Dissertations / Theses on the topic 'Nickel'
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1
El, Allam Driss. "Les enthalpies de formation des alliages liquides : palladium-nickel, palladium-gallium, palladium-indium, nickel-gallium, nickel-indium, palladium-nickel-gallium et paladium-nickel-indium." Aix-Marseille 1, 1989. http://www.theses.fr/1989AIX11239.
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A l'aide d'un calorimetre tres haute temperature (1000c
2
Lehmberg, Claudia Erdmuthe. "Structure of nickel-iron and nickel-zinc electrodeposits." Thesis, Sheffield Hallam University, 1998. http://shura.shu.ac.uk/3118/.
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Electrodeposited nickel-iron and nickel-zinc alloys have been studied using `direct' methods e. g. XRD, microscopy, EDX and GDOES on coatings having different thicknesses and deposited on different substrates. The work has confirmed and extended the ideas of Finch et al. (2, 51), Piontelli et al. (3) and Pangarov (49.120, 121) applicable to alloy deposition. It has shown that a better understanding, particularly of the initial deposition stages, can be obtained by considering crystallographic, energy and electrochemical aspects in combination rather than individually. Initially alloy is deposited on a `foreign' substrate but subsequently the growing alloy itself serves as the `substrate'. Similarly `old' crystallites have to compete for growth with `newly' nucleated ones as the deposit develops. The three stages of growth observed in nickel-iron and nickel-zinc are discussed. Crystallographic strain, resulting from mismatch between substrate and deposit structures and the presence of impurities, along with the energies required to produce different structures are considered to play a major role in determining structure during alloy deposition. Competition for discharge between hydrogen and metallic ions at the changing deposit surface, including changes in its electrochemical nature are considered. In addition possible effects resulting from adsorbed species, including co-discharged hydrogen as well as other species such as hydroxyl ions or precipitated hydroxides are discussed. Whereas during initial nucleation the original substrate is the dominating influence, in the later stages the electrolytic parameters determine the structure of the deposit. If the structure of the outer deposit differs markedly from that of the deposit during the initial stages, then a transitional growth stage may be involved. The structures of deposits studied in the present work tended to be fine grained in the initial stages but developed coarser columnar structures due to selected grain growth with favoured grains becoming broader during the intermediate and final stages of growth.
3
Wang, Shangyu. "Electrochemical properties of nanocrystalline nickel and nickel-molybdenum alloys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22500.pdf.
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Abraham, Matthias. "Electrodeposition and characterisation of nanocrystalline nickel and nickel alloys." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269947.
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Hankin, Anna. "Electrochemical recovery of nickel from nickel sulfamate plating effluents." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9241.
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Acidic aqueous nickel(II) sulfamate solutions are widely used for industrial nickel electroplating. The finite lifetimes of these baths are caused by the hydrolysis of sulfamate ions to ammonium ions which raise the stress in the nickel deposits. Spent solutions require treatment to recover the NiII, typically present at ca. 10³ mol m-³ , because consent concentrations for discharge to sewers are ca. 2x10-² mol m-³ . The aim of this project was to develop an electrochemical process and suitable control methods for treating the concentrated effluents by electrodeposition of NiII. The electrochemical reactor designed with a nickel mesh cathode, a Pt/Ti oxygen-evolving anode, and a cation-permeable membrane, was operated at constant current in batch-recycle mode. Elemental nickel was electrodeposited onto the cathode from the catholyte-effluent, separated from the aqueous sodium sulfate anolyte by the membrane, which prevented the oxidation of the sulfamate ions in the effluent and thus restricted the anodic reaction to the evolution of O2. Experiments with this system demonstrated that NiII could be recovered at current efficiencies greater than 90 % if the catholyte-effluent pH was maintained in the range 2.5 - 4.5 and if the magnitude of the applied current was regulated to be smaller than the mass transport limited NiII reduction current. Continuous additions of NaOH into the anolyte during reactor operation effectively decreased the rate of proton migration through the membrane from anolyte to catholyte and prevented the catholyte pH decreasing, so minimising the hydrogen evolution rate, the primary cause of the current efficiency always being less than 100 %. Increase in catholyte pH to values above 4.5 occured when effluents were contaminated with iron(III), present as either Fe2O3 or Fe(OH)3, the reduction of which consumed protons and caused cathode passivation due to formation of Ni(OH)2. The magnitude of the applied current was adjusted during the NiII depletion process to ensure it did not exceed the mass transport limited value for a given solution flow rate at any time. km(NiII) values, used to predict the limiting current densities, were derived from results of separate experiments in which mass transport limited reduction current densities of hexacyanoferrate(III) ions were measured as a function of flow rate in alkaline solution. Using these control methods, which were optimised using a reactor model incorporating mass balances, NiII concentrations in the effluent could be decreased by over 90 %. Using the typically measured average current efficiency of 95 % and the cell potential difference, typically 4.5 V in the presence of a Pt/Ti mesh anode, the specific electrical energy consumption was evaluated as ca. 4 300 kW h (tonne Ni)-¹, equivalent to ca. $650 (tonne Ni)-¹, which is two orders of magnitude lower than the price of elemental nickel, currently $22k tonne-¹. A micro-kinetic model was developed to describe the reduction mechanisms of nickel(II) and protons, considered as sequential one-electron charge transfers via separate adsorbed intermediates, as functions of electrode potential, ion concentrations and mass transport rates. This was coupled with the reactor model to facilitate predictions of reactor performance, based on the kinetic rate coe fficients and transfer coefficients. In order to determine these kinetic parameters the kinetics of nickel(II) and proton / water reduction were measured in sulfamate solutions on a rotating Ni disc electrode and on a Au EQCM as a function of NiII concentration, bulk pH, electrode potential and rotation rate.
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Woodcock, Thomas George. "The crystallographic texture and morphology of nickel oxide layers grown on textured nickel and nickel alloy substrates." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289750.
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GIRON, JEAN-CHRISTOPHE. "Couches minces d'hydroxyde de nickel et d'oxydes mixtes nickel/lithium et nickel/sodium. Application aux systemes electrochromes." Paris 6, 1994. http://www.theses.fr/1994PA066373.
