The diploma thesis deals with the heterogeneous technique of preparation of grafted polypropylene g maleic anhydride (PP-g-MAH). The knowledge of the course of the reaction and its impact on the PP grafting process are summarized in the theoretical part. The preparation of the grafted PP was carried out in a fluidized polymerization reactor at 115 °C, speed of mixing 210 rpm, reaction time 60 min and pressure 6 bar. The amount of grafted MAH was monitored by using a MAH concentration 3 and 5 wt% and an initiator concentration 0.25; 0.5; 1; and 1.5 wt%. Modification efficiency was compared by using 3 types of PP with different particle morphology and specific surface area. By creating the theoretical model, the maximum surface concentration of MAH was calculated and compared with experimental data. Characterization of PP materials was performed by Electron Scanning Microscopy (SEM), Differential Scanning Calorimetry (DSC) and particle surface analysis by BET. Quantitative analysis of grafted MAH was determined by FTIR spectroscopy and acid-base titration.

Porous ceramic materials are an interesting group of materials due to a wide range of physical properties, low density, and good permeability. Production of a monolith with a shape stability that would also have a high specific surface area and high porosity is a common problem with porous ceramics. The goal of this work was to maintain the high specific surface area and to produce a monolith with a shape stability. Two forms of porous silica nanofibers (as prepared and milled) were used and partially sintered using the Spark Plasma Sintering method (SPS). Different sintering times and temperatures for SPS were tested. The findings revealed that the best SPS conditions were as follows: temperature: 600 °C, sintering time: 5 minutes, pressure: 3 MPa, and the heating rate: 144 °C/min. These sintering conditions resulted in a stable silica based machinable monolith made from fibers or milled fibers. The monoliths have the specific surface area of up to 470 m^2/g and porosity of 72 %, or the specific surface area of up to 422 m^2/g and porosity of 69 % for as prepared fibers and milled fibers, respectively.

Yes / This paper aims to evaluate the influence of surface area and amount of nano silica (NS) on the performance of concrete with different water/binder (w/b) ratios. For this purpose, 63 different mixes were produced using three NS having three differentsurface areas (52, 250 and 500 m2/g) and w/b ratios (0.4, 0.5 and 0.6). Compressive strengths , workability, water absorption and the microstrcture of concrete mixtures were measured and analysed. and the optimum ratio for each type was determined. The results indicated that the performance of NS particles in concrete is significantly dependent on its amount and surface area as well as w/b ratio. As the w/b ratio increased, a better performance was observed for all types of NS used, whilst NS having 250m2/g surface area was found to be the most effective. The optimum amount of NS ranged from 2 to 5%, depending on NS surface area. / The full-text of this article will be released for public view at the end of the publisher embargo on 15 May 2020.

Les poudres d'aluminium sont depuis longtemps utilisées comme additifs dans de nombreuses formulations pour la pyrotechnie ou les propergols. Introduites en quantité relativement faible dans les propergols des fusées, elles permettent d'accroître significativement les vitesses de combustion. Cependant, les mécanismes à l'origine de cette meilleure réactivité restent encore mal compris et vont bien au-delà d'une simple explication en terme d'augmentation de l'état de division. Au cours de cette thèse nous avons élaboré des poudres d'aluminium par broyage à haute énergie, technique mécanique peu couteuse qui pourrait être une alternative aux procédés de fabrication actuels. Nous montrons que cette méthode permet l'obtention de particules micrométriques ou nanométriques suivant les conditions de broyage. Les particules sont polycristallines et présentent une morphologie en plaquette. Les poudres nanométriques obtenues présentent une réactivité comparable voire même supérieure aux nanopoudres sphériques actuellement élaborées par électro-explosion de fil ou voie plasma. Nous montrons que cette bonne réactivité est lié à la morphologie des particules ainsi qu'à la microstructure de la couche d'alumine native qui passive l'aluminium. / Aluminium nanopowders have been using for a long time as additives in many formulations for propergol or in pyrotechnics. Introduced in small quantity in rocket propergol they allow to increase the combustion rate. However, the reactivity of aluminium particles is not really understood and not just linked to the size reduction effect. All along this study, we have elaborated aluminium powders using high energy mechanical milling, a mechanical technique with a low cost which could be an alternative process of powders fabrication. We prove that this method allows elaboration of micro and nano-particles as a function of the mechanical parameters. The particles are polycristallines with flake morphology. The obtained nanopowders have a similar reactivity, or better than spherical nanopowders obtained by wire electrical explosion or plasma. We proove that this good reactivity is linked to the particles morphology, as well as also to the microstructure of the native alumina core shell.

