Дисертації з теми "Bimetallic alloys"
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Aas, C. J. "Ab initio calculations of the magnetic properties of bimetallic alloys." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/4302/.
Повний текст джерелаHaire, Andrew Richard. "Probing the influence of bimetallic composition on the Pd/Au catalysed synthesis of vinyl acetate monomer." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1018.
Повний текст джерелаMerritt, Travis Robert. "Optoperforation of Intact Plant Cells, Spectral Characterization of Alloy Disorder in InAsP Alloy Disorder in InAsP Alloys, and Bimetallic Concentric Surfaces for Metal-Enhanced Fluorescence in Upconverting Nanocrystals." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25148.
Повний текст джерелаPh. D.
Ikpo, Chinwe Oluchi. "Development of high performance composite lithium ion battery cathode systems with carbon nanotubes functionalised with bimetallic inorganic nanocrystal alloys." Thesis, University of Western Cape, 2011. http://hdl.handle.net/11394/3797.
Повний текст джерелаLithium ion cathode systems based on composites of lithium iron phosphate (LiFePO₄), iron-cobalt-derivatised carbon nanotubes (FeCo-CNT) and polyaniline (PA) nanomaterials were developed. The FeCo-functionalised CNTs were obtained through in-situ reductive precipitation of iron (II) sulfate heptahydrate (FeSO₄.7H₂O) and cobalt (II) chloride hexahydrate (CoCl₂.6H₂O) within a CNT suspension via sodium borohydrate (NaBH₄) reduction protocol. Results from high Resolution Transmission Electron Microscopy (HRTEM) and Scanning Electron Microscopy (SEM) showed the successful attachment FeCo nanoclusters at the ends and walls of the CNTs. The nanoclusters provided viable routes for the facile transfer of electrons during lithium ion deinsertion/insertion in the 3-D nanonetwork formed between the CNTs and adjacent LiFePO₄ particles.
Alcantara, Ortigoza Marisol. "Theoretical studies of electronic, vibrational, and magnetic properties of chemisorbed surfaces and nanoalloys." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/496.
Повний текст джерелаOwens, Thomas Graham. "The promoting role of Au in the Pd-catalysed synthesis of vinyl acetate monomer." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/352.
Повний текст джерелаMacLeod, Norman. "Alloy formation in bimetallic reforming catalysts." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388553.
Повний текст джерелаRoss, Nick Mark. "Interfacial Electrochemistry of Cu/Al Alloys for IC Packaging and Chemical Bonding Characterization of Boron Doped Hydrogenated Amorphous Silicon Films for Infrared Cameras." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc849696/.
Повний текст джерелаWise, Anna MacDonald. "Characterisation of bimetallic alloy and core-shell electrocatalysts." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/341819/.
Повний текст джерелаRoss, Nick. "Interfacial Electrochemistry of Cu/Al Alloys for IC Packaging and Chemical Bonding Characterization of Boron Doped Hydrogenated Amorphous Silicon Films for Infrared Cameras." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849696/.
Повний текст джерелаKühn, Laura. "Bimetallic aerogels for electrocatalytic applications." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-226469.
Повний текст джерелаMigliaccio, Luca. "Bimetallic catalysts for CO2 electroreduction." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14470/.
Повний текст джерелаLi, Molly Meng-Jung. "Bimetallic alloy catalysts for green methanol production via CO2 and renewable hydrogen." Thesis, University of Oxford, 2018. https://ora.ox.ac.uk/objects/uuid:7e28950e-85e9-4d9a-b791-3f5d1172065e.
Повний текст джерелаYi, Cheol-Woo. "Surface spectroscopic studies of mono- and bimetallic model catalysts." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4787.
Повний текст джерелаChiang, Wei-Hung. "Engineering Nanocatalysts for Selective Growth of Carbon Nanotubes." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1238692060.
Повний текст джерелаMeng, Zhengong. "Direct synthesis of magnetic bimetallic alloy nanoparticles from organometallic precursors and their applications." HKBU Institutional Repository, 2016. https://repository.hkbu.edu.hk/etd_oa/283.
