Health-care associated infections (HAIs) on medical implant surfaces present a unique challenge to physicians due to their existence in the biofilm phenotype which defends the pathogen from antibiotics and the host’s own immune system. A 2004 study in the U.S. showed that 2 to 4% of implanted devices become infected and must be treated via surgical explantation—a process that is both expensive and dangerous for the patient. A potential, alternative strategy to antibiotics and surgery is to use heat delivered wirelessly by a magnetic coating. This thermal treatment strategy has the potential to kill these HAIs directly on the implanted surface and without the patient requiring surgery. This thesis introduces an iron oxide nanoparticle composite coating that is wirelessly heated using energy converted from an alternating magnetic field. Iron oxide nanoparticle composites are demonstrated to be remotely heated in both hydrophilic and hydrophobic polymer composites. In designing the composite coating, multiple parameters were investigated for how they impact the normalized heating rate of the material. Specifically, the amount of iron in the coating, the coating thickness, the polymer type, and the orientation of the coating relative to the applied magnetic field were investigated. Power output was shown to increase proportionally with iron loading whereas nearly two times the amount of power output was observed for the same coatings positioned parallel to magnetic field lines versus those positioned perpendicular—a result believed to be due to magnetic shielding from neighboring particles. Microscope slides coated with 226 µm of composite delivered up to 10.9 W cm⁻² of power when loaded with 30.0% Fe and positioned parallel in a 2.3 kA m⁻¹AMF. Pseudomonas aeruginosa biofilms were grown directly on these coatings and heated for times ranging from 1 to 30 min and temperatures from 50 to 80 °C. Less than one order of magnitude of cell death was observed for temperatures less than 60 °C and heat shock times less than 5 min. Up to six orders of magnitude reduction in viable bacteria were observed for the most extreme heat shock (80 °C for 30 min). Introducing this wirelessly heated composite into the body has the potential to kill harmful bacteria but at the risk of thermally damaging the surrounding tissue and organs if the treatment is not designed and predicted intelligently. Thermal energy will propagate differently depending on the surrounding heat sink, with convective heat sinks (i.e. those due to blood flow) requiring much more power to reach the same surface temperature than a conduction-only heat sink. To study how heat is transferred in biological tissues, a robust, poly(vinyl alcohol) tissue phantom was developed that can be poured to accommodate any geometry, is volume stable in water and under thermal stress, and can be modified with inert particle fillers to adjust its thermal conductivity from 0.475 to 0.795 W m⁻¹°C⁻¹. In vitro heat transfer was measured through this hydrogel tissue phantom with at least 10 °C of temperature rise, penetrating 5 mm of tissue in less than 120 sec for an 80 °C boundary condition. A computational model was used to solve three-dimensional energy transfer through a combined fluid mimic/tissue mimic heat sink spanning the same surface boundary condition. The model was validated with experimental models using a custom designed heat transfer station. This scenario is applicable in the instance where the same coating is subject to starkly different heat sinks: half subject to convective heat loss, half to conductive heat loss. Based on these conditions, a magnetic coating would need to be designed that has a power gradient up to 15 times larger on the fluid half versus the other.

This thesis focuses on identifying hard material pairs with low roughness, high coefficient of static friction, high wear resistance and high modulus of elasticity, suitable for sliding in dry friction conditions under a normal load. A wide range of materials including various steels, various coatings on tool steels deposited by various deposition techniques and different ceramics were examined and considered for tribological testing. Procedures and sequences were developed for conducting tribology tests on the material pairs. High endurance - low cycle tests were conducted and based on the performance of material pairs with respect to friction, wear and surface roughness a small set of material pairs and coatings was selected for further testing. High endurance - high cycle tests were performed on an additional seventeen pairs of material pairs selected for long term sliding. Material pairs were selected for low endurance tests based on high corrosion resistance along with all the above specified design parameters. Low endurance tests were conducted to identify material pairs sliding for a short distance in humid environments. Results are tabulated and pictures of the material pairs after wear tests are presented. It was found that four material pairs for high endurance applications and two pairs for the low endurance applications performed very well in regard of design specifications. These material pairs find a major application in friction clamps of an Inchworm motor resulting in enhancement of force output of the motor.

