Hyaluronan (HA) is a substance that is commonly used in biomedical applications in the form of hydrogels. One of these biomedical applications is dermatological fillers where HA is cross-linked with 1,4-Butanediol diglycidyl ether (BDDE) to reduce its rapid turnover within tissue. The filler gives a volumetric effect that can fill out wrinkles. This literature study was conducted in collaboration with Galderma to determine if there is research that explores additives to HA hydrogels that give both volumetric and biological effects when applied as filler. Biological effects that improve the skin's appearance and complexion such as a rejuvenation of the skin was preferable. Both polynucleotides and mannitol show great potential to act as additives in injectable hyaluronan hydrogels.  The main effect of polynucleotides (PN) added in hydrogels is that it is collagen stimulating and provides a more natural tissue regeneration. Rheological properties of the filler change with the addition of PN, where elasticity, viscosity and viscoelasticity have been shown to increase. PNs show no toxicity and are considered safe to inject. The study of mannitol has shown that it does not give a volumetric effect after the injected hydrogel has been broken down. What mannitol can help with, is to prolong the life of the hydrogel and reduce the swelling that is a common side effect after an injection. In addition to this, mannitol is a safe substance to inject.

Autoignition characteristics of pre-vaporized iso-octane, primary reference fuels, gasolines, and dimethyl ether (DME) have been investigated experimentally in a coflow with elevated temperature of air. With the coflow air at relatively low initial temperatures below autoignition temperature Tauto, an external ignition source was required to stabilize the flame. Non-autoignited lifted flames had tribrachial edge structures and their liftoff heights correlated well with the jet velocity scaled by the stoichiometric laminar burning velocity, indicating the importance of the edge propagation speed on flame stabilization balanced with local flow velocity. At high initial temperatures over Tauto, the autoignited flames were stabilized without requiring an external ignition source. The autoignited lifted flames exhibited either tribrachial edge structures or Mild combustion behaviors depending on the level of fuel dilution. For the iso-octane and n-heptane fuels, two distinct transition behaviors were observed in the autoignition regime from a nozzle-attached flame to a lifted tribrachial-edge flame and then a sudden transition to lifted Mild combustion as the jet velocity increased at a certain fuel dilution level. The liftoff data of the autoignited flames with tribrachial edges were analyzed based on calculated ignition delay times for the pre-vaporized fuels. Analysis of the experimental data suggested that ignition delay time may be much less sensitive to initial temperature under atmospheric pressure conditions as compared with predictions. For the gasoline fuels for advanced combustion engines (FACEs), and primary reference fuels (PRFs), autoignited liftoff data were correlated with Research Octane Number and Cetane Number. For the DME fuel, planar laser-induced fluorescence (PLIF) of formaldehyde (CH2O) and CH* chemiluminescence were visualized qualitatively. In the autoignition regime for both tribrachial structure and mild combustion, formaldehyde were found mainly between the fuel nozzle and the lifted flame edge. On the other hand, they were formed just prior to the flame edge for the non-autoignited lifted flames. The effect of fuel pyrolysis and partial oxidation were found to be important in explaining autoignited liftoff heights, especially in the Mild combustion regime. Flame structures of autoignited flames were investigated numerically for syngas (CO/H2) and methane fuels. The simulations of syngas fuel accounting for the differential diffusion have been performed by adopting several kinetic mechanisms to test the models ability in predicting the flame behaviors observed previously. The results agreed well with the observed nozzle-attached flame characteristics in case of non-autoignited flames. For autoignited lifted flames in high temperature regime, a unique autoignition behavior can be predicted having HO2 and H2O2 radicals in a broad region between the nozzle and stabilized lifted flame edge. Autoignition characteristics of laminar nonpremixed methane jet flames in high- temperature coflow air were studied numerically. Several flame configurations were investigated by varying the initial temperature and fuel mole fraction. Characteristics of chemical kinetics structures for autoignited lifted flames were discussed based on the kinetic structures of homogeneous autoignition and flame propagation of premixed mixtures. Results showed that for autoignited lifted flame with tribrachial structure, a transition from autoignition to flame propagation modes occurs for reasonably stoichiometric mixtures. Characteristics of Mild combustion can be treated as an autoignited lean premixed lifted flame. Transition behavior from Mild combustion to a nozzle-attached flame was also investigated by increasing the fuel mole fraction.

