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Sample records for metal catalytic particle

  1. Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage

    Science.gov (United States)

    Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

    2005-01-01

    We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

  2. X-ray Fluorescence Tomography of Aged Fluid-Catalytic-Cracking Catalyst Particles Reveals Insight into Metal Deposition Processes

    NARCIS (Netherlands)

    Kalirai, Samanbir; Boesenberg, Ulrike; Falkenberg, Gerald; Meirer, Florian; Weckhuysen, Bert M.

    2015-01-01

    Microprobe X-ray fluorescence tomography was used to investigate metal poison deposition in individual, intact and industrially deactivated fluid catalytic cracking (FCC) particles at two differing catalytic life-stages. 3D multi-element imaging, at submicron resolution was achieved by using a large

  3. X-ray Fluorescence Tomography of Aged Fluid-Catalytic-Cracking Catalyst Particles Reveals Insight into Metal Deposition Processes

    NARCIS (Netherlands)

    Kalirai, Samanbir; Boesenberg, Ulrike; Falkenberg, Gerald; Meirer, Florian; Weckhuysen, Bert M.

    2015-01-01

    Microprobe X-ray fluorescence tomography was used to investigate metal poison deposition in individual, intact and industrially deactivated fluid catalytic cracking (FCC) particles at two differing catalytic life-stages. 3D multi-element imaging, at submicron resolution was achieved by using a

  4. [Catalytic degradation of PCB77 by microwave-induced nano-particle metal oxides in diatomite].

    Science.gov (United States)

    Huang, Guan-yi; Zhao, Ling; Dong, Yuan-hua

    2009-08-15

    The degradation of PCB77 in diatomite by microwave-induced catalytic oxidation was studied in a sealed vial, including four effects such as microwave (MV) radiating time, addition of different nano-particle metal oxides, concentration and type of acids and dosage of MnO2. The results indicated that PCB77 could be removed significantly by microwave-induced catalytic oxidation. Compared to control reactor (without MV radiation), the removal rate of PCB77 increased by twice after 1 min. In addition, the removal rate of PCB77 under MV radiation was gradually increased with time of radiation and then reached equilibrium after 10 min. The removal rates are about 50% and 20% by addition of H2SO4 and ultrapure water respectively. No significant removal was observed by addition of NaOH and without aqueous media. Moreover, catalytic degradation of PCB77 by microwave-induced nano-particle MnO2 had best removal rate was up to 90% after 1 min, in contrast with addition of nano-particle Fe2O3, CuO and Al2O3. The removal rate raised from 37.0% to 98.5% rapidly with the concentration of H2SO4 ranged from 1 mol/L to 8 mol/L, and H2SO4 mainly played a role of acidification but not oxidation. The addition of 0.01, 0.03 and 0.05 g MnO2 showed the similar result.

  5. Catalytic behavior of metallic particles in anisotropic etching of Ge(100) surfaces in water mediated by dissolved oxygen

    Science.gov (United States)

    Kawase, Tatsuya; Mura, Atsushi; Nishitani, Keisuke; Kawai, Yoshie; Kawai, Kentaro; Uchikoshi, Junichi; Morita, Mizuho; Arima, Kenta

    2012-06-01

    The authors demonstrate that Ge(100) surfaces containing metallic particles are etched anisotropically in water. This originates from the catalytic reduction of dissolved oxygen (O2) in water to water molecules (H2O) on the metallic particles, which is followed by the enhanced oxidation of Ge around the particles. The soluble nature of Ge oxide (GeO2) in water promotes the formation of inverted pyramidal etch pits composed of (111) microfacets. On the basis of the results, the authors propose strategies for avoiding unwanted surface roughening during the wet cleaning of Ge.

  6. Catalytically driven assembly of trisegmented metallic nanorods and polystyrene tracer particles.

    Science.gov (United States)

    Jewell, Erik L; Wang, Wei; Mallouk, Thomas E

    2016-03-07

    Trisegmented Au-Ru-Au and Ru-Au-Ru nanorods catalyze the decomposition of hydrogen peroxide, pumping fluid along their axis as "pullers" and "pushers" respectively. Numerical simulations and experiments with passive tracer particles show that catalytically generated hydrodynamic and electrostatic forces both contribute to pairwise and collective particle assembly.

  7. Green Synthesis of Smart Metal/Polymer Nanocomposite Particles and Their Tuneable Catalytic Activities

    Directory of Open Access Journals (Sweden)

    Noel Peter Bengzon Tan

    2016-03-01

    Full Text Available Herein we report a simple and green synthesis of smart Au and Ag@Au nanocomposite particles using poly(N-isopropylacrylamide/polyethyleneimine (PNIPAm/PEI core-shell microgels as dual reductant and templates in an aqueous system. The nanocomposite particles were synthesized through a spontaneous reduction of tetrachloroauric (III acid to gold nanoparticles at room temperature, and in situ encapsulation and stabilization of the resultant gold nanoparticles (AuNPs with amine-rich PEI shells. The preformed gold nanoparticles then acted as seed nanoparticles for further generation of Ag@Au bimetallic nanoparticles within the microgel templates at 60 °C. These nanocomposite particles were characterized by TEM, AFM, XPS, UV-vis spectroscopy, zeta-potential, and particle size analysis. The synergistic effects of the smart nanocomposite particles were studied via the reduction of p-nitrophenol to p-aminophenol. The catalytic performance of the bimetallic Ag@Au nanocomposite particles was 25-fold higher than that of the monometallic Au nanoparticles. Finally, the controllable catalytic activities of the Au@PNIPAm/PEI nanocomposite particles were demonstrated via tuning the solution pH and temperature.

  8. Catalytic effect of nano-particle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling

    OpenAIRE

    Hanada, Nobuko; Ichikawa, Takayuki; Fujii, Hironobu

    2004-01-01

    We examined the catalytic effect of nano-particle 3d-transition metals on hydrogen desorption (HD) properties of MgH2 prepared by mechanical ball milling method. All the MgH2 composites prepared by adding a small amount of nano-particle Fenano, Conano, Ninano and Cunano metals and by ball milling for 2h showed much better HD properties than the pure ball-milled MgH2 itself. Especially, the 2 mol% Ninano-doped MgH2 composite prepared by soft milling for a short milling time of 15 min under a s...

  9. Atomically Precise Metal Nanoclusters for Catalytic Application

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Rongchao [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-11-18

    The central goal of this project is to explore the catalytic application of atomically precise gold nanoclusters. By solving the total structures of ligand-protected nanoclusters, we aim to correlate the catalytic properties of metal nanoclusters with their atomic/electronic structures. Such correlation unravel some fundamental aspects of nanocatalysis, such as the nature of particle size effect, origin of catalytic selectivity, particle-support interactions, the identification of catalytically active centers, etc. The well-defined nanocluster catalysts mediate the knowledge gap between single crystal model catalysts and real-world conventional nanocatalysts. These nanoclusters also hold great promise in catalyzing certain types of reactions with extraordinarily high selectivity. These aims are in line with the overall goals of the catalytic science and technology of DOE and advance the BES mission “to support fundamental research to understand, predict, and ultimately control matter and energy at the level of electrons, atoms, and molecules”. Our group has successfully prepared different sized, robust gold nanoclusters protected by thiolates, such as Au25(SR)18, Au28(SR)20, Au38(SR)24, Au99(SR)42, Au144(SR)60, etc. Some of these nanoclusters have been crystallographically characterized through X-ray crystallography. These ultrasmall nanoclusters (< 2 nm diameter) exhibit discrete electronic structures due to quantum size effect, as opposed to quasicontinuous band structure of conventional metal nanoparticles or bulk metals. The available atomic structures (metal core plus surface ligands) of nanoclusters serve as the basis for structure-property correlations. We have investigated the unique catalytic properties of nanoclusters (i.e. not observed in conventional nanogold catalysts) and revealed the structure-selectivity relationships. Highlights of our

  10. Highly Dense Isolated Metal Atom Catalytic Sites

    DEFF Research Database (Denmark)

    Chen, Yaxin; Kasama, Takeshi; Huang, Zhiwei

    2015-01-01

    Atomically dispersed noble-metal catalysts with highly dense active sites are promising materials with which to maximise metal efficiency and to enhance catalytic performance; however, their fabrication remains challenging because metal atoms are prone to sintering, especially at a high metal...... loading. A dynamic process of formation of isolated metal atom catalytic sites on the surface of the support, which was achieved starting from silver nanoparticles by using a thermal surface-mediated diffusion method, was observed directly by using in situ electron microscopy and in situ synchrotron X......-ray diffraction. A combination of electron microscopy images with X-ray absorption spectra demonstrated that the silver atoms were anchored on five-fold oxygen-terminated cavities on the surface of the support to form highly dense isolated metal active sites, leading to excellent reactivity in catalytic oxidation...

  11. Metal hybrid nanoparticles for catalytic organic and photochemical transformations.

    Science.gov (United States)

    Song, Hyunjoon

    2015-03-17

    functions, such as magnetism and light absorption, to the catalytic properties. In particular, metal-semiconductor hybrid nanostructures could behave as effective visible photocatalysts for hydrogen evolution and CO oxidation reactions. Resulting from the large surface area and high local concentration of the reactants, a double-shell hollow structure showed reaction activities higher than those of filled nanoparticles. The introduction of plasmonic Au probes into the Pt-CdS double-shell hollow particles facilitated the monitoring of photocatalytic hydrogen generation that occurred on an individual particle surface by single particle measurements. Further development of catalysis research using well-defined metal hybrid nanocatalysts with various in situ spectroscopic tools provides a means of maximizing catalytic performances until they are comparable to or better than those of homogeneous catalysts, and this would have possibly useful implications for industrial applications.

  12. Carbon nanofibers grown on metallic filters as novel catalytic materials

    OpenAIRE

    Tribolet, Pascal; Kiwi-Minsker, Lioubov

    2005-01-01

    Carbon nanofibers (CNF) were synthesized on sintered metal fibers (SMF) filters of nickel and Ni-containing alloys (Inconel, stainless steel (SS)) by thermal chemical vapor deposition of ethane in the presence of hydrogen at not, vert, similar660 °C. The CNFs were formed directly over the SMF filters without deposition of metal particles. The catalytic active sites leading to the CNF formation were attained by oxidation–reduction of the SMF filter. The CNFs present platelet morphology as dete...

  13. Life and death of a single catalytic cracking particle

    Science.gov (United States)

    Meirer, Florian; Kalirai, Sam; Morris, Darius; Soparawalla, Santosh; Liu, Yijin; Mesu, Gerbrand; Andrews, Joy C.; Weckhuysen, Bert M.

    2015-01-01

    Fluid catalytic cracking (FCC) particles account for 40 to 45% of worldwide gasoline production. The hierarchical complex particle pore structure allows access of long-chain feedstock molecules into active catalyst domains where they are cracked into smaller, more valuable hydrocarbon products (for example, gasoline). In this process, metal deposition and intrusion is a major cause for irreversible catalyst deactivation and shifts in product distribution. We used x-ray nanotomography of industrial FCC particles at differing degrees of deactivation to quantify changes in single-particle macroporosity and pore connectivity, correlated to iron and nickel deposition. Our study reveals that these metals are incorporated almost exclusively in near-surface regions, severely limiting macropore accessibility as metal concentrations increase. Because macropore channels are “highways” of the pore network, blocking them prevents feedstock molecules from reaching the catalytically active domains. Consequently, metal deposition reduces conversion with time on stream because the internal pore volume, although itself unobstructed, becomes largely inaccessible. PMID:26601160

  14. On the role of metal particle size and surface coverage for photo-catalytic hydrogen production; a case study of the Au/CdS system

    KAUST Repository

    Majeed, I.

    2015-09-25

    Photo-catalytic hydrogen production has been studied on Au supported CdS catalysts under visible light irradiation in order to understand the effect of Au particle size as well as the reaction medium properties. Au nanoparticles of size about 2-5 nm were deposited over hexagonal CdS particles using a new simple method involving reduction of Au3+ ions with iodide ions. Within the investigated range of Au (between 1 and 5 wt. %) fresh particles with mean size of 4 nm and XPS Au4f/Cd3d surface ratio of 0.07 showed the highest performance (ca. 1 molecule of H2 / Auatom s−1) under visible light irradiation (>420 nm and a flux of 35 mW/cm2). The highest hydrogen production rate was obtained from water (92%)-ethanol (8%) in an electrolyte medium (Na2S-Na2SO3). TEM studies of fresh and used catalysts showed that Au particle size increases (almost 5 fold) with increasing photo-irradiation time due to photo-agglomeration effect yet no sign of deactivation was observed. A mechanism for hydrogen production from ethanol-water electrolyte mixture is presented and discussed.

  15. Catalytic dehydrogenation of light alkanes on metals and metal oxides

    NARCIS (Netherlands)

    Sattler, Jesper J H B|info:eu-repo/dai/nl/328235601; Ruiz-Martinez, Javier|info:eu-repo/dai/nl/341386405; Santillan-Jimenez, Eduardo|info:eu-repo/dai/nl/323171958; Weckhuysen, Bert M.|info:eu-repo/dai/nl/285484397

    2014-01-01

    A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors,

  16. Mechanism of Transition-Metal Nanoparticle Catalytic Graphene Cutting.

    Science.gov (United States)

    Ma, Liang; Wang, Jinlan; Yip, Joanne; Ding, Feng

    2014-04-03

    Catalytic cutting by transition-metal (TM) particles is a promising method for the synthesizing of high-quality graphene quantum dots and nanoribbons with smooth edges. Experimentally, it is observed that the cutting always results in channels with zigzag (ZZ) or armchair (AC) edges. However, the driving force that is responsible for such a cutting behavior remains a puzzle. Here, by calculating the interfacial formation energies of the TM-graphene edges with ab initio method, we show that the surface of a catalyst particle tends to be aligned along either AC or ZZ direction of the graphene lattice, and thus the cutting of graphene is guided as such. The different cutting behaviors of various catalysts are well-explained based on the competition between TM-passivated graphene edges and the etching-agent-terminated ones. Furthermore, the kinetics of graphene catalytic cutting along ZZ and AC directions, respectively, are explored at the atomic level.

  17. CATALYTIC PROPERTIES OF POLYMER-STABILIZED COLLOIDAL METAL NANOPARTICLES SYNTHESIZED BY MICROWAVE IRRADIATION

    Institute of Scientific and Technical Information of China (English)

    Wei-xia Tu; Bao-lin He; Han-fan Liu; Xue-lan Luo; Xun Liang

    2005-01-01

    Catalytic properties of polymer-stabilized colloidal metal nanoparticles synthesized by microwave irradiation were studied in the selective hydrogenation of unsaturated aldehydes, o-chloronitrobenzene and the hydrogenation of alkenes. The results show that nanosized metal particles synthesized by microwave irradiation have similar catalytic performance in selective hydrogenation of unsaturated aldehydes, better selectivity to o-chloroaniline in hydrogenation of o-chloronitrobenzene and higher catalytic activities in hydrogenation of alkenes, compared with metal clusters prepared by conventional heating. The same apparent activation energy (Ea = 29 kJ mol-1) for hydrogenation of 1-heptene catalyzed with platinum nanoparticles prepared by both heating modes implied that the reaction followed the same mechanism.

  18. Catalytic extraction processing of contaminated scrap metal

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, T.P.; Johnston, J.E.; Payea, B.M. [Molten Metal Technology, Inc., Waltham, MA (United States)] [and others

    1995-10-01

    The U.S. Department of Energy issued a Planned Research and Development Announcement (PRDA) in 1993, with the objective of identifying unique technologies which could be applied to the most hazardous waste streams at DOE sites. The combination of radioactive contamination with additional contamination by hazardous constituents such as those identified by the Resource Conservation and Recovery Act (RCRA) pose an especially challenging problem. Traditional remediation technologies are increasingly becoming less acceptable to stakeholders and regulators because of the risks they pose to public health and safety. Desirable recycling technologies were described by the DOE as: (1) easily installed, operated, and maintained; (2) exhibiting superior environmental performance; (3) protective of worker and public health and safety; (4) readily acceptable to a wide spectrum of evaluators; and (5) economically feasible. Molten Metal Technology, Inc. (MMT) was awarded a contract as a result of the PRDA initiative to demonstrate the applicability of Catalytic Extraction Processing (CEP), MMT`s proprietary elemental recycling technology, to DOE`s inventory of low level mixed waste. This includes DOE`s inventory of radioactively- and RCRA-contaminated scrap metal and other waste forms expected to be generated by the decontamination and decommissioning (D&D) of DOE sites.

  19. Guiding catalytically active particles with chemically patterned surfaces

    CERN Document Server

    Uspal, W E; Dietrich, S; Tasinkevych, M

    2016-01-01

    Catalytically active Janus particles suspended in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemi-osmosis, providing an additional contribution to self-motility. Chemi-osmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate "point-particle" approach, that by chemically patterning a planar substrate one can direct the motion of Janus particles: the induced chemi-osmotic flows can cause particles to either "dock" at the chemical step between the two materials, or to follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe-following occurs in the opposite case. Our analysis reveals the physical mechanisms governi...

  20. Enantiocontrol in Macrocycle Formation from Catalytic MetalCarbene Transformations

    Institute of Scientific and Technical Information of China (English)

    DOYLE, Michael P.; DOYLE, Michael P; HU, Wen-Hao(胡文浩); 胡文浩

    2001-01-01

    The development of catalytic metal carbene transformations for the construction of macrocyclic lactones has dramatically increased their synthetic advantages.This is the first review of this developing methodology.

  1. Novel catalytic applications of carbon nanofibers on sintered metal fibers filters as structured supports

    OpenAIRE

    2009-01-01

    Supported metal catalysts are important from both an industrial and a scientific point of view. They are used, amongst others, in large-scale processes such as catalytic reforming, hydrotreating, polymerization reactions and hydrogenations. Often, these catalysts consist of nanosized metal particles deposited on a suitable support, which acts as an anchor for the active phase and, in several cases, contributes to improve the overall catalyst performances. The growth of carbon nanofibers on si...

  2. Novel catalytic applications of carbon nanofibers on sintered metal fibers filters as structured supports

    OpenAIRE

    2008-01-01

    Supported metal catalysts are important from both an industrial and a scientific point of view. They are used, amongst others, in large-scale processes such as catalytic reforming, hydrotreating, polymerization reactions and hydrogenations. Often, these catalysts consist of nanosized metal particles deposited on a suitable support, which acts as an anchor for the active phase and, in several cases, contributes to improve the overall catalyst performances. The growth of carbon nanofibers on si...

  3. High-spatial-resolution mapping of catalytic reactions on single particles

    Science.gov (United States)

    Wu, Chung-Yeh; Wolf, William J.; Levartovsky, Yehonatan; Bechtel, Hans A.; Martin, Michael C.; Toste, F. Dean; Gross, Elad

    2017-01-01

    The critical role in surface reactions and heterogeneous catalysis of metal atoms with low coordination numbers, such as found at atomic steps and surface defects, is firmly established. But despite the growing availability of tools that enable detailed in situ characterization, so far it has not been possible to document this role directly. Surface properties can be mapped with high spatial resolution, and catalytic conversion can be tracked with a clear chemical signature; however, the combination of the two, which would enable high-spatial-resolution detection of reactions on catalytic surfaces, has rarely been achieved. Single-molecule fluorescence spectroscopy has been used to image and characterize single turnover sites at catalytic surfaces, but is restricted to reactions that generate highly fluorescing product molecules. Herein the chemical conversion of N-heterocyclic carbene molecules attached to catalytic particles is mapped using synchrotron-radiation-based infrared nanospectroscopy with a spatial resolution of 25 nanometres, which enabled particle regions that differ in reactivity to be distinguished. These observations demonstrate that, compared to the flat regions on top of the particles, the peripheries of the particles—which contain metal atoms with low coordination numbers—are more active in catalysing oxidation and reduction of chemically active groups in surface-anchored N-heterocyclic carbene molecules.

  4. The synthesis of metal nanoparticulate catalysts within functional microgel particles

    Science.gov (United States)

    Kaliva, Maria; Pavlopoulou, Eleni; Christodoulakis, Konstantinos; Vamvakaki, Maria; Anastasiadis, Spiros H.

    2012-02-01

    Electrostatically and sterically stabilized polymer microgel particles have been prepared containing either amino (poly(2-(diethylamino)ethyl methacrylate), PDEA) or carboxylic acid (poly(acrylic acid), PAA; poly(methacrylic acid), PMMA) functional groups. The PDEA, PAA and PMAA particles can be used for the incorporation of a large variety of metal nanoparticulate catalysts due to their functional amine and carboxylic acid groups; Pd, Ru and Ni nanoparticles have been synthesized. The more polar PAA microgels were designed as the nanocatalyst carrier system in aqueous reaction media while the less polar PMAA particles were prepared as the metal nanoparticle template for use in catalytic reactions that take place in organic solvents. The sterically and electrostatically stabilized microgel particles possess surface functional groups that can potentially interact with the microchannel walls of microfluidic catalytic reactors.

  5. Possibilities Of Metals Extracton From Spent Metallic Automotive Catalytic Converters By Using Biometallurgical Method

    Directory of Open Access Journals (Sweden)

    Willner J.

    2015-09-01

    Full Text Available The main task of automotive catalytic converters is reducing the amount of harmful components of exhaust gases. Metallic catalytic converters are an alternative to standard ceramic catalytic converters. Metallic carriers are usually made from FeCrAl steel, which is covered by a layer of Precious Group Metals (PGMs acting as a catalyst. There are many methods used for recovery of platinum from ceramic carriers in the world, but the issue of platinum and other metals recovery from metallic carriers is poorly described. The article presents results of preliminary experiments of metals biooxidation (Fe, Cr and Al from spent catalytic converters with metallic carrier, using bacteria of the Acidithiobacillus genus.

  6. Catalytic Conversion of Cellulose to Levulinic Acid by Metal Chlorides

    Directory of Open Access Journals (Sweden)

    Beixiao Zhang

    2010-08-01

    Full Text Available The catalytic performance of various metal chlorides in the conversion of cellulose to levulinic acid in liquid water at high temperatures was investigated. The effects of reaction parameters on the yield of levulinic acid were also explored. The results showed that alkali and alkaline earth metal chlorides were not effective in conversion of cellulose, while transition metal chlorides, especially CrCl3, FeCl3 and CuCl2 and a group IIIA metal chloride (AlCl3, exhibited high catalytic activity. The catalytic performance was correlated with the acidity of the reaction system due to the addition of the metal chlorides, but more dependent on the type of metal chloride. Among those metal chlorides, chromium chloride was found to be exceptionally effective for the conversion of cellulose to levulinic acid, affording an optimum yield of 67 mol % after a reaction time of 180 min, at 200 °C, with a catalyst dosage of 0.02 M and substrate concentration of 50 wt %. Chromium metal, most of which was present in its oxide form in the solid sample and only a small part in solution as Cr3+ ion, can be easily separated from the resulting product mixture and recycled. Finally, a plausible reaction scheme for the chromium chloride catalyzed conversion of cellulose in water was proposed.

  7. Guiding catalytically active particles with chemically patterned surfaces

    Science.gov (United States)

    Uspal, William; Popescu, Mihail; Dietrich, Siegfried; Tasinkevych, Mykola

    Catalytically active Janus particles in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemi-osmosis, providing an additional contribution to self-motility. Chemi-osmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate ``point-particle'' approach, that by chemically patterning a planar substrate (e.g., by adsorbing two different materials) one can direct the motion of Janus particles: the induced chemi-osmotic flows can cause particles to either ``dock'' at a chemical step between the two materials, or to follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe-following occurs in the opposite case. Our analysis reveals the physical mechanisms governing this behavior.

  8. Nanoporous carbon supported metal particles: their synthesis and characterisation

    Energy Technology Data Exchange (ETDEWEB)

    Yang Yunxia, E-mail: yunxia.yang@csiro.au; Tang Liangguang; Burke, Nick; Chiang, Ken [CSIRO Earth Science and Resource Engineering (Australia)

    2012-08-15

    In the current work, a simplified hard templating approach is used to synthesise metal (Ag, Rh, Ir and Pt) containing structured carbon. The target metals are first introduced into the NaY zeolite template by wetness impregnation. The metals are carried in the super cages of the zeolite and subsequently embedded in the final structures after the steps of carbonisation and the template removal. Scanning electron microscopy images have confirmed that the carbon structures produced by this method retain the morphology of the original template. Transmission electron microscopy reveals the presence of dispersed metal particles in all the carbon structures produced. The metal loadings in these templated structures can reach 35 wt% without significant losses of surface areas and pore volumes. Selected carbon supported metals are tested for their catalytic activity for the methanation of carbon monoxide. The finding suggested that this method is effective in preparing metal nanoparticles for use as catalysts.

  9. Trends in catalytic NO decomposition over transition metal surfaces

    DEFF Research Database (Denmark)

    Falsig, Hanne; Bligaard, Thomas; Rass-Hansen, Jeppe

    2007-01-01

    The formation of NOx from combustion of fossil and renewable fuels continues to be a dominant environmental issue. We take one step towards rationalizing trends in catalytic activity of transition metal catalysts for NO decomposition by combining microkinetic modelling with density functional...... theory calculations. We show specifically why the key problem in using transition metal surfaces to catalyze direct NO decomposition is their significant relative overbinding of atomic oxygen compared to atomic nitrogen....

  10. Well-defined transition metal hydrides in catalytic isomerizations.

    Science.gov (United States)

    Larionov, Evgeny; Li, Houhua; Mazet, Clément

    2014-09-07

    This Feature Article intends to provide an overview of a variety of catalytic isomerization reactions that have been performed using well-defined transition metal hydride precatalysts. A particular emphasis is placed on the underlying mechanistic features of the transformations discussed. These have been categorized depending upon the nature of the substrate and in most cases discussed following a chronological order.

  11. Designing functional metalloproteins: from structural to catalytic metal sites.

    Science.gov (United States)

    Zastrow, Melissa L; Pecoraro, Vincent L

    2013-09-01

    Metalloenzymes efficiently catalyze some of the most important and difficult reactions in nature. For many years, coordination chemists have effectively used small molecule models to understand these systems. More recently, protein design has been shown to be an effective approach for mimicking metal coordination environments. Since the first designed proteins were reported, much success has been seen for incorporating metal sites into proteins and attaining the desired coordination environment but until recently, this has been with a lack of significant catalytic activity. Now there are examples of designed metalloproteins that, although not yet reaching the activity of native enzymes, are considerably closer. In this review, we highlight work leading up to the design of a small metalloprotein containing two metal sites, one for structural stability (HgS3) and the other a separate catalytic zinc site to mimic carbonic anhydrase activity (ZnN3O). The first section will describe previous studies that allowed for a high affinity thiolate site that binds heavy metals in a way that stabilizes three-stranded coiled coils. The second section will examine ways of preparing histidine rich environments that lead to metal based hydrolytic catalysts. We will also discuss other recent examples of the design of structural metal sites and functional metalloenzymes. Our work demonstrates that attaining the proper first coordination geometry of a metal site can lead to a significant fraction of catalytic activity, apparently independent of the type of secondary structure of the surrounding protein environment. We are now in a position to begin to meet the challenge of building a metalloenzyme systematically from the bottom-up by engineering and analyzing interactions directly around the metal site and beyond.

  12. Catalytic combustion over high temperature stable metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Berg, M. [TPS Termiska Processer AB, Nykoeping (Sweden)

    1996-12-31

    This thesis presents a study of the catalytic effects of two interesting high temperature stable metal oxides - magnesium oxide and manganese substituted barium hexa-aluminate (BMA) - both of which can be used in the development of new monolithic catalysts for such applications. In the first part of the thesis, the development of catalytic combustion for gas turbine applications is reviewed, with special attention to alternative fuels such as low-BTU gas, e.g. produced in an air blown gasifier. When catalytic combustion is applied for such a fuel, the primary advantage is the possibility of decreasing the conversion of fuel nitrogen to NO{sub x}, and achieving flame stability. In the experimental work, MgO was shown to have a significant activity for the catalytic combustion of methane, lowering the temperature needed to achieve 10 percent conversion by 270 deg C compared with homogeneous combustion.The reaction kinetics for methane combustion over MgO was also studied. It was shown that the heterogeneous catalytic reactions were dominant but that the catalytically initiated homogeneous gas phase reactions were also important, specially at high temperatures. MgO and BMA were compared. The latter showed a higher catalytic activity, even when the differences in activity decreased with increasing calcination temperature. For BMA, CO{sub 2} was the only product detected, but for MgO significant amounts of CO and C{sub 2}-hydrocarbons were formed. BMA needed a much lower temperature to achieve total conversion of other fuels, e.g. CO and hydrogen, compared to the temperature for total conversion of methane. This shows that BMA-like catalysts are interesting for combustion of fuel mixtures with high CO and H{sub 2} content, e.g. gas produced from gasification of biomass. 74 refs

  13. Polyporphyrin Complexes of Some Transition Metals. Synthesis and Catalytic Properties

    Directory of Open Access Journals (Sweden)

    A.V. Shakhvorostov

    2016-10-01

    Full Text Available The paper presents the results of synthesis of polyporphyrin structures and metal complex catalyzers at their basis. Porphyrin to be derived from the addition reaction of pyrrole and formaldehyde. Metal complex catalyzers to be derived at the reaction of complex formation of ions of Mn2+, Co2+, Ni2+ and Fe3+ with porphyrin. The structure, physical and chemical properties of derived materials to be examined with IR spectroscopy, differential thermal analysis, thermogravimetric analysis, scanning electron microscopy investigation. Catalytic activity of synthesized catalytic systems to be established at the reaction of decompounding of hydrogen peroxide and alkylaromatics oxidation by hydrogen peroxide. The processes have been conducted under soft conditions, and also at different organic solvents.

  14. Tuning CNT Properties for Metal-Free Environmental Catalytic Applications

    Directory of Open Access Journals (Sweden)

    Raquel P. Rocha

    2016-06-01

    Full Text Available The application of carbon nanotubes (CNTs as metal-free catalysts is a novel approach for heterogeneous liquid phase catalytic systems. Textural and chemical modifications by liquid/gas phase or mechanical treatments, as well as solid state reactions, were successfully applied to obtain carbon nanotubes with different surface functionalities. Oxygen, nitrogen, and sulfur are the most common heteroatoms introduced on the carbon surface. This short-review highlights different routes used to develop metal-free carbon nanotube catalysts with enhanced properties for Advanced Oxidation Processes.

  15. Size Controlled Synthesis of Transition Metal Nanoparticles for Catalytic Applications

    KAUST Repository

    Esparza, Angel

    2011-07-07

    Catalysis offers cleaner and more efficient chemical reactions for environmental scientists. More than 90% of industrial processes are performed with a catalyst involved, however research it is still required to improve the catalyst materials. The purpose of this work is to contribute with the development of catalysts synthesis with two different approaches. First, the precise size control of non-noble metals nanoparticles. Second, a new one-pot synthesis method based on a microemulsion system was developed to synthesize size-controlled metal nanoparticles in oxide supports. The one-pot method represents a simple approach to synthesize both support and immobilized nanometer-sized non-noble metal nanoparticles in the same reaction system. Narrow size distribution nickel, cobalt, iron and cobalt-nickel nanoparticles were obtained. High metal dispersions are attainable regardless the metal or support used in the synthesis. Thus, the methodology is adaptable and robust. The sizecontrolled supported metal nanoparticles offer the opportunity to study size effects and metal-support interactions on different catalytic reactions with different sets of metals and supports.

  16. Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, G.A.

    2009-09-14

    The design of high performance catalyst achieving near 100% product selectivity at maximum activity is one of the most important goals in the modern catalytic science research. To this end, the preparation of model catalysts whose catalytic performances can be predicted in a systematic and rational manner is of significant importance, which thereby allows understanding of the molecular ingredients affecting the catalytic performances. We have designed novel 3-dimensional (3D) high surface area model catalysts by the integration of colloidal metal nanoparticles and mesoporous silica supports. Monodisperse colloidal metal NPs with controllable size and shape were synthesized using dendrimers, polymers, or surfactants as the surface stabilizers. The size of Pt, and Rh nanoparticles can be varied from sub 1 nm to 15 nm, while the shape of Pt can be controlled to cube, cuboctahedron, and octahedron. The 3D model catalysts were generated by the incorporation of metal nanoparticles into the pores of mesoporous silica supports via two methods: capillary inclusion (CI) and nanoparticle encapsulation (NE). The former method relies on the sonication-induced inclusion of metal nanoparticles into the pores of mesoporous silica, whereas the latter is performed by the encapsulation of metal nanoparticles during the hydrothermal synthesis of mesoporous silica. The 3D model catalysts were comprehensively characterized by a variety of physical and chemical methods. These catalysts were found to show structure sensitivity in hydrocarbon conversion reactions. The Pt NPs supported on mesoporous SBA-15 silica (Pt/SBA-15) displayed significant particle size sensitivity in ethane hydrogenolysis over the size range of 1-7 nm. The Pt/SBA-15 catalysts also exhibited particle size dependent product selectivity in cyclohexene hydrogenation, crotonaldehyde hydrogenation, and pyrrole hydrogenation. The Rh loaded SBA-15 silica catalyst showed structure sensitivity in CO oxidation reaction. In

  17. Functional identification of catalytic metal ion binding sites within RNA.

    Directory of Open Access Journals (Sweden)

    James L Hougland

    2005-09-01

    Full Text Available The viability of living systems depends inextricably on enzymes that catalyze phosphoryl transfer reactions. For many enzymes in this class, including several ribozymes, divalent metal ions serve as obligate cofactors. Understanding how metal ions mediate catalysis requires elucidation of metal ion interactions with both the enzyme and the substrate(s. In the Tetrahymena group I intron, previous work using atomic mutagenesis and quantitative analysis of metal ion rescue behavior identified three metal ions (MA, MB, and MC that make five interactions with the ribozyme substrates in the reaction's transition state. Here, we combine substrate atomic mutagenesis with site-specific phosphorothioate substitutions in the ribozyme backbone to develop a powerful, general strategy for defining the ligands of catalytic metal ions within RNA. In applying this strategy to the Tetrahymena group I intron, we have identified the pro-SP phosphoryl oxygen at nucleotide C262 as a ribozyme ligand for MC. Our findings establish a direct connection between the ribozyme core and the functionally defined model of the chemical transition state, thereby extending the known set of transition-state interactions and providing information critical for the application of the recent group I intron crystallographic structures to the understanding of catalysis.

  18. Bio-palladium: from metal recovery to catalytic applications

    OpenAIRE

    2012-01-01

    Summary While precious metals are available to a very limited extent, there is an increasing demand to use them as catalyst. This is also true for palladium (Pd) catalysts and their sustainable recycling and production are required. Since Pd catalysts exist nowadays mostly under the form of nanoparticles, these particles need to be produced in an environment‐friendly way. Biological synthesis of Pd nanoparticles (‘bio‐Pd’) is an innovative method for both metal recovery and nanocatalyst synth...

  19. Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening?

    DEFF Research Database (Denmark)

    Hansen, Thomas Willum; DeLaRiva, Andrew T.; Challa, Sivakumar R.

    2013-01-01

    Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal...... review recent evidence obtained via in situ methods to determine the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that, in phase I, OR is responsible for the rapid loss of activity that occurs when particles are very small. Surprisingly, very...

  20. Metal organic frameworks for the catalytic detoxification of chemical warfare nerve agents

    Energy Technology Data Exchange (ETDEWEB)

    Hupp, Joseph T.; Farha, Omar K.; Katz, Michael J.; Mondloch, Joseph E.

    2017-04-18

    A method of using a metal organic framework (MOF) comprising a metal ion and an at least bidendate organic ligand to catalytically detoxify chemical warfare nerve agents including exposing the metal-organic-framework (MOF) to the chemical warfare nerve agent and catalytically decomposing the nerve agent with the MOF.

  1. Depositing nanometer-sized particles of metals onto carbon allotropes

    Science.gov (United States)

    Watson, Kent A. (Inventor); Fallbach, Michael J. (Inventor); Ghose, Sayata (Inventor); Smith, Joseph G. (Inventor); Delozier, Donavon M. (Inventor); Connell, John W. (Inventor)

    2010-01-01

    A process for depositing nanometer-sized metal particles onto a substrate in the absence of aqueous solvents, organic solvents, and reducing agents, and without any required pre-treatment of the substrate, includes preparing an admixture of a metal compound and a substrate by dry mixing a chosen amount of the metal compound with a chosen amount of the substrate; and supplying energy to the admixture in an amount sufficient to deposit zero valance metal particles onto the substrate. This process gives rise to a number of deposited metallic particle sizes which may be controlled. The compositions prepared by this process are used to produce polymer composites by combining them with readily available commodity and engineering plastics. The polymer composites are used as coatings, or they are used to fabricate articles, such as free-standing films, fibers, fabrics, foams, molded and laminated articles, tubes, adhesives, and fiber reinforced articles. These articles are well-suited for many applications requiring thermal conductivity, electrical conductivity, antibacterial activity, catalytic activity, and combinations thereof.

  2. Metallic magnetic bolometers for particle detection

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Enss, C.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M. (Brown Univ., Providence, RI (United States))

    1993-11-01

    The magnetization of localized spins in metals is discussed as a sensor for the low temperature calorimetric detection of particles. The magnetization of localized paramagnetic ions in metals can be used as a very sensitive sensor for the calorimetric detection of particles at low temperatures. The strong coupling of the localized spins to the conduction electrons results in very fast thermal equilibration between the two systems. Even though the concentration of spins must be kept small in metals to avoid spin-spin coupling by indirect exchange, the metallic magnetic bolometer can achieve very high sensitivities. In general, the sensitivity increases very rapidly with decreasing temperature.

  3. Anchoring noble metal nanoparticles on CeO2 modified reduced graphene oxide nanosheets and their enhanced catalytic properties.

    Science.gov (United States)

    Ji, Zhenyuan; Shen, Xiaoping; Xu, Yuling; Zhu, Guoxing; Chen, Kangmin

    2014-10-15

    The strategy of structurally integrating noble metal, metal oxide, and graphene is expected to offer prodigious opportunities toward emerging functions of graphene-based nanocomposites. In this study, we develop a facile two-step approach to disperse noble metal (Pt and Au) nanoparticles on the surface of CeO2 functionalized reduced graphene oxide (RGO) nanosheets. It is shown that Pt and Au with particle sizes of about 5 and 2nm are well dispersed on the surface of RGO/CeO2. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 was used as a model reaction to quantitatively evaluate the catalytic properties of the as-synthesized RGO/Pt/CeO2 and RGO/Au/CeO2 ternary nanocomposites. In such triple-component catalysts, CeO2 nanocrystals provide unique and critical roles for optimizing the catalytic performance of noble metallic Pt and Au, allowing them to express enhanced catalytic activities in comparison with RGO/Pt and RGO/Au catalysts. In addition, a possible mechanism for the enhanced catalytic activities of the RGO/Pt/CeO2 and RGO/Au/CeO2 ternary catalysts in the reduction of 4-NP is proposed. It is expected that our prepared graphene-based triple-component composites, which inherit peculiar properties of graphene, metal oxide, and noble metal, are attractive candidates for catalysis and other applications.

  4. New Catalytic DNA Biosensors for Radionuclides and Metal ion

    Energy Technology Data Exchange (ETDEWEB)

    Yi Lu

    2008-03-01

    We aim to develop new DNA biosensors for simultaneous detection and quantification of bioavailable radionuclides, such as uranium, technetium, and plutonium, and metal contaminants, such as lead, chromium, and mercury. The sensors will be highly sensitive and selective. They will be applied to on-site, real-time assessment of concentration, speciation, and stability of the individual contaminants before and during bioremediation, and for long-term monitoring of DOE contaminated sites. To achieve this goal, we have employed a combinatorial method called “in vitro selection” to search from a large DNA library (~ 1015 different molecules) for catalytic DNA molecules that are highly specific for radionuclides or other metal ions through intricate 3-dimensional interactions as in metalloproteins. Comprehensive biochemical and biophysical studies have been performed on the selected DNA molecules. The findings from these studies have helped to elucidate fundamental principles for designing effective sensors for radionuclides and metal ions. Based on the study, the DNA have been converted to fluorescent or colorimetric sensors by attaching to it fluorescent donor/acceptor pairs or gold nanoparticles, with 11 part-per-trillion detection limit (for uranium) and over million fold selectivity (over other radionuclides and metal ions tested). Practical application of the biosensors for samples from the Environmental Remediation Sciences Program (ERSP) Field Research Center (FRC) at Oak Ridge has also been demonstrated.

  5. Catalytic

    Directory of Open Access Journals (Sweden)

    S.A. Hanafi

    2014-03-01

    Full Text Available A series of dealuminated Y-zeolites impregnated by 0.5 wt% Pt catalysts promoted by different amounts of Ni, Pd or Cr (0.3 and 0.6 wt% were prepared and characterized as hydrocracking catalysts. The physicochemical and structural characterization of the solid catalysts were investigated and reported through N2 physisorption, XRD, TGA-DSC, FT-IR and TEM techniques. Solid catalysts surface acidities were investigated through FT-IR spectroscopy aided by pyridine adsorption. The solid catalytic activities were evaluated through hydroconversion of n-hexane and n-heptane employing micro-catalytic pulse technique directly connected to a gas chromatograph analyzer. The thermal stability of the solids was also investigated up to 800 °C. Crystallinity studies using the XRD technique of all modified samples proved analogous to the parent Y-zeolite, exhibiting nearly an amorphous and microcrystalline character of the second metal oxides. Disclosure of bimetallic catalysts crystalline characterization, through XRD, was not viable. The nitrogen adsorption–desorption isotherms for all samples concluded type I adsorption isotherms, without any hysteresis loop, indicating that the entire pore system is composed of micropores. TEM micrographs of the solid catalysts demonstrate well-dispersed Pt, Ni and Cr nanoparticles having sizes of 2–4 nm and 7–8 nm, respectively. The catalytic activity results indicate that the bimetallic (0.5Pt–0.3Cr/D18H–Y catalyst is the most active towards n-hexane and n-heptane isomerization while (0.5Pt–0.6Ni/D18H–Y catalyst can be designed as most suitable as a cracking catalyst.

  6. Laser Pulse Heating of Spherical Metal Particles

    Science.gov (United States)

    Tribelsky, Michael I.; Miroshnichenko, Andrey E.; Kivshar, Yuri S.; Luk'Yanchuk, Boris S.; Khokhlov, Alexei R.

    2011-10-01

    We consider the general problem of laser pulse heating of spherical metal particles with the sizes ranging from nanometers to millimeters. We employ the exact Mie solution of the diffraction problem and solve the heat-transfer equation to determine the maximum temperature rise at the particle surface as a function of optical and thermometric parameters of the problem. Primary attention is paid to the case when the thermal diffusivity of the particle is much larger than that of the environment, as it is in the case of metal particles in fluids. We show that, in this case, for any given duration of the laser pulse, the maximum temperature rise as a function of the particle size reaches a maximum at a certain finite size of the particle. We suggest simple approximate analytical expressions for this dependence, which cover the entire parameter range of the problem and agree well with direct numerical simulations.

  7. Performance Assessment of Sintered Metal Fiber Filters in Fluid Catalytic Cracking Unit

    Directory of Open Access Journals (Sweden)

    Liang Yang

    2014-01-01

    Full Text Available A long-term test was performed in a fluid catalytic cracking (FCC hot gas filtration facility using sintered metal candle filters. The operating temperature and pressure were maximum 55°C and 0.28 MPa, respectively. Specific particle sampling systems were used to measure the particle size and concentration directly at high temperature. The range of inlet particle concentration is from 150 to 165 mg/Nm3. The outlet particle concentration is in the range of 0.71–2.77 mg/Nm3 in stable operation. The filtration efficiency is from 98.23% to 99.55%. The inlet volume median diameter and the outlet volume median diameter of the particle are about 1 μm and 2.2 μm, respectively. The cake thickness is calculated based on the equation of Carman-Kozeny. The effects of operating parameters including face velocity, gas cleaning pressure, pulse duration, and maximum pressure drop were investigated. The optimal operating conditions and cleaning strategies were determined. The results show that sintered metal fiber filters are suitable for industrial application due to the good performance and high efficiency observed.

  8. A review of recent advances on the effects of microstructural refinement and nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Varin, R. A.; Zbroniec, L. [University of Waterloo, Department of Mechanical and Mechatronics Engineering, Waterloo, Ontario (Canada); Polanski, M.; Bystrzycki, J. [Faculty of Advanced Technology and Chemistry, Military University of Technology, Warsaw (Poland)

    2011-07-01

    The recent advances on the effects of microstructural refinement and various nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides obtained in the last few years in the allied laboratories at the University of Waterloo (Canada) and Military University of Technology (Warsaw, Poland) are critically reviewed in this paper. The research results indicate that microstructural refinement (particle and grain size) induced by ball milling influences quite modestly the hydrogen storage properties of simple metal and complex metal hydrides. On the other hand, the addition of nanometric elemental metals acting as potent catalysts and/or metal halide catalytic precursors brings about profound improvements in the hydrogen absorption/desorption kinetics for simple metal and complex metal hydrides alike. In general, catalytic precursors react with the hydride matrix forming a metal salt and free nanometric or amorphous elemental metals/intermetallics which, in turn, act catalytically. However, these catalysts change only kinetic properties i.e. the hydrogen absorption/desorption rate but they do not change thermodynamics (e.g., enthalpy change of hydrogen sorption reactions). It is shown that a complex metal hydride, LiAlH{sub 4}, after high energy ball milling with a nanometric Ni metal catalyst and/or MnCl{sub 2} catalytic precursor, is able to desorb relatively large quantities of hydrogen at room temperature, 40 and 80 {sup o}C. This kind of behavior is very encouraging for the future development of solid state hydrogen systems. (authors)

  9. A Review of Recent Advances on the Effects of Microstructural Refinement and Nano-Catalytic Additives on the Hydrogen Storage Properties of Metal and Complex Hydrides

    Directory of Open Access Journals (Sweden)

    Jerzy Bystrzycki

    2010-12-01

    Full Text Available The recent advances on the effects of microstructural refinement and various nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides obtained in the last few years in the allied laboratories at the University of Waterloo (Canada and Military University of Technology (Warsaw, Poland are critically reviewed in this paper. The research results indicate that microstructural refinement (particle and grain size induced by ball milling influences quite modestly the hydrogen storage properties of simple metal and complex metal hydrides. On the other hand, the addition of nanometric elemental metals acting as potent catalysts and/or metal halide catalytic precursors brings about profound improvements in the hydrogen absorption/desorption kinetics for simple metal and complex metal hydrides alike. In general, catalytic precursors react with the hydride matrix forming a metal salt and free nanometric or amorphous elemental metals/intermetallics which, in turn, act catalytically. However, these catalysts change only kinetic properties i.e. the hydrogen absorption/desorption rate but they do not change thermodynamics (e.g., enthalpy change of hydrogen sorption reactions. It is shown that a complex metal hydride, LiAlH4, after high energy ball milling with a nanometric Ni metal catalyst and/or MnCl2 catalytic precursor, is able to desorb relatively large quantities of hydrogen at RT, 40 and 80 °C. This kind of behavior is very encouraging for the future development of solid state hydrogen systems.

  10. Preparation and Catalytic Properties of Polymer Supported Dendritic Metal Complex

    Institute of Scientific and Technical Information of China (English)

    LI Cui-ling; YANG Zhi-wang; KANG Qiao-xiang; MA Heng-chang; MA Xiao-peng; GAO Qi-kuan; GUO Zhen; LEI Zi-qiang

    2004-01-01

    Polymer supported materials are extensively used as oxidizing agent, reducing agent catalysts, photosensitizers ion exchange resins and agriculturally and pharmacologically active agents1. The application of polymer metal complexes has been widely investigated2. The polymer supported complex undergoes swelling in a suitable solvent medium and provides enough surface area in carrying out electron transfer reactions, which clearly emphasizes the influence of a polymer network in heterogeneous catalysis.In the present, we have succeeded in the grafting of "dendrimer-like" hyperbranched polymer onto the surface of chloromethyl polystyrene reactions.All the catalysts show promising catalytic activities for the oxidation of iso-propylbenzene in the mild reaction condition, in each case, hypnone 1, 2-phenyl-2-propanol 2 were obtained as the major products

  11. Metal-insulator-metal waveguides for particle trapping and separation.

    Science.gov (United States)

    Khan, Saara A; Chang, Chia-Ming; Zaidi, Zain; Shin, Wonseok; Shi, Yu; Ellerbee Bowden, Audrey K; Solgaard, Olav

    2016-06-21

    Optical particle trapping and separation are essential techniques in the fields of biology and chemistry. In many applications, it is important to identify passive separation techniques that only rely on intrinsic forces in a system with a fixed device geometry. We present a dual-waveguide sorter that utilizes the loss of metal-insulator-metal (MIM) waveguides for completely passive particle trapping and separation and is created using a unique angle sidewall deposition process. Our experiments show that an inner Au-Si3N4-Au waveguide is able to trap particles within the propagation distance of its dominant modes and release the particles into an outer Au-H2O-Au waveguide. The outer waveguide then propels the particles and separates them by size. The separation results are accurately modeled by a first-principles, analytical model.

  12. Bio-palladium: from metal recovery to catalytic applications.

    Science.gov (United States)

    De Corte, Simon; Hennebel, Tom; De Gusseme, Bart; Verstraete, Willy; Boon, Nico

    2012-01-01

    While precious metals are available to a very limited extent, there is an increasing demand to use them as catalyst. This is also true for palladium (Pd) catalysts and their sustainable recycling and production are required. Since Pd catalysts exist nowadays mostly under the form of nanoparticles, these particles need to be produced in an environment-friendly way. Biological synthesis of Pd nanoparticles ('bio-Pd') is an innovative method for both metal recovery and nanocatalyst synthesis. This review will discuss the different bio-Pd precipitating microorganisms, the applications of the catalyst (both for environmental purposes and in organic chemistry) and the state of the art of the reactors based on the bio-Pd concept. In addition, some main challenges are discussed, which need to be overcome in order to create a sustainable nanocatalyst. Finally, some outlooks for bio-Pd in environmental technology are presented.

  13. Variation of Pore Metrics in Metal-Organic Frameworks for Enhanced Storage and Catalytic Applications

    OpenAIRE

    Brown, Jonathan Ward

    2015-01-01

    With the principles of reticular chemistry, metal-organic frameworks (MOFs)with enhanced storage and catalytic capabilities have been prepared. This dissertationpresents the synthesis of azo-IRMOF-74-III for controllable release of cargomolecules as well as the catalytic testing of MOF-525-Mn and an isoreticular seriesof MOFs based on the MOF-5 framework. The variation of pore metrics inthese frameworks show the versatility of reticular chemistry and their applicationin catalytic reactions.Fi...

  14. Regulating the spatial distribution of metal nanoparticles within metal-organic frameworks to enhance catalytic efficiency

    Science.gov (United States)

    Yang, Qiu; Liu, Wenxian; Wang, Bingqing; Zhang, Weina; Zeng, Xiaoqiao; Zhang, Cong; Qin, Yongji; Sun, Xiaoming; Wu, Tianpin; Liu, Junfeng; Huo, Fengwei; Lu, Jun

    2017-01-01

    Composites incorporating metal nanoparticles (MNPs) within metal-organic frameworks (MOFs) have broad applications in many fields. However, the controlled spatial distribution of the MNPs within MOFs remains a challenge for addressing key issues in catalysis, for example, the efficiency of catalysts due to the limitation of molecular diffusion within MOF channels. Here we report a facile strategy that enables MNPs to be encapsulated into MOFs with controllable spatial localization by using metal oxide both as support to load MNPs and as a sacrificial template to grow MOFs. This strategy is versatile to a variety of MNPs and MOF crystals. By localizing the encapsulated MNPs closer to the surface of MOFs, the resultant MNPs@MOF composites not only exhibit effective selectivity derived from MOF cavities, but also enhanced catalytic activity due to the spatial regulation of MNPs as close as possible to the MOF surface. PMID:28195131

  15. Regulating the spatial distribution of metal nanoparticles within metal-organic frameworks to enhance catalytic efficiency

    Science.gov (United States)

    Yang, Qiu; Liu, Wenxian; Wang, Bingqing; Zhang, Weina; Zeng, Xiaoqiao; Zhang, Cong; Qin, Yongji; Sun, Xiaoming; Wu, Tianpin; Liu, Junfeng; Huo, Fengwei; Lu, Jun

    2017-02-01

    Composites incorporating metal nanoparticles (MNPs) within metal-organic frameworks (MOFs) have broad applications in many fields. However, the controlled spatial distribution of the MNPs within MOFs remains a challenge for addressing key issues in catalysis, for example, the efficiency of catalysts due to the limitation of molecular diffusion within MOF channels. Here we report a facile strategy that enables MNPs to be encapsulated into MOFs with controllable spatial localization by using metal oxide both as support to load MNPs and as a sacrificial template to grow MOFs. This strategy is versatile to a variety of MNPs and MOF crystals. By localizing the encapsulated MNPs closer to the surface of MOFs, the resultant MNPs@MOF composites not only exhibit effective selectivity derived from MOF cavities, but also enhanced catalytic activity due to the spatial regulation of MNPs as close as possible to the MOF surface.

  16. Investigation of metal nanoparticles encapsulated in polyelectrolyte multilayers for catalytic and antibacterial applications

    Science.gov (United States)

    Kidambi, Srividhya

    Metal nanoparticles are an interesting class of materials because they often exhibit properties different from those of the corresponding bulk metals. For example, bulk Au is not catalytically active, but recent studies show that Au nanoparticles can serve as catalysts for oxidation and hydrogenation reactions. Without a suitable support, however, metal particles aggregate, reducing surface area and eventually affecting the particle properties. To overcome this problem, this research employs the layer-by-layer (LbL) assembly technique, which was introduced by Decher in 1991, as a convenient method to prevent the aggregation of nanoparticles and immobilize them on solid supports. While the multilayers help in stabilizing the nanoparticles, they also aid in retaining important properties of Pd (catalytic) and silver (antibacterial) nanoparticles. Catalytic Pd nanoparticles in multilayer polyelectrolyte films can be easily prepared by alternating depositions of poly(acrylic acid) (PAA) and a polyethylenimine (PEI)-Pd(II) complex on alumina, and subsequent reduction of the Pd(II) by NaBH4. The polyelectrolytes limit aggregation of the particles and impart catalytic selectivity in the hydrogenation of alpha-substituted unsaturated alcohols by restricting access to catalytic sites. Hydrogenation of allyl alcohol by encapsulated Pd(0) nanoparticles can occur as much as 24-fold faster than hydrogenation of 3-methyl-l-penten-3-ol. In a related system, alternating adsorption of PdCl42- and polyethylenimine (PEI), followed by reduction of Pd(II), yields catalysts with a higher activity than found in [PAA/PEI-Pd(0)]nPAA films due to greater accessibility of the Pd nanocatalysts. In the [PAA/PEI-Pd(0)] nPAA system, turnover frequency decreases with the number of layers deposited, suggesting that the outer layer of the film is primarily responsible for catalysis. In contrast, turnover frequency increases with the number of deposited layers for reduced [PdCl42-/PEI] n films. We

  17. Influence of Catalyst Particle Size on the Critical Conditions of Catalytic Oxidation of Gases

    Science.gov (United States)

    Kalinchak, V. V.; Chernenko, A. S.; Kalugin, V. V.

    2014-03-01

    A method of determination of the critical conditions of catalytic surface ignition and firing of small contents of gases in a mixture of constant composition on a catalyst particle in the form of the dependence of the gas-mixture temperature on the particle size has been proposed. It has been shown that heat exchange by radiation with surrounding bodies that are cold relative to the gas mixture gives rise to a minimum on the dependences under study and to the upper limit for regions of self-ignition and firing on the catalyst diameter. Limiting conditions for catalytic self-ignition and firing of gases have been obtained.

  18. Catalytic copyrolysis of particle board and polypropylene over Al-MCM-48

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hannah; Choi, Suek Ju [School of Environmental Engineering, University of Seoul, Seoul 02504 (Korea, Republic of); Kim, Ji Man [Department of Chemistry, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Jeon, Jong-Ki [Department of Chemical Engineering, Kongju National University, Cheonan 31080 (Korea, Republic of); Park, Sung Hoon; Jung, Sang-Chul [Department of Environmental Engineering, Sunchon National University, Suncheon 57922 (Korea, Republic of); Kim, Sang Chai [Department of Environmental Education, Mokpo National University, Muan 58554 (Korea, Republic of); Park, Young-Kwon, E-mail: catalica@uos.ac.kr [School of Environmental Engineering, University of Seoul, Seoul 02504 (Korea, Republic of)

    2016-10-15

    Highlights: • Al-MCM-48 was used for catalytic copyrolysis of particle board and polypropylene. • Catalytic produced mainly hydrocarbons. • The hydrocarbons produced were mainly in the diesel range. - Abstract: Particle board and polypropylene (PP) at a mixing ratio of 1:1 were copyrolyzed over two Al-MCM-48 catalysts with Si/Al ratios of 20 and 80. The catalyst characteristics were examined by measuring the Brunauer-Emmett-Teller surface area, temperature programmed desorption of ammonia, and X-ray diffraction. The main pyrolysis products of particle board were oxygenates, acids, and phenolics, whereas a large quantity of hydrocarbons within the diesel fuel range was produced from copyrolysis with polypropylene. The catalytic copyrolysis of particle board and PP over the Al-MCM-48 catalysts produced bio-oil with a much larger hydrocarbon content than that from the catalytic pyrolysis of particle board only. The hydrocarbons produced were mainly in the diesel range, highlighting the potential for the production of high-quality fuel.

  19. Nanostructure of Metallic Particles in Light Water Reactor Used Nuclear Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Buck, Edgar C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mausolf, Edward J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mcnamara, Bruce K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Soderquist, Chuck Z. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schwantes, Jon M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-03-11

    The extraordinary nano-structure of metallic particles in light water reactor fuels points to possible high reactivity through increased surface area and a high concentration of high energy defect sites. We have analyzed the metallic epsilon particles from a high burn-up fuel from a boiling water reactor using transmission electron microscopy and have observed a much finer nanostructure in these particles than has been reported previously. The individual round particles that varying in size between ~20 and ~50 nm appear to consist of individual crystallites on the order of 2-3 nm in diameter. It is likely that in-reactor irradiation induce displacement cascades results in the formation of the nano-structure. The composition of these metallic phases is variable yet the structure of the material is consistent with the hexagonal close packed structure of epsilon-ruthenium. These findings suggest that unusual catalytic behavior of these materials might be expected, particularly under accident conditions.

  20. Impact of Inert Metal Particles Flow on Aluminium Plate

    Institute of Scientific and Technical Information of China (English)

    WANG Zhongqi; LIU Yi; CHEN Yahong; BAI Chunhua

    2008-01-01

    Inert metal explosive, a new kind of explosive, is a mixture of high explosive and inert metal particle.When this kind of explosive is detonated, an inert metal particle flow will be formed by the explosive product driving.To determine the characteristics of the movement of the metal particle flow, a series of aluminium plates were designed to be the targets on which the metal particle flow impacted.The test result was presented and a numerical model was set up to analyze the impact of the high speed inert metal particles on aluminium plate.Based on the numerical analysis, the relationship between the characteristic of the mark on the target plate and the initial condition of the inert metal particles was proposed.From the analysis of the impact on target plates, more information about the movement of the metal particles could be reconstructed.

  1. Dynamical quorum sensing and synchronization in collections of excitable and oscillatory catalytic particles

    Science.gov (United States)

    Tinsley, M. R.; Taylor, A. F.; Huang, Z.; Wang, F.; Showalter, K.

    2010-06-01

    We present experimental studies of interacting excitable and oscillatory catalytic particles in well-stirred and spatially distributed systems. A number of distinct paths to synchronized oscillatory behavior are described. We present an example of a Kuramoto type transition in a well-stirred system with a collective rhythm emerging on increasing the number density of oscillatory particles. Groups of spatially distributed oscillatory particles become entrained to a common frequency by organizing centers. Quorum sensing type transitions are found in populations of globally and locally coupled excitable particles, with a sharp transition from steady state to fully synchronized behavior at a critical density or group size.

  2. Metallization of DNA hydrogel: application of soft matter host for preparation and nesting of catalytic nanoparticles

    Science.gov (United States)

    Zinchenko, Anatoly; Che, Yuxin; Taniguchi, Shota; Lopatina, Larisa I.; G. Sergeyev, Vladimir; Murata, Shizuaki

    2016-07-01

    Nanoparticles (NPs) of Au, Ag, Pt, Pd, Cu and Ni of 2-3 nm average-size and narrow-size distributions were synthesized in DNA cross-linked hydrogels by reducing corresponding metal precursors by sodium borohydride. DNA hydrogel plays a role of a universal reactor in which the reduction of metal precursor results in the formation of 2-3 nm ultrafine metal NPs regardless of metal used. Hydrogels metallized with various metals showed catalytic activity in the reduction of nitroaromatic compounds, and the catalytic activity of metallized hydrogels changed as follows: Pd > Ag ≈ Au ≈ Cu > Ni > Pt. DNA hydrogel-based "soft catalysts" elaborated in this study are promising for green organic synthesis in aqueous media as well as for biomedical in vivo applications.

  3. Peruvian perovskite Between Transition-metal to PGM/PlatinumGroupMetal Catalytic Fusion

    Science.gov (United States)

    Maksoed, Wh-

    2016-11-01

    Strongly correlated electronic materials made of simple building blocks, such as a transition-metal ion in an octahedral oxygen cage forming a perovskite structure- Dagotto & Tokura for examples are the high-temperature superconductivity & the CMR/Colossal Magnetoresistance . Helium-4 denotes from LC Case,ScD: "Catalytic Fusion of Deuterium into Helium-4"- 1998 dealt with gaseous D2- "contacted with a supported metallic catalyst at superatmospheric pressure". The catalyst is a platinum-group metal, at about 0.5% - 1% by weight, on activated C. Accompanies Stephen J Geier, 2010 quotes "transition metal complexes", the Energy thus produced is enormous, and because the deuterium is very cheap in the form of heavy water (less than US 1/g), the fuel cost is very low (<<1 %/KwH). "The oceans contain enough deuterium to satisfy the Earth's energy needs for many millions of year" to keep "maria"/Latin name of seas &Deuteronomy to be eternally preserves. Heartfelt Gratitudes to HE. Mr. Prof. Ir. HANDOJO.

  4. Encapsulation of Bimetallic Metal Nanoparticles into Robust Zirconium-Based Metal-Organic Frameworks: Evaluation of the Catalytic Potential for Size-Selective Hydrogenation.

    Science.gov (United States)

    Rösler, Christoph; Dissegna, Stefano; Rechac, Victor L; Kauer, Max; Guo, Penghu; Turner, Stuart; Ollegott, Kevin; Kobayashi, Hirokazu; Yamamoto, Tomokazu; Peeters, Daniel; Wang, Yuemin; Matsumura, Syo; Van Tendeloo, Gustaaf; Kitagawa, Hiroshi; Muhler, Martin; Llabrés I Xamena, Francesc X; Fischer, Roland A

    2017-03-13

    The realization of metal nanoparticles (NPs) with bimetallic character and distinct composition for specific catalytic applications is an intensively studied field. Due to the synergy between metals, most bimetallic particles exhibit unique properties that are hardly provided by the individual monometallic counterparts. However, as small-sized NPs possess high surface energy, agglomeration during catalytic reactions is favored. Sufficient stabilization can be achieved by confinement of NPs in porous support materials. In this sense, metal-organic frameworks (MOFs) in particular have gained a lot of attention during the last years; however, encapsulation of bimetallic species remains challenging. Herein, the exclusive embedding of preformed core-shell PdPt and RuPt NPs into chemically robust Zr-based MOFs is presented. Microstructural characterization manifests partial retention of the core-shell systems after successful encapsulation without harming the crystallinity of the microporous support. The resulting chemically robust NP@UiO-66 materials exhibit enhanced catalytic activity towards the liquid-phase hydrogenation of nitrobenzene, competitive with commercially used Pt on activated carbon, but with superior size-selectivity for sterically varied substrates. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Porous Au-Ag Alloy Particles Inlaid AgCl Membranes As Versatile Plasmonic Catalytic Interfaces with Simultaneous, in Situ SERS Monitoring.

    Science.gov (United States)

    Cao, Qi; Yuan, Kaiping; Liu, Qinghe; Liang, Chongyun; Wang, Xiang; Cheng, Yi-Feng; Li, Qingqing; Wang, Min; Che, Renchao

    2015-08-26

    We present a novel porous Au-Ag alloy particles inlaid AgCl membrane as plasmonic catalytic interfaces with real-time, in situ surface-enhanced Raman spectroscopy (SERS) monitoring. The Au-Ag alloy particles inlaid AgCl membranes were obtained via a facile two-step, air-exposed, and room-temperature immersion reaction with appropriate annealing process. Owing to the designed integration of semiconductor component AgCl and noble metal Au-Ag particles, both the catalytic reduction and visible-light-driven photocatalytic activities toward organic contaminants were attained. Specifically, the efficiencies of about 94% of 4-nitrophenol (4-NP, 5 × 10(-5) M) reduction after 8 min of reaction, and degradation of rhodamine 6G (R6G, 10(-5) M) after 12 min of visible light irradiation were demonstrated. Moreover, efficiencies of above 85% of conversion of 4-NP to 4-aminophenol (4-AP) and 90% of R6G degradation were achieved as well after 6 cycles of reactions, by which robust recyclability was confirmed. Further, with distinct SERS signals generated simultaneously from the surfaces of Au-Ag particles under laser excitation, in situ SERS monitoring of the process of catalytic reactions with superior sensitivity and linearity has been realized. Overall, the capability of the Au-Ag particles inlaid AgCl membranes to provide SERS monitored catalytic and visible-light-driven photocatalytic conversion of organic pollutants, along with their mild and cost-effective fabrication method, would make sense for in-depth understanding of the mechanisms of (photo)catalytic reactions, and also future development of potable, multifunctional and integrated catalytic and sensing devices.

  6. Progress toward a catalytic alkenation using transition metal alkylidene and oxo complexes

    CERN Document Server

    Broughton, S

    2002-01-01

    We are seeking to develop a new methodology for the synthesis of alkenes. Our desire is to develop an efficient, versatile and highly atom efficient process that offers an environmentally sound and cost effective alternative for the synthetic and industrial chemist to consider over current, well established methodologies. We have conceived a transition metal mediated hypothetical catalytic cycle, the basis of which is a series of ligand interconversions effected by cycloaddition chemistry. This thesis represents a feasibility study into our hypothetical catalytic cycle. Chapter 1 introduces the established methodologies, our hypothetical catalytic cycle and gives a review of the most relevant chemistry. Chapter 2 details our results. Particular attention is paid to relevant concepts in catalysis and transition metal chemistry. Chapter 2.1 reports our experiences in synthesising ketenes. An efficient synthesis of diphenylketene sup 1 sup 3 C sub 2 is described. Our hypothetical catalytic cycle requires a chemo...

  7. Catalytic particles induced Marangoni flow: motion, pumping and self-assembly

    Science.gov (United States)

    Malgaretti, Paolo; Dominguez, Alvaro; Popescu, Mihail N.; Dietrich, Siegfried

    When catalytic particles, such as Janus particles, or enzymes are in the vicinity of a fluid-fluid interface, their behavior can be strongly modulated by the presence of the interface and/or by the inhomogeneity in the transport properties of the two fluid phases. Hence, the effective interaction with the interface can lead to novel dynamical regimes absent in homogeneous fluids. For example, if the by-products of the catalysis are surface active their spatial distribution will affect the local value of the surface tension. In such a scenario, when a catalytic particle approaches a fluid-fluid interface a Marangoni flow will set up as a response to the inhomogeneity in the surface tension induced by the byproducts of the catalysis. The onset of such a flow will attract the catalytic particle towards the interface. Interestingly the strength of such an effective attraction is strongly affected by the affinity of the byproduct to the interface as well as by the transport properties of the two fluid phases. In particular, for water-oil interfaces such an effect overwhelms other means of active transport such as self-diffusiophoresis and makes it suitable to enhance particle accumulation close to fluid-fluid interfaces. Finally I will discuss the onset of collective behavior.

  8. Biodiesel by catalytic reactive distillation powered by metal oxides

    NARCIS (Netherlands)

    Kiss, A.A.; Dimian, A.C.; Rothenberg, G.

    2008-01-01

    The properties and use of biodiesel as a renewable fuel as well as the problems associated with its current production processes are outlined. A novel sustainable esterification process based on catalytic reactive distillation is proposed. The pros and cons of manufacturing biodiesel via fatty acid

  9. Biodiesel by catalytic reactive distillation powered by metal oxides

    NARCIS (Netherlands)

    Kiss, A.A.; Dimian, A.C.; Rothenberg, G.

