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In the present study, dilute alloys in the Mg-rich corner of the Mg-Ce-In ternary system in the composition range 0 to 3% In and 0 to 1.5% Ce were synthesized. Cooling curve analysis was used to determine the liquidus points in order to construct the liquidus surface of the ternary phase diagram in the Mg corner. Energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), and x-ray diffraction (XRD) techniques were used to examine phases present at the compositions studied. A thermal arrest presumed to represent a eutectic transformation was discovered at 580°C. Two new intermetallic compounds, designated tau and theta, were found. Trace silicon present in the alloys was found to concentrate in one of the intermetallic compounds. / To further investigate these compounds, an induction furnace was used to synthesize alloys containing the concentrations of Ce and In seen in electron probe micro-analysis (EPMA) examinations of these compounds. The alloys were examined using the cooling curve technique and XRD, and proved to contain the compounds already observed with some variation in dissolved indium content. In addition, differential scanning calorimetry (DSC) was used to confirm the liquidus and solidus values determined using cooling curve analysis. / A diffusion couple with terminal compositions of pure Ce and a Mg-In alloy was prepared in order to determine the equilibrium phases present in the system between these two compositions at 390°C. EPMA was used to identify the zones obtained, and confirmed the presence of several Mg-Ce compounds with 1 at% dissolved indium, as well as a ternary compound corresponding to the theta compound found in the dilute alloys. / Finally, literature values and experimental data were used to calculate a preliminary ternary phase diagram using FACTSage, in collaboration with the CTRC at Ecole Polytechnique, in order to affirm the validity of the experimentally determined values as well as to project the diagram beyond the studied composition range.

Studies various nanostructured materials have gained considerable interest within the past several decades. This novel class of materials has opened up a new realm of possibilities, both for the fundamental comprehension of matter, but also for innovative applications. The size-dependent effect observed for these systems often lies in their interaction with the surrounding environment and understanding such interactions is the pivotal point for the investigations undertaken in this thesis. Three families of nanoparticles are analyzed: semiconductor quantum dots, metallic silver nanoparticles and rare-earth oxide nanomaterials. The radical scavenging ability of cerium oxide nanoparticles (CeO2) is quite controversial since they have been labeled as both oxidizing and antioxidant species for biological systems. Here, both aqueous and organic stabilized nanoparticles are examined in straightforward systems containing only one reactive oxygen species to ensure a controlled release. The apparent absence of their direct radical scavenging ability is demonstrated despite the ease at which CeO2 nanoparticles generate stable surface Ce3+ clusters, which is used to explain the redox activity of these nanomaterials. On the contrary, CeO2 nanoparticles are shown to have an indirect scavenging effect in Fenton reactions by annihilating the reactivity of Fe2+ salts. Cadmium selenide quantum dots (CdSe QD) constitute another highly appealing family of nanocolloids in part due to their tunable, size-dependent luminescence across the visible spectrum. The effect of elemental sulfur treatment is investigated to overcome one of the main drawbacks of CdSe QD: low fluorescence quantum yield. Herein, we report a constant and reproducible quantum yield of 15%. The effect of sulfur surface treatment is also assessed following the growth of a silica shell, as well as the response towards a solution quencher (4-amino-TEMPO). The sulfur treated QD is also tested for interaction with pyronin Y, a xanthene dye that offers potential energy and electron transfer applications with the QD. Interaction with the dye molecule is compared to results obtained with untreated quantum dots, as well as CdSe/ZnS core shell examples. In another chapter of this thesis, the catalytic potential of silver nanoparticles is addressed for the grafting of polyhydrosiloxane polymer chains with various alkoxy groups. A simple one-pot synthesis is presented with silver salts and the polymer. the latter serves as a mild reducing agent and a stabilizing ligand, once silver nanoparticles are formed in-situ. We evaluate the conversion of silane into silyl ethers groups with the addition of several alcohols, whether primary, secondary or tertiary, and report the yields of grafting under the mildest conditions: room temperature, under air and atmospheric pressure.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Pennsylvania, 1903. / Includes bibliographical references.

