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1
Souza, NatÃlia Dantas Gomes de. "Obtaining magnetic nanobiocompÃsitos consisting of galactomannan, glycerol and nickel ferrite and zinc." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11766.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior<br>FundaÃÃo de Amparo à Pesquisa do Estado do CearÃ<br>Nos Ãltimos anos, um grande interesse na associaÃÃo de materiais magnÃticos e biolÃgicos tem sido relatado na literatura. A obtenÃÃo de novos compÃsitos constituÃdos de galactomanana (GM), nanopartÃculas magnÃticas (MNPs) de NiZn e glicerol (GL) foram produzidos em diferentes proporÃÃes com finalidade de potencializar as caracterÃsticas individuais de cada material para futuras aplicaÃÃes. Sendo assim, as propriedades estruturais, magnÃticas e dielÃtricas dos nanobiocompÃsitos foram investigadas por DifraÃÃo de Raios-X (DRX), Espectroscopia de AbsorÃÃo na RegiÃo de Infravermelho (FTIR), AnÃlise TÃrmica (TG), Calorimetria ExploratÃria Diferencial (DSC), Microscopia EletrÃnica de Varredura (MEV), Microscopia EletrÃnica de TransmissÃo (TEM), Medidas MagnÃticas e Medidas DielÃtricas. A estrutura de espinÃlio da ferrita de NiZn foi confirmada por DRX e TEM e a amostra GMGL apesar de ser um material amorfo apresentou em seus nanobiocompÃsitos picos caracteristicos da fase de NiZn. As bandas caracterÃsticas para as amostras foram confirmadas por FTIR. Estas por sua vez seguiram um perfil de degradaÃÃo de acordo com as quantidades de NiZn incorporados, confirmados nos termogramas de DSC. A caracterizaÃÃo por MEV foi importante para avaliaÃÃo da morfologia. Os resultados das medidas dielÃtricas apresentaram baixas perdas dielÃtricas e das medidas magnÃticas mostraram comportamento magnÃtico para todos os nanobiocompÃsitos. Portanto, os resultados da caracterizaÃÃo dos nanobiocompÃsitos foram satisfatÃrios para possÃveis aplicaÃÃes como biomaterias, dispositivos eletrÃnicos ou em Ãreas afins.<br>In recent years, a great interest in the association of magnetic and biological materials has been reported in the literature. New composite consisting of galactomannan (GM), magnetic nanoparticles (NPs) of NiZn and glycerol (GL) were produced in different proportions with the purpose of enhancing the individual characteristics of each material for future applications. Thus, the structural, magnetic and dielectric properties of nanobiocomposites were investigated by Absorption Spectroscopy in the Region of Infrared (FTIR), X-Ray Diffraction (XRD), Thermal Analysis (TG), Differential Scanning Calorimetry (DSC), Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Magnetic Measurements and Dielectric Measurements. The structure of spinel NiZn ferrite was confirmed by XRD and TEM. Sample GMGL despite being an amorphous material presented in their nanobiocomposites characteristic peaks of phase NiZn. The characteristic bands in the samples were confirmed by FTIR. These in turn followed a degradation profile in accordance with the amounts of NiZn incorporated, which was confirmed in the DSC thermograms. The characterization by SEM was important to assess the morphology. The results of dielectric measurements showed low dielectric loss and magnetic measurements showed magnetic behavior for all nanobiocomposites. Therefore, the results of the characterization of nanobiocomposites were satisfactory for potential applications as biomaterials, electronic devices or related areas.
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Channing, Amanda Chemical Sciences & Engineering Faculty of Engineering UNSW. "Inert anodes for aluminium electrowinning: nickel ferrite based cermets." Awarded by:University of New South Wales. Chemical Sciences & Engineering, 2007. http://handle.unsw.edu.au/1959.4/40686.
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Greenhouse gases including carbon dioxide are formed by the consumption of carbon anodes during aluminium production, making it a major contributor to global emissions. This consumption necessitates replacement of the anodes in electrolysis cells every 2-3 weeks. A solution to the environmental and economic problems posed may be found in an inert anode which facilitates direct decomposition of alumina to aluminium and oxygen. Finding a material which is stable in the aggressive high temperature electrolyte poses a major materials engineering challenge. In this study, apparatus was designed and constructed to allow cermets to be manufactured in the laboratory, and a method of establishing electrical contact developed. Additionally, apparatus was designed to perform high temperature conductivity measurements on the cermets. Nickel ferrite-nickel oxide-copper-silver cermets were prepared and conductivity measured. No significant change in the activation energy of the conduction process was observed for cermets with 40wt% excess NiO compared to those with no excess. No significant difference in conductivity was observed between the compositions at cell operating temperatures. Voltammetric techniques were used to identify anode processes. High anodic currents associated with oxidation of anode constituents were observed repeatedly, the magnitude of which could not simply explained by oxidation of the metal phase. This suggested the formation of other reduced species during sintering (confirmed by thermodynamic analysis). Gaseous oxidation products were confirmed at the anode at potentials expected for oxygen evolution, and the application of high potentials (>4V vs Al/A13+) was found to passivate the cermets. Voltammetry and chemical microanalysis (using scanning electron microscopy (SEM) with energy dispersive x-ray spectrometry (EDS)) showed that copper in the cermets was depleted at the anode surface, apparently by oxidation then dissolution into the electrolyte. The inclusion of silver powder into the cermets was not found to improve the corrosion resistance of the cermets, existing almost entirely as a discrete phase. Preliminary SEM and EDS results highlighted several areas for further investigation regarding the compounds formed during sintering and electrolysis and the anode corrosion mechanisms. Of particular interest were a copper nickel oxide formed during sintering and complex oxyfluorides containing anode and bath constituents, formed during electrolysis.
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Karakas, K. Z., R. Boncukcuoglu, I. H. Karakas, and M. T. Yılmaz. "The Effect of pH in Nickel Ferrite Nanoparticles Synthesis by Hydrothermal Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35022.
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In this study, NiFe2O4 nano particles was prepared with aqueous solutions of nickel nitrate and ferric
nitrate salts. An appropriate ratio of solutions nickel nitrate and ferric nitrate were dissolved in deionized water and poured into a crucible. Later, polyethylene glycol 600 (PEG 600) was added to this mixture.
Samples were adjusted to various pH values. In experiments, samples obtained by hydrothermal method
were heat treated at 700 oC for 8 h to enhance their crystallinity and remove the residual organic materials. The structural and morphological properties of NiFe2O4 nano particles were determined by X-ray powder diffraction (XRD) and Scanning Electron microscopy (SEM). Results showed that increasing calcination
temperature contributed to cyristallinity of NiFe2O4 nano particles. But also average particle size increased. As a result, average particle size was calculated by using Debye-Scherrer Formula as aproximately 30 nm. However, this results was confirmed with SEM analysis.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35022
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Karakas, Z. K., R. Boncukcuoglu, I. H. Karakas, and M. Ertugrul. "Investigation of the Effects of Reaction Temperature in NiFe2O4 Nanoparticles Synthesis by Hydrothermal Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35028.
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In this experimental study was investigated the effect of reaction temperature in NiFe2O4 nanoparticles synthesis with hydrothermal method. An appropriate ratio of solutions nickel nitrate and ferric nitrate were dissolved in deionized water and poured into a crucible. Later, polyethylene glycol 600 (PEG
600) was added to this mixture. Samples were adjusted to pH 11 values using NaOH solution. Accordingly,
experiments were made at 180, 200 and 250 oC, respectively. The other parameters, were fixed as reaction
time 24 h and pH value 11. The structural and morphological properties of NiFe2O4 nanoparticles were determined by X-ray powder diffraction (XRD) and Scanning Electron microscopy (SEM). Results showed
that increasing calcination temperature contributed to cyristallinity of NiFe2O4 nano particles. But also average particle size increased. As a result, average particle size was calculated by using Debye-Scherrer
Formula as approximately 30 nm. However, this results was confirmed with SEM and TEM analysis.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35028
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Jatkar, Kasturie. "Measuring magnetization in Nickel Ferrite samples using odd and even harmonics." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-411159.
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Okatan, Mahmut Baris. "Microstructure Development In Nickel Zinc Ferrites." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606924/index.pdf.
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Nickel zinc ferrites (NZF) have been considered as one of the basic components in high frequency electromagnetic applications especially in the field of telecommunications. In the present study, the aim was to produce high quality nickel zinc ferrite ceramics at low soaking temperatures. For this purpose, conventional ceramic manufacturing method based on mixed oxide precursors was followed using calcium fluoride, CaF2, as sintering additive.
During the sintering studies, it was noticed that both the microstructure and the electromagnetic properties of the NZF ceramics were modified to a great extent by CaF2. Therefore, material characterization studies involving microstructural, dielectric and magnetic properties were conducted with respect to CaF2 content of ceramics and soak duration.
The results showed that due to the presence of CaF2 in ceramics, significant improvements were achieved not only in kinetics of sintering but also in the parameters<br>DC electrical resistivity, dielectric constant and dielectric loss factor. For example, 1.0 wt% CaF2 added NZF ceramic produced in this study had a DC electrical resistivity of 1011 &<br>#61527<br>-cm which was 100,000 times bigger than the one attained in pure NZF ceramic. On the other hand, the dielectric constant exhibited a flat behavior up to 40 MHz with a value around 16. In addition, no resonance peak was observed in dielectric loss factor spectra, and the typical values of dielectric loss factor lied below 0.01. Besides the achievements mentioned, the magnetic properties such as relative magnetic loss factor and hysteresis parameters were also improved.
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Karakas, K. Z., R. Boncukcuoglu, I. H. Karakas, and M. T. Yılmaz. "The Effect of Calcination Temperature in NiFe2O4 Nanoparticles Synthesis with Microvawe Combustion Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35025.
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Magnetic ferrites are a group of technologically important magnetic materials. Synthesis of nanocrystalline spinel ferrite has been investigated intensively in recent years due to their potential applications in
high-density magnetic recording, microwave devices, and magnetic fluids In this study, NiFe2O4 nano particles were prepared with microvawe combustion methods. In experiments, samples obtained by microvawe
method were calcined at various temperatures. The structural and morphological properties of NiFe2O4
nano particles was determined by X-ray powder diffraction (XRD) and Scanning Electron microscopy
(SEM). Results showed that increasing calcination temperature contributed to cyristallinity of NiFe2O4
nanoparticles. But also average particle size increased. As a result, average particle size calculated by using Debye-Scherrer Formula as aproximately 30 nm. However, this results was confirmed with SEM
analysis.
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Neumann, James 1958. "THE INITIATION AND PROPAGATION OF HERTZIAN AND RADIAL CRACKS IN NICKEL-ZINC FERRITE." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/276523.
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This investigation was initiated by IBM to determine the types of cracks formed in hot-isostatic-pressed (HIP) Ni-Zn ferrite under impact and static loading conditions. A 1/8-inch tungsten carbide (WC) ball was used to apply the load in both cases. The impact loading condition was accomplished by dropping the WC ball from various heights between 40 and 200 cm. The static loading condition was accomplished by applying loads of 10 kg, 15 kg, and 30 kg on a Rockwell Hardness Tester. The response of HIP Ni-Zn ferrite to impact and static loading was elastic/plastic yielding permanent indentations. "Dimple" impressions, Hertzian-ring cracks, and radial cracks were formed upon applying increasing loads to the HIP Ni-Zn ferrite. As the grain size of the material was increased, both the Hertzian-ring and radial cracks were formed at lower loads compared to the as-received samples. The "dimple" impressions were not observed to follow this trend.
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Brachwitz, Kerstin. "Defekt-induzierte Leitungsmechanismen und magnetische Eigenschaften spinellartiger Ferrite." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-141251.
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Im Rahmen dieser Arbeit wurde der Einfluss von Defekten auf die Eigenschaften von Ferrit-Dünnfilmen untersucht. Die Dünnfilme wurden mit Hilfe von gepulster Laserabscheidung bei verschiedenen Züchtungsparametern hergestellt. Durch Variation der Substrattemperatur und des Sauerstoffpartialdrucks wurden Dünnfilme verschiedener kristalliner Qualität gezüchtet. Diese wurden hinsichtlich ihrer chemischen Komposition mit Hilfe von energie-dispersiver Röntgenspektroskopie und Röntgenphotoelektronenspektroskopie untersucht. Durch Korrelation der Ergebnisse mit Messungen zum zirkularen magnetischen Röntgendichroismus, konnte eine partielle Inversion der Spinellstruktur nachgewiesen werden. Der Grad der Inversion ist höher für geringe Abscheidetemperaturen. Für diese defektreichen Dünnfilme zeigen Röntgenbeugungsuntersuchungen eine geringere kristalline Ordnung der Dünnfilme. Die strukturellen Defekte haben einen maßgeblichen Einfluss auf die elektrischen und magnetischen Eigenschaften der Ferrit-Dünnfilme. So zeigen die Ferrit-Dünnfilme für geringe Züchtungstemperaturen eine erhöhte elektrische Leitfähigkeit, während Dünnfilme, die bei hohen Substrattemperaturen gezüchtet wurden, isolierend sind. Die Temperaturabhängigkeit der elektrischen Leitfähigkeit kann auf thermisch aktivierte Hopping-Leitung oder die Leitung zwischen Clustern, die in einer Matrix eingebettet sind, zurückgeführt werden.
