of the "as-received" ZVI-T indicated the iron was mainly covered with the ferrous oxide (FeO) wustite, which is non-conducting and led to a low rate of PCP dechlorination. In contrast, the dominant oxide on the "as-received" ZVI-H was magnetite which is conducting and, compared to ZVI-T, the ZVI-H rate of PCP dechlorination was four times faster. Treating the ZVI-H sample with 1 N H 2 SO 4 made small change to the composition of the oxide layers and also minute change to the rate of PCP dechlorination. However, treating the ZVI-T sample with H 2 SO 4 led to the loss of wustite so that magnetite became the dominant oxide and the rate of PCP dechlorination increased to that of the ZVI-H material. In conclusion, this study clearly shows that iron oxide mineralogy can be a contributing factor to apparent inconsistencies in the literature related to ZVI performance towards dechlorination and the effect of acid treatment on ZVI reactivity.

Kinetics and mechanisms of the oxidation of iodide and bromide in aqueous solutions by a trans-dioxoruthenium(VI) complex.

Science.gov (United States)

Lam, William W Y; Man, Wai-Lun; Wang, Yi-Ning; Lau, Tai-Chu

2008-08-04

The kinetics and mechanisms of the oxidation of I (-) and Br (-) by trans-[Ru (VI)(N 2O 2)(O) 2] (2+) have been investigated in aqueous solutions. The reactions have the following stoichiometry: trans-[Ru (VI)(N 2O 2)(O) 2] (2+) + 3X (-) + 2H (+) --> trans-[Ru (IV)(N 2O 2)(O)(OH 2)] (2+) + X 3 (-) (X = Br, I). In the oxidation of I (-) the I 3 (-)is produced in two distinct phases. The first phase produces 45% of I 3 (-) with the rate law d[I 3 (-)]/dt = ( k a + k b[H (+)])[Ru (VI)][I (-)]. The remaining I 3 (-) is produced in the second phase which is much slower, and it follows first-order kinetics but the rate constant is independent of [I (-)], [H (+)], and ionic strength. In the proposed mechanism the first phase involves formation of a charge-transfer complex between Ru (VI) and I (-), which then undergoes a parallel acid-catalyzed oxygen atom transfer to produce [Ru (IV)(N 2O 2)(O)(OHI)] (2+), and a one electron transfer to give [Ru (V)(N 2O 2)(O)(OH)] (2+) and I (*). [Ru (V)(N 2O 2)(O)(OH)] (2+) is a stronger oxidant than [Ru (VI)(N 2O 2)(O) 2] (2+) and will rapidly oxidize another I (-) to I (*). In the second phase the [Ru (IV)(N 2O 2)(O)(OHI)] (2+) undergoes rate-limiting aquation to produce HOI which reacts rapidly with I (-) to produce I 2. In the oxidation of Br (-) the rate law is -d[Ru (VI)]/d t = {( k a2 + k b2[H (+)]) + ( k a3 + k b3[H (+)]) [Br (-)]}[Ru (VI)][Br (-)]. At 298.0 K and I = 0.1 M, k a2 = (2.03 +/- 0.03) x 10 (-2) M (-1) s (-1), k b2 = (1.50 +/- 0.07) x 10 (-1) M (-2) s (-1), k a3 = (7.22 +/- 2.19) x 10 (-1) M (-2) s (-1) and k b3 = (4.85 +/- 0.04) x 10 (2) M (-3) s (-1). The proposed mechanism involves initial oxygen atom transfer from trans-[Ru (VI)(N 2O 2)(O) 2] (2+) to Br (-) to give trans-[Ru (IV)(N 2O 2)(O)(OBr)] (+), which then undergoes parallel aquation and oxidation of Br (-), and both reactions are acid-catalyzed.

Influence of cobalt oxide on structure and phase composition of zirconium-containing materials

International Nuclear Information System (INIS)

Vladimirova, O.S.; Gruzdev, A.I.; Koposova, Z.L.; Lyutsareva, L.A.

1986-01-01

Effect of Co 3 O 4 addition in a quantity from 10 to 90% on microstructure, phase content, lattice parameter and structure of ZrO 2 ceramics spallings stabilized with yttrium oxide, is studied. It is found out that in the process of ceramics synthesis the formation of three-phased heterogeneous system of matrix type occurs. At cobalt oxide content within the range of 10-30% a matrix consist of ZrO 2 base solid solution, at cobalt oxide content from 50 to 90% it is a matrix base, at 40% Co 3 O 4 the regions with both type matrixes exist. Cobalt oxide introduction decreases the sintering temperature without loss in operation indices of heat sensitive ceramics for resistance transducers

One-Pot Synthesis of Cu(II Complex with Partially Oxidized TTF Moieties

Directory of Open Access Journals (Sweden)

Hiroki Oshio

2012-07-01

Full Text Available The one-pot synthesis of a Cu(II complex with partially oxidized tetrathiafulvalene (TTF moieties in its capping MT-Hsae-TTF ligands, [CuII(MT-sae-TTF2] [CuICl2] was realized by the simultaneous occurrence of Cu(II complexation and CuIICl2 mediated oxidation of TTF moieties. The crystal structure was composed of one-dimensional columns formed by partially oxidized TTF moieties and thus the cation radical salt showed relatively high electrical conductivity. Tight binding band structure calculations indicated the existence of a Peierls gap due to the tetramerization of the TTF moieties in the one-dimensional stacking column at room temperature, which is consistent with the semiconducting behavior of this salt.

Oxygen-Rich Lithium Oxide Phases Formed at High Pressure for Potential Lithium-Air Battery Electrode.

Science.gov (United States)

Yang, Wenge; Kim, Duck Young; Yang, Liuxiang; Li, Nana; Tang, Lingyun; Amine, Khalil; Mao, Ho-Kwang

2017-09-01

The lithium-air battery has great potential of achieving specific energy density comparable to that of gasoline. Several lithium oxide phases involved in the charge-discharge process greatly affect the overall performance of lithium-air batteries. One of the key issues is linked to the environmental oxygen-rich conditions during battery cycling. Here, the theoretical prediction and experimental confirmation of new stable oxygen-rich lithium oxides under high pressure conditions are reported. Three new high pressure oxide phases that form at high temperature and pressure are identified: Li 2 O 3 , LiO 2 , and LiO 4 . The LiO 2 and LiO 4 consist of a lithium layer sandwiched by an oxygen ring structure inherited from high pressure ε-O 8 phase, while Li 2 O 3 inherits the local arrangements from ambient LiO 2 and Li 2 O 2 phases. These novel lithium oxides beyond the ambient Li 2 O, Li 2 O 2 , and LiO 2 phases show great potential in improving battery design and performance in large battery applications under extreme conditions.

Zeolite-encapsulated Co(II), Mn(II), Cu(II) and Cr(III) salen complexes as catalysts for efficient selective oxidation of benzyl alcohol

Science.gov (United States)

Li, F. H.; Bi, H.; Huang, D. X.; Zhang, M.; Song, Y. B.

2018-01-01

Co(II), Mn(II), Cu(II) and Cr(III) salen type complexes were synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. Data of characterization indicates the formation of metal salen complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activity results show that Cosalcyen Y exhibited higher catalytic activity in the water phase selective oxidation of benzyl alcohol, which could be attributed to their geometry and the steric environment of the metal actives sites.

Complexation of Plutonium (IV) With Sulfate At Variable Temperatures

International Nuclear Information System (INIS)

Y. Xia; J.I. Friese; D.A. Moore; P.P. Bachelor; L. Rao

2006-01-01

The complexation of plutonium(IV) with sulfate at variable temperatures has been investigated by solvent extraction method. A NaBrO 3 solution was used as holding oxidant to maintain the plutonium(IV) oxidation state throughout the experiments. The distribution ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of sulfate were increased. Stability constants of the 1:1 and 1:2 Pu(IV)-HSO 4 - complexes, dominant in the aqueous phase, were calculated from the effect of [HSO 4 - ] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures using the Van't Hoff equation

Gas phase reactions of nitrogen oxides with olefins

Energy Technology Data Exchange (ETDEWEB)

Altshuller, A P; Cohen, I

1961-01-01

The nature of the condensation products formed in the gas phase reactions of nitrogen dioxide and nitric oxide with pentene-1, 2-methylbutene-2, and 2-methylbutadiene-1,3 was investigated. The reactants were combined at partial pressures in the range of 0.1 to 2.5 mm with the total pressure at one atmosphere. The products were determined by infrared and ultraviolet spectroscopy and colorimetry. The condensates included primary and secondary nitro compounds and alkyl nitrates. Strong hydroxyl and single bond carbon to oxygen stretching vibrations indicate the presence of either nitroalcohols or simple aliphatic alcohols formed through oxidation reactions. Carbonyl stretching frequencies observable in some of the reactions support the conclusion that a portion of the reactants disappear by oxidation rather than by nitration processes. The available results do not indicate the presence of appreciable amounts of tert.-nitro compounds, conjugated nitro-olefins, or gem-dinitro-alkanes. The reactivities of the olefins with the nitrogen oxides are in the decreasing order: 2-methyl-butadiene-1,3, 2-methylbutene-2, pentene-1. 20 references.

Synthesis of titanium oxide nanoparticles using DNA-complex as template for solution-processable hybrid dielectric composites

Energy Technology Data Exchange (ETDEWEB)

Ramos, J.C. [Center for Sustainable Materials Chemistry, 153 Gilbert Hall, Oregon State University, Corvallis, OR (United States); Mejia, I.; Murphy, J.; Quevedo, M. [Department of Materials Science and Engineering, University of Texas at Dallas, Dallas, TX (United States); Garcia, P.; Martinez, C.A. [Engineering and Technology Institute, Autonomous University of Ciudad Juarez, Ciudad Juarez, Chihuahua (Mexico)

2015-09-15

Highlights: • We developed a synthesis method to produce TiO{sub 2} nanoparticles using a DNA complex. • The nanoparticles were anatase phase (~6 nm diameter), and stable in alcohols. • Composites showed a k of 13.4, 4.6 times larger than the k of polycarbonate. • Maximum processing temperature was 90 °C. • Low temperature enables their use in low-voltage, low-cost, flexible electronics. - Abstract: We report the synthesis of TiO{sub 2} nanoparticles prepared by the hydrolysis of titanium isopropoxide (TTIP) in the presence of a DNA complex for solution processable dielectric composites. The nanoparticles were incorporated as fillers in polycarbonate at low concentrations (1.5, 5 and 7 wt%) to produce hybrid dielectric films with dielectric constant higher than thermally grown silicon oxide. It was found that the DNA complex plays an important role as capping agent in the formation and suspension stability of nanocrystalline anatase phase TiO{sub 2} at room temperature with uniform size (∼6 nm) and narrow distribution. The effective dielectric constant of spin-cast polycarbonate thin-films increased from 2.84 to 13.43 with the incorporation of TiO{sub 2} nanoparticles into the polymer host. These composites can be solution processed with a maximum temperature of 90 °C and could be potential candidates for its application in low-cost macro-electronics.

Aqueous phase oxidation techniques as an alternative to incineration

International Nuclear Information System (INIS)

Gray, L.W.; Adamson, M.G.; Hickman, R.G.; Farmer, J.C.; Chiba, Z.; Gregg, D.W.; Wang, F.T.

1992-03-01

The Lawrence Livermore National Laboratory (LLNL) has three aqueous phase techniques under development for oxidation of high value or high risk waste steams. One is direct electrochemical oxidation and one is mediated electrochemical oxidation utilizing regenerable, strongly oxidizing cations such as Ag(II), Co (III), Ce(IV), etc. These cations can either attack oxidizable materials directly and/or indirectly via first reacting with water to generate OH radicals which then attack the oxidizable materials. The third system utilizes H 2 O 2 and UV light to generate OH radicals directly which in turn attack the oxidizable materials. All systems have the advantage of a chemical off-switch in that when the power is turned off, the reaction quickly subsides. All systems operate with low concentrations (typically <5 wt %) of oxidizable materials, therefore, the stored energy for possible run-away reactions is very low. 15 figures, 22 references

Oxidation behaviour of a Ti{sub 2}AlN MAX-phase coating

Energy Technology Data Exchange (ETDEWEB)

Wang Qimin; Kim, Kwangho [National Core Research Center for Hybrid Materials Solution, Pusan National University, Busan 609-735 (Korea, Republic of); Garkas, W; Renteria, A Flores [Chair of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, 03046 Cottbus (Germany); Leyens, C [Institute of Materials Science, Technical University of Dresden, Helmholtzstrasse 7, 01069 Dresden (Germany); Sun Chao, E-mail: qmwang@pusan.ac.kr, E-mail: kwhokim@pusan.ac.kr [Division of Surface Engineering of Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2011-10-29

In this paper, we reported the oxidation behaviour of Ti{sub 2}AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti{sub 2}AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti{sub 2}AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

A Complex Solar Coronal Jet with Two Phases

Energy Technology Data Exchange (ETDEWEB)

Chen, Jie; Su, Jiangtao; Deng, Yuanyong [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Priest, E. R., E-mail: chenjie@bao.ac.cn [Mathematical Institute, University of St Andrews, North Haugh, St Andrews, KY16 9SS (United Kingdom)

2017-05-01

Jets often occur repeatedly from almost the same location. In this paper, a complex solar jet was observed with two phases to the west of NOAA AR 11513 on 2012 July 2. If it had been observed at only moderate resolution, the two phases and their points of origin would have been regarded as identical. However, at high resolution we find that the two phases merge into one another and the accompanying footpoint brightenings occur at different locations. The phases originate from different magnetic patches rather than being one phase originating from the same patch. Photospheric line of sight (LOS) magnetograms show that the bases of the two phases lie in two different patches of magnetic flux that decrease in size during the occurrence of the two phases. Based on these observations, we suggest that the driving mechanism of the two successive phases is magnetic cancellation of two separate magnetic fragments with an opposite-polarity fragment between them.

Decomposition of uranyl peroxo-carbonato complex ion in the presence of metal oxides in carbonate media

International Nuclear Information System (INIS)

Dong-Yong Chung; Min-Sung Park; Keun-Young Lee; Eil-Hee Lee; Kwang-Wook Kim; Jei-Kwon Moon

2015-01-01

Uranium oxide was dissolved in the form of the uranyl peroxo-carbonato complex ion, UO 2 (O 2 )(CO 3 ) 2 4- in carbonate solutions with hydrogen peroxide. When UO 2 (O 2 )(CO 3 ) 2 4- ions lose their peroxide component, they become a stable species of uranyl tricarbonato complex ion, UO 2 (O 2 )(CO 3 ) 2 4- . The uranyl peroxo-carbonato complex self-decomposed more rapidly into the uranyl tricarbonato complex ion in the presence of a metal oxide in the carbonate solution. In this study, decomposition of the uranyl peroxo-carbonato complex in a carbonate solution was investigated in the presence of several metal oxides using absorption spectroscopy. (author)

Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework.

Science.gov (United States)

Das, Biswanath; Lee, Bao-Lin; Karlsson, Erik A; Åkermark, Torbjörn; Shatskiy, Andrey; Demeshko, Serhiy; Liao, Rong-Zhen; Laine, Tanja M; Haukka, Matti; Zeglio, Erica; Abdel-Magied, Ahmed F; Siegbahn, Per E M; Meyer, Franc; Kärkäs, Markus D; Johnston, Eric V; Nordlander, Ebbe; Åkermark, Björn

2016-09-14

The synthesis of two molecular iron complexes, a dinuclear iron(iii,iii) complex and a nonanuclear iron complex, based on the dinucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)3](3+).

Closed-cage tungsten oxide clusters in the gas phase.

Science.gov (United States)

Singh, D M David Jeba; Pradeep, T; Thirumoorthy, Krishnan; Balasubramanian, Krishnan

2010-05-06

During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) mass spectrometry, we observed several anionic W-O clusters. Three distinct species, W(6)O(19)(-), W(13)O(29)(-), and W(14)O(32)(-), stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W(13) and W(14) clusters were observed for the first time in the gas phase.

Kinematics and thermodynamics of non-stoichiometric oxidation phase transitions in spent fuel

International Nuclear Information System (INIS)

Stout, R.B.; Kansa, E.J.; Wijesinghe, A.M.

1993-01-01

At low temperatures ( 2 lattice to a U 4 O 9 lattice but with an oxygen-to-uranium (O/U) ratio of ∼2.4. Also, the weight gain time response has a plateau as the O/U approaches 2.4. Part of this response results from a geometrical dependency as a U 4 O 9 oxidation front propagates into grain volumes Of UO 2 It may also be indicative of a metastable, non-stoichiometric U 4 O 9 phase whose existence may inhibit the transition kinetics to the next expected phase Of U 3 O 8 . To gain a mechanistic understanding and to plan future oxidation tests, lattice kinematic and thermodynamic models are developed for lattice deformations and energetics of lattice phase changes (UO 2 → U 4 O 9 → U 3 0 7 → U 3 O 8) that include zeroth order influences on oxidation kinetics due to interstitial oxygen atoms and vacancies plus interstitial and substitutional actinides and fission decay products in spent fuel

Oxidative potential of gas phase combustion emissions - An underestimated and potentially harmful component of air pollution from combustion processes

Science.gov (United States)

Stevanovic, S.; Vaughan, A.; Hedayat, F.; Salimi, F.; Rahman, M. M.; Zare, A.; Brown, R. A.; Brown, R. J.; Wang, H.; Zhang, Z.; Wang, X.; Bottle, S. E.; Yang, I. A.; Ristovski, Z. D.

2017-06-01

The oxidative potential (OP) of the gas phase is an important and neglected aspect of environmental toxicity. Whilst prolonged exposure to particulate matter (PM) associated reactive oxygen species (ROS) have been shown to lead to negative health effects, the potential for compounds in gas phase to cause similar effects is yet to be understood. In this study we describe: the significance of the gas phase OP generated through vehicle emissions; discuss the origin and evolution of species contributing to measured OP; and report on the impact of gas phase OP on human lung cells. The model aerosol for this study was exhaust emitted from a Euro III Common-rail diesel engine fuelled with different blends of diesel and biodiesel. The gas phase of these emissions was found to be potentially as hazardous as the particle phase. Fuel oxygen content was found to negatively correlate with the gas phase OP, and positively correlate with particle phase OP. This signifies a complex interaction between reactive species present in gas and particle phase. Furthermore, this interaction has an overarching effect on the OP of both particle and gas phase, and therefore the toxicity of combustion emissions.

Natively oxidized amino acid residues in the spinach cytochrome b 6 f complex.

Science.gov (United States)

Taylor, Ryan M; Sallans, Larry; Frankel, Laurie K; Bricker, Terry M

2018-01-29

The cytochrome b 6 f complex of oxygenic photosynthesis produces substantial levels of reactive oxygen species (ROS). It has been observed that the ROS production rate by b 6 f is 10-20 fold higher than that observed for the analogous respiratory cytochrome bc 1 complex. The types of ROS produced (O 2 •-, 1 O 2 , and, possibly, H 2 O 2 ) and the site(s) of ROS production within the b 6 f complex have been the subject of some debate. Proposed sources of ROS have included the heme b p , PQ p •- (possible sources for O 2 •- ), the Rieske iron-sulfur cluster (possible source of O 2 •- and/or 1 O 2 ), Chl a (possible source of 1 O 2 ), and heme c n (possible source of O 2 •- and/or H 2 O 2 ). Our working hypothesis is that amino acid residues proximal to the ROS production sites will be more susceptible to oxidative modification than distant residues. In the current study, we have identified natively oxidized amino acid residues in the subunits of the spinach cytochrome b 6 f complex. The oxidized residues were identified by tandem mass spectrometry using the MassMatrix Program. Our results indicate that numerous residues, principally localized near p-side cofactors and Chl a, were oxidatively modified. We hypothesize that these sites are sources for ROS generation in the spinach cytochrome b 6 f complex.

Simplified paraboloid phase model-based phase tracker for demodulation of a single complex fringe.

Science.gov (United States)

He, A; Deepan, B; Quan, C

2017-09-01

A regularized phase tracker (RPT) is an effective method for demodulation of single closed-fringe patterns. However, lengthy calculation time, specially designed scanning strategy, and sign-ambiguity problems caused by noise and saddle points reduce its effectiveness, especially for demodulating large and complex fringe patterns. In this paper, a simplified paraboloid phase model-based regularized phase tracker (SPRPT) is proposed. In SPRPT, first and second phase derivatives are pre-determined by the density-direction-combined method and discrete higher-order demodulation algorithm, respectively. Hence, cost function is effectively simplified to reduce the computation time significantly. Moreover, pre-determined phase derivatives improve the robustness of the demodulation of closed, complex fringe patterns. Thus, no specifically designed scanning strategy is needed; nevertheless, it is robust against the sign-ambiguity problem. The paraboloid phase model also assures better accuracy and robustness against noise. Both the simulated and experimental fringe patterns (obtained using electronic speckle pattern interferometry) are used to validate the proposed method, and a comparison of the proposed method with existing RPT methods is carried out. The simulation results show that the proposed method has achieved the highest accuracy with less computational time. The experimental result proves the robustness and the accuracy of the proposed method for demodulation of noisy fringe patterns and its feasibility for static and dynamic applications.

Gas-Phase Photocatalytic Oxidation of Dimethylamine: The Reaction Pathway and Kinetics

Directory of Open Access Journals (Sweden)

Anna Kachina

2007-01-01

Full Text Available Gas-phase photocatalytic oxidation (PCO and thermal catalytic oxidation (TCO of dimethylamine (DMA on titanium dioxide was studied in a continuous flow simple tubular reactor. Volatile PCO products of DMA included ammonia, formamide, carbon dioxide, and water. Ammonia was further oxidized in minor amounts to nitrous oxide and nitrogen dioxide. Effective at 573 K, TCO resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The PCO kinetic data fit well to the monomolecular Langmuir-Hinshelwood model, whereas TCO kinetic behaviour matched the first-order process. No deactivation of the photocatalyst during the multiple long-run experiments was observed.

Complexation-Induced Phase Separation: Preparation of Metal-Rich Polymeric Membranes

KAUST Repository

Villalobos, Luis Francisco

2017-01-01

The majority of state-of-the-art polymeric membranes for industrial or medical applications are fabricated by phase inversion. Complexation induced phase separation (CIPS)—a surprising variation of this well-known process—allows direct fabrication

Manipulating oxygen sublattice in ultrathin cuprates: a new direction to engineer oxides

NARCIS (Netherlands)

Samal, D.; Koster, Gertjan

2015-01-01

Atomic engineering of complex oxide thin films is now reaching a new paradigm: the possibility to control the cation coordination by oxygen anions. Here, we show two examples of stabilization of novel structural phases by manipulating the oxygen sublattices in complex Cu-based oxide thin films grown

Study of the phase composition of nanostructures produced by the local anodic oxidation of titanium films

International Nuclear Information System (INIS)

Avilov, V. I.; Ageev, O. A.; Konoplev, B. G.; Smirnov, V. A.; Solodovnik, M. S.; Tsukanova, O. G.

2016-01-01

The results of experimental studies of the phase composition of oxide nanostructures formed by the local anodic oxidation of a titanium thin film are reported. The data of the phase analysis of titanium-oxide nanostructures are obtained by X-ray photoelectron spectroscopy in the ion profiling mode of measurements. It is established that the surface of titanium-oxide nanostructures 4.5 ± 0.2 nm in height possesses a binding energy of core levels characteristic of TiO_2 (458.4 eV). By analyzing the titanium-oxide nanostructures in depth by X-ray photoelectron spectroscopy, the formation of phases with binding energies of core levels characteristic of Ti_2O_3 (456.6 eV) and TiO (454.8 eV) is established. The results can be used in developing the technological processes of the formation of a future electronic-component base for nanoelectronics on the basis of titanium-oxide nanostructures and probe nanotechnologies.

Phase effects in masking by harmonic complexes: speech recognition.

Science.gov (United States)

Deroche, Mickael L D; Culling, John F; Chatterjee, Monita

2013-12-01

Harmonic complexes that generate highly modulated temporal envelopes on the basilar membrane (BM) mask a tone less effectively than complexes that generate relatively flat temporal envelopes, because the non-linear active gain of the BM selectively amplifies a low-level tone in the dips of a modulated masker envelope. The present study examines a similar effect in speech recognition. Speech reception thresholds (SRTs) were measured for a voice masked by harmonic complexes with partials in sine phase (SP) or in random phase (RP). The masker's fundamental frequency (F0) was 50, 100 or 200 Hz. SRTs were considerably lower for SP than for RP maskers at 50-Hz F0, but the two converged at 100-Hz F0, while at 200-Hz F0, SRTs were a little higher for SP than RP maskers. The results were similar whether the target voice was male or female and whether the masker's spectral profile was flat or speech-shaped. Although listening in the masker dips has been shown to play a large role for artificial stimuli such as Schroeder-phase complexes at high levels, it contributes weakly to speech recognition in the presence of harmonic maskers with different crest factors at more moderate sound levels (65 dB SPL). Copyright © 2013 Elsevier B.V. All rights reserved.

Oxidation of lignin-carbohydrate complex from bamboo with hydrogen peroxide catalyzed by Co(salen

Directory of Open Access Journals (Sweden)

Zhou Xue-Fei

2014-01-01

Full Text Available The reactivity of salen complexes toward hydrogen peroxide has been long recognized. Co(salen was tested as catalyst for the aqueous oxidation of a refractory lignin-carbohydrate complex (LCC isolated from sweet bamboo (Dendrocalamushamiltonii in the presence of hydrogen peroxide as oxidant. Co(salen catalyzed the reaction of hydrogen peroxide with LCC. From the spectra analyses, lignin units in LCC were undergoing ring-opening, side chain oxidation, demethoxylation, β-O-4 cleavage with Co(salen catalytic oxidation. The degradation was also observed in the carbohydrate of LCC. The investigation on the refractory LCC degradation catalyzed by Co(salen may be an important aspect for environmentally-oriented biomimetic bleaching in pulp and paper industry.

Metal Oxide-Carbon Nanocomposites for Aqueous and Nonaqueous Supercapacitors, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This Small Business Innovation Research Phase I effort focuses on development of novel metal-oxide-carbon nanocomposites for application in pseudocapacitive...

Characterization of Schottky barrier diodes fabricated from electrochemical oxidation of {alpha} phase brass

Energy Technology Data Exchange (ETDEWEB)

Bond, John W., E-mail: jwb13@le.ac.u [Forensic Research Centre, University of Leicester, Leicester LE1 7 EA (United Kingdom)

2011-04-01

By careful selection of chloride ion concentration in aqueous sodium chloride, electrochemical oxidation of {alpha} phase brass is shown to permit fabrication of either p-type copper (I) oxide/metal or n-type zinc oxide/metal Schottky barrier diodes. X-ray photoelectron and Auger electron spectroscopies provide evidence that barrier formation and rectifying qualities depend on the relative surface abundance of copper (I) oxide and zinc oxide. X-ray diffraction of the resulting diodes shows polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional I/V characteristics of these diodes show good rectifying qualities. When neither of the oxides dominate, the semiconductor/metal junction displays an absence of rectification.

Heavy haze in winter Beijing driven by fast gas phase oxidation

Science.gov (United States)

Lu, K.; Tan, Z.; Wang, H.; Li, X.; Wu, Z.; Chen, Q.; Wu, Y.; Ma, X.; Liu, Y.; Chen, X.; Shang, D.; Dong, H.; Zeng, L.; Shao, M.; Hu, M.; Fuchs, H.; Novelli, A.; Broch, S.; Hofzumahaus, A.; Holland, F.; Rohrer, F.; Bohn, B.; Georgios, G.; Schmitt, S. H.; Schlag, P.; Kiendler-Scharr, A.; Wahner, A.; Zhang, Y.

2017-12-01

Heavy haze conditions were frequently presented in the airsheds of Beijing and surrounding areas, especially during winter time. To explore the trace gas oxidation and the subsequent formation of aerosols, a comprehensive field campaign was performed at a regional site (in the campus of University of Chinese Academy of Science, UCAS) in Beijing winter 2016. Serious haze pollution processes were often observed with the fast increase of inorganic salt (especially nitrate) and these pollutions were always associated with enhanced humidity and the concentrations of PAN (PeroxyAcyl Nitrates) which is normally a marker of gas phase oxidations from NOx and VOCs. Moreover, based on the measurements of OH, HO2, RO2, total OH reactivity, N2O5, NO, NO2, SO2, particle concentrations/distributions/chemical compositions, and meteorological parameters, the gas phase oxidation rates that leads to the formation of sulfate, nitrate and secondary organic aerosols were estimated. These determined formation rates were clearly enhanced by several folds during pollution episodes compared to that of the clean air masses. Preliminary analysis result showed that the gas phase formation potential of nitrate and secondary organic aerosols were larger than the observed concentrations of nitrate and SOA of which the excess production may be explained by deposition and dilution.

The initial growth of complex oxides : study and manipulation

NARCIS (Netherlands)

Rijnders, Augustinus J.H.M.

2001-01-01

In this thesis, the initial growth stage, i.e., nucleation and growth of the first few unit cell layers, of complex oxides was studied in real time during pulsed laser deposition (PLD). These studies were performed at their optimal epitaxial growth conditions, i.e., high temperature and high oxygen

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide-natural organic matter complexes.

Science.gov (United States)

Yan, Jinlong; Jiang, Tao; Yao, Ying; Wang, Jun; Cai, Yuanli; Green, Nelson W; Wei, Shiqiang

2017-05-01

The phosphorus (P) fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid (HA) complexes were analyzed using the ultrafiltration method in this study. With an initial P concentration of 20mg/L (I=0.01mol/L and pH=7), it was shown that the colloid (1kDa-0.45μm) component of P accounted for 10.6%, 11.6%, 6.5%, and 4.0% of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite (FH), goethite (GE), ferrihydrite-humic acid complex (FH-HA), goethite-humic acid complex (GE-HA), respectively. The oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant. And colloidal adsorbent particles co-existing in the supernatant were another important reason for it. Additionally, dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant. Ultimately, we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P, even when considering other contaminants such as organic pollutants, heavy metal ions, and arsenate at the sediment/soil-water interface in the real environment. Copyright © 2016. Published by Elsevier B.V.

Psychophysical estimates of cochlear phase response: masking by harmonic complexes.

Science.gov (United States)

Lentz, J J; Leek, M R

2001-12-01

Harmonic complexes with identical component frequencies and amplitudes but different phase spectra may be differentially effective as maskers. Such harmonic waveforms, constructed with positive or negative Schroeder phases, have similar envelopes and identical long-term power spectra, but the positive Schroeder-phase waveform is typically a less effective masker than the negative Schroeder-phase waveform. These masking differences have been attributed to an interaction between the masker phase spectrum and the phase characteristic of the basilar membrane. To explore this relationship, the gradient of stimulus phase change across masker bandwidth was varied by systematically altering the Schroeder-phase algorithm. Observers detected a signal tone added in-phase to a single component of a masker whose frequencies ranged from 200 to 5000 Hz, with a fundamental frequency of 100 Hz. For signal frequencies of 1000-4000 Hz, differences in masking across the harmonic complexes could be as large as 5-10 dB for phase gradients changing by only 10%. The phase gradient that resulted in a minimum amount of masking varied with signal frequency, with low frequencies masked least effectively by stimuli with rapidly changing component phases and high frequencies masked by stimuli with more shallow phase gradients. A gammachirp filter was implemented to model these results, predicting the qualitative changes in curvature of the phase-byfrequency function estimated from the empirical data: In some cases, small modifications to the gammachirp filter produced better quantitative predictions of curvature changes across frequency, but this filter, as implemented here, was unable to accurately represent all the data.

Radionuclide sorption in soils and sediments: oxide-organic matter competition

International Nuclear Information System (INIS)

Maes, A.; Cremers, A.

1986-01-01

This paper deals with the speciation of europium in the solid phase and liquid phase extracts of Boom Clay under in situ conditions. Using a new method for measuring the europium-humic acid complex stability constant at high pH, it is shown that carbonate complexation is poorly competitive with humic acid, europium being quantitatively present as humic acid complex, its stability constant being of the order of 10 12 -10 13 . It is furthermore shown that partial oxidation of the sediment, which is strongly reducing under in situ conditions, leads to a significant increase in Ksub(D) values, whatever the liquid/solid ratio used. This effect is ascribed to the involvement of ferric oxides which are generated in the solid phase and which lead to a displacement of the metal from the humic acid sink. Some examples are presented which demonstrate that at high pH, around 9, ferric oxides may be competitive with humic acids for metal sorption and that this effect increases with pH. (author)

Radionuclide sorption in soils and sediments: Oxide - organic matter competition

International Nuclear Information System (INIS)

Maes, A.; Cremers, A.

1985-01-01

This paper deals with the speciation of europium in the solid phase and liquid phase extracts of Boom clay under in situ conditions. Using a new method for measuring the europium-humic acid complex stability constant at high pH, it is shown that carbonate complexation is poorly competitive with humic acid, europium being quantitatively present as humic acid complex, its stability constant being of the order of 10/sup 12/--10/sup 13/. It is furthermore shown that partial oxidation of the sediment, which is strongly reducing under in situ conditions, leads to a significant increase in K/sub D/ values, whatever the liquid/solid ratio used. This effect is ascribed to the involvement of ferric oxides which are generated in the solid phase and which lead to a displacement of the metal from the humic acid sink. Some examples are presented which demonstrate that a high pH, around 9, ferric oxides may be competitive with humic acids for metal sorption and that this effect increases with pH

Oxidation of Alumina-Forming MAX Phases in Turbine Environments

Science.gov (United States)

Smialek, James; Garg, Anita; Harder, Bryan; Nesbitt, James; Gabb, Timothy; Gray, SImon

2017-01-01

Protective coatings for high temperature turbine components are based on YSZ thermal barriers and oxidation resistant, alumina-forming NiAl or NiCoCrAlY bond coats. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that can match Al2O3 and YSZ. Their alumina scales grow according to cubic kinetics due to grain growth in the scale, with initial heating dominated by fast TiO2 growth. Protective cubic kinetics are also found in high pressure burner rig tests of MAXthal 211 Ti2AlC, but with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on bulk Ti2AlC exhibit remarkable durability up to 1300C in furnace tests and at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy disk material. Accordingly, sputtered Cr2AlC coatings on disk specimens prevented hot corrosion detriments on LCF. Breakaway oxidation (Ti2AlC), scale spallation (Cr2AlC), interdiffusion, and processing as coatings still present serious challenges. However the basic properties of MAX phases provide some unusual opportunities for use in high temperature turbines.

Nonlinear analysis of gas-water/oil-water two-phase flow in complex networks

CERN Document Server

Gao, Zhong-Ke; Wang, Wen-Xu

2014-01-01

Understanding the dynamics of multi-phase flows has been a challenge in the fields of nonlinear dynamics and fluid mechanics. This chapter reviews our work on two-phase flow dynamics in combination with complex network theory. We systematically carried out gas-water/oil-water two-phase flow experiments for measuring the time series of flow signals which is studied in terms of the mapping from time series to complex networks. Three network mapping methods were proposed for the analysis and identification of flow patterns, i.e. Flow Pattern Complex Network (FPCN), Fluid Dynamic Complex Network (FDCN) and Fluid Structure Complex Network (FSCN). Through detecting the community structure of FPCN based on K-means clustering, distinct flow patterns can be successfully distinguished and identified. A number of FDCN’s under different flow conditions were constructed in order to reveal the dynamical characteristics of two-phase flows. The FDCNs exhibit universal power-law degree distributions. The power-law exponent ...

