Ce travail concerne l’élaboration, l’étude de la microstructure semicristalline et les propriétés de films de chitosane, envisagés pour le relargage de principes actifs. La microstructure semicristalline des films de chitosane influence fortement leurs propriétés physicochimiques et fonctionnelles. Dans ce contexte, nous avons réalisé une étude systématique par diffraction de rayons X en faisant varier différents paramètres structuraux de chitosane statistiques (DA) et les paramètres d’élaboration des films (l’état de neutralisation, la nature du contre-ion et le pourcentage d’eau dans les films avant neutralisation, et la situation de l’étape de neutralisation dans le procédé). Nous avons obtenus différentes microstructures semicristallines en terme d’allomorphes hydratés ou anhydres, en jouant sur les conditions plus ou moins hydrophobes au moment de la neutralisation. Par ailleurs, une étude de la mobilité moléculaire par spectroscopies diélectrique et mécanique a permis de mettre en évidence différentes relaxations secondaires, toujours en fonctions des paramètres physicochimiques qui conditionnent la balance des interactions hydrophiles/hydrophobes. De plus, la Spectroscopie mécanique a montré une transition réversible de comportement hydrophile / hydrophobe dépendant du traitement thermique appliqué. Cette étude nous a montré que le degré d’acétylation n’influence pas directement la mobilité moléculaire dans les films de chitosane, mais c’est encore la balance des interactions hydrophiles / hydrophobes qui gouverne la réponse viscoélastique et diélectrique. Finalement, nous avons réalisé une étude du gonflement de films de chitosane en relation avec les paramètres de mise en oeuvre. Les résultats sont reliés à la microstructure semicristalline. Le relargage de protéines a été abordé par l’étude d’une protéine modèle (Ovalbumine). La technique de dichroïsme circulaire a permis d’étudier les interactions ovalbumine/chitosane à l’état solide (dans le film) comme à l’état solution (après relargage). Les cinétiques de relargage ont été déterminées et discutées en fonction du gonflement et de la morphologie cristalline / This work concerns the elaboration, semicrystalline microstructure and properties study of chitosan films for application of release of active principle. The semicrystalline microstructure of chitosan films strongly influences their physicochemical and functional properties, so their control becomes very important for the aimed application. In this context, we have performed a systematic study by X-ray diffraction on chitosan films varying different parameters that influence their semicrystalline microstructure, particularly, the degree of acetylation, the elaboration routes, the neutralization state, the counter-ion nature and the water content before neutralization. We have achieved to control the semicrystalline microstructure by the combination of these parameters. Furthermore, the study of the molecular mobility behaviour was carried out showing the different relaxation processes present in the chitosan films. A viscoelastic study by mechanical spectroscopy showed hydrophilic/hydrophobic transitions as a function of he thermal treatment. This study showed that the degree of acetylation does not have a strong influence on the molecular mobility in the chitosane films. Finally, we have conducted a study of swelling of chitosan film in relation to the semicrystalline microstructure. Then, a model protein (Ovalbumin) has been incorporated to study its interaction with chitosan in the solid state (in the film) and in solution (after release) and in order to evaluate its release

<p> Environmental Barrier Coatings (EBCs) protect ceramic gas turbine engine components from corrosion by high temperature water vapor, but the coatings often form complex metastable microstructures upon plasma spray deposition. In ytterbium disilicate (YbDS) and its yttrium-doped counterpart (Y/YbDS), two coatings compatible with SiC/SiC parts, plasma spray forms a largely cracked, mechanically weak amorphous phase comprising up to ~80% of the coating’s volume. Therefore, the coatings must undergo a pre-service heat treatment to crystallize into stable phases and heal cracks. During the treatment, however, interplay between thermal expansion and crystallization contraction can cause vertical cracks which expose the component to the corrosive atmosphere. Remedial treatments with long, high temperature holds (~1300 ºC) can both crystallize the coating and heal existing cracks. However, these temperatures cause unnecessary grain growth that reduces the structural integrity of the coating over its lifetime.</p> <p>Here we propose an alternate heat treatment informed by experiments and modelling that removes metastable phases, heals cracks, and reduces time at temperature to prevent significant grain growth. First, we determine crystallization and phase change kinetics by applying the Ozawa-Flynn-Wall and Vyazovkin kinetic methods to differential scanning calorimetry (DSC) data. Next, we track locations and microstructural effects of phase evolution using correlative Raman spectroscopic mapping, scanning electron microscopy (SEM), and X-Ray diffraction (XRD). We interpret the formation of three distinct phases – a major phase of stable β-YbDS, and minor phases of stable Χ2-YbMS and metastable α-YbDS – within the existing framework of kinetic theory and quantify differences in their transformations between YbDS and Y/YbDS. We find that cracks in the coating heal through the crystallization of the amorphous phase and the transformation of the metastable phase although the mechanisms remain unclear. Each phase transformation causes a bulk volumetric change which we measure using dilatometry and use to calculate delamination stresses during a simulated heat treatment. Lastly, we determine the viability of our heat treatment compared to the industry standard.</p>

Various silicone elastomers have been evaluated for use in the prosthetic reconstruction of facial defects. Their strength, texture, flexibility, hardness, ease of preparation, pigment receptivity and retention, and their resistance to cleaning were compared and the data consulted when an elastomer was chosen to restore defects, improve aesthetics and reestablish the confidence of a selection of patients. Detailed case reports are provided, together with information on the adhesives or mechanical methods available for retaining the facial prosetheses. Cyanoacrylate adhesives for use on skin surfaces and as tissue adhesives have been studied in detail. A novel n-butyl 413 cyanoacrylate has been developed with a viscosity, haemostatic property and stability to make it particularly suitable for use in skin grafting and tissue repair. It has already been used with good results on patients with severe burns. An improved formulation, containing a fluorescent dye, can be precisely applied through a specially constructed foot-controlled dispenser illuminated by a fibre-optic supplying UV-light. Cyanoacrylates are already being used as tissue adhesives in place of the conventional but potentially disfiguring suture. The availability of improved, imperceptible adhesives and a precision applicator, which can be used in a modern operating theatre, will extend their effectiveness and satisfy some of the needs of Plastic, and Oral and Maxillo-Facial Surgeons. Portable applicators have potential use in battlefield and in veterinary surgery and overcome the imprecision characteristic of earlier methods. / Loctite UK

Environmental concerns are becoming increasingly relevant during a period of hemorrhaging ecosystem goods and services. Restoring these would result in positive outcomes for public health and economic benefit. This thesis seeks to address two environmental concerns: (1) accurate soil mapping and (2) treatment of nitrogen to affect water quality change.The current method of soil mapping, SSURGO (USDA‐NRCS Soil survey), is often erroneous and misleading. Two studies in this dissertation are conducted to evaluate the potential that different resolution digital elevation models (DEMs) have to distribute soil characteristics successfully. These studies are conducted in southwest Virginia and western Vermont. The aforementioned studies evaluated 36 and 59 soil samples, respectively. Spatial characteristics, including slope, catchment area, and topographic wetness, are derived from several DEMs. In chapter 2, these characteristics are spatially compared, and we found that small resolution rasters result in narrow flow paths relative to coarser rasters. In chapter 3, we isolate the analysis to focus on resolution size, instead of a mix of both resolution size and generation method. This is done by recursively coarsening small rasters, deriving spatial attributes from said rasters and evaluating their potential to fit the soil characteristics of interest. Here we found that slopes generated from resolutions smaller than 11m were poor predictors of soil characteristics. Both chapters are finished by proposing and evaluating a soil map. Proposed regressions beat SSURGO in all investigated properties. Furthermore, proposed maps consistently beat out uninformed smallest resolution derived maps.Chesapeake bay water quality managers are struggling to achieve targets for nitrogen loading. This is in part due to the widespread presence of legacy nitrogen. Legacy nitrogen is an emerging issue, and springs exporting high levels of nitrogen are not uncommon in northern Virginia. This thesis explores, in part, a novel concept of treating large loads of nitrogen exported from a spring with a bioreactor. Bioreactors are a young science that most typically pair carbon heavy subterranean receptacles to agricultural drainage. This provides a location for nitrogen fixing bacteria to consume nitrate/nitrite, turning these into inert nitrogen gas. A spring fed bioreactor is studied for 10 months, and bioreactor conditions including influent and effluent nitrogen concentrations, bioreactor flow, and temperature are collected. A model driven by first order reaction equations is found to be most accurate with inputs of temperature and bioreactor age. The resulting marginal effects of these inputs were consistent with previously reported studies. / Doctor of Philosophy / Centuries of industrialization have resulted in widespread human progress but have, at times, adversely impacted the environment. Constituents rely heavily on environmental services, such as clean air and water, to subsist. Environmental degradation has resulted in detrimental effects to public health, and remediation is currently economically viable. As such, there are strong incentives for researchers to understand environmental processes at a fundamental level. One such process is soil characteristic distribution. The distribution of soil characteristics, such as soil texture or organic matter, is especially important for agriculturalists, hydrologists and geotechnicians. Soil texture and organic matter distribution can affect crop yield, nitrogen export to surface waters, and structural stability of soils. Thus, accurate characterization of measured soil properties is paramount to multiple fields. The most typically used soil map is USDA‐NRCS Soil survey (commonly referred to as SSURGO). Currently, the SSURGO database is a poor predictor of soil characteristics. There is an opportunity to improve soil characteristic distribution using digital elevation models (DEMs). As DEMs become cheaper to develop, they are typically available in multiple resolutions and generation methods. In this research, several DEMs are used to better soil maps for watersheds in Southwest Virginia and Western Vermont. Both studies showed that DEMs can better distribute soils when compared to the current SSURGO maps. Additionally, we showed that the finest resolution dataset was not always best, and mixed resolution topographic wetness indices to be most advantageous for distributing soils.Another such process is remediation of surface waters from high loads of nitrogen and phosphorus. The Haber-Bosch method of producing nitrogen fertilizer is one of the most important human innovations in recent history. This method is likely responsible for the aversion of widespread famine in the early 1900s. However, residents of multiple river systems, including the Chesapeake Bay and the Mississippi River, are suffering from the adverse effects of widespread hypoxic/anoxic (with little/no oxygen, respectively) zones within water. These have partially been responsible for the decline of commercial ventures such as fisheries and tourism. These zones are caused by eutrophication, a process of unsustainable plant growth in the presence of nitrogen and phosphorus. Water quality managers typically target agricultural runoff and point source polluters when trying to eliminate anthropogenic nitrogen. However, legacy nitrogen (nitrogen stored in groundwater in excess of a year) has become an emerging concern for water quality. It is not uncommon for springs in karst areas to be contaminated with high concentrations of nitrogen. These springs present a point source that can be treated by an emerging technology: bioreactors. Bioreactors are subterranean, woodchip filled basins that provide a location for microbes to exchange water soluble nitrogen for inert nitrogen gas. The consistency in nitrogen loading and constant flow provide stability relative to more traditional bioreactor installations. Most typically, bioreactors are installed downstream of agricultural drainage systems, and influent flow and nitrogen load depend wholly on precipitation/irrigation and nitrogen application. In this thesis, a novel spring fed bioreactor is studied. Removal rates of nitrogen are quantified using a regression driven by reaction kinetics. The analysis showed bioreactor efficiency was intimately related to hydraulic residence time, nitrogen loading, bioreactor bed temperature, and bioreactor age. The spring fed bioreactor is found to be advantageous because of its consistency, and disadvantages because springs are colder and thus less efficient than typical irrigated runoff.

Impelled by the increase in the number of tunnel fires in the last decade alone, wide spread attention has been drawn towards tunnel fire safety studies. Many of these fires occurred in road and railway tunnels involving vehicles and trains. These fire incidents have claimed lives, caused structural damages to the tunnel infrastructure and even economic losses to the government, businesses and communities concerned. When there is a fire in a tunnel, the temperature inside the tunnel increases rapidly to magnitudes as high as 1500°C. At such high temperatures costly damages to the tunnel structure is inevitable. Having an understanding of the detrimental effects of such high temperatures is essential and valuable when carrying out preliminary assessment of the type and extent of damage in the tunnel. This would in turn provide useful information in determining the appropriate remedial measures required to make the tunnel safe and usable again in the aftermath of a tunnel fire. In most tunnel fire safety studies, the focus has been on the behaviour of concrete, since of course concrete is one of the major support elements in tunnels. However, in several cases, such as in Scandinavia for example, where the rock mass is competent enough to support itself only a thin layer of shotcrete is used usually on tunnel walls. In such cases the rock will be fully exposed to heat in an instance of fire. In this case, whether it is prevention or maintenance of the tunnel, it would require knowledge on the effect of elevated heat on the rock mass. Hence, it is line with this thinking that a study was initiated by the Swedish Transport Administration (Trafikverket), Kärnbränslehantering AB, SKB and Vattenfall to study the effect of heat on the physical and mechanical properties of some common rock types, and hence the focus of this thesis. This thesis presents the results of a series of laboratory studies which was carried out to investigate the effect of heat on the physical and mechanical properties of selected rock types, namely; diabase, granite and quartzitic schist. Samples from these rock types were heat treated at temperature levels of 400°C, 750°C and 1100°C, before investigating their mechanical and physical properties through mechanical testing and microscopic investigations of thin sections. Because the effect of heat on rock can be affected by the heating rate and exposure time, the test were conducted under controlled conditions in order to avoid significant variation in the results. The results clearly show that the rock types behave differently at different temperature levels, which tend to depend on the mineral composition and micro cracks distribution. As the temperature increases the rock forming minerals undergo changes in their chemical structure thus causing them to alter from the original phase they had existed in. With these phase changes different reactions take place such as re-crystallization, the loss of crystal bound water, thermal expansion and micro cracking of mineral grains as well as the development of voids. These microscopic changes were manifested in the macro-scale by the variations observed in the behaviour of strength and stiffness of the samples in the mechanical tests.

<p dir="ltr">The process of metal additive manufacturing is characterized by the layer-by-layer construction of components, where each individual layer may be subjected to distinct thermal variations, resulting in differences in cooling rates and thermal gradients. These variations can impact the microstructure and, subsequently, mechanical properties of the final product, especially as the height of the build increases. In the present investigation, an evaluation was undertaken to ascertain the impact of build height on the structural integrity of Ti-6Al-4V samples produced using the laser powder bed fusion (LPBF) technique. The study encompassed a comprehensive examination of microstructural features, the microhardness measurement, as well as an evaluation of defect characteristics including size, location, and distribution, with respect to the build height. Tensile and fatigue tests were conducted to elucidate the potential dependence of fatigue and tensile failures on the build height. Two groups of specimens were fabricated: the first, underwent continuous fabrication, while the second involved a pause at the half height, with the process resuming after a 24-hour interval. The results of this investigation unveiled a discernible influence of the height of the build on the structural integrity of components under cyclic loading. Most fatigue specimens were observed to exhibit failure in the upper portion of the gage section with respect to the build direction. Analyses of microstructure revealed a consistent grain morphology in alignment with the build direction, and a uniform distribution of hardness throughout the build height was noted. However, for the specimens in the first group, more process-induced defects were detected within the top half of the gage section in comparison to the bottom half, while there was no noticeable difference in the distribution of defects in the second group. The results suggest that in LPBF process, as the build height is increased, there is a higher likelihood of process-induced defect formation, ultimately resulting in a reduction in structural integrity at greater build heights.</p>

This thesis work aimed to provide a better knowledge of inclusion behavior at the steel-slag interface. All results are based on mathematical modeling of liquid and solid inclusion separation to the slag. The model descriptions of the inclusion transfer are based on the equation of motion at the system. It is assumed that the inclusion transfer is governed by four forces acting on the inclusion as it has reached the steel-slag interface. These are the buoyancy force, the added mass force, the drag force and the rebound force. The models assume two cases of inclusion separation depending on the inclusion Reynolds number. In the case where Reynolds number is larger or equal to unity, Re≥1, a steel film is formed between the inclusion and the slag. This steel film must first be drained before the inclusion can separate to the slag. If Reynolds number, Re&lt;1, then no steel film is formed and the inclusion will be in direct contact with the slag. The mathematical models also propose three types of inclusion behavior as the inclusion crosses the steel-slag interface. The inclusion can either, pass and separate to the slag, oscillate at the interface with the possibility of reentering the steel bath with the steel flow or it can remain at the interface not completely separated to the slag. A parameter study for 20 μm inclusions showed that the most important parameters controlling the inclusion behavior at the steel-slag interface are the slag viscosity and the interfacial tensions between the phases. For 100μm inclusions also the inclusion density affects the inclusion behavior. The models were applied to ladle and tundish conditions. Since the slags in the chosen industrial conditions have not been studied experimentally before, estimations of the important physical property parameters were made. Future measurements will therefore be needed in order to make predictions of inclusion transfer behavior at the steel-slag interface which are more relevant for the industry. The main conclusion is that useful plots can be made in order to illustrate the tendency for the inclusion transfer and how to manipulate the physical property parameters in order to increase the inclusion separation in ladles and tundishes. / QC 20101221

