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Sample records for metal alloy catalysts

  1. Supported metal alloy catalysts

    Science.gov (United States)

    Barrera, Joseph; Smith, David C.

    2000-01-01

    A process of preparing a Group IV, V, or VI metal carbonitride including reacting a Group IV, V, or VI metal amide complex with ammonia to obtain an intermediate product; and, heating the intermediate product to temperatures and for times sufficient to form a Group IV, V, or VI metal carbonitride is provided together with the product of the process and a process of reforming an n-alkane by use of the product.

  2. Catalyst Alloys Processing

    Science.gov (United States)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  3. High-Performance Transition Metal Phosphide Alloy Catalyst for Oxygen Evolution Reaction.

    Science.gov (United States)

    Liu, Kewei; Zhang, Changlin; Sun, Yuandong; Zhang, Guanghui; Shen, Xiaochen; Zou, Feng; Zhang, Haichang; Wu, Zhenwei; Wegener, Evan C; Taubert, Clinton J; Miller, Jeffrey T; Peng, Zhenmeng; Zhu, Yu

    2018-01-23

    Oxygen evolution reaction (OER) is a pivotal process in many energy conversion and storage techniques, such as water splitting, regenerative fuel cells, and rechargeable metal-air batteries. The synthesis of stable, efficient, non-noble metal-based electrocatalysts for OER has been a long-standing challenge. In this work, a facile and scalable method to synthesize hollow and conductive iron-cobalt phosphide (Fe-Co-P) alloy nanostructures using an Fe-Co metal organic complex as a precursor is described. The Fe-Co-P alloy exhibits excellent OER activity with a specific current density of 10 mA/cm 2 being achieved at an overpotential as low as 252 mV. The current density at 1.5 V (vs reversible hydrogen electrode) of the Fe-Co-P catalyst is 30.7 mA/cm 2 , which is more than 3 orders of magnitude greater than that obtained with state-of-the-art Fe-Co oxide catalysts. Our mechanistic experiments and theoretical analysis suggest that the electrochemical-induced high-valent iron stabilizes the cobalt in a low-valent state, leading to the simultaneous enhancement of activity and stability of the OER catalyst.

  4. Alloy catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel alloy catalyst material for use in the synthesis of hydrogen peroxide from oxygen and hydrogen, or from oxygen and water. The present invention also relates to a cathode and an electrochemical cell comprising the novel catalyst material, and the process use...... of the novel catalyst material for synthesising hydrogen peroxide from oxygen and hydrogen, or from oxygen and water....

  5. Identification of non-precious metal alloy catalysts for selective hydrogenation of acetylene

    DEFF Research Database (Denmark)

    Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas

    2008-01-01

    The removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts ( often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional...... dispersed on an oxide support were selective for acetylene hydrogenation at low pressures....

  6. Supported molten-metal catalysts

    Science.gov (United States)

    Datta, Ravindra; Singh, Ajeet; Halasz, Istvan; Serban, Manuela

    2001-01-01

    An entirely new class of catalysts called supported molten-metal catalysts, SMMC, which can replace some of the existing precious metal catalysts used in the production of fuels, commodity chemicals, and fine chemicals, as well as in combating pollution. SMMC are based on supporting ultra-thin films or micro-droplets of the relatively low-melting (metals and semimetals from groups 1, 12, 13, 14, 15 and 16, of the periodic table, or their alloys and intermetallic compounds, on porous refractory supports, much like supported microcrystallites of the traditional solid metal catalysts. It thus provides orders of magnitude higher surface area than is obtainable in conventional reactors containing molten metals in pool form and also avoids corrosion. These have so far been the chief stumbling blocks in the application of molten metal catalysts.

  7. Combined high-pressure cell-ultrahigh vacuum system for fast testing of model metal alloy catalysts using scanning mass spectrometry

    DEFF Research Database (Denmark)

    Johansson, Martin; Jørgensen, Jan Hoffmann; Chorkendorff, Ib

    2004-01-01

    An apparatus for fabrication, surface analysis in ultrahigh vacuum, and testing of the catalytic activity of model metal alloy catalysts is described. Arrays of model catalysts are produced by electron-beam deposition of up to four metals simultaneously onto a substrate. The surface analysis...... be studied on a substrate 10 mm in diameter. A high pressure cell with an all-metal sealed ultrahigh vacuum lock is also described as part of the work. ©2004 American Institute of Physics....

  8. Unsupported NiPt alloy metal catalysts prepared by water-in-oil (W/O) microemulsion method for methane cracking

    KAUST Repository

    Zhou, Lu

    2016-05-18

    Unsupported NiPt metal catalyst with Ni/Pt molar ratio of 88/12 is prepared by water-in-oil (W/O) microemulsion method in this study. Compared to monometallic Ni and Pt catalysts, the NiPt catalyst exhibits superior activity and stability for methane cracking. By XRD (X-ray powder diffraction), XPS (X-ray photoelectron spectroscopy) and TEM (Transmission electron microscopy) analyses, the formation of Ni(0)Pt(0) alloy is believed to be the main reason for the reactivity improvement of this catalyst. Carbon nano tube (CNT) with Ni(0)Pt(0) particles anchored on the top of tube are found for the NiPt catalyst. © 2016 Elsevier Ltd.

  9. Performance of metal alloys as hydrogen evolution reaction catalysts in a microbial electrolysis cell

    NARCIS (Netherlands)

    Jeremiasse, A.W.; Bergsma, J.; Kleijn, J.M.; Saakes, M.; Buisman, C.J.N.; Cohen Stuart, M.A.; Hamelers, H.V.M.

    2011-01-01

    H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease the energy input and increase the H2 production rate of an MEC, a catalyst is used at the cathode. Platinum is an effective catalyst, but its high costs stimulate searching for alternatives, such as

  10. New Platinum Alloy Catalysts for Oxygen Electroreduction Based on Alkaline Earth Metals

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg; Escudero-Escribano, M.; Velazquez-Palenzuela, Amado Andres

    2017-01-01

    The energy efficiency of polymer electrolyte membrane fuel cells is mainly limited by overpotentials related to the oxygen reduction reaction (ORR). In this paper, we present new platinum alloys which are active for the ORR and based on alloying Pt with very abundant elements, such as Ca. Theoret...

  11. Self-disintegrating Raney metal alloys

    Science.gov (United States)

    Oden, Laurance L.; Russell, James H.

    1979-01-01

    A method of preparing a Raney metal alloy which is capable of self-disintegrating when contacted with water vapor. The self-disintegrating property is imparted to the alloy by incorporating into the alloy from 0.4 to 0.8 weight percent carbon. The alloy is useful in forming powder which can be converted to a Raney metal catalyst with increased surface area and catalytic activity.

  12. Noble metal ionic catalysts.

    Science.gov (United States)

    Hegde, M S; Madras, Giridhar; Patil, K C

    2009-06-16

    Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NO(x), and unburned hydrocarbons-need to be fully converted to CO(2), N(2), and H(2)O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al(2)O(3) or SiO(2) promoted by CeO(2). However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce(1-x)M(x)O(2-delta) and Ce(1-x-y)Ti(y)M(x)O(2-delta) (M = Pt, Pd, Rh; x = 0.01-0.02, delta approximately x, y = 0.15-0.25) oxides in fluorite structure. In these oxide catalysts, Pt(2+), Pd(2+), or Rh(3+) ions are substituted only to the extent of 1-2% of Ce(4+) ion. Lower-valent noble metal ion substitution in CeO(2) creates oxygen vacancies. Reducing molecules (CO, H(2), NH(3)) are adsorbed onto electron-deficient noble metal ions, while oxidizing (O(2), NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NO(x) reduction (with >80% N(2) selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO(2) or Ce(1-x)Ti(x)O(2) were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the

  13. Highly dispersed metal catalyst

    Science.gov (United States)

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  14. Ductile transplutonium metal alloys

    Science.gov (United States)

    Conner, William V.

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  15. Dispersion enhanced metal/zeolite catalysts

    Science.gov (United States)

    Sachtler, Wolfgang M. H.; Tzou, Ming-Shin; Jiang, Hui-Jong

    1987-01-01

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  16. Thermodynamic Constraints in Using AuM (M = Fe, Co, Ni, and Mo) Alloys as N₂ Dissociation Catalysts: Functionalizing a Plasmon-Active Metal.

    Science.gov (United States)

    Martirez, John Mark P; Carter, Emily A

    2016-02-23

    The Haber-Bosch process for NH3 synthesis is arguably one of the greatest inventions of the 20th century, with a massive footprint in agriculture and, historically, warfare. Current catalysts for this reaction use Fe for N2 activation, conducted at high temperatures and pressures to improve conversion rate and efficiency. A recent finding shows that plasmonic metal nanoparticles can either generate highly reactive electrons and holes or induce resonant surface excitations through plasmonic decay, which catalyze dissociation and redox reactions under mild conditions. It is therefore appealing to consider AuM (M = Fe, Co, Ni, and Mo) alloys to combine the strongly plasmonic nature of Au and the catalytic nature of M metals toward N2 dissociation, which together might facilitate ammonia production. To this end, through density functional theory, we (i) explore the feasibility of forming these surface alloys, (ii) find a pathway that may stabilize/deactivate surface M substituents during fabrication, and (iii) define a complementary route to reactivate them under operational conditions. Finally, we evaluate their reactivity toward N2, as well as their ability to support a pathway for N2 dissociation with a low thermodynamic barrier. We find that AuFe possesses similar appealing qualities, including relative stability with respect to phase separation, reversibility of Fe oxidation and reduction, and reactivity toward N2. While AuMo achieves the best affinity toward N2, its strong propensity toward oxidation could greatly limit its use.

  17. Multiple allergies to metal alloys

    Directory of Open Access Journals (Sweden)

    Mei-Eng Tu

    2011-06-01

    Conclusions: Metal alloys may induce multiple metal allergies. Patients suspected of having a metal allergy should be patch tested with an extended series of metals. We recommend adding palladium and gold, at least, to the standard series.

  18. Rare earth metals for automotive exhaust catalysts

    International Nuclear Information System (INIS)

    Shinjoh, Hirohumi

    2006-01-01

    The usage of rare earth metals for automotive exhaust catalysts is demonstrated in this paper. Rare earth metals have been widely used in automotive catalysts. In particular, three-way catalysts require the use of ceria compounds as oxygen storage materials, and lanthana as both a stabilizer of alumina and a promoter. The application for diesel catalysts is also illustrated. Effects of inclusion of rare earth metals in automotive catalysts are discussed

  19. Metal phthalocyanine catalysts

    Science.gov (United States)

    Ellis, Jr., Paul E.; Lyons, James E.

    1994-01-01

    As a new composition of matter, alkali metal or ammonium or tetraalkylammonium diazidoperfluorophthalocyanatoferrate. Other embodiments of the invention comprise compositions wherein the metal of the coordination complex is cobalt, manganese and chromium.

  20. Novel non-platinum metal catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel non-platinum metal catalyst material for use in low temperature fuel cells and electrolysers and to fuel cells and electrolysers comprising the novel non-platinum metal catalyst material. The present invention also relates to a novel method for synthesizing...... the novel non-platinum metal catalyst material....

  1. Thin film hydrous metal oxide catalysts

    Science.gov (United States)

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

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

  2. Copper-Zinc Alloy Nanopowder : A Robust Precious-Metal-Free Catalyst for the Conversion of 5-Hydroxymethylfurfural

    NARCIS (Netherlands)

    Bottari, Giovanni; Kumalaputri, Angela J; Krawczyk, Krzysztof K; Feringa, Ben L; Heeres, Hero J; Barta, Katalin

    2015-01-01

    Noble-metal-free copper-zinc nanoalloy (<150 nm) is found to be uniquely suited for the highly selective catalytic conversion of 5-hydroxymethylfurfural (HMF) to potential biofuels or chemical building blocks. Clean mixtures of 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) with

  3. Mechanochemical processing for metals and metal alloys

    Science.gov (United States)

    Froes, Francis H.; Eranezhuth, Baburaj G.; Prisbrey, Keith

    2001-01-01

    A set of processes for preparing metal powders, including metal alloy powders, by ambient temperature reduction of a reducible metal compound by a reactive metal or metal hydride through mechanochemical processing. The reduction process includes milling reactants to induce and complete the reduction reaction. The preferred reducing agents include magnesium and calcium hydride powders. A process of pre-milling magnesium as a reducing agent to increase the activity of the magnesium has been established as one part of the invention.

  4. Studies on PEM fuel cell noble metal catalyst dissolution

    DEFF Research Database (Denmark)

    Andersen, S. M.; Grahl-Madsen, L.; Skou, E. M.

    2011-01-01

    A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium catalysts dissolution, and the membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were...... found to dissolve in 1 M sulfuric acid solution and the dissolution increased exponentially with the upper potential limit (UPL) between 0.6 and 1.6 vs. RHE. 2-20% of the Pt (depending on the catalyst type) was found to be dissolved during the experiments. Under the same conditions, 30-100% of the Ru...... (depending on the catalyst type) was found to be dissolved. The faster dissolution of ruthenium compared to platinum in the alloy type catalysts was also confirmed by X-ray diffraction measurements. The dissolution of the carbon supported catalyst was found one order of magnitude higher than the unsupported...

  5. Nanoparticular metal oxide/anatase catalysts

    DEFF Research Database (Denmark)

    2010-01-01

    the catalyst metai oxide is co-precipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step. The present invention also concerns processes wherein the nanoparticular metal oxide catalysts of the invention are used, such as SCR (deNOx) reactions...

  6. Stereogenic-Only-at-Metal Asymmetric Catalysts.

    Science.gov (United States)

    Zhang, Lilu; Meggers, Eric

    2017-09-19

    Chirality is an essential feature of asymmetric catalysts. This review summarizes asymmetric catalysts that derive their chirality exclusively from stereogenic metal centers. Reported chiral-at-metal catalysts can be divided into two classes, namely, inert metal complexes, in which the metal fulfills a purely structural role, so catalysis is mediated entirely through the ligand sphere, and reactive metal complexes. The latter are particularly appealing because structural simplicity (only achiral ligands) is combined with the prospect of particularly effective asymmetric induction (direct contact of the substrate with the chiral metal center). Challenges and solutions for the design of such reactive stereogenic-only-at-metal asymmetric catalysts are discussed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Studies on PEM Fuel Cell Noble Metal Catalyst Dissolution

    DEFF Research Database (Denmark)

    Ma, Shuang; Skou, Eivind Morten

    Incredibly vast advance has been achieved in fuel cell technology regarding to catalyst efficiency, improvement of electrolyte conductivity and optimization of cell system. With breathtakingly accelerating progress, Proton Exchange Membrane Fuel Cells (PEMFC) is the most promising and most widely....... Membrane Electrode Assembly (MEA) is commonly considered as the heart of cell system [2]. Degradation of the noble metal catalysts in MEAs especially Three-Phase-Boundary (TPB) is a key factor directly influencing fuel cell durability. In this work, electrochemical degradation of Pt and Pt/Ru alloy were...

  8. Metal nanoparticles as a conductive catalyst

    Science.gov (United States)

    Coker, Eric N [Albuquerque, NM

    2010-08-03

    A metal nanocluster composite material for use as a conductive catalyst. The metal nanocluster composite material has metal nanoclusters on a carbon substrate formed within a porous zeolitic material, forming stable metal nanoclusters with a size distribution between 0.6-10 nm and, more particularly, nanoclusters with a size distribution in a range as low as 0.6-0.9 nm.

  9. Highly Dispersed Alloy Catalyst for Durability

    Energy Technology Data Exchange (ETDEWEB)

    Murthi, Vivek S.; Izzo, Elise; Bi, Wu; Guerrero, Sandra; Protsailo, Lesia

    2013-01-08

    Achieving DOE's stated 5000-hr durability goal for light-duty vehicles by 2015 will require MEAs with characteristics that are beyond the current state of the art. Significant effort was placed on developing advanced durable cathode catalysts to arrive at the best possible electrode for high performance and durability, as well as developing manufacturing processes that yield significant cost benefit. Accordingly, the overall goal of this project was to develop and construct advanced MEAs that will improve performance and durability while reducing the cost of PEMFC stacks. The project, led by UTC Power, focused on developing new catalysts/supports and integrating them with existing materials (membranes and gas diffusion layers (GDLs)) using state-of-the-art fabrication methods capable of meeting the durability requirements essential for automotive applications. Specifically, the project work aimed to lower platinum group metals (PGM) loading while increasing performance and durability. Appropriate catalysts and MEA configuration were down-selected that protects the membrane, and the layers were tailored to optimize the movements of reactants and product water through the cell to maximize performance while maintaining durability.

  10. ALLOYING OF CUPOLA IRON WITH CAST IRON DUE TO APPLICATION OF USED COPPER-MAGNESIUM CATALYSTS

    Directory of Open Access Journals (Sweden)

    O. S. Komarov

    2011-01-01

    Full Text Available Alloying process of cupola iron by means of input into charge structure of briquettes of the worked-out coppermagnesium catalysts is investigated. This technology allows to carry out recycling of expensive metals, such as copper, and to raise strength properties of cast iron melted in a cupola.

  11. Making A Noble-Metal-On-Metal-Oxide Catalyst

    Science.gov (United States)

    Miller, Irvin M.; Davis, Patricia P.; Upchurch, Billy T.

    1989-01-01

    Catalyst exhibits superior performance in oxidation of CO in CO2 lasers. Two-step process developed for preparing platinum- or palladium-on-tin-oxide catalyst for recombination of CO and O2, decomposition products that occur in high-voltage discharge region of closed-cycle CO2 laser. Process also applicable to other noble-metal/metal-oxide combinations.

  12. New catalysts for coal processing: Metal carbides and nitrides

    Energy Technology Data Exchange (ETDEWEB)

    S. Ted Oyama; David F. Cox

    1999-12-03

    The subject of this research project was to investigate the catalytic properties of a new class of materials, transition metal carbides and nitrides, for treatment of coal liquid and petroleum feedstocks. The main objectives were: (1) preparation of catalysts in unsupported and supported form; (2) characterization of the materials; (3) evaluation of their catalytic properties in HDS and HDN; (4) measurement of the surface properties; and (5) observation of adsorbed species. All of the objectives were substantially carried out and the results will be described in detail below. The catalysts were transition metal carbides and nitrides spanning Groups 4--6 in the Periodic Table. They were chosen for study because initial work had shown they were promising materials for hydrotreating. The basic strategy was first to prepare the materials in unsupported form to identify the most promising catalyst, and then to synthesize a supported form of the material. Already work had been carried out on the synthesis of the Group VI compounds Mo{sub 2}C, Mo{sub 2}N, and WC, and new methods were developed for the Group V compounds VC and NbC. All the catalysts were then evaluated in a hydrotreating test at realistic conditions. It was found that the most active catalyst was Mo{sub 2}C, and further investigations of the material were carried out in supported form. A new technique was employed for the study of the bulk and surface properties of the catalysts, near edge x-ray absorption spectroscopy (NEXAFS), that fingerprinted the electronic structure of the materials. Finally, two new research direction were explored. Bimetallic alloys formed between two transition metals were prepared, resulting in catalysts having even higher activity than Mo{sub 2}C. The performance of the catalysts in hydrodechloration was also investigated.

  13. Structure, activity, and stability of platinum alloys as catalysts for the oxygen reduction reaction

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg

    In this thesis I present our work on theoretical modelling of platinum alloys as catalysts for the Oxygen Reduction Reaction (ORR). The losses associated with the kinetics of the ORR is the main bottleneck in low-temperature fuel cells for transport applications, and more active catalysts...... and dealloying due to kinetic barriers, despite the thermodynamic driving force for dissolution. This is followed by our results on trying to decouple the strain and ligand effects for platinum skin structures, and determining whether there is any correlation between adsorption energy and surface stability......), depending on the length and time scales involved. Using DFT, we show how diffusion barriers in transition metal alloys in the L12 structure depend on the alloying energy, supporting the assumption that an intrinsically more stable alloy is also more stable towards diffusion-related degradation...

  14. Hyperfine interactions in metallic catalysts

    International Nuclear Information System (INIS)

    Saitovitch, Henrique; Silva, Paulo R.J.; Passos, Fabio B.

    2005-01-01

    Heterogeneous catalysts are of fundamental importance in several modern chemical processes. The characterization of catalysts is an issue of very present interest as it can provide a better understanding of the fundamental aspects of the catalytic phenomena, thus helping in the development of more efficient catalysts. In order to extend and improve the characterization of catalysts, new and less conventional methods are being applied, such as nuclear spectroscopies. In this paper we focus on the application of angular correlation, with can be used to resolve different local environments of probe atoms in solids and can be applied, as shown here, in the characterization of heterogeneous catalysts. A brief theoretical introduction is given and experimental results related to catalytic systems of alumina and niobia-supported Pt-In and Pd-In catalysts are presented. (author)

  15. Bi-metallic catalysts, methods of making, and uses thereof

    KAUST Repository

    Basset, Jean-Marie

    2017-01-19

    Provided herein are bi-metallic catalysts, methods of making, and uses thereof. In some embodiments, the bi-metallic catalyst contains two different metal catalysts that can be used in hydrocarbon metathesis reactions, in some embodiments, the methods of making the bi-metallic catalysts can include two steps utilizing a surface organometallic chemistry approach in which the two different metal catalysts are sequentially grafted onto a support.

  16. Laser surface alloying of aluminium-transition metal alloys

    International Nuclear Information System (INIS)

    Almeida, A.; Vilar, R.

    1998-01-01

    Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM) alloys. Cr and Mo are particularly interesting alloying elements to produce stable high-strength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO 2 laser . This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloy, over the last years. (Author) 16 refs

  17. Metal catalysts for steam reforming of tar derived from the gasification of lignocellulosic biomass.

    Science.gov (United States)

    Li, Dalin; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

    2015-02-01

    Biomass gasification is one of the most important technologies for the conversion of biomass to electricity, fuels, and chemicals. The main obstacle preventing the commercial application of this technology is the presence of tar in the product gas. Catalytic reforming of tar appears a promising approach to remove tar and supported metal catalysts are among the most effective catalysts. Nevertheless, improvement of catalytic performances including activity, stability, resistance to coke deposition and aggregation of metal particles, as well as catalyst regenerability is greatly needed. This review focuses on the design and catalysis of supported metal catalysts for the removal of tar in the gasification of biomass. The recent development of metal catalysts including Rh, Ni, Co, and their alloys for steam reforming of biomass tar and tar model compounds is introduced. The role of metal species, support materials, promoters, and their interfaces is described. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Germanium nanowires grown using different catalyst metals

    Energy Technology Data Exchange (ETDEWEB)

    Gouveia, R.C., E-mail: riama@ifsp.edu.br [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Área de Ciências, Instituto Federal de Educação Ciência e Tecnologia de São Paulo, Rua Américo Ambrósio, 269, Jd. Canaã, Sertãozinho, CEP 14169-263 (Brazil); Kamimura, H.; Munhoz, R.; Rodrigues, A.D. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil); Leite, E.R. [Departamento de Química – LIEC, Universidade Federal de São Carlos, São Carlos, CEP 13565-905 (Brazil); Chiquito, A.J. [Departamento de Física – NanO Lab, Universidade Federal de São Carlos, Rod. Washington Luís, Km 235 – SP 310, São Carlos, CEP 13565-905 (Brazil)

    2016-11-01

    Germanium nanowires have been synthesized by the well known vapor-liquid-solid growth mechanism using gold, silver, cooper, indium and nickel as catalyst metals. The influence of metal seeds on nanowires structural and electronic transport properties was also investigated. Electron microscopy images demonstrated that, despite differences in diameters, all nanowires obtained presented single crystalline structures. X-ray patterns showed that all nanowires were composed by germanium with a small amount of germanium oxide, and the catalyst metal was restricted at the nanowires' tips. Raman spectroscopy evidenced the long range order in the crystalline structure of each sample. Electrical measurements indicated that variable range hopping was the dominant mechanism in carrier transport for all devices, with similar hopping distance, regardless the material used as catalyst. Then, in spite of the differences in synthesis temperatures and nanowires diameters, the catalyst metals have not affected the composition and crystalline quality of the germanium nanowires nor the carrier transport in the germanium nanowire network devices. - Highlights: • Ge nanowires were grown by VLS method using Au, Ag, Cu, In and Ni as catalysts. • All nanowires presented high single crystalline quality and long range order. • Devices showed semiconducting behavior having VRH as dominant transport mechanism. • The metal catalyst did not influence structural properties or the transport mechanism.

  19. Interaction Of Hydrogen With Metal Alloys

    Science.gov (United States)

    Danford, M. D.; Montano, J. W.

    1993-01-01

    Report describes experiments on interaction of hydrogen with number of metal alloys. Discusses relationship between metallurgical and crystallographic aspects of structures of alloys and observed distributions of hydrogen on charging. Also discusses effect of formation of hydrides on resistances of alloys to hydrogen. Describes attempt to correlate structures and compositions of alloys with their abilities to resist embrittlement by hydrogen.

  20. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    Science.gov (United States)

    Gangwal, Santosh; Jothimurugesan, Kandaswamy

    1999-01-01

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption processes, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gasses from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or "passivating" the heavy metals on the spent FCC catalyst as an intermediate step.

  1. Alloy catalysts for fuel cell-based alcohol sensors

    Science.gov (United States)

    Ghavidel, Mohammadreza Zamanzad

    Direct ethanol fuel cells (DEFCs) are attractive from both economic and environmental standpoints for generating renewable energy and powering vehicles and portable electronic devices. There is a great interest recently in developing DEFC systems. The cost and performance of the DEFCs are mainly controlled by the Pt-base catalysts used at each electrode. In addition to energy conversion, DEFC technology is commonly employed in the fuel-cell based breath alcohol sensors (BrAS). BrAS is a device commonly used to measure blood alcohol concentration (BAC) and enforce drinking and driving laws. The BrAS is non-invasive and has a fast respond time. However, one of the most important drawback of the commercially available BrAS is the very high loading of Pt employed. One well-known and cost effective method to reduce the Pt loading is developing Pt-alloy catalysts. Recent studies have shown that Pt-transition metal alloy catalysts enhanced the electroactivity while decreasing the required loadings of the Pt catalysts. In this thesis, carbon supported Pt-Mn and Pt-Cu electrocatalysts were synthesized by different methods and the effects of heat treatment and structural modification on the ethanol oxidation reaction (EOR) activity, oxygen reduction reaction (ORR) activity and durability of these samples were thoroughly studied. Finally, the selected Pt-Mn and Pt-Cu samples with the highest EOR activity were examined in a prototype BrAS system and compared to the Pt/C and Pt 3Sn/C commercial electrocatalysts. Studies on the Pt-Mn catalysts produced with and without additives indicate that adding trisodium citrate (SC) to the impregnation solution improved the particle dispersion, decreased particle sizes and reduced the time required for heat treatment. Further studies show that the optimum weight ratio of SC to the metal loading in the impregnation solution was 2:1 and optimum results achieved at pH lower than 4. In addition, powder X-ray diffraction (XRD) analyses indicate

  2. Single-layer transition metal sulfide catalysts

    Science.gov (United States)

    Thoma, Steven G [Albuquerque, NM

    2011-05-31

    Transition Metal Sulfides (TMS), such as molybdenum disulfide (MoS.sub.2), are the petroleum industry's "workhorse" catalysts for upgrading heavy petroleum feedstocks and removing sulfur, nitrogen and other pollutants from fuels. We have developed an improved synthesis technique to produce SLTMS catalysts, such as molybdenum disulfide, with potentially greater activity and specificity than those currently available. Applications for this technology include heavy feed upgrading, in-situ catalysis, bio-fuel conversion and coal liquefaction.

  3. Design of a surface alloy catalyst for steam reforming

    DEFF Research Database (Denmark)

    Besenbacher, F.; Chorkendorff, Ib; Clausen, B.S.

    1998-01-01

    Detailed studies of elementary chemical processes on well-characterized single crystal surfaces have contributed substantially to the understanding of heterogeneous catalysis. insight into the structure of surface alloys combined with an understanding of the relation between the surface compositi...... and reactivity is shown to lead directly to new ideas for catalyst design, The feasibility of such an approach is illustrated by the synthesis, characterization, and tests of a high-surface area gold-nickel catalyst for steam reforming....

  4. Filler metal alloy for welding cast nickel aluminide alloys

    Science.gov (United States)

    Santella, Michael L.; Sikka, Vinod K.

    1998-01-01

    A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.

  5. Carbon-supported platinum alloy catalysts for phenol hydrogenation for making industrial chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, S.T.; Song, C.

    1999-07-01

    Phenol is available in large quantities in liquids derived from coal and biomass. Phenol hydrogenation is an industrially important reaction to produce cyclohexanone and cyclohexanol. Cyclohexane, cyclohexene and benzene are obtained as minor products in this reaction. Cyclohexanone is an important intermediate in the production of caprolactam for nylon 6 and cyclohexanol for adipic acid production. In USA, cyclohexanol and cyclohexanone are produced by benzene hydrogenation to cyclohexane over nickel or noble metal catalysts, followed by oxidation of cyclohexane to produce a mixture of cyclohexanol and cyclohexanone. Then cyclohexanol is dehydrogenated in the presence of Cu-Zn catalyst to cyclohexanone. Usually phenol hydrogenation is also carried out by using Ni catalyst in liquid phase. However, a direct single-step vapor phase hydrogenation of phenol to give cyclohexanone selectively is more advantageous in terms of energy savings and process economics, since processing is simplified and the endothermic step of cyclohexanol dehydrogenation can be avoided, as demonstrated by Montedipe and Johnson Matthey using promoted Pd/Al{sub 2}O{sub 3} catalyst. While it is not the purpose of this paper to dwell on the relative merits of these routes, it is necessary to mention that while using monometallic catalysts, generally the problem of catalyst deactivation of sintering as well as coking is frequently encountered. Addition and alloying of noble metal (e.g. Pt) with a second metal can result in a catalyst with better selectivity and activity in the reaction which is more resistant to deactivation. This paper presents the results on the single-step vapor phase hydrogenation of phenol over carbon-supported Pt-M (M=Cr, V, Zr) alloy catalysts to yield mainly cyclohexanone or cyclohexanol.

  6. Pt Monolayer Shell on Nitrided Alloy Core—A Path to Highly Stable Oxygen Reduction Catalyst

    Directory of Open Access Journals (Sweden)

    Jue Hu

    2015-07-01

    Full Text Available The inadequate activity and stability of Pt as a cathode catalyst under the severe operation conditions are the critical problems facing the application of the proton exchange membrane fuel cell (PEMFC. Here we report on a novel route to synthesize highly active and stable oxygen reduction catalysts by depositing Pt monolayer on a nitrided alloy core. The prepared PtMLPdNiN/C catalyst retains 89% of the initial electrochemical surface area after 50,000 cycles between potentials 0.6 and 1.0 V. By correlating electron energy-loss spectroscopy and X-ray absorption spectroscopy analyses with electrochemical measurements, we found that the significant improvement of stability of the PtMLPdNiN/C catalyst is caused by nitrogen doping while reducing the total precious metal loading.

  7. Liquid metal corrosion considerations in alloy development

    International Nuclear Information System (INIS)

    Tortorelli, P.F.; DeVan, J.H.

    1984-01-01

    Liquid metal corrosion can be an important consideration in developing alloys for fusion and fast breeder reactors and other applications. Because of the many different forms of liquid metal corrosion (dissolution, alloying, carbon transfer, etc.), alloy optimization based on corrosion resistance depends on a number of factors such as the application temperatures, the particular liquid metal, and the level and nature of impurities in the liquid and solid metals. The present paper reviews the various forms of corrosion by lithium, lead, and sodium and indicates how such corrosion reactions can influence the alloy development process

  8. PDTI metal alloy as a hydrogen or hydrocarbon sensitive metal

    Science.gov (United States)

    Hunter, Gary W. (Inventor)

    1996-01-01

    A hydrogen sensitive metal alloy contains palladium and titanium to provide a larger change in electrical resistance when exposed to the presence of hydrogen. The alloy can be used for improved hydrogen detection.

  9. Genetic Algorithm Procreation Operators for Alloy Nanoparticle Catalysts

    DEFF Research Database (Denmark)

    Lysgaard, Steen; Landis, David Dominic; Bligaard, Thomas

    2014-01-01

    The long-term stability of binary nanoparticles and clusters is one of the main challenges in the development of novel (electro-)catalysts for e.g. CO2 reduction. Here, we present a method for predicting the optimal composition and structure of alloy nanoparticles and clusters, with particular...

  10. An introduction to surface alloying of metals

    CERN Document Server

    Hosmani, Santosh S; Goyal, Rajendra Kumar

    2014-01-01

    An Introduction to Surface Alloying of Metals aims to serve as a primer to the basic aspects of surface alloying of metals. The book serves to elucidate fundamentals of surface modification and their engineering applications. The book starts with basics of surface alloying and goes on to cover key surface alloying methods, such as carburizing, nitriding, chromizing, duplex treatment, and the characterization of surface layers. The book will prove useful to students at both the undergraduate and graduate levels, as also to researchers and practitioners looking for a quick introduction to surface alloying.

  11. A generic process of growing aligned carbon nanotube arrays on metals and metal alloys

    International Nuclear Information System (INIS)

    Parthangal, Prahalad M; Cavicchi, Richard E; Zachariah, Michael R

    2007-01-01

    Aligned carbon nanotube (CNT) arrays are integral towards the development of several applications such as field emission, interconnects in silicon technology, and chemical and biological sensing. Even though the synthesis of CNTs has been described extensively in the literature, there has not been significant success in growing uniform, well-aligned CNT arrays on pure metal surfaces other than metals that catalyse CNT growth themselves. In this paper, we describe a method of growing aligned CNT arrays on a variety of pure metals, metal alloys, and conductive ceramics using a bimetallic iron/alumina composite catalyst at low temperatures (550 to 700 deg. C). We believe that the addition of alumina to the iron catalyst significantly reduces catalyst-metal underlayer interactions that have traditionally proven to be a barrier for the growth of CNTs on metals. The alumina also minimizes surface diffusion of iron and allows the formation of a high density of uniformly dispersed catalyst nanoparticles to act as nucleation sites for well-aligned CNT arrays. Despite the presence of non-conducting alumina from the catalyst, the contact resistance between the CNTs and the metal underlayer was observed to be quite low, emphasizing the usefulness of this approach to practical applications. Our process was successful in growing aligned CNTs even on commercial steel plates and may be applicable for substrates of any shape or size

  12. Pyrometallurgical Recovery of Platinum Group Metals from Spent Catalysts

    Science.gov (United States)

    Peng, Zhiwei; Li, Zhizhong; Lin, Xiaolong; Tang, Huimin; Ye, Lei; Ma, Yutian; Rao, Mingjun; Zhang, Yuanbo; Li, Guanghui; Jiang, Tao

    2017-09-01

    As an important secondary resource with abundant platinum group metals (PGMs), spent catalysts demand recycling for both economic and environmental benefits. This article reviews the main pyrometallurgical processes for PGM recovery from spent catalysts. Existing processes, including smelting, vaporization, and sintering processes, are discussed based in part on a review of the physiochemical characteristics of PGMs in spent catalysts. The smelting technology, which produces a PGM-containing alloy, is significantly influenced by the addition of various collectors, such as lead, copper, iron, matte, or printed circuit board (PCB), considering their chemical affinities for PGMs. The vaporization process can recover PGMs in vapor form at low temperatures (250-700°C), but it suffers high corrosion and potential environmental and health risks as a result of involvement of the hazardous gases, mainly Cl2 and CO. The sintering process serves as a reforming means for recycling of the spent catalysts by in situ reduction of their oxidized PGMs components. Among these processes, the smelting process seems more promising although its overall performance can be further improved by seeking a suitable target-oriented collector and flux, together with proper pretreatment and process intensification using an external field.

  13. Synthesis, characterization and optimization of platinum-alloy nanoparticle catalysts in proton exchange membrane fuel cells

    Science.gov (United States)

    Srivastava, Ratndeep

    Renewable hydrogen-fuelled proton exchange membrane (PEMFC) fuel cells have consistently demonstrated great promise as a future source of energy due to their high conversion efficiency, lower temperature of operation and lack of greenhouse emissions. One of the major impediments in the commercialization of polymer electrolyte membrane fuel cells is the insufficient catalytic reactivity and higher cost of Pt electrocatalysts which are utilized for the electroreduction of oxygen from air. This dissertation focuses primarily on a family of Pt alloy fuel cell electrocatalysts referred to as de-alloyed core-shell electrocatalysts. These materials are bimetallic or multimetallic nanoparticles, mostly supported on conductive supports which were first described in a dissertation by Dr. S. Koh earlier in 2009.1 De-alloyed Pt nanoparticle electrocatalysts are formed from base metal rich binary Pt-M and ternary Pt-M1-M 2 (M, M1, M2 = Cu, Co, Ni, Fe and Cr) alloy nanoparticle precursors. The precursors are transformed and activated by electrochemical selective dissolution of the less noble metal component of the precursors (de-alloying). They have shown exceptional activity for oxygen reduction reaction (ORR) in idealized electrochemical half cell measurements, in particular rotating disk electrode experiments. However, these materials were never tested or implemented in realistic Membrane Electrode Assemblies (MEA) and single PEM fuel cells. The objective of this work was to implement de-alloyed Pt particle catalysts in realistic fuel cell electrode layers as well as a detailed characterization of their behavior and stability. The major challenges of MEA implementation consists of the behavior of the new nanostructured electrocatalysts inside the complex three-phase interface of polymer membrane ionomer, liquid water, metal catalyst, support, and reactant gas. Activity measurements were followed by medium and long-term durability analysis by potential cycling of the membrane

  14. Nickel Alloy Catalysts for the Anode of a High Temperature PEM Direct Propane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Shadi Vafaeyan

    2014-01-01

    Full Text Available High temperature polymer electrode membrane fuel cells that use hydrocarbon as the fuel have many theoretical advantages over those that use hydrogen. For example, nonprecious metal catalysts can replace platinum. In this work, two of the four propane fuel cell reactions, propane dehydrogenation and water dissociation, were examined using nickel alloy catalysts. The adsorption energies of both propane and water decreased as the Fe content of Ni/Fe alloys increased. In contrast, they both increased as the Cu content of Ni/Cu alloys increased. The activation energy for the dehydrogenation of propane (a nonpolar molecule changed very little, even though the adsorption energy changed substantially as a function of alloy composition. In contrast, the activation energy for dissociation of water (a molecule that can be polarized decreased markedly as the energy of adsorption decreased. The different relationship between activation energy and adsorption energy for propane dehydrogenation and water dissociation alloys was attributed to propane being a nonpolar molecule and water being a molecule that can be polarized.

  15. Alkaline earth metal catalysts for asymmetric reactions.

    Science.gov (United States)

    Kobayashi, Shū; Yamashita, Yasuhiro

    2011-01-18

    The group 2 alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) are among the most common elements on Earth, abundant in both the sea and the Earth's crust. Although they are familiar in our daily lives, their application to organic synthesis has, so far, been limited. Some particularly useful properties of these elements include (i) low electronegativity, (ii) a stable oxidation state of +2, meaning that they can potentially form two covalent bonds with anions, and (iii) the ability to occupy a variety of coordination sites due to their large ionic radius. Furthermore, the alkaline earth metals, found between the group 1 and group 3 elements, show mild but significant Lewis acidity, which can be harnessed to control coordinative molecules via a Lewis acid-base interaction. Taken together, these characteristics make the metals Ca, Sr, and Ba very promising components of highly functionalized acid-base catalysts. In this Account, we describe the development of chiral alkaline earth metal catalysts for asymmetric carbon-carbon bond-forming reactions. Recently prepared chiral alkaline earth metal complexes have shown high diastereo- and enantioselectivities in fundamental and important chemical transformations. We chose chiral bisoxazoline (Box) derivatives bearing a methylene tether as a ligand for chiral modification. These molecules are very useful because they can covalently coordinate to alkaline earth metals in a bidentate fashion through deprotonation of the tether portion. It was found that chiral calcium-Box complexes could successfully promote catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions with high diastereo- and enantioselectivities. Both the calcium-Box complexes and chiral strontium-bis-sulfonamide and chiral barium-BINOLate complexes could catalyze asymmetric 1,4-addition reactions with high enantioselectivities. Furthermore, we designed a calcium-neutral coordinative ligand complex as a new type of chiral alkaline

  16. Development of Metallic Sensory Alloys

    Science.gov (United States)

    Wallace Terryl A.; Newman, John A.; Horne, Michael R.; Messick, Peter L.

    2010-01-01

    Existing nondestructive evaluation (NDE) technologies are inherently limited by the physical response of the structural material being inspected and are therefore not generally effective at the identification of small discontinuities, making the detection of incipient damage extremely difficult. One innovative solution to this problem is to enhance or complement the NDE signature of structural materials to dramatically improve the ability of existing NDE tools to detect damage. To address this need, a multifunctional metallic material has been developed that can be used in structural applications. The material is processed to contain second phase sensory particles that significantly improve the NDE response, enhancing the ability of conventional NDE techniques to detect incipient damage both during and after flight. Ferromagnetic shape-memory alloys (FSMAs) are an ideal material for these sensory particles as they undergo a uniform and repeatable change in both magnetic properties and crystallographic structure (martensitic transformation) when subjected to strain and/or temperature changes which can be detected using conventional NDE techniques. In this study, the use of a ferromagnetic shape memory alloy (FSMA) as the sensory particles was investigated.

  17. Vibrational entropies in metallic alloys

    Science.gov (United States)

    Ozolins, Vidvuds; Asta, Mark; Wolverton, Christopher

    2000-03-01

    Recently, it has been recognized that vibrational entropy can have significant effects on the phase stability of metallic alloys. Using density functional linear response calculations and molecular dynamics simulations we study three representative cases: (i) phase diagram of Al-rich Al-Sc alloys, (ii) stability of precipitate phases in CuAl_2, and (iii) phonon dynamics in bcc Zr. We find large vibrational entropy effects in all cases. In the Al-Sc system, vibrations increase the solid solubility of Sc in Al by decreasing the stability of the L12 (Al_3Sc) phase. This leads to a nearly ten-fold increase in the solid solubility of Sc in Al at T=800 K. In the Cu-Al system, our calculations predict that the tetragonal Laves phase of CuAl2 has 0.35 kB/atom higher vibrational entropy than the cubic CaF_2-type phase (the latter is predicted to be the T=0 K ground state of CuAl_2). This entropy difference causes a structural transformation in CuAl2 precipitates from the fluorite to the tetragonal Laves phase around T=500 K. Finally, we analyze the highly unusual dynamics of anharmonically stabilized bcc Zr, finding large diffuse-scattering intensity streaks between the bcc Bragg peaks.

  18. Filler metal development for Hastelloy alloy XR

    International Nuclear Information System (INIS)

    Watanabe, Katsutoshi; Nakajima, Hajime; Sahira, Kensho

    1991-11-01

    In order to develop the filler metal for Hastelloy alloy XR structure with thick wall, the weldability and high temperature strength properties of Hastelloy alloy XR weldment were investigated using the filler metals, which were alloy-designed on the basis of multiple regression analysis. The former was examined through the chemical analysis in the deposited metal, bend test, FISCO cracking test, optical microscopy and hardness measurement. The latter was investigated by means of tensile and creep test. It was found from these results that the crack susceptibility in the weldment was apparent to be lowered without degrading the high temperature strength properties. Therefore, it is concluded that these filler metals possess excellent performance as the filler metal for Hastelloy alloy XR structure with thick wall. (author)

  19. Mesoporous metal catalysts formed by ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Schaeferhans, Jana; Pazos Perez, Nicolas; Andreeva, Daria [Physikalische Chemie II, Universitaet Bayreuth (Germany)

    2010-07-01

    We study the ultrasound-driven formation of mesoporous metal sponges. The collapse of acoustic cavitations leads to very high temperatures and pressures on very short scales. Therefore, structures may be formed and quenched far from equilibrium. Mechanism of metal modification by ultrasound is complex and involves a variety of aspects. We propose that modification of metal particles and formation of mesoporous inner structures can be achieved due to thermal etching of metals by ultrasound stimulated high speed jets of liquid. Simultaneously, oxidation of metal surfaces by free radicals produced in water during cavitation stabilizes developed metal structures. Duration and intensity of the ultrasonication treatment is able to control the structure and morphology of metal sponges. We expect that this approach to the formation of nanoscale composite sponges is universal and opens perspective for a whole new class of catalytic materials that can be prepared in a one-step process. The developed method makes it possible to control the sponge morphology and can be used for formation of modern types of catalysts. For example, the sonication technique allows to combine the fabrication of mesoporous support and distribution of metal (Cu, Pd, Au, Pt etc.) nanoparticles in its pores into a single step.

  20. Plasma deposition of amorphous metal alloys

    Science.gov (United States)

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  1. Metal Nanoparticle Catalysts for Carbon Nanotube Growth

    Science.gov (United States)

    Pierce, Benjamin F.

    2003-01-01

    Work this summer involved and new and unique process for producing the metal nanoparticle catalysts needed for carbon nanotube (CNT) growth. There are many applications attributed to CNT's, and their properties have deemed them to be a hot spot in research today. Many groups have demonstrated the versatility in CNT's by exploring a wide spectrum of roles that these nanotubes are able to fill. A short list of such promising applications are: nanoscaled electronic circuitry, storage media, chemical sensors, microscope enhancement, and coating reinforcement. Different methods have been used to grow these CNT's. Some examples are laser ablation, flame synthesis, or furnace synthesis. Every single approach requires the presence of a metal catalyst (Fe, Co, and Ni are among the best) that is small enough to produce a CNT. Herein lies the uniqueness of this work. Microemulsions (containing inverse micelles) were used to generate these metal particles for subsequent CNT growth. The goal of this summer work was basically to accomplish as much preliminary work as possible. I strived to pinpoint which variable (experimental process, metal product, substrate, method of application, CVD conditions, etc.) was the determining factor in the results. The resulting SEM images were sufficient for the appropriate comparisons to be made. The future work of this project consists of the optimization of the more promising experimental procedures and further exploration onto what exactly dictated the results.

  2. Defining a Materials Database for the Design of Copper Binary Alloy Catalysts for Electrochemical CO2Conversion.

    Science.gov (United States)

    Lee, Chan Woo; Yang, Ki Dong; Nam, Dae-Hyun; Jang, Jun Ho; Cho, Nam Heon; Im, Sang Won; Nam, Ki Tae

    2018-01-24

    While Cu electrodes are a versatile material in the electrochemical production of desired hydrocarbon fuels, Cu binary alloy electrodes are recently proposed to further tune reaction directionality and, more importantly, overcome the intrinsic limitation of scaling relations. Despite encouraging empirical demonstrations of various Cu-based metal alloy systems, the underlying principles of their outstanding performance are not fully addressed. In particular, possible phase segregation with concurrent composition changes, which is widely observed in the field of metallurgy, is not at all considered. Moreover, surface-exposed metals can easily form oxide species, which is another pivotal factor that determines overall catalytic properties. Here, the understanding of Cu binary alloy catalysts for CO 2 reduction and recent progress in this field are discussed. From the viewpoint of the thermodynamic stability of the alloy system and elemental mixing, possible microstructures and naturally generated surface oxide species are proposed. These basic principles of material science can help to predict and understand metal alloy structure and, moreover, act as an inspiration for the development of new binary alloy catalysts to further improve CO 2 conversion and, ultimately, achieve a carbon-neutral cycle. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. The interaction of hydrogen with metal alloys

    Science.gov (United States)

    Danford, M. D.; Montano, J. W.

    1991-01-01

    Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition.

  4. Noble metal alloys for metal-ceramic restorations.

    Science.gov (United States)

    Anusavice, K J

    1985-10-01

    A review of the comparative characteristics and properties of noble metal alloys used for metal-ceramic restorations has been presented. Selection of an alloy for one's practice should be based on long-term clinical data, physical properties, esthetic potential, and laboratory data on metal-ceramic bond strength and thermal compatibility with commercial dental porcelains. Although gold-based alloys, such as the Au-Pt-Pd, Au-Pd-Ag, and Au-Pd classes, may appear to be costly compared with the palladium-based alloys, they have clearly established their clinical integrity and acceptability over an extended period of time. Other than the relatively low sag resistance of the high gold-low silver content alloys and the potential thermal incompatibility with some commercial porcelain products, few clinical failures have been observed. The palladium-based alloys are less costly than the gold-based alloys. Palladium-silver alloys require extra precautions to minimize porcelain discoloration. Palladium-copper and palladium-cobalt alloys may also cause porcelain discoloration, as copper and cobalt are used as colorants in glasses. The palladium-cobalt alloys are least susceptible to high-temperature creep compared with all classes of noble metals. Nevertheless, insufficient clinical data exist to advocate the general use of the palladium-copper and palladium-cobalt alloys at the present time. One should base the selection and use of these alloys in part on their ability to meet the requirements of the ADA Acceptance Program. A list of acceptable or provisionally acceptable alloys is available from the American Dental Association and is published annually in the Journal of the American Dental Association. Dentists have the legal and ethical responsibility for selection of alloys used for cast restorations. This responsibility should not be delegated to the dental laboratory technician. It is advisable to discuss the criteria for selection of an alloy with the technician and the

  5. Non-noble metal fuel cell catalysts

    CERN Document Server

    Chen, Zhongwei; Zhang, Jiujun

    2014-01-01

    Written and edited by a group of top scientists and engineers in the field of fuel cell catalysts from both industry and academia, this book provides a complete overview of this hot topic. It covers the synthesis, characterization, activity validation and modeling of different non-noble metal and metalfree electrocatalysts for the reduction of oxygen, as well as their integration into acid or alkaline polymer exchange membrane (PEM) fuel cells and their performance validation, while also discussing those factors that will drive fuel cell commercialization. With its well-structured app

  6. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  7. Development of radioactive platinum group metal catalysts

    International Nuclear Information System (INIS)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E.

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m 2 /g. The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs

  8. Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems.

    Science.gov (United States)

    Gewirth, Andrew A; Varnell, Jason A; DiAscro, Angela M

    2018-01-31

    A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented. Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized. Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted. Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed. Additionally, the recent application of Cu-based catalysts for the ORR is reviewed. Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided.

  9. Peptide-templated noble metal catalysts: syntheses and applications.

    Science.gov (United States)

    Wang, Wei; Anderson, Caleb F; Wang, Zongyuan; Wu, Wei; Cui, Honggang; Liu, Chang-Jun

    2017-05-01

    Noble metal catalysts have been widely used in many applications because of their high activity and selectivity. However, a controllable preparation of noble metal catalysts still remains as a significant challenge. To overcome this challenge, peptide templates can play a critical role in the controllable syntheses of catalysts owing to their flexible binding with specific metallic surfaces and self-assembly characteristics. By employing peptide templates, the size, shape, facet, structure, and composition of obtained catalysts can all be specifically controlled under the mild synthesis conditions. In addition, catalysts with spherical, nanofiber, and nanofilm structures can all be produced by associating with the self-assembly characteristics of peptide templates. Furthermore, the peptide-templated noble metal catalysts also reveal significantly enhanced catalytic behaviours compared with conventional catalysts because the electron conductivity, metal dispersion, and reactive site exposure can all be improved. In this review, we summarize the research progresses in the syntheses of peptide-templated noble metal catalysts. The applications of the peptide-templated catalysts in organic reactions, photocatalysis, and electrocatalysis are discussed, and the relationship between structure and activity of these catalysts are addressed. Future opportunities, including new catalytic materials designed by using biological principles, are indicated to achieve selective, eco-friendly, and energy neutral synthesis approaches.

  10. Interaction between Nafion ionomer and noble metal catalyst for PEMFCs

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma

    The implement of polymer impregnation in electrode structure (catalyst layer) decreasing the noble metal catalyst loading by a factor of ten , , is one of the essential mile stones in the evolution of Proton Exchange Membrane Fuel Cells’ development among the application of catalyst support...... and electrode deposition etc. In fuel cell reactions, both electrons and protons are involved. Impregnation of Nafion ionomer in catalyst layer effectively increases the proton-electron contact, enlarge the reaction zone, extend the reaction from the surface to the entire electrode. Therefore, the entire...... catalyst layer conducts both electrons and protons so that catalyst utilization in the layer is improved dramatically. The catalyst layer will in turn generate and sustain a higher current density. One of the generally adapted methods to impregnate Nafion into the catalyst layer is to mix the catalysts...

  11. First-row transition metal hydrogenation and hydrosilylation catalysts

    Science.gov (United States)

    Trovitch, Ryan J.; Mukhopadhyay, Tufan K.; Pal, Raja; Levin, Hagit Ben-Daat; Porter, Tyler M.; Ghosh, Chandrani

    2017-07-18

    Transition metal compounds, and specifically transition metal compounds having a tetradentate and/or pentadentate supporting ligand are described, together with methods for the preparation thereof and the use of such compounds as hydrogenation and/or hydrosilylation catalysts.

  12. 21 CFR 872.3710 - Base metal alloy.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that is...

  13. 21 CFR 872.3060 - Noble metal alloy.

    Science.gov (United States)

    2010-04-01

    ... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food...

  14. An improved method of preparation of nanoparticular metal oxide catalysts

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention concerns an improved method of preparation of nanoparticular vanadium oxide/anatase titania catalysts having a narrow particle size distribution. In particular, the invention concerns preparation of nanoparticular vanadium oxide/anatase titania catalyst precursors comprising...... combustible crystallization seeds upon which the catalyst metal oxide is coprecipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step....

  15. Electrochemical Impedance Spectroscopy Of Metal Alloys

    Science.gov (United States)

    Macdowell, L. G.; Calle, L. M.

    1993-01-01

    Report describes use of electrochemical impedance spectroscopy (EIS) to investigate resistances of 19 alloys to corrosion under conditions similar to those of corrosive, chloride-laden seaside environment of Space Transportation System launch site. Alloys investigated: Hastelloy C-4, C-22, C-276, and B-2; Inconel(R) 600, 625, and 825; Inco(R) G-3; Monel 400; Zirconium 702; Stainless Steel 304L, 304LN, 316L, 317L, and 904L; 20Cb-3; 7Mo+N; ES2205; and Ferralium 255. Results suggest electrochemical impedance spectroscopy used to predict corrosion performances of metal alloys.

  16. Surface energy of metal alloy nanoparticles

    Science.gov (United States)

    Takrori, Fahed M.; Ayyad, Ahmed

    2017-04-01

    The measurement of surface energy of alloy nanoparticles experimentally is still a challenge therefore theoretical work is necessary to estimate its value. In continuation of our previous work on the calculation of the surface energy of pure metallic nanoparticles we have extended our work to calculate the surface energy of different alloy systems, namely, Co-Ni, Au-Cu, Cu-Al, Cu-Mg and Mo-Cs binary alloys. It is shown that the surface energy of metallic binary alloy decreases with decreasing particle size approaching relatively small values at small sizes. When both metals in the alloy obey the Hume-Rothery rules, the difference in the surface energy is small at the macroscopic as well as in the nano-scale. However when the alloy deviated from these rules the difference in surface energy is large in the macroscopic and in the nano scales. Interestingly when solid solution formation is not possible at the macroscopic scale according to the Hume-Rothery rules, it is shown it may form at the nano-scale. To our knowledge these findings here are presented for the first time and is challenging from fundamental as well as technological point of views.

  17. Application of a mixed metal oxide catalyst to a metallic substrate

    Science.gov (United States)

    Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

    2009-01-01

    A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

  18. Mechanical alloying of a hydrogenation catalyst used for the remediation of contaminated compounds

    Science.gov (United States)

    Quinn, Jacqueline W. (Inventor); Clausen, Christian A. (Inventor); Geiger, Cherie L. (Inventor); Aitken, Brian S. (Inventor)

    2012-01-01

    A hydrogenation catalyst including a base material coated with a catalytic metal is made using mechanical milling techniques. The hydrogenation catalysts are used as an excellent catalyst for the dehalogenation of contaminated compounds and the remediation of other industrial compounds. Preferably, the hydrogenation catalyst is a bimetallic particle including zero-valent metal particles coated with a catalytic material. The mechanical milling technique is simpler and cheaper than previously used methods for producing hydrogenation catalysts.

  19. Phase stability of transition metals and alloys

    International Nuclear Information System (INIS)

    Hixson, R.S.; Schiferl, D.; Wills, J.M.; Hill, M.A.

    1997-01-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project was focused on resolving unexplained differences in calculated and measured phase transition pressures in transition metals. Part of the approach was to do new, higher accuracy calculations of transmission pressures for group 4B and group 6B metals. Theory indicates that the transition pressures for these baseline metals should change if alloyed with a d-electron donor metal, and calculations done using the Local Density Approximation (LDA) and the Virtual Crystal Approximation (VCA) indicate that this is true. Alloy systems were calculated for Ti, Zr and Hf based alloys with various solute concentrations. The second part of the program was to do new Diamond Anvil Cell (DAC) measurements to experimentally verify calculational results. Alloys were prepared for these systems with grain size suitable for Diamond Anvil Cell experiments. Experiments were done on pure Ti as well as Ti-V and Ti-Ta alloys. Measuring unambiguous transition pressures for these systems proved difficult, but a new technique developed yielded good results

  20. Method of making metal-polymer composite catalysts

    Science.gov (United States)

    Zelena, Piotr [Los Alamos, NM; Bashyam, Rajesh [Los Alamos, NM

    2009-06-23

    A metal-polymer-carbon composite catalyst for use as a cathode electrocatalyst in fuel cells. The catalyst includes a heteroatomic polymer; a transition metal linked to the heteroatomic polymer by one of nitrogen, sulfur, and phosphorus, and a recast ionomer dispersed throughout the heteroatomic polymer-carbon composite. The method includes forming a heteroatomic polymer-carbon composite and loading the transition metal onto the composite. The invention also provides a method of making a membrane electrode assembly for a fuel cell that includes the metal-polymer-carbon composite catalyst.