Повний текст джерелаKhan, Munir Ullah [Verfasser]. "Synthesis of Bimetallic Pt3Co Alloy Nanocrystals for Heterogeneous Hydrogenation of CO2 to Methanol / Munir Ullah Khan." München : GRIN Verlag, 2019. http://d-nb.info/1181611504/34.
Повний текст джерелаFina, Federica. "Metal loaded g-C₃N₄ for visible light-driven H₂ production." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6322.
Повний текст джерелаZepon, Guilherme. "Spray forming of wear and corrosion resistant bimetallic pipes : from the alloy design to the semi- industrial process." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/7734.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
The oil exploitation and production at the pre-salt fields in a safety and efficient way depends on the development of materials that withstand the severe work conditions found in these fields. For instance, pipes, such as drilling risers and casings, are often subjected to severe wear and corrosion conditions. This thesis is dedicated to evaluate the technical feasibility to produce wear and corrosion resistant bimetallic pipes by spray forming. The processing-microstructure-properties relationship of the spray-formed boron-modified supermartensitic stainless steel (SMSS) grades was comprehensively studied. Deposits of SMSS with boron contents ranging from 0.3 %wt. to 1.0 %wt. were processed by spray forming. The spray-formed boron-modified SMSS deposits had the wear resistance evaluated through different wear tests and their corrosion resistances by means of electrochemical techniques. It was demonstrated that the wear resistance of the spray-formed boron-modified SMSS is determined by the presence of the eutectic network of M 2B-type borides resulted from the spray forming process. On the other hand, the corrosion resistance of the spray-formed boron-modified SMSS is controlled by the chemical composition of the martensitic matrix. Furthermore, spray-formed bimetallic pipes composed of boron-modified SMSS and conventional SMSS were produced in the unique semi-industrial scale spray-forming plant of the Foundation Institute of Materials Science (IWT-University of Bremen, Germany). The relationship between the process parameters and the metallurgical quality of the pipes was addressed. It was shown that the key to produce a spray-formed bimetallic pipe with good metallurgical quality is adjusting the process parameters in such a way that the deposition zone’s temperature is kept within the alloy’s solidification temperature range during the whole deposition process. Moreover, solidification and grain size evolution models in spray forming were proposed. Finally, the mechanical properties of one of the spray-formed bimetallic pipes in the as-spray formed condition and after heat treatments were evaluated.
A exploração e produção de petróleo nos poços do pré-sal de modo seguro e eficiente dependem do desenvolvimento de ligas que suportem severas condições de trabalho. Por exemplo, tubos como risers de perfuração e casings são frequentemente submetidos à severas condições de desgaste e corrosão. Esta tese se dedica a avaliar a viabilidade técnica de produzir tubos bimetálicos resistentes à corrosão e ao desgaste conformados por spray. A relação processamento-microestrutura-propriedade do aço inoxidável supermartensítico (AISM) modificado com boro e conformado por spray foi estudada de forma abrangente. Depósitos de AISM com teores de boro variando de 0,3%p. a 1,0%p. foram processados por conformação por spray. Os depósitos tiveram a resistência ao desgaste avaliada através de diferentes ensaios e a resistência à corrosão por meio de técnicas eletroquímicas. Demonstrou-se que a resistência ao desgaste das ligas modificadas com boro é determinada pela presença de boretos eutéticos, do tipo M2B, oriunda do processo de conformação por spray. Por outro lado, a resistência à corrosão das ligas modificadas com boro é controlada pela composição química da matriz. Além disso, tubos bimetálicos compostos de AISM modificado com boro e AISM convencional foram produzidos em escala semi-industrial na planta de conformação por spray do Instituto de Ciência dos Materiais (IWT-Universidade de Bremen). A relação entre os parâmetros de processo e a qualidade metalúrgica dos tubos foi tratada. Mostrou-se que a chave para produzir tubos bimetálicos conformados por spray com boa qualidade metalúrgica é o ajustar os parâmetros do processo de tal modo que a temperatura da zona de deposição permaneça dentro do intervalo de solidificação da liga durante todo processo. Além disso, modelos de solidificação e evolução de tamanho de grão em conformação por spray foram propostos. Finalmente, avaliou-se as propriedades mecânicas de um dos tubos bimetálicos conformado por spray, com e sem tratamentos térmicos.
