De nos jours, l’utilisation de liants à faible teneur en clinker est de plus en plus courante. Or la cinétique de réaction des additions minérales utilisées est plus lente que celle du clinker. Si les conditions de cure ne sont pas adaptées, le matériau aura une structure poreuse plus importante, ce qui le rendra plus sensible à la pénétration des agents agressifs extérieurs comme le CO2 ou les Cl-. La carbonatation du béton est l’un des principaux phénomènes pouvant diminuer la durée de vie d’une structure en béton armé. En effet, elle entraine une diminution du pH de la solution interstitielle qui a pour conséquence une dépassivation des armatures, puis la corrosion de ces dernières si les conditions s’y prêtent.L’objectif de cette thèse est d’étudier l’impact de la carbonatation au jeune âge sur des liants à faible teneur en clinker. Pour cela l’étude se compose de deux aspects : le premier est l’étude de l’impact de l’hydratation et de la carbonatation sur les propriétés de transport et les isothermes de sorption hydrique, et le second est l’étude de l’impact du couplage hydratation-séchage-carbonatation sur la microstructure et la structure poreuse. Pour le premier aspect, les propriétés de transport étudiées sont la diffusion de l’O2, la diffusion de la vapeur d’eau, la perméabilité à l’eau liquide qui sont des données d’entrée dans les modèles de carbonatation ainsi que la perméabilité aux gaz qui est un indicateur de durabilité. Pour le second aspect, l’impact du couplage est mesuré par ATG et DRX pour déterminer l’assemblage de phases, de plus de la porosimétrie par intrusion de Mercure et des pesées hydrostatiques sont effectuées pour détecter le changement de la structure poreuse. Les matériaux étudiés sont des pâtes de ciment et des bétons avec un rapport eau/ liant de 0,57 avec l’un des trois liants suivants : CEM I, CEM I +30% de cendres volantes et CEM I +60% de laitiers.Pour le premier aspect, les résultats montrent que pour les pâtes de CEM I le temps de cure a un faible impact sur les isothermes de sorption de vapeur d’eau s’il est compris entre 3 jours et 6 mois. Alors que, pour les pâtes de CEM I + 60% de laitier, l’augmentation du temps de cure accroit significativement la teneur en eau (pour HR=65%, tcure=3 jours et pour tcure=6 mois ) dû à une augmentation de la teneur en C-S-H. D’autre part, la carbonatation entraine une diminution de la teneur en eau de l’échantillon, ainsi que l’amplitude de l’hystérésis. De plus, le gel a une porosité plus grossière. Par ailleurs, la carbonatation entraine une augmentation de la perméabilité aux gaz des matériaux. Pour le second aspect, les résultats montrent que l’utilisation d’additions minérales diminue la résistance à la carbonatation du matériau et que cette résistance augmente avec le temps de cure si l’échantillon contient des additions. La carbonatation de la portlandite, des C-S-H et des aluminates est concomitante. De plus, pour les matériaux aux laitiers, les résultats montrent qu’ils sont plus sensibles à la carbonatation des C-S-H et des aluminates que les CEM I. En effet quand le rapport variation molaire de CaCO3 sur variation molaire de Portlandite est calculé, il vaut 1.8 pour le CEM I et environ 3.5 pour les matériaux aux laitiers. Enfin, la carbonatation entraine une diminution du degré de saturation de l’échantillon. En effet, le degré de saturation à la surface de l’échantillon passe de 50% à 35% après carbonatation pour les échantillons de CEM I et de 50% à 5% pour les échantillons de CEM I + 60% de laitiers. Cette diminution peut s’expliquer par la diminution de la surface spécifique qui est divisée par 2 après carbonatation due à la décalcification des C-S-H. Même si la carbonatation entraine une diminution de porosité cette dernière est trop faible dans ce cas pour contrer cet effet / Nowaday, low clinker content binders are used more and more often. But the kinetics reactions of the supplementary cementitious materials (SCM) are slower than this one of clinker. If the curing conditions are not adapted, material will have a bigger pore structure and becomes more sensitive to the ingress of aggressive species from the environment like the CO2 or Cl-. Carbonation is one of main phenomena which can lead to decrease the life time of reinforced concrete structure. Indeed, it leads to a decrease of pore solution pH which leads to the depassivation of rebar. Then these rebars can be corroded if the conditions are appropriate.The aim of this thesis is to study the impact of carbonation at early age for binder with a low clinker content. This study was composed of two aspects: the first one is focus on the impact of hydration and carbonation on the transport properties and the water vapour sorption isotherms (WVSI), and the second one is focus on the impact of coupling hydration – drying-carbonation on the microstructure and the pore structure. For the first aspect, the studied transport properties was O2 diffusivity, water vapour diffusivity, water liquid permeability which are inputs for carbonation