  1. Formation of amorphous alloys by mechanical alloying for platinum group metal-M(M=Zr or Al) system; Mechanical alloying ni yoru kikinzoku (Pd,Pt) to M(Zr aruiwa Al) tono kongo funmatsu no hishoshitsuka

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzuki, T.; Arakawa, T. [Kinki Univ., Higashi-Osaka, Osaka (Japan)

    1998-08-15

    The intermetallic compounds containing precious metals such as platinum white gold are widely used in chemistry or industry as catalysts. These alloy catalysts are mainly used in grinding the materials prepared by solidifying liquids. The authors of the paper attempt to prepare alloy powders of precious metal with Zr or Al by mechanical alloying (MA). As an object of applying them on a catalyst, alloy powders of precious metals (Pd and Pt) and M (Zr or Al) are regulated by the mechanical alloying reaction, and the results show that the Pd and Pt show different MA reaction while using Al as the M, the former generates an intermetallic compound as PdAl during the halfway point of the MA reaction, but the later generates amorphous powders. But, each of them generates amorphous alloys only while using Zr and the M. As a result of differential thermal analysis and electrical resistivity measurement investigating the crystalline process of the obtained amorphous alloys, it is clarified that the Pt-Al base alloy shows higher crystalline temperature compared with the other alloys. 8 refs., 6 figs.

  2. Metals and Alloys Material Stabilization Process Plan

    Energy Technology Data Exchange (ETDEWEB)

    RISENMAY, H.R.; BURK, R.A.

    2000-05-18

    This Plan outlines the process for brushing metal and alloys in accordance with the path forward discussed in the Integrated Project Management Plan for the Plutonium Finishing Plant Stabilization and Deactivation Project, HNF-3617, and requirements set forth in the Project Management Plan for Materials Stabilization, HNF-3605. This plan provides the basis for selection of the location to process, the processes involved, equipment to be used, and the characterization of the contents of the can. The scope of the process is from retrieval of metals and alloys from storage to transfer back to storage in a repackaged configuration.

  3. Metals and Alloys Material Stabilization Process Plan

    International Nuclear Information System (INIS)

    RISENMAY, H.R.; BURK, R.A.

    2000-01-01

    This Plan outlines the process for brushing metal and alloys in accordance with the path forward discussed in the Integrated Project Management Plan for the Plutonium Finishing Plant Stabilization and Deactivation Project, HNF-3617, and requirements set forth in the Project Management Plan for Materials Stabilization, HNF-3605. This plan provides the basis for selection of the location to process, the processes involved, equipment to be used, and the characterization of the contents of the can. The scope of the process is from retrieval of metals and alloys from storage to transfer back to storage in a repackaged configuration

  4. Development of Sulfur and Carbon Tolerant Reforming Alloy Catalysts Aided Fundamental Atomistic Insights

    Energy Technology Data Exchange (ETDEWEB)

    Suljo Linic

    2008-12-31

    Current hydrocarbon reforming catalysts suffer from rapid carbon and sulfur poisoning. Even though there is a tremendous incentive to develop more efficient catalysts, these materials are currently formulated using inefficient trial and error experimental approaches. We have utilized a hybrid experimental/theoretical approach, combining quantum Density Functional Theory (DFT) calculations and various state-of-the-art experimental tools, to formulate carbon tolerant reforming catalysts. We have employed DFT calculations to develop molecular insights into the elementary chemical transformations that lead to carbon poisoning of Ni catalysts. Based on the obtained molecular insights, we have identified, using DFT quantum calculation, various Ni alloy catalysts as potential carbon tolerant reforming catalysts. The alloy catalysts were synthesized and tested in steam reforming and partial oxidation of methane, propane, and isooctane. We demonstrated that the alloy catalysts are much more carbon-tolerant than monometallic Ni catalysts under nearly stoichiometric steam-to-carbon ratios. Under these conditions, monometallic Ni is rapidly poisoned by sp2 carbon deposits. The research approach is distinguished by two characteristics: (a) knowledge-based, bottomup approach, compared to the traditional trial and error approach, allows for a more efficient and systematic discovery of improved catalysts. (b) the focus is on exploring alloy materials which have been largely unexplored as potential reforming catalysts.

  5. Subnanometer to nanometer transition metal CO oxidation catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Vajda, Stefan; Fortunelli, Alessandro; Yasumatsu, Hisato

    2017-12-26

    The present invention provides a catalyst defined in part by a conductive substrate; a film overlaying a surface of the substrate; and a plurality of metal clusters supported by the layer, wherein each cluster comprises between 8 and 11 atoms. Further provided is a catalyst defined in part by a conductive substrate; a layer overlaying a surface of the substrate; and a plurality of metal clusters supported by the layer, wherein each cluster comprises at least two metals.

  6. Theoretical studies of metallic alloys

    International Nuclear Information System (INIS)

    Faulkner, J.S.; Wille, L.T.

    1991-07-01

    A new method to predict and understand the structure and phase stability of solid-solution alloys from a knowledge only of the atomic numbers of the constituent atoms is being developed. The coherent potential approximation will be used to obtain the electronic contribution to the energy and the Monte Carlo method of statistical mechanics will be used for the thermodynamic part of the calculation. An improved coherent potential approximation will be developed by combining the standard approach with the quadratic KKR (QKKR) band theory method. This will make it easier to predict the properties of alloys from first principles. The QKKR method will be developed further

  7. Pd-Au/C catalysts with different alloying degrees for ethanol oxidation in alkaline media

    International Nuclear Information System (INIS)

    Qin, Yuan-Hang; Li, Yunfeng; Lv, Ren-Liang; Wang, Tie-Lin; Wang, Wei-Guo; Wang, Cun-Wen

    2014-01-01

    High alloyed Pd-Au/C catalyst is prepared through a rate-limiting strategy in water/ethylene glycol solution. Pd/C and low alloyed Pd-Au/C catalysts are prepared with trisodium citrate and sodium borohydride as stabilizing and reducing agents, respectively. Transmission electron microscopy (TEM) shows that the synthesized Pd(Au) particles are well dispersed on the catalysts. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) show that the high alloyed Pd-Au/C catalyst presents a relatively homogenous structure while the low alloyed Pd-Au/C catalyst presents a Pd-rich shell/Au-rich core structure. Electrochemical characterization shows that the low alloyed Pd-Au/C catalyst exhibits the best catalytic activity for ethanol oxidation reaction (EOR) in alkaline media, which could be attributed to its relatively large exposed Pd surface area as compared with the high alloyed Pd-Au/C catalyst due to its Pd-rich shell structure and its enhanced adsorption of OH ads as compared with Pd/C catalyst due to its core-shell structure

  8. Thermal aging effects in refractory metal alloys

    Science.gov (United States)

    Stephens, Joseph R.

    1987-01-01

    The alloys of niobium and tantalum are attractive from a strength and compatibility viewpoint for high operating temperatures required in materials for fuel cladding, liquid metal transfer, and heat pipe applications in space power systems that will supply from 100 kWe to multi-megawatts for advanced space systems. To meet the system requirements, operating temperatures ranging from 1100 to 1600 K have been proposed. Expected lives of these space power systems are from 7 to 10 yr. A program is conducted at NASA Lewis to determine the effects of long-term, high-temperature exposure on the microstructural stability of several commercial tantalum and niobium alloys. Variables studied in the investigation include alloy composition, pre-age annealing temperature, aging time, temperature, and environment (lithium or vacuum), welding, and hydrogen doping. Alloys are investigated by means of cryogenic bend tests and tensile tests. Results show that the combination of tungsten and hafnium or zirconium found in commercial alloys such as T-111 and Cb-752 can lead to aging embrittlement and increased susceptibility to hydrogen embrittlement of ternary and more complex alloys. Modification of alloy composition helps to eliminate the embrittlement problem.

  9. Metal-Free Boron-Containing Heterogeneous Catalysts.

    Science.gov (United States)

    Fang, Yuanxing; Wang, Xinchen

    2017-12-04

    Metal-free catalysts have distinct advantages over metal and metal oxide catalysts, such as lower cost as well as higher reliability and sustainability. Among the nonmetal compounds used in catalysis, boron-containing compounds with a few unique properties have been developed. In this Minireview, the recent advances in the field of boron-containing metal-free catalysts are presented, including binary and ternary boron-containing catalytic materials. Additionally, the three main applications in catalysis are considered, namely, electrocatalysis, thermal catalysis, and photocatalysis, with the role of boron discussed in depth for each specific catalytic application. Boron-containing compounds could have a substantial impact on the field of metal-free catalysts in the future. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Comparison of methanol and ethylene glycol oxidation by alloy and Core-Shell platinum based catalysts

    Science.gov (United States)

    Kaplan, D.; Burstein, L.; Rosenberg, Yu.; Peled, E.

    2011-10-01

    Two Core-Shell, RuCore-PtShell and IrNiCore-PtRuShell, XC72-supported catalyst were synthesized in a two-step deposition process with NaBH4 as reducing agent. The structure and composition of the Core-Shell catalysts were determined by EDS, XPS and XRD. Electrochemical characterization was performed with the use of cyclic voltammetry. Methanol and ethylene glycol oxidation activities of the Core-Shell catalysts (in terms of surface and mass activities) were studied at 80 °C and compared to those of a commercial Pt-Ru alloy catalyst. The surface activity of the alloy based catalyst, in the case of methanol oxidation, was found to be superior as a result of optimized surface Pt:Ru composition. However, the mass activity of the PtRu/IrNi/XC72 was higher than that of the alloy based catalyst by ∼50%. Regarding ethylene glycol oxidation, while the surface activity of the alloy based catalyst was slightly higher than that of the Pt/Ru/XC72 catalyst, the latter showed ∼66% higher activities in terms of A g-1 of Pt. These results show the potential of Core-Shell catalysts for reducing the cost of catalysts for DMFC and DEGFC.

  11. Fatigue Characteristics of Selected Light Metal Alloys

    Directory of Open Access Journals (Sweden)

    Cieśla M.

    2016-03-01

    Full Text Available The paper addresses results of fatigue testing of light metal alloys used in the automotive as well as aerospace and aviation industries, among others. The material subject to testing comprised hot-worked rods made of the AZ31 alloy, the Ti-6Al-4V two-phase titanium alloy and the 2017A (T451 aluminium alloy. Both low- and high-cycle fatigue tests were conducted at room temperature on the cycle asymmetry ratio of R=-1. The low-cycle fatigue tests were performed using the MTS-810 machine on two levels of total strain, i.e.Δεc= 1.0% and 1.2%. The high-cycle fatigue tests, on the other hand, were performed using a machine from VEB Werkstoffprufmaschinen-Leipzig under conditions of rotary bending. Based on the results thus obtained, one could develop fatigue life characteristics of the materials examined (expressed as the number of cycles until failure of sample Nf as well as characteristics of cyclic material strain σa=f(N under the conditions of low-cycle fatigue testing. The Ti-6Al-4V titanium alloy was found to be characterised by the highest value of fatigue life Nf, both in lowand high-cycle tests. The lowest fatigue life, on the other hand, was established for the aluminium alloys examined. Under the high-cycle fatigue tests, the life of the 2017A aluminium and the AZ31 magnesium alloy studied was determined by the value of stress amplitude σa. With the stress exceeding 150 MPa, it was the aluminium alloy which displayed higher fatigue life, whereas the magnesium alloy proved better on lower stress.

  12. Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis

    Directory of Open Access Journals (Sweden)

    Masahiko Arai

    2015-05-01

    Full Text Available Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling [1]. The recycling of metal catalysts is important from economic and environmental points of view. When supported and bulk metal catalysts are used in liquid-phase organic reactions, there is a possibility that active metal species are leaching away into the liquid phases [2,3]. The metal leaching would make it difficult for the catalysts to maintain their desired initial performance for repeated batch reactions and during continuous ones. The metal leaching would also cause some undesired contamination of products by the metal species dissolved in the reaction mixture, and the separation of the metal contaminants would be required to purify the products. Therefore, various novel methods have been proposed so far to immobilize/stabilize the active metal species and to separate/collect/reuse the dissolved metal species [4]. In addition, knowledge on the heterogeneous and homogeneous natures of organic reactions using heterogeneous catalysts is important to discuss their reaction mechanisms and catalytically working active species. [...

  13. Dissolution of Metal Supported Spent Auto Catalysts in Acids

    Directory of Open Access Journals (Sweden)

    Fornalczyk A.

    2016-03-01

    Full Text Available Metal supported auto catalysts, have been used in sports and racing cars initially, but nowadays their application systematically increases. In Metal Substrate (supported Converters (MSC, catalytic functions are performed by the Platinum Group Metals (PGM: Pt, Pd, Rh, similarly to the catalysts on ceramic carriers. The contents of these metals make that spent catalytic converters are valuable source of precious metals. All over the world there are many methods for the metals recovery from the ceramic carriers, however, the issue of platinum recovery from metal supported catalysts has not been studied sufficiently yet. The paper presents preliminary results of dissolution of spent automotive catalyst on a metal carrier by means of acids: H2SO4, HCl, HNO3, H3PO4. The main assumption of the research was the dissolution of base metals (Fe, Cr, Al from metallic carrier of catalyst, avoiding dissolution of PGMs. Dissolution was the most effective when concentrated hydrochloric acid, and 2M sulfuric acid (VI was used. It was observed that the dust, remaining after leaching, contained platinum in the level of 0.8% and 0.7%, respectively.

  14. Metal-free phenanthrenequinone cyclotrimer as an effective heterogeneous catalyst.

    Science.gov (United States)

    Zhang, Jian; Wang, Xuan; Su, Qi; Zhi, Linjie; Thomas, Arne; Feng, Xinliang; Su, Dang Sheng; Schlögl, Robert; Müllen, Klaus

    2009-08-19

    A phenanthrenequinone macrocyclic trimer was synthesized and used as a heterogeneous catalyst for oxidative dehydrogenation of ethylbenzene. This model molecule under comparable kinetic conditions is up to 47 times more active than extended solid catalysts including nanocarbons, metal phosphates, and oxides, confirming the hypothesis that diketone-like groups can serve as active sites.

  15. Platinum Group Metal-free Catalysts for Hydrogen Evolution Reaction in Microbial Electrolysis Cells.

    Science.gov (United States)

    Yuan, Heyang; He, Zhen

    2017-07-01

    Hydrogen gas is a green energy carrier with great environmental benefits. Microbial electrolysis cells (MECs) can convert low-grade organic matter to hydrogen gas with low energy consumption and have gained a growing interest in the past decade. Cathode catalysts for the hydrogen evolution reaction (HER) present a major challenge for the development and future applications of MECs. An ideal cathode catalyst should be catalytically active, simple to synthesize, durable in a complex environment, and cost-effective. A variety of noble-metal free catalysts have been developed and investigated for HER in MECs, including Nickel and its alloys, MoS 2 , carbon-based catalysts and biocatalysts. MECs in turn can serve as a research platform to study the durability of the HER catalysts. This personal account has reviewed, analyzed, and discussed those catalysts with an emphasis on synthesis and modification, system performance and potential for practical applications. It is expected to provide insights into the development of HER catalysts towards MEC applications. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Tackling CO Poisoning with Single Atom Alloy Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jilei; Lucci, Felicia R.; Yang, Ming; Lee, Sungsik; Marcinkowski, Matthew D.; Therrien, Andrew J.; Williams, Christopher T.; Sykes, E. Charles H.; Flytzani-Stephanopoulos, Maria

    2016-05-01

    Platinum (Pt) catalysts are extensively used in the chemical industry and as electrocatalysts in fuel cells. Pt is notorious for its sensitivity to poisoning by strong CO adsorption. Here we demonstrate that the single atom alloy (SAA) strat-egy applied to Pt reduces the binding strength of CO while maintaining catalytic performance. By using surface sensi-tive studies, we accurately determined the binding strength of CO to different Pt ensembles, and this in turn guided the preparation of PtCu alloy nanoparticles. The atomic ratio Pt:Cu = 1:120 yielded a SAA which exhibited excellent CO tolerance in H2 activation, the key elementary step for hy-drogenation and hydrogen electro-oxidation. As a probe reaction, the selective hydrogenation of acetylene to ethene was performed under flow conditions on the SAA nanopar-ticles supported on alumina without activity loss in the pres-ence of CO. The ability to maintain reactivity in the presence of CO is vital to other industrial reactions including fuel reforming and methanol/ethanol fuel cells.

  17. Nitrogen-doped carbon nanotubes as a metal catalyst support

    CSIR Research Space (South Africa)

    Mabena, LF

    2011-05-01

    Full Text Available The science and technology of catalysis is of fundamental importance to a national economy. Today about 90% of all technical chemicals are manufactured by the use of catalysts. Nanoparticles of noble metals are extremely important materials...

  18. Neutral bimetallic transition metal phenoxyiminato catalysts and related polymerization methods

    Science.gov (United States)

    Marks, Tobin J [Evanston, IL; Rodriguez, Brandon A [Evanston, IL; Delferro, Massimiliano [Chicago, IL

    2012-08-07

    A catalyst composition comprising a neutral bimetallic diphenoxydiiminate complex of group 10 metals or Ni, Pd or Pt is disclosed. The compositions can be used for the preparation of homo- and co-polymers of olefinic monomer compounds.

  19. Thermal expansion: Metallic elements and alloys. [Handbook

    Science.gov (United States)

    Touloukian, Y. S.; Kirby, R. K.; Taylor, R. E.; Desai, P. D.

    1975-01-01

    The introductory sections of the work are devoted to the theory of thermal expansion of solids and to methods for the measurement of the linear thermal expansion of solids (X-ray methods, high speed methods, interferometry, push-rod dilatometry, etc.). The bulk of the work is devoted to numerical data on the thermal linear expansion of all the metallic elements, a large number of intermetallics, and a large number of binary alloy systems and multiple alloy systems. A comprehensive bibliography is provided along with an index to the materials examined.

  20. Supported Molten Metal Catalysis. A New Class of Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ravindra Datta; Ajeet Singh; Manuela Serban; Istvan Halasz

    2006-06-02

    We describe a new class of heterogeneous catalysts called supported molten metal catalysis (SMMC), in which molten metal catalysts are dispersed as nanodroplets on the surface of porous supports, allowing much larger active surface area than is possible in conventional contacting techniques for catalytic metals that are molten under reaction conditions, thus greatly enhancing their activity and potential utility. Specific examples of different types of reactions are provided to demonstrate the broad applicability of the technique in designing active, selective, and stable new catalysts. It is shown that dispersing the molten metal on a support in the suggested manner can enhance the rate of a reaction by three to four orders of magnitude as a result of the concomitant increase in the active surface area. New reaction examples include {gamma}-Al{sub 2}O{sub 3} supported molten Te (melting point 450 C) and Ga (MP 30 C) catalysts for bifunctional methylcyclohexane dehydrogenation. These catalysts provide activity similar to conventional Pt-based catalysts for this with better resistance to coking. In addition, results are described for a controlled pore glass supported molten In (MP 157 C) catalyst for the selective catalytic reduction of NO with ethanol in the presence of water, demonstrating activities superior to conventional catalysts for this reaction. A discussion is also provided on the characterization of the active surface area and dispersion of these novel supported catalysts. It is clear based on the results described that the development of new active and selective supported molten metal catalysts for practical applications is entirely plausible.

  1. Stable carbides in transition metal alloys

    International Nuclear Information System (INIS)

    Piotrkowski, R.

    1991-01-01

    In the present work different techniques were employed for the identification of stable carbides in two sets of transition metal alloys of wide technological application: a set of three high alloy M2 type steels in which W and/or Mo were total or partially replaced by Nb, and a Zr-2.5 Nb alloy. The M2 steel is a high speed steel worldwide used and the Zr-2.5 Nb alloy is the base material for the pressure tubes in the CANDU type nuclear reactors. The stability of carbide was studied in the frame of Goldschmidt's theory of interstitial alloys. The identification of stable carbides in steels was performed by determining their metallic composition with an energy analyzer attached to the scanning electron microscope (SEM). By these means typical carbides of the M2 steel, MC and M 6 C, were found. Moreover, the spatial and size distribution of carbide particles were determined after different heat treatments, and both microstructure and microhardness were correlated with the appearance of the secondary hardening phenomenon. In the Zr-Nb alloy a study of the α and β phases present after different heat treatments was performed with optical and SEM metallographic techniques, with the guide of Abriata and Bolcich phase diagram. The α-β interphase boundaries were characterized as short circuits for diffusion with radiotracer techniques and applying Fisher-Bondy-Martin model. The precipitation of carbides was promoted by heat treatments that produced first the C diffusion into the samples at high temperatures (β phase), and then the precipitation of carbide particles at lower temperature (α phase or (α+β)) two phase field. The precipitated carbides were identified as (Zr, Nb)C 1-x with SEM, electron microprobe and X-ray diffraction techniques. (Author) [es

  2. Modification of surface properties of copper-refractory metal alloys

    Science.gov (United States)

    Verhoeven, J.D.; Gibson, E.D.

    1993-10-12

    The surface properties of copper-refractory metal (CU-RF) alloy bodies are modified by heat treatments which cause the refractory metal to form a coating on the exterior surfaces of the alloy body. The alloys have a copper matrix with particles or dendrites of the refractory metal dispersed therein, which may be niobium, vanadium, tantalum, chromium, molybdenum, or tungsten. The surface properties of the bodies are changed from those of copper to that of the refractory metal.

  3. Development of Sulfur and Carbon Tolerant Reforming Alloy Catalysts Aided by Fundamental Atomistics Insights

    Energy Technology Data Exchange (ETDEWEB)

    Suljo Linic

    2006-08-31

    Current hydrocarbon reforming catalysts suffer from rapid carbon and sulfur poisoning. Even though there is a tremendous incentive to develop more efficient catalysts, these materials are currently formulated using inefficient trial and error experimental approaches. We have utilized a novel hybrid experimental/theoretical approach, combining quantum Density Functional Theory (DFT) calculations and various state-of-the-art experimental tools, to formulate carbon tolerant reforming catalysts. We have employed DFT calculations to develop molecular insights into the elementary chemical transformations that lead to carbon poisoning of Ni catalysts. Based on the obtained molecular insights, we have identified, using DFT quantum calculation, Sn/Ni alloy as a potential carbon tolerant reforming catalyst. Sn/Ni alloy was synthesized and tested in steam reforming of methane, propane, and isooctane. We demonstrated that the alloy catalyst is carbon-tolerant under nearly stoichiometric steam-to-carbon ratios. Under these conditions, monometallic Ni is rapidly poisoned by sp2 carbon deposits. The research approach is distinguished by a few characteristics: (a) Knowledge-based, bottom-up approach, compared to the traditional trial and error approach, allows for a more efficient and systematic discovery of improved catalysts. (b) The focus is on exploring alloy materials which have been largely unexplored as potential reforming catalysts.

  4. Surface Structures of Model Metal Catalysts in Reactant Gases.

    Science.gov (United States)

    Tao, Franklin Feng; Ralston, Walter T; Liu, Huimin; Somorjai, Gabor A

    2018-01-18

    Atomic scale knowledge of the surface structure of a metal catalyst is essential for fundamentally understanding the catalytic reactions performed on it. A correlation between the true atomic surface structure of a metal catalyst under reaction conditions and the corresponding catalytic performance is the key in pursuing mechanistic insight at a molecular level. Here the surface structures of model, metal catalysts in both ultrahigh vacuum (UHV) and gaseous environments of CO at a wide range of pressures are discussed. The complexity of observed surface structures in CO is illustrated, driving the necessity for visualization of the catalytic metals under realistic reaction conditions. Technical barriers for visualization of metal surfaces in situ at high temperature and high pressure are discussed.

  5. Layered Structures in Deformed Metals and Alloys

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    2014-01-01

    Layered structures characterize metals and alloys deformed to high strain. The morphology is typical lamellar or fibrous and the interlamellar spacing can span several length scales down to the nanometer dimension. The layered structures can be observed in bulk or in surface regions, which is shown...... by the way of examples of different processing routes: friction, wire drawing, shot peening, high pressure torsion and rolling. The interlamellar spacing reaches from 5-10 nanometers to about one micrometer and the analysis will cover structural evolution, strengthening parameters and strength-structure...... relationships. Finally, the results will be discussed based on universal principles for the evolution of microstructure and properties during plastic deformation of metals and alloys from low to high strain....

  6. Reactivity of metal catalysts in glucose-fructose conversion.

    Science.gov (United States)

    Loerbroks, Claudia; van Rijn, Jeaphianne; Ruby, Marc-Philipp; Tong, Qiong; Schüth, Ferdi; Thiel, Walter

    2014-09-15

    A joint experimental and computational study on the glucose-fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen-atom transfer; the latter was the rate-determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa = 4-6), coordination with either water or weaker σ donors, energetically low-lying unoccupied orbitals, compact transition-state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Low platinum catalyst and method of preparation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Di-Jia; Chong, Lina

    2017-11-21

    A low platinum catalyst and method for making same. The catalyst comprises platinum-transition metal bimetallic alloy microcrystallites over a transition metal-nitrogen-carbon composite. A method of making a catalyst comprises preparation of transition metal organic frameworks, infusion of platinum, thermal treatment, and reduction to form the microcrystallites and composite.

  8. Hydrous metal oxide catalysts for oxidation of hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-07-01

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

  9. Precious metal compounds and recovery. Fischer-Tropsch catalysts and catalysts for hydroformylation and oxo processes

    Energy Technology Data Exchange (ETDEWEB)

    Schapp, J.; Arndt, M. [W.C. Heraeus GmbH, Hanau (Germany); Meyer, H. [Heraeus Metal Processing Inc., Santa Fe Springs, CA (United States)

    2006-07-01

    Solid-phase Fischer-Tropsch catalysts, which are used in the emerging field of interest known as ''Gas-to-Liquid'' (GTL), consist to a high percentage of cobalt. In addition, they contain on a value basis, a considerable amount of platinum group metals or rhenium as promoters. Therefore, there is an imperative need for economically feasible recycling processes triggered not only by the value of the metals in spent Fischer-Tropsch catalysts, but also by the potentially limited availability of promoters like rhenium. Heraeus, as a precious metal expert, is supporting this important technology with its profound know-how in developing tailor-made hydrometallurgical recycling processes for all kinds of catalyst systems. Besides giving an overview of state-of-the-art recovery processes, this paper will clarify the economic and environmental aspects involved. Hydroformylation and oxo processes are technologies which consume a major percentage of homogeneous catalysts worldwide. The focus lies on organometallic compounds with rhodium as the catalytic center. With significant rises of the rhodium price, many companies are being pushed to look more closely at the involved recycling terms. Accordingly, Heraeus is proud to offer its HeraCYCLE {sup registered} recovery process recently developed for homogeneous catalysts in particular. Furthermore, Heraeus manufactures the required quantities of fresh homogeneous catalysts ensuring highest quality standards. Key economic, technical, and environmental aspects of the precious metal loops will be covered by this paper. (orig.)

  10. An environmentally friendly process for the recovery of valuable metals from spent refinery catalysts.

    Science.gov (United States)

    Rocchetti, Laura; Fonti, Viviana; Vegliò, Francesco; Beolchini, Francesca

    2013-06-01

    The present study dealt with the whole valorization process of exhaust refinery catalysts, including metal extraction by ferric iron leaching and metal recovery by precipitation with sodium hydroxide. In the leaching operation the effects on metal recovery of the concentration and kind of acid, the concentration of catalyst and iron (III) were determined. The best operating conditions were 0.05 mol L(-1) sulfuric acid, 40 g L(-1) iron (III), 10% catalyst concentration; almost complete extraction of nickel and vanadium, and 50%extraction efficiency of aluminium and less than 20% for molybdenum. Sequential precipitation on the leach liquor showed that it was not possible to separate metals through such an approach and a recovery operation by means of a single-stage precipitation at pH 6.5 would simplify the procedures and give a product with an average content of iron (68%), aluminium (13%), vanadium (11%), nickel (6%) and molybdenum (1%) which would be potentially of interest in the iron alloy market. The environmental sustainability of the process was also assessed by means of life cycle assessment and yielded an estimate that the highest impact was in the category of global warming potential with 0.42 kg carbon dioxide per kg recovered metal.

  11. Metal-Support Cooperative Catalysts for Environmentally Benign Molecular Transformations.

    Science.gov (United States)

    Kaneda, Kiyotomi; Mitsudome, Takato

    2017-01-01

    Metal-support cooperative catalysts have been developed for sustainable and environmentally benign molecular transformations. The active metal centers and supports in these catalysts could cooperatively activate substrates, resulting in high catalytic performance for liquid-phase reactions under mild conditions. These catalysts involved hydrotalcite-supported gold and silver nanoparticles with high catalytic activity for organic reactions such as aerobic oxidation, oxidative carbonylation, and chemoselective reduction of epoxides to alkenes and nitrostyrenes to aminostyrenes using alcohols and CO/H 2 O as reducing reagents. This high catalytic performance was due to cooperative catalysis between the metal nanoparticles and basic sites of the hydrotalcite support. To increase the metal-support cooperative effect, core-shell nanostructured catalysts consisting of gold or silver nanoparticles in the core and ceria supports in the shell were designed. These core-shell nanocomposite catalysts were effective for the chemoselective hydrogenation of nitrostyrenes to aminostyrenes, unsaturated aldehydes to allyl alcohols, and alkynes to alkenes using H 2 as a clean reductant. In addition, these solid catalysts could be recovered easily from the reaction mixture by simple filtration, and were reusable with high catalytic activity. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Cast bulk metallic glass alloys: prospects as wear materials

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.; Dogan, Omer N.; Shiflet, Gary J. (Dept. of Materials Science and Engineering, University of Virginia, Charlottesville, VA)

    2005-01-01

    Bulk metallic glasses are single phase materials with unusual physical and mechanical properties. One intriguing area of possible use is as a wear material. Usually, pure metals and single phase dilute alloys do not perform well in tribological conditions. When the metal or alloy is lightweight, it is usually soft leading to galling in sliding situations. For the harder metals and alloys, their density is usually high, so there is an energy penalty when using these materials in wear situations. However, bulk metallic glasses at the same density are usually harder than corresponding metals and dilute single phase alloys, and so could offer better wear resistance. This work will discuss preliminary wear results for metallic glasses with densities in the range of 4.5 to 7.9 g/cc. The wear behavior of these materials will be compared to similar metals and alloys.

  13. Heterogeneous Metal Catalysts for Oxidation Reactions

    Directory of Open Access Journals (Sweden)

    Md. Eaqub Ali

    2014-01-01

    Full Text Available Oxidation reactions may be considered as the heart of chemical synthesis. However, the indiscriminate uses of harsh and corrosive chemicals in this endeavor are threating to the ecosystems, public health, and terrestrial, aquatic, and aerial flora and fauna. Heterogeneous catalysts with various supports are brought to the spotlight because of their excellent capabilities to accelerate the rate of chemical reactions with low cost. They also minimize the use of chemicals in industries and thus are friendly and green to the environment. However, heterogeneous oxidation catalysis are not comprehensively presented in literature. In this short review, we clearly depicted the current state of catalytic oxidation reactions in chemical industries with specific emphasis on heterogeneous catalysts. We outlined here both the synthesis and applications of important oxidation catalysts. We believe it would serve as a reference guide for the selection of oxidation catalysts for both industries and academics.

  14. Laser processing of metals and alloys

    International Nuclear Information System (INIS)

    Goswami, G.L.; Kumar, Dilip; Roy, P.R.

    1988-01-01

    Laser, due to its high degree of coherence can produce powder density in the range of 10 3 -10 11 W/mm 2 . This high power density of the laser beam enables it to be utilized for many industrial applications, e.g. welding, cutting, drilling, surface treatment, etc. Laser processing of materials has many advantages, e.g. good quality product at high processing speed, least heat affected zone, minimum distortion, etc. In addition, the same laser system can be utilized for different applications, a very cost effective factor for any industry. Therefore laser has been adopted for processing of different materials for a wide range of applications and is now replacing conventional materials processing techniques on commercial merits with several economic and metallurgical advantages. Applications of laser to process materials of different thicknesses varying from 0.1 mm to 100 mm have demonstrat ed its capability as an important manufacturing tool for engineering industries. While lasers have most widely been utilized in welding, cutting and drilling they have also found applications in surface treatment of metals and alloys, e.g. transfor mation hardening and annealing. More recently, there has been significant amount of research being undertaken in laser glazing, laser surface alloying and laser cladding for obtaining improved surface properties. This report reviews the stat us of laser processing of metals and alloys emphasising its metallurgical aspects a nd deals with the different laser processes like welding, cutting, drilling and surface treatment highlighting the types and choice of laser and its interaction with metals and alloys and the applications of these processes. (author). 93 refs., 32 figs., 7 tables

  15. Deriving the Metal and Alloy Networks of Modern Technology.

    Science.gov (United States)

    Ohno, Hajime; Nuss, Philip; Chen, Wei-Qiang; Graedel, Thomas E

    2016-04-05

    Metals have strongly contributed to the development of the human society. Today, large amounts of and various metals are utilized in a wide variety of products. Metals are rarely used individually but mostly together with other metals in the form of alloys and/or other combinational uses. This study reveals the intersectoral flows of metals by means of input-output (IO) based material flow analysis (MFA). Using the 2007 United States IO table, we calculate the flows of eight metals (i.e., manganese, chromium, nickel, molybdenum, niobium, vanadium, tungsten, and cobalt) and simultaneously visualize them as a network. We quantify the interrelationship of metals by means of flow path sharing. Furthermore, by looking at the flows of alloys into metal networks, the networks of the major metals iron, aluminum, and copper together with those of the eight alloying metals can be categorized into alloyed-, nonalloyed-(i.e., individual), and both mixed. The result shows that most metals are used primarily in alloy form and that functional recycling thereby requires identification, separation, and alloy-specific reprocessing if the physical properties of the alloys are to be retained for subsequent use. The quantified interrelation of metals helps us consider better metal uses and develop a sustainable cycle of metals.

  16. Aerobic Oxidations of Light Alkanes over Solid Metal Oxide Catalysts.

    Science.gov (United States)

    Grant, Joseph T; Venegas, Juan M; McDermott, William P; Hermans, Ive

    2017-11-07

    Heterogeneous metal oxide catalysts are widely studied for the aerobic oxidations of C 1 -C 4 alkanes to form olefins and oxygenates. In this review, we outline the properties of supported metal oxides, mixed-metal oxides, and zeolites and detail their most common applications as catalysts for partial oxidations of light alkanes. By doing this we establish similarities between different classes of metal oxides and identify common themes in reaction mechanisms and research strategies for catalyst improvement. For example, almost all partial alkane oxidations, regardless of the metal oxide, follow Mars-van Krevelen reaction kinetics, which utilize lattice oxygen atoms to reoxidize the reduced metal centers while the gaseous O 2 reactant replenishes these lattice oxygen vacancies. Many of the most-promising metal oxide catalysts include V 5+ surface species as a necessary constituent to convert the alkane. Transformations involving sequential oxidation steps (i.e., propane to acrylic acid) require specific reaction sites for each oxidation step and benefit from site isolation provided by spectator species. These themes, and others, are discussed in the text.

  17. Metal-ceramic alloys in dentistry: a review.

    Science.gov (United States)

    Roberts, Howard W; Berzins, David W; Moore, B Keith; Charlton, David G

    2009-02-01

    The purpose of this article is to review basic information about the alloys used for fabricating metal-ceramic restorations in dentistry. Their compositions, properties, advantages, and disadvantages are presented and compared. In addition to reviewing traditional noble-metal and base-metal metal-ceramic alloys, titanium and gold composite alloys are also discussed. A broad search of the published literature was performed using Medline to identify pertinent current articles on metal-ceramic alloys as well as articles providing a historical background about the development of these alloys. Textbooks, the internet, and manufacturers' literature were also used to supplement this information. The review discusses traditional as well as more recently-developed alloys and technologies used in dentistry for fabricating metal-ceramic restorations. Clear advantages and disadvantages for these alloy types are provided and discussed as well as the role that compositional variations have on the alloys' performance. This information should enable clinicians and technicians to easily identify the important physical properties of each type and their primary clinical indications. A number of alloys and metals are available for metal-ceramic use in dentistry. Each has its advantages and disadvantages, primarily based on its specific composition. Continuing research and development are resulting in the production of new technologies and products, giving clinicians even more choices in designing and fabricating metal-ceramic restorations.

  18. Mass transport in non crystalline metallic alloys

    International Nuclear Information System (INIS)

    Limoge, Y.

    1986-08-01

    In order to improve our understanding of mass transport in non crystalline metallic alloys we have developed indirect studies of diffusion based on electron irradiation and hydrostatic pressure effects upon crystallization. In a first part we present the models of crystallization which are used, then we give the experimental results. The main point is the first experimental measurement of the activation volume for diffusion in a metallic glass: the value of which is roughly one atomic volume. We show also recent quantitative results concerning radiation enhanced diffusion in metallic glasses (FeNi) 8 (PB) 2 and Ni 6 Nb 4 . In a last part we discuss the atomic model needed to explain our results

  19. Metal salt catalysts for enhancing hydrogen spillover

    Science.gov (United States)

    Yang, Ralph T; Wang, Yuhe

    2013-04-23

    A composition for hydrogen storage includes a receptor, a hydrogen dissociating metal doped on the receptor, and a metal salt doped on the receptor. The hydrogen dissociating metal is configured to spill over hydrogen to the receptor, and the metal salt is configured to increase a rate of the spill over of the hydrogen to the receptor.

  20. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

    Science.gov (United States)

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X; Urban, Ania; Thacker, Nathan C; Lin, Wenbin

    2016-08-30

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

  1. Hydrogenation of coal liquid utilizing a metal carbonyl catalyst

    Science.gov (United States)

    Feder, Harold M.; Rathke, Jerome W.

    1979-01-01

    Coal liquid having a dissolved transition metal, catalyst as a carbonyl complex such as Co.sub.2 (CO.sub.8) is hydrogenated with hydrogen gas or a hydrogen donor. A dissociating solvent contacts the coal liquid during hydrogenation to form an immiscible liquid mixture at a high carbon monoxide pressure. The dissociating solvent, e.g. ethylene glycol, is of moderate coordinating ability, while sufficiently polar to solvate the transition metal as a complex cation along with a transition metal, carbonyl anion in solution at a decreased carbon monoxide pressure. The carbon monoxide pressure is reduced and the liquids are separated to recover the hydrogenated coal liquid as product. The dissociating solvent with the catalyst in ionized form is recycled to the hydrogenation step at the elevated carbon monoxide pressure for reforming the catalyst complex within fresh coal liquid.

  2. Metal dusting of low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Grabke, H.J. (Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)); Bracho-Troconis, C.B. (Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)); Mueller-Lorenz, E.M. (Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany))

    1994-04-01

    The metal dusting of two low alloy steels was investigated at 475 C in flowing CO-H[sub 2]-H[sub 2]O mixtures at atmospheric pressure with a[sub C] > 1. The reaction sequence comprises: (1) oversaturation with C, formation of cementite and its decomposition to metal particles and carbon, and (2) additional carbon deposition on the metal particles from the atmosphere. The metal wastage rate r[sub 1] was determined by analysis of the corrosion product after exposures, this rate is constant with time and virtually independent of the environment. The carbon deposition from the atmosphere was determined by thermogravimetry, its rate r[sub 2] increases linearly with time, which can be explained by the catalytic action of the metal particles - periodic changes are superposed. The rate of carbon deposition r[sub 2] is proportional to the carbon activity in the atmosphere. The metal dusting could not be suppressed by increasing the oxygen activity or preoxidation, even if magnetite should be stable. Addition of H[sub 2]S, however, effectively suppresses the attack. (orig.)

  3. EXAFS characterization of supported metal catalysts in chemically dynamic environments

    International Nuclear Information System (INIS)

    Robota, H.J.

    1991-01-01

    Characterization of catalysts focuses on the identification of an active site responsible for accelerating desirable chemical reactions. The identification, characterization, and selective modification of such sites is fundamental to the development of structure-function relationships. Unfortunately, this goal is far from realized in nearly all catalysts, and particularly in catalysts comprised of small supported metal particles. X-ray absorption spectroscopy (XAS) has had a dramatic effect on our understanding of supported metal particles in their resting state. However, the performance of a catalyst can not be assessed from such simple resting state measurements. Among the factors which influence catalyst performance are the exact catalyst composition, including the support and any modifiers; particle size; catalyst finishing and pretreatment conditions; pressure, composition, and temperature of the operating environment; time. Gaining an understanding of how the structure of a catalytic site can change with such an array of variables requires that we begin to develop measurement methods which are effective under chemically dynamic conditions. Ideally, it should be possible to obtain a full X-ray absorption spectrum of each element thought to have a causal relationship with observed catalyst properties. From these spectra, we can optimally extract only a relatively limited amount of information which we must then piece together with information derived from other characterization methods and intuition to arrive at a hypothetical structure of the operating catalyst. Information about crystallinity, homogeneity, and general disorder can be obtained from the Debye-Waller factor. Finally, through analogy with known compounds, the electronic structure of the active atoms can be inferred from near edge absorption features

  4. Quantification of zinc atoms in a surface alloy on copper in an industrial-type methanol synthesis catalyst.

    Science.gov (United States)

    Kuld, Sebastian; Conradsen, Christian; Moses, Poul Georg; Chorkendorff, Ib; Sehested, Jens

    2014-06-02

    Methanol has recently attracted renewed interest because of its potential importance as a solar fuel. Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of ZnO as a promoter for this type of catalyst is still under intense debate. Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial-type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent picture of surface alloying between copper and zinc. This analysis enables a reinterpretation of the methods that have been used for the determination of the Cu surface area and provides an opportunity to independently quantify the specific Cu and Zn areas. This method may also be applied to other systems where metal-support interactions are important, and this work generally addresses the role of the carrier and the nature of the interactions between carrier and metal in heterogeneous catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Molecular metal catalysts on supports: organometallic chemistry meets surface science.

    Science.gov (United States)

    Serna, Pedro; Gates, Bruce C

    2014-08-19

    Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

  6. Propane Dehydrogenation on Metal and Metal Oxide Catalysts

    NARCIS (Netherlands)

    Sattler, Jesper

    2014-01-01

    In this PhD thesis, the catalytic performance and deactivation of various propane dehydrogenation catalysts is studied. First of all, a literature study is performed, where the three most commonly used formulations, namely Pt-, CrOx- and GaOx-based catalysts are compared in terms of yield relative

  7. Current advances in precious metal core–shell catalyst design

    Science.gov (United States)

    Wang, Xiaohong; He, Beibei; Hu, Zhiyu; Zeng, Zhigang; Han, Sheng

    2014-01-01

    Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core–shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core–shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core–shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core–shell nanoparticles in this paper. The current research trends of these core–shell catalysts are also highlighted. PMID:27877695

  8. Nanostructured Platinum Alloys for Use as Catalyst Materials

    Science.gov (United States)

    Hays, Charles C. (Inventor); Narayan, Sri R. (Inventor)

    2015-01-01

    A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

  9. Supported Dendrimer-Encapsulated Metal Clusters: Toward Heterogenizing Homogeneous Catalysts.

    Science.gov (United States)

    Ye, Rong; Zhukhovitskiy, Aleksandr V; Deraedt, Christophe V; Toste, F Dean; Somorjai, Gabor A

    2017-08-15

    Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles-some without homogeneous analogues-for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence, and structural uniformity, dendrimers have proven to be versatile scaffolds for the synthesis and stabilization of small nanoclusters. Then these dendrimer-encapsulated metal clusters (DEMCs) are adsorbed onto mesoporous silica. Through this method, we have achieved selective transformations that had been challenging to accomplish in a heterogeneous setting, e.g., π-bond activation and aldol reactions. Extensive investigation into the catalytic systems under reaction conditions allowed us to correlate the structural features (e.g., oxidation states) of the catalysts and their activity. Moreover, we have

  10. Radiation blistering in metals and alloys

    International Nuclear Information System (INIS)

    Das, S.K.; Kaminsky, M.

    1975-01-01

    Radiation blistering in solids has been identified as a process leading to damage and erosion of irradiated surfaces. Some of the major parameters governing the blistering process in metals and some metallic alloys are the type of projectile and its energy, total dose, dose rate, target temperature, channeling condition of the projectile, orientation of the irradiated surface plane, and target material and its microstructure. Experimental results and models proposed for blister formation and rupture are reviewed. The blistering phenomenon is important as an erosion process in applications such as fusion reactor technology (plasma-wall interactions) and accelerator technology (erosion of components and targets). A description of methods for the reduction of surface erosion caused by blistering is included

  11. Application of Metal Catalysts for High Selectivity of Glycerol Conversion to Alcohols

    Science.gov (United States)

    2010-11-01

    The objective of this project is to determine the applicability of metal-based catalysts and optimize the process conditions for thermochemically producing primary alcohols. Metal catalysts were evaluated for their selectivities for producing alcohol...

  12. Vapor phase synthesis and characterization of bimetallic alloy and supported nanoparticle catalysts

    Science.gov (United States)

    Abdelsayed, V.; Saoud, K. M.; El-Shall, M. Samy

    2006-08-01

    The laser vaporization controlled condensation (LVCC) technique coupled with a differential mobility analyzer (DMA) is used to synthesize size-selected alloy nanoparticles and nanoparticle catalyst systems. The formation of Au-Ag alloy nanoparticles is concluded from the observation of only one plasmon band. The maximum of the plasmon absorption is found to vary linearly with the gold mole fraction. For the Au-Pd system, the XRD data confirms the formation of the alloy nanoparticles with no evidence of any of the pure components. The Au/CeO2 nanoparticle catalyst prepared by the LVCC method is a promising catalyst for low temperature CO oxidation due to its high activity and stability.

  13. Process for Making a Noble Metal on Tin Oxide Catalyst

    Science.gov (United States)

    Davis, Patricia; Miller, Irvin; Upchurch, Billy

    2010-01-01

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

  14. Metal content determination in polymerization catalysts by direct methods

    International Nuclear Information System (INIS)

    Bichinho, K.M.; Pires, Gilvan P.; Stedile, F.C.; Santos, J.H.Z. dos

    2002-01-01

    Metal contents in polymerization catalysts were comparatively determined by Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) spectroscopy. Catalysts were prepared by grafting metallocene onto bare silica or onto silica chemically modified with methylaluminoxane (MAO). Catalysts were compressed as self-supporting pellets (RBS and XRF), or mounted on adhesive copper tape (XPS). The proximity of the mass of the atomic nuclei did not allow resolution by RBS of the signals corresponding to Zr and Nb, nor Si and Al in catalyst systems such as (nBuCp) 2 ZrCl 2 /Cp 2 NbCl 2 /MAO/SiO 2 . On the other hand, Zr, Nb, Si and Al lines were completely resolved in an XRF spectrum. For supported metallocenes on bare silica, XPS measurement was ca. 40% higher than that obtained by RBS. Silica-supported zirconocene showed good agreement in Zr content determination by XRF and RBS

  15. In vitro cytotoxicity of metallic ions released from dental alloys

    NARCIS (Netherlands)

    Milheiro, A.; Nozaki, K.; Kleverlaan, C.J.; Muris, J.; Miura, H.; Feilzer, A.J.

    2016-01-01

    The cytotoxicity of a dental alloy depends on, but is not limited to, the extent of its corrosion behavior. Individual ions may have effects on cell viability that are different from metals interacting within the alloy structure. We aimed to investigate the cytotoxicity of individual metal ions in

  16. PHENOL OXIDATION USING NATURAL ZEOLITE SUPPORTED METAL ION CATALYST

    Directory of Open Access Journals (Sweden)

    Sri Wardhani

    2010-06-01

    Full Text Available Phenol which contained in waste water has to be reduced and it could be done by oxygen oxidation.  In order to increase the rate of reaction it was needed a catalyst. In this research the capability of various catalysts, namely zeolite-Zn(II, zeolite-Cu(II and zeolite-Co(IIin oxidation of phenol has been investigated. The aim of this research was to study the type of metal ion catalyst towards the percentage of oxidated phenol. The oxidation process were carried out in an aqueous phenol of 100 ppm with oxygen flow rate of 200 mL/min. in the presence of catalysts with 0.2M of initial impregnation concentration. The capabilities of catalysts were performed by calculating the activation energy and it was done at two different temperatures, i.e. 70 and 90 oC. The percentage of oxidated phenol was determinated by measuring its concentration using UV-VIS spectrophotometer. In addition, the impregnated metal was calculated by measuring the ion concentration remains in the filtrate solution and it was determined using Atomic Absorption Spectrophotometer. The results showed that metal ion types affected the catalytic activity. The order of phenol oxidationactivity decreased as Co(II > Cu(II > Zn(II. The surface characteristics of catalysts were supported by pore volume and pore diameter i.e 0.009 cm3/g and 16.59 Å for Zn(II whereas specific surface area was 10.32 m2/g for Zn(II, 0.004 cm3/g and 24.37 Å for Cu(II whereas specific surface area was 3.57 m2/g for Cu(II, 0.001 cm3/g and 19.63 Å for Co(II whereas specific surface area was 10.26m2/g for Co(II.   Keywords: phenol,natural zeolite, catalyst, oxidation

  17. Electro catalyst in the last 30 years - from precious metals to cheaper but sophisticated complex systems

    International Nuclear Information System (INIS)

    Hadzi Jordanov, Svetomir; Paunovic, Perica; Dimitrov, Aleksandar; Slavkov, Dragan; Popovski, Orce

    2004-01-01

    The paper is concerned with the advance and diversification of materials used as electrodes for evolution of chlorine, hydrogen and oxygen. In the first part a survey is given of our research in the field of electro catalysis 30 years ago, when Ru and other precious metals were the exclusive electro catalyst materials. A brief scope of the achievements of electro catalysis in that period is given as well. The second part deals with our recent research on formulation and characterization of a new class of electrocatalysts, based on a combination of non-precious metals, but still exhibiting an ability to promote hydrogen evolution reaction as successful as platinum and other precious metals are. Among the produced (non-platinum) catalysts the best performance for the hydrogen evolution reaction was measured at the electro catalyst containing Co or CoNi as hyper d phase and TiO 2 as hypo d phase. A typical formulation of the electrodes is, e.g.: 18% (TiO 2 ) alloyed with 10% Co and applied on a substrat of carbon powder (Vulcan XC-72). At this electro catalyst hydrogen evolution overpotential at 10 mA·cm -2 was 40 mV higher than that on a corresponding electrode containing platinum as hyper d phase. For both electro catalyst systems of interest analysis is made and aimed to recognize the sources that cause the electrocatalytic activity. This is the proper way how to use the acquired knowledge for further improvement of the existing materials or/and to discover new ones. (Author)

  18. Polyol Synthesis of Cobalt–Copper Alloy Catalysts for Higher Alcohol Synthesis from Syngas

    DEFF Research Database (Denmark)

    Mendes, Laiza V.P.; Snider, Jonathan L.; Fleischman, Samuel D.

    2017-01-01

    Novel catalysts for the selective production of higher alcohols from syngas could offer improved pathways towards synthetic fuels and chemicals. Cobalt–copper alloy catalysts have shown promising results for this reaction. To improve control over particle properties, a liquid phase nanoparticle...... and after catalytic testing in a flow reactor at 250 °C and 40 bar. The results show alloyed phases were obtained using the polyol method, resulting in selectivity towards higher alcohols, as high as 11.3% when supported on alumina. Segregation of cobalt and the formation of cobalt carbide were observed...

  19. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    Science.gov (United States)

    Lyons, James E.; Ellis, Jr., Paul E.; Wagner, Richard W.

    1996-01-01

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

  20. Metal Phosphate-Supported Pt Catalysts for CO Oxidation

    Science.gov (United States)

    Qian, Xiaoshuang; Qin, Hongmei; Meng, Tao; Lin, Yi; Ma, Zhen

    2014-01-01

    Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2) have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO4)6(OH)2, denoted as Ca-P-O here) also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La) catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP) atomic emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO2 temperature-programmed desorption (CO2-TPD), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). This work furnishes a new catalyst system for CO oxidation and other possible reactions. PMID:28788293

  1. Synthesis-Structure-Performance Relationships for Supported Metal Catalysts

    NARCIS (Netherlands)

    Munnik, Peter|info:eu-repo/dai/nl/328228524

    2014-01-01

    Heterogeneous catalysts, which consist of many metal nanoparticles supported on highly porous, mechanically strong and chemically inert supports, are at the center of many existing as well as new and more sustainable processes, such as energy conversion and storage, nanoelectronics and the catalytic

  2. Metal Phosphate-Supported Pt Catalysts for CO Oxidation

    Directory of Open Access Journals (Sweden)

    Xiaoshuang Qian

    2014-12-01

    Full Text Available Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2 have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO46(OH2, denoted as Ca-P-O here also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP atomic emission spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectron spectroscopy (XPS, and H2 temperature-programmed reduction (H2-TPR. This work furnishes a new catalyst system for CO oxidation and other possible reactions.

  3. Transition metal complexes supported on metal-organic frameworks for heterogeneous catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Omar K.; Hupp, Joseph T.; Delferro, Massimiliano; Klet, Rachel C.

    2017-02-07

    A robust mesoporous metal-organic framework comprising a hafnium-based metal-organic framework and a single-site zirconium-benzyl species is provided. The hafnium, zirconium-benzyl metal-organic framework is useful as a catalyst for the polymerization of an alkene.

  4. Accelerated decarburization of Fe-C metal alloys

    Science.gov (United States)

    Pal, Uday B.; Sadoway, Donald R.

    1997-01-01

    A process for improving the rate of metal production and FeO utilization in a steelmaking process or a process combining iron-making and steelmaking in a single reactor that uses or generates Fe-C metal alloy droplets submerged in an FeO-containing slag. The process involves discharging a charge build-up (electron accumulation) in the slag at the slag-metal alloy interface by means of an electron conductor connected between the metal alloy droplets and a gas at a gas-slag interface, said gas having an oxygen partial pressure of at least about 0.01 atmosphere.

  5. Base metal alloys used for dental restorations and implants.

    Science.gov (United States)

    Roach, Michael

    2007-07-01

    One of the primary reasons for the development of base metal alloys for dental applications has been the escalating cost of gold throughout the 20th century. In addition to providing lower cost alternatives, these nonprecious alloys were also found to provide better mechanical properties and aesthetics for some oral applications. Additionally, certain base metal alloy systems are preferred because of their superior mechanical properties, lower density, and in some cases, their capability to osseo-integrate. The base metal alloy systems most commonly used in dentistry today include stainless steels, nickel-chromium, cobalt-chromium, titanium, and nickel-titanium alloys. Combined, these alloy systems provide a wide range of available properties to choose the correct material for both temporary and long-term restoration and implant applications.

  6. A versatile sonication-assisted deposition-reduction method for preparing supported metal catalysts for catalytic applications.

    Science.gov (United States)

    Padilla, Romen Herrera; Priecel, Peter; Lin, Ming; Lopez-Sanchez, Jose Antonio; Zhong, Ziyi

    2017-03-01

    This work aims to develop a rapid and efficient strategy for preparing supported metal catalysts for catalytic applications. The sonication-assisted reduction-precipitation method was employed to prepare the heterogeneous mono- and bi-metallic catalysts for photocatalytic degradation of methyl orange (MO) and preferential oxidation (PROX) of CO in H 2 -rich gas. In general, there are three advantages for the sonication-assisted method as compared with the conventional methods, including high dispersion of metal nanoparticles on the catalyst support, the much higher deposition efficiency (DE) than those of the deposition-precipitation (DP) and co-precipitation (CP) methods, and the very fast preparation, which only lasts 10-20s for the deposition. In the AuPd/TiO 2 catalysts series, the AuPd(3:1)/TiO 2 catalyst is the most active for MO photocatalytic degradation; while for PROX reaction, Ru/TiO 2 , Au-Cu/SBA-15 and Pt/γ-Al 2 O 3 catalysts are very active, and the last one showed high stability in the lifetime test. The structural characterization revealed that in the AuPd(3:1)/TiO 2 catalyst, Au-Pd alloy particles were formed and a high percentage of Au atoms was located at the surface. Therefore, this sonication-assisted method is efficient and rapid in the preparation of supported metal catalysts with obvious structural characteristics for various catalytic applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Recovering platinum-group metals from auto catalysts

    International Nuclear Information System (INIS)

    Hoffmann, J.E.

