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1
Adcock, Peter Anthony, University of Western Sydney, and School of Civic Engineering and Environment. "Zinc electrowinning in the presence of iron (II)." THESIS_XXX_CEE_Adcock_P.xml, 1999. http://handle.uws.edu.au:8081/1959.7/669.
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In the hydrometallurgical processing route for primary production of zinc, one of the most significant impurities in terms of cost of processing is iron. In the last two decades, electroplating of steel sheet with alloys such as zinc/iron has seen considerable industrial development. In this process, there is an 'anomalous co-deposition', in which zinc is deposited at a higher rate than iron, even though it is more cathodic in the electrochemical series.In the 1980's research papers reported high current efficiencies for zinc electroplating in the presence of a comparable concentration of iron. It is of interest to the zinc industry to know conditions under which zinc could be electrowon efficiently without prior separation of iron. The chief aim of the current project was to obtain data which would allow evaluation of a zinc electrowinning step carried out in the presence of iron. It was necessary to understand the robustness of such a process towards variations in parameters such as electrolyte composition and purity, temperature, and current density. Means of producing smooth, strippable deposits at high current efficiencies also required evaluation. In order to electrolyse high iron solutions at high current efficiency, it is necessary to introduce a separator into the cell, to prevent cycling of iron oxidation at the anode and reduction at the cathode. The focus of this project was on the cathode process, particularly the determination of factors influencing morphology and current efficiency. Experiments involved modifications of some cells typically used in studies of conventional zinc electrowinning. A range of techniques for morphological studies and for electrochemical tets was evaluated for application to this problem, as well as to studies of conventional zinc electrowinning operations<br>Doctor of Philosophy (PhD)
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Paramore, James D. "Candidate anode materials for iron production by molten oxide electrolysis." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62687.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 61-63).<br>Molten oxide electrolysis (MOE) has been identified by the American Iron and Steel Institute (AISI) as one of four possible breakthrough technologies to alleviate the environmental impact of iron and steel production. This process has also been identified by the National Aeronautics and Space Administration (NASA) as a means to produce oxygen gas, as well as iron and silicon raw materials on the Moon. MOE produces iron by electrolysis of an iron oxide containing electrolyte. The electrolysis results in the production of pure iron metal at the cathode and pure oxygen gas at the anode. Because of the low vapor pressure of the electrolyte at temperatures above 1538°C, MOE can be performed above the melting temperature of iron. The production of liquid metal, ready for continuous casting, is a prerequisite for any industrial-scale extractive metallurgical process. Therefore, if an inert anode can be identified, MOE could provide a an industrial process to produce iron from its ore with pure oxygen gas as the only direct emission. The feasibility of MOE as a carbon-neutral process hinges on the identification of an inert anode material. Therefore, the scope of this study was to determine the criteria of an inert anode for MOE, identify candidate materials, and evaluate the performance of these materials. Previous studies of MOE at MIT found iridium, a platinum group metal, to be an excellent candidate for an inert anode. The high cost of iridium makes it an unlikely candidate for a commercial iron production process. However, iridium provides a likely candidate for lunar production of oxygen, or high-purity iron production. Furthermore, the use of iridium on the laboratory-scale provides a widely available inert anode material to facilitate the study of other areas of MOE. Therefore, unique anode morphologies were evaluated as a means to reduce the economical strain of using an iridium anode. In addition to iridium, a wide array of readily available, high-temperature electrode materials were tested. Due to the highly corrosive environment of MOE, none of the readily available materials tested are compatible with the process. It is believed that the most likely candidate for an inert anode lies in an engineered material, composed of a refractory substrate and an oxide passivation layer. Therefore, the criteria for such a material were determined and likely candidates are discussed.<br>by James D. Paramore.<br>S.M.
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Adcock, Peter Anthony. "Zinc electrowinning in the presence of iron (II)." Thesis, View thesis, 1999. http://handle.uws.edu.au:8081/1959.7/669.
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In the hydrometallurgical processing route for primary production of zinc, one of the most significant impurities in terms of cost of processing is iron. In the last two decades, electroplating of steel sheet with alloys such as zinc/iron has seen considerable industrial development. In this process, there is an 'anomalous co-deposition', in which zinc is deposited at a higher rate than iron, even though it is more cathodic in the electrochemical series.In the 1980's research papers reported high current efficiencies for zinc electroplating in the presence of a comparable concentration of iron. It is of interest to the zinc industry to know conditions under which zinc could be electrowon efficiently without prior separation of iron. The chief aim of the current project was to obtain data which would allow evaluation of a zinc electrowinning step carried out in the presence of iron. It was necessary to understand the robustness of such a process towards variations in parameters such as electrolyte composition and purity, temperature, and current density. Means of producing smooth, strippable deposits at high current efficiencies also required evaluation. In order to electrolyse high iron solutions at high current efficiency, it is necessary to introduce a separator into the cell, to prevent cycling of iron oxidation at the anode and reduction at the cathode. The focus of this project was on the cathode process, particularly the determination of factors influencing morphology and current efficiency. Experiments involved modifications of some cells typically used in studies of conventional zinc electrowinning. A range of techniques for morphological studies and for electrochemical tets was evaluated for application to this problem, as well as to studies of conventional zinc electrowinning operations
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Yagi, Shunsuke. "Surface modification process for high-purity iron and carbon steel by alternating pulsed electrolysis." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136229.
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Adcock, Peter Anthony. "Zinc electrowinning in the presence of iron (II) /." View thesis, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20031112.143926/index.html.
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Wiencke, Jan-Christian. "Analysis of the electrochemical processes during the production of liquid iron by Molten Oxide Electrolysis." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0329.
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L'électrolyse en milieu oxydes fondus (MOE) peut être envisagée comme une nouvelle technologie de l’industrie sidérurgique pour la production de fer liquide sans émission de CO2. Dans ce concept, l'électrolyse est utilisée pour produire de l’oxygène gazeux et du fer liquide à des températures supérieures à 1810 K. Dans cette étude sont présentées les principales réactions électrochimiques lors de l’électrolyse en milieu fondu (MgO-Al2O3-SiO2). Une quantité importante de fer liquide a été produite lors d'électrolyses conduites pendant plusieurs heures. L'analyse MEB-EDS du dépôt a révélé un alliage de fer métallique quasi pur, uniquement contaminé par le matériau cathodique. Ce résultat traduit une sélectivité élevée du procédé électrolytique. L'étude de la réponse de l'électrolyte en fonction de la tension électrique et de la concentration de fer a révélé une limitation par la diffusion lors de l’électrolyse de bains de faibles concentrations en oxyde de fer, et à des potentiels inférieurs à 1,5 V. La demi-réaction de la cathode a été identifiée comme la réduction du fer ferreux en fer métallique. L’extrapolation des droites de Tafel sur les courbes courant-tension corrigées de la chute ohmique a conduit à des coefficients de transfert (de la réaction cathodique) proches à 0,6. L’ordre de réaction de réduction de FeII en Fe0 a été évalué autour de 1. L'analyse de la demi-réaction anodique dans les oxydes fondus à faible teneur en fer a montré que les premières espèces éctroactives sont les anions oxydes libres. Pour des tensions électriques croissantes, le transport des anions O2- libres devient limité et le transfert de charge est partiellement attribué à l’oxydation du fer ferreux. Au contraire, dans des mélanges d’oxydes fondus à concentrations élevées en fer, le transfert de charge est réalisé dans toute la gamme de tension par l'oxydation du fer ferreux. C’est seulement à haute tension, que l’oxydation des anions oxyde contribue au transfert des charges. Dans l'ensemble des compositions testées, aucune limitation du courant n’a été observée sur la réaction anodique<br>Molten oxide electrolysis (MOE) is an ambitious technique for the production of liquid iron by the use of renewable energies and thus lower CO2 emissions in the steel industry. In this concept, electrolysis is used to produce gaseous O2 and liquid iron metal at temperatures above 1810 K. In the experimental study presented here the key-parameters of the electrochemical reactions in a magnesio-aluminosilicate electrolyte and at the electrodes during MOE are investigated. A significant amount of liquid iron metal was produced during experiments of several hours. SEM-EDS analysis of the deposit revealed an alloy of iron metal and of the cathode material, which thereby indicates high process selectivity. Investigation of the electrolyte’s response in dependence of cell voltage and iron concentration inferred a diffusional limitation at low iron oxide concentrations at potentials below 1.5 V. The cathode half-reaction was identified as the reduction of ferrous iron to liquid iron metal. Using Tafel interpretation reaction-transfer coefficients close to 0.6 and an order of reaction around 1 were determined. The analysis of the anode half-reaction showed that in low iron bearing molten oxides, oxide anions were firstly oxidized into O2 gas. At high iron concentrations the charge transfer is conducted in the entire cell voltage range by the oxidation of ferrous iron. The participation of oxide anions in the charge transfer was only witnessed at high cell voltages. In the entire compositional range a limitation of the measured current due to the anode half reaction was not observed
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Allanore, Antoine. "Étude expérimentale de la production de fer électrolytique en milieu alcalin : mécanisme de réduction des oxydes et développement d'une cellule." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL109N/document.
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Le fer est l'un des rares métaux qui ne soit pas produit industriellement par électrolyse. Pour aider au développement d'un tel procédé pour l'acier, l'électrolyse des oxydes de fer en milieu sodique est examinée, selon deux approches. La première démarche consiste en l'étude expérimentale du mécanisme réactionnel. L'électrochimie des ions indique qu'il est possible de produire du métal par électrodéposition en milieu alcalin. Parallèlement, l'étude de la réduction d'une particule d'oxyde hématite révèle qu'elle subit, lors de sa conversion en fer métallique, une transformation macroscopique en phase solide. Les analyses démontrent la formation de magnétite comme intermédiaire réactionnel. La seconde démarche est dédiée à la production du fer métallique, par électrolyse d'une suspension de particules d'oxyde dans diverses configurations de cellules. L'incidence des paramètres de procédé a été établie et permet de proposer des éléments de conception d'une cellule industrielle<br>Iron is one of the few metals which is not industrially produced by electrolysis. The electrowinning of iron metal from its oxides in alkaline solution has been studied to develop such an ironmaking route. Two approaches have been adopted. The first one concerns the evaluation of the reaction mechanism. The study of iron ions electrochemistry in alkaline media shows that the electrodeposition of iron metal is possible. The study of a single iron oxide particle reduction reveals that a reaction of the hematite solid phase is possible. The analysis of a partially converted particle proves that magnetite is formed as an intermediate. The second field of study is dedicated to the production of iron metal in various electrochemical cells, using a suspension electrolysis process. The influence of the key operating parameters is established to assess the possible scale-up. All these elements are gathered to propose the main features of an industrial cell dedicated to the reaction
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Roessler, Maxie M. "EPR investigations of iron-sulfur cluster relays in enzymes." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:ac6fa892-f54a-490d-927b-161231f00777.
