The aim of this thesis was to synthesise CoAPO-34 and FeAPO-34 using ionothermal synthesis in the presence of organic amines. Using this method provides an alternative route to prepare such materials under low pressure instead of the higher pressure associated with hydrothermal or solvothermal synthesis. Both materials have chabazite (CHA) topology and they are known to act as catalysts. CoAPO-34 was ionothermally prepared using 1-ethyl-3-methylimidazolium bromide (EMIMBr) in presence of 1, 6-hexadiamine (HDA). This study has found that when the synthesis was carried out without HDA, AlPO-11 was preferentially obtained instead of CoAPO-34. Broad line signals which appear between 2000 to 5000 ppm in both spin-echo ³¹P NMR spectra of as-synthesised and calcined CoAPO-34 confirm that the Co²⁺ ions have been successfully incorporated within the framework of the material. FeAPO-34 was synthesised under ionothermal conditions using 1-ethyl-3-methylimidazolium chloride in the presence of ethylenediamine (EDA). In the absence of EDA, the synthesis has produced AlPO-34 instead of FeAPO-34. Broad line signals that appear between 1000 to 14000 ppm in spin-echo ³¹P NMR spectra of both as-synthesised and calcined FeAPO-34 are direct evidence of isomorphous substitution of framework aluminum by Fe(II) or Fe(III). Another aim of this study was to explore the ionothermal synthesis of copper containing aluminophoshate of DNL-1 (Cu/DNL-1). This material was attractive to explore because it contains 20 ring extra-large pores and Cu(I) species in the channels of the framework, potentially giving material the ability to simultaneous store NO and to generate NO from NO₂⁻ anions. Cu/DNL-1 was successfully prepared under ionothermal conditions using EMIMBr and HDA. Without HDA in the synthesis, AlPO-11 was obtained. In this material, copper ions were not incorporated in the Cu/DNL-1 skeleton framework. This was confirmed by absence of broadline signal at >500 ppm in spin-echo ³¹P NMR spectrum of the sample. The copper ions are expected to be present as extra-framework cations. Extra-framework Cu(I) species that were formed by high temperature calcination of Cu/DNL-1 are active to produce NO from NO₂⁻. Therefore, the calcined Cu/DNL-1 can be used to simultaneously store and produce NO from nitrite. This has the potential to significantly extend the lifetime of gas delivery in the material to prevent thrombus formation.

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Made available in DSpace on 2014-10-09T12:35:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:40Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:35:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:40Z (GMT). No. of bitstreams: 0 / A motivação deste trabalho foi o desenvolvimento e validação de um dispositivo para realizar os testes estabelecidos na ABNT NBR IEC 60601-1-3 nas versões publicadas de 2001[1] e 2011[2]. A finalidade dos ensaios é determinar a camada semirredutora - CSR (Half Value Layer - HVL) e a filtração com equivalência de qualidade, em mmAl, dos materiais que interceptam o feixe de raios X desde a sua emissão até o dispositivo receptor de imagem de raios X. Esta filtração inclui os materiais presentes no conjunto fonte de radiação X, formado pela cúpula de proteção radiológica com o tubo de raios X inserido, pelo sistema de colimação (filtração inerente) e pelos materiais presentes nos suportes de pacientes, como mesa e bucky mural sendo que ambos incorporam dispositivo receptor de imagem que também é avaliado. No desenvolvimento foi levada em consideração a rotina da execução do ensaio, com a finalidade de diminuir ao máximo a interação do operador com o sistema, a fim de reduzir o fator humano na execução, refletindo diretamente na incerteza de medição, na diminuição do tempo de execução e na segurança radiológica. O dispositivo desenvolvido foi validado com relação aos seguintes aspectos: a) Influência do dispositivo trocador de filtros quanto ao posicionamento e distribuição dos filtros; b) Influência da pureza dos filtros de alumínio utilizados no dispositivo, e a c) Comparação entre os ensaios realizados com dispositivo de ensaio desenvolvido com relação aos ensaios realizados com um gerador de raios X de referência. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