    2008-01-01

    The properties and use of biodiesel as a renewable fuel as well as the problems associated with its current production processes are outlined. A novel sustainable esterification process based on catalytic reactive distillation is proposed. The pros and cons of manufacturing biodiesel via fatty acid

  10. Catalytic synthesis of metal crystals using conductive polymers

    Science.gov (United States)

    Wang, Hsing-Lin; Li, Wenguang

    2008-01-15

    A method of forming metal nanoparticles using a polymer colloid that includes at least one conductive polymer and at least one polyelectrolyte. Metal ions are reduced in water by the conductive polymer to produce the nanoparticles, which may be then incorporated in the colloidal structure to form a colloid composite. The method can also be used to separate selected metal ions from aqueous solutions.

  11. Tuning interactions between zeolite and supported metal by physical-sputtering to achieve higher catalytic performances

    National Research Council Canada - National Science Library

    Li, Xin-Gang; Liu, Cheng; Sun, Jian; Xian, Hui; Tan, Yi-Sheng; Jiang, Zheng; Taguchi, Akira; Inoue, Mitsuhiro; Yoneyama, Yoshiharu; Abe, Takayuki; Tsubaki, Noritatsu

    2013-01-01

    .... Herein, we demonstrate a cobalt nano-catalyst synthesized by physical-sputtering method that the metallic cobalt nano-particles homogeneously disperse on the H-ZSM5 zeolite support with weak Metal-Support Interactions (MSI...

  12. Correlating metal poisoning with zeolite deactivation in an individual catalyst particle by chemical and phase sensitive X-ray microscopy

    NARCIS (Netherlands)

    Ruiz-Martinez, J.; Beale, A.M.; Deka, U.; O'Brien, M.G.; Quinn, P.D.; Mosselmans, J.F.W.; Weckhuysen, B.M.

    2013-01-01

    Fluid catalytic cracking (FCC) is the main conversion process used in oil refineries. An X-ray microscopy method is used to show that metal poisoning and related structural changes in the zeolite active material lead to a non-uniform core–shell deactivation of FCC catalyst particles. The study links

  13. Computer simulation of carburizers particles heating in liquid metal

    Directory of Open Access Journals (Sweden)

    K. Janerka

    2010-01-01

    Full Text Available In this article are introduced the problems of computer simulation of carburizers particles heating (anthracite, graphite and petroleum coke, which are present in liquid metal. The diameter of particles, their quantity, relative velocity of particles and liquid metal and the thermophysical properties of materials (thermal conductivity, specific heat and thermal diffusivity have been taken into account in calculations. The analysis has been carried out in the aspect of liquid metal carburization in metallurgical furnaces.

  14. Cross Linked Metal Particles for Low Noise Bolometer Materials

    Science.gov (United States)

    2016-12-12

    SECURITY CLASSIFICATION OF: This final report summarizes WSU’s progress from 4/2/2015 to 09/30/2016 on the project, "Cross-linked Metal Particles ...2016 Final Report: Cross-linked Metal Particles for Low-noise Bolometer Materials The views, opinions and/or findings contained in this report are...peer-reviewed journals: Number of Papers published in non peer-reviewed journals: Final Report: Cross-linked Metal Particles for Low-noise Bolometer

  15. A method for the separation of non-ferrous metal containing particles from a particle stream

    NARCIS (Netherlands)

    Van der Weijden, R.D.; Rem, P.C.

    2004-01-01

    The invention relates to a method for the recovery of non-ferrous metal-comprising particles from a particle stream. According to the invention, the particle stream is put onto a conveyor belt in the form of a monolayer such that with the aid of a liquid, at least the non-ferrous metal comprising

  16. Improvement of hydrogen isotope exchange reactions on Li4SiO4 ceramic pebble by catalytic metals

    Institute of Scientific and Technical Information of China (English)

    Cheng Jian Xiao; Chun Mei Kang; Xiao Jun Chen; Xiao Ling Gao; Yang Ming Luo; Sheng Hu; Xiao Lin Wang

    2012-01-01

    Li4SiO4 ceramic pebble is considered as a candidate tritium breeding material of Chinese Helium Cooled Solid Breeder Test Blanket Module (CH HCSB TBM) for the International Thermonuclear Experimental Reactor (ITER).In this paper,Li4SiO4 ceramic pebbles deposited with catalytic metals,including Pt,Pd,Ru and Ir,were prepared by wet impregnation method.The metal particles on Li4SiO4 pebble exhibit a good promotion of hydrogen isotope exchange reactions in H2-DzO gas system,with conversion equilibrium temperature reduction of 200-300 ℃.The out-of-pile tritium release experiments were performed using 1.0 wt% Pt/Li4SiO4 and Li4SiO4 pebbles irradiated in a thermal neutron reactor.The thermal desorption spectroscopy shows that Pt was effective to increase the tritium release rate at lower temperatures,and the ratio of tritium molecule (HT) to tritiated water (HTO) of 1.0 wt% Pt/Li4SiO4 was much more than that of Li4SiO4,which released mainly as HTO.Thus,catalytic metals deposited on Li4SiO4 pebble may help to accelerate the recovery of bred tritium particularly in low temperature region,and increase the tritium molecule form released from the tritium breeding materials.

  17. An improved d-band model of the catalytic activity of magnetic transition metal surfaces

    CERN Document Server

    Bhattacharjee, Satadeep; Lee, S C

    2016-01-01

    The d-band center model of Hammer and N{\\o}rskov is widely used in understanding and predicting catalytic activity on transition metal (TM) surfaces. Here, we demonstrate that this model is inadequate for capturing the complete catalytic activity of the magnetically polarized TM surfaces and propose its generalization. We validate the generalized model through comparison of adsorption energies of the NH$_3$ molecule on the surfaces of 3d TMs (V, Cr, Mn, Fe, Co, Ni, Cu and Zn) determined with spin-polarized density functional theory (DFT)-based methods with the predictions of our model. Compared to the conventional d-band model, where the nature of the metal-adsorbate interaction is entirely determined through the energy and the occupation of the d-band center, we emphasize that for the surfaces with high spin polarization, the metal-adsorbate system can be stabilized through a competition of the spin-dependent metal-adsorbate interactions.

  18. Corrosion of metal particle and metal evaporated tapes

    Science.gov (United States)

    Speliotis, Dennis E.

    Very high coercivity metal particle (MP) and metal evaporated (ME) tapes are being used in 8mm video and digital audio tape applications, and more recently in digital data recording applications. In view of the inherent susceptibility of such media to environmental corrosion, a number of recent studies have addressed their long term stability and archivability. These studies have used an accelerated corrosion test based either on elevated temperature-humidity or polluting gas atmospheres known as Battelle tests. A comparison of the Battelle test results performed at different laboratories reveals a large variation from one location to another, presumably due to incorrect replication of the Battelle condition. Furthermore, when the Battelle tests are performed on enclosed cartridges, it is quite possible that diffusion limits the penetration of the extremely low concentration polluting gaseous species to the inner layers of the tapes during the short time of the accelerated test, whereas in real life these diffusion limitations may not apply. To avoid this uncertainty, the corrosion behavior of commercial 8mm MP and ME tapes when cassettes without their external plastic cases were exposed to 50 deg C and 80 percent RH for 7.5 weeks is investigated.

  19. Catalytic incineration of CO and VOC emissions over supported metal oxide catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, Per-Olof

    1999-05-01

    Catalytic incineration is one of the methods to reduce the emissions of CO and VOCs. Low operation temperature and low catalyst cost are essential parameters for catalytic incinerators. Pt/Al{sub 2}O{sub 3} catalysts are frequently used today, but the cheaper metal oxide catalysts can be very competitive if comparable overall activity is obtained. This thesis concerns how it is possible to decrease the operation temperature for supported metal oxide catalysts by using different supports, active metal oxides and additives. In the thesis it is demonstrated that different copper oxide based catalysts have the best activity and durability for complete oxidation among several tested metal oxide catalysts. CuO{sub x} supported on TiO{sub 2} and Al{sub 2}O{sub 3} showed increased activity with the CuO{sub x} loading up to the threshold coverage for formation of crystalline CuO particles, which is 12 {mu}mol/m{sup 2} on TiO{sub 2} and 6 {mu}mol/m{sup 2} on Al{sub 2}O{sub 3}. Up to the threshold coverage for CuO formation, well dispersed copper oxide species were formed on TiO{sub 2}, and a dispersed copper aluminate surface phase was formed on Al{sub 2}O{sub 3}. Durability tests showed accelerated sintering of TiO{sub 2} by copper, but stabilisation was possible by modification of the TiO{sub 2} with CeO{sub x} before the deposition of CuO{sub x}. The stabilisation was obtained by formation of a Ce-O-Ti surface phase. Addition of CeO{sub x} also enhanced the activity of the copper oxide species thanks to favourable interaction between the active copper oxide species and the CeO{sub x} on the support, which could be seen as increased reducibility in TPR experiments. The increased activity and reducibility was also observed for CuO{sub x} supported on ceria modified Al{sub 2}O{sub 3}. In this regard it was shown that CuO{sub x} deposited on CeO{sub 2}(001) surfaces was substantially more active for CO oxidation than copper oxide deposited on CeO{sub 2}(111) Surfaces. This

  20. Engineering and Sizing Nanoreactors To Confine Metal Complexes for Enhanced Catalytic Performance

    NARCIS (Netherlands)

    Shakeri, Mozaffar; Roiban, Lucian; Yazerski, Vital; Prieto Gonzalez, Gonzalo; Klein Gebbink, Bert; de Jongh, Petra E.; de Jong, Krijn P.

    2014-01-01

    Homogeneous metal complexes often display superior activity and selectivity in catalysis of chemical transformations. Heterogenization of these complexes by immobilization on solid supports has been used to facilitate recovery, but this is often associated with a decrease in catalytic performance. W

  1. Nanostructure of metallic particles in light water reactor used nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Buck, Edgar C., E-mail: edgar.buck@pnnl.gov; Mausolf, Edward J.; McNamara, Bruce K.; Soderquist, Chuck Z.; Schwantes, Jon M.

    2015-06-15

    Highlights: • An extraordinary nano-structure has been observed in the noble metal particles that form in UO{sub 2} reactor fuels. • The composition of the particles was highly variable with low levels of uranium and plutonium present in the particles. • This nano-structure may play an important role in the behavior of nuclear fuels under accident conditions. - Abstract: An extraordinary nano-structure has been observed in the metallic (Mo–Tc–Ru–Rh–Pd) particles that are known to form during irradiated in light water nuclear reactor fuels. This structure points possible high catalytic reactivity through the occurrence of a very high surface area as well as defect sites. We have analyzed separated metallic particles from dissolved high burn-up spent nuclear fuel using scanning and transmission electron microscopy. The larger particles vary in diameter between ∼10 and ∼300 nm and possess a hexagonally close packed epsilon-ruthenium structure. These particles are not always single crystals but often consist of much smaller crystallites on the order of 1–3 nm in diameter with evidence suggesting the occurrence of some amorphous regions. It is possible that neutron irradiation and fission product recoils generated the unusual small crystallite size. The composition of the metallic particles was variable with low levels of uranium present in some of the particles. We hypothesize that the uranium may have induced the formation of the amorphous (or frustrated) metal structure. This unique nano-structure may play an important role in the environmental behavior of nuclear fuels.

  2. Anchoring and promotion effects of metal oxides on silica supported catalytic gold nanoparticles.

    Science.gov (United States)

    Luo, Jingjie; Ersen, Ovidiu; Chu, Wei; Dintzer, Thierry; Petit, Pierre; Petit, Corinne

    2016-11-15

    The understanding of the interactions between the different components of supported metal doped gold catalysts is of crucial importance for selecting and designing efficient gold catalysts for reactions such as CO oxidation. To progress in this direction, a unique supported nano gold catalyst Au/SS was prepared, and three doped samples (Au/SS@M) were elaborated. The samples before and after test were characterized by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). It is found that the doping metal species prefer to be located on the surface of gold nanoparticles and that a small amount of additional reductive metal leads to more efficient reaction. During the catalytic test, the nano-structure of the metal species transforms depending on its chemical nature. This study allows one to identify and address the contribution of each metal on the CO reaction in regard to oxidative species of gold, silica and dopants. Metal doping leads to different exposure of interface sites between Au and metal oxide, which is one of the key factors for the change of the catalytic activity. The metal oxides help the activation of oxygen by two actions: mobility inside the metal bulk and transfer of water species onto of gold nanoparticles.

  3. Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Shu-Lin; LI,Min-Jiao; OU,Zhong-Wen; CHEN,Guo-Xu; LIU,Fu-An; XIE,Jia-Qing

    2007-01-01

    It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p-nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.

  4. The catalytic behavior of La-Mn-O nanoparticle perovskite-type oxide catalysts for the combustion of the soot particle from the diesel engine

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; ZHAO Zhen; XU Chunming; LIU Jian; LU Zhixiao

    2005-01-01

    The La1-xMx MnO3(M=Li, Na, K, Rb, x=0, 0.10, 0.25) perovskite-type oxides whose sizes are nanoparticle have been prepared by the citric acid-ligated method. The characters of the catalysts were characterized by means of XRD, IR, SEM and BET surface area measurement. The catalytic activity for the combustion of soot particulate was evaluated by a technique of the temperature-programmed reaction. In the LaMnO3 catalyst, the partial substitution of alkali metal (Li, Na, K, Rb) into A-site enhanced the catalytic activity for the combustion of soot particle. The La0.75K0.25MnO3 oxides are good candidate catalysts for the soot particle removal reaction, and the combustion temperatures of soot particle are between 285℃ and 430℃ when the contact of catalysts and soot is loose, and their catalytic activities for the combustion of soot particle are as good as supported Pt catalysts, which is the best catalyst system so far reported for soot combustion under loose contact conditions.

  5. Flexible macrocycles as versatile supports for catalytically active metal clusters

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, JD; Gagnon, KJ; Teat, SJ; McIntosh, RD

    2016-02-12

    Here we present three structurally diverse clusters stabilised by the same macrocyclic polyphenol; t-butylcalix[8]arene. This work demonstrates the range of conformations the flexible ligand is capable of adopting, highlighting its versatility in metal coordination. In addition, a Ti complex displays activity for the ring-opening polymerisation of lactide

  6. Metal particle's precipitation behavior in direct reading ferrography precipitator tube

    Institute of Scientific and Technical Information of China (English)

    尹凤福; 李谋渭

    2004-01-01

    A new metal particle monitoring instrument was developed by improving the traditional direct reading ferrography. The precipitation behaviors of sub-magnetic particles, magnetic particles, and the mixture of these particles were examined with the instrument. The results show that the precipitation behavior of sub-magnetic metal particles of copper and aluminum is not random as it was believed previously. The sub-magnetic particles show a distribution in the precipitator tube, almost the same as the deposition curves as the magnetic particles have. The deposition amount of particles is increased in the oil which consists of several different kinds of particles. On the base of these experiments, a new index used for the total quantity of wear was redefined.

  7. Cylindrical dielectric barrier discharge plasma catalytic effect on chemical methods of silver nano-particle production

    Science.gov (United States)

    Bahrami, Zahra; Khani, Mohammad Reza; Shokri, Babak

    2016-11-01

    In this study, cylindrical dielectric barrier discharge plasma was used to study the catalytic effect on chemical methods of silver nano-particles for the first time. In this method, the processing time is short and the temperature of reaction is low. Also, the reactor is very simple, inexpensive, and accessible. In this work, pure AgNO3 as the precursor agent and poly vinyl pyrrolidone as the macromolecular surfactant were dissolved in ethanol as the solvent. UV-Vis and XRD were used to identify the colloidal and powder nano-particles, respectively. Optical emission spectroscopy was also used to identify the active species in plasma. Effects of gas flow rate, voltage, volume of solution, and processing time were also studied. Moreover, TEM and SEM images presented the mean diameter of nano-particle size around 10 to 20 nm. The results have been very promising.

  8. Effect of Metal Contamination on the Performance of Catalyst for Deep Catalytic Cracking Process

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhigang

    2009-01-01

    The effect of different metal contamination levels of catalysts for Deep Catalytic Cracking (DCC) on the distribu-tion and selectivity of DCC products was investigated in a FCC pilot unit. The pilot test results showed that the effects of the metal contamination level of catalyst on the propylene yield, the coke yield, the LPG yield, the gasoline yield, the selectivity of low carbon olefins, and coke selectivity was significant, and that the influence of metal contamination level on the conversion and dry gas yield was minor.

  9. Separating and recycling metals from mixed metallic particles of crushed electronic wastes by vacuum metallurgy.

    Science.gov (United States)

    Zhan, Lu; Xu, Zhenming

    2009-09-15

    During the treatment of electronic wastes, a crushing process is usually used to strip metals from various base plates. Several methods have been applied to separate metals from nonmetals. However, mixed metallic particles obtained from these processes are still a mixture of various metals, including some toxic heavy metals such as lead and cadmium. With emphasis on recovering copper and other precious metals, there have hitherto been no satisfactory methods to recover these toxic metals. In this paper, the criterion of separating metals from mixed metallic particles by vacuum metallurgy is built. The results show that the metals with high vapor pressure have been almost recovered completely, leading to a considerable reduction of environmental pollution. In addition, the purity of copper in mixed particles has been improved from about 80 wt % to over 98 wt %.

  10. Template Synthesis of Noble Metal Nanocrystals with Unusual Crystal Structures and Their Catalytic Applications.

    Science.gov (United States)

    Fan, Zhanxi; Zhang, Hua

    2016-12-20

    Noble metal nanocrystals own high chemical stability, unique plasmonic and distinctive catalytic properties, making them outstanding in many applications. However, their practical applications are limited by their high cost and scarcity on the earth. One promising strategy to solve these problems is to boost their catalytic performance in order to reduce their usage amount. To realize this target, great research efforts have been devoted to the size-, composition-, shape- and/or architecture-controlled syntheses of noble metal nanocrystals during the past two decades. Impressively, recent experimental studies have revealed that the crystal structure of noble metal nanocrystals can also significantly affect their physicochemical properties, such as optical, magnetic, catalytic, mechanical, electrical and electronic properties. Therefore, besides the well-established size, composition, shape, and architecture control, the rise of crystal structure-controlled synthesis of noble metal nanocrystals will open up new opportunities to further improve their functional properties, and thus promote their potential applications in energy conversion, catalysis, biosensing, information storage, surface enhanced Raman scattering, waveguide, near-infrared photothermal therapy, controlled release, bioimaging, biomedicine, and so on. In this Account, we review the recent research progress on the crystal structure control of noble metal nanocrystals with a template synthetic approach and their crystal structure-dependent catalytic properties. We first describe the template synthetic methods, such as epitaxial growth and galvanic replacement reaction methods, in which a presynthesized noble metal nanocrystal with either new or common crystal structure is used as the template to direct the growth of unusual crystal structures of other noble metals. Significantly, the template synthetic strategy described here provides an efficient, simple and straightforward way to synthesize unusual

  11. Impact of selective catalytic reduction on exhaust particle formation over excess ammonia events.

    Science.gov (United States)

    Amanatidis, Stavros; Ntziachristos, Leonidas; Giechaskiel, Barouch; Bergmann, Alexander; Samaras, Zissis

    2014-10-01

    The introduction of selective catalytic reduction (SCR) aftertreatment to meet stringent diesel NOx emission standards around the world increases exhaust ammonia. Further to the direct air quality and health implications of ammonia, this may also lead to particle formation in the exhaust. In this study, an ammonia SCR system was examined with respect to its impact on both solid and total exhaust particle number and size distribution, downstream of a diesel particulate filter (DPF). Fuel post-injection was conducted in some tests to investigate the effect of ammonia during active DPF regeneration. On average, the post-DPF solid >23 nm and total <23 nm particle number emissions were increased by 129% (range 80-193%) and by 67% (range 26-136%), respectively, when 100 ppm ammonia level was induced downstream of the SCR catalyst. This is a typical level during ammonia overdosing, often practiced for efficient NOx control. Ammonia did not have a significant additional effect on the high particle concentrations measured during DPF regeneration. Based on species availability and formation conditions, sulfate, nitrate, and chloride salts with ammonium are possible sources of the new particles formed. Ammonia-induced particle formation corresponds to an environmental problem which is not adequately addressed by current regulations.

  12. Assaying the catalytic potential of transition metal sulfides for abiotic carbon fixation

    Science.gov (United States)

    Cody, G. D.; Boctor, N. Z.; Brandes, J. A.; Filley, T. R.; Hazen, R. M.; Yoder, H. S.

    2004-05-01

    A suite of nickel, cobalt, iron, copper, and zinc containing sulfides are assayed for the promotion of a model carbon fixation reaction with relevance to local reducing environments of the early Earth. The assay tests the promotion of hydrocarboxylation (the Koch reaction) wherein a carboxylic acid is synthesized via carbonyl insertion at a metal-sulfide-bound alkyl group. The experimental conditions are chosen for optimal assay, i.e., high reactant concentrations and pressures (200 MPa) to enhance chemisorption, and high temperature (250°C) to enhance reaction kinetics. All of the metal sulfides studied, with the exception CuS, promote hydrocarboxylation. Two other significant reactions involve the catalytic reduction of CO to form a surface-bound methyl group, detected after nucleophilic attack by nonane thiol to form methyl nonyl sulfide, and the formation of dinonyl sulfide via a similar reaction. Estimation of the catalytic turnover frequencies for each of the metal sulfides with respect to each of the primary reactions reveals that NiS, Ni 3S 2, and CoS perform comparably to commonly employed industrial catalysts. A positive correlation between the yield of primary product to NiS and Ni 3S 2 surface areas provides strong evidence that the reactions are surface catalytic in these cases. The sulfides FeS and Fe (1-x)S are unique in that they exhibit evidence of extensive dissolution, thus, complicating interpretation regarding heterogeneous vs. homogeneous catalysis. With the exception of CuS, each of the metal sulfides promotes reactions that mimic key intermediate steps manifest in the mechanistic details of an important autotrophic enzyme, acetyl-CoA synthase. The relatively high temperatures chosen for assaying purposes, however, are incompatible with the accumulation of thioesters. The results of this study support the hypothesis that transition metal sulfides may have provided useful catalytic functionality for geochemical carbon fixation in a prebiotic

  13. Particle migration and gap healing around trabecular metal implants

    DEFF Research Database (Denmark)

    Rahbek, O; Kold, S; Zippor, B;

    2005-01-01

    Bone on-growth and peri-implant migration of polyethylene particles were studied in an experimental setting using trabecular metal and solid metal implants. Cylindrical implants of trabecular tantalum metal and solid titanium alloy implants with a glass bead blasted surface were inserted either...... in an exact surgical fit or with a peri-implant gap into a canine knee joint. We used a randomised paired design. Polyethylene particles were injected into the knee joint. In both types of surgical fit we found that the trabecular metal implants had superior bone ongrowth in comparison with solid metal...... implants (exact fit: 23% vs. 7% [p=0.02], peri-implant gap: 13% vs. 0% [p=0.02]. The number of peri-implant polyethylene particles was significantly reduced around the trabecular metal implants with a peri-implant gap compared with solid implants....

  14. Optimum Disposition of Metal Particles in the Propellant Grain

    Directory of Open Access Journals (Sweden)

    Leonid L. Minkov

    2014-01-01

    Full Text Available Using the dispersed metal in solid propellants to increase the temperature of combustion products leads to such a problem as the specific impulse loss due to the incomplete combustion of metal particles in the exhaust products. A redistribution of metal loaded into the propellant grain is one of the methods to decrease the specific impulse loss. This paper reports on the ways to obtain the optimum metal particle disposition for the case-bounded propellant grain of tube cross-sectional type. Three different approaches to analyze the metal combustion efficiency are discussed. The influence of the dynamic nonequilibrium of two-phase flow on the optimum metal particles disposition in the propellant grain of tube cross-sectional type is investigated.

  15. Impact electrochemistry: colloidal metal sulfide detection by cathodic particle coulometry.

    Science.gov (United States)

    Lim, Chee Shan; Pumera, Martin

    2015-10-28

    The determination of the size and concentration of colloidal nano and microparticles is of paramount importance to modern nanoscience. Application of the particle collision technique on metal and metal oxide nanoparticles has been intensively explored over the past decade owing to its ability to determine the particle size and concentration via reactions including the inherent oxidation or the reduction of nanoparticles as well as surface reactions catalysed by the nanoparticles. Transition metal dichalcogenide particles were previously quantified using the anodic (oxidative) particle coulometry method. Here we show that cathodic (reductive) particle coulometry can be favorably used for the detection of metal sulfide colloidal particles. The detection of sulfides of cobalt and lead was performed using the particle collision technique in this work. The presence of spikes confirmed the viability of detecting new and larger particles from compounds using reductive (cathodic) potentials. Such an expansion of the impact particle coulometry method will be useful and applicable to the determination of concentration and size of colloidal metal sulfide nanoparticles in general.

  16. Strong and coverage-independent promotion of catalytic activity of a noble metal by subsurface vanadium

    Science.gov (United States)

    Reichl, Wolfgang; Hayek, Konrad

    2003-07-01

    While common bimetallic surfaces have a variable composition, the stable subsurface alloys of V/Rh and V/Pd are characterised by a purely noble metal-terminated surface and the second metal positioned in near-surface layers. The uniform composition of the topmost surface layer excludes conventional ensemble effects in catalysis, and the activity of the surface can be controlled by the metal loading and by the temperature of annealing. For example, the activity of a polycrystalline Rh surface in CO hydrogenation is significantly increased by promotion with subsurface vanadium. The modification of the subsurface layer with a different metal must be considered a promising approach to improve the catalytic properties of a metal surface.

  17. Catalytic Activity of Dual Metal Cyanide Complex in Multi-component Coupling Reactions

    Institute of Scientific and Technical Information of China (English)

    Anaswara RAVINDRAN; Rajendra SRIVASTAVA

    2011-01-01

    Several dual metal cyanide catalysts were prepared from potassium ferrocyanide,metal chloride (where metal =Zn2+,Mn2+,Ni2+,Co2+ and Fe2+),t-butanol (complexing agent) and PEG-4000 (co-complexing agent).The catalysts were characterized by elemental analysis (CHN and X-ray fluorescence),X-ray diffraction,N2 adsorption-desorption,scanning electron microscopy,Fourier-transform infiared spectroscopy,and UV-Visible spectroscopy.The dual metal cyanide catalysts were used in several acid catalyzed multi-component coupling reactions for the synthesis of pharmaceutically important organic derivatives.In all these reactions,the Fe-Fe containing dual metal cyanide catalyst was the best catalyst.The catalysts can be recycled without loss in catalytic activity.The advantage of this method is the use of mild,efficient and reusable catalysts for various reactions,which makes them candidates for commercial use.

  18. Evaluation of Durable Metallic Supports for Catalytic Combustors

    Energy Technology Data Exchange (ETDEWEB)

    Pint, BA

    2003-10-08

    In 2000, a Cooperative Research and Development Agreement (CRADA) was undertaken between the Oak Ridge National Laboratory (ORNL) and Catalytica Energy Systems Incorporated (CESI) to determine the properties of current metallic catalyst supports and examine new candidate alloys for this application. A team was established at ORNL to examine oxidation-limited lifetime of these thin-walled metallic components using standard lifetime models and to measure the mechanical properties of the foils (40-200:m in thickness) which can differ substantially from bulk properties. Oxidation experiments were conducted on foil specimens at 700-1100 C in laboratory air and in air with 10 vol.% water vapor to better simulate the combustor environment. At the higher test temperatures, time to oxidation-induced (i.e. breakaway oxidation) failure was determined in 1h cycles in order to verify predictions from a standard reservoir-type oxidation lifetime model. Selected specimens were run for >10,000h in 100 or 500h cycles at lower test temperatures in order to determine the oxidation kinetics for the model. The creep properties of selected foils were measured for 4,000-8,000h at operation-relevant stresses and temperatures. None of the new candidate alloys significantly out-performed currently used alloys in laboratory testing, particularly in oxidation lifetime testing. Therefore, engine testing was not performed on any of the new candidate alloys. Both the oxidation- and creep-resistance of FeCrAl alloys was greater than expected and the results of the CRADA allowed CESI to extend life or increase operating temperatures for these lower cost substrate alloys in the next generation of catalyst modules. Three work areas were defined for the CRADA. The first area was investigating the oxidation behavior of current and candidate alloy foils. The goal was to obtain data such as the oxidation rate as a function of temperature and environment, the time to breakaway oxidation at high test

  19. Catalytic activity in individual cracking catalyst particles imaged throughout different life stages by selective staining

    Science.gov (United States)

    Buurmans, Inge L. C.; Ruiz-Martínez, Javier; Knowles, William V.; van der Beek, David; Bergwerff, Jaap A.; Vogt, Eelco T. C.; Weckhuysen, Bert M.

    2011-11-01

    Fluid catalytic cracking (FCC) is the major conversion process used in oil refineries to produce valuable hydrocarbons from crude oil fractions. Because the demand for oil-based products is ever increasing, research has been ongoing to improve the performance of FCC catalyst particles, which are complex mixtures of zeolite and binder materials. Unfortunately, there is limited insight into the distribution and activity of individual zeolitic domains at different life stages. Here we introduce a staining method to visualize the structure of zeolite particulates and other FCC components. Brønsted acidity maps have been constructed at the single particle level from fluorescence microscopy images. By applying a statistical methodology to a series of catalysts deactivated via industrial protocols, a correlation is established between Brønsted acidity and cracking activity. The generally applicable method has clear potential for catalyst diagnostics, as it determines intra- and interparticle Brønsted acidity distributions for industrial FCC materials.

  20. Nobel metal-TiO2 nanocomposites : synthesis, characterization and catalytic activity

    OpenAIRE

    Nascimento, Ana Cláudia Lobão do

    2016-01-01

    The work presented in this thesis is focused on the synthesis, characterization and catalytic activity of gold-TiO2 composites. We wanted to take advantage of the experience of the Colloid Chemistry Group, whose activity is strongly focused on the synthesis, characterization and evaluation of the formation mechanism of metal nanocrystals (mainly gold and silver) with size and shape control, which allows a fine-tuning of the optical response of these colloids in the UV-vis-NIR spectral range. ...

  1. Metal diffusion in smoothed particle hydrodynamics simulations of dwarf galaxies

    CERN Document Server

    Williamson, David John; Kawata, Daisuke

    2016-01-01

    We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows, and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths, by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]-[Fe/H] distribution in the gas, and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between "metal mass-loading" (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even...

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

    Science.gov (United States)

    Carnes, Corrie Leigh

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

  3. Catalytic decomposition of hydrogen peroxide on anthraquinonecyanine and phthalocyanine metal complexes in acid and alkaline electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Pobedinskiy, S.N.; Trofimenko, A.A.; Zharnikova, M.A.

    1985-12-01

    A study of octaoxyanthraquinonecyanines (OOATsM) and phthalocyanines (FTs) of cobalt, iron, and manganese determined their catalytic activity in the hydrogen peroxide decomposition reaction. Hydrogen peroxide decomposition on OOATsM and FTs of the metals studied follows the kinetic mechanisms of a reaction of the first order regardless of the central ion of the metal. Complexes with a central atom of iron are most active in decomposition of hydrogen peroxide. Catalytic activity of FTsFe exceeds that of FTsCo more than 10-fold. FTs are 10-fold greater than OOATsM in catalytic activity. Change from an acid to an alkali medium did not affect the kinetic mechanisms of the decomposition reaction but the reaction rate on both a carrier and on metal complexes is higher in an alkaline medium than in an acid medium. The affect of an alkaline medium on the hydrogen peroxide decomposition rate is greater for FTS complexes than for anthraquinone-cyanines. 5 references, 2 figures.

  4. Novel Base Metal-Palladium Catalytic Diesel Filter Coating with NO2 Reducing Properties

    DEFF Research Database (Denmark)

    Johansen, K.; Dahl, S.; Mogensen, G.

    2007-01-01

    A novel alternative base metal/palladium coat has been developed that has limited NO2 formation and which even removes NO2 in a wide temperature range.Soot combustion, HC conversion and CO conversion properties are comparable to current platinum based solutions but the coating has a more attractive...... price structure. The novel base metal/palladium catalytic coat has been applied on commercial silicon carbide wall flow diesel filters and tested in an engine test bench. Results from engine bench tests concerning soot combustion, HC-, CO-, NO2- removal with the novel coat will are compared to present...

  5. Bubbling bed catalytic hydropyrolysis process utilizinig larger catalyst particles and small biomass particles featuring an anti-slugging reactor

    Energy Technology Data Exchange (ETDEWEB)

    Marker, Terry L.; Felix, Larry G.; Linck, Martin B.; Roberts, Michael J.

    2016-12-06

    This invention relates to a process for thermochemically transforming biomass or other oxygenated feedstocks into high quality liquid hydrocarbon fuels. In particular, a catalytic hydropyrolysis reactor, containing a deep bed of fluidized catalyst particles is utilized to accept particles of biomass or other oxygenated feedstocks that are significantly smaller than the particles of catalyst in the fluidized bed. The reactor features an insert or other structure disposed within the reactor vessel that inhibits slugging of the bed and thereby minimizes attrition of the catalyst. Within the bed, the biomass feedstock is converted into a vapor-phase product, containing hydrocarbon molecules and other process vapors, and an entrained solid char product, which is separated from the vapor stream after the vapor stream has been exhausted from the top of the reactor. When the product vapor stream is cooled to ambient temperatures, a significant proportion of the hydrocarbons in the product vapor stream can be recovered as a liquid stream of hydrophobic hydrocarbons, with properties consistent with those of gasoline, kerosene, and diesel fuel. Separate streams of gasoline, kerosene, and diesel fuel may also be obtained, either via selective condensation of each type of fuel, or via later distillation of the combined hydrocarbon liquid.

  6. Bubbling bed catalytic hydropyrolysis process utilizing larger catalyst particles and smaller biomass particles featuring an anti-slugging reactor

    Science.gov (United States)

    Marker, Terry L; Felix, Larry G; Linck, Martin B; Roberts, Michael J

    2014-09-23

    This invention relates to a process for thermochemically transforming biomass or other oxygenated feedstocks into high quality liquid hydrocarbon fuels. In particular, a catalytic hydropyrolysis reactor, containing a deep bed of fluidized catalyst particles is utilized to accept particles of biomass or other oxygenated feedstocks that are significantly smaller than the particles of catalyst in the fluidized bed. The reactor features an insert or other structure disposed within the reactor vessel that inhibits slugging of the bed and thereby minimizes attrition of the catalyst. Within the bed, the biomass feedstock is converted into a vapor-phase product, containing hydrocarbon molecules and other process vapors, and an entrained solid char product, which is separated from the vapor stream after the vapor stream has been exhausted from the top of the reactor. When the product vapor stream is cooled to ambient temperatures, a significant proportion of the hydrocarbons in the product vapor stream can be recovered as a liquid stream of hydrophobic hydrocarbons, with properties consistent with those of gasoline, kerosene, and diesel fuel. Separate streams of gasoline, kerosene, and diesel fuel may also be obtained, either via selective condensation of each type of fuel, or via later distillation of the combined hydrocarbon liquid.

  7. Bubbling bed catalytic hydropyrolysis process utilizinig larger catalyst particles and small biomass particles featuring an anti-slugging reactor

    Science.gov (United States)

    Marker, Terry L.; Felix, Larry G.; Linck, Martin B.; Roberts, Michael J.

    2016-12-06

    This invention relates to a process for thermochemically transforming biomass or other oxygenated feedstocks into high quality liquid hydrocarbon fuels. In particular, a catalytic hydropyrolysis reactor, containing a deep bed of fluidized catalyst particles is utilized to accept particles of biomass or other oxygenated feedstocks that are significantly smaller than the particles of catalyst in the fluidized bed. The reactor features an insert or other structure disposed within the reactor vessel that inhibits slugging of the bed and thereby minimizes attrition of the catalyst. Within the bed, the biomass feedstock is converted into a vapor-phase product, containing hydrocarbon molecules and other process vapors, and an entrained solid char product, which is separated from the vapor stream after the vapor stream has been exhausted from the top of the reactor. When the product vapor stream is cooled to ambient temperatures, a significant proportion of the hydrocarbons in the product vapor stream can be recovered as a liquid stream of hydrophobic hydrocarbons, with properties consistent with those of gasoline, kerosene, and diesel fuel. Separate streams of gasoline, kerosene, and diesel fuel may also be obtained, either via selective condensation of each type of fuel, or via later distillation of the combined hydrocarbon liquid.

  8. Fluidized Bed Sputtering for Particle and Powder Metallization

    Science.gov (United States)

    2013-04-01

    Fluidized Bed Sputtering for Particle and Powder Metallization by Daniel M. Baechle, J. Derek Demaree, James K. Hirvonen, and Eric D...5069 ARL-TR-6435 April 2013 Fluidized Bed Sputtering for Particle and Powder Metallization Daniel M. Baechle, J. Derek Demaree, James K...YYYY) April 2013 2. REPORT TYPE Final 3. DATES COVERED (From - To) June 2008–June 2012 4. TITLE AND SUBTITLE Fluidized Bed Sputtering for

  9. Electronic spin susceptibility of metallic superconductive nano-particles

    Institute of Scientific and Technical Information of China (English)

    Li Feng; Chen Zhi-Qian; Li Qing

    2006-01-01

    We have observed the thermodynamic properties of metallic superconductive nano-particles in the grand canonical ensemble; and the level distribution and the level correlation between the discrete electronic energy levels are considered in the calculation of the electronic spin susceptibility of the ensemble numerically. The quantum effect, even-odd effect and other special effects existing in the metallic nano-particles are also studied in this article.

  10. Synthesis and Catalytic Features of Hybrid Metal Nanoparticles Supported on Cellulose Nanofibers

    Directory of Open Access Journals (Sweden)

    Hirotaka Koga

    2011-11-01

    Full Text Available The structural and functional design of metal nanoparticles has recently allowed remarkable progress in the development of high-performance catalysts. Gold nanoparticles (AuNPs are among the most innovative catalysts, despite bulk Au metal being regarded as stable and inactive. The hybridization of metal NPs has attracted major interest in the field of advanced nanocatalysts, due to electro-mediated ligand effects. In practical terms, metal NPs need to be supported on a suitable matrix to avoid any undesirable aggregation; many researchers have reported the potential of polymer-supported AuNPs. However, the use of conventional polymer matrices make it difficult to take full advantage of the inherent properties of the metal NPs, since most of active NPs are imbedded inside the polymer support. This results in poor accessibility for the reactants. Herein, we report the topochemical synthesis of Au and palladium (Pd bimetallic NPs over the surfaces of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-oxidized cellulose nanofibers (TOCNs, and their exceptional catalytic performance. Highly-dispersed AuPdNPs were successfully synthesized in situ on the crystal surfaces of TOCNs with a very high density of carboxylate groups. The AuPdNPs@TOCN nanocomposites exhibit excellent catalytic efficiencies in the aqueous reduction of 4-nitrophenol to 4-aminophenol, depending on the molar ratios of Au and Pd.

  11. Silver metal nano-matrixes as high efficiency and versatile catalytic reactors for environmental remediation

    Science.gov (United States)

    Dumée, Ludovic F.; Yi, Zhifeng; Tardy, Blaise; Merenda, Andrea; Des Ligneris, Elise; Dagastine, Ray R.; Kong, Lingxue

    2017-03-01

    Nano-porous metallic matrixes (NMMs) offer superior surface to volume ratios as well as enhanced optical, photonic, and electronic properties to bulk metallic materials. Such behaviours are correlated to the nano-scale inter-grain metal domains that favour the presence of electronic vacancies. In this work, continuous 3D NMMs were synthesized for the first time through a simple diffusion-reduction process whereby the aerogel matrix was functionalized with (3-Mercaptopropyl)trimethoxysilane. The surface energy of the silica monolith templates was tuned to improve the homogeneity of the reduction process while thiol functionalization facilitated the formation of a high density of seeding points for metal ions to reduce. The diameter of NMMs was between 2 and 1000 nm, corresponding to a silver loading between 1.23 and 41.16 at.%. A rates of catalytic degradation kinetics of these NMMS which is three orders of magnitude higher than those of the non-functionalized silver-silica structures. Furthermore, the enhancement in mechanical stability at nanoscale which was evaluated by Atomic Force Microscopy force measurements, electronic density and chemical inertness was assessed and critically correlated to their catalytic potential. This strategy opens up new avenues for design of complex architectures of either single or multi-metal alloy NMMs with enhanced surface properties for various applications.

  12. The Origin of the Catalytic Activity of a Metal Hydride in CO2 Reduction.

    Science.gov (United States)

    Kato, Shunsuke; Matam, Santhosh Kumar; Kerger, Philipp; Bernard, Laetitia; Battaglia, Corsin; Vogel, Dirk; Rohwerder, Michael; Züttel, Andreas

    2016-05-10

    Atomic hydrogen on the surface of a metal with high hydrogen solubility is of particular interest for the hydrogenation of carbon dioxide. In a mixture of hydrogen and carbon dioxide, methane was markedly formed on the metal hydride ZrCoHx in the course of the hydrogen desorption and not on the pristine intermetallic. The surface analysis was performed by means of time-of-flight secondary ion mass spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy, for the in situ analysis. The aim was to elucidate the origin of the catalytic activity of the metal hydride. Since at the initial stage the dissociation of impinging hydrogen molecules is hindered by a high activation barrier of the oxidised surface, the atomic hydrogen flux from the metal hydride is crucial for the reduction of carbon dioxide and surface oxides at interfacial sites.

  13. Plasma polymer-functionalized silica particles for heavy metals removal.

    Science.gov (United States)

    Akhavan, Behnam; Jarvis, Karyn; Majewski, Peter

    2015-02-25

    Highly negatively charged particles were fabricated via an innovative plasma-assisted approach for the removal of heavy metal ions. Thiophene plasma polymerization was used to deposit sulfur-rich films onto silica particles followed by the introduction of oxidized sulfur functionalities, such as sulfonate and sulfonic acid, via water-plasma treatments. Surface chemistry analyses were conducted by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Electrokinetic measurements quantified the zeta potentials and isoelectric points (IEPs) of modified particles and indicated significant decreases of zeta potentials and IEPs upon plasma modification of particles. Plasma polymerized thiophene-coated particles treated with water plasma for 10 min exhibited an IEP of less than 3.5. The effectiveness of developed surfaces in the adsorption of heavy metal ions was demonstrated through copper (Cu) and zinc (Zn) removal experiments. The removal of metal ions was examined through changing initial pH of solution, removal time, and mass of particles. Increasing the water plasma treatment time to 20 min significantly increased the metal removal efficiency (MRE) of modified particles, whereas further increasing the plasma treatment time reduced the MRE due to the influence of an ablation mechanism. The developed particulate surfaces were capable of removing more than 96.7% of both Cu and Zn ions in 1 h. The combination of plasma polymerization and oxidative plasma treatment is an effective method for the fabrication of new adsorbents for the removal of heavy metals.

  14. Metals in airpollution particles decrease whole blood coagulation time

    Science.gov (United States)

    The mechanism underlying the pro-coagulative effect of air pollution particle exposure is not known. We tested the postulate that 1) the soluble fraction ofan air pollution particle can affect whole blood coagulation time and 2) metals included in the soluble fraction are respons...

  15. Characterizations and Catalytic Properties of Transition Metal Ions Incorporated in Mesoporous Materials

    Institute of Scientific and Technical Information of China (English)

    WANG Ye

    2004-01-01

    Mesoporous materials typified by MCM-41 possess well-ordered mesoporous channels with controllable pore sizes from 2-30 nm, and are expected as desirable materials for catalysis.However, silicious mesoporous materials generally do not have sufficient intrinsic catalytic activities.Thus many studies have focused on introducing catalytically active sites. It is expected that different synthetic methods would result in different coordination structures of metal cations introduced in MCM-41, and thus different catalytic properties in catalytic reactions. The author's group has used two methods, i.e., direct hydrothermal synthesis (DHT) and template-ion exchange (TIE), for the syntheses of V-, Fe-, and Cr-MCM-41 and applied them as catalysts to selective oxidations of hydrocarbons. This paper highlights the characterizations of the coordination structures of these metal cations introduced into MCM-41 by the DHT and the TIE methods, and the structural-property relationships of these metal ion-containing MCM-41 materials in selective oxidation reactions.MCM-41 was prepared by hydrothermal synthesis using hexadecyltrimethylammonium bromide and sodium silicate as the sources of template and silicon, respectively. In the DHT method, metal cations were directly added into the synthesis gel before hydrothermal synthesis, while the exchanging of metal ions in ethanolic solutions with the template cations contained in the uncalcined MCM-41 was performed in the TIE method. XRD and N2-adsorption measurements showed that the mesoporous regularity was not destroyed with both synthetic methods for all the metal ion-containing MCM-41 with appropriate contents of metal cations.For V-MCM-41, the characterizations with mainly EXAFS suggested that V5+ cations were in tetrahedral coordination and mainly incorporated inside the framework of MCM-41 to substitute Si4+in the samples by the DHT method. Tetrahedrally coordinated Vanadyl species were also obtained by the TIE method, but the VO4

  16. Thermodynamic properties of ultra-small metallic particles

    Institute of Scientific and Technical Information of China (English)

    Cheng Nan-Pu; Zeng Su-Min; Chen Zhi-Qian

    2005-01-01

    The thermodynamic properties of ultra-small metallic particles within an ensemble are affected by the level distribution and the level correlation between the discrete electronic energy levels. The specific heat and spin susceptibility of ultra-small metallic particles in the canonical ensemble with an odd or even number of electrons are numerically calculated by considering the effects of the level statistics, and their behaviour at low and high temperatures is also discussed. As an example, the specific heat and spin susceptibility of nano-Al particles are calculated numerically in this paper.

  17. Les petites particules métalliques supportées Small Supported Metallic Particles

    Directory of Open Access Journals (Sweden)

    Rochefort A.

    2006-11-01

    Full Text Available Une étude critique des méthodes de préparation de catalyseurs monométalliques permet de voir que les techniques impliquant un échange (ionique ou chimique conduisent à des catalyseurs à forte dispersion avec des moyens relativement simples. Au niveau de la caractérisation des catalyseurs, il ne semble pas exister de méthodes exhaustives permettant d'étudier les phases métalliques contenant des cristallites de taille inférieure à 1. 0 nm. Les techniques de microscopie électronique à haute résolution, la spectroscopie XPS et l'EXAFS semblent par contre les plus prometteuses. L'influence du support joue à plusieurs niveaux, en particulier sur la morphologie, la structure et sur les propriétés électroniques de la phase métallique. L'intérêt particulier d'étudier les effets de support résulte dans la création de phase métallique plus active et sélective. The current aim of catalyst research is to develop more and more active and selective dispersed metallic phases for a given reaction as well as to improve their stability. Catalytic properties depend directly on the physicochemical characteristics of the metallic phase (size of crystallites, composition, electron structure, interactions with the support. This is why improving such catalysts requires mastering synthesis routes and the characterizing of small supported metallic particles. The aim of this critical study is to highlight both the preparation methods leading to well-controlled monometallic phases and the physical techniques suited for characterizing them. By considering the metal-support entity as a veritable catalytic space, we have examined the direct influence of the nature of the support on the end characteristics of the metallic particles (morphology, structure, electron properties. We have found that impregnation techniques with an interaction (physical or chemical can lead to high-dispersion metallic phases associated with a narrow dispersion of

  18. Catalytic-Metal/PdO(sub x)/SiC Schottky-Diode Gas Sensors

    Science.gov (United States)

    Hunter, Gary W.; Xu, Jennifer C.; Lukco, Dorothy

    2006-01-01

    Miniaturized hydrogen- and hydrocarbon-gas sensors, heretofore often consisting of Schottky diodes based on catalytic metal in contact with SiC, can be improved by incorporating palladium oxide (PdOx, where 0 less than or equal to x less than or equal to 1) between the catalytic metal and the SiC. In prior such sensors in which the catalytic metal was the alloy PdCr, diffusion and the consequent formation of oxides and silicides of Pd and Cr during operation at high temperature were observed to cause loss of sensitivity. However, it was also observed that any PdOx layers that formed and remained at PdCr/SiC interfaces acted as barriers to diffusion, preventing further deterioration by preventing the subsequent formation of metal silicides. In the present improvement, the lesson learned from these observations is applied by placing PdOx at the catalytic metal/SiC interfaces in a controlled and uniform manner to form stable diffusion barriers that prevent formation of metal silicides. A major advantage of PdOx over other candidate diffusion-barrier materials is that PdOx is a highly stable oxide that can be incorporated into gas sensor structures by use of deposition techniques that are standard in the semiconductor industry. The PdOx layer can be used in a gas sensor structure for improved sensor stability, while maintaining sensitivity. For example, in proof-of-concept experiments, Pt/PdOx/SiC Schottky-diode gas sensors were fabricated and tested. The fabrication process included controlled sputter deposition of PdOx to a thickness of 50 Angstroms on a 400-m-thick SiC substrate, followed by deposition of Pt to a thickness of 450 Angstroms on the PdOx. The SiC substrate (400 microns in thickness) was patterned with photoresist and a Schottky-diode photomask. A lift-off process completed the definition of the Schottky-diode pattern. The sensors were tested by measuring changes in forward currents at a bias potential of 1 V during exposure to H2 in N2 at temperatures

  19. Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nanoporous Carbons

    Science.gov (United States)

    Tang, Jing; Salunkhe, Rahul R.; Zhang, Huabin; Malgras, Victor; Ahamad, Tansir; Alshehri, Saad M.; Kobayashi, Naoya; Tominaka, Satoshi; Ide, Yusuke; Kim, Jung Ho; Yamauchi, Yusuke

    2016-07-01

    Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications.

  20. Tunable catalytic activity of solid solution metal-organic frameworks in one-pot multicomponent reactions.

    Science.gov (United States)

    Aguirre-Díaz, Lina María; Gándara, Felipe; Iglesias, Marta; Snejko, Natalia; Gutiérrez-Puebla, Enrique; Monge, M Ángeles

    2015-05-20

    The aim of this research is to establish how metal-organic frameworks (MOFs) composed of more than one metal in equivalent crystallographic sites (solid solution MOFs) exhibit catalytic activity, which is tunable by virtue of the metal ions ratio. New MOFs with general formula [InxGa1-x(O2C2H4)0.5(hfipbb)] were prepared by the combination of Ga and In. They are isostructural with their monometal counterparts, synthesized with Al, Ga, and In. Differences in their behavior as heterogeneous catalysts in the three-component, one pot Strecker reaction illustrate the potential of solid solution MOFs to provide the ability to address the various stages involved in the reaction mechanism.

  1. Simple tertiary phosphines to hexaphosphane ligands: Syntheses, transition metal chemistry and their catalytic applications

    Indian Academy of Sciences (India)

    Maravanji S Balakrishna; Sowmya Rao; Bimba Choubey

    2012-11-01

    Designing efficient phosphorus-based ligands to make catalysts for homogeneous catalysis has been a great challenge for chemists. Despite a plethora of phosphorus ligands ranging from simple tertiary phosphines to polyphosphines are known, the enthusiasm to generate new ones is mainly due to the demand from industry for economical and robust catalytic system operational under normal atmospheric conditions. In this context, we have developed new synthetic methodologies for making unusual inorganic ring systems containing trivalent phosphorus centres, novel phosphorus-based multidentate and hybrid ligands and explored their rich transition metal chemistry and catalytic applications. We have also fine tuned a few existing ligand systems with donor functionalities to employ them in homogeneous catalysis. The details are summarized in this account.

  2. The acanthocephalan Paratenuisentis ambiguus as a sensitive indicator of the precious metals Pt and Rh from automobile catalytic converters

    Energy Technology Data Exchange (ETDEWEB)

    Sures, B.; Zimmermann, S.; Sonntag, C.; Stueben, D.; Taraschewski, H

    2003-04-01

    The eel parasite, Paratenuisentis ambiguus, takes up and accumulates catalytic metals. - Recent studies revealed that intestinal acanthocephalans of fish can accumulate heavy metals to concentrations orders of magnitude higher than those in the host tissues or the aquatic environment. This significant heavy metal accumulation by acanthocephalans, even surpassing that of established free living accumulation bioindicators, encouraged us to study the bioavailability of the platinum-group-metals (PGM) Pt and Rh for parasites. These precious metals are used in catalytic converters of cars for exhaust gas purification in Europe since the early 1980s. In addition to the beneficial effect in reducing the emission of CH{sub x}, CO and NO{sub x} of cars there is an increasing emission of these metals. However, it still remains unclear if these elements become accumulated in the biosphere and whether they affect the health of organisms. The present study reveals that in European eels (Anguilla anguilla) naturally infected with the eoacanthocephalan parasite Paratenuisentis ambiguus and experimentally exposed to ground catalytic converter material, the parasites take up and accumulate the catalytic active metals Pt and Rh whereas in the examined host tissues we found no metal uptake. Compared with the PGM concentrations in the water the worms contained 1600 times higher Rh and 50 times higher Pt concentrations. Thus, the parasites can be used as sentinel organisms reflecting even very low levels of precious metals.

  3. One-Step Synthesis of Zeolite Membranes Containing Catalytic Metal Nanoclusters.

    Science.gov (United States)

    Kim, Seok-Jhin; Tan, Shuai; Taborga Claure, Micaela; Briones Gil, Laura; More, Karren L; Liu, Yujun; Moore, Jason S; Dixit, Ravindra S; Pendergast, John G; Sholl, David S; Jones, Christopher W; Nair, Sankar

    2016-09-21

    Metal-loaded zeolitic membranes are promising candidates as catalytic membrane reactors. We report a one-step synthesis method to synthesize zeolite membranes containing metal nanoclusters, that has advantages in comparison to multistep methods such as impregnation and ion exchange. Pure-silica MFI zeolite-Pt hybrid membranes were prepared by hydrothermal synthesis with addition of 3-mercaptopropyl-trimethoxysilane (MPS) and a platinum precursor. Composition analysis and mapping by energy-dispersive X-ray spectroscopy (EDX) reveal that Pt ions/clusters are uniformly distributed along the membrane cross-section. High-magnification scanning transmission electron microscopy (STEM) analysis shows that Pt metal clusters in the hybrid zeolite membrane have a diameter distribution in the range of 0.5-2.0 nm. In contrast, a pure-silica MFI membrane synthesized from an MPS-free solution shows negligible incorporation of Pt metal clusters. To characterize the properties of the hybrid (zeolite/metal) membrane, it was used as a catalytic membrane reactor (CMR) for high-temperature propane dehydrogenation (PDH) at 600 °C and 1 atm. The results indicate that Pt metal clusters formed within the MFI zeolite membrane can serve as effective catalysts for high-temperature PDH reaction along with H2 removal via membrane permeation, thereby increasing both conversion and selectivity in relation to a conventional membrane reactor containing an equivalent amount of packed Pt catalyst in contact with an MFI membrane. The hybrid zeolite-Pt CMR also showed stable conversion and selectivity upon extended high-temperature operation (12 h), indicating that encapsulation in the zeolite allowed thermal stabilization of the Pt nanoclusters and reduced catalyst deactivation.

  4. Oxidation Resistance Analysis Of Metallic (FeCrAl Foil Catalytic Converter Developed By Ultrasonic Approach

    Directory of Open Access Journals (Sweden)

    Leman A.M

    2016-01-01

    Full Text Available Mobile sources contribute about 44% of outdoor toxic emissions, approximately 50% of cancer risk and at around 74% of noncancer risk health problems. Catalytic converter is quite needed in removing the pollutant and in preventing a health problem. The main problem in the catalytic converter is low oxidation resistance when operated at high temperature. Therefore, this paper aimed to develop catalytic converter material in high-temperature operation at around 1100 °C using FeCrAl foils as a metallic catalytic converter which coated by γ-Al2O3. This research is conducted using 3 various techniques such as ultrasonic bath for 3, 4, and 5 hours, Nickel (Ni electroplating for 30, 45 and 60 minutes and the combination of ultrasonic bath and electroplating technique. Oxidation resistance analysis was conducted using tube furnace under argon gas for 60 hours in 3 cycles. Mass changes analysis of treated samples is showed by degradation mass. Lowest mass change of by ultrasonic bath samples is 0.3 wt%, for a combination of ultrasonic and electroplating samples is 0.3 wt% shown by UT 3 hours as well as 0.6 shown by EP 30 min. Parabolic rate constant is obtained by the time calculation based on the mass change of treated and untreated samples. It shown that UB 3 h is lowest parabolic rate constant of 2.258 × 10-20 g2 cm-4s -1 and UB 5 h is 1.13 × 10-20 g2 cm-4s -1. Lowest mass gain and lowest parabolic rate constant are become an indicator that the samples and that technique are recommended to fabricate the catalytic converter.

  5. Metal Diffusion in Smoothed Particle Hydrodynamics Simulations of Dwarf Galaxies

    Science.gov (United States)

    Williamson, David; Martel, Hugo; Kawata, Daisuke

    2016-05-01

    We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]-[Fe/H] distribution in the gas and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.

  6. High-Resolution Single-Molecule Fluorescence Imaging of Zeolite Aggregates within Real-Life Fluid Catalytic Cracking Particles**

    Science.gov (United States)

    Ristanović, Zoran; Kerssens, Marleen M; Kubarev, Alexey V; Hendriks, Frank C; Dedecker, Peter; Hofkens, Johan; Roeffaers, Maarten B J; Weckhuysen, Bert M

    2015-01-01

    Fluid catalytic cracking (FCC) is a major process in oil refineries to produce gasoline and base chemicals from crude oil fractions. The spatial distribution and acidity of zeolite aggregates embedded within the 50–150 μm-sized FCC spheres heavily influence their catalytic performance. Single-molecule fluorescence-based imaging methods, namely nanometer accuracy by stochastic chemical reactions (NASCA) and super-resolution optical fluctuation imaging (SOFI) were used to study the catalytic activity of sub-micrometer zeolite ZSM-5 domains within real-life FCC catalyst particles. The formation of fluorescent product molecules taking place at Brønsted acid sites was monitored with single turnover sensitivity and high spatiotemporal resolution, providing detailed insight in dispersion and catalytic activity of zeolite ZSM-5 aggregates. The results point towards substantial differences in turnover frequencies between the zeolite aggregates, revealing significant intraparticle heterogeneities in Brønsted reactivity. PMID:25504139

  7. Size-dependent structures and properties of metallic particles and thin films

    Science.gov (United States)

    Zhang, Zhenyuan

    Fundamental aspects of metallic nanoparticles, especially size-dependent properties and their interaction with their surrounding have been investigated. Several conclusions were reached as follows, (1) Au and Pt particles form dense SAMs on glass. Interparticle resonance is absent for 15 nm Au particles, but present for 30 nm ones. A new strategy was developed to deposit silica insulation layers in between Au particle monolayers. (2) Au particles, 1.5--20 nm in size, were encapsulated in silica shells. Their melting point was determined and we show that it decreases significantly as particle size decreases, leading to increased self-diffusion coefficient of the Au atoms. (3) Au core particles of different sizes were synthesized and Ag shells of different thickness were deposited on them. XAFS measurements show that Au/Ag alloy is spontaneously formed for the particles with small core size (2.5 nm). The alloy formation is size-dependent and molecular dynamics calculations demonstrate that vacancies at the bimetallic boundary dramatically enhance the rate of mixing. (4) EPR spectroscopy was used to study the interactions between stable free radicals and gold nanoparticles. The EPR signal is reduced upon adsorption of the radicals onto Au particle surface. We propose that the reduction in signal intensity arises from exchange interactions between the unpaired electrons of the adsorbed radicals and conduction-band electrons of the metallic particles. Catalytic autoxidation of TEMPAMINE to TEMPO was also observed and a mechanism for this unexpected reaction is proposed. (5) Redox/galvanic exchange reactions between Au and Pt nanoparticles and Ag(CN)2- were investigated. For Au particles, the exchange reaction is size dependent. 2.5 nm Au particles form an alloy with Ag and the extinction coefficient of the alloy particle linearly depends on the Au/Ag mole fraction. The full exchange for both 2 and 8 nm Pt particles indicates that the atom diffusion rate within particles

  8. Catalytic effect of transition metals on microwave-induced degradation of atrazine in mineral micropores.

    Science.gov (United States)

    Hu, Erdan; Cheng, Hefa

    2014-06-15

    With their high catalytic activity for redox reactions, transition metal ions (Cu(2+) and Fe(3+)) were exchanged into the micropores of dealuminated Y zeolites to prepare effective microporous mineral sorbents for sorption and microwave-induced degradation of atrazine. Due to its ability to complex with atrazine, loading of copper greatly increased the sorption of atrazine. Atrazine sorption on iron-exchanged zeolites was also significantly enhanced, which was attributed to the hydrolysis of Fe(3+) polycations in mineral micropores and electrostatic interactions of protonated atrazine molecules with the negatively charged pore wall surface. Copper and iron species in the micropores also significantly accelerated degradation of the sorbed atrazine (and its degradation intermediates) under microwave irradiation. The catalytic effect was attributed to the easy reducibility and high oxidation activity of Cu(2+) and Fe(3+) species stabilized in the micropores of the zeolites. It was postulated that the surface species of transition metals (monomeric Cu(2+), Cu(2+)-O-Cu(2+) complexes, FeO(+), and dinuclear Fe-O-Fe-like species) in the mineral micropores were thermally activated under microwave irradiation, and subsequently formed highly reactive sites catalyzing oxidative degradation of atrazine. The transition metal-exchanged zeolites, particularly the iron-exchanged ones, were relatively stable when leached under acidic conditions, which suggests that they are reusable in sorption and microwave-induced degradation. These findings offer valuable insights on designing of effective mineral sorbents that can selectively uptake atrazine from aqueous solutions and catalyze its degradation under microwave irradiation.

  9. Synthesis and catalytic properties of metal clusters encapsulated within small-pore (SOD, GIS, ANA) zeolites.

    Science.gov (United States)

    Goel, Sarika; Wu, Zhijie; Zones, Stacey I; Iglesia, Enrique

    2012-10-24

    The synthesis protocols for encapsulation of metal clusters reported here expand the diversity in catalytic chemistries made possible by the ability of microporous solids to select reactants, transition states, and products on the basis of their molecular size. We report a synthesis strategy for the encapsulation of noble metals and their oxides within SOD (Sodalite, 0.28 nm × 0.28 nm), GIS (Gismondine, 0.45 nm × 0.31 nm), and ANA (Analcime, 0.42 nm × 0.16 nm) zeolites. Encapsulation was achieved via direct hydrothermal synthesis for SOD and GIS using metal precursors stabilized by ammonia or organic amine ligands, which prevent their decomposition or precipitation as colloidal hydroxides at the conditions of hydrothermal synthesis (12), thereby causing precipitation of even ligand-stabilized metal precursors as hydroxides. As a result, encapsulation was achieved by the recrystallization of metal clusters containing GIS into ANA, which retained these metal clusters within voids throughout the GIS-ANA transformation.

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

    Science.gov (United States)

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

  11. The effect of microwave-assisted for photo-catalytic reaction in aqueous nano TiO2 particles dispersions.

    Science.gov (United States)

    Chae, Jeong-Seok; Chung, Minchul; Ahn, Ho-Geun; Jung, Sang-Chul

    2010-05-01

    In this study, the photo-catalytic degradation of methylene blue in TiO2 particles-dispersed aqueous solution was carried out by irradiating microwave and UV light simultaneously. The results of photocatalytic degradation of methylene blue showed that the decomposition rate increased with the microwave intensity, UV intensity, TiO2 particle dosages and the circulating fluid velocity. From the result of microwave-assisted photo-catalytic degradation of methylene blue, decomposition rate were shown gradually increased according to the increase of pH. The photo-catalytic degradation rate constant obtained under simultaneous irradiation of microwave and UV light case was about 1.5 times higher than irradiation of UV light only case. This result suggests that there is a synergy effect when the constituent techniques are applied together and that the additional irradiation of microwave can play a very important role in photo-catalysis of organic water pollutants.

  12. Controlled Shrinkage of Expanded Glass Particles in Metal Syntactic Foams.

    Science.gov (United States)

    Al-Sahlani, Kadhim; Taherishargh, Mehdi; Kisi, Erich; Fiedler, Thomas

    2017-09-13

    Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG) with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles' strength and tailor the mechanical properties of the expanded glass/metal syntactic foam (EG-MSF). The crushing strength of particles could be doubled by shrinking them for 20 min at 700 °C. Owing to the low density of EG (0.20-0.26 g/cm³), the resulting foam exhibits a low density (1.03-1.19 g/cm³) that increases slightly due to particle shrinkage. Chemical and physical analyses of EG particles and the resulting foams were conducted. Furthermore, metal syntactic foam samples were tested in uni-axial compression tests. The stress-strain curves obtained exhibit three distinct regions: elastic deformation followed by a stress plateau and densification commencing at 70-80% macroscopic strain. Particle shrinkage increased the mechanical strength of the foam samples and their average plateau stress increased from 15.5 MPa to 26.7 MPa.

  13. From Kinase to Cyclase: An Unusual Example of Catalytic Promiscuity Modulated by Metal Switching

    OpenAIRE

    Sánchez-Moreno, Israel; Iturrate Montoya, Laura; Martín-Hoyos, Rocio; Jimeno, M. Luisa; Mena, Montaña; Bastida, Ágatha; García-Junceda, Eduardo

    2009-01-01

    “This is the pre-peer reviewed version of the following article: Sánchez-Moreno, I., Iturrate, L., Martín-Hoyos, R., Jimeno, M. L., Mena, M., Bastida, A. and García-Junceda, E. (2009) From Kinase to Cyclase: An Unusual Example of Catalytic Promiscuity Modulated by Metal Switching. ChemBioChem. 10, 225-229, which has been published in final form at http://www3.interscience.wiley.com/journal/121544668/abstract?CRETRY=1&SRETRY=0.”

  14. Metals and metal oxides particles produced by pulsed laser ablation under high vacuum

    OpenAIRE

    SIRAJ, Khurram; TABASSUM, Yasir SOHAIL and Aasma

    2011-01-01

    A pulsed KrF Excimer laser (248 nm, 15 mJ) was utilized to synthesize different particles on (111) Si substrate under vacuum \\sim 10-6 torr using Aluminum (Al), Platinum (Pt), Tungsten (W), Molybdenum (Mo), Cadmium Oxide (CdO), and Yttrium Oxide (Y2O3) targets. Scanning electron microscope (SEM) was used to study particle size distribution on silicon substrate. The size of individual metal particles was found to be ranging from 71 nm to 2 m m whereas metal oxides particles were found...

  15. Instability of nanoscale metallic particles under electron irradiation in TEM

    Science.gov (United States)

    Chen, X. Y.; Zhang, S. G.; Xia, M. X.; Li, J. G.

    2016-03-01

    The stability of nano metallic glass under electron beam in transmission electron microscope (TEM) was investigated. The most common voltage of TEM used in metallic materials characterization was either 200 kV or 300 kV. Both situations were investigated in this work. An amorphous metallic particle with a dimension of a few hundred nanometers was tested under 300 keV electron irradiation. New phase decomposed from the parent phase was observed. Moreover, a crystal particle with the same composition and dimension was tested under 200 keV irradiation. Decomposition process also occurred in this situation. Besides, crystal orientation modification was observed during irradiation. These results proved that the electron beam in TEM have an effect on the stability of nanoscale samples during long time irradiation. Atomic displacement was induced and diffusion was enhanced by electron irradiation. Thus, artifacts would be induced when a nanoscale metallic sample was characterized in TEM.

  16. Kinetics study on catalytic wet air oxidation of phenol by several metal oxide catalysts

    Institute of Scientific and Technical Information of China (English)

    WAN Jia-feng; FENG Yu-jie; CAI Wei-min; YANG Shao-xia; SUN Xiao-jun

    2004-01-01

    Four metal oxide catalysts composed of copper (Cu), stannum (Sn), copper-stannum (Cu-Sn) and copper-cerium(Cu-Ce) respectively were prepared by the co-impregnation method, and γ-alumina(γ-Al2O3) is selected as support. A first-order kinetics model was established to study the catalytic wet air oxidation of phenol at different temperature when these catalysts were used. The model simulations are good agreement with present experimental data. Results showed that the reaction rate constants can be significantly increased when catalysts were used, and the catalyst of 6% Cu-10%Ce/γ-Al2O3 showed the best catalytic activity. This is consistent with the result of catalytic wet air oxidation of phenol and the COD removal can be arrived at 98.2% at temperature 210℃, oxygen partial pressure 3 MPa and reaction time 30 min. The activation energies of each reaction with different catalysts are nearly equal, which is found to be about 42 kJ/mol and the reaction in this study is proved to be kinetics control.

  17. Level Statistics and Specific Heat of Metallic Nano-Particles

    Institute of Scientific and Technical Information of China (English)

    程南璞; 陈志谦; 陈洪

    2003-01-01

    The thermodynamic properties of an ensemble of metallic nano-particles are affected by the level distribution and the level correlation between the discrete electronic energy levels. We numerically calculate the specific heat of metallic nano-particles in the canonical ensemble with an odd or even number of electrons by considering the effects of the level distribution and the level correlation. The behaviour of the specific heat at low and high temperatures, compared with the average nearest-neighbour level spacing, is also investigated.

