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Im Rahmen der vorliegenden Arbeit wurden Dibortetrahalogenide dargestellt, deren Eigenschaften strukturell sowie spektroskopisch analysiert und deren Reaktivität gegenüber Lewis-basischen Hauptgruppenelementverbindungen untersucht. Durch anschließende Reaktivitätsstudien konnten unter anderem neuartige Diborene dargestellt und analysiert werden. Weiterhin wurde die Verbindungsklasse der Elementhalogenide der Gruppe 13 in der Oxidationsstufe +2 (B, Ga, In) und +3 (In) bezüglich ihrer Reaktivität gegenüber Übergangsmetall Lewis-Basen untersucht. Die gebildeten, neuartigen Bindungsmodi der Gruppe 13 Elemente am Übergangsmetall wurden strukturell, spektroskopisch sowie quantenchemisch analysiert. / As a part of the present work diborontetrahalides were synthesized, analyzed and their reactivity was investigated towards Lewis-basic main group compounds. Subsequent reactivity studies were performed and novel Diborenes were synthesized and analyzed. Furthermore the reactivity of group 13 elemental halides in the oxidation state +2 (B, Ga, In) and +3 (In) was investigated towards Lewis-basic transition metal complexes. The novel bonding motifs of the group 13 elements at the metal center were investigated structurally, spectroscopically and by quantum chemical calculations.

Indium tin oxide is a transparent conductive oxide electrode which is widely used for organic electronics. Morphology of ITO plays an important role in the performance of organic electronics. To understand the influence of the substrate morphology in device performance, a controllable route for producing periodic and aperiodic roughness of ITO surfaces are necessary. In this thesis, this was attempted by using various approaches to forming ITO nanostructures. Initially, ITO was deposited by a traditional sputtering procedure. However, the roughness distribution of the sputtered ITO resulted in a s Gaussian distribution, unsuitable to further studies of roughness. ITO nanostructures can also be formed by depositing ITO nanoparticles on an ITO sub- strates. Using acetate and chloride precursors, ITO films were produced from solution and formed into nanoparticles using the reverse micelles deposition approach. The acetate route (InAc+SnCl2+ethanol), was the most successful prior to the nanoparticle formation, showing high quality ITO with bixbyte crystal structure and Sn percentages of 20%, low enough to form a conductive film. Nanoparticles were fabricated with diblock copolymer reverse micelles(PS-b-P2VP). Reverse micelles were found to act as a nano reactor, restricting the size of nanoparticles by having hydrophilic reactants undergo chemical reactions inside the micelles. However, nanoparticles from the reverse micelles revealed Sn percentages much above 20%. This was attributed to the solubility difference of the precursors leading to displacing or preventing of pre- cursor loading into the reverse micelles. The change of the stirring time, the micelles concentration, the sequence of precursors loading, and the weight of precursors were not found to affect the Sn concentration; moreover, large variations in Sn concentrations were observed. From quantitative nano mechanical testing of the micelles, a maximum load amount for the precursors was observed, confirming that the high concentration of Sn was likely due to the solubility differences between the precursors and their ability to penetrate the micelle. By manipulating the nanoparticles distribution through spin coating speeds, micelles concentration, and deposited volume, several degrees of order were obtained, though hexagonal packing was not observed. In general, even though Sn concentration were found to be above 20%, nanoparticles were successfully fabricated with reverse micelles, confirming that the reverse micelle technique is a good strategy for future studies of roughness. / Thesis / Master of Applied Science (MASc)

<p> The atomic beam magnetic resonance technique with radioactive detection has been used to investigate the hyperfine structure of In^117m. The present research is based on the work done by Cameron (1962) who could not obtain accurate values for the hyperfine interaction constants due to the low neutron flux at the time in the McMaster reactor.</p> <p> This thesis is an account of an attempt to complete that experiment by observing the field independent direct hyperfine transitions. The theory of the experiment, the apparatus and techniques, and the method of data analysis are described. Because of the counting errors, the data are not as conclusive as had been hoped. If the resonances have, in fact, been seen, then the results are: a1/2 = -932.996 ± 0.012 Mc/sec a3/2 = -99.005 ± 0.005 Mc/sec μI = -0.25146 ± 0.00003 nuclear magnetons.</p> / Thesis / Master of Science (MSc)