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La premiere partie de ce memoire est consacree a l'etude, par effet mirage, des flux ioniques mis en jeu lors de l'oxydo-reduction, dans une solution alcaline, d'un film d'hydroxyde de nickel electrodepose. La seconde partie concerne la croissance par ablation laser et par pulverisation magnetron de films d'oxydes mixtes nickel/lithium et nickel/sodium. Leur structure, leurs proprietes electrochimiques et leurs caracteristiques electrochromes ont ete etudiees par diverses techniques (diffraction x, microscopie electronique en transmission, spectroscopie infrarouge a transformee de fourier, xps, voltammetrie cyclique,). Finalement, un dispositif electrochrome incorporant un film d'oxyde de tungstene et un film d'oxyde mixte nickel/lithium a ete realise et ses performances ont ete caracterisees
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Meyer, Ralf Joachim. "Computersimulationen martensitischer Phasenübergänge in Eisen-Nickel- und Nickel-Aluminium-Legierungen." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=958804702.
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Piers, Newbery A. "Electric arc spray forming of nickel alloys and nickel aluminides." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359486.
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Lain, M. J. "Electrocatalytic hydrogenation on in-situ electrodeposited nickel and nickel alloys." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356694.
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Huang, Shanshan. "Nanoparticulate nickel sulfide." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54754/.
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Nickel sulfide possesses a variety of typical structures and stoichiometries that distinguish itself from iron sulfide and exhibits unique roles in the prebiotic reactions which are proposed to be involved in the origin of life. Nickel sulfide precipitate is hydrated and nanocrystalline, modelled as a 4 nm sphere with a 1 nm crystalline and anhydrous NiS (millerite) core, surrounded by a hydrated and defective mantle phase. It is a metastable but fairly robust structural configuration. It may be formulated as NiSxFbOx approximates to 1.5 and decreases on heating. The fresh nanoparticulate nickel sulfide precipitates undergo structural transformation from the initial millerite-like NiS to the more crystalline polydymite-like Ni3S4. This reaction is accompanied by the formation of a less crystalline Ni3S2 (heazlewoodite) phase. The reaction, happening in ambient conditions, occurs more readily for the solids precipitated from acidic environments (i.e., pH 3) and may be facilitated by the hydrogen and water bonding contained in this material. The performance of nickel sulfide and iron sulfide precipitates is investigated in the formaldehyde world under ambient and sulfidic environments which mimic the ambient ancient Earth environments to some extent. The catalytic capacity of the metal sulfides is not obvious in these experiments. An interesting finding is that, trithiane, the cyclic (SCH2)3, also suppresses the pyrite formation and thus promotes the greigite formation in the reaction between FeS and H2S. This provides another cause for the greigite formation in the Earth sedimentary systems and adds information to the origin-of-life theory in the iron sulfur world. Voltammetry experiments reveal that the nickel-cysteine complex lowers the overpotential for molecular H2 evolution in sea water to -1.53 V under ambient conditions. This catalytic property of the abiotic nickel-cysteine complex apparently mimics the Ni-S core in some hydrogenase enzymes functioning in physiological conditions. This bridges the abiotic and biotic worlds and supports the idea that life originated in the prebiotic ancient ocean.
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Altunoglu, Abdulkadir. "Hydrogen permeation through nickel and nickel alloys : surface reactions and trapping." Thesis, n.p, 1994. http://oro.open.ac.uk/19842/.
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Fritz, Thomas Michael. "Charakterisierung galvanisch abgeschiedener Nickel- und Nickel-Wolfram-Schichten für mikrotechnische Anwendungen." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965453731.
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Ratchev, Roumen [Verfasser]. "Thermisch-mechanische Ermüdung von Nickel-Gusslegierungen und Nickel-Schmiedelegierungen / Roumen Ratchev." Aachen : Shaker, 2006. http://d-nb.info/1186587571/34.
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Jensen, Jacob Michael. "Selective preparation of nickel silicides and nickel germanides from multilayer reactants /." view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3102168.
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Thesis (Ph. D.)--University of Oregon, 2003.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 153-163). Also available for download via the World Wide Web; free to University of Oregon users.
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Pane, Eric Wood Chris M. "Mechanistic analysis of the effects of nickel on Daphnia magna and rainbow trout /." *McMaster only, 2004.
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Potzger, Kay. "Ni-Einkristalloberflächen und Ni-Pd-Grenzflächen untersucht mit radioaktiven Sonden." [S.l.] : [s.n.], 2001. http://www.diss.fu-berlin.de/2001/223/index.html.
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Jin, Xiaolei. "Nickel toxicity and mechanisms of nickel resistance in Scenedesmus acutus f. alternans." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq35197.pdf.
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Kaya, Irfan. "SHAPE MEMORY BEHAVIOR OF SINGLE AND POLYCRYSTALLINE NICKEL RICH NICKEL TITANIUM ALLOYS." UKnowledge, 2014. http://uknowledge.uky.edu/me_etds/37.
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NiTi is the most commonly used shape memory alloy (SMA) and has been widely used for bio-medical, electrical and mechanical applications. Nickel rich NiTi shape memory alloys are coming into prominence due to their distinct superelasticity and shape memory properties as compared to near equi-atomic NiTi shape memory alloys. Besides, their lower density and higher work output than steels makes these alloys an excellent candidate for aerospace and automotive industry. Shape memory properties and phase transformation behavior of high Ni-rich Ni54Ti46 (at.%) polycrystals and Ni-rich Ni51Ti49 (at.%) single-crystals are determined. Their properties are sensitive to heat treatments that affect the phase transformation behavior of these alloys.
Phase transformation properties and microstructure were investigated in aged Ni54Ti46 alloys with differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) to reveal the precipitation characteristics and R-phase formation. It was found that Ni54Ti46 has the ability to exhibit perfect superelasticity under high stress levels (~2 GPa) with 4% total strain after 550°C-3h aging. Stress independent R-phase transformation was found to be responsible for the change in shape memory behavior with stress.
The shape memory responses of [001], [011] and [111] oriented Ni51Ti49 single-crystals alloy were reported under compression to reveal the orientation dependence of their shape memory behavior. It has been found that transformation strain, temperatures and hysteresis, Classius-Clapeyron slopes, critical stress for plastic deformation are highly orientation dependent.
The effects of precipitation formation and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]-oriented Ni51Ti49 shape memory alloy were revealed. Additionally, aligned Ni4Ti3 precipitates were formed in a single crystal of Ni51Ti49 alloy by aging under applied compression stress along the [111] direction. Formation of a single family of Ni4Ti3 precipitates were exhibited significant TWSME without any training or deformation. When the homogenized and aged specimens were loaded in martensite, positive TWSME was observed. After loading at high temperature in austenite, the homogenized specimen did not show TWSME while the aged specimen revealed negative TWSME.