FAPESP: 12/25352-4
Courtois, Julien. "Iridium-based bimetallic alloy catalysts for the ethanol oxidation reaction for fuel cells modeled by density functional theory." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/295.
Повний текст джерелаDamian, Alexis. "In situ STM study of the growth and dissolution processes on bimetallic Pd/Au(111) substrates and of ultrathin alloy layers on Au(111)." Phd thesis, Ecole Polytechnique X, 2009. http://pastel.archives-ouvertes.fr/pastel-00005915.
Повний текст джерелаSha, Jin. "Catalyseurs bimétalliques pour l'oxydation des hydrates de carbone : recherche d'effets de synergie." Thesis, Ecole centrale de Lille, 2018. http://www.theses.fr/2018ECLI0009/document.
Повний текст джерелаThe supported bimetallic nanoparticles are particularly attractive catalysts due to the increased activity and stability over their monometallic counterparts. In this thesis, gold-based solids have been studied as catalysts for the selective base-free oxidation of glucose. It has been demonstrated that the variation of the molar ratio between gold and the second metal (Pd, Pt, or Cu) has a different impact on the catalytic performances depending on the nature of the second metal, the support and the method of preparation. TiO2 supported Au-Pd series prepared by the sol-immobilization method and Au-Cu series prepared by the precipitation-reduction method showed a significant synergistic effect, particularly when the ratio of the two metals was 1. Under the reaction conditions used (T = 60 °C or 80 °C, P = 5 bar air, t = 5 h), these catalysts selectivity to gluconic acid and their activity was found to be greater than that of monometallic counterparts, especially when the catalyst is supported on TiO2. XPS analysis showed that the Au+δ, Pd+2 and CuOH species played an important role in the base-free reaction. Bismuth as the second metal showed no beneficial effect, unlike palladium and copper. The Au-Pt catalysts supported on ZrO2 proved to be still active when the gold content was less than 0.3 wt.%. Ultimately, the nature of the support has a very important impact on the mechanism of the base-free reaction conducted on gold-based catalysts (formation of H2O2 in situ). The reason lies in the interactions of the support with the bimetallic phase thus favoring the formation of the active species
Prunier, Hélène. "Synthèse et étude des propriétés structurales thermodynamiques et catalytiques de nanoparticules bimétalliques Au-Cu par microscopie électronique en transmission corrigée d'abérrations." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC122/document.
Повний текст джерелаThe emergence of new materials, structured at the nanoscale, with controlled properties, has opened new prospects regarding materials around us. In particular for metals and alloys, it seems crucial to connect their structural properties to their chemical and physical properties in order to optimise their use.Within this context, this thesis is focused on the synthesis and the characterisation of Au-Cu bimetallic alloy nanoparticles by transmission electron microscopy. On the basis of the bulk phase diagram, we especially studied particles with nominal compositions Au3Cu, AuCu et AuCu3.The first part of this work is dedicated to the synthesis of nanoparticles in two different ways. The chemical way is based on the polyol process and leads to nanoparticles exhibiting a cubic shape, and a systematically rich Au content. On the other hand, nanoparticles obtained by Pulsed Laser Deposition (PLD), a physical method of synthesis, display a well-controlled and tuneable composition. From a structural point of view, the annealing of the particles leads to chemical order and the stabilisation of L10 and L12 structures. However, we reveal that this phase transition is blocked in nanostructures with crystal defects. Moreover, we establish the evolution of the lattice parameter of the particles as a function of the composition and we demonstrate that, as in the bulk case, it is in agreement with Vegard’s law.In the second part, the nanoparticles synthesised via the physical method are studied using environmental transmission electron microscopy, i.e. in conditions close to those usually applied in catalytic reactors. Experiments performed at high temperature highlight that the dissolution of Au and Au-Cu nanoparticles occurs in a two-step process: fusion occurs first and is followed by evaporation for nanoparticles with a mean diameter of 10 nm.Coupling heating with gas flow (H2 or O2) in higher pressure condition than those usually reached allows us to study the thermodynamic behaviour of the nanoparticles in oxidative or reductive conditions. Most Notably, we show that oxidation-reduction cycles performed on nanoparticles with a diameter larger than 20 nm leads to a Kirkendall effect and the reversible formation of hollow particles (doughnuts).This cross-disciplinary thesis is a pioneering work towards understanding the bimetallic Au-Cu alloy system at atomic scale
Mailu, Stephen Nzioki. "Development of electrochemical sensors containing bimerallic silver and gold nanoparticles." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_7576_1305534870.
