Dissertations / Theses on the topic 'Polymer Hybrid Systems'

As an alternative to transverse spiral or hoop steel reinforcement, fiber reinforced polymers (FRPs) were introduced to the construction industry in the 1980's. The concept of concrete-filled FRP tube (CFFT) has raised great interest amongst researchers in the last decade. FRP tube can act as a pour form, protective jacket, and shear and flexural reinforcement for concrete. However, seismic performance of CFFT bridge substructure has not yet been fully investigated. Experimental work in this study included four two-column bent tests, several component tests and coupon tests. Four 1/6-scale bridge pier frames, consisting of a control reinforced concrete frame (RCF), glass FRP-concrete frame (GFF), carbon FRP-concrete frame (CFF), and hybrid glass/carbon FRP-concrete frame (HFF) were tested under reverse cyclic lateral loading with constant axial loads. Specimen GFF did not show any sign of cracking at a drift ratio as high as 15% with considerable loading capacity, whereas Specimen CFF showed that lowest ductility with similar load capacity as in Specimen GFF. FRP-concrete columns and pier cap beams were then cut from the pier frame specimens, and were tested again in three point flexure under monotonic loading with no axial load. The tests indicated that bonding between FRP and concrete and yielding of steel both affect the flexural strength and ductility of the components. The coupon tests were carried out to establish the tensile strength and elastic modulus of each FRP tube and the FRP mold for the pier cap beam in the two principle directions of loading. A nonlinear analytical model was developed to predict the load-deflection responses of the pier frames. The model was validated against test results. Subsequently, a parametric study was conducted with variables such as frame height to span ratio, steel reinforcement ratio, FRP tube thickness, axial force, and compressive strength of concrete. A typical bridge was also simulated under three different ground acceleration records and damping ratios. Based on the analytical damage index, the RCF bridge was most severely damaged, whereas the GFF bridge only suffered minor repairable damages. Damping ratio was shown to have a pronounced effect on FRP-concrete bridges, just the same as in conventional bridges. This research was part of a multi-university project, which is founded by the National Science Foundation (NSF) Network for Earthquake Engineering Simulation Research (NEESR) program.

During this EngD project, two pigmented, anti-corrosion polymer/sol-gel hybrid coatings were developed with the aim of producing an eco-friendly alternative to conventional, toxic hexavalent chromate conversion and anodized anti-corrosion alloy treatments for the aircraft manufacturer; Airbus S.A.S. The polymer/sol-gel hybrid coatings were then tested and validated as anti-corrosion coatings on the AA2024-T3 aluminium aerospace alloy and in certain cases, their performance was compared against that of the hexavalent chromate benchmark (Alocrom 1200). The mechanisms of corrosion inhibition exhibited by the coatings were also studied in depth. The polymer/sol-gel hybrid coatings that were developed in this project are silane based and the first, designated as B2, has polyester-methacrylic functionality and the second, designated as CA/MM, has polyester-amide functionality. Certain inhibitor compounds which were incorporated in the polymer/sol-gel hybrid coatings were chosen by the split-cell technique. The microstructure and elemental compositions of the polymer/sol-gel hybrid coatings and of the AA2024-T3 aluminium alloy were determined by Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopic (SEM-EDS) analysis of the specimens. The anti-corrosion performance and the corrosion protection mechanisms of the polymer/sol-gel hybrid coatings were determined by salt-water and electrochemical testing of the coated alloy specimens. The thermal resistance of the polymer/sol-gel hybrid coatings was ascertained by thermogravimetric analysis (TGA) of the coatings. The polymer/sol-gel hybrid coatings were also analysed by Fourier Transform Infrared (FTIR), Micro-Raman and X-ray Photoelectron (XPS) spectroscopic techniques to determine whether the desired polymer and silane coating networks formed during coating processing. Anti-corrosion performance test results revealed that both polymer/sol-gel hybrid coatings are self-healing due to their ability to implement a precipitation mechanism of corrosion inhibition. Analysis of the polymer/sol-gel hybrid coatings by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) after salt-water exposure suggested that the B2 coating precipitated the compound tungsten pyrophosphate, W(P2O7), within defects and that the CA/MM coating precipitated the compound iron carbide, Fe2C, within defects. However, anti-corrosion test results also shown that the anti-corrosion performance of the polymer/sol-gel hybrid coatings does not satisfy aerospace industry requirements. Therefore, it can be concluded that although the achievements of this project have not enabled Airbus to eliminate toxic chromium (VI) species from their operations, further optimisation of the polymer/sol-gel hybrid coatings developed during this project could potentially lead to a solution being found.

Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59).
An increasingly mobile US Navy surface fleet and oil price uncertainty contrast with the Navy's desire to lower the amount of money spent purchasing fuel. Operational restrictions limiting fuel use are temporary and cannot be dependably relied upon. Long term technical research toward improving fuel efficiency is ongoing and includes advanced gas turbines and integrated electric propulsion plants, but these will not be implemented fleet wide in the near future. The focus of this research is to determine if a hybrid fuel cell and gas turbine propulsion plant outweigh the potential ship design disadvantages of physically implementing the system. Based on the potential fuel savings available, the impact on surface ship architecture will be determined by modeling the hybrid fuel cell powered ship and conducting a side by side comparison to one traditionally powered. Another concern that this solution addresses is the trend in the commercial shipping industry of designing more cleanly running propulsion plants.
Douglas M. Kroll.
S.M.in Engineering and Management
Nav.E.

Thesis (M.S.)--Michigan State University. Dept. of Civil and Environmental Engineering, 2008.
Title from PDF t.p. (viewed on Aug. 3, 2009) Includes bibliographical references (p.129-132). Also issued in print.