modelling and the intrinsic gas permeability which is a durability factor. For the second aspect, the coupling impact was measured by TGA and DRX to determine the phase assemblage; moreover Mercury intrusion porosimetry (MIP) and hydrostatic weigh were carried out to measure the change in the pore structure. The studied materials were cement pastes and concretes with water to binder ratio of 0.57 with one of the following binders: CEM I, CEM I +30% PFA and CEM I + 60% GGBS.For the first part, results show that a curing time between 3 days and 6 months has a low impact on the WVSI for the CEM I paste. Whereas, in the CEM I +60% GGBS paste, when the curing time increases, the water content increases (for a RH=65%, tcuring=3 days and for tcuring=6 months ), this is due to the increase of the C-S-H content. Moreover, carbonation leads to decrease the water content and the hysteresis becomes flat. Additionally, carbonation leads to increase the intrinsic gas permeability. For the second part, the results show that the use of SCM decreases the carbonation resistance and this resistance increases with the curing time. Carbonation of Portlandite, C-S-H and aluminates occurs in the same time. Moreover, the CEM I +60% GGBS paste are more sensitive to the carbonation of C-S-H and aluminates than the CEM I paste. Indeed, the molar variation of CaCO3 to the molar variation of Portlandite ratio has a value around 3.5 for the CEM I +60% GGBS and 1.8 for the CEM I. Finally, carbonation leads to decrease the water saturation degree at the surface of sample. Indeed, the degree of saturation at the surface of the sample increases from 50% to 35% after carbonation for the CEM I paste and from 50% to 5% for the CEm I +60% GGBS paste. This decrease can be explained by the decrease of the BET specific surface which is divided by 2 after carbonation. It is due to the decalcification of C-S-H. Although carbonation leads to a decrease of porosity, this one is too small in this case to counter this effect

Rapporten innefattar en jämförande studie mellan olika typer av membran och beläggningar.Främst sker en jämförelse mellan materialens förmåga att andas. Vattentäthet testas på nyamaterial och efter olika sorters nötning så som martindale, flexing och tvätt för att få en ökadförståelse för materialen. Verktyget som används i studien för att mätaånggenomsläppligheten är hudmodellen. Resultatet presenteras med ett Ret-värde vilket är enförkortning på Evaporative resistance of a textile. Metoden används för att på ett bra sättsimulera hur huden svettas.Projektet har utförts på Swerea IVF som är ett forskningsinstitut beläget i Mölndal.Hudmodellen är en av de senaste stora investeringarna på Swereas textil och plast avdelning.Resultatet av studien visar att laminat andas bättre än beläggningar, dock har bärarmaterialetstor inverkan på resultaten. Ett tydligt samband mellan grövre material och sämre andning harobserverats. Många av de material som testats i studien uppvisar god förmåga att andas, därbåde flera av de mikroporösa och hydrofila materialen uppvisar Ret-värden under 13, vilketinnebär mycket god andning. En delstudie har varit att testa hur materialens andande förmågaförändras vid lägre relativ fuktighet. Resultatet blev att mikroporösa material inte påverkaslika mycket som de hydrofila materialen som då får en sämre andning.Efter de resultat studien har visat kan slutsatsen dras att tunna laminat är att föredra då högånggenomsläpplighet är ett krav. Behövs däremot ett högt motstånd mot nötning kan etttjockare material med fördel användas, vilket dock kan leda till högre ångmotstånd.This report is a comparative study between different types of membranes and coatings, thebreathability of the fabrics being the main focus of research. The fabrics' waterproofness wastested on new materials and by abrasion including martindale, flexing and washing. The toolthat has been used to measure water-vapour resistance is the skin model. The result ispresented by a Ret-value, which is short for evaporative resistance of a textile. The method isused to simulate the sweating body in a realistic way. Swerea IVF is the research institutelocated in Mölndal where the project has been carried out. The skin model is one of the latestbig investments at Swereas textile and plastic department.The results of the study shows that laminates breath better than coatings. It is important topoint out, however, that the carrier has great influence on the fabric in question. In addition,the results indicate a relation between thick fabrics and less breathability. Many of thematerials that have been tested show good permeability to breath, including bothmicropourous and hydrophilic materials. Most of them demonstrate a Ret-value less than 13,which means very good breathability. Further tests also show how the breathability changeswith lower relative humidity, indicating that microporous materials are less affected thanhydrophilic materials, thus having a higher resistance to water vapour.The conclusion of the study is that thin laminates is to prefer when high breathability isrequired. If the demand is high resistance to abrasion, a thicker material is prefered, whichalso yields a higher resistance to water permability. / Program: Textilingenjörsutbildningen