Le contexte du marché automobile actuel est conditionné par deux facteurs principaux : la prise de conscience del'impact sur l'écologie de ce mode de transport et une concurrence mondiale exacerbée. Ainsi, de nombreusesétudes soulignent l'intérêt de concevoir des moteurs dont le ratio puissance sur masse soit maximisé (Down Sizing).Ainsi les carters-cylindres traditionnellement réalisés en fonte pour des raisons de comportement tribologique sontreconçus pour être fabriqués à partir d'alliages d'aluminium. Ces derniers apportent un gain de masse au groupemotopropulseur mais présentent de piètres propriétés tribologiques. Pour pallier ce défaut, des chemises en fontesont généralement insérées dans les blocs lors de leur coulée. Toutefois cette solution n'est pas optimale et lesprocédés de projection thermique sont de plus en plus mis en oeuvre pour remplacer ces chemises par une mincecouche protectrice qui sera en contact avec les segments.Dans ce contexte ce travail se focalise sur l'application du procédé de projection thermique arc-fil rotatif pour ledépôt de revêtements en acier sur la paroi interne des fûts de carters-cylindres. L'objectif principal est de contribuerà cerner les mécanismes physiques reliant les paramètres de projection et les propriétés des revêtements. Desinvestigations ont été menées sur les différentes étapes de la vie des particules : les mécanismes d'atomisation ontété observés et quantifiés, les comportements à l'étalement des particules et les modes de refroidissement deslamelles ont été déterminés au moyen d'analyses des phases cristallines et les effets des paramètres opératoiressur la structure des dépôts ont été évalués. L'ensemble apporte ainsi de nouveaux éléments pour la maîtrise del'application de la projection thermique à l'arc-fil en milieu confiné et des pistes sont proposées pour optimiser lespropriétés des dépôts. / The current automotive market's context is conditioned by two main factors : the rising awareness of theenvironmental impact of this transportation mode and a strong competition between automakers at the world level.Thus, many studies already underlined the relevance of the « down sizing » of the engine blocks.Thus, cylinders-blocks, traditionally made from cast iron given its excellent tribological behavior and low cost, arenow designed with hypoeutectic aluminium-silicon cast alloys. However, the weight reduction brought by thesealloys is counteracted by their poor tribological properties. Therefore, Thermal spray processes are more and moresolicited to address this issue with the application of thin protective coatings on the working surfaces of thecylinders-blocks.In this frame, the present work was focused on the application of steel coatings on the bores' inner walls of cylinderblocks using the rotative twin-wire arc spray process. The main objective was to contribute to the understanding ofphysical mechanisms linking the spray parameters and the coating properties. Every stages of particles' life werethus investigated : the atomization mechanisms were observed and quantified, particles' spreading and coolingbehaviours were determined by mean of crystallographic examinations and process parameters' effects on coatingstructure were estimated. Globally, this document provides new elements contributing to the understanding and thecontrol of the process and solutions are proposed to raise the coatings properties.

Lithium ion batteries (LIBs) have gained increasing popularity due to their high potential, low self-discharge, zero priming and minimal memory effect. However, the emergence of electrical vehicles and hybrid electrical vehicles in the automobile industry, where LIBs are predominantly in use, instilled a need to improve LIB batteries by experimenting with new materials. Graphite, the commonly used anode material for LIBs suffers from low theoretical capacity (372 mA h g-1) and torpid rate performance. Germanium (Ge) seems to be a promising substitute of carbon due to its high theoretical capacity, high Li+ diffusivity and electrical conductivity. However, Ge undergoes large volumetric change (±370%). This causes deboning of the thin film Ge electrode from the substrate current collector, causing a rapid decrease in the electrolytic performance. The process of ion beam mixing claims to have overcome this problem. In our current study, the adhesion strength of Ge thin film over Nickel (Ni) substrate (with and without ion beam mixing) is being measured using nanoindentation and the superlayer indentation test. Nanoindentation is one of the popular techniques to measure the mechanical properties and adhesion of thin film coatings. In this technique, a very small indenter of a desired geometry indents the film/substrate pair and the work of adhesion is calculated by knowing the plastic depth of indentation and the radius of indentation. Superlayer indentation is analogous to normal indentation but with a highly stressed superlayer on top to restrict the out-of-plane displacements, it reduces the plastic pile up around the indenter tip. The results from our study strongly suggest the possibility of dramatically increasing the adhesion strength by ion bombardment, which can be achieved by atomic level intermixing of the film/substrate pair. These, in turn, suggest that Ge could be an effective successor to graphite in the near future.