A double Fe-Ti oxide and Fe-sulphide liquid immiscibility in the Itsindro Gabbro Complex, Madagascar

Science.gov (United States)

Augé, Thierry; Bailly, Laurent; Roig, Jean-Yves

2017-11-01

The petrology and mineralogy of the Itsindro complex in south-central Madagascar has been investigated through samples obtained from the 320.7 m-deep Lanjanina borehole. The section consists of a 254 m-thick pyroxenite unit with interbedded gabbro layers that overlies a gabbro unit and is itself overlain by a 19 m-thick granite unit. Most of the structures are sub-horizontal. A weak magmatic layering is locally observed but at the scale of the core, the intrusion does not appear to be a layered complex. Pyroxenite and gabbro show a systematic disseminated mineralization consisting of Fe-Ti-P oxides and Fe-(Cu-Ni) sulphides that takes the form of ilmenite-titanomagnetite ± apatite and pyrrhotite ± chalcopyrite ± pentlandite. In the upper zone, from 90 to 72 m, sub-massive centimetre-to decimetre-sized layers of oxides and sulphides comprise a total of 16 m of sub-massive sulphide (the main mineralized zone). In this mineralized zone the oxide/sulphide ratio is close to 1/1. The sulphide is strongly dominated by pyrrhotite, which may locally contain inclusions of molybdenite crystals with the Re sulphide rheniite (ReS2). Oxides are generally euhedral, included in or attached to the Fe-sulphide, and also locally form sub-massive centimetre-sized bands. Apatite as a cumulus phase is ubiquitous. Locally it may account for 30% of the ore-rich samples and some samples consist of apatite-Fe-Ti oxides-Fe-Cu-Ni sulphides with virtually no silicate. Apatite is the main REE carrier but the total REE content remains low (<90 ppm). Mineral compositions and whole rock geochemistry indicate that the rocks are highly differentiated, and in spite of a relatively limited thickness, the differentiation process is observed. Two zones can be distinguished: from the bottom to 162.8 m we see a decrease in the Mg number of olivine and pyroxene, and a drop in TiO2 and Al2O3 for the latter. A reverse trend is then observed within the pyroxenite unit from the 162.8 m level upwards. The

Oxidation kinetics of a Pb-64 at.% In single-phase alloy

International Nuclear Information System (INIS)

Zhang, M.X.; Chang, Y.A.; Marcotte, V.C.

1991-01-01

The solid-state oxidation kinetics of a Pb-64 at.% IN(50 wt.%) single-phase alloy were studied from room temperature to 150C using AES (Auger Electron Spectroscopy) depth profiling technique. The general oxidation behavior of this alloy is different from that of a Pb-3 at.% In alloy but similar to that of a Pb-30 at.% In alloy. The oxide formed on this alloy is almost pure In oxide (In 2 O 3 ) with the possible existence of some In suboxide near the oxide/alloy interface. At room temperature, oxidation of the alloy follows a direct logarithmic law, and the results can be described by the model proposed previously by Zhang, Chang, and Marcotte. At temperatures higher than 75C, rapid oxidation occurred initially followed by a slower parabolic oxidation at longer time. These data were described quantitatively by the model which assumes the existence of short-circuit diffusion in addition to lattice diffusion in the oxide as proposed by Smeltzer, Haering, and Kirkaldy. The effects of alloy composition in the oxidation kinetics of (pb, In) alloy are also examined by comparing the data for Pb-3, 30, and 64 at.% In alloys

Energy transfer processes in Tb(III)-dibenzoylmethanate complexes with phosphine oxide ligands

International Nuclear Information System (INIS)

Silva Junior, Francisco A.; Nascimento, Helenise A.; Pereira, Dariston K.S.; Teotonio, Ercules E.S.; Espinola, Jose Geraldo P.; Faustino, Wagner M.; Sa, Gilberto F.

2013-01-01

The Tb 3+ -β-diketonate complexes [Tb(DBM) 3 L], [Tb(DBM) 2 (NO 3 )L 2 ] and [Tb(DBM)(NO 3 ) 2 (HMPA) 2 ] (DBM = dibenzoylmethanate; L: TPPO triphenylphosphine oxide or HMPA=hexamethylphosphine oxide) were prepared and characterized by elemental analysis (CHN), complexometric titration with EDTA and Fourier transform infrared (FTIR) spectroscopy, and the photoluminescence properties evaluated. The triplet state energies of the coordinated DBM ligands were determined using time-resolved phosphorescence spectra of analogous Gd 3+ complexes. The results show that the energies increase along with the number of coordinated nitrate anions replacing the DBM ligand in the complexes. The luminescence spectra and emission lifetime measurements revealed that the ligand-to-metal energy transfer efficiency follows the same tendency. Unlike the tris-DBM complexes, bis- and mono-DBM presented high luminescence, and may act as promising candidates for preparation of the emitting layer of light converting molecular devices (LCMDs). (author)

Energy transfer processes in Tb(III)-dibenzoylmethanate complexes with phosphine oxide ligands

Energy Technology Data Exchange (ETDEWEB)

Silva Junior, Francisco A.; Nascimento, Helenise A.; Pereira, Dariston K.S.; Teotonio, Ercules E.S.; Espinola, Jose Geraldo P.; Faustino, Wagner M., E-mail: teotonioees@quimica.ufpb.br [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Departamento de Quimica; Brito, Hermi F. [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Quimica. Departamento de Quimica Fundamental; Felinto, Maria Claudia F.C. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), SP (Brazil); Sa, Gilberto F. [Universidade Federal de Pernambuco (UFPE/CCEN), Recife, PE (Brazil). Centro de Ciencias Exatas e da Natureza. Departamento de Quimica Fundamental

2013-04-15

The Tb{sup 3+}-{beta}-diketonate complexes [Tb(DBM){sub 3}L], [Tb(DBM){sub 2}(NO{sub 3})L{sub 2}] and [Tb(DBM)(NO{sub 3}){sub 2} (HMPA){sub 2}] (DBM = dibenzoylmethanate; L: TPPO triphenylphosphine oxide or HMPA=hexamethylphosphine oxide) were prepared and characterized by elemental analysis (CHN), complexometric titration with EDTA and Fourier transform infrared (FTIR) spectroscopy, and the photoluminescence properties evaluated. The triplet state energies of the coordinated DBM ligands were determined using time-resolved phosphorescence spectra of analogous Gd{sup 3+} complexes. The results show that the energies increase along with the number of coordinated nitrate anions replacing the DBM ligand in the complexes. The luminescence spectra and emission lifetime measurements revealed that the ligand-to-metal energy transfer efficiency follows the same tendency. Unlike the tris-DBM complexes, bis- and mono-DBM presented high luminescence, and may act as promising candidates for preparation of the emitting layer of light converting molecular devices (LCMDs). (author)

Complex PTSD and phased treatment in refugees : a debate piece

NARCIS (Netherlands)

Ter Heide, F Jackie June; Mooren, Trudy M; Kleber, Rolf J

2016-01-01

BACKGROUND: Asylum seekers and refugees have been claimed to be at increased risk of developing complex posttraumatic stress disorder (complex PTSD). Consequently, it has been recommended that refugees be treated with present-centred or phased treatment rather than stand-alone trauma-focused

Binding of properdin to solid-phase immune complexes

DEFF Research Database (Denmark)

Junker, A; Baatrup, G; Svehag, S E

1998-01-01

The capacity of serum to support deposition of C3, properdin and factor B was studied by enzyme-linked immunosorbent assay using solid-phase immune complexes (IC) for activation of complement. Deposition of C3 and properdin occurred in fairly dilute normal human serum (NHS), but factor B uptake...... fixed to IC was the principal ligand for properdin in the assay. The findings could have biological implications relating to complement-mediated modification of immune complexes in disease....

Topotactic oxidation pathway of ScTiO3 and high-temperature structure evolution of ScTiO3.5 and Sc4Ti3O12-type phases.

Science.gov (United States)

Shafi, Shahid P; Hernden, Bradley C; Cranswick, Lachlan M D; Hansen, Thomas C; Bieringer, Mario

2012-02-06

The novel oxide defect fluorite phase ScTiO(3.5) is formed during the topotactic oxidation of ScTiO(3) bixbyite. We report the oxidation pathway of ScTiO(3) and structure evolution of ScTiO(3.5), Sc(4)Ti(3)O(12), and related scandium-deficient phases as well as high-temperature phase transitions between room temperature and 1300 °Cusing in-situ X-ray diffraction. We provide the first detailed powder neutron diffraction study for ScTiO(3). ScTiO(3) crystallizes in the cubic bixbyite structure in space group Ia3 (206) with a = 9.7099(4) Å. The topotactic oxidation product ScTiO(3.5) crystallizes in an oxide defect fluorite structure in space group Fm3m (225) with a = 4.89199(5) Å. Thermogravimetric and differential thermal analysis experiments combined with in-situ X-ray powder diffraction studies illustrate a complex sequence of a topotactic oxidation pathway, phase segregation, and ion ordering at high temperatures. The optimized bulk synthesis for phase pure ScTiO(3.5) is presented. In contrast to the vanadium-based defect fluorite phases AVO(3.5+x) (A = Sc, In) the novel titanium analogue ScTiO(3.5) is stable over a wide temperature range. Above 950 °C ScTiO(3.5) undergoes decomposition with the final products being Sc(4)Ti(3)O(12) and TiO(2). Simultaneous Rietveld refinements against powder X-ray and neutron diffraction data showed that Sc(4)Ti(3)O(12) also exists in the defect fluorite structure in space group Fm3m (225) with a = 4.90077(4) Å. Sc(4)Ti(3)O(12) undergoes partial reduction in CO/Ar atmosphere to form Sc(4)Ti(3)O(11.69(2)).

Hysteresis phenomena at metal-semiconductor phase transformation in vanadium oxides

International Nuclear Information System (INIS)

Lanskaya, T.G.; Merkulov, I.A.; Chudnovski , F.A.

1978-01-01

The hysteresis phenomena during the metal-semiconductor phase transformation (MSPT) in vanadium oxides are investigated. It is shown experimentally that the hysteresis effects during MSPT in vanadium oxides are associated not only with the martensite nature of the transformation, but also with activation processes. It is shown that the hysteresis phenomena during MSPT may be described by the distribution function of microregions of the crystal in the phase transformation temperature T 0 and the coercive temperature Tsub(c). An experimental method for constructing this distribution function was worked out. An analysis of the experimental data shows that finely dispersed films are characterized by a wide range of values of T 0 and Tsub(c) (55 deg C 0 <65 deg C, 6 deg C< Tsub(c)<12 deg C). The peculiarities of the optical recording of information on monocrystal and finely dispersed films are considered

Strain-induced topological quantum phase transition in phosphorene oxide

Science.gov (United States)

Kang, Seoung-Hun; Park, Jejune; Woo, Sungjong; Kwon, Young-Kyun

Using ab initio density functional theory, we investigate the structural stability and electronic properties of phosphorene oxides (POx) with different oxygen compositions x. A variety of configurations are modeled and optimized geometrically to search for the equilibrium structure for each x value. Our electronic structure calculations on the equilibrium configuration obtained for each x reveal that the band gap tends to increase with the oxygen composition of x 0.5. We further explore the strain effect on the electronic structure of the fully oxidized phosphorene, PO, with x = 1. At a particular strain without spin-orbit coupling (SOC) is observed a band gap closure near the Γ point in the k space. We further find the strain in tandem with SOC induces an interesting band inversion with a reopened very small band gap (5 meV), and thus gives rise to a topological quantum phase transition from a normal insulator to a topological insulator. Such a topological phase transition is confirmed by the wave function analysis and the band topology identified by the Z2 invariant calculation.

Theory and Application of Photoelectron Diffraction for Complex Oxide Systems

Science.gov (United States)

Chassé, Angelika; Chassé, Thomas

2018-06-01

X-ray photoelectron diffraction (XPD) has been used to investigate film structures and local sites of surface and dopant atoms in complex oxide materials. We have performed angular-resolved measurements of intensity distribution curves (ADCs) and patterns (ADPs) of elemental core level intensities from binary to quaternary mixed oxide samples and compared them to multiple-scattering cluster (MSC) calculations in order to derive information on structural models and related parameters. MSC calculations permitted to describe both bulk diffraction features of binary oxide MnO(001) and the thickness-dependence of the tetragonal distortion of epitaxial MnO films on Ag(001). XPD was further used to investigate the surface termination of perovskite SrTiO3 and BaTiO3 substrates in order to evaluate influence of different ex situ and in situ preparation procedures on the surface layers, which are crucial for quality of following film growth. Despite the similarity of local environments of Sr (Ba) and Ti atoms in the perovskite film structure an angular region in the ADCs was identified as a fingerprint with the help of MSC simulations which provided clear conclusions on the perovskite oxide surfaces. Dopant sites in quaternary perovskite manganites La1-xCaxMnO3, La1-xSrxMnO3, and La1-xCexMnO3 were studied with polar angle scans of the photoemission intensities of host and dopant atoms. Both direct comparison of experimental ADCs and to the simulations within MSC models confirm the occupation of A sites by the dopants and the structural quality of the complex oxide films.

How Pt nanoparticles affect TiO2-induced gas-phase photocatalytic oxidation reactions

NARCIS (Netherlands)

Fraters, B.D.; Amrollahi Buky, Rezvaneh; Mul, Guido

2015-01-01

The effect of Pt nanoparticles on the gas-phase photocatalytic oxidation activity of TiO2 is shown to be largely dependent on the molecular functionality of the substrate. We demonstrate that Pt nanoparticles decrease rates in photocatalytic oxidation of propane, whereas a strong beneficial effect

Gas-phase advanced oxidation as an integrated air pollution control technique

Directory of Open Access Journals (Sweden)

Getachew A. Adnew

2016-03-01

Full Text Available Gas-phase advanced oxidation (GPAO is an emerging air cleaning technology based on the natural self-cleaning processes that occur in the Earth’s atmosphere. The technology uses ozone, UV-C lamps and water vapor to generate gas-phase hydroxyl radicals that initiate oxidation of a wide range of pollutants. In this study four types of GPAO systems are presented: a laboratory scale prototype, a shipping container prototype, a modular prototype, and commercial scale GPAO installations. The GPAO systems treat volatile organic compounds, reduced sulfur compounds, amines, ozone, nitrogen oxides, particles and odor. While the method covers a wide range of pollutants, effective treatment becomes difficult when temperature is outside the range of 0 to 80 °C, for anoxic gas streams and for pollution loads exceeding ca. 1000 ppm. Air residence time in the system and the rate of reaction of a given pollutant with hydroxyl radicals determine the removal efficiency of GPAO. For gas phase compounds and odors including VOCs (e.g. C6H6 and C3H8 and reduced sulfur compounds (e.g. H2S and CH3SH, removal efficiencies exceed 80%. The method is energy efficient relative to many established technologies and is applicable to pollutants emitted from diverse sources including food processing, foundries, water treatment, biofuel generation, and petrochemical industries.

Treatment of reduced sulphur compounds and SO2 by Gas Phase Advanced Oxidation

DEFF Research Database (Denmark)

Meusinger, Carl; Bluhme, Anders Brostrøm; Ingemar, Jonas L.

2017-01-01

Reduced sulphur compounds (RSCs) emitted from pig farms are a major problem for agriculture, due to their health and environmental impacts and foul odour. This study investigates the removal of RSCs, including H2S, and their oxidation product SO2 using Gas Phase Advanced Oxidation (GPAO). GPAO...... is a novel air cleaning technique which utilises accelerated atmospheric chemistry to oxidise pollutants before removing their oxidation products as particles. Removal efficiencies of 24.5% and 3.9% were found for 461 ppb of H2S and 714 ppb of SO2 in a laboratory system (volumetric flow Q = 75 m3/h......). A numerical model of the reactor system was developed to explore the basic features of the system; its output was in fair agreement with the experiment. The model verified the role of OH radicals in initiating the oxidation chemistry. All sulphur removed from the gas phase was detected as particulate matter...

Aqueous-phase oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Product identification from methyl jasmonate and methyl salicylate oxidation

Science.gov (United States)

Hansel, Amie K.; Ehrenhauser, Franz S.; Richards-Henderson, Nicole K.; Anastasio, Cort; Valsaraj, Kalliat T.

2015-02-01

Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation. BVOCs produce secondary organic aerosol (SOA) via gas-phase reactions, but little is known of their aqueous-phase oxidation as a source of SOA. GLVs can partition into atmospheric water phases, e.g., fog, mist, dew or rain, and be oxidized by hydroxyl radicals (˙OH). These reactions in the liquid phase also lead to products that have higher molecular weights, increased polarity, and lower vapor pressures, ultimately forming SOA after evaporation of the droplet. To examine this process, we investigated the aqueous, ˙OH-mediated oxidation of methyl jasmonate (MeJa) and methyl salicylate (MeSa), two GLVs that produce aqueous-phase SOA. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to monitor product formation. The oxidation products identified exhibit higher molecular mass than their parent GLV due to either dimerization or the addition of oxygen and hydroxyl functional groups. The proposed structures of potential products are based on mechanistic considerations combined with the HPLC/ESI-MS data. Based on the structures, the vapor pressure and the Henry's law constant were estimated with multiple methods (SPARC, SIMPOL, MPBPVP, Bond and Group Estimations). The estimated vapor pressures of the products identified are significantly (up to 7 orders of magnitude) lower than those of the associated parent compounds, and therefore, the GLV oxidation products may remain as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS responses relative to previous aqueous SOA mass yield measurements.

Fluorescence-based detection of nitric oxide in aqueous and methanol media using a copper(II) complex.

Science.gov (United States)

Mondal, Biplab; Kumar, Pankaj; Ghosh, Pokhraj; Kalita, Apurba

2011-03-14

The quenched fluorescent intensity of a copper(II) complex, 1, of a fluorescent ligand, in degassed methanol or aqueous (buffered at pH 7.2) solution, was found to reappear on exposure to nitric oxide. Thus, it can function as a fluorescence based nitric oxide sensor. It has been found that the present complex can be used to sense nanomolar quantities of nitric oxide in both methanol and pH 7.2 buffered-water medium.

Physiological Levels of Nitric Oxide Diminish Mitochondrial Superoxide. Potential Role of Mitochondrial Dinitrosyl Iron Complexes and Nitrosothiols

Directory of Open Access Journals (Sweden)

Sergey I. Dikalov

2017-11-01

Full Text Available Mitochondria are the major source of superoxide radicals and superoxide overproduction contributes to cardiovascular diseases and metabolic disorders. Endothelial dysfunction and diminished nitric oxide levels are early steps in the development of these pathological conditions. It is known that physiological production of nitric oxide reduces oxidative stress and inflammation, however, the precise mechanism of “antioxidant” effect of nitric oxide is not clear. In this work we tested the hypothesis that physiological levels of nitric oxide diminish mitochondrial superoxide production without inhibition of mitochondrial respiration. In order to test this hypothesis we analyzed effect of low physiological fluxes of nitric oxide (20 nM/min on superoxide and hydrogen peroxide production by ESR spin probes and Amplex Red in isolated rat brain mitochondria. Indeed, low levels of nitric oxide substantially attenuated both basal and antimycin A-stimulated production of reactive oxygen species in the presence of succinate or glutamate/malate as mitochondrial substrates. Furthermore, slow releasing NO donor DPTA-NONOate (100 μM did not change oxygen consumption in State 4 and State 3. However, the NO-donor strongly inhibited oxygen consumption in the presence of uncoupling agent CCCP, which is likely associated with inhibition of the over-reduced complex IV in uncoupled mitochondria. We have examined accumulation of dinitrosyl iron complexes and nitrosothiols in mitochondria treated with fast-releasing NO donor MAHMA NONOate (10 μM for 30 min until complete release of NO. Following treatment with NO donor, mitochondria were frozen for direct detection of dinitrosyl iron complexes using Electron Spin Resonance (ESR while accumulation of nitrosothiols was measured by ferrous-N-Methyl-D-glucamine dithiocarbamate complex, Fe(MGD2, in lysed mitochondria. Treatment of mitochondria with NO-donor gave rise to ESR signal of dinitrosyl iron complexes while ESR

The effect of microstructure and temperature on the oxidation behavior of two-phase Cr-Cr2X (X=Nb,Ta) alloys

International Nuclear Information System (INIS)

Brady, M.P.; Tortorelli, P.F.

1998-01-01

The oxidation behavior of Cr(X) solid solution (Cr ss ) and Cr 2 X Laves phases (X = Nb, Ta) was studied individually and in combination at 950--1,100 C in air. The Cr ss phase was significantly more oxidation resistant than the Cr 2 X Laves phase. At 950 C, two-phase alloys of Cr-Cr 2 Nb and Cr-Cr 2 Ta exhibited in-situ internal oxidation, in which remnants of the Cr 2 X Laves phase were incorporated into a growing chromia scale. At 1,100 C, the Cr-Cr 2 Nb alloys continued to exhibit in-situ internal oxidation, which resulted in extensive O/N penetration into the alloy ahead of the alloy-scale interface and catastrophic failure during cyclic oxidation. IN contrast, the Cr-Cr 2 Ta alloys exhibited a transition to selective Cr oxidation and the formation of a continuous chromia scale. The oxidation mechanism is interpreted in terms of multiphase oxidation theory

Graphene oxide for solid-phase extraction of bioactive phenolic acids.

Science.gov (United States)

Hou, Xiudan; Wang, Xusheng; Sun, Yingxin; Wang, Licheng; Guo, Yong

2017-05-01

A solid-phase extraction (SPE) method for the efficient analysis of trace phenolic acids (PAs, caffeic acid, ferulic acid, protocatechuic acid, cinnamic acid) in urine was established. In this work, a graphene oxide (GO) coating was grafted onto pure silica to be investigated as SPE material. The prepared GO surface had a layered and wrinkled structure that was rough and well organized, which could provide more open adsorption sites. Owing to its hydrophilicity and polarity, GO showed higher extraction efficiency toward PAs than reduced GO did, in agreement with the theoretical calculation results performed by Gaussian 09 software. The adsorption mechanism of PAs on GO@Sil was also investigated through static state and kinetic state adsorption experiments, which showed a monolayer surface adsorption. Extraction capacity of the as-prepared material was optimized using the response surface methodology. Under the optimized conditions, the as-established method provided wide linearity range (2-50 μg L -1 for protocatechuic acid and 1-50 μg L -1 for caffeic acid, ferulic acid, and cinnamic acid) and low limits of detection (0.25-1 μg L -1 ). Finally, the established method was applied for the analysis of urine from two healthy volunteers. The results indicate that the prepared material is a practical, cost-effective medium for the extraction and determination of phenolic acids in complex matrices. Graphical Abstract A graphene oxide coating was grafted onto pure silica as the SPE material for the extraction of phenolic acids in urines and the extraction mechanism was also mainly investigated.

Theoretical consideration on phase behaviors of poly(ethylene oxide-block-propylene oxide)/LiCF3SO3 systems in lithium battery

International Nuclear Information System (INIS)

Ko, Sung Jin; Kim, Sun Joon; Kong, Sung Ho; Bae, Young Chan

2004-01-01

A new thermodynamic model is developed based on the extended perturbed hard sphere chain (PHSC) model and melting point depression theory to describe the phase behaviors of copolymer electrolyte/salt systems. The phase behaviors of poly(ethylene oxide-block-propylene oxide)/LiCF 3 SO 3 systems are investigated by thermo-optical analysis (TOA) technique. Quantitative descriptions according to the proposed model are in good agreement with experimental data. The obtained results show that monomer ratio and sequence type of copolymers play a great role in determining eutectic points of the given systems

Electrocatalytic oxidation of organic substrates with molecular oxygen using tetradentate ruthenium(III)-Schiff base complexes as catalysts

International Nuclear Information System (INIS)

Ourari, Ali; Khelafi, Mostefa; Aggoun, Djouhra; Jutand, Anny; Amatore, Christian

2012-01-01

Three complexes Ru(III)ClL n involving different tetradentate Schiff base ligands L n (see L 1 , L 2 and L 3 in ) were used as catalysts in the oxidation of cyclooctene and tetraline in the presence of molecular dioxygen associated with benzoic anhydride. The efficiency of this oxidation reaction was tested in the presence of two apical bases: 1- or 2-methylimidazole. All complexes exhibit a quasi-reversible redox system. The electrolysis experiments were carried out at controlled potential for each complex, using different substrates such as cyclooctene and tetraline. The oxidized products are cyclooctene oxide (turnover 6.7), a mixture of 1-tetralol and 1-tetralone (turnover 7.6) respectively.

Flow-pattern identification and nonlinear dynamics of gas-liquid two-phase flow in complex networks.

Science.gov (United States)

Gao, Zhongke; Jin, Ningde

2009-06-01

The identification of flow pattern is a basic and important issue in multiphase systems. Because of the complexity of phase interaction in gas-liquid two-phase flow, it is difficult to discern its flow pattern objectively. In this paper, we make a systematic study on the vertical upward gas-liquid two-phase flow using complex network. Three unique network construction methods are proposed to build three types of networks, i.e., flow pattern complex network (FPCN), fluid dynamic complex network (FDCN), and fluid structure complex network (FSCN). Through detecting the community structure of FPCN by the community-detection algorithm based on K -mean clustering, useful and interesting results are found which can be used for identifying five vertical upward gas-liquid two-phase flow patterns. To investigate the dynamic characteristics of gas-liquid two-phase flow, we construct 50 FDCNs under different flow conditions, and find that the power-law exponent and the network information entropy, which are sensitive to the flow pattern transition, can both characterize the nonlinear dynamics of gas-liquid two-phase flow. Furthermore, we construct FSCN and demonstrate how network statistic can be used to reveal the fluid structure of gas-liquid two-phase flow. In this paper, from a different perspective, we not only introduce complex network theory to the study of gas-liquid two-phase flow but also indicate that complex network may be a powerful tool for exploring nonlinear time series in practice.

Oxidative dehydrogenation of the 2-aminomethylpyridine (EDTA) ruthenium (III) complex

International Nuclear Information System (INIS)

Toma, H.E.; Tsurumaki, M.

1990-01-01

The oxidative dehydrogenation of the 2-aminomethylpyridine (ampy) ligand coordinated to the (EDTA)RU(III) complex was investigated based on cyclic voltammetry, spectoelectrochemistry and stopped-flow kinetic measurements in aqueous solution. The reaction mechanism is consistent with the deprotonation of the ampy ligand (pk a =7.48), followed by a reversible one-electron transfer step. The intermediate species generated at this step undergoes a metal-induced electron transfer process, with k=227 s -1 , converting into the corresponding 2-iminomethylpyridine complex. (author) [pt

Complex-based OCT angiography algorithm recovers microvascular information better than amplitude- or phase-based algorithms in phase-stable systems.

Science.gov (United States)

Xu, Jingjiang; Song, Shaozhen; Li, Yuandong; Wang, Ruikang K

2017-12-19

Optical coherence tomography angiography (OCTA) is increasingly becoming a popular inspection tool for biomedical imaging applications. By exploring the amplitude, phase and complex information available in OCT signals, numerous algorithms have been proposed that contrast functional vessel networks within microcirculatory tissue beds. However, it is not clear which algorithm delivers optimal imaging performance. Here, we investigate systematically how amplitude and phase information have an impact on the OCTA imaging performance, to establish the relationship of amplitude and phase stability with OCT signal-to-noise ratio (SNR), time interval and particle dynamics. With either repeated A-scan or repeated B-scan imaging protocols, the amplitude noise increases with the increase of OCT SNR; however, the phase noise does the opposite, i.e. it increases with the decrease of OCT SNR. Coupled with experimental measurements, we utilize a simple Monte Carlo (MC) model to simulate the performance of amplitude-, phase- and complex-based algorithms for OCTA imaging, the results of which suggest that complex-based algorithms deliver the best performance when the phase noise is  algorithm delivers better performance than either the amplitude- or phase-based algorithms for both the repeated A-scan and the B-scan imaging protocols, which agrees well with the conclusion drawn from the MC simulations.

Selective oxidation of dual phase steel after annealing at different dew points

Science.gov (United States)

Lins, Vanessa de Freitas Cunha; Madeira, Laureanny; Vilela, Jose Mario Carneiro; Andrade, Margareth Spangler; Buono, Vicente Tadeu Lopes; Guimarães, Juliana Porto; Alvarenga, Evandro de Azevedo

2011-04-01

Hot galvanized steels have been extensively used in the automotive industry. Selective oxidation on the steel surface affects the wettability of zinc on steel and the grain orientation of inhibition layer (Fe-Al-Zn alloy) and reduces the iron diffusion to the zinc layer. The aim of this work is to identify and quantify selective oxidation on the surface of a dual phase steel, and an experimental steel with a lower content of manganese, annealed at different dew points. The techniques employed were atomic force microscopy, X-ray photoelectron spectroscopy, and glow discharge optical emission spectroscopy. External selective oxidation was observed for phosphorus on steel surface annealed at 0 °C dp, and for manganese, silicon, and aluminum at a lower dew point. The concentration of manganese was higher on the dual phase steel surface than on the surface of the experimental steel. The concentration of molybdenum on the surface of both steels increased as the depth increased.

Segregation across the metal/oxide interface occurring during oxidation at high temperatures of diluted iron based alloys

International Nuclear Information System (INIS)

Geneve, D.; Rouxel, D.; Weber, B.; Confente, M.

2006-01-01

Industrial steels being elaborated in air at high temperature oxidize and cover with a complex oxide layer. The oxidation reaction drastically alters the surface composition. Such modifications have been investigated, in this work, by Auger Electron Spectroscopy (AES) using an original method to characterize the composition of the metal/oxide interfaces. Analysis of the concentration gradients across the interfaces allows to better understand how the alloy elements contribute to the oxidation process. The development of new alloy phases, the interdependencies between elements and the diffusion of different species are discussed considering thermodynamic properties of each element

Enthalpy changes when passing from simple to complex perovskite-like oxides

International Nuclear Information System (INIS)

Reznitskij, L.A.

1999-01-01

Formation enthalpies of complex perovskite-like oxides and their hexagonal analogs of the composition: Ba 2 ReFeO 6 , Sr 2 ReFeO 6 , Sr 2 ReMnO 6 , Ca 2 ReMnO 6 , Sr 2 WCrO 6 , Sr 2 MoCrO 6 , Ca 2 MoCrO 6 , Ca 2 WCrO 6 , Ba 3 Fe 2 ReO 9 , Ba 3 Cr 2 ReO 9 , Ba 2 RhTaO 6 and B 2 ScIrO 6 from simple oxides were calculated by approximate method using enthalpies of the cations coordination change in oxygen medium. The conclusion was made that enthalpy stabilization of the oxide with regard to simple oxides is mainly determined by the change in enthalpies of alkaline earth metal cations [ru

Immobilization of Radioactive Rare Earth oxide Waste by Solid Phase Sintering

International Nuclear Information System (INIS)

Ahn, Byung Gil; Park, Hwan Seo; Kim, Hwan Young; Lee, Han Soo; Kim, In Tae

2010-01-01

In the pyroprocessing of spent nuclear fuels, LiCl-KCl waste salt containing radioactive rare earth chlorides are generated. The radioactive rare earth oxides are recovered by co-oxidative precipitation of rare earth elements. The powder phase of rare earth oxide waste must be immobilized to produce a monolithic wasteform suitable for storage and ultimate disposal. The immobilization of these waste developed in this study involves a solid state sintering of the waste with host borosilicate glass and zinc titanate based ceramic matrix (ZIT). And the rare-earth monazite which synthesised by reaction of ammonium di-hydrogen phosphate with the rare earth oxides waste, were immobilized with the borosilicate glass. It is shown that the developed ZIT ceramic wasteform is highly resistant the leaching process, high density and thermal conductivity.

Effect of intermetallic phases on the anodic oxidation and corrosion of 5A06 aluminum alloy

Science.gov (United States)

Li, Song-mei; Li, Ying-dong; Zhang, You; Liu, Jian-hua; Yu, Mei

2015-02-01

Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered intermetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaCl solution. The results show that the size of Al-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the anodic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.

Molecular Recognition in the Oxidation of Catechols by Dicobalt-BISDIEN Dioxygen Complexes

Science.gov (United States)

1992-01-30

Recognition in the Oxidation of Catechols by Dicobalt-RISDIEN Dioxygen Complexes Lizete F S Cezar and Bruno Szpoganicz Departamento de Quimica ...bridged bi- nuclear Co(II)-BISDIEN dioxygen complexes; Co20 2 LCat2 + is the bivalent form, and Co20 2 (OH)LCat + and Co 20 2 (OH)2 Cat° are hydroxo

Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

KAUST Repository

Turias, Francesc; Solà , Miquel; Falivene, Laura; Cavallo, Luigi; Poater, Albert

2015-01-01

The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

KAUST Repository

Turias, Francesc

2015-09-09

The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

Enhanced visible-light photocatalytic activity for selective oxidation of amines into imines over TiO2(B)/anatase mixed-phase nanowires

International Nuclear Information System (INIS)

Dai, Jun; Yang, Juan; Wang, Xiaohan; Zhang, Lei; Li, Yingjie

2015-01-01

Graphical abstract: Visible-light photocatalytic activities for selective oxidation of amines into imines are greatly affected by the crystal structure of TiO 2 catalysts and mixed-phase TiO 2 (B)/anatase possess higher photoactivity because of the moderate adsorption ability and efficient charge separation. - Highlights: • Visible-light photocatalytic oxidation of amines to imines is studied over different TiO 2 . • Photocatalytic activities are greatly affected by the crystal structure of TiO 2 nanowires. • Mixed-phase TiO 2 (B)/anatase exhibits higher catalytic activity than single-phase TiO 2 . • Enhanced activity is ascribed to efficient adsorption ability and interfacial charge separation. • Photoinduced charge transfer mechanism on TiO 2 (B)/anatase catalysts is also proposed. - Abstract: Wirelike catalysts of mixed-phase TiO 2 (B)/anatase TiO 2 , bare anatase TiO 2 and TiO 2 (B) are synthesized via calcining precursor hydrogen titanate obtained from hydrothermal process at different temperatures between 450 and 700 °C. Under visible light irradiation, mixed-phase TiO 2 (B)/anatase TiO 2 catalysts exhibit enhanced photocatalytic activity in comparison with pure TiO 2 (B) and anatase TiO 2 toward selective oxidation of benzylamines into imines and the highest photocatalytic activity is achieved by TW-550 sample consisting of 65% TiO 2 (B) and 35% anatase. The difference in photocatalytic activities of TiO 2 samples can be attributed to the different adsorption abilities resulted from their crystal structures and interfacial charge separation driven by surface-phase junctions between TiO 2 (B) and anatase TiO 2 . Moreover, the photoinduced charge transfer mechanism of surface complex is also proposed over mixed-phase TiO 2 (B)/anatase TiO 2 catalysts. Advantages of this photocatalytic system include efficient utilization of solar light, general suitability to amines, reusability and facile separation of nanowires catalysts

Cyclopentadienyl molybdenum(II/VI) N-heterocyclic carbene complexes: Synthesis, structure, and reactivity under oxidative conditions

KAUST Repository

Li, Shenyu

2010-04-26

A series of N-heterocyclic carbene (NHC) complexes CpMo(CO) 2(NHC)X (NHC = IMe = 1,3-dimethylimidazol-2-ylidene, X = Br, 1; NHC = 1,3-dipropylimidazol-2-ylidene, X = Br, 2; NHC = IMes = 1,3-bis(2,4,6- trimethylphenyl)imidazol-2-ylidene, X = Br, 3; NHC = IBz = 1,3-dibenzylimidazol- 2-ylidene, X = Br, 4a, and X = Cl, 4b; NHC = 1-methyl-3-propylimidazol-2- ylidene, X = Br, 5) and [CpMo(CO)2(IMes)(CH3CN)][BF 4] (6) have been synthesized and fully characterized. The stability of metal-NHC ligand bonds in these compounds under oxidative conditions has been investigated. The thermally stable Mo(VI) dioxo NHC complex [CpMoO 2(IMes)][BF4] (9) has been isolated by the oxidation of the ionic complex 6 by TBHP (tert-butyl hydrogen peroxide). Complex 6 can be applied as a very active (TOFs up to 3400 h-1) and selective olefin epoxidation catalyst. While under oxidative conditions (in the presence of TBHP), compounds 1-5 decompose into imidazolium bromide and imidazolium polyoxomolybdate. The formation of polyoxomolybdate as oxidation products had not been observed in a similar epoxidation catalyzed by Mo(II) and Mo(VI) complexes. DFT studies suggest that the presence of Br- destabilizes the CpMo(VI) oxo NHC carbene species, consistent with the experimental observations. © 2010 American Chemical Society.