The pore saturation of natural gas hydrate in sediments is a key parameter for estimating hydrate resources in a reservoir. For a better understanding of gas hydrate distribution, the experimental study of the pore saturation of methane hydrate in sediments from a hydrate reservoir in the Eastern Nankai Trough have been carried out. In total, eleven samples, comprising sand, silty sand, silt, and representative of the main sediment types identified in the Eastern Nankai trough, were tested. The results obtained clearly indicate a particle size and clay content dependent trend: almost 100% of pores were saturated with methane hydrate in sand when little silt and clay were present, decreasing to ~ 13% in silty sand (sand 54%, silt 41% and clay 5%), and ~ 4% in clayey silt. These results are generally consistent with NMR logging results for high-saturation samples, but somewhat different for samples with medium or low saturation levels.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Soil water retention stems from the action of attractive forces manifested by adsorption and capillary phenomena. Matric potential (ψ) expresses the soil water retention energy, which varies according to water content and is described by soil water retention curve (SWRC). The experimental obtainment of SWRC is difficult and costly, therefore, the use of pedotransfer functions (PTF) is preferred, because PTF estimate SWRC (or part of it) from other soil properties related to water retention. The use of available PTFs is limited for being calibrated from a particular set of soils and/or for not being able to represent the effect of structural changes (e. g. bulk density (Bd)) on water retention. Thus, the aim of this study is to propose and evaluate a mathematical model to estimate the volumetric moisture based on the specific surface area (SSA) and on the integration of the effect of the Bd with a physicoempirical parameter (fa). SWRCs were obtained experimentally from soils with different particle size and Bd variations were simulated by samples prepared in metal cylinders. The SSA was estimated by particle size distribution curve. Dependence of fa on ψ, SSA and Bd was described by Van Genuchten (1980) sigmoidal model, while the effect of SSA and Bd was incorporated in parameters of this same sigmoidal model by graphical and sensibility analysis. The estimates of the model were compared with the literature FPTs estimates for the same data set. Initially, the results showed that samples prepared in the laboratory did not ensure consistent experimental data of SWRC. This finding masked the model predictive ability. However, it is clear that the proposed FPT coherently described the effect of SSA and Bd with adsorption and capillarity phenomena, complying with the study purpose. In addition, the physicoempirical consistency of SSA and Bd with parameters of the Van Genuchten (1980) sigmoidal model allowed a better predictive performance compared to literature PTFs. In a broader sense, results reinforce the idea that models which mechanistically explore the relationship between predicted and predictor variables are more efficient in estimating the magnitude of the natural soil processes. and Bd was incorporated in parameters of this same sigmoidal model by graphical and sensibility analysis. The estimates of the model were compared with the literature FPTs estimates for the same data set. Initially, the results showed that samples prepared in the laboratory did not ensure consistent experimental data of SWRC. This finding masked the model predictive ability. However, it is clear that the proposed FPT coherently described the effect of SSA and Bd with adsorption and capillarity phenomena, complying with the study purpose. In addition, the physicoempirical consistency of SSA and Bd with parameters of the Van Genuchten (1980) sigmoidal model allowed a better predictive performance compared to literature PTFs. In a broader sense, results reinforce the idea that models which mechanistically explore the relationship between predicted and predictor variables are more efficient in estimating the magnitude of the natural soil processes. / A retenção de água no solo decorre da atuação de forças atrativas que se manifesta por meio dos fenômenos de adsorção e capilaridade. O potencial matricial (ψ) expressa a energia com que a água está retida no solo, que varia com a umidade volumétrica (Uv) e é descrita pela curva de retenção de água no solo (CRAS). A obtenção experimental da CRAS é difícil e onerosa, o que motiva o uso de funções de pedotransferência (FPT), que estimam a CRAS (ou parte dela) a partir de propriedades do solo ligadas à retenção de água. As FPTs disponíveis são limitadas quanto à aplicação para solos diferentes dos quais foram calibradas ou por não conseguirem representar o efeito de mudanças estruturais (variação na densidade do solo (Ds)) sobre a retenção de água. Portanto, o objetivo deste estudo é propor e avaliar um modelo matemático para estimar a umidade volumétrica, baseado na área superficial específica (ASE) e na integração do efeito da Ds a partir de um parâmetro físico-empírico (fa). Experimentalmente, CRAS foram obtidas a partir de solos com diferente granulometria, para os quais variações de Ds foram simuladas por meio da confecção de amostras em cilindros metálicos. A ASE foi estimada por meio da curva granulométrica. A dependência de fa em relação às variáveis ψ, ASE e Ds, foi descrita pelo modelo sigmoidal de Van Genuchten (1980), enquanto o efeito da ASE e Ds foi incorporado aos parâmetros desse modelo sigmoidal por meio de análise gráfica e de sensibilidade. As estimativas do modelo proposto foram comparadas com estimativas de FPTs da literatura para o mesmo conjunto de dados. Inicialmente, verificou-se que, mesmo utilizando amostras confeccionadas em laboratório, a obtenção experimental da CRAS demonstrou-se, por vezes, inconsistente, o que mascarou a capacidade preditiva do modelo. Contudo, é possível afirmar que a FPT proposta foi capaz de descrever o efeito da ASE e da Ds de forma fisicamente coerente com os fenômenos de adsorção e capilaridade, cumprindo com a proposta deste estudo. Além disso, a consistência física-empírica entre ASE e Ds e os parâmetros de ajuste do modelo sigmoidal de Van Genuchten (1980) permitiram melhor desempenho preditivo comparado às FPTs da literatura. De forma mais ampla, os resultados reforçam a ideia de que modelos que explorem mecanisticamente a relação entre variáveis preditas e preditoras são mais eficientes na estimativa da magnitude dos processos naturais ligados ao solo.

Le bilan d'énergie de surface du Plateau Antarctique est essentiellement contrôlé par les propriétés physiques des premiers centimètres du manteau neigeux. Or l'évolution de cette neige de surface est complexe car elle dépend de processus fondamentalement imbriqués: vitesse de métamorphisme, profils de température, pénétration du rayonnement solaire, précipitations, transport de neige par le vent, etc. L'objectif de ces travaux de thèse est d'étudier ces diverses composantes et leur couplage afin de simuler l'évolution de la densité de la neige et de la taille de grain (surface spécifique) sur le Plateau Antarctique. Pour représenter de manière physique l'absorption de l'énergie solaire à l'intérieur du manteau, un modèle de transfert radiatif à fine résolution spectrale (TARTES) a été implémenté dans le modèle de manteau neigeux détaillé Crocus. TARTES permet de calculer le profil vertical d'absorption d'énergie dans un manteau stratifié dont les caractéristiques sont connues. Parmi elles, la forme des grains, explicitement prise en compte dans TARTES, a été peu étudiée jusqu'à présent. C'est pourquoi une méthode de détermination expérimentale de la forme optique des grains est proposée et appliquée à un grand nombre d'échantillons de neige. Cette méthode, basée sur des mesures optiques, des simulations TARTES, et l'inférence bayésienne, a permis de déterminer la forme la plus adéquate pour simuler les propriétés optiques de la neige, et a mis en évidence le fait que représenter la neige par un ensemble de particules sphériques conduisait à surestimer la profondeur de pénétration du rayonnement d'environ 30%. L'impact de l'absorption en profondeur du rayonnement sur les profils de température dans le manteau et son métamorphisme est ensuite étudié par des approches analytique et numérique, mettant en valeur la sensibilité des profils aux propriétés de la neige proche de la surface. En particulier, la densité de la neige sur les premiers centimètres est cruciale pour le bilan d'énergie du manteau car elle impacte à la fois la profondeur de pénétration du rayonnement et la conductivité thermique du manteau. Puisque le modèle Crocus tient compte de ce couplage entre propriétés optiques et physiques du manteau, il est utilisé pour estimer l'influence des conditions météorologiques sur la variabilité temporelle des propriétés physiques de la neige de surface à Dôme C. Ces simulations sont évaluées au regard d'un jeu de données collectées lors de missions de terrain et de mesures automatiques de l'albédo spectral et de la pénétration du rayonnement dans la neige. Ces observations mettent en évidence le rôle primordial des précipitations dans les variations rapides de taille de grain en surface et l'existence d'un cycle saisonnier de cette taille de grain. Ces variations sont bien simulées par Crocus lorsque le forçage atmosphérique qui lui est imposé est adéquat. En particulier, l'impact du vent sur l'évolution du manteau est fondamental car il contrôle la densité de surface par le biais du transport de neige. Ce transport est aussi à l'origine de la variabilité spatiale des propriétés de la neige observée à Dôme C. C'est pourquoi une modélisation stochastique de l'érosion et du transport de neige dans Crocus est proposée. En plus d'expliquer la variabilité spatiale de la densité et de la taille de grain, elle permet de reproduire celle de l'accumulation annuelle ainsi que les variations rapides de hauteur de neige liées à des épisodes de vent. Ces travaux ont permis une meilleure représentation des processus physiques qui contrôlent les variations des propriétés de la neige de surface à Dôme C, tout en soulignant le rôle primordial du vent, dont l'impact sur le manteau est particulièrement complexe à simuler. / The surface energy balance of the Antarctic Plateau is mainly governed by the physical properties of the snowpack in the topmost centimeters, whose evolution is driven by intricated processes such as: snow metamorphism, temperature profiles variations, solar radiation penetration, precipitation, snow drift, etc. This thesis focuses on the interactions between all these components and aims at simulating the evolution of snow density and snow grain size (specific surface area) on the Antarctic Plateau. To physically model the absorption of solar radiation within the snowpack, a radiative transfer model with high spectral resolution (TARTES) is implemented in the detailed snowpack model Crocus. TARTES calculates the vertical profile of absorbed radiation in a layered snowpack whose characteristics are given. These characteristics include snow grain shape, a parameter that has been seldom studied. For this reason, an experimental method to estimate the optical grain shape is proposed and applied to a large number of snow samples. This method, which combines optical measurements, TARTES simulations and Bayesian inference, is used to estimate the optimal shape to be used in snow optical models. In addition, it highlights that representing snow as a