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Warburton, D. R. "Surface EXAFS and XANES studies of sulphur absorption on the (110) and (111) faces of nickel." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237271.
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Michel, Anne-Charlotte. "Structure et réactivité en chimisorption et catalyse des alliages Pd8Ni92 (111) et (110)." Lyon 1, 2000. http://www.theses.fr/2000LYO10264.
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Ce travail vise à caractériser au mieux les surface d'alliage Pd8Ni92 (111) et (110), et à étudier les propriétés chimisorptives et réactives de ces faces afin de déterminer les facteurs (géométriques, électroniques. . . ) qui influencent les propriétés catalytiques de ces systèmes bimétalliques. Un très fort enrichissement en Pd (80 % atomique) dans l'ultime plan de surface a été mis en évidence pour les deux faces de l'alliage conduisant à une reconstruction de surface dans le cas de la face (110). L'étude de l'adsorption de CO par spectrométrie vibrationnelle (HREELS) et thermodésorption a montré que les propriétés chimisorptives des faces (110) et (111) de l'alliage sont modifiées par rapport aux faces correspondantes du Pd pur, celles de la face (110) étant toutefois moins altérées que la face (111) : une diminution de l'énergie d'adsorption de CO a pu être observée sur les alliages et les sites d'adsorption ont pu être caractérisés (sites linéaires, pontés ternaires, Pd, Ni ou mixtes PdNi). Les mesures de réactivité en hydrogénation du butadiène indiquent que le Pd présent à la surface de l'alliage est beaucoup plus actif que le Pd pur et ceci d'autant plus sur la face (110), l'alliage étant vingt fois plus actif que le palladium. Contrairement à la face (110), la face (111) se désactive au cours de la réaction. L'étude de la chimisorption du butadiène par HREELS a permis de montrer une adsorption de type di-π sur la face (110) de l'alliage, identique à celle observée sur Pd (110). Sur la face (111), le butadiène se modifie par réaction de surface.
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Kuang, MingHui. "Catalytically active nickel (110) surfaces in the growth of carbon tubular structures." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15900.
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Mohsenzadeh, Abas. "Computational studies of nickel catalysed reactions relevant for hydrocarbon gasification." Doctoral thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-323.
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Sustainable energy sources are of great importance, and will become even more important in the future. Gasification of biomass is an important process for utilization of biomass, as a renewable energy carrier, to produce fuels and chemicals. Density functional theory (DFT) calculations were used to investigate i) the effect of co-adsorption of water and CO on the Ni(111) catalysed water splitting reaction, ii) water adsorption and dissociation on Ni(111), Ni(100) and Ni(110) surfaces, as well as iii) formyl oxidation and dissociation, iv) hydrocarbon combustion and synthesis, and v) the water gas shift (WGS) reaction on these surfaces. The results show that the structures of an adsorbed water molecule and its splitting transition state are significantly changed by co-adsorption of a CO molecule on the Ni(111) surface. This leads to less exothermic reaction energy and larger activation barrier in the presence of CO which means that far fewer water molecules will dissociate in the presence of CO. For the adsorption and dissociation of water on different Ni surfaces, the binding energies for H2O and OH decrease in the order Ni(110) > Ni(100) > Ni(111), and the binding energies for O and H atoms decrease in the order Ni(100) > Ni(111) > Ni(110). In total, the complete water dissociation reaction rate decreases in the order Ni(110) > Ni(100) > Ni(111). The reaction rates for both formyl dissociation to CH + O and to CO + H decrease in the order Ni(110) > Ni(111) > Ni(100). However, the dissociation to CO + H is kinetically favoured. The oxidation of formyl has the lowest activation energy on the Ni(111) surface. For combustion and synthesis of hydrocarbons, the Ni(110) surface shows a better catalytic activity for hydrocarbon combustion compared to the other surfaces. Calculations show that Ni is a better catalyst for the combustion reaction compared to the hydrocarbon synthesis, where the reaction rate constants are small. It was found that the WGS reaction occurs mainly via the direct pathway with the CO + O → CO2 reaction as the rate limiting step on all three surfaces. The activation barrier obtained for this rate limiting step decreases in the order Ni(110) > Ni(111) > Ni(100). Thus, the WGS reaction is fastest on the Ni(100) surface if O species are present on the surfaces. However, the barrier for desorption of water (as the source of the O species) is lower than its dissociation reaction on the Ni(111) and Ni(100) surfaces, but not on the Ni(110) surface. Therefore the direct pathway on the Ni(110) surface will dominate and will be the rate limiting step at low H2O(g) pressures. The calculations also reveal that the WGS reaction does not primarily occur via the formate pathway, since this species is a stable intermediate on all surfaces. All reactions studied in this work support the Brønsted-Evans-Polanyi (BEP) principles.
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Sanders, Helen Elizabeth. "Reflection-absorption infrared spectroscopy of adsorbates on Ni{110} and nickel oxide surfaces." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320051.
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Poirault, Richard. "Etude par spectrométrie de rendement photoélectrique, par spectrométrie Auger et par diffraction d'électrons lents des systèmes suivants : nickel (111) : adsorption du souffre et de cc. : stabilité thermique des faces (100), (001), et (110) de TiO2." Dijon, 1989. http://www.theses.fr/1989DIJOS007.
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La valeur du travail de sortie du nickel (111) est de 4,75 +ou- 0,05 eV. Il existe un état de surface électronique à 0,3 eV du niveau de fermi. Il à été montré que la présence de soufre ou de monoxyde de carbone entraine une variation du travail de sortie. Sur TiO2, les défauts localisés en surface jouent un rôle prépondérant. Sur la face (110), il y a en surface une structure d'un sous-oxyde de TiO2 : Ti8O15 après recuit. Il existe un pic à 40 eV sur nos spectres Auger non attribuable a une transition classique. Le nickel croit sur TiO2 (100) "quasi-stœchiométrique" suivant un mode de croissance Stransky-Krastanov modifié : 2 à 3 monocouches de nickel + ilots tridimensionnels. Le nickel diffuse dans TiO2 "non stœchiométrique" à température ambiante. Cette diffusion est d'autant plus importante que l'écart à la stœchiométrie et la température sont élevés
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Guigner, Jean-Michel. "Etude de l'alliage PdCu(100) et de dépôts de Pd sur Ni(110) : caratérisation de surface par microscopie à effet tunnel et relation avec la réactivité." Lyon 1, 1997. http://www.theses.fr/1997LYO10024.
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Le but de ce travail est la reconnaissance des sites catalytiques en surface d'alliages binaires a base de palladium. L'etude a porte sur la face (110) de l'alliage pdcu et sur l'alliage de surface obtenu par depot de pd sur ni(110). Les surfaces ont ete preparees sous haut vide et caracterisees a l'aide de diverses techniques d'etude de surfaces, principalement la microscopie a effet tunnel (stm) couplee a la diffraction d'electrons lents (leed). Leur reactivite a ete testee en catalyse d'hydrogenation du butadiene-1,3. La surface du pdcu(110) presente un enrichissement en cu. Elle est formee d'une succession de terrasses composees soit de cu pur, soit de pdcu ; celles-ci sont separees par des marches de hauteur parfois monoatomique mais souvent quatre fois plus hautes. Une surstructure d'ordre 221 selon la direction 110 est observee sur le diagramme leed, ainsi que par stm sur certaines zones de l'echantillon. On peut l'expliquer par une alternance des atomes pd et cu sur les terrasses de composition mixte, selon les rangees de cette direction. L'ensemble des resultats est bien coherent avec la formation d'une phase ordonnee '-pdcu#3 en surface. Elle permet aussi de comprendre la reactivite de cette echantillon en catalyse d'hydrogenation du butadiene, dans la mesure ou les paires de pd (sites d'adsorption de la molecule de butadiene comme montre par ailleurs) sont absentes aux endroits ou la surstructure se forme. Le depot d'une fraction de monocouche (ml) de pd a temperature ambiante sur ni(110) conduit a la formation d'ilots allonges selon la direction 110 du substrat. Les depots plus importants (de 0. 3 a 4 ml) se structurent par recuit a une temperature modere (<250c), sans que le pd ne diffuse vers l'interieur. Les images stm de ces depots recuits montrent des rangees alignees suivant la direction 001, separees de 2,7 a 1,8 nm les les unes des autres et presentant une corrugation verticale de 0,1 a 0,02 nm, pour les depots allant de 0,3 a 4 ml, respectivement. Ces arrangements se manifestent en leed par l'observation de surstructures, avec notamment l'apparition de taches supplementaires d'ordre n (n 11-7) selon 110. Les resulats peuvent s'interpreter par la formation d'arrangements particuliers des atomes de pd, dans lesquels ceux-ci sont contraints par le substrat (dont le parametre de maille est 10% inferieur a celui du metal depose) et ont une grande maille de coincidence selon la direction des rangees 110 du substrait. Ces couches contraintes se sont averees 20 a 40 fois plus actives en hydrogenation du butadiene-1,3 que le palladium pur portant reconnu jusqu'alors comme le catalyseur le plus performant pour cette reaction.