Die magnetischen Eigenschaften von Zinkferrit-Dünnfilmen werden maßgeblich durch Defekte in der Spinellstruktur bestimmt, da es nominell in der normalen Spinellstruktur kristallisiert und daher antiferromagnetisch ist. Die partielle Inversion der Eisen- und Zinkionen führt zu Ferrimagnetismus in den Zinkferrit-Dünnfilmen, der mit Hilfe von SQUID-Messungen in dieser Arbeit eingehend untersucht wurde.
Durch Korrelation der Ergebnisse der verschiedenen Untersuchungsmethoden konnten Rückschlüsse auf die dominierenden Defekte in den Ferrit-Dünnfilmen geschlossen werden. So sind zum einen Defekte auf atomarer Skala, wie Antisite-Defekte und divalenten Fe-Ionen für die erhöhte elektrische Leitfähigkeit und die größere Magnetisierung der defektreichen Dünnfilme verantwortlich. Zum anderen können ausgedehnte Defekte, im Speziellen Cluster, die in einer amorphen Matrix eingebettet sind, nicht ausgeschlossen werden.
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Kenfack, Flaurance. "Complex oxides of the system Cu-Ni-Fe-O: synthesis parameters, phase formation and properties." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1105366432765-06401.
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This thesis describes the convenient routes and the preparation conditions (temperature, oxygen partial presssure) which lead to the formation of single phase materials within the quaternary system Cu-Ni-Fe-O. The investigated compositions are the solid solutions CuxNi1-xFe2O4, the ferrites occurring in the phase triangle Cu0.5Ni0.5Fe2O4 -Cu0.9Fe2.1O4 - Cu0.5Fe2.5O4 and some copper-nickel oxide solid solutions. Three synthesis routes have been used, namely (i) the preparation and the thermal decomposition of freeze-dried carboxylate precursors, (ii) the preparation and the oxidation of intermetallic phases and (iii) the preparation and the heat treatment in air of mixed oxide/metallic powders. The thermal decomposition of freeze-dried Cu-Ni-Fe formate has been found as a suitable method for preparing single spinel phases within the Cu-Ni-Fe-O system. In comparison with the conventional solid state reaction, the required temperature is much lower. Concerning the solid solution CuxNi1-xFe2O4 , a single phase spinel is formed at 1000¢XC for x &lt; 0.7; for CuO is identified as second phase. In this latter range the formation of a pure phase required an increase of the iron content in the mixture. The other single spinel phases in the phase triangle Cu0.5Ni0.5Fe2O4 - Cu0.9Fe2.1O4 - Cu0.5Fe2.5O4 have been synthesized under special synthesis p(O2)/T-conditions. For copper ferrites Cu1-xFe2+xO4 with x ? 0.1, 0.2, 0.33, 0.4 and 0.5, the change in the conductivity with the temperature is irreversible. The deviation from the linearity of the conductivity ?ã as a function of the temperature occurs due to the thermal history of these samples. The saturation magnetic moment (nB) at 5K, of some synthesized CuxNi1-xFe2O4 compounds has been determined. It has been found that nB increases with the nickel content in the ferrite sample.
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Bastien, Samuel. "Nanopoudres de ferrite de nickel produites par plasma inductif et analyse in situ de leur comportement thermochimique." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10973.
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Des nanoparticules de ferrite de nickel ont été produites par une technique de plasma induc-tif à jet de solution. En contrôlant le ratio Ni/(Ni+Fe) dans la solution de précurseurs, une grande gamme de nanoparticules monophasées de ferrite de nickel NixFe3-xO4-δ (0 ≤ x ≤ 1) peuvent être produites, ainsi que des nanoparticules multiphasées de NiFe2O4 + (Ni,Fe)O. Des nanoparticules avec deux types de morphologie peuvent être obtenues dépendant de l’endroit où elles sont recueillies dans le réacteur : des octaèdres tronqués facettés, ayant une taille moyenne de 30 nm, ou un petit agglomérat de forme aléatoire, ayant une taille caractéristique de ~3-5 nm. Pour les nanoparticules multiphasées, il est démontré que la phase (Ni,Fe)O se dépose de façon sélective sur les facettes {110} et {111} de la ferrite de nickel, tout en laissant les facettes {100} exposées. En utilisant la même procédure, il est également possible de produire des nanocubes de NiO. Ces résultats démontrent la flexibilité des réacteurs à plasma inductif pour la production de nanoparticules mono ou multiphasées organisées avec un grand rendement. Des analyses de DRX in situ sur ces nanoparticules montrent que la réduction avec H2 enlève l'excès d'oxygène de la maille spinelle, si présent initialement, suivi d'une réduction vers les alliages métalliques (Ni,Fe). Leur réoxydation subséquente avec CO2 mène à un renversement partiel du processus de réduction par H2. Les expériences in situ ont été analysées avec un modèle cristallin qui lie le paramètre de maille d'un spinelle à sa déviation de sa stœchiométrie en oxygène (δ).<br>Abstract : Nickel ferrite spinel nanoparticles were produced by the solution spray induction plasma technique. By controlling the Ni/(Ni+Fe) ratio in the precursor solution, a wide range of single-phased nickel ferrite NixFe3-xO4-δ (0 ≤ x ≤ 1) nanoparticles can be produced, along with multiphased NiFe2O4 + (Ni,Fe)O nanoparticles. Nanoparticles with two types of morphologies can be obtained depending on where they are collected in the reactor: facetted truncated octa-hedrons, with an average size of about 30 nm, or a small-sized random agglomerate, with a characteristic length of ~3-5 nm. For the multiphased nanoparticles, it is demonstrated that the (Ni,Fe)O phase selectively deposits on the {110} and {111} facets of nickel ferrite, while leaving its {100} facet exposed. Using the same procedure, it is also possible to produce nanocubes of NiO. These results show the flexibility of the induction plasma method for the production of organized single or multiphased nanoparticles with a high throughput. In situ XRD catalytic experiments on those nanoparticles show that reduction with H2 will cause the removal of excess oxygen from the spinel lattice, if present initially, followed by a reduction to metallic (Ni,Fe) alloys. Their subsequent reoxidation with CO2 leads to a partial reversal of the H2 reduction process. In situ experiments were enhanced by the development of a crystal-lographic model that links the lattice parameter of a spinel to its deviation from oxygen stoechiometry (δ).
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Karakas, Z. K., R. Boncukcuoglu, and I. H. Karakas. "The Effects of Fuel Type Above Magnetic Properties of the Nickel Ferrite Nanoparticles Synthesized with Microwave Method." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35275.
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The synthesis of nickel ferrite nanoparticles was used various fuel substances such as glycine, urea and citric acid. The mixture prepared in stoichiometric rates was put in to the kitchen type microwave oven. In the end of reaction time was obtained a brown-black solid. The obtained solid was characterized with X-Ray Powder Diffraction and Scanning Electron Microscopy. The results of this analysis showed that all of the obtained particles have got nano-size particle size distribution. To determine the magnetic properties of the nanoparticles were analyzed by using a vibrating sample magnetometer. Fuel type used in synthesis is quite effective on the magnetic properties of NiFe2O4 nanoparticles.
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13
Karakas, Z. K., R. Boncukcuoglu, and I. H. Karakas. "The Effects of Fuel Type Above Adsorbtive Properties of the Nickel Ferrite Nanoparticles synthesized with Microwave Method." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35271.
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In this study, we were able to develop a new and practical method for the synthesis of the NiFe2O4 nanoparticles. The synthesis of nickel ferrite nanoparticles was used various fuel substances such as glycine, urea and citric acid. The synthesis mixture prepared in stoichiometric rates was put in to the kitchen type microwave oven. In the end of reaction time was obtained a brown-black solid. The obtained solid was characterized with X-Ray Powder Diffraction and Scanning Electron Microscopy. The results of this analysis showed that all of the obtained particles has got nano-size particle size distribution. Later, the nanoparticles were analyzed by using a surface area analyzer and their adsorptive properties were investigated such as surface area and average pore size. We observed that the nanoparticles prepared with urea has the highest surface area. However, fuel type used in synthesis is quite effective on the surface properties of NiFe2O4 nanoparticles.
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Le, Guen Emmanuel. "Élaboration et réalisation de matériaux magnétodiélectriques pour la miniaturisation d'antennes en bande UHF." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S016.
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La miniaturisation des antennes s'accompagne d'une dégradation leurs performances (bande passante, gain, efficacité), surtout avec l'utilisation de substrats matériaux diélectriques. Pour relever le défi « intégration / performances », la conception de nouveaux matériaux tels que les ferrites magnétoélectriques constitue une alternative des plus prometteuses. Ce travail met en avant les principaux paramètres à l'élaboration de ferrite spinelle par coprécipitation. Un traitement thermique modéré a permis l'obtention de céramiques semi poreuses pour la montée en fréquence. En parallèle, l'anisotropie magnétocristalline, liée à la composition (rapport Nickel / Zinc, Cobalt, Fer 2+…) ; ainsi que l'anisotropie magnétoélastique lors de l'application d'une contrainte, étendent encore le domaine des faibles pertes des ferrites de Nickel-Zinc de 400 MHz à plus de 1 GHz. Ces matériaux ont ainsi pu équiper des antennes sur les fréquences du DVH-H (470 – 830 MHz) et répondent aux normes du DVB-H. De façon à profiter pleinement de la miniaturisation, nous avons proposé une antenne imprimée. Une bonne corrélation est trouvée entre les résultats de simulation et de mesure, ainsi que des relations adaptées aux antennes patch. Enfin dans le domaine émergent des communications On / Off bodies, nous avons développé des antennes flexibles sur un substrat de type PDMS. Pour assurer une bonne efficacité de l'antenne, celle-ci est encapsulée, ce qui évite une métallisation hasardeuse (fissures, manque d'adhérence)<br>Antenna miniaturization, especially with dielectric substrates, is accompanied by a radiation loss (bandwidth, gain, efficiency). To meet the challenge "integration / performance", the design of new materials such as magnetodielectrics ferrites is a promising alternative. To satisfy these requirements, this work highlights the main parameters of ferrite spinel development by coprecipitation. A moderate thermal treatment leads to semi porous ceramics. In parallel, the magnetocrystalline anisotropy, related to the composition (ratio Nickel / Zinc, Cobalt, Iron 2+ ...), and the magnetoelastic anisotropy with application of stress, extend the field of low-loss from 400 MHz to over 1 GHz, in the Nickel-Zinc ferrite. These materials were able to equip antennas on DVH-H frequencies (470-830 MHz). In order to take full advantage of miniaturization, we proposed a printed antenna. A good correlation between simulation results and measurement is obtained, together with relations adapted to patch antennas. Finally, in the emerging field of communications On / Off bodies, we have developed flexible antennas on PDMS substrate. To ensure good antenna efficiency, it is encapsulated, thereby avoiding a hazardous metallization (cracks, loss of adhesion)
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Santos, Cochiran Pereira dos. "Síntese e caracterização de NiFe2O4 e efeitos da dopagem na magnetização de saturação." Universidade Federal de Sergipe, 2011. http://ri.ufs.br:8080/xmlui/handle/123456789/3515.
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The ferrites are a wide class of ferrimagnetic materials with great technological importance and are studied extensively for many decades. Their remarkable magnetic characteristics make it an element often used in induction transformers by his high magnetic permeability, high values of saturation magnetization and low coercivity, resulting in smaller losses in their hysteresis loops. In this work were characterized pure nickel ferrite (NiFe2O4), a soft magnetic material where the magnetic properties depend on the nature of the ions, their charges and their distribution among the tetrahedral and octahedral sites. Heat treatment and sintering time were emphasized. In order to improve one of the most important parameters for such an application, the saturation magnetization, new samples were doped with zinc at various concentrations (Ni1-xZnxFe2O4). Two new series were prepared starting from the higher value of the previous series (Ni0,6Zn0,4Fe2O4) with two new doping, indium and gadolinium. Finally, the values of saturation magnetization and initial permeability could be compared with samples of commercial cores, showing the potential of the compound to be used as the core of magnetic induction.<br>As ferritas formam uma ampla classe de materiais ferrimagnéticos com grande importância tecnológica e têm sido estudadas exaustivamente ao longo de décadas. Suas notáveis características magnéticas as tornam um elemento frequentemente utilizado em transformadores de indução por sua alta permeabilidade magnética, altos valores de magnetização de saturação e baixa coercividade, resultando em perdas menores observadas em seus ciclos de histerese. Neste trabalho foram caracterizadas ferritas de níquel pura (NiFe2O4), um material magnético mole onde as propriedades magnéticas dependem da natureza dos íons, suas cargas e sua distribuição entre os sítios tetraédricos e octaédricos. Nessa fase o tratamento térmico e o tempo de sinterização tiveram ênfase. A fim de melhorar um dos parâmetros mais importantes para tal aplicação, a magnetização de saturação, foram feitas novas amostras dopadas com zinco em várias concentrações (Ni1-xZnxFe2O4). Duas novas séries foram preparadas partindo-se do maior valor da série anterior (Ni0,6Zn0,4Fe2O4) com dois novos dopantes, o índio e o gadolínio. Finalmente, os valores de magnetização de saturação e permeabilidade inicial puderam ser comparados com amostras de núcleos comerciais, evidenciando a potencialidade do composto em ser utilizado como núcleo de indução magnética.
