M. Vilasi

Thermodynamic modelling of the O-Sn system

Thermodynamic and phase diagram data relative to the O–Sn system have been assessed. The existence, the type and the temperature of invariant equilibria Melt1(l)⇌Melt2(l)+SnO2(s) and Sn3O4(s)⇌2SnO(s)+SnO2(s) have been the subject of DSC and XRD experiments. The adjustable parameters of the modelling are obtained by the CALculation of PHAse Diagram (CALPHAD) method fitted thanks to diagram and thermodynamic data through Thermo-Calc™ software. In particular, the liquid phase is described by the way of the Hillert’s partially ionic liquid model. The final result is in good agreement with all of the experimental data available. Activities of tin and oxygen versus composition at different high temperatures can be calculated.

Experimental investigations and thermodynamic description of the PbO−Bi2O3 system

The knowledge of the quinary Pb–Bi–O–Fe–Hg is necessary for understanding the degradation mechanisms of the T91 steel used as structure material in future ADS nuclear reactors. In this device, the steel will be in direct contact with the liquid spallation target (which is constituted by lead or lead-bismuth eutectic) surrounded by a reduced oxygen pressure atmosphere. In the present work, the characterization of the pseudo-binary PbO–Fe2O3 cut has been performed. In order to complete the available data in the literature, some experimental investigations by differential thermal analysis (DTA), isothermal annealing, powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) have been done. These results have allowed proposing a thermodynamic assessment using the Calphad method.