Flores díclinas originam-se da ausência funcional/estrutural de um dos verticilos envolvidos na reprodução, seja desde o início ou no decorrer do desenvolvimento dos primórdios. Este trabalho visa ao estudo do desenvolvimento floral de Parkia multijuga e Stryphnodendron adstringens, leguminosas andromonoicas, a fim de verificar se as flores estaminadas se formam por ausência do carpelo desde o início do desenvolvimento ou por seu aborto no decorrer do desenvolvimento. Botões florais de vários tamanhos e flores foram coletados e processados para observações em microscopia eletrônica de varredura (MEV) e microscopia de luz (ML). O desenvolvimento dos órgãos florais inicia-se com o surgimento de cinco primórdios de sépalas no meristema floral, a partir do lado abaxial em P. multijuga e adaxial em S. adstringes: em alguns botões, um sexto primórdio de sépala inicia-se tardiamente; cinco primórdios de pétalas simultaneamente em P. multijuga e bidirecionalmente em S. adstringes; um primórdio de carpelo concomitante aos cinco primórdios de estames antessépalos em P. multijuga, e após a formação das pétalas em S. adstringes; e cinco primórdios de estames antepétalos. As etapas finais do desenvolvimento são similares entre as espécies. Os estames iniciados em dois verticilos, um mais externo (antessépalo) e outro mais interno (antepétalo), encontram-se arranjados em um único verticilo. Entretanto, os estames antessépalos, que se iniciaram primeiro, apresentam-se um pouco mais alongados que os antepétalos. Em P. multijuga os filetes unem-se na base durante seu alongamento, formando um tubo que, posteriormente, torna-se adnato às pétalas. Nas flores hermafroditas de ambas as espécies, o primórdio carpelar inicia-se, alonga-se, a fenda carpelar se fecha e, logo após, começa a diferenciação do estilete. Já nas flores estaminadas, o primórdio carpelar inicia-se e alonga-se, mas sua fenda não se fecha e o carpelo não termina seu desenvolvimento. Na fase final, as flores hermafroditas apresentam estigmas completamente diferenciados, enquanto que nas flores estaminadas, o primórdio carpelar permanece como um rudimento na base do botão floral. Não há iniciação de óvulos neste caso. Conclui-se que as flores estaminadas em ambas as espécies surgem por aborto do carpelo e não por sua ausência desde o início, semelhante a outros membros de Mimosoideae. / Diclinous flowers originate by functional/structural absence of one of the reproductive whorls, from the inception or by abortion in the development. This study aims to compare the floral development of two andromonoecious legumes, Parkia multijuga and Stryphnodendron adstringens, in order to verify which process acts in the staminate flower formation (carpel absence from inception or by abortion). Flowers and flower buds of various sizes were collected and processed for observations in scanning electron microscopy (SEM) and light microscopy (LM). The development of floral organs begins with the emergence of five sepal primordia in the floral meristem from the abaxial side (P. multijuga) and from the adaxial side (S. adstringens) in which in some buds, a sixth primordia arises late; five petal primordial simultaneously in P. multijuga and bidirectionally in S. adstringens, a carpel primordium emergence concomitantly to five antesepalous stamens primordia in P. multijuga, and after the petal formation in S. adstringens, and five antepetalous stamen primordium. In the final stages of the development, the stamens initiated in two whorls, one outer (antesepalous) and the other innermost (antepetalous), are arranged in a single whorl. However, the antesepalous stamens, which emerged first, are a little more elongated than the antepetalous ones. In P. multijuga the fillets join in the base while its elongation, forming a tube, which thereafter becomes adnate to the petals. In hermaphrodite flowers, in both species, the carpel primordium emerges, stretches, the carpel cleft closes and, soon after, the style begins its differentiation. In staminate flowers, the carpel primordium begins and stretches, but the carpel cleft does not close and the carpel does not end its development. In the mature stage, the hermaphrodite flowers present fully differentiated stigmas, while in the staminate flowers, the carpel primordium remains as a rudiment at the base of the bud. In this case, there is no initiation of any ovule. We conclude that staminate flowers in both species arise by carpel abortion and not from inception, alike the other members of Mimosoideae.