    1988-01-01

    A variety of technical challenges confront the prospective processor of spent automotive catalysts, including a frequently high (1-10%) lead content; the presence of alumina in both soluble, γ, and insoluble, α, forms; the need for recovery of greater than 90% to assure an economical process; the disposition and control of process effluents, refractory residues, and lead metal salts from catalyst processing; and the highly aggressive and corrosive reagents required. Six different processes for recovery of platinum, palladium and rhodium are described and compared on the basis of their utility and how well they meet these technical challenges

  8. [Systemic reactions to orally applied metal alloys].

    Science.gov (United States)

    Feilzer, A J; Kleverlaan, C J; Prahl, C; Muris, J

    2013-06-01

    Orally applied metal alloys can cause undesirable physical effects. A distinction needs to be made in this respect between local and systemic reactions and toxic and immunological reactions. A case is presented which illustrates this problem. In this case, the application of orthodontic appliances was probably the trigger for an exacerbation of nickel allergy. The oral exposure to nickel resulted in hand eczema. The patient was also exposed to nickel by single-unit fixed dental prostheses, a removable dental prosthesis, and food, as a result of which removal of the orthodontic appliances did not result in complete healing. Therefore, the single-unit fixed dental prostheses also had to be removed and food had to be prepared henceforward in nickel free pans.

  9. Investigation of americium-241 metal alloys for target applications

    International Nuclear Information System (INIS)

    Conner, W.V.; Rockwell International Corp., Golden, CO

    1982-01-01

    Several 241 Am metal alloys have been investigated for possible use in the Lawrence Livermore National Laboratory Radiochemical Diagnostic Tracer Program. Several properties were desired for an alloy to be useful for tracer program applications. A suitable alloy would have a fairly high density, be ductile, homogeneous and easy to prepare. Alloys investigated have included uranium-americium, aluminium-americium, and cerium-americium. Uranium-americium alloys with the desired properties proved to be difficult to prepare, and work with this alloy was discontinued. Aluminium-americium alloys were much easier to prepare, but the alloy consisted of an aluminium-americium intermetallic compound (AmAl 4 ) in an aluminum matrix. This alloy could be cast and formed into shapes, but the low density of aluminum, and other problems, made the alloy unsuitable for the intended application. Americium metal was found to have a high solid solubility in cerium and alloys prepared from these two elements exhibited all of the properties desired for the tracer program application. Cerium-americium alloys containing up to 34 wt% americium have been prepared using both co-melting and co-reduction techniques. The latter technique involves co-reduction of cerium tetrafluoride and americium tetrafluoride with calcium metal in a sealed reduction vessel. Casting techniques have been developed for preparing up to eight 2.2 cm (0.87 in) diameter disks in a single casting, and cerium-americium metal alloy disks containing from 10 to 25 wt% 241 Am have been prepared using these techniques. (orig.)

  10. Ozone Decomposition on the Surface of Metal Oxide Catalyst

    Directory of Open Access Journals (Sweden)

    Batakliev Todor Todorov

    2014-12-01

    Full Text Available The catalytic decomposition of ozone to molecular oxygen over catalytic mixture containing manganese, copper and nickel oxides was investigated in the present work. The catalytic activity was evaluated on the basis of the decomposition coefficient which is proportional to ozone decomposition rate, and it has been already used in other studies for catalytic activity estimation. The reaction was studied in the presence of thermally modified catalytic samples operating at different temperatures and ozone flow rates. The catalyst changes were followed by kinetic methods, surface measurements, temperature programmed reduction and IR-spectroscopy. The phase composition of the metal oxide catalyst was determined by X-ray diffraction. The catalyst mixture has shown high activity in ozone decomposition at wet and dry O3/O2 gas mixtures. The mechanism of catalytic ozone degradation was suggested.

  11. High performance, high durability non-precious metal fuel cell catalysts

    Science.gov (United States)

    Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

    2016-03-15

    This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

  12. Modeling of thermodiffusion in liquid metal alloys.

    Science.gov (United States)

    Eslamian, Morteza; Sabzi, Fatemeh; Saghir, M Ziad

    2010-11-07

    In this paper following the linear non-equilibrium thermodynamics approach, an expression is derived for the calculation of the thermodiffusion factor in binary liquid metal alloys. The expression is comprised of two terms; the first term accounts for the thermally driven interactions between metal ions, a phenomenon similar to that of the non-ionic binary mixtures, such as hydrocarbons; the second term is called the electronic contribution and is the mass diffusion due to an internal electric field that is induced as a result of the imposed thermal gradient. Both terms are formulated as functions of the net heats of transport. The ion-ion net heat of transport is simulated by the activation energy of viscous flow and the electronic net heat of transport is correlated with the force acting on the ions by the rearrangement of the conduction electrons and ions. A methodology is presented and used to estimate the liquid metal properties, such as the partial molar internal energies, enthalpies, volumes and the activity coefficients used for model validation. The prediction power of the proposed expression along with some other existing thermodiffusion models for liquid mixtures, such as the Haase, Kempers, Drickamer and Firoozabadi formulas are examined against available experimental data obtained on ground or in microgravity environment. The proposed model satisfactorily predicts the thermodiffusion data of mixtures that are composed of elements with comparable melting points. It is also potentially and qualitatively able to predict a sign change in thermodiffusion factor of Na-K liquid mixture. With some speculation, the sign change is attributed to an anomalous change in thermoelectric power of Na-K mixture with composition.

  13. Metal induced crystallization of silicon germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gjukic, M.

    2007-05-15

    In the framework of this thesis the applicability of the aluminium-induced layer exchange on binary silicon germanium alloys was studied. It is here for the first time shown that polycrstalline silicon-germanium layers can be fabricated over the whole composition range by the aluminium-induced layer exchange. The experimental results prove thet the resulting material exhibits a polycrystalline character with typocal grain sizes of 10-100 {mu}m. Raman measurements confirm that the structural properties of the resulting layers are because of the large crystallites more comparable with monocrystalline than with nano- or microcrystalline silicon-germanium. The alloy ratio of the polycrystalline layer correspondes to the chemical composition of the amorphous starting layer. The polycrystalline silicon-germanium layers possess in the range of the interband transitions a reflection spectrum, as it is otherwise only known from monocrystalline reference layers. The improvement of the absorption in the photovoltaically relevant spectral range aimed by the application of silicon-germanium could be also proved by absorption measurments. Strongly correlated with the structural properties of the polycrystalline layers and the electronic band structure resulting from this are beside the optical properties also the electrical properties of the material, especially the charge-carrier mobility and the doping concentration. For binary silicon-germanium layers the hole concentration of about 2 x 10{sup 18} cm{sup -3} for pure silicon increrases to about 5 x 10{sup 20} cm{sub -3} for pure germanium. Temperature-resolved measurements were applied in order to detect doping levels respectively semiconductor-metal transitions. In the last part of the thesis the hydrogen passivation of polycrystalline thin silicon-germanium layers, which were fabricated by means of aluminium-induced layer exchange, is treated.

  14. The solubility of metals in Pb-17Li liquid alloy

    International Nuclear Information System (INIS)

    Borgstedt, H.U.; Feuerstein, H.

    1992-01-01

    The solubility data of iron in the eutectic alloy Pb-17Li which were evaluated from corrosion tests in a turbulent flow of the molten alloy are discussed in the frame of solubilities of the transition metals in liquid lead. It is shown that the solubility of iron in the alloy is close to that in lead. This is also the fact for several other alloying elements of steels. A comparison of all known data shows that they are in agreement with generally shown trends for the solubility of the transition metals in low melting metals. These trends indicate comparably high solubilities of nickel and manganese in the liquid metals, lower saturation concentration of vanadium, chromium, iron, and cobalt, and extremely low solubility of molybdenum. (orig.)

  15. COATING OF POLYMERIC SUBSTRATE CATALYSTS ON METALLIC SURFACES

    Directory of Open Access Journals (Sweden)

    H. HOSSEINI

    2010-12-01

    Full Text Available This article presents results of a study on coating of a polymeric substrate ca-talyst on metallic surface. Stability of coating on metallic surfaces is a proper specification. Sol-gel technology was used to synthesize adhesion promoters of polysilane compounds that act as a mediator. The intermediate layer was coated by synthesized sulfonated polystyrene-divinylbenzene as a catalyst for production of MTBE in catalytic distillation process. Swelling of catalyst and its separation from the metal surface was improved by i increasing the quantity of divinylbenzene in the resin’s production process and ii applying adhesion pro¬moters based on the sol-gel process. The rate of ethyl silicate hydrolysis was intensified by increasing the concentration of utilized acid while the conden¬sation polymerization was enhanced in the presence of OH–. Sol was formed at pH 2, while the pH should be 8 for the formation of gel. By setting the ratio of the initial concentrations of water to ethyl silicate to 8, the gel formation time was minimized.

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

    Science.gov (United States)

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

    2012-07-03

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

  17. Noble metal catalysts in the production of biofuels

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, A.

    2013-11-01

    The energy demand is increasing in the world together with the need to ensure energy security and the desire to decrease greenhouse gas emissions. While several renewable alternatives are available for the production of electricity, e.g. solar energy, wind power, and hydrogen, biomass is the only renewable source that can meet the demand for carbon-based liquid fuels and chemicals. The technology applied in the conversion of biomass depends on the type and complexity of the biomass, and the desired fuel. Hydrogen and hydrogen-rich mixtures (synthesis gas) are promising energy sources as they are more efficient and cleaner than existing fuels, especially when they are used in fuel cells. Hydrotreatment is a catalytic process that can be used in the conversion of biomass or biomass-derived liquids into fuels. In autothermal reforming (ATR), catalysts are used in the production of hydrogen-rich mixtures from conventional fuels or bio-fuels. The different nature of biomass and biomass-derived liquids and mineral oil makes the use of catalysts developed for the petroleum industry challenging. This requires the improvement of available catalysts and the development of new ones. To overcome the limitations of conventional hydrotreatment and ATR catalysts, zirconia-supported mono- and bimetallic rhodium, palladium, and platinum catalysts were developed and tested in the upgrading of model compounds for wood-based pyrolysis oil and in the production of hydrogen, using model compounds for gasoline and diesel. Catalysts were also tested in the ATR of ethanol. For comparative purposes commercial catalysts were tested and the results obtained with model compounds were compared with those obtained with real feedstocks (hydrotreatmet tests with wood-based pyrolysis oil and ATR tests with NExBTL renewable diesel). Noble metal catalysts were active and selective in the hydrotreatment of guaiacol used as the model compound for the lignin fraction of wood-based pyrolysis oil and wood

  18. Catalytic Metallodrugs: Substrate-Selective Metal Catalysts as Therapeutics.

    Science.gov (United States)

    Yu, Zhen; Cowan, James A

    2017-10-12

    Metal complexes that catalyze inactivation and degradation of biomolecular targets can be developed into novel therapeutics (catalytic metallodrugs) against a variety of diseases. Despite recent advances in the field, a lack of substrate selectivity is a major hindrance to the development of catalytic metallodrugs for application in clinical practice. Improved targeting can minimize nonselective activity and the potential for side effects. Herein, we focus on recent developments toward novel metal catalysts that exhibit substrate selectivity against a variety of therapeutically relevant biomolecules. Design strategies for developing selective catalytic metallodrugs are also highlighted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Merging Metallic Catalysts and Sonication: A Periodic Table Overview

    Directory of Open Access Journals (Sweden)

    Claudia E. Domini

    2017-04-01

    Full Text Available This account summarizes and discusses recent examples in which the combination of ultrasonic waves and metal-based reagents, including metal nanoparticles, has proven to be a useful choice in synthetic planning. Not only does sonication often enhance the activity of the metal catalyst/reagent, but it also greatly enhances the synthetic transformation that can be conducted under milder conditions relative to conventional protocols. For the sake of clarity, we have adopted a structure according to the periodic-table elements or families, distinguishing between bulk metal reagents and nanoparticles, as well as the supported variations, thus illustrating the characteristics of the method under consideration in target synthesis. The coverage focuses essentially on the last decade, although the discussion also strikes a comparative balance between the more recent advancements and past literature.

  20. Carbon nanotubes and other nanostructures as support material for nanoparticulate noble-metal catalysts in fuel cells

    DEFF Research Database (Denmark)

    Veltzé, Sune; Larsen, Mikkel Juul; Elina, Yli-Rantala

    or platinum-alloy catalysts in the electrodes are required. To maximize the utilization of the noble metal it is frequently deposited as nanoparticles (1–5 nm) on a stabilizing support of carbon black. Carbon black provides good anchoring of the catalyst particles, but is prone to severe destructive oxidation...... carbon black they can conduct electrons to and from the reaction sites, and in addition their resistance to electrochemical degradation is better than that of carbon black due to their much higher structural perfection. This latter feature is indeed highly desired with a view to the durability...... for difficulties in contacting the nanotubes with other substances in the electrode or electrode preparation. Other promising candidate structures for catalyst support include carbon nanofibers (CNF) and various modifications of CNTs. We present some of our work with the investigation of surface properties...

  1. Carbon Nanotubes and Other Nanostructures as Support Material for Nanoparticulate Noble-Metal Catalysts in Fuel Cells

    DEFF Research Database (Denmark)

    Larsen, Mikkel Juul; Veltzé, Sune; Skou, Eivind Morten

    or platinum-alloy catalysts in the electrodes are required. To maximize the utilization of the noble metal it is frequently deposited as nanoparticles (1-5 nm) on a stabilizing support of carbon black. Carbon black provides good anchoring of the catalyst particles, but is prone to severe destructive oxidation...... carbon black they can conduct electrons to and from the reaction sites, and in addition their resistance to electrochemical degradation is better than that of carbon black due to their much higher structural perfection. This latter feature is indeed highly desired with a view to the durability...... for difficulties in contacting the nanotubes with other substances in the electrode or electrode preparation. Other promising candidate structures for catalyst support include carbon nanofibers (CNF) and various modifications of CNTs. We present some of our work with the investigation of surface properties...

  2. Metal Fluorides, Metal Chlorides and Halogenated Metal Oxides as Lewis Acidic Heterogeneous Catalysts. Providing Some Context for Nanostructured Metal Fluorides.

    Science.gov (United States)

    Lennon, David; Winfield, John M

    2017-01-28

    Aspects of the chemistry of selected metal fluorides, which are pertinent to their real or potential use as Lewis acidic, heterogeneous catalysts, are reviewed. Particular attention is paid to β-aluminum trifluoride, aluminum chlorofluoride and aluminas γ and η, whose surfaces become partially fluorinated or chlorinated, through pre-treatment with halogenating reagents or during a catalytic reaction. In these cases, direct comparisons with nanostructured metal fluorides are possible. In the second part of the review, attention is directed to iron(III) and copper(II) metal chlorides, whose Lewis acidity and potential redox function have had important catalytic implications in large-scale chlorohydrocarbons chemistry. Recent work, which highlights the complexity of reactions that can occur in the presence of supported copper(II) chloride as an oxychlorination catalyst, is featured. Although direct comparisons with nanostructured fluorides are not currently possible, the work could be relevant to possible future catalytic developments in nanostructured materials.

  3. Monte Carlo simulation of nanowires of different metals and two-metal alloys.

    Science.gov (United States)

    Giménez, M C; Schmicker, Wolfgang

    2011-02-14

    Nanowires of different metals and two-metal alloys have been studied by means of canonical Monte Carlo simulations and the embedded atom method for the interatomic potentials. For nanowires of gold, a relatively stable three-atom-wide chain was observed. The presence of one-atom-wide linear atomic chains is not stable in any case. For two-metal alloy nanowires, the metal with a higher surface energy tends to locate in the inner region of the nanowire.

  4. Hierarchical Pd-Sn alloy nanosheet dendrites: an economical and highly active catalyst for ethanol electrooxidation.

    Science.gov (United States)

    Ding, Liang-Xin; Wang, An-Liang; Ou, Yan-Nan; Li, Qi; Guo, Rui; Zhao, Wen-Xia; Tong, Ye-Xiang; Li, Gao-Ren

    2013-01-01

    Hierarchical alloy nanosheet dendrites (ANSDs) are highly favorable for superior catalytic performance and efficient utilization of catalyst because of the special characteristics of alloys, nanosheets, and dendritic nanostructures. In this paper, we demonstrate for the first time a facile and efficient electrodeposition approach for the controllable synthesis of Pd-Sn ANSDs with high surface area. These synthesized Pd-Sn ANSDs exhibit high electrocatalytic activity and superior long-term cycle stability toward ethanol oxidation in alkaline media. The enhanced electrocataytic activity of Pd-Sn ANSDs may be attributed to Pd-Sn alloys, nanosheet dendrite induced promotional effect, large number of active sites on dendrite surface, large surface area, and good electrical contact with the base electrode. Because of the simple implement and high flexibility, the proposed approach can be considered as a general and powerful strategy to synthesize the alloy electrocatalysts with high surface areas and open dendritic nanostructures.

  5. The Role of the Interface in Refractory Metal Alloy Composites

    Science.gov (United States)

    Grobstein, Toni; Yun, Hee M.

    1991-01-01

    Creep-rupture and tensile tests have been used to evaluate thoriated W-wire reinforced Nb-1 percent Zr alloy matrix composites fabricated via arc-spray monotape technique. A significant creep strength enhancement was observed over the unreinforced matrix alloy while matrix integrity was maintained; the fiber/matrix interface phase is noted to be a strong and ductile W/Nb alloy, which is formed due to the mutual solubility of the constituent metals. High strength, toughness, and thermal stability are demonstrated by this material system, which is also resistant to liquid alkali metal corrosion.

  6. Palladium-alloy catalysts as ethanol tolerant cathodes for direct alcohol fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Savadogo, O. [Ecole Polytechnique de Montreal, Montreal, PQ (Canada). Laboratoire de nouveaux materiaux pour l' energie et l' electrochimie; Varela, F.J.R. [Centro de Investigacion y de Estudios Avanzados, Coahuila (Mexico). Unidad Saltillo

    2008-07-01

    Recent studies have demonstrated that electroactive palladium (Pd) and Pd-alloy catalysts prepared using a sputtering technique possess a similar degree of activity as platinum (Pt) electrodes. This study demonstrated that Pd and Pd-alloys show a high degree of tolerance to ethanol during oxygen reduction reaction (ORR) processes. The onset potential of the ORR process in the presence of 0.5M of ethanol decreased by only 33 mV and 18 mV on Pd and Pd-cobalt (Co) catalysts. Linear sweep voltammetry experiments showed that no peak current density caused by the electro-oxidation of ethanol was observed in the Pd-based catalysts. The selective behaviour of the Pd and Pd-Co catalysts was attributed to a slow rate of adsorption of the ethanol as well as the presence of reaction intermediates on the catalytic surface. Results suggested that the Pd and Pd-Co catalysts are suitable candidates for direct alcohol fuel cell applications. 10 refs., 2 figs.

  7. Noble metal-free hydrogen evolution catalysts for water splitting.

    Science.gov (United States)

    Zou, Xiaoxin; Zhang, Yu

    2015-08-07

    Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

  8. Determination of hydrogen in metals and alloys

    International Nuclear Information System (INIS)

    Sayi, Y.S.; Ramanjaneyulu, P.S.; Ramakumar, K.L.

    2008-01-01

    Hydrogen will be invariably present in all materials. Its presence in excess is harmful and sometimes calamitous. Hydrogen embrittlement can occur quite readily in most high strength materials, irrespective of their composition or structure. It is therefore essential to maintain low levels of hydrogen. To know the amount of hydrogen present in the materials, it is essential to determine it with high degree of precision and accuracy. It is required to give the uncertainty associated with the measurement to increase the confidence on measurements. Several methodologies are available for the determination of hydrogen. It its isotope, deuterium, also co-exists it becomes all the more difficult to determine these individually. Hot vacuum extraction cum quadrupole mass spectrometry (HVE-QMS) developed in our laboratory to determine hydrogen and deuterium is routinely employed for the determination of hydrogen and deuterium in metals and alloys. The present paper deals in detail about our experiences with HVE-QMS and estimation of uncertainty associated in this methodology. (author)

  9. Nanostructured nonprecious metal catalysts for oxygen reduction reaction.

    Science.gov (United States)

    Wu, Gang; Zelenay, Piotr

    2013-08-20

    Platinum-based catalysts represent a state of the art in the electrocatalysis of oxygen reduction reaction (ORR) from the point of view of their activity and durability in harnessing the chemical energy via direct electrochemical conversion. However, because platinum is both expensive and scarce, its widespread implementation in such clean energy applications is limited. Recent breakthroughs in the synthesis of high-performance nonprecious metal catalysts (NPMCs) make replacement of Pt in ORR electrocatalysts with earth-abundant elements, such as Fe, Co, N, and C, a realistic possibility. In this Account, we discuss how we can obtain highly promising M-N-C (M: Fe and/or Co) catalysts by simultaneously heat-treating precursors of nitrogen, carbon, and transition metals at 800-1000 °C. The activity and durability of resulting catalysts depend greatly on the selection of precursors and synthesis chemistry. In addition, they correlate quite well with the catalyst nanostructure. While chemists have presented no conclusive description of the active catalytic site for this class of NPMCs, they have developed a designed approach to making active and durable materials, focusing on the catalyst nanostructure. The approach consists of nitrogen doping, in situ carbon graphitization, and the usage of graphitic structures (possibly graphene and graphene oxides) as carbon precursors. Various forms of nitrogen, particularly pyridinic and quaternary, can act as n-type carbon dopants in the M-N-C catalysts, assisting in the formation of disordered carbon nanostructures and donating electrons to the carbon. The CNx structures are likely a crucial part of the ORR active site(s). Noteworthy, the ORR activity is not necessarily governed by the amount of nitrogen, but by how the nitrogen is incorporated into the nanostructures. Apart from the possibility of a direct participation in the active site, the transition metal often plays an important role in the in situ formation of various

  10. Thermophysical Property Measurements of Silicon-Transition Metal Alloys

    Science.gov (United States)

    Banish, R. Michael; Erwin, William R.; Sansoucie, Michael P.; Lee, Jonghyun; Gave, Matthew A.

    2014-01-01

    Metals and metallic alloys often have high melting temperatures and highly reactive liquids. Processing reactive liquids in containers can result in significant contamination and limited undercooling. This is particularly true for molten silicon and it alloys. Silicon is commonly termed "the universal solvent". The viscosity, surface tension, and density of several silicon-transition metal alloys were determined using the Electrostatic Levitator system at the Marshall Space Flight Center. The temperature dependence of the viscosity followed an Arrhenius dependence, and the surface tension followed a linear temperature dependence. The density of the melts, including the undercooled region, showed a linear behavior as well. Viscosity and surface tension values were obtain for several of the alloys in the undercooled region.

  11. Single-site catalyst promoters accelerate metal-catalyzed nitroarene hydrogenation

    KAUST Repository

    Wang, Liang

    2018-04-04

    Atomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. The catalysts are used for the challenging nitroarene hydrogenation and found to have both high activity and selectivity. The promoters are single-site Sn on TiO2 supports that incorporate metal nanoparticle catalysts. Represented as M/Sn-TiO2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various reducible groups. The high activity and selectivity of these catalysts result from the creation of oxygen vacancies on the TiO2 surface by single-site Sn, which leads to efficient, selective activation of the nitro group coupled with a reaction involving hydrogen atoms activated on metal nanoparticles.

  12. Non-precious metal catalysts prepared from precursor comprising cyanamide

    Science.gov (United States)

    Chung, Hoon Taek; Zelenay, Piotr

    2015-10-27

    Catalyst comprising graphitic carbon and methods of making thereof; said graphitic carbon comprising a metal species, a nitrogen-containing species and a sulfur containing species. A catalyst for oxygen reduction reaction for an alkaline fuel cell was prepared by heating a mixture of cyanamide, carbon black, and a salt selected from an iron sulfate salt and an iron acetate salt at a temperature of from about 700.degree. C. to about 1100.degree. C. under an inert atmosphere. Afterward, the mixture was treated with sulfuric acid at elevated temperature to remove acid soluble components, and the resultant mixture was heated again under an inert atmosphere at the same temperature as the first heat treatment step.

  13. Oxide-supported metal clusters: models for heterogeneous catalysts

    International Nuclear Information System (INIS)

    Santra, A K; Goodman, D W

    2003-01-01

    Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grown on a refractory metal substrate. Reactivity and spectroscopic/microscopic studies have shown that these ultra-thin oxide films are excellent models for the corresponding bulk oxides, yet are sufficiently electrically conductive for use with various modern surface probes including scanning tunnelling microscopy (STM). Measurements on metal clusters have revealed a metal to nonmetal transition as well as changes in the crystal and electronic structures (including lattice parameters, band width, band splitting and core-level binding energy shifts) as a function of cluster size. Size-dependent catalytic reactivity studies have been carried out for several important reactions, and time-dependent catalytic deactivation has been shown to arise from sintering of metal particles under elevated gas pressures and/or reactor temperatures. In situ STM methodologies have been developed to follow the growth and sintering kinetics on a cluster-by-cluster basis. Although several critical issues have been addressed by several groups worldwide, much more remains to be done. This article highlights some of these accomplishments and summarizes the challenges that lie ahead. (topical review)

  14. Effect of the combination of dithiooctanoate monomers and acidic adhesive monomers on adhesion to precious metals, precious metal alloys and non-precious metal alloys.

    Science.gov (United States)

    Ikemura, Kunio; Kojima, Katsunori; Endo, Takeshi; Kadoma, Yoshinori

    2011-01-01

    This study investigated the effect of the combination of a dithiooctanoate monomer and an acidic adhesive monomer on adhesion to precious metals, precious and non-precious metal alloys. From a selection of four dithiooctanoate monomers and six acidic adhesive monomers, 14 experimental primers containing a combination of 5.0 wt% of a dithiooctanoate monomer and 1.0 wt% of an acidic adhesive monomer in acetone were prepared. Tensile bond strengths (TBSs) of MMA-PMMA/TBBO resin to nine kinds of precious metals, precious metal alloys, and non-precious metal alloys after 2,000 thermal cycles were measured. Results showed that there were no significant differences in TBS among the primers to all the precious and non-precious metal adherends tested (p>0.05). Highest TBS values (46.5-55.8 MPa) for bonding to Au alloy, Au-Ag-Pd alloy, Co-Cr alloy, and Ni-Cr alloy were achieved with the primer which contained 5.0 wt% 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) and 1.0 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA). Therefore, 5.0 wt% 10-MDDT and 1.0 wt% 6-MHPA was determined as the optimal combination for bonding to precious metals, precious and non-precious metal alloys.

  15. Analytic functions for calculating binary alloys of FCC metals ...

    African Journals Online (AJOL)

    The problem studied in this paper is that of obtaining appropriate electron density function and a pair potential function for an FCC metal within the EAM format. The approach adopted is to use the experimental dilute limit heats of solution of the binary alloys of FCC metals as input parameters into Johnson analytical model, ...

  16. Local Chemical Reactivity of a Metal Alloy Surface

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Scheffler, Matthias

    1995-01-01

    The chemical reactivity of a metal alloy surface is studied by density functional theory investigating the interaction of H2 with NiAl(110). The energy barrier for H2 dissociation is largely different over the Al and Ni sites without, however, reflecting the barriers over the single component metal...

  17. Mechanisms of diffusional phase transformations in metals and alloys

    CERN Document Server

    Aaronson, Hubert I; Lee, Jong K

    2010-01-01

    Developed by the late metallurgy professor and master experimentalist Hubert I. Aaronson, this collection of lecture notes details the fundamental principles of phase transformations in metals and alloys upon which steel and other metals industries are based. Mechanisms of Diffusional Phase Transformations in Metals and Alloys is devoted to solid-solid phase transformations in which elementary atomic processes are diffusional jumps, and these processes occur in a series of so-called nucleation and growth through interface migration. Instead of relying strictly on a pedagogical approach, it doc

  18. Degradation of TATP, TNT, and RDX using mechanically alloyed metals

    Science.gov (United States)

    Clausen, Christian (Inventor); Geiger, Cherie (Inventor); Sigman, Michael (Inventor); Fidler, Rebecca (Inventor)

    2012-01-01

    Bimetallic alloys prepared in a ball milling process, such as iron nickel (FeNi), iron palladium (FePd), and magnesium palladium (MgPd) provide in situ catalyst system for remediating and degrading nitro explosive compounds. Specifically, munitions, such as, 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), nitrocellulose and nitroglycerine that have become contaminants in groundwater, soil, and other structures are treated on site to remediate explosive contamination.

  19. Effects of preparation method and active metal content on of Ni/kieselguhr catalyst activity

    International Nuclear Information System (INIS)

    Galuh Widiyarti; Wuryaningsih Sri Rahayu

    2010-01-01

    The preparation and the active metal content influence the activity of catalyst. Study has been conducted to see the activity of Ni/kieselguhr based on preparation method and Nickel (Ni) contents in the catalyst in the laboratory scale. The Ni/kieselguhr catalyst were prepared by impregnation and precipitation methods, with Ni active contents of 10, 20, and 30 % by weight. The catalysts characterization was analyzed using X-Ray Diffraction (XRD). Catalysts activities were analyzed based on decreasing of iodine number from hydrogenation of crude palm oil for 2 hours. The activity tests results show that precipitation catalysts are more active than impregnation catalysts. The decreasing in iodine number of fatty acid after 2 hours of hydrogenation process using precipitation catalysts and impregnation catalysts are 51.53 and 21.85 %, respectively. In addition, the catalysts are more active with increasing Ni contents. (author)

  20. Development and fabrication of high strength alloy fibers for use in metal-metal matrix composites

    Science.gov (United States)

    King, G. W.; Petrasek, D. W.

    1979-01-01

    Metal fiber reinforced superalloys are being considered for construction of critical components in turbine engines that operate at high temperature. The problems involved in fabricating refractory metal alloys into wire form in such a manner as to maximize their strength properties without developing excessive structural defects are described. The fundamental principles underlying the development of such alloy fibers are also briefly discussed. The progress made to date in developing tungsten, tantalum and columbium base alloys for fiber reinforcement is reported and future prospects for alloy fiber development considered.

  1. Nano-structured noble metal catalysts based on hexametallate architecture for the reforming of hydrocarbon fuels

    Science.gov (United States)

    Gardner, Todd H.

    2015-09-15

    Nano-structured noble metal catalysts based on hexametallate lattices, of a spinel block type, and which are resistant to carbon deposition and metal sulfide formation are provided. The catalysts are designed for the reforming of hydrocarbon fuels to synthesis gas. The hexametallate lattices are doped with noble metals (Au, Pt, Rh, Ru) which are atomically dispersed as isolated sites throughout the lattice and take the place of hexametallate metal ions such as Cr, Ga, In, and/or Nb. Mirror cations in the crystal lattice are selected from alkali metals, alkaline earth metals, and the lanthanide metals, so as to reduce the acidity of the catalyst crystal lattice and enhance the desorption of carbon deposit forming moieties such as aromatics. The catalysts can be used at temperatures as high as 1000.degree. C. and pressures up to 30 atmospheres. A method for producing these catalysts and applications of their use also is provided.

  2. Preparation and Characterization of Double Metal Cyanide Complex Catalysts

    Directory of Open Access Journals (Sweden)

    Weilin Guo

    2003-01-01

    Full Text Available A series of double metal cyanide (DMC complex catalysts were prepared in two different methods by using ß-cyclodextrin, PEG-1000 and Tween-60 as an additional complex ligands respectively. It was showed that a mixture of crystalline and amorphous DMC was synthesized by using traditional method in which the additional complex ligand was added after the precipitation of DMC. Amorphous and dispersed DMC with higher activity could be obtained when the additional complex ligand was added in the reactant solution before reaction. The effect of additional complex ligand and preparation method on the crystalline state and catalytic property of DMC were also investigated.

  3. Metallic bionanocatalysts: potential applications as green catalysts and energy materials.

    Science.gov (United States)

    Macaskie, Lynne E; Mikheenko, Iryna P; Omajai, Jacob B; Stephen, Alan J; Wood, Joseph

    2017-09-01

    Microbially generated or supported nanocatalysts have potential applications in green chemistry and environmental application. However, precious (and base) metals biorefined from wastes may be useful for making cheap, low-grade catalysts for clean energy production. The concept of bionanomaterials for energy applications is reviewed with respect to potential fuel cell applications, bio-catalytic upgrading of oils and manufacturing 'drop-in fuel' precursors. Cheap, effective biomaterials would facilitate progress towards dual development goals of sustainable consumption and production patterns and help to ensure access to affordable, reliable, sustainable and modern energy. © 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

  4. Ambiphilic Molecules: From Organometallic Curiosity to Metal-Free Catalysts.

    Science.gov (United States)

    Fontaine, Frédéric-Georges; Rochette, Étienne

    2018-02-20

    Ambiphilic molecules were first used as functional ligands for transition elements, which could enable intriguing organometallic transformations. In the past decade, these intramolecular Lewis pairs, first considered organometallic curiosities, have become staples in organometallic chemistry and catalysis, acting as Z ligands, activating inert molecules using the concept of frustrated Lewis pair (FLP) chemistry, and acting as metal-free catalysts. In this Account, we detail our contribution to this blossoming field of research, focusing on the use of ambiphilic molecules as metal-free catalysts for CO 2 reduction and C-H borylation reactions. A major emphasis is put on the mechanistic investigations we carried out using reactivity studies and theoretical tools, which helped us steer our research from stoichiometric transformations to highly active catalytic processes. We first report the interaction of aluminum-phosphine ambiphilic molecules with carbon dioxide. Although these Lewis pairs can bind CO 2 , a study of the deactivation process in the presence of CO 2 and hydroboranes led us to discover that simple phosphinoborane molecules could act as active precatalysts for the hydroboration of carbon dioxide into methanol precursors. In these systems, the Lewis basic sites interact with the reducing agents rather than with the electrophilic carbon of CO 2 , increasing the nucleophilicity of hydroboranes. Simultaneously, the weak Lewis acids stabilize the oxygen of the gas molecule in the transition state, leading to high reaction rates. Replacing the phosphine by an amine leads to a system enabling CO 2 hydrogenation, albeit only in stoichiometric transformations. Investigation of the protodeborylation deactivation of aminoboranes led us to develop metal-free catalysts for the C-H borylation of heteroarenes. By protecting the Lewis acid sites of these catalysts using fluoride, we were able to synthesize practical, air-stable precatalysts allowing the convenient

  5. Electronic-Structure-Based Design of Ordered Alloys

    DEFF Research Database (Denmark)

    Bligaard, Thomas; Andersson, M.P.; Jacobsen, Karsten Wedel

    2006-01-01

    We describe some recent advances in the methodology of using electronic structure calculations for materials design. The methods have been developed for the design of ordered metallic alloys and metal alloy catalysts, but the considerations we present are relevant for the atomic-scale computational...... discovery of a promising catalytic metal alloy surface with high reactivity and low cost....

  6. Bioaccessibility of metals in alloys: evaluation of three surrogate biofluids.

    Science.gov (United States)

    Hillwalker, Wendy E; Anderson, Kim A

    2014-02-01

    Bioaccessibility in vitro tests measure the solubility of materials in surrogate biofluids. However, the lack of uniform methods and the effects of variable test parameters on material solubility limit interpretation. One aim of this study was to measure and compare bioaccessibility of selected economically important alloys and metals in surrogate physiologically based biofluids representing oral, inhalation and dermal exposures. A second aim was to experimentally test different biofluid formulations and residence times in vitro. A third aim was evaluation of dissolution behavior of alloys with in vitro lung and dermal biofluid surrogates. This study evaluated the bioaccessibility of sixteen elements in six alloys and 3 elemental/metal powders. We found that the alloys/metals, the chemical properties of the surrogate fluid, and residence time all had major impacts on metal solubility. The large variability of bioaccessibility indicates the relevancy of assessing alloys as toxicologically distinct relative to individual metals. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

  7. The influence of the pure metal components of four different casting alloys on the electrochemical properties of the alloys.

    Science.gov (United States)

    Tuna, Süleyman H; Pekmez, Nuran Ozçiçek; Keyf, Filiz; Canli, Fulya

    2009-09-01

    The aim of this study was to investigate the influence of the pure metal components of the four different casting alloys on the corrosion behaviors of these alloys tested. Potentiodynamic polarization tests were carried out on four different types of casting alloys and their pure metals at 37 degrees C in an artificial saliva solution. The ions released from the alloys into the solutions during the polarization test were also determined quantitatively using inductively coupled plasma-mass spectrometry (ICP-MS). Ni-Cr (M1) and Co-Cr (M2) alloys had a more homogenous structure than palladium based (M3) and gold based (M4) alloys in terms of the pitting potentials of the casting alloys and those of the pure metals composing the alloys. The total ion concentration released from M3 and M4 was less than from M1 and M2. This may be because M3 and M4 alloys contained noble metals. It was also found that the noble metals in the M3 and M4 samples decreased the current density in the anodic branch of the potentiodynamic polarization curves. In other words, noble metals contributed positively to dental materials. Corrosion resistance of the casting alloys can be affected by the pure metals they are composed of. Au and Pd based noble alloys dissolved less than Ni-Cr and Co-Cr based alloys.

  8. Selective propene oxidation on mixed metal oxide catalysts

    International Nuclear Information System (INIS)

    James, David William

    2002-01-01

    Selective catalytic oxidation processes represent a large segment of the modern chemical industry and a major application of these is the selective partial oxidation of propene to produce acrolein. Mixed metal oxide catalysts are particularly effective in promoting this reaction, and the two primary candidates for the industrial process are based on iron antimonate and bismuth molybdate. Some debate exists in the literature regarding the operation of these materials and the roles of their catalytic components. In particular, iron antimonate catalysts containing excess antimony are known to be highly selective towards acrolein, and a variety of proposals for the enhanced selectivity of such materials have been given. The aim of this work was to provide a direct comparison between the behaviour of bismuth molybdate and iron antimonate catalysts, with additional emphasis being placed on the component single oxide phases of the latter. Studies were also extended to other antimonate-based catalysts, including cobalt antimonate and vanadium antimonate. Reactivity measurements were made using a continuous flow microreactor, which was used in conjunction with a variety of characterisation techniques to determine relationships between the catalytic behaviour and the properties of the materials. The ratio of Fe/Sb in the iron antimonate catalyst affects the reactivity of the system under steady state conditions, with additional iron beyond the stoichiometric value being detrimental to the acrolein selectivity, while extra antimony provides a means of enhancing the selectivity by decreasing acrolein combustion. Studies on the single antimony oxides of iron antimonate have shown a similarity between the reactivity of 'Sb 2 O 5 ' and FeSbO 4 , and a significant difference between these and the Sb 2 O 3 and Sb 2 O 4 phases, implying that the mixed oxide catalyst has a surface mainly comprised of Sb 5+ . The lack of reactivity of Sb 2 O 4 implies a similarity of the surface with

  9. Properties of cemented carbides alloyed by metal melt treatment

    International Nuclear Information System (INIS)

    Lisovsky, A.F.

    2001-01-01

    The paper presents the results of investigations into the influence of alloying elements introduced by metal melt treatment (MMT-process) on properties of WC-Co and WC-Ni cemented carbides. Transition metals of the IV - VIll groups (Ti, Zr, Ta, Cr, Re, Ni) and silicon were used as alloying elements. It is shown that the MMT-process allows cemented carbides to be produced whose physico-mechanical properties (bending strength, fracture toughness, total deformation, total work of deformation and fatigue fracture toughness) are superior to those of cemented carbides produced following a traditional powder metallurgy (PM) process. The main mechanism and peculiarities of the influence of alloying elements added by the MMT-process on properties of cemented carbides have been first established. The effect of alloying elements on structure and substructure of phases has been analyzed. (author)

  10. Features of exoelectron emission in amorphous metallic alloys

    CERN Document Server

    Veksler, A S; Morozov, I L; Semenov, A L

    2001-01-01

    The peculiarities of the photothermostimulated exoelectron emission in amorphous metallic alloys of the Fe sub 6 sub 4 Co sub 2 sub 1 B sub 1 sub 5 composition are studied. It is established that the temperature dependences of the exoelectron emission spectrum adequately reflect the two-stage character of the amorphous alloy transition into the crystalline state. The exoelectron emission spectrum is sensitive to the variations in the modes of the studied sample thermal treatment. The thermal treatment of the amorphous metallic alloy leads to growth in the intensity of the exoelectrons yield. The highest growth in the intensify of the exoelectron emission was observed in the alloys at the initial stage of their crystallization

  11. Metal-support bonds in supported metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gates, B.C.

    1990-01-01

    This research project, now in its third year, is an investigation of the synthesis, structure, and bonding of a family of metal complexes, clusters, and particles on the surfaces of high-area metal oxide supports. The focus is the structure of the metal-support interface. Surface species have been prepared by synthetic organometallic chemistry on the support surfaces. The organometallic precursors are complexes of W, Re, Os, Ir, and Pt, including W(CO){sub 6}, HRe(CO){sub 5}, Re{sub 2}(CO){sub 10}, H{sub 3}Re{sub 3}(CO){sub 12}, H{sub 2}Os(CO){sub 4}, Ir({eta}{sup 3}-C{sub 3}H{sub 5}){sub 3}, and Pt({eta}{sup 3}-C{sub 3}H{sub 5}){sub 2}. The supports are primarily MgO and {gamma}-Al{sub 2}O{sub 3}. The surface species have been characterized by infrared and EXAFS spectroscopies, among other techniques. 7 refs., 5 figs., 4 tabs.

  12. Cleavage crystallography of liquid metal embrittled aluminum alloys

    Science.gov (United States)

    Reynolds, A. P.; Stoner, G. E.

    1991-01-01

    The crystallography of liquid metal-induced transgranular cleavage in six aluminum alloys having a variety of microstructures has been determined via Laue X-ray back reflection. The cleavage crystallography was independent of alloy microstructure, and the cleavage plane was 100-plane oriented in all cases. It was further determined that the cleavage crystallography was not influenced by alloy texture. Examination of the fracture surface indicated that there was not a unique direction of crack propagation. In addition, the existence of 100-plane cleavage on alloy 2024 fracture surfaces was inferred by comparison of secondary cleavage crack intersection geometry on the 2024 surfaces with the geometry of secondary cleavage crack intersections on the test alloys.

  13. Method for hydrogen production and metal winning, and a catalyst/cocatalyst composition useful therefor

    Science.gov (United States)

    Dhooge, Patrick M.

    1987-10-13

    A catalyst/cocatalyst/organics composition of matter is useful in electrolytically producing hydrogen or electrowinning metals. Use of the catalyst/cocatalyst/organics composition causes the anode potential and the energy required for the reaction to decrease. An electrolyte, including the catalyst/cocatalyst composition, and a reaction medium composition further including organic material are also described.

  14. Metal-organic framework catalysts for selective cleavage of aryl-ether bonds

    Science.gov (United States)

    Allendorf, Mark D.; Stavila, Vitalie

    2017-08-01

    The present invention relates to methods of employing a metal-organic framework (MOF) as a catalyst for cleaving chemical bonds. In particular instances, the MOF results in selective bond cleavage that results in hydrogenolyzis. Furthermore, the MOF catalyst can be reused in multiple cycles. Such MOF-based catalysts can be useful, e.g., to convert biomass components.

  15. Platinum group metal recovery and catalyst manufacturing process

    International Nuclear Information System (INIS)

    Chung, H. S.; Kim, Y. S.; Yoo, J. H.; Lee, H. S.; Ahn, D. H.; Kim, K. R.; Lee, S. H.; Paek, S. W.; Kang, H. S.

    1998-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metal such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solution was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400 m 2 /g. The content of palladium impregnated on the support was 10 wt.%. Hydrogen isotope exchange efficiency of 93 % to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its actively is unimportant as in nuclear industries. (author). 63 refs., 38 tabs., 36 figs

  16. Platinum group metal recovery and catalyst manufacturing process

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. S.; Kim, Y. S.; Yoo, J. H.; Lee, H. S.; Ahn, D. H.; Kim, K. R.; Lee, S. H.; Paek, S. W.; Kang, H. S.

    1998-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metal such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solution was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400 m{sup 2}/g. The content of palladium impregnated on the support was 10 wt.%. Hydrogen isotope exchange efficiency of 93 % to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its actively is unimportant as in nuclear industries. (author). 63 refs., 38 tabs., 36 figs.

  17. Graded coatings for metallic implant alloys

    Energy Technology Data Exchange (ETDEWEB)

    Saiz, Eduardo; Tomsia, Antoni P.; Fujino, Shigeru; Gomez-Vega, Jose M.

    2002-08-01

    Graded glass and glass-hydroxyapatite coatings on Ti-based and Co-Cr alloys have been prepared using a simple enameling technique. The composition of the glasses has been tailored to match the thermal expansion of the alloys. By controlling the firing time, and temperature, it has been possible to control the reactivity between the glass and the alloy and to fabricate coatings (25 to 150 mu m thick) with excellent adhesion to the substrate, resistant to corrosion and able to precipitate hydroxyapatite during in vitro tests in simulated body fluid.

  18. Controlled metal nitrate decomposition for the preparation of supported metal Catalysts

    NARCIS (Netherlands)

    Wolters, M.

    2010-01-01

    High surface area supported metal (oxide) catalysts are essential for the production of fuels, chemicals, pharmaceuticals and the abatement of environmental pollution. Impregnation of high surface area supports, often silica or alumina, followed by drying, calcination and reduction is one of the

  19. A Facile Synthesis of Hollow Palladium/Copper Alloy Nanocubes Supported on N-Doped Graphene for Ethanol Electrooxidation Catalyst

    OpenAIRE

    Zhengyu Bai; Rumeng Huang; Lu Niu; Qing Zhang; Lin Yang; Jiujun Zhang

    2015-01-01

    In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG) is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG) and hollow PdCu alloy nanocubes supported on the reduced graphene oxide support (H-PdCu/RGO) are also prepared using the similar synthesis conditions for comparison. It is f...

  20. Graphene layer encapsulated metal nanoparticles as a new type of non-precious metal catalysts for oxygen reduction

    DEFF Research Database (Denmark)

    Hu, Yang; Zhong, Lijie; Jensen, Jens Oluf

    2016-01-01

    Cheap and efficient non-precious metal catalysts for oxygen reduction have been a focus of research in the field of low-temperature fuel cells. This review is devoted to a brief summary of the recent work on a new type of catalysts, i.e., the graphene layer encapsulated metal nanoparticles...

  1. Room temperature creep in metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Deibler, Lisa Anne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Materials Characterization and Performance

    2014-09-01

    Time dependent deformation in the form of creep and stress relaxation is not often considered a factor when designing structural alloy parts for use at room temperature. However, creep and stress relaxation do occur at room temperature (0.09-0.21 Tm for alloys in this report) in structural alloys. This report will summarize the available literature on room temperature creep, present creep data collected on various structural alloys, and finally compare the acquired data to equations used in the literature to model creep behavior. Based on evidence from the literature and fitting of various equations, the mechanism which causes room temperature creep is found to include dislocation generation as well as exhaustion.

  2. Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports

    Energy Technology Data Exchange (ETDEWEB)

    Stanger, Keith James [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    The tethered, chiral, chelating diphosphine rhodium complex, which catalyzes the enantioselective hydrogenation of methyl-α-acetamidocinnamate (MAC), has the illustrated structure as established by 31P NMR and IR studies. Spectral and catalytic investigations also suggest that the mechanism of action of the tethered complex is the same as that of the untethered complex in solution. The rhodium complexes, [Rh(COD)H]4, [Rh(COD)2]+BF4-, [Rh(COD)Cl]2, and RhCl3• 3H2O, adsorbed on SiO2 are optimally activated for toluene hydrogenation by pretreatment with H2 at 200 C. The same complexes on Pd-SiO2 are equally active without pretreatments. The active species in all cases is rhodium metal. The catalysts were characterized by XPS, TEM, DRIFTS, and mercury poisoning experiments. Rhodium on silica catalyzes the hydrogenation of fluorobenzene to produce predominantly fluorocyclohexane in heptane and 1,2-dichloroethane solvents. In heptane/methanol and heptane/water solvents, hydrodefluorination to benzene and subsequent hydrogenation to cyclohexane occurs exclusively. Benzene inhibits the hydrodefluorination of fluorobenzene. In DCE or heptane solvents, fluorocyclohexane reacts with hydrogen fluoride to form cyclohexene. Reaction conditions can be chosen to selectively yield fluorocyclohexane, cyclohexene, benzene, or cyclohexane. The oxorhenium(V) dithiolate catalyst [-S(CH2)3s-]Re(O)(Me)(PPh3) was modified by linking it to a tether that could be attached to a silica support. Spectroscopic investigation and catalytic oxidation reactivity showed the heterogenized catalyst's structure and reactivity to be similar to its homogeneous analog. However, the immobilized catalyst offered additional advantages of recyclability, extended stability, and increased resistance to deactivation.

  3. Multiple parameter cytotoxicity index on dental alloys and pure metals.

    Science.gov (United States)

    Hornez, J C; Lefèvre, A; Joly, D; Hildebrand, H F

    2002-08-01

    Palladium (Pd) is a metal frequently used for dental alloys. In order to elucidate controversial options about Pd concerning its biological performances, our study consists in the evaluation of commercial and experimental PFM and C&B precious and semi-precious dental alloys. This investigation was also designated to the establishment of a cytotoxicity index (CI) such as it was described for hemocompatibility testing. The following materials were tested: 36 commercial alloys (Au-, Pd- and Ag-base), 14 experimental alloys (Pd-base established by an experience plan) and pure metals (Ag, Au, Cu, Ni, Cr, In, Sn, Pt, Ti, Zn). The cells culture experiments were carried out with epithelial L132 cells and NIH 3T3 fibroblasts. In vitro cell viability tests show that Pt, Sn, In, Ti, Au and Pd have no cytotoxic effect; Cr, Cu and Ag are toxic, Ni, Zn, and Co are highly toxic. An identical ranking was found with the inflammatory and proliferation tests. Toxic and highly toxic metals induced slight or strong prosthetic dental restoration morphological alterations after 3-days cultures and mostly cell death after 6-days cultures. These effects are dependent on the leakage of the element into the culture medium as revealed by ICP. The addition of Au gives benefit to Pd-Ag alloys, but does not produce any major effect on Pd-Cu alloys. This qualitative ranking can quantitatively be confirmed by cytocompatibility testing after application of a CI.

  4. In situ XAFS studies of the oxygen reduction reaction on carbon supported platinum and platinum nickel nano-scale alloys as cathode catalysts in fuel cells

    Science.gov (United States)

    Jia, Qingying

    Platinum based bimetallic alloys have been investigated by conducting Pt L3 and Ni K edge in situ XAFS measurements on carbon supported Pt and PtNi(1:1) nanoscale catalysts under a wide range of operating potentials. We observed that (1) the Pt-Pt bond distance in PtNi alloys is shorter than that of Pt, and the bond distance between Pt and oxygen adsorbate is longer for PtNi. (2) Pt has a tendency to stay on the surface while Ni is mostly underneath the surface. (3) While a change in oxidation of pure Pt was clearly observed at different potentials, the Pt in the PtNi alloy remained nearly oxygen-free at all potentials, but an accompanying oxidation change of Ni was observed instead. (4) PtNi has higher open circuit voltage than Pt/C. These results indicate that the chemisorption energy between Pt and oxygen adsorbate is reduced in PtNi alloys, which prevents the poison of oxygen adsorbate and hence improves the reactivity. In addition, the strain and ligand effects in PtNi nanoparticle alloys were studied by FEW calculations using experimental data as a guide to understand the factors causing the reduction of chemisorptions energy of Pt. Our calculation indicates that Pt d-band is broader and lower in energy when the bond distance between Pt is shorter, resulting in weaker chemisorption energy between Pt and absorbed oxygen atom on top, and vice verse. Meanwhile, the investigation of ligand effect shows two trends in modifying Pt's properties within alloyed transition metals. The strain effect dominates in PtNi bimetallic system, corresponding to weaker chemisorptions energy and lower white intensity of Pt L3 edge, which is in consistent with our experimental results. The implications of these results afford a good guideline in understanding the reactivity enhancement mechanism and in the context of alloy catalysts design.

  5. Design of Embedded Metal Catalysts via Reverser Micro-Emulsion System: a Way to Suppress Catalyst Deactivation by Metal Sintering

    KAUST Repository

    AlMana, Noor

    2016-06-19

    The development of highly selective and active, long-lasting, robust, low-cost and environmentally benign catalytic materials is the greatest challenge in the area of catalysis study. In this context, core-shell structures where the active sites are embedded inside the protecting shell have attracted a lot of researchers working in the field of catalysis owing to their enhanced physical and chemical properties suppress catalyst deactivation. Also, a new active site generated at the interface between the core and shell may increases the activity and efficiency of the catalyst in catalytic reactions especially for oxide shells that exhibit redox properties such as TiO2 and CeO2. Moreover, coating oxide layer over metal nanoparticles (NPs) can be designed to provide porosity (micropore/mesopore) that gives selectivity of the various reactants by the different gas diffusion rates. In this thesis, we will discuss the concept of catalyst stabilization against metal sintering by a core-shell system. In particular we will study the mechanistic of forming core-shell particles and the key parameters that can influence the properties and morphology of the Pt metal particle core and SiO2 shell (Pt@SiO2) using the reverse micro-emulsion method. The Pt@SiO2 core-shell catalysts were investigated for low-temperature CO oxidation reaction. The study was further extended to other catalytic applications by varying the composition of the core as well as the chemical nature of the shell material. The Pt NPs were embedded within another oxide matrix such as ZrO2 and TiO2 for CO oxidation reaction. These materials were studied in details to identify the factors governing the coating of the oxide around the metal NPs. Next, a more challenging system, namely, bimetallic Ni9Pt NPs embedded in TiO2 and ZrO2 matrix were investigated for dry reforming of methane reaction at high temperatures. The challenges of designing Ni9Pt@oxide core-shell structure with TiO2 and ZrO2 and their tolerance

  6. In vitro cytotoxicity of metallic ions released from dental alloys.

    Science.gov (United States)

    Milheiro, Ana; Nozaki, Kosuke; Kleverlaan, Cornelis J; Muris, Joris; Miura, Hiroyuki; Feilzer, Albert J

    2016-05-01

    The cytotoxicity of a dental alloy depends on, but is not limited to, the extent of its corrosion behavior. Individual ions may have effects on cell viability that are different from metals interacting within the alloy structure. We aimed to investigate the cytotoxicity of individual metal ions in concentrations similar to those reported to be released from Pd-based dental alloys on mouse fibroblast cells. Metal salts were used to prepare seven solutions (concentration range 100 ppm-1 ppb) of the transition metals, such as Ni(II), Pd(II), Cu(II), and Ag(I), and the metals, such as Ga(III), In(III), and Sn(II). Cytotoxicity on mouse fibroblasts L929 was evaluated using the MTT assay. Ni, Cu, and Ag are cytotoxic at 10 ppm, Pd and Ga at 100 ppm. Sn and In were not able to induce cytotoxicity at the tested concentrations. Transition metals were able to induce cytotoxic effects in concentrations similar to those reported to be released from Pd-based dental alloys. Ni, Cu, and Ag were the most cytotoxic followed by Pd and Ga; Sn and In were not cytotoxic. Cytotoxic reactions might be considered in the etiopathogenesis of clinically observed local adverse reactions.

  7. Fundamentals of radiation materials science metals and alloys

    CERN Document Server

    Was, Gary S

    2017-01-01

    The revised second edition of this established text offers readers a significantly expanded introduction to the effects of radiation on metals and alloys. It describes the various processes that occur when energetic particles strike a solid, inducing changes to the physical and mechanical properties of the material. Specifically it covers particle interaction with the metals and alloys used in nuclear reactor cores and hence subject to intense radiation fields. It describes the basics of particle-atom interaction for a range of particle types, the amount and spatial extent of the resulting radiation damage, the physical effects of irradiation and the changes in mechanical behavior of irradiated metals and alloys. Updated throughout, some major enhancements for the new edition include improved treatment of low- and intermediate-energy elastic collisions and stopping power, expanded sections on molecular dynamics and kinetic Monte Carlo methodologies describing collision cascade evolution, new treatment of t...

  8. Method for low temperature preparation of a noble metal alloy

    Science.gov (United States)

    Even, Jr., William R.

    2002-01-01

    A method for producing fine, essentially contamination free, noble metal alloys is disclosed. The alloys comprise particles in a size range of 5 to 500 nm. The method comprises 1. A method for preparing a noble metal alloy at low temperature, the method comprising the steps of forming solution of organometallic compounds by dissolving the compounds into a quantity of a compatible solvent medium capable of solvating the organometallic, mixing a portion of each solution to provide a desired molarity ratio of ions in the mixed solution, adding a support material, rapidly quenching droplets of the mixed solution to initiate a solute-solvent phase separation as the solvent freezes, removing said liquid cryogen, collecting and freezing drying the frozen droplets to produce a dry powder, and finally reducing the powder to a metal by flowing dry hydrogen over the powder while warming the powder to a temperature of about 150.degree. C.

  9. Single-Atom Catalysts of Precious Metals for Electrochemical Reactions.

    Science.gov (United States)

    Kim, Jiwhan; Kim, Hee-Eun; Lee, Hyunjoo

    2018-01-10

    Single-atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO 2 reduction to methane or methanol production while suppressing H 2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N-doped covalent triazine frameworks, graphitic carbon nitride, S-doped zeolite-templated carbon, and Sb-doped SnO 2 surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Development of new metallic alloys for biomedical applications.

