Poly (glycerol-sebacate) (PGS) is a synthetic bioelastomer with a covalently crosslinked, three-dimensional network of random coils with hydroxyl groups attached to its backbone. This biodegradable polymer is biocompatible (in vitro and in vivo), tough, elastic, inexpensive, and flexible, and finds potential applications in tissue engineering and regenerative medicine. Due to the slow rate of step-growth polymerisation, the synthesis of PGS prepolymer requires 24-48 h. A batch and a continuous process, if developed, could address the inherent deficiencies (eg. long residence time, venting) associated with the large-scale synthesis of such bioelastomers. However, in order to assess whether this particular system may be adapted to continuous processes, such as reactive extrusion, studies on kinetics of controlled condensation reactions are of vital importance. FT-Raman spectroscopy was used to study the kinetics of the step-growth reactions between glycerol (G) and sebacic acid (SA) at three molar ratios (G:SA= 0.6,0.8,1.0) and three temperatures (120, 130, 140 ˚C). The rate curves followed first-order kinetics with respect to sebacic acid concentration in the kinetics regime. An increase in the molar ratio (G : SA) of the reactants decreased the average functionality of the system and the crosslinking density, resulting in the lowering of the activation energy and pre-exponential factor. The average functionality of the system had a profound effect on the crosslinking density, mechanical properties, and the reaction kinetics of the system. Three different PGS oligomers and films (PGS 0.6, PGS 0.8, PGS 1.0) were thoroughly characterised using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and contact angle measurements. FTIR spectra of PGS oligomers confirmed the formation of ester bonds (1740 cm -1). Quantification of various functional groups in PGS films using XPS was in agreement with the theoretical values of the proposed structure. WAXS results indicated that PGS system with a higher average functionality possesses a higher degree of crystallinity. Crystallisation exotherms and melting endotherms of PGS systems revealed that the average functionality influences the density of crosslinking, degree of crystallinity, and the network structure of bioelastomers. Contact angle studies confirmed that an increase in the average functionality of PGS system increases hydrophilicity, and the surface treatment through aminolysis further increases the hydrophilicity of the films. Batch studies were performed on a Brabender Plasticorder®. The samples collected over a reaction period of 5 h were characterised using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The number-average molecular weight (Mn) and the weight-average molecular weight (Mw) of the oligoesters were determined using matrix-assisted laser desroption/ionization time-of-flight spectroscopy (MALDI-TOF) and compared with the corresponding values from the benchtop synthesis. It was found that due to higher shear-mixing and better orientation of functional groups, the degree of polymerisation at any stage of the reaction was higher in the Brabender than in the benchtop process. The gel-point of the reaction was determined from the crossover point of storage and loss moduli, and the reaction rate constant was calculated using the torque vs time data of the rheometer. The kinetics rate constant and the extent of the reaction in the Brabender were found to be higher than the corresponding values obtained from the conventional benchtop process by a factor of 2. PGS was found to be thermo-mouldable and adaptable to high-shear mixing, and hence is a better candidate for making thermoplastic elastomers using reactive extrusion. The challenges and possibilities in scaling up a batch process to a continuous process were investigated. The use of a wiped film reactor or a disk reactor along with reactive extrusion and batch-mixing (as a post-extrusion operation) is a commercially viable method to synthesise PGS oligomers. Such a continuous process will boost the production of bioelastomers for tissue engineering application by addressing the constraints in step-growth polymerisation. Finally, the effect of PGS substrate stiffness and surface treatment (aminolysis, hydrolysis, layer-by-layer deposition) on the morphology and lineage of mesenchymal stem cells – which have a capacity to differentiate themselves into cartilage, adipose, tendon, and muscle tissues – was analysed using fluorescence microscopy and DNA and protein assays. Stiffness of the PGS surface and the method of treatment influenced the cell attachment and spreading on different surfaces. However, cells did not differentiate into definite phenotypes at the end of 14 d time-point, indicating that higher time-points are needed to be considered to study the effect of matrix stiffness and surface treatment on cell attachment and phenotype differentiation.