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Tanner, Robert E. "The structure of the rutile TiOâ‚‚(110) surface and Ni/TiOâ‚‚ nanoislands." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325929.
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Jeliazova, Yanka Martcheva. "The growth of multilayer systems, consisting of thin oxidic (Ga2O3, Al2O3) and metallic (Ga, Al, Co, Au) films on Ni(100) and Cu(111) surfaces." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96635611X.
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Barolo, Andrea. "Studio di catalizzatori a base di film sottili di ossidi metallici di transizione su substrato metallico monocristallino." Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3427523.
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This work discuss thin solid films of transition metal oxides on crystalline metal substrate morpholgy and reactivity toward gases. In particular the systems analyzed are: CoO on Pd(100), SnO on Pt(110) and NiO on Pd(100).Questo lavoro discute in proposito di film sottili di ossidi di metalli di transizione su substrato metallico cristallino in riferimento alla loro morfologia e reattività verso i gas. In particolare i sistemi analizzati sono CoO su Pd(100), SnO su Pt(110) and NiO su Pd(100).
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Paucksch, Roland. "Ein- und Zwei-Photon-Photoemissionsspektroskopie von Oberflächenzuständen an Ni(111)." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962829595.
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Lockman, Zainovia. "Surface oxidation epitaxy of (100) <001> nickel and nickel-based alloys." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407610.
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Kock, Matthias. "Grenzen und Möglichkeiten der elektrochemischen Mikrostrukturierung mit ultrakurzen Spannungspulsen." [S.l. : s.n.], 2004. http://www.diss.fu-berlin.de/2004/115/index.html.
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Sayar, Asli. "Quantum Mechanical Calculation Of Ethylene Hydrogenation On Nickel 111 Single Crystal Surface And Nickel Nanoclusters." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606622/index.pdf.
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Ethylene hydrogenation on Ni(111)equilibrium geometry calculations for Ni2 dimer, Ni13 and Ni55 nanoclusters
and ethylene adsorption on Ni(100), Ni(111), Ni2, and Ni13 were studied quantum mechanically by means of energetic and kinetic differences. Ethylene hydrogenation on Ni(111) was simulated by use of DFT/B3LYP/6-31G** formalism. The reaction mechanism was mainly composed of three elementary steps. Firstly, ethylene adsorption on bare Ni(111) surface was performed. Second step and third step were the formation of ethane from adsorbed ethylene by use of two types of hydrogen atom, bulk and surface. During the hydrogenation reaction of ethylene on Ni(111), bulk hydrogen atom, representing for hydrogen atoms emerging from the bulk of Ni metal, was determined to be rather reactive than surface hydrogen atom, as suggested by experimental findings. Small Ni clusters, Ni2 and Ni13, were investigated by means of DFT/B3LYP/modified-6-31G**. Equilibrium geometry calculations resulted in Ni2 binding energy of 1.078eV/atom, showing good agreement with experimental value. Ni13 was found to have a structure of icosahedral, suggested experimentally, and binding energy of 2.70eV/atom. Ni55 was, also, studied by semi-empirical PM3 formalism, resulting in expected icosahedral structure. Finally, DFT/B3LYP/6-31G** investigation of ethylene adsorption was performed on Ni(111), Ni(100) and Ni13 surfaces which were selected according to their nickel atom coordination numbers of 9, 8 and 6, respectively. Comparison of adsorption energies of -18.00kcal/mol, -31.4kcal/mol and -43.42kcal/mol, respectively, indicated that the change in energies for ethylene adsorption on different nickel surfaces was directly proportional to coordination number of the nickel atoms constructing the surfaces.
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Mosby_Jr, Dwight L. "Coadsorption of sodium and elemental sulfur on nickel (100) surfaces." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1996. http://digitalcommons.auctr.edu/dissertations/3655.
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This study examined the structural and electronic growth properties of the coadsorption of Sodium and elemental Sulfur on Nickel (100) surfaces at room temperature. The investigation was conducted in an ultra high vacuum system using low energy electron diffraction, Auger electron spectroscopy, and work function measurements. The main objective of the study was to create a low work function substrate that would be useful for low work function devices. The research occurred in four stages: (1) adsorption of S on clean Ni(100), (2) adsorption of Na on clean Ni(100), (3) coadsorption of Na on S covered Ni(100), and (4) coadsorption of S on Na covered Ni(100). The measurements obtained suggest that S grows on Ni(100) in a layer by layer mode, forming a p(2x2) initially and a c(2x2) at the completion of the first layer. The second layer of S is disordered. The measurements also indicate that deposition of Na at room temperature forms a single c(2x2) layer. The coadsorption studies showed that the presence of S on the surface of Ni(100) increased the amount of Na that can be deposited on the substrate. A low work function of 0.8eV was obtained during the study. Furthermore, the presence of Na on Ni(100) was found not to affect the deposition of S, however the S was found to destroy the metallic character of the underlying Na.
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Cooper, Elaine. "Infrared studies of hydrocarbon adsorption on Ni{111}." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296514.
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Reflection-absorption infrared spectroscopy (RAIRS) has been used to probe the interaction of cyclohexane, partially deuterated cyclohexane C6HD11, toluene and ethylene with the Ni{111} surface. The coadsorption of cyclohexane and oxygen on the Ni{111} surface has also been studied in some detail; the effects of differing coverages of both pre- and post- dosed oxygen on cyclohexane adsorption has been investigated. As these experiments were the first to be completed using a new UHV system, an important element of this PhD project involved commissioning the UHV system, including the LEED and Auger apparatus, and setting up the RAIRS optical system. On the clean Ni{111} surface at 110 K adsorbed cyclohexane exhibits a site symmetry of C3v which persists through to the multilayer regime. Adsorbed molecules in the first layer exhibit a broadened and downshifted vCh stretching vibrational band, thought to arise from CH...M interactions and observed on many metal single crystal surfaces. The effect of coadsorbed oxygen on cyclohexane adsorption is strongly coverage dependent. At lower oxygen coverages, θO ≤ 0.25, a further downshifting of the softened vCH stretching vibration is observed, indicating the importance of charge transfer from the filled CHσ orbital to the metal in weakening the C-H bond. Adsorption of cyclohexane on the Ni{111}-(√3x√3)R30°-O surface, θO = 0.33, leads to total suppression of any C-H...M interaction, attributed to blocking of the bare metal sites by the adsorbed atoms. Post-dosing of oxygen on the cyclohexane adlayer leads to compression of existing islands of cyclohexane, involving molecular transfer from the first layer to the second. This is attributed to the difference in heats of adsorption of the two adsorbates.
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Gouttebaron, Rachel. "Etude de l'interaction cyanogène/argent, comparaison avec la face (100) du nickel." Dijon, 1996. http://www.theses.fr/1996DIJOS037.
