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No description available.

A tese de doutorado tem como foco o desenvolvimento de nanopartículas superparamagnéticas (Fe3O4 - magnetita) hidrofílicas e lipofílicas aplicadas à nanotecnologia do petróleo. Inicialmente, os objetivos foram voltados para a elaboração e transferência de tecnologia envolvendo uma rota de síntese de nanopartículas lipofílicas, em escala semi-industrial. Para isso, foram realizados ensaios piloto num reator com capacidade de uma tonelada, visando a produção de nanopartículas magnéticas recobertas com ácido esteárico. Mais tarde, esse trabalho foi otimizado, permitindo sua execução em laboratório, prosseguindo depois, com um escopo mais amplo, incluindo a síntese de nanopartículas recobertas com polímero hidrofílico. Nesse sentido, foram desenvolvidas duas rotas inéditas para produção desses nanomateriais. Em um segundo estágio, as investigações foram voltadas para a utilização das nanopartículas sintetizadas, em estudos de avaliação das condições dos reservatórios de petróleo. Para isso, a técnica de ressonância magnética nuclear (RMN) foi explorada, monitorando o efeito da concentração dessas nanopartículas superparamagnéticas sobre o tempo de relaxação dos prótons, e o consequente efeito de contraste nas imagens em função da magnetização. A aplicação desse tipo de ferramenta (RMN) já vem sendo feita (sem nanopartículas magnéticas) pelas empresas prestadoras de serviço ao setor de petróleo e gás, na avaliação e perfilagem de reservatórios. Isso motivou o estudo dos nanomateriais magnéticos como sondas para melhorar o mapeamento de fluidos em meio poroso. Eles seriam aplicados como aditivos em fluidos de injeção em reservatórios, tanto para imageamento, como para a obtenção de parâmetros petrofísicos. Por fim, devido à presença de grupos carboxílicos na superfície das nanopartículas hidrofílicas, foram investigadas suas interações com microcristais de carbonato de cálcio, pensando no modelo de reservatório petrolífero do tipo carbonáceo. Explorando técnicas de microscopia eletrônica de varredura (MEV) e de microscopia Raman confocal, a presença das nanopartículas magnéticas sobre a superfície da matriz mineral foi constatada, confirmando sua interação efetiva com o CaCO3. Abordando a síntese, caracterização e aplicações das nanopartículas superparamagnéticas, esta tese proporciona uma base para estudos de aplicação de nanomateriais, assunto cada vez mais relevante, diante dos inúmeros problemas e desafios enfrentados pelo setor de petróleo e gás. / The Ph.D thesis is focused on the preparation of hydrophilic and lipophilic superparamagnetic nanoparticles (Fe3O4 - magnetite) for application in oil nanotechnology. The initial efforts have been directed to the upscaling of a laboratory route of synthesis of lipophilic nanoparticles, aiming technology transfer to the industry. Accordingly, a pilot process, involving a one ton reactor, has been tested for the production of magnetic nanoparticles coated with stearic acid. After this, the research has evolved, allowing the production in the laboratory scale, and continued, pursuing the development of nanoparticles coated with a hydrophilic polymer. Two new routes for the production of these nanomaterials have been developed. In a second step, the investigations were directed to the application of these nanoparticles to the evaluation of oil reservoirs, by monitoring the proton relaxation times, using nuclear magnetic resonance (NMR), and the consequent contrasting effects observed on the images, as a function of the magnetization and the concentration of these particles. Currently, NMR tools are being employed in the oil and gas sector for the evaluation and profiling of reservoirs. This fact has stimulated the use of such nanomaterials for improving the mapping of the fluids in porous media. Introduced as additives for fluid injection into reservoirs, they can enhance the imaging and also perform the rating of petrophysical parameters. Finally, the presence of carboxylic groups on the surface of the hydrophilic nanoparticles has been explored in studies of interaction with calcium carbonate, simulating a carbonaceous type reservoir. Based on electron microscopy (SEM) and confocal Raman microscopy, the presence of magnetic nanoparticles on the surface of the mineral matrix has confirmed the interaction of these particles with the CaCO3 surface. By developing the synthesis, characterization and application of superparamagnetic nanoparticles, this work provides a useful starting point for further research on the use nanoparticles, for solving problems and challenges in the oil and gas sector.