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Lebourgeois, Richard. "Elaboration et caractérisations de ferrite spinelle de nickel-zinc sous forme de céramique et de monocristaux pour applications aux hyperfréquences." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0097.
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Afin d'ameliorer les proprietes absorbantes des ferrites spinelles ni-zn, des plaquettes de composition chimique ni#0#,#4#5zn#0#,#5#5fe#2o#4 ont ete synthetisees selon deux methodes: la premiere est une reaction en sels fondus a partir de fe#2o#3 micace en poudre et permet d'obtenir des plaquettes de 10 a 30 microns, la seconde est une reaction d'echange a partir de kfe#1#1o#1#7 monocristallin et permet d'obtenir des plaquettes de 50 microns a plusieurs millimetres. Grace a une technique de mesure en ligne coaxiale, on a mesure la permeabilite complexe des plaquettes de ferrite spinelle en fonction de la frequence sur des ceramiques et des echantillons monocristallins
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Cassayre, Laurent. "Mécanismes de dégradation électrochimique de matériaux d'anodes pour l'électrolyse de l'aluminium." Toulouse 3, 2005. http://www.theses.fr/2005TOU30040.
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L'objectif de ce travail était de comprendre les mécanismes de dégradation d'un matériau d'anode destiné à être utilisé pour la production de l'aluminium par électrolyse dans un mélange cryolithique fondu à 960°C. Une anode inerte vis-à-vis de la réaction électrochimique permettrait de remplacer le dégagement de CO2, produit de la réaction anodique classique, par celui de l'oxygène. Le matériau étudié est un composite cermet constitué de deux phases oxydes à base de ferrite de nickel et d'un alliage cuivre-nickel. La démarche a consisté à étudier la dégradation des différents composants puis celle du cermet. L'application des méthodes électrochimiques, couplées aux caractérisations chimiques et structurales ainsi qu'à la modélisation thermodynamique, a permis de comprendre l'évolution des différentes familles de matériaux dans les conditions d'électrolyse. Hormis quelques métaux nobles, les anodes subissent une oxydation interne menant à une dégradation progressive de leurs propriétés<br>The purpose of this study was to understand the degradation mechanisms of an anode material, for an application in aluminium electrolysis cells. An inert anode would allow replacing the evolution of CO2, which is the anodic product in the classic process, by the evolution of oxygen, and then suppress the massive emission of green-house gases. The cermet is composed of two ceramic phases (nickel ferrite and nickel monoxide) and of a metallic copper-nickel alloy. Before considering the behaviour of this composite material, the electrochemical properties of different ceramics and metals were first studied separately. The combination of electrochemical techniques, chemical and structural characterizations and thermodynamical calculations allowed understanding the evolution of the anodes. Some noble metals proved to be resistant to oxygen evolution, but most of the studied materials were shown to undergo internal oxidation reactions leading to a degradation of their properties
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Bellefleur, Alexandre. "Cinétique de réaction et solubilité des produits de corrosion dans les conditions physico-chimiques du circuit primaire des réacteurs à eau sous pression (REP)." Phd thesis, Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1767/.
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L'objectif du travail présenté est d'acquérir expérimentalement de nouvelles données thermodynamiques sur les espèces qui constituent les produits de corrosion présents dans le circuit primaire des REP. Le volet expérimental de cette étude se focalise sur deux phases solides du nickel : l'oxyde de nickel NiO (ou bunsenite) et le ferrite de nickel NiFe2O4. La vitesse de dissolution de l'oxyde de nickel a été mesurée jusqu'à 130°C en milieu acide (pH 3 à 5). Un modèle cinétique a été utilisé afin de décrire les vitesses de dissolution mesurées expérimentalement. Ce modèle a permis de déterminer l'énergie d'activation réelle de la réaction de dissolution de l'oxyde de nickel. La solubilité d'un ferrite de nickel stœchiométrique synthétisé expérimentalement a été mesurée entre 100 et 200°C dans une cellule potentiométrique à électrodes à hydrogène. La spéciation du fer et du nickel dans la solution expérimentale a été discutée au regard des données thermodynamiques disponibles à haute température et des constantes d'équilibre calculées par le code MULTEQ. L'un des aspects de cette étude a consisté en la conception et la mise en route d'une cellule de mesure de solubilité à haute température : la boucle SOLO. Les spécifications techniques et le fonctionnement de cette installation seront présentés en détail<br>A better understanding of the behavior of the corrosion products at operating conditions of PWR is required. This study aims to collect new thermodynamic data on the species composing the corrosion products. The experimental work, described in this paper, focuses on the study of two solid phases: nickel oxide NiO and nickel ferrite NiFe2O4. Dissolution rate of nickel oxide has been measured to 130 °C in acidic conditions (pH 3 to 5). A kinetic model has been used to describe the measured dissolution rates. This calculation allowed us to determine the real activation energy of the dissolution reaction of nickel oxide which is equal to 56,5 ± 3,7 kJ. Mol-1. The dissolution rates of nickel oxide are slow and as a consequence, only a limited amount of nickel oxide can be dissolved during reactor shutdown. Solubility of a stoichiometric nickel ferrite, experimentally synthesized, has been measured from 100 to 200 °C in acidic conditions with a hydrogen electrode concentration cell. The results show a non-congruent dissolution of nickel ferrite with an iron excess. The speciation of soluble iron and nickel was studied based on the available thermodynamic data at high temperature and the measured concentrations were compared with the equilibrium constants with the MULTEQ code. The solubility of nickel ferrite in a reducing acidic solution is reasonably well described by the available thermodynamic data. A new high temperature solubility measurement cell was designed and built. This paper describes in detail the design of the cell and the first tests that have been conducted
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Rigo, Caroline. "PREPARAÇÃO DO COMPÓSITO FERRITA DE NÍQUEL/NANOTUBOS DE CARBONO POR MICRO-ONDAS PARA USO NA REAÇÃO DE FOTO-FENTON." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/7999.
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Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul<br>In this study, the synthesis of the nickel ferrite composite/carbon nanotubes was accomplished through two different routes: conventional solvothermal method and solvothermal method assisted by microwave. The influence of the synthesis route into material's physical properties was investigated. Furthermore, the nickel ferrite, without carbon nanotubes presence, was synthesized by the solvothermal method assisted by microwave. The obtained materials were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), surface area and adsorption-desorption measurements by the Brunauer-Emmett-Teller method (BET), Differential Thermal Analysis (TGA) and Raman spectroscopy The materials produced were used as photo-Fenton catalysts for heterogeneous reactions, aiming the degradation of an organic dye (Acid Red 27) under the irradiation of visible light. The assays were performed in order to analyze the different process variables, citing pH, dye concentration, the mass of the catalyst and the hydrogen peroxide aliquot. The reactions rates constants were determined only for the material obtained through the route assisted by microwave, since the two composites present similar physical properties, and therefore we chose this composite , once the synthesis is performed in less time (30 minutes versus 20 hours the conventional method). The photo-Fenton reaction assays indicate that this composite has effective performance into degradation of organic pollutants in solution, with total color removal in 60 minutes of reaction for Acid Red dye concentration of 50 mg.L-1.<br>Neste trabalho foi realizada a síntese do compósito de ferrita de níquel/ nanotubos de carbono por duas rotas distintas: método solvotérmico convencional e método solvotérmico assistido por micro-ondas. A influência da rota de síntese sobre as propriedades físicas do material foi investigada. Além disso, ferrita de níquel sem presença de nanotubos de carbono foi sintetizada pelo método solvotérmico assistido por micro-ondas. Os materiais obtidos foram caracterizados por difração de raios-X (DRX), espectroscopia no infravermelho com transformada de Fourier (FTIR), área superficial e medições de adsorção-dessorção pelo método Brunauer-Emmet-Teller (BET), análise térmica diferencial (TGA/DTG) e espectroscopia RAMAN. Os materiais produzidos foram utilizados como catalisadores em reações de foto-Fenton heterogêneo, visando à degradação de um corante orgânico (Vermelho Ácido 27) sob a irradiação de luz visível. Os ensaios foram realizados de modo a se analisar diferentes variáveis do processo, citando-se pH, concentração de corante, massa de catalisador e alíquota de peróxido de hidrogênio. As constantes de velocidade das reações foram determinadas apenas para o material obtido pela rota assistida por micro-ondas, visto que os dois compósitos apresentam propriedades físicas idênticas e, portanto optou-se por este compósito, uma vez que a síntese é realizada em menos tempo (30 minutos contra 20 horas do método convencional). Os ensaios de reação de foto-Fenton apontam que esse compósito tem desempenho efetivo para a degradação de poluente orgânico em solução, com remoção total de cor em 60 min de reação para o corante Vermelho Ácido 27, em concentração de 50 mg.L-1.
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Basaran, Yanki. "Studies On The Development Of Magnetoelectric Ceramic Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609612/index.pdf.
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The aim of this thesis work was to develop magnetoelectric (ME) composites consisting of piezoelectric and magnetostrictive components. The piezoelectric constituent was selected as a PZT ceramic modified by strontium, bismuth and manganese. The magnetostrictive phase was nickel ferrite (NF) ceramic doped by cobalt, copper and manganese. The properties of component phases were optimized in order to enhance the ME effect in the composite.
In the first part of the thesis, effects of sintering temperature on the dielectric and piezoelectric properties of PZT and on the electrical and magnetic properties of NF ceramics were investigated in the temperature range covered from 1150 to 1250 °<br>C. The best piezoelectric properties in PZT were attained at 1250 °<br>C. At this sintering temperature, values of piezoelectric strain coefficient, dielectric constant, and electromechanical coupling coefficient were 434 pC/N, 1320 and 0.48, respectively. NF ceramics showed poor densification<br>80 %TD was attained at 1250 °<br>C. In order to obtain higher densities in ferrites, Bi2O3 was used as a sintering aid. Addition of Bi2O3 enhanced densification up to 97 %TD, and improved electrical and magnetic properties of ferrites. Highest DC-resistivity of 1.15*10^8 ohm-cm and highest magnetostriction of ~26 ppm were attained in NF ceramics doped with 1 wt% Bi2O3.
In the second part of the thesis, ME composites were manufactured either as bulk composites or as laminated composites. The efficiency of different composite types was evaluated in terms of voltage output in response to the applied magnetic field. Higher outputs were observed in laminated composites.
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Fracari, Tiago Ost. "Síntese e caracterização de nanopartículas magnéticas de ferrita de níquel para detecção de ácido ascórbico e peróxido de hidrogênio." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/181184.