The aim of this work was the generation of carbon materials with high surface area, exhibiting a hierarchical pore system in the macro- and mesorange. Such a pore system facilitates the transport through the material and enhances the interaction with the carbon matrix (macropores are pores with diameters > 50 nm, mesopores between 2 – 50 nm). Thereto, new strategies for the synthesis of novel carbon materials with designed porosity were developed that are in particular useful for the storage of energy. Besides the porosity, it is the graphene structure itself that determines the properties of a carbon material. Non-graphitic carbon materials usually exhibit a quite large degree of disorder with many defects in the graphene structure, and thus exhibit inherent microporosity (d < 2nm). These pores are traps and oppose reversible interaction with the carbon matrix. Furthermore they reduce the stability and conductivity of the carbon material, which was undesired for the proposed applications. As one part of this work, the graphene structures of different non-graphitic carbon materials were studied in detail using a novel wide-angle x-ray scattering model that allowed precise information about the nature of the carbon building units (graphene stacks). Different carbon precursors were evaluated regarding their potential use for the synthesis shown in this work, whereas mesophase pitch proved to be advantageous when a less disordered carbon microstructure is desired. By using mesophase pitch as carbon precursor, two templating strategies were developed using the nanocasting approach. The synthesized (monolithic) materials combined for the first time the advantages of a hierarchical interconnected pore system in the macro- and mesorange with the advantages of mesophase pitch as carbon precursor. In the first case, hierarchical macro- / mesoporous carbon monoliths were synthesized by replication of hard (silica) templates. Thus, a suitable synthesis procedure was developed that allowed the infiltration of the template with the hardly soluble carbon precursor. In the second case, hierarchical macro- / mesoporous carbon materials were synthesized by a novel soft-templating technique, taking advantage of the phase separation (spinodal decomposition) between mesophase pitch and polystyrene. The synthesis also allowed the generation of monolithic samples and incorporation of functional nanoparticles into the material. The synthesized materials showed excellent properties as an anode material in lithium batteries and support material for supercapacitors. / Kohlenstoffmaterialien finden aufgrund ihrer Vielseitigkeit heute in den unterschiedlichsten Bereichen des täglichen Lebens ihren Einsatz. Bekannte Beispiele sind Kohlenstofffasern in Verbundwerkstoffen, Graphit als trockenes Schmiermittel, oder Aktivkohlen in Filtersystemen. Ferner wird Graphit als Elektrodenmaterial auch in Lithium-Ionen-Batterien verwendet. Wegen knapper werdender Ressourcen von Öl und Gas wurde in den letzten Jahren verstärkt an der Entwicklung neuer Materialien für die Speicherung von Wasserstoff und elektrischer Energie gearbeitet. Die Nanotechnologie ist dabei auch für neue Kohlenstoffmaterialien zukunftsweisend, denn sie stellt weitere Anwendungsmöglichkeiten in Aussicht. In dieser Arbeit wurden hierzu mittels des sogenannten Nanocastings neue Kohlenstoffmaterialien für Energieanwendungen, insbesondere zur Speicherung von elektrischer Energie entwickelt. Die Eigenschaften eines Kohlenstoffmaterials beruhen im Wesentlichen auf der Struktur des Kohlenstoffs im molekularen Bereich. Die in dieser Arbeit hergestellten Materialen bestehen aus nichtgraphitischem Kohlenstoff und wurden im ersten Teil der Arbeit mit den Methoden der Röntgenstreuung genau untersucht. Eine speziell für diese Art von Kohlenstoffen kürzlich entwickelte Modellfunktion wurde dazu an die experimentellen Streubilder angepasst. Das verwendete Modell basiert dabei auf den wesentlichen Strukturmerkmalen von nichtgraphitischem Kohlenstoff und ermöglichte von daher eine detaillierte Beschreibung der Materialien. Im Gegensatz zu den meisten nichtgraphitischen Kohlenstoffen konnte gezeigt werden, dass die Verwendung von Mesophasen-Pech als Vorläufersubstanz (Precursor) ein Material mit vergleichsweise geringem Grad an Unordnung ermöglicht. Solch ein Material erlaubt eine ähnlich reversible Einlagerung von Lithium-Ionen wie Graphit, weist aber gleichzeitig wegen des nichtgraphitischen Charakters eine deutlich höhere Speicherfähigkeit auf. Zur Beschreibung der Porosität eines Materials verwendet man die Begriffe der Makro-, Meso-, und Mikroporen. Die Aktivität eines Materials kann durch die Erhöhung der Oberfläche noch erheblich gesteigert werden. Hohe Oberflächen können insbesondere durch die Schaffung von Poren im Nanometerbereich erzielt werden. Um die Zugänglichkeit zu diesen Poren zu steigern, weist ein Material idealerweise zusätzlich ein kontinuierliches makroporöses Transportsystem (Porendurchmesser d > 50 nm) auf. Solch eine Art von Porosität über mehrere Größenordnungen wird allgemein als „hierarchische Porosität“ bezeichnet. Für elektrochemische Anwendungen sind sogenannte Mesoporen (d = 2 – 50 nm) relevant, da noch kleinere Poren (Mikroporen, d < 2 nm) z.B. zu einer irreversiblen Bindung von Lithium- Ionen führen können. Wird Mesophasen-Pech als Kohlenstoffprekursor verwendet, kann die Entstehung dieser Mikroporen verhindert werden. Im zweiten und dritten Teil der Arbeit konnte mit den Methoden des „Nanocastings“ zum ersten Mal die spezielle Struktur des Mesophasen-Pech basierenden Kohlenstoffmaterials mit den Vorteilen einer hierarchischen (makro- / meso-) Porosität kombiniert werden. Im ersten Syntheseverfahren wurde dazu ein sogenanntes „hartes Templat“ mit entsprechender Porosität aus Siliziumdioxid repliziert. Aufgrund der hohen Viskosität des Pechs und der geringen Löslichkeit wurde dazu ein Verfahren entwickelt, das die Infiltration des Templates auch auf der Nanometerebene ermöglicht. Das Material konnte in Form größerer Körper (Monolithen) hergestellt werden, die im Vergleich zu Pulvern eine bessere technische Verwendung ermöglichen. Im zweiten Syntheseverfahren konnte die Herstellung eines hierarchisch makro- / mesoporösen Kohlenstoffmaterials erstmals mittels eines weichen Templates (organisches Polymer) erreicht werden. Die einfache Entfernung von weichen Templaten durch eine geeignete Temperaturbehandlung, macht dieses Verfahren im Vergleich zu hart templatierten Materialien kostengünstiger und stellt eine technische Umsetzung in Aussicht. Desweiteren erlaubt das Syntheseverfahren die Herstellung von monolithischen Körpern und die Einbindung funktionaler Nanopartikel. Die hergestellten Materialien zeigen exzellente Eigenschaften als Elektrodenmaterial in Lithium-Ionen-Batterien und als Trägermaterial für Superkondensatoren.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第22708号 / 人博第958号 / 新制||人||227(附属図書館) / 2020||人博||958(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 高木 紀明, 教授 中村 敏浩 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

No description available.

Perovskite solar cells have garnered significant interest thanks to the impressive rise of their efficiency over the last few years to a power conversion efficiency (PCE) of 25.2% despite being processable using cheap and potentially high-throughput solution coating techniques. Using the two-step conversion process high-quality perovskite films with high quality and uniformity can be produced, however, this process still needs a deeper and fundamental understanding. This thesis has shed light on the ink-to-solid conversion during the two-step solution process of hybrid perovskite formulations. We demonstrated that the conversion of PbI2 to perovskite is largely dictated by the state of the PbI2 precursor film in terms of its solvated states. We used several in situ diagnostic measurments such as grazing incidence wide-angle x-ray scattering (GIWAXS), quartz crystal microbalance with dissipation monitoring (QCM-D), and optical reflectance and absorbance all performed during spin coating, to monitor the nucleation and growth of crystalline phases, the mass deposition at the solid-liquid interface and the rigidity as well as the solution thinning behavior and the changes in optical absorbance of the precursor and perovskite. We compare conversion behaviors from different lead states by using methylammonium iodide (MAI), formamidinium iodide (FAI), and/or mixtures of halides (I, Br) and show that conversion can occur spontaneously and quite rapidly at room temperature without requiring further thermal annealing. We confirm this by demonstrating improvements in the morphology, microstructure and optoelectronics properties of the resulting perovskite films, as well as their impact on the PCE of solar cells using complimentary measurements such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and with steady-state photoluminescence.

No description available.

No description available.

The declining population of black rhinoceroses in Tsavo West national park, Kenya, has served as the driving force behind Project Ngulia, with Ngulia serving as an enclosed area within the park. As of now, the area is equipped with multiple cameras connected to a system that automatically classify animals and humans. This thesis aims to investigate the suitability of the Insta360 One X2 camera acting as a virtual watch tower for capturing and streaming 360° images. This will work in real-time, providing a remote surveillance experience for the park rangers thereby optimizing their work. A system was implemented to create a efficient workflow, which includes stitching of the 360° images, file transfer protocol for image transmission and storage, as well as socket programming to facilitate port monitoring and communication. Additionally, the compat- ibility of two single board computers, LattePanda and Rock 4 SE, with the implemented system was evaluated. User experience methods as field studies, workshops and a user interview were also performed. The work has been developed in Sweden, resulting in limited availability for testing at the target location during the initial months. The outcome was a both locally and remotely working system, together with LattePanda, capturing images of the waterhole in Ngulia. However, because of the conclusions drawn regarding the power supply and the lack of essential functions in the 360° camera, the system was taken home for further research. Propositions is presented regarding future work, some being that the projects within Ngulia team may collaborate to enhance hardware efficiency and explore the utilization of 360° images in educational and entertainment contexts.

No description available.

This thesis presents a study on two types of X-ray diffraction methodologies applied to the characterization of amorphous materials. The purpose of this study was to assess the feasibility of measuring the diffractive spectrum of amorphous materials by Energy-Dispersive X-ray Diffraction (EDXRD) utilizing Cadmium Zinc Telluride detectors. The total scattering intensity (coherent plus incoherent scatter) spectra precisely measured by high-energy Wide-Angle X-ray Scattering (WAXS) were compared to the EDXRD spectra to determine the level of agreement between the two techniques. The EDXRD spectra were constructed by applying a spectra fusing technique which combined the EDXRD spectra collected at different scattering angles rendering a continuous total scattering spectrum. The spectra fusing technique extended the momentum transfer range of the observed scattered spectrum beyond the limitations of the X-ray source and CZT detection efficiencies. Agreement between the WAXS and fused EDXRD spectra was achieved. In addition, this thesis presents the atomic pair correlation functions and coordination numbers of the first coordination shell for four hydrogen peroxide solutions of varying mass concentrations using Empirical Potential Structural Refinement (EPSR). The results are compared to the state-of-the art ad initio quantum mechanical charge field molecular dynamics (QMCF MD) model of the hydrogen peroxide in solution to support the model's predictions on why hydrogen peroxide is stable in water. The EPSR results using the coherent scattering intensity calculated from the WAXS data set predicts a hydration shell of 6.4 molecules of water surrounding hydrogen peroxide. The results also indicate that hydrogen peroxide is more likely to behave as a proton donor than acceptor. These findings are in agreement with QMCF MD model of aqueous hydrogen peroxide. / Physics