Des films composites et nanocomposites ont été élaborés par la méthode du casting à partir d’amidon natif de manioc. Ils ont été plastifiés par le glycérol et renforcés par des chargesminérales synthétiques de zéolithe Beta et de beidellite sodique. L’influence du type de charge, de l’état de la charge (lyophilisé ou non-lyophilisé ou séchage à l’air) ainsi que du taux de charge sur les propriétés mécaniques et barrières à la vapeur d’eau des films correspondants a été étudiée. Les valeurs de la solubilité dans l’eau et de la perméabilité à la vapeur d’eau des échantillons renforcés par des nanocristaux de zéolithe Beta lyophilisés sont plus grandes que celles du film de contrôle. Une augmentation significative des propriétés mécaniques, en particulier le module d’Young de ces films a aussi été observée. Une amélioration de la perméabilité à la vapeur d’eau des films composites contenant des cristaux de beidellite sodique et des films nanocomposites contenant des nanocristaux de zéolithe Beta a été trouvée. Tous les films ont été caractérisés par diffraction de rayons X. / Composite and nanocomposite films were prepared by casting method, using native cassava starch. The films were plasticized with glycerol and reinforced with synthetic Beta zeolite nanocrystals and Na-beidellite crystals. We studied the effect of the filler contents and type on the mechanical and water barrier properties of the resulting films. We found that filmsreinforced with lyophilized Beta zeolite nanocrystals present both high water solubility (WS) and high water vapor permeability (WVP) values compared to those of the pristine film. A drastic increase of the mechanical properties, especially in the Young’s modulus, of these films was also observed. An improvement of the WVP was found for composites prepared from Na-beidellite crystals and for nanocomposites from non-lyophilized Beta zeolite nanocrystals. All the films were characterized by X-ray diffraction.

New methods, based on tracer gas measurements and isotopicanalysis can be used to evaluate the moisture properties ofbuilding materials and provide the means for forensic analysisof the origins and history of excessive water in buildings, theimmediate practical consequences of which will be the abilityto improve the moisture performance of constructions. It is shown, in theory and through measurements how thewater vapour permeability of porous building materials can witha good degree of accuracy be estimated with tracer gasmeasurements that provide an efficient alternative to the cupmethod. Complementary measurements may be carried out in orderto evaluate the contribution of surface diffusion and theeventual enhancing effects of moisture content on the diffusioncoefficient. The Random Hopping Model is used to illustrate howthe surface diffusion coefficient depends on the amountadsorbed and the activation energy of migration that can beevaluated from the sorption isotherms. It is explained how the abundance ratios of two of the mostordinary isotopes of hydrogen and oxygen in water can be usedto determine its history. These isotopes are stable and givethe water a distinct signature that can be used to reveal itssource as shown in a case study. In a contrary manner themeasured isotopic separation can be used to determine therelevance of different transport processes and reactions. It isof central importance that not only does the magnitude ofisotopic separation for the reactions vary for deuterium andoxygen-18 but even the ratio thereof. One of the challenges hasbeen to construct an experimental method for retrieving samplesof water for comparison. Furthermore this thesis includes an evaluation of a new typeof a light weight construction with loose-fill cellulose fibre,in which the conventional polyethylene vapour barrier has beenreplaced with polypropylene fabric. With a verified model ithas been investigated how the construction would perform fordifferent internal moisture loads and reference climate fromthe literature. The results suggest that this type ofconstruction is not to be recommended. KEYWORDS:tracer gas, water vapour permeability,diffusion, surface diffusion, isotopic analysis, deuterium,oxygen-18, fractionation, vapour barrier, transient numericalmodelling of diffusion. / QC 20100611

