It is usually difficult to deposit effectively spray particles with a much limited melting in thermal spraying. In the present study, flame spraying was employed to produce yttria-stabilized zirconia (YSZ) particles at a limited melting. The melting degree of YSZ particles was controlled by flame combustion intensity and flying distance of spray particles within gas flame. The velocity of spray particles was quantitatively measured. The effects of spray distance and acetylene flow rate on the particle velocity, and deposition behavior were examined. The surface morphology of deposited particles was characterized by scanning electron microscopy. The bonding between deposited YSZ particles and YSZ substrate was examined from cross section. The spray particles in different melting states were obtained by changing flame spray parameters. The deposition experiment revealed that the YSZ particles at different melting states from only surface layer melted state, semi-melted state to substantially melted state can be successfully deposited on YSZ substrate by controlling substrate temperature. As a result, YSZ surfaces with different morphologies of particles from a near spherical shape, hat-on-frustum shape and hat-shape with different neck sizes, to a pancake shape and well spread disk shape have been created.

Solution precursor plasma spraying (SPPS) was employed to prepare porous Sm 0.5 Sr 0.5 CoO 3 (SSC) cathode for solid oxide fuel cell (SOFC). The surface and cross-sectional morphology of the SSC deposit were characterized by scanning electron microscopy. The effect of annealing on SSPS SSC microstructure was examined. The electrochemical behavior was investigated through the impedance spectroscopy. The results showed that the SPPS SSC cathode deposited at a spray distance of 80 mm exhibits multidimensional porous microstructure. The porous film of the partially crystalline perovskite phase with a fine microstructure was obtained after annealing at 900 °C for 2 hours in air. The electrochemical measurement showed that the specific surface resistance of SSC decreased significantly with the increase of test temperature and yielded a specific surface resistance of 2.6 Ω·cm 2 at 800°C.

Plasma-sprayed yttria-stabilized zirconia (YSZ) can be potentially employed as electrolyte coating in solid oxide fuel cells (SOFCs). The formation of a convex coating surface with semi-melted particles will increase the specific surface area and subsequently improve the output performance of SOFCs. However, using completely molten YSZ particles during plasma spraying leads to the formation of locally flat surface owing to the spreading of the liquid droplets on impact. In this study, flame spraying was employed to deposit YSZ particles on YSZ substrate using surface-melted particles. 4.5 mol% YSZ powder particles were used as spray materials. The deposition was carried out at different spray distances on the YSZ substrate preheated to 650 °C. The surface morphology of YSZ particles was characterized by SEM. The bonding of YSZ particles with the underlying YSZ substrate was examined from cross section. The electrochemical behavior of a single cell with a structured cathode was analyzed by electrochemical impedance spectroscopy. The results show that spray distance has significant influence on the morphology of deposited YSZ particles. The cathode polarization of a structured cathode was decreased by about 30% compared to a flat cathode.