Η διασπορά κβαντικών τελειών ως πυρήνων αταξίας σε οργανωμένα συστήματα, έχει προσελκύσει επιστημονικό ενδιαφέρον και ερευνητικές δραστηριότητες, τόσο στο πεδίο της φυσικής στερεάς κατάστασης, όσο και σε αυτό της επιστήμης των υλικών. Δεν είναι σπάνια η διαπίστωση ότι υβριδικά συστήματα που προκύπτουν από συνδυασμούς όπως αυτός των υγρών κρυστάλλων και των νανοσωματιδίων, παρουσιάζουν αξιοσημείωτες και συχνά αναπάντεχες νέες ιδιότητες. Το θέμα της παρούσας διδακτορικής διατριβή κινείται σε δύο άξονες: το σχεδιασμό και την χημική σύνθεση κβαντικών τελειών επιφανειακά κατεργασμένων, για ελεγχόμενη αλληλεπίδραση με υγρούς κρυστάλλους, και τη μελέτη των φυσικών ιδιοτήτων των σύνθετων νανοδομημένων υγροκρυσταλλικών συστημάτων, που σχηματίζονται με διασπορά των νανοσωματιδίων αυτών σε χειρόμορφους θερμοτροπικούς υγρούς κρυστάλλους. Στο πρώτο μέρος της διατριβής παρουσιάζεται η χημική σύνθεση και επιφανειακή τροποποίηση κβαντικών τελειών CdSe, με υδρόφοβες επιφανειοδραστικές ομάδες τρι– οκτυλοφωσφίνης (TOP)/ελαϊκής αμίνης (ΟΑ), TOP/οκταδεκυλαμίνης, ΤOP/δωδεκυλα-μίνης, TOP/οκτυλαμίνης και τριφαινυλφωσφίνης/τριφαινυλαμίνης. Ο χαρακτηρισμός της δομής και των οπτικών ιδιοτήτων των νανοσωματιδίων έγινε με περίθλαση σκόνης ακτίνων Χ, φασματοσκοπία υπεριώδους–ορατού και φασματοσκοπία υπερύθρου, ενώ για τη διερεύνηση της μορφολογίας τους και τον προσδιορισμό των διαστάσεών τους, χρησιμοποιήθηκε ηλεκτρονική μικροσκοπία διέλευσης. Οι χημικές συνθέσεις, βασισμένες στην θερμολυτική διάσπαση οργανομεταλλικών ενώσεων, οδήγησαν σε επιτυχημένη παραγωγή σφαιρικών νανοσωματιδίων, μέσης διαμέτρου 3–4 nm, με στενή κατανομή μεγεθών και καλή διαλυτότητα σε οργανικούς διαλύτες. Στη συνέχεια μελετήθηκαν οι επιπτώσεις από τη διασπορά των νανοσωματιδίων CdSe με TOP και OA, με μέση διάμετρο 3.2 nm στη θερμοδυναμική και μοριακή οργάνωση χειρόμορφων υγρών κρυστάλλων, με τις τεχνικές της θερμιδομετρίας εναλλασσόμενης θερμικής εισόδου και με περίθλαση σκόνης ακτίνων Χ. Το ενδιαφέρον επικεντρώθηκε στη θερμοκρασιακή περιοχή των Μπλε φάσεων και στη μετάπτωση φάσης SmA–SmC*. Οι Μπλε φάσεις παρόλο που παρουσιάζουν εξέχουσες ιδιότητες για καινοτόμες εφαρμογές στη βιομηχανία οθονών και αισθητήρων, ωστόσο, είναι σταθερές σε πολύ στενά θερμοκρασιακά εύρη, μεταξύ Ισοτροπικής και Χειρόμορφης Νηματικής φάσης, γεγονός που δεν ευνοεί τη χρήση τους. Οι πειραματικές μετρήσεις αποκάλυψαν νέα φαινόμενα, όπως τη σταθεροποίηση της θερμοκρασιακής περιοχής της Μπλε φάσης ΙΙΙ (BPIII) σε μεγάλο θερμοκρασιακό εύρος, σε σχέση με τον αμιγή υγρό κρύσταλλο, και τη μετατόπιση των θερμοκρασιών μετάπτωσης σε μικρότερες τιμές. Η θεωρητική μελέτη που πραγματοποιήθηκε καταδεικνύει ισχυρή αλληλεπίδραση των νανοσωματιδίων με τις σειρές πλεγματικών ατελειών του υγρού κρυστάλλου. Παράλληλα τα αποτελέσματα φανερώνουν ότι ο χαρακτήρας Μέσου Πεδίου–Landau της μετάπτωσης SmA–SmC*, για το ίδιο σύστημα, δεν αλλοιώνεται. Η αλληλεπίδραση των κβαντικών τελειών CdSe με επιφανειακή δραστικοποίηση ΟΑ και TOP με χειρόμορφους υγρούς κρυστάλλους, παρέχει δυνατότητες και δημιουργεί σημαντικές προϋποθέσεις για νέες τεχνολογικές εφαρμογές και επιστημονικές