Los sistemas de posicionamiento global GNSS (GPS y GLONASS) se han convertido en una herramienta básica para obtener medidas geodésicas de la Tierra y en una fuente de datos para el estudio atmosférico. Proporcionan cobertura global y permanente y por la precisión, exactitud y densidad de datos, las señales radio transmitidas pueden ser usadas para la representación espacio-temporal de la atmósfera.La tecnología de los receptores GPS ha evolucionado con una sorprendente rapidez, resultando en instrumentos con suficiente calidad de medida para ser utilizados en estudios geodésicos, comparables a los resultados de técnicas como la interferometría de muy larga base (VLBI), y estudios atmosféricos cuyos resultados pueden ser usados en meteorología.En la tesis Tomografía Atmosférica utilizando Señales Radio de Satélites nos hemos centrado en el uso del sistema GPS por disponer mayor cantidad y calidad de referencias y herramientas para el procesado de los datos. No obstante, se ha demostrado la posibilidad de extender el concepto a cualquier sistema de transmisión radio desde satélite como sondeador atmosférico. La estructura de la tesis se ha dividido en dos áreas: el procesado de datos GPS para extraer información referente a los parámetros atmosféricos de interés, y la aplicación de técnicas tomográficas para la resolución de problemas inversos. En particular, la tomografía se ha aplicado a la ionosfera y la atmósfera neutra. En ambos casos, los resultados tienen un innegable impacto socio-económico: a) la monitorización del estado ionosférico es fundamental por las perturbaciones que la ionosfera provoca en las transmisiones radio que la atraviesan, y b) la estimación del contenido de vapor de agua de la troposfera es de utilidad en la predicción meteorológica y climática.La tomografía ionosférica se empezó a desarrollar usando únicamente datos de la red global IGS. A continuación se mejoró la resolución vertical mediante la utilización de datos de ocultaciones del experimento GPS/MET. La mejora de la resolución se ve limitada a la región en la que estos datos existen. Finalmente, se utilizaron datos de altimetría del satélite TOPEX/POSEIDON para mejorar los mapas y para demostrar la posibilidad de calibración instrumental de los altímetros radar usando técnicas tomográficas.La aplicación a la troposfera se obtuvo tras la mejora y refinamiento tanto del procesado de datos GPS como del proceso de inversión tomográfica. Los primeros resultados se obtuvieron mediante los datos experimentales de la red permanente en Kilauea, Hawaii, por la configuración particular de los receptores. Estos resultados demostraban la capacidad de obtener representaciones espacio-temporales de la troposfera mediante datos GPS. El análisis de los datos de la campaña REGINA, realizada en el Onsala Space Observatory, nos permitió la descripción de un fenómeno meteorológico complejo mediante la tomografía troposférica usando datos GPS y su verificación por comparación directa con medidas realizadas por radiosondeo.En conclusión, se ha demostrado la posibilidad de aplicar tomografía a la atmósfera utilizando señales radio de satélites y, en particular, la constelación GPS. / The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they transmit can be used for the spatio-temporal representation of the atmosphere.GPS receivers technology has evolved at a surprising pace: nowadays they have sufficient measurement quality as to be used in geodetic studies, together with other techniques such as the Very Long Base Interferometry (VLBI), and in atmospheric studies whose results can be input into meteorological analysis.In the thesis "Atmospheric Tomography Using Satellite Radio Signals" we have focused on the use of GPS system due to the better quality and quantity of references and tools for the data processing. This notwithstanding, we have proven the possibility to broaden the concept to include any other radio signal transmitting satellite system as an atmospheric sounder. The thesis has been divided into two main areas: GPS data processing to extract the information related to the atmospheric parameters under study, and the implementation of tomographic techniques to the solution of the inverse problem. In particular, tomography has been applied to the ionosphere and to the neutral atmosphere. In both cases, results have a socio-economic impact: a) monitoring the ionosphere is essential for radio transmissions across it because of the perturbations it may produce on the signal, and b) estimating water vapour content in the troposphere is highly useful for meteorological and climate forecastFor the ionospheric tomography we initally only used the data from the global IGS network. Vertical resolution was afterwards improved using the occultation data of the GPS/MET experiment. The improvement, however, was limited to the region where these data existed. Finally, we used altimeter data from the TOPEX/POSEIDON satellite to improve the maps and to prove the radar altimeter calibration capability of the tomographic technique.The application to the troposphere was possible after the improvement and refinement of both the GPS data processing and the tomographic inversion. The first results were obtained using the experimental data from the permanent network in Kilauea, Hawaii. The particular geometry of the receivers in this local network made it highly suited for these initial results, which proved the possibility of obtaining spatio-temporal representations of the troposphere using GPS data. The data analysis of the REGINA campaign, which took place at the Onsala Space Observatory, provided the description of a complex meteorological phenomenon using only GPS data tropospheric tomography. We verified the results with a direct comparison with radiosonde data.Concluding, we have demonstrated the capabilities of atmospheric tomography using satellite radio signals, with particular emphasis on the GPS signals.