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Neste estudo apresenta-se a síntese de duas amostras de nanopartículas de ferrita de níquel, denominadas C-NiFe2O4 e NiFe2O4, através de um método simples, de baixo custo e ambientalmente amigável. Estudos morfológicos, estruturais, eletrônicos, ópticos e magnéticos foram realizados com o intuito de caracterizar as propriedades desses materiais para que possibilitassem, além de maior grau de conhecimento, sua aplicação como sensores colorimétricos para detecção de ácido ascórbico e peróxido de hidrogênio. Mediante a análise térmica dos precursores, foi possível determinar os intervalos de temperatura de decomposição, assim como a temperatura ótima de formação das nanopartículas. A amostra NiFe2O4 é ferromagnética e corresponde a uma fase cúbica de espinélio inverso. Os dados de difração de raios X, espectroscopia Mössbauer e o modelo iônico sugerem a presença de um certo grau de substituição, possuindo em sua estrutura um cátion divalente como agente dopante. As nanopartículas de C-NiFe2O4 foram utilizadas como catalisador na oxidação do 3,3',5,5'-tetrametilbenzidina (TMB) em meio ácido para formar uma solução azul sem adição de outro reagente. Como resultado foi utilizado como sensor colorimétrico para detecção de ácido ascórbico, visto que este reduz o complexo de transferência de carga, TMBOX, novamente para TMB. A calibração analítica apresentou uma faixa linear entre 1-20 μM para a concentração de ácido ascórbico, com limite de detecção (3/m) de 0,93 μM. A determinação em suplementos de vitamina C através do método de adição de padrão mostrou a eficiência do sensor para detectar ácido ascórbico em amostras reais. Já a amostra de NiFe2O4 demonstrou atividade catalítica semelhante as peroxidases naturais, oxidando o TMB na presença de H2O2 para formar TMBOX, que dá coloração azul a solução. Dessa forma, NiFe2O4 foi utilizado em um sensor colorimétrico para detecção de H2O2 e a calibração analítica revelou duas faixas lineares, uma entre 2,28 - 28,60 μM e a outra entre 28,60 μM - 114,20 μM. O limite de detecção (3/m) foi de 1,94 μM. Ambos os métodos apresentaram boa repetibilidade, com coeficiente de variação de 3,5% e 4% respectivamente.<br>This study presents the synthesis of two samples of nickel ferrite nanoparticles, termed C-NiFe2O4 and NiFe2O4, through a simple, low cost and environmentally friendly method. Morphological, structural, electronic, optical and magnetic studies were carried out with the aim of characterizing the properties of these materials, which allowed the application of colorimetric sensors for the detection of ascorbic acid and hydrogen peroxide. Through the thermal analysis of the precursors, it was possible to determine the decomposition temperature ranges, as well as the optimum temperature of formation of the nanoparticles. The sample NiFe2O4 is ferromagnetic and corresponds to a cubic phase of inverse spinel. The X-ray diffraction data, Mössbauer spectroscopy and the ionic model suggest the presence of a certain degree of substitution, having in its structure a divalent cation as a doping agent. The C-NiFe2O4 nanoparticles were used as catalysts in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in acidic medium to form a blue solution without addition of another reagent. As a result, it was used as a colorimetric sensor for the detection of ascorbic acid, as it reduces the charge transfer complex, TMBOX, again to TMB. The analytical calibration showed a linear range between 1-20 μM for the concentration of ascorbic acid, with a detection limit (3 /m) of 0.93 μM. The determination of vitamin C supplements using the standard addition method showed the efficiency of the sensor to detect ascorbic acid in actual samples. Already NiFe2O4 sample demonstrated catalytic activity similar to natural peroxidases, oxidizing the TMB in the presence of H2O2 to form TMBOX, which gives blue coloration to the solution. Thus, NiFe2O4 was used in a colorimetric sensor to detect H2O2, and the analytical calibration revealed two linear ranges, one between 2.28 - 28.60 μM and the other between 28.60 μM - 114.20 μM. The detection limit (3 /m) was 1.94 μM. Both methods presented good repeatability, with a coefficient of variation of 3.5% and 4% respectively.
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Bellefleur, Alexandre. "Cinétique de réaction et solubilité des produits de corrosion dans les conditions physico-chimiques du circuit primaire des réacteurs à eau sous pression (REP)." Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00767055.
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L'objectif du travail présenté est d'acquérir expérimentalement de nouvelles données thermodynamiques sur les espèces qui constituent les produits de corrosion présents dans le circuit primaire des REP. Le volet expérimental de cette étude se focalise sur deux phases solides du nickel : l'oxyde de nickel NiO (ou bunsenite) et le ferrite de nickel NiFe2O4. La vitesse de dissolution de l'oxyde de nickel a été mesurée jusqu'à 130°C en milieu acide (pH 3 à 5). Un modèle cinétique a été utilisé afin de décrire les vitesses de dissolution mesurées expérimentalement. Ce modèle a permis de déterminer l'énergie d'activation réelle de la réaction de dissolution de l'oxyde de nickel. La solubilité d'un ferrite de nickel stœchiométrique synthétisé expérimentalement a été mesurée entre 100 et 200°C dans une cellule potentiométrique à électrodes à hydrogène. La spéciation du fer et du nickel dans la solution expérimentale a été discutée au regard des données thermodynamiques disponibles à haute température et des constantes d'équilibre calculées par le code MULTEQ. L'un des aspects de cette étude a consisté en la conception et la mise en route d'une cellule de mesure de solubilité à haute température : la boucle SOLO. Les spécifications techniques et le fonctionnement de cette installation seront présentés en détail.
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Kuper, Michael W. "Investigations Near the Fusion Boundary of Grade 91 Steel Dissimilar Metal Welds with Nickel Based Filler Metals." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543505600533312.
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BENLOUCIF, MOHAMMED-RIDA. "Oxydes de type k#2nif#4, ferrite bicalcique ca#2fe#2o#5 et nd#2banio#5 a base de fer et de nickel : structure, proprietes electriques et magnetiques." Caen, 1992. http://www.theses.fr/1992CAEN2002.
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Plusieurs oxydes de structure type k#2nif#4 de formulation la#2#(#x#+#y)sr#x#+#yni#1##y fe#yo#4##(#x#/#2#)#+# ont ete prepares. L'etat d'oxydation du fer et du nickel a ete determine par analyse chimique et spectroscopie mossbauer. Un ordre antiferromagnetique a ete observe a t=200 k pour ces phases. Les proprietes de transport electronique de ces composes sont lies etroitement a la non-stchiometrie en oxygene et aux proprietes magnetiques. Cette relation est discutee et interpretee sur la base de deux modeles de diagramme d'energie. Sur la seconde famille de composes etudies ca#2fe#2##xm#xo#5#(#x#/#2) (m=cu, ni, mg, zn) de type ferrite bicalcique, une etude mossbauer a permis de montrer la seule presence de fe(iii) et confirmer la non-stchiometrie en oxygene. Elle suggere l'existence de sites pyramidaux et d'une distribution cationique ordonnee. L'etude de la susceptibilite magnetique en fonction de la temperature montre une large transition anti-ferromagnetique avec une classique diminution de t#n avec x. Dans le type structural nd#2banio#5, un nouveau compose a ete synthetise y#2banio#5 et etudie du point de vue structural (symetrie orthorhombique, groupe d'espace immm avec z=2). Cette etude a mis en evidence l'influence de la taille des ions y et nd sur la deformation des octaedres nio#6 qui forment des chaines isolees les unes des autres dans cette structure. Les mesures de la susceptibilite magnetique en fonction de la temperature de la solution solide nd#2##xy#xbanio#5 (o<x<2) montrent une transition progressive d'un etat tridimensionnel a un etat unidimensionnel
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Emo, Jonathan. "Etude expérimentale et par simulation Monte Carlo des transformations de phase dans la ferrite des aciers austéno-ferritiques et de leurs alliages modèles." Rouen, 2014. http://www.theses.fr/2014ROUES054.
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Les aciers inoxydables austéno-ferritiques constituants les coudes moulés du circuit primaire des centrales nucléaires de deuxième génération, vieillissent aux températures de service (285°C-323°C). Ceci se traduit par une augmentation de leur dureté et une baisse de leur résilience. L’évolution de ces propriétés est attribuée aux transformations de phases qui opèrent dans la ferrite. S'il est admis que la composition de l’acier influe sur l’évolution de ces propriétés (les aciers moins riches en Ni et Mo sont moins sensibles au vieillissement), l’origine de ces différences n’est pas clairement identifiée. Dans cette étude, la cinétique des transformations de phase de la ferrite d'un acier austéno-ferritique pauvre en Mo et Ni ainsi que de celle d'alliages modèles duplex de composition ciblée a été étudiée par sonde atomique. Ces études ont permis de montrer que : i) l'intensité de la précipitation de la phase G est plus faible et la cinétique de la décomposition spinodale plus lente pour l'acier pauvre en Ni et Mo que pour des aciers riches en Mo et Ni analysés dans le cadre de travaux antérieurs, ii) la synergie entre décomposition spinodale et phase G est également observée dans cet acier, iii) le Mo n’a pas d’influence sur les premiers stades de précipitation de la phase G, iv) le mécanisme de précipitation de la phase G a lieu en au moins deux étapes, v) lorsque la densité de phase G est faible, le durcissement est contrôlé par l'amplitude et la longueur d'onde de la décomposition spinodale et vi) le rôle de la phase G sur le durcissement n'est peut-être pas si négligeable qu'on pouvait le supposer lorsque la densité est importante. Un modèle en simulation Monte Carlo cinétique a également été développé pour expliquer la synergie qui observée expérimentalement entre la décomposition spinodale et la précipitation de phase G. Ce modèle a permis de montrer que la coalescence des particules de phase G procède via la diffusion le long des interfaces α/α' et non par diffusion en volume<br>Duplex stainless steels used in primary circuit of 2nd generation nuclear power plant endure thermal ageing at service temperatures (285°C-323°C). This leads to an increase of their hardness and to a decrease of their Charpy toughness. The evolution of these properties is due to the phase transformations which occur in ferrite. Even if it is well known that the steel composition plays a role on the mechanical properties evolution (steels with low Ni and Mo contents are less sensitive to thermal ageing), the origin of this difference of behaviour has not been clearly identified yet. In this study, the kinetics of the phase transformations in the ferrite of a duplex stainless steel with low Ni and Mo contents and duplex model alloys with specific compositions have been studied by atom probe tomography. This work showed that: i) G phase precipitation is less intense and the kinetic of the spinodal decomposition is slower for this steel than for steels with higher Ni and Mo contents, ii) the synergy between spinodal decomposition and G phase precipitation is also observed in this steel, iii) the Mo does not affect the early stages of the G phase precipitation, iv) the formation mechanism of G phase precipitates is at least a two steps mechanism, v) when the number density of G phase precipitates is low, hardening is mainly controlled by the amplitude and the mean wavelength of the spinodal decomposition, vi) when the number density of G phase precipitates is high, the hardening due to G phase precipitates may not be negligible. A kinetic Monte Carlo model has been developed to explain the synergy observed experimentally between the spinodal decomposition and the G phase precipitation. This model allowed us to show that the coarsening of G phase precipitates is driven by a diffusion mechanism along α/α’ interfaces, and not by a bulk diffusion mechanism
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SILVEIRA, Angélica Soares da. "Aproveitamento das Cinzas da Casca de Arroz como Suporte Catalítico Heterogêneo na Síntese do Biodiesel por Reação de Hidroesterificação." Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/809.
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Previous issue date: 2014-08<br>A tendência do aproveitamento integral de resíduos da agroindústria, tais como: a casca de arroz, as fibras da casca de coco, bagaço da cana de açúcar, dentre outros, vem sendo uma necessidade e, ao mesmo tempo, um desafio tecnológico e ambiental para a indústria moderna e a sociedade. Por isso, esta pesquisa versa sobre o comportamento do resíduo da agroindústria (cascas de arroz), como suporte catalítico na impregnação da ferrita de níquel (NiFe2O4), para a síntese de biodiesel pelo método da hidroesterificação. As cascas de arroz foram calcinadas por 3h nas temperaturas de 500, 700 e 1000 ºC, e, em seguida, impregnadas com a Ferrita de Níquel (NiFe2O4) a 110 ºC, resultando nos catalisadores identificados por: NiFe2O4-CCA 500 ºC, NiFe2O4-CCA 700 ºC e NiFe2O4-CCA 1000 ºC. Os biodieseis foram sintetizados, separadamente, utilizando os referidos catalisadores através do método de hidroesterificação, no qual envolve as etapas de hidrólise, seguida da esterificação. Esta ultima etapa, foi realizada na razão óleo de algodão/álcool etílico de 1:6 com 1% do catalisador obtido, a 200 ºC por 2h. Os resultados apontaram que as propriedades físico-químicas, índices de acidez e viscosidade, estão dentro dos limites permitidos pela Legislação Brasileira, Agência Nacional do Petróleo, Gás Natural e Biocombustível (ANP), sendo que, o biodiesel sintetizado pelo catalisador a 500 ºC obteve os menores índices de acidez e viscosidade. As Curvas TG e DTG evidenciaram de três (BCat 500 ºC) a quatro (BCat 700 e 1000 ºC) etapas de decomposição térmica, atribuídas à volatilização e/ou decomposição dos ésteres de ácidos graxos etílicos (principalmente dos seus maiores componentes linoleato e oleato de etila). Essas curvas mostraram, ainda, temperaturas de estabilidade de cada produto, sendo o BCat 1000 ºC o mais estável em relação aos demais, atingindo temperatura de 226 ºC, proporcionando maior segurança ao biocombustível, no que concerne ao processo de armazenamento. Os espectros de absorção na região do infravermelho confirmaram a presença dos ésteres de ácidos graxos etílicos de banda vibracional com forte intensidade em 1749,7 cm-1. Em síntese, os resultados obtidos demonstraram ser satisfatórios, para o viés do objetivo, propondo uma alternativa de aplicação do resíduo da agroindústria (casca de arroz), a fim de reduzir um problema ambiental gerado por este no setor.<br>The tendency of comprehensive utilization of agro-industrial residues such as rice husk, the fibers of the coconut husk, bagasse of sugar cane, among others, has been a need and at the same time, a technological and environmental challenge for modern industry and society. Therefore this research deals with the agribusiness residue behavior (rice husks), as a catalyst support in the impregnation of nickel ferrite (NiFe2O4), for the biodiesel synthesis by the method of hidroesterification. The rice husks were calcined by 3 h at 500, 700 and 1000 ° C, and then impregnated with ferrite Nickel (NiFe2O4) at 110 °C, resulting in the catalysts identified by NiFe2O4-CCA 500 °C, NiFe2O4-CCA 700 ºC and NiFe2O4-CCA 1000 ºC. The biodiesels were synthesized separately using these catalysts by the method of hidroesterification, which involves the hydrolysis steps, followed by esterification. This last step was performed on reason cotton oil / ethanol 1:6 with 1% of the catalyst obtained, at 200 ° C by 2 h. The results showed that the physicochemical properties, acidity and viscosity levels, are within the limits allowed by Brazilian Legislation, the Petroleum, Natural Gas and Biofuels National Agency (ANP), since biodiesel synthesized by the catalyst at 500 °C presented the lowest levels of acidity and viscosity. The TG and DTG curves showed three (BCat 500 ºC) to four (BCat 700 and 1000 °C) steps of thermal decomposition, attributed to volatilization and /or decomposition of the ethyl fatty acids esters (mainly of its biggest linoleate and ethyl oleate components). These curves also showed temperature stability of each product, with the BCat 1000 °C more stable compared to the other, reaching a temperature of 226 ºC providing increased safety to the biofuel regarding to the storage process. Absorption spectra in the infrared region confirmed the presence of ethyl fatty acids esters with vibrational band with strong intensity at 1749.7 cm-1. In summary, the results proved demonstrated to be satisfactory for the purpose of the aim, offering an alternative of implementation of agribusiness residue (rice husks) to reduce an environmental problem generated by it in this sector.