The primary focus of my work has been to prepare new solid adsorbents for solid phase microextraction (SPME) via sputtering of silicon. The orientation of the silica substrates/fibers and the sputtering pressure induced the formation of porous and columnar structures. Sputtering was performed for different times to yield fibers with different thicknesses. Piranha treatment of the surface increased the concentration of silanol groups, which underwent condensation with vapor deposited octadecyldimethylmonomethoxy silane to incorporate octadecyl chains onto the fiber surfaces. Silanized, sputtered fibers were preconditioned for 3 h at 320 °C to remove the unreacted chains. Comparison of the extraction efficiencies of 1.0 and 2.0 µm sputtered, silanized fibers with a commercial fiber (7 µm PDMS) for a series of analyte mixtures, which included alkanes, alcohols, aldehydes, esters, and amines, was demonstrated. The silanized, sputtered fiber performed better than the commercial fiber in extraction of most of the compounds. These fibers demonstrated long life as no degradation was seen even after 300 extractions. Carry-over between runs was not observed. The repeatability of the sputtered fibers was similar to commercial ones. The extraction of more than 50 compounds from a real world botanical sample using the 2.0 µm sputtered, silanized fiber was also demonstrated. In my second project, a facile method for the preparation of superhydrophobic surfaces (SHS) on glass and silicon surfaces was developed. A two-tier topography (needed for an SHS) was created in 60 min by the aggregation of nanosilica during in situ urea-formaldehyde polymerization. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrated rough topography. Vapor deposition of a low surface energy silane imparted hydrophobicity, which was confirmed by the presence of an F 1s signal in X-ray photoelectron spectroscopy (XPS). The prepared surfaces exhibited water contact angles (WCA) of greater than 150 °C with very low sliding angles. In my third project, a multilayer assembly of nitrilotris(methylene)triphosphonic acid, a corrosion inhibitor, and zirconium was constructed on alumina at room temperature. Attempts to prepare a layer-by-layer assembly at higher temperature (70 °C) was unsuccessful due to etching of the alumina surface. A suite of analytical techniques, XPS, AFM, time-of-flight secondary ion mass spectrometry, and spectroscopic ellipsometry was used to characterize these surfaces. This thesis also contains appendices of tutorial articles I wrote on modeling in ellipsometry, and data analysis tools (classical least squares and multivariate curve resolution).

Abstract not available

This thesis presents the results of a study focussed on the elucidation of the mechanisms responsible for determining the structural integrity of carbon coatings on ductile substrates. Through elucidation of these mechanisms, two different coating systems are designed; a multilayered coating and a functionally graded coating. While concentrating upon carbon coatings, the findings of this study are applicable to a broad range of hard coatings on ductile substrates. The thesis concludes with a chapter outlining a brief study of the effects of gold coatings on silicon under contact load at moderate temperatures to complement the major part of the thesis. Carbon coatings with differing mechanical properties were deposited using plasma enhanced chemical vapour deposition (PECVD), filtered assisted deposition (FAD) and magnetron sputtering deposition methods. Combinations of these techniques plus variation of deposition parameters enabled composite multilayered and functionally-graded coatings to also be deposited. Substrates were ductile metals; stainless steel and aluminium. Characterisation of the coating mechanical properties was undertaken using nanoindentation and nano-scratch tests. The same techniques were used to induce fracture within the coatings to allow subsequent analysis of the fracture mechanism. These were ascertained with the assistance of cross-sectional imaging of indents prepared using a focussed ion beam (FIB) mill and transmission electron microscopy (TEM) using specimen preparation techniques also utilising the focussed ion beam mill. A two dimensional axisymmetric finite element model (FEM) was built of the coating systems using the commercial software package, ANSYS. Substrate elastic-plastic properties were ascertained by calibrating load-displacement curves on substrate materials with the finite element model results. Utilising the simulation of spherical indentation, the distribution of stresses and the locations for fracture initiation were ascertained using finite element models. This enabled determination of the influence such factors as substrate mechanical properties, residual stresses in the coatings and importantly the variation of elastic properties of the different coating materials. Based upon the studies of monolithic coatings, simulations were undertaken on multilayer and functionally-graded coatings to optimise design of these coating types. Based on the results of the modelling, multilayered and functionally graded coatings were then deposited and mechanical testing undertaken to confirm the models. Three major crack types were observed to occur as the result of the spherical nanoindentation on the coatings; ring, radial and lateral cracks. Ring cracks were found to initiate from the top surface of the film, usually at some distance from the edge of the spherical contact. Radial cracks usually initiated from the interface between the coating and the substrate directly under the symmetry axis of indentation and propagated outwards in a non symmetrical star-like fashion. Lateral cracks formed either between layers in the multilayer coatings or at the interface with substrate. Ring and radial cracks were found to form upon loading whereas lateral cracks formed upon both loading and unloading depending upon the crack driving mechanism. Pop-in events in the load displacement indentation curve were found to be indicative of the formation of ring cracks, while the formation of the other types of cracks was not signified by pop-ins but rather by variations in the slope of the curve. The substrate yield strength was found to influence the initiation of all crack systems while compressive stresses in the coating were seen to only influence the formation of ring and radial cracks. However, it was also noted that the initiation of one form of crack tended to then hinder the subsequent formation of others. In multilayer coatings, the lateral cracks were suppressed, as opposed to the monolayer coating system, but a ring crack was observed. This drawback in the multilayer system was successfully addressed by the design of a graded coating having the highest Young??s modulus at the middle of the film thickness. In this coating, due to the graded nature of the elastic modulus, the stresses at the deleterious locations (top surface and interface) were guided toward the middle of coating and hence increased the load bearing capabilities. The effect of substrate roughness upon the subsequent surface roughness of the coating and also upon the fracture process of the coating during indentation was also investigated. For the coatings deposited on rough substrates, the radial cracks were observed to form initially and this eventfully delayed the initiation of ring cracks. Also the number of radial cracks observed at the interface was found to be proportional to the distribution of the interfacial asperities. In summary, the study elucidated the fracture mechanisms of monolayer, multilayer and graded carbon coatings on ductile substrates under uniaxial and sliding contact loading. The effects of the yield strength, surface roughness of the substrate, along with the residual stress and elastic modulus of the coatings on the fracture of coatings were investigated. The study utilised finite element modelling to explain the experiments observations and to design coating systems.

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Materials Science and Engineering Program, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2006. / Full text release at OhioLINK's ETD Center delayed at author's request

Greaseproof paper has a dense structure and therefore provides a natural barrier against materials like fat and oils. The barrier is obtained by extensive refining of the pulp. This refining is however a costly operation, not only in terms of direct costs for the refining but also in terms of indirect costs because the energy consumption for the drying of the paper is affected by the refining. A full-scale trial was performed to investigate the role of the pulp with respect to the energy demand and the barrier properties of the final papers. Paper made of 100% sulphite pulp with a low degree of refining exhibited the lowest energy consumption at a given level of air permeance. In addition, the effect of refining on the air permeance was compared with that of calendering. The calendering affected the air permeance less than the refining. The papers produced in the full-scale trial were later used as substrates for coatings and for detailed studies of the paper structure. Coating with chitosan was examined on a bench-scale and on a pilot scale. The studies showed that greaseproof paper can be upgraded with an oxygen barrier, but also that suitable coating techniques are lacking for the application of the coating in a sufficient amount. The influence of the base paper on the barrier properties of chitosan-coated paper was investigated in another study, in which it was found that greaseproof paper possesses a unique coating hold-out which cannot be met by other types of paper with a more open structure. It was also found that the coated paper had a lower oxygen permeability than the chitosan coating itself, and this indicates that the dense surface layer of greaseproof paper contributed to the oxygen permeability of the coated paper. The pore volume fraction of the greaseproof paper was found to be approximately 40% and it is therefore surprising that its air permeance is so low. To bring understanding to this question, the structure of greaseproof paper was studied using several methods. It was found that the structure was dominated by very small pores with a median diameter of <0.3 µm. The fraction of closed pores was also substantial. A porosity gradient was also found, indicating that the papers used in the study had a closed surface. The hypothesis that the surface layer of the paper contributed to the oxygen barrier was tested in an experiment in which greaseproof paper was extrusion-coated with polyethylene. The oxygen permeability was measured at 0%, 50% and 90% relative humidity, and the permeability was found to increase with increasing moisture content. Because only the cellulose layer in the paper and not the polyethylene layer in the coating is affected by moisture, this result supports the hypothesis that the surface layer of the paper contributed to the oxygen barrier properties of the coated paper.