The importance of further research in the field of solar cells is crucial for the transition to cleaner energy. The aim of this project is to design and manufacture a contact system that can measure busbarless solar cells with an LBIC-system. In this project mono-crystalline busbarless solar cells were utilized, busbarless solar cells only have small fingers that go vertically. When an incident photon hits the solar cell it can be absorbed by the bulk material, by the pn-junction an electrical field will set the electrons in motion so an electrical current can be harvested. LBIC, which stands for light beam induced current is a technique to spatially map the quantum efficiency of a solar cell, there is also an availability to make phasemeasurements. There are two different quantum efficiencies, External quantum efficiency (EQE) and Internal quantum efficiency (IQE). The phase measurement of the LBIC shows how much resistance exists between the point of current-generation and the contacts where the current is collected. A contact system with a comb-like figure of phosphor bronze was manufactured and mounted on to the LBIC-machine. Several measurements were executed on two solar cells. This new contact system can measure busbarless solar cells, with a good connection to almost all the fingers on the solar cell. The lack of contact with some fingers seemed to not affect the end result too much. It isn’t vital to have contact with all fingers to get a decent LBIC-mapping. / Vikten av ytterligare forskning inom området solceller är avgörande för omställningen till renare energi. Syftet med detta projekt är att designa och tillverka ett kontaktsystem som kan mäta solceller utan busbars med ett LBIC-system. I detta projekt användes monokristallina solceller utan busbars, solceller utan busbars har endast smala fingrar som går vertikalt. När en infallande foton träffar solcellen kan den absorberas av bulkmaterialet, vid pn-övergången kommer ett elektriskt fält att sätta elektronerna i rörelse så att en elektriskström kan samlas in. LBIC, som står för light beam induced current är en teknik för att rumsligt kartlägga kvantverkningsgraden för en solcell, det finns även en möjlighet att göra fasmätningar. Det finns två olika kvanteffektiviteter, Extern kvanteffektivitet (EQE) och Intern kvanteffektivitet (IQE). Fasmätningen av LBIC visar hur mycket motstånd som finns mellan punkten för strömgenerering och kontakterna där strömmen samlas. Ett kontaktsystem med en kamliknande figur gjord av fosforbrons tillverkades och monterades på LBIC-maskinen. Flera mätningar utfördes på två solceller. Detta nya kontaktsystemet kan mäta solceller utan busbars, med bra anslutning till nästan alla fingrar på solcellen. Bristen på kontakt med enskilda fingrar verkade inte påverka slutresultatet alltför mycket. Det är alltså då inte nödvändigt att ha kontakt med alla fingrar för att få en anständig LBIC-mätning.

Material Extrusion additive manufacturing (MEX) represents the most widely implemented form of additive manufacturing due to its high performance-cost ratio and robustness. Being an extrusion process in its essence, this process enables the free form fabrication of a wide range of thermoplastic materials. However, in most typical MEX processes, only amorphous polymers are being used as feedstock material owing to their smaller dimensional shrinkage during cooling and well-stablished process/structure/property (P/S/P) relationship. Semi-crystalline polymers, with their crystalline nature, possess unique properties such as enhanced mechanical properties and improved chemical resistance. However, due to the inherent processing challenges in MEX of semi-crystalline polymers, the P/S/P relationships are much less established, thus limits the application of semi-crystalline polymers in MEX. The overall aim of this thesis is to advance the understanding of P/S/P relationship of semi-crystalline polymers in MEX. This is accomplished through both experimental and simulation-based research. With a typical commodity semi-crystalline polymer, Poly (ethylene terephthalate) (PET), selected as the benchmark material. First, we experimentally explored the MEX printing of both neat and glass fiber (GF) reinforced recycled PET (rPET). Excellent MEX printability were shown for both neat and composite materials, with GF reinforced parts showing a significant improved mechanical property. Notably, a gradient of crystallinity induced by a different toolpathing time was highlighted. In the second project, to further investigate the impact of MEX parameter on crystallinity and mechanical properties, a series of benchmark parts were printed with neat PET and analyzed. The effect of part design and MEX parameter on thermal history during printing was revealed though a comparative analysis of IR thermography. Subsequent Raman spectroscopy and mechanical test indicated that crystallinity developed during the MEX process can adversely affects the interlayer adhesion. In the third project, a 3D heat transfer model was developed to simulate and understand the thermal history of MEX feedstock material during printing, this model is then thoroughly validated against the experimental IR thermography data. While good prediction accuracy was shown for some scenarios, the research identified and discussed several unreported challenges that significantly affect the model's prediction performance in certain conditions. In the fourth project, we employed a non-isothermal crystallization model to directly predict the development of crystallinity based on given temperature profiles, whether monitored experimentally or predicted by the heat transfer model. The research documented notable discrepancies between the model's predictions and actual crystallinity measurements, and the potential source of the error was addressed. In summary, this thesis explored the MEX printing of semi-crystalline polymer and its fiber reinforced composite. The influence of MEX parameters and part designs on the printed part's thermal history, crystallinity