The ever-growing Internet of Things is promoting more data acquisition, data exchange and fewer human interactions, engendering a higher demand for sensors and therefore power. While in most cases it is possible to directly connect these sensors to the power grid, it will not always be feasible with emerging technologies, especially in remote areas where human access is limited. Moisture-Electric Energy Transformation (MEET) devices are components that use moisture as a “fuel” to generate electrical power. Upon contact with moisture, a potential difference results from a diffusion mechanism, allowing charge to be stored locally in capacitors or rechargeable batteries to be utilized for useful work. The focus of the present work was to investigate the potential of Cold Gas Dynamic Spray (CGDS) as an additive manufacturing (AM) process for the fabrication of MEET devices. Following a layer-by-layer approach, MEET devices were successfully built by CGDS, by combining aluminum (electrode material) and an in-situ composite of polyether ether ketone (PEEK) and alumina (diffusion medium). The main challenges of this work were the determination of the spray parameters of PEEK and the investigation of the MEET capability of the manufactured devices. On the other hand, the main contributions of this work were the demonstration of the viability of CGDS in the deposition of PEEK/Al2O3 on aluminum 6061-T6 substrates, as well as the potential of PEEK as a MEET-capable material. The diffusion mechanisms that govern power generation were also hypothesized, explained and summarized. Initial tests of a MEET device of 66 mm x 34 mm indicate an uninterrupted power generation cycle of over 30 hours, and a maximum output voltage of 268 mV with a 6.8 MΩ load. The output power and power per unit area of the device were computed to be 10.63 nW and 4.736 µW/m2 respectively. The output current and current density were evaluated to 39.53 nA and 17.62 µA/m2.

Photoelectron Photoion Coincidence (PEPICO) Spectroscopy studies on two small oxygenated species are presented here. Diethyl Ether (Et2O) and Acetic Anhydride (AcOAc) were chosen because of their and their fragments' relevance to combustion chemistry. The Imaging PEPICO (iPEPICO) experiment at the VUV beamline of the Swiss Light Source (SLS) was utilized to provide dissociative ionization data of the two molecules of interest. In this experiment, the unimolecular fragmentation pathways of energy selected ions can be studied with high energy resolution. The iPEPICO experimental setup also allows the measurement of the dissociation rates, which is indispensable to derive accurate thermochemical information on large ions. The experimental data on the fragmentation of ions of interest are then examined through modeling the experimental ion fractional abundances (breakdown curves, BDCs) and reaction rates, in a modeling framework based on the RRKM statistical theory. In our first project, diethyl ether was studied to provide the appearance energies of its daughter ions along with the dissociation pathways of the molecular ion, leading to thermochemical data (such as heats of formation) pertinent to combustion chemistry. A revised ionization energy (IE) differing from the reviewed National Institute of Standards and Technology (NIST) was also proposed. In the second project presented, AcOAc was also measured on the iPEPICO apparatus to understand its dissociative photoionization processes. The appearance of trace amounts of acetone in the ionization spectra, discrepancies in the statistical models of the branching ratios, and the quantum chemical calculations all point to the existence of a post-transition-state bifurcation, when a single TS separates multiple products, namely a methyl-loss fragment and acetone, as well. The acetyl cation, as well as the methyl cation at higher energies, appear to be formed by both parallel and sequential dissociation processes.

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Tesis por compendio / [ES] El desarrollo de membranas poliméricas capaces de actuar como electrolito en pilas de combustible tipo PEMFC a temperaturas intermedias constituye uno de los principales retos para conseguir la generación eficiente de energía por medio de estos dispositivos. Actualmente, las membranas basadas en polímeros perfluorosulfonados como el Nafion® son las más extendidas en pilas de combustible, ya que presentan una buena conductividad protónica además de ser estables mecánica y químicamente. Sin embargo, este tipo de membranas no son capaces de ofrecer buenos rendimientos por encima de 80 ¿C. En este sentido, el objetivo fundamental de esta tesis ha sido la síntesis y caracterización de membranas poliméricas que permitan su potencial utilización en el rango de temperaturas intermedias, por encima de 100 ¿C, donde la cinética de los electrodos y el transporte de protones a través de la membrana mejoran considerablemente, aumentando con ello el rendimiento de la celda. La investigación llevada a cabo se ha centrado en dos tipos de polímeros: poli(eter-eter-cetona) sulfonada (SPEEK) y polibencimidazol (PBI). Las membranas basadas en SPEEK ofrecen una elevada conductividad protónica y una buena estabilidad tanto mecánica como química. Si bien, estas propiedades dependen drásticamente de su grado de sulfonación. Así, altos grados de sulfonación resultan en muy buenas conductividades protónicas, aunque por el contrario, originan un excesivo hinchamiento de las membranas provocando un empeoramiento de sus propiedades mecánicas. Además, cuando la temperatura supera los 80 ¿C su conductividad disminuye debido a la deshidratación de la membrana. La estrategia seguida en este caso para mantener las propiedades mecánicas y la conductividad de las membranas basadas en SPEEK a temperaturas intermedias ha consistido en utilizar un polímero con un índice de intercambio catiónico no excesivamente alto (1.75 meq g-1), el cual ha sido dopado con dos tipos de compuestos organometálicos diferentes de tipo ZIF (Zeolitic Imidazolate Framework ) y con una mezcla de ambos. Este tipo de compuestos constituyen una subclase de los conocidos como Metal Organic Framework (MOF), los cuales adoptan una estructura tipo zeolita donde la parte orgánica está constituida por un anillo de imidazol y el nodo inorgánico es un metal. En este caso Zinc para el Z8 y Cobalto para el Z67. Las membranas compuestas SPEEK-ZIF mejoraron claramente las prestaciones de las de SPEEK puro a temperaturas intermedias. En base a los resultados anteriores, se seleccionaron las membranas dopadas con ZIF-67 para su evaluación en monocelda donde ofrecieron valores superiores a los de las membranas de SPEEK puro sin la adición de cargas y a los obtenidos con membranas de Nafion®117 a temperaturas superiores a 100 °C. En el caso de las membranas en base PBI, estas han sido capaces de ofrecer valores elevados de conductividad a altas temperaturas cuando eran dopadas con ácido fosfórico. Sin embargo, la pérdida del ácido por parte de la membrana (leaching) con el tiempo de operación y la degradación que este ácido provoca en los componentes de la celda, hacen que sea necesaria la utilización de otros agentes dopantes no volátiles y menos agresivos capaces de aportar al polímero la conductividad de la que carece. Los líquidos iónicos son sales fundidas a temperatura ambiente que poseen presiones de vapor despreciables y ofrecen buenas conductividades a temperaturas elevadas. En esta tesis, se prepararon por el método de casting, membranas de PBI conteniendo el líquido iónico 1-butil-3-metil imidazolio bis(trifluorometil sulfonil) imida (BMIM-NTf2) en diferentes porcentajes. Estas membranas alcanzaron a partir de un 10 % wt. de líquido iónico un valor de conductividad del orden de 10-2 S cm-1 a 160 ¿C. Señalando su potencial como electrolito polimérico basado en PBI libre de ácido fosfórico. / [CA] El desenvolupament de membranes polimèriques vàlides per a actuar com a electròlit en piles de combustible tipus PEMFC a temperatures intermèdies. Constitueix un dels reptes principals per aconseguir la generació eficient d'energia amb aquests dispositius. Actualment, les membranes basades en polímers perfluorosulfonats com el Nafion® són les més utilitzades en piles de combustible, ja que presenten una bona conductivitat protònica a més de tindre una bona estabilitat química i mecànica. Tot i això, aquest tipus de membranes no oferixen