Les matériaux composites à matrice polymère thermodurcissable interviennent dans de nombreux domaines d’application, parmi lesquels le secteur des transports. Ils présentent toutefois une faible tenue au feu qui limite leur utilisation pour des raisons évidentes de sécurité. De par les restrictions de plus en plus exigeantes de la Commission Européenne (REACH), il existe un réel besoin de se tourner vers des solutions alternatives. Des études récentes ont prouvé l’intérêt des Silsesquioxanes Oligomériques Polyhédriques (POSS) comme agents ignifuges, et particulièrement les POSS portant des ligands phenyl. L’objectif de ce travail a été d’étudier comment la tenue au feu de réseaux hybrides époxy-amine pouvait être améliorée par l’ajout de POSS dans ces matériaux. En faisant varier la nature des comonomères époxydes et amines, ainsi que la structure des POSS sélectionnés, des éléments de réponse ont pu être apportés à la question : existe-t-il une relation structure-propriété en ce qui concerne le comportement au feu des réseaux époxydes ? Des POSS fonctionnels et inertes ont été choisis pour cette étude, et une attention particulière a été portée sur le trisilanolphenyl POSS (POSSOH), pour lequel différents procédés de dispersion ont été mis en œuvre. Il a été montré que l’état de dispersion des POSS était significativement influencé par le type de ligands de ces POSS, mais également par le type de prépolymère époxyde utilisé. En particulier, des structures complexes, jamais observées, ont été découvertes dans les réseaux hybrides basés sur la Tétraglycidyl(diaminodiphenyl) méthane (TGDDM). Des études cinétiques visant à comprendre les interactions développées par les POSS au sein des réseaux ont été menées. Un fort pouvoir catalytique de l’association POSSOH avec un composé à base d’aluminium sur les réactions de réticulation a notamment été mis en évidence. D’autre part, les propriétés thermomécaniques des réseaux finals n’ont pas été modifiées de manière significative par l’ajout de POSS. Finalement, une amélioration remarquable de la tenue au feu a été obtenue dans certains cas, notamment par l’ajout de POSSOH en combinaison avec le composé métallique. La tenue au feu des réseaux à base de TGDDM a été identifiée comme étant liée à un mécanisme d’intumescence
Thermoset polymer composite materials are used in a number of application domains, amongst which the transports sector, but they suffer from poor fire resistance which limits their use for obvious safety and security issues. With the increasingly demanding restrictions from the European Commission, there is a real need to seek for alternative solutions. Recent studies have found the Polyhedral Oligomeric Silsesquioxane (POSS) compounds interesting as fire retardant agents, particularly the POSS bearing phenyl ligands. The present work aimed at investigating how the fire retardancy of hybrid epoxy networks can be improved by incorporating Polyhedral Oligomeric Silsesquioxanes (POSS). In this study, the nature of the epoxy-amine comonomers was varied, as well as the POSS structure. An inert POSS and two multifunctional POSS were selected in order to generate various morphologies. The aim was to answer the question: does a structure-property relationship exist as concerns the fire behaviour of epoxy networks? Particular attention was dedicated to systems containing the trisilanolphenyl POSS (POSSOH) for which different processes of dispersion were implemented. The POSS dispersion state was shown to be greatly influenced by the type of POSS ligands, but also by the epoxy prepolymer nature in the case of the versatile POSSOH. In particular, intricate, never-observed morphologies were discovered in the networks based on Tetraglycidyl(diaminodiphenyl) methane (TGDDM) and containing POSSOH. The study of functional POSS-involving interactions and epoxy-amine kinetics in the model systems revealed the high catalytic power of the combined presence of POSSOH and an aluminium-based catalyst in the model epoxy networks, as well as the occurrence of homopolymerisation. The thermo-mechanical properties were not significantly modified by the addition of POSS. Finally, spectacular improvements in fire retardancy were obtained in some cases, in particular when the POSSOH and the Al-based catalyst were introduced in combination. The fire protection mechanism was attributed to intumescence in the TGDDM-based networks. The addition of POSSOH and the Al-catalyst was found to be efficient in all the epoxy-amine network types, which could not be clearly related to the POSSOH structures but was rather attributed to a chemical synergistic effect

The goal of this dissertation consists of improving the efficiency of energy harvesting using pyroelectric and piezoelectric materials in a system by the proper characterization of electrical parameters, widening frequency, and coupling of both effects with the appropriate parameters. A new simple stand-alone method of characterizing the impedance of a pyroelectric cell has been demonstrated. This method utilizes a Pyroelectric single pole low pass filter technique, PSLPF. Utilizing the properties of a PSLPF, where a known input voltage is applied and capacitance Cp and resistance Rp can be calculated at a frequency of 1 mHz to 1 Hz. This method demonstrates that for pyroelectric materials the impedance depends on two major factors: average working temperature, and the heating rate. Design and implementation of a hybrid approach using multiple piezoelectric cantilevers is presented. This is done to achieve mechanical and electrical tuning, along with bandwidth widening. In addition, a hybrid tuning technique with an improved adjusting capacitor method was applied. An toroid inductor of 700 mH is shunted in to the load resistance and shunt capacitance. Results show an extended frequency range up to 12 resonance frequencies (300% improvement) with improved power up to 197%. Finally, a hybrid piezoelectric and pyroelectric system is designed and tested. Using a voltage doubler, circuit for rectifying and collecting pyroelectric and piezoelectric voltages individually is proposed. The investigation showed that the hybrid energy is possible using the voltage doubler circuit from two independent sources for pyroelectrictity and piezoelectricity due to marked differences of optimal performance.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.
Gee-Kung Chang, Committee Chair ; Thomas K. Gaylord, Committee Co-Chair ; Glenn S. Smith, Committee Member ; John A. Buck, Committee Member ; Ali Adibi, Committee Member ; C. P. Wong, Committee Member.

This research project was concerned with the establishment and characterisation of a quartz crystal microbalance (QCM) - conductimetric interdigitated electrode hybrid "second generation" Electronic Nose system. Research objectives covered a number of technical limitations and analytical difficulties existed in the "first generation" Electronic Nose system. A wide variety of work was carried out, including the design and fabrication of the electronic nose system, the optimisation of sensors response, the device modelling, the studies of vapour-polymer interaction mechanisms and the application of the electronic nose in multi-component analysis. A QCM-interdigitated electrode hybrid sensor odour measurement system was established, and sensor fabrication techniques developed. Some important parameters corresponding to sensor characteristics were investigated such as the conditions for polymer film polymerisation. By studying 16 different coatings, "optimal" individual initial resistances were proposed, which minimise long-term baseline resistance drift, whilst maintaining good sensitivity. A set of sensors was made with low initial resistance variation. Sensor detection dynamic range was found to be dependent on the type of the coating material and the film thickness. The response of a combined hybrid sensor pair remained stable during a test period of 45 days, which showed an improved stability. The principle of the sensor's response and device modelling were addressed. The vapour-polymer interactions and sensor pair's response were linked by a sensitivity coefficient (S), which was defined as the relative resistivity change by a single molecule absorbed into the polymer film. A pair of sensors showing concentration independence over a wide concentration range can be formed on separate QCM and interdigitated electrodes with the same polymer. The combined response (Srf) can be used to identify a particular vapour. Based on the concentration independence, the proposed "odour maps" showed the feasibility of distinguishing odourants using a significantly lower number of different types of sensor coatings. This demonstrated the improved selectivity of a hybrid system compared with the single property system.