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Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for obtaining structural information about chemical centres with unpaired electrons. In complex biological systems, EPR spectroscopy can be used to probe these paramagnetic centres and the long-range interactions between them. This thesis investigates two important types of enzymes, and in particular the role of the iron-sulfur electron-transfer centres they contain, with a variety of EPR techniques. Complex I (NADH:Ubiquinone Oxidoreductase) plays a key role in the electron transfer chain essential to the formation of ATP, and its malfunction has been related to numerous human diseases. It is a giant enzyme that contains the longest relay of iron-sulfur clusters known. EPR experiments conducted on complex I from bovine mitochondria yield crucial insight into the mechanism of efficient long-range electron transfer and bring us a step closer to understanding the functioning of this important complex. Hydrogenases are produced by micro-organisms and catalyse the reversible oxidation of H2. Most hydrogenases, including Hyd-2 from Escherichia coli, are very air-sensitive, but some, including E. coli Hyd-1 and Salmonella Hyd-5, are able to function in the presence of atmospheric levels of O2. Understanding the origins of this 'O2-tolerance' is of paramount importance if hydrogenases are to be exploited in future energy technologies. In this thesis, native E. coli Hyd-1 and Hyd-2, Salmonella Hyd-5, as well as O2-tolerant and O2-sensitive variants of E. coli Hyd-1 are characterised using EPR. The EPR investigations elucidate properties of the active site and the electron-transfer relay and, in conjunction with other techniques, reveal structural and mechanistic details of how a highly unusual iron-sulfur cluster in the electron-transfer chain enables some hydrogenases to sustain catalytic activity in the presence of O2.
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Karakurkchi, A. V., M. V. Ved, N. D. Sakhnenko, I. Yu Yermolenko, and S. I. Zyubanova. "Electroplating and functional properties of amorphous Fe-Mo(W) and Fe-Mo-W coatings." Thesis, Институт химии растворов им. Г. А. Крестова РАН, 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22618.
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Sporar, Daniel. "Sputter Deposition of Iron Oxide and Tin Oxide Based Films and the Fabrication of Metal Alloy Based Electrodes for Solar Hydrogen Production." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1183481021.
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Thesis (M.S.Ch.E.)--University of Toledo, 2007.<br>Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science degree in Chemical Engineering." Bibliography: leaves 72-77.
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Moraes, Juliana Pires de. "Eletrólise da salmoura para a geração de cloro empregando cátodos de difusão de oxigênio modificados com ferro." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/262967.
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Orientadores: Christiane de Arruda Rodrigues, Rodnei Bertazzoli<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-18T16:59:20Z (GMT). No. of bitstreams: 1
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Previous issue date: 2011<br>Resumo: Na indústria de cloro-soda, há um crescente interesse no desenvolvimento de tecnologias que resultem numa redução do consumo de energia destinado ao processo de produção de cloro. As células eletroquímicas empregadas no processo cloro-soda são: Mercúrio, Diafragma e Membrana. Atualmente está havendo uma substituição progressiva dos processos empregando mercúrio e difragma por células com membranas trocadoras de íons, pois este processo apresenta melhor eficiência, menor gasto energético e a não geração de resíduos tóxicos. O objetivo deste trabalho envolve a aplicação de eletrodos de difusão gasosa (EDG) modificado com catalisador ferro para a redução do oxigênio, visando à otimização da produção de cloro e maior economia energética nos processos de cloro-soda. Na produção do EDG empregou-se a adição de catalisador ferro nas seguintes proporções: 5%, 10%, 15% e 20% (m/m) em relação à massa de carbono Printex 6L. Duas granulometrias de partículas do catalisador Fe foram empregadas para o preparo dos eletrodos. Ensaios voltamétricos foram realizados para avaliar o efeito da introdução do catalisador de Fe no EDG na reação de redução do oxigênio, além de identificar qual a melhor concentração de Fe e granulometria do catalisador. Os ensaios de voltametria foram realizados em uma célula de compartimento único na temperatura de 25 ºC e solução de trabalho NaOH 320 g/L. Em seguida, ensaios de eletrólises foram realizados para avaliar o desempenho dos EDG, modificado ou não com catalisador Fe, na geração de cloro e DDP da célula, empregando as melhores condições de operação encontradas nos estudos voltamétricos. Os ensaios de eletrólise foram realizados em uma célula com dois compartimentos, separados por uma membrana catiônica Náfion® N242. Nos ensaios de eletrólise foi utilizada uma solução de NaOH 320 g/L, com temperatura de 25 ºC, no compartimento catódico e no compartimento anódico, uma solução de NaCl 250 g/L com temperatura de 70 ºC. A condição de trabalho que apresentou maior redução do consumo de energia e maior geração de cloro foi empregando o EDG com 10% Fe com tamanho de partículas em torno de 0,16 mm2. Comparado ao EDG sem catalisador, verificou-se uma redução no gasto energético de aproximadamente 66%. Isto comprova que o metal de transição Fe atua como o centro ativo e que a atividade eletrocatalítica depende principalmente das propriedades redox do eletrodo modificado<br>Abstract: The interesting in the developing of technologies that contribute in a reduction of energy consumption in chlor-alkali process is growing. The electrochemical cells used in production of chlorine area: Mercury, Diaphragm and membrane. Currently, the mercury and diaphragm cell have been replaced for membrane technology because this cell is more efficient, presents low energy consumption and does not generate toxic waste. The main of this work involves the investigation the performance of gaseous diffusion electrodes modified with particles of iron, for reduction of oxygen in the production of chorine during the electrolysis of brine. In preparing the cathodes of diffusion of oxygen, was used a mass precursor, composed of carbonaceous pigment Printex and suspension of the PTFE powder. The catalyst was introduced in form of Fe metal power in the following percentages: 5%, 10%, 15% e 20% (m/m). For sintering of the electrode of gaseous diffusion (GDE) was weighed 0.2 g of mass precursor and placed on the mold. The mold was heated to a temperature of 340ºC for the sintering of the electrode, under pressure of 146 Kgf/cm2 for 2 hours. After sintering, the electrodes were tested for permeability. In next stage, the electrodes of gaseous diffusion were used in voltammetric studies to examine the influence of catalyst in the reactions of reduction of oxygen in the GDE and identify the best grain size and percentage of iron in electrode. Then, the tests were performed using a single cell compartment, with the type DSA® as counter electrode and the Ag/AgCl as reference electrode in 320 g/L NaOH solution at 25ºC. After, the electrolysis were performed using constant current electrolysis to the GDE or pyrolytic graphite as cathode and DSA® as anode. These tests were carried out in a cell with two compartments, separated by a membrane cationic Nafion N242. The anolyte was a solution of 250 g/L NaCl at 70 ºC and the catholyte was a solution of 320 g/L NaOH, at 25 ºC. During the electrolysis the chorine dissolved in the form of hypochlorite and chlorine gas were quantified by iodometry titration. The electrode that had a better performance in chlorine generation and lower energy consumption was modified with Fe 10% (m/m) with small particle size. This electrode shown around 66% reduction of energy consumption when compared to GDE without iron metal catalyst. This behavior proves that the transition metal Fe acting as the active center and that the electrocatalytic activity depends mainly on the redox properties of the modified electrode<br>Mestrado<br>Materiais e Processos de Fabricação<br>Mestre em Engenharia Mecânica
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Feynerol, Vincent. "Traitement de minerais de fer par lixiviation alcaline suivi de leur électrolyse en milieu alcalin." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0163.
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Un procédé innovant de production de fer par électrolyse d’une suspension d’oxydes de fer en milieu alcalin concentré est développé au centre de recherche d’ArcelorMittal de Maizières-lès-Metz. Ce procédé s’il atteignait la maturité industrielle permettrait de réduire significativement les émissions de dioxyde de carbone associées à l’industrie sidérurgique, en remplaçant le carbone utilisé comme agent réducteur dans les hauts-fourneaux par de l’électricité. Bien que ce procédé permette la production de fer à partir d’hématite commerciale (Fe2O3) à une densité de courant de l’ordre de 1000 A.m-2 avec une efficacité faradique supérieure à 80%, une dégradation des performances est systématiquement constatée lors de l’électrolyse de minerais de fer. Les impuretés majoritaires de ces minerais sont les oxydes et hydroxydes d’aluminium et de silicium, des composés solubles dans la soude concentrée. Ces composés pourraient donc être à l’origine de la baisse de réactivité observée lors de l’alimentation du procédé par des minerais de fer. Ainsi afin de tenter d’améliorer les performances de l’électrolyse alcaline à partir de minerais, des traitements de lixiviation alcaline sur un minerai défini ont été effectués dans cette thèse. La réactivité des minerais avant et après traitement a été comparée par chronoampérométrie. Bien que suite à l’élimination de ses composés alumineux, le minerai traité ait vu son rendement faradique réhaussé à environ 80% pour une valeur avant pré-traitement de 65%, sa densité de courant est restée deux fois moins élevée que celle de l’hématite pour une même tension électrique appliquée. Des expériences d’ajout d’ions aluminates et d’ions silicates lors de l’électrolyse d’hématite pure n’ont de plus eu pratiquement aucun effet indésirable sur son électrolyse. Les diverses expériences conduites dans cette thèse laissent supposer que les impuretés traitées n’ont que peu d’influence sur la réactivité des minerais. Le procédé est en revanche très sensible à la granulométrie des particules de minerais. Par ailleurs de forts phénomènes d’agglomération, qui n’ont pas lieu avec les oxydes de fer purs, ont été constatés lors de mesure de granulométrie du minerai étudié. Ainsi les expériences réalisées laissent supposer qu’un autre phénomène, probablement lié à la granulométrie secondaire des minerais en milieu alcalin concentré, soit à l’origine de la baisse de réactivité observée lors de leur électrolyse. Parallèlement une analyse thermodynamique avancée a été menée afin de déterminer les meilleures conditions théoriques de pression, de température et de concentration en NaOH pour effectuer l’électrolyse de l’hématite. La solubilité des composés de la gangue a été représentée avec des équations de Pitzer, et de nouveaux paramètres ont été calculés pour les interactions Na-SiO3-Al(OH)4. Cette étude thermodynamique a permis la conception et le pré-dimensionnement d’une étape de traitement des minerais par lixiviation alcaline<br>An innovative ironmaking process by alkaline electrolysis of suspended iron oxides is being developed at ArcelorMittal Global R&D Maizières-lès-Metz. Were it to achieve industrial maturity, this process would permit a significant reduction of steelmaking CO2 emissions. Indeed, the use of carbon as a reducing agent in blast furnace would be replaced by electricity. Although this process enables iron production from commercial hematite (Fe2O3) at current density of 1000 A.m-2 with faradaic efficiency higher than 80%, these performances are systematically lower when using iron ore instead. The main impurities in these ores are aluminium and silicon oxides and hydroxides, these compounds are soluble in concentrated sodium hydroxide solutions. These compounds could be the source of the decrease in reactivity observed when feeding the process with iron ores. To raise the electrolysis performance with iron ores, alkaline leaching treatments were conducted on a defined iron ore. Reactivity of iron ores before and after treatment was compared by chronoamperometry. Although the elimination of aluminous compounds resulted in the ore gaining a faradaic yield increase to a value of 80%, compared with 65% before treatment, its current density remained twice as low as the one of hematite for a same applied voltage. Furthermore, complementary experiments of aluminate and silicate ions addition during pure hematite electrolysis did not have any deleterious effect on its electrolysis. Based on all the experiments undertaken in this PhD, it seems unlikely that siliceous and aluminous impurities hold an important effect on iron ore reactivity in alkaline electrolysis. The process is nonetheless very sensitive to iron ores granulometry. On this subject, strong agglomeration phenomena were witnessed when measuring iron ores granulometry but did not occur with pure iron oxides. Therefore, it would seem that other phenomena may be the main cause of reactivity loss, these phenomena may well be linked to secondary granulometry of iron ores in concentrated alkaline media. In parallel, an advanced thermodynamic analysis was carried out to describe the best theoretical conditions for pressure, temperature and NaOH concentration to realize hematite electrolysis. Gangue compounds solubility was represented with Pitzer equations, and new parameters were calculated for Na-SiO3-Al(OH)4 interactions. This thermodynamic study enabled the design and pre-sizing of a treatment step for iron ores by alkaline leaching
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Wulff, Philip. "Principles of hydrogen catalysis in the presence of oxygen by a [NiFe] hydrogenase from E. coli." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:9e434467-d50b-484a-a17e-ef3091636269.