    Science.gov (United States)

    Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko

    2012-11-01

    New low modulus β-type titanium alloys for biomedical applications are still currently being developed. Strong and enduring β-type titanium alloy with a low Young's modulus are being investigated. A low modulus has been proved to be effective in inhibiting bone atrophy, leading to good bone remodeling in a bone fracture model in the rabbit tibia. Very recently β-type titanium alloys with a self-tunable modulus have been proposed for the construction of removable implants. Nickel-free low modulus β-type titanium alloys showing shape memory and super elastic behavior are also currently being developed. Nickel-free stainless steel and cobalt-chromium alloys for biomedical applications are receiving attention as well. Newly developed zirconium-based alloys for biomedical applications are proving very interesting. Magnesium-based or iron-based biodegradable biomaterials are under development. Further, tantalum, and niobium and its alloys are being investigated for biomedical applications. The development of new metallic alloys for biomedical applications is described in this paper. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  11. Hydrogen as a New Alloying Element in Metals

    International Nuclear Information System (INIS)

    Shapovalov, Vladimir

    1999-01-01

    Hydrogen was regarded as a harmful impurity in many alloys and particularly in steels where it gives rise to a specific type of embrittlement and forms various discontinuities like flakes and blowholes. For this reason, the researcher efforts were mainly focused on eliminating hydrogen's negative impacts and explaining its uncommonly high diffusivity in condensed phases. Meanwhile, positive characteristics of hydrogen as an alloying element remained unknown for quite a long time. Initial reports in this field did not appear before the early 1970s. Data on new phase diagrams are given for metal-hydrogen systems where the metal may or may not form hydrides. Various kinds of hydrogen impact on structure formation in solidification, melting and solid-solid transformations are covered. Special attention is given to the most popular alloys based on iron, aluminum, copper, nickel, magnesium and titanium. Detailed is what is called gas-eutectic reaction resulting in a special type of gas-solid structure named gasarite. Properties and applications of gasars - gasaritic porous materials - are dealt with. Various versions of solid-state alloying with hydrogen are discussed that change physical properties and fabrication characteristics of metals. Details are given on a unique phenomenon of anomalous spontaneous deformation due to combination of hydrogen environment and polymorphic transformation. All currently known versions of alloying with hydrogen are categorized for both hydride-forming and non-hydrid forming metals

  12. Ni-Based Catalysts for Low Temperature Methane Steam Reforming: Recent Results on Ni-Au and Comparison with Other Bi-Metallic Systems

    Directory of Open Access Journals (Sweden)

    Anna M. Venezia

    2013-06-01

    Full Text Available Steam reforming of light hydrocarbons provides a promising method for hydrogen production. Ni-based catalysts are so far the best and the most commonly used catalysts for steam reforming because of their acceptably high activity and significantly lower cost in comparison with alternative precious metal-based catalysts. However, nickel catalysts are susceptible to deactivation from the deposition of carbon, even when operating at steam-to-carbon ratios predicted to be thermodynamically outside of the carbon-forming regime. Reactivity and deactivation by carbon formation can be tuned by modifying Ni surfaces with a second metal, such as Au through alloy formation. In the present review, we summarize the very recent progress in the design, synthesis, and characterization of supported bimetallic Ni-based catalysts for steam reforming. The progress in the modification of Ni with noble metals (such as Au and Ag is discussed in terms of preparation, characterization and pretreatment methods. Moreover, the comparison with the effects of other metals (such as Sn, Cu, Co, Mo, Fe, Gd and B is addressed. The differences of catalytic activity, thermal stability and carbon species between bimetallic and monometallic Ni-based catalysts are also briefly shown.

  13. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    Science.gov (United States)

    Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

  14. In situ X-ray absorption spectroscopy of transition metal based water oxidation catalysts.

    Science.gov (United States)

    van Oversteeg, Christina H M; Doan, Hoang Q; de Groot, Frank M F; Cuk, Tanja

    2017-01-03

    X-ray absorption studies of the geometric and electronic structure of primarily heterogeneous Co, Ni, and Mn based water oxidation catalysts are reviewed. The X-ray absorption near edge and extended X-ray absorption fine structure studies of the metal K-edge, characterize the metal oxidation state, metal-oxygen bond distance, metal-metal distance, and degree of disorder of the catalysts. These properties guide the coordination environment of the transition metal oxide radical that localizes surface holes and is required to oxidize water. The catalysts are investigated both as-prepared, in their native state, and under reaction conditions, while transition metal oxide radicals are generated. The findings of many experiments are summarized in tables. The advantages of future X-ray experiments on water oxidation catalysts, which include the limited data available of the oxygen K-edge, metal L-edge, and resonant inelastic X-ray scattering, are discussed.

  15. Metallic ion release from biocompatible cobalt-based alloy

    Directory of Open Access Journals (Sweden)

    Dimić Ivana D.

    2014-01-01

    Full Text Available Metallic biomaterials, which are mainly used for the damaged hard tissue replacements, are materials with high strength, excellent toughness and good wear resistance. The disadvantages of metals as implant materials are their susceptibility to corrosion, the elastic modulus mismatch between metals and human hard tissues, relatively high density and metallic ion release which can cause serious health problems. The aim of this study was to examine metallic ion release from Co-Cr-Mo alloy in artificial saliva. In that purpose, alloy samples were immersed into artificial saliva with different pH values (4.0, 5.5 and 7.5. After a certain immersion period (1, 3 and 6 weeks the concentrations of released ions were determined using Inductively Coupled Plasma - Mass Spectrophotometer (ICP-MS. The research findings were used in order to define the dependence between the concentration of released metallic ions, artificial saliva pH values and immersion time. The determined released metallic ions concentrations were compared with literature data in order to describe and better understand the phenomenon of metallic ion release from the biocompatible cobalt-based alloy. [Projekat Ministarstva nauke Republike Srbije, br. III 46010 i br. ON 174004

  16. Convective effects on directional solidification of a simulated metal alloy

    Science.gov (United States)

    Mccay, T. D.; Mccay, M. H.; Lowry, S. A.; Smith, L. M.

    1988-01-01

    The first significant results of a ground-based experimental program which supports a low gravity space processing Spacelab experiment are reported. The phenomena which precipitate pluming and thus freckling in a metal alloy analog (ammonium chloride and water) are studied in detail and the sequential events leading to massive channeling and convection are optically documented. The pluming is shown to be other than a random burst of unstable fluid from a preferred channel but rather a natural occurrence resulting from a fundamental (Rayleigh-Benard) fluid dynamic instability at the density inversion interface. This extrapolates to critical size parameters appropriate to processing of actual metal alloys.

  17. Elementary characterization of Ti metal alloys used in implant dentistry

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Catarina A. M. P.; Paschuk, Sergei A.; Rocha, Anna S. S.; Corrêa, Janine Nicolosi [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Deniak, Valeriy [Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, PR (Brazil); Camargo, Liliane [Universidade Paranaense, Umuarama, PR (Brazil); Assis, J.T, E-mail: cata-montenegro@bol.com.br, E-mail: spaschuk@gmail.com, E-mail: denyak@gmail.com, E-mail: lili_camargo2@hotmail.com, E-mail: joaquim@iprj.uerj.br [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil)

    2017-07-01

    The main goal of present work is analytical characterization of standard dental implants broadly used by Brazilian dentists. An ideal biological alloy for dental implants must have very high biocompatibility, which means that such material should not provoke any serious adverse tissue response. Dental implants are generally marketed as commercially pure titanium (TiCP) due to their excellent mechanical and physical properties. However, sometimes other alloys are employed and consequently it is essential to study the chemical elements present in those alloys that could bring prejudice for the health. Present work investigated TiCP metal alloys used for dental implant manufacturing and evaluated the presence of elements. For alloy characterization and identification of elements it was used EDXRF technique. This method allows to perform the qualitative and quantitative analysis of the materials using the spectra of the characteristic X-rays emitted by the elements present in the metal samples. The experimental setup was based on two X- ray tubes, Mini X model with Ag and Au targets and X-123SDD detector (AMPTEK) and a 0.5 mm Cu collimator, developed due to specific sample geometrical and topography characteristics. Obtained results showed that implant alloys are not exactly TiCP but were manufactured using Ti-Al-V alloy, which contained Fe, Ni, Cu and Zn. The presence of such metals as Al and V in all studied samples shows very clear that studied implants were not manufactured from TiCP alloy. Moreover, according to the American Society for Testing and Materials (ASTM), these elements should not be present in TiCP. (author)

  18. Elementary characterization of Ti metal alloys used in implant dentistry

    International Nuclear Information System (INIS)

    Torres, Catarina A. M. P.; Paschuk, Sergei A.; Rocha, Anna S. S.; Corrêa, Janine Nicolosi; Deniak, Valeriy; Camargo, Liliane; Assis, J.T

    2017-01-01

    The main goal of present work is analytical characterization of standard dental implants broadly used by Brazilian dentists. An ideal biological alloy for dental implants must have very high biocompatibility, which means that such material should not provoke any serious adverse tissue response. Dental implants are generally marketed as commercially pure titanium (TiCP) due to their excellent mechanical and physical properties. However, sometimes other alloys are employed and consequently it is essential to study the chemical elements present in those alloys that could bring prejudice for the health. Present work investigated TiCP metal alloys used for dental implant manufacturing and evaluated the presence of elements. For alloy characterization and identification of elements it was used EDXRF technique. This method allows to perform the qualitative and quantitative analysis of the materials using the spectra of the characteristic X-rays emitted by the elements present in the metal samples. The experimental setup was based on two X- ray tubes, Mini X model with Ag and Au targets and X-123SDD detector (AMPTEK) and a 0.5 mm Cu collimator, developed due to specific sample geometrical and topography characteristics. Obtained results showed that implant alloys are not exactly TiCP but were manufactured using Ti-Al-V alloy, which contained Fe, Ni, Cu and Zn. The presence of such metals as Al and V in all studied samples shows very clear that studied implants were not manufactured from TiCP alloy. Moreover, according to the American Society for Testing and Materials (ASTM), these elements should not be present in TiCP. (author)

  19. Oxidation catalysts comprising metal exchanged hexaaluminate wherein the metal is Sr, Pd, La, and/or Mn

    Science.gov (United States)

    Wickham, David [Boulder, CO; Cook, Ronald [Lakewood, CO

    2008-10-28

    The present invention provides metal-exchanged hexaaluminate catalysts that exhibit good catalytic activity and/or stability at high temperatures for extended periods with retention of activity as combustion catalysts, and more generally as oxidation catalysts, that make them eminently suitable for use in methane combustion, particularly for use in natural gas fired gas turbines. The hexaaluminate catalysts of this invention are of particular interest for methane combustion processes for minimization of the generation of undesired levels (less than about 10 ppm) of NOx species. Metal exchanged hexaaluminate oxidation catalysts are also useful for oxidation of volatile organic compounds (VOC), particularly hydrocarbons. Metal exchanged hexaaluminate oxidation catalysts are further useful for partial oxidation, particularly at high temperatures, of reduced species, particularly hydrocarbons (alkanes and alkenes).

  20. Silver and palladium alloy nanoparticle catalysts: reductive coupling of nitrobenzene through light irradiation.

    Science.gov (United States)

    Peiris, Sunari; Sarina, Sarina; Han, Chenhui; Xiao, Qi; Zhu, Huai-Yong

    2017-08-15

    Silver-palladium (Ag-Pd) alloy nanoparticles strongly absorb visible light and exhibit significantly higher photocatalytic activity compared to both pure palladium (Pd) and silver (Ag) nanoparticles. Photocatalysts of Ag-Pd alloy nanoparticles on ZrO 2 and Al 2 O 3 supports are developed to catalyze the nitroaromatic coupling to the corresponding azo compounds under visible light irradiation. Ag-Pd alloy NP/ZrO 2 exhibited the highest photocatalytic activity for nitrobenzene coupling to azobenzene (yield of ∼80% in 3 hours). The photocatalytic efficiency could be optimized by altering the Ag : Pd ratio of the alloy nanoparticles, irradiation light intensity, temperature and wavelength. The rate of the reaction depends on the population and energy of the excited electrons, which can be improved by increasing the light intensity or by using a shorter wavelength. The knowledge developed in this study may inspire further studies on Ag alloy photocatalysts and organic syntheses using Ag-Pd nanoparticle catalysts driven under visible light Irradiation.

  1. Electromagnetic Characterization Of Metallic Sensory Alloy

    Science.gov (United States)

    Wincheski, Russell A.; Simpson, John; Wallace, Terryl A.; Newman, John A.; Leser, Paul; Lahue, Rob

    2012-01-01

    Ferromagnetic shape-memory alloy (FSMA) particles undergo changes in both electromagnetic properties and crystallographic structure when strained. When embedded in a structural material, these attributes can provide sensory output of the strain state of the structure. In this work, a detailed characterization of the electromagnetic properties of a FSMA under development for sensory applications is performed. In addition, a new eddy current probe is used to interrogate the electromagnetic properties of individual FSMA particles embedded in the sensory alloy during controlled fatigue tests on the multifunctional material.

  2. Ancient Metal Mirror Alloy Revisited: Quasicrystalline Nanoparticles Observed

    Science.gov (United States)

    Sekhar, J. A.; Mantri, A. S.; Yamjala, S.; Saha, Sabyasachi; Balamuralikrishnan, R.; Rao, P. Rama

    2015-12-01

    This article presents, for the first time, evidence of nanocrystalline structure, through direct transmission electron microscopy (TEM) observations, in a Cu-32 wt.% Sn alloy that has been made by an age-old, uniquely crafted casting process. This alloy has been used as a metal mirror for centuries. The TEM images also reveal five-sided projections of nano-particles. The convergent beam nano-diffraction patterns obtained from the nano-particles point to the nano-phase being quasicrystalline, a feature that has never before been reported for a copper alloy, although there have been reports of the presence of icosahedral `clusters' within large unit cell intermetallic phases. This observation has been substantiated by x-ray diffraction, wherein the observed peaks could be indexed to an icosahedral quasi-crystalline phase. The mirror alloy casting has been valued for its high hardness and high reflectance properties, both of which result from its unique internal microstructure that include nano-grains as well as quasi-crystallinity. We further postulate that this microstructure is a consequence of the raw materials used and the manufacturing process, including the choice of mold material. While the alloy consists primarily of copper and tin, impurity elements such as zinc, iron, sulfur, aluminum and nickel are also present, in individual amounts not exceeding one wt.%. It is believed that these trace impurities could have influenced the microstructure and, consequently, the properties of the metal mirror alloy.

  3. Processing of Refractory Metal Alloys for JOYO Irradiations

    International Nuclear Information System (INIS)

    RF Luther; ME Petrichek

    2006-01-01

    This is a summary of the refractory metal processing experienced by candidate Prometheus materiats as they were fabricated into specimens destined for testing within the JOYO test reactor, ex-reactor testing at Oak Ridge National Laboratory (ORNL), or testing within the NRPCT. The processing is described for each alloy from the point of inception to the point where processing was terminated due to the cancellation of Naval Reactor's involvement in the Prometheus Project. The alloys included three tantalum-base alloys (T-111, Ta-10W, and ASTAR-811C), a niobium-base alloy, (FS-85), and two molybdenum-rhenium alloys, one containing 44.5 w/o rhenium, and the other 47.5 w/o rhenium. Each of these alloys was either a primary candidate or back-up candidate for cladding and structural applications within the space reactor. Their production was intended to serve as a forerunner for large scale production ingots that were to be procured from commercial refractory metal vendors such as Wah Chang

  4. Processing of Refractory Metal Alloys for JOYO Irradiations

    Energy Technology Data Exchange (ETDEWEB)

    RF Luther; ME Petrichek

    2006-02-21

    This is a summary of the refractory metal processing experienced by candidate Prometheus materiats as they were fabricated into specimens destined for testing within the JOYO test reactor, ex-reactor testing at Oak Ridge National Laboratory (ORNL), or testing within the NRPCT. The processing is described for each alloy from the point of inception to the point where processing was terminated due to the cancellation of Naval Reactor's involvement in the Prometheus Project. The alloys included three tantalum-base alloys (T-111, Ta-10W, and ASTAR-811C), a niobium-base alloy, (FS-85), and two molybdenum-rhenium alloys, one containing 44.5 w/o rhenium, and the other 47.5 w/o rhenium. Each of these alloys was either a primary candidate or back-up candidate for cladding and structural applications within the space reactor. Their production was intended to serve as a forerunner for large scale production ingots that were to be procured from commercial refractory metal vendors such as Wah Chang.

  5. Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

    Science.gov (United States)

    Steeves, Arthur F.; Stewart, James C.

    1981-01-01

    A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

  6. 49 CFR 173.187 - Pyrophoric solids, metals or alloys, n.o.s.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Pyrophoric solids, metals or alloys, n.o.s. 173... Class 1 and Class 7 § 173.187 Pyrophoric solids, metals or alloys, n.o.s. Packagings for pyrophoric solids, metals, or alloys, n.o.s. must conform to the requirements of part 178 of this subchapter at the...

  7. Activation and discovery of earth-abundant metal catalysts using sodium tert-butoxide.

    Science.gov (United States)

    Docherty, Jamie H; Peng, Jingying; Dominey, Andrew P; Thomas, Stephen P

    2017-06-01

    First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air- and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general activation with sodium tert-butoxide. Using only robust air- and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydroboration, hydrovinylation, hydrogenation and [2π+2π] alkene cycloaddition. This activation method allows for the easy use of earth-abundant metals, including iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis.

  8. Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C-H activation

    Science.gov (United States)

    Marcinkowski, Matthew D.; Darby, Matthew T.; Liu, Jilei; Wimble, Joshua M.; Lucci, Felicia R.; Lee, Sungsik; Michaelides, Angelos; Flytzani-Stephanopoulos, Maria; Stamatakis, Michail; Sykes, E. Charles H.

    2018-03-01

    The recent availability of shale gas has led to a renewed interest in C-H bond activation as the first step towards the synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu-based catalysts are not practical due to high C-H activation barriers, but their weaker binding to adsorbates offers resilience to coking. Using Pt/Cu single-atom alloys (SAAs), we examine C-H activation in a number of systems including methyl groups, methane and butane using a combination of simulations, surface science and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke-resistant C-H activation chemistry, with the added economic benefit that the precious metal is diluted at the atomic limit.

  9. Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C–H activation

    Energy Technology Data Exchange (ETDEWEB)

    Marcinkowski, Matthew D.; Darby, Matthew T.; Liu, Jilei; Wimble, Joshua M.; Lucci, Felicia R.; Lee, Sungsik; Michaelides, Angelos; Flytzani-Stephanopoulos, Maria; Stamatakis, Michail; Sykes, E. Charles H.

    2018-01-08

    The recent availability of shale gas has led to a renewed interest in C-H bond activation as the first step towards synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu- based catalysts are not practical for this chemistry due to high C-H activation barriers, but their weaker binding to adsorbates offers resilience to coking. Utilizing Pt/Cu single atom alloys (SAAs) we examine C-H activation in a number of systems including methyl groups, methane, and butane using a combination of simulations, surface science, and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke resistant C-H activation chemistry with the added economic benefit that the precious metal is diluted at the atomic limit.

  10. A Novel 3D Printer to Support Additive Manufacturing of Gradient Metal Alloy Structures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Gradient metal alloy structures possess multi-functional properties that conventional monolithic metal counterparts do not have. Such structures can potentially...

  11. A Novel 3D Printer to Support Additive Manufacturing of Gradient Metal Alloy Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Gradient metal alloy structures possess multi-functional properties that conventional monolithic metal counterparts do not have. Such structures can potentially...

  12. Prospects for use of radiation for metal and alloy treatment

    International Nuclear Information System (INIS)

    Markovskij, E.A.; Krasnoshchekov, M.M.; Pereverzev, D.D.

    1978-01-01

    Analyzed were the prospects for electron and neutron irradiation application for metal and alloy heat treatment. Advantages of such treatment are as follows: possibility of local treatments; possibility of production of surface hardened layers with differentiated characteristics; decrease in heat treatment time; improvement of characteristics of diffusion and electrolytic coatings; possibility of metal treatment in gaseous or liquid medium; improvement of strength and antifrictional characteristics of metals etc. These advantages show application prospects for the treatment method with irradiation for the increase of durability of carburized and sulphidized surfaces of pieces, of various electrolytic coatings and non-hardening metal friction surfaces

  13. Ultrasound-driven design of new mesoporous metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Schaeferhans, Jana; Pazos Perez, Nicolas; Andreeva, Daria [Physikalische Chemie II, Univ. Bayreuth (Germany); Skorb, Ekaterina [Max-Planck-Institut fuer Kolloid- und Grenzflaechenforschung, Golm (Germany)

    2011-07-01

    Mesoporous metal nanocomposites were formed by a ''green chemistry'' method with ultrasound irradiation. The sonication technique combines the fabrication of a mesoporous support consisting of metallic particles (Al, Mg) several tens of micrometers in size and the subsequent incorporation of metal (Ag, Au, Pt etc.) nanoparticles into its pores. Next to filling the mesoporous support with particles we are also able to form mesoporous alloys e.g. AlNi or CoAlFe. The resulting material is analyzed by transmission electron microscopy, powder X-ray diffraction, small-angle neutron scattering and the Brunauer-Emmett-Teller and the Barrett-Joyner-Halenda method. Surface areas up to 200 m{sup 2}/g with a narrow pore size distribution around 3 nm can be achieved. The mesoporous structures are analyzed by confocal light microscopy after coloring the particles with dye. We explain the formation of the mesoporous inner structures by the following mechanism: Thermal etching and recrystallization of metals by ultrasound-stimulated high-speed jets of liquid form the porous structure that is stabilized by surface oxidation through free radicals generated during cavitation. We expect this approach to be universal and opening perspectives for a whole new class of catalytic materials that can be prepared in a fairly easy and cost effective way.

  14. High temperature strain of metals and alloys. Physical fundamentals

    Energy Technology Data Exchange (ETDEWEB)

    Levitin, V. [National Technical Univ., Zaporozhye (Ukraine)

    2006-07-01

    The author shows how new in-situ X-ray investigations and transmission electron microscope studies lead to novel explanations of high-temperature deformation and creep in pure metals, solid solutions and super alloys. This approach is the first to find unequivocal and quantitative expressions for the macroscopic deformation rate by means of three groups of parameters: substructural characteristics, physical material constants and external conditions. Creep strength of the studied uptodate single crystal super alloys is greatly increased over conventional polycrystalline super alloys. The contents of this book include: macroscopic characteristics of strain at high temperatures; experimental equipment and technique of in situ X-ray investigations; experimental data and structural parameters in deformed metals; sub-boundaries as dislocation sources and obstacles; the physical mechanism of creep and the quantitative structural model; simulation of the parameters evolution; system of differential equations; high-temperature deformation of industrial super alloys; single crystals of super alloys; effect of composition, orientation and temperature on properties; and creep of some refractory metals.

  15. Metastability and thermophysical properties of metallic bulk glass forming alloys

    International Nuclear Information System (INIS)

    Wunderlich, R.K.; Fecht, H.J.

    1998-01-01

    The absence of crystallization over a wide time/temperature window can be used to produce bulk metallic glass by relatively slow cooling of the melt. For a number of alloys, including several multicomponent Zr-based alloys, the relevant thermodynamic and thermomechanical properties of the metastable glassy and undercooled liquid states have been measured below and above the glass transition temperature. These measurements include specific heat, viscosity, volume, and elastic properties as a function of temperature. As a result, it becomes obvious that the maximum undercooling for these alloys is given by an isentropic condition before an enthalpic or isochoric instability is reached. Alternatively, these glasses can also be produced by mechanical alloying, thus replacing the thermal disorder by static disorder and resulting in the same thermodynamic glass state. During heating through the undercooled liquid, a nanoscale phase separation occurs for most glasses as a precursor of crystallization

  16. Molybdenum-A Key Component of Metal Alloys

    Science.gov (United States)

    Kropschot, S.J.

    2010-01-01

    Molybdenum, whose chemical symbol is Mo, was first recognized as an element in 1778. Until that time, the mineral molybdenite-the most important source of molybdenum-was believed to be a lead mineral because of its metallic gray color, greasy feel, and softness. In the late 19th century, French metallurgists discovered that molybdenum, when alloyed (mixed) with steel in small quantities, creates a substance that is remarkably tougher than steel alone and is highly resistant to heat. The alloy was found to be ideal for making tools and armor plate. Today, the most common use of molybdenum is as an alloying agent in stainless steel, alloy steels, and superalloys to enhance hardness, strength, and resistance to corrosion.

  17. High temperature seal for joining ceramics and metal alloys

    Science.gov (United States)

    Maiya, P. Subraya; Picciolo, John J.; Emerson, James E.; Dusek, Joseph T.; Balachandran, Uthamalingam

    1998-01-01

    For a combination of a membrane of SrFeCo.sub.0.5 O.sub.x and an Inconel alloy, a high-temperature seal is formed between the membrane and the alloy. The seal is interposed between the alloy and the membrane, and is a fritted compound of Sr oxide and boric oxide and a fritted compound of Sr, Fe and Co oxides. The fritted compound of SrFeCo.sub.0.50 O.sub.x is present in the range of from about 30 to 70 percent by weight of the total sealant material and the fritted compound of Sr oxide and boric oxide has a mole ratio of 2 moles of the Sr oxide for each mole of boric oxide. A method of sealing a ceramic to an Inconel metal alloy is also disclosed.

  18. Development of new transition metal oxide catalysts for the destruction of PCDD/Fs.

    Science.gov (United States)

    Yu, Ming-Feng; Li, Wen-Wei; Li, Xiao-Dong; Lin, Xiao-Qing; Chen, Tong; Yan, Jian-Hua

    2016-08-01

    Various transition metal oxide and vanadium-containing multi-metallic oxide catalysts were developed for the destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans). A stable PCDD/Fs generating system was installed to support the catalytic destruction tests in this study. Nano-titania supported vanadium catalyst (VOx/TiO2) showed the highest activity, followed by CeOx, MnOx, WOx and finally MoOx. Multi-metallic oxide catalysts, prepared by doping WOx, MoOx, MnOx and CeOx into VOx/TiO2 catalysts, showed different activities on the decomposition of PCDD/Fs. The highest destruction efficiency of 92.5% was observed from the destruction test over VOxCeOx/TiO2 catalyst. However, the addition of WOx and MoOx even played a negative role in multi-metallic VOx/TiO2 catalysts. Characterizations of transition metal oxides and multi-metallic VOx/TiO2 catalysts were also investigated with XRD and TPR. After the catalysts were used, the conversion from high valent metals to low valence states was observed by XPS. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Water oxidation using earth-abundant transition metal catalysts: opportunities and challenges.

    Science.gov (United States)

    Kärkäs, Markus D; Åkermark, Björn

    2016-10-07

    Catalysts for the oxidation of H2O are an integral component of solar energy to fuel conversion technologies. Although catalysts based on scarce and precious metals have been recognized as efficient catalysts for H2O oxidation, catalysts composed of inexpensive and earth-abundant element(s) are essential for realizing economically viable energy conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu. It reviews the state of the art catalysts, provides insight into their catalytic mechanisms and discusses future challenges in designing bioinspired catalysts based on earth-abundant metals for the oxidation of H2O.

  20. Amorphous Metallic Alloys: Pathways for Enhanced Wear and Corrosion Resistance

    Science.gov (United States)

    Aditya, Ayyagari; Felix Wu, H.; Arora, Harpreet; Mukherjee, Sundeep

    2017-11-01

    Amorphous metallic alloys are widely used in bulk form and as coatings for their desirable corrosion and wear behavior. Nevertheless, the effects of heat treatment and thermal cycling on these surface properties are not well understood. In this study, the corrosion and wear behavior of two Zr-based bulk metallic glasses were evaluated in as-cast and thermally relaxed states. Significant improvement in wear rate, friction coefficient, and corrosion penetration rate was seen for both alloys after thermal relaxation. A fully amorphous structure was retained with thermal relaxation below the glass transition. There was an increase in surface hardness and elastic modulus for both alloys after relaxation. The improvement in surface properties was explained based on annihilation of free volume.

  1. Diffusion and surface alloying of gradient nanostructured metals

    Directory of Open Access Journals (Sweden)

    Zhenbo Wang

    2017-03-01

    Full Text Available Gradient nanostructures (GNSs have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed.

  2. Hydrogen formation in metals and alloys during fusion reactor operation

    International Nuclear Information System (INIS)

    Zimin, S.; Takatsu, Hideyuki; Mori, Seiji

    1994-08-01

    The results of neutron transport calculations of the hydrogen formation based on the JENDL gas-production cross section file are discussed for some metals and alloys, namely 51 V, Cr, Fe, Ni, Mo, austenitic stainless steel (Ti modified 316SS:PCA), ferritic steel (Fe-8Cr-2W:F82H) and the vanadium-base alloy (V-5Cr-5Ti). Impact of the steel fraction in steel/water homogeneous blanket/shield compositions on the hydrogen formation rate in above-mentioned metals and alloys is discussed both for the hydrogen formation in the first wall and the blanket/shield components. The results obtained for the first wall are compared with those for the helium formation obtained at JAERI by the same calculational conditions. Hydrogen formation rates at the first wall having 51 V, Cr, Fe, Ni and Mo are larger than those of helium by 3-8 times. (author)

  3. Allotropic Carbon Nanoforms as Advanced Metal-Free Catalysts or as Supports

    Directory of Open Access Journals (Sweden)

    Hermenegildo Garcia

    2014-01-01

    Full Text Available This perspective paper summarizes the use of three nanostructured carbon allotropes as metal-free catalysts (“carbocatalysts” or as supports of metal nanoparticles. After an introductory section commenting the interest of developing metal-free catalysts and main features of carbon nanoforms, the main body of this paper is focused on exemplifying the opportunities that carbon nanotubes, graphene, and diamond nanoparticles offer to develop advanced catalysts having active sites based on carbon in the absence of transition metals or as large area supports with special morphology and unique properties. The final section provides my personal view on future developments in this field.

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

    Science.gov (United States)

    Herz, Richard K.

    1990-01-01

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

  5. Separation of matrix alloy and reinforcement from aluminum metal ...

    Indian Academy of Sciences (India)

    TECS

    Separation of matrix alloy and reinforcements from pure Al–SiCp composite scrap by salt flux addi- tion has been theoretically predicted .... zero and the salt fluxes have only little solubility in the matrix metal, separation of the matrix ... aluminum melt with SiC at this temperature did not exceed. 30 min. In order to change the ...

  6. Fatigue damage assessment of recycled metals and alloys | Ayensu ...

    African Journals Online (AJOL)

    Cyclic fatigue tests were conducted on recycled polycrystalline metals and alloys at room and elevated tempera-ures to determine the fatigue strength, endurance limit and endurance ratio. Annealed and polished stainless steel (Fe-18Cr-8Ni), mild steel (Fe-0.25Cr), aluminium (Al), alpha-brass (Cu-30 % Zn) and copper ...

  7. Special about transition metals in alloy phase formation

    Energy Technology Data Exchange (ETDEWEB)

    Watson, R E; Bennett, L H

    1979-01-01

    The d-electrons are special, though their bonding properties remain to be completely understood. It is recognized that d band broadening is the dominant term contributing to transition metal cohesion. It is also generally recognized that in compound formation between transition-metals and polyvalent metals, hybridization between d-bands and polyvalent atom p bands provides a significant contribution to the energy (for example there is such a term in Miedema's scheme). Less generally realized is that d-band hybridization leads to changes in d-electron counts at a transition metal site which are opposite in sign to the net charge transfer on or off the site. The renormalized atom picture of cohesion of the pure transition metals and consider the experimental evidence and the theoretical understanding of d charge transfer going the wrong way are reviewed. A picture of the electronegativity of transition metals based on this trend is developed. Charge transfer associated with equalizing the local chemical potentials in alloys is estimated. Friedel type model alloy calculations are reviewed. The implications of the experimental charge transfer information from Moessbauer isomer shifts to such model alloy calculations and to the strength of the Coulomb enery associated with charge transfer is considered.

  8. Water Splitting by Thin Film Metal-Oxo Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Nocera, Daniel [Harvard Univ., Cambridge, MA (United States)

    2013-03-15

    The dropping price of silicon photovoltaics in the United States is causing load defection to solar supply at an accelerated pace. This conversion to solar and, more generally, other renewable energy sources has accordingly turned the energy research focus from generation to one of storage. Truly disruptive improvements in energy storage technologies are limited by energy density. This limitation, however, does not apply to fuels, which possess the energy density needed for large-scale energy storage. The first step of the basic science needed to drive such historic restructuring of the U.S. energy infrastructure begins with the solar-driven generation of hydrogen and oxygen from water. The solar-produced hydrogen may then be combined with carbon dioxide to deliver any number of fuels. Obviously, light does not directly act on water to engender its splitting into its elemental components. Hence, catalysts are needed to drive the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Of these two reactions, the four-electron, four-proton oxidation of OER is the more kinetically challenging reaction, and therefore the development of energy efficient solar fuels processes demands that OER be accomplished at a minimal overpotential. The research completed in this program developed catalysts that drive OER and at the same time meet the important criteria of (1) using non-critical materials that (2) are easy to assemble and (3) accomplish OER under simple conditions. Research was designed to uncover the chemical principles that underlie the self-assembly of metal oxide oxygen evolving catalysts (M-OEC) from the metals of M = Mn, Co, and Ni. For example, a dogma of heterogeneous catalysis of any sort is that “edges” matter in promoting catalytic transformations. We provided a rationale for such dogma by showing that the OER in Co-OEC occurred at a dimensionally reduced dicobalt edge site. Edge site reactivity was clearly revealed analyzing 18O labeled

  9. Enhanced carbon tolerance on Ni-based reforming catalyst with Ir alloying: A DFT study

    Science.gov (United States)

    Ahn, Kiyong; Choi, Sungjun; Lee, Jong-Ho; Kim, Byung-Kook; Kim, Jedo; Kim, Hyoungchul

    2017-10-01

    Carbon deposition is a major cause of performance degradation for the Ni-based catalyst used in steam reforming of hydrocarbons. In this work, we perform first principle calculations to show that carbon tolerance behavior can be significantly enhanced by alloying Ni with Ir. The most stable atomic structure predicted by the surface phased diagram shows that Ir atoms prefer to stay on the surface of the alloy ensuring their exposure to the incoming gas. We find that the presence of Ir atoms suppress the surface migration of carbon atoms and weaken the stability of the adsorbed carbon agglomerates. Finally, we elucidate that the local reactivity change caused by the shift in the d-band structure is responsible for such good carbon tolerance behavior.

  10. Effect of catalyst properties and operating conditions on hydroprocessing high metals feeds

    Energy Technology Data Exchange (ETDEWEB)

    Pazos, J.M.; Gonzalez, J.C.; Saluzar-Gullen, A.J.

    1983-10-01

    Catalytic hydroprocessing of high metals heavy oils, containing over 480 ppm Ni + V, was carried out in trickle bed pilot units. The analyses of the used catalysts (coke, metals content, and vanadium distribution) were correlated with the deactivation runs. The deactivation by coke is very much dependent on the catalyst physical properties (mean pore diameter), rather than on the chemical properties, and on the nature of the feed. As metals removal is a diffusion-controlled reaction, catalysts and operating conditions that increase the Thiele modulus, e.g., high activity and small pore catalysts, high hydrogen pressures and temperatures, show a stronger deactivation by feed metals. In this case, most of the vanadium was deposited in the outer edge of the catalyst particle. Unconventional vanadium profiles along the reactor length were obtained under certain conditions. Based on these data, a kinetic model was proposed which considers that demetallization is a complex reaction that occurs through a series of consecutive and parallel reactions.

  11. Process for continuous production of metallic uranium and uranium alloys

    Science.gov (United States)

    Hayden, Jr., Howard W.; Horton, James A.; Elliott, Guy R. B.

    1995-01-01

    A method is described for forming metallic uranium, or a uranium alloy, from uranium oxide in a manner which substantially eliminates the formation of uranium-containing wastes. A source of uranium dioxide is first provided, for example, by reducing uranium trioxide (UO.sub.3), or any other substantially stable uranium oxide, to form the uranium dioxide (UO.sub.2). This uranium dioxide is then chlorinated to form uranium tetrachloride (UCl.sub.4), and the uranium tetrachloride is then reduced to metallic uranium by reacting the uranium chloride with a metal which will form the chloride of the metal. This last step may be carried out in the presence of another metal capable of forming one or more alloys with metallic uranium to thereby lower the melting point of the reduced uranium product. The metal chloride formed during the uranium tetrachloride reduction step may then be reduced in an electrolysis cell to recover and recycle the metal back to the uranium tetrachloride reduction operation and the chlorine gas back to the uranium dioxide chlorination operation.

  12. Process for continuous production of metallic uranium and uranium alloys

    Science.gov (United States)

    Hayden, H.W. Jr.; Horton, J.A.; Elliott, G.R.B.

    1995-06-06

    A method is described for forming metallic uranium, or a uranium alloy, from uranium oxide in a manner which substantially eliminates the formation of uranium-containing wastes. A source of uranium dioxide is first provided, for example, by reducing uranium trioxide (UO{sub 3}), or any other substantially stable uranium oxide, to form the uranium dioxide (UO{sub 2}). This uranium dioxide is then chlorinated to form uranium tetrachloride (UCl{sub 4}), and the uranium tetrachloride is then reduced to metallic uranium by reacting the uranium chloride with a metal which will form the chloride of the metal. This last step may be carried out in the presence of another metal capable of forming one or more alloys with metallic uranium to thereby lower the melting point of the reduced uranium product. The metal chloride formed during the uranium tetrachloride reduction step may then be reduced in an electrolysis cell to recover and recycle the metal back to the uranium tetrachloride reduction operation and the chlorine gas back to the uranium dioxide chlorination operation. 4 figs.

  13. COST 507: Thermophysical properties of light metal alloys. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Jaroma-Weiland, G.; Brandt, R.; Neuer, G.

    1994-02-15

    The thermophysical properties of Al-, Mg- and Ti-based light metal alloys have been studied by reviewing the literature published so far, evaluating the empirical results and by empirical investigations. The properties to the covered in the literature research are: thermal conductivity, thermal diffusivity, specific heat capacity, thermal expansion and electrical resistivity. The data have been stored in the factual data base THERSYST together with the results of experimental measurements supplied from participants of the COST 507-action (Group D). Altogether 1325 data-sets referring to 146 alloys have been stored. They have been uniformly represented and critically analyzed by means of the THERSYST program moduli. These numerical data cover a number of systems with variing chemical composition and thermal treatment. Partly large discrepancies especially of the thermal conductivity have been found for similar alloys. The problem of experimental uncertainities has been studied in detail by investigation of AA-8090 alloy (Al-2.5Li-1.1Cu). The thermophysical properties of monolithic alloy KS1275 (AlSi12CuNi) and metal matrix composite (KS1275 reinforced with Al2O3 short fibre) have been determined experimentally. (orig.)

  14. CuAu–ZnO–graphene nanocomposite: A novel graphene-based bimetallic alloy-semiconductor catalyst with its enhanced photocatalytic degradation performance

    International Nuclear Information System (INIS)

    Xie, Hong; Ye, Xiaoliang; Duan, Kaiyue; Xue, Muyin; Du, Yongling; Ye, Weichun; Wang, Chunming

    2015-01-01

    Graphical abstract: In this work, we have successfully synthesized a novel graphene-based bimetallic alloy-semiconductor catalyst: CuAu–ZnO–Gr nanocomposite, and which behaved an enhanced photocatalytic activity. - Highlights: • A bimetallic alloy-based catalyst: CuAu–ZnO–Gr is synthesized. • CuAu–ZnO–Gr behaves an enhanced photocatalytic activity. • The detailed explanation of photocatalytic mechanism of CuAu–ZnO–Gr. - Abstract: The bimetallic alloy CuAu nanoparticles (NPs) can produce more photogenerated electrons when compared with single metal Au NPs. Moreover, graphene (Gr) sheets can help the charge separation and slow down the recombination of the electron hole pairs of ZnO. Hence, a novel graphene-based bimetallic alloy-semiconductor catalyst: CuAu–ZnO–Gr nanocomposite is synthesized. Due to the synergistic effect among CuAu NPs, ZnO nanopyramids, and Gr sheets, CuAu–ZnO–Gr behaves an enhanced photocatalytic activity for the photocatalytic degradation of synthetic colorants methyl orange (MO), methylene blue (MB), indigotin (IN), sunset yellow (SY), and tartrazine (TT) under the simulated sunlight irradiation. Furthermore, the apparent rate constants (k app ) of MO, MB, IN, SY, and TT degradation are estimated respectively. In addition, the as-prepared CuAu–ZnO–Gr nanocomposite is characterized by X-ray diffraction, UV–vis spectrum, transmission electron microscopy, energy dispersive X-ray analysis (EDX), and EDX mapping. As a result of the facile synthesis route and the enhanced photocatalytic activity, this new material CuAu–ZnO–Gr can be a promising photocatalyst for the degradation of dyes

  15. CuAu–ZnO–graphene nanocomposite: A novel graphene-based bimetallic alloy-semiconductor catalyst with its enhanced photocatalytic degradation performance

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Hong [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Ye, Xiaoliang [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Duan, Kaiyue; Xue, Muyin; Du, Yongling; Ye, Weichun [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Wang, Chunming, E-mail: wangcm@lzu.edu.cn [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China)

    2015-07-05

    Graphical abstract: In this work, we have successfully synthesized a novel graphene-based bimetallic alloy-semiconductor catalyst: CuAu–ZnO–Gr nanocomposite, and which behaved an enhanced photocatalytic activity. - Highlights: • A bimetallic alloy-based catalyst: CuAu–ZnO–Gr is synthesized. • CuAu–ZnO–Gr behaves an enhanced photocatalytic activity. • The detailed explanation of photocatalytic mechanism of CuAu–ZnO–Gr. - Abstract: The bimetallic alloy CuAu nanoparticles (NPs) can produce more photogenerated electrons when compared with single metal Au NPs. Moreover, graphene (Gr) sheets can help the charge separation and slow down the recombination of the electron hole pairs of ZnO. Hence, a novel graphene-based bimetallic alloy-semiconductor catalyst: CuAu–ZnO–Gr nanocomposite is synthesized. Due to the synergistic effect among CuAu NPs, ZnO nanopyramids, and Gr sheets, CuAu–ZnO–Gr behaves an enhanced photocatalytic activity for the photocatalytic degradation of synthetic colorants methyl orange (MO), methylene blue (MB), indigotin (IN), sunset yellow (SY), and tartrazine (TT) under the simulated sunlight irradiation. Furthermore, the apparent rate constants (k{sub app}) of MO, MB, IN, SY, and TT degradation are estimated respectively. In addition, the as-prepared CuAu–ZnO–Gr nanocomposite is characterized by X-ray diffraction, UV–vis spectrum, transmission electron microscopy, energy dispersive X-ray analysis (EDX), and EDX mapping. As a result of the facile synthesis route and the enhanced photocatalytic activity, this new material CuAu–ZnO–Gr can be a promising photocatalyst for the degradation of dyes.

  16. Computational dynamics of laser alloyed metallic materials for improved corrosion performance: computational dynamics of laser alloyed metallic materials

    CSIR Research Space (South Africa)

    Fatoba, OS

    2016-04-01

    Full Text Available Laser alloying is a material processing method which utilizes the high power density available from defocused laser beam to melt both metal coatings and a part of the underlying substrate. Since melting occur solitary at the surface, large...

  17. Atomic-level Electron Microscopy of Metal and Alloy Electrocatalysts

    DEFF Research Database (Denmark)

    Deiana, Davide

    This thesis presents the application of transmission electron microscopy techniques towards the characterisation of novel metal nanoparticle catalysts. Two main subjects have been covered: first, the sintering-resistance behaviour of monomodal mass-selected Pt cluster catalysts have been studied...... flat surfaces and exposed to different sintering conditions. Ex situ STEM imaging has been used to monitor the variation of the particle dimensions through the analysis of particle area distributions. Clusters with a monomodal size distribution exhibited intrinsic sintering resistance on different...... peroxide H2O2. The active surface is predicted to be formed by reactive Pt or Pd atoms surrounded by more inert Hg atoms. Electrochemical measurements on the two catalysts have shown performance exceeding the current state-of-the-art in both forms of extended surface and nanoparticles. Electron microscopy...

  18. Bulk metallic glasses and high entropy alloys for reprocessing applications

    International Nuclear Information System (INIS)

    Kamachi Mudali, U.; Jayaraj, J.

    2016-01-01

    Recent breakthroughs in materials engineering have generated complex alloys that retain a glassy state in bulk form (bulk metallic glasses or BMGs) via ingot casting. High corrosion resistance is expected for BMGs (amorphous) as they are free from defects associated with the crystalline state such as grain boundaries, dislocations and stacking faults. Compared with conventional alloys containing one or two principal elements, the recently developed HEAs are usually composed of five or more elements with equimolar or near equimolar elemental fractions, which forms single solid solution phase. These HEAs exhibit excellent microstructural stability with better mechanical, wear and corrosion resistance properties as they are essentially single phase. Reprocessing of spent fuel from the fast breeder reactor involves the use of high concentration of (11.5 M) nitric acid under boiling conditions for the dissolution of the fuel. Conventional AISI type 304LSS and nitric acid grade 304L stainless steel would undergo inter-granular corrosion under these conditions and cannot be used for the fabrication of dissolver vessel. Currently titanium is used and zirconium alloys are proposed for future dissolver applications. Thus searching for newer materials with higher corrosion resistance suggests metallic glasses and HEAs for critical components of the dissolver application. Several Zr-based glassy alloys with different microstructural states and Ni-Nb based glassy alloys and TiZrHfNbTa HEA were cast and characterized for microstructure and corrosion resistance in nitric acid medium. From these studies, factors such as the corrosive environment (nitric acid, chloride and fluoride), and the presence of passivating elements in the alloy were emphasized for better corrosion resistance of BMGs and HEA. Attempts were also made to prepare coatings of Zr-and Ni-based glassy alloys on 304LSS by laser based deposition technique and their corrosion properties were evaluated. (author)

  19. New applications and novel processing of refractory metal alloys

    International Nuclear Information System (INIS)

    Briant, C.L.

    2001-01-01

    Refractory metals have often been limited in their application because of their propensity to oxidize and to undergo a loos of yield strength at elevated temperatures. However, recent developments in both processing and alloy composition have opened the possibility that these materials might be used in structural applications that were not considered possible in the past. At the same time, the use of refractory metals in the electronics industry is growing, particularly with the use of tantalum as a diffusion barrier for copper metallization. Finally, the application of grain boundary engineering to the problem of intergranular fracture in these materials may allow processes to be developed that will produce alloys with a greater resistance to fracture. (author)

  20. Development of Ultra-Low Platinum Alloy Cathode Catalysts for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Branko N. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering; Weidner, John [Univ. of South Carolina, Columbia, SC (United States)

    2016-01-07

    The goal of this project is to synthesize a low cost PEM fuel cell cathode catalyst and support with optimized average mass activity, stability of mass activity, initial high current density performance under H2/air (power density), and catalyst and support stability able to meet 2017 DOE targets for electrocatalysts for transportation applications. Pt*/ACCS-2 catalyst was synthesized according to a novel methodology developed at USC through: (i) surface modification, (ii) metal catalyzed pyrolysis and (iii) chemical leaching to remove excess meal used to dope the support. Pt* stands for suppressed platinum catalyst synthesized with Co doped platinum. The procedure results in increasing carbon graphitization, inclusion of cobalt in the bulk and formation of non-metallic active sites on the carbon surface. Catalytic activity of the support shows an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass transfer regions and 2.5% H2O2 production. Pt*/ACCS-2 catalyst durability under 0.6-1.0 V potential cycling and support stability under 1.0-1.5 V potential cycling was evaluated. The results indicated excellent catalyst and support performance under simulated start-up/shut down operating conditions (1.0 – 1.5 V, 5000 cycles) which satisfy DOE 2017 catalyst and support durability and activity. The 30% Pt*/ACCS-2 catalyst showed high initial mass activity of 0.34 A/mgPGM at 0.9 ViR-free and loss of mass activity of 45% after 30,000 cycles (0.6-1.0 V). The catalyst performance under H2-air fuel cell operating conditions showed only 24 mV (iR-free) loss at 0.8 A/cm2 with an ECSA loss of 42% after 30,000 cycles (0.6-1.0 V). The support stability under 1.0-1.5 V potential cycling showed mass activity loss of 50% and potential loss of 8 mV (iR-free) at 1.5 A/cm2. The ECSA loss was 22% after 5,000 cycles. Furthermore, the Pt*/ACCS-2 catalyst showed an

  1. The Integration of a Structural Water Gas Shift Catalyst with a Vanadium Alloy Hydrogen Transport Device

    Energy Technology Data Exchange (ETDEWEB)

    Barton, Thomas; Argyle, Morris; Popa, Tiberiu

    2009-06-30

    This project is in response to a requirement for a system that combines water gas shift technology with separation technology for coal derived synthesis gas. The justification of such a system would be improved efficiency for the overall hydrogen production. By removing hydrogen from the synthesis gas stream, the water gas shift equilibrium would force more carbon monoxide to carbon dioxide and maximize the total hydrogen produced. Additional benefit would derive from the reduction in capital cost of plant by the removal of one step in the process by integrating water gas shift with the membrane separation device. The answer turns out to be that the integration of hydrogen separation and water gas shift catalysis is possible and desirable. There are no significant roadblocks to that combination of technologies. The problem becomes one of design and selection of materials to optimize, or at least maximize performance of the two integrated steps. A goal of the project was to investigate the effects of alloying elements on the performance of vanadium membranes with respect to hydrogen flux and fabricability. Vanadium was chosen as a compromise between performance and cost. It is clear that the vanadium alloys for this application can be produced, but the approach is not simple and the results inconsistent. For any future contracts, large single batches of alloy would be obtained and rolled with larger facilities to produce the most consistent thin foils possible. Brazing was identified as a very likely choice for sealing the membranes to structural components. As alloying was beneficial to hydrogen transport, it became important to identify where those alloying elements might be detrimental to brazing. Cataloging positive and negative alloying effects was a significant portion of the initial project work on vanadium alloying. A water gas shift catalyst with ceramic like structural characteristics was the second large goal of the project. Alumina was added as a

  2. Fabrication and characterization of nanostructured mechanically alloyed Pt-Co catalyst for oxygen gas-diffusion-electrode

    International Nuclear Information System (INIS)

    Pharkya, P.; Farhat, Z.; Czech, E.; Hawthorne, H.; Alfantazi, A.

    2003-01-01

    The use of PEM fuel cells depends largely upon the cost of materials, processing and fabrication. The cost of Pt catalyst is a significant cost of a fuel cell. Alternative low cost catalyst that promotes high rate of oxygen reduction is needed. To achieve this, a mechanochemical technique was employed to refine the catalyst layer structure (i.e. increasing the effective catalyst surface area) and reducing the amount of Pt used, by alloying with a cheaper element. An investigation is carried out to study the relationship between the new catalyst structure refinement, morphology, microstructure and its electrocatalytic behaviour. Nanostructured Pt, Co and Pt 0.2 5 Co 0.75 alloy was fabricated from high purity Pt (99.9%) and Co (99.5%) powders using a Laboratory Planetary Ball Mill 'Pulverisette 6'. Optimum milling conditions, that produce fine, uniform and mechanically alloyed microstructure, were determined during fabrication, by varying process parameters (i.e., rpm, milling time, ball to powder ratio, milling atmosphere, surface-agents and milling/cooling cycle). Mechanically induced chemical and physical reactions and thermal effects were monitored 'in-situ' using a GTM system, which recorded temperature and pressure changes during milling. The alloy catalysts were characterized using TEM, SEM, EDX, XRD and BET techniques. Electrochemical tests were carried out on prepared powders. Exchange currents were determined from a potentiodynamic polarization tests and used to compare relative electrocatalytic behaviour of the new catalyst. Structure/property relationships were discussed and conclusions were drawn on the production of improved low cost catalyst. (author)

  3. Alloy with metallic glass and quasi-crystalline properties

    Science.gov (United States)

    Xing, Li-Qian; Hufnagel, Todd C.; Ramesh, Kaliat T.

    2004-02-17

    An alloy is described that is capable of forming a metallic glass at moderate cooling rates and exhibits large plastic flow at ambient temperature. Preferably, the alloy has a composition of (Zr, Hf).sub.a Ta.sub.b Ti.sub.c Cu.sub.d Ni.sub.e Al.sub.f, where the composition ranges (in atomic percent) are 45.ltoreq.a.ltoreq.70, 3.ltoreq.b.ltoreq.7.5, 0.ltoreq.c.ltoreq.4, 3.ltoreq.b+c.ltoreq.10, 10.ltoreq.d.ltoreq.30, 0.ltoreq.e.ltoreq.20, 10.ltoreq.d+e.ltoreq.35, and 5.ltoreq.f.ltoreq.15. The alloy may be cast into a bulk solid with disordered atomic-scale structure, i.e., a metallic glass, by a variety of techniques including copper mold die casting and planar flow casting. The as-cast amorphous solid has good ductility while retaining all of the characteristic features of known metallic glasses, including a distinct glass transition, a supercooled liquid region, and an absence of long-range atomic order. The alloy may be used to form a composite structure including quasi-crystals embedded in an amorphous matrix. Such a composite quasi-crystalline structure has much higher mechanical strength than a crystalline structure.

  4. Chemical-disorder effects in half-metallic Heusler alloys

    Science.gov (United States)

    Skomski, Ralph; Jin, Yunlong; Waybright, Jace; Kharel, Parashu; Pathak, Rohit; Choudhary, Renu; Kashyap, Arti; Sellmyer, D. J.

    The electronic structure, magnetism, and conductivity of disordered Heusler alloys are investigated theoretically and experimentally. Emphasis is on Heuslers that are predicted to be half-metallic or spin-gapless semiconducting in their fully ordered states, such as CoFeCrAl. Experimental alloys often exhibit resistivities of the order of 200 μΩ cm, which is consistent with both dirty-metal and spin-gapless semiconducting behaviors, but a distinction can be made by comparing the residual resistivities of samples having different degrees of order. The corresponding analysis shows that careful processing is necessary to keep the alloys in the spin-gapless semiconducting regime. Several types of disorder occur in Y-type Heusler alloys, with different negative effects on half-metallicity and spin-gapless semiconductivity. A2 (or bcc) disorder is most harmful but can be limited experimentally in CoFeCrAl thin films. B2 (or CsCl) disorder is less harmful, whereas L21 (normal Heusler) disorder, corresponding to Fe-Co solid solubility is least harmful. The residual resistivity of the partially diorderd alluys is discussed as a carrier-localization effect. This work is supported by DOE BES (DE-FG02-04ER46152, R.S.) and NSF DMREF (SusChEM 1436385, D.J.S.).

  5. Metallic glass alloys of Zr, Ti, Cu and Ni

    Science.gov (United States)

    Lin, Xianghong; Peker, Atakan; Johnson, William L.

    1997-01-01

    At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula (ETM.sub.1-x Ti.sub.x).sub.a Cu.sub.b (Ni.sub.1-y Co.sub.y).sub.c wherein x is from 0.1 to 0.3, y.cndot.c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content, b.

  6. Metal hydrides as electrode/catalyst materials for oxygen evolution/reduction in electrochemical devices

    Science.gov (United States)

    Bugga, Ratnakumar V. (Inventor); Halpert, Gerald (Inventor); Fultz, Brent (Inventor); Witham, Charles K. (Inventor); Bowman, Robert C. (Inventor); Hightower, Adrian (Inventor)

    1997-01-01

    An at least ternary metal alloy of the formula, AB.sub.(5-Y)X(.sub.y), is claimed. In this formula, A is selected from the rare earth elements, B is selected from the elements of groups 8, 9, and 10 of the periodic table of the elements, and X includes at least one of the following: antimony, arsenic, and bismuth. Ternary or higher-order substitutions, to the base AB.sub.5 alloys, that form strong kinetic interactions with the predominant metals in the base metal hydride are used to form metal alloys with high structural integrity after multiple cycles of hydrogen sorption.

  7. Biocompatibility evaluation of nickel-titanium shape memory metal alloy

    OpenAIRE

    Ryhänen, J. (Jorma)

    1999-01-01

    Abstract The shape memory effect, superelasticity, and good damping properties, uncommon in other implant alloys, make the nickel-titanium shape memory metal alloy (Nitinol or NiTi) a fascinating material for surgical applications. It provides a possibility to make self-locking, self-expanding and self-compressing implants. The purpose of this work was to determine if NiTi is a safe material for surgical implant applications. The primary cytotoxicity and the corrosion rate of NiTi were...

