Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : leaves 77-79. / M.S.

<p> In this thesis the Mössbauer spectroscopic technique was applied to a wide variety of antimony compounds. </p> <p> Antimony chalcogenides, oxides and a phosphate were studied. No evidence could be found to support the existence of Sb₂S₅. Sb₂O₄ was found to contain Sb(III) and Sb(V) rather than Sb(IV). SbPO₄ and the Sb(III) site in Sb₂O₄ had similar Mössbauer parameters in agreement with their structures. </p> <p> Hexahalo complexes of antimony, some of which contain both (III) and (V) oxidation states, have been examined. These exhibit extremely large isomer shifts which are interpreted as indicating no involvement of the 5s electron pair of Sb in the bonding scheme. </p> <p> A study was made of some antimony-fluorine systems. The spectra of KSbF₅, KSbF₄ and KSb₂F₇ and similar salts were interpreted in terms of the known structures. Other complex antimony fluorides and fluorosulphates have also been examined and possible structures suggested. </p> <p> Three antimony-containing minerals, nadorite, tetrahedrite, and boulangerite have been examined, and attempts made to rationalise the Mössbauer data in terms of known structural parameters. </p> / Thesis / Master of Science (MSc)

Neste trabalho introduzimos a representação de estados coerentes de fônons e desenvolvemos o formalismo para o tratamento do campo sujeito a excitações lineares. Obtemos a equação de Fokker-Planck para a função distribuição associada ao operador densidade assim como as amplitudes dos estados devidas à excitação. Como aplicação, usamos a interação fóton-núcleo para o estudo de algumas propriedades fundamentais do efeito Mössbauer. Obtivemos, de uma maneira muito simples, a energia e o momento linear transferidos ao cristal devido à absorção ou emissão de um raio gama e a relação entre o operador criação do estado coerente /&#946;> e a função de espalhamento Fs(k, t). Mostramos claramente que o efeito Mössbauer é devido a transições de zero-fonons O efeito da temperatura sobre probabilidades de trasições e sobre medições também aparece de um modo claro / We introduce the representation of coherent states of phonons and develop the procedures to treat the field with linear excitation. We obtain the Fokker-Planck equation of the distribution function associated with the density operator as well as the amplitudes of the states due to the excitation. As an application, we use the interaction photon-nucleus in the study of some fundamental properties of Mössbauer effect. We obtain, in a very simple way, the energy and linear momentum transferred to the crystal due to absorption or emission of a gamma ray and the connection between the creation operator of the /&#946;> coherent state and the scattering function Fs(k, t). We show clearly that Mössbauer effect is due to zero-phonon transitions. The effect of temperature on transition probabilities and measurements arises in a clear way

Realizamos medidas Mossbauer a temperatura ambiente das ligas de SM IND.2 (CO IND.1-XFE IND.X) ind.17, COM X = 0.1 A 0.6, E DAS LIGAS sm (CO IND.0.90-VFE IND.VCU IND.0.08ZR IND.0.02) ind.8.35, Com V variando de 0.23 A 0.27. Estas amostras foram caracterizadas por difração de raio X. elas apresentaram a estrutura romboédrica do tipo th ind.2zn ind.17 (R3barraM) com os átomos de Fe ocupando quatro sítios cristalográficos distintos todos os espectros obtidos apresentaram desdobramento magnético e um nível de complexidade alto, resultado da sobreposição de quatro sítios distintos de átomos de fe. Os espectros foram ajustados e através desse ajuste determinados os parâmetros hiperfinos associados a cada sítio e suas respectivas populações. Os resultados obtidos das populações dos sítios nas series de compostos Sm ind.2 (CO IND.1-XFE IND.X) ind.17 revelaram a forte preferência dos átomos de FE de ocupar os sítios halteres (2c). No modelo proposto por ray, à função do ZR e o de deslocar pares de FE dos sítios halteres, substituindo-os por pares ZR-vacância. Através dos resultados obtidos pudemos também comprovar esta hipótese através da análise das populações dos sítios das duas series de amostras. / Mössbauer measurements were carried out at room temperature for Sm2(Co1-xFex)17 alloys with x=0,1 to 0,6 and Sm2(Co0.9-vFevCu0.08Zr0.02)8.35, with v=0.23 to 0.27. All samples were characterized by X-ray diffraction. They showed rhombohedral structure of th2Zn17 type (R3m), where Fe atoms occupy four crystallographic sites. All spectra showed magnetic splitting and a high complexity resulting from the superposition of four Fe sites. Hyperfine parameters and site populations were obtained by least-squares fitting of the spectra. For Sm2(Co1-xFex)17 alloys, Fe atoms show a strong preference for 2c (dumbbell) sites. In the Zr-containing alloys, on the other hand, this tendency is significantly reduced, confirming A. E. Rays hypothesis on the role of Zr in the improvement of the magnetic properties of these alloys through metallurgical treatments.