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[NiFe] hydrogenases are metalloenzymes that act as highly efficient molecular electrocatalysts for the interconversion of protons and molecular hydrogen. Unlike any other known molecular electrocatalyst, the members of a subgroup of respiratory membrane-bound [NiFe] hydrogenases are able to maintain H<sub>2</sub> catalysis in the sustained presence of O<sub>2</sub>. This O<sub>2</sub>-tolerance depends on the ability to respond to oxidative inactivation by O<sub>2</sub> by exclusively forming rapidly reactivated active site states, thus implying a catalytic cycle in which O<sub>2</sub> acts as a competing substrate to H<sub>2</sub>. Using isotope ratio mass spectrometry it is proven that the O2-tolerant Escherichia coli Hydrogenase 1 responds to O<sub>2</sub> attack by acting as a four-electron oxidoreductase, catalysing the reaction 2 H<sub>2</sub> + O<sub>2</sub> → 2 H<sub>2</sub>O, equivalent to hydrogen combustion. Special features of the enzyme’s electron relay system enable delivery of the required electrons. A small fraction of the H<sub>2</sub>O produced arises from side reactions proceeding via reactive oxygen species, an unavoidable consequence of the presence of low-potential relay centres that release electrons from H<sub>2</sub> oxidation. While the ability to fully reduce O<sub>2</sub> to harmless H<sub>2</sub>O at the active site to generate the rapidly reactivated state Ni-B, determines if a hydrogenase is O<sub>2</sub>-tolerant, the ratio of oxidative inactivation to reductive reactivation rates determines how tolerant the enzyme is. It is shown by protein film electrochemistry that the (αβ)<sub>2</sub> dimeric assembly of Hyd-1 plays an important role in O<sub>2</sub>-tolerance by aiding reactivation of one catalytic unit through electron transfer from the other. The teamwork between two redundant partners implicates a new role for dimerisation and represents a new example of cooperativity in biology. Finally, the non-natural amino acid p-azido-L-phenylalanine was synthesised and incorporated into Hyd-1, testing the possibility of introducing labels at specific sites.
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Єрмоленко, Ірина Юріївна. "Наукові основи електрохімічної технології покриттів тернарними сплавами заліза з тугоплавкими металами". Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37459.
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Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.03 ‒ технічна електрохімія. ‒ Національний технічний університет "Харківський політехнічний інститут", Харків, 2018. Дисертацію присвячено розробці наукових основ електрохімічних технологій покриттів тернарними сплавами заліза та кобальту з молібденом і вольфрамом підвищеної функціональності. Експериментально доведено гіпотезу що-до конкурентного відновлення металів тріади заліза з тугоплавкими компонентами, обумовленого взаємним впливом термодинамічних, кристалохімічних характеристик сплавотвірних металів і кінетичних параметрів катодного процесу. Встановлено кінетичні закономірності співвідновлення в системах Fe³⁺ ‒ MoO₄²⁻ ‒ WO₄²⁻ ‒ Cit³⁻, Fe³⁺ ‒ Со²+ ‒ WO₄²⁻ (MoO₄²⁻) ‒ Cit³⁻ і обґрунтовано механізм осадження тернарних сплавів Fe-Mo-W, Fe-Co-W(Mo). Визначено вплив складу електролітів і режимів електролізу на елементний, фазовий склад і морфологію поверхні одержаних покриттів. Доведено можливість керування складом та морфологією багатокомпонентних покриттів на основі заліза і кобальту варіюванням складу електроліту (співвідношення концентрацій компонентів, співвідношення ліганду і комплексотвірників) і застосуванням гальваностатичного та імпульсного режимів електролізу з варіюванням густини струму 2,5 ‒ 6,5 А/дм², тривалості імпульсу / паузи 5 ‒ 10 / 5 ‒ 20 мс. Розроблено електроліти та режими осадження, що забезпечують осадження покриттів Fe-Co-W з вмістом Со 32 ‒ 47 ат. %, W 5 ‒ 13 ат. %, покриттів Fe-Mo-W з вмістом вольфраму 5 ‒ 11 ат. %, молібдену 26 ‒ 32 ат. % і покриттів Fe-Сo-Мо з діапазоном вмісту Сo 26 ‒ 48 ат. % і Мо 15 ‒ 31 ат. % та виходом за струмом до 58 – 82 %. Розроблено варіативні схеми електрохімічних процесів осадження покриттів сплавами Fe-Mo-W, Fe-Co-W(Mo) залежно від їх практичного застосування. За результатами експериментальних досліджень і тестувань функціональних властивостей покриттів в модельних середовищах і технологічних умовах визначено перспективні напрямки застосування одержаних матеріалів.<br>Dissertation for the Degree of the Doctor of Engineering Sciences in the Specialty of 05.17.03 – Technical Electrochemistry. – National Technical University "Kharkіv Polytechnic Institute", Kharkіv, 2018. This doctoral thesis is devoted to the development of scientific basics for electrochemical technologies used for the application of coatings consisting of ternary iron and cobalt alloys combined with molybdenum and tungsten of improved functionality. The hypothesis as for the competitive reduction of iron ternary metals with refractory components preconditioned by the mutual interaction of thermal-&-dynamic and crystal-&-chemical characteristics of the alloy-forming metals and the kinetic parameters of cathode process and it was proved experimentally. The kinetic regularities of the co-reduction in Fe³⁺ ‒ MoO₄²⁻ ‒ WO₄²⁻ ‒ Cit³⁻, Fe³⁺ ‒ Со²+ ‒ WO₄²⁻ (MoO₄²⁻) ‒ Cit³⁻ systems have been defined and the mechanism of deposition of ternary Fe-Mo-W, Fe-Co-W (Mo) alloys has been substantiated. The influence of composition of electrolytes and modes of electrolysis on elemental, phase composition and surface morphology of the obtained coatings has been deter-mined. The possibility of controlling the composition and morphology of multicomponent coatings on the basis of iron and cobalt by varying the composition of the electrolyte (the ratio of component concentrations, the ratio of ligand and complexing agent), and by used of galvanostatic and pulsed electrolysis regimes with a ranging of current density 2.5 ‒ 6.5 A/dm², and durations pulse/pause 5 ‒ 10 / 5 ‒ 20 ms, has been proved. The electrolytes and the deposition modes were developed that provide the deposition of Fe-Co-W coatings with the Co content of 32 to 47 аt. %, and W of 5 to 13 аt. %, and Fe-Mo-W coatings with the tungsten content of 5 to 11 at. %, and the molybdenum contents of 26 to 32 at. %, and the Fe-Сo-Мо coatings with the Co content ranging from 26 to 48 at. %, and Mo content ranging from 15 to 31 at. %, and the current efficiency ranging from 58 to 82 %. The variation schemes of electrochemical processes were suggested and these allow for the deposition of Fe-Mo-W and Fe-Co-W(Мо) coatings depending on their practical application. The perspective directions of the application of the obtained materials according to the results of experimental researches and tests of functional properties in model environments and technological conditions are determined.
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Єрмоленко, Ірина Юріївна. "Наукові основи електрохімічної технології покриттів тернарними сплавами заліза з тугоплавкими металами". Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37455.