Повний текст джерелаIn this work, a simple, less time consuming electrochemical method in the form of an electrochemical sensor has been developed for the detection of PAHs. The sensor was fabricated by the deposition of silver-gold (1:3) alloy nanoparticles (Ag-AuNPs) on ultrathin overoxidized polypyrrole (PPyox) film which formed a PPyox/Ag-AuNPs composite on glassy carbon electrode (PPyox/Ag-AuNPs/GCE). The silver-gold alloy nanoparticles deposited to form the composite were chemically prepared by simultaneous reduction of silver nitrate (AgNO3) and chloroauric acid (HAuCl4) using sodium citrate and characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the alloy nanoparticles.
Conn, Brian E. "Revealing the Magic in Silver Magic Number Clusters: The Development of Size-Evolutionary Patterns for Monolayer Coated Silver-Thiolate Nanoclusters." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1481294367098454.
Повний текст джерелаFodor, Anna. "Heterogeneous metal-catalysed C-C coupling reactions : research and development." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2256/document.
Повний текст джерелаNew bimetallic palladium/copper catalysts were developed by successive impregnation (TSI) and co-impregnation (CI) on 4Å molecular sieve (4A) and MgAlO mixed oxides supports. The fresh catalysts were characterised and tested in the Suzuki–Miyaura reaction to test their activity, selectivity and stability. It was observed that while the Cu-Pd-4A-TSI catalyst kept its activity during six cycles that of the Cu-Pd-4A-CI dropped. On MgAlO support the catalyst prepared with CI proved to be stable even for six runs contrary to TSI. The active phase of the reaction – namely the Cu–Pd alloy with atomic ratio 1:1 - was determined with the help of catalyst characterisation of the recovered catalysts. This observation confirms that whatever the way of preparation or the support is, the key-point is the presence of Pd-Cu 1:1 particles to enhance the catalytic performances. A crucial difference between the MgAlO and 4A supported catalyst was found in the reaction time necessary for the Suzuki–Miyaura reaction. With the Cu-Pd-MgAl-CI catalyst the reaction time could be reduced to thirty minutes contrary to one hour with Cu-Pd-4A-TSI. Moreover it was concluded that with a more basic support the reduction of the quantity of the base was possible however it brought slightly decreasing yield. The Petasis-borono Mannich reaction was also performed in the presence of each mono-and bimetallic catalysts
Zhe, Miao. "Réactivité et propriétés mécaniques des interfaces entre un alliage Al-Si et un renfort Fe ou Ti." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00648832.
Повний текст джерелаBasha, D. Althaf. "Phase Transformation Behavior Of Embedded Bimetallic Nanoscaled Alloy Particles In Immiscible Matrices." Thesis, 2013. http://hdl.handle.net/2005/2599.
Повний текст джерелаTaufany, Fadlilatul, and 陶凡. "Nanostructructured Engineering of Pt-based Bimetallic Alloy and Core-Shell Electrocatalysts for DMFCs Applications." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/79455454439023420313.
