Hybridizing, in general, is the approach of combining multiple technologies, materials, or designs such to mitigate the drawbacks and enhance the benefits. The result of this combination can be referred to as a hybrid. The projects described in this work concern a number of these hybrids. The collection of projects are limited to optical applications, but are otherwise enormously different. There is perhaps no better way to illustrate this breadth than their characteristic length-scale. That is, the general size of the elements being hybridized. Ten orders of magnitude lie between the smallest system described and largest systems. At the several-nanometer scale, a single component of a composite optical material. Diamond possesses a unique combination of refractive and dispersive optical properties, making it an attractive optical material. Unfortunately, the lowest cost diamond available possesses large amounts of impurities and color. In an attempt to remove the visible color from commercially available detonation-origin nanodiamond powders we developed a facile three-step cleaning process. This process and the resulting qualities of the nanodiamond are discussed. At tens to hundreds of nanometers scale, we have worked to optimize a complete composite material system; a combination of Polystyrene-b-poly (2-vinyl pyridine) (PS-b-P2VP), a block co-polymer with self-assembly properties, and controlled size iron platinum (FePt) nanoparticles. The applications in mind are magnetic field sensors, used in medical testing and physical experiments, and fiber optic isolators, used extensively in telecommunications networks. These composites exhibited commercially significant Verdet constants in room temperature Faraday rotation measurements, and possess processing benefits over the current state-of-the-art magneto-optically active materials. Several behaviors with respect to wavelength, particle loading, and primary particle size are discussed. At the micron to centimeter scale, we have designed and characterized a high-speed fiber-optic switch for telecommunications networks capable of reconfiguring 100 times faster than currently available technologies with comparable port counts. The switch is an unconventional hybrid of the micron-scale optics of single-mode fiber modes, and the centimeter scale of free-space holography. Built primarily using off-the-shelf components and a commercially available digital micro-mirror device (DMD), the switch is protocol and bit-rate agnostic, robust against random mirror failure, and provides the basic building block for a fully reconfigurable optical add drop multiplexer (ROADM).Finally, at the scale of several meters, we address a system that hybridizes two established methods for harvesting solar energy. Sunlight can be captured as electricity using photovoltaics (PV), as well as heat, often called concentrated solar power (CSP). Each approach has benefits and drawbacks which will be discussed. A system possessing the peak efficiency of PV, with the deployable storage of CSP, would most effectively meet demand around the clock. In order to combine these technologies, we have developed an approach for designing a dichroic coating to optimize performance of such a system utilizing multi-junction photovoltaic cells while diverting unused light to heat collection. Through careful design substantial improvement to system efficiencies are shown to be possible.

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Polydimethylsiloxane (PDMS) compounds are utilized in outdoor high voltage insulation due to their low weight, vandalism resistance, better anti-contamination performance and their superior hydrophobic nature. Under severe environmental conditions and over prolonged service time, however, the hydrophobic surface can gradually become hydrophilic and then recover with adequate resting period. In this study, room temperature vulcanized (RTV) PDMS samples were prepared with different formulations and then exposed to corona discharge to evaluate its effect. The influence of different additives, such as different types and amount of fillers and additionally added low molar mass silicone oils, on the hydrophobicity recovery of the material was investigated. The effects of two types of corona treatment were also evaluated. Hydrophobicity recovery of corona and UV-C aged PDMS samples