This work is generally aimed to synthesize POSS based BCPs via RAFT polymerization, to study their self-assembly behaviors, to research on the effect of POSS self-assembly structure on the bulk properties and to prepare nanostructured hybrid epoxy via self-assembly of POSS based copolymer. In Chapter1, We studied the RAFT polymerization of POSS macromers and capable to synthesize well defined POSS based BCPs with high POSS fraction and different topology such as AB，BAB and (BA)3. The vertex group and the morphology effect on thermo-mechanical properties of POSS based BCPs as well as the structure-property relationship was investigated. Dispersion RAFT polymerization in apolar solvent was applied and various aggregates with different morphology in Chapter2. Cooling induced reversible micelle formation and transition was found and the pathway selection in vesicle formation was investigated. Nano-construction of O/I hybrid epoxy materials based on POSS based copolymers was investigated in Chapter4. The effect of functional group content on miscibility of POSS based statistic copolymer and epoxy was investigated. A novel method to nanostructure epoxy hybrid involving self-assembly of POSS based BCPs in epoxy was presented. High homogeneity and well size/morphology control of core-corona structure containing rigid POSS core and soluble PMMA corona in networks were obtained.

Supramolecular interactions are of great importance in the fabrication of new functional materials. In particular, colloidal assembly via supramolecular pathway has contributed to numerous innovations in material chemistry, on account of its specific, directional and dynamic non-covalent interactions. By taking advantage of the non-covalent supramolecular interactions, tailored complementary colloidal building blocks which are normally incompatible with each other could be integrated interdependently, forming novel hybrid materials with emerging properties. This thesis mainly focuses on the design, preparation and characterization of novel colloidal assemblies based on cucurbit[n]urils host-guest interactions, including hybrid ‘raspberry-like’ colloids, catalytic polymeric nanocomposites, advanced structured colloids, and supramolecular polymer colloidal hydrogel.

Yes
This paper presents test results of six full scale reinforced concrete continuous T beams. One beam was reinforced with glass fibre reinforced polymer (GFRP) bars while the other five beams were reinforced with a different combination of GFRP and steel bars. The ratio of GFRP to steel reinforcement at both mid-span and middle-support sections was the main parameter investigated. The results showed that adding steel reinforcement to GFRP reinforced concrete T-beams improves the flexural stiffness, ductility and serviceability in terms of crack width and deflection control. However, the moment redistribution at failure was limited because of the early yielding of steel reinforcement at a beam section that does not reach its moment capacity and could still carry more loads due to the presence of FRP reinforcement. The experimental results were compared with the ultimate moment prediction of ACI 440.2R-17, and with the existing theoretical equations for deflection prediction. It was found that the ACI 440.2R-17 reasonably estimated the moment capacity of both mid-span and middle support sections. Conversely, the available theoretical deflection models underestimated the deflection of hybrid reinforced concrete T-beams at all load stages.
The full-text of this article will be released for public view after the publisher embargo on 10 Aug 2021.

Les sources d’énergies utilisées pour le chauffage de l’eau dans les bâtiments commerciaux et résidentielles sont multiples. Ces ressources sont essentiellement électriques dans les milieux urbains et utilisent le bois dans les milieux ruraux. Le pourcentage de l’énergie solaire utilisé reste assez faible. Les méthodes les utilisées pour produire l’eau chaude sont pour basés pour l’essentielle sur l’utilisation des résistances électrique ou des capteurs solaire plat. Le travail présenté dans cette thèse est basé sur l’utilisation des concentrateurs solaires pour chauffer des collecteurs d’énergie. Le rendement est augmenté par le développement de nouveau matériaux pour le stockage.La structure pour le support du collecteur a été conçue et analysée utilisant le logiciel Solidworks®. Les forces agissant sur les éléments de la structure sont simulées pour assurer la fiabilité du support lors des différentes conditions de fonctionnement. L’analyse par la méthode des éléments finis a permis la vérification de la structure utilisée pour le réflecteur et son support.Les performances énergétiques ont été simulées pour cinq ans d’opération utilisant le logiciel Matlab Simulink®. Cette simulation a été basée sur l’utilisation de trois données différentes. La première est une base de données météorologique de cinq ans en Afrique du Sud dans la Ville de Tshwane. La deuxième est un profil d’utilisation pour un foyer type. La troisième est le coût de complément de chauffage en électricité dépendant de l’heure de l’utilisation. Cette simulation a permis la validation des choix de dimensions de différents éléments du système de chauffage.Cette étude a permis le développement d’une approche pour la conception d’un système de chauffage solaire en optimisant les dimensions des différents éléments pour un foyer type et une région spécifique.De plus, nous avons conçu un autre réservoir d’eau chaude. Nous avons démontré que l'utilisation de matériaux polymères et d'autres matériaux comme le polyuréthane, le sel et l'aluminium est possible pour le développement d'un réservoir de stockage d'eau chaude en fonction de leurs propriétés inhérentes.L'extension des résultats de cette thèse améliorera encore les conceptions des technologies de concentrateurs solaires et des systèmes de chauffage solaire de l'eau. Par conséquent, certaines recommandations et suggestions sont mises en évidence afin d'améliorer la conception, l'analyse et les performances globales du système
In recent years, various energy sources and methods have been used to heat water in domestic and commercial buildings. The known sources for water heating include electrical energy and solar radiation energy in the urban regions or burning of firewood in the rural areas. Several water heating methods may be used such as electrical heating elements, solar concentrators, flat plate collectors and evacuated tube collectors. This thesis focuses on ways to further improve the system’s performance for water heating through the combined use of solar energy and solar concentrator technique. Furthermore, the study proposed an alternative design method for the hot water storage tank.The solar collector-supporting frame was designed and analysed using Solidworks®. The forces acting on the structural members were simulated to determine the capacity of the frame to sustain the load, and the possible regions on the supporting frame, which could potentially fail while in operation.Energy performance was simulated for five years of operation using Matlab Simulink® software. This simulation was based on the use of three different data. The first is a five-year weather database of the City of Tshwane in South Africa. The second is a hot water consumption profile for a typical household. The third is the cost of additional heating with electricity depending on the time of use. This simulation allowed the validation of the choices of the different elements of the heating system.This study allowed the development of an approach for the design of a solar heating system by optimising the dimensions of the different elements for a typical household and a specific region.In addition, the use of polymeric materials and other materials like polyurethane, salt and aluminium is possible for the development of a hot water storage tank based on their inherent properties.Extending the findings in this thesis will further improve the designs for solar concentrator technologies and solar water heating systems. Therefore, some recommendations and suggestions are highlighted in order to improve the overall system design, analysis and performance