Realizamos medidas Mossbauer a temperatura ambiente das ligas de SM IND.2 (CO IND.1-XFE IND.X) ind.17, COM X = 0.1 A 0.6, E DAS LIGAS sm (CO IND.0.90-VFE IND.VCU IND.0.08ZR IND.0.02) ind.8.35, Com V variando de 0.23 A 0.27. Estas amostras foram caracterizadas por difração de raio X. elas apresentaram a estrutura romboédrica do tipo th ind.2zn ind.17 (R3barraM) com os átomos de Fe ocupando quatro sítios cristalográficos distintos todos os espectros obtidos apresentaram desdobramento magnético e um nível de complexidade alto, resultado da sobreposição de quatro sítios distintos de átomos de fe. Os espectros foram ajustados e através desse ajuste determinados os parâmetros hiperfinos associados a cada sítio e suas respectivas populações. Os resultados obtidos das populações dos sítios nas series de compostos Sm ind.2 (CO IND.1-XFE IND.X) ind.17 revelaram a forte preferência dos átomos de FE de ocupar os sítios halteres (2c). No modelo proposto por ray, à função do ZR e o de deslocar pares de FE dos sítios halteres, substituindo-os por pares ZR-vacância. Através dos resultados obtidos pudemos também comprovar esta hipótese através da análise das populações dos sítios das duas series de amostras. / Mössbauer measurements were carried out at room temperature for Sm2(Co1-xFex)17 alloys with x=0,1 to 0,6 and Sm2(Co0.9-vFevCu0.08Zr0.02)8.35, with v=0.23 to 0.27. All samples were characterized by X-ray diffraction. They showed rhombohedral structure of th2Zn17 type (R3m), where Fe atoms occupy four crystallographic sites. All spectra showed magnetic splitting and a high complexity resulting from the superposition of four Fe sites. Hyperfine parameters and site populations were obtained by least-squares fitting of the spectra. For Sm2(Co1-xFex)17 alloys, Fe atoms show a strong preference for 2c (dumbbell) sites. In the Zr-containing alloys, on the other hand, this tendency is significantly reduced, confirming A. E. Rays hypothesis on the role of Zr in the improvement of the magnetic properties of these alloys through metallurgical treatments.

Une radiothérapie efficace nécessite un dépôt de dose localisé à la tumeur, et donc un contraste entre le tissu tumoral et les tissus sains environnants. Une irradiation de basse énergie monochromatique au synchrotron d'une tumeur chargée en éléments lourds permet de maximiser l'interaction photoélectrique dans la tumeur et d'épargner les tissus sains, car les photoélectrons et les électrons Auger produits ont un TEL très élevé et déposent leur énergie autour des éléments lourds, augmentant fortement le dépôt de dose. Ils peuvent induire des dommages à l'ADN (cassures double brin) fortement létaux. Un autre phénomène permet également de promouvoir l'émission d'électrons Auger et d'augmenter ainsi la dose, l'effet Mössbauer. Cette interaction résonante et sans recul spécifique à certains isotopes dont le 57Fe présente une section efficace 450 fois plus importante que celle de l'effet photoélectrique. Ce travail de doctorat a évalué l'utilisation in vitro de nanoparticules de magnétite combinées à ces deux effets physiques. Les nanoparticules présentent une internalisation et une distribution dans les cellules F98 qui sont très propices à la radiosensibilisation : de grandes concentrations proches du noyau des cellules, et peu de toxicité ont été obtenues. Ceci a permis d'obtenir par photoactivation des NPFe un facteur d'augmentation de 3 ce qui est considérable. Ce travail multidisciplinaire rassemble des expériences de physique, de biologie et de chimie, pour évaluer les applications de nanoparticules de fer à la radiothérapie. / An efficient radiotherapy needs a localized dose to the tumour, which means a high contrast between tumorous and healthy tissues. A synchrotron low energy monochromatic irradiation of a tumour charged in high-Z elements allows maximizing photoelectric interactions in the tumour and spare the healthy tissues. Photoelectrons and high LET Auger electrons thus produced deposit their energy locally, enhancing radiation dose to tumor cells. Another interaction allows to enhance the dose by Auger electrons: the Mössbauer effect. This resonant and recoilless interaction specific to some isotopes like 57Fe has a cross section 450 times bigger than photoelectric effect. This thesis evaluates the in vitro use of magnetite nanoparticles combined with those 2 types of interactions. The nanoparticles evaluated present a high internalisation and a perinuclear distribution inside F98 cells. A dose-enhancement factor of 3 was obtained by photo activation of the iron Nps, this represents a huge increase. This multidisciplinary work encompasses experiments in chemistry, physics and biology in order to evaluate the applications of magnetite nanoparticles to radiotherapy.