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Gonçalves, Nizomar de Sousa. "Utilização da água de coco em pó na preparação de nanopartículas de ferritas." reponame:Repositório Institucional da UFC, 2007. http://www.repositorio.ufc.br/handle/riufc/9793.
Full textAbstract:
GONÇALVES, Nizomar de Sousa. Utilização da água de coco em pó na preparação de nanopartículas de ferritas. 2007. 46 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2007.<br>Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-11-13T22:17:28Z
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Previous issue date: 2007<br>The present work is dedicated to the studies of the preparation and characterization of the nickel ferrites and cobalt. These ferrites were synthesized by the sun-gel process in suspension of water of coconut lyophilized (ACP) manufactured in Cear´a. This synthesis method allowed to obtain in way efficient ferrite nanoparticles. The samples were treated for 4 hours at 400, 600, 800, 1000 and 1200 C. A preliminary study of the cobalt ferrite varying the concentration of the coconut water above your critical micelle concentration (8,3 mmol/l) it showed as that can influence in the quality of the nanoparticles. The Xray difraction (XRD), the Raman spectroscopy and Scanning Eletron Microscopy (SEM) were applied to study the dependence of the size of the nanoparticle of nickel ferrite with the temperature of the thermal treatment, and the correlation of your electrical properties and the results of M¨ossbauer spectroscopy with your morphologic characteristics. The cristalinity of the ferrites increases with the temperature of the thermal treatment. Measurements of the complex permitivity carried out in cavity resonators at 5,9 and 9,0 GHz have showed that your values of the real part decrease with the increase of the temperature of the thermal treatment (3,6 - 2,4), while the imaginary part stay low for more elevated temperatures of the thermal treatment (about 10−3). Measurements of complex impedance to lower frequencies (75 KHz to 30 MHz), have showed that it increases with the increase of the temperature of the thermal treatment. The results of M¨ossbauer spectroscopy showed that the ferrites presents a structure inverse spinel with the ions Ni2+ occupying the site B and the ions Fe3+ equally distributed in the sites A and and B. To temperatures of thermal treatment below 800 ºC, favored the presence in the grains of a phase Grain Boundary (greater condutivity) observed so much in the behavior of the electric properties as in the answers of the M¨ossbauer spectroscopy.<br>Este trabalho é dedicado aos estudos da preparação e caracterização das ferritas de níquel e cobalto. Estas ferritas foram sintetizadas pelo processo de sol-gel em suspensão de água de coco liofilizada (ACP) fabricada no Ceará. Este método de síntese permitiu obter de forma eficiente nanopartículas de ferritas. As amostras foram calcinadas durante 4 horas a 400, 600, 800, 1000 e 1200 °C. Um estudo preliminar da ferrita de cobalto variando a concentração da água de coco acima da sua concentração micelar crítica (8,3 mmol/litro) mostrou como isso pode influenciar na qualidade e na homogeneização das nanopartículas. A difração de raios-X (XRD), a espectroscopia Raman e a Microscopia Eletrônica de Varredura (SEM) foram aplicadas para estudar a dependência do tamanho da nanopartícula de ferrita de níquel com a temperatura do tratamento térmico, e a correlação de suas propriedades elétricas e os resultados de espectroscopia Mössbauer com as suas características morfológicas. A cristalinidade das ferritas aumenta com a temperatura do tratamento térmico. Medidas da permissividade complexa realizadas em cavidades ressonantes a 5,9 e 9,0 GHz mostraram que seus valores da parte real decrescem com o aumento da temperatura do tratamento térmico (3,6 - 2,4), enquanto os da parte imaginária permanecem baixos para as temperaturas mais altas do tratamento térmico (cerca de 10-3). Medidas de impedância complexa a frequências mais baixas (75 KHz a 30 MHz), mostraram que ela aumenta com o aumento da temperatura do tratamento térmico. Os resultados de espectroscopia Mössbauer mostraram que as ferritas apresentam uma estrutura espinélio inverso com os íons Ni2+ ocupando os sítios B e os íons Fe3+ distribuídos igualmente nos sítios A e B. Para temperaturas de tratamento térmico abaixo de 800°C favoreceram a presença nos grãos de uma fase mais condutora (Grain Boundary), observada tanto no comportamento das propriedades elétricas quanto nas respostas da espectroscopia Mössbauer.
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Hawkes, Joshua Mahlon. "The Simulation and Study of Conditions Leading to Axial Offset Anomaly in Pressurized Water Reactors." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7612.
Full textAbstract:
Axial offset anomaly (AOA) in pressurized water reactors (PWR) refers to deviation of the measured neutron flux in the top half of the core from the predicted values. Among other difficulties, AOA reduces the shutdown margin, and may force the plant to reduce power output. AOA is believed to be caused by three related phenomena occurring in the core while operating at full power: sub-cooled nucleate boiling concentrated mainly in the upper half of the core, corrosion product deposition on the cladding surface (crud), and the deposition of boron within the porous crud layer in regions of vigorous sub-cooled boiling.
This study replicates the conditions within the PWR primary coolant; specifically, the temperature, pressure, peak surface heat flux, coolant velocity and water chemistry are simulated in order to produce prototypical crud on an electrically heated Zircaloy-4 test element. At the conclusion of each test run, the heated Zircaloy-4 test element is rapidly isolated from the coolant in order to trap any soluble boron species that may be present in the crud layer. The results of this investigation indicate that prototypical crud with significant boron deposition can be produced. The deposited boron compound has been determined to be lithium tetraborate (Li2B4O7). Comparative experiments have been run to determine the effect of coolant pH, concentration and type of additives, and duration of exposure on the thickness of the crud deposit. The data obtained in this investigation can be used to validate mechanistic models for crud deposition and AOA in pressurized water reactors.
29
Lesik, S. M., and I. M. Ivanenko. "Nickel ferrites and its catalytic properties." Thesis, Sumy State University, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67686.
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Gonçalves, Nizomar de Sousa. "Síntese e caracterização de nanopartículas de ferritas de níquel e de colbalto preparadas pelo método sol-gel proteico." reponame:Repositório Institucional da UFC, 2011. http://www.repositorio.ufc.br/handle/riufc/9794.
Full textAbstract:
GONÇALVES, Nizomar de Sousa. Síntese e caracterização de nanopartículas de ferritas de níquel e de colbalto preparadas pelo método sol-gel proteico. 2011. 119 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2011.<br>Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-11-14T18:02:46Z
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Previous issue date: 2011<br>In this work we present the study of the synthesis of nanosized nickel and cobalt ferrites by sol-gel proteic method. This work revisited the method of X-ray powder diffraction analysis known as Williamson-Hall plotting. This method provides size-strain studies in nanoparticles samples. Nickel ferrites has presented particle sizes that increase when the calcination temperature increases. Nickel ferrites nanoparticles were characterized by Mössbauer spectroscopy. Sample calcined at 400°C has presented superparamagnetic properties and those calcined at higher temperatures behavior as magnetic materials. Cobalt ferrites nanoparticles were charcterized by X-ray powder diffraction, small angle X-ray scattering e magnetization. Cobalt ferrites has not presented superparamagnetic behavior. For the synthesis of cobalt ferrites some parameters that are important to the process control were studied: calcination temperature, calcination time, heat rate. We have shown the relation among those parameters and the particle size and properties control to the cobalt ferrite nanoparticles.<br>Este trabalho apresenta o estudo da síntese de nanopartículas de ferritas de níquel e de cobalto usando o método sol-gel proteico. Inicialmente, é resgatado o método do gráfico de Williamson-Hall na análise dos dados de difração de raios X. Este método permite calcular o tamanho médio de partícula e a microdeformação. Ferritas de níquel apresentaram tamanhos de partículas que crescem com o aumento da temperatura de calcinação. Nanopartículas de ferrita de níquel foram caracterizadas por espectroscopia Mössbauer. As amostras calcinadas a 400 °C apresentaram comportamento superparamagnético ao passo que aquelas calcinadas em temperaturas superiores apresentaram comportamento magnético. As ferritas de cobalto foram caracterizadas usando difração de raios X, espalhamento de raios X a baixo ângulo e medidas de magnetização. As ferritas de cobalto não apresentaram comportamento superparamagnético. Na síntese das ferritas de cobalto, alguns parâmetros associados com o controle do processo foram estudados: temperatura de calcinação, tempo de calcinação, taxa de aquecimento/resfriamento. Deduziu-se a relação de cada parâmetro com o controle do tamanho de partícula e das propriedades das ferritas de cobalto.
31
Corso, Stéphanie. "Élaboration et caractérisation de céramiques à base de ferrites de nickel : étude de leurs propriétés en vue de la conception d'anodes inertes de type oxydes ou cermets destinées à l'électrolyse de l'aluminium." Toulouse 3, 2004. http://www.theses.fr/2004TOU30305.
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32
GonÃalves, Nizomar de Sousa. "Sintese e caracterizaÃÃo de nanoparticulas de ferritas de nÃquel e de colbalto preparadas pelo mÃtodo sol-gel proteico." Universidade Federal do CearÃ, 2011. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=6787.
Full textAbstract:
CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior<br>Este trabalho apresenta o estudo da sÃntese de nanopartÃculas de ferritas de nÃquel e de cobalto usando o mÃtodo sol-gel proteico. Inicialmente, Ã resgatado o mÃtodo do grÃfico de Williamson-Hall na anÃlise dos dados de difraÃÃo de raios X. Este mÃtodo permite calcular o tamanho mÃdio de partÃcula e a microdeformaÃÃo. Ferritas de nÃquel apresentaram tamanhos de partÃculas que crescem com o aumento da temperatura de calcinaÃÃo. NanopartÃculas de ferrita de nÃquel foram caracterizadas por espectroscopia MÃssbauer. As amostras calcinadas a 400 ÂC apresentaram comportamento superparamagnÃtico ao passo que aquelas calcinadas em temperaturas superiores apresentaram comportamento magnÃtico. As ferritas de cobalto foram caracterizadas usando difraÃÃo de raios X, espalhamento de raios X a baixo Ãngulo e medidas de magnetizaÃÃo. As ferritas de cobalto nÃo apresentaram comportamento superparamagnÃtico. Na sÃntese das ferritas de cobalto, alguns parÃmetros associados com o controle do processo foram estudados: temperatura de calcinaÃÃo, tempo de calcinaÃÃo, taxa de aquecimento/resfriamento. Deduziu-se a relaÃÃo de cada parÃmetro com o controle do tamanho de partÃcula e das propriedades das ferritas de cobalto.<br>In this work we present the study of the synthesis of nanosized nickel and cobalt ferrites by sol-gel proteic method. This work revisited the method of X-ray powder diffraction analysis known as Williamson-Hall plotting. This method provides size-strain studies in nanoparticles samples. Nickel ferrites has presented particle sizes that increase when the calcination temperature increases. Nickel ferrites nanoparticles were characterized by MÃssbauer spectroscopy. Sample calcined at 400ÂC has presented superparamagnetic properties and those calcined at higher temperatures behavior as magnetic materials.