  8. Life Cycle Assessment of Biochar versus Metal Catalysts Used in Syngas Cleaning

    Directory of Open Access Journals (Sweden)

    Robert S. Frazier

    2015-01-01

    Full Text Available Biomass gasification has the potential to produce renewable fuels, chemicals and power at large utility scale facilities. In these plants catalysts would likely be used to reform and clean the generated biomass syngas. Traditional catalysts are made from transition metals, while catalysts made from biochar are being studied. A life cycle assessment (LCA study was performed to analyze the sustainability, via impact assessments, of producing a metal catalyst versus a dedicated biochar catalyst. The LCA results indicate that biochar has a 93% reduction in greenhouse gas (GHG emissions and requires 95.7% less energy than the metal catalyst to produce. The study also estimated that biochar production would also have fewer impacts on human health (e.g., carcinogens and respiratory impacts than the production of a metal catalyst. The possible disadvantage of biochar production in the ecosystem quality is due mostly to its impacts on agricultural land occupation. Sensitivity analysis was carried out to assess environmental impacts of variability in the two production systems. In the metal catalyst manufacture, the extraction and production of nickel (Ni had significant negative effects on the environmental impacts. For biochar production, low moisture content (MC, 9% and high yield type (8 tons/acre switchgrass appeared more sustainable.

  9. A Facile Synthesis of Hollow Palladium/Copper Alloy Nanocubes Supported on N-Doped Graphene for Ethanol Electrooxidation Catalyst

    Directory of Open Access Journals (Sweden)

    Zhengyu Bai

    2015-04-01

    Full Text Available In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG and hollow PdCu alloy nanocubes supported on the reduced graphene oxide support (H-PdCu/RGO are also prepared using the similar synthesis conditions for comparison. It is found that, among these three catalyst materials, H-PdCu/ppy-NG gives the highest electrochemical active area and both the most uniformity and dispersibility of H-PdCu particles. Electrochemical tests show that the H-PdCu/ppy-NG catalyst can give the best electrocatalytic activity and stability towards the ethanol electrooxidation when compared to other two catalysts. Therefore, H-PdCu/ppy-NG should be a promising catalyst candidate for anodic ethanol oxidation in direct ethanol fuel cells.

  10. Biphasic catalysis using amphiphilic polyphenols-chelated noble metals as highly active and selective catalysts

    Science.gov (United States)

    Mao, Hui; Yu, Hong; Chen, Jing; Liao, Xuepin

    2013-01-01

    In the field of catalysis, it is highly desired to develop novel catalysts that combine the advantages of both homogeneous and heterogeneous catalysts. Here we disclose that the use of plant pholyphenol as amphiphilic large molecule ligand/stabilizer allows for the preparation of noble metal complex and noble metal nanoparticle catalysts. These catalysts are found to be highly selective and active in aqueous-organic biphasic catalysis of cinnamaldehyde and quinoline, and can be reused at least 3 times without significant loss of activity. Moreover, the catalytic activity and reusability of the catalysts can be rationally controlled by simply adjusting the content of polyphenols in the catalysts. Our strategy may be extended to design a wide range of aqueous-organic biphasic catalysis system. PMID:23863916

  11. Non-Noble Metal Oxide Catalysts for Methane Catalytic Combustion: Sonochemical Synthesis and Characterisation.

    Science.gov (United States)

    Jodłowski, Przemysław J; Jędrzejczyk, Roman J; Chlebda, Damian K; Dziedzicka, Anna; Kuterasiński, Łukasz; Gancarczyk, Anna; Sitarz, Maciej

    2017-07-07

    The aim of this study was to obtain nanocrystalline mixed metal-oxide-ZrO₂ catalysts via a sonochemically-induced preparation method. The effect of a stabiliser's addition on the catalyst parameters was investigated by several characterisation methods including X-ray Diffraction (XRD), nitrogen adsorption, X-ray fluorescence (XRF), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and µRaman. The sonochemical preparation method allowed us to manufacture the catalysts with uniformly dispersed metal-oxide nanoparticles at the support surface. The catalytic activity was tested in a methane combustion reaction. The activity of the catalysts prepared by the sonochemical method was higher than that of the reference catalysts prepared by the incipient wetness method without ultrasonic irradiation. The cobalt and chromium mixed zirconia catalysts revealed their high activities, which are comparable with those presented in the literature.

  12. Biphasic catalysis using amphiphilic polyphenols-chelated noble metals as highly active and selective catalysts.

    Science.gov (United States)

    Mao, Hui; Yu, Hong; Chen, Jing; Liao, Xuepin

    2013-01-01

    In the field of catalysis, it is highly desired to develop novel catalysts that combine the advantages of both homogeneous and heterogeneous catalysts. Here we disclose that the use of plant polyphenol as amphiphilic large molecule ligand/stabilizer allows for the preparation of noble metal complex and noble metal nanoparticle catalysts. These catalysts are found to be highly selective and active in aqueous-organic biphasic catalysis of cinnamaldehyde and quinoline, and can be reused at least 3 times without significant loss of activity. Moreover, the catalytic activity and reusability of the catalysts can be rationally controlled by simply adjusting the content of polyphenols in the catalysts. Our strategy may be extended to design a wide range of aqueous-organic biphasic catalysis system.

  13. Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X.; Urban, Ania; Thacker, Nathan C.; Lin, Wenbin (UC)

    2016-08-30

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal–organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C–H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

  14. Transforming nonselective into chemoselective metal catalysts for the hydrogenation of substituted nitroaromatics.

    Science.gov (United States)

    Corma, Avelino; Serna, Pedro; Concepción, Patricia; Calvino, José Juan

    2008-07-09

    It is generally accepted that good hydrogenation noble and nonnoble metal catalysts such as Pt, Ru, or Ni are not chemoselective for hydrogenation of nitro groups in substituted aromatic molecules. We have found that it is possible to transform nonchemoselective into highly chemoselective metal catalysts by controlling the coordination of metal surface atoms while introducing a cooperative effect between the metal and a properly selected support. Thus, highly chemoselective and general hydrogenation Pt, Ru, and Ni catalysts can be prepared by generating nanosized crystals of the metals on the surface of a TiO 2 support and decorating the exposed (111) and (100) crystal faces by means of a simple catalyst activation procedure. By doing this, it has been possible to change the relative rate for hydrogenating competitive groups present in the molecule by almost 2 orders of magnitude, increasing the chemoselectivity from less than 1% to more than 95%.

  15. Effect of alloying on elastic properties of ZrN based transition metal nitride alloys

    KAUST Repository

    Kanoun, Mohammed

    2014-09-01

    We report the effect of composition and metal sublattice substitutional element on the structural, elastic and electronic properties of ternary transition metal nitrides Zr1-xMxN with M=Al, Ti, Hf, V, Nb, W and Mo. The analysis of the elastic constants, bulk modulus, shear modulus, Young\\'s modulus, and Poisson\\'s ratio provides insights regarding the mechanical behavior of Zr1-xMxN. We predict that ternary alloys are more ductile compared to their parent binary compounds. The revealed trend in the mechanical behavior might help for experimentalists on the ability of tuning the mechanical properties during the alloying process by varying the concentration of the transition metal. © 2014 Elsevier B.V.

  16. Development of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane

    KAUST Repository

    Al-ShaikhAli, Anaam H.

    2016-11-30

    Liquid organic chemical hydride is a promising candidate for hydrogen storage and transport. Methylcyclohexane (MCH) to toluene (TOL) cycle has been considered as one of the feasible hydrogen carrier systems, but selective dehydrogenation of MCH to TOL has only been achieved using the noble Pt-based catalysts. The aim of this study is to develop non-noble, cost-effective metal catalysts that can show excellent catalytic performance, mainly maintaining high TOL selectivity achievable by Pt based catalysts. Mono-metallic Ni based catalyst is a well-known dehydrogenation catalyst, but the major drawback with Ni is its hydrogenolysis activity to cleave C-C bonds, which leads to inferior selectivity towards dehydrogenation of MCH to TOL. This study elucidate addition of the second metal to Ni based catalyst to improve the TOL selectivity. Herein, ubiquitous bi-metallic nanoparticles catalysts were investigated including (Ni–M, M: Ag, Zn, Sn or In) based catalysts. Among the catalysts investigated, the high TOL selectivity (> 99%) at low conversions was achieved effectively using the supported NiZn catalyst under flow of excess H2. In this work, a combined study of experimental and computational approaches was conducted to determine the main role of Zn over Ni based catalyst in promoting the TOL selectivity. A kinetic study using mono- and bimetallic Ni based catalysts was conducted to elucidate reaction mechanism and site requirement for MCH dehydrogenation reaction. The impact of different reaction conditions (feed compositions, temperature, space velocity and stability) and catalyst properties were evaluated. This study elucidates a distinctive mechanism of MCH dehydrogenation to TOL reaction over the Ni-based catalysts. Distinctive from Pt catalyst, a nearly positive half order with respect to H2 pressure was obtained for mono- and bi-metallic Ni based catalysts. This kinetic data was consistent with rate determining step as (somewhat paradoxically) hydrogenation

  17. [Should metal alloy discs be used for patch testing in suspected metal implant intolerance reaction?].

    Science.gov (United States)

    Thomas, P; Geier, J; Dickel, H; Diepgen, T; Hillen, U; Kreft, B; Schnuch, A; Szliska, C; Mahler, V

    2015-11-01

    Intolerance reactions to metal implants may be caused by metal allergy. However, prior to implantation, patch testing should not be done in a prophylactic-prophetic approach. Pre-implant patch testing should only be performed to verify or exclude metal allergy in patients with a reported respective history. In the case of implant-in particular arthroplasty-related complications like, for example, pain, effusion, skin changes, reduced range of motion, or loosening, orthopedic-surgical differential diagnostics should be performed first. Allergological workup of suspected metal implant allergy should be done with the DKG baseline series which contains nickel-, cobalt- and chromium-preparations. Various studies assessing the usefulness of metal alloy discs for patch testing proved that this approach does not give reliable information about metal allergy. Positive patch test reactions to the discs cannot be assigned to a specific metal within the disc alloy components. Furthermore, availability of such metal discs might be an invitation to uncritical testing. Accordingly, due to lack of benefit in comparison to patch testing with standardized metal salt preparations, we do not recommend patch testing with metal alloy discs.

  18. Analysis of noble metal on automotive exhaust catalysts by radioisotope-induce x-ray fluorescence

    International Nuclear Information System (INIS)

    Elgart, M.F.

    1976-01-01

    A technique was developed for the in-situ analysis of noble metals deposited on monolithic automotive exhaust catalysts. This technique is based on radioisotope-induced x-ray fluorescence, and provides a detailed picture of the distribution of palladium and platinum on catalyst samples. The experimental results for the cross section of a monolithic exhaust catalyst, analyzed in increments of 0.2 cm 3 , are compared with analyses for palladium and platinum obtained by instrumental neutron activation analysis

  19. Stability of noble metal catalysts for the hydrogen-oxygen reaction.

    Science.gov (United States)

    Armstrong, W. E.; Jennings, T. J.; Voge, H. H.

    1972-01-01

    Stability of various supported noble metal catalysts for initiation of the hydrogen-oxygen reaction was tested by means of steam-hydrogen treatment at 1000-1200 C followed by a simple activity test. Many catalysts were stable to 1100 C, but all lost some activity at 1200 C. The most active with very good stability was an iridium/alumina catalyst of high iridium content.

  20. Aqueous reductive amination using a dendritic metal catalyst in a dialysis bag

    OpenAIRE

    Willemsen, J.S.; Hest, J.C.M. van; Rutjes, F.P.J.T.

    2013-01-01

    Summary Water-soluble dendritic iridium catalysts were synthesized by attaching a reactive metal complex to DAB-Am dendrimers via an adapted asymmetric bipyridine ligand. These dendritic catalysts were applied in the aqueous reductive amination of valine while contained in a dialysis bag. Comparable conversions were observed as for the noncompartmentalized counterparts, albeit with somewhat longer reaction times. These results clearly show that the encapsulated catalyst system is suitable to ...

  1. Recent Progress on Transition Metal Catalyst Separation and Recycling in ATRP.

    Science.gov (United States)

    Ding, Mingqiang; Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

    2015-10-01

    Atom transfer radical polymerization (ATRP) is a versatile and robust tool to synthesize a wide spectrum of monomers with various designable structures. However, it usually needs large amounts of transition metal as the catalyst to mediate the equilibrium between the dormant and propagating species. Unfortunately, the catalyst residue may contaminate or color the resultant polymers, which limits its application, especially in biomedical and electronic materials. How to efficiently and economically remove or reduce the catalyst residue from its products is a challenging and encouraging task. Herein, recent advances in catalyst separation and recycling are highlighted with a focus on (1) highly active ppm level transition metal or metal free catalyzed ATRP; (2) post-purification method; (3) various soluble, insoluble, immobilized/soluble, and reversible supported catalyst systems; and (4) liquid-liquid biphasic catalyzed systems, especially thermo-regulated catalysis systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. PASSIVATION LAYER STABILITY OF A METALLIC ALLOY WASTE FORM

    International Nuclear Information System (INIS)

    Williamson, M.; Mickalonis, J.; Fisher, D.; Sindelar, R.

    2010-01-01

    Alloy waste form development under the Waste Forms Campaign of the DOE-NE Fuel Cycle Research and Development program includes the process development and characterization of an alloy system to incorporate metal species from the waste streams generated during nuclear fuel recycling. This report describes the tests and results from the FY10 activities to further investigate an Fe-based waste form that uses 300-series stainless steel as the base alloy in an induction furnace melt process to incorporate the waste species from a closed nuclear fuel recycle separations scheme. This report is focused on the initial activities to investigate the formation of oxyhydroxide layer(s) that would be expected to develop on the Fe-based waste form as it corrodes under aqueous repository conditions. Corrosion tests were used to evaluate the stability of the layer(s) that can act as a passivation layer against further corrosion and would affect waste form durability in a disposal environment.

  3. Pt-Ni/WC Alloy Nanorods Arrays as ORR Catalyst for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Begum, Mahbuba; Yurukcu, Mesut; Yurtsever, Fatma; Ergul, Busra; Kariuki, Nancy; Myers, Deborah J.; Karabacak, Tansel

    2017-08-24

    Polymer electrolyte membrane fuel cells (PEMFCs) among the other types of fuel cell technology are attractive power sources, especially for electric vehicle applications. While significant progress and plausible prospects of PEMFCs have been achieved, there are still some challenges related to the performance, durability, and cost that need to be overcome to make them economically viable for widespread commercialization. Our strategy is to develop thin films of high-active and stable catalyst coated on vertically aligned nanorod arrays of conductive and stable support. In this work, we fabricated tungsten carbide (WC) nanorods as support and coated them with a platinum-nickel (Pt-Ni) alloy shell denoted as Pt-Ni/WC catalysts. The Pt- Ni/WC nanorods were deposited on glassy carbon disks as well as on silicon substrates for evaluation of their electrocatalytic oxygen reduction reaction (ORR) activity and physical properties. Cyclic voltammetry experiments using rotating disk electrode were performed in perchloric acid (0.1 M HClO4) electrolyte at room temperature to characterize the ORR activity and stability of Pt-Ni/WC nanorods catalysts. Scanning electron microscopy and X-ray diffraction techniques were utilized to study the morphology and crystallographic properties, respectively.

  4. Combinations of Aminocatalysts and Metal Catalysts: A Powerful Cooperative Approach in Selective Organic Synthesis.

    Science.gov (United States)

    Afewerki, Samson; Córdova, Armando

    2016-11-23

    The cooperation and interplay between organic and metal catalyst systems is of utmost importance in nature and chemical synthesis. Here innovative and selective cooperative catalyst systems can be designed by combining two catalysts that complement rather than inhibit one another. This refined strategy can permit chemical transformations unmanageable by either of the catalysts alone. This review summarizes innovations and developments in selective organic synthesis that have used cooperative dual catalysis by combining simple aminocatalysts with metal catalysts. Considerable efforts have been devoted to this fruitful field. This emerging area employs the different activation modes of amine and metal catalysts as a platform to address challenging reactions. Here, aminocatalysis (e.g., enamine activation catalysis, iminium activation catalysis, single occupied molecular orbital (SOMO) activation catalysis, and photoredox activation catalysis) is employed to activate unreactive carbonyl substrates. The transition metal catalyst complements by activating a variety of substrates through a range of interactions (e.g., electrophilic π-allyl complex formation, Lewis acid activation, allenylidene complex formation, photoredox activation, C-H activation, etc.), and thereby novel concepts within catalysis are created. The inclusion of heterogeneous catalysis strategies allows for "green" chemistry development, catalyst recyclability, and the more eco-friendly synthesis of valuable compounds.

  5. Mechanical Alloying of Metal-Organic Frameworks.

    Science.gov (United States)

    Panda, Tamas; Horike, Satoshi; Hagi, Keisuke; Ogiwara, Naoki; Kadota, Kentaro; Itakura, Tomoya; Tsujimoto, Masahiko; Kitagawa, Susumu

    2017-02-20

    The solvent-free mechanical milling process for two distinct metal-organic framework (MOF) crystals induced the formation of a solid solution, which is not feasible by conventional solution-based syntheses. X-ray and STEM-EDX studies revealed that performing mechanical milling under an Ar atmosphere promotes the high diffusivity of each metal ion in an amorphous solid matrix; the amorphous state turns into the porous crystalline structure by vapor exposure treatment to form a new phase of a MOF solid solution. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. 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.

  7. Determining eutectic composition in metal alloys

    Science.gov (United States)

    Ashbrook, R. L.; Kim, Y. G.

    1977-01-01

    Tube crucible and furnace are used to separate eutectic mixture from trial-melt ingot. As ingot is a slowly heated to melting point, initial surface meeting will be eutectic mixture. Molten metal is collected at bottom of crucible, where it is solidified.

  8. Intracluster atomic and electronic structural heterogeneities in supported nanoscale metal catalysts

    NARCIS (Netherlands)

    Elsen, A.; Jung, U.; Vila, F.; Li, Y.; Safonova, O.V.; Thomas, R.; Tromp, M.; Rehr, J.J.; Nuzzo, R.G.; Frenkel, A.I.

    2015-01-01

    This work reveals and quantifies the inherent intracluster heterogeneity in the atomic structure and charge distribution present in supported metal catalysts. The results demonstrate that these distributions are pronounced and strongly coupled to both structural and dynamic perturbations. They also

  9. On the unit rupture work of metals and alloys

    International Nuclear Information System (INIS)

    Verkhoturov, A.D.; Kovalenko, V.S.; Dyatel, V.P.

    1980-01-01

    Studied is the effect of the nature of the treated material treatment regimes on their unit rupture work at laser treatment in the regime of quasistationary evaporation. It is shown that the unit rupture work changes its values depending on the treatment regimes, coincidences between experimental and calculation values of unit rupture work are not being observed, especially for refractory metals of the 6th group and for solid alloys. Established are optimum regimes for determination of stable values of unit rupture work

  10. Gas porosity in metals and alloys irradiated by helium ions

    International Nuclear Information System (INIS)

    Kalin, B.A.; Korshunov, S.N.; Chernov, I.I.

    1987-01-01

    Experimental studies of the development of gas porosity in metals and alloys during irradiation with helium ions up to high doses and during post-irradiation annealings, are reviewed. The main theoretical problems of the mechanisms of bubble formation and growth, the regularities and peculiarities of bubble development in a thin near-the surface layer during the introduction of helium with the energy of tens of kiloelectron volt, are considered

  11. Semiquantitative activation analysis in metallic alloys submitted to irregular irradiation

    International Nuclear Information System (INIS)

    Veissid, N.; Lucki, G.

    1979-01-01

    An analytic semiquantitative method using neutron activation was developed to determine the impurities and verify the composition of metallic alloys. By the radioactive transformation law, the number of atoms of each element present in the sample is determined measuring the activity in a multichannel. Two samples were analysed: a) Sample of nominal compositions FeNiCr (49,95-49,95 - 0,1% at). b) Sample of nominal composition NiCr (80,20% at). (Author) [pt

  12. Magnetic properties of fcc Ni-based transition metal alloy

    Czech Academy of Sciences Publication Activity Database

    Kudrnovský, Josef; Drchal, Václav

    2009-01-01

    Roč. 100, č. 9 (2009), s. 1193-1196 ISSN 1862-5282 R&D Projects: GA MŠk OC 150; GA AV ČR IAA100100616 Institutional research plan: CEZ:AV0Z10100520 Keywords : transition metal alloys * Ni-based * pair exchange interactions * Curie temperatures * renormalized RPA Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.862, year: 2009

  13. The temperature variation of hydrogen diffusion coefficients in metal alloys

    Science.gov (United States)

    Danford, M. D.

    1990-01-01

    Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.

  14. Formation of amorphous metal alloys by chemical vapor deposition

    Science.gov (United States)

    Mullendore, Arthur W.

    1990-01-01

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures or organometallic compounds and metalloid hydrides, e.g., transition metal carbonyl such as nickel carbonyl, and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit.

  15. Synthesis and stabilization of supported metal catalysts by atomic layer deposition.

    Science.gov (United States)

    Lu, Junling; Elam, Jeffrey W; Stair, Peter C

    2013-08-20

    Supported metal nanoparticles are among the most important catalysts for many practical reactions, including petroleum refining, automobile exhaust treatment, and Fischer-Tropsch synthesis. The catalytic performance strongly depends on the size, composition, and structure of the metal nanoparticles, as well as the underlying support. Scientists have used conventional synthesis methods including impregnation, ion exchange, and deposition-precipitation to control and tune these factors, to establish structure-performance relationships, and to develop better catalysts. Meanwhile, chemists have improved the stability of metal nanoparticles against sintering by the application of protective layers, such as polymers and oxides that encapsulate the metal particle. This often leads to decreased catalytic activity due to a lack of precise control over the thickness of the protective layer. A promising method of catalyst synthesis is atomic layer deposition (ALD). ALD is a variation on chemical vapor deposition in which metals, oxides, and other materials are deposited on surfaces by a sequence of self-limiting reactions. The self-limiting character of these reactions makes it possible to achieve uniform deposits on high-surface-area porous solids. Therefore, design and synthesis of advanced catalysts on the nanoscale becomes possible through precise control over the structure and composition of the underlying support, the catalytic active sites, and the protective layer. In this Account, we describe our advances in the synthesis and stabilization of supported metal catalysts by ALD. After a short introduction to the technique of ALD, we show several strategies for metal catalyst synthesis by ALD that take advantage of its self-limiting feature. Monometallic and bimetallic catalysts with precise control over the metal particle size, composition, and structure were achieved by combining ALD sequences, surface treatments, and deposition temperature control. Next, we describe

  16. Carbon-Based Metal-Free Catalysts for Electrocatalysis beyond the ORR.

    Science.gov (United States)

    Hu, Chuangang; Dai, Liming

    2016-09-19

    Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon-based metal-free catalysts have also been demonstrated to be promising alternatives to noble-metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal-air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon-based metal-free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal-free electrocatalysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. X-ray diffraction broadening effects in metallic alloys

    International Nuclear Information System (INIS)

    Kimmel, G.; Dayan, D.

    1996-01-01

    Although an extensive work had been done in the last decade in the field of line broadening analysis of XRPD there is still little agreement whether this method can be accepted as a characterization tool. The purpose of the present work is to demonstrate that a valuable information can be retrieved from line broadening effects in XRPD. In this work it was focused on the line broadening effects accompanied with typical processes in metallic systems. The following systems were studied:, pure iron, steels, and alloying effects in uranium alloys. The broadening analysis was linked to different variables like hardness, Izod notch toughness, amount of cold work, surface treatment, concentration of additional elements in solid solutions. The Williamson-Hall method was adopted providing fast and global view of resolved 'strain'-'size' effects, considering the entire diffraction spectrum. The size effect was occasionally approved by direct observations of STM or SEM for example. The results of the broadening analysis were well correlated with other measured parameters like toughness and hardness. It was found that alloying in metallic system is sometimes expressed by pure strain effect but cold work results in a mix of strain and size broadening. The complete view of our results lead us to believe that broadening effect can be quantified. Hence, it is recommended to establish a quantitative XRD line broadening analysis method as a novel tool for characterization of metallic materials. (author)

  18. Refractory metal alloys and composites for space nuclear power systems

    Science.gov (United States)

    Titran, Robert H.; Stephens, Joseph R.; Petrasek, Donald W.

    1988-01-01

    Space power requirements for future NASA and other U.S. missions will range from a few kilowatts to megawatts of electricity. Maximum efficiency is a key goal of any power system in order to minimize weight and size so that the Space Shuttle may be used a minimum number of times to put the power supply into orbit. Nuclear power has been identified as the primary power source to meet these high levels of electrical demand. One method to achieve maximum efficiency is to operate the power supply, energy conservation system, and related components at relatively high temperatures. For systems now in the planning stages, design temperatures range from 1300 K for the immediate future to as high as 1700 K for the advanced systems. NASA Lewis Research Center has undertaken a research program on advanced technology of refractory metal alloys and composites that will provide baseline information for space power systems in the 1900's and the 21st century. Special emphasis is focused on the refractory metal alloys of niobium and on the refractory metal composites which utilize tungsten alloy wires for reinforcement. Basic research on the creep and creep-rupture properties of wires, matrices, and composites are discussed.

  19. CO oxidation studies over supported noble metal catalysts and single crystals: A review

    Science.gov (United States)

    Boecker, Dirk; Gonzalez, Richard D.

    1987-01-01

    The catalytic oxidation of CO over noble metal catalysts is reviewed. Results obtained on supported noble metal catalysts and single crystals both at high pressures and under UHV conditions are compared. The underlying causes which result in surface instabilities and multiple steady-state oscillations are considered, in particular, the occurrence of hot spots. CO islands of reactivity, surface oxide formation and phase transformations under oscillatory conditions are discussed.

  20. Plating on some difficult-to-plate metals and alloys

    International Nuclear Information System (INIS)

    Dini, J.W.; Johnson, H.R.

    1980-02-01

    Electrodeposition of coatings on metals such as beryllium, beryllium-copper, Kovar, lead, magnesium, thorium, titanium, tungsten, uranium, zirconium, and their alloys can be problematic. This is due in most cases to a natural oxide surface film that readily reforms after being removed. The procedures we recommend for plating on these metals rely on replacing the oxide film with a displacement coating, or etching to allow mechanical keying between the substrate and plated deposit. The effectiveness of the procedures is demonstrated by interface bond strengths found in ring-shear and conical-head tensile tests

  1. Molecular metal-Oxo catalysts for generating hydrogen from water

    Science.gov (United States)

    Long, Jeffrey R; Chang, Christopher J; Karunadasa, Hemamala I

    2015-02-24

    A composition of matter suitable for the generation of hydrogen from water is described, the positively charged cation of the composition having the general formula [(PY5W.sub.2)MO].sup.2+, wherein PY5W.sub.2 is (NC.sub.5XYZ)(NC.sub.5H.sub.4).sub.4C.sub.2W.sub.2, M is a transition metal, and W, X, Y, and Z can be H, R, a halide, CF.sub.3, or SiR.sub.3, where R can be an alkyl or aryl group. The two accompanying counter anions, in one embodiment, can be selected from the following Cl.sup.-, I.sup.-, PF.sub.6.sup.-, and CF.sub.3SO.sub.3.sup.-. In embodiments of the invention, water, such as tap water containing electrolyte or straight sea water can be subject to an electric potential of between 1.0 V and 1.4 V relative to the standard hydrogen electrode, which at pH 7 corresponds to an overpotential of 0.6 to 1.0 V, with the result being, among other things, the generation of hydrogen with an optimal turnover frequency of ca. 1.5 million mol H.sub.2/mol catalyst per h.

  2. Isotopic exchange of cyclic ethers with deuterium over metal catalysts

    International Nuclear Information System (INIS)

    Duchet, J.C.; Cornet, D.

    1976-01-01

    The exchange reaction between deuterium and cyclic ethers (oxolane and α-methyl derivatives) has been investigated using rhodium and palladium catalysts. The first hydrogen undergoing exchange has been found to be located on a β-carbon. This fact, and the poisoning of the exchange of cyclopentane in the presence of ether, suggest that the O atom participates in the exchange mechanism of ethers. It appears, however, that the oxygen--metal bonding occurs only during this simple exchange process; simultaneous adsorption of oxygen and a vicinal carbon causes hydrogenolysis of the O--C bond. In each case multiple exchange is important. In the oxolane molecule two sets of exchangeable hydrogens are distinguished according to their reactivities, as could be expected by analogy with cycloalkanes. However, this distinction is not so clear in the exchange patterns of substituted oxolanes, since intermediate maxima are observed in these cases. It is suggested that the conformational properties of the substituted rings cause a constraint in the formation of 3,4-diadsorbed oxolanes. Thus, multiple exchange, based on α,β-process, and epimerization via the ''roll-over'' mechanism occur preferentially in certain parts of the molecules

  3. Oxygen-assisted conversion of propane over metal and metal oxide catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Laate, Leiv

    2002-07-01

    An experimental set-up has been build and applied in activity/selectivity studies of the oxygen-assisted conversion of propane over metals and metal oxide catalysts. The apparatus has been used in order to achieve an improved understanding of the reactions between alkanes/alkenes and oxygen. Processes that have been studied arc the oxidative dehydrogenation of propane over a VMgO catalyst and the selective combustion of hydrogen in the presence of hydrocarbons over Pt-based catalysts and metal oxide catalysts. From the experiments, the following conclusions are drawn: A study of the oxidative dehydrogenation of propane over a vanadium-magnesium-oxide catalyst confirmed that the main problem with this system is the lack of selectivity due to complete combustion. Selectivity to propene up to about 60% was obtained at 10% conversion at 500{sup o}C, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by- products were CO and CO{sub 2}. The selectivity to propene is a strong function of the conversion of propane. The reaction rate of propane was found to be 1.0 {+-} 0.1 order in propane and 0.07 {+-} 0.02 order in oxygen. The kinetic results are in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbons as the slow step. The rate of propene oxidation to CO{sub 2} was studied and found to be significantly higher than that of propane. Another possible process involves the simultaneous equilibrium dehydrogenation of alkanes to alkenes and combustion of the hydrogen formed to shift the equilibrium dehydrogenation reaction further to the product alkenes. A study of the selective combustion of hydrogen in the presence of propane/propene was found to be possible under certain reaction conditions over some metal oxide catalysts. In{sub 2}O{sub 3}/SiO{sub 2}, unsupported Bi{sub 2}O{sub 3} and ZSM-5 show the ability to combust hydrogen in a gas mixture with propane and oxygen with good selectivity. Bi{sub 2

  4. Evaluation of mechanical properties in metal wire mesh supported selective catalytic reduction (SCR) catalyst structures

    Science.gov (United States)

    Rajath, S.; Siddaraju, C.; Nandakishora, Y.; Roy, Sukumar

    2018-04-01

    The objective of this research is to evaluate certain specific mechanical properties of certain stainless steel wire mesh supported Selective catalytic reduction catalysts structures wherein the physical properties of the metal wire mesh and also its surface treatments played vital role thereby influencing the mechanical properties. As the adhesion between the stainless steel wire mesh and the catalyst material determines the bond strength and the erosion resistance of catalyst structures, surface modifications of the metal- wire mesh structure in order to facilitate the interface bonding is therefore very important to realize enhanced level of mechanical properties. One way to enhance such adhesion properties, the stainless steel wire mesh is treated with the various acids, i.e., chromic acid, phosphoric acid including certain mineral acids and combination of all those in various molar ratios that could generate surface active groups on metal surface that promotes good interface structure between the metal- wire mesh and metal oxide-based catalyst material and then the stainless steel wire mesh is dipped in the glass powder slurry containing some amount of organic binder. As a result of which the said catalyst material adheres to the metal-wire mesh surface more effectively that improves the erosion profile of supported catalysts structure including bond strength.

  5. Hydrogen production from bio-fuels using precious metal catalysts

    Directory of Open Access Journals (Sweden)

    Pasel Joachim

    2017-01-01

    Full Text Available Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3 and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability.

  6. Hydrogen production from bio-fuels using precious metal catalysts

    Science.gov (United States)

    Pasel, Joachim; Wohlrab, Sebastian; Rotov, Mikhail; Löhken, Katrin; Peters, Ralf; Stolten, Detlef

    2017-11-01

    Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability.

  7. Application of ASA supported noble metal catalysts in the deep hydrodesulphurisation of diesel fuel

    Energy Technology Data Exchange (ETDEWEB)

    Reinhoudt, H.R.; Troost, R.; Van Schalkwijk, S.; Van Langeveld, A.D.; Sie, S.T.; Moulijn, J.A. [Delft University of Technology, Delft (Netherlands); Schulz, H. [Universitaet Karlsruhe, Engler Bunte Institut, Karlsruhe (Germany); Chadwick, D. [Imperial College of Science, Technology and Medicine, London (United Kingdom); Cambra, J. [Escuela de Ingenierios, Bilbao (Spain); De Beer, V.H.J.; Van Veen, J.A.R. [Eindhoven University of Technology, Eindhoven (Netherlands); Fierro, J.L.G. [C.S.I.C., Madrid (Spain)

    1997-07-01

    The potential of Amorphous Silica Alumina (ASA) supported Pt and Pd catalysts for deep hydrodesulphurisation (HDS) of diesel fuels was investigated. It appeared that the ASA supported catalysts exhibit an excellent activity for the conversion of 4-Ethyl, 6-Methyl Dibenzothiophene (4-E,6-M DBT) under model conditions as compared to conventional HDS catalysts and {gamma}-Al{sub 2}O{sub 3} supported noble metal catalysts. Pt/ASA was also tested under practical conditions using a diesel fuel feed. The Pt/ASA catalyst showed a comparable activity to the NiW/{gamma}-Al{sub 2}O{sub 3} catalyst which was higher than that of the conventional CoMo/{gamma}-Al{sub 2}O{sub 3} catalyst. The main difference of the catalyst was the better hydroconversion of the 4,6 di-alkylated DBT's. The better performance of Pt/ASA in the testing under model conditions as compared to the diesel fuel HDS can be attributed to poisoning of part of the active phase by basic nitrogen compounds like quinoline. It is concluded that ASA supported noble metal catalysts have a promising potential for deep HDS processing. 5 refs.

  8. Platinum and palladium alloys suitable as fuel cell electrodes

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention concerns electrode catalysts used in fuel cells, such as proton exchange membrane (PEM) fuel cells. The invention is related to the reduction of the noble metal content and the improvement of the catalytic5 efficiency by low level substitution of the noble metal to provide new...... and innovative catalyst compositions in fuel cell electrodes. The novel electrode catalysts of the invention comprise a noble metal selected from Pt and Pd alloyed with a lanthanide metal....

  9. Recycling of spent noble metal catalysts with emphasis on pyrometallurgical processing

    Energy Technology Data Exchange (ETDEWEB)

    Hagelueken, C. [Degussa Huels AG, Hanau (Germany)

    1999-09-01

    Precious metal catalysts for catalytic Naphta Reforming, Isomerization, Hydrogenation and other chemical and petrochemical processes are valuable assets for oil refineries and chemical companies. At the end of the service life of a reactor load of catalyst, the efficient and reliable recovery of the precious metals contained in the catalyst is of paramount importance. More than 150 years of technological advances at Degussa-Huels have resulted in refining methods for all kinds of precious metal containing materials which guarantee an optimum technical yield of the precious metals included. The refining of catalysts today is one of the important activities in the precious metals business unit. In the state-of-the-art precious metal refinery at Hanau in the centre of Germany, a wide variety of processes for the recovery of all precious metals is offered. These processes include accurate preparation, sampling and analysis as well as both wet-chemical and pyrometallurgical recovery techniques. Special emphasis in this presentation is laid on the advantages of pyrometallurgical processes for certain kinds of catalysts. To avoid any risks during transport, sampling and treatment of the spent catalyst, all parties involved in the recycling chain strictly have to follow the relevant safety regulations. Under its commitment to 'Responsible Care' standard procedures have been developed which include pre-shipment samples, safety data sheets/questionnaires and inspection of spent catalysts. These measures not only support a safe and environmentally sound catalyst recycling but also enable to determine the most suitable and economic recovery process - for the benefit of the customer. (orig.)

  10. A review of dry (CO2) reforming of methane over noble metal catalysts.

    Science.gov (United States)

    Pakhare, Devendra; Spivey, James

    2014-11-21

    Dry (CO2) reforming of methane (DRM) is a well-studied reaction that is of both scientific and industrial importance. This reaction produces syngas that can be used to produce a wide range of products, such as higher alkanes and oxygenates by means of Fischer-Tropsch synthesis. DRM is inevitably accompanied by deactivation due to carbon deposition. DRM is also a highly endothermic reaction and requires operating temperatures of 800-1000 °C to attain high equilibrium conversion of CH4 and CO2 to H2 and CO and to minimize the thermodynamic driving force for carbon deposition. The most widely used catalysts for DRM are based on Ni. However, many of these catalysts undergo severe deactivation due to carbon deposition. Noble metals have also been studied and are typically found to be much more resistant to carbon deposition than Ni catalysts, but are generally uneconomical. Noble metals can also be used to promote the Ni catalysts in order to increase their resistance to deactivation. In order to design catalysts that minimize deactivation, it is necessary to understand the elementary steps involved in the activation and conversion of CH4 and CO2. This review will cover DRM literature for catalysts based on Rh, Ru, Pt, and Pd metals. This includes the effect of these noble metals on the kinetics, mechanism and deactivation of these catalysts.

  11. Polymeric heterogeneous catalysts of transition-metal oxides: surface characterization, physicomechanical properties, and catalytic activity.

    Science.gov (United States)

    Nhi, Bui Dinh; Akhmadullin, Renat Maratovich; Akhmadullina, Alfiya Garipovna; Samuilov, Yakov Dmitrievich; Aghajanian, Svetlana Ivanova

    2013-12-16

    We investigate the physicomechanical properties of polymeric heterogeneous catalysts of transition-metal oxides, specifically, the specific surface area, elongation at break, breaking strength, specific electrical resistance, and volume resistivity. Digital microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive analysis are used to study the surfaces of the catalysts. The experimental results show that polymeric heterogeneous catalysts of transition-metal oxides exhibit high stability and can maintain their catalytic activity under extreme reaction conditions for long-term use. The oxidation mechanism of sulfur-containing compounds in the presence of polymeric heterogeneous catalysts of transition-metal oxides is confirmed. Microstructural characterization of the catalysts is performed by using X-ray computed tomography. The activity of various catalysts in the oxidation of sulfur-containing compounds is determined. We demonstrate the potential application of polymeric heterogeneous catalysts of transition-metal oxides in industrial wastewater treatment. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Method for inhibiting alkali metal corrosion of nickel-containing alloys

    Science.gov (United States)

    DeVan, Jackson H.; Selle, James E.

    1983-01-01

    Structural components of nickel-containing alloys within molten alkali metal systems are protected against corrosion during the course of service by dissolving therein sufficient aluminum, silicon, or manganese to cause the formation and maintenance of a corrosion-resistant intermetallic reaction layer created by the interaction of the molten metal, selected metal, and alloy.

  13. beads immobilized metal nanoparticle catalysts for the reduction of ...

    Indian Academy of Sciences (India)

    economic advantage. Further, the existing catalyst cannot be continuously packed into ... neous NP catalysts with higher efficiency, stability, economy, easy synthesis and reusability for potential degradation ... then the solution was refluxed in an oil bath at 80◦C. The reaction mixture has been protected from light to avoid the.

  14. Transition metal oxide loaded MCM catalysts for photocatalytic ...

    Indian Academy of Sciences (India)

    Nanoporous, high surface area compounds were obtained after calcination of the compounds. The catalysts were characterized by SEM, XRD, XPS, UV-vis and BET surface area analysis. The catalysts showed high activity for the photocatalytic degradation of both anionic and cationic dyes. The degradation of the dyes was ...

  15. Development of ternary alloy cathode catalysts for phosphoric acid fuel cells: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Jalan, V.; Kosek, J.; Giner, J.; Taylor, E. J.; Anderson, E.; Bianchi, V.; Brooks, C.; Cahill, K.; Cropley, C.; Desai, M.; Frost, D.; Morriseau, B.; Paul, B.; Poirier, J.; Rousseau, M.; Swette, L.; Waterhouse, R.

    1988-11-01

    The overall objective of the program was the identification development and incorporation of high activity platinum ternary alloys on corrosion resistant supports, for use in advanced phosphoric acid fuel cells. Two high activity ternary alloys, Pr-Cr-Ce and Pt-Ni-Co, both supported on Vulcan XC-72, were identified during the course of the program. The Pr-Ni-Co system was selected for optimization, including preparation and evaluation on corrosion resistant supports such as 2700/degree/C heat-treated Vulcan XC-72 and 2700/degree/ heat-treated Black Pearls 2000. A series of tests identified optimum metal ratios, heat-treatment temperatures and heat-treatment atmospheres for the Pr-Ni-Co system. During characterization testing, it was discovered that approximately 50% of the nickel and cobalt present in the starting material could be removed, subsequent to alloy formation, without degrading performance. Extremely stable full cell performance was observed for the Pt-Ni-Co system during a 10,000 hour atmosphere pressure life test. Several theories are proposed to explain the enhancement in activity due to alloy formation. Recommendations are made for future research in this area. 62 refs., 23 figs., 27 tabs.

  16. Metal oxides modified NiO catalysts for oxidative dehydrogenation of ethane to ethylene

    KAUST Repository

    Zhu, Haibo

    2014-06-01

    The sol-gel method was applied to the synthesis of Zr, Ti, Mo, W, and V modified NiO based catalysts for the ethane oxidative dehydrogenation reaction. The synthesized catalysts were characterized by XRD, N2 adsorption, SEM and TPR techniques. The results showed that the doping metals could be highly dispersed into NiO domains without the formation of large amount of other bulk metal oxide. The modified NiO materials have small particle size, larger surface area, and higher reduction temperature in contrast to pure NiO. The introduction of group IV, V and VI transition metals into NiO decreases the catalytic activity in ethane ODH. However, the ethylene selectivity is enhanced with the highest level for the Ni-W-O and Ni-Ti-O catalysts. As a result, these two catalysts show improved efficiency of ethylene production in the ethane ODH reaction. © 2014 Elsevier B.V. All rights reserved.

  17. Method of synthesizing bulk transition metal carbide, nitride and phosphide catalysts

    Science.gov (United States)

    Choi, Jae Soon; Armstrong, Beth L; Schwartz, Viviane

    2015-04-21

    A method for synthesizing catalyst beads of bulk transmission metal carbides, nitrides and phosphides is provided. The method includes providing an aqueous suspension of transition metal oxide particles in a gel forming base, dropping the suspension into an aqueous solution to form a gel bead matrix, heating the bead to remove the binder, and carburizing, nitriding or phosphiding the bead to form a transition metal carbide, nitride, or phosphide catalyst bead. The method can be tuned for control of porosity, mechanical strength, and dopant content of the beads. The produced catalyst beads are catalytically active, mechanically robust, and suitable for packed-bed reactor applications. The produced catalyst beads are suitable for biomass conversion, petrochemistry, petroleum refining, electrocatalysis, and other applications.

  18. Alloys for a liquid metal fast breeder reactor

    Science.gov (United States)

    Rowcliffe, Arthur F.; Bleiberg, Melvin L.; Diamond, Sidney; Bajaj, Ram

    1979-01-01

    An essentially gamma-prime precipitation-hardened iron-chromium-nickel alloy has been designed with emphasis on minimum nickel and chromium contents to reduce the swelling tendencies of these alloys when used in liquid metal fast breeder reactors. The precipitation-hardening components have been designed for phase stability and such residual elements as silicon and boron, also have been selected to minimize swelling. Using the properties of these alloys in one design would result in an increased breeding ratio over 20% cold worked stainless steel, a reference material, of 1.239 to 1.310 and a reduced doubling time from 15.8 to 11.4 years. The gross stoichiometry of the alloying composition comprises from about 0.04% to about 0.06% carbon, from about 0.05% to about 1.0% silicon, up to about 0.1% zirconium, up to about 0.5% vanadium, from about 24% to about 31% nickel, from 8% to about 11% chromium, from about 1.7% to about 3.5% titanium, from about 1.0% to about 1.8% aluminum, from about 0.9% to about 3.7% molybdenum, from about 0.04% to about 0.8% boron, and the balance iron with incidental impurities.

  19. Automated image analysis of microstructure changes in metal alloys

    Science.gov (United States)

    Hoque, Mohammed E.; Ford, Ralph M.; Roth, John T.

    2005-02-01

    The ability to identify and quantify changes in the microstructure of metal alloys is valuable in metal cutting and shaping applications. For example, certain metals, after being cryogenically and electrically treated, have shown large increases in their tool life when used in manufacturing cutting and shaping processes. However, the mechanisms of microstructure changes in alloys under various treatments, which cause them to behave differently, are not yet fully understood. The changes are currently evaluated in a semi-quantitative manner by visual inspection of images of the microstructure. This research applies pattern recognition technology to quantitatively measure the changes in microstructure and to validate the initial assertion of increased tool life under certain treatments. Heterogeneous images of aluminum and tungsten carbide of various categories were analyzed using a process including background correction, adaptive thresholding, edge detection and other algorithms for automated analysis of microstructures. The algorithms are robust across a variety of operating conditions. This research not only facilitates better understanding of the effects of electric and cryogenic treatment of these materials, but also their impact on tooling and metal-cutting processes.

  20. Metal Compression Forming of aluminum alloys and metal matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, S.; Ren, W.; Porter, W.D.; Brinkman, C.R.; Sabau, A.S.; Purgert, R.M.

    2000-02-01

    Metal Compression Forming (MCF) is a variant of the squeeze casting process, in which molten metal is allowed to solidify under pressure in order to close porosity and form a sound part. However, the MCF process applies pressure on the entire mold face, thereby directing pressure on all regions of the casting and producing a uniformly sound part. The process is capable of producing parts with properties close to those of forgings, while retaining the near net shape, complexity in geometry, and relatively low cost of the casting process.

  1. Corrosion fatigue of biomedical metallic alloys: mechanisms and mitigation.

    Science.gov (United States)

    Antunes, Renato Altobelli; de Oliveira, Mara Cristina Lopes

    2012-03-01

    Cyclic stresses are often related to the premature mechanical failure of metallic biomaterials. The complex interaction between fatigue and corrosion in the physiological environment has been subject of many investigations. In this context, microstructure, heat treatments, plastic deformation, surface finishing and coatings have decisive influence on the mechanisms of fatigue crack nucleation and growth. Furthermore, wear is frequently present and contributes to the process. However, despite all the effort at elucidating the mechanisms that govern corrosion fatigue of biomedical alloys, failures continue to occur. This work reviews the literature on corrosion-fatigue-related phenomena of Ti alloys, surgical stainless steels, Co-Cr-Mo and Mg alloys. The aim was to discuss the correlation between structural and surface aspects of these materials and the onset of fatigue in the highly saline environment of the human body. By understanding such correlation, mitigation of corrosion fatigue failure may be achieved in a reliable scientific-based manner. Different mitigation methods are also reviewed and discussed throughout the text. It is intended that the information condensed in this article should be a valuable tool in the development of increasingly successful designs against the corrosion fatigue of metallic implants. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Molecular dynamics simulations of Pd-Ni transition metal alloys

    International Nuclear Information System (INIS)

    Kart, S. O.; Kart, H. H.; Uludogan, M.; Tomak, M.; Cagin, T.

    2002-01-01

    Molecular Dynamics simulations are performed to study bulk properties of fcc metals and metal alloys by using the quantum Sutton-Chen many-body potentials within the context of the tight-binding approach. The Molecular Dynamics algorithms we used in the simulations of Pd-Ni alloys are based on an extended Hamiltonian formalism arising from the works of Andersen (1980), Parinello and Rahman (1980), Nose (1984), Hoover (1985) and Cagin (1988). In these simulations, the effect of temperature and concentration on the solid and liquid properties are studied. Elastic constants and phonon dispersion relation are the solid properties we simulated in this work. Dynamic and static properties of liquid Pd-Ni are also computed by examining the behavior of density, enthalpy, pair distribution function and structure factor. The melting temperatures of Pd-Ni alloys are investigated. The diffusion coefficients are calculated from the mean square displacement using Einstein relation and from velocity auto-correlation function using Green-Kubo relations. The simulation results are in good agreement with the experiments

  3. Refractory metal alloys and composites for space power systems

    Science.gov (United States)

    Stephens, R.; Petrasek, D. W.; Titran, R. H.

    1990-01-01

    Results are presented on recent studies of refractory-metal-alloy and refractory-metal-composite technologies for space power systems, with emphasis on work performed at the Lewis Research Center in support of the Ground Engineering System (GES) for the SP-100 reactor. Special attention is given to the mechanical properties of alloys with compositions Nb-1Zr and Nb-0.1Zr-0.1C (the PWC-11 alloy) and to advanced fiber-reinforced composites. The results to date indicate that, for the GES at a power level of about 100 kWe, the PWC-11 has attractive creep properties that will extend the capabilities of the SP-100 reactor compared to a similar system fabricated from Nb-1Zr. On the other hand, tungsten-reinforced Nb-1Zr composites were found to provide a ten-fold and four-fold creep strength over Nb-1Zr and PWC-11, respectively, at 1400 to 1500 K.

  4. Photo-oxidation catalysts

    Science.gov (United States)

    Pitts, J Roland [Lakewood, CO; Liu, Ping [Irvine, CA; Smith, R Davis [Golden, CO

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  5. The corrosion behaviour of nanograined metals and alloys

    Directory of Open Access Journals (Sweden)

    Herrasti, P.

    2012-10-01

    Full Text Available There has been considerable interest in the properties of nanocrystalline materials over the last decade. Such materials include metals and alloys with a crystal size within the order of 1 to 100 nm. The interest arises due to the substantial differences in electrical, optical and magnetic properties and also due to their high adsorption capability and chemical reactivity compared to their larger grained counterparts. In this paper, the corrosion of nanocrystalline metals and alloys is investigated and compared to the corrosion of microcrystalline materials having a similar composition. The focus is on the corrosion of nickel, copper, cobalt and iron alloys. Key aspects of different corrosion behaviour such grain boundaries and size are identified.

    En la última década ha habido un gran interes en las propiedades de materiales nanocristalinos. Estos materiales incluyen metales y aleaciones con un tamaño de cristal del orden de 1 a 100 nm. El interes por estos materiales es debido a las grandes diferencias en cuanto a sus propiedades electricas, opticas y magneticas, asi como a su alta capacidad de adsorción y reactividad química en relación a los mismos materiales con tamaños de grano mayores. En este trabajo se ha investigado y comparado la corrosión de materiales nano y microcristalinos de similar composición química. Principalmente se ha centrado en la corrosión de metales tales como niquel, cobre, cobalto y aleaciones de hierro. Se ha comprobado que los diferentes comportamientos frente al proceso de corrosión están intimamente ligados con los bordes de grano y el tamaño de dichos granos.

  6. Catalysts for oxidation of mercury in flue gas

    Science.gov (United States)

    Granite, Evan J [Wexford, PA; Pennline, Henry W [Bethel Park, PA

    2010-08-17

    Two new classes of catalysts for the removal of heavy metal contaminants, especially mercury (Hg) from effluent gases. Both of these classes of catalysts are excellent absorbers of HCl and Cl.sub.2 present in effluent gases. This adsorption of oxidizing agents aids in the oxidation of heavy metal contaminants. The catalysts remove mercury by oxidizing the Hg into mercury (II) moieties. For one class of catalysts, the active component is selected from the group consisting of iridium (Ir) and iridum-platinum (Ir/Pt) alloys. The Ir and Ir/Pt alloy catalysts are especially corrosion resistant. For the other class of catalyst, the active component is partially combusted coal or "Thief" carbon impregnated with Cl.sub.2. Untreated Thief carbon catalyst can be self-activating in the presence of effluent gas streams. The Thief carbon catalyst is disposable by means of capture from the effluent gas stream in a particulate collection device (PCD).

  7. Development of Coke-tolerant Transition Metal Catalysts for Dry Reforming of Methane

    KAUST Repository

    Al-Sabban, Bedour E.

    2016-11-07

    Dry reforming of methane (DRM) is an attractive and promising process for the conversion of methane and carbon dioxide which are the most abundant carbon sources into valuable syngas. The produced syngas, which is a mixture of hydrogen and carbon monoxide, can be used as intermediates in the manufacture of numerous chemicals. To achieve high conversion, DRM reaction is operated at high temperatures (700-900 °C) that can cause major drawbacks of catalyst deactivation by carbon deposition, metal sintering or metal oxidation. Therefore, the primary goal is to develop a metal based catalyst for DRM that can completely suppress carbon formation by designing the catalyst composition. The strategy of this work was to synthesize Ni-based catalysts all of which prepared by homogeneous deposition precipitation method (HDP) to produce nanoparticles with narrow size distribution. In addition, control the reactivity of the metal by finely tuning the bimetallic composition and the reaction conditions in terms of reaction temperature and pressure. The highly endothermic dry reforming of methane proceeds via CH4 decomposition to leave surface carbon species, followed by removal of C with CO2-derived species to give CO. Tuning the reactivity of the active metal towards these reactions during DRM allows in principle the catalyst surface to remain active and clean without carbon deposition for a long-term. The initial attempt was to improve the resistance of Ni catalyst towards carbon deposition, therefore, a series of 5 wt.% bimetallic Ni9Pt1 were supported on various metal oxides (Al2O3, CeO2, and ZrO2). The addition of small amount of noble metal improved the stability of the catalyst compared to their monometallic Ni and Pt catalysts, but still high amount of carbon (> 0.1 wt.%) was formed after 24 h of the reaction. The obtained results showed that the catalytic performance, particle size and amount of deposited carbon depends on the nature of support. Among the tested

  8. Biomass Conversion Strategies and the Renewable Production of Hydrogen using Heterogeneous Metal Catalysts

    Science.gov (United States)

    Carrasquillo-Flores, Ronald

    Biomass is a renewable carbon source that can be processed into fuels and chemicals in a biorefinery. However, there are a number of challenges that need to be overcome for biomass utilization to be viable. The work presented herein aims to address two existing challenges in biomass processing schemes, namely the efficient utilization of all fractions of lignocellulosic biomass and the renewable production of the hydrogen necessary to reduce the oxygen functionalities native in biomass. First, lignin was depolymerized to produce a renewable phenolic solvent mixture. Biphasic reactions with this solvent and aqueous solution of glucose or xylose produce 5-hydroxymethylfurfural (HMF) and furfural, respectively, at high yields. HMF and furfuryl alcohol could also be upgraded into levulinic acid at high yields. The yields are due to the capacity of the solvent to partition these molecules and prevent their degradation. Second, propyl guaiacol, a component of the phenolic solvent, was used for biphasic reactions where ball milled biomass substrates were used. These substrates are converted to furfural and HMF at high yields due to the partition of these molecules into the solvent and the on-demand production of glucose and xylose from the substrate, minimizing the formation of humins. A study of the water-gas shift reaction over Pt-based catalysts was conducted. Alloying Pt with Re was found to increase the catalytic activity and microkinetic modeling revealed Pt is a good representation of the active site and Re acts as a promoter slightly destabilizing CO binding. A study on formic acid decomposition over Au catalysts was performed. Experiments, density functional theory and microkinetic modeling results indicate the reaction proceeds completely on highly undercoordinated Au atoms with any high coordination atom being largely inert. Motivated by the results on Au catalysts, the metal-support interaction was investigated for the reverse water-gas shift reaction. Using a

  9. Direct Solid-State Conversion of Recyclable Metals and Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Z; Manchiraju, K [Southwire Co.

    2012-02-22

    This project is to develop and demonstrate the concept feasibility of a highly energy-efficient solid-state material synthesis process, friction stir extrusion (FSE) technology. Specifically, the project seeks to explore and demonstrate the feasibility to recycle metals, produce nano-particle dispersion strengthened bulk materials and/or nano-composite materials from powders, chips or other recyclable feedstock metals or scraps through mechanical alloying and thermo-mechanical processing in a single-step. In this study, we focused on metal recycling, producing nano-engineered wires and evaluating their potential use in future generation long-distance electric power delivery infrastructure. More comprehensive R&D on the technology fundamentals and system scale-up toward early-stage applications in two targeted “showcase” fields of use: nano engineered bulk materials and Al recycling will be considered and planned as part of Project Continuation Plan.