collection of spherical particles results in overestimation of the penetration depth of solar radiation. The influence of the penetration of solar radiation on the snow temperature profiles is then investigated with analytical and numerical tools. The results point out the high sensitivity of the temperature profiles to surface snow physical properties. In particular, the density of the topmost centimeters of the snowpack is critical for the energy budget of the snowpack because it impacts both the effective thermal conductivity and the penetration depth of light. To simulate the evolution of snow physical properties at Dome C by taking into account their interdependence with snow optical properties, the model Crocus is used, driven by meteorological data. These simulations are evaluated against a set of data collected during field missions as well as automatic measurements of snow spectral albedo and penetration depth. These observations highlight the influence of weather conditions on the temporal variability of surface snow properties. They show the existence of a slow decrease of snow grain size at the surface during summer. Rapid changes are also observed, essentially due to precipitation. These variations are well simulated by Crocus when forced by an appropriate atmospheric forcing. In particular, the impact of wind on the evolution of the snowpack is crucial because it controls the surface density through snow transport. This transport is also responsible for the spatial variability of snow properties observed at Dome C. That is why a stochastic representation of snow erosion and transport in Crocus is proposed. It explains well the observations of the spatial variability of density and grain size, and reproduces the variability of the annual accumulation as well as rapid changes in snow height resulting from drift events. This study improves our understanding of the physical processes which drive the properties of snow close to the surface on the Antarctic Plateau, and also points out the critical role of wind, the impact of which is very difficult to account for in models yet.

Made available in DSpace on 2014-10-09T12:41:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:03Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:41:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:03Z (GMT). No. of bitstreams: 0 / O titânio e suas ligas são biomateriais metálicos extensamente utilizados em aplicações médicas e odontológicas, apesar de não formarem ligação química com o osso circundante. Por isto é desejável técnicas que proporcionem a bioatividade na superfície desses metais. A proposta deste estudo foi avaliar e comparar, por testes in vitro e in vivo o comportamento de Ticp e da liga Ti-13Nb-13Zr utilizando diferentes tratamentos de superfície frente à formação do recobrimento biomimético e ao processo de osteointegração. Foram utilizadas placas comerciais de Ti e amostras da liga e de Ticp, obtidas por M/P. As amostras foram submetidas a quatro diferentes tratamentos de superfície (padrão - tratamento alcalino; 1°- tratamento alcalino e térmico; 2°- tratamento ácido e alcalino; 3º- tratamento alcalino, CaCl2, térmico e água quente), analisadas quanto à formação de apatita em SBF em períodos de 1 a 21 dias. Os recobrimentos obtidos foram caracterizado por MEV e DRIFT. Para a avaliação in vivo dos implantes, obtidos por M/P, de Ticp e da liga, com e sem tratamentos superficiais, foram utilizados coelhos adultos machos. A avaliação teve duração de 7 semanas em que foram aplicados marcadores celulares ósseos em tempos e sequência específicos do pós-operatório. Na avaliação in vitro, os recobrimentos de maior espessura foram nas amostras obtidas por M/P, comparativamente à amostra laminada. Todos os tratamentos foram efetivos na promoção da bioatividade. O 2º tratamento obteve recobrimento com maior espessura nos períodos avaliados para todas as superfícies. Na avaliação in vivo, ocorreu crescimento ósseo com osteointegração em todos os implantes com e sem tratamentos superficiais. O crescimento ósseo na interface osso/implante ocorreu de forma contínua em todo o período de reparação para o Ticp, o Ticp com tratamento padrão, o Ticp com o 2º tratamento e a liga com o 1° tratamento; e ocorreu de forma mais intensa no primeiro e terceiro período de reparação para os demais implantes. Os resultados dos testes in vitro e in vivo não são passíveis de analogia direta neste estudo, pois forneceram informações importantes sobre a formação, morfologia e taxa de aposição do recobrimento aos diferentes tratamentos de superfície e a efetividade da osteointegração destes tratamentos de superfície em modelo animal. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This thesis describes research carried out to investigate techniques for (i) rapidly assessing the reactivity of fly ash; and (ii) evaluating its interaction with air-entraining admixtures (AEAs), both with regard to use in concrete. The materials considered for the project included, 54 fly ashes from 8 UK sources, and an additional three materials from Bangladesh, covering a range of fineness, loss-on-ignition (LOI) and production conditions (run-of-station, carbon removed, air-classified, co-combustion, oxy-fuel technology); Portland Cements (PCs) from five UK sources with various properties (strength classes 32.5 R, 42.5 N and 52.5 N); laboratory grade hydrated and quick limes; and three commercial AEAs and a standard laboratory grade reagent (surfactant). The research examining fly ash reactivity considered activity index tests to BS EN 450 (BSI, 2005c) as the reference and investigated tests covering fly ash properties/providing measures of fly ash behaviour to rapidly assess this. These included (i) fly ash fineness (45 µm sieve residue, or LASER particle size distribution (PSD) parameters), LOI and flow properties; (ii) accelerated curing of PC and lime-based mortars (iii) lime consumption by fly ash when combined with PC in paste or suspension (Frattini) or from a saturated lime solution; (iv) various measures of fly ash chemical composition (based on oxide/mineralogical analysis); and (v) a quicklime slaking test. The test results were validated by strength tests with 100 mm concrete cube. Results of the above indicated good correlations between fly ash fineness, mortar flow/water requirement and (pozzolanic) activity index (standard or accelerated curing). However, fly ash reactivity and fresh properties appeared to be influenced by the properties of the test PC (e.g. chemical composition and fineness) and there is a need to take this into account during assessment. Generally, finer fly ashes gave better flow; however, there is an optimum fineness (d90 ~40 µm) for best performance, and which is similar to the fineness of the test PC. Strong correlations between the accelerated and standard cured PC-based mortar indicate the latter can be used to estimate the former taking account of the fly ash properties. In view of eliminating the effect of PC properties on reactivity, mortar tests with laboratory grade hydrated lime suggested potential for this. However, for better assessment, this approach requires further work to address issues relating to slower rates of strength gain and increased time requirements, although high temperature conditions were used for curing. Measuring Ca(OH)2 consumption from fly ash/PC paste or suspension agreed with the behaviour in mortar, but needs special instruments (e.g. TGA or XRF). A similar approach with saturated lime did not work well, despite several measures being taken to try and improve this. The oxide and mineralogical analysis results of fly ash did not give good correlations with activity index, but improved when a factor combining them with fineness was considered. The test results were validated in concrete and with air-classified fly ashes from single sources which gave clear trend/behaviour. The lime slaking test was found to be ineffective for identifying fly ash reactivity. The reactivity assessment results were validated by carrying out concrete strength tests. In general, more consistent trends were obtained for fly ash from single source as noted with mortar earlier. Methods adopted/developed to assess the interaction of fly ash with AEA included (i) the foam index test; (ii) acid blue 80 (AB80) dye adsorption test (spectroscopic method); and (iii) methylene blue test. High variability in foam index test results between different operators were noted, which reflected differences in the degree of shaking applied and difficulties in identification of the test end point. Adoption of an automatic shaker and determination of suitable test conditions reduced this by more than 50%. Reliable test procedures were also established for the AB80 dye adsorption method. The results obtained from these tests gave very good correlations with fly ash specific surface area and the AEA dose required (both with commercial AEAs and standard reagent) for achieving target air contents in mortar and concrete. The methylene blue dye test also gave good correlations with these parameters, but was less effective for low LOI fly ashes. Between laboratory tests were carried out at three UKQAA members and considered, LOI, fineness (45 µm sieve and LASER PSD), and activity index. The results gave good agreement with those obtained at the Concrete Technology Unit for this work and again emphasized the role of fly ash fineness on its reactivity. Overall, fly ash fineness was found to be the best means of rapidly assessing its reactivity. Some of the other methods considered gave promising behaviour but require further refinements. Therefore, it is suggested that in addition to 45 µm sieve residue, other types of fineness measurement (e.g. sub 10 µm quantities, d50 and d90) can be considered suitable alternatives to activity index. Similarly, foam index tests with the automatic shaker or the AB80 test method could both be used as fly ash physical requirement tests, or in production control for air-entrained concrete.