and mechanical performance was then thoroughly investigated. A heat transfer model and a non-isothermal crystallization model were constructed and employed. With rigorous validation against experimental data, previously unreported challenges in MEX thermal and crystallization modeling was highlighted. Overall, this thesis deepens the understanding of current semi-crystalline polymer's P/S/P relationship in MEX, and offers insights for the optimization and future research in the field of both experiment and simulation of MEX. / Doctor of Philosophy / Material extrusion additive manufacturing (MEX), also known as fused filament fabrication (FFF), is a popular form of 3D printing known for its cost-effectiveness and versatility in creating objects from plastic materials. Traditionally, MEX utilizes amorphous polymers because they are less prone to shrinkage and thus easier to print. However, semi-crystalline polymers, offer enhanced strength and chemicals resistance, yet they pose significant challenges in printing due to a limited understanding of their process/structure/property (P/S/P) relationships in MEX. This research aims to improve our understanding of P/S/P relationships of semi-crystalline polymers in MEX. The study utilizes a typical semi-crystalline polymer, Poly (ethylene terephthalate) (PET), as the benchmark material. The study begins with the exploration of the MEX printing of recycled PET (rPET) and its glass fiber composite, finding that with appropriate MEX parameters, both feedstocks are highly printable, and the incorporation of glass fibers substantially increased the strength of the printed parts. Subsequently, a comprehensive investigation regarding the intricate relationship between crystallinity development, mechanical properties, and the MEX printing process is conducted. Our research revealed that the MEX process and the design of the part both considerably affect the crystallinity of the final part, thereby influencing its mechanical properties. In the third chapter, a 3D heat transfer model is constructed to better understand and predict the temperature evolution of materials during MEX printing. Most importantly, the modeling results are rigorously validated against experimental data, showing promising results. However, it also reveals challenges in precisely predicting the temperature of parts under certain conditions. The research then evaluates the applicability of Nakamura non-isothermal crystallization model for MEX printing scenarios. It is found that this model underestimates crystallinity in MEX, primarily because it does not account for shear-induced crystallization, a critical factor in the process. This finding underscores the necessity for more advanced models that can effectively capture the complex dynamics of MEX. In summary, this dissertation significantly enhances our understanding of the behavior of semi-crystalline polymers in MEX printing. It sheds light on the complex relationship between the printing process, the structure of the material, and the final properties of the printed object. This work not only advances our knowledge in 3D printing but also paves the way for more sophisticated modeling approaches, optimizing the MEX process and expanding its potential applications.

Analytic methods of elastic wave scattering in fiber-reinforced composite materials are investigated in this study to calculate the effective static stiffness (axial shear modulus, m) and wave properties (axially shear wave speed, B and attenuation, Y) in composites. For simplicity only out-of-plane shear waves are modeled propagating in a plane transverse to the fiber axis. Statistical averaging of a spatially random distribution of fibers is performed and a simultaneous system of linear equations are obtained from which the effective global wave numbers are numerically calculated. The wave numbers, K=Re(K)+iIm(K), are complex numbers where the real parts are used to compute the effective axial shear static stiffness and wave speed; the imaginary parts are used to compute the effective axial shear wave attenuation in composites. Three major parts of this study are presented. The first part is the discussion of multiple scattering phenomena in a successive-events scattering approach. The successive-events scattering approach is proven to be mathematically exact by comparing the results obtained by the many-bodies-single-event approach. Scattering cross-section is computed and comparison of the first five scattering orders is made. Furthermore, the ubiquitous quasi-crystalline approximation theorem is given a justifiable foundation in the fiber-matrix composite context. The second part is to calculate m, B and Y for fiber-reinforced composites with interfacial layers between fibers and matrix. The material properties of the layers are assumed to be either linearly or exponentially distributed between the fibers and matrix. A concise formula is obtained where parameters can be computed using a computationally easy-to-program determinant of a square matrix. The numerical computations show, among other things, that the smoother (more divisional layers), or thinner, the interfacial region the less damped are the composite materials. Additionally composites with exponential order distribution of the interfacial region are more damped than the linear distribution ones. The third part is to calculate m, B and Y for fiber-reinforced composites with interfacial cracks. The procedures and computational techniques are similar to those in the second part except that the singularity near the crack tip needs the Chebychev function as a series expansion to be adopted in the computation. Both the interfacial layers and interfacial crack cases are analyzed in the low frequency range. The analytic results show that waves in both cases are attenuated and non-dispersive in the low frequency range. The composites with interfacial layers are transversely isotropic, while composites with interfacial cracks are generally transversely anisotropic. / Ph. D.