Cobalt ferrites nanoparticles were charcterized by X-ray powder diffraction, small angle X-ray scattering e magnetization. Cobalt ferrites has not presented superparamagnetic behavior. For the synthesis of cobalt ferrites some parameters that are important to the process control were studied: calcination temperature, calcination time, heat rate. We have shown the relation among those parameters and the particle size and properties
control to the cobalt ferrite nanoparticles.
33
Hochepied, Jean-François. "Précipitation d'hydroxydes et d'oxydes métalliques en solution aqueuse : vers le contrôle morphologique d'objets multi-échelles." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2009. http://tel.archives-ouvertes.fr/tel-00574750.
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Adair, Antony. "Observed super-spin class behavior in Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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35
GonÃalves, Nizomar de Sousa. "UtilizaÃÃo da Ãgua de coco em pà na preparaÃÃo de nanopartÃculas de ferritas." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=5247.
Full textAbstract:
CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior<br>Este trabalho à dedicado aos estudos da preparaÃÃo e caracterizaÃÃo das ferritas de nÃquel e cobalto. Estas ferritas foram sintetizadas pelo processo de sol-gel em suspensÃo de Ãgua de coco liofilizada (ACP) fabricada no CearÃ. Este mÃtodo de sÃntese permitiu obter de forma eficiente nanopartÃculas de ferritas. As amostras foram calcinadas durante 4 horas a 400, 600, 800, 1000 e 1200 ÂC. Um estudo preliminar da ferrita de cobalto variando a concentraÃÃo da Ãgua de coco acima da sua concentraÃÃo micelar crÃtica (8,3 mmol/litro) mostrou como isso pode influenciar na qualidade e na homogeneizaÃÃo das nanopartÃculas. A difraÃÃo de raios-X (XRD), a espectroscopia Raman e a Microscopia EletrÃnica de Varredura (SEM) foram aplicadas para estudar a dependÃncia do tamanho da nanopartÃcula de ferrita de nÃquel com a temperatura do tratamento tÃrmico, e a correlaÃÃo de suas propriedades elÃtricas e os resultados de espectroscopia MÃssbauer com as suas caracterÃsticas morfolÃgicas. A cristalinidade das ferritas aumenta com a temperatura do tratamento tÃrmico. Medidas da permissividade complexa realizadas em cavidades ressonantes a 5,9 e 9,0 GHz mostraram que seus valores da parte real decrescem com o aumento da temperatura do tratamento tÃrmico (3,6 - 2,4), enquanto os da parte imaginÃria permanecem baixos para as temperaturas mais altas do tratamento tÃrmico (cerca de 10-3). Medidas de impedÃncia complexa a frequÃncias mais baixas (75 KHz a 30 MHz), mostraram que ela aumenta com o aumento da temperatura do tratamento tÃrmico. Os resultados de espectroscopia MÃssbauer mostraram que as ferritas apresentam uma estrutura espinÃlio inverso com os Ãons Ni2+ ocupando os sÃtios B e os Ãons Fe3+ distribuÃdos igualmente nos sÃtios A e B. Para temperaturas de tratamento tÃrmico abaixo de 800ÂC favoreceram a presenÃa nos grÃos de uma fase mais condutora (Grain Boundary), observada tanto no comportamento das propriedades elÃtricas quanto nas respostas da espectroscopia MÃssbauer.<br>The present work is dedicated to the studies of the preparation and characterization
of the nickel ferrites and cobalt. These ferrites were synthesized by the sun-gel process in
suspension of water of coconut lyophilized (ACP) manufactured in CearÂa. This synthesis
method allowed to obtain in way efficient ferrite nanoparticles. The samples were treated
for 4 hours at 400, 600, 800, 1000 and 1200 C. A preliminary study of the cobalt ferrite
varying the concentration of the coconut water above your critical micelle concentration
(8,3 mmol/l) it showed as that can influence in the quality of the nanoparticles. The Xray
difraction (XRD), the Raman spectroscopy and Scanning Eletron Microscopy (SEM)
were applied to study the dependence of the size of the nanoparticle of nickel ferrite with
the temperature of the thermal treatment, and the correlation of your electrical properties
and the results of MÂossbauer spectroscopy with your morphologic characteristics.
The cristalinity of the ferrites increases with the temperature of the thermal treatment.
Measurements of the complex permitivity carried out in cavity resonators at 5,9 and 9,0
GHz have showed that your values of the real part decrease with the increase of the temperature
of the thermal treatment (3,6 - 2,4), while the imaginary part stay low for more
elevated temperatures of the thermal treatment (about 10−3). Measurements of complex
impedance to lower frequencies (75 KHz to 30 MHz), have showed that it increases with
the increase of the temperature of the thermal treatment. The results of MÂossbauer spectroscopy
showed that the ferrites presents a structure inverse spinel with the ions Ni2+
occupying the site B and the ions Fe3+ equally distributed in the sites A and and B. To
temperatures of thermal treatment below 800 C, favored the presence in the grains of
a phase Grain Boundary (greater condutivity) observed so much in the behavior of the
electric properties as in the answers of the MÂossbauer spectroscopy.
36
Sandford, Andrew Robert Brian. "Effect of manganese and nickel on the cleavage fracture strength of ferritic weld metal." Thesis, London Metropolitan University, 1990. http://repository.londonmet.ac.uk/3058/.
Full textAbstract:
All weld metal test pieces were produced from two commercial and six experimental 7016 type electrodes, each having different contents of manganese and nickel. These were tested in three point bending over a range of depressed temperatures in a cryostatic cell of the author’s devising. Notched samples were used to obtain values for the cleavage fracture strength. This was calculated by reference to slip line field theory from the fracture load at the test temperature where fracture was first coincident with general yielding. The commercial electrodes were first tested in the as welded condition and all eight electrodes were then tested after a heat treatment designed to give a microstructure similar to that found in re-heated weld metal. Notched and pre-cracked samples were then tested in the heat treated condition to determine KI values. Fracture surfaces were examined by scanning electron microscope and grain size measurements made by optical microscopy. Lower shelf impact energy measurements were also made. The results show that both manganese and nickel individually increased the cleavage fracture strength. In combination the best cleavage properties were given by alloying contents of 1.0% manganese and 1.5% nickel increasing alloying beyond this level had a detrimental effect. The mechanism for this was a combination of grain size effects, changes in the slip characteristics of the material, the size, distribution and nature of inclusions and the effects of alloying on grain boundary and matrix/inclusion cohesion. In re-heated material at test temperatures studied the plane strain fracture toughness is influenced by similar factors to those which determine cleavage fracture strength.
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Santos, Paulo Roberto Cunha dos. "S?ntese, sinteriza??o e caracteriza??o de ferrita de n?quel." Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18676.
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Previous issue date: 2014-05-27<br>Universidade Federal do Rio Grande do Norte<br>In this work we obtain nickel ferrite by the combustion synthesis method whcih
involves synthesising in an oven at temperatures of 750oC, 950oC and 125oC.
The precursors oxidizing used were nickel nitrate, ferric as an oxidizing and reducing
urea (fuel). After obtaining the mixture, the product was deagglomerated
and past through a 270 mesh sieve. To assess the structure, morphology, particle
size, magnetic and electrical properties of nanoparticles obtained the samples were
sintered and characterized by x-ray distraction (XRD), x-ray fluorescence spectroscopy
(FRX); scanning electron microscopy (SEM), energy dispersive spectroscopy
(EDS), vibrating sample magnetometer (MAV ) and electrical permittivity. The results
indicated the majority of phase inverse spinel ferrite and Hematite secondary
phase nickel and nickel oxide. Through the intensity of the distraction, the average
size of the crystallization peaks were half-height width which was calculated using
the Scherrer equation. From observing the peaks of all the reflections, it appears
that samples are crystal clear with the formation of nanoparticles. Morphologically,
the nanoferritas sintered nickel pellet formation was observed with three systems of
particle size below 100mn, which favored the formation of soft pellets. The average
size of the grains in their micrometric scale. FRX and EDS showed qualitatively
the presence of iron elements nickel and oxygen, where through quantitative data
we can observe the presence of the secondary phase. The magnetic properties and
the saturation magnetization and the coercive field are in accordance with the nickel,
ferrite where the curve of hysteresis has aspects of a soft material. Dielectric
constant values are below 10 and low tangent loss<br>Este trabalho descreve a obten??o de ferrita de n?quel pelo m?todo de s?ntese
de combust?o, seguida pela sinteriza??o em forno, ?s temperatura de 750oC, 950oC
e 1250oC. Os precursores oxidantes utilizados foram: nitratos de n?quel e ferro III
como redutor, foi usada a ur?ia (combust?vel). Depois da obten??o do p?s-misturas,
o produto foi desaglomerado e passado em uma peneira de mesch 270. A estrutura, a
morfologia, o tamanho das part?culas e as propriedades magn?ticas e el?tricas das nanopart
?culas obtidas das amostras p?s sinterizadas foram caracterizadas por difra??o
de raios-X (DRX), espectroscopia de uoresc?ncia de raios-X (FRX), microscopia
eletr?nica de varredura (MEV ), espectroscopia de energia dispersiva (EDS), magnet
?metro de amostra vibrante (MAV ) e an?lise el?trica. Os resultados indicaram
a fase majorit?ria do espin?lio inverso ferrita de n?quel e a fase secund?ria de hematita
e ?xido de n?quel. Atrav?s da intensidade dos picos de difra??o de raios-X e
da largura de meia altura no espectro, foi calculado o tamanho m?dio do cristalito
pela equa??o Scherrer, observando-se os picos de todas as re ex?es, veri cando a
cristalinidade das amostras, e com forma??o de nanopart?culas. Morfologicamente,
para as nanoferritas de n?quel sinterizadas, observou-se a forma??o de aglomerados
moles nos tr?s sistemas com part?culas de tamanho inferior a 100nm. O tamanho
m?dio dos gr?os est? em escala microm?trica. Os espectros de FRX e EDS mostraram
qualitativamente a presen?a dos elementos ferro, n?quel e oxig?nio. Atrav?s
dos dados quantitativos, pode-se observar a presen?a da fase secund?ria. As propriedades
magn?ticas, como a magnetiza??o de satura??o e o campo coercitivo, est?o
de acordo com a ferrita de n?quel, em que a curva de histerese tem aspectos de um
material mole. Os valores de constante diel?trica est?o abaixo de 10 e baixa tangente
de perdas.
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Smith, Thomas. "Studies of p-type semiconductor photoelectrodes for tandem solar cells." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14522.
Full textAbstract:
Photoelectrodes and photovoltaic devices have been prepared via multiple thin film deposition methods. Aerosol assisted chemical vapour deposition (AACVD), electrodeposition (ED), chemical bath deposition (CBD) and doctor blade technique (DB) have been used to deposit binary and ternary metal oxide films on FTO glass substrates. The prepared thin films were characterised by a combination of SEM (Scanning Electron Microscopy), powder X-ray diffraction, mechanical strength tests and photochemical measurements. Nickel oxide (NiO) thin films prepared by AACVD were determined to have good mechanical strength . with a photocurrent of 7.6 μA cm-2 at 0 V and an onset potential of about 0.10 V. This contrasted with the dark current density of 0.3 μA cm-2 at 0 V. These NiO samples have very high porosity with crystalline columns evidenced by SEM. In comparison with the AACVD methodology, NiO films prepared using a combination of ED and DB show good mechanical strength but a higher photocurrent of 24 μA cm-2 at 0 V and an onset potential of about 0.10 V with a significantly greater dark current density of 7 μA cm-2 at 0 V. The characteristic features shown in the SEM are smaller pores compared to the AACVD method. Copper (II) oxide (CuO) and copper (I) oxide (Cu2O) films were fabricated by AACVD by varying the annealing temperature between 100-325°C in air using a fixed annealing time of 30 min. It was shown by photocurrent density (J-V) measurements that CuO produced at 325 °C was most stable and provided the highest photocurrent of 173 μA cm-2 at 0 V with an onset potential of about 0.23 V. The alignment of zinc oxide (ZnO) nano-rods and nano-tubes fabricated by CBD have been shown to be strongly affected by the seed layer on the FTO substrate. SEM images showed that AACVD provided the best seed layer for aligning the growth of the nano-rods perpendicular to the surface. Nano-rods were successfully altered into nano-tubes using a potassium chloride bath etching method. NiO prepared by both AACVD and the combined ED/DB method were sensitized to absorb more of the solar spectrum using AACVD to deposit CuO over the NiO. A large increase in the photocurrent was observed for the p-type photoelectrode. These p-type photoelectrode showed a photocurrent density of approximately 100 μA cm-2 at 0 V and an onset potential of 0.3 V. This photocathode was then used as a base to produce a solid state p-type solar cell. For the construction of the solid state solar cells several n-type semiconductors were used, these were ZnO, WO3 and BiVO4. WO3 and BiVO4 were successfully produced with BiVO4 proving to be the optimum choice. This cell was then studied more in depth and optimised by controlling the thickness of each layer and annealing temperatures. The best solid state solar cell produced had a Jsc of 0.541 μA cm-2 (541 nA) and a Voc of 0.14 V, TX146 made up of NiO 20 min, CuFe2O4 50 min, CuO 10 min, BiVO4 27 min, using AACVD and then annealed for 30 min at 600°C.
