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

Die Bestrahlung von tetraedrisch amorphen Kohlenstoff (ta-C) mit schnellen schweren Ionen führt zur Bildung von mikroskopischen elektrisch leitfähigen Ionenspuren mit Durchmessern um 10 nm. Dieses Phänomen ist auf das sp² zu sp³ Hybridisierungsverhältnis des amorphen Kohlenstoffes zurückzuführen. Das einschlagende Ion deponiert eine große Menge Energie innerhalb des Spurvolumens, so dass eine Materialtransformation hin zu höheren sp² Hybridisierung stattfindet. Hierdurch wird die elektrische Leitfähigkeit der Ionenspur stark erhöht. Dieser Effekt kann durch die Zugabe von Verunreinigungen wie Kupfer verstärkt werden. Das Ziel dieser Arbeit ist die umfassende Analyse des elektrischen Verhaltens von ta-C mit besonderen Augenmerk auf die Auswirkungen von Kupferverunreinigungen und Ionenspuren. Der Effekt von Kupferverunreinigungen auf das wichtige Hybridisierungsverhältnis vom amorphen Kohlenstoff wird vermessen. Darüber hinaus wurden alle Proben elektrisch mit makroskopischen Kontakten im Temperaturbeireich von 20 K bis 380 K analysiert. Mikroskopisch wurden einzelne leitfähige Ionenspuren mit Hilfe von atomarer Kraftmikroskopie betrachtet. Die statistische Verteilung der Spureigenschaften in Kohlenstofffilmen mit verschiedenen Kupferkonzentrationen werden verglichen, um die Spurbildung besser zu verstehen. Die normalisierten durchschnittlichen Spurleitfähigkeiten aus mikroskopischen und makroskopischen Messungen werden verglichen. Hierbei kann die Zuverlässigkeit der beiden experimentellen Methoden bewertet werden und mögliche Fehlerquellen ausfindig gemacht werden. Schließlich wird ein Konzept für eine Anwendung unterbrochener Ionenspuren gezeigt.

<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>

<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>

In this thesis, conventional and unconventional technologies have been studied and combined in order to make heterogeneous microfluidics with potential advantages, especially in biological applications. Many conventional materials, like silicon, glass, thermoplastic polymers, polyimide and polydimethylsiloxane (PDMS) have been combined in building heterogeneous microfluidic devices or demonstrators. Aside from these materials, unconventional materials for microfluidics such as stainless steel and the fluoroelastomer Viton have been explored. The advantages of the heterogeneous technologies presented were demonstrated in several examples: (1) For instance, in cell biology, surface properties play an important role. Different functions were achieved by combining microengineering and surface modification. Two examples were made by depositing a Teflon-like film: a) a non-textured surface was made hydrophobic to allow higher pressures for cell migration studies and b) a surface textured by ion track technology was even made super-hydrophobic. (2) In microfluidics, microactuators used for fluid handling are important, e.g. in valves and pumps. Here, microactuators that can handle high-pressures were presented, which may allow miniaturization of high performance bioanalyses that until now have been restricted to larger instruments. (3) In some applications the elastomer PDMS cannot be used due to its high permeability and poor solvent resistivity. Viton can be a good replacement when elasticity is needed, like in the demonstrated paraffin actuated membrane.(4) Sensing of bio-molecules in aquatic solutions has potential in diagnostics on-site. A proof-of-principle demonstration of a potentially highly sensitive biosensor was made by integrating a robust solidly mounted resonator in a PDMS based microfluidic system. It is concluded that heterogeneous technologies are important for microfluidic systems like micro total analysis systems (µTAS) and lab-on-chip (LOC) devices.

