Le grippage dans le cas des aciers inoxydables est un phénomène complexe nécessitant une approche multi-échelle et multi-physique. Les 6 nuances d’aciers inoxydables sélectionnées au cours de cette thèse (316L, 316LN, Nitronic60, AISI660, Uranus45N et 17-4PH) ont été étudiées à l’état de réception et après traitements thermochimique de surface de type S3P. Ces matériaux ont subi un essai de grippage selon la norme ASTM G98 et les échantillons qui en résultent ont été caractérisés selon une approche d’abord surfacique (évolution de la morphologie de la surface, observations MEB…) puis en volume, notamment par le biais de l’approche originale de la microstructure (EBSD, DRX et MET notamment). Cette thèse a ainsi permis d’étudier les différents mécanismes intervenant lors du grippage des aciers inoxydables ainsi que d’étudier l’impact de différentes microstructures et composition chimiques sur ce phénomène. / Galling is a complex phenomenon requiring a multi-scale and multi-physical approach. During this thesis, 6 stainless steel grades (316L, 316LN, Nitronic60, AIS1660, Uranus45N et 17-4PH) are studied, both untreated and after S3P thermochemical heat surface treatment. These materials are tested according to ASTM G98 galling test and resulting samples are then characterized. This characterization is at first realized on the surface (surface morphology evolution, SEM investigations...), then on the bulk material, consisting mainly into a microstructural characterization based on EBSD, XRD and TEM investigations. It results from this thesis a better comprehension of the galling mechanisms in the case of stainless steel. The various effects of material composition, microstructure and material properties in general are also discussed.

This thesis highlights generic aspects of contact angle hysteresis and stick-slip motion,encountered in most practical wetting situations.First, we study the scaling relation between the heterogeneity strength and the amplitudeof the contact angle hysteresis it induces in the model configuration of a chemicallyheterogeneous microchannel. A key parameter which determines the qualitativefeatures is the heterogeneity wavelength. In particular, we identify a near-thresholdbehavior where the quadratic scaling between the heterogeneity amplitude and the resultinghysteresis, already known for a dilute system of wetting defects, is explainedby the closeness to the threshold, and a macroscopic limit without observable stick-slipwhere this scaling is linear.In the second part, we adapt the description to the configuration of a meniscusaround a wavy fibre. This adaptation brings the generic results of the first part in thereach of experiments. A comparison with experiments is achieved at the level of theindividual topography-induced jumps.In the third part, we expand the formulation to treat the quasi-steady interface shapecontact line dynamics and study how the the presence of stick-slip motion at the observableor unobservable scale modifies the scaling relation between the contact linevelocity and contact angle. We recover the known result that the scaling exponent dependson the nature of the externally controlled parameter, identify the causes of thisdependency in the corresponding static limits, and predict the disappearance of this dependencyabove a critical velocity which decreases with the heterogeneity wavelength.Finally, we show trough examples how the modelling framework which permitscapturing contact angle hysteresis and stick-slip motion in a minimalistic way can beadopted to treat configurations with a finite amount of contact points, or the 3D problemof a drop with a deformed contact line. We discuss the arising configuration-specificeffects, also in configurations of biomimetic interest. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

A study of the nucleation, growth and final microstructure of vacuum deposited nickel films has been performed using scanning tunneling microscopy (STM) as the primary research instrument. Typical nucleation conditions are reported for nickel films grown on partially shadowed highly-oriented pyrolytic graphite (HOPG), and techniques are developed for using the STM to catalog film islands instead of more conventional electron microscopes. Values for the activation energy of surface diffusion, critical nucleus size, changes in the saturation nucleation density with temperature, and spatial variations in the nucleation rate are included. Roughening and microstructure changes observed with STM are reported as functions of substrate temperature and deposition angle for nickel films grown on highly-oriented pyrolytic graphite and fused silica. Conventional film RMS roughness values are compared to microRMS values derived from STM data and STM images of film microstructure are compared with SEM and optical microscope photographs.

This thesis reports the methods, the deployment strategies and the resulting system performance improvement of in-building environmental modification. With the increasing use of mobile computing devices such as PDAs, laptops, and the expansion of wireless local area networks (WLANs), there is growing interest in increasing productivity and efficiency through enhancing received signal power. This thesis proposes the deployment of waveguides consisting of frequency selective surfaces (FSSs) in indoor wireless environments and investigates their effect on radio wave propagation. The received power of the obstructed (OBS) path is attenuated significantly as compared with that of the line of sight (LOS) path, thereby requiring an additional link budget margin as well as increased battery power drain. In this thesis, the use of an innovative model is also presented to selectively enhance radio propagation in indoor areas under OBS conditions by reflecting the channel radio signals into areas of interest in order to avoid significant propagation loss. An FSS is a surface which exhibits reflection and/or transmission properties as a function of frequency. An FSS with a pass band frequency response was applied to an ordinary or modified wall as a wallpaper to transform the wall into a frequency selective (FS) wall (FS-WALL) or frequency selective modified wall (FS-MWALL). Measurements have shown that the innovative model prototype can enhance 2.4GHz (IEEE 802.11b/g/n) transmissions in addition to the unmodified wall, whereas other radio services, such as cellular telephony at 1.8GHz, have other routes to penetrate or escape. The FSS performance has been examined intensely by both equivalent circuit modelling, simulation, and practical measurements. Factors that influence FSS performance such as the FSS element dimensions, element conductivities, dielectric substrates adjacent to the FSS, and signal incident angles, were investigated. By keeping the elements small and densely packed, a largely angle-insensitive FSS was developed as a promising prototype for FSS wallpaper. Accordingly, the resultant can be modelled by cascading the effects of the FSS wallpaper and the ordinary wall (FSWALL) or modified wall (FS-MWALL). Good agreement between the modelled, simulated, and the measured results was observed. Finally, a small-scale indoor environment has been constructed and measured in a half-wave chamber and free space measurements in order to practically verify this approach and through the usage of the deterministic ray tracing technique. An initial investigation showing that the use of an innovative model can increase capacity in MIMO systems. This can be explained by the presence of strong multipath components which give rise to a low correlated Rayleigh Channel. This research work has linked the fields of antenna design, communication systems, and building architecture.

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

This thesis presents the study of organic layers covalently assembled onto carbon surfaces. As a result of their attachment, the properties of carbon surfaces were controllably adjusted so that these surfaces could be used for desired applications. In order that a wide range of properties were imparted onto the carbon surface, many different modifiers were attached and thoroughly characterised. Three applications that the modified carbon surfaces were used for were the subsequent coupling of molecular species, adsorption of protein and assembly of aldehyde/sulfate-functionalised polystyrene (PS) and citrate-capped gold nanoparticles (NPs). Finally, patterning of different organic layers at pre-determined spatially defined locations on the one carbon surface was also investigated. The carbon surfaces used in this work were glassy carbon (GC) and pyrolysed photoresist film (PPF) surfaces. For PPF, methods for the reproducible fabrication of electrochemically suitable surfaces were investigated. The properties of GC and PPF surfaces are very similar apart from the surface roughness. PPF has near atomic smoothness and has RMS roughness values that are approximately four times smaller than GC. The first series of modifier layers attached to the carbon surfaces was via the oxidation of seven different primary amines. The different layers allowed the modulation of the wettability of the surface. Both n-tridecylamine (TDA, monoamine) and 1,12-diaminododecane (DAD, diamine) are able to form multilayers. The stability of TDA and DAD layers were tested by scanning, soaking and sonicating the layers in different media. Changes in the layer were monitored by the probe response of ferrocene monocarboxylic acid (FCA). However, atomic force microscope (AFM) depth profiling experiments showed that changes in the probe response did not indicate cleavage of the covalently attached layer and mechanisms are proposed to account for the changes in the response of the probe. Surface concentrations of the amine modifiers were estimated by the coupling of an electrochemically active species, FCA and nitrobenzoyl chloride (NBC). The electrochemical reduction of the 4-nitrophenylethylamine (NPEA) layer in acid caused the layer to 'shrink'. Surface concentration estimates of NPEA from acid reduction of layers with different thicknesses suggested that only a limited fraction of the p-nitrophenyl groups were reduced in acid. However, in ACN (acetonitrile)/0.1 M [Bu4N]BF4 (tetrabutyl ammonium fluoroborate) the relationship between the concentration of electroactive surface groups and layer thickness was linear. The other series of modifiers that was attached to alter the surface properties was performed by the reduction of aryl diazonium salts. Subsequent coupling reactions of tetraethylene glycol diamine (TGD) to para methylene carboxylic acid phenyl (MCA) and NBC to electrochemically reduced para nitro phenyl (NPh) layers were carried out. Surface concentrations of NPh as estimated from reduction scans was higher when reduction was performed in ethanol/water compared to acid. Four peaks at N1s binding energies were observed in x-ray photoelectron spectroscopy (XPS) spectra for both acid and ethanol/water reduced layers. The ability of attached amine and aryl layers to modulate the adsorption of protein was investigated using fluorescently labelled protein, bovine serum albumin-fluorescein isothiocynate (BSA-FITC) and fluorescence microscopy. TGD, para methyl phenyl (MP), para hexyl phenyl (HP) and para polyethylene glycol phenyl (PEG)-modified GC surfaces promoted protein adsorption relative to as-prepared GC, whereas n-hexylamine (HA) and polyethylene glycol diamine (PGD) layers reduced protein adsorption. The assembly of two types of NPs, aldehyde/sulfate-functionalised PS and citrate-capped gold NPs, onto amine-containing modifiers layers was examined. Citrate-capped gold NPs were synthesised and characterised. The surface coverage of the gold NPs was controlled by using different modifiers of different chemical compositions, tuning the modification conditions and adjusting the immersion time, concentration and pH of gold NP solution. Approaches to creating patterns of modifiers in pre-determined spatially defined locations on GC and PPF surfaces using poly(dimethyl)siloxane (PDMS), poly(vinyl)alcohol (PVA) and thin metal films were investigated. With the "fill-in" approach using PDMS, the smallest pattern of modifiers was the parallel lines with a line width of 20 µm and straight edges and was created by performing electrochemistry in PDMS microchannels which has not been previously investigated. Visualisation techniques, based on optical and scanning electron microscopy, were demonstrated for the molecular patterns.

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