Fibrous materials are used in a variety of applications due to their relatively high surface area to volume ratio as well as anisotropic behaviour. Electrospinning is a popular fabrication technique which produces polymer nanofibres with a potentially high molecular orientation. The surface of polymer fibres plays a significant role in many applications thus measurement of their surface properties is essential but challenging due to their relatively small size. In this thesis, ultrafine nanofibres have been produced by electrospinning with their nanofibre morphology controlled by varying different processing parameters. Atomic force microscopy (AFM) adhesion contact mechanics and individual nanofibre wetting measurements have been conducted to explore surface properties of the produced electrospun polymer fibres. Results using traditional Owens-Wendt plots applied to our nanomaterials show electrospun nanofibres have a higher dispersive surface free energy compared to bulk polymer film but a lower polar contribution, giving a total surface free energy in excess of bulk equivalents. A novel proposed model indicates that this nanofibre dispersive surface free energy is intimately linked to density of the polymer and ultimately the molecular spacing or orientation for the polymer chains. Comparisons are made with bulk polymer films to show that a high degree of molecular orientation is present at least at the surface of the polymer nanofibre. Structure investigations on electrospun fibres of polyvinyl alcohol using FTIR and XPS surface techniques explore how an increase in hydrogen bonds formed within nanofibres rather than on the fibre surface enhance this dispersive contribution but lowers the polar contribution. The wetting behaviour of electrospun fibre is extended to assemblies at length scales above individual fibres to highlight how superhydrophobic surfaces can be produced from nanofibre networks with defined spacings and geometries. This superhydrophobicity was adequately described by a Cassie-Baxter model modified to account for the fibrous geometry.

Ad hoc wireless networks have emerged as a promising communication scheme to meet the ever growing portability and infrastructureless demand of wireless services. The transmission power level affects signal quality and interference which causes congestion and thus impacts the communication performance. Hence, power control has been the focus of extensive research. In this thesis, we examine the problem of power control in wireless networks, specially in ad hoc wireless networks. Two important types of power control, which are power control with fixed SNIR targets and power control with variable SNIR targets, are discussed in the thesis. We first introduce some important techniques and results involved in the development of power control algorithms and give literature review. A PI power control approach from literature is introduced. Due to lack of stability analysis, we show there are problems in the existing algorithm. We then propose a stable Proportional-integral (PI) power control algorithm. A forgetting factor is adopted to improve the transient performance. Distributed power control algorithms for systems with fixed SNIR targets might diverge when the feasibility condition is not satisfied. Multi-objective optimisation (MO) is adopted to deal with power control with variable SNIR targets. After discussing the existing MO algorithm, we propose a quadratic multiobjective-optimisation (QMO) algorithm where a quadratic objective function and the greedy methodology are adopted for the dynamics. Theoretical and simulation results of convergence of the new algorithms are given. We also provide review of some important power control frameworks which can be used to show convergence of power control algorithms. However, the QMO algorithm does not fall into any existing framework. In order to show convergence of the QMO algorithm, we suggest a new generalised framework in this thesis.

Thesis (Ph. D.)--Syracuse University, 2005. / "Publication number AAT 3194027."

This work is an investigation of the "foam structure" of puffed, carbohydrate-based extrudates. A range of extrudates, produced to vary widely in cell structure through formulation and selection of processing parameters, were evaluated using image analysis and Instron testing. Specifically, cell size distributions were measured and described by different mathematical functions. In addition, the deformation behavior of the extrudates, which was found to conform to classic "brittle" compression models, was characterized by Fourier and Fractal analysis. And finally, the effects of various treatments on--and relationships between--structure and strength--were determined. Results of this work were that the extrudates, despite formulation or processing history, had highly skewed cell area size distributions that were closely described by both the log Normal and Rosen-Rammler models. The deformation behavior of these materials was dependent on relative humidity, and the extremely jagged nature of low RH compression curves could be quantitatively described by both the Blanket Algorithm, which determines fractal dimension, and the Fast Fourier Transform. Relationships between cell structure and mechanical properties were observed in chemically homogeneous samples produced from the same formulation (but using various process parameters) in that extrudate strength was positively associated with density and negatively associated with mean cell size. Additives also influenced extrudate properties, but the direction and magnitude of these effects depended on the specific ingredient used.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 4042. Adviser: Pascal Bellon. Includes bibliographical references (leaves 193-197) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 4044. Adviser: Ralph G. Nuzzo. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