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Lors de l'exposition des surfaces d'argent à un flux d'oxygène ultra pur, nous avons observé l'apparition en SIMS d'espèces cyanurées adsorbées sur la surface de l'argent, la présence d'oxygène étant indétectable. Afin de comprendre l'origine d'une telle réaction, nous avons étudié par SIMS, par spectroscopie d'électrons Auger et photoémission X et UV l'adsorption du cyanogène sur l'argent et le rôle joue par l'oxygène dans cette réaction d'adsorption. De plus une étude préalable de l'adsorption sur une surface de nickel a été réalisée. Nous avons montré que les espèces cyanurées observées sur la surface de l'argent lors des expositions à l'oxygène provenaient d'une impureté présente en très faible concentration dans l'oxygène utilisé. Ces espèces sont adsorbées en très faible quantité sur l'argent puisque leur présence n'est visible que par spectrométrie de masse d'ions secondaires, les autres techniques d'analyse de surface comme l'XPS, l'UPS et l'Auger étant aveugles. La présence d'oxygène en phase gazeuse lors des expositions au cyanogène de la surface de l'argent modifie radicalement la réactivité de cette surface. Les quantités adsorbées en surface sont considérablement augmentées et l'on note également un changement dans le mode de fixation des molécules avec les atomes du substrat. La présence d'oxygène entraine la formation en surface de sites à caractère acide mou de Lewis capables de réagir facilement avec des bases molles de Lewis. En UPS où nous n'avons pu mettre en évidence la présence de CN, sur la surface de l'argent, que lorsque, initialement, il y a présence en surface d'atomes d'oxygène. Une étude en fonction de la température du système (CN) 2/argent suivie par SIMS a montré qu’à partir de 450k les molécules de cyanogène s'organisaient sur la surface
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Quintero, Soltero Oscar. "Microstructural characterization of overaged GTD-111 HP turbine buckets." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Cullen, William G. "The role of place-exchange, dislocations and substrate symmetry in Ni/Au (111) heteroepitaxy." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30520.
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Gao, Shuang. "INVESTIGATION OF TRANSITION-METAL IONS IN THE NICKEL-RICH LAYERED POSITIVE ELECTRODE MATERIALS FOR LITHIUM-ION BATTERIES." UKnowledge, 2019. https://uknowledge.uky.edu/cme_etds/100.
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Layered lithium transition-metal oxides (LMOs) are used as the positive electrode material in rechargeable lithium-ion batteries. Because transition metals undergo redox reactions when lithium ions intercalate in and disintercalate from the lattice, the selection and composition of transition metals largely influence the electrochemical performance of LMOs. Recently, a Ni-rich compound, LiNi0.8Co0.1Mn0.1O2 (NCM811), has drawn much attention. It is expected to replace its state-of-the-art cousins, LiCoO2 (LCO) and LiNi1/3Co1/3Mn1/3O2 (NCM111), because of its higher capacity, lower cost, and reduced toxicity. However, the excess Ni, as a transition-metal element in NCM811, can cause structural and cycling instability.
Starting from NCM811, I modified the composition of transition metals by two approaches: 1) introducing cobalt deficiency and 2) substituting Ni, Co, and Mn with Zr. Their influences on the phase, structure, cycling performance, rate capability, and ionic transport were investigated by a variety of characterization techniques. I found that cobalt non-stoichiometry can suppress Ni2+/Li+ cation mixing, but simultaneously promotes the formation of oxygen vacancies, leading to rapid capacity fade and inferior rate capability compared to pristine NCM811. On the other hand, Zr can reside on and expand the lattice of NCM811, and form Li-rich lithium zirconates on their surfaces. In particular, 1% Zr substitution can increase the stability of NCM811 and facilitate Li-ion transport, resulting in enhanced cycling durability and high-rate performance. My studies help improve the understanding of the effects of transition metals on the degradation of the Ni-rich layered positive electrode material and provide modification strategies to enhance its performance and durability for Li-ion battery applications.
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Gordon, Diana Evelyn Agnes. "Comparative studies on the interaction of adsorbates with clean and oxygen-modified Ni(111)." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308318.
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Zander, Anne [Verfasser], and S. [Akademischer Betreuer] Nickel. "Demand and Capacity Management for Medical Practices / Anne Zander ; Betreuer: S. Nickel." Karlsruhe : KIT-Bibliothek, 2021. http://nbn-resolving.de/urn:nbn:de:101:1-2021092904593877249509.
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Rjeb, Mohammed. "Etude critique de l'analyse des structures fines observées en SEELFS : application au seuil M23 du nickel face (111)." Lyon 1, 1990. http://www.theses.fr/1990LYO10090.
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Le premier chapitre rappelle les principes du seelfs et ses liens avec l'exafs et le sexafs, ainsi que les difficultes specifiques du traitement des spectres seelfs. Pour la premiere fois, le chapitre ii etablit le veritable lien entre signaux seelfs, acquis en mode derivee premiere ou seconde par rapport a l'energie, et distribution radiale f(r). Le role et l'influence des divers traitements numeriques effectues pour obtenir f(r) sont ensuite analyses en detail. On arrive a la conclusion qu'ils peuvent etre parfaitement maitrises. Dans le chapitre iii la procedure de traitement mise au point est appliquee a deux spectres seelfs associes au seuil m#2#3 de ni(111). On parvient a une fonction r#2f(r) mieux resolue que celles publiees auparavant. Les raisons de la mauvaise qualite des resultats anterieurs sont mises en evidence. Toutefois, la position obtenue pour la premiere couche d'atomes est pres de 1 a en dessous de la position attendue. Cette conclusion, masquee dans les travaux anterieurs par la confusion deliberee entre les fonctions f(r) et r#2. F(r), relance le debat sur la validite de l'approximation qui consiste a utiliser les dephasages des seuils l#2#3 pour interpreter les seuils m#2#3. La maitrise acquise dans le traitement des spectres de type exafs est illustree dans le chapitre iv sur le seuil k de ni(111), observe en sexafs. La fonction f(r) obtenue permet d'identifier les positions des neuf premieres couches, avec un decalage voisin de celui predit par les tables de teo et lee
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Bengone, Olivier. "Étude des propriétés électroniques et structurales de NiO massif et des surfaces NiO(001) et NiO(111)." Metz, 2000. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2000/Bengone.Olivier.SMZ0043.pdf.
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Dans ce travail, nous avons étudié la structure électronique de l'oxyde de nickel massif, ainsi que les effets de reconstruction structurale des surfaces NiO(001) et NiO(111) terminée par un plan d'atomes d'oxygène. Pour se faire, nous avons utilise la méthode des ondes planes augmentées par projection (PAW), qui permet de déterminer la configuration géométrique et électronique de l'état fondamental grâce au concept de minimisation globale de la fonctionnelle énergie totale, développé par Car-Parrinello. Afin de tenir compte des effets de corrélation pour les électrons d, qui jouent un rôle prépondérant dans les propriétés électroniques de NiO, nous avons implémenté une correction de Hubbard multi-orbitales (LDA + U). Ceci nous a permis de reproduire correctement l'état fondamental antiferromagnétique isolant, ainsi que les propriétés optiques de NiO massif. Nous avons égalemment appliqué cette méthode aux surfaces NiO(001) et NiO(111). Les effets de reconstruction et les modifications de la structure électronique de la surface (001) de NiO comparé au volume restent faibles. En revanche, la surface polaire (111) en reconstruction octopolaire p(22) terminée par un plan d'atomes d'oxygène présente de profondes modifications dans la structure électronique ainsi que de relaxation atomiques.
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Wu, Yuk Kuen. "LEED crystallographic studies of sulfur chemisorbed on the (111) surfaces of nickel and rhodium." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27751.
