O estranho e o próprio: projeção, diferença e reminiscência em "A missão" de Heiner Müller

From the very beginning literary discourse plays a decisive role in the context of colonial discourse of power. Even Anna Seghers, a progressive socialist authoress with a fixation on the Enlightenment, the French Revolution and the Jewish-Christian tradition is unable to detach herself from the European claim on universality. In a tensely opposed relationship of projection and otherness, of "memoria" and intertextuality, Heiner Müller, however, understands literature in the sense of Emanuel Lévina's respect for the other being as a work on difference.Vom Anfang an spielt im kolonialen Machtdiskurs der Literaturdiskurs eine entscheidende Rolle. Auch Anna Seghers als fortschrittliche, sozialistische Autorin kann sich mit ihrer Fixierung auf Aufklärung, Französische Revolution und jüdisch-christliche Tradition nicht vom europäischen Universalismus-Anspruch lösen. In einem Spannungsverhältnis von Projektion und Alterität, von Memoria und Intertextualität versteht Heiner Müller dagegen Literatur im Sinne von Emanuel Lévinas' Achtung des Anderen als Arbeit an der Differenz

Environmental barrier coatings deposited by suspension plasma spraying

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Thermal Stability of Novel Multilayer Lanthanum Zirconate Based Thermal Barrier Coatings

This chapter discusses the thermal stability of SCL and DCL porous La2Zr2O7 coats by depositing three types of SCL and DCL La2Zr2O7 and 8YSZ structures in an experiment. Heat treatment, cyclic furnace cycle test and jet engine thermal shock test were conducted for the thermal barrier coatings (TBC) samples. The heating and cooling cycles were repeated until cracks or spallation were spotted on the TBC surface. Both the front and back surface temperatures were measured using pyrometer. The delamination is caused by the thermal residual stress induced by CTE difference between La2Zr2O7 and 8YSZ. All the La2Zr2O7 coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. Microstructure images of heat treated samples were taken using a scanning electron microscope

Phase Transformation-Induced Changes in Microstructure and Residual Stresses in Thermally Sprayed MnCoFeO4 Protective Coatings

The contribution comprises the investigation of the microstructure and residual stresses in thermally sprayed Mn$_{1.0}$Co$_{1.9}$Fe$_{0.1}$O$_{4.0}$ (MCF) protective coatings for interconnectors of SOFC stacks, deposited on ferritic steel Crofer 22 APU via atmospheric plasma spraying (APS). The coatings are designated to prevent Cr evaporation during high operation temperature of the SOFCs. The local microstructure, pore distributions and pore shapes, phase fractions, micro-hardness, Youngs’ modulus and residual stresses through the coating thickness were characterized in as-sprayed state and compared with longtime (10-100 h) heat-treated samples (700 and 850 C). The results show that the long-term thermal aging treatment causes a successive high sintering of the coatings characterized by a reduction in pore density, by phase transformation from the metastable rock salt structure that gradually transformed to a spinel structure and by a slight relaxation of the processinduced tensile residual stresses in the coating. For SOFC application of the MCF coating, this indicates an improvement in the coatings integrity. During operation, a self-repair proceeds leading to dense and gas-proof coatings, while the mechanical properties are mainly retained

Columnar Thermal Barrier Coatings Manufactured by Novel Laser Cladding Process

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Environmental barrier coatings for SiC/SiC and Ox/Ox CMCs

Environmental barrier coatings (EBCs) are being developed for next-generation gas turbine engines to protect hot-section SiC/SiC or Ox/Ox (alumina-based) ceramic matrix composite (CMC) components in the harsh operating environments. In this paper, high-velocity water vapor recession (v=100m/s, PO2=0.15atm T=1200°C) and thermal gradient cycling behavior (Tsurface=1250°C) of thermally sprayed Yb2Si2O7/Si EBCs on SiC using different processing conditions will be presented. Phase composition and microstructural changes in the coatings prior and after the tests will be examined. Furthermore, the potential of different (Yb, Sc)-zirconate and hafnate compositions with high melting points as EBC materials will be discussed based on their investigated bulk properties. Characteristics of the solid-state synthesized materials, which were high energy ball milled into submicron particle sizes and subsequently densified with field assisted sintering technology (FAST), such as phase stability (HT-XRD), thermophysical (dilatometry, thermal diffusivity) and mechanical properties (hardness, indentation fracture toughness) will be demonstrated

Microstructure and Phase Composition Evolution of Thermal Sprayed Yb- Silicate Coatings during Post Heat Treatment and Burner Rig Test

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Superior performance of plasma sprayed YSZ thermal barrier coatings with oxide dispersion strengthened bond coats

Advanced thermal barrier coatings are essential to increase the efficiency of next-generation gas turbine engines. Different materials and process technologies give the possibility to extend the lifetime of TBCs. One limiting factor of the TBC lifetime is the growth of the TGO during thermal exposure resulting in a accelerated crack growth at the top coat- bond coat interface. The oxidation resistance and the temperature of the bond coat are key factors influencing the TGO growth rate. Oxide dispersion strengthened (ODS) bond coats have a slower oxygen scale growth during thermal exposure in comparison to standard bond coats. In previous studies TBC systems with an additional thin ODS bond coat on top of a standard bond coat showed a higher thermal cycling performance. These studies used Inconel 738 and Amdry 386 as substrate and bond coat material, respectively. This study investigates in the thermal cycling performance of the ODS bond coat TBC systems combined with a different substrate ERBO 1 and bond coat material Amdry 995. TBC systems with the new material combination show high cycling lifetimes and superior performance in comparison to previous samples. Samples were tested by a cyclic burner rig facility. Surface was heated by a gas burner to 1400°C while the backside is cooled by pressurized air to 1050°C. One cycle consists of 5 min heating followed by 2 min cooling. Cross sections of the samples were analyzed by SEM and laser microscope. The lifetime of the samples was evaluated especially with respect to diffusion processes, material properties, and bond coat temperature. ODS powders with higher aluminum oxide additions were produced by high energy milling to fit the CTE of the ODS bond coat to the one of the top coat. This will reduce the initial crack formation on the top a wavy top coat - bond coat interface and increase lifetime. The advanced bond coats were applied by low pressure plasma spraying, the standard YSZ top coat by atmospheric plasma spraying. The performance was evaluated by a gas burner rig test

Development of thermally sprayed environmental barrier coatings

Ceramic matrix composites (CMCs) are candidate materials for high-temperature applications such as gas turbines. As corrosion by water vapor and deposits is a limiting issue, the application of suitable environmental barrier coatings (EBCs) is inevitable. Gas tightness, chemical stability and a good adhesion of the EBC are crucial aspects for providing an effective barrier against the combustion atmosphere. Thermal spray technologies offer a variety of promising process routes to the manufacturing of ceramic coating systems complying with these demands. This contribution covers coatings for both silicon and oxide based CMCs. Different EBC materials (e.g. silicates, aluminates, rare-earth oxides) were examined and optimized for use as EBC by air plasma spraying (APS). Different thermal spray techniques including high-velocity oxygen-fuel spraying (HVOF), suspension plasma spraying (SPS) and plasma-spray physical vapor deposition (PS-PVD) techniques were assessed for the manufacture of coatings with low amorphous phase content. The application of bond coat as well as alternative surface modification technologies was tested to increase the adhesion of the EBCs. Microstructures and chemical stability of the coatings were analyzed and the performance was tested in terms of adhesion strength or degradation under high-temperature exposure including cyclic oxidation

Fracture toughness of thermal barrier coatings determined by micro cantilever bending tests

To investigate the local fracture toughness of thin coatings new small scale methods like FIB milling of micro cantilever are used. Webler et al. used this technique for measuring the fracture toughness of NiAl bond [1]. This method can also be used to investigate the local fracture toughness of thermal barrier coatings. The fracture toughness of ceramic coatings can be determined by different indentation techniques [2]. The drawback of these methods is the analysis of the KIc-value without the specific knowledge of the crack front propagation, which can only be determined after the experiment. By using micro-cantilever produced by ion beam milling it is possible to measure the local fracture toughness with freestanding micro-cantilever independent of the substrate. Therefore two yttrium stabilized zirconia (YSZ) top coats with a thickness of 250μm, which were deposited by suspension plasma spraying on a layer of Amdry 9954 bond coat and IN 738 substrate with different standoff distances of about 70 and 100 mm, were investigated. Figure 1. shows the micro-cantilever with the initial crack (a) before testing. Please click Additional Files below to see the full abstract