bons rendiments a temperaturas superiors a 80 ¿C. En aquest sentit, l'objectiu fonamental d'aquesta tesi ha segut la síntesi i caracterització de membranes polimèriques amb les característiques adequades per poder treballar a temperatures intermèdies, per damunt de 100 ¿C. En aquestes condicions la cinètica dels elèctrodes i el transport de protons a través de la membrana milloren considerablement augmentant amb això el rendiment de la cel·la. La investigació duta a terme s'ha centrat en dos tipus de polímers: poli(eter-eter-cetona) sulfonada (SPEEK) i polibencimidazol (PBI). Les membranes basades en SPEEK ofereixen una elevada conductivitat protònica i una bona estabilitat tant mecànica com a química. No obstant això, aquestes caracteristiques depenen dràsticament del seu grau de sulfonació. Així, alts graus de sulfonació resulten en molt bones conductivitats protòniques. Encara que per contra, originen un excessiu unflament de les membranes en aigua calenta provocant un empitjorament de les seves propietats mecàniques. A més, quan la temperatura supera els 80 ¿C la seva conductivitat baixa a causa de la deshidratació de la membrana. L'estratègia seguida en aquest cas per mantenir les propietats mecàniques i la conductivitat de les membranes basades en SPEEK a temperatures intermèdies. Ha segut partir d'un polímer amb un índex d'intercanvi catiònic no gaire alt (1.75 meq g-1). El qual ha segut dopat amb dos tipus de compostos órganometàl.lics diferents de tipus ZIF (Zeolitic Imidazolate Framework) (ZIF) i amb una barreja de tots dos. Aquest tipus de compostos constitueixen una subclasse dels coneguts com a Metal Organic Framework (MOF). Els quals adopten una estructura tipus zeolita on la part orgànica està constituïda per un anell d'imidazol i el node inorgànic és el metall. En aquest cas Zinc per al Z8 i Cobalt per al Z67. Les membranes compostes SPEEK-ZIF van millorar clarament les prestacions de les de SPEEK pur a temperatures intermèdies. En base als resultats anteriors es van seleccionar les membranes dopades amb ZIF-67 per a la seva avaluació en monocel·la on van oferir valors superiors als de les membranes de SPEEK pur sense l'addició de càrregues i als obtinguts amb membranes de Nafion®117 en les mateixes condicions a temperatures superiors a 100 °C. En el cas de les membranes en base PBI, aquestes han oferit valors elevats de conductivitat a altes temperatures, quan han segut dopades amb àcid fosfòric. Tot i això, la pèrdua de l'àcid per part de la membrana (leaching) amb el temps d'operació i la degradació que aquest àcid provoca en els components de la cel·la, fan que siga necessària la utilització d'altres agents dopants no volàtils i menys agressius capaços d'aportar al polímer conductivitat iònica. Els líquids iònics són sals foses a temperatura ambient que tenen pressions de vapor molt febles i ofereixen bones conductivitats a temperatures elevades. En aquesta tesi es van preparar pel mètode de càsting, membranes de PBI contenint el líquid iònic 1-butil-3-metil imidazoli bis(trifluorometil sulfonil) imida (BMIM-NTf2) en diferents percentatges. Aquestes membranes van assolir a partir d'un 10% wt. de líquid iònic un valor de conductivitat de l'ordre de 10-2 S cm-1 a 160 ¿C. Assenyalant el seu potencial com a electròlit polimèric basat en PBI lliure d'àcid fosfòric. / [EN] The development of polymeric membranes capable of acting as an electrolyte in a proton exchange membrane fuel cells (PEMFC) at intermediate temperatures. It constitutes one of the main challenges to achieve efficient energy generation through these kinds of devices. Currently, membranes based on perfluorosulfonated polymers such as Nafion® are the most widespread in fuel cells, since they have good proton conductivity as well as being mechanically and chemically stable. However, these types of membranes are not capable of offering good performance above 80 ¿C. In this sense, the main objective of this thesis has been the synthesis and characterization of polymeric membranes with potential use in the range of intermediate temperatures, above 100 ¿C, where the kinetics of the electrodes and the transport of protons through of the membrane and the performance of the cell are greatly improved. The research carried out has focused on two types of polymers: sulfonated poly(ether-ether-ketone) (SPEEK) and polybenzimidazole (PBI). SPEEK-based membranes offer high proton conductivity and good mechanical and chemical stability. However, their properties depend dramatically on its degree of sulfonation. Thus, high degrees of sulfonation result in excellent proton conductivities. On the other hand, the large amount of sulphonic groups in the membrane cause an excessive swelling in hot water, leading to a worsening of their mechanical properties, even reaching its dissolution. Furthermore, as also happens with perfluorosulfonated membranes, when the temperature is increased above 80 ¿C their proton conductivity decreases due to membrane dehydration. Focused on maintain the mechanical properties and conductivity of SPEEK-based membranes at intermediate temperatures. Membranes have been prepared from a polymer with a not excessively high cation exchange rate (1.75 meq g-1). Which has been doped with two different ZIF-type (Zeolitic Imidazolate Framework) organometallic compounds and with a mixture of both. This type of compounds constitutes a subclass of those known as Metal Organic Framework (MOF). Which adopt a zeolite-type structure where the organic part is made up of an imidazole ring and the inorganic node is the metal. In this case Zinc for Z8 and Cobalt for Z67. SPEEK-ZIF. Composite membranes clearly improved the performance of pure SPEEK membranes at intermediate tempe-ratures. Based on the previous results, the membranes doped with ZIF-67 were selected for their evaluation in a single fuel cell, where they offered higher values than those of the pure SPEEK membranes without the addition of fillers and those obtained with membranes of Nafion®117 under the same conditions at temperatures above 100 °C. PBI based membranes, have been capable of offering high conductivity values at high temperatures, when they have been doped with phosphoric acid. However, the loss of acid by the membrane (leaching) with the operation time and the degradation that this acid causes in the cell components. In this sense, it is necessary to explore the use of other non-volatile and less aggressive doping agents capable of providing ionic conductivity to the polymer. Ionic liquids are molten salts at room temperature that have negligible vapor pressures and offer good conductivities at elevated temperatures. In this thesis, PBI membranes containing the ionic liquid 1-butyl-3-methyl imidazolium bis(trifluoromethyl sulfonyl)imide (BMIM-NTf2) at different percentages were prepared by the casting method. These membranes containing 10 wt.% of ionic liquid reached a conductivity value in the range of 10-2 S cm-1 at 160 ¿C. Noting its potential as a phosphoric acid-free PBI-based polymeric electrolyte. / This work was sponsored by the Ministerio de Economia y Competitividad (MINECO) under the project ENE/2015-69203-R. The authors acknowledge the Electron Microscopy Service from Universitat Politècnica de València for the use of instruments and staff assistance. / Barjola Ruiz, A. (2023). Membranas poliméricas de intercambio iónico con aplicación en pilas de combustible de temperatura intermedia [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/193081 / Compendio

Structures made of the thermoplastic polymer polyether ether ketone (PEEK) are widely used in dynamically-loaded applications due to their high-temperature resistance and high mechanical properties. To design these dynamic applications, in addition to the well-known stiffness and strength properties the vibration-damping properties at the given frequencies are required. Depending on the application, frequencies from a few hertz to the ultrasonic range are of interest here. To characterize the frequency-dependent behavior, an experimental approach was chosen and applied to a sample polymer PEEK. The test setup consists of a piezoelectrically driven base excitation of the polymeric specimen and the non-contact measurement of the velocity as well as the surface temperature. The beam’s bending vibrations were analyzed by means of the Timoshenko theory to determine the polymer’s storage modulus. The mechanical loss factor was calculated using the half-power bandwidth method. For PEEK and a considered frequency range of 1 kHz to 16 kHz, a storage modulus between 3.9 GPa and 4.2 GPa and a loss factor between 9 103 and 17 103 were determined. For the used experimental parameters, the resulting mechanical properties were not essentially influenced by the amplitude of excitation, the duration of excitation, or thermal degrad.ation due to self-heating, but rather slightly by the clamping force within the fixation area.

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