The coupling between longitudinal-optical (LO) phonons and neutral excitons in two different kinds of InGaAs pyramidal quantum dots embedded in either AlGaAs or GaAs barriers is experimentally examined. We find a slightly weaker exciton-LO-phonon coupling and increased linewidth of the phonon replicas for the quantum dots with GaAs barriers compared to the ones with AlGaAs barriers. These results, combined with the fact that the LO-phonon energy of the exciton is the same for both kinds of dots, are taken as evidence that the excitons mainly couple to LO-phonons within the QDs. / Original Publication:Daniel Dufåker, L. O. Mereni, Fredrik K. Karlsson, V. Dimastrodonato, G. Juska, Per-Olof Holtz and E. Pelucchi, Exciton-phonon coupling in single quantum dots with different barriers, 2011, Applied Physics Letters, (98), 25, 251911.http://dx.doi.org/10.1063/1.3600781Copyright: American Institute of Physicshttp://www.aip.org/

Issues of major relevance to the n-type conductivity of Al0.77Ga0.23N associated with Si and O incorporation, their shallow donor or deep donor level behavior, and carrier compensation are elucidated by allying (i) study of Si and O incorporation kinetics at high process temperature and low growth rate, and (ii) electron paramagnetic resonance measurements. The Al0.77Ga0.23N composition correlates to that Al content for which a drastic reduction of the conductivity of AlxGa1−xN is commonly reported. We note the incorporation of carbon, the role of which for the transport properties of AlxGa1−xN has not been widely discussed.

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Luminescence measurements have been applied to three different structures namely, sulphate, fluorides and YAG. In all cases the RE doping suppresses the intrinsic emission and results in intense luminescence characteristic of the RE dopant. Additionally, in double doped samples, or contaminated ones, the TL data show that each dopant defines a glow peak, which is displaced in temperature relative to the others. Examples of this were discussed for CaS04:Ce,Mn; YAG:Nd,Tb,Cr,Mn; BaF2:Ho,Ce and BaF2:Tm,Ce. The data are discussed in terms of an energy transfer model between different parts of extended defect complexes which encompass the RE ion and the lattice defects. Calcium sulphate doped with Dy define a TL peak near 200°C suitable for radiation measurements, but when co-doped with Ag the TL peak move to higher temperatures with minor effects on the peak sensitivity. In Ce,Mn double doped samples, the peak temperatures differ by -7°C between the Ce and Mn sites. The TL glow curves from alkaline earth fluorides are complex and contain several overlapping peaks. Curve fitting show that the peak maxima below room temperature are insensitive to the RE dopant. Additionally the host material has a modest effect on the peak positions. Above room temperature each dopant provides a TL curve specific to the added RE ion and do not show common peaks. Concentration has many effects on the resultant glow curve, and even at the lowest concentration used here (0.01%) there is evidence of cluster formation. Samples with high RE content show low values of the frequency factor consistent with the energy transfer model in that the emission from RE-RE cluster dominates over the emission from direct charge recombination within the defect complex. The effect of concentration and the TL mechanism operating below room temperature are also discussed. Luminescence signals from the near surface of YAG:Nd (via CL) were contrasted with those from the bulk material via RL. Results indicate that the outer few micron layers differ significantly in luminescence response from the bulk crystal. The differences were ascribed to result from solvents that enter the YAG lattice during the growth stage or subsequently from cleaning treatments via the dislocations caused by cutting and polishing. Additionally, the growth stage may include gases from the residual air in the growth furnace trapped into the YAG lattice. In each case there is a discontinuity in luminescence intensity and/or emission wavelengths at temperatures which mach the phase transitions of the contaminants. At the transition temperature there will be a sudden pressure change and this will induce surface expansion or bulk compression. The differences between the two cases were detected by the alternatives of CL and RL excitation, where the Nd or Er lines have moved in opposite directions. The detection of such low concentrations of solvents/trapped gases by luminescence is extremely difficult due to experimental limitations. Hence their role in luminescence generation is normally ignored.