  10. Fundamental Studies of the Reforming of Oxygenated Compounds over Supported Metal Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Dumesic, James A. [Univ. of Wisconsin, Madison, WI (United States)

    2016-01-04

    The main objective of our research has been to elucidate fundamental concepts associated with controlling the activity, selectivity, and stability of bifunctional, metal-based heterogeneous catalysts for tandem reactions, such as liquid-phase conversion of oxygenated hydrocarbons derived from biomass. We have shown that bimetallic catalysts that combine a highly-reducible metal (e.g., platinum) with an oxygen-containing metal promoter (e.g., molybdenum) are promising materials for conversion of oxygenated hydrocarbons because of their high activity for selective cleavage for carbon-oxygen bonds. We have developed methods to stabilize metal nanoparticles against leaching and sintering under liquid-phase reaction conditions by using atomic layer deposition (ALD) to apply oxide overcoat layers. We have used controlled surface reactions to produce bimetallic catalysts with controlled particle size and controlled composition, with an important application being the selective conversion of biomass-derived molecules. The synthesis of catalysts by traditional methods may produce a wide distribution of metal particle sizes and compositions; and thus, results from spectroscopic and reactions kinetics measurements have contributions from a distribution of active sites, making it difficult to assess how the size and composition of the metal particles affect the nature of the surface, the active sites, and the catalytic behavior. Thus, we have developed methods to synthesize bimetallic nanoparticles with controlled particle size and controlled composition to achieve an effective link between characterization and reactivity, and between theory and experiment. We have also used ALD to modify supported metal catalysts by addition of promoters with atomic-level precision, to produce new bifunctional sites for selective catalytic transformations. We have used a variety of techniques to characterize the metal nanoparticles in our catalysts, including scanning transmission electron

  11. Recent Advances in Supported Metal Catalysts for Syngas Production from Methane

    Directory of Open Access Journals (Sweden)

    Mohanned Mohamedali

    2018-03-01

    Full Text Available Over the past few years, great attention is paid to syngas production processes from different resources especially from abundant sources, such as methane. This review of the literature is intended for syngas production from methane through the dry reforming (DRM and the steam reforming of methane (SRM. The catalyst development for DRM and SRM represents the key factor to realize a commercial application through the utilization of more efficient catalytic systems. Due to the enormous amount of published literature in this field, the current work is mainly dedicated to the most recent achievements in the metal-oxide catalyst development for DRM and SRM in the past five years. Ni-based supported catalysts are considered the most widely used catalysts for DRM and SRM, which are commercially available; hence, this review has focused on the recent advancements achieved in Ni catalysts with special focus on the various attempts to address the catalyst deactivation challenge in both DRM and SRM applications. Furthermore, other catalytic systems, including Co-based catalysts, noble metals (Pt, Rh, Ru, and Ir, and bimetallic systems have been included in this literature review to understand the observed improvements in the catalytic activities and coke suppression property of these catalysts.

  12. Transport mechanisms in the laser alloying of metals

    Science.gov (United States)

    Pawlak, Ryszard; Tomczyk, Mariusz; Walczak, Maria

    2003-10-01

    This article presents some investigations of a laser alloyed surface layer of nickel doped with gold and of copper doped with aluminum. The velocity of the convectino flow in the laser pool predicted by computation implies that there may exist good miscibility for the range of components different from those obtained by the conventional method. This indicates a predominant role of the Marangoni convection for mixing elements. Some metallurgical cross-sections of Ni-Au; Mo-Au; Cu-Al; Cu-Au layers, alloyed by an Nd-YAG laser, for different contents of doping elements are presented. They may be interesting information about miscibility of these metals during laser pulse τ1=4ms.

  13. Non-stoichiometric AB5 alloys for metal hydride electrodes

    Science.gov (United States)

    Reilly, James J.; Adzic, Gordana D.; Johnson, John R.; Vogt, Thomas; McBreen, James

    2001-01-01

    The present invention provides a non-stoichiometric alloy comprising a composition having the formula AB.sub.5+X an atomic ratio wherein A is selected from the group consisting of the rare earth metals, yttrium, mischmetal, or a combination thereof; B is nickel and tin, or nickel and tin and at least a third element selected from the group consisting of the elements in group IVA of the periodic table, aluminum, manganese, iron, cobalt, copper, antimony or a combination thereof; X is greater than 0 and less than or equal to about 2.0; and wherein at least one substituted A site is occupied by at least one of the B elements. An electrode incorporating said alloy and an electrochemical cell incorporating said electrode are also described.

  14. The effect of recasting on bond strength between porcelain and base-metal alloys.

    Science.gov (United States)

    Madani, Azam S; Rokni, Shahin Rezaii; Mohammadi, Abolghasem; Bahrami, Mehran

    2011-04-01

    Long-term success of metal ceramic restorations depends on metal ceramic bond strength. The purpose of this study was to determine whether recasting of base-metal alloys has any effect on metal ceramic bond strength. Super Cast and Verabond base-metal alloys were used to cast 260 wax patterns. The alloy specimens were equally divided into five groups and cast as: group A 0.0%, B 25%, C 50%, D 75%, and E 100% once-cast alloy. Each group was divided into two subgroups: the first group was cast with Super Cast and the second with Verabond. In each subgroup half of the cast alloys were veneered with Vita VMK 68 and the others with Ceramco 3. Recasting decreased bond strength (p alloy. Group E with 100% new Super Cast alloy veneered with Vita VMK 68 porcelain had the highest bond strength (30.75 ± 9.58 MPa), and group B including 25% new and 75% recast Super Cast alloy veneered with the same porcelain had the lowest bond strength (21.72 ± 5.19 MPa). By adding over 50% once-cast alloy in base-metal alloys, metal-ceramic bond strength decreases significantly. © 2011 by The American College of Prosthodontists.

  15. Behaviour of metals and alloys in molten fluoride media

    International Nuclear Information System (INIS)

    Fabre, St.

    2009-01-01

    Fluoride salts are contemplated for Generation IV nuclear systems which structural materials need to resist corrosion at high temperatures. Corrosion of metals in molten fluorides has been investigated in support of the Molten Salt Reactor's development and led to an optimized alloy, Hastelloy-N, but it lacked fundamentals data for the comprehension of materials' degradation mechanisms. The main objective of this work is then to help with the understanding of the corrosion behaviour of nickel and its alloys in fluoride salts. An experimental method was built up using electrochemical techniques and enabled to investigate the thermochemical conditions of the media and the influence of different parameters (media, temperature and quantity of impurities) on the behaviour of the materials. Most tests were performed in LiF-NaF mixtures between 800 and 1000 C. Pure metals can be classified as follows: Cr ≤ Fe ≤ Ni ≤ Mo ≤ W in increasing stability order and two specific behaviours were evidenced: Cr and Fe corrode in the melt, whereas Ni, Mo and W are stable, underlining the significance level of the redox couple controlling the reactions in the mixture. Moreover, corrosion current densities increase with temperature, fluoro-acidity and the quantity of dissolved oxide in the melt. Binary Ni-Cr alloys were also tested; selective attack of Cr is first observed before both elements are oxidized. Combining thermochemical calculations and experimental results enables to propose an approach to establish an optimized composition for a stable alloy. Immersion tests were finally achieved in addition to the electrochemical tests: interpretations of both methods were compared and completed. (author)

  16. Surface/structure functionalization of copper-based catalysts by metal-support and/or metal-metal interactions

    Science.gov (United States)

    Konsolakis, Michalis; Ioakeimidis, Zisis

    2014-11-01

    Cu-based catalysts have recently attracted great attention both in catalysis and electro-catalysis fields due to their excellent catalytic performance and low cost. Given that their performance is determined, to a great extent, by Cu sites local environment, considerable efforts have been devoted on the strategic modifications of the electronic and structural properties of Cu sites. In this regard, the feasibility of tuning the local structure of Cu entities by means of metal-support or metal-metal interactions is investigated. More specifically, the physicochemical properties of Cu entities are modified by employing: (i) different oxides (CeO2, La2O3, Sm2O3), or (ii) ceria-based mixed oxides (Ce1-xSmxOδ) as supporting carriers, and (iii) a second metal (Cobalt) adjacent to Cu (bimetallic Cu-Co/CeO2). A characterization study, involving BET, XRD, TPR, and XPS, reveal that significant modifications on structural, redox and electronic properties of Cu sites can be induced by adopting either different oxide carriers or bimetallic complexes. Fundamental insights into the tuning of Cu local environment by metal-support or metal-metal interactions are provided, paving the way for real-life industrial applications.

  17. Biodiesel production using alkali earth metal oxides catalysts synthesized by sol-gel method

    Directory of Open Access Journals (Sweden)

    Majid Mohadesi

    2014-03-01

    Full Text Available Biodiesel fuel is considered as an alternative to diesel fuel. This fuel is produced through transesterification reactions of vegetable oils or animal fat by alcohols in the presence of different catalysts. Recent studies on this process have shown that, basic heterogeneous catalysts have a higher performance than other catalysts. In this study different alkali earth metal oxides (CaO, MgO and BaO doped SiO2 were used as catalyst for the biodiesel production process. These catalysts were synthesis by using the sol-gel method. A transesterification reaction was studied after 8h by mixing corn oil, methanol (methanol to oil molar ratio of 16:1, and 6 wt. % catalyst (based on oil at 60oC and 600rpm. Catalyst loading was studied for different catalysts ranging in amounts from 40, 60 to 80%. The purity and yield of the produced biodiesel for 60% CaO/SiO2 was higher than other catalysts and at 97.3% and 82.1%, respectively.

  18. In situ X-ray absorption spectroscopy of transition metal based water oxidation catalysts

    NARCIS (Netherlands)

    van Oversteeg, Christina H M|info:eu-repo/dai/nl/413490483; Doan, Hoang Q; de Groot, Frank M F|info:eu-repo/dai/nl/08747610X; Cuk, Tanja

    2016-01-01

    X-ray absorption studies of the geometric and electronic structure of primarily heterogeneous Co, Ni, and Mn based water oxidation catalysts are reviewed. The X-ray absorption near edge and extended X-ray absorption fine structure studies of the metal K-edge, characterize the metal oxidation state,

  19. Revisiting formic acid decomposition on metallic powder catalysts: Exploding the HCOOH decomposition volcano curve

    Science.gov (United States)

    Tang, Yadan; Roberts, Charles A.; Perkins, Ryan T.; Wachs, Israel E.

    2016-08-01

    This study revisits the classic volcano curve for HCOOH decomposition by metal catalysts by taking a modern catalysis approach. The metal catalysts (Au, Ag, Cu, Pt, Pd, Ni, Rh, Co and Fe) were prepared by H2 reduction of the corresponding metal oxides. The number of surface active sites (Ns) was determined by formic acid chemisorption. In situ IR indicated that both monodentate and bidentate/bridged surface HCOO* were present on the metals. Heats of adsorption (ΔHads) for surface HCOO* values on metals were taken from recently reported DFT calculations. Kinetics for surface HCOO* decomposition (krds) were determined with TPD spectroscopy. Steady-state specific activity (TOF = activity/Ns) for HCOOH decomposition over the metals was calculated from steady-state activity (μmol/g-s) and Ns (μmol/g). Steady-state TOFs for HCOOH decomposition weakly correlated with surface HCOO* decomposition kinetics (krds) and ΔHads of surface HCOO* intermediates. The plot of TOF vs. ΔHads for HCOOH decomposition on metal catalysts does not reproduce the classic volcano curve, but shows that TOF depends on both ΔHads and decomposition kinetics (krds) of surface HCOO* intermediates. This is the first time that the classic catalysis study of HCOOH decomposition on metallic powder catalysts has been repeated since its original publication.

  20. Chemoselective Oxidation of Bio-Glycerol with Nano-Sized Metal Catalysts

    DEFF Research Database (Denmark)

    Li, Hu; Kotni, Ramakrishna; Zhang, Qiuyun

    2015-01-01

    to selectively oxidize glycerol and yield products with good selectivity is the use of nano-sized metal particles as heterogeneous catalysts. In this short review, recent developments in chemoselective oxidation of glycerol to specific products over nano-sized metal catalysts are described. Attention is drawn...... to various reaction parameters such as the type of the support, the size of the metal particles, and the acid/base properties of the reaction medium which were illustrated to largely influence the activity of the nanocatalyst and selectivity to the target product. - See more at: http...

  1. Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts

    Science.gov (United States)

    Sahraie, Nastaran Ranjbar; Kramm, Ulrike I.; Steinberg, Julian; Zhang, Yuanjian; Thomas, Arne; Reier, Tobias; Paraknowitsch, Jens-Peter; Strasser, Peter

    2015-01-01

    Carbon materials doped with transition metal and nitrogen are highly active, non-precious metal catalysts for the electrochemical conversion of molecular oxygen in fuel cells, metal air batteries, and electrolytic processes. However, accurate measurement of their intrinsic turn-over frequency and active-site density based on metal centres in bulk and surface has remained difficult to date, which has hampered a more rational catalyst design. Here we report a successful quantification of bulk and surface-based active-site density and associated turn-over frequency values of mono- and bimetallic Fe/N-doped carbons using a combination of chemisorption, desorption and 57Fe Mössbauer spectroscopy techniques. Our general approach yields an experimental descriptor for the intrinsic activity and the active-site utilization, aiding in the catalyst development process and enabling a previously unachieved level of understanding of reactivity trends owing to a deconvolution of site density and intrinsic activity. PMID:26486465

  2. Atomically Thin Ordered Alloys of Transition Metal Dichalcogenides: Stability and Band Structures

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    We explore the possibility of modulating the electronic band edges of the transition metal dichalcogenides (TMD) via alloying of different semiconductors within the same group (intra-group alloying). The stability of the ordered alloys is assessed from the calculated mixing enthalpy which is found...

  3. Direct Solid-State Conversion of Recyclable Metals and Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kiran Manchiraju

    2012-03-27

    Friction Stir Extrusion (FSE) is a novel energy-efficient solid-state material synthesis and recycling technology capable of producing large quantity of bulk nano-engineered materials with tailored, mechanical, and physical properties. The novelty of FSE is that it utilizes the frictional heating and extensive plastic deformation inherent to the process to stir, consolidate, mechanically alloy, and convert the powders, chips, and other recyclable feedstock materials directly into useable product forms of highly engineered materials in a single step (see Figure 1). Fundamentally, FSE shares the same deformation and metallurgical bonding principles as in the revolutionary friction stir welding process. Being a solid-state process, FSE eliminates the energy intensive melting and solidification steps, which are necessary in the conventional metal synthesis processes. Therefore, FSE is highly energy-efficient, practically zero emissions, and economically competitive. It represents a potentially transformational and pervasive sustainable manufacturing technology for metal recycling and synthesis. The goal of this project was to develop the technological basis and demonstrate the commercial viability of FSE technology to produce the next generation highly functional electric cables for electricity delivery infrastructure (a multi-billion dollar market). Specific focus of this project was to (1) establish the process and material parameters to synthesize novel alloys such as nano-engineered materials with enhanced mechanical, physical, and/or functional properties through the unique mechanical alloying capability of FSE, (2) verifying the expected major energy, environmental, and economic benefits of FSE technology for both the early stage 'showcase' electric cable market and the anticipated pervasive future multi-market applications across several industry sectors and material systems for metal recycling and sustainable manufacturing.

  4. Homogeneity of Surface Sites in Supported Single-Site Metal Catalysts: Assessment with Band Widths of Metal Carbonyl Infrared Spectra.

    Science.gov (United States)

    Hoffman, Adam S; Fang, Chia-Yu; Gates, Bruce C

    2016-10-06

    Determining and controlling the uniformity of isolated metal sites on surfaces of supports are central goals in investigations of single-site catalysts because well-defined species provide opportunities for fundamental understanding of the surface sites. CO is a useful probe of surface metal sites, often reacting with them to form metal carbonyls, the infrared spectra of which provide insights into the nature of the sites and the metal-support interface. Metals bonded to various support surface sites give broad bands in the spectra, and when narrow bands are observed, they indicate a high degree of uniformity of the metal sites. Much recent work on single-site catalysts has been done with supports that are inherently nonuniform, giving supported metal species that are therefore nonuniform. Herein we summarize values of ν CO data characterizing supported iridium gem-dicarbonyls, showing that the most nearly uniform of them are those supported on zeolites and the least uniform are those supported on metal oxides. Guided by ν CO data of supported iridium gem-dicarbonyls, we have determined new, general synthesis methods to maximize the degree of uniformity of iridium species on zeolites and on MgO. We report results for a zeolite HY-supported iridium gem-dicarbonyl with full width at half-maximum values of only 4.6 and 5.2 cm -1 characterizing the symmetric and asymmetric CO stretches and implying that this is the most nearly uniform supported single-site metal catalyst.

  5. Optimization of fuel cell membrane electrode assemblies for transition metal ion-chelating ordered mesoporous carbon cathode catalysts

    Directory of Open Access Journals (Sweden)

    Johanna K. Dombrovskis

    2014-12-01

    Full Text Available Transition metal ion-chelating ordered mesoporous carbon (TM-OMC materials were recently shown to be efficient polymer electrolyte membrane fuel cell (PEMFC catalysts. The structure and properties of these catalysts are largely different from conventional catalyst materials, thus rendering membrane electrode assembly (MEA preparation parameters developed for conventional catalysts not useful for applications of TM-OMC catalysts. This necessitates development of a methodology to incorporate TM-OMC catalysts in the MEA. Here, an efficient method for MEA preparation using TM-OMC catalyst materials for PEMFC is developed including effects of catalyst/ionomer loading and catalyst/ionomer-mixing and application procedures. An optimized protocol for MEA preparation using TM-OMC catalysts is described.

  6. Mechanical properties of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2007-01-01

    Full Text Available Background/Aim. Metal-ceramic bond strength and alloys' elastic modulus clearly determine the potential of alloy application, because the ceramic integrity during mastication depends on these two characteristics. The aim of this study was to evaluate metal-ceramic bond strength and elastic modulus of cobalt-chromium alloys in making porcelainfused- to-metal restorations, regarding the application of the most frequent nickel-chromium alloy. Methods. The research was performed as an experimental study. Six metalceramic samples were made from nickel-chromium alloy (Wiron 99 and cobalt-chromium alloy (Wirobond C, according to the manufactures manuals and instructions from ISO 9693: 1996. Three-point bending test was performed up to the ceramic fracture. The fracture load was measured on an universal testing machine (Zwick, type 1464, with cross-head speed of 0,05mm/min. Results. The results of this study confirmed the significant differences between the metal-ceramic bond strength (p < 0.01 and elastic modulus (p < 0.001 of nickel-chromium and cobalt-chromium alloys, where cobalt-chromium alloys showed higher values for both tested parameters. Conclusion. Cobalt-chromium metal-ceramic alloys can successfully replace nickel-chromium alloys, especially for fabrication of long-span metal-ceramic bridges due to the great flexural strength.

  7. A combinatorial study on catalytic synergism in supported metal catalysts for fuel cell technology

    Science.gov (United States)

    Kobayashi, Tetsuhiko; Ueda, Atsushi; Yamada, Yusuke; Shioyama, Hiroshi

    2004-02-01

    In order to accelerate the catalyst development for the increasing demand on the fuel cell technology, it has been attempted to adopt a combinatorial approach. The catalytic synergism, often observed on the supported metal catalysts for the fuel cell utilization, has been subjected to study. It is proposed herein that not only a comparison of catalysts in one reaction, but also the comparison of interrelated reactions by use of a common catalyst library brings about important information to elucidate the catalytic synergism. Preliminary results of the comparison between the water-gas shift reaction and the steam reforming of MeOH on a given set of catalyst library are presented. An important indicator to predict the serendipitous synergism is expected to be obtained from such information by use of artificial intelligence.

  8. Scalable shape- and size-controlled synthesis of metal nano-alloys

    KAUST Repository

    Bakr, Osman M.

    2016-01-21

    Embodiments of the present disclosure provide for a continuous-flow reactor, methods of making metal nano-alloys, and metal nano-alloys. An embodiment of the continuous-flow reactor includes a first tubular component having a tubular inlet and a tubular outlet, and a heated tube-in-tube gas reactor fluidly connected to the first tubular component, wherein the heated tube-in-tube gas reactor comprises an inner tube having a gas permeable surface and an outer tube. An embodiment of the method of producing metal nano-alloys, includes contacting a reducible metal precursor and a reducing fluid in a continuous-flow reactor to form a mixed solution; and flowing the mixed solution through the continuous-flow reactor for a residence time to form the metal nano-alloys. An embodiment of the composition includes a plurality of metal nano-alloys having a monodisperse size distribution and a uniform shape distribution.

  9. Effect of metal primers and tarnish treatment on bonding between dental alloys and veneer resin.

    Science.gov (United States)

    Choo, Seung-Sik; Huh, Yoon-Hyuk; Cho, Lee-Ra; Park, Chan-Jin

    2015-10-01

    The aim of this study was to evaluate the effect of metal primers on the bonding of dental alloys and veneer resin. Polyvinylpyrrolidone solution's tarnish effect on bonding strength was also investigated. Disk-shape metal specimens (diameter 8 mm, thickness 1.5 mm) were made from 3 kinds of alloy (Co-Cr, Ti and Au-Ag-Pd alloy) and divided into 4 groups per each alloy. Half specimens (n=12 per group) in tarnished group were immersed into polyvinylpyrrolidone solution for 24 hours. In Co-Cr and Ti-alloy, Alloy Primer (MDP + VBATDT) and MAC-Bond II (MAC-10) were applied, while Alloy Primer and V-Primer (VBATDT) were applied to Au-Ag-Pd alloys. After surface treatment, veneering composite resin were applied and shear bond strength test were conducted. Alloy Primer showed higher shear bond strength than MAC-Bond II in Co-Cr alloys and Au-Ag-Pd alloy (PAg-Pd alloy surfaces presented significantly decreased shear bond strength. Combined use of MDP and VBATDT were effective in bonding of the resin to Co-Cr and Au-Ag-Pd alloy. Tarnish using polyvinylpyrrolidone solution negatively affected on the bonding of veneer resin to Co-Cr and Au-Ag-Pd alloys.

  10. Enhancement of surface integrity of titanium alloy with copper by means of laser metal deposition process

    CSIR Research Space (South Africa)

    Erinosho, MF

    2016-04-01

    Full Text Available The laser metal deposition process possesses the combination of metallic powder and laser beam respectively. However, these combinations create an adhesive bonding that permanently solidifies the laser-enhanced-deposited powders. Titanium alloys (Ti...

  11. Synthesis, Characterizations, and Applications of Metal-Ions Incorporated High Quality MCM-41 Catalysts

    International Nuclear Information System (INIS)

    Lim, Steven S.; Haller, Gary L.

    2013-01-01

    Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically V 5+ , Co 2+ , and Ni 2+ -incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated

  12. Gallium-rich Pd-Ga phases as supported liquid metal catalysts

    Science.gov (United States)

    Taccardi, N.; Grabau, M.; Debuschewitz, J.; Distaso, M.; Brandl, M.; Hock, R.; Maier, F.; Papp, C.; Erhard, J.; Neiss, C.; Peukert, W.; Görling, A.; Steinrück, H.-P.; Wasserscheid, P.

    2017-09-01

    A strategy to develop improved catalysts is to create systems that merge the advantages of heterogeneous and molecular catalysis. One such system involves supported liquid-phase catalysts, which feature a molecularly defined, catalytically active liquid film/droplet layer adsorbed on a porous solid support. In the past decade, this concept has also been extended to supported ionic liquid-phase catalysts. Here we develop this idea further and describe supported catalytically active liquid metal solutions (SCALMS). We report a liquid mixture of gallium and palladium deposited on porous glass that forms an active catalyst for alkane dehydrogenation that is resistant to coke formation and is thus highly stable. X-ray diffraction and X-ray photoelectron spectroscopy, supported by theoretical calculations, confirm the liquid state of the catalytic phase under the reaction conditions. Unlike traditional heterogeneous catalysts, the supported liquid metal reported here is highly dynamic and catalysis does not proceed at the surface of the metal nanoparticles, but presumably at homogeneously distributed metal atoms at the surface of a liquid metallic phase.

  13. Allergic reactions associated with metal alloys in porcelain-fused-to-metal fixed prosthodontic devices-A systematic review.

    Science.gov (United States)

    Levi, Lauren; Barak, Shlomo; Katz, Joseph

    2012-01-01

    To systematically review the allergic reactions associated with metal alloys in porcelain-fused-to-metal (PFM) fixed prosthetic devices. After reviewing the titles and abstracts of the articles as well as removing duplicates, 22 articles were considered relevant. PubMed, Web of Science, ScienceDirect, and Google Scholar from 1970 to 2012 were evaluated, and randomized studies, review articles, case reports, cross-sectional surveys, and abstracts were included. Conference papers and posters were excluded. Although reported, allergic reactions to metallic alloys in the context of PFM devices are not well documented. Allergic reactions to high noble and noble metal alloy cores of palladium and gold and to base metal alloys nickel and cobalt in the context of PFM fixed partial dentures (FPDs) are reported. Each type of metal is associated with a different rate of allergic reactions, which may be attributed to the extent of corrosion of the alloy, population exposure, and the biologic environment. Because few studies document allergic reactions to metals that comprise PFM crowns and partial dentures, further research in this field is necessary to determine the frequency and type of reactions elicited. Though allergic reactions to metal alloys used in dentistry are well documented, only few articles focus on the correlation between FPDs and metal allergies. Thus, this paper surveys case reports of hypersensitivity reactions linked to FPDs and reviews the current literature on allergic reactions to the metallic elements comprising those devices.

  14. Quantification of zinc atoms in a surface alloy on copper in an industrial-type methanol synthesis catalyst

    DEFF Research Database (Denmark)

    Kuld, Sebastian; Moses, Poul Georg; Sehested, Jens

    2014-01-01

    Methanol has recently attracted renewed interest because of its potential importance as a solar fuel. Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of Zn......O as a promoter for this type of catalyst is still under intense debate. Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial-type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent...... where metal-support interactions are important, and this work generally addresses the role of the carrier and the nature of the interactions between carrier and metal in heterogeneous catalysts....

  15. Potential of a Hydrometallurgical Recycling Process for Catalysts to Cover the Demand for Critical Metals, Like PGMs and Cerium

    Science.gov (United States)

    Steinlechner, Stefan; Antrekowitsch, Jürgen

    2015-02-01

    The metals from the platinum group are used in many different industries, for example dental, jewelry, and chemicals. Nevertheless, the most important use is based on their catalytic properties. Approximately 50% of platinum and palladium are used as automotive and industrial catalysts. In case of rhodium, an even higher percentage (around 80-90%) is used as an alloying element in the active layer of different catalysts. The high required amount of 300-900 kg of treated ore to obtain approximately 1 g of PGM is responsible for the high prices. On average, the contents in the ore of Pt and Pd are 5-10 times higher than Rh and Ru and around 50 times higher than Ir and Os. Additionally, the regional limitation of ore bodies leads to a strong dependence on mainly South Africa and Russia as PGM suppliers. Based on the strong discrepancy in supply and demand of PGM's around the world, recycling of catalysts is mandatory and meaningful from the ecological and economical point of view. Based on the high prices of PGM, the industry is forced to improve the efficiency of catalysts, which is done by improving the wash coat technology. By using rare-earth elements, like cerium oxide, the surface can be increased and the ability to supply oxygen is secured. As a side effect, cerium as an additional critical element is introduced into the recycling circuit of catalytic converters, forming a further valuable component and forming a major challenge for common pyrometallurgical converter recycling. Therefore, this article introduces a hydrometallurgical process, developed together with Railly&Hill Inc., for PGM as well as cerium recovery from catalytic converters.

  16. Removal Of Phenol From Wastewater By Using Low-Cost Catalyst From Metal Production

    Directory of Open Access Journals (Sweden)

    Galbičková Blanka

    2014-12-01

    Full Text Available Utilization of AOPs (Advanced oxidation processes as an emerging technology for removing of pollutants from wastewater is developed. In this paper, UV photodegradation was used for removing of phenol from wastewater. As a source of UV radiation medium pressure mercury lamp with output 400W was used. The influence of low-cost catalysts on this process was also monitored. Wastes from metal production, red mud and black nickel mud, were used as catalysts.

  17. Removal Of Phenol From Wastewater By Using Low-Cost Catalyst From Metal Production

    Science.gov (United States)

    Galbičková, Blanka; Soldán, Maroš; Belčík, Michal; Balog, Karol

    2014-12-01

    Utilization of AOPs (Advanced oxidation processes) as an emerging technology for removing of pollutants from wastewater is developed. In this paper, UV photodegradation was used for removing of phenol from wastewater. As a source of UV radiation medium pressure mercury lamp with output 400W was used. The influence of low-cost catalysts on this process was also monitored. Wastes from metal production, red mud and black nickel mud, were used as catalysts.

  18. Metal Injection Molding (MIM of Magnesium and Its Alloys

    Directory of Open Access Journals (Sweden)

    Martin Wolff

    2016-05-01

    Full Text Available Current research has highlighted that magnesium and its alloys as biodegradable material are highly suitable for biomedical applications. The new material fully degrades into nontoxic elements and offers material properties matching those of human bone tissue. As biomedical implants are rather small and complex in shape, the metal injection molding (MIM technique seems to be well suited for the near net shape mass production of such parts. Furthermore, MIM of Mg-alloys is of high interest in further technical fields. This study focusses on the performance of MIM-processing of magnesium alloy powders. It includes Mg-specific development of powder blending, feedstock preparation, injection molding, solvent and thermal debinding and final sintering. Even though Mg is a highly oxygen-affine material forming a stable oxide layer on each particle surface, the material can be sintered to nearly dense parts, providing mechanical properties matching those of as cast material. An ultimate tensile strength of 142 MPa, yield strength of 67 MPa, elastic modulus of 40 GPa and 8% elongation at fracture could be achieved using novel organic polymer binders for the feedstock preparation. Thus, first implant demonstrator parts could be successfully produced by the MIM technique.

  19. Stable iridium dinuclear heterogeneous catalysts supported on metal-oxide substrate for solar water oxidation.

    Science.gov (United States)

    Zhao, Yanyan; Yang, Ke R; Wang, Zechao; Yan, Xingxu; Cao, Sufeng; Ye, Yifan; Dong, Qi; Zhang, Xizi; Thorne, James E; Jin, Lei; Materna, Kelly L; Trimpalis, Antonios; Bai, Hongye; Fakra, Sirine C; Zhong, Xiaoyan; Wang, Peng; Pan, Xiaoqing; Guo, Jinghua; Flytzani-Stephanopoulos, Maria; Brudvig, Gary W; Batista, Victor S; Wang, Dunwei

    2018-03-05

    Atomically dispersed catalysts refer to substrate-supported heterogeneous catalysts featuring one or a few active metal atoms that are separated from one another. They represent an important class of materials ranging from single-atom catalysts (SACs) and nanoparticles (NPs). While SACs and NPs have been extensively reported, catalysts featuring a few atoms with well-defined structures are poorly studied. The difficulty in synthesizing such structures has been a critical challenge. Here we report a facile photochemical method that produces catalytic centers consisting of two Ir metal cations, bridged by O and stably bound to a support. Direct evidence unambiguously supporting the dinuclear nature of the catalysts anchored on α-Fe 2 O 3 is obtained by aberration-corrected scanning transmission electron microscopy (AC-STEM). Experimental and computational results further reveal that the threefold hollow binding sites on the OH-terminated surface of α-Fe 2 O 3 anchor the catalysts to provide outstanding stability against detachment or aggregation. The resulting catalysts exhibit high activities toward H 2 O photooxidation.

  20. Comparison of nickel molybdenum hydrous metal oxides with commercial catalysts for HDS/HDN of coal liquids

    Energy Technology Data Exchange (ETDEWEB)

    Lott, S.E.; Gardner, T.J.; McLaughlin, L.I.; Oelfke, J.B.

    1994-06-01

    Improved efficiency in direct coal liquefaction processes can be obtained by developing catalysts with better activity, selectivity, and life. In previous exploratory research at Sandia National Laboratories, catalysts prepared via hydrous metal oxide (HMO) ion exchangers have been shown to have potential for application to a number of reactions associated with the conversion of coal to liquid fuels. In the present effort, one member of this class of catalysts, hydrous titanium oxide (HTO), has been used to develop catalysts for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of coal liquids. For HYD of pyrone, unsupported NiMoHTO catalysts performed better than commercial benchmark catalysts on either a catalyst weight or active metals basis. In a side-by-side comparison of supported NiMoHTO catalysts with commercial counterparts, the supported NiMoHTO catalysts outperformed the Shell 324 and Amocat 1C catalysts for HYD of pyrene. For HDS/HDN of coal liquids, the supported and bulk forms of the NiMoHTO catalysts equaled the performance of the commercial catalysts at 500, 1000, and 1500 psig while containing less active metals. Possible reasons for the high activity of the NiMoHTO catalysts are a high dispersion of the active MoS{sub 2} phase and a high acidity of the bulk NiMoHTO.

  1. In Situ Fabrication of PtCo Alloy Embedded in Nitrogen-Doped Graphene Nanopores as Synergistic Catalyst for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Xing; Wang, Lei; Zhou, Hu; Qin, Yingying; Xu, Wenlei; Jiang, Yu; Sun, Youyi; Shi, Zheqi; Zhuang, Guilin; Li, Xiaonian; Mei, Donghai; Wang, Jian-guo

    2015-11-23

    A novel PtCo alloy in situ etched and embedded in graphene nanopores (PtCo/NPG) as a high-performance catalyst for ORR was reported. Graphene nanopores were fabricated in situ while forming PtCo nanoparticles that were uniformly embedded in the graphene nanopores. Given the synergistic effect between PtCo alloy and nanopores, PtCo/NPG exhibited 11.5 times higher mass activity than that of the commercial Pt/C cathode electrocatalyst. DFT calculations indicated that the nanopores in NPG cannot only stabilize PtCo nanoparticles but can also definitely change the electronic structures, thereby change its adsorption abilities. This enhancement can lead to a favorable reaction pathway on PtCo/NPG for ORR. This study showed that PtCo/NPG is a potential candidate for the next generation of Pt-based catalysts in fuel cells. This study also offered a promising alternative strategy and enabled the fabrication of various kinds of metal/graphene nanopore nanohybrids with potential applications in catalysts and potential use for other technological devices. The authors acknowledge the financial support from the National Basic Research Program (973 program, No. 2013CB733501), Zhejiang Provincial Education Department Research Program (Y201326554) and the National Natural Science Foundation of China (No. 21306169, 21101137, 21136001, 21176221 and 91334013). D. Mei acknowledges the support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) and by the National Energy Research Scientific Computing Center (NERSC).

  2. Metallic Thin-Film Bonding and Alloy Generation

    Science.gov (United States)

    Fryer, Jack Merrill (Inventor); Campbell, Geoff (Inventor); Peotter, Brian S. (Inventor); Droppers, Lloyd (Inventor)

    2016-01-01

    Diffusion bonding a stack of aluminum thin films is particularly challenging due to a stable aluminum oxide coating that rapidly forms on the aluminum thin films when they are exposed to atmosphere and the relatively low meting temperature of aluminum. By plating the individual aluminum thin films with a metal that does not rapidly form a stable oxide coating, the individual aluminum thin films may be readily diffusion bonded together using heat and pressure. The resulting diffusion bonded structure can be an alloy of choice through the use of a carefully selected base and plating metals. The aluminum thin films may also be etched with distinct patterns that form a microfluidic fluid flow path through the stack of aluminum thin films when diffusion bonded together.

  3. Hydrogen production by steam reforming of acetic acid: Comparison of conventional supported metal catalysts and metal-incorporated mesoporous smectite-like catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Iwasa, Nobuhiro; Yamane, Toshiyuki; Arai, Masahiko [Division of Chemical Process Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Takei, Masaaki; Ozaki, Jun-ichi [Department of Chemical and Environmental Engineering, Graduate School of Engineering, Gunma University, Kiryu 376-8515 (Japan)

    2010-01-15

    The activities of various metal catalysts were tested in steam reforming of acetic acid for the production of H{sub 2}, using conventional metal oxides and transition metal-incorporated mesoporous smectite-like materials as supports. It has been found that Pt is superior to Ni, Co, and Fe among Al{sub 2}O{sub 3} supported catalysts, Al{sub 2}O{sub 3} is more effective than ZrO{sub 2} and SiO{sub 2} as support for Pt, Ni incorporated smectite (SM(Ni)) support is more effective than Fe and Co incorporated ones for Pt, and SM(Ni) is also active in the absence of Pt. The total activity for the conversion of acetic acid is in the order of Pt/Al{sub 2}O{sub 3} > Pt/SM(Ni) > SM(Ni) but the ability of H{sub 2} production is comparable among these catalysts. These catalysts (and the other ones) were observed to lose their activities during the reforming reactions. The activity of Pt/Al{sub 2}O{sub 3} decreased during the whole course of reaction up to 10 h. In contrast, the activity of SM(Ni) also decreased within 2 h but it showed a stable activity in the following stage of reaction. The initial activity of the used Pt/SM(Ni) and SM(Ni) was able to be almost completely restored by thermal treatment with H{sub 2} but less effectively for the used Pt/Al{sub 2}O{sub 3}. The catalyst deactivation was shown to occur by the formation and deposition of carbon materials on the catalysts (XRD, TEM, thermal analysis). The properties of carbon deposits formed on Pt/Al{sub 2}O{sub 3} and SM(Ni) catalysts should be different and this may be responsible for the differences in the extent of deactivation and in the regeneration behavior between the two catalysts. (author)

  4. Investigation of irradiation strengthening of bcc metals and their alloys. Progress report, January 1977--October 1977

    International Nuclear Information System (INIS)

    1977-01-01

    Progress is reported in the areas of (a) the effect of neutron damage on the dislocation kinetics in bcc metals and their alloys, and (b) the effect of 3 He on the deformation characteristics of body centered cubic metals and their alloys. Results obtained from these projects are discussed

  5. On the resistivity of metal-tellurium alloys for low concentrations of tellurium

    International Nuclear Information System (INIS)

    Gorecki, J.

    1982-04-01

    The resistivity and thermoelectric power of metal-tellurium liquid alloys have been discussed for the case of small tellurium concentration. Nearly free electron model of conduction band has been used. The rapid increase of resistivity in transition metal-tellurium alloys has been predicted. (author)

  6. Mitigation of hydrogen by oxidation using nitrous oxide and noble metal catalysts

    International Nuclear Information System (INIS)

    Britton, M.D.

    1995-01-01

    This test studied the ability of a blend of nuclear-grade, noble-metal catalysts to catalyze a hydrogen/nitrous oxide reaction in an effort to mitigate a potential hydrogen (H 2 ) gas buildup in the Hanford Site Grout Disposal Facility. For gases having H 2 and a stoichiometric excess of either nitrous oxide or oxygen, the catalyst blend can effectively catalyze the H 2 oxidation reaction at a rate exceeding 380 μmoles of H 2 per hour per gram of catalyst (μmol/h/g) and leave the gas with less than a 0.15 residual H 2 Concentration. This holds true in gases with up to 2.25% water vapor and 0.1% methane. This should also hold true for gases with up to 0.1% carbon monoxide (CO) but only until the catalyst is exposed to enough CO to block the catalytic sites and stop the reaction. Gases with ammonia up to 1% may be slightly inhibited but can have reaction rates greater than 250 μmol/h/g with less than a 0.20% residual H 2 concentration. The mechanism for CO poisoning of the catalyst is the chemisorption of CO to the active catalyst sites. The CO sorption capacity (SC) of the catalyst is the total amount of CO that the catalyst will chemisorb. The average SC for virgin catalyst was determined to be 19.3 ± 2.0 μmoles of CO chemisorbed to each gram of catalyst (μmol/g). The average SC for catalyst regenerated with air was 17.3 ± 1.9 μmol/g

  7. Evaluation of different finish line designs in base metal alloys

    Directory of Open Access Journals (Sweden)

    Aghandeh R

    1999-06-01

    Full Text Available This investigation was performed according to the widespread application of base metal alloys"nand few articles published about the marginal integrity of restorations fabricated by these metals."nThree standard dies of a maxillary first premolar were prepared with a flat shoulder finish line in buccal"naspect and chamfer in palatal. One of them left with no change. On the buccal aspect of the second and"nthird dies 135?and 1607 bevel were added respectively"nUsing dual wax technique, nine wax patterns were formed on each die and casting procedure of selected"nnon precious alloy was performed by centrifugal method. Marginal gaps of each copping seated on dies"nwere measured by scanning electron microscope (SEM with X500 magnification. Measurements were"ndone on three areas of marked dies on buccal aspect. Measurement son palatal aspect was done on"nmarked midpalatal point as control."nResults and statistical analysis showed no significant difference among marginal gaps in lingual aspect."nBut on the buccal aspect there were statistically significant differences among the groups (P<0.001. Flat"nshoulder had the best marginal integrity (mean 4 micron. Shoulder with 160' bevel had the most marginal"ngap (mean 26.5 micron and shoulder with 1357 bevel was between two other groups (mean 15.7 micron.

  8. Thermodynamic studies on molybdenum-noble metal alloys

    International Nuclear Information System (INIS)

    Yamawaki, M.; Kanno, M.

    1979-01-01

    Electromotive force cells have been used to determine the activities of molybdenum for Mo-Pd, Mo-Rh and Mo-Ru-Pd alloys over the temperature range 1200-1300K, and thermodynamic functions were derived from the results. Solid ZrO 2 -11 mol-% CaO was used as the electrolyte. In ternary Mo-Rud-Pd alloy the ratio Ru:Pd was fixed to 72,5:27.5 in atomic % in order to simulate the white metallic inclusions in irradiated (U, Pu)O 2 fuel. Activities of molybdenum showed negative deviations from Raoult's law in the composition range where the atomic fraction of molybdenum Nsub(Mo) being less than about 0.3, and then positive deviations in the intermediate Nsub(Mo) range. It was shown that the estimation of activities of molybdenum in the white metallic inclusions based on the regular solution approximation were generally fairly good, but might lead to error in the intermediate and higher Nsub(Mo) ranges. Standard Gibbs energy of formation of Mo-Rh intermetallic epsilon phase was shown to be negatively larger than those of some other Mo intermetallic phases, showing higher thermodynamic stability of this phase. (orig.) [de

  9. Ultrashort pulse laser machining of metals and alloys

    Science.gov (United States)

    Perry, Michael D.; Stuart, Brent C.

    2003-09-16

    The invention consists of a method for high precision machining (cutting, drilling, sculpting) of metals and alloys. By using pulses of a duration in the range of 10 femtoseconds to 100 picoseconds, extremely precise machining can be achieved with essentially no heat or shock affected zone. Because the pulses are so short, there is negligible thermal conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond approximately 0.1-1 micron (dependent upon the particular material) from the laser machined surface. Due to the short duration, the high intensity (>10.sup.12 W/cm.sup.2) associated with the interaction converts the material directly from the solid-state into an ionized plasma. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces with negligible redeposition either within the kerf or on the surface. Since there is negligible heating beyond the depth of material removed, the composition of the remaining material is unaffected by the laser machining process. This enables high precision machining of alloys and even pure metals with no change in grain structure.

  10. Near-infrared two-color pyrometer for determining ignition temperatures of metals and metal alloys

    Science.gov (United States)

    Nguyen, K.; Branch, M. C.

    1985-01-01

    A two-color pyrometer has been designed, constructed, and used to measure the ignition temperatures of metals and metal alloys. Cylindrical metal and metal alloy specimens were ignited by a focused cw CO2 laser beam in a cool, static, pure oxygen environment. The pyrometer operates in the near-infrared at two narrow spectral regions, with a nominal bandwidth of 10 nm centered at 0.9051 and 1.06 micron, and has a temperature range from 1000 to 4000 K. In the present design the temperature of a spot, about 0.5 mm in diameter, can be recorded with a maximum time resolution of 25 microseconds and with an accuracy of a few percent. Results of CO2 laser ignition of cylindrical specimens of 6061 aluminum alloy and 302 SS in a pure oxygen environment were obtained from the two-color pyrometer and were compared with those obtained from a thermocouple placed inside the specimen near the laser-irradiated surface.

  11. Water Oxidation Mechanisms of Metal Oxide Catalysts by Vibrational Spectroscopy of Transient Intermediates

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Miao [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division; Univ. of California, Berkeley, CA (United States); Frei, Heinz [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Univ. of California, Berkeley, CA (United States)

    2017-02-22

    Water oxidation is an essential reaction of an artificial photosystem for solar fuel generation because it provides electrons needed to reduce carbon dioxide or protons to a fuel. Earth-abundant metal oxides are among the most attractive catalytic materials for this reaction because of their robustness and scalability, but their efficiency poses a challenge. Knowledge of catalytic surface intermediates gained by vibrational spectroscopy under reaction conditions plays a key role in uncovering kinetic bottlenecks and provides a basis for catalyst design improvements. Recent dynamic infrared and Raman studies reveal the molecular identity of transient surface intermediates of water oxidation on metal oxides. In conclusion, combined with ultrafast infrared observations of how charges are delivered to active sites of the metal oxide catalyst and drive the multielectron reaction, spectroscopic advances are poised to play a key role in accelerating progress toward improved catalysts for artificial photosynthesis.

  12. Esterification of phenyl acetic acid withp-cresol using metal cation exchanged montmorillonite nanoclay catalysts.

    Science.gov (United States)

    Bhaskar, M; Surekha, M; Suma, N

    2018-02-01

    The liquid phase esterification of phenyl acetic acid with p -cresol over different metal cation exchanged montmorillonite nanoclays yields p -cresyl phenyl acetate. Different metal cation exchanged montmorillonite nanoclays (M n +  = Al 3+ , Zn 2+ , Mn 2+ , Fe 3+ , Cu 2+ ) were prepared and the catalytic activity was studied. The esterification reaction was conducted by varying molar ratio of the reactants, reaction time and catalyst amount on the yield of the ester. Among the different metal cation exchanged catalysts used, Al 3+ -montmorillonite nanoclay was found to be more active. The characterization of the material used was studied under different techniques, namely X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. The product obtained, p -cresyl phenyl acetate, was identified by thin-layer chromotography and confirmed by Fourier transform infrared, 1 H NMR and 13 C NMR. The regeneration activity of used catalyst was also investigated up to fourth generation.

  13. Directed light fabrication of refractory metals and alloys

    International Nuclear Information System (INIS)

    Fonseca, J.C.; Lewis, G.K.; Dickerson, P.G.; Nemec, R.B.

    1999-01-01

    This report covers deposition of refractory pure metals and alloys using the Directed Light Fabrication (DLF) process and represents progress in depositing these materials through September 1998. In extending the DLF process technology to refractory metals for producing fully dense, structurally sound deposits, several problems have become evident. (1) Control of porosity in DLF-deposited refractory metal is difficult because of gases, apparently present in commercially purchased refractory metal powder starting materials. (2) The radiant heat from the molten pool during deposition melts the DLF powder feed nozzle. (3) The high reflectivity of molten refractory metals, at the Nd-YAG laser wavelength (1.06microm), produces damaging back reflections to the optical train and fiber optic delivery system that can terminate DLF processing. (4) The current limits on the maximum available laser power to prevent back reflection damage limit the parameter range available for densification of refractory metals. The work to date concentrated on niobium, W-25Re, and spherodized tungsten. Niobium samples, made from hydride-dehydride powder, had minimal gas porosity and the deposition parameters were optimized; however, test plates were not made at this time. W-25Re samples, containing sodium and potassium from a precipitation process, were made and porosity was a problem for all samples although minimized with some process parameters. Deposits made from potassium reduced tungsten that was plasma spherodized were made with minimized porosity. Results of this work indicate that further gas analysis of starting powders and de-gassing of starting powders and/or gas removal during deposition of refractory metals is required

  14. Study of Metal-Humic Catalysts before and After the Gas Desulphurization Process Using Thermal Analysis

    Science.gov (United States)

    Szyszka, Danuta; Wieckowska, Jadwiga

    2017-12-01

    The study of metal-humic catalysts before and after the SO2 conversion has been carried out using thermal analysis. The thermogravimetric analysis and differential thermal analysis has been carried out using Perkin-Elmer TGA 7 and DTA 7 equipment in an argonic atmosphere. The heating rate of samples in the DTA was 10 °C/min., and in the TGA 40 °C/min. The following catalysts have been chosen for analysis: H-Pb2+/450 °C, H-B/450 °C, H-Sn2+/450 °C, H-Ce 4+. The study of metal-humic catalysts using thermal analysis has shown that, in the DTA curves of studied catalysts before SO2 conversion, endothermic peaks related to decomposition of metal carbonates, melting of metals or decomposition of metal-humic bonding. In the DTA curves after the SO2 conversion process, there are additional endothermic peaks related to the presence of sulphur in the metal-humic compounds and to thermal decomposition of those bonds.

  15. Influence of S. mutans on base-metal dental casting alloy toxicity.

    Science.gov (United States)

    McGinley, E L; Dowling, A H; Moran, G P; Fleming, G J P

    2013-01-01

    We have highlighted that exposure of base-metal dental casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) dental casting alloys were shown to leach elevated levels of metal ions compared with untreated dental casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated dental casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p dental casting alloys induced elevated levels of cellular toxicity compared with S. mutans-treated Co-Cr-based dental casting alloys. While our findings indicated that the exacerbated release of metal ions from S. mutans-treated base-metal dental casting alloys was the likely result of the pH reduction during S. mutans growth, the exact nature of mechanisms leading to accelerated dissolution of alloy-discs is not yet fully understood. Given the predominance of S. mutans oral carriage and the exacerbated cytotoxicity observed in TR146 cells following exposure to S. mutans-treated base-metal dental casting alloys, the implications for the long-term stability of base-metal dental restorations in the oral cavity are a cause for concern.

  16. The evaluation of the use of metal alloy fuels in pressurized water reactors

    International Nuclear Information System (INIS)

    Lancaster, D.

    1992-01-01

    The use of metal alloy fuels in a PWR was investigated. It was found that it would be feasible and competitive to design PWRs with metal alloy fuels but that there seemed to be no significant benefits. The new technology would carry with it added economic uncertainty and since no large benefits were found it was determined that metal alloy fuels are not recommended. Initially, a benefit was found for metal alloy fuels but when the oxide core was equally optimized the benefit faded. On review of the optimization of the current generation of ''advanced reactors,'' it became clear that reactor design optimization has been under emphasized. Current ''advanced reactors'' are severely constrained. The AP-600 required the use of a fuel design from the 1970's. In order to find the best metal alloy fuel design, core optimization became a central effort. This work is ongoing

  17. The evaluation of the use of metal alloy fuels in pressurized water reactors. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lancaster, D.

    1992-10-26

    The use of metal alloy fuels in a PWR was investigated. It was found that it would be feasible and competitive to design PWRs with metal alloy fuels but that there seemed to be no significant benefits. The new technology would carry with it added economic uncertainty and since no large benefits were found it was determined that metal alloy fuels are not recommended. Initially, a benefit was found for metal alloy fuels but when the oxide core was equally optimized the benefit faded. On review of the optimization of the current generation of ``advanced reactors,`` it became clear that reactor design optimization has been under emphasized. Current ``advanced reactors`` are severely constrained. The AP-600 required the use of a fuel design from the 1970`s. In order to find the best metal alloy fuel design, core optimization became a central effort. This work is ongoing.

  18. Ceria doped mixed metal oxide nanoparticles as oxidation catalysts: Synthesis and their characterization

    Directory of Open Access Journals (Sweden)

    S.S.P. Sultana

    2015-11-01

    Full Text Available Mixed metal nanoparticles (NPs have attracted significant attention as catalysts for various organic transformations. In this study, we have demonstrated the preparation of nickel–manganese mixed metal oxide NPs doped with X% nano cerium oxide (X = 1, 3, 5 mol% by a facile co-precipitation technique using surfactant and surfactant free methodologies. The as-synthesized materials were calcined at different temperatures (300 °C, 400 °C, and 500 °C, and were characterized using various spectroscopic techniques, including, FTIR and XRD. SEM analysis, TEM analysis and TGA were employed to evaluate the structural properties of the as-prepared catalyst. These were evaluated for their catalytic behaviour towards the conversion of benzyl alcohol to benzaldehyde, which was used as a model reaction with molecular oxygen as oxidant. Furthermore, the effect of the variation of the percentage of nano ceria doping and the calcination temperature on the performance of as-prepared mixed metal catalysts was also evaluated. The kinetic studies of the reactions performed employing gas chromatographic technique have revealed that the mixed metal oxide catalyst doped with 5% nano ceria displayed excellent catalytc activity, among various catalysts synthesized.

  19. Power generation in microbial fuel cells using platinum group metal-free cathode catalyst: Effect of the catalyst loading on performance and costs

    Science.gov (United States)

    Santoro, Carlo; Kodali, Mounika; Herrera, Sergio; Serov, Alexey; Ieropoulos, Ioannis; Atanassov, Plamen

    2018-02-01

    Platinum group metal-free (PGM-free) catalyst with different loadings was investigated in air breathing electrodes microbial fuel cells (MFCs). Firstly, the electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalyst was investigated by rotating ring disk electrode (RRDE) setup with different catalyst loadings. The results showed that higher loading led to an increased in the half wave potential and the limiting current and to a further decrease in the peroxide production. The electrons transferred also slightly increased with the catalyst loading up to the value of ≈3.75. This variation probably indicates that the catalyst investigated follow a 2x2e- transfer mechanism. The catalyst was integrated within activated carbon pellet-like air-breathing cathode in eight different loadings varying between 0.1 mgcm-2 and 10 mgcm-2. Performance were enhanced gradually with the increase in catalyst content. Power densities varied between 90 ± 9 μWcm-2 and 262 ± 4 μWcm-2 with catalyst loading of 0.1 mgcm-2 and 10 mgcm-2 respectively. Cost assessments related to the catalyst performance are presented. An increase in catalyst utilization led to an increase in power generated with a substantial increase in the whole costs. Also a decrease in performance due to cathode/catalyst deterioration over time led to a further increase in the costs.

  20. Power generation in microbial fuel cells using platinum group metal-free cathode catalyst: Effect of the catalyst loading on performance and costs.

    Science.gov (United States)

    Santoro, Carlo; Kodali, Mounika; Herrera, Sergio; Serov, Alexey; Ieropoulos, Ioannis; Atanassov, Plamen

    2018-02-28

    Platinum group metal-free (PGM-free) catalyst with different loadings was investigated in air breathing electrodes microbial fuel cells (MFCs). Firstly, the electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalyst was investigated by rotating ring disk electrode (RRDE) setup with different catalyst loadings. The results showed that higher loading led to an increased in the half wave potential and the limiting current and to a further decrease in the peroxide production. The electrons transferred also slightly increased with the catalyst loading up to the value of ≈3.75. This variation probably indicates that the catalyst investigated follow a 2x2e - transfer mechanism. The catalyst was integrated within activated carbon pellet-like air-breathing cathode in eight different loadings varying between 0.1 mgcm -2 and 10 mgcm -2 . Performance were enhanced gradually with the increase in catalyst content. Power densities varied between 90 ± 9 μWcm -2 and 262 ± 4 μWcm -2 with catalyst loading of 0.1 mgcm -2 and 10 mgcm -2 respectively. Cost assessments related to the catalyst performance are presented. An increase in catalyst utilization led to an increase in power generated with a substantial increase in the whole costs. Also a decrease in performance due to cathode/catalyst deterioration over time led to a further increase in the costs.

  1. Enantioselection on Heterogeneous Noble Metal Catalyst: Proline-Induced Asymmetry in the Hydrogenation of Isophorone on Pd Catalyst.

    Science.gov (United States)

    Rodríguez-García, Laura; Hungerbühler, Konrad; Baiker, Alfons; Meemken, Fabian

    2015-09-23

    In the (S)-proline-mediated asymmetric hydrogenation of isophorone (IP) on supported Pd catalyst, excellent enantioselectivity is achieved, with an enantiomeric excess of up to 99%. The role of the heterogeneous catalyst has been the subject of a controversial debate, and the current mechanistic understanding cannot explain the observed enantioselectivity of this catalytic system. The lack of in situ information about the role of the heterogeneous catalyst has prompted us to investigate the surface processes occurring at the methanol-Pd catalyst interface using attenuated total reflection infrared spectroscopy. Time-resolved monitoring of the homogeneous solution and of the catalytic solid-liquid interface coupled with catalytic data provides crucial information on the catalytically relevant enantiodifferentiating processes. While the condensation of IP and the corresponding chiral product 3,3,5-trimethylcyclohexanone with the chiral amine is connected to the enantiodifferentiation, it was found that the crucial enantioselectivity-controlling steps take place on the metal surface, and the reaction has to be classified as heterogeneous asymmetric hydrogenation. The presented spectroscopic and catalytic results provide strong evidence for the existence of two competing enantioselective processes leading to opposing enantioselection. Depending on surface coverage of the Pd catalyst, the reaction is controlled either by kinetic resolution ((S)-pathway) or by chiral catalysis ((R)-pathway). Steering the hydrogenation on the (R)-reaction pathway requires sufficient concentration of IP-(S)-proline condensate, as this chiral reactive intermediate becomes the most abundant surface species, inhibiting the competing kinetic resolution. The unraveled (R)-reaction pathway emphasizes an intriguing strategy for inducing chirality in heterogeneous asymmetric catalysis.

  2. Dispersed metal cluster catalysts by design. Synthesis, characterization, structure, and performance

    Energy Technology Data Exchange (ETDEWEB)

    Arslan, Ilke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dixon, David A. [Univ. of Alabama, Tuscaloosa, AL (United States); Gates, Bruce C. [Univ. of California, Davis, CA (United States); Katz, Alexander [Univ. of California, Berkeley, CA (United States)

    2015-09-30

    To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically—including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site—thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify

  3. Adsorbate-mediated strong metal-support interactions in oxide-supported Rh catalysts.

    Science.gov (United States)

    Matsubu, John C; Zhang, Shuyi; DeRita, Leo; Marinkovic, Nebojsa S; Chen, Jingguang G; Graham, George W; Pan, Xiaoqing; Christopher, Phillip

    2017-02-01

    The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal-support interactions can be exploited to optimize metal active-site properties are lacking. Here we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCO x ) on reducible oxide supports (TiO 2 and Nb 2 O 5 ) that induce oxygen-vacancy formation in the support and cause HCO x -functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO 2 -reduction selectivity.