The application of glass fiber reinforced composites has grown rapidly due to their high strength-to-weight ratio, low cost, and chemical resistance. However, the increasing demand for fiber reinforced composites results in the generation of more composite wastes. Mechanical recycling is a cost-effective and environmentally-friendly recycling method, but the loss in the quality of recycled glass or carbon fiber composite hinders the wide-spread use of this recycling method. It is important to develop novel composite materials with higher recyclability. Thermotropic liquid crystalline polymers (TLCPs) are high-performance engineering thermoplastics, which have comparable mechanical performance to that of glass fiber. The TLCP reinforced composites, called in situ composites, can form the reinforcing TLCP fibrils during processing avoiding the fiber breakage problem. The first part of this dissertation is to study the influence of mechanical recycling on the properties of injection molded TLCP and glass fiber (GF) reinforced polypropylene (PP). The processing temperature of the injection molding process was optimized using a differential scanning calorimeter (DSC) and a rheometer to minimize the thermal degradation of PP. The TLCP and GF reinforced PP materials were mechanically recycled up to three times by repeated injection molding and grinding. The mechanical recycling had almost no influence on the mechanical, thermal, and thermo-mechanical properties of TLCP/PP because of the regeneration of TLCP fibrils during the mold filling process. On the other hand, glass fiber/PP composites decreased 30% in tensile strength and 5% in tensile modulus after three reprocessing cycles. The micro-mechanical modeling demonstrated the deterioration in mechanical properties of GF/PP was mainly attributed to the fiber breakage that occurred during compounding and grinding. The second part of this dissertation is concerned with the development of recyclable and light weight hybrid composites through the use of TLCP and glass fiber. Rheological tests were used to determine the optimal processing temperature of the injection molding process. At this processing temperature, the thermal degradation of matrix material was mitigated and the processability of the hybrid composite was improved. The best formulation of TLCP and glass fiber in the composite was determined giving rise to the generation of a recyclable hybrid composite with low melt viscosity, low mechanical anisotropy, and improved mechanical properties. Finally, TLCP reinforced polyamide composites were utilized in an additive manufacturing application. The method of selecting the processing temperature to blend TLCP and polyamide in the dual extrusion process was devised using rheological analyses to take advantage of the supercooling behavior of TLCP and minimize the thermal degradation of the matrix polymer. The composite filament prepared by dual extrusion was printed and the printing temperature of the composite filament that led to the highest mechanical properties was determined. Although the tensile strength of the TLCP composite was lower than the glass fiber or carbon fiber composites, the tensile modulus of 3D printed 60 wt% TLCP reinforced polyamide was comparable to traditional glass or carbon fiber reinforced composites in 3D printing. / Doctor of Philosophy / The large demand for high performance and light weight composite materials in various industries (e.g., automotive, aerospace, and construction) has resulted in accumulation of composite wastes in the environment. Reuse and recycling of fiber reinforced composites are beneficial from the environmental and economical point of view. However, mechanical recycling deteriorates the quality of traditional fiber reinforced composite (e.g., glass fiber and carbon fiber). There is a need to develop novel composites with greater recyclability and high-performance. Thermotropic liquid crystalline polymers (TLCP) are attractive high performance materials because of their excellent mechanical properties and light weight. The goal of this work is to generate recyclable thermotropic liquid crystalline polymer (TLCP) reinforced composites for use in injection molding and 3D printing. In the first part of this work, a novel recyclable TLCP reinforced composite was generated using the grinding and injection molding. Recycled TLCP composites were as strong as the virgin TLCP composites, and the mechanical properties of TLCP composites were found to be competitive with the glass fiber reinforced counterparts. In the second part, a hybrid TLCP and glass fiber reinforced composite with great recyclability and excellent processability was developed. The processing conditions of injection molding were optimized by rheological tests to mitigate fiber breakage and improve the processability. Finally, a high performance and light weight TLCP reinforced composite filament was generated using the dual extrusion process which allowed the processing of two polymers with different processing temperatures. This composite filament could be directly 3D printed using a benchtop 3D printer. The mechanical properties of 3D printed TLCP composites could rival 3D printed traditional fiber composites but with the potential to have a wider range of processing shapes.

A 3- to 5-fold increase in Ca2+ accompanies cataract formation induced by selenite. The mechanism of selenite cataractogenesis involves calcium activation of calpain with subsequent proteolysis within the lens nucleus. This study was undertaken to investigate the biochemical mechanisms that lead to calcium accumulation in these circumstances. The components responsible for rat lens calcium regulation were defined by using either lens membrane vesicle preparations or intact lenses. Both Na+ gradient-dependent Ca2+ uptake and efflux occurred in lens membrane vesicles. Experiments with intact lenses showed that Na + ICa2 + exchange plays an important role in lens calcium regulation. ATP-dependent Ca2+ uptake and Ca2+ -dependent ATP hydrolytic activity have been characterized in lens membrane vesicles. Therefore, both Ca2+ -ATPase and Na + ICa2+ exchange participate in rat lens calcium regulation. Calcium accumulation in lenses treated by selenite may result from either increased influx (via non-selective cation channel), decreased efflux (via Ca2 +-ATPase and Na+ ICa 2+ exchange) or both. The selenite effects on the different components involved in lens calcium regulation were tested. / Ph. D.

Soil organic matter (SOM) is the largest terrestrial pool of organic carbon (C), and potential carbon-climate feedbacks involving SOM decomposition could exacerbate anthropogenic climate change. Despite the importance of SOM in the global C cycle, our understanding of the controls on SOM stabilization and decomposition is still developing, and as such, SOM dynamics are a source of major uncertainty in current Earth system models (ESMs), which reduces the effectiveness of these models in predicting the efficacy of climate change mitigation strategies. To improve our understanding of controls on SOM decomposition at scales relevant to such modeling efforts, A and upper B horizon soil samples from 22 National Ecological Observatory Network (NEON) sites spanning the conterminous U.S. were incubated for 52 weeks under conditions representing site-specific mean summer temperature and horizon-specific field capacity (-33 kPa) water potential. Cumulative CO2 respired was periodically measured and normalized by soil organic C content to obtain cumulative specific respiration (CSR). A two-pool decomposition model was fitted to the CSR data to calculate decomposition rates of fast- (kfast) and slow-cycling pools (kslow). Post-LASSO best subsets multiple linear regression was used to construct horizon-specific models of significant predictors for CSR, kfast, and kslow. Significant predictors for all three response variables consisted mostly of proximal factors related to clay-sized fraction mineralogy and SOM composition. Non-crystalline minerals and lower SOM lability negatively affected CSR for both A and B horizons. Significant predictors for decomposition rates varied by horizon and pool. B horizon decomposition rates were positively influenced by nitrogen (N) availability, while an index of pyrogenic C had a negative effect on kfast in both horizons. These results reinforce the recognized need to explicitly represent SOM stabilization via interactions with non-crystalline minerals in ESMs, and they also suggest that increased N inputs could enhance SOM decomposition in the subsoil, highlighting another mechanism beyond shifts in temperature and precipitation regimes that could alter SOM decomposition rates. / Master of Science / Soils contain a large amount of carbon (C) in the form of soil organic matter (SOM), and there is the potential for the increased decomposition of SOM due to warmer temperatures to cause climate change to become worse through the release of additional CO₂ into the atmosphere. However, we still do not know exactly what is most important for predicting how vulnerable SOM is to decomposition at continental scales, and this results in a substantial amount of uncertainty in Earth system models used to predict climate change. To address this question, the proportion of organic C decomposed in soil samples from the topsoil and subsoil from 22 sites across the conterminous U.S. was monitored over the course of a year under optimal moisture conditions and at site-specific summer temperature. Additionally, a mathematical model was fitted to the proportion of organic C decomposed over time to estimate decomposition rates of a quickly decomposing pool of SOM and a slowly decomposing pool of SOM. The proportion of organic C decomposed and decomposition rates were related to soil and site properties using multiple linear regression to find which soil and site properties were most important for predicting these response variables. The type of clay-sized mineral and SOM chemical composition were found to be important predictors of the proportion of organic C decomposed for both topsoil and subsoil samples. The important predictors for decomposition rates varied by pool and by topsoil vs. subsoil. For subsoil decomposition rates, it was found that a greater availability of nitrogen (N) increased decomposition rates, and in the quickly decomposing pool, it was found that fire-derived organic matter slowed decomposition rates. The results of this study showed the general importance of local factors for controlling SOM decomposition. Specifically, it showed that the type of clay-sized mineral present at a site needs to be considered as well as the fact that N might increase SOM decomposition in the subsoil.

