L’imagerie 3γ est une technique innovante d’imagerie médicale nucléaire qui est étudiée au laboratoire SUBATECH. Elle repose sur la localisation tridimensionnelle d’un radioisotope émetteur (β+, γ), le 44Sc, à l’aide d’un télescope Compton au xénon liquide. Le lieu de désintégration de ce radioisotope est obtenu par l’intersection de la ligne de réponse, construite à partir de la détection des deux photons de 511 keV issus de l’annihilation d’un positron, et du cône déterminé à partir du troisième photon. Un prototype de petite dimension XEMIS1 (XEnon Medical Imaging System) a été développé afin de faire la preuve expérimentale de la faisabilité de l’imagerie à 3γ. Les résultats de ce prototype sont très promoteurs en terme de résolution en énergie, de pureté du xénon liquide et de faible bruit électronique. La simulation Monte Carlo est un outil indispensable pour accompagner la R&D et évaluer les performances de la nouvelle technique d’imagerie proposée. Les travaux rapportés dans cette thèse concernent le développement de la simulation du système d’imagerie 3γ avec GATE (Geant4 Application for Tomographic Emission). De nouvelles fonctionnalités ont été implémentées dans GATE afin de simuler un détecteur de type TPC (Time Projection Chamber). Nous avons effectué une simulation du prototype XEMIS1 et obtenu des résultats en bon accord avec nos données expérimentales. La prochaine étape du projet consiste à construire une caméra cylindrique au xénon liquide pour l’imagerie du petit animal. Les résultats des simulations de cette caméra présentés dans cette thèse montrent la possibilité de localiser chaque désintégration le long de la ligne de réponse avec une très bonne précision et une bonne sensibilité de détection. Des premières images de fantômes simples, réalisées évènements par événements, et après reconstruction tomographiques ont également présentées. / Nuclear medical 3γ imaging is an innovative technique which is studied at the SUBATECH laboratory. It isbased on the three-dimensional localization of a (β+, γ) radioisotope emitter, the 44Sc, by using a liquid xenon Compton telescope. The position of the disintegration of this radioisotope is obtained by the intersection of the line of response, built by the detection of two 511 keVphotons from the annihilation of a positron, and the cone determined by the third photon. A small prototype XEMIS1 (XEnon Medical Imaging System) was developed to demonstrate experimentally the feasibility of 3γ imaging. The results of this prototype are quite encouraging in terms of energy resolution, purity of liquid xenon and electronic noise. The Monte Carlo simulation is an indispensable tool to support the R&D and to evaluate the new proposed technique of imaging ; this thesis work is to develop the simulation of 3γ imaging system by using GATE (Geant4 Application for Tomographic Emission). New functionalities have been added to GATE to simulate a TPC (Time Projection Chamber) detector. We performed a simulation of XEMIS1 prototype and obtained results in good agreement with our experimental data. The next step of the project is to build a full liquid xenon cylindrical camera for the small animal imaging. The results presented in this thesis of the simulations of this camera demonstrate the ability to locate every decayalong the line of response with very good accuracy and good detection sensitivity. The first direct images of simple phantoms, realized event by event, and after tomographic reconstruction are also presented.