First principles studies of complex oxide surfaces and interfaces

International Nuclear Information System (INIS)

Noguera, Claudine; Finocchi, Fabio; Goniakowski, Jacek

2004-01-01

Oxides enter our everyday life and exhibit an impressive variety of physical and chemical properties. The understanding of their behaviour, which is often determined by the electronic and atomic structures of their surfaces and interfaces, is a key question in many fields, such as geology, environmental chemistry, catalysis, thermal coatings, microelectronics, and bioengineering. In the last decade, first principles methods, mainly those based on the density functional theory, have been frequently applied to study complex oxide surfaces and interfaces, complementing the experimental observations. In this work, we discuss some of these contributions, with emphasis on several issues that are especially important when dealing with oxides: the local electronic structure at interfaces, and its connection with chemical reactivity; the charge redistribution and the bonding variations, in relation to screening properties; and the possibility of bridging the gap between model and real systems by taking into account the chemical environments and the effect of finite temperatures, and by performing simulations on systems of an adequate (large) size

Nonheme oxoiron(IV) complexes of pentadentate N5 ligands: spectroscopy, electrochemistry, and oxidative reactivity

OpenAIRE

Wang, Dong; Ray, Kallol; Collins, Michael J.; Farquhar, Erik R.; Frisch, Jonathan R.; Gomez, Laura; Jackson, Timothy A.; Kerscher, Marion; Waleska, Arkadius; Comba, Peter; Costas, Miquel; Que, Lawrence, Jr.

2013-01-01

Oxoiron(IV) species have been found to act as the oxidants in the catalytic cycles of several mononuclear nonheme iron enzymes that activate dioxygen. To gain insight into the factors that govern the oxidative reactivity of such complexes, a series of five synthetic S = 1 [FeIV(O)(LN5)]2+ complexes has been characterized with respect to their spectroscopic and electrochemical properties as well as their relative abilities to carry out oxo transfer and hydrogen atom abstraction. The Fe=O units...

Preparation and characterization of perovskite structure lanthanum gallate and lanthanum aluminate based oxides

OpenAIRE

Li, Shuai

2009-01-01

The present work was initiated to study the synthesis and properties of lanthanum gallate based oxides as intermediate temperature electrolyte for solid oxide fuel cells. The wet chemical method, polymer complexing route, was used to prepare the precursor powders. To further investigate the polymer complexing method, it was also applied to the preparation of lanthanum aluminate based oxides.   Single perovskite phase La0.8Sr0.2Ga0.83Mg0.17O2.815 can be prepared by the polymer complexing meth...

Nitric Oxide Synthase and Cyclooxygenase Pathways: A Complex Interplay in Cellular Signaling.

Science.gov (United States)

Sorokin, Andrey

2016-01-01

The cellular reaction to external challenges is a tightly regulated process consisting of integrated processes mediated by a variety of signaling molecules, generated as a result of modulation of corresponding biosynthetic systems. Both, nitric oxide synthase (NOS) and cyclooxygenase (COX) systems, consist of constitutive forms (NOS1, NOS3 and COX-1), which are mostly involved in housekeeping tasks, and inducible forms (NOS2 and COX-2), which shape the cellular response to stress and variety of bioactive agents. The complex interplay between NOS and COX pathways can be observed at least at three levels. Firstly, products of NOS and Cox systems can mediate the regulation and the expression of inducible forms (NOS2 and COX-2) in response of similar and dissimilar stimulus. Secondly, the reciprocal modulation of cyclooxygenase activity by nitric oxide and NOS activity by prostaglandins at the posttranslational level has been shown to occur. Mechanisms by which nitric oxide can modulate prostaglandin synthesis include direct S-nitrosylation of COX and inactivation of prostaglandin I synthase by peroxynitrite, product of superoxide reaction with nitric oxide. Prostaglandins, conversely, can promote an increased association of dynein light chain (DLC) (also known as protein inhibitor of neuronal nitric oxide synthase) with NOS1, thereby reducing its activity. The third level of interplay is provided by intracellular crosstalk of signaling pathways stimulated by products of NOS and COX which contributes significantly to the complexity of cellular signaling. Since modulation of COX and NOS pathways was shown to be principally involved in a variety of pathological conditions, the dissection of their complex relationship is needed for better understanding of possible therapeutic strategies. This review focuses on implications of interplay between NOS and COX for cellular function and signal integration.

Nonequilibrium phase formation in oxides prepared at low temperature: Fergusonite-related phases

International Nuclear Information System (INIS)

Mather, S.A.; Davies, P.K.

1995-01-01

Sol-gel methods have been developed to prepare YNbO 4 , YTaO 4 , and other rare-earth niobates and tantalates with fergusonite-related crystal structures. At low temperatures, all of the fergusonites, with the exception of SmTaO 4 , crystallize in a metastable tetragonal (T') structure similar to that of tetragonal zirconia. Although all of the equilibrium forms of these oxides adopt a crystal structure containing an ordered distribution of the trivalent and pentavalent cations, a random cation distribution is obtained in the metastable T' phase. Metastable phase formation is often ascribed solely to kinetically limited topotactic crystallization. However, the changes in the grain size and unit-cell volumes that accompany the metastable-to-equilibrium fergusonite conversions imply that other physical phenomena induced by small-particle synthesis, namely the Gibbs-Thompson pressure effect and the increased contribution of surface energy, cannot be ignored

Gas-phase spectroscopy of ferric heme-NO complexes

DEFF Research Database (Denmark)

Wyer, J.A.; Jørgensen, Anders; Pedersen, Bjarke

2013-01-01

and significantly blue-shifted compared to ferric heme nitrosyl proteins (maxima between 408 and 422 nm). This is in stark contrast to the Q-band absorption where the protein microenvironment is nearly innocent in perturbing the electronic structure of the porphyrin macrocycle. Photodissociation is primarily...... maxima of heme and its complexes with amino acids and NO. Not so innocent: Weakly bound complexes between ferric heme and NO were synthesised in the gas phase, and their absorption measured from photodissociation yields. Opposite absorption trends in the Soret-band are seen upon NO addition to heme ions...

Characterization of 10 μm thick porous silicon dioxide obtained by complex oxidation process for RF application

International Nuclear Information System (INIS)

Park, Jeong-Yong; Lee, Jong-Hyun

2003-01-01

This paper proposes a 10 μm thick oxide layer structure, which can be used as a substrate for RF circuits. The structure has been fabricated by anodic reaction and complex oxidation, which is a combined process of low temperature thermal oxidation (500 deg. C, for 1 h at H 2 O/O 2 ) and a rapid thermal oxidation (RTO) process (1050 deg. C, for 1 min). The electrical characteristics of oxidized porous silicon layer (OPSL) were almost the same as those of standard thermal silicon dioxide. The leakage current through the OPSL of 10 μm was about 100-500 pA in the range of 0-50 V. The average value of breakdown field was about 3.9 MV cm -1 . From the X-ray photo-electron spectroscopy (XPS) analysis, surface and internal oxide films of OPSL, prepared by complex process were confirmed to be completely oxidized and also the role of RTO process was important for the densification of porous silicon layer (PSL) oxidized at a lower temperature. For the RF-test of Si substrate with thick silicon dioxide layer, we have fabricated high performance passive devices such as coplanar waveguide (CPW) on OPSL substrate. The insertion loss of CPW on OPSL prepared by complex oxidation process was -0.39 dB at 4 GHz and similar to that of CPW on OPSL prepared by a temperature of 1050 deg. C (1 h at H 2 O/O 2 ). Also the return loss of CPW on OPSL prepared by complex oxidation process was -23 dB at 10 GHz, which is similar to that of CPW on OPSL prepared by high temperature

Three-phase boundary length in solid-oxide fuel cells: A mathematical model

Energy Technology Data Exchange (ETDEWEB)

Janardhanan, Vinod M. [Institutefor Chemical Technology and Polymer Chemistry, University of Karlsruhe (TH), Kaiserstr. 12, D-76128 Karlsruhe (Germany); Heuveline, Vincent; Deutschmann, Olaf [Institute for Applied and Numerical Mathematics, University of Karlsruhe (TH), Kaiserstr. 12, D-76128 Karlsruhe (Germany)

2008-03-15

A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution. (author)

Three-phase boundary length in solid-oxide fuel cells: A mathematical model

Science.gov (United States)

Janardhanan, Vinod M.; Heuveline, Vincent; Deutschmann, Olaf

A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution.

Complex 3D Vortex Lattice Formation by Phase-Engineered Multiple Beam Interference

Directory of Open Access Journals (Sweden)

Jolly Xavier

2012-01-01

Full Text Available We present the computational results on the formation of diverse complex 3D vortex lattices by a designed superposition of multiple plane waves. Special combinations of multiples of three noncoplanar plane waves with a designed relative phase shift between one another are perturbed by a nonsingular beam to generate various complex 3D vortex lattice structures. The formation of complex gyrating lattice structures carrying designed vortices by means of relatively phase-engineered plane waves is also computationally investigated. The generated structures are configured with both periodic as well as transversely quasicrystallographic basis, while these whirling complex lattices possess a long-range order of designed symmetry in a given plane. Various computational analytical tools are used to verify the presence of engineered geometry of vortices in these complex 3D vortex lattices.

Complex network analysis of phase dynamics underlying oil-water two-phase flows

Science.gov (United States)

Gao, Zhong-Ke; Zhang, Shan-Shan; Cai, Qing; Yang, Yu-Xuan; Jin, Ning-De

2016-01-01

Characterizing the complicated flow behaviors arising from high water cut and low velocity oil-water flows is an important problem of significant challenge. We design a high-speed cycle motivation conductance sensor and carry out experiments for measuring the local flow information from different oil-in-water flow patterns. We first use multivariate time-frequency analysis to probe the typical features of three flow patterns from the perspective of energy and frequency. Then we infer complex networks from multi-channel measurements in terms of phase lag index, aiming to uncovering the phase dynamics governing the transition and evolution of different oil-in-water flow patterns. In particular, we employ spectral radius and weighted clustering coefficient entropy to characterize the derived unweighted and weighted networks and the results indicate that our approach yields quantitative insights into the phase dynamics underlying the high water cut and low velocity oil-water flows. PMID:27306101

Complex Quasi-Two-Dimensional Crystalline Order Embedded in VO2 and Other Crystals

Science.gov (United States)

Lovorn, Timothy; Sarker, Sanjoy K.

2017-07-01

Metal oxides such as VO2 undergo structural transitions to low-symmetry phases characterized by intricate crystalline order, accompanied by rich electronic behavior. We derive a minimal ionic Hamiltonian based on symmetry and local energetics which describes structural transitions involving all four observed phases, in the correct order. An exact analysis shows that complexity results from the symmetry-induced constraints of the parent phase, which forces ionic displacements to form multiple interpenetrating groups using low-dimensional pathways and distant neighbors. Displacements within each group exhibit independent, quasi-two-dimensional order, which is frustrated and fragile. This selective ordering mechanism is not restricted to VO2 : it applies to other oxides that show similar complex order.

Strategies towards controlling strain-induced mesoscopic phase separation in manganite thin films

Science.gov (United States)

Habermeier, H.-U.

2008-10-01

Complex oxides represent a class of materials with a plethora of fascinating intrinsic physical functionalities. The intriguing interplay of charge, spin and orbital ordering in these systems superimposed by lattice effects opens a scientifically rewarding playground for both fundamental as well as application oriented research. The existence of nanoscale electronic phase separation in correlated complex oxides is one of the areas in this field whose impact on the current understanding of their physics and potential applications is not yet clear. In this paper this issue is treated from the point of view of complex oxide thin film technology. Commenting on aspects of complex oxide thin film growth gives an insight into the complexity of a reliable thin film technology for these materials. Exploring fundamentals of interfacial strain generation and strain accommodation paves the way to intentionally manipulate thin film properties. Furthermore, examples are given for an extrinsic continuous tuning of intrinsic electronic inhomogeneities in perovskite-type complex oxide thin films.

Strategies towards controlling strain-induced mesoscopic phase separation in manganite thin films

International Nuclear Information System (INIS)

Habermeier, H-U

2008-01-01

Complex oxides represent a class of materials with a plethora of fascinating intrinsic physical functionalities. The intriguing interplay of charge, spin and orbital ordering in these systems superimposed by lattice effects opens a scientifically rewarding playground for both fundamental as well as application oriented research. The existence of nanoscale electronic phase separation in correlated complex oxides is one of the areas in this field whose impact on the current understanding of their physics and potential applications is not yet clear. In this paper this issue is treated from the point of view of complex oxide thin film technology. Commenting on aspects of complex oxide thin film growth gives an insight into the complexity of a reliable thin film technology for these materials. Exploring fundamentals of interfacial strain generation and strain accommodation paves the way to intentionally manipulate thin film properties. Furthermore, examples are given for an extrinsic continuous tuning of intrinsic electronic inhomogeneities in perovskite-type complex oxide thin films.

Phase Transformation Behavior of Oxide Particles Formed in Mechanically Alloyed Fe-5Y{sub 2}O{sub 3} Powder

Energy Technology Data Exchange (ETDEWEB)

Kim, Ga Eon; Choi, Jung-Sun; Noh, Sanghoon; Kang, Suk Hoon; Choi, Byoung Kwon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Deajeon (Korea, Republic of); Kim, Young Do [Hanyang University, Seoul (Korea, Republic of)

2017-05-15

The phase transformation behavior of the oxides formed in mechanically alloyed Fe-5Y{sub 2}O{sub 3} powder is investigated. Non-stoichiometric Y-rich and Fe-rich oxides with sizes of less than 300 nm are observed in the mechanically alloyed powder. The diffusion and redistribution reactions of the elements in these oxides during heating of the powder above 800 ℃ were observed, and these reactions result in the formation of a Y{sub 3}Fe{sub 5}O{sub 12} phase after heating at 1050 ℃. Thus, it is considered that the Y{sub 2}O{sub 3} powder and some Fe powder are formed from the non-stoichiometric Y-rich and Fe-rich oxides after the mechanical alloying process, and a considerable energy accumulated during the mechanical alloying process leads to a phase transformation of the Y-rich and Fe-rich oxides to Y{sub α}Fe{sub β}O{sub γ}-type phase during heating.

Online Measurements of Highly Oxidized Organics in the Gas and Particle phase during SOAS and SENEX

Science.gov (United States)

Lopez-Hilfiker, F.; Lee, B. H.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Thornton, J. A.

2014-12-01

We present measurements of a large suite of gas and particle phase organic compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington and with airborne HR-ToF-CIMS measurements. The FIGAERO instrument was deployed on the Jülich Plant Atmosphere Chamber to study α-pinene oxidation, and subsequently at the SMEAR II forest station in Hyytiälä, Finland and the SOAS ground site, in Brent Alabama. During the Southern Atmosphere Study, a gas-phase only version of the HR-ToF-CIMS was deployed on the NOAA WP-3 aircraft as part of SENEX. We focus here on highly oxygenated organic compounds derived from monoterpene oxidation detected both aloft during SENEX and at the ground-based site during SOAS. In both chamber and the atmosphere, many highly oxidized, low volatility compounds were observed in the gas and particles and many of the same compositions detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition such as O/C ratios, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. The detailed structure in the thermograms reveals a significant contribution from large molecular weight organics and/or oligomers in both chamber and ambient aerosol samples. Approximately 50% of the measured organics in the particle phase are associated with compounds having effective vapour pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. We discuss the implications of these findings for measurements of gas-particle partitioning and for evaluating the contribution of monoterpene oxidation to organic aerosol formation and growth. We also use the aircraft measurements and a

PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION

Directory of Open Access Journals (Sweden)

Jan Setiawan

2016-10-01

Full Text Available ABSTRACT PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION. The oxidation on two silicon carbide contain 6H phase and contains 6H and 4H phases has been done.  Silicon carbide is ceramic non-oxide with excellent properties that potentially used in industry.  Silicon carbide is used in nuclear industry as structure material that developed as light water reactor (LWR fuel cladding and as a coating layer in the high temperature gas-cooled reactor (HTGR fuel.  In this study silicon carbide oxidation simulation take place in case the accident in primary cooling pipe is ruptured.  Sample silicon carbide made of powder that pressed into pellet with diameter 12.7 mm and thickness 1.0 mm, then oxidized at temperature 1000 oC, 1200 oC dan 1400 oC for 1 hour.  The samples were weighted before and after oxidized.  X-ray diffraction con-ducted to the samples using Panalytical Empyrean diffractometer with Cu as X-ray source.  Diffraction pattern analysis has been done using General Structure Analysis System (GSAS software. This software was resulting the lattice parameter changes and content of SiC phases.  The result showed all of the oxidation samples undergoes weight gain.  The 6S samples showed the highest weight change at oxidation temperature 1200 oC, for the 46S samples showed increasing tendency with the oxidation temperature.  X-ray diffraction pattern analysis showed the 6S samples contain dominan phase 6H-SiC that matched to ICSD 98-001-5325 card.  Diffraction pattern on 6S showed lattice parameter, composition and crystallite size changes.  Lattice parameters changes had smaller tendency from the model and before oxidation.  However, the lowest silicon carbide composition or the highest converted into other phases up to 66.85 %, occurred at oxidation temperature 1200 oC.  The 46S samples contains two polytypes silicon car-bide.  The 6H-SiC phases matched by ICSD 98-016-4972 card and 4H-SiC phase matched by ICSD 98

The liquid phase oxidation of n-butane: a search for plausible mechanisms

Energy Technology Data Exchange (ETDEWEB)

Hobbs, C.C. [Celanese Ltd., TX (United States). Corpus Christi Technical Center

1998-12-31

This articles deals with an approach that has given some key information about the mechanisms of the liquid phase oxidation of butane to acetic acid. This procedure has been developed over the last 34 years; however, much of what will be discussed represents a synthesis of previous insights. Many of the observations are relatively recent and have not been previously published. In principle, this approach should be applicable to many oxidation processes. (orig.)

Bright electroluminescence from a chelate phosphine oxide Eu{sup III} complex with high thermal performance

Energy Technology Data Exchange (ETDEWEB)

Xu Hui [School of Chemistry and Materials, Heilongjiang University, 74 Xuefu Road, Nangang District, Harbin 150080, Heilongjiang Province (China); Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 66 Xinmofan Road, Nanjing 21003, Jiangsu Province (China); Yin Kun; Wang Lianhui [Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 66 Xinmofan Road, Nanjing 21003, Jiangsu Province (China); Huang Wei [Institute of Advanced Materials (IAM), Fudan University, 220 Handan Road, Shanghai 200433 (China)], E-mail: wei-huang@njupt.edu.cn

2008-10-01

The chelate phosphine oxide ligand 1,8-bis(diphenylphosphino)naphthalene oxide (NaPO) was used to prepare complex 1 tris(2-thenoyltrifluoroacetonate)(1,8-bis(diphenylphosphino)naphthalene oxide)europium(III). The rigid structure of NaPO makes 1 have more compact structure resulting in a temperature of glass transition as high as 147 deg. C, which is the highest in luminescent Eu{sup III} complexes, and a higher decomposition temperature of 349 deg. C. The improvement of carrier transfer ability of NaPO was proved by Gaussian simulation. The multi-layered electroluminescent device based on 1 had a low turn-on voltage of 6.0 V, the maximum brightness of 601 cd m{sup -2} at 21.5 V and 481.4 mA cm{sup -2}, and the excellent voltage-independent spectral stability. These properties demonstrated NaPO cannot only be favorable to form the rigid and compact complex structure, and increase the thermal and morphological stability of the complex, but also reduce the formation of the exciplex.

Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

International Nuclear Information System (INIS)

Zhu Jingxi; Holcomb, Gordon R.; Jablonski, Paul D.; Wise, Adam; Li Jia; Laughlin, David E.; Sridhar, Seetharaman

2012-01-01

Highlights: ►Oxidation products of Ni-based superalloy were studied in oxy-fuel combustion conditions. ► An oxidation-induced phase transformation occurred in the subsurface region. ► One of the two product phases was not in the Ni database of Thermo-Calc. ► This unknown phase is an ordered derivative of FCC structure of Ni–Ti(–Ta) system. ► This phase is likely detrimental to the mechanical integrity of the alloy in use. - Abstract: In the integration of oxy-fuel combustion to turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO 2 and O 2 . While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation. In this study, bare metal coupons of Ni-base superalloys were exposed in oxy-fuel combustion environment for up to 1000 h and the oxidation-related microstructures were examined. Phase transformation occurred in the subsurface region in Ni-based superalloy and led to twinning. The transformation product phases were analyzed through thermodynamic equilibrium calculations and various electron microscopy techniques, including scanning electron microscopy (SEM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The mechanism by which the phase transformation and the formation of the microstructure occurred was also discussed. The possible effects of the product phases on the performance of the alloy in service were discussed.

Enhanced visible-light photocatalytic activity for selective oxidation of amines into imines over TiO{sub 2}(B)/anatase mixed-phase nanowires

Energy Technology Data Exchange (ETDEWEB)

Dai, Jun [Institute of Applied Chemistry, Henan Polytechnic University, Jiaozuo 454003 (China); State Key Laboratory Cultivation Base for Gas Geology and Gas Control, School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003 (China); Yang, Juan, E-mail: yangjuanhpu@yahoo.com [Institute of Applied Chemistry, Henan Polytechnic University, Jiaozuo 454003 (China); Wang, Xiaohan; Zhang, Lei; Li, Yingjie [Institute of Applied Chemistry, Henan Polytechnic University, Jiaozuo 454003 (China)

2015-09-15

Graphical abstract: Visible-light photocatalytic activities for selective oxidation of amines into imines are greatly affected by the crystal structure of TiO{sub 2} catalysts and mixed-phase TiO{sub 2}(B)/anatase possess higher photoactivity because of the moderate adsorption ability and efficient charge separation. - Highlights: • Visible-light photocatalytic oxidation of amines to imines is studied over different TiO{sub 2}. • Photocatalytic activities are greatly affected by the crystal structure of TiO{sub 2} nanowires. • Mixed-phase TiO{sub 2}(B)/anatase exhibits higher catalytic activity than single-phase TiO{sub 2}. • Enhanced activity is ascribed to efficient adsorption ability and interfacial charge separation. • Photoinduced charge transfer mechanism on TiO{sub 2}(B)/anatase catalysts is also proposed. - Abstract: Wirelike catalysts of mixed-phase TiO{sub 2}(B)/anatase TiO{sub 2}, bare anatase TiO{sub 2} and TiO{sub 2}(B) are synthesized via calcining precursor hydrogen titanate obtained from hydrothermal process at different temperatures between 450 and 700 °C. Under visible light irradiation, mixed-phase TiO{sub 2}(B)/anatase TiO{sub 2} catalysts exhibit enhanced photocatalytic activity in comparison with pure TiO{sub 2}(B) and anatase TiO{sub 2} toward selective oxidation of benzylamines into imines and the highest photocatalytic activity is achieved by TW-550 sample consisting of 65% TiO{sub 2}(B) and 35% anatase. The difference in photocatalytic activities of TiO{sub 2} samples can be attributed to the different adsorption abilities resulted from their crystal structures and interfacial charge separation driven by surface-phase junctions between TiO{sub 2}(B) and anatase TiO{sub 2}. Moreover, the photoinduced charge transfer mechanism of surface complex is also proposed over mixed-phase TiO{sub 2}(B)/anatase TiO{sub 2} catalysts. Advantages of this photocatalytic system include efficient utilization of solar light, general suitability to

Directing the phase behavior of polyelectrolyte complexes using chiral patterned peptides

Science.gov (United States)

Pacalin, Naomi M.; Leon, Lorraine; Tirrell, Matthew

2016-10-01

Polyelectrolyte complexes (PECs) have a broad range of promising applications as soft materials due to their self-assembly and diversity of structure and chemical composition. Peptide polymer PECs are highly biocompatible and biodegradable, making them particularly useful for encapsulation of food additives and flavors, micellar drug delivery, medical and underwater adhesives, fetal membrane patches, and scaffolds for cell growth in tissue engineering. While parameters affecting PEC formation and stability in regards to charge effects are well researched, little is known about the effects of van der Waals interactions, hydrogen bonding, and secondary structure in these materials. Peptide chirality provides a unique opportunity to manipulate PEC phase to modulate the amount of solid-like (precipitate) or liquid-like (coacervate) character by influencing hydrogen bonding interactions among peptide chains. In previous work, we showed that chiral peptides form solid complexes, while complexes with even one racemic peptide were fluid. This raised the interesting question of how long a homochiral sequence must be to result in solid phase formation. In this work, we designed chiral patterned peptides of polyglutamic acid and polylysine ranging from 50 to 90% L-chiral residues with increasing numbers of sequential L-chiral residues before a chirality change. These polymers were mixed together to form PECs. We observed that 8 or more sequential L-chiral residues are necessary to achieve both the appearance of a precipitate phase and sustained β-sheets in the complex, as determined by optical imaging and FTIR Spectroscopy. Less homochiral content results in formation of a coacervate phase. Thus, we show that chiral sequence can be used to control the phase transition of PECs. Understanding how to manipulate PEC phase using chiral sequence as presented here may enable tuning of the material properties to achieve the desired mechanical strength for coatings and polymer

Directing the phase behavior of polyelectrolyte complexes using chiral patterned peptides

Energy Technology Data Exchange (ETDEWEB)

Pacalin, Naomi M.; Leon, Lorraine; Tirrell, Matthew

2016-10-01

Polyelectrolyte complexes (PECs) have a broad range of promising applications as soft materials due to their self-assembly and diversity of structure and chemical composition. Peptide polymer PECs are highly biocompatible and biodegradable, making them particularly useful for encapsulation of food additives and flavors, micellar drug delivery, medical and underwater adhesives, fetal membrane patches, and scaffolds for cell growth in tissue engineering. While parameters affecting PEC formation and stability in regards to charge effects are well researched, little is known about the effects of van der Waals interactions, hydrogen bonding, and secondary structure in these materials. Peptide chirality provides a unique opportunity to manipulate PEC phase to modulate the amount of solid-like (precipitate) or liquid-like (coacervate) character by influencing hydrogen bonding interactions among peptide chains. In previous work, we showed that chiral peptides form solid complexes, while complexes with even one racemic peptide were fluid. This raised the interesting question of how long a homochiral sequence must be to result in solid phase formation. In this work, we designed chiral patterned peptides of polyglutamic acid and polylysine ranging from 50 to 90% L-chiral residues with increasing numbers of sequential L-chiral residues before a chirality change. These polymers were mixed together to form PECs. We observed that 8 or more sequential L-chiral residues are necessary to achieve both the appearance of a precipitate phase and sustained beta-sheets in the complex, as determined by optical imaging and FTIR Spectroscopy. Less homochiral content results in formation of a coacervate phase. Thus, we show that chiral sequence can be used to control the phase transition of PECs. Understanding how to manipulate PEC phase using chiral sequence as presented here may enable tuning of the material properties to achieve the desired mechanical strength for coatings and polymer

Iridium complexes for electrocatalysis

Science.gov (United States)

Sheehan, Stafford Wheeler; Hintermair, Ulrich; Thomsen, Julianne M; Brudvig, Gary W; Crabtree, Robert H

2017-10-17

Solution-phase (e.g., homogeneous) or surface-immobilized (e.g., heterogeneous) electrode-driven oxidation catalysts based on iridium coordination compounds which self-assemble upon chemical or electrochemical oxidation of suitable precursors and methods of making and using thereof are. Iridium species such as {[Ir(LX).sub.x(H.sub.2O).sub.y(.mu.-O)].sub.z.sup.m+}.sub.n wherein x, y, m are integers from 0-4, z and n from 1-4 and LX is an oxidation-resistant chelate ligand or ligands, such as such as 2(2-pyridyl)-2-propanolate, form upon oxidation of various molecular iridium complexes, for instance [Cp*Ir(LX)OH] or [(cod)Ir(LX)] (Cp*=pentamethylcyclopentadienyl, cod=cis-cis,1,5-cyclooctadiene) when exposed to oxidative conditions, such as sodium periodate (NaIO.sub.4) in aqueous solution at ambient conditions.

Spin trapping combined with quantitative mass spectrometry defines free radical redistribution within the oxidized hemoglobin:haptoglobin complex.

Science.gov (United States)

Vallelian, Florence; Garcia-Rubio, Ines; Puglia, Michele; Kahraman, Abdullah; Deuel, Jeremy W; Engelsberger, Wolfgang R; Mason, Ronald P; Buehler, Paul W; Schaer, Dominik J

2015-08-01

Extracellular or free hemoglobin (Hb) accumulates during hemolysis, tissue damage, and inflammation. Heme-triggered oxidative reactions can lead to diverse structural modifications of lipids and proteins, which contribute to the propagation of tissue damage. One important target of Hb׳s peroxidase reactivity is its own globin structure. Amino acid oxidation and crosslinking events destabilize the protein and ultimately cause accumulation of proinflammatory and cytotoxic Hb degradation products. The Hb scavenger haptoglobin (Hp) attenuates oxidation-induced Hb degradation. In this study we show that in the presence of hydrogen peroxide (H2O2), Hb and the Hb:Hp complex share comparable peroxidative reactivity and free radical generation. While oxidation of both free Hb and Hb:Hp complex generates a common tyrosine-based free radical, the spin-trapping reaction with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) yields dissimilar paramagnetic products in Hb and Hb:Hp, suggesting that radicals are differently redistributed within the complex before reacting with the spin trap. With LC-MS(2) mass spectrometry we assigned multiple known and novel DMPO adduct sites. Quantification of these adducts suggested that the Hb:Hp complex formation causes extensive delocalization of accessible free radicals with drastic reduction of the major tryptophan and cysteine modifications in the β-globin chain of the Hb:Hp complex, including decreased βCys93 DMPO adduction. In contrast, the quantitative changes in DMPO adduct formation on Hb:Hp complex formation were less pronounced in the Hb α-globin chain. In contrast to earlier speculations, we found no evidence that free Hb radicals are delocalized to the Hp chain of the complex. The observation that Hb:Hp complex formation alters free radical distribution in Hb may help to better understand the structural basis for Hp as an antioxidant protein. Copyright © 2015 Elsevier Inc. All rights reserved.

Ion irradiation-induced diffusion in bixbyite-fluorite related oxides: Dislocations and phase transformation

Energy Technology Data Exchange (ETDEWEB)

Rolly, Gaboriaud, E-mail: Rolly.gaboriaud@univ-poitiers.fr [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Fabien, Paumier [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Bertrand, Lacroix [CSIC – University of Sevilla, Avenida Américo Vespucio, 49, 41092 Sevilla (Spain)

2014-05-01

Ion-irradiation induced diffusion and the phase transformation of a bixbyite-fluorite related rare earth oxide thin films are studied. This work is focused on yttrium sesquioxide, Y{sub 2}O{sub 3}, thin films deposited on Si (1 0 0) substrates using the ion beam sputtering technique (IBS). As-deposited samples were annealed ant then irradiated at cryogenic temperature (80 K) with 260 keV Xe{sup 2+} at different fluences. The irradiated thin oxide films are characterized by X-ray diffraction. A cubic to monoclinic phase transformation was observed. Analysis of this phenomenon is done in terms of residual stresses. Stress measurements as a function of irradiation fluences were realised using the XRD-sin{sup 2}ψ method. Stress evolution and kinetic of the phase transformation are compared and leads to the role-played by the nucleation of point and extended defects.

Catalytic oxidation of cyanides in an aqueous phase over individual and manganese-modified cobalt oxide systems

International Nuclear Information System (INIS)

Christoskova, St.; Stoyanova, M.

2009-01-01

The possibility for purification of wastewaters containing free cyanides by applying of a new method based on cyanides catalytic oxidation with air to CO 2 and N 2 at low temperature and atmospheric pressure was investigated. On this purpose, individual and modified with manganese Co-oxide systems as active phase of environmental catalysts were synthesized. The applied method of synthesis favours the preparation of oxide catalytic systems with high active oxygen content (total-O* and surface-O* s ) possessing high mobility, and the metal ions being in a high oxidation state and in an octahedral coordination-factors determining high activity in reactions of complete oxidation. The catalysts employed were characterized by powder X-ray diffraction, Infrared spectroscopy, and chemical analysis. The effect of pH of the medium and catalyst loading on the effectiveness of the cyanide oxidation process, expressed by the degree of conversion (α, %), by the rate constant (k, min -1 ), and COD was studied. The results obtained reveal that using catalysts investigated a high cyanide removal efficiency could be achieved even in strong alkaline medium. The higher activity of the manganese promoted catalytic sample could be explained on the basis of higher total active oxygen content and its higher mobility both depending on the conditions, under which the synthesis of catalyst is being carried out.

Liquid Phase Plasma Synthesis of Iron Oxide/Carbon Composite as Dielectric Material for Capacitor

Directory of Open Access Journals (Sweden)

Heon Lee

2014-01-01

Full Text Available Iron oxide/carbon composite was synthesized using a liquid phase plasma process to be used as the electrode of supercapacitor. Spherical iron oxide nanoparticles with the size of 5~10 nm were dispersed uniformly on carbon powder surface. The specific capacitance of the composite increased with increasing quantity of iron oxide precipitate on the carbon powder up to a certain quantity. When the quantity of the iron oxide precipitate exceeds the threshold, however, the specific capacitance was rather reduced by the addition of precipitate. The iron oxide/carbon composite containing an optimum quantity (0.33 atomic % of iron oxide precipitate exhibited the smallest resistance and the largest initial resistance slope.

Multi-metal oxide ceramic nanomaterial

Science.gov (United States)

O'Brien, Stephen; Liu, Shuangyi; Huang, Limin

2016-06-07

A convenient and versatile method for preparing complex metal oxides is disclosed. The method uses a low temperature, environmentally friendly gel-collection method to form a single phase nanomaterial. In one embodiment, the nanomaterial consists of Ba.sub.AMn.sub.BTi.sub.CO.sub.D in a controlled stoichiometry.

Base-Free Selective Oxidation of Glycerol over LDH Hosted Transition Metal Complexes Using 3% H2O2 as Oxidant

Directory of Open Access Journals (Sweden)

Xiaoli Wang

2016-07-01

Full Text Available A series of transition metal sulphonato-Schiff base complexes were intercalated into Mg–Al layered-double hydroxides (LDHs. The obtained catalysts were characterized by FTIR, XRD, N2 sorption, SEM and elemental analysis, and then were used in the selective oxidation of glycerol (GLY using 3% H2O2 as an oxidant. It was found that their catalytic performances were closely related to the loading of active complexes, the Schiff base ligands and the metal centers of the catalysts, as well as the reaction conditions. The optimal conversion of GLY was 85.0%, while the selectivity of 1,3-dihydroxyacetone (DHA was 56.5%. Moreover, the catalysts could be reused at least 10 times.

Phase composition and catalytic properties of oxide multicomponent molybdenum-containing catalysts for partial oxidation of propylene

International Nuclear Information System (INIS)

Malakhov, V.V.; Vlasov, A.A.; Boldyreva, N.N.; Dovlitova, L.S.; Plyasova, L.M.; Andrushkevich, T.V.; Kuznetsova, T.G.

