A study on the formation mechanism of liquid calcium aluminate inclusions from MgO·A1203 spinel was carried out. It was found that spinel reacted with dissolved Ca in liquid steel forming liquid calcium aluminate phase. Stability calculations showed good agreement with the experimental result. According to the thermodynamic calculation, liquid calcium aluminate inclusions would form from spinel even at very low level of dissolved Ca content at 1873 K. At lower temperatures, the compound CaO·2AI 20 3 was found to be the stable phase at the spinelmetal interlace. Potential sources of dissolved Ca during ladle processes were also discussed.

Elemental composition, dimensionality and morphology are the main factors that influence the catalytic activity and stability of platinum-based and noble metal alloy nanocatalysts.

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Cracking is a major problem during constrained sintering of ceramic films. A local variation of density in a green film, referred to as a defect in this work, is the leading cause for cracking. This article presents analytical and numerical studies of the behavior of such defects during constrained sintering. An interesting behavior of de-sintering and healing of the defects is revealed. It is demonstrated that the healing process can be made to start earlier during sintering by using (a) larger particles, (b) lower sintering temperature, and (c) lower initial density. However, a uniform distribution of initial density in the film is shown to be the most effective means to avoid cracking. It is realized that most of the factors beneficial to defect healing are detrimental to sintering a film to high density because the driving force for sintering also drives cracking. The analytical and numerical studies also offer some simple explanations to why thin films are less susceptible to cracking than thick ones. Finally, the constitutive model has been combined with a simple empirical failure criterion, to simulate the initiation and propagation of multiple cracks in a sintering film. The cracking patterns predicted by the simulations resemble those observed during sintering experiments.