The application of current soy protein films are limited due to their low mechanical strength and high moisture sensitivity compared to synthetic materials. This research studied several methods to improve the mechanical properties [tensile strength (TS), elongation at break (EAB), Young’s modulus of elasticity (YM)] of solvent cast soy protein isolate (SPI) films. Drying times were significantly reduced through the use of a heated casting surface. Neutral (pH 7) SPI films were prepared but were found to have lower TS, EAB and YM than control films prepared under alkaline conditions. Cellulose was extracted from soybean wastes and transmission electron microscopy (TEM) verified the existence of nano-sized fibres. Composite SPI films were prepared using either extracted cellulose fibres or titanium dioxide (TiO2) nanoparticles and their mechanical and barrier properties (water vapour, and oxygen permeability) were evaluated under different relative humidity (RH) conditions. In general, TS and YM decreased and EAB increased with increasing RH. Films with 5% (w/w) added cellulose exhibited significant (p-value < 0.05) improvements in TS and YM but decreased EAB. TiO2 composites possessed similar TS, YM, and EAB values to control films. Barrier properties were comparable across all samples, and decreased with increasing RH. Samples were characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Preliminary work investigating synthesis of filler materials using cross-linked sodium alginate particles increased the TS and YM of SPI films to a similar extent as extracted cellulose. A method for electrospinning cellulose using ionic liquids was developed, but requires further process optimization to be used for fibre/filler synthesis. / OMAFRA; Hannam Soy Utilization Fund

Vapour pressure (interchangeably referred to as atmospheric humidity) and solar radiation data are, for different reasons, difficult data to obtain in South Africa. Relative humidity measuring instruments (from which vapour pressure values can be obtained) require constant maintenance , while solar radiation can only be measured electronically. Data from both of these variables are, however, required as inputs to the Penman-Monteith equation, which has become the internationally accepted reference for the estimation of potential evaporation. It is necessary, therefore, to produce estimates of vapour pressure and solar radiation over South Africa from more common surrogates, e.g. rainfall and temperature data. Several methods of estimating vapour pressure and solar radiation from the literature are reviewed in this dissertation. Considerably greater attention is focused on models of vapour pressure than solar radiation , as less literature exists on this subject. In general, the methods involved in estimating vapour pressure tend to be relatively rudimentary. The FAO 56 documentation advises using saturated vapour pressure at minimum air temperature as an estimate of vapour pressure, yet the implicit assumptions of using this approach can fail in many circumstances, particularly in the more arid regions . It was found that monthly vapour pressure at any given location in South Africa could be estimated from geographical (invariate) data alone. It was also found that the most influential factor affecting daily vapour pressure at a given location within a given time frame (less than one month) was "air masses". Air masses proved too complicated to model from surrogate data of temperature and rainfall , however, and were thus omitted from the final model. Daily values of vapour pressure and vapour pressure deficit were estimated by holding vapour pressure for a given month constant, but varying temperature on a daily basis It was found that this method produced acceptable results for both elements throughout South Africa. The need for estimating solar radiation has existed for considerably longer than for vapour pressure. Professions other than agriculture, principally architecture and civil engineering, have long required solar radiation data/values. For this reason the art of estimating solar radiation values is better established and more models were available in the literature. Several suitable and recently developed solar radiation models, which use surrogate data (temperature and rainfall) , were identified from the literature survey. These models were then applied in situ and the results were compared with observed values. It was found that the majority of models produced similar output to one another. However, the Liu and Scott (2001) model, which is an enhancement of the Bristow and Campbell (1984) model, was found to be the best available model of those