This work investigated the synthesis, characterisation and properties of known and novel scandium carboxylate Metal-organic Frameworks (MOFs). The first part reports the performance of these Sc-MOFs as Lewis acid catalysts. The porous MOF scandium trimesate MIL-100(Sc) and the scandium terephthalates such as MIL-101(Sc), MIL-88B(Sc) and MIL-68(Sc) (prepared as the Sc-analogue for the first time), and scandium biphenyldicarboxylate MIL-88D(Sc) were prepared and tested as Lewis acid catalysts. Chromium MIL-101 and MIL-100 and scandium-exchanged zeolites were prepared for comparison. Moreover, successful encapsulation of the phosphotungstate polyoxometalates (POMs) in the cavities of MIL-101(Sc) enhanced the stability of this material. These scandium and chromium MOFs, POM-MOF composites and scandium-exchanged zeolite were tested as heterogeneous catalysts in the carbonyl ene reaction between α-methyl styrene and ethyl trifluoropyruvate. This showed that MIL-100(Sc) was the best catalyst for this reaction, achieving a conversion of 99% to the desired product. The stabilized MIL-101(Sc) was also very active, but less selective for this reaction. Acetalisation of acetaldehyde was also studied, and in this reaction the isoreticular MOFs MIL-88(B) and MIL-88D(Sc) were the most active and selective catalysts. For this reaction, the activity of MIL-100(Sc) was low, which was attributed to reduce pore size and blockage. Functionalisation of the range of scandium terephthalates such as MIL-101(Sc), MIL-88B(Sc), MIL-68(Sc), Sc₂BDC₃,and MIL-53(Sc) particularly with –NH₂ groups, made up the second main part of this research. Solvothermal synthesis were performed at lower temperatures and using mixed solvents to synthesize these amino-terephthalate MOFs, often for the first time, and their adsorption properties were studied, particularly for the adsorption of CO₂. The synthesis of pure Sc₂(NH₂-BDC)₃ and Sc₂(Br-BDC)₃ was achieved for first time by a solvothermal route, lower temperatures, and mixed solvents. This approach yielded large crystals suitable for single crystal diffraction and microcrystal IR spectroscopy. Post-synthetic modification (PSM) of Sc₂(NH₂-BDC)₃ was explored by incorporation of NO₂-groups into the framework by solvent-assisted ligand exchange. The adsorption properties of functionalised and post-modified materials were compared with those of Sc₂BDC₃ and Sc₂(NO₂-BDC)₃ for methanol and hydrocarbons This study demonstrated that Sc₂BDC₃ and Sc₂(NH₂-BDC)₃ give the higher uptakes while the –Br and –NO₂ forms display shape selectivity for n-alkanes over iso-alkanes. Amino-functionalised MIL-53(Sc) was prepared for the first time using a mixed ligand approach, so that 10-20% of a second functionalised terephthalate ligand (NO₂, Br, -(OH)₂) was required for successful single phase synthesis in addition to amino-terephthalic acid. The materials were characterised using PXRD, TGA and gas adsorption, which confirms the samples show a range of behaviour for CO₂ adsorption. Notably, the `breathing´ behaviour is strongly dependent on the type of functionalisation. Finally, the exploratory synthesis of novel scandium MOFs, using isophthalic acid (IA) and its amino and nitro- derivatives, 2,5-furandicarboxylate (FDA) and the porphyrin tetra(carboxyphenyl)porphyrin (TCPP) as linkers was carried out and six novel materials were synthesized, three of which gave crystals large enough for their structure to be determined by single crystal diffraction. Further characterisation was carried out by PXRD, TGA and solid-state NMR. Some of these materials have been shown to be porous to CO₂ and N₂.

This study reports on the physical and optical characterization of scandium oxide thin films. Thin films of scandium oxide, 20-40 nm thick, were deposited on silicon wafers, quartz slides, and silicon photodiodes by reactively sputtering scandium in an oxygen environment. These samples were characterized using ellipsometry, high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis. A 28.46 nm thick scandium oxide thin film was measured in the Extreme Ultraviolet (EUV) from 2.7 to 50 nm (459.3 to 24.8 eV) using synchrotron radiation at the Advanced Light Source Beamline 6.3.2 at the Lawrence Berkeley National Laboratory. In these measurements, a new method for data collection was used, in which the reflection and transmission data were collected simultaneously. Analysis of the EUV reflection and transmission data was performed using a front-side reflection, matrix-multiplication technique, which is novel among EUV analytical practice. During data analysis, a new weighting scheme was used, named "adaptive weighting". This analysis provides the first experimentally determined optical constants n and k for scandium oxide thin films from 4.5-30 nm. Also, the positions of the L2 and L3 electronic transitions of scandium oxide have been measured, at 3.069 and 3.101 nm (404.0 and 399.9 eV), respectively, while the measurements near the M transition suggest it to be at approximately 31.5 nm (39.4 eV). Comparing the electronic transition positions of scandium oxide to those of scandium show that the oxidation of scandium shifts the positions to lower energies. For L2 the shift is about 1.8 eV, for L3 the shift is about 1.4 eV, and for M the shift is about 1.9 eV. The binding energies of scandium oxide are greater than those of scandium, as is expected for an oxide compared to its parent metal. This trend in the shift of the transition positions is unexpected, and warrants further investigation.

No description available.