εξελίξεις. / One dimensional semiconductor structures are intriguing materials for both fundamental research and industrial applications. On the other hand the long-range nature of the orientational order of liquid crystals is responsible for many fascinating optical, electromechanical and critical properties of these materials. Hybridization of these two fields may lead to novel materials with unusual optical and physical properties that are of considerable importance for technological applications as well as for basic physics studies on phase transitions and critical phenomena. In this context, complex soft materials were formulated that result from the dispersion of surface functionalized quantum dots in thermotropic chiral LCs. Special attention was paid to the synthesis and properties of the nanocrystals and to the dispersion state, as well as to the thermal and structural study of the composite materials. In the first part of this Thesis a chemical approach for the synthesis of semiconducting quantum dots is presented. The method, based on the thermolytic decomposition of organometallic compounds, leads to the production of spherical nanocrystalline particles highly soluble in organic media, with an average diameter of 3.2 nm, capped with a variety of amine and phosphine molecules. The as-synthesized nanoparticles were characterized by means of powder X-ray diffraction, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy and transition electron microscopy. The second part of the Thesis is concentrated on the effects upon the Blue phases and smectic-A to chiral smectic-C* phase transition of the liquid crystal CE8, arising from the dispersion of CdSe quantum dots, surface-treated with oleylamine and trioctylphosphine. For this purpose, ac calorimetry and X-ray scattering studies have been carried out. Liquid– crystalline blue phases exhibit exceptional properties for applications in the display and sensor industry. However, in single component systems, they are stable only for a very narrow temperature range between the isotropic and the chiral nematic phase, a feature that severely hinders their applicability. The systematic high-resolution calorimetric studies revealed that Blue phase III is effectively stabilized in a wide temperature range by mixing surface-functionalized nanoparticles with chiral liquid crystals. The calorimetric measurements also revealed substantial downshifts of the transition temperature. Theoretical arguments show that the aggregation of nanoparticles at disclination lines is responsible for the observed effects. Furthermore, it was found that at the SmA–SmC* phase transition, as a function of increasing nanoparticle concentration, the heat capacity anomalies display an extended-mean-field to mean-field–like crossover behavior, while the temperature dependence of the tilt angle remains bulk-like with no occurrence of pretransitional effects. The interaction of CdSe quantum dots with the cores of disclination lines gains further support, as bound disclination lines are expected to affect smectic–smectic phase transitions in a very limited manner.