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The work in this thesis includes investigations of adsorbate-induced metal relaxations with low-energy electron diffraction (LEED) for the surface structures designated Ni(111)-(2x2)-S and Rh(111)-(√3x√3)30'-S; a set of LEED intensity-versus-energy (I(E)) curves have also been measured for normal incidence on the Ni(111)-(2x2)-O surface. In the investigations of adsorbate-induced metal relaxations, 1(E) curves measured for a set of diffracted beams were compared with the corresponding curves calculated by multiple scattering methods for various structural models. The objective is to find the structure that gives the best correspondence between experiment and calculation. Levels of correspondence between experimental and calculated I(E) curves were assessed with the reliability indices proposed by Zanazzi-Jona and Pendry as well as with visual comparison.
In the LEED intensity analysis for the Ni(111)-(2x2)-S surface structure, the S-Ni interlayer spacing (d₀₁), the lateral displacement (Δ) of the first nickel layer and vertical
relaxations of the first two Ni-Ni interlayer spacings (d₁₂, d₂₃) were investigated. The best geometrical parameters were determined to be d₀₁=1.50 Å, Δ =+0.02 Å (1.4% expansion), d₁₂=2.09 Å (2.8% expansion) and d₂₃=2.08 Å (2.3% expansion) with the S atoms adsorbed on the "expected" 3f sites of the Ni(111) surface. The present study leads to a nearest-neighbour S-Ni bond distance of 2.10 Å, which is a little shorter than those obtained by low energy ion scattering (2.16 Å) and the surface extended X-ray adsorption fine structure technique (2.20 Å) but agrees rather well with the value 2.12 Å predicted by a bond length-bond order analysis.
In the investigation of adsorbate-induced metal relaxations for the Rh(111)-(√3x√3)30°-S surface, theoretical I(E) curves were calculated for a range of models involving either unreconstructed or reconstructed rhodium structure at the surface. These calculations were done over appropriate ranges of the S-Rh interlayer spacing (d₀₁), the lateral displacement (Δ) for the first Rh layer, and the first Rh-Rh interlayer spacing (d₁₂). The best level of correspondence between calculation and experiment appears for the 3F1 model with d₀₁=1.57 Å, Δ =M).025 A (1.6 % contraction) and d₁₂=2.18 Å (0.5 % contraction). In this model the nearest-neighbor S-Rh bond distance is found to be 2.19 Å.Science, Faculty of
Chemistry, Department of
Graduate
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Stanescu, Stefan. "Structure and morphology of NiO / Cu(111) and NiO / FeNi / Cu(111) ultra-thin layers and nanostructures." Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13099.
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Les premiers stades de la croissance du NiO/Cu(111) ont été caractérisés du point de vue chimique, morphologique et structurale à une échelle microscopique. Pour cela, nous avons utilisé différentes méthodes d'élaboration et combiné différentes techniques de laboratoire in situ ainsi que le rayonnement synchrotron. Les bicouches à couplage d'échange NiO/FeNi/Cu(111) ont aussi été étudiées. L'interface Ni/Cu(111) a été étudié en mettant en évidence les liens entre la morphologie, la structure et les propriétés magnétiques. Les valeurs réduites du moment de spin sont reliées à l'hybridation 3d à l'interface Ni-Cu et au recouvrement de Cu. Dans toute la gamme des épaisseurs étudiées l'anisotropie du moment orbital est dans le plan, déterminant l'orientation de l'axe de facile aimantation. Cette axe peut être reliée à la tétragonalisation du réseau cristallin du Ni. Des couches ultraminces de NiO ont été obtenues par évaporation à partir de pépites de NiO à température ambiante ainsi qu'à 250ʿC. Les couches minces peuvent être décrite par une bicouche NiO/Ni/Cu(111). Le GISAXS permettent de confirmer les observations STM et de mettre en évidence l'auto-organisation des îlots de NiO. Due à la faible efficacité d'oxydation, les couches minces de NiO déposées à partir du Ni métallique sous oxygène, présentent quelques différences par rapport aux couches déposées à partir des pépites. Le mécanisme de formation des îlots proposé est basé sur un processus de nucléation/agrégation de clusters. Les résultats structurales (LEED et GIXD) peuvent être attribués soit à la formation d'une phase hexagonale a-Ni2O3, soit à une distorsion structurale de la maille NiO(111)( )R30ʿ. Le système à couplage d'échange NiO/FeNi/Cu(111) a été élaboré en utilisant les deux méthodes d'élaboration du NiO. L'interface NiO/FeNi est très abrupte, présentant une texturation suivant les axes cristallographiques. Les analyses structurales montrent une bonne épitaxie du NiO sur les films d'alliage FeNiThe very first stages of the growth of NiO/Cu(111) interface, were characterized on a microscopic scale including chemical, morphological, and structural aspects. Different elaboration procedures were used and we combined in-situ laboratory and synchrotron radiation techniques. Complete exchange coupled NiO/FeNi/Cu(111) bilayer system have also been investigated. The metallic Ni/Cu(111) interface has been studied, evidencing the close relationship between morphology, structure and magnetic properties. The reduced spin magnetic moments were correlated with the Ni-Cu 3d hybridization and with the Cu capping. The in-plane orbital moment anisotropy, related with the Ni tetragonalization, confirms that the easy axis of magnetization is in the plane for all measured thin nickel films. Ultra-thin NiO films, obtained through MBE evaporation of NiO nuggets, were grown at room temperature and at 250ʿC. The resulting system can globally be described in terms of a spontaneous NiO/Ni/Cu(111) layering. Confirming the STM real-space observations, GISAXS experiments and calculations allowed evidencing the self-organized nature of the NiO islands obtained at room temperature. Due to the poor oxidizing efficiency of the molecular oxygen, the NiO films deposited from metallic Ni at 250ʿC, exhibit several differences with respect to those obtained by NiO nuggets evaporation at room temperature. A cluster nucleation/aggregation mechanism was proposed, based on the STM observations. Formation of a-Ni2O3 hexagonal phase, or structural distortion of the NiO(111)( )R30ʿ structure could both explain the LEED and GIXD results. Exchange coupled NiO/FeNi/Cu(111) bilayer was elaborated using both, NiO nuggets and metallic Ni in oxygen partial pressure evaporation. Sharp NiO/FeNi interfaces were obtained, with textured NiO. Structural analysis of the NiO films deposited on FeNi/Cu(111) films evidenced twinned NiO(111), in much better epitaxy than the oxides deposited on the Cu(111) substrate
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Chandavarkar, Sumant. "Low-energy electron diffraction study of potassium adsorbed on nickle(111)." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279665.
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Lovis, Florian [Verfasser]. "Self-organization of composite model catalysts : vanadium and nickel oxides on Rh(111) / Florian Lovis." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover, 2011. http://d-nb.info/1011398354/34.
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Wing, Hayden. "Implementing best practice protocols for occupational hygiene monitoring." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2005. https://ro.ecu.edu.au/theses/111.
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This thesis outlines the results of an occupational hygiene monitoring program implemented at Minara Resources' Murrin Murrin mine site. The research was conducted as part of a collaborative agreement between Edith Cowan University and Minara Resources, the title of which was "Establishing best practice protocols in the management of occupational and environmental health in a high risk mining and ore processing environment". To form the basis of this research it was hypothesised that chemical hazards had not been adequately identified, that existing occupational hygiene monitoring programs did not adequately quantify employee exposures to these hazards, and that the implementation of a comprehensive hazard identification and monitoring program would greatly improve the capacity to quantify the health risks posed to employees.
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Léglise, Mélissa. "Amélioration des propriétés mécaniques et chimiques de superalliages base nickel et base cobalt de fonderie utilisés pour le fibrage du verre fondu à 1000°C - 1100°C." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0228.
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Les assiettes de fibrage utilisées pour la production de fibres de verre subissent d’importantes contraintes mécaniques, chimiques et thermiques. Par conséquent, cette pièce se dégrade et doit être périodiquement remplacée. Le but de ces travaux est d’augmenter la durée de vie des assiettes de fibrage en améliorant les propriétés mécaniques et chimiques des superalliages qui les constituent. Plus précisément, l’objectif de cette thèse est, dans un premier temps, d’améliorer les alliages utilisés pour le fibrage à 1000°C, puis dans un second temps, de trouver un superalliage pouvant fibrer à 1125°C. Ces travaux ont été menés sur deux familles de superalliages : base nickel et base cobalt. Les propriétés chimiques ont été caractérisées par des essais thermogravimétriques et les propriétés mécaniques par des essais de fluage flexion 3 points. Pour l’alliage base Ni, l’influence des éléments minoritaires subis, Mn et Si, a été étudiée. Les propriétés mécaniques de cet alliage ont fait, ensuite, l’objet d’essais d’amélioration par l’addition de titane, zirconium, tantale, hafnium et de niobium. L’addition d’aluminium a été aussi expérimentée mais ayant pour but d’améliorer les propriétés chimiques de l’alliage. Enfin, des études ont été aussi menées sur l’addition de métaux nobles (Pd et Ru) et de terres rares (Y, La et Ce). Concernant les superalliages base cobalt, l’étude s’est portée sur un alliage base Co qui a antérieurement montré de bonnes propriétés générales pour une utilisation à 1125°C et non à 1000°C. Des variantes avec une teneur abaissée en tantale, sans hafnium et sans tungstène ont été étudiées. Pour clore ces travaux, l’augmentation de la teneur en nickel et un traitement thermique ont été étudiés afin d’améliorer la résistance à l’oxydation de ce second alliageThe fiberizing spinners used to produce the glass fibers undergo sizable mechanical, chemical and thermal solicitations. Therefore, this piece is degraded and must be periodically replaced. The purpose of these works is to increase the lifetime of the fiberizing spinners by improving the mechanical and chemical properties of the superalloys that constitute them. More precisely, the objective of this thesis is, in the first time, to improve the alloys used to fiberize at 1000°C, and in a second time, to find a superalloy that can fiberize at 1125°C. These works are focused on two families of superalloys: nickel-based and cobalt-based. The chemical properties are characterized by the thermogravimetry tests and the mechanical properties by 3 points flexural creep tests. For the Ni-based alloy, the influences of unwanted minority elements, Mn and Si, were studied. The mechanical properties of this alloy are subject to improvement tests by the addition titanium, zirconium, tantalum, hafnium and niobium. The aluminium addition was also experimented but with the aim of improving the chemical properties of the alloy. Finally, the studies were also driven on the addition of noble metals (Pd and Ru) and of rare earths (Y, La and Ce). Concerning the cobalt-based superalloys, the study focused on an alloy which has previously shown good general properties to be used at 1125°C and no at 1000°C. The versius with a lowered content in tantalum, without tungsten and without hafnium were studied. To close this work, the increase of nickel and a heat treatment were studied in order to improve the oxidation resistance of this second alloy
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Polemēs, I. "Theophanes of Nicaea : his life and works." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357764.
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Peronio, Angelo. "A closer look at heterogeneous catalysis: reaction intermediates at the single-molecule level." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8577.
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2011/2012The present work pertains to the surface science approach to heterogeneous catalysis. In particular model systems for CO2 hydrogenation to methanol, and NO selective catalytic reduction, are investigated by means of a combined approach, where the molecular-level insight provided by a low-temperature scanning tunneling microscope is complemented by density functional theory (DFT) calculations of their electronic structure. To this end, the Inelastic Electron Tunneling Spectroscopy (STM-IETS) technique was introduced for the first time in our laboratory, a recent development which allows to measure the vibrational spectrum of individual molecules adsorbed on a surface. Regarding CO2, we provide single molecule imaging and characterization of CO2/Ni(110), chemisorbed with high charge transfer from the substrate, in an activated state that plays a crucial role in the hydrogenation process. We obtain a detailed characterization of the adsorption geometries and an estimate of the energies corresponding to the different adsorbed states. A consistent picture of CO2 chemisorption on Ni(110) is provided on the basis of the newly available information, yielding a deeper insight into the previously existing spectroscopic and theoretical data. In the Selective Catalytic Reduction (SCR) process, nitrogen oxide is selectively transformed to N2 by reductants such as ammonia. The specificity of this reaction was tentatively attributed to the formation of NH3-NO coadsorption complexes, as indicated by several surface science techniques. Here we characterize the NH3-NO complex at the atomic scale on the (111) surface of platinum, investigating the intermolecular interactions that tune the selectivity. The structures that arise upon coadsorption of NH3 and NO are analyzed in terms of adsorption sites, geometry, energetics and charge rearrangement. An ordered 2 × 2 adlayer forms, where the two molecules are arranged in a configuration that maximizes mutual interactions. In this structure, NH3 adsorbs on top and NO on fcc-hollow sites, leading to a cohesional stabilization of the extended layer by 0.29 eV/unit cell. The calculated vibrational energies of the individually-adsorbed species and of the coadsorption structure fit the experimental values found in literature within less than 6%. The characterizations and optimizations that had to be tackled in order to successfully perform STM-IETS measurement are eventually presented, focusing in particular on an original method which allows to increase the achieved resolution. Namely, the modulation broadening associated to phase-sensitive detection is reduced by employing a tailored modulation function, different from the commonly-used sinusoid. This method is not limited to STM-IETS, but can be easily applied whenever a lock-in amplifier is used to measure a second derivative.
XXV Ciclo
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Green, Riho Thomas Seljamae. "Supramolecular assemblies of bioinorganic complexes formed via reaction of (S)-proline with nickel clusters on Au(111)." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/11956.
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Considerable research over several decades has been directed at the development of heterogeneous enantioselective hydrogenation catalysts via the chiral modification of Ni catalysts by chiral molecules such as α-hydroxy acids and α-amino acids. Some of these systems have proved to be very successful yielding catalysts achieving very high enantioselectivity. However, the modified surfaces display relatively poor stability under catalytic conditions, so there is a demand to produce more robust chiral architectures for application in this area of catalysis. The formation of metal organic coordination networks on surfaces has been the subject of intensive study in the last decade. This thesis reports the formation of metal organic structures via the reaction of (S)-proline with nanoscale Ni islands grown on Au(111). Initially, (S)-proline was studied Au(111) using low temperature scanning tunnelling microscopy (LT-STM), XPS and high resolution electron energy loss spectroscopy (HREELS). Adsorpton of (S)-proline at 300 K resulted in the formation of a mixture of the zwitterionic and anionic forms of proline. The former species condensed into ordered arrangements at 77 K giving a structure very similar to one crystal plane of solid proline. Proline species were relatively weakly bound and the vast majority of adsorbed proline desorbed by 370 K. (S)-proline adsorption was examined on Ni/Au(111) over a range of Ni coverages from 0.05 ML up to >1.0 ML STM, XPS, HREELS and DFT calculations. (S)-proline was found to oxidise Ni from the edges of the Ni islands producing nickel prolinate species. Five distinct classes of supramolecular assemblies were produced depending on Ni coverage and annealing temperature. The nature of each of these structures is described. It is concluded that one assembly is built up from Ni(prolinate)₂ (square planar) complexes, three of the assemblies have a fundamental building block consisting of a Ni(prolinate)₃ octahedral complex and the final structure, observed at high annealing temperatures, is constructed from oligomerized proline species. The interaction of the prochiral reagent, methyl acetoacetate, with some of these supramolecular assemblies is reported.
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Haroun, Mohamed Fahim. "Simulation numérique de l'activation du méthane sur la surface (111) du nickel idéale et avec un adatome." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/restreint/theses_doctorat/2007/HAROUN_Mohamed_Fahim_2007.pdf.
