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Materials with length scales in the nanometer regime demonstrate properties that are remarkably different from analogous bulk matter. As a result, researchers are striving to catalog the changes in properties that occur with decreasing size, and more importantly, understand the reason behind novel nanomaterial properties. By learning the true nature of nanomaterials, scientists and engineers can design better materials for a variety of applications. Inert gas-phase condensation synthesis of metal oxide nanoparticles was used to develop materials to explore the optical and chemical properties of metal oxide nanoparticles. One potential application for nanomaterials is use in optical applications. The possibility of interparticle energy transfer was investigated for lanthanide-doped yttrium oxide nanoparticles using laser spectroscopy. Experimental evidence collected with this study indicates that interparticle, lanthanide-mediated energy transfer may have been observed. In addition, lanthanide-doped gadolinium oxide nanoparticles were synthesized and investigated with optical spectroscopy to identify the best potential candidates for bioanalytical applications of this material. The influence of particle annealing and dopant concentration were also studied. Nanoparticle film structure was investigated with scanning electron microscopy. Two different film structures composed of oxide nanoparticles were found to grow under different synthesis conditions. The film structure was found to be determined by the degree of particle aggregation in the gas phase during synthesis. Aggregation of the particles was found to be controlled by a combination of gas pressure and properties. Chemical properties of metal oxide nanoparticles also are very important. Reflection-absorption Infrared Spectroscopy and vacuum surface analytical techniques were used to explore the chemistry of the chemical warfare agent dimethyl methylphosphonate (DMMP) on yttrium oxide as well as other metal oxide nanoparticles. DMMP was found to dissociate at room temperature on several types of metal oxide nanoparticles. Hydroxyl groups were found to be critical for the adsorption of DMMP onto the particles. Finally, the reactivity of the nanoparticles was found to increase with decreasing particle size. This was attributed to a relative increase in the number of high-energy surface defects for the smaller particles. / Ph. D.

The goal of this research was the fabrication of thin films with magneto-optic (MO) properties. Accomplishment of this task was achieved via sol-gel processing of rare-earth and aluminum substituted yttrium-iron garnet (RxY3-xAlyFe5-yO12, R,Al:YIG), where R= Bi, Gd, Er, Ho. Detailed are the processing conditions, parameters and results leading to R,Al:YIG films with MO response. Success was attained with a 0.25M Gd,Al:YIG solution spin coated for 120 seconds at 3500rpm onto a (111) gadolinium gallium garnet (GGG) substrate and calcinated at 900°C for 4 hours. Samples were characterized via x-ray diffraction (XRD), magneto-optical loop tracer, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), profilometry and optical microscopy. / Master of Science

L'assiette de fibrage utilisée pour la production de la laine de verre d'isolation subit à haute température de nombreuses contraintes (chimiques, mécaniques et thermiques). La ruine des assiettes peut être due à l'oxydation par les gaz chauds, à la corrosion par le verre fondu ou à la déformation par fluage. La première partie des travaux de thèse a porté sur l'amélioration des propriétés mécaniques des alliages pour le fibrage à 1200°C. Dans un premier temps, la teneur en chrome au coeur d'alliages à base de cobalt a été réduite afin d'augmenter la réfractarité en conservant la microstructure. Cependant, cette réduction a dégradé le comportement en oxydation de ces alliages. Afin de conserver un bon niveau en oxydation, un enrichissement en chrome de la surface a été réalisé à l'aide de la technique de pack-cémentation. Le comportement en fluage de ces alliages a été maintenu à un niveau correct. Dans un second temps, de nouveaux systèmes métallurgiques ont été explorés, basés sur le nickel et le fer, et ont été renforcés mécaniquement par des éléments lourds en solution solide ou par des précipités intermétalliques. La réfractarité et le comportement en oxydation se sont révélés intéressants mais la tenue en fluage a été décevante. La seconde partie de ces travaux a consisté à améliorer le comportement en oxydation de l'alliage utilisé lors du fibrage à 1000-1050°C. Deux voies ont été explorées : un enrichissement en chrome de la surface de l'alliage par pack-cémentation ou l'addition d'un élément réactif, l'yttrium. La seconde solution a apporté des résultats intéressants avec une amélioration significative du comportement en oxydation cyclique / The spinner used to product glass wool for thermal building insulation undergoes several stresses (chemical, mechanical and thermal) at high temperature. The lifetime of the spinner is limited by oxidation by hot gases, corrosion by molten glass or creep deformation. The first part of this thesis has concerned the improvement of the mechanical properties of the alloys for the fiberizing at 1200°C. First, the bulk chromium content of the usual cobalt-base alloys has been decreased to increase their refractoriness at constant microstructure. However, this reduction has degraded the oxidation behavior of these alloys. To keep a good oxidation behavior, a surface chromium enrichment of the Cr-impoverished alloys is achieved by pack-cementation technique. The creep behavior of these alloys is kept at a good level. Secondly, several new metallurgical systems were explored: alloys based on nickel and iron and reinforced by heavy elements in solid solution or by precipitates inter metallic particles. The refractoriness and the oxidation behavior appeared to be interesting but the creep deformation was disappointing. The second part of this work has concerned the improvement of the oxidation and corrosion properties of the alloys for the process at 1000-1050°C. Two ways have been explored: a chromium enrichment on the sub-surface or an addition of a reactive element, as yttrium. The second solution has given interesting results with a significant improvement of the oxidation behavior, and particularly in cyclic oxidation

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Made available in DSpace on 2014-10-09T12:51:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:31Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP