Mechanical Properties of Porous MgO Substrates for Membrane Applications

Advanced design concepts for the application of oxygen transport ceramic membranes are based on thin layers supported by porous substrates. One suitable support material in this respect is porous MgO. However, a careful consideration of the mechanical stability is required to warrant long term performance and reliability under application relevant thermo-mechanical loads. The current work summarizes the effect of the sintering conditions on porosity and mechanical properties and gives elastic modulus and fracture stress as a function of temperature. An enhancement of the strength by the addition of boehmite to MgO was tested. Elastic moduli are determined and compared as obtained by indentation and bending tests. With respect to fracture, specimens in planar geometry are investigated using ring-on-ring bending tests; tubes are tested using an O-ring set-up. Fracture stresses are statistically analyzed. The obtained mechanical parameters are compared to that of other potential porous substrate materials

Stability aspects of porous Ba0.5Sr0.5Co0.8Fe0.2O3−δ

Porous substrates are a prerequisite for advanced oxygen transport membranes. In particular, phase stability and mechanical robustness are of concern for long term performance and reliability. These aspects were investigated for porous Ba0.5Sr0.5Co0.8Fe0.2O3−δ material using annealing experiments along with microstructural investigations, depth-sensitive micro-indentation and ring-on-ring bi-axial bending tests. Annealing studies revealed phase instabilities at elevated temperatures that were also characterized by X-ray diffraction analysis. Elastic modulus and fracture stress were strongly affected by the porosity, whereas their temperature dependency agreed with the behavior of dense material

Mechanical properties of pure and doped cerium oxide

Advanced concepts for oxygen transport membranes focus on thin layers supported by a porous substrate. To warrant long term reliable operation of such systems, an assessment of the mechanical stability of each membrane component is required. With respect to chemical stability, cerium oxide and doped cerium oxides are promising materials for this application. The present work addresses the mechanical properties of cerium oxide variants, aiming to elucidate properties of relevance to the manufacture of reliable cerium oxide components. In particular Ce0.8Gd0.2−yPryO2−δ membrane materials and the influence of an addition 2 mol% of CoO is assessed. Materials preparation and compositional variations are compared with respect to elastic modulus, hardness and fracture toughness, as characterized using depth sensitive indentation. Furthermore, the creep behavior of doped and undoped cerium oxides, that is important for the long term structural stability at temperatures relevant to the oxygen-membranes operation, is assessed and critically discussed

Strength and Elastic Modulus of Lanthanum Strontium Cobalt Ferrite Membrane Materials

Mixed ionic electronic ceramic transport membranes have a large potential for industrial oxygen supply and carbon emission reduced fossil power plant concepts. Although permeation and phase stability are main development aspects, mechanical robustness is of concern especially for the long term performance and reliability under application relevant thermo-mechanical loads. Lanthanum strontium cobalt ferrite materials appear to be advantageous, especially with respect to CO2 stability. However, the effect of the A-site stoichiometry on the mechanical properties needs to be assessed. Furthermore, advanced design concepts rely on thin layers supported by a porous substrate and therefore also the porosity is an important factor. Hence, these aspects were investigated for dense and porous La0.6Sr0.4Co0.2Fe0.8O3−δ and dense La0.38Sr0.62Co0.2Fe0.8O3−δ. The specimens were investigated using a ring-on-ring bending set-up. The work summarizes the effect of the stoichiometry and porosity on the mechanical properties and compares the temperature dependencies of elastic moduli and fracture stresses

Single-crystal plasticity of the complex metallic alloy phase ß-Al-Mg

We have determined the macroscopic plastic deformation behaviour of high-quality single-crystalline samples of the complex metallic alloy beta-Al-Mg. Uniaxial deformation experiments at a constant strain rate of 10(-4) s(-1) were performed at temperatures between 200 and 375 degrees C. The material exhibits ductile behaviour down to temperatures of 225 degrees C. At this temperature an upper yield stress of 780 MPa was observed, which is a very high value compared to commercial Al-Mg alloys. The upper yield point is followed by an almost constant flow stress level up to strains of about 6%. Stress-relaxation tests and temperature changes were carried out in order to determine the thermodynamic activation parameters of the deformation process. (C) 2006 Elsevier Ltd. All rights reserved

High Resolution (S)Tem Characterization of Deformation Mechanisms in High-Mn TWIP Steels

Proceedings:Wolfgang Bleck, Dierk RaabeEditing: Sonja Brühl4th HMnS / IEHK, RWTH Aachen UniversityProceedings (2019) 238 - 241RWTH-2019-0375

Improving hydrogen embrittlement resistance in high manganese austenitic steels by microstructure optimization

Proceedings: Wolfgang Bleck; Dierk RaabeEditing: Sonja Brühl4th HMnS / IEHK, RWTH Aachen University; Proceedings (2019) 328 - 33