The current, commercially available, press and sinter Al-Mg-Si-Cu alloys are based on wrought or cast alloy compositions and have not been tailored for the press and sinter process. The limited development of the Al-Mg-Si-Cu alloys for the press and sinter process can be partly attributed to a poor understanding of the effects of processing conditions on the sintering behaviour. The primary objective of this work was to investigate and understand the effects of processing conditions on the sintering behaviour of Al-Mg-Si-Cu-(Sn) alloys. Dilatometry was used in conjunction with other experimental techniques to elucidate and understand the expansion and shrinkage events that occur during the liquid-phase sintering of Al-Mg-Si-Cu-(Sn) powder metallurgy alloys. Samples were uni-axially pressed from elemental metal powder blends, de-waxed, and then sintered in a horizontal push-rod dilatometer to record the dimensional changes in the pressing direction. The processing conditions examined included the alloy composition, temperature, green density and atmosphere. A liquid forms during heating due to reactions between the alloying elements and the aluminium. This liquid is initially non-wetting on the oxide layer of the aluminium particles, resulting in separation of the particles, which is manifested by expansion of the sample. The oxide is reduced as sintering progresses, alleviating the non-wetting conditions. When more liquid forms, further expansion occurs, despite the improved wetting conditions. It is proposed that atmospheric oxygen and/or nitrogen can react with the liquid, forming a solid phase (‘shell’) at the liquid-vapour interfaces. These shells prevent the liquid from wetting the particles, resulting in further expansion and preventing shrinkage. Unbalanced diffusivities (the Kirkendall effect) between the aluminium and silicon contribute to the expansion. A mechanism is proposed to account for the transition to shrinkage, whereby the shells at the liquid-vapour interface rupture when there is a rapid increase in the volume of contained liquid. The liquid then flows out and over the shells, onto the aluminium substrate, causing shrinkage. Magnesium and nitrogen delay the transition to shrinkage by facilitating nitride shell formation at the solid-liquid interface. Silicon and tin cause an earlier transition to shrinkage by increasing the liquid volume. In addition, tin promotes shrinkage by segregating to the liquid-vapour interfaces, limiting the thickness of the shells at the liquid-vapour interfaces. The two dominant liquid-phase shrinkage mechanisms during the sintering of Al-Mg-Si-Cu-(Sn) alloys are rearrangement and pore-filling. Contact-flattening is not a dominant shrinkage mechanism, but may occur concurrently with the other mechanisms. If contact flattening occurs, a decrease in the pressure of isolated pores increases the total shrinkage rate. Nitrogen increases the shrinkage rate during rearrangement by restricting grain-growth. Magnesium increases the shrinkage rate during rearrangement by reducing the solid-liquid interface energy. Magnesium and nitrogen are essential for the formation of nitride within isolated pores, which decreases the pore pressure and increases the contribution of contact-flattening on the total shrinkage rate. Silicon reduces the beneficial influence of magnesium during rearrangement by diluting the magnesium content in the liquid. Silicon increases the pore-filling rate due to an increase in the liquid volume. Magnesium increases the pore-filling rate by facilitating aluminium nitride formation within isolated pores and by increasing the pore-filling. Tin additions can decrease the pore-filling rate due to its segregation to the liquid-vapour interface, limiting the consumption of nitrogen within isolated pores.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this study, the effects of Aluminium (Al) and of different diets, both individually and in association, were investigated through the determination of NTPDase, 5 -nucleotidase and acetylcholinesterase (AChE) activities in rat brain. In addition, we investigated said effects on oxidative stress by determining activity of the antioxidant enzyme catalase as well as lipid peroxidation by measuring TBARS levels. Male rats were exposed to Al (50 mg/kg/day) by gavage during three months. NTPDase and 5 -nucleotidase activities were then determined in synaptosomes of cerebral cortex and hippocampus, as well as in platelets. ATP, ADP and AMP hydrolysis was increased in both synaptosomes of cerebral cortex and hippocampus, as well as in platelets. AChE activity and TBARS levels were determined in homogenate of different brain structures in mice exposed to Al (2.7 mg/kg/day) by gavage during three months. The group that received Al+sodium citrate presented an increase in AChE activity in hippocampus, striatum, cortex and hypothalamus. On the other hand, the group that received only Al presented a decrease in AChE activity in hypothalamus and an increase in striatum. Moreover, AChE was determined in S1 of different brain structures, synaptosomes of cerebral cortex and erythrocytes of male rats exposed to Al (50 mg/kg/day) by gavage during three months. There was an increase in AChE activity in S1 of striatum and hypothalamus and in synaptosomes of cerebral cortex and erythrocytes. However, in S1 of cerebellum, hippocampus and cortex there was a decrease. In addition, the effect of diets rich in saturated fat and refined sugar on AChE activity in homogenate of different brain structures, on catalase activity in liver and on TBARS levels in plasma and liver were determined in female and male rats. There was a decrease in AChE activity in hippocampus, cortex and hypothalamus of male and female rats given both a diet rich in saturated fat and a diet rich in refined sugar. There was no alteration of AChE activity in cerebellum and striatum. For both diets, catalase activity was increased in liver of male and female rats. In addition, considering the alterations brought about by the individual exposure to both environmental factors, Al and diets, the effect of the association of both factors was evaluated. Thus, after a period of three months of exposure to both Al (50 mg/kg/day) by gavage and diets rich in saturated fat and saturated/polyunsaturated fat ad libitum, NTPDase and 5 -nucleotidase activities were determined in synaptosomes of cerebral cortex and platelets of rats. Animals receiving both diets in association with Al and Al/Ci presented an increase in ATP, ADP and AMP hydrolysis in synaptosomes of cerebral cortex and platelets. The results obtained in the present study demonstrate that exposure to both environmental factors, Al and diets rich in saturated fat and refined sugar, either individually or in association, affected the purinergic and cholinergic systems and caused oxidative stress in rats. / Neste estudo, investigamos os efeitos do alumínio (Al) e de diferentes dietas, individualmente e em associação, através da determinação da atividade das enzimas NTPDase, 5 -nucleotidase e acetilcolinesterase (AChE) no encéfalo de roedores. Adicionalmente, investigamos o estresse oxidativo, através da atividade da enzima antioxidante catalase, e a peroxidação lipídica pela medida dos níveis de TBARS. Ratos machos foram expostos ao Al (50 mg/kg/dia) através de gavagem, por um período de 3 meses. Após o tratamento, foi determinada a atividade das enzimas NTPDase e 5 -nucleotidase em sinaptossoma de córtex cerebral, hipocampo e plaquetas. A hidrólise dos nucleotídeos ATP, ADP e AMP foi aumentada, nas frações sinaptossomais de córtex cerebral e hipocampo bem como nas plaquetas. A atividade da AChE e os níveis de TBARS foram determinados em homogeneizado de diferentes estruturas cerebrais de camundongos expostos ao Al (2,7 mg/kg/dia), através de gavagem, por um período de 3 meses. Quanto à atividade da AChE, o grupo que recebeu Al+citrato de sódio apresentou um aumento da atividade desta enzima em hipocampo, estriado, córtex e hipotálamo. Já o grupo que recebeu só Al apresentou uma diminuição da atividade em hipotálamo e um aumento em estriado. Além disto, a atividade da AChE foi determinada em S1 de diferentes estruturas cerebrais, sinaptossoma de córtex cerebral, e em eritrócitos de ratos machos expostos à Al (50 mg/kg/dia), através de gavagem, por 3 meses. A atividade da AChE apresentou um aumento em S1 de estriado e hipotálamo, e em sinaptossoma de córtex cerebral e eritrócitos. Porém, em sobrenadante (S1) de cerebelo, hipocampo e córtex houve uma diminuição. Adicionalmente, foi determinado o efeito de dietas ricas em gordura saturada e açúcar refinado sobre a atividade da enzima AChE em homogeneizado de diferentes estruturas encefálicas, e atividade da enzima catalase em fígado, e os níveis de TBARS em plasma e fígado de ratos machos e fêmeas. A atividade da AChE em hipocampo, córtex e hipotálamo de ratos machos e fêmeas foi diminuída, após exposição a ambas as dietas, rica em gordura e rica em açúcar. Nas estruturas cerebelo e estriado não houve alteração na atividade da AChE. Após o consumo de ambas as dietas, a atividade da enzima catalase foi aumentada em fígado de ratos machos e fêmeas. Adicionalmente, considerando todas as alterações ocasionadas pela exposição individual aos fatores ambientais, Al e dietas, foi avaliado o efeito da associação entre esses dois fatores. Dessa forma, após um período de 3 meses de exposição conjunta ao Al (50 mg/kg/dia) através de gavagem e o consumo ad libitum de dietas ricas em gordura saturada e gordura saturada/poliinsaturada, foram determinadas a atividade das enzimas NTPDase e 5 - nucleotidase em sinaptossomas de córtex cerebral e plaquetas de ratos. Os animais que receberam ambas as dietas administradas em conjunto com Al e Al/Ci apresentaram um aumento na hidrólise dos nucleotídeos ATP, ADP e AMP, em sinaptossoma de córtex cerebral e plaquetas. Os resultados obtidos no presente estudo relatam que a exposição de roedores a ambos os fatores ambientais Al e dietas ricas em gordura saturada e açúcar refinado, individualmente e em conjunto, afetam os sistemas purinérico e colinérgico, e causam estresse oxidativo.

Das Ziel dieser Arbeit ist die ganzheitliche Erfassung der Haftmechanismen zwischen Metallbeschichtungen (Kupfer, Aluminium) und Polymersubstraten (Polyetheretherketon) funktionalisiert durch Draht-Lichtbogenspritzen. Hierzu werden die Vorbehandlung sowie der Applikationsprozess erforscht. An den hergestellten Fügeverbindungen erfolgen unterschiedliche mechanische Versuche zur Ermittlung der Hafteigenschaften und der Auswirkungen des Beschichtungsvorgangs auf die Substrate. Zur Analyse des Interfaces kommen mikroskopische (REM, TEM, HR-TEM), spektroskopische (EDX) und diffraktometrische (SAED, XRD) Verfahren zum Einsatz. Anhand der Ergebnisse erfolgt die Durchdringung des Anbindungsprozesses. Die thermisch und mechanisch bedingten Einflüsse auf das Substrat sowie dessen Eigenschaftsprofil sind in ihrer geometrischen Ausdehnung (mikroskopisch) begrenzt. Die Bestätigung für die mechanische Verklammerung wird erbracht. Durch eine HR-TEM-Untersuchung des Interfaces erfolgt der Nachweis von Oxiden und Hydroxiden. Diese stellen die Voraussetzung für physikalisch und chemisch bedingte Haftmechanismen dar.:1 Einleitung und Problemstellung 19 2 Stand von Wissenschaft und Technik 21 2.1 Hochpolymere Werkstoffe 21 2.1.1 Bildungsreaktionen 21 2.1.2 Einteilung der Polymere 24 2.1.3 Mechanische und thermische Eigenschaften 28 2.2 Thermisches Spritzen nach DIN EN 657 28 2.2.1 Draht-Lichtbogenspritzen 30 2.2.2 Substratvorbehandlung nach DIN EN 13507 31 2.2.3 Analyse von thermisch applizierten Schichten 33 2.2.3.1 Haftzugfestigkeit (DIN EN 582) 33 2.2.3.2 Eigenspannungen 37 2.3 Polyetheretherketon als Konstruktions- und Substratwerkstoff 41 2.4 Haftmechanismen zwischen Polymer und Metall 47 2.4.1 Haftungstheorien 47 2.4.2 Resultierende Gesamthaftung 55 2.4.3 Metalloxid-Polymer-Komplexe 56 3 Zielstellung und methodische Vorgehensweise 59 4 Metallisierung von Polyetheretherketon 62 4.1 Analyse der Substratwerkstoffe 62 4.2 Auswahl der Spritzzusatzwerkstoffe 67 4.3 Substratvorbehandlung 68 4.4 Applikation metallischer Schichten durch Draht-Lichtbogenspritzen 77 5 Ergebnisse und Diskussion 85 5.1 Metallographische Analyse 85 5.2 Mechanische Charakterisierung des funktionalisierten Polyetheretherketon 90 5.2.1 Nano-Eindringprüfung 90 5.2.2 Haftzugversuch 95 5.2.3 Zugversuch und Grauwertanalyse 102 5.2.4 Scratch-Test 109 5.2.5 Biegeversuch 115 5.2.6 Schlagbiegeversuch (CHARPY) 119 5.2.7 Fazit der mechanischen Charakterisierung 122 5.3 Eigenspannungsanalyse (Krümmungsmethode) 124 5.4 Analyse des Interfaces 129 5.4.1 Rasterelektronenmikroskopie und Röntgenspektroskopie 129 5.4.2 Hochauflösende Transmissionselektronenmikroskopie (HR-TEM) 134 6 Fazit 142 7 Zusammenfassung 144 8 Ausblick 147 9 Literaturverzeichnis 148 10 Anhang 156 / The aim of this work is the holistic detection of the adhesion mechanisms between metal coatings (copper, aluminum) and polymer substrates (polyetheretherketone) functionalized by wire arc spraying. For this purpose, the pretreatment and the application process are researched. Different mechanical tests are carried out on the manufactured joints to determine the adhesive properties and the effects of the coating process on the substrates. For the analysis of the interface, microscopic (SEM, TEM, HR-TEM), spectroscopic (EDX) and diffractometric (SAED, XRD) methods are used. Based on the results, the investigation of the connection process is carried out. The ther-mally and mechanically conditioned influences on the substrate as well as its property profile are limited in their geometrical extent (microscopically). The confirmation for the mechanical clamping is provided. An HR-TEM examination of the interface reveals the presence of oxides and hydroxides. These are the requirements for physically and chemically induced adhesive mechanisms.:1 Einleitung und Problemstellung 19 2 Stand von Wissenschaft und Technik 21 2.1 Hochpolymere Werkstoffe 21 2.1.1 Bildungsreaktionen 21 2.1.2 Einteilung der Polymere 24 2.1.3 Mechanische und thermische Eigenschaften 28 2.2 Thermisches Spritzen nach DIN EN 657 28 2.2.1 Draht-Lichtbogenspritzen 30 2.2.2 Substratvorbehandlung nach DIN EN 13507 31 2.2.3 Analyse von thermisch applizierten Schichten 33 2.2.3.1 Haftzugfestigkeit (DIN EN 582) 33 2.2.3.2 Eigenspannungen 37 2.3 Polyetheretherketon als Konstruktions- und Substratwerkstoff 41 2.4 Haftmechanismen zwischen Polymer und Metall 47 2.4.1 Haftungstheorien 47 2.4.2 Resultierende Gesamthaftung 55 2.4.3 Metalloxid-Polymer-Komplexe 56 3 Zielstellung und methodische Vorgehensweise 59 4 Metallisierung von Polyetheretherketon 62 4.1 Analyse der Substratwerkstoffe 62 4.2 Auswahl der Spritzzusatzwerkstoffe 67 4.3 Substratvorbehandlung 68 4.4 Applikation metallischer Schichten durch Draht-Lichtbogenspritzen 77 5 Ergebnisse und Diskussion 85 5.1 Metallographische Analyse 85 5.2 Mechanische Charakterisierung des funktionalisierten Polyetheretherketon 90 5.2.1 Nano-Eindringprüfung 90 5.2.2 Haftzugversuch 95 5.2.3 Zugversuch und Grauwertanalyse 102 5.2.4 Scratch-Test 109 5.2.5 Biegeversuch 115 5.2.6 Schlagbiegeversuch (CHARPY) 119 5.2.7 Fazit der mechanischen Charakterisierung 122 5.3 Eigenspannungsanalyse (Krümmungsmethode) 124 5.4 Analyse des Interfaces 129 5.4.1 Rasterelektronenmikroskopie und Röntgenspektroskopie 129 5.4.2 Hochauflösende Transmissionselektronenmikroskopie (HR-TEM) 134 6 Fazit 142 7 Zusammenfassung 144 8 Ausblick 147 9 Literaturverzeichnis 148 10 Anhang 156