The Direct Methanol Fuel Cell (DMFC) has been considered as one of the competitive alternatives for battery technology as it has much higher energy density, faster recharging and does not require complicated control systems like a fuel reformer or compressed gas tank as needed by a hydrogen fuel cell. However, current DMFC technology suffers from the low power density caused by low reaction rate and undesired “methanol crossover” issues, which brings a big challenge for its application in practical systems. This thesis presents a practical design and prototype development of a DMFC/battery hybrid energy management system, which can be provided as one possible solution for the low power and cold start issues. First of all the existing fuel cell hybrid system schemes and design of the auxiliary units (BOP) are surveyed and compared. Based on the analysis above a microcontroller-based DMFC and Lithium Polymer Battery hybrid system is proposed. After that a novel “Battery-Current-Based Hybrid Control (BCBHC)” is proposed to provide active load sharing and proper battery charging and protection. The DMFC will follow the average battery current by neglecting the battery current transients and charge the battery by following the Constant-Current and Constant Voltage charging scheme when possible. A variety of battery protections, such as overcharging, overcurrent and charging current limitation, are implemented by the BCBHC and protection circuit. A detailed system design and modeling are then presented. The models are developed and simulated in PSIM. The simulation results are analyzed and showed the validity of proposed hybrid control. At the end a prototype hybrid EMS controller board has been implemented to further validate the hybrid system design. The dynamic behavior of DMFC/Battery hybrid system is examined and tested under a series of load experiments. The measured results have proved the feasibility and stability of the designed hybrid control.

In this study, a series of denim fiberboards are fabricated using two different resins, malamine urea formaldehyde (MUF) and polymeric methylene diphenyl diisocyanate (pMDI). Two experimental design factors (1) adhesive content and (2) MUF-pMDI weight ratio, were studied. All the denim fiberboard samples were fabricated following the same resin blending, cold-press and hot-press procedures. The physical and mechanical tests were conducted on the fiberboard following the procedures described in ASTM D1037 to obtain such as modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), thickness swell (TS), and water absorption (WA). The results indicated that the MOE was significantly affected by both factors. IB was affected significantly by weight ratio of different glue types, with 17 wt% more MDI resin portion in the core layer of the denim boards, the IB for total adhesive content 15% fiberboard was enhanced by 306%, while for total adhesive content 25% fiberboard, enhanced by 205%. TS and WA, with higher adhesive content used in denim boards' fabrication, and more pMDI portion in the core layer of the boards, the boards' TS and WA was reduced by up to 64.2% and 78.8%, respectively.

Les limites des nanovecteurs commerciaux ou actuellement en développement ont motivé l’élaboration de nouvelles nanoparticules mésoporeuses de silice (MSNP), hybrides et multiphasées, pour le contrôle de la délivrance d’actifs à application théranostique. Ainsi, de nouvelles MSNP ont été conçues pour la pénétration intracellulaire (diamètre entre 30 et 60 nm, taille des pores de 2,8 nm). Afin de les rendre hémocompatibles et de contrôler la cinétique de délivrance de principes actifs encapsulés, ces MSNP ont été enrobées d’une bicouche lipidique (MSNP+@SLB-). La composition lipidique s’inspire des membranes asymétriques des globules rouges ciblés par la présente étude.La technologie MSNP+@SLB- ayant montré des limites avec une cinétique de libération trop élevée de la calcéine et trop lente de la rhodamine B, deux améliorations majeures ont été apportées :1- Le recouvrement des SLB par un nanogel d’alginate, permettant un excellent contrôle de la libération d’actifs.2- L’insertion de nanoparticules magnétiques dans le coeur des MSNP, déclenchant la libération de l’actif par hyperthermie.Ces nouvelles architectures de nanovecteurs permettent de moduler les cinétiques de délivrance d’actifs, renforçant et élargissant ainsi le champ d’applications des vecteurs silicés dans les domaines biomédical ( Voie orale et intraveineuse) et dermato-cosmétique (Voie topique)
The limitations of commercial nanovectors or currently under development have motivated the development of new hybrid and core shell mesoporous silica nanoparticles (MSNP) for the control of molecular delivery.Therefore, new MSNP were designed for intracellular penetration (diameter between 30 and 60 nm, pore size of 2.8 nm). In order to make them hemocompatible and to control the kinetics of delivery of encapsulated active ingredients, these MSNP were coated with a lipid bilayer (MSNP+@SLB-). The lipid composition is inspired by the asymmetric membranes of the red blood cells.Since the MSNP+@SLB- technology has shown some limitations associated to the release of payloads which can be too fast (in the case of calcein) or to slow (case of rhodamine B), two major improvements have been made:1- The coating of SLB by an alginate nanogel, allowing an excellent control of the release of active molecules.2- Insertion of magnetic nanoparticles in the MSNP core, triggering the release of the active ingredient by hyperthermia.These new nanovector architectures enable the fine tuning of active ingredient delivery kinetics, reinforcing and expanding the applications of silicated vectors in the fields of biomedicine (oral and intravenous) and dermato-cosmetics (topical)

A ce jour l’os est le tissu le plus greffé au monde et les défets osseux suite à une ostéoporose, cancer et fractures restent problématiques avec un risque d’infections élevé. L’administration d’antibiotiques par voie systémique n'est pas satisfaisante car leur diffusion dans l'os est très faible, une administration locale est donc nécessaire. La stratégie de cette thèse est de développer deux substituts hybrides (hydroxyapatite/hydrogel), l'un massif, l'autre injectable, pour l'administration d'une association d'antibiotiques (ciprofloxacine/gentamicine). Un double système à libération sera ainsi développé pour traiter au long terme l'infection, l'un permettra une libération rapide (via la diffusion dans l'hydrogel), l'autre permettra une diffusion lente (via des microparticules). La première partie a permis de développer des microparticules de PLGA chargées de gentamicine (GM) par la technique de double émulsion par évaporation du solvant. La méthode de préparation des microparticules a été optimisée pour obtenir des microparticules de 50 à 80 µm, compatible avec la macroporosité de l'hydroxyapatite (HA) et une libération prolongée pendant 25-30 jours. Ainsi le temps de sonification de la première émulsion a été fixé à 2 minutes pour obtenir une efficacité d'encapsulation maximale et la vitesse de rotation de la seconde émulsion fixée à 700 rpm pour obtenir des microparticules d'environ 60 µm. Les microparticules ont été analysées par DSC, ATG et MEB. L'activité antibactérienne des microparticules chargées de GM a été démontrée sur le S. aureus (CIP224).La seconde partie a permis de développer un scaffold où l'hydrogel de chitosan (CHT) se formera in situ dans la macroporosité d'une pièce tridmensionnelle en HA. Cet hydrogel a été obtenu par voie chimique avec un agent réticulant (genipine) pour permettre une injection et une gélification relativement lente. Le suivi de la formation de l'hydrogel de CHT (2%-wt) par spectrophotométrie et rhéologie a permis d'optimiser le temps (24 heures) et la température (40°C) de gélification ainsi que la concentration de génipine (0.05%-wt). L'étude de la cinétique de libération de la ciprofloxacine (CFX) incorporée dans l'hydrogel lors de la formulation (0.1; 0.5 et 1%) a montré une libération rapide (<5 heures) en flux dynamique (30 ml/min). L'ajout de cyclodextrine(CD) dans la formulation pour ralentir la diffusion de la CFX n'a pas montré d'amélioration, elle est même responsable d'un ralentissement de la gélification par inclusion de la génipine dans la CD. Finalement l'hydrogel a été incorporé dans la macroporosité de l'HA avant la gélification; les études biologiques ont montré sa cytocompatibilité et une activité antibactérienne de 24 heures sur E. coli.La dernière partie a permis de développer un hydrogel injectable où les particules d'HA (90 µm) ont été incorporées dans l'hydrogel pendant la préparation. Cet hydrogel est obtenu par voie physique avec le polymère de cyclodextrine (PCD) pour une gélification rapide (<10 sec.) évitant la sédimentation de l'HA. Une étude plus approfondie a permis de montrer qu'une proportion d’au moins de 3% de CHT et d’au moins 3% de PCD était nécessaire pour la formation de l'hydrogel. Les études du gonflement et des propriétés rhéologiques ont montré l’impact du ratio PCD/CHT, de la forme soluble et insoluble du PCD et l'ajout d'HA sur la formation de l'hydrogel. Après lyophilisation, l'éponge a été hydratée dans une solution de CFX (2 mg/ml); les études biologiques n'ont pas montré de cytotoxicité et l'évaluation microbiologique a montré une activité prolongée (72 heures) sur E. coli [...]
Bone is the most transplanted tissue in the world and bone defects after osteoporosis, cancer and fractures remain problematic with a high level of infections. Systemic drug delivery is not efficient due to a low migration of drug into the bone, a local administration is necessary. The strategy of this thesis is to develop two hybrid substitutes (hydroxyapatite / hydrogel), the first one could be injectable and the other one could be directly implanted for the release of a combination of antibiotics (ciprofloxacin / gentamicin). A dual release system will be developed to treat long term infection with a rapid release (via diffusion into the hydrogel) and a slow release (via microparticles).In the first part, gentamicin (GM)-loaded PLGA microparticles were prepared by double emulsion with evaporation of the solvent. The microparticle preparation method has been optimized to obtain a size of microparticles compatible with the macroporosity of the hydroxyapatite (HA) and a sustained release over 25-30 days. Thus, the time of sonification of the first emulsion was set at 2 minutes in order to obtain a maximal efficacy of encapsulation. The speed of rotation of the second emulsion was fixed at 700 rpm to obtain a 60µm-diameter size of microparticles. The microparticles were analyzed by DSC, TGA and SEM. The antibacterial activity of gentamicin loaded microparticles was demonstrated on S. aureus (CIP224).In the second part we developed a bone substitute where chitosan (CHT) hydrogel was formed in situ in the macroporosity of a tridimensional hydroxyapatite printed piece. This hydrogel was obtained chemically with a crosslinking agent (genipin) to allow injection and a relatively slow gelation. The formation of the CHT hydrogel (2%-wt) was analyzed by UV-Vis spectrophotometry and rheology to optimize the time (24 hours), the temperature (40°C) and the concentration of genipin (0.05%-wt). The study of the release kinetics of ciprofloxacin (CFX) incorporated into the hydrogel (0.1; 0.5 and 1%) showed rapid release (<5 hours) in dynamic system (30 ml/min). The addition of cyclodextrin (CD) in the formulation did not shown a prolonged release of CFX, itself responsible to an increase of the gelation time due to an inclusion of genipin in the CD. Finally the hydrogel was incorporated in the macroporosity of HA before the gelation. Biological evaluation showed its cytocompatibility and antibacterial activity up to 24 hours on E. coli._x000D_In the last part, we developed an injectable bone substitute where HA particles (90 microns) were incorporated into the hydrogel during the preparation. This hydrogel was obtained by a physical way with an anionic polymer of cyclodextrin (PCD) for a fast gelation time (<10 seconds) avoiding sedimentation of the HA. Further study showed that a proportion of at least 3% of CHT and at least 3% of PCD was required for the formation of the hydrogel. Swelling and rheological properties showed the impact of the ratio PCD / CHT, the soluble and insoluble form of the PCD and the addition of HA on the formation of the hydrogel. After lyophilization, the sponge was hydrated in a solution of CFX (2 mg/ml). Biological studies did not shown cytotoxicity and microbiological evaluation showed a prolonged antibacterial activity up to 72 hours on E. coli.In conclusion, this thesis allowed the development of two hybrid bone substitutes for rapid release of CFX (<72 hours) and slow release of gentamicin-loaded microparticles (25-30 days). The incorporation of gentamicin loaded microparticles was possible in both bone substitutes allowing an antibacterial activity until 3 days against S. aureus and E. coli