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Kimpton, Harriet J. "The production and properties of zinc-nickel and zinc-nickel-manganese electroplate." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/12951.
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The aim of this research proj ect was to produce compositionally modulated zincnickel and zinc-nickel-manganese coatings usi ng a single bath process by variation of the applied electroplating current density. These could then be considered as possible replacements for electroplated cadmium. Zinc-nickel electrodeposits from both a simple bath and one containing the complexant tris(hydroxymethyl)methylamine (TRIS) were produced using either bath or by selective electroplating onto mild steel, 2014-T6 aluminium and 2000 series aluminium alloy connector shells. Zinc-nickelmanganese coatings were electroplated onto mild steel, using both DC and pulse electroplating from sulphate based baths containing either the complexant TRIS or sodium citrate. The coatings and the various electrodeposition processes were evaluated by thickness measurements, cun'ent efficiency calculations, composition detennination using energy dispersive X-ray anal ys is and SEM to examine the morphology. Corrosion characteristics were investigated by neutral salt fog exposure, alternate immersion, atmospheric trials, and electrochemical immersion tests including potential monitoring, galvanic and polarisation measurements. Other properties such as microhardness and surface electrical conductivity were also investigated. Compositionally modulated zinc-nickel and ziJlc-nickel-manganese were successfully deposited from single baths with nickel contents ranging from 5-20% Ni and manganese contents varying from 0-12% Mn. Current efficiency measurements showed the efficiency to be low especially for the zinc-nickel-manganese coatings, which exhibited a distinct morphology when electroplated from the citrate bath. Corrosion testing indicated that both coatings had a lower corrosion resistance than cadmium especially in accelerated tests, with a reduction in corrosion resistance being seen as the nickel content was increased; due to a decrease in density of the electroplate. This, and increasing through-thickness porosity promoted ennoblement of zinc-nickel and zinc-nickel-manganese leading to the coatings becoming nonsacri ficial to the substrate in accelerated tests. Zinc-nickel-manganese showed less white rust than zinc-nickel and exhibited lligher micro-hardness than zinc, cadmium and zinc-nickel. Electrical measurements indicated that both coatings were sufficiently conductive to meet the surface conductivity requirements for use on electrical connector shells.
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Pouderoux, Patrick. "Codéposition électrolytique par courant pulsé d'alliages nickel-phosphore et fer-chrome-nickel." Toulouse 3, 1991. http://www.theses.fr/1991TOU30245.
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Les conditions de syntheses electrochimiques d'alliages nickel-phosphore et fer-chrome-nickel, ont ete etudiees dans le but de diversifier les applications d'un nouveau materiau composite constitue de spheres creuses obtenues par electroformage. La technique d'elaboration par courant pulse permet de maitriser les mecanismes reactionnels de codeposition des alliages nickel-phosphore. Les conditions de cinetique et de thermodynamiques electrochimiques induites par les systemes d'impulsions conduisent a l'obtention d'alliages metal-metalloide de composition chimique et de morphologie controlees. La microstructure et les proprietes mecaniques dependent essentiellement de la composition chimique. L'enthalpie de cristallisation et la contraction liee au passage d'une structure amorphe a une structure cristallisee, sont en outre, fonctions lineaires de la teneur en phosphore. Les alliages fer-chrome-nickel ont ete elabores par une methode originale de codeposition/diffusion. La codeposition de particules de chrome dans une matrice fer-nickel n'est optimale que pour certaines combinaisons parametriques de courant pulse. La presence de particules modifie considerablement la morphologie des depots puisqu'elle inhibe la croissance colonnaire. Celle-ci s'effectue par contre a partir des particules conductrices codeposees en donnant naissance a une interface entre particule et matrice. Un traitement thermique de diffusion permet l'homogeneisation chimique de ces alliages. Suivant leur composition chimique, ces alliages presentent des resistances a la rupture 3 a 10 fois superieures a celles du nickel. De plus, la resistance a l'oxydation a haute temperature de l'alliage fe78,5 cr18,0 ni3,5 est equivalente a celle des aciers inoxydables. Les essais preliminaires de transposition a l'electroformage de spheres creuses ont permis d'aboutir a l'optimisation des proprietes mecaniques du materiau. Le remplacement du nickel par des alliages fer-chrome-nickel a ainsi conduit a doubler, apres recuit, la resistance mecanique a la compression des spheres
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Bimaghra, Itto. "Etude de dépôts électrolytiques de cuivre, de nickel et de cuivre-nickel." Aix-Marseille 1, 1991. http://www.theses.fr/1991AIX11332.
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Ce travail est consacre a l'etude de l'electrodeposition de cuivre, de nickel et de codepot cuivre-nickel a partir de solution sulfate et chlorure sur une electrode de carbone vitreux. L'etude par voltametrie cyclique et polarisation potentiostatique, employees pour determiner les mecanismes de formation de depot, a montre la necessite de corriger la chute ohmique en milieu sulfate. L'effet des cations autre que le cuivre est beaucoup plus important en milieu sulfate qu'en milieu chlorure, ceci est du a l'adsorption des especes chlorurees qui inhibe toute autre influence. Le vieillissement des solutions chlorures implique le changement de mecanisme et la quantite de cuivre deposee. La deposition de nickel en milieu sulfate ou chlorure se produit en deux etapes mises en evidence par deux maxima lors de l'etude potentiostatique. Le codepot de cuivre et de nickel se produit de facon differente suivant le milieu, sulfate ou chlorure, dans lequel on opere. En milieu sulfate le nickel influe sur le depot de cuivre dont la surtension de nucleation diminue avec l'augmentation de la concentration en nickel. En milieu chlorure, la presence de nickel n'influe pas sur le depot de cuivre a cause de l'adsorption des ions chlorures qui empeche l'influence des cations
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Vohra, A. A. "Nickel chelates as dyes." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601469.
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The chelates of seven commercial disperse dyes with nickel, copper and chromium have been formed in cotton and in nylon 6 fabrics. Exhaustion dyeing was satisfactory on nylon 6 and subsequent treatment in the metal salt solution at optimum pH was followed by steaming. The cotton was pretreated with a urea/melamine precondensate with glyoxal formaldehyde, and a polyethylene glycol. Dye was introduced by vapor-transfer from coated paper. Chelation was achieved in a final step. The hue and brightness, fastness to Light, washing and perspiration were assessed for the dyed fabrics. The nickel complexes were in general found to be slightly better than the chromium and copper complexes. Photodegeration of the fibres was reduced by the presence of the nickel complexes. Average stabilisation of nylon 6 was found to be 43% and that of cotton 23%. It may be possible to use selected nickel chelates as dyes that stabilise photodegradabLe fibres. The amount of nickel reacting with the dyed cotton fabric was determined by employing atomic absorption spectroscopy.