Thesis (Ph. D.)--University of Pennsylvania, 1903. / Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-08Bitstream added on 2014-06-13T18:09:38Z : No. of bitstreams: 1 silva_riv_me_bauru_prot.pdf: 20922417 bytes, checksum: 7a0be809afb7e675e99bba1b3539c247 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O presente trabalho teve como objetivo preparar o compósito de 1% (massa) de rutênio suportado sobre o condutor misto cerâmico (iônico e eletrônico), 'Ti IND. x'('Gd IND. 0,2''Ce IND. 0,8')'IND. (1-x)''O IND. (2-δ)', onde 0'< OU ='x'<OU='0,1, para utilizar como catalisador de reforma e ânodo (eletrodo tipo reforma interna) em Células a Combustível de Óxido Sólido (SOFC). O suporte cerâmico foi sintetizado pelo Método do Precursor Polimérico e calcinado a 400ºC, 700ºC, 1000ºC e 1150ºC em atmosfera estática de ar, sendo caracterizado por análise térmica simultânea (TG/DTA), Difração de Raio X (DRX) com refinamento estrutural pelo Método de Rietveld (REMR), análise textural por adsorção de 'N IND. 2' a 77K, Microscopia Eletrônica de Varredura (MEV) e Energia Dispersiva de Raio X (EDX). O Ru foi depositado (1% em massa) sobre o suporte cerâmico pelo Método do Ácido Fórmico. Em seguida foi calcinado a 300ºC em atmosfera de 'N. IND. 2' e tratado a 1000ºC em atmosfera de 'H IND. 2' (20% em 'H IND. 2' ). A deposição do Ru foi confirmada pela Espectrometria de Emissão Atômica com plasma acoplado indutivamente (ICP-AES). A caracterização do compósito foi feita mediante DRX, MEV com Fonte de Emissão Eletrostática (MEV-FEG) e Microscopia Eletrônica de Transmissão (MET). por último, o material compósito de Ru foi submetido a testes catalíticos para hidro-reforma de glicerol. A análise térmica do suporte cerâmico mostrou que os compostos orgânicos são eliminados até 700ºC. Os resultados de DRX e REMR mostraram a presença fase única de fluorita (g.e. Fm3m) em T=700ºC para 0'< OU ='x'<OU='0,1 e em T=1000ºC, para x<0,1. Em T=1000ºC e em T=1150ºC observou-se a presença da segunda fase, de titanato de gadolínio ('Gd IND. 2''Ti IND. 2''O IND. 7', g.e. Fd3m) para x'>OU='0,1 e x'>OU='0,025, respectivamente... / The current work aimed to prepare the composite of ruthenium supported on the ceramic mixed conductor (ionic and electronic), 'Ti IND. x'('Gd IND. 0,2''Ce IND. 0,8')'IND. (1-x)''O IND. (2-δ)',where 0'< OU ='x'<OU='0,1, to be used as a catalyst for the reforming and anode (internal reforming electrode) in Oxide Solid Fuel Cells (SOFC). The ceramic supports were synthesized by Polymeric Precursor Method and calcined at 400ºC, 700ºC, 1000ºC and 1150ºC in air. The characterization was carried out by simultaneous thermal analysis (TG/DTA), X-ray Diffraction (XRD) being the structure refined by Rietveld Method (SRRM), textural analysis by adsorption of 'N IND. 2' at 77K, Scanning Electronic Microscopy (SEM) and Energy Dispersive X-ray (EDX). The Ru was deposited on ceramic support by Formic Acid Method, calcined at 300ºC in 'N. IND. 2' and calcined at 1000ºC under 20vol% 'H IND. 2' flow. The deposition was confirmed by Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES). The characterization of the composite was performed by XRD, Field Emission Gun - Scanning Electronic Microscopy (FEG-SEM) and Transmission Electronic Microscopy (TEM). Finally, the catalytical activity of the composite material for glycerol steam reforming reaction was evaluated. The thermal analysis showed that most of organic compounds derived from the synthesis is eliminated up to 700ºC. The XRD and SRRM results showed that the samples crystallized as fluorite single phase (s.g.Fm3m) at T=700ºC for 0'< OU ='x'<OU='0,1and T=1000ºC,for x<0,1. The secondary phase of ('Gd IND. 2''Ti IND. 2''O IND. 7', g.e. Fd3m) was observed in the sample with x'>OU='0,1 when calcined at T=1000ºC and x'>OU='0.025 for the calcination temperature of 1150ºC. The textural analysis showed that the samples treated at 700ºC are mesoporous solids and, significant surface and porosity loss took place when treated at 1000ºC... (Complete abstract click electronic access below)

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