Carbon fibre reinforced ceramic composites (Cf/C-SiC) have been explored as lightweight and durable disc in a friction brake. This composite was manufactured through infiltration of liquid silicon into a Cf/C perform. It has heterogeneous microstructure, composed of three key phases, silicon carbide, Cf/C, and un-reacted residual silicon. The development of the transfer layer on the friction surface of Cf/C-SiC was studied through microstructural image registration of the surface after a range of braking stops on a laboratory-scale dynamometer test rig. When an organic pad was used as the counter face brake pad, it was found that a steady transfer layer was developed in silicon regions right after initial stops; in carbon-fibre/carbon (Cf/C) regions and most of the silicon carbide region, the friction surfaces were unsteady and any possible friction transfer layers were hardly built up. Large voids and cracks/crevices likely became pools to quickly and efficiently collect the transferred materials generated by the friction, but the compacts formed inside the pools were susceptible to be stripped off by further braking operation. Three types of friction surfaces were generalized: type I, the friction transfer layer had a steady relationship with the matrix and respectable longevity; type II, the transfer layer had an unstable relationship with the matrix and poor durability; type III, the friction transfer layer had a steady relationship with the matrix but short lifetime. After testing against organic pads under the laboratory scale dynamometer testing condition, the friction surface of each key phase in Cf/C-SiC composites disc was studied by transmission electron microscopy (TEM). It was found that the transfer layer developed on Si consists of fine particles of metal silicides, silicates and minerals. The substrate damage of Si was not observed, while the precipitates having high oxygen content were found in the substrate. Formation of an interfacial bonding between transfer layer and silicon substrate is believed to be the key factor for the formation of a stable transfer layer on Si. However, the interfacial bonding between transferred materials and SiC was not detected. Kinks are common features developed on the friction surface of SiC. The interface between carbon fibre and carbon matrix was experienced mechanical damage, in form of microcracks, and the transferred material was developed in the interface. Instead of transfer layer, a thin amorphous film, produced by friction induced amorphisation of carbon fibre, was developed on top of carbon fibre.

Objectif—Comparer les effets de la stérilisation au plasma de gaz de peroxyde d’hydrogène (HPGP) à l’oxyde d’éthylène (EO) et à la vapeur (ST) sur les propriétés physico-chimiques et d’adhésion bactérienne de fils de nylon et de polyéthylène. Design expérimental—Etude in vitro. Matériel—Des brins non stérilisés, stérilisés au HPGP, à l’EO et ST; de fil nylon leader (FNL), de fil de nylon pêche (FNP) et de fil de polyéthylène (PE) ont été utilisés. Méthodes—Une analyse de surface au spectroscope photo-électronique à rayons X (XPS), une mesure de l’angle de contact, une analyse par microscopie à force atomique (AFM) et l’adhésion bactérienne de Staphylococcus intermedius et d’Escherichia Coli ont été testés sur les brins. Résultats—Une oxydation de la surface de tous les échantillons stérilisés a été observée quelque soit la méthode de stérilisation. La stérilisation a augmenté significativement l’angle de contact pour tous les types de fil quelque soit la méthode. La rugosité n’a pas été affectée significativement par la méthode de stérilisation pour le FNL et FNP. L’adhésion bactérienne a été affectée significativement par la méthode de stérilisation. Le PE a un angle de contact, une rugosité et une adhésion bactérienne significativement plus élevée que le FNL et FNP, peu importe la méthode de