was evaluated by means of static contact angle measurements. Positron annihilation spectroscopy (PAS) gave important information on the micro structural change after corona treatment of RTV PDMS as well as naturally aged high temperature vulcanized (HTV) PDMS samples. The different formulations of the RTV PDMS samples and the effect of the additives were studied with this technique. The formation of a thin, highly crosslinked inorganic silica-like (SiOx) layer was confirmed even at the early stage of degradation. It was also possible to estimate the thickness of the silica-like layer formed during corona exposure that is responsible for the loss and recovery of hydrophobicity. The surface hardness and hydrophilicity change of PDMS samples due to corona treatment were studied simultaneously with force distance measurements by atomic force microscopy (AFM). The adhesive force calculated from the pull-off force-distance curves showed that the adhesive force between the probe and the sample decreased with increasing corona treatment time, indicating hydrophobicity recovery. In addition to this, the increase in hardness after corona exposure provides indirect evidence of the formation of a silica-like layer. In all cases the hydrophilicity and the surface hardness of the PDMS samples increased directly after corona treatment and recovered with time. Two types of FTIR spectroscopy were used to analyse the surface of the polymer. / AFRIKAANSE OPSOMMINGS: Polidimetielsiloksaan (PDMS) word in buitelug hoogspanninginsulasie gebruik as gevolg van sy lae massa, weerstand teen vandalisme, verbeterde anti-kontaminasie werkverrigting en superieure hidrofobiese karakter. Die hidrofobiese oppervlakte kan egter gelydelik hidrofillies word onder uiterste omgewingsomstandighede en oor langdurige dienstyd. PDMS materiaal herstel egter nadat dit genoeg rustyd toegelaat is. Kamertemperatuur-gevulkaniseerde (KTV) PDMS met verskillende formulasies is in hierdie studie voorberei, aan korona ontlading blootgestel, geëvalueer en vergelyk. Die invloed van bymiddels soos verskillende tipes en hoeveelhede vuiler, asook addisionele lae molekulêre massa silikoonolie, op die herstel van hidrofobisiteit van die materiaal is ondersoek. Twee verskillende metodes van korona behandeling is ook geëvalueer. Die herstel van hidrofobisiteit van korona en UV-C verouderde PDMS monsters is met statiese kontakhoekmeting geëvalueer. Positronvernietigingspektroskopie (PVS) is 'n kragtige tegniek wat belangrike inligting oor die mikrostrukturele verandering van korona behandelde van KTV PDMS sowel as natuurlik-verouderde hoë temperatuur gevulkaniseerde (HTV) PDMS monsters gee. Die verskillende formulasies van die KTV PDMS monsters, sowel as die effek van die vullers, is met behulp van hierdie tegniek ondersoek. Die vorming van 'n dun, hoogskruisgebinde, anorganiese silika-agtige (SiOx) laag op die PDMS oppervlak, selfs tydens die vroeë stadium van degradasie, is bevestig. Dit was ook moontlik om die dikte van die silika-agtige laag wat gedurende die korona blootstelling gevorm het, en wat verantwoordelik is vir die verlies aan hidrofobisiteit, te bepaal. Die oppervlakhardheid en hidrofilisiteit verandering van PDMS monsters as gevolg van korona behandeling, was gelyktydig met krag-afstand metings deur middel van atoomkragmikroskopie (AKM) bestudeer. Die kleefkrag, soos bereken van aftrek kragafstandkurwes, dui daarop dat kleefkragte tussen die taster en die monster afneem met toenemende korona behandelingstyd, wat beduidend is op die herstel van hidrofobisiteit. Daarbenewens is die toename van oppervlakhardheid na korona blootstelling "n indirekte bewys van die formasie van 'n silika-agtige laag. In alle gevalle het die hidrofilisiteit en die oppervlakhardheid van die PDMS monsters toegeneem direk na afloop van korona behandeling en gevolglik herstel met tyd. Twee tipes IR spektroskopie metodes is gebruik vir die chemiese-oppervlak analises