1996-01-01

The catalytic properties and phase composition of multicomponent molybdenum-containing catalyst treated under various redox conditions have been studied. The phase composition has been considered by the methods of X-ray phase analysis and noncalibrated methods of differentiating dissolution (DD). Using the DD method the data on element composition, stoichiometry and quantitative content of phases of complex molybdates have been obtained for the first time. Data on modification of basic phases of the catalyst-cobalt and iron molybdates - by other cations from its composition suggest that the mechanism of action of the multicomponent catalyst is defined by the properties of one or several formed modified phases combining all the functions of an effective catalyst. 18 refs., 7 figs., 2 tabs

Constraints on superoxide mediated formation of manganese oxides

Directory of Open Access Journals (Sweden)

Deric R. Learman

2013-09-01

Full Text Available Manganese (Mn oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2- (both of biogenic and abiogenic origin as an effective oxidant of Mn(II leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III and Mn(III/IV oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide, a product of the reaction of O2- with Mn(II, inhibits the oxidation process presumably through the reduction of Mn(III. Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III-ligand complexes. While complexing ligands played a role in stabilizing Mn(III, they did not eliminate the inhibition of net Mn(III formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

Phase and structural transformations in annealed copper coatings in relation to oxide whisker growth

Energy Technology Data Exchange (ETDEWEB)

Dorogov, M.V.; Priezzheva, A.N. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Vlassov, S., E-mail: vlassovs@ut.ee [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Kink, I.; Shulga, E. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Dorogin, L.M. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); ITMO University, Kronverkskiy 49, 197101 Saint Petersburg (Russian Federation); Lõhmus, R. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Tyurkov, M.N.; Vikarchuk, A.A. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Romanov, A.E. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); ITMO University, Kronverkskiy 49, 197101 Saint Petersburg (Russian Federation); Ioffe Physical Technical Institute, RAS, Polytechnicheskaya 26, 194021 Saint Petersburg (Russian Federation)

2015-08-15

Highlights: • Coatings prepared by Cu microparticle electrodeposition. • Structural and phase transformation in Cu coatings annealed at 400 °C. • Annealing is accompanied by intensive growth of CuO whiskers. • Layered oxide phases (Cu{sub 2}O and CuO) in the coating are characterized. • Formation of volumetric defects in the coating is demonstrated. - Abstract: We describe structural and phase transformation in copper coatings made of microparticles during heating and annealing in air in the temperature range up to 400 °C. Such thermal treatment is accompanied by intensive CuO nanowhisker growth on the coating surface and the formation of the layered oxide phases (Cu{sub 2}O and CuO) in the coating interior. X-ray diffraction and focused ion beam (FIB) are employed to characterize the multilayer structure of annealed copper coatings. Formation of volumetric defects such as voids and cracks in the coating is demonstrated.

A rhodium(III) complex inhibits LPS-induced nitric oxide production and angiogenic activity in cellulo.

Science.gov (United States)

Liu, Li-Juan; Lin, Sheng; Chan, Daniel Shiu-Hin; Vong, Chi Teng; Hoi, Pui Man; Wong, Chun-Yuen; Ma, Dik-Lung; Leung, Chung-Hang

2014-11-01

Metal-containing complexes have arisen as viable alternatives to organic molecules as therapeutic agents. Metal complexes possess a number of advantages compared to conventional carbon-based compounds, such as distinct geometries, interesting electronic properties, variable oxidation states and the ability to arrange different ligands around the metal centre in a precise fashion. Meanwhile, nitric oxide (NO) plays key roles in the regulation of angiogenesis, vascular permeability and inflammation. We herein report a novel cyclometalated rhodium(III) complex as an inhibitor of lipopolysaccharides (LPS)-induced NO production in RAW264.7 macrophages. Experiments suggested that the inhibition of NO production in cells by complex 1 was mediated through the down-regulation of nuclear factor-κB (NF-κB) activity. Furthermore, complex 1 inhibited angiogenesis in human umbilical vein endothelial cells (HUVECs) as revealed by an endothelial tube formation assay. This study demonstrates that kinetically inert rhodium(III) complexes may be potentially developed as effective anti-angiogenic agents. Copyright © 2014 Elsevier Inc. All rights reserved.

Formation of high oxide ion conductive phases in the sintered oxides of the system Bi2O3-Ln2O3 (Ln = La-Yb)

International Nuclear Information System (INIS)

Iwahara, H.; Esaka, T.; Sato, T.; Takahashi, T.

1981-01-01

The electrical conduction in various phases of the system Bi 2 O 3 -Ln 2 O 3 (Ln = La, Nd, Sm, Dy, Er, or Yb) was investigated by measuring ac conductivity and the emf of the oxygen gas concentration cell. High-oxide-ion conduction was observed in the rhombohedral and face-centered cubic (fcc) phase in these systems. The fcc phase could be stabilized over a wide range of temperature by adding a certain amount of Ln 2 O 3 . In these cases, the larger the atomic number of Ln, the lower the content of Ln 2 O 3 required to form the fcc solid solution, except in the case of Yb 2 O 3 . The oxide ion conductivity of this phase decreased with increasing content of Ln 2 O 3 . Maximum conductivity was obtained at the lower limit of the fcc solid solution formation range in each system, which was more than one order of magnitude higher than those of conventional stabilized zirconias. Lattice parameters of the fcc phase were calculated from the x-ray diffraction patterns. The relationship between the oxide ion conductivity and the lattice parameter was also discussed

Effect of beta phase composition and surface machining on the oxidation behavior of Zr-2.5Nb pressure tube material

International Nuclear Information System (INIS)

Nouduru, S.K.; Kiran Kumar, M.; Kain, V.; Khanna, A.S.

2015-01-01

Zr-2.5Nb is commonly used as the pressure tube material in pressurized heavy water reactors. it is also the pressure tube material for Advanced Heavy Water Reactor (AHWR) being developed indigenously in India with light water as coolant and water chemistry similar to Boiling Water Reactors (BWR). Oxidation of the pressure tube depends on various factors like material composition, microstructure, fabrication route, and water chemistry. In the present research, the role of the composition and morphology of second phase β on the high temperature and pressure oxidation behavior of Zr-2.5Nb pressure tube material in steam was systematically studied. The as-received pressure tube material (fabricated through cold worked and stress relieved, CWSR route) was subjected to selective heat treatments to generate microstructures containing predominantly β(Zr) (∼ 20% Nb) and β(Nb) (∼ 80% Nb) phases. The presence of such phases was characterized by X-ray diffraction and transmission electron microscopy-energy dispersive spectroscopy. Subsequently both the heat treated materials were subjected to surface machining. The Zr-2.5Nb material in different microstructural conditions was subjected to accelerated oxidation exposures in steam at 400 C. degrees, and 10 MPa pressure up to 30 days. Raman spectroscopy was carried out on the oxide surfaces to observe the variation in tetragonal versus monoclinic phase fractions with oxidation duration. The microstructure consisting of predominantly β(Nb) showed a relatively improved oxidation resistance as compared to the one with predominantly β(Zr). The tetragonal phase fraction in the oxide film decreased with oxidation time in all microstructural conditions and was found to be the least in the microstructure containing β(Zr) after 10 days of exposures. The explanation for the observed higher oxidation resistance of β(Nb) microstructure lies in the context of depleted matrix Nb content in the case of β(Nb). Surface machining

Heterogeneous inhibition of the liquid phase oxidation of hydrocarbons by molybdenum compounds

Energy Technology Data Exchange (ETDEWEB)

Tavadyan, L.A.; Karapetyan, A.P.; Madatovyan, V.M.

1988-05-01

The heterogeneous action of molybdenum compounds: MoB, MoSe/sub 2/, MoSi/sub 2/, Mo/sub 2/C, MoO/sub 3/, Mo on the oxidation of n-decane, ethylbenzene, and nonene-1 has been investigated. A parameter representing the inhibiting effect of the heterogeneous catalyst was calculated theoretically. It was found that NoB, MoSe/sub 2/, and MoSi/sub 2/ inhibited the oxidation of n-decane at 408 K while the remaining heterogeneous contacts catalyzed it. A critical phenomenon was detected in the inhibition by MoSi/sub 2/. All the molybdenum compounds investigated inhibited the oxidation of ethylbenzene at 393 K owing to the formation of phenol by catalytic decomposition of the hydroperoxide. The liquid phase oxidation autoinhibited by phenol is described theoretically.

Zirconium oxide crystal phase: The role of the pH and time to attain the final pH for precipitation of the hydrous oxide

International Nuclear Information System (INIS)

Srinivasan, R.; Harris, M.B.; Simpson, S.F.; De Angelis, R.J.; Davis, B.H.

1988-01-01

Precipitated hydrous zirconium oxide can be calcined to produce either a monoclinic or tetragonal product. It has been observed that the time taken to attain the final pH of the solution in contact with the precipitate plays a dominant role in determining the crystal structure of the zirconium oxide after calcination at 500 0 C. The dependence of crystal structure on the rate of precipitation is observed only in the pH range 7--11. Rapid precipitation in this pH range yields predominately monoclinic zirconia, whereas slow (8 h) precipitation produces the tetragonal phase. At pH of approximately 13.0, only the tetragonal phase is formed from both slowly and rapidly precipitated hydrous oxide. The present results, together with earlier results, show that both the pH of the supernatant liquid and the time taken to attain this pH play dominant roles in determining the crystal structure of zirconia that is formed after calcination of the hydrous oxide. The factors that determine the crystal phase are therefore imparted in a mechanism of precipitation that depends upon the pH, and it is inferred that it is the hydroxyl concentration that is the dominant factor

Investigation of the effects of phase transformations in micro and nano aluminum powders on kinetics of oxidation using thermogravimetric analysis.

Science.gov (United States)

Saceleanu, Florin; Atashin, Sanam; Wen, John Z

2017-07-26

Aluminum micro and nanoparticles are key ingredients in the synthesis of nano energetic materials. Hence it is important to characterize the kinetics and the rate controlling process of their oxidation. The literature shows that the mass diffusion and phase transformation within the aluminum oxide shell are important. However, the description of physical processes regarding simultaneous oxidation and phase transformation is lacking. In this paper, the controlled thermogravimetric (TGA) oxidation of 40-60 nm and 1 µm Al powders is investigated at constant heating rates and under isothermal conditions, respectively, upon varying the partial pressure of oxygen. It is found that the core-shell model of homogenous oxidation is applicable to explain the TGA results when the shell does not undergo phase transformation, which predicts the apparent activation energy in good agreement with the literature data. On the other hand, the simultaneous oxidation and phase transformation is able to be addressed using the JMAK model which reveals key parameters of the rate controlling processes. Mass diffusion is indeed rate determining during the oxidation of Al micro and nanopowders while the kinetics of the reaction is fast. Unlike the micron powders, the particle size distribution has a significant effect on the shape of the oxidation curves of the nanopowders.

Thermal oxidation of cesium loaded Prussian blue as a precaution for exothermic phase change in extreme conditions

International Nuclear Information System (INIS)

Parajuli, Durga; Tanaka, Hisashi; Takahashi, Akira; Kawamoto, Tohru

2013-01-01

Cesium adsorbed Prussian blue is studied for the thermal oxidation. The TG-DTA shows exothermic phase change of micro aggregates of nano-PB at above 270°C. For this reason, Cs loaded PB was heated between 180 to 260°C. Heating at 180 removed only the water. Neither the oxidation of Iron nor the removal of cyanide is observed at this temperature. Oxidation of cyanide is observed upon heating above 200°C while loaded Cs is released after heating at >250°C followed by washing with water. Thermal oxidation between 200 to 220°C for more than 2 h showed control on exothermic phase change and loaded Cs is also not solubilized. (author)

Laboratory Investigation of Complex Conductivity and Magnetic Susceptibility on Natural Iron Oxide Coated Sand

Science.gov (United States)

Wang, C.; Slater, L. D.; Day-Lewis, F. D.; Briggs, M. A.

2017-12-01

Redox reactions occurring at the oxic/anoxic interface where groundwater discharges to surface water commonly result in iron oxide deposition that coats sediment grains. With relatively large total surface area, these iron oxide coated sediments serve as a sink for sorption of dissolved contaminants, although this sink may be temporary if redox conditions fluctuate with varied flow conditions. Characterization of the distribution of iron oxides in streambed sediments could provide valuable understanding of biogeochemical reactions and the ability of a natural system to sorb contaminants. Towards developing a field methodology, we conducted laboratory spectral induced polarization (SIP) and magnetic susceptibility (MS) measurements on natural iron oxide coated sand (Fe-sand) with grain sizes ranging from 0.3 to 2.0 mm in order to assess the sensitivity of these measurements to iron oxides in sediments. The Fe-sand was also sorted by sieving into various grain sizes to study the impact of grain size on the polarization mechanisms. The unsorted Fe-sand saturated with 0.01 S/m NaCl solution exhibited a distinct phase response ( > 4 mrad) in the frequency range from 0.001 to 100 Hz whereas regular silica sand was characterized by a phase response less than 1 mrad under the same conditions. The presence of iron oxide substantially increased MS (3.08×10-3 SI) over that of regular sand ( Laboratory results demonstrated that SIP and MS may be well suited to mapping the distribution of iron oxides in streambed sediments associated with anoxic groundwater discharge.

Oxygen incorporation into GST phase-change memory matrix

Energy Technology Data Exchange (ETDEWEB)

Golovchak, R., E-mail: holovchakr@apsu.edu [Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN 37044 (United States); Choi, Y.G. [Department of Materials Science and Engineering, Korea Aerospace University, Gyeonggi 412-791 (Korea, Republic of); Kozyukhin, S. [Kurnakov Institute of General and Inorganic Chemistry of RAS, 31 Leninsky Pr., Moscow 119991 (Russian Federation); National Research Tomsk State University, 36 Lenin Pr., Tomsk 634050 (Russian Federation); Chigirinsky, Yu. [Scientific-Research Physicotechnical Institute at the Nizhnii Novgorod State University, Nizhnii Novgorod 603600 (Russian Federation); Kovalskiy, A.; Xiong-Skiba, P.; Trimble, J. [Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN 37044 (United States); Pafchek, R.; Jain, H. [Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States)

2015-03-30

Graphical abstract: - Highlights: • Surfaces of GST-225 films are depleted in Te as a result of the reaction with oxygen. • Top layers of oxidized GST-225 are formed by Sb and Ge oxide complexes. • Depth profiles of Sb and Ge oxide complexes are found to be different. • Crystallization at 300 °C in O{sub 2} atmosphere leads to Ge redistribution. - Abstract: Structural changes in amorphous and crystallized GST-225 films induced by the reaction with oxygen are studied at different depth scales. The mechanism of interaction of the very top surface layers with oxygen is studied with low-energy ion scattering (LEIS) technique, while the modifications of chemistry in the underlying surface layers are investigated with high-resolution X-ray photoelectron spectroscopy (XPS). The changes averaged through the overall film thickness are characterized by micro-Raman spectroscopy. The oxygen exposure leads to a depletion of GST-225 film surfaces in Te and formation of the antimony and germanium oxides. The antimony oxide complexes are found throughout the whole thickness of the films after their prolonged storage in air, whereas no evidence for formation of pure GeO{sub 2} phase is found in the volume of the films through Raman spectroscopy. A tendency to form Ge-rich phase within the ∼10 nm surface layer is additionally observed by LEIS profiling during crystallization of GST-225 film at 300 °C in oxygen atmosphere.

The calculation of phase equilibria of oxide core-concrete systems

International Nuclear Information System (INIS)

Ball, R.G.J.; Mignanelli, M.A.; Barry, T.I.; Gisby, J.A.

1993-01-01

Thermodynamic models have been developed to describe the phase equilibria of oxide solutions appropriate for the understanding of the chemical interactions between nuclear reactor core debris and concrete. For this purpose, the Gibbs energy of the liquid phase is described by the inclusion of associate species and nonideal interactions between the components and associate species. Assessments of the thermodynamic and phase equilibrium data for the subsystems of the CaO-Al 2 O 3 -SiO 2 -UO 2 -ZrO 2 system have been used to obtain a thermodynamic description of the crystalline and liquid phases in good agreement with published data. The data for the subsystems have then been combined, using well established principles, to predict the phase relationships in the ternary and quaternary sytsems and in the overall quinary system. The results show that he overall system cannot properly be treated as a pseudo-ideal liquid and solid solution, as used in some computer codes which attempt to model the physics and chemistry of core-concrete interactions. The limitations of the current model are discussed. (orig.)

In situ growth of capping-free magnetic iron oxide nanoparticles on liquid-phase exfoliated graphene

NARCIS (Netherlands)

Tsoufis, T.; Syrgiannis, Z.; Akhtar, N.; Prato, M.; Katsaros, F.; Sideratou, Z.; Kouloumpis, A.; Gournis, D.; Rudolf, P.

2015-01-01

We report a facile approach for the in situ synthesis of very small iron oxide nanoparticles on the surface of high-quality graphene sheets. Our synthetic strategy involved the direct, liquid-phase exfoliation of highly crystalline graphite (avoiding any oxidation treatment) and the subsequent

Complexation of Phenol and Thiophenol by Amine N-Oxides: Isothermal Titration Caloritmetry and ab Initio Calculations

NARCIS (Netherlands)

Cuypers, R.; Sukumaran, M.; Marcelis, A.T.M.; Sudhölter, E.J.R.; Zuilhof, H.

2010-01-01

To develop a new solvent-impregnated resin (SIR) system for removal of phenols from water the complex formation of dimethyldodecylamine. N-oxide (DMDAO), trioctylamine N-oxide (TOAO), and tris(2-ethylhexyl)amine N-oxide (TEHAO) with phenol (PhOH) and thiophenol (PhSH) is studied To this end we use

Influence of bidentate structure of an aryl phosphine oxide ligand on photophysical properties of its Eu~Ⅲ complex

Institute of Scientific and Technical Information of China (English)

许辉; 魏莹; 赵保敏; 黄维

2010-01-01

The bidentate phosphine oxide ligand 1,8-bis(diphenylphosphino) naphthalene oxide (NAPO) and its EuⅢ complex 1 Eu(TTA)3(NAPO) (TTA=2-thenoyltrifluoroacetonate) were chosen to study the effect of bidentate phosphine oxide ligand on the photophysical properties of the corresponding complex. The intramolecular energy transfer processes of 1 were studied. The investigation showed that with bidentate structure NAPO could suppress solvent-induced quenching by enforcing the ligand-ligand interaction and the rigidi...

Zinc oxide crystal whiskers as a novel sorbent for solid-phase extraction of flavonoids.

Science.gov (United States)

Wang, Licheng; Shangguan, Yangnan; Hou, Xiudan; Jia, Yong; Liu, Shujuan; Sun, Yingxin; Guo, Yong

2017-08-15

As a novel solid-phase extraction material, zinc oxide crystal whiskers were used to extract flavonoid compounds and showed good extraction abilities. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and surface area/pore volume characterized the sorbent. The zinc oxide was packed into a solid-phase extraction micro-column and its extraction ability was evaluated by four model flavonoid compounds. The sample loading and elution parameters were optimized and the zinc oxide based analytical method for flavonoids was established. It showed that the method has wide linearities from 1 to 150μg/L and low limits of detection at 0.25μg/L. The relative standard deviations of a single column repeatability and column to column reproducibility were less than 6.8% and 10.6%. Several real samples were analyzed by the established method and satisfactory results were obtained. The interactions between flavonoids and zinc oxide were calculated and proved to be from the Van der Waals' forces between the 4p and 5d orbitals from zinc atom and the neighboring π orbitals from flavonoid phenyl groups. Moreover, the zinc oxide crystal whiskers showed good stability and could be reused more than 50 times under the operation conditions. This work proves that the zinc oxide crystal whiskers are a good candidate for flavonoids enrichment. Copyright © 2017. Published by Elsevier B.V.

Novel synthesis of manganese and vanadium mixed oxide (V2O5/OMS-2) as an efficient and selective catalyst for the oxidation of alcohols in liquid phase

International Nuclear Information System (INIS)

Mahdavi, Vahid; Soleimani, Shima

2014-01-01

Graphical abstract: Oxidation of various alcohols is studied in the liquid phase over new composite mixed oxide (V 2 O 5 /OMS-2) catalyst using tert-butyl hydroperoxide (TBHP). The activity of V 2 O 5 /OMS-2 samples was considerably increased with respect to OMS-2 catalyst and these samples are found to be suitable for the selective oxidation of alcohols. - Highlights: • V 2 O 5 /K-OMS-2 with different V/Mn molar ratios prepared by the impregnation method. • Oxidation of alcohols was studied in the liquid phase over V 2 O 5 /K-OMS-2 catalyst. • V 2 O 5 /K-OMS-2 catalyst had excellent activity for alcohol oxidation. • Benzyl alcohol oxidation using excess TBHP followed a pseudo-first order kinetic. • The selected catalyst was reused without significant loss of activity. - Abstract: This work reports the synthesis and characterization of mixed oxide vanadium–manganese V 2 O 5 /K-OMS-2 at various V/Mn molar ratios and prepared by the impregnation method. Characterization of these new composite materials was made by elemental analysis, BET, XRD, FT-IR, SEM and TEM techniques. Results of these analyses showed that vanadium impregnated samples contained mixed phases of cryptomelane and crystalline V 2 O 5 species. Oxidation of various alcohols was studied in the liquid phase over the V 2 O 5 /K-OMS-2 catalyst using tert-butyl hydroperoxide (TBHP) and H 2 O 2 as the oxidant. Activity of the V 2 O 5 /K-OMS-2 samples was increased considerably with respect to K-OMS-2 catalyst due to the interaction of manganese oxide and V 2 O 5 . The kinetic of benzyl alcohol oxidation using excess TBHP over V 2 O 5 /K-OMS-2 catalyst was investigated at different temperatures and a pseudo-first order reaction was determined with respect to benzyl alcohol. The effects of reaction time, oxidant/alcohol molar ratio, reaction temperature, solvents, catalyst recycling potential and leaching were investigated

Phase identification and internal stress analysis of steamside oxides on superheater tubes by means of X-ray diffraction

DEFF Research Database (Denmark)

Pantleon, Karen; Montgomery, Melanie

Steamside oxides formed on plant exposed superheated tubes were investigated using X-ray diffraction. Phase identification and stress analysis revealed that on ferritic X20CrMoV12-1 pure Hematite and pure Magnetite formed and both phases are under tensile stress. IN contrast, on austenitic TP347H...... Mn-, Cr- and/or Ni-containing oxides are observed, instead of pure Magnetite, underneath a pure Hematite surface layer. Oxides on the austenitic steel are under compressive stress or even stress-free....

Solid-phase synthesis of complex and pharmacologically interesting heterocycles

DEFF Research Database (Denmark)

Nielsen, Thomas Eiland

2009-01-01

Efficient routes for the creation of heterocycles continue to be one of the primary goals for solid-phase synthesis. Recent advances in this field rely most notably on transition-metal-catalysis and N-acyliminium chemistry to mediate a range of cyclization processes for the generation of compounds...... with significant structural complexity and diversity. This review describes some of the most systematic solid-phase approaches that are potentially suited for pharmaceutical applications, that is, the methods described are useful for the synthesis of compound collections, and exhibit tunable stereochemistry...

The single-phase multiferroic oxides: from bulk to thin film

International Nuclear Information System (INIS)

Prellier, W; Singh, M P; Murugavel, P

2005-01-01

Complex perovskite oxides exhibit a rich spectrum of properties, including magnetism, ferroelectricity, strongly correlated electron behaviour, superconductivity and magnetoresistance, which have been research areas of great interest among the scientific and technological community for decades. There exist very few materials which exhibit multiple functional properties; one such class of materials is called the multiferroics. Multiferroics are interesting because they exhibit simultaneously ferromagnetic and ferroelectric polarizations and a coupling between them. Due to the nontrivial lattice coupling between the magnetic and electronic domains (the magnetoelectric effect), the magnetic polarization can be switched by applying an electric field; likewise the ferroelectric polarization can be switched by applying a magnetic field. As a consequence, multiferroics offer rich physics and novel devices concepts, which have recently become of great interest to researchers. In this review article the recent experimental status, for both the bulk single phase and the thin film form, has been presented. Current studies on the ceramic compounds in the bulk form including Bi(Fe,Mn)O 3 , REMnO 3 and the series of REMn 2 O 5 single crystals (RE = rare earth) are discussed in the first section and a detailed overview on multiferroic thin films grown artificially (multilayers and nanocomposites) is presented in the second section. (topical review)

Extraction complexes of Pu(IV) with carbamoylmethylphosphine oxide ligands. A relativistic density functional study

International Nuclear Information System (INIS)

Wang, Cong-Zhi; Lan, Jian-Hui; Feng, Yi-Xiao; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun; Wei, Yue-Zhou

2014-01-01

The extraction complexes of Pu(IV) with n-octyl(phenyl)-N,N-diisobutyl-methylcarbamoyl phosphine oxide (CMPO) and diphenyl-N,N-diisobutyl carbamoyl phosphine oxide (Ph 2 CMPO) have been studied by using density functional theory (DFT) combined with relativistic small-core pseudopotentials. For most complexes, the CMPO and Ph 2 CMPO molecules are coordinated as bidentate chelating ligands through the carbonyl oxygen and phosphoric oxygen atoms. The metal-ligand bonding is mainly ionic for all of these complexes. The neutral PuL(NO 3 ) 4 and PuL 2 (NO 3 ) 4 complexes are predicted to be the most thermodynamically stable molecules according to the metal-ligand complexation reactions. In addition, hydration energies may also play a significant role in the extractability of CMPO and Ph 2 CMPO for the plutonium cations. In most cases, the complexes with CMPO possess qualitatively similar geometries and electron structures to those with Ph 2 CMPO, and they also have comparable metal-ligand binding energies. Thus, replacement of alkyl groups by phenyl groups at the phosphorus atom of CMPO seems to have no obvious influence on the extraction of Pu(IV). (orig.)

Oxidation of ammonium sulfite by a multi-needle-to-plate gas phase pulsed corona discharge reactor

Science.gov (United States)

Ren, Hua; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-03-01

The oxidation of ammonium sulfite in the ammonia-based flue gas desulfurization (FGD) process was investigated in a multi-needle-to-plate gas phase pulsed corona discharge reactor in this paper. The effect of several parameters, including capacitance and peak pulse voltage of discharge system, electrode gap and bubbling gas flow rate on the oxidation rate of ammonium sulfite was reviewed. The oxidation rate of ammonium sulfite could reach 47.2% at the capacitance, the peak pulse voltage, electrode gap and bubbling gas flow rate equal to 2 nF, -24.6 k V, 35 mm and 4 L min-1 within treatment time of 40 min The experimental results indicate that the gas phase pulsed discharge system with a multi-needle-to-plate electrode can oxide the ammonium sulfite. The oxidation rate increased with the applied capacitance and peak pulse voltage and decreased with the electrode gap. As the bubbling gas flow rate increased, the oxidation rate increased first and then tended to reach a stationary value. These results would be important for the process optimization of the (NH4)2SO3 to (NH4)2SO4 oxidation.

Assessment of antibacterial and cytotoxic effects of orthodontic stainless steel brackets coated with different phases of titanium oxide: An in-vitro study.

Science.gov (United States)

Baby, Roshen Daniel; Subramaniam, Siva; Arumugam, Ilakkiya; Padmanabhan, Sridevi

2017-04-01

Our objective was to assess the antibacterial and cytotoxic effects of orthodontic stainless steel brackets coated with different phases of photocatalytic titanium oxide. From a total sample of 115 brackets, 68 orthodontic stainless steel brackets were coated with titanium oxide using a radiofrequency magnetron sputtering machine. The coated brackets were then converted into 34 each of the anatase and rutile phases of titanium oxide. These brackets were subdivided into 4 groups for antibacterial study and 3 groups for cytotoxicity study. Brackets for the antibacterial study were assessed against the Streptococcus mutans species using microbiologic tests. Three groups for the cytotoxicity study were assessed using the thiazolyl tetrazolium bromide assay. The antibacterial study showed that both phases were effective, but the rutile phase of photocatalytic titanium oxide had a greater bactericidal effect than did the anatase phase. The cytotoxicity study showed that the rutile phase had a greater decrease in viability of cells compared with the anatase phase. It is recommended that orthodontic brackets be coated with the anatase phase of titanium oxide since they exhibited a significant antibacterial property and were only slightly cytotoxic. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Preparation of yttrium iron garnet (YIG) by modified domestic iron oxide

International Nuclear Information System (INIS)

Mozaffari, M.; Amighian

2002-01-01

Iron oxide by product of a local steel complex was modified to use for preparation of Yttrium iron garnet (YIG). The improvement was necessary to reduce impurities, especially the Si0 2 and Cl contents, which have deteriorative effects on magnetic properties and equipment used for preparation of the samples. The modified iron oxide was then mixed with Yttrium oxide of Merck Company in appropriate proportion to obtain a stoichiometric single phase YIG, using the conventional ceramic technique. XRD and SEM equipments were used to identify the resulting phases and microstructure respectively. Magnetic parameters were measured by VSM. Curie temperature of the samples was obtained by DTG (M) method. The results were compared with those obtained from samples that made by Merck iron oxide. There are small differences between the results. This was discussed according to extra pores and minute secondary phase in the samples made by domestic iron oxide. (Author)

Enlightening intracellular complexity of living cells with quantitative phase microscopy

Science.gov (United States)

Martinez Torres, C.; Laperrousaz, B.; Berguiga, L.; Boyer Provera, E.; Elezgaray, J.; Nicolini, F. E.; Maguer-Satta, V.; Arneodo, A.; Argoul, F.

2016-03-01

The internal distribution of refractive indices (RIs) of a living cell is much more complex than usually admitted in multi-shell models. The reconstruction of RI maps from single phase images has rarely been achieved for several reasons: (i) we still have very little knowledge of the impact of internal macromolecular complexes on the local RI and (ii) phase changes produced by light propagation through the sample are mixed with diffraction effects by internal cell bodies. We propose the implementation a 2D wavelet-based contour chain detection method to distinguish internal boundaries thanks to their greatest optical path difference gradients. These contour chains correspond to the highest image phase contrast and follow the local RI inhomogeneities linked to the intracellular structural intricacy. Their statistics and spatial distribution are morphological indicators for distinguishing cells of different origins and to follow their transformation in pathologic situations. We use this method to compare non adherent blood cells from primary and laboratory culture origins, in healthy and pathological situations (chronic myelogenous leukaemia). In a second part of this presentation, we concentrate on the temporal dynamics of the phase contour chains and we discuss the spectral decomposition of their dynamics in both health and disease.

Gas-Phase Oxidation of Aqueous Ethanol by Nanoparticle Vanadia/Anatase Catalysts

DEFF Research Database (Denmark)

Jørgensen, Betina; Kristensen, Steffen Buus; Kunov-Kruse, Andreas Jonas

2009-01-01

The gas-phase oxidation of aqueous ethanol with dioxygen has been examined with a new nanoparticle V2O5/TiO2 catalyst. Product selectivity could to a large extent be controlled by small alterations of reaction parameters, allowing production of acetaldehyde at a selectivity higher than 90%, near...

Phase identification and internal stress analysis of steamside oxides on superheater tubes by means of X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Pantleon, Karen; Montgomery, Melanie [Technical Univ. of Denmark, Lyngby (Denmark). Inst. of Manufacturing Engineering and Management

2005-05-01

For superheater tubes, the adherence of the inner steamside oxide is especially important as spallation of this oxide results in a) blockage of loops which cause insufficient steam flow through the superheaters and subsequently overheating and tube failure and b) spalled oxide can cause erosion of turbine blades. Oxide spallation is a serious problem for austenitic steels where the significant differences of the thermal expansion coefficients of steel and oxide cause relatively high thermal stresses. Usually, various oxides layered within the scale are suggested from microscopical observations of the morphology and/or topography of the oxide scale accompanied by the analysis of chemical elements present. Reports about the application of X-ray diffraction on the study of steamside oxide formation are very scarce in literature. If applied at all, XRD-studies are restricted to ideally flat samples oxidized under laboratory conditions, but relation to real operating conditions and the effect of the real sample geometry is missing. Within the frame of the project, steamside oxides on plant exposed components of ferritic/ martensitic X20CrMoV12-1 as well as fine- and coarse-grained austenitic TP347H were studied by means of X-ray diffraction. Depth dependent phase analysis on sample segments cut from the tubes was carried out by means of grazing incidence diffraction and, in order to obtain information from a larger depth, conventional XRD was combination with stepwise mechanical removal of the steamside oxides. After each removal step phase analysis was performed both on the segments and on the removed powders. Phase specific stress analysis was carried out on rings cut from the tube. Results show that steamside oxides on X20CrMoV12-1 consist of pure Hematite at the surface followed by a relatively thick layer of pure Magnetite. Both phases are under relatively high tensile stresses. While the phase composition of the Hematite layer appears to be the same for all

Physicochemical study of properties of complex oxides of the system Li2O-MoO3-SnO2

International Nuclear Information System (INIS)

Safonov, V.V.; Chaban, N.G.; Kuz'mina, N.P.; Vashman, A.A.; Petrov, K.I.

1990-01-01

By the method of differential thermal analysis using X-ray phase analysis in the Li 2 O-MoO 3 -SnO 2 system (Li 2 Sn(MoO 4 ) 3 -Sn(MoO 4 ) 2 cross section) formation of a new complex of the composition Li 2 Sn 3 (MoO 4 ) 7 incongruently melting at 480 deg C is ascertained. IR, Raman and NMR spectra of Li 4 SnMo 2 O 10 , Li 2 Sn(MoO 4 ) 3 and Li 2 Sn 3 (MoO 4 ) 7 complex oxides are presented. According to 7 Li NMR spectra of Li 4 SnMo 2 O 10 , Li 2 Sn(MoO 4 ) 3 and Li 2 Sn 3 (MoO 4 ) 7 complex are presented. According to 7 Li NMR spectra the value of the lithium diffusion increases in the series Li 4 SnMo 2 O 10 →Li 2 Sn(MoO 4 ) 3 →Li 2 Sn 3 (MoO 4 ) 7

Gas-phase advanced oxidation for effective, efficient in situ control of pollution

DEFF Research Database (Denmark)

Johnson, Matthew Stanley; Nilsson, Elna Johanna Kristina; Svensson, Erik Anders

2014-01-01

In this article, gas-phase advanced oxidation, a new method for pollution control building on the photo-oxidation and particle formation chemistry occurring in the atmosphere, is introduced and characterized. The process uses ozone and UV-C light to produce in situ radicals to oxidize pollution......, generating particles that are removed by a filter; ozone is removed using a MnO2 honeycomb catalyst. This combination of in situ processes removes a wide range of pollutants with a comparatively low specific energy input. Two proof-of-concept devices were built to test and optimize the process...... particulate mass. Secondary pollution including formaldehyde and ultrafine particles might be generated, depending on the composition of the primary pollution....

Bio-inspired iron and manganese complexes derived from mixed N,O ligands for the oxidation of olefins

NARCIS (Netherlands)

Moelands, M.A.H.

2014-01-01

This Thesis describes the synthesis and structural analysis of bio-inspired iron and manganese complexes used for the catalytic oxidation of olefin substrates. The development of catalytic systems for oxidation chemistry that are based on first row transition metals and that apply a green oxidant

Ionic Mobility and Phase Transitions in Perovskite Oxides for Energy Application

Directory of Open Access Journals (Sweden)

Francesco Cordero

2017-02-01

Full Text Available Perovskite oxides find applications or are studied in many fields related to energy production, accumulation and saving. The most obvious application is oxygen or proton conductors in fuel cells (SOFCs, but the (antiferroelectric compositions may find application in high energy capacitors for energy storage, efficient electrocaloric cooling, and electromechanical energy harvesting. In SOFCs, the diffusion of O vacancies and other mobile ionic species, such as H+, are at the base of the functioning of the device, while in the other cases they constitute unwanted defects that reduce the performance and life-time of the device. Similarly, the (antiferroelectric phase transitions are a requisite for the use of some types of devices, but the accompanying domain walls can generate extended defects detrimental to the life of the material, and structural phase transformations should be avoided in SOFCs. All these phenomena can be studied by mechanical spectroscopy, the measurement of the complex elastic compliance as a function of temperature and frequency, which is the mechanical analogue of the dielectric susceptibility, but probes the elastic response and elastic dipoles instead of the dielectric response and electric dipoles. The two techniques can be combined to provide a comprehensive picture of the material properties. Examples are shown of the study of structural transitions and hopping and tunnelling processes of O vacancies and H in the ion conductor BaCe1-xYxO3-x and in SrTiO3-x, and of the aging and fatigue effects found in PZT at compositions where the ferro- and antiferroelectric states coexist.

Toluidine blue-sodium lauryl ether sulfate complexes : Influence of ethylene oxide length

NARCIS (Netherlands)

Vleugels, L.F.W.; Féat, A.; Voets, I.K.; Tuinier, R.

