Supersonically expanding stationary thermal plasma, formed by a thermal cascaded arc is studied. Due to the low chamber pressure (20-100 Pa) the results of continuum mechanics model can be doubtful. This is why these results are validated against kinetic Monte Carlo simulation and experimental data obtained by means of laser induced fluorescence. The analysis proves that continuum mechanics is still applicable for the velocity and temperature field predictions downstream of the shock region. However, the shock formation and some non-equilibrium effects typical for supersonic flow can be correctly studied only with the help of kinetic simulations. We show that the errors in the results using continuum mechanics can be attributed to the presence of flow gradients. These errors diminish when the shock regions are thickened due to rarefaction, viscosity and heat conductivity. Besides, both methods show that the effect of the chamber geometry on the plasma flow field is important.

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Mathematical modelling was applied to study the dynamical and physical properties of the supersonically expanding rare gas plasma formed by a cascaded arc. Keeping constant the volume flow rate and the power input into the plasma, the Ne, Ar and Xe flows are compared. We demonstrate that the difference in mass flow rate affects the dynamic properties of plasma expansion. Modelling and experimental results show that the recombination heating of electrons is more significant in a gas that has a lower ionization potential.

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In the continuing progress of fuel cell technology, CeO2 double doped electrolytes appears to be promising for lowering the SOFC's working temperatures. Ceria electrolytes have better ionic conductivities than YSZ but, at low oxygen partial pressures, the chemical reduction of ceria leads to increasing electronic conduction. Double doping of the ceria increases the electrolytic conduction range without changing its conductivity. To avoid stress development within the ceria crystallographic structure, the dopants mix must have a mean ionic radius as close as possible to the critical ionic radius. Ceria electrolytes with various compositions and dopant concentrations are synthesized with a combinatorial chemistry approach. To synthesize new electrolytes, solution plasma spraying with nitrate salt precursor is used. The reaction is completed and nanocrystalline thin layers of ceramic are formed in the plasma. Comparative studies of plasma spraying techniques, with YSZ powder plasma spraying as electrolyte reference, were performed. Also, comparative impedance spectroscopy measurements are to be performed to validate the double doping hypothesis and thence to identify the best electrolytes in the suite of over 300 new materials.