The proton exchange membrane is one key component of direct methanol fuel cells, which has double functions of conducting protons, separating fuels and oxidant. At present, the performance and price of sulfonic acid proton exchange membrane used in direct methanol fuel cells are deeply concerned. In order to reduce membrane 's cost and improve performance of Nafion membrane, three different kinds of membranes have been studied in this thesis. These membranes are SPEEK membranes, SPEEK/ZP composite membranes and Nafion/ZP composite membranes.

<p>For a direct methanol fuel cell (DMFC), the proton exchange membrane must conduct protons and be a good methanol barrier. In addition to the high methanol permeability achieved by these membranes, they are very expensive and contribute greatly to theoverall cost of fuel cell set up. The high cost of the DMFC components is one of the main issues preventing its commercialization. The main objective of this study was thus to produce highly proton conductive membranes that are cheap to manufacture and have low methanol permeability.</p>

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The mutant mouse stargazer shows both ataxia and absence epilepsy from P14 onwards. A PGR amplification strategy was utilised to identify adult (i.e. > 3 months) +/stg from +/+ mice, which share the same phenotype, for use for breeding purposes. The same technique was employed to identify +/+, +/stg and stg/stg neonates (i.e. < 7 days old) for cell culture purposes, since the stargazer phenotype is not apparent at this age. GABA(_A) receptor α(_6) subunit expression levels were significantly decreased in adult stargazer (stg/stg) cerebella when compared to control (+/+ and +/stg) cerebella. Interestingly, autoradiography using [(^3)H] Ro15-4513 revealed an apparent upregulation in α(_4)γ-containing receptors in the adult stargazer dentate gyrus. No significant differences in the expression of NMDAR subunits were detected between adult control and stargazer brain membranes. A significant decrease was observed in AMPAR subunit expression within the adult stargazer cerebellum, particularly with the GIuR2 subunit, which was reduced by 73 %. This decrease was replicated in cerebellar granule cells cultured from stargazer neonates, which also expressed at the cell surface only 18 % of the total GluR2 found in control granule cells. Inmunohistochemistry analyses using mouse anti-stargazin antibodies revealed stargazin to be found throughout the adult control brain, with highest levels of expression being within the hippocampus and cerebellum. Stargazin protein, however, was not expressed in adult stargazer forebrain nor in adult stargazer cerebellar membranes. Finally, immunoaffinity columns using the anti-stargazin antibodies were prepared and demonstrated that stargazin could be purified from adult control mouse brain extracts. Moreover, AMPAR subunits co-immunoprecipitated, indicating an association in vivo.

Perhaps mankind's most urgent challenge at present is anthropogenic climate change, with the associated sea-level rise and desertification set to produce major losses of arable land and living space, as well as loss of life. The key to preventing the worst effects of AGW lies in limiting humanity's emissions of the greenhouse gas carbon dioxide, of which the vast majority comes from the burning of fossil fuels such as coal, oil and natural gas. However, fossil fuels are embedded in all of the world's economies, responsible for almost all of the provision of electrical power and transport, making the sizable reductions required in the timescale necessary somewhat impractical. One solution lies in Carbon Capture and Storage (CCS), which involves, in one incarnation, the combustion of fossil fuels in pure oxygen, simplifying the processing and storage of the carbon dioxide produced. There is potential for very high process efficiencies if oxygen is provided by Oxygen Transport Membranes (OTM). This thesis is concerned with the development of membranes and test procedures for mixed-phase OTM, which typically consist of a dense, gastight layer of perovskite and fluorite phases. An inactive support layer may also be present. The surface area, and therefore surface exchange of either side is improved by the addition of exchange layers to either side. Oxide ion migration is accomplished by applying a pO2 differential to the membrane at high temperature. Causes and mechanisms for degradation are not fully understood, and there is potential to improve oxygen flux. One way to achieve this is by the use of very thin, supported membranes, and this thesis demonstrates that such membranes can be fabricated with well-understood manufacturing processes. Another method of improving oxygen flux is by the use of catalysts on the exchange layers of the membrane. The most popular method of introducing 6 catalysts to an exchange layer or electrode involves impregnation of a metal salt into a ceramic backbone, followed by reduction to yield a catalytically active phase. However, this process is wasteful of catalyst, labour-intensive and control of the distribution of catalyst is difficult or impossible. An alternative exists, where metals doped into a perovskite migrate to the surface and form nanoparticles on exposure to a sufficiently high temperature and reducing atmosphere, and this thesis demonstrates the benefits of using such an approach. Improvements in oxygen flux of up to a factor of 7 over an undoped perovskite exchange layer have been demonstrated. The conductivity and crystal structures of (La0.8Sr0.2)0.95Cr0.5Fe0.5O3-δ and (Sc2O3)0.19(CrO2)0.01(ZrO2)0.789O1.94 under oxidising and reducing atmospheres at high temperatures have been evaluated using neutron powder diffraction and a novel in-situ rig, demonstrating that the OTM composition is a p-type conductor, and quantifying the effect of oxygen stoichiometry on conductivity and unit cell parameters.

by Maggie M. Shi. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1987. / Bibliography: leaves [147]-[173].

This thesis reports research activity on suspended graphene membranes. Scientific results in the form of peer-reviewed publications are presented, along with supporting information to provide context, detailed experimental procedures, and recommendations of future work. The four papers cover a wide variety of topics, but are linked by common experimental sample fabrication techniques. Understanding the mechanical properties of suspended graphene membranes is crucial to the development of graphene nano-electromechanical devices. In the first presented paper, PeakForce QNM (quantitative nanomechanical mapping) atomic force microscopy imaging was used to rapidly map the nanomechanical properties of a range of suspended graphene membranes. The force-displacement behaviour of monolayer graphene extracted from the peak force imaging map was found to be comparable to that taken using standard nanoindentation. By fitting to a simple elastic model, the two-dimensional elastic modulus was measured at around 350Nm-1, corresponding to a Young's modulus of around 1 TPa. The second paper examines the near-IR light-matter interaction for graphene integrated cavity ring resonators based on silicon-on-insulator (SOI) racetrack waveguides. Fitting of the cavity resonances from the predicted transmission spectra reveal the real part of the effective refractive index for graphene, neff = 2.23 ± 0.02 and linear absorption coefficient, alphagTE = 0.11 ±0.01dB micro metre-1. The evanescent nature of the guided mode coupling to graphene at resonance depends strongly on the height of the graphene above the cavity, which places limits on the cavity length for optical sensing applications. Twisted-bilayer graphene (tBLG) exhibits van Hove singularities in the density of states that can be tuned by changing the twisting angle θ. In the third paper, θ-defined tBLG was produced and characterized using optical reflectivity and resonance Raman scattering. This represents the first reported fabrication of a rationally designed (twist engineered) tBLG structure. The θ-engineered optical response is shown to be consistent with persistent saddlepoint excitons. Separate resonances with Stokes and anti-Stokes Raman scattering components can be achieved due to the sharpness of the two-dimensional saddle-point excitons, similar to what has been previously observed for one-dimensional carbon nanotubes. The excitation power dependence for the Stokes and anti-Stokes emissions indicate that the two processes are correlated and that they share the same phonon. Nano-patterned and suspended graphene membranes find applications in electronic devices, filtration and nano-pore DNA sequencing. However, the fabrication of suspended graphene structures with nanoscale features is challenging. In the fourth and final paper, the direct patterning of suspended membranes consisting of a graphene layer on top of a thin layer of hexagonal boron nitride which acts as a mechanical support is demonstrated for the first time, using a highly focused electron beam to fabricate structures with extremely high resolution within the scanning transmission electron microscope. The boron nitride support enables the fabrication of stable graphene geometries which would otherwise be unachievable, by preventing intrinsic strain in graphene membranes from distorting the patterned features after areas are mechanically separated. Line cuts with widths below 2 nm are reported. It is also demonstrated that the cutting can be monitored in-situ utilising electron energy loss spectroscopy (EELS).

The work reported in this thesis describes the successful preparation of three classes of polymer that were designed to possess intrinisic microporosity from a range of aromatic tetrahydroxy and diamine monomers. The tetrahydroxy family of monomers were used to prepare a number of polybenzodioxane polymers and co-polymers using the chemistry developed for the archetypal PIM-1. Two co-polymers formed films suitable for gas permeability measurements indicating that they transport gases at high selectivity but lower permeability as compared to PIM-1. The diamino-containing monomers were used to prepare a number of polyimides (PIM-PIs) using well-established polymerisation chemistry and also some Troger’s base polymers (PIMTBs) using a recently developed polymerisation method. A series of TB-PIMs with different substituents next to the amino group (H and CH3) and containing various pendant groups were prepared in order to establish structure-property relationships. Some of these polymers proved microporous with surface areas ranging from 22-510 m2/g. Unfortunately, none were suitable for film formation or gas permeation measurements. PIM-PIs were prepared from diamino monomers based on bulky 1,4-ditritylbenzene (BAB), adamantane (AD) and trifluorodiaminoaryl (TFA) units by reaction with commercial 4,4′- (hexafluoroisopropylidene)diphthalic anhydride (6FDA). Some of these polymers also demonstrated microporosity with surface areas ranging from 8-560 m2/g. Two polymers (PIM-AD5- PI and PIM-AD6-PI), exhibited good solubility, excellent thermal stability and intrinsic microporosity, with the introduction of highly rigid and bulky groups adjacent to the imide group. PIM-AD5-PI and PIM-AD6-PI demonstrate a very good combination of high permeability and good selectivity for CO2/CH4, H2/N2 and H2/CH4 gas pairs with data that lie close to the Robeson 2008 upper bounds, which is the benchmark for the evaluation of the potential of a new polymer for making gas separation membranes. Finally, a series of trifluoromethyl (CF3) containing PIM-PIs were prepared. Again, it was found that by increasing the rigidity of the polymers by increasing the number of methyl substituents a greater amount of intrinsic microporosity is generated by the polymer. Seven polymers of this series formed robust films suitable for gas permeability measurements and demonstrated good selectivity for CO2/CH4, O2/N2, H2/N2 and H2/CH4 gas pairs with data that lie near the 2008 upper bounds.