2017-01-01

Sodium Lauryl Ether Sulfates (SLES) are an increasingly important and versatile type of surfactants. The complexation between ortho-Toluidine blue (TBO) and a homologous series of SLES, including Sodium Lauryl Sulfate (SDS) without Ethylene Oxide (EO), has been investigated using visible

US-UK Phase 3 Task 1 Oxidation in Supercritical Fluids

Energy Technology Data Exchange (ETDEWEB)

Holcomb, Gordon R. [National Energy Technology Lab. (NETL), Albany, OR (United States)

2017-03-20

A presentation of the US-UK Phase 3 Task 1 Oxidation in Supercritical Fluids. Includes slides on Supercritical Steam, sCO₂ Power Cycles – Indirect, sCO₂ Power Cycles – Direct, Experimental Exposures, Alloys, Why Si, Results—Ni-xCr Alloys (5-24Cr), Fatigue Crack Growth$-$Experiment, and Alloys and Samples, Fatigue Crack Growth—Results (H282).

Catalytic water oxidation by ruthenium(II) quaterpyridine (qpy) complexes: evidence for ruthenium(III) qpy-N,N'''-dioxide as the real catalysts.

Science.gov (United States)

Liu, Yingying; Ng, Siu-Mui; Yiu, Shek-Man; Lam, William W Y; Wei, Xi-Guang; Lau, Kai-Chung; Lau, Tai-Chu

2014-12-22

Polypyridyl and related ligands have been widely used for the development of water oxidation catalysts. Supposedly these ligands are oxidation-resistant and can stabilize high-oxidation-state intermediates. In this work a series of ruthenium(II) complexes [Ru(qpy)(L)2 ](2+) (qpy=2,2':6',2'':6'',2'''-quaterpyridine; L=substituted pyridine) have been synthesized and found to catalyze Ce(IV) -driven water oxidation, with turnover numbers of up to 2100. However, these ruthenium complexes are found to function only as precatalysts; first, they have to be oxidized to the qpy-N,N'''-dioxide (ONNO) complexes [Ru(ONNO)(L)2 ](3+) which are the real catalysts for water oxidation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoscale Phase Stability Reversal During the Nucleation and Growth of Titanium Oxide Minerals

Science.gov (United States)

Hummmer, D. R.; Heaney, P. J.; Kubicki, J. D.; Kent, P. R.; Post, J. E.

2008-12-01

Fine-grained titanium oxide minerals are important in soils, where they affect a variety of geochemical processes. They are also industrially important as catalysts, pigments, food additives, and dielectrics. Recent research has indicated an apparent reversal of thermodynamic stability between TiO2 phases at the nanoscale thought to be caused by an increased contribution of surface energy to the total free energy. Time-resolved X-ray diffraction (XRD) experiments in which titanium oxides crystallize from aqueous TiCl4 solutions confirm that anatase, a metastable phase, is always the first phase to nucleate under our range of initial conditions. Rutile peaks are observed only minutes after the first appearance of anatase, after which anatase abundance slowly decreases while rutile continues to form. Whole pattern refinement of diffraction data reveals that lattice constants of both phases increase throughout the crystallization process. In addition, transmission electron microscope (TEM) observations and kinetic modeling indicate that anatase does not undergo a solid-state transformation to the rutile structure as once thought. Instead, anatase appears to re-dissolve and then feed the growth of already nucleated rutile nanocrystals. Density functional theory (DFT) calculations were employed to model 1, 2, and 3 nm particles of both mineral phases. The total surface energies calculated from these models did yield lower values for anatase than for rutile by 8-13 kJ/mol depending on particle size, indicating that surface free energy is sufficient to account for stability reversal. However, these whole-particle surface energies were much higher than the sum of energies of each particle's constituent crystallographic surfaces. We attribute the excess energy to defects associated with the edges and corners of nanoparticles, which are not present on a 2-D periodic surface. This previously unreported edge and corner energy may play a dominant role in the stability reversal

Heterogeneous catalysis in the liquid-phase oxidation of olefins--3. The activity of supported vanadium-chromium binary oxide catalyst for the oxidation of cyclohexene

Energy Technology Data Exchange (ETDEWEB)

Takehira, K; Hayakawa, T; Ishikawa, T

1979-03-01

The activity of supported vanadium-chromium binary oxide catalyst for the oxidation of cyclohexene to 1-cyclohexenyl hydroperoxide, 2-cyclohexene-1-one, 2-cyclohexene-1-ol, and cyclohexene oxide was due to the interaction between the metal oxides and the carriers. The oxidation reaction was carried out in benzene at 60/sup 0/C for four hours with the binary oxide supported on (GAMMA)-alumina or silica; three series of catalysts were prepared by combining the vanadium and chromium oxide components with alumina hydrate or silica sol by a kneading method. The silica-supported catalysts had the greatest activity, the highest being the V/sub 2/O/sub 5//SiO/sub 2/ system, which lost its activity quickly during the reaction. This was followed in activity by the Cr/sub 2/O/sub 3//SiO/sub 2/ system, containing the chromium(V) species. The Cr/sub 2/O/sub 3//Al/sub 2/O/sub 3/ system also had high activity and the chromium(V) species. The vanadium and chromium metal ions are probably coordinated tetrahedrally on the support, and these complexes catalyze cyclohexene autoxidation by decomposing 1-cyclohexenyl hydroperoxide.

Rare earth [beta]-diketonate and carboxylate metal complexes as precursors for MOCVD of oxide films

Energy Technology Data Exchange (ETDEWEB)

Kuzmina, N.P. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Martynenko, L.I. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Tu, Z.A. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Kaul, A.R. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Girichev, G.V. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Giricheva, N.I. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Rykov, A.N. (Dept. of Chemistry, Moscow State Univ. (Russian Federation)); Korenev, Y.M. (Dept. of Chemistry, Moscow State Univ. (Russian Federation))

1993-08-01

Volatile and thermostable complexes of lanthanide acetylacetonates and pivalates were obtained and investigated by different methods. These compounds were used for lanthanide oxide containing film producing and for fabrication of silica optical fibers doped by lanthanide oxide. The properties of these and already known volatile precursors are compared. (orig.).

Rare earth β-diketonate and carboxylate metal complexes as precursors for MOCVD of oxide films

International Nuclear Information System (INIS)

Kuzmina, N.P.; Martynenko, L.I.; Tu, Z.A.; Kaul, A.R.; Girichev, G.V.; Giricheva, N.I.; Rykov, A.N.; Korenev, Y.M.

1993-01-01

Volatile and thermostable complexes of lanthanide acetylacetonates and pivalates were obtained and investigated by different methods. These compounds were used for lanthanide oxide containing film producing and for fabrication of silica optical fibers doped by lanthanide oxide. The properties of these and already known volatile precursors are compared. (orig.)

Factors affecting radium removal using mixed iron-manganese oxides

International Nuclear Information System (INIS)

Mott, H.V. Singh, S.; Kondapally, V.R.

1993-01-01

Batch experiments confirmed that sorption of radium by a mixed iron-manganese oxide solid phase shows promise for treating radium-contaminated water. The capacities of these mixed oxides for sorption of radium depend on the composition of the solid phase, the pH of the aqueous solution, and the presence of competing cations. The removal of the oxide-radium complexes from aqueous suspension by manganese greensand filtration was also investigated. It was found that influent radium concentrations of 100 pCi/L were reduced to 2--9 pCi/L by this process. Additional study of the fate of radium in manganese greensand filters is recommended before this procedure is used for drinking water treatment

Factors affecting radium removal using mixed iron-manganese oxides

Energy Technology Data Exchange (ETDEWEB)

Mott, H.V. Singh, S.; Kondapally, V.R. (South Dakota School of Mines and Technology, Rapid City, SD (United States))

1993-10-01

Batch experiments confirmed that sorption of radium by a mixed iron-manganese oxide solid phase shows promise for treating radium-contaminated water. The capacities of these mixed oxides for sorption of radium depend on the composition of the solid phase, the pH of the aqueous solution, and the presence of competing cations. The removal of the oxide-radium complexes from aqueous suspension by manganese greensand filtration was also investigated. It was found that influent radium concentrations of 100 pCi/L were reduced to 2--9 pCi/L by this process. Additional study of the fate of radium in manganese greensand filters is recommended before this procedure is used for drinking water treatment.

Kinetics and mechanism of the selective oxidation of primary aliphatic alcohols under phase transfer catalysis

Directory of Open Access Journals (Sweden)

K. Bijudas

2014-03-01

Full Text Available Kinetics of the oxidation of primary aliphatic alcohols has been carried out using phase transferred monochromate in benzene. Tetrabutylammonium bromide (TBAB and tetrabutylphosphonium bromide (TBPB are used as phase transfer catalysts (PT catalyst. The reaction shows first order dependence on both [alcohol] and [monochromate ion]. The oxidation leads to the formation of corresponding aldehyde and no traces of carboxylic acid has been detected. The reaction mixture failed to induce the polymerization of added acrylonitrile which rules out the presence radical intermediates in the reaction. Various thermodynamic parameters have been evaluated and a suitable mechanism has been proposed.

Composition dependence of the kinetics and mechanisms of thermal oxidation of titanium-tantalum alloys

International Nuclear Information System (INIS)

Park, Y.S.; Butt, D.P.

1999-01-01

The oxidation behavior of titanium-tantalum alloys was investigated with respective concentrations of each element ranging from 0 to 100 wt.%. Alloys were exposed to argon-20% oxygen at 800 to 1400 C. The slowest oxidation rates were observed in alloys with 5--20% Ta. The oxidation kinetics of alloys containing less than approximately 40% Ta were approximately parabolic. Pure Ta exhibited nearly linear kinetics. Alloys containing 50% or more Ta exhibited paralinear kinetics. The activation energies for oxidation ranged between 232 kJ/mole for pure Ti and 119 kJ/mole for pure Ta, with the activation energies of the alloys falling between these values and generally decreasing with increasing Ta content. The activation energies for oxidation of the end members, Ti and Ta, agree well with published values for the activation energies for diffusion of oxygen in α-Ti and Ta. Scale formation in the alloys was found to be complex exhibiting various layers of Ti-, Ta-, and TiTa-oxides. The outermost layer of the oxidized alloys was predominantly rutile (TiO 2 ). Beneath the TiO 2 grew a variety of other oxides with the Ta content generally increasing with proximity to the metal-oxide interface. It was found that the most oxidation-resistant alloys had compositions falling between Ti-5Ta and Ti-15Ta. Although Ta stabilizes the β-phase of Ti, the kinetics of oxidation appeared to be rate limited by oxygen transport through the oxygen-stabilized α-phase. However, the kinetics are complicated by the formation of a complex oxide, which cracks periodically. Tantalum appears to increase the compositional range of oxygen-stabilized α-phase and reduces both the solubility of oxygen and diffusivity of Ti in the α- and β-phases

Local Symmetry and Domain Patterns: Ordering Phenomena in Transition-Metal Oxides

OpenAIRE

Buchholz, Marcel

2013-01-01

Transition-metal oxides (TMOs) show rich phase diagrams with various magnetic and electronic phases that arise from the complex interplay between spin, charge, orbital, and lattice degrees of freedom. The most prominent class of materials, which has attracted a lot of attention in the last decades, are probably high-temperature superconductors (HTS), in which the resitivity drops to zero below a critical temperature. Further examples are different kind of complex ordering phenomena, for examp...

Deep desulfurization of diesel via peroxide oxidation using phosphotungstic acid as phase transfer catalyst

Energy Technology Data Exchange (ETDEWEB)

Sachdeva, T.O.; Pant, K.K. [Department of Chemical Engineering, Indian Institute of Technology, Delhi, New Delhi, 110016 (India)

2010-09-15

High sulfur level in diesel fuel has been identified as a major contributor to air pollutant in term of sulfur dioxide (SO{sub x}) through diesel fueled vehicles. The main aim of the present work is to develop a promising methodology for ultra deep desulfurization of diesel fuel using oxidation followed by phase transfer of oxidized sulfur. Experiments were carried out in a batch reactor using n-decane as the model diesel compound and also using commercial diesel feedstock. To remove sulfur tetraoctylammonium bromide, phosphotungstic acid, and hydrogen peroxide were used as phase transfer agent, catalyst and oxidant respectively. The percent sulfur removal increases with increasing the initial concentration of sulfur in fuel and with increasing the reaction temperature. Similar trends were observed when commercial diesel was used to carry out desulfurization studies. The amphiphilic catalyst serves as a catalyst and also as an emulsifying agent to stabilize the emulsion droplets. The effects of temperature, agitation speed, quantity of catalyst and the phase transfer agent were studied to estimate the optimal conditions for the reactions. The sulfur removal from a commercial diesel by phase transfer catalysis has been found effective and removal efficiency was more than 98%. Kinetic experiments carried out for the desulfurization revealed that the sulfur removal results are best fitted to a pseudo first order kinetics and the apparent activation energy of desulfurization was 30.6 kJ/mol. (author)

Deep desulfurization of diesel via peroxide oxidation using phosphotungstic acid as phase transfer catalyst

International Nuclear Information System (INIS)

Sachdeva, T.O.; Pant, K.K.

2010-01-01

High sulfur level in diesel fuel has been identified as a major contributor to air pollutant in term of sulfur dioxide (SO x ) through diesel fueled vehicles. The main aim of the present work is to develop a promising methodology for ultra deep desulfurization of diesel fuel using oxidation followed by phase transfer of oxidized sulfur. Experiments were carried out in a batch reactor using n-decane as the model diesel compound and also using commercial diesel feedstock. To remove sulfur tetraoctylammonium bromide, phosphotungstic acid, and hydrogen peroxide were used as phase transfer agent, catalyst and oxidant respectively. The percent sulfur removal increases with increasing the initial concentration of sulfur in fuel and with increasing the reaction temperature. Similar trends were observed when commercial diesel was used to carry out desulfurization studies. The amphiphilic catalyst serves as a catalyst and also as an emulsifying agent to stabilize the emulsion droplets. The effects of temperature, agitation speed, quantity of catalyst and the phase transfer agent were studied to estimate the optimal conditions for the reactions. The sulfur removal from a commercial diesel by phase transfer catalysis has been found effective and removal efficiency was more than 98%. Kinetic experiments carried out for the desulfurization revealed that the sulfur removal results are best fitted to a pseudo first order kinetics and the apparent activation energy of desulfurization was 30.6 kJ/mol. (author)

Evaluation of umbilical cord mesenchymal stem cells labeling with superparamagnetic iron oxide nanoparticles coated with dextran and complexed with Poly-L-Lysine

International Nuclear Information System (INIS)

Sibov, Tatiana Tais; Mamani, Javier Bustamante; Pavon, Lorena Favaro; Cardenas, Walter Humberto; Gamarra, Lionel Fernel; Miyaki, Liza Aya Mabuchi; Marti, Luciana Cavalheiro; Sardinha, Luiz Roberto; Oliveira, Daniela Mara de

2012-01-01

Objective: The objective of this study was to evaluate the effect of the labeling of umbilical cord vein derived mesenchymal stem cells with superparamagnetic iron oxide nanoparticles coated with dextran and complexed to a non-viral transfector agent transfector poly-L-lysine. Methods: The labeling of mesenchymal stem cells was performed using the superparamagnetic iron oxide nanoparticles/dextran complexed and not complexed to poly-L-lysine. Superparamagnetic iron oxide nanoparticles/dextran was incubated with poly-L-lysine in an ultrasonic sonicator at 37 deg C for 10 minutes for complex formation superparamagnetic iron oxide nanoparticles/dextran/poly-L-lysine by electrostatic interaction. Then, the mesenchymal stem cells were incubated overnight with the complex superparamagnetic iron oxide nanoparticles/dextran/poly-L-lysine and superparamagnetic iron oxide nanoparticles/dextran. After the incubation period the mesenchymal stem cells were evaluated by internalization of the complex superparamagnetic iron oxide nanoparticles/dextran/polyL-lysine and superparamagnetic iron oxide nanoparticles/dextran by Prussian Blue stain. Cellular viability of labeled mesenchymal stem cells was evaluated by cellular proliferation assay using 5,6-carboxyfluorescein-succinimidyl ester method and apoptosis detection by Annexin V- Propidium Iodide assay. Results: mesenchymal stem cells labeled with superparamagnetic iron oxide nanoparticles/ dextran without poly-L-lysine not internalized efficiently the superparamagnetic iron oxide nanoparticles due to its low presence detected within cells. Mesenchymal stem cells labeled with the complex superparamagnetic iron oxide nanoparticles/dextran/polyL-lysine efficiently internalized the superparamagnetic iron oxide nanoparticles due to greater presence in the cells interior. The viability and apoptosis assays demonstrated that the mesenchymal stem cells labeled and not labeled respectively with the superparamagnetic iron oxide

Investigation of phase stability and oxide ion performance in new perovskite-type bismuth vanadate

International Nuclear Information System (INIS)

Al-Alas, Ahlam; Beg, Saba; Al-Areqi, Niyazi A.S.

2012-01-01

Samples of the BICDVOX system, formulated as Bi 4 Cd x V 2−x O 11−(3x/2)−δ in the Cd substitution range 0 ≤ x ≤ 0.25 were synthesized using the standard solid state reaction.The correlation between phase stability and oxide ion performance were investigated by variable temperature XRPD, DSC and AC impedance spectroscopy. The substitution of V 5+ by Cd 2+ exhibited different phase transitions upon varying composition. For compositions with x ≤ 0.05, two successive transitions; α↔β↔γ are evident, while the β↔γ transition exists in the composition range 0.05 4+ → V 5+ re–oxidation results in increased defect trapping effects in the system at higher temperatures. -- Highlights: ► γ-Stabilized BICDVOX at lower dopant concentrations. ► Good oxide-ion conductivity at lower temperatures. ► High temperature-vanadium reduction with lower dopant concentrations.

Evidence of an Intermediate Phase in bulk alloy oxide glass sysem

Science.gov (United States)

Chakraborty, S.; Boolchand, P.

2011-03-01

Reversibility windows have been observed in modified oxides (alkali-silicates and -germanates) and identified with Intermediate Phases(IPs). Here we find preliminary evidence of an IP in a ternary oxide glass, (B2 O3)5 (Te O2)95-x (V2O5)x , which is composed of network formers. Bulk glasses are synthesized across the 18% x 35 % composition range, and examined in Raman scattering, modulated DSC and molar volume experiments. Glass transition temperatures Tg (x) steadily decrease with V2O5 content x, and reveal the enthalpy of relaxation at Tg to show a global minimum in the 24% x < 27 range, the reversibility window (IP). Molar volumes reveal a minimum in this window. Raman scattering reveals a Boson mode, and at least six other vibrational bands in the 100cm-1 < ν < 1700cm-1 range. Compositional trends in vibrational mode strengths and frequency are established. These results will be presented in relation to glass structure evolution with vanadia content and the underlying elastic phases. Supported by NSF grant DMR 08-53957.

Thermochemistry of the complex oxides of uranium, vanadium, and alkali metals

International Nuclear Information System (INIS)

Karyakin, N.V.; Chernorukov, N.G.; Suleimanov, E.V.; Kharyushina, E.A.

1992-01-01

The standard enthalpies of the formation at T 298.15 K of complex oxides of uranium(VI), vanadium(V) and alkali metals with the general formula M 1 VUO 6 where M 1 = Na, K, Rb, and Cs, were calculated from the results of calorimetric experiments and from published data. 8 refs., 1 tab

Phase stability of zirconium oxide films during focused ion beam milling

Science.gov (United States)

Baxter, Felicity; Garner, Alistair; Topping, Matthew; Hulme, Helen; Preuss, Michael; Frankel, Philipp

2018-06-01

Focused ion beam (FIB) is a widely used technique for preparation of electron transparent samples and so it is vital to understand the potential for introduction of FIB-induced microstructural artefacts. The bombardment of both Xe+ and Ga+ ions is observed to cause extensive monoclinic to tetragonal phase transformation in ZrO2 corrosion films, however, this effect is diminished with reduced energy and is not observed below 5 KeV. This study emphasises the importance of careful FIB sample preparation with a low energy cleaning step, and also gives insight into the stabilisation mechanism of the tetragonal phase during oxidation.

Impact of environmental chemistry on mycogenic Mn oxide minerals

Science.gov (United States)

Santelli, C. M.; Farfan, G. A.; Post, A.; Post, J. E.

2012-12-01

Manganese (Mn) oxide minerals are ubiquitous in aquatic and terrestrial environments and their presence can have broad environmental consequences. In particular, Mn oxides scavenge nutrients and metals, degrade complex organics, and oxidize a variety of inorganic contaminants. The "reactivity" of Mn oxides, however, is highly dependent upon crystallite size, composition, and structure, which are largely determined by environmental factors such as solution chemistry. It is has been suggested that most Mn oxides in terrestrial and aquatic environments are formed by microbial activity; indeed, a diversity of Mn(II)-oxidizing bacteria and fungi have been isolated and their mineral byproducts are consistent with those observed in natural systems. Previous studies showed that Mn(II)-oxidizing Ascomycete fungi produce highly-disordered, nanocrystalline Mn oxides that are structurally similar to synthetic δ-MnO2 or natural vernadite. Unlike related studies with Mn-oxidizing bacteria, Mn oxides produced by these fungi did not "age" or transform to more crystalline mineral phases with time. We hypothesize that fungal growth conditions, in particular the low concentration of cations, are inhibiting secondary mineral formation. The overall goal of this research is to examine the structure and speciation of fungally-precipitated Mn oxides with respect to fungal species, time, and concentration of soluble Mn(II), Na, and Ca - three environmentally relevant cations that promote the transformation of δ-MnO2 to more crystalline mineral phases such as feitknechtite, birnessite, or ranciéite. For this study, we examined the Mn oxides formed by different species of Mn(II)-oxidizing fungi (Pyrenochaeta sp., Stagonospora sp., Plectosphaerella cucumerina., and Acremonium strictum). Isolates were grown for 8 or 16 days in a nutrient lean media consisting of yeast extract, trace elements and 0.2 mM MnCl2 supplemented with varying concentrations of Na, Ca, or Mn(II) compounds. The

Phase transformation, oxidation and shape memory properties of Ti–50Au–10Zr alloy for high temperature applications

International Nuclear Information System (INIS)

Wadood, A.; Hosoda, H.; Yamabe-Mitarai, Y.

2014-01-01

Highlights: • Ti–50Au–10Zr exhibited better thermo-mechanical and shape memory properties than Ti–50Au. • Improvement was related to solid solution and precipitation strengthening. • No oxidation problem as oxidation was observed at 100 K higher than A f . • TMA was used not only for thermo-mechanical but also for shape memory and oxidation. - Abstract: In this study, we investigated the phase transformation, oxidation and high temperature mechanical and shape memory properties of Ti–50Au–10Zr (all compositions in atomic%) alloy. Thermo-mechanical analyzer (TMA) was used not only for phase transformation but also for the measurement of shape memory effect and oxidation behavior in air environment. Ti–50Au–10Zr exhibited lower martensitic transformation temperature of 758 K than TiAu stoichiometric alloy exhibiting 870 K since Zr addition stabilizes B2 parent phase. Oxidation was initiated at 873 K that was about 100 K higher than the austenite finish temperature, indicating no such oxidation problems for practical use. Shape memory effect was improved by partial substitution of Ti with Zr in Ti–50Au–10Zr alloy. Compression test of Ti–50Au–10Zr revealed high compressive strength of 1239 MPa of martensite at 691 K (=M f − 50 K) and 924 MPa of B2 parent phase at 834 K (=A f + 50 K) in comparison with Ti–50Au. It is concluded that Zr is effective to improve the mechanical and shape memory properties of TiAu alloy, and that Ti–50Au–10Zr shape memory alloy has potential for high temperature (∼650–850 K) practical applications

Pulsed cathodoluminescence of nanoscale aluminum oxide with different phase compositions

International Nuclear Information System (INIS)

Kortov, V.S.; Zvonarev, S.V.; Medvedev, A.I.

2011-01-01

The methods of pulsed cathodoluminescence have been used to study compacted powders and ceramics containing different phases of aluminum oxide. An intensive luminescence of the samples under study in the visible, NIR, and UV regions of the spectrum has been found. The luminescence bands are very broad and include a few components. The number of the bands depends on the phase composition of the samples. The oxygen vacancies, which capture one or two electrons, produce luminescence centers in the near UV region. The most probable in the visible region is the luminescence of aggregate defects, impurities, and surface centers. - Highlights: → We investigate pulsed cathodoluminescence spectra of nanoscale alumina. → We found the intensive luminescence in the visible, NIR, and UV regions. → The transformation of R-line structure depends on phase composition of alumina. → We substantiate the relation of luminescence bands with concrete centers.

Complement fixation by solid phase immune complexes. Reduced capacity in SLE sera

DEFF Research Database (Denmark)

Baatrup, G; Jonsson, H; Sjöholm, A

1988-01-01

We describe an ELISA for assessment of complement function based on the capacity of serum to support fixation of complement components to solid phase immune complexes (IC). Microplates were coated with aggregated bovine serum albumin (BSA) followed by rabbit anti-BSA IgG. The solid phase IC were...

Multiscale Informatics for Low-Temperature Propane Oxidation: Further Complexities in Studies of Complex Reactions

Energy Technology Data Exchange (ETDEWEB)

Burke, Michael P.; Goldsmith, C. Franklin; Klippenstein, Stephen J.; Welz, Oliver; Huang, Haifeng; Antonov, Ivan O.; Savee, John D.; Osborn, David L.; Zádor, Judit; Taatjes, Craig A.; Sheps, Leonid

2015-07-16

We have developed a multi-scale approach (Burke, M. P.; Klippenstein, S. J.; Harding, L. B. Proc. Combust. Inst. 2013, 34, 547–555.) to kinetic model formulation that directly incorporates elementary kinetic theories as a means to provide reliable, physics-based extrapolation to unexplored conditions. Here, we extend and generalize the multi-scale modeling strategy to treat systems of considerable complexity – involving multi-well reactions, potentially missing reactions, non-statistical product branching ratios, and non-Boltzmann (i.e. non-thermal) reactant distributions. The methodology is demonstrated here for a subsystem of low-temperature propane oxidation, as a representative system for low-temperature fuel oxidation. A multi-scale model is assembled and informed by a wide variety of targets that include ab initio calculations of molecular properties, rate constant measurements of isolated reactions, and complex systems measurements. Active model parameters are chosen to accommodate both “parametric” and “structural” uncertainties. Theoretical parameters (e.g. barrier heights) are included as active model parameters to account for parametric uncertainties in the theoretical treatment; experimental parameters (e.g. initial temperatures) are included to account for parametric uncertainties in the physical models of the experiments. RMG software is used to assess potential structural uncertainties due to missing reactions. Additionally, branching ratios among product channels are included as active model parameters to account for structural uncertainties related to difficulties in modeling sequences of multiple chemically activated steps. The approach is demonstrated here for interpreting time-resolved measurements of OH, HO2, n-propyl, i-propyl, propene, oxetane, and methyloxirane from photolysis-initiated low-temperature oxidation of propane at pressures from 4 to 60 Torr and temperatures from 300 to 700 K. In particular, the multi-scale informed

Photodegradation of polycyclic aromatic hydrocarbon pyrene by iron oxide in solid phase

International Nuclear Information System (INIS)

Wang, Y.; Liu, C.S.; Li, F.B.; Liu, C.P.; Liang, J.B.

2009-01-01

To better understand the photodegradation of polycyclic aromatic hydrocarbons (PAH) in solid phase in natural environment, laboratory experiments were conducted to study the influencing factors, kinetics and intermediate compound of pyrene photodegradation by iron oxides. The results showed that the pyrene photodegradation rate followed the order of α-FeOOH > α-Fe 2 O 3 > γ-Fe 2 O 3 > γ-FeOOH at the same reaction conditions. Lower dosage of α-FeOOH and higher light intensity increased the photodegradation rate of pyrene. Iron oxides and oxalic acid can set up a photo-Fenton-like system without additional H 2 O 2 in solid phase to enhance the photodegradation of pyrene under UV irradiation. All reaction followed the first-order reaction kinetics. The half-life (t 1/2 ) of pyrene in the system showed the higher efficiencies of using iron oxide as photocatalyst to degrade pyrene. Intermediate compound pyreno was found during photodegradation reactions by gas chromatography-mass spectrometry (GC-MS). The photodegradation efficiency for PAHs in this photo-Fenton-like system was also confirmed by using the contaminated soil samples. This work provides some useful information to understand the remediation of PAHs contaminated soils by photochemical techniques under practical condition

Complex motion of a vehicle through a series of signals controlled by power-law phase

Science.gov (United States)

Nagatani, Takashi

2017-07-01

We study the dynamic motion of a vehicle moving through the series of traffic signals controlled by the position-dependent phase of power law. All signals are controlled by both cycle time and position-dependent phase. The dynamic model of the vehicular motion is described in terms of the nonlinear map. The vehicular motion varies in a complex manner by varying cycle time for various values of the power of the position-dependent phase. The vehicle displays the periodic motion with a long cycle for the integer power of the phase, while the vehicular motion exhibits the very complex behavior for the non-integer power of the phase.

Oxidation behavior and compositional analysis of aluminized superalloy

International Nuclear Information System (INIS)

Khalid, F.A.; Nawaz, F.

2003-01-01

The high temperature oxidation behavior of superalloy specimens used for the manufacture of turbine blades has been examined using scanning electron microscopy (SEM) and fine-probe spot and line scan EDS microanalysis techniques. The performance of aluminized coating applied to the specimens has also been examined. It was observed that complex oxides are formed in both coated and uncoated specimens. However the coated specimens revealed a greater stability of gamma phase and integrity of aluminized coating as compared with uncoated specimens. The microchemical and microstructural changes that occurred during oxidation have been analyzed to examine characteristics of oxide layers. (author)

Use of gas-phase ethanol to mitigate extreme UV/water oxidation of extreme UV optics

Science.gov (United States)

Klebanoff, L. E.; Malinowski, M. E.; Clift, W. M.; Steinhaus, C.; Grunow, P.

2004-03-01

A technique is described that uses a gas-phase species to mitigate the oxidation of a Mo/Si multilayer optic caused by either extreme UV (EUV) or electron-induced dissociation of adsorbed water vapor. It is found that introduction of ethanol (EtOH) into a water-rich gas-phase environment inhibits oxidation of the outermost Si layer of the Mo/Si EUV reflective coating. Auger electron spectroscopy, sputter Auger depth profiling, EUV reflectivity, and photocurrent measurements are presented that reveal the EUV/water- and electron/water-derived optic oxidation can be suppressed at the water partial pressures used in the tests (~2×10-7-2×10-5 Torr). The ethanol appears to function differently in two time regimes. At early times, ethanol decomposes on the optic surface, providing reactive carbon atoms that scavenge reactive oxygen atoms before they can oxidize the outermost Si layer. At later times, the reactive carbon atoms form a thin (~5 Å), possibly self-limited, graphitic layer that inhibits water adsorption on the optic surface. .

Room temperature chemically oxidized La2CuO4+y: Phase separation induced by thermal treatment

DEFF Research Database (Denmark)

Rial,C.; Moran, E.; Alario-Franco, M.A.

1997-01-01

The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured for this m......The structure of roam temperature chemically oxidized La2CuO4+y [y = 0.103(4)] has been refined from powder neutron diffraction data using the space group Bmab. The modifications induced in the CuO2 and the LaO planes by the insertion of oxygen are consistent with the high T-c measured...... a short treatment at 433 K, La2CuO4.103(4) undergoes a phase separation into two phases: phase 1, with estimated y(1) = 0.086(4) and T-cl = 30 K, and phase 2, with estimated y(2) = 0.12(1) and T-c2 = 17 K. By increasing the annealing times, phase 2 transforms to phase I and finally disappears. Therefore...

Structural evolution of epitaxial SrCoOx films near topotactic phase transition

OpenAIRE

Hyoungjeen Jeen; Ho Nyung Lee

2015-01-01

Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx) epitaxially grown by pulsed laser epitaxy (PLE) as a model syste...

Preparation of Zinc Oxide (ZnO) Thin Film as Transparent Conductive Oxide (TCO) from Zinc Complex Compound on Thin Film Solar Cells: A Study of O2 Effect on Annealing Process

Science.gov (United States)

Muslih, E. Y.; Kim, K. H.

2017-07-01

Zinc oxide (ZnO) thin film as a transparent conductive oxide (TCO) for thin film solar cell application was successfully prepared through two step preparations which consisted of deposition by spin coating at 2000 rpm for 10 second and followed by annealing at 500 °C for 2 hours under O2 and ambient atmosphere. Zinc acetate dehydrate was used as a precursor which dissolved in ethanol and acetone (1:1 mol) mixture in order to make a zinc complex compound. In this work, we reported the O2 effect, reaction mechanism, structure, morphology, optical and electrical properties. ZnO thin film in this work shows a single phase of wurtzite, with n-type semiconductor and has band gap, carrier concentration, mobility, and resistivity as 3.18 eV, 1.21 × 10-19cm3, 11 cm2/Vs, 2.35 × 10-3 Ωcm respectively which is suitable for TCO at thin film solar cell.

Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

Energy Technology Data Exchange (ETDEWEB)

Dong, Xiaoling [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Ma, Lena Q., E-mail: lqma@ufl.edu [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046 (China); Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Gress, Julia; Harris, Willie [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Li, Yuncong [Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, FL 33031-3314 (United States)

2014-02-01

Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L{sup −1} enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO{sub 2}. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions.

The oxidative p-dichlorobenzene dechlorinating in the presence of copper (ΙΙ complexes and nitrogen (ΙΙ, ΙV oxides

Directory of Open Access Journals (Sweden)

Valentina Yemelyanova

2012-12-01

Full Text Available The results of dechlorination in the solution CuCl2–TBP–NaNO2–О2–Н2О kinetics research are presented in the article. All system components influence to the dechlorination process is studied and quantitatively described. The composition of copper intermediate complexes participating in reaction is studied by the instrumentality of UV-spectroscopy. Established part of binuclear copper complexes in the catalytic intermediate complex constants of formation were estimated and compared with the kinetic and spectrophotometric methods. The composition of the intermediate complexes responsible for process is defined, the mechanism scheme is offered, the p-dichlorobenzene dechlorination limiting stage including redox-disintegration of the intermediate complex consisting of dimeric complex of copper (II, I chloride, nitrogen oxide and p-dichlorobenzene is defined.

On the role of complex phases in the quantum statistics of weak measurements

International Nuclear Information System (INIS)

Hofmann, Holger F

2011-01-01

Weak measurements carried out between quantum state preparation and post-selection result in complex values for self-adjoint operators, corresponding to complex conditional probabilities for the projections on specific eigenstates. In this paper it is shown that the complex phases of these weak conditional probabilities describe the dynamic response of the system to unitary transformations. Quantum mechanics thus unifies the statistical overlap of different states with the dynamical structure of transformations between these states. Specifically, it is possible to identify the phase of weak conditional probabilities directly with the action of a unitary transform that maximizes the overlap of initial and final states. This action provides a quantitative measure of how much quantum correlations can diverge from the deterministic relations between physical properties expected from classical physics or hidden variable theories. In terms of quantum information, the phases of weak conditional probabilities thus represent the logical tension between sets of three quantum states that is at the heart of quantum paradoxes. (paper)

Characteristics of growth of complex ferroelectric oxide films by plasma-ion sputtering

Science.gov (United States)

Mukhortov, V. M.; Golovko, Yu. I.; Mukhortov, Vl. M.; Dudkevich, V. P.

1981-02-01

An experimental investigation was made of the process of growth of a complex oxide film, such as BaTiO3 or (Ba, Sr)TiO3, by plasma-ion sputtering. It was found that ion bombardment of a ceramic target knocked out neutral excited atoms. These atoms lost energy away from the target by collisions and at a certain critical distance hcr they were capable of oxidation to produce BaO, TiO, TiO2, and SrO. Therefore, depending on the distance between the cathode and the substrate, the “construction” material arrived in the form of atoms or molecules of simple oxides. These two (atomic and molecular) deposition mechanisms corresponded to two mechanisms of synthesis and crystallization differing in respect of the dependences of the growth rate, unit cell parameters, and other structural properties on the deposition temperature. The role of re-evaporation and of oxidation-reduction processes was analyzed.