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Prédire comment les interactions catalytiques ont lieu est une question scientifiquement et technologiquement importante car cela peut aider à fabriquer des catalyseurs performants. Dans cette thèse, l’adsorption de CH4, CH3, H, CH3 + H, la dissociation de CH4 → CH3 + H et la réaction inverse sur les surfaces Ni(111) plane et défective ont été étudiées à l’aide de la DFT. Nous adsorbons systématiquement les espèces moléculaires et CH3 + H en plusieurs configurations géométriques. Pour CH4, CH3 et CH3 + H, la présence de l’adatome sur Ni(111) stabilise mieux les fragments que la surface plane. Tandis que pour l’hydrogène, la stabilisation est presque la même sur les deux surfaces. La barrière d’activation de la liaison C-H du méthane est réduite sur Ni(111) + adatome. La barrière d’association de CH3 + H est aussi réduite en présence de l’adatome. Nous faisons une analyse quantitative sur les performances de la surface défective en termes d’effets électroniques et géométriques.
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Haroun, Mohamed Fahim Légaré Pierre Maamache Mustapha. "Simulation numérique de l'activation du méthane sur la surface (111) du nickel idéale et avec un adatome." Strasbourg : Université Louis Pasteur, 2008. http://eprints-scd-ulp.u-strasbg.fr:8080/00000932.
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Banerjee, Tanushree. "Impact of Nickel Doping on Hydrogen Storage in Porous Metal-Organic Frameworks." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2265.
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A supply of clean, carbon neutral and sustainable energy is the most scientific and technical challenge that humanity is facing in the 21st century. Though there is enough fossil fuels available for a few centuries, their use would increase the level of CO2 in the atmosphere. This would lead to global warming and may pose serious threats such as rising of sea level, change in hydrological cycle, etc. Hence there is a need for an alternative source of fuel that is clean and sustainable. Among the many resources considered as an alternative power source, hydrogen is considered one of the most promising candidates. To use hydrogen commercially, appropriate hydrogen storage system is required. Various options to store hydrogen for onboard use include gaseous form in high-pressure tanks, liquid form in cryogenic conditions, solid form in chemical or metal hydrides, or by physisorption of hydrogen on porous materials. One of the emerging porous materials are metal-organic frameworks (MOFs) which provide several advantages over zeolites and carbon materials because the MOFs can be designed to possess variable pore size, dimensions, and metrics. In general, MOFs adsorb hydrogen through weak interactions such as London dispersion and electrostatic potential which lead to low binding enthalpies in the range of 4 to 10 kJ/mol. As a result, cryogenic conditions are required to store sufficient amounts of hydrogen inside MOFs. Up to date several MOFs have been designed and tested for hydrogen storage at variable temperature and pressure levels. The overall results thus far suggest that the use of MOFs for hydrogen storage without chemical and electronic modifications such as doping with electropositive metals or incorporating low density elements such as boron in the MOFs backbone will not yield practical storage media. Such modifications are required to meet gravimetric and volumetric constraints. With these considerations in mind, we have selected a Cr-based MOF (MIL-101; Cr(F,OH)-(H2O)2O[(O2C)-C6H4-(CO2)]3•nH2O (n ≈ 25)) to investigate the impact of nickel inclusion inside the pores of MIL-101 on its performance in hydrogen storage. MIL-101 has a very high Langmuir surface area (5900 m2/g) and two types of mesoporous cavities (2.7 and 3.4 nm) and exhibits exceptional chemical and thermal stabilities. Without any modifications, MIL-101 can store hydrogen reversibly with adsorption enthalpy of 10 kJ/mol which is the highest ever reported among MOFs. At 298 K and 86 bar, MIL-101 can store only 0.36 wt% of hydrogen. Further improvement of hydrogen storage to 5.5 wt% at 40 bar was achieved only at low temperatures (77.3 K). As reported in the literature, hydrogen storage could be improved by doping metals such as Pt. Doping is known to improve hydrogen storage by spillover mechanism and Kubas interaction. Hence we proposed that doping MIL-101 with a relatively light metal possessing large electron density could improve hydrogen adsorption. Preferential Ni doping of the MIL-101’s large cavities which usually do not contribute to hydrogen uptake is believed to improve hydrogen uptake by increasing the potential surface in those cavities. We have used incipient wetness impregnation method to dope MIL-101 with Ni nanoparticles (NPs) and investigated their effect on hydrogen uptake at 77.3 K and 298 K, at 1 bar. In addition, the impact of metal doping on the surface area and pore size distribution of the parent MIL-101 was addressed. Metal content and NPs size was investigated by ICP and TEM, respectively. Furthermore, crystallinity of the resulting doped samples was confirmed by Powder X-ray Diffraction (PXRD) technique. The results of our studies on the successful doping with Ni NPs and their impact on hydrogen adsorption are discussed.
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Scantlebury, Matthew John. "Coadsorption of potassium and nitrogen on the Ni(100) surface." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365913.
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Stanescu, Stefan. "Structure et morphologie de couches ultraminces et nanostructures de NiO / Cu(111) et NiO / FeNi / Cu(111)." Phd thesis, Université Louis Pasteur - Strasbourg I, 2002. http://tel.archives-ouvertes.fr/tel-00010139.
Full textAbstract:
Les premiers stades de la croissance du NiO/Cu(111) ont été caractérisés du point de vue chimique, morphologique et structurale à une échelle microscopique. Pour cela, nous avons utilisé différentes méthodes d'élaboration et combiné différentes techniques de laboratoire in situ ainsi que le rayonnement synchrotron. Les bicouches à couplage d'échange NiO/FeNi/Cu(111) ont aussi été étudiées. L'interface Ni/Cu(111) a été étudié en mettant en évidence les liens entre la morphologie, la structure et les propriétés magnétiques. Les valeurs réduites du moment de spin sont reliées à l'hybridation 3d à l'interface Ni-Cu et au recouvrement de Cu. Dans toute la gamme des épaisseurs étudiées l'anisotropie du moment orbital est dans le plan, déterminant l'orientation de l'axe de facile aimantation. Cette axe peut être reliée à la tétragonalisation du réseau cristallin du Ni. Des couches ultraminces de NiO ont été obtenues par évaporation à partir de pépites de NiO à température ambiante ainsi qu'à 250°C. Les couches minces peuvent être décrite par une bicouche NiO/Ni/Cu(111). Le GISAXS permettent de confirmer les observations STM et de mettre en évidence l'auto-organisation des îlots de NiO. Due à la faible efficacité d'oxydation, les couches minces de NiO déposées à partir du Ni métallique sous oxygène, présentent quelques différences par rapport aux couches déposées à partir des pépites. Le mécanisme de formation des îlots proposé est basé sur un processus de nucléation/agrégation de clusters. Les résultats structurales (LEED et GIXD) peuvent être attribués soit à la formation d'une phase hexagonale alpha-Ni2O3, soit à une distorsion structurale de la maille NiO(111)(sqrt(3)xsqrt(3))R30°. Le système à couplage d'échange NiO/FeNi/Cu(111) a été élaboré en utilisant les deux méthodes d'élaboration du NiO. L'interface NiO/FeNi est très abrupte, présentant une texturation suivant les axes cristallographiques. Les analyses structurales montrent une bonne épitaxie du NiO sur les films d'alliage FeNi.
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Devillard, Didier. "Interaction du thiophène avec les oxydes de nickel et de cobalt : face (100) de monocristaux et surfaces modèles de catalyseurs d'oxydes mixtes Ni-Mo et Co-Mo : étude par spectrométrie Auger et diffraction d'électrons de haute énergie sous incidence rasante." Dijon, 1990. http://www.theses.fr/1990DIJOS019.