<p>Flexible printed circuit boards (flex PCBs) are used in a wide range of electronic devices today due to their light weight, bendability, extensive wiring possibilities, and low-cost manufacturing techniques. The general trend in the flex PCB industry is further miniaturization alongside increasing functionality per device and reduced costs. To meet these demands, a new generation of low cost manufacturing technologies is being developed to enable structures with smaller lateral dimensions and higher packing densities.</p><p>Wet etching is today the most cost-efficient method for producing a large number of through-foil structures in flex PCBs. However, conventional wet etch techniques do not allow for through-foil structures with aspect ratios over 1 – a fact that either necessitates thin and mechanically weak foils or puts severe limitations on the packing density. The fabrication techniques presented in this thesis allow for through-foil structures with higher aspect ratios and packing densities using wet etching. To achieve high aspect ratios with wet etching, the flex PCB foils are pre-treated with irradiation by swift heavy ions. Each ion that passes through the foil leaves a track of damaged material which can be subsequently etched to form highly vertical pores. By using conventional flex PCB process techniques on the porous foils, high aspect ratio metallized through-foil structures are demonstrated.</p><p>The resulting structures consist of multiple sub-micrometer sized wires. These structures are superior to their conventional counterparts when it comes to their higher aspect ratios, higher possible packing densities and low metallic cross-section. Furthermore, metallized through-foil structures with larger areas and more complicated geometries are possible without losing the mechanical stability of the foil. This in turn enables applications that are not possible using conventional techniques and structures. In this thesis, two such applications are demonstrated: flex PCB vertical thermopile sensors and substrate integrated waveguides for use in millimeter wave applications.</p>

A method is described for preset-count irradiations between 1 and 100 ions singling-out individual ions from an ion beam with more than a billion ions arriving per second. The ion tracks are etched in a conductometric system with real-time evaluation of the acquired data. The etch process can be interrupted when reaching a preset channel diameter. Cylindrical channels are obtained by adding surfactants to the etch solution forming a self-assembled barrier between etching medium and polymer. Asymmetric etching of single ion tracks leads to pH sensitive conical pores with diode-like properties. Using etched channels as template, homogeneous and multilayer magnetic single-wires are electrodeposited. The magnetoresistivity of the wires is studied. Single-track applications comprise critical apertures (cylindric, conic, necked), asymmetric pores (pH sensitive, biospecific), Giant Magneto Resistance sensors, and spintronic devices. On the basis of studies with individual ion tracks we tackled tilted multiporous systems such as ion beam lithography with a masked ion beam leading to micro-structures with inclined walls and anisotropic superhydrophobic ion track textures, analogous to biological shingle structures on butterfly wings. We demonstrated qualitatively, that the asymmetry of the texture translates into motion under ultrasonic agitation. This could lead to the development of rotary drives.

Flexible printed circuit boards (flex PCBs) are used in a wide range of electronic devices today due to their light weight, bendability, extensive wiring possibilities, and low-cost manufacturing techniques. The general trend in the flex PCB industry is further miniaturization alongside increasing functionality per device and reduced costs. To meet these demands, a new generation of low cost manufacturing technologies is being developed to enable structures with smaller lateral dimensions and higher packing densities. Wet etching is today the most cost-efficient method for producing a large number of through-foil structures in flex PCBs. However, conventional wet etch techniques do not allow for through-foil structures with aspect ratios over 1 – a fact that either necessitates thin and mechanically weak foils or puts severe limitations on the packing density. The fabrication techniques presented in this thesis allow for through-foil structures with higher aspect ratios and packing densities using wet etching. To achieve high aspect ratios with wet etching, the flex PCB foils are pre-treated with irradiation by swift heavy ions. Each ion that passes through the foil leaves a track of damaged material which can be subsequently etched to form highly vertical pores. By using conventional flex PCB process techniques on the porous foils, high aspect ratio metallized through-foil structures are demonstrated. The resulting structures consist of multiple sub-micrometer sized wires. These structures are superior to their conventional counterparts when it comes to their higher aspect ratios, higher possible packing densities and low metallic cross-section. Furthermore, metallized through-foil structures with larger areas and more complicated geometries are possible without losing the mechanical stability of the foil. This in turn enables applications that are not possible using conventional techniques and structures. In this thesis, two such applications are demonstrated: flex PCB vertical thermopile sensors and substrate integrated waveguides for use in millimeter wave applications. / wisenet

Le mémoire qui suit vise à vérifier si la formation de traces latentes par des ions lourds et rapides passe par une phase liquide. Compte tenu du fait que le processus de formation des traces est trop rapide pour être directement étudié, notre expérience vise à mesurer après coup des éléments qui seraient indicateurs d’une fusion. Dans cette optique, nous étudierons s’il y a eu une redistribution d’ions d’or (initialement présents par dopage dans des échantillons de silicium amorphe) à la suite de l’irradiation des échantillons. Cette redistribution d’or s’expliquerait par le phénomène de raffinage de la zone fondue, qui surviendrait pendant une hausse de température lors de la création de traces ioniques latentes prévue par le modèle théorique du pic thermique. Les échantillons étudiés sont des membranes de silicium amorphes de 2 µm d’épaisseur, dopés à l’or selon différents pourcentages (pur, moyen et élevé) et irradiés avec des ions lourds rapides d’or à 1,1 GeV ou d’argent à 75 MeV. Aucune image SAXS n’a pu révéler la présence de traces ioniques latentes pour les échantillons irradiés par des ions argent à 75 MeV. Bien que le pouvoir d’arrêt de ceux-ci est bas (9,5 keV/nm) [1], il dépasse tout de même le seuil observé pour plusieurs autres phénomènes associés avec des traces. [2] [3] Nous aurions donc trouvé un régime où il y a des effets causés par des ions lourds et rapides, mais sans signature visible en SAXS. À l’inverse, les échantillons irradiés d’ions d’or ont démontré la présence de traces ioniques latentes via des images SAXS. Ces images démontrent un motif de diffusion caractéristique à des traces de type core-shell. Toutefois, ces résultats ne démontrent pas de différences de ségrégation d’or selon le niveau de dopage initial. Tous les échantillons (dopage pur, moyen et élevé) présentent un noyau de rayon de (2,5 ± 0,1)nm et un rayon total de (9,9 ± 0,5)nm, ce qui rejoint des valeurs similaires à ceux obtenus dans la littérature. [4] Par contre, l’absence de différence selon le dopage pourrait s’expliquer par le fait que la resolidification après la fusion serait trop rapide au point où l’or subirait du solute trapping qui empêcherait la ségrégation. Une autre explication possible serait qu’il n’y aurait pas de fusion du tout lors de la formation de la trace. En premier lieu, ce mémoire traite de toutes les étapes nécessaires à la conception des échantillons, soit leur amorphisation, l’implantation d’impuretés d’or, puis l’irradiation. Deux catégories d’échantillons sont abordées : les échantillons de validation, puis les véritables échantillons qui ont été étudiés. Par la suite, ce mémoire aborde la détection des traces ioniques latentes, d’abord avec un AFM (qui s’est avéré insuffisant), puis avec des mesures SAXS. Finalement, un code théorique pour reproduire les mesures expérimentales obtenues a été développé en se basant sur la littérature. Il génère des résultats numériques prometteurs par rapport aux données expérimentales obtenues. / The following thesis aims to verify whether the formation of latent traces by heavy and fast ions passes through a liquid phase. Given the fact that the process of trace formation is too fast to be directly studied, our experience aims to measure after the fact elements that would be indicative of a merger. In this context, we will study whether there has been a redistribution of gold ions (initially present by doping in amorphous silicon samples) following the irradiation of the samples. This redistribution of gold could be explained by the phenomenon of refining the melted zone, which would occur during a rise in temperature during the creation of latent ionic traces predicted by the theoretical model of the thermal peak. The samples studied are amorphous silicon membranes of 2 µm in thickness, doped with gold at different percentages (pure, medium and high) and irradiated with fast heavy ions of gold at 1.1 GeV or silver at 75 MeV. No SAXS image was able to reveal the presence of latent ionic traces for samples irradiated with silver ions at 75 MeV. Although the stopping power of the latter is low (9.5 keV/nm), it exceeds the threshold observed for several other phenomena associated with traces. [2] [3] We would therefore have found a regime where there are effects of heavy and fast ions, but without a visible signature in SAXS. In contrast, irradiated samples of gold ions demonstrated the presence of latent ionic traces via SAXS images. These images demonstrate a diffusion pattern characteristic of core-shell type traces. However, these results do not show differences in gold segregation according to the initial doping level. All samples (pure, medium and high doping) have a core radius of (2.5 ± 0.1) nm and a total radius of (9.9 ± 0.5) nm, which are values similar to those obtained in the literature. [4] On the other hand, the absence of a difference according to the doping could be explained by the fact that the resolidification after the fusion would be too fast, to the point where the gold would undergo solute trapping which would prevent the segregation. Another possible explanation would be that there would be no fusion at all during the formation of the trace. First of all, this thesis deals with all the steps necessary for the design of the samples, namely their amorphization, the implantation of gold impurities, then the irradiation. Two categories of samples are discussed: the validation samples, then the actual samples that were studied. Subsequently, this thesis addresses the detection of latent ion traces, first with an AFM (which proved to be insufficient), then with SAXS measurements. Finally, a theoretical code to reproduce the experimental measurements obtained was developed based on the literature. It generates promising numerical results compared to the experimental data obtained.

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