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Ahnoux, Marie-Claude. "La métallurgie du nickel." Paris 5, 1988. http://www.theses.fr/1988PA05P171.
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Muteba, Itone. "Research on nickel alloy sensitivity." Title page, Contents and Abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09DM/09dmm992.pdf.
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"April 1999." Includes bibliographical references (leaves 46-51). Aims to collect information about the numbers of dental workers who are sensitive or allergic to nickel and to help identify signs which might predict those people who are most likely to be sensitive to nickel. Uses a standard patch test to identify sensitive subjects.
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Ho, Elizabeth M. "An electrochemical study of reactions of nickel matte in acid media." Murdoch University, 1998. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060815.140539.
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Nickel matte is a nickel &de concentrate produced by smelting. It consists mainly of two components: a nickel-copper alloy and heazlewoodite (Ni3S2); but also contains
varying amounts of djurleite,Cu 1.96 S.There are several hydrometallurgical routes for processing nickel matte. The most recent of these involves an oxidative leach in acid
chloride or sulfate solution. Nickel is subsequently recovered fiom the leach solution by electrowinning or by hydrogen reduction. In the work described in this thesis,
various aspects of the acid leaching of nickel matte are investigated using mostly
electrochemical methods.
The first section concerns the use of copper(II) as an oxidant for the alloy component of nickel matte. In this cementation reaction, nickel goes into solution while copper is deposited on the dissolving metal swf8ce. The same reaction is important in removing traces of copper present in the nickel solution. Here nickel powder is added to the process liquor. A survey of the literature pertaining to the cementation of copper by nickel shows that there is considerable dispute as to the conditions under which cementation takes place. Evans' diagrams for the cementation reaction were constructed by superimposing the polarisation curves for the oxidation of nickel and
the reduction of copper. It was found that cementation occurred provided that the two polarisation curves intersected in the region of active nickel dissolution. Outside this region, a copper deposit could not be seen.
The second part of the thesis presents some investigations into the electrochemistry of nickel sulfides and nickel matte, and compares both chloride and sulfate media.
Oxidation and dissolution rates of nickel matte powders using copper(I1) as an oxidant were also carried out. Dissolution was chemically controlled and so the rate was very dependent upon temperature and solution potential. Displacement of copper(II) from solution to form copper sulfide was also found to be important.
In addition to the above studies, which relate directly to the oxidative leaching ofnickel matte, an investigation of the oxidation of HzS to sulfUr in acidic solution was
carried out. S u k deposition was found to be strongly dependent on substrate and pH. Under some conditions, two types of sulfUr were deposited, with the more crystalline s u k being reduced at the more negative potential.
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Barbero, Bernal Laura Isabel. "Cyclic Behavior of Superelastic Nickel-Titanium and Nickel-Titanium-Chromium Shape Memory Alloys." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4937.
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Shape memory alloys (SMAs) are a class of alloys that display the unique ability to undergo nonlinear deformations and return to their original shape when heat is applied or the stress causing the deformation is removed. This unique shape memory characteristic is a result of a martensitic phase-change, which can be temperature induced (shape memory effect) or stress induced (superelastic effect).
In this study, the cyclical behavior of NiTi, a binary shape memory alloy, is compared to the cyclical behavior of NiTiCr, a ternary SMA. The purpose of this study is to compare the behavior of a 0.085-in. diameter NiTiCr wire with the behavior of the same size NiTi wire to determine whether ternary SMAs are more viable ways to take advantage of the unique properties of SMAs for seismic applications. The experimental results showing the superelastic behavior of these alloys under cyclical tensile loading are summarized with attention to the effects of annealing temperature, strain rate, and cyclical training on the stress-strain hysteresis, maximum recoverable strain and equivalent viscous damping.
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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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Wang, Belle Ewei 1977. "Field emission from carbon nanotubes deposited on platinum and nickel/nickel oxide multilayers." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9098.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 81-84).
Although carbon nanotubes have been shown to be excellent field emitters, very little is known about the emission mechanism. This work strives to gain insight on field enhancement in films of single-walled carbon nanotubes by studying the internal field emission between the back contact metal and the nanotubes, and the external field emission between the nanotubes and vacuum. Test devices of different work functions were fabricated from platinum and from nickel / nickel oxide. Nickel oxide was deposited by e-beam evaporation or grown by thermal oxidation and characterized by Auger electron spectroscopy, x-ray diffraction and ellipsometry. Carbon nanotubes were deposited onto these test structures and current-voltage measurements were taken. Fowler-Nordheim plots were constructed from this data and analyzed. It was determined that external field emission was most likely to be responsible for electron emission.
by Belle Ewei Wang.
M.Eng.
30
Talah, Habib. "Influence du soufre sur la corrosion localisée du nickel et d'alliages base nickel." Paris 6, 1986. http://www.theses.fr/1986PA066027.
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Étude de la corrosion localisée du nickel pur et d'alliages base nickel dopés en soufre à des teneurs contrôlées. On montre que le soufre présent dans la masse des alliages peut provoquer la rupture différée du film passif en s'enrichissant à l'interface métal/film passif. Il en résulte une corrosion localisée, induite par le soufre qui ségrége. Cet effet est observé aussi bien dans des conditions non stationnaires de passivation (cycle de passivation-activation) que dans des conditions stationnaires de passivation. Les seuils de concentration en soufre causant la corrosion localisée par piqures et par crevasses ont été déterminés.
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Talah, Habib. "Influence du soufre sur la corrosion localisée du nickel et d'alliages base nickel." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37601427r.
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Demourgues-Guerlou, Liliane. "Sur de nouveaux hydroxydes et oxydroxydes de nickel substitués au fer et au manganèse pour batteries nickel-cadmium ou nickel-hydrure métallique." Bordeaux 1, 1992. http://www.theses.fr/1992BOR10670.