No estudo de sistemas híbridos orgânico-inorgânico, o uso de materiais como polímeros conjugados e óxidos de metal de transição tem despertado grande interes- se. Em particular, destacam-se sistemas compostos de tiofenos e óxido de titânio, que encontram uma importante aplicação em células solares. Para um melhor entendimento da interação entre os dois sistemas, torna-se necessário conhecer a organização do polímero sobre o substrato inorgânico. Desse modo, investigamos neste trabalho a formação da interface entre oligômeros de tiofeno e a superfície (101) de TiO2-anatase utilizando um enfoque de multiformalismo, que inclui simulações de dinâmica molecular clássica, e uma combinação de cálculos de primeiros princípios segundo Hartree-Fock e Teoria do Funcional da Densidade (DFT) para a determinação de propriedades estruturais e eletrônicas. A deposição de oligômeros de tiofeno sobre TiO2, constituindo sistemas de milhares de átomos, foi simulada por meio de dinâmica molecular clássica. Como requisito do cálculo clássico para estes sistemas, realizamos a reparametrização do campo de forças Universal tanto para os oligômeros, cujas estruturas não são bem descritas pelos campos de força padrões, como para o cristal e a superfície de TiO2. Foi observada a formação de filmes desordenados e densos de quatertiofeno, com a presença de uma maioria de moléculas de orientação quase perpendicular em relação ao plano superficial. Na camada de interface também se encontram moléculas dispostas paralelamente ao substrato, aumentando o contato entre os sistemas orgânico e inorgânico. A deposição de oligômeros isolados de quatertiofeno e de hexatiofeno mostra ainda que as moléculas se dispõem paralelas na superfície, alinhadas segundo direções de periodicidade dos átomos da superfície. Estudamos desta forma as propriedades eletrônicas de um sistema composto de politiofeno sobre TiO2, com o polímero paralelo na superfície e disposto na direção preferencial, através de um formalismo ab initio DFT. Apesar do tratamento DFT apresentar problemas conhecidos quanto na definição do gap, o que é mais relevante ainda no nosso caso de sistemas híbridos, os resultados revelam um deslocamento do topo da banda de valência do material orgânico em relação ao inorgânico. Isto possibilita o aprisionamento de um buraco no polímero, condição necessária para o uso deste tipo de sistema em células fotovoltaicas. Verifica-se ainda o acoplamento entre átomos de enxofre do politiofeno e de oxigênio do TiO2 através da presença de um estado associado a uma densidade eletrônica que se estende do polímero na superfície. Nossos resultados indicam assim um bom acoplamento eletrônico da superfície (101) de TiO2-anatase com politiofenos.
In the study of organic-inorganic hybrid systems, the use of materials such as conjugated polymers and transition metal oxides has attracted great interest. In particular, it is worth mentioning systems composed by thiophenes and titanium oxide, which have an important application in solar cells. For a better understand- ing of the interaction between these systems, it is necessary to know the polymer organization over the inorganic substrate. Therefore, we investigated in this work the formation of the interface between thiophene oligomers and the (101) surface of TiO2-anatase by means of a multi-formalism approach, which includes classical molecular dynamics simulations, and a combination of ¯rst principles calculations based on Hartree-Fock and Density Functional Theory (DFT) for structural and electronic properties. The simulation of deposition of thiophene oligomers on TiO2, which demands systems with thousands of atoms, was performed by classical molecular dynamics. As a prerequisite for the classical calculation for these systems, we performed a re-parameterization of the Universal force ¯eld for the oligomers, whose structures are not well described by standard force ¯elds, and for the TiO2 bulk and surface. We observed the formation of disordered and dense quaterthiophene ¯lms, with presence of a majority of molecules oriented almost perpendicularly to the surface plane. In the ¯rst interfacial layer we ¯nd also molecules oriented parallel to the sub- strate, which increases the contact between the organic and the inorganic systems. The deposition of isolated quaterthiophene and sexithiophene oligomers resulted in molecules disposed parallel to the surface and aligned along directions of periodicity of the surface atoms. We therefore studied the electronic properties of a system composed of poly- thiophene on TiO2, with the polymer parallel to the surface and oriented along a preferential direction, by means of DFT formalism. Although DFT treatments present known problems in the de¯nition of the energy gap, even of more relevance in our case of hybrid systems, the results for the occupied states revealed a sizeable displacement of the top of the valence band of one system with respect to the other. The misalignment will prevent the passage of a hole from the polymer to the oxide, providing in this way the necessary condition for the use of this type of system in solar cells. It was also seen electronic coupling between sulfur atoms from polythio- phene, and oxygen atoms from TiO2 through the presence of a state associated with an electronic density extended from the polymer to the surface. Our results thus indicate there is good electronic coupling between the (101) surface of TiO2-anatase and polythiophenes.

La thèse détermine les principaux paramètres de la formation des structures de la phase conductrice de nanocomposites polymères chargés avec des nanotubes de carbone (NTC) ou des nanocharges combinées, pour étudier l'influence de la morphologie de la structure hétérogène du composite et l'interaction des nanocharges sur les propriétés électriques, thermophysiques et mécaniques des composites. Les trois types de systèmes polymères ont été étudiés, à savoir: 1) les systèmes ségrégés avec distribution ordonnée de nanocharges, 2) les mélanges polymère conducteur; 3) les composites avec des charges binaires où les nanotubes de carbone ont été combinés avec des composés organo-argileux modifiés (MOC) dans un cas et des nanoparticules métalliques d'autre part. Les résultats sur les composites polymères ségrégés chargés avec des NTC ont montré que dans de tels systèmes, la charge conductrice crée un réseau continu conducteur au sein de la matrice polymère. Cela conduit à un seuil de percolation ultra faible avec la valeur de φc~0,045vol.%. Il a été démontré que les systèmes conducteurs à base de mélanges de polymères ont un seuil de percolation inférieur en raison d'effet de double percolation. Il a été constaté que l'introduction simultanée de composés MOC et de NTC dans la matrice thermoplastique permet une meilleure répartition des nanotubes de carbone, ce qui empêche leur agrégation. Il en résulte une diminution du seuil de percolation des composites. Il a été démontré que la formation de la phase conductrice est plus efficace avec des charges mixtes CNT/nanométal en comparaison avec les charges individuelles

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.
Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7602. Adviser: John A. Rogers. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

The thesis consists of two major parts. The first part contains a theoretical-experimental study of confocal micro-Raman spectroscopy on hybrid polymer coatings and an application of this spectroscopic method on PDMS-membranes. The theoretical-experimental study includes the application of a model that describes the influence of the refraction effect on the focus length on confocal Raman experiments, and the development of a new model that additionally takes into account the effect of diffraction on the focus dimensions. A parallel comparison between these two theoretical approaches and experimental data has been also drawn and a better agreement between theory and experiment was observed, when both refraction and diffraction effects were considered. Further, confocal resonance micro-Raman spectroscopy has been applied to characterise the diffusion processes of pharmacologically relevant molecules (b-carotene dissolved in dimethylsulfoxide) through a polydimethylsiloxane (PDMS)-membrane. The diffusion rate as a function of the measurement depth and diffusion time as well as the concentration gradient under a steady flux have been determined. The measurements shown that the confocal micro-Raman technique is a powerful tool to investigate the kinetics of diffusion processes within a membrane before the steady state has been reached. The second part of the thesis contains infrared and Raman spectroscopic studies of copper and iron doped B2O3-Bi2O3 glass systems. These studies were performed to obtain specific data regarding their local structure and the role played by dopant ions on boron and bismuthate units. The changes of B2O3 and Bi2O3 structural units due to the relaxation of the amorphous structure, which was induced in these samples by the thermal treatment, were also evidenced
Die vorliegende Arbeit besteht aus zwei Teilen. Der erste Teil beschäftigt sich mit theoretischen und experimentellen Untersuchungen der konfokalen Mikro-Raman-Spektroskopie hybrider Polymer-Schichten und PDMS-Membranen. Dabei wurden besonders die Dimensionen des Fokus in den Proben untersucht, um so einen tieferen Einblick in die bei solchen Messungen auftretenden physikalischen Phänomene zu erhalten. Es wurde zur Berechnung des konfokalen Mikro-Raman-Response-Profils für verschiedene Eindringtiefen innerhalb zweier unterschiedlich beschichteter Proben eine auf Strahlverfolgung basierende Analyse durchgeführt, wobei die sphärische Aberration, die an der Luft/Beschichtungs-Grenzfläche entsteht, mit berücksichtigt wurde. Außerdem wurde ein theoretischer Ansatz entwickelt, der den Einfluss von Brechung und Beugung auf die Fokusverlängerung bei konfokalen Mikro-Raman-Experimenten beschreibt. Im Vergleich zu dem Modell, das nur den Brechungseffekt in Betracht zieht, wird eine Verkürzung der Fokuslänge erreicht, wenn Brechungs- und Beugungseffekte betrachtet werden, was die Übereinstimmung zwischen experimentellen und theoretischen Daten verbessert. Desweiteren wurden die Diffusion von ß-Carotin durch PDMS-Membranen mittels der konfokalen Resonanz-Mikro-Raman-Spektroskopie untersucht. Zunächst wurden Untersuchungen der Diffusionskinetik vor Erreichen des stationären Zustandes durchgeführt. Hierbei konnte die Diffusionsgeschwindigkeit in Abhängigkeit von der Messtiefe und der Messzeit ermittelt werden. Es wurde zusätzlich der Konzentrationsgradient im stationären Fluss von b-Carotin in PDMS-Membranen untersucht. Die Untersuchungen mit der konfokalen Resonanz-Mikro-Raman-Spektroskopie zeigten, dass diese Methode geeignet ist, Diffusionskinetiken im nicht stationären Zustand innerhalb der Membranen zu beobachten. Derartige Untersuchungen sind extrem wichtig für die Entwicklung neuer Applikationsysteme zur kontrollierten Wirkstofffreisetzung. Im zweiten Teil der vorliegenden Arbeit wurden strukturelle Untersuchungen an Kupfer- und Eisen-dotierten B2O3-Bi2O3 Glas-Systemen mittels Infrarot- und Raman-Spektroskopie durchgeführt. Die lokale Struktur des Glas-Netzwerks und der Einfluss der dotierenden Ionen auf die Bismut-Borat Matrix wurden diskutiert. Desweiteren wurde der Einfluss des Bor-Netzes auf die strukturellen Einheiten des Bismuts in den wärmebehandelten Proben bewiesen. Raman- und Infrarot-Spektren der Proben nach Wärmebehandlung zeigten, dass sich die Glasstabilität verringert, wenn der Bismutgehalt zunimmt

Recently, integrated silicon photonics has become a topic of rising interests, due to its great potential to induce significant improvements in modern communication and computation systems. While optics is often viewed as a favorable solution to many issues faced by the rapidly evolving microelectronic technology, the high cost, large physical size, and discrete configuration of conventional optics have largely restricted its applications. The introduction of silicon nanophotonics permits a new look at the idea of incorporating optics with traditional electronic integrated circuits in a sensible and feasible fashion.

In this dissertation, emphasis is placed on investigating nonlinear devices built in silicon but complemented by nonlinear polymer materials. Basic optical guiding and coupling components for silicon on insulator platform are first discussed, followed by a detailed description of the design, fabrication, and testing procedures of a Pockels effect electro-optic modulator based on nonlinear polymer-coated silicon nanostructures. Discussion is further expanded on other related devices that also make use of the second-order nonlinear effect, and designs to improve the speed and efficiency of existing devices are also elaborated. Finally, a third-order nonlinear all-optical modulation device is presented with a series of carefully designed experiments to verify its ultrafast operation.

碩士
國立雲林科技大學
工業化學與災害防治研究所
92
In this study，the assembly of aqueous colloidal gold nanoparticles on the surface of polyaniline-based nanoparticles through the electrostatic interaction is leading to the colloid gold nanoparticles “shells” – polymer nanospheres “cores” or fractal-like superstructures. Polyaniline nanospheres (PANi) prepared in a conventional micellar solution with Cetyltrimethylammonium bromide (CTAB) as the emulsifier. The negative charge colloidal gold nanparticles (AuCl4-) can be routinely prepared by borohydride reduction of gold salt. We demonstrate that the negative charge colloidal gold nanparticles (AuCl4-) is attracted onto the surface of the polymer (PANi-CTAB+) nanosparticles by electrostatic interaction. Zeta potential of gold nanoparticles and polyaniline nanospheres were respective –55.38mV、+52.46mV。 The absolute values of zeta potentials were larger than 30mV，the result show that gold and polyaniline nanoparticles were very stable. The dynamics about the adsorption of gold nanoparticles on surface of polyaniline nanospheres had been examined by UV-Vis absorption spectroscopy. From UV-Vis absorption spectra，it was found that the gold nanoparticles’ absorption intensity decreased linearly with increasing time. The morphology analyses of TEM、FE-SEM images revealed that gold and polyaniline nanoparticles average particle sizes were 12nm、15nm。 The 3wt% polyaniline nanospheres had conductivity of 7.6×10-3 S/cm.