tested, particularly in the more humid locations of South Africa . Verification analyses revealed that the Liu and Scott (2001) model could be used to interpolate solar radiation where a sparse network of solar radiation measuring stations exists, e.g. in the arid locations of South Africa . The structure of the Liu and Scott (2001) model , however, prevented it from being employed in a subsequent exercise on mapping solar radiation over South Africa . For this purpose, the Hunt et al . (1998) model was employed. The estimation of two elements , vapour pressure and solar radiation , was improved upon, and the Penman-Monteith equation can thus now be more confidently applied throughout South Africa. Of these two elements, it is vapour pressure , which, because of a paucity of research to date on the subject, lends itself to expansive research in the future . / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

An important goal in modern weather prediction is to improve short-term weather forecasts, especially of severe weather and precipitation. However, the ability to achieve this goal is hindered by the lack of timely and accurate observations of atmospheric water vapour, which is one of the most poorly measured and least understood constituents of the Earth's atmosphere due to its high temporal and spatial variability. This situation is being addressed by the Global Positioning System (GPS) technology. GPS radio signals are slowed and bent by changes in temperature, pressure and water vapour in the atmosphere. Traditionally, the GPS signal propagation delay is considered a nuisance parameter that is an impediment to obtaining precise coordinates using GPS. Recent development in GPS precise positioning and orbit determination has enabled the atmospheric parameters to be determined to a high degree of accuracy on a routine basis, using continuous tracking data from ground-based GPS receivers. The aim of this research is to address several critical scientific challenges in estimating the atmospheric water vapour content in near-real-time (NRT) in Australia. Contributions are made to the field of GPS meteorology in the following five areas: First of all, research efforts were made to develop a technical platform for the ground-based GPS meteorology studies and demonstration of GPS Precipitable Water Vapour (PWV) estimation using observations from Australian Regional GPS Networks (ARGN). Methods of estimation of water vapour from GPS and radiosonde data have been developed and tested. GAMIT-based GPS data processing strategies and compare analysis with radiosonde water vapour solutions from the Australia Upper Air Network (AUAN) were undertaken, providing an effective technical basis for further studies. Secondly, the research has developed techniques to allow estimation of atmospheric water vapour from GPS data and surface meteorological observations collected around the GPS sites. Ideally a dedicated meteorological sensor is installed adjacent to the GPS antenna. However, meteorological sensors are normally not installed at most Australian GPS stations. Installing a new meteorological sensor at each GPS station would involve additional cost at the level of one-third or half of the geodetic GPS receiver cost. We have experimentally developed and demonstrated interpolation methods for making use of hourly collected surface meteorological data from the Australian Automatic Weather Station (AWS) network operated by the Bureau of Meteorology (BOM) to estimate atmospheric water vapour. Thirdly, the research has studied ocean tidal loading and its effects on GPS derived precipitable water vapour estimates. The periodic motion of the Earth's surface due to ocean loading is one of the largest periodic motions. However, very little work has been done to quantify their effects on GPS-derived solutions at the GPS sites in the Australian region surrounded by ocean waters. The research presents the theoretical analysis and experimental results from the ARGN network, focusing on ocean loading and its effects on GPS derived precipitable water vapour estimates. The fourth important effort was the development of techniques for estimating highrate Slant Water Vapour (SWV) values for future operational meteorological applications in Australia, including addressing such issues as slant-path delay recovery from post-fit double-difference residuals, and overcoming site multipath effects. The experimental results have demonstrated the efficiency of the proposed methods. Finally, in order to address the meteorological applications with the existing and anticipated GPS reference stations in the Australian region, and measure the atmospheric water vapour content in near-real-time, the technical issues to implement NRT GPS water vapour estimation were identified and discussed, including the data requirements for meteorological and climate applications, NRT data processing and quality control procedures for GPS orbits. The experimental GPS PWV results from NRT and post data processing are compared and presented.