  18. Quantum particle interacting with a metallic particle: Spectra from quantum Langevin theory

    Science.gov (United States)

    Loh, W. M. Edmund; Ooi, C. H. Raymond

    2017-01-01

    The effect of a nearby metallic particle on the quantum optical properties of a quantum particle in the four-level double Raman configuration is studied using the quantum Langevin approach. We obtain analytical expressions for the correlated quantum fields of Stokes and anti-Stokes photons emitted from the system and perform analysis on how the interparticle distance, the direction of observation or detection, the strengths of controllable laser fields, the presence of surface plasmon resonance, and the number density of the quantum particle affect the quantum spectra of the Stokes and anti-Stokes fields. We explore the physics behind the quantum-particle-metallic-nanoparticle interaction within the dipole approximation, that is, when the interparticle distance is much larger than the sizes of the particles. Our results show the dependence of the spectra on the interparticle distance in the form of oscillatory behavior with damping as the interparticle distance increases. At weaker laser fields the enhancement of quantum fields which manifests itself in the form of a Fano dip in the central peak of the spectra becomes significant. Also, the quantum-particle-metallic-nanoparticle coupling, which is affected by the size of the metallic nanoparticle and the number density of the quantum particle, changes the angular dependence of the spectra by breaking the angular rotational symmetry. In the presence of surface plasmon resonance the oscillatory dependence of the spectra on the interparticle distance and angles of observation becomes even stronger due to the plasmonic enhancement effect.

  19. A comparative DFT study of the catalytic activity of the 3d transition metal sulphides surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Balderas, R. (Depto de F& amp; #237; s. y Qu& amp; #237; m. Te& amp; #243; rica. Edif. B, Fac. de Qu& amp; #237; mica, UNAM ); Oviedo-Roa, R (Instituto Mexicano del Petroleo); Martinez-Magadan, J M.(Instituto Mexicano del Petroleo); Amador, C. (Depto de F& amp; #237; s. y Qu& amp; #237; m. Te& amp; #243; rica. Edif. B, Fac. de Qu& amp; #237; mica, UNAM ); Dixon, David A.(BATTELLE (PACIFIC NW LAB))

    2002-10-10

    The catalytic activity of the first transition metal series sulphides for hydrodesulfurization (HDS) reactions exhibits a particular behaviour when analysed as a function of the metal position in the Periodic Table. This work reports a comparative study of the electronic structure of the bulk and of the (0 0 1) metal surface (assumed to be the reactive surface) for the Sc-Zn monosulphides. The systems were modeled using the NiAs prototype crystal structure for the bulk and by applying the supercell model with seven atomic layers for (0 0 1) surfaces. The electronic structure of closed-packed solids code based on the density-functional theory and adopting the muffin-tin approximation to the potential was employed in the calculations of the electronic properties. For the Co and Ni sulphides, the density of states (DOS) variations between the metal atom present in the bulk and the ones exposed at the surface show that at the surface, there exists a higher DOS in the occupied states region just below the Fermi level. This feature might indicate a good performance of these two metal sulphides substrates in the HDS reactions favouring a donation, back-donation mechanism. In contrast, the DOS at the surface of Mn is increased in the unoccupied states region, just above the Fermi level. This suggests the possibility of a strong interaction with charge dontating sulphur adsorbate atoms poisoning the active substrate surface.

  20. Controlled Shrinkage of Expanded Glass Particles in Metal Syntactic Foams

    Directory of Open Access Journals (Sweden)

    Kadhim Al-Sahlani

    2017-09-01

    Full Text Available Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles’ strength and tailor the mechanical properties of the expanded glass/metal syntactic foam (EG-MSF. The crushing strength of particles could be doubled by shrinking them for 20 min at 700 °C. Owing to the low density of EG (0.20–0.26 g/cm3, the resulting foam exhibits a low density (1.03–1.19 g/cm3 that increases slightly due to particle shrinkage. Chemical and physical analyses of EG particles and the resulting foams were conducted. Furthermore, metal syntactic foam samples were tested in uni-axial compression tests. The stress-strain curves obtained exhibit three distinct regions: elastic deformation followed by a stress plateau and densification commencing at 70–80% macroscopic strain. Particle shrinkage increased the mechanical strength of the foam samples and their average plateau stress increased from 15.5 MPa to 26.7 MPa.

  1. Catalytic combustion of methane over alumina-supported palladium: Relationships between the oxidation state, particle size, morphology and activity

    Science.gov (United States)

    Lyubovsky, Maxim R.

    Supported palladium was studied as a catalyst for combustion of natural gas. The influence of variations in temperature and oxygen concentration, of addition of CO and water and of in situ hydrogen reduction on catalyst activity was studied experimentally. The activation energy for methane oxidation over crystalline PdO is about 17.5 kcal/mole and over metallic Pd - 40--45 kcal/mole. The difference in the activation energy is compensated by the preexponential coefficient that is 5--6 orders of magnitude higher for Pd than for PdO. In this work the activity variations under the different reaction conditions were correlated with the corresponding changes in the catalyst oxidation state, particle size and morphology. Formation of metallic hexagonal crystallites 100--200 nm in size was observed by TEM after PdO reduction, which resulted in an increase in the catalyst activity. Redispersion of these metallic crystallites into PdO clusters of 3--5 nm in size occurred during the Pd reoxidation, which resulted in a reversible increase of the catalyst activity on the cooling cycle, known as "negative activation." Activation of the methane molecule is the limiting step of the reaction over both the Pd and the PdO states. We propose that on the Pd surface the reaction occurs through the Langmuir-Hinshelwood mechanism. Under conditions of catalytic combustion the surface is completely covered with oxygen and competitive dissociative adsorption of methane is the limiting step of the process. The high heat of oxygen adsorption explains the high activation energy for the overall process. On the PdO surface the reaction occurs through a redox mechanism. A methane molecule interacts with a surface Pd-O dimer resulting in adsorbed CH3 and OH species. The activation energy of this interaction is about 15 kcal/mole and the probability is low due to the different multiplicity of the initial and final states of the transition complex. Oscillations in the reaction rate under fuel

  2. Supercritical Fluid Synthesis and Characterization of Catalytic Metal Nanoparticles on Carbon Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Xiangrong; Lin, Yuehe; Wang, Chong M.; Engelhard, Mark H.; Wang, Yong; Wai, Chien M.

    2004-02-27

    A rapid, convenient and environmentally benign method has been developed for the fabrication of metal nanoparticle/multiwall carbon nanotube (MWCNT) composites. Nanoparticles of palladium, rhodium and ruthenium are deposited onto functionalized MWCNTs through a simple hydrogen reduction of metal-?-diketone precursors in supercritical carbon dioxide, and are characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses. These highly dispersed nanoparticles, with a narrow range of size distribution and good adhesion on MWCNT surfaces, are expected to exhibit promising catalytic properties for a variety of chemical reactions. Preliminary experiments demonstrate that Pd nanoparticles supported on MWCNTs are effective catalysts for hydrogenation of olefins in carbon dioxide. The Pd nanoparticle?MWCNT composite also shows a high electrocatalytic activity in oxygen reduction for potential fuel cell application.

  3. Degradation of phenylamine by catalytic wet air oxidation using metal catalysts with modified supports.

    Science.gov (United States)

    Torrellas, Silvia A; Escudero, Gabriel O; Rodriguez, Araceli R; Rodriguez, Juan G

    2015-01-01

    The effect of acid treatments with HCl and HNO3 on the surface area and surface chemistry of three granular activated carbons was studied. These supports were characterized and the hydrochloric acid treatment leads to the best activated carbon support (AC2-C). The catalytic behavior of Pt, Ru and Fe (1 wt.%) supported on granular activated carbon treated with HCl was tested in the phenylamine continuous catalytic wet air oxidation in a three-phase, high-pressure catalytic reactor over a range of reaction temperatures 130-170ºC and total pressure of 1.0-3.0 MPa at LHSV = 0.4-1 h(-1), whereas the phenylamine concentration range and the catalyst loading were 5-16 mol.m(-3) and 0.5-1.5 g, respectively. Activity as well as conversion varied as a function of the metal, the catalyst preparation method and operation conditions. Higher activities were obtained with Pt incorporated on hydrochloric acid -treated activated carbon by the ion exchange method. In steady state, approximately 98% phenylamine conversion, 77% of TOC and 94% of COD removal, was recorded at 150ºC, 11 mol m(-3) of phenylamine concentration and 1.5 g of catalyst, and the selectivity to non-organic compounds was 78%. Several reaction intermediaries were detected. A Langmuir-Hinshelwood model gave an excellent fit of the kinetic data of phenylamine continuous catalytic wet air oxidation over the catalysts of this work.

  4. Highly reusability surface loaded metal particles magnetic catalyst microspheres (MCM-MPs) for treatment of dye-contaminated water

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying; Zhang, Kun, E-mail: kun4219@njtech.edu.cn; Yin, Xiaoshuang; Yang, Wenzhong; Zhu, Hongjun

    2016-04-01

    The metal-deposited magnetic catalyst microspheres (MCM-MPs) were successfully synthesized by one facile, high yield and controllable approach. Here, the bare magnetic microspheres were firstly synthesized according to the solvothermal method. Then silica shell were coated on the surface of the magnetic microspheres via sol–gel method, and subsequently with surface modifying with amino in the purpose to form SiO{sub 2}–NH{sub 2} shell. Thus, metal particles were easily adsorbed into the SiO{sub 2}–NH{sub 2} shell and in-situ reduced by NaBH{sub 4} solution. All the obtained products (MCM-Cu, MCM-Ag, MCM-Pd) which were monodisperse and constitutionally stable were exhibited high magnetization and excellent catalytic activity towards dyes solution reduction. The catalytic rate ratio of MCM-Pd: MCM-Cu: MCM-Ag could be 10:3:1. Besides, some special coordination compound Cu{sub 2}(OH){sub 3}Br had been generated in the in-situ reduced process of MCM-Cu, which produced superior cyclical stability (>20 times) than that of MCM-Ag and MCM-Pd. In all, those highly reusability and great catalytic efficiency of MCM-MPs show promising and great potential for treatment of dye-contaminated water. - Graphical abstract: Surface loaded metal particles magnetic catalyst microspheres MCM-MPs for rapid decolorizing dye-contaminated water: Synthesis, characterization and possible mechanisms. - Highlights: • A simple and high yield synthetic method for fabricate multi MCM-MPs is proposed with adequately optimize. • The highest reusability of MCM-Cu is attribute to the coordination compounds Cu{sub 2}(OH){sub 3}Br. • MCM-MPs show excellent catalytic properties under different situations for various dyes • The catalytic mechanism of MCM-MPs is presented.

  5. Preparation of rare-earth metal complex oxide catalysts for catalytic wet air oxidation

    Institute of Scientific and Technical Information of China (English)

    LI Ning; LI Guangming; YAO Zhenya; ZHAO Jianfu

    2007-01-01

    Catalytic wet air oxidation(CWAO)is one of the most promising technologies for pollution abatement.Developing catalysts with high activity and stability is crucial for the application of the CWAO process.The Mn/Ce complex oxide catalyrsts for CWAO of high concentration phenol containing wastewater were prepared by coprecipitation.The catalyst preparation conditions were optimized by using an orthogonal layout method and single-factor experimental analysis.The Mn/Ce serial catalysts were characterized by Brunauer-Emmett-Teller(BET)analysis and the metal cation leaching was measured by inductively coupled plasma torch-atomic emission spectrometry(ICP-AES).The results show that the catalysts have high catalytic activities even at a low temperature(80℃)and low oxygen partial pressure(0.5 MPa)in a batch reactor.The metallic ion leaching is comparatively low(Mn<6.577 mg/L and Ce<0.6910 mg/L,respectively)in the CWAO process.The phenol,CODCD and TOC removal efficiencies in the solution exceed 98.5% using the optimal catalyst(named CSP).The new catalyst would have a promising application in CWAO treatment of high concentration organic wastewater.

  6. Understanding the Enhanced Catalytic Performance of Ultrafine Transition Metal Nanoparticles–Graphene Composites

    KAUST Repository

    Liu, Xin

    2015-08-11

    Catalysis, as the key to minimize the energy requirement and environmental impact of today\\'s chemical industry, plays a vital role in many fields directly related to our daily life and economy, including energy generation, environment control, manufacture of chemicals, medicine synthesis, etc. Rational design and fabrication of highly efficient catalysts have become the ultimate goal of today\\'s catalysis research. For the purpose of handling and product separation, heterogeneous catalysts are highly preferred for industrial applications and a large part of which are the composites of transition metal nanoparticles (TMNPs). With the fast development of nanoscience and nanotechnology and assisted with theoretical investigations, basic understanding on tailoring the electronic structure of these nanocomposites has been gained, mainly by precise control of the composition, morphology, interfacial structure and electronic states. With the rise of graphene, chemical routes to prepare graphene were developed and various graphene-based composites were fabricated. Transition metal nanoparticles-reduced graphene oxide (TMNPs–rGO) composites have attracted considerable attention, because of their intriguing catalytic performance which have been extensively explored for energy- and environment-related applications to date. This review summarizes our recent experimental and theoretical efforts on understanding the superior catalytic performance of subnanosized TMNPs–rGO composites.

  7. Efficient selective catalytic reduction of NO by novel carbon-doped metal catalysts made from electroplating sludge.

    Science.gov (United States)

    Zhang, Jia; Zhang, Jingyi; Xu, Yunfeng; Su, Huimin; Li, Xiaoman; Zhou, Ji Zhi; Qian, Guangren; Li, Li; Xu, Zhi Ping

    2014-10-07

    Electroplating sludges, once regarded as industrial wastes, are precious resources of various transition metals. This research has thus investigated the recycling of an electroplating sludge as a novel carbon-doped metal (Fe, Ni, Mg, Cu, and Zn) catalyst, which was different from a traditional carbon-supported metal catalyst, for effective NO selective catalytic reduction (SCR). This catalyst removed >99.7% NO at a temperature as low as 300 °C. It also removed NO steadily (>99%) with a maximum specific accumulative reduced amount (MSARA) of 3.4 mmol/g. Gas species analyses showed that NO removal was accompanied by evolving N2 and CO2. Moreover, in a wide temperature window, the sludge catalyst showed a higher CO2 selectivity (>99%) than an activated carbon-supported metal catalyst. Structure characterizations revealed that carbon-doped metal was transformed to metal oxide in the sludge catalyst after the catalytic test, with most carbon (2.33 wt %) being consumed. These observations suggest that NO removal over the sludge catalyst is a typical SCR where metals/metal oxides act as the catalytic center and carbon as the reducing reagent. Therefore, our report probably provides an opportunity for high value-added utilizations of heavy-metal wastes in mitigating atmospheric pollutions.

  8. Nanostructured films of metal particles obtained by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Muniz-Miranda, M., E-mail: muniz@unifi.it [Dipartimento di Chimica “U. Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Gellini, C. [Dipartimento di Chimica “U. Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Giorgetti, E.; Margheri, G.; Marsili, P. [Istituto Sistemi Complessi (CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Lascialfari, L.; Becucci, L. [Dipartimento di Chimica “U. Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Trigari, S. [Istituto Sistemi Complessi (CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Giammanco, F. [Dipartimento di Fisica “E. Fermi”, Università di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy)

    2013-09-30

    Colloidal dispersions of silver and gold nanoparticles were obtained in pure water by ablation with nanosecond pulsed laser. Then, by filtration of the metal particles on alumina, we fabricated nanostructured films, whose surface morphology was examined by atomic force microscopy (AFM) and related to surface-enhanced Raman scattering (SERS) after adsorption of adenine. - Highlights: • Ag and Au colloidal nanoparticles were obtained by laser ablation. • Nanostructured Ag and Au films were fabricated by filtration of metal nanoparticles. • Surface morphology of metal films was investigated by atomic force microscopy. • Surface-enhanced Raman spectra (SERS) of adenine on metal films were obtained. • SERS enhancements were related to the surface roughness of the metal films.

  9. Interaction mechanism of non-metallic particles with crystallization front

    Directory of Open Access Journals (Sweden)

    Żak P. L.

    2017-03-01

    Full Text Available The process of steel solidification in the CCS mould is accompanied by a number of phenomena relating to the formation of non-metallic phase, as well as the mechanism of its interaction with the existing precipitations and the advancing crystallization front. In the solidification process the non-metallic inclusions may be absorbed or repelled by the moving front. As a result a specific distribution of non-metallic inclusions is obtained in the solidified ingot, and their distribution is a consequence of these processes. The interaction of a non-metallic inclusion with the solidification front was analyzed for alumina, for different values of the particle radius. The simulation was performed with the use of own computer program. Each time a balance of forces acting on a particle in its specific position was calculated. On this basis the change of position of alumina particle in relation to the front was defined for a specific radius and original location of the particle with respect to the front.

  10. The role of transition metal sulfides in hydrotreatment. 3. Acidity, XPS and catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    De Agudelo, M.M.; Reyes, L.G.; Do Campo, N.

    1987-05-15

    Although, recently, most of the research on catalysis has been devoted to hydrotreatment, attention has been paid to hydrodesulfurization (HDS) but very little has been done on hydrodemetallization (HDM). This article is part of a systematic study directed towards defining the role of transition metal sulfides in hydrotreatment reactions. Catalysts supported on silica or alumina have been considered. Acidity has been evaluated using pyridine as probe molecule. This property can be attributed to the sulfide phase of the catalysts. The alumina supported catalysts were more acid than the silica supported catalysts. Since the acidity might exclusively be of Lewis type, the pattern observed through the first row transition metal sulfides reflects the trend of the electron-acceptor character of these sulfides. The XPS results indicate that catalysts are partially sulfided (at 400 C). At the same time, the results corroborate a better Me-support interaction on alumina than on silica. The HDM and HDS intrinsic activities, using a desalphalted (DAO) Morichal as feed were evaluated normalizing conversion in terms of the surface metal sites per surface area. The intrinsic activity patterns obtained for the first row transition metal sulfides, were very similar to those mentioned of acidity, reaffirming the importance of the electronic structure of the sulfide phase on its catalytic activity. 21 refs.

  11. Nanostructured metal particle-modified electrodes for electrocatalytic and sensor applications

    Indian Academy of Sciences (India)

    Ramasamy Ramaraj

    2006-11-01

    Nanotechnology has become one of the most exciting frontier fields in analytical chemistry. The huge interest in nanomaterials, for example in chemical sensors and catalysis, is driven by their many desirable properties. Although metal is a poor catalyst in bulk form, nanometre-sized particles can exhibit excellent catalytic activity due to their relative high surface area-to-volume ratio and their interface-dominated properties, which significantly differ from those of the bulk material. The integration of metal nanoparticles into thin film of permselective membrane is particularly important for various applications, for example in biological sensing and in electrocatalysis. We have already established different techniques to design permselective membrane-coated chemically modified electrodes with incorporated redox molecules for electrocatalytic, electrochromic and sensor applications. Recently, we have prepared nanostructured platinum and copper (represented Mnano, M = Pt and Cu) modified GC/Nafion electrodes (GC/Nf/Mnano) and characterized by using AFM, XPS, XRD and electrochemical techniques. The nanostructured Mnano modified electrodes were utilized for efficient electrocatalytic selective oxidation of neurotransmitter molecules in the presence of interfering species such as ascorbic acid (AA) and uric acid (UA). It has been also shown that the modified electrodes could be used as sensors for the detection of submicromolar concentrations of biomolecules with practical applications to real samples such as blood plasma and dopamine hydrochloride injection solution. The GC/Cunano electrode has been used for catalytic reduction of oxygen.

  12. Metallogel templated synthesis and stabilization of silver-particles and its application in catalytic reduction of nitro-arene.

    Science.gov (United States)

    Sharma, Mukesh; Sarma, Plaban Jyoti; Goswami, Manash Jyoti; Bania, Kusum K

    2017-03-15

    Metallogel of iron-carboxylates was obtained from trans-1,2-cyclohexanedicarboxylic acid in dimethylformamide (DMF) at basic condition. Spectroscopic and SEM morphology study of the iron-metallogel revealed that the iron complex with dicarboxylic acid was linked together via carboxylates and led to a supramolecular helical like architecture. The synthesized metallogel served as an excellent template for in-situ reduction of silver ion to silver particles micro to nano scale range. Variation of AgNO3 concentration shepherd to change the morphology of the Ag-particles. AgNO3 concentration was found to affect the shape and size of silver particles. On going from lower to higher concentration shape of silver particles changed from spherical to large agglomerated particles. Cubic shape Ag-particles were found on treatment of 0.05M AgNO3 solution with metallogel. Cubical shape silver particles were found to be effective catalyst for nitro-arene reduction in presence of NaBH4. Density functional theory (DFT) calculations were performed to rationalize the role of Ag-particles in catalytic reduction of 4-nitrophenol to 4-aminophenol. Based on DFT study, we proposed that catalytic reduction occurred via Ag-hydride complex formation. Since metallogels as well as the 4-aminophenol are finding large application in pharmaceuticals industries therefore the current work can provide an alternatives path in production of 4-aminophenols. In addition to this, the synthesis of Ag-nanomaterials using metallogel as template can pave a new direction in the development of nanotechnology and might find wide applications in catalytic industrial processes. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. The effect of noble metals on catalytic methanation reaction over supported Mn/Ni oxide based catalysts

    Directory of Open Access Journals (Sweden)

    Wan Azelee Wan Abu Bakar

    2015-09-01

    Full Text Available Carbon dioxide (CO2 in sour natural gas can be removed using green technology via catalytic methanation reaction by converting CO2 to methane (CH4 gas. Using waste to wealth concept, production of CH4 would increase as well as creating environmental friendly approach for the purification of natural gas. In this research, a series of alumina supported manganese–nickel oxide based catalysts doped with noble metals such as ruthenium and palladium were prepared by wetness impregnation method. The prepared catalysts were run catalytic screening process using in-house built micro reactor coupled with Fourier Transform Infra Red (FTIR spectroscopy to study the percentage CO2 conversion and CH4 formation analyzed by GC. Ru/Mn/Ni(5:35:60/Al2O3 calcined at 1000 °C was found to be the potential catalyst which gave 99.74% of CO2 conversion and 72.36% of CH4 formation at 400 °C reaction temperature. XRD diffractogram illustrated that the supported catalyst was in polycrystalline with some amorphous state at 1000 °C calcination temperature with the presence of NiO as active site. According to FESEM micrographs, both fresh and used catalysts displayed spherical shape with small particle sizes in agglomerated and aggregated mixture. Nitrogen Adsorption analysis revealed that both catalysts were in mesoporous structures with BET surface area in the range of 46–60 m2/g. All the impurities have been removed at 1000 °C calcination temperature as presented by FTIR, TGA–DTA and EDX data.

  14. Visualizing Dealumination of a Single Zeolite Domain in a Real-Life Catalytic Cracking Particle.

    Science.gov (United States)

    Kalirai, Sam; Paalanen, Pasi P; Wang, Jian; Meirer, Florian; Weckhuysen, Bert M

    2016-09-05

    Fluid catalytic cracking (FCC) catalysts play a central role in the chemical conversion of crude oil fractions. Using scanning transmission X-ray microscopy (STXM) we investigate the chemistry of one fresh and two industrially deactivated (ECAT) FCC catalysts at the single zeolite domain level. Spectro-microscopic data at the Fe L3 , La M5 , and Al K X-ray absorption edges reveal differing levels of deposited Fe on the ECAT catalysts corresponding with an overall loss in tetrahedral Al within the zeolite domains. Using La as a localization marker, we have developed a novel methodology to map the changing Al distribution of single zeolite domains within real-life FCC catalysts. It was found that significant changes in the zeolite domain size distributions as well as the loss of Al from the zeolite framework occur. Furthermore, inter- and intraparticle heterogeneities in the dealumination process were observed, revealing the complex interplay between metal-mediated pore accessibility loss and zeolite dealumination.

  15. Method for removing strongly adsorbed surfactants and capping agents from metal to facilitate their catalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Adzic, Radoslav R.; Gong, Kuanping; Cai, Yun; Wong, Stanislaus; Koenigsmann, Christopher

    2016-11-08

    A method of synthesizing activated electrocatalyst, preferably having a morphology of a nanostructure, is disclosed. The method includes safely and efficiently removing surfactants and capping agents from the surface of the metal structures. With regard to metal nanoparticles, the method includes synthesis of nanoparticle(s) in polar or non-polar solution with surfactants or capping agents and subsequent activation by CO-adsorption-induced surfactant/capping agent desorption and electrochemical oxidation. The method produces activated macroparticle or nanoparticle electrocatalysts without damaging the surface of the electrocatalyst that includes breaking, increasing particle thickness or increasing the number of low coordination sites.

  16. Decoration of Micro-/Nanoscale Noble Metal Particles on 3D Porous Nickel Using Electrodeposition Technique as Electrocatalyst for Hydrogen Evolution Reaction in Alkaline Electrolyte.

    Science.gov (United States)

    Qian, Xin; Hang, Tao; Shanmugam, Sangaraju; Li, Ming

    2015-07-29

    Micro-/nanoscale noble metal (Ag, Au, and Pt) particle-decorated 3D porous nickel electrodes for hydrogen evolution reaction (HER) in alkaline electrolyte are fabricated via galvanostatic electrodeposition technique. The developed electrodes are characterized by field emission scanning electron microscopy and electrochemical measurements including Tafel polarization curves, cyclic voltammetry, and electrochemical impedance spectroscopy. It is clearly shown that the enlarged real surface area caused by 3D highly porous dendritic structure has greatly reinforced the electrocatalytic activity toward HER. Comparative analysis of electrodeposited Ag, Au, and Pt particle-decorated porous nickel electrodes for HER indicates that both intrinsic property and size of the noble metal particles can lead to distinct catalytic activities. Both nanoscale Au and Pt particles have further reinforcement effect toward HER, whereas microscale Ag particles exhibit the reverse effect. As an effective 3D hydrogen evolution cathode, the nanoscale Pt-particle-decorated 3D porous nickel electrode demonstrates the highest catalytic activity with an extremely low overpotential of -0.045 V for hydrogen production, a considerable exchange current density of 9.47 mA cm(-2) at 25 °C, and high durability in long-term electrolysis, all of which are attributed to the intrinsic catalytic property and the extremely small size of Pt particles.

  17. Metal nanoparticle/ionic liquid/cellulose: new catalytically active membrane materials for hydrogenation reactions.

    Science.gov (United States)

    Gelesky, Marcos A; Scheeren, Carla W; Foppa, Lucas; Pavan, Flavio A; Dias, Silvio L P; Dupont, Jairton

    2009-07-13

    Transition metal-containing membrane films of 10, 20, and 40 μm thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 ± 1.1 nm (Rh(0)) and 3.0 ± 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI·(NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 μm, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and better formability of the cellulose material. The nanoparticle/IL/CA combinations exhibit an excellent synergistic effect that enhances the activity and durability of the catalyst for the hydrogenation of cyclohexene. The nanoparticle/IL/cellulose acetate film membranes display higher catalytic activity (up to 7353 h(-1) for the 20 μm film of CA/IL/Pt(0)) and stability than the nanoparticles dispersed only in the IL.

  18. Research on atomic states, physical properties and catalytic performance of Ru metal

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Using the one-atom theory (OA) of pure metals, the atomic states of Ru metal with hcp structure, fcc structure, bcc structure and liquid state were determined as fol- lows: [Kr](4dn)3.78(4dc)2.22(5sc)1.77(5sf)0.23,Ψa(fcc-Ru)=[Kr](4dn)3.70(4dc)2.44 (5sc)1.42(5sf)0.44, Ψ a(bcc-Ru)=[Kr](4dn)4.00(4dc)2.22(5sc)1.56(5sf)0.22, Ψ a(L-Ru)=[Kr](4dn)4.00(4dc)2.00(5sc)1.52 (5sf)0.48. The potential curve and physical properties as a function of temperature for hcp-Ru such as lattice constant, cohesive energy, linear thermal expansion coeffi- cient, specific heat and Gibbs energy and so on were calculated quantitatively. The theoretical results are in excellent agreement with experimental value. The rela- tionship between the atomic states and catalytic performance was explained qualitatively and these supplied the designation of Ru metal and relative materials with theoretical instruction and complete data.

  19. Understanding Trends in Catalytic Activity: The Effect of Adsorbate-Adsorbate Interactions for CO Oxidation Over Transition Metals

    DEFF Research Database (Denmark)

    Grabow, Lars; Larsen, Britt Hvolbæk; Nørskov, Jens Kehlet

    2010-01-01

    Using high temperature CO oxidation as the example, trends in the reactivity of transition metals are discussed on the basis of density functional theory (DFT) calculations. Volcano type relations between the catalytic rate and adsorption energies of important intermediates are introduced...... and the effect of adsorbate-adsorbate interaction on the trends is discussed. We find that adsorbate-adsorbate interactions significantly increase the activity of strong binding metals (left side of the volcano) but the interactions do not change the relative activity of different metals and have a very small...... influence on the position of the top of the volcano, that is, on which metal is the best catalyst....

  20. 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.)

  1. Catalytic co-pyrolysis of waste particle board and polyproplylene over nanoporous Al-MCM-41 catalysts.

    Science.gov (United States)

    Lee, Hyung Won; Choi, Suek Joo; Jeon, Jong-Ki; Park, Sung Hoon; Park, Young-Kwon

    2014-11-01

    Catalytic co-pyrolysis of particle board, a waste wood biomass, and polypropylene (PP), a petroleum-based plastic, was carried out with a mixing ratio of 1:1 over a representative mesoporous material, Al-MCM-41 catalyst. The Si/Al ratios of the Al-MCM-41 catalysts were controlled at 20 and 80 to investigate the effect of the acidity of the catalyst. The characterization of the catalyst was performed by X-ray diffraction, N2 adsorption-desorption, and NH3 temperature-programmed desorption. The catalytic pyrolysis of the particle board showed a higher yield of gas and lower yield of oil than the non-catalytic pyrolysis. In oil, the concentration of levoglucosan decreased, and those of furans, furanones, cyclopentanones, aromatics, and light phenolics increased. In the case of the co-pyrolysis of the particle board and PP, C10-C17 products corresponding to the diesel range greatly increased and resulted in an improvement of the bio-oil quality. This suggests that PP is decomposed on the acidic sites of the Al-MCM-41 catalyst, resulting in an increased production of hydrocarbons in the range of diesel.

  2. Fluorine-doped carbon nanotubes as an efficient metal-free catalyst for destruction of organic pollutants in catalytic ozonation.

    Science.gov (United States)

    Wang, Jing; Chen, Shuo; Quan, Xie; Yu, Hongtao

    2017-09-27

    Metal-free carbon materials have been presented to be potential alternatives to metal-based catalysts for heterogeneous catalytic ozonation, yet the catalytic performance still needs to be enhanced. Doping carbon with non-metallic heteroatoms (e.g., N, B, and F) could alter the electronic structure and electrochemical properties of original carbon materials, has been considered to be an effective method for improving the catalytic activity of carbon materials. Herein, fluorine-doped carbon nanotubes (F-CNTs) were synthesized via a facile method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The as-synthesized F-CNTs exhibited notably enhanced catalytic activity towards catalytic ozonation for the degradation of organic pollutants. The oxalic acid removal efficiency of optimized F-CNTs was approximately two times as much as that of pristine CNTs, and even exceeded those of four conventional metal-based catalysts (ZnO, Al2O3, Fe2O3, and MnO2). The XPS and Raman studies confirmed that the covalent CF bonds were formed at the sp(3) C sites instead of sp(2) C sites on CNTs, not only resulting in high positive charge density of C atoms adjacent to F atoms, but remaining the delocalized π-system with intact carbon structure of F-CNTs, which then favored the conversion of ozone molecules (O3) into reactive oxygen species (ROS) and contributed to the high oxalic acid removal efficiency. Furthermore, electron spin resonance (ESR) studies revealed that superoxide radicals (O2(-)) and singlet oxygen ((1)O2) might be the dominant ROS that responsible for the degradation of oxalic acid in these catalytic systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Catalytic upgrading of sugar fractions from pyrolysis oils in supercritical mono-alcohols over Cu doped porous metal oxide

    NARCIS (Netherlands)

    Yin, Wang; Venderbosch, Hendrikus; Bottari, Giovanni; Krawzcyk, Krzysztof K.; Barta, Katalin; Heeres, Hero Jan

    In this work, we report on the catalytic valorization of sugar fractions, obtained by aqueous phase extraction of fast pyrolysis oils, in supercritical methanol (scMeOH) and ethanol (scEtOH) over a copper doped porous metal oxide (Cu-PMO). The product mixtures obtained are, in principle, suitable

  4. From Electronic Structure to Catalytic Activity: A Single Descriptor for Adsorption and Reactivity on Transition-Metal Carbides

    DEFF Research Database (Denmark)

    Vojvodic, A.; Hellman, Anders; Ruberto, C.

    2009-01-01

    Adsorption and catalytic properties of the polar (111) surface of transition-metal carbides (TMC's) are investigated by density-functional theory. Atomic and molecular adsorption are rationalized with the concerted-coupling model, in which two types of TMC surface resonances (SR's) play key roles...

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

    Science.gov (United States)

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

  6. Catalytic upgrading of sugar fractions from pyrolysis oils in supercritical mono-alcohols over Cu doped porous metal oxide

    NARCIS (Netherlands)

    Yin, Wang; Venderbosch, Hendrikus; Bottari, Giovanni; Krawzcyk, Krzysztof K.; Barta, Katalin; Heeres, Hero Jan

    2015-01-01

    In this work, we report on the catalytic valorization of sugar fractions, obtained by aqueous phase extraction of fast pyrolysis oils, in supercritical methanol (scMeOH) and ethanol (scEtOH) over a copper doped porous metal oxide (Cu-PMO). The product mixtures obtained are, in principle, suitable fo

  7. Solvent templates induced porous metal-organic materials: conformational isomerism and catalytic activity.

    Science.gov (United States)

    Ding, Ran; Huang, Chao; Lu, Jingjing; Wang, Junning; Song, Chuanjun; Wu, Jie; Hou, Hongwei; Fan, Yaoting

    2015-02-16

    Solvent templates induced Co-based metal-organic materials; conformational isomers {[Co2(pdpa)(CH3CN)(H2O)3]·CH3OH·H2O}n (1) and {[Co2(pdpa)(CH3CN)(H2O)3]}n (2) and {[Co5(pdpa)2(μ3-OH)2(H2O)6]·2H2O}n (3) [H4pdpa = 5,5'-(pentane-1,2-diyl)-bis(oxy)diisophthalic acid] were synthesized under the same solvothermal conditions except with different concentrations of cyclic ethers (1,4-dioxane or tetrahydrofuran) as structure-directing agents. Structural transformations from a three-dimensional (3D) framework of 1 containing channels with dimensions of ∼6 Å × 6 Å to a two-dimensional layer structure of 2 consisting of large open channels with a size of ∼15 Å × 8 Å and then to a 3D nonporous framework of 3, resulting from the different concentrations of cyclic ethers, were observed. The anion-π interactions between electron-efficient oxygen atoms of cyclic ethers and electron-deficient dicarboxylic acid aromatic cores in H4pdpa imported into the synthetic process accounted for the conformational change of the ligand H4pdpa and the following structural variations. A systematic investigation was conducted to explore how different concentrations of structure-directing agents affected the frameworks of resultant metal-organic frameworks. Furthermore, 1-3 were shown to be available heterogeneous catalysts for the synthesis of 2-imidazoline and 1,4,5,6-tetrahydropyrimidine derivatives by the cascade cycloaddition reactions of aromatic nitriles with diamines. The results showed that the catalytic activity of 2 was much higher than that of 1 and 3, because of its unique structural features, including accessible catalytic sites and suitable channel size and shape. In addition, a plausible mechanism for these catalytic reactions was proposed, and the reactivity-structure relationship was further clarified.

  8. Metal particles produced by laser ablation for ICP-MSmeasurements

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Jhanis J.; Liu, Chunyi; Wen, Sy-Bor; Mao, Xianglei; Russo, Richard E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm{sup -2}. Characterization of particles and correlation with Inductively Coupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of {approx} 50 and {approx} 12 for fs vs. ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the {sup 66}Zn transient signal by a factor of ten compared to nanosecond laser pulses.

  9. Synthesis of nanosized metal particles from an aerosol

    Directory of Open Access Journals (Sweden)

    Srećko R. Stopić

    2013-10-01

    Full Text Available The synthesis of metallic nanoparticles from the precursor solution of salts using the ultrasonic spray pyrolysis method was considered in this work. During the control of process parameters (surface tension and density, the concentration of solution, residence time of aerosol in the reactor, presence of additives, gas flow rate, decomposition temperature of aerosol, type of precursor and working atmosphere it is possible to guide the process in order to obtain powders with such a morphology which satisfies more complex requirements for the desired properties of advanced engineering materials.  Significant advance in the improvement of powder characteristics (lower particles sizes, better spheroidity, higher surface area was obtained by the application of the ultrasonic generator for the preparation of aerosols. Ultrasonic spray pyrolysis is performed by the action of a powerful source of ultrasound on the corresponding precursor solution forming the aerosol with a constant droplet size, which depends on the characteristics of liquid and the frequency of ultrasound. The produced aerosols were transported into the hot reactor, which enables the reaction to occur in a very small volume of a particle and formation of  nanosized powder. Spherical, nanosized particles of metals (Cu, Ag, Au, Co were produced with new and improved physical and chemical characteristics at the IME, RWTH Aachen University. The high costs associated with small quantities of produced nanosized particles represent a limitation of the USP-method. Therefore, scale up of the ultrasonic spray pyrolysis was performed as a final target in the synthesis of nanosized powder.

  10. Effect of metal particles in cermets on spectral selectivity

    Science.gov (United States)

    Gao, J. D.; Zhao, C. Y.; Wang, B. X.

    2017-03-01

    Most cermet-based coatings achieve their solar selectivities by the tandem interference effect, which has been widely studied. This study focused on the spectral selectivity achieved by the scattering effect of metal particles in cermet-based coatings. Previous research proved that reasonable solar selectivities can be obtained for cermets in the regime of particles with a radius of the order of 100 nm, but their solar absorptance is low (Cr, Ni, and W particles with radii of 10 nm, 50 nm, 100 nm, and 200 nm, which were embedded in Al2O3 and occupied 5% of the volume fraction. It was found that by arranging different particles in different layers, a very high solar absorptance (95.6%) could be achieved. Since their thermal emittance (˜25% at 600 °C) was higher than that of normal coatings, these coatings are recommended to be used in solar absorbers that have a high concentration factor. Finally, the dependent scattering effect was qualitatively considered by the coupled-dipole approach. With a metal volume fraction of 5%, it was found that the effect of dependent scattering was small and should not change the conclusions made based on independent scattering.

  11. Supported noble metal catalysts in the catalytic wet air oxidation of industrial wastewaters and sewage sludges.

    Science.gov (United States)

    Besson, M; Descorme, C; Bernardi, M; Gallezot, P; di Gregorio, F; Grosjean, N; Minh, D Pham; Pintar, A

    2010-12-01

    This paper reviews some catalytic wet air oxidation (CWAO) investigations of industrial wastewaters over platinum and ruthenium catalysts supported on TiO2 and ZrO2 formulated to be active and resistant to leaching, with particular focus on the stability of the catalyst. Catalyst recycling experiments were performed in batch reactors and long-term stability tests were conducted in trickle-bed reactors. The catalyst did not leach upon treatment of Kraft bleaching plant and olive oil mill effluents, and could be either recycled or used for long periods of time in continuous reactors. Conversely, these catalysts were rapidly leached when used to treat effluents from the production of polymeric membranes containing N,N-dimethylformamide. The intermediate formation of amines, such as dimethylamine and methylamine with a high complexing capacity for the metal, was shown to be responsible for the metal leaching. These heterogeneous catalysts also deactivated upon CWAO of sewage sludges due to the adsorption of the solid organic matter. Pre-sonication of the sludge to disintegrate the flocs and improve solubility was inefficient.

  12. ACIDIC REMOVAL OF METALS FROM FLUIDIZED CATALYTIC CRACKING CATALYST WASTE ASSISTED BY ELECTROKINETIC TREATMENT

    Directory of Open Access Journals (Sweden)

    R. B. G. Valt

    2015-06-01

    Full Text Available AbstractOne of the main uses of catalysts in the oil industry is in the fluidized catalytic cracking process, which generates large quantities of waste material after use and regeneration cycles and that can be treated by the electrokinetic remediation technique, in which the contaminant metals are transported by migration. In this study, deactivated FCC catalyst was characterized before and after the electrokinetic remediation process to evaluate the amount of metal removed, and assess structural modifications, in order to indicate a possible use as an adsorbent material. The analyses included pH measurement and the concentration profile of vanadium ions along the reactor, X-ray microtomography, X-ray fluorescence, BET analysis and DTA analysis. The results indicated that 40% of the surface area of the material was recovered in relation to the disabled material, showing an increase in the available area for the adsorption. The remediation process removed nearly 31% of the vanadium and 72% of the P2O5 adhering to the surface of the catalyst, without causing structural or thermal stability changes.

  13. Porphyrin-Metalation-Mediated Tuning of Photoredox Catalytic Properties in Metal–Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Jacob A.; Luo, Jian; Zhang, Xu; Chen, Yu-Sheng; Morton, Martha D.; Echeverría, Elena; Torres, Fernand E.; Zhang, Jian

    2015-09-04

    Photoredox catalytic activation of organic molecules via single-electron transfer processes has proven to be a mild and efficient synthetic methodology. However, the heavy reliance on expensive ruthenium and iridium complexes limits their applications for scale-up synthesis. To this end, photoactive metal–organic frameworks (MOFs) exhibit unique advantages as novel heterogeneous photocatalytic systems, yet their utilization toward organic transformations has been limited. Here we describe the preparation and synthetic applications of four isostructural porphyrinic MOFs, namely, UNLPF-10a, -10b, -11, and -12, which are composed of free base, InIII-, SnIVCl2-, and SnIV-porphyrin building blocks, respectively. We demonstrate that the metalation with high valent metal cations (InIII and SnIV) significantly modifies the electronic structure of porphyrin macrocycle and provides a highly oxidative photoexcited state that can undergo efficient reductive quenching processes to facilitate organic reactions. In particular, UNLPF-12 exhibits both outstanding photostability and efficient photocatalytic activities toward a range of important organic transformations including aerobic hydroxylation of arylboronic acids, amine coupling, and the Mannich reaction.

  14. Mimicking Catalytic Properties of Precious Metals by Using Common Metal Nanostructured Particles

    Science.gov (United States)

    2011-12-19

    Professor Renzo Rosei Consorzio per la Fisica Department of Physics Strada Costiera 11 Trieste, Italy 34151 EOARD Grant 10-3060...3060 Grant 10-3060 61102F Prof Renzo Rosei Consorzio per la Fisica Department of Physics Strada Costiera 11 Trieste, Italy 34151 N/A European Office...Physics Department, University of Trieste, Trieste, Italy and Consorzio per la Fisica , Trieste, Italy 1. Project motivation and Synopsis of

  15. Fe-Mn bi-metallic oxides loaded on granular activated carbon to enhance dye removal by catalytic ozonation.

    Science.gov (United States)

    Tang, Shoufeng; Yuan, Deling; Zhang, Qi; Liu, Yameng; Zhang, Qi; Liu, Zhengquan; Huang, Haiming

    2016-09-01

    A Fe-Mn bi-metallic oxide supported on granular activated carbon (Fe-Mn GAC) has been fabricated by an impregnation-desiccation method and tested in the catalytic ozonation of methyl orange (MO) degradation and mineralization. X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy characterizations revealed that Fe-Mn oxides were successfully loaded and uniformly distributed on the GAC, and nitrogen adsorption isotherms showed that the supported GAC retained a large surface area and a high pore volume compared with the pristine GAC. The catalytic activity was systematically assessed by monitoring the MO removal efficiencies at different operational parameters, such as catalyst dosage, initial solution pH, and ozone flow rate. The Fe-Mn GAC exhibited better catalytic activity relative to ozone alone and GAC alone, improving the TOC removal by 24.5 and 11.5 % and COD removal by 13.6 and 7.3 %, respectively. The reusability of the hybrid was examined over five consecutive cyclic treatments. The Fe-Mn GAC catalytic activity was only a slight loss in the cycles, showing good stability. The addition of Na2CO3 as hydroxyl radicals (•OH) scavengers proved that the catalytic ozonation mechanism was the enhanced generation of •OH by the Fe-Mn GAC. The above results render the Fe-Mn GAC an industrially promising candidate for catalytic ozonation of dye contaminant removal.

  16. Silver nanoparticles supported on CeO2-SBA-15 by microwave irradiation possess metal-support interactions and enhanced catalytic activity.

    Science.gov (United States)

    Qian, Xufang; Kuwahara, Yasutaka; Mori, Kohsuke; Yamashita, Hiromi

    2014-11-24

    Metal-support interactions (MSIs) and particle size play important roles in catalytic reactions. For the first time, silver nanoparticles supported on CeO2-SBA-15 supports are reported that possess tunable particle size and MSIs, as prepared by microwave (MW) irradiation, owing to strong charge polarization of CeO2 clusters (i.e., MW absorption). Characterizations, including TEM, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure, were carried out to disclose the influence of CeO2 contents on the Ag particle size, MSI effect between Ag nanoparticles and CeO2-SBA-15 supports, and the strong MW absorption of CeO2 clusters that contribute to the MSIs during Ag deposition. The Ag particle sizes were controllably tuned from 1.9 to 3.9 nm by changing the loading amounts of CeO2 from 0.5 to 2.0 wt%. The Ag nanoparticle size was predominantly responsible for the high turnover frequency (TOF) of 0.41 min(-1) in ammonia borane dehydrogenation, whereas both particle size and MSIs contributed to the high TOF of 555 min(-1) in 4-nitrophenol reduction for Ag/0.5CeO2-SBA-15, which were twice as large as those of Ag/SBA-15 without CeO2 and Ag/CeO2-SBA-15 prepared by conventional oil-bath heating.

  17. Bis(imidazolin-2-iminato) rare earth metal complexes: synthesis, structural characterization, and catalytic application.

    Science.gov (United States)

    Trambitas, Alexandra G; Melcher, Daniel; Hartenstein, Larissa; Roesky, Peter W; Daniliuc, Constantin; Jones, Peter G; Tamm, Matthias

    2012-06-18

    Reaction of anhydrous rare earth metal halides MCl(3) with 2 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH) and 2 equiv of trimethylsilylmethyl lithium (Me(3)SiCH(2)Li) in THF furnished the complexes [(Im(Dipp)N)(2)MCl(THF)(n)] (M = Sc, Y, Lu). The molecular structures of all three compounds were established by single-crystal X-ray diffraction analyses. The coordination spheres around the pentacoordinate metal atoms are best described as trigonal bipyramids. Reaction of YbI(2) with 2 equiv of LiCH(2)SiMe(3) and 2 equiv of the imino ligand Im(Dipp)NH in tetrahydrofuran did not result in a divalent complex, but instead the Yb(III) complex [(Im(Dipp)N)(2)YbI(THF)(2)] was obtained and structurally characterized. Treatment of [(Im(Dipp)N)(2)MCl(THF)(n)] with 1 equiv of LiCH(2)SiMe(3) resulted in the formation of [(Im(Dipp)N)(2)M(CH(2)SiMe(3))(THF)(n)]. The coordination arrangement of these compounds in the solid state at the metal atoms is similar to that found for the starting materials, although the introduction of the neosilyl ligand induces a significantly greater distortion from the ideal trigonal-bipyramidal geometry. [(Im(Dipp)N)(2)Y(CH(2)SiMe(3))(THF)(2)] was used as precatalyst in the intramolecular hydroamination/cyclization reaction of various terminal aminoalkenes and of one aminoalkyne. The complex showed high catalytic activity and selectivity. A comparison with the previously reported dialkyl yttrium complex [(Im(Dipp)N)Y(CH(2)SiMe(3))(2)(THF)(3)] showed no clear tendency in terms of activity.

  18. Efficient photothermal catalytic hydrogen production over nonplasmonic Pt metal supported on TiO2

    Science.gov (United States)

    Song, Rui; Luo, Bing; Jing, Dengwei

    2016-10-01

    Most of the traditional photocatalytic hydrogen productions were conducted under room temperature. In this work, we selected nonplasmonic Pt metal anchored on TiO2 nanoparticles with photothermal activity to explore more efficient hydrogen production technology over the whole solar spectrum. Photothermal experiments were carried out in a carefully designed top irradiated photocatalytic reactor that can withstand high temperature and relatively higher pressure. Four typical organic materials, i.e., methyl alcohol (MeOH), trielthanolamne (TEOA), formic acid (HCOOH) and glucose, were investigated. Formic acid, a typical hydrogen carrier, was found to show the best activity. In addition, the effects of different basic parameters such as sacrificial agent concentration and the temperature on the activity of hydrogen generation were systematically investigated for understanding the qualitative and quantitative effects of the photothermal catalytic reaction process. The hydrogen yields at 90 °C of the photothermal catalytic reaction with Pt/TiO2 are around 8.1 and 4.2 times higher than those of reactions carried out under photo or thermal conditions alone. We can see that the photothermal hydrogen yield is not the simple sum of the photo and thermal effects. This result indicated that the Pt/TiO2 nanoparticles can efficiently couple photo and thermal energy to more effectively drive hydrogen production. As a result, the excellent ability makes it superior to other conventional semiconductor photocatalysts and thermal catalysts. Future works could concentrate on exploring photothermal catalysis as well as the potential synergism between photo and thermal effects to find more efficient hydrogen production technology using the whole solar spectrum.

  19. The different catalytic roles of the metal-binding ligands in human 4-hydroxyphenylpyruvate dioxygenase.

    Science.gov (United States)

    Huang, Chih-Wei; Liu, Hsiu-Chen; Shen, Chia-Pei; Chen, Yi-Tong; Lee, Sung-Jai; Lloyd, Matthew D; Lee, Hwei-Jen

    2016-05-01

    4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a non-haem iron(II)-dependent oxygenase that catalyses the conversion of 4-hydroxyphenylpyruvate (HPP) to homogentisate (HG). In the active site, a strictly conserved 2-His-1-Glu facial triad co-ordinates the iron ready for catalysis. Substitution of these residues resulted in about a 10-fold decrease in the metal binding affinity, as measured by isothermal titration calorimetry, and a large reduction in enzyme catalytic efficiencies. The present study revealed the vital role of the ligand Glu(349) in enzyme function. Replacing this residue with alanine resulted in loss of activity. The E349G variant retained 5% activity for the coupled reaction, suggesting that co-ordinating water may be able to support activation of the trans-bound dioxygen upon substrate binding. The reaction catalysed by the H183A variant was fully uncoupled. H183A variant catalytic activity resulted in protein cleavage between Ile(267) and Ala(268) and the production of an N-terminal fragment. The H266A variant was able to produce 4-hydroxyphenylacetate (HPA), demonstrating that decarboxylation had occurred but that there was no subsequent product formation. Structural modelling of the variant enzyme with bound dioxygen revealed the rearrangement of the co-ordination environment and the dynamic behaviour of bound dioxygen in the H266A and H183A variants respectively. These models suggest that the residues regulate the geometry of the reactive oxygen intermediate during the oxidation reaction. The mutagenesis and structural simulation studies demonstrate the critical and unique role of each ligand in the function of HPPD, and which correlates with their respective co-ordination position.

  20. Two ligand-functionalized Pb(II) metal-organic frameworks: structures and catalytic performances.

    Science.gov (United States)

    Lin, Xiao-Ming; Li, Ting-Ting; Chen, Lian-Fen; Zhang, Li; Su, Cheng-Yong

    2012-09-14

    A microporous Pb(II) metal-organic framework (MOF) [PbL(2)]·2DMF·6H(2)O (1) has been assembled from a N-oxide and amide doubly functionalized ligand HL (= N-(4-carboxyphenyl)isonicotinamide 1-oxide). Complex 1 features a three-dimensional (3D) framework possessing one-dimensional (1D) rhombic channels with dimensions of 13 × 13 Å(2). The 3D framework is built up from 1D PbO(2) chains that link ligands in parallel fashion to construct single-wall channels. When recrystallizing 1 in a DMSO-DMF mixture (3 : 5 v/v), a new coordination polymer, [PbL(2)]·DMF·2H(2)O (2), was obtained. Complex 2 is also a 3D framework containing 1D rectangular channels, but the channel dimensions become reduced in size to 13 × 8 Å(2) due to reorganization of the Pb(ii) coordination environment. The PbO(2) chains in 2 are reformed to link ligands in a double-wall fashion, significantly reducing the channel size. Even though, the guest exchange study indicates that the DMF molecules in 2 could be replaced with benzene molecules when immersing in benzene solvent, showing single-crystal-to-single-crystal (SC-SC) guest exchange in the solid state and leading to a daughter crystal [PbL(2)]·0.5C(6)H(6)·2H(2)O (2'). Desolvated 1 and 2 display preferential adsorption behaviors of water vapour over CO(2) due to the hydrophilic nature of the channels and the strong host-guest interactions. Catalytic tests indicate that desolvated 1 and 2 have size-selective catalytic activity towards the Knoevenagel condensation reaction.

  1. Vascular effects of ambient pollutant particles and metals.

    Science.gov (United States)

    Huang, Yuh-Chin T; Ghio, Andrew J

    2006-07-01

    Exposure to ambient pollutant particle (APP) is associated with increased cardiovascular morbidity and mortality. Recent evidence indicates that APP-induced vasoconstriction may be an important mechanism. APP constricts systemic arteries and increases blood pressure in human. APP decreases the diameter of pulmonary arterioles in animals. Intratracheal instillation of APP increases pulmonary artery resistance in isolated buffer-perfused lungs, and APP constricts isolated arterial rings. APP-induced vasoconstriction may be secondary to the release of inflammatory mediators from lung cells, which then activate vascular endothelial and smooth muscle cells. The vasoconstriction may also be caused by alterations in autonomic nervous system balance. Some soluble metals (e.g., vanadium) can produce acute vasoconstriction in in vitro and in vivo systems, and contribute to the systemic health effects of APP since they can more easily permeate the alveolar-capillary membrane than the whole particle. Both APP and its associated metals have been shown to enhance the release of endothelin 1 and reactive oxygen species, activate epithelial growth factor receptor and mitogen-activated protein kinases, and inhibit nitric oxide vasodilator activity. The vasoactive properties of APP and metals raised the possibility that patients with vascular diseases may be more susceptible to APP-induced adverse health effects, and that people who are regularly exposed to high amount of metals, e.g., vanadium contained in certain dietary and muscle-building regimens or in the air of boiler making plants, may have increased risk for vascular diseases. Understanding how metals induce vasoconstriction may lead to the development of novel vasodilator therapies for vascular diseases.

  2. The effect of microwave-assisted for photo-catalytic degradation of rhodamine B in aqueous nano TiO2 particles dispersions.

    Science.gov (United States)

    Shin, Hyun-Chung; Park, Sung Hoon; Ahn, Ho-Geun; Chung, Minchul; Kim, Byung Whan; Kim, Sun-Jae; Seo, Seong-Gyu; Jung, Sang-Chul

    2011-02-01

    The photo-catalytic decomposition of rhodamine B was examined in aqueous nano TiO2 particles dispersions to assess effects of the microwave radiation assisted photo-catalytic process driven by UV radiation. The results of photo-catalytic degradation of rhodamine B showed that the decomposition rate increased with the microwave intensity, UV intensity, TiO2 particle dosages and the circulating fluid velocity. Addition of oxygen gas in the photo-catalytic degradation of rhodamine B increased the reaction rate. The effect of addition of H2O2 was not significant when photo-catalysis was used without additional microwave radiation or when microwave was irradiated without the use of photo-catalysts. When H2O2 was added under simultaneous use of photo-catalysis and microwave irradiation, however, considerably higher degradation reaction rates were observed. This study demonstrates that the microwave irradiation can play a very important role in photo-catalytic degradation.

  3. Metal/Diamond Composite Thin-Film Electrodes: New Carbon Supported Catalytic Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Greg M. Swain, PI

    2009-03-10

    The DOE-funded research conducted by the Swain group was focused on (i) understanding structure-function relationships at boron-doped diamond thin-film electrodes, (ii) understanding metal phase formation on diamond thin films and developing electrochemical approaches for producing highly dispersed electrocatalyst particles (e.g., Pt) of small nominal particle size, (iii) studying the electrochemical activity of the electrocatalytic electrodes for hydrogen oxidation and oxygen reduction and (iv) conducting the initial synthesis of high surface area diamond powders and evaluating their electrical and electrochemical properties when mixed with a Teflon binder. (Note: All potentials are reported versus Ag/AgCl (sat'd KCl) and cm{sup 2} refers to the electrode geometric area, unless otherwise stated).

  4. Noble metal-based bimetallic nanoparticles: the effect of the structure on the optical, catalytic and photocatalytic properties.

    Science.gov (United States)

    Zaleska-Medynska, Adriana; Marchelek, Martyna; Diak, Magdalena; Grabowska, Ewelina

    2016-03-01

    Nanoparticles composed of two different metal elements show novel electronic, optical, catalytic or photocatalytic properties from monometallic nanoparticles. Bimetallic nanoparticles could show not only the combination of the properties related to the presence of two individual metals, but also new properties due to a synergy between two metals. The structure of bimetallic nanoparticles can be oriented in random alloy, alloy with an intermetallic compound, cluster-in-cluster or core-shell structures and is strictly dependent on the relative strengths of metal-metal bond, surface energies of bulk elements, relative atomic sizes, preparation method and conditions, etc. In this review, selected properties, such as structure, optical, catalytic and photocatalytic of noble metals-based bimetallic nanoparticles, are discussed together with preparation routes. The effects of preparation method conditions as well as metal properties on the final structure of bimetallic nanoparticles (from alloy to core-shell structure) are followed. The role of bimetallic nanoparticles in heterogeneous catalysis and photocatalysis are discussed. Furthermore, structure and optical characteristics of bimetallic nanoparticles are described in relation to the some features of monometallic NPs. Such a complex approach allows to systematize knowledge and to identify the future direction of research.

  5. Removal of ammonia from aqueous solutions by catalytic oxidation with copper-based rare earth composite metal materials: catalytic performance, characterization, and cytotoxicity evaluation

    Institute of Scientific and Technical Information of China (English)

    Chang-Mao Hung

    2011-01-01

    Ammonia (NH3) has an important use in the chemical industry and is widely found in industrial wastewater.For this investigation of copper-based rare earth composite metal materials,aqueous solutions containing 400 mg/L of ammonia were oxidized in a batch-bed reactor with a catalyst prepared by the co-precipitation of copper nitrate,lanthanum nitrate and cerium nitrate.Barely any of the dissolved ammonia was removed by wet oxidation without a catalyst,but about 88% of the ammonia was reduced during wet oxidation over the catalysts at 423 K with an oxygen partial pressure of 4.0 MPa.The catalytic redox behavior was determined by cyclic voltammetry (CV).Furthermore,the catalysts were characterized using thermogravimetric analyzer (TGA) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX),which showed that the catalytic behavior was related to the metal oxide properties of the catalyst.In addition,the copper-lanthanum-cerium composite-induced cytotoxicity in the human lung MRC-5 cell line was tested,and the percentage cell survival was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetra-zolium (MTS) analysis in vitro.No apparent cytotoxicity was observed when the human lung cells were exposed to the copper-lanthanum-cerium composite.

  6. Optical trapping of metallic Rayleigh particle by combined beam

    Institute of Scientific and Technical Information of China (English)

    CHENG Ke; ZHONG Xian-qiong; XIANG An-ping

    2012-01-01

    Radiation forces and trapping stability of metallic (i.e.gold) Rayleigh particle by combined beam are analyzed,and the combined beam is formed by superimposing two partially coherent off-axis fiat-topped beams.The dependences of radiation forces on off-axis distance parameter,correlation length and particle radius are illustrated by numerical examples.The results show that there exist critical values d0,cand σ0,c for the combined beam.For 0<d ≤ d0,c or 0<σ0 ≤σ0,c the Gaussianlike intensity profile takes place at the geometrical focal plane,so that the transverse gradient force can act as restoring force.As the off-axis distance parameter increases or the correlation length decreases,the maximal intensity,the radiation force and trapping stiffness become smaller,while the transverse and longitudinal trapping ranges become larger.In comparison with a single beam,the combined beam is more favourable for trapping metallic Rayleigh particle owing to the stronger trapping stiffness and the larger trapping range.

  7. The fate of meteoric metals in ice particles: Effects of sublimation and energetic particle bombardment

    Science.gov (United States)

    Mangan, T. P.; Frankland, V. L.; Murray, B. J.; Plane, J. M. C.

    2017-08-01

    The uptake and potential reactivity of metal atoms on water ice can be an important process in planetary atmospheres and on icy bodies in the interplanetary and interstellar medium. For instance, metal atom uptake affects the gas-phase chemistry of the Earth's mesosphere, and has been proposed to influence the agglomeration of matter into planets in protoplanetary disks. In this study the fate of Mg and K atoms incorporated into water-ice films, prepared under ultra-high vacuum conditions at temperatures of 110-140 K, was investigated. Temperature-programmed desorption experiments reveal that Mg- and K-containing species do not co-desorb when the ice sublimates, demonstrating that uptake on ice particles causes irreversible removal of the metals from the gas phase. This implies that uptake on ice particles in terrestrial polar mesospheric clouds accelerates the formation of large meteoric smoke particles (≥1 nm radius above 80 km) following sublimation of the ice. Energetic sputtering of metal-dosed ice layers by 500 eV Ar+ and Kr+ ions shows that whereas K reacts on (or within) the ice surface to form KOH, adsorbed Mg atoms are chemically inert. These experimental results are consistent with electronic structure calculations of the metals bound to an ice surface, where theoretical adsorption energies on ice are calculated to be -68 kJ mol-1 for K, -91 kJ mol-1 for Mg, and -306 kJ mol-1 for Fe. K can also insert into a surface H2O to produce KOH and a dangling H atom, in a reaction that is slightly exothermic.

  8. Alternating-current relaxation of a rotating metallic particle

    Science.gov (United States)

    Guo-Xi, Nie; Wen-Jia, Tian; Ji-Ping, Huang; Guo-Qing, Gu

    2016-06-01

    Based on a first-principles approach, we establish an alternating-current (AC) relaxation theory for a rotating metallic particle with complex dielectric constant . Here is the real part, the conductivity, ω 0 the angular frequency of an AC electric field, and . Our theory yields an accurate interparticle force, which is in good agreement with the existing experiment. The agreement helps to show that the relaxations of two kinds of charges, namely, surface polarized charges (described by ) and free charges (corresponding to ), contribute to the unusually large reduction in the attracting interparticle force. This theory can be adopted to determine the relaxation time of dynamic particles in various fields. Project supported by the National Natural Science Foundation of China (Grant No. 11222544), the Fok Ying Tung Education Foundation (Grant No. 131008), the Program for New Century Excellent Talents in University, China (Grant No. NCET-12-0121), and the National Key Basic Research Program of China (Grant No. 2011CB922004).

  9. Modeling of catalytically active metal complex species and intermediates in reactions of organic halides electroreduction.

    Science.gov (United States)

    Lytvynenko, Anton S; Kolotilov, Sergey V; Kiskin, Mikhail A; Eremenko, Igor L; Novotortsev, Vladimir M

    2015-02-28

    The results of quantum chemical modeling of organic and metal-containing intermediates that occur in electrocatalytic dehalogenation reactions of organic chlorides are presented. Modeling of processes that take place in successive steps of the electrochemical reduction of representative C1 and C2 chlorides - CHCl3 and Freon R113 (1,1,2-trifluoro-1,2,2-trichloroethane) - was carried out by density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2). It was found that taking solvation into account using an implicit solvent model (conductor-like screening model, COSMO) or considering explicit solvent molecules gave similar results. In addition to modeling of simple non-catalytic dehalogenation, processes with a number of complexes and their reduced forms, some of which were catalytically active, were investigated by DFT. Complexes M(L1)2 (M = Fe, Co, Ni, Cu, Zn, L1H = Schiff base from 2-pyridinecarbaldehyde and the hydrazide of 4-pyridinecarboxylic acid), Ni(L2) (H2L2 is the Schiff base from salicylaldehyde and 1,2-ethylenediamine, known as salen) and Co(L3)2Cl2, representing a fragment of a redox-active coordination polymer [Co(L3)Cl2]n (L3 is the dithioamide of 1,3-benzenedicarboxylic acid), were considered. Gradual changes in electronic structure in a series of compounds M(L1)2 were observed, and correlations between [M(L1)2](0) spin-up and spin-down LUMO energies and the relative energies of the corresponding high-spin and low-spin reduced forms, as well as the shape of the orbitals, were proposed. These results can be helpful for determination of the nature of redox-processes in similar systems by DFT. No specific covalent interactions between [M(L1)2](-) and the R113 molecule (M = Fe, Co, Ni, Zn) were found, which indicates that M(L1)2 electrocatalysts act rather like electron transfer mediators via outer-shell electron transfer. A relaxed surface scan of the adducts {M(L1)2·R113}(-) (M = Ni or Co) versus the distance between the

  10. Synthesis, Characterization, and Catalytic Applications of Transition Metal Oxide/Carbonate Nanomaterials

    Science.gov (United States)

    Jin, Lei

    2011-12-01

    topic in this thesis presents studies of ethane oxydehydrogenation (ODH) in the presence of CO2 over the octahedral molecular sieve (OMS-2) catalyst. Conversion of CO2 into organic compounds has been studied intensively. Ethane catalytic oxydehydrogenation in the presence of CO2 offers an attractive route for converting CO2. In this study, using OMS-2 as the catalyst in C2H6 dehydrogenation in the presence of CO2 is an example where extreme conditions are used to drive high conversions of ethane (> 70%) and CO2 (up to 56%) with high selectivity towards ethylene (87%) with a short contact time (0.6 s). This inexpensive material also showed high stability during the process, and the presence of CO2 removed coke depositions throughout the catalyst. The results obtained from this study open up new possibilities for olefin dehydrogenations in the presence of CO2, a perfect feedstock for any process involving ethylene carbonylation with the recycling of the greenhouse gas. The fourth part of this thesis presents a ZnO/La2O2CO 3 composite prepared by a new and easy method and discusses the use of these materials as heterogeneous catalysts for ultra-fast microwave biodiesel production at low temperatures. The search for solid state materials with high catalytic activities is one of the key steps toward reducing the cost of producing biodiesel. We present a high biodiesel yield (> 95%) in less than 5 minutes under mild reaction conditions ( 95%) in a short reaction time (< 20 minutes). The results of low temperature activities and short reaction times with minimum energy consumption show them to have solid potential as alkali metal hydroxide/alkoxide alternatives for industrial applications.

  11. Determination of silica coating efficiency on metal particles using multiple digestion methods.

    Science.gov (United States)

    Wang, Jun; Topham, Nathan; Wu, Chang-Yu

    2011-10-15

    Nano-sized metal particles, including both elemental and oxidized metals, have received significant interest due to their biotoxicity and presence in a wide range of industrial systems. A novel silica technology has been recently explored to minimize the biotoxicity of metal particles by encapsulating them with an amorphous silica shell. In this study, a method to determine silica coating efficiency on metal particles was developed. Metal particles with silica coating were generated using gas metal arc welding (GMAW) process with a silica precursor tetramethylsilane (TMS) added to the shielding gas. Microwave digestion and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were employed to solubilize the metal content in the particles and analyze the concentration, respectively. Three acid mixtures were tested to acquire the appropriate digestion method targeting at metals and silica coating. Metal recovery efficiencies of different digestion methods were compared through analysis of spiked samples. HNO(3)/HF mixture was found to be a more aggressive digestion method for metal particles with silica coating. Aqua regia was able to effectively dissolve metal particles not trapped in the silica shell. Silica coating efficiencies were thus calculated based on the measured concentrations following digestion by HNO(3)/HF mixture and aqua regia. The results showed 14-39% of welding fume particles were encapsulated in silica coating under various conditions. This newly developed method could also be used to examine the silica coverage on particles of silica shell/metal core structure in other nanotechnology areas.

  12. Catalytic ozonation not relying on hydroxyl radical oxidation: A selective and competitive reaction process related to metal-carboxylate complexes

    KAUST Repository

    Zhang, Tao

    2014-01-01

    Catalytic ozonation following non-hydroxyl radical pathway is an important technique not only to degrade refractory carboxylic-containing organic compounds/matter but also to avoid catalyst deactivation caused by metal-carboxylate complexation. It is unknown whether this process is effective for all carboxylates or selective to special molecule structures. In this work, the selectivity was confirmed using O3/(CuO/CeO2) and six distinct ozone-resistant probe carboxylates (i.e., acetate, citrate, malonate, oxalate, pyruvate and succinate). Among these probe compounds, pyruvate, oxalate, and citrate were readily degraded following the rate order of oxalate>citrate>pyruvate, while the degradation of acetate, malonate, and succinate was not promoted. The selectivity was independent on carboxylate group number of the probe compounds and solution pH. Competitive degradation was observed for carboxylate mixtures following the preference order of citrate, oxalate, and finally pyruvate. The competitive degradation was ascribed to competitive adsorption on the catalyst surface. It was revealed that the catalytically degradable compounds formed bidentate chelating or bridging complexes with surface copper sites of the catalyst, i.e., the active sites. The catalytically undegradable carboxylates formed monodentate complexes with surface copper sites or just electrostatically adsorbed on the catalyst surface. The selectivity, relying on the structure of surface metal-carboxylate complex, should be considered in the design of catalytic ozonation process. © 2013 Elsevier B.V.

  13. NO-CO-O2 Reaction on a Metal Catalytic Surface using Eley-Rideal Mechanism

    Institute of Scientific and Technical Information of China (English)

    Waqar Ahmad

    2008-01-01

    Interactions among the reacting species NO, CO and O2 on metal catalytic surfaces are studied by means of Monte Carlo simulation using the Eley-Rideal (ER) mechanism. The study of this three-component system is important for understanding of the reaction kinetics by varying the relative ratios of the reactants. It is found that contrary to the conventional Langmuir-Hinshelwood (LH) thermal mechanism in which two irreversible phase transitions are obtained between active states and poisoned states, a single phase transition is observed when the ER mechanism is combined with the LH mechanism. The phase diagrams of the surface coverage and the steady state production of CO2, N2 and N2O are evaluated as a function of the partial pressures of the reactants in the gas phase. The continuous production of CO2 starts as soon as the CO pressure is switched on and the second order phase transition at the first critical point is eliminated, which is in agreement with the experimental findings.

  14. Effects of digestion protocols on the isolation and characterization of metal-metal wear particles. I. Analysis of particle size and shape.

    Science.gov (United States)

    Catelas, I; Bobyn, J D; Medley, J B; Krygier, J J; Zukor, D J; Petit, A; Huk, O L

    2001-06-01

    Isolation of metal wear particles from hip simulator lubricants or tissues surrounding implants is a challenging problem because of small particle size, their tendency to agglomerate, and their potential for chemical degradation by digestion reagents. To provide realistic measurements of size, shape, and composition of metal wear particles, it is important to optimize particle isolation and minimize particle changes due to the effects of the reagents. In this study (Part I of II), transmission electron microscopy (TEM) was used to examine and compare the effects of different isolation protocols, using enzymes or alkaline solutions, on the size and shape of three different types of cobalt-based alloy particles produced from metal-metal bearings. The effect on particle composition was examined in a subsequent study (Part II). Large particles (particles (water or a 95% bovine serum solution. The reagents changed particle size and to a lesser extent particle shape. For both large particles and small particles generated in water, the changes in size were more extensive after alkaline than after enzymatic protocols and increased with alkaline concentration and time in solution, up to twofold at 2 h and threefold at 48 h. However, when isolating particles from 95% serum, an initial protective effect of serum proteins and/or lipids was observed. Because of this protective effect, there was no significant difference in particle size and shape for both oval and needle-shaped particles after 2 h in 2N KOH and after enzymatic treatments. However, round particles were significantly smaller after 2 h in 2N KOH than after enzymatic treatments. Particle composition may also have been affected by the 2N KOH treatment, as suggested by a difference in particle contrast under TEM, an issue examined in detail in Part II.

  15. Fuzzy, copper-based multi-functional composite particles serving simultaneous catalytic and signal-enhancing roles

    Science.gov (United States)

    Li, Xiangming; Hu, Yingmo; An, Qi; Luan, Xinglong; Zhang, Qian; Zhang, Yihe

    2016-04-01

    Multifunctional plasmonic particles serving simultaneously as catalysts and label-free reporting agents are highly pursued due to their great potential in enhancing reaction operational efficiencies. Copper is an abundant and economic resource, and it possesses practical applicability in industries, but no dual-functional copper-based catalytic and self-reporting particles have been reported so far. This study proposes a facile strategy to prepare high-performance dual-functional copper-based composite particles that catalyze reactions and simultaneously serve as a SERS (surface enhanced Raman spectra) active, label-free reporting agent. Polyelectrolyte-modified reduced graphene oxide particles are used as the reactive precursors in the fabrication method. Upon adding Cu(NO3)2 solutions into the precursor dispersions, composite particles comprised by copper/copper oxide core and polyelectrolyte-graphene shell were facilely obtained under sonication. The as-prepared composite particles efficiently catalyzed the conversion of 4-nitrophenol to 4-aminophenol and simultaneously acted as the SERS-active substrate to give enhanced Raman spectra of the produced 4-aminophenol. Taking advantage of the assembling capabilities of polyelectrolyte shells, the composite particles could be further assembled onto a planar substrate to catalyze organic reactions, facilitating their application in various conditions. We expect this report to promote the fabrication and application of copper-based multifunctional particles.Multifunctional plasmonic particles serving simultaneously as catalysts and label-free reporting agents are highly pursued due to their great potential in enhancing reaction operational efficiencies. Copper is an abundant and economic resource, and it possesses practical applicability in industries, but no dual-functional copper-based catalytic and self-reporting particles have been reported so far. This study proposes a facile strategy to prepare high

  16. Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles

    Science.gov (United States)

    Wang, Jia X.; Adzic, Radoslav R.

    2009-03-24

    The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

  17. One-pot synthesis of Cu{sub 2}O octahedron particles and their catalytic application

    Energy Technology Data Exchange (ETDEWEB)

    Li, Biao; Li, Dan; Mu, Lei; Yang, Sung Ik [Dept. of Applied Chemistry, Kyung Hee University, Yongin (Korea, Republic of)

    2017-04-15

    We report a facile one-step synthesis method of cuprous oxide (Cu{sub 2}O) hollow octahedrons with controllable size Cu{sub 2}O exhibited a great catalytic activity for the reduction of methylene blue by N{sub 2}H{sub 4} as well as NABH{sub 4}.

  18. Chemistry and thermal history of metal particles in Luna 20 soils.

    Science.gov (United States)

    Goldstein, J. I.; Blau, P. J.

    1973-01-01

    Individual metal particles from Luna 20 thin sections 521, 513 and 514 as well as several small metallic inclusions in silicate particles from Luna 20 thin sections 501 and 502 were examined using optical microscopy and the electron microprobe. All the metallic particles and inclusions analyzed are of meteoritic Co-Ni content as are most of the metallic particles from the Fra Mauro and the Apollo 16 highlands sites. It is proposed that most of the metal at these 3 sites had its origin in the meteoritic projectiles that bombarded and accumulated in the early lunar crust. It is apparent that the metallic particles and some of the metallic inclusions in the Luna 20 soil have been subjected to reheating on the moon and this process has removed any evidence of the original meteoritic microstructure of the metal.

  19. Metal–Organic Frameworks Stabilize Mono(phosphine)–Metal Complexes for Broad-Scope Catalytic Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sawano, Takahiro; Lin, Zekai; Boures, Dean; An, Bing; Wang, Cheng; Lin, Wenbin (UC); (Xiamen)

    2016-08-10

    Mono(phosphine)–M (M–PR3; M = Rh and Ir) complexes selectively prepared by postsynthetic metalation of a porous triarylphosphine-based metal–organic framework (MOF) exhibited excellent activity in the hydrosilylation of ketones and alkenes, the hydrogenation of alkenes, and the C–H borylation of arenes. The recyclable and reusable MOF catalysts significantly outperformed their homogeneous counterparts, presumably via stabilizing M–PR3 intermediates by preventing deleterious disproportionation reactions/ligand exchanges in the catalytic cycles.

  20. Modelling of non-metallic particles motion process in foundry alloys

    Directory of Open Access Journals (Sweden)

    P. L. Żak

    2015-04-01

    Full Text Available The behaviour of non-metallic particles in the selected composites was analysed, in the current study. The calculations of particles floating in liquids differing in viscosity were performed. Simulations based on the Stokes equation were made for spherical SiC particles and additionally the particle size influence on Reynolds number was analysed.The movement of the particles in the liquid metal matrix is strictly connected with the agglomerate formation problem.Some of collisions between non-metallic particles lead to a permanent connection between them. Creation of the two spherical particles and a metallic phase system generates the adhesion force. It was found that the adhesion force mainly depends on the surface tension of the liquid alloy and radius of non-metallic particles.

  1. Synthesis and characterization of transition metal carbides and their catalytic applications

    Science.gov (United States)

    Wan, Cheng

    Transition metal (both monometallic and bimetallic) carbides have been synthesized by an amine-metal oxide composite (AMOC) method. The composite reduces the diffusion distances among each element and allows the formation of carbides to take place as low as 610°C, which is significantly lower than traditional carbide synthesis methods (above 1500°C). Additionally, amines act not only as carbon sources and reducing agents, but also morphological templates which helps to make uniform transition metal carbide (TMC) nanocrystals with various shapes. Beyond morphology control, AMOC method can also help to synthesize multiple phases of monometallic carbides, which includes four phases of molybdenum carbides (alpha-MoC1-x, beta-Mo2C, eta-MoC, and gamma-MoC), two phases of tungsten carbides (W2C and WC), and three phases of chromium carbides (Cr3C2-x, Cr7C3, and Cr3C2). Molybdenum carbide has been proposed as a possible alternative to platinum for catalyzing the hydrogen evolution reaction (HER). Previous studies were limited to only one phase, which is beta-Mo2C with an Fe 2N structure. Here, four molybdenum carbide materials including gamma-MoC with a WC type structure which was stabilized for the first time as a phase pure nanomaterial. Moreover, a wide range of magnetic iron-doped molybdenum carbide (Mo2-xFexC) nanomaterials were also synthesized, which exhibits a better HER activity to non-doped beta-Mo2C. A group of (CrxFe1-x)7C3 (0.2< x<1) solid solutions have also been synthesized for the first time as nanomaterials via AMOC method, which demonstrate excellent catalytic activities for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Other carbides/nitrides made from AMOCs include WN1-x, Fe3C, Fe3-xN, Fe3Mo3C, N 2Mo3C, Ni3Mo3C, Ni6Mo 6C, and Mo0.5W0.5C.

  2. Solid hydrocarbon assisted reduction: a new process of generating micron scale metal particles

    OpenAIRE

    Ryan M McCabe

    2015-01-01

    Approved for public release; distribution is unlimited The goal of this research is to test a central hypothesis: that gas species generated by the thermal and/or catalytically assisted decomposition of hydrocarbons in an inert atmosphere can reduce metal oxides to a metallic state. It is postulated that the decomposition releases gas phase radicals that can bind with oxygen in the metal oxides, forming volatile, stable oxides such as CO2 and water. This research consisted of thermally dec...

  3. Catalytic transformations of fatty acids derivatives for food, oleochemicals and fuels over carbon supported platinum group metals

    Energy Technology Data Exchange (ETDEWEB)

    Simakova, I.

    2010-07-01

    prominent in linoleic acid deoxygenation giving only 3 % conversion of fatty acids in 330 min. The deactivation originated from the formation of C17 aromatic compounds and fatty acid dimers via Diels-Alder reaction. Thus hydrogenation of unsaturated fatty acids can be considered as preliminary chemical modification step in the green diesel production. In this work particular care was taken to strengthen the nano level understanding of the Pd role, in particular metal size effect, in the catalytic hydrogenation and deoxygenation. Pd/C catalysts were synthesized with the same Pd loading and systematically varied metal dispersion via the controllable formation of Pd particles over carbon support surface. The effect of metal dispersion on hydrogenation rate and trans/cis ratio was revealed. An optimum metal dispersion giving the highest decarboxylation reaction rate was observed. In addition to the particle size effect, the impact of mass transfer was elucidated and detail discussions on temperature programmed desorption of CO from the fresh and spent samples was provided. Hydrogenation of vegetable feedstocks was performed in batch and continuous modes, using powdered and granulated Pd/C catalysts correspondingly. One of the main focuses of the work was put on the scale-up of the hydrogenation process. There are several challenges attributed to the scale-up of a chemical process which have to be recognized before progressing to an industrial application. In terms of the high production volumes the logical step is to investigate the performance of hydrogenation as a continuous process. A laboratory study in a continuous fixed bed reactor was performed, giving crucial information about the catalyst long-term stability and catalyst deactivation. Furthermore, the impact of using free fatty acids or triglycerides feedstocks as well as the effect of catalyst particle size and Pd loading were investigated in continuous mode. Finally, the production capacities for different operation

  4. Encapsulating Metal Clusters and Acid Sites within Small Voids: Synthetic Strategies and Catalytic Consequences

    Science.gov (United States)

    Goel, Sarika

    active sites. We have demonstrated the selectivity of the encapsulation processes by combining transmission electron microscopy and chemisorptive titrations with rigorous catalytic assessments of the ability of these materials to catalyze reactions of small molecules, which can access the intracrystalline voids, but not of larger molecules that cannot access the metal clusters within such voids. The selective confinement of clusters also prevented their contact with sulfur compounds (e.g., thiophene and H2S), thus allowing reactions to occur at conditions that otherwise render unconfined clusters unreactive. We have also developed synthetic protocols and guiding principles, inspired by mechanistic considerations, for the synthesis of zeolites via interzeolite transformations without the use of organic structure-directing agents (OSDA). More specifically, we have synthesized high-silica MFI (ZSM-5), CHA (chabazite), STF (SSZ-35) and MTW (ZSM-12) zeolites from FAU (faujasite) or BEA (beta) parent materials. Structures with lower framework densities (FAU or BEA) were successfully transformed into thermodynamically-favored, more stable structures with higher framework densities (MFI, CHA, STF, and MTW); to date, target materials with higher Si/Al ratios (Si/Al >10) have not been synthesized via interzeolite transformations without the aid of the OSDA species used to discover these zeolite structures and deemed essential up until now for their successful synthesis. Overcoming kinetic hurdles in such transformations required either the presence of common composite building units (CBU) between parent and target structures or, in their absence, the introduction of small amount of seeds of the daughter structures. The NaOH/SiO2 ratio, H2O/SiO2 ratio and Al content in reagents are used to enforce synchronization between the swelling and local restructuring within parent zeolite domains with the spalling of fragments or building units from seeds of the target structure. The

  5. Functional Role of Infective Viral Particles on Metal Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Coates, John D.

    2014-04-01

    A proposed strategy for the remediation of uranium (U) contaminated sites was based on the immobilization of U by reducing the oxidized soluble U, U(VI), to form a reduced insoluble end product, U(IV). Previous studies identified Geobacter sp., including G. sulfurreducens and G. metallireducens, as predominant U(VI)-reducing bacteria under acetate-oxidizing and U(VI)-reducing conditions. Examination of the finished genome sequence annotation of the canonical metal reducing species Geobacter sulfurreducens strain PCA and G. metallireduceans strain GS-15 as well as the draft genome sequence of G. uraniumreducens strain Rf4 identified phage related proteins. In addition, the completed genome for Anaeromyxobacter dehalogenans and the draft genome sequence of Desulfovibrio desulfuricans strain G20, two more model metal-reducing bacteria, also revealed phage related sequences. The presence of these gene sequences indicated that Geobacter spp., Anaeromyxobacter spp., and Desulfovibrio spp. are susceptible to viral infection. Furthermore, viral populations in soils and sedimentary environments in the order of 6.4×10{sup 6}–2.7×10{sup 10} VLP’s cm{sup -3} have been observed. In some cases, viral populations exceed bacterial populations in these environments suggesting that a relationship may exist between viruses and bacteria. Our preliminary screens of samples collected from the ESR FRC indicated that viral like particles were observed in significant numbers. The objective of this study was to investigate the potential functional role viruses play in metal reduction specifically Fe(III) and U(VI) reduction, the environmental parameters affecting viral infection of metal reducing bacteria, and the subsequent effects on U transport.

  6. Formation of Ultrafine Metal Particles and Metal Oxide Precursor on Anodized Al by Electrolysis Deposition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Nickel was deposited by ac electrolysis deposition in the pores of the porous oxide film of Al produced by anodizing in phosphoric acid. Ultrafine rod-shaped Ni particles were formed in the pores. At the same time a film of Ni oxide precursor was developed on the surface of the porous oxide film. The Ni particles and the Ni oxide precursor were examined by SEM, TEM and X-ray diffraction. The thickness of the barrier layer of the porous oxide film was thin and it attributed to the formation of the metal particles, while the formation of the oxide precursor was associated with the surface pits which were developed in the pretreatment of Al.

  7. Sustainability Study on Heavy Metal Uptake in Neem Biodiesel Using Selective Catalytic Preparation and Hyphenated Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Mirella Elkadi

    2014-04-01

    Full Text Available It is common knowledge that the presence of trace metals in biofuels can be detrimental to the environment and long-term sustainable development. This study provides an insight into selective catalytic preparation of biofuel to compare uptake of trace metals in the biodiesel fraction with preferential base catalysts. The role of specific metal hydroxides in controlling trace metal content in biofuel production is relatively unexplored, and the effect of different homogeneous catalysts (NaOH, KOH on metal retention in biodiesel from commercial neem oil was examined. A detailed study of this nature of catalyst vs. metal uptake is in the interest of sustainable living and could make a significant contribution to biofuels research. Both catalysts displayed variable uptake for certain toxic elements, which was attributed to the behavior of the catalyst in the reaction mixture. A general comparison reflected specific trends in metal retention (ICP-MS with the use of different base catalysts. Challenges encountered by extending the study and using a heterogeneous catalyst (CaO are presented. Our work could play a significant role in influencing catalyzed transesterfication processes to control elemental and toxic metal uptake in biofuels. The impact of our work on sustainable living is presented.

  8. Catalytic activity of Au nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Janssens, Ton V.W.; Clausen, Bjerne

    2007-01-01

    Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change with par......Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change...... with particle size. We find that the fraction of low-coordinated Au atoms scales approximately with the catalytic activity, suggesting that atoms on the corners and edges of Au nanoparticles are the active sites. This effect is explained using density functional calculations....

  9. Catalytic ozonation of propanal using wood fly ash and metal oxide nanoparticle impregnated carbon.

    Science.gov (United States)

    Kastner, James R; Ganagavaram, Rangan; Kolar, Praveen; Teja, Amyn; Xu, Chunbao

    2008-01-15

    Catalytic ozonation of propanal at ambient temperatures (23-25 degrees C) was investigated by varying propanal and ozone concentrations and catalyst type. The catalysts tested included wood fly ash (WFA), magnetically separated ash, synthetic hematite and magnetite, and metal oxide nanoparticle impregnated activated carbon and peanut hull char. A power law model independent of ozone concentration for WFA (r(w), moles g(-1) s(-1)) and magnetite (r(m)) were, respectively, r(w) = k'(w) C(R(0.89)) and r(m) = k'(m)C(R(1.55)), where kw, and k'(m) were 2.36 x 10(-6) g(-1) s(-1) (moles)(-0.11) (m3)(0.89) and 6.5 x 10(-4) g(-1) s(-1) (moles)(-0.55) (m3)(1.55), respectively (5-15 ppmv). Magnetite and hematite present in the WFA were theorized to be the primary active sites, since magnetically separated WFA had a significantly higher reaction rate (approximately 12x, mol m(-2) s(-1)) than that of WFA. X-ray diffraction analysis demonstrated a qualitative increase in magnetite and hematite in the magnetically separated ash, and synthetic magnetite and hematite had reaction rates >80x and 200x that of WFA or activated carbon (surface area basis). Supercritical deposition of hematite on/in peanut hull char successfully generated a porous, pelleted catalystfrom an agricultural residue capable of oxidizing propanal at rates 12x activated carbon and similar to commercially available catalysts (per mass basis). Water vapor significantly increased the propanal reaction rate when using wood fly ash and activated carbon.

  10. Ruthenium Metal-Organic Frameworks with Different Defect Types: Influence on Porosity, Sorption, and Catalytic Properties.

    Science.gov (United States)

    Zhang, Wenhua; Kauer, Max; Halbherr, Olesia; Epp, Konstantin; Guo, Penghu; Gonzalez, Miguel I; Xiao, Dianne J; Wiktor, Christian; LIabrés I Xamena, Francesc X; Wöll, Christof; Wang, Yuemin; Muhler, Martin; Fischer, Roland A

    2016-09-26

    By employing the mixed-component, solid-solution approach, various functionalized ditopic isophthalate (ip) defect-generating linkers denoted 5-X-ipH2 , where X=OH (1), H (2), NH2 (3), Br (4), were introduced into the mixed-valent ruthenium analogue of [Cu3 (btc)2 ]n (HKUST-1, btc=benzene-1,3,5-tricarboxylate) to yield Ru-DEMOFs (defect-engineered metal-organic frameworks) of the general empirical formula [Ru3 (btc)2-x (5-X-ip)x Yy ]n . Framework incorporation of 5-X-ip was confirmed by powder XRD, FTIR spectroscopy, ultrahigh-vacuum IR spectroscopy, thermogravimetric analysis, (1) H NMR spectroscopy, N2 sorption, and X-ray absorption near edge structure. Interestingly, Ru-DEMOF 1 c with 32 % framework incorporation of 5-OH-ip shows the highest BET surface area (≈1300 m(2)  g(-1) , N2 adsorption, 77 K) among all materials (including the parent framework [Ru3 (btc)2 Yy ]n ). The characterization data are consistent with two kinds of structural defects induced by framework incorporation of 5-X-ip: modified paddlewheel nodes featuring reduced ruthenium sites (Ru(δ+) , 0<δ<2, type A) and missing nodes leading to enhanced porosity (type B). Their relative abundances depend on the choice of the functional group X in the defect linkers. Defects A and B also appeared to play a key role in sorption of small molecules (i.e., CO2 , CO, H2 ) and the catalytic properties of the materials (i.e., ethylene dimerization and the Paal-Knorr reaction). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Catalytic Activity of Mono- and Bi-Metallic Nanoparticles Synthesized via Microemulsions

    Directory of Open Access Journals (Sweden)

    Ramona Y.G. König

    2014-07-01

    Full Text Available Water-in-oil (w/o microemulsions were used as a template for the synthesis of mono- and bi-metallic nanoparticles. For that purpose, w/o-microemulsions containing H2PtCl6, H2PtCl6 + Pb(NO32 and H2PtCl6 + Bi(NO3, respectively, were mixed with a w/o-microemulsion containing the reducing agent, NaBH4. The results revealed that it is possible to synthesize Pt, PtPb and PtBi nanoparticles of ~3–8 nm in diameter at temperatures of about 30°C. The catalytic properties of the bimetallic PtBi and PtPb nanoparticles were studied and compared with monometallic platinum nanoparticles. Firstly, the electrochemical oxidation of formic acid to carbon monoxide was investigated, and it was found that the resistance of the PtBi and PtPb nanoparticles against the catalyst-poisoning carbon monoxide was significantly higher compared to the Pt nanoparticles. Secondly, investigating the reduction of 4-nitrophenol to 4-aminophenol,we found that the bimetallic NPs are most active at 23 °C, while the order of the activity changes at higher temperatures, i.e., that the Pt nanoparticles are the most active ones at 36 and 49 °C. Furthermore, we observed a strong influence of the support, which was either a polymer or Al2O3. Thirdly, for the hydrogenation of allylbenzene to propylbenzene, the monometallic Pt NPs turned out to be the most active catalysts, followed by the PtPb and PtBi NPs. Comparing the two bimetallic nanoparticles, one sees that the PtPb NPs are significantly more active than the respective PtBi NPs.

  12. Fundamental studies into the catalytic properties of metal-oxide supported gold and copper nanoparticles

    CERN Document Server

    Carew, A J

    2001-01-01

    Au/Metal oxide experiments. The ratio of C sub 2 H sub 2 :C sub 6 H sub 6 in the gas phase is further found to be critically dependent on the cluster size with the maximum benzene evolution occurring on 800-1000 atoms of Cu. The adsorption and reaction of NO on Al sub 2 O sub 3 supported Cu particles was also investigated using RAIRS and MBARS techniques over the temperature range, 90-300K. Both techniques show the adsorption and reactivity of the particles to be very similar to that observed on Cu single crystals. It is clear from the results obtained from both techniques that, upon adsorption of the NO molecule, an, immediate reaction to produce N sub 2 O occurs, even at temperatures as low as 98K. Isothermal experiments show that, depending on the progress of the reactive uptake, the N sub 2 O which is produced can either remain adsorbed, desorb intact or dissociate to produce gaseous N sub 2. The observation of N sub 2 O at 98K is indicative of a mechanism, which involves the formation of NO dimers as int...

  13. One-step synthesis of metal@titania core-shell materials for visible-light photocatalysis and catalytic reduction reaction.

    Science.gov (United States)

    Xiong, Zhigang; Zhang, Luhong; Zhao, Xiu Song

    2014-11-03

    Metal@TiO2 composites with a core-shell structure possess multifunctional properties. The demonstrated protocols for synthesizing such materials involve multiple steps, requiring precise control over the particle uniformity of the core and shell thickness, as well as complex surface modification. A simple approach to synthesizing metal@TiO2 hybrid nanostructures remains a great challenge. Herein, we report on a one-step method for the preparation of metal@TiO2 core-shell nanospheres, which exhibited excellent performance in photocatalytic degradation of recalcitrant organic pollutants under visible light irradiation, and in catalytic reduction of nitrophenol in water. The simple method described here represents a sustainable approach to preparing core-shell materials at low cost, involving fewer chemicals, and requiring less energy, which will make a significant contribution toward large-scale synthesis of high-performance hybrid materials for photocatalytic applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Mathematical Modeling of the Melting Rate of Metallic Particles in the Electric Arc Furnace

    National Research Council Canada - National Science Library

    González, O. J. P; Ramírez-Argáez, Marco A; Conejo, A. N

    2010-01-01

    A computational fluid dynamics model coupled to a lagrangian model of melting/solidifying particles has been developed to describe the melting kinetics of metallic particles in an industrial Electric Arc Furnace (EAF...

  15. Introducing asymmetric functionality into MOFs via the generation of metallic Janus MOF particles.

    Science.gov (United States)

    Ayala, Abraham; Carbonell, Carlos; Imaz, Inhar; Maspoch, Daniel

    2016-04-14

    Herein we report a versatile methodology for engineering metallic Janus MOF particles based on desymmetrization at interfaces, whereby each MOF particle is partially coated with a desired metal. We demonstrate that it enables the fabrication of homogeneous Janus MOF particles according to the MOF (ZIF-8, UiO-66 or UiO-66-SH), the metal (Au, Co or Pt), the MOF particle size (from the micrometer to the submicrometer regime) and the metal-film thickness (from 5 nm to 50 nm) employed. We anticipate that our strategy could be applied to impart new functionalities to MOFs, including asymmetric functionalization, magnetic-guidance and motorization.

  16. Oxalate metal complexes in aerosol particles: implications for the hygroscopicity of oxalate-containing particles

    Directory of Open Access Journals (Sweden)

    T. Furukawa

    2011-05-01

    Full Text Available Atmospheric aerosols have both a direct and an indirect cooling effect that influences the radiative balance at the Earth's surface. It has been estimated that the degree of cooling is large enough to weaken the warming effect of carbon dioxide. Among the cooling factors, secondary organic aerosols (SOA play an important role in the solar radiation balance in the troposphere as SOA can act as cloud condensation nuclei (CCN and extend the lifespan of clouds because of their high hygroscopic and water soluble nature. Oxalic acid is an important component of SOA, and is produced via several formation pathways in the atmosphere. However, it is not certain whether oxalic acid exists as free oxalic acid or as metal oxalate complexes in aerosols, although there is a marked difference in their solubility in water and their hygroscopicity. We employed X-ray absorption fine structure spectroscopy to characterize the calcium (Ca and zinc (Zn in aerosols collected at Tsukuba in Japan. Size-fractionated aerosol samples were collected for this purpose using an impactor aerosol sampler. It was shown that 10–60% and 20–100% of the total Ca and Zn in the finer particles (<2.1 μm were present as Ca and Zn oxalate complexes, respectively. Oxalic acid is hygroscopic and can thus increase the CCN activity of aerosol particles, while complexes with various polyvalent metal ions such as Ca and Zn are not hygroscopic, which cannot contribute to the increase of the CCN activity of aerosols. Based on the concentrations of noncomplexed and metal-complexed oxalate species, we found that most of the oxalic acid is present as metal oxalate complexes in the aerosols, suggesting that oxalic acid does not always increase the hygroscopicity of aerosols in the atmosphere. Similar results are expected for other dicarboxylic acids, such as malonic and succinic acids. Thus, it is advisable that the cooling effect of organic aerosols should be estimated by including the

  17. Size-confined growth of atom-precise nanoclusters in metal-organic frameworks and their catalytic applications

    Science.gov (United States)

    Liu, Lingli; Song, Yongbo; Chong, Hanbao; Yang, Sha; Xiang, Ji; Jin, Shan; Kang, Xi; Zhang, Jun; Yu, Haizhu; Zhu, Manzhou

    2016-01-01

    Using MOFs as size-selection templates, we have for the first time synthesized atom-precise Au11:PPh3 nanoclusters (NCs) and Au13Ag12:PPh3 NCs with high purity by a one-step, in situ reduction method. Specifically, we found that the product released from the frameworks of ZIF-8 is exclusively the Au11:PPh3 NCs rather than polydispersed NCs, and inside MIL-101(Cr) the Au13Ag12:PPh3 NCs constitute the exclusive product. The metal NC@MOF composites are also demonstrated for catalytic application. The high catalytic efficiency for the oxidation of benzyl alcohol indicates that atom-precise noble metal NCs@MOFs may act as a promising class of heterogeneous catalysts. The atom-precise NCs obtained in the MOF templated synthesis imply the future possibility of using MOFs of various pore sizes for the size-selective synthesis of atomically precise NCs. Meanwhile, metal NCs@MOFs will contribute to the understanding of the mechanism of nanocatalyst surface reactions and hence opens up enormous opportunities in heterogeneous catalysis.Using MOFs as size-selection templates, we have for the first time synthesized atom-precise Au11:PPh3 nanoclusters (NCs) and Au13Ag12:PPh3 NCs with high purity by a one-step, in situ reduction method. Specifically, we found that the product released from the frameworks of ZIF-8 is exclusively the Au11:PPh3 NCs rather than polydispersed NCs, and inside MIL-101(Cr) the Au13Ag12:PPh3 NCs constitute the exclusive product. The metal NC@MOF composites are also demonstrated for catalytic application. The high catalytic efficiency for the oxidation of benzyl alcohol indicates that atom-precise noble metal NCs@MOFs may act as a promising class of heterogeneous catalysts. The atom-precise NCs obtained in the MOF templated synthesis imply the future possibility of using MOFs of various pore sizes for the size-selective synthesis of atomically precise NCs. Meanwhile, metal NCs@MOFs will contribute to the understanding of the mechanism of nanocatalyst

  18. The particle as microreactor: catalytic propylene polymerizations with supported metallocenes and Ziegler-Natta catalysts

    NARCIS (Netherlands)

    Weickert, G.; Meier, G.B.; Pater, J.T.M.; Westerterp, K.R.

    1999-01-01

    This paper deals with some current problems of single-particle modelling of fastly growing porous polypropylene particles. Precise kinetic measurements, investigations in monomer absorption, and microscopic morphology studies have been performed to prove the model assumptions usually made by several

  19. Cobalt particle size effects on catalytic performance for ethanol steam reforming - Smaller is better

    NARCIS (Netherlands)

    Da Silva, Andre L M; Den Breejen, Johan P.; Mattos, Lisiane V.; Bitter, Johannes H.; De Jong, Krijn P.; Noronha, Fábio B.

    2014-01-01

    The effect of the cobalt particle size in the ethanol steam reforming reaction at 773 K for hydrogen production was investigated using cobalt on carbon nanofiber catalysts. It was found that the turnover frequency increases with decreasing Co particle size, which was attributed to the increasing fra

  20. Cobalt particle size effects on catalytic performance for ethanol steam reforming – Smaller is better

    NARCIS (Netherlands)

    Silva, da A.L.M.; Breejen, den J.P.; Mattos, L.V.; Bitter, J.H.; Jong, de K.P.; Noronha, F.B.

    2014-01-01

    The effect of the cobalt particle size in the ethanol steam reforming reaction at 773 K for hydrogen production was investigated using cobalt on carbon nanofiber catalysts. It was found that the turnover frequency increases with decreasing Co particle size, which was attributed to the increasing fra

  1. Engineering interface and surface of noble metal nanoparticle nanotubes toward enhanced catalytic activity for fuel cell applications.

    Science.gov (United States)

    Cui, Chun-Hua; Yu, Shu-Hong

    2013-07-16

    In order for fuel cells to have commercial viability as alternative fuel sources, researchers need to develop highly active and robust fuel cell electrocatalysts. In recent years, the focus has been on the design and synthesis of novel catalytic materials with controlled interface and surface structures. Another goal is to uncover potential catalytic activity and selectivity, as well as understand their fundamental catalytic mechanisms. Scientists have achieved great progress in the experimental and theoretical investigation due to the urgent demand for broad commercialization of fuel cells in automotive applications. However, there are still three main problems: cost, performance, and stability. To meet these targets, the catalyst needs to have multisynergic functions. In addition, the composition and structure changes of the catalysts during the reactions still need to be explored. Activity in catalytic nanomaterials is generally controlled by the size, shape, composition, and interface and surface engineering. As such, one-dimensional nanostructures such as nanowires and nanotubes are of special interest. However, these structures tend to lose the nanoparticle morphology and inhibit the use of catalysts in both fuel cell anodes and cathodes. In 2003, Rubinstein and co-workers proposed the idea of nanoparticle nanotubes (NNs), which combine the geometry of nanotubes and the morphology of nanoparticles. This concept gives both the high surface-to-volume ratio and the size effect, which are both appealing in electrocatalyst design. In this Account, we describe our developments in the construction of highly active NNs with unique surface and heterogeneous interface structures. We try to clarify enhanced activity and stability in catalytic systems by taking into account the activity impact factors. We briefly introduce material structural effects on the electrocatalytic reactivity including metal oxide/metal and metal/metal interfaces, dealloyed pure Pt, and mixed Pt

  2. Polyvinylpyrrolidone adsorption effects on the morphologies of synthesized platinum particles and its catalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Ooi, Mahayatun Dayana Johan [Nano - Optoelectronic Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang (Malaysia); Aziz, Azlan Abdul [Nano - Optoelectronic Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang (Malaysia); Nanobiotechnology Research and Innovation (NanoBRI), INFORMM, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang (Malaysia)

    2015-04-24

    Flower-like Platinum micro-structures were synthesized from different concentration of the PVP using solvothermal method. At 5.0×10{sup −3} mmol of PVP, well-defined flower-like pattern consists of triangular petals radiating from the centre were produced whereas larger flower network developed at higher PVP concentration. High degree of crystallinity was obtained upon each increment of PVP. The well defined flower like pattern synthesized using 5.0×10{sup −3} mmol PVP exhibit the highest catalytic activity and stability towards electro-oxidation of formic acid.

  3. Electrosynthesis and catalytic activity of polymer-nickel particles composite electrode materials

    Energy Technology Data Exchange (ETDEWEB)

    Melki, Tahar; Zouaoui, Ahmed; Bendemagh, Barkahoum [Universite Ferhat Abbas, Setif (Algeria). Faculte des Sciences de l' Ingenieur. Dept. du Tronc Commun; Oliveira, Ione M.F. de; Oliveira, Gilver F. de [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Quimica; Lepretre, Jean-Claude [UMR-5631 CNRS-INPG-UJF, St. Martin d' Heres Cedex (France). Lab. d' Electrochimie et de Physicochimie des Materiaux et Interfaces; Bucher, Christophe; Mou tet, Jean-Claude [Universite Joseph Fourier Grenoble 1 (France). Dept. de Chimie Moleculaire], e-mail: Jean-Claude.Moutet@ujf-grenoble.fr

    2009-07-01

    Nickel-polymer composite electrode materials have been synthesized using various strategies, all comprising the electrochemical reduction of nickel(II) cations or complexes, incorporated by either ion-exchange or complexation into various poly(pyrrole-carboxylate) thin films coated by oxidative electropolymerization onto carbon electrodes. The electrocatalytic activity and the stability of the different composites have been then evaluated in the course of the electrocatalytic hydrogenation of ketones and enones in aqueous electrolytes. The best results were obtained using nickel-polymer composites synthesized by electroreduction of nickel(II) ions complexed into polycarboxylate films, which are characterized by a high catalytic activity and a good operational stability. (author)

  4. Polyvinylpyrrolidone adsorption effects on the morphologies of synthesized platinum particles and its catalytic activity

    Science.gov (United States)

    Ooi, Mahayatun Dayana Johan; Aziz, Azlan Abdul

    2015-04-01

    Flower-like Platinum micro-structures were synthesized from different concentration of the PVP using solvothermal method. At 5.0×10-3 mmol of PVP, well-defined flower-like pattern consists of triangular petals radiating from the centre were produced whereas larger flower network developed at higher PVP concentration. High degree of crystallinity was obtained upon each increment of PVP. The well defined flower like pattern synthesized using 5.0×10-3 mmol PVP exhibit the highest catalytic activity and stability towards electro-oxidation of formic acid.

  5. Non ideal detonation of emulsion explosives mixed with metal particles

    Science.gov (United States)

    Mendes, Ricardo; Ribeiro, José B.; Plaksin, I.; Campos, Jose

    2012-03-01

    The detonation of ammonium nitrate based compositions like emulsion explosives mixed with metal particles was experimentally investigated. Aluminum powder with a mean particle size of 6 μm was used, and the mass concentration of aluminum on the explosive charge ranged from 0 to 30% wt. The values of the detonation velocity, the pressure attenuation - P(x) - of the shock front amplitude in a standard PMMA monitor and manganin gauges pressure-time histories are shown as a function of the explosive charge porosity and specific mass. All these parameters except the pressuretimes histories have been evaluated using the multi-fiber optical probe (MFOP) method which is based on the use of an optical fiber strip, with 64 independent optical fibers. The MFOP allows a quasicontinuous evaluation of the detonation wave run propagation and the assessment of spatial resolved measurements of the shock wave induced in the PMMA barrier. Results of that characterization process are presented and discussed for aluminized and non-aluminized emulsion explosives. The experimental results have shown that the detonation velocity decreases monotonically with the increase of aluminum content. Nevertheless the peak of detonation pressure profiles presents a non-monotonic behavior increasing its value up to an Al content of 20% wt, after which it starts to decrease.

  6. Non ideal detonation of emulsion explosives mixed with metal particles

    Science.gov (United States)

    Mendes, R.; Ribeiro, J.; Plaksin, I.; Campos, J.

    2011-06-01

    The detonation of ammonium nitrate based compositions like emulsion explosives (EX) mixed with metal particles has been investigated experimentally. Aluminium powder with a mean particle size of 10 μm was used, and the mass concentration of aluminum on the explosive charge was ranged from 0 to 30%. The values of the detonation velocity, the pressure attenuation - P(x) - of detonation front amplitude in a standard PMMA monitor and manganin gauges pressure-time histories are shown as a function of the explosive charge porosity and specific mass. All these parameters except the pressure-times histories have been evaluated using the multi fiber optical probe (MFOP) method which is based on the use of an optical fiber strip, with 64 independent optical fibers. The MFOP allow a quasi continuous evaluation of the detonation wave run propagation and the assessment to spatial resolved measurements of the shock wave induced in the PMMA barrier which in turns allows a detailed characterization of the detonation reaction zone structure. Results of that characterization process are presented and discussed for aluminized and non aluminized EX. Moreover, the effect of the mass concentration of the sensitizing agent (hollow glass micro-balloons) on the non monotonic detonation velocity variation, for EX, will be discussed.

  7. Molecular studies of model surfaces of metals from single crystals to nanoparticles under catalytic reaction conditions. Evolution from prenatal and postmortem studies of catalysts.

    Science.gov (United States)

    Somorjai, Gabor A; Aliaga, Cesar

    2010-11-02

    Molecular level studies of metal crystal and nanoparticle surfaces under catalytic reaction conditions at ambient pressures during turnover were made possible by the use of instruments developed at the University of California at Berkeley. Sum frequency generation vibrational spectroscopy (SFGVS), owing to its surface specificity and sensitivity, is able to identify the vibrational features of adsorbed monolayers of molecules. We identified reaction intermediates, different from reactants and products, under reaction conditions and for multipath reactions on metal single crystals and nanoparticles of varying size and shape. The high-pressure scanning tunneling microscope (HP-STM) revealed the dynamics of a catalytically active metallic surface by detecting the mobility of the adsorbed species during catalytic turnover. It also demonstrated the reversible and adsorbate-driven surface restructuring of platinum when exposed to molecules such as CO and ethylene. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) detected the reversible changes of surface composition in rhodium-palladium, platinum-palladium, and other bimetallic nanoparticles as the reactant atmosphere changed from oxidizing to reducing. It was found that metal nanoparticles of less than 2 nm in size are present in higher oxidation states, which alters and enhances their catalytic activity. The catalytic nanodiode (CND) confirmed that a catalytic reaction-induced current flow exists at oxide-metal interfaces, which correlates well with the reaction turnover.

  8. Improved catalytic activity of laser generated bimetallic and trimetallic nanoparticles.

    Science.gov (United States)

    Singh, Rina; Soni, R K

    2014-09-01

    We report synthesis of silver nanoparticles, bimetallic (Al2O3@Ag) nanoparticles and trimetallic (Al2O3@AgAu) nanoparticles by nanosecond pulse laser ablation (PLA) in deionized water. Two-step laser ablation methodologies were adopted for the synthesis of bi- and tri-metallic nanoparticles. In this method a silver or gold target was ablated in colloidal solution of γ-alumina nanoparticles prepared by PLA. The TEM image analysis of bimetallic and trimetallic particles reveals deposition of fine silver particles and Ag-Au alloy particles, respectively, on large alumina particles. The laser generated nanoparticles were tested for catalytic reduction of 4-nitrophenol to 4-aminophenol and showed excellent catalytic behaviour. The catalytic rate was greatly improved by incorporation of additional metal in silver nanoparticles. The catalytic efficiency of trimetallic Al2O3@AgAu for reduction of 4-nitrophenol to 4-aminophenol was remarkably enhanced and the catalytic reaction was completed in just 5 sec. Even at very low concentration, both Al2O3@Ag nanoparticles and Al2O3@AgAu nanoparticles showed improved rate of catalytic reduction than monometallic silver nanoparticles. Our results demonstrate that alumina particles in the solution not only provide the active sites for particle dispersion but also improve the catalytic activity.

  9. Catalytic behavior of Sn/Bi metal powder in anhydride-based epoxy curing.

    Science.gov (United States)

    Jang, Keon-Soo; Eom, Yong-Sung; Moon, Jong-Tae; Oh, Yong-Soo; Nam, Jae-Do

    2009-12-01

    In this paper, we report the catalytic activity of the Sn/Bi alloy beads and its acceleration of the exothermic epoxy curing reactions in various thermal conditions and bead compositions. As being used as low-melting solder balls in electronic interconnection processes with various epoxy systems, it was found that the Sn/Bi beads substantially lowered the exothermic peak temperature of the diglycidyl ether of bisphenol A (DGEBA)/anhydride systems in up to ca. 140 degrees C depending on different types of anhydride curing agents. The catalytic activation of Sn/Bi powder was initiated with a small amount of Sn/Bi powder, for example, lowering ca. 50 degrees C of the exothermic peak temperature by adding only 0.1 vol% of Sn/Bi powder. The catalytic capability of the powder was increased by using smaller sized beads corresponding to larger catalytic surface area at the same volume fraction. Exhibiting a latent catalytic effect, the catalytic activity of Sn/Bi powder was remained latent at temperatures lower than 100 degrees C in isothermal conditions.

  10. Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

    Science.gov (United States)

    Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

    2015-05-21

    Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

  11. Cobalt bioavailability from hard metal particles. Further evidence that cobalt alone is not responsible for the toxicity of hard metal particles

    Energy Technology Data Exchange (ETDEWEB)

    Lison, D. (Industrial Toxicology and Occupational Medicine Unit, Catholic Univ. of Louvain, Brussels (Belgium)); Lauwerys, R. (Industrial Toxicology and Occupational Medicine Unit, Catholic Univ. of Louvain, Brussels (Belgium))

    1994-08-01

    Hard metal is an alloy of tungsten carbide (WC) in a matrix of cobalt metal (Co). The inhalation of hard metal dust can cause an alveolitis which may progress to interstitial fibrosis. This study was undertaken to compare, both in vivo and in vitro, the bioavailability of cobalt metal when mixed or not with WC and to assess whether this factor had any influence on the cellular toxicity of hard metal particles. In vivo, non-toxic doses of cobalt metal were administered intratracheally in the rat, alone (Co, 0.03 mg/100 g) or mixed with tungsten carbide (WC-Co, 0.5 mg/100 g containing 6.3% of cobalt metal particles). Sequential measurements of cobalt in the lung and in urine demonstrated that the retention time of the metal in the lung was longer in Co- than in WC-Co-treated animals. In vitro, the cellular cobalt uptake was higher when the metal was presented to the macrophages as WC-Co. However, there was no relationship between the cellular uptake of cobalt and the occurrence of toxicity, since the intracellular concentration of cobalt associated with the occurrence of a cytotoxic effect of WC-Co particles was insufficient to exert the same effect when resulting from exposure to Co alone. This clearly indicates that increased bioavailability of cobalt is not the mechanism by which hard metal particles exhibit their cellular toxicity. These observations confirm and extend our previous findings supporting the view that cobalt is not the only component responsible for the toxicity of hard metal particles which should be considered as a specific toxic entity. (orig.)

  12. Flame assisted synthesis of catalytic ceramic membranes

    DEFF Research Database (Denmark)

    Johansen, Johnny; Mosleh, Majid; Johannessen, Tue

    2004-01-01

    technology it is possible to make supported catalysts, composite metal oxides, catalytically active surfaces, and porous ceramic membranes. Membrane layers can be formed by using a porous substrate tube (or surface) as a nano-particle filter. The aerosol gas from the flame is led through a porous substrate...

  13. Hydrogenation-controlled phase transition on two-dimensional transition metal dichalcogenides and their unique physical and catalytic properties

    Science.gov (United States)

    Qu, Yuanju; Pan, Hui; Kwok, Chi Tat

    2016-09-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been widely used from nanodevices to energy harvesting/storage because of their tunable physical and chemical properties. In this work, we systematically investigate the effects of hydrogenation on the structural, electronic, magnetic, and catalytic properties of 33 TMDs based on first-principles calculations. We find that the stable phases of TMD monolayers can transit from 1T to 2H phase or vice versa upon the hydrogenation. We show that the hydrogenation can switch their magnetic and electronic states accompanying with the phase transition. The hydrogenation can tune the magnetic states of TMDs among non-, ferro, para-, and antiferro-magnetism and their electronic states among semiconductor, metal, and half-metal. We further show that, out of 33 TMD monolayers, 2H-TiS2 has impressive catalytic ability comparable to Pt in hydrogen evolution reaction in a wide range of hydrogen coverages. Our findings would shed the light on the multi-functional applications of TMDs.

  14. Being two is better than one-catalytic reductions with dendrimer encapsulated copper- and copper-cobalt-subnanoparticles.

    Science.gov (United States)

    Ficker, Mario; Petersen, Johannes F; Gschneidtner, Tina; Rasmussen, Ann-Louise; Purdy, Trevor; Hansen, Jon S; Hansen, Thomas H; Husted, Søren; Moth Poulsen, Kasper; Olsson, Eva; Christensen, Jørn B

    2015-06-21

    Copper and copper-cobalt subnanoparticles have been synthesized using 4-carbomethoxypyrrolidone terminated PAMAM-dendrimers as templates. The metal particles were applied in catalytic reduction reactions. While Cu subnanoparticles were only capable of reducing conjugated double bonds, enhancing the Cu particles with Co led to a surprising increase in catalytic activity, reducing also isolated carbon double and triple bonds.

  15. Coordination kinetics of different metal ions with the amidoximated polyacrylonitrile nanofibrous membranes and catalytic behaviors of their complexes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fu; Dong, Yong Chun; Kang, Wei Min; Cheng, Bowen; Qu, Xiang; Cui, Guixin [School of Textiles, Tianjin Polytechnic University, Tianjin (China)

    2016-12-15

    Two transition metal ions (Fe{sup 3+} and Cu{sup 2+}) and a rare earth metal ion (Ce{sup 3+}) were selected to coordinate with amidoximated polyacrylonitrile (PAN) nanofibrous membrane for preparing three metal modified PAN nanofibrous membrane complexes (M-AO-n-PANs, M = Fe, Cu, or Ce) as the heterogeneous Fenton catalysts for the dye degradation in water under visible irradiation. The coordination kinetics of three metal ions with modified PAN nanofibrous membranes was studied and the catalytic properties of the resulting complexes were also compared. The results indicated that increasing metal ion concentrations in solution or higher coordination temperature led to a significant increase in metal content, particularly in Fe and Cu contents of the complexes. Their coordination process could be described using Langmuir isotherm and pseudo-second-order kinetic equations. Moreover, Fe-AO-n-PAN had the best photocatalytic efficiency for the dye degradation in acidic medium, but a lower photocatalytic activity than Cu-AO-n-PAN in alkali medium.

  16. Effects of acido-basic support properties on the catalytic hydrogenation of acetylene on gold nano-particles

    Science.gov (United States)

    Manda, Abdullah Ahmed

    Metallic gold nanoparticles supported on gamma-Al2O 3 and magnesia-alumina mixed oxide, with different magnesia content have been prepared by sol-gel method and characterized by different techniques (inductive coupled plasma-mass spectroscopy (ICP-MS), XRD, BET surface area analysis, transmission electron microscopy (TEM), CO2 and NH 3 temperature programmed desorption (TPD), H2 temperature programmed reduction (TPR) and FTIR of adsorbed CO2). Such systems were found to produce catalysts with controllable acidity, varying from catalyst possessing large density of acidic and low density of basic sites, others with acidic and basic sites of equal strength and density, and others with large basic and low acid sites densities, respectively. The catalytic assessment of the generated acidity was carried out using 2-propanol decomposition as a test reaction. The results obtained indicate that the presence of magnesia and reduced gold nanopartilces has imparted the catalysts, 1%Au/4%Mg-Al 2O3 and 1%Au/8%Mg-Al2O3, with significant base-catalytic properties. Acetylene hydrogenation and formation of coke deposits were investigated on a gold catalyst supported on gamma-Al2O3 and gold supported on alumina-magnisia mixed oxide with different gold content; 1%Au/gamma-Al 2O3, 1%Au/15%Mg-Al2O3, 2%Au/15%Mg-Al 2O3 and 4%Au/15%Mg-Al2O3. The effect of the H2/C2H2 ratio was studied over a range of values. The catalytic activity and selectivity towards ethylene and other products were investigated at different reaction temperatures. Acetylene hydrogenation was investigated in the presence and absence of ethylene in stream. It is investigated that the adsorption of the triple bond is preferred over the double bond and during selective catalytic (SCR) of C2H2 the two hydrocarbons do not compete for the same adsorption sites. The deactivation of catalysts was studied by temperature programmed oxidation (TPO). Higher content of coke over 1%Au/Al2O3 catalyst was investigated in contrast to

  17. Screening study of transition metal oxide catalysts supported on ceria-modified titania for catalytic oxidation of toluene

    Institute of Scientific and Technical Information of China (English)

    Dan-qing YU; Yue LIU; Zhong-biao WU

    2011-01-01

    Six transition metal oxides were added in ceria-modified titania using a sol-gel method for catalytic oxidation of toluene. An MnOx based catalyst was found to be the most active one, with which toluene could be decomposed completely at 200 ℃. The greatest Mn/Ti and molar ratio of the mobile oxygen to the total oxygen concentration, together with a large surface area and a low reduction peak-starting temperature, would result in its best activity in toluene oxidation.

  18. Promiscuity comes at a price: catalytic versatility vs efficiency in different metal ion derivatives of the potential bioremediator GpdQ.

    Science.gov (United States)

    Daumann, Lena J; McCarthy, Bianca Y; Hadler, Kieran S; Murray, Tracy P; Gahan, Lawrence R; Larrabee, James A; Ollis, David L; Schenk, Gerhard

    2013-01-01

    The glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) is a highly promiscuous dinuclear metallohydrolase with respect to both substrate specificity and metal ion composition. While this promiscuity may adversely affect the enzyme's catalytic efficiency its ability to hydrolyse some organophosphates (OPs) and by-products of OP degradation have turned GpdQ into a promising candidate for bioremedial applications. Here, we investigated both metal ion binding and the effect of the metal ion composition on catalysis. The prevalent in vivo metal ion composition for GpdQ is proposed to be of the type Fe(II)Zn(II), a reflection of natural abundance rather than catalytic optimisation. The Fe(II) appears to have lower binding affinity than other divalent metal ions, and the catalytic efficiency of this mixed metal center is considerably smaller than that of Mn(II), Co(II) or Cd(II)-containing derivatives of GpdQ. Interestingly, metal ion replacements do not only affect catalytic efficiency but also the optimal pH range for the reaction, suggesting that different metal ion combinations may employ different mechanistic strategies. These metal ion-triggered modulations are likely to be mediated via an extensive hydrogen bond network that links the two metal ion binding sites via residues in the substrate binding pocket. The observed functional diversity may be the cause for the modest catalytic efficiency of wild-type GpdQ but may also be essential to enable the enzyme to evolve rapidly to alter substrate specificity and enhance k(cat) values, as has recently been demonstrated in a directed evolution experiment. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases.

  19. Catalytic activity of metallic nanoisland coatings. The influence of size effects on the recombination properties

    Science.gov (United States)

    Tomilina, O. A.; Berzhansky, V. N.; Tomilin, S. V.; Shaposhnikov, A. N.

    2016-08-01

    The results of investigations of the quantum-size effects influence on selective properties of heterogeneous nanocatalysts are presents. As etalon exothermic reaction was used the reaction of atomic hydrogen recombination. The nanostructured Pd and Pt films on Teflon substrate were used as a samples of heterogeneous nanocatalysts. It was shown that for nanoparticles with various sizes the catalytic activity has the periodic dependence. It has been found that for certain sizes of nanoparticles their catalytic activity is less than that of Teflon substrate.

  20. Characterization of typical metal particles during haze episodes in Shanghai, China.

    Science.gov (United States)

    Li, Rui; Yang, Xin; Fu, Hongbo; Hu, Qingqing; Zhang, Liwu; Chen, Jianmin

    2017-08-01

    Aerosol particles were collected during three heavy haze episodes at Shanghai in the winter of 2013. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy was used to study the morphology and speciation of typical metal particles at a single-particle level. In addition, time-of-flight aerosol mass spectrometry (ATOFMS) was applied to identify the speciation of the Fe-containing particles. TEM analysis indicated that various metal-containing particles were hosted by sulfates, nitrates, and oxides. Fe-bearing particles mainly originated from vehicle emissions and/or steel production. Pb-, Zn-, and Sb-bearing particles were mainly contributed by anthropogenic sources. Fe-bearing particles were clustered into six groups by ATOFMS: Fe-Carbon, Fe-Inorganic, Fe-Trace metal, Fe-CN, Fe-PO3, and Fe-NO3. ATOFMS data suggested that Fe-containing particles corresponded to different origins, including industrial activities, resuspension of dusts, and vehicle emissions. Fe-Carbon and Fe-CN particles displayed significant diurnal variation, and high levels were observed during the morning rush hours. Fe-Inorganic and Fe-Trace metal particle levels peaked at night. Furthermore, Fe-Carbon and Fe-PO3 were mainly concentrated in the fine particles. Fe-CN, Fe-Inorganic, and Fe-Trace metal exhibited bimodal distribution. The mixing state of the particles revealed that all Fe-bearing particles tended to be mixed with sulfate and nitrate. The data presented herein is essential for elucidating the origin, evolution processes, and health effects of metal-bearing particles. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Silicon carbide-based membranes with high soot particle filtration efficiency, durability and catalytic activity for CO/HC oxidation and soot combustion

    NARCIS (Netherlands)

    Sandra, F.; Ballestero, A.; NGuyen, V. L.; Tsampas, M. N.; Vernoux, P.; Balan, C.; Iwamoto, Y.; Demirci, U. B.; Miele, P.; Bernard, S.

    2016-01-01

    We report here the solution coatings of Diesel Particulate Filter (DPF) with allylhydridopolycarbosilane (AHPCS)-based polymers leading to supported silicon carbide (SiC)-based membranes with high temperature soot particle filtration efficiency, durability and catalytic activity. In a first part of

  2. Heavy metal in inhalable and respirable particles in urban atmosphere

    Directory of Open Access Journals (Sweden)

    T.F. Ediagbonya

    2013-09-01

    Full Text Available Human activities in Sapele are veritable sources of particulate pollution which are exuded into the atmosphere. These activities include bush burning which is one of the pre-planting activities, transportation, gas flaring, incineration of wastes refuse disposal and the use of wood as a source of fuel. The objective of this study is to determine the concentration of the trace metal in particulate matter captured in glass fibre filter paper. High volume sampler was used to collect the respirable and inhalable suspended particulate matter at ten different sites located in Sapele, from December 2010 to April 2011. The foam and the glass fibre filter were analysed for nine (Mn, Ni, Cr, Cd, Zn, Cu, Co, Fe, and Pb respectively by Flame Atomic Absorption Spectrophotometer (FAAS. The concentration of the respirable particle ranged from 104.17 to 145.83ug/cubic meter while the inhalable concentration ranged from 166.67 to 812.50ug/cubic meter. From the analysis the element Cd was moderately enriched.

  3. Synthesis, structural characterization, catalytic, thermal and electrochemical investigations of bidentate Schiff base ligand and its metal complexes.

    Science.gov (United States)

    Dolaz, Mustafa; McKee, Vickie; Uruş, Serhan; Demir, Necmettin; Sabik, Ali E; Gölcü, Ayşegül; Tümer, Mehmet

    2010-07-01

    In this study, we prepared the Schiff base ligand (L) and its Cu(II), Co(II) and Ni(II) complexes. The compounds were characterized by the analytical and spectroscopic methods. The ligand (L) behaves as a bidentate ligand and coordinates to the metal ions via the nitrogen atoms. The complexes have the mononuclear structures. The analytical and spectroscopic results indicated that the chloride ions coordinate to the metal ions. The complexes have the general formulae [M(L)(Cl)(2)] (M: Cu(II), Co(II) and Ni(II) metal ions). Electrochemical properties were investigated as ligand and metal centres in the different solvents and at the scan rates, respectively. The thermal properties of the metal complexes were studied in the N(2) atmosphere. We investigated the improved catalytic activity of the Cu(II), Co(II) and Ni(II) complexes on the cyclohexane as a substrate. Obtained data showed that the best catalyst is the Cu(II) complex. The single crystal of the ligand (L) was obtained from CH(3)CN solution. There is a C-H...N H-bond linking the molecules into chains (C6)...N(2) 3.4415(18)A under symmetry operation (x+1,y,z) as well as pi-pi stacking on the outside of the "V" shape--nothing on the inside.

  4. Deactivating Metal Particle by Optimizing Insulation Configuration in Spark Gap Switch

    Institute of Scientific and Technical Information of China (English)

    JIA Jiangbo; ZHANG Qiaogen; ZHU Taiyun; ZHA Wei; SUN Fu; YANG Lanjun

    2008-01-01

    -As a new method to protect the spark gap from metal particle contamination, the effect of the metal inserted insulator on the controlling behavior of metal particles was investigated in a quasi-uniform electric field. Considering that the inserted metal electrodes can decrease the electric field around the insulator and divert the electrostatic force away from the insulator, the method can be used to prevent the particles from moving toward the insulator so as to reduce the possibility of a breakdown. The inserted metal electrodes can reverse the direction of the particles' horizontal motion. A study on the insulator shape indicates that the inserted metal electrodes can repulse the particle and improve the particle lifting voltage significantly near the vertical surface of the insulator or ribbed insulator. For the insulator with a tilting surface the inserted metal electrodes have little influence on the particle motion. In addition, the size of the inserted electrodes shows a significant effect on the control of particle motion.

  5. Effect of Transition Metals on Catalytic Performance of Ru/Sepiolite Catalyst for Methanation of Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    Laitao Luo; Songjun Li

    2004-01-01

    The effects of Mo, Mn and Zr transitional metals on the catalytic performance of Ru/sepiolite for CO2 methanation were investigated. The results indicated that addition of the transitional metals affected the activity of the Ru/sepiolite remarkably, and the activities of the catalysts were closely associated with the electronic state of the ruthenium surface. The addition of Mo increased the active surface area, the Ru dispersity, the number of active sites, and the resistance to poisoning. According to the Transition State Theory, when Mo is added into the Ru/sepiolite catalyst, the decrease in surface energy is at a cost of an increment in steric hindrance. When T ≤674 K, the energy factor was dominating, and resulted in a decreasing in the ratio of S(CH4)/S(CO). Otherwise, the steric factor dominated the reaction course.

  6. 重油催化裂化的金属钝化剂%Metal passivator for dead oil catalytic cracking

    Institute of Scientific and Technical Information of China (English)

    孙利; 沈本贤

    2001-01-01

    重油中所含的金属Ni、V、Na在流化催化裂化(FCC)过程中,会污染催化剂,导致催化剂失活。本文综述了国内外金属钝化剂的研究进展,提出研制无毒、高效以及多功能的金属钝化剂是今后发展的方向。%Ni,V,Na in the dead oil will pollute catalysts seriously duringfluid catalytic cracking(FCC).The research progress inland and abroad of metal passivator was reviewed.It pointed out that development of nontoxic,high effective and multifunction metal passivator was a new direction in research work.

  7. Behavior of particles in front of metallic solid/liquid interface in electromagnetic field

    Institute of Scientific and Technical Information of China (English)

    钟云波; 任忠鸣; 孙秋霞; 江志文; 邓康; 徐匡迪

    2003-01-01

    The first part deals with the behavior of particles theoretically, and the critical electromagnetic force needed to alter the behavior of particles was deduced under different conditions. It was proposed that applying electromagnetic force would change the distribution coefficient of the particles. By using the data from literatures, the migrating rate of SiC particle by electromagnetic force was calculated, which is far more than the critical rate of solidifying interface which will result in the engulfment of the SiC particle in the Al-SiC matrix metal. Therefore the possibility of controlling the behavior of the particles in front of the solidifying interface by electromagnetic field was confirmed. In the second part, by using simulative experiments, the man-made alternation of the behavior of the particles in front of the solidifying interface under electromagnetic field was observed, and the idea of changing the distribution of the particles in solidified metal by electromagnetic force was verified experimentally. It is shown that, the particle, which would be engulfed by the solidifying interface, would escape from the interface under electromagnetic buoyant force (EMBF), and the particles adherent to the interface would migrate toward it and be engulfed finally under EMBF. Further more, the particles being pushed by the interface would stay at the interface, the repulsive force exerted on the particles would be counteracted by EMBF, and then the particle would turn to be engulfed. Adjusting the direction and magnitude of EMBF could alter the distribution of the particles in the solidifying metal.

  8. Metal-ligand cooperation in catalytic intramolecular hydroamination: a computational study of iridium-pyrazolato cooperative activation of aminoalkenes.

    Science.gov (United States)

    Tobisch, Sven

    2012-06-04

    The present study comprehensively explores diverse mechanistic pathways for intramolecular hydroamination of prototype 2,2-dimethyl-4-penten-1-amine by Cp*Ir chloropyrazole (1; Cp*=pentamethylcyclopentadienyl) in the presence of KOtBu base with the aid of density functional theory (DFT) calculations. The most accessible mechanistic pathway for catalytic turnover commences from Cp*Ir pyrazolato (Pz) substrate adduct 2⋅S, representing the catalytically competent compound and proceeds via initial electrophilic activation of the olefin C=C bond by the metal centre. It entails 1) facile and reversible anti nucleophilic amine attack on the iridium-olefin linkage; 2) Ir-C bond protonolysis via stepwise transfer of the ammonium N-H proton at the zwitterionic [Cp*IrPz-alkyl] intermediate onto the metal that is linked to turnover-limiting, reductive, cycloamine elimination commencing from a high-energy, metastable [Cp*IrPz-hydrido-alkyl] species; and 3) subsequent facile cycloamine liberation to regenerate the active catalyst species. The amine-iridium bound 2 a⋅S likely corresponds to the catalyst resting state and the catalytic reaction is expected to proceed with a significant primary kinetic isotope. This study unveils the vital role of a supportive hydrogen-bonded network involving suitably aligned β-basic pyrazolato and cycloamido moieties together with an external amine molecule in facilitating metal protonation and reductive elimination. Cooperative hydrogen bonding thus appears pivotal for effective catalysis. The mechanistic scenario is consonant with catalyst performance data and furthermore accounts for the variation in performance for [Cp*IrPz] compounds featuring a β- or γ-basic pyrazolato unit. As far as the route that involves amine N-H bond activation is concerned, a thus far undocumented pathway for concerted amidoalkene → cycloamine conversion through olefin protonation by the pyrazole N-H concurrent with N-C ring closure is disclosed as a

  9. Characterisation of a metal matrix composite produced with laser particle injection

    NARCIS (Netherlands)

    Kloosterman, AB; De Hosson, JTM; Sudarshan, TS; Jeandin, M; Khor, KA

    1998-01-01

    This paper concentrates on the laser particle injection process. TiC, TiN end SiC particles were injected into Ti-6Al-4V, which resulted in the formation of a metal matrix composite with modest dissolution of the added particles. The laser tracks with SIC exhibited a diversity of microstructures

  10. Characterisation of a metal matrix composite produced with laser particle injection

    NARCIS (Netherlands)

    Kloosterman, AB; De Hosson, JTM; Sudarshan, TS; Jeandin, M; Khor, KA

    1998-01-01

    This paper concentrates on the laser particle injection process. TiC, TiN end SiC particles were injected into Ti-6Al-4V, which resulted in the formation of a metal matrix composite with modest dissolution of the added particles. The laser tracks with SIC exhibited a diversity of microstructures wit

  11. Channeling and electromagnetic radiation of relativistic charged particles in metal-organic frameworks

    Science.gov (United States)

    Zhevago, N. K.; Glebov, V. I.

    2017-06-01

    We have developed the theory of electromagnetic interaction of relativistic charged particles with metal-organic frameworks (MOFs). The electrostatic potential and electron number density distribution in MOFs were calculated using the most accurate data for the atomic form factors. Peculiarities of axial channeling of fast charged particles and various types of electromagnetic radiation from relativistic particles has been discussed.

  12. Efficient H{sub 2}-producing photo-catalytic systems based on cyclo-metallated iridium- and tricarbonyl-rhenium-diimine photosensitizers and cobaloxime catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Fihri, A.; Artero, V.; Fontecave, M. [Univ Grenoble 1, Lab Chim et Biol Metaux, Grenoble (France); Fihri, A.; Artero, V.; Fontecave, M. [CNRS, UMR 5249, F-75700 Paris (France); Fihri, A.; Artero, V.; Fontecave, M. [CEA, DSV, iRTSV, F-38054 Grenoble 9 (France); Pereira, A. [CEA, DRT, Liten, DTNM, LTS, Grenoble (France)

    2008-07-01

    Quantum yield values up to 16% under visible irradiation associated with high turnover frequencies ({approx} 50 h{sup -1}) and stability (up to 273 turnovers), characterize the new photo-catalytic systems for hydrogen production, based on diimine derivatives of ruthenium, cyclo-metallated iridium or tricarbonyl-rhenium as photosensitizers and cobaloxime H{sub 2}-evolving catalytic centers, which are among the most efficient molecular systems reported so far and compete with some platinum-based systems. (authors)

  13. 40 CFR 63.1564 - What are my requirements for metal HAP emissions from catalytic cracking units?

    Science.gov (United States)

    2010-07-01

    ... concentration in the catalytic cracking unit catalyst regenerator flue gas as measured by Method 29 in appendix... emissions from catalytic cracking units? 63.1564 Section 63.1564 Protection of Environment ENVIRONMENTAL... Refineries: Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units Catalytic Cracking...

  14. Catalytic Behavior of Lipase Immobilized onto Congo Red and PEG-Decorated Particles

    Directory of Open Access Journals (Sweden)

    Rubens A. Silva

    2014-06-01

    Full Text Available Poly(ethylene glycol (PEG-decorated polystyrene (PS nanoparticles with mean hydrodynamic diameter (D and zeta–potential (ζ of (286 ± 15 nm and (−50 ± 5 mV, respectively, were modified by the adsorption of Congo red (CR. The PS/PEG/CR particles presented D and ζ values of (290 ± 19 nm and (−36 ± 5 mV, respectively. The adsorption of lipase onto PS/PEG or PS/PEG/CR particles at (24 ± 1 °C and pH 7 changed the mean D value to (380 ± 20 and (405 ± 11 nm, respectively, and ζ value to (−32 ± 4 mV and (−25 ± 2 mV, respectively. The kinetic parameters of the hydrolysis of p-nitrophenyl butyrate were determined for free lipase, lipase immobilized onto PS/PEG and PS/PEG/CR particles. Lipase on PS/PEG/CR presented the largest Michaelis-Menten constant (KM, but also the highest Vmax and kcat values. Moreover, it could be recycled seven times, losing a maximum 10% or 30% of the original enzymatic activity at 40 °C or 25 °C, respectively. Although lipases immobilized onto PS/PEG particles presented the smallest KM values, the reactions were comparatively the slowest and recycling was not possible. Hydrolysis reactions performed in the temperature range of 25 °C to 60 °C with free lipases and lipases immobilized onto PS/PEG/CR particles presented an optimal temperature at 40 °C. At 60 °C free lipases and lipases immobilized onto PS/PEG/CR presented ~80% and ~50% of the activity measured at 40 °C, indicating good thermal stability. Bioconjugation effects between CR and lipase were evidenced by circular dichroism spectroscopy and spectrophotometry. CR molecules mediate the open state conformation of the lipase lid and favor the substrate approaching.