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Polymer composites, and in particular wood-polymer composites have become commercially and environmentally important materials. Studies in polyolefin-wood composites have mostly focused on polypropylene (PP) and polyethylene (PE). To our knowledge, no study has been undertaken on advancing impact polypropylene copolymer (IPPC)-wood composites as a suitable alternative to using PP and PE. IPPC have proven to be a suitable alternative to PP at low temperatures to improve impact resistance for manufactured polymer products, and could be a great addition to improved properties for wood polymer composites. This study shows that the physical properties of IPPC-wood composites can be markedly improved when compatibilizer(s) are used to improve the distribution of the wood within the matrix, as well as improving the interaction between the wood and the polymer matrix.. The use of different compatibilizers, vi polypropylene-graft-maleic anhydride (PPgMA) and poly(ethylene-co-vinyl alcohol) (EvOH) results in different physical properties. Using simple admixtures of the PPgMA and EvOH in IPPC-wood composites result in a large spread of results, while pre-reacting the PPgMA and EvOH to form a joint compatibilizer gives reproducible results w.r.t the physical testing. A study of the fundamental interactions of the compatibilizer(s) with the molecular components of the IPPCs was undertaken. The IPPCs used were fractionated by preparative temperature rising elution fractionation, and the fractions were mixed with the compatibilizers. To this end, fluorescence microscopy was utilized to study the interaction. The results clearly indicate that the interaction of the PPgMA with the fractions differ from that of the EvOH. These differences can be explained in terms of the chemical composition distribution within the IPPC fractions. Atomic force microscopy (AFM) was used to study adhesive forces between compatibilizer, polymer and cellulose and lignin. Successful coating of AFM tips with PPgMA and EvOH was achieved. Whilst interactions based on chemical force microscopy (CFM) could not be quantified, the AFM results in conjunction with fluorescence spectroscopy provided meaningful insight in the way that compatibilizers interact with both the wood and the impact copolymers used in this study. / AFRIKAANSE OPSOMMING: Polimeer saamgestelde material, en meer spesifiek hout-polimeer saamgestelde material het die afgelope tyd belangrike produkte geword, beide kommersieel en in verband met omgewingvriendelikheid. Navorsing op die gebied van poli(olefien)-hout komposiete het tot op hede meestal gefokus op die grbruik van poli(propileen) (PP) en poli(etileen) (PE). Sover dit on kennis strek is daar nog geen studie gedoen om die gebied van impak polipropileen kopolimere (IPPK)-hout komposiete uit te bou nie. IPPKs is ‘n geskikte alternatief vir PP in veral laetemperatuur aanwendings. Die gebruik van IPPKs as matriks vir die hout komposiete kan ‘n groot staqp vorentoe beteken. Hierdie studie wys dat die fisiese eienskappe van iPPK-hout komposiete merkwaardig verbeter kan word waneer versoeningmateriale gebruik word om die verspreiding van die hout in die polimeermatriks sowel as die interaksie tussen die hout en polimeer te verbeter. Die gebruik van verskillende versoenings material, t.w poli(propileen-ent-maleinsuur anhidried) (PPeMA) en pol(etlieen-ko-viniel alkohol) (EVOH). Deur gebruik te maak van eenvoudige mengsels van PPeMA en EVOH in IPPK-hout composite het ‘n geweldige wye verpreiding van resultate tot gevolg gehad, terwyl ‘n voorafgaande reaksie tussen die PPeMA en die EVOH om ‘n saamgestelde versoeningmateriaal te maak tot gevolg gehad het dat reproduseerbare resultate verkry kon word. ‘n Studie van die fundamentele interaksies van die versoeningsmateriale met die molkulêre komponente van die IPPKs is uitgevoer. Die IPPKs is gefraksioneer deur preparatiewe temperatuur-stygende uitloog frakasionering en die fraksies is gemeng met die versoeningmateriale. Fluoressensie mikroskopie is gebruik om hierdie interaksies te bestudeer. Die resultate dui duidelik daarop dat die interaksie van die PPeMA met die fraksies verskil met die van die EVOH. Die verskille kan verduidelik word aan die hand van die chemiese samestelling verspreiding van die IPPK fraksies. Atoomkrag mikroskopie (AKM) is gebruik om die adhesive-kragte tussen die versoeningmateriale, polimere, sellulose en lignien. AKM tippe is suksesvol bedek met PPeMA en EVOH, onderskeidelik. Alhoewel interaksies gebaseer op chemiese krag mikroskopie (CKM) nie gekwantifiseer kon word nie, lewer hierdie resultate tesame met die fluoressensie spektroskopie unieke insig in die manier wat versoeningmateriale met beide die hout en die polimeer reageer.