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Sousa, Marcelo Henrique. "Propriétés magnétiques et magnéto-optiques de fluides magnétiques à base de nanoparticules de ferrites de nickel, de cuivre et de zinc." Paris 6, 2003. http://www.theses.fr/2003PA066591.
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Hajjaji, Mohamed el. "Caractérisation et simulation des joints de phases C. C. -C. F. C. : applications à des alliages Fe-Cr-Ni de différentes puretés." Lyon 1, 1986. http://www.theses.fr/1986LYO10015.
Full textAbstract:
Presentation des resultats de simulation des joints de phase entre structures cubiques centrees (c. C), cubiques et cubiques a faces centrees (c. F. C. ). Calcul des indices de coincidence entre les phases cubiques centrees et cubiques a faces centrees liees par une famille de relations d'orientation cristallographique. Etude experimentale des joints de phases entre structures c. C-c. F. C sur des alliages fe-ni-cr. La presence d'aluminium dans ces alliages aboutit a l'apparition de certains precipites. La diffusion des impuretes c ou s dans des alliages de tres haute purete provoque un arrangement localise des atomes autour des joints de phases, ce nouvel arrangement modifiant les relations d'orientation cristalline
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Martin, Cabanas Bruna. "Comportement des produits de corrosion dans le circuit primaire des centrales REP - sorption du cobalt et du nickel sur des ferrites représentatifs." Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00595061.
Full textAbstract:
La corrosion des parties métalliques du circuit primaire des centrales REP engendre la formation de produits de corrosion. Ceux-ci peuvent circuler dans le circuit primaire sous forme de particules colloïdales ou d'espèces dissoutes qui peuvent être activées lors de leur passage sous flux puis adhérer sur les parties métalliques des circuits et sur les gaines des assemblages combustible. Le dépôt des particules ou d'ions activés sur les zones hors flux est alors responsable de la contamination surfacique. Afin d'avoir une meilleure maîtrise de la contamination, la caractérisation (surface spécifique, granulométrie, PCN...) des différentes particules présentes dans le circuit primaire ainsi que l'étude des interactions des produits de corrosion entre eux ou avec les parois (adhésion, sorption...) est nécessaire. Les espèces prises en compte dans cette étude sont, pour les particules : les ferrites de cobalt et de nickel ainsi que la magnétite, pour les matériaux du circuit primaire : l'Inconel 690, le Zircaloy 4 et l'acier inoxydable 304L. La sorption du cobalt et du nickel, principaux responsables de la contamination surfacique, sur les différents produits de corrosion a été réalisée expérimentalement et modélisée grâce au code de calcul ECOSAT. L'évolution de leur charge de surface a également été étudiée. Les données obtenues alimenteront, in fine, différents codes permettant la modélisation de la contamination dans les circuits en tenant compte de l'hydraulique. Le phénomène de sorption est en compétition avec celui de précipitation pour des teneurs en ions supérieures à 10-5 M et un pH élevé. Le dépôt des produits de corrosion, ayant subi ou non la sorption, est favorisé sur une large gamme de pH et quelque soit l'épaisseur de la couche d'oxyde à la surface des matériaux métalliques du circuit. La modélisation confirme que l'hydraulique est à prendre en compte lors de l'étude des phénomènes de dépôt.
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Martin, Cabañas Bruna. "Comportement des produits de corrosion dans le circuit primaire des centrales REP : sorption du cobalt et du nickel sur des ferrites représentatifs." Paris 11, 2010. http://www.theses.fr/2010PA112245.
Full textAbstract:
La corrosion des parties métalliques du circuit primaire des centrales REP engendre la formation de produits de corrosion. Ceux-ci peuvent circuler dans le circuit primaire sous forme de particules colloïdales ou d'espèces dissoutes qui peuvent être activées lors de leur passage sous flux puis adhérer sur les parties métalliques des circuits. Le dépôt des particules activées sur les zones hors flux est alors responsable de la contamination surfacique. Ces particules peuvent également interagir avec les espèces ioniques dissoutes dans le milieu primaire. Alin d'avoir une meilleure maîtrise de la contamination, la caractérisation (surface spécifique, granulométrie, PCN. . . ) des différentes particules présentes dans le circuit primaire ainsi que l'étude de leur interaction avec les espèces dissoutes et les parois (adhésion, sorption. . . ) est nécessaire. Les espèces prises en compte dans cette étude sont, pour les particules : les ferrites de cobalt et de nickel ainsi que la magnétite, pour les matériaux du circuit primaire : l'Inconel 690, le Zircaloy 4 et l'acier inoxydable 304L. La sorption du cobalt et du nickel, principaux responsables de la contamination surfacique, sur les différents produits de corrosion a été réalisée expérimentalement et modélisée grâce au code de calcul ECOSAT. L'évolution de leur charge de surface a également été étudiée. Les données obtenues alimenteront, in fine, différents codes permettant la modélisation de la contamination dans les circuits en tenant compte de l'hydraulique<br>The corrosion of the metal parts in the primary circuit of PWR Ieads to the release of metal oxides particles and ionic species. These corrosion products circulate through the primary circuit and may be activated when they pass through the core. The deposition of the activated particles in areas out of flux is then responsible for surface contamination. These particles can also interact with thc ionic species in the primary medium, contributing to their transport and to their deposition on surfaces outside the flux. Ln order to have better contamination control, characterization (specific surface, sire, PZC. . . ) of differents particles of primary circuit and study of their interaction with soluble species and surfaces (adhesion, sorption. . . ) is necessary. Species take into account in this study are for particles : nickel and cobalt ferrites and magnetite, for primary circuit materials: Inconel 690, Zircaloy 4 and stainless steel 304L. Cobalt and nickel sorption, main responsible of primary circuit contamination, on several corrosion products were experimentally realized and modelised with ECOSAT code. Surface charge were also studied. Data obtained will be introduced in different calculation code in order to modelised contamination in primary circuit under dynamics conditions
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Al-Motasem, Al-Asqalani Ahmed Tamer. "Nanoclusters in Diluted Fe-Based Alloys Containing Vacancies, Copper and Nickel: Structure, Energetics and Thermodynamics." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-89355.
Full textAbstract:
The formation of nano–sized precipitates is considered to be the origin of hardening and embrittlement of ferritic steel used as structural material for pressure vessels of nuclear reactors, since these nanoclusters hinder the motion of dislocations within the grains
of the polycrystalline bcc–Fe matrix. Previous investigations showed that these small precipitates are coherent and may consist of Cu, Ni, other foreign atoms, and vacancies. In this work a combination of on–lattice simulated annealing based on Metropolis Monte Carlo simulations and off–lattice relaxation by Molecular Dynamics is applied in
order to determine the structure, energetics and thermodynamics of coherent clusters in bcc–Fe. The most recent interatomic potentials for Fe–Cu–Ni alloys are used. The atomic structure and the formation energy of the most stable configurations as well as their total and monomer binding energy are calculated.
Atomistic simulation results show that pure (vacancy and copper) as well as mixed (vacancy-copper, copper-nickel and vacancy-copper-nickel) clusters show facets which correspond to the main crystallographic planes. Besides facets, mixed clusters exhibit a core-shell structure. In the case of v_lCu_m, a core of vacancy cluster coated with copper atoms is found. In binary Cum_Ni_n, Ni atoms cover the outer surface of copper cluster.
Ternary v_lCu_mNi_n clusters show a core–shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. It has been shown qualitatively that these core–shell structures are formed in order to minimize the interface energy
between the cluster and the bcc-Fe matrix. Pure nickel consist of an agglomeration of Ni atoms at second nearest neighbor distance, whereas vacancy-nickel are formed by a vacancy cluster surrounded by a nickel agglomeration. Both types of clusters are called quasi-cluster because of their non-compact structure. The atomic configurations of quasiclusters can be understood by the peculiarities of the binding between Ni atoms and vacancies. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The structure of the clusters found in the present work is consistent with experimental observations and with results of pairwise calculations. In agreement with experimental observations and with recent results of atomic kinetic Monte Carlo simulation it is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu.
For pure vacancy and pure copper clusters an atomistic nucleation model is established, and for typical irradiation conditions the nucleation free energy and the critical size for cluster formation have been estimated. For further application in rate theory and object kinetic Monte Carlo simulations compact and physically–based fit formulae are
derived from the atomistic data for the total and the monomer binding energy. The fit is based on the structure of the clusters (core-shell and quasi-cluster) and on the classical capillary model.
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Junior, Amilton Barbosa Botelho. "Recuperação de níquel e cobalto a partir de lixiviado de níquel laterítico utilizando resinas quelantes e processo de pré-redução." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-25032019-091140/.