Au cours des dernières années, le nombre de travaux scientifiques portant sur le développement de capteurs chimiques simples a significativement augmenté. Les études sont principalement orientées vers la recherche de nouveaux schémas de transduction du signal et vers le développement de capteurs dont les propriétés peuvent être programmées. Trois approches originales pour la transduction du signal des membranes polymères des capteurs potentiométriques sont présentées. La première partie est consacrée à la description d’une nouvelle technique pour la détection indirecte de cations métalliques au moyen de la spectrométrie micro-Raman. Le spectre Raman est mesuré à la surface de la membrane polymère au contact avec la solution échantillon. Ce spectre est converti en information analytique quantitative par étalonnage multivarié. Dans la deuxième partie, nous étudions la faisabilité de capteurs ne contenant pas d’ionophore, les membranes n’étant alors composées que des différents échangeurs d'ions et plastifiants. La performance de ces capteurs pour l’analyse quantitative de mélanges binaires de Ca2+-Mg2+ est évaluée en combinant une approche originale basée sur des capteurs multiples. Les résultats sont comparés à ceux obtenus avec des capteurs à base d’ionophores traditionnels. Enfin, la modification à façon des schémas de sensibilité des capteurs utilisant des membranes contenant plusieurs ionophores est présentée dans la dernière partie. Trois ionophores ont été choisis pour la préparation de la membrane. Les performances de ce réseau de capteurs sont testées sur des mélanges de Ln3+ et les résultats sont comparés à ceux des capteurs mono-ionophores conventionnels. / In recent years, the number of studies devoted to the development of simple and inexpensive chemical sensors has significantly increased. The development of new approaches is mainly aimed at novel sensor signal transduction schemes and designing sensors with programmable properties.This thesis presents three new approaches to the analytical signal transduction in the polymeric membranes of potentiometric sensors. The first part of the study describes a novel technique for indirect metal cations detection with micro-Raman spectroscopy. The evolution of the Raman spectrum of the polymeric membrane, upon contact with the sample solution, is used as the analytical signal. Multivariate calibration methods were used to provide a quantitative estimation of the metal content in the aqueous solutions from the measured Raman spectra. The second part of the thesis reports on studying the feasibility of ionophore-free sensor array with membranes based on various ion-exchangers and plasticizers only. The sensor performance in the analysis of Ca2+-Mg2+ mixtures was evaluated through a combination of multisensor approach and multivariate calibration and was compared to traditional ionophore-based selective sensors.The final part of the thesis is aimed at programmable modification of the sensor sensitivity patterns using the membranes containing several ionophores. Three ionophores, which were previously used for the determination of the lanthanide cations, were chosen for the membrane preparation. The performance of the corresponding multi-ionophore array was tested in the analysis of Ln3+ mixtures and compared to conventional mono-ionophore sensors.

This study focuses on the optimisation of submerged hollow fibre membrane performance by analysing the role of air sparging on the reduction of membrane fouling. In submerged hollow fibre membranes, rising bubbles have been shown to induce shear, liquid movement and fibre displacement. The interaction between fibre movement induced by bubbling and the microfiltration performance was assessed for various parameters (fibre tightness, fibre length, fibre diameter, air flowrate, nozzle size, and feed concentration). A model feed of yeast suspension and a series of isolated fibres were used. The fibre movement was assessed by monitoring the displacement using video recording. Bubble population parameters were also measured. The results suggest that bubbleinduced fibre movement plays an important role in controlling membrane fouling. Investigations of the critical flux at various operating conditions also supported these conclusions. Since energy consumption for aeration is a major contributor to the cost in submerged membranes, the potential to minimise the aeration cost has been tested by implementing intermittent aeration and different nozzle sizes. It was found that an optimum condition associated with a low fouling rate could be reached by combining various aeration intermittencies and nozzle sizes. An attempt to suppress fouling without aeration was made by incorporating vibrations into a submerged hollow fibre membrane system. The effects of vibration frequency, type of yeast (washed and unwashed) on the filtration performance were observed. The impact of coagulant addition on filtration enhancement was also analysed. The performance of microfiltration was evaluated based on its critical flux value. The findings in this preliminary study indicated potential fouling control by applying vibrations to submerged membranes. A semi-empirical model was developed to predict the filtration behaviour by taking into account the bubble-induced shear and fibre movement. The predicted critical flux values suggested that membrane fouling appears to be more prominent at low air flowrate, with tight fibres, and higher feed concentrations. The model fits the experimental data with discrepancies from approximately 0.3% to 20%. The predicted filtration profiles at different operating modes demonstrate the importance of bubble-induced shear and fibre movement in the improvement of filtration performance.