Full textAbstract:
Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.03 ‒ технічна електрохімія. ‒ Національний технічний університет "Харківський політехнічний інститут", Харків, 2018. Дисертацію присвячено розробці наукових основ електрохімічних технологій покриттів тернарними сплавами заліза та кобальту з молібденом і вольфрамом підвищеної функціональності. Експериментально доведено гіпотезу що-до конкурентного відновлення металів тріади заліза з тугоплавкими компонентами, обумовленого взаємним впливом термодинамічних, кристалохімічних характеристик сплавотвірних металів і кінетичних параметрів катодного процесу. Встановлено кінетичні закономірності співвідновлення в системах Fe³⁺ ‒ MoO₄²⁻ ‒ WO₄²⁻ ‒ Cit³⁻, Fe³⁺ ‒ Со²+ ‒ WO₄²⁻ (MoO₄²⁻) ‒ Cit³⁻ і обґрунтовано механізм осадження тернарних сплавів Fe-Mo-W, Fe-Co-W(Mo). Визначено вплив складу електролітів і режимів електролізу на елементний, фазовий склад і морфологію поверхні одержаних покриттів. Доведено можливість керування складом та морфологією багатокомпонентних покриттів на основі заліза і кобальту варіюванням складу електроліту (співвідношення концентрацій компонентів, співвідношення ліганду і комплексотвірників) і застосуванням гальваностатичного та імпульсного режимів електролізу з варіюванням густини струму 2,5 ‒ 6,5 А/дм², тривалості імпульсу / паузи 5 ‒ 10 / 5 ‒ 20 мс. Розроблено електроліти та режими осадження, що забезпечують осадження покриттів Fe-Co-W з вмістом Со 32 ‒ 47 ат. %, W 5 ‒ 13 ат. %, покриттів Fe-Mo-W з вмістом вольфраму 5 ‒ 11 ат. %, молібдену 26 ‒ 32 ат. % і покриттів Fe-Сo-Мо з діапазоном вмісту Сo 26 ‒ 48 ат. % і Мо 15 ‒ 31 ат. % та виходом за струмом до 58 – 82 %. Розроблено варіативні схеми електрохімічних процесів осадження покриттів сплавами Fe-Mo-W, Fe-Co-W(Mo) залежно від їх практичного застосування. За результатами експериментальних досліджень і тестувань функціональних властивостей покриттів в модельних середовищах і технологічних умовах визначено перспективні напрямки застосування одержаних матеріалів.<br>Dissertation for the Degree of the Doctor of Engineering Sciences in the Specialty of 05.17.03 – Technical Electrochemistry. – National Technical University "Kharkіv Polytechnic Institute", Kharkіv, 2018. This doctoral thesis is devoted to the development of scientific basics for electrochemical technologies used for the application of coatings consisting of ternary iron and cobalt alloys combined with molybdenum and tungsten of improved functionality. The hypothesis as for the competitive reduction of iron ternary metals with refractory components preconditioned by the mutual interaction of thermal-&-dynamic and crystal-&-chemical characteristics of the alloy-forming metals and the kinetic parameters of cathode process and it was proved experimentally. The kinetic regularities of the co-reduction in Fe³⁺ ‒ MoO₄²⁻ ‒ WO₄²⁻ ‒ Cit³⁻, Fe³⁺ ‒ Со²+ ‒ WO₄²⁻ (MoO₄²⁻) ‒ Cit³⁻ systems have been defined and the mechanism of deposition of ternary Fe-Mo-W, Fe-Co-W (Mo) alloys has been substantiated. The influence of composition of electrolytes and modes of electrolysis on elemental, phase composition and surface morphology of the obtained coatings has been deter-mined. The possibility of controlling the composition and morphology of multicomponent coatings on the basis of iron and cobalt by varying the composition of the electrolyte (the ratio of component concentrations, the ratio of ligand and complexing agent), and by used of galvanostatic and pulsed electrolysis regimes with a ranging of current density 2.5 ‒ 6.5 A/dm², and durations pulse/pause 5 ‒ 10 / 5 ‒ 20 ms, has been proved. The electrolytes and the deposition modes were developed that provide the deposition of Fe-Co-W coatings with the Co content of 32 to 47 аt. %, and W of 5 to 13 аt. %, and Fe-Mo-W coatings with the tungsten content of 5 to 11 at. %, and the molybdenum contents of 26 to 32 at. %, and the Fe-Сo-Мо coatings with the Co content ranging from 26 to 48 at. %, and Mo content ranging from 15 to 31 at. %, and the current efficiency ranging from 58 to 82 %. The variation schemes of electrochemical processes were suggested and these allow for the deposition of Fe-Mo-W and Fe-Co-W(Мо) coatings depending on their practical application. The perspective directions of the application of the obtained materials according to the results of experimental researches and tests of functional properties in model environments and technological conditions are determined.
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Feynerol, Vincent. "Traitement de minerais de fer par lixiviation alcaline suivi de leur électrolyse en milieu alcalin." Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0163.
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Un procédé innovant de production de fer par électrolyse d’une suspension d’oxydes de fer en milieu alcalin concentré est développé au centre de recherche d’ArcelorMittal de Maizières-lès-Metz. Ce procédé s’il atteignait la maturité industrielle permettrait de réduire significativement les émissions de dioxyde de carbone associées à l’industrie sidérurgique, en remplaçant le carbone utilisé comme agent réducteur dans les hauts-fourneaux par de l’électricité. Bien que ce procédé permette la production de fer à partir d’hématite commerciale (Fe2O3) à une densité de courant de l’ordre de 1000 A.m-2 avec une efficacité faradique supérieure à 80%, une dégradation des performances est systématiquement constatée lors de l’électrolyse de minerais de fer. Les impuretés majoritaires de ces minerais sont les oxydes et hydroxydes d’aluminium et de silicium, des composés solubles dans la soude concentrée. Ces composés pourraient donc être à l’origine de la baisse de réactivité observée lors de l’alimentation du procédé par des minerais de fer. Ainsi afin de tenter d’améliorer les performances de l’électrolyse alcaline à partir de minerais, des traitements de lixiviation alcaline sur un minerai défini ont été effectués dans cette thèse. La réactivité des minerais avant et après traitement a été comparée par chronoampérométrie. Bien que suite à l’élimination de ses composés alumineux, le minerai traité ait vu son rendement faradique réhaussé à environ 80% pour une valeur avant pré-traitement de 65%, sa densité de courant est restée deux fois moins élevée que celle de l’hématite pour une même tension électrique appliquée. Des expériences d’ajout d’ions aluminates et d’ions silicates lors de l’électrolyse d’hématite pure n’ont de plus eu pratiquement aucun effet indésirable sur son électrolyse. Les diverses expériences conduites dans cette thèse laissent supposer que les impuretés traitées n’ont que peu d’influence sur la réactivité des minerais. Le procédé est en revanche très sensible à la granulométrie des particules de minerais. Par ailleurs de forts phénomènes d’agglomération, qui n’ont pas lieu avec les oxydes de fer purs, ont été constatés lors de mesure de granulométrie du minerai étudié. Ainsi les expériences réalisées laissent supposer qu’un autre phénomène, probablement lié à la granulométrie secondaire des minerais en milieu alcalin concentré, soit à l’origine de la baisse de réactivité observée lors de leur électrolyse. Parallèlement une analyse thermodynamique avancée a été menée afin de déterminer les meilleures conditions théoriques de pression, de température et de concentration en NaOH pour effectuer l’électrolyse de l’hématite. La solubilité des composés de la gangue a été représentée avec des équations de Pitzer, et de nouveaux paramètres ont été calculés pour les interactions Na-SiO3-Al(OH)4. Cette étude thermodynamique a permis la conception et le pré-dimensionnement d’une étape de traitement des minerais par lixiviation alcaline<br>An innovative ironmaking process by alkaline electrolysis of suspended iron oxides is being developed at ArcelorMittal Global R&D Maizières-lès-Metz. Were it to achieve industrial maturity, this process would permit a significant reduction of steelmaking CO2 emissions. Indeed, the use of carbon as a reducing agent in blast furnace would be replaced by electricity. Although this process enables iron production from commercial hematite (Fe2O3) at current density of 1000 A.m-2 with faradaic efficiency higher than 80%, these performances are systematically lower when using iron ore instead. The main impurities in these ores are aluminium and silicon oxides and hydroxides, these compounds are soluble in concentrated sodium hydroxide solutions. These compounds could be the source of the decrease in reactivity observed when feeding the process with iron ores. To raise the electrolysis performance with iron ores, alkaline leaching treatments were conducted on a defined iron ore. Reactivity of iron ores before and after treatment was compared by chronoamperometry. Although the elimination of aluminous compounds resulted in the ore gaining a faradaic yield increase to a value of 80%, compared with 65% before treatment, its current density remained twice as low as the one of hematite for a same applied voltage. Furthermore, complementary experiments of aluminate and silicate ions addition during pure hematite electrolysis did not have any deleterious effect on its electrolysis. Based on all the experiments undertaken in this PhD, it seems unlikely that siliceous and aluminous impurities hold an important effect on iron ore reactivity in alkaline electrolysis. The process is nonetheless very sensitive to iron ores granulometry. On this subject, strong agglomeration phenomena were witnessed when measuring iron ores granulometry but did not occur with pure iron oxides. Therefore, it would seem that other phenomena may be the main cause of reactivity loss, these phenomena may well be linked to secondary granulometry of iron ores in concentrated alkaline media. In parallel, an advanced thermodynamic analysis was carried out to describe the best theoretical conditions for pressure, temperature and NaOH concentration to realize hematite electrolysis. Gangue compounds solubility was represented with Pitzer equations, and new parameters were calculated for Na-SiO3-Al(OH)4 interactions. This thermodynamic study enabled the design and pre-sizing of a treatment step for iron ores by alkaline leaching
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Doyle, Olivia. "Electrodeposition of tin/cobalt/iron alloy systems from environmentally acceptable electrolytes." Thesis, Glasgow Caledonian University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404999.
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Anderson, Avril M. H. "Continuous codeposition of chromium-iron-nickel alloys from stable aqueous electrolytes." Thesis, Glasgow Caledonian University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.688232.
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Matinise, Nolubabalo. "Electrolytic determination of phthalates organic pollutants with n nostructured titanium and iron oxides sensors." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1177_1305892404.
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<p>This work reports the chemical synthesis, characterisation and electrochemical application of titanium dioxide (TiO2) and iron oxide (Fe2O3) nanoparticles in the determination of phthalates. The other part of this work involved electrochemical polymerization of aniline doped with titanium and iron oxide nanoparticles for the sensor platform in the electrolytic determination of phthalates. The TiO2 and Fe2O3 nanoparticles were prepared by sol gel and hydrothermal methods respectively. Particle sizes of 20 nm (TiO2) and 50 nm (Fe2O3) were estimated from transmission electron microscopy (TEM) The other technical methods used in this study for the characterization of the TiO2 and iron oxide Fe2O3 NPs were SEM, XRD and UV- visible spectroscopy. Cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties of the nanoparticles. These electrochemical studies of the nanoparticles were performed with a Fe2O3 or TiO2/nafion/glassy carbon membrane electrode in 0.1 M phosphate buffer (pH 7.0) and 0.1 M lithium perchlorate (pH 6.8) under an aerobic condition.</p>
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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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Wagner, Thomas. "High rate electrochemical dissolution of iron-based alloys in NaCl and NaNO 3 electrolytes." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10361099.
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Binding, Samantha Carys. "Synthesis and characterisation of permethylpentalene complexes and permethylpentalene derivatives." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:7855e90d-7ce9-42eb-b962-b68606ade746.
