In this research it was shown that the electroless plated palladium deposited as large number of randomly oriented grains, which were separated by grain boundaries (GB). The nano-scale dimensions of these grain boundaries allowed the diffusion of helium through the palladium membrane. This implied that in a dense palladium membrane, the grain boundary network was so convoluted that helium flux could be neglected. The transmission electron microscope (TEM) images of the palladium at room temperature showed grains of about 50 nm in size and nuclei of about 5 nm in size. The TEM images of a pre-annealed Pd sample at 500ºC in hydrogen atmosphere for 48 hours, showed big grains of 100 to 200 nm in size and most of the grain boundary intersections had dihedral angles very close to 120°. However, the pre-annealed Pd sample at 500ºC in helium atmosphere for 48 hours, showed grains of the size of 70 to 100 nm and many of the grain boundary intersections did not show dihedral angles of 120°. This proved that high temperature annealing not only caused significant grain growth and grain boundary (straightening) migration, but also the grain boundary migration was faster in hydrogen than in helium atmosphere. Also, the hydrogen and helium characterization of the palladium membranes showed that the leak formed faster in hydrogen than in helium. Thus, combining the TEM observations with the membrane characterization results, it is possible to conclude that grain boundary migration is one of the most probable reasons for leak formation in palladium composite membranes. The TEM images of the pre-annealed Pd sample also showed that the grain boundaries can achieve an equilibrium configuration within 48 hours of annealing at 500°C in hydrogen. This research helped in better understanding of the role of grain boundary migration on the leak formation in the composite palladium membranes and this information can be useful for the production of leak resistant stable membranes in the future.

In this study, two different strategies were carried out to modify the polyvinylidene fluoride (PVDF) distillation membrane for desalination. The first strategy was the addition of TiO2 nanoparticles into the target membranes and a synergistic effect of hydrophilic and hydrophobic nanoparticles was found for the first time in this work. And the other strategy was the introduction of another polymer material, polytetrafluoroethylene (PTFE), to the PVDF membranes to fabricate a flat sheet PVDF-PTFE composite membrane and this is the first attempt that such a membrane to be made. Two types of membranes were characterized by scanning electron microscopy (SEM) detection, porosity measurement, energy dispersive X-ray spectroscopy (EDX), Attenuated total reflectance (ATR)-Fourier transformed infrared spectroscopy (FTIR), contact angle (CA) measurement, atomic force spectroscopy (AFM) detection and liquid entry pressure of water (LEPw) measurement. Their performance was evaluated by vacuum membrane distillation (VMD) experiments. And the best VMD pure water permeate flux of the membranes fabricated under these two modify strategies could achieve 4.26 kg/m2h (M-L5-B2) and 5.61 kg/m2h (M-40), respectively, when that of pure PVDF membrane is only 0.71 kg/m2h. The salt rejection of the prepared composite membranes are all stably higher than 99.5% which demonstrate their capacity for desalination.

Novel composite membrane systems have been devised for use in direct methanol fuel cell (DMFC) with the ultimate aim of improving overall fuel cell performance in terms of achievable power density. The composite membrane system takes the form of a multilayered structure composing of commercial Nafion117 membrane and a novel composite binding layer situated between the anode and the membrane. Within the composite binding layer, inorganic filler particles are evenly dispersed throughout the Nafion matrix presenting a barrier that impedes methanol crossover. Through the current research, three novel membrane electrode assemblies (MEA) have been fabricated, each employing the composite binding layer system with different filler. Mass of filler used is kept constant at 0.5 wt% of Nafion117 membrane. When tested in a DMFC system, the first MEA which utilizes hydrogen form mordenite filler particles yields optimum power density of 60 mW/cm2 with the operation at 90°C, 1M methanol fuel concentration. This represents an improvement of 34.7% compared to the standard MEA which do not include the composite binding layer. Silanefunctionalized hydrogen form mordenite filler is used in the second MEA which yields optimum power density of 64 mW/cm2 at 90°C, 1M methanol, outperforming the standard MEA by 42.5%. The third MEA makes use of TS-1 particles as fillers. This yields an optimum performance of 38 mW/cm2 at 90°C, 1M methanol, a 14.3% reduction in performance compared to the standard. Through the results obtained, it can be deduced that the novel composite binding layer presents a valid approach in reducing methanol crossover, however, the nature of filler particles used exerts a great influence on its performance. Therefore, further research is recommended in exploring new filler materials for use within the composite membrane system.