  15. Catalytic Efficiency Is a Function of How Rhodium(I) (5 + 2) Catalysts Accommodate a Conserved Substrate Transition State Geometry: Induced Fit Model for Explaining Transition Metal Catalysis.

    Science.gov (United States)

    Mustard, Thomas J L; Wender, Paul A; Cheong, Paul Ha-Yeon

    2015-03-06

    The origins of differential catalytic reactivities of four Rh(I) catalysts and their derivatives in the (5 + 2) cycloaddition reaction were elucidated using density functional theory. Computed free energy spans are in excellent agreement with known experimental rates. For every catalyst, the substrate geometries in the transition state remained constant (Catalytic efficiency is shown to be a function of how well the catalyst accommodates the substrate transition state geometry and electronics. This shows that the induced fit model for explaining biological catalysis may be relevant to transition metal catalysis. This could serve as a general model for understanding the origins of efficiencies of catalytic reactions.

  16. Strategies for Enhancing the Catalytic Performance of Metal-Organic Frameworks in the Fixation of CO2 into Cyclic Carbonates.

    Science.gov (United States)

    Taherimehr, Masoumeh; Van de Voorde, Ben; Wee, Lik H; Martens, Johan A; De Vos, Dirk E; Pescarmona, Paolo P

    2017-03-22

    Metal-organic frameworks (MOFs) with accessible Lewis acid sites are finding increasing application in the field of heterogeneous catalysis. However, the structural instability of MOFs when they are exposed to high temperature and/or high pressure often limits their applicability. In this study, two strategies were applied to achieve a MOF catalyst with high stability, activity and selectivity in the reaction of CO2 with styrene oxide to produce styrene carbonate. In the first approach, a MOF with linkers with high connectivity as MIL-100(Cr) was studied, leading to promising activity and recyclability in consecutive catalytic runs without loss of activity. In the second strategy, a MOF with linkers with lower connectivity but with encapsulated Keggin phosphotungstic acid (MIL-101(Cr)[PTA]) was prepared. However, the activity of this catalyst decreased upon reuse as a consequence of deterioration of the MOF. Further investigations were dedicated to the enhancement of the catalytic performance of MIL-100 and included the variation of the metal centre as well as the type and loading of organic salt acting as nucleophile source. This allowed tuning the nature of the organic halide to the specific porous structure of MIL-100(Cr) to prevent diffusion limitations. The best catalytic performance was obtained for MIL-100(Cr) in combination with EMIMBr ionic liquid, which gave very high styrene carbonate yield (94 %) with complete selectivity after 18 h of reaction at mild temperature (60 °C). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Arthroscopic surgical tools: A source of metal particles and possible joint damage

    Science.gov (United States)

    Pedowitz, Robert A.; Billi, Fabrizio; Kavanaugh, Aaron; Colbert, Andrew; Liu, Sen; Savoie, Felix H.; You, Zongbing

    2013-01-01

    Purpose Our goals were (1) to characterize metal micro-particles created by standard arthroscopic instruments, and (2) to examine the in-vitro cellular responses induced by those particles, including possible synergistic effects with local anesthetic. Methods We applied standard surgical tools to 16 foam bone blocks immersed in saline (plus 3 non-instrumented controls). Eight specimens had four minutes of exposure to a 4.0 mm full radius shaver rotating forward at 6,000 RPM. In the other blocks, four holes were created with a 3.0 mm drill via a sleeve. Particles were isolated onto silicon wafers by density gradient ultra-centrifugation, and SEM analyzed a minimum of 1000 particles per wafer. Metal particles were then isolated and purified. Aliquots of sterilized micro-particles were applied to cultured bovine chondrocytes (+/- local anesthetic) and to cultured human or bovine synoviocytes. Chondrocyte viability was assessed with live/dead cell assay by flow cytometry. Synoviocyte responses were assessed with qPCR. Results Stainless steel or aluminum particles were found in each sample (same composition as surgical instruments). Average particle size was 1 to 2 μm (range 50 nm to 20 μm). Chondrocyte exposure (1 hour) to metal debris induced a small but statistically significant increase in cell death, without any synergistic effect of local anesthetic. Proinflammatory chemokines were consistently upregulated in both human and bovine synoviocytes exposed to metallic micro-particles for 3, 24, and 48 hours. Conclusions The current study demonstrates that metallic microdebris is liberated by common arthroscopic instruments, at scales much smaller than previously recognized. These particles are bioactive as demonstrated by the in-vitro synoviocyte responses initiated by metallic micro-particles. Clinical Relevance Our findings suggest that metallic micro-particles could induce intra-articular damage via a synoviocyte-mediated cytokine response if their concentrations

  18. Multiscale Modeling of Metallic Materials Containing Embedded Particles

    Science.gov (United States)

    Phillips, Dawn R.; Iesulauro, Erin; Glaessgen, Edward H.

    2004-01-01

    Multiscale modeling at small length scales (10(exp -9) to 10(exp -3) m) is discussed for aluminum matrices with embedded particles. A configuration containing one particle surrounded by about 50 grains and subjected to uniform tension and lateral constraint is considered. The analyses are performed to better understand the effects of material configuration on the initiation and progression of debonding of the particles from the surrounding aluminum matrix. Configurational parameters considered include particle aspect ratio and orientation within the surrounding matrix. Both configurational parameters are shown to have a significant effect on the behavior of the materials as a whole. For elliptical particles with the major axis perpendicular to the direction of loading, a particle with a 1:1 aspect ratio completely debonds from the surrounding matrix at higher loads than particles with higher aspect ratios. As the particle major axis is aligned with the direction of the applied load, increasing amounts of load are required to completely debond the particles.

  19. PREPARATION AND CHARACTERIZATION OF NANOSTRUCTURED GRANULAR SUPPORT PARTICLES AND CATALYTIC MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Zhenchen Zhong

    2002-01-15

    We have set up successfully two experimental systems during the past time of the project. The first system is sol-gel chemical method for preparing {gamma}-Al{sub 2}O{sub 3}, SiO{sub 2}, Cr{sub 2}O{sub 3} granular support particles. The second system is the laser-induced solution deposition (LISD) technique for nanoparticle catalysts containing Fe/Cu, and Co/Cu on the granular support. We have successfully deposited {gamma}-Al{sub 2}O{sub 3}, SiO{sub 2}, Cr{sub 2}O{sub 3} granular support particles by sol-gel method and Co and CoO nanoparticles by LISD novel fabrication technique. The characterization methods we have used include scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM) and X-Ray diffraction (XRD). The research toward to the proposed direction is in good progress. We have given three presentations in national and local materials meetings and have submitted another two papers in another two key national meetings in nanotechnology and American Physical Annual March Meeting 2002. A couple of papers are in preparation.

  20. Processes of conversion of a hot metal particle into aerogel through clusters

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, B. M., E-mail: bmsmirnov@gmail.com [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2015-10-15

    Processes are considered for conversion into a fractal structure of a hot metal micron-size particle that is located in a buffer gas or a gas flow and is heated by an external electric or electromagnetic source or by a plasma. The parameter of this heating is the particle temperature, which is the same in the entire particle volume because of its small size and high conductivity. Three processes determine the particle heat balance: particle radiation, evaporation of metal atoms from the particle surface, and heat transport to the surrounding gas due to its thermal conductivity. The particle heat balance is analyzed based on these processes, which are analogous to those for bulk metals with the small particle size, and its high temperature taken into account. Outside the particle, where the gas temperature is lower than on its surface, the formed metal vapor in a buffer gas flow is converted into clusters. Clusters grow as a result of coagulation until they become liquid, and then clusters form fractal aggregates if they are removed form the gas flow. Subsequently, associations of fractal aggregates join into a fractal structure. The rate of this process increases in medium electric fields, and the formed fractal structure has features of aerogels and fractal fibers. As a result of a chain of the above processes, a porous metal film may be manufactured for use as a filter or catalyst for gas flows.

  1. Transition metal exchanged β zeolites: Characterization of the metal state and catalytic application in the methanol conversion to hydrocarbons

    NARCIS (Netherlands)

    Esquivel, D.; Cruz-Cabeza, A.J.; Jiménez-Sanchidrián, C.; Romero-Salguero, F.J.

    2013-01-01

    Various first-row transition metal cations (Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) have been introduced to zeolite beta using ion exchange procedures. Both aluminum and transition metal sites were studied by UV-Vis spectroscopy, XPS and Al-27 NMR. Generally, ion exchange favored the incorporat

  2. Transition metal exchanged β zeolites: Characterization of the metal state and catalytic application in the methanol conversion to hydrocarbons

    NARCIS (Netherlands)

    Esquivel, D.; Cruz-Cabeza, A.J.; Jiménez-Sanchidrián, C.; Romero-Salguero, F.J.

    2013-01-01

    Various first-row transition metal cations (Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) have been introduced to zeolite beta using ion exchange procedures. Both aluminum and transition metal sites were studied by UV-Vis spectroscopy, XPS and Al-27 NMR. Generally, ion exchange favored the

  3. Electromechanical characterization of individual micron-sized metal coated polymer particles

    Science.gov (United States)

    Bazilchuk, Molly; Pettersen, Sigurd Rolland; Kristiansen, Helge; Zhang, Zhiliang; He, Jianying

    2016-06-01

    Micron-sized polymer particles with nanoscale metal coatings are essential in conductive adhesives for electronics assembly. The particles function in a compressed state in the adhesives. The link between mechanical properties and electrical conductivity is thus of the utmost importance in the formation of good electrical contact. A custom flat punch set-up based on nanoindentation has been developed to simultaneously deform and electrically probe individual particles. The set-up has a sufficiently low internal resistance to allow the measurement of sub-Ohm contact resistances. Additionally, the set-up can capture mechanical failure of the particles. Combining this data yields a fundamental understanding of contact behavior. We demonstrate that this method can clearly distinguish between particles of different sizes, with different thicknesses of metal coating, and different metallization schemes. The technique provides good repeatability and physical insight into the behavior of these particles that can guide adhesive design and the optimization of bonding processes.

  4. Electromechanical characterization of individual micron-sized metal coated polymer particles

    Energy Technology Data Exchange (ETDEWEB)

    Bazilchuk, Molly; Kristiansen, Helge [Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim 7491 (Norway); Conpart AS, Skjetten 2013 (Norway); Pettersen, Sigurd Rolland; Zhang, Zhiliang; He, Jianying, E-mail: jianying.he@ntnu.no [Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim 7491 (Norway)

    2016-06-28

    Micron-sized polymer particles with nanoscale metal coatings are essential in conductive adhesives for electronics assembly. The particles function in a compressed state in the adhesives. The link between mechanical properties and electrical conductivity is thus of the utmost importance in the formation of good electrical contact. A custom flat punch set-up based on nanoindentation has been developed to simultaneously deform and electrically probe individual particles. The set-up has a sufficiently low internal resistance to allow the measurement of sub-Ohm contact resistances. Additionally, the set-up can capture mechanical failure of the particles. Combining this data yields a fundamental understanding of contact behavior. We demonstrate that this method can clearly distinguish between particles of different sizes, with different thicknesses of metal coating, and different metallization schemes. The technique provides good repeatability and physical insight into the behavior of these particles that can guide adhesive design and the optimization of bonding processes.

  5. Phase structuring in metal alloys: Ultrasound-assisted top-down approach to engineering of nanostructured catalytic materials.

    Science.gov (United States)

    Cherepanov, Pavel V; Andreeva, Daria V

    2017-03-01

    High intensity ultrasound (HIUS) is a novel and efficient tool for top-down nanostructuring of multi-phase metal systems. Ultrasound-assisted structuring of the phase in metal alloys relies on two main mechanisms including interfacial red/ox reactions and temperature driven solid state phase transformations which affect surface composition and morphology of metals. Physical and chemical properties of sonication medium strongly affects the structuring pathways as well as morphology and composition of catalysts. HIUS can serve as a simple, fast, and effective approach for the tuning of structure and surface properties of metal particles, opening the new perspectives in design of robust and efficient catalysts. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Catalytic Addition of Simple Alkenes to Carbonyl Compounds Using Group 10 Metals.

    Science.gov (United States)

    Ho, Chun-Yu; Schleicher, Kristin D; Jamison, Timothy F

    2009-10-01

    Recent advances using nickel complexes in the activation of unactivated monosubstituted olefins for catalytic intermolecular carbon-carbon bond-forming reactions with carbonyl compounds, such as simple aldehydes, isocyanates, and conjugated aldehydes and ketones, are discussed. In these reactions, the olefins function as vinyl- and allylmetal equivalents, providing a new strategy for organic synthesis. Current limitations and the outlook for this new strategy are also discussed.

  7. Density functional study of structural and catalytic properties of free and supported metal nano cluster; Dichtefunktionalstudie der strukturellen und katalytischen Eigenschaften freier und getraegerter Metallnanocluster

    Energy Technology Data Exchange (ETDEWEB)

    Huber, B.

    2007-04-11

    The structural and catalytic properties of metal clusters were determined in the framework of density functional theory. The first part of this work investigates the electronic and geometrical structure of sodium clusters with up to 309 atoms. The ground-state structures of the clusters are determined and the corresponding electronic density of states is compared to experimental photoelectron spectras. The excellent agreement to the experimental results indicates that the correct growth motive of the sodium clusters was found. Small clusters from Na{sup -}{sub 20} to Na{sup -}{sub 42} prefer pentagonal and icosahedral structures with anti-Mackay overlayers, while clusters larger than Na{sup -}{sub 50} prefer icosahedral structures with Mackay overlayers. Clusters between the closed-shell Mackay Clusters often exhibit a twist deformation with respect to the regular Mackay positions. The second part of this work investigates the catalytic properties of free and supported palladium clusters. For both cases the oxidation of small Pd{sub N} clusters (N {<=} 9) was studied. It turned out that MgO supported Pd-clusters dissociate oxygen with a significant lower reaction energy than free clusters or supported systems with particles consisting of several thousands of atoms. The reaction with oxygen transforms the non-crystalline Pd-clusters into crystalline Pd{sub x}O{sub y} nano-oxide clusters that are in epitaxy with the underlying support. Simulations of the CO oxidation on the Pd{sub x}O{sub y} cluster predict a low-temperature reaction mechanism. By calculating the electronic density of states and CO stretch frequencies, different ways of verifying the results experimentally are discussed. (orig.)

  8. Preparation of Mg-doped Ce-Zr Solid Catalysts and Their Catalytic ...

    African Journals Online (AJOL)

    NICO

    Addition of MgO to the Ce-Zr mixed metal oxides affected both particle size and catalytic activity. KEYWORDS ... effect on vascular smooth muscle.6 2,4-TZD has an active methy- ... catalytic properties and for a given reaction the activity and selectivity of the ... heterogeneous catalysts for fine chemical synthesis under green.

  9. Application of vacuum metallurgy to separate pure metal from mixed metallic particles of crushed waste printed circuit board scraps.

    Science.gov (United States)

    Zhan, Lu; Xu, Zhenming

    2008-10-15

    The principle of separating pure metal from mixed metallic particles (MMPs) byvacuum metallurgy is that the vapor pressures of various metals at the same temperature are different As a result, the metal with high vapor pressure and low boiling point can be separated from the mixed metals through distillation or sublimation, and then it can be recycled through condensation under a certain condition. The vacuum metallurgy separation (VMS) of MMPs of crushed waste printed circuit boards (WPCBs) has been studied in this paper. Theoretical analyses show that the MMPs (copper, zinc, bismuth, lead, and indium, for example) can be separated by vacuum metallurgy. The copper particles (0.15-0.20 mm) and zinc particles (<0.30 mm) were chosen to simulate the MMPs of crushed WPCBs. Experimental results show that the separated efficiency of zinc in the copper-rich particles achieves 96.19 wt % when the vacuum pressure is 0.01-0.10 Pa, the heating temperature is 1123 K, and the heating time is 105 min. Under this operation condition, the separated efficiency of zinc in the copper-rich particles from crushed WPCBs achieves 97.00 wt % and the copper purity increases from 90.68 to 99.84 wt %.

  10. Catalytic hydrothermal treatment of pulping effluent using a mixture of Cu and Mn metals supported on activated carbon as catalyst.

    Science.gov (United States)

    Yadav, Bholu Ram; Garg, Anurag

    2016-10-01

    The present study was performed to investigate the performance of activated carbon-supported copper and manganese base catalyst for catalytic wet oxidation (CWO) of pulping effluent. CWO reaction was performed in a high pressure reactor (capacity = 0.7 l) at temperatures ranging from 120 to 190 °C and oxygen partial pressures of 0.5 to 0.9 MPa with the catalyst concentration of 3 g/l for 3 h duration. With Cu/Mn/AC catalyst at 190 °C temperature and 0.9 MPa oxygen partial pressures, the maximum chemical oxygen demand (COD), total organic carbon (TOC), lignin, and color removals of 73, 71, 86, and 85 %, respectively, were achieved compared to only 52, 51, 53, and 54 % removals during the non-catalytic process. Biodegradability (in terms of 5-day biochemical oxygen demand (BOD5) to COD ratio) of the pulping effluent was improved to 0.38 from an initial value of 0.16 after the catalytic reaction. The adsorbed carbonaceous fraction on the used catalyst was also determined which contributed meager TOC reduction of 3-4 %. The leaching test showed dissolution of the metals (i.e., Cu and Mn) from the catalysts in the wastewater during CWO reaction at 190 °C temperature and 0.9 MPa oxygen partial pressures. In the future, the investigations should focus on the catalyst reusability.

  11. Novel relationship between hydroxyl radical initiation and surface group of ceramic honeycomb supported metals for the catalytic ozonation of nitrobenzene in aqueous solution.

    Science.gov (United States)

    Zhao, Lei; Sun, Zhizhong; Ma, Jun

    2009-06-01

    Comparative experiments have been performed to investigate the degradation efficiency of nitrobenzene and the removal efficiency of TOC in aqueous solution bythe processes of ceramic honeycomb supported different metals (Fe, Ni, and Zn) catalytic ozonation, indicating that the modification with metals can enhance the activity of ceramic honeycomb for the catalytic ozonation of nitrobenzene, and the loading percentage of metal and the metallicity respectively presents a positive influence on the degradation of nitrobenzene. The degradation efficiency of nitrobenzene is determined by the initiation of hydroxyl radical (*OH) according to a good linear correlation in all the processes of modified ceramic honeycomb catalytic ozonation at the different loading percentages of metals. The modification of ceramic honeycomb with metals results in the conversion of the pH at the point of zero charge (pHpzc) and the evolution of surface groups. Divergence from the conventional phenomenon, the enhancement mechanism of ozone decomposition on the modified ceramic honeycomb with metals is proposed due to the basic attractive forces of electrostatic forces or/and hydrogen bonding. Consequently, a novel relationship between the initiation of *OH and the surface-OH2+ group on the modified catalyst is established based on the synergetic effect between homogeneous and heterogeneous reaction systems.

  12. Biomedical and Catalytic Opportunities of Virus-Like Particles in Nanotechnology.

    Science.gov (United States)

    Schwarz, B; Uchida, M; Douglas, T

    2017-01-01

    Within biology, molecules are arranged in hierarchical structures that coordinate and control the many processes that allow for complex organisms to exist. Proteins and other functional macromolecules are often studied outside their natural nanostructural context because it remains difficult to create controlled arrangements of proteins at this size scale. Viruses are elegantly simple nanosystems that exist at the interface of living organisms and nonliving biological machines. Studied and viewed primarily as pathogens to be combatted, viruses have emerged as models of structural efficiency at the nanoscale and have spurred the development of biomimetic nanoparticle systems. Virus-like particles (VLPs) are noninfectious protein cages derived from viruses or other cage-forming systems. VLPs provide incredibly regular scaffolds for building at the nanoscale. Composed of self-assembling protein subunits, VLPs provide both a model for studying materials' assembly at the nanoscale and useful building blocks for materials design. The robustness and degree of understanding of many VLP structures allow for the ready use of these systems as versatile nanoparticle platforms for the conjugation of active molecules or as scaffolds for the structural organization of chemical processes. Lastly the prevalence of viruses in all domains of life has led to unique activities of VLPs in biological systems most notably the immune system. Here we discuss recent efforts to apply VLPs in a wide variety of applications with the aim of highlighting how the common structural elements of VLPs have led to their emergence as paradigms for the understanding and design of biological nanomaterials. © 2017 Elsevier Inc. All rights reserved.

  13. Nonisothermal particle modeling of municipal solid waste combustion with heavy metal vaporization

    Energy Technology Data Exchange (ETDEWEB)

    Mazza, G. [Facultad de Ingenieria, Departamento de Quimica, Universidad Nacional del Comahue, IDEPA (CONICET - UNCo), Buenos Aires 1400, 8300 Neuquen (Argentina); Falcoz, Q.; Gauthier, D.; Flamant, G. [Laboratoire Procedes et Materiaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu Cedex (France); Soria, J. [Facultad de Ingenieria, Departamento de Quimica, Universidad Nacional del Comahue, IDEPA (CONICET - UNCo), Buenos Aires 1400, 8300 Neuquen (Argentina); Laboratoire Procedes et Materiaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu Cedex (France)

    2010-12-15

    A particulate model was developed for municipal solid-waste incineration in a fluidized bed combining solid-waste-particle combustion and heavy metal vaporization from the burning particles. Based on a simpler, isothermal version presented previously, this model combines an asymptotic-combustion model for carbonaceous-solid combustion and a shrinking-core model to describe the heavy metal vaporization phenomenon, in which the particle is now considered nonisothermal. A parametric study is presented that shows the influence of temperature on the global metal-vaporization process. The simulation results are compared to experimental data obtained with a lab-scale fluid bed incinerator and to the results of the simpler isothermal model. It is shown that conduction in the particle strongly affects the variation of the vaporization rate with time and that the present version of the model well fits both the shape of the plots and the maximum heavy metal vaporization rates for all bed temperatures. (author)

  14. Metal uptake by corn grown on media treated with particle-size fractionated biosolids

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weiping [Department of Environmental Sciences, University of California, Riverside, CA 92521 (United States)], E-mail: chenweip@yahoo.com.cn; Chang, Andrew C.; Wu, Laosheng [Department of Environmental Sciences, University of California, Riverside, CA 92521 (United States); Zhang, Yongsong [School of Environmental and Natural Resources Sciences, Zhejiang University, Hangzhou, Zhejiang, 31009 (China)

    2008-03-15

    Particle-size of biosolids may affect plant uptake of heavy metals when the biosolids are land applied. In this study, corn (Zea mays L.) was grown on sand media treated with biosolids to study how particle-size of biosolids affected the plant uptake of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Two biosolids, the Nu-Earth biosolids and the Los Angeles biosolids, of dissimilar surface morphology were utilized. The former exhibited a porous and spongy structure and had considerably greater specific surface area than that of the latter, which was granular and blocky. The specific surface area of the Los Angeles biosolids was inversely proportional to its particle-size, while that of Nu-Earth biosolids did not change significantly with particle-size. For each biosolid, the metal concentrations were not affected by particle sizes. The biomass yields of plants grown on the treated media increased as the biosolid particle-size decreased, indicating that plant uptake of nutrients from biosolids was dependent on interactions at the root-biosolids interface. The effect of particle-size on a metal's availability to plants was element-specific. The uptake rate of Cd, Zn, Cu, and Ni was correlated with the surface area of the particles, i.e., smaller particles having higher specific area provided greater root-biosolids contact and resulted in enhanced uptake of Cd and Zn and slightly less increased uptake of Cu and Ni. The particle morphology of biosolids had limited influence on the plant tissue concentrations of Cr and Pb. For both types of biosolids, total metal uptake increased as biosolid particle-size decreased. Our research indicates that biosolid particle-size distribution plays a deciding role in plant uptake of heavy metals when they are land applied.

  15. Synthesis of copper/nickel nanoparticles using newly synthesized Schiff-base metals complexes and their cytotoxicity/catalytic activities.

    Science.gov (United States)

    Aazam, Elham S; El-Said, Waleed Ahmed

    2014-12-01

    Transition metal complexes compounds with Schiff bases ligand representing an important class of compounds that could be used to develop new metal-based anticancer agents and as precursors of metal NPs. Herein, 2,3-bis-[(3-ethoxy-2-hydroxybenzylidene)amino]but-2-enedinitrile Schiff base ligand and its corresponding copper/nickel complexes were synthesized. Also, we reported a facile and rapid method for synthesis nickel/copper nanoparticles based on thermal reduction of their complexes. Free ligand, its metal complexes and metals nanoparticles have been characterized based on elemental analysis, transmission electron microscopy, powder X-ray diffraction, magnetic measurements and by various spectroscopic (UV-vis, FT-IR, (1)H NMR, GC-MS) techniques. Additionally, the in vitro cytotoxic activity of free ligand and its complexes compounds were assessed against two cancer cell lines (HeLa and MCF-7 cells)and one healthy cell line (HEK293 cell). The copper complex was found to be active against these cancer cell lines at very low LD50 than the free ligand, while nickel complex did not show any anticancer activity against these cell lines. Also, the antibacterial activity of as-prepared copper nanoparticles were screened against Escherichia coli, which demonstrated minimum inhibitory concentration and minimum bactericidal concentration values lower than those values of the commercial Cu NPs as well as the previous reported values. Moreover, the synthesized nickel nanoparticles demonstrated remarkable catalytic performance toward hydrogenation of nitrobenzene that producing clean aniline with high selectivity (98%). This reactivity could be attributed to the high degree of dispersion of Ni nanoparticles. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Evaluation of first-row transition metal oxides supported on clay minerals for catalytic growth of carbon nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tsoufis, Theodoros [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); Jankovic, Lubos [Department of Physics, University of Ioannina, GR-45110 Ioannina (Greece); Gournis, Dimitrios [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece)], E-mail: dgourni@cc.uoi.gr; Trikalitis, Pantelis N. [Department of Chemistry, University of Crete, GR-71409 Heraklion (Greece); Bakas, Thomas [Department of Physics, University of Ioannina, GR-45110 Ioannina (Greece)], E-mail: tbakas@cc.uoi.gr

    2008-08-25

    In the present work we employed various transition metals (Cr, Mn, Fe, Co, Ni, Cu and Zn) loaded on different smectite clays (laponite and montmorillonite) as catalysts in synthesis of carbon nanostructures (mainly nanotubes) and we report the effect of the nature of the catalytic centers and type of aluminosilicate layers in the morphology, quality and structure on the final products. Owing to their unique swelling, ion-exchange and intercalation properties smectite clays were easily, uniformly and reproducibly loaded with metal cations. Different homoionic forms of montmorillonite and laponite were prepared containing first-row transition metals and the synthesis of carbon nanostructures was carried out at 700 deg. C using an acetylene/nitrogen mixture. A variety of analytical techniques (XRD, Raman, SEM, TEM and thermal analysis) were used to fully characterize the final materials. Iron-, cobalt-, nickel- and manganese-exchanged clays showed to be effective catalysts for the production of carbon nanotubes, while acetylene decomposition over copper-exchanged clays resulted to the creation of carbon spheres. The resulting hybrid systems are particularly attractive for polymer reinforcing applications since the combined action of clay-carbon nanotubes in polymer matrixes can provide outstanding properties to the resulting composite materials.

  17. Screening of catalytic oxygen reduction reaction activity of metal-doped graphene by density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xin, E-mail: chenxin830107@pku.edu.cn; Chen, Shuangjing; Wang, Jinyu

    2016-08-30

    Highlights: • The screened M-G structures are very thermodynamically stable, and the stability is even higher than that of the corresponding bulk metal surfaces. • The binding energies of ORR intermediates suggest that they are not linear dependence, which are different form the cases found on some metal-based catalysts. • The Au-, Co-, and Ag-G structures could be used as the ORR catalysts. - Abstract: Graphene doping is a promising direction for developing effective oxygen reduction reaction (ORR) catalysts. In this paper, we computationally investigated the ORR performance of 10 kinds of metal-doped graphene (M-G) catalysts, namely, Al-, Si-, Mn-, Fe-, Co-, Ni-, Pd-, Ag-, Pt-, and Au-G. The results shown that the binding energies of the metal atoms incorporated into the graphene vacancy are higher than their bulk cohesive energies, indicating the formed M-G catalysts are even more stable than the corresponding bulk metal surfaces, and thus avoid the metals dissolution in the reaction environment. We demonstrated that the linear relation among the binding energies of the ORR intermediates that found on metal-based materials does not hold for the M-G catalysts, therefore a single binding energy of intermediate alone is not sufficient to evaluate the ORR activity of an arbitrary catalyst. By analysis of the detailed ORR processes, we predicted that the Au-, Co-, and Ag-G materials can be used as the ORR catalysts.

  18. Formation of Splats from Suspension Particles with Solid Inclusions Finely Dispersed in a Melted Metal Matrix

    Science.gov (United States)

    Solonenko, O. P.

    2012-12-01

    A theoretical model has been developed to describe the splats formation from composite particles of several tens of micrometers in size whose liquid metal binder contains a high volume concentration of ultra-fine refractory solid inclusions uniformly distributed in the binder. A theoretical solution was derived, enabling evaluation of splat thickness and diameter, and also the contact temperature at the particle-substrate interface, under complete control of key physical parameters (KPPs) of the spray process (impact velocity, temperature, and size of the particle, and substrate temperature) versus the concentration of solid inclusions suspended in the metal-binder melt. Using the solution obtained, the calculations performed demonstrate the possibility of formulating adequate requirements on the KPPs of particle-substrate interaction providing a deposition of ceramic-metal coatings with predictable splat thickness and degree of particle flattening on the substrate, and also with desired contact temperature during the formation of the first coating monolayer.

  19. Catalytic Hydrolysis of Phosphate Diester with Metal Complexesof Macrocyclic Tetraamine in Comicellar Solution

    Institute of Scientific and Technical Information of China (English)

    XIANG Qing-Xiang; YU Xiao-Qi; YOU Jing-Song; YAN Qian-Shun; XIE Ru-Gang

    2001-01-01

    Four novel pyridine or benzene ring-containing pendant macrocyclic dioxotetraanines 2,6-dioxo-1,4,7,10-tetraazacy-clododeane ligands have been synthesized.Their metal com-plexes have been investigated as catalysts for the hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) in aqueous comicellar solution.The results indicate that the hydrophobic interaction between substrate and metal complex, the nature of transition metal ion, and the micellar microenvironment are important factors for the hydrolysis, of BNPP.Large rate enhancement (up to over two-three orders magnitude) employing 5 hasbeen observed.

  20. Multi-metallic Nanomaterials From Ni, Ag, Pd With Pt's Catalytic Activity

    KAUST Repository

    Huang, Kuo-Wei

    2015-06-04

    A trimetallic catalyst that is a combination of nickel, silver and palladium metal is described. The trimetallic catalyst can be used to produce hydrogen and is useful as a replacement for platinum in hydrogenation reactions.

  1. Influence of rare-earth metal doping on the catalytic performance of CuO-CeO2 for the preferential oxidation of CO in excess hydrogen

    Institute of Scientific and Technical Information of China (English)

    Zhigang Liu; Renxian Zhou; Xiaoming Zheng

    2008-01-01

    Doping of different rare-earth metals(Pr,Nd,Y and La)had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation(PROX)Of CO in excess hydrogen.As for Pr,the doping enhanced the catalytic activity of CuO-CeO2 for PROX.For example,the CO conversion over the above catalyst for PROX was higher than 99%at 120℃.Especially.the doping of Pr widened the temperature window by 20℃ over CuO-CeO2 with 99%CO conversion.For Nd,Y and La,the doping depressed the catalytic activity of CuO-CeO2 for PROX.However,the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.

  2. Novel Base Metal-Palladium Catalytic Diesel Filter Coating with NO2 Reducing Properties

    DEFF Research Database (Denmark)

    Johansen, K.; Dahl, S.; Mogensen, G.

    2007-01-01

    A novel alternative base metal/palladium coat has been developed that has limited NO2 formation and which even removes NO2 in a wide temperature range.Soot combustion, HC conversion and CO conversion properties are comparable to current platinum based solutions but the coating has a more attracti...... solutions. Furthermore, durability results from base metal/Pd coated DPFs installed on operating taxis and related tests cycle data is given....

  3. Electrochemical method for synthesizing metal-containing particles and other objects

    Energy Technology Data Exchange (ETDEWEB)

    Rondinone, Adam Justin; Ivanov, Ilia N.; Smith, Sean Campbell; Liang, Chengdu; Hensley, Dale K.; Moon, Ji-Won; Phelps, Tommy Joe

    2017-05-02

    The invention is directed to a method for producing metal-containing (e.g., non-oxide, oxide, or elemental) nano-objects, which may be nanoparticles or nanowires, the method comprising contacting an aqueous solution comprising a metal salt and water with an electrically powered electrode to form said metal-containing nano-objects dislodged from the electrode, wherein said electrode possesses a nanotextured surface that functions to confine the particle growth process to form said metal-containing nano-objects. The invention is also directed to the resulting metal-containing compositions as well as devices in which they are incorporated.

  4. Synthesis of Supported Ultrafine Non-noble Subnanometer-Scale Metal Particles Derived from Metal-Organic Frameworks as Highly Efficient Heterogeneous Catalysts.

    Science.gov (United States)

    Kang, Xinchen; Liu, Huizhen; Hou, Minqiang; Sun, Xiaofu; Han, Hongling; Jiang, Tao; Zhang, Zhaofu; Han, Buxing

    2016-01-18

    The properties of supported non-noble metal particles with a size of less than 1 nm are unknown because their synthesis is a challenge. A strategy has now been created to immobilize ultrafine non-noble metal particles on supports using metal-organic frameworks (MOFs) as metal precursors. Ni/SiO2 and Co/SiO2 catalysts were synthesized with an average metal particle size of 0.9 nm. The metal nanoparticles were immobilized uniformly on the support with a metal loading of about 20 wt%. Interestingly, the ultrafine non-noble metal particles exhibited very high activity for liquid-phase hydrogenation of benzene to cyclohexane even at 80 °C, while Ni/SiO2 with larger Ni particles fabricated by a conventional method was not active under the same conditions.

  5. Effect of Particle Size Upon Pt/SiO2 Catalytic Cracking of n-Dodecane Under Supercritical Conditions: in situ SAXS and XANES Studies

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sungwon; Lee, Sungsik; Kumbhalkar, Mrunmayi; Wiaderek, Kamila M.; Dumesic, James A; Winans, Randall E.

    2017-01-01

    The endothermic cracking and dehydrogenation of n-dodecane is investigated over well-defined nanometer size platinum catalysts supported on SiO2 to study the particle size effects in the catalytic cracking reaction, with simultaneous in situ monitoring of the particle size and oxidation state of the working catalysts by in situ SAXS (small angle X-ray scattering) and XAS (X-ray absorption spectroscopy). The selectivity toward olefins products was found dominant in the 1 nm size platinum catalysts, whereas paraffins are dominant in the 2 nm catalysts. This reveals a strong correlation between catalytic performance and catalyst size as well as the stability of the nanoparticles in supercritical condition of n-dodecane. The presented results suggest that controlling the size and geometric structure of platinum nanocatalysts could lead to a fundamentally new level of understanding of nanoscale materials by monitoring the catalysts in realistic reaction conditions.

  6. Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts.

    Science.gov (United States)

    Murahashi, Shun-Ichi

    2011-01-01

    This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. (Communicated by Ryoji Noyori, M.J.A.).

  7. Steric, electronic, and secondary effects on the coordination chemistry of ionic phosphine ligands and the catalytic behavior of their metal complexes

    NARCIS (Netherlands)

    Snelders, D.J.M.; van Koten, G.; Klein Gebbink, R.J.M.

    2011-01-01

    The effects of introducing ionic functionalities in phosphine ligands on the coordination chemistry of these ligands and the catalytic behavior of the corresponding metal complexes are reviewed. The steric and electronic consequences of such functionalizations are discussed. Apart from these steric

  8. Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts

    Science.gov (United States)

    MURAHASHI, Shun-Ichi

    2011-01-01

    This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. PMID:21558760

  9. Steric, electronic, and secondary effects on the coordination chemistry of ionic phosphine ligands and the catalytic behavior of their metal complexes

    NARCIS (Netherlands)

    Snelders, D.J.M.; van Koten, G.; Klein Gebbink, R.J.M.

    2011-01-01

    The effects of introducing ionic functionalities in phosphine ligands on the coordination chemistry of these ligands and the catalytic behavior of the corresponding metal complexes are reviewed. The steric and electronic consequences of such functionalizations are discussed. Apart from these steric

  10. A novel method of preparing metallic Janus silica particles using supercritical carbon dioxide

    NARCIS (Netherlands)

    Yang, Qiuyan; de Vries, Marcel H; Picchioni, Francesco; Loos, Katja

    2013-01-01

    In this study, we demonstrate a novel fabrication method to prepare metallic Janus silica particles by embedding nanosized silica particles on a spherical polystyrene (PS) substrate in supercritical carbon dioxide (sc CO2), followed by labelling with gold nanoparticles on the exposed part of the

  11. A novel method of preparing metallic Janus silica particles using supercritical carbon dioxide

    NARCIS (Netherlands)

    Yang, Qiuyan; de Vries, Marcel H; Picchioni, Francesco; Loos, Katja

    2013-01-01

    In this study, we demonstrate a novel fabrication method to prepare metallic Janus silica particles by embedding nanosized silica particles on a spherical polystyrene (PS) substrate in supercritical carbon dioxide (sc CO2), followed by labelling with gold nanoparticles on the exposed part of the sil

  12. Graphene nanosheet as support of catalytically active metal particles in DMC synthesis

    Institute of Scientific and Technical Information of China (English)

    Jun Bian; Xiao Wei Wei; Ling Wang; Zheng Ping Guan

    2011-01-01

    Novel graphene nanosheet(GNS) supported Cu-Ni bimetal catalysts were firstly synthesized and used for the direct synthesis of dimethyl carbonate(DMC).The experimental results demonstrated that GNS was an effective and convenient support for the fabrication of Cu-Ni/GNS bimetal catalyst.

  13. Stabilization of Heavy Metal Particles in AL2O3-W Suspensions

    Directory of Open Access Journals (Sweden)

    Kędzierska – Sar A.

    2016-09-01

    Full Text Available Ceramic – metal composites are widely used materials in a whole world. There were invented many fabrication methods for those kind of materials, but still exists some problems which need to be fixed. Stability of high density metal particles (e.g. W, Mo, Nb in ceramic-metal composite suspensions is one of crucial issues to be solved in order to obtain homogenous composite material with desired properties such as high fracture toughness, mechanical strength, hardness, wear resistance.

  14. Effect of erodent particles on the erosion of metal specimens

    Science.gov (United States)

    Razzaque, M. Mahbubur; Alam, M. Khorshed; Khan, M. Ishak

    2016-07-01

    This paper presents the experimental results of the measurement of erosion rate of carbon steel specimens in sand water slurry system in a slurry pot tester. Sylhet sand has been sieved to get three sizes of erodent particles; namely, less than 250 micron, 250 to 590 micron and 590 to 1190 micron. Experiments are done with three sand concentrations (10%, 15% and 20%). The rate of erosion of the carbon steel specimens is measured as the loss of weight per unit surface area per unit time under the dynamic action of solid particles. The eroded surfaces of the specimens are examined using Scanning Electron Microscopy (SEM) to visualize the impact of the slurry of various conditions. It is seen that irrespective of the particle size the rate of erosion increases with the increase of slurry concentration. This increment of erosion rate at high concentration is high for large particles. High erosion rate is observed in case of large sand particles. In case of small and fine particles erosion rate is small because of low impact energy as well as the wastage of energy to overcome the hindrance of the finer particles before striking on the specimen surface.

  15. Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

    Directory of Open Access Journals (Sweden)

    Syed Z. Islam

    2017-03-01

    Full Text Available Mesoporous titania (mp-TiO2 has drawn tremendous attention for a diverse set of applications due to its high surface area, interfacial structure, and tunable combination of pore size, pore orientation, wall thickness, and pore connectivity. Its pore structure facilitates rapid diffusion of reactants and charge carriers to the photocatalytically active interface of TiO2. However, because the large band gap of TiO2 limits its ability to utilize visible light, non-metal doping has been extensively studied to tune the energy levels of TiO2. While first-principles calculations support the efficacy of this approach, it is challenging to efficiently introduce active non-metal dopants into the lattice of TiO2. This review surveys recent advances in the preparation of mp-TiO2 and their doping with non-metal atoms. Different doping strategies and dopant sources are discussed. Further, co-doping with combinations of non-metal dopants are discussed as strategies to reduce the band gap, improve photogenerated charge separation, and enhance visible light absorption. The improvements resulting from each doping strategy are discussed in light of potential changes in mesoporous architecture, dopant composition and chemical state, extent of band gap reduction, and improvement in photocatalytic activities. Finally, potential applications of non-metal-doped mp-TiO2 are explored in water splitting, CO2 reduction, and environmental remediation with visible light.

  16. Characterization of metal particles on supporting materials mordenite, ultra stable Y zeolita, and natural zeolit

    Science.gov (United States)

    Sesario, Rujito; Dwi, Khoirina; Rahmawati, Fitria; Heraldy, Eddy; Rachmadani

    2017-08-01

    This research aims to prepare, characterize, and determine the metal particles of Molybdenum (Mo) and Cobalt (Co) metal on the supporting material Mordenite, Ultra Stable Y-Zeolite (USY), and Natural Zeolite (ZAA). In this research the catalysts were prepared, activated, and characterized. The bimetallic catalysts CoMo/Mordenite, CoMo/USY, CoMo/ZAA were prepared by coimpregnation method with ratio amount of Co : Mo metals 1 : 2. Activation of the catalyst included calcination and reduction. The crystallinity was characterized using X-ray diffraction (XRD), minerals present in the catalyst was analyzed using X-Ray Fluorescence (XRF). The results based on characterization, it is known that catalyst CoMo/USY shows best amount metal impregnated (Co metal content is 0.09657 mmol/g and metal content of Mo is 0.62723 mmol/g). The CoMo/Mordenite and CoMo/USY metal particles contained of CoO, MoO3, CoMoO4, Co, Mo, and CoMo. Thus CoMo/ZAA metal particles consisted of CoO, MoO3, CoMoO4, Co, Mo, CoMo. Based on the characterization of the crystal structure and the metal content it is known that the CoMo/USY was the best sample compared to CoMo/Mordenite and CoMo/ZAA.

  17. Review on preparation techniques of particle reinforced metal matrix composites

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper reviews the investigation status of the techniques for preparation of metal matrix composites and the research outcomes achieved recently. The mechanisms, characteristics, application ranges and levels of development of these preparatior techniques are analyzed. The advantages and the disadvantages of each technique are synthetically evaluated. Lastly, the future directions of research and the prospects for the preparation techniques of metal matrix composites are forecasted.

  18. Review on preparation techniques of particle reinforced metal matrix composites

    Directory of Open Access Journals (Sweden)

    HAO Bin

    2006-02-01

    Full Text Available This paper reviews the investigation status of the techniques for preparation of metal matrix composites and the research outcomes achieved recently. The mechanisms, characteristics, application ranges and levels of development of these preparation techniques are analyzed. The advantages and the disadvantages of each technique are synthetically evaluated. Lastly, the future directions of research and the prospects for the preparation techniques of metal matrix composites are forecasted.

  19. Self Assembly of Nano Metric Metallic Particles for Realization of Photonic and Electronic Nano Transistors

    Directory of Open Access Journals (Sweden)

    Asaf Shahmoon

    2010-05-01

    Full Text Available In this paper, we present the self assembly procedure as well as experimental results of a novel method for constructing well defined arrangements of self assembly metallic nano particles into sophisticated nano structures. The self assembly concept is based on focused ion beam (FIB technology, where metallic nano particles are self assembled due to implantation of positive gallium ions into the insulating material (e.g., silica as in silicon on insulator wafers that acts as intermediary layer between the substrate and the negatively charge metallic nanoparticles.

  20. Influence of Fine Metal Particles on Surface Discharge Characteristics of Outdoor Insulators

    Directory of Open Access Journals (Sweden)

    Yong Liu

    2016-01-01

    Full Text Available Focusing on the influence of fine metal particles on the insulation characteristics of outdoor insulators, spherical micrometer-level iron powders were used to represent fine metal particles of different parameters on a polymer insulator specimen surface. Dynamic movement and lift-off behavior of fine particles, as well as the triggered surface discharges under AC voltage were investigated in a uniform electric field under different experimental conditions. The results reveal that the inception, propagation and intensity of surface discharges are significantly affected by the particle parameters, including particle size, amount and distributing characteristic. Based on the measurement of light emission during the flashover process using a high-speed camera, the process of surface discharge to flashover triggered by the fine metal particles were investigated to obtain a relationship between flashover voltage, discharge light intensity and particle parameters. It is suggested that particle size smaller than 28 µm and particle amount more than 40 mg in contact with the non-uniform distribution can cause a significant distortion and intensification of the electric field resulting in a higher risk of surface discharges leading to flashover. Such investigations can enhance the operating reliability of outdoor insulators subjected to these conditions.

  1. Surface Modification of α-Fe Metal Particles by Chemical Surface Coating

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The structure of α-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms.

  2. Metal-mediated Multiporphyrin Arrays at Interfaces:Preparation, Electrochemistry, Catalytic Oxidation of Nitrite and NO

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    1 Results Manganese porphyrins have attracted growing interest because of their unique physical and chemical properties,such as mimicking the role of Mn complex in photosystem Ⅱ and acting as electrocatalysts towards the oxidation of nitric oxide and nitrite.As one of the bottom-up techniques,we are currently investigating the design,preparation and opto-electrochemical properties of metal-mediated multiporphyrin arrays on the solid surfaces.Because the porphyrins are connected by metal ions via coordin...

  3. The evolution of model catalytic systems; studies of structure, bonding and dynamics from single crystal metal surfaces to nanoparticles, and from low pressure (10(-3) Torr) to liquid interfaces.

    Science.gov (United States)

    Somorjai, Gabor A; York, Roger L; Butcher, Derek; Park, Jeong Y

    2007-07-21

    The material and pressure gap has been a long standing challenge in the field of heterogeneous catalysis and have transformed surface science and biointerfacial research. In heterogeneous catalysis, the material gap refers to the discontinuity between well-characterized model systems and industrially relevant catalysts. Single crystal metal surfaces have been useful model systems to elucidate the role of surface defects and the mobility of reaction intermediates in catalytic reactivity and selectivity. As nanoscience advances, we have developed nanoparticle catalysts with lithographic techniques and colloidal syntheses. Nanoparticle catalysts on oxide supports allow us to investigate several important ingredients of heterogeneous catalysis such as the metal-oxide interface and the influence of noble metal particle size and surface structure on catalytic selectivity. Monodispersed nanoparticle and nanowire arrays were fabricated for use as model catalysts by lithographic techniques. Platinum and rhodium nanoparticles in the 1-10 nm range were synthesized in colloidal solutions in the presence of polymer capping agents. The most catalytically active systems are employed at high pressure or at solid-liquid interfaces. In order to study the high pressure and liquid interfaces on the molecular level, experimental techniques with which we bridged the pressure gap in catalysis have been developed. These techniques include the ultrahigh vacuum system equipped with high pressure reaction cell, high pressure Sum Frequency Generation (SFG) vibration spectroscopy, High Pressure Scanning Tunneling Microscopy (HP-STM), and High Pressure X-ray Photoemission Spectroscopy (HP-XPS), and Quartz Crystal Microbalance (QCM). In this article, we overview the development of experimental techniques and evolution of the model systems for the research of heterogeneous catalysis and biointerfacial studies that can shed light on the long-standing issues of materials and pressure gaps.

  4. Submicron writing by laser irradiation on metal nano-particle dispersed films toward flexible electronics

    Science.gov (United States)

    Watanabe, Akira; Aminuzzaman, Mohammod; Miyashita, Tokuji

    2009-02-01

    The requirement for microwiring technology by a wet process has significantly increased recently toward the achievement of printable and flexible electronics. We have developed the metal microwiring with a resolution higher than 1 μm by the laser direct writing technique using Ag and Cu nano-particle-dispersed films as precursors. The technique was applied to the microwiring on a flexible and transparent polymer film. The metallization is caused in a micro-region by focused laser beam, which reduces the thermal damage of the flexible polymer substrate during the metallization process. The laser direct writing technique is based on the efficient and fast conversion of photon energy to thermal energy by direct excitation of the plasmon absorption of a metal nano-particle, which provides Cu microwiring with a low resistivity owing to the inhibition of the surface oxidation of the Cu nano-particle.

  5. Aerosol synthesis of nano and micro-scale zero valent metal particles from oxide precursors

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Jonathan [Los Alamos National Laboratory; Luhrs, Claudia [UNM; Lesman, Zayd [UNM; Soliman, Haytham [UNM; Zea, Hugo [UNM

    2010-01-01

    In this work a novel aerosol method, derived form the batch Reduction/Expansion Synthesis (RES) method, for production of nano / micro-scale metal particles from oxides and hydroxides is presented. In the Aerosol-RES (A-RES) method, an aerosol, consisting of a physical mixture of urea and metal oxide or hydroxides, is passed through a heated oven (1000 C) with a residence time of the order of 1 second, producing pure (zero valent) metal particles. It appears that the process is flexible regarding metal or alloy identity, allows control of particle size and can be readily scaled to very large throughput. Current work is focused on creating nanoparticles of metal and metal alloy using this method. Although this is primarily a report on observations, some key elements of the chemistry are clear. In particular, the reducing species produced by urea decomposition are the primary agents responsible for reduction of oxides and hydroxides to metal. It is also likely that the rapid expansion that takes place when solid/liquid urea decomposes to form gas species influences the final morphology of the particles.

  6. Metal-Particle-Decorated ZnO Nanocrystals: Photocatalysis and Charge Dynamics.

    Science.gov (United States)

    Lin, Wei-Hao; Chiu, Yi-Hsuan; Shao, Pao-Wen; Hsu, Yung-Jung

    2016-12-07

    Understanding of charge transfer processes is determinant to the performance optimization for semiconductor photocatalysts. As a representative model of composite photocatalysts, metal-particle-decorated ZnO has been widely employed for a great deal of photocatalytic applications; however, the dependence of charge carrier dynamics on the metal content and metal composition and their correlation with the photocatalytic properties have seldom been reported. Here, the interfacial charge dynamics for metal-decorated ZnO nanocrystals were investigated and their correspondence with the photocatalytic properties was evaluated. The samples were prepared with a delicate antisolvent approach, in which ZnO nanocrystals were grown along with metal particle decoration in a deep eutectic solvent. By modulating the experimental conditions, the metal content (from 0.6 to 2.3 at%) and metal composition (including Ag, Au, and Pd) in the resulting metal-decorated ZnO could be readily controlled. Time-resolved photoluminescence spectra showed that an optimal Au content of 1.3 at% could effectuate the largest electron transfer rate constant for Au-decorated ZnO nanocrystals, in conformity with the highest photocatalytic efficiency observed. The relevance of charge carrier dynamics to the metal composition was also inspected and realized in terms of the energy level difference between ZnO and metal. Among the three metal-decorated ZnO samples tested, ZnO-Pd displayed the highest photocatalytic activity, fundamentally according with the largest electron transfer rate constant deduced in carrier dynamics measurements. The current work was the first study to present the correlations among charge carrier dynamics, metal content, metal composition, and the resultant photocatalytic properties for semiconductor/metal heterostructures. The findings not only helped to resolve the standing issues regarding the mechanistic foundation of photocatalysis but also shed light on the intelligent design

  7. Reliability Tests of Aluminium Wedge Wire Bonding on Auto-catalytic Silver Immersion Gold (ASIG) PCB Metallization

    CERN Document Server

    Drozd, A; Kaufmann, S; Manolescu, F; McGill, I

    2011-01-01

    The Auto-catalytic Silver Immersion Gold (ASIG) PCB metallization is a new process that has clear advantages for PCB assembly especially with regard to lead-free soldering. As it may become a popular process in the future for electronics used in physics experiments, the quality of this metallization for aluminium wire bonding has been studied. Aluminium wedge wire bonding continues to be the interconnection method of choice for many physics detector sensors, for high density signal routing and for unpackaged die. Although advertised as having good quality for aluminium wire bonding, this study was performed to verify this claim as well as to test the longer term reliability of the wire bonds taking into consideration the environmental conditions and life-expectancy of devices, in particular for high energy physics detector applications. The tests were performed on PCBs made with the ASIG and ENIG (Electro-less Nickel Immersion Gold) processes at the same time in order to make a comparison with the current ind...

  8. Hierarchical plasmonic-metal/semiconductor micro/nanostructures: green synthesis and application in catalytic reduction of p-nitrophenol

    Science.gov (United States)

    Gao, Shuyan; Jia, Xiaoxia; Li, Zhengdao; Chen, Yanli

    2012-03-01

    Hierarchical micro/nano arrays can offer both the advantages of nano-sized building blocks and micro- or submicrometer-sized ordered arrays, therefore representing one kind of potential functional materials and having received enormous attention for a wealth of applications. In this study, four-dimensionally flower-like CuO micro/nanostructures decorated by Au nanoparticles are synthesized via an environmentally friendly route assisted by polyethylene glycol. Experiments reveal that the product demonstrates high catalytic performance for the reduction of 4-nitrophenol using NaBH4 as the reducing agent, which could be attributed to the rich Au/CuO interfaces in the samples. Compared to the pure noble metal catalysts, the obtained sample is quite economic. In terms of methodology and cost-effectiveness, this study proposes an economically useful and green method to produce a highly efficient metal-based catalyst. It is also a good example for the organic combination of green chemistry and functional materials.

  9. Catalytic co-pyrolysis of peat and polymeric wastes in the presence of iron sub-group metal chlorides

    Energy Technology Data Exchange (ETDEWEB)

    Sulman, E.M.; Kosivtsov, Y.Y.; Lugovoy, Y.V. [Tver Technical University, Tver (Russian Federation)

    2008-07-01

    The purpose of this investigation is the study of activity of iron sub-group metal chlorides in co-processing of peat and polymeric wastes by low-temperature catalytic pyrolysis method. Iron sub-group metal chlorides in concentration varied from 1 to 10% (wt) were used as the catalysts of pyrolysis. The process was conducted in fixed bed reactor in inert gaseous atmosphere at the temperature interval of 350-550{sup o}C. All the investigated catalysts were found to promote the increase of liquid fraction mass and the decrease of solid carbon-containing residue mass up to 10-30%. Cobalt catalyst revealed the highest selectivity with respect to liquid products formation. The use of the catalysts in low-temperature peat and polymeric wastes pyrolysis process was found to favour the increase gaseous products volume up to 20-50% as well as unsaturated hydrocarbons volume in 1.2 folds in comparison to uncatalysed process. 9 refs., 3 figs., 2 tabs.

  10. Catalytic Ring Hydrogenation of Benzoic Acid with Supported Transition Metal Catalysts in scCO2

    OpenAIRE

    2007-01-01

    The ring hydrogenation of benzoic acid to cyclohexanecarboxylic acid over charcoal-supported transition metal catalysts in supercritical CO2 medium has been studied in the present work. The cyclohexanecarboxylic acid can be produced efficiently in supercritical CO2 at the low reaction temperature of 323 K. The presence of CO2 increases the reaction rate and several parameters have been discussed.

  11. Lanthanide-Based Metal Organic Frameworks: Synthetic Strategies and Catalytic Applications

    NARCIS (Netherlands)

    Pagis, C.; Ferbinteanu, M.; Rothenberg, G.; Grecea, S.

    2016-01-01

    This short critical review outlines the main synthetic strategies used in the designed synthesis of lanthanide-based metal organic frameworks (Ln-MOFs). It explains the impact of the choice of organic linker on the final network topology, and it highlights the applications of Ln-MOFs in the

  12. Metal-ion dependent catalytic properties of Sulfolobus solfataricus class II α-mannosidase

    DEFF Research Database (Denmark)

    Nielsen, Jonas Willum; Poulsen, Nina Rødtness; Johnsson, Anna Margit Susanne;

    2012-01-01

    The active site for the family GH38 class II α-mannosidase is constituted in part by a divalent metal ion, mostly Zn(2+), as revealed in the crystal structures of enzymes from both animal and bacterial sources. The metal ion coordinates to the bound substrate and side chains of conserved amino acid...... residues. Recently, evidence has accumulated that class II α-mannosidase is active in complex with a range of divalent metal ions. In the present work, with employment of the class II α-mannosidase, ManA, from the hyperthermophilic archaeon Sulfolobus solfataricus, we explored the influence of the divalent...... metal ion on the associated steady-state kinetic parameters, K(M) and k(cat), for various substrates. With p-nitrophenyl-α-d-mannoside as a substrate, the enzyme showed activity in the presence of Co(2+), Cd(2+), Mn(2+), and Zn(2+), whereas Ni(2+) and Cu(2+) were inhibitory and nonactivating. Co(2...

  13. Catalytic Ring Hydrogenation of Benzoic Acid with Supported Transition Metal Catalysts in scCO2

    Directory of Open Access Journals (Sweden)

    Fengyu Zhao

    2007-07-01

    Full Text Available The ring hydrogenation of benzoic acid to cyclohexanecarboxylic acid overcharcoal-supported transition metal catalysts in supercritical CO2 medium has been studiedin the present work. The cyclohexanecarboxylic acid can be produced efficiently insupercritical CO2 at the low reaction temperature of 323 K. The presence of CO2 increasesthe reaction rate and several parameters have been discussed.

  14. Support effects and catalytic trends for water gas shift activity of transition metals

    DEFF Research Database (Denmark)

    Boisen, Astrid; Janssens, T.V.W.; Schumacher, Nana Maria Pii

    2010-01-01

    Water gas shift activity measurements for 12 transition metals (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Re, Ir, Pt, Au) supported on inert MgAl2O4 and Ce0.75Zr0.25O2 are presented, to elucidate the influence of the active metal and the support. The activity is related to the adsorption energy of molecular...... CO and atomic oxygen on the metal; the latter is a good measure for the reactivity of the metal towards H2O. Generally, the activity of the catalysts with the Ce0.75Zr0.25O2 support is higher, compared to the corresponding MgAl2O4-supported catalysts. Exceptions are Cu and Au, which have a higher...... around −2.5 eV. No clear correlation exists with the adsorption energy of CO. In contrast, the activity for the Ce0.75Zr0.25O2 support increases with increasing adsorption strength for CO, and based on a relatively low activity of Cu the activity does not seem to depend on the adsorption energy of oxygen...

  15. Lanthanide-Based Metal Organic Frameworks: Synthetic Strategies and Catalytic Applications

    NARCIS (Netherlands)

    C. Pagis; M. Ferbinteanu; G. Rothenberg; S. Grecea

    2016-01-01

    This short critical review outlines the main synthetic strategies used in the designed synthesis of lanthanide-based metal organic frameworks (Ln-MOFs). It explains the impact of the choice of organic linker on the final network topology, and it highlights the applications of Ln-MOFs in the catalysi

  16. The Influence of the Particle Size on the Adhesion Between Ceramic Particles and Metal Matrix in MMC Composites

    Science.gov (United States)

    Jarzabek, Dariusz M.; Chmielewski, Marcin; Dulnik, Judyta; Strojny-Nedza, Agata

    2016-08-01

    This study investigated the influence of the particle size on the adhesion force between ceramic particles and metal matrix in ceramic-reinforced metal matrix composites. The Cu-Al2O3 composites with 5 vol.% of ceramic phase were prepared by a powder metallurgy process. Alumina oxide powder as an electrocorundum (Al2O3) powder with different particle sizes, i.e., fine powder <3 µm and coarse powder of 180 µm was used as a reinforcement. Microstructural investigations included analyses using scanning electron microscopy with an integrated EDS microanalysis system and transmission microscopy. In order to measure the adhesion force (interface strength), we prepared the microwires made of the investigated materials and carried out the experiments with the use of the self-made tensile tester. We have observed that the interface strength is higher for the sample with coarse particles and is equal to 74 ± 4 MPa and it is equal to 68 ± 3 MPa for the sample with fine ceramic particles.

  17. Effects of particle size and surrounding media on optical radiation efficiencies of spherical plasmonic metal nanoparticles

    Indian Academy of Sciences (India)

    Vinayak A Dhumale; Preeti V Shah; Rishi B Sharma; Katsuaki Tanabe

    2012-04-01

    The optical radiation efficiency (), the ratio of scattering cross-section to extinction cross-section, of spherical metal nanoparticles (M= Al, Ag, Au and Cu) surrounded by glass and water was calculated using classical electrostatics. The effect of varying particle diameter (∼100 nm) on was also studied for free space wavelengths in the range of 400–1200 nm. The variations in the value of with the diameter () of the metal nanoparticles were calculated on the basis of quasi-static approximation. The increases with the size of metal nanoparticles. Corresponding to a metal nanoparticle, was found to exhibit a sharp dip (dip) at a characteristic wavelength ()M in a particular medium ( = air, glass and water). ()M was independent of particle size. The (medium)M was found to be slightly blue shifted for all metal nanoparticles surrounded by glass or water with respect to those in the air.

  18. Availability and bioaccessibility of metals in fine particles of some urban soils.

    Science.gov (United States)

    Madrid, F; Biasioli, M; Ajmone-Marsan, F

    2008-07-01

    Metals in urban soils might be transferred to humans via ingestion, dermal contact, or breathing, especially to children due to the "hand to mouth" activity during outdoor activities in playground and recreational areas. This involuntary soil ingestion depends on soil adherence to skin; it is known that the adhesion process tends to exclude particles greater than 50 microm, so the fraction below this diameter would be the most dangerous for health. The aim of this work was to study the "availability", estimated by the EDTA extraction, and "oral bioaccessibility", estimated by the Simple Bioaccessibility Extraction Test (SBET), of several metals in urban soils of two European cities (Sevilla and Torino), as related to the soil particle size distribution. Torino and Sevilla showed different levels of metal contents, availability, and bioaccessibility. In Torino, the finer particles showed metal enrichment of Cu, Zn, and, to a lesser extent, Pb, whereas in Sevilla, all of the studied metals showed this enrichment compared to the whole soils. The whole soil cannot be used as a good general indicator of the bioaccessibility of metals in the finest fractions of the soil. Metal availability was higher in the clay fraction (soils in both cities, and principal component analysis shows that availability is especially due to this fraction. In contrast, Cu and Pb bioaccessibility in the clay fraction seems to be slightly lower than, or comparable to, all of the other fractions and the whole soil. Bioaccessibility of Cr and Ni is clearly greater in the coarser fractions of Sevilla than those of Torino, despite the considerably greater total contents of both metals in the latter city. Adsorbed metal forms are assumed to be preferentially responsible for metals released by EDTA. A different origin is attributed to bioaccessible metal forms. Anthropic influence seems more important in determining metal availability and bioaccessibility in urban soils of both cities than the

  19. Pulsed laser deposition of metallic films on the surface of diamond particles for diamond saw blades

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Chao [State Key Laboratory of Laser Technology, Huazhong University of Science and Technology, WuHan, Hubei 430074 (China); Luo Fei [State Key Laboratory of Laser Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Long Hua [State Key Laboratory of Laser Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Hu Shaoliu [State Key Laboratory of Laser Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Li Bo [State Key Laboratory of Laser Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wang Youqing [State Key Laboratory of Laser Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)]. E-mail: lchwan@hust.edu.cn

    2005-06-15

    Ti or Ni films have been deposited on the diamond particle surfaces by pulsed laser deposition. Compressive resistance of the uncoated and coated diamond particles was measured, respectively, in the experiments. The compressive resistance of the Ti-coated diamonds particles was found much higher than that of the uncoated ones. It increased by 39%. The surface morphology is observed by the metallography microscope. The surface of the uncoated diamonds particles had many hollows and flaws, while the surface of Ni-coated diamond particles was flat and smooth, and the surface of Ti-coated diamond particles had some metal masses that stood out of the surface of the Ti-coated film. The components of the metallic films of diamond particles were examined by X-ray diffractometry (XRD). TiC was found formed on the Ti-coated diamond surface, which resulted in increased surface bonding strength between the diamond particles and the Ti films. Meanwhile, TiC also favored improving the bonding strength between the coated diamond particles and the binding materials. Moreover, the bending resistance of the diamond saw blade made of Ti-coated diamond was drastically higher than that of other diamond saw blades, which also played an important role in improving the blade's cutting ability and lifetime. Therefore, it was most appropriate that the diamond saw blade was made of Ti-coated diamond particles rather than other materials.

  20. Motion behavior of non-metallic particles under high frequency magnetic field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhong-tao; GUO Qing-tao; YU Feng-yun; LI Jie; ZHANG Jian; LI Ting-ju

    2009-01-01

    Non-metallic particles, especially alumina, are the main inclusions in aluminum and its alloys. Numerical simulation and the corresponding experiments were carried out to study the motion behavior of alumina particles in commercial pure aluminum under high frequency magnetic field. At the meantime, multi-pipe experiment was also done to discuss the prospect of continuous elimination of non-metallic particles under high frequency magnetic field. It is shown that: 1) results of numerical simulation are in good agreement with the experimental results, which certificates the rationality of the simulation model; 2) when the intensity of high frequency magnetic field is 0.06 T, the 30 μm alumina particles in melt inner could migrate to the edge and be removed within 2 s; 3) multi-pipe elimination of alumina particles under high frequency magnetic field is also effective and has a good prospect in industrial application.

  1. PARTICULATE SIZE EFFECTS IN THE PARTICLE-REINFORCED METAL-MATRIX COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    魏悦广

    2001-01-01

    The influences of particle size on the mechanical properties of the particulate metal matrix composite are obviously displayed in the experimental observations. However, the phenomenon can not be predicted directly using the conventional elastic-plastic theory. It is because that no length scale parameters are involved in the conventional theory. In the present research, using the strain gradient plasticity theory, a systematic research of the particle size effect in the particulate metal matrix composite is carried out. The roles of many composite factors, such as: the particle size, the Young's modulus of the particle, the particle aspect ratio and volume fraction, as well as the plastic strain hardening exponent of the matrix material,are studied in detail. In order to obtain a general understanding for the composite behavior, two kinds of particle shapes, ellipsoid and cylinder, are considered to check the strength dependence of the smooth or non-smooth particle surface. Finally,the prediction results will be applied to the several experiments about the ceramic particle-reinforced metal-matrix composites. The material length scale parameter is predicted.

  2. Catalytic ozone aqueous decomposition of methylene blue using composite metal oxides

    Science.gov (United States)

    Liu, Xuan; Hou, Yongjiang; Guo, Jie; Wang, Yaquan; Zuo, Qian; Wang, Chunyu

    2015-07-01

    By using the method of co-precipitation, Fe-Mn, Al-Mn, Al-Mg composite metal oxides were prepared. Using X-ray diffractometer(XRD), the phases of catalysts synthesized were observed to be Mn3O4 and Fe2O3. With the increase of the calcination temperature, Mn3O4 was gradually transformed into Mn2O3. The experimental results show that: the best catalyst is the Fe-Mn composite metal oxide with the calcination temperature of 650 °C. In this experimental condition, when the ozone amount was 1.92mg/min, and the dosage of catalyst was 0.5g, the removal rate of methylene blue (MB) was the best. The decolorization rate can reach to 100%. Compared with the effect of ozonation alone, the total organic carbon removal rate increased from 29.19% up to 65.78% after adding catalysts.

  3. Investigation of the ignition behaviour of the noble metal catalyzed catalytic partial oxidation of methane

    Energy Technology Data Exchange (ETDEWEB)

    Stoetzel, J; Luetzenkirchen-Hecht, D; Frahm, R [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany); Kimmerle, B; Baiker, A [Department of Chemistry and Applied Biosciences, ETH Zuerich, CH-8093 Zuerich (Switzerland); Nachtegaal, M [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Beier, M J; Grunwaldt, J-D, E-mail: j.stoetzel@uni-wuppertal.d [Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800 Kgs. Lyngby (Denmark)

    2009-11-15

    Catalytic partial oxidation (CPO) of methane to hydrogen and carbon monoxide over Pt-Rh/Al{sub 2}O{sub 3} and Pt/Al{sub 2}O{sub 3} was studied in-situ with a new QEXAFS setup. The structural changes of the catalysts were investigated on the subsecond timescale during two reaction steps by recording both XANES and full EXAFS spectra: (1) heating and ignition in 6%CH{sub 4}/3%O{sub 2}/He, (2) periodic changes between the reaction gas mixture and H{sub 2} atmosphere. The results showed that the ignition occurred at lower temperatures for Pt-Rh/Al{sub 2}O{sub 3} while it was completed in a significant shorter time interval for Pt/Al{sub 2}O{sub 3}. Some structural changes during the heating phase were detectable before the reaction ignited, especially for Pt/Al{sub 2}O{sub 3}, as reflected by the performed principle component analysis. However, a closer analysis of the FT-QEXAFS data did not evidence a defined intermediate. In addition, the composition of the gas atmosphere was altered between hydrogen and the reaction mixture, enabling modulation excitation spectroscopy. This technique was for the first time applied to QEXAFS data and resulted in significantly enhanced data quality.