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This thesis expands the scope for using the permethylpentalene ligand and its precursors in the synthesis of organometallic complexes. <strong>Chapter one</strong> begins with a brief review of linked metallocenes, with which multimetallic compounds bridged by pentalene ligands have often been compared, followed by a comprehensive review of the routes used to make pentalenes and substituted pentalenes. Organometallic compounds of pentalenes are introduced, with a focus on bimetallic systems. <strong>Chapter two</strong> explores the diversification of substituents added to the permethylpentalene (Pn*) precursor WeissH<sub>4</sub>, to include ethyl and isopropyl groups. Low-symmetry mono-, di-, tri- and tetraalkylated products are formed, eight such organic molecules have been identified by NMR spectroscopy, and two characterised crystallographically. It has been demonstrated that subsequent hydrolysis and decarboxylation of two of these products produces low-symmetry alkylpentalene precursors. The chapter concludes with discussions on the selectivity exhibited in these reactions, and the assignment of stereochemistry. <strong>Chapter three</strong> describes the synthesis of the first homoleptic double metallocene complex of iron. Fe<sub>2</sub>Pn*<sub>2</sub> has been characterised by X ray diffraction, and cyclic voltammetry studies demonstrate four accessible oxidation states (-1, 0, +1, +2). Magnetic measurements in the solid and solution state reveal an unusual triplet configuration, and DFT calculations indicate the origin of a high magnetic moment likely resides in unquenched orbital angular momentum contributions from SOMOs which have metal d character. Fe<sub>2</sub>Pn*<sub>2</sub> is EPR silent at 5, 40, and 300 K both in solution and the solid state, suggesting a large zero-field splitting parameter. The reaction of the di-iron complex with carbon monoxide, ethylene and H2 is reported; the bimetallic CO adduct, Fe<sub>2</sub>(μ η<sup>5</sup>,η<sup>3</sup> Pn*)(μ η<sup>5</sup>,η<sup>1</sup> Pn*)(CO)<sub>2</sub>, has been crystallographically characterised, and contains a highly distorted allylic bonding motif, which to the author’s knowledge is believed to be unique among iron complexes. <strong>Chapter four</strong> discusses the interaction of the bidentate Pn* ligand in anti bimetallic fused metallocenes. A new ligand exchange route has been developed to access the complexes (MCp)<sub>2</sub>Pn* (M = Co, Ni), and the isostructural complexes (MCp*)<sub>2</sub>Pn* have been made for M = Fe, Co, Ni by salt metathesis reactions. All five complexes have been characterised by single crystal X-ray crystallography, and have diamagnetic ground states in solution in common with their Pn bridged analogues. Variable temperature NMR studies reveal a spin-equilibrium between S = 0 and S = 1 in the dinickel complexes. DFT calculations reproduce the spin states found, and suggest the distortion towards η<sup>3</sup> coordination observed on crossing from Fe, to Co, to Ni, results from population of orbitals with M―bridgehead antibonding character. The electronic structures show it is important to draw comparisons between isoelectronic linked metallocenes. Electrochemical studies on the diiron, dicobalt, and (NiCp)<sub>2</sub>Pn* complexes reveal at least three redox events for each. <strong>Chapter five</strong> documents the successful synthesis and characterisation of monometallic complexes of iron and manganese with Pn*H ligands. The isostructural complexes Fe(Pn*H)<sub>2</sub> and Mn(Pn*H)<sub>2</sub> can have been characterised crystallographically, and are potential precursors for accessing heterometallic, and multimetallic complexes. Mn(Pn*H)<sub>2</sub> is a rare example of a manganese sandwich compound and magnetic studies on a single isomer in the solution and solid states suggest it adopts intermediate spin states of S = 2 in solution, and S = 3/2 in the solid state. <strong>Chapter six</strong> gives experimental details for all syntheses and studies described in the preceding chapters. <strong>Chapter seven</strong> provides characterising data for all new compounds. Fitting data for VT NMR and SQUID studies are provided in the <strong>appendix</strong> at the end of this thesis. Crystallographic data in the form of .cif files, DFT output files, and raw SQUID data, can be found in the <strong>electronic appendix</strong>.
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Каракуркчі, Ганна Володимирівна. "Електрохімічне формування функціональних покриттів сплавами заліза з молібденом і вольфрамом". Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21865.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.17.03 – технічна електрохімія. – Національний технічний університет “Харківський політехнічний інститут”, Харків, 2015 р. Дисертацію присвячено розробці технології електрохімічного формування функціональних покриттів сплавами заліза з молібденом і вольфрамом із цитратних електролітів для одержання матеріалів з високою корозійною стійкістю, фізико-механічними та трибологічними характеристиками. На підставі аналізу кінетичних закономірностей встановлено механізм електрохімічного одержання сплавів Fe-Mo і Fe-Mo-W, за яким співосадження заліза з молібденом і вольфрамом із цитратного електроліту в інтервалі pH 3,0–4,0 відбувається за двома маршрутами: перший – стадійне відновлення металів із гетероядерних комплексів складу [FeHCitMO₄]⁻, (М = Mo, W), розряд яких супроводжується хімічною реакцією вивільнення ліганду, а другий – стадійне відновлення феруму (ІІІ) із цитратних електролітів переважно з адсорбованих комплексів складу [FeHCit]⁺, й частково – з FeOH²⁺, та супроводжується хімічною стадією вивільнення ліганду. Експериментальні дослідження функціональних властивостей електролітичних сплавів довели, що покриття Fe-Mo і Fe-Mo-W володіють підвищеною корозійною стійкістю у кислому середовищі, що зумовлене кислотним характером оксидів тугоплавких компонентів, у нейтральному – опором пітинговій корозії, що загалом перевищує хімічний опір сталі та чавуна. Запропоновані електролітичні сплави переважають за мікротвердістю основу зі сталі у 2–3 рази, а чавуну – у 4–5 рази, причому вміст вольфраму забезпечує зростання механічних та триботехнічних характеристик. Мікротвердість, антифрикційні властивості та зносостійкість електролітичних сплавів Fe-Mo і Fe-Mo-W зростають за рахунок утворення аморфної структури. Запропоновано технологічну схему електрохімічного формування функціональних покриттів сплавами заліза з молібденом і вольфрамом та розроблено технологічні інструкції для процесів їх осадження.<br>Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.17.03 – Technical Electrochemistry. – National Technical University “Kharkiv Politechnical Institute”, 2015. The thesis is devoted to the development of technology for iron alloys electrochemical functional
coatings with molybdenum and tungsten electrodeposition from citrate electrolyte to produce materials with high corrosion resistance, physical, mechanical and tribological properties. On the basis of kinetic regularities the mechanism of Fe-Mo, Fe-Mo-W alloys’ formation was established as co-precipitation of iron with molybdenum and tungsten in the range pH 3,0–4,0 happening on two routes, one-alloying metals reduction from heteronuclear complexes [FeHCitMO₄]⁻ is accompanied by chemical reaction of ligand releasing, and the second-reduction of iron (III) from the adsorbed complexes [FeHCit]⁺ and in part – from FeOH²⁺ accompanied by the chemical stage of ligand release. Experimental study of the electrolytic alloys functional properties have shown the high corrosion resistance of FeMo and Fe-Mo-W coatings in acidic and neutral media stimulated by acidic nature of refractory oxide components which exceeds the resistance of steel and cast iron. Proposed electrolytic alloys dominated by microhardness steel substrates in 2–3 times, and cast iron – in 4–5 times, the increasing tungsten content provides increasing in physical, mechanical and tribological properties of electrolytic alloys due to the formation of amorphous structure. A technological scheme for electrochemical synthesis of iron alloys functional coatings with molybdenum and tungsten was designed and technological instructions were prepared for implementation.
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Ferreira, Nuno Miguel Freitas. "Materials and concepts for CO2 lean ironmaking by pyroelectrolysis." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14004.
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Doutoramento em Engenharia Física<br>The main purpose of this PhD thesis was to provide convincing demonstration
for a breakthrough concept of pyroelectrolysis at laboratory scale. One
attempted to identify fundamental objections and/or the most critical
constraints, to propose workable concepts for the overall process and for
feasible electrodes, and to establish the main requirements on a clearer basis.
The main effort was dedicated to studying suitable anode materials to be
developed for large scale industrial units with molten silicate electrolyte. This
concept relies on consumable anodes based on iron oxides, and a liquid Fe
cathode, separated from the refractory materials by a freeze lining (solid)
layer. In addition, one assessed an alternative concept of pyroelectrolysis with
electron blocking membranes, and developed a prototype at small laboratory
scale.
The main composition of the molten electrolyte was based on a magnesium
aluminosilicate composition, with minimum liquidus temperature, and with
different additions of iron oxide. One studied the dynamics of devitrification of
these melts, crystallization of iron oxides or other phases, and Fe2+/Fe3+ redox
changes under laser zone melting, at different pulling rates. These studies
were intended to provide guidelines for dissolution of raw materials (iron
oxides) in the molten electrolyte, to assess compatibility with magnetite based
consumable anodes, and to account for thermal gradients or insufficient
thermal management in large scale cells.
Several laboratory scale prototype cells were used to demonstrate the concept
of pyroelectrolysis with electron blocking, and to identify the most critical
issues and challenges. Operation with and without electron blocking provided
useful information on transport properties of the molten electrolyte (i.e., ionic
and electronic conductivities), their expected dependence on anodic and
cathodic overpotentials, limitations in faradaic efficiency, and onset of side
electrochemical reactions.
The concept of consumable anodes was based on magnetite and derived
spinel compositions, for their expected redox stability at high temperatures,
even under oxidising conditions. Spinel compositions were designed for
prospective gains in refractoriness and redox stability in wider ranges of
conditions (T, pO2 and anodic overpotentials), without excessive penalty for
electrical conductivity, thermomechanical stability or other requirements.
Composition changes were also mainly based on components of the molten
aluminosilicate melt, to avoid undue contamination and to minimize the
dissolution rate of consumable anodes. Additional changes in composition
were intended for prospective pyroelectrolysis of Fe alloys, with additions of
different elements (Cr, Mn, Ni, Ti).<br>Esta tese de doutoramento pretendeu demonstrar o conceito de piroeletrólise
de ferro à escala laboratorial. Visou-se a deteção de objeções fundamentais
e/ou restrições críticas, de modo a propor conceitos exequíveis para o método
global e para elétrodos adequados, e identificar mais claramente os principais
requisitos. O principal esforço foi dedicado ao estudo de materiais de ânodo
adequados para o desenvolvimento de unidades industriais de larga escala,
com eletrólito fundido à base de silicatos. O conceito compreende ânodos
consumíveis à base de óxidos de ferro e um elétrodo de Fe fundido, com uma
camada intermédia de Fe sólido entre o metal fundido e os refratários.
Adicionalmente, foi testado um conceito alternativo de piroeletrólise com
membrana bloqueadora eletrónica, e foram desenvolvidos protótipos com
base neste conceito.
O eletrólito fundido baseou-se numa composição de aluminosilicato de
magnésio com um mínimo de temperatura liquidus, com diferentes teores de
óxido de ferro. Foram realizados estudos de desvitrificação, cristalização de
óxidos de ferro ou outras fases e alterações redox da razão Fe2+/Fe3+,
recorrendo à fusão de zona por laser, a diferentes velocidades. Estes estudos
visaram a obtenção de critérios fundamentais para a dissolução de matériasprimas
(óxidos de ferro) no eletrólito fundido, para avaliar a compatibilidade de
espinelas à base de magnetite com potenciais ânodos e para prever as
implicações de gradientes térmicos e/ou deficiente regulação térmica.