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L'interaction du thiophène, avec la force (100) des oxydes de nickel et de cobalt et des surfaces modèles de catalyseurs d'oxydes mixtes Ni-Mo et Co-Mo, a été étudiée à une échelle subnanométrique, par spectrométrie d'électrons Auger et diffraction d'électrons de haute énergie sous incidence rasante. A) sur toutes les faces étudiées : *la couche d'adsorption est désordonnée quels que soient : la nature et la composition de la surface d'oxyde ; le taux de couverture en cristallites métalliques ; l'arrangement cristallographique des phases superficielles mixtes Ni, Mo, Co, O, S, C. Le soufre préadsorbé sur des cristallites métalliques ou sur l'oxyde inhibe l'adsorption du thiophène. L'ajout de molybdène sur NiO(100) ou COO(100) améliore considérablement le taux d'adsorption. B) dans le cas de COO(100), une élévation de la température de 150 K (373 à 523 K) favorise la dissociation de C4H4S en phase adsorbée. Un film amorphe de MOOX (x<3) déposé sur COO(100) dissocie moins le thiophène en phase adsorbée et en fixe davantage que COO(100). C) dans le cas de NiO(100), la quantite de thiophène adsorbée est d'autant plus grande que la concentration superficielle en atomes métalliques est importante. Le nickel métallique joue donc un rôle particulier dans la constitution des sites d'adsorption dont la nature exacte n'a pas pu être définie dans le cadre de cette étude. L'effet de synergie dû à la présence simultanée de Mo, Co ou Ni et S à la surface du catalyseur est confirmé. L'interaction du thiophène avec les différentes surfaces préparées au cours de ce travail se limite à l'étape d'adsorption sans autre forme d'évolution (aucune nucléation et croissance de nouvelles phases n'ont été détectées, notamment sulfures bidimensionnels ou tridimensionnels). Cette propriété semble tout à fait compatible avec un processus catalytique : adsorption du réactif, réactions en phase adsorbée, désorption des produits.
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Gommlich, Tim [Verfasser], Wolfgang [Akademischer Betreuer] Bleck, and Günter [Akademischer Betreuer] Schmitt. "Zur Vermeidung von Wasserstoffschäden am höchstfesten Stahl 300M bei der galvanischen Abscheidung von Zink-Nickel-Überzügen / Tim Gommlich ; Wolfgang Peter Bleck, Günter Schmitt." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://nbn-resolving.de/urn:nbn:de:101:1-2018071806144070941452.
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Bogosian, III Victor. "Habitat Niche Modeling in the Texas Horned Lizard (Phrynosoma cornutum): Applications to Planned Translocation." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/dissertations/160.
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I studied translocation of Texas horned lizards on Tinker Air Force Base, Midwest City, Oklahoma, using correlative and mechanistic habitat suitability models. My goals were broadly classified into two categories: first, to determine if the addition of mechanistic data layers (i.e., habitat-niche models) in a correlative model improved the overall accuracy of model predictions, and second, to apply the best model produced from my dataset to a planned translocation event on Tinker Air Force Base. Correlative data layers (i.e., habitat models) included typically applied datasets such as vegetative components, Euclidean distance statistics, neighborhood analyses, and topographically-derived information. Mechanistic data layers were estimates of thermal suitability derived from field-collected datasets and biophysical calculations, and estimates of prey availability taken from interpolated datasets. I estimated habitat suitability using the partitioned Mahalanobis distance statistic, which is a suitable model technique for presence-only data. Translocated and resident lizards were monitored via radiotelemetry and using fluorescent powder trails. Telemetry locations and powder trails were overlaid onto habitat suitability models to provide the datasets used to quantify interaction between site occupancy and habitat model predictions. Lizard paths were tested against random walk models to determine efficiency of travel, and site occupancy metrics (powder track and telemetry Mahalanobis distance values) were tested using parametric (repeated-measures ANOVA) and nonparametric (Wilcoxon rank-sum and signed-rank tests) tests. Mechanistic data layers did not substantially improve model accuracy over correlative-only layers, and data layers taken from mixed bare soil-vegetation, shrub, and grassland habitat types dominated important eigenvector weights. Analyses of fluorescent powder track data suggested that lizards did not move through habitat differently from a random walk model, potentially due to neighborhood factor loadings strongly influencing the area in which entire trails traveled. Wilcoxon tests and repeated-measures ANOVA results suggested that although lizards experienced different median Mahalanobis distance values by group (translocated, resident), there appeared to be an overall decrease in distance scores for translocated individuals over time. In this context, translocated individuals seemed to acclimate their behavior to areas that were predicted to be more suitable by Mahalanobis classifiers. Although survival results were not encouraging and habitat models did not suggest that my translocation site was ideal, my data supports the idea that translocations may be aided in the future by modeling efforts. My models suggest that mechanistic data layers may not improve classification accuracy over correlative processes, but this may be due to inaccurate representation of specific mechanisms over spatial and temporal scales. Future work should focus on including more explicit measures of mechanisms, as well as broadening biotic influences on species distributions (i.e., predator distribution, intra- and interspecific competition).
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Laksono, Endang Widjajanti. "Etude de l'interaction de l'ammoniac avec des surfaces de Ni(111) pré-traitées sous oxygène et influence de l'hydroxylation." Paris 6, 2001. http://www.theses.fr/2001PA066446.
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Carazzolle, Marcelo Falsarella 1975. "Estudo de filmes ultra-finos de Sb/In crescidos sobre Ni (111)." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277066.
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Orientadores: Richard Landers, Abner de SiervoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin.
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Resumo: Neste trabalho foi estudado o crescimento de filmes ultra-finos de Sb sobre Ni(111) e In sobre Ni(111), no regime de frações de monocamadas, com o interesse no entendimento da estrutura cristalográfica e eletrônica destas ligas de superfície. Os filmes foram preparadas em ambiente de UHV e caracterizados do ponto de vista da estrutura eletrônica através da técnica experimental de espectroscopia de elétrons (XPS) e cálculos de teoria do funcional da densidade (DFT). Na determinação da estrutura cristalográfica das ligas de superfície foram utilizados LEED-qualitativo e PED (difração de fotoelétrons) e DFT. Os filmes de Sb sobre Ni(111) formaram uma liga substitucional de superfície ordenada na estrutura (Ö 3 x Ö 3) R30 °, seguindo o empacotamento fcc do substrato. Os filmes de In sobre Ni(111) formaram duas fases ordenadas, 2 x 2 e (Ö 3 x Ö 3) R30 ° e , coexistindo na superfície em forma de domínios, ambas as fases formaram ligas substitucionais seguindo o empacotamento fcc do substrato. A estrutura eletrônica do filmes foram estudadas por XPS e interpretadas com a ajuda das simulações de DFT. Em ambos os filmes não houve tranferência de cargas entre os átomos, mas tivemos evidências de uma redistribuição de cargas intra-atômica nos átomos do substrato.
Abstract: In this thesis we present a studied the growth of the ultra-thin films of Sb on Ni(111) and In on Ni(111), in the sub-monolayer regime. The main interest was on the understanding of the crystallography and electronic structure theses surface alloys. The films were grown under UHV conditions and characterized as to their electronic structure by X-ray Photoelectron Spectroscopy (XPS) and simulated theoretically by density functional theory (DFT). To determine the crystallography structure, LEED and photoelectron diffraction (PED) was used. The Sb on Ni(111) films after annealing stabilized as a substitution surface alloy in the ( Ö 3 x Ö 3 ) R 30 ° structure following the fcc substrate. The In on Ni(111) films formed two ordered phases 2x2 and (Ö 3 x Ö 3) R30 ° coexisting on the surface, both the phases formed substitution alloys following the fcc substrate. The electronic structure of both the films didn¿t show evidence of charge transfer between the atoms, but of a possible charge redistribution between the states of the Ni atoms in contact with the evaporated film.
Mestrado
Superfícies e Interfaces ; Peliculas e Filamentos
Mestre em Física
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Wei, Haoming, Marius Grundmann, and Michael Lorenz. "Confinement-driven metal-insulator transition and polarity-controlled conductivity of epitaxial LaNiO3/LaAlO3 (111) superlattices." American Institute of Physics, 2016. https://ul.qucosa.de/id/qucosa%3A23553.