In this study, two types of chemical mechanical polishing wastewaters (designated Cu-CMP wastewater and mixed-CMP wastewater, respectively) from a wafer fabrication plant was treated by a simultaneous electrocoagulation/electrofiltration (EC/EF) process using laboratory-prepared TiO2/Al2O3 composite membranes. First, tubular membrane supports of Al2O3 were prepared by the extrusion method. Then the slip composed of nanoscale TiO2 (prepared by sol-gel process) and 1 wt% of corn starch was applied on the aforementioned tubular membrane supports by the dip-coating method, followed by sintering to obtain tubular TiO2/Al2O3 composite membranes. These tubular inorganic composite membranes then were incorporated into an EC/EF treatment module for the treatment of CMP wastewaters. The permeate qualities were evaluated. In addition, the effects of different operating modes (i.e., the flow-through mode and recirculation mode) on membrane flux and permeate quality were conducted. Finally, the effects of changing the backwash time and backwash cycle on the membrane flux were also investigated. Experimental results have shown that the slip containing 75 v/v% of TiO2 sol and 25 v/v% of corn starch solution would yield a membrane layer with a thickness of 13 £gm and a pore size of 15 nm. On the CMP wastewater treatment, the removal efficiencies of copper ion and total organic carbon (TOC) were found to increase with the increasing electric field strength. This relationship, however, did not apply to other water quality items. Under the optimal operating conditions of using the recirculation mode, the removal efficiencies for turbidity and TOC for Cu-CMP wastewater were determined to be 98% and 90%, respectively. Similarly, a turbidity of < 1 NTU (a removal efficiency of 99%) was obtained for mixed-CMP wastewater. By using the same optimal operating conditions for the recirculation mode to treat Cu-CMP wastewater, initial fluxes of 300 L/h¡Em2 and 280 L/h¡Em2 were obtained for the flow-through mode and recirculation mode, respectively. The corresponding initial fluxes for mixed-CMP wastewater were 370 L/h¡Em2 and 360 L/h¡Em2, respectively. For the case of the recirculation mode, the removal efficiencies of total solids content, silicon, copper ion, TOC, and turbidity for Cu-CMP wastewater were 71%, 85%, 72%, 90% and 99%, respectively. The corresponding removal efficiencies of 68%, 88%, 78%, 90% and 99%, respectively were determined for the case of the flow-through mode. On the other hand, the removal efficiencies of total solids content, silicon, TOC, and turbidity for mixed-CMP wastewater using the recirculation mode were 76%, 84%, 78% and 99%, respectively; whereas 78%, 86%, 72% and 99%, respectively for the flow-through mode. Based on the above findings, the operating mode is not a significant parameter in influencing the membrane flux and quality. Permeate obtained in this work was found to be recyclable for the use in irrigation and make-up water for cooling towers. Backwashing was found to be important to the membrane flux in this study.

Water is essential for life as well as industrial growth. Therefore, this research is mainly to explore the treatment capacity of LCD (Liguid Crystal Display) industrial wastewater recycling by a simultaneous electrocoagulation/electrofiltration (EC/EF) process using laboratory-prepared multi-tubular TiO2/Al2O3 composite membranes. First, tubular membrane supports of Al2O3 were prepared by the extrusion method. Then the slip composed of nanoscale TiO2 (prepared by sol-gel process) was applied on the aforementioned tubular membrane supports by the dip-coating method, followed by sintering to obtain tubular TiO2/Al2O3 composite membranes. Then, two types of LCD industrial wastewaters (designated TFT-LCD wastewater and STN-LCD wastewater, respectively) from different LCD fabrication plants were treated by EC/EF process using TiO2/Al2O3 composite membranes. Moreover, the permeate qualities were evaluated under the recirculation-mode operation. In addition, the effects of different operating parameters (i.e., electric field strength, trans-membrane pressure, and crossflow velocity) on membrane flux and permeate quality were evaluated. Relations of the water quality and the different operation modes (i.e., the recirculation mode, flow-through mode, and secondary treatment mode) were also discussed. Finally, the effects of changing the backwash time and backwash cycle on membrane flux were investigated. In the recirculation mode, both kinds of wastewater achieved a satisfactory organics and anion removal. An average of about 90¢H of COD (Chemical Oxygen Demand) and TKN (Total Kjeldahl Nitrogen) could be removed. For anions (i.e., NO3¡Ð, NO2¡Ð, Cl¡Ð and SO42¡Ð), their removal efficiencies were all over 90%. Furthermore, TOC (Total Organic Carbon) and turbidity also had removal efficiencies of over 98%. When the operation mode was changed from the recirculation mode to flow-through mode, the changes of permeate quality were not obvious. But the cumulative quantity of permeate of the flow-through mode was greater than that of the recirculation mode. As for the experimental result of the secondary treatment mode, the permeate qualities were found to be improved. In this case, an average removal of over 95% of NO3¡Ð, NO2¡Ð, Cl¡Ð, and SO42¡Ð could be obtained. According to experimental results shown above, the treated water could be recycled and reused as the cooling tower make-up water if its pH and conductivity values were reduced. However, these problems could be easily resolved by proper adjustments of pH. Overall speaking, the tubular TiO2/Al2O3 composite membranes and simultaneous EC/EF treatment module employed in this work are capable of treating LCD industrial wastewater for the purpose of reclamation.

Magister Scientiae - MSc / South Africa s coal and platinum mineral resources are crucial resources towards creating an alternative and environmentally sustainable energy system. The beneficiation of these natural resources can help to enhance a sustainable and effective clean energy base infrastructure and further promote their exploration and exportation for economics gains. By diversification of these resources, coal and the platinum group metals (PGMs) especially palladium market can be further harnessed in the foreseeable future hence SA energy security can be guaranteed from the technological point of view. The South Africa power industry is a critical sector, and has served as a major platform in the South African socio-economic development. This sector has also been identified as a route towards an independent energy base, with global relevance through the development of membrane technologies to effectively and economically separate and purify hydrogen from the gas mixtures released during coal gasification. The South Africa power industry is a critical sector, and has served as a major platform in the SA's socio-economic development. This sector has also been identified as a route towards an independent energy base, with global relevance through the development of membrane technologies to effectively and economically separate and purify hydrogen from the gas mixtures released during coal gasification. Coal gasification is considered as a source of hydrogen gas and the effluent gases released during this process include hydrogen sulphide, oxides of carbon and nitrogen, hydrogen and other particulates. In developing an alternative hydrogen gas separating method, composite membrane based on organic-inorganic system is being considered since the other available methods of hydrogen separation are relatively expensive. The scientific approach of this study involves the use of palladium modified polyimide composite membrane. Palladium metal serves as hydrogen sorption material, deposited on polyimide substrates (composite film) by electroless technique. Polyimide is a class of polymer with excellent physico-chemical properties such as good mechanical strength, superior thermal stability and high resistance to chemical attack. In this study, a composite polymer-palladium membrane was developed and investigated to determine the prospect of using this membrane as a cheap, accessible, reliable and efficient system to separate and purify hydrogen gas. Prior to the palladium metal plating, the challenge of metal adhesion on glassy polymer such as polyimide film was addressed by chemical etching and unirradiated and irradiated polyimide film surface using NaOH, NaOCl and a mixture of NaOH/NaOCl solutions. The time of etching was varied and the overall effect of this surface treatment was deeply investigated using Fourier transform infrared (FTIR) spectroscopy. The FTIR study focused on the structural deformation of the polyimide functional group units and the emergence of ‘active sites’ along the polyimide backbone structures that have been identified to allow the Pd metal exchange on the functionalised polyimide film. The detailed use of FTIR spectroscopic technique in this study on the etched unirradiated and irradiated polyimide film was to understand the chemical interaction between the polyimide functional group units and the chemical etchants. The surface morphology of unirradiated and irradiated polyimide samples was studied using SEM, the depth profile (penetration) of palladium particles after electroless deposition on the polyimide matrix was investigated by SEM and TEM analysis. As for the alkaline etched irradiated polyimide, pore distribution, shape and size depended on the etching time and solution. In the XRD analysis, the palladium modified unirradiated polyimide film indicated the diffraction peaks of palladium metal in the (1,1,1), (2,2,0) and (2,0,0) planes present in the polyimide surface, and the peel test showed that the strength of adhesion of palladium on unirradiated surface was low compared to the palladium modified irradiated polyimide. The NaOH solution showed the best etchant at 20 minutes for the unirradiated palladium modified polyimide. The hallmark of this study was the design, fabrication and assemblage of home-built hydrogen diffusion reactor unit used to measure rate of hydrogen diffusion property of unirradiated and irradiated polyimide films from 25 °C to 325 °C. The rate of hydrogen diffusion was observed to depend on the etching time of polyimide surface before and after the polyimide surface irradiation treatment. / South Africa

The controlled release of therapeutics has been one of the major challenges for scientists and engineers during the past three decades. To address this outstanding problem, the design and fabrication of stimuli-responsive materials are pursued to guarantee the controlled release of cargo at a specific time and with an accurate amount. Upon applying different stimuli such as light, magnetic field, heat, pH change, enzymes or redox, functional materials change their physicochemical properties through physical transformation or chemical reactions, allowing the release of payload agents on demand. This dissertation studied three stimuli-responsive membrane systems for controlled release from films of macro sizes to microcapsules of nano sizes. The first membrane system is a polymeric composite film which can decrease and sustain diffusion upon light irradiation. The photo-response of membranes is based on the photoreaction of cinnamic derivatives. The second one is composite membrane which can improve diffusion upon heating. The thermo-response of membranes comes from the volume phase transition ability of hydrogels. The third one is microcapsule which can release encapsulated agents upon light irradiation. The photo-response of capsules results from the photoreaction of nitrobenzyl derivatives. The study on these membrane systems reveals that stimuli-responsive release can be achieved by utilizing different functional materials on either macro or micro level. Based on the abundant family of smart materials, designing and fabricating stimuli-responsive systems shall lead to various advanced release processes on demand for biomedical applications.

The major objective of this research is a systematic experimental exploration of hydrophilic materials that can be applied as coating materials for conventional ultrafiltration (UF) membranes to improve their fouling resistance against organic components. This objective is achieved by developing new, fouling-reducing membrane coatings and applying these coatings to conventional UF membranes, which can provide unprecedented reduction in membrane fouling and marked improvements in membrane lifetime. Novel polymeric materials are synthesized via free-radical photopolymerization of mixtures containing poly(ethylene glycol) diacrylate (PEGDA), photoinitiator, and water. PEGDA chain length (n=10-45, where n is the average number of ethylene oxide units in the PEGDA molecule) and water content in the prepolymerization mixture (0-80 wt.%) were varied. Crosslinked PEGDA (XLPEGDA) exhibited high water permeability and good fouling resistance to oil/water mixtures. Water permeability increased strongly with increasing the water content in the prepolymerization mixture. Specifically, for XLPEGDA prepared with PEGDA (n=13), water permeability increased from 0.6 to 150 L um/(m2 h bar) as prepolymerization water content increased from 0 to 80 wt.%. Water permeability also increased with increasing PEGDA chain length. Moreover, water permeability exhibits a strong correlation with equilibrium water uptake. However, solute rejection, probed using poly(ethylene glycol)s of well defined molar mass, decreased with increasing prepolymerization water content and increasing PEGDA chain length. That is, there is a tradeoff between water permeability and separation properties: Materials with high water permeability typically exhibit low solute rejections, and vice versa. The fouling resistance of XLPEGDA materials was characterized via contact angle measurements and static protein adhesion experiments. From these results, XLPEGDA surfaces are more hydrophilic in samples prepared at higher prepolymerization water content or with longer PEGDA chains, and the more hydrophilic surfaces generally exhibit less BSA accumulation. These materials were applied to polysulfone (PSF) UF membranes to form coatings on the surface of the PSF membranes. Oil/water crossflow filtration experiments showed that the coated PSF membranes had water flux values 400% higher than that of an uncoated PSF membrane after 24 h of operation, and the coated membranes had higher organic rejection than the uncoated membranes. / text

Consideraremos o problema elípitco $-\\Delta u + \\alpha\\chi_Du = \\lambda u$ em $\\Omega$, onde $\\Omega$ é um domínio de R^n com fronteira regular, e $D\\subset \\Omega$ é um subconjunto fechado de medida de Lebesgue fixada. A motivação para este problema vem da Mecânica, onde esta equação é encontrada no estudo de vibrações de uma membrana composta. Seja $\\lambda_1(D)$ o primeiro autovalor do problema, como função do conjunto D. Nesse trabalho mostraremos que $\\lambda_1$ é um autovalor simples, e estudaremos o problema de minimizar $\\lambda_1$ ao variarmos D no conjunto de todos os subconjuntos de medida fixada de $\\Omega$. Mais especificamente, determinaremos fórmulas para a variação primeira e segunda de $\\lambda_1$. / We will consider the elliptic problem $-\\Delta u + \\alpha\\chi_Du = \\lambda u in $\\Omega$, where $\\Omega$ is a domain in R^n with regular boundary, and $D \\subset\\Omega$ is a closed subset with prescribed Lebesgue measure. The motivation for this problem comes from Mechanics, where this equation models the vibrations of a composite membrane. Let $\\lambda_1(D)$ be the first eigenvalue of the problem, which is seen as a function of the set D. In this work, we will show that $\\lambda_1$ is a simple eigenvalue, and we will study the problem of minimizing $\\lambda_1(D)$ when D varies in the family of all closed subsets of $\\Omega$ with a given Lebesgue measure. More precisely, we will determine formulas for the first and the second variation of $\\lambda_1$.

<p>South Africa s coal and platinum mineral resources are crucial resources towards creating an alternative and environmentally sustainable energy system. The beneficiation of these natural resources can help to enhance a sustainable and effective clean energy base infrastructure and further promote their exploration and exportation for economics gains. By diversification of these resources, coal and the platinum group metals (PGMs) especially palladium market can be further harnessed in the foreseeable future hence SA energy security can be guaranteed from the technological point of view. The South Africa power industry is a critical sector, and has served as a major platform in the South African socio-economic development. This sector has also been identified as a route towards an independent energy base, with global relevance through the development of membrane technologies to effectively and economically separate and purify hydrogen from the gas mixtures released during coal gasification. The South Africa power industry is a critical sector, and has served as a major platform in the SA&rsquo / s socio-economic development. This sector has also been identified as a route towards an independent energy base, with global relevance through the development of membrane technologies to effectively and economically separate and purify hydrogen from the gas mixtures released during coal gasification. Coal gasification is considered as a source of hydrogen gas and the effluent gases released during this process include hydrogen sulphide, oxides of carbon and nitrogen, hydrogen and other particulates. In developing an alternative hydrogen gas separating method, composite membrane based on organic-inorganic system is being considered since the other available methods of hydrogen separation are relatively expensive.<br /> &nbsp / </p>