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Ce travail est consacre a la caracterisation de nouveaux hydroxydes et oxyhydroxydes de nickel substitues au fer ou au manganese. Dans les hydroxydes, les ions nickel restent a l'etat divalent alors que les ions fer et manganese sont trivalents. La compensation de l'exces de charge positive resulte de l'insertion d'anions dans l'espace interfeuillet. Selon le taux d'ions substituants, ces anions sont soit statistiquement distribues (phase ) soit segregues dans certains espaces interfeuillets (phase interstratifiee). Les hydroxydes substitues au manganese sont instables en milieu potassique du fait de l'oxydation des ions manganese trivalents a l'etat tetravalent; ce comportement donne lieu a un deuxieme type d'interstratification. L'ensemble des materiaux a ete caracterise par analyse chimique, diffraction x et spectroscopie infrarouge. Les etudes magnetique et par spectroscopie mossbauer des oxyhydroxydes substitues au fer ont montre la presence d'ions fer tetravalents, essentiellement dans la configuration spin faible. L'etude du cyclage electrochimique des materiaux substitues au fer (diffraction x et spectroscopie mossbauer in situ) a revele la stabilisation complete du couple / ainsi qu'une augmentation notable du potentiel. La substitution du manganese induit quant a elle une bonne chargeabilite ainsi qu'une stabilisation tres interessante de la capacite au cours du temps. Enfin, il s'est avere que la substitution mixte du fer, du cobalt ou du manganese conduit a des performances electrochimiques tres prometteuses sur le plan applique
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Blaylock, Donnie Wayne. "Computational heterogeneous catalysis applied to steam methane reforming over nickel and nickel/silver catalysts." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/62730.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 182-188).
The steam methane reforming (SMR) reaction is the primary industrial means for producing hydrogen gas. As such, it is a critical support process for applications including petrochemical processing and ammonia synthesis. In addition, SMR could be an important component of future energy infrastructures as a means for producing hydrogen as an energy carrier for applications including fuel cells in automobiles and direct combustion for electricity generation. Nickel is the preferred SMR catalyst; however, the efficiency of SMR over nickel can be severely hindered by carbon formation, which leads to the deactivation or even destruction of the catalyst particles. Thus, there is significant interest in catalysts that inhibit carbon formation yet retain activity to SMR. In order to develop improved catalysts for SMR, a thorough understanding of the processes occurring on the nickel surface is needed. In this thesis, computational heterogeneous catalysis is applied to investigate steam methane reforming over nickel (Ni) and silver-alloyed nickel (Ni/Ag) catalysts. Electronic structure calculations using density functional theory (DFT) are employed to develop thermochemical landscapes describing the relative stabilities of SMR intermediates on the catalyst surfaces. In addition, DFT calculations are used to obtain kinetic parameters that describe elementary surface reactions taking place during SMR. A detailed statistical thermodynamics framework is developed to allow for the calculation of enthalpies, entropies, and free energies of the surface species at the temperatures and pressures relevant to industrial SMR. The data from the DFT calculations are used to build detailed ab inito microkinetic models of SMR over the multi-faceted nickel catalyst. The resulting microkinetic models are used to provide insight into the processes occurring on the catalyst surface through identifying the most important intermediate species and reactions occurring on the catalyst. The effects of alloying the nickel catalyst with silver are predicted through modeling the dissociative methane adsorption reaction on multiple facets of the Ni/Ag surface with varying concentrations of silver. In addition, DFT calculations are used to investigate carbon formation on the Ni and Ni/Ag catalyst surfaces, including relative stabilities of various carbon-containing intermediates and the effects of alloying the nickel surface with silver on carbon formation.
by Donnie Wayne Blaylock.
Ph.D.
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El-Sharif, M. R. "Continuous codeposition of chromium-nickel and chromium-nickel-iron alloys from aqueous amide electrolytes." Thesis, University of the West of Scotland, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376533.
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There are numerous reports of attempts to deposit thick coatings of chromium-nickel and chromium-nickel-iron and although high quality deposits have been obtained these have been limited to very thin coatings only. The purpose of the present work was to identify and understand the controlling factors preventing continuous deposition and the build-up of thick coatings, and to develop a suitable process for such thick coatings. An amide electrolyte system was chosen asworking model for its relative simplicity and the high quality chromium-nickel deposits obtained from this system. This bath was investigated initially using conventional operating techniques (Constant Current) to establish its general characteristics. High quality deposits were obtained for thin coatings only. The need for a major change of operating philosophy was identified as essential. A number of published hypotheses explaining the failure of continuous deposition were experimentally tested and shown not to apply. Electrolytically generated chromium (II) has been identified to be an important controlling factor on the quality and composition of chromium-nickel alloys codeposited from amide electrolytes. The control of the low transient chromium (II) level, necessary for the maintenance of high quality codeposition with constant composition, can be achieved as follows. A controlled potential is required, in combination with circulation and agitation of the electrolyte and the generation of the chlorine gas as the preferred anodic product. The combination of the three techniques is necessary for the control of chromium (II) and if any of the three techniques are not employed sustained deposition fails. Chromium (II) has further been identified to catalyse an electrochemical ageing of the bath. Reproducible high quality true metallic deposits of constant composition of chromium-nickel and chromium-nickel-iron can be obtained to a thickness of several hundred microns. These have shown to display a laminar structure on etching and possible causes have been considered. Mossbauer spectroscopy and x-ray diffraction have shown that chromium-nickel-iron deposits contain a significant quantity of micro-crystalline austenite phase ~, fcc) with a dominant ferrite (e<, bcc) phase.
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Perry, Richard. "Towards environmentally friendly electrodeposition : using citrate based electrolytes to deposit nickel and nickel-iron." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/16184.
