The aim of this thesis is to investigate the effects of additives, reactive elements and impurities, on the lifetime of thermal barrier coatings. The thesis consists of a number of studies on interface adhesion, impurity diffusion, grain boundary sliding and cleavage processes and their impact on the mechanical behaviour of grain boundaries. The effects of additives and impurity on interface adhesion were elaborated by using total energy calculations, electron localization and density of states, and by looking into the atomic separations. The results of these calculations allow the assessment of atomic level contributions to changes in the adhesive trend. Formation of new bonds across the interface is determined to improve the adhesion in reactive element(RE)-doped structures. Breaking of the cross interface bonds and sulfur(S)-oxygen(O) repulsion is found responsible for the decreased adhesion after S segregation. Interstitial and vacancy mediated S diffusion and the effects of Hf and Pt on the diffusion rate of S in bulk NiAl are studied. Hf is shown to reduce the diffusion rate, and the preferred diffusion mechanism of S and the influence of Pt are revealed to be temperature dependent. Finally, the effects of reactive elements on alumina grain boundary strength are studied. Reactive elements are shown to improve both the sliding and cleavage resistance, and the analysis of atomic separations suggest an increased ductility after the addition of quadrivalent Hf and Zr to the alumina grain boundaries.

The aim of this thesis is to investigate the effects of additives, reactive elements and impurities, on the lifetime of thermal barrier coatings. The thesis consists of a number of studies on interface adhesion, impurity diffusion, grain boundary sliding and cleavage processes and their impact on the mechanical behaviour of grain boundaries. The effects of additives and impurity on interface adhesion were elaborated by using total energy calculations, electron localization and density of states, and by looking into the atomic separations. The results of these calculations allow the assessment of atomic level contributions to changes in the adhesive trend. Formation of new bonds across the interface is determined to improve the adhesion in reactive element(RE)-doped structures. Breaking of the cross interface bonds and sulfur(S)-oxygen(O) repulsion is found responsible for the decreased adhesion after S segregation. Interstitial and vacancy mediated S diffusion and the effects of Hf and Pt on the diffusion rate of S in bulk NiAl are studied. Hf is shown to reduce the diffusion rate, and the preferred diffusion mechanism of S and the influence of Pt are revealed to be temperature dependent. Finally, the effects of reactive elements on alumina grain boundary strength are studied. Reactive elements are shown to improve both the sliding and cleavage resistance, and the analysis of atomic separations suggest an increased ductility after the addition of quadrivalent Hf and Zr to the alumina grain boundaries.

The aim of this thesis is to investigate the effects of additives, reactive elements and impurities, on the lifetime of thermal barrier coatings. The thesis consists of a number of studies on interface adhesion, impurity diffusion, grain boundary sliding and cleavage processes and their impact on the mechanical behaviour of grain boundaries. The effects of additives and impurity on interface adhesion were elaborated by using total energy calculations, electron localization and density of states, and by looking into the atomic separations. The results of these calculations allow the assessment of atomic level contributions to changes in the adhesive trend. Formation of new bonds across the interface is determined to improve the adhesion in reactive element(RE)-doped structures. Breaking of the cross interface bonds and sulfur(S)-oxygen(O) repulsion is found responsible for the decreased adhesion after S segregation. Interstitial and vacancy mediated S diffusion and the effects of Hf and Pt on the diffusion rate of S in bulk NiAl are studied. Hf is shown to reduce the diffusion rate, and the preferred diffusion mechanism of S and the influence of Pt are revealed to be temperature dependent. Finally, the effects of reactive elements on alumina grain boundary strength are studied. Reactive elements are shown to improve both the sliding and cleavage resistance, and the analysis of atomic separations suggest an increased ductility after the addition of quadrivalent Hf and Zr to the alumina grain boundaries.

The aim of this thesis is to investigate the effects of additives, reactive elements and impurities, on the lifetime of thermal barrier coatings. The thesis consists of a number of studies on interface adhesion, impurity diffusion, grain boundary sliding and cleavage processes and their impact on the mechanical behaviour of grain boundaries. The effects of additives and impurity on interface adhesion were elaborated by using total energy calculations, electron localization and density of states, and by looking into the atomic separations. The results of these calculations allow the assessment of atomic level contributions to changes in the adhesive trend. Formation of new bonds across the interface is determined to improve the adhesion in reactive element(RE)-doped structures. Breaking of the cross interface bonds and sulfur(S)-oxygen(O) repulsion is found responsible for the decreased adhesion after S segregation. Interstitial and vacancy mediated S diffusion and the effects of Hf and Pt on the diffusion rate of S in bulk NiAl are studied. Hf is shown to reduce the diffusion rate, and the preferred diffusion mechanism of S and the influence of Pt are revealed to be temperature dependent. Finally, the effects of reactive elements on alumina grain boundary strength are studied. Reactive elements are shown to improve both the sliding and cleavage resistance, and the analysis of atomic separations suggest an increased ductility after the addition of quadrivalent Hf and Zr to the alumina grain boundaries.

This diploma thesis is focused on monitoring of mechanical response of long-fiber reinforced polymer composite. Main part of this thesis was preparation of long-fiber reinforced composite specimens, on which matrix was reinforced by commercially sized glass fibers. For comparison of properties were prepared specimens reinforced by unsized glass fibers. Apart from preparing specimens reinforced by long glass fibers were prepared specimens contains long carbon fibers. For evaluation of mechanical response of the prepared composite specimen were used flexural test and short beam shear test. Mechanical response was evaluated with universal testing machine ZWICK Z010 and data were processed in OriginPro 8 program. Thanks to evaluation of the mechanical response of the prepared specimens was assessed adhesion to fiber-matrix interface. By examining the mechanical response or adhesion can be assessed efficiency of commercial fiber surface treatment and so standardize measurement to compare other options of surface treatments.

The doctoral thesis is aimed at preparation of glass fiber reinforced polymer composites with controlled interphase formed by plasma-polymerized tetravinylsilane and tetravinylsilane/oxygen thin films. The thin polymer films of specific physico-chemical properties and thickness were deposited to improve interfacial adhesion of glass fiber/polyester composites. The fiber surface modification was performed by using plasma enhanced chemical vapor deposition in low-temperature RF plasma operating in an various effective power range and different treatment time. Test results were examined in relation to the interlayer thickness and different treatment conditions. The prepared interlayers were analyzed to evaluate physico-chemical composition and properties (XPS, RBS, ERDA, FTIR and spectroscopic elipsometry). Selected mechanical properties were evaluated by AFM. Mechanical response of plasma interlayers was evaluated by short beam shear test and direct method of testing the interfacial shear strength using microindentation. The interphase shear failure was controlled by the shear strength at the interlayer/fiber interface as follows from experimental and model data.

Das Verständnis über die Ausbildung der Grenzfläche eines hybriden Bauteils aus thermoplastischem Kunststoff und Metall sowie die maßgeblichen Faktoren zum Erreichen einer hohen Verbundhaftung und Mediendichtheit in der Grenzfläche stellen nach wie vor eine große Herausforderung dar. Am Beispiel einer spritzgegossenen Kunststoff-Metall-Verbundprobe werden diese Zusammenhänge untersucht und bewertet. Es wird eine Methode zur Herstellung stoffschlüssig gefügter Verbunde mit hoher Mediendichtheit auf Basis einer hohen Kontakttemperatur beim Fügen entwickelt, indem Verbundspritzgießen und nachträgliches thermisches Fügen durch Induktionsheizen kombiniert werden. Eine stoffschlüssige Verbindung mit hoher Mediendichtheit zwischen thermoplastischem Kunststoff und Metall erfordert eine Haftung in der Grenzfläche der Verbundpartner auf Basis intermolekularer Wechselwirkungen. Die Quantifizierung der Mediendichtheit in der Grenzfläche erfolgt über eine eigens entwickelte Messmethode. Die entwickelte Vorgehensweise ermöglichet die Differenzierung zwischen intermolekularen Wechselwirkungen und mechanischen Verklammerungen als Ursache für eine Haftungsausbildung und deren Einfluss auf die Grenzflächeneigenschaften. Die gewonnenen Erkenntnisse tragen zum Verständnis der Grenzflächenausbildung, insbesondere zum Einfluss der Oberflächenbeschaffenheit des metallischen Verbundpartners sowie der Fügeprozessbedingungen zur Fertigung von Kunststoff-Metall-Verbunden mit hoher Mediendichtheit, bei.:1 Einleitung und Motivation 2 Stand der Technik und Forschung 3 Zielsetzung und Lösungsansatz 4 Experimentelles 5 Analytik 6 Ergebnisse 7 Diskussion der Ergebnisse 8 Zusammenfassung und Ausblick / Understanding the formation of the interface of a hybrid component made of thermoplastic and metal as well as the decisive factors for achieving high adhe-sion and media tightness in the interface still represent a major challenge. These relationships are investigated and elucidated using the example of an injection-molded plastic-metal part. A method for the production of firmly bonded hybrid parts with high media tightness based on a high contact temperature during joining of the hybrid part is developed by combining injection molding and subsequent thermal joining by induction heating. A firm bond with high media tightness between a thermoplastic and a metal requires an adhesion in the inter-face of the joint materials based on molecular interactions. The quantification of the media tightness in the interface is done by using a specially developed measurement method. The investigations enable the differentiation between molecular interactions and mechanical interlocking as the cause of adhesion formation and their influence on the properties of the interface. The gained knowledge contributes to the understanding of interface formation and its prop-erties, in particular the influence of the surface properties of the metallic bond partner and the joining process conditions for the production of plastic-metal parts with high media tightness.:1 Einleitung und Motivation 2 Stand der Technik und Forschung 3 Zielsetzung und Lösungsansatz 4 Experimentelles 5 Analytik 6 Ergebnisse 7 Diskussion der Ergebnisse 8 Zusammenfassung und Ausblick