Повний текст джерела國立臺灣科技大學
化學工程系
99
This dissertation summarizes the author’s research efforts to synthesize Pt-based bimetallic alloy and core-shell nanostructured electrocatalysts for applications in direct methanol fuel cells (DMFCs) that can be applied to both their anode and cathode sides. The behavior of bimetallic Pt-based catalysts are fundamentally different to their counter-monometallic catalysts, i.e. Pt and M (M is the second metal, e.g. Pd, Cr, Co, Fe, Sn, Ru, etc.). The addition of the second metal to Pt significantly enhances the rate of electrochemical oxidation and/or reduction in fuel cells; thereby achieving the maximum activity, together with exceptional selectivity and stability. The state-of-the-art of bimetallic Pt-based catalysts is highly dependent on the composition, structure, morphology, particle size, degree of alloying, and other properties. Overall, Pt-based alloy and core-shell nanostructured catalysts are emerging as one of the most promising solutions to address the existing challenges in DMFCs, namely the cost of the catalysts (Pt as the ‘common catalyst’, but it is scarce and extremely expensive) and the sluggish nature of the Pt-kinetic activity with respect to both the anode and cathode reactions. In this dissertation, three synthesis methods have been developed and used to prepare three different Pt-based electrocatalysts with well-controlled sizes, structures, and compositions. Structurally these Pt-based alloyed electrocatalysts are carbon-supported Pt-Cr (Pt-Cr/C), and Pt-Ru (Pt-Ru/C) catalysts; while for the core-shell structure, a carbon-supported Pt-monolayered shell on a Pd-core (PdcorePtmonoshell/C) was developed. Since these catalysts have their own characteristics in the functionalities in the anode or cathode reactions, each of them will be discussed in detail as a separate topic. In the search for an alternative to core-shell structured nanoparticle catalysts, with an active Pt-monolayer, supported on the surface of a dimensionally-stable (PdcorePtmonoshell), here we report a kinetically-controlled autocatalytic chemical process, in which a sacrificial Cu-monolayer on Pd nanoparticles (NPs) is autocatalytically deposited under kinetically-controlled conditions and which is later displaced to form a Pt-monolayer via redox-transmetallation. This process is also adaptable for use as a general protocol for the fabrication of bimetallic core@shell structured NPs, some examples being: Pt@Pd, Ir@Pt, and Ir@Pd. Unlike the thermodynamically-controlled under-potential deposition (UPD) process, the method presented here allows for the scaling-up of production of well-defined core@monolayered shell Pd@Pt nanoparticles without the need for any additional reducing agents and/or electrochemical treatments. Having immediate and obvious commercial potential PdcorePtmonoshell/C NPs have been systematically characterized by in situ X-ray absorption (XAS), electrochemical-FTIR, transmission electron microscopy (TEM), and electrochemical techniques; both during synthesis, and subsequent testing in one particularly important catalytic reaction, namely the oxygen reduction reaction (ORR) which is pivotal in fuel cell operation. It was found that the bimetallic Pd@Pt NPs exhibited a significantly enhanced electrocatalytic activity, with respect to this reaction, in comparison with their monometallic counterparts. In the development of Pt-Cr/C catalysts, two different methods were used to prepare bimetallic Pt3Cr1/C nanocatalysts from similar compositions where the resulting materials exhibit different alloying extents (structure). We investigated how these variations in alloying extent impact the catalytic activity, stability, and selectivity in the ORR. One method, based on the slow thermal decomposition of the Cr precursor at a rate that matches the chemical reduction of the Pt precursor, allows fine control of the Pt3Cr1/C alloy’s composition; whereas the second approach, using the conventional ethylene glycol method results in considerable deviation (> 25%) from the projected composition. Consequently these two methods give variations in the alloying extent that has a strong influence on the Pt d-band vacancy and the Pt-electroactive surface area (Pt-ECSA). This relationship was systematically evaluated using TEM, XAS, and electrochemical analyses. The ORR activity depends on two effects that nullify each other, namely the number of active Pt-sites and their activity. Here the Pt-site activity dominates in governing the ORR