Foram preparados e testados diversos protótipos laboratoriais, para
demonstrar o conceito de piroeletrólise com bloqueamento eletrónico e para
identificar as questões mais críticas e desafios deste conceito. O
comportamento destas células em condições de operação com e sem
bloqueamento eletrónico originou informações muito pertinentes sobre as
propriedades de transporte do eletrólito fundido (i.e., condutividades iónica e
eletrónica), a sua variação sob polarização anódica e catódica, as limitações
de eficiência faradaica e a ocorrência de reações eletroquímicas parasitas ou
secundárias.
O conceito de ânodos consumíveis baseou-se em espinelas com
composições derivadas da magnetite, em virtude da esperada estabilidade
redox a altas temperaturas, mesmo em condições oxidantes. A composição
destas espinelas foi ajustada para melhorar a sua refrataridade e a
estabilidade em condições redox mais alargadas (T, pO2 e sobretensão
anódica), sem excessivo prejuízo para a condutividade elétrica, estabilidade
termomecânica e outros requisitos. As alterações de composição dos
materiais de ânodo consumíveis também foram determinadas pelos
constituintes do eletrólito fundido, de modo a prevenir contaminações
inaceitáveis e para minimizar a velocidade de dissolução dos ânodos
consumíveis. Outras alterações de composição tiveram o propósito de incluir
componentes de aços ou ligas de ferro (Cr, Mn, Ni, Ti).
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Chen, Chih-Yao. "A study on positive electrode materials for sodium secondary batteries utilizing ionic liquids as electrolytes." Kyoto University, 2014. http://hdl.handle.net/2433/192207.
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Lenoble, Marie-Anne. "Dépot électrolytique de CoFeCu, matériau magnétique doux de forte induction pour tetes magnétiques." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0156.
Full textAbstract:
L'alliage cofecu a ete choisi pour son aptitude a repondre aux criteres que doit remplir tout nouveau materiau magnetique doux des tetes magnetiques. Une etude electrochimique des phenomenes de depot, a permis de preciser les parametres operatoires qui influent sur la composition de l'alliage. Des depots sont d'abord realises sur de grandes surfaces pour les caracterisations magnetiques et structurales: un lien est etabli entre la composition donnant les proprietes optimales et la structure de l'alliage. Les depots dans des caissons de taille micronique pour les tetes magnetiques couches minces sont ensuite etudies pour optimiser l'obtention de la piece polaire superieure. Le depot est enfin realise sur de vraies tetes qui sont ensuite testees. Les resultats obtenus sont encourageants car l'overwrite et le wiggle sont bien ameliores. La tenue en frequence pourrait etre amelioree en appliquant un champ magnetique plus eleve pendant le depot. Des ajouts de molybdene dans l'alliage ont conduit a de meilleures proprietes magnetiques laissant esperer une reponse encore meilleure de la tete
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Nabeel, Muhammad. "A study of micro-particles in the dust and melt at different stages of iron and steelmaking." Doctoral thesis, KTH, Tillämpad processmetallurgi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-196805.
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The dust particles generated due to mechanical wear of iron ore pellets and clusters formed in molten stainless steel alloyed with rare earth metals (REM) are considered in this study. Firstly, the influence of the characteristics of iron ore pellets, applied load on a pellet bed and partial reduction of the pellets on the size distribution of the generated dust was investigated. Secondly, REM clusters are investigated to evaluate the size distribution of the clusters. Also, an extreme value distribution (EVD) analysis has been applied for the observed REM clusters. The large sized pellets showed 10-20% higher wear rate than small sized pellets during wear in a planetary mill. Moreover, an increase of ~67% was observed in the friction and dust generation in the pellet bed as the applied load increased from 1 to 3 kg. Also, it was observed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. The mechanical wear experiments of pellets reduced at 500 °C (P500) and 850 °C (P850) showed that P500 pellets exhibit ~16-35% higher wear rate than unreduced pellets. For the P850 pellets, the wear is inhibited by formation of a metallic layer at the outer surface of the pellets. The mechanism of dust generation has been explained using the obtained results. A reliable cluster size distribution of REM clusters was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM clusters. The results show that the growth of clusters is governed by different types of collisions depending on the size of the clusters. For EVD analysis three different size parameters were considered. Moreover, using the maximum length of clusters results in a better correlation of EVD regression lines compared to other size parameters. Moreover, a comparison of predicted and observed maximum lengths of clusters showed that further work is required for the application of EVD analyses for REM clusters.<br>Studien fokuserar på två olika typer av mikropartiklar som är valda från olika delar av järn- och ståltillverkningsprocessen. Dessa partiklar är dels stoft som genereras på grund av mekanisk nötning av partiklar och dels klusters som bildas i flytande rostfria stål legerade med sällsynta jordartsmetaller (REM). Inledningsvis så undersöktes inverkan av tre faktorer på storleksfördelningen hos stoft som bildas vid hantering av järnoxidpellets. De undersökta faktorerna inkluderade karakteristiken hos järnoxidpellets, det applicerade trycket på pelletsbädden och den partiella reduktionen av järnoxidpellets. Därefter så utfördes tredimensionella undersökningar av REM kluster som extraherats med hjälp av elektrolytisk extraction för att bestämma storleksfördelningen hos klustren. Dessutom så utfördes en extremvärdesdistribution (EVD) studie för de studerade klustren. En planetkvarn användes för att undersöka inverkan of karakeristiken hos pellets på stoftbildningen. Resultaten visade att storleken på pellets kan påverka nötningshastigheten under dessa försöksförhållanden. Pellets som hade en större storlek (13.5< Deq <15.0 mm) uppvisade en 10 till 20% högre nötningshastighet i jämförelse med mindre pellets (9.5< Deq <12.5 mm). Baserat på analyserna av stoftet som genererades under nötningsexperimenten så konstaterades att nötningsmekanismerna för dessa pellets var abrasions- och kollisionsnötning. En pelletsbädd skapades för att möjliggöra studier av inverkan av ett applicerat tryck på stoftbildningen och friktionskrafterna i en pelletsbädd. Ett varierat tryck på mellan 1 till 3 kg applicerades på pelletsbädden. Resultaten visade att en ökning på ~67% av friktionskraften och stoftbildningen ägde rum när det applicerade trycket ökades från 1 till 3kg. Dessutom så visade resultaten att en högre friktionskraft i pelletsbädden kan resultera in en ökad mängd luftburna partiklar. Den mekaniska nötningen av pellets som reducerats vid 500 °C (P500) och 850 °C (P850) studerades också genom användande av en planetkvarn. Resultaten visade att P500 pellets uppvisade en ~ 16 till 35% högre nötningshastighet i jämförelse med oreducerade referenspellets. Resultaten för P850 pellets visade att den mekaniska nötningen motverkades genom bildningen av ett metalliskt skikt på den yttre delen av pelletsen. Resultaten visade också att stoftet som bildats pga mekanisk nötning av reducerade pellets innehöll 3 till 6 gånger mer grova partiklar (>20µm) i jämförelse med stoft som bildats från oreducerade pellets. Slutligen så diskuterades hur dessa resultat kan relateras till industriella förhållanden med avseende på mekanismerna som är involverade i den mekaniska nötningen av pellets samt med avseende på relationen mellan hastigheten av de utgående gaserna och storlken och morfologin hos stoftpartiklarna. Klusters innehållande REM-oxider som extraherats från en 253MA rostfri stålsort undersöktes med användande av en tredimensionell teknik. En trovärdig storleksfördelning av klusters (CSD) erhölls genom att förbättra undersökningsmetoden och denna användes för att studera bildningen och tillväxten av REM oxider. Dessutom så användes cirkularitetsfaktorn hos klusters för att dela in klustren i två olika grupper, vilka bildas och tillväxer enligt olika mekanismer. Resultaten visade också att tillväxten av klusters gynnas av olika typer av kollisioner som beror av av storleken på klusters. För REM-klusters så drogs slutsatsen att turbulenta kollisioner är den huvudsakliga mekanismen som påverkar tillväxten. Avhandlingen behandlar även problemet om hur det är möjligt att hantera synfält där det inte förekommer kluster vid en extremvärdesdistribution (EVD) analys. Tre olika parametrar undersöktes i EVD analysen. Resultaten visar att om den maximala längden på kluster (LC) används i analysen så erhålls den bästa korrelationen gällande regressionslinjen för en EVD analys. Specifikt så var R2 värdet upp till 0.9876 i jämförelse med de andra storleksparametrarna som har värden i intervallet 0.9656 – 0.9774. Slutligen så visar resultaten från en jämförelse mellan beräknade och observerade maximala klusterlängder att EVD analyser för studier av REM kluster behöver undersökas ytterligare i framtiden.<br><p>QC 20161128</p>
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Maihatchi, Ahamed Abdoulaye. "Valorisation de résidus miniers riches en fer : Conception et développement d’un procédé de production de fer électrolytique à partir de matrices complexes." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0028.