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Thesis (M.Sc. (Physics)) -- University of Limpopo, 2017 / The undoped ZnO nanoparticles, In or Co single doped ZnO nanoparticles and the In and Co combinational doped ZnO nanoparticles were synthesised through sol-gel technique. The samples were characterised using XRD, TEM, FTIR, Raman spectroscopy, UV-Vis, PL and also tested for the gas sensing applications. XRD patterns revealed that the synthesised samples were of ZnO hexagonal wurtzite structure. The lattice parameters and the bond length of all the undoped and doped ZnO samples were determined and found to be similar to that of the Bulk ZnO. The average particle size of the undoped and doped ZnO nanoparticles were calculated and found to reduce with an introduction of dopants while increasing with an increase in temperature. The strain of all the prepared samples were also determined and observed to be in an inverse relation to the particle size. TEM images showed that the synthesised samples were spherically shaped and that was in agreement with XRD results, while the EDS results showed that In and Co were successfully doped into the ZnO nanoparticles. Raman and FTIR spectroscopy indicated that the prepared samples were indeed ZnO nanoparticles which confirmed the XRD results. The UV-Vis results showed a red-shift in the energy band gap with an introduction of dopants and that was related to the reduction of the particle size, this results were consistent with the PL results. Gas sensing results showed that doping Co and In into the ZnO nanoparticles has an effect into ZnO properties. Combinational-doping of In and Co was found to increase the response to the gases CH4, CO, NH3 and H2 as compared to the undoped and singly doped ZnO nanoparticle sensors. The response\recovery time was found to be affected with introduction of In and Co. Improvements were also observed in the operating temperature and the selectivity of the single doped and co-doped ZnO nanoparticles towards different gases used in this study. / University of Limpopo IBSA National Research Foundation (NRF)

Efficient reconfigurable antennas are highly sought after in all communication applications for the ability to reduce space cost while maintaining the ability to control the frequency, gain, and polarization. The ability to control these parameters allows a single antenna to maximize its performance in a wide range of scenarios to satisfy changing operating requirements. This thesis will describe reconfigurable antennas using liquid-metal alloys that give the system this ability by injecting or retracting the liquid metal from various channels. After simulations were performed in an electromagnetic simulation software, proof-of-concept models were built, tested, and compared to the simulations to verify the results. / Master of Science / Antennas that can change the tuned center frequency and/or the direction they are pointing are needed in many different applications. Antenna adaptability allows the system to maximize the physical dimensions of the antenna to satisfy a wide range of situations without losing performance. This thesis describes antennas using a liquid-metal alloy that can make physical adaptations for the need at hand. After simulations were performed using computer software, proof-of-concept models were constructed and empirically validated to verify the simulation models.

Une lentille à cristaux liquides est un volume fixe de molécules anisotropes dont l'orientation spatiale de celles-ci peut être modifiée radialement afin d'obtenir un effet lentille. La réorientation des molécules de cristaux liquides se fait à partir d'un certain profil de champ électrique. La grandeur de ce profil de champ électrique peut être changée en modifiant les signaux électriques d'alimentation, modifiant ainsi la puissance optique de la lentille. Cette propriété de distance focale variable leur donne de nombreuses applications d'imagerie où les dimensions sont restreintes et ne permettent pas de déplacement relatif entre différentes lentilles classiques. Les travaux de recherche effectués pendant la maîtrise portaient sur le développement d'un nouveau design de lentille à cristaux liquides. Plus spécifiquement, ce nouveau design devait simplifier considérablement le modèle de lentille présentement existant qui utilise une couche mince semi-conductrice afin de générer le profil de champ électrique. Cette couche mince semi-conductrice est difficile à concevoir, car elle requiert d'être isolée par plusieurs autres couches minces, rendant ainsi sa reproduction exacte difficile à accomplir. Le profil de champ dans le nouveau design de lentille est généré à partir de deux électrodes d'oxyde d'indium-étain (ITO) en forme de serpentin ainsi qu'avec quatre signaux alternatifs ayant chacun une phase bien spécifique. Une modification de la phase de ces quatre signaux permet d'obtenir soit une lentille sphérique, un prisme cale, un axicon ou bien une lentille cylindrique. De plus, les limites des dimensions de l'électrode d'ITO en serpentin seront montrées ainsi que leurs effets sur le profil de champ électrique. Des lentilles avec des diamètres de 2 mm, 3 mm, 4 mm et 5 mm ont été conçues pendant la maîtrise. Les propriétés d'imagerie de la lentille de 2 mm ont été caractérisées à partir d'un montage de polarimétrie, d'un capteur Shack-Hartmann et d'un montage de « Point Spread Function » (PSF). / A liquid crystal lens is a fixed volume of anisotropic molecules whose spatial orientation can be radially changed in order to obtain a lens effect. The reorientation of liquid crystal molecules occurs from a certain electric field profile. The magnitude of this electric field profile can be modified by changing the electrical power signals, thereby changing the optical power of the lens. This property of variable focal length gives them many imaging applications where dimensions are restricted and do not allow relative displacement between different conventional lenses. The research work carried out during the master's degree focused on the development of a new liquid crystal lens design. More specifically, this new design greatly simplifies the currently existing lens model which uses a semiconductor thin film to generate the electric field profile. This semiconductor thin film is difficult to design, since it requires isolation by several other thin films, thus making its exact reproduction difficult to accomplish. The field profile in the new lens design is generated from two coil-shaped indium tin oxide (ITO) electrodes as well as four AC signals each with a very specific phase. A modification of the phase of these four signals makes it possible to obtain either a spherical lens, a wedge prism, an axicon or acylindrical lens. In addition, the size limits of the serpentine ITO electrode will be shown as well as their effects on the electric field profile. Lenses with diameters of 2 mm, 3 mm, 4 mm and 5 mm were designed during the master's degree. The imaging properties of the 2 mm lens were characterized from a polarimetry setup, a Shack-Hartmann sensor and a Point Spread Function (PSF) setup.