activity. The nanocatalyst’s selectivity towards the ORR and the competitive methanol oxidation reaction (MOR) depend on these two effects acting in cooperation to give enhanced ORR activity with suppressed MOR. The number of active Pt-sites is associated with the Pt-ECSA value, while the Pt-site activity is associated with the alloying extent and Pt d-band vacancy (electronic) effects. The presence of Cr atoms in Pt3Cr1/C enhances stability during electrochemical treatment. Overall, the Pt3Cr1/C catalyst prepared by the controlled composition synthesis was shown to be superior in ORR activity, selectivity, and stability owing to its favorable alloying extent, Pt d-band vacancy, and Pt-ECSA. While for the development of Pt-Ru/C catalysts, a controlled composition–based method, i.e. the microwave-assisted ethylene glycol (MEG) method was successfully developed to prepare bimetallic PtxRu100–x/C nanocatalysts with different alloy compositions. This study highlights the impact of the variation in alloy composition of PtxRu100–x/C catalysts on their alloying extent (structure) and subsequently their catalytic activity toward the MOR. The alloying extent of these PtxRu100–x/C catalysts has a strong influence on their Pt d–band vacancy and Pt–ECSA: this relationship was systematically evaluated using XAS, scanning electron microscopy-coupled with energy dispersive X–ray spectroscopy, TEM, density functional theory calculations, and electrochemical analyses. The MOR activity depends the on the number and activity of the Pt-sites. Here the number of active Pt-sites is associated with the Pt–ECSA value, while the Pt–site activity is associated with the alloying extent and Pt d–band vacancy (electronic) effects. Among the PtxRu100–x/C nanocatalyts with various Pt:Ru atomic ratios (x= 25, 50, and 75), the Pt75Ru25/C nanocatalyst was shown to be superior with respect to the MOR activity owing to its favorable alloying extent, Pt d–band vacancy, and Pt–ECSA.
Stephens, John Adam. "Simulation tools for predicting the atomic configuration of bimetallic catalytic surfaces." 2012. http://hdl.handle.net/2152/22175.
Повний текст джерелаtext
Sinha, Shyam Kanta. "Synthesis and Transformation of AuCu Intermetallic Nanoparticles." Thesis, 2013. http://etd.iisc.ernet.in/2005/3407.
Повний текст джерела(8953583), Nicole J. Libretto. "ADVANCED CHARACTERIZATIONS FOR THE IDENTIFICATION OF CATALYST STRUCTURES AND REACTION INTERMEDIATES." Thesis, 2020.
Знайти повний текст джерелаIn recent decades, alternatives to traditional coal and fossil fuels were utilized to reduce carbon emissions. Among these alternatives, natural gas is a cleaner fuel and is abundant globally. Shale gas, a form of natural gas that also contains light alkanes (C2-C4), is presently being employed to produce olefins, which can be upgraded to higher molecular weight hydrocarbons. This thesis describes efforts to develop new catalytic materials and characterizations for the conversion of shale gas to fuels.
In the first half, silica supported Pt-Cr alloys containing varying compositions of Pt and Pt3Cr were used for propane dehydrogenation at 550°C. Although a change in selective performance was observed on catalysts with varying promoter compositions, the average nano-particle structures determined by in situ, synchrotron x-ray absorption spectroscopy (XAS) and x-ray diffraction (XRD) were identical. Further, this work presents a method for the characterization of the catalytic surface by these methods to understand its relationship with olefin selectivity. From this, we can gain an atomically precise control of new alloys compositions with tunable surface structures.
Once formed by dehydrogenation, the intermediate olefins are converted to fuel-range hydrocarbons. In the second half, previously unknown single site, main group Zn2+ and Ga3+ catalysts are shown to be effective for oligomerization and the resulting products follow a Schutlz Flory distribution. Mechanistic studies suggest these catalysts form metal hydride and metal alkyl reaction intermediates and are active for olefin insertion and b-H elimination elementary steps, typical for the homogeneous, Cossee-Arlman oligomerization mechanism. Evidence of metal hydride and metal alkyl species were observed by XAS, Fourier transform infrared spectroscopy (FTIR), and H2/D2 isotope exchange. Understanding the reaction intermediates and elementary steps is critical for identifying novel oligomerization catalysts with tunable product selectivity for targeted applications.