Exploring the Photoreduction of Au(III) Complexes in the Gas-Phase

Science.gov (United States)

Marcum, Jesse C.; Kaufman, Sydney H.; Weber, J. Mathias

2010-06-01

We have used photodissociation spectroscopy to probe the electronic structure and photoreduction of Au(III) in gas-phase complexes containing Cl- and OH-. The gas-phase electronic spectrum of [AuCl_4]- closely resembles the aqueous solution spectrum, showing a lack of strong solvatochromic shifts. Substitution of Cl- ligands with OH- results in a strong blue shift, in agreement with ligand-field theory. Upon excitation, [AuCl_4]- can dissociate by loss of either one or two neutral Cl atoms, resulting in the reduction of gold from Au(III) to Au(II) and Au(I) respectively. The hydroxide substituted complex, [AuCl_2(OH)_2]-, demonstrates similar behavior but the only observable fragment channel is the loss of two neutral OH ligands, leading only to Au(I).

Complex magnetic monopoles, geometric phases and quantum evolution in the vicinity of diabolic and exceptional points

International Nuclear Information System (INIS)

Nesterov, Alexander I; Aceves de la Cruz, F

2008-01-01

We consider the geometric phase and quantum tunneling in the vicinity of diabolic and exceptional points. We show that the geometric phase associated with the degeneracy points is defined by the flux of complex magnetic monopoles. In the limit of weak coupling, the leading contribution to the real part of the geometric phase is given by the flux of the Dirac monopole plus a quadrupole term, and the expansion of the imaginary part starts with a dipole-like field. For a two-level system governed by a generic non-Hermitian Hamiltonian, we derive a formula to compute the non-adiabatic, complex, geometric phase by integrating over the complex Bloch sphere. We apply our results to study a dissipative two-level system driven by a periodic electromagnetic field and show that, in the vicinity of the exceptional point, the complex geometric phase behaves like a step-function. Studying the tunneling process near and at the exceptional point, we find two different regimes: coherent and incoherent. The coherent regime is characterized by Rabi oscillations, with a one-sheeted hyperbolic monopole emerging in this region of the parameters. The two-sheeted hyperbolic monopole is associated with the incoherent regime. We show that the dissipation results in a series of pulses in the complex geometric phase which disappear when the dissipation dies out. Such a strong coupling effect of the environment is beyond the conventional adiabatic treatment of the Berry phase

Synthesis and characterization of a novel stationary phase, Si-Zr/Ti(PMTDS), based upon ternary oxide support for high performance liquid chromatography

Energy Technology Data Exchange (ETDEWEB)

Amparo, Maura R.; Marques, Fabiana A.; Faria, Anizio M., E-mail: anizio@pontal.ufu.br [Universidade Federal de Uberlandia (FACIP/UFU), Ituiutaba, MG (Brazil). Faculdade de Ciencias Integradas do Pontal

2013-09-15

A new stationary phase based on the thermal immobilization of poly(methyltetradecylsiloxane) (PMTDS) on silica particles coated with a mixture of zirconia and titania was prepared and evaluated for the chromatographic separation of test mixtures. The spherical particles were characterized by elemental analysis, SEM, FTIR and {sup 29}Si NMR. The physicochemical properties of PMTDS phase supported on Si-Zr/Ti were intermediate between PMTDS phases supported on titanized silica and zirconized silica. The chromatographic performance of Si-Zr/Ti(PMTDS) phase was similar to PMTDS phases based on metal oxide coated silica having only one metal oxide and the preparation of a Si-Zr/Ti(PMTDS) phase allowed evaluation of the effect of each oxide, zirconia and titania, on the separation process and on the stability of the immobilized polymer phase. The hydrolytic stability of Si-Zr/Ti(PMTDS) stationary phase was similar to the Si-Ti(PMTDS) phase, improving the chemical stability of the silica-based PMTDS phase by about 100%. (author)

Synthesis and characterization of alumina-supported vanadium oxide catalysts prepared by the molecular designed dispersion of VO(acac)2 complexes

NARCIS (Netherlands)

Weckhuysen, B.M.; Baltes, M.; Voort, P. van der; Ramachandra Rao, R.; Catana, Gabriela; Schoonheydt, R.A.; Vansant, E.F.

2000-01-01

Alumina-supported vanadium oxide catalysts have been prepared by the molecular designed dispersion method, using the vanadyl acetylacetonate complex (VO(acac)2). The complex has been adsorbed on the support from solution, followed by thermal conversion into the corresponding supported vanadium oxide

Complex Nonlinearity Chaos, Phase Transitions, Topology Change and Path Integrals

CERN Document Server

Ivancevic, Vladimir G

2008-01-01

Complex Nonlinearity: Chaos, Phase Transitions, Topology Change and Path Integrals is a book about prediction & control of general nonlinear and chaotic dynamics of high-dimensional complex systems of various physical and non-physical nature and their underpinning geometro-topological change. The book starts with a textbook-like expose on nonlinear dynamics, attractors and chaos, both temporal and spatio-temporal, including modern techniques of chaos–control. Chapter 2 turns to the edge of chaos, in the form of phase transitions (equilibrium and non-equilibrium, oscillatory, fractal and noise-induced), as well as the related field of synergetics. While the natural stage for linear dynamics comprises of flat, Euclidean geometry (with the corresponding calculation tools from linear algebra and analysis), the natural stage for nonlinear dynamics is curved, Riemannian geometry (with the corresponding tools from nonlinear, tensor algebra and analysis). The extreme nonlinearity – chaos – corresponds to th...

Direct gas-phase epoxidation of propylene to propylene oxide through radical reactions: A theoretical study

Science.gov (United States)

Kizilkaya, Ali Can; Fellah, Mehmet Ferdi; Onal, Isik

2010-03-01

The gas-phase radical chain reactions which utilize O 2 as the oxidant to produce propylene oxide (PO) are investigated through theoretical calculations. The transition states and energy profiles were obtained for each path. The rate constants were also calculated. The energetics for the competing pathways indicate that PO can be formed selectively due to its relatively low activation barrier (9.3 kcal/mol) which is in a good agreement with the experimental value (11 kcal/mol) of gas-phase propylene epoxidation. The formation of the acrolein and combustion products have relatively high activation barriers and are not favored. These results also support the recent experimental findings.

Nitric oxide activation by distal redox modulation in tetranuclear iron nitrosyl complexes.

Science.gov (United States)

de Ruiter, Graham; Thompson, Niklas B; Lionetti, Davide; Agapie, Theodor

2015-11-11

A series of tetranuclear iron complexes displaying a site-differentiated metal center was synthesized. Three of the metal centers are coordinated to our previously reported ligand, based on a 1,3,5-triarylbenzene motif with nitrogen and oxygen donors. The fourth (apical) iron center is coordinatively unsaturated and appended to the trinuclear core through three bridging pyrazolates and an interstitial μ4-oxide moiety. Electrochemical studies of complex [LFe3(PhPz)3OFe][OTf]2 revealed three reversible redox events assigned to the Fe(II)4/Fe(II)3Fe(III) (-1.733 V), Fe(II)3Fe(III)/Fe(II)2Fe(III)2 (-0.727 V), and Fe(II)2Fe(III)2/Fe(II)Fe(III)3 (0.018 V) redox couples. Combined Mössbauer and crystallographic studies indicate that the change in oxidation state is exclusively localized at the triiron core, without changing the oxidation state of the apical metal center. This phenomenon is assigned to differences in the coordination environment of the two metal sites and provides a strategy for storing electron and hole equivalents without affecting the oxidation state of the coordinatively unsaturated metal. The presence of a ligand-binding site allowed the effect of redox modulation on nitric oxide activation by an Fe(II) metal center to be studied. Treatment of the clusters with nitric oxide resulted in binding of NO to the apical iron center, generating a {FeNO}(7) moiety. As with the NO-free precursors, the three reversible redox events are localized at the iron centers distal from the NO ligand. Altering the redox state of the triiron core resulted in significant change in the NO stretching frequency, by as much as 100 cm(-1). The increased activation of NO is attributed to structural changes within the clusters, in particular, those related to the interaction of the metal centers with the interstitial atom. The differences in NO activation were further shown to lead to differential reactivity, with NO disproportionation and N2O formation performed by the more

Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

Science.gov (United States)

Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

2014-08-01

We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕinterface with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

OpenAIRE

Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

2014-01-01

We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ_ with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

Formation, transformation and dissolution of phases formed on surfaces

International Nuclear Information System (INIS)

Shoesmith, D.W.

1983-03-01

The basic mechanisms of film growth, transformation, and dissolution of phases formed on surfaces are discussed. Film growth can occur via solid-state processes or via substrate (usally metal or alloy) dissolution, followed by local supersaturation and precipitation of an insoluble phase. The phase(s) formed may be metastable and transform to a more stable phase, via either solid-state or dissolution-reprecipitation processes. Film dissolution reactions can also occur via a variety of mechanisms, including: (i) direct chemical dissolution when no oxidation state change occurs; (ii) redox dissolution when the film dissolves via a redox reaction involving a reducing or oxidizing agent in solution; and (iii) autoreduction, where film dissolution is coupled to metal dissolution. Such film-growth and dissolution processes, which often produce complex multilayer films, are common in the nuclear industry. A number of examples are discussed

New Oxide Materials for an Ultra High Temperature Environment

Energy Technology Data Exchange (ETDEWEB)

Perepezko, John H. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering

2017-11-13

In this project, a new oxide material, Hf₆Ta₂O₁₇ has been successfully synthesized by the controlled oxidization of Hf-Ta alloys. This oxide exhibits good oxidation resistance, high temperature phase stability up to more than 2000°C, low thermal conductivity and thus could serve as a component or a coating material in an ultrahigh temperature environment. We have examined the microstructure evolution and phase formation sequence during the oxidation exposure of Hf-Ta alloys at 1500°C and identified that the oxidation of a Hf-26.7atomic %Ta alloy leads to the formation of a single phase adherent Hf₆Ta₂O₁₇ with a complex atomic structure i.e. superstructure. The overall reactive diffusion pathway is consistent with the calculated Hf-Ta-O ternary phase diagram. Besides the synthesis of Hf₆Ta₂O₁₇ superstructure by oxidizing Hf-Ta alloys, we have also developed a synthesis method based upon the reactive sintering of the correct ratios of mixed powders of HfO₂ and Ta₂O₅ and verified the low thermal conductivity of Hf₆Ta₂O₁₇ superstructure on these samples. We have completed a preliminary analysis of the oxidation kinetics for Hf₆Ta₂O₁₇, which shows an initial parabolic oxidation kinetics.

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H2O2, O3 and iron catalysis

Directory of Open Access Journals (Sweden)

J. N. Crowley

2012-01-01

Full Text Available The oxidation of SO2 to sulfate is a key reaction in determining the role of sulfate in the environment through its effect on aerosol size distribution and composition. Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sulfate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in major transformation pathways. This paper presents laboratory measurements of the fractionation factors for the major atmospheric oxidation reactions for SO2: Gas-phase oxidation by OH radicals, and aqueous oxidation by H2O2, O3 and a radical chain reaction initiated by iron. The measured fractionation factor for 34S/32S during the gas-phase reaction is αOH = (1.0089±0.0007−((4±5×10−5 T(°C. The measured fractionation factor for 34S/32S during aqueous oxidation by H2O2 or O3 is αaq = (1.0167±0.0019−((8.7±3.5 ×10−5T(°C. The observed fractionation during oxidation by H2O2 and O3 appeared to be controlled primarily by protonation and acid-base equilibria of S(IV in solution, which is the reason that there is no significant difference between the fractionation produced by the two oxidants within the experimental error. The isotopic fractionation factor from a radical chain reaction in solution catalysed by iron is αFe = (0.9894±0.0043 at 19 °C for 34S/32S. Fractionation was mass-dependent with regards to 33S/32S for all the reactions investigated. The radical chain reaction mechanism was the only measured reaction that had a faster rate for the light isotopes. The results presented in this study will be particularly useful to determine the importance of the transition metal-catalysed oxidation pathway compared to other oxidation pathways, but other main oxidation pathways can not be distinguished based on stable sulfur isotope measurements alone.

Continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process: An efficient diesel treatment by injection of the aqueous phase.

Science.gov (United States)

Rahimi, Masoud; Shahhosseini, Shahrokh; Movahedirad, Salman

2017-11-01

A new continuous-flow ultrasound assisted oxidative desulfurization (UAOD) process was developed in order to decrease energy and aqueous phase consumption. In this process the aqueous phase is injected below the horn tip leading to enhanced mixing of the phases. Diesel fuel as the oil phase with sulfur content of 1550ppmw and an appropriate mixture of hydrogen peroxide and formic acid as the aqueous phase were used. At the first step, the optimized condition for the sulfur removal has been obtained in the batch mode operation. Hence, the effect of more important oxidation parameters; oxidant-to-sulfur molar ratio, acid-to-sulfur molar ratio and sonication time were investigated. Then the optimized conditions were obtained using Response Surface Methodology (RSM) technique. Afterwards, some experiments corresponding to the best batch condition and also with objective of minimizing the residence time and aqueous phase to fuel volume ratio have been conducted in a newly designed double-compartment reactor with injection of the aqueous phase to evaluate the process in a continuous flow operation. In addition, the effect of nozzle diameter has been examined. Significant improvement on the sulfur removal was observed specially in lower sonication time in the case of dispersion method in comparison with the conventional contact between two phases. Ultimately, the flow pattern induced by ultrasonic device, and also injection of the aqueous phase were analyzed quantitatively and qualitatively by capturing the sequential images. Copyright © 2017 Elsevier B.V. All rights reserved.

Electric-Field Control of Oxygen Vacancies and Magnetic Phase Transition in a Cobaltite/Manganite Bilayer

Science.gov (United States)

Cui, B.; Song, C.; Li, F.; Zhong, X. Y.; Wang, Z. C.; Werner, P.; Gu, Y. D.; Wu, H. Q.; Saleem, M. S.; Parkin, S. S. P.; Pan, F.

2017-10-01

Manipulation of oxygen vacancies (VO ) in single oxide layers by varying the electric field can result in significant modulation of the ground state. However, in many oxide multilayers with strong application potentials, e.g., ferroelectric tunnel junctions and solid-oxide fuel cells, understanding VO behavior in various layers under an applied electric field remains a challenge, owing to complex VO transport between different layers. By sweeping the external voltage, a reversible manipulation of VO and a corresponding fixed magnetic phase transition sequence in cobaltite/manganite (SrCoO3 -x/La0.45Sr0.55MnO3 -y ) heterostructures are reported. The magnetic phase transition sequence confirms that the priority of electric-field-induced VO formation or annihilation in the complex bilayer system is mainly determined by the VO formation energies and Gibbs free-energy differences, which is supported by theoretical analysis. We not only realize a reversible manipulation of the magnetic phase transition in an oxide bilayer but also provide insight into the electric-field control of VO engineering in heterostructures.

Phase behaviour and structure of stable complexes of oppositely charged polyelectrolytes

Science.gov (United States)

Mengarelli, V.; Auvray, L.; Zeghal, M.

2009-03-01

We study the formation and structure of stable electrostatic complexes between oppositely charged polyelectrolytes, a long polymethacrylic acid and a shorter polyethylenimine, at low pH, where the polyacid is weakly charged. We explore the phase diagram as a function of the charge and concentration ratio of the constituents. In agreement with theory, turbidity and ζ potential measurements show two distinct regimes of weak and strong complexation, which appear successively as the pH is increased and are separated by a well-defined limit. Weak complexes observed by neutron scattering and contrast matching have an open, non-compact structure, while strong complexes are condensed.

Petrogenesis and metallogenesis of the Wajilitag and Puchang Fe-Ti oxide-rich intrusive complexes, northwestern Tarim Large Igneous Province

Science.gov (United States)

Zhang, Dongyang; Zhang, Zhaochong; Huang, He; Cheng, Zhiguo; Charlier, Bernard

2018-04-01

The Wajilitag and Puchang intrusive complexes of the Tarim large igneous province (TLIP) are associated with significant resources of Fe-Ti oxide ores. These two mafic-ultramafic intrusions show differences in lithology and mineral chemistry. Clinopyroxenite and melagabbro are the dominant rock types in the Wajilitag complex, whereas the Puchang complex is generally gabbroic and anorthositic in composition with minor plagioclase-bearing clinopyroxenites in the marginal zone. Disseminated Fe-Ti oxide ores are found in the Wajilitag complex and closely associated with clinopyroxenites, whereas the Puchang complex hosts massive to disseminated Fe-Ti oxide ores mainly within its gabbroic rocks. The Wajilitag intrusive rocks are characterized by a restricted range of initial 87Sr/86Sr ratios (0.7038-0.7048) and positive εNd(t) (+0.04 - +3.01), indicating insignificant involvement of continental crustal contamination. The slightly higher initial 87Sr/86Sr ratios (0.7039-0.7059) and lower εNd(t) values (-1.05 - +2.35) of the Puchang intrusive rocks also suggest that the isotopic characteristics was controlled primarily by their mantle source, rather than by crustal contamination. Both complexes have Sr-Nd isotopic compositions close the neighboring kimberlitic rocks and their hosted mantle xenoliths in the TLIP. This indicates that the ferrobasaltic parental magmas were most probably originated from partial melting of a metasomatized subcontinental lithospheric mantle, modified recently with subduction-related materials by the impingement of the ascending mantle plume. The recycled subduction-related materials preserved in the lithospheric mantle could play a key role in the formation of the parental Fe-rich magmas in the context of an overall LIP system. The distinct variations in mineral assemblage for each complex and modeled results indicated that the Wajilitag and Puchang complexes experienced different crystallization path. Fe-Ti oxides in Wajilitag joined the

Neutral complexes as oxidants for the reduced form of parsley (Petroselinum crispum) [2Fe--2S] ferredoxin. Evidence for partial blocking by redox-inactive Cr(III) complexes.

Science.gov (United States)

Adzamli, I K; Kim, H O; Sykes, A G

1982-01-01

The 1 : 1 reactions of three neutral Co(III) oxidants, Co(acac)3, Co(NH3)3(NO2)3 and Co(acac)2(NH3)(NO2), with reduced parsley (Petroselinum crispum) [2Fe--2S] ferredoxin (which carries a substantial negative charge), have been studied at 25 degrees C, pH 8.0 (Tris/HCl), I0.10 (NaCl). Whereas it has previously been demonstrated that with Co(NH3)6+ as oxidant the reaction if completely blocked by redox-inactive Cr(NH3)63+, the neutral oxidants are only partially blocked by this same complex. The effects of three Cr(III) complexes, Cr(NH3)63+%, Cr(en)33+ and (en)2Cr . mu(OH,O2CCH3) . CR(en)24+ have been investigated. Kinetic data for the response of 3+, neutral, as well as 1--oxidants to the presence of 3+ (and 4+) Cr(III) complexes can now be rationalized in terms of a single functional site on the protein for electron transfer. Electrostatics have a significant influence on association at this site. PMID:7115307

Mechanistic Study of Monodisperse Iron Oxide Nanocrystals ...

African Journals Online (AJOL)

To gain better insight into the formation of iron oxide nanocrystals from the solution phase thermal decomposition of iron (III) oleate complex, different reaction conditions including time, heating ramp, as well as concentrations of iron oleate precursor and oleic acid ligand were systematically varied and the resulting ...

Disruption of the Class IIa HDAC Corepressor Complex Increases Energy Expenditure and Lipid Oxidation

Directory of Open Access Journals (Sweden)

Vidhi Gaur

2016-09-01

Full Text Available Drugs that recapitulate aspects of the exercise adaptive response have the potential to provide better treatment for diseases associated with physical inactivity. We previously observed reduced skeletal muscle class IIa HDAC (histone deacetylase transcriptional repressive activity during exercise. Here, we find that exercise-like adaptations are induced by skeletal muscle expression of class IIa HDAC mutants that cannot form a corepressor complex. Adaptations include increased metabolic gene expression, mitochondrial capacity, and lipid oxidation. An existing HDAC inhibitor, Scriptaid, had similar phenotypic effects through disruption of the class IIa HDAC corepressor complex. Acute Scriptaid administration to mice increased the expression of metabolic genes, which required an intact class IIa HDAC corepressor complex. Chronic Scriptaid administration increased exercise capacity, whole-body energy expenditure and lipid oxidation, and reduced fasting blood lipids and glucose. Therefore, compounds that disrupt class IIa HDAC function could be used to enhance metabolic health in chronic diseases driven by physical inactivity.

Mechanism of mechanochemical synthesis of complex oxides and the peculiarities of their nano-structurization determining sintering

Directory of Open Access Journals (Sweden)

Zyryanov V.V.

2005-01-01

Full Text Available A mechanism of superfast mechanosynthesis reaction for oxide systems is proposed on the base of a dynamics study. The threshold effect and linear dependence of the chemical response on the effective temperature of the reaction zone are established. Major factors are determined: molecular mass of reagents, enthalpy and difference of reagents in Mohs’s hardness, which also influence the composition of the primary product. Primary acts are characterized by a superfast roller mechanism of mass transfer with the formation of a transient dynamic state (D*. Secondary acts slowly approximate the composition of the product to the composition of the starting mixture by diffusion mass transfer in a deformation mixing regime with a contribution of a rotation (roller mechanism. The list of structure types for complex oxides derived by mechanosynthesis includes perovskites, fluorites, pyrochlors, sheelites, and some other ones. Powders of crystal products display multilevel structurization. In all studied complex oxides strong disordering of the “anti-glass” type was observed. The mechanism of sintering was studied in BaTiO3 powders of different origin and in metastable complex oxides derived by mechanosynthesis. The major contribution in shrinkage belongs to rearrangements of crystalline particles as a whole. Structure transformations accompany, as a rule, sintering of inhomogeneous powders derived by mechanosynthesis.

Comparison of topotactic fluorination methods for complex oxide films

Science.gov (United States)

Moon, E. J.; Choquette, A. K.; Huon, A.; Kulesa, S. Z.; Barbash, D.; May, S. J.

2015-06-01

We have investigated the synthesis of SrFeO3-αFγ (α and γ ≤ 1) perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride) as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO2.5 films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

Effect of complex polyphenols and tannins from red wine on DNA oxidative damage of rat colon mucosa in vivo.

Science.gov (United States)

Giovannelli, L; Testa, G; De Filippo, C; Cheynier, V; Clifford, M N; Dolara, P

2000-10-01

Dietary polyphenols have been reported to have a variety of biological actions, including anti-carcinogenic, antioxidant and anti-inflammatory activities. In the present study we have evaluated the effect of an oral treatment with complex polyphenols and tannins from red wine and tea on DNA oxidative damage in the rat colon mucosa. Isolated colonocytes were prepared from the colon mucosa of rats treated for ten days with either wine complex polyphenols (57.2 mg/kg/d) or thearubigin (40 mg/kg/d) by oral gavage. Colonocyte oxidative DNA damage was analysed at the single cell level using a modification of the comet assay technique. The results show that wine complex polyphenols and tannins induce a significant decrease (-62% for pyrimidine and -57% for purine oxidation) in basal DNA oxidative damage in colon mucosal cells without affecting the basal level of single-strand breaks. On the other hand, tea polyphenols, namely a crude extract of thearubigin, did not affect either strand breaks or pyrimidine oxidation in colon mucosal cells. Our experiments are the first demonstration that dietary polyphenols can modulate in vivo oxidative damage in the gastrointestinal tract of rodents. These data support the hypothesis that dietary polyphenols might have both a protective and a therapeutic potential in oxidative damage-related pathologies.

Complex quantum network geometries: Evolution and phase transitions

Science.gov (United States)

Bianconi, Ginestra; Rahmede, Christoph; Wu, Zhihao

2015-08-01

Networks are topological and geometric structures used to describe systems as different as the Internet, the brain, or the quantum structure of space-time. Here we define complex quantum network geometries, describing the underlying structure of growing simplicial 2-complexes, i.e., simplicial complexes formed by triangles. These networks are geometric networks with energies of the links that grow according to a nonequilibrium dynamics. The evolution in time of the geometric networks is a classical evolution describing a given path of a path integral defining the evolution of quantum network states. The quantum network states are characterized by quantum occupation numbers that can be mapped, respectively, to the nodes, links, and triangles incident to each link of the network. We call the geometric networks describing the evolution of quantum network states the quantum geometric networks. The quantum geometric networks have many properties common to complex networks, including small-world property, high clustering coefficient, high modularity, and scale-free degree distribution. Moreover, they can be distinguished between the Fermi-Dirac network and the Bose-Einstein network obeying, respectively, the Fermi-Dirac and Bose-Einstein statistics. We show that these networks can undergo structural phase transitions where the geometrical properties of the networks change drastically. Finally, we comment on the relation between quantum complex network geometries, spin networks, and triangulations.

Metastable phases in yttrium oxide plasma spray deposits and their effect on coating properties

International Nuclear Information System (INIS)

Gourlaouen, V.; Schnedecker, G.; Boncoeur, M.; Lejus, A.M.; Collongues, R.

1993-01-01

Yttrium oxide coatings were obtained by plasma spray. Structural investigations on these deposits show that, due to the drastic conditions of this technique, a minor monoclinic B phase is formed in the neighborhood of the major cubic C form. The authors discuss here the influence of different plasma spray parameters on the amount of the B phase formed. They describe also the main properties of Y 2 O 3 B and C phases in these deposits such as structural characteristics, thermal stability and mechanical behavior

Method of encapsulating a phase change material with a metal oxide

Science.gov (United States)

Ram, Manoj Kumar; Jotshi, Chand K.; Stefanakos, Elias K.; Goswami, Dharendra Yogi

2016-11-15

Storage systems based on latent heat storage have high-energy storage density, which reduces the footprint of the system and the cost. However, phase change materials (PCMs), such as NaNO.sub.3, NaCl, KNO.sub.3, have very low thermal conductivities. To enhave the storage of PCMs, macroencapsulation of PCMs was performed using a metal oxide, such as SiO.sub.2 or a graphene-SiO.sub.2, over polyimide-coated or nickel-embedded, polyimide-coated pellets The macro encapsulation provides a self-supporting structure, enhances the heat transfer rate, and provides a cost effective and reliable solution for thermal energy storage for use in solar thermal power plants. NaNO.sub.3 was selected for thermal storage in a temperature range of 300.degree. C. to 500.degree. C. The PCM was encapsulated in a metal oxide cell using self-assembly reactions, hydrolysis, and simultaneous chemical oxidation at various temperatures.

Tin-antimony oxide oxidation catalysts

Energy Technology Data Exchange (ETDEWEB)

Berry, Frank J. [Open University, Department of Chemistry (United Kingdom)

1998-12-15

Tin-antimony oxide catalysts for the selective oxidation of hydrocarbons have been made by precipitation techniques. The dehydration of the amorphous dried precipitate by calcination at increasingly higher temperatures induces the crystallisation of a rutile-related tin dioxide-type phase and the segregation of antimony oxides which volatilise at elevated temperatures. The rutile-related tin dioxide-type phase contains antimony(V) in the bulk and antimony(III) in the surface. Specific catalytic activity for the oxidative dehydrogenation of butene to butadiene is associated with materials with large concentrations of antimony(III) in the surface.

Applications of STEM-EELS to complex oxides

KAUST Repository

Gá zquez, Jaume; Sá nchez-Santolino, Gabriel; Biškup, Neven; Roldá n, Manuel A.; Cabero, M.; Pennycook, Stephen J.; Varela, Marí a

2016-01-01

In this chapter we will review a few examples of applications of atomic resolution aberration corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) to complex oxide materials. These are most challenging systems where subtle changes in structure or chemistry may result in colossal responses in macroscopic physical behavior. Here, we will review how atomic resolution compositional mapping can be achieved in manganite thin films and single crystals, highlighting the importance of considering artifacts during quantification. Besides, minor changes in near edge fine structure may take place when the crystalline environment, and hence nearest neighbor configuration, is modified. These can also be tracked by atomic resolution EELS, as will be shown through the study of binary Fe oxides. Also, examples regarding the study of distributions of point defects such as O vacancies in cobaltite thin films will be discussed. In these materials, a combination of epitaxial strain and defects may promote physical behaviors not present in bulk, such as the stabilization of unexpected spin state superlattices. Last, a study of extended defects such as dislocation lines will be reviewed. In particular, we will show how chemical segregation at dislocation cores in yttria-stabilized zirconia grain boundaries results in the generation of static O vacancies that affect the local electrostatic potential and hence, the macroscopic ionic conduction properties. © 2016.

Applications of STEM-EELS to complex oxides

KAUST Repository

Gázquez, Jaume

2016-06-26

In this chapter we will review a few examples of applications of atomic resolution aberration corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) to complex oxide materials. These are most challenging systems where subtle changes in structure or chemistry may result in colossal responses in macroscopic physical behavior. Here, we will review how atomic resolution compositional mapping can be achieved in manganite thin films and single crystals, highlighting the importance of considering artifacts during quantification. Besides, minor changes in near edge fine structure may take place when the crystalline environment, and hence nearest neighbor configuration, is modified. These can also be tracked by atomic resolution EELS, as will be shown through the study of binary Fe oxides. Also, examples regarding the study of distributions of point defects such as O vacancies in cobaltite thin films will be discussed. In these materials, a combination of epitaxial strain and defects may promote physical behaviors not present in bulk, such as the stabilization of unexpected spin state superlattices. Last, a study of extended defects such as dislocation lines will be reviewed. In particular, we will show how chemical segregation at dislocation cores in yttria-stabilized zirconia grain boundaries results in the generation of static O vacancies that affect the local electrostatic potential and hence, the macroscopic ionic conduction properties. © 2016.

Effective oxidation of benzylic and alkane C-H bonds catalyzed by sodium o-iodobenzenesulfonate with Oxone as a terminal oxidant under phase-transfer conditions.

Science.gov (United States)

Cui, Li-Qian; Liu, Kai; Zhang, Chi

2011-04-07

Catalytic oxidation of benzylic C-H bonds could be efficiently realized using IBS as a catalyst which was generated in situ from the oxidation of sodium 2-iodobenzenesulfonate (1b) by Oxone in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydrogen sulfate, in anhydrous acetonitrile at 60 °C. Various alkylbenzenes, including toluenes and ethylbenzenes, several oxygen-containing functionalities substituted alkylbenzenes, and a cyclic benzyl ether could be efficiently oxidized. And, the same reagent system of cat. 1b/Oxone/cat. n-Bu(4)NHSO(4) could be applied to the effective oxidation of alkanes as well.

Uranium(iii) complexes supported by hydrobis(mercaptoimidazolyl)borates: synthesis and oxidation chemistry.

Science.gov (United States)

Maria, Leonor; Santos, Isabel C; Santos, Isabel

2018-05-23

The reaction of [UI3(thf)4] with the sodium or lithium salts of hydrobis(2-mercapto-1-methylimidazolyl)borate ligands ([H(R)B(timMe)2]-) in a 1 : 2 ratio, in tetrahydrofuran, gave the U(iii) complexes [UI{κ3-H,S,S'-H(R)B(timMe)2}2(thf)2] (R = H (1), Ph (2)) in good yields. Crystals of [UI{κ3-H,S,S'-H(Ph)B(timMe)2}2(thf)2] (2) were obtained by recrystallization from a tetrahydrofuran/acetonitrile solution, and the ion-separated uranium complex [U{κ3-H,S,S'-H(Ph)B(timMe)2}2(CH3CN)3][I] (3-I) was obtained by dissolution of 2 in acetonitrile followed by recrystallization. One-electron oxidation of 2 with AgBPh4 or I2 resulted in the formation of the cationic U(iv) complexes [U{κ3-H,S,S'-H(Ph)B(timMe)2}3][X] (X = BPh4 (6-BPh4), I (6-I)), due to a ligand redistribution process. These complexes are the first examples of homoleptic poly(azolyl)borate U(iv) complexes. Treatment of complex 2 with azobenzene led to the isolation of crystals of the U(iv) compound [UI{κ3-H(Ph)B(timMe)2}2(κ2-timMe)] (7). Treatment of 2 with pyridine-N oxide (pyNO) led to the formation of the uranyl complex [UO2{κ2-S,S'-H(Ph)B(timMe)2}2] (8) and of complex 6-I, while from the reaction of [U{κ3-H(Ph)B(timMe)2}2(thf)3][BPh4] (5) with pyNO, the oxo-bridged U(iv) complex [{U{κ3-H(Ph)B(timMe)2}2(pyNO)}2(μ-O)][BPh4]2 (9) was also obtained. In the U(iii) and U(iv) complexes, the bis(azolyl)borate ligands bind to the uranium center in a κ3-H,S,S' coordination mode, while in the U(vi) complex the ligands bind to the metal in a κ2-S,S' mode. The presence of UH-B interactions in the solid-state, for the nine-coordinate complexes 1, 2, 3, 6 and 7 and for the eight-coordinate complex 9, was supported by IR spectroscopy and/or X-ray diffraction analysis.

TEMPERATURE TRENDS OF THE PERMITTIVITY IN COMPLEX OXIDES OF RARE-EARTH ELEMENTS WITH PEROVSKITE-TYPE STRUCTURE

Directory of Open Access Journals (Sweden)

A.G.Belous

2003-01-01

Full Text Available Ceramic materials based on complex oxides with both the perovskite structure (Ln2/3Nb2O6 and the structure of tetragonal tungsten bronze (Ba6-xLn8+2x/3Ti18O54 have been investigated over a wide frequency and temperature ranges. The results obtained for certain structures denote the presence of the temperature anomalies of dielectric parameters (ε, tanδ. These anomalies occur over the wide frequency range including submilimeter (SMM wavelength range, and are related neither with the processing peculiarities nor with the presence of the phase transitions. Temperature behavior of the permittivity has been considered in terms of the polarization mechanism based on the elastic-strain lattice oscillations. It has been assumed that the observed anomalies could be ascribed to a superposition of harmonic and anharmonic contribution to lattice oscillations that determines τε sign and magnitude.

Characterization of pH dependent Mn(II) oxidation strategies and formation of a bixbyite-like phase by Mesorhizobium australicum T-G1

Science.gov (United States)

Bohu, Tsing; Santelli, Cara M; Akob, Denise M.; Neu, Thomas R; Ciobota, Valerian; Rösch, Petra; Popp, Jürgen; Nietzsche, Sándor; Küsel, Kirsten

2015-01-01

Despite the ubiquity of Mn oxides in natural environments, there are only a few observations of biological Mn(II) oxidation at pH MOB) isolates limits our understanding of how pH influences biological Mn(II) oxidation in extreme environments. Here, we report that a novel MOB isolate, Mesorhizobium australicum strain T-G1, isolated from an acidic and metalliferous uranium mining area, can oxidize Mn(II) at both acidic and neutral pH using different enzymatic pathways. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy revealed that T-G1 initiated bixbyite-like Mn oxide formation at pH 5.5 which coincided with multi-copper oxidase expression from early exponential phase to late stationary phase. In contrast, reactive oxygen species (ROS), particularly superoxide, appeared to be more important for T-G1 mediated Mn(II) oxidation at neutral pH. ROS was produced in parallel with the occurrence of Mn(II) oxidation at pH 7.2 from early stationary phase. Solid phase Mn oxides did not precipitate, which is consistent with the presence of a high amount of H2O2 and lower activity of catalase in the liquid culture at pH 7.2. Our results show that M. australicum T-G1, an acid tolerant MOB, can initiate Mn(II) oxidation by varying its oxidation mechanisms depending on the pH and may play an important role in low pH manganese biogeochemical cycling.

Dynamic\tmodelling of catalytic three-phase reactors for hydrogenation and oxidation processes

Directory of Open Access Journals (Sweden)

Salmi T.

2000-01-01

Full Text Available The dynamic modelling principles for typical catalytic three-phase reactors, batch autoclaves and fixed (trickle beds were described. The models consist of balance equations for the catalyst particles as well as for the bulk phases of gas and liquid. Rate equations, transport models and mass balances were coupled to generalized heterogeneous models which were solved with respect to time and space with algorithms suitable for stiff differential equations. The aspects of numerical solution strategies were discussed and the procedure was illustrated with three case studies: hydrogenation of aromatics, hydrogenation of aldehydes and oxidation of ferrosulphate. The case studies revealed the importance of mass transfer resistance inside the catalyst pallets as well as the dynamics of the different phases being present in the reactor. Reliable three-phase reactor simulation and scale-up should be based on dynamic heterogeneous models.