La vapeur d'eau est une composante clé du système climatique. Sa distribution et sa variabilité sont des sources d'incertitude dans les modèles climatiques. L'utilisation d'observations et des réanalyses des Contenus Intégrés en Vapeur d'Eau (CIVE) peut faciliter leur évaluation. Dans ce travail, des données CIVE-GPS retraitées du réseau mondial ont été utilisées pour la période 1995-2010. Afin d'évaluer les incertitudes et les inhomogénéités dans les séries GPS, une comparaison globale avec les données de réanalyse ERA-Interim a été faite. Un bon accord général a été trouvé sur les moyennes, la variabilité et les tendances ait été trouvé. Des interruptions et inhomogénéités ont été constatées dans les séries GPS, ainsi que les problèmes de représentativité dans les zones côtières et de topographie complexe. Dans ERA-Interim, des tendances trop fortes ont été constatées dans certaines régions. ERA-Interim a aussi été comparé avec d'autres réanalyses (MERRA-2, ERA-20C, 20CR), et des différences ont été trouvées dans les tendances de les CIVE sur l'Afrique, l'Australie et l'Antarctique. Enfin, les jeux de données CIVE-GPS et CIVE-ERA-Interim ont été utilisés pour évaluer quatre configurations du modèle de circulation générale atmosphérique LMDZ avec deux physiques, libres et guidées avec les vents d'ERA-Interim. Il a été trouvé que la nouvelle physique est plus humide aux latitudes tropicales. Sans guidage, pour les deux physiques, le modèle présente des difficultés à reproduire les tendances et la variabilité obtenues par GPS et par ERA-Interim. Cela confirme l'importance de la dynamique à grande échelle pour les tendances et la variabilité des CIVE. / Water vapour is a key component of the Earth’s climate system, and its distribution and variability are sources of uncertainty in climate models. The use of long-term integrated water vapour (IWV) observations and reanalyses can help in their assessment. This work pioneered the use of reprocessed GPS IWV data for 1995-2010, converted from estimates of Zenith Total Delay. The conversion was assessed, with the goal of producing a high quality long-term IWV data set. Due to uncertainties in the GPS observations and homogeneity concerns, a global comparison with ERA-Interim reanalysis data was made. Although a general good agreement in means, variability and trends was found, issues in both data sets were highlighted. In GPS, gaps and inhomogeneities in the time series were evidenced, as well as representativeness differences in coastal areas and regions of complex topography. In ERA-Interim, too strong trends in certain regions were found. ERA-Interim was also compared with other reanalyses (MERRA-2, ERA-20C, 20CR), and differences were found in the IWV trends over Africa, Australia, and Antarctica. Finally, GPS and ERA-Interim IWV were used to assess four configurations of the LMDZ atmospheric general circulation model with two different physics and with or without nudging towards ERA-Interim wind fields. Impact of the model physics on the IWV mean was found, with the new physics being moister at tropical latitudes. Overall, the model free runs in both physics have difficulty reproducing the trends and variability observed in ERA-Interim and GPS. This is improved with the nudging, which confirms the importance of large-scale dynamics on IWV trends and variability.