Rare-earth ions co-doped lanthanum fluoride (LaF3) nanoparticles (NPs) were synthesized and the effect of different annealing temperatures investigated. We have also investigated the thermo-optical properties of Tm3+ and Eu3+ doped Y2O3 transparent ceramics. The LaF3:Yb3+/Ho3+ and LaF3:Yb3+/Tm3+ NPs were treated thermally by 3 hs at 300, 500, 700, and 900 °C and then characterized with respect to crystalline structures, sizes, shapes, presence of other crystalline phases and luminescent properties. From the experimental results, optimization of optical and structural properties were obtained for the thermal treatment at 500 °C while maintaining the LaF3 crystalline phase. However, it was observed the formation of lanthanum oxifluoride (LaOF) under thermal annealing at 900 °C, with higher luminescence in the near infrared, which makes this host to deserve further study. It was also synthesized LaF3 NPs varying the Tm3+ and Ho3+ ions concentrations with fixed Yb3+ one and these samples were thermally treated at 500 and 900 °C by 3 hs. The 1.2, 1.47, 1.8, and 2 μm emissions behaviors of Tm3+ and Ho3+ ions were investigated, in order to obtain the best concentrations for these emissions in these two hosts: LaF3 and LaOF. We also synthesized Yb3+/Tm3+ and Yb3+/Ho3+ co-doped LaF3 using nitrate and chloride precursors and these samples were annealed at 500 and 900° C to observe what occurs in the structural, morphological, and optical properties of the LaF3 and LaOF. As a result, no significant difference was observed in their structural and optical properties, thus facilitating the use of nitrate and chloride precursors for further researches using these hosts. Another very interesting and promising material is the yttrium oxide (Y2O3) transparent ceramics. In this case, we investigated using the thermal lens technique, conventional spectroscopy of luminescence and temporal dynamic, the thermal and optical properties of Y2O3:Tm3+ and Y2O3:Eu3+. The thermal properties obtained were: thermal diffusivity =26.06x10-3cm2/s, thermal conductivity =5.8 W/m.K, and the temperature coefficient of the optical path length change ⁄=2.978x10-6K-1. Small values for D and k were obtained in comparison to those of the literature, and this was attributed to the grain size of the investigated ceramics. The luminescence decays along with the thermal lens spectroscopy results were complementary to a complete characterization of the Y2O3:Tm3+ ceramics, enabling obtaining the fluorescence quantum efficiency of the Tm3+ 3F4 level emitting at 1.8 μm, which was estimated at η1=0.84. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nanopartículas (NPs) de fluoreto de lantânio (LaF3) codopadas com íons terras-rara foram sintetizadas e avaliado o efeito de tratamento térmico em diferentes temperaturas. Também investigamos as propriedades termo-ópticas de cerâmicas transparentes de Y2O3 dopadas com os íons Tm3+ e Eu3+. As NPs de LaF3:Yb3+/Ho3+ e LaF3:Yb3+/Tm3+ foram tratadas termicamente por 3 horas nas temperaturas de 300, 500, 700 e 900 °C para então caracterizá-las com relação as suas estruturas cristalinas, tamanhos, formas, presença de outras fases cristalinas e propriedades luminescentes. A partir de resultados experimentais, verificou-se a otimização das propriedades estrutural e óptica no tratamento térmico de 500 °C, mantendo a fase cristalina de LaF3. No entanto, foi observada à formação de óxifluoreto de lantânio (LaOF) no tratamento térmico a 900 °C, resultando em maior luminescência no infravermelho próximo, o que faz essa matriz merecer um estudo mais aprofundado. Também, foram sintetizadas NPs de LaF3, mudando a concentração dos dopantes Tm3+ e Ho3+, mantendo fixa a de Yb3+, e essas amostras foram tratadas termicamente a 500 e 900 °C por 3 horas. Foram investigados os comportamentos das emissões em 1,2; 1,47; 1,8 e 2 μm dos íons Tm3+ e Ho3+, com intuito de se obter as melhores concentrações para essas emissões nessas duas matrizes: LaF3 e LaOF. Sintetizamos também LaF3 codopadas com Yb3+/Tm3+ e Yb3+/Ho3+, usando precursores nitratos e cloretos e as tratamos termicamente a 500 e 900 °C para se observar o que ocorre nas propriedades estruturais, morfológicas e ópticas nas matrizes LaF3 e LaOF. Como resultado, não foram observadas diferenças significativas em suas propriedades estruturais e ópticas, facilitando assim o uso de precursores nitratos e cloretos para futuras pesquisas usando essas matrizes. Outra matriz promissora é a cerâmica transparente de óxido de ítrio (Y2O3). Neste caso, investigamos usando a técnica de lente térmica e espectroscopia convencional de luminescência e dinâmica temporal, as propriedades térmicas e ópticas de Y2O3:Tm3+ e Y2O3:Eu3+. As propriedades termo-ópticas obtidas foram: difusividade térmica =26,06×10-3 cm2/s, condutividade térmica =5,8 W/m.K e o coeficiente de variação do caminho óptico com a temperatura ⁄=2,978×10-6 K-1. Valores pequenos para D e foram obtidos, quando comparados com os da literatura. Tais valores foram atribuídos ao tamanho dos grãos das nossas cerâmicas. Os decaimentos das luminescências, juntamente com os resultados da espectroscopia de lente térmica, foram complementares para uma caracterização completa da cerâmica de Y2O3:Tm3+, possibilitando a obtenção da eficiência quântica de fluorescência do nível 34 do íon Tm3+ emitindo em 1,8 μm, a qual foi estimada em 1=0,84.