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The production of magnetic materials is of great interest for use in the micro-fabrication industry. In particular, Permalloy (Ni80Fe20) is used in the production of micro-electromechanical systems (MEMS) due to its favourable magnetic properties (high relative permeability, low coercivity and high magnetic saturation). This leads to applications in devices such as inductors, transformers and micro-actuators. The electrodeposition of NiFe is also of fundamental electrochemical interest, as there is anomalous thermodynamic behaviour, with the less noble (iron) metal depositing preferentially to the more noble (nickel) metal. To enable consistent alloy deposition nickel and nickel-iron baths are currently almost exclusively based on boric acid. Boric acid has an important role in the deposition of NiFe films but its role(s) in the electro-deposition mechanism is (are) not wholly understood. Recently (2011) boric acid has been identified as a “substance of very high concern” based on the criteria established by EU chemical regulation, REACH. In anticipation of increased regulation an alternative was sought to provide a benign alternative to boric acid in the NiFe plating bath suitable for use in micro-fabrication. Initial work was performed to benchmark the performance of existing boric acid based electro-deposition baths. Cyclic voltammetry was performed, which demonstrated the deposition of nickel and nickel-iron from boric acid baths. Coulombic efficiencies up to 93 % were measured for the deposition of nickel using the electrochemical quartz crystal microbalance (EQCM) on platinum electrodes. For nickel-iron deposition control of the film composition was demonstrated on copper electrodes through varying the iron (II) concentration, current density and temperature. A citrate bath for the deposition of nickel-iron was then developed and characterised. Cyclic voltammetry was performed in these citrate baths demonstrating the deposition of nickel and nickel-iron. Optimal conditions for depositing Ni80Fe20 were demonstrated to be an elevated temperature (60 °C) with a current density of 20 mA cm-2 and a pH of 3. Using the EQCM the efficiency for nickel deposition was measured to be > 80 %. The effects of sodium saccharin and sodium dodecyl sulfate as additives were investigated; these were shown to influence morphology but not the coulombic efficiency. Decreasing the pH was shown to lower the efficiency of nickel deposition from the citrate bath. Comparisons of key properties were made between NiFe films deposited from a boric acid bath and the citrate bath developed in this work. Test structures were used to compare the strain in the films; no significant difference was found. For 2.2 μm thick Ni80Fe20 films the sheet resistance was measured using Greek cross structures as 0.078 ± 0.004 Ω/square for films deposited from the boric acid bath and 0.090 ± 0.006 Ω/square from the citrate bath. The magnetic saturation, Ms, was measured as 895 ± 66 emu cm-3 for deposits from the boric acid bath and 923 ± 111 emu cm-3 from the citrate bath. These again show no significant difference in these values within experimental error. Coercivities for these films were measured to be between 20 and 120 A m-1. In combination, this work demonstrates the development and characterisation of a new citrate based electrodeposition bath for nickel and nickel-iron. Similar chemical, electrical, mechanical and magnetic properties were found from films deposited from both baths, thus demonstrating the suitability of the citrate bath for the deposition of nickel-iron films in microfabrication.
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Ravi, Vilupanur Alwar. "Simultaneous chromizing-aluminizing of nickel and nickel base alloys by halide activated pack cementation /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487597424136616.
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Rousseau, Thomas. "Modélisation multi-échelle de la modification de structure d'un alliage à base de nickel soumis à de très fortes déformations plastiques en surface." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC016/document.
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La compréhension des effets du grenaillage ultrasonore sur l’intégrité de surface des composants métalliques représente un enjeu industriel important. Dans le cadre de cette thèse, une modélisation physique multi-échelle de la plasticité cristalline à la DEM (Discrete Element Model) a été développée. Le grenaillage ultrasonore consiste à mettre en mouvement des billes à l’intérieur d’une enceinte par vibration de la sonotrode. Les impacts répétés sur le matériau entraînent un écrouissage en surface, l’établissement de contraintes résiduelles de compression et la formation d’une couche nanostructurée. L’objectif de cette thèse est d’obtenir une meilleure compréhension des mécanismes conduisant à ces modifications sur un alliage à base nickel. Le mouvement des billes obtenu par DEM est relié aux modifications de la microstructure sous impacts via un modèle éléments finis utilisant une loi de plasticité cristalline. Après validation de chaque étape par des mesures expérimentales, le modèle a permis d’étudier l’effet de la quantité de billes utilisées dans le procédé. Ainsi, un nombre croissant de billes induit une augmentation d’impacts en biais de faible vitesse permettant de concentrer les contraintes résiduelles de compression en extrême surface. De plus, les simulations multi-impacts utilisant une loi de plasticité cristalline ont montré que ces impacts en biais engendraient une densité totale de dislocations et un niveau de désorientations élevées pouvant expliquer la fragmentation des grains et la nanostructuration de la surface. Enfin, ces modifications de la microstructure, visibles jusqu’à 300 µm de profondeur, sont en accord avec les profils de dureté obtenus par nano-indentation et les profils de désorientation issus de l’analyse EBSD (Electron BackScatter Diffraction)Ultrasonic shot peening is widely used to improve mechanical properties of metallic components. Mastering the effects of this surface treatment is a major industrial issue. A physical multi-scale modelling based on crystal plasticity and DEM (Discrete Element Model) was developed in this PhD thesis. This process is performed in a closed chamber where spherical balls are moved by sonotrode vibration. Thousands of impacts induce hardening, residual compressive stress and microstructure modification leading to a nanostructured layer. The aim of this work was to improve our understanding of the mechanisms occurring during this process on nickel-based alloys. Ball motion was computed by DEM and linked to microstructure modifications induced by impacts through a crystal plasticity finite element model. Experimental analyses were performed in order to validate each step of the multi-scale modelling. Then the model was applied to investigate ball quantity effects on peened surface modification. Increasing the number of balls created a larger quantity of low speed oblique impacts which concentrated the residual compressive stress near the surface. Furthermore multi-impacts performed with a crystal plasticity law showed oblique impacts enhanced dislocation storage and disorientations within grains, which could explain the nanostructuration of the peened surface. Moreover, the numerical microstructure modification, observed up to 300 µm in depth, was in agreement with hardness profiles obtained by nanoindentation and disorientation profiles measured by EBSD (Electron BackScatter Diffraction) analysis
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Köstlin, Kathrin Eva. "Nickel-induzierte Signaltransduktionswege in Endothelzellen /." Würzburg, 2007. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000253017.
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Steeb, Jennifer L. "Nickel-63 microirradiators and applications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34773.