  4. Catalytically Active Bimetallic Nanoparticles Supported on Porous Carbon Capsules Derived From Metal-Organic Framework Composites.

    Science.gov (United States)

    Yang, Hui; Bradley, Siobhan J; Chan, Andrew; Waterhouse, Geoffrey I N; Nann, Thomas; Kruger, Paul E; Telfer, Shane G

    2016-09-14

    We report a new methodology for producing monometallic or bimetallic nanoparticles confined within hollow nitrogen-doped porous carbon capsules. The capsules are derived from metal-organic framework (MOF) crystals that are coated with a shell of a secondary material comprising either a metal-tannic acid coordination polymer or a resorcinol-formaldehyde polymer. Platinum nanoparticles are optionally sandwiched between the MOF core and the shell. Pyrolysis of the MOF-shell composites produces hollow capsules of porous nitrogen-doped carbon that bear either monometallic (Pt, Co, and Ni) or alloyed (PtCo and PtNi) metal nanoparticles. The Co and Ni components of the bimetallic nanoparticles are derived from the shell surrounding the MOF crystals. The hollow capsules prevent sintering and detachment of the nanoparticles, and their porous walls allow for efficient mass transport. Alloyed PtCo nanoparticles embedded in the capsule walls are highly active, selective, and recyclable catalysts for the hydrogenation of nitroarenes to anilines.

  5. Transition metal associations with primary biological particles in sea spray aerosol generated in a wave channel.

    Science.gov (United States)

    Guasco, Timothy L; Cuadra-Rodriguez, Luis A; Pedler, Byron E; Ault, Andrew P; Collins, Douglas B; Zhao, Defeng; Kim, Michelle J; Ruppel, Matthew J; Wilson, Scott C; Pomeroy, Robert S; Grassian, Vicki H; Azam, Farooq; Bertram, Timothy H; Prather, Kimberly A

    2014-01-21

    In the ocean, breaking waves generate air bubbles which burst at the surface and eject sea spray aerosol (SSA), consisting of sea salt, biogenic organic species, and primary biological aerosol particles (PBAP). Our overall understanding of atmospheric biological particles of marine origin remains poor. Here, we perform a control experiment, using an aerosol time-of-flight mass spectrometer to measure the mass spectral signatures of individual particles generated by bubbling a salt solution before and after addition of heterotrophic marine bacteria. Upon addition of bacteria, an immediate increase occurs in the fraction of individual particle mass spectra containing magnesium, organic nitrogen, and phosphate marker ions. These biological signatures are consistent with 21% of the supermicrometer SSA particles generated in a previous study using breaking waves in an ocean-atmosphere wave channel. Interestingly, the wave flume mass spectral signatures also contain metal ions including silver, iron, and chromium. The nascent SSA bioparticles produced in the wave channel are hypothesized to be as follows: (1) whole or fragmented bacterial cells which bioaccumulated metals and/or (2) bacteria-derived colloids or biofilms which adhered to the metals. This study highlights the potential for transition metals, in combination with specific biomarkers, to serve as unique indicators for the presence of marine PBAP, especially in metal-impacted coastal regions.

  6. Comparison of the DiSCmini aerosol monitor to a handheld condensation particle counter and a scanning mobility particle sizer for submicrometer sodium chloride and metal aerosols

    OpenAIRE

    Mills, Jessica B.; Park, Jae Hong; Peters, Thomas M.

    2013-01-01

    We evaluated the robust, lightweight DiSCmini (DM) aerosol monitor for its ability to measure the concentration and mean diameter of submicrometer aerosols. Tests were conducted with monodispersed and polydispersed aerosols composed of two particle types (sodium chloride, NaCl, and spark generated metal particles, which simulate particles found in welding fume) at three different steady-state concentration ranges (Low, 104 particles/cm3). Particle number concentration, lung deposited surface ...

  7. TEM-EDS study of metals' partition at particle level after their sorption in soil

    Science.gov (United States)

    Sipos, Peter; Kovács Kis, Viktória; Németh, Tibor; Balázs, Réka

    2016-04-01

    Association of soil mineral particles could significantly modify the sorption capacity of the individual soil components. We studied this phenomena using single element and competitive batch Cd, Cu, Pb and Zn sorption experiments on six soil samples with contrasting characteristics. Their sorption properties were characterized by XRD and FTIRS analyses, as well as sorption curve evaluation. TEM-EDS analyses were used to characterize the soil mineral particle associations and their metal sorption capacities. Submicron sized smectite particles were found to be associated to tiny ferryhidrite and goethite patches in the acidic forest soil samples, whereas the alkaline meadow soils could be characterized by goethite and smectite particles attached to large carbonate grains. Point chemical analyses carried out on such associations showed that significant metal separation may occur at particle level within the mineral associations observed. This is primarily obvious for Cu and Pb, which are preferentially sorbed by iron oxides over clay mineral particles. This phenomenon is more pronounced in competitive situation. Highest affinity to clay minerals was found for Zn and it may be also characteristic for Cd in acid conditions. However, decrease in available sorption sites and increase in pH may result in enhanced precipitation for the studied metals. Our results suggest that estimation of the role of soil components in metals' sorption can not be adequate enough when the sorption properties of a set of bulk soils are studied exclusively. Direct observation of metals' partition at particle level may result in a deeper insight into soil-metal interaction. This study was financially supported by the Hungarian Scientific Research Fund (OTKA K105009).

  8. Hetero-metal cation control of CuO nanostructures and their high catalytic performance for CO oxidation

    Science.gov (United States)

    Huang, Hongwen; Zhang, Liqiang; Wu, Kewei; Yu, Qing; Chen, Ru; Yang, Hangsheng; Peng, Xinsheng; Ye, Zhizhen

    2012-11-01

    A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal-ion complexes plays an important role in slowing the release rate of OH- and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous CuO quasi-monocrystalline nanosheets prepared at 25 °C with a thickness of ca. 10 nm and large specific surface area of 80.32 m2 g-1 is investigated intensively. These CuO nanosheets demonstrate a superior catalytic activity for CO oxidation, with features of high CO conversion efficiency (47.77 mmolCO g-1CuO h-1 at 200 °C), which is close to that reported for previously investigated supported-CuO catalysts, and a low apparent activation energy Ea (53.3 kJ mol-1).A controllable synthesis of various morphologies of CuO nanostructures with tuning by hetero-metal cations has been developed in aqueous solution at room temperature. The morphologies of CuO can be engineered from nanosheets to nanoparticles with different length ratios of the long axis to the short axis. The formation of many metal-ion complexes plays an important role in slowing the release rate of OH- and affects the reaction kinetics further. We found that the effect of hetero-metal cations on the final morphology of the CuO nanostructures was the same as that of the cooling temperature. A series of temperature-controlled experiments demonstrated this. Furthermore, among all the synthesized CuO nanostructures, the fascinating colloidal mesoporous Cu

  9. Vapor-Particle Separation Using Microporous Metallic Membrane in Crossflow Filtration

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Mengdawn [ORNL

    2013-01-01

    Simultaneous separation of vapor and particles in industrial processes could be a key step toward manufacturing of high-quality goods. The separation is critical for successful measurement of volatile or semi-volatile aerosol particles, which no reliable technique exists. We have developed a technique for separation of vapor and particles simultaneously using a specialty microporous metallic membrane. The separator allows the thermally denuded particles traverse straight through the membrane tube, while the vapor molecules permeate through the membrane, separate from the particles and are removed subsequently. The separation technique virtually eliminates the possibility of contamination by vapor re- condensation. We tested the prototype of the vapor-particle separator (VPS) using aerosols prepared from sodium chloride to represent non-volatile aerosols. Chemical like dioctyl phthalate was chosen to represent volatile particles. The test aerosol particles were generated by an atomizer followed by a tandem differential mobility analyser to produce a stream of monodisperse particles in the size range of 10 to 100 nm. In real world particles, we tested the VPS using diesel engine particles that is a mixture of complex chemical composition. Number concentration of the nonvolatile particles reduced as the temperature increased, but the mode diameter of the aerosol population remained unchanged. Number concentration of the volatile particles was also reduced as the temperature increased, but their mode diameters became smaller as particles shrunk in diameter. Differences in the thermal behaviour of the particles were attributed to its transition energy barrier and evaporation rate. Mass balance analysis suggests the separation of vapor and test particles was reasonably complete. Thus, we conclude the VPS could provide an effective means for quantitative characterization of aerosol volatility and separation of vapors from particles.

  10. The Zeta Potential of Surface-Functionalized Metallic Nanorod Particles in Aqueous Solution

    Energy Technology Data Exchange (ETDEWEB)

    Dougherty, G M; Rose, K A; Tok, J B; Pannu, S S; Chuang, F S; Sha, M Y; Chakarova, G; Penn, S G

    2007-05-07

    Metallic nanoparticles suspended in aqueous solutions, and functionalized with chemical and biological surface coatings, are important elements in basic and applied nanoscience research. Many applications require an understanding of the electrokinetic or colloidal properties of such particles. In this paper we describe the results of experiments to measure the zeta potential of metallic nanorod particles in aqueous saline solutions, including the effects of pH, ionic strength, metallic composition, and surface functionalization state. Particle substrates tested include gold, silver, and palladium monometallic particles as well as gold/silver bimetallic particles. Surface functionalization conditions included 11-mercaptoundecanoic acid (MUA), mercaptoethanol (ME), and mercaptoethanesulfonic acid (MESA) self-assembled monolayers (SAMs), as well as MUA layers subsequently derivatized with proteins. Zeta potential data for typical charge-stabilized polystyrene particles are also presented for comparison. Experimental data are compared with theory. The results of these studies are useful in predicting and controlling the aggregation, adhesion, and transport of functionalized metallic nanoparticles within microfluidic devices and other systems.

  11. Detection of small metal particles by a quasi-optical system at sub-millimeter wavelength

    Science.gov (United States)

    Kitahara, Yasuyuki; Domier, C. W.; Ikeda, Makoto; Pham, Anh-Vu; Luhmann, Neville C.

    2016-04-01

    Inspection of alien metal particles in electronic materials such as glass fibers and resins is a critical issue to control the quality and guarantee the safety of products. In this paper, we present a new detection technique using sub-millimeter wave for films as electric materials in product lines. The advantage of using sub-millimeter wave frequency is that it is easy to distinguish conductive particles from a nonconductive material such as plastic films. Scattering of a submillimeter wave by a metal particle is used as the detection principle. By simulation, it is observed that the scattering pattern varies intricately as the diameter varies from 10 to 700 μm at 300 GHz. The demonstration system is composed of a Keysight performance network analyzer (N5247A PNA-X) with 150-330 GHz VDI extension modules, transmitting and receiving antennas, and focusing dielectric lens. An output signal is radiated via an antenna and focused onto a metal particle on a film. The wave scattered by the metal particle is detected by an identical antenna through a lens. The signal scattered from a metal particle is evaluated from the insertion loss between antennas (S21). The result shows that a particle of diameter 300 μm is detectable at 150-330 GHz through S21 in the experimental system that we prepared. Peaks calculated in simulation were detected in experimental data as well as in the curves of the particle diameter versus S21. It was shown that using this peak frequency could improve S21 level without higher frequency.

  12. Catalytic Asymmetric Carbon-Carbon Forming Reactions Catalyzed Chiral Schiff Base-Metal Complexes

    Institute of Scientific and Technical Information of China (English)

    Takanori; Tanaka; Masahiko; Hayashi

    2007-01-01

    1 Results In 1991, we disclosed the novel asymmetric catalysts prepared from chiral Schiff base and titanium alkoxide in the reaction of asymmetric silylcyanation of aldehydes (eq.1)[1]. Since our first report, chiral Schiff base-metal complex was proven to be efficient in a variety of asymmetric reactions. We reported the first example of enantioselective addition of diketene to aldehydes promoted by chiral Schiff base-titanium alkoxide complexes (eq.2)[2]. The products of this reaction have been cove...

  13. Oxides Catalysts of Rare Earth and Transient Metal for Catalytic Oxidation of Benzene

    Institute of Scientific and Technical Information of China (English)

    Liang Kun; Li Rong; Chen Jianjun; Ma Jiantai

    2004-01-01

    The catalysts of CeO2 and the mixture of CeO2 and CuO were prepared, and the activities of these catalysts for completely oxidizing benzene were studied.The results show that the optimal proportion of CeO2/CuO is 6: 4.The highest temperature at which benzene was completely oxidized on these catalysts at different airspeed was measured.Compared these catalysts with the noble metal used, our catalysts had superiority in the resources and the industrial cost besides good activities.

  14. Catalytic C–H Functionalization by Metal Carbenoid and Nitrenoid Insertion

    Science.gov (United States)

    Davies, Huw M. L.; Manning, James R.

    2010-01-01

    Selective methods for C–H functionalization are of intense current interest because they offer new strategic approaches for synthesis. A very promising C–H functionalization method is the insertion of metal carbenes and nitrenes into C–H bonds. This chemistry has experienced considerable growth in the last decade, particularly in the area of enantioselective intermolecular reactions. This review will bring together the major aspects of this C–H functionalization chemistry and provide a useful perspective on how this methodology can impact the synthesis and accessibility of natural products and pharmaceutical targets. PMID:18216847

  15. Preparation of Metallic Aluminum Compound Particles by Submerged Arc Discharge Method in Aqueous Media

    Science.gov (United States)

    Liao, Chih-Yu; Tseng, Kuo-Hsiung; Lin, Hong-Shiou

    2013-02-01

    Fine metal particles are produced by chemical methods, which add surfactants to control particle size and concentration. This study used the submerged arc discharge method (SADM) to prepare metal fluid containing nanoparticles and submicron particles in pure dielectric fluid (deionized water or alcohol). The process is fast and simple, and it does not require the addition of chemical agents. The SADM uses electrical discharge machining (EDM) equipment, and the key parameters of the production process include discharge voltage, current, and pulse discharge on-off duration. This study added a capacitive component between the electrodes and the electrode Z-axis regulation in the control parameters to render the aluminum fluid process smooth, which is the main difference of this article from the literature. The experimental results showed that SADM can produce aluminum particles from nanometer to submicron grade, and it can obtain different compounds from different dielectric fluids. The dielectric fluids used in this study were deionized water and ethanol, and aluminum hydroxide Al(OH)3 particles with suspending power and precipitated aluminum particles were obtained, respectively. The preparations of metal colloid and particles by the SADM process have the characteristics of low cost, high efficiency, high speed, and mass production. Thus, the process has high research value and developmental opportunities.

  16. Gold nanoparticles immobilized on metal-organic frameworks with enhanced catalytic performance for DNA detection.

    Science.gov (United States)

    Liu, Ya Li; Fu, Wen Liang; Li, Chun Mei; Huang, Cheng Zhi; Li, Yuan Fang

    2015-02-25

    In this work, gold nanoparticles (AuNPs) assembled on the surface of iron based metal-organic frameworks (MOFs), Fe-MIL-88, are facilely prepared through electrostatic interactions using polyethyleneimine (PEI) molecules as linker. The resulting hybrid materials possess synergetic peroxidase-like activity. Because iron based metal-organic frameworks, Fe-MIL-88, exhibits highly peroxidase-like activity, and AuNPs has the distinct adsorption property to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The peroxidase-like activity of Au@Fe-MIL-88 exhibit excellent switchable in response to specific DNA, ssDNA is easily adsorbed on the surface of the Au@Fe-MIL-88 hybrids, resulting in the reduce of the peroxidase-like activity of the hybrids. While it is recovered by the addition of target DNA, and the recovery degree is proportional to the target DNA concentration over the range of 30-150 nM with a detection limit of 11.4 nM. Based on these unique properties, we develop a label-free colorimetric method for DNA hybridization detection. In control experiment, base-mismatched DNA cannot induce recovery of the peroxidase-like activity. This detection method is simple, cheap, rapid and colorimetric.

  17. Catalytic behavior of Cu, Ag and Au nanoparticles. A comparison

    NARCIS (Netherlands)

    Lippits, Meindert Jan

    2010-01-01

    Clearly gold deposited as nanoparticles on a support is a very active catalyst in contrast to bulk gold which does not show any catalytic activity. The question arises if this particle size effect is exclusively valid for gold catalysis or can a similar effect be found in other metals? In the resear

  18. Catalytic behavior of Cu, Ag and Au nanoparticles. A comparison

    NARCIS (Netherlands)

    Lippits, Meindert Jan

    2010-01-01

    Clearly gold deposited as nanoparticles on a support is a very active catalyst in contrast to bulk gold which does not show any catalytic activity. The question arises if this particle size effect is exclusively valid for gold catalysis or can a similar effect be found in other metals? In the resear

  19. Catalytic behavior of Cu, Ag and Au nanoparticles. A comparison

    NARCIS (Netherlands)

    Lippits, Meindert Jan

    2010-01-01

    Clearly gold deposited as nanoparticles on a support is a very active catalyst in contrast to bulk gold which does not show any catalytic activity. The question arises if this particle size effect is exclusively valid for gold catalysis or can a similar effect be found in other metals? In the

  20. On airborne nano/micro-sized wear particles released from low-metallic automotive brakes.

    Science.gov (United States)

    Kukutschová, Jana; Moravec, Pavel; Tomášek, Vladimír; Matějka, Vlastimil; Smolík, Jiří; Schwarz, Jaroslav; Seidlerová, Jana; Safářová, Klára; Filip, Peter

    2011-04-01

    The paper addresses the wear particles released from commercially available "low-metallic" automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 μm were released into the air. The numbers of nanoparticles (release of nanoparticles was measured when the average temperature of the rotor reached 300°C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles.

  1. Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane

    Institute of Scientific and Technical Information of China (English)

    V.H.Rane; S.T.Chaudhari; V.R.Choudhary

    2008-01-01

    Surface properties (viz. surface area, basicity/base strength distribution, and crystal phases) of alkali metal doped CaO (alkali metal/Ca = 0.1 and 0.4) catalysts and their catalytic activity/selectivity in oxidative coupling of methane (OCM) to higher hydrocarbons at different reaction conditions (viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm3·g-1·h-1) have been investigated. The influence of catalyst calcination temperature on the activity/selectivity has also been investigated. The surface properties (viz. surface area, basicity/base strength distribution) and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity (strong basic sites) and the C2+ selectivity and yield of the catalysts in the OCM process. The activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO (Na/Ca = 0.1, before calcination) catalyst (calcined at 750 ℃), showed best performance (C2+selectivity of 68.8% with 24.7% methane conversion), whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process.

  2. Evaluation of Durable Metallic Supports for Catalytic Combustors, CRADA Final Report ORNL 00-0570

    Energy Technology Data Exchange (ETDEWEB)

    Pint, B. A. [ORNL; Wright, I. G. [ORNL; Lara-Curzio, E. [ORNL; McCarty, J. [Catalytica Energy Systems, Inc.; Barnes, J. [Catalytica Energy Systems, Inc.

    2003-10-01

    In 2000, a Cooperative Research and Development Agreement (CRADA) was undertaken between the Oak Ridge National Laboratory (ORNL) and Catalytica Energy Systems Incorporated (CESI) to determine the properties of current metallic catalyst supports and examine new candidate alloys for this application. A team was established at ORNL to examine oxidation-limited lifetime of these thin-walled metallic components using standard lifetime models and to measure the mechanical properties of the foils (40-200:m in thickness) which can differ substantially from bulk properties. Oxidation experiments were conducted on foil specimens at 700/-1100/C in laboratory air and in air with 10 vol.% water vapor to better simulate the combustor environment. At the higher test temperatures, time to oxidation-induced (i.e. breakaway oxidation) failure was determined in 1h cycles in order to verify predictions from a standard reservoir-type oxidation lifetime model. Selected specimens were run for >10,000h in 100 or 500h cycles at lower test temperatures in order to determine the oxidation kinetics for the model. The creep properties of selected foils were measured for 4,000-8,000h at operation-relevant stresses and temperatures. None of the new candidate alloys significantly out-performed currently used alloys in laboratory testing, particularly in oxidation lifetime testing. Therefore, engine testing was not performed on any of the new candidate alloys. Both the oxidation- and creep-resistance of FeCrAl alloys was greater than expected and the results of the CRADA allowed CESI to extend life or increase operating temperatures for these lower cost substrate alloys in the next generation of catalyst modules.

  3. Herbo-mineral based Schiff base ligand and its metal complexes: Synthesis, characterization, catalytic potential and biological applications.

    Science.gov (United States)

    Kareem, Abdul; Laxmi; Arshad, Mohammad; Nami, Shahab A A; Nishat, Nahid

    2016-07-01

    Schiff base ligand, (L), derived from condensation reaction of 1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, (curcumin), with pyridine-3-carboxamide, (nicotinamide), and its complexes of Co(II), Ni(II) and Cu(II) ions, containing 1,10-phenanthroline as auxiliary ligand were synthesized and characterized by various physico-chemical techniques. From the micro analytical data, the stoichiometry of the complexes 1:1 (metal: ligand) was ascertained. The Co(II) and Cu(II) forms octahedral complexes, while the geometric structure around Ni(II) atom can be described as square planar. The catalytic potential of the metal complexes have been evaluated by recording the rate of decomposition of hydrogen peroxide. The results reveal that the percent decomposition of H2O2increases with time and the highest value (50.50%) was recorded for Co(II) complex. The ligand and its complexes were also screened for their in vitro antibacterial activity against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pyogenes and Pseudomonas aeruginosa. The relative order of antibacterial activity against S. Pyogenes, S. aureus and E. coli is Cu(II)>Ni(II)>Co(II)>(L); while with P. aeruginosa, K. pneumoniae the order of activity is Cu(II)>Co(II)>Ni(II)>(L). The anthelmintic screening was performed using Pheretima posthuma. The order of anthelmintic activity of ligand and its complexes is [(Phen)CuLCl2]>[(Phen)CoLCl2]>[(Phen)NiL]Cl2>(L). Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Dry deposition and resuspension of particle-associated metals near a freeway in Los Angeles

    Science.gov (United States)

    Sabin, Lisa D.; Hee Lim, Jeong; Teresa Venezia, Maria; Winer, Arthur M.; Schiff, Kenneth C.; Stolzenbach, Keith D.

    Dry atmospheric deposition represents a potentially large source of pollutant metal contamination in urban stormwater runoff, yet there is a limited amount of research on the relationship between atmospheric emissions and water quality problems in urban areas. In Los Angeles, with air quality that ranks among the worst in the United States, significant quantities of toxic materials are released into the atmosphere every day, and paved road dust represents the largest source of particle-associated metal emissions to the atmosphere. In order to better understand the role of roadways as a source of localized metal deposition, we characterized the horizontal dry deposition patterns of chromium, copper, lead, nickel and zinc upwind and at increasing distances downwind of the I-405 Freeway in coastal Los Angeles. Dry deposition fluxes and atmospheric concentrations of these metals were highest at the site closest to the freeway, and reduced to approximately urban background concentrations between 10 and 150 m downwind of the freeway. Compared with urban background, atmospheric particle size distributions indicated the freeway was a significant source of these metals on large particles >6 μm in diameter, which deposit close to their source and account for the increased dry deposition flux rates observed near the freeway. The spatial pattern of measured deposition flux was well predicted by a relatively simple line-source Gaussian plume model modified to include particle deposition and resuspension. The model results indicated dilution by vertical dispersion of the plume was the most important mechanism regulating downwind concentrations and deposition.

  5. Metal-particle-induced enhancement of the photoluminescence from biomolecule-functionalized carbon nanotubes

    Science.gov (United States)

    2014-01-01

    The effect of metal particles on the photoluminescence (PL) and the Raman spectra of functionalized SWCNTs in aqueous solutions was systematically investigated by studying three different metal particles (gold, cobalt, and nickel) on three different SWCNT suspensions (DNA-, RNA-, and sodium deoxycholate salt (DOC)-functionalized SWCNTs). Substantial enhancement of the PL intensities was observed, while the Raman spectra remained unchanged, after gold, cobalt, or nickel particles were introduced into RNA-SWCNT aqueous suspensions. Almost the same results were obtained after the same metal particles were added to DNA-SWCNT aqueous suspensions. However, both the PL and the Raman spectra did not exhibit any change at all after the same metal particles were introduced into DOC-SWCNT aqueous suspensions. The unusual PL enhancements observed in this work cannot be accounted for by the three well-known mechanisms in the literature: surface-enhanced Raman scattering effect, Förster resonance energy transfer in a rebundling of isolated SWCNTs, and pH changes of the aqueous solutions. PMID:24548588

  6. Catalytic activity of thiacalix[4]arenetetrasulfonate metal complexes on modified anion-exchangers for ascorbic acid oxidation.

    Science.gov (United States)

    Odo, Junichi; Hirashima, Tomomi; Hayashida, Tomoko; Miyauchi, Asuka; Minemoto, Mami; Iuchi, Masato; Inoguchi, Masahiko

    2013-01-01

    The catalysis of ascorbic acid (AsA) oxidation by anion-exchangers modified with metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4]A-500, Me=Mn(3+), Fe(3+), Co(3+), Ce(4+), Cu(2+), Zn(2+), Ni(2+), and H2) were investigated. Me-TCAS[4]A-500 (Me=Mn(3+), Fe(3+), Ce(4+), and Cu(2+)) all exhibited the ability to catalyze the oxidative reaction of AsA to dehydroascorbic acid. However, in the presence of high concentrations of AsA, only Cu(2+)-TCAS[4]A-500 was capable of complete oxidation of the acid. Moreover, after six repeat uses, Cu(2+)-TCAS[4]A-500 maintained high and relatively constant catalytic activity. Prior treatment of glucose solutions with Cu(2+)-TCAS[4]A-500, even in the presence of high AsA concentrations, enabled the satisfactory determination of glucose without interference by AsA. Cu(2+)-TCAS[4]A-500 will therefore be applicable as an artificial substitute for ascorbate oxidase, and may be useful as a means to eliminate AsA interference during the analysis of vital compounds such as glucose and uric acid.

  7. Noble Metal-Free Ceria-Zirconia Solid Solutions Templated by Tobacco Materials for Catalytic Oxidation of CO

    Directory of Open Access Journals (Sweden)

    Donglai Zhu

    2016-09-01

    Full Text Available A series of ceria-zirconia solid solutions were synthesized using tobacco leaves, stems and stem-silks as biotemplates. A combination of physicochemical techniques such as powder X-ray diffraction (XRD, N2 adsorption/desorption measurement, scanning electron microscopy (SEM, and transmission electron microscopy (TEM were used to characterize the as-synthesized samples. The results show that the morphologies of the templates were well replicated in the obtained ceria-zirconia solid solutions. Catalytic oxidation activities of CO over the ceria-zirconia solid solutions were then investigated. The catalyst templated by tobacco stem-silk exhibited higher conversion of CO at lower temperature than that of ceria-zirconia solid solutions templated by tobacco leaves and stems or without templates due to its special morphology. The catalyst even showed similar CO conversion when compared to ceria-zirconia solid solutions doped with 1.0 wt % noble metals such as Pt, Ag and Au. The results highlighted the advantages of using tobacco as biotemplate.

  8. Synthesis, Thermal, Electrical and Catalytic Studies of Some Transition Metal Polychelates of Bis-bidentate Schiff Base

    Institute of Scientific and Technical Information of China (English)

    BANSOD Ashish; ASWAR Anand

    2007-01-01

    Polychelates of Mn(Ⅱ),Fe(Ⅱ),Co(Ⅱ), Ni(Ⅱ),Cu(Ⅱ),Zn(Ⅱ) and Cd(Ⅱ) with the bis salen-type ligand derivedfrom 4,4'-bis[(salicylaldehyde-5)azo]biphenyl and 1,4-diaminobutane have been synthesized.All the polychelates have been characterized by elemental analysis,magnetic susceptibility measurements,IR,electronic spectra and thermogravimetric studies.All the complexes isolated in solid state are dark coloured and insoluble in water and common organic solvents.The ligand behaves as a bis-bidentate molecule coordinating through the phenolic oxygen and azomethine nitrogen atoms.The thermal decomposition of these metal complexes was investigated by thermogravimetric analysis and data have been analyzed for kinetic parameters using Broido equation.The solid-state electrical conductivity of the ligand and its polychelates in the form of compressed pellet was studied in the temperature range from 313 to 413 K.All the polychelates were found to show semiconducting nature.The Mn(Ⅱ),Fe(Ⅱ),Co(Ⅱ) and Ni(Ⅱ) polychelates have been assessed for the catalytic epoxidation of styrene.

  9. The effect of metal transfer modes and shielding gas composition on the emission of ultrafine particles in MAG steel welding

    OpenAIRE

    Gomes, J. F.; R. M. Miranda; Carvalho,P.A.; Quintino,M. L.

    2014-01-01

    The present study aims to characterize ultrafine particles emitted during gas metal arc welding of mild steel and stainless steel, using different shielding gas mixtures, and to evaluate the effect of metal transfer modes, controlled by both processing parameters and shielding gas composition, on the quantity and morphology of the ultrafine particles. It was found that the amount of emitted ultrafine particles (measured by particle number and alveolar deposited surface area) are clearly depen...

  10. Deposition of toxic metal particles on rough nanofiltration membranes

    Energy Technology Data Exchange (ETDEWEB)

    Agboola, Oluranti; Maree, Jannie; Mbaya, Richard; Zvinowanda, Caliphs Musa [Tshwane University of Technology, Pretoria (South Africa); Molelekwa, Gomotsegang Fred; Jullok, Nora; Bruggen, Bart Van der; Volodine, Alexander; Haesendonck, Chris Van [KU Leuven, Heverlee (Belgium)

    2014-08-15

    Two nanofiltration (NF90 and Nano-Pro-3012) membranes were investigated for their capacity to remove metal ions. This study presents the effect of membrane roughness on the removal of toxic metal ions during dead end membrane filtration. Atomic force microscopy, scanning electron microscopy, WSXM software and ImageJ were used to characterize the roughness of the membranes. Gradual decrease in filtration permeate flux was observed as foulants accumulated at the interface of the membranes; filtration permeate flux varied from 20 L/m{sup 2}/h to 14 L/m{sup 2}/h and 11 L/ m{sup 2}/h to 6 L/m{sup 2}/h for NF90 and Nano-Pro-3012, respectively. NF90 membrane was more prone to fouling than the Nano-Pro-3012 membrane: the percentage flux reduction was higher for NF90 (3.6%) than Nano-Pro-3012 (0.98%). The bearing ratio of the fouled NF90 exhibited a high peak of 7.09 nm than the fouled Nano-Pro-3012 with the peak of 6.8 nm.

  11. Optimized process parameters for fabricating metal particles reinforced 5083 Al composite by friction stir processing.

    Science.gov (United States)

    Bauri, Ranjit; Yadav, Devinder; Shyam Kumar, C N; Janaki Ram, G D

    2015-12-01

    Metal matrix composites (MMCs) exhibit improved strength but suffer from low ductility. Metal particles reinforcement can be an alternative to retain the ductility in MMCs (Bauri and Yadav, 2010; Thakur and Gupta, 2007) [1,2]. However, processing such composites by conventional routes is difficult. The data presented here relates to friction stir processing (FSP) that was used to process metal particles reinforced aluminum matrix composites. The data is the processing parameters, rotation and traverse speeds, which were optimized to incorporate Ni particles. A wide range of parameters covering tool rotation speeds from 1000 rpm to 1800 rpm and a range of traverse speeds from 6 mm/min to 24 mm/min were explored in order to get a defect free stir zone and uniform distribution of particles. The right combination of rotation and traverse speed was found from these experiments. Both as-received coarse particles (70 μm) and ball-milled finer particles (10 μm) were incorporated in the Al matrix using the optimized parameters.

  12. Optimized process parameters for fabricating metal particles reinforced 5083 Al composite by friction stir processing

    Directory of Open Access Journals (Sweden)

    Ranjit Bauri

    2015-12-01

    Full Text Available Metal matrix composites (MMCs exhibit improved strength but suffer from low ductility. Metal particles reinforcement can be an alternative to retain the ductility in MMCs (Bauri and Yadav, 2010; Thakur and Gupta, 2007 [1,2]. However, processing such composites by conventional routes is difficult. The data presented here relates to friction stir processing (FSP that was used to process metal particles reinforced aluminum matrix composites. The data is the processing parameters, rotation and traverse speeds, which were optimized to incorporate Ni particles. A wide range of parameters covering tool rotation speeds from 1000 rpm to 1800 rpm and a range of traverse speeds from 6 mm/min to 24 mm/min were explored in order to get a defect free stir zone and uniform distribution of particles. The right combination of rotation and traverse speed was found from these experiments. Both as-received coarse particles (70 μm and ball-milled finer particles (10 μm were incorporated in the Al matrix using the optimized parameters.

  13. Mathematical Modeling of Particle Segregation During Centrifugal Casting of Metal Matrix Composites

    Science.gov (United States)

    Balout, B.; Litwin, J.

    2012-04-01

    When a metal matrix composite undergoes centrifugal casting, the velocity, deceleration, displacement, and segregation of its particles are modeled according to changes in the centrifugal radius, as well as by variations in the molten metal viscosity as the temperature decreases during the cooling process. A cast aluminum alloy A356 reinforced by 10 V% of silicon carbide particles (SiC), with a median diameter of 12 μm, was used to conduct the experiments, and a mathematical modeling showed that the particles' volume fraction on the outer casting face varied according to whether the viscosity of the liquid metal used was constant or variable. If variations in viscosity during the cooling process are taken into account, then the volume fraction of the particles for a given time of centrifugation changes on the outer casting face, while it increases if the viscosity was constant. Modeling the particle segregation with variable viscosity produces results that are closer to those obtained with experiments than is the case when a constant viscosity is used. In fact, the higher the initial pouring and mold temperatures, the higher the effect of the viscosity variation on particle segregation.

  14. Adsorption, separation, and catalytic properties of densified metal-organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Nandasiri, Manjula I.; Jambovane, Sachin R.; McGrail, B. Peter; Schaef, Herbert T.; Nune, Satish. K.

    2016-03-01

    Metal-organic frameworks (MOFs) are one of the widely investigated materials of 21st century due to their unique properties such as structural tailorability, controlled porosity and crystallinity. These exceptional properties make them promising candidates for various applications including gas adsorption and storage, separation, and catalysis. However, commercial applications of MOFs produced by conventional methods including solvothermal or hydrothermal synthesis are rather limited or restricted because they often produce fine powders. The use of MOF powders for industrial applications often results in pressure drop problems similar to the case with Zeolites. To realize these materials for practical applications, densification of MOFs is routinely employed to form pellets, extrudates or beads to improve the overall density, volumetric adsorption, mechanical and thermal properties. However, the improvements come with some drawbacks such as reduction in overall porosity, surface area, and gravimetric adsorption capacity. Thus, optimizing the properties of densified MOF’s by tuning the packing density is very crucial for realizing these materials for industrial applications. In this review, various methods of densification of MOFs, their properties, and applications are discussed.

  15. Influence of catalyst dilution by inert particles on the effectivity of a catalytical process in a fluidized bed. [Increasing selectivity by decreasing local reaction kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Augenblick, A.A. (Karpov Physico-Chemical Inst., Moscow, USSR); Kernerman, V.A.; Abayev, G.N.; Slin' ko, M.G.; Sergeev, Yu.A.

    1983-01-01

    The method of the increasing a selectivity of catalytic processes in fluidized bed reactor by decreasing local chemical reaction rates together with increasing a reactive volume is discussed. Based on the two-phase model of a fluidized bed it is shown that the dilution of a catalyst by inert particles leads to an increasing of effective interphase exchange coefficients and a decreasing of effective axial mixing coefficients. Restrictions to applications of the method connected with local features of a bed structure are discussed. 3 figures.

  16. Flow characteristics and micro-scale metallic particle formation in the laser supersonic heating technique

    Science.gov (United States)

    Lin, Shih-Lung; Lin, Jehnming

    2007-02-01

    The characteristics of the supersonic flow of the laser heating technique for producing micro-scale metallic particles were investigated in this study. A numerical model was established to predict the flow fields and particle trajectories leaving a spray nozzle with shock wave effects. The compressible flow of the shock waves and the trajectories of particles in diameters of 1-20 μm were simulated and compared with the flow visualization. In the experiment, a pulsed Nd-YAG laser was used as heat source on a carbon steel target within the nozzle, and the carbon steel particles were ejected by high-pressure air. The result shows that the shock wave structures were generated at various entrance pressures, and there is a significant increase in the amount of carbon steel particles and the spraying angles by increasing the entrance air pressure.

  17. TISSUE REMODELING IN THE HUMAN LUNG IN RELATION TO PARTICLE CONCENTRATION AND METAL CONTENT

    Science.gov (United States)

    TISSUE REMODELING IN THE HUMAN LUNG IN RELATION TO PARTICLE CONCENTRATION AND METAL CONTENT. J Gallagher1, J Inmon1, S Schlaegle2, A Levine2, T Rogers3, J Scott1, F Green4, M Schenker5, K Pinkerton5 1NHEERL, US-EPA, RTP, NC, USA; 2RJ Lee Group Inc, Monroeville, Pa, USA; ...

  18. Thermal conductivity and interfacial conductance of AlN particle reinforced metal matrix composites

    Science.gov (United States)

    Kida, M.; Weber, L.; Monachon, C.; Mortensen, A.

    2011-03-01

    Aluminum nitride (AlN) particle reinforced metal-matrix-composites produced by pressure infiltration are characterized in terms of their thermal conductivity. The composites are designed to cover a wide range of phase contrast between the dispersed particles and the matrix; this is achieved by changing the matrix conductivity using Cu, Al, Sn, and Pb as the matrix. The interface thermal conductance (hc) between AlN and the matrix metals is determined by varying the size of the AlN particles using the Hasselman-Johnson approach and the differential effective medium (DEM) model to calculate hc from measured composite conductivity values. In addition, hc is measured directly at the AlN/Al interface using the transient thermoreflectance (TTR) method on thin aluminum layers deposited on flat AlN substrates to find good agreement with the value derived directly from Al/AlN composites of variable particle size and thus confirm the approach used here to measure hc. Data from the study show that hc at AlN-metal interfaces increases with the metal/AlN Debye temperature ratio; however, the increase is much less than predicted by currently accepted models.

  19. Laser melt injection of ceramic particles in metals : Processing, microstructure and properties

    NARCIS (Netherlands)

    Ocelík, V.; De Hosson, J.Th.M.

    2010-01-01

    The objective of this paper is to present an overview of the possibilities of the laser melt injection (LMI) methodology to enhance the surface of light-weighted metals by adding hard ceramic particles in the top layer, with the aim to enhance the wear resistance and to increase the hardness. In par

  20. Complexation- and ligand-induced metal release from 316L particles: importance of particle size and crystallographic structure.

    Science.gov (United States)

    Hedberg, Yolanda; Hedberg, Jonas; Liu, Yi; Wallinder, Inger Odnevall

    2011-12-01

    Iron, chromium, nickel, and manganese released from gas-atomized AISI 316L stainless steel powders (sized 316L particles immersed in ALF. Iron was mainly released, while manganese was preferentially released as a consequence of the reduction of manganese oxide on the surface. These processes resulted in highly complexing media in a partial oxidation of trivalent chromium to hexavalent chromium on the surface. The extent of metal release was partially controlled by surface properties (e.g., availability of elements on the surface and structure of the outermost surface) and partially by the complexation capacity of the different metals with the complexing agents of the different media. In general, compared to the coarse powder (<45 μm), the fine (<4 μm) powder displayed significantly higher released amounts of metals per surface area, increased with increased solution complexation capacity, while less amounts of metals were released into non-complexing solutions. Due to the ferritic structure of lower solubility for nickel of the fine powder, more nickel was released into all solutions compared with the coarser powder.

  1. Fuel rich and fuel lean catalytic combustion of the stabilized confined turbulent gaseous diffusion flames over noble metal disc burners

    Directory of Open Access Journals (Sweden)

    Amal S. Zakhary

    2014-03-01

    Full Text Available Catalytic combustion of stabilized confined turbulent gaseous diffusion flames using Pt/Al2O3 and Pd/Al2O3 disc burners situated in the combustion domain under both fuel-rich and fuel-lean conditions was experimentally studied. Commercial LPG fuel having an average composition of: 23% propane, 76% butane, and 1% pentane was used. The thermal structure of these catalytic flames developed over Pt/Al2O3 and Pd/Al2O3 burners were examined via measuring the mean temperature distribution in the radial direction at different axial locations along the flames. Under-fuel-rich condition the flames operated over Pt catalytic disc attained high temperature values in order to express the progress of combustion and were found to achieve higher activity as compared to the flames developed over Pd catalytic disc. These two types of catalytic flames demonstrated an increase in the reaction rate with the downstream axial distance and hence, an increase in the flame temperatures was associated with partial oxidation towards CO due to the lack of oxygen. However, under fuel-lean conditions the catalytic flame over Pd catalyst recorded comparatively higher temperatures within the flame core in the near region of the main reaction zone than over Pt disc burner. These two catalytic flames over Pt and Pd disc burners showed complete oxidation to CO2 since the catalytic surface is covered by more rich oxygen under the fuel-lean condition.

  2. Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Du, Guodong [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    -, bis-alkoxo, and chelating diolato complexes, depending on the identity of diols and the stoichiometry employed. It was also found that tin porphyrin complexes promoted the oxidative cleavage of vicinal diols and the oxidation of α-ketols to α-diketones with dioxygen. In extending the chemistry of metalloporphyrins and analogous complexes, a series of chiral tetraaza macrocyclic ligands and metal complexes were designed and synthesized. Examination of iron(II) complexes showed that they were efficient catalysts for the cyclopropanation of styrene by diazo reagents. Good yields and high diastereoselectivity were obtained with modest enantioselectivity. A rationalization of the stereoselectivity was presented on the basis of structural factors in a carbene intermediate.

  3. Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Guodong Du

    2004-12-19

    products, including mono-, bis-alkoxo, and chelating diolato complexes, depending on the identity of diols and the stoichiometry employed. It was also found that tin porphyrin complexes promoted the oxidative cleavage of vicinal diols and the oxidation of {alpha}-ketols to {alpha}-diketones with dioxygen. In extending the chemistry of metalloporphyrins and analogous complexes, a series of chiral tetraaza macrocyclic ligands and metal complexes were designed and synthesized. Examination of iron(II) complexes showed that they were efficient catalysts for the cyclopropanation of styrene by diazo reagents. Good yields and high diastereoselectivity were obtained with modest enantioselectivity. A rationalization of the stereoselectivity was presented on the basis of structural factors in a carbene intermediate.

  4. Tribological properties of metal-matrix composite materials reinforced by superelastic hard carbon particles

    Science.gov (United States)

    Ushakova, I. N.; Drozdova, E. I.; Chernogorova, O. P.; Blinov, V. M.; Ekimov, E. A.

    2016-05-01

    Metal-matrix composite materials (CMs) are synthesized from a mixture of a metal powder (Ti, Fe, Co, Ni, Cu, Al-based alloy) and fullerenes (10 wt %). The thermobaric synthesis conditions (700-1000°C, 5-8 GPa) ensure the collapse of fullerene molecules and their transformation into superelastic carbon phase particles with an indentation hardness H IT = 10-37 GPa, an elastic modulus E IT = 60-260 GPa, and an elastic recovery of >80% upon indentation. After reinforcing by superelastic hard carbon, the friction coefficient of CM decreases by a factor of 2-4 as compared to the friction coefficient of the matrix metal, and the abrasive wear resistance increases by a factor of 4-200. Superelastic hard carbon particles are a unique reinforcing material for an increase in the wear resistance and a simultaneous decrease in the friction coefficient of CM.

  5. Near-Infrared Super Resolution Imaging with Metallic Nanoshell Particle Chain Array

    CERN Document Server

    Kong, Weijie; Cao, Penfei; Cheng, Lin; Gong, Li; Zhao, Xining; Yang, Lili

    2012-01-01

    We propose a near-infrared super resolution imaging system without a lens or a mirror but with an array of metallic nanoshell particle chain. The imaging array can plasmonically transfer the near-field components of dipole sources in the incoherent and coherent manners and the super resolution images can be reconstructed in the output plane. By tunning the parameters of the metallic nanoshell particle, the plasmon resonance band of the isolate nanoshell particle red-shifts to the near-infrared region. The near-infrared super resolution images are obtained subsequently. We calculate the field intensity distribution at the different planes of imaging process using the finite element method and find that the array has super resolution imaging capability at near-infrared wavelengths. We also show that the image formation highly depends on the coherence of the dipole sources and the image-array distance.

  6. Impregnation of Catalytic Metals in Single-Walled Carbon Nanotubes for Toxic Gas Conversion in Life Support System

    Science.gov (United States)

    Li, Jing; Wignarajah, Kanapathipillai; Cinke, Marty; Partridge, Harry; Fisher, John

    2004-01-01

    Carbon nanotubes (CNTs) possess extraordinary properties such as high surface area, ordered chemical structure that allows functionalization, larger pore volume, and very narrow pore size distribution that have attracted considerable research attention from around the world since their discovery in 1991. The development and characterization of an original and innovative approach for the control and elimination of gaseous toxins using single walled carbon nanotubes (SWNTs) promise superior performance over conventional approaches due to the ability to direct the selective uptake of gaseous species based on their controlled pore size, increased adsorptive capacity due to their increased surface area and the effectiveness of carbon nanotubes as catalyst supports for gaseous conversion. We present our recent investigation of using SWNTs as catalytic supporting materials to impregnate metals, such as rhodium (Rh), palladium (Pd) and other catalysts. A protocol has been developed to oxidize the SWNTs first and then impregnate the Rh in aqueous rhodium chloride solution, according to unique surface properties of SWNTs. The Rh has been successfully impregnated in SWNTs. The Rh-SWNTs have been characterized by various techniques, such as TGA, XPS, TEM, and FTIR. The project is funded by a NASA Research Announcement Grant to find applications of single walled nanocarbons in eliminating toxic gas Contaminant in life support system. This knowledge will be utilized in the development of a prototype SWNT KO, gas purification system that would represent a significant step in the development of high efficiency systems capable of selectively removing specific gaseous for use in regenerative life support system for human exploration missions.

  7. Design, synthesis and characterization of a Pt-Gd metal-organic framework containing potentially catalytically active sites.

    Science.gov (United States)

    Szeto, Kai C; Kongshaug, Kjell Ove; Jakobsen, Søren; Tilset, Mats; Lillerud, Karl Petter

    2008-04-21

    The heterobimetallic metal-organic framework {[(BPDC)PtCl(2)](3)(Gd(H(2)O)(3))(2)}.5H(2)O (BPDC = 2,2'-bipyridine-5,5'-dicarboxylate) has been designed and synthesized by hydrothermal methods. The new coordination polymer contains subunits of (BPDC)PtCl(2) (1) where both N atoms of the BPDC ligand are attached to a square-planar Pt(II) center. The two remaining cis coordination sites at Pt(II) are occupied by chloride ions. The final structure (2) of the polymeric network is obtained when Gd(III) ions link together the (BPDC)PtCl(2) units, which are organized in sheets, into larger blocks. These blocks are stacked along the crystallographic [010] direction and are held together by a hydrogen bonding scheme that involves carboxylate oxygen atoms and water molecules in the coordination sphere of Gd. The coordination polymer 2 can be obtained in a single-step reaction or in a two-step synthesis where the corresponding Pt complex (1) was first synthesized followed by reacting 1 with Gd(NO(3))(3).6H(2)O. In situ high temperature powder X-ray diffraction shows that the crystalline coordination polymer transforms into an anhydrous modification at 100 degrees C. This modification is stable to 350 degrees C, at which temperature the structure starts to decompose. The coordination sphere around platinum in the polymer closely resembles organometallic Pt complexes that have been previously found to catalytically or stoichiometrically activate and functionalize hydrocarbon C-H bonds in homogeneous systems.

  8. Impregnation of Catalytic Metals in Single-Walled Carbon Nanotubes for Toxic Gas Conversion in Life Support System

    Science.gov (United States)

    Li, Jing; Wignarajah, Kanapathipillai; Cinke, Marty; Partridge, Harry; Fisher, John

    2004-01-01

    Carbon nanotubes (CNTs) possess extraordinary properties such as high surface area, ordered chemical structure that allows functionalization, larger pore volume, and very narrow pore size distribution that have attracted considerable research attention from around the world since their discovery in 1991. The development and characterization of an original and innovative approach for the control and elimination of gaseous toxins using single walled carbon nanotubes (SWNTs) promise superior performance over conventional approaches due to the ability to direct the selective uptake of gaseous species based on their controlled pore size, increased adsorptive capacity due to their increased surface area and the effectiveness of carbon nanotubes as catalyst supports for gaseous conversion. We present our recent investigation of using SWNTs as catalytic supporting materials to impregnate metals, such as rhodium (Rh), palladium (Pd) and other catalysts. A protocol has been developed to oxidize the SWNTs first and then impregnate the Rh in aqueous rhodium chloride solution, according to unique surface properties of SWNTs. The Rh has been successfully impregnated in SWNTs. The Rh-SWNTs have been characterized by various techniques, such as TGA, XPS, TEM, and FTIR. The project is funded by a NASA Research Announcement Grant to find applications of single walled nanocarbons in eliminating toxic gas Contaminant in life support system. This knowledge will be utilized in the development of a prototype SWNT KO, gas purification system that would represent a significant step in the development of high efficiency systems capable of selectively removing specific gaseous for use in regenerative life support system for human exploration missions.

  9. Occurrence of dead core in catalytic particles containing immobilized enzymes: analysis for the Michaelis-Menten kinetics and assessment of numerical methods.

    Science.gov (United States)

    Pereira, Félix Monteiro; Oliveira, Samuel Conceição

    2016-11-01

    In this article, the occurrence of dead core in catalytic particles containing immobilized enzymes is analyzed for the Michaelis-Menten kinetics. An assessment of numerical methods is performed to solve the boundary value problem generated by the mathematical modeling of diffusion and reaction processes under steady state and isothermal conditions. Two classes of numerical methods were employed: shooting and collocation. The shooting method used the ode function from Scilab software. The collocation methods included: that implemented by the bvode function of Scilab, the orthogonal collocation, and the orthogonal collocation on finite elements. The methods were validated for simplified forms of the Michaelis-Menten equation (zero-order and first-order kinetics), for which analytical solutions are available. Among the methods covered in this article, the orthogonal collocation on finite elements proved to be the most robust and efficient method to solve the boundary value problem concerning Michaelis-Menten kinetics. For this enzyme kinetics, it was found that the dead core can occur when verified certain conditions of diffusion-reaction within the catalytic particle. The application of the concepts and methods presented in this study will allow for a more generalized analysis and more accurate designs of heterogeneous enzymatic reactors.

  10. Particle size distribution of aerosols and associated heavy metals in kitchen environments.

    Science.gov (United States)

    Gupta, Sandeep; Srivastava, Arun; Jain, V K

    2008-07-01

    Mass size distributions of total suspended particulate matter (TSPM) was measured from Sep 2002 to April 2003 in indoor kitchen environments of five locations in Jawaharlal Nehru University (JNU), New Delhi, with the help of a high volume cascade impactor. Particulate matters were separated in five different size ranges, i.e. >10.9 microm, 10.9-5.4 microm, 5.4-1.6 microm, 1.6-0.7 microm and particle size distribution at various sites appears to follow uni-modal trend corresponding to fine particles i.e. size range particles are estimated to be approximately 50% of TSPM and PM10.9, while PM10.9 comprises 80% of TSPM. Good correlations were observed between various size fractions. Regression results reveal that TSPM can adequately act as a surrogate for PM10.9 and fine particles, while PM10.9 can also act as surrogate for fine particles. The concentrations of heavy metals are found to be dominantly associated with fine particles. However, the concentration of some metals and their size distribution, to some extent is also site specific (fuel type used).

  11. 催化裂化提升管反应器中颗粒聚团裂化反应的数值模拟%Numerical Predication of Cracking Reaction of Particle Clusters in Fluid Catalytic Cracking Riser Reactors

    Institute of Scientific and Technical Information of China (English)

    王淑彦; 陆慧林; 高金森; 徐春明; 孙丹

    2008-01-01

    Behavior of catalytic cracking reactions of particle cluster in fluid catalytic cracking(FCC)riser reac-tors was numerically analyzed using a four-lump mathematical model.Effects of the cluster porosity.inlet gas ve-locity and temperature,and coke deposition on cracking reactions of the cluster were investigated. Distributions of temperature,gases,and gasoline from both catalyst particle cluster and an isolated catalyst particle are presented.The reaction rates from vacuum gas oil(VGO)to gasoline,gas and coke of individual particle in the cluster arehigher than those of the isolated particle,but it reverses for the reaction rates from gasoline to gas and coke.Less gasoline is produccd bv particle clustering.Simulated results show that the produced mass fluxes of gas and gasolineincrease with the operating temperature and molar concentration of VGO,and decrease due to the formation of coke.

  12. Transformations of particles, metal elements and natural organic matter in different water treatment processes

    Institute of Scientific and Technical Information of China (English)

    YAN Ming-quan; WANG Dong-sheng; SHI Bao-you; WEI Qun-shan; QU Jiu-hui; TANG Hong-xiao

    2007-01-01

    Characterizing namral organic matter(NOM),particles and elements in different water treatment processes Can give a useful information to optimize water treatment operations.In this article,transformations of particles,metal elements and NOM in a pilot-scale water treatment plant were investigated by laser light granularity system,particle counter,glass-fiber membrane filtration,inductively coupled plasma-optical emission spectroscopy,ultra filtration and resin absorbents fractionation.The results showed that particles,NOM and trihalomethane formation precursors were removed synergistically by sequential treamaent of different processes. Preozonation markedly changed the polarity and molecular weight of NOM.and it could be conducive to the following coagulation processthrough destabilizing particles and colloids;mid-ozonation enhanced the subsequent granular activated carbon(GAC)filtration process by decreasing molecular weight of organic matters.Coagulation-flotation and GAC were more efficient in removing fixed suspended solids and larger particles;while sand-filtration was more effcient in removing volatile suspended solids and smaller particles.Flotation performed better than sedimentation in terms of particle and NOM removal.The type of coagulant could greatly affect the performance of coagulation-flotation.Pre-hydrolyzed composite coagulant(HPAC)was superior to FeCl3 concerning the removals of hydrophobic dissolved organic carbon and volatile suspended solids.The leakages of flocs from sand-filtration and microorganisms from GAC should be mitigated to ensure the reliability of the whole treatment system.

  13. Characteristics of laser supersonic heating method for producing micro metallic particles

    Science.gov (United States)

    Lin, Shih-Lung; Lin, Jehnming

    2005-10-01

    In this article, the authors analyzed the process characteristics of laser supersonic heating method for producing metallic particles and predicted the in-flight tracks and shapes of micro-particles. A pulse Nd-YAG laser was used to heat the carbon steel target placed within an air nozzle. The high-pressure air with supersonic velocity was used to carry out carbon steel particles in the nozzle. The shock wave structures at the nozzle exit were visualized by the shadowgraph method. The carbon steel particles produced by laser supersonic heating method were grabbed and the spraying angles of the particle tracks were visualized. The velocity of the in-flight particles was measured by a photodiode sensor and compared with the numerical result. The solidification of carbon steel particles with diameters of 1-50 μm in compressible flow fields were investigated. The result shows that there is no significant difference in the dimension of solid carbon steel particles produced at shock wave fields under various entrance pressures (3-7 bar) with a constant laser energy radiation.

  14. Synthesis and optical properties of quantum-size metal sulfide particles in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Nedeljkovic, J.M.; Patel, R.C.; Kaufman, P.; Joyce-Pruden, C.; O' Leary, N. (Clarkson Univ., Potsdam, NY (United States))

    1993-04-01

    During the past decade, small-particle' research has become quite popular in various fields of chemistry and physics. The recognition of quantum-size effects in very small colloidal particles has led to renewed interest in this area. Small particles' are clusters of atoms or molecules ranging in size from 1 nm to almost 10 nm or having agglomeration numbers from 10 up to a few hundred. In other words, small particles fall in size between single atoms or molecules and bulk materials. The agglomeration number specifies the number of individual atoms or molecules in a given cluster. The research in this area is interdisciplinary, and it links colloidal science and molecular chemistry. The symbiosis of these two areas of research has revealed some intriguing characteristics of small particles. This experiment illustrates the following: simple colloidal techniques for the preparation of two different types of quantum-size metal sulfide particles; the blue shift of the measured optical absorption spectra when the particle size is decreased in the quantum-size regime; and use of a simple quantum mechanical model to calculate the particle size from the absorption onset measured for CdS.

  15. Reduction of the pea ferredoxin-NADP(H) reductase catalytic efficiency by the structuring of a carboxyl-terminal artificial metal binding site.

    Science.gov (United States)

    Catalano-Dupuy, Daniela L; Orecchia, Martín; Rial, Daniela V; Ceccarelli, Eduardo A

    2006-11-21

    Ferredoxin (flavodoxin)-NADP(H) reductases (FNRs) are ubiquitous flavoenzymes that deliver NADPH or low-potential one-electron donors (ferredoxin, flavodoxin, and adrenodoxin) to redox-based metabolisms in plastids, mitochondria, and bacteria. The FNRs from plants and most eubacteria constitute a unique family, the plant-type ferredoxin-NADP(H) reductases. Plastidic FNRs are quite efficient at sustaining the demands of the photosynthetic process. At variance, FNRs from organisms with heterotrophic metabolisms or anoxygenic photosynthesis display turnover numbers that are 20-100-fold lower than those of their plastidic and cyanobacterial counterparts. To gain insight into the FNR structural features that modulate enzyme catalytic efficiency, we constructed a recombinant FNR in which the carboxyl-terminal amino acid (Tyr308) is followed by an artificial metal binding site of nine amino acids, including four histidine residues. This added structure binds Zn2+ or Co2+ and, as a consequence, significantly reduces the catalytic efficiency of the enzyme by decreasing its kcat. The Km for NADPH and the Kd for NADP+ were increased 2 and 3 times, respectively, by the addition of the amino acid extension in the absence of Zn2+. Nevertheless, the structuring of the metal binding site did not change the Km for NADPH or the Kd for NADP+ of the FNR-tail enzyme. Our results provide experimental evidence which indicates that mobility of the carboxyl-terminal backbone region of the FNR, mainly Tyr308, is essential for obtaining an FNR enzyme with high catalytic efficiency.

  16. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    Energy Technology Data Exchange (ETDEWEB)

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-08-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O{sub 3}, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than {approx}8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

  17. Ultrafine particles emitted by flame and electric arc guns for thermal spraying of metals.

    Science.gov (United States)

    Bémer, Denis; Régnier, Roland; Subra, Isabelle; Sutter, Benjamin; Lecler, Marie T; Morele, Yves

    2010-08-01

    The ultrafine aerosol emitted by thermal spraying of metals using flame and electric arc processes has been characterized in terms of particle size distribution and emission rates based on both particle number and mass. Thermal spraying of Zn, Zn/Al, and Al was studied. Measurements taken using an electrical low pressure impactor and a condensation nucleus counter reveal an aerosol made up of very fine particles (80-95% of number distribution electric arc process are very high, the largest values being recorded during spraying of pure aluminium. This process generates high particle emissions and therefore requires careful consideration and possible rethinking of currently implemented protection measures: ventilated cabins, dust collectors, and personal protective equipment.

  18. Enhanced Laser Cooling of Rare-Earth-Ion-Doped Glass Containing Nanometer-Sized Metallic Particles

    Institute of Scientific and Technical Information of China (English)

    JIA You-Hun; ZHONG Biao; YIN Jian-Ping

    2009-01-01

    The enhanced laser cooling performance of rare-earth-ions-doped glasses containing small particles is predicted. This is achieved by the enhancement of local field around rare earth ions, owing to the surface plasmon resonance of small metallic particles. The role of energy transfer between ions and the particle is theoretical discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption and the fluorescence is predicted. Moreover, taking Yb3+-doped ZBLAN as example, the cooling power and heat-light converting efficiency are calculated. It is finally concluded that the absorption and the fluorescence are greatly enhanced in these composite materials, the cooling power is increased compared to the bulk material.

  19. Digital image processing of nanometer-size metal particles on amorphous substrates

    Science.gov (United States)

    Soria, F.; Artal, P.; Bescos, J.; Heinemann, K.

    1989-01-01

    The task of differentiating very small metal aggregates supported on amorphous films from the phase contrast image features inherently stemming from the support is extremely difficult in the nanometer particle size range. Digital image processing was employed to overcome some of the ambiguities in evaluating such micrographs. It was demonstrated that such processing allowed positive particle detection and a limited degree of statistical size analysis even for micrographs where by bare eye examination the distribution between particles and erroneous substrate features would seem highly ambiguous. The smallest size class detected for Pd/C samples peaks at 0.8 nm. This size class was found in various samples prepared under different evaporation conditions and it is concluded that these particles consist of 'a magic number' of 13 atoms and have cubooctahedral or icosahedral crystal structure.

  20. 希夫碱类金属配合物催化剂催化氧化烯烃研究进展%Progress in research of Schiff base metal complexes catalytic using for olefins catalytic oxidation

    Institute of Scientific and Technical Information of China (English)

    冯辉霞; 李汉峰; 王利杰

    2011-01-01

    The structure of metal complexes characteristic of Schiff base was analyzed and catalytic oxidation olefins was studied on current situation systematically.And it expressed the classification application of Schiff base which used in type of homogeneous catalysis oxidization and metal complexes of solid catalyst.By analyzing the defects of small molecules metal complexes catalysis-oxidization olefins,the conclusion indicated that the heterogeneous load type of metal complexes of Schiff base in category catalyst is the main development direction in present.%分析了希夫碱金属配合物的结构特点及其催化氧化烯烃的研究现状,阐述了用于均相催化氧化的希夫碱、固载型希夫碱金属配合物催化剂的分类及其在氧化烯烃领域的应用研究.通过分析希夫碱类小分子金属配合物催化氧化烯烃的缺陷,得出非均相的负载型希夫碱类金属配合物催化剂是目前主要发展方向的结论.

  1. Gas phase metal cluster model systems for heterogeneous catalysis.

    Science.gov (United States)

    Lang, Sandra M; Bernhardt, Thorsten M

    2012-07-14

    Since the advent of intense cluster sources, physical and chemical properties of isolated metal clusters are an active field of research. In particular, gas phase metal clusters represent ideal model systems to gain molecular level insight into the energetics and kinetics of metal-mediated catalytic reactions. Here we summarize experimental reactivity studies as well as investigations of thermal catalytic reaction cycles on small gas phase metal clusters, mostly in relation to the surprising catalytic activity of nanoscale gold particles. A particular emphasis is put on the importance of conceptual insights gained through the study of gas phase model systems. Based on these concepts future perspectives are formulated in terms of variation and optimization of catalytic materials e.g. by utilization of bimetals and metal oxides. Furthermore, the future potential of bio-inspired catalytic material systems are highlighted and technical developments are discussed.

  2. Synthesis of supported metallic nano-particles and their use in air depollution; Des nanoparticules metalliques supportees pour la depollution de l'air

    Energy Technology Data Exchange (ETDEWEB)

    Barrault, J. [Centre National de la Recherche Scientifique (CNRS), 86 - Poitiers (France); Valange, S. [Poitiers Univ., 86 (France); Tatibouet, J.M. [Centre National de la Recherche Scientifique (CNRS), Lab. de Catalyse en Chimie Organique, UMR CNRS 6503, 86 - Poitiers (France); Thollon, St. [CEA Grenoble (DRT/DTNM/LTS), 38 (France); Herlin-Boime, N. [CEA Saclay, IRAMIS, Service des Photons, Atomes et Molecules, Lab. Francis Perrin, CEA-CNRS URA 2453, 91 - Gif-sur-Yvette (France); Giraud, S. [CEA Saclay (DEN/SRMA), 91 - Gif-sur-Yvette (France); Ruiz, J.Ch. [CEA Marcoule (DTCD/SPDE/LFSM), 30 (France); Bergaya, B. [CRT Plasma lASER, 45 - Orleans (France); Joulin, J.P.; Delbianco, N. [Ceramiques Techniques Industrielles (CTI-SA), 30 - Salindres (France); Gabelica, Z. [Universite de Haute-Alsace (LPI-GSEC), ENSCMu, 68 - Mulhouse (France); Daturi, M. [Ecole Nationale Superieure d' Ingenieurs de Caen (ENSICAEN), CNRS-LCS, UMR 6506, 14 - Caen (France)

    2009-06-15

    The main objectives of the 'NACACOMO' Consortium ('Nano-materials: Catalysts for the Conversion of organic Molecules. Uses in fine chemicals and environment protection ') consisted in generating novel catalysts composed of nanoparticles of metals (Pt, Pd, Ag...) and/or oxides (TiO{sub 2}...) stabilized and well distributed over the surface of a support (foams, ceramics), by monitoring both the particle size and the 'coating' process itself, using new technologies: CVD, plasma-spray, laser pyrolysis, supercritical preparation, which were compared to conventional soft chemistry recipes. The most accurate characterization of particle morphology, local structure, texture, spatial arrangement but also of their reactivity, were achieved by privileging the utilization of various in situ methods. Details on formation mechanisms of a solid nano-particle at the atomic level (nucleation, growth and particle (re)distribution over the support...) could be obtained in selected cases, with opportunities for scaling up and shaping. The (chemical) nature of the so-obtained nano-materials was monitored for selected catalytic applications involving the development of environmental friendly processes, such as oxidation of VOC, with a priority for aromatics and chlorinated compounds. (authors)

  3. Improving the porosity and catalytic capacity of a zinc paddlewheel metal-organic framework (MOF) through metal-ion metathesis in a single-crystal-to-single-crystal fashion.

    Science.gov (United States)

    Yang, Jie; Wang, Xiaoqing; Dai, Fangna; Zhang, Liangliang; Wang, Rongming; Sun, Daofeng

    2014-10-06

    Zinc paddlewheel metal-organic frameworks (MOFs) frequently exhibit low stability or complete collapse upon the removal of axial ligands. Hence, there are very few reports on gas adsorption of zinc paddlewheel MOFs. In this work, the N2 and H2 adsorption measurements were carried out for a zinc MOF (namely, SDU-1) based on two types of paddlewheel secondary building units (SBUs): [Zn2(COO)3] and [Zn2(COO)4]. Because of the existence of inherent surface instability upon removal of solvates in zinc paddlewheel SBU, SDU-1 possesses a very low surface area. Through metal-ion metathesis in a single-crystal-to-single-crystal fashion, the Zn(2+) ions in SDU-1 were exchanged by Cu(2+) ions to generate Cu-SDU-1. Through the measurements of gas adsorption and catalytic test, the porosity and catalytic capacity of Cu-SDU-1 have been improved significantly, compared to SDU-1.

  4. Persistence of Metal-rich Particles Downstream Zones of Acid Drainage Mixing in Andean Rivers

    Science.gov (United States)

    Pasten, P.; Montecinos, M.; Guerra, P. A.; Bonilla, C. A.; Escauriaza, C. R.; Dabrin, A.; Coquery, M.

    2016-12-01

    The Andes mountain range provides the setting for watersheds with high natural background of metals and for mining operations that enhance contaminant mobilization, notably in Northern and Central Chile. Dissolved and solid metal species are actively transported by streams to the Pacific Ocean from area and point sources, like acid drainage. We examine the response of metal rich particle suspensions downstream zones of mixing where shifts in the chemical environment occur. We propose a conceptual model which is used to analyze the fate of copper in the upper Mapocho watershed. The main source of copper is the Yerba Loca river, a naturally impacted stream with pH ranging from 3 to 7 and high concentrations of Cu (0.8 - 6.3 mg/L), Al (1.3 - 7.6 mg/L) and Fe (0.4 - 4.2 mg/L). Steep chemical shifts occur after the confluences with the San Francisco and the Molina rivers. We characterized stream chemistry, hydrological variables and suspended particles, including particle size distribution (PSD), turbidity, and total suspended solids. A marked seasonal behavior was observed, with a higher total Cu flux during smelting periods and a shift towards the dissolved phase during summer. When acid drainage is discharged into a receiving stream, incomplete mixing occurs thereby promoting the formation of a range of metal-rich solids with a characteristic PSD. Similarly, areas of chemical heterogeneity control the partition of metals associated to suspended geomaterials coming from bank and slope erosion. A highly dynamic process ensues where metastable phases shift to new equilibria as fully mixed conditions are reached. Depending on the reaction kinetics, some particles persist despite being exposed to thermodynamically unfavorable chemical environments. The persistence of metal-rich particles downstream zones of acid drainage mixing is important because it ultimately controls the flux of metals being delivered to the ocean by watersheds impacted by acid drainage. Funding from

  5. An Analysis of the Retention of a Diamond Particle in a Metallic Matrix after Hot Pressing

    Directory of Open Access Journals (Sweden)

    Borowiecka-Jamrozek J.