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Recently, topological conductivity has been predicted theoretically in LaNiO3(111)-based
superlattices. Here we report high-quality epitaxial LaNiO3/LaAlO3 superlattices on (111)-oriented
SrTiO3 and LaAlO3 single crystals. For both substrates a metal-insulator transition with decreasing
number of LaNiO3 monolayers is found. While the electrical transport is dominated by twodimensional
variable range hopping for superlattices grown on polar mismatched SrTiO3(111), it
switches to a thermally activated single gap behavior on polar matched LaAlO3(111). The gap
energy of the polar double-layer LaNiO3 superlattices can be tuned via the thickness of the insulating
LaAlO3 layers.
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Barker, Vincent Mark. "Thermo-mechanical fatigue crack growth modeling of a nickel-based superalloy." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44714.
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A model was created to predict the thermo-mechanical fatigue crack growth rates under typical engine spectrum loading conditions. This model serves as both a crack growth analysis tool to determine residual lifetime of ageing turbine components and as a design tool to assess the effects of temperature and loading variables on crack propagation. The material used in the development of this model was a polycrystalline superalloy, Inconel 100 (IN-100).
The first step in creating a reliable model was to define the first order effects that influence TMF crack growth in a typical engine spectrum. Load interaction effects were determined to be major contributors to lifetime estimates by influencing crack growth rates based upon previous load histories. A yield zone model was modified to include temperature dependent properties that controlled the effects of crack growth retardation and acceleration based upon overloads and underloads, respectively. Multiple overload effects were included in the model to create enhanced retardation compared to single overload tests. Temperature interaction effects were also considered very important due to the wide temperature ranges of turbine engine components. Oxidation and changing temperature effects were accounted for by accelerating crack growth in regions that had been affected by higher temperatures. Constant amplitude crack growth rates were used as a baseline, upon which load and temperature interaction effects were applied. Experimental data of isolated first order effects was used to calibrate and verify the model.
Experimental data provided the means to verify that the model was a good fit to experimental results. The load interaction effects were described by a yield zone model, which included temperature dependent properties. These properties were determined experimentally and were essential in the model's development to include load and temperature contributions. Other interesting factors became apparent through testing. It was seen that specific combinations of strain rate and temperature would lead to serrated yielding, discovered to be the Portevin-Le Chatelier effect. This effect manifested itself as enhanced hardening, leading to unstable strain bursts in specimens that cyclically yielded while changing temperature.
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Llopiz, Joel Kent. "The Trophic Ecologies of Larval Billfishes, Tunas, and Coral Reef Fishes in the Straits of Florida: Piscivory, Selectivity, and Niche Separation." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/130.
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The processes influencing larval fish survival in the low-latitude open ocean are poorly understood, especially with regard to feeding. As part of a large-scale study that included two years of monthly sampling in the Straits of Florida (SOF), the objectives of this dissertation were to elucidate the larval fish feeding behaviors and strategies of 1) istiophorid billfishes, 2) tunas, and 3) coral reef fishes, while also 4) characterizing the feeding environment, synthesizing the dominant trophic pathways to fish larvae, and reviewing the literature for evidence of latitudinal distinctions in larval fish trophodynamics. Larval billfishes exhibited highly selective feeding, and their diets were numerically dominated (90%) by two genera of crustaceans, Farranula copepods and Evadne cladocerans. These prey were consumed throughout early larval ontogeny, from first-feeding through piscivorous lengths (> 5 mm), until piscivory became exclusive near 12 mm. High feeding incidence (0.94) and rapid digestion (~3.5 hrs) suggests frequent and successful feeding by billfish larvae. For tunas, nearly all larvae examined (>98%) contained prey. Thunnus spp. exhibited a mixed diet, while skipjack, little tunny, and Auxis spp. nearly exclusively consumed appendicularians. All four tuna taxa co-occurred in the western SOF where prey was more abundant, while in the central and eastern SOF (where prey availability was lower), only Thunnus spp. and skipjack were present. Additionally, these two taxa exhibited significantly different vertical distributions. Estimates of predatory impact indicated the potential for depletion of resources in the absence of the spatial and dietary niches of larval tunas. Coral reef fish families examined included Serranidae, Lutjanidae, Mullidae, Pomacentridae, Labridae, Scaridae, and Acanthuridae. Feeding incidences were high (0.94 to 1.0) for all taxa except scarids (0.04), and diets were narrow and predator-specific. Cluster analysis yielded clear groupings based on the selective feeding exhibited by the taxa, while within taxa, canonical correspondence analysis illustrated the change in diet with a variety of variables. The physical and biological environment varied markedly across the SOF, largely influenced by the Florida Current. Characteristics examined included thermocline depth, fluorescence, and abundances of total plankton and copepod nauplii. The feeding ecologies of the 21 taxa of fish larvae in this work were synthesized into qualitative and quantitative webs that illustrate the variable trophodynamic strategies of larvae in the SOF and the levels of community reliance upon zooplankton prey types. A review of 170 investigations on larval fish feeding revealed notable distinctions between high- and low-latitude regions, highlighting the substantial variability across environments in the role of larval fishes within the planktonic food web.
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Le, Pévédic Séverine. "Etude de la formation et de l'oxydation de couches minces d'alliages Al-Ni après dépôt d'Al sur un monocristal de Ni(111)." Paris 6, 2007. https://tel.archives-ouvertes.fr/tel-00165301.
Full textAbstract:
Cette étude porte sur la formation et l’oxydation de couches minces d’alliages Al-Ni après dépôt d’Al, à 130 K, sur un monocristal de Ni(111), sous UHV. Leur composition, leur structure, en surface et en volume, et leur relation d’épitaxie ont été déterminées in situ par analyse par faisceau d’ions, diffraction d’électrons lents et spectroscopie Auger, en fonction de la quantité d'Al déposée et de la température de recuit. La formation d’une couche ordonnée et épitaxiée de Ni3Al(111) est suivie, au-delà d’une épaisseur critique d’Al de 3,8 nm, par celle d’une couche ordonnée et relaxée de NiAl(110). La cinétique de formation de ces couches alliées est complexe et correspond probablement à une croissance hétérogène. En oxydant à 300 K puis en recuisant à 1000 K ces alliages minces on obtient une couche ultramince (épaisse d'environ 5 Å) d'oxyde d’aluminium épitaxiée sur Ni(111), de stoechiométrie voisine d'Al2O3.
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Ehlers, Gertrude Andrea Nicole [Verfasser]. "The binational city Eurode : The social legitimacy of a border-crossing town / Nicole Ehlers." Aachen : Shaker, 2007. http://nbn-resolving.de/urn:nbn:de:101:1-2018081205394950166177.
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Eychmüller, Alexander, Chengzhou Zhu, Dan Wen, Susanne Leubner, Martin Oschatz, Wei Liu, Matthias Holzschuh, Frank Simon, and Stefan Kaskel. "Nickel cobalt oxide hollow nanosponges as advanced electrocatalysts for the oxygen evolution reaction." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-188848.
Full textAbstract:
A class of novel nickel cobalt oxide hollow nanosponges were synthesized through a sodium borohydride reduction strategy. Due to their porous and hollow nanostructures, and synergetic effects between their components, the optimized nickel cobalt oxide nanosponges exhibited excellent catalytic activity towards oxygen evolution reaction.
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Chaubet, Danièle. "Étude des propriétés de transport de couches d'alumine développées par oxydation a 1100°C d'un alliage NiAl β." Paris 11, 1989. http://www.theses.fr/1989PA112014.
Full textAbstract:
Détermination des propriétés de transport de la couche d'alumine au moyen d'une méthode électrochimique sur l'étude des courbes caractéristiques V-I obtenues pour différentes pressions partielles d'oxygène. Développement théorique d'un formalisme reliant les courbes caractéristiques aux propriétés de conductivité des couches d'alumine, application à l'oxydation d'un alliage NiAl à 1100°C dans l'oxygène pur et l'air synthétique.