<p>The development of nanocomposite materials has had significant influence on modern material design. Novel properties can be achieved and controlled for a diverse range of applications. The work presented here focused on characterization of polyurethane based coatings with ITO nano-inclusions. The coatings displayed high transparency in the visible range, and UV/IR shielding properties when studied with UV-Vis spectroscopy. UV/IR shielding improved with greater ITO density, with minor affect on visible transmittance. The effective medium approximation was successfully applied to ellipsometry modeling. Coatings with varying fractions of nanoparticles were analyzed. The modeled volume percent of the nanoparticles followed a strong linear trend with the known weight percentages. SEM and TEM imaging determined that majority of the particles existed in clusters. The nanoparticles were oblong shaped, 10-20nm big, randomly distributed, with no segregation to interfaces. Agglomerates varied in size, with the largest observed agglomerate being 250nm.</p> <p>Thermal stability was studied by TGA and DSC. No degradation occurred until 238°C. DSC revealed that the matrix continued to undergo modifications with consecutive runs. It was inconclusive whether the changes were from the polyurethane or dispersive agents in the system. Electron micrographs showed that segregation did not occur post-annealing. Average surface roughness increased from 3.5nm to 5nm after annealing at 120°C for several weeks. Ellipsometry results showed that film thickness decreased 20nm and 50nm before equilibriating for the 80°C and 120°C anneals respectively. The optical and thermal measurements demonstrated that the coating has great potential for improving the PV performance.</p> / Master of Applied Science (MASc)

L'objectif de cette thèse est l'identification de couplages (nanoparticules / matrice de poly(methyl-methacrylate) PMMA) qui renforcent la rigidité de surface du PMMA tout en conservant le maximum de transparence. Le choix s'est porté sur trois type de nanoparticules carbonées : du graphène multicouches (FLG), de l'oxyde de graphène (GO) et des nanotubes de carbones (MWCNT). Une première décrit la préparation et la fonctionnalisation de ces trois types de nanoparticules pour assurer une meilleure dispersion dans la matrice. Deux méthodes ont été retenues pour réaliser ces matériaux composites : la polymérisation en masse et le mélange en solution. Une seconde partie présente la caractérisation des propriétés mécaniques de ces revêtements en trois étapes : en volume, en surface et sous forme de revêtement en couches minces (15-20µm). Les résultats majeurs montrent que les nano-composites réalisés retardent l'apparition de la plasticité comparé à un PMMA pur, même à faible pourcentage, et permettent ainsi de limiter les effets de rayures de surfaces. Le faible pourcentage de renfort permet de conserver la transparence et plus l'épaisseur diminue plus on peut augmenter ce taux de renfort sans dégrader les propriétés mécaniques du revêtement. Les nanoparticules choisies comme agents de renfort de la matrice polymère s'avèrent être également de très bons candidats pour la diminution du frottement comparée à un plastifiant type Erucamide / The goal of this thesis is the identification of couplings (nanoparticles / matrix poly (methyl methacrylate) PMMA) which ensure PMMA surface rigidity while maintaining maximum transparency. The choice fell on three types of carbonaceous nanoparticles: Few layer graphene (FLG), graphene oxide (GO) and carbon nanotubes (MWCNT). A first part describes the preparation and functionalization of these three types of nanoparticles to provide a better dispersion in the matrix. Two methods were used to prepare nanocomposite materials: bulk polymerization and solution blending. A second part presents the characterization of the mechanical properties of these coatings in three stages: volume, surface and thin layer coating (15-20μm). The main results show that nanocomposites made delay the onset of plasticity compared with pure PMMA, even at a low percentage, and help to limit the effects of surface scratches. The small percentage of reinforcement keeps the transparency and the more the thickness decreases the more the rate of reinforcement can increase without degrading the mechanical properties of the coating. Moreover, nanoparticles chosen as the polymer matrix of reinforcing agents prove to be very good candidates for reduction in friction compared to a plasticizer such Erucamide.

An environmentally sustainable production of electrical power is important for preserving the earth’s natural resources. In order to utilize this power as efficiently as possible, it is of great importance to minimize the losses, for example in sliding electrical contacts. A sliding electrical contact is where current is transferred from one rotating to one stationary component and power is lost due to friction and contact resistance. Also in some signal applications, high performance sliding contacts are crucial to ensure stable signal transfer with low noise. Although sliding electrical contacts are primarily designed for good electrical performance, the system will benefit also from optimization of the tribological properties. The aim of this thesis is to increase the fundamental knowledge of the tribological and electrical performance of metal-graphite composite materials for sliding electrical contacts. The influence of mechanical and electrical load was investigated. Different stationary materials, from pure copper to nanocomposite coatings, were tested against copper- and silver-graphites. Two complementary test setups were used, one with reciprocating and one with unidirectional sliding. Surface analysis was essential to gain deepened understanding of the influence of the interaction on the surfaces. Especially my novel imaging of cross-sections has advanced the level on knowledge in this research field. On the stationary material surface, a tribofilm forms with constituents from the metal-graphite and the surrounding atmosphere. Cross-sectioning reveals a material flow that indicates turbulence. Furthermore, the presence of oxides in the tribofilm is not necessarily detrimental for the contact resistance as long as there is also pure metal available. The presence of graphite is vital for low friction and wear. It is shown that the tribological and electrical behaviour of this system is only marginally influenced by the material selection of the stationary contact. Increasing the metal content in the composite, on the other hand, greatly reduces the contact resistance while there is no significant impact on friction and wear. The mechanical load has to be optimized to compromise between low wear (achieved with low load) and low contact resistance (achieved with high load). Pure mechanical tests show a lower friction and higher wear rate in comparison to tests with a five ampere current.