    2017-03-01

    Full Text Available This paper deals with computer modelling of the retention of a synthetic diamond particle in a metallic matrix produced by powder metallurgy. The analyzed sintered powders can be used as matrices for diamond impregnated tools. First, the behaviour of sintered cobalt powder was analyzed. The model of a diamond particle embedded in a metallic matrix was created using Abaqus software. The preliminary analysis was performed to determine the mechanical parameters that are independent of the shape of the crystal. The calculation results were compared with the experimental data. Next, sintered specimens obtained from two commercially available powder mixtures were studied. The aim of the investigations was to determine the influence of the mechanical and thermal parameters of the matrix materials on their retentive properties. The analysis indicated the mechanical parameters that are responsible for the retention of diamond particles in a matrix. These mechanical variables have been: the elastic energy of particle, the elastic energy of matrix and the radius of plastic zone around particle.

  6. Growth dynamics of carbon-metal particles and nanotubes synthesized by CO2 laser vaporization

    Science.gov (United States)

    Kokai, F.; Takahashi, K.; Yudasaka, M.; Iijima, S.

    To study the growth of carbon-Co/Ni particles and single-wall carbon nanotubes (SWNTs) by 20 ms CO2 laser-pulse irradiation of a graphite-Co/Ni (1.2 at.%) target in an Ar gas atmosphere (600 Torr), we used emission imaging spectroscopy and shadowgraphy with a temporal resolution of 1.67 ms. Wavelength-selected emission images showed that C2 emission was strong in the region close to the target (within 2 cm), while for the same region the blackbody radiation from the large clusters or particles increased with increasing distance from the target. Shadowgraph images showed that the viscous flow of carbon and metal species formed a mushroom or a turbulent cloud spreading slowly into the Ar atmosphere, indicating that particles and SWNTs continued to grow as the ejected material cooled. In addition, emission imaging spectroscopy at 1200 °C showed that C2 and hot clusters and particles with higher emission intensities were distributed over much wider areas. We discuss the growth dynamics of the particles and SWNTs through the interaction of the ambient Ar with the carbon and metal species released from the target by the laser pulse.

  7. Solidification analysis of micro-scale metallic particles in the laser supersonic heating technique

    Science.gov (United States)

    Lin, Shih-Lung; Lin, Jehnming

    2004-04-01

    In this paper, the authors analysed the solidification phenomenon in the laser supersonic heating technique used for producing metallic particles. A mathematical model was established to predict the velocity, temperature and solidification situation of metallic particles leaving a spray nozzle. The numerical analysis method was used to simulate the flow field structure of shock waves and to proceed with related experiment. In the experiment, a pulsed Nd-YAG laser was used as the heat source on a carbon steel target within the nozzle, and carbon steel particles were ejected by high pressure air. The solidification problem of carbon steel particles with radii of 1-50 µm in the compressible flow field was calculated and compared with experimental results. The result shows that the shock wave flow fields are generated at different entrance pressures (3-7 bar), and there is no significant difference in the radii of carbon steel particles produced by a fixed laser energy; however, in the flow field without the shock wave effect, the cooling effect is less evident in the solidification process.

  8. Characterization of airborne particles generated from metal active gas welding process.

    Science.gov (United States)

    Guerreiro, C; Gomes, J F; Carvalho, P; Santos, T J G; Miranda, R M; Albuquerque, P

    2014-05-01

    This study is focused on the characterization of particles emitted in the metal active gas welding of carbon steel using mixture of Ar + CO2, and intends to analyze which are the main process parameters that influence the emission itself. It was found that the amount of emitted particles (measured by particle number and alveolar deposited surface area) are clearly dependent on the distance to the welding front and also on the main welding parameters, namely the current intensity and heat input in the welding process. The emission of airborne fine particles seems to increase with the current intensity as fume-formation rate does. When comparing the tested gas mixtures, higher emissions are observed for more oxidant mixtures, that is, mixtures with higher CO2 content, which result in higher arc stability. These mixtures originate higher concentrations of fine particles (as measured by number of particles by cm(3) of air) and higher values of alveolar deposited surface area of particles, thus resulting in a more severe worker's exposure.

  9. Effect of Phosphine Doping and the Surface Metal State of Ni on the Catalytic Performance of Ni/Al2O3 Catalyst

    Directory of Open Access Journals (Sweden)

    Xiaoru Li

    2015-04-01

    Full Text Available Ni-based catalysts as replacement for noble metal catalysts are of particular interest in the catalytic conversion of biomass due to their cheap and satisfactory catalytic activity. The Ni/SiO2 catalyst has been studied for the hydrogenolysis of glycerol, and doping with phosphorus (P found to improve the catalytic performance significantly because of the formation of Ni2P alloys. However, in the present work we disclose a different catalytic phenomenon for the P-doped Ni/Al2O3 catalyst. We found that doping with P has a significant effect on the state of the active Ni species, and thus improves the selectivity to 1,2-propanediol (1,2-PDO significantly in the hydrogenolysis of glycerol, although Ni-P alloys were not observed in our catalytic system. The structure and selectivity correlations were determined from the experimental data, combining the results of X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, hydrogen temperature-programmed reduction (H2-TPR and ammonia temperature-programmed desorption (NH3-TPD. The presence of NiO species, formed from P-doped Ni/Al2O3 catalyst, was shown to benefit the formation of 1,2-PDO. This was supported by the results of the Ni/Al2O3 catalyst containing NiO species with incomplete reduction. Furthermore, the role the NiO species played in the reaction and the potential reaction mechanism over the P-doped Ni/Al2O3 catalyst is discussed. The new findings in the present work open a new vision for Ni catalysis and will benefit researchers in designing Ni-based catalysts.

  10. Absorbed dose assessment in particle-beam irradiated metal-oxide and metal-nonmetal memristors

    Directory of Open Access Journals (Sweden)

    Knežević Ivan D.

    2012-01-01

    Full Text Available Absorbed dose was estimated after Monte Carlo simulation of proton and ion beam irradiation on metal-oxide and metal-nonmetal memristors. A memristive device comprises two electrodes, each of a nanoscale width, and a double-layer active region disposed between and in electrical contact with electrodes. Following materials were considered for the active region: titanium dioxide, zirconium dioxide, hafnium dioxide, strontium titanium trioxide and galium nitride. Obtained results show that significant amount of oxygen ion - oxygen and nonmetal ion - nonmetal vacancy pairs is to be generated. The loss of such vacancies from the device is believed to deteriorate the device performance over time. Estimated absorbed dose values in the memristor for different constituting materials are of the same order of magnitude because of the close values of treshold displacement energies for the investigated materials.

  11. In-flight behavior of dissimilar co-injected particles in the spraying of metal-ceramic functionally gradient materials

    Energy Technology Data Exchange (ETDEWEB)

    Fincke, J.R.; Swank, W.D.; Haggard, D.C. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1997-12-31

    In the spraying of functionally gradient coatings the particle ensemble delivered to the substrate can vary from a relatively low melting point metallic particle to a significantly higher melting point ceramic particle. At various stages in the spray process the particle ensemble can be either predominantly metallic, ceramic, or an intermediate combination. For co-injected particles the mixtures do not behave as a simple linear superposition of the spray patterns of the individual particle types. The particle temperature, velocity, size distributions, and pattern characteristics of the resulting spray fields is examined for all ceramic particle sprays (ZrO{sub 2}), all metallic particle sprays (NiCrAlY), and for a 1:1 mixture. The major particle-particle interaction occurs in the injector itself and results in a modified spray pattern which is different from that of either material sprayed alone. The particle velocity distributions generally exhibit a bimodal nature which is dependent on the size and density of the injected particles.

  12. Metal-contaminated resuspended sediment particles are a minor metal-uptake route for the Sydney rock oyster (Saccostrea glomerata)--A mesocosm study, Sydney Harbour estuary, Australia.

    Science.gov (United States)

    Lee, J-H; Birch, G F; Simpson, S L

    2016-03-15

    Resuspension of surficial sediments is considered a key process influencing bioaccumulation of metals in filter-feeders in the contaminated Sydney Harbour estuary (Australia). However, previous investigations were unable to establish a significant relationship between metals in sediments or suspended particulate matter (SPM) and oyster tissue concentrations. This study used a 60-d laboratory mesocosm experiment to expose Sydney rock oysters, Saccostrea glomerata, to a natural range of SPM concentrations with different SPM-metal concentrations. Dissolved metal concentrations were low and the availability of algae provided as food was constant for all treatments. Tissue metal concentrations of Cu, Pb and Zn increased significantly, however, no relationship was determined between tissue metal concentrations in the oyster and either SPM or SPM-metal concentrations. The results indicated that exposure to resuspended contaminated sediment particles contributed little to the observed metal uptake. Dissolved or algae food sources appear to be more important for metal accumulation in these oysters.

  13. Theoretic model and computer simulation of separating mixture metal particles from waste printed circuit board by electrostatic separator.

    Science.gov (United States)

    Li, Jia; Xu, Zhenming; Zhou, Yaohe

    2008-05-30

    Traditionally, the mixture metals from waste printed circuit board (PCB) were sent to the smelt factory to refine pure copper. Some valuable metals (aluminum, zinc and tin) with low content in PCB were lost during smelt. A new method which used roll-type electrostatic separator (RES) to recovery low content metals in waste PCB was presented in this study. The theoretic model which was established from computing electric field and the analysis of forces on the particles was used to write a program by MATLAB language. The program was design to simulate the process of separating mixture metal particles. Electrical, material and mechanical factors were analyzed to optimize the operating parameters of separator. The experiment results of separating copper and aluminum particles by RES had a good agreement with computer simulation results. The model could be used to simulate separating other metal (tin, zinc, etc.) particles during the process of recycling waste PCBs by RES.

  14. Data on the histological and immune cell response in the popliteal lymph node in mice following exposure to metal particles and ions.

    Science.gov (United States)

    Winans, Bethany; Tvermoes, Brooke E; Unice, Kenneth M; Kovochich, Michael; Fung, Ernest S; Christian, Whitney V; Donovan, Ellen; Finley, Brent L; Kimber, Ian; Paustenbach, Dennis J

    2016-12-01

    Hip implants containing cobalt-chromium (CoCr) have been used for over 80 years. In patients with metal-on-metal (MoM) hip implants, it has been suggested that wear debris particles may contribute to metal sensitization in some individuals, leading to adverse reactions. This article presents data from a study in which the popliteal lymph node assay (PLNA) was used to assess immune responses in mice treated with chromium-oxide (Cr2O3) particles, metal salts (CoCl2, CrCl3, and NiCl2) or Cr2O3 particles with metal salts ("A preliminary evaluation of immune stimulation following exposure to metal particles and ions using the mouse popliteal lymph node assay" (B.E. Tvermoes, K.M. Unice, B. Winans, M. Kovochich, E.S. Fung, W.V. Christian, E. Donovan, B.L. Finley, B.L. Kimber, I. Kimber, D.J. Paustenbach, 2016) [1]). Data are presented on (1) the chemical characterization of TiO2 particles (used as a particle control), (2) clinical observations in mice treated with Cr2O3 particles, metal salts or Cr2O3 particles with metal salts, (3) PLN weight and weight index (WI) in mice treated with Cr2O3 particles, metal salts or Cr2O3 particles with metal salts, (4) histological changes in PLNs of mice treated with Cr2O3 particles, metal salts or Cr2O3 particles with metal salts, (5) percentages of immune cells in the PLNs of mice treated with Cr2O3 particles, metal salts or Cr2O3 particles with metal salts, and (6) percentages of proliferating cells in the PLNs of mice treated with Cr2O3 particles, metal salts or Cr2O3 particles with metal salts.

  15. Effects of particle composition and environmental parameters on catalytic hydrodechlorination of trichloroethylene by nanoscale bimetallic Ni-Fe.

    Science.gov (United States)

    Wei, Jianjun; Qian, Yajing; Liu, Wenjuan; Wang, Lutao; Ge, Yijie; Zhang, Jianghao; Yu, Jiang; Ma, Xingmao

    2014-05-01

    Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene (TCE), one of the most commonly detected chlorinated organic compounds in groundwater. Ethane was the predominant product. The greatest dechlorination efficiency was achieved at 22 molar percent of nickel. This nanoscale Ni-Fe is poorly ordered and inhomogeneous; iron dissolution occurred whereas nickel was relatively stable during the 24-hr reaction. The morphological characterization provided significant new insights on the mechanism of catalytic hydrodechlorination by bimetallic nanoparticles. TCE degradation and ethane production rates were greatly affected by environmental parameters such as solution pH, temperature and common groundwater ions. Both rate constants decreased and then increased over the pH range of 6.5 to 8.0, with the minimum value occurring at pH 7.5. TCE degradation rate constant showed an increasing trend over the temperature range of 10 to 25°C. However, ethane production rate constant increased and then decreased over the range, with the maximum value occurring at 20°C. Most salts in the solution appeared to enhance the reaction in the first half hour but overall they displayed an inhibitory effect. Combined ions showed a similar effect as individual salts.

  16. Effect of selective catalytic reduction (SCR) on fine particle emission from two coal-fired power plants in China

    Science.gov (United States)

    Li, Zhen; Jiang, Jingkun; Ma, Zizhen; Wang, Shuxiao; Duan, Lei

    2015-11-01

    Nitrogen oxides (NOx) emission abatement of coal-fired power plants (CFPPs) requires large-scaled installation of selective catalytic reduction (SCR), which would reduce secondary fine particulate matter (PM2.5) (by reducing nitrate aerosol) in the atmosphere. However, our field measurement of two CFPPs equipped with SCR indicates a significant increase of SO42- and NH4+ emission in primary PM2.5, due to catalytic enhancement of SO2 oxidation to SO3 and introducing of NH3 as reducing agent. The subsequent formation of (NH4)2SO4 or NH4HSO4 aerosol is commonly concentrated in sub-micrometer particulate matter (PM1) with a bimodal pattern. The measurement at the inlet of stack also showed doubled primary PM2.5 emission by SCR operation. This effect should therefore be considered when updating emission inventory of CFPPs. By rough estimation, the enhanced primary PM2.5 emission from CFPPs by SCR operation would offset 12% of the ambient PM2.5 concentration reduction in cities as the benefit of national NOx emission abatement, which should draw attention of policy-makers for air pollution control.

  17. Effect of promoter and noble metals and suspension pH on catalytic nitrate reduction by bimetallic nanoscale Fe(0) catalysts.

    Science.gov (United States)

    Bae, Sungjun; Hamid, Shanawar; Jung, Junyoung; Sihn, Youngho; Lee, Woojin

    2016-01-01

    Experiments were conducted to investigate the effect of experimental factors (types of promotor and noble metals, H2 injection, and suspension pH) on catalytic nitrate reduction by bimetallic catalysts supported by nanoscale zero-valent iron (NZVI). NZVI without H2 injection showed 71% of nitrate reduction in 1 h. Cu/NZVI showed the almost complete nitrate reduction (96%) in 1 h, while 67% of nitrate was reduced by Ni/NZVI. The presence of noble metals (Pd and Pt) on Cu/NZVI without H2 injection resulted in the decrease of removal efficiency to 89% and 84%, respectively, due probably to the electron loss of NZVI for formation of metallic Pd and Pt. H2 injection into Cu-Pd/NZVI suspension significantly improved both catalytic nitrate reduction (>97% in 30 min) and N2 selectivity (18%), indicating that adsorbed H on active Pd sites played an important role for the enhanced nitrate reduction and N2 selectivity. The rapid passivation of NZVI surface resulted in a dramatic decrease in nitrate reduction (79-28%) with an increase in N2 selectivity (8-66%) as the suspension pH increased from 8 to 10.

  18. Catalytic property of an indium-deposited powder-type material containing silicon and its dependence on the dose of indium nano-particles irradiated by a pulse arc plasma process

    Directory of Open Access Journals (Sweden)

    Satoru Yoshimura

    2017-06-01

    Full Text Available Indium nano-particle irradiations onto zeolite powders were carried out using a pulse arc plasma source system. X-ray photoelectron spectroscopic and scanning electron microscopic studies of an indium irradiated zeolite sample revealed that indium nano-particles were successfully deposited on the sample. Besides, the sample was found to be capable of catalyzing an organic chemical reaction (i.e., Friedel-Crafts alkylation. Then, we examined whether or not the catalytic ability depends on the irradiated indium dose, having established the optimal indium dose for inducing the catalytic effect.

  19. Magnetic response from a composite of metal-dielectric particles in the visible range: T-matrix simulation

    Directory of Open Access Journals (Sweden)

    O. Zhuromskyy

    2011-09-01

    Full Text Available The optical response of a particle composed of a dielectric core surrounded by a densely packed shell of small metal spheres is simulated with the superposition Tmatrix method for realistic material parameters. In order to compute the electric and magnetic particle polarizabilities a single expansion T-matrix is derived from a particle centered T-matrix. Finally the permeability of a medium comprising such particles is found to deviate considerable from unity resulting in a noticeable optical response.

  20. High Activity of Ce1-xNixO2-y for H2 Production through Ethanol Steam Reforming: Tuning Catalytic Performance through Metal-Oxide Interactions

    Energy Technology Data Exchange (ETDEWEB)

    G Zhou; L Barrio; S Agnoli; S Senanayake; J Evans; A Kubacka; M Estrella; J Hanson; A Martinez-Arias; et al.

    2011-12-31

    The importance of the oxide: Ce{sub 0.8}Ni{sub 0.2}O{sub 2-y} is an excellent catalyst for ethanol steam reforming. Metal-oxide interactions perturb the electronic properties of the small particles of metallic nickel present in the catalyst under the reaction conditions and thus suppress any methanation activity. The nickel embedded in ceria induces the formation of O vacancies, which facilitate cleavage of the OH bonds in ethanol and water.

  1. Environmental and health impacts of fine and ultrafine metallic particles: Assessment of threat scores

    Energy Technology Data Exchange (ETDEWEB)

    Goix, Sylvaine [Université de Toulouse, INP-ENSAT, Av. Agrobiopôle, 31326 Castanet-Tolosan (France); UMR 5245 CNRS-INP-UPS, EcoLab (Laboratoire d' écologie fonctionnelle), Avenue de l' Agrobiopôle, BP 32607, 31326 Castanet-Tolosan (France); Lévêque, Thibaut [Université de Toulouse, INP-ENSAT, Av. Agrobiopôle, 31326 Castanet-Tolosan (France); UMR 5245 CNRS-INP-UPS, EcoLab (Laboratoire d' écologie fonctionnelle), Avenue de l' Agrobiopôle, BP 32607, 31326 Castanet-Tolosan (France); ADEME (French Agency for Environment and Energy Management), 20 Avenue du Grésillé, BP 90406, 49004 Angers Cedex 01 (France); Xiong, Tian-Tian [Université de Toulouse, INP-ENSAT, Av. Agrobiopôle, 31326 Castanet-Tolosan (France); UMR 5245 CNRS-INP-UPS, EcoLab (Laboratoire d' écologie fonctionnelle), Avenue de l' Agrobiopôle, BP 32607, 31326 Castanet-Tolosan (France); Schreck, Eva [Géosciences Environnement Toulouse (GET), Observatoire Midi Pyrénées, Université de Toulouse, CNRS, IRD, 14 Avenue E. Belin, F-31400 Toulouse (France); and others

    2014-08-15

    This study proposes global threat scores to prioritize the harmfulness of anthropogenic fine and ultrafine metallic particles (FMP) emitted into the atmosphere at the global scale. (Eco)toxicity of physicochemically characterized FMP oxides for metals currently observed in the atmosphere (CdO, CuO, PbO, PbSO{sub 4}, Sb{sub 2}O{sub 3}, and ZnO) was assessed by performing complementary in vitro tests: ecotoxicity, human bioaccessibility, cytotoxicity, and oxidative potential. Using an innovative methodology based on the combination of (eco)toxicity and physicochemical results, the following hazard classification of the particles is proposed: CdCl{sub 2}∼CdO>CuO>PbO>ZnO>PbSO{sub 4}>Sb{sub 2}O{sub 3}. Both cadmium compounds exhibited the highest threat score due to their high cytotoxicity and bioaccessible dose, whatever their solubility and speciation, suggesting that cadmium toxicity is due to its chemical form rather than its physical form. In contrast, the Sb{sub 2}O{sub 3} threat score was the lowest due to particles with low specific area and solubility, with no effects except a slight oxidative stress. As FMP physicochemical properties reveal differences in specific area, crystallization systems, dissolution process, and speciation, various mechanisms may influence their biological impact. Finally, this newly developed and global approach could be widely used in various contexts of pollution by complex metal particles and may improve risk management. - Highlights: • Seven micro- and nano- monometallic characterized particles were studied as references. • Bioaccessibility, eco and cytotoxicity, and oxidative potential assays were performed. • According to calculated threat scores: CdCl{sub 2}∼CdO>CuO>PbO>ZnO>PbSO{sub 4}>Sb{sub 2}O{sub 3}.

  2. Effect of particle size on thermal decomposition of alkali metal picrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Rui; Zhang, Tonglai, E-mail: ztlbit@bit.edu.cn; Yang, Li; Zhou, Zunning

    2014-05-01

    Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate.

  3. RESEARCH ON REUSE OF PAPERMAKING LIGNIN-CONVERSION OF LIGNIN TO BTX BY CATALYTIC PYROLYSIS IN A POWDER PARTICLE FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    Chang Wang; Chongwo Li; Qingzhu Jia

    2004-01-01

    Experiments on the catalytic pyrolysis of the papermaking lignin were conduced by using a new type of powder-particle fluidized bed to improve the yield of the light aromatic hydrocarbon, i.e. benzene,toluene, xylene and naphthalene (BTXN), in which the primary decomposition and secondary catalytic reaction occur simultaneously at ambient pressure.The effect of catalyst species, fluidizing gases and pyrolysis temperature on the yield of the BTXN were investigated. The content of sulfur is high in the papermaking lignin, and the volatile matter is effected by the temperature. In the case of the inert media silica sand, the yield and the distribution of the pyrolysis products were almost unchanged under the different kind of atmosphere. In the case of the catalyst CoMo-B with hydrogen atmosphere, the intermediate BTXN yield reached 2.52wt%, dry, 3.3 times as much as that in the case of silica sand.Therefore, in order to obtain valuable BTXN as an intermediate in the pyrolysis as much as possible, it is extremely important to select high sulfur resistance and hydrogenization activity catalyst.

  4. RESEARCH ON REUSE OF PAPERMAKING LIGNIN-CONVERSION OF LIGNIN TO BTX BY CATALYTIC PYROLYSIS IN A POWDER PARTICLE FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    ChangWang; ChongwoLi; QingzhuJia

    2004-01-01

    Experiments on the catalytic pyrolysis of the papermaking lignin were conduced by using a new type of powder-particle fluidized bed to improve the yield of the light aromatic hydrocarbon, i.e. benzene, toluene, xylene and naphthalene (BTXN), in which the primary decomposition and secondary catalytic reaction occur simultaneously at ambient pressure. The effect of catalyst species, fluidizing gases and pyrolysis temperature on the yield of the BTXN were investigated. The content of sulfur is high in the papermaking lignin, and the volatile matter is effected by the temperature. In the case of the inert media silica sand, the yield and the distribution of the pyrolysis products were almost unchanged under the different kind of atmosphere. In the case of the catalyst CoMo-B with hydrogen atmosphere, the intermediate BTXN yield reached 2.52wt%, dry, 3.3 times as much as that in the case of silica sand. Therefore, in order to obtain valuable BTXN as an intermediate in the pyrolysis as much as possible, it is extremely important to select high sulfur resistance and hydrogenization activity catalyst.

  5. The catalytic activity of the iron-coated pumice particles used as heterogeneous catalysts in the oxidation of natural organic matter by H2O2.

    Science.gov (United States)

    Alver, Alper; Karaarslan, Mihrican; Kılıç, Ahmet

    2016-08-01

    The oxidative removal of natural organic matter (NOM) from waters was investigated by hydrogen peroxide (H2O2) and iron-coated pumice particles in heterogeneous catalytic oxidation process (HCOP). Removal of trihalomethane (THM) precursors, which is formed THM by the reacts with chloride, was performed with the hydroxyl radicals. Coating the original pumice particles with iron oxides significantly enhanced the removal of NOM with peroxide. The studies were carried out in two sections: (1) decomposition of hydrogen peroxide in pure water with iron-coated pumice and (2) oxidation of THM Precursor (NOM) by hydrogen peroxide with iron-coated pumice. The monitored parameters in this study include dissolved organic carbon and trihalomethanes formation potential. The results show that iron-coated pumice catalyst significantly increased the removal efficiency of NOM in the HCOP. The results show that iron-coated pumice catalyst significantly increased the removal efficiency of NOM in the HCOP. Results show that the oxidation of NOM and remaining NOM with H2O2 is improved by the addition of iron-coated pumice particles which activate the H2O2 molecule, leading to the formation of hydroxyl radicals in a Fenton-like process.

  6. Anisotropic Metal Deposition on TiO2 Particles by Electric-Field-Induced Charge Separation.

    Science.gov (United States)

    Tiewcharoen, Supakit; Warakulwit, Chompunuch; Lapeyre, Veronique; Garrigue, Patrick; Fourier, Lucas; Elissalde, Catherine; Buffière, Sonia; Legros, Philippe; Gayot, Marion; Limtrakul, Jumras; Kuhn, Alexander

    2017-09-11

    Deposition of metals on TiO2 semiconductor particles (M-TiO2 ) results in hybrid Janus objects combining the properties of both materials. One of the techniques proposed to generate Janus particles is bipolar electrochemistry (BPE). The concept can be applied in a straightforward way for the site-selective modification of conducting particles, but is much less obvious to use for semiconductors. Herein we report the bulk synthesis of anisotropic M-TiO2 particles based on the synergy of BPE and photochemistry, allowing the intrinsic limitations, when they are used separately, to be overcome. When applying electric fields during irradiation, electrons and holes can be efficiently separated, thus breaking the symmetry of particles by modifying them selectively and in a wireless way on one side with either gold or platinum. Such hybrid materials are an important first step towards high-performance designer catalyst particles, for example for photosplitting of water. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Metallic particles into mechanical and hydraulic systems in agricultural and construction machines

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Jair Rosas da; Silva, Deise Paula da [Instituto Agronomico de Campinas (IAC), Campinas, SP (Brazil). Centro de Engenharia Agricola; Bormio, Marcos Roberto [Universidade Estadual Paulista (UNESP), Bauru, SP (Brazil). Fac. de Engenharia

    2008-07-01

    The lubricant oil analysis are an indicator of the conditions how the lubricant is, may to allow the prevision of damages that occurred into machine due to the internal abrasion of hydraulic and mechanical components of the machines. The present study had the objective to determine the kind and quantity of the metallic particles that occurred into the lubricant oil of the mechanical and hydraulic compartments of the energy transmission systems of three kinds of machines: a tracked-tractor, a sugarcane harvester and a group of power-shovels. The metallic particles presents into these compartments were determined under laboratory tests and concerning to the following elements: iron, copper, chromium, lead, nickel, aluminum, silex, tin and molybdenum. About to the tracked-tractor, the metallic contaminators into to the oil charges surpasses the tolerate levels, considering the technical standards adopted in this evaluation. In the sugarcane harvester only a metallic element in excess was identified and, in a power-shovel group it was showed the need to correct air false entrances in the hydraulic or mechanical systems due the high presence of silex element. (author)

  8. Improved field emission performance of carbon nanotube by introducing copper metallic particles

    Directory of Open Access Journals (Sweden)

    Chen Yiren

    2011-01-01

    Full Text Available Abstract To improve the field emission performance of carbon nanotubes (CNTs, a simple and low-cost method was adopted in this article. We introduced copper particles for decorating the CNTs so as to form copper particle-CNT composites. The composites were fabricated by electrophoretic deposition technique which produced copper metallic particles localized on the outer wall of CNTs and deposited them onto indium tin oxide (ITO electrode. The results showed that the conductivity increased from 10-5 to 4 × 10-5 S while the turn-on field was reduced from 3.4 to 2.2 V/μm. Moreover, the field emission current tended to be undiminished after continuous emission for 24 h. The reasons were summarized that introducing copper metallic particles to decorate CNTs could increase the surface roughness of the CNTs which was beneficial to field emission, restrain field emission current from saturating when the applied electric field was above the critical field. In addition, it could also improve the electrical contact by increasing the contact area between CNT and ITO electrode that was beneficial to the electron transport and avoided instable electron emission caused by thermal injury of CNTs.

  9. Controllable synthesis of metal particles by a direct current electrochemical approach

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Shapes of copper and silver particles were successfully controlled by using a very simple,effective direct-current electrochemical approach without introducing any additives or templates. A diverse range of shapes and also different inner structures were thus accessible. The products prepared at relatively high potentials have flowerlike morphologies and exhibit flakes as building blocks. The uniformly thick flakes intersect mutually,have smooth surfaces and outwardly wavy edges. The particle diameter and the flake density can be easily controlled by changing potential and/or deposition time. With a decrease of potential,the particles’ shapes changed from flower to bud,to sphere and to octahedron. Surface plasmon resonance (SPR) properties of the supported metal particles were investigated by UV-Vis diffuse reflectance spectra (UV-Vis DRS) and surface enhanced Raman scattering (SERS). It was found that the copper octahedra exhibited three characteristic bands,and SERS effect increases with the number of flakes within individual particles. Based on the experimental results,the mechanism for direct-current electrochemical growth of metal nanostructures was discussed.

  10. Improved field emission performance of carbon nanotube by introducing copper metallic particles.

    Science.gov (United States)

    Chen, Yiren; Jiang, Hong; Li, Dabing; Song, Hang; Li, Zhiming; Sun, Xiaojuan; Miao, Guoqing; Zhao, Haifeng

    2011-10-03

    To improve the field emission performance of carbon nanotubes (CNTs), a simple and low-cost method was adopted in this article. We introduced copper particles for decorating the CNTs so as to form copper particle-CNT composites. The composites were fabricated by electrophoretic deposition technique which produced copper metallic particles localized on the outer wall of CNTs and deposited them onto indium tin oxide (ITO) electrode. The results showed that the conductivity increased from 10-5 to 4 × 10-5 S while the turn-on field was reduced from 3.4 to 2.2 V/μm. Moreover, the field emission current tended to be undiminished after continuous emission for 24 h. The reasons were summarized that introducing copper metallic particles to decorate CNTs could increase the surface roughness of the CNTs which was beneficial to field emission, restrain field emission current from saturating when the applied electric field was above the critical field. In addition, it could also improve the electrical contact by increasing the contact area between CNT and ITO electrode that was beneficial to the electron transport and avoided instable electron emission caused by thermal injury of CNTs.

  11. Surface modification of tin oxide by VUV rays and charge particle treatment: An effective method to improve the efficiency of surface catalytic behavior

    Science.gov (United States)

    Ganesan, Rajesh

    2011-10-01

    Plasma processing is a promising method to modify the chemical and physical properties of the semiconductor oxide surfaces. However, the tuning of surface characteristics is also influenced by plasma-emitted VUV and UV radiations. Different combinations of argon and oxygen partial pressures were applied in the capacitively coupled plasma. The highest surface conductivity was achieved with increasing plasma power, which was attributed to the interstitial defects with increased Tamm states created by the following two processes. First, the charge particle bombardment on the oxide surface, which etches the surface atoms and second, the absorption of VUV and UV radiation in the exposed layers of tin oxide nanoflakes scission the covalent bonds connecting the Sn-O atoms. The catalytic behavior of the tin oxide nanoflakes towards reducing gases have been studied as the function of Ar-O partial pressures, plasma power and voltage, and the ambient sensing temperature. Modified surface characteristics were also supported by SEM, TEM and XPS analysis.

  12. Dynamics of spherical metallic particles in cylinder electrostatic separators/purifiers.

    Science.gov (United States)

    Lu, Hong-Zhou; Li, Jia; Guo, Jie; Xu, Zhen-Ming

    2008-08-15

    This paper presents a theoretical analysis of the dynamics of spherical metallic particles in electrostatic separators/purifiers (ESPs). The particle equations of motion are numerically solved in two dimensions using a computational algorithm. The ESPs consist of a pair of conductor cylinder electrodes. The upper cylinder is energized by HVdc, while the lower one is grounded and fixed horizontally on a revolvable axis. Some phenomena and aspects of separation process are explained and depicted including lifting off, impact, "motion collapse" and "sudden bouncing". The results reveal that the several phenomena depend on initial position, radius and density of the particle, curvature of the cylinder electrodes, distance between the electrodes and amplitude of the applied voltage. Optimization of the parameters is presented in order to get better separation/purification processes.

  13. Modeling of laser radiation transport in powder beds with high-dispersive metal particles

    Energy Technology Data Exchange (ETDEWEB)

    Kharanzhevskiy, Evgeny, E-mail: eh@udsu.ru [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation); Kostenkov, Sergey [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation)

    2014-02-15

    Highlights: ► Transport of laser energy in dispersive powder beds was numerically simulated. ► The results of simulating are compared with physicals experiments. ► We established the dependence of the extinction coefficient from powder properties. ► A confirmation of a geometric optic approach for monodisperse powders was proposed. -- Abstract: Two-dimensional transfer of laser radiation in a high-dispersive powder heterogeneous media is numerically calculated. The size of particles is comparable with the wave length of laser radiation so the model takes into account all known physical effects that are occurred on the vacuum–metal surface interface. It is shown that in case of small particles size both morphology of powder particles and porosity of beds influence on absorptance by the solid phase and laser radiation penetrate deep into the area of geometric shadow. Intensity of laser radiation may be described as a function corresponded to the Beer–Lambert–Bouguer law.

  14. Dynamic Effects in Elastothermodynamic Damping of Hollow Particle Reinforced Metal-Matrix Composites

    Science.gov (United States)

    Srivastava, Sunil Kumar; Mishra, Bhanu Kumar

    2016-06-01

    The Metal-Matrix Composites (MMCs) containing hollow spherical reinforcements are under active development for the applications such as space structures, submarine hulls etc. where weight is of critical importance. When these materials are subjected to a time varying strain field, energy is dissipated because of the thermoelastic effect (Elastothermodynamic Damping or ETD). The quasi-static ETD analysis for the MMCs containing hollow spherical particles has been reported in literature. The entropic approach, which is better suited for composite materials with perfect or imperfect interfaces, is used for the analysis. In the present work, the effect of inertia forces is carried out on ETD of hollow particle-reinforced MMCs. For given particle volume fractions (V p ), the inertia forces are found to be more significant at higher value of thermal parameter (Ω T1) (alternatively, frequency of vibration if reinforcement radius is fixed), large cavity volume fraction (V h ) and low value of the parameter B1.

  15. Cardiopulmonary responses of intratracheally instilled tire particles and constituent metal components

    Science.gov (United States)

    Gottipolu, R.R.; Landa, E.R.; Schladweiler, M.C.; McGee, J.K.; Ledbetter, A.D.; Richards, J.H.; Wallenborn, G.J.; Kodavanti, U.P.

    2008-01-01

    Tire and brake wear particles contain transition metals, and contribute to near-road PM. We hypothesized that acute cardiopulmonary injury from respirable tire particles (TP) will depend on the amount of soluble metals. Respirable fractions of two types of TP (TP1 and TP2) were analyzed for water and acid-leachable metals using ICP-AES. Both TP types contained a variety of transition metals, including zinc (Zn), copper (Cu), aluminum, and iron. Zn and Cu were detected at high levels in water-soluble fractions (TP2 > TP1). Male Wistar Kyoto rats (12-14 wk) were intratracheally instilled, in the first study, with saline, TP1 or TP2 (5 mg/kg), and in the second study, with soluble Zn, Cu (0.5 ??mol/kg), or both. Pulmonary toxicity and cardiac mitochondrial enzymes were analyzed 1 d, 1 wk, or 4 wk later for TP and 4 or 24 h later for metals. Increases in lavage fluid markers of inflammation and injury were observed at d 1 (TP2 > TP1), but these changes reversed by wk 1. No effects on cardiac enzymes were noted with either TP. Exposure of rats to soluble Zn and Cu caused marked pulmonary inflammation and injury but temporal differences were apparent (Cu effects peaked at 4 h and Zn at 24 h). Instillation of Zn, Cu, and Zn+ Cu decreased the activity of cardiac aconitase, isocitrate dehydrogenase, succinate dehydrogenase, cytochrome-c-oxidase and superoxide dismutase suggesting mitochondrial oxidative stress. The observed acute pulmonary toxicity of TP could be due to the presence of water soluble Zn and Cu. At high concentrations these metals may induce cardiac oxidative stress. Copyright ?? Informa Healthcare USA, Inc.

  16. Thermodynamics of catalytic nanoparticle morphology

    Science.gov (United States)

    Zwolak, Michael; Sharma, Renu; Lin, Pin Ann

    Metallic nanoparticles are an important class of industrial catalysts. The variability of their properties and the environment in which they act, from their chemical nature & surface modification to their dispersion and support, allows their performance to be optimized for many chemical processes useful in, e.g., energy applications and other areas. Their large surface area to volume ratio, as well as varying sizes and faceting, in particular, makes them an efficient source for catalytically active sites. These characteristics of nanoparticles - i.e., their morphology - can often display intriguing behavior as a catalytic process progresses. We develop a thermodynamic model of nanoparticle morphology, one that captures the competition of surface energy with other interactions, to predict structural changes during catalytic processes. Comparing the model to environmental transmission electron microscope images of nickel nanoparticles during carbon nanotube (and other product) growth demonstrates that nickel deformation in response to the nanotube growth is due to a favorable interaction with carbon. Moreover, this deformation is halted due to insufficient volume of the particles. We will discuss the factors that influence morphology and also how the model can be used to extract interaction strengths from experimental observations.

  17. Influence of the particle size of zeolite HZSM-5 on the catalytic performance in the ethene-to-propene reaction

    Energy Technology Data Exchange (ETDEWEB)

    Follmann, S.; Ernst, S. [Kaiserslautern Univ. (Germany). Dept. of Chemistry; Vetter, A.; Ripperger, S. [Kaiserslautern Univ. (Germany). Dept. of Mechanical and Process Engineering

    2013-11-01

    In this study, HZSM-5-type zeolites with comparable nSi/nAl-ratios but different crystallite sizes (6 {mu}m, 27 {mu}m, 40 {mu}m and 62 {mu}m) were synthesized and their physicochemical properties characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and nitrogen physisorption. Their catalytic properties were explored in the acid-catalyzed conversion of ethene to propene (and higher hydrocarbons). The results show that there is a significant influence of the crystallite size of the zeolite catalyst on the activity and time-on-steam stability. While the yields of short-chain olefins do not significantly differ for all materials investigated, the formation of aromatics is significantly suppressed over the catalyst with the largest crystallite size. (orig.)

  18. Catalytic membranes prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle films in porous supports.

    Science.gov (United States)

    Dotzauer, David M; Dai, Jinhua; Sun, Lei; Bruening, Merlin L

    2006-10-01

    Layer-by-layer adsorption of polyelectrolytes and gold nanoparticles within porous supports provides a convenient method for forming catalytic membranes. The polyelectrolyte film effectively immobilizes the gold nanoparticles without inhibiting access to catalytic sites, as shown by the similar rate constants for nanoparticle-catalyzed 4-nitrophenol reduction in solution and in membranes. Modified alumina membranes reduce >99% of 0.4 mM 4-nitrophenol at linear flow rates of 0.98 cm/s, and the modification process is also applicable to track-etched polycarbonate supports.

  19. Preparation and formation mechanisms of metallic particles with controlled size, shape, structure and surface functionality

    Science.gov (United States)

    Lu, Lu

    Due to their excellent conductivity and chemical stability, particles of silver (Ag), gold (Au), copper (Cu) and their alloys are widely used in the electronic industry. Other unique properties extend their uses to the biomedical, optical and catalysis fields. All of these applications rely on particles with well controlled size, morphology, structure, and surface properties. Chemical precipitation from homogeneous solutions was selected as the synthetic route for the investigations described in this work. Based on the evaluation of key process parameters (temperature, reactant concentrations, reactant addition rate, mixing, etc.) the general formation mechanisms of metallic particles in various selected precipitation systems were investigated and elucidated. Five different systems for preparing particles with controlled size, morphology, structure and surface functionality are discussed. The first system involves the precipitation of Ag nanoparticles with spherical and anisotropic (platy or fiber-like) morphology. It will be shown that the formation of a stable Ag/Daxad complex has a significant impact on the reaction kinetics, and that the chromonic properties of Daxad molecules are responsible for the particle anisotropy. In the second system, Au-Ag core-shell nanoparticles were prepared in aqueous solution by a two-step precipitation process. The optical properties of these particles can be tailored by varying the thickness of the Ag shell. It was also determined that the stability of the bimetallic metallic sols depends on the Cl-ion concentration in solution. The third system discussed deals with preparation by the polyol process of well dispersed Cu nanospheres with high crystallinity and excellent oxidation resistance. We show that the heterogeneous nucleation (seeding) approach has significant merit in controlling particle size and uniformity. The functionalization of Au nanoparticle surfaces with glutathione molecules is discussed in the next section. The

  20. Transition metal complexes of 5-bromosalicylidene-4-amino-3-mercapto-1,2,4-triazine-5-one: Synthesis, characterization, catalytic and antibacterial studies

    Directory of Open Access Journals (Sweden)

    AYALOOR SUBRAMANIAN RAMASUBRAMANIAN

    2011-01-01

    Full Text Available Transition metal complexes of 5-bromosalicylidene-4-amino-3-mercapto-1,2,4-triazine-5-one with metal precursors, such as Cu(II, Ni(II, Co(II and Pd(II, were synthesized and characterized by physico–chemical and spectroscopic techniques. All the complexes are of the ML type. Based on analytical, spectral data and magnetic moments, the Co(II and Ni(II complexes were assigned octahedral geometries, while the Cu (II and Pd(II complexes square planar. A study on the catalytic oxidation of benzyl alcohol, cyclohexanol, cinnamyl alcohol, 2-propanol and 2-methyl-1-propanol was performed with N-methylmorpholine-N-oxide (NMO as co-oxidant. All the complexes and their parent organic moiety were screened for their biological activity on several pathogenic bacteria and were found to possess appreciable bactericidal properties.

  1. Thermoelectric properties of semiconductor-metal composites produced by particle blending

    Directory of Open Access Journals (Sweden)

    Yu Liu

    2016-10-01

    Full Text Available In the quest for more efficient thermoelectric material able to convert thermal to electrical energy and vice versa, composites that combine a semiconductor host having a large Seebeck coefficient with metal nanodomains that provide phonon scattering and free charge carriers are particularly appealing. Here, we present our experimental results on the thermal and electrical transport properties of PbS-metal composites produced by a versatile particle blending procedure, and where the metal work function allows injecting electrons to the intrinsic PbS host. We compare the thermoelectric performance of composites with microcrystalline or nanocrystalline structures. The electrical conductivity of the microcrystalline host can be increased several orders of magnitude with the metal inclusion, while relatively high Seebeck coefficient can be simultaneously conserved. On the other hand, in nanostructured materials, the host crystallites are not able to sustain a band bending at its interface with the metal, becoming flooded with electrons. This translates into even higher electrical conductivities than the microcrystalline material, but at the expense of lower Seebeck coefficient values.

  2. The relation between heavy metals distribution and particle size fractions in some egyptian soils

    Directory of Open Access Journals (Sweden)

    Monier Morad Wahba

    Full Text Available Soil as a part of the environment receives pollutants from all types of human activities. Heavy metals originating from various organic waste sources and industrial activities accumulate in the soil surface, and their fate depends not only on the types and amounts of waste applied, but on soil properties. Furthermore, soils differ in their retention power for various heavy or trace elements. Twelve soil samples were selected from different sites irrigated with industrial and sewage wastes at Helwan city (Cairo Governorate in the north and El-Saff (Giza Governorate in the south. Separation of clay, silt and sand fractions were carried out. Chemical analyses of trace elements in the form of total and available contents (Fe, Mn, Zn and Pb were determined in each fraction. The obtained results show that the average amounts of heavy metals in different fractions are related to the particle size of the soil especially the fine fraction. Heavy metals content was always in the surface layers higher than sub-surface. All metals were highest in clay fraction followed by silt and sand fractions respectively. This investigation discussed the importance of the fine fractions in the accumulation of heavy metals by coordination number in the lattice structure.

  3. Thermoelectric properties of semiconductor-metal composites produced by particle blending

    Science.gov (United States)

    Liu, Yu; Cadavid, Doris; Ibáñez, Maria; Ortega, Silvia; Martí-Sánchez, Sara; Dobrozhan, Oleksandr; Kovalenko, Maksym V.; Arbiol, Jordi; Cabot, Andreu

    2016-10-01

    In the quest for more efficient thermoelectric material able to convert thermal to electrical energy and vice versa, composites that combine a semiconductor host having a large Seebeck coefficient with metal nanodomains that provide phonon scattering and free charge carriers are particularly appealing. Here, we present our experimental results on the thermal and electrical transport properties of PbS-metal composites produced by a versatile particle blending procedure, and where the metal work function allows injecting electrons to the intrinsic PbS host. We compare the thermoelectric performance of composites with microcrystalline or nanocrystalline structures. The electrical conductivity of the microcrystalline host can be increased several orders of magnitude with the metal inclusion, while relatively high Seebeck coefficient can be simultaneously conserved. On the other hand, in nanostructured materials, the host crystallites are not able to sustain a band bending at its interface with the metal, becoming flooded with electrons. This translates into even higher electrical conductivities than the microcrystalline material, but at the expense of lower Seebeck coefficient values.

  4. Effect of Charging and Position of Metallic Particle Adhered to Spacer on PDIV and PRPD Characteristics in GIS

    Directory of Open Access Journals (Sweden)

    Y. Khan

    2014-07-01

    Full Text Available Gas Insulated Switchgears (GIS are widely used due to their many benefits. The reliability of GIS is challenged due to the presence of spacer defects and/or metallic particles. Free metallic particles can tremendously reduce the insulation strength of GIS especially when they enter the triple junction region (consisting of the spacer, the electrode and the gaseous medium interface around the spacer. Therefore, there a need to investigate the effect of charged metallic particle on the field intensification produced along the spacer surface and its consequences on the Partial Discharge Inception Voltage (PDIV. In this study, simulation and experimental results are reported for metallic particles adhering to a cylindrical spacer. The effect of particle charging on the resulting field intensification, particle initiated partial discharge inception voltage as well as Phase Resolved Partial Discharge (PRPD characteristics are presented in this study. The particle adversely affects the electric field uniformity in the area between the two electrodes. A particle in contact with the electrode causes the most severe intensification in the electric field, while the effect caused by the particle at the gap centre is the least severe.

  5. Metallic ions in organs of rats injected with metallic particles of stainless steel 316L and Ti6Al4V alloy

    Directory of Open Access Journals (Sweden)

    Silvia Helena Giertz

    2010-03-01

    Full Text Available Despite the interest in identifying systemic effects caused by the metallic particles released from long term metallic implants in the body, few works support reliable conclusions about the effects of those particles in organs. The aim of the present work is to look for damages in tissues of liver, kidney, lung and heart of rats submitted to injection of Hank's solution contained particles of Ti6Al4V alloy and Stainless Steel 316L, obtained by metal friction. The particles size ranges from 50 to 200 µm for the Ti alloy and from 100 to 500 µm for the 316L. Tissues isolated from the organs after the euthanasia were prepared and analyzed in an optical microscope and Energy Dispersive Spectrometer (EDS. Lesions caused by an inflammatory response such as strange body epithelioid granuloma and giant cells were found in some of the tissues containing yttrium and aluminum.

  6. TiO2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NOx with NH3

    Institute of Scientific and Technical Information of China (English)

    WU Bi-jun; LIU Xiao-qin; XIAO Ping; WANG Shu-gang

    2008-01-01

    Binary metal oxide(MnOx-A/TiO2) catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2),where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order:Mn-W/TiO2>Mn-Fe/TiO2>Mn-Cr/TiO2>Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order:Mn-Fe/TiO2>Mn-W/TiO2>Mn-Mo/TiO2>Mn-Cr/TiO2.In the presence of 0.01% SO2 and 6% H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8% and 94.2%,respectively,after 8 h at 120 ℃ at GHSV 12600 h-1.As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared(FTIR) spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.

  7. Atomically Precise Growth of Catalytically Active Cobalt Sulfide on Flat Surfaces and within a Metal-Organic Framework via Atomic Layer Deposition.

    Science.gov (United States)

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2015-08-25

    Atomic layer deposition (ALD) has been employed as a new synthetic route to thin films of cobalt sulfide on silicon and fluorine-doped tin oxide platforms. The self-limiting nature of the stepwise synthesis is established through growth rate studies at different pulse times and temperatures. Additionally, characterization of the materials by X-ray diffraction and X-ray photoelectron spectroscopy indicates that the crystalline phase of these films has the composition Co9S8. The nodes of the metal-organic framework (MOF) NU-1000 were then selectively functionalized with cobalt sulfide via ALD in MOFs (AIM). Spectroscopic techniques confirm uniform deposition of cobalt sulfide throughout the crystallites, with no loss in crystallinity or porosity. The resulting material, CoS-AIM, is catalytically active for selective hydrogenation of m-nitrophenol to m-aminophenol, and outperforms the analogous oxide AIM material (CoO-AIM) as well as an amorphous CoSx reference material. These results reveal AIM to be an effective method of incorporating high surface area and catalytically active cobalt sulfide in metal-organic frameworks.

  8. Nanosphere lithography based technique for fabrication of large area well ordered metal particle arrays

    Science.gov (United States)

    Barcelo, Steven J.; Lam, Si-Ty; Gibson, Gary A.; Sheng, Xia; Henze, Dick

    2012-03-01

    Nanosphere lithography is an effective technique for high throughput fabrication of well-ordered patterns, but expanding the method to large area coverage of nanoparticles less than 300 nm in diameter while maintaining good order has proven challenging. Here we demonstrate a nanosphere lithography based technique for fabricating large area, wellordered arrays of hemispherical metal particles which pushes the limits of these size constraints. First, large area monolayers of polystyrene (PS) nanospheres are assembled at an air-water interface and then transferred to a submerged substrate. The submerged substrate is supported at a 10° angle so that the water draining speed can be used to control the transfer rate, which is essential for hydrophobic substrates such as the polymer-coated glass used in our work. A double liftoff procedure was used to transfer the PS pattern to a silver particle array on an arbitrary substrate, achieving tunable control over the final metal particle diameter and spacing in the range of 50-150 nm and 100-200 nm, respectively. Additional control over particle shape and diameter can be obtained by modifying the substrate surface energy. For example, depositing silver on ITO-coated glass rather than a more hydrophilic clean glass substrate leads to a more hemispherical particle shape and a diameter reduction of 20%. Peak wavelength-selective reflection greater than 70% and total extinction greater than 90% were measured. The intensity, position and bandwidth of the main plasmon resonance of the arrays were shown to have minimal angle dependence up to at least 30° off normal.

  9. Metal and silicate particles including nanoparticles are present in electronic cigarette cartomizer fluid and aerosol.

    Directory of Open Access Journals (Sweden)

    Monique Williams

    Full Text Available Electronic cigarettes (EC deliver aerosol by heating fluid containing nicotine. Cartomizer EC combine the fluid chamber and heating element in a single unit. Because EC do not burn tobacco, they may be safer than conventional cigarettes. Their use is rapidly increasing worldwide with little prior testing of their aerosol.We tested the hypothesis that EC aerosol contains metals derived from various components in EC.Cartomizer contents and aerosols were analyzed using light and electron microscopy, cytotoxicity testing, x-ray microanalysis, particle counting, and inductively coupled plasma optical emission spectrometry.The filament, a nickel-chromium wire, was coupled to a thicker copper wire coated with silver. The silver coating was sometimes missing. Four tin solder joints attached the wires to each other and coupled the copper/silver wire to the air tube and mouthpiece. All cartomizers had evidence of use before packaging (burn spots on the fibers and electrophoretic movement of fluid in the fibers. Fibers in two cartomizers had green deposits that contained copper. Centrifugation of the fibers produced large pellets containing tin. Tin particles and tin whiskers were identified in cartridge fluid and outer fibers. Cartomizer fluid with tin particles was cytotoxic in assays using human pulmonary fibroblasts. The aerosol contained particles >1 µm comprised of tin, silver, iron, nickel, aluminum, and silicate and nanoparticles (<100 nm of tin, chromium and nickel. The concentrations of nine of eleven elements in EC aerosol were higher than or equal to the corresponding concentrations in conventional cigarette smoke. Many of the elements identified in EC aerosol are known to cause respiratory distress and disease.The presence of metal and silicate particles in cartomizer aerosol demonstrates the need for improved quality control in EC design and manufacture and studies on how EC aerosol impacts the health of users and bystanders.

  10. Catalytic methanation reaction over alumina supported cobalt oxide doped noble metal oxides for the purification of simulated natural gas

    Institute of Scientific and Technical Information of China (English)

    Wan Azelee Wan Abu Bakar; Rusmidah Ali; Abdul Aziz Abdul Kadir; Salmiah Jamal Mat Rosid; Nurul Shafeeqa Mohammad

    2012-01-01

    A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co( 10∶90 )/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co( 10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co( 10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis (EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co( 10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co( 10∶90)/Al2O3 catalyst.

  11. Insights into metals in individual fine particles from municipal solid waste using synchrotron radiation-based micro-analytical techniques

    Institute of Scientific and Technical Information of China (English)

    Yumin Zhu; Hua Zhang; Liming Shao; Pinjing He

    2015-01-01

    Excessive inter-contamination with heavy metals hampers the application of biological treatment products derived from mixed or mechanically-sorted municipal solid waste (MSW).In this study,we investigated fine particles of <2 mm,which are small fractions in MSW but constitute a significant component of the total heavy metal content,using bulk detection techniques.A total of 17 individual fine particles were evaluated using synchrotron radiation-based micro-X-ray fluorescence and micro-X-ray diffraction.We also discussed the association,speciation and source apportionment of heavy metals.Metals were found to exist in a diffuse distribution with heterogeneous intensities and intense hot-spots of <10 μm within the fine particles.Zn-Cu,Pb-Fe and Fe-Mn-Cr had significant correlations in terms of spatial distribution.The overlapped enrichment,spatial association,and the mineral phases of metals revealed the potential sources of fine particles from size-reduced waste fractions (such as scraps of organic wastes or ceramics) or from the importation of other particles.The diverse sources of heavy metal pollutants within the fine particles suggested that separate collection and treatment of the biodegradable waste fraction (such as food waste) is a preferable means of facilitating the beneficial utilization of the stabilized products.

  12. Theoretical study on hydrogenation catalysts containing a metal hydride as additional hydrogen supply

    NARCIS (Netherlands)

    Snijder, E.D.; Versteeg, G.F.; Swaaij, W.P.M. van

    1992-01-01

    A hypothetical hydrogenation catalyst consisting of porous, catalytically active particles embedded with metal hydride powder was evaluated. The metal hydride provides temporarily additional hydrogen if the mass transfer rate of the hydrogen to the internal of the particle is not sufficient. A numer

  13. On Absorption-Enhanced Organic Photovoltaic By Incorporating Metallic Nano Pyramid Particles

    Science.gov (United States)

    Qasem, Hussamaldeen Saif

    A lattice structure of metallic Nano pyramids (NPY) particles was planted on the interface between hole transport layer (HTL) and the transparent conductive layer (TCL) of an organic photovoltaic (OPV) cell. Standard metal evaporation along with Nano sphere lithography was used to grow the metallic NPY mesh structure. Silver (Ag) and Gold (Au) were the primary choice of the NPY mesh structure due to the excellent overlap of their peak localized surface Plasmon resonance (LSPR) frequency with the active layer absorption wavelengths. The current-voltage curve displayed an improvement in the efficiency and fill factor values of OPVs that used NPY lattice structure over devices that used regular sphere-shaped Nano particles. Despite the better-shaped and strong (LSPR) peak frequency of the Ag NPY lattice structure, Au NPY lattice structure exhibited an enhanced absorption and overall efficiency, which was owed to the wider (LSPR) frequency peak that Au possesses. The effect of NPY lattice structure could be further investigated with several approaches such as using different NPY materials, using core-shill approach, and growing the NPY on different layers or interfaces.

  14. Slow waves in microchannel metal waveguides and application to particle acceleration

    Directory of Open Access Journals (Sweden)

    L. C. Steinhauer

    2003-06-01

    Full Text Available Conventional metal-wall waveguides support waveguide modes with phase velocities exceeding the speed of light. However, for infrared frequencies and guide dimensions of a fraction of a millimeter, one of the waveguide modes can have a phase velocity equal to or less than the speed of light. Such a metal microchannel then acts as a slow-wave structure. Furthermore, if it is a transverse magnetic mode, the electric field has a component along the direction of propagation. Therefore, a strong exchange of energy can occur between a beam of charged particles and this slow-waveguide mode. Moreover, the energy exchange can be sustained over a distance limited only by the natural damping of the wave. This makes the microchannel metal waveguide an attractive possibility for high-gradient electron laser acceleration because the wave can be directly energized by a long-wavelength laser. Indeed the frequency of CO_{2} lasers lies at a fortuitous wavelength that produces a strong laser-particle interaction in a channel of reasonable macroscopic size (e.g., ∼0.6  mm. The dispersion properties including phase velocity and damping for the slow wave are developed. The performance and other issues related to laser accelerator applications are discussed.

  15. Shape and catalytic mechanism of RuO{sub 2} particles at CO oxidation reaction conditions. First-principles based multi-scale modeling

    Energy Technology Data Exchange (ETDEWEB)

    Reuter, Karsten [TU Muenchen (Germany). Lehrstuhl fuer Theoretische Chemie

    2016-11-01

    For model catalyst studies on low-index single-crystal surfaces close agreement between detailed measurements and quantitative microkinetic modeling can increasingly be achieved. However, for 'real' catalyst particles, such structure-morphology-activity relationships are only scarcely established. This is prototypically reflected by the situation for RuO{sub 2}, as a most active catalyst for CO oxidation. Here, existing first-principles kinetic modeling is restricted to just one facet, namely the RuO{sub 2}(110) surface, which is not able to fully account for activity data obtained from polycrystalline RuO{sub 2} powder catalysts. The overarching objective of this project was correspondingly to close this gap and demonstrate that similarly close agreement as for individual single-crystal model catalysts can also be achieved for catalyst particles. Specifically, we addressed experiments where an intact RuO{sub 2} bulk structure is conserved, and establish the atomic-scale structure and reactivity of other RuO{sub 2} low-index facets under the gas-phase conditions characteristic for catalytic CO oxidation.

  16. The influence of particle size distribution on the properties of metal-injection-moulded 17-4 PH stainless steel

    CSIR Research Space (South Africa)

    Seerane, Mandy

    2016-10-01

    Full Text Available Metal injection moulding (MIM) is a near-net-shaping powder metallurgy technique suitable for the cost-effective mass production of small and complex components. In this paper, the effects of the metal powder particle size on the final properties...

  17. On the effect of particle size distribution on the discharge performance of nickel-metal hydride cells

    Energy Technology Data Exchange (ETDEWEB)

    Heikonen, J.M. [Center for Scientific Computing, Espoo (Finland); Nagarajan, G.S.; Zee, J.W. van [Department of Chemical Engineering, University of South Carolina, Columbia, SC (United States)

    1997-12-31

    The effect of particle size distribution on the discharge performance of nickel-metal hydride cells with mathematical models is investigated. A model with a continuous size distribution is presented and a simplified discrete version with two particle sizes is numerically analyzed for various parameter values. Simulation results are compared with experiments from another article and the deviations are analyzed. (orig.) 13 refs.

  18. Ball-milled sulfur-doped graphene materials contain metallic impurities originating from ball-milling apparatus: their influence on the catalytic properties.

    Science.gov (United States)

    Chua, Chun Kiang; Sofer, Zdeněk; Khezri, Bahareh; Webster, Richard D; Pumera, Martin

    2016-07-21

    Graphene materials have found applications in a wide range of devices over the past decade. In order to meet the demand for graphene materials, various synthesis methods are constantly being improved or invented. Ball-milling of graphite to obtain graphene materials is one of the many versatile methods to easily obtain bulk quantities. In this work, we show that the graphene materials produced by ball-milling are spontaneously contaminated with metallic impurities originating from the grinding bowls and balls. Ball-milled sulfur-doped graphene materials obtained from two types of ball-milling apparatus, specifically made up of stainless steel and zirconium dioxide, were investigated. Zirconium dioxide-based ball-milled sulfur-doped graphene materials contain a drastically lower amount of metallic impurities than stainless steel-based ball-milled sulfur-doped graphene materials. The presence of metallic impurities is demonstrated by their catalytic effects toward the electrochemical catalysis of hydrazine and cumene hydroperoxide. The general impression toward ball-milling of graphite as a versatile method for the bulk production of 'metal-free' graphene materials without the need for post-processing and the selection of ball-milling tools should be cautioned. These findings would have wide-reaching implications for graphene research.

  19. Lanthanide Metal-Organic Frameworks with Six-Coordinated Ln(III) Ions and Free Functional Organic Sites for Adsorptions and Extensive Catalytic Activities

    Science.gov (United States)

    Zhu, Yu; Zhu, Min; Xia, Li; Wu, Yunlong; Hua, Hui; Xie, Jimin

    2016-07-01

    Three chelating-amino-functionalized lanthanide metal-organic frameworks, Y-DDQ, Dy-DDQ and Eu-DDQ, were synthesized with a flexible dicarboxylate ligand based on quinoxaline (H2DDQ = N, N‧-dibenzoic acid-2,3-diaminoquinoxaline). The three-dimensional framework is constructed by the H2DDQ linkers connecting the zigzag ladders, showing a net of sra topology. In the structures, one kind of Ln(III) ions metal centers are six-coordinated and thus can potentially behave as open metal sites (OMSs), while the free chelating amino groups can act as free functional organic sites (FOSs). The N2 and Ar adsorption behaviors indicate that these Ln-DDQ exhibits stable microporous frameworks with high surface area after remove of the solvents. Owing to presence of OMSs and FOSs, these MOFs show good ability of CO2, dyes captures and Lewis acid catalyst for cyanosilylation reaction. In view of the existing FOSs in the framework, Pd NPs were immobilized onto the MOFs through graft interactions between free chelating amino groups and metal ions precursor using postsynthetic modification. The well dispersed Pd@Ln-DDQs exhibit efficient and recyclable catalytic reduction of 4-nitrophenol to 4-aminophenol, and they can also act as an excellent catalyst for Suzuki-Miyaura cross-coupling reactions with the exposed Pd NPs.

  20. Evaluation of heavy metal contamination hazards in nuisance dust particles, in Kurdistan Province, western Iran.

    Science.gov (United States)

    Khuzestani, Reza Bashiri; Souri, Bubak

    2013-07-01

    The effects of natural and geochemical factors depending on heavy metal contamination in nuisance dust particles were evaluated. The nuisance dust particles were sampled using passive deposit gauge method for one year from April 2010 to March 2011 and the obtained samples were measured for the total contents and the contamination levels of Fe, Mn, Cu and As using geo-accumulation index (l(geo)), enrichment factor (EF) and the integrated pollution index (IPI). The results showed that, the contamination levels of Fe and Mn based on I(geo) values, were uncontaminated (I(geo) < 0) (variations of the I(geo) index was from -3.11 to -1.751 for Fe, from -0.630 to -1.925 for Mn), while the values of Cu and As were demonstrated to have moderate contamination based on l(geo) values (variations of I(geo) index was from -1.125 to 0.848 for Cu, and from -2.002 to 1.249 for As). The analysis of EF also revealed minor to moderate enrichment for Mn (1.215-4.214), minor to moderately severe enrichment for Cu (2.791-6.484), and As (1.370-8.462), respectively. The variation of the IPI index also showed low to moderate level of heavy metal pollution in nuisance dust particulates (0.511-1.829). The analysis of the results also approved that the natural processes and geochemical variables (the changing meteorological parameters) can significantly affect the availability of heavy metals in nuisance dust particles in Western Iran.

  1. Damage analysis for particle reinforced metal matrix composite by ultrasonic method

    Institute of Scientific and Technical Information of China (English)

    YANG Zhi-guo; LONG Shi-guo

    2006-01-01

    The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load,the ultrasonic wave that propagated in the sample were collected. The damage parameter was defined by ultrasonic parameter and the wave signals were analyzed by correlation method. The results show that with the increase of tensile load,the damage parameter increases and the correlation coefficient decreases. The fracture section morphologies of PMMC under tensile load were observed by SEM. It is found that there are many concaves in the metal matrix. Therefore the damage evolution can be concluded. The initial damage is induced by void nucleation,growth and subsequent coalescence in the matrix or interface separation.

  2. Large Relative Raman Shift for Molecules Adsorbed on Metallic Nano-particles

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-Yun; XIA Yu-Xing; ZHAN Li; LENG Jiang-Hua

    2008-01-01

    The enhancement of two order-of-magnitudes is observed in surface-enhanced Raman spectroscopy (SERS) of gases (CO, C2H2, C2H4, etc) adsorbed on nitric acid-roughened metal foil. In addition, some Raman lines of gases adsorbed on these active substrates show larger frequency shifts and linewidth broadening, compared with the Raman spectroscopy of free gases. Using the two-oscillator electromagnetic model, we explain this phenomenon. It is related to the large non-regular particles on the active substrate we prepared. It is found that the parameters of the surface-plasmon dispersion, the distance of molecules from the surface and the radius of particles play crucial roles on the relative large Raman shifts.

  3. Performance of nitrogen-doped graphene aerogel particle electrodes for electro-catalytic oxidation of simulated Bisphenol A wastewaters

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhuang [Environmental Research Academy, North China Electric Power University, Beijing 102206 (China); Labortory of Environmental Remediation and Functional Material, Suzhou Research Academy of North China Electric Power University, Suzhou, Jiangsu, 215026 (China); Zhang, Yimei, E-mail: yimei.zhang1@gmail.com [Environmental Research Academy, North China Electric Power University, Beijing 102206 (China); Labortory of Environmental Remediation and Functional Material, Suzhou Research Academy of North China Electric Power University, Suzhou, Jiangsu, 215026 (China); Zhou, Lincheng; Zhu, Hao; Wan, Fei; Wang, Yue [Labortory of Environmental Remediation and Functional Material, Suzhou Research Academy of North China Electric Power University, Suzhou, Jiangsu, 215026 (China); Zhang, Dandan [Environmental Research Academy, North China Electric Power University, Beijing 102206 (China)

    2017-06-15

    Highlights: • The new three-dimensional electrode system with the nitrogen-doped graphene aerogels particle electrodes is developed. • The optimal technique parameters were explored. • Simulated BPA waste waters are effectively degraded. • Degradation pathway and intermediates are proposed. • Three-dimensional electrode system shows good and stable removal performance. - Abstract: The treatment of effluent containing Bisphenol A (BPA) was investigated experimentally using nitrogen-doped graphene aerogel (NGAs) as particle electrodes in a three-dimensional electrode reactor for the electrochemical treatment was studied. The effects of the cell voltage, pH, the ratio of NGAs mass to solution volume and repeated times on the removal efficiency were investigated. Compared with commercial carbon particle electrodes, the NGAs exhibited stronger activity to remove BPA simulated wastewater. For 15 mg L{sup −1} of BPA solution, the degradation rate of BPA exceeded 90% after treatment for only 30 min under the optimum conditions. The COD{sub Cr} removal rate of BPA was 85%. Moreover, in the process of reused 50 times, the degradation rate of BPA can be kept in more than 85%. The COD{sub Cr} removal rate was stable at about 73%. The intermediate products of electrochemical degradation of BPA were identified by liquid chromatography-mass spectrometry liquid chromatography (LC–MS), and a probable BPA degradation pathway was proposed. It was considered that ·OH radicals by water electrolysis could constantly attack the aromatic ring to form various intermediates such as hydroxylated-BPA, isopropylphenol, hydroquinone, phenol and butantetraol, maleic acid, oxalic acid. These compounds were eventually mineralized by electrolysis into CO{sub 2} and H{sub 2}O.