Full textAbstract:
L’augmentation de la démographie mondiale (de 2,5 milliards en 1950 à 10 milliards d’habitants en 2050 selon l’Organisation des Nations Unies) entraine une augmentation des besoins en métaux. Ces métaux proviennent des mines, mais leur production à partir des minerais engendre d’énormes quantités de résidus. Ces derniers occupent de grands espaces de stockage et contiennent encore des métaux qui peuvent être extraits. La valorisation de ces résidus permettrait non seulement de réduire leurs volumes et leurs empreintes écologiques, mais aussi et surtout de produire des métaux à forte valeur ajoutée pour répondre aux besoins des nouvelles technologies. Deux types de résidus riches en fer ont été étudiés dans ce travail afin d’extraire le fer et le zinc qu’ils contiennent par électrodéposition : les boues rouges et la jarosite. Dans le premier cas, il s’agit des résidus provenant de la production de l’alumine à partir du minerai de bauxite par le procédé Bayer (procédé alcalin). Le deuxième type de résidu, la jarosite, provient de la production du zinc par le procédé « jarosite » en milieu acide. Pour ce faire, deux approches expérimentales ont été mises en place. Une électrodéposition directe dans le cas de boues rouges : les échantillons sont directement mis en suspension dans une solution de NaOH 12,5 mol/L et le fer (sous forme d’hématite et/ou de goethite) est électrodéposé sur une cathode en graphite à une température de 110°C. Pour le cas de la jarosite, une démarche différente a été mise en place : (i) une lixiviation de la jarosite en milieu acide sulfurique, (ii) une lixiviation de blende pour réduire le fer ferrique en fer ferreux et enrichir le bain en zinc, (iii) une cémentation du cuivre par une poudre de zinc et enfin (iv) une étape d’électrodéposition d’alliage fer-zinc. Dans les deux cas de résidus, plusieurs paramètres opératoires ont été testés afin d’optimiser les rendements de lixiviation, de cémentation, la qualité des dépôts et les rendements faradiques. En ce qui concerne les boues rouges, les meilleurs rendements faradiques (72%) ont été obtenus pour un ratio solide/liquide de 1/3 (g/mL), une concentration en NaOH de 12,5 mol/L, une densité de courant de 41 A/m² et une température de 110°C. Les dépôts du fer électrolytique, analysés par ICP-AES, DRX, MEB/EDX, présentent une pureté supérieure à 97% massique en fer. Pour la jarosite, les meilleurs rendements de lixiviation (en zinc et en fer étaient de 73% et 70% respectivement) ont été obtenus pour une concentration d’acide sulfurique égale à 1,5 M, un rapport solide/liquide 1/10 (g/mL) et une température de 80°C pendant 7 heures. Les essais d’électrodéposition ont permis de produire des alliages zinc –fer à différentes teneurs en fer. Les rendements faradiques obtenus dans les conditions optimales (densité de courant de 800 A/m² et une température de 20°C) étaient de l’ordre de 89%. Les résultats obtenus dans cette étude confirment la faisabilité technique d’électrodéposition du fer et d’alliage fer-zinc à partir des matrices complexe. Cela ouvre une nouvelle alternative à la valorisation des résidus miniers par la technique d’électrodéposition des métaux<br>The increase in world population (from 2.5 billion in 1950 to 10 billion in 2050 according to the United Nations) is leading to an increase in the need for metals. These metals come from mines, but their production from ores generates huge quantities of tailings. These tailings occupy large storage areas and very often contain metals that can be extracted. The recovery of these metals would not only make it possible to reduce their volume and ecological footprint, but also and above all to produce metals with high added value to meet the needs of new technologies. Two types of iron-rich residues were studied in this work in order to extract iron and zinc by electroplating: red mud and jarosite. In the first case, these are residues from the production of alumina from bauxite ore by the Bayer process (alkaline process). The second type of residues, jarosite, comes from the production of zinc by the "jarosite" process. Two experimental approaches have been set up for this purpose. Direct electrodeposition in the case of red mud: the samples are directly suspended in a 12.5 mol/L NaOH solution and the iron (in the form of hematite and/or goethite) is electrodeposited on a graphite cathode at a temperature of 110°C. In the case of jarosite, a different approach has been used: (i) a leaching of the jarosite in a sulphuric acid medium, (ii) a blende leaching to reduce the ferric iron to ferrous iron and to enrich the bath in zinc, (iii) a cementation of the copper by a zinc powder and finally (iv) an iron-zinc alloy electrodeposition step. In both cases of residues, several operating parameters were tested in order to optimize leaching yield, electrodeposition, deposit quality and faradaic yield. For the red mud, the best faradaic yield (72%) were obtained for a solid/liquid ratio of 1/3 (g/mL), a NaOH concentration of 12.5 mol/L, a current density of 41 A/m² and a temperature of 110°C. The electrolytic iron deposits, analyzed by ICP-AES, DRX, SEM/EDX, have a purity of more than 97% iron by mass. For jarosite, the best leaching yield (for zinc and iron were 73% and 70% respectively) were obtained for a sulphuric acid concentration of 1.5 M, a solid/liquid ratio of 1/10 (g/mL) and a temperature of 80°C for 7 hours. Electrodeposition tests produced zinc-iron alloys with different iron contents. The faradaic yield obtained under optimal conditions (current density of 800 A/m² and a temperature of 20°C) was of the order of 89%. The results obtained in this study confirm the technical feasibility of iron and iron-zinc alloy electroplating from complex matrices. This opens up a new alternative to the valorisation of mining residues by the metal electrodeposition technique
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FLORIO, DANIEL Z. de. "Analise de eletrolitos de ZrO sub(2):Y sub(2) O sub(3) + B sub(2) O sub(3) e de eletrodos de La sub(0,8) Sr sub(0,2) Co sub (0,8) Fe sub (0,2) O sub (3-delta) por espectroscopia de impedancia." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11130.
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Cartwright, John Alexander. "Study of the leaching of polymetallic sulphide ores using ion selective membranes." Thesis, Queensland University of Technology, 1998.
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Tchoumou, Martin. "Hydrometallurgie du cuivre en milieu chlorure : attaques de minerais dosages polarographiques des solutions resultant de l'attaque et depot cathodique du cuivre." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13154.
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Etude dans le cadre de l'extraction de cu des minerais de type chalcopyrite. Lors de l'attaque des minerais de type chalcopyrite par des solutions de cu(ii) en milieu fortement chlorure, les metaux presents dans le minerai sous forme de sulfures passent en solution soit partiellement soit en totalite, et s elementaire precipite. Mise au point du dosage polarographique des ions cu, pb, zn et fe dissous. L'electrolyse de solutions a teneur elevee en cu(i) et contenant pb(ii), zn(ii) ou fe(ii) a mis en evidence un phenomene de codeposition de pb avec cu lorsqu'on opere a des densites de courant elevees, tandis que ni zn ni fe ne se codeposent avec cu
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Cheng, Ya-Wen, and 鄭雅文. "Electrolysis-Enhanced Nanosacle Iron Reactive Barrier of Trichloroethylene Solubilized by TX-100 from Aquifer." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/65002778077483695113.
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碩士<br>國立屏東科技大學<br>環境工程與科學系<br>94<br>Organic chlorinated solvents are widely used in manufacturing processes. They are not easy to be degraded or decomposed in the environment owing to their special physical, chemical and biological characterization. If those solvents are not proper handled or disposal, they may possibly leaked into soil and further pollute the aquifer. Among the remediation technology, permeable reactive barrier (PRB) packed with zero iron is non-destructive and safe. Furthermore the particle sizes of iron can be nanoized to increase the reaction rate that enhances the degradation rate of organic solvents from groundwater.
The objective of this study is to investigate the effects of nanosacle iron PRB on the trichloroethylene (TCE) degradation efficiency enhanced by surfactant solubilization and electrolysis. The experiments were divided into two stages. Experiments in the first stage were designed and performed in a lab-scale sand box to determine the optimal parameters such as potential, iron barrier site, iron amount) of electrolysis-enhanced nanosacle iron PRB (ENIPRB) degradation of TCE. The second stage was experiments of solutes′ transport through porous media in a bench-scale sand box. The results from preliminary study showed that the average particle size and BET specific surface area of lab synthesized nanosacle iron were 189.7 nm and 30.0 m2/g.
The iron component of particles was detected through X-ray powder diffraction (XRD) examination at 2θ=44.74°. The results from experiments of the first stage showed that TCE removal efficiency was only 54﹪by addition of 5 grams of nano iron (Fe) and enhanced by electrolysis to 96% As the potential gradient increased to 1 V/cm, removal efficiency of TCE in the outlet of sand box could reach to 96﹪after 14 hour of operation. TCE removal efficiency was enhanced by the potential gradient set at 2V/cm and reach to 100% after 8 hour of operation. TCE removal efficiency of the potential gradient set at 0.5V/cm was approximately the same as that of non- electrolysis. Although the TCE removal efficiency increased with higher potential gradient, some precipitates deposited on the iron surface and could block the pores of reactive barrier as potential gradient set at 2V/cm that was not suitable for a long-term operation. Furthermore, Surface normalized reaction rate constants (Ksa) increased with the iron amount that raised TCE removal efficiency. The site of iron barrier located behind anode was better for TCE removal.
The results from experiments of the second stage showed that breakthrough time of solutes was slightly slower than that of water flow owing to the influence of advection and dispersion. The recovery rate of TX-100 could reach to 92％.The concentration of TCE ranged from 250 mg/L to 270 mg/L in the absence of TX-100 while increased to 700 mg/L with addition of 0.07 grams of TX-100 that indicated the solubility and mobility of TCE was significantly enhanced by surfactant. The concentration of TCE at sampling point D located behind iron wall reduced from 320 mg/L to 180 mg/L with addition of 5 grams of iron while conductivity and concentration of chlorine and ferrous increased. After 20 hours of operation, the TCE concentration raised again due to the increase of pH that resulted in precipitation of iron hydroxide and formation of non-reactive sites on the surface of nanosacle iron. As the voltage was applied, TCE concentration reduced from 220 mg/L to 135 mg/L because H+ released from anode by water electrolysis could wash away the deposits on the surface of nanosacle iron to enhanced the reactivity of iron surface. The potential difference would accelerate the release of electrons from iron near anode that induced TCE reduction. From the results of the first and second addition of TX-100 into sand box through injection well showed the mobility of TCE was not significantly different. This study shows TX-100 combined with electrolysis-enhanced nanosacle iron reactive barrier can effectively degrade TCE in groundwater and this technique can be referred as an alternative for in-situ remediation of organic chlorinated solvents in aquifer.
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Chen, Shin-Shian, and 陳信憲. "Remediation of Tetrachloroethylene in Groundwater by Dispersed Bimetallic Palladium-Iron Reactive Barrier Enhanced by Electrolysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/01283469086661187722.
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博士<br>國立屏東科技大學<br>環境工程與科學系所<br>102<br>Chlorinated organic solvents are widely used in industry, mainly as solvents and raw materials in the manufacture of commodity chemicals. Most of chlorinated solvents such as tetrachloroethylene (PCE) belong to Dense Non-Aqueous Phase Liquids (DNAPLs), with the properties of low solubility in water, denser than water, low viscosity, low flammability, high evaporability, and stable chemical property. Many kinds of chlorinated solvents had been recognized as carcinogens and/or toxins to human being, and they are resistant to degrade in environment that causes great impacts to groundwater resources. For their toxicity and strong bioaccumulation potential, chlorinated solvents are regarded as the pollutants that must be prior treated in many countries.
The purpose of this study is to develop a bimetallic reactive barrier system for the remediation of groundwater contaminated by chlorinated solvents. Nanoscale palladized-iron (Pd/Fe) bimetallic particles and two kinds of dispersed Pd/Fe suspensions, using carboxymethyl cellulose (CMC) as dispersant, were synthesized and utilized to react with PCE to investigate their degradation capability. Batch tests were proceeded in a 1,000 mL reaction bottle. The results showed that the kobs increased with the amount of Pd/Fe addition. The kobs and kSA increased as the reaction temperature was raised from 20 to 40C. CMC enhanced the kSA values of Pd/Fe particles to PCE degradation about 4 times. The sandbox experiments were performed in a 130 x 10 x 20 cm (length x width x height) glass box. Two kinds of nanoscale dispersed Pd/Fe suspensions were added into the permeable reactive barrier individually to degradate the PCE in aquifer. The results showed that PCE degradation ability of the first-kind dispersed Pd/Fe suspension (CMC was added during the synthesis process of Pd/Fe particles) was better than the second one (CMC was added after Pd/Fe particles were synthesized). Besides, when the electrolysis was integrated with the permeable reactive barrier packed with Pd/Fe particles, the active period of Pd/Fe particles could be extended. No potential chlorinated byproducts including trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), cis-1,2-dichloroethylene (cis-1,2-DCE), tran-1,2-dichloroethylene (tran-1,2-DCE), and vinyl chloride (VC) were detected in the batch and sandbox experiments. Because of the high recovery rate of Cl- in the batch tests, PCE must be completely dechlorinated by Pd/Fe particles. The results of this study may provide a useful alternative method for the in-situ remediation of chlorinated solvents.