Thesis (PhD)--Stellenbosch University, 1994. / ENGLISH ABSTRACT: An artificial chiral medium can be made by embedding metal helices (chiral or handed structures) with random orientation inside au achiral hnst medium. The electromagnetic behaviour of such artificial chiral media can be explained by an additional (to p. and t') constitutive parameter, the chirality parameter e. Chiral media have certain special properties of which optical activity is the most prominent. Optical activity is the term used to describe the rotation of the polarization plane of a linearly polarized wave as it travels through a chiral medium. The chirality parameter is directly linked with this rotation. The reflection and the transmission coefficients from a chiral slab are well known in terms of the constitutive parameters and the thickness of the sample. In the thesis a set of .inversion equations are derived that can be used to determine the constitutive parameters (p., £, e) of a chiral medium from the measured S-parameters 811, S21x and S2l'jJ (Le. the reflection and co- and cross-polarized transmission coefficients respectively). An accuracy analysis of the measurement method is made. This is done by using the first order partial derivatives of the inversion equations. A sensitivity analysis is done on the inversion equations and the results are in an analytical form. This makes it possible to determine the contribution of each of the measurement errors to the total expected error. A statistical root mean square method is used to predict the expected error in the measured constitutive parameters. Several artificial chiral samples are measured and an accuracy analysis done on the measurements. The inaccuracy of the method of inversion for low loss samples that are multiples of half a wavelength thick is illustrated by example and explained by the sensitivity analysis. The free-space system (11-17 GHz) used to measure the S-parameters is described in detail. The radiation patterns of the focused lens antennas are measured and compared to those obtained from two theoretical models. A free-space calibration procedure is developed and the dispersion in the focal region of the antennas incorporated into it. The results from different combinations of calibration standards are compared and related to the idea of minimum sensitivity calibration. The possible use of an artificial chiral medium as a microwave absorber is also discussed. / AFRIKAANSE OPSOMMING: Kunsmatige kirale media kan gemaak word deur metaalhelikse lukraak te orienteer in 'n mekirale (bv. diEHektriese) medium. Die mikrogolfeienskappe van kirale media kan toegeskryf word aan die anti-simmetrie van die mikroskopiese insluitings. 'n Voorwerp word as kiraal beskryf indien dit nie deur translasie of rotasie op die spieelbeeld daarvan gepas kan word nie. Die menslike hand is 'n goeie voorbeeld van so 'n kirale struktuur. Die elektromagnetise eienskappe van 'n kunsmatige kirale medium kan beskryf word deuT 'n addisionele (tot j.t en E) samestellingsparameter, die kiraliteitsparameter ~. Kirale media het verskeie ongewone eienskappe waarvan opti~se aktiwiteit waarskynlik die prominentste is. Optiese aktiwiteit beskryf die verskynsel waar die polarisasierigting van 'n lineer-gepolariseerde golf geroteer word terwyl dit deur 'n kirale medium beweeg. 'n Direkte verband bestaan tussen die rotasie en die kiraliteitsparameter. Die weerkaats- en transmissiekotHfisiente van 'n kirale plaat is bekend in terme van die samestellingsparameters (j.t, f. en {) en die dikte van die plaat. In die tesis word 'n ste1 inversievergelykings afgelei wat gebruik kan word om die samestellingsparameters van 'n kirale medium te bepaal vanuit die gemete weerkaats- en transmissiekoeffisiente, Sl1, S'lIz en SUg. (S213/ is die kruis-gepolariseerde komponent van die transmissiekoeffisient wat 'n aanduiding van die rotasie gee.) ,n Analise word gedoen op die akkuraatheid waarmee metings uitgevoer kan word. Dit word gedoen deur gebruik te maak van die eerste orde parsHHe afgeleide van die inversievergelykings. 'n Sensitiwiteitsanalise van die inversievergelykings word gedoen en in 'n analitiese vurm aangebied. Die vorm maak dit moontlik om die bydrae van elke meetfout in S11, S2l:c en S21'!J tot die totale meetfout in p., € en ete bepaal. 