The effect of sintering aid B2O3 and the effect of sintering temperatures were evaluated in this thesis. A 7:3 ratio of alumina to 3 mol% yttria stabilized zirconia tape cast layers sintered at temperatures of 1500°C, 1550°C, and 1600°C were evaluated with an addition of 0 mol%, 1 mol%, and 3 mol% B2O3 additions to the yttria stabilized zirconia layer. X-ray microscopy were used to evaluate crack propagation to correlate with the flexural strengths found in three-point bend testing. Dilatometry was used to show the effect that the B2O3 addition had on the thermal expansion of the system. The addition of B2O3 was found to decrease the flexural strength of the alumina/YSZ laminate system. X-ray microscopy shows significant damage in the 1 mol% and 3 mol% B2O3 additions. The dilatometry suggests that 3 mol% destabilizes the YSZ layer, causing the YSZ to transform back into the monoclinic phase on cool down. The cracks rarely continued to propagate into the alumina layer, further confirming that the alumina/YSZ laminate combination has optimally weak interfaces. The temperature with the highest flexural strength for the 0 mol% B2O3 samples was shown to be 1600°C while the temperature with the highest flexural strength for the 1 mol% and 3 mol% B2O3 samples were shown to be 1550°C.

The objective of this study was to model the hot rolling behavior of austenite (B2-cubic) phase NiTi shape memory alloy with FORGE NxT, a finite element analysis (FEA) software package developed by Transvalor. Isothermal hot compression data was used to fit the Hansel-Spittel constitutive model for flow stress used by the software to determine the material specific coefficients. Compression models were simulated to verify the Hansel-Spittel coefficients. The coefficients were found to be a sufficient fit with the isothermal hot compression data. A hot rolling model was simulated to compare with experimentally hot rolled NiTi shape memory alloy using the fitted Hansel-Spittel constitutive model. The reduction in area of the hot rolled experimental specimen and the simulated specimen were compared, and the model proved accurate, particularly for a higher strain rate and lower temperature. The application of this model is discussed, and potential processing applications are presented.

Nanoporous ceramic structures are very important for a wide range of applications such as in gas sensors, catalysts, antireflective coatings, self-cleaning surfaces, among others, due to the high surface area in these coatings that facilitate enhanced performances in areas where they are deployed. In comparison with other synthesis techniques, the design of these porous ceramic coatings with the polymer template infiltration approach offers controllability over the porous structures, coating thickness, and composition. Due to these unique qualities, polymer infiltration synthesis has attracted a lot of interest from the scientific community for the design of hybrid organic-inorganic composites and all-inorganic porous ceramic structures, so therefore, there is the need to expand the applicability of this polymer infiltration synthesis technique to various materials for different applications. This thesis aims to understand the fundamental mechanisms controlling the polymer infiltration process and the effects of the processing parameters on the structure, composition, and resulting characteristics of the single components, such as ZnO, Al2O3, and TiO2, and multicomponent, such as Al2O3, and ZnO with the inclusion of FeO-CoO and FeO-NiO nanoporous ceramic coatings. This work highlights the importance of the processing parameters, such as Swelling based infiltration-liquid phase vs Swelling assisted sequential infiltration synthesis-gas phase on the resulting crystallinity, and surface functionalization of the materials. Swelling of the polymer template is accompanied by the formation of the reactive groups that accelerates absorption of the precursor molecules. Modification of the coating surfaces affects their accessibility and affinity to solvents and their mechanical properties. Combining liquid and gas phase infiltration enables the development of nanoporous heterostructures with composition being affected by the precursor salt reactivity. Specifically, the intermixing of the multicomponent metal oxide precursors infiltrated into the polymer template revealed the formation of uniformly distributed alloyed metal oxide nanoparticles, with the polymer removal temperature influencing the phase and sizes of nanoparticle formation. These heterostructures demonstrate promising potential as catalysts for oxygen evolution reaction (OER). The results of this work provide a foundation for understanding the polymer infiltration mechanisms and the effect of processing conditions on the functionalization of the coatings. The obtained knowledge opens new possibilities for designing multifunctional materials.

This dissertation investigates sodium aluminosilicate (NAS) glasses and their interactions in an aqueous environment using reactive potential-based molecular dynamics (MD) simulations. The study explores how alumina content, cooling rate, system size, and interatomic potentials impact NAS glass structures and properties. Two types of MD potentials were compared: a fixed-charge pair-wise potential and a diffusive charge reactive potential (DCRP). Both generated structures that aligned well with experimental results, confirming the accuracy of the simulations. The simulations revealed critical structural features such as high-coordination aluminum, triclusters, and Al-O-Al bonds. NAS glass-water interfacial models generated from DCRP at various temperatures, from ambient temperature to 90 °C, were used to investigate these reactions over a simulation period of 4 ns. The key findings revealed that defects in the glass network initiate hydration reactions. Water penetration up to ~2 nm was observed, depending on temperature and glass composition. Temperature accelerated water penetration and sodium ion leaching, increasing the solution's pH, with sodium silicate glass exhibiting the highest values. These results provide a deeper understanding of the structural origin of properties and reaction mechanisms in aluminosilicate glasses for specific applications.