Complex I and complex III inhibition specifically increase cytosolic hydrogen peroxide levels without inducing oxidative stress in HEK293 cells

NARCIS (Netherlands)

Forkink, M.; Basit, F.; Teixeira, J.; Swarts, H.G.; Koopman, W.J.H.; Willems, P.H.G.M.

2015-01-01

Inhibitor studies with isolated mitochondria demonstrated that complex I (CI) and III (CIII) of the electron transport chain (ETC) can act as relevant sources of mitochondrial reactive oxygen species (ROS). Here we studied ROS generation and oxidative stress induction during chronic (24h) inhibition

Algebrodynamics over complex space and phase extension of the Minkowski geometry

International Nuclear Information System (INIS)

Kassandrov, V. V.

2009-01-01

First principles should predetermine physical geometry and dynamics both together. In the 'algebrodynamics' they follow solely from the properties of biquaternion algebra B and the analysis over B. We briefly present the algebrodynamics over Minkowski background based on a nonlinear generalization to B of the Cauchi-Riemann analyticity conditions. Further, we consider the effective real geometry uniquely resulting from the structure of B multiplication and found it to be of the Minkowski type, with an additional phase invariant. Then we pass to study the primordial dynamics that takes place in the complex B space and brings into consideration a number of remarkable structures: an ensemble of identical correlated matter pre-elements ('duplicons'), caustic-like signals (interaction carriers), a concept of random complex time resulting in irreversibility of physical time at macrolevel, etc. In partucular, the concept of 'dimerous electron' naturally arises in the framework of complex algebrodynamics and, together with the above-mentioned phase invariant, allows for a novel approach to explanation of quantum interference phenomena alternative to recently accepted wave-particle dualism paradigm.

Potential Impacts of two SO2 oxidation pathways on regional sulfate concentrations: acqueous-hase oxidation by NO2 and gas-phase oxidation by Stabilized Criegee Intermediates

Science.gov (United States)

We examine the potential impacts of two additional sulfate production pathways using the Community Multiscale Air Quality modeling system. First we evaluate the impact of the aqueous-phase oxidation of S(IV) by nitrogen dioxide using two published rate constants, differing by 1-2...

Characterization of pH dependent Mn(II) oxidation strategies and formation of a bixbyite-like phase by Mesorhizobium australicum T-G1

Science.gov (United States)

Bohu, Tsing; Santelli, Cara M; Akob, Denise M.; Neu, Thomas R; Ciobota, Valerian; Rösch, Petra; Popp, Jürgen; Nietzsche, Sándor; Küsel, Kirsten

2015-01-01

Despite the ubiquity of Mn oxides in natural environments, there are only a few observations of biological Mn(II) oxidation at pH < 6. The lack of low pH Mn-oxidizing bacteria (MOB) isolates limits our understanding of how pH influences biological Mn(II) oxidation in extreme environments. Here, we report that a novel MOB isolate, Mesorhizobium australicum strain T-G1, isolated from an acidic and metalliferous uranium mining area, can oxidize Mn(II) at both acidic and neutral pH using different enzymatic pathways. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy revealed that T-G1 initiated bixbyite-like Mn oxide formation at pH 5.5 which coincided with multi-copper oxidase expression from early exponential phase to late stationary phase. In contrast, reactive oxygen species (ROS), particularly superoxide, appeared to be more important for T-G1 mediated Mn(II) oxidation at neutral pH. ROS was produced in parallel with the occurrence of Mn(II) oxidation at pH 7.2 from early stationary phase. Solid phase Mn oxides did not precipitate, which is consistent with the presence of a high amount of H2O2 and lower activity of catalase in the liquid culture at pH 7.2. Our results show that M. australicum T-G1, an acid tolerant MOB, can initiate Mn(II) oxidation by varying its oxidation mechanisms depending on the pH and may play an important role in low pH manganese biogeochemical cycling.

Study of the degradation of organic molecules complexing radionuclides by using Advanced Oxidation Processes

International Nuclear Information System (INIS)

Rekab, K.

2014-01-01

This research thesis reports the study of the application of two AOPs (Advanced Oxidation Processes) to degrade and mineralise organic molecules which are complexing radio-elements, and thus to allow their concentrations by trapping on mineral matrices. EDTA (ethylene diamine tetraacetic acid) is chosen as reference organic complexing agent for preliminary tests performed with inactive cobalt 59 before addressing actual nuclear effluents with active cobalt 60. The author first presents the industrial context (existing nuclear wastes, notably liquid effluents and their processing) and proposes an overview of the state of the art on adsorption and precipitation of cobalt (natural and radioactive isotope). Then, the author presents the characteristics of the various studied oxides, the photochemical reactor used to perform tests, experimental techniques and operational modes. Results are then presented regarding various issues: adsorption of EDTA and the Co-EDTA complex, and cobalt precipitation; determination of the lamp photon flow by chemical actinometry and by using the Keitz method; efficiency of different processes (UV, UV/TiO 2 , UV/H 2 O 2 ) to degrade EDTA and to degrade the Co-EDTA complex; processing of a nuclear effluent coming from La Hague pools with determination of decontamination factors

Oxidation-induced phase transformations and lifetime limits of chromia-forming nickel-base alloy 625

Energy Technology Data Exchange (ETDEWEB)

Chyrkin, Anton

2011-12-05

For its high creep resistance the commercial nickel-base alloy 625 relies on solid solution strengthening in combination with precipitation hardening by formation of δ-Ni{sub 3}Nb and (Ni,Mo,Si){sub 6}C precipitates during high-temperature service. In oxidizing environments the alloy forms a slow growing, continuous chromia layer on the material surface which protects the alloy against rapid oxidation attack. The growth of the chromia base oxide scale results during exposure at 900-1000 C in oxidation-induced chromium depletion in the subsurface zone of the alloy. Microstructural analyses of the cross-sectioned specimens revealed that this process results in formation of a wide subsurface zone in which the mentioned strengthening phases are dissolved, in spite of the fact that both phases do not contain substantial amounts of the scale-forming element chromium. The cross-sectional analyses revealed that, in parallel to the formation of a precipitate depleted zone, a thin, continuous layer of niobium-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. The Subsurface Phase Enrichment (abbreviated as SPE) was shown to be the result of an uphill-diffusion of niobium, i.e. the element stabilizing the strengthening precipitates δ-Ni{sub 3}Nb, in the chromium activity gradient and is thus a natural consequence of the oxidation-induced chromium depletion beneath the chromia scale. The thermodynamic calculations carried out using the Thermo-Calc/DICTRA software packages revealed that in alloy 625 the chemical activity of niobium decreases with decreasing chromium content. As chromium is being continuously removed from the alloy as the result of the chromia scale growth, the zone of lowest Nb-activity is formed in the location with the lowest chromium concentration, i.e. the scale/alloy interface. This creates a driving force for Nb to diffuse towards the scale/alloy interface against its own concentration gradient, which is known

Oxidation properties of laser clad Nb-Al alloys

International Nuclear Information System (INIS)

Tewari, S.K.; Mazumder, J.

1992-01-01

This paper reports on laser cladding parameters for non-equilibrium synthesis for several ternary and complex Nb-Al base alloys containing Ti, Cr, Si, Ni, B and C that have been established. Phase transformations occurring below 1500 degrees C have been determined using differential thermal analysis. Ductility of the clads is qualitatively evaluated from the extent of cracking around the microhardness indentations. Oxidation resistance of the clads in flowing air is measured at 800 degrees C, 1200 degrees C and 1400 degrees C and parabolic rate constants are calculated. Microstructure of the clads is studied using optical and scanning electron microscopes. X-ray diffraction and EDX techniques are used for identification of the oxides formed and the phases formed in as clad material. Oxide morphology is studied using SEM. Effect of alloying additions on the ductility and oxidation resistance of the laser clad Nb-Al alloys is discussed. The results are compared with those reported in literature for similar alloys produced by conventional processing methods

Symmetry-induced deformation and reconstructive phase transformation in metal-oxide interface: the Fe (001) example

International Nuclear Information System (INIS)

Lahoche, L.; Universite de Technologie de Compiegne; Lorman, V.; Roelandt, J.M.; Rochal, S.B.

1996-01-01

A model is proposed for the structural transformation and corresponding induced deformation in physical three-dimensional interface of the metal-oxide system. The thermodynamical and elastic state of the system is described by the Landau-Ginzbourg free energy. Calculated theoretical phase diagram shows several different types of isothermal growth processes. The model is applied to the case of the oxidation of the (001) Fe surface. (orig.)

Positronium formation studies in crystalline molecular complexes: Triphenylphosphine oxide - Acetanilide

Science.gov (United States)

Oliveira, F. C.; Denadai, A. M. L.; Guerra, L. D. L.; Fulgêncio, F. H.; Windmöller, D.; Santos, G. C.; Fernandes, N. G.; Yoshida, M. I.; Donnici, C. L.; Magalhães, W. F.; Machado, J. C.

2013-04-01

Hydrogen bond formation in the triphenylphosphine oxide (TPPO), acetanilide (ACN) supramolecular heterosynton system, named [TPPO0.5·ACN0.5], has been studied by Positron Annihilation Lifetime Spectroscopy (PALS) and supported by several analytical techniques. In toluene solution, Isothermal Titration Calorimetry (ITC) presented a 1:1 stoichiometry and indicated that the complexation process is driven by entropy, with low enthalpy contribution. X-ray structure determination showed the existence of a three-dimensional network of hydrogen bonds, allowing also the confirmation of the existence of a 1:1 crystalline molecular complex in solid state. The results of thermal analysis (TGA, DTA and DSC) and FTIR spectroscopy showed that the interactions in the complex are relatively weaker than those found in pure precursors, leading to a higher positronium formation probability at [TPPO0.5·ACN0.5]. These weak interactions in the complex enhance the possibility of the n- and π-electrons to interact with positrons and consequently, the probability of positronium formation is higher. Through the present work is shown that PALS is a sensible powerful tool to investigate intermolecular interactions in solid heterosynton supramolecular systems.

Molecular organization and dynamics of micellar phase of polyelectrolyte-surfactant complexes: ESR spin probe study

Science.gov (United States)

Wasserman, A. M.; Kasaikin, V. A.; Zakharova, Yu. A.; Aliev, I. I.; Baranovsky, V. Yu.; Doseva, V.; Yasina, L. L.

2002-04-01

Molecular dynamics and organization of the micellar phase of complexes of linear polyelectrolytes with ionogenic and non-ionogenic surfactants was studied by the ESR spin probe method. Complexes of polyacrylic acid (PAA) and sodium polystyrenesulfonate (PSS) with alkyltrimethylammonium bromides (ATAB), as well as complexes of poly- N, N'-dimethyldiallylammonium chloride (PDACL) with sodium dodecylsulfate (SDS) were studied. The micellar phase of such complexes is highly organized molecular system, molecular ordering of which near the polymeric chain is much higher than in the 'center' of the micelle, it depends on the polymer-detergent interaction, flexibility of polymeric chain and length of carbonic part of the detergent molecule. Complexes of polymethacrylic acid (PMAA) with non-ionic detergent (dodecyl-substituted polyethyleneglycol), show that the local mobility of surfactant in such complexes is significantly lower than in 'free' micelles and depends on the number of micellar particles participating in formation of complexes.

Complex formation in aqueous trimethylamine-N-oxide (TMAO) solutions.

Science.gov (United States)

Hunger, Johannes; Tielrooij, Klaas-Jan; Buchner, Richard; Bonn, Mischa; Bakker, Huib J

2012-04-26

We study aqueous solutions of the amphiphilic osmolyte trimethylamine-N-oxide (TMAO) using broadband dielectric spectroscopy and femtosecond mid-infrared spectroscopy. Both experiments provide strong evidence for distinctively slower rotation dynamics for water molecules interacting with the hydrophobic part of the TMAO molecules. Further, water is found to interact more strongly at the hydrophilic site of the TMAO molecules: we find evidence for the formation of stable, TMAO·2H2O and/or TMAO·3H2O complexes. While this coordination structure seems obvious, the lifetime of these complexes is found to be extraordinarily long (>50 ps). The existence of these long-lived complexes leads to pronounced parallel dipole correlations between water and TMAO, reflected in enhanced amplitudes in the dielectric spectra. The strong interaction between water and TMAO also results in a red-shifted band for the O-D stretching vibration of HDO molecules in an isotopically diluted aqueous TMAO solution. This O-D stretching vibration has a vibrational lifetime of 670 fs, which is significantly shorter than the lifetime of the O-D stretch vibration of bulk-like HDO molecules, presumably due to efficient coupling to vibrational modes of TMAO. The rotational dynamics of these O-D groups are slowed down dramatically, and are limited by the rotation of the whole complex, while the O-D vector oriented away from TMAO probably shows an accelerated reorientation.

Phase transition and computational complexity in a stochastic prime number generator

Energy Technology Data Exchange (ETDEWEB)

Lacasa, L; Luque, B [Departamento de Matematica Aplicada y EstadIstica, ETSI Aeronauticos, Universidad Politecnica de Madrid, Plaza Cardenal Cisneros 3, Madrid 28040 (Spain); Miramontes, O [Departamento de Sistemas Complejos, Instituto de FIsica, Universidad Nacional Autonoma de Mexico, Mexico 01415 DF (Mexico)], E-mail: lucas@dmae.upm.es

2008-02-15

We introduce a prime number generator in the form of a stochastic algorithm. The character of this algorithm gives rise to a continuous phase transition which distinguishes a phase where the algorithm is able to reduce the whole system of numbers into primes and a phase where the system reaches a frozen state with low prime density. In this paper, we firstly present a broader characterization of this phase transition, both in analytical and numerical terms. Critical exponents are calculated, and data collapse is provided. Further on, we redefine the model as a search problem, fitting it in the hallmark of computational complexity theory. We suggest that the system belongs to the class NP. The computational cost is maximal around the threshold, as is common in many algorithmic phase transitions, revealing the presence of an easy-hard-easy pattern. We finally relate the nature of the phase transition to an average-case classification of the problem.

A peroxynitrite complex of copper: formation from a copper-nitrosyl complex, transformation to nitrite and exogenous phenol oxidative coupling or nitration.

Science.gov (United States)

Park, Ga Young; Deepalatha, Subramanian; Puiu, Simona C; Lee, Dong-Heon; Mondal, Biplab; Narducci Sarjeant, Amy A; del Rio, Diego; Pau, Monita Y M; Solomon, Edward I; Karlin, Kenneth D

2009-11-01

Reaction of nitrogen monoxide with a copper(I) complex possessing a tridentate alkylamine ligand gives a Cu(I)-(*NO) adduct, which when exposed to dioxygen generates a peroxynitrite (O=NOO(-))-Cu(II) species. This undergoes thermal transformation to produce a copper(II) nitrito (NO(2) (-)) complex and 0.5 mol equiv O(2). In the presence of a substituted phenol, the peroxynitrite complex effects oxidative coupling, whereas addition of chloride ion to dissociate the peroxynitrite moiety instead leads to phenol ortho nitration. Discussions include the structures (including electronic description) of the copper-nitrosyl and copper-peroxynitrite complexes and the formation of the latter, based on density functional theory calculations and accompanying spectroscopic data.

The formation of non-oxidic oxygen phases on Ru(0001). From the first stages of the oxygen take-up to oxidation

International Nuclear Information System (INIS)

Blume, R.

2005-01-01

The aim of the thesis presented here was the investigation of the formation of non oxidic oxygen phases on the Ru(0001) surface. Smooth and defect rich surfaces were exposed to high oxygen pressures (up to 1 bar) at moderate temperatures (550 K). The characterisation was performed under UHV conditions using Thermal Desorption Spectroscopy (TDS), Scanning Photoemission Microscopy (SPEM), Thermal Energy Atomic Scattering (TEAS), Ultraviolett Photoelectron Spectroscopy (UPS) and Low Energy Electron Diff raction (LEED) as well as In situ by the In Situ X-Ray Photoelectron Spectroscopy (In Situ XPS). The application of this Low Temperature preparation procedure (LT) leads to an Oxygen uptake up to 3 MLE of ''subsurface'' oxygen into a smooth Ru(0001) surface without the typical indications of oxidation (MLE: Monolayer Equivalent). The accumulation of oxygen beneath the surface starts immediatly after the completion of a full chemisorbed layer. Here, the local saturation of the adsorbed oxygen is the decisive step. Diff usion of oxygen directly through the chemisorbed layer only slightly contributes to the overall uptake. Oxygen is mostly accomodated in the vicinity of the surface via surface defects which has been shown on defect rich surfaces created by mild Ar+ sputtering. The maximum oxygen capacity is 10 Atoms/Defect. The uptake is thermally activated with an activation energy of 0.15 eV. The oxygen uptake causes a massive structural change of at least the top two ruthenium layers. Whereas the ruthenium atoms of the first layer are coordinated with up to four, those of the second layer are coordinated with up to two oxygen atoms. These binding condition are metastable and can be changed by annealing the surface. With reaching the desorption temperature two distinct desorption peaks are observed with TDS. For an accumulation of about 0.5 MLE of ''subsurface'' oxygen the desorption proceeds exclusively at the characteristic temperature of the chemisorbed layer at 1040

Characterization of pH dependent Mn(II oxidation strategies and formation of a bixbyite-like phase by Mesorhizobium australicum T-G1

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Tsing eBohu

2015-07-01

Full Text Available Despite the ubiquity of Mn oxides in natural environments, there are only a few observations of biological Mn(II oxidation at pH < 6. The lack of low pH Mn-oxidizing bacteria (MOB isolates limits our understanding of how pH influences biological Mn(II oxidation in extreme environments. Here, we report that a novel MOB isolate, Mesorhizobium australicum strain T-G1, isolated from an acidic and metalliferous uranium mining area, can oxidize Mn(II at both acidic and neutral pH using different enzymatic pathways. X-ray diffraction (XRD, Raman spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS revealed that T-G1 initiated bixbyite-like Mn oxide formation at pH 5.5 which coincided with multi-copper oxidase (MCO expression from early exponential phase to late stationary phase. In contrast, reactive oxygen species (ROS, particularly superoxide, appeared to be more important for T-G1 mediated Mn(II oxidation at neutral pH. ROS was produced in parallel with the occurrence of Mn(II oxidation at pH 7.2 from early stationary phase. Solid phase Mn oxides did not precipitate, which is consistent with the presence of a high amount of H2O2 and lower activity of catalase in the liquid culture at pH 7.2. Our results show that M. australicum T-G1, an acid tolerant MOB, can initiate Mn(II oxidation by varying its oxidation mechanisms depending on the pH and may play an important role in low pH manganese biogeochemical cycling.

Comparison of topotactic fluorination methods for complex oxide films

Energy Technology Data Exchange (ETDEWEB)

Moon, E. J., E-mail: em582@drexel.edu; Choquette, A. K.; Huon, A.; Kulesa, S. Z.; May, S. J., E-mail: smay@coe.drexel.edu [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Barbash, D. [Centralized Research Facilities, Drexel University, Philadelphia, Pennsylvania 19104 (United States)

2015-06-01

We have investigated the synthesis of SrFeO{sub 3−α}F{sub γ} (α and γ ≤ 1) perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride) as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO{sub 2.5} films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

Comparison of topotactic fluorination methods for complex oxide films

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E. J. Moon

2015-06-01

Full Text Available We have investigated the synthesis of SrFeO3−αFγ (α and γ ≤ 1 perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO2.5 films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

Engineering Interfacial Energetics: A Novel Hybrid System of Metal Oxide Quantum Dots and Cobalt Complex for Photocatalytic Water Oxidation

International Nuclear Information System (INIS)

Niu, Fujun; Shen, Shaohua; Wang, Jian; Guo, Liejin

2016-01-01

Graphical abstract: A cobalt complex engineers the interfacial energetics of metal oxide quantum dots (n- or p-type) and electrolytes for highly efficient O_2 generation under visible light irradiation. - Highlights: • A noble-metal-free hybrid photocatalytic system using a single-site cobalt catalyst was developed for O_2 generation. • Considerable activity and excellent stability for O_2 production were achieved by this novel system. • CoSlp engineered the QDs/electrolyte interfacical energetics for efficient hole transfer. - Abstract: Here we reported a novel hybrid photocatalytic water oxidation system, containing metal oxide (n-Fe_2O_3 or p-Co_3O_4) quantum dots (QDs) as light harvester, a salophen cobalt(II) complex (CoSlp) as redox catalyst and persulfate (S_2O_8"2"−) as sacrificial electron acceptor, for oxygen generation from fully aqueous solution. The n-Fe_2O_3 QDs/CoSlp and p-Co_3O_4 QDs/CoSlp systems exhibited good O_2 evolution performances, giving turnover numbers (TONs) of ca. 33 and ca. 35 over CoSlp after visible light irradiation for 72 h, respectively. The excellent photocatalytic performance could be ascribed to the efficient hole transfer from QDs to CoSlp catalyst, leading to reduced photogenerated charge recombination, as well as the CoSlp engineered interfacial band bending of QDs, increasing the driving force or decreasing the energy barrier for hole transfer and then benefiting the following O_2 generation at the QDs/electrolyte interface. The present work successfully demonstrated a novel hybrid system for photocatalytic O_2 evolution from fully aqueous solution; and the essential role of cobalt complexes in engineering the interfacial energetics of semiconductors (n- or p-type) and electrolytes could be informative for designing efficient systems for solar water splitting.

Electron localization in a mixed-valence diniobium benzene complex.

Science.gov (United States)

Gianetti, Thomas L; Nocton, Grégory; Minasian, Stefan G; Kaltsoyannis, Nikolas; Kilcoyne, A L David; Kozimor, Stosh A; Shuh, David K; Tyliszczak, Tolek; Bergman, Robert G; Arnold, John

2015-02-01

Reaction of the neutral diniobium benzene complex {[Nb(BDI)N t Bu] 2 (μ-C 6 H 6 )} (BDI = N , N '-diisopropylbenzene-β-diketiminate) with Ag[B(C 6 F 5 ) 4 ] results in a single electron oxidation to produce a cationic diniobium arene complex, {[Nb(BDI)N t Bu] 2 (μ-C 6 H 6 )}{B(C 6 F 5 ) 4 }. Investigation of the solid state and solution phase structure using single-crystal X-ray diffraction, cyclic voltammetry, magnetic susceptibility, and multinuclear NMR spectroscopy indicates that the oxidation results in an asymmetric molecule with two chemically inequivalent Nb atoms. Further characterization using density functional theory (DFT) calculations, UV-visible, Nb L 3,2 -edge X-ray absorption near-edge structure (XANES), and EPR spectroscopies supports assignment of a diniobium complex, in which one Nb atom carries a single unpaired electron that is not largely delocalized on the second Nb atom. During the oxidative transformation, one electron is removed from the δ-bonding HOMO, which causes a destabilization of the molecule and formation of an asymmetric product. Subsequent reactivity studies indicate that the oxidized product allows access to metal-based chemistry with substrates that did not exhibit reactivity with the starting neutral complex.

Population structure of manganese-oxidizing bacteria in stratified soils and properties of manganese oxide aggregates under manganese-complex medium enrichment.

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Weihong Yang

Full Text Available Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II-oxidizing activities at the range of 1 µM to 240 µM of the equivalent MnO2. The high Mn(II-oxidizing isolates (>50 mM MnO2 were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II-oxidizing bacterial genera (species, namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II to Mn(III/IV by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the

Effect of phase interaction on catalytic CO oxidation over the SnO_2/Al_2O_3 model catalyst

International Nuclear Information System (INIS)

Chai, Shujing; Bai, Xueqin; Li, Jing; Liu, Cheng; Ding, Tong; Tian, Ye; Liu, Chang; Xian, Hui; Mi, Wenbo; Li, Xingang

2017-01-01

Highlights: • Activity for CO oxidation is greatly enhanced by interaction between SnO_2 and Al_2O_3. • Interaction between SnO_2 and Al_2O_3 phases can generate oxygen vacancies. • Oxygen vacancies play an import role for catalytic CO oxidation. • Sn"4"+ cations are the effective sites for catalytic CO oxidation. • Langmuir-Hinshelwood model is preferred for catalytic CO oxidation. - Abstract: We investigated the catalytic CO oxidation over the SnO_2/Al_2O_3 model catalysts. Our results show that interaction between the Al_2O_3 and SnO_2 phases results in the significantly improved catalytic activity because of the formation of the oxygen vacancies. The oxygen storage capacity of the SnO_2/Al_2O_3 catalyst prepared by the physically mixed method is nearly two times higher than that of the SnO_2, which probably results from the change of electron concentration on the interface of the SnO_2 and Al_2O_3 phases. Introducing water vapor to the feeding gas would a little decrease the activity of the catalysts, but the reaction rate could completely recover after removal of water vapor. The kinetics results suggest that the surface Sn"4"+ cations are effective CO adsorptive sites, and the surface adsorbed oxygen plays an important role upon CO oxidation. The reaction pathways upon the SnO_2-based catalysts for CO oxidation follow the Langmuir-Hinshelwood model.

Partitioning of metals in different binding phases of tropical estuarine sediments: importance of metal chemistry

Digital Repository Service at National Institute of Oceanography (India)

Chakraborty, P.; Chakraborty, S.; Vudamala, K.; Sarkar, Arindam; Nath, B.N.

association with Fe/Mn oxide phases followed by Ni and Cu. Faster k_-w of Cu (II) (1×10⁹ s^-1) increased the rate of complex formation of Cu²⁺ ion with ligand in the organic phases. The Cu–ligand (from organic phase...

Microstructure and Oxidation of a MAX Phase/Superalloy Hybrid Interface

Science.gov (United States)

Smialek, James L.; Garg, Anita

2014-01-01

Corrosion resistant, strain tolerant MAX phase coatings are of interest for turbine applications. Thin Cr2AlC MAX phase wafers were vacuum diffusion bonded to an advanced turbine disk alloy, LSHR, at 1100 C. The interface, examined by optical and scanning electron microscopy, revealed a primary diffusion zone consisting of 10 micrometers of beta-Ni(Co)Al, decorated with various NiCoCrAl, MC and M3B2 precipitates. On the Cr2AlC side, an additional 40 micrometers Al-depletion zone of Cr7C3 formed in an interconnected network with the beta-Ni(Co)Al. Oxidation of an exposed edge at 800 C for 100 h produced a fine-grained lenticular alumina scale over Cr2AlC and beta-Ni(Co)Al, with coarser chromia granules over the Cr7C3 regions. Subsequent growth of the diffusion layers was only 5 micrometers in total. A residual stress of 500 MPa was estimated for the MAX phase layer, but no interfacial damage was observed. Subsequent tests for 1000 h reveal similar results.

Oxidation of Bromide to Bromine by Ruthenium(II) Bipyridine-Type Complexes Using the Flash-Quench Technique.

Science.gov (United States)

Tsai, Kelvin Yun-Da; Chang, I-Jy

2017-07-17

Six ruthenium complexes, [Ru(bpy) 3 ] 2+ (1), [Ru(bpy) 2 (deeb)] 2+ (2), [Ru(deeb) 2 (dmbpy)] 2+ (3), [Ru(deeb) 2 (bpy)] 2+ (4), [Ru(deeb) 3 ] 2+ (5), and [Ru(deeb) 2 (bpz)] 2+ (6) (bpy: 2,2'-bipyridine; deeb: 4,4'-diethylester-2,2'-bipyridine; dmbpy: 4,4'-dimethyl-2,2'-bipyridine, bpz: 2,2'-bipyrazine), have been employed to sensitize photochemical oxidation of bromide to bromine. The oxidation potential for complexes 1-6 are 1.26, 1.36, 1.42, 1.46, 1.56, and 1.66 V vs SCE, respectively. The bimolecular rate constants for the quenching of complexes 1-6 by ArN 2 + (bromobenzenediazonium) are determined as 1.1 × 10 9 , 1.6 × 10 8 , 1.4 × 10 8 , 1.2 × 10 8 , 6.4 × 10 7 , and 8.9 × 10 6 M -1 s -1 , respectively. Transient kinetics indicated that Br - reacted with photogenerated Ru(III) species at different rates. Bimolecular rate constants for the oxidation of Br - by the Ru(III) species derived from complexes 1-5 are observed as 1.2 × 10 8 , 1.3 × 10 9 , 4.0 × 10 9 , 4.8 × 10 9 , and 1.1 × 10 10 , M -1 s -1 , respectively. The last reaction kinetics observed in the three-component system consisting of a Ru sensitizer, quencher, and bromide is shown to be independent of the Ru sensitizer. The final product was identified as bromine by its reaction with hexene. The last reaction kinetics is assigned to the disproportionation reaction of Br 2 -• ions, for which the rate constant is determined as 5 × 10 9 M -1 s -1 . Though complex 6 has the highest oxidation potential in the Ru(II)/Ru(III) couple, its excited state fails to react with ArN 2 + sufficiently for subsequent reactions. The Ru(III) species derived from complex 1 reacts with Br - at the slowest rate. Complexes 2-5 are excellent photosensitizers to drive photooxidation of bromide to bromine.

Peculiarities in film growth of ferroelectric complex oxides in ion-plasma sputtering

International Nuclear Information System (INIS)

Mukhortov, V.M.; Golovko, Yu.I.; Mukhortov, Vl.M.; Dudkevich, V.P.

1981-01-01

Experimental investigation into the process of complex oxide film growth (using BaTiO 3 and (Ba,Sr)TiO 3 as an example) during ion-plasma sputtering has been carried out. It is shown that neutral excited atoms are knocked out of a ceramic target during its ion bombardment. Removing from the target they loss energy at the expence of collisions and at some distance hsub(cr) the oxidation reaction (BaO, TiO, TiO 2 , SrO) becomes possible. So the ''construction'' material comes in either in the form of atoms or in the form of molecules of simple oxides depending on a distance between cathode and substrate. Two mechanisms of synthesis and crystallization distinguished with dependences of growth rate, elementary cell parameters and other structure characteristics on precipitation temperature correspond to two precipitation mechanisms. Part of re-evaporation and reduction processes is discussed [ru

Kinetic studies on the oxidation of oxyhemoglobin by biologically active iron thiosemicarbazone complexes: relevance to iron-chelator-induced methemoglobinemia.

Science.gov (United States)

Basha, Maram T; Rodríguez, Carlos; Richardson, Des R; Martínez, Manuel; Bernhardt, Paul V

2014-03-01

The oxidation of oxyhemoglobin to methemoglobin has been found to be facilitated by low molecular weight iron(III) thiosemicarbazone complexes. This deleterious reaction, which produces hemoglobin protein units unable to bind dioxygen and occurs during the administration of iron chelators such as the well-known 3-aminopyridine-2-pyridinecarbaldehyde thiosemicarbazone (3-AP; Triapine), has been observed in the reaction with Fe(III) complexes of some members of the 3-AP structurally-related thiosemicarbazone ligands derived from di-2-pyridyl ketone (HDpxxT series). We have studied the kinetics of this oxidation reaction in vitro using human hemoglobin and found that the reaction proceeds with two distinct time-resolved steps. These have been associated with sequential oxidation of the two different oxyheme cofactors in the α and β protein chains. Unexpected steric and hydrogen-bonding effects on the Fe(III) complexes appear to be the responsible for the observed differences in the reaction rate across the series of HDpxxT ligand complexes used in this study.

Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

International Nuclear Information System (INIS)

Comes, Ryan; Liu Hongxue; Lu Jiwei; Gu, Man; Khokhlov, Mikhail; Wolf, Stuart A.

2013-01-01

Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

Highly efficient one-step synthesis of carbon encapsulated nanocrystals by the oxidation of metal π-complexes

Science.gov (United States)

Liu, Boyang; Shao, Yingfeng; Xiang, Xin; Zhang, Fuhua; Yan, Shengchang; Li, Wenge

2017-08-01

Various carbon encapsulated nanocrystals, including MnS and MnO, Cr2O3, MoO2, Fe7S8 and Fe3O4, and ZrO2, are prepared in one step and in situ by a simple and highly efficient synthesis approach. The nanocrystals have an equiaxed morphology and a median size smaller than 30 nm. Tens and hundreds of these nanocrystals are entirely encapsulated by a wormlike amorphous carbon shell. The formation of a core-shell structure depends on the strongly exothermic reaction of metal π-complexes with ammonium persulfate in an autoclave at below 200 °C. During the oxidation process, the generated significant amounts of heat will destroy the molecular structure of the metal π-complex and cleave the ligands into small carbon fragments, which further transform into an amorphous carbon shell. The central metal atoms are oxidized to metal oxide/sulfide nanocrystals. The formation of a core-shell structure is independent of the numbers of ligands and carbon atoms as well as the metal types, implying that any metal π-complex can serve as a precursor and that various carbon encapsulated nanocrystals can be synthesized by this method.

The influence of surfactant on the synthesis of gamma ferric oxide: implications on phase composition and magnetic properties

International Nuclear Information System (INIS)

Narasimhan, B.R.V.; Prabhakar, S.; Manohar, P.; Gnanam, F.D.

2002-01-01

It has already been established that ferrous carbonate precipitated from the reaction of ferrous sulphate and sodium carbonate, on direct thermal decomposition yields gamma ferric oxide. The present work describes the effect of sodium lauryl sulphate (Sodium dodecyl sulphate) on the synthesis of gamma ferric oxide when it is introduced during the precipitation of ferrous carbonate. Since ferrous carbonate undergoes rapid oxidation on standing in air, the extent of oxidation in presence of sodium lauryl sulphate is also studied using oxidation-reduction potential measurements. The ferric oxide powders are characterized for phase analysis (XRD), magnetic properties (VSM) and particle size analysis. (author)

Kinetics of the gas-phase tritium oxidation reaction

International Nuclear Information System (INIS)

Failor, R.A.

1989-01-01

Homogeneous gas-phase kinetics of tritium oxidation (2T 2 + O 2 →2T 2 O) have been studied with a model that accounts explicitly for radiolysis of the major species and the kinetics of the subsequent reactions of ionic, excited-state, and neutral species. Results from model calculations are given for 10 -4 -1.0 mol% T 2 in O 2 (298 K, 1 atm). As the reaction evolves three different mechanisms control T 2 O production, each with a different overall rate expression and a different order with respect to the T 2 concentration. The effects of self-radiolysis of pure T 2 on the tritium oxidation reaction were calculated. Tritium atoms, the primary product of T 2 self-radiolysis, altered the oxidation mechanism only during the first few seconds following the initiation of the T 2 -O 2 reaction. Ozone, an important intermediate in T 2 oxidation, was monitored in-situ by U.V. absorption spectroscopy for 0.01-1.0 mol% T 2 an 1 atm O 2 . The shape of the experimental ozone time profile agreed with the model predictions. As predicted, the measured initial rate of ozone production varied linearly with initial T 2 concentration ([T 2 ] 0.6 o ), but at an initial rate one-third the predicted value. The steady-state ozone concentration ([O 3 ]ss) was predicted to be dependent on [T 2 ] 0.3 o , but the measured value was [T 2 ] 0.6 o , resulting in four times higher [O 3 ]ss than predicted for a 1.0% T 2 -O 2 mixture. Adding H 2 to the T 2 -O 2 mixture, to provide insight into the differences between the radiolytic and chemical behavior of the tritium, produced a greater decrease in [O 3 ]ss than predicted. Adjusting the reaction cell surface-to-volume ratio showed implications of minor surface removal of ozone

Deteriorated stress response in stationary-phase yeast: Sir2 and Yap1 are essential for Hsf1 activation by heat shock and oxidative stress, respectively.