<p dir="ltr">This dissertation addresses the significant challenge of enhancing the performance of lithium-ion batteries (LIBs) in extremely low-temperature environments, which is critical for applications in defense and space exploration. By innovating both electrolyte formulations and electrode materials, this research extends the operational boundaries of LIBs to temperatures below -100 ℃. </p>

La tesis presentada se enfoca en un estudio experimental que busca establecer correlaciones entre tres ensayos realizados en suelo cohesivo: Ensayo de Penetración Estándar (SPT), Corte Directo y Triaxial. Las pruebas se realizaron en un terreno de 3 hectáreas denominado AA.HH. Sol naciente, llegando hasta una profundidad de 3.50 metros debido a características geotécnicas del suelo. A continuación, llevaron a cabo un estudio sobre las propiedades físicas del suelo utilizando varias pruebas estándar, incluyendo granulometría, límites de Atterberg, contenido de humedad y gravedad específica. Con base en la recopilación de datos existentes y las correlaciones de los ensayos, que fueron un total de 7 pruebas de cada ensayo en el terreno, con la ayuda de equipos y operadores locales. El propósito final del estudio es proponer correlaciones entre los resultados obtenidos de los tres tipos de ensayos. Esta investigación proporciona un aporte significativo al campo de la geotecnia y la ingeniería civil, ya que los hallazgos podrían mejorar el entendimiento de las propiedades del suelo y permitir cálculos más precisos en cuanto a resistencia y comportamiento del suelo bajo diversas condiciones de carga y presión. En última instancia, estos resultados pueden aumentar la seguridad y estabilidad de las construcciones futuras en estos suelos, proporcionando un enfoque más sólidoy fiable para el análisis de suelos y la planificación de proyectos de construcción. / The presented thesis focuses on an experimental study aiming to establish correlations among three tests performed on cohesive soil: Standard Penetration Test (SPT), Direct Shear, and Triaxial. The tests were carried out on a 3-hectare land plot called AA.HH. Sol Naciente, reaching a depth of 3.50 meters due to the soil's geotechnical characteristics. Subsequently, they conducted a study on the soil's physical properties using various standard tests, including particle size distribution, Atterberg limits, moisture content, and specific gravity. Based on the existing data compilation and the tests' correlations, a total of 7 tests of each were performed on the field, with the assistance of local equipment and operators. The final purpose of the study is to propose correlations among the results obtained from the three types of tests. This research provides a significant contribution to the field of geotechnical and civil engineering, as the findings could enhance the understanding of soil properties and allow more precise calculations regarding soil strength and behavior under various load and pressure conditions. Ultimately,these results may increase the safety and stability of future constructions on these soils, providing a more robust and reliable approach for soil analysis and construction project planning.

Master of Science / Department of Grain Science and Industry / Keith C. Behnke / The effect of tracer particle size on the accuracy of measuring retention time inside the conditioner of a pellet mill was studied. Three experiments were conducted using tracers with different particle sizes. The control retention time was calculated using the hold-up capacity method, while retention times for treatments were calculated using the pulse-input method. In addition to the previously prepared tracers, crystalline salt and powder color dye were used as tracers in this study to represent small particle tracers. In experiment one, large, medium, and small tracers were used. The treatment with large particle size was closer to the control with differences around 1.5%. Conversely, using the tracer with small particle size resulted in larger differences, approximately 18%. Two tracers were used in experiment two, resulted in 33% difference between treatment and control using a small particle size tracer, and a 10% difference using a tracer with similar particle size to the main materials. A tracer similar in particle size to the materials flowing inside the conditioner was used in the third experiment in addition to the salt and dye. Statistical analyses for this experiment indicated that particle size affects the accuracy of retention time measurements. There was a significant difference (P<0.05) in the comparison between salt and red color dye in treatment two, while there was no significant difference (P>0.05) between them in treatment one (same particle size). Moreover, in another comparison of the differences between treatments and their related controls, there was significant difference (P<0.05). However, the P-value for the red dye comparison (0.0126) was higher than that of salt (0.0026), which adds density as another influential factor that affects retention time measurement.