Through controlled synthesis and atomic level in situ characterizations, new catalysts compositions can be developed with high control over the resulting performance. An atomically precise control of the catalyst structure and understanding how it evolves under reaction conditions can help shed light on the fundamental principles required for rational catalyst design.
Wu, shiuan-yau, and 吳亘曜. "Theoretical Calculation to study the Following Reactions:I.The Interaction of NOx on Ni(111) surface.II.The NO Dissociation on Ni-Pt bimetallic SurfacesIII.The CO2 Reaction on WC and WC-Co alloy Surfaces." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/4p2e26.
Повний текст джерела國立臺灣師範大學
化學系
100
Abstract 1st part: The interaction of NOx on Ni(111) surface investigated with quantum-chemical calculations We applied periodic density-functional theory to investigate the interaction of NOx on Ni(111) surface for small and large coverages. For a small coverage, adsorbed species such as NO, N2O and NO2 tend to dissociate to form atomic N and atomic O on the surface, but a large barrier, 2.34 eV, hinders the recombination of adsorbed N to form N¬2. At a large coverage, the recombination of N and NO to form N2O is favorable; this species might either desorb or break the N-O bond to form N2. Our calculated results agree satisfactorily with experimental observations. The formation of N2 via paths that vary with coverage is analyzed and discussed. 2nd part: The NO reaction on Ni-Pt bimetallic surfaces investigated with theoretical calculations We applied periodic density-functional theory to investigate the adsorption and dissociation of NO on bimetallic surfaces, including the xNi@Pt(111), NixPt4-x(111), and (4–x)Pt@Ni(111) surfaces ( x = 0~4). For all bimetallic surfaces, NO is preferentially adsorbed on Ni-rich sites, and the adsorption energies increase with the increasing number of top-layer Ni atoms on the surface. When the top-layer compositions are equal (but with varied composition of inner layers), the adsorption energy of NO on these surfaces decreases in the order xNi@Pt(111) > NixPt4-x(111) > (4 – x) Pt@Ni(111), whereas the NO dissociation barriers increase in the opposite order; a larger adsorption energy of NO leads to a smaller NO dissociation barrier. We employed the local density of states to study the inner-layer effect of the various surfaces, and found that the inner-layer Pt atoms of the 4Ni@Pt(111) surface caused the greatest up-shift of the d-band center (of top-layer Ni atoms) toward the Fermi energy. 3rd part: The CO2 reaction on WC(0001) and WC-Co alloy surfaces investigated with theoretical calculations We applied periodic density-functional theory to investigate the adsorption of CO2 on WC(0001) and various WC-Co alloy surfaces, and discussed the reaction trend of CO2 dissociation or hydrogenation on these surfaces. We employed the electron localization function, ELF to study the electron localization or delocalization effect of the various Co-ratio WC-Co alloy surfaces, and found that the partial-delocalization surfaces (WC-Co(0.25ML) surface) exhibit largest adsorption energy to CO2 molecule (–1.61 eV) in all of our calculated surfaces. Incidentally, when we increased the Co-ratio to form WC-2Co(0.50ML) surface, the activation energy of CO2 dissociation (CO2→CO+O) was reduced to 0.57 eV; it also decrease the CO2 hydrogenation, CO2+H → HCOO (formate), due to the cause of electron delocalization on the increased Co-ratio WC-Co alloy surfaces.
Sanyal, Udishnu. "Modulation of Nanostructures in the Solid and Solution States and under an Electron Beam." Thesis, 2013. http://etd.iisc.ernet.in/2005/3303.
Повний текст джерелаBhaskar, Srilakshmi P. "A Study on Digestive Ripening Mediated Size and Structure Control in Nanoparticles Prepared by Solvated Metal Atom Dispersion Method." Thesis, 2016. http://hdl.handle.net/2005/2924.
Повний текст джерела