Neste trabalho, a técnica de Lente Térmica (LT) foi usada para determinar o valor absoluto da difusividade térmica (D), da condutividade térmica (K) e do coeficiente de temperatura do caminho óptico (ds/tD) de vidros fluoretos dopados com cobalto e neodímio, calcogenetos, calcohaletos (mistura de calcogenetos com haletos), aluminate de cálcio e de um cristal fluoreto. Estas medidas foram efetuadas na temperatura ambiente e próxima de Tg para algumas amostras. Para o vidro ZBLAN, realizamos experimentos de LT da temperatura ambiente até ~ 330°C, observando um grande decréscimo de D na região de transição do vidro (Tg ~ 290°C). Nós também aplicamos a técnica de LT para determinar a eficiência quântica fluorescente do ZBLAN dopado com Nd+3. A utilidade desta técnica para determinar as propriedades termo-ópticas dos materiais transparentes em função da temperatura foi demonstrado. / In this work the Thermal Lens (TL) technique was used to determine the absolute values of the thermal diffusivity (D), thermal conductivity (K) and temperature coefficient of the optical path length (ds/dT) of fluoride, chalcogenide, chalcohalide (chalcogenides and halides mixture) and calcium aluminate glass and of a fluoride cristal. These measurements were developed at ambient temperature and near Tg for some samples. For the ZBLAN glass, we performed the TL experiment from ambient to ~ 330°C, observing na abrupt decrease on D close to the glass transition temperature (Tg ~ 290°C). We also applied the TL technique to determine the fluorescence quantum efficiency of Nd+3 doped ZBLAN. The usefulness of this technique to determine thermo-optical properties of transparent materials as a function of the temperature was demonstrated.

Neste trabalho, a técnica de Lente Térmica (LT) foi usada para determinar o valor absoluto da difusividade térmica (D), da condutividade térmica (K) e do coeficiente de temperatura do caminho óptico (ds/tD) de vidros fluoretos dopados com cobalto e neodímio, calcogenetos, calcohaletos (mistura de calcogenetos com haletos), aluminate de cálcio e de um cristal fluoreto. Estas medidas foram efetuadas na temperatura ambiente e próxima de Tg para algumas amostras. Para o vidro ZBLAN, realizamos experimentos de LT da temperatura ambiente até ~ 330°C, observando um grande decréscimo de D na região de transição do vidro (Tg ~ 290°C). Nós também aplicamos a técnica de LT para determinar a eficiência quântica fluorescente do ZBLAN dopado com Nd+3. A utilidade desta técnica para determinar as propriedades termo-ópticas dos materiais transparentes em função da temperatura foi demonstrado. / In this work the Thermal Lens (TL) technique was used to determine the absolute values of the thermal diffusivity (D), thermal conductivity (K) and temperature coefficient of the optical path length (ds/dT) of fluoride, chalcogenide, chalcohalide (chalcogenides and halides mixture) and calcium aluminate glass and of a fluoride cristal. These measurements were developed at ambient temperature and near Tg for some samples. For the ZBLAN glass, we performed the TL experiment from ambient to ~ 330°C, observing na abrupt decrease on D close to the glass transition temperature (Tg ~ 290°C). We also applied the TL technique to determine the fluorescence quantum efficiency of Nd+3 doped ZBLAN. The usefulness of this technique to determine thermo-optical properties of transparent materials as a function of the temperature was demonstrated.

L'utilisation de caméras infrarouges bas coûts pour la surveillance long-terme d'infrastructures est prometteuse grâce aux dernières avancées technologiques du domaine. Une mesure précise de la température des surfaces observées in-situ se heurte au manque de connaissance des propriétés radiatives de la scène. L'utilisation d'une instrumentation multi-capteurs permet d'affiner le modèle de mesure afin d'obtenir une estimation plus précise de la température. A contrario, il est montré qu'il est toujours possible d'exploiter des données climatiques en ligne pour pallier un manque de capteur. Des méthodes bayésiennes d'estimation conjointe d'émissivité et de température sont ensuite développées et comparées aux méthodes de la littérature. Un simulateur d'échanges radiatifs diffus de scènes 3D a été implémenté afin de tester ces différentes méthodes. Ce logiciel utilise l'accélération matérielle de la machine pour réduire les temps de calcul. Les résultats numériques obtenus mettent en perspective une utilisation avancée de la thermographie infrarouge multi-spectrale pour la surveillance de structures. Cette estimation conjointe permet alors d'obtenir un estimé de la température par thermographie infrarouge avec une incertitude connue. / The latest technological improvements in low-cost infrared cameras have brought new opportunities for long-term infrastructures monitoring. The accurate measurement of surfaces' temperatures is facing the lack of knowledge of radiatives properties of the scene. By using multi-sensors instrumentation, the measurement model can be refined to get a better estimate of the temperature. To overcome a lack of sensors instrumentation, it is shown that online and free available climatic data can be used. Then, Bayesian methods to estimate simultaneously the emissivity and temperature have been developed and compared to literature's methods. A radiative exchange simulator of 3D scenes have been developed to compare those different methods on numerical data. This software uses the hardware acceleration as well as a GPGPU approach to reduce the computation time. As a consequence, obtained numerical results emphasized an advanced use of multi-spectral infrared thermography for the monitoring of structures. This simultaneous estimation enables to have an estimate of the temperature by infrared thermography with a known uncertainty.