Additive manufacturing (AM) is a layer-based manufacturing process aimed at producing parts directly from a Computer-aided design (CAD) model. There are various types of AM systems, which can be classified based on: (i) the base material being used for fabrication, such as polymers, ceramics, and metals; (ii) indirect and direct processes depending on the bonding method; and (iii) the state of the input raw material, i.e., liquid, molten, powder, and solid layer. The current research in AM processes includes technology development for the printing of multi-material parts using two or more materials such as metal, polymer, glass, ceramics, and graphene. The multi-material additive manufacturing (MMAM) processes are complex and challenging due to the significant differences in material deposition techniques, material processing temperature, or pre/post-processing methods involved for an individual material. Our work focuses on the hybrid metal/polymer printing process where liquid metal printing is achieved using a novel design of a molten metal droplet-on-demand (MMDoD) system. The metal is fed into the MMDoD system in the form of solid wire and is melted using a zero-voltage-switching circuit based induction heater. The magnetic field, eddy current density, and power transfer from the induction coil to the molten metal pool are studied using experiments, theoretical formulation, and FEM simulations. The influence of workpiece geometry on the induction heating process is also studied for solder alloy and aluminum billets. These studies show that for a given geometry of induction coil and workpiece, the power transferred to the workpiece is a non-monotonic function of the workpiece’s resistivity. Also, the heating rate of the workpiece depends on the thermal mass and the magnetic field flux in and around the workpiece. Using these studies, the resistivity of the workpiece, and the geometry of the workpiece and induction coil, can be chosen to achieve faster heating and melting of the metal. Once the raw material is in the liquid state, it can be used to generate molten metal droplets (MMDs). To generate the MMD, a novel MMDoD system is designed and developed using a thermally insulating piston and magnetostrictive actuator. Using the MMDoD mechanism, the molten metal is deposited on the printing bed surface (glass) or partially formed part (metal or polymer – PLA/ABS). To find the optimal parameters of MMD generation process, a parametric study of the MMDoD mechanism is conducted by varying the size and material (Brass, Stainless-Steel, Nickel-plated steel alloy) of the nozzle, the gap between nozzle and piston, unfiltered vs. low-pass filtered actuation pulse, and the actuation pulse amplitude. This shows the following regions where, DoD process is not achieved, and the DoD is achieved with the generation of single or multiple droplets for each actuation. The droplet size, Feret width and length, and standard deviation are measured using snapshots from the high-speed camera of the droplet formation process. The region where a single MMD is generated for each actuation of the MMDoD mechanism with the least standard deviation is most desirable for the reproducible metal AM process. A parametric study is conducted to find the optimal printing parameters of the metal AM system by varying the gap between each droplet to print the 2D connected metal lines on the substrate. Other parameters like the size of MMDs, droplet ejection rate (20Hz), and liquid metal temperature are kept fixed. The 3D metal printing can be achieved by printing these metal lines layer-by-layer. MMDoD system is extended to multi-material additive manufacturing (MMAM) system by combining it with polymer extrusion system. The designed MMAM system consists of a controller board to control the overall system, an induction heater, a computer numeric control (CNC) build platform/positioning system, MMDoD mechanism, and the polymer extruder. The system is designed and developed to print metal (Solder alloys - Sn99Cu1, Sn63Pb37, and Sn96.5Ag3.5) with polymer (PLA and ABS). To demonstrate the hybrid AM of metal and polymer, a few mechanical structures (2D planar text, hollow tube, hollow square pyramid, hollow hexagon) and electronic device (RC-LED circuit) are fabricated. The deposition of molten metal on polymer substrate leads to good bonding of metal on polymer due to remelting of the polymer surface. The working of the printed, electronic device is tested and found satisfactory. The testing is conducted by checking the electrical connectivity along the track and the functionality of the electronic device by measuring the output signal waveform. In the future, the combined metal and polymer AM system can be combined with a pick-and-place mechanism that can help achieve a rapid AM of functional 3D electronic devices.

碩士
國立臺灣大學
材料科學與工程學研究所
98
Polymer photovoltaic devices have attracted considerable interest over the past decade owing to the advantages of low-cost, low weight, solution fabrication process, large area and flexibility. The hybrid materials made from conducting polymers and inorganic semiconducting nanocrystals have potential application in solar cell due to their physical stability. In the first part and second part of our study, we have tried to develop new systems of polymer solar cell based on either P3HT / Bi2S3 nanorods or P3HT / Cu2S nanoparticles hybrid. Nanocrystals of Bi2S3 and Cu2S are environmental friendly and low cost. Both nanocrystals have low band gap (lower than 1.8 eV) which show potentials in sun light harvesting. The synthesis and characterization of Bi2S3 nanorods and Cu2S nanoparticles were conducted. Additionally, the properties of hybrid films of P3HT / Bi2S3 nanorods or P3HT / Cu2S nanoparticles were performed. TypeⅡ band alignment between P3HT and low band gap nanocrystals gives chances for charge separation at the interfaces. The photovoltaic devices based on P3HT / Bi2S3 and P3HT / Cu2S hybrid exhibit power conversion efficiency of 0.06 % and 0.1% respectively under AM 1.5, 100 mW/cm2 illumination. In the third part of this research, we incorporated Cu2S nanoparticles as an additive to improve the power conversion efficiency of P3HT / PCBM system. A 16 % increase in power conversion efficiency (from 3.7 % to 4.3 %) has been achieved by incorporating 0.05 mg ml-1 Cu2S nanoparticles in the P3HT / PCBM active layer under proper thermal treatment. The additive induced morphology variations of active layer were analyzed by AFM and grazing incidence X-ray diffraction. The results reveal the Cu2S nanoparticles hinder the growth of PCBM clusters and compress the crystallization of P3HT during thermal treatment. The smaller crystal dimension of P3HT and reduced size of PCBM clusters result in finer structures, larger interfaces, and closer interconnecting between P3HT and PCBM which enhance the power conversion efficiency. Other nanoparticles such as CdSe with similar size to Cu2S also lead to the similar effect. We therefore conclude that the incorporation of adequate amount of nanoparticles in the active layer is an effective strategy to improve the performance of P3HT / PCBM solar cells.

Dottorato di Ricerca in Ingegneria Meccanica Ciclo XXVII Ciclo, a.a. 2015-2016
Uno dei maggiori settori di consumo di petrolio e combustibili fossili è il settore dei trasporti. Questo comporta conseguenze negative per ciò che riguarda l’inquinamento ambientale ed i cambiamenti climatici. Le previsioni di un aumento mondiale del numero di veicoli a due ruote ed a quattro ruote, implicano una speciale attenzione per i combustibili alternativi e sostenibili dal punto di vista ambientale. In questo contesto l’idrogeno gioca un ruolo chiave. Le celle a combustibile, infatti, ad elettrolita polimerico si presentano come la più promettente tecnologia nel lungo periodo per produrre energia a bordo dei veicoli. Tale tecnologia trova applicazione nei veicoli ibridi in cui i flussi energetici sono ottimizzati. L’attività di ricerca svolta ha avuto come principale obiettivo l’analisi numerica di sistemi a propulsione innovativa equipaggiati con celle a combustibile. Questi studi sono stati condotti attraverso la definizione di modelli matematici di simulazione numerica in ambiente Matlab/Simulink®. I risultati consentono una dettagliata analisi delle celle a combustibile e delle configurazioni di veicoli ibridi con particolare riferimento ai flussi di potenza, al bilancio energetico, ai consumi, alla logica di controllo, all’umidificazione della membrana, al controllo termico, all’efficienza, ecc., al fine di dimensionare correttamente i vari componenti. L’utilizzo della simulazione numerica consente un’analisi più veloce ed economica rispetto alla realizzazione dei prototipi. Pertanto, essa può essere considerata come il primo passo nella progettazione e nella sperimentazione di questi veicoli. Il modello in Matlab/Simulink® consiste in un modello a blocchi dove i vari parametri operativi sono stimati in diverse condizioni operative nel rispetto di alcuni vincoli predefiniti. Le simulazioni sono svolte per diverse applicazioni per una vasta gamma di veicoli che comprendono veicoli a due ruote ed automobili di diversi segmenti per tragitti, definiti teoricamente, urbani, misti ed extra-urbani. Nel caso specifico di una veicolo a due ruote, derivato da una bicicletta elettrica con l’aggiunta di una cella a combustibile, i cicli di guida presi in considerazione non sono teorici, ma reali, in quanto ottenuti direttamente tramite misurazioni a bordo del veicolo
Università degli Studi della Calabria