stérilisation. Conclusion—La stérilisation au HPGP constitue une alternative intéressante à la vapeur et l’EO. Le PE n’est peut être pas un matériel idéal par sa capacité d’adhésion bactérienne. De futures études sont nécessaires pour déterminer la signification clinique de ces trouvailles. / Objective—To compare the effects of hydrogen peroxide gas plasma (HPGP), ethylene oxide (EO) and steam (ST) sterilizations on the physicochemical and bioadhesive properties of nylon and polyethylene lines used for stabilization of the canine stifle joint. Study Design—In vitro study. Samples—Non-sterilized, HPGP-, EO- and ST- sterilized samples of 36.3-kg test nylon leader line (NLL), 57.8-kg test nylon fishing line (NFL) and 2-mm Ultra High Molecular Weight Polyethylene (UHMPE) were used. Methods—Surface analysis of NLL, NFL and UHMPE non-sterilized and HPGP-, EO- and ST-sterilized samples was carried out by X-ray photoelectron spectroscopy (XPS), contact angle (CA) measurement, and atomic force microscopy (AFM). Staphylococcus intermedius and Escherichia Coli bacterial adherence were also tested. Results—Surface oxidation was observed on all samples sterilized with HPGP, EO or ST process. All sterilization methods significantly increased the CA for the NLL, NFL and UHMPE. The roughness was not significantly affected by the method of sterilization for NLL, NFL and UHMPE. Bacterial adherence was significantly affected by the method of sterilization for NLL, NFL and UHMPE. UHMPE had significantly higher CA, roughness and bacterial adherence compared to NLL and NFL, no matter which sterilization method was used. Conclusion—The effects of HPGP on the chemico-physical and bioadhesive properties of nylon and polyethylene lines compared positively to EO or ST, making HPGP an attractive alternative. UHMPE may not be a suitable material for suture prostheses regarding bacterial adherence properties. Future studies are required to determine the clinical significance of these findings.

The current requirements in automotive lubrication impose complex formulation. Among all the additives present in oil, the presence of molybdenum dithiocarbamate and zinc dithiophosphate, both tribological additives containing sulfur and phosphorous is found. For environmental reasons, it is important to reduce or eliminate the presence of these two elements contained in oil. Organic molecules based on carbon, oxygen and hydrogen seems to be good candidate. The lubrication mechanism of fatty acids (e.g. stearic, oleic and linoleic acids) is revisited with a new approach combining experimental and computational chemistry studies. First, the adsorption mechanisms of fatty acids on iron-based surfaces are investigated by Ultra-Accelerated Quantum Chemistry Molecular Dynamics simulations. The adsorption of fatty acids on iron oxide surface occurred through the acid group. Depending on the nature of the substrate, on the density of the film and on the tilt angle between the molecule and the surface, different adsorption mechanisms (physisorption and chemisorption) can occur. Stearic acid molecules form a close-packed and well-arranged monolayer whereas unsaturation acids cannot because of steric effects induced by double carbon-carbon bonds. The friction process favors the formation of carboxylate function. Results are confirmed by surface analysis (XPS and PM-IRRAS). Tribological properties of pure fatty acids, blended in PAO 4 and mixture of saturated/unsaturated acids are studied by MD simulations and tribotests. Low friction coefficient with no visible wear is reported for pure stearic acid and single stearic acid blended in PAO 4 at 1%w at high temperature. This lubricating behavior is inhibited in the presence of unsaturated acids, especially at 150 °C. MD simulation results show a faster diffusion toward the surface for unsaturated fatty acids than for stearic acid at all studied temperature.

Thesis (MComm)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Work Engagement is one construct of many that forms part of the complex nomological network of constructs underlying the behaviour of working man2. Work Engagement is an important construct both from an individual as well as from an organisational perspective. Human resource management interventions aimed at enhancing Work Engagement aspire to contribute to the achievement of the organisation’s primary objective and the well-being of the organisation’s employees. Such interventions will most likely also be valued by individuals within the workplace, as individuals will be able to experience a sense of personal fulfilment through self-expression at work. It is therefore essential to gain a valid understanding of the Work Engagement construct and the psychological mechanism that underpins it, in order to design human resource interventions that will successfully enhance Work Engagement. The current study raises the question why variance in Work Engagement exists amongst different employees working in different organisational contexts. The research objective of the current study is to develop and empirically test an explanatory Work Engagement structural model that will provide a valid answer to this question. In this study, a comprehensive Work Engagement structural model was proposed. An ex post facto correlational design with structural equation modelling (SEM) as the statistical analysis technique was used to test the substantive research hypotheses as represented by the Work Engagement structural model. Furthermore, the current study tested two additional narrow-focus structural models describing the impact of value congruence on Work Engagement by using an ex post facto correlational design with polynomial regression as the statistical analysis technique. A convenience sample of 227 teachers working in public sector schools falling under the jurisdiction of the Western Cape Education Department (WCED) participated in the study. The comprehensive Work Engagement model achieved reasonable close fit. Support was found for all of the hypothesised theoretical relationships in the Work Engagement structural model, except for the influence of the PsyCap*Job Characteristics interaction effect on Meaningfulness and for three of the five latent polynomial regression terms added in the model in an attempt to derive response surface test values. The response surface analyses findings were mixed. Based on the obtained results, meaningful practical recommendations were derived. / AFRIKAANSE OPSOMMING: Werkverbintenis1 is een van ‘n groot verskeidenheid konstrukte wat deel vorm van die komplekse nomologiese netwerk van konstrukte wat die gedrag van die arbeidende mens onderlê. Werkverbintenis word as ‘n belangrike konstruk beskou vanuit ‘n individuele sowel as vanuit ‘n organisatoriese perspektief. Menslike hulpbronbestuurs-intervensies gerig op die bevordering van Werkverbintenis streef daarna om by te dra tot die bereiking van die organisasie se primêre doel sowel as tot die welstand van die organisasie se werknemers. Sodanige intervensies sal waarskynlik ook deur werknemers waardeer word, aangesien sodanige intervensies die kanse verhoog dat individue selfvervulling in hul werk sal ervaar omdat die werk hul die geleentheid bied om hulself in hul werk uit te leef. Dit is gevolglik noodsaaklik om ‘n geldige begrip te ontwikkel van die Werkverbintenis-konstruk en die sielkundige meganisme wat dit onderlê ten einde menslike hulpronbestuurs-intervensies te ontwerp wat suksesvol Werkverbintenis sal bevorder. Die huidige studie stel die vraag aan die orde waarom variansie in Werkverbintenis tussen verskillende werknemers bestaan wat in verskillende organisatoriese kontekste werk. Die navorsingsdoelstelling van die huidige studie is om ‘n verklarende Werkverbintenisstrukturele model te ontwikkel en te toets wat ‘n geldige antwoord op hierdie vraag sal bied. ‘n Omvattende Werkverbintenis strukturele model is in hierdie studie voorgestel. ‘n Ex post facto korrelatiewe ontwerp met strukturele vergelykingsmodellering (SVM) as die statistiese ontledingstegniek is gebruik om die substantiewe navorsingshipotese soos voorgestel deur die Werkverbintenis strukturele model te toets. Die huidige studie het voorts twee addisionele nouer-fokus strukturele modelle getoets wat die impak van waardekongruensie op Werkverbintenis beskryf deur middel van ‘n ex post facto korrelatiewe ontwerp met polinomiese regressie-ontleding as statistiese ontledingstegniek. ‘n Geriefsteekproef van 227 onderwysers wat in openbare skole werksaam is wat onder die beheer van die Wes Kaapse Department van Onderwys val (WKDO) het aan die studie deelgeneem. Die omvattende Werkverbintenis-model het redelik goeie pasgehalte getoon. Steun is gevind vir all die voorgestelde teoretiese verwantskappe in die Werkverbintenis strukturele model, behalwe vir die invloed van die Sielkundige kapitaal*Werk eienskappe-interaksie-effek op Betekenisvolheid en vir drie van die vyf polinomiese latente regressie-terme wat in die model ingesluit is in ‘n poging om responsoppervlakte-waardes af te lei. Gemengde resultate is verkry vir die responsoppervlakte-ontleding. Betekenisvolle praktiese aanbevelings is gemaak op grond van die navorsingsresultate.

Flores díclinas originam-se da ausência funcional/estrutural de um dos verticilos envolvidos na reprodução, seja desde o início ou no decorrer do desenvolvimento dos primórdios. Este trabalho visa ao estudo do desenvolvimento floral de Parkia multijuga e Stryphnodendron adstringens, leguminosas andromonoicas, a fim de verificar se as flores estaminadas se formam por ausência do carpelo desde o início do desenvolvimento ou por seu aborto no decorrer do desenvolvimento. Botões florais de vários tamanhos e flores foram coletados e processados para observações em microscopia eletrônica de varredura (MEV) e microscopia de luz (ML). O desenvolvimento dos órgãos florais inicia-se com o surgimento de cinco primórdios de sépalas no meristema floral, a partir do lado abaxial em P. multijuga e adaxial em S. adstringes: em alguns botões, um sexto primórdio de sépala inicia-se tardiamente; cinco primórdios de pétalas simultaneamente em P. multijuga e bidirecionalmente em S. adstringes; um primórdio de carpelo concomitante aos cinco primórdios de estames antessépalos em P. multijuga, e após a formação das pétalas em S. adstringes; e cinco primórdios de estames antepétalos. As etapas finais do desenvolvimento são similares entre as espécies. Os estames iniciados em dois verticilos, um mais externo (antessépalo) e outro mais interno (antepétalo), encontram-se arranjados em um único verticilo. Entretanto, os estames antessépalos, que se iniciaram primeiro, apresentam-se um pouco mais alongados que os antepétalos. Em P. multijuga os filetes unem-se na base durante seu alongamento, formando um tubo que, posteriormente, torna-se adnato às pétalas. Nas flores hermafroditas de ambas as espécies, o primórdio carpelar inicia-se, alonga-se, a fenda carpelar se fecha e, logo após, começa a diferenciação do estilete. Já nas flores estaminadas, o primórdio carpelar inicia-se e alonga-se, mas sua fenda não se fecha e o carpelo não termina seu desenvolvimento. Na fase final, as flores hermafroditas apresentam estigmas completamente diferenciados, enquanto que nas flores estaminadas, o primórdio carpelar permanece como um rudimento na base do botão floral. Não há iniciação de óvulos neste caso. Conclui-se que as flores estaminadas em ambas as espécies surgem por aborto do carpelo e não por sua ausência desde o início, semelhante a outros membros de Mimosoideae. / Diclinous flowers originate by functional/structural absence of one of the reproductive whorls, from the inception or by abortion in the development. This study aims to compare the floral development of two andromonoecious legumes, Parkia multijuga and Stryphnodendron adstringens, in order to verify which process acts in the staminate flower formation (carpel absence from inception or by abortion). Flowers and flower buds of various sizes were collected and processed for observations in scanning electron microscopy (SEM) and light microscopy (LM). The development of floral organs begins with the emergence of five sepal primordia in the floral meristem from the abaxial side (P. multijuga) and from the adaxial side (S. adstringens) in which in some buds, a sixth primordia arises late; five petal primordial simultaneously in P. multijuga and bidirectionally in S. adstringens, a carpel primordium emergence concomitantly to five antesepalous stamens primordia in P. multijuga, and after the petal formation in S. adstringens, and five antepetalous stamen primordium. In the final stages of the development, the stamens initiated in two whorls, one outer (antesepalous) and the other innermost (antepetalous), are arranged in a single whorl. However, the antesepalous stamens, which emerged first, are a little more elongated than the antepetalous ones. In P. multijuga the fillets join in the base while its elongation, forming a tube, which thereafter becomes adnate to the petals. In hermaphrodite flowers, in both species, the carpel primordium emerges, stretches, the carpel cleft closes and, soon after, the style begins its differentiation. In staminate flowers, the carpel primordium begins and stretches, but the carpel cleft does not close and the carpel does not end its development. In the mature stage, the hermaphrodite flowers present fully differentiated stigmas, while in the staminate flowers, the carpel primordium remains as a rudiment at the base of the bud. In this case, there is no initiation of any ovule. We conclude that staminate flowers in both species arise by carpel abortion and not from inception, alike the other members of Mimosoideae.

Ce travail de thèse s'est inscrit dans le cadre d'un projet collaboratif à finalité industrielle ayant pour but de développer des matériaux composites à propriétés photocatalytiques (à base de nanoparticules de TiO2) obtenus par voie sol-gel pour une application sur substrats organiques (textiles et papiers) : intégration de nanoparticules de TiO2 dans une matrice sol-gel hybride (organique-inorganique) et dispersion de nanoparticules de TiO2 dans des microparticules de silice mésoporeuses. La contribution originale du travail de thèse a consisté à développer des caractérisations par analyse de surface (SEM, XPS et ToF-SIMS) et corréler ces résultats à ceux des tests photocatalytiques (suivi de la dégradation d'un polluant modèle (acide formique) en solution aqueuse sous irradiation UV). En complémentarité avec la question des différents niveaux de porosité des matrices utilisées, les techniques SEM, XPS et ToF-SIMS ont permis de définir différents critères tels que la disponibilité du photocatalyseur (TiO2) en extrême surface mais aussi la modification de la matrice autour du TiO2. Ces critères ont contribué à mieux comprendre les différences de propriétés photocatalytiques des différents matériaux composites déposés en surface des substrats organiques / This thesis work is part of a collaborative project with an industrial purpose aiming at the development of composite materials with photocatalytic properties (composed of TiO2 nanoparticles) obtained by sol-gel process for application on organic substrates (textiles and paper): integration of TiO2 nanoparticles into a sol-gel hybrid (organic-inorganic) matrix and dispersion of TiO2 nanoparticles in mesoporous silica microparticles. The original contribution of this work was to develop characterization by surface analysis techniques (SEM, XPS and ToF-SIMS) and correlate these results to those from the photocatalytic tests (following the degradation of a model pollutant (formic acid) in aqueous solution under UV irradiation). Complementarily to the issue of matrices porosity, surface analysis techniques (SEM, XPS and ToF –SIMS) allowed to define criteria such as availability of photocatalyst (TiO2) at the outermost surface but also the modification of the matrix around the TiO2. These criteria were used to better understand the differences in photocatalytic properties of various composite materials deposited on the surface of organic substrates

L'électronique organique a connu durant la dernière décennie un essor considérable. La production de dispositifs à base de matériaux organiques reste néanmoins freinée par différents verrous technologiques. La caractérisation de ce type de systèmes conduit à des besoins analytiques spécifiques et la spectrométrie de masse des ions secondaires à temps de vol (Timeof-Flight Secondary Ion Mass Spectrometry – ToF SIMS) est a priori très pertinente notamment grâce à l'utilisation d'un nouveau type de faisceau d'ions à base d'agrégats d'argon (Arn +). L'objectif principal de ce travail a donc été de comprendre l'interaction ions-matière d'un tel faisceau avec les matériaux organiques utilisés en électronique organique. Une étude fondamentale a d'abord été réalisée en comparant différents faisceaux d'ions de décapage (Cs+, C60 ++, Arn +) sur des échantillons organiques structurés (tels que les copolymères à blocs PS-b-PMMA) et il est apparu que, bien que la taille des agrégats et leur énergie ont peu d'effet sur l'endommagement observable sur les échantillons, les agrégats d'argon de grande taille induisent de la rugosité lors du profil en profondeur ToF SIMS, sans modification chimique, ce qui a été confirmé par des analyses complémentaires – AFM (Atomic Force Microscopy) et XPS (X-ray Photoelectron Spectroscopy) – et une modélisation géométrique. Ensuite, différents dispositifs du domaine de l'électronique organique ont été caractérisés. Ainsi, l'étude de l'auto structuration des copolymères à blocs PS-b-PMMA a permis d'évaluer l'influence du temps de recuit et de l'épaisseur de la couche. Par ailleurs, un protocole a été développé pour l'analyse d'empilements de couches inorganiques/organiques, notamment ceux des OLED. Il a ainsi été possible de caractériser par profil en profondeur ToF-SIMS les différents empilements d'un dispositif de l'électronique organique en conservant la détection d'un signal moléculaire et une haute résolution en profondeur de 2 nm. Parallèlement, nous avons identifié la dégradation chimique d'un matériau organique du multicouche constitutif de l'empilement et évalué la protection de celui-ci via des couches barrières. Plus précisément, les signatures de la réaction d'hydrolyse de la couche ont été identifiées ainsi que la teneur en humidité après encapsulation / During the last decade, organic electronics have developed rapidly. However, the production of organic electronic devices is still impeded because of various technological barriers. Such systems have specific analytical needs and time-of-flight secondary ion mass spectrometry (ToF-SIMS) is per se highly relevant, particularly when considering the use of a new type of ion source based on argon clusters (Arn +). The main objective of this work was therefore to understand the ion-matter interactions of such a cluster beam with the organic materials used in organic electronics. A fundamental study was carried out by comparing sputtering with three different ion beams (Cs+, C60 ++, Arn +) on organic structured samples (such as PS-b-PMMA block copolymers) and it transpired that although cluster size and energy has little effect on the observable damage to the sample, larger argon clusters induce more roughness during ToFSIMS depth profiling. This was confirmed by AFM (Atomic Force Microscopy) and XPS (Xray Photoelectron Spectroscopy) and a geometric model. Next, different devices in organic electronics were characterized by ToF-SIMS. The study of self-assembling PS-b-PMMA block copolymers made possible to evaluate the influence of the annealing duration and of the thickness of the layer. Furthermore, a protocol was developed to analyse stacks of inorganic/organic layers, in particular those contained in OLED devices. It was then possible to characterize the stacks of a complete organic light-emitting device whilst maintaining molecular signal and a high depth resolution of 2 nm. In parallel we identified the chemical degradation of an organic material in the stack and evaluated the efficiency of barrier layers designed to protect it. More precisely, specific signatures to the hydrolysis reaction of the layer as well as increase in moisture level after encapsulation were identified

La Spectrométrie de Masse d'Ions Secondaires à Temps de Vol (ToF-SIMS) permet la caractérisation de l'extrême surface à haute sensibilité via la détection d'ions secondaires atomiques et moléculaires. Ces travaux ont visé à étudier son application pour l'analyse de textiles industriels auxquels ont été conférées des propriétés dermatologiques (cosmétotextiles). Trois démarches analytiques adaptées aux spécificités des agents actifs et des technologies utilisées ont été présentées. Elles ont nécessité un développement particulier des méthodes employées (étude préliminaire, calibration, traitement et interprétation des données) et de tenir compte des possibilités et des limites de la technique ou de l'appareillage utilisé dans le contexte particulier de l'analyse des fibres textiles (topographie, effet de charge localisé, contaminations, formulations complexes, ségrégation et concentration de certains constituants des traitements en extrême surface).Dans la première démarche, la cartographie chimique ToF-SIMS a été utilisée avec succès pour illustrer l'existence d'un gradient de concentration en agent actif près de l'extrême surface de matrices polyamides. La capacité à identifier les signatures caractéristiques des agents actifs et valider leur présence en surface des échantillons textiles a pu être confirmée dans la majorité des cas. Cependant l'utilisation de signatures différentes de celles de l'agent actif a été nécessaire pour valider la présence de traitement dans le cas des textiles traités par co-précipitation. Enfin, un protocole de décapage doux a été testé pour faire face au problème particulier du recouvrement des textiles industriels par des apprêts siliconés / Time-of-Flight Secondary Ion Mass spectrometry (ToF-SIMS) allows the characterization of the outermost surface with high sensitivity by mass detection of atomic and molecular secondary ions. The objective of this work was to study its application in the context of the analysis of industrial textiles on which dermatological properties are given (cosmetotextiles). Three analytical approaches based on the specific properties of the active agents and technologies are presented. They required peculiar developments of methods (preliminary study, calibration, data processing and interpretation ...) and to consider the possibilities and limitations of the technique or the equipment in the particular context of these textile fibers analysis (topography, localized charge effect, contamination, complex formulations, segregation and concentration of some components from the treatments at the outermost surface ...).In the first approach, ToF-SIMS chemical mapping was used to successfully illustrate an active agent concentration gradient close to the outermost surface of polyamide matrices. The ability to identify the characteristic signatures of active agents and to validate their presence at the surface of textile samples was confirmed in most cases. However, signatures different from those from the active agent were needed to validate the treatment in the case of textiles treated by co-precipitation. Finally, a gentle sputtering protocol was tested to address the particular issue of industrial textiles covered with silicone based textile finishing

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.