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In this thesis, manufacturing of microirradiators, electrodeposition of radioactive elements such as Ni-63, and applications of these radioactive sources are discussed. Ni-63 has a half life of 100 years and a low energy beta electron of 67 keV, ideal for low dose low linear energy transfer (LET) research. The main focus of the research is on the novel Ni-63 microirradiator. It contains a small amount of total activity of radiation but a large flux, allowing the user to safely handle the microirradiator without extensive shielding. This thesis is divided into nine chapters. Properties of microirradiators and various competing radioactive sources are compared in the introduction (chapter 1). Detailed description of manufacturing Ni-63 microirradiator using the microelectrode as the starting point is outlined in chapter 2. The microelectrode is a 25 µm in diameter Pt disk sealed in a pulled 1 mm diameter borosilicate capillary tube, as a protruding wire or recessed disk microelectrode. The electrochemically active surface area of each is verified by cyclic voltammetry. Electrodeposition of nickel with a detailed description of formulation of the electrochemical bath in a cold "non-radioactive setting" was optimized by using parameters as defined by pourbaix diagrams, radioactive electroplating of Ni-63, and incorporation of safety regulations into electrodeposition. Calibration and characterization of the Ni-63 microirradiators as protruding wire and recessed disk microirradiators is presented in chapter 3. In chapters 4 through 6, applications of the Ni-63 microirradiators and wire sources are presented. Chapter 4 provides a radiobiological application of the recessed disk microirradiator and a modified flush microirradiator with osteosarcoma cancer cells. Cells were irradiated with 2000 to 1 Bq, and real time observations of DNA double strand breaks were observed. A novel benchtop detection system for the microirradiators is presented in chapter 5. Ni-63 is most commonly measured by liquid scintillation counters, which are expensive and not easily accessible within a benchtop setting. Results show liquid scintillation measurements overestimates the amount of radiation coming from the recessed disk. A novel 10 µCi Ni-63 electrochemically deposited wire acting as an ambient chemical ionization source for pharmaceutical tablets in mass spectrometry is in chapter 6. Typically, larger radioactive sources (15 mCi) of Ni-63 have been used in an ambient ionization scenario. Additionally, this is the first application of using Ni-63 to ionize in atmosphere pharmaceutical tablets, leading to a possible field portable device. In the last chapters, chapters 7 through 8, previous microirradiator experiments and future work are summarized. Chapter 7 illustrates the prototype of the electrochemically deposited microirradiator, the Te-125 microirradiator. In conjunction with Oak Ridge National Laboratory, Te-125m is a low dose x-ray emitting element determined to be the best first prototype of an electrochemically deposited microirradiator. Manufacturing, characterization, and experiments that were not successful leading to the development of the Ni-63 microirradiator are discussed. In chapter 8, future work is entailed in continuing on with this thesis project. The work presented in the thesis is concluded in chapter 9.
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Ahtesham, Babar. "Treatment of nickel plating waste." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/MQ45893.pdf.
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Bansa, Patrice B. "Property characterization of CVD nickel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63137.pdf.
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Goodall, Graeme. "Nickel recovery from reject laterite." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99763.
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Falconbridge Dominicana C. Por A. operating in the Dominican Republic produces nickel as an iron-nickel alloy from laterite ore. Material that is rejected from their mining operations due to its incompatible chemistry is currently being stockpiled against mine depletion. Recent interest in recuperating nickel from this reject material led to the examination of the suitability of carbothermic reduction followed by magnetic separation for nickel recovery from this reject ore. Five parameters were considered in a Design of Experiment framework, namely: heating time; temperature; material type, coke addition and oxygen partial pressure. Magnetic separation was conducted with a Davis Tube and a low intensity hand magnet.It was found that this reject material can successfully be treated using a carbothermic reduction process to produce 50 to 75 mum diameter metallic components within a gangue matrix. The recovery of nickel ranged from 61.7% to 21.9% to 16.4% in the high, low and non magnetic fractions, respectively, separated from the reduced material. The grade of nickel ranged from 1.97 wt% Ni to 1.58% to 0.75 wt% Ni in the high, low and non magnetic fractions, respectively.
Heating temperature had the greatest positive influence on the performance of the process followed by material type and heating time. Oxygen activity and coke addition were seen not to influence the performance. The Boudouard reaction was considered to be the rate controlling step and a maximum possible operating temperature was considered to depend on the physical properties of the material, specifically the softening temperature.
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Clark, A. C. "Forging of nickel-base superalloys." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636261.
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The properties of the nickel based superalloy Inconel 718 (IN 718) are insufficient for its use in the higher temperature stages at the rear of the gas turbine jet engine compressor. Considerable effort is being made to adapt the microstructure and improve the properties by thermomechanical processing, to enable the cheaper IN 718 alloy to replace the current alloy, Waspaloy, in the fabrications of these rear-end compressor disks. The initial casting of the alloy leads to an unsuitably coarse microstructure. The alloy is therefore forged in order to optimise the microstructure and hence mechanical properties. Isothermal compression tests were carried out on the alloy in the as-cast condition to investigate both dynamic and static microstructural events between 900°C and 1121°C. Strain rates ranged from 0.001s-1 to 10.0s-1 with strains from 0.1 to 0.6. Microstructural investigations revealed that complete dynamic recrystallisation was not evident in any of the samples, however partial recrystallisation occurred in samples forged at the higher temperatures and strain rates. The amount of dynamic recrystallation was found to increase primarily with temperature but also with strain rate. Complete static recrystallation was found to have occurred in tests conducted with a post-forge hold time at temperature. The degree of this recrystallisation and the resulting grain size were found to depend primarily on temperature and strain and less so on strain rate. Stress levels varied systematically with temperature and strain rates. Higher stress levels resulted from lower testing temperatures and higher strain rates. Currently property data of material in the as-cast condition is not widely available. Constitutive analysis was performed on the Stress-strain data for subsequent implementation in the forging simulation program "BILLIE". These results would then be used to provide simulations of the industrial Inco Alloys forging process.
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Claudio, Mendicute Fierro. "Synthesis of nickel-thiolate complexes." Thesis, Manchester Metropolitan University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403779.
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Zhao, Xinjin 1961. "Nickel deposition on hydrodemetallation catalysts." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/31037.
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Watkins, Shaun Gareth. "Wear fatigue in nickel superalloys." Thesis, Swansea University, 2015. https://cronfa.swan.ac.uk/Record/cronfa43108.
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To date, work to assess the progression of wear and the effects of wear damage on low cycle fatigue has tended to be focused on specific components and their operating conditions. Although effective in the short term to solve today’s problems, these efforts often deliver insufficient understanding of the overall design space limits to have much influence of future component design. Therefore, the following research attempts to understand how wear damage progresses and how it impacts on fatigue performance in order to develop more accurate lifing models to predict the behaviour and life of real engine components. In order to do this, a survey of the internal Rolls-Royce database and public literature on wear damage on components from ex-service and current service engines was performed. Information relating to the wear scar morphologies in the reports was extracted as well as physically measuring and analysing wear damage on worn components within the Rolls- Royce failure investigation department. The wear damage was then replicated onto Udimet720Li laboratory fatigue specimens by a means of altering the pad pressure and pad sliding distance to produce a range of wear damage in order to carry out fatigue testing. Fatigue testing of the damaged specimens allowed fatigue knockdown factors to be calculated to determine the impact of wear on the fatigue life. A fretting fatigue rig was also designed and built for this research to focus on in-situ fretting fatigue at high temperatures of 600°C.