Neste trabalho introduzimos a representação de estados coerentes de fônons e desenvolvemos o formalismo para o tratamento do campo sujeito a excitações lineares. Obtemos a equação de Fokker-Planck para a função distribuição associada ao operador densidade assim como as amplitudes dos estados devidas à excitação. Como aplicação, usamos a interação fóton-núcleo para o estudo de algumas propriedades fundamentais do efeito Mössbauer. Obtivemos, de uma maneira muito simples, a energia e o momento linear transferidos ao cristal devido à absorção ou emissão de um raio gama e a relação entre o operador criação do estado coerente /&#946;> e a função de espalhamento Fs(k, t). Mostramos claramente que o efeito Mössbauer é devido a transições de zero-fonons O efeito da temperatura sobre probabilidades de trasições e sobre medições também aparece de um modo claro / We introduce the representation of coherent states of phonons and develop the procedures to treat the field with linear excitation. We obtain the Fokker-Planck equation of the distribution function associated with the density operator as well as the amplitudes of the states due to the excitation. As an application, we use the interaction photon-nucleus in the study of some fundamental properties of Mössbauer effect. We obtain, in a very simple way, the energy and linear momentum transferred to the crystal due to absorption or emission of a gamma ray and the connection between the creation operator of the /&#946;> coherent state and the scattering function Fs(k, t). We show clearly that Mössbauer effect is due to zero-phonon transitions. The effect of temperature on transition probabilities and measurements arises in a clear way

Ce mémoire est consacré à la recherche de matériaux d'électrode positive pour batteries Li-ion et plus particulièrement aux phases de type olivine : LiFePO4, LiFe1-yMnyPO4, LiFe1-yCoyPO4 et LiMnyCo1-yPO4 obtenues par voie céramique. Une étude des propriétés physico-chimiques et structurales de ces composés a été réalisée par les techniques classiques de la Chimie du Solide et de la Science des Matériaux : spectrométrie Mössbauer de 57Fe, microscopie MEB et diffraction des rayons X. L'objectif de cette étude est d'identifier et de comprendre les mécanismes de réaction lors du cyclage de la batterie qui peuvent améliorer ou limiter les performances de la batterie.Cette étude a permis de montrer la complémentarité de la spectrométrie Mössbauer et de la diffraction des rayons X pour l'analyse des mécanismes d'oxydo-réduction mis en jeu dans les réactions électrochimiques. A partir du mécanisme biphasé bien connu de LiFePO4, des mécanismes électrochimiques en trois étapes et les phases formées lors du cyclage ont été identifiés pour les phases substituées au manganèse. L'aptitude de ces composés à fonctionner comme matériaux d'électrode positive de batteries Li-Ion de puissance a été démontrée par des cyclages à longue durée à différentes températures et vitesses de cyclage. / This thesis is devoted to finding positive electrode materials for Li-ion batteries and more particularlycompounds of olivine type: LiFePO4, LiFe1-yMnyPO4, LiFe1-yCoyPO4 and LiMnyCo1-yPO4. An in-depth study of their physicochemical and structural properties was done combining Solid State Chemistry and Material Sciences techniques: Mössbauer spectrometry of 57Fe, microscopy SEM and X-ray diffraction. The aim of this study is to identify and understand the electrochemical mechanism during the cycling of the battery that can enhance or limit the battery performance. This study has shown the complementarity of Mössbauer spectrometry and X-ray diffraction to analyze the redox mechanisms involved into the electrochemical reactions. From the well-known two-phase mechanism of LiFePO4, electrochemical mechanisms in three steps and phases formed during cycling have been identified for phase substituted manganese. The ability of these compounds to be used as positive electrode materials for powerful Li-Ion batteries was demonstrated by long-term cycling at different temperatures and rates of cycling.