Master of Science / Department of Electrical and Computer Engineering / Andrew Rys / It is important in semiconductor manufacturing to understand the physical and electrical characteristics of new proposed semiconductors to determine their usefulness. Many tests are used in order to achieve this goal, such as x-ray diffraction, Hall effect measurements, and the scanning electron microscope. With these tests, the usefulness of the semiconductor can be determined, leading to more possibilities for growth in industry. The purpose of the present study was to look at the semiconductor scandium nitride (ScN), grown using the hydride vapor phase epitaxy (HVPE) method on various substrates, and determine the physical and electrical properties of the sample. This study also sought to answer the following questions: 1) Can any trends be found from the results?, and 2) What possible application could scandium nitride be used for in the future? A sample set of scandium nitride samples was selected. Each one of these samples was checked for contaminants from the growth procedure, such as chlorine, under the scanning electron microscope and checked for good conduction of current needed for the Hall effect measurements. The thickness of the scandium nitride layer was computed using the scanning electron microscope. Using the thickness of the scandium nitride, Hall effect measurement values were computed. The plane the samples lie on was checked using x-ray diffraction. The test results shed light on many trends in the scandium nitride. Many of the samples were determined to have an aluminum nitride (AlN) contamination. This contamination led to a much higher resistivity and a much lower mobility no matter what thickness the scandium nitride was. The data from the samples was then used to offer suggestions on how to improve the growth process.

No description available.

The rotational spectrum of ScO (X-2 Sigma(+)) has been measured in the gas phase in the frequency range 30-493 GHz using a combination of Fourier transform microwave/millimeter-wave (FTM/mmW) and submillimeter direct absorption methods. This work is the first pure rotational study of this radical. Both the ground vibrational and v=1 states were observed. ScO was created from the reaction of metal vapor, produced either by a laser ablation source or a Broida-type oven, and N2O, in the former case heavily diluted in argon. Extensive hyperfine structure was observed in the FTM/mmW data, although the spin-rotation splitting was found to be small (similar to 3 MHz). In the mm-wave spectra, however, the fine and hyperfine structure was blended together, resulting in broad, single lines for a given transition N + 1 <- N. The data were analyzed in a combined fit using the very accurate hyperfine measurements of Childs and Steimle (1988), employing a Hund's case b Hamiltonian, and an improved set of rotational and centrifugal distortion constants were determined. These measurements improve the accuracy of predicted frequencies for astronomical searches by 14-18 MHz, or 16-20 km/s, in the 1 mm region - a difference of half to a full linewidth for certain interstellar sources. This work also demonstrates the capabilities of the FTM/mmW spectrometer at 61 GHz.