A tese de doutorado tem como foco o desenvolvimento de nanopartículas superparamagnéticas (Fe3O4 - magnetita) hidrofílicas e lipofílicas aplicadas à nanotecnologia do petróleo. Inicialmente, os objetivos foram voltados para a elaboração e transferência de tecnologia envolvendo uma rota de síntese de nanopartículas lipofílicas, em escala semi-industrial. Para isso, foram realizados ensaios piloto num reator com capacidade de uma tonelada, visando a produção de nanopartículas magnéticas recobertas com ácido esteárico. Mais tarde, esse trabalho foi otimizado, permitindo sua execução em laboratório, prosseguindo depois, com um escopo mais amplo, incluindo a síntese de nanopartículas recobertas com polímero hidrofílico. Nesse sentido, foram desenvolvidas duas rotas inéditas para produção desses nanomateriais. Em um segundo estágio, as investigações foram voltadas para a utilização das nanopartículas sintetizadas, em estudos de avaliação das condições dos reservatórios de petróleo. Para isso, a técnica de ressonância magnética nuclear (RMN) foi explorada, monitorando o efeito da concentração dessas nanopartículas superparamagnéticas sobre o tempo de relaxação dos prótons, e o consequente efeito de contraste nas imagens em função da magnetização. A aplicação desse tipo de ferramenta (RMN) já vem sendo feita (sem nanopartículas magnéticas) pelas empresas prestadoras de serviço ao setor de petróleo e gás, na avaliação e perfilagem de reservatórios. Isso motivou o estudo dos nanomateriais magnéticos como sondas para melhorar o mapeamento de fluidos em meio poroso. Eles seriam aplicados como aditivos em fluidos de injeção em reservatórios, tanto para imageamento, como para a obtenção de parâmetros petrofísicos. Por fim, devido à presença de grupos carboxílicos na superfície das nanopartículas hidrofílicas, foram investigadas suas interações com microcristais de carbonato de cálcio, pensando no modelo de reservatório petrolífero do tipo carbonáceo. Explorando técnicas de microscopia eletrônica de varredura (MEV) e de microscopia Raman confocal, a presença das nanopartículas magnéticas sobre a superfície da matriz mineral foi constatada, confirmando sua interação efetiva com o CaCO3. Abordando a síntese, caracterização e aplicações das nanopartículas superparamagnéticas, esta tese proporciona uma base para estudos de aplicação de nanomateriais, assunto cada vez mais relevante, diante dos inúmeros problemas e desafios enfrentados pelo setor de petróleo e gás. / The Ph.D thesis is focused on the preparation of hydrophilic and lipophilic superparamagnetic nanoparticles (Fe3O4 - magnetite) for application in oil nanotechnology. The initial efforts have been directed to the upscaling of a laboratory route of synthesis of lipophilic nanoparticles, aiming technology transfer to the industry. Accordingly, a pilot process, involving a one ton reactor, has been tested for the production of magnetic nanoparticles coated with stearic acid. After this, the research has evolved, allowing the production in the laboratory scale, and continued, pursuing the development of nanoparticles coated with a hydrophilic polymer. Two new routes for the production of these nanomaterials have been developed. In a second step, the investigations were directed to the application of these nanoparticles to the evaluation of oil reservoirs, by monitoring the proton relaxation times, using nuclear magnetic resonance (NMR), and the consequent contrasting effects observed on the images, as a function of the magnetization and the concentration of these particles. Currently, NMR tools are being employed in the oil and gas sector for the evaluation and profiling of reservoirs. This fact has stimulated the use of such nanomaterials for improving the mapping of the fluids in porous media. Introduced as additives for fluid injection into reservoirs, they can enhance the imaging and also perform the rating of petrophysical parameters. Finally, the presence of carboxylic groups on the surface of the hydrophilic nanoparticles has been explored in studies of interaction with calcium carbonate, simulating a carbonaceous type reservoir. Based on electron microscopy (SEM) and confocal Raman microscopy, the presence of magnetic nanoparticles on the surface of the mineral matrix has confirmed the interaction of these particles with the CaCO3 surface. By developing the synthesis, characterization and application of superparamagnetic nanoparticles, this work provides a useful starting point for further research on the use nanoparticles, for solving problems and challenges in the oil and gas sector.