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Thorne, Robert L. "Nickel laterites, origin and climate." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/191955/.
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Nickel laterites account for ?40 % of global nickel production and contain 60 % of the world's total land based nickel resources. Despite the importance of these deposits published studies, detailing their morphology and formation processes are relatively few and the interaction of variables responsible for the formation of different nickel laterites are poorly understood. To better understand the process of nickel laterite formation, the Caldag and Bitincke paleodeposits were studied and their geological history established. The Caldag laterite, western Turkey, formed by intense chemical weathering of a serpentinite protolith in a region with a high water table and relatively low topography, resulting in the formation of an oxide deposit. In addition silica precipitation is common in the upper horizons of the deposit, where it creates an indurated layer, protecting the deposit from erosion. The Bitincke Nickel laterite, Albania is composed of two distinct zones characterized by silicate nickel and iron oxide phases. At Bitincke laterite formation and variations in thickness were controlled by the interaction between topography, faulting and protolith fracture density. The morphological and geochemical study of the Caldag and Bitincke paleodeposits indicates that there is a complex interplay between structures, topography, water table height and climate. Therefore nickel laterite deposits developed on very similar protoliths can form deposits with distinct and different characteristics. By comparing climatic data for regions where suitable ultramafic rocks are exposed and defining the climatic conditions favourable for the formation of nickel laterite deposits, the optimum temperatures and precipitation rates for nickel laterite development can be identified. A compilation of paleoclimatic data from western Turkey and Albania allows for the optimum periods of laterite formation within these regions to be established. Calculation of temperatures of formation from goethite oxygen and hydrogen isotopes could provide additional data on paleoclimaitc conditions. However due to the heterogeneity of laterite deposits and an extended weathering history, data gained from goethite appears not to provide a robust measure of paleotemperature. The study of the Caldag and Bitincke deposits combined with the analysis of the optimum conditions for nickel laterite formation has shown that there are four main factors which effect laterite formation: 1) Exposure of a suitable protolith; 2) Optimum climatic condition; 3) Geological variables; 4) Environment of preservation. Knowledge of these variables will assist in future laterite studies and will improve predictability of the location of new deposits.
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Chiang, Ray-Tung, and 江瑞童. "The Synthesis of Nickel Nanoparticles and their Transformation to Nickel Phosphides and Nickel Sulfides." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/32287255121202993407.
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碩士遠東技術學院
機械研究所
95
This thesis mainly focuses on studies of the synthesis of stable FCC and HCP Ni nanoparticle (NPs) and their transformation to nickel phosphides and nickel Sulfides NPs. Synthesis of colloid hollow Ni2P NPs can be via a simple one-pot reaction with nickel acetate (Ni(Ac)2), oleylamine (OLA), trioctylphosphine (TOP), and 1-octadecene (1-ODE) as reactants. The mechanism of formation of the hollow structure is related to the diffusion mechnaism, the nano-scale Kirkendall effect. The whole process includes two key points. First, the existence of OLA ensures the nickel NPs stabilized, which forms protecting layers on the surface of NPs and prevents the erosion from TOP, and reduce diffusion rate of P atoms. Second, when the concentration of TOP and temperature are adjusted and controlled properly, the solid state reaction will take place and lead to the formation of hollow Ni2P nanoparticles. Synthesis of HCP phase Ni NPs with star-shaped and spherical morphology are both through thermal decomposition method, but using different precursors, namely, nickel acetate and nickel acetylacetonate (Ni(acac)2). The different precursors may have different decomposition rate that could affect the monomers concentration during the reaction. By using the precursor of Ni(Ac)2, the star-shaped HCP Ni NPs were obtained by anisotropic growth in the high monomers concentration, while using Ni(acac)2, spherical HCP Ni NPs were obtained. The size of NPs can be controlled through the different reaction times. Also, the obtained HCP Ni NPs can be differentiated from Ni3C by temperature-dependent powder X-ray experiments. Magnetic properties of the obtained HCP Ni NPs were also carried out on SQUID. The results indicated the HCP Ni is not as ferromagnetic as FCC Ni; it is nonmagnetic. Furthermore, the star-shaped HCP Ni particles can be also transformed to Ni2P and Ni9S8 via the diffusion reaction using trioctylphosphine and 1-hexadecanethiol.
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Lee, Cheng-Chang, and 李政漳. "Dynamic analysis of nickel-iron, nickel-chrome alloys." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/15744764148681823751.
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碩士元智工學院
化學工程學系
84
Abstract We are using dynamic methods:ring-disk and pulse current technologys toanalyse the contents of Ni-Fe, Ni-Cr, and Ni-Cr-P alloys. Ni-Fe plating was carried out using the rotating ring-disk electrode under different operating conditions. Various ferrous ion concentrations, bath pH values, and additives were used in the plating baths to study their influences on themetal deposition rates and alloy compositions. Experimental results indicate that the nickel plating rate decreases withthe increase of ferrous ion concentration. Iron and nickel current density increase with an increased bath pH value. Citrate ion inhibits both nickel and iron reduction rate. Ni-Cr and Ni-Cr-P alloys plating were carried out using galvanostatic pulse technique on the rotating disk electrode under different operating conditions were to study the effect of pulse parameter on the metal deposition rate, alloy composition and surface morphology. Results indicate that similar results are obtained for both Ni- Cr and Ni-Cr-P platings. The influence of disk rotation speed on nickel plating rate is different at low and high duty cycles. In low duty cycle region, nickel plating rate decreases with an increase of rotation speed.In high duty cycle region, nickel deposition rate increases at an increased disk rotation speed. Disc rotation speed has a positive effect on chrome and phosphorus deposition rates. Nickel deposition rate increases while chrome deposition rate decreases with an increased bath pH value. Nickel and phosphorus deposition rate increases while chrome deposition rate decreases with an increase of pulse frequency. Chrome and phosphorus deposition rate are enhanced with an increase of pulse current density. Nickel deposition rate is decreased at an increased pulse current density in high duty cycle region. Alloys surface morphology was studied by scanning electron micrograph. X-ray diffraction was used to study the noncrystal structure of the resulting deposits.
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Wang, Lu-Min. "Microstructure of ion irradiated nickel and nickel-copper alloys." 1988. http://catalog.hathitrust.org/api/volumes/oclc/20387833.html.
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