<p>The aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.<br /><br />The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.</p>

The aim of this thesis is to investigate how material surfaces are affected by various surface treatments and how this relates to the adhesion of the coating. The materials that were studied were WC-Co and Cermets and the surface treatments used were polishing, grinding with coarser and finer abrasive grains, and finally wet blasting and dry blasting. Focus was on deformations and residual stresses in the surface, surface roughness and cracks. The test methods used for examining the samples included surface roughness measurements, residual stress measurements, adhesion tests using Rockwell indentation and SEM images of the surface and the cross section.<br /><br />The results concluded that polishing gives very good adhesion. Additionally, the adhesion for ground surfaces was good for WC-Co but very poor for Cermets. Furthermore, it was observed that finer abrasive grains did not result in better adhesion. In fact, the coarser grains gave slightly better results. Finally, it was concluded that wet blasting has a clear advantage over dry blasting and results in much better adhesion, especially for the Cermets. The results for the WC-Co were a bit inconsistent and so further research is required.

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Problembakgrund: Finansiella rapporter är ett sätt för företagen att kommunicera med investerare och intressenter. Samtidigt som det finns lagar och förordningar som styr redovisning och rapporterns utseende finns det goda möjligheter för företagsledningen att påverka de siffror som presenteras i de publika rapporterna genom periodiseringar. Denna studie tar konceptet kring att investera baserat på graden av periodiseringar till den svenska aktiemarknaden. Problemformulering: Är det möjligt att generera riskjusterad överavkastning på den svenska aktiemarknaden med periodiseringsbaserade investeringsstrategier? Syfte: Huvudsyftet med studien är att undersöka investerares möjlighet till riskjusterad överavkastning på den svenska aktiemarknaden utifrån investeringsstrategier baserade på graden av periodiseringar. Ett delsyfte är att jämföra två delperioder för att undersöka om periodiseringsanomalins förekomst förändrats över den totala undersökningsperioden. Ett annat delsyfte är att undersöka om den svenska aktiemarknaden effektivt värderar offentlig redovisningsinformation. Teori: Studien baseras huvudsakligen på tidigare periodiseringsbaserad forskning utförd på den amerikanska aktiemarknaden där Sloan (1996) anses vara den som introducerade teorin kring periodiseringsanomalier så som den ter sig idag. Metod: En kvantitativ studie med en deduktiv ansats. Den empiriska undersökningen baseras på redovisnings- och aktiedata under tidsperioden 1996-12-31 till 2013-06-30 som kommer från Thomson Reuters Datastream och Worldscope. Empiri &amp; analys: Resultatet av studien tyder på att det finns en negativ korrelation mellan periodiseringar och avkastning samt visar stöd för att periodiseringsanomalin existerar på den svenska aktiemarknaden. Av de periodiseringsmått som testats visade det sig att ΔNOA och ΔWC gav högst överavkastning. Slutsats: Studien indikerar att felprissättningar förekommer och att periodiseringsanomalin existerar på den svenska aktiemarknaden. Den höga exponeringen mot riskfyllda småbolag innebär att vinstmöjligheterna minskar något på grund av höga implementeringskostnader samtidigt som det gör strategierna mindre attraktiva för institutionella investerare. Det är därför upp till privata investerare att utnyttja dessa felprissättningar.

Les carbures et oxydes des métaux de transition sont d'une importance capitale dans le domaine industriel voir catalytique. Le carbure de tungstène WC a été identifié comme un bon substituant des métaux nobles tel que le platine dans le domaine catalytique. Le but de ce travail de thèse est d'appliquer des méthodes de chimie quantique les plus poussées pour déterminer la structure électronique, la stabilité et la nature de liaison chimique des diatomiques WC et WC2+. Notre recherche préliminaire est motivée par les données spectroscopiques disponibles sur W, W+, W2+, WC et WC2+. La méthodologie adoptée, CASSCF/MRCI/MRCI+Q/aug-cc-pV5Z(-PP) implémentée dans le code MOLPRO, consiste à réaliser des calculs quantique tenant en compte des effets de corrélation et relativistes avec un traitement spécifique du couplage spin−orbite pour la recherche des courbes d'énergie potentielle de l'état fondamental et des états excités de plus basses énergies de WCn+ (n=0-2) tout en utilisant une base suffisamment étendue. Les résultats de ce travail sont en bon accord avec ceux disponibles dans la littérature. En outre, dans ce travail nous avons confirmé pour la première fois que le carbure diatomique dicationique WC2+ est thermodynamiquement stable / Metal carbides and oxides are more interesting in catalytic and industrial domains. Tungsten carbide WC has been detected as serious substituent of platinum Pt catalytic. The ultimate goal of this thesis is theoretical studies of electronic structure, stability and the bound nature on WC, WO and its cations. Our preliminary research were motiving by the available spectroscopic data on W, W+, W2+, WC et WC2+. We used the methodology (CASSCF/MRCI/MRCI+Q/aug-cc-pV5Z(-PP)) implemented on MOLPRO package to perform quantum calculations with high accuracy taking into account the correlation and relativistic effects with a specific treatment of spin orbit coupling for some low lying excited electronic states of WCn+, (n=0, 1 et 2). Our results are shown in good agreement with those available in the literature. Furthermore, in this work for the first time we demonstrated that a carbide dication (WC2+) is thermodynamically stable

Submitted by FERNANDO SANTOS DA SILVA null (fernandoquimicauems@hotmail.com) on 2017-09-28T02:21:06Z No. of bitstreams: 1 Tese_Fernando_Santos_da_Silva_IQ_UNESP.pdf: 19317124 bytes, checksum: b4f79b295bc22505ca8f3f01bd3db519 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-28T14:59:57Z (GMT) No. of bitstreams: 1 silva_fs_dr_araiq.pdf: 19317124 bytes, checksum: b4f79b295bc22505ca8f3f01bd3db519 (MD5) / Made available in DSpace on 2017-09-28T14:59:57Z (GMT). No. of bitstreams: 1 silva_fs_dr_araiq.pdf: 19317124 bytes, checksum: b4f79b295bc22505ca8f3f01bd3db519 (MD5) Previous issue date: 2017-09-15 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho teve como objetivo investigar a microestrutura, resistência à corrosão e propriedades mecânicas de revestimentos produzidos por Aspersão Fria (AF) a base de: (I) pó de alumínio (Al), com ou sem alumina (Al2O3), depositados sobre aço comum; (II) revestimentos metálico-cerâmicos de WC-12Co e WC-25Co depositados sobre a liga Al7075-T6 e (III) revestimentos de cobre depositados sobre aço e obtidos a partir de pós submetidos a diferentes tratamentos. A análise dos materiais de partida e dos revestimentos, antes e após os ensaios de corrosão, foi realizada por difração a laser (DL), microscopia óptica (OM), microscopia eletrônica de varredura (SEM) acoplado a um sistema de espectroscopia de dispersão de energia de raios X (EDS) e difração de raios X (DRX). Foram realizadas medidas de dureza e ensaios de resistência ao desgaste por abrasão (Rubber Wheel) e por deslizamento (Ball on disk). A resistência à corrosão dos revestimentos foi avaliada por medidas eletroquímicas em meio de NaCl 3,5% e testes de névoa salina. Foram realizadas medidas de potencial em circuito aberto (ECA), espectroscopia de impedância eletroquímica (EIS) e curvas de polarização linear e cíclica. As imagens de SEM da secção transversal mostram que os revestimentos são densos, não possuem porosidade interconectada e nem trincas. Os resultados eletroquímicos e de névoa salina mostram que todos os revestimentos investigados protegem o substrato por longos tempos de imersão por serem compactos quando obtidos pela tecnologia de AF. Para os revestimentos a base de alumínio, os estudos mostram que o eletrólito atinge o substrato em alguns pontos somente após 2000 h de imersão e os ensaios de desgaste indicam que o revestimento compósito Al-Al2O3 apresenta melhores propriedades mecânicas. Quanto aos revestimentos metálicocerâmicos, o revestimento de WC-25Co apresentou maior espessura e também maior proteção contra corrosão até tempos maiores do que 2000 h. A caracterização dos revestimentos de cobre mostra claramente que os diferentes tratamentos dos materiais de partida exercem influência na eficiência de deposição, formação dos revestimentos e principalmente na sua resistência à corrosão. / The purpose of this work was to investigate the microstructure, corrosion resistance and mechanical properties of coatings prepared by Cold Gas Spray (CGS) based on: (I) aluminum (Al) powder with or without alumina (Al2O3), deposited on common steel; (II) WC-12Co and WC-25Co metallic-ceramic coatings deposited onto Al7075- T6 alloy and (III) copper coatings deposited onto common steel and obtained from powders submitted to different treatments. The analysis of the feedstock materials and the coatings before and after the corrosion tests were performed by laser diffraction (LD), optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy system (EDS) and X-ray diffraction (XRD). Hardness measurements, abrasion testing (Rubber Wheel) and sliding wear test (Ball on disk) were performed. The corrosion resistance of the coatings was evaluated by electrochemical measurements in 3.5% NaCl medium, and salt fog tests. Open circuit potential (EOC), electrochemical impedance spectroscopy (EIS), linear and cyclic polarization measurements were performed. SEM images of the cross section showed that coatings are dense, without interconnected porosity and cracks. Electrochemical and salt fog results show that all investigated coatings protect the substrate during long immersion times because they are compact when obtained by CGS technology. For the aluminum based coatings, the studies show that the electrolyte reaches the substrate at some points only after 2000 h of immersion and the wear tests show that the Al-Al2O3 composite coating has better mechanical properties. For the metal-ceramic coatings, the WC-25Co coating show higher thickness and corrosion protection up to 2000 h of immersion when compared to WC-12Co. Copper coatings characterization clearly shows that the different treatments of the feedstock materials exert influence on the deposition efficiency, coating formation and especially on their corrosion resistance. / CNPq: 153177/2014-4