Los materiales autosanables son materiales con la capacidad de reparar sus daños de forma autónoma o con ayuda mínima de estímulos externos. En el campo de la construcción, el desarrollo de elementos autosanables aumentará la durabilidad de las estructuras y reducirá las acciones de mantenimiento y reparación. Los elementos de hormigón armado presentan frecuentemente pequeñas fisuras (< 0.3 mm), no relevantes mecánicamente, pero que pueden suponer un punto de entrada para agentes agresivos. El hormigón tiene una cierta capacidad de autosanación, capaz de cerrar pequeñas fisuras, producida principalmente por la hidratación continuada y la carbonatación. Estudios recientes han intentado mejorar dicha capacidad y diseñar productos específicos para conseguirla. Estos productos incluyen, entre otros, aditivos cristalinos, agentes micro o macroencapsulados, e incluso el uso de bacterias. Los aditivos cristalinos (CA) son un tipo de aditivo para hormigón que se considera que aporta propiedades de autosanación. No obstante, la falta de conocimiento sobre su comportamiento limita su uso. Además, los métodos para evaluar la autosanación en hormigones no están estandarizados todavía. Esto complica la realización de un análisis crítico de los diferentes productos y métodos de evaluación propuestos en la literatura. Para responder a esta falta de conocimiento, los objetivos de esta tesis son: 1) estudiar y proponer procedimientos experimentales para evaluar los fenómenos de autosanación en hormigón y, 2) evaluar experimentalmente las mejoras producidas al introducir aditivos cristalinos. Esta tesis incluye como ensayos para la determinación de la autosanación: la evaluación del cierre de fisuras, la permeabilidad al agua, flexión a tres puntos y absorción capilar. Además, se han realizado varias campañas experimentales para validar los ensayos propuestos. Posteriormente, estos ensayos se han utilizado para analizar la influencia de varios parámetros, incluyendo entre otros: presencia de aditivos cristalinos, nivel de daño, tiempo necesario para el sanado, composición del hormigón y condiciones de sanado. Finalmente, se analizan los efectos producidos al añadir aditivos cristalinos en hormigón en la fluidez, resistencia e hidratación. Los resultados muestran que el cierre de fisuras es un ensayo eficaz y sencillo para evaluar la autosanación. Sin embargo, la orientación de la fisura durante el sanado ha resultado ser de gran importancia, y no considerar este aspecto puede llevar a conclusiones engañosas. El ensayo de permeabilidad al agua propuesto en este trabajo presenta una buena estabilidad y es fácil de implementar en laboratorios. Además, las relaciones obtenidas entre los parámetros de fisura y la permeabilidad del agua han confirmado la relación cúbica indicada en la literatura. Este trabajo muestra que analizar la eficiencia de autosanado mediante el cierre de fisuras puede llevar a una sobreestimación de la capacidad de sanación, comparada con los resultados obtenidos mediante permeabilidad. Los ensayos de sorptividad resultaron fáciles de implementar, sin embargo, los resultados obtenidos mostraron una alta dispersión y sensibilidad a las variaciones en las fisuras producidas durante el proceso de prefisuración. En cuanto a la evaluación de la recuperación mecánica, los resultados muestran que la evolución de las propiedades del hormigón con el tiempo es un parámetro que debe considerarse, especialmente en fisuras de edades tempranas. En este trabajo se ha obtenido que los aditivos cristalinos potencian las reacciones de autosanación, pero tienen una capacidad limitada. La proximidad de los CA a la industria es un punto positivo para su inclusión como un nuevo tipo de aditivo de hormigón. Sin embargo, los resultados obtenidos en esta tesis indican que se necesitan más análisis para determinar sus efectos completos en hormigón, especialmente con respect / Self-healing materials are materials with the capability to repair their damage autonomously or with minimal help from an external stimulus. In the construction field, the development of self-healing elements will increase the durability of structures and reduce their maintenance and repair actions. Reinforced concrete elements frequently suffer small cracks (< 0.3 mm), not relevant mechanically, but they can be an entrance point for aggressive agents. Concrete has a natural self-healing capability able to seal small cracks, produced by the continuing hydration and carbonation processes. Recent studies have attempted to improve that healing capability and to design specific products to achieve it. These products include, among others: crystalline admixtures, micro- or macro-encapsulated agents, and