'n Statistiese metode (wortel gemiddelde kwadraat) word gebruik om die verwagte foutwaardes in die gemete samestellingsparameters te bepaal. Verskeie kunsmatige kirale media word gemeet en 'n analise word gedoen op die akkuraatheid waarmee elk gemeet is. Die onakkuraatheid van die inversiemetode vir plate met lae verliese en wat veelvoude van 'nhalwe golflengte dik is, word getoon deur middel van 'n sensitiwiteitsanalise. Die vryeruimte meetstelsel (11-17 GHz) wat gebruik word om die weerkaats- en transmissiekoeffisH~ nte te meet, word breedvoerig bespreek. Die gemete stralingspatrone van die gefokusseerde lens antennes word vergelyk met teoreties bepaalde waardes. 'n Vryeruimte kalibrasietegniek word ontwikkel en die gemete dispersie in die fokusgebied word daarby ingesluit. Die resultate, soos verkry van verskillende kalibrasiestandaarde, word vergelyk en in verband gebring met die tegniek van kalibrasie-met-minimum-sensitiwiteit. Ten slotte word die moontlike gebruik van kunsmatige kirale media as mikrogolfabsorbeerders ondersoek.

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Montmorillonite reinforced polymers are a new development in the area of nanocomposite materials. Since reinforcement of epoxy is important to the development of high strength adhesives and composite matrices, the introduction of montmorillonite to epoxy is of interest. Compositional effects on epoxy reactivity, on molecular relaxation, and on mechanical properties were investigated. Change in reactivity was determined by Differential Scanning Calorimetry. Tensile properties at room temperature indicated improved modulus and retention of strength of the epoxy matrix but a decreased elongation to failure. Depression of dry nanocomposite glass transition was observed for nanocomposites beyond 5% by weight montmorillonite. Samples that were saturated with water showed lower moduli due to the epoxy matrix. The greatest moisture absorption rate was found at 7%, the least at 3%.

Smart structures are relevant and significant because of their relevance to phenomena such as hazard mitigation, structural health monitoring and energy saving. Electrical resistance could potentially serve as an indicator of structural well-being or damage in the structure. To this end, the development of a microprocessor-based automated resistance measurement system with customized GUI is desired. In this research, a nodal electrical resistance acquisition circuit (NERAC) system was designed. The system hardware interfaces to a laptop, which houses a customized GUI developed using DAQFactory software. Resistance/impedance was measured using DC/AC methods with four-point probes technique, on three substrates. Baseline reading before damage was noted and compared with the resistance measured after damage. The device was calibrated and validated on three different substrates. Resistance measurements were taken from PVDF samples, composite panels and smart concrete. Results conformed to previous work done on these substrates, validating the effective working of the NERAC device.

The potential of Calcium-Vanadium garnet loaded binary composites for use in the production of planar frequency agile microwave devices has been investigated. A WR90 rectangular waveguide system using the transmission/reflection technique has been used to compare effective medium theory predicted permittivities and permeabilities for unmagnetised and transversely magnetised composites with actual measured composite properties. Use of the the Bruggeman effective medium theory with manufacturer supplied garnet permittivity and values of garnet permeability calculated using simple empirical models were demonstrated to be as accurate as predictions made using the measured properties of the composites' individual constituents. Errors in predicted material properties for unmagnetised and transversely magnetised samples relative to measured data were less than 5% across almost half of the 8.2 -12.4GHz measurement band and within a worst-case error of 15% across the whole band. A series of end-coupled linear microstrip resonators using garnet-loaded composite substrates has been fabricated and tested. Tunabilities in resonance of up to 3.9% at 9.2GHz have been demonstrated for DC magnetic bias fields applied transverse to the microwave magnetic field component. An entirely new and previously unpublished broadband microstrip technique for the measurement of the effective permittivity and permeability of bulk gyromagnetic and gyromagnetic material loaded composite substrates subject to transverse DC magnetic bias fields is presented. This will have wide application in the design of frequency agile microwave integrated circuits.