Full textAbstract:
Níquel laterítico compõe 70% das reservas disponíveis do metal. A produção de níquel a partir dessas reservas representa 40%, dos quais é possível extrair também cobre e cobalto. Isso ocorre devido ao alto teor de impurezas, principalmente ferro. Com a crescente demanda desses metais, o uso das reservas de lateritas de níquel passou a ser mais profundamente investigado, assim como o desenvolvimento de processos hidrometalúrgicos. Nesse caso, o íon férrico prejudica a recuperação do níquel e do cobalto, uma vez que em trocas iônicas esse metal compete na ocupação dos sítios catiônicos. Em processos de extração por solvente um efeito semelhante é observado. Além disso, durante a eventual precipitação do ferro ocorre a coprecipitação. Assim, para a troca iônica, o íon ferroso pode ser menos prejudicial do que o férrico. O presente trabalho teve por objetivo o estudo do processo de redução do íon férrico em solução aquosa, e também a posterior obtenção de cobalto e níquel por meio de resinas quelantes. Estudou-se o processo de redução do íon férrico e o efeito na adsorção de metais por troca iônica. Os ensaios de redução química do íon férrico em solução foram estudados utilizando ditionito de sódio, metabissulfito de sódio e sulfito de sódio. Os ensaios com os agentes redutores ditionito e metabissulfito de sódio foram feitos em São Paulo, e os ensaios com o sulfito de sódio foram feitos na The University of British Columbia. Os agentes redutores foram adicionados na solução monoelementar de ferro para redução do potencial redox. As variáveis potencial redox, entre 860mV e 240mV; pH, entre 0,5 e 3,5; temperatura, entre 25°C e 60°C; e tempo, entre 30min e 96 horas, foram estudadas em frascos erlenmeyer sob agitação constante. Analisou-se, então, a redução do íon férrico em solução multielementar de níquel laterítico. Nos ensaios de troca iônica, realizados em batelada e em coluna, utilizou-se a resina quelante Lewatit TP 207, de grupo funcional iminodiacetato, e a resina Lewatit TP220, de grupo funcional bis-picolilamina. Três soluções foram estudadas: uma preparada com Fe(III), outra com Fe(II) e a terceira com Fe(III) após o processo de pré-redução. Os ensaios em batelada foram realizados com a utilização de frascos erlenmeyer, sob agitação constante, com 100mL de solução para 1mL de resina. Estudou-se o efeito do pH, entre 0,5 e 3,5; tempo, entre 30min e 480min; e temperatura, entre 25°C e 60°C. Nos ensaios em sistema contínuo, as três soluções foram alimentadas em colunas de vidro preenchidas com resina. A solução foi alimentada com bombas peristálticas a vazão constante. Para eluição das colunas, ácido sulfúrico 1mol.L-1 foi alimentado na coluna com utilização de bomba peristáltica. A segunda parte do trabalho, realizado na The University of British Columbia, foi o estudo do uso de sulfito de sódio no processo de pré-redução. Foram estudadas duas resinas: a Lewatit TP 207, seletiva para cobre; e a Lewatit TP 220, seletiva para níquel e cobalto. O sulfito de sódio foi adicionado na solução para redução do potencial, em frascos, e colocado sob agitação constante. Após reação, as soluções foram colocadas em contato com a resina quelante, e ficaram em agitação. Os ensaios em batelada foram realizados e o efeito do pH estudado entre 0,5 e 3,5. No processo em coluna, a Coluna 1, preenchida com a resina Lewatit TP 207, foi utilizada para remoção do cobre; e a solução de saída foi alimentada na Coluna 2, preenchida com a resina Lewatit TP 220. Para a eluição, foram estudados os ácidos clorídricos e sulfúricos em duas diferentes concentrações, 1mol.L-1 e 2mol.L-1. Hidróxido de sódio foi utilizado para remover o ferro na solução obtida na saída da Coluna 2. A separação do cobalto da solução foi feita utilizando a técnica de extração por solventes (Cyanex 272 20%), estudando o efeito do pH, 4,0 e 5,0, e da temperatura, 25°C e 65°C. Os resultados mostraram que a redução do íon férrico utilizando ditionito de sódio foi de 100% na solução monoelementar e de 70% na multielementar contendo os outros metais. Nos ensaios de troca iônica em batelada, utilizando a resina TP 207, 62% do cobre foi adsorvido na solução após processo de pré-redução. Para solução com Fe(II), a adsorção de cobre foi de 61%; e para solução com Fe(III), 49%. Nos ensaios de troca iônica após pré-redução do ferro com sulfito de sódio, a adsorção do cobre foi de 69% em pH 2,0 pela resina TP 207. A resina TP 220 foi mais seletiva para níquel e cobalto em pH 2,0, em que as adsorções destes metais foram 32,5% e 69%, respectivamente. Nos ensaios em coluna, a Coluna 1 foi utilizada para remoção de cobre, porém houve perda de 17% de níquel e 7% de cobalto. Na alimentação da Coluna 2, verificou-se que 98% do níquel e 84% do cobalto foram adsorvidos. A solução obtida da Coluna 2 teve concentração de 618mg.L-1 de ferro, 13231mg.L-1 de níquel e 179mg.L-1 de cobalto. A remoção de 100% do ferro foi possível em pH 4,0. Para separação do cobalto da solução rica em níquel, utilizou-se a extração por solventes com o Cyanex 272 20% em querosene, no qual 99% do cobalto foi separado da solução a 65°C e pH 5,0, sem perda de níquel. Para estudos futuros, a remoção do cobre no início do processo pode ser explorada com a utilização de outras técnicas, a fim de se evitarem perdas de níquel e cobalto. Outro ponto que pode vir a ser explorado é a máxima utilização das colunas de troca iônica nas mesmas condições deste trabalho - solução com Fe(III), com Fe(II) e após processo de pré-redução - sobretudo em escala piloto, para estudar o efeito do estado de oxidação do ferro em um possível envenenamento da resina.<br>Nickel laterite ores represent 70% of the available metal reserves. The nickel production from these reserves represents 40%, where it is also possible extract copper and cobalt. It occurs due to the high impurities content, mainly iron. With the growing demand of these metals, the use of nickel laterite reserves became more deeply investigated, as well as hydrometallurgical process development. In this case, the ferric iron difficult the nickel and cobalt recovery, once in ion exchange processes this metal competes in the occupation of the cationic sites. In solvent extraction processes the same effect is observed. Besides that, during the eventual iron precipitation there is a co-precipitation. Therefore, for ion exchange, ferrous iron may be less damaging than ferric iron. The aim of this work was to study the reducing process of ferric iron in aqueous solution, and also the subsequent obtaining of cobalt and nickel through chelating resins. It was studied the reducing process of ferric iron and the effect of it in metals adsorption by ion exchange. Experiments of chemical reduction of ferric iron in solution were studied using sodium dithionite, sodium metabisulfite and sodium sulfite. Experiments with reducing agents sodium dithionite and metabisulfite were performed in São Paulo, and experiments with sodium sulfite were performed in The University of British Columbia. Reducing agents were added in ferric iron mono-elementary solution to decrease the redox potential. The variables potential redox, between 860mV and 240mV; pH, between 0,5 and 3,5; temperature, between 25°C e 60°C; and time, between 30min and 96 hours were studied in erlenmeyer flasks under constant stirring. Then, analyzed ferric iron reduction in multielementary solution of nickel laterite. In ion exchange experiments, performed in batch and column, it was used chelating resin Lewatit TP 207, with iminodiacetate functional group, and resin Lewatit TP 220, with bis-picolylamine functional group. Three solutions were studied: prepared with Fe(III), other with Fe(III) and the third with Fe(III) after pre-reducing process. Experiments in batch system were performed using erlenmeyer flasks, under constant stirring, with 100mL of solution to 1mL of resin. It was studied the effect of pH, between 0,5 and 3,5, time, between 30min and 480min, and temperature, between 25°C e 60°C. In experiments in continuous system, the three solutions were fed in glass columns filled with resin. The solution was fed using peristaltic pumps at constant flow rate. For column elution, sulfuric acid 1mol.L-1 was fed to the column using peristaltic pumps. The second part of this work, performed at The University of British Columbia, was the study of sodium sulfite application at prereducing process. It was studied two resins: Lewatit TP 207, selective for copper, and Lewatit TP 220, selective for nickel and cobalt. Sodium sulfite was added to the solution to decrease the potential, in flasks and it was placed under constant stirring. After reaction, the solution was placed in contact to the chelating resin, which was placed under stirring. Batch experiments were performed, and the effect of pH was studied between 0,5 and 3,5. In column process, the Column 1, filled with Lewatit TP 207, was used for copper removal, and output solution was feed in Column 2, filled with Lewatit TP 220. For the elution, it was studied sulfuric and hydrochloric acids in two different concentrations, 1mol.L-1 e 2mol.L-1. Sodium hydroxide was used for iron removal from solution obtained in Column 2 output. Cobalt separation was performed using solvent extraction technique (Cyanex 272 20%), studying the effect of pH, 4,0 and 5,0, and temperature, 25°C e 65°C. Results shows that ferric iron reduction using sodium dithionite was 100% in mono-elementary solution and 70% in multi-elementary solution with other metals. In ion exchange experiments performed in batch using resin TP 207, 62% of copper was adsorbed by the resin after pre-reducing process. For solution with Fe(II), the copper adsorption was 61%, and for solution with Fe(III), 49%. In ion exchange experiments after pre-reducing process using sodium sulfite, the copper adsorption was 69% at pH 2,0 by the resin TP 207. The resin TP 220 was more selective for nickel and cobalt at pH 2,0, where these metals adsorptions were 32,5% and 69%, respectively. In experiments performed in column, the Column 1 was used for copper removal, however there were losses of nickel (17%) and cobalt (7%). In the feeding of Column 2, it was found that 98% of nickel and 84% of cobalt were adsorbed. Solution obtained in Column 2 had concentration of iron 618mg.L-1, nickel was 13231mg.L-1 and cobalt 179mg.L-1. The iron removal was 100% at pH 4,0. For cobalt separation in nickel-rich solution, it was used the solvent extraction with Cyanex 272 20% with kerosene, where 99% of cobalt was separated from solution at 65°C and pH 5,0, without nickel loss. For future studies, the copper removal in the beginning of the process can be explored using other techniques, in order to avoid nickel and cobalt losses. Another point that can be explored is the maximum use of ion exchange columns in the same conditions of this work - solution with Fe(III), with Fe(II) and after the pre-reducing process - mostly on a pilot scale, to study the effect of iron oxidation state on possible resin poisoning.
45
Abbali, Zineb. "Etude de la cristallisation de ferrites spinelles dans des verres borates." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376110731.
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Lundberg, Daniel, Filip Wilson, Hjalmar Gunnarsson, Leo Sjörén, Robin Xu, and Erik Djurberg. "Long term aging and creep exposure for advanced heat resistant alloys : A phase analysis." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446407.
Full textAbstract:
This project was ordered by Sandvik Materials Technology and was performed by a group of students at Uppsala university. The purpose of the project was to study precipitation behavior and structure stability in six advanced heat resistant alloys. Each sample were subjected to a creep rupture test in 600 or 700°C depending on the alloy type. Two parts of each alloy where examined; one part which had been affected by creep and another part which was unaffected by creep. A literature study was performed first to gain knowledge of the scientific theory utilized in this project, namely creep, precipitation hardening, and about the different materials which were analyzed. Preliminary results for the phase composition of the materials were obtained from a Thermo-Calc (TC) simulation. The SEM-images showed nothing noteworthy for any sample due to the roughness of the sample surfaces. The EDS-analysis showed chromium depletion in the centers of the aged samples of HT9 and Sanicro® 75X. Other minority phases such as Cr23C6 in Sanicro®70, P-phase and a titanium nitride phase in sanicro® 60X, VB in Esshete 1250 and Sigma-phase in 4C54 were identified using EDSmapping. It was found that when using XRD to analyze the phase compositions of small samples it is impractical to have the samples cast in bakelite beforehand. The XRD-results obtained in this project showed that more than 90% of the XRD diffractogram for every sample was graphite, which made the identification of minority phases impossible. The quality of the LOM-images varied greatly between samples, for 4C54 grain sizes were measured in all images, for Esshete 1250 grain sizes were measured for the crept sample, and for Sanicro® 60X measurements could only be taken from one image. Most of the sample preparation was insufficient to achieve the test results necessary for complete microstructural analysis and phase analysis of the samples. The mistakes in the practical steps of the project were noted and improvements for these mistakes are presented in the conclusion.
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Karlsson, Lovisa. "Waste Water Treatment - A Case Study : Removal of Ni, Cu and Zn through precipitation and adsorption." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-26130.
Full textAbstract:
Waste water containing high concentrations of dissolved metals were delivered to the environmental company SAKAB. After standard treatment procedure, involving regulation of pH and addition of flocculation agents, the water still contained nickel concentrations of 26 mg/l. Since SAKAB’s regulatory concentration limit value for nickel in outgoing water is 0.5 mg/l, further treatment was necessary. According to the supplier of the water, a complexing agent similar to EDTA had been added to the water. The aim of this study was to decrease concentrations of nickel, zinc and copper. One part of this study was the precipitation experiments as hydroxide, sulphide and adsorption to hydrous ferric oxide. The other part was adsorption to natural, organic materials such as peat, wood chips and one commercial bark compost. Adsorption to hydrous ferric oxide was the most efficient of the precipitation experiments. When 2000 mg FeCl3 was added to 100 ml waste water and pH of the solution was adjusted to pH 8, a decrease up to 74 % of total nickel concentrations was achieved. Most efficient of the adsorption experiments were the one with commercial bark compost which decreased nickel concentrations in solution up to 94 % after 20 hours of agitation.
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Pappas, Adlreburg Nickolas. "To Make Iron of Iron : A Comprehensive Analytical Study of Spade Shaped Iron Bars." Thesis, Stockholms universitet, Arkeologiska forskningslaboratoriet, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-145694.
Full textAbstract:
This thesis aims to provide adequate analytical information on the spade shaped iron bars of Norrland and central Sweden. While their significance has been thoroughly debated for decades, analytical research on them has been confined to cases of single artefacts or theoretical interpretations of their value, meaning and origin. In this study a comprehensive approach is taken into consideration. Based on X-Ray fluorescence (XRF), scanning electron microscopy (SEM) and metallographical analysis this thesis seeks to facilitate new interpretations on quality, production centres and usage based on analytical results. Aiming to settle some of the long lasting questions regarding the artefacts while producing results which can further the discussion by raising new questions, previously unasked.
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Tesařová, Hana. "Strukturní a mechanické charakteristiky niklových litin s kuličkovým grafitem." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233891.
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The aim of this dissertation work is the evaluation of the influence of nickel alloying on the structure and mechanical properties, both monotonic and dynamic, of nodular cast iron with ferritic and bainitic matrix. Two chock melts with 0.5 and 2.7 % Ni were used to study the nickel influence. The quantitative evaluation of structure of these melts using image analysis was done and basic tensile mechanical properties were determined. Subsequently, the time optimization of two-stage ferritic annealing and isothermal austempered heat treatment at 375 °C was performed with the aim to obtain optimal ferritic and bainitic structures with best static and dynamic mechanical properties. After ferritic annealing the nickel alloying contributes to substitution hardening of ferritic matrix which positively affects its strength and other mechanical properties. The higher nickel content in the bainitic structure causes the shift of phase transformation times to longer times which results in restricted production of small carbides and in bigger volume of retained austenite. These features were confirmed by observation in transmission electron microscope. Precise tensile and low cycle fatigue tests at temperatures 23 and – 45 °C were performed on the optimized structures of both nodular cast irons. As a result of the notch effect of graphite nodules, microplastic deformation of both nodular cast irons was observed at stresses which were lower than the yield stress. The Hollomon's equation very well describes the individual parts of tensile curves for both nodular cast irons including their mutual comparison. From the low cycle fatigue tests, the cyclic hardening/softening curves, the evolution of elastic modulus and hysteresis loop shape parameters, cyclic stress-strain curves and fatigue life curves were obtained for both temperatures and materials. Moreover, the decrease of retained austenite volume was measured by neutron diffraction and the evolution of surface relief was characterized during cyclic straining for both austempered nodular cast irons at both temperatures. On the basis of these results both cyclic plasticity and fatigue degradation mechanisms in relation to the cyclic strain localization were described for both nodular cast irons.
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Ying-HaoWang and 王盈皓. "The Effects of Nickel Substitution on Bismuth Ferrite." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/20251920478389202766.
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