L'approvisionnement en métaux rares est devenu un sujet de préoccupation majeur du fait de nombreuses incertitudes géopolitiques et de leur utilisation croissante dans des produits de haute technologie. Cependant, pour assurer l'approvisionnement, des progrès doivent être accomplis dans la compréhension de la ressource. Parmi les métaux rares, la demande potentielle pour le scandium (Sc) est croissante, du fait de son utilisation dans des alliages de haute technologie ainsi que dans les piles à combustible. L'approvisionnement n'est actuellement pas assuré mais les gisements latéritiques sont des cibles prometteuses. Le Sc pourrait devenir un sous-produit de nombreuses latérites nickélifères, et même le principal produit des minerais latéritiques à fortes teneurs découverts dans l'est australien. Pour comprendre l'origine de ces enrichissements latéritiques en Sc, nous avons étudié les processus géochimiques et cristallochimiques qui forment l'un de ces gisements (Syerston–Flemington, Nouvelle-Galle du Sud). Une méta-analyse des études géochimiques portant sur les roches et minéraux mantelliques, qui forment les roches mères de toutes les latérites enrichies en Sc connues à ce jour, révèle que les lithotypes les plus favorables sont les cumulats à clinopyroxène ou amphibole. Cette étude montre aussi un changement drastique dans la compatibilité du Sc avec la profondeur dans le manteau, allant d'incompatible dans le faciès à spinelle à compatible dans le faciès à grenat. Cette dualité est particulièrement intéressante pour tracer la profondeur de fusion partielle des roches extrusives.Une étude intégrée combinant diffraction des rayons X, analyses chimiques en roche totale et à l'échelle microscopique, ainsi que l'absorption des rayons X, a été menée dans le but de comprendre les processus de concentration du Sc durant l'altération latéritique. Les profils latéritiques riches en Sc résultent de la dissolution des minéraux primaires présentant des enrichissements en Sc légers, mais significatifs. Ensuite, le Sc est piégé successivement par les smectites, puis les oxydes de fer après la dissolution des phases argileuses. Les teneurs en Sc reflètent la haute capacité d'adsorption de cet élément par la goethite. Avec les mécanismes de dissolution–précipitation formant des générations successives de goethite, cette capacité préserve l'immobilité du Sc alors que la plupart des autres éléments sont lessivés, amenant à de hautes concentrations résiduelles. / The supply of rare metals has become a great concern due to the combination of geopolitical uncertainties and increasing use in new high-technology materials. However, to secure supply, progress on the understanding of the resource is needed. Among rare metals, there is a growing potential demand for scandium (Sc), resulting from its use in high-performance alloys and solid oxide fuel cells. The current supply is not guaranteed but lateritic deposits are a promising target. Scandium could become a by-product of many nickel laterites, and even the main product of high-grade lateritic Sc ores in eastern Australia. To understand the origin of lateritic Sc enrichment, we investigated the geochemical and crystal-chemical processes forming one of these deposits (Syerston–Flemington, New South Wales). A meta-analysis of geochemical studies on mantle-derived rocks and minerals, which form the parent rocks of all known Sc-enriched laterites reveals that the most favourable lithotypes are cumulates of clinopyroxene or amphibole. It also shows a drastic change in the compatibility of Sc with increasing depth in the mantle, ranging from incompatible in the spinel facies to compatible in the garnet facies. This dichotomy is of great interest for tracing the depth of partial melting of extrusive rocks.Integrated X-ray diffraction, whole-rock and microscopic chemical analyses and X-ray absorption spectroscopy have been used to understand the processes that concentrate Sc during lateritisation. Scandium-rich lateritic profiles result from the dissolution of primary minerals containing slight but significant Sc enrichment, followed by successive trapping by smectite and iron oxides after dissolution of the clay phases. Scandium grades reflect the high capacity of goethite to adsorb this element. Along with mechanisms of dissolution–precipitation forming successive generations of goethite, it preserves Sc immobility while most other elements are leached, leading to high residual concentrations of Sc.

Thesis (Ph.D.)--Ohio University, November, 2005. / Title from PDF t.p. Includes bibliographical references (p. 89-93)

De nouveaux radio-isotopes pour la médecine nucléaire peuvent être produits par des accélérateurs de particules. C'est l'un des buts d'Arronax, un cyclotron de hautes énergies - 70 MeV - et hautes intensités - 2*350 µA - installé à Nantes. Une liste d'émetteurs b- - 47Sc, 67Cu - b+ - 44Sc, 64Cu, 82Sr/82Rb, 68Ge/68Ga - et a - 211At - à étudier en priorité a été établie. Parmi ceux là, le 47Sc et le 67Cu présentent un intérêt en thérapie ciblée. L'optimisation de leurs productions nécessite la bonne connaissance de leurs sections efficaces, mais aussi de celles de tous les contaminants créés. Nous avons lancé sur Arronax un programme de mesures de sections efficaces utilisant la technique des Stacked-foils. Elle consiste en l'irradiation simultanée d'un groupe de feuilles - cibles, moniteurs et dégradeurs - et la mesure par spectro-gamma de la production d'isotopes. Les moniteurs permettent un contrôle des pertes de faisceau tandis que les dégradeurs en diminuent l'énergie. Nous avons étudié les réactions natTi(p,X)47Sc et 68Zn(p,2p)67Cu. Les cibles étant respectivement des feuilles de natTi - achetées chez Goodfellow - ou des électrodépositions sur Ag de 68Zn enrichi. Nous les réalisons nous même ainsi que la séparation chimique des isotopes de Cuivre et de Gallium indispensable avant de procéder au comptage gamma. Les sections efficaces de plus de 40 réactions ont ainsi été obtenues sur l'intervalle de 18 MeV à 70 MeV. Une comparaison avec le code Talys est systématiquement faite, et plusieurs paramètres des modèles théoriques étudiés. Nous montrons qu'il est impossible de reproduire avec exactitude toutes les sections efficaces à partir d'un seul jeu de ces paramètres.