Les mécanismes de formation et de croissance des films d'oxydes à la surface des bronzes Cu-Sn sont encore peu connus. Dans ce contexte, cette étude a pour objectif de lever l'ambiguïté concernant la nature, la structure et la localisation des produits de corrosion formés à la surface des bronzes. Pour cela des électrodes de bronze ont été élaborées, mises en forme, puis oxydées par immersion et par polarisation anodique en milieu sulfate à 10 2 mol.L-1. Les espèces ainsi formées en surface sont ensuite réduites en mode galvanostatique. Les courbes font apparaître des paliers caractéristiques des réactions électroniques qui opèrent à l'électrode. Les valeurs de potentiel correspondant aux différents paliers sont comparées à celles obtenues sur des composés modèles. Cette étude comparative permet d'attribuer certains paliers à certains composés mais pas tous.Pour compléter l'identification, la diffraction des rayons X, la spectroscopie Mössbauer et la micro-spectrométrie Raman ont été mises en œuvre afin d'observer la présence d'oxyde d'étain (+ IV) en plus des composés du cuivre. La spectroscopie d'électrons Auger et la spectroscopie de photoélectrons X (XPS-AES) ont permis une analyse en profondeur des films par érosion progressive de la surface, qui a révélé qu'en premier lieu un film d'oxyde d'étain se forme à la surface de l'alliage Cu-Sn et, qu'ensuite, une couche d'oxyde de cuivre croit à l'interface oxyde/électrolyte. Les observations effectuées par microscopie électronique en transmission (MET) confirment ces résultats. Dans un second temps, les techniques électrochimiques conventionnelles, et plus particulièrement la spectroscopie d'impédance électrochimique, ont été utilisées afin d'identifier la structure des couches ainsi que les processus mis en jeu lors de l'oxydation. Elles ont permis d'en déduire un mécanisme réactionnel d'oxydation possible / Formation and growth mechanisms of oxides films on monophased copper-tin bronzes are still in discussion. In the literature two different patterns of corrosion are exposed. The first one claims that the bronze corrosion is similar to that of copper whereas the second one asserts that the copper-tin alloys oxidation lead to a double layer structure. The inner layer is enriched in tin consequently to copper selective dissolution. The outer layer is essentially composed of copper oxides.To The present study deals with the chemical-physical and electrochemical characterisations of artificial patinas, thin layer of corrosion products electrochemically formed at the surface of copper-tin alloys. A bronze containing 7 wt% of tin is oxidised in a 10-2 mol.L-1 desaerated sulphate solution, buffered at pH = 6.8. The synthesised species are cathodically reduced. The successive steps of the potential vs time curves, characteristic of the electrochemical reactions occurring at the electrode surface, are successfully calibrated with reference oxides.In order to complete the previous results, X-Ray Photoelectron Spectroscopy (XPS) depth profiles are carried out by abrading progressively the oxidised surface. The deconvoluted XPS and Auger Electron Spectroscopy (AES) spectra speak in favour of an “alloy/SnO2/Cu2O” layered structure similar to that reported in the literature. Analyses carried out on the oxidised samples by Transmission Electron Microscopy (TEM) confirm this pattern.The characterisation techniques carried out on archeological artefacts produce conclusions that are compared to those obtained on the electrochemical samples. This multi analytical study gives crucial piece of information. The reactional sequence that will be deduced is an essential tool for the good preservation of the world cultural heritage

Desarrolla el estudio de las características, de tres disposiciones de los ligandos PO3-4 a través de la interacción hiperfina eléctrica con el Fe2t en (A)Fe3 (PO4)2. En la estructura de la fase graftonita del Fe3 (PO4)2, mientras que la estructura nuclear del nucleido FE57 se mantiene constante, la configuración electrónica del ión Fe2t sí cambia significativamente, según las disposiciones distintas de los ligandos PO3-4, dando lugar a las variaciones apreciables de la interacción hiperfina, posibles de ser medidas por espectroscopía Mossbauer. Se observa que el orden creciente de las contribución de la interacción cuadropolar eléctrica es como sigue: D5h, D3h, C4v, mientras que, la contribución creciente e interacción monopolar eléctrica ws D5h, C4v, D3h. / Tesis