As ligas do sistema Fe-Mn-Al-C constituem-se numa das famílias mais promissoras para o atendimento dos requisitos crescentes de disponibilidade de aços com altas relações resistência/peso, principalmente nas indústrias de transporte aeronáutica e automotiva, visando a redução no consumo de combustível e a consequente emissão de CO2. Suas densidades, cerca de 10% a 13% inferiores aos dos aços convencionais e a possibilidade de aumento de resistência mecânica por tratamentos de endurecimento pela precipitação de carboneto k (Fe,Mn)Al3C possibilitam a obtenção de elevadas resistências específicas. O uso de técnicas da Engenharia de Superfícies, associadas aos tratamentos térmicos adequados, podem ampliar a faixa de desempenho dessas ligas. Neste trabalho foram realizados tratamentos termoquímicos de boretação em sais fundidos, nitrocementação a plasma e cromização por pó em amostras de um aço com a composição Fe-31,2Mn-7,5Al-1,3Si-0,9C (% em peso), visando à obtenção de camadas de elevados desempenhos mecânicos e físicos. As camadas produzidas foram caracterizadas por meio de ensaios micrográficos, de dureza, desgaste e corrosão. Todos os tipos de tratamentos produziram camadas com resistências ao desgaste muito superiores às do substrato, com destaque para os tratamentos de boretação e de cromização, que produziram camadas com resistências ao desgaste cerca de nove e seis vezes superiores às do substrato, respectivamente. O tratamento de cromização produziu camada com resistência à corrosão por pites muito superior à do substrato. / The alloys of the Fe-Mn-Al-C system belong to one of the most promising families to meet the increasing requirements of availability of steels with high resistance/weight ratio, particularly in the aeronautics and automotive industries, aimed at reducing the consumption of fuel and consequent CO2 emissions. Their densities, between 10% to 13% lower than those of conventional steels, and the possibility of increased strength by hardening treatment by the precipitation of k carbides (Fe, Mn)Al3C, allow to obtain high specific resistance. The use of techniques of surface engineering, attached to suitable heat treatment, can extend the performance range of these alloys. In this work were carried out thermochemical boriding treatment in molten salts, plasma nitrocarburizing and pack chromizing in a Fe-31,2Mn 7,5Al-1,3Si-0,9C(wt%) steel, in order to obtain coatings with high mechanical and physical performances. The layers produced were characterized using micrographic, hardness, wear and corrosion tests. All treatments produced layers with wear resistance superior to that the substrate, especially the boriding and chromizing treatments, which produced layers with wear resistance around nine and six times higher than that of substrate, respectively. The chromizing treatment produced layer with pitting corrosion resistance superior to that of the substrate.

L’étude est focalisée sur l’activation d’alcynes fonctionnalisés par des complexes hétérobimétalliques [(OC)3Fe(µ-CO)(µ-Ph2PXPPh2)Pt(PPh3)] (X = CH2, NH) et [(OC)3Fe(Si(OMe)3)(µ-dppm)Pt(H)(PPh3)] conduisant à la formation de composés de type dimétallacyclopenténone et µ-vinylidène dont la réactivité a été exploitée. En particulier, un travail systématique a été mené avec divers alcynols et les données cristallographiques ont révélé l’existence de liaisons hydrogènes variées, intra ou intermoléculaires ; par ailleurs, la déshydratation de ces composés par HBF4 a généré des espèces de type allènylidène cationiques. Egalement, les réactions de diynes aliphatiques et aromatiques terminaux conduisent à des complexes Fe‒Pt [(OC)2Fe(µ-dppm)(µ-C(=O)CH=C{E-C≡CH}Pt(PPh3)] (E = espaceur) portant un alcyne libre, permettant la construction de systèmes tétranucléaires Fe‒Pt symétriques et asymétriques ou des assemblages hétéropolynucléaires Fe‒Pt-Co‒Co. La réaction de cycloaddition a été aussi réalisée sur la triple liaison libre avec des azotures R-N3 pour former des 1,2,3-triazoles organométalliques. Finalement, des études préliminaires concernant l’immobilisation des composés hétérobimétalliques Fe‒Pt sur des particules de silice Aerosil 200 ont été initiées. / The study deals on the heterobimetallic activation of functionalized alkynes by the complexes [(OC)3Fe(µ-CO)(µ-Ph2PXPPh2)Pt(PPh3)] (X = CH2, NH) and [(OC)3Fe(Si(OMe)3)(µ-dppm)Pt(H)(PPh3)] leading to the formation of various species such as dimetallacyclopentenones and μ-vinylidenes, whose reactivity has been investigated. In particular, a detailed study was carried using divers alkynols as substrates. X-ray crystallographic data reveal the occurrence of intra- and intermolecular hydrogen bonding; dehydratation of these compounds by HBF4 leads to formation of cationic allenylidene species. The reactions of aliphatic and aromatic diynes affords Fe‒Pt complexes [(OC)2Fe(µ-dppm)(µ-C(=O)CH=C{E-C≡CH}Pt(PPh3)] (E = spacer) bearing a second alkyne unit, allowing the construction of tetranuclear symmetric and asymmetric Fe‒Pt or heteropolynuclear Fe‒Pt-Co‒Co assemblies. Cycloaddition reactions using azides R-N3 were also performed on the pendant alkyne unit to form a series of organometallic 1,2,3-triazoles. Finally, preliminary studies have been undertaken to immobilize heterobimetallic Fe‒Pt compounds on the surface of Aerosil 200 silica particles.

I samband med att intresset för att bygga högre trähus har ökat så krävs nya lösningar för att t.ex. kunna möta efterfrågan på stora öppna ytor och långa spännvidder. Träbjälklag med lång spännvidd har dock oftast svårigheter med att klara kraven på svikt och vibrationer. Ett nyutvecklat förslag på träbjälklag som förmodas klara dessa krav bättre än traditionella träbjälklag har varit utgångspunkten för detta examensarbete där syftet har varit att undersöka bjälklagets styvhet. Detta gjordes laborativt genom att bygga och testa en prototyp av det föreslagna bjälklaget och genom att en numerisk modell baserad på finita element metoden togs fram och användes för att studera hur olika parametrar påverkar bjälklagets styvhetsegenskaper. Bjälklagets design bygger på fackverksprincipen i primärriktningen och på balkverkan i sekundärriktningen. De ingående komponenterna har kommit prefabricerade till Växjö universitet där de har monterats ihop till ett fullskaligt bjälklagselement. Elementet har sedan utsatts för ett antal belastningsfall där nedböjningarna uppmätts vilka sedan givit underlag för att få värden på bjälklagets effektiva styvhetsegenskaper. Både de laborativa och de simulerade resultaten visar på en hög böjstyvhet i primärriktningen d.v.s. 18,9•106 Nm2/m [EI/b] respektive 18,6•106 Nm2/m [EI/b]. Även böjstyvheten i sekundärriktningen är hög d.v.s. motsvarar 21,2 % respektive 17,1 % av styvheten i primärriktningen. I beräkningsmodellen har det dessutom undersökts hur ett övre lager av spånskivor inverkar på bjälklagets styvhet. / The interest for building higher and larger wooden houses has increased in Sweden during the last decade resulting in higher requirements on the technical performance of such structures in order to met demands on large open surfaces and large spans of floors. Wooden floor systems with large spans often have difficulties, however, to meet the vibration requirements. A novel floor system, likely to handle the vibration requirements better than traditional wooden floor systems, is the basis for this master thesis. The purpose is to examine the stiffness of the floor by building and testing a prototype and by producing a numerical model based on the finite element method. In the longitudinal, main load-bearing direction the floor system works as a truss with flanges of longitudinal oriented timber members and web diagonals of transversely oriented members. In the transverse direction the web diagonals work as beams. The components were prefabricated elsewhere and assembled at Växjö University into a prototype. The prototype was then exposed to a number of different load cases. Deflections were measured and stiffness properties of the floor were derived. In addition to the experimental analysis the numerical model was used to calculate deflections when subjected to different load cases and for evaluating the principal stiffness properties of the floor. Both the experimental and the calculated results using the numerical model show high bending stiffness in the longitudinal direction, EI/b = 18,9•106 Nm2/m and 18,6•106 Nm2/m respectively. Also the bending stiffness in the transversal direction is high and equivalent to 21,2 % or 17,1 % (testing and simulation respectively) of the bending stiffness in the longitudinal direction. Using numerical analysis, also the effect on the stiffness of adding an upper layer of a 22 mm particleboard was examined.

<p>I samband med att intresset för att bygga högre trähus har ökat så krävs nya lösningar för att t.ex. kunna möta efterfrågan på stora öppna ytor och långa spännvidder. Träbjälklag med lång spännvidd har dock oftast svårigheter med att klara kraven på svikt och vibrationer. Ett nyutvecklat förslag på träbjälklag som förmodas klara dessa krav bättre än traditionella träbjälklag har varit utgångspunkten för detta examensarbete där syftet har varit att undersöka bjälklagets styvhet. Detta gjordes laborativt genom att bygga och testa en prototyp av det föreslagna bjälklaget och genom att en numerisk modell baserad på finita element metoden togs fram och användes för att studera hur olika parametrar påverkar bjälklagets styvhetsegenskaper.</p><p>Bjälklagets design bygger på fackverksprincipen i primärriktningen och på balkverkan i sekundärriktningen. De ingående komponenterna har kommit prefabricerade till Växjö universitet där de har monterats ihop till ett fullskaligt bjälklagselement. Elementet har sedan utsatts för ett antal belastningsfall där nedböjningarna uppmätts vilka sedan givit underlag för att få värden på bjälklagets effektiva styvhetsegenskaper.</p><p>Både de laborativa och de simulerade resultaten visar på en hög böjstyvhet i primärriktningen d.v.s. 18,9•106 Nm2/m [EI/b] respektive 18,6•106 Nm2/m [EI/b]. Även böjstyvheten i sekundärriktningen är hög d.v.s. motsvarar 21,2 % respektive 17,1 % av styvheten i primärriktningen.</p><p>I beräkningsmodellen har det dessutom undersökts hur ett övre lager av spånskivor inverkar på bjälklagets styvhet.</p> / <p>The interest for building higher and larger wooden houses has increased in Sweden during the last decade resulting in higher requirements on the technical performance of such structures in order to met demands on large open surfaces and large spans of floors. Wooden floor systems with large spans often have difficulties, however, to meet the vibration requirements. A novel floor system, likely to handle the vibration requirements better than traditional wooden floor systems, is the basis for this master thesis. The purpose is to examine the stiffness of the floor by building and testing a prototype and by producing a numerical model based on the finite element method.</p><p>In the longitudinal, main load-bearing direction the floor system works as a truss with flanges of longitudinal oriented timber members and web diagonals of transversely oriented members. In the transverse direction the web diagonals work as beams. The components were prefabricated elsewhere and assembled at Växjö University into a prototype. The prototype was then exposed to a number of different load cases. Deflections were measured and stiffness properties of the floor were derived. In addition to the experimental analysis the numerical model was used to calculate deflections when subjected to different load cases and for evaluating the principal stiffness properties of the floor.</p><p>Both the experimental and the calculated results using the numerical model show high bending stiffness in the longitudinal direction, EI/b = 18,9•106 Nm2/m and 18,6•106 Nm2/m respectively. Also the bending stiffness in the transversal direction is high and equivalent to 21,2 % or 17,1 % (testing and simulation respectively) of the bending stiffness in the longitudinal direction. Using numerical analysis, also the effect on the stiffness of adding an upper layer of a 22 mm particleboard was examined.</p>

Iron (Fe) speciation is important for many biogeochemical processes. The high abundance and limited solubility of Fe(III) are responsible for the widespread occurrence of Fe(III) minerals in the environment. Co-precipitation and adsorption onto mineral surfaces limits the free concentrations of compounds such as arsenate (As(V)), Fe(III) and, phosphate (P(V)). Mineral dissolution, on the other hand, might lead to elevated concentrations of these compounds. Fe speciation is strongly affected by natural organic matter (NOM), which suppresses hydrolysis of Fe(III) via complexation. It limits the formation of Fe(III) minerals and Fe(III) co-precipitation. This thesis is focused on interactions between Fe(III) and NOM as well as their impact on other elements (i.e. As(V) and P(V)). X-ray absorption spectroscopy (XAS) was used to obtain molecular scale information on Fe and As speciation. This was complemented with infrared spectroscopy, as well as traditional wet-chemical analysis, such as pH and total concentration determinations. Natural stream waters, soil solutions, ground water and soil samples from the Krycklan Catchment, in northern Sweden, were analyzed together with model compounds with different types of NOM. A protocol based on ion exchange resins was developed to concentrate Fe from dilute natural waters prior to XAS measurements. Iron speciation varied between the stream waters and was strongly affected by the surrounding landscape. Stream waters originating from forested or mixed sites contained both Fe(II, III)-NOM complexes and precipitated Fe(III) (hydr)oxides. The distribution between these two pools was influenced by pH, total concentrations and, properties of NOM. In contrast, stream waters from wetland sites and soil solutions from a forested site only contained organically complexed Fe. Furthermore, the soil solutions contained a significant fraction Fe(II)-NOM complexes. The soil samples were dominated by organically complexed Fe and a biotite-like phase. Two pools of Fe were also identified in the ternary systems with As(V) or P(V) mixed with Fe(III) and NOM: all Fe(III) was complexed with NOM at low total concentrations of Fe(III), As(V) and/or P(V). Hence, Fe(III) complexation by NOM reduced Fe(III)-As(V)/P(V) interactions at low Fe(III) concentrations, which led to higher bioavailability. Exceeding the Fe(III)-NOM complex equilibrium resulted in the occurrence of Fe(III)-As(V)/P(V) (co-)-precipitates.

In this study a series of novel Fe-based materials derived from a bulk metallic glass-forming composition was investigated to improve the ductility of this high-strength glassy alloy. The interplay between the factors chemistry, structure and resulting mechanical properties was analyzed in detail. It has been recognized that subtle modifications of the chemical composition (carbon addition) lead to appreciable changes in the phase formation, which occurs upon solidification (from a single-phase structure to composite materials). As a consequence, significant differences in the mechanical response of the particular samples have been observed. The materials developed here were fabricated by centrifugal casting. To explore the structure features of the as-cast cylinders, manifold experimental techniques (X-ray diffraction, optical, as well as electron microscopy) were employed. The occurrence of the numerous reflections on the X-ray diffraction patterns has confirmed the crystalline nature of the studied Fe-based alloy systems. The subsequent extensive research on their deformation behavior (Vickers hardness and room temperature compression tests) has revealed that, although the glass-forming ability of the investigated compositions is not high enough to obtain a glassy phase as a product of casting, excellent mechanical characteristics (high strength - comparable to that of the reference bulk metallic glass (BMG) - associated with good ductility) were achieved for the “composite-like” alloys. In contrast, the single phase cylinders, subjected to compressive loading, manifested an amazing capacity for plastic deformation – no failure occurred. The fracture motives developed during deformation of the “composite-structured” samples were studied by scanning electron microscopy. The main emphasis has been put on understanding the mechanisms of crack propagation. Owing to the structural complexity of the deformed samples, it was crucial to elucidate the properties of the individual compounds. Based on the obtained results it was concluded that the coexistence of a soft f.c.c. γ-Fe phase in combination with a hard complex matrix is responsible for the outstanding mechanical response of the tested composites. While the soft particles of an austenite contribute to the ductility (they hinder the crack propagation and hence, cause unequivocal strain-hardening), the hard constituents of the matrix phase yield the strength.

The thesis is carried out in order to improve the transfer case in trucks with all-wheel-drive. When the truck loses traction at the rear wheels, due to slippery surfaces, wheel-spin occurs. If the driver engages the all-wheel-drive at a point where traction already has been lost, a relative rotational speed in the dog clutch will occur. If this relative speed is too high the dog clutch bounces of itself before coupling or it does not couple at all. To avoid this problem, the geometry of the teeth is modified. FE simulations are done for the existing model as well as for all the new models in order to find out which of them can handle the highest relative rotational speed. The results show that the original model is not the best one. Simple modifications of the teeth’s chamfer distance and chamfer angle shows that the dog clutch can handle up to 120 rpm of relative rotational speed whereas the original model only handles 50 rpm. / Examensarbetet är utfört för att försöka förbättra inkopplingen av allhjulsdrift på lastbilar. När en lastbil kör på halt eller löst väglag kan hjulspinn uppstå vid bakhjulen. Om föraren kopplar in allhjulsdriften när hjulen börjat slira uppstår en relativ rotationshastighet mellan halvorna i klokopplingen. Om denna relativa rotationshastighet är för hög kommer halvorna i kopplingen studsa mot varandra innan de kopplas ihop eller inte koppla ihop alls. För att undvika detta problem har klokopplingens tandgeometri modifierats. FE simuleringar är gjorda på den ursprungliga modellen samt alla nya modeller för att ta reda på vilken som kopplar vid högst relativa rotationshastighet. Resultaten visar att förbättringar kan göras. Enkla modifieringar på avfasningarnas avstånd och vinklar visar att klokopplingen kan klara upp till 120 rpm i relativ rotationshastighet jämfört med den ursprungliga modellen som endast klarar 50 rpm.

Ce travail de thèse est axé sur le développement d'une technique de traitement chimique par déchloration réductrice de l'hexachlorobutadiène (HCBD) et de l'hexachloroéthane (HCA). La première partie a consisté en l'acquisition de données expérimentales de solubilité des deux composés (i) à différentes températures et (ii) en présence de surfactants. Les essais en température ont notamment permis de proposer, par le calcul des variations des grandeurs thermodynamiques de dissolution, une explication physique à la présence d'un minimum de solubilité entre 12 et 45 °C. La seconde partie, basée sur une étude préalable de sélection d'un réactif pour son efficacité, a consisté principalement en l'étude du mécanisme de déchloration réductrice par les microparticules de Pd/Fe en suspension dans l'acide polylactique, un polymère biodégradable. Différentes conditions expérimentales ont permis de démontrer que l'hydrogène atomique est le principal réducteur du système. Plusieurs lois cinétiques ont ensuite été utilisées pour la modélisation de la disparition de HCBD et HCA en études individuelles et en mélange. / This work focused on the reductive dechlorination of hexachlorobutadiene (HCBD) and hexachloroethane (HCA). The first part consisted of experimental measurement of solubility data for both compounds (i) at different temperatures and (ii) in the presence of surfactants. Thermodynamic parameters for dissolution have been calculated in order to propose a physical explacation of the minimum solubility observed between 12 and 45 °C. The second part, based on a preliminary selection of a reaction for its efficiency, aimed to investigate the mechanism of the reductive dechlorination of HCBD and HCA by Pd/Fe microparticles in suspension in polylactic acid. Different experimental conditions have shown that atomic hydrogen is the main reductant of the system. Different kinetic laws were then used for the modeling of the disappearance of HCBD and HCA, taken separately and in mixture.

Made available in DSpace on 2015-05-08T15:00:07Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2402829 bytes, checksum: 4c7bc88fa5d8c55de36b5f29f4cc3cf0 (MD5) Previous issue date: 2011-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents a study about microstructural evolution of nanocrystalline alloys Fe50%Si processed by milling of high energy. With the objective of pondering the process variables, a factorial design 2² with central point was used. The design formed the basis for the development of a semi-empirical model of Fe-Si phase formation, which subsequently led to the response surface equation. The samples were characterized by Xray Fluorescence, Scanning Electron Microscope (SEM), Mössbauer Spectroscopy and Xray diffraction. The structural changes are discussed based on obtained diffractograms and using the Rietveld refinement in the TOPAS software. By calculating the effects of variables, it's shown that for the characteristics of the used system, the milling time has a preponderant effect on the other ones. The study on the evolution of the performed lattice parameter shows the occurrence of two distinct phases with increasing rotation speed and milling time. This evolution demonstrates a transition from disordered to ordered phase of Fe-Si intermetallic compound. / Este trabalho apresenta um estudo sobre a evolução microestrutural de ligas nanocristalinas de Fe50%Si formadas através do processo de moagem de alta energia. Com o objetivo de ponderar sobre as variáveis do processo, um planejamento fatorial 2² com ponto central foi utilizado. O planejamento serviu de base para o desenvolvimento de um modelo semi-empírico de formação da fase Fe-Si que, posteriormente, originou a superfície de resposta da equação. As amostras foram caracterizadas por Fluorescência de Raios-X, Microscopia Eletrônica de Varredura, Espectros de Mössbauer e Difração de Raios-X. As mudanças estruturais são discutidas com base nos difratogramas obtidos e utilizando o refinamento de Rietveld no programa TOPAS. Através do cálculo dos efeitos das variáveis, mostra-se que para as características do sistema utilizado, o tempo de moagem possui um efeito preponderante sobre as demais. O estudo sobre a evolução do parâmetro de rede realizado mostra a ocorrência de duas fases distintas com o incremento da velocidade de rotação e do tempo de moagem. Tal evolução revela a passagem da fase desordenada para ordenada do composto intermetálico Fe-Si.

As ligas do sistema Fe-Mn-Al-C constituem-se numa das famílias mais promissoras para o atendimento dos requisitos crescentes de disponibilidade de aços com altas relações resistência/peso, principalmente nas indústrias de transporte aeronáutica e automotiva, visando a redução no consumo de combustível e a consequente emissão de CO2. Suas densidades, cerca de 10% a 13% inferiores aos dos aços convencionais e a possibilidade de aumento de resistência mecânica por tratamentos de endurecimento pela precipitação de carboneto k (Fe,Mn)Al3C possibilitam a obtenção de elevadas resistências específicas. O uso de técnicas da Engenharia de Superfícies, associadas aos tratamentos térmicos adequados, podem ampliar a faixa de desempenho dessas ligas. Neste trabalho foram realizados tratamentos termoquímicos de boretação em sais fundidos, nitrocementação a plasma e cromização por pó em amostras de um aço com a composição Fe-31,2Mn-7,5Al-1,3Si-0,9C (% em peso), visando à obtenção de camadas de elevados desempenhos mecânicos e físicos. As camadas produzidas foram caracterizadas por meio de ensaios micrográficos, de dureza, desgaste e corrosão. Todos os tipos de tratamentos produziram camadas com resistências ao desgaste muito superiores às do substrato, com destaque para os tratamentos de boretação e de cromização, que produziram camadas com resistências ao desgaste cerca de nove e seis vezes superiores às do substrato, respectivamente. O tratamento de cromização produziu camada com resistência à corrosão por pites muito superior à do substrato. / The alloys of the Fe-Mn-Al-C system belong to one of the most promising families to meet the increasing requirements of availability of steels with high resistance/weight ratio, particularly in the aeronautics and automotive industries, aimed at reducing the consumption of fuel and consequent CO2 emissions. Their densities, between 10% to 13% lower than those of conventional steels, and the possibility of increased strength by hardening treatment by the precipitation of k carbides (Fe, Mn)Al3C, allow to obtain high specific resistance. The use of techniques of surface engineering, attached to suitable heat treatment, can extend the performance range of these alloys. In this work were carried out thermochemical boriding treatment in molten salts, plasma nitrocarburizing and pack chromizing in a Fe-31,2Mn 7,5Al-1,3Si-0,9C(wt%) steel, in order to obtain coatings with high mechanical and physical performances. The layers produced were characterized using micrographic, hardness, wear and corrosion tests. All treatments produced layers with wear resistance superior to that the substrate, especially the boriding and chromizing treatments, which produced layers with wear resistance around nine and six times higher than that of substrate, respectively. The chromizing treatment produced layer with pitting corrosion resistance superior to that of the substrate.