  4. Metal catalyst in CVD growth of carbon nanotubes: role of chemical composition

    Science.gov (United States)

    Yazyev, Oleg V.; Pasquarello, Alfredo

    2010-01-01

    Using first principles methods, we systematically study the crucial steps of CVD growth of CNTs, the binding and the diffusion of the carbon feedstock as well as the nucleation of CNTs. Late transition (Ni, Pd, Pt) and coinage (Cu, Ag, Au) metal catalysts were investigated. For all metals, we considered various diffusion mechanisms including both surface and subsurface channels, finding the lowest activation barriers for carbon adatoms on nanoparticles of coinage metals. For these metals, our calculations further show that the diffusion is restricted to the nanoparticle surface when diatomic carbon is initially obtained from the decomposition of the precursor gas. From the binding energies of armchair and zigzag edges of CNT fragments, we infer a high preference for the growth of armchair CNTs. These results indicate that coinage metal catalysts, in particular Cu, favor CVD growth of CNTs at low temperatures and with narrow chirality distributions.

  5. 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

  6. Synthesis and characterization of metal oxide promoted alumina catalyst for biofuel production

    Science.gov (United States)

    Anisuzzaman, S. M.; Krishnaiah, D.; Bono, A.; Abang, S.; Sundang, M.; Suali, E.; Lahin, F. A.; Shaik Alawodeen, A.

    2016-06-01

    Alumina has been widely used as a support in catalysis process which owing to its extremely thermal and mechanical stability, high surface area, large pore size and pore volume. The aim of this study was to synthesize calcium oxide-supported basic alumina catalysts (CaO/Al2O3) by impregnation method and to characterize the properties of the catalyst based on its surface area and porosity, functional group, surface morphology and particle size. Impregnation method was chosen for the synthesization of catalyst which involved contacting the support with the impregnating solution for a particular period of time, drying the support to remove the imbibed liquid and calcination process. In the preparation of catalyst, catalytic performance of CaO/Al2O3 catalyst was measured at different calcined temperatures (650°C, 750°C and 800°C). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Mercury intrusion porosimetry (MIP), and particle size analyzer (Zetasizer) was used to characterize the catalyst. The highest total specific area and the total porosity of the catalyst was obtained at 750oC. FTIR analysis basically studied on the functional groups present in each catalyst synthesized, while SEM analysis was observed to have pores on its surface. Moreover, CaO/Al2O3 catalysts at 650°C produced the smallest particle size (396.1 mn), while at 750°C produced the largest particle size (712.4 mn). Thus it can be concluded that CaO/Al2O3 catalysts has great potential coimnercialization since CaO has attracted many attentions compared to other alkali earth metal oxides especially on the transesterification reaction.

  7. Wire gauze and cordierite supported noble metal catalysts for passive autocatalytic recombiner

    International Nuclear Information System (INIS)

    Sanap, Kiran K.; Varma, S.; Waghmode, S.B.; Bharadwaj, S.R.

    2015-01-01

    Highlights: • Synthesis by electroless deposition method and chemical reduction route. • Particle size of 0.1–0.5 μm & 3.5–5 nm for Pt–Pd/Wg & Pt–Pd/Cord catalysts. • Active for H 2 and O 2 reaction with initial H 2 concentration of 1.5 to 7% in air. • Active in presence of different contaminants like CO 2 , CH 4 , CO & relative humidity. • Enhanced resistance of Pt–Pd/Cord catalyst towards the poisoning of CO. - Abstract: Hydrogen released in nuclear reactor containment under severe accident scenario poses a threat to containment and hence needs to be regulated by catalytic recombination. Mixed noble metal catalysts with platinum–palladium supported on stainless steel wire gauze and cordierite support have been developed for this purpose. The developed catalysts have been found to be highly efficient for removal of hydrogen concentration in the range of 1.5 to 7.0% v/v in air. Though both the catalysts exhibit similar kinetics for lower hydrogen concentration, cordierite supported catalysts exhibits better kinetic rate at higher hydrogen concentration. The performances of these catalysts in presence of various probable catalytic poison like carbon monoxide and catalytic inhibitors like moisture, carbon dioxide, and hydrocarbons provide data for use of these catalysts under the actual scenario. Compared to stainless steel wire gauze supported catalyst, the cordierite based catalyst are found to exhibit enhanced resistance towards carbon monoxide and limited temperature rise for safer application at higher hydrogen concentrations.

  8. 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.

  9. Engineering catalyst microenvironments for metal-catalyzed hydrogenation of biologically derived platform chemicals.

    Science.gov (United States)

    Schwartz, Thomas J; Johnson, Robert L; Cardenas, Javier; Okerlund, Adam; Da Silva, Nancy A; Schmidt-Rohr, Klaus; Dumesic, James A

    2014-11-17

    It is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur-containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA-overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA-overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Addressing aquatic hazard classification for metals, metal compounds and alloys in marine systems.

    Science.gov (United States)

    Huntsman-Mapila, P; Skeaff, J M; Pawlak, M; Beaudoin, R

    2016-08-15

    New International Maritime Organization regulations require shippers to classify all solid bulk cargo to indicate whether they are Harmful to the Marine Environment (HME). The objective of this work was to adapt the freshwater Transformation/Dissolution Protocol (T/DP) to marine water to provide a method to determine, when compared with marine Ecotoxicity Reference Values (ERVs), whether a metal-bearing substance is HME. The substances examined were: Cu2O powder; Ni metal powder; Co3O4 powder; and a Ni-Co-Fe alloy, as wire cuttings, which were the same substances examined in the freshwater T/D validation study and afforded comparisons of the reactivity, or measure of the rate and extent of metal release from the metal-bearing substances in freshwater versus marine conditions. The marine T/D method is suitable for conducting examinations of metal-bearing substances with a wide range of reactivities, from the relatively reactive Cu2O powder and the alloy to the Co3O4 powder, which was the least reactive. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  11. High quality syngas production from microwave pyrolysis of rice husk with char-supported metallic catalysts.

    Science.gov (United States)

    Zhang, Shuping; Dong, Qing; Zhang, Li; Xiong, Yuanquan

    2015-09-01

    This study aimed to obtain the maximum possible gas yield and the high quality syngas production from microwave pyrolysis of rice husk with rice husk char and rice husk char-supported metallic (Ni, Fe and Cu) catalysts. The rice husk char-supported metallic catalysts had developed pore structure and catalytic activity for gas productions and tar conversion. The temperature-rising characteristic, product yields, properties of gas products and tar conversion mechanisms were investigated. It was found that three rice husk char-supported metallic catalysts improved the microwave absorption capability and increased heating rate and final temperature. Rice husk char-supported Ni catalyst presented most effective effects on gas production, e.g. the gas yield is 53.9%, and the volume concentration of desired syngas is 69.96%. Rice husk char-supported Ni and Fe catalysts played pivotal roles in tar conversion that less heavy compounds can be detected along with the reduction of organic compound number. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Two-dimensional metallic tantalum disulfide as a hydrogen evolution catalyst.

    Science.gov (United States)

    Shi, Jianping; Wang, Xina; Zhang, Shuai; Xiao, Lingfeng; Huan, Yahuan; Gong, Yue; Zhang, Zhepeng; Li, Yuanchang; Zhou, Xiebo; Hong, Min; Fang, Qiyi; Zhang, Qing; Liu, Xinfeng; Gu, Lin; Liu, Zhongfan; Zhang, Yanfeng

    2017-10-16

    Two-dimensional metallic transition metal dichalcogenides are emerging as prototypes for uncovering fundamental physical phenomena, such as superconductivity and charge-density waves, as well as for engineering-related applications. However, the batch production of such envisioned transition metal dichalcogenides remains challenging, which has hindered the aforementioned explorations. Herein, we fabricate thickness-tunable tantalum disulfide flakes and centimetre-sized ultrathin films on an electrode material of gold foil via a facile chemical vapour deposition route. Through temperature-dependent Raman characterization, we observe the transition from nearly commensurate to commensurate charge-density wave phases with our ultrathin tantalum disulfide flakes. We have obtained high hydrogen evolution reaction efficiency with the as-grown tantalum disulfide flakes directly synthesized on gold foils comparable to traditional platinum catalysts. This work could promote further efforts for exploring new efficient catalysts in the large materials family of metallic transition metal dichalcogenides, as well as exploiting their applications towards more versatile applications.Metallic transition metal dichalcogenides are important materials for catalysis, but scalable and controllable preparation methods are scarce. Here, the authors synthesize 2H-TaS 2 as centimetre-scale films of tunable thickness and show they are an efficient catalyst for hydrogen evolution.

  13. Supported transition metal catalysts for para- to ortho-hydrogen conversion

    Science.gov (United States)

    Brooks, Christopher J.; Wang, Wei; Eyman, Darrell P.

    1994-01-01

    The main goal of this study was to develop and improve on existing catalysts for the conversion of ortho- to para-hydrogen. Starting with a commercially available Air Products nickel silicate, which had a beta value of 20, we were trying to synthesize catalysts that would be an improvement to AP. This was accomplished by preparing silicates with various metals as well as different preparation methods. We also prepared supported ruthenium catalysts by various techniques using several metal precursors to improve present technology. What was also found was that the activation conditions prior to catalytic testing was highly important for both the silicates and the supported ruthenium catalysts. While not the initial focus of the research, we made some interesting observations into the adsorption of H2 on ruthenium. This helped us to get a better understanding of how ortho- to para-H2 conversion takes place, and what features in a catalyst are important to optimize activity. Reactor design was the final area in which some interesting conclusions were drawn. As discussed earlier, the reactor catalyst bed must be constructed using straight 1/8 feet OD stainless steel tubing. It was determined that the use of 1/4 feet OD tubing caused two problems. First, the radius from the center of the bed to the wall was too great for thermal equilibrium. Since the reaction of ortho- to para-H2 is exothermic, the catalyst bed center was warmer than the edges. Second, the catalyst bed was too shallow using a 1/4 feet tube. This caused reactant blow-by which was thought to decrease the measured activity when the flow rate was increased. The 1/8 feet tube corrected both of these concerns.

  14. 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.

  15. Applications for Gradient Metal Alloys Fabricated Using Additive Manufacturing

    Science.gov (United States)

    Hofmann, Douglas C.; Borgonia, John Paul C.; Dillon, Robert P.; Suh, Eric J.; Mulder, jerry L.; Gardner, Paul B.

    2013-01-01

    assortment of "post-processing" methods to locally alter properties (such as coating, heat treating, work hardening, shot peening, etching, anodizing, among others). Building the final part in an additive process allows for the development of an entirely new class of metals, so-called "functionally graded metals" or "gradient alloys." By carefully blending feedstock materials with different properties in an AM process, hardware can be developed with properties that cannot be obtained using other techniques but with the added benefit of the net-shaped fabrication that AM allows.

  16. Testing metals and alloys for use in oxygen systems

    Science.gov (United States)

    Stoltzfus, Joel M.

    1986-01-01

    When oxygen is present in high concentrations or large quantities, as in oxygen-based life-support systems, the likelihood of combustion and the probable intensity of a conflagration increase, together with the severity of the damage caused. Even stainless steel will burn vigorously when ignited in a 1000-psi oxygen environment. The hazards involved in the use of oxygen increase with system operation at the elevated temperatures typical of propulsion systems. Fires in oxygen systems are generally catastrophic, causing a threat to life in manned vehicles. When mechanical components of a mechanism generate friction heat in the presence of oxygen, many commonly used metal alloys ignite and burn. Attention is presently given to frictional heating, particle impact, and flame propagation tests conducted in oxygen environments.

  17. Standard test method for macroetching metals and alloys

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 These test procedures describe the methods of macro- etching metals and alloys to reveal their macrostructure. 1.2 The values stated in inch-pound units are to be regarded as the standard. The SI equivalents of inch-pound units may be approximate. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 6.2, 7.1, 8.1.3, 8.2.1, 8.8.3, 8.10.1.1, and 8.13.2.

  18. Full Electroresistance Modulation in a Mixed-Phase Metallic Alloy

    Science.gov (United States)

    Liu, Z. Q.; Li, L.; Gai, Z.; Clarkson, J. D.; Hsu, S. L.; Wong, A. T.; Fan, L. S.; Lin, M.-W.; Rouleau, C. M.; Ward, T. Z.; Lee, H. N.; Sefat, A. S.; Christen, H. M.; Ramesh, R.

    2016-03-01

    We report a giant, ˜22 %, electroresistance modulation for a metallic alloy above room temperature. It is achieved by a small electric field of 2 kV /cm via piezoelectric strain-mediated magnetoelectric coupling and the resulting magnetic phase transition in epitaxial FeRh /BaTiO3 heterostructures. This work presents detailed experimental evidence for an isothermal magnetic phase transition driven by tetragonality modulation in FeRh thin films, which is in contrast to the large volume expansion in the conventional temperature-driven magnetic phase transition in FeRh. Moreover, all the experimental results in this work illustrate FeRh as a mixed-phase model system well similar to phase-separated colossal magnetoresistance systems with phase instability therein.

  19. Recycling of platinum group metals from the automotive catalysts; Reciclagem de metais do grupo da platina proveniente de catalisadores automotivos

    Energy Technology Data Exchange (ETDEWEB)

    Benevit, Mariana; Petter, Patricia Melo Halmenschlager; Veit, Hugo Marcelo, E-mail: patymhp@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Faculdade de Engenharia. Departamento de Materiais

    2014-07-01

    Currently it is very important to use alternative sources of raw material for obtaining metals, avoiding the traditional mining. This work aims to characterize and evaluate the recoverability of platinum group metals present in automotive catalysts. Thus, the catalysts were divided into two groups: the first was catalysts used in 1.0 cars and the second was catalyst used in 2.0 cars. DRX and FRX techniques and chemical analysis performed by ICP/OES was used to characterized these materials. The results showed that there is a significant amount of platinum group elements in catalyst waste, which can be separated and reused. In the next step, hydro and pyrometallurgical routes, for metals extraction from catalyst waste, will be studied. (author)

  20. Towards stable catalysts by control over the collective features of supported metal nanoparticles

    NARCIS (Netherlands)

    Prieto, G.; Zecevic, J.|info:eu-repo/dai/nl/341386715; Friedrich, H.|info:eu-repo/dai/nl/304837350; de Jong, K.P.|info:eu-repo/dai/nl/06885580X; de Jongh, P.E.|info:eu-repo/dai/nl/186125372

    2013-01-01

    Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage/conversion1 and as catalysts for the sustainable production of fuels and chemicals2–4. However, the tendency of nanoparticles to grow into larger crystallites is an impediment for stable

  1. Oxidative coupling of 1-naphthols over noble and base metal catalysts

    CSIR Research Space (South Africa)

    Maphoru, MV

    2014-01-01

    Full Text Available by the competitive cleavage of one of the two O[BOND]Me bonds at higher temperature. Unpromoted platinum and a range of other metallic catalysts, including gold and Raney nickel, were also found to be active. The products obtained are brightly colored solids...

  2. Comparison Of Different Noble Metal Catalysts For The Low Temperature Catalytic Partial Oxidation Of Methane

    Energy Technology Data Exchange (ETDEWEB)

    Rabe, S.; Truong, T.-B.; Vogel, F.

    2005-03-01

    The generation of synthesis gas at low temperatures can contribute to a more economic production of clean transportation fuels (Fischer-Tropsch liquids) from natural gas. In this report, the performance of different noble metal catalysts in a low temperature catalytic partial oxidation process is presented. (author)

  3. 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.

  4. Activity and selectivity control in reductive amination of butyraldehyde over noble metal catalysts.

    NARCIS (Netherlands)

    Bodis, E.; Lefferts, Leonardus; Muller, T.E.; Pestman, R.; Lercher, J.A.

    2005-01-01

    Approaches to control selectivity and activity in the catalytic reductive amination of butyraldehyde with ammonia over carbon supported noble metal catalysts (Ru, Rh, Pd, and Pt) were explored. Detailed analysis of the reaction network shows that the Schiff base N-[butylidene]butan-1-amine is the

  5. Neutral versus cationic Group 3 metal alkyl catalysts : performance in intramolecular hydroamination/cyclisation

    NARCIS (Netherlands)

    de Araujo Bambirra, Sergio; Tsurugi, H; van Leusen, D; Hessen, B

    2006-01-01

    The relative catalytic activity of neutral dialkyl versus cationic monoalkyl Group 3 metal catalysts in the intramolecular hydroamination/cyclisation of the 2,2-dimethyl-4-pentenylamine reference substrate was investigated. This was found to depend strongly on the nature of the monoanionic ancillary

  6. Direct observation of surface reconstruction and termination on a complex metal oxide catalyst by electron microscopy

    KAUST Repository

    Zhu, Yihan

    2012-03-19

    On the surface: The surface reconstruction of an MoVTeO complex metal oxide catalyst was observed directly by various electron microscopic techniques and the results explain the puzzling catalytic behavior. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    Science.gov (United States)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

  8. Preparation of supported vanadium and molybdenum oxide catalysts using metal acetylacetonate complexes

    NARCIS (Netherlands)

    van Hengstum, A.J.; van Ommen, J.G.; Bosch, H.; Gellings, P.J.

    1983-01-01

    Supported vanadium and molybdenum oxide catalysts were prepared by reaction of the corresponding acetylacetonate complex in a non-aqueous solution with the surface hydroxyl groups of the carrier. Continuous or batch adsorption of the metal acetylacetonate from toluene, as well as wet impregnation

  9. Porphyrin-Based Metal-Organic Frameworks as Heterogeneous Catalysts in Oxidation Reactions

    Directory of Open Access Journals (Sweden)

    Carla F. Pereira

    2016-10-01

    Full Text Available Porphyrin-based Metal-Organic Frameworks (Por-MOFs constitute a special branch of the wide MOF family that has proven its own value and high potential in different applications. In this mini-review the application of these materials as catalysts in oxidation reactions is highlighted.

  10. Synthesis of Single-Walled Carbon Nanotubes: Effects of Active Metals, Catalyst Supports, and Metal Loading Percentage

    Directory of Open Access Journals (Sweden)

    Wei-Wen Liu

    2013-01-01

    Full Text Available The effects of active metals, catalyst supports, and metal loading percentage on the formation of single-walled carbon nanotubes (SWNTs were studied. In particular, iron, cobalt, and nickel were investigated for SWNTs synthesis. Iron was found to grow better-quality SWNTs compared to cobalt and nickel. To study the effect of catalyst supports, magnesium oxide, silicon oxide, and aluminium oxide were chosen for iron. Among the studied supports, MgO was identified to be a suitable support for iron as it produced SWNTs with better graphitisation determined by Raman analysis. Increasing the iron loading decreased the quality of SWNTs due to extensive agglomeration of the iron particles. Thus, lower metal loading percentage is preferred to grow better-quality SWNTs with uniform diameters.

  11. PREPARATION AND CHARACTERIZATION THE NON-SULFIDED METAL CATALYST: Ni/USY and NiMo/USY

    Directory of Open Access Journals (Sweden)

    Khoirina Dwi Nugrahaningtyas

    2010-06-01

    Full Text Available The two-new catalysts had been prepared by using the impregnation method according to Nugrahaningtyas [6] and Li [4]. One catalyst is of Nickel (Ni, supported on Ultra Stable Zeolite Y (USY, whereas the other one is NiMo supported on same supporting agent. These new catalysts are expected to be more effective when applied on the hydrotreatment reaction in standpoint of its capabilities on removing the unwanted-heteroatom. Characterization those two types of catalysts then carried out by using the criteria of acidity, porosity and, metal content. The result shows that these non-sulfide catalysts have several good characters that supporting their usefulness in hydrotreatment-catalytic reaction. In addition, catalyst NiMo/USY - 1 performs many ideal criteria as the best functional catalyst.   Keywords: Non-sulfided Catalyst, hydro-treating, preparation, characterization

  12. Corrosion behaviour of cobalt-chromium dental alloys doped with precious metals.

    Science.gov (United States)

    Reclaru, Lucien; Lüthy, Heinz; Eschler, Pierre-Yves; Blatter, Andreas; Susz, Christian

    2005-07-01

    Precious metal based dental alloys generally exhibit a superior corrosion resistance, in particular enhanced resistance to pitting and crevice corrosion, compared to non-precious metal based alloys such as CoCr alloys. A new generation of Co-Cr alloys enriched with precious metals (Au, Pt, Ru) have now appeared on the market. The goal of this study was to clarify the effect of the precious metals additions on the corrosion behaviour of such alloys. Various commercial alloys with different doping levels were tested by electrochemical techniques in two different milieus based on the Fusayama artificial saliva and an electrolyte containing NaCl. Open circuit potentials, corrosion currents, polarization resistances, and crevices potentials were determined for the various alloys and completed by a coulometric analysis of the potentiodynamic curves. In addition, the microstructures were characterised by metallography and phase compositions analysed by EDX. The results show that the presence of precious metals can deteriorate the corrosion behaviour of Co-Cr alloys in a significant way. Gold doping, in particular, produces heterogeneous microstructures that are vulnerable to corrosive attack.

  13. Dissolution of metallic uranium and its alloys. Part 1. Review of analytical and process-scale metallic uranium dissolution

    International Nuclear Information System (INIS)

    Laue, C.A.; Gates-Anderson, D.; Fitch, T.E.

    2004-01-01

    This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties. The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National Laboratory (LLNL). (author)

  14. Mesoporous diphosphine-transition metal complex catalyst for hydroformylation

    NARCIS (Netherlands)

    Reek, J.N.H.; Coppens, M.O.

    2012-01-01

    The invention pertains to a diphosphine-transition metal complex comprising a diphosphine-transition metal ligand that is covalently bonded to an insoluble mesoporous support having an average pore diameter of from 4.5 nm to 50 nm, characterized in that the ligand as attached to the support has the

  15. Solid state reactions in mechanically alloyed Al-Y alloy with addition of metal oxides; Al-Y gokin to kinzoku sankabutsu tono mechanical alloying to koso hanno

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, M. [Nihon University, Tokyo (Japan); Kaneko, J.; Sugamata, M. [Nihon University, Tokyo (Japan). College of Industrial Technology

    1999-12-15

    With a purpose of attesting preferential oxidation of an alloying element which has low solid solubility in aluminum, an Al-5at%Y alloy was mechanically alloyed with or without addition of metal oxides. Y was chosen as an alloying element since it has higher oxidation tendency than Al and a low maximum solid solubility of 0.17mass% in Al. Mechanically alloyed powders were consolidated by hot-extrusion to the P/M materials of which constituent phases, microstructures and mechanical properties were examined. The added oxygen, either from the process control agent or from oxide powders, acted as oxygen sources for internal oxidation, and Y in Al was shown to be preferentially oxidized to Y{sub 2}O{sub 3} and Al{sub 5}Y{sub 3}O{sub 12}. The P/M materials with addition of oxide powders showed high tensile strength of about 600MPa at room temperature. (author)

  16. Pt-based Bi-metallic Monolith Catalysts for Partial Upgrading of Microalgae Oil

    Energy Technology Data Exchange (ETDEWEB)

    Lawal, Adeniyi [Stevens Inst. of Technology, Hoboken, NJ (United States); Manganaro, James [Anasyn LLC, Princeton, NJ (United States); Goodall, Brian [Valicor Renewables LLC, Dexter, MI (United States); Farrauto, Robert [Columbia Univ., New York, NY (United States)

    2015-03-24

    Valicor’s proprietary wet extraction process in conjunction with thermochemical pre-treatment was performed on algal biomass from two different algae strains, Nannochloropsis Salina (N.S.) and Chlorella to produce algae oils. Polar lipids such as phospholipids were hydrolyzed, and metals and metalloids, known catalyst poisons, were separated into the aqueous phase, creating an attractive “pre-refined” oil for hydrodeoxygenation (HDO) upgrading by Stevens. Oil content and oil extraction efficiency of approximately 30 and 90% respectively were achieved. At Stevens, we formulated a Pt-based bi-metallic catalyst which was demonstrated to be effective in the hydro-treating of the algae oils to produce ‘green’ diesel. The bi-metallic catalyst was wash-coated on a monolith, and in conjunction with a high throughput high pressure (pilot plant) reactor system, was used in hydrotreating algae oils from N.S. and Chlorella. Mixtures of these algae oils and refinery light atmospheric gas oil (LAGO) supplied by our petroleum refiner partner, Marathon Petroleum Corporation, were co-processed in the pilot plant reactor system using the Pt-based bi-metallic monolith catalyst. A 26 wt% N.S. algae oil/74 wt % LAGO mixture hydrotreated in the reactor system was subjected to the ASTM D975 Diesel Fuel Specification Test and it met all the important requirements, including a cetane index of 50.5. An elemental oxygen analysis performed by an independent and reputable lab reported an oxygen content of trace to none found. The successful co-processing of a mixture of algae oil and LAGO will enable integration of algae oil as a refinery feedstock which is one of the goals of DOE-BETO. We have presented experimental data that show that our precious metal-based catalysts consume less hydrogen than the conventional hydrotreating catalyst NiMo Precious metal catalysts favor the hydrodecarbonylation/hydrodecarboxylation route of HDO over the dehydration route preferred by base metal

  17. Activity Tests of Macro-Meso Porous Catalysts over Metal Foam Plate for Steam Reforming of Bio-Ethanol.

    Science.gov (United States)

    Park, No-Kuk; Jeong, Yong Han; Kang, Misook; Lee, Tae Jin

    2018-09-01

    The catalytic activity of a macro-mesoporous catalyst coated on a metal foam plate in the reforming of bio-ethanol to synthesis gas was investigated. The catalysts were prepared by coating a support with a noble metal and transition metal. The catalytic activity for the production of synthetic gas by the reforming of bio-ethanol was compared according to the support material, reaction temperature, and steam/carbon ratio. The catalysts coated on the metal foams were prepared using a template method, in which macro-pores and meso-pores were formed by mixing polymer beads. In particular, the thermodynamic equilibrium composition of bio-ethanol reforming with the reaction temperature and steam/carbon ratio to produce synthetic gas was examined using the HSC (Enthalpy-Entropy-Heat capacity) chemistry program in this study. The composition of hydrogen and carbon monoxide in the reformate gas produced by steam reforming over the Rh/Ni-Ce-Zr/Al2O3-based pellet type catalysts and metal foam catalysts that had been coated with the Rh/Al-Ce-Zr-based catalysts was investigated by experimental activity tests. The activity of the metal foam catalyst was higher than that of the pellet type catalyst.

  18. Solidification mechanism of highly undercooled metal alloys. [tin-lead and nickel-tin alloys

    Science.gov (United States)

    Shiohara, Y.; Chu, M. G.; Macisaac, D. G.; Flemings, M. C.

    1982-01-01

    Experiments were conducted on metal droplet undercooling, using Sn-25wt%Pb and Ni-34wt%Sn alloys. To achieve the high degree of undercooling, emulsification treatments were employed. Results show the fraction of supersaturated primary phase is a function of the amount of undercooling, as is the fineness of the structures. The solidification behavior of the tin-lead droplets during recalescence was analyzed using three different hypotheses; (1) solid forming throughout recalescence is of the maximum thermodynamically stable composition; (2) partitionless solidification below the T sub o temperature, and solid forming thereafter is of the maximum thermodynamically stable composition; and (3) partitionless solidification below the T sub o temperature with solid forming thereafter that is of the maximum thermodynamically metastable composition that is possible. The T sub o temperature is calculated from the equal molar free energies of the liquid solid using the regular solution approximation.

  19. Fatigue and creep crack growth behaviour at high temperatures for weld metals of Alloy 800 and Alloy 617

    International Nuclear Information System (INIS)

    Roedig, M.; Choudhary, B.K.

    1993-01-01

    High temperature fatigue crack growth (FCG) and creep crack growth (CCG) experiments have been conducted in air on weld metal, heat affected zone (HAZ) and base metal of the austenitic Alloy 800 and the nickel base Alloy 617. Tests were performed on specimens machined from pipes, in the temperature range 550-900 deg. C. The crack propagation mode was examined. At all temperatures and for both materials, FCG of base metal was found to be the highest, whereas the weld metal exhibited the lowest FCG rate. The FCG rate in the HAZ was found to lie in between of those observed for base and weld metal. The crack propagation mode remained transgranular in base metal and transdendritic in weld metal at all temperatures. CCG behaviour could be described using the energy rate integral C*. Base metal and weld metal exhibited similar CCG rate at same C*. The crack propagation mode under CCG condition was found to be intergranular in base metal and HAZ and interdendritic in the weld metal. (author)

  20. Ultrahigh figure-of-merit for hydrogen generation from sodium borohydride using ternary metal catalysts

    Science.gov (United States)

    Hu, Lunghao; Ceccato, R.; Raj, R.

    We report further increase in the figure-of-merit (FOM) for hydrogen generation from NaBH 4 than reported in an earlier paper [1], where a sub-nanometer layer of metal catalysts are deposited on carbon nanotube paper (CNT paper) that has been functionalized with polymer-derived silicon carbonitride (SiCN) ceramic film. Ternary, Ru-Pd-Pt, instead of the binary Pd-Pt catalyst used earlier, together with a thinner CNT paper is shown to increase the figure-of-merit by up to a factor of six, putting is above any other known catalyst for hydrogen generation from NaBH 4. The catalysts are prepared by first impregnating the functionalized CNT-paper with solutions of the metal salts, followed by reduction in a sodium borohydride solution. The reaction mechanism and the catalyst efficiency are described in terms of an electric charge transfer, whereby the negative charge on the BH 4 - ion is exchanged with hydrogen via the electronically conducting SiCN/CNT substrate [1].

  1. A review of metal recovery from spent petroleum catalysts and ash.

    Science.gov (United States)

    Akcil, Ata; Vegliò, Francesco; Ferella, Francesco; Okudan, Mediha Demet; Tuncuk, Aysenur

    2015-11-01

    With the increase in environmental awareness, the disposal of any form of hazardous waste has become a great concern for the industrial sector. Spent catalysts contribute to a significant amount of the solid waste generated by the petrochemical and petroleum refining industry. Hydro-cracking and hydrodesulfurization (HDS) catalysts are extensively used in the petroleum refining and petrochemical industries. The catalysts used in the refining processes lose their effectiveness over time. When the activity of catalysts decline below the acceptable level, they are usually regenerated and reused but regeneration is not possible every time. Recycling of some industrial waste containing base metals (such as V, Ni, Co, Mo) is estimated as an economical opportunity in the exploitation of these wastes. Alkali roasted catalysts can be leached in water to get the Mo and V in solution (in which temperature plays an important role during leaching). Several techniques are possible to separate the different metals, among those selective precipitation and solvent extraction are the most used. Pyrometallurgical treatment and bio-hydrometallurgical leaching were also proposed in the scientific literature but up to now they did not have any industrial application. An overview on patented and commercial processes was also presented. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Hydrogenation and dehydrogenation iron pincer catalysts capable of metal-ligand cooperation by aromatization/dearomatization.

    Science.gov (United States)

    Zell, Thomas; Milstein, David

    2015-07-21

    The substitution of expensive and potentially toxic noble-metal catalysts by cheap, abundant, environmentally benign, and less toxic metals is highly desirable and in line with green chemistry guidelines. We have recently discovered a new type of metal-ligand cooperation, which is based on the reversible dearomatization/aromatization of different heteroaromatic ligand cores caused by deprotonation/protonation of the ligand. More specifically, we have studied complexes of various transition metals (Ru, Fe, Co, Rh, Ir, Ni, Pd, Pt, and Re) bearing pyridine- and bipyridine-based PNP and PNN pincer ligands, which have slightly acidic methylene protons. In addition, we have discovered long-range metal-ligand cooperation in acridine-based pincer ligands, where the cooperation takes place at the electrophilic C-9 position of the acridine moiety leading to dearomatization of its middle ring. This type of metal-ligand cooperation was used for the activation of chemical bonds, including H-H, C-H (sp(2) and sp(3)), O-H, N-H, and B-H bonds. This unusual reactivity likely takes place in various catalytic hydrogenation, dehydrogenation, and related reactions. In this Account, we summarize our studies on novel bifunctional iron PNP and PNN pincer complexes, which were designed on the basis of their ruthenium congeners. Iron PNP pincer complexes serve as efficient (pre)catalysts for hydrogenation and dehydrogenation reactions under remarkably mild conditions. Their catalytic applications include atom-efficient and industrially important hydrogenation reactions of ketones, aldehydes, and esters to the corresponding alcohols. Moreover, they catalyze the hydrogenation of carbon dioxide to sodium formate in the presence of sodium hydroxide, the selective decomposition of formic acid to carbon dioxide and hydrogen, and the E-selective semihydrogenation of alkynes to give E-alkenes. These catalysts feature, compared to other iron-based catalysts, very high catalytic activities which in

  3. The origins of strengthening in nanostructured metals and alloys

    Directory of Open Access Journals (Sweden)

    Morris, D. G.

    2010-04-01

    Full Text Available Nanostructured metals and alloys have a variety of chemical and physical properties that are greatly modified by the nano-scale of their microstructure. At the same time, these materials generally show very high strength, although ductility or toughness may not be good. Strength increases as the microstructure scale reduces from the macro-micro level and even finer, but sometimes the strength appears to fall as the structure scale approaches the nano level. These strength variations are examined here, and the mechanisms responsible for both strengthening and weakening are discussed. The fall in ductility and toughness as materials become nanostructured is a complex topic that requires extensive analysis, but this will not be treated in the present overview.

    Los metales y aleaciones nanoestructuradas muestran una serie de propiedades químicas y físicas fuertemente modificadas cuando su microestructura entra en la escala nano. A la vez, estos materiales muestran generalmente alta resistencia pero mediocre ductilidad o tenacidad. La resistencia aumenta cuando baja la escala de la microestructura desde el nivel micro hacia el nivel nano, pero a veces la resistencia parece reducir por las microestructuras mas finas. Se examinan aquí todas estas variaciones y se discuten los mecanismos responsables del endurecimiento y ablandamiento. Los cambios de ductilidad o tenacidad cuando la microestructura entra en la escala nano necesitan un análisis detallado que no se trata en este articulo.

  4. Physical chemistry of the chlorination reactions of metals and alloys

    International Nuclear Information System (INIS)

    De Micco, Georgina

    2007-01-01

    This thesis has contributed towards the knowledge of complex systems.The chlorination reactions are non-catalytic solid-gas heterogeneous reactions which, in addition to the difficulties associated with the reactions occurring in an interface, have the particular features of chlorides compounds and their interactions.The questions arising from this type of study can not be solved by the application of an individual analysis technique.From the experimental point of view it is complicated, and many instrumental techniques need to be applied in order to obtain significant results as well as meaningful interpretations.The system under study is the chlorination of ternary and binary alloys containing Al, Cu and Zn and the pure metals, as these elements belong to the spent nuclear fuel cladding.The aim of the research has been to develop a process that eliminates most of the aluminium, which is the more abundant specie. In this way, the amount of material to be conditioned (vitrified) is reduced.The objectives proposed for each system have been achieved, and the results obtained can also be applied to similar systems for metal recycling [es

  5. Identification of carbon-encapsulated iron nanoparticles as active species in non-precious metal oxygen reduction catalysts.

    Science.gov (United States)

    Varnell, Jason A; Tse, Edmund C M; Schulz, Charles E; Fister, Tim T; Haasch, Richard T; Timoshenko, Janis; Frenkel, Anatoly I; Gewirth, Andrew A

    2016-08-19

    The widespread use of fuel cells is currently limited by the lack of efficient and cost-effective catalysts for the oxygen reduction reaction. Iron-based non-precious metal catalysts exhibit promising activity and stability, as an alternative to state-of-the-art platinum catalysts. However, the identity of the active species in non-precious metal catalysts remains elusive, impeding the development of new catalysts. Here we demonstrate the reversible deactivation and reactivation of an iron-based non-precious metal oxygen reduction catalyst achieved using high-temperature gas-phase chlorine and hydrogen treatments. In addition, we observe a decrease in catalyst heterogeneity following treatment with chlorine and hydrogen, using Mössbauer and X-ray absorption spectroscopy. Our study reveals that protected sites adjacent to iron nanoparticles are responsible for the observed activity and stability of the catalyst. These findings may allow for the design and synthesis of enhanced non-precious metal oxygen reduction catalysts with a higher density of active sites.

  6. Ultrafast Transient Absorption Spectroscopy of Polymer-Based Organophotoredox Catalysts Mimicking Transition-Metal Complexes

    Science.gov (United States)

    Jamhawi, Abdelqader; Paul, Anam C.; Smith, Justin D.; Handa, Sachin; Liu, Jinjun

    2017-06-01

    Transition-metal complexes of rare earth metals including ruthenium and iridium are most commonly employed as visible-light photocatalysts. Despite their highly important and broad applications, they have many disadvantages including high cost associated with low abundance in earth crust, potential toxicity, requirement of specialized ligands for desired activity, and difficulty in recycling of metal contents as well as associated ligands. Polymer-based organophotoredox catalysts are promising alternatives and possess unique advantages such as easier synthesis from inexpensive starting material, longer excited state life time, broad range of activity, sustainability, and recyclability. In this research talk, time-resolved photoluminescence and femtosecond transient absorption (TA) spectroscopy measurements of three novel polymer-based organophotoredox catalysts will be presented. By our synthetic team, their catalytic activity has been proven in some highly valuable chemical transformations, that otherwise require transition metal complexes. Time-resolved spectroscopic investigations have demonstrated that photoinduced processes in these catalysts are similar to the transition metal complexes. Especially, intramolecular vibrational relaxation, internal conversion, and intersystem crossing from the S1 state to the T1 state all occur on a sub-picosecond timescale. The long lifetime of the T1 state ( 2-3 microsecond) renders these polymers potent oxidizing and reducing agents. A spectroscopic and kinetic model has been developed for global fitting of TA spectra in both the frequency and time domains. Implication of the current ultrafast spectroscopy studies of these novel molecules to their roles in photocatalysis will be discussed.

  7. Metal recovery from spent refinery catalysts by means of biotechnological strategies.

    Science.gov (United States)

    Beolchini, F; Fonti, V; Ferella, F; Vegliò, F

    2010-06-15

    A bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5 mg/g), vanadium (9.4 mg/g) and molybdenum (4.4 mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30-40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts. Copyright 2010 Elsevier B.V. All rights reserved.

  8. Bimetallic platinum group metal-free catalysts for high power generating microbial fuel cells.

    Science.gov (United States)

    Kodali, Mounika; Santoro, Carlo; Herrera, Sergio; Serov, Alexey; Atanassov, Plamen

    2017-10-31

    M1-M2-N-C bimetallic catalysts with M1 as Fe and Co and M2 as Fe, Co, Ni and Mn were synthesized and investigated as cathode catalysts for oxygen reduction reaction (ORR). The catalysts were prepared by Sacrificial Support Method in which silica was the template and aminoantipyrine (AAPyr) was the organic precursor. The electro-catalytic properties of these catalysts were investigated by using rotating ring disk (RRDE) electrode setup in neutral electrolyte. Fe-Mn-AAPyr outperformed Fe-AAPyr that showed higher performances compared to Fe-Co-AAPyr and Fe-Ni-AAPyr in terms of half-wave potential. In parallel, Fe-Co-AAPyr, Co-Mn-AAPyr and Co-Ni-AAPyr outperformed Co-AAPyr. The presence of Co within the catalyst contributed to high peroxide production not desired for efficient ORR. The catalytic capability of the catalysts integrated in air-breathing cathode was also verified. It was found that Co-based catalysts showed an improvement in performance by the addition of second metal compared to simple Co- AAPyr. Fe-based bimetallic materials didn't show improvement compared to Fe-AAPyr with the exception of Fe-Mn-AAPyr catalyst that had the highest performance recorded in this study with maximum power density of 221.8 ± 6.6 μWcm -2 . Activated carbon (AC) was used as control and had the lowest performances in RRDE and achieved only 95.6 ± 5.8 μWcm -2 when tested in MFC.

  9. Effects of different production technologies on mechanical and metallurgical properties of precious metal denture alloys

    Science.gov (United States)

    Ferro, Paolo; Battaglia, Eleonora; Capuzzi, Stefano; Berto, Filippo

    2017-12-01

    Precious metal alloys can be supplied in traditional plate form or innovative drop form with high degree of purity. The aim of the present work is to evaluate the influence of precious metal alloy form on metallurgical and mechanical properties of the final dental products with particular reference to metal-ceramic bond strength and casting defects. A widely used alloy for denture was selected; its nominal composition was close to 55 wt% Pd - 34 wt% Ag - 6 wt% In - 3 wt% Sn. Specimens were produced starting from the alloy in both plate and drop forms. A specific test method was developed to obtain results that could be representative of the real conditions of use. In order to achieve further information about the adhesion behaviour and resistance, the fracture surfaces of the samples were observed using `Scanning Electron Microscopy (SEM)'. Moreover, material defects caused by the moulding process were studied. The form of the alloy before casting does not significantly influence the shear bond strength between the metal and the ceramic material (p-value=0,976); however, according to SEM images, products from drop form alloy show less solidification defects compared to products obtained with plate form alloy. This was attributed to the absence of polluting additives used in the production of drop form alloy. This study shows that the use of precious metal denture alloys supplied in drop form does not affect the metal-ceramic bond strength compared to alloys supplied in the traditional plate form. However, compared to the plate form, the drop form is found free of solidification defects, less expensive to produce and characterized by minor environmental impacts.

  10. Extraction of metals from spent hydrotreating catalysts: physico-mechanical pre-treatments and leaching stage.

    Science.gov (United States)

    Ferella, Francesco; Ognyanova, Albena; De Michelis, Ida; Taglieri, Giuliana; Vegliò, Francesco

    2011-08-15

    The present paper is focused on physico-mechanical pre-treatments of spent hydrotreating catalysts aimed at concentration of at least one of the valuable metals contained in such secondary raw material. In particular, dry Ni-Mo and Co-Mo as well as wet Ni-Mo catalysts were used. Flotation, grain size separation and attrition processes were tested. After that, a rods vibrating mill and a ball mill were used to ground the catalysts in order to understand the best mechanical pre-treatment before leaching extraction. The results showed that flotation is not able to concentrate any metals due to the presence of coke or other depressant compounds. The particle size separation produces two fractions enriched in Mo and Co when dry Co-Mo catalyst is used, whereas attrition is not suitable as metals are uniformely distributed in rings' volume. Roasting at 550°C and vibrating grinding are the most suitable pre-treatments able to produce fractions easily leached by NaOH and H(2)SO(4) after grain size separation. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Transition metal oxide loaded MCM catalysts for photocatalytic degradation of dyes

    OpenAIRE

    Jyothi, Divya; Deshpande, Parag A; Venugopal, BR; Chandrasekaran, Srinivasan; Madras, Giridhar

    2012-01-01

    Transition metal oxide (TiO2, Pe(2)O(3), CoO) loaded MCM-41 and MCM-48 were synthesized by a two-step surfactant-based process. Nanoporous, high surface area compounds were obtained after calcination of the compounds. The catalysts were characterized by SEM, XRD, XPS, UV-vis and BET surface area analysis. The catalysts showed high activity for the photocatalytic degradation of both anionic and cationic dyes. The degradation of the dyes was described using Langmuir-Hinshelwood kinetics and the...

  12. A direct borohydride fuel cell with a polymer fiber membrane and non-noble metal catalysts

    OpenAIRE

    Yang, Xiaodong; Liu, Yongning; Li, Sai; Wei, Xiaozhu; Wang, Li; Chen, Yuanzhen

    2012-01-01

    Polymer electrolyte membranes (PEM) and Pt-based catalysts are two crucial components which determine the properties and price of fuel cells. Even though, PEM faces problem of fuel crossover in liquid fuel cells such as direct methanol fuel cell (DMFC) and direct borohydride fuel cell (DBFC), which lowers power output greatly. Here, we report a DBFC in which a polymer fiber membrane (PFM) was used, and metal oxides, such as LaNiO3 and MnO2, were used as cathode catalysts, meanwhile CoO was us...

  13. Effects of thermomechanical processing on strength and toughness of iron - 12-percent-nickel - reactive metal alloys at -196 C

    Science.gov (United States)

    Stephens, J. R.; Witzke, W. R.

    1978-01-01

    Thermomechanical processing (TMP) was evaluated as a method of strengthening normally tough iron-12-nickel-reactive metal alloys at cryogenic temperatures. Five iron-12 nickel alloys with reactive metal additions of aluminum, niobium, titanium, vanadium, and aluminum plus niobium were investigated. Primary evaluation was based on the yield strength and fracture toughness of the thermomechanically processed alloys at -196 C.

  14. Comparison of heat treatment response of semisolid metal processed alloys A356 and F357

    CSIR Research Space (South Africa)

    Moller, H

    2010-01-01

    Full Text Available The heat treatment response of semisolid metal high pressure die cast Al-7Si-Mg alloys A356 and F357 was studied and compared. It was found that the heat treatment behaviour of alloy F357 is influenced markedly by the stability of the Mg containing...

  15. Study by positron annihilation of defects in metals, crystalline or amorphous alloys and in semiconductors

    International Nuclear Information System (INIS)

    Moumene, M.

    1984-07-01

    In this work lifetime of positron is used to study vacancies in different systems irradiated by electrons: pure metals (Fe, Zn), diluted (FeCo, FeAu) and concentrated (Cu 3 Au) alloys, semiconductors (CdTe, ZnTe) and amorphous alloys. Results on vacancy migration temperature and of the formation of two or three-dimensional vacancy clusters are given [fr

  16. Local lattice relaxations in random metallic alloys: Effective tetrahedron model and supercell approach

    DEFF Research Database (Denmark)

    Ruban, Andrei; Simak, S.I.; Shallcross, S.

    2003-01-01

    We present a simple effective tetrahedron model for local lattice relaxation effects in random metallic alloys on simple primitive lattices. A comparison with direct ab initio calculations for supercells representing random Ni0.50Pt0.50 and Cu0.25Au0.75 alloys as well as the dilute limit of Au...

  17. Analysis of sulphur, phosphorus and silica in metals, alloys, inorganic compounds and solvents

    International Nuclear Information System (INIS)

    Upadhya, J.C.; Naik, S.S.; Khedikar, W.K.; Sudersanan, M.; Mathur, P.K

    1999-10-01

    Procedures for the analysis of sulphur, phosphorus and silica in various metals and alloys like mild steel, carbon steel and stainless steel as well as nickel base alloys are described. Procedures were also developed for the analysis of sulphur in thoria pellets and in other materials like crack check fluids, coal etc. Typical results obtained are summarised. (author)

  18. Method and Apparatus for the Detection of Hydrogen Using a Metal Alloy

    Science.gov (United States)

    Hunter, Gary W. (Inventor)

    1997-01-01

    A hydrogen sensitive metal alloy contains palladium and titanium to provide a larger change in electrical resistance when exposed to the presence of hydrogen. The alloy is deposited on a substrate and a thin film and connected across electrical circuitry to provide a sensor device that can be used for improved sensitivity and accuracy of hydrogen detection.

  19. Rational control of nano-scale metal-catalysts for biomass conversion.

    Science.gov (United States)

    Wang, Yunzhu; De, Sudipta; Yan, Ning

    2016-05-07

    Nano-scale metal particles have huge potential due to their wide range of diverse catalytic applications. Recently, they have found numerous applications in the field of biomass conversion. The proposed contribution is aimed at providing a brief account of remarkable recent findings and advances in the design of metal-based nanocatalysts for biomass valorization. We have discussed the rational control of the size, shape, composition and surface properties of nano-scale metal catalysts. Following that, the interplay between various structural parameters and the catalytic properties in the transformation of cellulose, chitin, lignin and lipids has been critically discussed.

  20. Preparation of chiral-at-metal catalysts and their use in asymmetric photoredox chemistry.

    Science.gov (United States)

    Ma, Jiajia; Zhang, Xiao; Huang, Xiaoqiang; Luo, Shipeng; Meggers, Eric

    2018-04-01

    Asymmetric catalysis is a powerful approach for the synthesis of optically active compounds, and visible light constitutes an abundant source of energy to enable chemical transformations, which are often triggered by photoinduced electron transfer (photoredox chemistry). Recently, bis-cyclometalated iridium(III) and rhodium(III) complexes were introduced as a novel class of catalysts for combining asymmetric catalysis with visible-light-induced photoredox chemistry. These catalysts are attractive because of their unusual feature of chirality originating exclusively from a stereogenic metal center, which offers the prospect of an especially effective asymmetric induction upon direct coordination of the substrate to the metal center. As these chiral catalysts contain only achiral ligands, special strategies are required for their synthesis. In this protocol, we describe strategies for preparing two types of chiral-at-metal catalysts, namely the Λ- and Δ-enantiomers (left- and right-handed propellers, respectively) of the iridium complex IrS and the rhodium complex RhS. Both contain two cyclometalating 5-tert-butyl-2-phenylbenzothiazoles in addition to two acetonitrile ligands and a hexafluorophosphate counterion. The two cyclometalated ligands set the propeller-shaped chiral geometry, but the acetonitriles are labile and can be replaced by substrate molecules. The synthesis protocol consists of three stages: first, preparation of the ligand 5-tert-butyl-2-phenylbenzothiazole; second, preparation of salicylthiazoline (used for iridium) and salicyloxazoline (used for rhodium) chiral auxiliaries; and third, the auxiliary-mediated synthesis of the individual enantiopure Λ- and Δ-configured catalysts. This class of stereogenic-only-at-metal complexes is of substantial value in the field of asymmetric catalysis, offering stereocontrolled radical reactions based on visible-light-activated photoredox chemistry. Representative examples of visible-light-induced asymmetric

  1. Formation of Fe-Nb-X (X=Zr, Ti) amorphous alloys from pure metal elements by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Zhiyu [National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640 (China); Tang Cuiyong, E-mail: hnrtcy@163.com [National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640 (China); Ngai, Tungwai Leo; Yang Chao; Li Yuanyuan [National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640 (China)

    2012-01-15

    Fe-based amorphous powders of Fe{sub 56}Nb{sub 6}Zr{sub 38} and Fe{sub 60}Nb{sub 6}Ti{sub 34} based on binary eutectic were prepared by mechanical alloying starting from mixtures of pure metal powders. The amorphization behavior and thermal stability were examined by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry. Results show that Fe{sub 56}Nb{sub 6}Zr{sub 38} alloy has a better glass forming ability and a relatively lower thermal stability comparing with Fe{sub 60}Nb{sub 6}Ti{sub 34} alloy. The prepared amorphous powders have homogeneous element distribution and no obvious contaminants coming from mechanical alloying. The synthesized amorphous powders offer the potential for consolidation to full density with desirable mechanical properties through the powder metallurgy methods.

  2. The efficacy of noble metal alloy urinary catheters in reducing catheter-associated urinary tract infection

    Directory of Open Access Journals (Sweden)

    Alanood Ahmed Aljohi

    2016-01-01

    Results: A 90% relative risk reduction in the rate of CAUTI was observed with the noble metal alloy catheter compared to the standard catheter (10 vs. 1 cases, P = 0.006. When considering both catheter-associated asymptomatic bacteriuria and CAUTI, the relative risk reduction was 83% (12 vs. 2 cases, P = 0.005. In addition to CAUTI, the risk of acquiring secondary bacteremia was lower (100% for the patients using noble metal alloy catheters (3 cases in the standard group vs. 0 case in the noble metal alloy catheter group, P = 0.24. No adverse events related to any of the used catheters were recorded. Conclusion: Results from this study revealed that noble metal alloy catheters are safe to use and significantly reduce CAUTI rate in ICU patients after 3 days of use.

  3. Polarographic methods for the analysis of beryllium metal and its alloys

    International Nuclear Information System (INIS)

    Wells, J.M.

    1975-10-01

    This report describes polarographic methods for the analysis of beryllium metal and its alloys. The elements covered by these methods are aluminium, bismuth, cadmium, cobalt, copper, iron, lead, molybdenum, nickel, thallium, tungsten, uranium, vanadium and zinc. (author)

  4. Pumped lithium loop test to evaluate advanced refractory metal alloys and simulated nuclear fuel elements

    Science.gov (United States)

    Brandenburf, G. P.; Hoffman, E. E.; Smith, J. P.

    1974-01-01

    The performance was determined of refractory metal alloys and uranium nitride fuel element specimens in flowing 1900F (1083C) lithium. The results demonstrate the suitability of the selected materials to perform satisfactorily from a chemical compatibility standpoint.

  5. Studies on mixed metal oxides solid solutions as heterogeneous catalysts

    Directory of Open Access Journals (Sweden)

    H. R. Arandiyan

    2009-03-01

    Full Text Available In this work, a series of perovskite-type mixed oxide LaMo xV1-xO3+δ powder catalysts (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0, with 0.5 < δ < 1.5, prepared by the sol-gel process and calcined at 750ºC, provide an attractive and effective alternative means of synthesizing materials with better control of morphology. Structures of resins obtained during the gel formation process by FT-IR spectroscopy and XRD analysis showed that all the LaMo xV1-xO3+δ samples are single phase perovskite-type solid solutions. The surface area (BET between 2.5 - 5.0 m²/g (x = 0.1 and 1.0 respectively increases with increasing Mo ratio in the samples. They show high purity, good chemical homogeneity, and lower calcinations temperatures as compared with the solid-state chemistry route. SEM coupled to EDS and thermogravimetric analysis/differential thermal analyses (TGA/DTA have been carried out in order to evaluate the homogeneity of the catalyst. Finally, the experimental studies show that the calcination temperature and Mo content exhibited a significant influence on catalytic activity. Among the LaMo xV1-xO3+δ samples, LaMo0.7V0.3O4.2 showed the best catalytic activity for the topic reaction and the best activity and stability for ethane reforming at 850ºC under 8 bar.

  6. Platinum and Palladium Alloys Suitable as Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    2011-01-01

    and innovative catalyst compositions in fuel cell electrodes. The novel electrode catalysts of the invention comprise a noble metal selected from Pt, Pd and mixtures thereof alloyed with a further element selected from Sc, Y and La as well as any mixtures thereof, wherein said alloy is supported on a conductive......The present invention concerns electrode catalysts used in fuel cells, such as proton exchange membrane (PEM) fuel cells. The invention is related to the reduction of the noble metal content and the improvement of the catalytic efficiency by low level substitution of the noble metal to provide new...

  7. Effect of Repeated Firings of Porcelain on Bond Strength of Two Base Metal Alloys

    Directory of Open Access Journals (Sweden)

    Gerami Panah F

    2001-05-01

    Full Text Available The formation of oxides on the surface of the metal are proven to contribute to the formation of strong bonding. However, The base metal alloys are expected to exhibit more oxidation than high gold alloys, increase in oxide layer thickness due to repeated firing in them can reduce the bond strength. The aim of this study was to compare the effect of repeated porcelain firing on the bond strength of two base metal alloys (Minalux and Verabond II. Sixteen metal plates (20x5x0.5 from each alloy were cast and prepared according to the manufacturers' instruction. Porcelain with uniform thickness (Imm was applied on the middle one third of metal plates. After this stage, each alloy group divided to three subgroups. Group I was fired for the second time to form the final glaze, group II and III were fired two and four more times respectively. Specimens were subjected to 3-point flexural test in a digital tritest machine. Results showed no significant differences between bond strength of two alloys. Also results showed repeated firing had no significant effect on bond strength. Due to these findings, this study support similarity of two alloys (Minalux and Verabond II in their bond strength with porcelain.

  8. A Microstructural Investigation of Gas Atomized Raney Type Al-27.5 at.%Ni Catalyst Precursor Alloys

    OpenAIRE

    Mullis, AM; Bigg, TD; Adkins, NJ

    2015-01-01

    Quantitative image analysis has been used to investigate the phase composition of gas atomized powders of a Raney type Ni catalyst precursor alloys of composition Al-27.5 at.% Ni in the powder size range 150-212 μm. We find that there are considerable variations in phase composition both between powders from the same batch and as a function distance from the particle surface within individual particles. Such variations may have significant implications for the future production and uptake of ...

  9. A direct borohydride fuel cell with a polymer fiber membrane and non-noble metal catalysts.

    Science.gov (United States)

    Yang, Xiaodong; Liu, Yongning; Li, Sai; Wei, Xiaozhu; Wang, Li; Chen, Yuanzhen

    2012-01-01

    Polymer electrolyte membranes (PEM) and Pt-based catalysts are two crucial components which determine the properties and price of fuel cells. Even though, PEM faces problem of fuel crossover in liquid fuel cells such as direct methanol fuel cell (DMFC) and direct borohydride fuel cell (DBFC), which lowers power output greatly. Here, we report a DBFC in which a polymer fiber membrane (PFM) was used, and metal oxides, such as LaNiO₃ and MnO₂, were used as cathode catalysts, meanwhile CoO was used as anode catalyst. Peak power density of 663 mW·cm⁻² has been achieved at 65°C, which increases by a factor of 1.7-3.7 compared with classic DBFCs. This fuel cell structure can also be extended to other liquid fuel cells, such as DMFC.