even the use of bacteria. Crystalline admixtures (CA) are a concrete admixture that is claimed to provide self-healing properties. However, the lack of knowledge on their behavior and self-healing properties limits their usage. In addition, the methods to evaluate the self-healing capability of mortar and concrete are not standardized yet. This complicates the performance of a critical analysis of the different self-healing products and evaluation methods found in the literature. In order to answer to this lack of knowledge, the objectives of this thesis are: 1) to study and propose experimental procedures in order to evaluate self-healing in concrete and, 2) to evaluate experimentally the self-healing enhancements produced when introducing crystalline admixtures. This thesis includes the following tests for the determination of the self-healing: the evaluation of crack closing, water permeability, three point bending tests and capillary absorption test. In addition, several experimental campaigns have been performed with the objective of validating the proposed tests. Afterwards, these methods have been used to analyze the influence of several parameters, including among others: the presence of crystalline admixtures, the damage extent, healing time needed, concrete composition and healing conditions. Finally, the effects that crystalline admixtures produce in concrete are analyzed in terms of slump, strength and hydration. The results show that crack closing is an effective and simple method to evaluate self-healing. However, the orientation of the crack during healing is of great importance, and disregarding this aspect may lead to misleading conclusions. The water permeability method proposed in this work has good stability and it is easy to implement in concrete laboratories. Moreover, the relations obtained between crack parameters and water permeability confirmed the cubic relation, as reported in the literature. This work shows that analyzing healing efficiency by means of crack closing tends to overestimate self-healing if compared with the results obtained by means of water permeability. Sorptivity analysis tests were easy to implement, however, the results obtained in this work showed high dispersion and sensitivity to the variations of the cracks introduced during the precracking process. Regarding the evaluation of mechanical recoveries, the results show that the evolution of concrete properties with time is a parameter of importance that, therefore, should be considered, especially for early age cracks. In this work, crystalline admixtures have been reported as an enhancer of self-healing reactions, but with a limited capacity of enhancement. The proximity of CA to the industry is a positive point to their inclusion as a new type of admixture for concrete. However, the results obtained in this thesis indicate further analyses are needed to determine their full effects on concrete, especially regarding self-healing. / Els materials autosanables són materials amb la capacitat de reparar els seus danys de forma autònoma o amb ajuda mínima d'estímuls externs. En el camp de la construcció, el desenvolupament d'elements autosanables augmentarà la durabilitat de les estructures i reduirà les accions de manteniment i reparació. Els elements de formigó armat presenten freqüentment fissures menudes (< 0.3 mm), no rellevants des del punt de vista mecànic, però poden suposar un punt d'entrada per a agents agressius. El formigó té una capacitat de autosanació capaç de tancar fissures menudes, produïda principalment per la hidratació continuada i la carbonatació. Estudis recents han intentat millorar eixa capacitat i dissenyar productes específics per aconseguir-la. Aquests productes inclouen, entre d'altres, additius cristal·lins, agents micro- o macroencapsulats, i fins i tot l'ús de bacteris. Els additius cristal·lins (CA) són un tipus d'additiu reductor per formigó que es considera que proporciona propietats de autosanació. No obstant, la manca de coneixement sobre el seu comportament limita el seu ús. A més, els mètodes per avaluar la autosanació de formigons encara no estan estandarditzats. Açò complica la realització d'una anàlisi crítica dels diferents productes i mètodes d'avaluació proposats a la literatura. Per respondre a aquesta manca de coneixement, els objectius d'aquesta tesi són: 1) estudiar i proposar procediments experimentals per avaluar els fenòmens d'autosanació en formigó i, 2) avaluar experimentalment les millores produïdes en introduir additius cristal·lins. Aquesta tesi inclou com assajos per a la determinació de l'autosanació: l'avaluació del tancament de fissures, la permeabilitat a l'aigua, flexió a tres punts i absorció