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O'Donovan-Zavada, Robert Anthony. "Hierarchical three-dimensional Fe-Ni hydroxide nanosheet arrays on carbon fiber electrodes for oxygen evolution reaction." Thesis, 2014. http://hdl.handle.net/2152/26199.
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As demands for alternative sources of energy increase over the coming decades, water electrolysis will play a larger role in meeting our needs. The oxygen evolution reaction (OER) component of water electrolysis suffers from slow kinetics. An efficient, inexpensive, alternative electrocatalyst is needed. We present here high-activity, low onset potential, stable catalyst materials for OER based on a hierarchical network architecture consisting of Fe and Ni coated on carbon fiber paper (CFP). Several compositions of Fe-Ni electrodes were grown on CFP using a hydrothermal method, which produced an interconnected nanosheet network morphology. The materials were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical performance of the catalyst was examined by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The best electrodes showed favorable activity (23 mA/cm², 60 mA/mg), onset potential (1.42 V vs. RHE), and cyclability.<br>text
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Chagonda, Trevor. "Solution density modelling for single and mixed base metal electrolytes at ionic level." Thesis, 2015. http://hdl.handle.net/10539/16726.
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Solution density modelling is important in hydrometallurgical processes as accurate predictions of single and mixed electrolytes can be used in the design of equipment and their sizing, heat transfer calculations and choosing of materials for construction.
This research project entails modeling of electrolyte solutions by extending the Laliberte and Cooper (compound level) model to ionic level where an electrolyte solution is modeled as a mixture of cations, anions and water molecules. This modeling predicts single and mixed electrolyte density as a function of electrolyte temperature in degrees Celsius; water, cation and anion apparent volumes in cubic centimeters; and their respective concentrations in the electrolyte as mass fractions.
The model was developed by fitting single electrolyte density data reported in literature using the least squares method in Microsoft Excel®. The following 26 single electrolyte solutions were used in the fitting exercise: Al2(SO4)3, BaCl2, CaCl2, CdSO4, CoCl2, CuSO4, FeCl3, FeSO4, HCl, HCN, HNO3, K2CO3, LiCl, MgSO4, MnCl2, Na2SO3, NaF, NaI, NaOH, (NH4)2SO4, NiCl2, SrCl2, ZnCl2, ZnBr2, (NH4)2C2O4 and KNO2. The above electrolytes attributed to the following ions: Al3+, Ba2+, Ca2+ Cd2+, Co2+, Cu2+, Fe3+, Fe2+, H+1, K+1, Li+1, Mg2+, Mn+2, Na+1, NH4+1, Ni2+, Sr+2, Zn2+, SO42-, Cl-1, CN-1, NO3-1, CO32-, OH-1, SO32-, Br-1, F-1, I-1, C2O4-2 and NO2-1. This translated to a combination of at least 216 single electrolyte solutions which could be feasibly modeled, and a solution with at most 10 anions for mixed electrolytes, which is comparable with practical hydrometallurgical solutions.
A database of volumetric parameters was generated comprising a total of 18 cations and 12 anions. The validation of the developed model was done by predicting densities for both single and mixed electrolytes not used in the fitting exercise. The average density error i.e. the difference between experimental and model density for the single electrolyte solutions was 22.62 kg m-3 with a standard deviation of 39.66 kg m-3. For the mixed electrolytes, the average density error was 12.34 kg m-3 with a standard deviation of 24.48 kg m-3. These calculated errors translated to a maximum percentage average error of less than 4% for single electrolyte solutions and maximum average percentage of less than 3% for mixed electrolyte solutions.
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TSAO, JING-YUAN, and 曹景源. "Composition Optimization and Characterization of IrO2 - Based Electrocatalysts for Water Electrolysis." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/86428753059718658024.
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Hong, Miao Zeng, and 洪妙蓁. "Study of efficiency of electrocatalytic generation regulated by electrolytes and anions of Dinitrosyl Iron Complexs (DNICs)." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/57178262467959235996.
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Tang, Jyun-Yan, and 湯俊彥. "Study on IrO2/RGO hybrid as an oxygen evolution electrocatalysts in the performance of water electrolysis." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/01106693970136393244.
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碩士<br>國立中央大學<br>能源工程研究所<br>103<br>Hydrogen is clean and environmentally friendly as a green fuel, and has been regarded as one of the most potential energy resources. Among
the methods of hydrogen production combined with the renewable energy, water electrolysis is the most promising solution, and the simplest method to obtain high-purity hydrogen.
First of all the study, graphene supported IrO2 catalyst (IrO2/RGO) is composite by hydrothermal method. XRD, TEM, EDS and Raman tests are conducted to synthesis catalyst characterization, which reveal that IrO2 nanoparticle is uniformly supported on RGO surface.
Secondly, by changing thin film forming parameters, e.g., catalyst loading, spin coating speed, and rotation of working electrode, attempts and performs to find out the connections between thin film process and electrochemical measurement like LSV, EIS, etc.
Experimental results show that with the more catalyst loading, the better electrolysis performs; and the loading of 70μL gives the best performance in water electrolysis. By increasing the spin coating rate, electrolysis get worse; and the spin coating of 250rpm yields the best performance. As to the rotation of working electrode, 2000rpm gives the best hydrogen production efficiency and the lowest concentration polarization.
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Sifelani, Justice Bhekizulu. "The effect of replacing electrolytic iron in a multi-micronutrient fortification mix with sodium iron(III) ethylenediaminetetraacetate (NaFeEDTA) on the sensory properties of porridge from maize meal." Diss., 2016. http://hdl.handle.net/2263/57287.
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In developing countries, iron deficiency (ID) and the related iron deficiency anaemia (IDA) affects about 50 % of children and woman and about 25 % of men. In total, an estimated two billion people is affected worldwide. In developing countries, a typical diet is based on cereals, legumes and vegetables and these contain many iron inhibitors like phytic acid and polyphenols. Iron fortification of maize meal, a staple food in South Africa is regarded as a cost effective, sustainable way to improve iron status in that country. The replacement of electrolytic iron with sodium iron (III) ethylenediaminetetraacetate (NaFeEDTA) (a more bioavailable source of iron) in the current multi-micronutrient fortificant premix added to maize meal as an iron fortificant compound has the potential to greatly enhance the efforts to improve the iron status of populations consuming high-phytate cereal-based diets. However, poor consumer acceptance, unacceptable taste and discolouration of iron fortified foods have been frequently listed as causes of unsuccessful iron fortification programmes. This study evaluated the effects of replacing electrolytic iron (35 mg iron/kg maize meal) in a multi-micronutrient fortificant premix with NaFeEDTA (at 15 and 30 mg iron/kg maize meal) added to special maize meal on the colour (L* a* b*) and sensory properties (appearance and flavour) of stiff porridges. The porridges were prepared using three different types of cooking vessels (stainless steel, cast iron and aluminium pots) and was evaluated fresh (within 30 minutes of preparation) and after 24 hour refrigerated storage (3 - 5 oC). The porridges were subjected to analytical sensory evaluation to test for difference or similarity and a consumer acceptance test (n = 80 consumers).
Electrolytic iron significantly reduced L* and a* colour values in fortified maize meal when compared to maize meal fortified with the multi-micronutrient mix excluding iron. Elemental iron powders (e.g. electrolytic iron) being black or dark grey powders may have caused slight darkening of cereal flours. The spot iron test showed a uniform distribution of iron in maize meal with NaFeEDTA 15 (fortified with 15 mg iron/kg maize meal), NaFeEDTA 30 (fortified at 30 mg iron/kg maize meal) and electrolytic iron as well commercially fortified maize meals.
Electrolytic iron or NaFeEDTA 15 and 30 maize meals resulted in stiff maize porridge prepared in aluminium, cast iron and stainless steel having lower L* values when compared to porridge prepared from maize meal fortified with the multi-micronutrient premix excluding iron. This could be attributed to interaction between polyphenols (ferulic and p-coumaric acid) found in maize meal and iron ions (Fe2+/Fe3+). This interaction has been suggested to induce structural changes and polymerisation in the polyphenols and thereby influencing their light absorption pattern and thus leading to darkening of maize porridges. Cast iron cookware showed significant differences (p < 0.05) between iron treated porridges and control porridge (fortified with premix excluding iron) in both appearance and flavour while stainless steel showed significant differences (p < 0.05) between iron treated porridges and control porridge only in flavour and aluminium cookware showed significant differences (p < 0.05) between iron treated porridges and control porridge only in appearance. These differences could be attributed to the differences in thermal conductivity and heat transfer of the materials of the different cooking vessels and possible leaching of iron ions (Fe3+/Fe2+) from cast iron and stainless steel cookware and aluminium (Al3+) ions from aluminium cookware at different concentrations and/or rates during the cooking process. Appearance changes are probably due to the interaction between ion irons and polyphenols while flavour changes could be attributed to possible lipid oxidation of linoleic acid, a major polyunsaturated fatty acid found in maize meal. Iron ions (Fe3+/Fe2+) promotes lipid oxidation of linoleic acid leading to the development of hexanal, a major off-flavour compound in iron fortified maize meal porridge.
Findings from this study indicate that a change from fortifying maize meal with electrolytic iron to NaFeEDTA will not lead to changes in appearance and flavour of maize porridge. However, an excess amount of NaFeEDTA (30 mg iron/kg maize meal) might lead to acceptability (taste) problems if porridge is prepared in cast iron cookware. Fortification of maize meal porridge with a more bioavailable source of iron (NaFeEDTA) may reduce the prevalence of iron deficiency in South Africa.<br>Dissertation (MSc)--University of Pretoria, 2016.<br>tm2016<br>Food Science<br>MSc<br>Unrestricted
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Wagner, Thomas [Verfasser]. "High rate electrochemical dissolution of iron based alloys in NaCl and NaNO3 electrolytes / vorgelegt von Thomas Wagner (geb. Haisch)." 2003. http://d-nb.info/966389646/34.
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