  10. A direct borohydride fuel cell with a polymer fiber membrane and non-noble metal catalysts

    Science.gov (United States)

    Yang, Xiaodong; Liu, Yongning; Li, Sai; Wei, Xiaozhu; Wang, Li; Chen, Yuanzhen

    2012-08-01

    Polymer electrolyte membranes (PEM) and Pt-based catalysts are two crucial components which determine the properties and price of fuel cells. Even though, PEM faces problem of fuel crossover in liquid fuel cells such as direct methanol fuel cell (DMFC) and direct borohydride fuel cell (DBFC), which lowers power output greatly. Here, we report a DBFC in which a polymer fiber membrane (PFM) was used, and metal oxides, such as LaNiO3 and MnO2, were used as cathode catalysts, meanwhile CoO was used as anode catalyst. Peak power density of 663 mW.cm-2 has been achieved at 65°C, which increases by a factor of 1.7-3.7 compared with classic DBFCs. This fuel cell structure can also be extended to other liquid fuel cells, such as DMFC.

  11. Metal oxides as heterogeneous catalysts for esterification of fatty acids obtained from soybean oil

    Energy Technology Data Exchange (ETDEWEB)

    Mello, Vinicius M.; Pousa, Gabriella P.A.G.; Pereira, Mirian S.C.; Dias, Ingrid M.; Suarez, Paulo A.Z. [Laboratorio de Materiais e Combustiveis, Instituto de Quimica, Universidade de Brasilia (Brazil)

    2011-01-15

    The growing demand for renewable energy sources stimulates the development of new technologies for biofuel production. Biodiesel synthesis by esterification of fatty acids is a favorable route, because, differently from transesterification, it does not produce glycerin and uses cheaper raw materials. In this work the study of metal oxides and their performance as Lewis acid catalysts in the esterification of fatty acids obtained from soybean oil presented promising results in heterogeneous catalysis, with reaction yields as high as 89%. The influence of variables such as temperature, reaction time and the amount of catalyst in the reaction yield was also evaluated. The possibility of recycling tin oxide was also studied, showing that it was possible to reuse the catalyst up to ten times without significant losses in its catalytic activity. (author)

  12. CO Hydrogenation over Transition Metals (Fe, Co, or Ni Modified K/Mo2C Catalysts

    Directory of Open Access Journals (Sweden)

    Minglin Xiang

    2013-01-01

    Full Text Available Transition metals (Fe, Co, or Ni modified K/Mo2C catalysts were prepared and investigated as catalysts for CO hydrogenation. The addition of Fe, Co, or Ni to K/Mo2C catalyst led to a sharp increase in both the activity and selectivity of C2+OH, but the promotion effects were quite different and followed the sequence: Ni > Co > Fe for the activity and Fe > Co > Ni for the alcohol selectivity. For the products distributions, it also displayed some differences; Co promoter showed much higher C5+ hydrocarbon selectivity than Fe or Ni promoter, but Fe or Co promoter gave lower methane selectivity than Ni promoter, and Fe promoter showed the highest C2=-C4= selectivity.

  13. A direct borohydride fuel cell with a polymer fiber membrane and non-noble metal catalysts

    Science.gov (United States)

    Yang, Xiaodong; Liu, Yongning; Li, Sai; Wei, Xiaozhu; Wang, Li; Chen, Yuanzhen

    2012-01-01

    Polymer electrolyte membranes (PEM) and Pt-based catalysts are two crucial components which determine the properties and price of fuel cells. Even though, PEM faces problem of fuel crossover in liquid fuel cells such as direct methanol fuel cell (DMFC) and direct borohydride fuel cell (DBFC), which lowers power output greatly. Here, we report a DBFC in which a polymer fiber membrane (PFM) was used, and metal oxides, such as LaNiO3 and MnO2, were used as cathode catalysts, meanwhile CoO was used as anode catalyst. Peak power density of 663 mW·cm−2 has been achieved at 65°C, which increases by a factor of 1.7–3.7 compared with classic DBFCs. This fuel cell structure can also be extended to other liquid fuel cells, such as DMFC. PMID:22880160

  14. Zeolites Modified Metal Cations as Catalysts in Hydrocarbon Oxidation and the Alkyl Alcohol

    Directory of Open Access Journals (Sweden)

    Agadadsh Makhmud Aliyev

    2014-09-01

    Full Text Available The results of studies on the creation of highly metalltceolitnyh systems and the study of their catalytic activities in the oxidation of lower olefin hydrocarbons (ethylene to acetaldehyde, acetone, propylene, butylene methyl ethyl ketone; aliphatic C1-C5 alcohols to their corresponding aldehydes, ketones, carboxylic acids and carboxylic acid esters; oxidative dehydrogenation of naphthenes in the alicyclic diene hydrocarbons and the oxidative dimerization of methane to acetylene. It has been established that the selectivity of these catalysts determined optimal combination of metal components with the acidity and the structure of the zeolite. Selected highly effective catalysts for the reactions studied. Based on the results of experimental studies of the kinetics of the reactions of oxidation of lower olefin hydrocarbons and aliphatic alcohols, the oxidative dehydrogenation of naphthenes and oxidative coupling of methane on the synthesized catalysts are represented by their probable stepwise mechanism and kinetic models developed reactions.

  15. Ni catalyst wash-coated on metal monolith with enhanced heat-transfer capability for steam reforming

    Science.gov (United States)

    Ryu, Jae-Hong; Lee, Kwan-Young; La, Howon; Kim, Hak-Joo; Yang, Jung-Il; Jung, Heon

    A commercial Ni-based catalyst is wash-coated on a monolith made of 50 μm-thick fecralloy plates. Compared with the same volume of coarsely powdered Ni catalysts, the monolith wash-coated Ni catalysts give higher methane conversion in the steam reforming reaction, especially at gas hourly space velocities (GHSV) higher than 28,000 h -1, and with no pressure drop. A higher conversion of the monolith catalyst is obtained, even though it contains a lower amount of active catalyst (3 g versus 17 g for a powdered catalyst), which indicates that the heat-transfer capability of the wash-coated Ni catalyst is significantly enhanced by the use of a metal monolith. The efficacy of the monolith catalyst is tested using a shell-and-tube type heat-exchanger reactor with 912 cm 3 of the monolith catalyst charged on to the tube side and hot combusted gas supplied to the shell side in a counter-current direction to the reactant flow. A methane conversion greater than 94% is obtained at a GHSV of 7300 h -1 and an average temperature of 640 °C. Nickel catalysts should first be reduced to become active for steam reforming. Doping a small amount (0.12 wt.%) of noble metal (Ru or Pt) in the commercial Ni catalyst renders the wash-coated catalyst as active as a pre-reduced Ni catalyst. Thus, noble metal-doped Ni appears useful for steam reforming without any pre-reduction procedure.

  16. Multifunctionality of organometallic quinonoid metal complexes: surface chemistry, coordination polymers, and catalysts.

    Science.gov (United States)

    Kim, Sang Bok; Pike, Robert D; Sweigart, Dwight A

    2013-11-19

    Quinonoid metal complexes have potential applications in surface chemistry, coordination polymers, and catalysts. Although quinonoid manganese tricarbonyl complexes have been used as secondary building units (SBUs) in the formation of novel metal-organometallic coordination networks and polymers, the potentially wider applications of these versatile linkers have not yet been recognized. In this Account, we focus on these diverse new applications of quinonoid metal complexes, and report on the variety of quinonoid metal complexes that we have synthesized. Through the use of [(η(6)-hydroquinone)Mn(CO)3](+), we are able to modify the surface of Fe3O4 and FePt nanoparticles (NPs). This process occurs either by the replacement of oleylamine with neutral [(η(5)-semiquinone)Mn(CO)3] at the NP surface, or by the binding of anionic [(η(4)-quinone)Mn(CO)3](-) upon further deprotonation of [(η(5)-semiquinone)Mn(CO)3] at the NP surface. We have demonstrated chemistry at the intersection of surface-modified NPs and coordination polymers through the growth of organometallic coordination polymers onto the surface modified Fe3O4 NPs. The resulting magnetic NP/organometallic coordination polymer hybrid material exhibited both the unique superparamagnetic behavior associated with Fe3O4 NPs and the paramagnetism attributable to the metal nodes, depending upon the magnetic range examined. By the use of functionalized [(η(5)-semiquinone)Mn(CO)3] complexes, we attained the formation of an organometallic monolayer on the surface of highly ordered pyrolitic graphite (HOPG). The resulting organometallic monolayer was not simply a random array of manganese atoms on the surface, but rather consisted of an alternating "up and down" spatial arrangement of Mn atoms extending from the HOPG surface due to hydrogen bonding of the quinonoid complexes. We also showed that the topology of metal atoms on the surface could be controlled through the use of quinonoid metal complexes. A quinonoid

  17. Stability and Activity of Non-Noble-Metal-Based Catalysts Toward the Hydrogen Evolution Reaction.

    Science.gov (United States)

    Ledendecker, Marc; Mondschein, Jared S; Kasian, Olga; Geiger, Simon; Göhl, Daniel; Schalenbach, Max; Zeradjanin, Aleksandar; Cherevko, Serhiy; Schaak, Raymond E; Mayrhofer, Karl

    2017-08-07

    A fundamental understanding of the behavior of non-noble based materials toward the hydrogen evolution reaction is crucial for the successful implementation into practical devices. Through the implementation of a highly sensitive inductively coupled plasma mass spectrometer coupled to a scanning flow cell, the activity and stability of non-noble electrocatalysts is presented. The studied catalysts comprise a range of compositions, including metal carbides (WC), sulfides (MoS 2 ), phosphides (Ni 5 P 4 , Co 2 P), and their base metals (W, Ni, Mo, Co); their activity, stability, and degradation behavior was elaborated and compared to the state-of-the-art catalyst platinum. The non-noble materials are stable at HER potentials but dissolve substantially when no current is flowing. Through pre- and post-characterization of the catalysts, explanations of their stability (thermodynamics and kinetics) are discussed, challenges for the application in real devices are analyzed, and strategies for circumventing dissolution are suggested. The precise correlation of metal dissolution with applied potential/current density allows for narrowing down suitable material choices as replacement for precious group metals as for example, platinum and opens up new ways in finding cost-efficient, active, and stable new-generation electrocatalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Molecular polypyridine-based metal complexes as catalysts for the reduction of CO2.

    Science.gov (United States)

    Elgrishi, Noémie; Chambers, Matthew B; Wang, Xia; Fontecave, Marc

    2017-02-06

    Polypyridyl transition metal complexes represent one of the more thoroughly studied classes of molecular catalysts towards CO 2 reduction to date. Initial reports in the 1980s began with an emphasis on 2nd and 3rd row late transition metals, but more recently the focus has shifted towards earlier metals and base metals. Polypyridyl platforms have proven quite versatile and amenable to studying various parameters that govern product distribution for CO 2 reduction. However, open questions remain regarding the key mechanistic steps that govern product selectivity and efficiency. Polypyridyl complexes have also been immobilized through a variety of methods to afford active catalytic materials for CO 2 reductions. While still an emerging field, materials incorporating molecular catalysts represent a promising strategy for electrochemical and photoelectrochemical devices capable of CO 2 reduction. In general, this class of compounds remains the most promising for the continued development of molecular systems for CO 2 reduction and an inspiration for the design of related non-polypyridyl catalysts.

  19. Hydrogenation of nitrocompounds with supported palladium catalysts: influence of metal dispersion and nitrocompound nature

    Energy Technology Data Exchange (ETDEWEB)

    Carturan, G.; Facchin, G.; Cocco, G.; Navazio, G.; Gubitosa, G.

    1983-07-01

    Nitrobenzene, Et-NO/sub 2/, and t-Bu-NO/sub 2/ are hydrogenated to corresponding amines using Pd catalysts in n-octane suspension at 90/sup 0/C and at constant H/sub 2/ pressure. Nitrobenzene reduction to aniline has been studied with several Pd catalysts having a different degree of metal dispersion determined by X-ray methods and chemisorption analysis. Results indicate that the process is a structure sensitive reaction; a peculiar lowering in catalytic activity as the degree of Pd dispersion increases is observed. This fact is discussed in terms of metallic surface oxidation due to the sorbed nitrocompound. Hydrogenation kinetic patterns change with the nature of the nitrocompound. Reduction of Et-NO/sub 2/ and t-Bu-NO/sub 2/ depends on substrate concentration, while nitrobenzene hydrogenation is independent of this parameter. The relevant kinetic experiments allow the formulation of a general reaction mechanism accounting for the different kinetic patterns observed on changing the substrate. The discussion illustrates the possibility that in nitrocompound reduction with metal catalysts the rate determining step may be hydrogenation of the metallic surface oxidized by the sorbed nitrocompound.

  20. Transition Metal Sulfide Hydrogen Evolution Catalysts for Hydrobromic Acid Electrolysis

    NARCIS (Netherlands)

    Ivanovskaya, Anna; Singh, Nirala; Liu, Ru-Fen; Kreutzer, Haley; Baltrusaitis, Jonas; Nguyen, Trung Van; Metiu, Horia; McFarland, Eric

    2013-01-01

    Mixed metal sulfides containing combinations of W, Fe, Mo, Ni, and Ru were synthesized and screened for activity and stability for the hydrogen evolution reaction (HER) in aqueous hydrobromic acid (HBr). Co- and Ni-substituted RuS2 were identified as potentially active HER electrocatalysts by

  1. Scattering cross section of metal catalyst atoms in silicon nanowires

    DEFF Research Database (Denmark)

    Markussen, Troels; Rurali, R.; Cartoixa, X.

    2010-01-01

    strength of the different metal atoms. We find that Au, Ag, and Cu impurities have very similar scattering cross sections, while Al differs from the rest. Impurities located in the center of the wires scatter significantly more than impurities close to or at the surface. The results for nanowires...

  2. Oxidatively Electrodeposited Thin-Film Transition Metal (Oxy)hydroxides as Oxygen Evolution Catalysts.

    Science.gov (United States)

    Morales-Guio, Carlos G; Liardet, Laurent; Hu, Xile

    2016-07-20

    The electrolysis of water to produce hydrogen and oxygen is a simple and attractive approach to store renewable energies in the form of chemical fuels. The oxygen evolution reaction (OER) is a complex four-electron process that constitutes the most energy-inefficient step in water electrolysis. Here we describe a novel electrochemical method for the deposition of a family of thin-film transition metal (oxy)hydroxides as OER catalysts. The thin films have nanodomains of crystallinity with lattice spacing similar to those of double-layered hydroxides. The loadings of these thin-film catalysts were accurately determined with a resolution of below 1 μg cm(-2) using an electrochemical quartz microcrystal balance. The loading-activity relations for various catalysts were established using voltammetry and impedance spectroscopy. The thin-film catalysts have up to four types of loading-activity dependence due to film nucleation and growth as well as the resistance of the films. A zone of intrinsic activity has been identified for all of the catalysts where the mass-averaged activity remains constant while the loading is increased. According to their intrinsic activities, the metal oxides can be classified into three categories: NiOx, MnOx, and FeOx belong to category I, which is the least active; CoOx and CoNiOx belong to category II, which has medium activity; and FeNiOx, CoFeOx, and CoFeNiOx belong to category III, which is the most active. The high turnover frequencies of CoFeOx and CoFeNiOx at low overpotentials and the simple deposition method allow the fabrication of high-performance anode electrodes coated with these catalysts. In 1 M KOH and with the most active electrode, overpotentials as low as 240 and 270 mV are required to reach 10 and 100 mA cm(-2), respectively.

  3. Processing of Zn-3Mg alloy by equal channel angular pressing for biodegradable metal implants

    OpenAIRE

    Murtala Sule Dambatta; Sudin Izman; Denni Kurniawan; Hendra Hermawan

    2017-01-01

    Zn-based alloys have been studied as new biodegradable metals owing to its slower corrosion rate compared to Mg-based alloys and its high potential for mechanical properties improvement. The present work attempts to improve mainly the mechanical properties of a eutectic Zn-3Mg alloy via equal channels angular pressing (ECAP). Cast Zn-3Mg alloy was homogenized at 370 °C for 15 h and quenched in water before subjected to 2 steps ECAP process. Results showed that the process decreases the alloy’...

  4. Review of alkali metal and refractory alloy compatibility for Rankine cycle applications

    International Nuclear Information System (INIS)

    DiStefano, J.R.

    1989-01-01

    The principal corrosion mechanisms in refractory metal-alkali systems are dissolution, mass transfer, and impurity reactions. In general, niobium, tantalum, molybdenum, and tungsten have low solubilities in the alkali metals, even to very high temperatures, and static corrosion studies have verified that the systems are basically compatible. Loop studies with niobium and tantalum based alloys do not indicate any serious problems due to temperature gradient mass transfer. Above 1000 K, dissimilar metal mass transfer is noted between the refractory metals and iron or nickel based alloys. The most serious corrosion problems encountered are related to impurity reactions associated with oxygen

  5. Effects of metal primers on the bonding of an adhesive resin cement to noble metal ceramic alloys after thermal cycling.

    Science.gov (United States)

    Minami, Hiroyuki; Murahara, Sadaaki; Suzuki, Shiro; Tanaka, Takuo

    2011-12-01

    Although the effectiveness of primers for resin bonding to noble alloys has been demonstrated, no effective clinical technique for bonding to noble metal ceramic alloys has been established. The purpose of this study was to evaluate the effects of metal primers on the shear bond strength of an adhesive resin to noble metal ceramic alloys after thermal cycling. Sixty-three disk-shaped specimens (10 × 2.5 mm) were cast from high-gold-content alloys (Super Metal W-85: W85 or IFK88 GR: IFK88), a high-palladium-content alloy (Super Metal N-40: N40), and an Ag-Pd-Cu-Au alloy (Castwell M.C.12: MC12). Smaller-sized disk-shaped specimens (8 × 2.5 mm) were fabricated with MC12. Bonding surfaces were finished with 600-grit SiC-paper and airborne-particle abraded with 50-μm alumina. Pairs of disks were primed (V-Primer: VP; ML Primer: ML; or Metaltite: MT) and bonded with an adhesive resin (Super-Bond C&B). The bond strengths were determined before and after 20,000 and 50,000 thermal cycles (n=7). Data were analyzed by using a 3-way ANOVA and the Bonferroni test (α=.05). Failure modes were determined by optical microscope and SEM observation. Bond strengths to high-gold-content alloys with VP and MT significantly decreased after the thermal cycling (Palloys were not degraded up to 50,000 thermal cycles when primed with ML. None of the primers evaluated was effective for high-palladium-content alloy. Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  6. A comparative study of metal oxide and sulfate catalysts for selective catalytic reduction of NO with NH3.

    Science.gov (United States)

    Zhu, Lin; Zhong, Zhaoping; Yang, Han; Wang, Chunhua

    2017-05-01

    The properties and characteristics of metal oxide and sulfate catalysts with different active elements for selective catalytic reduction of NO with NH 3 were investigated. Cerium-based oxide catalyst showed the widest temperature window for NO x removal and manganese-based oxide catalyst exhibited the best catalytic performance at low temperature. For all the catalysts, the SCR activities at low temperature were directly related with the redox abilities of catalysts. The existence of sulfate groups inhibited the redox abilities of active species for sulfate catalysts compared with the metal oxide catalysts. The catalytic activities of CeWTi-S and MnWTi-S were seriously decreased in contrast to CeWTi-N and MnWTi-N. The temperature window of CuWTi-S was shifted toward higher temperature comparing with CuWTi-N. The FeWTi-N and FeWTi-S catalysts both showed high NO x conversion in the temperature range between 300°C and 400°C and N 2 O concentrations for iron-based samples were least among the same kind of catalysts. The abundance of acid sites and weak stability of surface sulfate groups for iron- and copper-based sulfate catalysts might be the main reasons accounting for the better NO x conversion in the medium-temperature range.

  7. Novel application of a Fe-Zn double-metal cyanide catalyst in the synthesis of biodegradable, hyperbranched polymers.

    Science.gov (United States)

    Sebastian, Joby; Srinivas, Darbha

    2011-10-07

    The use of Fe-Zn double-metal cyanide as a solid catalyst for synthesizing biodegradable, hyperbranched polymers from diacids and glycerol has been reported, for the first time, wherein acidity, micro-mesoporosity and hydrophobicity of the catalyst played an important role in controlling gelation. This journal is © The Royal Society of Chemistry 2011

  8. Tandem isomerization-decarboxylation of unsaturated fatty acids to olefins via ruthenium metal-as-ligand catalysts

    Science.gov (United States)

    A new facile Ru-catalyzed route to bio-olefins3 from unsaturated fatty acids via readily accessible metal-as-ligand type catalyst precursors, [Ru(CO)2RCO2]n and Ru3(CO)12, will be described. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds i...

  9. KF-loaded mesoporous Mg-Fe bi-metal oxides: high performance transesterification catalysts for biodiesel production.

    Science.gov (United States)

    Tao, Guiju; Hua, Zile; Gao, Zhe; Zhu, Yan; Zhu, Yan; Chen, Yu; Shu, Zhu; Zhang, Lingxia; Shi, Jianlin

    2013-09-21

    Using newly developed mesoporous Mg-Fe bi-metal oxides as supports, a novel kind of high performance transesterification catalysts for biodiesel production has been synthesized. More importantly, the impregnation solvent was for the first time found to substantially affect the structures and catalytic performances of the resultant transesterification catalysts.

  10. Mono-, bi-, and tri-metallic Ni-based catalysts for the catalytic hydrotreatment of pyrolysis liquids

    NARCIS (Netherlands)

    Yin, Wang; Venderbosch, Robbie H.; He, Songbo; Bykova, Maria V.; Khromova, Sofia A.; Yakovlev, Vadim A.; Heeres, Hero J.

    Catalytic hydrotreatment is a promising technology to convert pyrolysis liquids into intermediates with improved properties. Here, we report a catalyst screening study on the catalytic hydrotreatment of pyrolysis liquids using bi- and tri-metallic nickel-based catalysts in a batch autoclave (initial

  11. Carbon deposition in the Bosch process with ruthenium and ruthenium-iron alloy catalysts. M.S. Thesis. Final Report, Jan. 1981 - Jul. 1982

    Science.gov (United States)

    Manning, M. P.; Reid, R. C.; Sophonpanich, C.

    1982-01-01

    The effectiveness of ruthenium and the alloys 50Ru50Fe and 33Ru67Fe as alternatives to iron, nickel, and cobalt catalysts in recovering oxygen from metabolic carbon dioxide was investigated. Carbon deposition boundaries over the unsupported alloys are reported. Experiments were also carried out over 50Ru50Fe and 97Ru3Fe3 catalysts supported on gamma-alumina to determine their performance in the synthesis of low molecular weight olefins. High production of ethylene and propylene would be beneficial for an improvement of an overall Bosch process, as a gas phase containing high olefin content would enhance carbon deposition in a Bosch reactor.

  12. Nanosheet Supported Single-Metal Atom Bifunctional Catalyst for Overall Water Splitting.

    Science.gov (United States)

    Ling, Chongyi; Shi, Li; Ouyang, Yixin; Zeng, Xiao Cheng; Wang, Jinlan

    2017-08-09

    Nanosheet supported single-atom catalysts (SACs) can make full use of metal atoms and yet entail high selectivity and activity, and bifunctional catalysts can enable higher performance while lowering the cost than two separate unifunctional catalysts. Supported single-atom bifunctional catalysts are therefore of great economic interest and scientific importance. Here, on the basis of first-principles computations, we report a design of the first single-atom bifunctional eletrocatalyst, namely, isolated nickel atom supported on β 12 boron monolayer (Ni 1 /β 12 -BM), to achieve overall water splitting. This nanosheet supported SAC exhibits remarkable electrocatalytic performance with the computed overpotential for oxygen/hydrogen evolution reaction being just 0.40/0.06 V. The ab initio molecular dynamics simulation shows that the SAC can survive up to 800 K elevated temperature, while enacting a high energy barrier of 1.68 eV to prevent isolated Ni atoms from clustering. A viable experimental route for the synthesis of Ni 1 /β 12 -BM SAC is demonstrated from computer simulation. The desired nanosheet supported single-atom bifunctional catalysts not only show great potential for achieving overall water splitting but also offer cost-effective opportunities for advancing clean energy technology.

  13. Sintering-Resistant Single-Site Nickel Catalyst Supported by Metal-Organic Framework.

    Science.gov (United States)

    Li, Zhanyong; Schweitzer, Neil M; League, Aaron B; Bernales, Varinia; Peters, Aaron W; Getsoian, Andrew Bean; Wang, Timothy C; Miller, Jeffrey T; Vjunov, Aleksei; Fulton, John L; Lercher, Johannes A; Cramer, Christopher J; Gagliardi, Laura; Hupp, Joseph T; Farha, Omar K

    2016-02-17

    Developing supported single-site catalysts is an important goal in heterogeneous catalysis since the well-defined active sites afford opportunities for detailed mechanistic studies, thereby facilitating the design of improved catalysts. We present herein a method for installing Ni ions uniformly and precisely on the node of a Zr-based metal-organic framework (MOF), NU-1000, in high density and large quantity (denoted as Ni-AIM) using atomic layer deposition (ALD) in a MOF (AIM). Ni-AIM is demonstrated to be an efficient gas-phase hydrogenation catalyst upon activation. The structure of the active sites in Ni-AIM is proposed, revealing its single-site nature. More importantly, due to the organic linker used to construct the MOF support, the Ni ions stay isolated throughout the hydrogenation catalysis, in accord with its long-term stability. A quantum chemical characterization of the catalyst and the catalytic process complements the experimental results. With validation of computational modeling protocols, we further targeted ethylene oligomerization catalysis by Ni-AIM guided by theoretical prediction. Given the generality of the AIM methodology, this emerging class of materials should prove ripe for the discovery of new catalysts for the transformation of volatile substrates.

  14. Biogenic metallic nanoparticles as catalyst for bioelectricity production: A novel approach in microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Saravanakumar, Kandasamy, E-mail: saravana732@gmail.com [School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai (China); State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai (China); Key Laboratory of Urban Agriculture (South), Ministry of Agriculture, Shanghai (China); MubarakAli, Davoodbasha [Microbial Genetic Engineering Laboratory, Division of Bioengineering, College of Life Science and Bioengineering, Incheon National University, Songdo 406772, Incheon (Korea, Republic of); Department of Microbiology, School of Lifesciences, Bharathidasan University, Tiruchirappalli 620024 (India); Kathiresan, Kandasamy [Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai 608 502, Tamil Nadu (India); Thajuddin, Nooruddin [Department of Microbiology, School of Lifesciences, Bharathidasan University, Tiruchirappalli 620024 (India); Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia); Alharbi, Naiyf S. [Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia); Chen, Jie, E-mail: jiechen59@sjtu.edu.cn [School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai (China); State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai (China); Key Laboratory of Urban Agriculture (South), Ministry of Agriculture, Shanghai (China)

    2016-01-15

    Highlights: • Trichoderma sp., showed an abilities to synthesis of AgNPs and AuNPs with an excellent stability. • AuNPs significantly enhanced the bioelectricity production by MFC of anaerobic fermentation as catalyst. • Maximum bioelectricity production was optimized and obtained the voltage of 432.80 mA using RSM. - Abstract: The present work aimed to use the biogenic metallic nanoparticles as catalyst for bioelectricity production in microbial fuel cell (MFC) approach under anaerobic condition. Silver and gold nanoparticles (AuNPs) were synthesized using Trichoderma sp. Particle size and cystallinity were measured by X-ray diffraction revealed the crystalline structure with average size of 36.17 nm. Electron microscopic studies showed spherical shaped silver nanoparticles (AgNPs) and cubical shaped AuNPs with size ranges from 50 to 150 nm. The concentration of biogenic metallic nanoparticles as catalyst for enhanced bioelectricity generations and estimated by response surface methodology (RSM) and found at the greatest of 342.80 mA under optimized conditions are time interval, temperature, nanoparticles used as 63 h, 28 ± 2.0 °C, 22.54 mg l{sup −1} (AgNPs) and 25.62 mg l{sup −1} (AuNPs) in a batch reactor. AuNPs acted as an excellent catalyst to enhance the bioelectricity production. This novel technique could be used for eco-friendly, economically feasible and facile electricity production.

  15. Nitrogen-Doped Activated Carbon as Metal-Free Catalysts Having Various Functions

    Directory of Open Access Journals (Sweden)

    Shin-Ichiro Fujita

    2017-10-01

    Full Text Available Nitrogen-doped carbon materials have been gaining increasing interest as metal-free catalysts. In this article, the authors have briefly introduced their recent studies on the utilization of nitrogen-doped activated carbon (N-AC for several organic synthesis reactions, which include base catalyzed reactions of Knoevenagel condensation and transesterification, aerobic oxidation of xanthene and alcohols, and transfer hydrogenation of nitrobenzene, 3-nitrostyrene, styrene, and phenylacetylene with hydrazine. Doped-nitrogen species existed on the AC surface in different structures. For example, pyridine-type nitrogen species appear to be involved in the active sites for Knoevenagel condensation and for the oxidation of xanthene, while graphite-type nitrogen species appear to be involved for the oxidation of alcohols. Being different from these reactions, both surface nitrogen and oxygen species are involved in the active sites for the hydrogenation of nitrobenzene. N-AC was practically inactive for the transfer hydrogenation of vinyl and ethynyl groups, but it can catalyze those hydrogenation reactions assisted by co-existing nitrobenzene. Comparison of N-AC with conventional catalysts shows that N-AC can alternate with conventional solid base catalysts and supported metal catalysts for the Knoevenagel condensation and oxidation reactions.

  16. A review of heat-treatment effects on activity and stability of PEM fuel cell catalysts for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Bezerra, Cicero W.B. [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada); Department of Chemistry, Universidade Federal do Maranhao, Av. dos Portugueses, S/N 65.080-040 Sao Luis, MA (Brazil); Zhang, Lei; Liu, Hansan; Lee, Kunchan; Wang, Haijiang; Zhang, Jiujun [Institute for Fuel Cell Innovation, National Research Council of Canada, Vancouver, BC V6T 1W5 (Canada); Marques, Aldalea L.B. [Department of Technology Chemistry, Universidade Federal do Maranhao, Sao Luis, MA (Brazil); Marques, Edmar P. [Department of Chemistry, Universidade Federal do Maranhao, Av. dos Portugueses, S/N 65.080-040 Sao Luis, MA (Brazil)

    2007-11-15

    This paper reviews over 120 papers regarding the effect of heat treatment on the catalytic activity and stability of proton exchange membrane (PEM) fuel cell catalysts. These catalysts include primarily unsupported and carbon-supported platinum (Pt), Pt alloys, non-Pt alloys, and transition metal macrocycles. The heat treatment can induce changes in catalyst properties such as particle size, morphology, dispersion of the metal on the support, alloying degree, active site formation, catalytic activity, and catalytic stability. The optimum heat-treatment temperature and time period are strongly dependent on the individual catalyst. With respect to Pt-based catalysts, heat treatment can induce particle-size growth, better alloying degree, and changes in the catalyst surface morphology from amorphous to more ordered states, all of which have a remarkable effect on oxygen reduction reaction (ORR) activity and stability. However, heat treatment of the catalyst carbon supports can also significantly affect the ORR catalytic activity of the supported catalyst. Regarding non-noble catalysts, in particular transition metal macrocycles, heat treatment is also important in ORR activity and stability improvement. In fact, heat treatment is a necessary step for introducing more active catalytic sites. For metal chalcogenide catalysts, it seems that heat treatment may not be necessary for catalytic activity and stability improvement. More research is necessary to improve our fundamental understanding and to develop a new strategy that includes innovative heat-treatment processes for enhancing fuel cell catalyst activity and stability. (author)

  17. A review of heat-treatment effects on activity and stability of PEM fuel cell catalysts for oxygen reduction reaction

    Science.gov (United States)

    Bezerra, Cicero W. B.; Zhang, Lei; Liu, Hansan; Lee, Kunchan; Marques, Aldaléa L. B.; Marques, Edmar P.; Wang, Haijiang; Zhang, Jiujun

    This paper reviews over 120 papers regarding the effect of heat treatment on the catalytic activity and stability of proton exchange membrane (PEM) fuel cell catalysts. These catalysts include primarily unsupported and carbon-supported platinum (Pt), Pt alloys, non-Pt alloys, and transition metal macrocycles. The heat treatment can induce changes in catalyst properties such as particle size, morphology, dispersion of the metal on the support, alloying degree, active site formation, catalytic activity, and catalytic stability. The optimum heat-treatment temperature and time period are strongly dependent on the individual catalyst. With respect to Pt-based catalysts, heat treatment can induce particle-size growth, better alloying degree, and changes in the catalyst surface morphology from amorphous to more ordered states, all of which have a remarkable effect on oxygen reduction reaction (ORR) activity and stability. However, heat treatment of the catalyst carbon supports can also significantly affect the ORR catalytic activity of the supported catalyst. Regarding non-noble catalysts, in particular transition metal macrocycles, heat treatment is also important in ORR activity and stability improvement. In fact, heat treatment is a necessary step for introducing more active catalytic sites. For metal chalcogenide catalysts, it seems that heat treatment may not be necessary for catalytic activity and stability improvement. More research is necessary to improve our fundamental understanding and to develop a new strategy that includes innovative heat-treatment processes for enhancing fuel cell catalyst activity and stability.

  18. Comparative study of ceramometal tensile bonding strength in two base metal alloys

    Directory of Open Access Journals (Sweden)

    Comparative study of ceramometal tensile bonding strength in two base metal alloys

    2005-06-01

    Full Text Available Statement of Problem: One of the greatest problems in metal –ceramic restorations is debonding of porcelain from dental alloys. Production of dental alloys by Iranian companies necessitates the evaluation of physical and handling properties of these products. Purpose: In this study the bond strength between porcelain and two types of base metal alloys, Supercast (with beryllium and Minalux (without beryllium was investigated. Materials and Methods: In this experimental study 10 cylindric bars from each base metal alloy were prepared. The bars were degassed and porcelain was applied around them in a disc form (8 mm diameter and 2 mm thickness. The bond strength of porcelain to metal bars was tested with the shear strength test by Instron. Data were analyzed with student t-test and P<0.05 was considered as the limit of significance. Results: The mean failure load was 71.58±6.4 KgF for Supercast and 67.34±5.48 for Minalux alloy. The bond strength of Supercast and Minalux were 55.85±4.99 MPa and 52.54±4.27 MPa respectively. The difference was statistically significant (P0.001. Conclusions: This study showed that nickel-chromium-beryllium alloy (Supercast produced significantly better ceramometal bonding than nickel chromium alloy without beryllium (Minalux.

  19. Ultrasonic characterization of microstructure in powder metal alloy

    Science.gov (United States)

    Tittmann, B. R.; Ahlberg, L. A.; Fertig, K.

    1986-01-01

    The ultrasonic wave propagation characteristics were measured for IN-100, a powder metallurgy alloy used for aircraft engine components. This material was as a model system for testing the feasibility of characterizing the microstructure of a variety of inhomogeneous media including powder metals, ceramics, castings and components. The data were obtained for a frequency range from about 2 to 20 MHz and were statistically averaged over numerous volume elements of the samples. Micrographical examination provided size and number distributions for grain and pore structure. The results showed that the predominant source for the ultrasonic attenuation and backscatter was a dense (approx. 100/cubic mm) distribution of small micropores (approx. 10 micron radius). Two samples with different micropore densities were studied in detail to test the feasibility of calculating from observed microstructural parameters the frequency dependence of the microstructural backscatter in the regime for which the wavelength is much larger than the size of the individual scattering centers. Excellent agreement was found between predicted and observed values so as to demonstrate the feasibility of solving the forward problem. The results suggest a way towards the nondestructive detection and characterization of anomalous distributions of micropores when conventional ultrasonic imaging is difficult. The findings are potentially significant toward the application of the early detection of porosity during the materials fabrication process and after manufacturing of potential sites for stress induced void coalescence leading to crack initiation and subsequent failure.

  20. Corrosion resistance of metals and alloys in molten alkalies

    International Nuclear Information System (INIS)

    Zarubitskij, O.G.; Dmitruk, B.F.; Minets, L.A.

    1979-01-01

    Literature data on the corrosion of non-ferrous and noble metals, iron and steels in the molten alkalis and mixtures of their base are presented. It is shown that zirconium, niobium and tantalum are characterized by high corrosion stability in the molten NaOH. Additions of NaOH and KOH to the alkali chloride melts result in a 1000 time decrease of zirconium corrosion rate at 850 deg. The data testify to the characteristic passivating properties of OH - ions; Mo and W do not possess an ability to selfpassivation in hydroxide melts. Corrosion resistance of carbon and chromium-nickel steels in hydroxide melts depends considerably on the temperature, electrolyte composition and atmosphere over them. At the temperatures up to 600 deg C chromium-nickel steel is corrosion resistant in the molten alkali only in the inert atmosphere. Corrosion rate of chromium-nickel alloy is the lower the less chromium and the more nickel it contains. For the small installations the 4Kh18N25S2 and Kh23N28M3D3T steels can be recommended

  1. Computing elastic anisotropy to discover gum-metal-like structural alloys

    Science.gov (United States)

    Winter, I. S.; de Jong, M.; Asta, M.; Chrzan, D. C.

    2017-08-01

    The computer aided discovery of structural alloys is a burgeoning but still challenging area of research. A primary challenge in the field is to identify computable screening parameters that embody key structural alloy properties. Here, an elastic anisotropy parameter that captures a material's susceptibility to solute solution strengthening is identified. The parameter has many applications in the discovery and optimization of structural materials. As a first example, the parameter is used to identify alloys that might display the super elasticity, super strength, and high ductility of the class of TiNb alloys known as gum metals. In addition, it is noted that the parameter can be used to screen candidate alloys for shape memory response, and potentially aid in the optimization of the mechanical properties of high-entropy alloys.

  2. Advanced Testing Techniques to Measure the PWSCC Resistance of Alloy 690 and its Weld Metals

    Energy Technology Data Exchange (ETDEWEB)

    P.Andreson

    2004-10-01

    Wrought Alloy 600 and its weld metals (Alloy 182 and Alloy 82) were originally used in pressurized water reactors (PWRs) due to the material's inherent resistance to general corrosion in a number of aggressive environments and because of a coefficient of thermal expansion that is very close to that of low alloy and carbon steel. Over the last thirty years, stress corrosion cracking in PWR primary water (PWSCC) has been observed in numerous Alloy 600 component items and associated welds, sometimes after relatively long incubation times. The occurrence of PWSCC has been responsible for significant downtime and replacement power costs. As part of an ongoing, comprehensive program involving utilities, reactor vendors and engineering/research organizations, this report will help to ensure that corrosion degradation of nickel-base alloys does not limit service life and that full benefit can be obtained from improved designs for both replacement components and new reactors.

  3. Development of high-capacity nickel-metal hydride batteries using superlattice hydrogen-absorbing alloys

    International Nuclear Information System (INIS)

    Yasuoka, Shigekazu; Magari, Yoshifumi; Murata, Tetsuyuki; Tanaka, Tadayoshi; Ishida, Jun; Nakamura, Hiroshi; Nohma, Toshiyuki; Kihara, Masaru; Baba, Yoshitaka; Teraoka, Hirohito

    2006-01-01

    New R-Mg-Ni (R: rare earths) superlattice alloys with higher-capacity and higher-durability than the conventional Mm-Ni alloys with CaCu 5 structure have been developed. The oxidation resistibility of the superlattice alloys has been improved by optimizing the alloy composition by such as substituting aluminum for nickel and optimizing the magnesium content in order to prolong the battery life. High-capacity nickel-metal hydride batteries for the retail market, the Ni-MH2500/900 series (AA size type 2500mAh, AAA size type 900mAh), have been developed and commercialized by using an improved superlattice alloy for negative electrode material. alized by using an improved superlattice alloy for negative electrode material. (author)

  4. Development of high-capacity nickel-metal hydride batteries using superlattice hydrogen-absorbing alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yasuoka, Shigekazu; Magari, Yoshifumi; Murata, Tetsuyuki; Tanaka, Tadayoshi; Ishida, Jun; Nakamura, Hiroshi; Nohma, Toshiyuki [Mobile Energy Company, Sanyo Electric Co. Ltd., 7-3-2, Ibukidai-higashimachi Nishi-ku, Kobe, Hyogo 651-2242 (Japan); Kihara, Masaru; Baba, Yoshitaka; Teraoka, Hirohito [Sanyo Energy Twicell Co. Ltd., 307-2 Koyagimachi, Takasaki, Gunma 370-0071 (Japan)

    2006-06-01

    New R-Mg-Ni (R: rare earths) superlattice alloys with higher-capacity and higher-durability than the conventional Mm-Ni alloys with CaCu{sub 5} structure have been developed. The oxidation resistibility of the superlattice alloys has been improved by optimizing the alloy composition by such as substituting aluminum for nickel and optimizing the magnesium content in order to prolong the battery life. High-capacity nickel-metal hydride batteries for the retail market, the Ni-MH2500/900 series (AA size type 2500mAh, AAA size type 900mAh), have been developed and commercialized by using an improved superlattice alloy for negative electrode material. alized by using an improved superlattice alloy for negative electrode material. (author)

  5. Atomic Resolution Imaging of Nanoscale Structural Ordering in a Complex Metal Oxide Catalyst

    KAUST Repository

    Zhu, Yihan

    2012-08-28

    The determination of the atomic structure of a functional material is crucial to understanding its "structure-to-property" relationship (e.g., the active sites in a catalyst), which is however challenging if the structure possesses complex inhomogeneities. Here, we report an atomic structure study of an important MoVTeO complex metal oxide catalyst that is potentially useful for the industrially relevant propane-based BP/SOHIO process. We combined aberration-corrected scanning transmission electron microscopy with synchrotron powder X-ray crystallography to explore the structure at both nanoscopic and macroscopic scales. At the nanoscopic scale, this material exhibits structural and compositional order within nanosized "domains", while the domains show disordered distribution at the macroscopic scale. We proposed that the intradomain compositional ordering and the interdomain electric dipolar interaction synergistically induce the displacement of Te atoms in the Mo-V-O channels, which determines the geometry of the multifunctional metal oxo-active sites.

  6. Growth of carbon nanocone arrays on a metal catalyst: The effect of carbon flux ionization

    International Nuclear Information System (INIS)

    Levchenko, I.; Khachan, J.; Vladimirov, S. V.; Ostrikov, K.

    2008-01-01

    The growth of carbon nanocone arrays on metal catalyst particles by deposition from a low-temperature plasma is studied by multiscale Monte Carlo/surface diffusion numerical simulation. It is demonstrated that the variation in the degree of ionization of the carbon flux provides an effective control of the growth kinetics of the carbon nanocones, and leads to the formation of more uniform arrays of nanostructures. In the case of zero degree of ionization (neutral gas process), a width of the distribution of nanocone heights reaches 360 nm with the nanocone mean height of 150 nm. When the carbon flux of 75% ionization is used, the width of the distribution of nanocone heights decreases to 100 nm, i.e., by a factor of 3.6. A higher degree of ionization leads to a better uniformity of the metal catalyst saturation and the nanocone growth, thus contributing to the formation of more height-uniform arrays of carbon nanostructures.

  7. Selective dissolution of critical metals from diesel and naptha spent hydrodesulphurization catalysts

    International Nuclear Information System (INIS)

    Angelidis, T.N.; Tourasanidis, E.; Marinou, E.; Stalidis, G.A.

    1995-01-01

    The petroleum refining industry makes extensive use of catalysts, containing critical metals, such as, Mo, Co and Ni, for the desulphurization of various oil fractions. The selective recovery of these metals from two uncrushed and at low temperature calcined industrial hydrodesulphurization (Mo-Co/Al 2 O 3 and Mo-Ni/Al 2 O 3 -SiO 2 ) catalysts was studied, applying a two-step alkali-acid procedure. Fundamental kinetic aspects of the process, such as, reaction time, leaching reagents concentration and reaction temperature, were studied. Recoveries up to 97% for Mo and up to 92% for Co or Ni in separate solutions were achieved, using low cost and easily available reagents, such as sodium hydroxide and sulphuric acid

  8. First Principles Calculations of Transition Metal Binary Alloys: Phase Stability and Surface Effects

    Science.gov (United States)

    Aspera, Susan Meñez; Arevalo, Ryan Lacdao; Shimizu, Koji; Kishida, Ryo; Kojima, Kazuki; Linh, Nguyen Hoang; Nakanishi, Hiroshi; Kasai, Hideaki

    2017-06-01

    The phase stability and surface effects on binary transition metal nano-alloy systems were investigated using density functional theory-based first principles calculations. In this study, we evaluated the cohesive and alloying energies of six binary metal alloy bulk systems that sample each type of alloys according to miscibility, i.e., Au-Ag and Pd-Ag for the solid solution-type alloys (SS), Pd-Ir and Pd-Rh for the high-temperature solid solution-type alloys (HTSS), and Au-Ir and Ag-Rh for the phase-separation (PS)-type alloys. Our results and analysis show consistency with experimental observations on the type of materials in the bulk phase. Varying the lattice parameter was also shown to have an effect on the stability of the bulk mixed alloy system. It was observed, particularly for the PS- and HTSS-type materials, that mixing gains energy from the increasing lattice constant. We furthermore evaluated the surface effects, which is an important factor to consider for nanoparticle-sized alloys, through analysis of the (001) and (111) surface facets. We found that the stability of the surface depends on the optimization of atomic positions and segregation of atoms near/at the surface, particularly for the HTSS and the PS types of metal alloys. Furthermore, the increase in energy for mixing atoms at the interface of the atomic boundaries of PS- and HTSS-type materials is low enough to overcome by the gain in energy through entropy. These, therefore, are the main proponents for the possibility of mixing alloys near the surface.

  9. Heat of solution and site energies of hydrogen in disordered transition-metal alloys

    International Nuclear Information System (INIS)

    Brouwer, R.C.; Griessen, R.

    1989-01-01

    Site energies, long-range effective hydrogen-hydrogen interactions, and the enthalpy of solution in transition-metal alloys are calculated by means of an embedded-cluster model. The energy of a hydrogen atom is assumed to be predominantly determined by the first shell of neighboring metal atoms. The semiempirical local band-structure model is used to calculate the energy of the hydrogen atoms in the cluster, taking into account local deviations from the average lattice constant. The increase in the solubility limit and the weak dependence of the enthalpy of solution on hydrogen concentration in disordered alloys are discussed. Calculated site energies and enthalpies of solution in the alloys are compared with experimental data, and good agreement is found. Due to the strong interactions with the nearest-neighbor metal atoms, hydrogen atoms can be used to determine local lattice separations and the extent of short-range order in ''disordered'' alloys

  10. A novel dynamic kinetic model of oxygen isotopic exchange on a supported metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Galdikas, Arvaidas; Duprez, Daniel; Descorme, Claude

    2004-09-15

    A time-resolved kinetic analysis has been developed for modeling experimental results of {sup 18}O/{sup 16}O isotopic exchange over oxide-supported metal catalysts. Model is based on two very important points: (1) the parallel calculation of surface and bulk diffusion and (2) the implication of certain O species such as superoxides. The model includes adsorption-desorption processes on metal clusters and oxygen spillover from the metal to the surface of support and vice versa. Different mechanisms of exchange were also taken into account via mononuclear (O atoms, O{sup -}, OH) or binuclear (superoxides) oxygen species. A refined model taking into account surface diffusion, direct exchange on surface of support by binuclear oxygen species and bulk diffusion was also developed. Kinetic (reaction rates and diffusion coefficients) as well as thermodynamic parameters (activation energies) were derived by fitting theoretical and experimental curves of {sup 18}O{sub 2}, {sup 18}O{sup 16}O and {sup 16}O{sub 2} gas phase concentrations versus time. The experimental results of Pt/CeZrO{sub 2} catalyst samples obtained in the 200-450 deg. C range of temperatures are examined. The refined model provides a very good fitting of the kinetic curves recorded with ceria-zirconia-supported catalysts. Moreover, values of diffusion coefficients and activation energies are in good agreement with already published values found by other methods. For a better understanding of all the steps of exchange, the kinetics of {sup 18}O and {sup 16}O distribution on the surface of metal clusters and on the surface of support are calculated and analyzed. On the basis of this model, a computer code is developed for analysis and calculations of kinetic and thermodynamic parameters of automotive catalysts.

  11. Graphene from Alginate Pyrolysis as a Metal-Free Catalyst for Hydrogenation of Nitro Compounds.

    Science.gov (United States)

    Trandafir, Mihaela-Mirela; Florea, Mihaela; Neaţu, Florentina; Primo, Ana; Parvulescu, Vasile I; García, Hermenegildo

    2016-07-07

    Graphene obtained by pyrolysis of alginate at 900 °C under inert atmosphere and exfoliation is used as a metal-free catalyst for reduction of nitro to amino groups with hydrogen as a reagent. The process is general for aromatic and aliphatic, conjugated and isolated nitro groups, and occurs with low selectivity over hydrogenation of carbon-carbon double bonds. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Pd Metal Catalysts for Cross-Couplings and Related Reactions in the 21st Century: A Critical Review.

    Science.gov (United States)

    Biffis, Andrea; Centomo, Paolo; Del Zotto, Alessandro; Zecca, Marco

    2018-02-28

    Cross-couplings and related reactions are a class of highly efficient synthetic protocols that are generally promoted by molecular Pd species as catalysts. However, catalysts based on more or less highly dispersed Pd metal have been also employed for this purpose, and their use, which was largely limited to the Heck reaction until the turn of the century, has been extended in recent years to most reactions of this class. This review provides a critical overview on these recent applications of Pd metal catalysts. Particular attention is devoted to the discussion of the mechanistic pathways that have been proposed to explain the catalytic role of Pd metal. Furthermore, the most outstanding Pd metal based catalytic systems that have emerged are illustrated, together with the development of novel approaches to boost the reactivity of Pd metal. A section summarizing the current industrial applications of Pd metal catalyzed reactions of this kind concludes the review.

  13. NF ISO 10270. Corrosion of metals and alloys. Aqueous corrosion tests of zirconium alloys used in nuclear reactors

    International Nuclear Information System (INIS)

    2002-06-01

    This international standard prescribes the determination of the mass gain and the superficial control of zirconium and zirconium alloy products after a corrosion test performed in water at 360 deg. C and in steam at 400 deg. C or more. A pressure of 10.3 MPa (1500 psi) is applied during the tests performed in vapor. This standard applies to welded and molded products, to powder metallurgy products and to filler metals for welding application. The method has been widely used in the development of new alloys and new techniques of thermal treatment and in the evaluation of welding techniques. (J.S.)

  14. DKG statement on the use of metal alloy discs for patch testing in suspected intolerance to metal implants.

    Science.gov (United States)

    Thomas, Peter; Geier, Johannes; Dickel, Heinrich; Diepgen, Thomas; Hillen, Uwe; Kreft, Burkhard; Schnuch, Axel; Szliska, Christiane; Mahler, Vera

    2015-10-01

    Intolerance reactions to metal implants may be caused by metal allergy. However, prior to implantation, 'prophetic'/prophylactic patch testing should not be performed. Pre-implant patch testing should only be done to verify or exclude metal allergy in patients with a corresponding history. In case of implant-related complications - in particular following replacement arthroplasty - such as pain, effusion, skin lesions, reduced range of motion or implant loosening, orthopedic causes should be ruled out first. Workup of suspected metal implant allergy should then be done using the DKG standard series, which includes nickel, cobalt, and chromium preparations. Various studies assessing the usefulness of metal alloy discs for patch testing have shown this particular approach to be ineffective with respect to providing reliable information on metal allergy. Any positive reaction in such tests cannot be assigned to a specific metal contained within the alloy. Furthermore, there is a risk of broad and indiscriminate use of these readily available discs. Accordingly, given the lack of additional benefit compared to patch testing with standardized metal salt preparations, we do not recommend patch testing with metal alloy discs. © 2015 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.

  15. Alloyed Ni-Fe nanoparticles as catalysts for NH3 decomposition

    DEFF Research Database (Denmark)

    Simonsen, Søren Bredmose; Chakraborty, Debasish; Chorkendorff, Ib

    2012-01-01

    temperatures and a low NH3-to-H2 ratio, the catalytic activity of the best Ni-Fe/Al2O3 catalyst was found to be comparable or even better to that of a more expensive Ru-based catalyst. Small Ni-Fe nanoparticle sizes are crucial for an optimal overall NH3 conversion because of a structural effect favoring...

  16. Noble metal nanoparticle@metal oxide core/yolk-shell nanostructures as catalysts: recent progress and perspective.

    Science.gov (United States)

    Li, Guodong; Tang, Zhiyong

    2014-04-21

    Controllable integration of noble metals (e.g., Au, Ag, Pt, and Pd) and metal oxides (e.g., TiO₂, CeO₂, and ZrO₂) into single nanostructures has attracted immense research interest in heterogeneous catalysis, because they not only combine the properties of both noble metals and metal oxides, but also bring unique collective and synergetic functions in comparison with single-component materials. Among many strategies recently developed, one of the most efficient ways is to encapsulate and protect individual noble metal nanoparticles by a metal oxide shell of a certain thickness to generate the core-shell or yolk-shell structure, which exhibits enhanced catalytic performance compared with conventional supported catalysts. In this review article, we summarize the state-of-the art progress in synthesis and catalytic application of noble metal nanoparticle@metal oxide core/yolk-shell nanostructures. We hope that this review will help the readers to obtain better insight into the design and application of well-defined nanocomposites in both the energy and environmental fields.

  17. Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

    Directory of Open Access Journals (Sweden)

    Hui Dai

    2017-06-01

    Full Text Available Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction.

  18. Oxidation of ethoxylated fatty alcohols to alkylpolyglycol carboxylic acids using noble metals as catalysts

    Directory of Open Access Journals (Sweden)

    Sagredos, Angelos

    2009-09-01

    Full Text Available The conversion of ethoxylated fatty alcohols to the corresponding carboxylic acids through dehydrogenation/ oxidation using noble-metal catalysts has been studied. Ethoxylated primary aliphatic alcohols, ethoxylated random secondary aliphatic alcohols and ethoxylated alkylphenols have been converted to the corresponding acids in the presence of a base. The noble metal catalysts Palladium and Platinum were used without significant degradation of the ethoxyl chain in yields that exceeded 90%. On the other hand, the catalysts Rhodium and Ruthenium gave yields of about 80% and 60% respectively.La conversión de alcoholes grasos etoxilados a los correspondientes ácidos carboxílicos por deshidrogenación/ oxidación con metales nobles como catalizador ha sido estudiada. Alcoholes primarios alifáticos etoxilados, alcoholes alifáticos secundarios etoxilados al azar y alquilfenoles etoxilados han sido convertidos a los correspondientes ácidos en presencia de base. Los catalizadores paladio y platino fueron usados sin degradación significativa de las cadenas etoxiladas con un rendimiento que excedió del 90%. Por otra parte catalizadores de rodio y rutenio produjeron rendimientos del 80 y 60%, respectivamente.

  19. Outstanding resistance and passivation behaviour of new Fe-Co metal-metal glassy alloys in alkaline media.

    Directory of Open Access Journals (Sweden)

    Khadijah M Emran

    Full Text Available The electrochemical behavior of the oxide layers on two metal-metal glassy alloys, Fe78Co9Cr10Mo2Al1 (VX9and Fe49Co49V2 (VX50 (at.%, were studied using electrochemical techniques including electrochemical frequency modulation (EFM, electrochemical impedance spectroscopy (EIS and cyclic polarization (CP measurements. The morphology and composition of the alloy surfaces were investigated using X-ray photoelectron spectroscopy (XPS, scanning electron microscopy (SEM and atomic force microscopy (AFM. The corrosion rate and surface roughness of both alloys increased as the concentration of NaOH in aqueous solution was raised. The presence of some protective elements in the composition of the alloys led to the formation of a spontaneous passive layer on the alloy surface. The higher resistance values of both alloys were associated with the magnitude of the dielectric properties of the passive films formed on their surfaces. Both alloys are classified as having outstanding resistance to corrosion, which results from the formation of a passive film that acts as an efficient barrier to corrosion in alkaline solution.

  20. Outstanding resistance and passivation behaviour of new Fe-Co metal-metal glassy alloys in alkaline media.

    Science.gov (United States)

    Emran, Khadijah M; Al-Harbi, Albandaree K

    2018-01-01

    The electrochemical behavior of the oxide layers on two metal-metal glassy alloys, Fe78Co9Cr10Mo2Al1 (VX9)and Fe49Co49V2 (VX50) (at.%), were studied using electrochemical techniques including electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and cyclic polarization (CP) measurements. The morphology and composition of the alloy surfaces were investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion rate and surface roughness of both alloys increased as the concentration of NaOH in aqueous solution was raised. The presence of some protective elements in the composition of the alloys led to the formation of a spontaneous passive layer on the alloy surface. The higher resistance values of both alloys were associated with the magnitude of the dielectric properties of the passive films formed on their surfaces. Both alloys are classified as having outstanding resistance to corrosion, which results from the formation of a passive film that acts as an efficient barrier to corrosion in alkaline solution.