Les aciers inoxydables ferritiques sont actuellement les meilleurs candidats pour répondre au cahier des charges des matériaux destinés aux interconnexions de piles à combustibles à oxyde solide (SOFC acronyme anglo-saxon pour Solid Oxide Fuel Cell). Cependant, du coté du compartiment cathodique de ces piles, le phénomène de sublimation du chrome à haute température conduit à des dégradations importantes, réduisant ainsi la durée de vie en service des SOFC. Les objectifs de ce travail de thèse sont (i) d'étudier le phénomène de sublimation du chrome sur l'acier inoxydable ferritique AISI 441 et (ii) de rechercher le ou les moyen(s) d'atténuer cette même sublimation. Sur le deuxième point, des méthodes de protection ont été mises en œuvre, en particulier avec le dépôt de films minces de spinelle Mn-Co obtenues via un procédé de galvanoplastie ou bien encore en procédant à des pré-oxydations des alliages dans des atmosphères contrôlées de type argon impur ou mélanges gazeux équimolaires CO / CO2 (250 ° C et 850 ° C, pour une durée totale de 3 h).Concernant l'étude de la sublimation du chrome, des essais d'oxydation simulant les conditions de service ont été conduites dans des mélanges gazeux : 5% de O2 dans H2O à 800 °C pendant 96 h. A vitesse de gaz oxydants faible, de 1 à 3 cm / s, la sublimation du chrome est limitée par un phénomène de diffusion dans la phase gazeuse de l'espèce volatile oxo-hydroxyde de chrome. A vitesse plus élevée, de 3 à 10 cm / s, la sublimation du chrome semble limitée par un phénomène interfacial. La vitesse de sublimation apparait indépendante de la rugosité de surface des échantillons, elle même variant selon la préparation des échantillons. Du point de vue de la caractérisation morphologique des couches d'oxydation thermiques obtenues, sur les surfaces de plus forte rugosité (surface industrielle), nous avons noté le développement de nodules riches en titane et en niobium avec une partie externe et une autre interne. Dans le substrat, des phases de lave de type Fe2Nb ont été observées le long des joints de grain métalliques.Dans une deuxième partie, la sublimation du chrome a été étudiée sur échantillons revêtus ou pré-oxydés. Les films minces de spinelle Mn-Co ne conduisent pas à l'abaissement de la vitesse de sublimation du chrome et sont donc pas protecteurs. L'adhérence de ces revêtements est de mauvaise qualité. Les couches présentent de nombreuses fissures. La pré-oxydation conduit quant à elle à une réduction considérable (jusqu'à un facteur 10) de la vitesse de sublimation du chrome (sauf dans le cas de la pré-oxydation dans l'argon à 850 °C). La formation d'un film riche en fer obtenu à basse température (250 °C) peut expliquer cette réduction par l'établissement d'une barrière de diffusion. Cette même réduction est cependant surprenante sur les films riches en chrome obtenus par pré-oxydation à 850 °C dans CO / CO2. Nous proposons dans ce travail une interprétation originale basée sur les différences de nature semi-conductrice des films de chromine formées à haute pression d'oxygène (proche de l'atmosphère) et identifiés comme étant de type p par rapport à ceux obtenus à basse pression (dans CO/CO2) qui sont connu pour être de type n. Après l'oxydation à haute température de 96 heures, tous les échantillons préalablement pré-oxydés ont été observés comme étant composés d'oxyde de chrome et d'un spinelle Mn-Cr.Au terme de ce travail de thèse, il peut être conclu que la pré-oxydation de l'alliage 441 à basse température (250 °C) dans l'argon ou le mélange CO/CO2 ou encore à plus haute température (850 °C) dans le mélange CO/CO2 sont des traitements qui conduisent à l'abaissement de la vitesse de sublimation du chrome et par voie de conséquence à l'amélioration de la tenue de cet alliage en condition d'oxydation dans le compartiment cathodique des SOFC. / Ferritic stainless steels are the most attractive materials that are able to fulfil SOFC(Solid Oxide Fuel Cell) interconnect properties. However, in cathodic SOFC condition, Crvolatilisation from ferritic steels leads to degradations of interconnect and cathode materialsand shorter service lifetime of SOFC. The objectives of this work are (i) to study Crvolatilisation from AISI 441 ferritic stainless steel and (ii) to find the way out to suppress Crvolatilisation. The Cr volatilisation protective methods used in this work were coating withMn-Co spinel by an electroplating method and preoxidation in the condition of Ar or CO/CO2at either 250°C or 850°C, for 3 h. Cr volatilisation experiments were performed in 5%H2O inO2 at 800°C for 96 h. According to the results, it can be concluded that the preoxidation ofthe AISI 441 in Ar or CO/CO2 at low temperature (250°C) or in the CO/CO2 at a highertemperature (850°C) are treatments that lead to lowering the sublimation rate of the Cr andimprovement in the oxidation resistance of this alloy in the cathodic compartment of theSOFC.