capil·lar. A més, s'han realitzat diverses campanyes experimentals per validar els assajos proposats. Posteriorment, aquests assajos s'han utilitzat per analitzar la influència de diversos paràmetres: presència d'additius cristal·lins, nivell de dany, temps necessari per a la sanació, composició del formigó i condicions de sanació. Finalment, s'analitzen els efectes produïts en afegir additius cristal·lins en formigó en fluïdesa, resistència i hidratació. Els resultats mostren que el tancament de fissures és un assaig eficaç i senzill per avaluar l'autosanació. No obstant això, l'orientació de la fissura durant la sanació ha resultat ser de gran importància, i no considerar aquest aspecte pot portar a conclusions enganyoses. L'assaig de permeabilitat a l'aigua proposat presenta una bona estabilitat i és fàcil d'implementar en laboratoris. A més, les relacions obtingudes entre els paràmetres de fissura i la permeabilitat a l'aigua han confirmat la relació cúbica de la literatura. Aquest treball mostra que analitzar l'eficiència de l'autosanació amb el tancament de fissures pot sobreestimar la capacitat de sanació, comparada amb els resultats obtinguts-dues mitjançant permeabilitat a l'aigua. Els assajos de sorptivitat van resultar fàcils d'implementar, però, els resultats obtinguts en aquest treball van mostrar una alta dispersió i sensibilitat a les variacions en les fissures produïdes durant el procés de prefissuració. Pel que fa a l'avaluació de la recuperació mecànica, els resultats mostren que l'evolució de les propietats del formigó amb el temps és un paràmetre d'importància que, per tant, s'ha de considerar, especialment per fissures primerenques. En aquest treball s'ha obtingut que els additius cristal·lins potencien les reaccions d'autosanació, però tenen una capacitat limitada. La proximitat dels CA a la indústria és un punt positiu per a la seva inclusió com un nou tipus d'additiu de formigó. Tanmateix, els resultats obtinguts en aquesta tesi indiquen que calen més anàlisis per determinar els seus efectes complets en formigó, especialment pel que fa a l'autosanació. / Roig Flores, M. (2018). Self-healing concrete: efficiency evaluation and enhancement with crystalline admixtures [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/100082

Poly(lactic acid) is biodegradable polymer derived from renewable resources and non-toxic, which has become most interested polymer to substitute petroleum-based polymer. However, it has low glass transition temperature and poor gas barrier properties to restrict the application on hot contents packaging and long-term food packaging. The objectives of this research are: (a) to reduce coagulation of graphene oxide/single-walled carbon nanotube (GOCNT) nanocomposite in poly(lactic acid) matrix and (b) to improve mechanical strength and oxygen barrier property, which extend the application of poly(lactic acid). Graphene oxide has been found to have relatively even dispersion in poly(lactic acid) matrix while its own coagulation has become significant draw back for properties of nanocomposite such as gas barrier, mechanical properties and thermo stability as well as crystallinity. Here, single-walled carbon nanotube was hybrid with graphene oxide to reduce irreversible coagulation by preventing van der Waals of graphene oxide. Mass ratio of graphene oxide and carbon nanotube was determined as 3:1 at presenting greatest performance of preventing coagulation. Four different weight percentage of GOCNT nanocomposite, which are 0.05, 0.2, 0.3 and 0.4 weight percent, were composited with poly(lactic acid) by solution blending method. FESEM morphology determined minor coagulation of GOCNT nanocomopsite for different weight percentage composites. Insignificant crystallinity change was observed in DSC and XRD data. At 0.4 weight percent, it prevented most of UV-B light but was least transparent. GOCNT nanocomposite weight percent was linearly related to ultimate tensile strength of nanocomposite film. The greatest ultimate tensile strength was found at 0.4 weight percent which is 175% stronger than neat poly(lactic acid) film. Oxygen barrier property was improved as GOCNT weight percent increased. 66.57% of oxygen transmission rate was reduced at 0.4 weight percent compared to neat poly(lactic acid). The enhanced oxygen barrier property was ascribed to the outstanding impermeability of hybrid structure GOCNT as well as the strong interfacial adhesion of GOCNT and poly(lactic acid) rather than change of crystallinity. Such a small amount of GOCNT nanocomposite improved mechanical strength and oxygen barrier property while there were no significant change of crystallinity and thermal behavior found. / Master of Science