<p>In the present work, the thermodynamic activites of ironoxide, denoted as "FeO" in the slag systems Al₂O₃-"FeO", CaO-"FeO", "FeO"-SiO₂, Al₂O₃-"FeO"-SiO₂, CaO-"FeO"-SiO₂and "FeO"-MgO-SiO₂were investigated by employing the gasequilibration technique at steelmaking temperatures. Thestrategy was to expose the molten slag mixtures kept inplatinum crucibles for an oxygen potential, determined by aCO/CO₂-ratio. A part of the iron reduced from the "FeO"in the slag phase was dissolved into the Pt crucible.</p><p>In order to obtain the activites of "FeO", chemical analysisof the quenched slag samples together with thermodynamicinformation of the binary metallic system Fe-Pt is required.Careful experimental work was carried out by employing asolid-state galvanic cell technique as well as calorimetricmeasurements in the temperature ranges of 1073-1273 K and300-1988 K respectively. The outcome of these experiments wasincorporated along with previous studies into a CALPHAD-type ofthermodynamic assessment performed with the Thermo-Calc™software. The proposed equilibrium diagram enabledextrapolation to higher temperatures.</p><p>The experimentally obtained activites of "FeO" in thepresent work, along with earlier investigations were assessedwith the KTH slag model, THERMOSLAG©. New binaryparameters were evolved and incorporated in THERMOSLAG©.The present model calculations are compared with othercommercially available software such as F*A*C*T™andThermo-Calc™. The validity of the modified model wasinvestigated by measurements carried out in case of Al₂O₃-"FeO"-SiO₂, CaO-"FeO"-SiO₂and "FeO"-MgO-SiO₂ternary slags. The potential of the model tocompute the activities in the case of multicomponent slags wasdemonstrated.</p><p>A correlation between the activity of a metallic oxide in aternary slag system and the sulphide capacity of the slag wasinvestigated by using the solubility of sulphur in the binarysystems CaO-SiO₂and Al₂O₃-CaO along with the sulphide capacity of the Al₂O₃-CaO-SiO₂system. The estimated values of the activitieswere found to be in good agreement with the measured values.This correlation also gives the possibility to elucidate theapplicability of Henry's law to the activity of a metallicsulphide and to determine the order in the affinity of a cationto sulphur between two metallic oxides in a slag.</p><p>Model calculations were performed with THERMOSLAG^©, by using plant data from the ladle refiningprocess at OVAKO Steel, Hofors, Sweden. It was found thatoxygen estimations in the metal from the "FeO" analyses ofslags, obtained by conventional sampling and analysis methodwere less reliable. Reliable estimation of the oxygen levelsutilising the sulphur partition between the slag and the metalwere carried out using THERMOSLAG© software.</p><p><b>Keywords:</b>Thermodynamics, Activity, Galvanic cell,Calorimetry, Gas equilibration technique, Iron-platinum alloys,FeO, Slags, Modelling, Ladle</p>

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Une méthode de dépôt de platine sur or a récemment été développée. Le substrat est, dans une première phase, modifié par un dépôt d’un métal moins noble que le platine, tel que le cuivre ou le plomb. Ce dépôt métallique est, dans une seconde phase, mis en contact avec une solution de sel de platine et la substitution spontanée du cuivre ou du plomb par du platine métallique se produit.<p><p>\ / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Iron platinum (FePt) has attracted growing interest because of its high Curie temperature, magneto-crystalline anisotropy and chemical stability. Nanoparticles (NPs) made of this alloy are promising candidates for a wide range of biomedical applications including magnetic separation, magnetic targeted drug delivery, hyperthermia for cancer therapy and also as magnetic resonance imaging (MRI) contrast agents. This thesis presents the synthesis, functionalization and characterization of FePt NPs along with a toxicity study and an investigation into their application as MRI contrast agents. Regarding their synthesis, different approaches have been explored including the co-reduction of Fe and Pt precursors in an aqueous media, the thermal decomposition in a conventional high-boiling solvent such as benzyl ether, and in low-melting organic salts (ionic liquids). The data revealed an inhomogeneous composition distribution of Fe and Pt between particles obtained in aqueous media, due to the iron salts hydrolysis, and a mismatch in the co-reduction kinetic of the two metal precursors. While the iron content in the NPs could be increased by using more hydrolytically stable iron precursors or stronger reducing agents, there are remaining limiting parameters which prevent further Fe content increase in NPs. In contrast, by excluding the water from the reaction system and using a Fe²⁻ iron precursor, homogenous 1:1 Fe to Pt ratio NPs can be obtained through a modified thermal decomposition pathway in benzyl ether. Based on the study of synthesis in this conventional chemical, the potential of ionic liquids (ILs) to be used as novel solvents for FePt NPs synthesis was further explored. It was then demonstrated that ionic liquids (ILs) can not only be used as a solvent for synthesis of FePt NPs, but also can provide an exciting alternative pathway to direct synthesis fct-FePt NPs. In the context of the bioapplication of FePt NPs, a family of FePt NPs was specifically designed to enhance their MRI contrast agents properties. In contrast with previous reports, this thesis demonstrates that FePt NPs can be made non-toxic and provides the first data on their cellular uptake mechanisms. A six times increase in the FePt based T₂ contrast properties compared to clinical iron oxide NPs is reported. The relationship between the MRI contrast properties and the NPs architecture is explored and rationalised as the basis for the design of NPs as enhanced MRI contrast agents. Finally, the first observations of cellular and in vivo MR imaging with FePt NPs is also reported. This study opens the way for several applications of FePt NPs such as regenerative medicine and stem cell therapy, thus providing a bio-platform to develop novel diagnostic and therapeutic agents.

Made available in DSpace on 2014-10-09T12:42:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:52Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:42:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:52Z (GMT). No. of bitstreams: 0 / Células a combustível de membrana polimérica têm cada vez mais se destacado como meio na obtenção de energia, pela sua alta eficiência e potencial para fazê-la de modo sustentável. Entretanto muitos ainda são os desafios para consolidá-la comercialmente. Dentre eles, a aglomeração e a perda de área ativa em catalisadores suportados em carbono recebem um destaque especial, principalmente em células PEM de temperatura elevada de operação. Eletrocatalisadores não suportados, baseados em nanoarquiteturas de geometria controlada, têm se tornado uma tendência em diversas frentes de pesquisa. Tal fato se deve à alta eficiência e estabilidade atingidas por sistemas nanométricos organizados, além da possibilidade em se criar superfícies funcionais adaptadas a reações específicas. O trabalho de pesquisa buscou o desenvolvimento de sistemas catalíticos não suportados, de alta área superficial, como alternativa a eletrocatalisadores nanoparticulados suportados em carbono, a fim de se reduzir a perda sobre a área ativa quando submetidos às condições de operação em células a combustível. O trabalho explorou dois conceitos, a confecção de nanotubos de platina e a confecção de nanofios nanoporosos à base de platina vítrea. Para este desenvolvimento foram estudados e caracterizados os efeitos da dissolução seletiva, em escala nanométrica, acoplados à conformabilidade de metais amorfos e à utilização da troca galvânica como ferramenta de síntese de superfícies. Tais estudos foram utilizados como base para o projeto de sistemas catalíticos não suportados. Os materiais propostos foram avaliados quanto a sua atividade e estabilidade frente a reações comuns em células a combustível. Tais sistemas demonstraram uma alta estabilidade em relação à sua área ativa, em ensaios de durabilidade, assim como uma alta utilização do metal nobre, tornando-os promissores para a tecnologia de células a combustível. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP