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Thin-walled 3D-customized ceramic components can be used, e.g. for inert and thermal resistant housings as well as special surface structured kiln furniture. For manufacturing such components, deep drawing of ceramic green tapes has been used. The technology has been almost not applied for processing of ceramic green tapes. A new approach was developed to realize a homogenous ceramic particle packing and hence uniform green density within a deep drawn green tape. After debinding and sintering, defect-free model structures with a dense microstructure (density > 99%) were achieved. Within this study, the deep drawing of ceramic green tapes by using a new approach was investigated. The developed approach brings several beneficial properties together, e.g. a reproducible form deviation and more importantly a homogeneous particle distribution allowing homogeneous and dense structures. With this results, the transformation of non-complex and cheap ceramic green tapes to 3D-customized and near-net-shape thin-walled mouldings becomes possible. [ABSTRACT FROM AUTHOR]

The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly. [ABSTRACT FROM AUTHOR]

Abstract: Sintered silicon carbide materials have found widespread use due to their high corrosion stability. This corrosion stability can be affected by electrochemical processes. Electrochemical corrosion experiments conducted on a SSiC material in H2SO4 at different voltages and subsequent detailed investigation of the formed surfaces was carried out. The first time a systematic local measurement of the thickness of the oxide layers was carried out. The measurements revealed the formation of SiO2 surface layers with thickness up to 125μm. The measured values also showed a strong deviation from grain to grain. The thickness of the layers does not correlate with the crystallographic orientation of the grains or the SiC-polytypes. The data indicate that the behaviour is caused by the variation of the resistivity of the grain boundaries. The measured thicknesses as a function of the electrical charge transferred indicate that the electrochemical oxidation results in the SiO2 and carbon dioxide. [Copyright &y& Elsevier]

Abstract: Materials with enhanced wear resistance are of great interest for modern industry. The different ways of producing superhard ceramic materials are shortly reviewed. In detail, the preparation of diamond–silicon carbide composites by reactive infiltration of diamond preforms with liquid silicon at ambient pressure is investigated. In addition to homogeneous SiC/diamond materials with nearly 50vol.% of diamond layered composites were also prepared. The microstructures of the materials prepared under different infiltration conditions were analyzed using X-ray diffraction, electron microscopy, electron back-scatter diffraction (EBSD) and Raman spectroscopy. The properties of the materials depend strongly on the formation of graphite interlayers at the boundary between SiC and diamond. Hardness of 47GPa was reached for materials where the formation of the interlayer was prevented. [Copyright &y& Elsevier]

Solid oxide fuel cells are the most promising power conversion units for fossil and biomass fuels combining ceramic and metallic components. Because of long-term high temperature operation and thermal cycling the standard materials cannot be applied for integration of active ceramic components. Different approaches are used nowadays for the integration of ceramic cells into stacks and of system components in the power plant. In this paper an overview on the application of glass and glass ceramic sealants, active and reactive air brazes as well as compressive mica sealants for solid oxide fuel cells is made. The crystallizing glasses are more favorable for cell integration in the stack for operation in a broad temperature range. Metallic brazes are mainly limited to integration of anode or metal supported cells in ferritic alloy gaskets for operation at T < 750°C and mica is a most suitable solution for system component integration in hot regions of power plants as well as for gas tight electrical isolation. In addition, this study regards aspects of degradation processes of glass ceramic and metallic sealants which allow estimations for the long-term behavior of joints. [ABSTRACT FROM AUTHOR]

Abstract: Planar solid oxide fuel cells (SOFC) are considered to be power generators with high efficiency and low emission at small power units (1–200kWel). Many prototype systems are already successfully realized. For mass production the costs have to be reduced and the long-term stability has to be enhanced. Power losses <0.5%/1000h is the target value for stacks in stationary SOFC-based power systems. To reach this goal, the factors influencing degradation have to be found and reduced. In this work the interaction between interconnect and different ceramic materials such as perovskites (La0.8Sr0.2(Mn,Co)O3, La0.65Sr0.3MnO3, La0.65Sr0.3(Mn,Co)O3) and spinels (Mn(Co,Fe)O4, (Cu,Ni)Mn2O4) was investigated on the cathode (air) side of conventional ferritic interconnect materials (CroFer22APU, ITMLC, ZMG232L). The method to determine the value of the area specific resistance between interconnect and contact layer (R #ICC) within a tolerance of 10% has been developed to provide reliable data for ASR values and their degradation. The R #ICC-value increases with annealing time. The degree of this increase depends on used materials and their combination. The spinel contact layers form a thin dense ceramic layer at the beginning of the annealing process. This layer reduces the oxidation rate of the alloy. Because of this protection layer a thinner oxide scale grows and the ASR aging rate is much lower (0.4–0.9mΩcm2/1000h). The comparison of the aging rates of different alloys with La0.8Sr0.2(Mn,Co)O3 contact layer reveals remarkable differences: 3.1mΩcm2/1000h for CroFer22APU, 10.9mΩcm2/1000h for ITMLC and 21.2mΩcm2/1000h for ZMG232L. The degradation in a stack has been determined from the R #ICC-values and geometric factors. The impact of oxidation at the cathode side of interconnect is about one third of the total stack degradation. The method opens the possibility for comparing area specific resistances of special material combinations with high accuracy. By optimized material combinations the degradation in stacks can be reduced to <0.5%/1000h. [Copyright &y& Elsevier]