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.

Les thermoplastiques et les composites thermoplastiques sont généralement mis en œuvre par thermoformage et sont alors le plus souvent préchauffés en utilisant un chauffage IR. L’avantage du chauffage radiatif est qu'il permet de chauffer les polymères à cœur grâce au caractère semi-transparent des polymères. Néanmoins, dans le cas des polymères semi-cristallins, le chauffage radiatif est affecté par la structure cristalline et cette thèse a donc eu pour objectif d’améliorer la compréhension de l'interaction entre la structure cristalline et les propriétés optiques dans le but de proposer un modèle prédictif de chauffage de thermoplastiques semi-cristallins.Cette étude répond à une problématique industrielle relative au contrôle de la température des thermoplastiques semi-cristallins dans les procédés recourant au chauffage radiatif. L’optimisation de ces procédés requiert un code de calcul suffisamment robuste pour permettre une bonne prédiction du champ de température tout en conservant des temps de calcul acceptables. Une approche combinée expérimentale et numérique a ainsi été proposée dans le but de modéliser la capacité d’absorption du rayonnement thermique de milieux polymères semi-cristallins et le transfert de chaleur par rayonnement avec changement des phases de cristaux/amorphe. Ces travaux se concentrent sur le PEHD, qui présente un intérêt particulier pour l’entreprise Procter&Gamble.Dans cette thèse, après avoir établi une revue bibliographique mettant en avant les couplages existants entre les phénomènes de diffusion optique, la microstructure des polymères semi-cristallins et la température, une caractérisation et une analyse poussées des propriétés radiatives de deux polyéthylènes sont proposées. Les analyses morphologiques et optiques ont été réalisées à température ambiante et dans des conditions de chauffage afin d’identifier les formations cristallines à l’origine de la diffusion optique dans des polymères semi-cristallins et l’évolution de ce couplage au cours du chauffage. A travers ce travail de recherche, un coefficient d’extinction spectral thermo-dépendant a été proposé afin de décrire le caractère optiquement hétérogène du milieu semi-cristallin par un milieu homogène équivalent. Sur la base de la caractérisation de la capacité d'absorption du rayonnement thermique, un modèle thermique conducto-radiatif thermo-dépendant a été développé. Afin d’évaluer la précision de la modélisation, une méthodologie expérimentale spécifique a été proposée pour mesurer la température de surface par thermographie IR dans le cas du PEHD semi-transparent. L’étape finale a consisté à confronter les résultats issus des simulations numériques basées sur cette modélisation à plusieurs campagnes de mesures expérimentales. Les résultats de ces travaux démontrent la forte influence de la structure morphologique des polymères semi-cristallins sur les transferts de chaleur radiatifs. / Thermoplastics and thermoplastic composites are promising candidates for manufacturing highly cost- effective and environmental-friendly components in terms of rapid forming and recyclability. Thermoforming is extensively used for the processing of thermoplastics where IR heating is widely applied. The major advantage of radiative heating is that the significant portion of radiation penetrates into the semi-transparent polymer media.This thesis focuses on understanding of IR heating of semi-crystalline thermoplastics which aims to analyze the driven mechanisms for radiation transport in optically heterogeneous unfilled semi-crystalline polymer media. Considering the relatively narrow thermoforming window of semi-crystalline thermoplastics, accurate temperature control and close monitoring of temperature field is crucially important for successful forming process. It is thus required to build a numerical model robust enough to allow a good prediction of the temperature field while maintaining acceptable calculation times. In this research work, a combined experimental-numerical approach has been proposed which enables both to characterize the radiation absorption capacity of semi-crystalline polymer media and, to model the radiation heat transfer considering the crystalline/amorphous phases change under heating. This research focuses on a particular polymer - highly crystalline HDPE- which is supported by Procter & Gamble.In this thesis, the literature was reviewed at first for highlighting the existing coupled relation between the optical properties and the crystalline structure of semi-crystalline polymers. The role of crystalline morphology on the optical properties and optical scattering of two type of polyethylene, namely HDPE and LLDPE, were addressed. More specifically, the morphological and optical analyses were performed at room temperature and under heating to determine: which crystalline formations are responsible for optical scattering in semi-crystalline polymer media and, how does their coupled relationship evolve under heating conditions? Hence, one of the key contributions of this research is on establishing a temperature-dependent spectral extinction coefficient of HDPE allowing to describe temperature- dependent radiation absorption capacity of its semi-crystalline medium and, to model radiative transfer considering an equivalent homogeneous medium. Based on the characterization of radiation absorption capacity of semi-crystalline media, a temperature-dependent conduction-radiation model was developed. In order to assess the modeling accuracy, an experimental methodology was proposed for non-invasive surface temperature measurements via IR thermography on semi-transparent polymer media. The final step was to compare the results of numerical simulations with the several IR heating experiments to prove the strong influence of the crystalline morphology on heat transfer.