On the Matano Plane Position in Multicomponent Diffusion Couples

Even though several methods of diffusion analysis avoid a necessity for the Matano plane determination, the Matano plane locations are of interest in the multicomponent couples and when tracer experiments are performed. The positions of the Matano plane calculated from the concentration profiles should be exactly the same. However, due to experimental errors, the results can differ significantly. In the paper we consider Matano plane for multi-component couples of conserved and non-conserved overall volumes. We use Darken method and Sauer-Freise scheme, respectively and show that looking for the Matano plane as an inverse problem leads to a system of linear algebraic equations which are over-determined. The relations for the Matano plane position are derived by virtue of the least-squares methodology. The exemplary computations shows that the method is particularly useful in analysis of experimental data and allows decreasing computing errors.

Study on Diffusion of Copper of SOFC Cu-Based Anodes in Co-Sintering with Electrolyte

Cu-based anode has no or little catalytic activity to reaction of precipitating carbon during using carbon-hydrogen fuel, which can avoid failure or disintegration of SOFC caused by catalytically precipitating carbon resulting from Ni-based anode. However, the melting point of CuO, that is 1148°C, is far below the sintering temperature of electrolyte which limits the use of Cu-based anode. So the property of sintering of Cu-based anode between 1050°C and 1150°C was studied by co-pressing and co-sintering Cu-based anode with electrolyte. The result shows that the diffusion of copper in the electrolyte is not apparent when the co-sintering temperature is below 1130°C. At 1140°C, the Matano plane moved to anode side and the diffusion coefficient of copper in the electrolyte is relevant to concentration of copper which is 0.543×10-8-1.74×10-8(cm2•s-1) when the content of copper is 1.51%~18.7%.

Study of Kirkendall Effect in Ni/Ni3Al Welded Joint after the High Temperature Annealing

The study of composition and microstructure of welded joints was performed before and after the diffusion annealing at elevated temperatures for different annealing time. The Kirkendall effect in the Ni/Ni3Al diffusion couples was observed by means of different methods, e.g. using light, scanning electron and atomic force microscopies. The study suitably completes and specifies the morphology features of Kirkendall voids at different evolution stages, i.e. at nucleation, growing and coalescence. Kirkendall voids occurred in the region between the Matano and γ/γ´interface planes. The location of the γ/γ´ interface that moved in the direction of Ni3Al phase during the annealing resulted from the Al concentration profile measured by EDAX. The Matano plane location was determined by means of Boltzmann-Matano’s method using concentration profile data. It was observed that the void size was increasing in the direction from the Matano plane to the γ/γ´ interface. The obtained results were completed by surface topography of Kirkendall voids of slightly etched specimens by atomic force microscopy (AFM).