  4. Particle beam experiments for the analysis of reactive sputtering processes in metals and polymer surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Corbella, Carles; Grosse-Kreul, Simon; Kreiter, Oliver; Arcos, Teresa de los; Benedikt, Jan; Keudell, Achim von [RD Plasmas with Complex Interactions, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum (Germany)

    2013-10-15

    A beam experiment is presented to study heterogeneous reactions relevant to plasma-surface interactions in reactive sputtering applications. Atom and ion sources are focused onto the sample to expose it to quantified beams of oxygen, nitrogen, hydrogen, noble gas ions, and metal vapor. The heterogeneous surface processes are monitored in situ by means of a quartz crystal microbalance and Fourier transform infrared spectroscopy. Two examples illustrate the capabilities of the particle beam setup: oxidation and nitriding of aluminum as a model of target poisoning during reactive magnetron sputtering, and plasma pre-treatment of polymers (PET, PP)

  5. Particle beam experiments for the analysis of reactive sputtering processes in metals and polymer surfaces.

    Science.gov (United States)

    Corbella, Carles; Grosse-Kreul, Simon; Kreiter, Oliver; de los Arcos, Teresa; Benedikt, Jan; von Keudell, Achim

    2013-10-01

    A beam experiment is presented to study heterogeneous reactions relevant to plasma-surface interactions in reactive sputtering applications. Atom and ion sources are focused onto the sample to expose it to quantified beams of oxygen, nitrogen, hydrogen, noble gas ions, and metal vapor. The heterogeneous surface processes are monitored in situ by means of a quartz crystal microbalance and Fourier transform infrared spectroscopy. Two examples illustrate the capabilities of the particle beam setup: oxidation and nitriding of aluminum as a model of target poisoning during reactive magnetron sputtering, and plasma pre-treatment of polymers (PET, PP).

  6. A QM/MM investigation of the catalytic mechanism of metal-ion-independent core 2 β1,6-N-acetylglucosaminyltransferase.

    Science.gov (United States)

    Tvaroška, Igor; Kozmon, Stanislav; Wimmerová, Michaela; Koča, Jaroslav

    2013-06-17

    β1,6-GlcNAc-transferase (C2GnT) is an important controlling factor of biological functions for many glycoproteins and its activity has been found to be altered in breast, colon, and lung cancer cells, in leukemia cells, in the lymhomonocytes of multiple sclerosis patients, leukocytes from diabetes patients, and in conditions causing an immune deficiency. The result of the action of C2GnT is the core 2 structure that is essential for the further elongation of the carbohydrate chains of O-glycans. The catalytic mechanism of this metal-ion-independent glycosyltransferase is of paramount importance and is investigated here by using quantum mechanical (QM) (density functional theory (DFT))/molecular modeling (MM) methods with different levels of theory. The structural model of the reaction site used in this report is based on the crystal structures of C2GnT. The entire enzyme-substrate system was subdivided into two different subsystems: the QM subsystem containing 206 atoms and the MM region containing 5914 atoms. Three predefined reaction coordinates were employed to investigate the catalytic mechanism. The calculated potential energy surfaces discovered the existence of a concerted SN 2-like mechanism. In this mechanism, a nucleophilic attack by O6 facilitated by proton transfer to the catalytic base and the separation of the leaving group all occur almost simultaneously. The transition state for the proposed reaction mechanism at the M06-2X/6-31G** (with diffuse functions on the O1', O5', OGlu , and O6 atoms) level was located at C1-O6=1.74 Å and C1-O1=2.86 Å. The activation energy for this mechanism was estimated to be between 20 and 29 kcal mol⁻¹, depending on the method used. These calculations also identified a low-barrier hydrogen bond between the nucleophile O6H and the catalytic base Glu320, and a hydrogen bond between the N-acetamino group and the glycosidic oxygen of the donor in the TS. It is proposed that these interactions contribute to a

  7. Distribution, bioavailability, and leachability of heavy metals in soil particle size fractions of urban soils (northeastern China).

    Science.gov (United States)

    Yutong, Zong; Qing, Xiao; Shenggao, Lu

    2016-07-01

    This study examines the distribution, mobility, and potential environmental risks of heavy metals in various particle size fractions of urban soils. Representative urban topsoils (ten) collected from Anshan, Liaoning (northeastern China), were separated into six particle size fractions and their heavy metal contents (Cr, Cu, Cd, Pb, and Zn) were determined. The bioaccessibility and leachability of heavy metals in particle size fractions were evaluated using the toxicity characteristic leaching procedure (TCLP) and ethylenediaminetetraacetic acid (EDTA) extraction, respectively. The results indicated that the contents of five heavy metals (Cd, Cr, Cu, Pb and Zn) in the size fractions increased with the decrease of particle size. The clay fraction of fraction was polluted by heavy metals more seriously than the other size fractions in urban topsoils. Cr also concentrated in the coarse fraction of 2000-1000 μm, indicating a lithogenic contribution. However, the dominant size fraction responsible for heavy metal accumulation appeared to belong to particle fraction of 50-2 μm. The lowest distribution factors (DFs) of heavy metals were recorded in the 2000- to 1000-μm size fraction, while the highest in the clay fraction. The DFs of heavy metals in the clay fraction followed Zn (3.22) > Cu (2.84) > Pb (2.61) > Cr (2.19) > Cd (2.05). The enrichment factor suggested that the enrichment degree of heavy metal increased with the decrease of the particle size, especially for Cd and Zn. The TCLP- and EDTA-extractable concentrations of heavy metals in the clay fraction were relatively higher than those in coarse particles. Cd bioavailability was higher in the clay fraction than in other fractions or whole soils. In contrast, Cr exhibits similar bioaccessibilities in the six size fractions of soils. The results suggested that fine particles were the main sources of potentially toxic metals in urban soils. The variation of heavy metals in various size fractions

  8. [Dust particles and metals in outdoor and indoor air of Upper Silesia].

    Science.gov (United States)

    Górny, R L; Jedrzejczak, A; Pastuszka, J S

    1995-01-01

    This work contains the results of the aerosol mass size distribution and preliminary studies on concentrations and size distribution of heavy metals (Pb, Zn, Cu, Mn, Fe and Cd) in indoor and outdoor environment in Upper Silesia (the highly industrialized region in the southern part of Poland). In studies, the measurements of aerosol concentration, mass size distribution, and evaluation of heavy metals concentration were made from December 1992 to April 1994 in some apartments in five towns in Upper Silesia and in one village in the Beskidy Mountains in both indoor and outdoor environments. The particles were fractionated in Andersen cascade impactor. The sampling time was 6-7 days and 4-5 days for indoor and outdoor respectively. Aerosol particulates were collected on A-type glass fiber collection substrate used later for determination of heavy concentrations by atomic absorption spectrophotometry (AAS 3, Carl Zeiss Jena). The dust was mineralized by the means of the mixture of hydrofluoric and nitric acids. The results of mass size distribution as well as the measurements of TSP for indoor and outdoor aerosol show that the main source of particulate matter indoors, in this region, are heavy polluted outdoor air and cigarette smoking. It can be said that, except homes in Knurów and Sosnowiec with hard smokers, the indoor levels of particulate pollution were significant lower than the outdoors levels. Whenever in the indoor environment appear additional source of particulate emission situation can changed. When we compare mass size distribution for outdoor aerosol and indoor aerosol contaminated by tobacco smoke, we can observed considerable increase of indoor aerosol level in the 0.33-0.54 microns size range. Besides, indoor aerosol status may be changed by coal stove emission (displacement of maximum peak to direction of coarse particles). The observed differences in concentration of particulate matter may also indicate the important differences in chemical and

  9. Behaviour and fate of urban particles in coastal waters: Settling rate, size distribution and metals contamination characterization

    Science.gov (United States)

    Oursel, B.; Garnier, C.; Pairaud, I.; Omanović, D.; Durrieu, G.; Syakti, A. D.; Le Poupon, C.; Thouvenin, B.; Lucas, Y.

    2014-02-01

    The evaluation of contaminant net fluxes from the coast to the open sea requires the study of terrigeneous particles behaviour and fate. We studied the particles issued from two small coastal rivers whose waters are mixed with treated wastewater (TWW) coming from the Marseille wastewater treatment plant (WWTP) just before discharge to the Mediterranean Sea. An experimental device was developed and used to investigate particles settling rates, size distribution and metallic contamination when mixing with seawater. The particles were sampled in flood deposits of rivers and outlets during rainy periods and in the outlet water during dry periods. The flood deposits were mainly composed of 50-200 μm-sized particles, higher metals content being observed in the finest fractions. Dry period particles showed the stronger influence of wastewater inputs. Al, Ca, Cs, Li, Rb, Ti, and Tl were mainly of terrigeneous origin, whereas Ag, Ba, Cd, Cr, Cu, Hg, Mg, Mo, Ni, Pb, POC, Sb, Sn and Zn were of anthropogenic origin, issued from non-treated sewage, TWW or industrial waste. In seafloor sediments, all metals exhibited a continuous increase of concentration from the outlet to, at least, 800 m offshore. Implementation of settling particles characteristics in a 3D hydrodynamic and sediment transport model reproduced well the observed deposition of polluted particles in the coastal zone and indicated a non-negligible offshore export of the finest particles and their accompanying pollutants.

  10. The role of soil's particle-size fractions in the adsorption of heavy metals

    Directory of Open Access Journals (Sweden)

    Saglara Mandzhieva

    2014-08-01

    Full Text Available The parameters of adsorption of Cu2+, Pb2+, and Zn2+ cations by southern chernozem and their particle-size fractions were studied. The adsorption of metals by soils and the strength of their fixation on the surface of soil particles under both mono- and poly-element contamination decreased with the decreasing proportion of fine fractions in the soil. The aim of this work was to study the effect of the particle-size distribution and the silt and physical clay fractions on the adsorption of copper, lead, and zinc by chernozems. The objects of study included the upper humus horizons of different southern chernozems of the Rostov oblast. To study the ion-exchange adsorption of the Cu2+, Pb2+, and Zn2+ cations, the soil in the natural ionic form was disaggregated using a pestle with a rubber head and sieved through a 1mm sieve. The soil samples were treated with solutions of Cu2+, Pb2+, and Zn2+ nitrates and acetates at the separate and simultaneous presence of heavy metals (HMs. In the solutions with the simultaneous presence of HMs, their molar concentrations were similar. The concentrations of the initial solutions varied in the range from 0.05 to 1 mM/l. The soil: solution ratio was 1:10. The contents of HMs in the filtrates were determined by atomic absorption spectrophotometry. The contents of adsorbed HM cations were calculated from the difference between the metal concentrations in the initial and equilibrium solutions. The increase in the degree of dispersion of the particle-size fractions in similar soils resulted not only in an increase in the content of adsorbed HMs but also in an enhancement of their fixation on the surface of the fine particles. Therefore, the adsorption capacity of the Lower Don soils for Cu2+, Pb2+, and Zn2+ decreased in the following sequence: clay loamy southern chernozem > loamy southern chernozem > loamy sandy southern chernozem. This was related to the qualitative differences in the mineralogy and chemistry of

  11. Insights into metals in individual fine particles from municipal solid waste using synchrotron radiation-based micro-analytical techniques.

    Science.gov (United States)

    Zhu, Yumin; Zhang, Hua; Shao, Liming; He, Pinjing

    2015-01-01

    Excessive inter-contamination with heavy metals hampers the application of biological treatment products derived from mixed or mechanically-sorted municipal solid waste (MSW). In this study, we investigated fine particles of radiation-based micro-X-ray fluorescence and micro-X-ray diffraction. We also discussed the association, speciation and source apportionment of heavy metals. Metals were found to exist in a diffuse distribution with heterogeneous intensities and intense hot-spots of waste fractions (such as scraps of organic wastes or ceramics) or from the importation of other particles. The diverse sources of heavy metal pollutants within the fine particles suggested that separate collection and treatment of the biodegradable waste fraction (such as food waste) is a preferable means of facilitating the beneficial utilization of the stabilized products.

  12. Patterning of Metal Films on Arbitrary Substrates by Using Polydopamine as a UV-Sensitive Catalytic Layer for Electroless Deposition.

    Science.gov (United States)

    Zhao, Lei; Chen, Daqun; Hu, Weihua

    2016-05-31

    Patterning metal films on various substrates is essentially important and yet challenging for developing a wide variety of innovative devices. We herein report a versatile approach to pattern metal (gold, silver, or copper) films on arbitrary substrates by using the bio-inspired polydopamine (PDA) thin film as a UV-sensitive adhesive layer for electroless deposition. The PDA film is able to be formed on virtually any solid surfaces under mild condition, and its rich catechol groups allow for electroless deposition of metal films with high adhesion stability. Upon UV irradiation, spatially selective oxidation of PDA film occurs and the local metal deposition is inhibited, thus facilitating successful patterning of metal films. Considering its versatility and simplicity, this strategy may demonstrate great applications in manufacturing various innovative devices.

  13. Light-induced catalytic and cytotoxic properties of phosphorescent transition metal compounds with a d8 electronic configuration.

    Science.gov (United States)

    To, Wai-Pong; Zou, Taotao; Sun, Raymond Wai-Yin; Che, Chi-Ming

    2013-07-28

    Transition metal compounds are well documented to have diverse applications such as in catalysis, light-emitting materials and therapeutics. In the areas of photocatalysis and photodynamic therapy, metal compounds of heavy transition metals are highly sought after because they can give rise to triplet excited states upon photoexcitation. The long lifetimes (more than 1 μs) of the triplet states of transition metal compounds allow for bimolecular reactions/processes such as energy transfer and/or electron transfer to occur. Reactions of triplet excited states of luminescent metal compounds with oxygen in cells may generate reactive oxygen species and/or induce damage to DNA, leading to cell death. This article recaps the recent findings on photochemical and phototoxic properties of luminescent platinum(II) and gold(III) compounds both from the literature and experimental results from our group.

  14. Characterization of suspended solids and particle-bound heavy metals in a first flush of highway runoff

    Institute of Scientific and Technical Information of China (English)

    Fa-hui NIE; Tian LI; Hai-feng YAO; Man FENG; Guang-kai ZHANG

    2008-01-01

    To investigate the dynamic characteristics of total suspended solids(TSS)and their particle-bound heavy metals in a first flush,the runoffsampling together with its flow rate measuring was conducted for three rainfall events at outfalls of highway in Shanghai from June to September 2007.Field samples were analyzed to determine the concentrations of TSS and particle-bound heavy metals,such as Zn,Pb,and Cu.Results show that the wash off behavior of TSS under varying runoff rate condition can be explained by different antecedent dry weather period(ADWP).Contribution of fine fraction(45 μm).When the runoff flow increased obviously,a significant contribution of the coarse fraction was observed for a certain rainfall events with long antecedent dry weather condition.The changes of total metals concentration and particle-bound metal concentrations were strongly dependent on the TSS variation.TSS was generally well correlated with most particulate-bound heavy metals.Of the heavy metals,the concentration of Zn was found considerably high and that of Pb was significantly low at North Zhongshan 2 Road,in Shanghai,China,but they are still within the range reported in the literature.Fluctuation of heavy metal contents in the coarse fraction during a first flush period was more significant compared with that in the fine fraction.The results will assist in the development of effective control strategies to minimize heavy metals and solids in highway runoff.

  15. Exposure vs toxicity levels of airborne quartz, metal and carbon particles in cast iron foundries.

    Science.gov (United States)

    Moroni, Beatrice; Viti, Cecilia; Cappelletti, David

    2014-01-01

    Aerosol dust samples and quartz raw materials from different working stations in foundry plants were characterized in order to assess the health risk in this working environment. Samples were analysed by scanning and transmission electron microscopy coupled with image analysis and microanalysis, and by cathodoluminescence spectroscopy. In addition, the concentration and the solubility degree of Fe and other metals of potential health effect (Mn, Zn and Pb) in the bulk samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Overall, the results indicate substantial changes in quartz crystal structure and texture when passing from the raw material to the airborne dust, which include lattice defects, non-bridging oxygen hole centres and contamination of quartz grains by metal and/or graphite particles. All these aspects point towards the relevance of surface properties on reactivity. Exposure doses have been estimated based on surface area, and compared with threshold levels resulting from toxicology. The possible synergistic effects of concomitant exposure to inhalable magnetite, quartz and/or graphite particles in the same working environment have been properly remarked.

  16. Metal-based magnetic fluids with core-shell structure FeB@SiO2 amorphous particles.

    Science.gov (United States)

    Yu, Mengchun; Bian, Xiufang; Wang, Tianqi; Wang, Junzhang

    2017-09-27

    FeB@SiO2 amorphous particles were firstly introduced into Ga85.8In14.2 alloys to prepare metal-based magnetic fluids. The morphology of the FeB amorphous particles is spherical with an average particle size of about 190 nm. The shape of the particles is regular and the particle size is homogeneous. Stable core-shell structure SiO2 modified FeB amorphous particles are obtained and the thickness of the SiO2 coatings is observed to be about 40 nm. The results of VSM confirm that the saturation magnetization of the FeB amorphous particles is 131.5 emu g(-1), which is almost two times higher than that of the Fe3O4 particles. The saturation magnetization of the FeB@SiO2 amorphous particles is 106.9 emu g(-1), an approximate decrease of 18.7% due to the non-magnetic SiO2 coatings. The results from the torsional oscillation viscometer show that the metal-based magnetic fluids with FeB amorphous particles exhibit a desirable high temperature performance and are ideal candidates for high temperature use.

  17. Catalytic hydrotreating process

    Science.gov (United States)

    Karr, Jr., Clarence; McCaskill, Kenneth B.

    1978-01-01

    Carbonaceous liquids boiling above about 300.degree. C such as tars, petroleum residuals, shale oils and coal-derived liquids are catalytically hydrotreated by introducing the carbonaceous liquid into a reaction zone at a temperature in the range of 300.degree. to 450.degree. C and a pressure in the range of 300 to 4000 psig for effecting contact between the carbonaceous liquid and a catalytic transition metal sulfide in the reaction zone as a layer on a hydrogen permeable transition metal substrate and then introducing hydrogen into the reaction zone by diffusing the hydrogen through the substrate to effect the hydrogenation of the carbonaceous liquid in the presence of the catalytic sulfide layer.

  18. Catalytic Proton Coupled Electron Transfer from Metal Hydrides to Titanocene Amides, Hydrazides and Imides: Determination of Thermodynamic Parameters Relevant to Nitrogen Fixation.

    Science.gov (United States)

    Pappas, Iraklis; Chirik, Paul J

    2016-10-03

    The hydrogenolysis of titanium-nitrogen bonds in a series of bis(cyclopentadienyl) titanium amides, hydrazides and imides by proton coupled electron transfer (PCET) is described. Twelve different N-H bond dissociation free energies (BDFEs) among the various nitrogen-containing ligands were measured or calculated, and effects of metal oxidation state and N-ligand substituent were determined. Two metal hydride complexes, (η(5)-C5Me5)(py-Ph)Rh-H (py-Ph = 2-pyridylphenyl, [Rh]-H) and (η(5)-C5R5)(CO)3Cr-H ([Cr](R)-H, R= H, Me) were evaluated for formal H atom transfer reactivity and were selected due to their relatively weak M-H bond strengths yet ability to activate and cleave molecular hydrogen. Despite comparable M-H BDFEs, disparate reactivity between the two compounds was observed and was traced to the vastly different acidities of the M-H bonds and overall redox potentials of the molecules. With [Rh]-H, catalytic syntheses of ammonia, silylamine and N,N-dimethylhydrazine have been accomplished from the corresponding titanium(IV) complex using H2 as the stoichiometric H atom source. The data presented in this study provides the thermochemical foundation for the synthesis of NH3 by proton coupled electron transfer at a well-defined transition metal center.

  19. Catalytic effect of nanoparticle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling.

    Science.gov (United States)

    Hanada, Nobuko; Ichikawa, Takayuki; Fujii, Hironobu

    2005-04-21

    We examined the catalytic effect of nanoparticle 3d-transition metals on hydrogen desorption (HD) properties of MgH(2) prepared by mechanical ball milling method. All the MgH(2) composites prepared by adding a small amount of nanoparticle Fe(nano), Co(nano), Ni(nano), and Cu(nano) metals and by ball milling for 2 h showed much better HD properties than the pure ball-milled MgH(2) itself. In particular, the 2 mol % Ni(nano)-doped MgH(2) composite prepared by soft milling for a short milling time of 15 min under a slow milling revolution speed of 200 rpm shows the most superior hydrogen storage properties: A large amount of hydrogen ( approximately 6.5 wt %) is desorbed in the temperature range from 150 to 250 degrees C at a heating rate of 5 degrees C/min under He gas flow with no partial pressure of hydrogen. The EDX micrographs corresponding to Mg and Ni elemental profiles indicated that nanoparticle Ni metals as catalyst homogeneously dispersed on the surface of MgH(2). In addition, it was confirmed that the product revealed good reversible hydriding/dehydriding cycles even at 150 degrees C. The hydrogen desorption kinetics of catalyzed and noncatalyzed MgH(2) could be understood by a modified first-order reaction model, in which the surface condition was taken into account.

  20. Catalytic behavior of metal catalysts in high-temperature RWGS reaction: In-situ FT-IR experiments and first-principles calculations

    Science.gov (United States)

    Choi, Sungjun; Sang, Byoung-In; Hong, Jongsup; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook; Kim, Hyoungchul

    2017-01-01

    High-temperature chemical reactions are ubiquitous in (electro) chemical applications designed to meet the growing demands of environmental and energy protection. However, the fundamental understanding and optimization of such reactions are great challenges because they are hampered by the spontaneous, dynamic, and high-temperature conditions. Here, we investigated the roles of metal catalysts (Pd, Ni, Cu, and Ag) in the high-temperature reverse water-gas shift (RWGS) reaction using in-situ surface analyses and density functional theory (DFT) calculations. Catalysts were prepared by the deposition-precipitation method with urea hydrolysis and freeze-drying. Most metals show a maximum catalytic activity during the RWGS reaction (reaching the thermodynamic conversion limit) with formate groups as an intermediate adsorbed species, while Ag metal has limited activity with the carbonate species on its surface. According to DFT calculations, such carbonate groups result from the suppressed dissociation and adsorption of hydrogen on the Ag surface, which is in good agreement with the experimental RWGS results.

  1. Formation of {open_quotes}metal wool{close_quotes} structures and dynamics of catalytic etching of platinum surfaces during ammonia oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Lyubovsky, M.R.; Barelko, V.V. [Institute of Chemical Physics in Chernogolovka, Moscow (Russian Federation)

    1994-09-01

    Reconstruction of a clean surface of a platinum catalyst and a platinum surface covered with gold during ammonia oxidation was studied by SEM observations. It was found that the process of catalytic etching had two sequential stages in which different crystal structures with different rates of growth formed on the surface. The first stage was the formation of parallel facets, and the second stage was the formation of individual microcrystals with perfect crystal faces. It was also found that the second state had a threshold character, beginning after some delay from the start of the reaction. A structure resembling metal wool and consisting of interlaced platinum filaments was found to form on the surface of gold-covered platinum catalysts. Characteristic features of this structure`s development are reported. The growth of filaments is attributed to the vapor-liquid-solid mechanism of whisker growth. On the basis of the observed platinum whisker formation and behavior during ammonia oxidation, a mechanism of catalyst surface reconstruction that explains observed characteristic features of the process of catalytic etching is proposed. 25 refs., 8 figs.

  2. EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

    Directory of Open Access Journals (Sweden)

    B. JOTHI THIRUMAL

    2015-11-01

    Full Text Available This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performance, and emissions are studied, and the dosing level of the additive is optimized. Cerium oxide acts as an oxygen-donating catalyst and provides oxygen for the oxidation of CO during combustion. The active energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall which results in reduction in HC emission by 56.5%. Furthermore, a low-cost metal oxide coated SCR (selective catalyst reduction, using urea as a reducing agent, along with different types of CC (catalytic converter, has been implemented in the exhaust pipe to reduce NOx. It was observed that a reduction in NOx emission is 50–60%. The tests revealed that cerium oxide nanoparticles can be used as an additive in diesel to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

  3. Surface passivation of silicon nanowires based metal nano-particle assisted chemical etching for photovoltaic applications

    Science.gov (United States)

    Ben Rabha, Mohamed; Khezami, Lotfi; Jemai, Abdelbasset Bessadok; Alhathlool, Raed; Ajbar, Abdelhamid

    2017-03-01

    Metal Nano-particle Assisted Chemical Etching (MNpACE) is an extraordinary developed wet etching method for producing uniform semiconductor nanostructure (silicon nanowires) from patterned metallic film on crystalline silicon surface. The metal films facilitate the etching in HF and H2O2 solution and produce silicon nanowires (SiNWs).The creation of different SiNWs morphologies by changing the etching time and its effects on optical and optoelectronic properties was investigated. The combination effect of formed SiNWs and stain etching treatment in acid (HF/HNO3/H2O) solution on the surface morphology of Si wafers as well as on the optical and optoelectronic properties especially a PL response at 640 nm are presented. As a results, the effective lifetime (τeff) and surface recombination velocity (Seff) evolution of SiNWs after stain etching treatment showed significant improvements and less than 1% reflectance was achieved over the wavelength range of 400-800 nm and more than 36% reduction was observed compared to untreated surface. It has, thus, been demonstrated that all these factors may lead to improved energy efficiency from 8% to nearly 14.2% for a cell with SiNWs treated in acid (HF/HNO3/H2O) solution.

  4. Enhanced metal loading in SBA-15-type catalysts facilitated by salt addition. Synthesis, characterization and catalytic epoxide alcoholysis activity of molybdenum incorporated porous silica

    Energy Technology Data Exchange (ETDEWEB)

    Budhi, Sridhar [Iowa State Univ., Ames, IA (United States); Colorado School of Mines, Golden, CO (United States); Peeraphatdit, Chorthip [Iowa State Univ., Ames, IA (United States); Pylypenko, Svitlana [Colorado School of Mines, Golden, CO (United States); Nguyen, Vy H.T. [Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States); Smith, Emily A. [Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States); Trewyn, Brian G. [Iowa State Univ., Ames, IA (United States); Colorado School of Mines, Golden, CO (United States)

    2014-02-07

    We report a novel method to increase the metal loading in SBA-15 silica matrix via direct synthesis. It was demonstrated through the synthesis and characterization of a series of molybdenum containing SBA-15 mesoporous silica catalysts prepared with and without diammonium hydrogen phosphate (DHP) as an additive. Catalysts prepared with DHP show a 2–3 times increase in incorporation of molybdenum in the silica matrix and pore size enlargement. The synthesized catalysts were characterized using nitrogen sorption, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma–optical emission spectroscopy (ICP–OES). The catalytic activity of catalysts prepared with DHP for alcoholysis of epoxides was superior than the catalyst prepared without DHP. Alcoholysis of epoxides was demonstrated for a range of alcohols and epoxides under ambient conditions in as little as 30 min with high selectivity.

  5. Transition metal (Co, Ni) nanoparticles wrapped with carbon and their superior catalytic activities for the reversible hydrogen storage of magnesium hydride.

    Science.gov (United States)

    Huang, Xu; Xiao, Xuezhang; Zhang, Wei; Fan, Xiulin; Zhang, Liuting; Cheng, Changjun; Li, Shouquan; Ge, Hongwei; Wang, Qidong; Chen, Lixin

    2017-02-01

    Magnesium hydride (MgH2) exhibits long-term stability and has recently been developed as a safe alternative to store hydrogen in the solid state, due to its high capacity of 7.6 wt% H2 and low cost compared to other metal hydrides. However, the high activation energy and poor kinetics of MgH2 lead to inadequate hydrogen storage properties, resulting in low energy efficiency. Nano-catalysis is deemed to be the most effective strategy in improving the kinetics performance of hydrogen storage materials. In this work, robust and efficient architectures of carbon-wrapped transition metal (Co/C, Ni/C) nanoparticles (8-16 nm) were prepared and used as catalysts in the MgH2 system via ball milling to improve its de/rehydrogenation kinetics. Between the two kinds of nano-catalysts, the Ni/C nanoparticles exhibit a better catalytic efficiency. MgH2 doped with 6% Ni/C (MgH2-6%Ni/C) exhibits a peak dehydrogenation temperature of 275.7 °C, which is 142.7, 54.2 and 32.5 °C lower than that of commercial MgH2, milled MgH2 and MgH2 doped with 6% Co/C (MgH2-6%Co/C), respectively. MgH2 doped with 6% Ni/C can release about 6.1 wt% H2 at 250 °C. More importantly, the dehydrogenated MgH2-6%Ni/C is even able to uptake 5.0 wt% H2 at 100 °C within 20 s. Moreover, a cycling test of MgH2 doped with 8% Ni/C demonstrates its excellent hydrogen absorption/desorption stability with respect to both capacity (up to 6.5 wt%) and kinetics (within 8 min at 275 °C for dehydrogenation and within 10 s at 200 °C for rehydrogenation). Mechanistic research reveals that the in situ formed Mg2Ni and Mg2NiH4 nanoparticles can be regarded as advanced catalytically active species in the MgH2-Ni/C system. Meanwhile, the carbon attached around the surface of transition metal nanoparticles can successfully inhibit the aggregation of the catalysts and achieve the steadily, prompting de/rehydrogenation during the subsequent cycling process. The intrinsic catalytic effects and the uniform distributions of Mg2Ni

  6. Selectively catalytic activity of metal-organic frameworks depending on the N-position within the pyridine ring of their building blocks

    Science.gov (United States)

    Xu, Haitao; Gou, Yongxia; Ye, Jing; Xu, Zhen-liang; Wang, Zixuan

    2016-05-01

    Iron metal-organic frameworks (MOFs) [Fe(L)2(SCN)2]∝ (L1: 4-bpdh=2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene for 1Fe; and L2: 3-bpdh=2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene for 2Fe) were assembled in a MeOH-H2O solvent system. 1Fe exhibits a two-dimensional extended-grid network, whereas 2Fe exhibits a stair-like double-chain; the N-position within the pyridine ring of the complexes was observed to regulate the MOF structure as layers or chains. Furthermore, selectively catalytic activity was observed for the layered MOF but not the chain-structured MOF; micro/nanoparticles of the layered MOF were therefore investigated for new potential applications of micro/nano MOFs.

  7. Micromechanical and macroscopic models of ductile fracture in particle reinforced metallic materials

    Science.gov (United States)

    Hu, Chao; Bai, Jie; Ghosh, Somnath

    2007-06-01

    This paper is aimed at developing two modules contributing to the overall framework of multi-scale modelling of ductile fracture of particle reinforced metallic materials. The first module is for detailed micromechanical analysis of particle fragmentation and matrix cracking of heterogeneous microstructures. The Voronoi cell FEM for particle fragmentation is extended in this paper to incorporate ductile failure through matrix cracking in the form of void growth and coalescence using a non-local Gurson-Tvergaard-Needleman (GTN) model. In the resulting enriched Voronoi cell finite element model (VCFEM) or E-VCFEM, the assumed stress-based hybrid VCFEM formulation is overlaid with narrow bands of displacement based elements to accommodate strain softening in the constitutive behaviour. The second module develops an anisotropic plasticity-damage model in the form of the GTN model for macroscopic analysis in the multi-scale material model. Parameters in this model are calibrated from results of homogenization of microstructural variables obtained by E-VCFEM analysis of microstructural representative volume element. Numerical examples conducted yield satisfactory results.

  8. Metal-bearing fine particle sources in a coastal industrialized environment

    Science.gov (United States)

    Mbengue, Saliou; Alleman, Laurent Y.; Flament, Pascal

    2017-01-01

    Fine (primary or secondary submicron particles and mechanical procedures in open air, or local traffic, which lead to the emission of coarser particles (> 1 μm). The trace elements As, Cd, Ni, Pb, Sb, V and Zn, characteristics of the local industrial activities display 60% to 85% of their mass in the submicron and ultrafine fractions and appear highly enriched, by reference to the crustal source. High atmospheric pressure periods, corresponding to northeasterly winds, induce the highest contributions of metalworking emissions and the highest PM2.5 concentrations (32.5 ± 11.9 μg·m- 3). A Principal Component Analysis of the dataset produces 7 factors associated to metallurgy-, steelworks-, oil processing-, coal combustion-, neighboring traffic-, dust resuspension- and sea salt-sources, that explain the obtained concentrations. A Multiple Linear Regression Analysis confirms that Fe-Mn alloy refining, iron- and steel-making are the main sources (> 40%) controlling metal concentrations in PM2.5. Less predictably, resuspended dust and fresh/aged sea salts are also significant contributors (≈ 20%). Considering the related health hazards, authorities should pay more attention to the exposure of people living in this area and the possible impact of fine particles in terms of public health.

  9. Development of Thermal Spraying and Coating Techniques by Using Thixotropic Slurries Including Metals and Ceramics Particles

    Science.gov (United States)

    Kirihara, S.; Itakura, Y.; Tasaki, S.

    2013-03-01

    Thermal nanoparticles coating and microlines patterning were newly developed as novel technologies to fabricate fine ceramics layers and geometrical intermetallics patterns for mechanical properties modulations of practical alloys substrates. Nanometer sized alumina particles were dispersed into acrylic liquid resins, and the obtained slurries were sputtered by using compressed air jet. The slurry mists could blow into the arc plasma with argon gas spraying. On stainless steels substrates, the fine surface layers with high wear resistance were formed. In cross sectional microstructures of the coated layers, micromater sized cracks or pores were not observed. Subsequently, pure aluminum particles were dispersed into photo solidified acrylic resins, and the slurry was spread on the stainless steel substrates by using a mechanical knife blade. On the substrates, microline patterns with self similar fractal structures were drawn and fixed by using scanning of an ultra violet laser beam. The patterned pure metal particles were heated by the argon arc plasma spray assisting, and the intermetallics or alloys phases with high hardness were created through reaction diffusions. Microstructures in the coated layers and the patterned lines were observed by using a scanning electron microscopy.

  10. Complexation of trace metals in size-segregated aerosol particles at nine sites in Germany

    Science.gov (United States)

    Scheinhardt, Sebastian; Müller, Konrad; Spindler, Gerald; Herrmann, Hartmut

    2013-08-01

    The complexation of trace metal ions (TMI) was studied in size-segregated ambient aerosol particles collected at nine sites in Germany (urban, rural and coastal). Samples were analysed in terms of TMI (Fe, Mn, Cu), potential inorganic and organic ligands and pH. Using a thermodynamic model (E-AIM III), the concentrations of these compounds in the particle liquid phase were estimated. The resulting liquid phase concentrations were then used as input parameters for a speciation model (Visual MINTEQ) and the equilibrium complexation was calculated under realistic conditions. The complexation was found to be controlled by the availability of strong organic ligands, especially oxalate, whose occurrence in turn was governed by the formation of insoluble Ca-oxalate. Likewise, the pH influenced oxalate availability because it alters the concentrations of the chelating mono- and dianions. As a qualitative result, Fe3+ was found to be mainly complexed by oxalate, while Fe2+ and Mn2+ were rather associated with nitrate. Cu2+ showed mixed organic and nitrate complexation. Complexation by HULIS was only significant for Fe3+ and Cu2+ and was generally less important than other ligands like oxalate and nitrate. Oxalate was found to exist mainly in the solid phase while higher dicarboxylic acids mostly did not form complexes due to protonation. Complexation was shown to be influenced by season, air mass origin, particle size and sampling site.

  11. Assessment of Microwave/UV/O3 in the Photo-Catalytic Degradation of Bromothymol Blue in Aqueous Nano TiO2 Particles Dispersions

    Directory of Open Access Journals (Sweden)

    Kim Sun-Jae

    2010-01-01

    Full Text Available Abstract In this study, a microwave/UV/TiO2/ozone/H2O2 hybrid process system, in which various techniques that have been used for water treatment are combined, is evaluated to develop an advanced technology to treat non-biodegradable water pollutants efficiently. In particular, the objective of this study is to develop a novel advanced oxidation process that overcomes the limitations of existing single-process water treatment methods by adding microwave irradiation to maximize the formation of active intermediate products, e.g., OH radicals, with the aid of UV irradiation by microwave discharge electrodeless lamp, photo-catalysts, and auxiliary oxidants. The results of photo-catalytic degradation of BTB showed that the decomposition rate increased with the TiO2 particle dosages and microwave intensity. When an auxiliary oxidant such as ozone or hydrogen peroxide was added to the microwave-assisted photo-catalysis, however, a synergy effect that enhanced the reaction rate considerably was observed.

  12. Comparison of the DiSCmini aerosol monitor to a handheld condensation particle counter and a scanning mobility particle sizer for submicrometer sodium chloride and metal aerosols.

    Science.gov (United States)

    Mills, Jessica B; Park, Jae Hong; Peters, Thomas M

    2013-01-01

    We evaluated the robust, lightweight DiSCmini (DM) aerosol monitor for its ability to measure the concentration and mean diameter of submicrometer aerosols. Tests were conducted with monodispersed and polydispersed aerosols composed of two particle types (sodium chloride [NaCl] and spark-generated metal particles, which simulate particles found in welding fume) at three different steady-state concentration ranges (Low, 10(4) particles/cm(3)). Particle number concentration, lung deposited surface area (LDSA) concentration, and mean size measured with the DM were compared with those measured with reference instruments, a scanning mobility particle sizer (SMPS), and a handheld condensation particle counter (CPC). Particle number concentrations measured with the DM were within 16% of those measured by the CPC for polydispersed aerosols. Poorer agreement was observed for monodispersed aerosols (±35% for most tests and +101% for 300-nm NaCl). LDSA concentrations measured by the DM were 96% to 155% of those estimated with the SMPS. The geometric mean diameters measured with the DM were within 30% of those measured with the SMPS for monodispersed aerosols and within 25% for polydispersed aerosols (except for the case when the aerosol contained a substantial number of particles larger than 300 nm). The accuracy of the DM is reasonable for particles smaller than 300 nm, but caution should be exercised when particles larger than 300 nm are present. [Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resources: manufacturer-reported capabilities of instruments used, and information from the SMPS measurements for polydispersed test particles.].

  13. Modeling and Simulation of the Hydrogenation of α-Methylstyrene on Catalytically Active Metal Foams as Tubular Reactor Packing

    Directory of Open Access Journals (Sweden)

    Farzad Lali

    2016-01-01

    Full Text Available This work presents a one-dimensional reactor model for a tubular reactor packed with a catalytically active foam packing with a pore density of 30 PPI in cocurrent upward flow in the example of hydrogenation reaction of α-methylstyrene to cumene. This model includes material, enthalpy, and momentum balances as well as continuity equations. The model was solved within the parameter space applied for experimental studies under assumption of a bubbly flow. The method of orthogonal collocation on finite elements was applied. For isothermal and polytropic processes and steady state conditions, axial profiles for concentration, temperature, fluid velocities, pressure, and liquid holdup were computed and the conversions for various gas and liquid flow rates were validated with experimental results. The obtained results were also compared in terms of space time yield and catalytic activity with experimental results and stirred tank and also with random packed bed reactor. The comparison shows that the application of solid foams as reactor packing is advantageous compared to the monolithic honeycombs and random packed beds.

  14. Catalytic Upgrading of Biomass Fast Pyrolysis Vapors with Nano Metal Oxides: An Analytical Py-GC/MS Study

    Directory of Open Access Journals (Sweden)

    Qiang Lu

    2010-11-01

    Full Text Available Fast pyrolysis of poplar wood followed with catalytic cracking of the pyrolysis vapors was performed using analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS. The catalysts applied in this study were nano MgO, CaO, TiO2, Fe2O3, NiO and ZnO. These catalysts displayed different catalytic capabilities towards the pyrolytic products. The catalysis by CaO significantly reduced the levels of phenols and anhydrosugars, and eliminated the acids, while it increased the formation of cyclopentanones, hydrocarbons and several light compounds. ZnO was a mild catalyst, as it only slightly altered the pyrolytic products. The other four catalysts all decreased the linear aldehydes dramatically, while the increased the ketones and cyclopentanones. They also reduced the anhydrosugars, except for NiO. Moreover, the catalysis by Fe2O3 resulted in the formation of various hydrocarbons. However, none of these catalysts except CaO were able to greatly reduce the acids.

  15. [Particle Size Distribution, Seasonal Variation Characteristics and Human Exposure Assessment of Heavy Metals in Typical Settled Dust from Beijing].

    Science.gov (United States)

    Cao, Zhi-guo; Yu, Gang; Lü, Xiang-ying; Wang, Meng-lei; Li, Qi-lu; Feng, Jing-lan; Yan, Guang-xuan; Yu, Hao; Sun, Jian-hui

    2016-04-15

    Four types of dust from dormitories, offices, hotels and roads in Beijing were collected and fractionated into 9 fractions, respectively. Totally 36 samples were obtained and analyzed for heavy metals including Cu, Zn, Cr, Pb, Cd and Ni. Particle size distributions of those heavy metals in these four types of dust were investigated and the influencing mechanisms were discussed. Distribution patterns of the same heavy metal in different types of dust showed various characteristics. Also different metals in the same type of dust represented different distribution patterns. Heavy metals in road dust tended to concentrate in finer particles. Two offices from the same building, located in Beijing, China, were selected to study the seasonality of heavy metals in dust. Dust sampling from Office A was conducted at weekly intervals between March 2012 and August 2012, while dust from Office B was sampled fortnightly from March 2012 to December 2012. Generally, levels of all heavy metals remained stable among different seasons, however, Cr and Pb represented more significant fluctuations than other four heavy metals. Based on the geo-accumulation index method, the pollution of Zn, Cu and Pb was more serious in the investigated samples, and dust from offices and hotels were moderately polluted by Zn. According to the risk assessment results, the carcinogenic health risks of the six heavy metals in the four types of dust were negligible.

  16. Encapsulation of metal clusters within MFI via interzeolite transformations and direct hydrothermal syntheses and catalytic consequences of their confinement.

    Science.gov (United States)

    Goel, Sarika; Zones, Stacey I; Iglesia, Enrique

    2014-10-29

    The encapsulation of metal clusters (Pt, Ru, Rh) within MFI was achieved by exchanging cationic metal precursors into a parent zeolite (BEA, FAU), reducing them with H2 to form metal clusters, and transforming these zeolites into daughter structures of higher framework density (MFI) under hydrothermal conditions. These transformations required MFI seeds or organic templates for FAU parent zeolites, but not for BEA, and occurred with the retention of encapsulated clusters. Clusters uniform in size (1.3-1.7 nm) and exposing clean and accessible surfaces formed in BEA and FAU zeolites; their size remained essentially unchanged upon transformation into MFI. Encapsulation selectivities, determined from the relative hydrogenation rates of small (toluene) and large (alkyl arenes) molecules and defined as the ratio of the surface areas of all the clusters in the sample to that of external clusters, were very high (8.1-40.9) for both parent and daughter zeolites. Encapsulation into MFI via direct hydrothermal syntheses was unsuccessful because metal precursors precipitated prematurely at the pH and temperatures required for MFI synthesis. Delayed introduction of metal precursors and F(-) (instead of OH(-)) as the mineralizing agent in hydrothermal syntheses increased encapsulation selectivities, but they remained lower than those achieved via interzeolite transformations. These interconversions provide a general and robust strategy for encapsulation of metals when precursors can be introduced via exchange into a zeolite that can be transformed into target daughter zeolites with higher framework densities, whether spontaneously or by using seeds or structure-directing agents (SDA).

  17. Catalytic potential of selected metal ions for bioleaching, and potential techno-economic and environmental issues: A critical review.

    Science.gov (United States)

    Pathak, Ashish; Morrison, Liam; Healy, Mark Gerard

    2017-04-01

    Bioleaching is considered to be a low-cost, eco-friendly technique for leaching valuable metals from a variety of matrixes. However, the inherent slow dissolution kinetics and low metal leaching yields have restricted its wider commercial applicability. Recent advancements in bio-hydrometallurgy have suggested that these critical issues can be successfully alleviated through the addition of a catalyst. The catalyzing properties of a variety of metals ions (Ag(+), Hg(++), Bi(+++), Cu(++), Co(++) etc.) during bioleaching have been successfully demonstrated. In this article, the role and mechanisms of these metal species in catalyzing bioleaching from different minerals (chalcopyrite, complex sulfides, etc.) and waste materials (spent batteries) are reviewed, techno-economic and environmental challenges associated with the use of metals ions as catalysts are identified, and future prospectives are discussed. Based on the analysis, it is suggested that metal ion-catalyzed bioleaching will play a key role in the development of future industrial bio-hydrometallurgical processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Scanning electron microscope and statistical analysis of suspended heavy metal particles in San Luis Potosi, Mexico

    Science.gov (United States)

    Piña, A. Aragón; Villaseñor, G. Torres; Fernández, M. Monroy; Luszczewski Kudra, A.; Leyva Ramos, R.

    Three hundred samples of urban aerosol were collected in high-volume samplers from five urban locations situated near an important metallurgical plant in the city of San Luis Potosi, Mexico. Whole samples were analyzed by atomic absorption (AA) for Pb, Cd, As, Cu, Ni, Fe and Cr. One hundred eighty of these samples were subjected to X-ray microanalysis (EDS) coupled with a scanning electron microscope to classify individual particles according to their chemical or mineralogical composition. The principal component analysis (PCA) obtained from the bulk sample analysis, and X-ray microanalysis from individual particles, confirmed chemical associations among elements directly and indirectly. PCA from bulk assays made the most effective use of X-ray microanalysis to characterize major particle types. Some chemical associations would be difficult to detect using microanalysis, alone, for example, in anthropogenic complex phases. In this work, the combined use of microanalysis and statistical methods permitted identification of associations among elements. We observed an association of Pb-As-Cd and Fe-Mn among the samples. In a second order, Pb-Fe, Pb-Mn, Fe-As, Fe-Cd, Cd-Mn and As-Mn showed a lower association. Only Ni and Cu appeared unassociated with any other element analyzed by AA. We characterized the mineral phases by size range, morphology and chemical composition using SEM-EDS to obtain a compositional approach of anthropogenic phases and peculiar morphology and size. A high percentage of heavy metal particles smaller than 2 μm were detected.

  19. Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

    Science.gov (United States)

    Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

    2015-08-01

    The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys.

  20. Mutagenic definition of a papain-like catalytic triad, sufficiency of the N-terminal domain for single-site core catalytic enzyme acylation, and C-terminal domain for augmentative metal activation of a eukaryotic phytochelatin synthase.

    Science.gov (United States)

    Romanyuk, Nataliya D; Rigden, Daniel J; Vatamaniuk, Olena K; Lang, Albert; Cahoon, Rebecca E; Jez, Joseph M; Rea, Philip A

    2006-07-01

    in the case of AtPCS1, for formation of the biosynthetically competent gamma-Glu-Cys enzyme acyl intermediate, the primary data from experiments directed at determining whether the other two residues, His-162 and Asp-180 of the putative papain-like catalytic triad of AtPCS1, are essential for catalysis have yet to be presented. This shortfall in our basic understanding of AtPCS1 is addressed here by the results of systematic site-directed mutagenesis studies that demonstrate that not only Cys-56 but also His-162 and Asp-180 are indeed required for net PC synthesis. It is therefore established experimentally that AtPCS1 and, by implication, other eukaryotic PC synthases are papain Cys protease superfamily members but ones, unlike their prokaryotic counterparts, which, in addition to having a papain-like N-terminal catalytic domain that undergoes primary gamma-Glu-Cys acylation, contain an auxiliary metal-sensing C-terminal domain that undergoes secondary gamma-Glu-Cys acylation.

  1. Particles, sweat, and tears: a comparative study on bioaccessibility of ferrochromium alloy and stainless steel particles, the pure metals and their metal oxides, in simulated skin and eye contact.

    Science.gov (United States)

    Hedberg, Yolanda; Midander, Klara; Wallinder, Inger Odnevall

    2010-07-01

    Ferrochromium alloys are manufactured in large quantities and placed on the global market for use as master alloys (secondary raw materials), primarily for stainless steel production. Any potential human exposure to ferrochromium alloy particles is related to occupational activities during production and use, with 2 main exposure routes, dermal contact and inhalation and subsequent digestion. Alloy and reference particles exposed in vitro in synthetic biological fluids relevant for these main exposure routes have been investigated in a large research effort combining bioaccessibility; chemical speciation; and material, surface, and particle characteristics. In this paper, data for the dermal exposure route, including skin and eye contact, will be presented and discussed. Bioaccessibility data have been generated for particles of a ferrochromium alloy, stainless steel grade AISI 316L, pure Fe, pure Cr, iron(II,III)oxide, and chromium(III)oxide, upon immersion in artificial sweat (pH 6.5) and artificial tear (pH 8.0) fluids for various time periods. Measured released amounts of Fe, Cr, and Ni are presented in terms of average Fe and Cr release rates and amounts released per amount of particles loaded. The results are discussed in relation to bulk and surface composition of the particles. Additional information, essential to assess the bioavailability of Cr released, was generated by determining its chemical speciation and by providing information on its complexation and oxidation states in both media investigated. The effect of differences in experimental temperature, 30 degrees C and 37 degrees C, on the extent of metal release in artificial sweat is demonstrated. Iron was the preferentially released element in all test media and for all time periods and iron-containing particles investigated. The extent of metal release was highly pH dependent and was also dependent on the medium composition. Released amounts of Cr and Fe were very low (close to the limit of

  2. Dendritic structure DNA for specific metal ion biosensor based on catalytic hairpin assembly and a sensitive synergistic amplification strategy.

    Science.gov (United States)

    Zhao, Jianmin; Jing, Pei; Xue, Shuyan; Xu, Wenju

    2017-01-15

    In this work, a sensitive electrochemical biosensing to Pb(2+) was proposed based on the high specificity of DNAzymes to Pb(2+). The response signal was efficiently amplified by the catalytic hairpin assembly induced by strand replacement reaction and the formation of dendritic structure DNA (DSDNA) by layer-by-layer assembly. Firstly, in the presence of Pb(2+), the substrate strand (S1) of the Pb(2+)-specific DNAzymes was specifically cleaved by Pb(2+). Secondly, one of the two fragments (rS1) introduced into the electrode surface was hybridized with a hairpin DNA (H1) and further replaced by another hairpin DNA (H2) by the hybridization reaction of H1 with H2. The released rS1 then induced the next hybridization with H1. After repeated cycles, the catalytic recycling assembly of H2 with H1 was completed. Thirdly, two bioconjugates of Pt@Pd nanocages (Pt@PdNCs) labeled with DNA S3/S4 and electroactive toluidine blue (Tb) (Tb-S3-Pt@PdNCs and Tb-S4-Pt@PdNCs) were captured onto the resultant electrode surface through the hybridization of S3 and H2, S3 and S4, resulting in the formation of DSDNA triggered by layer-by-layer assembly. This formed DSDNA greatly facilitated the immobilization of manganese(III) meso-tetrakis (4-N-methylpyridiniumyl)-porphyrin (MnTMPyP) as mimicking enzyme. Under the synergistic catalysis of Pt@PdNCs and MnTMPyP to H2O2 reduction, the effective signal amplification of the developed Pb(2+) biosensor was achieved. As a result, the sensitive detection of the proposed electrochemical strategy for Pb(2+) was greatly improved in the range of 0.1pM-200nM with a detection limit of 0.033pM.

  3. Particle size distribution and characteristics of heavy metals in road-deposited sediments from Beijing Olympic Park.

    Science.gov (United States)

    Li, Haiyan; Shi, Anbang; Zhang, Xiaoran

    2015-06-01

    Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments (RDSs) of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents' and tourists' health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size (heavy metal (i.e., Cu, Zn, Pb and Cd) content was the largest in particles with small size (Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index (Igeo) decreased in the order: Cd>Pb>Cu>Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order: Cd>Zn≈Pb>Cu. Copyright © 2015. Published by Elsevier B.V.

  4. Electrical four-point probing of spherical metallic thin films coated onto micron sized polymer particles

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Sigurd R., E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang; He, Jianying, E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Kristiansen, Helge [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway); Njagi, John; Goia, Dan V. [Center for Advanced Materials Processing, Clarkson University, Potsdam, New York 13699-5814 (United States); Redford, Keith [Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway)

    2016-07-25

    Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental results with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.

  5. Strain-dependent conductivity of granular metals prepared by focused particle beam induced deposition

    Energy Technology Data Exchange (ETDEWEB)

    Grimm, Christina; Baranowski, Markus; Huth, Michael [Physikalisches Institut, Goethe-Universitaet, Frankfurt am Main (Germany); Voelklein, Friedemann [Institut fuer Mikrotechnologien, Hochschule RheinMain, Ruesselsheim (Germany)

    2010-07-01

    We report on the strain-dependence of the electrical conductivity of granular metals prepared by focused particle beam induced deposition. The samples were prepared in a dual-beam electron / Ga ion scanning microscope using selected precursors, such as W(CO){sub 6}. Stripe-like deposits were fabricated on dedicated cantilevers pre-patterned with contact pads made from Cr/Au. The cantilever deflection was induced in-situ by means of a four axes nano-manipulator and the conductivity change was recorded by lock-in technique employing a Wheatstone resistance bridge. Current-voltage characteristics and strain-dependence were measured for samples of various thicknesses and composition. For selected samples time-dependent conductivity data were taken as the samples were slowly exposed to air.

  6. Weibull Probability Model for Fracture Strength of Aluminium (1101)-Alumina Particle Reinforced Metal Matrix Composite

    Institute of Scientific and Technical Information of China (English)

    A.Suresh Babu; V.Jayabalan

    2009-01-01

    In recent times, conventional materials are replaced by metal matrix composites (MMCs) due to their high specific strength and modulus.Strength reliability, one of the key factors restricting wider use of composite materials in various applications, is commonly characterized by Weibull strength distribution function.In the present work, statistical analysis of the strength data of 15% volume alumina particle (mean size 15 μm)reinforced in aluminum alloy (1101 grade alloy) fabricated by stir casting method was carried out using Weibull probability model.Twelve tension tests were performed according to ASTM B577 standards and the test data, the corresponding Weibull distribution was obtained.Finally the reliability of the composite behavior in terms of its fracture strength was presented to ensure the reliability of composites for suitable applications.An important implication of the present study is that the Weibull distribution describes the experimentally measured strength data more appropriately.

  7. Characteristics of ionic polymer-metal composite with chemically doped TiO2 particles

    Science.gov (United States)

    Jung, Youngsoo; Kim, Seong Jun; Kim, Kwang J.; Lee, Deuk Yong

    2011-12-01

    Many studies have investigated techniques to improve the bending performance of ionic polymer-metal composite (IPMC) actuators, including 'doping' of metal particles in the polymer membrane usually by means of physical processes. This study is mainly focused on the characterization of the physical, electrochemical and electromechanical properties of TiO2-doped ionic polymer membranes and IPMCs prepared by the sol-gel method, which results in a uniform distribution of the particles inside the polymer membrane. X-ray and UV-visible spectra indicate the presence of anatase-TiO2 in the modified membranes. TiO2-doped membranes (0.16 wt%) exhibit the highest level of water uptake. The glass transition temperature of these membranes, measured using differential scanning calorimetry (DSC), increases with the increase of the amount of TiO2 in the membrane. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus of dried TiO2-doped ionic polymer membranes increases as the amount of TiO2 in the membrane increases, whereas the storage modulus of hydrated samples is closely related to the level of water uptake. Electrochemical impedance spectroscopy (EIS) shows that the conductivity of TiO2-doped membranes decreases with increasing TiO2 content in spite of an internal resistance drop in the samples. Above all, bending deflection of TiO2-doped IPMC decreased with higher TiO2 content in the membrane while the blocking force of each sample increased with the higher TiO2 content. Additionally, it was determined that the lifetime of IPMC is strongly dependent on the level of water uptake.

  8. 40 CFR Table 3 to Subpart Uuu of... - Continous Monitoring Systems for Metal HAP Emissions From Catalytic Cracking Units

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 12 2010-07-01 2010-07-01 true Continous Monitoring Systems for Metal... Units Pt. 63, Subpt. UUU, Table 3 Table 3 to Subpart UUU of Part 63—Continous Monitoring Systems for... CFR 60.102 a. Over 20,000 barrels per day fresh feed capacity Electrostatic precipitator Continuous...

  9. Removal of bisphenol A and some heavy metal ions by polydivinylbenzene magnetic latex particles.

    Science.gov (United States)

    Marzougui, Zied; Chaabouni, Amel; Elleuch, Boubaker; Elaissari, Abdelhamid

    2016-08-01

    In this study, magnetic polydivinylbenzene latex particles MPDVB with a core-shell structure were tested for the removal of bisphenol A (BPA), copper Cu(II), lead Pb(II), and zinc Zn(II) from aqueous solutions by a batch-adsorption technique. The effect of different parameters, such as initial concentration of pollutant, contact time, adsorbent dose, and initial pH solution on the adsorption of the different adsorbates considered was investigated. The adsorption of BPA, Cu(II), Pb(II), and Zn(II) was found to be fast, and the equilibrium was achieved within 30 min. The pH 5-5.5 was found to be the most suitable pH for metal removal. The presence of electrolytes and their increasing concentration reduced the metal adsorption capacity of the adsorbent. Whereas, the optimal pH for BPA adsorption was found 7, both hydrogen bonds and π-π interaction were thought responsible for the adsorption of BPA on MPDVB. The adsorption kinetics of BPA, Cu(II), Pb(II), and Zn(II) were found to follow a pseudo-second-order kinetic model. Equilibrium data for BPA, Cu(II), Pb(II), and Zn(II) adsorption were fitted well by the Langmuir isotherm model. Furthermore, the desorption and regeneration studies have proven that MPDVB can be employed repeatedly without impacting its adsorption capacity.

  10. Suspended sediment concentration and particle size distribution, and their relationship with heavy metal content

    Indian Academy of Sciences (India)

    S H R Sadeghi; M Kiani Harchegani; H A Younesi

    2012-02-01

    This paper aims at assessing the feasibility of suspended sediment concentration (SSC) estimation by using predictor variables of heavy metal concentration (HMC, viz., iron, chromium, zinc and nickel) transported in solution and solid. The study was conducted in the Research and Educational Forest Watershed of the Tarbiat Modares University (Kojour) which comprises an area of ca. 50000 ha. For this study, suspended sediment samples were collected from the left bank of the Kojour River twice a week, as well as during runoff events from November 2007 to June 2008. The samples were then prepared through direct digestion and finally analyzed by atomic absorption spectrophotometry (AAS). The relationship between SSC and particle size distribution (PSD) were correlated with HMC by using bivariate and multivariate regression models. Proposed models were then selected based on statistical criteria. The results showed high correlation between dissolved and particulate chromium content with efficiency coefficients beyond 77% ( > 0.001). However, a lower relationship was found between SSC and nickel content. From these results, it is clearly shown that the HMC can practically be estimated by SSC in watersheds with different accuracy and vice versa. It is also understood that heavy metal pollution can be easily managed by controlling SSC.

  11. Nanoscale Metal-Organic Particles with Rapid Clearance for Magnetic Resonance Imaging-Guided Photothermal Therapy.

    Science.gov (United States)

    Yang, Yu; Liu, Jingjing; Liang, Chao; Feng, Liangzhu; Fu, Tingting; Dong, Ziliang; Chao, Yu; Li, Yonggang; Lu, Guang; Chen, Meiwan; Liu, Zhuang

    2016-02-23

    Nanoscale metal-organic particles (NMOPs) are constructed from metal ions and organic bridging ligands via the self-assembly process. Herein, we fabricate NMOPs composed of Mn(2+) and a near-infrared (NIR) dye, IR825, obtaining Mn-IR825 NMOPs, which are then coated with a shell of polydopamine (PDA) and further functionalized with polyethylene glycol (PEG). While Mn(2+) in such Mn-IR825@PDA-PEG NMOPs offers strong contrast in T1-weighted magnetic resonance (MR) imaging, IR825 with strong NIR optical absorbance shows efficient photothermal conversion with great photostability in the NMOP structure. Upon intravenous injection, Mn-IR825@PDA-PEG shows efficient tumor homing together with rapid renal excretion behaviors, as revealed by MR imaging and confirmed by biodistribution measurement. Notably, when irradiated with an 808 nm laser, tumors on mice with Mn-IR825@PDA-PEG injection are completely eliminated without recurrence within 60 days, demonstrating the high efficacy of photothermal therapy with this agent. This study demonstrates the use of NMOPs as a potential photothermal agent, which features excellent tumor-targeted imaging and therapeutic functions, together with rapid renal excretion behavior, the latter of which would be particularly important for future clinical translation of nanomedicine.

  12. XPS study of nitrogen dioxide adsorption on metal oxide particle surfaces under different environmental conditions.

    Science.gov (United States)

    Baltrusaitis, Jonas; Jayaweera, Pradeep M; Grassian, Vicki H

    2009-10-01

    photoreaction on metal oxide particle surfaces under different conditions of relative humidity, presence of molecular oxygen and UV light.

  13. Characterization of compositional modifications in metal-organic frameworks using carbon and alpha particle microbeams

    Science.gov (United States)

    Paneta, V.; Fluch, U.; Petersson, P.; Ott, S.; Primetzhofer, D.

    2017-08-01

    Zirconium-oxide based metal-organic frameworks (MOFs) were grown on p-type Si wafers. A modified linker molecule containing iodine was introduced by post synthetic exchange (PSE). Samples have been studied using Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE) techniques, employing the 5 MV 15SDH-2 Pelletron Tandem accelerator at the Ångström laboratory. The degree of post synthetic uptake of the iodine-containing linker has been investigated with both a broad beam and a focused beam of carbon and alpha particles targeting different kind of MOF crystals which were of ∼1-10 μm in size, depending on the linker used. Iodine concentrations in MOF crystallites were also measured by Nuclear Magnetic Resonance Spectroscopy (NMR) and are compared to the RBS results. In parallel to the ion beam studies, samples were investigated by Scanning Electron Microscopy (SEM) to quantify possible crystallite clustering, develop optimum sample preparation routines and to characterize the potential ion beam induced sample damage and its dependence on different parameters. Based on these results the reliability and accuracy of ion beam data is assessed.

  14. Damage evaluation in metal structures subjected to high energy deposition due to particle beams

    CERN Document Server

    Peroni, L; Dallocchio, A

    2011-01-01

    The unprecedented energy intensities of modern hadron accelerators yield special problems with the materials that are placed close to or into the high intensity beams. The energy stored in a single beam of LHC particle accelerator is equivalent to about 80 kg of TNT explosive, stored in a transverse beam area with a typical value of 0.2 mm×0.2 mm. The materials placed close to the beam are used at, or even beyond, their damage limits. However, it is very difficult to predict structural efficiency and robustness accurately: beam-induced damage for high energy and high intensity occurs in a regime where practical experience does not exist. The interaction between high energy particle beams and metals induces a sudden non uniform temperature increase. This provokes a dynamic response of the structure entailing thermal stress waves and thermally induced vibrations or even the failure of the component. This study is performed in order to estimate the damage on a copper component due to the impact with a 7 TeV pro...

  15. Influence on the oxidative potential of a heavy-duty engine particle emission due to selective catalytic reduction system and biodiesel blend.

    Science.gov (United States)

    Godoi, Ricardo H M; Polezer, Gabriela; Borillo, Guilherme C; Brown, Andrew; Valebona, Fabio B; Silva, Thiago O B; Ingberman, Aline B G; Nalin, Marcelo; Yamamoto, Carlos I; Potgieter-Vermaak, Sanja; Penteado Neto, Renato A; de Marchi, Mary Rosa R; Saldiva, Paulo H N; Pauliquevis, Theotonio; Godoi, Ana Flavia L

    2016-08-01

    Although the particulate matter (PM) emissions from biodiesel fuelled engines are acknowledged to be lower than those of fossil diesel, there is a concern on the impact of PM produced by biodiesel to human health. As the oxidative potential of PM has been suggested as trigger for adverse health effects, it was measured using the Electron Spin Resonance (OP(ESR)) technique. Additionally, Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was employed to determine elemental concentration, and Raman Spectroscopy was used to describe the amorphous carbon character of the soot collected on exhaust PM from biodiesel blends fuelled test-bed engine, with and without Selective Catalytic Reduction (SCR). OP(ESR) results showed higher oxidative potential per kWh of PM produced from a blend of 20% soybean biodiesel and 80% ULSD (B20) engine compared with a blend of 5% soybean biodiesel and 95% ULSD (B5), whereas the SCR was able to reduce oxidative potential for each fuel. EDXRF data indicates a correlation of 0.99 between concentration of copper and oxidative potential. Raman Spectroscopy centered on the expected carbon peaks between 1100cm(-1) and 1600cm(-1) indicate lower molecular disorder for the B20 particulate matter, an indicative of a more graphitic carbon structure. The analytical techniques used in this study highlight the link between biodiesel engine exhaust and increased oxidative potential relative to biodiesel addition on fossil diesel combustion. The EDXRF analysis confirmed the prominent role of metals on free radical production. As a whole, these results suggest that 20% of biodiesel blends run without SCR may pose an increased health risk due to an increase in OH radical generation. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Rare earth metal doped CeO2-based catalytic materials for diesel soot oxidation at lower temperatures

    Institute of Scientific and Technical Information of China (English)

    A Rangaswamy; Putla Sudarsanam; Benjaram M Reddy

    2015-01-01

    In this work, the influence of trivalent rare-earth dopants (Sm and La) on the structure-activity properties of CeO2 was thor-oughly studied for diesel soot oxidation. For this, an optimized 40%of Sm and La was incorporated into the CeO2 using a facile co-precipitation method from ultra-high dilute aqueous solutions. A systematic physicochemical characterization was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), Brumauer-Emmett-teller method (BET) surface area, X-ray pho-toelectron spectroscopy (XPS), Raman, and H2-temperature programmed reduction (TPR) techniques. The soot oxidation efficiency of the catalysts was investigated using a thermogravimetric method. The XRD results suggested the formation of nanocrystalline sin-gle phase CeO2-Sm2O3 and CeO2-La2O3 solid solutions. The Sm-and La-doped CeO2 materials exhibited smaller crystallite size and higher BET surface area compared with the pure CeO2. Owing to the difference in the oxidation states of the dopants (Sm3+and La3+) and the Ce4+, a number of oxygen vacancies were generated in CeO2-Sm2O3 and CeO2-La2O3 samples. The H2-TPR studies evidenced the improved reducible nature of the CeO2-Sm2O3 and CeO2-La2O3 samples compared with the CeO2. It was found that the addition of Sm and La to the CeO2 outstandingly enhanced its catalytic efficiency for the oxidation of diesel soot. The observed 50%soot con-version temperatures for the CeO2-Sm2O3, CeO2-La2O3 and CeO2 were~790, 843 and 864 K (loose contact), respectively, and similar activity order was also found under the tight contact condition. The high soot oxidation efficacy of the CeO2-Sm2O3 sample was at-tributed to numerous catalytically favourable properties, like smaller crystallite size, larger surface area, abundant oxygen vacancies, and superior reducible nature.

  17. Sources and the distribution of heavy metals in the particle size of soil polluted by gold mining upstream of Miyun Reservoir, Beijing: implications for assessing the potential risks.

    Science.gov (United States)

    Li, Qian; Ji, Hongbing; Qin, Fei; Tang, Lei; Guo, Xinyue; Feng, Jinguo

    2014-10-01

    Mining has been carried out upstream of Miyun Reservoir, Beijing, for several decades, and has caused metal emissions to the environment, threatening human health. We conducted a soil survey to assess metal contamination in this area and to determine distribution of heavy metals in the particle size. We attempted to determine the possible sources of the metals and the significance of metals in the fine particle fractions to soil risk assessments. Thirty-four soil samples were collected, and eight samples were partitioned into seven size fractions. Most of the metal concentrations in the soils were higher than the background levels in Beijing, and the metal concentrations and total organic matter (TOC) contents generally increased as the particle size decreased. Each metal except Hg significantly positively correlated with the TOC. The metals in the coarse-grained soils were mainly derived from parent materials, but the metals in the fine fractions were mostly anthropogenic. Statistical analyses showed that there were three metal sources: Cd, Cu, Hg, Pb, and Zn had anthropogenic sources; Co, Cr, Ni, and V had mixed anthropogenic and natural sources; and As and Be had natural sources. The trace metals were primarily in the clay and fine silt fractions, and they might pose health risks through the inhalation of resuspended soil particles (PM10 and PM2.5). The elevated accumulation factors, enrichment factors, and ecological risk indices for the metals in the fine fractions suggest that risk assessments should be based on the fine particle size.

  18. Catalytic wet oxidation of aqueous methylamine: comparative study on the catalytic performance of platinum-ruthenium, platinum, and ruthenium catalysts supported on titania.

    Science.gov (United States)

    Song, Aiying; Lu, Gongxuan

    2015-01-01

    Promotion of the dispersion of Ru species supported on TiO2 was achieved by introduction of Pt component and the role of Pt in enhancing the catalytic performances of Pt-Ru was investigated with catalytic wet air oxidation of methylamine used as a probing reaction. It was found that Pt-Ru/TiO2 displayed a much better catalytic performance compared with Pt/TiO2 and Ru/TiO2 catalysts due to having the highest dispersion of active species. Both high total organic carbon conversion and nitrogen selectivity (∼100%) over Pt-Ru/TiO2 catalyst were achieved at low temperature (200 °C). X-ray photoelectron spectroscopy characterization indicated that there were strong interactio