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Inbal Nussbaum

Full Text Available Stationary-phase cultures have been used as an important model of aging, a complex process involving multiple pathways and signaling networks. However, the molecular processes underlying stress response of non-dividing cells are poorly understood, although deteriorated stress response is one of the hallmarks of aging. The budding yeast Saccharomyces cerevisiae is a valuable model organism to study the genetics of aging, because yeast ages within days and are amenable to genetic manipulations. As a unicellular organism, yeast has evolved robust systems to respond to environmental challenges. This response is orchestrated largely by the conserved transcription factor Hsf1, which in S. cerevisiae regulates expression of multiple genes in response to diverse stresses. Here we demonstrate that Hsf1 response to heat shock and oxidative stress deteriorates during yeast transition from exponential growth to stationary-phase, whereas Hsf1 activation by glucose starvation is maintained. Overexpressing Hsf1 does not significantly improve heat shock response, indicating that Hsf1 dwindling is not the major cause for Hsf1 attenuated response in stationary-phase yeast. Rather, factors that participate in Hsf1 activation appear to be compromised. We uncover two factors, Yap1 and Sir2, which discretely function in Hsf1 activation by oxidative stress and heat shock. In Δyap1 mutant, Hsf1 does not respond to oxidative stress, while in Δsir2 mutant, Hsf1 does not respond to heat shock. Moreover, excess Sir2 mimics the heat shock response. This role of the NAD+-dependent Sir2 is supported by our finding that supplementing NAD+ precursors improves Hsf1 heat shock response in stationary-phase yeast, especially when combined with expression of excess Sir2. Finally, the combination of excess Hsf1, excess Sir2 and NAD+ precursors rejuvenates the heat shock response.

Deteriorated stress response in stationary-phase yeast: Sir2 and Yap1 are essential for Hsf1 activation by heat shock and oxidative stress, respectively.

Science.gov (United States)

Nussbaum, Inbal; Weindling, Esther; Jubran, Ritta; Cohen, Aviv; Bar-Nun, Shoshana

2014-01-01

Stationary-phase cultures have been used as an important model of aging, a complex process involving multiple pathways and signaling networks. However, the molecular processes underlying stress response of non-dividing cells are poorly understood, although deteriorated stress response is one of the hallmarks of aging. The budding yeast Saccharomyces cerevisiae is a valuable model organism to study the genetics of aging, because yeast ages within days and are amenable to genetic manipulations. As a unicellular organism, yeast has evolved robust systems to respond to environmental challenges. This response is orchestrated largely by the conserved transcription factor Hsf1, which in S. cerevisiae regulates expression of multiple genes in response to diverse stresses. Here we demonstrate that Hsf1 response to heat shock and oxidative stress deteriorates during yeast transition from exponential growth to stationary-phase, whereas Hsf1 activation by glucose starvation is maintained. Overexpressing Hsf1 does not significantly improve heat shock response, indicating that Hsf1 dwindling is not the major cause for Hsf1 attenuated response in stationary-phase yeast. Rather, factors that participate in Hsf1 activation appear to be compromised. We uncover two factors, Yap1 and Sir2, which discretely function in Hsf1 activation by oxidative stress and heat shock. In Δyap1 mutant, Hsf1 does not respond to oxidative stress, while in Δsir2 mutant, Hsf1 does not respond to heat shock. Moreover, excess Sir2 mimics the heat shock response. This role of the NAD+-dependent Sir2 is supported by our finding that supplementing NAD+ precursors improves Hsf1 heat shock response in stationary-phase yeast, especially when combined with expression of excess Sir2. Finally, the combination of excess Hsf1, excess Sir2 and NAD+ precursors rejuvenates the heat shock response.

Oxidative stress accumulates in adipose tissue during aging and inhibits adipogenesis.

Science.gov (United States)

Findeisen, Hannes M; Pearson, Kevin J; Gizard, Florence; Zhao, Yue; Qing, Hua; Jones, Karrie L; Cohn, Dianne; Heywood, Elizabeth B; de Cabo, Rafael; Bruemmer, Dennis

2011-04-14

Aging constitutes a major independent risk factor for the development of type 2 diabetes and is accompanied by insulin resistance and adipose tissue dysfunction. One of the most important factors implicitly linked to aging and age-related chronic diseases is the accumulation of oxidative stress. However, the effect of increased oxidative stress on adipose tissue biology remains elusive. In this study, we demonstrate that aging in mice results in a loss of fat mass and the accumulation of oxidative stress in adipose tissue. In vitro, increased oxidative stress through glutathione depletion inhibits preadipocyte differentiation. This inhibition of adipogenesis is at least in part the result of reduced cell proliferation and an inhibition of G(1)→S-phase transition during the initial mitotic clonal expansion of the adipocyte differentiation process. While phosphorylation of the retinoblastoma protein (Rb) by cyclin/cdk complexes remains unaffected, oxidative stress decreases the expression of S-phase genes downstream of Rb. This silencing of S phase gene expression by increased oxidative stress is mediated through a transcriptional mechanism involving the inhibition of E2F recruitment and transactivation of its target promoters. Collectively, these data demonstrate a previously unrecognized role of oxidative stress in the regulation of adipogenesis which may contribute to age-associated adipose tissue dysfunction.

Synthesis, structures, and luminescent properties of lanthanide complexes with triphenylphospine oxide

Energy Technology Data Exchange (ETDEWEB)

Ma, Yan; Xu, Shan; Wang, Xin; Li, Yue-Xue; Jin, Qiong-Hua [Department of Chemistry, Capital Normal University, Beijing (China); Liu, Min [The College of Materials Science and Engineering, Beijing University of Technology (China); Xin, Xiu-Lan [School of Food and Chemical Engineering, Beijing Technology and Business University (China)

2017-07-03

Seven lanthanide complexes [Ln(OPPh{sub 3}){sub 3}(NO{sub 3}){sub 3}] (1-3) (OPPh{sub 3} = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}) (4), [Ln(OPPh{sub 3}){sub 3}(NO{sub 3}){sub 3}]{sub 2} (5-7) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh{sub 3} ligand in the air. These complexes were characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1-4 are mononuclear complexes formed by OPPh{sub 3} ligands and nitrates. The asymmetric units of complexes 5-7 consist of two crystallographic-separate molecules. Complex 1 is self-assembled to construct a 2D layer-structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain-like structure that was assembled by OPPh{sub 3} ligands and nitrate ions through C-H..O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb{sup 3+} (λ{sub em} = 480, 574 nm) and Eu{sup 3+} (λ{sub em} = 552, 593, 619, 668 nm). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Kinetics of Oxidation of Cobalt(III Complexes of a Acids by Hydrogen Peroxide in the Presence of Surfactants

Directory of Open Access Journals (Sweden)

Mansur Ahmed

2008-01-01

Full Text Available Hydrogen peroxide oxidation of pentaamminecobalt(III complexes of α-hydroxy acids at 35°C in micellar medium has been attempted. In this reaction the rate of oxidation shows first order kinetics each in [cobalt(III] and [H2O2]. Hydrogen peroxide induced electron transfer in [(NH35 CoIII-L]2+ complexes of α-hydroxy acids readily yields 100% of cobalt(II with nearly 100% of C-C bond cleavage products suggesting that it behaves mainly as one equivalent oxidant in micellar medium. With unbound ligand also it behaves only as C-C cleavage agent rather than C-H cleavage agent. With increasing micellar concentration an increase in the rate is observed.

Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma

International Nuclear Information System (INIS)

Yar, Mazher Ahmed; Wahlberg, Sverker; Bergqvist, Hans; Salem, Hanadi G.; Johnsson, Mats; Muhammed, Mamoun

2011-01-01

High purity W and W-0.9La 2 O 3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 o C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals.

Knocking on wood: base metal complexes as catalysts for selective oxidation of lignin models and extracts.

Science.gov (United States)

Hanson, Susan K; Baker, R Tom

2015-07-21

This work began as part of a biomass conversion catalysis project with UC Santa Barbara funded by the first NSF Chemical Bonding Center, CATSB. Recognizing that catalytic aerobic oxidation of diol C-C bonds could potentially be used to break down lignocellulose, we began to synthesize oxovanadium complexes and explore their fundamental reactivity. Of course there were theories regarding the oxidation mechanism, but our mechanistic studies soon revealed a number of surprises of the type that keep all chemists coming back to the bench! We realized that these reactions were also exciting in that they actually used the oxygen-on-every-carbon property of biomass-derived molecules to control the selectivity of the oxidation. When we found that these oxovanadium complexes tended to convert sugars predominantly to formic acid and carbon dioxide, we replaced one of the OH groups with an ether and entered the dark world of lignin chemistry. In this Account, we summarize results from our collaboration and from our individual labs. In particular, we show that oxidation selectivity (C-C vs C-O bond cleavage) of lignin models using air and vanadium complexes depends on the ancillary ligands, the reaction solvent, and the substrate structure (i.e., phenolic vs non-phenolic). Selected vanadium complexes in the presence of added base serve as effective alcohol oxidation catalysts via a novel base-assisted dehydrogenation pathway. In contrast, copper catalysts effect direct C-C bond cleavage of these lignin models, presumably through a radical pathway. The most active vanadium catalyst exhibits unique activity for the depolymerization of organosolv lignin. After Weckhuysen's excellent 2010 review on lignin valorization, the number of catalysis studies and approaches on both lignin models and extracts has expanded rapidly. Today we are seeing new start-ups and lignin production facilities sprouting up across the globe as we all work to prove wrong the old pulp and paper chemist

Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber

Directory of Open Access Journals (Sweden)

Wei Zheng

2015-12-01

Full Text Available Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La complex were added as a filler to form natural rubber (NR composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR and thermogravimetric analysis (TGA, a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD.

Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber.

Science.gov (United States)

Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W; Wu, Sizhu

2015-12-01

Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and thermogravimetric analysis (TGA), a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT) calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD.

Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber

Science.gov (United States)

Zheng, Wei; Liu, Li; Zhao, Xiuying; He, Jingwei; Wang, Ao; Chan, Tung W.; Wu, Sizhu

2015-01-01

Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La) complex were added as a filler to form natural rubber (NR) composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and thermogravimetric analysis (TGA), a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT) calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD. PMID:26693513

Oxidative Stress in Patients with Drug Resistant Partial Complex Seizure

Directory of Open Access Journals (Sweden)

Lourdes Lorigados Pedre

2018-06-01

Full Text Available Oxidative stress (OS has been implicated as a pathophysiological mechanism of drug-resistant epilepsy, but little is known about the relationship between OS markers and clinical parameters, such as the number of drugs, age onset of seizure and frequency of seizures per month. The current study’s aim was to evaluate several oxidative stress markers and antioxidants in 18 drug-resistant partial complex seizure (DRPCS patients compared to a control group (age and sex matched, and the results were related to clinical variables. We examined malondialdehyde (MDA, advanced oxidation protein products (AOPP, advanced glycation end products (AGEs, nitric oxide (NO, uric acid, superoxide dismutase (SOD, glutathione, vitamin C, 4-hydroxy-2-nonenal (4-HNE and nitrotyrosine (3-NT. All markers except 4-HNE and 3-NT were studied by spectrophotometry. The expressions of 4-HNE and 3-NT were evaluated by Western blot analysis. MDA levels in patients were significantly increased (p ≤ 0.0001 while AOPP levels were similar to the control group. AGEs, NO and uric acid concentrations were significantly decreased (p ≤ 0.004, p ≤ 0.005, p ≤ 0.0001, respectively. Expressions of 3-NT and 4-HNE were increased (p ≤ 0.005 similarly to SOD activity (p = 0.0001, whereas vitamin C was considerably diminished (p = 0.0001. Glutathione levels were similar to the control group. There was a positive correlation between NO and MDA with the number of drugs. The expression of 3-NT was positively related with the frequency of seizures per month. There was a negative relationship between MDA and age at onset of seizures, as well as vitamin C with seizure frequency/month. We detected an imbalance in the redox state in patients with DRCPS, supporting oxidative stress as a relevant mechanism in this pathology. Thus, it is apparent that some oxidant and antioxidant parameters are closely linked with clinical variables.

Application of advanced oxidation processes for cleaning of industrial water generated in wet dedusting of shaft furnace gases.

Science.gov (United States)

Czaplicka, Marianna; Kurowski, Ryszard; Jaworek, Katarzyna; Bratek, Łukasz

2013-01-01

The paper presents results of studies into advanced oxidation processes in 03 and 03/UV systems. An advanced oxidation process (AOP) was conducted to reduce the load of impurities in circulating waters from wet de-dusting of shaft furnace gases. Besides inorganic impurities, i.e. mainly arsenic compounds (16 g As L(-1) on average), lead, zinc, chlorides and sulphates, the waters also contain some organic material. The organic material is composed of a complex mixture that contains, amongst others, aliphatic compounds, phenol and its derivatives, pyridine bases, including pyridine, and its derivatives. The test results show degradation of organic and inorganic compounds during ozonation and photo-oxidation processes. Analysis of the solutions from the processes demonstrated that the complex organic material in the industrial water was oxidized in ozonation and in photo-oxidation, which resulted in formation of aldehydes and carboxylic acids. Kinetic degradation of selected pollutants is presented. Obtained results indicated that the O3/UV process is more effective in degradation of organic matter than ozonation. Depending on the process type, precipitation of the solid phase was observed. The efficiency of solid-phase formation was higher in photo-oxidation with ozone. It was found that the precipitated solid phase is composed mainly of arsenic, iron and oxygen.

Characterizing oxidative flow reactor SOA production and OH radical exposure from laboratory experiments of complex mixtures (engine exhaust) and simple precursors (monoterpenes)

Science.gov (United States)

Michael Link, M. L.; Friedman, B.; Ortega, J. V.; Son, J.; Kim, J.; Park, G.; Park, T.; Kim, K.; Lee, T.; Farmer, D.

2016-12-01

Recent commercialization of the Oxidative Flow Reactor (OFR, occasionally described in the literature as a "Potential Aerosol Mass") has created the opportunity for many researchers to explore the mechanisms behind OH-driven aerosol formation on a wide range of oxidative timescales (hours to weeks) in both laboratory and field measurements. These experiments have been conducted in both laboratory and field settings, including simple (i.e. single component) and complex (multi-component) precursors. Standard practices for performing OFR experiments, and interpreting data from the measurements, are still being developed. Measurement of gas and particle phase chemistry, from oxidation products generated in the OFR, through laboratory studies on single precursors and the measurement of SOA from vehicle emissions on short atmospheric timescales represent two very different experiments in which careful experimental design is essential for exploring reaction mechanisms and SOA yields. Two parameters essential in experimental design are (1) the role of seed aerosol in controlling gas-particle partitioning and SOA yields, and (2) the accurate determination of OH exposure during any one experiment. We investigated the role of seed aerosol surface area in controlling the observed SOA yields and gas/particle composition from the OH-initiated oxidation of four monoterpenes using an aerosol chemical ionization time-of-flight mass spectrometer and scanning mobility particle sizer. While the OH exposure during laboratory experiments is simple to constrain, complex mixtures such as diesel exhaust have high estimated OH reactivity values, and thus require careful consideration. We developed methods for constraining OH radical exposure in the OFR during vehicle exhaust oxidation experiments. We observe changes in O/C ratios and highly functionalized species over the temperature gradient employed in the aerosol-CIMS measurement. We relate this observed, speciated chemistry to the

submitter Aqueous phase oxidation of sulphur dioxide by ozone in cloud droplets

CERN Document Server

Hoyle, C R; Järvinen, E; Saathoff, H; Dias, A; El Haddad, I; Gysel, M; Coburn, S C; Tröstl, J; Bernhammer, A -K; Bianchi, F; Breitenlechner, M; Corbin, J C; Craven, J; Donahue, N M; Duplissy, J; Ehrhart, S; Frege, C; Gordon, H; Höppel, N; Heinritzi, M; Kristensen, T B; Molteni, U; Nichman, L; Pinterich, T; Prévôt, A S H; Simon, M; Slowik, J G; Steiner, G; Tomé, A; Vogel, A L; Volkamer, R; Wagner, A C; Wagner, R; Wexler, A S; Williamson, C; Winkler, P M; Yan, C; Amorim, A; Dommen, J; Curtius, J; Gallagher, M W; Flagan, R C; Hansel, A; Kirkby, J; Kulmala, M; Möhler, O; Stratmann, F; Worsnop, D R; Baltensperger, U

2016-01-01

The growth of aerosol due to the aqueous phase oxidation of sulfur dioxide by ozone was measured in laboratory-generated clouds created in the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN). Experiments were performed at 10 and −10 °C, on acidic (sulfuric acid) and on partially to fully neutralised (ammonium sulfate) seed aerosol. Clouds were generated by performing an adiabatic expansion – pressurising the chamber to 220 hPa above atmospheric pressure, and then rapidly releasing the excess pressure, resulting in a cooling, condensation of water on the aerosol and a cloud lifetime of approximately 6 min. A model was developed to compare the observed aerosol growth with that predicted using oxidation rate constants previously measured in bulk solutions. The model captured the measured aerosol growth very well for experiments performed at 10 and −10 °C, indicating that, in contrast to some previous studies, the oxidation rates of SO2 in ...

The effect on phase separation of the oxidation state of molybdenum in a Na2O-B2O3-SiO2 glass

International Nuclear Information System (INIS)

Kawamoto, Y.; Clemens, K.; Tomozawa, M.; Warden, J.T.

1981-01-01

The effect of oxidation state on phase separation was studied for 13Na 2 O, 49B 2 O 3 , 38SiO 2 (mol%) glasses containing 1 mol% Mo oxide. The glasses were melted under various conditions to vary the oxidation states of Mo ions. The oxidation states of Mo ions were determined by chemical analysis and ESR. The crystallisation tendency, the immiscibility temperature, and the phase separation morphology of the glasses were examined by DTA, x-ray diffraction, opalescence method, and replica electron microscopy. Glasses containing Mo 4+ ions have a great tendency to precipitate MoO 2 crystals. The immiscibility temperature of glass goes through a minimum when the oxidation states of Mo ions are changed. It was suggested that there is an optimum oxidation state to prevent crystallisation and to suppress the phase separation tendency of this system. (author)

Oxidative Reactivity and Cytotoxic Properties of a Platinum(II) Complex Prepared by Outer-Sphere Amide Bond Coupling

Science.gov (United States)

Wilson, Justin J.; Lippard, Stephen J.

2012-01-01

Benzyl amine was coupled to the dangling carboxylic acid groups of the platinum(II) complex [Pt(edda)Cl2], where edda = ethylenediamine-N,N’-diacetic acid, to give the diamidetethered complex [Pt(L)Cl2] (1), where L = ethylenediamine-N,N’-bis(N-benzylacetamide). Complex 1 was oxidized with both PhICl2 and Br2. Oxidation with PhICl2 cleanly afforded the tetrachloride complex, [Pt(L)Cl4] (2), whereas oxidation with Br2 gave rise to several mixed halide complexes of the general formula, [Pt(L)ClxBr4-x], where x = 1, 2, or 3. Complexes 1 and 2 were fully characterized by 1H, 13C, and 195Pt NMR spectroscopy, as well as by ESI-MS. These compounds exist as a mixture of diastereomers that arise from the chirality of the two coordinated nitrogen atoms. Crystal structures of 1, 2, and [Pt(L)ClxBry] (3) are reported. Although refined as the tetrabromide complex [Pt(L)Br4], the crystal structure of 3 is a mixture of species with site-occupancy disorder of chloride and bromide ligands. DFT calculations indicate that the two sets of diastereomers of 1 and 2 are effectively thermoneutral, a conclusion that is also supported by the observation of both members of each pair by NMR spectroscopy. The cytotoxicity of 1 and 2 was measured by the MTT assay in HeLa cells and compared to that of cisplatin. Both exhibit IC50 values close to 50 μM and are therefore substantially less toxic than cisplatin, for which the IC50 is 1 μM. PMID:24489429

Synthesis and characterization of lanthanide picrate complexes with 4-picoline-N-oxide (4-pic N O)

International Nuclear Information System (INIS)

Silva, E.M. da.

1991-01-01

The lanthanide picrate complexes with 4-picoline-N-oxide were obtained from ethanolic solutions of the hydrated lanthanide picrate and the ligand. The lanthanide content was determined by complexometric titration with EDTA. Carbon, Nitrogen and Hydrogen were determined by microanalytical procedures. Chemical analysis of the lanthanide picrate complexes are also presented. (author)

Complex catalysts from self-repairing ensembles to highly reactive air-based oxidation systems

Science.gov (United States)

Craig L. Hill; Laurent Delannoy; Dean C. Duncan; Ira A. Weinstock; Roman F. Renneke; Richard S. Reiner; Rajai H. Atalla; Jong Woo Han; Daniel A. Hillesheim; Rui Cao; Travis M. Anderson; Nelya M. Okun; Djamaladdin G. Musaev; Yurii V. Geletii

2007-01-01

Progress in four interrelated catalysis research efforts in our laboratory are summarized: (1) catalytic photochemical functionalization of unactivated CeH bonds by polyoxometalates (POMs); (2) self-repairing catalysts; (3) catalysts for air-based oxidations under ambient conditions; and (4) terminal oxo complexes of the late-transition metal elements and their...

Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

Energy Technology Data Exchange (ETDEWEB)

Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.; Piro, Nicholas A.; Carroll, Patrick J.; Booth, Corwin H.; Schelter, Eric J.

2014-06-25

Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

Oxidation behaviour of Ti2AIN films composed mainly of nanolaminated MAX phase.

Science.gov (United States)

Wang, Q M; Garkas, W; Renteria, A Flores; Leyens, C; Kim, K H

2011-10-01

In this paper, we reported the oxidation behaviour of Ti2AIN films on polycrystalline Al2O3 substrates. The Ti2AIN films composed mainly of nanolaminated MAX phase was obtained by first depositing Ti-Al-N films using reactive sputtering of two elemental Ti and Al targets in Ar/N2 atmosphere and subsequent vacuum annealing at 800 degrees C for 1 h. The Ti2AIN films exhibited excellent oxidation resistance and thermal stability at 600-900 degrees C in air. Very low mass gain was observed. At low temperature (600 degrees C), no oxide crystals were observed on film surface. Blade-like Theta-Al2O3 fine crystals formed on film surfaces at 700-800 degrees C. At high temperature (900 degrees C), firstly Theta-Al2O3 formed on film surface and then transformed into alpha-Al2O3. At 700-900 degrees C, a continuous Al2O3 layer formed on Ti2AIN films surface, acting as diffusion barrier preventing further oxidation attack. The mechanism of the excellent oxidation resistance of Ti2AIN films was discussed based on the experimental results.

Thin-film transistors with a channel composed of semiconducting metal oxide nanoparticles deposited from the gas phase

International Nuclear Information System (INIS)

Busch, C.; Schierning, G.; Theissmann, R.; Nedic, A.; Kruis, F. E.; Schmechel, R.

2012-01-01

The fabrication of semiconducting functional layers using low-temperature processes is of high interest for flexible printable electronics applications. Here, the one-step deposition of semiconducting nanoparticles from the gas phase for an active layer within a thin-film transistor is described. Layers of semiconducting nanoparticles with a particle size between 10 and 25 nm were prepared by the use of a simple aerosol deposition system, excluding potentially unwanted technological procedures like substrate heating or the use of solvents. The nanoparticles were deposited directly onto standard thin-film transistor test devices, using thermally grown silicon oxide as gate dielectric. Proof-of-principle experiments were done deploying two different wide-band gap semiconducting oxides, tin oxide, SnO x , and indium oxide, In 2 O 3 . The tin oxide spots prepared from the gas phase were too conducting to be used as channel material in thin-film transistors, most probably due to a high concentration of oxygen defects. Using indium oxide nanoparticles, thin-film transistor devices with significant field effect were obtained. Even though the electron mobility of the investigated devices was only in the range of 10 −6 cm 2V−1s−1 , the operability of this method for the fabrication of transistors was demonstrated. With respect to the possibilities to control the particle size and layer morphology in situ during deposition, improvements are expected.

Morphology and phase transformations of tin oxide nanostructures synthesized by the hydrothermal method in the presence of dicarboxylic acids

International Nuclear Information System (INIS)

Zima, Tatyana; Bataev, Ivan

2016-01-01

A new approach to the synthesis of non-stoichiometric tin oxide structures with different morphologies and the phase compositions has been evaluated. The nanostructures were synthesized by hydrothermal treatment of the mixtures of dicarboxylic acids ― aminoterephthalic or oxalic ― with nanocrystalline SnO 2 powder, which was obtained via the sol-gel technology. The products were characterized by Raman and IR spectroscopy, SEM, HRTEM, and XRD analysis. It was shown that the controlled addition of a dicarboxylic acid leads not only to a change in the morphology of the nanostructures, but also to SnO 2 –SnO 2 /Sn 3 O 4 –Sn 3 O 4 –SnO phase transformations. A single-phase Sn 3 O 4 in the form of the well-separated hexagonal nanoplates and mixed SnO 2 /Sn 3 O 4 phases in the form of hierarchical flower-like structures were obtained in the presence of organic additives. The effects of concentration, redox activity of the acids and heat treatment on the basic characteristics of the synthesized tin oxide nanostructures and phase transformations in the synthesized materials are discussed. - Graphical abstract: The controlled addition of aminoterephthalic or oxalic acid leads not only to a change in the morphology of the nanostructures, but also to SnO 2 –SnO 2 /Sn 3 O 4 –Sn 3 O 4 –SnO phase transformations. - Highlights: • A new approach to the synthesis of non-stoichiometric tin oxide structures is studied. • Tin oxide structures are synthesized via hydrothermal method with dicarboxylic acids. • Morphology and phase composition are changed with redox activity and dosage of acid. • The redox activity of acid has an effect on ratio of SnO and SnO 2 in crystal structure. • A pure phase Sn 3 O 4 nanoplates and SnO 2 /Sn 3 O 4 hierarchical structures are formed.

Real-time generation of the Wigner distribution of complex functions using phase conjugation in photorefractive materials.

Science.gov (United States)

Sun, P C; Fainman, Y

1990-09-01

An optical processor for real-time generation of the Wigner distribution of complex amplitude functions is introduced. The phase conjugation of the input signal is accomplished by a highly efficient self-pumped phase conjugator based on a 45 degrees -cut barium titanate photorefractive crystal. Experimental results on the real-time generation of Wigner distribution slices for complex amplitude two-dimensional optical functions are presented and discussed.

Photochemical preparation of aluminium oxide layers via vacuum ultraviolet irradiation of a polymeric hexanoato aluminium complex

International Nuclear Information System (INIS)

Wennrich, L.; Khalil, H.; Bundesmann, C.; Decker, U.; Gerlach, J.W.; Helmstedt, U.; Manova, D.; Naumov, S.; Prager, L.

2013-01-01

By means of photochemical conversion of thin layers of a polymeric hexanoato aluminium complex as the precursor, thin aluminium oxide layers were prepared onto silicon wafers. The precursor compound was synthesized and characterized by several analytical techniques like NMR, FTIR, XPS, ICP, and found to be a polymeric aluminium-containing coordination compound which has been proposed to be a hydroxo-bridged aluminium chain with pendant hexanoyl side-chains ascertained as catena-poly[{di(κ-O,O-hexanoato)aluminium}(μ-hydroxo)] (PHAH). Thin layers deposited from a solution of PHAH in toluene onto silicon wafers were irradiated using VUV radiation from a xenon excimer lamp. The layers were characterized by XPS, XRD, XRR, and spectroscopic ellipsometry. VUV radiation with a radiant exposure of E = 36 J cm −2 led to almost carbon-free amorphous layers with a composition close to that of alumina having a density of about 2.1 g cm −3 . Thus, using the example of a polymeric aluminium complex, the potential of the photochemical conversion of metal complexes into oxides could be shown as an alternative method, in addition to sol–gel techniques, for the generation of thin plane metal-oxide layers at normal temperature and pressure. Highlights: ► A polymeric aluminium complex was synthesized and characterized by NMR, FTIR, XPS and ICP. ► Thin layers of the compound were irradiated using vacuum-UV radiation and converted to AlO x . ► Quantum-chemical calculations explain the conversion mechanism.

Structural evolution of epitaxial SrCoOx films near topotactic phase transition

Science.gov (United States)

Jeen, Hyoungjeen; Lee, Ho Nyung

2015-12-01

Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

Structural evolution of epitaxial SrCoOx films near topotactic phase transition

Directory of Open Access Journals (Sweden)

Hyoungjeen Jeen

2015-12-01

Full Text Available Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx epitaxially grown by pulsed laser epitaxy (PLE as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ. We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

Vibrational Spectra of Discrete UO22+ Halide Complexes in the Gas Phase

International Nuclear Information System (INIS)

Groenewold, G.S.; Van Stipdonk, Michael J.; Oomens, Jos; De Jong, Wibe A.; Gresham, Garold L.; Mcilwain, Michael

2010-01-01

The intrinsic binding of halide ions to the metal center in the uranyl molecule is a topic of ongoing research interest in both the actinide separations and theoretical communities. Investigations of structure in the condensed phases is frequently obfuscated by solvent interactions that can alter ligand binding and spectroscopic properties. The approach taken in this study is to move the uranyl halide complexes into the gas phase where they are free from solvent interactions, and then interrogate their vibrational spectroscopy using infrared multiple photon dissociation (IRMPD). The spectra of cationic coordination complexes having the composition (UO 2 (X)(ACO) 3 ) + (where X = F, Cl, Br and I; ACO = acetone) were acquired using electrospray for ion formation, and monitoring the ion signal from the photoelimination of ACO ligands. The studies showed that the asymmetric ν 3 UO 2 frequency was insensitive to halide identity as X was varied from Cl to I, suggesting that in these pseudo-octahedral complexes, changing the nucleophilicity of the halide did not appreciably alter its binding in the complex. The ν 3 peak in the spectrum of the F-containing complex was 9 cm -1 lower indicating stronger coordination in this complex. Similarly the ACO carbonyl stretches showed that the C=O frequency was relatively insensitive to the identity of the halide, although a modest shift to higher wavenumber was seen for the complexes with the more nucleophilic anions, consistent with the idea that they loosen solvent binding. Surprisingly, the ν 1 stretch was activated when the softer anions Cl, Br and I were present in the complexes. IR studies of the anionic complexes (UO 2 X 3 ) - (where X = Cl - , Br - and I - ) compared the ν 3 UO 2 modes versus halide, and showed that the ν 3 values decreased with increasing anion nucleophilicity. This observation was consistent with DFT calculations that indicated that (UO 2 X 2 ) - -X, and (UO 2 X 2 )·-X - dissociation energies

Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

International Nuclear Information System (INIS)

Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

2014-01-01

Highlights: • SHG phase from the interfaces of ITO/CuPc and ITO/pentacene was observed. • Optical dispersion of the organic thin film was taken into account. • Phase shift from bare ITO was 140° for ITO/CuPc and 160° for ITO/pentacene. - Abstract: We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ interface with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°

Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

Energy Technology Data Exchange (ETDEWEB)

Ngah Demon, Siti Zulaikha [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan); Department of Physics, Centre of Defence Foundation Studies, National Defence University of Malaysia, 53 000 Kuala Lumpur (Malaysia); Miyauchi, Yoshihiro [Department of Applied Physics, School of Applied Sciences, National Defense Academy of Japan, 239-8686 Kanagawa (Japan); Mizutani, Goro, E-mail: mizutani@jaist.ac.jp [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan); Matsushima, Toshinori; Murata, Hideyuki [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan)

2014-08-30

Highlights: • SHG phase from the interfaces of ITO/CuPc and ITO/pentacene was observed. • Optical dispersion of the organic thin film was taken into account. • Phase shift from bare ITO was 140° for ITO/CuPc and 160° for ITO/pentacene. - Abstract: We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ{sub interface} with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

Selective Oxidation of Glycerol with 3% H2O2 Catalyzed by LDH-Hosted Cr(III Complex

Directory of Open Access Journals (Sweden)

Gongde Wu

2015-11-01

Full Text Available A series of layered double hydroxides (LDHs –hosted sulphonato-salen Cr(III complexes were prepared and characterized by various physico-chemical measurements, such as Fourier transform infrared spectroscopy (FTIR, ultraviolet-visible spectroscopy (UV-Vis, powder X-ray diffraction (XRD, transmission electron microscope (TEM, scanning electron microscope (SEM and elemental analysis. Additionally, their catalytic performances were investigated in the selective oxidation of glycerol (GLY using 3% H2O2 as an oxidant. It was found that all the LDH-hosted Cr(III complexes exhibited significantly enhanced catalytic performance compared to the homogeneous Cr(III complex. Additionally, it was worth mentioning that the metal composition of LDH plates played an important role in the catalytic performances of LDH-hosted Cr(III complex catalysts. Under the optimal reaction conditions, the highest GLY conversion reached 85.5% with 59.3% of the selectivity to 1,3-dihydroxyacetone (DHA. In addition, the catalytic activity remained after being recycled five times.

Transformers: the changing phases of low-dimensional vanadium oxide bronzes.

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Marley, Peter M; Horrocks, Gregory A; Pelcher, Kate E; Banerjee, Sarbajit

2015-03-28

In this feature article, we explore the electronic and structural phase transformations of ternary vanadium oxides with the composition MxV2O5 where M is an intercalated cation. The periodic arrays of intercalated cations ordered along quasi-1D tunnels or layered between 2D sheets of the V2O5 framework induce partial reduction of the framework vanadium atoms giving rise to charge ordering patterns that are specific to the metal M and stoichiometry x. This periodic charge ordering makes these materials remarkably versatile platforms for studying electron correlation and underpins the manifestation of phenomena such as colossal metal-insulator transitions, quantized charge corrals, and superconductivity. We describe current mechanistic understanding of these emergent phenomena with a particular emphasis on the benefits derived from scaling these materials to nanostructured dimensions wherein precise ordering of cations can be obtained and phase relationships can be derived that are entirely inaccessible in the bulk. In particular, structural transformations induced by intercalation are dramatically accelerated due to the shorter diffusion path lengths at nanometer-sized dimensions, which cause a dramatic reduction of kinetic barriers to phase transformations and facilitate interconversion between the different frameworks. We conclude by summarizing numerous technological applications that have become feasible due to recent advances in controlling the structural chemistry and both electronic and structural phase transitions in these versatile frameworks.

ZnO Nanowires Synthesized by Vapor Phase Transport Deposition on Transparent Oxide Substrates

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Taylor Curtis

2010-01-01

Full Text Available Abstract Zinc oxide nanowires have been synthesized without using metal catalyst seed layers on fluorine-doped tin oxide (FTO substrates by a modified vapor phase transport deposition process using a double-tube reactor. The unique reactor configuration creates a Zn-rich vapor environment that facilitates formation and growth of zinc oxide nanoparticles and wires (20–80 nm in diameter, up to 6 μm in length, density <40 nm apart at substrate temperatures down to 300°C. Electron microscopy and other characterization techniques show nanowires with distinct morphologies when grown under different conditions. The effect of reaction parameters including reaction time, temperature, and carrier gas flow rate on the size, morphology, crystalline structure, and density of ZnO nanowires has been investigated. The nanowires grown by this method have a diameter, length, and density appropriate for use in fabricating hybrid polymer/metal oxide nanostructure solar cells. For example, it is preferable to have nanowires no more than 40 nm apart to minimize exciton recombination in polymer solar cells.

Two-harmonic complex spectral-domain optical coherence tomography using achromatic sinusoidal phase modulation

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Lu, Sheng-Hua; Huang, Siang-Ru; Chou, Che-Chung

2018-03-01

We resolve the complex conjugate ambiguity in spectral-domain optical coherence tomography (SD-OCT) by using achromatic two-harmonic method. Unlike previous researches, the optical phase of the fiber interferometer is modulated by an achromatic phase shifter based on an optical delay line. The achromatic phase modulation leads to a wavelength-independent scaling coefficient for the two harmonics. Dividing the mean absolute value of the first harmonic by that of the second harmonic in a B-scan interferogram directly gives the scaling coefficient. It greatly simplifies the determination of the magnitude ratio between the two harmonics without the need of third harmonic and cumbersome iterative calculations. The inverse fast Fourier transform of the complex-valued interferogram constructed with the scaling coefficient, first and second harmonics yields a full-range OCT image. Experimental results confirm the effectiveness of the proposed achromatic two-harmonic technique for suppressing the mirror artifacts in SD-OCT images.